FIGURE 5.

Schematic representation of iWAT remodeling for hibernation in Syrian hamster. Prolonged SD-Cold stimuli induce iWAT remodeling prior to initiating hibernation in Syrian hamsters. The morphology and cell population of adipocytes in iWAT changes during the transition from the non-hibernation to the hibernation state. Small adipocyte population increases, and beige-like cells emerge during Pre-HIB and HIB. Prolonged SD-Cold stimuli also alter the mRNA expression of genes in the insulin-PPAR signaling pathway. Up-regulation of lipid metabolism genes before the onset of hibernation could enhance the capacity for both lipid catabolism and anabolism in iWAT to prepare for metabolic challenges during the HIB. Thus, seasonal cues mediated by the ambient temperature and photoperiod alter the mTORC1-PPAR signaling network and induce iWAT remodeling prior to hibernation.