What is MOTS-c
MOTS-c (Mitochondrial Open reading frame of the 12S rRNA type-c) is a 16-amino acid peptide encoded within the mitochondrial genome. Unlike nearly every other circulating signaling peptide, it is synthesized from a short open reading frame inside the sequence that codes for the 12S ribosomal RNA subunit of mitochondrial DNA. The peptide was first characterized in 2015 by Changhan Lee, Jennifer Zeng, Brian G. Drew, Pinchas Cohen, and colleagues at the USC Leonard Davis School of Gerontology, published in Cell Metabolism (Lee et al., Cell Metabolism 21(3):443-454, 2015).
MOTS-c belongs to a broader family of mitochondrial-derived peptides (MDPs) that includes Humanin, SHLP1-6, and other short open reading frame products of the mitochondrial genome. MDPs as a biologically active class were not widely recognized until Humanin was identified as a cytoprotective factor in Alzheimer's disease models in the early 2000s. MOTS-c was the second major MDP to be characterized and is the most studied for metabolic and exercise-related effects.
Plasma MOTS-c is detectable in healthy humans, and its concentration declines with age. Data from the 2021 Reynolds et al. study in Nature Communications (Reynolds et al., Nature Communications 12:1, January 2021) documented an 11% reduction in circulating MOTS-c among middle-aged adults (45-55 years) and a 21% reduction in older adults (70-81 years) compared with a young adult reference group (18-30 years). Whether that decline contributes to age-related metabolic dysfunction or is a downstream consequence of reduced mitochondrial activity has not been determined.
How MOTS-c signals: the folate-AICAR-AMPK pathway
The primary signaling cascade runs through the folate-methionine cycle. MOTS-c disrupts folate-dependent one-carbon metabolism, which reduces flux through the tetrahydrofolate pathway and limits de novo purine synthesis. Reduced purine synthesis raises intracellular AMP levels, which activates AMP-activated protein kinase (AMPK), the master regulator of cellular energy homeostasis. Activated AMPK suppresses anabolic processes, increases fatty acid oxidation, enhances glucose uptake, and promotes mitochondrial biogenesis.
Under conditions of metabolic stress, MOTS-c also translocates from the cytoplasm to the nucleus. Lee et al. demonstrated this in a 2018 Cell Metabolism paper (PMID 29983246, cell culture and mouse models) using glucose restriction as the stressor. Inside the nucleus, MOTS-c interacts with antioxidant response elements (ARE) and drives expression of genes regulated by NRF2 (NFE2L2), ATF1, and ATF7. These are stress-responsive transcription factors that protect cells from oxidative damage and promote metabolic adaptation.
This retrograde signaling direction is mechanistically unusual. The mitochondrial genome is normally regulated by nuclear-encoded proteins; MOTS-c reverses the flow, allowing mitochondria to relay stress status to the nucleus and alter transcription directly. The 2015 Lee et al. paper described MOTS-c as a "mitochondrial hormone" for this reason: it is produced in the mitochondria, circulates in plasma, and acts on distant tissues in a manner analogous to a conventional endocrine signal.
What MOTS-c research shows in animal models
The 2015 founding study tested MOTS-c in two mouse models: C57BL/6 mice fed a high-fat diet for 10 weeks, and aged mice with established insulin resistance (Lee et al., Cell Metabolism 2015). MOTS-c treatment improved insulin sensitivity, reduced fat accumulation, and prevented diet-induced weight gain in the obese cohort. In aged insulin-resistant mice, it restored insulin sensitivity to levels comparable to younger controls. The effects required functional AMPK: AMPK knockout abolished the metabolic improvements, confirming the pathway dependency.
The 2021 Reynolds et al. Nature Communications study focused on physical performance and muscle homeostasis across three age groups of mice: young (2 months), middle-aged (12 months), and old (22 months). MOTS-c administration improved performance in grip strength and treadmill endurance tests across all three groups. The effect was most pronounced in old mice. A separate cohort of 23.5-month-old mice received MOTS-c injections three times per week for eight weeks; that group showed measurable gains in physical capacity and healthspan markers versus saline controls. The study was notable for testing late-life initiation of treatment rather than continuous administration from youth.
Gene expression data from both studies implicate skeletal muscle metabolism and proteostasis pathways as primary downstream targets. MOTS-c treatment in aged mice produced transcriptional changes consistent with improved mitochondrial function and reduced protein aggregation, which are hallmarks of muscle aging.
MOTS-c and exercise
The Reynolds 2021 paper included human exercise data from healthy adult volunteers. Skeletal muscle biopsies taken before and after a single acute exercise bout showed MOTS-c concentrations approximately 12-fold higher in post-exercise muscle tissue, with partial elevation still measurable four hours into recovery. Circulating plasma MOTS-c rose approximately 1.5-fold during the exercise session and remained elevated afterward.
These observations classified MOTS-c as an exerkine, a signaling molecule released during physical activity with potential downstream metabolic effects. The pattern parallels other exercise-regulated myokines such as irisin, but with a mitochondrial genomic origin that is unusual for circulating signals of this type.
A 2024 study in professional endurance athletes found lower resting serum MOTS-c concentrations compared with sedentary controls, despite the athletes having higher aerobic capacity and more favorable metabolic profiles overall. The authors proposed a chronic adaptation interpretation: highly trained individuals may maintain downstream pathway activation with lower circulating peptide concentrations. The study was observational with a small sample, and the proposed mechanism has not been confirmed experimentally.
Human data and evidence gaps
No completed Phase 2 or Phase 3 interventional trials administering exogenous MOTS-c to humans have been published as of June 2026. Human data comes from two sources: exercise physiology studies tracking acute changes in MOTS-c levels in response to physical activity, and cross-sectional biomarker analyses associating plasma MOTS-c with age and metabolic indicators. Neither source establishes a therapeutic dose or confirms human efficacy.
NCT04027712, registered on ClinicalTrials.gov (NCT04027712), includes MOTS-c as an observational measurement endpoint in a study of platelet reactivity, amyloid markers, and mortality in Type II diabetes patients with coronary artery disease. It is not a MOTS-c administration trial.
Translating rodent metabolic efficacy to human clinical outcomes is a common bottleneck in peptide research. For MOTS-c specifically, two practical obstacles stand out: the peptide has a short circulating half-life, and the pharmacologically relevant dose for human metabolic or physical capacity endpoints has not been established from human pharmacokinetic data.
Research handling and storage
MOTS-c for research use is supplied as a lyophilized powder, typically as the acetate salt at 98%+ purity. Standard cold-chain protocols apply: -80 degrees C for long-term storage (6-12 months), -20 degrees C for short-term working stock. Freeze-thaw cycling accelerates peptide degradation and should be minimized by aliquoting before initial freezing.
Researchers in Bali and Indonesia working under tropical ambient conditions face additional challenges in maintaining the required temperature range. Ambient humidity above 75% RH and temperatures regularly above 30 degrees C can compromise lyophilized peptide integrity within hours if cold-chain discipline lapses. A two-tier storage setup suited to ICH Zone IV humidity conditions is covered in the lyophilized peptide storage guide.
Reconstitution uses bacteriostatic water (BAC water) as the standard diluent, providing a 30-day working window under refrigerated conditions. The peptide dosing calculator works out volume-to-concentration ratios from a given vial mass and reconstitution volume. MOTS-c is listed in the compound catalog with current format and availability. All handling described here is for in vitro and in vivo research use only, and does not constitute dosing guidance for human use.