TERT activation targets DNA methylation and multiple aging hallmarks
Many thanks to Chemically_Charmed for supplying the paper.
Background: This is a paper authored among others by Ron Depinho, famous years ago for this paper [1] where they induced (human-like) ageing in mice through telomerase deactivation and then reversed it by reactivating telomerase.
In the current paper [2] mice were genetically engineered to carry the HTERT gene plus its cis regulatory elements. This enabled researchers to see effects on this gene as it would occur in humans rather than upon the MTERT gene, which is generally active in most mice tissues but downregulated with age. Tests were carried out both on cells extracted from those mice (from the ears) and on the mice themselves.
Tests were also carried out in human cells: lung fibroblasts and Werner Syndrome fibroblasts. Presumably this allowed them to eliminate the possibility that the MTERT gene was also stimulated. I would have far preferred they used normal human cells passaged to near senescence rather than WS cells, but it is better than nothing.
Screening found a small molecule which upregulated the human telomerase gene (HTERT) in all tissues examined.
In a nutshell, what's good, what's bad?
Bad: TERT RNA upregulation was mild, maybe x2, if that
Good: TERT RNA upregulation occurred across all tissues tested
Bad: There is no comparison with HELA or any other TERT positive cell type for the extent of HTERT activation;
Bad: and there is no TRAP assay for telomerase activity; but
Good: They did show the molecule increased telomere length in human cells
Good: and reduced DNA damage foci due to short telomeres
Good: and increased proliferative ability in cells beginning to slow divisions
Bad: but that was in Werner Syndrome cells!
Good: TERT activation was VERY specific; only a couple of genes upregulated and translation in general not affected at all (means this may synergise with other approaches)
Good: The molecule has wide distribution in the body, including nervous system and brain; clearance took 3 hours (in mice)
Good: protein levels of TERT increased in PBMCs in proportion to increase in RNA levels, which is useful to know
Bad: but they looked at protein level using immunoblotting (not accurate)
Good: but they didn’t use the antibody NCL-HTERT known to be non specific to telomerase [3]
On to the effects…
Good: with only a week course of this molecule, senescence and inflammatory markers were reduced (more than halved) in old mice
Good: and this occurred across a wide range of tissues, not just blood cells
Good: and increased general markers of growth and natural killer cell activity
Good: and longer term treatment (6 months) in old mice reduced senescent cell burden
Bad: this was all injected 6mg/Kg/day
Good: The molecule had strong effects in the brain, increasing adult neurogenesis and decreasing microglia activation and inflammation. Aside: TERT seems to have particularly strong effects in the brain, as we've seen before with gotu kola extracts [4], and I speculate that this is due to high mitochondrial densities in those tissues.
Good: The molecular benefits in the brain also extended to actual benefits in old mice, including cognitive tests, balance and strength when injected with the substance 3 times/week.
Stepping back
Unlike with TAM818 no medicinal chemistry was done, they simply worked with the best molecule they found from screening. So, this molecule is unlikely to represent the best possible. Having said that, its molecular action was incredibly precise, with no side effects.
I am disappointed they didn't do more and better measurements of the extent of telomerase activation; I assume it was because the increase in levels were so mild. Nevertheless the benefits were real. Again, I speculate most of these effects were through non canonical mitochondrial benefits rather than through lengthening telomeres.
The study could be taken most usefully as a proof of the benefits of mild telomerase activation, rather than this being a super molecule, and secondarily that HTERT RNA upregulation does seem to feed through to actual telomerase production.
Other molecules like TAM818 do not have this level of evidence behind them, and other compounds like gotu kola extracts have a plethora of effects, some good, some bad. We do have evidence for the effects of TA-65 on mice, and they are not as promising as these results. So overall I'd say we have strong evidence for good effects with this molecule rather than weak evidence for very good effects (TAM818) or strong evidence for weak effects (TA-65). So, this paper is a step forward.
The big question is bioavailability. It is a small molecule and it gets everywhere once it is injected. Is it orally bioavailable? I suspect so because of its low molecular weight and the fact it is fat soluble.
References
[1] Jaskelioff M, Muller FL, Paik JH, Thomas E, Jiang S, Adams AC, Sahin E, Kost-Alimova M, Protopopov A, Cadiñanos J, Horner JW, Maratos-Flier E, Depinho RA. Telomerase reactivation reverses tissue degeneration in aged telomerase-deficient mice. Nature. 2011 Jan 6;469(7328):102-6. doi: 10.1038/nature09603. Epub 2010 Nov 28. PMID: 21113150; PMCID: PMC3057569.
[2] Shim HS, Iaconelli J, Shang X, Li J, Lan ZD, Jiang S, Nutsch K, Beyer BA, Lairson LL, Boutin AT, Bollong MJ, Schultz PG, DePinho RA. TERT activation targets DNA methylation and multiple aging hallmarks. Cell. 2024 Jun 21:S0092-8674(24)00592-0. doi: 10.1016/j.cell.2024.05.048. Epub ahead of print. PMID: 38908367.
[3] https://www.longecity.org/forum/topic/102169-alternative-methods-to-extend-telomeres/page-34#entry931391
[4] Tsoukalas D, Buga AM, Docea AO, Sarandi E, Mitrut R, Renieri E, Spandidos DA, Rogoveanu I, Cercelaru L, Niculescu M, Tsatsakis A, Calina D. Reversal of brain aging by targeting telomerase: A nutraceutical approach. Int J Mol Med. 2021 Nov;48(5):199. doi: 10.3892/ijmm.2021.5032. Epub 2021 Sep 13. PMID: 34515324; PMCID: PMC8448543.
Edited by QuestforLife, 06 July 2024 - 10:04 AM.