clock-circadian-nightshift

Daytime Eating May Limit Glucose Intolerance in Night Shift Workers

MedicalResearch.com Interview with:
Sarah L. Chellappa, MD PhD

Medical Chronobiology Program
Division of Sleep and Circadian Disorders
Departments of Medicine and Neurology
Brigham and Women’s Hospital
Division of Sleep Medicine, Harvard Medical School
Boston, MA
Department of Nuclear Medicine
Faculty of Medicine and University Hospital Cologne
University of Cologne, Cologne, Germany.

Frank A.J.L. Scheer, M.Sc., Ph.D. Professor of Medicine.
Medical Chronobiology Program
Division of Sleep and Circadian Disorders
Departments of Medicine and Neurology
Brigham and Women’s Hospital
Division of Sleep Medicine, Harvard Medical School
Boston, MA

MedicalResearch.com: What is the background for this study? Would you explain the difference between the central circadian ‘clock’ and endogenous circadian glucose rhythms? 

Response: Night work increases diabetes risk. This increased risk is not fully explained by differences in lifestyle, family history, and/or socioeconomic status, thus other mechanisms are likely involved. Laboratory studies in humans have shown glucose intolerance in both non-shift workers and shift workers exposed to simulated night work. Animal experimental data suggests that this may be in part due to a misalignment between central and peripheral rhythms. Central circadian rhythms (e.g., body temperature) are primarily modulated by the central circadian “clock”, which is located in the brain’s suprachiasmatic nucleus and is responsible for synchronizing our physiology and behavior with the 24-hour cycle. Peripheral rhythms, including endogenous circadian glucose rhythms, are likely modulated by peripheral “clocks” across the body that play an integral role in modulating the circadian expression of physiology, including metabolic functions.

These central and peripheral clocks share a common molecular mechanism underlying their circadian rhythm generating capacity, including transcription-translation feedback loops of circadian “clock” genes. 

MedicalResearch.com: What are the main findings? What should readers take away from your report?

Response: In our study, participants exposed to simulated night shift work and who ate during the nighttime (as is common in night workers) showed impaired glucose tolerance. In contrast, such adverse effects were prevented in those who ate only during the daytime even though they were still engaged in simulated night work, and thus were awake at night and slept during the day. This impairment in glucose tolerance was likely caused—at least in part—by impaired pancreatic beta-cell function. Indeed, also this impaired pancreatic beta-cell function was prevented by eating only during the daytime.

Beta cells produce insulin, a hormone that escorts glucose into body tissues. Furthermore, nighttime eating caused a misalignment between the central circadian “clock,” estimated from the endogenous circadian rhythm in core body temperature, and the endogenous circadian glucose rhythms. On the other hand, these circadian rhythms remained normally aligned when participants ate meals only during the daytime despite their mistimed sleep. Taken together, our study’s take-home message is that daytime eating, despite mistimed sleep, maintains internal circadian alignment and prevents glucose intolerance.

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: Our study aimed at answering fundamental research questions; hence, we used a stringently controlled 14-day laboratory protocol. Because of that, it is challenging to make a direct translation of the daytime meal intervention used in our study to meal schedules to real-life shift workers.

Future research using practical interventions to implement daytime eating in night workers, without disrupting their sleep and daily activities, are needed. Until such approaches are implemented, it would be helpful in night workers reconsidered the amount of calories, and especially carbohydrates, consumed in the nighttime.

Citation:

Chellappa, S. L., et al. (2021) Daytime eating prevents internal circadian misalignment and glucose intolerance in night work. Science Advancesdoi.org/10.1126/sciadv.abg9910.

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Dec 6, 2021 @ 10:23 pm

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