DNA Methylation and Cardiovascular Disease: Getting to the Heart of the Issue
Elliott MK, McCaughan JA, McKnight AJ, Maxwell AP
Nephrology Research Group, Queen's University, Belfast, Northern Ireland
End-stage renal disease is associated with an increased risk of cardiovascular morbidity. Despite the substantial survival benefit conferred by renal transplantation, premature death is common and cardiovascular disease remains the major cause of mortality in this population. DNA methylation has been associated with atherosclerosis in chronic kidney disease patients and in the general population. This study aimed to investigate the association between DNA methylation at the time of renal transplantation and the development of cardiovascular disease in renal transplant recipients.
Clinical outcome data was recorded prospectively. Cardiovascular disease was defined as myocardial infarction, ischaemic stroke, intervention for peripheral vascular disease, or coronary revascularization. DNA was extracted from whole blood immediately prior to transplantation from 469 recipients of first, deceased donor kidney transplants performed between 1986 and 2005. An epigenome wide association study was performed using the Infinium® methylation 450K BeadChip array (Illumina, Inc, USA). Following stringent quality control, beta values were calculated and results adjusted for multiple testing. Beta values were compared between recipients who developed cardiovascular disease and controls (recipients with no cardiovascular disease in the follow up period) using ANOVA, with adjustment for clinically relevant covariates. Two genes associated with the top ranked CpGs contained multiple CpG sites displaying differential methylation. Fifteen CpG sites in these two genes were selected for further study. Sanger sequencing was performed to identify single nucleotide polymorphisms (SNPs) and to fine map top-ranked CpG sites before and after bisulphite treatment.
Cardiovascular disease was associated with differences in DNA methylation between cases and controls at 174 CpG sites where P < 10-5. Top ranked clusters of CpG sites were associated with genes that have previously been implicated in amyloid angiopathy, apolipoprotein E function, and obesity. A C/T SNP was detected at a CpG site in one of these genes demonstrating the importance of this ‘explore and validate’ technique.
This is the first study to show an association between DNA methylation profile and development of cardiovascular disease in a kidney transplant population. Several potential biomarkers of cardiovascular disease in renal transplant recipients were identified. These markers could be used to improve risk reduction strategies or may suggest novel pathophysiological mechanisms. Further work is required to investigate the role of DNA methylation in the pathogenesis of cardiovascular disease in other CKD and non-CKD populations.