Global DNA methylation not increased in chronic hemodialysis patients: a case-control study

Patients with chronic kidney disease have an increased risk of cardiovascular disease and mortality. Since DNA methylation is an important mechanism modulating the gene expression associated with aging, inflammation, and atherosclerosis, the objective of this study was to determine the possible effect of the uremic milieu on global DNA methylation and DNA methyltransferase (DNMT) expression in uremic status by comparing chronic hemodialysis (HD) patients with the normal population. Twenty normal subjects and twenty chronic dialysis patients with similar ages, sex, and body mass indexes (BMIs) were included. We evaluated the clinical characteristics; the levels of homocysteine, total indoxyl sulfate (IS), and total p-cresol sulfate (PCS); and the DNMT messenger RNA expression and global DNA methylation in the peripheral blood leukocytes. The chronic HD patients had significantly higher blood urea nitrogen (BUN), creatinine (Cr), uric acid, Ca, P, intact parathyroid harmone (iPTH), cholesterol, high-sensitivity C-reactive protein (hs-CRP), total indoxyl sulphate (IS) and p-cresol sulphate (PCS), and homocysteine than the normal subjects. The expression of DNMT 1 and 3a did not differ significantly between these two study groups. The chronic HD patients had significantly decreased DNMT 3b expression in the leukocytes. There were no significant correlations between the global DNA methylation and the levels of IS, PCS, and homocysteine. We concluded that chronic HD patients may have lower DNMT 3b expression than normal subjects. However, the status of global DNA methylation may not change significantly in uremic patients when compared with the normal population.