Pleiotropic effect of ABCG2 in gout: involvement in serum urate levels and progression from hyperuricemia to gout

BackgroundThe ABCG2 Q141K (rs2231142) andrs10011796variants associate with hyperuricaemia (HU). The effect size ofABCG2 rs2231142on urate is ∼60% that ofSLC2A9, yet the effect size on gout is greater. We tested the hypothesis that ABCG2 plays a role in the progression from HU to gout by testing for association ofABCG2 rs2231142andrs10011796with gout using HU controls.MethodsWe analysed 1,699 European gout cases and 14,350 normourciemic (NU) and HU controls, and 912 New Zealand (NZ) Polynesian (divided into Eastern and Western Polynesian) gout cases and 696 controls. Association testing was performed using logistic and linear regression with multivariate adjusting for confounding variables.ResultsIn Europeans and Polynesians, theABCG2141K (T) allele was associated with gout using HU controls (OR=1.85,P=3.8E-21and ORmeta=1.85,P=1.3E-03, respectively). There was evidence for an effect of 141K in determining HU in European (OR=1.56,P=1.7E-18) but not in Polynesian (ORmeta=1.49,P=0.057). ForSLC2A9 rs11942223, the T allele associated with gout in the presence of HU in European (OR=1.37,P=4.7E-06), however significantly weaker thanABCG2 rs2231142141K (PHet=0.0023). In Western Polynesian and European, there was epistatic interaction betweenABCG2 rs2231142and the genetically-independentrs10011796. Combining the presence of the 141K allele with thers10011796CC-genotype increased gout risk, in the presence of HU, 21.5-fold in Western Polynesian (P=0.009) and 2.6-fold in European (P=9.9E-06). The 141K allele positively associated with flare frequency in Polynesian (Pmeta=2.5E-03).ConclusionThese data are consistent with a role forABCG2141K in gout in the presence of established HU.