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SNP in factor VII gene may be protective
Variation might explain absence of myocardial infarction in some atherosclerosis patients
  
By
Edward R. Winstead


Polymorphisms of the factor VII gene may help protect some individuals with coronary artery disease from myocardial infarction. Researchers in Italy found an association between certain forms of the gene and a lower risk for developing life-threatening cardiac injuries, even in individuals with severe coronary atherosclerosis, or 'hardening' of the arteries. The findings appear in the current issue of The New England Journal of Medicine.

Domenico Girelli, of the University of Verona, Italy, and colleagues studied three polymorphisms of the gene that encodes coagulating factor VII, a protein that for decades has been suspected in coronary artery disease. Blood levels of factor VII are influenced by both genetic and environmental factors, and the rare forms of the gene are generally associated with lower blood levels of the protein, according to the researchers.

A number of studies have proposed that high levels of coagulating factor VII in blood are a risk factor for death due to coronary artery disease. But as the researchers note in their paper, the published data on the subject are conflicting.

The current study included 444 patients, 311 of which had severe coronary atherosclerosis. Of these 311 patients, 175 had documentation of previous myocardial infarction. The control group consisted of 133 individuals who had no evidence of cardiac-related problems.

The researchers found that all three polymorphisms (5'F7, R353Q, and IVS7) influenced blood levels of factor VII. The distribution and frequency of each polymorphism was essentially the same among the two groups of patients. A significant difference was found, however, between the distribution of variants among patients who experienced myocardial infarction and those who had not, according to the study.

Patients with the lowest levels of factor VII were more likely to have forms of the 5'F7 or IVS7 polymorphisms than other variants. And the lower levels of factor VII were statistically associated with a reduced risk for myocardial infarction.

The researchers conclude that certain combinations of the polymorphism "have a role in protecting against myocardial infarction. This may explain why some patients do not have myocardial infarction despite the presence of severe coronary atherosclerosis."

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Girelli, D. et al. Polymorphisms in the factor VII gene and the risk of myocardial infarction in patients with coronary artery disease. N Engl J Med 343, 774-780 (September 14, 2000).
 

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