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GENE VARIANT AFFECTS ALCOHOL "HIGH," FAMILIAL ALCOHOLISM RISK
People with a gene variant that enhances the brain's response
to opioids appear to get a larger "kick" from alcohol than people
without this variant, according to new research. In addition, these
individuals are much more likely to have a family history of
alcoholism.
Alcohol releases natural opium-like chemicals called opioids,
which in turn influence the dopamine system. This system, says
researcher Kent Hutchison, is involved in cravings and the desire
to use alcohol or drugs. "Thus," he says, "it is alcohol's effects on
endogenous [naturally occurring] opioids that act as the gateway
through which alcohol may influence this system." He notes that
children of alcoholics have lower levels of opioids called beta-
endorphins than children of non-alcoholic parents, and that young
adults with a family history of alcoholism show larger increases in
beta-endorphin levels when they drink than peers without such a
family history.
To further investigate the role of opioids in alcoholism,
Hutchison and Lara Ray studied 20 male and 18 female college
students who were moderate to heavy drinkers, dividing them into
two groups. One group possessed one copy of the "G" allele (gene
variant) of a gene encoding for mu-opioid receptors and one copy
of the "A" allele. The other group had two copies of the "A" allele.
The G allele causes receptors to bind three times more tightly to
beta-endorphins, meaning that a nerve cell with the G allele is
much more sensitive to these chemicals.
Hutchison and Ray administered intravenous doses of alcohol
to the participants and queried them about their reactions. The
researchers found that those with the G allele reported higher
levels of intoxication, stimulation, sedation, and happiness when
they drank than did those with two A alleles. In addition,
they found that individuals with one G allele were nearly three times
more likely than those with two A alleles to have family histories of
alcoholism.
In separate research, David Oslin and colleagues found that
individuals with at least one G allele appear to respond better to
treatment with naltrexone, a drug that blocks the effects of opioids,
than those without this allele. This makes sense, say Hutchison
and Ray, because "a medication that reduces feelings of euphoria
after alcohol consumption may be more successful among
individuals with a genetic predisposition to greater feelings of
euphoria after consuming alcohol."
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"A polymorphism of the mu-opioid receptor gene (OPRM1) and
sensitivity to the effects of alcohol in humans," L. A. Ray and K. E.
Hutchison, Alcoholism: Clinical and Experimental Research, Vol. 28,
No. 12, December 2004, 1789-95. Address: Kent E. Hutchison,
Department of Psychology, University of Colorado, Campus Box 345,
Boulder, CO 80309-0345, KentH@psychology.colorado.edu.
-- and --
"A genetic difference at the opiate receptor gene affects a person's
response to alcohol," news release, Alcoholism: Clinical and
Experimental Research, December 14, 2004.
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