LINE-1 Hypomethylation is Associated with the Risk of Coronary Heart Disease in Chinese Population

BACKGROUND: Global methylation level in blood leukocyte DNA has been associated with the risk of coronary heart disease (CHD), with inconsistent results in various populations. Similar data are lacking in Chinese population where different genetic, lifestyle and environmental factors may affect DNA methylation and its risk relationship with CHD. OBJECTIVES: To examine whether global methylation is associated with the risk of CHD in Chinese population. METHODS: A total of 334 cases with CHD and 788 healthy controls were included. Global methylation in blood leukocyte DNA was estimated by analyzing LINE-1 repeats using bisulfite pyrosequencing. RESULTS: In an initial analysis restricted to control subjects, LINE-1 level reduced significantly with aging, elevated total cholesterol, and diagnosis of diabetes. In the case-control analysis, reduced LINE-1 methylation was associated with increased risk of CHD; analysis by quartile revealed odds ratios (95%CI) of 0.9 (0.6-1.4), 1.9 (1.3-2.9) and 2.3 (1.6-3.5) for the third, second and first (lowest) quartile (P(trend )< 0.001), respectively, compared to the fourth (highest) quartile. Lower (<median) LINE-1 methylation was associated with a 2.2-fold (95%CI = 1.7-3.0) increased risk of CHD. The lower LINE-1-related CHD risk estimates tended to be stronger among subjects with the highest tertile of homocysteine (P(interaction )= 0.042) and those with diagnosis of hypertension (P(interaction )= 0.012). CONCLUSION: LINE-1 hypomethylation is associated with the risk of CHD in Chinese population. Potential CHD risk factors such as older age, elevated total cholesterol, and diagnosis of diabetes may have impact on global DNA methylation, whereby exerting their effect on CHD risk.