Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans

• DOI: 10.1073/pnas.1418955112
• Publication Date: 2015-04-14T02:41:48Z
• Authors: Christopher J. Mo...; Jessica N. Yang; Joanna I. Garcia; Samantha Myers; Isadora Bozzi; Wei Wang; Orfeu M. Buxton; Steven A. Shea; Frank A. J. L. Sc...
• Keywords: Adult; Blood Glucose; Male; 0303 health sciences; Glucose Tolerance Test; Middle Aged; Postprandial Period; Circadian Rhythm; 03 medical and health sciences; Insulin-Secreting Cells; Diabetes Mellitus; Humans; Female; Sleep

Glucose tolerance is lower in the evening and at night than morning. However, relative contribution of circadian system vs. behavioral cycle (including sleep/wake fasting/feeding cycles) unclear. Furthermore, although shift work a diabetes risk factor, separate impact on glucose cycle, phase, disruption (i.e., misalignment between central pacemaker cycle) has not been systematically studied. Here we show--by using two 8-d laboratory protocols--in healthy adults that have distinct influences tolerance, both from cycle. First, postprandial was 17% higher tolerance) biological (8:00 PM) morning AM; i.e., phase effect), independent effect. Second, itself (12-h inversion) increased by 6%. Third, these variations appeared to be explained, least part, different mechanisms: during decreased pancreatic β-cell function (27% early-phase insulin) presumably insulin sensitivity (elevated despite 14% late-phase without change insulin. We explored possible contributing factors, including changes polysomnographic sleep 24-h hormonal profiles. demonstrate importantly contributes reduced observed compared with Separately, reduces providing mechanism help explain workers.