Catabolism of chylomicron remnants in normolipidemic subjects in relation to the apoprotein E phenotype

• Published in: Journal of lipid research Vol. 28; no. 4; pp. 361 - 370
• Main Authors: Brenninkmeijer, B J, Stuyt, P M, Demacker, P N, Stalenhoef, A F, van 't Laar, A
• Format: Journal Article
• Language: English
• Published: United States Elsevier 01-04-1987
• Subjects: Adult; Apolipoprotein E2; Apolipoproteins E - blood; Apolipoproteins E - genetics; Chylomicrons - blood; Diterpenes; Heterozygote; Homozygote; Humans; Lipids - blood; Lipoproteins - blood; Lipoproteins, VLDL - blood; Male; Phenotype; Retinyl Esters; Vitamin A - analogs & derivatives; Vitamin A - blood
• ISSN: 0022-2275
• DOI: 10.1016/S0022-2275(20)38689-2

The role of the various apolipoprotein E isoproteins in the removal of chylomicrons and their remnants from plasma was studied in 16 normolipidemic subjects with various apoE phenotypes: 5 homozygous for apoE-2, 6 heterozygous for apoE-2 (phenotype E3/2), and 5 without apoE-2 (phenotypes E3/3, E4/4, and E4/3). The subjects were given an oral fat load as cream (50 g/m2). Retinyl palmitate was added as a marker for chylomicrons and their remnants. Blood was sampled at regular time intervals for 8 hr. Remnant particles were isolated from the d less than 1.019 g/ml fraction by heparin-Sepharose chromatography (heparin-bound fraction) after removing the large chylomicrons by flotation at 7,8 X 10(5) g-min. All groups showed a rise in triglycerides in serum and in the chylomicron fraction between 3 and 6 hr to about twice the basal value, followed by a decrease to nearly fasting values. In the homozygous E-2 subjects, fasting lipids in the remnant fraction were increased. In all three groups the fat load did not induce a significant rise in the lipids of the remnant fraction. The homozygous E-2 group showed a strong continuing rise in the retinyl palmitate concentration in the chylomicron and remnant fractions up to 8 hr, whereas in the other groups its maximum was already reached at 5 hr at a much lower level. At 8 hr similar retinyl palmitate concentrations were found in both fractions in the heterozygous E-2 subjects compared to the non-E-2 subjects. These results indicate a delayed removal of chylomicrons and chylomicron remnants in normolipidemic homozygous E-2, but not in heterozygous E-2 subjects.