Myeloperoxidase predicts progression of carotid stenosis in states of low high-density lipoprotein cholesterol

OBJECTIVES We investigated the effect of myeloperoxidase (MPO) on progression of carotid stenosis in states of high and low high-density tipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C) levels. BACKGROUND Myeloperoxidase is pivotally involved in the pathogenesis of atherosclerosis. In vitro data suggest that MPO exerts deleterious effects via oxidative modulation of lipoproteins. METHODS We prospectively studied 1,019 of 1,268 consecutive patients who were asymptomatic with respect to carotid artery disease. Patients underwent serial carotid ultrasound investigations at baseline and after a follow-up interval of median 7.5 months (range 6 to 9 months), categorizing carotid arteries as 0% to 29%, 30% to 49%, 50% to 69%, 70% to 89%, or 90% to 99% stenosed or occluded. The MPO, HDL-C, and LDL-C levels were measured at baseline, grouped by medians, and correlated with progression of carotid atherosclerosis. RESULTS Progression of carotid atherosclerosis was found in 100 of 1,019 patients (9.8%). Myeloperoxidase (p = 0.014) but not HDL-C (p = 0.95) or LDL-C (p = 0.30) were associated with progressive disease. However, MPO >= 310 ng/ml was significantly associated with progressive disease (adjusted odds ratio [OR] 2.57, 95% confidence interval [CI] 1.39 to 4.75) only in patients with HDL-C levels < 49 mg/dl. Otherwise, in patients with higher HDL-C levels (>= 49 mg/dl), MPO >= 310 ng/ml did not predict disease progression (adjusted OR 1.42, 95% CI 0.72 to 2.78). No interaction of MPO with LDL-C was observed. CONCLUSIONS Myeloperoxidase was associated with progression of carotid atherosclerosis in patients with HDL cholesterol levels below 49 mg/dl.