MOTS-c: mitochondrial signaling, exercise and ageing research

For most of the history of cell biology, mitochondria were treated as power plants that take instructions from the nucleus. MOTS-c helped change that picture. It is a 16-amino-acid peptide encoded within the mitochondrial genome itself, and research since 2015 suggests it acts as a messenger travelling from mitochondria to the rest of the cell and beyond. This article looks at three threads of that research: how the peptide signals, how it relates to exercise, and why it appears in ageing studies.

A peptide encoded by mitochondrial DNA

MOTS-c (mitochondrial open reading frame of the 12S rRNA type-c) was first described by Lee and colleagues in Cell Metabolism in 2015. Its sequence sits inside a short open reading frame in the mitochondrial 12S rRNA region, which places it in a small family of mitochondrial-derived peptides alongside humanin and the SHLPs. That origin is what makes it interesting to researchers: it offers a way to study how mitochondria might communicate their metabolic state outward, rather than only receiving signals from the nucleus.

How MOTS-c is thought to signal

• Folate cycle and AMPK. In the original mouse and cell work, MOTS-c inhibited the folate cycle, which led to accumulation of the metabolite AICAR and activation of AMPK, a central cellular energy sensor. Skeletal muscle appeared to be a primary target tissue.
• Movement into the nucleus. A 2018 follow-up study (Kim et al., Cell Metabolism) reported that under metabolic stress MOTS-c moves from the cytoplasm into the nucleus, where it was associated with changes in the expression of stress-response genes, including those regulated by NRF2.
• Effects across the body. MOTS-c has been detected in circulation in both rodents and humans, which is why it is often described as a mitochondrial hormone, or mitokine, in the research literature.

The exercise connection

One of the more cited recent findings comes from Reynolds and colleagues (Nature Communications, 2021). In human volunteers, MOTS-c levels rose in skeletal muscle and in circulation after a bout of exercise. In mouse models, administering the peptide was associated with improved physical performance measures in young, middle-aged and older animals. These results have made MOTS-c a reference point in research asking whether some of the metabolic effects of exercise are carried by mitochondrial signals.

As with much of this field, the human data are observational and early. Showing that a peptide rises with exercise is different from showing that it causes exercise-related adaptations, and that distinction remains an open research question.

Why MOTS-c appears in ageing research

Several studies have reported that circulating MOTS-c levels tend to be lower in older subjects and in models of insulin resistance. Genetic research adds another angle: a naturally occurring variant in the MOTS-c sequence, reported mainly in people of Northeast Asian ancestry, has been associated with a higher risk of type 2 diabetes in some populations (Zempo et al., 2021). Together these findings keep MOTS-c in discussions of metabolic ageing, though association studies alone cannot establish cause and effect.

Where the research stands

• Mechanistic evidence in cells and rodents is reasonably consistent, particularly for AMPK activation and skeletal muscle effects.
• Human evidence is largely limited to measuring natural MOTS-c levels and genetic associations, not controlled intervention trials.
• MOTS-c is not an approved drug, and research findings should not be read as established effects in people.

Handling MOTS-c in the laboratory

MOTS-c is supplied as a freeze-dried (lyophilised) powder and must be reconstituted with a suitable diluent before use. Store sealed vials cold and away from light, and record the labelled mass and diluent volume so concentrations are always clear. See the MOTS-c product page for current vial sizes, pricing and availability.

Summary

MOTS-c is a mitochondrial-encoded peptide studied for its role in signaling between mitochondria and cellular systems. Research links it to AMPK activation, stress-responsive gene expression, exercise physiology and metabolic ageing. The preclinical picture is detailed and growing, while human evidence remains early and mostly observational, so it is best treated as an active research area rather than a settled one.