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Diet affects genetic expression, study finds

3 August 2006: In a study that shows more than ever you are what you eat, US scientists say they have changed the coat colours of baby mice simply by altering their mothers' diets.

The study shows that common nutrients can influence which genes turn on and off in a developing fetus, and help explain some of the factors that decide which genes "express" and which remain silent.

Writing in Friday's issue of the journal Molecular and Cellular Biology, the scientists at Duke University Medical Centre said they changed the colour of baby mouse fur by feeding pregnant mice four supplements - vitamin B12, folic acid, choline and betaine.

Mice given the four supplements gave birth to babies predominantly with brown coats. Pregnant mice not fed the supplements gave birth mostly to babies with yellow coats.

Careful study showed the extra nutrients turned down expression of a gene called Agouti, which affects fur color.

"We have long known that maternal nutrition profoundly impacts disease susceptibility in their offspring but we never understood the cause-and-effect link," said Randy Jirtle, a professor of radiation oncology at Duke who directed the study.

"For the first time ever, we have shown precisely how nutritional supplementation to the mother can permanently alter gene expression in her offspring without altering the genes themselves," he said in a statement.

The findings have not been shown in humans but the researchers said there is much support for the idea that nutrition can affect gene expression in people.

Several studies have shown, for instance, that women who eat a poor diet while pregnant have children who grow up with a tendency to diabetes and heart disease.

This study could help explain that. The Agouti gene not only affects coat color but also metabolic factors involved in diabetes and heart disease.

Mice with overactive Agouti genes tend to be obese and susceptible to diabetes because the protein controlled by the gene affects one brain signal involved in appetite.

"Diet, nutritional supplements and other seemingly innocuous compounds can alter the development in utero to such an extent that it changes the offspring's characteristics for life, and potentially that of future generations," said researcher Rob Waterland, who worked on the study.

Nutrition is likely to be one of the "environmental factors" that decides which genes turn on and which stay silent.

Everyone inherits two copies of each gene - one from each parent. For most functions, only one gene expresses while the other is silent.

This idea, first explained by 19th century genetic pioneer Gregor Mendel with his experiments on green and yellow peas, can explain why two brown-eyed parents can have a blue-eyed child - who may be expressing a grandparents' gene that was silent in the parent.

"Our study demonstrates how early environmental factors can alter gene expression without mutating the gene itself," said Waterland said.