Shobhan Gaddameedhi, Ph.D.
Washington State University
Being awake at night and asleep during the day, such as the pattern that occurs in night-shift workers, may be linked to disruptions in certain metabolites and pathways without affecting the brain’s master clock, according to an NIEHS-funded study.
Using a laboratory-based sleep study, researchers studied differences between night-shift and day-shift sleep patterns of ten men and four women, ages 22 to 34 years. For three days, half the participants had a night-shift sleep pattern and half had a day-shift pattern. Both groups were then kept awake for a full 24 hours, during which they received identical hourly snacks and provided blood samples every three hours.
The research team found only small differences between day-shift and night-shift patterns for the hormones melatonin and cortisol, which are traditional markers of the body’s circadian clock. Of the 135 metabolites measured in blood, 65 of the metabolites had a significant daily rhythm. Of those, 24 showed a 12-hour shift in rhythm for the night-shift pattern after only three days. The metabolites and pathways affected by the night-shift pattern were related to the liver, pancreas, and digestive tract.
According to the authors, these findings suggest that night-shift sleep patterns may lead to differences in some, but not other, biological signals in shift workers’ bodies, which could disrupt metabolism. This may help explain why night-shift sleep patterns have been linked to certain metabolic disorders, such as obesity and diabetes.
Citation: Skene DJ, Skornyakov E, Chowdhury NR, Gajula RP, Middleton B, Satterfield BC, Porter KI, Van Dongen HPA, Gaddameedhi S. 2018. Separation of circadian- and behavior-driven metabolite rhythms in humans provides a window on peripheral oscillators and metabolism. Proc Natl Acad Sci U S A 115(30):7825–7830.