DIFFERENCES IN APOLIPOPROTEIN AND LIPID-COMPOSITION BETWEEN HUMAN CHYLOMICRON REMNANTS AND VERY-LOW-DENSITY LIPOPROTEINS ISOLATED FROM FASTING AND POSTPRANDIAL PLASMA

Triglyceride-rich lipoproteins (TRLs) that are modified during aliment ary lipemia and their remnants are indicated to play an important role in the development of atherosclerosis,,Although recent studies in tra nsgenic and gene knock-out animal models have shed new light on the fu nction of different apolipoproteins (apos) in the metabolism of TRLs a nd on their respective role in atherogenesis in these models, little i s known about the compositional properties of human chylomicron remnan ts and very lo rv density lipoprotein (VLDL). To address this issue, a pos E, C-I, C-II, and G-III and lipids (triglycerides, phospholipids a nd cholesterol) were measured in Svedberg flotation rate (S-f) 60-400 and S-f 20-60 subfractions of VLDL and chylomicron remnants isolated f rom fasting and postprandial plasma samples in ten normotriglyceridemi c men.VLDL was separated from chylomicron remnants by immunoaffinity c hromatography using monoclonal antibodies (4G3 and 5E11) recognizing a poB-100 but not apoB-48 epitopes, The triglyceride, cholesterol and ap oC-II contents of large (S-f 60-400) chylomicron remnants were signifi cantly higher compared with large VLDL particles, while the small (S-f 20-60) chylomicron remnants contained significantly more apoC-II mole cules but fewer apoC-I molecules than small VLDL. Whereas the apoC-III contents of large chylomicrons decreased, the apoC-III contents of la rge VLDL increased postprandially, The cholesterol to triglyceride rat io of large VLDL particles increased transiently by 50% in response to the oral fat load, whereas the cholesterol to triglyceride ratio of l arge chylomicron remnant particles and small TRL remnants increased 50 -100% throughout the entire postprandial period. The specific alterati ons of the apolipoprotein and lipid composition of chylomicron remnant s and VLDL particles observed during alimentary lipemia are likely to target these lipoprotein species differently to metabolic routes and t o confer both endogenous and exogenous remnant lipoprotein roles in at herogenesis.