bims-ciryme Biomed News
on Circadian rhythms and metabolism
Issue of 2020‒01‒05
two papers selected by
Gabriela Da Silva Xavier
University of Birmingham

  1. J Mol Biol. 2019 Dec 27. pii: S0022-2836(19)30746-6. [Epub ahead of print]
      The mammalian circadian clockwork has evolved as a timing system that allows the daily environmental changes to be anticipated, so that behavior and tissue physiology can be adjusted accordingly. The circadian clock synchronizes the function of all cells within tissues in order to temporally separate preclusive and potentially harmful physiologic processes, and to establish a coherent temporal organismal physiology. Thus, proper functioning of the circadian clockwork is essential for maintaining cellular and tissue homeostasis. Importantly, aging reduces the robustness of the circadian clock, resulting in disturbed sleep-wake cycles, a lowered capacity to synchronize circadian rhythms in peripheral tissues and reprogramming of the circadian clock output at the molecular function levels. These circadian clock-dependent behavioral and molecular changes in turn further accelerate the process of aging. Here we review the current knowledge about how aging affects the circadian clock, how the functional decline of the circadian clock affects aging and how the circadian clock machinery and the molecular processes that underlie aging are intertwined.
    Keywords:  SIRT1; circadian reprogramming; deregulated nutrient sensing; mTOR; mitochondrial dysfunction; stem cell exhaustion; tissue homeostasis
  2. JCI Insight. 2020 Jan 02. pii: 134270. [Epub ahead of print]
      BACKGROUND: The circadian system entrains behavioral and physiological rhythms to environmental cycles and modern lifestyles disrupt this entrainment. We investigated a timed exercise intervention to phase shift the internal circadian rhythm.METHODS: In fifty-two young, sedentary adults, dim light melatonin onset (DLMO) was measured before and after five days of morning (10h after DLMO; n = 26) or evening (20h after DLMO; n = 26) exercise. Phase shifts were calculated as the difference in DLMO before and after exercise.
    RESULTS: Morning exercise induced phase advance shifts (0.62 ± 0.18h) that were significantly greater than phase shifts from evening exercise (-0.02 ± 0.18h; P = 0.01). Chronotype also influenced the effect of timed exercise. For later chronotypes, both morning and evening exercise induced phase advances (0.54 ± 0.29h and 0.46 ±0.25h, respectively). In contrast, earlier chronotypes had phase advances from morning exercise (0.49 ± 0.25h), but phase delays from evening exercise (-0.41 ± 0.29h).
    CONCLUSION: Late chronotypes, who experience the most severe circadian misalignment, may benefit from phase advances induced by exercise in the morning or evening, but evening exercise may exacerbate circadian misalignment in early chronotypes. Thus, personalized exercise timing prescription based on chronotype could alleviate circadian misalignment in young adults.
    FUNDING: National Institutes of Health grants UL1TR001998 and TL1TR001997, the Barnstable Brown Diabetes and Obesity Center, the Pediatric Exercise Physiology Laboratory Endowment, the Arvle and Ellen Turner Thacker Research Fund, and the University of Kentucky.
    Keywords:  Behavior; Clinical Trials