Summary
Several studies have found an association between high plasminogen activator inhibitor-1
(PAI-1) levels and myocardial infarction. Whether this is causal or a consequence
of atherosclerosis or tissue damage, remains unclear. Homozygous carriers of the 4G
allele of the 4G/5G polymorphism in the PAI-1 gene have higher PAI-1 levels compared
to carriers of the 5G allele in healthy persons in some studies, but not all. If PAI-1
levels are causally related to myocardial infarction, one would expect more homozygous
carriers of the 4G allele among patients, provided that these carriers have high PAI-1
levels among healthy persons in that population. We investigated the distribution
of this polymorphism in the “Study of Myocardial Infarctions Leiden” (SMILE), including
331 men with a myocardial infarction and 302 control subjects and measured PAI-1 antigen
levels among the latter. Secondly, we looked into the association of cardiovascular
risk factors with PAI-1 levels.
We did not find an increase in risk of myocardial infarction in carriers of the 4G
allele. Neither did we find an association, nor a trend, between the 4G/5G polymorphism
and PAI-1 antigen levels in control subjects. Controls with obesity, hypertension,
or who smoked had significant higher PAI-1 antigen levels compared with persons without
these factors. High cholesterol and triglyceride levels were also associated with
high PAI-1 antigen levels, and HDL-cholesterol levels showed an inverse association.
We conclude that the 4G/5G polymorphism in the PAI-1 gene is not associated with the
risk of myocardial infarction. As we did not find any association between this polymorphism
and PAI-1 antigen levels in healthy persons, we cannot draw any conclusions about
the causality of PAI-1 itself for myocardial infarction.