Further clarification of the contribution of the ADH1C gene to vulnerability of alcoholism and selected liver diseases

The alcohol dehydrogenase 1C (ADH1C) subunit is an important member of the alcohol dehydrogenase family, a set of genes that plays a major role in the catabolism of ethanol. Numerous association studies have provided compelling evidence that ADH1C gene variation (formerly ADH3) is associated with altered genetic susceptibility to alcoholism and alcohol-related liver disease, cirrhosis, or pancreatitis. However, the results have been inconsistent, partially, because each study involved a limited number of subjects, and some were underpowered. Using cumulative data over the past two decades, this meta-analysis (6,796 cases and 6,938 controls) considered samples of Asian, European, African, and Native American origins to examine whether the aggregate genotype provide statistically significant evidence of association. The results showed strong evidence of association between ADH1C Ile350Val (rs698, formerly ADH1C *1/*2) and alcohol dependence (AD) and abuse in the combined studies. The overall allelic (Val vs. Ile or *2 vs. *1) P value was 1 x 10(-8) and odds ratio (OR) was 1.51 (1.31, 1.73). The Asian populations produced stronger evidence of association with an allelic P value of 4 x 10(-33) [OR 2.14 (1.89, 2.43)] with no evidence of heterogeneity, and the dominant and recessive models revealed even stronger effect sizes. The strong evidence remained when stricter criteria and sub-group analyses were applied, while Asians always showed stronger associations than other populations. Our findings support that ADH1C Ile may lower the risk of AD and alcohol abuse as well as alcohol-related cirrhosis in pooled populations, with the strongest and most consistent effects in Asians.