Seasonal variations of adipose tissue in Tupaia belangeri (Mammalia: Scandentia: Tupaiidae)

Animals employ various strategies to adapt to different natural habitats. In order to investigate the relationship between thermogenesis of adipose tissue and seasonal variations in Tupaia belangeri, body mass, food intake, adipose tissue morphology, and expression levels of three adipose differentiation-related genes - peroxisome proliferators-activated receptor alpha (PPAR alpha), cyclooxygenase-2 (COX-2) and peroxisome proliferator-activated receptor. coactivator 1-alpha (PGC1a) -were measured in the present study. The results show that body mass and food intake increased significantly in winter compared with summer. White adipose tissue (WAT) in winter demonstrated the characteristic appearance of beige adipocytes, including smaller and multi-chamber lipid droplets, darker hue, and increased expression levels of COX-2 and PGC-1a genes, which would increase thermogenic properties in T. belangeri to make up for the lack of thermogenesis in nonshivering thermogenesis (NST) caused by brown adipose tissue (BAT). Moreover, analysis of BAT morphology showed smaller lipid droplets, and COX-2 and PPARa gene expression in BAT increased significantly in winter, indicating that uncoupling protein 1 (UCP1) had been activated to increase NST. All of these results suggest that T. belangeri enhanced thermogenic capacity in winter, including WAT undergoing browning and enhanced NST in BAT, which played important roles in the strategies of thermal physiology and bioenergetics in T. belangeri during seasonal change.