INFLUENCE OF HDL SUBFRACTIONS ON ERYTHROCYTE AGGREGATION IN HYPERCHOLESTEROLEMIC MEN

Recent studies have suggested that theological mechanisms may be involved in the pathogenesis of ischemic syndromes in hyperlipidemias. We investigated the association between erythrocyte aggregation and components of lipoproteins in the blood of 60 normotensive, hypercholesterolemic men aged 45+/-8 years. The theological parameters assessed were aggregation index (AI) and disaggregation shear rate threshold (gamma t) as determined by laser reflectometry, plasma fibrinogen, total serum protein, and hematocrit. The lipoprotein variables included total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol and its subfractions HDL(2) cholesterol and HDL(3) cholesterol, apolipoprotein (apo) B, apoA-I, HDL particles containing apoA-I without apoA-II (LpA-I), and HDL particles containing both apoA-I and apoA-II (LpA-I/A-II). Covariables considered for possible confounding effects were age, body mass index, and smoking behavior. Fibrinogen, total serum protein, and both aggregation parameters (AI and gamma t) were elevated in this hypercholesterolemic population. Univariate analysis showed that both AI and gamma t correlated positively with fibrinogen (P<.001) and total serum protein (P<.01) and negatively with HDL, cholesterol (P<.01) and LpA-I (P<.01); gamma t also provided a positive correlation with LpA-I/A-II (P<.05). A multivariate model analysis demonstrated that HDL(2) cholesterol, LpA-I, and LpA-I/A-II also emerged as significant factors influencing erythrocyte aggregation; 60% to 68% of the variance of AI and 47% to 64% of the variance of gamma t could be explained by these factors. The negative relation with5 HDL(2) cholesterol, containing mainly LpA-I, suggested a possible role of these HDL subfractions in modifying erythrocyte aggregation induced by fibrinogen or other macromolecules. However, since LpA-I/A-II is positively related to gamma t, the possible influence of HDL particles on erythrocyte interactions might result from a balance between the respective effects of heterogeneous par tides.