Evidence of growth hormone effect on plasma leptin in diet-induced obesity and die resistant rats

Background: Plasma leptin is regulated by several factors, including growth hormone (GH) which influences the pathophysiology of obesity. Objective: To demonstrate the short-term effect of GE on plasma leptin levels in 3 conditions in vivo with the different amount of body fat mass. Methods: Adult male Wistar rats were fed with standard chow or hypercaloric diet (HC). The HC rats were demonstrated as HC-feeding obese (HC-O) and HC-feeding resistant (HC-R) rats. Then, they were treated with GH or saline for 3 days. Basal plasma leptin levels were measured at 24 and 32 h. For meal-induced condition, all rats were fed for 2 hand plasma leptin was measured. Further 16-h fasting period, plasma leptin, insulin, and insulin sensitivity indexes were determined. Results: The short-term GH treatment decreased basal plasma leptin at 32 h after the first GH injection in HC-O rats. However, OH treatment had no effect on meal-induced plasma leptin in all rats. Furthermore, OH treatment attenuated fasting effect on plasma leptin in control and HC-R rats. The insulin resistance (IR) induced by the short-term OH treatment was demonstrated by higher fasting plasma insulin and the increased homeostasis model of IR in HC-R rats. Conclusions: The study demonstrates the important role of greater fat mass in HC-O rats, which results in decreased basal plasma leptin after short-term GH treatment. For meal-induced condition, GH had no effect on plasma leptin in all rats. Interestingly, GH could attenuate fasting effect on plasma leptin in rats that have lower fat mass.