Telomere

Telomeres are the protective end-caps on chromosomes — repetitive DNA sequences that buffer the coding regions from damage during cell division. Every time a cell divides, the telomeres get a little shorter. When they're too short to protect the chromosome, the cell stops dividing (senescence) or dies. The shortening is measurable. Average telomere length is used as a proxy biomarker for biological age in the longevity literature — shorter telomeres, in aggregate, correlate with older biological age and a higher risk of age-related disease. The correlation is real; the causation is still being worked out. Epithalon is the primary research peptide associated with telomere biology. Studies by Khavinson et al. showed it activated telomerase (the enzyme that extends telomeres) in cultured human cells and extended telomere length in those models. Rodent lifespan studies from the same group showed extended mean lifespan. That research comes predominantly from one Russian group, working in vitro and in animals. Human clinical data is absent. There's a complication worth knowing. Telomeres shorten to limit the number of times damaged cells can replicate — including potentially cancerous ones. Telomere lengthening sounds straightforwardly beneficial. In practice, telomerase activation is also how some cancer cells become immortal. The biology isn't as simple as "longer is better."