31. January 2010 by admin.

Any reader of a vampire novel knows that acquiring the blood of a young person is the secret of a vampire’s eternal youth.  In fact, the essence of being a vampire is a constant quest for such acquisition.  According to a news stories that broke today, it seems like scientific knowledge is finally catching up. 

It is also common knowledge among us longevity-science types that somatic stem cells are subject to senescence and that, with aging, these stem cells progressively lose their capability to reproduce and differentiate. (See the discussion in my treatise related to the Stem Cell Supply Chain Breakdown theory of aging.)  “Buildup of levels of Ink4a/P16 associated with aging slows down the rate of differentiation of adult stem cells.” Further, age-related loss of capability to reproduce and differentiate has to do with what is going on in the niches in which stem cells live.  “Our results reveal that aged differentiated niches dominantly inhibit the expression of Oct4 in hESCs and Myf-5 in activated satellite cells, and reduce proliferation and myogenic differentiation of both embryonic and tissue-specific adult stem cells (ASCs). Therefore, despite their general neoorganogenesis potential, the ability of hESCs, and the more differentiated myogenic ASCs to contribute to tissue repair in the old will be greatly restricted due to the conserved inhibitory influence of aged differentiated niches(ref).”  Along with this decline in stem cell renewal capability comes a breakdown in the efficacy of the stem cell supply chain, aging and death.  According to a January 30 2010 news item appearing in Science Daily “A team of Howard Hughes Medical Institute (HHMI) researchers has found that in old mice, a several-week exposure to the blood of young mice causes their bone marrow stem cells to act “young” again.”  Dracula, why are you acting bored? 

The publication related to the new research is Systemic signals regulate ageing and rejuvenation of blood stem cell niches and appeared in the January 28 issue of Nature. “Ageing in multicellular organisms typically involves a progressive decline in cell replacement and repair processes, resulting in several physiological deficiencies, including inefficient muscle repair, reduced bone mass, and dysregulation of blood formation (haematopoiesis). Although defects in tissue-resident stem cells clearly contribute to these phenotypes, it is unclear to what extent they reflect stem cell intrinsic alterations or age-related changes in the stem cell supportive microenvironment, or niche. Here, using complementary in vivo and in vitro heterochronic models, we show that age-associated changes in stem cell supportive niche cells deregulate normal haematopoiesis by causing haematopoietic stem cell dysfunction. Furthermore, we find that age-dependent defects in niche cells are systemically regulated and can be reversed by exposure to a young circulation or by neutralization of the conserved longevity regulator, insulin-like growth factor-1, in the marrow microenvironment. Together, these results show a new and critical role for local and systemic factors in signaling age-related haematopoietic decline, and highlight a new model in which blood-borne factors in aged animals act through local niche cells to induce age-dependent disruption of stem cell function.”

This does not sound much like vampire talk.  Some of the press reports about the work are more lucid if not lurid.  According to the Science Daily writeup “Hematopoietic stem cells give rise to all the cells of the blood system, including immune cells and red blood cells. As animals age, these stem cells become more numerous, but less effective at regenerating the blood system, Wagers says. That translates into a less effective immune system and a greater susceptibility to disease. — To see if younger blood could reverse the sluggishness of aging blood cells, the researchers began by surgically joining the bloodstreams of pairs of mice that were of different ages, but nearly clones of one another.” (Hmmn, joining bloodstreams?  That does sound rather vampire-like.)  “Each mouse carried distinctive genetic markers so that researchers could differentiate between its cells and those of its partner. The technique, called parabiosis, enables researchers to test the long-term effects of one animal’s blood on the tissues and organs of the other. “It’s the only model that really allows us to come close to mimicking an in vivo systemic environment,” Wagers (Amy Wagners, the lead investigator) said. “There is a constant exposure to any cell or soluble factor that circulates, at close to physiologic levels.”  – After several weeks of sharing their blood systems with young mice, the hematopoietic stem cells of the older mice changed markedly. Exposure to a younger animal’s blood somehow pushed the older animal’s hematopoietic stem cells back to a more youthful state, in which they were fewer in number but recovered nearly all of their blood-cell-generating capacity. When transplanted into mice whose own blood-producing cells had been eliminated by radiation, the “rejuvenated” stem cells repopulated the blood with a mixture of cell types similar to that generated by transplanted young stem cells. No such changes occurred in the young mice in these pairings, or among age-matched pairs of animals.”

There is significantly more to the recent research findings, and that is that IGF-1 expression in osteoblasts present in the haematopoietic stem cell bone marrow niches is responsible for the decline in vitality and differentiation capabilities of haematopoietic stem cells in older mice, and neutralizing the IGF-1 in the bone marrow also restores the vitality and differentiation capabilities of these stem cells.

In more detail, ” Wagers and her team haven’t yet discovered the blood-borne factor that triggers this apparent restoration of youthfulness in aged hematopoietic stem cells. But they did find two important clues to how it transmits its effects.  – First, they found evidence that this factor works via bone-forming cells known as osteoblasts, which also are present in bone marrow and help regulate hematopoietic stem cells. When old animals were exposed to young blood, their osteoblasts reverted to more youthful numbers. They also behaved more like younger osteoblasts in their interactions with hematopoietic stem cells. Hematopoietic stem cells grown in cultures with these “rejuvenated” osteoblasts regained the blood-cell-generating capacity characteristic of youthful stem cells. For osteoblasts, the opposite was also true: the bone-forming cells of young animals- from humans as well as mice — showed signs of aging when they were exposed to blood from an older animal. — The team also found that the insulin-like growth factor 1 (IGF-1) hormone appears to be necessary to maintain these stem-cell-regulating osteoblasts in an aged state. When they blocked IGF-1 activity in osteoblast cells in culture or in bone marrow, aged osteoblasts reverted to a “younger” state, and could pass that rejuvenation effect on to hematopoietic stem cells. Blocking IGF-1 activity in the bloodstream of mice didn’t have the same effect, which suggests that IGF-1 acts specifically through osteoblasts. — Oddly enough, IGF-1 is best known for its growth-promoting and potentially anti-aging effects in other tissues, including muscles and bones. “Our findings highlight the fact that IGF-1 signaling is complex and depends in part on the tissue involved,” said Wagers(ref).”

Getting back to vampires, the results of the new study suggests a cure for their centuries-old thirst for blood, since it suggests that blocking the effects of IGF-1 in bone marrow osteoblasts could have the same rejuvenating affect as the blood of a young person.  Of course this would have to be validated by a clinical trial.  Can you imagine a drug company setting up such a trial for vampires where half the participants take a drug that blocks bone marrow IGF-1 and the control group participants go out and hunt human victims and drink their blood in normal vampire fashion? 

Seriously, there just could be some longevity benefit to selective blocking of IGF-1 in osteoblasts.  More must be learned about this possibility.  And the mouse results must be validated in humans.

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29. January 2010 by admin.

Do you remember the Monopoly card that says “Go to jail.  Go directly to jail.  Do not pass Go, Do not collect $200?”  Well, imagine that there is a cell reprogramming card that says, say when you land on skin cell, “Go to nerve cell, go directly to nerve cell.  Do not pass iPSC status. Do not collect pluripotent reprogramming factors.”  Very recent research shows that that card exists, and its existence is giving us a broad new perspective on epigenetic regulation of cell fates.  By modifying epigenetic factors, it appears that one type of body cell can be changed, very likely, into any other type of body cell, directly and without a need for reversion into induced pluripotent stem cell (iPSC) status. And the process is efficient.  This post reviews background on cell reprogramming, the new research in context, and speculates on the implications.

Background on cell reprogramming

Research on reprogramming cells from one type to another goes back to the 1980s, long before the first iPSC was produced.  The first work in this area involved fusing two different kinds of cells together to form heterokaryons.  A hetrokaryon is “A cell with two separate nuclei formed by the experimental fusion of two genetically different cells(ref).”  A 1986 publication reports Rapid reprogramming of globin gene expression in transient heterokaryons, where “Interspecific heterokaryons were formed by fusing adult mouse erythroleukemia (MEL) cells and human embryonic/fetal erythroid (K562) cells with each other, or with a variety of mouse and human nonerythroid cell types.”  A series of other publications based on studies of heterokaryons followed.  A 1993 publication Reversibility of the differentiated state in somatic cells reported “Analysis of de novo gene activation in multinucleated heterokaryons has shown that the differentiated state, although stable, is not irreversible, and can be reprogrammed in the presence of appropriate combinations of trans-acting regulatory molecules.”

A 1999 publication Use of somatic cell fusion to reprogram globin genes reports “Experiments with heterokaryons demonstrate that the reprogramming is due to trans-acting factors that are developmental-stage-specific. These results suggest the feasibility of using fusisome-carried sets of nuclear factors to reprogram somatic cells.”  A relatively recent January 2009 study Nuclear reprogramming in heterokaryons is rapid, extensive, and bidirectional reports “Here, we show that hundreds of genes are activated or repressed within hours of fusion of human keratinocytes and mouse muscle cells in heterokaryons, and extensive changes are observed within 4 days.”

Another thread of research related to cell reprogramming was cloning.  Dolly, the world’s most famous sheep, was cloned in 1996.  “The production of Dolly showed that genes in the nucleus of such a mature differentiated somatic cell are still capable of reverting back to an embryonic totipotent state, creating a cell that can then go on to develop into any part of an animal(ref).^[11]”

Another chain of studies in the mid 2000s related to cell reprogramming involved the impact of microenvironment on cell fate.  It was found that when cloned liver stem cells were placed into a cardiac microenvironment, they transformed themselves to acquire a cardiac phenotype and function(ref)(ref)(ref). “Collectively, these results support the conclusion that these adult-derived liver stem cells respond to signals generated in a cardiac microenvironment ex vivo acquiring a cardiomyocyte phenotype and function(ref).”

The hetrokaryon studies, the cloning work and the studies related to the effect of microenvironment indicate that cells of one kind can be directly reprogrammed into cells of another kind and that there is some kind of molecular signaling process involved.  The big more-recent cell reprogramming news of course was the ability to revert any cell to embryonic stem cell-like pluripotency, the creation of induced pluripotent stem cells (iPSCs) starting in 2006.  The first comprehensive discussion of iPSCs in this blog was the March 2009 post Rebooting cells and longevity, and iPSCs have been mentioned or discussed in many subsequent blog posts.  The first studies described the use of four transcription factor proteins to create iPSCs: Oct4, Sox2, Klf4, and c-Myc.  Much progress in creating iPSCs in the last year including use of other transcription factor combinations, safer less-oncogenic vectors for insertion of the transcription factors, induction of stem cell expression without using transgenes, and, most recently, the use of vitamin C to improve the efficiency of reprogramming(ref)(ref). 

The 2008 publication Reprogramming of somatic cell identity summarized the situation as of the time “Nuclear transfer and cell-fusion experiments demonstrate that the epigenetic signature directing a cell identity can be erased and modified into that of another cell type. Furthermore, in the case of cloning, differentiated cells can be reprogrammed back to pluripotency to support the reexpression of all developmental programs. Recent breakthroughs highlight the importance of transcription factors as well as epigenetic modifiers in the establishment, maintenance, and rewiring of cell identity.” 

Nonetheless, the excitement about iPSCs led many researchers to forget or ignore the earlier research on cell reprogramming and assume that if one wants to start with, say, skin cells and end up with nerve (or heart or liver) cells, just about the only practical approach is a two-step one: 1.  Take some skin cells and revert them to being iPSCs, an inefficient process even when using vitamin C, and then  2.  Somehow convince those iPSCs to progressively differentiate to become nerve cells, possibly a quite tricky thing to do in-vivo.  The new research finding suggests that with the right transcription factors it might be possible to start out with any kind of cell and end up with any other kind of cell without going through an intermediate stage. 

Direct cell reprogramming

2008 saw the publication of a breakthrough study In vivo reprogramming of adult pancreatic exocrine cells to beta cells.  “Here, using a strategy of re-expressing key developmental regulators in vivo, we identify a specific combination of three transcription factors (Ngn3 (also known as Neurog3) Pdx1 and Mafa) that reprograms differentiated pancreatic exocrine cells in adult mice into cells that closely resemble -cells. The induced -cells are indistinguishable from endogenous islet -cells in size, shape and ultrastructure. They express genes essential for -cell function and can ameliorate hyperglycaemia by remodeling local vasculature and secreting insulin. This study provides an example of cellular reprogramming using defined factors in an adult organ and suggests a general paradigm for directing cell reprogramming without reversion to a pluripotent stem cell state.”

The new January 2010 research study report Direct conversion of fibroblasts to functional neurons by defined factors reports “Recent work has shown that mouse and human fibroblasts can be reprogrammed to a pluripotent state with a combination of four transcription factors. This raised the question of whether transcription factors could directly induce other defined somatic cell fates, and not only an undifferentiated state. We hypothesized that combinatorial expression of neural-lineage-specific transcription factors could directly convert fibroblasts into neurons. Starting from a pool of nineteen candidate genes, we identified a combination of only three factors, Ascl1, Brn2 (also called Pou3f2) and Myt1l, that suffice to rapidly and efficiently convert mouse embryonic and postnatal fibroblasts into functional neurons in vitro. These induced neuronal (iN) cells express multiple neuron-specific proteins, generate action potentials and form functional synapses.”

The transcription factors used in both studies are different than those used to create iPSCs and the cell-type conversion process is much more efficient than that of reverting cells to iPSC status.  The 2008 study was exciting because it described direct cell reprogramming in-vivo in a way that addresses a disease, albeit in a mouse model.  Regarding the 2010 study, the “neurons could integrate into pre-existing neural networks and form independent synapses with each other.  – This system bypasses production of tumorigenic pluripotent cells, a main barrier to using iPSCs in regenerative medicine, and may provide a platform for more efficient disease modeling and drug discovery(ref).” “They also tested the procedure on skin cells from the tails of adult mice. They found that about 20 percent of the former skin cells transformed into neural cells in less than a week. That may not, at first, sound like a quick change, but it is vast improvement over iPS cells, which can take weeks. What’s more, the iPS process is very inefficient: Usually only about 1 to 2 percent of the original cells become pluripotent(ref).”

Implications include:

·        hESCs, iPSCs and other stem cell types are likely to turn out to be extremely important, but are not the only games-in-town for producing desired cells where and as needed.

·        Cloning taught us that all body cells encompass the same genes and that any one cell encompasses the possibilities in all other cells.  The differences among cells are ones of epigenetic gene expression.  The latest research indicates it may be possible freely to change one cell type to another via introducing highly specific transcription factors.

·        It may turn out to be practical to convert many cell types to other cell types in-vitro, in-vivo or both, allowing the development of many new regenerative medicine applications.  The challenge is discovering the transcription factors and other epigenetic modifiers needed and how to introduce them so as safely get a desired result.

·        The new work probably makes addressing cell senescence even more critical.  I suspect that transforming an old-near-senescent skin cell into a nerve cell will produce an old near-senescent nerve cell unless issues like telomere lengths are also addressed.

·        The new work is likely to contribute to an acceleration in research relating to the discovery and isolation of gene transcription factors(ref), micro-RNAs(ref), HATs and HDACs(ref), DNA demethylases(ref) and other gene regulatory factors.  Unraveling all of those may well take decades. 

I am not worried about running out of work here.

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26. January 2010 by admin.

In the blog entry The stem cell supply chain – closing the loop for very long lives, I have suggested that it might be possible to re-introduce fully pluripotent stem cells into the body so as to close the loop in the stem cell supply chain and enable much longer lives. This post reports progress towards that point, again a topic related to Vitamin C suggested by reader jeg3.

Background

Recapitulating the essence of the stem cell supply chain concept: “Stem Cell Supply Chain Breakdown is the newest theory of aging described in my treatise and the one I am currently most excited about.  According to a simplified model of this theory a newly-conceived human embryo consists of pluripotent stem cells (Type A), ones that can potentially divide into any body cells.  With growth, these proliferate and, in a remarkably articulated manner, progressively differentiate into multipotent stem cells (Type B), progenitor cells (Type C), mature body somatic cells (Type D), and many eventually become senescent cells (Type E).”  — ‘According to the best current understanding of stem cells this is an open-loop once-through process.  The above list is in order of increasing cell-type specificity and decreasing cell-type potency to differentiate into other cell types.  Starting at conception and throughout life, all cells on this list except the senescent ones will selectively reproduce and possibly differentiate into cells of types further down in the list.  The state of the body in terms of makeup of cell types continues to change through life and the process goes inexplicably from start (conception) leading to end (death’).  The stem cells themselves are subject to replicative senescence.   Early in life, Type A cells tend to vanish.  With aging, pools of type B and type C cells become exhausted and are less capable of differentiation to renew the supply of Type D cells.  The stem cell supply chain slows down and ceases to function well.  There are fewer healthy Type D cells and more Type E cells, and disease and death soon follow.

The blog entry The stem cell supply chain – closing the loop for very long lives suggests an approach that could conceivably transform the stem cell supply chain from being a once-through process to being a continuous open-loop process.   “There is a possibility of keeping the stem cell supply chain active indefinitely.  The key idea is to use induced Pluripotent Stem cells (iPSCs) which are fully pluripotent and equivalent to embryonic stem cells(ref)(ref)(ref) as feedstock Type A cells in adults to make the stem cell supply chain as a continuous loop process instead of a once-through process.”

I assume the reader is generally familiar with iPSCs and the general approaches to reprogramming cells to iPSC status.  See, for example, the blog posts Rebooting cells and longevity, Update on induced pluripotent stem cells and “Footprint-free” iPSCs – and a crazy wager offer.

This blog post reports research progress on creating iPSCs which may eventually lead to closing the loop.  An old dear friend seems to be involved, Vitamin C.  The study Vitamin C Enhances the Generation of Mouse and Human Induced Pluripotent Stem Cells was timed as a Christmas present and published December 24 2009.  Some of the points related to the new study are:

1.     The approaches to reverting cells to iPSC status have been remarkably inefficient.  “Soon after the exciting discovery of a method to transform human skin cells into stem cells in 2007 came the frustration of actually trying to make a sufficient amount of these induced pluripotent stem (iPSC) cells.  The process is so inefficient that scientists typically only get 0.01 percent of a sample of human skin, or fibroblast, cells to form iPS cell colonies after they infect fibroblasts with the retroviruses used to induce pluripotency(ref).”  The new study report indicates  “However, the low efficiency of iPSC generation is a significant handicap for mechanistic studies and high throughput screening, and also makes bona fide colony isolation time consuming and costly. The efficiency of alkaline phosphatase-positive (AP⁺) colony formation with the four Yamanaka’s factors (Sox2, Klf4, Oct4, c-Myc; SKOM) in mouse fibroblasts is about 1% of the starting population, but only around 1 in 10 of those colonies is sufficiently reprogrammed to be chimera competent – -. ”  This iPSC reprogramming inefficiency has been noted by others as well(ref)(ref).

2.     It is hard to revert old or near-senescent cells to iPSC status given age-related upregulation of tumor suppressor genes. “While our work was in progress, six independent laboratories identified cell senescence as a roadblock for reprogramming (Hong et al. 2009) — “Functional analyses of these genes demonstrate that the p53-p21 pathway serves as a barrier not only in tumorigenicity, but also in iPS cell generation,”  Kawamura et al., 2009, Li et al. 2009 “In murine cells, Arf, rather than Ink4a, is the main barrier to reprogramming by activation of p53 (encoded by Trp53) and p21 (encoded by Cdkn1a); whereas, in human fibroblasts, INK4a is more important than ARF. Furthermore, organismal ageing upregulates the Ink4/Arf locus and, accordingly, reprogramming is less efficient in cells from old organisms,” Marión et al. 2009 “These observations indicate that during reprogramming cells increase their intolerance to different types of DNA damage and that p53 is critical in preventing the generation of human and mouse pluripotent cells from suboptimal parental cells,”  Utikal et al., 2009, Zhao et al., 2008).”  This has led to significant interest in finding compounds that “alleviate cell senescence without increasing the risk of mutations.”  The researchers set out testing antioxidants for this purpose.  The one that worked was vitamin C.

3.    The main finding of the study is that vitamin C can markedly improve the efficiency of the reprogramming process for both mouse and human cells. “We show here that vitamin C, a common nutrient vital to human health, enhances the reprogramming of somatic cells to pluripotent stem cells. By adding Vc to the culture medium, we can now obtain high-quality iPSCs from mouse and human cells routinely.”   Exactly how vitamin C works to achieve this end is not clear.  Other tested antioxidants appeared not to have an effect.  It is highly possible that epigenetic factors are involved.  “Besides reducing p53, Vc accelerates transcriptome changes during reprogramming and allows the conversion of pre-iPSCs to iPSCs. The extent to which these observations relate to cell senescence is unclear, and it is possible that Vc is acting in other ways as well. For example, it could accelerate stochastic events during reprogramming, perhaps by promoting epigenetic modifications that allow further changes to proceed. In this regard, Vc is a cofactor in reactions driven by dioxygenases including collagen prolyl hydroxylases, HIF (hypoxia-inducible factor) prolyl hydroxylases, and histone demethylases (Shi, 2007), and it is interesting to consider that Vc might influence reprogramming by increasing the activity of these enzymes. Histone demethylases are important for development and modulate the expression of the ESC master transcription factor Nanog (Cloos et al., 2008), so it is possible that Vc allows the reprogramming to run more smoothly by facilitating histone demethylation.” 

The new finding can result in increased productivity in creating iPSCs.  However, there is still a way to go before the “closing the stem cell supply chain loop” hypothesis can be tested.  If iPSCs are created outside the body from a person’s tissue, safe ways must be found to introduce them back into the body so they will go about replenishing stocks of Type B and Type C stem cells without creating problems such as tumors or teratomas.

Oh Spirit of Linus Pauling Great Father of Vitamin C, are you listening?  A few days ago I wrote a blog entry Surprise!  Just when we thought we knew everything about vitamin C, pointing to new research indicating that vitamin C could be a cure for Werner’s Syndrome.  It looks like regularly taking vitamin C does a myriad of other things besides serving as a good antioxidant, things like preventing DNA damage induced by renovascular hypertension, and helping to control obesity.  This week’s new finding relates to the usefulness of Vitamin C in creating iPSCs, possibly an important finding for regenerative medicine.

We have new powerful frameworks for looking at old familiar substances like vitamin C, frameworks like epigenetics, proteomics, telomere science and cell cycle molecular biology, and these frameworks are telling us things about vitamin C that Linus may have intuited but could not have put into words.  Because most of the needed words did not exist in his time.

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25. January 2010 by admin.

The  responses to my blog posts tell me that many of you readers out there join me in being telomerase life-extension aficionados.  In case you don’t already know about it, you might want to have a look at the Sierra Sciences website.  Sierra Sciences is a small biotech research company (30 scientists), completely devoted to discovering new activators of the telomerase gene to serve the cause of human longevity.  The company was founded by Bill Andrews, one of the discoverers of the telomerase gene back when he was in charge of the molecular biology research group at Geron.

Going to the Sierra Sciences website you are greeted by a video presentation featuring Bill Andrews.  Going on to the home page you are greeted with the slogan “Cure Aging of Die Trying,” which I can personally identify with.  “Sierra Sciences, LLC is a company devoted to finding ways to extend our healthspans and lifespans beyond the theoretical maximum of 125 years.” 

Basically, the company is screening substances, searching for telomerase inducers. The home page reports: “As of January 20, 2010: We have screened 189,264 compounds — We have found 555 telomerase inducers — These represent 34 distinct drug families — Most potent compound = 6% of goal — Check back frequently for updates! — We are screening 4,000 compounds per week”. 

The website features a few fairly current video presentations relating to telomerase as well as older ones.   Finally, the company is seeking the involvement of others:  “Sierra Sciences is seeking individuals passionate about finding the cure for aging to get involved in the company at levels of grant funding, strategy, and management. — We are looking for individuals who will be interested in giving us their input on strategies and helping us to take whatever steps necessary to achieve this cure within our lifetimes.”

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24. January 2010 by admin.

This blog is now a year old and represents an accumulation of 232 posts and 270 comments.  My favorite thing seems to be reporting recent research findings in context, providing discussion and a network of citations for understanding how newly-reported research fits in to what is already known.  This has required much thinking on my part and many ideas that are original to me have appeared here.  But there also have been two streams of brand-new original thinking that have appeared in this blog, ideas that did not exist “out there” before they appeared here.  The purpose of this post is to highlight those two streams and point to the posts that contain them.

Giuliano’s Law

The first stream relates to Giuliano’s Law, which is “Starting now, every seven years will see the emergence of practical age-extension interventions (ones that have a potential of leading to extraordinary longevity) that double the power of the interventions available at the start of the 7 year period.  That is, on an average basis, the practical anti-aging interventions available at the end of a seven-year period will enable twice the number of years of life extension than did the interventions available at the start of the period.  Life extension is measured in years of life expectancy beyond those actuarially predicted for a given population.

This law and some of the rationale for it was laid out in the March 2009 post Giuliano’s Law: Prospects for breaking through the 122 year human age limit.  It is an analog of Moore’s law for the power of computers and is valid for many of the same reasons.  The post Factors that drive Giuliano’s Law goes into those reasons in detail, a positive feedback loop  of interaction exists between societal need, market, marketing channels and economics, changes in user expectations, market vehicles, user applications, marketing channels, advancement in the relevant basic science, advancement in technology, advancement in manufacturing, and entrepreneurial environment. 

I argue that the juggernaut defined by these interacting factors is already immense, growing mightily in power and on the road just as surely as the computer revolution was on the road in 1958.  The same advances that further health and medicine will further the cause of longevity.  Anti-aging science is not some arcane discipline off to the side.  It is a natural byproduct of the life sciences revolution that is well underway.  

The blog post More on Giuliano’s Law; calculating my longevity prospects is a more personal one, looking at my own life expectancy assuming Giuliano’s law is correct under three scenarios: Case 1:  I discontinue my anti-aging firewalls program and go about living a normal life.  Case 2: I continue pursuing my existing anti-aging firewall program keeping it exactly as it is now and Case 3: I continue to follow all the relevant threads of anti-aging research, to update the Anti-Aging Firewalls Treatise weekly or more as I have been doing, and periodically update the firewalls and firewall program to reflect this emerging new knowledge.  Further, I incorporate new science-based anti-aging substances and procedures into the firewall program as they become available. As you might guess, the Case 3 projection is that I have a good shot at breaking the 123 years maximum age barrier.  I hope that I am right!

The stem cell supply chain theory of aging

After generating a number of blog posts related to stem cells and stem cell differentiation I started to see a whole new viewpoint on aging connected with stem cells.  I first laid this viewpoint out in my September 2009 blog post An emerging new view of aging – the stem cell supply chain.  The idea is that there is a hierarchy of stem cells in human bodies ranging from pluripotent embryonic-like stem cells at the top to specialized progenitor cells just above ordinary somatic cells, with senescent cells at the very bottom of the heap.  In a healthy living organism, a supply chain is in constant operation.  Cells at one level are replenished by differentiation of cells at a higher level.  In aging the pools of stem cells at the higher levels become exhausted, cell regeneration via differentiation of stem cells is compromised, and sickness and death follow. 

The blog entry The stem cell supply chain – closing the loop for very long lives suggests an approach that could conceivably transform the stem cell supply chain from being a once-through process to being a continuous loop.  The idea is to generate autologous induced pluripotent stem cells in order to keep the stem cell supply chain operating indefinitely.  I have created a large number of posts about stem cells and the stem cell supply chain is an underlying concept of several of them.

A follow-up posting will comment on how my views of aging and anti-aging interventions have evolved since starting this blog.

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22. January 2010 by admin.

It seems like scarcely a day goes by now without new telomerase research news items showing up in the popular press, the latest having to do with fish oil.  I mention this news here but my purpose is to make a few broader points:

1.      Taking a number of popular supplements in the anti-aging firewalls Supplement Regimen like Vitamin E, fish oils, Vitamin D3 and resveratrol can lead to telomeres being longer than they otherwise might be, possibly because they induce the production of telomerase, possibly for other reasons.  As such, these supplements are quite possibly life-extending.

2.     Despite the popular conception, telomere lengths do not uniformly get shorter with advancing age.  Sometimes they get longer over substantial periods of time.  Nobody is quite sure of how or why.

3.     Many of the same supplements that lead to longer telomeres in healthy people seem to have the capacity to turn off telomerase and shorten telomeres in cancer cells and help kill them.

Fish Oil and longer telomeres

Yesterday’s news is based on a January 20 publication in JAMA: Association of marine omega-3 fatty acid levels with telomeric aging in patients with coronary heart disease.  “Context  Increased dietary intake of marine omega-3 fatty acids is associated with prolonged survival in patients with coronary heart disease. However, the mechanisms underlying this protective effect are poorly understood. ^— Objective  To investigate the association of omega-3 fatty acid blood levels with temporal changes in telomere length, an emerging marker of biological age. ^— Design, Setting, and Participants  Prospective cohort study of 608 ambulatory outpatients in California with stable coronary artery disease recruited from the Heart and Soul Study between September 2000 and December 2002 and followed up to January 2009 (median, 6.0 years; range, 5.0-8.1 years). ^— Main Outcome Measures  We measured leukocyte telomere length at baseline and again after 5 years of follow-up. — Results  Individuals in the lowest quartile of DHA+EPA experienced the fastest rate of telomere shortening (0.13 telomere-to-single-copy gene ratio [T/S] units over 5 years; 95% confidence interval [CI], 0.09-0.17), whereas those in the highest quartile experienced the slowest rate of telomere shortening (0.05 T/S units over 5 years; 95% CI, 0.02-0.08; P < .001 for linear trend across quartiles). –. Each 1-SD increase in DHA+EPA levels was associated with a 32% reduction in the odds of telomere shortening (adjusted odds ratio, 0.68; 95% CI, 0.47-0.98). ^— Conclusion  Among this cohort of patients with coronary artery disease, there was an inverse relationship between baseline blood levels of marine omega-3 fatty acids and the rate of telomere shortening over 5 years.”

The temptation is to conclude that “taking fish oils leads to less telomere length shortening,” but that is not what the study says.  The conclusions of this study are based on levels of DHA and EPA measured at baseline and do not take possible supplementation during the study period into account.  Further, the study population was a very special one, people with coronary artery disease.  Another temptation is to conclude that fish oil leads to the expression of telomerase, but this conclusion is also not directly supported.  The study does not say why the rate of telomere shortening was less in those with higher baseline levels of the fish oils.  Nontheless, the popular press has yielded to these temptations with news story titles like Is Fish Oil the Elixir of Life? And  Stay young by eating fish oil, say scientists. I chalk this up to a general hunger in the population for anti-aging news.  And now, after Blackburn, Greider and Szostak  have received a Nobel prize for work on telomeres and telomerase, it is almost household news that longer telomeres are associated with longevity and are better for health.

Natural telomere lengthening with age

The report on omega-3 fish oils and telomeres was preceded two weeks ago by another PLoS ONE report based on data for the same 608 individuals in the Heart and Soul Study Telomere length trajectory and its determinants in persons with coronary artery disease: longitudinal findings from the heart and soul study.  “METHODOLOGY/PRINCIPAL FINDINGS: In a prospective cohort study of 608 individuals with stable coronary artery disease, we measured leukocyte telomere length at baseline, and again after five years of follow-up. We used multivariable linear and logistic regression models to identify the independent predictors of leukocyte telomere trajectory. Baseline and follow-up telomere lengths were normally distributed. Mean telomere length decreased by 42 base pairs per year (p<0.001). Three distinct telomere trajectories were observed: shortening in 45%, maintenance in 32%, and lengthening in 23% of participants. The most powerful predictor of telomere shortening was baseline telomere length (OR per SD increase = 7.6; 95% CI 5.5, 10.6). Other independent predictors of telomere shortening were age (OR per 10 years = 1.6; 95% CI 1.3, 2.1), male sex (OR = 2.4; 95% CI 1.3, 4.7), and waist-to-hip ratio (OR per 0.1 increase = 1.4; 95% CI 1.0, 2.0). CONCLUSIONS/SIGNIFICANCE: Leukocyte telomere length may increase as well as decrease in persons with coronary artery disease. Telomere length trajectory is powerfully influenced by baseline telomere length, possibly suggesting negative feedback regulation. Age, male sex, and abdominal obesity independently predict telomere shortening.”

Note that this is not the first study to show average telomere length increasing for a substantial part of the study population over a substantial period of time. According to a large Swedish study, a third of the population experienced telomere lengthening over 9 to 11 year intervals(ref).

Fish Oil, other supplements and turning off telomerase in cancers

According to the 2005 report Polyunsaturated fatty acids inhibit telomerase activity in DLD-1 human colorectal adenocarcinoma cells: a dual mechanism approach “We investigated the inhibitory effect of various fatty acids on telomerase, with particular emphasis on those with antitumor properties, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).  – In contrast, cis-unsaturated fatty acids significantly inhibited the enzyme, and the inhibitory potency was elevated with an increase in the number of double bonds. Accordingly, polyunsaturated fatty acids (PUFAs), like EPA and DHA, appeared to be powerful telomerase inhibitors. — Culturing DLD-1 cells with either EPA or DHA resulted in a remarkable decrease in telomerase activity. EPA and DHA inhibited telomerase by down-regulating human telomerase reverse transcriptase (hTERT) and c-myc expression via protein kinase C inhibition. These results indicate that PUFAs can directly inhibit the enzymatic activity of telomerase as well as modulate the telomerase at the transcriptional level.” 

So there we have it.  The same DHA and EPA fish oils that seem to be correlated with longer telomeres in the recent population study also clobber telomerase in a cancer cell line.  This property seems to be shared by several other popular supplements as well. 

Alpha-tocopherol (Vitamin E) seems to repress age-related telomere shortening(ref). Yet, the 2007 study Vitamin E suppresses telomerase activity in ovarian cancer cells concludes “Our data suggest that, by suppressing telomerase activity, Vitamin E may be an important protective agent against ovarian cancer cell growth as well as a potentially effective therapeutic adjuvant.”  

Another supplement that is both associated with longer telomere lengths and that inhibits telomerase expression in cancer cells is Vitamin D3.   The 2007 paper Higher serum vitamin D concentrations are associated with longer leukocyte telomere length in women reports ”Serum vitamin D concentrations were measured in 2160 women aged 18–79 y (mean age: 49.4)  – Serum vitamin D concentrations were positively associated with LTL (longer telomere length) (r = 0.07, P = 0.0010), and this relation persisted after adjustment for age (r = 0.09, P < 0.0001) and other covariates (age, season of vitamin D measurement, menopausal status, use of hormone replacement therapy, and physical activity; P for trend across tertiles = 0.003). The difference in LTL between the highest and lowest tertiles of vitamin D was 107 base pairs (P = 0.0009), which is equivalent to 5.0 y of telomeric aging.” Yet, D3  is another substance that can help inhibit the expression of telomerase in cancer cells as pointed out in the 2003 publication Combination treatment with 1alpha,25-dihydroxyvitamin D3 and 9-cis-retinoic acid directly inhibits human telomerase reverse transcriptase transcription in prostate cancer cells.  Also, see Induction of Ovarian Cancer Cell Apoptosis by 1,25-Dihydroxyvitamin D3 through the Down-regulation of Telomerase.

Resveratrol is another supplement substance that seems to have a dual personality, on the one hand associated with enhancing telomerase activity in healthy cells(ref)(ref) and on the other hand inhibiting expression of telomerase in cancer cells(ref)(ref).   

The active ingredient in green tea EGCG appears to be yet another dietary substance with the dual personality characteristic.  Drinking ample quantities of green tea appears to slow down age-dependent telomere shortening on the one hand(ref),  and EGCG represses telomerase expression in cancer cells(ref)(ref).  I am sure the same point can be made for other substances in the anti-aging supplement regimen.

Telomerase regulation is in fact a very complex process(ref).   As I have put it in my treatise “These results suggests to me that telomere shortening is a complex process involving a balance of shortening due to cell division, lengthening due to natural telomerase expression and perhaps cell replacement due to differentiation of stem cells. And these in turn are affected by many lifestyle and dietary factors and moderated by cell-signaling feedback loops.” 

Yet, it could well be the case that management of telomere length is our best hope for realizing extraordinary longevity in the nearer future.  The 12^th theory of aging in my treatise Telomere Shortening and Damage forwards the hypothesis that longer telomere lengths are likely to be correlated with longer lifespans and that keeping one’s telomeres as long as possible through expression of telomerase is vital for health and longevity. Telomeres and telomerase are among my favorite subjects for treatment in this blog.  Among the many relevant blog postings are the recent postings Exercise, telomerase and telomeres, Timely telomerase tidbits, Breakthrough telomere research finding, and Telomere and telomerase writings. And, as time proceeds, I expect there will be more.

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20. January 2010 by admin.

In researching the previous blog post Changing the threshold for neuromuscular fatigue in the young and old, carnosine or beta-alanine supplementation, I discovered a fascinating set of relationships among the substances mentioned in the title of this post and promised to report further on them.  I do that here, requiring a review of some of the basic biochemistry involved.  Although I am not clear of all the implications involved, I flag a few of these in the areas of pain management, synapse development and learning, maintaining mental balance, sleep and mental acuity.   

GABA

GABA (gamma-Aminobutyric acid) “is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays a role in regulating neuronal excitability throughout the nervous system. In humans, GABA is also directly responsible for the regulation of muscle tone.^[1] (ref)”  The operation of GABA is complex.  “In vertebrates, GABA acts at inhibitory synapses in the brain by binding to specific transmembrane receptors in the plasma membrane of both pre- and postsynaptic neuronal processes. This binding causes the opening of ion channels to allow the flow of either negatively charged chloride ions into the cell or positively charged potassium ions out of the cell. This action results in a negative change in the transmembrane potential, usually causing hyperpolarization. Two general classes of GABA receptor are known: GABA_A in which the receptor is part of a ligand-gated ion channel complex, and GABA_B metabotropic receptors, which are G protein-coupled receptors that open or close ion channels via intermediaries (G proteins).  GABA_A receptors are chloride channels, that is, when activated by GABA, they allow the flow of chloride ions across the membrane of the cell (ref).” “GABA_B receptors (GABA_BR) are metabotropic transmembrane receptors for gamma-aminobutyric acid (GABA) that are linked via G-proteins to potassium channels.^[1] These receptors are found in the central and peripheral autonomic nervous system^[2](ref). 

Carnosine, homocarnosine, anserine and beta-alanine

Carnosine and homocarnosine are closely related dipeptide substances, both found in substantial quantities in the mammalian brain and muscles, and they are similar also to anserine found in bird muscles and brains as well as humans.  L-Carnosine is a dipeptide composed of the two amino acids L-histidine and beta-alanine.  And Homocarnosine is a dipeptide composed of the amino acids L-histidine and GABA.  The chemical structures of the two substances are remarkably similar; you can see them diagrammed here.  (Unfortunately, the way this blog software is set up it is hard for me to include diagrams here).  This little article L-Carnosine and Related Histamine-Derived Molecules comments further on the three substances. “Carnosine and homocarnosine are both produced by the same ATP-driven enzyme, carnosine synthetase, and both molecules exhibit very similar properties. The concentration of homocarnosine in the human brain, however, is about 100 times that of carnosine. It is manufactured by glial cells (oligodendrocytes) except in the olfactory bulb, where it is synthesized by neurons. The highest brain homocarnosine concentrations are found in the substantia nigra, dentate gyrus and olfactory bulb as well as in the cerebrospinal fluid.”

So, going back to the discussion of the previous blog entry, Changing the threshold for neuromuscular fatigue in the young and old, carnosine or beta-alanine supplementation, chemically, beta-alanine is one of the dipeptide components of l-carnosine, the wonderful stuff discussed in the blog entry The curious case of l-carnosine.  Homocarnosine, on the other hand, molecularly substitutes GABA for beta-alanine. 

The three dipeptides Carnosine, homocarnosine, and anserine, have a number of biological properties in common.  All appear to be antioxidants(ref).  All three are protective against peroxyl radical-mediated Cu,Zn-superoxide dismutase modification(ref).  Both carnosine and homocarnosine can detoxify the highly reactive aldehyde acrolein(ref).  Of particular note, all three are inhibitors of GABA metabolism.  That is, they lead to higher levels of GABA in the brain.  This was pointed out in a 1978 publication Homocarnosine, carnosine and anserine on uptake and metabolism of GABA in different subcellular fractions of rat brain.  “L-Carnosine, L-homocarnosine and L-anserine are inhibitors of GABA metabolism. They show differential action on GABA-transaminase from synaptosomes compared to the extrasynaptosomal enzyme.” A 2004 publication also identifies beta-alanine as a GABA uptake inhibitor. 

Much of the research literature on these substances was published prior to 2000. The more-recent literature has since been scanty and scattered as indicated in the 2005 title Carnosine and homocarnosine, the forgotten, enigmatic peptides of the brain.  

Carnosine and homocarnosine are degraded in the body by carnosinase, “An enzyme that hydrolyzes carnosine (amino-acyl-l-histidine) and other dipeptides containing l-histidine into their constituent amino acids(ref).”  Activity of carnosinase tends to increase with age, leading to lower levels of carnosine in older people, however a very recent publication suggests that the presence of homocarnosine tends to inhibit the degradation of carnosine by carnosinase.  “Activity of carnosinase (CN1), the only dipeptidase with substrate specificity for carnosine or homocarnosine, varies greatly between individuals but increases clearly and significantly with age. — Further, CN1 activity was dose dependently inhibited by homocarnosine. — Homocarnosine inhibits carnosine degradation and high homocarnosine concentrations in cerebrospinal fluid (CSF) may explain the lower carnosine degradation in CSF compared to serum. Because CN1 is implicated in the susceptibility for diabetic nephropathy (DN), our findings may have clinical implications for the treatment of diabetic patients with a high risk to develop DN. Homocarnosine treatment can be expected to reduce CN1 activity toward carnosine, resulting in higher carnosine levels.”

Further background information on carnosine, homocarnosine, anserine and other related nerve and muscle histidine can be found in the online monograph Carnosine and Oxidative Stress in Cells and Tissues. This monograph also describes several pathways through which these substances can be created as metabolic products of each other.

A few of the key points for the purpose of this discussion are:

·        While carnosine can play key health and longevity-supporting roles, it or beta-alanine are far from the only games in town.  Carnosine acts in synergy with homocarnosine and its levels are controlled by carnosinase. 

·        Although exogenous supplementation is possible with one or several of these dipeptides, they are created and broken down in the body in complex ways.  Homocarnosine can be formed when GABA replaces the beta-alanine component in carnosine.  It appears that carnosine and beta-alanine release is stimulated by glutamatergic receptors, at least in cultured rat oligodendrocytes(ref).  

·        Supplementation with carnosine and/or beta-alanine may be valuable for athletes and older people as described in the blog entry Changing the threshold for neuromuscular fatigue in the young and old, carnosine or beta-alanine supplementation.

·        Carnosine, beta-alanine and homocarnosine increase levels of GABA. 

Gabapentin

I have discussed the drug gabapentin in the blog entry Spinal cord injury pain – a personal story and a new paradigm. As pointed out there it has been both a very popular as well as controversial drug used as an antic-convulsant, for control of neuropathic pain and, off-label, for a number of other psychiatric and medical conditions.  Gabapentin, like carnosine, beta-alanine and homocarnosine, is a GABA agonist that increases GABA levels in the brain(ref)(ref).  Further, gabapentin increases brain levels of homocarnosine(ref)(ref).  The studies cited were on patients or on tissues from patients prone to seizures, but I would wager that at least some increases in GABA and homocarnosine levels due to taking gabapentin would apply in general.

In my blog entry on neuropathic pain, I highlighted the possible role of gabapentin in quieting pathological pain due to over-excited microglia.  A July 2009 e-publication suggests that carnosine and N-acetyl carnosine might possibly be able to accomplish a similar result.  “Chronic inflammation and oxidative stress have been implicated in the pathogenesis of neurodegenerative diseases. A growing body of research focuses on the role of microglia, the primary immune cells in the brain, in modulating brain inflammation and oxidative stress. One of the most abundant antioxidants in the brain, particularly in glia, is the dipeptide carnosine, beta-alanyl-L-histidine. — The aim of the present study was to examine the role of carnosine and N-acetyl carnosine in the regulation of lipopolysaccharide (LPS)-induced microglial inflammation and oxidative damage. –. The data shows that both carnosine and N-acetyl carnosine significantly attenuated the LPS-induced nitric oxide synthesis and the expression of inducible nitric oxide synthase by 60% and 70%, respectively.  – we demonstrated a direct interaction of N-acetyl carnosine with nitric oxide. LPS-induced TNFalpha secretion and carbonyl formation were also significantly attenuated by both compounds. N-acetyl carnosine was more potent than carnosine in inhibiting the release of the inflammatory and oxidative stress mediators. These observations suggest the presence of a novel regulatory pathway through which carnosine and N-acetyl carnosine inhibit the synthesis of microglial inflammatory and oxidative stress mediators, and thus may prove to play a role in brain inflammation.”

Having been on gabapentin for three months now has contributed to vanishing my neuropathic pain due to a spinal injury and keeps me sleeping soundly.  See my blog entry Spinal cord injury pain – a personal story and a new paradigm. 

However, there are a few things I don’t like about gabapentin, one being that it often leaves me sleepy in the mornings making it difficult to concentrate. More seriously, I recently discovered something that bothers me a lot: gabapentin inhibits neuron synapse formation and therefore probably impairs new learning.  This was reported in an October 2009 study Gabapentin receptor alpha2delta-1 is a neuronal thrombospondin receptor responsible for excitatory CNS synaptogenesis. “We have previously identified thrombospondin as an astrocyte-secreted protein that promotes central nervous system (CNS) synaptogenesis. Here, we identify the neuronal thrombospondin receptor involved in CNS synapse formation as alpha2delta-1, the receptor for the anti-epileptic and analgesic drug gabapentin.“  As explained in the LA Times Booster Shots: “Stanford University researchers examined the interaction between neurons and brain cells called astrocytes. Previous studies showed that a protein that astrocytes secrete, thrombospondin, is critical to the formation of the brain’s circuitry. In the study, researchers found that thrombospondin binds to a receptor, called alpha2delta-1, on the outer membrane of neurons. In a study in mice, they showed that the neurons that lacked alpha2delta-1 could not form synapses in response to the presence of thrombospondin. — Alpha2delta-1 is the receptor for gabapentin. That has been known, although scientists did not understand how gabapentin worked. But the new research revealed that when gabapentin was given to mice, it prevented thrombospondin from binding to the receptor, thus stopping the synapse formation.  While gabapentin, which is sold under the trade name Neurontin, does not dissolve pre-existing synapses, it prevents the formation of new ones. That’s why the medication may be dangerous if given to pregnant women or young children, the authors said. The majority of the brain’s synapses are formed in uteri and early childhood.”  We now know that synapse formation goes on throughout life, and I don’t like the idea of it being stopped in me. 

Some of the questions I am left with are:

·        Is seizure control associated with taking gabapentin due to higher levels of brain homocarnosine or GABA, or due to some other effect of the drug?

·        Can l-carnosine or N-acetyl carnosine achieve some of the pain control and other benefits attributed to gabapentin?

·        What if any of the general health benefits of supplementation by l-carnosine are also achieved by supplementation with beta-alanine, by taking gabapentin?  Is gabapentin a “longevity drug?”

·        What are the actual implications on adult learning of gabapentin inhibiting new synapse formation?

·        What are the differential effects of supplementation with l-carnosine, supplementation with beta-alanine, supplementation with GABA or taking the drug gabapentin on brain neurons, in CNS glial cells and in muscle tissues? 

My current personal plans are 1. to stay on 500mg of l-carnosine twice daily, 2.   To phase off of gabapentin as soon as possible consistent with my neuropathic pain not returning; pursuant to this,I have just phased down from 900mg a day to 600mg, and 3. Of course to keep alert to any new research developments that might affect these decisions.

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18. January 2010 by admin.

First of all, my thanks to reader Jeg3 who put me onto this topic via a comment to the blog post Exercise, telomerase and telomeres.  It seems that both younger people who participate in strenuous sports and old folks who are in danger because of loss of muscle strength can benefit considerably from increasing the carnosine levels in their muscles.  And this can be accomplished to some extent by eating meat, supplementation with l-carnosine or supplementation with beta-alanine.  This blog post reviews the research in this area and steps towards muscle strengthening that can be taken by both athletes and older folks like me. 

I am also planning a follow-up blog post that looks at a fascinating set of similarities and relationships in behavior of beta-alanine, l-carnosine and gabapentin in terms of actions on GABA receptors in nerves and glia.  This post will relate these substances to topics like pain management, maintaining mental balance, sleep and mental acuity. 

I fell in love with l-carnosine over ten years ago when I learned how it could delay or reverse cellular senescence.  It can triple the replicative lifespan of fibroblasts in culture.  For an introduction to this fascinating substance, see the blog post The curious case of l-carnosine.  L-carnosine has long been part of my personal supplement regimen and is in my suggested anti-aging Supplement Regimen.

Beta-alanine and carnosine

The research of relevance to this blog entry has to do with supplementation to increase muscle carnosine levels in two populations: those who participate in high-intensity exercise like long-distance running, and the elderly. The studies I cite are mostly concerned with beta-alanine supplementation, though I am not completely convinced that this is the best approach to building up carnosine levels in muscles.  Beta alanine “is a naturally occurring beta amino acid, — is a component of the naturally occurring peptides carnosine and anserine and also of pantothenic acid (vitamin B₅) which itself is a component of coenzyme A. Under normal conditions, β-alanine is metabolized into acetic acid. — β-Alanine is the rate-limiting precursor of carnosine, which is to say carnosine levels are limited by the amount of available β-alanine(ref).” 

Another source indicates “The greatest natural dietary sources of beta-alanine are believed to be obtained through ingesting the beta-alanine containing dipeptides: carnosine, anserine and balenine, rather than directly ingesting beta-alanine. These dipeptides are found in protein rich foods such as chicken, beef, pork and fish. It is predominantly through ingesting the dipeptide carnosine that we ingest most of our beta-alanine, as the two other dipeptides are not found nearly as plentiful in our typical coniferous diet. However, obtaining beta-alanine through these dipeptides is not the only way, as our bodies can synthesize it in the liver from the catabolism of pyrimidine nucleotides which are broken down into uracil and thymine and then metabolized into beta-alanine and B-aminoisobutyrate.” 

Simply put, in the body both carnosine and beta alanine create each other and the presence of one leads the body to create the other.  Beta alanine has been a very popular sports and body-building supplement but carnosine itself is just now emerging to be known as a sports supplement(ref). 

A 2009 study looks at how long carnosine stays in muscles, once its level has been built up by supplements, Carnosine loading and washout in human skeletal muscles. “The oral ingestion of β-alanine, the rate-limiting precursor in carnosine synthesis, has been shown to elevate the muscle carnosine content both in trained and untrained humans.– The β-alanine supplementation significantly increased the carnosine content in soleus by 39%, in tibialis by 27%, and in gastrocnemius by 23% and declined postsupplementation at a rate of 2–4%/wk. Average muscle carnosine remained increased compared with baseline at 3 wk of washout (only one-third of the supplementation-induced increase had disappeared) and returned to baseline values within 9 wk at group level. — It can be concluded that carnosine is a stable compound in human skeletal muscle, confirming the absence of carnosinase in myocytes. The present study shows that washout periods for crossover designs in supplementation studies for muscle metabolites may sometimes require months rather than weeks.” It is remarkably persistent stuff!

Beta alanine supplementation for endurance athletes

The 2007 publication β-Alanine supplementation augments muscle carnosine content and attenuates fatigue during repeated isokinetic contraction bouts in trained sprinters states “The ingestion of β-alanine, the rate-limiting precursor of carnosine, has been shown to elevate the muscle carnosine content. We aimed to investigate, using proton magnetic resonance spectroscopy (proton MRS), whether oral supplementation with β-alanine during 4 wk would elevate the calf muscle carnosine content and affect exercise performance in 400-m sprint-trained competitive athletes. Fifteen male athletes participated in a placebo-controlled, double-blind study and were supplemented orally for 4 wk with either 4.8 g/day β-alanine or placebo. — In conclusion, 1) proton MRS can be used to noninvasively quantify human muscle carnosine content; 2) muscle carnosine is increased by oral β-alanine supplementation in sprint-trained athletes; 3) carnosine loading slightly but significantly attenuated fatigue in repeated bouts of exhaustive dynamic contractions; and 4) the increase in muscle carnosine did not improve isometric endurance or 400-m race time.”

The 2007 study Influence of beta-alanine supplementation on skeletal muscle carnosine concentrations and high intensity cycling capacity concludes: “Muscle carnosine was significantly increased by +58.8% and +80.1% after 4 and 10 wks beta-alanine supplementation. Carnosine, initially 1.71 times higher in type IIa fibres, increased equally in both type I and IIa fibres. No increase was seen in control subjects. Taurine was unchanged by 10 wks of supplementation. 4 wks beta-alanine supplementation resulted in a significant increase in TWD (total work done) (+13.0%); with a further +3.2% increase at 10 wks. TWD was unchanged at 4 and 10 wks in the control subjects. The increase in TWD with supplementation followed the increase in muscle carnosine.” 

The purpose of the 2009 study Effects of beta-alanine supplementation and high-intensity interval training on endurance performance and body composition in men; a double-blind trial “was to evaluate the effects of combining beta-alanine supplementation with high-intensity interval training (HIIT) on endurance performance and aerobic metabolism in recreationally active college-aged men. — CONCLUSION: The use of HIIT to induce significant aerobic improvements is effective and efficient. Chronic BA supplementation may further enhance HIIT, improving endurance performance and lean body mass.”

The 2006 study Effects of twenty-eight days of beta-alanine and creatine monohydrate supplementation on the physical working capacity at neuromuscular fatigue threshold looked at non-athletes. “ — findings suggested that b-Ala supplementation may delay the onset of neuromuscular fatigue. Furthermore, there appeared to be no additive or unique effects of CrM vs. b-Ala alone on PWCFT (neuromuscular threshold fatigue test).”

Beta-alanine supplementation for the elderly

Of course there is much to the conventional wisdom that exercise is an important part of any anti-aging program for the elderly as well as for the young(ref).   But what about muscular carnosine?

The 2008 study The effect of beta-alanine supplementation on neuromuscular fatigue in elderly (55-92 Years): a double-blind randomized study looked at a small sample of elderly people. In the introduction, the article makes a compelling argument for strengthening the carnosine concentrations in muscles of older people: “Carnosine (beta-alanyl-L-histidine), a dipeptide is an efficient hydrogen ion (H⁺) buffer over the physiological pH range [1,2]. In muscle, where its concentration is highest, carnosine makes an important contribution to the maintenance of intracellular pH, which is vital for normal muscle function during intense exercise [1]. While the dipeptide is found in both Type I and Type II muscle, its concentration is highest in Type II muscle. Studies in humans and rats have demonstrated an inverse relationship between age and muscle carnosine content [3,4]. Sarcopenia, the loss in muscle mass with age, is associated with significant reductions in strength, power, and the ability to resist fatigue in elderly men and women [5,6]. Significant decreases in skeletal muscle and decline in muscle function are clearly evident after the age of fifty [5,7]. Deterioration of motor coordination, as a result of losses in strength and/or fatigue, is related to an increase in the frequency of falls [6,8] which repeatedly lead to injury and even deaths among the elderly [9].”  – “Twenty-six elderly men and women (Table 1) from independent-living communities in South Florida volunteered to participate in the study. None of the participants had any previous history of BA supplementation and maintained their regular activity and dietary patterns throughout the study”

The study looked at Pre- to post-test values for physical working capacity (PWC) at fatigue threshold (PWC_FT) for BA and PL groups.  A significant difference was found.  “Data from this study suggest that ninety days of BA supplementation may increase physical working capacity in elderly men and women. These findings may be clinically significant, as a decrease in functional capacity to perform daily living tasks has been associated with an increase in mortality [18], primarily due to increased risk of falls [9]. Further, deVries et al. [13] and Alexander et al. [8] have suggested that falls may be related to fatigue-induced deterioration of motor coordination. Thus, an improved resistance to fatigue, as reported in this study, may be important to consider when working with a similar population.  – The results of this study suggest that ninety days of BA supplementation may have significantly increased intramuscular carnosine resulting in a 28.5% increase in PWCFT due to a greater H+ buffering capacity.” This study also contains an excellent set of hyperlinked references relating to muscular fatigue,  muscular carnosine and age-related muscle functioning. 

I surmise that changing the fatigue threshold for exercise via raising muscle carnosine levels would also change the point where telomere shortening due to exercise over-stress might occur.  However, none of the papers regarding muscular carnosine and beta-alanine supplementation shed direct light on this issue, an issue raised in the blog entry Exercise, telomerase and telomeres. 

The new-to-me citations listed above leave me impressed with how important carnosine augmentation in muscles might be for health and functionality in the elderly.  On the other hand I am not sure at this point that beta-alanine supplementation is the best way to go. 

Supplementation: beta-alanine vs. l-carnosine

Studies in the literature about augmenting muscular carnosine seem to be mostly about supplementation using beta-alanine.  I am not sure the reasons for that including possibly a) the sport-medicine oriented researchers have always thought in terms of using beta-alanine instead of directly taking carnosine, b) the research was motivated or influenced by commercial makers of beta-alanine supplements, no doubt large money-makers, or c) beta-alanine is in fact the best approach to augmenting muscular carnosine.

As mentioned earlier, muscle levels of carnosine can also be raised by eating meat or by directly taking carnosine supplements.  I have had difficulty finding any study that systematically compares the efficacy of these approaches vs beta-alanine supplementation.  I have seen claims on body-building sites that beta-alanine is possibly less expensive and more bioavailable  than directly taking carnosine. 

One such site recommends taking a combination of beta-alanine and Histidine.  On the other hand, the 2006 report The absorption of orally supplied beta-alanine and its effect on muscle carnosine synthesis in human vastus lateralis states “Dietary supplementation with I) 3.2 and II) 6.4 g . d(-1) beta-alanine (as multiple doses of 400 or 800 mg) or III) L-carnosine (isomolar to II) for 4 w resulted in significant increases in muscle carnosine estimated at 42.1, 64.2 and 65.8%.”

I also found a seemingly-credible blog entry relative to beta-alanine and carnosine: “Anti-crosslinking properties of carnosine: significance of histidine. — Hobart LJ, Seibel I, Yeargans GS, Seidler NW. Department of Biochemistry, University of Health Sciences, 1750 Independence Avenue, Kansas City, MO 64106-1453, USA.  Carnosine, a histidine-containing dipeptide, is a potential treatment for Alzheimer’s disease. There is evidence that carnosine prevents oxidation and glycation, both of which contribute to the crosslinking of proteins; and protein crosslinking promotes beta-amyloid plaque formation.  It was previously shown that carnosine has anti-crosslinking activity, but it is not known which of the chemical constituents are responsible. We tested the individual amino acids in carnosine (beta-alanine, histidine) as well as modified forms of histidine (alpha-acetyl-histidine, 1-methyl-histidine) and methylated carnosine (anserine) using glycation-induced crosslinking of cytosolic aspartate aminotransferase as our model. beta-Alanine showed anti-crosslinking activity but less than that of carnosine, suggesting that the beta-amino group is required in preventing protein crosslinking. Interestingly, histidine, which has both alpha-amino and imidazolium groups, was more effective than carnosine.  Acetylation of histidine’s alpha-amino group or methylation of its imidazolium group abolished anti-crosslinking activity. Furthermore, methylation of carnosine’s imidazolium group decreased its anti-crosslinking activity. The results suggest that histidine is the representative structure for an anti-crosslinking agent, containing the necessary functional groups for optimal protection against crosslinking agents. We propose that the imidazolium group of histidine or carnosine may stabilize adducts formed at the primary amino group.” 

At this time I will not stop taking l-carnosine as a supplement and substitute beta-alanine in its place because of the multiple demonstrated benefits of l-carnosine that are independent of its effects in muscle tissues(ref)(ref).   I am open, however, to the question of whether adding beta-alanine to my regimen could be useful or would be redundant, and will be on the lookout for further research on this issue. I am planning a follow-up blog entry that will go deeper into the biochemical actions of carnosine, beta-alanine and gabapentin insofar as they impact on GABA receptors in nerve cells and glia.

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16. January 2010 by admin.

It has long been suspected that polymorphisms in the cholesterol ester transfer protein (CETP) gene confer important longevity benefits.  This post is prompted by recent news about the gene.  The post reviews what is known about the actions of the gene and its variants, and speculates about how this knowledge could lead to a new anti-aging intervention.

CEPT inhibition and coronary heart disease

The interest in the CEPT gene goes back a long time.  A 2000 publication states “Cholesteryl ester transfer protein (CETP) is a plasma glycoprotein that mediates the transfer of cholesteryl ester from high density lipoproteins (HDL) to triglyceride-rich lipoproteins in exchange for triglycerides. — Several genetic variants at CETP locus have been identified and they have been generally associated with increased HDL-cholesterol concentrations.”  Thus, it was originally thought that these gene variations could be life-extending because the higher HDL would be cardioprotective.   Interest developed in drugs that limit the expression of CEPT, the hope being that they would have a profound effect on raising HDL cholesterol.  “In our view, CETP inhibitors in combination with statins will be profoundly beneficial in reducing human atherosclerosis, primarily because they normalize HDL particles and prevent the transfer of cholesteryl ester from HDL to atherogenic lipoproteins(ref).” “A relative new strategy for raising HDL cholesterol, inhibition of cholesteryl ester transfer protein (CETP), is markedly effective. CETP inhibitors prevent the transfer of cholesteryl ester from HDL to triglyceride-rich lipoproteins in exchange for triglyceride. One inhibitor, torcetrapib, binds to CETP on HDL, markedly increases HDL cholesteryl ester, — (ref) .“   

Unfortunately torcetrapib had serious problems.  “A large clinical trial in patients with CAD who were taking atorvastatin was recently stopped prematurely because of excess mortality in those receiving torcetrapib versus placebo, and 2 other trials reported no benefit of torcetrapib on coronary atherosclerosis or carotid intima-media thickness as compared with subjects on atorvastatin alone. The adverse effects of torcetrapib may be compound specific, and because the crystal structure of CETP is now known, it should be possible to develop more optimal CETP inhibitors that do not form a nonproductive complex with CETP on the HDL particle, as has been reported for torcetrapib(ref).”  A 2009 report indicates ”Recently, Phase III clinical studies of torcetrapib, one of the CETP inhibitors developed by researchers at Pfizer, were unexpectedly terminated because of an increase in cardiovascular events and mortality. Torcetrapib has some compound-specific and off-target effects, such as raising blood pressure and aldosterone, which could affect an increase in cardiovascular events and mortality.”

The abandonment  of torcetrapib due to side effects dealt a mighty blow to the area of pharmacologic CETP inhibition, although not necessarily a fatal one.  See JTT-705: is there still future for a CETP inhibitor after torcetrapib? Also, “Dalcetrapib (JTT-705) and anacetrapib, which have not been reported to have the off-target effects of torcetrapib, are currently in Phase III. They are expected to reveal whether CETP inhibition is beneficial for atherosclerosis-related diseases(ref).”  Results of the safety and tolerability study of Dalcetrapib were promising(ref).  A clinical trial of the Tolerability and Efficacy of Anacetrapib for patients with coronary heart disease is ongoing(ref).

CEPT gene variations and cardiovascular diseases

Most of the studies of CEPT have looked at the CEPT gene and its variants in the context of HDL and impact on cardiovascular disease processes.  The 2009 report Polymorphism in the CETP gene region, HDL cholesterol, and risk of future myocardial infarction: Genomewide analysis among 18 245 initially healthy women from the Women’s Genome Health Study looks at whether CEPT and HDL-C have causal roles in atherothrombosis. “One method to evaluate this issue is to examine whether polymorphisms in the CETP gene that impact on HDL-C levels also impact on the future development of myocardial infarction. METHODS AND RESULTS: In a prospective cohort of 18 245 initially healthy American women, we examined over 350 000 singe-nucleotide polymorphisms (SNPs) first to identify loci associated with HDL-C and then to evaluate whether significant SNPs within these loci also impact on rates of incident myocardial infarction during an average 10-year follow-up period. Nine loci on 9 chromosomes had 1 or more SNPs associated with HDL-C at genome-wide statistical significance (P<5×10(-8)). However, only SNPs near or in the CETP gene at 16q13 were associated with both HDL-C and risk of incident myocardial infarction (198 events). For example, SNP rs708272 in the CETP gene was associated with a per-allele increase in HDL-C levels of 3.1 mg/dL and a concordant 24% lower risk of future myocardial infarction (age-adjusted hazard ratio, 0.76; 95% CI, 0.62 to 0.94), consistent with recent meta-analysis. Independent and again concordant effects on HDL-C and incident myocardial infarction were also observed at the CETP locus for rs4329913 and rs7202364. Adjustment for HDL-C attenuated but did not eliminate these effects. CONCLUSIONS: In this prospective cohort of initially healthy women, SNPs at the CETP locus impact on future risk of myocardial infarction, supporting a causal role for CETP in atherothrombosis, possibly through an HDL-C mediated pathway.”

A 2006 study I405V polymorphism of the cholesteryl ester transfer protein (CETP) gene in young and very old people reports “We recruited 100 healthy young people (median age 31 years) and 100 very old people (median age 89 years) and analysed their DNA for the presence of I405V polymorphism. — The frequency of the VV genotype in very old people was more than double that in the young population. Subjects with this genotype had lower serum concentrations of CETP. Young people with the V/V genotype had a less atherogenic lipoprotein profile (lower total cholesterol, LDL cholesterol, Apo B, and Apo B/Apo A-I ratio) than those with the I/V or I/I genotypes. The older subjects, particularly the older women with the V/V genotype, had larger LDL than the young people. The prevalence of clinical endpoints was much lower among the very old people with the V/V genotype. In conclusion, the V/V genotype of the I405V CETP polymorphism is more frequent among very old people than young ones, and is associated with a lower incidence of vascular damage.”

A number of other studies have supported a possible life-extending role for CEPT polymorphisms, but always in the contexts of lipids, raising HDL, and preventing cardiovascular diseases.  See, for example, this list of citations.  

Latest news: CEPT and dementia

A break in the pattern was reported two days ago.   Going back a couple of years, researchers at the Albert Einstein College of Medicine of Yeshiva University conducted a study where they searched for the presence of “longevity genes” in a cohort of aged Ashkenazi Jews.  As reported in a 2008 Science Daily article “Participating in the study were 305 Ashkenazi Jews more than 95 years old and a control group of 408 unrelated Ashkenazi Jews. — All participants were grouped into cohorts representing each decade of lifespan from the 50’s on up. Using DNA samples, the researchers determined the prevalence in each cohort of 66 genetic markers present in 36 genes associated with aging. — The Einstein researchers were able to construct a network of gene interactions that contributes to the understanding of longevity. In particular, they found that the favorable variant of the gene CETP acts to buffer the harmful effects of the disease-causing gene Lp(a).” 

A January 13 2010 report ‘Longevity Gene’ Helps Prevent Memory Decline and Dementia in Science Daily discusses a January report on JAMA describing further investigations by the same researchers relating the CEPT gene in the Ashkenazi Jews to the risks of Alzheimer’s Disease.  The JAMA report is entitled Association of a Functional Polymorphism in the Cholesteryl Ester Transfer Protein (CETP) Gene With Memory Decline and Incidence of Dementia.  “Objective  To test the hypothesis that a single-nucleotide polymorphism (SNP) at CETP codon 405 (isoleucine to valine V405; SNP rs5882) is associated with a lower rate of memory decline and lower risk of incident dementia, including Alzheimer disease (AD).”  “The researchers of the current study hypothesized that the CETP longevity gene might also be associated with less cognitive decline as people grow older. To find out, they examined data from 523 participants from the Einstein Aging Study, an ongoing federally funded project that has followed a racially and ethnically diverse population of elderly Bronx residents for 25 years. — At the beginning of the study, the 523 participants — all of them 70 or over — were cognitively healthy, and their blood samples were analyzed to determine which CETP gene variant they carried. They were then followed for an average of four years and tested annually to assess their rates of cognitive decline, the incidence of Alzheimer’s disease and other changes.  - - “We found that people with two copies of the longevity variant of CETP had slower memory decline and a lower risk for developing dementia and Alzheimer’s disease,” says Amy E. Sanders, M.D., assistant professor in the Saul R. Korey Department of Neurology at Einstein and lead author of the paper. “More specifically, those participants who carried two copies of the favorable CETP variant had a 70 percent reduction in their risk for developing Alzheimer’s disease compared with participants who carried no copies of this gene variant. — The favorable gene variant alters CETP so that the protein functions less well than usual(ref).”

The new news is in fact not completely new.  A  December 2006 news report states “An Israeli study involving 158 people who lived to 95 or beyond has found that those who inherit a particular version of the gene CETP are twice as likely to have a sharp and alert brain when they are elderly. — They are also five times less likely than people with a different version of CETP to develop Alzheimer’s disease and other forms of dementia, according to the study by a team at the Albert Einstein College of Medicine at Yeshiva University. — About 8 per cent of people aged 70 have the CETP variant, but this rises to 25 per cent among centenarians. This is thought to play a key role in explaining why some people live to very old ages.  The research, published in the journal Neurology, found that those with CETP VV were twice as likely as the others to have good brain function. — A separate investigation of 124 Ashkenazi Jews aged between 75 and 85 found that CETP VV appeared to protect against dementia: those with the variant were five times less likely to suffer from it.”

The researchers at the Albert Einstein College of Medicine also have found that telomere maintenance plays a very important role in maintaining the longevity of the centenarian Ashkenazi Jews, as reported in the November 2009 blog entry Timely telomerase tidbits. From a November 2009 Science Daily story: “As we suspected, humans of exceptional longevity are better able to maintain the length of their telomeres,” said Yousin Suh, Ph.D., associate professor of medicine and of genetics at Einstein and senior author of the paper. “And we found that they owe their longevity, at least in part, to advantageous variants of genes involved in telomere maintenance. — More specifically, the researchers found that participants who have lived to a very old age have inherited mutant genes that make their telomerase-making system extra active and able to maintain telomere length more effectively. For the most part, these people were spared age-related diseases such as cardiovascular disease and diabetes, which cause most deaths among elderly people.” 

So, variants in the CEPT gene appear to be protective against cardiovascular diseases and also protective against memory decline and dementia. Further, drugs are in Phase III clinical trials that may mimic the effects of these gene variants.   As usual several questions are still to be answered including: 

·        Do variations in the CEPT gene actually confer overall additional longevity or simply accompany longevity conferred by other genes?  If so, which variations are most effective and how much additional longevity can they provide? 

·        In the centenarians, what is the relationship between having extraordinary telomerase- maintenance genes and CEPT polymorphic genes?  Is it coincidental or in any sense causative that some centenarians have both of these kinds of gene variations?

·        In the event that effective and safe pharmacological means are established to inhibit CEPT expression (Dalcetrapib or Anacetrapib), will these be longevity-enhancing drugs? 

·        If so, how will they work: by maintaining high HDL levels and protecting cardiovascular health, by protecting mental functioning and preventing dementia, and/or by additional means yet to be characterized?

·        Are there nutraceuticals that inhibit CEPT expression and that could provide similar benefits?

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14. January 2010 by admin.

A new study reported in the press this week looks at the relationship of exercise to expression of telomerase and telomere lengths in athletes and non-athletes.  Other studies on the same topic have appeared in the last year or so.  My purpose here is to review these studies in the context of some earlier studies. It is not just a simple matter of “the more and the harder the exercise, the better.”

The 12^th theory of aging in my treatise Telomere Shortening and Damage forwards the hypothesis that longer telomere lengths are likely to be correlated with longer lifespans and that keeping one’s telomeres as long as possible through expression of telomerase is vital for health and longevity. I have devoted numerous blog entries to telomeres and telomerase, including most recently Timely telomerase tidbits, Breakthrough telomere research finding, and Telomere and telomerase writings. On the other hand, it is also well established that regular exercise is also strongly supportive of longevity(ref)(ref)(ref).  The mechanisms through which exercise improves health and life expectancy hitherto appeared to be complex and unclear.  The new research suggests that telomere extension may be a key mediator of the health and longevity benefits of regular exercise.

Sustained exercise can keep leukocytes younger

The latest study, an e-publication dated January 8 2010 from a University of Colarado group, is Leukocyte Telomere Length is Preserved with Aging in Endurance Exercise-Trained Adults and Related to Maximal Aerobic Capacity.  “To determine if age-associated reductions in TL (telomere length) are related to habitual endurance exercise and maximal aerobic exercise capacity (maximal oxygen consumption, VO(2)max), we studied groups of young (18 - 32 years; n = 15, 7m) and older (55 - 72 years; n = 15, 9m) sedentary and young (n = 10, 7m) and older endurance exercise-trained (n = 17, 11m) healthy adults. Leukocyte TL (LTL) was shorter in the older (7059 +/- 141bp) vs. young (8407 +/- 218) sedentary adults (P < 0.01). LTL of the older endurance-trained adults (7992 +/- 169bp) was approximately 900bp greater than their sedentary peers (P < 0.01) and was not significantly different (P=0.12) from young exercise-trained adults (8579 +/- 413). — Our results indicate that LTL is preserved in healthy older adults who perform vigorous aerobic exercise and is positively related to maximal aerobic exercise capacity. This may represent a novel molecular mechanism underlying the “anti-aging” effects of maintaining high aerobic fitness.”

So, older folks who vigorously exercise keep up their leukocyte telomere lengths and folks who sit around watching TV instead do not.  This message seems repeated in several other research reports. A 2009 study, this time from a German group, is: Beneficial Effects of Long-term Endurance Exercise on Leukocyte Telomere Biology.  “This study examines telomere biology and senescence-associated factors in endurance athletes and matched controls without physical activity. –Methods: Leukocytes where isolated from the peripheral blood of professional young track & field athletes (n=32, age 20.4 years, running 73±5 km/week), aged athletes performing regular endurance training (n=25, age 51.1 years, running 80±8 km/week, 35 years training history) and two control groups of age-matched, physically inactive healthy volunteers (26 young and 21 aged subjects).  –Results: Telomere repeat amplification protocols revealed an activation of leukocyte telomerase in young athletes to 256±19% and in elderly athletes to 182±11% compared to controls. Western blots showed an up-regulation of the telomere-capping protein TRF2 in young (179±1%) as well as in aged athletes (176±10%). FlowFISH assays and real-time PCR measurements of leukocyte telomere length showed no difference between young athletes and young controls. Sedentary elder controls exhibited a significant reduction of leukocyte telomere length (FF: 53±3%; PCR: 70±8%; vs. young controls). Importantly, there was a striking conservation of telomere length in aged athletes (FF: 88±4%; PCR: 84±7%; vs. young controls). Further analysis of telomere-associated proteins and cellular senescence regulators demonstrated an increase of TRF2, Ku70 and Ku80 mRNA and a reduced protein expression of Chk2, p16 and p53 in aged athletes compared to untrained elder controls.”

More or less the same story.  Among the younger people exercise seems to have a strong effect on leukocyte telomerase expression but no effect on telomere lengths.  But in the older folks, only those who exercised kept up most of their telomere lengths.  Further, their cells showed markedly lower levels of senescence markers.  As far as leukocytes are concerned, vigorous regular exercise definitely seems to keep them young. 

A 2009 mouse and human study Physical Exercise Prevents Cellular Senescence in Circulating Leukocytes and in the Vessel Wall looks a bit further at the molecular dynamics of exercise and comes to a consistent conclusion.  “Exercise upregulated telomerase activity in the thoracic aorta and in circulating mononuclear cells compared with sedentary controls, increased vascular expression of telomere repeat-binding factor 2 and Ku70, and reduced the expression of vascular apoptosis regulators such as cell-cycle–checkpoint kinase 2, p16, and p53. Mice preconditioned by voluntary running exhibited a marked reduction in lipopolysaccharide-induced aortic endothelial apoptosis. Transgenic mouse studies showed that endothelial nitric oxide synthase and telomerase reverse transcriptase synergize to confer endothelial stress resistance after physical activity. To test the significance of these data in humans, telomere biology in circulating leukocytes of young and middle-aged track and field athletes was analyzed. Peripheral blood leukocytes isolated from endurance athletes showed increased telomerase activity, expression of telomere-stabilizing proteins, and downregulation of cell-cycle inhibitors compared with untrained individuals. Long-term endurance training was associated with reduced leukocyte telomere erosion compared with untrained controls. — Conclusions— Physical activity regulates telomere-stabilizing proteins in mice and in humans and thereby protects from stress-induced vascular apoptosis.”

Watch out for your muscle satellite cells

There is a caution however, for more or harder exercise is not always better.  And leukocytes are not the only relevant cells to consider.  Earlier studies indicate that too strenuous or prolonged exercise can lead to serious depletion of telomerase in muscle satellite cells.  Muscle satellite cells “are small mononuclear progenitor cells with virtually no cytoplasm found in mature muscle. They are found sandwiched between the basement membrane and sarcolemma (cell membrane) of individual muscle fibres, and can be difficult to distinguish from the sub-sarcolemmal nuclei of the fibres. Satellite cells are able to differentiate and fuse to augment existing muscle fibres and to form new fibres. These cells represent the oldest known adult stem cell niche, and are involved in the normal growth of muscle, as well as regeneration following injury or disease.”   

Under conditions of hard exercise satellite cells can be forced into multiple rounds of duplication and differentiation leading to telomere shortening.  The 2003 publication Athletes with exercise-associated fatigue have abnormally short muscle DNA telomeres tells the story. “Although the beneficial health effects of regular moderate exercise are well established, there is substantial evidence that the heavy training and racing carried out by endurance athletes can cause skeletal muscle damage. This damage is repaired by satellite cells that can undergo a finite number of cell divisions. — In this study, we have compared a marker of skeletal muscle regeneration of athletes with exercise-associated chronic fatigue, a condition labeled the “fatigued athlete myopathic syndrome” (FAMS), with healthy asymptomatic age- and mileage-matched control endurance athletes. — Three of the FAMS patients had extremely short telomeres (1.0 +/- 0.3 kb). The minimum TRF lengths of the remaining 10 symptomatic athletes (4.9 +/- 0.5 kb, P < 0.05) were also significantly shorter that those of the control athletes. CONCLUSION: These findings suggest that skeletal muscle from symptomatic athletes with FAMS show extensive regeneration which most probably results from more frequent bouts of satellite cell proliferation in response to recurrent training- and racing-induced muscle injury.”

The 2008 study The effects of regular strength training on telomere length in human skeletal muscle looked at power lifters and showed that long-term exercise is not necessarily associated with satellite cell telomere loss although lifting heavier loads mean more loss.  “These results show for the first time that long-term training is not associated with an abnormal shortening of skeletal muscle telomere length. Although the minimum telomere length in PL (power lifters) remains within normal physiological ranges, a heavier load put on the muscles means a shorter minimum TRF length in skeletal muscle.”

The effect of exercise on telomeres in satellite cells is further reported in the 2009 publication The biology of satellite cells and telomeres in human skeletal muscle: effects of aging and physical activity.  “New insights suggest that telomeres in skeletal muscle are dynamic structures under the influence of their environment. When satellite cells are heavily recruited for regenerative events as in the skeletal muscle of athletes, telomere length has been found to be either dramatically shortened or maintained and even longer than in non-trained individuals. This suggests the existence of mechanisms allowing the control of telomere length in vivo.”  Whether satellite cell telomeres get shorter or longer or stay the same with exercise depend, among other matters, on the expression of telomerase in the satellite cells as a result of the exercise, and this in turn depends on several factors including physical condition of the person and the nature of the exercise.

Finally a late 2008 study report Relationship between physical activity level, telomere length, and telomerase activity looks at the results of exercise on telomeres in peripheral blood mononuclear cells (PBMCs). “A Peripheral Blood Mononuclear Cell (PBMC) is any blood cell having a round nucleus. For example: a lymphocyte, a monocyte or a macrophage. These blood cells are a critical component in the immune system to fight infection and adapt to intruders. The lymphocyte population consists of T cells (CD4 and CD8 positive ~75%), B cells and NK cells (~25% combined)(ref).”  According to the report:  “The purpose of this study was to examine the relationship of exercise energy expenditure (EEE) with both telomere length and telomerase activity in addition to accounting for hTERT C-1327T promoter genotype. — Sixty-nine (n = 34 males; n = 35 females) participants 50-70 yr were assessed for weekly EEE level using the Yale Physical Activity Survey. Lifetime consistency of EEE was also determined. Subjects were recruited across a large range of EEE levels and separated into quartiles: 0-990, 991-2340, 2341-3540, and >3541 kcal x wk(-1). Relative telomere length and telomerase activity were measured in peripheral blood mononuclear cells (PBMC). — CONCLUSION: These results indicate that moderate physical activity levels may provide a protective effect on PBMC telomere length compared with both low and high EEE levels.”

These studies leave me tentatively concluding:

·        Regular mildly cardiovascular exercise is likely to protect telomere lengths with aging across the three cell categories studied.

·        Vigorous aerobic exercise approaching “maximal aerobic exercise activity” may further serve to keep telomere lengths at youthful levels in leukocytes.

·        However, excessively strenuous exercise such as lifting very heavy weights or leading to exercise-associated fatigue may lead to compromised telomere lengths in muscle and/or PBMC cells and be life-shortening.

So, I believe moderation should be the rule.  See the suggestions for regular exercise in my treatise.

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