Alcohol dehydrogenase genotype (ADH2 and ADH3) in alcoholism of Iraqi people

Abstract

Objective The polymorphic human liver enzyme alcohol dehydrogenase (ADH) is responsible for the oxidative metabolism of ethanol. An
allele encoding active form of cytosolic enzyme is known to reduce the likelihood of alcoholism in Iraqi men. The polymorphisms of ADH
modifies the predisposition to the development of alcoholism. Determination of genotypes ADH2 and ADH3 loci in alcoholic and nonalcoholic
Iraqi men.
Method Using leukocyte DNA extraction and then amplifying by polymerase chain reaction (PCR) by using specified primers, then allele
specific primer extension and PCR-restriction fragment length polymorphism (RFLP) methods with another set of primers is employed in
order to determine the variants of ADH2 and ADH3, respectively.
Results The Iraqi alcoholics had significantly lower frequencies of ADH2*2 and ADH3*1 alleles than did the non-alcoholic as compared
with the general population of East Asians but more than in Caucasians population, suggesting that genetic variation in ADH enzyme
modulating the rate of metabolism of ethanol to acetaldehyde influences drinking and the risk of developing alcoholism. The simplest
explanation of the significant lower frequency of ADH2*2 and ADH3*1 alleles among Iraqi alcoholic men is that each can produce higher
transient level of acetaldehyde, which trigger aversive reactions; these alleles are less likely to become alcoholic.
Conclusion This study suggests that both ADH2 and ADH3 genotypes exert an influence on alcohol metabolic rate, alcohol-flush reaction
and susceptibility to develop alcoholism. ADH2 and ADH3 genotypes may have a protective role in the risk for alcoholism in Iraqi alcoholic
population.