Significance of the tissue kallikrein promoter and transforming growth factor-β1 polymorphisms with renal progression in children with vesicoureteral reflux

Background. Tissue kallikrein regulates blood circulation. Low urinary kallikrein excretion was associated with hypertension and renal disease in blacks. The polymorphic KLK1 promoter includes -130 G_N coupled with multiple single base substitutions. The -130 G₁₂ allele in the KLK1 promoter was associated with lower transcriptional activity and hypertensive end-stage renal disease (ESRD) in blacks. Transforming growth factor-β1 (TGF-β1) regulates matrix production, and induces fibrosis in a variety of tissues. High circulating TGF-β1 levels mediating renal fibrosis and loss of function in transgenic mice. The -509 T allele in the TGF-β1 promoter showed marginally higher transcriptional activity, and was associated with increased TGF-β1 production in humans. The aim of this study was to investigate whether the tissue KLK1 promoter and TGF-β1 polymorphism are involved in primary vesicoureteric reflux (VUR) with renal progression in children. Methods. Seventy-four primary VUR children were studied with regular annual follow-up for more than 18 years, all of them more than grade II (diagnosed by voiding cystourethroradiography). All of them were born before 1984. Patients were classified into two groups according to the renal function with progressive deterioration or not. Patients with baseline creatinine clearance (CCr) less than 25 mL/min were defined as having chronic renal insufficiency (CRI). The TGF-β1 -509 T-C polymorphism was analyzed by Bsu36I restriction fragment length polymorphism (RFLP)-polymerase chain reaction (PCR). In KLK1 promoter, the -130 G_N length polymorphism and multiple single base substitutions were analyzed by electrophoresis of fluoresced PCR products in sequencing gels, single strand conformation polymorphism (SSCP), allele-specific PCR, and DNA sequencing. Patients' TGF-β1 and KLK1 promoter polymorphisms were evaluated for association with VUR susceptibility and progression in Taiwanese children. Annual echocardiography study was used to evaluate left ventricular mass index (LVMI). Results. Four alleles were identified in the complex KLK1 promoter: A (-130 G₁₀), B (-130 G₂CG₇), H (-130 G₁₁), and K (-130 G₁₂). The polymorphic KLK1 promoter showed no association with VUR susceptibility. However, the frequency distribution of KLK1 promoter among VUR patients with or without CRI (A, 50.0% and 67.5%; B, 17.9% and 8.3%; H, 14.3% and 18.3%; K, 17.9% and 5.8%, respectively) was statistically different (P = 0.008). Significantly higher K allele frequency was present in primary VUR with CRI children, as it was in the renal survival curve study. A significant increase of LVMI was also found in the A allele group compared with the non-A allele group of KLK1 promoter gene at the age of 18 years old with renal progression. The TGF-β1 gene polymorphism was determined, and we found significant over-representation of the TT genotype in primary VUR patients with CRI compared with normal renal function (P = 0.0035). Conclusion. The K allele of KLK1 promoter and TT genotype of TGF-β1 may be a genetic KLK1 -130 G_N and -128 G-C, and the susceptibility factor contributing to progressive renal deterioration in Taiwanese primary VUR children.