Significance of acidic sugar chains of apolipoprotein B-100 in cellular metabolism of low-density lipoproteins.
We have elucidated the carbohydrate structures of the N-linked sugar chains of human and rabbit apolipoprotein B-100 (apo B-100), which is similar in composition to oligosaccharides (Arch Biochem Biophys 1989;273:197-205, Arteriosclerosis 1990; 10:386-93). We have also shown the negative correlation of the ratio of acidic sugar chains of apo B-100 to the serum cholesterol levels in Watanabe heritable hyperlipidemic rabbits (Atherosclerosis 1992;93:229-35). The acidity of sugar chains is determined by the existence of sialic acid residues at the terminal of oligosaccharides. In the present study we investigated N-linked sugar chains of apo B-100 from patients with coronary artery disease (CAD) who had moderate hypercholesterolemia (less than 400 mg/dL). There was no difference in the structure of their oligosaccharides and the ratio of acidic sugar chains of apo B-100 from CAD patients as compared with that from healthy individuals reported previously. To clarify the role of sialic acid residues in apo B-100 for lipoprotein metabolism, we studied cellular uptake of low-density lipoproteins (LDLs) treated with sialidase (desialylated LDL). Desialylated LDLs were taken up and degraded to a 2-fold greater degree than control LDL by human monocyte-derived macrophages and stimulated cholesterol esterification in these cells. These results indicate that sialic acid residues of apo B- 100 play an important role in cellular uptake and degradation of LDL.
Fujioka
Y
Y
The First Department of Internal Medicine and The Faculty of Health Sciences, Kobe University School of Medicine, Japan.
Taniguchi
T
T
Ishikawa
Y
Y
Yokoyama
M
M
D000818:Animals; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000737:chemistry / Q000502:physiology*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D011817:Rabbits; D011973:Receptors, LDL / Q000378:metabolism
D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D008077:Lipoproteins, LDL; D011973:Receptors, LDL; D019158:N-Acetylneuraminic Acid