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A Mouse of a Different Color

What mom eats can change coat color in offspring

(HealthDay is the new name for HealthScoutNews.)

FRIDAY, Aug. 1, 2003 (HealthDayNews) -- For years, nutritionists have been saying you are what you eat. Well, you may be what your mother ate, too.

At least if you're a mouse, a new study says.

Duke University researchers found that when they gave pregnant mice supplements of four different nutrients, it changed the color of the fur of their offspring. It may also have reduced the babies' risk for obesity, diabetes and cancer, the scientists say.

"Early nutritional changes can clearly effect adult phenotypes," says senior researcher Randy Jirtle, a professor of radiation oncology at Duke University Medical Center.

Results of the study appear in the Aug. 1 issue of Molecular and Cellular Biology.

Jirtle and his colleagues, including lead author Rob Waterland, a research fellow at Duke, gave the mouse moms-to-be dietary supplements of folic acid, vitamin B-12, choline and betaine. None of the mice was deficient in these nutrients before the study.

According to Jirtle, the fur on these mice is normally yellow, brown or a mixture of the two, like a Calico cat. Mice with yellow fur have a higher risk for obesity, diabetes and cancer, Jirtle adds.

Mouse mothers who received the supplements gave birth to offspring with predominantly brown fur, while those who didn't receive the supplements gave birth to babies with mostly yellow fur.

Jirtle says a change in the way one gene expresses itself is responsible for the change in fur color. The gene, known as Agouti, remains unchanged by the added nutrients, but the messages it sends out to the body are partially blocked through a process called methylation.

Methylation occurs when a "methyl group" -- a cluster of four atoms -- attaches to a gene. Jirtle likens the process to boulders being thrown into the road, which blocks the gene from being expressed. Methylation can be good or bad, depending on what gene expression it is blocking. For example, if a methyl group blocks the gene that suppresses the growth of tumors, cancer could result.

In the mice, methylation occurred very early in the pregnancy.

Jirtle says the results aren't directly applicable to humans. He says while humans also have an Agouti gene, it isn't identical to the one in the mice.

What does concern him is the dramatic effects the researchers were able to achieve with dietary supplements such as folic acid -- which are routinely used in pregnant women to reduce the risk of birth defects.

He says that while the results achieved in the mice will likely reduce their risk of disease, scientists don't know what vitamins might cause good gene expression to be methylated.

"We make the assumption that folic acid supplements in people that don't need them are safe. We don't know what the implications are though. I'm not saying it causes problems, but I can't say it's innocuous either," Jirtle says.

Nutritionist Jyni Holland of New York University Medical Center says people shouldn't worry about their vitamin supplements because of the results of one study.

"We've known that most vitamins and nutrients have an effect on the molecular level," says Holland. "This study may help us understand just how much nutrition can affect us on the cellular level. But just because it works in a mouse, doesn't mean it will work in humans."

Jirtle says the best advice is what you've probably been hearing from your mother all along -- stick to a healthy diet and be sure to eat your vegetables.

More information

The March of Dimes offers these tips on preparing for a healthy pregnancy. To learn about eating a healthful diet and staying fit, visit the American Heart Association's Nutrition Web site.

SOURCES: Randy Jirtle, Ph.D., professor, radiation oncology, Duke University Medical Center, Durham, N.C.; Jyni Holland, M.S., R.D., nutritionist, New York University Medical Center, New York City; Aug. 1, 2003, Molecular and Cellular Biology
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