Association between mu opioid receptor gene polymorphisms and alcohol dependence in a Japanese population

Abstract

Alcohol dependence is an addiction that causes psychological and physical dependence and makes it difficult for those affected to control their intake of alcohol. The μ (mu), δ (delta) and κ (kappa) opioid receptors are thought to be associated with the development of alcohol dependence. Research has shown that μ opioid receptor knockout mice exhibit reduced alcohol consumption and reduced preference for alcohol. In this study, we confirmed whether mu opioid receptor (OPRM1) polymorphisms (IVS2+691C/G, −172G/T and −1748G/A) indeed have an effect on alcohol dependence formation in 64 patients, with 73 healthy people used as a control group. We compared the genotype, allele, carrier (minor allele carriers versus major allele homozygous carriers) and haplotype frequencies between these groups. In addition, the 1510A allele of acetaldehyde dehydrogenase 2 (ALDH2) polymorphism (1510G/A) causes poor metabolism of acetaldehyde, a major metabolite of alcohol. We also focused on ALDH2 1510G/G (ALDH2 *1/*1) carriers in the subjects. Three OPRM1 and one ALDH2 genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. No significant differences were found in the frequency of OPRM1 polymorphisms between those suffering from alcohol dependence and the control group. We concluded that the three OPRM1 polymorphisms (IVS2+691C/G, −172G/T and −1748G/A) were not likely to be risk factors for alcohol dependence in a Japanese population. This report is the first in a Japanese population. Nevertheless, further analysis of the opioid receptor gene in a large sample size is required.