What is MOTS-c?

What is MOTS-c?

MOTS-c is a peptide of 16 amino acids built from a short open reading frame, a stretch of DNA that can be read to make a peptide, inside the gene for 12S ribosomal RNA in mitochondrial DNA. Lee and colleagues found it by searching the human 12S rRNA for small reading frames and spotting a 51-base-pair candidate with a strong Kozak sequence, the signal that starts translation, a computational human-sequence screen rather than evidence of clinical effects (Lee et al., Cell Metabolism, 2015). They then tested the peptide in cultured cells and mice (Lee et al., Cell Metabolism, 2015).

The mitochondrial origin makes MOTS-c unusual. Most of the proteins in your mitochondria are written in your nuclear DNA and shipped in. MOTS-c is written by the mitochondria's own small genome. In a computational comparison of candidate human nuclear and mitochondrial sequences, the authors checked whether the sequence might be a stray copy from the nuclear genome and found that none of the candidate copies matched the mitochondrial sequence completely; sequence matching alone is not evidence of a clinical effect (Lee et al., Cell Metabolism, 2015).

The 2015 paper is indexed in PubMed, the biomedical library run by the US National Institutes of Health, and its full text is free in PubMed Central. The MOTS-c research guide walks through the studies that followed.

What does 'mitochondrial open reading frame of the 12S rRNA' mean?

Each part of the name is an address. Mitochondrial means the instructions sit in the small genome inside mitochondria rather than in the cell nucleus. An open reading frame is a stretch of genetic code that can be read to build a peptide or protein. The 12S rRNA is a mitochondrial gene for a ribosomal RNA, a molecule that belongs to the cell's protein-making machinery. The 'type-c' label follows the 2015 naming by Lee and colleagues, who describe MOTS-c as a 16-amino-acid peptide within that gene (Lee et al., Cell Metabolism, 2015).

A gene for one kind of RNA that also hides a peptide is a surprise, a bit like finding a second message written between the lines of a letter. It also shows how the discovery happened: the authors ran a computer search of the human 12S rRNA for small open reading frames rather than starting from a known protein. Humanin, found earlier, is another peptide of this type, and the MOTS-c paper cites it as the reason to look for additional ones (Lee et al., Cell Metabolism, 2015).

Is MOTS-c considered a peptide?

Yes. MOTS-c is a peptide, a short chain of 16 amino acids, and the original paper calls it one (Lee et al., Cell Metabolism, 2015). Later papers also call it a mitochondrial microprotein, which describes the same molecule by its small size, and a mitochondrial-derived peptide, which describes it by origin (Kumagai et al., iScience, 2024; Reynolds et al., Nature Communications, 2021). The words are not competing definitions. They answer different questions: how long is it, and where does it come from.

Where a peptide ends and a protein begins is a convention, not a law of nature, and chains of 16 units sit comfortably on the peptide side. The same peptide-or-not question comes up for other compounds, and the guide on whether NAD+ is a peptide shows how the answer turns on structure.

What does research show MOTS-c does in the body?

In cells and mice, Lee et al. found that MOTS-c inhibits the folate pathway and the purine synthesis tied to it, which activates AMPK, an enzyme that senses cellular energy, with skeletal muscle as a major target organ in mice, a laboratory result that does not establish the same action in people (Lee et al., Cell Metabolism, 2015). In cell lines under glucose restriction, later work reported that MOTS-c moves into the cell nucleus and changes gene activity, a cell-culture result which does not establish the same action in people (Kim et al., Cell Metabolism, 2018). In cell-free tests and mouse muscle, Kumagai et al. reported that MOTS-c binds and activates the enzyme CK2, a laboratory and mouse result which does not establish the same action in people (iScience, 2024).

The table below shows why the setting matters. A cell experiment can show a mechanism, a mouse can show a whole-animal response, and neither can show what a person would experience. The natural K14Q variant adds a human clue: in Japanese cohorts of 1,241 people for muscle mass, 4,966 men and 6,890 women for type 2 diabetes, K14Q carriers had a higher prevalence of low muscle mass, a marker of sarcopenia (age-related muscle loss), and of type 2 diabetes in men in their 60s, but a lower diabetes prevalence in women in their 50s; these associations differed by sex and did not test supplied MOTS-c (Kumagai et al., iScience, 2024).

Does the human body make MOTS-c, and does it change with exercise?

Studies have measured MOTS-c made by the body in human muscle and blood. In 10 sedentary healthy young men who exercised on a stationary bicycle, muscle MOTS-c rose about 12-fold after exercise, and circulating MOTS-c rose about 1.6-fold during and 1.5-fold after exercise, then returned to baseline after four hours of rest while muscle levels were still elevated at that mark; this is one small group measured for the body's own peptide (Reynolds et al., Nature Communications, 2021). In a cross-sectional comparison of 26 young, 26 middle-aged and 26 older healthy men, circulating MOTS-c fell with age while muscle MOTS-c was about 1.5-fold higher in middle-aged and older men than in young men, again a measurement of the natural peptide in one cohort (D'Souza et al., Aging, 2020).

Measurements like these show that the body has its own MOTS-c signal and that it moves with circumstances. They do not show what happens when MOTS-c is supplied from outside, which is a different experiment. In a 2018 case-control study in China, circulating MOTS-c was lower in 40 obese children and adolescents than in 57 controls, a difference seen in males and not in females, and in males it correlated with markers of insulin resistance; this is an association in one small study and not a cause (Du et al., Pediatric Diabetes, 2018).

What do studies show about MOTS-c and appetite?

No human study measuring appetite after exposure to MOTS-c was found in the sources searched. In male mice on a normal diet treated for four days, modest reductions in food intake, body weight and blood glucose were observed, a mouse finding that does not establish appetite or weight effects in people (Lee et al., Cell Metabolism, 2015). In mice on a high-fat diet, caloric intake was identical in treated and untreated groups, a mouse finding that does not establish appetite or weight effects in people (Lee et al., Cell Metabolism, 2015). Old mice treated from late life ate less in total than untreated mice while body weight stayed comparable, a mouse finding that does not establish appetite or weight effects in people (Reynolds et al., Nature Communications, 2021). For the analogue CB4211, a different molecule, the sponsor reported a trend toward lower body weight after four weeks in 20 adults with fatty liver disease (11 on CB4211, 9 on placebo), a company press release and not a peer-reviewed paper (CohBar press release, 10 August 2021).

The mouse papers recorded how much food was eaten, which is a weight of pellets, not whether the animals felt hungry. That is a different measurement, and no human measurement of appetite after MOTS-c exposure was found in the sources searched for this page on 14 October 2026.

What do studies show about MOTS-c and the liver?

No study of MOTS-c in the human liver was found in the sources searched. In mice with bone cancer, chronic MOTS-c treatment had little effect on liver, renal, lipid or cardiac function, a mouse result that does not establish human safety (Yang et al., Acta Biochimica et Biophysica Sinica, 2024). In mice on a high-fat diet, MOTS-c treatment reduced liver fat build-up, a mouse result that does not establish human liver effects (Lee et al., Cell Metabolism, 2015). In mice fed a diet that causes fatty-liver disease with inflammation (NASH), MOTS-c treatment alleviated liver steatosis, cell death, inflammation and fibrosis, a mouse result that does not establish human liver effects (Lu et al., Cell Reports, 2024). In the trial of the analogue CB4211, a different molecule, the sponsor reported larger falls in ALT and AST, two blood markers of liver injury, than on placebo in 11 adults with fatty liver disease against 9 over four weeks, an exploratory result in a company press release and not a peer-reviewed paper (CohBar press release, 10 August 2021).

The trial result came from exploratory endpoints in 20 people, and the registry lists no results (ClinicalTrials.gov NCT03998514). The registry also shows that participants in the first two parts had to start with normal liver enzymes, and the fatty-liver part set limits on how high their enzymes could be. The FDA states that it has not identified any human exposure data on drug products containing MOTS-c (FDA page, content current as of 22 April 2026). That leaves the human liver question for MOTS-c itself open.

Which groups has MOTS-c research left out?

The two registered human trials, one of the analogue CB4211 and one of MOTS-c, each set exclusions. The registry record of the analogue trial (ClinicalTrials.gov NCT03998514) lists adults aged 18 to 60 and women only if they could not become pregnant, and for its first two parts it excludes significant kidney or liver disorders, heart-rhythm abnormalities, active infection and positive hepatitis or HIV tests. The registry record of the MOTS-c trial (NCT07505745) lists adults aged 18 to 65 with prediabetes and a body mass index of 27 to 40, and excludes diabetes, pregnancy, breastfeeding, active cancer needing treatment and clinically significant liver, kidney or cardiovascular disease. Safety data for the excluded groups were not found in the sources searched.

A trial's exclusion list records who researchers chose not to enrol. It is a map of missing data, not a safety finding about those groups. Athletes are a separate case: the WADA 2026 Prohibited List, in force from 1 January 2026, names MOTS-c as an example of AMPK activators in its metabolic-modulator class, and the doping-control laboratory of the German Sport University Cologne repeats that entry (page last updated 1 June 2026); this is a sport-rule record and not a safety finding. The MOTS-c in Perth page covers the sport and Australian listings.

Evidence limits

How strong is the evidence for MOTS-c, and what do online reports add?

Evidence can show how much weight a claim deserves, and for MOTS-c the human weight is light. The MOTS-c side-effects page sets out the safety record, and the quality and verification hub explains how research material is documented. The site catalogue lists MOTS-c reference material as a laboratory reference, not a medicine and not for human or animal use.