Limited Oxidative Stress Favors Resistance to Skeletal Muscle Atrophy in Hibernating Brown Bears (Ursus Arctos)

International audienceOxidative stress, which is believed to promote muscle atrophy, has been reported to occurin a few hibernators. However, hibernating bears exhibit ecient energy savings and muscle proteinsparing, despite long-term physical inactivity and fasting. We hypothesized that the regulation ofthe oxidant/antioxidant balance and oxidative stress could favor skeletal muscle maintenance inhibernating brown bears. We showed that increased expressions of cold-inducible proteins CIRBPand RBM3 could favor muscle mass maintenance and alleviate oxidative stress during hibernation.Downregulation of the subunits of the mitochondrial electron transfer chain complexes I, II, and III,and antioxidant enzymes, possibly due to the reduced mitochondrial content, indicated a possiblereduction of the production of reactive oxygen species in the hibernating muscle. Concomitantly, theupregulation of cytosolic antioxidant systems, under the control of the transcription factor NRF2, andthe maintenance of the GSH/GSSG ratio suggested that bear skeletal muscle is not under a significantoxidative insult during hibernation. Accordingly, lower levels of oxidative damage were recorded inhibernating bear skeletal muscles. These results identify mechanisms by which limited oxidativestress may underlie the resistance to skeletal muscle atrophy in hibernati