Effects of Intracerebroventricular Injection of Recombinant Leptin on Food Intake, Body Weight and Blood Lipids in Diet induced Obese Rats

Abstract:

OBJECTIVE: To investigate the effects of intracerebroventricular injection of recombinant murine leptin on the food intake, body weight and blood lipids in diet induced obese rats and normal rats. METHODS: Male SD rats were put on a standard diet (n=15) and highnutrition diet (n=20) for 7 weeks. After 7 weeks, the rats received cannulas implanted into the right lateral ventricles. Allowed 7 days to recover, the rats received an intracerebroventricular injection of recombinant murine leptin (5 μg/rat) for 5 days. On each test day, the body weight and food intake were measured before the injection. Blood lipids were measured after the experiment. RESULTS: ① The body weight of the rats on the highnutrition diet was more significantly increased than that in the normal rats. At the end of the 7th week, the body weight of each group was (342.05±39.27) g and (302.87±31.93) g (P<0.01), with an increase of (270.00±39.99) g and (226.13±30.04) g (P<0.01), respectively. In the dietinduced obese rats, the inhibition of body weight and food intake was observed after the intracerebroventricular leptin injection on the 1st day, more significant on the 5th day ［body weight from (336.3±52.1) g to (287.9±53.4) g (P<0.01), and a decrease of (48.4±17.9) g; food intake from (35.6±13.7) g to (21.1±11.8) g (P<0.01), a decrease of (14.6±4.8) g］. But in the normal group, the effects were observed on the 3rd day ［body weight from (294.5±29.9) g to (269.5±30.9) g (P<0.05), a decrease of (25.0±17.8) g; food intake from (31.0±3.5) g to (25.6±3.6) g (P<0.05), a decrease of (5.3±3.3) g］. ② In the obesity group with leptin administration, the levels of TC, TG and LDL-C decreased more significantly than those in the normal control group ［TC (1.51±0.27) mmol/L vs. (2.22±0.36) mmol/L, P<0.01; TG (0.43±0.06) mmol/L vs. (0.76±0.17) mmol/L; LDL (0.47±0.12)mmol/L vs. (0.86±0.20) mmol/L, P<0.01］. But there was no obvious change of HDL-C in any of the groups. CONCLUSIONS: Recombinant leptin could reduce the body weight and blood lipids, and inhibit the food intake in dietinduced obese rats after intracerebroventricular injection, and also had a certain effect on normal rats.