Serum metalloproteinase 9 levels in patients with coronary artery disease: A novel marker of inflammation

Background: The finding that expression of metalloproteinases (MMPs) is induced in atherosclerotic plaques prone to rupture suggests the possibility that patients with atherosclerotic diseases would show enhanced blood levels of MMPs and that MMPs might represent a potential inflammatory risk factor for atherosclerosis. Therefore, the present study was aimed at verifying whether MMPs may represent sensitive markers of inflammation in patients with coronary artery disease. Methods: MMP-2, MMP-9, interleukin (IL)-6, C-reactive protein (CRIP), and fibrinogen levels were measured in blood samples obtained from 66 cases with previous acute myocardial infarction and 66 control subjects similar for age, sex, and major atherosclerotic risk factors but without history or evidence of atherothrombotic diseases. Results: Biohumoral markers of inflammation and MMP-9 levels were significantly elevated in cases compared with controls (median values 40.6 versus 9.8 ng/mL; p <.0001), whereas MMP2 levels did not differ between the two groups (median values 839 versus 873 ng/mL; p =.53). A direct correlation was found among MMP-9, CRP, IL-6, and fibrinogen levels. Conditional logistic regression analysis showed that MMP-9 is related to myocardial infarction (p =.006) even after adjusting for cardiovascular medications and CRP. Conclusion: These findings suggest that measurement of serum MMP-9 levels may represent a novel marker of inflammation in patients with known coronary artery disease and might provide an index of plaque activity in this clinical setting.