Objective: Human urate transporter 1 (hURAT1) is a member of the organic anion transporter family (SLC22A12) that mainly regulates tubular urate reabsorption. Loss-of-function mutations result in idiopathic hypouricemia. The present case-control study was designed to analyze whether hURAT1 might also be a candidate gene for hyperuricemia with primary reduced renal urate excretion.
Methods: DNA samples from 389 individuals with reduced fractional excretion of uric acid (FEUA) (< or =6.5%) and from 263 controls (FEUA >6.5%) were sequenced. Genotype frequencies between groups were compared by Cochran-Armitage trend test.
Results: Significantly different genotype distributions could be demonstrated for the -788 T >A (promoter; P = 0.014), the C258T (exon 1; P = 0.006), and the C426T (exon 2; P = 0.0002) polymorphisms, but not for the T1309C (exon 8) and the +18 C >T (intron 9) polymorphisms. The strongest association with reduced FEUA was observed for the C426T polymorphism, with odds ratios (ORs) of 1.59 and 2.54 (P = 0.0002) for the CT and TT genotypes, respectively. Adjusted values for FEUA in the C426T genotype, were significantly reduced decreasing to 7.3%, 6.7%, and 6.3% in individuals with the CC, CT, and TT genotypes, respectively (P = 0.004). Haplotypes were constructed from the -788 T >A, C258T, and C426T polymorphisms. Individuals carrying at least 1 ACT haplotype (n = 349) had a significantly higher risk for reduced FEUA than individuals without any ACT haplotype (n = 303) (OR 1.39, P = 0.041).
Conclusion: These results indicate that polymorphisms in the N-terminus of the hURAT1 gene were significantly associated with reduced renal uric acid excretion. The main regulating factor seems to be located close to the C426T polymorphism or is in strong linkage disequilibrium.