|A town weighs in for obesity researchers|
By Ricki Lewis
November 8, 2002
etween 1971 and 1998, more than a thousand people in a Massachusetts community willingly stood on the scale for science, revealing their heights and weights to researchers. That information has now been used to identify regions of the human genome that may contain genes involved in obesity. The study implicates three of the 33 chromosomal segments that other studies have identified as likely to contain weight-related genes.
What's new about this study is how the data were collected. The researchers took height and weight measurements on six occasions over nearly three decades. (Most studies use one-time measurements.) About 1,400 individuals participated in the most recent measurement a few years ago.
The researchers used data on body mass index (BMI)weight with height factored infor members of 330 families. The data came from the Framingham Heart Study, which was launched in 1948 to identify risk factors for cardiovascular disease by tracking a population's health over many years.
The Framingham study was founded by the National Heart Institute (now known as the National Heart, Lung, and Blood Institute) and is conducted in collaboration with Boston University. It has produced a number of noteworthy medical discoveries such as the finding, reported in 1960, that cigarette smoking increases the risk for heart disease.
In the new study, Larry D. Atwood, of the Boston University School of Public Health, and his colleagues used the Framingham data to link body weight to regions of chromosomes 6, 11 and 8. No specific genes have been identified, and at least 18 genes on these chromosomes are already candidates to influence obesity.
"We don't know which, if any, of these might be affecting BMI," says Atwood.
But the suspected regions of the genome are familiar to obesity researchers. The region on chromosome 6 contains a gene (or genes) that controls response to insulin, which plays a role in the storage of fats.
The region of chromosome 11 contains weight-related genes found in studies of the Pima Indians of Arizona. This population has a genetic predisposition to obesity and diabetes, and their weights increased significantly in the 1970s as diet and exercise habits changed. Today, half of the Pima population develops diabetes by age 35.
The third genome region, on chromosome 8, contains genes for lipoprotein lipase, an enzyme that breaks down fat in small blood vessels.
"People are interested in identifying genes for the variation of BMI, whether the sampling is for high or low BMI," says Hong-Wen Deng, who directs the genetics laboratory at Creighton University in Omaha, Nebraska, and studies low BMI in people with osteoporosis, a bone-thinning disorder. Deng suspects that variants of the same genes influence whether a person's weight is average or at either extreme.
Like other highly variable traits, body weight is likely to involve the action and interaction of many genes as well as environmental factors. "We are still years away from knowing which genes are important, how they function, and how they interact with each other and the environment," says Atwood.
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