Abstract
There is no evidence for a genetic association between organic anion transporters 1-3 (SLC22A6, SLC22A7, and SLC22A8) and multidrug resistance protein 4 (MRP4; encoded by ABCC4) with the levels of serum urate or gout. The Māori and Pacific (Polynesian) population of New Zealand has the highest prevalence of gout worldwide. The aim of this study was to determine whether any Polynesian population-specific genetic variants in SLC22A6-8 and ABCC4 are associated with gout.
All participants had ≥3 self-reported Māori and/or Pacific grandparents. Among the total sample set of 1,808 participants, 191 hyperuricemic and 202 normouricemic individuals were resequenced over the 4 genes, and the remaining 1,415 individuals were used for replication. Regression analyses were performed, adjusting for age, sex, and Polynesian ancestry. To study the functional effect of nonsynonymous variants of ABCC4, transport assays were performed in Xenopus laevis oocytes.
A total of 39 common variants were detected, with an ABCC4 variant (rs4148500) significantly associated with hyperuricemia and gout. This variant was monomorphic for the urate-lowering allele in Europeans. There was evidence for an association of rs4148500 with gout in the resequenced samples (odds ratio [OR] 1.62 [P = 0.012]) that was replicated (OR 1.25 [P = 0.033]) and restricted to men (OR 1.43 [P = 0.001] versus OR 0.98 [P = 0.89] in women). The gout risk allele was associated with fractional excretion of uric acid in male individuals (β = -0.570 [P = 0.01]). A rare population-specific allele (P1036L) with predicted strong functional consequence reduced the uric acid transport activity of ABCC4 by 30%.
An association between ABCC4 and gout and fractional excretion of uric acid is consistent with the established role of MRP4 as a unidirectional renal uric acid efflux pump.