Dysfunctional ABCG2 gene polymorphisms are associated with serum uric acid levels and all-cause mortality in hemodialysis patients

Dysfunctional variants of ATP-binding cassette transporter subfamily G member 2 (ABCG2), a urate transporter in the kidney and intestine, are the major causes of hyperuricemia and gout. A recent study found that ABCG2 is a major transporter of uremic toxins; however, few studies have investigated the relationship between ABCG2 gene polymorphisms and mortality. This prospective cohort study of 1214 hemodialysis patients investigated the association between serum uric acid levels and ABCG2 genotype and mortality. Genotyping of dysfunctional ABCG2 variants, Q126X (rs72552713) and Q141K (rs2231142), was performed using the patients' DNA. During the study period, 220 patients died. Lower serum uric acid levels were associated with higher mortality (hazard ratio [HR] 1.89, 95% confidence interval [CI] 1.14-3.10, P <= 0.001). ABCG2 dysfunction, estimated by genetic variants, had a significant positive association with serum uric acid levels (full function: 7.4 +/- 1.2 mg/dl, 3/4 function: 7.9 +/- 1.3 mg/dl, 1/2 function: 8.2 +/- 1.4 mg/dl, <= 1/4 function: 8.7 +/- 1.3 mg/dl, P <= 0.001). This association remained significant on multiple regression analysis. The Cox proportional hazard analysis indicated that the ABCG2 <= 1/4 function type was significantly associated with higher mortality (HR 6.66, 95% CI 2.49 to 17.8, P <= 0.001) than the other function types. These results showed that ABCG2 plays a physiologically important role in uric acid excretion, and that ABCG2 dysfunction is a risk factor for mortality in hemodialysis patients.