Objective:To observe the effects of in tracerebroventricular injection of leptin on the expression of obese gene in adipose tissue and the level of serum leptin and serum insulin, C-peptide in diet-induced obese rats and analyze the correlation among the expression of obese gene and the level of serum leptin and the correlation among serum leptin and insulin and C-peptide.Methods:①Total RNA from the adipose tissue was extracted by using TRIzol isolation kit. Obese gene mRNA expression and semiquantitation were studied by reverse transcription-PCR.②At the time of sacrifice, blood samples were collected by cardiopuncture directly and centrifuged at 2 0 00rlm for 20 minutes.Serum was stored at- 20'C and serum insulin and C –peptide and leptin were detected by using radioimmunoassay and the murine leptin ELISA kit. Results:①The levels of obese gene mRNA expression in retroperitoneal adipose tissue were decreased in obese rats after leptin administration, and lower than in the groups with the saline and the obese control group.In addition,there was no si gnificant difference in all normal groups.② Compared with the ratswith leptin injection and the normal groups, the level of serum leptin in obese rats with the saline and without treatment was increased more significantly. The concentration of serum leptin had significant positive correlation with the level of obese gene expression.③ In obese groups with leptin injection, the levels of serum insulin and C-peptide decreased significantly than those in obese rats with the saline and without treatment. Moreover, there were no obvious changes between the obese groups with leptin injection and all normal groups. The serum insulin and C-peptide concentrations were strongly positively correlated with the level of serum leptin in rats. Conclusion: Leptin could decline the expression of obese gene and the level of serum leptin and insulin and C-peptide in diet-induced obese rats after intracerebroventricular injection so as to improve the leptin and insulin resistance.