Baseline Diene Conjugation in LDL Lipids as a Direct Measure of In Vivo LDL Oxidation

Objectives: To additionally test validity of the recently developed method (LDL baseline diene conjugation, LDL-BDC) for determination of circulating oxidized LDL. Design and methods: A detailed comparison between the ultracentrifugation and heparin precipitation methods for LDL isolation was performed to test suitability of the fast precipitation method. Validity of LDL-BDC as an indicator of circulating oxidized LDL was tested by comparing LDL-BDC to results obtained by the immunological autoantibody method. Results: BDC values in LDL isolated by heparin precipitation did not differ from those isolated by sequential ultracentrifugation. While highest amount of diene conjugation was found in LDL (40% of that in serum), substantial amounts were also found in VLDL (31%) and HDL (25%). When analyzed in the same samples, assays for the titer of autoantibodies against oxidized LDL and LDL-BDC were found to show good correlation ( r = 0.57, p = 0.001, n = 29). Conclusions: These results, together with thus far conducted studies on clinical applicability of the method, indicate that LDL-BDC is a promising candidate in search for a method for estimation of LDL oxidation in vivo.