The search for candidate genes for alcohol dependence has been inconclusive and much of the research has been confined to a few specific ethnic groups. A study published in the Indian Journal of Medical Research explored specific candidate genes for alcohol dependence in a north Indian male population.
210 males with alcohol dependence and 200 controls matched for age, gender and ethnicity were recruited to the study. Cases were diagnosed with Semistructured Assessment for Genetics of Alcoholism-II. Single-nucleotide polymorphism genotyping was done by real-time quantitative-polymerase chain reaction (PCR) using Taq Man assay (ABI 7500) fast real-time PCR system.
Both at the genotypic level and at allelic frequency, Met158 variant of catechol-O-methyl transferase (COMT) showed significant increase in alcohol dependent cases compared to controls. The frequency of heterozygous genotype (A/G) of gamma-aminobutyric acid receptor A1 (GABRA1) was significantly lower in the alcohol dependent participants compared to controls. Likewise, for GABRA2, the frequency of homozygous recessive genotype (G/G) was significantly higher in the control group.
There was no significant difference between the cases and the controls with respect to the 5-hydroxytryptamine (5HT) transporter long promoter region (5HTTLPR), cholinergic receptor muscarinic (CHRM2) and alcohol dehydrogenase 1B (ADH1B) genes. Aldehyde dehydrogenase (ALDH2) gene was found to be monomorphic in the study population.
The study indicates that COMT polymorphism confers risk and GABRA polymorphism acts as a protective genotype for alcohol dependence in Indian males.
Genes for alcohol metabolism, serotonin transporter and cholinergic receptor gene polymorphism may not contribute to alcohol dependence for the Indian population, the authors add.
Source: Candidate genes for alcohol dependence: A genetic association study from India. Malhotra S, Basu D, Khullar M, Ghosh A, Chugh N. Indian J Med Res. 2016 Nov;144(5):689-696.