The relationship between serum levels of vascular calcification inhibitors and carotid plaque vulnerability

Objective: Osteopontin (OPN) and osteoprotegerin (OPG) are well-known vascular calcification inhibitors, which have been recently demonstrated to correlate with inflammation and cardiovascular events incidence. The aim of this cross-sectional study is to survey whether OPN and OPG are involved in carotid plaque vulnerability. For this reason, we assessed serum OPN and OPG levels in patients with carotid stenosis, and we explored their relationship with carotid plaque echogenicity and subsequent cerebrovascular ischemic events. Methods. A total of 164 Whites were selected from a large cohort of 297 subjects to participate. In particular, 114 patients (61 men, 53 women), aged 55 to 80, had recently-diagnosed ICA stenosis higher than 50%. A group of 50 age-, sex-, and body mass index (BMI)-matched healthy individuals served as healthy controls. Patients with renal failure, hypothyroidism, osteoporosis, and lipid-lowering therapy were excluded. Images of both carotids were obtained from all participants using a high-resolution color duplex ultrasound and the gray-scale median (GSM) score was calculated. Brain computed tomography (CT), and magnetic resonance imaging (MRI) scans when CT was questionable, were performed on all patients with carotid stenosis. Clinical parameters, lipid and glycemic indexes, hsCRP, fibrinogen, white blood cells (WBC) count, OPN, and OPG were measured. Independent t test, one-way ANOVA, Pearson correlation, and multiple regression analysis were used for statistical analysis. Results. Among patients with carotid stenosis, 60 had history of ipsilateral stroke or TIA and positive CT or MRI findings (group A), while 54 had no neurological symptoms and negative CT and MRI scan (group B). Overall, patients with carotid stenosis showed worse lipid profile and increased waist circumference, blood pressure, hsCRP, fibrinogen, WBC count, OPN, and OPG levels compared with healthy subjects (group C) (P < .05). Statistical analysis revealed that group A had significantly lower levels of GSM than group B (57.41 +/- 38.19 vs 76.32 +/- 36.72; P = .008) and higher levels of hsCRP, OPN, and OPG than groups B and C (P < .05). Concerning the latter, biochemical markers group B showed only elevated OPG levels compared with group C (P = .038). Notably, GSM was considerably associated with serum OPN and OPG and waist circumference in patients with carotid atherosclerosis in univariate (r = -0.333; P = .032, r = -0.575; P < .001, r = -0.590; P = .006, respectively) and multiple regression analysis (R-2 = 0.445; P = .006). Conclusions. The present study demonstrated elevated serum OPN and OPG levels in patients with carotid stenosis and documented an independent association between these biochemical markers, GSM and carotid-induced symptomatology. Therefore bone-matrix proteins combined with GSM could be potential markers for vulnerable carotid plaques.