Impaired Insulin Signaling in Human Adipocytes After Experimental Sleep Restriction

Abstract

BACKGROUND: Insufficient sleep increases the risk for insulin resistance, type 2 diabetes, and obesity, suggesting that sleep restriction may impair peripheral metabolic pathways. Yet, a direct link between sleep restriction and alterations in molecular metabolic pathways in any peripheral human tissue has not been shown. OBJECTIVE: To determine whether sleep restriction results in reduced insulin sensitivity in subcutaneous fat, a peripheral tissue that plays a pivotal role in energy metabolism and balance. DESIGN: Randomized, 2-period, 2-condition, crossover clinical study. SETTING: University of Chicago Clinical Resource Center. PARTICIPANTS: Seven healthy adults (1 woman, 6 men) with a mean age of 23.7 years (SD, 3.8) and mean body mass index of 22.8 kg/m(2) (SD, 1.6). INTERVENTION: Four days of 4.5 hours in bed or 8.5 hours in bed under controlled conditions of caloric intake and physical activity. MEASUREMENTS: Adipocytes collected from subcutaneous fat biopsy samples after normal and restricted sleep conditions were exposed to incremental insulin concentrations. The ability of insulin to increase levels of phosphorylated Akt (pAkt), a crucial step in the insulin-signaling pathway, was assessed. Total Akt (tAkt) served as a loading control. The insulin concentration for the half-maximal stimulation of the pAkt-tAkt ratio was used as a measure of cellular insulin sensitivity. Total body insulin sensitivity was assessed using a frequently sampled intravenous glucose tolerance test. RESULTS: The insulin concentration for the half-maximal pAkt-tAkt response was nearly 3-fold higher (mean, 0.71 nM [SD, 0.27] vs. 0.24 nM [SD, 0.24]; P = 0.01; mean difference, 0.47 nM [SD, 0.33]; P = 0.01), and the total area under the receiver-operating characteristic curve of the pAkt-tAkt response was 30% lower (P = 0.01) during sleep restriction than during normal sleep. A reduction in total body insulin sensitivity (P = 0.02) paralleled this impaired cellular insulin sensitivity. LIMITATION: This was a single-center study with a small sample size. CONCLUSION: Sleep restriction results in an insulin-resistant state in human adipocytes. Sleep may be an important regulator of energy metabolism in peripheral tissues. PRIMARY FUNDING SOURCE: National Institutes of Health.