Acute effect of leptin and ghrelin injection on postprandial glycogen and lipid synthesis in rats

Aim: The study was designed to investigate the immediate (1 h) effect of leptin and ghrelin injection on in vivo postprandial hepatic glycogen and lipid synthesis. Animals and Methods: Adult Sprague-Dawley male rats were fed a semisynthetic control diet ad libitum. Overnight-fasted rats were gavaged with 4 ml of water containing 1.25 g of the diet and immediately injected intraperitoneally with 4 mCi of 3H2O. After 1 h, rats were either intraperitoneally injected with saline (control), leptin (20 microgram/rat) or ghrelin (10 microgram/rat) and sacrificed 1 h later. Blood, liver and epididymal fat pads (EFP) were taken for analysis. Results: Plasma triglyceride level was higher in the leptin group compared to control. Leptin injection reduced hepatic glycogen synthesis while glycogen accumulation was not affected and ghrelin injection did not affect hepatic glycogen synthesis. Both hepatic and EFP lipogenesis were not affected by leptin or ghrelin. Conclusion: Leptin and ghrelin administration had no immediate effect on hepatic and adipose tissue lipogenesis. Leptin reduced in vivo postprandial hepatic glycogenesis and increased plasma triglyceride level which may be due to reduced uptake by peripheral tissues. Thus, leptin was found to exert an immediate effect on lipid and carbohydrate metabolism unlike that of ghrelin.