In this study, we found significant atherosclerotic plaques and decreased ER-α expression in aortae of double knockout ApoE/Lepr mice treated with insulin, and we demonstrated that insulin signaling leads to epigenetic modifications that promote atherosclerosis, including inducing hypermethylation of the ER-α second exon region, which subsequently decreased ER-α mRNA and protein expression. The gene discussed is INS; the disease is atherosclerosis.