Limited Oxidative Stress Favors Resistance to Skeletal Muscle Atrophy in Hibernating Brown Bears (Ursus Arctos)
Résumé
Oxidative stress, which is believed to promote muscle atrophy, has been reported to occur
in a few hibernators. However, hibernating bears exhibit ecient energy savings and muscle protein
sparing, despite long-term physical inactivity and fasting. We hypothesized that the regulation of
the oxidant/antioxidant balance and oxidative stress could favor skeletal muscle maintenance in
hibernating brown bears. We showed that increased expressions of cold-inducible proteins CIRBP
and 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 possible
reduction of the production of reactive oxygen species in the hibernating muscle. Concomitantly, the
upregulation of cytosolic antioxidant systems, under the control of the transcription factor NRF2, and
the maintenance of the GSH/GSSG ratio suggested that bear skeletal muscle is not under a significant
oxidative insult during hibernation. Accordingly, lower levels of oxidative damage were recorded in
hibernating bear skeletal muscles. These results identify mechanisms by which limited oxidative
stress may underlie the resistance to skeletal muscle atrophy in hibernatin
Domaines
Sciences de l'environnement
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