DIFFERENT HYDROLYTIC EFFICIENCIES OF ADIPOSE-TISSUE LIPOPROTEIN-LIPASE ON VERY-LOW-DENSITY LIPOPROTEIN SUBFRACTIONS SEPARATED BY HEPARIN-SEPHAROSE CHROMATOGRAPHY

Human very-low-density lipoproteins (VLDL) were subfractionated by heparin-Sepharose chromatography into an unbound (A) and three bound (B, C and D) populations at increasing ionic strengths. Subfractions were characterized regarding their chemical composition and efficiency of triacylglycerol hydrolysis by rat adipose tissue LPL. The triacylglycerol content decreased, whereas the cholesterol and protein contents increased from subfractions A and B to subfraction D. VLDL-D showed the highest apo E/apo C ratio, though all the subfractions contained appreciable apo E. Appearance of VLDL-A resulted from exceeding the binding capacity of the column, since practically all its particles eluted at positions of bound VLDL under re-chromatography. Subfractions B, C and D stimulated LPL activity on emulsified tri[C-14]oleoylglycerol to a similar extent, indicating that their apo C-II content was equally effective activating LPL. Incubation of tri[C-14]oleoylglycerol labeled VLDL subfractions with fat pad pieces in the presence or absence of heparin resulted in greater hydrolysis and fatty acid uptake for VLDL-B and -C than for VLDL-D, a pattern observed over a wide range of LPL activities in the media. We conclude: (1) any VLDL particle can interact with heparin, which is consistent with the presence of apo E in all the subfractions, and (2) triacylglycerols in apo E-rich VLDL are less efficiently hydrolyzed by LPL than those in apo E-poor particles. We propose that richness in apo E impairs LPL action upon VLDL and decreases the rate of delivery of fatty acids to peripheral tissues.