Abstract: Objective: To investigate the relationship between visfatin and insulin resistance (IR)of type 2 diabetes mellitus(T2DM) through the classic insulin signaling pathway phosphatidy inositol-3 kinase (PI3K). Methods: The human T2DM preadipocyte cells were recoveried, extended and differentiated. The visfatin overexpression vectors were built, transformated, cultivated and extracted. The fat cells were transfected with different overexpression levels (0.0, 1.0, 2.5 and 5.0 μg); 0.0 μg group was used as control group,and the remaining three groups as observation groups. The mRNA expression levels of visfatin, insulin receptor substrate-1(IRS-1), insulin receptor substrate-2(IRS-2) and PI3K (P85α) were detected by Q-PCR. The protein expression levels of visfatin, IRS-1, IRS-2, PI3K (P85α), IRS-1 and IRS-2 phosphorylation levels were measured by Western blotting method.The glucose uptake rates of fat cells were determined by [³H]-2-deoxidation-D-glucose uptake assay. Results: The expression levels of visfatin mRNA and protein in various groups were increased with the increase of transfection concentration gradient (P<0.01); and the constructed overexpression vector of visfatin was effective. With the increase of visfatin expression, the mRNA and protein expression levels of IRS-1 and PI3K (P85α) and IRS-1 phosphorylation degrees in various groups were increased (P<0.01), but the IRS-2 mRNA and protein expression levels had no obvious changes(P>0.05).The glucose uptake rates of fat cells were elevated with the increasing of visfatin expression (P<0.05). Conclusion: The visfatin overexpression of fat cells in vitro can increase the expression levels of IRS-1 and PI3K.

Key words: insulin resistance, diabetes mellitus,type 2, visfatin, insulin receptor substrate