Regulation of body weight and thermogenesis in seasonally acclimatized Brandt's voles (Microtus brandti).

Seasonal changes in an animal's morphology, physiology, and behavior are considered to be an adaptive strategy for survival and reproductive success. In the present study, we examined body weight and several behavioral, physiological, hormonal, and biochemical markers in seasonally acclimatized Brandt's voles (Microtus brandti) to test our hypothesis that Brandt's voles can decrease energy intake associated with decrease in body weight, body fat content, serum leptin level, and increasing thermogenesis in winter conditions. We found that the body weight of Brandt's voles was lowest in winter (December to February) and highest in spring and early summer (May to June). This seasonal variation in body weight was associated with changes in other markers examined. For example, the winter decrease in body weight was accompanied by increased energy intake and enhanced nonshivering thermogenesis (NST) as well as by decreased body fat mass and reduced levels of circulating leptin. Further, circulating levels of leptin were positively correlated with body weight and body fat mass, and negatively correlated with energy intake and uncoupling protein 1 contents. Together, these data do not support our hypothesis and suggest that leptin may be involved in this process and serve as a starvation signal in Brandt's voles.