title: Distinct metabolism of apolipoproteins (a) and B-100 within plasma lipoprotein(a).
abstract: OBJECTIVE
  Lipoprotein(a) [Lp(a)] is mainly similar in composition to LDL, but differs in having apolipoprotein (apo) (a) covalently linked to apoB-100. Our purpose was to examine the individual metabolism of apo(a) and apoB-100 within plasma Lp(a).
  
  
  METHODS
  The kinetics of apo(a) and apoB-100 in plasma Lp(a) were assessed in four men with dyslipidemia [Lp(a) concentration: 8.9-124.7nmol/L]. All subjects received a primed constant infusion of [5,5,5-(2)H3] L-leucine while in the constantly fed state. Lp(a) was immunoprecipitated directly from whole plasma; apo(a) and apoB-100 were separated by gel electrophoresis; and isotopic enrichment was determined by gas chromatography/mass spectrometry.
  
  
  RESULTS
  Multicompartmental modeling analysis indicated that the median fractional catabolic rates of apo(a) and apoB-100 within Lp(a) were significantly different at 0.104 and 0.263 pools/day, respectively (P=0.04). The median Lp(a) apo(a) production rate at 0.248nmol/kg·day(-1) was significantly lower than that of Lp(a) apoB-100 at 0.514nmol/kg·day(-1) (P=0.03).
  
  
  CONCLUSIONS
  Our data indicate that apo(a) has a plasma residence time (11days) that is more than twice as long as that of apoB-100 (4days) within Lp(a), supporting the concept that apo(a) and apoB-100 within plasma Lp(a) are not catabolized from the bloodstream as a unit in humans in the fed state.
authors.affiliation: Cardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, MA 02111, USA. Electronic address: margaret.diffenderfer@tufts.edu.
authors.forename: Margaret R
authors.initials: MR
authors.lastname: Diffenderfer
authors.affiliation: Cardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, MA 02111, USA. Electronic address: stefania.lamon-fava@tufts.edu.
authors.forename: Stefania
authors.initials: S
authors.lastname: Lamon-Fava
authors.affiliation: Northwest Lipid Metabolism and Diabetes Research Laboratories, University of Washington, 401 Queen Anne Avenue North, Seattle, WA 98109, USA. Electronic address: smm@uw.edu.
authors.forename: Santica M
authors.initials: SM
authors.lastname: Marcovina
authors.affiliation: School of Medicine and Pharmacology and Faculty of Engineering, Computing and Mathematics, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia. Electronic address: hugh.barrett@uwa.edu.au.
authors.forename: P Hugh R
authors.initials: PH
authors.lastname: Barrett
authors.affiliation: Cardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, MA 02111, USA. Electronic address: julian.lel@gmail.com.
authors.forename: Julian
authors.initials: J
authors.lastname: Lel
authors.affiliation: Mass Spectrometry Unit, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, MA 02111, USA. Electronic address: gregory.dolnikowski@tufts.edu.
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Dolnikowski
authors.affiliation: Clinical and Translational Science Center, University of California, Davis, 2921 Stockton Boulevard, Suite 1400, Sacramento, CA 95817, USA. Electronic address: lars.berglund@ucdmc.usdavis.edu.
authors.forename: Lars
authors.initials: L
authors.lastname: Berglund
authors.affiliation: Cardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, MA 02111, USA. Electronic address: ernst.schaefer@tufts.edu.
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Schaefer
mesh_terms: D053299:Apolipoprotein B-100 / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism*; D001054:Apolipoproteins A / Q000096:biosynthesis / Q000378:metabolism*; D050171:Dyslipidemias / Q000097:blood; D006801:Humans; D015228:Hypertriglyceridemia / Q000378:metabolism; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D008055:Lipids / Q000097:blood; D017270:Lipoprotein(a) / Q000096:biosynthesis / Q000378:metabolism*; D008297:Male; D008875:Middle Aged
chemical_list: C569471:APOB protein, human; D053299:Apolipoprotein B-100; D001054:Apolipoproteins A; D008055:Lipids; D017270:Lipoprotein(a); D007930:Leucine
keywords: Fed state; Hypertriglyceridemia; Kinetics; Lipoprotein(a)