MOTS-C is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis. Mitochondria are known to be functional organelles, but their role as a signaling unit is increasingly being appreciated. The identification of a short open reading frame (SORF) in the mitochondrial DNA (mtDNA) that encodes a signaling peptide, humanin, suggests the possible existence of additional SORFS in the …