Effects of various fasting periods on serum, pituitary and hypothalamic leptin levels in rats

Abstract

Leptin has long been recognised as the potent appetite mediator and body mass regulator. We compared the effects of various fasting periods on leptin concentration in rat serum, pituitary and hypothalamus. The animals were food deprived for 6 h, 12 h, 24 h, 48 h and 72 h (n=6). Each of the fasted groups was sacrificed simultaneously with the group of ad libitum fed animals which (n=6). Serum leptin in starved animals was either lower than the control level (6 h, 12 h) or showed no significant change to the controls (24 h, 48 h, 72 h). Pituitary leptin was increased in the two groups which were subjected to shortest fasting periods (6 h, 12 h) and the group with the longest fasting period (72 h). Hypothalamic leptin was first higher in fasted animlas (6 h), then reached (12 h) and finaly declined beneath the control level (24 h, 48 h, 72 h). The corresponding metabolic parametars, such as blood glucose, insulin, urea, free fatty acids and corticosterone levels were also measured to help estimate which of the three fasting phases was ongoing at the time of decapitation. Collectively, our results suggest that the changes in leptin concentrations display tissue specific patterns in different phases of fasting implying that leptin also plays roles other than that of the appetite regulator.