Subchronic sleep restriction causes tissue-specific insulin resistance

Abstract

Context: Short sleep duration is associated with an increased risk of type 2 diabetes. Subchronic sleep restriction (SR) causes insulin resistance, but the mechanisms and roles of specific tissues are unclear.

Objective: The purpose of this article was to determine whether subchronic SR altered (1) hepatic insulin sensitivity, (2) peripheral insulin sensitivity, and (3) substrate utilization.

Design: This was a randomized crossover study in which 14 subjects underwent 2 admissions separated by a washout period. Each admission had 2 acclimatization nights followed by 5 nights of either SR (4 hours time in bed) or normal sleep (8 hours time in bed). MAIN OUTCOME MEASURE/METHODS: Insulin sensitivity (measured by hyperinsulinemic-euglycemic clamp) and hepatic insulin sensitivity (measured by stable isotope techniques) were measured. In addition, we assayed stress hormone (24-hour urine free cortisol, metanephrine, and normetanephrine), nonesterified fatty acid (NEFA), and β-hydroxybutyrate (β-OH butyrate) levels. Resting energy expenditure (REE) and respiratory quotient (RQ) were measured by indirect calorimetry.

Results: Compared to normal sleep, whole-body insulin sensitivity decreased by 25% (P = .008) with SR and peripheral insulin sensitivity decreased by 29% (P = .003). Whereas hepatic insulin sensitivity (endogenous glucose production) did not change significantly, percent gluconeogenesis increased (P = .03). Stress hormones increased modestly (cortisol by 21%, P = .04; metanephrine by 8%, P = .014; normetanephrine by 18%, P = .002). Fasting NEFA and β-OH butyrate levels increased substantially (62% and 55%, respectively). REE did not change (P = 0.98), but RQ decreased (0.81 ± .02 vs 0.75 ± 0.02, P = .045).

Conclusion: Subchronic SR causes unique metabolic disturbances characterized by peripheral, but not hepatic, insulin resistance; this was associated with a robust increase in fasting NEFA levels (indicative of increased lipolysis), decreased RQ, and increased β-OH butyrate levels (indicative of whole-body and hepatic fat oxidation, respectively). We postulate that elevated NEFA levels are partially responsible for the decrease in peripheral sensitivity and modulation of hepatic metabolism (ie, increase in gluconeogenesis without increase in endogenous glucose production). Elevated cortisol and metanephrine levels may contribute to insulin resistance by increasing lipolysis and NEFA levels.

Figure 1.

Sleep duration and architecture during normal sleep and sleep restriction. Total sleep time (TST) and sleep stages (N1, N2, N3, and REM), as determined by polysomnography, on the last night of the sleep condition are shown. Mean ± SEM TST was lower during the sleep-restricted condition than during the normal sleep condition, as were minutes of N1 stage sleep, N2 stage sleep, and REM sleep. Minutes of N3 stage sleep were not significantly different between the 2 study conditions.

Figure 2.

Effects of sleep restriction on whole-body and peripheral insulin sensitivity. Whole-body insulin sensitivity (ie, insulin-mediated glucose uptake [M/I]) decreased by an average of 25% (P = .008) with sleep restriction (SR) compared with that for normal sleep (NS). A, Mean ± SEM values. B, Subject level data (color coded by sex) as a percentage. C and D, Peripheral insulin sensitivity (ie, EGP-corrected M/I), determined in 11 subjects, was 29% lower with sleep restriction (P = .003).

Figure 3.

Changes in hormones, NEFAs and β-OH butyrate with sleep restriction. Mean ± SEM levels of 24-hour urine free cortisol were higher with sleep restriction (SR) that with normal sleep (NS), as were urine metanephrine and normetanephrine, serum NEFA, and β-hydroxybutyrate levels. P values were calculated by the Wilcoxon signed rank test.