Dissociation of leptin secretion and adiposity during prehibernatory fattening in little brown bats

Hibernating animals deposit adipose tissue before hibernation to withstand long periods of reduced energy intake. Normally, adiposity is positively co rrelated with increased secretion from adipose tissue of the satiety hormon e, leptin. During the prehibernatory phase of the little brown bat, Myotis lucifugus, body mass and adiposity increased to a maximum within 12 days. L eptin secretion from adipose tissue in vitro and plasma leptin, however, in creased before the increase in adiposity, then significantly decreased when adiposity increased. Basal metabolic rate (BMR) decreased when plasma lept in was increasing. This was followed by an increase in nonshivering thermog enic capacity and brown adipose tissue mass. We conclude that in the early prehibernatory phase, BMR decreases despite increasing plasma leptin levels , suggesting a state of relative leptin resistance at that time. At later s tages, adiposity increases as BMR continues to decrease, and plasma leptin becomes dissociated from adiposity. Thus, in M. lucifugus, hibernation may be achieved partly by removing the metabolic signal of leptin during the fa ttening period of prehibernation.