#2256 Rate of HMGCR gene methylation in diabetic patients on hemodialysis

Abstract Background and Aims Patients with chronic kidney disease, especially those on hemodialysis (HD), exhibit a pronounced risk for cardiovascular mortality. Unfortunately and conversely to general population, cholesterol-lowering medication, such as inhibitors of HMGCR-statins, does not reduce this CV risk. The incidence and severity of CV complications in CKD patients correlates with changed epigenetic mechanisms. The most studied epigenetic phenomenon is DNA methylation, i.e. methyl group bound at the cytosine of DNA. Methylated parts of DNA are not readily accessible to the transcriptional machinery. Therefore final gene expression is suppressed. The aim of this study was to elucidate the methylation status of HMGCR gene in diabetic patients during hemodialysis procedure and its interplay with statins medication and LDL cholesterol plasma levels. Method Cell-free DNA was isolated in pre- and post-HD plasma samples of 45 HD patients (26 diabetics and 19 non-diabetics; 17 of them on statin medication). LDL cholesterol plasma levels were measured in these patients. Bisulfite conversion was carried out to distinguish methylated and unmethylated form of the DNA. The primers of HMGCR genes promotors were designed, after that methylation specific PCR and sequential analysis of PCR products were performed. Percentage of methylated cytosines in HMGCR gene promoter amplicons was subsequently assessed. Results The lower methylation rate of HMGCR gene was found in diabetic compared withnondiabetic patients before dialysis session (68.39% versus 78.24%, P < 0.005). Additionally HD procedure itself led to the increase of methylation status just in diabetics (68.39% versus 74.94%, P < 0.005) (Fig. 1). A significantly higher rate of HMGCR gene methylation before HD was associated with statin therapy (79.82% versus 68.95%, P < 0.05). After dialysis there was no statistically significant difference (Fig. 2). Methylation of HMGCR gene was not associated with LDL cholesterol concentration. Conclusion This pilot study showed that HMGCR gene before dialysis was hypomethylated just in diabetic patients. Only in this group the methylation rose during the dialysis session. We confirmed higher methylation status of HMGCR gene in patients treated using HMGCR inhibitors.