Plasma apolipoprotein B metabolism in familial type III dysbetalipoproteinaemia

Abstract

Lipoprotein metabolism was studied in 11 patients with Type III hyperlipoproteinemia, 1 with normolipidemic dysbetalipoproteinemia and 8 controls. Apolipoprotein B kinetics in very low density, intermediate density and low density lipoproteins (VLDL, IDL and LDL) was investigated. Fractional catabolic rates (FCR) of VLDL-apo B and IDL-apo B were lower (P < 0.005 and P < 0.001) in the patients: 0.064 .+-. 0.018 and 0.059 .+-. 0.006 h-1, respectively, (mean .+-. SE), compared with 0.219 .+-. 0.035 and 0.243 .+-. 0.028 h-1. Synthetic rates (SR) of IDL-apo B varied widely from 1.5 mg kg-1 day-1 in the subject with normolipidemic dysbetalipoproteinemia to 2.8-25.2 mg kg-1 day-1 in Type III. The mean time for conversion of IDL-apo B to LDL-apo B was prolonged, 18.7 h compared with 3.8 h in the controls (P < 0.001). LDL-apo B pool size and SR were lower in the patients (P < 0.05 for both). Two patients treated with gemfibrozil showed reduced by hyperlipidemia and decreased SR of VLDL-apo B and IDL-apo B. Dysbetalipoproteinemia is associated with pronounced impairment of IDL and VLDL-remnant catabolism, lipoprotien levels reflecting an interaction between this defect and SR of these lipoproteins.