Conversion of very low density lipoprotein to low density lipoprotein. A metabolic study of apolipoprotein B kinetics in human subjects.
The interrelationship between apolipoprotein B in very low density lipoprotein (VLDL-B) and in low density lipoprotein (LDL-B) was studied in seven normal and hyperlipidemic men and women, with purified radioiodinated VLDL. The time-course of the appearance of radioactivity in LDL was followed. As the specific activity curves intersected at the masimal height of the LDL-B curve, it was inferred that all or most LDL-B peptide is derived from VLDL-B peptide. This transfer was further quantitated in seven normotriglyceridemic subjects by simultaneous i.v. injection of purified 131I-VLDL and 125I-LDL. By a deconvolution method, a quantitative description of the rate of entry of 131Ivldl-b into 131I-LDL-B was derived by analysis of 131I-LDL-B and 125I-ldl-b radioactivity in plasma. The results indicate that approximately 90% of VLDL-B mass is converted into LDL-B in subjects with normal serum triglyceride concentrations. The synthetic rates of VLDL-B and LDL-B peptide were simultaneously measured in six normal subjects, and two patients with heterozygous familial hypercholesterolemia (type IIa). The turnover rates for VLDL-B and LDL-B peptide were similar in these subjects. The findings in the three parts of this study were consistent with the view that most if not all VLDL-B is converted into LDL-B peptide, and most if not all LDL-B is derived from VLDL-B peptide in normotriglyceridemic subjects.
D000328:Adult; D001059:Apoproteins / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D002914:Chylomicrons / Q000097:blood; D005260:Female; D006579:Heterozygote; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood / Q000235:genetics; D006949:Hyperlipidemias / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008079:Lipoproteins, VLDL / Q000097:blood / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D014280:Triglycerides / Q000097:blood
D001059:Apoproteins; D002914:Chylomicrons; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D014280:Triglycerides; D002784:Cholesterol