Genotypes of alcohol dehydrogenase and aldehyde dehydrogenase loci in Japanese alcohol flushers and nonflushers

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Abstract
A much higher incidence of alcohol flushing among Orientals in comparison to Caucasians, i.e., >50% vs 5%–10%, has been attributed to racial differences in alcohol-metabolizing enzymes. A large majority of Orientals are “atypical” in alcohol dehydrogenase-2 locus (ADH 2 ), and their livers exhibit significantly higher ADH activity than the livers of most Caucasians. Approximately 50% of Orientals lack the mitochondrial aldehyde dehydrogenase (ALDH2) activity, and elimination of acetaldehyde might be disturbed. We determined by means of hybridization of genomic DNA samples with allele specific oligonucleotide probes, genotypes of the ADH 2 and ALDH 2 loci in Japanese alcohol flushers and nonflushers. We found that all individuals with homozygous atypical ALDH 2 2 /ALDH 2 2 and most of those with heterozygous atypical ALDH 1 2 /ALDH 2 2 were alcohol flushers, while all subjects with homozygous usual ALDH 1 2 /ALDH 1 2 were nonflushers. Frequency of the atypical ADH 2 2 was found to be higher in alcohol flushers than in nonflushers, but the statistical significance was not established in the sample size examined.