ABSTRACT

Injury to muscle tissue induces the resident, quiescent, skeletal muscle stem cells (MuSCs) to activate - to exit quiescence and enter the cell cycle. Previous work has shown that MuSC activation is associated with significant metabolic changes, however the substrates that MuSCs consume to support activation are poorly understood. Here, we show that MuSCs generate the majority of their energy through mitochondrial respiration, and that oxidative phosphorylation is required for MuSC activation. Furthermore, we have found that while glucose, glutamine, and fatty acids all significantly, and roughly equally, contribute to ATP production in MuSCs during activation, they do not have equal functional role in the dynamics of MuSC activation. Pharmacologic suppression of glycolysis, using 2-deoxy-D-glucose, or glutaminolysis, using BPTES, significantly impairs MuSC cell cycle entry. However, etomoxir-mediated inhibition of mitochondrial fatty acid transport has minimal effect on MuSC cell cycle progression. Our findings suggest that apart from their roles in fueling ATP production by the mitochondria, glucose and glutamine may generate metabolic intermediates needed for MuSC activation.