NGAL and MMP-9/NGAL as biomarkers of plaque vulnerability and targets of statins in patients with carotid atherosclerosis

Background: Neutrophil gelatinase associated lipocalin (NGAL) is expressed in atherosclerotic lesions and was recently implicated in the pathogenesis of cardiovascular pathologies. Statins are known to exert stabilizing effects on atherosclerotic plaque. The aims of our study were (1) to investigate the association of serum NGAL and metalloproteinase (MMP)-9/NGAL complex with the vulnerability of the atherosclerotic plaque, and (2) to reveal the effects of statin treatment on circulating NGAL and MMP-9/NGAL levels in patients with carotid artery stenosis. Methods: We examined the levels of NGAL and MMP-9/NGAL in blood samples from 136 patients with carotid artery stenosis by specific enzyme-linked immunosorbent assays. Results: Patients with vulnerable plaques, as determined by ultrasound (plaques with decreased echogenicity) and histological analysis (type VI according to the classification of American Heart Association [AHA]), displayed the highest levels of NGAL (both p < 0.0001) and MMP-9/NGAL complex (p = 0.0004 and p = 0.004, respectively). Moreover, patients with symptomatic carotid atherosclerosis had significantly higher NGAL levels compared to asymptomatic patients (p = 0.0007). The statin-treated group (n = 108) demonstrated lower NGAL (73.9 vs. 128.0 mu g/L, p < 0.0001) and MMP-9/NGAL (28.9 vs. 40.6 mu g/L, p = 0.046) as compared to the non-statin group (n = 28). Furthermore, in multivariate regression analysis NGAL, but not MMP-9/NGAL levels, were independently associated with symptomatic carotid artery stenosis. In addition, statin treatment was independently associated with lower NGAL levels. Conclusions: Circulating NGAL and MMP-9/NGAL are associated with plaque vulnerability in patients with carotid artery stenosis. Statin treatment could contribute to plaque stabilization by reducing circulating NGAL and MMP-9/NGAL levels.