Quantitative Trait Analysis of Polymorphisms in Two Bilirubin Metabolism Enzymes to Physiologic Bilirubin Levels in Chinese Newborns

ObjectiveTo explore the effects of variants in Uridine Diphosphate Glucuronosyl Transferase 1A1 (UGT1A1) and Heme Oxygenase-1 (HMOX1) on daily physiological bilirubin levels and bilirubin changes during the first week after birth in Chinese newborns. Both UGT1A1 and HMOX1 code rate-limiting enzymes in the bilirubin metabolism pathway.Study designWe conducted a retrospective quantitative trait study to analyze 4154 daily bilirubin values, 3129 bilirubin changes, and 11 polymorphisms of 988 newborns during the natural course of physiological hyperbilirubinemia.ResultsFor UGT1A1, we found minor allele A of rs4148323 (G211A, UGT1A1*6) contributed to higher daily bilirubin levels on days 4-6 (with contributions to variations increasing from 4.8% to 12.3%), minor allele T of rs887829 (c-364t) contributed to lower daily bilirubin levels for days 6 and 7 (with contributions to variations increasing from 7.0% to 10.2%) (P < .03 for all). In addition, minor alleles of rs887829 and (TA)n repeat (UGT1A1*28), and haplotype T-long-G at rs887829-(TA)n-rs4148323 were associated with a decrease in bilirubin levels from day 5 to day 6 (P < .01 for all). No contribution from HMOX1 was found.ConclusionBilirubin levels and changes during the middle and late parts of the first week were attributed to variants and haplotypes in UGT1A1. This quantitative trait study may provide a more robust statistical method for determining the association of genetic factors and bilirubin kinetics to predict the development of neonatal bilirubin in early postnatal life.