Human stomach class IV alcohol dehydrogenase: molecular genetic analysis

Diet and the evolution of ADH7 across seven orders of mammals

Dietary variation within and across species drives the eco-evolutionary responsiveness of genes necessary to metabolize nutrients and other components. Recent evidence from humans and other mammals suggests that sugar-rich diets of floral nectar and ripe fruit have favoured mutations in, and functional preservation of, the ADH7 gene, which encodes the ADH class 4 enzyme responsible for metabolizing ethanol. Here we interrogate a large, comparative dataset of ADH7 gene sequence variation, including that underlying the amino acid residue located at the key site (294) that regulates the affinity of ADH7 for ethanol. Our analyses span 171 mammal species, including 59 newly sequenced. We report extensive variation, especially among frugivorous and nectarivorous bats, with potential for functional impact. We also report widespread variation in the retention and probable pseudogenization of ADH7. However, we find little statistical evidence of an overarching impact of dietary behaviour on putative ADH7 function or presence of derived alleles at site 294 across mammals, which suggests that the evolution of ADH7 is shaped by complex factors. Our study reports extensive new diversity in a gene of longstanding ecological interest, offers new sources of variation to be explored in functional assays in future study, and advances our understanding of the processes of molecular evolution.

Effects of cimetidine on blood ethanol levels after alcohol ingestion and genetic polymorphisms of sigma-alcohol dehydrogenase in Japanese

Administration of cimetidine, an H2-receptor antagonist increases blood alcohol concentrations. This has been attributed to decreased gastric first-pass metabolism of ethanol caused by cimetidine's inhibitory effect on gastric alcohol dehydrogenase (sigma-ADH) activity. Molecular studies on sigma-ADH showed that a point mutation might occur at position 287 (G --> T) of the sigma-ADH gene in Japanese deficient type of sigma-ADH activity. To clarify the relationship between first-pass metabolism of ethanol and polymorphism of sigma-ADH, we analyzed the nucleotide sequence at positions 287 and 294 of sigma-ADH in 11 individuals who were administered ethanol orally before and after treatment with cimetidine. Higher blood ethanol levels after cimetidine administration were found in 4 of 11 cases (group A), whereas high blood ethanol levels were observed in 7 of 11 cases (B group), irrespective of cimetidine administration. Genetic polymorphisms at position 287 and 294 were not observed in all subjects. Even in 59 Japanese men with various alcoholic liver diseases, no polymorphisms at position 287 were observed by restriction-length polymorphisms with Avail digestion after polymerase chain reaction.