Blame Sire for Kid's Spare Tire

Dad's gene may lead to obese child, says study

MONDAY, Aug. 13, 2001 (HealthDayNews) -- Some dads may be giving their children a genetic one-way ticket to Fat City.

A variation of a gene inherited only from a father may raise a child's risk of early-onset obesity, say French and American researchers in the Aug. 13 issue of the journal Nature Genetics.

Previous studies had suggested to the researchers that a gene variant called class I INS VNTR might be linked to childhood obesity.

Every parent passes on one copy, or allele, of a gene to a child. In this case, either parent can pass along a class I INS VNTR or a class III INS VNTR.

The researchers studied genetic samples from 402 children who became obese before age 6 and found that children who inherited the class I INS VNTR variant from their fathers were 1.8 times more likely to become obese in childhood.

However, inheriting the class I INS VNTR variant from mothers did not seem to raise the risk of obesity. "It's surprising that you'd see a parent-of-origin effect. That's not a very common finding," says co-author Danièle Fallin, an assistant professor of epidemiology at Johns Hopkins University's School of Public Health in Baltimore, Md.

In the study, which involved children of Mediterranean and central European descent, Fallin and her colleagues found the frequency of the class I INS VNTR allele put 65 percent to 70 percent of children at risk of inheriting the gene variant.

"This is a rather common allele," says Fallin. "If a lot of people already have that allele, and it does confer some increased risk when it comes from the father, then that could potentially affect quite a few children." However, she says more studies are needed of children from different populations.

The researchers now can only speculate about how the gene variant affects childhood obesity.

Fallin says, "This gene region has previously been shown to regulate expression of insulin. It's also been shown that during fetal development, it looks like only the paternal copy of this region is expressed. One working theory that we have is that if that's true, then it may make sense that the father's genotype is actually influencing things."

Fallin says the finding will help scientists understand the mechanisms that contribute to childhood obesity, especially what happens during fetal development. "That can tell us ways that we may be able to prevent [obesity] or treat children in ways so that the complications that arise because of early-onset childhood obesity can be dealt with sooner rather than later."

Fallin says other studies have discovered rare gene mutations in disorders primarily characterized by obesity, such as a deficiency in leptin, a protein that seems to manage the body's supply of fat.

Dr. Barbara Dennison, an associate professor of clinical pediatrics at Columbia University in New York City, says several studies have suggested that genetics play a role in childhood obesity.

"Overweight parents are more likely to have overweight kids," says Dennison, although she says non-genetic factors play a large role too. "Right now, there's an epidemic going on in the United States, as well as worldwide, and genetics hasn't changed," says Dennison.

Roughly 25 percent to 30 percent of U.S. children are obese, and the percentage is rising steadily. Lack of exercise, eating too much or a diet high in fats all are risk factors for childhood obesity, say experts.

Overweight children are highly likely to be overweight adults and have a higher lifetime risk of heart disease, diabetes, high blood pressure, kidney problems and even certain cancers.

What To Do:

For more information about childhood obesity, check this publication from the American Academy of Family Physicians.

The National Institutes of Health provide information about the health implications of obesity.

You can also check the Healthy Eating Healthy Living Program or KidSource.com.

SOURCES: Interviews with M. Danièle Fallin, Ph.D., assistant professor, Department of Epidemiology, School of Public Health, Johns Hopkins University, Baltimore, Md., and Barbara A. Dennison, M.D., associate professor of clinical pediatrics, Columbia University, New York City, and senior research scientist, Bassett Healthcare Research Institute, Cooperstown, N.Y.; Aug. 13, 2001, Nature Genetics
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