bims-ciryme Biomed News
on Circadian rhythms and metabolism
Issue of 2024–12–01
two papers selected by
Gabriela Da Silva Xavier, University of Birmingham
  1. Circadian regulation of endoplasmic reticulum calcium response in cultured mouse astrocytes.
  2. The effect of altered sleep timing on glycaemic outcomes: Systematic review of human intervention studies.
  1. Elife. 2024 Nov 27. pii: RP96357. [Epub ahead of print]13
    Circadian regulation of endoplasmic reticulum calcium response in cultured mouse astrocytes.
    Ji Eun Ryu, Kyu-Won Shim, Hyun Woong Roh, Minsung Park, Jae-Hyung Lee, Eun Young Kim.
      The circadian clock, an internal time-keeping system orchestrates 24 hr rhythms in physiology and behavior by regulating rhythmic transcription in cells. Astrocytes, the most abundant glial cells, play crucial roles in CNS functions, but the impact of the circadian clock on astrocyte functions remains largely unexplored. In this study, we identified 412 circadian rhythmic transcripts in cultured mouse cortical astrocytes through RNA sequencing. Gene Ontology analysis indicated that genes involved in Ca2+ homeostasis are under circadian control. Notably, Herpud1 (Herp) exhibited robust circadian rhythmicity at both mRNA and protein levels, a rhythm disrupted in astrocytes lacking the circadian transcription factor, BMAL1. HERP regulated endoplasmic reticulum (ER) Ca2+ release by modulating the degradation of inositol 1,4,5-trisphosphate receptors (ITPRs). ATP-stimulated ER Ca2+ release varied with the circadian phase, being more pronounced at subjective night phase, likely due to the rhythmic expression of ITPR2. Correspondingly, ATP-stimulated cytosolic Ca2+ increases were heightened at the subjective night phase. This rhythmic ER Ca2+ response led to circadian phase-dependent variations in the phosphorylation of Connexin 43 (Ser368) and gap junctional communication. Given the role of gap junction channel (GJC) in propagating Ca2+ signals, we suggest that this circadian regulation of ER Ca2+ responses could affect astrocytic modulation of synaptic activity according to the time of day. Overall, our study enhances the understanding of how the circadian clock influences astrocyte function in the CNS, shedding light on their potential role in daily variations of brain activity and health.
    Keywords:  Ca2+; ER; Herpud1; astrocytes; circadian; endoplasmic reticulum; gap junctions; mouse; neuroscience
    DOI:  https://doi.org/10.7554/eLife.96357
  2. Diabetes Obes Metab. 2024 Nov 28.
    The effect of altered sleep timing on glycaemic outcomes: Systematic review of human intervention studies.
    Romy Slebe, Jane J Splinter, Linda J Schoonmade, Denis P Blondin, David J T Campbell, André C Carpentier, Jean-Pierre Després, Joris Hoeks, Andries Kalsbeek, Parminder Raina, Patrick Schrauwen, Mireille J Serlie, Dirk Jan Stenvers, Chun-Xia Yi, Renée de Mutsert, Joline W J Beulens, Femke Rutters.
       AIMS: Alterations in sleep timing can lead to disturbances in glycaemic control, although the evidence is inconsistent. Therefore, this systematic review summarizes results from human intervention studies of altered sleep timing on glycaemic outcomes.
    MATERIALS AND METHODS: As part of a broader search on the effect of altering timing of sleep, physical activity and dietary intake, Medline and Embase were searched from inception to February 2023, and subsequent reference searches were done. With the help of a machine learning-aided program 'ASReview', we selected any type of intervention study in the general adult population, which acutely delayed sleep by ≥2 h for at least one night, while the total time in bed was the same between early and late sleep. Quality assessment was done using the quality assessment tool for quantitative studies.
    RESULTS: In total, 14 studies (159 adults with normal or increased weight) were identified. Methodological quality was high (n = 4), moderate (n = 7) or low (n = 3). Acute delays of sleep onset showed unfavourable effects in 10 out of 27 measured glycaemic outcomes (one-six studies reported on each outcome) with outcomes mostly measured in the postprandial period, compared to (early) nighttime sleep.
    CONCLUSIONS: Acutely delaying sleep timing might have unfavourable effects on glycaemic outcomes, compared to (early) nighttime sleep. Future research does however need better controlled trials, also measuring and controlling sleep quantity, sleep quality, physical activity and dietary intake, with longer follow-up periods, consistent outcomes and designs and more diverse populations to provide targeted advice regarding the optimal timing for sleep.
    PROTOCOL REGISTRATION: This review is part of a larger search 'The effect of altering timing of physical activity, sleep and energy intake on glycaemia and Type 2 Diabetes risk in humans', of which the protocol was registered in the PROSPERO database on 27 November 2021 under number: CRD42021287828.
    Keywords:  circadian clocks; circadian dysregulation; glucose metabolism; glycemic control; sleep
    DOI:  https://doi.org/10.1111/dom.16104
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