DALLAS, Sept. 16 -- Researchers have found a mutation in a fat-dissolving gene that raises the risk of heart attack by five-fold compared to individuals with a normal gene.
Reporting in today's American Heart Association journal Circulation, they say the gene mutation may place 1 in 1,500 individuals at increased risk for heart attack.
The normal gene directs the production of lipoprotein lipase, an enzyme important in breaking down triglycerides and other blood fats. Individuals with the mutation have low levels of lipase, which result in below-normal amounts of the good "HDL" cholesterol and higher amounts of triglyerides, fats which increase the risk of heart attack, reports Borge Nordestgaard, M.D., Ph.D., of the department of clinical biochemistry, Herlev University Hospital, Denmark. HDL, or high-density lipoprotein, helps clear blood vessels of cholesterol.
Researchers searched for the gene mutation in blood samples of 948 men and women with heart attack or severe coronary artery blockages and 9,259 men and women from a general population sample from the Copenhagen City Heart Study.
The researchers were looking for a specific mutation that was identified previously in individuals with a severe triglyceride disorder called chylomicronemia syndrome. Individuals with this problem have both copies of the mutation and produce virtually no lipase. This leads to severely elevated triglycerides in the blood and lipid-filled sores on their skin. However, it doesn't appear to increase their risk for heart disease because the fat containing particles in the blood are too large to enter blood vessels.
The Danish researchers were interested in studying the individuals who may carry just one copy of the gene mutation. It turned out that people with only one copy of the gene mutation had less severe triglycerides and somewhat smaller cholesterol containing fat particles in the blood, particles particularly prone to cause heart disease. They wanted to know how common the mutation was and if it was associated with the same type of blood fat abnormalities that characterized people with two copies of the gene mutation.
The prevalence of the gene mutation in the Danish population was 1 in 1,500 individuals and in the heart disease population it was 1 in 300 individuals.
"It would be possible to screen individuals at risk of heart disease as well as their families for this mutation," comments Nordestgaard. "Individuals could also be screened for raised triglycerides along with raised cholesterol because individuals are at particularly high risk of heart attack with both lipids raised."
Such patients should adhere to a cholesterol lowering diet and could be potentially treated with drugs to lower both triglycerides and cholesterol. "Drugs like fibrates, nicotinic acids and some statins, could be used to reduce their risk of heart attack," adds Nordestgaard.
Co-authors are Susanne Abildgaard, MSc; Hans Wittrup, M.D.; Rolf Steffensen, M.D.; Gorm Jensen, M.D., Ph.D.; Anne Tybjaerg-Hansen, M.D., Ph.D.
Circulation is one of five medical journals published by the Dallas-based American Heart Association.
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Media advisory: Dr. Nordestgaard can be reached at 45-43-23-2472 or by fax at 45-43-23-3929. His e-mail address is bn@dcb-glostrup.dk. Between the dates of Sept. 14-17, he may be reached in New York at (212) 288-0362. (Please do not publish telephone numbers.)