Consequences of circadian dysregulation on metabolism

Most organisms display endogenously produced rhythms in physiology and behavior of ~24 hours in duration. These rhythms, termed circadian rhythms, are entrained to precisely 24 hours by the daily extrinsic light–dark cycle. Circadian rhythms are driven by a transcriptional–translational feedback loop that is hierarchically expressed throughout the brain and body; the suprachiasmatic nucleus of the hypothalamus is the master circadian oscillator at the top of the hierarchy. Precise timing of the circadian clocks is critical for many homeostatic processes, including energy regulation and metabolism. Many genes involved in metabolism display rhythmic oscillations. Because circadian rhythms are most potently synchronized with the external environment by light, exposure to light at night potentially disrupts circadian regulation. Other potential disruptors of circadian organization include night shift work, social jet lag, restricted sleep, and misaligned feeding. Each of these environmental conditions has been associated with metabolic changes and obesity. The goal of this review is to highlight how disruption of circadian organization, primarily due to night shift work and exposure to light at night, has downstream effects on metabolic function.