Device helps find fat gene
SCIENTISTS USE SILICON VALLEY TOOL TO STUDY OBESITY TENDENCY
By Steve Johnson
Mercury News
Posted on Fri, Apr. 14, 2006
Using a gene-mapping tool developed by Silicon Valley's Affymetrix, Boston scientists reported Thursday they have found that one in 10 people carry a common genetic variation that may make it particularly tough for them to keep their weight down.
These unlucky souls have a small piece of DNA on one chromosome that the other 90 percent do not have, according to the study of 923 people.
Scientists have studied obesity for years and have found other evidence that made them suspect heredity played a key role in obesity. But they weren't able to precisely identify the genetic factors involved until gene-mapping tools were developed in recent years that could look at the entire genome -- 3 billion DNA molecules -- in detail.
It's unclear if the genetic variant involves one or more genes, and more work will have to be done to determine that, said Michael Christman, chairman of Boston University Medical School's department of genetics and genomics, who worked on the study published Thursday in the journal Science.
The scientists identified the genetic variation in a group of 923 people who were part of the Framingham Heart Study, a long-running study that has followed families through generations to look at various health issues. They found that obese people in the study all shared a single molecule in their DNA that was different from the other 90 percent of people in the study.
From there, they collaborated with more researchers to test the findings in other populations. Of the 10 percent who had the genetic variation, 22 percent more were likely to be obese regardless of their gender and age. In follow-up studies, the researchers found the same genetic pattern in four out of five independent groups, including people of Western European ancestry, African-Americans and children.
Christman also said it's likely other genetic variations also may play a role in obesity. But given the gene-mapping technology pioneered by Affymetrix that's also available from others, he added, locating all of those genetic variations probably can be done in a few years.
Christman stressed that unhealthy eating and failure to exercise are probably just as responsible for obesity as are genes. But given the hereditary factors involved in many other people, he added, it may be possible to develop drugs to combat the genetic variations that contribute to obesity.
Obesity has become a major target for drug treatment now that 30 percent of U.S. adults, or 60 million people, are obese.
Previous studies have found evidence suggesting obesity has a genetic basis. But Judith Stern, professor of nutrition and internal medicine at the University of California-Davis, and vice president of the American Obesity Association, said the Boston University study is the first one she knows of that has clearly identified a genetic factor in a large segment of the population. She said the discovery should help ease some stereotypes about obesity.
``If somebody is obese, we say, `if you just eat less and exercise more, you won't be overweight,' '' she said. ``We actually think it's a moral failing. Here in this study, they say, `Hey, it's a genetic variation.' . . . We should stop being holier than thou.''
The Affymetrix genome tool, called a 100K array, enabled scientists to effectively compare, side by side, the genetic differences of everyone in the study, and then correlate those differences to their weight.
While the genetic mapping array used by the Boston scientists was relatively advanced, enabling scientists to sift through 100,000 gene variations, it isn't the most cutting-edge technology available from Affymetrix. The Santa Clara company, which was founded in 1991, unveiled an array in September that is five times as powerful.
Tom Willis, Affymetrix's vice president of DNA product marketing, said the Boston study should help validate the usefulness of the company's arrays. But he noted that the devices already are widely used by scientists and drug companies examining everything from the causes of cancer to the potential toxic side effects of medicines under development.
``This technology really has been adopted in a major way by a large number of researchers,'' Willis said.
Contact Steve Johnson at sjohnson@mercurynews.com or (408) 920-5043. |
