Simple methods of quantifying oxidation products and antioxidant potential of low density lipoproteins

Objectives: The present study describes new methods for the measurement of oxidation products and antioxidant potential of low density lipoproteins (LDL). Design and methods: LDL is isolated by precipitation with buffered heparin. The assay for LDL oxidation products (LDL-BDC) is based on determination of baseline levels of conjugated dienes (BDC) in lipids extracted from LDL. The assay for antioxidant potential of LDL (LDL-TRAP) is based on the ability of LDL to trap peroxyl radicals. Results: LDL-BDC was found to increase linearly over a range from 100 to 1750 mu L, LDL-TRAP from 250 to 1750 mu L of serum taken for precipitation. For LDL-BDC, the CV was 4.4% and 4.5% for within- and between-assay precision, respectively. For the LDL-TRAP, the CV was 8.1% and 8.7% for within- and between-assay precisions, respectively. Freezing of the serum (2 weeks at -70 degrees C) did not affect LDL-BDC or LDL-TRAP levels. A negative correlation was found to exist between the LDL-BDC and LDL-TRAP values. LDL-BDC and LDL-TRAP values were at the same level in both sexes. The LDL-BDC was found to increase with age. Short-term intervention with antioxidants increased LDL-TRAP substantially, but did not affect the LDL-BDC level. Conclusions: These methods are fast and simple to perform, and can, therefore, be applied to clinical purposes.