Article

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.

Download full-text

Full-text

Available from: Linda Morgan, Jul 09, 2014
0 Followers
 · 
107 Views
  • Source
    • "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]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective: Efficient treatments to phase-advance human circadian rhythms are needed to attenuate circadian misalignment and the associated negative health outcomes that accompany early-morning shift work, early school start times, jet lag, and delayed sleep phase disorder. This study compared three morning bright-light exposure patterns from a single light box (to mimic home treatment) in combination with afternoon melatonin. Methods: Fifty adults (27 males) aged 25.9 ± 5.1 years participated. Sleep/dark was advanced 1 h/day for three treatment days. Participants took 0.5 mg of melatonin 5 h before the baseline bedtime on treatment day 1, and an hour earlier each treatment day. They were exposed to one of three bright-light (~5000 lux) patterns upon waking each morning: four 30-min exposures separated by 30 min of room light (2-h group), four 15-min exposures separated by 45 min of room light (1-h group), and one 30-min exposure (0.5-h group). Dim-light melatonin onsets (DLMOs) before and after treatment determined the phase advance. Results: Compared to the 2-h group (phase shift = 2.4 ± 0.8 h), smaller phase-advance shifts were seen in the 1-h (1.7 ± 0.7 h) and 0.5-h (1.8 ± 0.8 h) groups. The 2-h pattern produced the largest phase advance; however, the single 30-min bright-light exposure was as effective as 1 h of bright light spread over 3.25 h, and it produced 75% of the phase shift observed with 2 h of bright light. Conclusions: A 30-min morning bright-light exposure with afternoon melatonin is an efficient treatment to phase-advance human circadian rhythms.
    Sleep Medicine 12/2014; 16(2). DOI:10.1016/j.sleep.2014.12.004 · 3.10 Impact Factor
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    ABSTRACT: This review consolidates research employing human correlational and experimental work across brain and body with experimental animal models to provide a more complete representation of how circadian rhythms influence almost all aspects of life. In doing so, we will cover the morphological and biochemical pathways responsible for rhythm generation as well as interactions between these systems and others (e.g., stress, feeding, reproduction). The effects of circadian disruption on the health of humans, including time of day effects, cognitive sequelae, dementia, Alzheimer's disease, diet, obesity, food preferences, mood disorders, and cancer will also be discussed. Subsequently, experimental support for these largely correlational human studies conducted in non-human animal models will be described.
    Neuroscience & Biobehavioral Reviews 01/2014; 40C. DOI:10.1016/j.neubiorev.2014.01.007 · 10.28 Impact Factor
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Rationale We test methods to advance (shift earlier) circadian rhythms without producing misalignment between rhythms and sleep. We previously tested (1) a gradually advancing sleep/dark schedule plus morning bright light and afternoon/evening melatonin and (2) the same sleep schedule with only morning bright light. Now we report on the same sleep schedule with only afternoon/evening melatonin. Objectives This study aims to examine phase advances, sleepiness, and performance in response to melatonin compared to placebo. Methods Twelve adults (five female individuals) aged 20–45 years (mean ± SD = 28.3 ± 7.3 years) completed this within-subjects placebo-controlled counterbalanced study. The participants slept on fixed 8-h sleep schedules for nine days. Then, sleep/dark was advanced by 1 h/day for three consecutive days of treatment. The participants took 3 mg of melatonin or placebo 11 h before baseline sleep midpoint (the optimal time to produce phase advances) on the first treatment day and 1 h earlier on each subsequent day. We measured the dim light melatonin onset before and after treatment. The participants rated subjective symptoms throughout the study. They completed the Psychomotor Vigilance Task and rated sleepiness from 1 h before pill ingestion until bedtime on each treatment day. Results Melatonin produced significantly larger advances (1.3 ± 0.7 h) compared to placebo (0.7 ± 0.7 h); however, in the hours between melatonin ingestion and bed, melatonin caused sleepiness and performance decrements. Conclusions Adding afternoon/evening melatonin to the gradually advancing sleep schedule increased the phase advance, but given the side effects, like sleepiness, it is better to use morning bright light and perhaps a lower dose of melatonin.
    Psychopharmacology 09/2012; 225(4). DOI:10.1007/s00213-012-2869-8 · 3.99 Impact Factor
Show more