Ethanol consumption and DRD2 gene TaqI a polymorphism among socially drinking males

Abstract

The dopaminergic system in the human brain is thought to play a major role in the development of alcohol consumption habits and alcoholism. It has been reported that homozygous D2-/- knock-out mice lacking D2 receptors consume about 50% to 60% less ethanol than wild-type D2+/+ mice, and heterozygous mice have an intermediate level of alcohol consumption. The DRD2 gene TaqI A polymorphism has been suggested to associate with a low D2 receptor density in post mortem and in vivo measurements. Numerous association studies on this polymorphism and alcoholism have shown most controversial results. We studied whether DRD2 TaqI A genotype affects alcohol consumption in an ethnically homogeneous, representative sample of 1,019 Finnish Caucasian males. After excluding the abstainers from the study, the self-reported alcohol consumption among the remaining 884 non-abstainers was compared in the TaqI A genotype groups (A1/A1, A1/A2, A2/A2). The alcohol consumption of the homozygous A1/A1 group was about 30% lower than in A1/A2 group, and 40% lower than in A2/A2 group (P = 0.042 and 0.041 in a sociodemographic variable-adjusted multivariate model). The results indicate an association between DRD2 genotype and alcohol consumption habits in humans. These results in the large sample of non-alcoholic males are also opposite to some previous findings on the higher A1 allele frequency among alcoholic populations.

Association between the DRD2 gene Taq1A (C32806T) polymorphism and alcohol consumption in social drinkers

“…The mean levels of alcohol consumption were somewhat higher in our study than in the previous report, 18 with the mean self-reported alcohol consumption among A2A2 men in our combined sample equivalent to 137 g of alcohol per week, compared to 97 g/week in the Finnish sample. In our combined sample, men possessing at least one copy of the A1 allele consumed 106 g/week, while in the Finnish sample A1A2 men consumed 82 g/week and A1A1 men 58 g/week.…”

“…We replicated and extended the findings of a recent study 18 demonstrating an association between the DRD2 Taq1A polymorphism and alcohol consumption among social drinkers in two independent samples drawn from the United Kingdom general population. Those possessing one or more copies of the A1 allele consumed less alcohol than those homozygous for the A2 allele.…”

“…18 This may, therefore, explain the opposite direction of effect found by both ourselves and the Finnish study 18 between the DRD2 Taq1A polymorphism and social alcohol consumption compared to alcoholism. It has been suggested that substance abuse is one potential consequence of 'reward deficiency syndrome', 22 a defective functioning of normal reward pathways, with substance abuse resulting from a desire to seek enhanced stimulation of reward pathways.…”

“…18 This represents the first published report of an association between the DRD2 Taq1A polymorphism and social alcohol consumption (instead of alcoholic case status). Although the association was modest and mainly suggestive, the data indicated an association in the opposite direction to that typically reported between the A1 allele and alcoholism, with the A1 allele being associated with lower self-reported alcohol consumption.…”

“…We also extended on the previous report 18 by including male and female participants in order to determine whether any association between the DRD2 Taq1A polymorphism and social alcohol consumption is restricted to males only or exists in males and females.…”