Abstract: Objective To establish an ideal model animal of PCOS and to detect the DNA methylation states of LHR, INSR and AR genes in this model. Methods 24-days-old female Sprague-Dawley (SD) rats were randomly divided into two groups. The rats in the experimental group were given subcutaneous implanting of levonorgestrel silica gel staff (3mm per rat) and begun to inject 1.5 IU hCG twice daily for 9 days from the 4th day. The rats in the control group were injected with normal saline at the same time. Ovarian morphologic changes, sex hormone levels, fasting serum insulin and glucose were detected. The LHR, INSR and AR genes' DNA methylation patterns were checked by methylation specific PCR in modeling group and control group. Results The ovarian weight and volume in modeling group were higher than those in control group (both P< 0.001). The ovaries in modeling group showed multiple follicular cysts, and the number of theca cells and interstitial cells increased. Less developing follicles and corpus lutea were seem. The serum level of progesterone, testosterone, luteinizing hormone, fasting insulin and glucose were significantly higher in experimental group than those in control group (P<0.05), so as the LH/FSH ratio and HOMA index (both P< 0.001). No methylation of LHR and AR genes were detected in both groups. The methylation frequency of INSR gene (76.7%) was significantly higher in modeling group than that in control group (P< 0.001). Conclusions The depression of INSR gene's transcriptional induced by DNA methylation is a good supplement to he pathogenesis of insulin resistance in PCOS.

Key words: PCOS, DNA methylation, animal model