Study Casts Doubt on Finding of Gene Linked to Alcoholism
WASHINGTON — Findings released Tuesday cast doubt on the much-publicized discovery of a gene linked to severe alcoholism, but California scientists who conducted the original research insist that their discovery is solid.
Government researchers said their study of 40 alcoholics and 127 other patients did not find widespread or consistent ties between alcoholism and a type of gene known as the dopamine-2, or D-2, receptor gene.
“Even though we have not found a linkage to this particular gene, it is wrong to conclude that there is not a genetic influence in alcoholism. What this tells us is that we may have a long way to go to identify the specific gene or genes,” said Dr. David Goldman of the National Institute of Alcohol Abuse and Alcoholism.
Pinpointing the gene or genes associated with alcoholism could lead to better ways to identify people at risk of becoming alcoholics, as well as a greater understanding of the underlying causes of the disease, which in turn could lead to new treatments and preventive measures.
In April, a team headed by Dr. Ernest Noble, director of the UCLA Alcohol Research Center, reported that the D-2 receptor gene was present in the brains of nearly 70% of 35 people who died of alcohol-related illness, compared to 20% of deceased non-alcoholics.
That finding, published in the Journal of the American Medical Assn., represented the first reported link between a particular gene and alcoholism, although there has been a growing body of evidence suggesting that heredity plays a role in the disorder.
Scientists believe that dopamine--a brain chemical--could be associated with “pleasure seeking” that allows alcohol to stimulate brain cells in a way that results in a sense of enjoyment. A defect in the D-2 receptor gene may interfere with the dopamine response so people who have the gene need to drink more alcohol to get the same pleasurable effect.
However, Goldman and his colleagues said their work failed to uncover any strong tie between the D-2 receptor gene and susceptibility to alcoholism. “Close linkage of the (dopamine) gene to alcoholism was ruled out,” the researchers wrote in their study.
The conflicting results indicate that “there is either a subgroup of alcoholics that have mutation in the D-2 receptor gene” or that Noble’s finding represents a statistical fluke, Goldman said.
However, Noble said some results of the new study could be interpreted to support his findings.
The new study showed the type of D-2 receptor gene that Nobel identified was more common in severe alcoholics, with about 45% having the gene, he said. In contrast, only about 30% of moderate alcoholics had the gene. That supports the likelihood that the gene plays a role in severe alcoholism , he said.
