Circadian Aspects of Skeletal Muscle Biology

Abstract

Metabolic flexibility is critical to survival for all species. Mammalian metabolism undergoes numerous predictable daily fluctuations, alternating between preferential utilization of carbohydrates and lipids. These variations are partly driven by the circadian clock, an evolutionarily conserved time-keeping molecular mechanism that is present in virtually all cells of the body. In this chapter, we first provide an overview of the mammalian circadian clock and its influence on the skeletal muscle transcriptome. Next, we present key studies demonstrating the involvement of the circadian clock in muscle growth and regeneration, highlighting various transcription factors and pathways directly impacted by clock proteins. We also discuss the relevance of the muscle-intrinsic clock to the regulation of energy homeostasis, outlining the diverse and multifaceted ways through which glucose, lipid, and mitochondrial metabolism are regulated on a daily basis within muscle cells. We conclude with a discussion of the relationships between timed exercise, food, and circadian aspects of muscle biology, with some directions for future studies.