BINDING-AFFINITY AND PARTICLE-SIZE OF LDL IN SUBJECTS WITH MODERATE HYPERCHOLESTEROLEMIA - RELATIONSHIP WITH IN-VIVO LDL METABOLISM

The aim of this study was to examine relationships between low density lipoprotein (LDL) metabolism, in vitro binding, and particle size. Tw enty four study subjects, 17 men and 7 women, had elevated plasma tota l cholesterol (TC), ranging from 174 to 232 mg/dl, and LDL cholesterol (LDLC) ranging from 113 to 195 mg/dl after 12 weeks on a Step I diet. The fractional clearance rate (FCR) for LDL ranged from 0.233 to 0.61 9 pools/day (0.366 +/- 0.021) and was significantly correlated with pl asma triglycerides (TG) (P < 0.05). Although there was no relation bet ween FCR and binding in the study group as a whole, those subjects wit h an FCR within the normal range (<0.45, n = 20), showed a significant negative correlation between FCR and the K-D for LDL binding, (r = -0 .52). A subset of four subjects with an elevated FCR (>0.45) had highe r production rate (PR) (P < 0.005) and a significant positive correlat ion between the K-D for LDL binding and FCR (P < 0.05). LDL size varie d from 240.0 to 265.8 Angstrom and was significantly inversely correla ted with plasma TG (P < 0.001) but there was no relation between LDL s ize and metabolism or binding affinity. Thus, there appears to be a co rrelation between binding affinity and clearance for subjects who had normal LDL production and clearance rates. On the other hand, mechanis ms other than binding affinity appear to influence clearance in subjec ts with elevated rates of production and clearance.