A mitochondrial peptide studied in the context of AMPK, metabolism, physical activity, and aging
Overview
MOTS-C is a short peptide of 16 amino acids, encoded within a region of mitochondrial DNA inside the 12S rRNA sequence. Its full name is Mitochondrial Open Reading Frame of the 12S rRNA-c, and it belongs to the family of mitochondrial-derived peptides, peptides that originate in the mitochondria [1]. The interest in MOTS-C stems from the view that the mitochondrion is not only a source of ATP production, but also an organelle that produces biological signals affecting the cell and the body as a whole. Mitochondrial peptides may participate in communication between the mitochondria and the nucleus, in the regulation of metabolic stress, in inflammation, in insulin sensitivity, and in aging processes [1,2,5]. Most of the knowledge about MOTS-C comes from cell studies, animal studies, and biological measurements in humans. There is evidence that its levels or expression change in response to physical activity and under various metabolic conditions, but this does not constitute proof of clinical efficacy of external administration in humans [4,6].
Biological Mechanism
One of the main mechanisms studied around MOTS-C is related to the folate pathway and to purine biosynthesis. The original study found that MOTS-C affects these pathways in a manner associated with an increase in endogenous AICAR and with activation of AMPK [1]. AMPK is a central energy sensor in the cell, activated under conditions of energetic load or a need for metabolic efficiency. When AMPK is activated, the cell tends to increase energy-producing processes, such as fatty acid oxidation and glucose uptake, and to reduce energy-consuming processes that are not essential at that moment. Therefore, the link between MOTS-C and AMPK explains the interest in it in the contexts of insulin sensitivity, skeletal muscle, physical activity, and metabolism [1,4,5]. A 2018 study showed that under conditions of metabolic stress MOTS-C can translocate to the cell nucleus and affect the expression of genes related to the stress response, including pathways related to NRF2 and to antioxidant response elements [2]. This finding is important because it presents MOTS-C as part of a broader cellular adaptation system, and not merely as a single metabolic switch.
Research Evidence
In a study published in 2015 in Cell Metabolism, administration of MOTS-C to mice in models of high-fat diet and metabolic aging was associated with improved insulin sensitivity, reduced diet-induced obesity, and changes in skeletal muscle metabolism [1]. A 2019 study proposed that MOTS-C affects the plasma metabolite profile and improves insulin sensitivity in experimental models, including effects on lipid pathways and various metabolites [3]. In 2021, a study published in Nature Communications presented MOTS-C as a peptide influenced by physical activity and as a regulator of age-related functional decline in mouse models [4]. A further study from 2026 examined the effect of MOTS-C on mitochondrial bioenergetics in muscle, and proposed that certain effects depend on PGC-1α and AMPK [5]. In humans, a systematic review and meta-analysis from 2024 found associations between MOTS-C levels and metabolic conditions, but also emphasized inconsistency between studies and populations [6].
Mitochondria–Nucleus Communication and Its Link to Exercise
One of the important features of MOTS-C is that it connects the mitochondrial genome with nuclear responses. Most mitochondria-associated proteins are encoded in the nucleus, but MOTS-C demonstrates that the mitochondrion itself can contribute peptide signals that reach broader control systems [1,2]. The translocation to the nucleus under conditions of metabolic stress, described in 2018, suggests a role for MOTS-C as part of an adaptation mechanism and not merely as a single metabolic molecule [2]. The link to physical activity is particularly important because it places MOTS-C within an entire network of biological signals. Physical activity alters ATP, NAD, calcium, ROS, AMPK, PGC-1α, hormones, myokines, and inflammatory markers. Therefore, when a study shows that physical activity increases the expression or levels of MOTS-C, one should not conclude that it alone explains the effects of training [4]. It is more accurate to understand it as one of the possible markers or mediators of muscular and metabolic adaptation. In mouse models, MOTS-C has been associated with improved physical function at different ages and with changes in skeletal muscle metabolism [4]. The 2026 study added a bioenergetic layer and proposed that certain effects in muscle depend on AMPK and PGC-1α, with improved mitochondrial efficiency and not merely an increase in the quantity of mitochondria [5]. The distinction between mitochondrial quality and mitochondrial quantity is meaningful, because a tissue can contain many mitochondria yet still function inefficiently. In humans, most of the data are not therapeutic intervention trials but rather level measurements, statistical associations, and responses to physical activity [4,6]. Therefore there is a gap between impressive biology and clinical conclusions. The 2024 meta-analysis emphasized inconsistency between studies, including differences by metabolic state, measurement methods, and populations [6]. This means that the field is still at a stage where MOTS-C helps to understand metabolism and aging, but does not allow broad medical conclusions to be drawn.
Safety & Regulation
The clinical information on MOTS-C in humans is still limited. Measuring peptide levels in the blood or a change in expression following physical activity is not equivalent to proof of efficacy or safety of external exposure. Questions such as pharmacokinetics, degradation, immunogenicity, exposure ranges, and long-term effects are not adequately resolved. The FDA notes that for drug products containing MOTS-C no adequate human exposure data have been identified, and that there are concerns related to immunogenicity, peptide-related impurities, and characterization of the active substance in the context of compounding [7]. In addition, in competitive sports settings, substances affecting AMPK and metabolism may be relevant to anti-doping rules, and therefore regulatory distinction is important [8].
The Difference Between a Biomarker and an Intervention
A finding that MOTS-C levels change following physical activity or a metabolic state does not prove that the peptide is the direct cause of the health change [4,6]. It could be a mediator, a marker, a result of energetic stress, or part of a broad feedback system. This is an important distinction because popular discourse tends to turn molecules that respond to training into 'training substitutes,' whereas the biology of physical activity involves hundreds of pathways acting together. The metabolic associations in humans are also not uniform. In the 2024 review and meta-analysis, associations were found between MOTS-C and conditions such as diabetes and obesity, but not in a simple and identical direction across all studies [6]. Such variability may arise from differences in age, sex, BMI, physical activity, measurement method, background inflammation, or metabolic morbidity. Therefore, high or low levels of MOTS-C cannot at this stage serve as a diagnosis or as a therapeutic recommendation. In terms of aging research, MOTS-C is important because it points to a link between mitochondria, skeletal muscle, and stress resistance. Functional decline with age is not the result of a single pathway alone, but of changes in mitochondria, chronic inflammation, loss of muscle mass, neural changes, hormones, and movement. MOTS-C adds a layer to this research, but does not by itself explain the aging process. In the context of bone and osteoporosis, which also appears in recent regulatory discussions on MOTS-C, the level of evidence is still more preliminary than that of metabolism and muscle [7]. The possible biological link passes through cellular energy, inflammation, and mitochondrial function, but there is not yet a broad clinical basis that allows describing a direct effect on bone density or fracture risk in humans.
Summary
MOTS-c is a mitochondrial peptide studied in the context of mitochondria-nucleus communication, the AMPK pathway, metabolic stress and aging [1-5]. The preclinical findings are interesting, but the knowledge in humans is still limited and inconsistent [6]. Its primary value is in research — for understanding the effect of mitochondria on metabolism; the substance is intended for laboratory research use only.
Selected Research Sources
- Lee C. et al. The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance. Cell Metabolism, 2015. PMID: 25738459
- Kim K.H. et al. The Mitochondrial-Encoded Peptide MOTS-c Translocates to the Nucleus to Regulate Nuclear Gene Expression in Response to Metabolic Stress. Cell Metabolism, 2018. PMID: 29983246
- Kim S.J. et al. The mitochondrial-derived peptide MOTS-c is a regulator of plasma metabolites and enhances insulin sensitivity. Physiological Reports, 2019. PMID: 31293078
- Reynolds J.C. et al. MOTS-c is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis. Nature Communications, 2021. PMID: 33473109
- Gudiksen A. et al. MOTS-c improves intrinsic muscle mitochondrial bioenergetic health and efficiency in a PGC-1α/AMPK-dependent manner. Free Radical Biology and Medicine, 2026. PMID: 41520850
- The correlation between mitochondrial derived peptide and metabolic states: a systematic review and meta-analysis. PubMed, 2024. PMID: 39160573
- U.S. Food and Drug Administration. Safety risks associated with certain bulk drug substances nominated for use in compounding. Entry for MOTS-C. FDA.gov
- World Anti-Doping Agency. The Prohibited List. Section on metabolic modulators. WADA-ama.org
