Contribution of Leptin to Energy Expenditure and Glucose Metabolism in Fasting

Leptin regulates energy homeostasis and is involved in glucose metabolism. It is known that leptin plays an important role in neuroendocrine response to fasting; therefore, the essential role of leptin may be the response to starvation. In this study, we examined the role of leptin in energy expenditure and glucose metabolism in fasting. Methods: C57BL/6 and leptin mutant ob/ob mice were fasted for 48 hours. Oxygen consumption and blood glucose levels were examined before and after fasting. Next, leptin was continuously infused (20ng/g/h) by osmotic pump in C57BL/6 and ob/ob mice to blunt the fall of leptin in fasting. These mice were fasted for 48 hours and the same parameters were measured before and after fasting during the infusion of leptin. Results: After fasting, there was lesser decrease in oxygen consumption in ob/ ob mice (C57BL/6: -1162±274ml/kg/h; ob/ob:-150±150ml/kg/h, p<0.05). The reduction in blood glucose was greater in ob/ob mice, though it didn’t reach the statistical significance (C57BL/6: -24±8mg/dl; ob/ob: -45±6mg/dl). By continuous infusion of leptin in C57BL/6 mice, decrease in oxygen consumption after fasting was blunted (leptin infusion-: -1162±274, leptin infusion+: 250±294ml/kg/h, p<0.01) in C57BL/6 mice. Decrease in blood glucose was greater in C57BL/6 mice by infusion of leptin (leptin infusion-: -24±8, leptin infusion+: -56±6mg/dl, p<0.05). There were no differences in those parameters after fasting by leptin infusion in ob/ob mice. Conclusions: Leptin-fall may be, at least in part, a regulatory factor of energy expenditure and glucose metabolism in starvation.