Post-prandial triglyceride-rich lipoprotein metabolism: possible role of sialilated apolipoprotein E isoproteins

While serum concentrations of triglyceride (TG) and apolipoprotein (apo) E decreased significantly after 75 g glucose load, serum triglyceride concentration increased markedly and apoB concentration decreased significantly after 100 g fat load in 10 healthy men. Chylomicrons and very low density lipoproteins (VLDL) increased after the fat load but decreased after the glucose load. ApoB-100/B-48 ratio in VLDL fraction decreased slightly at 30 min and increased markedly at 60 min after the glucose load. On the other hand, the ratio decreased definitely at 30 min and then increased until 90 min after the fat load. Isoelectric focusing (IEF) and two-dimensional gel electrophoresis revealed that the relative concentration of sialilated apoE in VLDL fraction decreased after the glucose load and increased after the fat load. In hypertriglyceridaemic patients, apoE3S1/E3 ratio in VLDL fraction was significantly higher than that in normal and hypercholesterolaemic patients. The results suggest that some structural changes in apoE, due probably to sialilation, may exert an influence on the hepatic uptake of the lipoproteins.