LDL oxidation in patients with severe carotid atherosclerosis. A study of in vitro and in vivo oxidation markers.

Among the various risk factors involved in the development and progression of carotid atherosclerosis, the oxidation of LDL has been proposed to play a relevant role. LDL oxidation has been investigated in 94 patients with severe carotid atherosclerosis undergoing elective carotid artery endarterectomy and in 42 matched control subjects. LDL oxidation was evaluated in all patients as (1) the susceptibility to in vitro oxidation, (2) vitamin E concentration and its efficiency in LDL, and (3) the presence of autoantibodies against oxidatively modified lipoprotein to monitor the occurrence of the oxidative processes taking place in vivo. No difference was detected between control subjects and patients concerning vitamin E concentration and the kinetics of conjugated diene formation in isolated LDL exposed to CuSO4. However, vitamin E efficiency was lower (9.6 +/- 4.2 versus 30.2 +/- 7.6 min/nmol vitamin E) and the duration of the vitamin E-independent lag phase was longer (105.5 +/- 16.5 versus 58 +/- 11.8 minutes) in the patient group. Autoantibodies against oxidatively modified lipoproteins were measured with an ELISA method using native LDL, Cu(2+)-oxidized LDL (oxLDL), or malondialdehyde-derivatized LDL (MDA-LDL) as antigens. To monitor cross-reactivity of the antibodies detected with other oxidatively modified proteins, human serum albumin (HSA) and MDA-derivatized HSA (MDA-HSA) were also employed. The antibody titer was calculated as the ratio of antibodies against modified versus native proteins.(ABSTRACT TRUNCATED AT 250 WORDS)