Aim To detect the methylation and expression of CpG island in the gene promoter region of live CuZnSOD during the occurrence of atherosclerosis(As) on apolipoprotein E-deficient mouse,explore the effects of betaine on atherosclerosis and its possible mechanisms.Methods Normal C.57BL/6J mouse were taken as control group,apolipoprotein E-deficient mouse were randomly divided into model group,1%,2%and 3%betaine group.Oil red O staining method was used to detect the lipid plaque area in mouse aortic sinus,methylation-specific polymerase chain reaction (MSP) was applied to examine the gene methylation of liver CuZnSOD,quantitative fluorescence reverse transcription-polymerase chain reaction(real-time RT-PCR) was taken to detect the expression of mRNA in CuZnSOD gene and by immunohistochemical method its protein expression was detected.Results In 14th week,the lipid plaque areas of aortic sinus in 2%and 4%betaine mouse group were less than the model group,the difference was significant(P<0.05);The CpG island methylation status of CuZnSOD gene in each group had no significant difference(P>0.05);in all time the expression of mRNA in the normal groups were higher than that in the model groups;the 7th week,the expression of mRNA in 1%betaine group was higher than that in 2%and 4%betaine group;the 14th week,the expression of mRNA in 1% betaine group was higher than that in model group and 2%betaine group.In all time the expression of CuZnSOD protein in the normal group was higher than that in the other four groups(P<0.05),but the expression in the other four groups had no signifcant difference.Conclusions CuZnSOD gene may not be involved in the abnormal DNA methylation changes in the process of atherosclerosis,supplement of betaine can increase the expression of CuZnSOD gene mRNA in liver,thus improve the lipid aggradation of apolipoprotein E-deficient mouse and reduce the plaque area of aortic.