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The Alcoholism Protection Gene
Alcohol dehydrogenase is an enzyme found in the liver that allows humans to drink alcoholic beverages. This enzyme converts alcohol to acetaldehyde (PDB 2003). The genes ADH1, ADH2, and ADH3 encode for the alpha, beta and gamma versions of alchol dehydrogenase respectively (OMIM). Recent studies have found a variant form of ADH2 refered to as ADH2*2. This variant metabolizes alcohol in a way that leads to a more disturbing reaction. Humans with this allele appear to have lower levels of alcohol consumption and dependence (OMIM).
For more information on Alcohol Dehydrogenase click here.
To see PDB's salute to their molecule of the month, Alchohol Dehydrogenase click here.
The Popular Press:
The Jerusalem Post "Ashkenazi gene linked to lower alcoholism" by Judy Siegel, September 18, 2002
This article begins with a quick opening paragraph stating the simple fact that "Researchers at Columbia University in New York have linked a rare gene variation found significantly more frequently in Jews with a reduced rate of clinical dependence on alcohol." This opening remark in an Israeli newspaper will most likely catch the attention of numerous readers.
As the article continues the author explains that the recent scientific article supports a previous study conducted by an Israeli research team. In both studies Israelis with the ADH2*2 gene variant consumed less alcohol. The author explains in simple terms the function of ADH2 and its role in alcohol metabolism. The author also indicates that this study reinforces the idea that genetics and not religous practices cause Jews to consume less alcohol. Through this statement the author implies that genetics have a greater influence on the habits of Jews than does their environment.
Towards the end of the popular press article the author begins to give a more accurate description of the scientific article. The author discusses the findings that the ADH2*2 allele had different outcomes among Ashkenazi and Sephardic Jewish populations. The author also states the findings that recent Jewish immigrants from the former Soviet Union to Israel with the ADH2*2 allelic variation have the highest level of alcohol dependence. This finding indicates that the environment experienced by the Russian Jews overcame their genetic protection against alcoholism.
The Scientific Article:
"Alcohol Dependence Symptoms and Alcohol Dehydrogenase 2 Polymorphisms: Israeli Ashkenazis, Sephardics, and Recent Russian Immigrants. By Deborah Hasin et al. Alcoholism: Clinical and Experimental Research. Vol. 26, No. 9, September 2002.
The introduction of this scientific article discusses alcoholism among Jews and the function of ADH2. Originally, the Jewish culture's low alcoholism rates were attributed to their religous practices. Recent research, however, has begun to connect low rates of alcohol consumption with genetic factors. The majority of this research indicates a relationship between alcohol consumption and the alcohol dehydrogenase genes (ADH) found on the fourth chromosome. Polymorphisms of the ADH2 gene can lead to the formation of isozymes with varying catalytic properties. The authors discuss a recent study that found a connection between low levels of alcohol consumption among Jews and the prevalence of the ADH2*2 gene. They then explain that, unlike previous studies, thier study examines alcohol dependence among three groups of Israeli Jews; Ashkenazi's, of European origin, recent Ashkenazi immigrants from the former Soviet Union, and Sephardics of Middle Eastern and Northern African origin.
In the methods section the authors describe the methods utilized for determining alcohol dependence. This study used the DSM-IV alcohol and abuse criteria created by the Alcohol Use Disorders and Associated Disabilities Interview Schedule. These interview formats used seven symptoms in both past and current time frames in order to diagnose a person with DSM-IV alcohol dependence. The studies were performed on 25 Jews of Sephardic origin, 23 Ashkenazi's of European origin, and 27 recent Russian Ashkenazi immigrants. Genotypes for each subject were also found.
Surprisingly the researchers discovered a higher prevalence of the ADH2*2 allele among Sephardic Jews. In contrast the Ashkenazi Jews of both European and Russian decent had the same allele frequencies. The researchers found 5.3% of all the individuals homozygous dominant (ADH2*1/*1) to have alcohol dependence, 4.2% of heterozygotes (ADH2*2/*1) to have alcohol dependence and 0% of all homozygous recessive (ADH2*2/*2) to have alcohol dependence.
While all the alcohol dependence levels across all three groups were consistent with the genotype analysis the surprising data was found when the three groups were examined individually and contrasted. All three groups consisted of community members with numerous "current or past drinkers." The variability developed when extreme alcohol consumption was studied. The researchers found the ADH2*2 allele to be protective against severity of alcohol dependence symptoms but discovered a need to control for environmental factors. Amongst the recent Russian immigrants the ADH2*2 allele was not protective against peak lifetime alcohol consumption. In contrast to the non-Russian Ashkenazi's and Sephardics, the recent Russian immigrants spent the majority of their lifetime in Russia, where the alcohol consumption rate is much higher than Israel. This finding suggests that in many cases the environmental influences were stronger than their genetic protection.
Through its investigation of three separate Jewish groups, this study shows that the affects of ADH2*2 are consistent among individuals from many origins. They also demonstrate the need for further "studies of the gene-environment interactions [which] can provide valuable general information on the relative contribution of genetic and environmental causes." The researchers indicate the need for further investigations involving larger sample sizes.
The popular press article does a fair job of expressing the outcome of the scientific article in clear and concise manner. This article, however, attempts to catch the attention of its readers by indicating the presence of a link between an Ashkenazi gene and lower rates of alcoholism. The author makes this statement as if it were thoroughly proven. Throughout the first two paragraphs of the article the author makes no mention of possible environmental influences or the need for further studies. In the fifth and sixth paragraphs the author finally discusses a few of the researcher's methods. In these closing statements the different levels of protection among Ashkenazi, Sephardic and recent Russian immigrants are discussed. In the final two paragraphs the author acknowledges the fact that the recent Russian immigrants had higher rates of alcohol dependence due to their environmental background.
In this manner of presentation the popular press article misses much of the importance of the scientific article. While the article does mention some of the details of the research it does not do so until the last few paragraphs. The author focuses on the more catchy conclusions in order to attract readers. The statements about possible environmental relationships are only added at the end and appear to be unimportant aspects of the research. The author also includes no information on the scientists' methods of deciding what constitutes alcohol dependence.
After comparing the popular press article to the scientific article, it is apparent that the articles' purpose is to attract readers and not to inform them. While the article does touch on many aspects of the scientific research it only covers these ideas at the end of the article when most readers have quit reading. Through its manner of presentation the popular press article draws readers in only to leave them without the full story.
To view a chime image of the alcohol dehydrogenase 2 protein click here.
To read the abstract of the scientific article click here
"Alcohol Dehydrogenase 1B, Beta Polypeptide; ADH2" Online Mendelian Inheritance in Man. Accessed 2003September 14.
Goodsell, D.S. 2003 "Alcohol Dehydrogenase." Protein Data Bank. Accessed 2003 September 14. http://nist.rcsb.org/pdb/molecules/pdb13_1.html
Hasin, D., E. Aharanovich, X. Liu, Z. Mamman, K. Matseoane, L.G. Carr, and T. Li. September 2002. "Alcohol Dependence Symptoms and Alcohol Dehydrogenase
2 Polymorphisms: Israeli Ashkenazis, Sephardics, and Recent Russian Immigrants." Alcoholism: Clinical and Experimental Research. 26 (9). 1315-1321.
Siegal, J. September 18, 2002. "Ashkenazi gene linked to lower alcoholism" The Jerusalem Post. 4. Lexis Nexis. Accessed 2003 September 7.