aging - Inovacure

Transcription

aging - Inovacure

aging
Protein that Transforms your Life
Reversing the Effects of Time
Collagen concentrated beverage enriched with anti-oxidants
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Green Tean and Cranberry
Improves skin’s texture
Reduces wrinkles and fine lines
Increases skin’s elasticity
Regenerates tissues
aging
Inovacure Anti-Aging
Concentrated Beverage
Anti-oxidants contained in the anti-aging beverage
are:
Inovacure anti-aging beverage is a natural
way of staying in shape, healthy and physically
independent as long as possible. Aging speed
varies from one person to the next. Indeed,
chronological age, which is celebrated each year,
can be different from our physical age. Here are
three reasons explaining this physical aging:
1. Vitamin C as an anti-oxidant is very well
documented. Moreover, it helps other anti-oxidant
vitamins, such as vitamin E and beta-carotene.
It restores their anti-oxidizing power (up to 18% for
vitamin E and 13% for beta-carotene).
Moreover, vitamin C is beneficial to different
systems in your body, such as the skin’s, ligaments’,
cartilage’s, bones’, teeth’s and gums’ regeneration
as it acts in the formation of collagen. Vitamin C
also supports a good immune system and increases
the speed of cicatrisation.
1.Attacks from free radicals;
2.Changes in the immune system;
3.A decline in the protective anti-oxidants.
The theory using the free radicals as an explanation
of aging and as an explanation of the increase in
illnesses linked to age started to be accepted in the
1980s by scientists and in the 1990s by the public.
2. Vitamin E is a powerful anti-oxidant. It plays an
essential role in protecting membranes surrounding
body cells. Vitamin E possesses other characteristics
not related to its anti-oxidizing activity, but that are
also very important at the cardioprotective level
(anti-inflammatory, anti-platelet and vasodilator
characteristics). It is also a useful re-inforcer of the
immune system.
There are several negative effects of free radicals.
Here are some examples:
• They increase the speed of aging;
• They weaken the immune system;
• They maintain inflammation;
• They are involved in the evolution of several
illnesses: degenerative diseases (multiple
sclerosis, Alzheimer), cardiovascular diseases,
diabetes, articular diseases, cancers (breast,
lungs, stomach, bowels, etc.), pain, fibromyalgia,
chronic fatigue syndrome, etc.
Moreover, vitamins E and C could provide a
protection against the Alzheimer’s disease when
taken together. These anti-oxidants could help
protect the brain against free radicals attacks
associated with the Alzheimer’s disease and with
aging.
Therefore, some studies show that vitamin E has a
higher therapeutic potential when it is associated
with other anti-oxidants, such as vitamin C, vitamin
A and beta-carotene.
Anti-oxidants have the capacity to reduce the free
radicals process. Indeed, anti-oxidants protect our
body’s cells against damage caused by the attack
of free radicals.
3. Flavonoids contained in the grape seeds extract
are a powerful anti-oxidant. Their anti-oxidizing
capacities are 20 to 50 times greater than those
contained in vitamins C and E. Flavonoids possess
other characteristics linked to aging, such as
Taking an anti-oxidant supplement, such as the
Inovacure anti-aging beverage, insures a good
protection against an excess of free radicals.
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aging
protecting against insulin resistance, which often
appears with age, reducing the risks of cancers,
stimulating joint flexibility, decreasing arthritis
inflammation, reducing the immune system’s
resistance and reducing retina disorders, such as
macular degeneration.
We know that the body makes its own collagen
each day and that this production is reduced with
age. After 25 years old, the collagen ratio decreases
in the body, leading to the first sings of aging. At 70
years old, collagen loss has increased to more than
30%.
4. Beta-carotene is well known for its powerful
anti‑oxidizing characteristics for skin, eyes, hair,
liver and lungs protection. Beta-carotene is also well
known for its role as a protector of cardiovascular
health. It has an anti-platelets role as, as an antioxidant, it helps prevent LDL (bad cholesterol)
oxidation. Moreover, beta-carotene also plays a
role in the immune system.
One of the first signs of collagen production reduction
is the apparition of wrinkles. A collagen supplement
can greatly help skin tissues’ regeneration and
contribute to slow the aging process down. Collagen
helps strengthen, invigorate and moisturize your
skin, all while increasing its elasticity, which helps
reducing wrinkles and fine lines.
Finally, Inovacure’s anti-aging beverage also
contains FOS (fructooligosaccharides). FOS have
several functions. They act as a prebiotic as they
feed the bifidobacterias (beneficial bacteria to the
intestinal flora), which supports the immune system.
As they improve the intestinal flora, they have a
great influence on the resistance against illnesses,
such as cancers or inflammatory illnesses.
5. The Q10 coenzyme is a powerful, less known,
anti-oxidant. At the age of 50, a healthy person
produces 25% less of it than at 20 years old. The
Q10 coenzyme protects the structure of several
molecules, such as vitamin E and lipids. Moreover,
it has other very important roles, such as reducing
risks of blood clots, facilitating diabetics’ glycaemia
stabilization, helping reduce hypertension and
reducing the appearance of wrinkles.
FOS also have a beneficial influence on lipid profiling.
They have effects on the total cholesterolemia
and on LDLs, all while decreasing triglycerides.
Moreover, a chronic consumption of FOS favours a
reduction of the hepatic production of glucose in
a fasting state, which reduces diabetics’ glycemia
in a fasting state. In conclusion, a FOS supplement
strengthens the absorption of magnesium and
calcium, which improves bone density.
It is important to note that anti-oxidants don’t act
all in the same way. For a protection as wide as
possible, do not get satisfied with only one antioxidant, but consume them all.
Inovacure anti-aging beverage also contains
collagen. Collagen is the most abundant protein
in the body. It is produced by the connective
tissues’ cells, which are found in muscles, tendons,
ligaments, cartilage, bones, lungs and skin.
Collagen represents around 80% of the connective
tissues’ weight and from 30% to 35% of the body’s
total proteins.
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aging
The Anti-Aging Beverage’s Roles
the food becomes inefficient as an anti‑oxidant. By
taking an anti‑oxidant supplement, you stay sure
that you are keeping a good protection against an
excess of free radicals.
Inovacure anti-aging beverage is a natural
way of staying in shape, healthy and physically
independent as long as possible. Several studies
have demonstrated that it is possible to slow the
aging process down.
What are the Negative Effects of Free Radicals?
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We know that the speed of aging varies from one
person to the next. Indeed, chronological age, that
is celebrated each year, can be different from our
physical age. Here are three reasons explaining this
physical aging:
1. Changes in the immune system;
2. Attacks from free radicals;
3. A decline in the protective anti-oxidants.
They increase the speed of aging;
They weaken the immune system;
They maintain inflammation;
They are involved in the evolution of several
illnesses: degenerative diseases (multiple
sclerosis, Alzheimer), cardiovascular diseases,
diabetes, articular diseases, cancers (breast,
lungs, stomach, bowels, etc.), pain, fibromyalgia,
chronic fatigue syndrome, etc.
What are the Factors Encouraging the Formation of
Free Radicals?
What are Free Radicals?
• A diet low in anti‑oxidants (fruits, vegetables
and whole grains);
• Alcohol excesses (more than one drink per day
for women and more than two drinks per day
for men);
• Too much red meat, such as beef, pork and
lamb (more than 500g per week);
• Fishes and smoked meats;
• Modified and transgenic foods, or meat from
animals that were fed hormones;
• Nitrites contained in deli meats and cold cuts;
• Rancid, fried or burned fats (for example,
carbonized meats (BBQ), blackened butter, oils
that have passed their expiry date);
• Weight excess, especially in the waist area as it
increases the production of growth hormones,
which, in high quantities, increase the risk of
some cancers (breast);
• Pesticides;
• Tobacco smoke: more than 4000 toxic products
contained in cigarettes are a source of free
radicals;
• Excesses in ultraviolet radiations;
• Emotional stress;
• Pollutants.
The theory using free radicals as an explanation of
aging and of the increase in illnesses linked to age
started to be accepted in the 1980s by scientists
and in the 1990s by the public.
Free radicals are incomplete and very unstable
substances as they are unpaired (single) electrons.
These electrons tend to try and stabilize with
electrons from different molecules. By completing
themselves, free radicals destabilize close by
molecules, causing a chain reaction, which also
destroys cells. Problems arise when there are
too many free radicals, because of a lack of
anti‑oxidants or because of an overload of factors
enabling their production. Anti-oxidants can stop
this chain reaction process.
An anti‑oxidant is a relatively unstable substance
that can give away one electron in order to
neutralize a free radical. This is what we are
looking for within the body. However, under some
conditions (for example, heat, light, cooking,
extended storing, etc.), this reaction in foods
can happen before the food is consumed. The
anti‑oxidant becomes oxidized too quickly and
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aging
What is an Anti-Oxidant?
What is the Role of Anti-Oxidants?
Anti-oxidants protect our body’s cells from
anti‑oxidation or degeneration caused by the
attack of free radicals. The popularity of antioxidants can be explained by the fact that a
number of studies have demonstrated that people
consuming several portions of fruits and vegetables
per day tend to suffer less from illnesses linked to
oxidative stress, such as: cardiovascular illnesses,
cancer, dementia, diabetes, ocular degenerative
diseases (for example, cataracts, macula lutea
degeneration), the Parkinson’s disease, etc.
• They insure cell, unsaturated fats, proteins, DNA
and LDL cholesterol protection while stopping
the formation of free radicals;
• They play a role in preventing some illnesses;
• They reinforce the immune system.
aging
Vitamin C and the
Anti‑Aging Beverage
Daily intake for adults 19 years and older is 75mg for
women and 90mg for men. Since smoking increases
oxidative stress and the amount of metabolic
renewal of vitamin C, the need for vitamin C is
increased by 35mg/day for smokers. Pregnant
women need 85mg and those who are nursing
need 120mg.
Vitamin C, or ascorbic acid, is a water-soluble
nutrient. One of its major roles is its anti-oxidizing
effect that protects cells against damages caused
by free radicals. It puts out “fires lit” by free radicals
before they damage anything.
A Little Experience to Explain the Anti-Oxidizing
Power of Vitamin C
Moreover, vitamin C is useful to other anti-oxidant
vitamins, such as vitamin E and beta-carotene.
When these vitamins are blocked because they
already neutralized a free radical, vitamin C restores
this anti-oxidizing power (up to 18% for vitamin E and
up to 13% for beta-carotene).
Cut an apple in two halves. Take one half and add
lemon, orange or grapefruit juice. Then, leave the
two halves on the counter. You will notice that the
half that was not covered with juice has become
brown because of oxygen while the other half
was protected by the anti-oxidizing role of vitamin
C. The same way vitamin C protected the apple
from damages caused by oxygen, it will protect the
inside of your body.
Moreover, vitamin C is beneficial to different systems
in the body, such as skin, ligaments, cartilage, bones,
teeth and gums regeneration, as it intervenes in the
collagen formation. Vitamin C supports a good
immune system and speeds up scarring.
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aging
Some studies show that vitamin E has a higher
therapeutic potential when associated with other
anti-oxidants, such as vitamin C, vitamin A and
beta-carotene (provitamin A)
Vitamin E and the
Vitamin E is a liposoluble nutrient (it is soluble in fatty
tissues). Therefore, it can be stored. Vitamin E is a
major anti-oxidant.
Vitamin E has other characteristics unrelated to its
anti-oxidizing activity, but that are very important at
the cartioprotective level (anti-inflammatory, antiplatelets and vasodilator properties). Moreover, it is
used to reinforce the immune system.
The powerful anti-oxidizing role of vitamin E is
explained in the following way: vitamin E plays an
essential role in protecting membranes surrounding
body cells by stopping the free radicals’ chain
reaction. It therefore slows early aging down.
Vitamin E is the best anti-oxidant for this job, as it is
soluble in lipids; and cell membranes are made of
fat molecules.
Vitamin E also has an effect on skin. It increases skin’s
water-retention characteristics, which reduces
wrinkles.
The dose and nature of vitamin E could be
important aspects affecting its efficiency. Some
studies show that tocotrienols are more active
then tocopherols. However, tocotrienols are more
expensive. Moreover, natural vitamin E seems to
be preferable to synthetic vitamin E. Therefore, we
can note that several studies are missing in order to
really understand the effects of vitamin E. However,
it is still good that the anti-aging beverage contains
some.
Vitamin E also plays a role in protecting red blood
cells and body tissues. Moreover, it helps reduce
the risk of cardiovascular diseases by its antiinflammatory and vasodilator characteristics and
by reducing the low-density lipoproteins’ oxidation
(LDL: often called “bad cholesterol”). LDLs are a
choice target for free radicals. Once oxidized,
they participate to atherosclerosis (fat deposits in
arteries). The attack of LDL by free radicals is done
in two parts: the first part is done by liposoluble
free radicals and the second by water-soluble free
radicals. This is why a synergic action of liposoluble
anti-oxidants (e.g. vitamin E) and of water-soluble
anti-oxidants (e.g. vitamin C) is necessary.
Recommended daily nutritional intake for women
and men 14 years and older are of 15mg (22.5UI).
Pregnant women need 15mg while those nursing
need 19mg.
It is similar for the Alzheimer’s disease. Vitamins E and
C could protect against the Alzheimer’s disease
when taken together. These anti-oxidants could
help protect the brain against free radicals’ attacks
associated to this disease and to aging.
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aging
for skin’s, eyes’, hair’s, liver’s and lungs’ protection.
Therefore, it defends cells against free radicals.
Beta-carotene is also widely known for its role in
cardiovascular health’s maintenance. It has an
anti-platelets role because, as an anti-oxidant, it
can help preventing the LDL oxidation.
Moreover, beta-carotene also plays a role on the
immune system.
Vitamin A, Beta-Carotene and
the Anti-Aging Beverage
Vitamin A in multivitamins (anti-oxidants)
Brand
Vitamin A is a liposoluble vitamin (it is soluble in fatty
tissues). Therefore, it can be stored. It is present in
your body as differerent substances: retinol, retinal,
retinoic acid or retinyl palmitate. Vitamin A plays
an important role for your vision during aging
(especially for night vision). It also helps regulating
the immune system and contributes to skin’s health.
Vitamin A (UI
equivalent)
Betacarotene (UI
equivalent)
0
5 000
2 000
1 500
Pure Essence,
Longevity, Anti-Aging
0
10 000
Garden of Life,
Living Multi
0
10 000
Nature’s Way, Alive!
1 500
1 000
Source Naturals,
Life Force Multi
2 500
10 000
Nature’s Answer,
Anti-Oxydant
Supreme
0
0
Nature’s Plus,
Source of Life
0
15 000
Thorne Research,
Anti-Oxidant
0
0
Jamieson
Beta-Carotene with
vitamins C and E
0
25 000
Now, Super
Anti‑Oxydants
0
12 500
Natural Factors, La
beauté de l’intérieur
(for 4 capsules)
0
2 500
SISU Optimal Health
Multi 2 (anti-oxidant)
Swiss Total One
anti-oxidant
Your body can transform some carotenoids,
provitamin A, into vitamin A, as long as the body
needs it. Beta-carotene is the most important
provitamin A.
Note:
self-medicating
vitamin
A
is
not
recommended, as dangers of malformations and
possibilities of osteoporosis exist. Moreover, vitamin
A is less and less recognized as a major anti-oxidant,
but beta-carotene is known as a powerful antioxidant. Moreover, there are no disadvantages
to taking beta-carotene supplement, unless if in
the long run and in very high doses (e.g. 20mg
to 30mg of beta-carotene could slightly raise the
impact of lung cancer. Beta-carotene is sensitive
to oxidation caused by cigarette smoke. Since
smokers’ bodies don’t have the capacity to
recycle oxidized carotene by-products, the latter
become prooxydizing and can aggravate the
carcinogenesis process). Beta-carotene is well
known for its powerful anti-oxidizing characteristics
Note: Even though there are not any officially recommended
beta‑carotene daily doses effectively dosage usually varies between
5000 and 25000IU.
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aging
Grape Seeds Extract and
the Anti‑Aging Beverage
also gives them a capacity to regenerate internal
tissues, notably the inside of blood vessels. Vessels
are therefore reinforced, more elastic and less
permeable. This increases bloodstream efficiency.
Oligo-proanthocyanidins (OPC) are the most
powerful flavonoid sub-group. These flavonoids
are mostly concentrated within grape seeds.
Their powerful anti-oxidizing properties were the
object of several studies in the past few years.
Their anti‑oxidizing activity is 20 to 50 times greater
than that of vitamins C and E. Moreover, OPCs are
both water-soluble and liposoluble and as such,
have anti-oxidizing properties in both water and
lipidic environments.
OPCs have a positive effect on several
cardiovascular diseases’ factors. As an example,
they reduce the amount of LDL, stop the
aggregation of blood platelets and reduce the
negative effects of free radicals. OPCs are also
otherwise linked to aging, such as protecting against
insulin resistance, which often appears with age,
reducing risks of cancers, stimulating joint flexibility,
reducing arthritis inflammation, lessening mental
deterioration, increasing the immune system’s
resistance and reducing retina disorders, such as
diabetic retinopathy and macular degeneration.
OPCs have an affinity with collagen. The antioxidizing effect of OPCs is efficient in protecting
collagen. They link with collagen and contribute to
protecting the structure of connective tissues, which,
in turn, helps reduce visible signs of early aging, such
as wrinkles and soft skin. Their affinity with collagen
Since OPCs are not considered as essential nutrients,
there is no recommended daily intake.
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aging
Collagen and the
Hormonal changes in menopause also act on
women’s skin. We then note that skin gets a little
thinner and tends to dehydrate more. After, skin
changes colour and pigmentation and as a result,
brown spots appear.
It is with great pleasure that Inovacure presents its
new collagen beverage in its Mode de Vie and
Fitness kits.
We can help the skin’s tissues regeneration with our
collagen beverage. Our beverage helps nourish skin
from the inside. This method, named nutricosmetics
or cosmetofood, is defined by the consumption
of foods rich in active principles. Nutricosmetics or
cosmetofood is a direction in full growth in Europe
and in Japan.
Collagen is the most abundant protein in your body.
It is produced by connective tissue cells found in
muscles, tendons, ligaments, cartilage, bones, lungs
and skin.
Most of your body mass is composed of connective
tissues. They represent around 65% of the total
volume for men. To explain the importance of
collagen, we must mention that it represents around
80% of the connective tissues’ weight and 30% of
the body proteins.
Since health starts from the inside of your body,
our collagen beverage acts at the source of the
problem. A collagen supplement can greatly help
regenerate skin tissues and contribute to slow the
aging process down. Collagen therefore helps
strengthening and invigorating skin. It also helps
increasing skin’s elasticity, which, in turn, helps
reducing wrinkles and fine lines.
In Latin, “colla” and “genmen” mean producing
glue. Therefore, in its definition, collagen is both
material and glue holding our body.
We know that our body produces its own collagen
every day and that this production decreases with
age. One of the first signs of collagen production
reduction is the apparition of wrinkles. Skin holds less
water, gets thinner and starts wrinkling. This process
starts at age 25 and speeds up between 40 and 50.
Collagen is the most abundant protein in the body.
It is produced by connective tissues’ cells, which are
present in muscles, tendons, ligaments, cartilage,
bones, lungs and skin.
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aging
Most of the body mass is made of connective tissues.
They represent around 65% of the total volume
for men. To explain the importance of collagen,
we must mention that it represents around 80%
of the connective tissues’ weight and 30% of the
body proteins.
In Latin, “colla” and “genmen” mean producing
glue. Therefore, in its definition, collagen is both
material and glue holding our body. We know that
our body produces its own collagen every day and
that this production decreases with age. After 25
years old, the collagen ratio decreases in the body,
leading to the first sings of aging. At 70 years old,
collagen loss has increased to more than 30%. One
of the first signs of collagen production reduction is
the apparition of wrinkles. Skin holds less water, gets
thinner and starts wrinkling. This process starts at the
age of 25 and speeds up at 40 and 50 years old.
Moreover, hormonal changes in menopause also
act on women’s skin. We then note that skin gets
a little thinner and tends to dehydrate more. After,
skin changes colour and pigmentation and as a
result, brown spots appear.
A collagen supplement can greatly help regenerate
skin tissues and contribute to slow the aging process
down. Collagen therefore helps strengthen and
invigorate skin all while increasing skin’s elasticity,
which, in turn, helps reduce wrinkles and fine lines.
Collagen contributes to restore derma’s tissues
while providing essential proteins on which to mould
its original structure.
aging
FOS and the Anti-Aging Beverage
The effects of fructooligosaccharides (FOS) on
aging are numerous. FOS hold several functions.
Studies show that they have a beneficial effect on
the immune system. FOS also act as a prebiotic as
they nourish bifidobacteriae (beneficial bacteria
for the intestinal flora), which supports the immune
system. As they improve the intestinal flora, they
have a great influence on the resistance to illnesses,
such as cancers or to inflammatory pathologies.
FOS also have a beneficial influence on lipid
profiling. The growth of good lactic acid bacteria,
which causes a production of short chain acids
(lactic, propionic acid, etc.), has effects on the total
cholesterolemia and on LDLs, while reducing even
triglycerides. Moreover, a chronic consumption
of FOS supports the reduction of the hepatic
production of glucose on an empty stomach for
healthy people, which reduces glycaemia on an
empty stomach on diabetics.
In conclusion, a FOS supplement reinforces the
magnesium and calcium absorption, which
improves mineral bone density.
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aging
Fructooligosaccharides (FOS),
Inovacure’ New Fibre Supplement
FOS are non-bioavailable polysaccharides, usually
called dietary fibre. Commercially used FOS usually
come from chicory roots. As they are not digested
in the small intestine, FOS end up in the colon.
Characteristics of a daily consumption of at least
2.5g of FOS (Inovafibre contains 5g per portion)
were demonstrated in several studies. Here is a
summary of the FOS’ functions:
• Being prebiotics, FOS nourishes beneficial
intestinal bacteria (probiotics). This way, the
proliferation of pathogenic bacteria is limited.
• FOS have a beneficial influence on lipidic
profiling. LDL (bad cholesterol) and triglycerides
are reduced.
• FOS increase magnesium and calcium
absorption, which improves bone density.
• FOS have a beneficial impact on the immune
system. While improving the intestinal flora, FOS
have a positive influence on the resistance to
illnesses.
• FOS support a reduction of the hepatic
production of glucose on an empty stomach,
which reduces the amount of sugar in diabetics.
When you suggest taking FOS to clients, it is
important to mention that one should progressively
increase his consumption as every person’s
absorption capacity varies. Some individuals even
have difficulties do absorb more than one gram
at a time! These clients could suffer from digestive
symptoms, such as abdominal pains and cramps,
bloating, flatulence, increased borborygmi (bowel
sounds), constipation and/or diarrhea. However, for
most people, there are no undesired effects up to
20g per day. One should not take more than 30g
per day of FOS supplements.
Annie Jolicoeur
, R.D.
aging
Scientific Articles
aging
Skin aging
N. Puizina-Ivi}
S
U M M A R Y
There are two main processes that induce skin aging: intrinsic and extrinsic. A stochastic process that
implies random cell damage as a result of mutations during metabolic processes due to the production
of free radicals is also implicated. Extrinsic aging is caused by environmental factors such as sun exposure, air pollution, smoking, alcohol abuse, and poor nutrition.
Intrinsic aging reflects the genetic background and depends on time. Various expressions of intrinsic
aging include smooth, thinning skin with exaggerated expression lines. Extrinsically aged skin is characterized by photo damage as wrinkles, pigmented lesions, patchy hypopigmentations, and actinic keratoses.
Timely protection including physical and chemical sunscreens, as well as avoiding exposure to intense
UV irradiation, is most important. A network of antioxidants such as vitamins E and C, coenzyme Q10,
alpha-lipoic acid, glutathione, and others can reduce signs of aging. Further anti-aging products are
three generations of retinoids, among which the first generation is broadly accepted. A diet with lot of
fruits and vegetables containing antioxidants is recommended as well as exercise two or three times a
week.
K
E
Y Skin aging
WORDS
Life expectancy is continuously rising in developed
skin aging,
damage,
extrinsic aging,
intrinsic aging,
stochastic
damage,
prevention
countries, but the mystery of aging remains partially
unresolved. The prevalence of mental and physical disability and diseases related to aging has increased. In
many countries a demographic transition is occurring,
involving aging of the population and reduced birthrates,
as well as large-scale migrations. Advances in medical
care have brought about a significant increase in life
expectancy, especially throughout the 20th century. In
the next 50 years, about one-third of women will be
15
menopausal, and anti-aging medicine will gain importance.
Skin aging is particularly important because of its
social impact. It is visible and also represents an ideal
model organ for investigating the aging process (1). The
“biological clock” affects both the skin and the internal
organs in a similar way, causing irreversible degeneration (2, 3). However, Nicholas Perricone, a prominent
American dermatologist, begins his book with the words
“Wrinkled, sagging skin is not the inevitable result of
aging
getting older. It’s a disease, and you can fight it” (4). The
five top cosmetic non-surgical procedures are botulinum
toxin injection, microdermabrasion, filler injection, laser hair removal, and chemical peeling, whereas important cosmetic surgical procedures include liposuction,
breast augmentation, eyelid surgery, nose reshaping, and
breast reduction.
The factors that play a role in the aging process are
genetic, extrinsic, and stochastic damage.
Intrinsic aging
Intrinsic aging depends on time. The changes occur
partially as the result of cumulative endogenous damage due to the continuous formation of reactive oxygen species (ROS), which are generated by oxidative
cellular metabolism. Despite a strong antioxidant defense system, damage generated by ROS affects cellular constituents such as membranes, enzymes, and DNA
(5, 6). It has a genetic background, but is also due to
decreased sex hormone levels. The telomere, a terminal portion of the eukaryotic chromosome, plays an
important role. With each cell division, the length of the
human telomere shortens. Even in fibroblasts of quiescent skin more than 30% of the telomere length is lost
during adulthood (7). Telomeres are short sequences
of bases in all mammals, and are arranged in the same
mode (TTAGGG). The enzyme telomerase is responsible for its maintenance. It seems that telomeres are
responsible for longevity (8). The progressive erosion
of the telomere sequence (50–100 bp per mitosis)
through successive cycles of replication eventually precludes protection of the ends of the chromosomes, thus
preventing end-to-end fusions, which is incompatible
with normal cell function. The majority of cells have the
capacity for about 60 to 70 postnatal doublings during
their lifecycles, and thereafter they reach senescence,
remaining viable but incapable of proliferation. This
event facilitates end-to-end chromosomal fusions resulting in karyotype disarray with subsequent apoptosis,
thus serving as the “biological clock” (9).
Skin aging is affected by growth factor modifications and hormone activity that declines with age. The
best-known decline is that of sex steroids such estrogen, testosterone, dehydroepiandrosterone (DHEA),
and its sulfate ester (DHEAS) (10–12). Other hormones
such as melatonin, insulin, cortisol, thyroxine, and growth
hormone decline too. At the same time, induced levels
of certain signaling molecules such as cytokines and
chemokines decline as well, leading to the deterioration of several skin functions (13). Also, the levels of
their receptors decline as well (14). At the same time,
some signaling molecules increase with age. One of
these is a cytokine called transforming growth factorbeta1, which induces fibroblast senescence. Cellular
senescence is a result of molecular alterations in the
cellular milieu as well as in DNA and proteins within the
cell. All of these changes gradually lead to aberrant cellular response to environmental factors, which can decrease viability and lead to cell death (15).
Clinical manifestations of aged skin are xerosis, laxity, wrinkles, slackness, and the occurrence of benign
neoplasms such as seborrheic keratoses and cherry angiomas. There are histological features that accompany
these changes. In the epidermis, there is no alteration
in the stratum corneum and epidermal thickness,
keratinocyte shape, and their adhesion, but a decreased
number of melanocytes and Langerhans cells is evident
(6). The most obvious changes are at the epidermaldermal junction: flattening of the rete ridges with reduced surface contact of the epidermis and dermis. This
results in a reduced exchange of nutrients and metabolites between these two parts. In the dermis several
fibroblasts may be seen, as well as a loss of dermal volume (6, 16). A decrease in blood supply due to a reduced number of blood vessels also occurs. There is
also a depressed sensory and autonomic innervation of
epidermis and dermis. Cutaneous appendages are affected as well. Terminal hair converts to vellus hair. As
melanocytes from the bulb are lost, hairs begin to gray.
Further reasons for graying are decreased tyrosinase
activity, less efficient melanosomal transfer and migration, and melanocyte proliferation (17).
Factors that contribute to wrinkling include changes
in muscles, the loss of subcutaneous fat tissue, gravitational forces, and the loss of substance of facial bones
and cartilage. Expression lines appear as result of repeated tractions caused by facial muscles that lead to
formation of deep creases over the forehead and between eyebrows, and in nasolabial folds and periorbital
areas. Repeated folding of the skin during sleeping in
the same position on the side of the face contributes to
appearance of “sleeping lines.” Histologically, thick connective tissue strands containing muscle cells are present
beneath the wrinkle (18). In the muscles an accumulation of lipofuscin (the “age pigment”), a marker of cellular damage, appears. The deterioration of neuromuscular control contributes to wrinkle formation (19). The
constant gravitational force also acts on the facial skin,
resulting in an altered distribution of fat and sagging.
Skin becomes lax and soft tissue support is diminished.
Gravitational effects with advanced years play an important role and contribute to advanced sagging. This
factor is particularly prominent in the upper and lower
eyelids, on the cheeks, and in the neck region.
16
aging
Table 1. Glogau’s photoaging classification (5, 31).
Type
Characteristics
1: No wrinkles
Typical age 20s to 30s
Early photoaging
Mild pigmentary changes
No keratosis
No or minimal wrinkles
2: Wrinkles
in motion
Typical ages late 30s to 40s
Early to moderate photoaging
Early senile lentigines
Palpable but not visible keratoses
Parallel smile lines beginning to
appear laterally to mouth
3: Wrinkles at rest Typical age 50 or older
Advanced photoaging
Obvious dyschromias,
telangiectasias
Visible keratoses
4: Only wrinkles
Typical age 60 or older
Severe photoaging
Yellow-gray skin
Precancerous lesions
No normal skin
Fat depletion and accumulation at unusual sites contributes to the altered appearance of the face (20). It
affects the forehead, periorbital, and buccal areas, the
inner line of nasolabial folds, and the temporal and perioral regions. At the same time it accumulates
submentally, around the jaws, at outer lines of nasolabial folds and at lateral malar areas. In contrast to the
young, in whom fat tissue is diffusely distributed, in aged
skin fat tends to accumulate in pockets, which droop
and sag due to the force of gravity (20, 21). The mass of
facial bones and skeletal bones reduces with age. Resorption affects the mandible, maxilla, and frontal bones.
This loss of bone enhances facial sagging and wrinkling
with obliteration of the demarcation between the jaw
and neck that is so distinct in young persons (22). Steven
Hoefflin states that in the aging face the quantity and
position of subcutaneous fat makes the difference. It
also seems that estrogen and progesterone contribute
to elastic fiber maintenance (23).
Extrinsic aging
Extrinsic aging develops due to several factors: ionizing radiation, severe physical and psychological stress,
17
alcohol intake, poor nutrition, overeating, environmental pollution, and exposure to UV radiation. Among all
these environmental factors, UV radiation contributes
up to 80%. It is the most important factor in skin aging,
especially in premature aging. Both UVB (290–320 nm),
and UVA (320–400 nm) are responsible, and the skin
alterations caused by UV radiation depend upon the
phenotype of photoexposed skin (5, 24).
UVB induces alterations mainly at the epidermal
level, where the bulk of UVB is absorbed. It damages
the DNA in keratinocytes and melanocytes, and induces
production of the soluble epidermal factor (ESF) and
proteolytic enzymes, which can be found in the dermis
after UV exposure. UVB is responsible for appearance
of thymidine dimers, which are also called “UV fingerprints.” That is, after UVB exposure, a strong covalent
bond between two thymidines occurs. With aging, this
bond cannot be dissolved quickly, and accumulation of
mutations occurs. Affected cells appear as sunburn cells
8 to 12 hours after exposure. Reduced production of
DNA can be observed during the next 12 hours. Actinic
keratoses, lentigines, carcinomas, and melanomas represent delayed effects. A mnemonic for UVB is B as in
burn or bad.
UVA penetrates more deeply into the dermis and
damages both the epidermis and dermis. The amount
of UVA in ambient light exceeds the UVB by 10 to 100
times, but UVB has biological effects 1,000 times stronger than UVA. It is accepted that UVA radiation plays an
important role in the pathogenesis of photoaging, so
the mnemonic for UVA is A as in aging (24). The exact
mechanism of how UV radiation causes skin aging is not
clear. The dermal extracellular matrix consists of type I
and III collagens, elastin, proteoglycans, and fibronectin,
and collagen fibrils strengthen the skin. Photoaged skin
is characterized by alterations in dermal connective tissue. The amount and structure of this tissue seems to
be responsible for wrinkle formation. In photoaged skin,
collagen fibrils are disorganized and elastin-containing
material accumulates (25). Levels of precursors as well
as cross-links between type I and III collagens are reduced, whereas elastin is increased (26, 27). UV radiation increases the production of collagen-degrading
enzymes, matrix metalloproteinases (MMPs), and the
xeroderma pigmentosum factor (XPF), which can also
be found in the epidermis. XPF induces epidermal-dermal invagination, representing the beginning of wrinkle
formation. At the base of wrinkles, less type IV and VII
collagen is found. This instability deepens the wrinkles.
Each MMP degrades a different dermal matrix protein;
for example, MMP-1 cleaves collagen types I, II, and III,
and MMP-9 (gelatinase) degrades type IV and V and
aging
gelatin. Under normal conditions, MMPs are part of a
coordinated network and are regulated by their endogenous inhibitors (TIMPs). The imbalance between activation and inhibition can lead to proteolysis (28). The
activation of MMPs can be triggered by UVA and UVB,
but molecular mechanisms differ depending upon the
type of radiation. UVA radiation can generate ROS that
affect lipid peroxidation and generate DNA strand
breaks (29). On the other hand, within minutes after
exposure UVB radiation causes MMP activity and DNA
damage. These effects can be observed after exposing
human skin to one-tenth of the minimal erythema dose.
Topical pretreatment with tretinoin inhibits activation of
MMPs in UVB-exposed skin (30). The degree of skin damage following long-lasting UV irradiation also depends on
the skin phototype according to Fitzpatrick. In lighter
complexes (types I and II) more serious degenerative
changes are elicited than in types III and IV, in which
melanosomes in the upper epidermal layer serve as relatively good UVA and UVB protection. Glogau developed
a photoaging scale that is used to clinically classify the
extent of photodamage (Table 1) (5, 31). It has been
stated that the number of melanocytes decreases by 8 to
20% every 10 years.
Another environmental factor contributing to premature aging is smoking. “Smoker’s face” or “cigarette skin”
are characteristic, implying increased facial wrinkling and
an ashen and gray skin appearance (32, 33). A prematurely old appearance is a symptom of long-term smokers. Yellow and irregularly thickened skin is result of elastic tissue breakdown due to smoking (34) or to UV. Premature facial wrinkling is not reduced in women on hormone replacement therapy (35). Genetic predisposition
may also influence the development of facial wrinkling
(36). It seems that cigarette smoking induces the activation of MMPs in the same mode as in persons with significant sun exposure (37). Smoking also reduces facial stratum corneum moisture as well as vitamin A levels, which
is important in reducing the extent of collagen damage
(5). The photochemical activity of smog is due to the
reduction of air pollutants such as nitrogen oxides and
volatile organic compounds created from fossil fuel combustion in the presence of sunlight. Emission from factories and motor vehicle exhaust are primary sources of
these compounds. The major targets of ozone in the skin
are the superficial epidermal layers; this results in the
depletion of antioxidants such as alpha-tocopherol (vitamin E) and ascorbic acid (vitamin C) in the superficial
epidermal layers (38).
As stochastic damage is explained, the damage is initiated by random cosmic radiation and triggered by free
radicals during cell metabolism, which damages cell lipid
compounds, especially membrane structures. The free
18
radical theory is one of the most widely accepted theories to explain the cause of skin aging. These compounds
are formed when oxygen molecules combine with other
molecules, yielding an odd number of electrons. That is,
an oxygen molecule with paired electrons is stable, but
one with an unpaired electron is very reactive and it takes
electrons from other vital components. As result, cell death
or mutation appear (4, 5).
Protection of the skin
The skin is equipped with two photoprotective
mechanisms: the melanin in the lower layer of epidermis,
and the urocanic acid barrier of the stratum corneum,
which reflects and absorbs a significant amount of UVB
radiation. The thickness of the stratum corneum appears
to be highly significant for photoprotection (39).
Antioxidants provide protection against UVB-induced
oxidative stress, especially in stratum corneum lipids. Even
systemically applied antioxidants accumulate in the stratum corneum and play an important role against UV-induced skin damage (40, 41).
The body has developed further defense mechanisms
that protect against UV radiation and dangerous free radicals. Antioxidants naturally occurring in the skin are superoxide dismutase, catalase, alpha-tocopherol, ascorbic
acid, ubiquinone, and glutathione. Many of them are inhibited by UV and visible light (42). The antioxidant program consists of a diet containing large amounts of vitamins A, E, and C, grape-seed extracts, coenzyme Q10,
and alpha-lipoic acid (4). The most highly recommended
foods include: avocados, berries, dark green leafy vegetables, orange-colored vegetables and fruits, pineapples,
salmon, and tomatoes.
The mainstay in the prevention of skin aging is
photoprotection. UV filters are now present in cosmetic
products for daily use, such as makeup, creams, lotions,
and hair sprays. The general requirements are that modern sunscreens should protect against UVA and UVB rays
and be photo-stable and water resistant.
Chemical UV filters have the capacity to absorb shortwavelength UV and transform photons into heat-emitting long-wavelength (infrared) radiation. Most of them
absorb a small wavelength range. They can be divided
into three groups. The first group consists of molecules
that primarily absorb the UVB spectrum (p-aminobenzoic acid derivatives and zincacid esters), and second of
molecules that primarily absorb the UVA spectrum (butyl-methoxydibenzoylmethane). The third group consists
of molecules that absorb UVA and UVB photons (benzophenone). A combination of different filters in the same
product renders the whole filter system photo-unstable.
aging
That means that UV exposure causes photochemical reactions that generate ROS with subsequent phototoxic
and photoallergic reactions. Great efforts have been made
to stabilize molecules in UV filters, which has improved
the efficacy of photoprotection with chemical UV filters.
Today there is a growing need for standardization and
evaluation of UVA photoprotection, while for UVB there
is already consensus on the international level (1, 43).
The use of physical filters is encouraged. The most
frequently used of these are microparticles of zinc oxide and titanium dioxide with diameters in the range of
10 to 100 nm. They are capable of reflecting a broad
spectrum of UVA and UVB rays. They do not penetrate
into the skin and thus have low potential for developing toxic or allergic effects. Today they are increasingly
being used in combination with chemical filters. One
disadvantage of the inorganic micropigments is that
they reflect visible light, creating a “ghost” effect. This
is one reason such sunscreens are often rejected by
consumers (5, 43, 44).
Conclusion
This overview shows that, during the human life
cycle, the skin is exposed to a number of unavoidable
as well as avoidable damaging factors. Genetics also
play a highly important role. In addition to all the conditions mentioned above, further processes pertaining to
oxygenation and reduction are active in skin aging.
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A U T H O R S '
A D D R E S S E S
Neira Puizina-Ivi}, MD, PhD, Asst. Professor, Laboratory of
Dermatopathology, Department of Dermatovenerology, Split Clinical
Hospital Center, [oltanska 1, 21 000 Split, Croatia,
E-mail: neiraradogost.com
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American Journal of Epidemiology
Copyright ª 2005 by the Johns Hopkins Bloomberg School of Public Health
All rights reserved; printed in U.S.A.
Vol. 163, No. 1
DOI: 10.1093/aje/kwj007
Advance Access publication November 23, 2005
Original Contribution
Serum Antioxidants, Inflammation, and Total Mortality in Older Women
J. Walston1, Q. Xue1, R. D. Semba1, L. Ferrucci2, A. R. Cappola3, M. Ricks1, J. Guralnik1, and
L. P. Fried1
1
School of Medicine, Johns Hopkins University, Baltimore, MD.
National Institute of Aging, Baltimore, MD.
3
School of Medicine, University of Pennsylvania, Philadelphia, PA.
2
The inflammatory cytokine interleukin-6 (IL-6) has been linked to poor health outcomes in older adults. Oxidative
stress triggers the production of IL-6, and antioxidant micronutrients play a critical role in decreasing this inflammatory response. The authors sought to identify the relations between serum levels of antioxidant nutrients and IL-6
and mortality in older women. Levels of a- and b-carotene, lycopene, lutein/zeaxanthin, a-cryptoxanthin, total
carotenoids, retinol, a-tocopherol, zinc, and selenium were measured at baseline in 619 participants in Women’s
Health and Aging Study I (Baltimore, Maryland, 1992–1998). IL-6 was measured at baseline and at follow-up 1 and
2 years later, and all-cause mortality was determined over a 5-year period. Participants with the highest serum
levels of a-carotene, total carotenoids, and selenium were significantly less likely to be in the highest tertile of serum
IL-6 at baseline (p < 0.0001). Those with the lowest levels of a- and b-carotene, lutein/zeaxanthin, and total
carotenoids were significantly more likely to have increasing IL-6 levels over a period of 2 years. Those with the
lowest selenium levels had a significantly higher risk of total mortality over a period of 5 years (hazard ratio 1.54,
95% confidence interval: 1.03, 2.32). These findings suggest that specific antioxidant nutrients may play an important role in suppressing IL-6 levels in disabled older women.
aging; antioxidants; carotenoids; inflammation; interleukin-6; mortality; selenium
Abbreviations: CI, confidence interval; OR, odds ratio; SD, standard deviation; WHAS I, Women’s Health and Aging Study I.
known to enhance proinflammatory nuclear factor jB signal
transduction pathways and hence interleukin 6 production
(6, 10).
Prior studies have suggested that several categories of
dietary antioxidants, including the carotenoids, retinol, a
tocopherol, zinc, and selenium, may be effective in suppressing
activation of these proinflammatory pathways through the
quenching of free radical molecules (11, 12). Few studies
have investigated the cross sectional and longitudinal rela
tions between specific antioxidants and inflammation, as
measured by serum interleukin 6 level, and ultimately mor
tality in older adults. Therefore, we studied the relations of
Older adults with the highest serum levels of interleukin 6
are more likely to develop disability and worsening chronic
disease and are more likely to be frail and to die earlier than
those with the lowest levels (1 5). These poor health out
comes are probably directly mediated by elevated interleu
kin 6 concentrations, which can induce muscle and bone
loss, anemia, immune dysfunction, and altered production
and function of multiple hormones (6 9). The etiology of
chronic interleukin 6 elevations in older adults is multifac
torial, with declines in sex steroid hormones, increased prev
alence of inflammatory disease, increased fat mass, and
increased generation of free radicals of oxygen all being
Reprint requests to Dr. Jeremy D. Walston, Johns Hopkins University School of Medicine, John R. Burton Pavilion, 5505 Hopkins Bayview
Circle, Baltimore, MD 21224 (e mail: [email protected]).
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43
Downloaded from http://aje.oxfordjournals.org/ by guest on January 13, 2012
Received for publication March 11, 2005; accepted for publication July 19, 2005.
aging
MATERIALS AND METHODS
Human subjects
Women’s Health and Aging Study I (WHAS I) is a
longitudinal cohort study of the one third most disabled
community dwelling older women in Baltimore, Maryland.
Subjects were women aged �65 years residing in 12 contig
uous zip code areas in Baltimore who were recruited from
a random sample of the Health Care Financing Administra
tion’s Medicare enrollment file (N ¼ 32,538 women). An
age stratified (65 74, 75 84, and �85 years) sample of these
women was randomly selected. Of those, 5,316 were eligible
for screening, 4,135 were screened for disability, 1,409 met
the study criteria, 1,002 agreed to participate in the study,
and 783 agreed to have blood drawn starting in 1992 (13, 14).
Of these 783 persons, 619 had stored serum samples and data
on all reported variables recorded in the database. This left
383 WHAS I participants who were not included in these
analyses.
Study participants received an extensive interview and
examination in their homes at baseline and every 6 months
for 3 years, for a total of seven examinations. Physical ac
tivity was measured by participant report, with persons who
walked more than eight blocks per week being deemed ac
tive and those who walked less than eight blocks deemed
inactive, as validated in prior WHAS I studies (15). Smok
ing status was analyzed by dividing pack years into four
categories: none, mild (1 30 pack years), moderate (31
56 pack years), and heavy (>56 pack years) (16). Blood
was drawn at baseline and at 1 year intervals. Information
on physician diagnosis of 16 major chronic diseases was
obtained at each examination, and the presence/absence of
each disease was adjudicated by trained physicians using
abstracted medical records and following standardized
state of the art algorithms (13). Information on vital status
was obtained through follow up interviews with proxies,
obituaries, and matching with the National Death Index over
a 5 year period. The Johns Hopkins University Institutional
Review Board approved the study, and all participants gave
informed consent.
Statistical analysis
Baseline demographic and health related characteristics
for the 619 WHAS I women with complete outcome and
covariate information were compared by tertile of interleu
kin 6 values, using the v2 test for categorical variables and
analysis of variance for continuous variables. We calculated
summary statistics for micronutrients, including means,
medians, standard deviations (SDs), and ranges, and com
pared the log transformed micronutrient values by tertile of
interleukin 6 using analysis of variance. Sequential logistic
regressions for being in the highest interleukin 6 tertile com
pared with the lowest two tertiles were fitted against each of
the micronutrients, with adjustment for age, Black race, years
of education, pack years of smoking, body mass index
(weight (kg)/height (m)2), and physical activity. In addition,
adjustments were made in the final model for four prevalent
chronic diseases known to be associated with inflammation:
chronic obstructive pulmonary disease, peripheral arterial
disease, angina, and diabetes mellitus. Micronutrient values
were logarithmically transformed to approximate normality
in all regression models. To validly assess the relative
strength of associations between interleukin 6 and micro
nutrients, we calculated odds ratios and 95 percent confi
dence intervals associated with a 1 SD increase in log
micronutrient values. A random effects model was used to
examine both population averaged and individual changes
in log interleukin 6 levels over time while accounting for
between person heterogeneity in baseline interleukin 6 lev
els and individual rate of change over time.
To determine whether low levels of specific micro
nutrients at baseline predicted a significant increase in
interleukin 6 over time, we divided subjects with nutrient
measurements into tertiles, and the percentages of those who
had a 0.5 SD increase in interleukin 6 level over 1 year and
2 year spans were determined. We selected the 0.5 SD in
crement to achieve a balance between sample size limitation
Laboratory analyses
Blood samples were obtained by venipuncture, and se
rum was separated by centrifugation and stored at 70C
until analysis. Levels of serum a carotene, b carotene,
b cryptoxanthin, lycopene, lutein/zeaxanthin (not separated
with this procedure), and a tocopherol were determined by
high performance liquid chromatography (17). The internal
standards used were tocol (Hoffmann LaRoche, Inc., Nutley,
New Jersey) at 320 nm and all trans ethyl b apo 8#
carotenoate (purified sample, courtesy of Dr. Fred Khachik,
University of Maryland) at 450 nm. Within run and between
run coefficients of variation for pooled standards were 10.7
Am J Epidemiol 2006;163:18–26
44
percent and 23.9 percent for a carotene, 7.0 percent and
19.1 percent for b carotene, 4.7 percent and 8.5 percent
for b cryptoxanthin, 4.1 percent and 4.6 percent for lutein/
zeaxanthin, and 4.1 percent and 9.7 percent for a tocopherol,
respectively. Total cholesterol was measured using an au
tomated enzymatic method, and the values were used to
compute the a tocopherol:cholesterol ratio (18). Serum se
lenium and zinc levels were measured by graphite furnace
atomic absorption spectrometry using a Perkin Elmer
Analyst 600 with Zeeman background correction (Perkin
Elmer Corporation, Norwalk, Connecticut). Within run and
between run coefficients of variation were 5.8 percent and
4.8 percent for selenium and 2.8 percent and 3.9 percent for
zinc, respectively. Plasma interleukin 6 was measured using
an enzyme linked immunosorbent assay (Quantikine human
interleukin 6; R&D Systems, Inc., Minneapolis, Minne
sota). Quality control was assessed by repeated analysis of
standard reference material (SRMb; National Institute of
Standards and Technology, Gaithersburg, Maryland) and
pooled reference standards. All samples were analyzed in
a masked fashion.
dietary carotenoids, retinol, a tocopherol, zinc, and sele
nium with interleukin 6 and mortality in a cohort of older
women.
aging
20
Walston et al.
TABLE 1. Demographic and health related characteristics of 619* study participants with measurements
of interleukin 6 and antioxidant nutrient levels, by tertile of interleukin 6 at baseline, Women’s Health and
Aging Study I, Baltimore, Maryland, 1992 1993
Tertile of interleukin-6
Total
�2.80 pg/ml
(n 208)
Mean age (years)
77.3 (7.8)z
76.7 (7.8)
77.5 (7.9)
77.6 (7.6)
0.45
Black race (%)
27.3
23.1
26.3
32.7
0.09
Mean years of education
9.9 (4.9)
>2.80 �4.81 pg/ml
(n 209)
10.5 (6.7)
9.9 (3.5)
>4.81 pg/ml
(n 202)
9.3 (3.4)
Level of smoking and pack years (%)
0.08
<0.01
None: 0
52.3
64.3
48.8
43.5
Mild: 1 30
27.0
24.2
30.4
26.5
Moderate: 31 56
11.1
7.2
12.1
14.0
9.6
4.3
8.7
Heavy: >56
p valuey
16.0
28.8 (6.8)
27.3 (5.3)
29.2 (7.2)
29.8 (7.6)
<0.01
Ability to walk �8 blocks (%)
31.1
40.5
32.0
20.4
<0.01
Prevalent chronic diseases (%)
Cardiovascular disease
23.6
22.7
34.5
37.6
Peripheral arterial disease
20.2
17.3
15.8
28.7
0.003
Chronic obstructive pulmonary
disease
15.0
12.0
17.2
15.8
0.30
Diabetes mellitus
16.2
9.1
15.8
23.8
<0.01
<0.01
* All participants with baseline data on serum carotenoid levels, corrected interleukin 6 level, age, race, educa
tion, pack years of smoking, body mass index, chronic obstructive pulmonary disease, peripheral arterial disease,
cardiovascular disease, and diabetes.
y p value for comparison between the three interleukin 6 tertiles.
z Numbers in parentheses, standard deviation.
§ Weight (kg)/height (m)2.
able longitudinal interleukin 6 measurements together and
modeling log interleukin 6 as a continuous outcome in or
der to explicitly model the effect of baseline micronutrient
levels in tertiles on individual rate of change in log inter
leukin 6 levels over time. Cox proportional hazards regres
sion models were used to determine the relations between
and clinical significance. Crude incidence rates for having
a greater than 0.5 SD increase in interleukin 6 were plotted
by micronutrient tertile; logistic regression analyses were
used to calculate the adjusted odds ratios, with the highest
tertiles of micronutrients being used as reference groups.
We also applied random effects models by pooling all avail
TABLE 2. Summary data on levels of micronutrients and interleukin 6 among 619 participants at baseline,
Women’s Health and Aging Study I, Baltimore, Maryland, 1992 1993*
Median
Minimum
a Carotene (lmol/liter)
Micronutrient
Mean
0.09
Standard deviation
0.09
0.07
0.00
Maximum
0.93
b Carotene (lmol/liter)
0.44
0.38
0.31
0.03
3.34
Lycopene (lmol/liter)
0.56
0.31
0.51
0.02
2.00
Lutein/zeaxanthin (lmol/liter)
0.38
0.20
0.35
0.04
1.72
b Cryptoxanthin (lmol/liter)
0.14
0.15
0.1
0.01
1.41
Total carotenoids (lmol/liter)
1.60
0.73
1.5
0.13
4.49
Retinol (lmol/liter)
2.60
0.93
2.4
0.67
7.16
21.83
8.90
19.7
5.05
66.53
4.23
1.65
3.8
0.90
12.39
a Tocopherol (lmol/liter)
a Tocopherol:cholesterol ratio (mg/g)
Zinc (lg/liter)
889.7
229.8
854.4
188.2
Selenium (lg/liter)
118.2
19.2
116.4
58.2
Interleukin 6 (pg/ml)
5.51
12.69
3.70
0.66
2,661.5
245.8
289.72
* n ¼ 619 for all analyses except a tocopherol:cholesterol ratio (n ¼ 605), zinc (n ¼ 615), and selenium (n ¼ 591).
45
Body mass index§
aging
Antioxidants, Inflammation, and Mortality in Older Women 21
TABLE 3. Odds ratios (cross sectional association) for being in the highest tertile of
interleukin 6 level as compared with the two lowest tertiles, according to micronutrient
intake at baseline, Women’s Health and Aging Study I, Baltimore, Maryland, 1992 1993*
Odds ratioy
95% confidence interval
p value
Micronutrient
0.65
0.53, 0.80
<0.0001
0.72
0.59, 0.87
0.001
0.75
0.63, 0.91
0.003
0.72
0.59, 0.89
0.004
0.77
0.63, 0.94
0.016
0.038
0.87
0.72, 1.05
0.91
0.74, 1.11
0.5
a Tocopherol:cholesterol ratio (mg/g)
1.01
0.82, 1.24
0.777
0.65
0.53, 0.79
<0.0001
Selenium (lg/liter)
0.65
0.52, 0.80
<0.0001
Zinc (lg/liter)
0.99
0.82, 1.20
0.948
Given that there were 383 WHAS I participants with miss
ing data, we compared demographic characteristics in per
sons with blood values and those without blood values. We
found that, compared with the 383 persons who did not have
blood information available for analysis, persons with data
on all blood variables were younger (77.3 years (SD, 7.8) vs.
80.0 years (SD, 8.3); p < 0.01), had a higher body mass
index (28.8 (SD, 6.8) vs. 27.5 (SD, 6.6); p < 0.01), and had
higher levels of physical activity (31.1 percent vs. 19.3
percent; p < 0.01), as measured by the percentage in each
group who had walked more than eight blocks in the past
week. To explore the impact of these differences on our
inference, we stratified the results shown in table 3 by
age, body mass index, and physical activity and calculated
the micronutrients with the strongest inverse association
with interleukin 6 and mortality.
RESULTS
Demographic and health related characteristics of the 619
WHAS I participants with complete blood measurements are
displayed in table 1 by interleukin 6 tertile (�2.80 pg/ml,
>2.80 �4.81 pg/ml, and >4.81 pg/ml). Mean and median
nutrient and interleukin 6 values for these 619 partici
pants are displayed in table 2. Persons in the highest tertile
of interleukin 6 were more likely to be smokers, to have a
greater body mass index, to have peripheral arterial disease,
diabetes, or cardiovascular disease, and to be inactive (table 1).
FIGURE 1. Crude incidence rate for an increase of more than 0.5 standard deviation (3.21 pg/ml) in interleukin 6 level, by micronutrient tertile and
duration of follow up, Women’s Health and Aging Study I, Baltimore, Maryland, 1992 1998. The lowest, middle, and highest tertiles are
distinguished by bars with diagonal lines, bars with horizontal lines, and black bars, respectively. The differences in 1 year incidence rates by
a carotene tertile were significant at the 0.01 level; the differences in 2 year incidence rates by a carotene and total carotenoid tertiles were
significant at the 0.05 level.
46
* n ¼ 619 for all analyses except a tocopherol:cholesterol ratio (n ¼ 605), zinc (n ¼ 615), and
selenium (n ¼ 591).
y Calculated for a one standard deviation increase in log transformed micronutrient level in
a logistic regression model with adjustment for age, race, years of education, smoking status,
body mass index, chronic obstructive pulmonary disease, peripheral arterial disease, angina,
diabetes, physical activity, and incident cardiovascular disease.
aging
22
Walston et al.
TABLE 4. Adjusted odds ratio for having an interleukin 6 level that increased longitudinally by more than
0.5 standard deviation (3.21 pg/ml) over a 2 year period, with the highest tertile of each micronutrient at
baseline used as the reference group, Women’s Health and Aging Study I, Baltimore, Maryland, 1992 1995
Baseline nutrient tertile
Year 1
No.
ORy,z
Year 2
95% CIy
No.
ORz
95% CI
0.039
>0.039, 0.094
>0.094
146
2.48
1.05, 5.88*
112
7.99
2.27, 28.21**
126
1.49
0.60, 3.72
111
7.12
2.08, 24.38**
155
1
119
1
138
141
1.68
0.96
115
108
4.09
3.52
148
1
119
1
0.23
>0.23, 0.45
>0.45
0.74, 3.84
0.42, 2.21
1.38, 12.11*
1.19, 10.39 *
0.38
>0.38, 0.64
1.01
0.44, 2.31
109
1.71
0.63, 4.62
1.40
0.63, 3.09
118
2.14
0.83, 5.52
155
1
115
1
132
144
1.12
1.34
105
114
5.57
3.18
151
1
123
1
0.27
>0.27, 0.41
>0.41
0.46, 2.74
0.61, 2.94
1.74, 17.80**
1.08, 9.39*
0.074
>0.074, 0.14
>0.14
129
1.58
0.69, 3.62
102
2.00
0.75, 5.37
147
1.40
0.63, 3.11
118
1.71
0.67, 4.39
151
1
122
1
148
143
0.70
0.70
111
121
0.48
0.66
136
1
110
1
2.13
>2.13, 2.90
>2.90
0.31, 1.56
0.31, 1.59
0.19, 1.23
0.27, 1.61
17.43
>17.43, 23.08
>23.08
138
0.46
0.18, 1.13
116
1.00
0.37, 2.72
141
1.00
0.46, 2.18
106
2.17
0.86, 5.47
148
1
120
1
a Tocopherol:cholesterol ratio
(lmol/liter)
3.31
>3.31, 4.47
>4.47
141
0.84
0.35, 2.02
109
1.05
0.38, 2.94
131
1.23
0.54, 2.81
105
1.70
0.64, 4.52
134
1
112
1
1.17
132
2.05
0.86, 4.91
113
3.98
1.51, 10.49**
142
153
1.94
1
0.83, 4.52
103
126
1.40
1
0.47, 4.14
110.00
131
0.53
0.23, 1.27
99
0.94
0.36, 2.45
138
0.76
0.34, 1.68
115
0.81
0.32, 2.03
>122.90
140
1
122
1
135
0.94
0.39, 2.26
103
1.05
0.38, 2.94
147
145
1.76
1
0.81, 3.85
124
119
1.70
1
0.64, 4.52
>1.17, 1.80
>1.80
Selenium (lg/liter)
>110.00, 122.90
Zinc (lg/liter)
770.85
>770.85, 938.68
>938.68
* p 0.05; **p 0.01.
y OR, odds ratio; CI, confidence interval.
z Adjusted for age, Black race, years of education, smoking status, body mass index, baseline cardiovascular
disease, chronic obstructive pulmonary disease, diabetes, peripheral vascular disease, physical activity, incident
cardiovascular disease, and baseline interleukin 6 level.
47
>0.64
134
138
aging
TABLE 5. Mortality hazard over a 5 year period in relation to baseline levels of three micronutrients in a Cox proportional hazards
model, Women’s Health and Aging Study I, Baltimore, Maryland, 1992 1998
No. of deaths
over 5 years
Unadjusted
HRy
95% CIy
Age- and raceadjusted HR
�0.040
71
1.19
0.85, 1.68
1.44*
1.02, 2.04
1.06
0.70, 1.59
73
1.21
0.86, 1.69
1.30
0.92, 1.82
1.19
0.81, 1.74
>0.094
62
1
�1.167
75
1.23
0.88, 1.72
1.32
0.95, 1.85
1.07
0.72, 1.58
67
1.03
0.73, 1.45
1.09
0.78, 1.54
1.02
0.69, 1.50
>1.806
64
1
�109.9
78
1.66*
1.17, 2.37
1.48*
1.03, 2.13
1.54*
1.03, 2.32
68
1.40
0.98, 2.02
1.24
0.86, 1.79
1.30
0.86, 1.96
>122.8
51
1
Micronutrient
95% CI
Fully
adjusted HRz
95% CI
>0.040, �0.094
1
1
>1.167, �1.806
1
1
Selenium (lg/liter)
>109.9, �122.8
1
1
2 years (figure 1). The associations between increasing
interleukin 6 and a carotene remained significant in the
fully adjusted model for year 1 (OR ¼ 2.48, p < 0.05). For
year 2, the associations remained significant for a carotene
(OR ¼ 7.99, p < 0.01), b carotene (OR ¼ 4.09, p <
0.05), lutein/zeaxanthin (OR ¼ 5.57, p < 0.01), and total
carotenoids (OR ¼ 3.98, p < 0.01) (table 4). Selenium
levels were unrelated to interleukin 6 increase in both
models (table 4), probably partly because of the large
number of subjects in the lowest selenium tertile who
did not return for follow up visits in this longitudinal
study. Further investigation of the potential reasons why
many persons in the lowest selenium tertile at baseline
were missing from subsequent analyses showed that those
participants had a significantly greater risk of all cause mor
tality over a 5 year period than participants in the other
tertiles (hazard ratio ¼ 1.54, 95 percent CI: 1.03, 2.32;
p < 0.05), even in unadjusted and fully adjusted models
(table 5). We identified no significant increase in 5 year
cardiovascular disease mortality hazard in the two lower
tertiles of selenium in relation to the highest tertile (data
not shown). We also identified an increased risk of mor
tality for persons with the lowest levels of a carotene in
the model adjusted for age and race, but we identified no
increased mortality risk in persons with the lowest base
line levels of a carotene or total carotenoids over 5 years
in the fully adjusted model (table 5). No other cause of
death grouping was large enough for analysis of differ
ences between groups.
coefficients for the relations between micronutrients and log
interleukin 6 levels. We found that associations and corre
lations were generally higher for older women, women with
a higher body mass index, and women with lower physical
activity than for women without these risk factors (data not
shown).
In the cross sectional analysis adjusting for multiple con
founders, we identified highly significant inverse relations
between serum interleukin 6 levels and a carotene (odds
ratio (OR) ¼ 0.65, 95 percent confidence interval (CI): 0.53,
0.80), total carotenoids (OR ¼ 0.65, 95 percent CI: 0.53, 0.79),
and selenium (OR ¼ 0.65, 95 percent CI: 0.52, 0.80) (p <
0.0001 for each) a 35 percent reduction in risk of being in
the highest interleukin 6 tertile for every 1 SD increase in
log nutrient value (table 3). Persons with the highest levels
of b carotene, lycopene, lutein/zeaxanthin, b cryptoxanthin,
and retinol were also significantly less likely to be in the
highest interleukin 6 tertile (table 3). There was no identifi
able relation between serum levels of zinc, a tocopherol, or
a tocopherol:cholesterol ratio and serum interleukin 6 in
these analyses (table 3).
We found an increasing but not statistically significant
time trend in the population mean interleukin 6 level using
the random effects model. There was substantial between
person heterogeneity in the rate of change (i.e., time slope)
in interleukin 6 levels over time (p < 0.01; data not shown),
suggesting that any population average approach in this
case could underestimate critical changes in interleukin 6
on an individual level. Therefore, we examined the longitu
dinal effect of baseline micronutrient levels on individual
level changes in serum interleukin 6. The percentage increase
of more than 0.5 SD in interleukin 6 values (3.21 pg/ml)
over 1 year and 2 year periods significantly increased as the
a carotene level decreased (figure 1). A similar finding was
observed among the total carotenoid groups over a period of
DISCUSSION
These findings demonstrate robust inverse cross sectional
relations between the potent inflammatory cytokine inter
leukin 6 and several antioxidant carotenoids and selenium.
48
* p � 0.05.
y HR, hazard ratio; CI, confidence interval.
z Adjusted for age (years), Black race, years of education, current smoking, body mass index, chronic obstructive pulmonary disease,
peripheral arterial disease, angina, diabetes, and physical activity at baseline.
aging
24
Walston et al.
The increased 5 year mortality in persons with the lowest
selenium levels was identified after we found that many per
sons in the lowest selenium tertile did not return for subse
quent study visits. Selenium deficiency is associated with a
host of inflammatory tissue responses and with disease pro
gression, including myocarditis related to Coxsackievirus
and human immunodeficiency virus, thyroid dysfunction,
arthritis, cancer, depression, and cardiovascular disease
(27, 32). This selenium deficiency related acceleration of
many disease processes may partly explain the association
between mortality and lower selenium levels observed in this
population. Further exploration of the specific etiology of
mortality beyond cardiovascular disease may help add bio
logic and tissue specificity to this finding.
It is not clear why we did not identify a relation between
the carotenoids and mortality. Although we cannot rule out
residual confounding, other plausible explanations exist.
First, the set of micronutrients included in this study com
prises only a small part of a large family of antioxidants and
nutrients. It may well be that other nutrients and biomedia
tors that we did not measure (e.g., vitamin C) can modulate
interleukin 6 as well, thereby independently contributing to
mortality. Second, we had hypothesized that micronutrients
represent more distal correlates relative to interleukin 6 in
relation to mortality; therefore, the effects are more likely to
be indirect. Third, WHAS I was designed to study the one
third most disabled older women, which could have resulted
in limited variability of micronutrient levels that is, a floor
ing effect in the study population. Finally, since we do not
have longitudinal data on serum antioxidants because of the
prohibitive cost, we are not able to confirm a causal relation
without taking into account the changes in carotenoid levels
over time.
A number of questions remained unanswered in this
study. First, it is unclear whether low dietary intake, high
oxidative stress, or both contributed to the observed lower
antioxidant levels. Although inflammation has minimal im
pact on selenium levels, serum carotenoid levels are mod
estly decreased by inflammatory processes in younger and
older adults (33, 34). Second, although we adjusted for dis
eases known to trigger inflammation, it was not possible
to characterize all clinical and subclinical inflammation
inducing conditions and hence capture all potentially con
founding variables in this population. Third, although there
is some knowledge of specificity in function of antioxidant
nutrients and enzymes, many studies have been performed in
in vitro systems, making any findings regarding specificity
of function of individual nutrients less than conclusive.
Fourth, we had 383 missing data points because of lack of
or insufficient amounts of serum for measuring the relevant
variables. Given that persons with insufficient data were
older, less obese, and less physically active, we would hy
pothesize that our findings would have been even stronger if
we had had those missing data. Finally, we did not have
longitudinal measurements of antioxidant levels for this
analysis, which, combined with longitudinal interleukin 6
measurements, might help determine directionality and
the utility of specific antioxidant nutrient interventions in
suppressing elevated interleukin 6 levels in at risk older
adults.
49
No relations were demonstrated between a tocopherol or
zinc levels and serum interleukin 6. Importantly, longitudi
nal analyses demonstrated that baseline levels of a carotene,
b carotene, lutein/zeaxanthin, and total carotenoids were
significantly associated with increasing levels of interleu
kin 6 over a period of 2 years and that low levels of selenium
were associated with increased risk of all cause mortality
over a period of 5 years. The identification of differences in
relations between individual antioxidant micronutrients and
interleukin 6 may provide specific clues as to which oxida
tive pathways most contribute to the inflammatory charac
teristics observed in frail and disabled older adults (1, 3, 19).
Additional longitudinal nutritional data and analyses may
help in determining which serum antioxidant measurements
might be useful guides in the suppression of oxidative
stress induced inflammation.
Dietary carotenoids are powerful antioxidants that are
embedded within lipid bi layers (the two lipid layers that
make up cell membranes) and function to quench free rad
icals generated by intracellular oxidative processes (20).
Although all of the individual carotenoids analyzed for
this study showed significant relations with interleukin 6,
b carotene and (especially) a carotene demonstrated the most
robust cross sectional and longitudinal relations. Lower
levels of a carotene have been linked to atherosclerotic
processes in older adults, and low levels of a carotene and
b carotene correlate with a higher risk of coronary artery
disease in adult women (21, 22). This may be partly because
a and b carotene constitute a major benign sink for oxida
tion in lipid particles; hence, lower levels of these caroten
oids could lead to more oxidized lipids and increased
activation of inflammatory pathways (23 25). Although de
ficiencies in lutein/zeaxanthin have most often been linked to
macular degeneration, studies also show a strong relation
between low levels of these nutrients and cardiovascular
disease (26). Thus, our longitudinal findings suggest that
low levels of a and b carotene, lutein/zeaxanthin, and total
carotenoids may drive interleukin 6 increases, perhaps
through decreased availability of these antioxidants for
quenching free radicals in the cardiovascular system.
Selenium is a critical constituent of glutathione peroxi
dase, the major reducing enzyme for both hydrogen peroxide
and lipid peroxides (27). Zinc, like selenium, is an important
component of a cytosolic antioxidant enzyme, copper zinc
superoxide dismutase (28). Although we found a strong rela
tion between low selenium and high interleukin 6, we found
no relation between zinc and interleukin 6. Superoxide mol
ecules are converted to hydrogen peroxide by copper zinc
superoxide dismutase, which in turn activates inflammatory
pathways (25). Elevation of copper zinc superoxide dismu
tase to selenium dependent glutathione peroxidase activity
has been demonstrated to correlate with increased lipid per
oxidation and nuclear factor jB activation through increased
hydrogen peroxide activity (29, 30). This evidence from
prior studies, along with our findings of a strong relation
between selenium and interleukin 6 and no relation between
zinc and interleukin 6, suggests that oxidative processes
driven by increased hydrogen peroxide and lipid peroxides
rather than superoxide radicals may partly drive generation
of interleukin 6 in older adults (31).
aging
In summary, in this study, we identified robust inverse
cross sectional and longitudinal relations between several
specific carotenoids and serum interleukin 6. We identified
a robust cross sectional inverse relation between selenium
and interleukin 6 and increased mortality among persons with
lower selenium levels. These findings suggest that specific
antioxidant nutrients, which act mechanistically to decrease
levels of hydrogen peroxide and lipid peroxides, may play an
important role in suppressing expression of interleukin 6 in
disabled older women.
ACKNOWLEDGMENTS
This research was supported by National Institutes of
Health contract N01 AG12112, National Institutes of
Health grant R37 AG19905, Older American Independence
Center grant P30 AG021334, and General Clinical Re
search Center National Center for Research Resources
grant M01 RR0000052.
Conflict of interest: none declared.
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51
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1513
The Journal of Experimental Biology 203, 1513–1521 (2000)
Printed in Great Britain © The Company of Biologists Limited 2000
JEB2594
REVIEW
SURFACE OXIDASE AND OXIDATIVE STRESS PROPAGATION IN AGING
DOROTHY M. MORRÉ1,*, GIORGIO LENAZ2 AND D. JAMES MORRÉ3
of Foods and Nutrition, Purdue University, West Lafayette, IN 47907, USA, 2Departimento di
Biochimica, Bologna, Italy and 3Department of Medicinal Chemistry and Molecular Pharmacology,
Purdue University, West Lafayette, IN 47907, USA
1Department
*e-mail: [email protected]
Accepted 23 February; published on WWW 18 April 2000
Summary
activity has been shown to be necessary to maintain the
This report summarizes new evidence for a plasmaNAD+/NADH homeostasis essential for survival. Our
membrane-associated hydroquinone oxidase designated
as CNOX (constitutive plasma membrane NADH
findings demonstrate that the hyperactivity of the PMOR
oxidase) that functions as a terminal oxidase for a
system results in an NADH oxidase (NOX) activity
plasma membrane oxidoreductase (PMOR) electron
capable of generating reactive oxygen species at the cell
transport chain to link the accumulation of lesions in
surface. This would serve to propagate the aging cascade
mitochondrial DNA to cell-surface accumulations of
both to adjacent cells and to circulating blood
reactive oxygen species. Previous considerations of
components. The generation of superoxide by NOX forms
plasma membrane redox changes during aging have
associated with aging is inhibited by coenzyme Q and
lacked evidence for a specific terminal oxidase to catalyze
provides a rational basis for the anti-aging activity of
a flow of electrons from cytosolic NADH to molecular
circulating coenzyme Q.
oxygen (or to protein disulfides). Cells with functionally
deficient mitochondria become characterized by an
Key words: hydroquinone (NADH) oxidase, mitochondria, ageing,
cell surface, plasma membrane, electron transport, coenzyme Q,
anaerobic metabolism. As a result, NADH accumulates
oxidative stress.
from the glycolytic production of ATP. Elevated PMOR
A plasma membrane redox system essential to survival of
mitochondrial-deficient cells during aging
A consistent characteristic of aging cells is the accumulation
of somatic mutations of mitochondrial DNA (mtDNA) leading
to defective oxidative phosphorylation through alterations that
affect exclusively the four mitochondrial complexes involved
in proton translocation (Harman, 1956, 1972; Miquel et al.,
1980; Linnane et al., 1989; Arnheim and Cortopassi, 1992;
Ozawa, 1995; de Grey, 1997, 1998; Lenaz et al., 1997, 1998).
A major piece of the puzzle missing from our information is
how mitochondrial lesions are propagated to adjacent cells and
blood components during the aging cascade. Progress towards
understanding how this might occur is provided by the studies
of de Grey (1997, 1998), in which a largely hypothetical
plasma membrane oxidoreductase (PMOR) system has been
suggested to augment survival of mitochondrially deficient
cells through the regeneration of oxidized pyridine nucleotide
required to sustain glycolytic ATP production in the presence
of diminished respiratory chain activity (Yoneda et al., 1995;
Schon et al., 1996; Ozawa, 1997; Lenaz, 1998).
In this report, we describe a newly discovered cell-surface
protein with hydroquinone (NADH) oxidase activity
(designated NOX) (Kishi et al., 1999) that functions as a
terminal oxidase of the PMOR system together with a complete
electron transport chain involving a cytosolic hydroquinone
reductase, plasma-membrane-located quinones and the NOX
protein (Morré, 1998). This system, described in detail since
the studies of de Grey (1997, 1998) appeared, provides a
rational basis for the operation of the mitochondrial theory of
aging and for the propagation of aging-related mitochondrial
lesions, including a decline in mitochondrial ATP synthetic
capacity (Boffoli et al., 1996) and other energy-dependent
processes (Lenaz et al., 1998) during aging.
Alterations in mitochondrial DNA (mtDNA) are by far the
most common sources of genetic lesions associated with cell
aging and senescence. It has been widely noted that mtDNAs
are located at the inner mitochondrial membrane near sites
where highly reactive oxygen species and their products
might be formed. Several subunits of the electron transport
chain together with components of the ATP synthase and
mitochondrial tRNAs and rRNAs are encoded by the
mitochondrial genome. The flow of electrons through the
52
aging
1514
D. M. MORRÉ, G. LENAZ AND D. J. MORRÉ
mitochondrial electron transport chain is not fully efficient,
and up to 2–4 % of the oxygen metabolized by mitochondria
has been estimated to be converted to oxygen radicals
(Boveris et al., 1972; Richter et al., 1988). A major tenet of
the mitochondrial theory of aging is that mtDNA may be
unable to counteract the damage inflicted by oxygen radicals
and their products because of a lack of excision and
recombination repair mechanisms (Miquel, 1992). This has
been demonstrated in cultured cells in which damage to
mtDNA resulting from oxidase stress is not only greater but
persists longer than does damage to nuclear DNA (Yakes and
Van Houten, 1997). Using the amount of 8-oxo-2′deoxyguanosine formed by the reaction of hydroxyl free
radicals with guanine in mtDNA as a biomarker of oxidative
DNA damage, the steady-state level of oxidative changes in
mtDNA was found to be approximately 10–16 times greater
than that of changes in nuclear DNA (Richter et al., 1988;
Shigenaga et al., 1994). Even lipid peroxidation of
mitochondrial membranes seems to lead to damage to
mtDNA (Balcavage, 1982).
Despite this overwhelming mass of evidence, alterations
to mtDNA per se and other forms of cellular and tissue
changes related to aging have been difficult to link. Chief
among these is the oxidation of low-density lipoproteins
(LDLs) and its implications as causal to atherogenesis
(Steinberg, 1997).
A model to link accumulation of lesions in mtDNA to an
extracellular response such as the oxidation of lipids in LDLs
and the attendant arterial changes was first proposed by de
Grey (1997, 1998) on the basis of the observations of Larm
et al. (1994) and Lawen et al. (1994) with Namalwa ρ0 cells.
These cells lack mtDNA and are unable to carry out oxidative
phosphorylation. Larm et al. (1994) and Lawen et al. (1994)
first demonstrated that the plasma membrane PMOR system
actually functions to regenerate NAD+ from NADH. In the
absence of a functional mitochondrial respiratory chain,
NADH accumulates as the result of glycolytic production of
ATP (Fig. 1). The ρ0 cells lacking functional mitochondria
apparently survive through enhanced electron flow to
molecular oxygen via PMOR. In addition, it may be possible
that aging cells over-express PMOR when mitochondrial
functions are depressed. Unpublished data from the
laboratory of G. Lenaz (Table 1) has demonstrated that, in
lymphocytes from insulin-dependent diabetic subjects, the
mitochondrial membrane potential exhibits increased
sensitivity to uncouplers as a result of decreased electron
input from the respiratory chain. PMOR is accordingly overexpressed in these cells. Oxidative stress and LDL oxidation
are common complicating features in diabetics (Kennedy and
Lyons, 1998).
The capacity of cells to generate ATP is determined either
by reoxidation of NADH by mitochondrial respiratory
mechanisms (reduction of oxygen to water) or by cytosolic
glycolytic mechanisms (reduction of pyruvate to lactate). If
sufficient pyruvate and uridine are provided, cells can grow
without a functional mitochondrial electron transport chain and
Table 1. Bioenergetic parameters in peripheral lymphocytes
from patients with insulin-dependent diabetes mellitus
Patients
Controls
P
Site I
respiration*
Site II
respiration*
Sensitivity
to FCCP‡
PMOR
activity§
(nmol min−1
10−6 cells−1)
0.12±0.05
0.26±0.12
0.08±0.08
0.21±0.07
19.7±7.5
5.2±1.9
2.7±0.6
1.9±0.5
<0.02
<0.01
<0.001
<0.005
Values are means ± S.E.M. (N=14 for patients and 13 for controls).
*O2 uptake with glutamate/malate (site I) and with succinate/
glycerol 3-phosphate (site II) are normalized to cytochrome c
oxidase activity (the ratio of activity measured to cytochrome
oxidase activity measured by ascorbate/N,N,N′,N′-tetramethyl-pphenylenediamine (TMPD) oxidation). The measurements were
performed in digitonin-permeabilized lymphocytes.
‡Slope of the green to red fluorescence ratio of 5,5′,6,6′tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine
iodide
(JC1) measured in flow cytometry after addition of increasing
concentrations
of
the
uncoupler
4-trifluoromethoxycarbonylcyanidephenylhydrazone (FCCP) (expressed in arbitrary
units).
§Dichlorophenolindophenol (DCIP) reduction by endogenous
NADH in intact lymphocytes.
PMOR, plasma membrane oxidoreductase activity.
oxidative phosphorylation. As shown by Vaillant et al. (1996),
transformed human cells in culture provided with excess
pyruvate grow anaerobically on a glucose medium because
NAD+ is regenerated from the NADH that is produced during
glycolysis. This continual regeneration of NAD+, including
that generated by the PMOR, ensures that the glycolytic
pathway will provide sufficient ATP to sustain cell growth and
viability.
Glucose
Plasma
membrane
ADP
Glycolysis
NAD +
ATP
NADH
+ H+
AH2
PMOR
A
Pyruvate
Fig. 1. Relationship between the plasma membrane oxidoreductase
(PMOR) system and the regeneration of NAD+ from NADH formed
during glycolysis. A is the external acceptor.
53
aging
1515
Surface oxidase and oxidative stress propagation during aging
oxidase protein, designated NOX, capable of oxidizing
hydroquinones (Kishi et al., 1999). This protein, which is
located at the exterior of the cell (Morré, 1995; DeHahn et al.,
1997), appears to be multifunctional but may have a major
function as a terminal oxidase of the PMOR system. These
findings make it possible, for the first time, to delineate a
complete electron transfer chain in the plasma membrane
capable of transferring electrons from NADH to an external
electron acceptor via a reduced quinone intermediate.
Mammalian plasma membranes are enriched in coenzyme Q
(ubiquinone) (Table 3). The plasma membrane at the cytosolic
surface contains a quinone reductase capable of oxidizing
NADH and reducing coenzyme Q. The electron acceptor at the
external cell surface is either molecular oxygen or, under
certain conditions, both molecular oxygen and protein
disulfides (Morré, 1994; Chueh et al., 1997; Morré et al.,
1998). The enzyme can alternate between the two acceptors
(Morré, 1998). Hormones and growth factors stimulate NADH
oxidation and favor protein disulfide reduction at the expense
of oxygen consumption (Brightman et al., 1992; Morré, 1994;
Chueh et al., 1997). Chueh et al. (1997) demonstrated
stoichiometric relationships among protein disulfide reduction,
NADH oxidation and protein-thiol formation using isolated
plasma membranes from a plant source stimulated by an auxin
Glycolysis
Glucose
Pyruvate
Mitochondrial
DNA mutations
Anaerobic
cell
Glucose
ADP
NAD
Glycolysis
New evidence for a plasma membrane oxidoreductase chain
important to aging
As demonstrated with ρ0 cells, a functional PMOR is
essential to aging cells expressing mitochondrial lesions.
Mitochondrial DNA encodes respiration and oxidative
phosphorylation enzymes exclusively, so that cells with
functionally deficient mitochondria become metabolically
anaerobic. In such cells, the PMOR could regenerate sufficient
reducing equivalents to maintain NAD+/NADH homeostasis
and ensure the survival even of cells completely deficient in
aerobic respiratory capacity.
Our work demonstrates that, in cells in which the PMOR is
over-expressed/activated, electrons are transferred from
NADH to external acceptors via a recently defined electron
transport chain in the plasma membrane (Kishi et al., 1999).
The resultant transfer of electrons could result subsequently in
the generation of superoxide and ultimately other reactive
oxygen species (ROS) at the cell surface (Table 2). Such cellsurface-generated ROS would then be capable of propagating
an aging cascade originating in mitochondria both to adjacent
cells and to circulating blood components such as LDLs and
to the vasculature (Fig. 2).
Work done in collaboration with Professor T. Kishi, KobeGakuin University, Japan, has described a cell-surface NADH
AT P
NADH
+H
ATP production
by glycolysis
Pyruvate
NAD
A
PMOR
NADH
+H
Enhanced PMOR activity
to oxidize NADH
Adjacent cells
Fig. 2. Hypothesis to explain the
mechanism whereby anaerobiosis
resulting from mitochondrial lesions,
the resultant stimulation of glycolysis
and the enhancement of the plasma
membrane oxidoreductase (PMOR)
system result in the formation of
reactive oxygen species (ROS) at the
cell surface that can be propagated and
affect both adjacent cells and
circulating blood components. LDL,
low-density lipoprotein.
LDL
2H
+
2e−
GO 2
Atherosclerosis
H 2O
O 2.
H 2O 2
Oxidised
LDL
OH−
Generation of
ROS at plasma membrane
54
Propagation
of response
AH2
aging
1516
plant growth factor 2,4-dichlorophenoxyacetic acid (2,4-D). A
similar stoichiometry has been demonstrated for NADH
oxidation in HeLa cells (Morré et al., 1998).
As a terminal oxidase of the PMOR electron transport chain,
the NOX protein may be responsible not only for maintaining
NAD+/NADH homeostasis in metabolically anaerobic cells
but may also play a role in the enhanced generation of ROS in
aged cells expressing mitochondrial mutations that lead to
impaired oxidative phosphorylation. Since oxygen appears to
be the principal natural electron acceptor for the PMOR
electron transport chain, a number of factors, including metals
(iron or copper), could interrupt the orderly two-electron flow
to molecular oxygen that ordinarily forms water and initiates
a one-electron process producing superoxide (O2• or O2−) (Fig.
2). Superoxide then probably initiates a reaction that generates
H2O2 and other aggressive oxidants such as the hydroxyl
radical (OH•) (Papa and Skulachev, 1997). These ROS then
would be released into the environment to react with
neighboring cells and circulating molecules such as LDL
(Steinberg, 1997).
1992; Morré and Morré, 1995; Morré et al., 1995a,b, 1996a,
1997c).
Because the NOX protein is located at the external plasma
membrane surface and is not a transmembrane protein (Morré,
1994; DeHahn et al., 1997), a functional role as an NADH
oxidase is not considered likely (Morré, 1998). Although the
oxidation of NADH provides a basis for a convenient method
to assay the activity, the ultimate physiological electron donors
are most probably hydroquinones (Kishi et al., 1999), as
depicted in Fig. 3, with specific activities for hydroquinone
oxidation being greater than or equal to those of NADH
oxidation and/or protein-disulfide–thiol interchange.
The NOX protein partially purified from the surface of HeLa
cells also exhibits ubiquinol oxidase activity (Kishi et al.,
1999). These preparations completely lack NADH:ubiquinone
reductase activity and oxidize the dihydroquinone Q10H2 at a
rate of 3–6 nmol min−1 mg−1 protein. The Km for Q10H2 is
30 µmol l−1. Activities are inhibited competitively by the
cancer-cell-specific NADH oxidase inhibitors capsaicin (8methyl-N-vanillyl-6-noneamide) (Morré et al., 1995a, 1996a)
and the antitumor sulfonylurea N-(4-methylphenylsulfonyl)N′-(4-chlorophenyl)urea (LY181984) (Morré et al., 1995b).
The oxidation of Q10H2 proceeds with what appears to be a
normal two-electron transfer, in keeping with the participation
of the plasma membrane NADH oxidase as a terminal oxidase
of plasma membrane electron transport from cytosolic
NAD(P)H via coenzyme Q to acceptors at the cell surface, as
depicted in Fig. 3.
The NOX protein is distinguished from other oxidase
activities by differential susceptibility of the activity to several
common oxidoreductase inhibitors (Morré and Brightman,
1991) and to thiol reagents (Morré and Morré, 1994). In
addition, the activity of tNOX correlates with the growth of
transformed cells (Morré et al., 1995a, 1996a; Ozawa, 1995).
When inhibited by tNOX-specific vanilloids or antitumor
sulfonylureas, the cells initially divide normally, and DNA and
protein synthesis is not inhibited, but the cells fail to enlarge
(Morré and Morré, 1995; Morré et al., 1995a). The resultant
small cells, however, fail to divide and, after a few days, begin
to undergo apoptotic cell death (Morré and Morré, 1995; Morré
et al., 1995a; DeHahn et al., 1997). Two monoclonal antibodies
directed against tNOX, designated MAB 12.1 and MAB 12.5,
were generated and were shown also to be inhibitory to cell
enlargement in cancer cells but not in normal cells and to
induce apoptotic cell death even more efficiently than did the
drug inhibitors of tNOX (Morré, 1998).
In cancer cells, the tumor-associated (tNOX) activity was
constitutively activated (Morré et al., 1995a) and inhibited by
retinoids (Dai et al., 1997) and by other potential quinone-siteinhibitory drugs, such as the antitumor sulfonylurea LY181984
(Morré et al., 1995b) and capsaicin (Morré et al., 1995a), but
was no longer hormone- or growth-factor responsive (Bruno et
al., 1992; Morré et al., 1995a). The ability to oxidize NADH
was reflected in the ability of the protein to function as an
NADH:protein disulfide reductase or protein-disulfide–thiol
oxidoreductase with protein-disulfide–thiol interchange
Plasma membrane hydroquinone (NADH) oxidase (NOX)
The plasma membrane NADH oxidase (NOX) is a unique
cell-surface protein with hydroquinone (NADH) oxidase and
protein-disulfide–thiol interchange activities that normally
respond to hormones and growth factors (Brightman et al.,
1992; Morré, 1994, 1998). A hormone-insensitive and drugresponsive form of the activity designated tNOX also has
been described that is specific for cancer cells (Bruno et al.,
2O2 .
Plasma membrane
Outside
Inside
NOX
2O2
Q10
H2 O
GO2
Protein
S
S
Protein
SH
SH
Q10 H 2
Quinone
reductase
NAD(P)H
+ H+
NAD(P) +
Fig. 3. Diagram showing the spatial relationships between the
intracellular NAD(P)H:quinone reductase, the membrane pool of
coenzyme Q (Q10) and the external NADH oxidase (NOX) protein
across the plasma membrane. In this manner, the NOX protein could
function as a terminal oxidase of plasma membrane electron
transport, donating electrons from cytosolic NADH either to
molecular oxygen or to protein disulfides as electron acceptors.
55
aging
1517
activity (Morré et al., 1997b). The latter may be related to low
levels of a protein disulfide isomerase-like activity reported at
the cell surface (Mandel et al., 1993). The protein is associated
with the enlargement phase of cell growth (Morré, 1998).
When NOX activity is inhibited, growth is also inhibited. In
the presence of capsaicin (Morré et al., 1995a), the antitumor
sulfonylurea LY181984 (Morré and Morré, 1995) and NOXinhibitory retinoids (Dai et al., 1997), the inhibited cells fail to
enlarge, division ceases and apoptotic cell death is the ultimate
fate of the inhibited cells.
CNOX was originally defined as a drug-indifferent
constitutive NADH oxidase activity associated with the plasma
membrane of non-transformed cells that was the normal
counterpart to tNOX. Indeed, a 36 kDa protein isolated from
rat liver and from plants has NOX activity that is unresponsive
to tNOX inhibitors.
While cancer cells exhibit both drug-responsive and
hormone- and growth-factor-indifferent (tNOX) as well as
drug-inhibited and hormone- and growth-factor-dependent
(CNOX) activities, non-transformed cells exhibit only the
drug-indifferent, hormone- and drug-responsive CNOX.
Among the first descriptions of the so-called constitutive or
CNOX activity of non-transformed cells and tissues was that
in rat liver plasma membranes, in which the activity was
stimulated by the growth factor diferric transferrin (Sun et al.,
1987). Subsequent work demonstrated that this NADH
oxidation was catalyzed by a unique enzyme exhibiting
responsiveness to several hormones and growth factors (Bruno
et al., 1992). Unlike mitochondrial oxidases, the hormonestimulated NADH oxidase activity of rat liver plasma
membranes was not inhibited by cyanide. The enzyme was also
distinguished from other oxidase activities by its response to
several common oxidoreductase inhibitors (i.e. catalase, azide
and chloroquine) and to various detergents (i.e. sodium
cholate, Triton X-100 and Chaps) (Morré and Brightman,
1991; Morré et al., 1997c). Like the tNOX of cancer cells,
CNOX is a unique membrane-associated protein that is capable
of oxidizing NADH, but its activity is modulated by hormones
and growth factors.
Table 2 presents evidence that NOX proteins under certain
conditions are capable of the production of ROS. We have used
ultraviolet light as a source of oxidative stress in cultured cells
to initiate superoxide generation (Morré et al., 1999). Such
generation is presumably due to the NADH oxidase because in
cell lines (HeLa, a human cervical carcinoma, and BT-20, a
human mammary carcinoma) that contain a capsaicinresponsive NADH oxidase, the response to ultraviolet light is
inhibited by capsaicin. In the MCF-10A cell line (a human
mammary epithelium), lacking tNOX activity and not
cancerous, the ultraviolet-light-induced generation of
superoxide is unaffected by capsaicin and, presumably, the
resultant effect of ultraviolet light on the plasma membrane
CNOX (Table 2).
The switch whereby the oxidase may reduce oxygen by
either a one-electron or a four-electron mechanism is not
understood at present, but it may reside in a delicate redox
Table 2. Reduction of cytochrome c as a measure of
superoxide production by cell lines in response to ultraviolet
irradiation and inhibition by superoxide dismutase and by
capsaicin
Rate of reduction of cytochrome c
(mol min−1 106 cells−1)
After ultraviolet treatment2
Cell
line1
HeLa S
BT-20
MCF-10A
Initial rate
No addition
+SOD3
+Capsaicin4
0.8±0.16
0.7±0.2
1.5±0.2
4.0±1.0
5.1±2.1
7.2±0.1
1.1
–0.1
–0.7
0.8
–3.7
7.2
Values are means ± S.D., N=3.
1HeLa S, human cervical carcinoma; BT-20, human mammary
adenocarcinoma; MCF-10A, human mammary epithelium (noncancer).
2Treatment for 10 min with short-wavelength ultraviolet light.
3Treatment with 7.5 µg ml−1 superoxide dismutase (SOD) (Sigma).
4Treatment with 2.5 µmol l−1 capsaicin in dimethylsulfoxide
(DMSO). Rates were corrected for a DMSO blank.
The generation of superoxide radical was determined by assaying
the rate of SOD-inhibitable cytochrome c reduction (Mayo and
Curnutte, 1990; McCord and Fridovich, 1968). The cytochrome c
was from horse heart mitochondria (type VI, Sigma) and was
dissolved in PBSG buffer (138 mmol l−1 NaCl, 2.7 mmol l−1 KC1,
8.1 mmol l−1 Na2HPO4 and 1.47 mmol l−1 KH2PO4, final
pH 7.37–7.42, then supplemented with 0.9 mmol l−1 CaCl2,
0.5 mmol l−1 MgCl2 and 7.5 mmol l−1 glucose) to make a solution
with a final concentration of 1 mg ml−1. Air-saturated reaction
mixtures of 100 µl of cytochrome c stock solution and 50 µl of cell
suspension (suspended in PBSG buffer) with a concentration of
approximately 5×106 cells ml−1 were added to 2 ml of PBSG buffer .
The formation of reduced cytochrome c was measured in the
presence and absence of 5 µl of SOD or capsaicin (in 1 mmol l−1 in
DMSO) by comparing the absorbance of the mixture at 550 and
540 nm. The SOD was obtained from Sigma, and a stock solution of
3 mg protein ml−1 H2O was prepared and stored at 4 °C. Superoxide
radical formation was stimulated by using a hand-held ultraviolet
light (short-wavelength). Plastic cuvettes were used to allow the light
to penetrate and reach the cells. The extent of cytochrome c
reduction was monitored spectrophotometrically at 550 nm every
10 s, with gentle mixing between readings. Data were analyzed from
the slope of the change in the difference in absorbance between 550
and 540 nm before and after ultraviolet treatment and then again after
SOD or capsaicin treatment.
Results are expressed as nmol superoxide 106 cells−1, using a value
of Em550nm of 2.1×103 l mol−1 cm−1 (Butler et al., 1982).
balance between the carriers involved. Such a balance may be
broken by oxidative stress or cell damage. Metal ions such as
iron and copper, released by tissue damage (Hershko, 1992),
may also play a role.
Plasma membrane levels of coenzyme Q
In the model depicted in Fig. 3, plasma membrane ubiquinone
or coenzyme Q is a major player in the PMOR system that we
56
aging
1518
Table 3. The distribution of ubiquinone in subcellular
fractions from rat liver
Fraction
Homogenate
Golgi apparatus
Lysosomes
Mitochondria
Inner mitochondrial membranes
Microsomes
Peroxisomes
Plasma membranes
Supernatant
superoxide production and its inhibition by coenzyme Q in
serum from young (21–46 years old) and aged (76–95 years
old) individuals
[Ubiquinone-9]
(µg mg−1 protein)
(nmol min−1 ml−1 serum)
0.79±0.08
2.62±0.15
1.86±0.18
1.40±0.16
1.86±0.13
0.15±0.02
0.29±0.04
0.74±0.07
0.02±0.004
Group
N
21–46 years
76–82 years
83–95 years
16
15
15
No addition +0.1 mmol l−1 Q10
0.02±0.1
1.5±0.9
3.9±1.6
–
0.6±0.2
2.5±1.4
Values are means ± S.D.
Q10, ubiquinone-10 (CoQ10).
The values are means ± S.E.M. of seven experiments (see Kalén et
al., 1987).
The predominant coenzyme Q species isolated from rat liver
has nine isoprenoid units; hence, ubiquinone-9 or CoQ9. The
predominant coenzyme Q species from most other mammalian
species has 10 isoprenoid units; hence, ubiquinone-10 or CoQ10.
hepatocytes (Beyer et al., 1996), the anti-cancer quinone
glycoside adriamycin induced oxidative stress by enhancing
ROS production. Exogenous addition of coenzyme Q
prevented this ROS production and concomitantly protected
the cells from oxidative damage. We have observed similar
effects of exogenous coenzyme Q on NOX-mediated ROS
production (Table 4). Such an antioxidant effect at the plasma
membrane may very well ameliorate LDL oxidation by
scavenging ROS through the PMOR produced at the cell
surface (Fig. 2) (Thomas et al., 1997).
Some studies have shown that coenzyme Q levels decrease
with age (Beyer et al., 1985; Kalén et al., 1990; Genova et al.,
1995). However, this is not true for all tissues and especially
for the brain, where high levels of coenzyme Q are maintained
throughout aging (Söderberg et al., 1990; Battino et al., 1995).
However, most important would be circulating levels of
coenzyme Q that could come into contact with an overactive
or aberrant cell surface PMOR system or with circulating NOX
isoforms that may also play roles in aging related to oxidative
stress.
postulate as being responsible for the propagation of oxidative
stress to the extracellular environment. Ubiquinone or coenzyme
Q occurs ubiquitously among tissues. In rat liver, the highest
levels are found in the Golgi apparatus (Crane and Morré, 1977),
but it is also concentrated in the plasma membrane (Table 3)
(Kalén et al., 1987). The ubiquinone content of plasma
membrane is 2–5 times that of microsomes and only
approximately half that of mitochondria.
Ubiquinone has long been considered to have both pro- and
antioxidant roles (Ernster and Dallner, 1995) in addition to its
more conventional role in mediating electron transport
between NADH and succinic dehydrogenase and the
cytochrome system of mitochondria (Crane and Barr, 1985).
Both pro- and antioxidant and electron transport roles may now
be considered for ubiquinone in the plasma membrane.
Coenzyme Q is normally a product of cellular biosynthesis
(Andersson et al., 1994; Appelkvist et al., 1994) and provides
a potentially important source of one-electron pro-oxidant
oxygen reduction. In its reduced hydroquinone form
(ubiquinol), it is a powerful antioxidant acting either directly
on superoxide or indirectly on lipid radicals (Crane and Barr,
1985; Beyer and Ernster, 1990; Beyer, 1994) either alone or
together with vitamin E (α-tocopherol) (Kagan et al., 1990;
Ernster et al., 1992).
The antioxidant action of ubiquinol normally yields the
ubisemiquinone radical. The latter is converted back to
ubiquinol by re-reduction through the electron transfer chain
in mitochondria or by various quinone reductases in various
cellular compartments (Takahashi et al., 1995, 1996; Beyer et
al., 1996, 1997) including the plasma membrane (Navarro et
al., 1995; Villalba et al., 1995, 1997; Arroyo et al., 1999).
Thus, ubiquinone may transform from a beneficial one- or twoelectron carrier to a superoxide generator if the ubisemiquinone
anion becomes protonated (Nohl et al., 1996).
In perfused rat liver (Valls et al., 1994) and in isolated rat
CNOX is shed by cells and circulates – preliminary
evidence for an aging-related CNOX protein
The NOX protein is bound at the outer leaflet of the plasma
membrane (Morré, 1995; DeHahn et al., 1997), and NOX
activity has been shown to be shed in soluble form from the
cell surface (Morré et al., 1996b). The presence of the activity
in culture medium conditioned by the growth of cells
prompted a search for a comparable shed activity in the serum
of cancer patients. Serum from healthy volunteers or from
cancer patients does contain NADH oxidase activities with
properties similar, if not identical, to those of CNOX and
tNOX, respectively, found at the cell surface (Morré and
Reust, 1997; Morré et al., 1997a). The presence of the shed
form in the circulation provides an opportunity to use serum
from cancer patients as a source of the NOX protein for largescale isolation and characterization studies and to examine
NOX activity in the serum of subjects of advanced age in a
simple and non-invasive procedure that permits side-by-side
comparisons with serum from young adults. In this manner,
57
aging
The original findings reported from the laboratory of G.
Lenaz was supported by a PRIN ‘Bioenergetics and
Membrane Transport’ from MURST, Rome.
superoxide production by buffy coats from the blood of aged
individuals and inhibition by coenzyme Q
(nmol min−1 106 cells−1)
Group
N
35–65 years
80–89 years
90–94 years
5
6
6
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No addition +0.1 mmol l−1 Q10
ND
0.05±0.02
0.36±0.07
1519
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Q10, ubiquinone-10 (CoQ10).
we have identified a serum form of the CNOX activity that
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60
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See related article on page 826
How to Prevent Photoaging?
Leslie Baumann
Department of Dermatology, University of Miami, Miami, Florida, USA
There are several theories on photoaging and its etiology. At
this time, however, the only defenses commonly believed to
prevent photoaging are the use of sunscreens to reduce the
amount of ultraviolet (UV) that reaches the skin, the use of
retinoids to prevent production of collagenase and stimulate
collagen production, and the use of antioxidants to reduce
and neutralize free radicals. The Pinnell paper in this issue of
the Journal of Investigative Dermatology that examines ferulic acid combined with vitamins C and E shows that this
formulation seems to provide two of the above defenses: a
sunscreen effect, and an antioxidant effect. Not all sunscreens confer an antioxidant effect and not all antioxidants
yield a sunscreen effect (Pinnell et al, 2005b). For example,
Kang et al (2003) showed that although genistein and Nacetyl cysteine exhibit antioxidant activity, they produced
no effect on ultraviolet-induced erythema.
UV exposure results in skin damage through several
mechanisms including sunburn cell development, thymine
dimer formation, collagenase production, and the provocation of an inflammatory response. Sunburn cells, or UV-induced apoptotic cells, have long been used to assess skin
damage due to ultraviolet exposure. UV-induced apoptosis
is mediated by caspase-3 (Lin et al, 2005). Activation occurs
in a pathway that involves caspase-7 (Pinnell et al, 2005a). It
is believed that capsase-3 levels are good indicators of the
presence of cellular apotosis (Kang et al, 2003; Philips et al,
2003; Lin et al, 2005; Yao et al, 2005). Theoretically, the
fewer sunburn cells present, less the ‘‘skin damage’’ from
UV exposure. At this time, sun avoidance and use of sunscreens are the only defenses against sunburn cell formation. Sunscreens and sun avoidance can also protect
against thymine dimer formation.
Antioxidants protect the skin from free radicals through
several mechanisms in the early stages of elucidation. Free
radicals can act directly on growth factors and cytokine receptors in keratinocytes and dermal cells, leading to skin
inflammation. Kang et al have shown that free radical activation of the mitogen-activated protein (MAP) kinase pathways results in production of collagenase, which leads to
degradation of collagen (Saliou et al, 2001; Greul et al, 2002;
Kang et al, 2003; Papucci et al, 2003; Passi et al, 2003;
Middelkamp-Hup et al, 2004a, b; Sime and Reeve, 2004;
Katiyar, 2005). Blocking these pathways with antioxidants is
thought to prevent photoaging by preventing the production
of collagenase. This theory has been buttressed by re-
search on human skin performed by Kang et al. In this
study, investigators showed that when human skin was
pretreated with the antioxidants genistein and N-acetyl
cysteine, the UV induction of the cJun-driven enzyme collagenase was inhibited.
Many antioxidants are now available in oral and topical
preparations. Studies such as the one by Pinnell suggest that combinations of various antioxidants may have
synergistic effects, yielding formulations with greater efficacy than any of the individual antioxidant compounds used
alone. Each antioxidant is endowed with various properties
that distinguish it from other antioxidants. Some examples
of popular antioxidants and their characteristics will be
briefly discussed.
Pycnogenol is a trademark name for a standardized extract of the bark of the French maritime pine plant, which is
rich in procyanidins, also called proanthocyanidins. These
potent free-radical scavengers can also be found in grape
seed, grape skin, bilberry, cranberry, black currant, green
tea, black tea, blueberry, blackberry, strawberry, black
cherry, red wine, and red cabbage. In one study (Sime
and Reeve, 2004), Pycnogenol concentrations of 0.05%–
0.2% were applied to the irradiated dorsal skin of Skh:hr
hairless mice exposed daily to minimally inflammatory solarsimulated UV radiation. Mice pretreated with Pycnogenol
demonstrated a concentration-dependent reduction of the
inflammatory sunburn reaction (edema). In a study (Saliou
et al, 2001) evaluating the capacity of pine bark extract
to protect human skin against erythema induced by solar
radiation, 21 volunteers received oral supplementation of
Pycnogenol. During supplementation, the UVR level necessary to reach one minimal erythema dose (MED) was significantly elevated, suggesting that oral pine bark extract
supplementation mitigates the effects of UV radiation on the
skin, lowering erythema. The mechanism of action of
Pycnogenol may transcend its free-radical scavenging activities, as suggested by its anti-inflammatory effects, which
are partially ascribed to the fact that Pycnogenol inhibits
IFN-g-induced expression of ICAM-1 (Bito et al, 2000).
Silymarin is a naturally occurring polyphenolic flavonoid
compound or flavonolignans antioxidant derived from the
seeds of the milk thistle plant Silybum marianu. The beneficial effects of silymarin are primarily the result of its main
active constituent silybin, which was shown to be bioavailable in the skin and other tissues following systemic administration (Zhao and Agarwal, 1999). Topical application
of silybin before or immediately after UV irradiation has been
found to impart strong protection against UV-induced dam-
Abbreviations: CoQ10, coenzyme Q10; UV, ultraviolet
Copyright r 2005 by The Society for Investigative Dermatology, Inc.
xii
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aging
125 : 4 OCTOBER 2005
HOW TO PREVENT PHOTOAGING?
age in epidermal tissue by a reduction in thymine dimerpositive cells (Dhanalakshmi et al, 2004). A wide range of
in vivo animal studies suggests that silymarin possesses antioxidant, anti-inflammatory, and immunomodulatory
properties that may help prevent skin cancer as well as
photoaging (Katiyar, 2005).
Coenzyme Q10 (CoQ10) or ubiquinone is a naturally occurring antioxidant found in fish, shellfish, spinach, and
nuts. It is a fat-soluble compound also present in all human
cells as part of the electron transportation chain responsible
for energy production that has been recently found to exhibit antiapoptotic activity (Papucci et al, 2003). Researchers have identified an age-related decline of CoQ10 levels in
animals and humans (Beyer and Ernster, 1990). UV light
depletes vitamin E, vitamin C, glutathione, and CoQ10 from
the dermis as well as epidermis of the skin; however, CoQ10
is consistently found to be the first antioxidant depleted in
the skin.
Polypodium leucotomos (PL) extract is derived from
tropical fern and has demonstrated potent antioxidant activity. Orally administered PL was recently shown to decrease the incidence of phototoxicity in subjects receiving
PUVA treatment and in normal healthy subjects (Middelkamp-Hup et al, 2004a). UV-exposed keratinocytes and
fibroblasts treated with PL have also exhibited significantly
improved membrane integrity, reduced lipid peroxidation,
enhanced elastin expression, and inhibited matrix metalloproteinases-1 (MMP-1) expression (Philips et al, 2003).
Using antioxidants in combination is likely to impart
synergistic benefits. A randomized, double-blind, parallel
group, placebo-controlled study (Greul et al, 2002) examining the effects of an antioxidant preparation containing
vitamins E and C, carotenoids, selenium, and proanthocyanidins orally administered to subjects and then
exposed to UVB showed a difference in MMP-1 production
between the treatment and placebo groups (po0.05). The
assessment of MED of the skin, however, did not reveal any
statistically significant differences between the oral antioxidant group and the placebo group.
Although copious data have shown that both topical application and oral administration of individual antioxidants
impart benefits to the skin, it is reasonable to investigate a
cumulative or additive benefit derived from using oral and
topical antioxidant products in combination. In a study
(Passi et al, 2003) evaluating two groups of individuals,
Group A was treated daily with a base cream containing
0.05% ubiquinone, 0.1% vitamin E, and 1% squalene. In
addition, 50 mg of CoQ10 þ 50 mg of d-RRR-a-tocopheryl
acetate þ 50 mg of selenium were administered orally.
Group B was treated with the base cream alone. Sebum,
stratum corneum, and plasma levels of CoQ10, vitamin E,
and squalene were measured every 15 d. The patients
treated only with the topical antioxidant formulation showed
a significant increase of CoQ10, d-RRR-a-tocopherol, and
squalene in the sebum, with no significant changes observed in their stratum corneum or plasma concentrations.
Those treated with concomitant oral administration also
exhibited elevated levels of vitamin E and CoQ10 in the
stratum corneum.
xiii
Antioxidants clearly play an important role in the prevention of aging. It is unknown as to which antioxidants are the
most effective. Combining them both topically and orally
will likely be the leading therapeutic approach in the near
future. Antioxidants should be used in combination with sunscreens and retinoids to enhance their protective effects.
DOI: 10.1111/j.0022 202X.2005.23810.x
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  
 
 
            
                 
               
           
                   
             
                 
             
       
              
           
           
           
            
            
                
             
    
              
            
           
          
63
aging
               
      
           
                 
               
                
          
              
      
              
            

  
    
            
  
       
          
    
             
    
 
          
     
               
      
   
 
      
         
   
   
64
aging
         





              
          
   
      
          

       
            
      
   
          
 
         
         
              
               

           
  

     

     
     
 
 
     
   

      
   
 
      
      
    
  
      
    
      
   

  

       
        
 
     
     
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   
 
      
     
      
      
      
 
 
     
      
      
 
 
       
     
     
         
    
      
  

  
 
     
 
      
      
      
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

           
  

           
       
           
           

             
              
   

           
      

     

           

    
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 INTRODUCTION - ANTIOXIDANTS & AGING, FREE RADICAL
CENEGENICS NEWSLETTER
NOV 2010
THEORY OF AGING (Pg. 1)
For any questions or recommendations please contact:
MEDICAL EDITOR
Michale J Barber, M D
843-577-8484
mbarber@cenegenics-carolinas com
PHARMACY
1-888-222-2956
cenegenics@mqrx com
 ANTIOXIDANTS 101 &
ANTIOXIDANT NUTRITION (Pg. 2)

REFERENCES
(Pg. 3)
PHARMACY
DISCUSSING RELEVANT ISSUES PERTAINING TO THE WORLD OF COMPOUNDING
PHARMACY
Introduction - Antioxidants & Aging
focus
How do you prevent accelerated aging? While there may not be a specific antidote or fountain of youth,
lifestyle habits, genetics, and free radical accumulation may all be associated with how well you age
Specifically, antioxidants can discourage the aging process by deterring the progression of free radicals
Free radicals are unstable molecules that cause destructive reactions in the body by damaging cellular
health They are not in short supply and are a primary cause of accelerated aging
Environmental toxins, stress, infections, poor nutrition, intensive exercise training, and smoking can all
lead to the accumulation of free radicals in the body Furthermore, everyday metabolic processes, such as
breathing and eating, form free radicals The proliferation of these highly reactive molecules can cause
a rapid decline in health, leading to cardiovascular disease, Alzheimer’s, arthritis, macular degeneration,
cancer, and other age-related ailments
Antioxidants stabilize free radicals by adding an electron to the unbalanced molecule While certain
antioxidants, including coenzyme Q10, superoxide dismutase, catalase, and glutathione peroxidase,
are naturally produced in the body, levels can decline with age This leads to more oxidative stress
that can damage DNA, proteins, and mitochondria Through weight management, a diet rich in fruits
and vegetables, and nutritional supplementation, antioxidant levels can be restored and destructive free
radicals can be thwarted
This month, we look at the basic concepts surrounding free radicals, antioxidants, and aging An
introduction on the free radical theory of aging and the role antioxidants may play in diminishing the
aging process is reviewed Antioxidant-rich nutrients, including alpha lipoic acid, garlic, grape seed
extract and resveratrol, are also discussed to provide considerations for nutritional supplementation
Free Radical Theory of Aging
As one of the most widely accepted theories on aging, the free radical theory of aging finds that cells constantly produce free radicals through normal metabolic
processes, ultraviolet light, and environmental toxins Free radicals generate a chemical process known as oxidation, which causes cellular degeneration This is
considered a major contributor to the aging process
The free radical theory of aging was first identified over fifty years ago by Denham Harman, PhD Since then, scientists have added to Dr Harman’s theory and
questioned its relation to the aging process Supporters of the theory advocate calorie restriction, a reduction in copper and iron intake, a decrease in polyunsaturated
fats, and an increase in antioxidant consumption can moderate free radical proliferation Those opposed to the theory find that reactive oxygen species (ROS) have
minimal influence on aging They suggest a certain amount of free radicals are needed for cellular signaling While some critics oppose the free radical theory of
aging, more studies suggest lower levels of oxidative stress and higher levels of antioxidants can be related to longevity
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ANTIOXIDANTS 101
Grape Seed Extract
Grape seed extract is rich in flavonoids, known as proanthocyanidins As
a strong antioxidant compound, proanthocyanidins can protect the body
from a variety of free radicals and decrease lipid peroxidation in the cells
Its antioxidant potential is considered stronger than vitamins C and E, and
beta-carotene Researchers gave 300 mg of grape seed extract to 20 young
volunteers for five days finding that serum antioxidant levels increased
among those taking grape seed extract Grape seed extract was given to
young and aged rats for 15 to 30 days, finding that it restored cellular
activity and membrane integrity This suggests it can delay the aging
process by maintaining normal cellular function Furthermore, grape seed
extract can reduce oxidative stress and free radical damage associated with
myocardial ischemia-reperfusion injuries
Several forms of free radicals exist in our environment making it
essential to receive a variety of antioxidants The body naturally
produces certain types of antioxidants, including glutathione, uric acid,
coenzyme Q10, and lipoic acid Other antioxidants need to be obtained
through diet, such as vitamins C and E, selenium, and phytochemicals
Free radicals can be formed in lipid or aqueous areas of the body This
makes it essential to receive both fat and water-soluble antioxidants
to neutralize different oxidative intruders Vitamin C, glutathione,
and lipoic acid are examples of water-soluble antioxidants,
while vitamins A and E are considered fat-soluble antioxidants
A high consumption of antioxidant-rich fruits and vegetables can
significantly improve antioxidant levels in the body Carotenoids, flavonoids,
polyphenols, lutein, and lycopene are antioxidant compounds found in several
fruits and vegetables Carotenoids are commonly found in produce with
red, orange or yellow pigment (carrots, squash, sweet potatoes, cantaloupe,
peaches, etc ) Flavonoids and polyphenols can be found in pomegranate,
cranberries, tea, concord grapes, soy, and red wine Dark green vegetables,
including broccoli, kale, spinach, and brussels sprouts contain lutein
Tomatoes, pink grapefruit, and watermelon are good sources for lycopene
Lutein
Lutein, a yellow pigment in the carotenoid family, has antioxidant
properties that are particularly important to ocular health Lutein is one
of the most abundant carotenoids in the eye, as it filters out high-energy
blue light that can create free radical damage in the macular region of
the eye Lutein can protect vision from cataracts and age-related macular
degeneration, as low levels have been related to vision ailments Twoyear lutein supplementation (15 mg, 3x/week) was given to patients with
cataracts, finding long-term use improved visual acuity and had no side
effects A twelve-month study gave 91 patients with macular degeneration
10 mg of lutein, which improved optical density, contrast sensitivity, glare
recovery, and vision acuity
Endogenous antioxidants, including coenzyme Q10, superoxide dismutase,
catalase, and glutathione peroxidase, are abundant in youth However,
these levels decrease with age This decline can lead to mitochondrial
dysfunction Restoring antioxidant levels can promote a life of health and
longevity, as research has shown centenarians have higher antioxidant
levels in their blood, in comparison to their younger counterparts
N-Acetyl-L-Cysteine
N-Acetyl-L-Cysteine (NAC), also known as L-cysteine, is a sulfurcontaining amino acid that is vital to glutathione production By increasing
glutathione levels, NAC lessens the development of oxidative stress NAC’s
antioxidant activity has been shown to protect liver cells from oxidative
stress that can accumulate during exposure to arsenic, lead, and electric
fields NAC’s ability to increase glutathione production may be the reason
for its protective cellular effects
ANTIOXIDANT NUTRITION
Alpha Lipoic Acid
Alpha Lipoic Acid (ALA) is a “universal antioxidant”, as it is able to
protect the body from a wide range of free radicals It is a fat and watersoluble antioxidant, making it a protectant against water and lipid based
free radicals ALA deters the development of vascular oxidative stress
and inflammation that increase with age A combination of ALA and
acetyl-l-carnitine was given to aged rats, finding the nutrients reduced
mitochondrial decay that leads to accelerated aging Another study found
that ALA increased neurotransmitter levels in the brain, including serotonin,
dopamine, and norepinephrine The study concluded that ALA could be a
beneficial treatment for reducing oxidative stress in the central nervous
system
Pine Bark Extract
Pine bark extract is a rich source of procyanidin oligomers, which increase
antioxidant activity It improves glutathione levels and restores other
antioxidants, such as vitamins C and E Pine bark’s properties help to
reduce inflammation throughout the body Researchers gave 25 subjects
pine bark extract (150 mg/day) for six weeks finding the extract improved
antioxidant activity and cholesterol levels
Quercetin
Found in apples and onions, quercetin is a phytochemical with high
antioxidant activity that has been shown to benefit cardiovascular function
Quercetin can inhibit platelet aggregation and aid blood pressure levels,
as well as increase nitric oxide activity and improve endothelial function
Quercetin (150 mg/day) was given to 93 overweight subjects to determine
the effects on cardiovascular health Those taking the nutrient had a
reduction in systolic blood pressure and oxidized LDL cholesterol
CoQ10
Coenzyme Q10 is naturally produced in the body, but levels decline with
age This antioxidant is necessary for cellular health and energy production
It neutralizes free radicals and aids mitochondrial function CoQ10
deficiencies are related to a higher amount of oxidative stress, reactive
oxygen species, and cellular death CoQ10 was shown to reduce ECTONOX activity, an age-related indicator, in female subjects (45 to 55 years
old) taking CoQ10 supplements (180 mg/day) for 28 days A single dose of
CoQ10 (200 mg) increased CoQ10 levels and lowered oxidative stress in
the muscle of 22 aerobically-trained and 19 untrained subjects Similarly,
energy and workout capacity increased among subjects taking CoQ10 (200
mg/day) for fourteen-days
Resveratrol
Found in grapes and red wine, resveratrol is a potent antioxidant with
polyphenol compounds A higher intake of resveratrol has been associated
with an increase in nitric oxide activity and improvement in endothelial
function Resveratrol has also been shown to reduce inflammation and
oxidative stress, which can significantly benefit cardiovascular health
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150(1):57-83
Miquel J Can antioxidant diet supplementation protect against age-related
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Ames BN, Shigenaga MK, Hagen TM Oxidants, antioxidants, and the degenerative
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Montenegro MF, Neto-Neves EM, Dias-Junior CA, Ceron CS, et al Quercetin
restores plasma nitrite and nitroso species levels in renovascular hypertension
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Ames BN, Liu J Delaying the mitochondrial decay of aging with acetylcarnitine Ann
NY Acad Sci 2004 Nov; 1033:108-116
Morre DM, Morre DJ, Rehmus W, Kern D Supplementation with CoQ10 lowers
age-related (ar) NOX levels in healthy subjects Biofactors 2008; 32(1-4):221-230
Arivazhagan P, Panneerselvam C Neurochemical changes related to ageing in the rat
brain and the effect of DL-alpha-lipoic acid Exp Gerontol 2002 Dec; 37(12):14891494
Nuttall SL, Kendall MJ, Bombardelli E, Morazzoni P An evaluation of the
antioxidant activity of a standardized grape seed extract, Leucoselect J Clin Pharm
Ther 1998 Oct; 23(5):385-389
Bagchi D, Bagchi M, Stohs SJ, et al Free radicals and grape seed proanthocyanidin
extract: importance in human health and disease prevention Toxicology 2000 Aug 7;
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Olmedilla B, Granado F, Blanco I, Vaquero M Lutein, but not alpha-tocopherol,
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2-y double-blind, placebo-controlled pilot study Nutrition 2003 Jan; 19(1):21-24
Bagchi D, Ray SD, Patel D, Bagchi M Protection against drug- and chemical-induced
multiorgan toxicity by a novel IH636 grape seed proanthocyanidin extract Drugs Exp
Clin Res 2001; 27(1): 3-15
Perez VI, Bokov A, Van Remmen H, Mele J, et al Is the oxidative stress theory of
aging dead? Biochim Biophys Acta 2009 Oct; 1790(10):1005-1014
Quinzii CM, Lopez LC, Gilkerson RW, Dorado B, et al Reactive oxygen species,
oxidative stress, and cell death correlate with level of CoQ10 deficiency FASEB J
2010 Oct; 24(10):3733-3743
Beckman K, Ames B The free radical theory of aging matures Physiol Rev 1998;
78: 548-581
Bernstein PS, Zhao DY, Sharifzadeh M, Ermakov IV, Gellerman W Resonance Raman
measurement of macular carotenoids in the living human eye Arch Biochem Biophys
2004 Oct 15; 430(2):163-169
Borek C Antioxidants and radiation therapy J Nutr 2004 Nov; 134:3207S-3209S
Richer S, Stiles W, Statkute L, et al Double-masked, placebo-controlled, randomized
trial of Lutein and antioxidant supplementation in the intervention of atrophic
age-related macular degeneration: the Veterans LAST study (Lutein Antioxidant
Supplementation Trial) Optometry 2004 Apr; 75(4):216-230
Cooke M, Iosia M, Buford T, et al Effects of acute and 14-day coenzyme Q10
supplementation on exercise performance in both trained and untrained individuals J
Int Soc Sports Nutr 2008 Mar; 5:8
Rimbach G, Virgili F, Park YC, Packer L Effect of procyanidins from Pinus maritima
on glutathione levels in endothelial cells challenged by 3-morpholinosydnonimine or
activated macrophages Redox Rep 1999; 4(4): 171-177
De Magalhaes JP, Church GM Cells discover fire: employing reactive oxygen species
in development and consequences for aging Exp Gerontol 2006 Jan; 41(1):1-10
Rohdewald P A review of the French maritime pine bark extract (Pycnogenol), a
herbal medication with a diverse clinical pharmacology Int J Clin Pharmacol Ther
2002 Apr; 40(4): 158-168
Devaraj S, Vega-López S, Kaul N, et al Supplementation with a pine bark extract rich
in polyphenols increases plasma antioxidant capacity and alters the plasma lipoprotein
profile Lipids 2002 Oct; 37(10): 931-934
Sangeetha P, Balu M, Haripriya D, Panneerselvam C Age associated changes
in erythrocyte membrane surface charge: Modulatory role of grape seed
proanthocyanidins Exp Gerontol 2005 Oct; 40(10):820-828
Edwards RL, Lyon T, Litwin SE, Rabovsky A, et al Quercetin reduces blood pressure
in hypertensive subjects J Nutr 2007; 137(11):2405-2411
Santra A, Chowdhury A, Ghatak S, et al Arsenic induces apoptosis in mouse liver
is mitochondria dependent and is abrogated by N-acetylcysteine Toxicol Appl
Pharmacol 2007 Apr 15; 220(2): 146-155
Egert S, Bosy-Westphal A, Seiberl J, Kurbitz C, et al Quercetin reduces systolic blood
pressure and plasma oxidised low-density lipoprotein concentrations in overweight
subjects with a high-cardiovascular disease risk phenotype: a double-blinded, placebocontrolled cross-over study Br J Nutr 2009; 102(7):1065-1074
Singh KK Mitochondrial dysfunction is a common phenotype in aging and cancer
Ann NY Acad Sci 2004 Jun; 1019:260-264
Fisher-Posovszky P, Kukulus V, Tews D, Unterkircher T, et al Resveratrol regulates
human adipocyte number and function in a Sirt1-dependent manner Amer J of Clin
Nutr 2010; 92:5-15
Yedjou CG, Tchounwou PB N-acetyl-l-cysteine affords protection against leadinduced cytotoxicity and oxidative stress in human liver carcinoma (HepG2) cells
Int J Environ Res Public Health 2007 Jun; 4(2): 132-137
Ghanim H, Sia CL, Abuaysheh S, Korzeniewski K, et al An antiinflammatory and
reactive oxygen species suppressive effects of an extract of Polygonum cuspidatum
containing resveratrol J Clin Endocrin Metab 2010; 95(9):E1-E8
Guachalla LM, Rudolph KL ROS induced DNA damage and checkpoint responses:
influences on aging? Cell Cycle 2010 Oct 15; 9(20):4058-4060
Guler G, Turkozer Z, Tomruk A, Seyhan N The protective effects of N-acetyl-Lcysteine and Epigallocatechin-3-gallate on electric field-induced hepatic oxidative
stress Int J Radiat Biol 2008 Aug; 84(8): 669-680
Harman D Aging: Phenomena and theories Ann NY Acad Sci 1998; 854:1-7
Hubbard GP, Wolffram S, Lovegrove JA, Gibbins JM Ingestion of quercetin inhibits
platelet aggregation and essential components of the collagen-stimulated platelet
activation pathway in humans J Thromb Haemost 2004; 2(12):2138-2145
Johnson EJ, Hammond BR, Yeum KJ, et al Relation among serum and tissue
concentrations of lutein and zeaxanthin and macular pigment density Am J Clin Nutr
2000 Jun; 71(6):1555-1562
Li L, Smith A, Hagen TM, Frei B Vascular oxidative stress and inflammation increase
with age: ameliorating effects of alpha-lipoic acid supplementation Ann NY Acad Sci
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Mecocci P, Polidori MC, Troiano L, et al Plasma antioxidants and longevity: a study
on healthy centenarians Free Radic Biol Med 2000; 28(8):1243-1248
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Coenzyme Q10
AT A GLANCE
Introduction
Coenzyme Q10 is a fat-soluble compound that can be synthesized by the human body and hence cannot be
considered a vitamin. Coenzyme Q10 is a member of the ‘ubiquinone’ family, referring to the ubiquitous
presence of these compounds in living organisms. Coenzyme Q10 is also consumed in the diet.
Coenzyme Q10 is primarily found in the energy-producing center of the cell known as the ‘mitochondria’.
Therefore, the organs with the highest energy requirements, such as the heart and the liver, have the highest
coenzyme Q10 concentrations.
Health Functions
A sufficient intake of coenzyme Q10 (ubiquinone) is important as it helps the body to
•
•
convert energy from carbohydrates and fats to the form of energy used by the cells
protect, as an ‘antioxidant’, cells, tissues and organs against the damaging effects of free radicals,
believed to contribute to the aging process as well as the development of a number of health problems
including heart disease and cancer.
Disease Risk Reduction
Aging
As an antioxidant, coenzyme Q10 helps to neutralize harmful free radicals, which are one of the causes of
aging. Various factors, such as aging and stress, can lower the levels of coenzyme Q10 in the body and as a
result the ability of cells to withstand stress and regenerate declines. The levels of coenzyme Q10 in the body
almost inevitably decline with age.
In some animal studies, rodents treated with supplemental coenzyme Q10 lived longer than their untreated
counterparts. The effects of coenzyme Q10 supplements on human longevity remain unknown.
Heart disease
A symptom of many diseases involving the heart and blood vessels is atherosclerosis, the condition in which
an artery wall thickens as the result of a build-up of fatty materials such as cholesterol. As an antioxidant,
coenzyme Q10 can potentially inhibit damaging effects contributing to the development of atherosclerosis.
Coenzyme Q10 supplementation has shown promising effects in inhibiting atherosclerosis; more research is
needed to determine its role in disease prevention.
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Other Applications
Please note:
Any dietary or drug treatment with high-dosed micronutrients needs medical supervision.
Genetic mitochondrial disorders
Coenzyme Q10 supplementation has shown to be beneficial in individuals with inherited abnormalities in the
function of mitochondrial energy generation. In those rare patients with genetic defects in the body’s own
coenzyme Q10 production, supplementation has resulted in substantial improvement.
Heart disease
Research suggests that the beneficial effect of coenzyme Q10 in the prevention and treatment of heart
disease is mainly due to its ability to act as an antioxidant.
One clinical study, for example, found that people who received daily coenzyme Q10 supplements within
three days of a heart attack were significantly less likely to experience subsequent heart attacks and chest
pain. In addition, these same patients were less likely to die of heart disease than those who did not receive
the supplements.
Heart failure
Levels of coenzyme Q10 are low in people with congestive heart failure, a debilitating disease that occurs
when the heart is not able to pump blood effectively. This can cause blood to pool in parts of the body, such
as the lungs and legs.
Results from several clinical studies suggest that coenzyme Q10 supplements help to reduce swelling in the
legs, enhance breathing by reducing fluid in the lungs, and increase exercise capacity in people with heart
failure; other studies have not shown such effects.
High blood pressure
Several clinical studies involving small numbers of people suggest that coenzyme Q10 may lower blood
pressure.
More research with greater numbers of people is needed to assess the value of coenzyme Q10 in the
treatment of high blood pressure (‘hypertension’).
High cholesterol
Levels of coenzyme Q10 tend to be lower in people with high cholesterol compared to healthy individuals of
the same age. In addition, certain cholesterol-lowering drugs called ‘statins’ appear to deplete natural levels
of coenzyme Q10 in the body.
Taking coenzyme Q10 supplements has shown to correct the deficiency caused by statin medications without
affecting the medication's positive effects on cholesterol levels.
Heart surgery
Clinical research indicates that introducing coenzyme Q10 prior to heart surgery, including bypass surgery
and heart transplantation, can reduce damage caused by free radicals, strengthen heart function, and lower
the incidence of irregular heart beat (‘arrhythmias’) during the recovery phase.
Diabetes
High blood pressure, high cholesterol, and heart disease are all common problems associated with diabetes.
Research indicates that coenzyme Q10 supplements may improve heart health and blood sugar and may
help manage high cholesterol and high blood pressure in individuals with diabetes.
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Despite some concern that coenzyme Q10 may cause a sudden and dramatic drop in blood sugar
(‘hypoglycemia’), two clinical studies of people with diabetes given coenzyme Q10 showed no such adverse
effect. Thus, it has been concluded that coenzyme Q10 supplements could be used safely in diabetic patients
as adjunct therapy for cardiovascular diseases.
Parkinson’s disease
In Parkinson's disease, decreased activity of elements involved in energy production in mitochondria and
increased oxidative stress in a special part of the brain are thought to play a role. As part of the energyproducing process and antioxidant coenzyme Q10 might be beneficial in the treatment of Parkinson’s
disease.
A study in patients with early Parkinson's disease showed that supplementation with coenzyme Q10 was
associated with slower deterioration of brain function compared to placebo. These promising findings need to
be confirmed in larger clinical trials.
Breast cancer
Although a few case reports suggest that coenzyme Q10 supplementation may be beneficial as an additional
treatment to conventional therapy for breast cancer, the lack of controlled clinical trials makes it presently
impossible to determine the potential effects of coenzyme Q10 supplementation in cancer patients.
Periodontal (gum) disease
Gum disease is a widespread problem that is associated with swelling, bleeding, pain, and redness of the
gums. Clinical studies have reported that people with gum disease tend to have low levels of coenzyme Q10
in their gums.
In a few clinical studies involving small numbers of subjects, coenzyme Q10 supplements caused faster
healing and tissue repair.
Additional studies in humans are needed to evaluate the effectiveness of coenzyme Q10 when used together
with traditional therapy for periodontal disease.
Other disorders
Preliminary clinical studies also suggest that coenzyme Q10 may boost athletic performance, improve
immune function in individuals with immune deficiencies such as AIDS, improve symptoms of tinnitus, and
may be beneficial in cosmetics for healthy skin.
Intake Recommendations
Presently, health authorities have not established specific dietary intake recommendations for coenzyme
Q10.
Some researchers suggest daily doses of 30–200 mg coenzyme Q10 for adults 19 years and older.
As coenzyme Q10 is fat-soluble, it should be taken with a meal containing fat for optimal absorption.
Supply Situation
The average daily intake of coenzyme Q10 from food is estimated to be around 10 mg in several European
countries.
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Deficiency
It is generally assumed that with a varied diet, the body’s own production provides sufficient coenzyme Q10
for healthy individuals.
Decreased blood levels of coenzyme Q10 have been observed in individuals with diabetes, cancer, and
congestive heart failure, and in people taking lipid lowering medications (see Safety).
No coenzyme Q10 deficiency symptoms have been reported in the general population.
Sources
Primary dietary sources of coenzyme Q10 include oily fish (such as salmon and tuna), organ meats (such as
liver), and whole grains.
Safety
To date, there have been no reports of significant adverse side effects of coenzyme Q10 supplementation at
doses as high as 1,200 mg/day.
Some people have experienced gastrointestinal symptoms (e.g., nausea, diarrhea, appetite suppression,
and heartburn) when taking high doses of coenzyme Q10 supplements.
Because controlled safety studies in pregnant and breast-feeding women are not available, the use of
coenzyme Q10 supplements by such women should be avoided.
Drug interactions
Please note:
Because of the potential for interactions, dietary supplements should not be taken with medication without
first talking to an experienced healthcare provider.
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Coenzyme Q10 (CoQ10)
TRADE NAMES
       
      
        
 
DESCRIPTION
          
       
      
        
         
         
         
          
          
          
         
         
          
          
            
           
            
          
        
     
         
       
    
     
75
aging
 
           
        
         
    
ACTIONS AND PHARMACOLOGY
ACTIONS
      
 
MECHANISM OF ACTION
           
          
          
         
            
  
        
         
       
        
          
         
            
       
PHARMACOKINETICS
          
            
76
aging
           
            
             
           
          
    
           
       
            
            

INDICATIONS AND USAGE
        
           
           
          
         
            
       
            
  
RESEARCH SUMMARY
         
           
         
             
          
        
         
           
          
   
         
      
        
         
        
           
         

       
        
       
        
77
aging
          
          
           
       
        
          
    
          
         
         
           
       
          
        
    
        
       
      
          
           
        
           
   
           
        
          
          

           
       
     
        
CONTRAINDICATIONS, PRECAUTIONS, ADVERSE
REACTIONS
CONTRAINDICATIONS
 
WARNINGS AND PRECAUTIONS
          
        
78
aging
         
     
        
         
           
          
        
          

ADVERSE REACTIONS
       
        
    
INTERACTIONS
DRUGS
          

        
      
         
        
            

       

        
          
  
         
     
         
 
DOSAGE AND ADMINISTRATION
       
      
        
  
79
aging
            
         
             
           
    
            
       
          
HOW SUPPLIED
             
      
    

         
     
LITERATURE
          
        
 
           
           
     
         
      
      

        
      
      
        
         
    
            
  
80
aging
           
         

          
        
        
           
         
         

          
          
        
        
         
            
       
      
            
         

           
      
         
       
         
   
           
          
       
          
       
       

          
       
       
 
81
aging
          
          
   
          
         
  
         
       
          
       
          
     
       
           
       
     
         
       
 
        
  
         
        
       
         
       
     
          
         
  
          
        
  
         
      
82
aging
Q10
Indication principale : prévention des rides
ACTIF PUR A01
Synthèse bibliographique
4Nom INCI : UBIQUINONE
4Molécule pure à plus de 97%
obtenue par biotechnologie
Le Q10 également connu sous le nom de coenzyme Q10 ou encore sous le nom d’ubiquinone, est une substance similaire à une
vitamine.
Le Q10, naturellement présent dans la peau, est vital pour le bon fonctionnement du corps humain.
Cette molécule est présente dans la peau à l’état naturel pour protéger les lipides du sébum contre le stress oxydatif. Cependant,
la concentration intrinsèque de la peau en Q10 diminue considérablement avec l’âge, ce qui rend la peau plus sensible aux
attaques des UV notamment.
Le Q10 est l’un des rares antioxydants à être lipophiles.
Egalement très utilisé dans l’industrie pharmaceutique, le Q10 est efficace contre l’hypertension artérielle, l’insuffisance cardiaque,
la migraine, les maladies parodontales…
4MECANISMES D’ACTION / PREUVES D’EFFICACITE
Des études récentes in vitro et in vivo montrent que l’utilisation du Q10 serait efficace pour prévenir l’apparition des premiers signes
de l’âge.
Grâce à son action antiradicalaire, le Q10 protège les cellules et le tissu cutané vis-à-vis du stress oxydatif généré par une irradiation
UV [1]. Le Q10 permet également de protéger les constituants de la matrice dermique (collagène, élastine, acide hyaluronique…)
en limitant significativement l’expression de collagénases [1] et des MMP-1 (métalloprotéinases) [2]. De plus, il stimule la prolifération
des GAG (glycoaminoglycanes), aidant ainsi au maintien de la densité dermique [1].
En diminuant la synthèse de médiateurs pro-inflammatoires tel que l’IL-6, le Q10 apaise la peau [2]. Par ailleurs, il possède une action
énergisante en stimulant la glycolyse par accumulation de glucose dans les kératinocytes [3]. Enfin, les mêmes études montrent que
l’application régulière sur le long terme d’un produit contenant du Q10 permet de réduire la profondeur des rides [1].
4L’AVIS DE NOTRE EXPERT
Le Q10, encore appelé ubiquinone, est une molécule dérivée de la quinone. La présence d’une chaine latérale hydrophobe lui confère
une bonne affinité pour les structures lipophiles comme les membranes cellulaires. La forme réduite est l’ubiquinol. Les formes oxydées
et réduites sont alternativement régénérées dans les transferts électroniques nécessaires qui conduisent à la phosphorylation de l’ADP
en ATP (très énergétique).
Le coenzyme Q10 possède des caractéristiques d’anti-oxydant (maximum sous sa forme quinol). Il se trouve être un co-facteur
enzymatique absolument nécessaire dans des chaines métaboliques où il favorise des réactions d’oxydo-réduction grâce à sa structure
permettant la circulation d’électrons. C’est un élément indispensable au métabolisme énergétique.
Son taux semble diminuer avec l’âge et son apport exogène favoriserait le métabolisme cellulaire, tout en apportant une défense
anti-radicalaire. De nombreuses études, in vitro, montrent des effets sur la diminution des facteurs de dégradation du collagène
(collagénase et MMP).
Il est à noter que la prise de statine peut diminuer les quantités de Q10 synthétisé par l’organisme. Il n’y a toutefois pas à notre connaissance de corrélation établie avec des troubles dermatologiques.
Contrairement aux vitamines dont on doit assurer un apport exogène, le coenzyme Q10 est synthétisé à partir de la tyrosine et de la
chaine polyisoprénique. Ceci fait intervenir les enzymes du métabolisme du cholestérol. On peut penser que certaines compétitions
métaboliques et contrôles s’effectuent dans la peau.
La dose n’est pas établie clairement in vivo, on peut estimer que les besoins sont variables en fonction de l’âge. Nous ne pouvons que
conseiller la dose maximale, à notre connaissance, utilisée dans les études cliniques, soit 0,3%.
La large utilisation et communication sur cet actif en cosmétique devrait inciter les chercheurs en dermatologie à explorer encore plus
largement cette molécule.
e t a t p u r. c o m
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4DOSE EFFICACE
L’ensemble des publications et études scientifiques, les usages habituels de cet actif et l’avis de notre expert ont conclu à utiliser l’Actif
pur Q10 à la dose de 40 mg par flacon.
4REFERENCES BIBLIOGRAPHIQUES
[1] Coenzyme Q10, a cutaneous antioxidant and energizer. Hoppe U, Bergemann et al., Biofactors. 9(2-4):371-8. 1999.
[2] Mechanisms of inhibitory effects of CoQ10 on UVB-induced wrinkle formation in vitro and in vivo. Inui M et al., Biofactors. 32
(1-4):237-43. 2008.
[3] Aging skin is functionally anaerobic: importance of coenzyme Q10 for anti aging skin care. Prahl S et al , Biofactors. 32(1-4):245-55.
2008.
Ces informations sont données à titre informatif, elles ne sauraient en aucun cas constituer une information médicale, ni engager notre
responsabilité. La copie et la reproduction de ces documents ne peuvent être faites qu’à des fins exclusives d’information pour un
usage personnel et privé. Toute utilisation de copie ou reproduction utilisée à d’autres fins est expressément interdite et engagerait la
responsabilité de l’utilisateur au sens de l’article L 122-3 du Code de la Propriété Intellectuelle.
e t a t p u r. c o m
84
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■ Anti âge
Notre organisme en a besoin
La coenzyme Q10,
une des stars anti-âge!
Il y a quelques années,
cette molécule au nom
barbare faisait la une
des publicités de produits
cosmétiques, juste le temps
d’une campagne
de marketing.
Ce n’est en fait qu’avec l’apparition des
effets toxiques des statines (médicaments
contre le cholestérol) qu’elle a lentement
gagné le cœur des personnes soucieuses
de conserver la pleine possession de leurs
moyens tout en vivant plus longtemps: non
seulement, elle réduisait significativement
voire totalement leurs douleurs musculaires invalidantes, mais de plus, elle leur
redonnait un bon tonus et le sentiment de
rajeunir.
Malgré cela, cette molécule naturellement
produite par notre organisme, essentielle
par nombreuses de ses fonctions, reste
inconnue de la plupart des médecins,
«bien» formatés par l’industrie pharmaceutique.
Parmi ses innombrables
interventions, en voici
quelques-unes:
Quelques mots
de physiologie
Présente uniquement dans les membranes des cellules, elle transporte l’hydrogène
et facilite l’action de nombreuses enzymes,
notamment l’action de celles impliquées
dans la production d’énergie. Elle participe
ainsi à la régénération du tissu musculaire
et donc du premier d’entre eux, le cœur!
Puissant anti-oxydant, elle réduit la toxicité du fer et protège la structure de nombre
de molécules, notamment la vitamine E et
les lipides.
Également puissant anti-agrégant plaquettaire, elle diminue les risques de
caillots sanguins.
Les réserves de l’organisme avoisinent les
2 grammes. Chaque jour, le quart environ
en est renouvelé. Que ce cycle de régénération diminue et le vieillissement s’accélère.
La co-enzyme Q10 est également connue
sous les noms d’ubiquinone et d’ubidécarénone. C’est une substance grasse dont
la structure chimique est proche de celle
des vitamines E et K. Présente partout dans
l’organisme, elle est produite de façon
croissante jusqu’aux environs des 20 ans,
puis lentement, de moins en moins: A 50
ans, une personne en bonne santé et sans
antécédent notable en produit 25% de
moins que 30 ans plus tôt.
La coenzyme Q10 est indispensable au
fonctionnement de certaines enzymes. Sans
elle, de nombreuses réactions chimiques
seraient moins performantes.
Alternatif-Bien-être No66 ■ Décembre 2008, janvier, février 2009
85
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86
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■ Anti-âge
gue diminuent. Les traitements allopathiques retrouvent plus d’efficacité: la tension
artérielle s’abaisse un peu plus, les taux
sanguins de glucose et de triglycérides se
normalisent, le taux de HDL cholestérol (le
«bon») augmente. Associez au coenzyme
Q10 du sélénium pour son action sur le
muscle cardiaque.
La complémentation aurait des effets favorables quel que soit le stade de l’insuffisance cardiaque, même au stade terminal
dans l’attente d’une greffe cardiaque.
Dans la perspective d’une chirurgie cardiaque: à la dose de 100 mg/j pendant les
2 semaines qui précèdent l’intervention et
les 4 suivantes, la coenzyme Q10 améliore
considérablement le pronostic post-opératoire. La pompe cardiaque est améliorée,
le temps de récupération est sensiblement
raccourci et le nombre de complications est
également diminué.
Au cours de certaines maladies
métaboliques
Au cours du diabète, la coenzyme Q10
est souvent déficitaire, parfois de façon
sévère. Dans tous les cas, elle améliore
le métabolisme des sucres et facilite la
normalisation de la glycémie.
En cas de surpoids, une complémen-
tation à la dose de 100 mg par jour facilite la perte pondérale, et ce d’autant plus
qu’une activité physique est régulièrement
pratiquée.
Au cours de certaines myopathies
métaboliques liées à un déficit congénital
de production de la coenzyme Q10: la
prise conjuguée - d’abord à fortes doses
puis de façon moindre mais continue - de
coenzyme Q10 et de riboflavine (vitamine
B2) permet souvent de faire disparaître
complètement cette symptomatologie. La
posologie est dans ce cas du ressort strict
d’un médecin.
Au cours des parodontopathies, (ces
atteintes des gencives qui ont tendance
à durer malgré de nombreux traitements
locaux), une cure de 3 semaines associant
50 mg/j de coenzyme Q10 et 100 mg/j de
vitamine C (soit un comprimé d’acérola à
500 mg) permet d’obtenir une nette amélioration, voire la guérison des phénomènes
inflammatoires et dégénératifs qui touchent
les gencives et les autres tissus de soutien
de la dent.
Deux associations fortement recommandées
Coenzyme et oméga 3 à longue chaîne (EPA, DHA (4)) sont déficitaires chez les per-
sonnes qui présentent une hypertension artérielle, une dyslipidémie (trop de cholestérol
ou/et de triglycérides), un diabète ou une insuffisance coronarienne (angine de poitrine,
infarctus).
Il est donc judicieux que celles-ci prennent ces deux types de compléments, mais pas
sous une forme les réunissant dans une même capsule. En effet, la vitamine E est systématiquement associée aux omégas 3 pour les protéger du phénomène d’oxydation. Oxydée,
elle cherche alors à se régénérer, ce qu’elle fait si dans la même capsule, elle se trouve en
présence et aux dépens de la coenzyme Q10.
Coenzyme Q10 + magnésium au cours des affections cardiaques caractérisées par
des troubles du rythme cardiaque. Certes l’arythmie ne sera pas guérie, mais réduite. Ses
conséquences seront donc moins graves.
En prévention de l’éclampsie. Les
femmes enceintes dont les chiffres tensionnels s’élèvent au fil de la grossesse, sont
fortement exposées à ce type particulier
d’épilepsie. Leur taux de coenzyme Q10 est
significativement abaissé par rapport aux
autres femmes enceintes (2). Aussi, paraîtil justifié de complémenter toute femme
enceinte qui présente une hypertension,
une albuminurie ou un diabète. Dose entre
50 et 100 mg/j.
physiques que des capacités intellectuelles
et de l’humeur (3).
Anecdotique: au cours de la maladie
de Parkinson. Des posologies atteignant
(1) CF « Journal of American College of Cardiology
», 2008 ; 52 : pp. 1435-1441.
(2) E. Teran, M. Racines-Orbe, S. Vivero, C.
Escudero, G. Molina, A. Calle: « Preeclampsia is
associated with a decrease in plasma coenzyme
Q10 levels” in “Free Radic. Biol. Med”, 2003 (dec),
1;35 (11): 1453-1456. (Experimental Pharmacology
and Cellular Metabolism Unit, Biomedical Center,
Central University of Ecuador, Quito, Ecuador.
CE: HYPERLINK «mailto:[email protected]»
[email protected])
(3) CF ‘’Le Quotidien du Médecin’’, n° 7.198 du
15.10 2002, page 10.
(4) OGA3 concentré, DHA2.
1.200 mg/j ont été utilisées pendant 16
mois chez des personnes dont la maladie
s’était déclarée moins de 3 ans auparavant
et qui n’avaient pas encore reçu de levodopa. Les patients traités par 300 ou 600 mg/j
présentaient une tendance à l’amélioration.
Seules les personnes traitées par 1.200
mg/j montraient une amélioration significative tant au niveau des performances
Alternatif-Bien-être No66 ■ Décembre 2008, janvier, février 2009
87
Enfin en cosmétologie, un traitement
buccal ou/et percutané pendant 6 mois
réduit significativement la profondeur des
rides.
Dr Naïma Ananda Bauplé
[email protected]
Voir carnet d’adresses D.Plantes page 4
aging
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Natural Ingredients
Preparation and Properties of Coenzyme Q10 Nanoemulsions
Authors: Fred Zülli*, Esther Belser, Daniel Schmid, Christina Liechti and Franz Suter, Mibelle AG Biochemistry, CH
Abstract
Since every cell consumes energy and needs antioxidant
Coenzyme Q10 (CoQ10), also known as ubiquinone, is used
protection, CoQ10 is present in all cellular membranes of every
for energy production within cells and acts as an anti-oxidant.
single cell of the body. Caused by this ubiquitous presence in
Due to this dual function CoQ10 finds its application in
the body, as well as in the rest of nature, CoQ10 is also known
different commercial branches such as drugs, food supplements,
as ubiquinone. However, deficiencies of CoQ10 in the human
or cosmetics.
body have been reported to occur frequently. In addition, CoQ10
Since CoQ10 is highly lipophilic, the topical and oral
levels decline rapidly under stress or with advancing age. In
bioavailability is very low. Several attempts have been made
case of deficiency CoQ10 has to be supplemented to guarantee
to improve absorption. Latest technical developments reveal
the body’s energy production and its essential antioxidant
that encapsulation of CoQ10 in nanoemulsions results in a
protection. (1,2)
significantly enhanced bioavailability. In addition, multiple
Use of CoQ10 as a drug, food supplement
and cosmetic ingredient
nanoemulsions prepared according to a patented process even
allow the administration of several incompatible substances at
the same time.
Although CoQ10 can be synthesized in the human body, it can
happen that the body’s synthetic capacity is not sufficient to meet
This article gives an overview of current key developments of
the required amount of CoQ10. Cases of deficiencies of CoQ10
the encapsulation of CoQ10 in nanoemulsions. It highlights
are reported in a variety of diseases, e.g. cardiovascular disorders.
how encapsulation upgrades the bioavailability of CoQ10 and
A randomized, double-blind clinical trial assessing 49 patients
with this the efficacy of CoQ10. In addition, this article presents
who experienced cardiac arrest (heart attack or accident), revealed
latest in vitro tests demonstrating the influence of CoQ10 on
the synthesis of collagen I and on the activity of mitochondria
and their resistance against stress of dermal fibroblasts and
keratinocytes, respectively.
that after an immediate treatment with a CoQ10 nanoemulsion
such as described in this paper the survival rate increased more
than 100 % versus placebo after 90 days. (3) Beside these life
saving properties, CoQ10 also shows positive effects in migraine
Introduction
and Parkinson treatments. Latest clinical research resulted in
Everyone requires energy to live. This energy is produced by
an excellent positive effect on attack frequencies, headache
combustion of carbohydrates or fats with oxygen. However, the
days and days with nausea in migraine patients. (4) In different
use of oxygen will always also generate reactive oxygen species
research programs for Parkinson’s disease the efficacy of CoQ10
(ROS) which will damage the cells and therefore reduce the
is now under investigation. Further interest in CoQ10 application
activity of cells. This will cause a general ageing process of cells
was reported for gastric ulcer, muscle dystrophy, allergy and even
and the whole body. Thanks to a compound named coenzyme
cancer or AIDS. (1)
Q10 (CoQ10) the human body possesses a pivotal player in
energy synthesis. In mitochondria CoQ10 helps to build up
CoQ10 found its uses not only as a remedy but also as a food
adenosine triphosphate (ATP), the body’s major form of stored
supplement and a cosmetic. Since the synthesis of CoQ10 in the
energy. A second task of CoQ10 is the activity as an essential
body weakens in correlation with advancing age, daily dietary
regenerating antioxidant scavenging free radicals such as ROS.
supplementation provides the required compensation for energy
B
Cosmetic Science Technology 2006
89
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Natural Ingredients
and health. Additionally, poor nutritional habits or mental and
to modify the molecular structure or change the compositions
physical stress may render CoQ10 supplementation advisable
of the CoQ10 preparations to improve the bioavailability. As a
as well. (5) To give an example, the integrity of mitochondria is
matter of fact, the investigation of both structure modifications
essential for the health of cells and organs. Mitochondrial DNA
and delivery systems revealed that bioavailability of CoQ10 after
repeatedly undergoes mutations caused by oxidative stress. In
oral application can be significantly enhanced choosing a proper
comparison to nuclear DNA having a SOS DNA repair system,
formulation. (13,14)
the mitochondrial DNA has no effective repair system to fight
Modern research now shows that CoQ10 nanoemulsions
such mutations. Therefore, all mutations will accumulate during
strikingly improve the bioavailability of the substance after oral
time and reduce the vitality of the cell. Hence, CoQ10 is an
application. (15) Daily application of 300 mg of powdered
essential antioxidant for mitochondria to protect the integrity of
CoQ10 results only in a serum concentration of 1.8 µg/ml after
its own DNA as good as possible. (6)
16 months. Thanks to encapsulation into nanoemulsions, the
As a cosmetic ingredient CoQ10 mainly acts as an antioxidant
same daily dosage of CoQ10 enhanced serum concentration up
to protect the cells against the ageing process induced by free
to 5.2 µg/ml after only 6 weeks. (16,17)
radicals. Oxidative stress caused by free radicals or UV-irradiation
These nanoemulsions improve dermal bioavailability as well.
plays a significant role in skin ageing. UV radiation is known
It is known that encapsulation of drugs in nanoemulsions and
to induce the formation of reactive oxygen species which are
liposomes enhance the drugs' concentrations in the dermis
implicated as toxic intermediates in the development of photo-
compared to conventional formulations. (18) Figure 1 shows
ageing. (7) The antioxidant activity of CoQ10 prevents untimely
the penetration of nanoparticles (nanoemulsion droplets) into
skin ageing and photo-ageing by enhancing the resistance of the
the skin and the release of the encapsulated material (CoQ10)
skin and scavenging radicals. (8,9) A German research group
(Figure 1).
found that CoQ10 also suppresses collagenase, an enzyme
Features of nanoemulsions
which causes damage of the connective tissue of the skin. The
group additionally showed that CoQ10 is effective against UV
mediated oxidative stress. (10) Taken together, these findings
turn CoQ10 into a unique cosmetic substance which protects
the skin from early ageing, wrinkle formation and loss of
cell activity.
Chemistry and bioavailability of Q10, and the
principle of nanoemulsions
CoQ10 belongs to the group of quinones. It is composed of a
p-benzoquinone ring system and a polyisoprenoid side-chain.
The length of the side-chain is responsible for the lipophilicity
of the molecule. The side-chain in CoQ10 consists of ten
isoprene units. This makes the molecule highly lipophilic. (11)
Therefore CoQ10 can freely move within the cellular membranes.
Unfortunately, the bioavailability of CoQ10 is very low in the
intestines after oral application. (12)
Several attempts have been made in the last few years to improve
the intestinal absorption of CoQ10. Researchers either tried
Figure 1:
Schematic illustration of the penetration of nanoemulsion droplets into the
stratum corneum of the skin. After the release of the encapsulated material the
substances can penetrate into deeper layers of the skin.
C
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Natural Ingredients
Figure 2:
Structure of a nanoemulsion droplet. Phospholipids are arranged according
their lipophilicity in the border area of the liquid oil droplet
Nanoemulsions (also named nanoparticles) are oil-in-water
emulsions having a small droplet size (30 – 300 nm). Figure 2
illustrates the structure of a nanoemulsion droplet (figure 2).
Phospholipids build the border area of the droplet and separate
the oily phase from the aqueous phase. Figure 3 shows an
electron microscope picture of a nanoemulsion containing CoQ10
(figure 3). The oil droplets containing CoQ10 are dispersed in the
water phase and have a diameter of about 50 nm. The small size
of the droplets is achieved through high pressure homogenization.
(19) A notable advantage of a nanoemulsion is its outstanding
stability, even at high temperatures up to 120 ºC.
Figure 4:
Nanoemulsions containing CoQ10. 1: 7% CoQ10, 2: 0.7% CoQ10, 3: 0.07%
CoQ10. The droplet size of all preparations is around 50 nm.
Figure 3:
Particle size of Q10 nanoparticles (around 50 nm) visualized by a TEM
(transmission electron microscope).
Of special interest is also the preparation of transparent CoQ10
nanoemulsions. These preparations can be obtained if a droplet
Figure 5:
Correlation between particle size and transparency. 1: 54 nm, 2: 79 nm,
3: 90 nm, 4: 102 nm, 5: 116 nm, 6: 197 nm.
size of less than 60 nm can be achieved. This small droplet size
Nanoemulsions containing droplets above 100 nm look white
will no longer scatter the light. However, CoQ10 will still absorb
where as dispersions around 70 – 100 nm appear opaque and
light and therefore this preparation looks orange (figure 4).
below that become transparent (figure 5).
D
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Novel CoQ10 nanoemulsions
The use of nanoemulsions in cell culture systems offers new
In this article we will present a novel CoQ10 double nanoemulsion
opportunities. Due to the small size these nanodroplets are easily
with special properties manufactured according to a patented
absorbed by cells by means of endocytosis. This technique is
procedure. (20) The preparation consists of two different
described in the US patent US 6,265,180 B1 and can be applied
nanoemulsions. These individual nanoemulsions can now
as a novel nutritional delivery system in cell cultures. Several
contain lipophilic compounds which are not compatible with
studies revealed that nanoemulsions containing CoQ10 in cell
each other such as vitamin E and Coenzyme Q10 (figure 6)
cultures reduce the need for blood serum, enhance the growth
which will form a dark complex when mixed together.
rate of the cells, and increase the production of antibodies. In
one study the production of antibodies in hybridoma cells was
enhanced by 42%. (21)
Use of CoQ10 nanoemulsions in cosmetics
CoQ10 encapsulated in the described nanoemulsions increases
the synthesis of collagen I in fibroblasts. This effect was recently
shown using normal human dermal fibroblasts (NHDF) and a
CoQ10 nanoemulsion at a concentration of 0.1%. Cells first
were cultured at standard conditions without CoQ10 during
Figure 6:
Illustration of a multiple nanoemulsion containing two different inner phases.
The substances of the two inner phases are not compatible with each other.
24 hours. Then the CoQ10 nanoemulsion was added and cells
were incubated for 72 hours.
CoQ10 is obtained in its oxidized form and must therefore be
The effect of CoQ10 was evaluated by visualization of the
reduced in the cell to act as an antioxidant. To facilitate this
protein using a polyclonal antibody anti-collagen I and a
reaction the reducing capacity of the cell has to be enhanced by
fluorescent
adding vitamin E (natural tocopherol). The double nanoemulsion
Results were photographed applying microscopy observation.
containing CoQ10 and tocopherol in individual droplets is
The photographs show an increased secretion of collagen I
therefore a very smart solution to activate the cell vitality in an
compared to the control. (figure 7)
efficient manner. Since both individual nanoemulsions are based
second
antibody
anti-immunglobuline-FITC.
This result demonstrates that CoQ10 encapsulated in nanodroplets
on a droplet size of around 50 nm the mixed preparation is
positively influences the expression of collagen I by fibroblasts.
transparent and has a high bioavailability.
In a second in vitro assay the influence of CoQ10 on the activity
The preparation of nanosize oil droplets offers another feature
of mitochondrial dehydrogenase in keratinocytes was assessed.
to overcome a limitation of CoQ10. The solubility of CoQ10 in
Cells (human adult low calcium high temperature cells, HaCaT)
oil is quite low. However, the solubility is enhanced at elevated
temperature. We therefore prepared saturated CoQ10 solutions at
were cultured according to standard procedures and incubated
60 ºC and used these solutions to manufacture nanoemulsions
for 72 hours with 0.1% of a CoQ10 nanoemulsion. In a further
at the same temperature. Due to the small droplet size these
step cells were incubated with sodium dodecylsulfate (SDS,
saturated CoQ10 oil solutions remained solutions even after
2µg/ml) for 24 hours to stress the cells.
the temperature has been reduced to room temperature.
The mitochondrial dehydrogenase activity was analyzed using
These supersaturated CoQ10 nanoemulsions can be stored at
the MTT test. The application of the CoQ10 nanoemulsion
refrigerated temperatures for many months without crystallization
enhanced the activity of the unstressed keratinocytes to 116.8%
of CoQ10 and are therefore very interesting products for the
application in cosmetics, food supplements and cell culture
+/-3.2% compared to the control 100.0% +/-1.3%. The SDS
systems.
treatment decreased the cell activity to 67.1% +/-4.1%.
E
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Figure 7:
Comparison of collagen I secretion by fibroblasts after incubation with CoQ10 (left) and control (right).
Pre-treatment with encapsulated CoQ10 downsized the
Since CoQ10 has a low bioavailability, strong endeavours have
damageing effect of SDS and the cell activity analyzed by the
been made to develop efficient delivery systems. Latest research
MTT test only decreased to 80.2% +/-1.6%. (figure 8)
established the encapsulation of CoQ10 in nanoemulsions. Data
The assessment reveals that CoQ10 nanoemulsions enhance the
mitochondrial activity of keratinocytes and protect them against
using nanoemulsions. This results in much higher CoQ10 serum
levels after oral application which is of great importance for the
necrotic stress factors.
treatment of different diseases.
The application of CoQ10 has been further improved by the
140
p<0.01
p<0.01
development of novel CoQ10 double nanoemulsions containing
p<0.01
120
Dehydrogenase activity %
show that the CoQ10 bioavailability is significantly enhanced by
tocopherol and CoQ10 in individual nanodroplets. In addition the
100
CoQ10 concentration in these nanoemulsions could be increased
80
by the development of a supersaturated CoQ10 nanoemulsion.
60
Cell Culture studies based on skin fibroblasts and keratinocytes
40
using these novel CoQ10 nanoemulsions revealed that
20
encapsulated CoQ10 supports the secretion of collagen I and
0
CoQ10
control
SDS
SDS + CoQ10
stimulates the mitochondrial cell activity. In addition a significant
control
protection against necrotic stress factors could also be shown.
Figure 8:
Activity of dehydrogenase. Left: Influence of CoQ10 compared to control;
right: influence of CoQ10 on necrotic activity of SDS.
References
Summary
CoQ10 proved to be a unique substance providing different
possibilities of application. In medicine, CoQ10 is used for
prevention and therapy of a variety of diseases. In nutrition,
CoQ10 finds its advantages as a food supplement. And, as a
cosmetic, CoQ10 becomes an indispensable ingredient as an
antioxidant and protective agent preventing skin ageing and
photo-ageing.
F
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The role of coenzyme Q10 in clinical medicine: Part 1,
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2. Grane FL
Biochemical functions of coenzyme Q10
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3. Damian MS et al.
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Coenzyme Q10--its importance, properties and use in
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6. Wei YH et al.
Oxidative stress, mitochondrial DNA mutation, and impairment of antioxidant enzymes in ageing.
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Effects of coenzyme Q10 in early Parkinson disease: evidence of slowing of the functional decline.
Arch Neurol. 2002;59:1541-1550
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Bioavailability of Q10 as powder vs Q10 in nanoparticles
Publication in preparation
18. Mezel M
Biodisposition of liposome-encapsulated active ingredients
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in O. Braun-Falco, H. C. Korting, and H. I. Maibach, eds,
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Mibelle AG, EP 1 516 662 A1, Patentblatt 2005/12
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Nanoemulsions for delivering lipophilic substances
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Mibelle AG, US 6 265 180 B1, Jul. 24, 2001
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Primary Authors Biography
Dr. Zülli obtained Ph.D. in Biochemistry from the Swiss Federal
Institute of Technology Zürich. His studies focused on structure
function analysis of enzymes using methods based on molecular biology. He worked in a postdoctoral position at the Nestlé
Research Center in the development of efficient expression
systems of recombinant DNA in yeast.
He is presently Head of Mibelle AG Biochemistry, a business
unit of Mibelle AG Cosmetics, the largest producer of cosmetic
products in Switzerland. In this position he is responsible for
the development, production and sale of active ingredients for
skin care.
14. Kommuru TR et al.
Self-emulsifying drug delivery systems (SEDDS) of coenzyme Q10: formulation development and bioavailability
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Mitochondrion 7S (2007) S34 S40
www.elsevier.com/locate/mito
The importance of plasma membrane coenzyme Q in aging
and stress responses
Plácido Navas
a,*
, José Manuel Villalba b, Rafael de Cabo
c
a
Centro Andaluz de Biologı́a del Desarrollo, Universidad Pablo de Olavide-CSIC, 41013 Sevilla, Spain
Departamento de Biologı́a Celular, Fisiologı́a e Inmunologı́a, Universidad de Córdoba, 14071 Córdoba, Spain
Laboratory of Experimental Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224-6825, USA
b
c
Received 26 October 2006; received in revised form 26 January 2007; accepted 3 February 2007
Available online 16 March 2007
Abstract
The plasma membrane of eukaryotic cells is the limit to interact with the environment. This position implies receiving stress signals
that affects its components such as phospholipids. Inserted inside these components is coenzyme Q that is a redox compound acting as
antioxidant. Coenzyme Q is reduced by diverse dehydrogenase enzymes mainly NADH cytochrome b5 reductase and NAD(P)H:quinone
reductase 1. Reduced coenzyme Q can prevent lipid peroxidation chain reaction by itself or by reducing other antioxidants such as a
tocopherol and ascorbate. The group formed by antioxidants and the enzymes able to reduce coenzyme Q constitutes a plasma mem
brane redox system that is regulated by conditions that induce oxidative stress. Growth factor removal, ethidium bromide induced q
cells, and vitamin E deficiency are some of the conditions where both coenzyme Q and its reductases are increased in the plasma mem
brane. This antioxidant system in the plasma membrane has been observed to participate in the healthy aging induced by calorie restric
tion. Furthermore, coenzyme Q regulates the release of ceramide from sphingomyelin, which is concentrated in the plasma membrane.
This results from the non competitive inhibition of the neutral sphingomyelinase by coenzyme Q particularly by its reduced form. Coen
zyme Q in the plasma membrane is then the center of a complex antioxidant system preventing the accumulation of oxidative damage
and regulating the externally initiated ceramide signaling pathway.
2007 Elsevier B.V. and Mitochondria Research Society. All rights reserved.
Keywords: Coenzyme Q; Plasma membrane; Aging; Oxidative stress
can be driven either by the simultaneous transfer of two
electrons in a single step, or by two sequential steps of
one electron transfer through a partially reduced semiqui
none intermediate. These redox forms allow CoQ to act
as antioxidant but also as pro oxidant mainly through
the semiquinone intermediate (Nakamura and Hayashi,
1994).
CoQ is the only lipid antioxidant that is synthesized in
mammals by all cells, and its biosynthesis is a very complex
process which involves the participation of at least nine
gene products in all the species studied (Johnson et al.,
2005; Tzagoloff and Dieckmann, 1990). Most of the pro
teins encoded by these genes have not yet been purified
and the regulation of this biosynthesis pathway is still lar
gely unknown (Rodriguez Aguilera et al., 2003; Turunen
et al., 2004).
1. Introduction
Coenzyme Q or ubiquinone (CoQ) is constituted by a
benzoquinone ring and a lipid side chain constructed with
several isoprenoid units, the number of units being species
specific. Saccharomyces cerevisiae has six isoprene units
(CoQ6), Caenorhabditis elegans CoQ isoform contains nine
isoprenoid units (CoQ9), and mammalian species have dif
ferent proportions of CoQ9 and CoQ10. Redox functions of
CoQ are due to its ability to exchange two electrons in a
redox cycle between the oxidized (ubiquinone, CoQ) and
the reduced form (ubiquinol, CoQH2). This redox reaction
*
Corresponding author. Tel.: +34 95 434 9385; fax: +34 95 434 9376.
E-mail address: [email protected] (P. Navas).
1567-7249/$ - see front matter 2007 Elsevier B.V. and Mitochondria Research Society. All rights reserved.
doi:10.1016/j.mito.2007.02.010
95
aging
P. Navas et al. / Mitochondrion 7S (2007) S34 S40
CoQ transports electrons from mitochondrial respira
tory chain complexes I and II to complex III and acts as
antioxidant as well (Crane and Navas, 1997; Turunen
et al., 2004). In addition, it functions as a cofactor for
uncoupling proteins (Echtay et al., 2000), regulates the per
meability transition pore opening (Fontaine et al., 1998),
and it is required for the biosynthesis of pyrimidine nucle
otides because it is the natural substrate of dihydroorotate
dehydrogenase, an enzyme located at the inner mitochon
drial membrane (Jones, 1980). CoQ also enhances survival
of chemotherapy treated cells (Brea Calvo et al., 2006) and
is required for the stabilization of complex III in mitochon
dria (Santos Ocana et al., 2002). Since the application of
the two phase partition method to isolate high purity
plasma membrane fractions from mammal cells (Navas
et al., 1989), it was confirmed that CoQ is present in all
the cellular membranes including plasma membrane
(Kalen et al., 1987; Mollinedo and Schneider, 1984). The
presence of CoQ in non mitochondrial membranes sug
gests not only an important role for CoQ in each mem
brane but also the existence of specific mechanisms for its
distribution since the final reactions of CoQ biosynthesis
pathway are located exclusively at the mitochondria in
yeast (Jonassen and Clarke, 2000) and mammal cells (Fer
nandez Ayala et al., 2005). CoQ is then driven to the
plasma membrane by the brefeldin A sensitive endomem
brane pathway (Fernandez Ayala et al., 2005).
CoQ contributes to stabilize the plasma membrane,
regenerates antioxidants such as ascorbate and a tocoph
erol, and regulates the extracellulary induced ceramide
dependent apoptosis pathway (Arroyo et al., 2004; Kagan
et al., 1996; Navas and Villalba, 2004; Turunen et al.,
2004). NAD(P)H dependent reductases act at the plasma
membrane to regenerate CoQH2, contributing to maintain
its antioxidant properties (Navas et al., 2005). As a whole,
both CoQ and its reductases constitute a trans plasma
membrane antioxidant system responsible of the above
described functions (Villalba et al., 1998).
This review will focus on the functions of CoQ and its
reductases in the plasma membrane, and its regulation
under aging and stress conditions. We will also emphasize
on the role of plasma membrane CoQ in the regulation of
stress induced apoptosis.
S35
signal of its free radical (Kagan et al., 1998). An inter
change of electrons could be possible between CoQ and
other redox compounds such as ascorbate (Roginsky
et al., 1998), DHLA (Nohl et al., 1997) and superoxide
(Kagan et al., 1998) leading to regenerate CoQH2, but
the major source of electrons comes from different
NAD(P)H dehydrogenases (Beyer et al., 1996; Nakamura
and Hayashi, 1994; Navarro et al., 1995; Takahashi
et al., 1996). It has been demonstrated that the incubation
of liver plasma membranes with NADH increases CoQH2
levels with the concomitant decrease in oxidized CoQ
(Arroyo et al., 1998), which acts through semiquinone rad
icals and also recycles vitamin E homologue in a superox
ide dependent reaction (Kagan et al., 1998). CoQ, but not
the intermediate form of CoQ biosynthesis, is also reduced
by NADH dependent dehydrogenases in plasma mem
brane of C. elegans (Arroyo et al., 2006).
Several enzymes have been reported to function as CoQ
reductases. These include the NADH cytochrome b5 reduc
tase (Constantinescu et al., 1994) (Navarro et al., 1995;
Villalba et al., 1995) and NADPH cytochrome P450 reduc
tase (Kagan et al., 1996), which are one electron CoQ
reductases (Nakamura and Hayashi, 1994); and
NAD(P)H:quinone reductase 1 (NQO1, formerly DT
diaphorase) (Beyer et al., 1996; Landi et al., 1997) and a
distinct NADPH CoQ reductase that is separate from
NQO1 (Takahashi et al., 1992, 1996), which are cytosolic
two electron CoQ reductases.
Both NADH cytochrome b5 reductase and NQO1 were
demonstrated to act at the plasma membrane to reduce
CoQ (De Cabo et al., 2004; Navarro et al., 1995). The
NADH cytochrome b5 reductase has been found in the
cytosolic side of the plasma membrane, where it is attached
through a myristic acid and a hydrophobic stretch of
aminoacids located at its N terminus (Borgese et al.,
1982; Navarro et al., 1995). As a CoQ reductase, the solu
bilized enzyme displays maximal activity with CoQ0, a
CoQ analogue which lacks the isoprenoid tail, whereas
reduction of CoQ10 requires reconstitution into phospho
lipids (Arroyo et al., 1998, 2004; Navarro et al., 1995).
NQO1 catalyses the reduction of CoQ to CoQH2 through
a two electron reaction (Ernster et al., 1962). This enzyme
is mostly located in the cytosol with a minor portion asso
ciated to the membranes, including plasma membrane,
where has been recognized to be of importance to maintain
the antioxidant capacity of membranes (Navarro et al.,
1998; Olsson et al., 1993). It has been shown that this
enzyme can generate and maintain the reduced state of
ubiquinones such as CoQ9 and CoQ10 in membrane sys
tems and liposomes, thereby promoting their antioxidant
function (Beyer et al., 1996; Landi et al., 1997).
These two enzymes would contribute to the trans
plasma membrane redox system providing the electrons
that are required to maintain its antioxidant properties
(Villalba et al., 1998). NADH ascorbate free radical reduc
tase, a trans oriented activity shows a strong dependency
on the CoQ status of liver plasma membrane (Arroyo
2. The antioxidant system of the plasma membrane
2.1. CoQ is reduced at the plasma membrane by NAD(P)H
oxidoreductases
The plasma membrane delimites the cell and different
insults from the environment, like oxidative stress, can
attack this structure. Diverse antioxidants are protecting
the cell under these conditions, particularly ascorbate at
the hydrophilic cell surface and both CoQ and a tocoph
erol in the hydrophobic phospholipid bilayer. The analysis
of CoQ at the plasma membrane has shown that both its
reduced and oxidized forms can be detected, and also the
96
aging
S36
et al., 2004) and NQO1 also contribute to the plasma mem
brane antioxidant system in different conditions such as
oxidative stress and aging (De Cabo et al., 2004, 2006;
López Lluch et al., 2005). The yeast model shows a high
level of analogies with mammalian systems (Steinmetz
et al., 2002) allowing a genetic evidence of CoQ participa
tion in plasma membrane redox activities that it is more
difficult to assess in mammal cells. The COQ3 gene of S.
cerevisiae encodes for a methyl transferase in CoQ biosyn
thesis pathway, and yeasts harboring a COQ3 gene deletion
(coq3D) do not synthesize CoQ (Clarke et al., 1991). Yeast
mutants coq3D displayed a significant decrease of NADH
ascorbate free radical reductase activity at the plasma
membrane, and its full restoration was achieved when
mutant cells were cultured either in presence of exogenous
CoQ, or when transformed with a plasmid harboring the
wild type COQ3 gene (Santos Ocaña et al., 1998).
Based on these results it is possible to scheme a plasma
membrane containing a trans membrane electron transport
system (Fig. 1) that drives electrons either from NADH
ascorbate free radical reductase, NQO1 or both to CoQ,
which follows a cycle to CoQH2 through the semiquinone
radical. This compound is then able to recycle other antiox
idants such as ascorbate and a tocopherol. Both CoQH2
and a tocopherol also prevent lipid peroxidation chain
reaction.
brane resulting in enhanced trans membrane redox activity
(Gómez Dı́az et al., 1997). Trans plasma membrane redox
system is then increased to reoxidize cytosolic NADH and
to export reducing equivalents to external acceptors, main
taining the NAD+/NADH ratio (Martinus et al., 1993),
which is important to guarantee the genome stabilization
through sirtuins (Sauve et al., 2006). This adaptation could
be thus considered as a general response of eukaryotic cells
to impaired mitochondrial function in order to regulate
cytosolic NAD+/NADH levels (Larm et al., 1994). A sim
ilar interpretation would be considered for the improve
ment of both plasma membrane antioxidant system (De
Cabo et al., 2004; Hyun et al., 2006a) and mitochondria
efficiency (Lopez Lluch et al., 2006) induced by caloric
restriction, a nutritional model that extends life span by
inducing sirtuins (Cohen et al., 2004).
CoQH2 protects membrane lipids from peroxidation
either directly or through the regeneration of a tocopherol
and ascorbate. However, CoQ is synthesized in all animal
species and it is possible to postulate a regulatory pathway
for CoQH2 in order to provide an antioxidant protection
of the cell. The oxidative stress induced by camptothecin in
mammal cells increase CoQ biosynthesis to prevent cell
death (Brea Calvo et al., 2006), as it was observed under sev
eral kinds of oxidative stress (Turunen et al., 2004), suggest
ing that it represents an adaptation rather than the cause of
the stress. According to this idea, enhanced biosynthesis of
CoQ and/or CoQ reductases could be responses evoked by
cells for protection against oxidative stress.
Mammals can not synthesize a tocopherol (vitamin E)
and require Se. A severe chronic oxidative stress can be
provoked by feeding rats with diets deficient in both nutri
ents (Hafeman and Hoekstra, 1977). After 3 weeks of defi
cient diet consumption, animals show markedly reduced
levels of a tocopherol in tissues, and display a dramatically
increased Ca2+ independent phospholipase A2 activity
(PLA2), which may play a protective role in cells leading
to increased metabolism of fatty acid hydroperoxides
(Kuo et al., 1995).
2.2. Oxidative stress modulates the CoQ dependent
antioxidant system of plasma membrane
The transfer of CoQ to the plasma membrane is an
active process that depends on the endomembrane system
after its biosynthesis in mitochondria (Fernandez Ayala
et al., 2005). It is interesting then to explore the mecha
nisms involved in the incorporation of CoQ in the plasma
membrane.
The impairment of mitochondrial function with ethi
dium bromide, which causes mitochondria deficient q
cells, induces an increase of CoQ levels at the plasma mem
Fig. 1. An scheme of the plasma membrane redox system. It involves an antioxidant system and its role on the sphingomyelinase regulation.
Abbreviations: n-SMase, neutral-sphingomyelinase; NQO1, NAD(P)H:quinone reductase 1.
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aging
Using this approach, an increase in both CoQ9 and
CoQ10 in liver plasma membranes was observed when a
tocopherol and selenium had reached minimum levels
(Navarro et al., 1998, 1999). CoQ increase at the plasma
membrane may be the result of enhanced biosynthesis
and/or translocation from intracellular reservoirs such as
the endoplasmic reticulum and mitochondria. These results
would be supported because lower levels of total CoQ have
been found in heart mitochondria isolated from vitamin E
deficient and vitamin E and Se deficient rats (Scholz et al.,
1997). An increase of CoQ biosynthesis under vitamin E
and Se deficiency might be not enough to compensate for
its accelerated consumption by oxidative degradation in
the heart, an organ with high demand for CoQ utilization
in oxidative metabolism. A transitional effect was observed
when rats were submitted only to vitamin E deficiency,
showing a milder adaptation to oxidative stress where anti
oxidants were induced earlier than the phospholipases (De
Cabo et al., 2006).
Consistent with higher CoQ levels, deficiency was
accompanied by a twofold increase in redox activities asso
ciated with trans plasma membrane electron transport such
as NQO1 and ascorbate free radical reductase (De Cabo
et al., 2006; Navarro et al., 1998). NQO1 was also
increased in liver of rats fed with a diet deficient in selenium
(Olsson et al., 1993), and it has been also shown that the
expression of the NQO1 gene was induced in rat liver after
7 weeks of consuming a vitamin E and selenium deficient
diet (Fischer et al., 2001). However, the increase of CoQ
and NADH cytochrome b5 reductase was earlier than
NQO1 translocation to the plasma membrane indicating
a timing of events leading to protect cells from oxidative
stress (De Cabo et al., 2006). This is apparently a general
aspect of response to endogenous oxidative stress (Bello
et al., 2005b). Although the mechanisms involved in regu
lating the changes of CoQ concentration in the plasma
membrane, and also the accumulation of its reductases
are still elusive, it is postulated that the activation of
stress dependent signaling pathways such as mitochondrial
retrograde signals would be involved.
S37
of docosahexaenoic acid to arachidonic acid are accompa
nied by a decrease in fluidity of the plasma membrane in aged
rats (Hashimoto et al., 2001). These findings support the
hypothesis that alteration of membranes by oxidative dam
age to their structural basic molecules, lipids and proteins,
can be involved in the basic biology of aging.
Rats fed with a diet enriched with polyunsaturated fatty
acids (PUFAn 6) and supplemented with CoQ10 show an
increased life span compared to those fed without the sup
plementation (Quiles et al., 2004). In these conditions,
CoQ10 was increased in plasma membrane at every time
point compared to control rats fed on a PUFAn 6 alone
diet. Also, ratios of CoQ9 to CoQ10 were significantly lower
in liver plasma membranes of CoQ10 supplemented ani
mals (Bello et al., 2005a). These results clearly support
the role of both CoQ and its content in plasma membrane
in the regulation of aging process.
Data from our laboratories and others, provide support
that the plasma membrane redox system is, at least in part,
responsible of the maintenance of the antioxidant capacity
during oxidative stress challenges induced by the diet and
aging. The up regulation of the plasma membrane redox
system that occurs during CR decreases the levels of oxida
tive stress in aged membranes (De Cabo et al., 2004; Hyun
et al., 2006b; López Lluch et al., 2005). CR is the only reli
able experimental model to extend life span in several
mammalian models (Heilbronn and Ravussin, 2003;
Ingram et al., 2006). CR extends life span of yeasts by
decreasing NADH levels (Lin et al., 2004), which would
connect this intervention to plasma membrane NADH
dependent dehydrogenases. CR modifies composition of
fatty acid in the plasma membrane, resulting in decreased
oxidative damage including lipid peroxidation (Yu, 2005;
Zheng et al., 2005). More importantly, plasma membrane
redox activities and also the content of CoQ, which decline
with age, are enhanced by CR providing protection to
phospholipids and preventing the lipid peroxidation reac
tion progression (De Cabo et al., 2004; Hyun et al.,
2006b; López Lluch et al., 2005).
3. CoQ participates in the regulation of apoptosis
2.3. The antioxidant system of plasma membrane is
associated to aging process
3.1. CoQ of the plasma membrane prevent stress induced
apoptosis
There are a number of the key players on the plasma mem
brane that are affected by aging and age associated diseases.
The levels of antioxidants a tocopherol and CoQ are
decreased with age and elderly non insulin dependent diabe
tes mellitus (NIDDM) patients, suggesting that the patho
genesis of NIDDM could be associated with the
impairment of an electron transfer mechanism by the plasma
membrane redox system (Yanagawa et al., 2001). Oxidative
damage to plasma membrane phospholipids in rat hepato
cytes and brain increases with age and is retarded by caloric
restriction (CR) (De Cabo et al., 2004; Hayashi and Miyaz
awa, 1998; Hyun et al., 2006b; López Lluch et al., 2005).
Increased levels of lipid peroxidation and decreased ratio
The supplementation of mammal cells cultures with CoQ
increases its concentration at the plasma membrane (Fer
nandez Ayala et al., 2005), and also enhances cell growth
(Crane et al., 1995). Also, molecular mechanisms that
increase cell growth also increase trans plasma membrane
reductases (Crowe et al., 1993), most of them depending on
the CoQ concentration in this membrane, as explained
above.
Since the maintenance of cell population depends on the
equilibrium among proliferation and cell death, it is impor
tant to understand the mechanisms that regulate cell sur
vival. Hormones and growth factors are required to
98
aging
S38
prevent apoptosis that occurs with a mild oxidative stress
(Ishizaki et al., 1995; Slater et al., 1995), and an increase
of peroxidation levels in membranes (Barroso et al.,
1997a; Ishizaki et al., 1995; Raff, 1992). As expected, the
supplementation of cell cultures with various antioxidants
in the absence of serum results in the protection against cell
death (Barroso et al., 1997a,b). Steady state levels of intra
cellular reactive oxygen species are significantly elevated in
cells with low CoQ levels, particularly under serum free
conditions. These effects can be ameliorated by restoration
with exogenous CoQ, indicating the major role of CoQ in
the control of oxidative stress in animal cells (Gonzalez
Aragon et al., 2005).
Plasma membrane can be also a source of reactive oxy
gen species through the transport of electrons in the trans
membrane system (Hekimi and Guarente, 2003), which can
be increased by antagonists of CoQ such as short chain
ubiquinone analogues and capsaicin that trigger apoptotic
program starting at the plasma membrane (Macho et al.,
1999; Wolvetang et al., 1996). This activity is different from
the plasma membrane NAD(P)H oxidase of some cells
such as neutrophils because it is currently accepted that this
enzyme does not produce oxygen free radicals. The oxidase
pumps electrons into the phagocytic vacuole, thereby
inducing a charge across the membrane that must be com
pensated. The movement of compensating ions produces
conditions in the vacuole conducive to microbial killing
(Segal, 2005). CoQ is involved not only in the prevention
of lipid peroxidation progression but also in recycling other
antioxidants as indicated above. However, cells showing a
higher concentration of CoQ in the plasma membrane
(Gómez Dı́az et al., 1997) were more resistant to serum
removal oxidative stress mediated apoptosis and accumu
lated lower levels of ceramide (Barroso et al., 1997b; Navas
et al., 2002). We proceed then to analyze the role of CoQ of
the plasma membrane in the ceramide signaling pathway.
in the regulation of the n SMase in vivo. The inhibition of
n SMase in the plasma membrane is carried out more effi
ciently by CoQH2, and also depends on the length of the
isoprenoid side chain (Martin et al., 2002) If the inhibition
of plasma membrane n SMase by ubiquinol has physiolog
ical significance, then endogenous levels of ubiquinol
should also exert this regulatory action. Moreover, since
endogenous CoQ can be reduced in plasma membrane by
the intrinsic trans membrane redox system, the activity of
plasma membrane NAD(P)H dependent dehydrogenases
should also modulate the activity of n SMase. This func
tion of CoQ occurs at the initiation phase of apoptosis
by preventing the activation of the n SMase in the plasma
membrane through the direct inhibition of this enzyme
and, as a consequence, the prevention of caspase activation
(Navas et al., 2002). Fig. 1 shows not only the antioxidant
function of CoQ and its reductases in the plasma mem
brane but also indicates the role of CoQ/CoQH2, and
probably lipid peroxides, in regulating the neutral
sphingomyelinase.
Interestingly, different experimental studies have indi
cated that the exogenous treatment with CoQ stimulates
the immune response (Bentinger et al., 2003). This latter
effect and the inhibition of n SMase by CoQ are factors
to be considered that could be related to its beneficial
effects on cells and organisms, beyond its participation in
mitochondrial energy production or as antioxidant.
4. Conclusions and future directions
The plasma membrane redox system is important in cel
lular life because it prevents membrane damage but also reg
ulates the apoptosis signaling that starts at this membrane.
It is currently known that this system responds to different
type of stress increasing the concentration in the plasma
membrane by new biosynthesis or translocation from the
cytosol. More precisely, the study of biosynthesis regulation
of both cytochrome b5 reductase and NQO1, and its loca
tion to the plasma membrane is very important because is
an essential enzyme not only for mammals but also to all
eukaryotes. It is then important to analyze the signaling
pathways responsible in the regulation of the plasma mem
brane redox system, and particularly its connection to mito
chondria, where coenzyme Q is particularly involved.
3.2. CoQ inhibits neutral sphingomyelinase of the plasma
membrane
The activation of a Mg2+ dependent neutral sphingo
myelinase (n SMase) located at the plasma membrane has
been recognized as one of the initial signaling events that
take place during apoptosis induced by growth factors
withdrawal (Jayadev et al., 1995; Liu and Anderson,
1995). Serum deprivation induces a progressive increase
of ceramide levels, which is then able to induce cell death
after its intracellular accumulation (Barroso et al., 1997b;
Jayadev et al., 1995; Obeid et al., 1993). These compounds
then activate caspases, the general executioners of apopto
sis (Navas et al., 2002; Wolf and Green, 1999).
Mg2+ dependent n SMase was purified from plasma
membrane showing that is highly inhibited by CoQ0, an
isoprenoid free ubiquinone. This enzyme was also observed
to be inhibited by CoQ10 in plasma membrane from pig
liver through a non competitive mechanism (Martin
et al., 2001). These results suggest that CoQ may play a role
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101
102
 Health Trust Alliance, Inc. 2000
Asendin, Elavil, Etrafon, Norpramin, Pamelor,
Sinequan, Tofranil
Tricyclic Antidepressants:
Navane, Mellaril, Prolixin, Thorazine
Lipitor
L-Dopa
Lovastatin
Major Tranquilizers:
Lescol, Mevacor, Pravachol, Zocor
Cholesterol Lowering Drugs:
Diazoxide, Propranolol, Metoprolol,
Hydrochlorothiazide, Hydralazine, Clonidine
Blood Pressure Medications:
Inderal, Lopressor, Tenormin, Visken
Beta Blockers:
Diabeta, Glynase, Tolinase, Micronase, Dymmelor
Adriamycin
Anti-Diabetic Drugs:
For more information on CoQ10, go to www.life-span.com
Alzheimer's disease
Asthma
Candidiasis
Chronic fatigue syndrome
Congestive heart failure/dilated cardiomyopathy
• Angina pectoris (chest pain due to heart disease)
• Atherosclerosis
• Coronary bypass surgery/heart surgery
• Mitral valve prolapse
Elevated total & LDL cholesterol
Heart disease
High blood pressure
HIV/AIDS
Hormone-dependent cancers (breast cancer, e.g.)
Insulin resistance, which is often associated with:
• adult-onset diabetes/elevated fasting blood sugar
• abdominal/central obesity
• high blood pressure
• elevated serum cholesterol and triglycerides
• heart disease
• sleep apnea
• polycystic ovary disease
• certain hormone-dependent cancers
Kearns-Sayre syndrome (a chronic progressive ophthalmoplegia
beginning in childhood, associated with short stature, hearing
loss, and heart conduction defects)
Leukemia (animal studies)
Male Infertility
Mitochondrial encephalomyopathy
Multiple sclerosis
Muscular dystrophy
Ophthalmoplegia (paralysis of some or all eye muscles)
Parkinson's disease
Periodontal disease
• Gingivitis
• Periodontitis
• Tooth loss
• Gum and tooth pain
• Tooth abscess
Aging
B12, C, &/or selenium deficiency, e.g.)
Bleeding of the gums with light brushing or probing.
Chronic gum disease (gingivitis, periodontitis)
Chronic intense exercise
Congestive heart failure
Coronary artery disease
Elevated cholesterol
Heart disease & heart surgery
High animal protein diet
High blood pressure (essential, systolic &/or
diastolic)
HIV/AIDS
Hormone dependent cancers (breast cancer, e.g.)
Low dietary intake of vegetables
Nutrient deficient diet (B2, B3, B5, B6, folic acid,
Poor or slow healing of diseased gums.
Swollen &/or infected gums.
Type 2 diabetes, insulin resistance
Use of anti-hypertensive medications (see list below)
Prescription
Medications
p
Me catio That May
M Increase
I
Risk
Deficiency
is of
o CoQ10
Co
f e
Medical Conditions Associated
A so
d with
Low
o Serum or
o Tissue Levels
L e of
o CoQ10
Q 0
Major
Majo Risk Factors Associated
with CoQ10
Deficiency
Co
n
Diets high in animal protein, low in vegetables
Diets deficient in riboflavin (vitamin B2), niacin (B3),
pantothenic acid (B5) pyridoxine (B6), folic acid, B12,
vitamin C &/or trace minerals such as selenium.
Diets
ts That Increase Riskk of CoQ10
1 Deficiency
n
Angina (severe chest pain, crushing chest pressure, e.g.)
Chronic coughing, wheezing, chest tightness
Chronic fatigue, lack of energy and vitality
Elevated blood sugar & insulin levels (insulin resistance,
type 2 diabetes--often associated with high blood
pressure, elevated cholesterol & triglycerides,
sleep apnea, & obesity)
Elevated cholesterol
Heart disease, scheduled for heart surgery
High blood pressure, systolic &/or diastolic
HIV infection/AIDS
Muscle weakness
Periodontal Disease:
• Gingivitis: Bleeding gums, gums that bleed with
light brushing or probing, swollen gums, reddened
gums
• Periodontitis: Bleeding and pus with probing at the
gum-tooth margins, chronic inflammation of gums,
infection, often with abscess formation, premature
loss of permanent teeth
• Diseased gums slow to heal
• Chronic dental and gum pain
Poor muscle work tolerance (early muscle exhaustion
with heavier or more intense workloads)
Progressive muscle weakness with seizures
Selenium deficiency
Shortness of breath, difficulty breathing at rest
Vitamin deficiencies (C, B2, B3, B5, B6, folic acid &or
B12
CoQ10
Deficiency
Co
Warning
Signs
n
n & Symptoms
m
“…topical application of CoQ10 improves adult periodontitis not only as a sole treatment but also in combination with traditional nonsurgical periodontal therapy.”36
“Treatment of periodontitis with CoEnyme Q10 [was so ‘extraordinarily effective’ that it] should be considered as adjunctive treatment with current dental practice.”35
COENZYME Q10 (COQ10) DEFICIENCY & RISK FACTORS
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35. Wilkinson EG et al. Bioenergetics in clinical medicine. II. Adjunctive treatment with coenzyme
Q in periodontal therapy. Res Commun Chem Pathol Pharmacol, 1975 September;
volume 12:1: pages 111-123.
36. Hanioka T; Folkers K et al. Department of Preventive Dentistry, Osaka University Faculty of
Dentistry, Japan. Effect of topical application of coenzyme Q10 on adult periodontitis. Mol
Aspects Med 1994; volume 15 Suppl: pages s241-248.
COENZYME Q10 (COQ10) DEFICIENCY & RISK FACTORS
SCIENTIFIC REFERENCES
aging
aging
NUTRITION – SANT�E
� re
� bral
Vitamine A et vieillissement ce
V�eronique PALLET
�rie ENDERLIN
Vale
UMR 1286, Nutrition and Integrative
Neurobiology, Inra Universit�e de
Bordeaux F 33076 France
<[email protected]>
Abstract: To date, convergent data on the role of retinoic acid in the mature brain have
established that this molecule, which acts as a hormone, helps to preserve cerebral
plasticity by controlling dendritic spine density as well as hippocampal neurogenesis.
Deterioration in cerebral plasticity seems to be at the base of the cognitive decline
disease. Furthermore, the transcription of several genes, known as muted, in Alzheimer’s
patients and whose transcripts are involved in the formation of senile plaques, are
controlled by retinoic acid. As seen in other nutrients, aging leads to a lower production
of retinoic acid; a phenomenon probably accentuated by the fact that Western
populations consume an insufficient amount of vitamin A (60 % of the population has a
consumption lower than the recommendations). These two phenomena (i.e. level of
consumption, the lack of activation of vitamin A) accompanied by important individual
differences, would help to explain why some patients have an almost normal aging
process, whereas others gradually develop cognitive disorders and then, the disease. A
better understanding of the role of a collapse of the retinoid status in the genesis of
Alzheimer lesions could, beyond the definition of a preventive nutritional strategy, open
therapeutic perspectives, through the use of molecules targeting the nuclear receptors.
Key words: aging, brain, memory, Retinoic acid nuclear receptors (RAR, RXR), Alzh
eimer’s disease
La vitamine A est une vitamine liposo
�sente des ro
^ les importants
luble qui pre
�rents tissus de l’organisme.
dans diffe
�e dans la vision, dans le
Elle est implique
�grite
� des surfaces
maintien de l’inte
�pithe
�liales, dans l’immunite
�, la repro
e
duction ou encore dans la croissance et
�veloppement (Blomhoff et
le de
^ le
Blomhoff, 2006). En dehors de son ro
dans la vision, la vitamine A agit
�diaire de
principalement par l’interme
�tabolite l’acide re
�tinoı̈que (AR)
son me
�cepteurs
qui, en se liant �
a des re
�aires, r�
�nes
nucle
egule l’expression de ge
dans les tissus cibles.
� tabolisme
Me
et transport
de la vitamine A
�rieurs la vita
Pour les mammif�
eres supe
mine A provient exclusivement de l’ali
mentation : soit sous forme de vitamine
�forme
�e (dans sa forme majoritaire il
pre
� par des acides
s’agit de r�
etinol est�
erifie
gras �
a longues chaı̂nes comme le palmi
�tinyle par exemple) dans les
tate de re
produits animaux, ou bien sous forme de
�noı̈des provitaminiques tels que le
carote
�ne, a carote
�ne, b cryptoxan
b carote
�sents dans les aliments d’ori
thine, pre
�ge
�tale (figure 1). On recom
gine ve
mande actuellement que 60 % de
l’apport en vitamine A soit sous la forme
�noı̈des (sources v�
�tales) et
de carote
ege
�tinol (sources
40 % sous forme de re
animales) (Cordain et al., 2005). L’ester
�tinol (RE) doit e
^tre hydrolyse
� avant
de re
^tre absorbe
� au niveau intestinal.
d’e
� d’absorption est meilleure
L’efficacite
�form�
pour la vitamine A pre
ee (80 �
a
�noı̈des (50
90 %) que pour les carote
�ne est converti en r�
60 %). Le carote
etinol
au niveau de la muqueuse intestinale. Le
� dans les
re�tinol est ensuite est�
erifie
cellules de la muqueuse par la LRAT
(Lecithin : retinol acyltransf�erase), le RE
�sultant de cette catalyse est incorpore
�
re
� via le
dans les chylomicrons et absorbe
�me lymphatique (Harrison, 2005).
syste
Dans des conditions nutritionnelles nor
males, la plupart de la vitamine A de
�e dans le foie
l’organisme est stocke
�tinyl
(essentiellement sous forme de re
ester : RE) pour une part dans les
�patocytes et pour la majorite
� sous
he
forme de gouttelettes lipidiques dans les
�toile
�es du foie (encore appele
�es
cellules e
�r�ebral. OCL 2011 ; 18(2) : 68-75. doi : 10.1684/ocl.2011.0375
Pour citer cet article : Pallet V, Enderlin V. Vitamine A et vieillissement ce
68
OCL VOL. 18 N8 2 MARS-AVRIL 2011
104
doi: 10.1684/ocl.2011.0375
�tinoı̈des, et en
Il est bien connu que les re
^ le capital
particulier l’AR, jouent un ro
�veloppement du syste
�me
dans le de
nerveux central, mais ce n’est que r�
ecem
ment que son action dans le cerveau
adulte a retenu l’attention des scientifi
�es actuellement disponi
ques. Les donne
�rent qu’une
bles sur ce sujet sugge
�gulation tre
�s fine de l’expression des
re
�nes cibles de l’AR est fondamentale
ge
�re
�brales optimales,
pour des fonctions ce
� synaptique,
telles que la plasticite
�moire. Plus
l’apprentissage et la me
�cemment encore, des donne
�es pro
re
�tudes mettent en
venant de plusieurs e
�vidence l’implication de la voie de
e
�tinoı̈des dans l’�
signalisation des re
etiolo
gie de la maladie d’Alzheimer (MA).
aging
Aliments d’origine animale
Fruits et légumes
RE
Ester de
rétinol (RE)
muqueuse intestinale
Retinol
CRBP-II
Provitamine A
Caroténoïdes
entérocyte Chylomicrons
APOE
sang
Ester de rétinol Chylomicrons
Rétinol-CRBP2
APOE
Rétinol-CRBP2
RBP
RétinolRBPTTR
TTR
RBP4
Hépatocyte
Ester de rétinol
Rétinol-RBP4-TTR
Cellule étoilée
Foie
Rétinol-APOD
Ester de rétinol-APOE
Rétinol
Rétinal
Acide rétinoïc
CRBP-I
CRABP
RA
RAR RXR
HRE
noyau
Cellule
cérébrale
Figure 1. M�etabolisme et action cellulaire de la vitamine A.
�, en fonction des
cellules de Ito). De la
besoins de l’organisme, elle sera
�e vers les tissus cibles
mobilise
(Bellovino et al., 2003). Pour ce faire, le
� et le r�
RE est hydrolyse
etinol libre est
� �
ensuite complexe
a la retinol binding
protein (RBP4). Approximativement
95 % de la RBP circule dans le plasma
sous forme d’un complexe avec la
�ine de transport de la thyroxine :
prote
la transthyretin ou pr�
ealbumine (TTR). Le
�tinol constitue le re
�tinoı̈de le plus
re
abondant dans le sang (95 % du r�
etinol
�ines vectrices permet
sont li�
es aux prote
tant leur transport). Le flux de r�
etinol
� r�
�gule
�
libe
e par le foie est tr�
es finement re
�re �
de manie
a maintenir une concentra
�tinol dans le plasma
tion constante de re
(2 mmol/L). Au del�
a des besoins
�diats, la vitamine A alimentaire sert
imme
�
�serves he
�patiques
a constituer des re
�es au cours
qui seront ensuite utilise
�riodes d’apports insuffisants
des pe
(Theodosiou et al., 2010). Au niveau de
la cellule cible, il semble que la RBP soit
�cepteur trans mem
reconnue par un re
branaire nomm�
e STRA6, qui prendrait en
charge le re�tinol en le faisant entrer dans
�
la cellule (Kawaguchi et al., 2007). A
�tinol peut alors
l’int�
erieur de celle ci, le re
�tabolisme non oxydatif,
subir un me
�tinyl esters, re
�tinyl
produisant des re
phosphate, 3 d�
ehydror�
etinol, ainsi
�tabolisme oxydatif donnant
qu’un me
�tinal (aussi appele
� re
�tinald�
du re
ehyde)
�tabolite actif de la
puis de l’AR, me
�tinol en
vitamine A. L’oxydation du re
AR est un processus enzymatique, qui se
�roule en deux e
�tapes, et dont le re
�tinal
de
�tabolite interm�
est le me
ediaire. La pre
�re oxydation est re
�versible, tandis
mie
�me est irre
�versible. Notons
que la deuxie
que des voies cytosoliques et microso
males dans les processus d’oxydation
�crites. La
du r�
etinol en AR ont �
et�
e de
� interm�ediaire, le
formation du compose
�tinal, peut e
^tre catalys�
re
ee par des
enzymes cytosoliques ou microsomales
�es re
�tinol de
�shydroge
�nases (RDH)
appele
(Gottesman et al., 2001 ; Pares et al.,
2008). Ces RDH peuvent ainsi appartenir
�
�shydrog�
a la famille des alcool de
enases
(ADH), enzymes cytosoliques, ou �
a la
�nases/re
�ductases
famille des d�
eshydroge
�
a chaı̂nes courtes (SDR), enzymes micro
�tinal
somales (Pares et al., 2008). Le re
^tre converti de manie
�re
peut ensuite e
�versible en AR par des ald�
irre
ehydes
�shydroge
�nases (ALDH) cytosoliques
de
(Chen et al., 1994). Par ailleurs, il a
�galement �
�, in vitro, qu’une
e
et�
e montre
vari�
et�
e de cytochromes P450 (CYP)
�taient implique
�s dans l’oxydation
e
�tinal en AR (Zhang
microsomale du re
et al., 2000). Enfin, signalons que la
�gradation et
CYP26 permet la de
�limination de l’AR tout trans spe
�cifi
l’e
^ le
quement, et contribue ainsi au contro
�tinoı̈de (Petkovich, 2001).
du signal re
� cepteurs nucle
� aires
Les re
� tinoı̈que
de l’acide re
Le fait que l’AR active des facteurs de
�aire a e
�te
� de
�couvert
transcription nucle
�cep
en 1987. Il existe deux types de re
teurs de l’AR (Mangelsdorf, 1994). Le
�cepteurs
premier type comprend les re
RAR (retinoic acid receptor) qui peuvent
lier l’AR tout trans et l’AR 9 cis. Le
�me type comprend les RXR (reti
deuxie
�couverts par
noid X receptor) de
�
Mangelsdorf et al. (1990), dont l’affinite
�leve
�e pour l’AR 9 cis, mais plus faible
est e
pour l’AR tout trans (Levin et al., 1992)
�cemment, il a
(Chambon, 1996). Plus re
�te
� de
�montr�
e
e que certains acides gras,
�noı̈que
dont le DHA (acide docosahexae
�galement des ligands
C22 : 6 n 3) sont e
�
du RXR, qu’ils lient avec une affinite
�tinoı̈que lui
comparable �
a l’acide re
m^
eme (de Urquiza et al., 2000). Pour
�cepteurs (RAR et
chacun de ces deux re
�ines, code
�es par
RXR), trois types de prote
�rents, ont e
�te
� isol�
trois g�
enes diffe
ees :
RARa, b, g et RXR a, b, g (Chambon,
1996).
�cepteurs appartiennent �
Ces re
a une
�cepteurs nucle
�aires
superfamille de re
�ines transre
�gulatrices
qui sont des prote
capables de se fixer principalement sous
105
69
aging
�res de RXR, ou
forme d’homodime
�res RAR RXR au niveau
d’h�
et�
erodime
�cifiques de l’ADN, appele
�s
de site spe
�el�ements de r�e ponse (RXRE et RARE)
�s en amont du ge
�ne cible
et situe
(occasionnellement dans les introns)
(Mangelsdorf et Evans, 1995). Il existe
une forte homologie de structure entre
�cepteurs
les membres de la famille des re
�aires, qui comprend les re
�cepteurs
nucle
de diff�
erents ligands hydrophobes tels
�roı̈des, les hormo
que les hormones ste
�rive
�s hydro
nes thyroı̈diennes, les de
�s de la vitamine D, l’acide re
�tinoı̈que
xyle
ou encore les acides gras et eicosanoı̈des
(Huang et al., 2010). Cependant, cer
�cepteurs n’ont pas encore �
tains re
a ce
jour de ligands connus, ce sont les
�cepteurs dits orphelins. En pre
�sence
re
de leur ligand et en association avec des
co activateurs ou co represseurs, ces
�cepteurs re
�gulent positivement ou
re
�gativement l’expression de leurs
ne
�nes cibles. RAR se lie principalement
ge
�re avec le
au RARE sous forme de dime
�pendamment de
RXR qui lui agit inde
son ligand. Il semble que le dim�
ere RAR/
�gule environ 500 ge
�nes
RXR re
(Blomhoff et Blomhoff, 2006).
^ le central dans
Notons que RXR joue un ro
�gulation ge
�nique puisqu’il est
la re
�re
� comme le partenaire commun
conside
�risation d’autres membres de la
de dime
�cepteurs
superfamille, dont les PPAR (re
des acides gras) (Germain et al., 2006).
�te
�rodime
�risation du RXR avec
Ainsi, l’he
les diff�
erents membres de la superfamille
implique une interaction, voire une
�tition, entre les diffe
�rentes voies
compe
�aires.
de signalisation nucle
� que l’AR
Certains auteurs ont montre
�galement agir selon une voie non
peut e
�nomique. Cette action ultra rapide
ge
participerait �
a la modulation de la
�tine,
formation des spinules dans la re
�
�gulation des GAP jonctions et
a la re
�pines dendriti
aurait des effets sur les e
ques dans l’hippocampe.
La vitamine A et le
cerveau adulte
La voie de signalisation de
l’acide r�etinoı̈que dans le cerveau
�veloppement, la vitamine
Au cours du de
�ment l’acide r�
A et plus pr�
ecise
etinoı̈que
^ le cle
� dans la structuration
joue un ro
�re
�brale, la neurogene
�se, l’adressage
ce
�e des neurites. Des
neuronal, la pousse
70
�tudes re
�centes rapportent que les re
�ti
e
�galement un ro
^ le impor
noı̈des jouent e
�me nerveux central
tant dans le syste
adulte (Lane et Bailey, 2005 ; Bremner et
McCaffery, 2007 ; Tafti et Ghyselinck,
�
2007) en particulier dans des r�
egions ou
� neuronale est tre
�s impor
la plasticite
tante, i.e. l’hippocampe, le cortex pr�
e
�dian ainsi que les re
�gions
frontal me
�trosple
�niales. Un ensemble de donne
�es
re
montre �
egalement l’importance de l’acide
�tinoı̈que dans le fonctionnement du
re
striatum et du noyau accubems. D’autres
travaux ont montr�
e que le striatum
�tise l’acide re
�tinoı̈que et contient
synthe
�culaire associe
�e �
toute la machinerie mole
a
�tabolisme et �
�.
son me
a son activite
Transport vers le cerveau
� ce jour, quelques donne
�es sont dis
A
ponibles sur le mode de passage du
�tinol �
�re he
�mato
re
a travers la barrie
enc�
ephalique (BHE). Yamagata et al.
�tudie
� le transport jusqu’au
(1993) ont e
� dans la cavite
�
cerveau d’AR injecte
�ritone
�ale. D’autres re
�sultats, obtenus
pe
dans des conditions d’apports suffisants
� que
en vitamine A chez le rat, ont montre
90 % de l’AR total du cerveau n’est pas
� localement mais provient du
synth�
etise
pool circulant dans le plasma
(Kurlandsky et al., 1995). Par la suite, il
�te
� montre
� que l’isome
�re tout trans de
ae
l’AR est la forme la plus largement
transport�
ee du sang au cerveau par
rapport aux deux autres isoformes, l’AR
13 cis et l’AR 9 cis (Le Doze et al., 2000).
Par ailleurs, la pr�
esence d’AR a �
et�
e mise en
�vidence au niveau c�
e
er�
ebral, chez des
�s en vitamine A traite
�s avec
rats carence
de l’AR, l’hippocampe et le cortex
contenant les proportions les plus impor
tantes (Werner et Deluca, 2002). L’ori
gine de l’AR dans le cerveau semble donc
�ne dans des situations
largement exoge
d’apports suffisants en vitamine A.
Me�tabolisme ce�re�bral
Bien que l’apport en AR au niveau
� re
�bral soit majoritairement d’origine
ce
exog�
ene, le cerveau adulte poss�
ede
toute la machinerie n�
ecessaire �
a la
�se de l’AR, �
synthe
a son transport et �
a
�aire (Lane et Bailey,
son action nucle
2005).
�ines de liaison
L’identification de prote
�tinoı̈des et des enzymes impliqu
des re
�es dans la biosynthe
�se de l’AR dans le
e
cerveau adulte plaide en faveur d’un
� re
�bral du re
�tinol. En
m�
etabolisme ce
�sence des prote
�ines de
effet, la pre
transport CRBP (cellular retinol binding
106
protein) et CRABP (cellular retinoic acid
binding protein) (Zetterstrom et al.,
1994) (Zetterstrom et al., 1999), des
enzymes de conversion ADH1, ADH4
(Martinez et al., 2001) et RALDH
� te
�
(McCaffery et Drager, 1994) a e
�ve
�le
�e dans certaines structures du
re
cerveau adulte telles que l’hippocampe
et le striatum, structures particu
�rement implique
�es dans les processus
lie
�siques.
mne
�vidence des enzymes
Outre la mise en e
intervenant dans le me�tabolisme de la
vitamine A, le cerveau adulte est capable
�tiser l’AR de novo et ce de façon
de synthe
efficace (Dev et al., 1993). La synth�
ese
� te
� mise en �
d’AR a en effet e
evidence
dans le cerveau de souris adulte et plus
�
particuli�
erement dans le striatum, ou
�se serait plus importante
cette synthe
que dans l’hippocampe (McCaffery and
�quipe de
Drager, 1994). De plus, l’e
� que l’AR est
Sakai et al. (2004) a montre
�tise
� par la RALDH2 au niveau des
synthe
m�
eninges adjacentes �
a l’hippocampe.
�sence de re
�tinol et surtout
Enfin, la pre
�tinyl esters a pu ^
des re
etre mise en
�vidence dans l’hippocampe de cerveau
e
humain mature (Connor et Sidell,
1997).
Modulation de la plasticite� ce�re�brale
�nes dont l’expres
Parmi les nombreux ge
�gule
�e par l’AR dans le cerveau
sion est re
adulte, il ya ceux codant pour ses propres
�cepteurs, et ceux codant pour des
re
�ines spe
�cifiques des neurones impli
prote
�es dans beaucoup de fonctions du
que
� titre d’exemples on
cerveau mature. A
peut citer : la synaptophysine, le NGF, les
�cepteurs au N methyl D aspartate
re
�cepteur 2 a� la dopamine,
(NMDA), le re
la choline acetyltransferase, la neurogra
nie ou encore la neuromoduline. Enfin,
�tinoı̈que et ses re
�cepteurs
l’acide re
�gulent aussi un certain nombre de
re
�nes codant pour des prote
�ines impli
ge
�es dans les processus neurode
�g�
que
e
�ratifs telles que l’APP (amyloid protein
ne
�ine tau.
precursor) ou en encore la prote
Il est actuellement admis que l’AR joue un
^ le dominant dans la pr�
ro
eservation des
�re
�brales. Ainsi, l’e
�tude des
fonctions ce
effets du statut en vitamine A, ou en acide
�tinoı̈que, dans le cerveau adulte est de
re
la plus grande importance, et en parti
culier au cours du vieillissement. En effet,
�es re
�centes ont montre
� que
des donne
�tinoı̈des
des modifications du statut en re
�rations
induisent la mise en place d’alte
�ines neuro
dans l’expression des prote
aging
nales cibles et en cons�
equence, affectent
le maintien des processus physiologiques
dans le cerveau adulte (Malik et al.,
�rations de la
2000). Ainsi, des alte
�re
�brale et des de
�ficits de
plasticit�
e ce
�te
� de
�crits chez l’animal
m�
emoire ont e
�te
�
carenc�
e en vitamine A. Il a aussi e
�montre
� que les souris Knockout pour
de
les r�
ecepteurs RARb et RXRb RXRg
�sentaient une alte
�ration de la LTP
pre
(potentialisation �
a long terme, une forme
� synaptique) ainsi que des
de plasticite
�ficits substantiels des performances
de
�siques, mis en e
�vidence dans un test
mne
�moire spatiale de
�pendante de
de me
l’hippocampe (Chiang et al., 1998 ;
Mingaud et al., 2008). La mutation du
RARb avec, soit celle du RXRb, soit celle
�ficits de loco
du RXRg, entraı̂ne des de
�ristiques d’une fonction
motion caracte
anormale du striatum et probablement
li�
es �
a une diminution de l’expression des
�cepteurs �
re
a la dopamine dans les
neurones striataux (Krezel et al., 1998 ;
Alfos et al., 2001).
�tinoı̈que re
�gule aussi l’expres
L’acide re
�nes codant pour des prote
�ines
sion de ge
�es dans les processus de neuro
implique
gen�
ese, telles que les neurotrophines
�cepteurs res
NGF et BDNF, et leurs re
pectifs TrkA et TrkB (Scheibe et Wagner,
�cemment, quelques e
�tudes se
1992). Re
�resse
�es aux effets d’une hypo
sont inte
� de la voie des re
�tinoı̈des sur les
activite
�se chez l’adulte,
processus de neurogene
en utilisant la carence nutritionnelle en
�le d’e
�tude.
vitamine A comme mode
�ra
Ainsi, une augmentation de la prolife
�rencia
tion et une diminution de la diffe
�te
� observe
�es dans le bulbe
tion ont e
�ficients (Asson
olfactif des animaux de
Batres et al., 2003). Une diminution de la
�renciation neuronale a
survie et de la diffe
�te
� mise en �
e
evidence dans l’hippocampe,
�s en vitamine A.
d’animaux carence
�gime enrichi en vita
Cependant, un re
�tablir le
mine A ne permettait pas de re
�se chez les souris
niveau de neurogene
carenc�
ees (Jacobs et al., 2006). Enfin, des
�cents ont mis en �
travaux re
evidence que
la carence en vitamine A induit une
�ration de la neurogene
�se hippocam
alte
�ration
pique (diminution de la prolife
�rencia
cellulaire, survie cellulaire et diffe
�lement �
tion neuronale) paralle
a une
�taient
diminution de TrkA. Ces effets e
�verse
�s par l’administration d’AR tout
re
trans (Bonnet et al., 2008).
Modulation des capacite�s mn�
e siques
La carence vitaminique A, induisant un
� de la voie des re
�tinoı̈des,
hypoactivite
entraı̂ne chez la souris adulte des d�
eficits
�ve
�le
�s dans un test de me
�moire
cognitifs re
relationnelle (Etchamendy et al., 2003).
De plus, l’administration d’AR �
a des rats
carenc�
es en vitamine A permet de corri
�ficits de me
�moire spatiale de
ger les de
�fe
�rence mesur�
re
es dans le labyrinthe
aquatique de Morris (Bonnet et al.,
�tudes confortent la
2008). D’autres e
� de la
relation entre le niveau d’activite
voie de signalisation des r�
etinoı̈des et les
�te
�
processus cognitifs. Pour exemple, il a e
�montre
� qu’une carence vitaminique A
de
induisait des de�ficits d’apprentissage et
de m�
emoire spatiale dans un test de
�men
labyrinthe radial, et qu’une supple
tation en vitamine A permettait de
�ficits observ�
corriger les de
es (Cocco
et al., 2002). En revanche, d’autres
�re
travaux mettant en oeuvre l’isome
�cule utilis�
13 cis de l’AR, mole
ee sous la
�nomination Accutane dans le traite
de
�e, ont montre
� des effets
ment de l’acne
�fastes de cette mole
�cule dans un test
ne
�moire hippocampo d�
de me
ependante
chez la souris jeune (Crandall et al.,
�sultat est �
2004). Ce re
a ce jour con
� par l’e
�tude de Ferguson et Berry
troverse
�montre, au contraire, que
(2007) qui de
le traitement par la forme 13 cis de l’AR
est sans effet sur l’apprentissage et la
m�
emoire spatiale chez le rat.
�es montre que
L’ensemble de ces donne
les situations nutritionnelles ou physio
�ficit
logiques conduisant �
a un de
d’activit�
e de la voie de signalisation des
�tinoı̈des, et en particulier �
re
a des modi
�cepteurs
fications de l’expression des re
�aires ou de leurs ge
�nes cibles dans le
nucle
�rables
cerveau, conduisent �
a de conside
dommages neurobiologiques et �
a des
�rations des performances mn�
alte
esiques.
Vitamine A et vieillissement
c�e r�e bral
�tabolisme
Une forte perturbation du me
de la vitamine A apparaı̂t au cours du
vieillissement. Elle peut conduire �
a des
concentrations �
elev�
ees de cette vitamine
dans le foie (van der Loo et al., 2004) alors
^me temps la capacite
� de
que dans le me
�serves
l’organisme �
a mobiliser les re
�tinol et �
h�
epatiques de re
a les utiliser
efficacement semble fortement affect�
ee
� (Azais Braesco et al.,
chez l’homme ^
age
�sulte une diminution de la
1995). Il en re
� cellulaire en acide
biodisponibilite
�tinoı̈que qui se traduit chez l’animal
re
^
�, dans plusieurs tissus cibles (foie,
age
� de la
cerveau) par une baisse d’activite
�tinoı̈des
voie de signalisation des re
(Enderlin et al., 1997 ; Pallet et al.,
� des
1997). Cette baisse d’activite
�tinoı̈des, dans les tissus cibles, a
re
�galement e
�te
� mise en e
�vidence chez
e
� (Feart et al., 2005).
l’homme ^
age
Il est maintenant admis que la baisse
d’activit�
e cellulaire de la vitamine A joue
^ le cle
� dans l’e
�tiologie de d�
un ro
eficits
�siques sp�
�s au vieil
mne
ecifiques associe
lissement et qu’un traitement par l’acide
�tinoı̈que (AR), est �
^me de restaurer
re
a me
�s mne
�siques des animaux
les capacite
^
�s. Enfin, plus r�
�mon
age
ecemment, la de
�men
stration de l’efficacit�
e d’une supple
tation nutritionnelle en vitamine A chez
les animaux adultes, permettant �
a la fois
le maintien de l’activit�
e de la voie de
�vention de l’appari
signalisation et la pre
�siques spe
�cifiques
tion de troubles mne
li�
es au vieillissement, a �
et�
e faite (Mingaud
et al., 2008). Il est donc aujourd’hui bien
�troite
admis qu’il existe une relation e
� ce
�re
�brale de la
entre le niveau d’activite
�tinoı̈des, l’expression
voie d’action des re
�nes cibles codant pour des pro
de ge
�ines neuronales implique
�es dans cer
te
tains processus de plasticit�
e (Husson
�si
et al., 2004), et les performances mne
ques au cours du vieillissement (Mingaud
et al., 2008).
�es sugge
�rent
�gulation pre
�cise de l’expression
qu’une re
�nes contro
^ le
�s par les re
�tinoı̈des est
des ge
fondamentalement importante pour le
fonctionnement optimal du cerveau et
pour le maintien des performances de
m�
emoire.
Vitamine A et maladie
d’Alzheimer
La maladie d’Alzheimer (MA) est la
�mence la plus re
�pandue chez les sujets
de
^
�s. C’est une maladie chronique de
�g�
age
e
�rative caracte
�rise
�e par la de
�te
�rioration
ne
progressive des fonctions cognitives
incluant la m�
emoire, le jugement, la
prise de d�
ecision, le langage, l’orienta
tion, etc. Les symptomes cliniques
�
incluent les alt�
erations de plasticite
neuronale (e.g. la perte selective des
neurones et des synapses) et la formation
de plaques s�
eniles extracellulaires consti
�es de peptides b amyloı̈des (Ab) ainsi
tue
^trements neurofibrillaires
que d’encheve
intracellulaires.
�cemment, des donne
�es issues de
Re
�tudes se
�pare
�es apportent
plusieurs e
^ le de
des arguments en faveur d’un ro
la voie de signalisation de l’acide
�tinoı̈que dans l’�
re
etiologie de la maladie
107
71
aging
lipocaline, apolipoprot�
eine D, un autre
�tinol dans le syste
�me
transporteur du re
�s dans
nerveux central sont augmente
les neurones de patients atteints de la
�gulation positive de son
MA. Une re
� te
� observe
�e in
expression par l’AR a e
vitro.
� re
�gulation de ge
�nes codant
ou �
a la de
�ines du me
�tabolisme des
pour des prote
�tinoı̈des et entraı̂nant des alte
�rations
re
�nes cibles de
dans l’expression de ge
ceux ci, pourrait alors ^
etre fortement
�tiologie de la forme
impliqu�
ee dans l’e
tardive (ou sporadique) de la MA
(Goodman et Pardee 2003 ; Goodman,
2006).
d’Alzheimer. Tout d’abord, Goodman a
�montre
� les liens g�
�tiques entre
de
ene
cette voie de signalisation et la MA, en
�vidence que les loci les plus
mettant en e
�quemment trouve
�s modifi�
fre
es chez les
sujets atteints de la maladie �
etait
�matiquement situe
�s sur des clusters
syste
�s proches de ge
�nes codant pour des
tre
�ines ayant un ro
^ le majeur dans le
prote
m�
etabolisme et la signalisation des
�tinoı̈des, �
re
a savoir : CYP26, RARa,
RXRbg, RXRb, CRABP II et RBP par
exemple. CYP26 est un cytochrome
P450 impliqu�
e dans le catabolisme de
^ le
l’AR et participant de ce fait au contro
du niveau d‘AR dans les tissus. Une
diminution de la concentration de
�tinol se
�rique a, par ailleurs, e
� te
�
re
�ve
�le
�e chez les patients Alzheimer,
re
ainsi qu’une diminution de l’expression
�hyde
et de l’activit�
e de la retinalde
�sydroge
�nase, enzyme implique
�e dans
de
la production de l’AR. Une diminution
�e �
de la biodisponibilit�
e de l’AR lie
a l’^
age
Vitamine A et encheve�trements
neurofibrillaires :
�nes potentiellement re
�gule
�s
Parmi les ge
�ne codant pour
par l’AR, on trouve un ge
�ine tau encore appele
�e MAPT
la prote
pour microtubules associated protein tau,
�ine pre
�ponde
�rante dans
et qui est la prote
^trements neu
la formation des encheve
rofibrillaires.
Les transporteurs de la vitamine A et la
MA
�ine E (ApoE), apolipo
L’apolipoprote
�ine majeure du liquide cere
�brospi
prote
�ment de RBP
nal, participerait en comple
�tinol et des re
�tinyl
au transport du re
�le e4 de son
esters dans le cerveau. L’alle
�ne a e
� te
� identifie
� comme un facteur
ge
de risque de la MA ; il semble favoriser
l’agr�
egation des peptides Ab. En revan
�le e2 de
che, un effet protecteur de l’alle
�tant le meilleur
l’ApoE, connu comme e
� te
� trouve
�
transporteur des r�
etinoı̈des, a e
dans plusieurs �
etudes. Les niveaux de
Compartiment extracellulaire
Vitamine A et b amyloıdes (Ab)
�se des
La voie biochimique de synthe
peptides Ab, peptides constituants de la
�nile, est une voie pathologique
plaque se
�e voie amyloı̈dog�
appele
e nique (figure 2).
�quences de cliva
Elle comporte deux se
�olytiques successifs de la
ges endoprote
Membrane
Cytoplasme
COOH
APPαCTF
APPsα
Voie physiologique
α –secrétase
(ADAM10)(clivage)
AR
NH2
AR
Voie amyloïdogènique,
(pathologique)
β β’
APP695
γ
COOH
β –secrétase
(BACE)(clivage)
+
APPsβ
APP-β CTF
APP-β’CTF
γ –secrétase
complexe Preseniline
(PS1,PS2)(clivage)
AR
+ APP-γ CTF
APOE
APOD
Aβ40/Aβ 42
AR
AR
IDE
Régulation négative par l’AR
Régulation positive par l’AR
Figure 2. Acide r�e tinoı̈que et processus de d�
e gradation de la prot�e ine pr�ecurseur du peptide Ab.
72
108
aging
�ine APP (Ab precursor protein)
prote
�es par deux prote
�ases distinctes
catalyse
�tases. La b secre
�tase ou
les b et g secre
b site cleaving enzyme (BACE) est hau
�e dans le cerveau des
tement exprime
�e sur les sites de
patients et est localise
production du peptide Ab. Le clivage de
�tase gene
�re des
l’APP par la b secre
fragments APPb dans l’espace extracel
�tase intervient ensuite
lulaire. La g secre
�dent
pour cliver la partie, issue du pr�
ece
�e dans la
clivage qui est demeure
�tape pro
membrane. Cette deuxi�
eme e
�olytique produit le petide Ab, le
te
composant central des plaques s�
eniles.
En condition physiologique, l’APP peut
^tre prote
�olyse
�e par une voie non
aussi e
amyloı̈dog�
enique. Cette autre voie de
�gradation de l’APP comporte une
de
�tape prote
�olytique par une a
e
�tase, dans la se
�quence Ab, emp^
secre
e
�finitivement la production
chant ainsi de
� a
du peptide Ab. Cette activite
�tase est attribue
�e aux metallo
secre
�ases ADAM9 et ADAM10.
prote
�te
� montre
� que l’hypoactivite
� de la
Il a e
�tinoı̈des
voie de signalisation des re
entraı̂ne la formation anormale et le
�po
^ t des petides Ab (Corcoran et al.,
de
�te
� montre
�
2004). Ceci a en particulier e
chez des rats carenc�
es en vitamine A.
�s consommation pendant 1 an
Apre
�pour
d’une alimentation totalement de
vue de cette vitamine, les animaux pr�
e
sentaient une hypoactivation de la voie de
signalisation de la vitamine A, et avaient
�velopp�
de
e des d�
epots b amyloı̈des dans
�men
leur cerveau. Des donn�
ees supple
�ve
�le
� que la carence en
taires ont re
�ne
�ratrice d’une diminu
vitamine A, ge
� de l’AR, induit
tion de la biodisponibilite
�nique
une activation de la voie amyloı̈doge
dans le cortex des rats, structure connue
�re
�e par la
comme �
etant la premi�
ere alte
maladie (Husson et al., 2006).
�rive
�s, par l’inter
La vitamine A ou ses de
�cepteurs, sont e
�galement
m�
ediaire des re
�
a m^
eme d’inhiber ou destabiliser les
�gats Ab pre
�form�
�venant ainsi la
agre
es, pre
formation des plaques (Ono et al., 2004)
(Sahin et al., 2005). Il y a de nombreuses
�es biochimiques qui vont dans le
donne
sens de l’implication de la voie de
signalisation de la vitamine A dans la
formation de Ab. En effet, comme on le
�tapes cle
�s du
voit sur la figure 2, les e
processus de formation des peptides
^ le de
amyloı̈des sont sous le contro
�ines dont l’expresssion a e
�te
�
prote
�e in vitro, comme e
�tant r�
montre
egul�
ee
par l’AR. Ceci comprend : APP, la b
secr�
etase, les presenilines 1 et 2 (PS1 et
�ines du complexe g
PS2), deux prote
�re
secr�
etase ainsi que ADAM10. De manie
�ressante, une e
�tude in vitro montre
inte
qu’un traitement par l’AR augmente
l’expression de ADAM10 au niveau
�ique, sugge
�rant ainsi que l’AR
prote
�gra
induit un basculement dans la de
dation de l’APP, en faveur de la voie a
secr�
etase ou voie dites physiologique.
L’insulin d�egrading enzyme (IDE), une
�ase responsable de la
mettaloprote
�gradation de l’insuline a e
�te
� montr�
de
ee
^ le capital dans la
comme jouant un ro
�gradation du peptide Ab �
de
a la fois in
�te
� mis en e
�vidence
vitro et in vivo. IDE a e
�re
�brospinal. Son niveau
dans le liquide ce
� de ses prote
�ine ou
d’activit�
e, la quantite
�s, sont diminue
�s dans le
ARNm exprime
�s �
cerveau des malades et sont associe
a
� de d�
^ ts
une diminution de la quantite
epo
�re que l’augmentation de
Ab. Ceci sugge
l’activit�
e IDE pourrait induire une dimi
nution du risque de d�
evelopper la MA.
�ne codant pour
Or, le promoteur du ge
�ment de re
�ponse aux
IDE pr�
esente un e�le
�f�
RAR (RARE), zone pre
erentielle de fixa
tion des r�
ecepteurs de l’AR, et la trans
�gule
�e positivement
cription de IDE est re
par l’AR.
�cents laissent sup
Enfin, des travaux re
^tre conside
�re
�
poser que l’AR pourrait e
�rapeutique poten
comme un agent the
tiel pour le traitement de la MA. L’admi
�niques
nistration d’AR �
a des souris transge
�veloppant les le
�sions de types Alzhei
de
mer induit, en effet, une importante
�pots amyloı̈des et des
diminution des de
^trements neurofibrillaires (Ding
encheve
et al., 2008).
Conclusion
�es sugge
�re
�gulation tre
�s pre
�cise de
qu’une re
�nes m�
�e par les
l’expression des ge
edie
�tinoı̈des est cruciale pour un fonction
re
� re
�bral optimal, et apporte des
nement ce
^ le impor
arguments en faveur d’un ro
�cepteurs
tant de la vitamine A, via ses re
�aires dans les multiples processus
nucle
impliqu�
es dans la formation des plaques
�niles.
se
�vention
Dans une perspective de pre
nutritionnelle de la maladie d’Alzhei
�cessaire de mieux com
mer, il sera ne
�
prendre l’implication de l’hypoactivite
�tinoı̈des
de la voie de signalisation des re
se mettant en place naturellement au
cours du vieillissement, dans la gen�
ese
�sions pathologiques.
des le
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