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Alcohol-Loving Rats Live Longer than Teetotalers

By Nancy Touchette

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Alcoholism

The effects of alcohol on human health and longevity are contradictory. Alcohol consumption can be either harmful or helpful, depending on how much a person drinks. Now a new study in rats weighs in with a surprising finding: Rats bred to prefer alcohol live longer than their non-imbibing counterparts.

People who drink large amounts of alcohol tend to die earlier and have more health problems than those who don’t. However people who drink more moderately—a glass of wine at dinner, for example—have a lower incidence of heart disease and tend to live longer than those who drink no alcohol at all. Some attribute this effect, sometimes called the French paradox, to beneficial substances present in red wine.

But the new study, conducted by researchers at the Public Health Institute in Helsinki, Finland, suggests that, at least in rats, the genetic predisposition to drink may be a more important predictor of longevity than the amount of alcohol consumed.

“What is exciting is that there was a huge difference between how long the alcohol-preferring rats lived compared to the alcohol avoiders, regardless of whether they actually drank alcohol,” says David Sinclair, who led the study.

But why should animals genetically developed to drink alcohol live longer than those bred to avoid alcohol?

“It’s likely that some of these genes have other effects,” Sinclair says. “Genes that make you more likely to drink may also have some other effects that are good for you.”

The Ratman. A researcher’s artistic interpretation of how rats help human alcohol studies.
For humans, the finding raises the question, why do human populations still harbor genes that predispose individuals to alcoholism if alcohol is bad for health?

The alcohol-preferring rats lived longer than the avoiders, whether they were offered only water or only alcohol throughout their lives. Over the course of 24 months, rats bred to avoid alcohol had a death rate that was 3.6 times higher than that of rats bred to prefer alcohol.

The researchers were also surprised to find that the amount of alcohol consumed by rats did not seem to affect their longevity. Among the two groups of rats, the incidences of most health problems were similar, whether they drank alcohol or water.

However, rats that lived for 24 months had more malignant tumors if they were given alcohol compared to those that received water. This was true for both groups of rats—those bred to like alcohol and those bred to avoid it. Rats given alcohol also had more brain damage, but that did not affect their survival rate.

Sinclair suspects that high alcohol consumption may affect rats less than humans because alcohol may be metabolized differently in rats than in humans.

If given a choice, rats bred to prefer alcohol drink 10 times as much as those bred to avoid it. But the researchers don’t know how closely these rats serve as a model for people with alcoholism. The rats may resemble social drinkers at a cocktail party rather than hard-core alcoholics, according to Petri Hyytiä, a colleague of Sinclair.

“These rats drink enough to be over the legal limit, but they don’t lose control like many humans do,” says Hyytiä. “They never become falling-down drunk.”

According to Hyytiä, people who drink moderate amounts of alcohol may have a particular set of gene variations that make them want to drink moderately. It may be these underlying genes and not the amount of alcohol they drink that contributes to longevity.

The researchers are now looking for differences in gene sequences and gene activity that might help explain their surprising results.

In separate research, scientists have identified many candidate genes associated with alcohol addiction, but no single genes have been identified that can predict alcoholic behavior. Most recently a gene called GABRG3, which helps regulate the metabolism of a key brain chemical, has been associated with alcoholism in humans.

M. Sarviharju, et al. Survival of AA and ANA rats during lifelong ethanol exposure. Alcohol. Clin. Exp. Res. 28 (January 2004).
Dick, D.M. et al. Association of GABRG3 with alcohol dependence. Alcohol Clin. Exp. Res. 28, (January 2004).

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