Polymorphisms in alcohol metabolizing genes ADH2 and ADH3 and susceptibility to pancreatitis in alcoholics

Abstract

In both developed and developing countries, overuse of alcohol is a considered as the major cause of acute and chronic pancreatitis. Prolonged overconsumption of alcohol for 5–10 years typically precedes the initial attack of acute alcoholic pancreatitis. It is observed that only a minority (around 5%) of alcoholics develop pancreatitis. It is now established that the pancreas has the capacity to metabolize ethanol. Previous studies have shown that there are two major pathways of ethanol metabolism, oxidative and non-oxidative. Oxidative ethanol metabolism involves the conversion of ethanol to acetaldehyde, a reaction that is catalysed by aldehyde dehydrogenase (ADH) with contributions from cytochrome P450 enzyme (CYP2E1) and possibly also catalase. Genetic factors regulating alcohol metabolism could predispose in developing alcoholic pancreatitis (AP). We investigated the association of polymorphisms in ADH enzymes with the alcoholic pancreatitis in North coastal Andhra Pradesh. Patients with alcoholic pancreatitis (AP; n = 100), alcoholic controls (AC; n = 100), and healthy controls (HC; n = 100) were included in the study. Blood samples were collected from the subjects in EDTA coated vials. DNA was extracted and genotyping for ADH2 and ADH3 was done by PCR-RFLP (polymerase chain reaction restriction fragment length polymorphism). The products were analysed by gel electrophoresis. The frequency distribution of ADH3*1/*1 genotype was significantly higher in AP group (54%) compared with AC (35%), and HC (42%), and was found to be associated with increased risk of alcoholic pancreatitis. There was no statistically significant difference between the frequency distribution of ADH3*1/*1, ADH3*1/*2, and ADH3*2/*2 genotypes between AC and HC. There was no statistically significant difference between the frequency distribution of ADH2*1/*1, ADH2*1/*2, and ADH2*2/*2 genotypes in AP compared with AC and HC. This study shows that carriers of ADH3*1/*1 individuals consuming alcohol are at higher risk for alcoholic pancreatitis than those with other genotypes such as ADH3*1/*2 and ADH3*2/*2.