MOTS-c Peptide

## What it is MOTS-c (Mitochondrial Open Reading Frame of the Twelve S rRNA-c) is a 16-amino-acid peptide encoded within the 12S rRNA region of mitochondrial DNA, identified by Lee, Cohen, and colleagues at USC in 2015. It belongs to the small but rapidly expanding family of mitochondrial-derived peptides (MDPs), alongside humanin and the SHLPs. Unlike most signaling peptides which are encoded in nuclear DNA and synthesized in the cytoplasm, MOTS-c is encoded in the mitochondrial genome and represents a rare class of mitochondrially-encoded peptides that exit the organelle and signal systemically. The peptide has no FDA, EMA, or PMDA approval and no active phase 3 trial. CohBar (the USC spinout commercializing MDPs) advanced an MOTS-c analog (CB4211) through phase 1b in NASH and discontinued the program in 2022 after a phase 1b readout did not meet target endpoints, and the company itself wound down in 2024. WADA has not yet placed MOTS-c on the Prohibited List as of 2026, though the compound's mechanistic position (an exercise-mimetic and insulin sensitizer) makes future scrutiny likely. User populations are predominantly longevity-focused biohackers and a small group of metabolic-syndrome users experimenting off-label. The grey-market supply is younger and more variable than for older peptides; quality control concerns are correspondingly higher. ## Mechanism of action MOTS-c regulates metabolic homeostasis primarily through AMPK activation. Lee 2015 demonstrated that exogenous MOTS-c administration in mice increased AMPK phosphorylation in skeletal muscle, improved insulin sensitivity, and protected against diet-induced obesity. The peptide also translocates to the nucleus under metabolic stress (Kim 2018), where it modulates expression of nuclear-encoded genes involved in stress response and metabolism, an unusual retrograde mitochondrial-to-nuclear signaling pattern. Downstream effects in preclinical models include increased glucose uptake in muscle (via GLUT4 translocation), upregulation of mitochondrial biogenesis pathways (PGC-1alpha), reduced hepatic gluconeogenesis, and improved exercise performance via augmented metabolic flexibility. The peptide circulates at low ng/mL levels in healthy humans and declines with age, which is the empirical hook for the longevity hypothesis: declining MOTS-c may contribute to age-related metabolic dysfunction, and exogenous restoration may be useful. Plasma half-life of injected MOTS-c is short (minutes), but the metabolic effects persist for hours to days, suggesting downstream signaling cascades or transient nuclear localization rather than direct receptor-mediated action throughout the response window. ## Evidence base Human trial data is sparse. CohBar's CB4211 phase 1b in NASH and obesity (n approximately 90) reported acceptable tolerability and some signal on weight and metabolic markers but did not meet primary endpoints clearly enough to support phase 2 advancement, and results were not published in full. A small Korean exercise-physiology study (Reynolds 2021) measured circulating endogenous MOTS-c response to acute and chronic exercise in healthy adults (n approximately 30), establishing the exercise-induction signal but not testing exogenous administration. The bulk of the evidence is rodent. Lee 2015 (the foundational paper) showed roughly 20 to 30% improvements in insulin sensitivity and protection against high-fat-diet weight gain in mice receiving daily MOTS-c. Reynolds 2021 also reported in mice that MOTS-c administration restored running capacity in aged animals to roughly 80% of young-animal baseline, an exercise-mimetic signal that grabbed substantial press attention. Subsequent rodent work has confirmed insulin sensitization signals across multiple labs but specific magnitudes vary. Long-term human safety, optimal dosing, and translation of the rodent exercise-capacity findings to humans all remain unestablished. The honest framing is that MOTS-c is mechanistically interesting biology with one foundational rodent paper and several preclinical replications, a single discontinued phase 1b program, and no controlled human evidence of metabolic benefit in healthy or diseased adults. ## Dosage and administration Anecdotal protocols circulating among longevity-focused users typically run 5 to 10 mg subcutaneously 2 to 3 times weekly, often timed pre-workout or pre-meal on the rationale of metabolic priming. Some users front-load with daily 10 mg injections for 2 to 4 weeks then taper to 2 to 3 times weekly. None of these specifics are derived from human dose-finding trials. They are extrapolated from rodent dosing (typically 0.5 to 5 mg/kg in mice) and refined by community feedback. A typical 10 mg vial reconstituted with 2 mL bacteriostatic water gives 5 mg/mL. A 5 mg dose draws 100 units on a U100 insulin syringe. Cycling structure varies wildly across user reports: 4 weeks on 4 weeks off, 8 weeks on 4 weeks off, and continuous dosing are all common. There is no controlled cycling data. ## Side effects and safety Reported anecdotal effects are mostly minor: injection-site irritation, transient fatigue in the first 1 to 2 weeks (sometimes attributed to AMPK-mediated metabolic shifts), and occasional headache. No serious adverse events have been documented in published literature, but post-marketing surveillance does not exist for a research-grade compound and the user base self-selects for tolerability. Contraindications are theoretical: pregnancy and lactation given total absence of human data, active malignancy on cautious mechanistic grounds (AMPK activation has mixed effects on tumor biology), and severe hypoglycemia risk in users on insulin or sulfonylureas given the insulin-sensitizing signal. There is no characterized drug-drug interaction profile because there is no human pharmacokinetic study published in full. The largest practical safety concern is product quality. Independent mass spec studies of grey-market mitochondrial-derived peptides have found wildly variable peptide content and impurity profiles. Sterility of reconstituted product depends entirely on bacteriostatic water and aseptic technique. ## Practical notes Lyophilized MOTS-c is stable at room temperature for the labeled shelf life and should be refrigerated for longer storage. Reconstituted vials should be refrigerated and used within 30 days. Bacteriostatic water is the standard reconstitution medium. Measurable subjective effects are inconsistent across user reports. Some report improved exercise capacity and recovery within 2 to 4 weeks; others report nothing distinguishable from baseline. Glucose monitoring (continuous or fasted spot checks) is the most accessible objective endpoint, since insulin sensitization is the most reproducible preclinical signal. Baseline fasting glucose and HbA1c before starting and recheck at 8 to 12 weeks; absence of measurable improvement suggests either non-responder status, under-dosed product, or inactive vial. The honest expected value is unknown. The mechanism is plausible and interesting; the human evidence base is thin and the one industrial program discontinued. Treat extended use as experimental.