title: Human apolipoprotein A-I kinetics within triglyceride-rich lipoproteins and high density lipoproteins.
abstract: Stable isotope methodology was used to determine the kinetic behavior of apolipoprotein (apo) A-I within the triglyceride-rich lipoprotein (TRL) fraction and to compare TRL apoA-I kinetics with that of apoA-I in high density lipoprotein (HDL) and TRL apoB-48. Eight subjects (5 males and 3 females) over the age of 40 were placed on a baseline average American diet and after 6 weeks received a primed-constant infusion of [5,5,5-(2)H(3)]-l-leucine for 15 h while consuming small hourly meals of identical composition. HDL and TRL apoA-I and TRL apoB-48 tracer/tracee enrichment curves were obtained by gas chromatography;-mass spectrometry. Data were fitted to a compartmental model to determine the fractional secretion rates of apoA-I and apoB-48 within each lipoprotein fraction. Mean plasma apoA-I levels in TRL and HDL fractions were 0. 204 +/- 0.057 and 134 +/- 15 mg/dl, respectively. The mean fractional catabolic rate (FCR) of TRL apoA-I was 0.250 +/- 0.069 and HDL apoA-I was 0.239 +/- 0.054 pools/day, with mean estimated residence times (RT) of 4.27 and 4.37 days, respectively. The mean TRL apoB-48 FCR was 5.2 +/- 2.0 pools/day and the estimated mean RT was 5.1 +/- 1.8 h. Our results indicate that apoA-I is catabolized at a slower rate than apoB-48 within TRL, and that apoA-I within TRL and HDL fractions are catabolized at similar rates.
authors.affiliation: Lipid Metabolism Laboratory, Mass Spectrometry Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.
authors.forename: W
authors.initials: W
authors.lastname: Vélez-Carrasco
authors.forename: A H
authors.initials: AH
authors.lastname: Lichtenstein
authors.forename: P H
authors.initials: PH
authors.lastname: Barrett
authors.forename: Z
authors.initials: Z
authors.lastname: Sun
authors.forename: G G
authors.initials: GG
authors.lastname: Dolnikowski
authors.forename: F K
authors.initials: FK
authors.lastname: Welty
authors.forename: E J
authors.initials: EJ
authors.lastname: Schaefer
mesh_terms: D000328:Adult; D000368:Aged; D016632:Apolipoprotein A-I / Q000097:blood*; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B / Q000097:blood; D005260:Female; D006801:Humans; D007700:Kinetics; D008074:Lipoproteins / Q000097:blood* / Q000737:chemistry; D008075:Lipoproteins, HDL / Q000097:blood* / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D014280:Triglycerides / Q000097:blood*
chemical_list: D016632:Apolipoprotein A-I; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B; D008074:Lipoproteins; D008075:Lipoproteins, HDL; D014280:Triglycerides