Does epigenetic markers of HLA gene show association with coronary artery disease in Indian subjects?

Background DNA methylation, one of the most stable forms of epigenetic modification is associated with the development and progression of coronary artery disease (CAD). Our previously reported study on epigenome-wide microarray analysis showed significantly methylated CpG sites. Top 5 significant CpGs from HLA gene were selected and analysed by Pyrosequencing (PSQ) to determine their association with severity of CAD. Methods Blood samples of 50-age matched angiographically CAD positive male cases with 50 angiographically CAD negative male controls were subjected to lipid profile estimation and PSQ for methylation level analysis. Findings and subgroup analysis were evaluated by Mann–Whitney U; Kruskal–Wallis’ rank test and two-way ANOVA by MedCalc (v19.6). Results Methylation levels in HLA-DQA1 for cg10217052 was 78.5 (37–85) and 76.5 (24–84); cg09411910 was 81 (72.0 to 93.0) and 81.5 (50.0 to 89.0) in cases and controls respectively. Levels in HLA-DQB1-cg03344051, were 28.88 + 9.41 for cases and 30.36 + 9.37 in controls. For HLA-DRB1-cg07889003, levels in cases and controls were 15.5 (5.00–39.00) and 10.5 (5.00–29.0); while in cg08269402 were 52 (16–65) and 42.5 (17–61) respectively. No association was observed between methylation levels and lipid profile. cg03344051, cg07889003 and cg08269402 were significantly differentiated in double or triple vessel disease (DVD or TVD) as compared to single vessel disease (SVD) suggesting an increase in the extent of methylation with the increase in CAD severity. Conclusion The present study shows significant increase in the extent of methylation in 3 CpG sites in DVD/TVD cases as compared to SVD cases. Additionally, a novel site, cg07889003 identified in our discovery phase has shown association with the severity of CAD.