DNA methylation profiling identifies epigenetic differences between diabetes patients with ESRD and diabetes patients without nephropathy

We identified potential epigenetic biomarkers for chronic kidney disease progression by comparing site-specific DNA methylation levels in more than 14,000 genes between African American and Hispanic diabetes patients with end stage renal disease (ESRD) and diabetes patients without nephropathy. We identified 187 genes that are differentially methylated between the two groups on at least two CpG sites in each gene in DNA extracted from saliva. Of the 187 genes whose mean methylation levels differed between the two groups, 39 genes or closely related gene family members, have been reported to be involved in kidney development or diabetic nephropathy, per se, or have been associated with dialysis-induced changes in gene expression in peripheral blood cells. The fact that such a substantial fraction (21%) of the 187 candidate genes have been implicated previously through genome association or transcription profiling studies suggests strongly that the DNA methylation differences we observe are associated with disease predisposition and/or treatment. The fact that these nephropathy and/or dialysis-associated differences between patients were identified in DNA extracted from saliva offers proof-of-principle that inter-individual epigenetic differences may prove useful as predictive biomarkers of disease susceptibility.