Chronic kidney disease (CKD), impairment of kidney function, is a serious public health problem, and the assessment of genetic factors influencing kidney function has substantial clinical relevance. Here, we report a meta-analysis of genome-wide association studies for kidney function–related traits, including 71,149 east Asian individuals from 18 studies in 11 population-, hospital- or family-based cohorts, conducted as part of the Asian Genetic Epidemiology Network (AGEN). Our meta-analysis identified 17 loci newly associated with kidney function–related traits, including the concentrations of blood urea nitrogen, uric acid and serum creatinine and estimated glomerular filtration rate based on serum creatinine levels (eGFRcrea) (P < 5.0 × 10−8). We further examined these loci with in silico replication in individuals of European ancestry from the KidneyGen, CKDGen and GUGC consortia, including a combined total of ~110,347 individuals. We identify pleiotropic associations among these loci with kidney function–related traits and risk of CKD. These findings provide new insights into the genetics of kidney function.

Chronic kidney disease (CKD), the result of permanent loss of kidney function, is a major global problem. We identify common genetic variants at chr2p12-p13, chr6q26, chr17q23 and chr19q13 associated with serum creatinine, a marker of kidney function (P=10−10 to 10−15). SNPs rs10206899 (near NAT8, chr2p12-p13) and rs4805834 (near SLC7A9, chr19q13) were also associated with CKD. Our findings provide new insight into metabolic, solute and drug-transport pathways underlying susceptibility to CKD.

Dioxin exposure has experimentally been associated with changes in DNA methylation, an epigenetic change that is associated with disease. The present study aims to investigate if serum levels of dioxin and other persistent environmental pollutants are related to global DNA methylation in a human sample. In the population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study (all aged 70), global DNA methylation was measured by the Luminometric Methylation Assay in 524 subjects. Twenty-three different POPs, including 16 PCBs, five pesticides, one dioxin (OCDD) and one brominated flame retardant (BDE47) were analysed by HRGC/HRMS. Ten single nucleotide polymorphisms (SNPs) in the Aryl hydrocarbon (Ah)-receptor were analysed by mini-sequencing. High levels of toxic equivalency (TEQ) for PCBs and dioxin were associated with DNA hypermethylation (p=0.030). This was mainly attributed to coplanar non-ortho PCBs. While no significant associations were found between DNA methylation and SNPs in the Ah-receptor, an interaction was found between the SNP rs2237297 and TEQ so that TEQ was associated with hypermethylation (p=0.009) only in subjects with one G-allele (n=103). Also high levels of the PCB126 congener, the OCDD, and the pesticide metabolite p,p'-DDE were related to DNA hypermethylation (p=0.01, 0.03 and 0.003, respectively). In conclusion, in a sample of elderly subjects, high TEQ including PCBs and the dioxin OCDD and high serum levels of PCB126, OCDD, and p,p'-DDE were related to global DNA hypermethylation in a cross-sectional analysis.

The CC-chemokine receptor 5 (CCR5) is a receptor for various proinflammatory chemokines, and a deletion variant of the CCR5 gene (CCR5⌬32) leads to deficiency of the receptor. We hypothesized that CCR5⌬32 modulates inflammation-driven mortality in patients with ESRD. We studied the interaction between CCR5 genotype and levels of high-sensitivity C-reactive protein (hsCRP) in 603 incident dialysis patients from the multicenter, prospective NEtherlands COoperative Study on the Adequacy of Dialysis (NECOSAD) cohort. CCR5 genotype and hsCRP levels were both available for 413 patients. During 5 yr of follow-up, 170 patients died; 87 from cardiovascular causes. Compared with the reference group of patients who had the wild-type CCR5 genotype and hsCRP Յ 10 mg/L (n ϭ 225), those carrying the deletion allele with hsCRP Յ 10 mg/L (n ϭ 55) had similar mortality, and those carrying the wild-type genotype with hsCRP Ͼ 10 mg/L (n ϭ 108) had an increased risk for mortality (HR: 1.82; 95% CI: 1.29 to 2.58). However, those carrying the deletion allele with hsCRP Ͼ 10 mg/L (n ϭ 25) had a mortality rate similar to the reference group; this seemingly protective effect of the CCR5 deletion was even more pronounced for cardiovascular mortality. We replicated these findings in an independent Swedish cohort of 302 ESRD patients. In conclusion, the CCR5⌬32 polymorphism attenuates the adverse effects of inflammation on overall and cardiovascular mortality in ESRD.

Patients with chronic kidney disease (CKD) display a progeric vascular phenotype linked to apoptosis, cellular senescence and osteogenic transformation. This has proven intractable to modelling appropriately in model organisms. We have therefore investigated this directly in man, using for the first time validated cellular biomarkers of ageing (CDKN2A/p16INK4a, SA-β-Gal) in arterial biopsies from 61 CKD patients undergoing living donor renal transplantation. We demonstrate that in the uremic milieu, increased arterial expression of CDKN2A/p16INK4a associated with vascular progeria in CKD, independently of chronological age. The arterial expression of CDKN2A/p16INK4a was significantly higher in patients with coronary calcification (p=0.01) and associated cardiovascular disease (CVD) (p=0.004). The correlation between CDKN2A/p16INK4a and media calcification was statistically significant (p=0.0003) after correction for chronological age. We further employed correlate expression of matrix Gla protein (MGP) and runt-related transcription factor 2 (RUNX2) as additional pathognomonic markers. Higher expression of CDKN2A/p16INK4a, RUNX2 and MGP were observed in arteries with severe media calcification. The number of p16INK4a and SA-β-Gal positive cells was higher in biopsies with severe media calcification. A strong inverse correlation was observed between CDKN2A/p16INK4a expression and carboxylated osteocalcin levels. Thus, impaired vitamin K mediated carboxylation may contribute to premature vascular senescence.

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The progression rate of chronic kidney disease (CKD) to its terminal stage, end-stage renal disease (ESRD), and the development and severity of various complications, are at least indirectly influenced by genetic--and epigenetic--factors. For years, scientists have held out hope that the rapidly evolving field of genetics could transform medical diagnosis and treatment, moving beyond a trial-and-error approach towards "personalized medicine." Indeed, there are now signs that the role of genetics and the pursuit of "personalized medicine" in medical care will be a priority for governments during years to come. But the vision of individualized treatment based on a patient's genetic makeup and other biological markers has yet to materialize in the field of CKD and ESRD. As the toxic uremic environment may render CKD patients more sensitive to the effects of genetic variants, it is likely that genetic factors could be of special importance in this high-risk population. Therefore, outcome in the CKD population may be improved by establishing individual genetic/epigenetic profiles, thus enabling physicians to design an individualized therapeutic strategy. Personalized medicine based on a more individualized therapy could be applied in, for example, pharmacotherapy (CYP genes), dialysis therapy, and nutritional and lifestyle modifications.

Epigenetic alterations regulate the utilization of the genome by permitting or inhibiting access of transcription factors and associated complexes. Although there are several different types of epigenetic alterations, such as acetylation and methylation of histone tails, the one which has been the most extensively studied is DNA-methylation, wherein the cytosine residue in a CpG dinucleotide is methylated. Luminometric Methylation Assay (LUMA) enables researchers to study global methylation by using methylation-sensitive restriction enzymes followed by Pyrosequencing(®) which quantitates the number of cuts in the genome relative to an internal standard. The relative measurement of global methylation levels is simple and enables up to 96 samples to be analyzed at the same time.