06 October 2006
Background/Aim:A significant phenotypical variability is observed in autosomal dominant polycystic kidney disease (ADPKD). The variability cannot be fully explained by the genetic heterogeneity of the disease. Endothelin-1 (ET-1) has been suggested to be a major promoting factor in renal diseases. The role of the ET-1 gene locus (EDN1) in the renal function in the general nondiabetic population was evaluated. We examined the influence of three single-nucleotide polymorphisms of the ET-1 gene (EDN1) – K198N, 3A/4A, and T-1370G – on the progression of ADPKD towards end-stage renal disease (ESRD). Methods: Two hundred and five ADPKD patients (113 males and 92 females) who had reached ESRD were analyzed. The patients were divided into three groups: (1) 48 patients (23 males and 25 females) with ESRD later than 63 years of age (slow progressors), (2) 74 patients (41 males and 33 females) with ESRD before 45 years of age (rapid progressors), and (3) 83 patients (49 males and 34 females) with ESRD between 45 and 63 years old. DNA samples from collected blood were genotyped for three single-nucleotide polymorphisms of EDN1: K198N, 3A/4A, and T-1370G. Haplotype analysis was also done in 200 healthy individuals. We compared the frequencies of the different genotypes between the groups of slow and rapid progressors and the ages at the time of ESRD regarding the EDN1 genotypes. Results: The EDN1 genotype distribution showed no differences among the groups of slow progressors, rapid progressors, the ADPKD group with ESRD between 45 and 63 years old, and the control group. Comparing the ages of ESRD of all patients, we did not find significant differences with regard to the different genotypes. Furthermore, we compared the combinations of the different haplotypes and the ages at the time of ESRD. We found no differences in ages at the time of ESRD in patients with different haplotypes in the endothelin promoter (T-1370G) in combination with 3A/4A or K198N polymorphisms. Comparing the ages at the time of ESRD in patients with different 3A/4A and K198N haplotypes, we found a significantly lower age at the time of ESRD (47.1 ± 8.7 years) in the carriers of the 4A allele in combination with the 198N allele (4A/4A, 3A/4A + 198KN,NN) than in the carriers of the 4A allele homozygous for the K198 allele (52.9 ± 10.9 years; 4A/4A, 3A/4A + 198KK; t test: p < 0.01) and in the carriers of the 198N allele homozygous for the 3A allele (53 ± 11.2 years; 3A/3A + 198KN,NN; t test: p < 0.05). Conclusions: We excluded an effect of K198N, 3A/4A, and T-1370G polymorphisms of EDN1 on the progression of ADPKD. However, a deleterious effect of the combination of 4A and 198N alleles of EDN1 was observed in APKDK individuals.