Wild‐Derived House Mice ( <i>Mus musculus</i> ) Are Able to Cope With a Constant Light Environment

Exposure to altered nighttime lighting conditions has become common in today's modern world. Light at night disrupts circadian processes that govern feeding patterns, sleep/wake cycles, and metabolic homoeostasis, increasing the risk of developing pathologies associated with cardiometabolic disease. Yet, the underlying mechanism(s) responsible for mediating the resulting physiological outcomes are not clear. Mitochondrial function may provide valuable insight into the physiological costs associated with light at night, given that mitochondria contribute to variation in metabolic performance that underpin human diseases. In this study, 36 male and female wild-derived house mice (Mus musculus) were exposed to continuous light, darkness, or a control light cycle for 6 weeks. We examined animals' bioenergetic capacity at the whole-organism and subcellular level while also measuring changes in body condition and oxidative damage. We found that 6 weeks of constant light and darkness resulted in negligible changes in all our variables of interest. We did not detect strong mitochondrial responses in the liver or skeletal muscle of either sex exposed to constant light or darkness. Furthermore, we did not detect any difference in mitochondrial volume or lipid peroxidation in the liver between treatment groups. Lastly, there was no difference in body condition between treatment groups. Our data indicate that wild-derived mice are able to circumvent challenges of an altered light environment and escape physiological consequences.