MOTS-C

MOTS-c (Mitochondrial Open Reading Frame of the Twelve S rRNA Type-C) is a 16-amino acid peptide encoded within the mitochondrial genome, discovered in 2015 by Changhan Lee's group at USC. It is the first mitochondrial-derived peptide shown to function as a systemic signaling molecule, challenging the traditional view that mitochondria primarily encode structural and enzymatic components of the electron transport chain. MOTS-c represents a new class of retrograde signals from mitochondria to the nucleus that regulate metabolic homeostasis.

MOTS-c circulates in blood and its levels respond to physiological stimuli — exercise increases circulating MOTS-c, while aging and metabolic disease are associated with declining levels. In preclinical models, exogenous MOTS-c administration prevents diet-induced obesity, improves insulin sensitivity, and reverses age-related physical decline. The peptide has generated significant research interest as a potential exercise mimetic and metabolic regulator, though no human clinical trials have been completed.

MOTS-c exerts its metabolic effects primarily through activation of AMP-activated protein kinase (AMPK), the master cellular energy sensor. AMPK activation triggers a cascade of metabolic adaptations: enhanced glucose uptake in skeletal muscle, increased fatty acid oxidation, inhibition of lipogenesis, and improved mitochondrial biogenesis. The AMPK activation occurs through MOTS-c's ability to inhibit the folate-methionine cycle, which reduces de novo purine synthesis and alters the cellular AMP:ATP ratio.

Under metabolic stress conditions, MOTS-c undergoes nuclear translocation — a remarkable finding for a mitochondrial-encoded peptide. In the nucleus, MOTS-c interacts with antioxidant response elements (ARE) and electrophile response elements (EpRE) to directly regulate transcription of stress-response and metabolic genes, including those in the NRF2 antioxidant pathway. This nuclear translocation is AMPK-dependent, creating a feedforward loop where metabolic stress activates AMPK, which promotes MOTS-c nuclear entry, which activates protective gene programs. The exercise-responsive nature of MOTS-c — with levels rising during physical activity — suggests it may be a molecular mediator of exercise's metabolic benefits.