Overnight wakefulness impairs next-day postprandial glucose in young women independent of sex hormones.

Abstract

Estradiol and progesterone may influence glucose regulation, but it remains unclear whether ovarian hormone levels modulate night shift-induced impairments in glucose metabolism. To investigate the effects of a night shift-like schedule on next-morning fasting and postprandial glucose metabolism in reproductive-aged women. Fifty-two women with an HbA1c <5.7% completed a protocol consisting of one night of sleep and one night of wakefulness in a laboratory environment. After each night, fasting blood samples were collected to measure estradiol, progesterone, insulin, leptin, and adiponectin. Insulin resistance was estimated using HOMA-IR, and the leptin-to-adiponectin ratio (LAR)-a marker of fasting and postprandial insulin sensitivity-was calculated. Morning postprandial glucose responses were assessed using an oral glucose tolerance test (OGTT), and substrate utilization was measured via respiratory quotient (RQ) using indirect calorimetry. Linear mixed-effects models were used to test the effects of condition and the progesterone-to-estradiol (P/E) ratio on all outcomes. Fasting glucose, HOMA-IR, and LAR did not differ between conditions. Post-OGTT blood glucose at 60 minutes (mean estimated difference: 0.58 mmol/L, p = 0.016) and peak glucose (0.42 mmol/L, p = 0.037) were higher following the night shift compared with sleep. The P/E ratio was not significantly associated with fasting or postprandial glucose. Pre-OGTT RQ was lower after the night shift (-0.029, p < 0.001), and adjusting for pre-OGTT RQ attenuated the post-OGTT glucose differences between conditions (p ≥ 0.097). One night of wakefulness-as occurs in night shift work-impaired next-morning glucose tolerance in women, independent of ovarian hormone variation. Accordingly, choosing low-glycemic index foods for the first meal after a night shift may help reduce postprandial glucose excursions.