New Test Could Mean Early Warning

Two research teams have identified genetic material strongly associated with a significantly increased risk of heart disease.

About one in every four Caucasians are thought to carry the genetic variants located on chromosome 9, and a test to identify those who are at high risk of heart attack could be available by the end of this year.

The discoveries are even more interesting because the same cluster has recently been strong. ly implicated in raising diabetes risk.

Implications

"This is an important finding, because it was replicated in different populations around the world," added Canadian scientist Dr. Ruth McPherson, director of the Ottawa Heart Institute's lipid clinic and lipid research laboratory, who led one research effort.

The two separate reports do not pinpoint specific genes. Instead, they cite what are called single nucleotide polymorphisms (SNPs)—slight variations in the sequence of units that make up the molecule of DNA that carries genetic information.

One report, led by scientists at an Icelandic biotechnology company, and one report from McPherson's group in Canada, cites two different genes. All are clustered together in a region of chromosome 9.

Regardless of where the study participants originated-Canada, Iceland or the United States-the SNPs bumped up heart risk. For example, people carrying the SNP cited in the Icelandic study had about a 60% raised risk for heart attack compared with noncarriers, while people carrying the two SNPs in the Canadian study had a 30% to 40% increased risk of heart disease.

"The discovery that these SNPs can impact heart risk remains puzzling, because they do not involve specific genes" McPherson said. "However, they do lie near two tumor-suppressor genes known to be associated with cell proliferation, aging and death. There might be other explanations for the association.

"They may be in a region that regulates the activity of genes," McPherson added. "It is possible that the region regulates genes that are a bit further away. But the finding so far does not tell us anything about their mechanism of action."

Still, there is a kind of excitement about such unexpected findings that could lead to genes with entirely different pathways," McPherson said.

Part of the excitement is that the genetic factors identified by the studies do not seem to be linked to known risk factors. That opens the possibility of new preventive measures aimed at whatever in the SNPs influences heart risk.

Another bonus found by a team led by Dr. Francis Collins, director of the US National Human Genome Research Institute, recently reported that the same genetic material is also highly linked to a boost in diabetes risk.

The Next Step

"The most important story here is that not only does this variant impose the risk of heart attack, but it imposes greater risk on younger people," said Dr. Kari Stefansson, a neurologist, formerly with Harvard Medical School. "For men under the age of 50 and women under the age of 60, it doubles the risk of heart attack."

A test based on the finding will be available probably before the end of this year, Stefansson said. "We plan to launch it ourselves." Regulatory approval is not required.

"The test would be aimed at two groups of people—those with known risk factors such as high cholesterol, high blood pressure and diabetes, and those whose physicians wanted to screen them for risk. When someone is found to carry two risk-associated SNPs, those are the people you want to follow meticulously," with close attention to risk factors, Stefansson said.

"Ultimately, such a test could be added to the whole package that we use to assess risk," McPherson said.