Overexpression of CPT1A disrupts the maintenance and regenerative function of muscle stem cells

The skeletal muscle satellite cells (SCs) mediate regeneration of myofibers upon injury. As they switch from maintenance (quiescence) to regeneration, their relative reliance on glucose and fatty acid metabolism alters. To explore the contribution of mitochondrial fatty acid oxidation (FAO) pathway to SCs and myogenesis, we examined the role of carnitine palmitoyltransferase 1A (CPT1A), the rate-limiting enzyme of FAO. CPT1A is highly expressed in quiescent SCs (QSCs) compared with activated and proliferating SCs, and its expression level decreases during myogenic differentiation. Myod1^Cre-driven overexpression (OE) of Cpt1a in embryonic myoblasts (Cpt1a^MTG) reduces muscle weight, grip strength, and contractile force without affecting treadmill endurance of adult mice. Adult Cpt1a^MTG mice have reduced number of SC, impairing muscle regeneration and promoting lipid infiltration. Similarly, Pax7^CreER-driven, tamoxifen-inducible Cpt1a-OE in QSCs of adult muscles (Cpt1a^PTG) leads to depletion of SCs and compromises muscle regeneration. The reduced proliferation of Cpt1a-OE SCs is associated with elevated level of acyl-carnitine, and acyl-carnitine treatment impedes proliferation of wildtype SCs. These findings indicate that aberrant level of CPT1A elevates acyl-carnitine to impair the maintenance, proliferation and regenerative function of SCs.