Relationships between serum levels of autoantibodies against oxidized low density lipoproteins, lipid-soluble antioxidants and apolipoprotein B in patients with coronary heart disease

High affinity IgG autoantibodies against oxidized low density lipoproteins (oxLDLs), apolipoprotein B and lipidsoluble antioxidants - alpha-tocopherol and beta-carotene, were tested in patients with coronary heart disease. Correlation relationships between these parameters were analysed. Fifty one patients with coronary heart disease (37 males/14 females) defined as Q-wave myocardial infarction and/or stenosis of more than 50%, and 51 healthy blood donors (34 males/17 females) as controls participated in this study. LDLs were isolated by density gradient ultracentrifugation and oxidized with Clu(2+) OxLDLs or native LDLs (nLDLs) were used as antigens in enzyme immunoassay (ELISA) to detect IgG autoantibodies in the serum. The contents of alpha-tocopherol and beta-carotene were measured by HPLC. Apolipoprotein B was determined by immunoturbidimetry. Correlation analysis of the parameters was carried out by Spearmann's test. Alpha-tocopherol was decreased significantly in the serum of patients with coronary heart disease (2.96+/-1.63 nmol/mg serum protein vs 6.23+/-2.28 nmol/mg serum protein in Control group) (p < 0.01). Also, the serum level of beta-carotene was decreased in patients with coronary heart disease (174.0+/-95.7 pmol/mg serum protein vs 313.2+/-141.5 pmol/mg serum protein in Control group) (p < 0.01), while apolipoprotein B was increased significantly (1.20+/-0.34 g/l in patients with coronary heart disease vs 0.86+/-0.23 g/l in Control group) (p < 0.001). In a previous study we established that the mean serum level of IgG autoantibodies against oxLDLs (expressed in optical density units) was about 2.5 times higher in patients with coronary heart disease as compared to control subjects (p < 0.001). A good positive linear correlation was observed between alpha-tocopherol and apolipoprotein B levels in Control group (r = 0.78, p < 0.001), as well as in the group of patients with coronary heart disease (r = 0.42, p < 0.001). Poor nonsignificant correlations were established between all another measured parameters. In conclusion, the lipid-soluble antioxidants - alpha-tocopherol and beta-carotene, are not informative with respect to the susceptibility of the serum to oxidative modifications and as to the extent of the subsequent humoral immune response. Presumably, the reduction of the correlation coefficient between apolipoprotein-B and alpha-tocopherol in patients with coronary heart disease ill comparison with control subjects could provide indirect information on modifications of apolipoprotein-B and on a decrease of its susceptibility to interact with this major lipid-soluble antioxidant in atherogenesis.