Objective       To determine the role of estrogen receptor α (ER-α) during the process of insulin-induced atherosclerosis.       Methods       Eight-week-old Apoe/Lepr double knockout mice (n=8) were randomly divided to control group (N) and experimental group (INS

4 IU

intra-peritoneal injection

5 times per week

for 3 months). The vascular atherosclerotic plaques and expression levels of ER-α

alpha smooth muscle actin (α-SMA) were detected by hematoxylin-eosin (HE) staining and immunohistochemical analysis. Insulin was applied to intervene rat vascular smooth muscle cells (VSMCs)

and the expression levels of DNA methyltransferase 3a (DNMT3a) and ER-α were assessed by RT-PCR and Western blotting. Furthermore

wound-healing assay and flow cytometry were used to detect the effect of ER-α on the proliferation and migration in VSMCs.       Results       The experimental mice showed atherosclerosis plaques and lower expression of ER-α and α-SMA than the control group (P0.05). The mRNA and protein expression of ER-α was significantly lower

while that of DNMT3a was obviously higher in the experimental group than the control group (P＜0.01)

but 5-Aza-2′-deoxycytidine (5-Aza) could eliminate these differences (P0.05). Wound-healing assay and flow cytometry showed that ER-α inhibited the proliferation and migration of VSMCs (P0.05).       Conclusion       By up-regulating the expression of DNMT3a and inducing the methylation of ER-α

insulin suppresses the expression of ER-α and then leads the formation of atherosclerosis.