Metabolic adaptation mechanisms of glycogen reduction and lipid accumulation in testicular protection in Daurian ground squirrels during hibernation

Abstract

The role of glycogen and lipid metabolism in the testes of Daurian ground squirrels (Spermophilus dauricus) during different stages of the hibernation cycle and their influence on reproductive function remain poorly understood. This study examined testicular morphology across hibernation stages and investigated potential molecular mechanisms. Results showed that: (1) Spermatocyte density was reduced in the torpor group compared to the pre-hibernation (PRE) group, suggesting a suppression of spermatogenesis during torpor. In the post-hibernation (POST) group, reduced spermatocyte density was speculated to correspond to the initial phase of spermatocyte maturation into spermatozoa. (2) Glycogen content was lower during interbout arousal (IBA), while glycogen phosphorylase (GP) activity was significantly elevated compared to the other stages. Sertoli cell density was higher in the IBA group relative to the torpor group, suggesting that elevated GP activity facilitates glycogen breakdown, providing glycolytic substrates for Sertoli cells during this phase. (3) During torpor, triglyceride and fatty acid levels, along with fatty acid synthase and acetyl-CoA carboxylase activities, remained consistent with PRE levels. These findings suggest that fatty acids are crucial for maintaining testicular reproductive function during torpor. In contrast, lipid metabolism indicators declined during the near post-hibernation (NP) and POST stages, likely supporting the rapid reactivation of reproductive processes required for the upcoming breeding season. In summary, this study highlights a dynamic interplay between lipid and glycogen metabolism across hibernation stages, with the transition from lipid-based metabolism during torpor to glycogen utilization during IBA playing a pivotal role in sustaining testicular homeostasis in Daurian ground squirrels.