Association of Promoter Methylation and Expression of Inflammatory Genes IL-6 and TNF-α with the Risk of Coronary Artery Disease in Diabetic and Obese Subjects among Asian Indians.

The inflammatory cytokines such as interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) are considered as the most important contributors to the endothelial dysfunction in subjects with type 2 diabetes mellitus (T2DM) and obesity. The hypomethylation of CpG sites in the promoter region of the IL-6 and TNF-α have shown to be associated with the increased expression of IL-6 and TNF-α. However, there are no studies on the methylation and expression of IL-6 and TNF-α with the risk of coronary artery disease (CAD) in subjects with T2DM and obesity in Asian Indians. Hence, the present study was aimed to investigate whether the IL-6, TNF-α promoter methylation and expression in blood leukocyte DNA is associated with the risk of CAD in diabetic and obese subjects in Asian Indians. For this study, we recruited 574 subjects which includes, 207 angiographically confirmed CAD patients, 100 T2DM patients, 82 obese subjects and 185 healthy controls. The methylation status of IL-6 and TNF-α gene loci was determined by methylation specific PCR (MPCR) and gene expression was determined by qPCR. We found significant hypomethylation of IL-6 in CAD and T2DM subjects (OR 1.98 95% CI: 1.32-2.97, p  = 0.001, OR: 2.23 95% CI:1.34-3.76, p  = 0.001, respectively). Further, a significant increase in the expression of IL-6 in CAD and T2DM subjects (fold change: 26.39 & 14.7, p  = 0.0001) compared to the control subjects was observed. A significant increase in the hypomethylation of TNF-α in CAD, T2DM and obese subjects was observed as compared to the control (OR: 2.04 95% CI: 1.36-3.05, p  = 0.0005, OR: 1.81 95% CI 1.10-2.96, p  = 0.01, and OR: 2.1 95% CI 1.24-3.57, p  = 0.007, respectively).We also found an increased expression of TNF-α in CAD, T2DM and obese subjects as compared to controls. In addition, presence of low folate, and hyperhomocysteinemia was observed in the present study, may be the contributing factors for the hypomethylation of IL-6 and TNF-α and oxidative stress. In conclusion, increased expression of IL-6 and TNF-α due to hypomethylation in T2DM and obese individuals may contribute to CAD risk in these subjects. The presence of hyperhomocysteinemia and increased oxidative risk may enhance the CAD risk further.