bims-ciryme Biomed News
on Circadian rhythms and metabolism
Issue of 2020‒09‒27
three papers selected by
Gabriela Da Silva Xavier
University of Birmingham

  1. Endocrinology. 2020 Sep 21. pii: bqaa167. [Epub ahead of print]
      Circadian rhythms are 24-hour biological rhythms within organisms that have developed over evolutionary time due to pre-defined environmental changes, mainly the light-dark cycle. Interestingly, metabolic tissues, which are largely responsible for establishing diurnal metabolic homeostasis, have been found to express cell-autonomous clocks that are entrained by food intake. Disruption of the circadian system, as seen in individuals who conduct shift-work, confers significant risk for the development of metabolic diseases such as type 2 diabetes and obesity. The gastrointestinal (GI) tract is the first point of contact for ingested nutrients and is, thus, an essential organ system for metabolic control. This review will focus on the circadian function of the GI tract with a particular emphasis on its role in metabolism through regulation of gut hormone release. Firstly, the circadian molecular clock as well as the organization of the mammalian circadian system is introduced. Next, a brief overview of the structure of the gut as well as the circadian regulation of key functions important in establishing metabolic homeostasis is discussed. Particularly, the focus of the review is centered around secretion of gut hormones; however, other functions of the gut such as barrier integrity and intestinal immunity, as well as digestion and absorption, all of which have relevance to metabolic control will be considered. Finally, we provide insight into the effects of circadian disruption on GI function and discuss chronotherapeutic intervention strategies for mitigating associated metabolic dysfunction.
  2. Diab Vasc Dis Res. 2020 May-Jun;17(5):17(5): 1479164120950616
      OBJECTIVES: Night shift workers are at cardiometabolic risk due to circadian misalignment. We investigated whether infrequent exercise before each night shift that intentionally would not improve physical performance improves glucose tolerance and 24-h blood pressure profiles and synchronizes circadian rhythms of melatonin and cortisol in rotating night shift workers.METHODS: A total of 24 rotating night shift workers (mean age, 35.7 ± 11.8 years) were randomized to exercise or no intervention. Workers in the exercise group performed 15.2 ± 4.5 exercise sessions within 2 h before each night shift. Before and after 12 weeks of exercise intervention and 12 weeks after the intervention, spiroergometry, oral glucose tolerance testing and 24-h blood pressure profiles were performed. Plasma melatonin and cortisol levels were measured in 3-hourly intervals during one 24-h period on each study day.
    RESULTS: Exercise did not significantly change serum glucose nor insulin levels during oral glucose tolerance testing. Timed physical exercise had no effect on physical performance, nor did it change the circadian rhythms of melatonin and cortisol or influence 24-h blood pressure profiles.
    CONCLUSION: Physical exercise before each night shift at a low intensity level that does not improve physical performance does not affect circadian timing, glucose tolerance or 24-h blood pressure profiles in rotating night shift workers.
    Keywords:  Night shift workers; diabetes mellitus; glucose tolerance; insulin; prospective study; vascular stiffness
  3. Life Sci. 2020 Sep 18. pii: S0024-3205(20)31206-6. [Epub ahead of print]261 118453
      Aging is associated with gradual decline in numerous physiological processes, including a reduction in metabolic functions and immunological system. The circadian rhythm plays a vital role in health, and prolonged clock disruptions are associated with chronic diseases. The relationships between clock genes, aging, and immunosenescence are not well understood. Inflammation is an immune response triggered in living organisms in response to the danger associated with pathogens and injury. The term 'inflammaging' has been used to describe the chronic low-grade-inflammation that develops with advancing age and predicts susceptibility to age-related pathologies. Equilibrium between pro-and anti-inflammatory cytokines is needed for healthy aging and longevity. Sedentary and poor nutrition style life indices a disruption in circadian rhythm promoting an increase in pro-inflammatory factors or leads for chronic low-grade inflammation. Moreover, signals mediated by pro-inflammatory cytokines, such as tumor necrosis factor-alpha and interleukin-6, might accentuate of the muscle loss during aging. Circadian clock is important to maintain the physiological functions, as maintenance of immune system. A strategy for imposes rhythmicity in the physiological systems may be adopted of exercise training routine. The lifelong regular practice of physical exercise decelerates the processes of aging, providing better quality and prolongation of life. Thus, in this review, we will focus on how aging affects circadian rhythms and its relationship to inflammatory processes (inflammaging), as well as the role of physical exercise as a regulator of the circadian rhythm, promoting aging with rhythmicity.
    Keywords:  Aging; Circadian rhythms; Clock genes; Immunosenescence; Inflammaging