The effects of URAT1/SLC22A12 nonfunctional variants, R90H and W258X, on serum uric acid levels and gout/hyperuricemia progression
SCIENTIFIC REPORTS
Authors: Sakiyama, Masayuki; Matsuo, Hirotaka; Shimizu, Seiko; Nakashima, Hiroshi; Nakamura, Takahiro; Nakayama, Akiyoshi; Higashino, Toshihide; Naito, Mariko; Suma, Shino; Hishida, Asahi; Satoh, Takahiro; Sakurai, Yutaka; Takada, Tappei; Ichida, Kimiyoshi; Ooyama, Hiroshi; Shimizu, Toru; Shinomiya, Nariyoshi
Abstract
Urate transporter 1 (URAT1/SLC22A12), a urate transporter gene, is a causative gene for renal hypouricemia type 1. Among several reported nonsynonymous URAT1 variants, R90H (rs121907896) and W258X (rs121907892) are frequent causative mutations for renal hypouricemia. However, no case-control study has evaluated the relationship between gout and these two variants. Additionally, the effect size of these two variants on serum uric acid (SUA) levels remains to be clarified. Here, 1,993 primary gout patients and 4,902 health examination participants (3,305 males and 1,597 females) were genotyped with R90H and W258X. These URAT1 variants were not observed in any gout cases, while 174 subjects had the URAT1 variant in 2,499 health examination participants, respectively (P = 8.3 x 10(-46)). Moreover, in 4,902 health examination participants, the URAT1 nonfunctional variants significantly reduce the risk of hyperuricemia (P = 6.7 x 10(-19); risk ratio = 0.036 in males). Males, having 1 or 2 nonfunctional variants of URAT1, show a marked decrease of 2.19 or 5.42 mg/dl SUA, respectively. Similarly, females, having 1 or 2 nonfunctional variants, also evidence a decrease of 1.08 or 3.89 mg/dl SUA, respectively. We show that URAT1 nonfunctional variants are protective genetic factors for gout/hyperuricemia, and also demonstrated the sex-dependent effect size of these URAT1 variants on SUA (P for interaction = 1.5 x 10(-12)).
Molecular basis of primary renal hyperuricemia. Role of the human urate transporter hURAT1
ZEITSCHRIFT FUR RHEUMATOLOGIE
Authors: Unger, S.; Tausche, A. -K.; Kopprasch, S.; Bornstein, S. R.; Aringer, M.; Graessler, J.
Abstract
In highly industrialized countries hyperuricemia is one of the most common metabolic disorders. High uric acid blood levels may lead to the manifestation of gout owing to the precipitation of urate crystals in connective tissue, the skeletal system and kidneys. A primary reduction of renal uric acid excretion can be detected in more than 90% of all cases of hyperuricemia. Despite the identification of several uric acid transporting proteins their pathogenetic role for the induction of primary reduced renal uric acid excretion has not yet been verified. As a result of a case-control study on individuals with normal and reduced renal uric acid excretion, an association of polymorphisms in the human urate transporter I gene (hURAT1) with primary reduced urate excretion has been demonstrated for the first time. The hURAT1 gene is an organic anion transporter (SLC22A12), which is preferentially expressed in the apical membrane of proximal renal tubule cells. Functioning as an antiporter, hURAT1 mediates the uptake of urate from the lumen into proximal tubule cells in exchange for organic and inorganic anions. Loss-of-function mutations in the hURAT1 gene are a cause of hereditary renal hypouricemia. The precisely regulated hURAT1 is a candidate gene for hyperuricemia and an important target for the development and optimization of new diagnostic approaches and pharmacological interventions of primary reduced renal uric acid excretion.