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Alcoholic Genes

About half of Maori people have a genetic protection against alcoholism, Victoria University researchers has found. Their project, which has involved a new method for detecting variation in genes related to alcoholism, might ultimately lead to a simple blood test for genetic predisposition to alcoholism.

It has been known for some time that alcoholism tends to run in families, which implies a genetic link. The new study looked at genes involved in the way the liver processes alcohol, detecting genes which provide some protection against the development of alcoholism [An Alcoholic Disposition, November 1990].

DNA sequencing was carried out on three groups of New Zealanders: 10 Europeans, 10 people of Asian descent, and 10 Maori, using a "novel and reliable method" for detecting the genes involved in alcoholism. Differences between the groups were discovered.

"The work that we have reported, and the other research which has yet to be presented, emphasise the importance of studying the population of New Zealand rather than depending on the work of overseas groups," says PhD student Stephen Marshall. "New Zealand has a unique combination of ethnic groups who are going to show a number of different genetic and environmental susceptibilities to disease. Solely depending on the work of overseas researchers will lead to a reduction in the quality of medical care and public health in New Zealand can only suffer as a result."

Earlier researchers had shown that Asians have some genetic protection against alcoholism, and the Wellington group extended this work by demonstrating that the same protection is found in Polynesians, though to a lesser extent.

Asians' combination of genes leads to a build-up of acetaldehyde in the body during the processing of alcohol; acetaldehyde is a poison which can make the heart race, the face flush and the sufferer feel very ill. This reaction is enough to make most people moderate their alcohol intake or reject it altogether.

"The basis of the response is behavioural avoidance of alcohol rather than tolerance to alcohol," says project supervisor Dr Geoff Chambers.

European-descended people lack this protection and are therefore potentially much more vulnerable to becoming alcoholics though, as Chambers emphasises, other factors are involved and a genetic predisposition does not mean a person will necessarily actually become an alcoholic.

The Maori group showed up as having one of the two protective genes, which should give about half of this population some defence against alcoholism. Chambers said this finding was a surprise, given the high impact of alcohol on this sector of the population. It appears that Polynesians are the only ethnic group so far described anywhere in the world that have a high incidence of one protective gene without the other.

This finding is also interesting in that it gives some genetic support to the theory that Polynesians originated in Southeast Asia before beginning their sea voyages to the Pacific Islands and New Zealand.

While this study looked at only 10 people in each ethnic group, the results are consistent with wider studies in the project.

The next stage of the study is research on Maori and Pacific Islanders in alcoholism treatment programmes. It is expected to show that Polynesians in this group have a much lower level of the protective gene than the overall Polynesian population in New Zealand.

"We have not shown that alcoholism has a specific genetic cure, we have shown that genetic factors are important in influencing the risk of alcohol abuse," Marshall says. "As far as individuals are concerned, however, you need to drink alcohol to excess to become an alcoholic -- no genetic susceptibility can make you drink irresponsibly. Unlike genetic predispositions to cancer, genetic predisposition to alcoholism can remain dormant and never influence an individual's health or productivity, provided that they do not consume alcohol to excess."

Chambers also thinks scientists could develop a straightforward test needing only a drop of blood from a finger and one-day processing that would tell people whether they ran a high danger of becoming alcoholics if they decide to drink. But, he says, that would raise ethical questions about the handling of such information.