Abstract: Objective: To investigate the protective effect of soy isoflavone on the oxidative stress injury of the perimenopause model rats with type 2 diabetes mellitus, and to elucidate its mechanism. Methods: Ten rats of all the sixty rats were randomly choosen as control group(n=10).The perimenopause models of rats with type 2 diabetes mellitus were established by feeding high sugar diet and removing both ovaries,and the rest 46 perimenopause model rats were randomly divided into sham operation group(n=9), model group(n=8), low(n=9), medium (n=10)and high(n=10) doses of soy isoflavone groups. The partial adipose tissue below both ovaries of the rats in sham operation group was removed, the rats in low, medium and high doses of soy isoflavone groups were given different doses (90, 180, and 360 mg·kg^-1) of soy isoflavone by gavage, while the rats in control group, sham operation group and model group were given the same volume of normal saline, lasted for 8 weeks. The body weights and the levels of fasting blood glucose (FBG) of the rats in various groups were measured.The levels of serum estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), nitric oxide (NO), malondialdehyde (MDA), and reactive oxygen species (ROS) of the rats in various groups were measured by ELISA method. Results: Compared with model group, the body weights and the FBG levels of the rats in low, medium and high doses of soy isoflavone groups were increased significantly (P<0.05); the levels of serum E2 were significantly increased (P<0.05),the levels of serum FSH and LH were significantly decreased (P<0.05), the levels of serum SOD, GSH-Px and NO were significantly increased (P<0.05), and the levels of serum MDA and ROS were significantly decreased (P<0.05). Conclusion: Soy isoflavone can regulate the level of serum estrogen, improve the ability of anti-oxidative stress, and protect the oxidative stress injury in the perimenopause model rats with type 2 diabetes mellitus in a non-dose-dependent manner.

Key words: soy isoflavone, oxidative stress, estrogen, type 2 diabetes, perimenopausal syndrome