title: Characterization and metabolic fate of two very-low-density lipoprotein subfractions separated by heparin-sepharose chromatography.
abstract: Human very-low-density lipoproteins (VLDL) have been separated into two discrete subfractions by heparin-Sepharose chromatography. The retained fraction relative to the unretained fraction is characterized by an increased cholesterol ester/triacylglycerol ratio and an increased ratio of apolipoprotein E relative to apolipoprotein C. We have subfractionated VLDL from type IV hyperlipoproteinemic subjects and characterized these subfractions with respect to (i) composition and (ii) the metabolic fate of apolipoprotein B of each subfraction. The unretained fraction accounted for an average of 42% of total VLDL in type IV subjects. A similar distribution was obtained with VLDL from Type III subjects; however, only 25% of normal VLDL is in the unretained fraction. The apolipoprotein E/apolipoprotein C ratio was 2-8-fold higher in the retained fraction. The distribution of apolipoprotein E isomorphs and the individual C apolipoproteins were similar in each fraction. Retained and unretained fractions were labelled with 125I and/or 131I and injected simultaneously into miniature pigs. Apolipoprotein B of retained fractions was catabolized at a greater rate (fractional catabolic rate = 0.98 h-1 vs. 0.54 h-1, n = 7, P less than 0.05) compared to unretained fractions. These results are consistent with the concept that reduced content of C apolipoproteins in VLDL is correlated with enhanced uptake by perfused rat livers. Apolipoprotein B from retained fractions was converted to intermediate-density lipoproteins (IDL) at a greater rate, and apolipoprotein B from both fractions were converted to low-density lipoproteins (LDL). Although the unretained fraction may be the precursor of the retained fraction, the possibility exists that each fraction is largely synthesized and catabolized independently.
mesh_terms: D002784:Cholesterol / Q000097:blood; D002846:Chromatography, Affinity; D006493:Heparin; D006801:Humans; D006951:Hyperlipoproteinemias / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood* / Q000302:isolation & purification; D010743:Phospholipids / Q000097:blood; D012685:Sepharose / Q000031:analogs & derivatives; D014280:Triglycerides / Q000097:blood
chemical_list: D008079:Lipoproteins, VLDL; D010743:Phospholipids; D014280:Triglycerides; C037405:heparin-sepharose; D006493:Heparin; D012685:Sepharose; D002784:Cholesterol