MOTS-c

MOTS-c is the most scientifically compelling compound in this reference and the one with the least human interventional data. The gap between what we know about its biology and what we know about what it does to humans at community doses is larger than for any other chapter. That gap is not a reason to dismiss it. It is the most important fact about it.

The central tension resolved: MOTS-c links mitochondrial biology, aging, exercise adaptation, and longevity genetics in a single peptide. Plasma levels decline with age in humans. A genetic variant is associated with exceptional longevity in centenarians. Marathon runners have significantly higher levels than sedentary controls. Late-life treatment in aged mice reverses physical capacity decline. Multiple independent groups have replicated its metabolic effects across diverse animal models. WADA has named it explicitly on the prohibited list as a metabolic modulator. None of this adds up to evidence that injecting 5-10 mg SubQ in a 50-year-old human will produce the benefits the animal studies suggest. The biology makes the prediction. The controlled human trial has not tested it.

The strongest argument for MOTS-c: the independent corroboration of the animal evidence is the most thorough of any longevity compound in this reference. The Reynolds 2021 Nature Communications study was not the Cohen lab — it was an independent group finding the same performance enhancement in aged mice. Kumagai 2024 was an international independent group finding direct muscle protein binding. The 2025 cardiac and senescence studies are independent groups confirming new mechanistic dimensions. The compound's biology is mechanistically coherent, evolutionary consistent (MOTS-c sequence is conserved across mammals), and supported by human observational data that points toward clinical relevance. The longevity genetic association is the kind of human evidence that makes a compelling biological argument for investigation.

The strongest argument for caution: every controlled interventional claim rests on animal data. The WADA ban means that athletes — the community most likely to benefit from the exercise mimetic properties — cannot use it without career risk. The dose used in community protocols may be substantially below the dose needed to replicate animal model effects. Hypoglycemia risk in combination with glucose-lowering medications is real and not characterized. Long-term effects of sustained exogenous MOTS-c on endogenous production, AMPK pathway sensitivity, or other systems have not been studied.