Effects of exogenous leptin on body mass, thermogenesis capacity and hormone concentrations of Yuman Chinese vole, Eothenomys miletus, under varied photoperiod.

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in wild small mammals. In the present study, we examined the effects of exogenous leptin on the adaptive thermogenesis and hormone concentrations in Eothenomys miletus by transferring them from a short (SD, 8h :16h L: D) to long day photoperiod (LD, 16h: 8h L:D). Body mass, body fat mass, rest metabolic rate (RMR), nonshivering thermogenesis (NST), energy intake, body compositions, mitochondrial cytochrome c oxidase (COX) activity and uncoupling protein1 (UCP1) content of brown adipose tissue (BAT), and serum triiodothyronine (T3), thyroxine (T4), leptin levels, hypothalamic thyrotropin-releasing hormone (TRH) and corticotrophin-releasing hormone (CRH) levels were measured. The results showed that RMR, NST and energy intake decreased by transferring to LD relative to those for SD, while body mass increased in the first 6 weeks acclimation. It shown that SD voles respond to the hormone by reducing body mass and energy intake by infusing with exogenous leptin. The exogenous leptin treatment induced higher COX activity, UCP1 content, serum T3, leptin levels, T3/T4, TRH and CRH levels in short photoperiod than did the LP at the end of the acclimation. SD voles responded to infusion of leptin by changes in BAT UCP1 content, but LD voles showed no significantly change. Our results indicated that exogenous leptin may induce an increased thermogenesis and hormone concentrations, and decreased body mass and body fat mass. It seemed that E. miletus of SD were more sensitive to exogenous leptin.