LEVELS AND PHYSICOCHEMICAL PROPERTIES OF LIPOPROTEIN SUBCLASSES IN MODERATE HYPERTRIGLYCERIDEMIA

Moderate hypertriglyceridemia is associated with several abnormalities of the plasma lipoprotein particles and it may be a risk factor for atherosclerotic vascular diseases. Plasma lipid, lipoprotein and apolipoprotein levels, as well as lipoprotein composition and physical properties, were examined by ultracentrifugation in a zonal rotor and by gradient gel electrophoresis in 14 patients with moderate hypertriglyceridemia (plasma triglycerides 4.00 +/- 0.32 mmol/l, mean +/- S.D.) and in 14 control subjects. Based on zonal ultracentrifugation hypertriglyceridemic patients have higher levels of cholesterol in all VLDL subclasses (Sf > 200, 100-200, 60-100 and 20-60), in IDL and in small and dense LDL. Both HDL2 and HDL3 cholesterol levels are reduced. The LDL flotation rate is inversely related to plasma triglyceride levels, thus indicating that the higher the plasma triglycerides the smaller and/or denser the LDL are. The triglyceride percent content of LDL2 and HDL3 is increased, while that of esterified cholesterol is reduced in hypertriglyceridemic patients. Gradient gel electrophoresis shows that the LDL peak size is lower (25.2 +/- 0.5 nm, mean +/- S.D.) in hypertriglyceridemic than in control subjects (27.1 +/- 0.4 nm; P < 0.0001). Considering both hypertriglyceridemic and control subjects the LDL peak effluent volume from the zonal rotor (which reflects the LDL flotation rate) is inversely related to the LDL peak size determined by gradient gel electrophoresis (r = -0. 7 1; P = 0.0006) and the plasma triglyceride levels are related to LDL peak effluent volume (r = 0.74; P = 0.0002) and to LDL peak size (r = -0.95; P < 0.0001). Plasma apolipoprotein A-I is reduced while apo B, C-II, C-III and E are increased in hypertriglyceridemic patients. High levels of IDL, the presence of small and dense LDL, low levels of HDL, low apo A-I and high apo B levels are associated with an increased risk of atherosclerotic vascular complications in observational studies.