Different fuel regulation in two types of myofiber results in different antioxidant strategies in Daurian ground squirrels (Spermophilus dauricus) during hibernation

Abstract

We previouslyshowed that different skeletalmuscles inDaurian ground squirrels (Spermophilus dauricus) possess different antioxidant strategies during hibernation; however, the reason for these varied strategies remains unclear. To clarify this issue, we studied REDD1, FOXO4, PGC-1α, FOXO1 and atrogin-1 proteins to determine the potential cause of the different antioxidant strategies in Daurian ground squirrels during hibernation, and to clarify whether different strategies affect atrophy-related signals. Results showed that the soleus (SOL) muscle experienced intracellular hypoxia during interbout arousal, but no oxidative stress. This may be due to increased PGC-1α expression enhancing antioxidant capacity in the SOL under hypoxic conditions. Extensor digitorum longus (EDL) muscle showed no change in oxidative stress, hypoxia or antioxidant capacity during hibernation. The FOXO1 and PGC-1α results strongly suggested differentially regulated fuel metabolism in the SOL and EDL muscles during hibernation, i.e. enhanced lipid oxidation and maintained anaerobic glycolysis, respectively. Atrogin-1 expression did not increase during hibernation in either the SOL or EDL, indicating that protein synthesis was not inhibited by atrogin-1. Thus, our results suggest that different fuel regulation may be one mechanism related to antioxidant defense strategy formation in different kinds of skeletalmuscle fibers of Daurian ground squirrels during hibernation.