2013年有关衰老的重要的12个问题的研究进展(上)

In summary, deficiency of NAD+ in the nucleus of muscle cells produces a state of “pseudohypoxia”, where there is adequate oxygen but high levels of HIF-1α.  This results in the inhibition of the mitochondrial transcription factor, TFAM, which inhibits the expression of mtDNA.  As a result, mitochondria do not produce the proteins encoded in mitochondrial DNA that are required for “forward electron transport” and ATP production.  “Reverse electron transport” occurs and high levels of free radicals are produced, giving the exact picture of aging.  In this picture cells are dependent on aerobic glycolysis in the cytoplasm and cannot burn fat.  They develop the exact metabolic picture of cancer, called the Warburg effect.  The mitochondrial dysfunction and this Warburg-type metabolism are fully reversible with the supplementation of NAD+ precursors.  This is the #1 story for 2013.

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2. Blocking two pathways that drive can produce synergistic effects.

The 2^nd most remarkable story in my “Top 10 List” for 2013 was the paper from the Buck Institute that was authored by Di Chen, et al. (Chen, 2013)(ref)(ref) which showed that when both the Insulin/IGF-1 pathway and the mTOR pathway were blocked in nematodes by “genetic knock out,” the nematodes lived 500% longer than normal nematodes.  This was a synergistic effect, since genetic knock-out of the Insulin/IGF-1 pathway in nematodes only increased lifespan by 80-100% and genetic knock-out of the mTOR pathway only increased lifespan by 30-40%. However, when both pathways were knocked out, there was a 5-fold increase in lifespan.  This dramatic increase was due to cross talk that occurs between the Insulin/IGF-1 pathway and the mTOR pathway via AMPK.  AMPK levels dramatically increased in these double knock-out worms and accounted for this synergistic effect.  The other component of this synergistic effect was the discovery that the location of this synergistic effect was germline cells, which activated DAF-16 (the nematode homolog of FOXO) in the intestine.  Thus, the 5-fold  synergistic lifespan extension was attributed not only to AMPK, but also to the fact that DAF-16 regulated fat metabolism in these worms (since intestinal fat is the primary reservoir of fat in nematodes). The diagram below illustrates the lifespan curves of the double-knock out worms, “AMPK crosstalk” between pathways, and the germline-to-intestinal signaling seen in this study:

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 3. The third story in my “top 10” list is another example of pathway synergy.  Combining exercise with Resveratrol supplementation enhances mitochondrial biogenesis more than is explainable due to summing the effects of the individual interventions.

A study Sirtuin 1-mediated effects of exercise and resveratrol on mitochondrial biogenesis published early in the year looked at molecular and biological impacts of combining Resveratrol supplementation with exercise on knockout mice.  The findings of the study were:

1. Resveratrol (RSV) induces AMPK phosphorylation by 1.7 fold.
2. Exercise induces AMPK phosphorylation by 3 fold.
3. RSV + Exercise did not have a synergistic effect on AMPK Phosphorylation. The effects of exercise on AMPK were SIRT-independent.
4. RSV increased p38 (an MAPK kinase) phosphorylation by 6-fold.
5. Exercise increased p38 phosphorylation by 8-fold.
6. RSV + Exercise increased p38 phosphorylation by 9.5-fold, which Is not a synergistic effect,  The effects of RSV and exercise on p38 were SIRT-independent.

Further:

1. Resveratrol (RSV) increased SIRT1 Protein expression by 2-fold,
2. Exercise did not increase SIRT1 Protein expression,
3. RSV did not increase PGC-1α  Protein levels,
4. Exercise increased PGC-1α Protein levels by 1.6 fold,
5. RSV + Exercise increased both SIRT1 and PGC-1α protein levels,  But the increase in PGC-1α  was NOT greater than that due to Exercise alone,
6. Exercise + RSV synergistically Increased ROS signaling and the Induction of mitochondrial biogenesis That totaled 6.1-fold, whereas with Exercise or RSV alone, the increase was only 3.1 fold or 1.6 fold. This effect was SIRT1 dependent.

Conclusion 1: the effects of Resveratrol and Exercise on AMPK Phosphorylation and p38 MAPK Phosphorylation are SIRT Independent.

Conclusion 2: whereas the AMPK and p38 mediated effects of Exercise and Resveratrol are not dependent on SIRT1, the PGC-1α  and ROS-mediated effects of Exercise and RSV are SIRT1 dependent. With Mitochondrial biogenesis, there is a powerful synergistic interaction of Exercise and RSV and this synergistic effect is SIRT1 dependent.

Stories 2 and 3 convey a very powerful message for anti-aging interventions: combining interventions in seemingly independent pathways may produce positive effects that are much greater than additive.

4. We now know what two proteins account for the anti-aging effects of heterochronic parabiosis – GDF-11 (declines with aging) and CCL11 (increases with aging)

My fourth story explains an interesting but unexplainable results previously observed in mouse Heterochronic parabiosis experiments. Heterochronic parabiosis is an old, but novel experimental way of determining if a circulating factor can account for a biological effect by surgically creating a “shared circulation” between two animals.  With heterochronic parabiosis (HP), an old animal is surgically connected to a young animal, which allows for a shared circulation to redistribute plasma factors to both animals.  Several researchers have used this HP mouse model in the past to study the causes of brain aging, heart aging, and skeletal muscle aging.  The diagram below 9;;istrates how HP rejuvenates the older animal.  Some rejuvenating factor(s) in the blood of the older animal effectively made the older animal younger in some respects.  But that rejuvenating factor(s) was not known. (reference)

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That rejuvenating factor (or at least one of several such factors) was identified in a 2013 publication Growth Differentiation Factor 11 Is a Circulating Factor that Reverses Age-Related Cardiac Hypertrophy by researchers at Harvard Universitiy.  They showed that in the heart, the rejuvenation effects of a shared circulation in heterochronic parabiosis could be explained by a circulating protein called Growth and differentiation factor-11. GDF-11 is a member of the TGF-β superfamily of growth factors. It is known that GDF-11 levels decline with aging. (Wagers, 2013).  Using a sophisticated experimental technique called “modified aptamer-based proteonomics,” they were able to figure out that this was the protein responsible for reversing the age-related cardiac hypertrophy and diastolic dysfunction seen in the heart with normal aging (often referred to as “normal ejection fraction heart failure). The most convincing evidence was that when this protein was purified and administered to the aging rodents, it recapitulated the effects of parabiosis.

GDF-11 is made by cells found in the spleen.  The exact reason why circulating levels of GDF-11 decline with aging has not yet been elucidated, but this is a huge breakthrough.

.Previous studies reported in 2011 used the heterochronic parabiosis model to study brain aging. Using similar techniques, they were able to show that brain aging is due reduce neurogenesis of brain stem cells and that a circulating factor called CCL11/Endotaxin increase with aging. (Villeda, 2011). The data below shows the overlap between the cytokines that are altered with normal aging and the ones that are altered in heterochronic parabiosis experiments(reference):

Going on to stories about how multivitamin and mineral dietary supplements may be useless

While the four stories above are basically positive, there were a number of negative and partially negative 2013 stories mainly related to antioxidant and vitamin supplementation.

(Vince comment regarding context of these following stories: The research studies behind the stories related below are basically concerned with longitudinal and large-population impacts of vitamin, multi-vitamin and essential mineral supplementation.  In interpreting these studies, it is important to keep certain distinctions in mind: 1. While vitamins can be packaged in dietary supplements, many very important dietary supplements are not vitamins, e.g. curcumin, green tea extract, resveratrol, fish oil).  It is fallacious to damn vitamin and mineral supplements for not making a difference and then go on to say that all dietary supplements are useless, as is common in the general press.   2.  Some vitamins like Vitamin D clearly do make a difference for health as documented by ample other research (actually vitamin D might better be classified as a hormone).  3. Many phyto-substance dietary supplements like curcumin and resveratrol have been broadly and falsely marketed as “antioxidants,” but they in fact primarily operate via epigenetic mechanisms.  And many “antioxidant” supplements like alpha-lipoic acid and melatonin were not included in these reported studies; further. they exercise their main benefits via other pathways than direct suppression of ROS.  4.  Comparing taking vitamins against eating fresh fruits and vegetables is significant in only one respect.  You can’t get the benefits of eating fruits and vegetables from consuming vitamins and minerals because these last substances don’t contain plant-based polyphenols!  But you may be able to get some and even more of the benefits of eating fresh fruits and vegetables by consuming other supplements such as green tea extract, resveratrol and curcumin.  Back to Jim;s points: I do agree with the general observation that multivitamin and mineral supplementation does not make sense for healthy people who consume well-balanced diets.  The message about the general uselessness of multivitamin/mineral supplements is a very important one.)

5. Taking multivitamins or antioxidant supplements does not prevent heart disease

2013 ended with the publication of several studies analyzing the health benefits of multivitamin supplements in large populations over long time periods or in carefully controlled clinical trials. (Fortman, 2013),(Myung, 2013),(Wang, 2013),(Grodstein, 2013), (Vollset, 2013), (Christen, 2013).  Since multivatimin and mineral supplements have been the de facto cornerstone of conventional “anti-aging medicine”, it is highly relevant to ANTI-AGING FIREWALLS – THE SCIENCE AND TECHNOLOGY OF LONGEVITY.  None of studies mentioned here were funded by Big Pharma, by the FDA, or by the American Medical Association. Instead they were either funded by academia or by peer-reviewed grants from several government agencies in the US, Europe, and Asian countries. (Please, conspiracy theorists, get rid of your paranoia!). Specifically, several were funded by the US Government’s Preventative Services Task Force to obtain objective, unbiased data on the efficacy of multivitamin supplementation for normal, healthy Americans. Specifically, funding was allocated to evaluation supplements for four specific indications: 1) heart disease prevention, 2) cancer prevention – Number 8 in my “top 11” list, 3) prevention of cognitive decline, 4) and for the prevention of a 2^nd heart attack. This section covers heart disease. Number 8 in my “top twelve list” will cover cancer prevention. Number 7 will cover cognitive decline, and number 6 will cover the prevention of a 2^nd heart attack.

The new meta-analysis data on heart disease prevention

The first new report in 2013 was released online in the November 12 issue of Annals of Internal Medicine (Fortman, 2013). This was a meta-analysis of 26 major multivitamin studies that specifically were designed for preventing chronic disease. The results showed no benefit to taking vitamins and mineral supplements to reduce the risk of heart disease. The 2^nd new report in 2013 was from Korea and had no funding from any government agency, trade group, Big Pharma, or FDA (Myung, 2013). This was a meta-analysis of 50 randomized controlled studies involving almost 300,000 research participants who were randomized to receiving multivitamins vs placebo or antioxidant supplements vs placebos. Of all of the outcome measures studied, vitamin and antioxidant supplementation was associated with a marginally increased risk of angina pectoris, whereas low dose vitamin B6 supplementation was associated with a slightly decreased risk of major cardiovascular events.  The benefits disappeared in subgroup meta-analysis of high-quality randomized controlled trials within each category, however.

The prospective, randomized, placebo controlled trial for heart disease prevention

A third major study in 2013 looked at the benefits of a multivitamin supplement for preventing heart disease and cancer in male physicians (Gaziano, 2013)(Sesso, 2012). This study was carried out at by the Division of Preventative Medicine at Harvard Medical School and was called the Physicians’ Health Study II (PHSII). The study was a prospective, randomized, double blind, placebo-controlled study in 14,641 male physicians aged 50 or older.  They were randomized to a Centrum Silver multivitamin or a placebo. (Centrum Silver is made by Pfizer, a Big Pharma company, and is one of the most popular multivitamin supplements sold). Pfizer did not fund this study and were not involved with the design, execution, or analysis of the data. The follow-up period was 11 years in this study. (The cancer data from this study are reported below under #8).  The PHSII showed no cardiovascular risk reduction compared to the placebo. In conclusion, multivitamin supplements for cardiovascular risk reduction “struck out three times” in 2013. Is this consistent with earlier studies published prior to 2013? Read on.

Major studies prior to 2013 that looked at cardiovascular risk and multivitamin supplementation

One must question if the three new 2013 studies were consistent with previous studies that evaluated multivitamin supplements for cardiovascular risk reduction. Two of the largest previous studies reported prior to 2013 were the Women’s Health Initiative (WHI), which was     a large cohort study of 161,000 women who were followed for 8 years.  The WHI did not show any reduction in cardiovascular risk with multivitamin supplementation (Neuhouser, 2009).

Another large, prospective, randomized clinical trial of Vitamin E supplementation was reported in 2000, called the Heart Outcomes Prevention Evaluation Study (HOPE). This Canadian trial enrolled 2,545 women and 6,995 men aged 55 or older and randomized them to receive 400 IU of Vitamin E vs a placebo for a mean follow-up of 4.5 years (Yusuf, 2000). The results of the HOPE trial showed no statistically significant differences in cardiovascular events or deaths from cardiovascular events in the two arms of the study. The HOPE trial was then extended as the HOPE-TOO trial, which followed 3,994 of the initial patient group who agreed to extend their participation for a mean follow-up of 7 years (Bosch, 2005). The results of the HOPE-TOO trial showed difference in cardiovascular events between Vitamin E and the placebo, but in the Vitamin E group, there was a statistically increased risk of heart failure (RR = 1.13) and hospitalization for heart failure (RR = 1.21).

Conclusion:  Old and new studies (2013) consistently show no cardiovascular disease benefit

In conclusion, the WHI study, the HOPE trial, the HOPE-TOO trial, the two meta-analsyis studies from 2013, as well as the Physicians Health Study II all showed the same results. The use of a multivitamin supplement does not reduce your risk of heart disease. On the contrary, all of the researchers involved in these studies emphasize that there is clear, convincing evidence that fruits and vegetables do reduce your risk of cardiovascular disease (Hung, 2004). As Lock said so clearly a few years ago, “if an individual increases fruit and vegetable intake up to 600 gms daily, the worldwide burden of cardiovascular disease could be reduced by 31% for ischemic heart disease and 19% for ischemic stroke”(Lock, 2005).  In summary, of all of these researchers agree that you should buy lots of fruits and vegetables for your heart, not supplements for your heart. The only people who strongly disagree with this conclusion are the multivitamin supplement manufacturers, supplement trade groups, and Big Pharma companies that sell multivitamins (Pfizer, Bayer, Novartis, GlaxoSmithKline, Unilever. (Associated Press, 2009). When it comes to taking sides with the supplement/Big Pharma vs the researchers, I could not agree more with the researchers on their conclusions in the above studies.

6. Vitamins and minerals do not prevent a 2^nd heart attack

Another major study on multivitamins was released in 2013 that evaluated the benefits of multivitamins and minerals in preventing a 2^nd heart attack. (Lamas, 2013).  This study was based on data that was extracted from the TACT trial (Trial to Assess Chelation Therapy), which looked at the therapeutic benefit of EDTA chelation therapy (TACT investigators, 2013). This study is very significant in that it was a prospective, double blinded, randomized study comparing a high dose multivitamin and mineral supplement to a placebo.  The study was a five-year study involving 1,708 people who had recently had a myocardial infarction within 6 weeks of the time of enrollment.  Unfortunately, the researchers found no different in rates of another heart attack, rates of chest pain, hospitalization rates, cardiac catheterization rates, rates of stroke, or early death in placebo vs multivitamin takers. The researchers stated that the interpretation of these results should be taken with caution, since some of the volunteers stopped taking their pills. (This occurs with both the placebo takers and with multivitamin takers).