Susceptibility of apolipoprotein B-containing lipoproteins to oxidation and antioxidant status in acute coronary syndromes

Background: Oxidized lipoproteins may play an important role in the pathoge nesis of atherosclerosis, and it has been shown that antioxidants have a pr otective effect against the progression of atherosclerosis. Hypothesis: The aim of this study was to investigate the oxidative suscepti bility of apolipoprotein B-containing lipoproteins and antioxidant status i n patients with acute coronary syndromes and chronic stable angina pectoris . Methods: The study population included 70 patients with acute coronary synd romes (14 with recent acute myocardial infarction and 56 with unstable angi na pectoris), 105 patients with stable angina pectoris, and 75 control subj ects. In addition to conventional lipid and lipoprotein analysis, the susce ptibility of apolipoprotein B-containing lipoproteins to in vitro oxidation (lag phase) and plasma vitamin E and total carotene levels was measured. Results: The lag phase was significantly shorter in patients with acute cor onary syndromes (45 +/- 12 min) than in patients with stable angina pectori s (51 +/- 10 min) and in control subjects (58 +/- 9 min) (p < 0.0001). Both plasma vitamin E and total carotene levels were lowest in patients with ac ute coronary syndromes (1.11 +/- 0.32 mg/dl and 119 +/- 32 mu g/dl, respect ive ly), followed by patients with stable angina pectoris (1.25 +/- 0.37 mg /dl and 132 +/- 37 mu g/dl) and then controls (1.52 +/- 0.31 mg/dl and 167 +/- 41 mu g/dl). Conclusions: These data suggest that there is an intense oxidative process and a lower antioxidant status in acute coronary syndromes. This may lead t o plaque instability due to the activation of the inflammatory response in coronary atherosclerotic lesions.