By Sean Henahan, Access Excellence

TORONTO, ONTARIO Can't button that top button? Maybe you need new genes. Canadian researchers have identified a gene associated with body shape in men, but not in women. This is the first gene to be identified with an association with body shape.

Dr. Robert Hegele and colleagues at St. Michael's Hospital, Toronto, Ontario, studied a large group of people belonging to the Hutterite Brethren, a utopian community of German Anabaptists established more than 100 years ago by the visionary Joseph Hutter.

The Hutterite community totals around 30,000 members in Western Canada and the Northwestern US. All modern Hutterites are descendants of less than 100 founder members of the exclusive group. This affords an excellent opportunity to detect genetic defects. The Hutterites eat a diet high in animal fat, prohibit smoking but permit alcohol.

Dr. Hegele evaluated 846 Hutterite men and women for variations in 11 genes. In the men, DNA polymorphisms in a gene on chromosome 1 called AGT were associated strongly with variations in waist-hip ratio, a measure of abdominal obesity. The AGT gene codes for angiotensinogen, a substance involved in the constriction of blood vessels.

The researchers believe the gene is associated with at least on inch of a man's waistline measurement. However, it is unlikely the AGT gene plays a direct role in the distribution of body fat, the researchers note. Rather, the believe the AGT gene may be a marker for another gene that is responsible for patterns of fat storage

No such variations in the AGT gene were seen in the Hutterite women. "The reason for this is not clear," said Dr. Hegele. " It could be that variation in the waist-to-hip ratio among women is determined more by environmental factors than it in men. Hormonal and genetic factors could also be at work."

The gene in question explains only a small proportion of the total variation in this trait, notes Dr. Hegele, emphasizing that diet, exercise and other genes also contribute to waist-hip ratio.

"Knowledge about the genetic aspects of weight is progressing at an incredibly rapid pace. A year ago, the closest we could come was an obesity gene in mice. recently, however, French and American researchers looking for a diabetes gene announced they had found a human gene which may regulate metabolism in populations with a high proportion of obesity. Today we can say we have a gene which- regardless of weightappears to influence how fat is distributed in the body. I'm confident that before much longer we'll have a very good idea of which genes are involved in the regulation of weight, metabolism and fat distribution, and how they interact with one another and the environment," he said.

The findings in this study tie in with epidemiologic observations that "apple shaped" men, i.e., those who accumulate fat around the waist, are at greater risk for heart attack than are "pear shaped" men, those who accumulate fat lower on the body. There is a growing consensus among health professionals that the waist-hip ratio is a better predictor of cardiac risk than the traditional body-mass index ( a ratio of weight to height).

"Finding this gene is a huge step forward in understanding the relationship between our genetic make-up and our environment and lifestyle choices. This is particularly important for the prevention of heart disease and stroke," said Dr. Marlene Rabinovitch, Vice-president of research at the Heart and Stroke Foundation of Ontario.

Having genetic tests available that would help identify people with a tendency to become "apples", with its associated risk of high blood pressure and heart disease would revolutionize risk-reduction programs, she said.

Dr. Hegele's study appeared in Circulation, Sept. 95.

Science Updates Index

What's News Index

Feedback