bims-ciryme Biomed News
on Circadian rhythms and metabolism
Issue of 2020‒08‒09
three papers selected by
Gabriela Da Silva Xavier
University of Birmingham

  1. Diabetologia. 2020 Aug 06.
      The proliferation in the rate of diagnosis of obesity and type 2 diabetes mellitus continues unabated, with current recommendations for primary lifestyle changes (i.e. modification to dietary patterns) having a limited impact in reducing the incidence of these metabolic diseases. Part of the reason for the failure to alter nutritional practices is that current dietary recommendations may be unrealistic for the majority of adults. Indeed, round-the-clock access to energy-dense, nutrient-poor food makes long-term changes to dietary habits challenging. Hence, there is urgent need for innovations in the delivery of evidence-based diet interventions to rescue some of the deleterious effects on circadian biology induced by our modern-day lifestyle. With the growing appreciation that the duration over which food is consumed during a day has profound effects on numerous physiological and metabolic processes, we discuss dietary protocols that modify the timing of food intake to deliberately alter the feeding-fasting cycle. Such chrono-nutrition functions to optimise metabolism by timing nutrient intake to the acrophases of metabolic rhythms to improve whole-body insulin sensitivity and glycaemic control, and thereby positively impact metabolic health. Graphical abstract.
    Keywords:  Chronic energy restriction; Circadian disruption; Circadian rhythm; Diet; Food; Glycaemia; Intermittent fasting; Metabolic disease; Obesity; Review; Time-restricted eating
  2. FEBS Lett. 2020 Aug 04.
      The circadian system is composed of coupled endogenous oscillators that allow living beings, including humans, to anticipate and adapt to daily changes in their environment. In mammals, circadian clocks form a hierarchically organized network with a "master clock" located in the suprachiasmatic nucleus (SCN) of the hypothalamus, which ensures entrainment of subsidiary oscillators to environmental cycles. Robust rhythmicity of body clocks is indispensable for temporally coordinating organ functions, and the disruption or misalignment of circadian rhythms caused for instance by modern lifestyle is strongly associated with various widespread diseases. This review aims to provide a comprehensive overview of our current knowledge about the molecular architecture and system-level organization of mammalian circadian oscillators. Furthermore, we discuss the regulatory roles of peripheral clocks for cell and organ physiology, and their implication in the temporal coordination of metabolism in human health and disease. Finally, we summarize methods for assessing circadian rhythmicity in humans.
    Keywords:  circadian disruption; circadian misalignment; human circadian system; intercellular coupling; metabolic diseases; peripheral clocks; physiology and metabolism
  3. J Endocrinol. 2020 Jul 01. pii: JOE-20-0124.R1. [Epub ahead of print]
      Endogenous circadian clocks adapt an organism's physiology and behavior to predictable changes in the environment as a consequence of the Earth's rotation around its axis. In mammals, circadian rhythms are the output of a ubiquitous network of cellular timers coordinated by a hypothalamic master pacemaker. Circadian clock function is closely connected to the stress response system which has evolved to ensure survival under less predictable situations of danger. Disruptions in both of these functions are highly prevalent in modern society and have been linked to pathologic alterations in metabolic setpoints, promoting overeating, obesity, and type-2 diabetes. This paper describes the different levels of interaction between the circadian clock and acute and chronic stress responses. It summarizes studies assessing clock-stress crosstalk in the context of metabolic homeostasis and outlines options to use this interaction for diagnostic and therapeutic measures targeting metabolic health and well-being in the highly chronodisruptive environment of modern 24-hour globalized societies.