bims-ciryme Biomed News
on Circadian rhythms and metabolism
Issue of 2019‒10‒20
three papers selected by
Gabriela Da Silva Xavier
University of Birmingham

  1. Front Neurosci. 2019 ;13 969
      People with diabetes are more likely to experience sleep disturbance than those without. Sleep disturbance can cause daytime sleepiness in diabetic patients, which may impair their daytime performance or even lead to workplace injuries. Therefore, restoring the normal sleep-wake cycle is critical for diabetic patients who experience daytime sleepiness. Previous data on a diabetic mouse model, the db/db mice, have demonstrated that the total sleep time and sleep fragmentation are increased and the daily rhythm of the sleep-wake cycle is attenuated. Accumulating evidence has shown that active time-restricted feeding (ATRF), in which the timing of food availability is restricted to the active-phase, is beneficial to metabolic health. However, it is unknown whether ATRF restores the normal sleep-wake cycle in diabetes. To test that, we used a non-invasive piezoelectric system to monitor the sleep-wake profile in the db/db mice with ad libitum feeding (ALF) as a baseline and then followed with ATRF. The results showed that at baseline, db/db mice exhibited abnormal sleep-wake patterns: the sleep time percent during the light-phase was decreased, while during the dark-phase it was increased with unusual cycling compared to control mice. In addition, the sleep bout length during both the light-phase and the full 24-h period was shortened in db/db mice. Analysis of the sleep-wake circadian rhythm showed that ATRF effectively restored the circadian but suppressed the ultradian oscillations of the sleep-wake cycle in the db/db mice. In conclusion, ATRF may serve as a novel strategy for treating diabetes-induced irregularity of the sleep-wake cycle.
    Keywords:  active time-restricted feeding; circadian rhythm; db/db mice; diabetes; sleep
  2. Am J Physiol Endocrinol Metab. 2019 Oct 15.
      The molecular circadian clock plays a role in metabolic homeostasis. We tested the hypothesis obesity and systemic factors associated with insulin resistance affect skeletal muscle clock gene expression. We determined clock gene expression in skeletal muscle of obese women (n=5) and men (n=18) before and 6 months after Roux-en-Y gastric bypass (RYGB) surgery and normal weight controls (women n=6, men n=8). Skeletal muscle clock gene expression was affected by obesity and weight loss. CRY1 mRNA (P=0.05) was increased and DBP mRNA (P<0.05) was decreased in obese versus normal weight women and restored to control levels after RYGB-induced weight loss. CLOCK, CRY1, CRY2 and DBP mRNA (P<0.05) was decreased in obese men as compared to normal weight men. Expression of all other clock genes was unaltered by obesity or weight loss in both cohorts. We correlated clock gene expression with clinical characteristics of the participants. Among the genes studied, DBP and PER3 expression was inversely correlated with plasma lipids in both cohorts. Circadian time-course studies revealed that core clock genes oscillate over time (P<0.05), with BMAL1, CIART, CRY2, DBP, PER1 and PER3 expression profiles altered by palmitate treatment. In conclusion, skeletal muscle clock gene expression and function is altered by obesity, coincident with changes in plasma lipid levels. Palmitate exposure disrupts clock gene expression in myotubes, indicating dyslipidemia directly alters the circadian program. Strategies to reduce lipid overload and prevent elevations in NEFA and cholesterol levels may sustain circadian clock signals in skeletal muscle.
    Keywords:  Circadian Rhythm; Clock Genes; Free Fatty Acids; Obesity; Skeletal Muscle
  3. Nutrients. 2019 Oct 13. pii: E2437. [Epub ahead of print]11(10):
      Emerging studies indicate that meal timing is linked to cardiometabolic risks by deterioration of circadian rhythms, however limited evidence is available in humans. This large-scale cross-sectional study explored the associations of meal timing and frequency with obesity and metabolic syndrome among Korean adults. Meal timing was defined as nightly fasting duration and morning, evening, and night eating, and meal frequency was estimated as the number of daily eating episodes using a single-day 24-hour dietary recall method. Meal frequency was inversely associated with prevalence of abdominal obesity, elevated blood pressure, and elevated triglycerides in men only. Independent of the nightly fasting duration and eating episodes, morning eating was associated with a lower prevalence of metabolic syndrome (odds ratio (OR), 0.73; 95% confidence interval (CI), 0.57-0.93 for men and OR, 0.69; 95% CI, 0.54-0.89 for women) than no morning eating, whereas night eating was associated with a 48% higher prevalence of metabolic syndrome (OR, 1.48; 95% CI, 1.15-1.90) than no night eating in men only. Longer fasting duration and less sleep were associated with obesity and metabolic syndrome. These findings suggest that overall eating patterns, including energy distribution across the day, eating frequency, and sleep duration, rather than fasting duration alone, are related to cardiometabolic risks in free-living Korean adults.
    Keywords:  Korean; meal frequency; metabolic syndrome; morning eating; night eating; nightly fasting duration; obesity