Postprandial hormone and metabolic responses in simulated shift work

School of Biological Sciences, University of Surrey, Guildford, UK.
Journal of Endocrinology (Impact Factor: 3.59). 11/1996; 151(2):259-67. DOI: 10.1677/joe.0.1510259
Source: PubMed

ABSTRACT This study was designed to investigate postprandial responses to a mixed meal in simulated shift work conditions. Nine normal healthy subjects (six males and three females) were studied on two occasions at the same clock time (1330 h) after consuming test meals, first in their normal environment and secondly after a 9 h phase advance (body clock time 2230 h). Plasma glucose, insulin, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), triacylglycerol (TAG) and non-esterified fatty acids (NEFAs) were determined at intervals for 6 h after each test meal. Postprandial plasma glucose, insulin, GIP and GLP-1 profiles were evaluated by calculating areas under the curve (AUC) for the first 2 h and the last 4 h of the sampling together with total AUC. Significantly higher postprandial glucose responses (total AUC) were observed after the phase shift than before (AUC 0-360 min, 2.01 (1.51-2.19) vs 1.79 (1.56-2.04) mmol/l.min; P < 0.02; mean (range)). No significant difference was observed when the first 2 h of each response was compared, but significantly higher glucose levels were observed in the last 4 h of the study after the phase shift than before (AUC 120-360 min, 1.32 (1.08-1.42) vs 1.16 (1.00-1.28) mmol/l.min; P < 0.05). Similar results were obtained for insulin (AUC 0-360 min, 81.72 (30.75-124.97) vs 58.98 (28.03-92.57) pmol/l.min; P < 0.01; AUC 120-360 min, 40.73 (16.20-65.25) vs 25.71 (14.25-37.33) pmol/l.min; P < 0.02). No differences were observed in postprandial plasma GIP and GLP-1 responses before and after the phase shift. Postprandial circulating lipid levels were affected by phase shifting. Peak plasma TAG levels occurred 5 h postprandially before the phase shift. Postprandial rises in plasma TAG were significantly delayed after the phase shift and TAG levels continued to rise throughout the study. Plasma postprandial NEFA levels fell during the first 3 h both before and after the phase shift. Their rate of return to basal levels was significantly delayed after the phase shift compared with before. This study demonstrates that a simulated phase shift can significantly alter pancreatic B-cell responses and postprandial glucose and lipid metabolism.

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Available from: Linda Morgan, Jul 09, 2014
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    • "The most recognized cause of circadian misalignment is jet lag after crossing multiple time zones, although night-shift work and early school or work times are other situations in which individuals can experience circadian misalignment. In laboratory studies that experimentally imposed severe acute circadian misalignment, healthy participants showed adverse metabolic responses that are risk factors for cardiovascular disease and type 2 diabetes [1] [8] [9]. When experienced chronically like in night-shift work, circadian misalignment increases the risk of a number of diseases , including cancer [13] [14] [15] [16] [17] [18]. "
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    • "Increased adiposity and altered glucose metabolism create a positive feedback loop that results in more profound adiposity (i.e., obesity) and poorer glucose metabolism that can culminate in diabetes or untimely death. Impaired glucose tolerance, which is thought to be a precursor to T ype 2 Diabetes, was observed in shift workers starting a new rotation (Lund et al., 2001) and in subjects who experienced simulated shift work (Hampton et al., 1996). Similarly, in addition to increased serum glucose, Scheer and colleagues observed decreased leptin, increased insulin, decreased sleep efficiency, increased blood pressure, and a change in the phase of the cortisol rhythm in people that were subjected to a seven day circadian disruption protocol meant to resemble shift work (Scheer et al., 2009). "
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    • "Author's personal copy suggest that for every 1 h increase in " social jet lag " (the difference between mid-sleep time on free and work days), the risk of obesity increases threefold (Roenneberg et al. 2012). Even short-term circadian misalignment in healthy participants impairs metabolic responses that are risk factors for cardiovascular disease and type II diabetes mellitus (Hampton et al. 1996; Scheer et al. 2009). The circadian system is capable of shifting to adjust to a new light/dark cycle, such as after jet travel; however, the shift is gradual, not instantaneous. "
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