HealthDay News — The endogenous circadian system, behavioral cycle, and circadian misalignment have distinct effects on insulin sensitivity and β-cell function, according to a study published online June 4 in Diabetes, Obesity and Metabolism.

Noting that shift workers, who experience circadian misalignment, have an increased risk of type 2 diabetes, Jingyi Qian, PhD, from Brigham and Women’s Hospital in Boston, and colleagues examined the separate and relative impacts of the circadian system, behavioral/environmental cycles, and their interaction (circadian misalignment) on insulin sensitivity and β-cell function. The major determinants of glucose control were quantitatively assessed in 14 healthy adults using a randomized, crossover design with 2 eight-day laboratory protocols that involved 3 baseline inpatient days with habitual sleep/wake cycles followed by 4 inpatient days with the same nocturnal bedtime or with 12-hour inverted behavioral/environmental cycles.  

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The researchers found that circadian phase and circadian misalignment impact glucose tolerance through different mechanisms. The circadian system mainly decreases both dynamic and static β-cell responsivity to reduce glucose tolerance in the biological evening versus the biological morning. In contrast, circadian misalignment did not affect β-cell function but reduced glucose tolerance mainly by lowering insulin sensitivity.

“The results show separate effects of the endogenous circadian system, the behavioral cycle, and circadian misalignment on insulin sensitivity and β-cell responsivity with relevance for daily glucose regulation in diurnally active people as well as night-shift workers,” the authors write.

Two authors disclosed financial ties to the pharmaceutical and nutrition industries.

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