Gene Increases Heart
Disease Risk in Blacks

NEW YORK (Reuters Health) - A specific version of a gene involved in blood clotting greatly increases the risk of heart disease in African Americans, but does not increase risk among whites.

Blacks who have the gene have six times the risk of heart disease compared with those who have another version of the gene, which controls the production of a molecule found on cells lining the blood vessels.

``Our findings underscore the importance of studying genetic risk factors by ethnic group,'' Dr. Kenneth Wu from the University of Texas-Houston Health Science Center said in a statement released by the American Heart Association. ``They also provide a genetic basis for differential risk factors of heart attacks between African-Americans and whites.'' The study appears in the April 24th issue of the journal Circulation: Journal of the American Heart Association.

Wu and associates conducted blood tests on heart attack patients and healthy individuals, looking for a particular form of the gene necessary for the manufacture of the protein thrombomodulin. Thrombomodulin is found on cells lining blood vessels, and is important because it converts the clot-producing protein, thrombin, to an anti-clotting agent. Thrombomodulin may also protect blood vessels from damage.

The ``V'' form of the gene, in which one of the protein's amino-acid building blocks is switched, has been linked to raised risk for heart attack. In general, people have two copies of the gene--one inherited from each parent.

Heart attack patients, in general, were 60% more likely than those without heart disease to have at least one copy of the V form of the gene, the authors report, whereas healthy individuals were more likely to have two copies of the ``A'' form of the gene.

This difference was most marked among black individuals. After adjustments for other heart disease risk factors, blacks with the V gene were 6.1 times more likely to have heart disease than were blacks who had only the A form of the gene. This did not seem to be true for whites.

The researchers have not yet discovered why this simple genetic difference has such a profound effect on heart disease risk. Perhaps, they suggest, subtle differences in the way blacks with the V gene respond to inflammation prevents their thrombomodulin from working effectively. Or perhaps other unidentified risk factors give thrombomodulin a greater role in the development of heart disease in blacks.

Whatever the mechanism, doctors now have another way of estimating the risk of heart disease in African Americans, the authors conclude.

The researchers caution, however, that larger studies need to confirm their results before genetic testing for thrombomodulin becomes part of the routine assessment of heart disease risk.

SOURCE: Circulation:Journal of the American Heart Association

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