79 replies to this topic

[LeeYa]

Here, we show that p16INK4a expression in PBTL has the properties of a useful peripheral blood biomarker of human molecular age. The test is an easily measured, low-cost assay that can be performed on a small specimen of whole blood with a short turnaround time. The test demonstrates low intra-individual variability and is highly dynamic with human age. Data from rodents systems suggest that p16INK4a expression is not merely epiphenomenally associated with aging, but may also play a causal role in the process in diverse tissues

https://www.ncbi.nlm...les/PMC2752333/

 

Is this blood test commercially available?

 

 

[johnhemming]

I don't know what is commercially available on this.  Testing for IL-10 or IL-6 may be better although they may come from sources other than senescent cells as well.

[Bike_to_120]

possible Senescent test for SA-β-galactosidase (β-gal)

https://www.jinfinit...ew-basic-panel/

not cheap

[CynthesisToday]

Not (yet) a clinical test. 

 

https://doi.org/10.1...596-021-00505-5 " Algorithmic assessment of cellular senescence in experimental and clinical specimens." (2021)

 

Abstract: The development of genetic tools allowed for the validation of the pro-aging and pro-disease functions of senescent cells in vivo. These discoveries prompted the development of senotherapies—pharmaceutical interventions aimed at interfering with the detrimental effect of senescent cells—that are now entering the clinical stage. However, unequivocal identification and examination of cellular senescence remains highly difficult because of the lack of universal and specific markers. Here, to overcome the limitation of measuring individual markers, we describe a detailed two-phase algorithmic assessment to quantify various senescence-associated parameters in the same specimen. In the first phase, we combine the measurement of lysosomal and proliferative features with the expression of general senescence-associated genes to validate the presence of senescent cells. In the second phase we measure the levels of pro-inflammatory markers for specification of the type of senescence. The protocol can help graduate-level basic scientists to improve the characterization of senescence-associated phenotypes and the identification of specific senescent subtypes. Moreover, it can serve as an important tool for the clinical validation of the role of senescent cells and the effectiveness of anti-senescence therapies.

 

Figure 1 Provides a schematic representation of the protocol.

 

[CynthesisToday]

This research article appears to be a science-based, quantified assessment of burden of senescent cells and dysfunction/death:

 

doi:10.1038/s41591-018-0092-9 "Senolytics Improve Physical Function and Increase Lifespan in Old Age" (2019) 

 

Transplanting 10^6 senescent cells into young mice resulted in decrease in various functional parameters and earlier death than age-matched controls while 2x10^5 did not. Obesity decreased the number of transplanted senescent cells it took to have negative function/death.

 

This article gives ways of considering senescent cells and research on same vs impact on health:

 

https://doi.org/10.1...mad.2021.111548 "Impact of Senescent Cell Subtypes on Tissue Dysfunction and Repair: Importance and Research Questions" (2021)

[Zarathrustra]

Thank you Phoebus 08Mar22 12:05 for this link. Alas, whilst it does provide support for senescent cell importance, it fails to show a direct metric for assessing the amount of senescent cells. Perhaps more importantly, it states that it is inflammation, however caused, is the real problem, not the senescent cells themselves:

 

Fisetin is a senotherapeutic that extends health and lifespan

 

19. Xu M., Tchkonia T., Ding H., Ogrodnik M., Lubbers E.R., Pirtskhalava T. JAK inhibition alleviates the cellular senescence-associated secretory phenotype and frailty in old age. Proc Natl Acad Sci U S A. 2015;112(46) E6301-E10. [PMC free article] [PubMed] [Google Scholar] “We found a higher burden of senescent cells in adipose tissue with aging.”

“The underlying mechanisms of age-related chronic inflammation, tissue dysfunction, and frailty remain elusive”

“Senescent cells accumulate with aging in the skin (13, 14), liver (15, 16), kidney (17), the cardiovascular system (18), and other tissues in various species (16)”

“We found that elimination of senescent cells delayed the onset of age-related phenotypes and enhanced healthspan (21, 22).”

 

21. Baker DJ, et al. Clearance of p16Ink4a-positive senescent cells delays ageing-associated disorders. Nature. 2011;479(7372):232–236. [PMC free article] [PubMed] [Google Scholar] “To address these fundamental questions, we made use of a biomarker for senescence, p16^Ink4a“[1] So this is a proxy or marker for senescent cells, not a direct metric for the amount of senescent cells. { Charlotte Y Dai, Greg H Enders “:text=The%20available%20data%20suggest%20that%20p16%20INK4a%20may,p16%20INK4a%20can%20induce%20some%20features%20of%20senescence.' class='bbc_url' title='External link' rel='nofollow external'>p16INK4a:text=The%20available%20data%20suggest%20that%20p16%20INK4a%20may,p16%20INK4a%20can%20induce%20some%20features%20of%20senescence.' class='bbc_url' title='External link' rel='nofollow external'> can initiate an autonomous senescence program ... (www.nature.com/articles/1203438_

The available data suggest that p16 INK4a may contribute to senescence, but do not address whether p16 INK4a induction per se is sufficient to induce senescence or is required to maintain it. Several recent studies indicate that p16 INK4a can induce some features of senescence.}

 

22. Zhu Y, et al. The Achilles’ heel of senescent cells: From transcriptome to senolytic drugs. Aging Cell. 2015;14(4):644–658. [PMC free article] [PubMed] [Google Scholar] “Even though senescent cell abundance in aging or diseased tissues is low, achieving a maximum of 15 percent of nucleated cells in very old primates, senescent cells can secrete pro-inflammatory cytokines, chemokines, and extracellular matrix proteases, which together constitute the senescence-associated secretory phenotype or SASP” [Note: the paper states that it is the inflammation that is the problem, not the amount of senescent cells. So if the senescent cells do not cause inflammation, there is presumably no problem with having senescent cells. Clearing away the senescent cells may not matter, especially if inflammation continues to be present].

 

 

[Zarathrustra]

Thanks CythesisToday [yesterday 06:45] for that.

 

This confirms my suspicion that there is at present no senescence burden, hence no research into the relationship between such a burden, ageing, and degenerative ailments.

 

All that said, adherents to this theory do seem to be producing research supporting the theory that some proposed Senolytics have a beneficial effect on ageing. So maybe the unproven theory is correct.

 

That said, research such as Protect against aging and age-related disease with the MondoA protein may be equally or more fruitful.

 

There remains the problem of different parts of the body ageing differently. Does that mean applying different Senolytics, or will each be effective on all parts of the body? Distinct biological ages across individuals’ various organs and systems

 

[Zarathrustra]

I have now spent the last two weeks searching and reading many papers relating to cellular senescence and senolytics, and give here my summary along with successive documents of my research (most previously attached, but here in one place for ease of reference), along with my own longevity references. Thank you colleagues for your references and critiques; these prompted me to do the work required to sort things out.

 

Summary:

The cellular senescence theory as one of the major causes of ageing is unproven. None of the underlying theory has been substantiated, all the way up from the Hayflick limit, through the human body accumulating senescent cells as the human ages, to proving that clearing away senescent cells reverses ageing or reduces degenerative diseases. There is no metric for the burden of senescent cells. Any supposed effect of an increasing amount of senescent cells is via increases of inflammation. Any supposed effect of supposed Senolytics is independent of the unproven theory – tho’ the empirical effect of the Senolytics is possibly real. The latter has not been tracked over sufficient time yet to detect any deleterious side-effects. Meanwhile, there is already established evidence that (a) various lifestyles directly effect longevity; (b) the effectiveness of the lifestyle components can be measured by established metrics and shown to correlate with extended age. My own use of senolytic supplements shows differing correlations with my biometrics, underlying the uncertainties of such products – even if they may be true for some people, they may not be for others.

 

Whilst the theory that there is increasing amounts of senescent cells as a body ages, and that this causes the problems of ageing, is plausible. That some senescent cells cause these problems by increasing the amount of inflammation is also plausible. And that clearing away such cells will reduce the amount of illnesses of ageing people. Further, that using this theory to discover means of clearing away such cells will cause rejuvenation may be successful; indeed, there is evidence it is so. However, this latter sentence is not itself proof that the underlying theory (as laid out in the earlier sentences) is correct.

 

First, the very basis of senescent cells is questionable – the Hayflick limit.

 

“In the simulation, the default Hayflick limit of a normal stem cell is 72 as an approximation of the realistic number between 50 and 70 (Shay and Wright, 2000).” It seems this is for cells in vitro, not vivo. It is not true for stem cells.

 

“It seemed to decrease with the age of the cell donor and, as a form of cell senescence, was thought to underlie the aging process. More discriminating analysis, however, showed that the fibroblasts decayed in a stochastic manner from the time of their explantation, at a rate that increased with the number of population doublings in culture. There was no consistent relation to the age of the donor.” Promise and problems in relating cellular senescence in ...

 

We do not know if this cell limit is true of humans – it may be more or less; different for different types of cells; that telomerase (which effects when the Hayflick limit is reached) may be more available for some cells and not others. We also do not know why there is a variation of the Hayflick limit. It is probable that there is a great variation in the speed and amount of senescent cells in a human, nor what proportion is cleared away by the normal biological processes (apoptosis; immune cells’ clearance).

 

Attached Files

•  Senescence and Senolytics.docx   22.86KB   0 downloads
•  Senescence and senolytics II.docx   20.14KB   0 downloads
•  Senescence and Senolytics III.docx   25.83KB   0 downloads
•  Senescence and Senolytics IV.docx   14.84KB   0 downloads
•  On Health - Longevity - and overcoming Illnesses Locked.pdf   1.75MB   0 downloads

[johnhemming]

We will have to agree to disagree.  I support the idea that stem cells that fail to differentiate become senescent.  There is plenty of evidence for the failure of differentiation being behind specific diseases such as osteoporosis and sarcopenia.  I have personally started to supplement on an experimental basis with citrate.  I am doing 4 weekly blood tests and started supplementing with citrate at the start of my current cycle (10th March).  I will know what the initial outcome is at the end of that period.   I am currently supplementing with about 1.5g of citrate per day and would plan on increasing that if needs be in the second four weekly period.

 

IMO there is good evidence that citrate supplementation could fix the problems with a shortage of Acetyl-CoA in the cytosol/nucleus of stem cells.

Edited by johnhemming, 15 March 2022 - 08:47 PM.

[Zarathrustra]

Thanks John.

 

I'm not sure we disagree regarding citrate; if it works, good. But you will have no evidence that will be because it has any effect on cellular senescence.

[johnhemming]

(for me) Citrate is primarily about ensuring that stem cells differentiate properly.  That would prevent them becoming senescent.  However, it may be the case that at times a senescent cell which is an improperly differentiated stem cell can be differentiated.  Time will tell.

[Zarathrustra]

I'll be interested to hear the results John.

 

You say "There is plenty of evidence for the failure of differentiation being behind specific diseases such as osteoporosis and sarcopenia." - any chance of a reference or two please?

 

How will you know if your experiment with Citrate works?

[johnhemming]

I  have done some videos explaining all of this on my channel and the comments section gives links to the research papers

https://www.youtube....ser/johnhemming

 

One possible outcome of my experiment with citrate is the growth of new hair or an increase in the range of High Frequency Hearing I have.  Currently my HF hearing level is 13kHz in the morning and 14kHz in the evening. If that goes up following citrate supplementation then that is likely to be the cause.  I am currently running blood tests every 4 weeks and will keep an eye on things.  I am also measuring the rate of growth of nails which is likely to be affected.  However, I may not be accurate enough to determine a variation there.  I have done some grip tests as well.  These may be affected.  

 

[Treon Verdery]

Thanks John Hemming and Mind.

[boylan]

I  have done some videos explaining all of this on my channel and the comments section gives links to the research papers

https://www.youtube....ser/johnhemming

 

One possible outcome of my experiment with citrate is the growth of new hair or an increase in the range of High Frequency Hearing I have.  Currently my HF hearing level is 13kHz in the morning and 14kHz in the evening. If that goes up following citrate supplementation then that is likely to be the cause.  I am currently running blood tests every 4 weeks and will keep an eye on things.  I am also measuring the rate of growth of nails which is likely to be affected.  However, I may not be accurate enough to determine a variation there.  I have done some grip tests as well.  These may be affected.  

John,

 

What is the form of citrate that you will be experimenting with?

[Rocket]

But that does not address the central issue: if there is no evidence that links the burden of senescent cells with illnesses or mortality, methinks you are not doing science, you are doing belief. Which may turn out to be true; but may not.

Given the centrality of senescence as the supposed root of ageing, it is odd that this untested (and maybe untestable) is being used to then try to find nostrums that may or may not reduce it - which we cannot know, as we have no measure of senescence. Not only that, but (a) the aforementioned nostrums may have deleterious side effects whilst perhaps not doing what is claimed (as its unmeasurable); (b) even if the senescence is reduced, it may have no effect on longevity or illnesses.

I don't know that too many researchers consider senescence the root of aging. The accepted root is the genetic malfunctions that build up in the tissues, telomeres, and loss of stem cell activity.

[Zarathrustra]

Thanks John.

 

I have no issue with the idea that senescent cells occur at times (and, as your first ref shows, it can happen at any age). Nor that the amound can be measured at a particular time in some organs. Nor that such cells are detrimental, not least (mainly?) by increasing inflammation.

 

My concern is (a) whether the total of senescent cells increases with age (plausable tho' this may be), as we have no measure of that; (b) whether a body's normal processes (exercise, nutrition, immune cells) moderate/remove such cells - so their quantity may rise and fall.

 

Lastly, does the quantity of senescent cells matter at all if inflammation if kept in check/reduced (the latter implying the body is actually coping with them). As far as I can make out, it is well established that inflammation itself is the bady all on its own - deal with that, and anything tending to increasing it is also dealt with.

 

All may be moot, 

[Zarathrustra]

Thanks Guest for "I don't know that too many researchers consider senescence the root of aging. The accepted root is the genetic malfunctions that build up in the tissues, telomeres, and loss of stem cell activity." Perhaps I've been readin too much into the lLongevity Newsletter, where I thought this was a major research area hoping to pay off in reversing ageing. Your opinion is a useful correction for me.

[johnhemming]

Thanks John.

 

I have no issue with the idea that senescent cells occur at times (and, as your first ref shows, it can happen at any age). Nor that the amound can be measured at a particular time in some organs. Nor that such cells are detrimental, not least (mainly?) by increasing inflammation.

 

My concern is (a) whether the total of senescent cells increases with age (plausable tho' this may be), as we have no measure of that; (b) whether a body's normal processes (exercise, nutrition, immune cells) moderate/remove such cells - so their quantity may rise and fall.

 

Lastly, does the quantity of senescent cells matter at all if inflammation if kept in check/reduced (the latter implying the body is actually coping with them). As far as I can make out, it is well established that inflammation itself is the bady all on its own - deal with that, and anything tending to increasing it is also dealt with.

 

All may be moot, 

 

C Reactive Protein responds to IL6 levels which inter alia are part of SASP.  Hence CRP gives a guide to the burden of senescence if there has not been a recent bacterial infection in which case the response to the bacteria takes CRP really high.

 

The number of senescent cells does increase with age.  I am not sure how much useful data there is on clearance and senolytics.

[Zarathrustra]

I understand CRP, and have monitored it for decades.

 

However, your assertion "The number of senescent cells does increase with age" is one I still can find no evidence for, or research papers supporting this. All my searches, as I've reported here, at best show that at some time, some aged organs have a lot of senescent cells. Nowhere is there any assessment of whole body burden of senescent cells; nor that this has increased with age; nor that it is alterable - unlike the evidence we have for inflammation.

 

Having said that, I am still open to someone quoting research papers that contradict my understanding and that back up your assertion.

 

Perhaps equally important would be research relating whole-body seneescent celll burden being casually related to degenerative diseases. 

[johnhemming]

Taking CRP (more precisely uninfected CRP) as a proxy, CRP increases with age.

[Zarathrustra]

Seemingly not for everyone.

 

My longevity programme appears to be working.

 

I'd post the data, but for some reason my 17KB Excel xlsm file isn't accepted. It shows over a 14 year period (age 73 - 86) my hsCRP has risen from about 1-8, fallen again to around 1, risen to 50 at one point, and for that last 5  years or so been under 5-ish, under 1/5 lately.

[johnhemming]

I have reduced mine to under 0.16mg/L, but for the population as a whole it increases with age.

 

The minimum CRP indicates the senescence burden.

 

Senescence is not the whole of the aging process,  but in that it drives further senescence and the cells are not functioning it is an important part.

[Zarathrustra]

Mine are in mmol/L; so your 0.16mg/L equates to 1.7 mmol/L. My latest one is 1.18 mmol/L, equating to 0.12 mg/L.

 

Averages are useful starting points, but as you imply, the critical metric is one's own. Mine shows a decline with age of late.

 

How do you know that minimum CRP has any relationship to overal quantity of senescent burden?

[johnhemming]

Could you please show your working on your conversion of units.   I thought the US measurements were normally mg/dL.  My experience of UK labs is that they use mg/L.

 

CRP links to IL-6 and IL-6 is part of sasp.  IL-6 is also created for other reasons (infection) which is why you need to look for the minimum over time.

 

Hence if it is going down that would imply a reduction in senescence load.

 

Edited by johnhemming, 26 March 2023 - 07:37 AM.

[Zarathrustra]

Just Googling 'conversion between mg/L and mmol/L' will find nlots of conversion helps. As a non-USA citizen, my labs use the International system of units that the rest of the World uses.

 

I appreciate that lower inflammation is good; that's why I've been tracking it for 14+ years. However, the causes of increased inflammation are many, but non can be emprically linked to senescent cells - try googling that. There are a lot of assertions but no empirical evidence - presumably because there's no emprical test for whole-body senescent cell burden.

 

That said, if such a theory has any importance it would probably be through the mediation of inflammation that it would cause problems. So imflammation itself is what is important, not the senescent cells themselves.

 

My own data shows either that the supposed increase of such cells with age is incorrect; or that it can be reversed without the need of additional senolytic interventions.

[johnhemming]

Mine are in mmol/L; so your 0.16mg/L equates to 1.7 mmol/L. My latest one is 1.18 mmol/L, equating to 0.12 mg/L.

 

 

You are saying 0.16 milligrams per litre is equivalent to 1.7 millimoles per litre.

 

a) That would imply a molecular weight for CRP that is under 1.

 

b) CRP has a molecular weight of around 120 kDa.

 

Hence there is something wrong with your conversion.  I, therefore, asked you to show your calculations.

 

I think realistically you are probably quoting the wrong units and need to go back to the source data.  1.7mmol/L is a very very high CRP figure.

[Zarathrustra]

John, you are entirely correct. My sincere apologies; and thank you for perservering in correcting me. My figures are indeed for mg/L.I'd been misled by most of my blood results are in mmol/L, and often the USA ones aren't. But no excuse; I was sloppy.

 

And though my CRP at 1.18 mg/L is not bad (<3 seems to be thought as good), it is still seven times yours.

 

Addendum: there seems to reference to senescent cells being a source of CRP increases in the standard searches, such as 12 Hidden Causes of High C Reactive Protein (CRP) - SelfDecode Labs

 

Once again, thanks again.

[johnhemming]

Thank you for your gracious response.  I live in the UK as well so I have UK style measurements.

 

Most importantly, although your CRP levels are good ... for your age ... they do indicate a senescent cell load that it would be good to reduce.

 

I am 63, but my CRP levels are lower than those of Bryan Johnson who is over 15 years younger than me and claims to have good biomarkers.

 

I have my own hypothesis about cellular deterioration (aging) which I have written up on my blog

 

https://johnhemming....op-working.html

 

https://johnhemming....-aging-why.html

 

(inter alia).

 

I continue down my route of aiming to improve the health of my cells (and therefore my own health).  As far as I can tell (and I monitor things on a daily basis) if you target these particular routes (which intersect with Acetyl-CoA levels in the cytosol/nucleus) then it does the job.

 

 

 

 

 

[Zarathrustra]

Thanks John.

 

I'll pass on anything further on the unproven theory of reversing cellular senescence, as there's no metric of it that can be tracked - until the 100+ tried and tested ones I do track (and correlate with my lifestyle variables). Anyway, it would appear that imflammation is a good proxy for whatever effect that cellualr senescence may or may not have; and is important in its own right. From all the stuff I've read, it is probable that some lifestyle factors act as senolytics.

 

There's the additional complication that what may be good for reversing cellular senescence may be detrimental elsewhere.