Abstract: 【Objective】 To investigate the effects of metformin on insulin sensitivity and possible mechanism in rats with polycystic ovary syndrome (PCOS). 【Methods】 PCOS rat model was induced by subcutaneous injecting dehydroeplandrosterone up to 20 days and then divided randomly into PCOS and metformin group. The rats of metformin group were intragastrically given metformin 140 mg?kg-1?d-1 for 15 days. Blood were collected to test free glucose and insulin levels before and after metformin intervention. Liver tissues were collected to test triglyceride content and protein expression. 【Results】 PCOS rats exhibit insulin resistance and metformin treatment can improve insulin sensitivity in PCOS rats. Triglyceride levels

GRP 78 and SREBP-1c protein expression in the liver of PCOS rats were higher than those of the controls

whereas P-AMPKa protein expression was lower than that of the normal controls (P < 0.05). After the treatment of metformin

triglyceride levels

GRP 78 and SREBP-1c protein expression in the liver of PCOS rats were significantly decreased (P < 0.05) and P-AMPKa protein expression was increased to the level similar with that of normal controls. 【Conclusion】 Metformin protect PCOS rats against insulin resistance and hepatocyticf at deposition largely through effects on activating AMPK pathway and on decreasing endoplasmic reticulum stress in liver.