SLOW-BETA-MIGRATING LIPOPROTEIN - AN ATHEROGENIC SUBCLASS OF LOW-DENSITY LIPOPROTEINS

Objective: To clarify the possibility that midband Lp in LDL fractions might act as an atherogenic lipoprotein in their interaction with mac rophages. Design and Methods: Low density lipoproteins (LDL) isolated by zonal ultracentrifugation from midband lipoprotein-positive serum i n type IIb hyperlipidemics were subjected to polyacrylamide gel disc e lectrophoresis. Results: A part of midband lipoprotein was observed be tween pre beta- and beta-band, in addition to the main beta-band. We n amed this midband lipoprotein ''slow beta-migrating Lp (slow beta-Lp). '' The larger LDL subfraction from midband-lipoprotein positive serum on Sepharose 28 column chromatography contained much slow beta-Lp, nam ed slow beta-Lp-rich LDL. The smaller LDL subfraction contained a litt le slow beta-Lp, named slow beta-Lp-poor LDL. Slow beta-Lp-rich LDL ha d similar composition to the control LDL except for apolipoprotein E. The uptake of [H-3]cholesteryl linoleate-labeled slow beta-Lp-rich LDL by J774 macrophages was higher than that of control LDL. The choleste rol ester content of J774 macrophages incubated with slow beta-Lp-rich LDL increased significantly compared with slow beta-Lp-poor LDL, beta -VLDL, and control LDL. Conclusion: These results suggest that slow be ta-Lp in type IIb might generate foam cells from macrophages in athero sclerotic lesions.