Elevated plasma lipid hydroperoxides in patients with coronary artery disease.

Sustained presence of lipid peroxides in the circulation and their plasma carrier is a controversial issue. Particularly, there is no firm evidence for an increased plasma lipid peroxide level in patients with atherosclerosis. In this study, a strong correlation was found between plasma total lipid hydroperoxide and lipid hydroperoxide content of LDL cholesterol (r = 0.882; p < 0.001; n = 16). Lipid hydroperoxides in plasma were carried almost exclusively (89%) in LDL. In 70 patients tested 3 months after coronary artery bypass graft surgery with a specific assay, plasma lipid hydroperoxide levels were significantly increased when compared with matched healthy controls (4.31 +/- 0.23 nmol/ml and 2.34 +/- 0.13 nmol/ml, p < 0.0001, patients vs controls, respectively). These concentrations are 10 times lower than those detected by the nonspecific thiobarbituric acid assay. However, considering the in vitro concentration range in which oxidized LDL exerts important atherogenic effects, the elevated plasma lipid hydroperoxide levels measured in atherosclerotic patients have pathologic significance.