How do circadian and sleep wake processes influence glucose and insulin levels?
Glucose and insulin levels are influenced by both process-C and SWH. Studies in normal adults have demonstrated a 30% increase in glucose and a 60% increase in insulin levels during nocturnal.
During sleep deprivation, glucose levels and insulin secretion rates increase at the habitual sleep time, although to a much lesser degree, suggesting circadian modulation.
In recovery sleep, however, glucose levels and insulin secretion both markedly increase, suggesting modulation by sleep itself.
In a recent review, evidence was presented suggesting that multiple processes within adipose tissue (e.g., inflammatory pathways, lipogenesis, lipolysis, and even insulin sensitivity, etc.) are controlled by the circadian clock; furthermore, with clock disruption, there is enhanced adiposity, insulin resistance, and increased susceptibility to T2DM development. Finally, compelling evidence was presented highlighting how circadian clocks contribute to islet cell function, having a critical role in the regulation of beta-cell and alpha-cell function and turnover. With regard to therapeutic targeting, as mentioned in question 13, melatonin can be regarded as hormonal output from the central circadian clock. Timed melatonin supplementation in rodents has been shown to reduce adiposity while also decreasing skeletal muscle and hepatic insulin resistance. In addition, islet cells from subjects with T2DM isolated in cell culture showed improved glucose-stimulated insulin secretion and beta cell survival in response to melatonin. The highlighted mechanisms included attenuation of induction of oxidative and endoplasmic reticulum stress.