Metabolic pathway for insulin effects of sleep identified

By Lucy Piper, Senior medwireNews Reporter

Sleep deprivation reduces insulin sensitivity in human fat cells, which could, over time, lead to metabolic disorders such as diabetes, researchers report.

They found an approximate 30% reduction in cellular insulin sensitivity in adipocytes from subcutaneous samples collected from volunteers after 4 nights of experimental sleep restriction.

"Our finding of a robust alteration in intracellular insulin signaling in a peripheral tissue that is pivotal in regulating energy balance and metabolism identifies a molecular mechanism underlying the adverse effect of sleep disturbance on insulin sensitivity," say Matthew Brady (University of Chicago, Illinois, USA) and colleagues.

"From a clinical standpoint, our study provides additional evidence that insufficient sleep may contribute to the development of or exacerbate metabolic disorders."

The team randomly assigned seven healthy adults with a mean age of 23.7 years to 4 nights of 8.5 hours of sleep and 4 nights of 4.5 hours of sleep, during two sleep laboratory studies conducted at least 4 weeks apart. Both studies were carried out under controlled conditions of caloric intake and physical activity.

Adipocytes collected from subcutaneous fat biopsies after normal and restricted sleep were exposed to incremental insulin concentrations and the ability of insulin to increase levels of phosphorylated Akt, a crucial step in the insulin-signaling pathway, was assessed.

As reported in the Annals of Internal Medicine, the insulin sensitivity of adipocytes was 30% lower after restricted than normal sleep.

"Our finding of marked alterations in adipocyte function after experimental sleep restriction challenges the widely held belief that the primary function of sleep is the restoration of central nervous system function and suggests that sleep may play an equally important role in peripheral energy metabolism," the researchers comment.

They also observed a 16% reduction in total body insulin sensitivity after restricted compared with normal sleep.

In a related editorial, Francesco Cappussio and Michelle Miller, from Warwick University in Coventry, commend the researchers.

"The effect size of a 30% reduction in peripheral insulin sensitivity is biologically relevant and, if sustained over longer periods and shared by other tissues, could be of clinical and public health relevance for understanding the development of diabetes and obesity," they write.

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