Comparative analysis of plasma and erythrocyte 7-ketocholesterol as a marker for oxidative stress in patients with diabetes mellitus

Objectives: To reveal increased lipid peroxidation in diabetics by quantification of cholesterol oxidation products (COPs) not only in plasma, but also in erythrocytes. Design and methods: We quantified 7-ketocholesterol (7-kCho) by gas chromatography-mass spectrometry as a surrogate measure for COPs. These assays were performed on both plasma and erythrocytes in 20 control subjects and 20 treated patients with relatively poorly controlled Type 2 diabetes. Results: Both plasma and erythrocyte 7-kCho levels in diabetics were significantly higher than those in control subjects. Although neither plasma nor erythrocyte 7-kCho levels were associated with markers for glucose tolerance in diabetics, a negative correlation of serum HDL-cholesterol levels with erythrocyte, but not plasma, 7-kCho levels was found. Conclusion: Increased oxidative stress in diabetics affects oxidation of cholesterol. Assays of COPs not only in plasma, but also in erythrocytes, may yield complementary information in lipid peroxidation. Copyright (C) 2000 The Canadian Society of Clinical Chemists.