Serum levels of remnant lipoprotein cholesterol and oxidized low-density lipoprotein in patients with coronary artery disease

Abstract

Oxidized low-density lipoprotein (OxLDL) and remnant lipoprotein play a crucial role in the development of atherosclerosis. Recently, a novel method for measuring remnant cholesterol levels (remnant lipoproteins cholesterol homogenous assay: RemL-C) has been established. However, the correlation between OxLDL and remnant lipoprotein, including RemL-C, has not been fully investigated. We enrolled 25 consecutive patients with documented coronary artery disease (CAD) and 20 controls. Remnant-like particle cholesterol (RLP-C) and RemL-C were used to determine the levels of remnant lipoprotein cholesterol. Serum levels of malondialdehyde-modified LDL (MDA-LDL) and OxLDL using a monoclonal antibody DLH3 (OxPC) were used to measure the concentration of circulating OxLDL. The CAD group had high levels of fasting glucose and glycosylated hemoglobin (HbA1c), and low levels of high-density lipoprotein cholesterol compared with the control group. Serum levels of total cholesterol or LDL cholesterol were not significantly different between the two groups. The levels of RemL-C (p = 0.035), MDA-LDL (p = 0.018), and MDA-LDL/LDL-C (p = 0.036) in the CAD group were significantly higher than those in the control group. The levels of RLP-C tended to be higher in the CAD group than those in the control group (p = 0.096). Positive correlations were demonstrated between remnant lipoprotein cholesterol and OxLDL (RLP-C and MDA-LDL/LDL-C, r = 0.45, p = 0.0024, RLP-C and OxPC, r = 0.51, p = 0.0005, RemL-C and MDA-LDL/LDL-C, r = 0.42, p = 0.0044, RemL-C and OxPC, r = 0.43, p = 0.0043). Similar trends were observed in non-diabetic subjects and in subjects without metabolic syndrome. Positive correlations were also observed between RLP-C and RemL-C (r = 0.94, p < 0.0001) and between MDA-LDL/LDL-C and OxPC (r = 0.40, p = 0.0074). These results suggest that the association between high levels of remnant lipoprotein cholesterol and high OxLDL levels might be linked to atherogenesis in patients with CAD.