Constant light exposure aggravates POMC-mediated muscle wasting associated with hypothalamic alteration of circadian clock and SIRT1 in endotoxemia rats

Circadian Disruption and Consequences on Innate Immunity and Inflammatory Response

Circadian rhythms control almost all aspects of physiology and behavior, allowing temporal synchrony of these processes between each other, as well as with the external environment. In the immune system, daily rhythms of leukocyte functions can determine the strength of the immune response, thereby regulating the efficiency of defense mechanisms to cope with infections or tissue injury. The natural light/dark cycle is the prominent synchronizing agent perceived by the circadian clock, but this role of light is highly compromised by irregular working schedules and unintentional exposure to artificial light at night (ALAN). The primary concern is disrupted circadian control of important physiological processes, underlying potential links to adverse health effects. Here, we first discuss the immune consequences of genetic circadian disruption induced by mutation or deletion of specific clock genes. Next, we evaluate experimental research into the effects of disruptive light/dark regimes, particularly light-phase shifts, dim ALAN, and constant light on the innate immune mechanisms under steady state and acute inflammation, and in the pathogenesis of common lifestyle diseases. We suggest that a better understanding of the mechanisms by which circadian disruption influences immune status can be of importance in the search for strategies to minimize the negative consequences of chronodisruption on health.

Adipose improves muscular atrophy caused by Sirtuin1 deficiency by promoting mitochondria synthesis

Muscular dysplasia is a common muscle disease, but its pathological mechanism is still unclear. Adipose is originally identified as a highly conservative and widely expressed anti-obesity gene, and our previous study has reported that Adipose is also a positive regulator of myogenesis. Considering the vital role of during muscle development, this study was to demonstrate a potential relationship between Sirtuin1 and Adipose and clarified the mechanism by which Adipose regulated muscle development. Our results showed that the muscle fiber cross-sectional area and myosin heavy chain protein level were significantly reduced in Sirtuin1^+/- mice. Moreover, the longitudinal section of muscle fibers was obviously irregular. Sirtuin1 knockdown significantly reduced the expression levels of Adipose and its upstream transcriptional regulator Kruppel like factor 15 and notably inhibited the AMP-activated protein kinase α-peroxisome proliferator-activated receptor gamma coactivator 1α signaling pathway in skeletal muscle. However, Adipose over-expression activated this signaling pathway and promoted mitochondrial biosynthesis in C2C12 myoblasts. Adipose over-expression also enhanced glucose absorption of C2C12 cells, suggesting the increased needs for cells for metabolic substrates. In C2C12 cells with hydrogen peroxide treatment, Adipose over-expression repressed hydrogen peroxide-elicited apoptosis and mitochondrial loss, while Sirtuin1-specific inhibitor dramatically weakened these roles of Adipose. Taken together, our findings reveal that Adipose rescues the adverse effects of Sirtuin1 deficiency or hydrogen peroxide on muscle development by activating the AMP-activated protein kinase α- peroxisome proliferator-activated receptor gamma coactivator 1α pathway to promote mitochondria synthesis, which provides theoretical basis for developing new therapeutic targets against some muscle diseases.