Differential Recovery Speed of Activity and Metabolic Rhythms in Rats After an Experimental Protocol of Shift-Work

Abstract

The circadian system drives the temporal organization of body physiology in relation to the changing daily environment. Shift-work (SW) disrupts this temporal order and is associated with the loss of homeostasis and metabolic syndrome. In a rodent model of SW based on forced activity in the rest phase for 4 weeks, we describe the occurrence of circadian desynchrony, as well as metabolic and liver dysfunction. To provide better evidence for the impact of altered timing of activity, this study explored how long it takes to recover metabolic rhythms and behavior. Rats were submitted to experimental SW for 4 weeks and then were left to recover for one week. Daily locomotor activity, food intake patterns, serum glucose and triglycerides, and the expression levels of hepatic Pparα, Srebp-1c, Pepck, Bmal1 and Per2 were assessed during the recovery period and were compared with expected data according to a control condition. SW triggered the circadian desynchronization of all of the analyzed parameters. A difference in the time required for realignment was observed among parameters. Locomotor activity achieved the expected phase on day 2, whereas the nocturnal feeding pattern was restored on the sixth recovery day. Daily rhythms of plasma glucose and triglycerides and of Pparα, Pepck and Bmal1 expression in the liver resynchronized on the seventh day, whereas Srebp-1c and Per2 persisted arrhythmic for the entire recovery week. SW does not equally affect behavior and metabolic rhythms, leading to internal desynchrony during the recovery phase.

Shift work-like patterns effect on female and male mouse behavior

“…For a better representation of the population, we have assessed the effect shift-work-like pattern on behaviors of both female and male mice. We mostly found no behavioural changes in mice that underwent shift-work paradigm, confirming a recovery effect as previously seen in male rats( Saderi et al, 2019 ). However, we have shown that only the alternated shift reduces voluntary movement activity of both male and female mice, and only the forward shift reduces light aversion of male mice.…”

“…We did not assess metabolism factors in these mice, but further study would be necessary to investigate whether the reduction of wheel running activity found in our alternated shifted mice is associated with metabolism dysfunctions and obesity( Karlsson et al, 2001 ). However, Saderi et al (2019) has previously shown locomotor activity, and behavioral and molecular metabolic-associated factors to recover at respectively day 2, day 6 and day 7 after a protocol of shift-work in male rats( Saderi et al, 2019 ), therefore we would not expect substantial changes in metabolism factors in our experiments after 2 weeks of re-entrainment from shift-work-like patterns.…”

Melatonin alleviates circadian system disruption induced by chronic shifts of the light‐dark cycle in Octodon degus

“…This shifting paradigm combines different shift work lighting schedules (Morning, Afternoon and Night) during the 5 working days, and a fixed Morning schedule during weekends (which is generally more frequently adopted by humans in order to increase compatibility of social and familial life). It must be stressed that here we did not engage the animal into forced work, as described elsewhere, but merely manipulating their LD cycles.…”

Sleep, circadian rhythms, and type 2 diabetes mellitus

“…For example, rats whose wheel‐running activity was restricted to the sleep period showed, even after 4 weeks of recovery, only some clock genes in the liver had returned to normal. 65 While this study did not probe gene expression in other peripheral sites, future studies may confirm the desynchrony.…”