Abstract: Objective: To investigate the effect of tansforming growth factor-β（TGF-β）on insulin gene expression in isolated rat islets,and to study the role of TGF-β in the treatment of type 2 diabetes mellitus. Methods: TGF-β was added to isolated islets at the final concentrations of 0,1,2,5,10,and 20ng/mL to RPMI1640 medium containing 2.2mmol/L（low）,5.5mmol/L（normal）and 11.1mmol/L（high）glucose.All islet samples were harvested after incubation for 24h,and total RNA was extracted from RPMI1640 medium for RT-PCR. Results: When glucose level was 2.2mmol/L,no change occurred in insulin gene expression at different concentrations of TGF-β.The low and normal physiologic concentrations of TGF-β had no effect on insulin gene expression at the glucose level of 5.5mmol/L.In contrast,physiologic concentrations of TGF-β stimulated insulin gene expression in a dose-dependent manner.The insulin mRNA levels were higher at the glucose level of 11.1mmol/L. Conclusion: TGF-β up-regulates insulin mRNA level in a glucose concentration-dependent manner.