1033 replies to this topic

[Castiel]

But you'd still have to make sure these cells didn't become 'selfish' through selection of random epimutations. They made immortal HSCs in mice before (they knocked out the de Novo methyl transferase DNMT3a; the stem cells' telomeres never shortened probably because they never differentiated). Unfortunately these immortal stem cells never made any blood cells for the mice they were transplanted into.


This is an example of how a systemic signal (methylation) can cause aging in the body through paradoxically immortalising a cell. So it might not be possible to cure aging just through super cell transplants. But the bright side is we might not need them.

They wouldn't supercells could have even better error correction, with even 4 strand error correction at certain time intervals.   Or they could have alternate molecules more stable than dna as information carriers, together with increased error correction.   Worse case you have a microscopic physical memory akin to the quartz memory superman crystal with billion year data lifespan, and synthesize brand new dna from this template.(it wouldn't surprise if more critical portions of the genome have more advanced error correction mechanisms, and perhaps some are yet to be discovered.   Any case advanced synthetic biology is the ultimate physical science, it is true nanotech, it has no limits.)

 

Any case the negligible senescence species have achieved negligible senescence and I'm pretty sure those near 400 year old sharks their bodies mostly work, and evolution didn't wait near 400 years to make sure the solutions worked.

 

Also one of the things that needs to be understood is that evolution can't lock a design to a function too strongly or it impedes evolvability.   But we humans sure can, we can design the molecular machinery to tightly work together, this already happens to a degree, but we can make it work more tightly such that any deviation from function results in cell line death.   Like a car cannot evolve, we can bake in fragility such that only the accepted functions work.   Or at least I think such should be possible.

Edited by Castiel, 11 August 2021 - 02:48 PM.

[QuestforLife]

They wouldn't supercells could have even better error correction, with even 4 strand error correction at certain time intervals. Or they could have alternate molecules more stable than dna as information carriers, together with increased error correction. Worse case you have a microscopic physical memory akin to the quartz memory superman crystal with billion year data lifespan, and synthesize brand new dna from this template.(it wouldn't surprise if more critical portions of the genome have more advanced error correction mechanisms, and perhaps some are yet to be discovered. Any case advanced synthetic biology is the ultimate physical science, it is true nanotech, it has no limits.)

Certainly all manner of things might be possible in the future, though I think the difficulty of actually doing this to cells and making them work in the expected way in the body is massively underrated. Hence I generally only look at small molecules and to a lesser extent gene therapy, which plausibly could be widely available in a decade or two.

Any case the negligible senescence species have achieved negligible senescence and I'm pretty sure those near 400 year old sharks their bodies mostly work, and evolution didn't wait near 400 years to make sure the solutions worked.

Yes, I would love to see how such creatures control the telomere-methylation aging 'double-bind'. It might just be that they have a very slow maturation rate. Or it might be to do with the fact certain animals never stop growing, so they have a completely different differentiation scheme, which could be much simpler.

Also one of the things that needs to be understood is that evolution can't lock a design to a function too strongly or it impedes evolvability. But we humans sure can, we can design the molecular machinery to tightly work together, this already happens to a degree, but we can make it work more tightly such that any deviation from function results in cell line death. Like a car cannot evolve, we can bake in fragility such that only the accepted functions work. Or at least I think such should be possible.

Certainly the longer you live, the slower the species can adapt through evolution. Currently humans are actively selecting for certain traits. Ageless people would be 'frozen' from an evolutionary point of view; even though their children would still have different gene combinations via meiosis, the fact the parents would still be around and theoretically breeding, would slow evolution right down.

[Castiel]

I studied biology and physics, as well as nutrition and lifestyle interventions to extend lifespan.    But I believe the key to true immortality, not just biological immortality, is through understanding of the mind.

 

I've seen how the limits of the human mind keep even Ph'd researchers within certain restraints, a group of artificial minds will be sufficient to break the limit in the rate of progress, currently the engine of progress, the engine of change, the human brain, is that which is limiting the rate of progress.   The time is now upon us to get new engines into play.

 

The singularity lay ahead, it is either years or mere decades from coming into being.    It will do centuries of synthetic biology within years, mastering true nanotech, what to us humans is too difficult to master, in such short time, won't be for it.

 

It was said in genesis that a sword of fire guarded the path to the tree of life in Eden, that is why I call a superintelligence with the ability to synthesize DNA, (DNA synthesizer)the pen of life, the celestial sword, the celestial sword weapon system.    DNA sequencing has been advancing sufficiently, as has computational ability,  DNA synthesis tech is a bit lacking, but the core of the system True AI, or more like True I,  is to be discovered in the near future.   Once inorganic technology merges with molecular machinery in a new form of life able to direct its own evolution, thinking orders of magnitude faster than human thoughtrate, the human era is ended.   Nuclear weapons cannot stop the final engine of change, an intelligence explosion can surpass a nuclear explosion in sheer power.

[Advocatus Diaboli]

Castiel, here is a place, more in accord with you post #663, where you can duke it out with Mag1; although his appearance there is sporadic at times (perhaps med changes):

 

https://www.longecit...-editing/page-1

[Castiel]

Castiel, here is a place, more in accord with you post #663, where you can duke it out with Mag1; although his appearance there is sporadic at times (perhaps med changes):

 

https://www.longecit...-editing/page-1

 

 

Will check it, but I believe that AI will exist first in silicon, or some other probably inorganic computing substrate, and then in nanotech computronium.

 

I'm not that fond of CRISPR,  I think far more precise gene editing will be done by AI designed artificial proteins, but given the vast number of defects in humans, entire chromosomal replacement may be needed.  Replacement with DNA synthesized brand new chromosomes, with optimal structure.    Variation might still be needed for disease resistance, but it is likely the combination of the strongest immune mechanisms from throughout the animal kingdom will yield vast resistance to all diseases, this is without taking into account unevolvable immune mechanisms designed by superintelligence.

[QuestforLife]

The singularity lay ahead, it is either years or mere decades from coming into being. It will do centuries of synthetic biology within years, mastering true nanotech, what to us humans is too difficult to master, in such short time, won't be for it.

Just my opinion, but I don't really believe in the Singularity.

The only way AI has helped is in doing all the dumb processing of things like methylation status of CpG islands or huge gene activity assays. Nothing conceptual.

And I don't think progress is accelerating, in fact I think it has been slowing for some time. I believe humans are actually getting sicker and less intelligent due to lack of harsh selection pressure. It might be possible to fix this with genetic engineering, but we're still too far away from understanding how all the genes work together with the various regulatory mechanisms . We don't even understand how the chromosomes work properly. I do think we can solve aging before things really deteriorate however.

[Castiel]

Just my opinion, but I don't really believe in the Singularity.

The only way AI has helped is in doing all the dumb processing of things like methylation status of CpG islands or huge gene activity assays. Nothing conceptual.

And I don't think progress is accelerating, in fact I think it has been slowing for some time. I believe humans are actually getting sicker and less intelligent due to lack of harsh selection pressure. It might be possible to fix this with genetic engineering, but we're still too far away from understanding how all the genes work together with the various regulatory mechanisms . We don't even understand how the chromosomes work properly. I do think we can solve aging before things really deteriorate however.

I'm seeing news thousands of discoveries happening each year, there are so many it is difficult to keep up.

 

You have to understand there is a difference between narrow ai and true ai.   What we have now is narrow ai, it is getting more general but it still doesn't embody the full power of intelligence, of true intelligence.

 

A general intelligence can think like a human, if we get a theory of intelligence, it can think like the humans of the greatest intellect or beyond them far beyond them.

 

It has been estimated that in optimal computronium the Artificial General Intelligence, could think upwards of several million times faster than any human.

 

If you think anything can withstand the assault of sustained thought.   You will come out very very surprised.

 

 

 

No problem can withstand the assault of sustained thinking. – Voltaire

 

 

We are nearing a point where millions of years of thinking will take place within mere years.   If this doesn't destroy your world and brings about what us transhumanist dream of,  nothing will.

 

All will be freed, all will be destroyed, or all will be enslaved.

Edited by Castiel, 12 August 2021 - 05:48 PM.

[QuestforLife]

Telomere length and telomerase activity in T cells are biomarkers of high performing centenarians

It is generally recognized that the function of the immune system declines with increased age and one of the major immune changes is impaired T cell responses upon antigen presentation/stimulation. Some “high‐performing” centenarians (100+ years old) are remarkably successful in escaping, or largely postponing, major age‐re-lated diseases. However, the majority of centenarians (“low‐performing”) have experienced these pathologies and are forced to reside in long‐term nursing facilities. Previous studies have pooled all centenarians examining heterogeneous populations of resting/unstimulated peripheral blood mononuclear cells (PBMCs). T cells represent around 60% of PBMC and are in a quiescence state when unstimulated. However, upon stimulation, T cells rapidly divide and exhibit dramatic changes in gene expression. We have compared stimulated T‐cell responses
and identified a set of transcripts expressed in vitro that are dramatically different in high‐ vs.low performing centenarians. We have also identified several other measurements that are different between high‐ and low‐performing centenarians: (a) The amount of proliferation following in vitro stimulation is dramatically greater in high‐performing centenarians compared to 67‐ to 83‐year‐old controls and low‐performing centenarians; (b) telomere length is greater in the high‐performing centenarians; and telomerase activity following stimulation is greater in the high‐performing centenarians. In addition, we have validated a number of genes whose
expression is directly related to telomere length and these are potential fundamental biomarkers of aging that may influence the risk and progression of multiple aging conditions.

Source: DOI: 10.1111/acel.12859

An interesting paper from Jerry Shay and co. looking at telomerase activity and proliferative ability of T cells in centenarians compared to old (67-83yo) and young (~23-39yo) controls. Telomerase activity was elevated in centenarians compared to the old group, as (unsurprisingly) was proliferative ability of T cells (more telomerase meant they could make more T cells on stimulation, correlation between the two 0.88, p value <0.001).

T cells are different from most human cell types, in that they retain telomerase activity on differentiation, but only after stimulation with antigens.

Shay et al. also looked at gene expression assays and determined a clear difference between old and young donors, as well as a separation of the centenarians into two groups. The centenarian group that had gene expression more akin to young than old controls were found to be much
healthier than the centenarian group members with gene expression closer to the old controls. This 'health' was measured by better physical and cognitive performance, as well as fewer age related diseases. They were then designated High Performing centenarians, with the others labelled as Low Performing Centenarians.

They then went back and looked at the HP and LP centenarians and found that the high performers had longer telomeres and their 20% shortest telomeres were also significantly longer than the LP centenarians.

Finally they looked at what genes were expressed differently between old and young, as well as those genes that had similar expression between young and high performing (but not low performing) centenarians or the old control group. Interestingly, they found the genes that were maintained at a high level in young and HP centenarians were enriched for antigen response
pathways, and that genes that were kept at lower levels in young and HP centenarians (compared to old control and LP centenarians) included inflammatory response, IGF-1 expression and apoptosis signalling. They also found the differentially expressed genes (between old/LPC and young/HPC) were not randomly located but on certain chromosomes. They further found many were on chromosomes within 10MB of the telomere, as predicted by their Telomere Position effect over-long distance (TPE-OLD) model, whereby a shortening
telomere loses contact with genes it was formerly in contact with (via chromosome compaction and curling), changing the genes' expression.

It is not difficult for me to interpret this in the light of my Selfish Cell theory. Longer lived leukocytes with longer telomeres will acquire random methylation selecting for those less sensitive to antigen stimulation, preserving themselves, but harming the immune response. Those leukocytes that do respond, suffer from telomere shortening (even with activated telomerase), and in time are eliminated. Hence stronger signalling is required to get the needed response, including inflammatory and IGF-1 stress signals. Apoptosis is the result of the attrition of the limited number of leukocytes that can be made to respond.

From the other horn of aging, telomere shortening over time can result in deleterious gene expression changes (possibly via TPE-OLD), as well as a direct slowing of proliferation. As I said, T cells are a special case, as their ability to express telomerase is maintained on differentiation. So it is likley that methylation is primary here. Nevertheless, telomere length and telomerase expression still mediate most of the deleterious effects of aging in T cells. More research is required here.

The high performance of some centenarians cannot be attributed to better immune function alone. As we've seen in other studies, telomere length in T cells is correlated with telomere length in other tissues, therefore (Selfish Stem cells) in those tissues will also play their part in
aging. It is interesting that the HP centenarians had higher BMI than LP centenarians, who may have been suffering from tissue atrophy.

As for treatment, I'd expect exogenous telomerase treatment to counter the inability of aged T cells to replicate sufficiently to ward off infection. But I would also expect upregulation of demethylators (TETs) to have a beneficial effect on the immune system, via the upregulation of
telomerase that is secondary to a restored antigen response (assuming its promoters are subject to methylation), independent of telomerase activators. It will be interesting to see if this is confirmed by further work with AKG treatment of mice (or humans for that matter), to see if the previously reported improvements in frailty and inflammation are accompanied by improved immune function.

Edited by QuestforLife, 16 August 2021 - 08:23 PM.

[QuestforLife]

The evolution of 'The Selfish Cell'

 

I want to clarify some points regarding my theory of aging. For years now I’ve been positing the existence of The Selfish Cell, good for itself but bad for the body, being increasingly selected for with age, citing evidence from papers on the skin, mitochondria, immune system and stem cell compartments. The basic idea was that cells maintain a range of epigenetic (rather than genetic) states, and this is the basis of their selection, with more selfish cells coming to predominate. I originally thought maybe the epigenetic variation was built in, a priori with cell formation, with aging being a process of whittling down to only those cell (-lines) predisposed to survive for a long time. This was an original concept being completely different to the mainstream view of aging being a process happens to cells, degrading the function of young cells and turning them into old cells. My idea turned this on its head, with good and bad cells always present, but ‘aging’ being the selection for the bad ones. 

 

Later, I looked for a better explanation for the epigenetic variation between cells, rather than taking it as written that such variation is pre-existing. It is undeniable that cells downregulate telomerase on differentiation, and therefore this might be the basis of selection, with cells less likely to differentiate more likely to survive. There seemed to be some evidence for this in Horvath’s pan species clock, with the gene promoters methylated with age often being related to differentiation. This suggests that maintaining cells with sufficient telomerase would eliminate the selection pressure to self-renew rather than differentiate. But this turned out not to be the case. Telomerase immortalised cells acquire the same methylation on promoters of differentiation. In hindsight this is not surprising, as in growth medium the cells most able to divide will obviously come to dominate as the culture is passaged multiple times, so this process selects for ‘faster breeders’ (so to speak). Even if we could give stem cells unlimited telomerase, the reticent differentiators would still take over.

 

This was the last piece of the puzzle and reveals aging to be a ‘double-bind’. Or phrased another way, if one horn (telomere attrition) doesn’t get you, the other one (methylation of differentiation promoters) certainly will. The methylation doesn’t need to be programmed (as it is with cellular senescence). It can be (I believe it is) entirely random. Random methylation of promoters is then the basis of the selection (evolution) of longer-lived cells to be selfish (not differentiating).  It need not matter for our purposes why methylation occurs on CpG islands near promoters, but demethylation occurs elsewhere in the genome: Horvath has shown us the most important element for aging is the methylation. I speculate that an excess of methylation in these locations is required to mature sex organs on a species-specific schedule, (which requires downregulation of TET1 and 2 enzymes to release gonadotropins). From there it either continues on autopilot (Blagosklonny’s pseudo-program) or escalates in a positive feedback loop involving further rises in sex hormones (Jeff Bowles’ stuff) causing further increases in methylation (via ROS mediated downregulation of TETs and probably histone demethylases too). The exact details will be provided by further research. But we don’t need to wait for this information to begin treatment.

 

How? Take telomerase activators or telomerase gene therapy and (to the extent that the treatment is successful) you’ll elongate telomeres and allow those cells that do ‘want’ to differentiate to do their job in the body. But by extending the life of those cell lines you’ll inevitably produce more cells that will acquire random methylation and eventually through selection pressure you’ll end up with cells that won’t differentiate. The probable result: extended health and lifespan, but not agelessness.

 

If instead you encourage demethylation and more differentiation the probable result will be improvements in health and youthfulness, and possibly cancer defence too, but at the cost of accelerated telomere shortening in the underlying stem cell niche, so lifespan extension will be small or non-existent. 

 

Note that the balance of the two horns of aging may be different in different tissues, perhaps with the gut requiring more self-renewal, but the endothelial lining requiring more differentiation. The balance will possibly also be different for different people, perhaps dependent on the age the treatment starts, and although less relevant here: will vary between species(*). But given human cells (with very few exceptions) abolish telomerase expression on differentiation, telomerase activation will be required. I still regard telomeres as the number one mediator of aging in humans. But I acknowledge that short telomeres can (also) be the result of the failure of stem cells to differentiate, not only the attrition of the telomeres of the cells that do. To keep us safe from the other horn of unhelpful methylation, we must use what treatments we can (GDF11, AKG, Vit A/retinol/VitC, etc.) to encourage proper and safe differentiation.

 

If we keep off both horns of aging, can we become ageless? It seems highly likely that life would be considerably extended with an (uncertain) degree of rejuvenation. But there may be residual problems that are not easily resolved. Particularly stubborn tissue might require surgery or replacement. Post mitotic cells may have suffered long lasting damage because of the past neglect of proliferating cells that support them (neurons harmed from the failure of glial cells, heart harmed from the failure of endothelial cells are but two examples). We might need telomerase and demethylation treatments that increase cell turnover to significantly greater levels than what is normal in youth, to accomplish significant and speedy rejuvenation. This is far from a done deal. But I feel that we now have the correct model to address aging – we at last understand aging – and can move forward with confidence towards a life without a sword dangling over our fearful heads.  

 

(*)as mice cells do not downregulate telomerase on differentiation as much as human cells do – probably because of the requirement for rapid healing – one would expect methylation to be primary and telomere shortening secondary in mouse aging compared to humans. Nevertheless, there are reasons to expect evolution not to allow a separation of aging mechanisms: if methylation is causing death X years before telomere exhaustion, there would be no selection pressure for longer telomeres, and over generations they would drift shorter. Conversely if excess methylation could be reduced from a mouse timescale to a human one then telomerase would not be free to elongate telomeres endlessly towards immortality, as this would allow methylation to build up over a greater time and block such cells from differentiating. Only by completely stopping this methylation would that be possible, and this would likely interfere with maturity if done from a young age. This might explain the enduring youthfulness of animals like my avatar the Axolotl, who does not age so long as he does not complete his development.

Edited by QuestforLife, 18 August 2021 - 12:57 PM.

[Castiel]

The evolution of 'The Selfish Cell'

 

I want to clarify some points regarding my theory of aging. For years now I’ve been positing the existence of The Selfish Cell, good for itself but bad for the body, being increasingly selected for with age, citing evidence from papers on the skin, mitochondria, immune system and stem cell compartments. The basic idea was that cells maintain a range of epigenetic (rather than genetic) states, and this is the basis of their selection, with more selfish cells coming to predominate. I originally thought maybe the epigenetic variation was built in, a priori with cell formation, with aging being a process of whittling down to only those cell (-lines) predisposed to survive for a long time. This was an original concept being completely different to the mainstream view of aging being a process happens to cells, degrading the function of young cells and turning them into old cells. My idea turned this on its head, with good and bad cells always present, but ‘aging’ being the selection for the bad ones. 

 

 

Are we sure this is not also affected by thymic involution and immune aging?    In some cases the immune system seems able to fight off all kinds of malignant cells even ones able to kill most organisms, might a youthful immune system not also fight or kill aberrant but less obviously detrimental cells?

Edited by Castiel, 18 August 2021 - 03:57 PM.

[QuestforLife]

Are we sure this is not also affected by thymic involution and immune aging? In some cases the immune system seems able to fight off all kinds of malignant cells even ones able to kill most organisms, might a youthful immune system not also fight or kill aberrant but less obviously detrimental cells?

Thymic involution can be reversed by growth hormone/DHEA/Metformin treatment [1], which also reversed epigenetic age as measured by methylation of CpG islands (Horvath clock).

The mere fact the thymus is this plastic, shows that thymic precursor cells must be present, but do not (continue to) differentiate in the adult.

And the fact that increasing the thymic size and improving immune function was coincident with a reduction in epigenetic age in [1], suggests that the same methylation of promoters may be responsible for thymic involution.

That this happens from a young age suggests that if this is the Selfish Cell, it must be highly accelerated compared to what happens in other adult stem cell niches.

I hypothesize that the differentiation of thymic precursor cells must be repressed by the same methylation that triggers growth/sexual maturity.

If anyone can find a paper that proves or disproves this hypothesis, I would be grateful.

Why this would be so is an open question. Maybe sexual maturity requires a downregulation of the immunity that was optimal for infants.

[1] https://doi.org/10.1111/acel.13028

Ps The fact thymic involution occurs so early in life eliminates cellular senescence (via direct telomere shortening) as a cause. I am not clear on whether senescent cell clearance requires a thymus, as it is accomplished by the innate immune system. Nevertheless, a restored thymus would almost certainly be anti-cancer.

[Andey]

I hypothesize that the differentiation of thymic precursor cells must be repressed by the same methylation that triggers growth/sexual maturity.
 

 

It could be the opposite. Melatonin declines in puberty and some argue that supplementation is linked with the delayed puberty. yet there is some data that its suppresses thymic involution.

 

Rejuvenation of degenerative thymus by oral melatonin administration and the antagonistic action of melatonin against hydroxyl radical-induced apoptosis of cultured thymocytes in mice - PubMed (nih.gov)

Effect of melatonin on the thymus, adrenal glands, and spleen in rats during acute stress - PubMed (nih.gov)

Possible effects of melatonin on thymus gland after pinealectomy in rats - PubMed (nih.gov)

Edited by Andey, 18 August 2021 - 09:48 PM.

[QuestforLife]

It could be the opposite. Melatonin declines in puberty and some argue that supplementation is linked with the delayed puberty. yet there is some data that its suppresses thymic involution.

 

Rejuvenation of degenerative thymus by oral melatonin administration and the antagonistic action of melatonin against hydroxyl radical-induced apoptosis of cultured thymocytes in mice - PubMed (nih.gov)

Effect of melatonin on the thymus, adrenal glands, and spleen in rats during acute stress - PubMed (nih.gov)

Possible effects of melatonin on thymus gland after pinealectomy in rats - PubMed (nih.gov)

 

Thanks for the references.

 

Melatonin is not a sex hormone, if anything it seems to be an anti-sex hormone. So the evidence that melatonin can delay sexual development and delay thymic atrophy is in agreement with my hypothesis.

[dlewis1453]

Thanks for the references.

 

Melatonin is not a sex hormone, if anything it seems to be an anti-sex hormone. So the evidence that melatonin can delay sexual development and delay thymic atrophy is in agreement with my hypothesis.

 

FYI, I found this patent, filed by Amy Wagers and a couple of other individuals, for the use of GDF11 to regenerate the thymus. 

 

https://patents.goog...0160120945A1/en

 

Some relevant quotes from the patent: 

 

• "The most dramatic enhancement of thymus regeneration is seen in aged male mice that have undergone castration. The thymuses of old (male) mice grow back to nearly the same size as young thymuses (Sutherland et al., 2005. J Immunol 175: 2741-2753). This finding indicates that the thymus is capable of extensive regeneration. In humans, reversible sex steroid ablation may be a feasible approach for inducing thymus regeneration, and initial results show some promise (Sutherland et al., 2005. J Immunol 175:2741-2753). However, this approach may be less beneficial in females, and has associated risks."
•  
• "As described herein, GDF11, a TGFbeta family member, is a potent inducer of thymus regeneration in aged mice. 24-month old female mice (roughly equivalent to 72-years of age in humans) that received daily injections of GDF11 for one month showed a dramatic increase in thymic cellularity compared to age-matched, control-injected mice (FIG. 1). The thymuses of GDF11 treated mice regenerated medullary and cortical thymic zones, and had a normal representation of thymocyte subpopulations as determined by histology and flow cytometry. Therefore, GDF11 drives thymic regeneration in aged mammals."

[QuestforLife]

"The most dramatic enhancement of thymus regeneration is seen in aged male mice that have undergone castration. The thymuses of old (male) mice grow back to nearly the same size as young thymuses. This finding indicates that the thymus is capable of extensive regeneration. In humans, reversible sex steroid ablation may be a feasible approach for inducing thymus regeneration,

"As described herein, GDF11, a TGFbeta family member, is a potent inducer of thymus regeneration in aged mice."

Thankyou for that. You have highlighted some very important points, which all support my hypothesis.

1. Thymus is plastic and can be re-grown
2. Sex hormones seem to be involved in thymic involution, and their ablation helps it to recover
3. Since GDF11 works to regenerate the thymus, and its MOA is re-establishing proper differentiation of stem cells (via TET2/3 - GDF11 promoter mutual upregulation, see Post #426), the thymus most likely atrophies because of a failure of differentiation secondary to methylation of promoters.

We haven't quite proven that the reason the thymus atrophies way earlier than other tissues is because of sex hormones, but certainly we've found nothing to contradict that idea.

Edited by QuestforLife, 19 August 2021 - 04:50 PM.

[QuestforLife]

Cancer and the Selfish Cell

 

Mammals rely on long lived stem cells to differentiate into various shorter lived cell lines that replenish tissues. All cells are subject to random methylation of CpG gene promoters [1]. At the present time the reason for the excess methylation with age at these locations is unknown, but I believe it may be related to sexual maturity signalling [2].

 

Differentiated cells have telomerase turned down; they have built-in obsolescence. This senescence involves a programmed (non-random) change of methylation patterns [1]. Stem cells have active telomerase so can persist for longer. But the longer lived the cell line the more random methylation can occur [3]. Selection pressure then favours the cells in which methylation has blocked differentiation in favour of self renewal [1].

 

I predict this will then result in tissues being starved of cell replacements. Their telomeres will shorten and the body will be forced to hold onto old, senescent cells. These cells release inflammatory cytokines that signal the stem cell compartment for replacements. Increased stress can force more stem cells to differentiate into the body at large, but they will increasingly have only a partially differentiated phenotype [1] because of the aforementioned selection for self renewing cells, and I believe this will make them more vulnerable to cancerous transformation.

 

As an analogy it is like shouting for help. The more desperate you get, the louder you shout, and the less helpful those that come to your aid tend to be.

 

The reason cancer rises with age is twofold. Short telomeres in tissues mean greater genomic instability and reduced DNA repair rates in those cells. This is cancerous in itself. But I'm skeptical cancer cells arise from normal somatic cells. I think the main reason cancer rises so precipitously with age is that more and more of the body is made up of cells with a pre-cancerous phenotype, because they have (belatedly and only partially) differentiated from stem cells, when the inflammatory signalling from tissues with short telomeres becomes strong enough to stimulate them.

 

Lowering inflammation will reduce this differentiation, which will reduce cancer rates but starve tissues further, leading to even shorter telomeres. Hence inflammation control is not going to be hugely effective against aging, but might reduce cancer rates.

 

Immune system failure also plays a part in the increase in cancer rates. It has a specific role in the clearance of cancerous cells. It has even been speculated that immune system decline is the main factor responsible for the rise in cancer rates with age [4]. Although it is no doubt important that the immune system declines, with a positive feedback loop into the cancer rates of other tissues,  I believe the exact same process is going on in immune cells as in the rest of the body.  As we've seen previously, leukocytes lose their ability to respond to stimulation [5] with age; it will be interesting to see if this can be shown to be due to methylation of CpG gene promoters.

 

References
[1] https://www.cell.com...6108(18)30008-4

[2] Post #632

[3] https://doi.org/10.1...21.01.18.426733
[4] https://www.pnas.org...tent/115/8/1883
[5] Post #668

[dlewis1453]

Thanks for this analysis, very interesting. 

 

Could the increase in mTOR with age also be due to the body increasing its differentiation signal to activate increasingly unresponsive stem cell reserves? 

 

Also, while we are on the topic of cancer, Steve Perry's cohort is having some success in treating cancer in dogs and cats with GDF11

 

https://gdf11rejuven...nd-cat-lymphoma

 

https://gdf11rejuven...hemangiosarcoma

[QuestforLife]

Thanks for this analysis, very interesting.

Could the increase in mTOR with age also be due to the body increasing its differentiation signal to activate increasingly unresponsive stem cell reserves?

There is still some argument over whether MTOR DOES increase with age. Blagoskonny claims that aging is due to MTOR just being left turned up to the level required for growth and development. So not being turned up at all.

But based on the (low) level of dosing at which I experience sides effects from Rapamycin (or everolimus) compared to the much greater dose being taken by older folks, I'd say MTOR must be turned up with age.

There is some evidence that MTOR is turned up in diabetic kidney disease by methylation. I haven't found any evidence (yet) it happens in aging in general.

Source: https://pubmed.ncbi....h.gov/31101365/

Aberrant DNA methylation of mTOR pathway genes promotes inflammatory activation of immune cells in diabetic kidney disease

Using genome-wide DNA methylation assays, we identified the differentially methylated cytosines in the promoter regions of mammalian target of rapamycin (mTOR) regulators in peripheral blood mononuclear cells of diabetic patients. Further, mRNA arrays confirmed the consistent induction of genes expressed in the mTOR pathway. Importantly, down-regulation of DNMT1 expression via RNA interference resulted in prominent cytosine demethylation of mTOR negative regulators and subsequent decrease of mTOR activity.

Also, while we are on the topic of cancer, Steve Perry's cohort is having some success in treating cancer in dogs and cats with GDF11

https://gdf11rejuven...nd-cat-lymphoma

https://gdf11rejuven...hemangiosarcoma

If cancer is being caused by cells that aren't properly differentiated, then GDF11 should be very effective as an anti-cancer treatment by forcing them to differentiate.

I don't know much about hemangiosarcoma apart from it being based in blood vessels.

But interestingly, carcinoma - the most common cancers in humans and the type that rises exponentially with age, are caused epithelial cells basically 'turning themselves' into mesenchymal like stem cells.

Epithelial-mesenchymal transition (EMT) is a complex developmental program that enables carcinoma cells to suppress their epithelial features changing to mesenchymal ones. This change allows cells to acquire mobility and the capacity to migrate from the primary site.
Source: DOI: 10.15761/ICST.1000243

The above paper considers EMT to be a kind of de-differentiation. But I suggest it could also be due to an alteration in the type of cells being supplied to the body making this type of change more probable.

Edited by QuestforLife, 01 September 2021 - 05:55 PM.

[Castiel]

Hmmm, didn't some of the Yamanaka factors rejuvenate epigenetics?

 

And I haven't been able to find it, but a paper I once found said gene expression is restored to youthful expression in telomerase positive cells with the exception of about 100~ genes.    Wouldn't that if true suggest the epigenetics was mostly rejuvenated?   The abnormal 100~ genes could be a byproduct of constant telomerase activation.    Dr Sinclair says epigenetics is upstream, but Dr. Fossel disagrees and suggests it is telomeres that are upstream, iirc.

[QuestforLife]

Dr Sinclair says epigenetics is upstream, but Dr. Fossel disagrees and suggests it is telomeres that are upstream, iirc.

It's both!

Shortening telomeres cause a programmed change of methylation that leads to a shutdown of metabolism and eventually cellular senescence.

Long telomeres allow random methylation (of CpG promoters) to build up. Selection pressure on such cells then leads to the survival of those cells better able to self renew. Unfortunately such cells are less likely to differentiate and when they do, appear to have a pre-canerous phenotype.

DNA methylation patterns separate senescence from
transformation potential and indicate cancer risk

Overall shared DNA methylation patterns between senescence (Sen) and cancers have led to the model that tumor promoting epigenetic patterns arise through senescence. We show that transformation-associated methylation changes arise stochastically and independently of programmatic changes during senescence. Promoter-hypermethylation events in transformation involve primarily pro-survival and developmental genes, similarly modified in primary tumors.
Senescence-associated hypermethylation mainly involve metabolic regulators, appears early in proliferating “near-senescent” cells which can be immortalized but are refractory to transformation. Importantly, a subset of transformation-associated hypermethylated developmental genes exhibits highest methylation gains at all age-associated cancer risk states across tissue-types. These epigenetic changes favoring cell self-renewal and survival, arising during tissue aging, are fundamentally important for stratifying cancer risk and concepts for cancer prevention.

Source: doi:10.1016/j.ccell.2018.01.008.

[Castiel]

It's both!

Shortening telomeres cause a programmed change of methylation that leads to a shutdown of metabolism and eventually cellular senescence.

Long telomeres allow random methylation (of CpG promoters) to build up. Selection pressure on such cells then leads to the survival of those cells better able to self renew. Unfortunately such cells are less likely to differentiate and when they do, appear to have a pre-canerous phenotype.
 

Might this affect species that appear not to age, since I've heard most are either telomerase positive throughout tissues or have alternate methods of maintaining long telomeres throughout their tissues?

 

And wouldn't substances that kill cancerous cells have a chance of killing these deviant cells?  Or what of the recent experiments of certain substances resulting in epigenetic rejuvenation of a few years?  Or Harold Katcher's even more impressive rejuvenation(if it is eventually verified)?

[QuestforLife]

Does the Selfish Cell imply programmed or accidental aging?

Long telomeres and active telomerase all but ensure the continued health of a cell line through mechanisms like mitophagy [1] and NAD+ levels [2] as well as telomere maintenance. But this is not enough to ensure the health of the body at large. Longer telomeres allow a cell line to accumulate methylation at gene promoters and this is the basis for the selection of the Selfish Cell: the cell may become immortal (perpetually self-renewing), but is also indolent (depriving the body of new cells) and treacherous (potentially cancerous). 

 

The result is an aging double bind: Extend telomeres and the cell eventually becomes selfish: it no longer serves the body. But shorten telomeres and the cell will die from gradual metabolic shutdown and eventually senescence.  It’s heads you die, tails you...die.(*)  Aubrey de Grey has argued for different aging systems to converge [3], though to my knowledge he never considered a double bind.
The question is, can the body solve an aging double-bind? And if it can, why doesn’t it?

 

Certainly at the level of a cell, it can solve it.

Epigenetic clocks reveal a rejuvenation event during embryogenesis followed by aging The notion that germline cells do not age goes back to the 19th century ideas of August Weismann. However, being in a metabolically active state, they accumulate damage and other age-related changes over time, i.e., they age. For new life to begin in the same young state, they must be rejuvenated in the offspring. Here, we developed a new multi-tissue epigenetic clock and applied it, together with other aging clocks, to track changes in biological age during mouse and human prenatal development. This analysis revealed a significant decrease in biological age, i.e. rejuvenation, during early stages of embryogenesis, followed by an increase in later stages. We further found that pluripotent stem cells do not age even after extensive passaging and that the examined epigenetic age dynamics is conserved across species.  Source: https://www.biorxiv.....03.11.435028v1

 

 

There is also some evidence through experimenters on this site that epigenetic age can be reversed body-wide (thus far to a limited degree). So why doesn't the body do this as a matter of course? I have speculated that the reason excess methylation occurs at gene promoters might be because methylation of TET1 is required for the development of sex organs [4]. It is possible that removing excess methylation might impair sex drive,and therefore would not be permitted by the body. But we also know sperm cells lose differentiation capacity with age [5], although we don’t know if this is caused by methylation or would be solved by removing methylation.  This seems like a key area we should look at for an answer.

 

Extended periods on alpha ketoglutarate have in the past reduced my energy and sex drive, whilst also reducing my epigenetic age (May 2021 Methylation age results). After a two month break I restarted AKG at the beginning of August. This time I have been taking it with vitamin A and (liposomal) vitamin C. My rationale for their inclusion is explained in the following paper.

 

Retinol and ascorbate drive erasure of epigenetic memory and enhance reprogramming to naïve pluripotency by complementary mechanisms
Epigenetic memory, in particular DNA methylation, is established during development in differentiating cells and must be erased to create naïve (induced) pluripotent stem cells. The ten-eleven translocation (TET) enzymes can catalyze the oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and further oxidized derivatives, thereby actively removing this memory. Nevertheless, the mechanism by which the TET enzymes are regulated, and the extent to which they can be manipulated, are poorly understood. Here we report that retinoic acid (RA) or retinol (vitamin A) and ascorbate (vitamin C) act as modulators of TET levels and activity. RA or retinol enhances 5hmC production in naïve embryonic stem cells  by activation of TET2 and TET3 transcription, whereas ascorbate potentiates TET activity and 5hmC production through enhanced Fe2+ recycling, and not as a cofactor as reported previously. We find that both ascorbate and RA or retinol promote the derivation of induced pluripotent stem cells synergistically and enhance the erasure of epigenetic memory.  Source: https://www.pnas.org...nt/113/43/12202

 

 

I made the liposomal vitamin C and I must say this time (1 month into my AKG cycle) I’m feeling fantastic. I am even contemplating increasing my AKG dosage. My best guess is that the side effects on previous cycles were down to the extra oxidised Fe3+ produced in the demethylation process. 

 

But this doesn’t lead us any closer to an answer on the question of programmed aging. The cell can reverse aging (both telomere shortening and methylation) and does so during embryogenesis. The body appears to be also able to do the same based on our experiments so far. It is looking an awful lot like the body doesn’t want to stop aging. What is the opinion of Longecity? Only a few years ago it appeared that the stochastic damage theories held sway. I was a supporter. I am now not so sure.

 

(*)Based on the evidence I have gathered here and elsewhere for many years, telomere shortening is clearly involved across the board in aging. But given telomere shortening is MUCH worse in people with a mutation in TERC (the RNA template component of telomerase) or closely related genes[6], this implies TERT (the protein component of telomerase that copies the template onto the DNA strand) must be active in the bone marrow. Therefore my best guess is that in humans the Selfish Cell is the primary cause of aging. But defeat this and ‘direct’ telomere shortening (due to proliferation of stem cells for a protracted period, say 120+ years), will then likely kill you, necessitating reactivation of telomerase.

 

References:
[1] https://www.nature.c...1419-020-2641-7
[2] https://www.embopres...embj.2019103420
[3] https://www.liebertp...9/rej.2021.0018
[4] https://www.pnas.org...nt/114/38/10131
[5] https://www.pnas.org...nt/116/33/16404
[6] https://doi.org/10.1...tem.2020.03.016

[QuestforLife]

Might this affect species that appear not to age, since I've heard most are either telomerase positive throughout tissues or have alternate methods of maintaining long telomeres throughout their tissues?

... Or Harold Katcher's even more impressive rejuvenation(if it is eventually verified)?

This is a very interesting question that I've touched upon a few times in the past. Indeed various reports of non-aging species show their telomeres remain stable with age (see this paper on Buffalo Fish [1], for example). There is no methylation clock for this species (or turtles or lobsters or sharks) to my knowledge - indeed it would not be possible to train a clock on such a species. The best we could do is use a clock pre trained on other aging species and show no change with age for non aging species. A big question is whether differentiation works differently in species that never stop growing. How do stem cell compartments even work in these species?

Regarding Harold Katcher, like the rest of the anti-aging community I await details of what E5 really is.

[1] https://www.nature.c...598-021-88626-5

Edited by QuestforLife, 02 September 2021 - 05:03 PM.

[QuestforLife]

I finally got hold of this intriguing paper.

 

Caffeine promotes the expression of telomerase reverse transcriptase to regulate cellular senescence and aging

 

Telomere shortening is one of the main causes of cellular senescence. Caffeine is a natural stimulant most commonly found in coffee and tea. In this study, caffeine was found to promote the expression of telomerase reverse transcriptase (TERT) at both mRNA and protein levels, and consequently extended the telomere length and prevented cellular senescence. Knockdown of TERT eliminated the effect of caffeine on telomere elongation. Moreover, animal studies indicated that caffeine promoted the expression of TERT and extended the telomere length in the thymus and spleen of mice treated with caffeine for a long period of eight months. In addition, caffeine restored the decline of organ index and improved the histo logical structural change of the thymus, spleen and liver of mice due to aging. These results suggest that caffeine promotes the expression of TERT to delay cellular senescence and aging, which help to under stand the mechanism for the beneficial effects of caffeine containing foods on health.

doi:10.1039/d0fo03246h

 

The first thing to note is that the in vitro data is on HELA and other cancer cell lines, which already have active telomerase. All they’ve shown here is that caffeine at a concentration of 0.5mM or greater increases the telomerase expression and telomere length of cancer cells (HELA, MCF-7 or HepG2) even further.

 

They nevertheless extend this to treating mice from 6 to 14 months old, with caffeine in the treatment groups’ drinking water (they don’t say at what concentration, but I assume it was 0.5mM). Organ indices were improved (preservation of organs as a % of total body weight, compared to old controls), with the thymus and spleen statistically significant. It was further shown that telomerase activity was increased in thymus and spleen as well as telomere length in the thymus, spleen and liver. Further, this was reflected in real morphological differences in the organs mentioned, with old treated animals closer to young than untreated old animals in thymus medulla size, white pulp proportions in the spleen and liver cell size and vacuole occurrence.

 

We know from Post #588 and #589 that differentiated mouse cells have less telomerase activity than HELA cells (by approximately 5-6x). This will vary from tissue to tissue, I mention this only as a general guide and also to emphasize that differentiated human cells have nearly ZERO telomerase expression. (See the attached figure for a comparison of telomerase levels in different human tissues). For this reason, we cannot assume caffeine would cause any telomerase activation in normal human cells. But based on these results it would likely boost telomerase expression in already telomerase positive human cells like in the bone marrow or the immune system. Caffeine might also further enhance the effectiveness of an activator shown to work in telomerase negative human cells, though this is speculation.

Attached Thumbnails

• 

[QuestforLife]

Species' cellular ROS level sets aging rate via down regulation of demethylases and failure of Circadian Rhythm

 

This is an alternative to the theory described in Post #632, which required hormonal changes to set off excess methylation and aging. It may be complimentary, as some hormones are oxidative [1]. It ties together ROS production, methylation of the genome, telomere attrition and of course, aging.

 

ROS oxidises Fe2+ to Fe3+. This decreases activity of the demethylases (mainly TET2, in some cells TET3); as the TET catalysed addition of the hydroxyl molecule to the methyl group itself oxidises Fe2+ [2]. The purpose of the TETs is keeping certain gene promoters ‘clean’ so the genes remain active. For example, the GDF11 promoter [3].

 

Circadian rhythm influences the cell’s activity profoundly including ROS therefore some periods of the day/night cycle will have higher TETs activity than others. Accuracy of the circadian rhythm to 24 hours is correlated with lifespan [4] between mouse species, and aging causes a divergence from this rhythm as measured by two clock proteins in the mouse brain (CLOCK and BMAL1) [5]. Further, another paper [6] shows BMAL1 deficit mice have increased cellular senescence levels and shortened lifespan; in vitro experiments show this is not related to replicative senescence but increased sensitivity to ROS. It is not clear what is driving and what is being driven; does ROS cause the circadian rhythm to fail or does circadian rhythm failing cause ROS to rise? We do know that age related methylation occurs in the brain [7], so I would hazard a guess that the ROS/TET/methylation axis is driving loss of circadian rhythm, which then makes ROS rise and accelerates aging further. We can conclude in any case that over the day/night cycle, on average the TETs will fall behind in their cleaning duties and methyl groups will accumulate on the gene promoters they are responsible for, including circadian clock proteins, so this gets worse over longer timescales. You can imagine from this why sleeping poorly can make you feel and look older. But once normal circadian rhythms are established, the TETs can ‘catch up’, so it is not permanent aging. Only if this is sustained over long periods do the TETs fall too far behind (without some intervention) and aging becomes set in.

 

Where exactly the methyl groups accumulate (which CpG islands) is largely random. Some methylation patterns can help the cell survive longer compared to others, and so this type of methylation pattern becomes more common across cells. This may be done by downregulating activities that are important to the body, for example stem cell differentiation. This is the birth of the Selfish Cell. A failure of differentiation leads to long lived stem cells that do not help the body. The rest of the body suffers from short telomeres because of this lack of replacement. Senescent cells accumulate. Increasing stress from the aging body may make some of these selfish stem cells partially differentiate. In some cases they may have long telomeres if their specific pattern of methylation has increased telomerase expression. But they are not fully functional cells in the sense that they do not have the normal gene expression expected of that cell type. They may also be prone to cancerous transformation due to their stem-like phenotype, as discussed previously [8].

 

Conclusion

With all this in mind, I hypothesise that species with a higher endogenous production of ROS and/or lower antioxidant defences will experience faster aging via an increased rate of methylation of important gene promoters, particularly those in the brain responsible for circadian rhythm, which further elevates ROS and exacerbates aging. 

 

[1] https://doi.org/10.1...62.2019.1702656
[2] https://doi.org/10.1...pnas.1608679113
[3] https://doi.org/10.1...20.03.30.008722
[4] https://doi.org/10.1098/rsbl.2010.0152
[5] https://doi.org/10.1...res.2010.03.113
[6] https://doi.org/10.4161/cc.10.23.18381
[7] https://doi.org/10.1...-2012-13-10-r97
[8] https://doi.org/10.1...ell.2018.01.008

Edited by QuestforLife, 09 September 2021 - 01:21 PM.

[dlewis1453]

So the oxidative stress theory of aging is not totally dead after all! It has just been relegated to one of several factors that drive the progress of the central aging pathways of telomere attrition and methylation of the genome. 

 

Do you have a preferred antioxidant to address ROS? I have personally experienced considerable benefit from molecular hydrogen. I am also very interested in Glyteine for its ability to greatly increase levels of intracellular glutathione. Glyteine is currently very expensive however. 

 

By the way, in an earlier post you mentioned that your liposomal vitamin C consumption prevented the unpleasant side effects of AKG, and you provided an explanation of the mechanism responsible for this effect. That is great news. Hopefully now we can consume AKG without side effects and increase our dosages of AKG for even more demethylation. 

[QuestforLife]

So the oxidative stress theory of aging is not totally dead after all! It has just been relegated to one of several factors that drive the progress of the central aging pathways of telomere attrition and methylation of the genome. 

 

Do you have a preferred antioxidant to address ROS? I have personally experienced considerable benefit from molecular hydrogen. I am also very interested in Glyteine for its ability to greatly increase levels of intracellular glutathione. Glyteine is currently very expensive however. 

 

By the way, in an earlier post you mentioned that your liposomal vitamin C consumption prevented the unpleasant side effects of AKG, and you provided an explanation of the mechanism responsible for this effect. That is great news. Hopefully now we can consume AKG without side effects and increase our dosages of AKG for even more demethylation. 

 

Exactly right, the ROS theory of aging just had to refocussed from a cause of molecular damage to its contribution to extra methylation.

 

I had never heard of Glyteine, so thanks for that. From my own experience high dose glycine works to upregulate glutathione - at least according to my urine Vit C levels, which went up considerably without supplementing it. One other way I have found you can tell that an antioxidant is working, is when the whites of your eyes get brighter. I know its only anecdotal; for evidence in the literature of what glycine (and cysteine) can do you don't have to look any further than the big splash the GlyNAC study made recently (DOI: 10.1002/ctm2.372)  

 

 

This study found that compared to healthy young adults, older humans have severely elevated oxidative stress, glutathione deficiency, impaired mitochondrial function, increased inflammation, insulin resistance and endothelial dysfunction, and lower muscle strength and mental cognition. We tested and found that supplementing GlyNAC (combination of glycine and N-acetylcysteine) improved all these defects, and that stopping GlyNAC resulted in a loss of benefits. The results of this trial suggests that GlyNAC supplementation could be a simple, safe and effective nutritional strategy to boost cellular defenses to protect against oxidative stress, correct mitochondrial defects to improve energy availability, increase muscle strength and cognition, and thereby promote healthy aging in humans.

 

 

It is quite suprising just how much they fixed with great big doses of glycine and NAC. Maybe something like Glyteine that does the same thing at a lower dose would be preferable. But the fact that it didn't take long after ceasing dosing for aging symptoms to reoccur shows they hadn't permanently fixed gene expression via demethylation of promoters.

 

I discussed antioxidants on this thread before; in Post #472 I talked about Melatonin, and there was a whole chat starting at about Post #447 about various forms of Vitamin C. Much of the past discussion was centred around preservation of telomeres. But in light of my previous post about circadian rhythm, I'd say Melatonin still looks very promising. 

 

There is also the fact there seems to be something special about Vitamin C that works well with reducing Fe3+ back to Fe2+, which is what is specifically required by the TETs to do their addition of the hydroxyl molecule as part of demethylation of CpG promoters. For example, look at the top bar chart in panel E (no pre-incubation) from Reference 2 of my last post, and see how much more effective (L-)ascorbate is than any of the other antioxidants at keeping the TET protein activity going, by converting Fe3+ to Fe2+. 

 

So vitamin C should always be part of any the antioxidant stack, even if there are other alternatives that are 'stronger' antioxidants (like molecular H, C60, etc.). Other antioxidants like glutathione (or taking  components like Glycine and cysteine) and  alpha lipoic acid are 'supporting' vitamin C by recycling it, so supplementing them may be worth it as well. Incidentally I intend to retest my epigenetic methylation age again soon to see what impact adding vitamin A and vitamin C to AKG have had. A follow on experiment to that might be to add supporting antioxidants like glycine. 

 

In terms of how I'm feeling, I am almost a month and half into the latest AKG cycle and I still feel good, even with increasing AKG from 900mg to 1200mg/day. I have started (last few weekends) having a break from supplementing on Sat/Sun, but I didn't do this because AKG was making me feel bad, I was just worried about taking too much Vitamin A. 

[QuestforLife]

But what about Post Mitotic Cells?

The role of telomeres and telomerase in the senescence of postmitotic cells
Senescence is a process related to the stopping of divisions and changes leading the cell to the SASP phenotype. Permanent senescence of many SASP cells contributes to faster aging of the body and development of age-related diseases due to the release of pro-inflammatory factors. Both mitotically active and non-dividing cells can undergo senescence as a result of activation of different molecular pathways. Telomeres, referred to as the molecular clock, direct the dividing cell into the aging pathway when reaching a critical length. In turn, the senescence of postmitotic cells depends not on the length of telomeres, but their functionality. Dysfunctional telomeres are responsible for triggering the signaling of DNA damage response (DDR). Telomerase subunits in post-mitotic cells translocate between the nucleus, cytoplasm and mitochondria, participating in the regulation of their activity. Among other things, they contribute to the reduction of reactive oxygen species generation, which leads to telomere dysfunction and, consequently, senescence. Some proteins of the shelterin complex also play a protective role by inhibiting senescence-initiating kinases and limiting ROS production by mitochondria. Source: https://doi.org/10.1...rep.2020.102956

It is a common refrain levelled against those of us who think telomeres are of prime importance in aging, that we forget all those post mitotic cells. My usual answer is that most non dividing cells (or mostly non dividing; many are slowly dividing) are critically dependent on dividing cells for support: endothelial cells for cardiomyocytes, astrocytes for neurons, etc. But in this recent paper they review the literature and show that telomerase and other telomere related proteins are critical in regulating senescence in non-dividing cells directly. What is so intriguing to me about this paper, is years ago (on this thread) I spent a long time trying to understand what the relationship between mitochondrial sirtuins like sirtuin 3 and the telomere was (I knew there was a relationship from worm studies). But I could never find anything definitive. Here they show that one of the telomere proteins (one of the ‘shelterins’, whose function it is to bend the telomere around at the end and tuck it in, so it doesn’t get recognised as a double strand break and trigger cell arrest), TRF2, interacts with sirtuin 3. Loss of TRF2 in the mitochondria leads to reduced SIRT3 and mitochondrial dysfunction (I assume through loss of mitophagy) and a rise in ROS, which in turn damages the highly sensitive telomere (it is particularly sensitive to ROS because it has so many guanine bases, which readily form 8-oxoguanosine when oxidised).

Although telomerase (TERT, the protein component) is inactivated in most cells of the human body, there is some evidence (cited here) that it is still active in post mitotic cells, at a level that is important to their function (cardiac cells, for example) and is independent of telomere elongation.

I have previously mentioned how TAM-818 gave me more energy and improved my exercise recovery. I mentioned it in post 682 (https://www.longecit...-21#entry908174) , where I link to a study showing how telomerase improves mitophagy. This current paper adds weight to that argument.

The paper also discusses TERC (the RNA template component), which unlike TERT is always present in human cells, so likely has a role besides that of telomere elongation, especially as it is imported into the mitochondria, processed into a shortened form, and whose presence in the mitochondria is associated with mitochondrial function. So it is likely TERC also plays a role in keeping mitochondria healthy.

Conclusions

Telomerase and healthy telomeres play an important part in keeping mitochondria healthy and ROS low in non-dividing cells. Conversely, if this process fails, rising ROS can induce senescence in non-dividing cells by damaging telomeres (regardless of their length). This means that the Selfish can also emerge from long lived post mitotic cells, just as it can in stem cells.

As explained previously, stem cells either die from telomere shortening induced senescence, or keep telomeres long and persist. But if they do persist, this gives methylation time to build up, selecting for cells that don’t differentiate.

In the case of post mitotic cells, we see a similar process: they cells either eventually die via senescence (this time mediated by telomere damage from ROS, not telomere shortening), or else if telomerase is sufficient to protect them from ROS, their continued existence allows for methylation based changes to accumulate and form the basis of selection for their own survival - in a manner that may not be suited to the body’s well being.

For an example of how this selection might happen, nuclear based epigenetic changes occurring with age in human fibroblasts (reversible through reprogramming,) was shown to downregulate the SHMT2 gene, irreplaceable in glycine production, and stopping the production of new mitochondrial DNA. This would obviously lower ROS (extending cellular life) but at the cost of ATP production (and the work accomplished by the cell for the body with that energy. Note that it was mitochondria that permitted multicellular life; single celled organisms get on fine with glycolysis alone). The relevant paper made quite a big splash in 2015 because of the potential for large doses of glycine to reverse age related mitochondrial dysfunction (see: DOI: 10.1038/srep10434).

[QuestforLife]

Are the oncogenic effects of telomerase mediated by methyl transferases?

 

I’ve never believed that long telomeres are a cause of cancer, other than the aforementioned ability of long telomeres to extend the life of a cell line, and hence increase the time over which errant methylation can build up. We’ve discussed this previously in Post#476 ; with age the body has more cells of a pre-cancerous phenotype. But how exactly does it work going between pre-cancerous and fully cancerous?

 

Cancer cells are known to have an altered epigenome. So part of the answer might be through further methylation-mediated changes to gene expression. This following paper shows that telomerase is involved in the upregulation of one of the de novo methyltransferase DNMT3B.

 

 

Telomerase reverse transcriptase regulates DNMT3B expression/aberrant DNA methylation phenotype and AKT activation in hepatocellular Carcinoma

Telomerase reverse transcriptase (TERT) acts as a master regulator of cancer hallmarks, but underlying mechanisms remain incompletely understood. We show that TERT is required for the aberrant DNA methyltransferase 3B (DNMT3B) expression and cancer-specific
methylation in hepatocellular carcinoma (HCC), through which AKT is activated. TERT depletion inhibited, while its over-expression promoted DNMT3B expression in HCC cells, respectively. Mechanistically, TERT cooperates with the transcription factor Sp1 to stimulate
DNMT3B transcription. The tumor suppressors PTEN and RASSF1A were de-repressed following DNMT3B inhibition in TERT-depleted HCC cells. The PTEN promoter analysis demonstrated significantly reduced methylation in these cells. TERT silencing also led to
diminished global DNA methylation. The analysis of the Cancer Genome Atlas (TCGA)4 dataset showed that higher levels of TERT and DNMT3B expression predicted significantly shorter survival in HCC patients. Collectively, our findings establish TERT as an important
contributor to cancer-specific DNA methylation and AKT hyperactivation in HCC cells. Given critical roles of both the aberrant DNA methylation and AKT activation in carcinogenesis, this TERT-regulated network or the TERT-DNMT3B-PTEN-AKT axis provides a biological explanation for multi-oncogenic activities of TERT and may be exploited in HCC treatment. Source: 10.1016/j.canlet.2018.07.013

 

 

This shows that telomerase is not merely needed by cancer cells to allow continued proliferation, whilst conveniently keeping telomeres short and mutation rate high (telomerase does not increase telomere length if its upregulation results in much faster division rate as discussed in Post#584, but telomerase also up-regulates the methylation required by cancer cells to maintain their aberrant epigenetic state.

 

In fact it is even more interesting than this. Even though the epigenetic controls on telomerase production are not yet understood, methylation of the subtelomeric region is known to be important for suppressing telomerase (note there are no CpG regions in the TTAGGG telomere itself). In the following paper they show that disabling one or more of the DNMTs results in much longer telomeres in mouse embryonic stem cells.

 

 

DNA methyltransferases control telomere length and telomere recombination in mammalian cells

Here, we describe a role for mammalian DNA methyltransferases (DNMTs) in telomere length control. Mouse embryonic stem (ES) cells genetically deficient for DNMT1, or both DNMT3a and DNMT3b have dramatically elongated telomeres compared with wild-type controls. Mammalian telomere repeats (TTAGGG) lack the canonical CpG methylation site. However, we demonstrate that mouse subtelomeric regions are heavily methylated, and that this modification is decreased in DNMT-deficient cells. We show that other heterochromatic marks, such as histone 3 Lys 9 (H3K9) and histone 4 Lys 20 (H4K20) trimethylation, remain at both subtelomeric and telomeric regions in these cells. Lack of DNMTs also resulted in increased telomeric recombination as indicated by sister-chromatid exchanges involving telomeric sequences, and by the presence of ‘alternative lengthening of telomeres’ (ALT)-associated promyelocytic leukaemia (PML) bodies (APBs). This increased telomeric recombination may lead to telomere length changes, although our results do not exclude a potential involvement of telomerase and telomere-binding proteins in the aberrant telomere elongation observed in DNMT-deficient cells. Together, these results demonstrate a previously unappreciated role for DNA methylation in maintaining telomere integrity. Source: DOI: 10.1038/ncb1386

 

 

This is in agreement with the paper I’ve pointed to numerous times, showing disabling DNMT3a immortalises hematopoietic stem cells in vivo in mice, but causes blood cell production to fail (See post #474  - surely a perfect example of the Selfish Cell!

 

Is there any evidence for the methyltransferases increasing their activity with age? It turns out the answer is yes.

 

 

Age and gender affect DNMT3a and DNMT3b expression in human liver

DNA methylation is catalyzed by a family of DNA methyltransferases (DNMTs) including the maintenance enzyme DNMT 1 and de novo methyltransferases DNMT 3a and DNMT 3b. Elevated levels of DNMTs have been found in cancer cells and in several types of human tumors. A polymorphism found in DNMT3b has been associated with increased risk for several cancers. The factors influencing DNMT expression in human tissues have not been clearly determined. The present study examined DNMT3a and DNMT3b levels in human liver tissue samples and compared the effect of ageing, cigarette smoking, and gender. DNMT3a and DNMT3b expression levels in the samples from older individuals (56–78 years, n=28) were both significantly higher than those of the younger group (16–48 years, n=27) (73.2±3.4 vs 8.3±2.8 and 56.1±1.9 vs 17.5±5.7, respectively; p<0.05). Source: DOI 10.1007/s10565-007-9035-9

 

 

Conclusions

DNMTs control telomerase expression via methylation of subtelomeric CpG islands. Disabling one or more DNMTs can dramatically elongate telomeres. Conversely, active telomerase can upregulate DNMT3b and help cancer cells maintain their epigenetic state. I wonder whether this would then self-limit telomerase production so the telomeres of cancer cells do not become too long (impeding mutation rate).

 

Given the importance of DNMTs to the cancer epigenome, they are likely also involved in the mechanism by which long lived stem cells maintain their stemness and self-renewal capability, whilst resisting differentiation (,which if you think about it is similar to what cancer cells do).

 

From a practical point of view and certainly for those of us taking telomerase activators, eliminating the excess methylation (caused by telomerase) should minimise cancer risk. Keeping a young epigenetic age, as measured by methylation, will be a good guide to cancer risk. As I have said before (in Post #476), cancer isn’t a consequence of aging, avoiding cancer isn’t the reason we have to age, cancer is aging.

[manofsan]

The full paper is now available and it is interesting that the authors propose a different mechanism for the benefits of HBOT:

 

 

 

 

source: https://www.aging-us...cle/202188/text

 

Essentially they are claiming the oxidative stress triggers a hormetic response that more than makes up for the harm.

 

I remain to be convinced. Feel free to make up your own mind/s. 

 

 

Couldn't taking something like the Piperlongumine during HBOT help by eliminating cells which have weaker anti-oxidative capability?

 

Wouldn't that potentially enhance the hormetic response?