Effects of polymorphisms in untranslated regions of the class I alcohol dehydrogenase (ADH) genes on alcohol metabolism in Japanese subjects and transcriptional activity in HepG2 cells.

ABSTRACT

Human class I ADH is a dimmer formed by the random association of three types of subunits (alpha, beta and gamma) encoded by ADH1A, ADH1B, and ADH1C, respectively. Different kinetic properties were reported due to polymorphisms of ADH1B Arg47His and ADHIC Ile349Val. Besides these polymorphisms in the coding region, various mutations in the promoter region and 3' untranslated (UTR) region, which possibly affect expression and degradation rate, were recently reported. In this study, to asses the involvement of each genotype in alcohol metabolism in humans, our previously collected data set of blood EtOH and AcH changes were reanalyzed with regard to the ALDH2 Glu487Lys genotype. The effects of genotypes and haplo-types on transcriptional activity were also examined by a luciferase reporter assay by cloning the promoter region and 3' UTR corresponding to each polymorphism and transfecting into HepG2 cells. Among the nine polymorphisms, including ADH1B Arg47His and ADH1C Ile349Val, blood EtOH levels were significantly affected by polymorphisms ADH1B -451G>T, ADH1B +52A>G, ADH1B +531G>A, ADH1B +1176AG>del. and ADH1A -55C>T in ALDH2 Glu/Glu subjects. In the ALDH2 Glu/Lys genotype background, only ADH1C -254G>C and ADH1B His47Arg showed significant effects on blood EtOH. These five loci (and the two loci which had significant effect on blood EtOH in ALDH2 Glu/Glu and Glu/Lys subjects) also showed strong linkage disequilibrium. In comparison to the in vivo study on alcohol metabolism, significantly higher transcriptional activities in ADH1B -451T (rather than C) promoter and ADH1C-254 G (rather than C) promoter were observed in a luciferase assay in HepG2 cells. In conclusion, polymorphisms in the untranslated regions of ADH class I genes were demonstrated to clearly affect individual differences in alcohol metabolism. Especially, ADH1B -451G>T, ADH1C-254G>C polymorphisms were suggested to have functional significance with regard to transcriptional activity to the linkage equilibrium of polymorphisms ADH1B His47Arg and ADH1C Ile349Val.