Metformin Mechanism of Insulin Resistance in Ovariectormized Female Rats

OBJECTIVE To investigate the improvement effect and mechanism of metformin(MF) on insulin resistance in castrated female rats. METHODS The levels of serum estradiol(E₂), progesterone (P) and insulin (INS) were determined by radioimmunoassay method. Tumor necrosis factor-a (TNF-α) level was measured by enzyme-linked immunosorbent assay. Gene expression of pancreas islet suppressor of cytokine sighting-3(SOCS-3) was determined by using reverse transcriptase polymerase chain reaction. RESULTS Compared with NS group, the serum E₂ and P content in OVX group were significantly decreased, the TNF-α, INS content were significantly increased , while the SOCS-3 mRNA expression of pancreas islets were significantly increased(P<0.01). Compared with the OVX group, MF low group has no significant change. Serum E₂ and P content were significantly increased (P<0.05) in MF high group. The TNF-α, INS content significantly decreased (P<0.05 or P<0.01), while the SOCS-3 mRNA expression of islets were significantly decreased (P<0.01). CONCLUSION Long-term with a large dose of MF 270 mg·kg^-1·d^-1can improve ovariectormized rats insulin resistance phenomenon. The mechanism may be related with the decreased of TNF-α and SOCS-3 mRNA expression of islets.