title: In vivo stable-isotope kinetic study suggests intracellular assembly of lipoprotein(a).
abstract: OBJECTIVE
  Lipoprotein(a) [Lp(a)] consists of apolipoprotein B-100 (apoB-100) as part of an LDL-like particle and the covalently linked glycoprotein apolipoprotein(a) [apo(a)]. Detailed mechanisms of its biosynthesis, assembly, secretion and catabolism are still poorly understood. To address the Lp(a) assembly mechanism, we studied the in vivo kinetics of apo(a) and apoB-100 from Lp(a) and LDL apoB-100 in nine healthy probands using stable-isotope methodology.
  
  
  METHODS
  The level of isotope enrichment was used to calculate the fractional synthesis rate (FSR), production rate (PR) and retention time (RT) using SAAMII software and multicompartmental modeling.
  
  
  RESULTS
  We observed a similar mean PR for apo(a) (1.15 nmol/kg/d) and apoB-100 (1.31 nmol/kg/d) from Lp(a), which differed significantly from the PR for apoB-100 from LDL (32.6 nmol/kg/d). Accordingly, mean FSR and RT values for Lp(a)-apo(a) were similar to those of Lp(a)-apoB and different from those for LDL-apoB.
  
  
  CONCLUSIONS
  Two different kinetic apoB pools within Lp(a) and LDL suggest intracellular Lp(a) assembly from apo(a) and newly synthesized LDL.
authors.affiliation: Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Austria.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Frischmann
authors.forename: Katsunori
authors.initials: K
authors.lastname: Ikewaki
authors.forename: Evi
authors.initials: E
authors.lastname: Trenkwalder
authors.forename: Claudia
authors.initials: C
authors.lastname: Lamina
authors.forename: Benjamin
authors.initials: B
authors.lastname: Dieplinger
authors.forename: Muhidien
authors.initials: M
authors.lastname: Soufi
authors.forename: Horst
authors.initials: H
authors.lastname: Schweer
authors.forename: Juergen R
authors.initials: JR
authors.lastname: Schaefer
authors.forename: Paul
authors.initials: P
authors.lastname: König
authors.forename: Florian
authors.initials: F
authors.lastname: Kronenberg
authors.forename: Hans
authors.initials: H
authors.lastname: Dieplinger
mesh_terms: D000328:Adult; D053299:Apolipoprotein B-100 / Q000097:blood; D001054:Apolipoproteins A / Q000097:blood; D003903:Deuterium; D006801:Humans; D007262:Infusions, Intravenous; D007700:Kinetics; D007930:Leucine / Q000008:administration & dosage; D017270:Lipoprotein(a) / Q000097:blood*; D008077:Lipoproteins, LDL / Q000097:blood; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D055503:Protein Multimerization; D055815:Young Adult
chemical_list: D053299:Apolipoprotein B-100; D001054:Apolipoproteins A; D017270:Lipoprotein(a); D008077:Lipoproteins, LDL; D003903:Deuterium; D007930:Leucine