What Does Peptide Longevity Research Actually Study? NAD+, MOTS-c, SS-31 and Epithalon Explained

Longevity is the noisiest corner of peptide research. The same four names, NAD+, MOTS-c, SS-31 and epithalon, appear together in forum threads, supplement marketing and serious journals, and they are rarely separated by the question each one is actually studied for. This article does that separation: what was measured, in which model, and what the published record does and does not support. It is written for people evaluating research materials, not as guidance for use in people.

Why does longevity research keep returning to mitochondria?

Because energy handling changes with age. Reviews of the field describe declining mitochondrial function, altered NAD+ availability and reduced stress resilience as recurring features of ageing tissues in animals, and the compounds discussed here each touch one of those mechanisms. That shared theme explains why they are discussed together; it does not make them interchangeable.

Three of the four are peptides or peptide-like molecules that act on mitochondrial signalling or structure. The fourth, NAD+, is a coenzyme consumed by enzymes that regulate mitochondrial and nuclear processes. Grouping them is a convenience of the marketplace, not a finding of the literature.

What is known about NAD+ decline with age?

Published reviews report that NAD+ concentrations fall in tissues of aged animals, and that raising NAD+ availability improved several age-related measures in rodents. A 2020 review in Experimental Gerontology stresses that human data are limited, that the mechanisms of the decline are not settled, and that the threshold at which lower NAD+ starts to matter is unknown for most tissues.

A 2021 review in Metabolism reaches a similar conclusion: reduced NAD+ is associated with ageing and with several metabolic and neurological diseases, and precursor molecules such as nicotinamide riboside are being studied in people, mostly as oral supplements. Research on NAD+ itself as an injectable reagent is a laboratory topic; the human trials in the literature concern precursors, not the coenzyme in a vial.

What did the MOTS-c studies actually show?

MOTS-c is a 16-amino-acid peptide encoded in the mitochondrial genome. The 2015 Cell Metabolism paper that named it reported that, in mice, the peptide acted on skeletal muscle, activated AMPK through the folate cycle, and prevented age-dependent and diet-induced insulin resistance. That is a mouse result with a defined mechanism.

A 2021 Nature Communications study extended the picture: MOTS-c treatment improved physical performance in young, middle-aged and old mice, and in humans, exercise raised the body's own MOTS-c in skeletal muscle and in circulation. The human part of that study measured endogenous MOTS-c after exercise; it did not administer the peptide to people. Controlled trials of administered MOTS-c in humans have not, to our knowledge, been published in the peer-reviewed literature.

What is SS-31 and why is it different from the others?

SS-31 is the research name of elamipretide, a four-amino-acid peptide that concentrates in the inner mitochondrial membrane and binds cardiolipin. It is different because it went through the full clinical pathway: on 19 September 2025 the FDA granted accelerated approval to Forzinity (elamipretide) as the first treatment for Barth syndrome, a rare mitochondrial disease, in patients weighing at least 30 kg, based on an improvement in knee extensor muscle strength, with a confirmatory trial required.

That approval is narrow. It covers one ultra-rare disease under a conditional pathway, and the sponsor continues to study the molecule in other conditions. It does not extend to ageing, and it says nothing about research-grade SS-31 sold as a laboratory reagent, which is manufactured and supplied outside the pharmaceutical system. The two products share a molecule and nothing else.

What did the epithalon study show?

Epithalon (Ala-Glu-Asp-Gly) is a synthetic tetrapeptide from the Russian bioregulator literature. The most cited paper, published in 2003 in the Bulletin of Experimental Biology and Medicine, reported that adding the peptide to telomerase-negative human fetal fibroblast cultures induced expression of the telomerase catalytic subunit, telomerase activity and telomere elongation.

That is a cell-culture observation from a single group, published more than twenty years ago and not widely replicated by independent laboratories. It is a legitimate reason for interest and an inadequate basis for any claim about people. Anyone quoting "epithalon lengthens telomeres" without adding "in cultured fibroblasts" is overstating the record.

How should you read longevity claims about peptides?

Three filters resolve most of the confusion. First, separate mechanism, model and outcome: a pathway activated in cells is not an effect in mice, and an effect in mice is not an outcome in people. Second, look at the evidence hierarchy: reviews and controlled studies outrank screenshots and forum summaries, but even reviews are only as good as the studies they collect. Third, ask whether the source names what remains uncertain. Confident pages with no caveats are usually marketing.

How are these compounds handled and verified in a laboratory?

All four ship as lyophilised powder in sealed vials. They are stored cold, dry and dark, reconstituted with bacteriostatic water, and kept refrigerated once in solution; NAD+ is the least stable of the four in solution and is prepared close to the time of use. The practical rules are in our storage guide and reconstitution guide.

Verification matters more here than in most categories, because purity claims travel faster than data. Every current Vitality Peps batch is analysed by Janoshik Analytical and listed on the lab results page with its batch reference, measured mass, purity and a link to the laboratory's own verification record. How to read such a report is covered in our COA article.

For laboratory research use only. Not for human or veterinary consumption. This article summarises published research; it does not describe an approved use of any compound.

Frequently asked questions

Is NAD+ a peptide?

No. NAD+ (nicotinamide adenine dinucleotide) is a coenzyme built from two nucleotides, not a chain of amino acids. It is grouped with research peptides commercially because it ships as a lyophilised research reagent in the same format, but chemically and biologically it belongs to a different class.

Does epithalon lengthen telomeres in humans?

The evidence is a 2003 study in cultured human fetal fibroblasts, where the peptide induced telomerase activity and telomere elongation in the dish. No controlled human trial has shown telomere lengthening in people, so the cell-culture result cannot be read as a human outcome.

Is SS-31 the same as elamipretide and Forzinity?

SS-31 is the research designation of elamipretide, the molecule in Forzinity, which the FDA approved under accelerated approval on 19 September 2025 for Barth syndrome. A research-grade SS-31 vial is not that medicine: it is manufactured, regulated and supplied as a laboratory reagent, with no approval for any use in people.

Which is better, epithalon or MOTS-c?

They are not comparable, because they are studied for different questions: telomerase activity in cell culture for epithalon, and mitochondrial signalling and metabolism in mice for MOTS-c. A researcher chooses by the model and the hypothesis, not by a ranking.

How long does reconstituted NAD+ last?

NAD+ is less stable in solution than as a dry powder and degrades faster at warm temperatures and at non-neutral pH. Laboratory practice is to reconstitute close to the time of use, keep the solution refrigerated and protected from light, and avoid freeze and thaw cycles. Our storage guide covers the general rules.

Are any of these compounds approved for anti-ageing?

No. There is no medicine approved anywhere for slowing ageing. Elamipretide's 2025 approval is for one rare mitochondrial disease, and the other three compounds have no marketing authorisation for any indication. Research reagents sold under these names are for laboratory use only.

Sources

• McReynolds MR, Chellappa K, Baur JA. Age-related NAD+ decline. Experimental Gerontology, 2020. https://doi.org/10.1016/j.exger.2020.110888
• Chu X, Raju RP. Regulation of NAD+ metabolism in aging and disease. Metabolism, 2021. https://doi.org/10.1016/j.metabol.2021.154923
• Lee C et al. The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance. Cell Metabolism, 2015. https://doi.org/10.1016/j.cmet.2015.02.009
• Reynolds JC et al. MOTS-c is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis. Nature Communications, 2021. https://doi.org/10.1038/s41467-020-20790-0
• Khavinson VK, Bondarev IE, Butyugov AA. Epithalon peptide induces telomerase activity and telomere elongation in human somatic cells. Bulletin of Experimental Biology and Medicine, 2003. https://doi.org/10.1023/a:1025493705728
• U.S. Food and Drug Administration. FDA Grants Accelerated Approval to First Treatment for Barth Syndrome, 19 September 2025. fda.gov
• FDA approval letter, NDA 215244, Forzinity (elamipretide). accessdata.fda.gov

Journal references were retrieved from PubMed.

Related reading

• Why promising peptide studies fail to translate from animals to humans
• How to read a peptide certificate of analysis without overinterpreting purity
• Longevity research compounds in the catalogue