Working atypical schedules leads to temporal misalignments between a worker's rest‐activity cycle and their endogenous circadian system. Several studies have reported disturbed centrally controlled rhythms, but little is known on shift workers' peripheral clocks. Here, we assessed central clock markers, urinary 6‐sulfatoxymelatonin and salivary cortisol, and clock gene expression in 2 peripheral clocks, oral mucosa cells and peripheral blood mononuclear cells (PBMCs), in 11 police officers. Before working 7 consecutive nights, officers' centrally controlled rhythms were aligned to a day‐oriented schedule. These rhythms were partially realigned to the shifted schedule and dampened after a week working nights. For peripheral clocks at baseline, Period (PER)1–3 and nuclear receptor subfamily 1, group D, member 1 (REV‐ERBα) in oral mucosa cells had a significant mRNA peak in the afternoon, whereas in PBMCs, higher PER1–3 expression was observed at 10:00 compared with 19:30. After a week working nights, PER1–3 and REV‐ERBα expression in oral mucosa cells lost rhythmicity, and in PBMCs, the morning/evening difference observed at baseline was lost. To our knowledge, this is the first study to demonstrate the disruption of several peripheral clocks in real shift workers. Molecular circadian disturbances are believed to have important clinical implications for the occurrence of shift work–associated medical disorders.—Koshy, A., Cuesta, M., Boudreau, P., Cermakian, N., Boivin, D. B. Disruption of central and peripheral circadian clocks in police officers working at night. FASEB J. 33, 6789–6800 (2019). http://www.fasebj.org
Shift workers face an increased risk of metabolic health problems, but the direct metabolic response to working nights is not fully understood. The aim of this study was to investigate the effect of night shifts on the 24-h urinary metabolome of shift workers. Eleven police officers working rotating shifts completed two 24-h laboratory visits that took place before and after they worked 7 consecutive nights. Sleep and meals were scheduled on a day schedule in the first visit and then on a night schedule (i.e., sleep and meals shifted by approximately 12 h) in the second visit. Targeted metabolomic analysis was performed on urine samples collected throughout these laboratory visits. Differential rhythmicity analysis was used to compare 24-h rhythms in urinary metabolites in both conditions. Our results show that on the day schedule, 24-h rhythms are present in the urinary levels of the majority of metabolites, but that this is significantly reduced on the night schedule, partly due to loss of organic acid rhythmicity. Furthermore, misalignment of 24-h metabolite rhythms with the shifted behavioral cycles in the night schedule was observed in more than half of the metabolites that were rhythmic in both conditions (all acylcarnitines). These results show that working nights alters the daily rhythms of the urinary metabolome in rotating shift workers, with the most notable impact observed for acylcarnitines and organic acids, 2 metabolite classes involved in mitochondrial function. Further research is warranted to study how these changes relate to the increased metabolic risks associated with shift work.
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