Factors involved in the pathogenesis of atherosclerosis, thrombosis and vasoconstriction contribute to the development of coronary heart disease. In a study comparing patients after myocardial infarction with controls, we have explored a possible association between coronary heart disease and a variation found in the gene encoding angiotensin-converting enzyme (ACE). The polymorphism ACE/ID is strongly associated with the level of circulating enzyme. This enzyme plays a key role in the production of angiotensin II and in the catabolism of bradykinin, two peptides involved in the modulation of vascular tone and in the proliferation of smooth muscle cells. Here we report that the DD genotype, which is associated with higher levels of circulating ACE than the ID and II genotypes, is significantly more frequent in patients with myocardial infarction (n = 610) than in controls (n = 733) (P = 0.007), especially among subjects with low body-mass index and low plasma levels of ApoB (P < 0.0001). The ACE/ID polymorphism seems to be a potent risk factor of coronary heart disease in subjects formerly considered to be at low risk according to common criteria.

Genetic variants of the beta fibrinogen gene are associated with an increased plasma level of fibrinogen, especially in smokers. The association with CAD appears to be the consequence of an increased risk of MI in subjects with severe CAD who carry the predisposing beta fibrinogen genotypes.

SummaryWe have investigated the interrelationships of plasma PAI-1 activity, the PAI-1 4G/5G polymorphism and risk of myocardial infarction (MI) in the ECTIM study, a case-control study of MI based in Belfast, Lille, Strasbourg and Toulouse. Mean PAI-1 levels in cases were similar across all centres but in controls, levels in the French centres were significantly higher. Only in Belfast were PAI-1 levels higher in cases (11.7AU/ml) than controls (10.5AU/ml). The PAI-1 4G allele frequency was similar in cases and controls (0.55 and 0.54). In all groups, 4G homozygotes had the highest mean plasma PAI-1 level (4G4G vs 5G5G; cases overall: 14.2 vs 12.1 AU/ml; controls overall: 15.0 vs 12.6AU/ml), with the heterozygotes generally intermediate. The data from Belfast are consistent with the literature implicating PAI-1 level as an MI risk factor. In ECTIM, the PAI-1 4G/5G polymorphism is not a genetic risk factor for MI but is associated with PAI-1 activity. Thus homozygosity for the 4G allele may predispose to elevated PAI-1 and impaired fibrinolysis, perhaps requiring interaction with other genetic or environmental factors to influence MI risk.

These results suggest that polymorphisms of the TNF-alpha gene are unlikely to contribute to CHD risk in an important way, but the TNF-alpha/-308 polymorphism should be investigated further in relation to obesity.