Physiological rhythms and metabolic regulation: Shining light on skeletal muscle.

Metabolic regulation is essential for maintaining homeostasis in response to fluctuating dietary nutrient availability. In this review, we explore how metabolic health can be affected by the temporal alignment between daily behavioural patterns (e.g., eating, physical activity and sleep) and recurring cycles in underlying physiology (e.g., 'circadian' rhythms). Misalignment within and/or between these patterns and cycles can lead to metabolic dysregulation, increasing the risk of chronic disease states such as obesity, type 2 diabetes and cardiovascular disease. Conversely, metabolic health can be improved by strategically aligning certain behavioural patterns with endogenous rhythms in physiology. Dietary interventions based upon this reasoning are referred to as chrono-nutrition strategies. Skeletal muscle is an important tissue in relation to both whole-body metabolism and behaviour and plays a central role in how physiological rhythms respond to the timing of nutrient delivery/availability. Few studies have examined rhythms in metabolism within human skeletal muscle, providing opportunities to advance current understanding of how nutrient timing affects muscle metabolism.