Shift in Food Intake and Changes in Metabolic Regulation and Gene Expression during Simulated Night-Shift Work: A Rat Model

Abstract

Night-shift work is linked to a shift in food intake toward the normal sleeping period, and to metabolic disturbance. We applied a rat model of night-shift work to assess the immediate effects of such a shift in food intake on metabolism. Male Wistar rats were subjected to 8 h of forced activity during their rest (ZT2-10) or active (ZT14-22) phase. Food intake, body weight, and body temperature were monitored across four work days and eight recovery days. Food intake gradually shifted toward rest-work hours, stabilizing on work day three. A subgroup of animals was euthanized after the third work session for analysis of metabolic gene expression in the liver by real-time polymerase chain reaction (PCR). Results show that work in the rest phase shifted food intake to rest-work hours. Moreover, liver genes related to energy storage and insulin metabolism were upregulated, and genes related to energy breakdown were downregulated compared to non-working time-matched controls. Both working groups lost weight during the protocol and regained weight during recovery, but animals that worked in the rest phase did not fully recover, even after eight days of recovery. In conclusion, three to four days of work in the rest phase is sufficient to induce disruption of several metabolic parameters, which requires more than eight days for full recovery.

No Escaping the Rat Race: Simulated Night Shift Work Alters the Time-of-Day Variation in BMAL1 Translational Activity in the Prefrontal Cortex

“…We have recently established a rat model of shift work, where rats are exposed to enforced ambulation in slowly rotating wheels for 8 h/day, either in their rest phase (“rest work”; to simulate night shift work) or in their active phase (“active work”; to simulate day shift work; Marti et al, 2016 ; Grønli et al, 2017 ). Using this model, we observed a progressive intrusion of spontaneous cortical slow waves and micro-sleeps during rest work across four consecutive days, which was not observed during active work (Grønli et al, 2017 ).…”

Genetic polymorphisms associated with circadian rhythm dysregulation provide new perspectives on bipolar disorder

“…The CR molecular clock may be modified by environmental changes and by our modern lifestyle, resulting in physiological changes and the risk of developing pathologies. Changes in the sleep‐wake cycle, such as those required by shift work, are associated with an increased risk of the development of conditions such as metabolic syndrome and depression . In addition to environmental factors related to sleep, many polymorphisms have been detected in the circadian genes, many of which have been associated with the risk of developing diseases.…”

Shift-work: is time of eating determining metabolic health? Evidence from animal models

“…Interestingly, only two groups have explored the metabolic outcome of shifted forced activity using a mild strategy to enforce activity. Both groups report shifted feeding patterns towards the rest phase and a resulting disrupted metabolism (59,61,62) . The study by Marti et al (59) imposed this protocol for only 4 d and could already observe in the liver a disturbed pattern of genes encoding insulin sensitivity and lipid metabolism.…”

“…Body weight was decreased (five out of eight studies) (56)(57)(58)(59)(60) , in two studies body weight was mildly (7 %) increased (61,62) and one study did not assess it (63) .…”