Total Cholesterol Content of Erythrocyte Membranes Is Increased in Patients With Acute Coronary Syndrome: A New Marker of Clinical Instability?

ObjectivesWe hypothesized that cholesterol content is increased in the circulating erythrocytes of patients with acute coronary syndrome (ACS) and may be a marker of clinical instability. We therefore sought to investigate whether cholesterol content differs in erythrocyte membranes of patients presenting with ACS compared to patients with chronic stable angina (CSA).BackgroundPlaque rupture in ACS depends at least partly on the volume of the necrotic lipid core. Histopathologic studies have suggested that cholesterol transported by erythrocytes and deposited into the necrotic core of atheromatous plaques contributes to lipid core growth.MethodsConsecutive angina patients were prospectively assessed; 120 had CSA (83 men, age 64 ± 11 years) and 92 ACS (67 men, 66 ± 11 years). Total cholesterol content in erythrocyte membranes (CEM) was measured using an enzymatic assay, and protein content was assessed by the Bradford method.ResultsThe CEM (median and interquartile range) was higher (p < 0.001) in ACS patients (184 μg/mg; range 130.4 to 260.4 μg/mg) compared with CSA patients (81.1 μg/mg; range 53.9 to 109.1 μg/mg) (analysis of covariance). Total plasma cholesterol concentrations did not correlate with CEM levels (r = −0.046, p = 0.628).ConclusionsThis study shows, for the first time, that CEM is significantly higher in patients with ACS compared with CSA patients. These findings suggest a potential role of CEM as a marker of atheromatous plaque growth and vulnerability. Large ad hoc studies are required to establish the clinical importance and pathogenic significance of CEM measurement.