title: Metabolism of apolipoprotein A-II containing triglyceride rich ApoB lipoproteins in humans.
abstract: OBJECTIVE
  To characterize human triglyceride-rich lipoproteins (TRL) with and without apoA-II and to study their metabolism in vivo.
  
  
  METHODS
  Plasma from 11 participants on a controlled diet given a bolus infusion of [D5]l-phenylalanine to label apoB was combined into four pools and applied to anti-apoA-II immunoaffinity columns. Fractions with and without apoA-II were separated into VLDL and IDL by ultracentrifugation; lipids and apolipoproteins were measured. For kinetic measurements, apoB was isolated and hydrolyzed to the constituent amino acids. Tracer enrichment was measured by GCMS. Metabolic rates were determined by SAAM-II.
  
  
  RESULTS
  VLDL and IDL with apoA-II comprised 7% and 9% of total VLDL and IDL apoB respectively. VLDL with apoA-II was enriched in apoC-III, apoE, and cholesterol compared to VLDL without apoA-II. Mean apoB FCR of VLDL with apoA-II was significantly lower than for VLDL without apoA-II (2.80 ± 0.96 pools/day v.s. 5.09 ± 1.69 pools/day, P = 0.009). A higher percentage of VLDL with apoA-II was converted to IDL than was cleared from circulation, compared to VLDL without apoA-II (96 ± 8% vs. 45 ± 22%; P = 0.007). The rate constants for conversion of VLDL to IDL were similar for VLDL with and without apoA-II. Thus, a very low rate constant for clearance accounted for the lower FCR of VLDL with apoA-II.
  
  
  CONCLUSIONS
  VLDL with apoA-II represents a small pool of VLDL particles that has a slow FCR and is predominantly converted to IDL rather than cleared from the circulation.
authors.affiliation: Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Boston, MA, USA; Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA.
authors.forename: Nirav K
authors.initials: NK
authors.lastname: Desai
authors.affiliation: School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia, Australia; Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA.
authors.forename: Esther M
authors.initials: EM
authors.lastname: Ooi
authors.affiliation: Clinical Research Center, Boston Children's Hospital, Boston, MA, USA.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Mitchell
authors.affiliation: Department of Nutrition, Harvard School of Public Health and Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Furtado
authors.affiliation: Department of Nutrition, Harvard School of Public Health and Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, MA, USA. Electronic address: fsacks@hsph.harvard.edu.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Sacks
mesh_terms: D016633:Apolipoprotein A-II / Q000097:blood*; D053299:Apolipoprotein B-100 / Q000097:blood*; D053305:Apolipoprotein C-III / Q000097:blood; D001057:Apolipoproteins E / Q000097:blood; D015415:Biomarkers / Q000097:blood; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007700:Kinetics; D053419:Lipoproteins, IDL / Q000097:blood*; D008079:Lipoproteins, VLDL / Q000097:blood*; D008297:Male; D008954:Models, Biological; D014280:Triglycerides / Q000097:blood*
chemical_list: C115794:APOA2 protein, human; C569471:APOB protein, human; D016633:Apolipoprotein A-II; D053299:Apolipoprotein B-100; D053305:Apolipoprotein C-III; D001057:Apolipoproteins E; D015415:Biomarkers; D053419:Lipoproteins, IDL; D008079:Lipoproteins, VLDL; D014280:Triglycerides; C030106:very low density lipoprotein triglyceride
keywords: Apolipoprotein A-II; Lipid metabolism; Triglyceride rich lipoproteins; VLDL