Abstract: To evaluate the role of serum leptin, TNFα and IL6 on insulin resistance in highfat diet induced obese rats. Methods: After fed with highfat diet for 8 weeks, the obese rats who were 30g heavier than controls were separated and fed for another 4 weeks. The blood samples were drawed by heart puncture. The serum levels of glucose were measured by glucose oxideperoxidase method, the levels of leptin and insulin by RIA, and the levels of TNFα, IL6 by ELISA. The ratio of insulin versus glucose(I/G) was used as an indicator for insulin resistance. Results: Compared with the controls, the serum levels of leptin, IL6 and I/G were higher in the obese rats, but the levels of TNFα were not different between two groups; The levels of leptin and IL6,but not TNFα, were closely related to the parameters evaluating insulin resistance in obese rats. Conclusions: The serum levels of leptin and IL6 are increased in highfat diet induced obese rats and contribute to insulin resistance. The levels of TNFα in obese rats are neither statistically increased nor related to insulin resistance.

Key words: Obesity, Leptin, Tumor necrosis factorα, Interleukin6, Rat, Wistar