Serum Bilirubin Affects Graft Outcomes through UDP-Glucuronosyltransferase Sequence Variation in Kidney Transplantation

BACKGROUND Oxidative stress is a major mediator of adverse outcome after kidney transplantation. Bilirubin is produced by heme oxygenase-1 (HO-1), catalyzed by UDP-glucuronosyltransferase (UGT1A1), and has potential as an antioxidant. In this study, we investigated the effects of HO-1 and UGT1A1 sequence variations on kidney allograft outcomes. METHODS Clinical data were collected from 429 Korean recipients who underwent kidney transplantation from 1990-2008. Genotyping for UGT1A1*28 and HO-1 (A-413T) was performed. Acute rejection and graft survival were monitored as end-points. RESULTS Serum levels of total bilirubin were significantly increased after transplantation (0.41 ± 0.19 mg/dL to 0.80 ± 0.33 mg/dL, P<0.001). Post-transplant 1-year bilirubin level was higher in 6/7 or 7/7 carriers compared with 6/6 homozygotes in terms of the UGT1A1*28 polymorphism (6/6 vs. 6/7 vs. 7/7: 0.71 ± 0.27 vs. 1.06 ± 0.36 vs. 1.10 ± 0.45 mg/dL, P<0.001). According to an additive model of genotype analysis, the 7-allele genotype had a protective effect on the development of acute rejection compared with the 6-allele (odds ratio 0.43, 95% CI 0.25-0.73, P for trend = 0.006). Multivariate Cox regression analysis revealed that individuals carrying the 7-allele had a decreased risk of graft loss, by a factor of 0.36 (95% CI 0.15-0.85, P = 0.019). The HO-1 (A-413T) polymorphism had no effect on serum bilirubin levels or graft outcomes. CONCLUSIONS The UGT1A1*28 polymorphism is associated with changes in serum bilirubin and with graft outcome after kidney transplantation.