LDL molecular size as risk factor in coronary artery disease

Sera of 65 fasting human subjects--32 patients with coronary artery disease (CAD) aged 42-80 years and 33 healthy individuals--were tested for determination of nine lipid-related laboratory parameters, including protein-enriched LDL (low density lipoprotein cholesterol (LDL apo B) which is proportional to the amount of cholesterol per LDL particle. Three of the investigated parameters: protein-enriched LDL, HDL cholesterol and apo B level differed significantly in the two groups (corrected P < 0.001, P < 0.009 and P < 0.009, respectively). Discriminant analysis revealed that protein-enriched LDL, LDL cholesterol, apo B and fasting triglyceride levels, but not HDL cholesterol, were the major discriminating factors for CAD in this study. Pearson correlation coefficients were calculated to describe the association between this size-related parameter and those which in both groups seem to be most strongly associated with it: apo B/A-I ratio (i), triglyceride (ii) and LDL/HDL ratio (iii). The analysis was done separately in the two groups. In the patients with CAD the influence of these three parameters were less decisive in the determination of the protein-enriched LDL than in the controls (corr. coeff.: (i) -0.155 vs -0.358; (ii) -0.624 vs -0.791; (iii) -0163 vs -0.471). In healthy volunteers the size-reducing effect of the same parameters was more profound, and at high values of LDL/HDL ratio, apo B/apo A-I ratio and triglyceride no distinction in LDL particle size can be made any longer between CAD patients and controls. Thus the improvement of the atherogenic profile does not seem to result in the reduction of risk for CAD in terms of LDL size and composition.