The Association Between Heterozygosity for UGT1A1*6, UGT1A1*28, and Variation in the Serum Total-Bilirubin Level in Healthy Young Japanese Adults

Aims: Considerable variations in the serum total-bilirubin concentrations are observed in healthy subjects. Both sex and the UGT1A1 homozygous genotypes,*6/*6 and *28/*28, are known to influence this variation. However, currently, there is no consensus on the relationship of the heterozygous genotypes *1/*6, *1/*28, or *6/*28 and interindividual variation in the serum total-bilirubin levels. In the present study, we sought to clarify the involvement of heterozygous alleles *6 and *28 in the interindividual difference in the serum total-bilirubin levels among healthy young Japanese adults. Methods: We enrolled 92 healthy Japanese aged 20–30 years (37 men and 55 women). The serum total-bilirubin levels were compared between men and women and with different UGT1A1 genotypes. Multiple regression analysis was used to investigate the relationships between individual differences in the serum total-bilirubin levels, UGT1A1 genetic variants, and sex. Results: Serum total-bilirubin levels were significantly lower i...