title: Effects of a National Cholesterol Education Program Step II Diet on apolipoprotein A-IV metabolism within triacylglycerol-rich lipoproteins and plasma.
abstract: BACKGROUND
  Apolipoprotein (apo) A-IV is a major component of triacylglycerol-rich lipoprotein (TRL) apolipoproteins.
  
  
  OBJECTIVE
  We investigated the effects of dietary saturated fat and cholesterol restriction on the metabolism of TRL and plasma apo A-IV.
  
  
  METHODS
  We assessed TRL and plasma apo A-IV kinetics in 16 and 4 subjects, respectively, consuming an average US (baseline) diet for 6 wk and a National Cholesterol Education Program Step II diet for 24 wk, respectively. At the end of each diet period, all subjects received a primed, constant infusion of deuterated leucine for 15 h with hourly feeding. Ratios of stable-isotope tracer to tracee were measured by using gas chromatography-mass spectrometry, and kinetic data were modeled by using SAAM II.
  
  
  RESULTS
  Mean apo A-IV concentrations during the isotope infusion period were 6.9 +/- 2.6 mg/L in TRL and 2.2 +/- 3.2 mg/L in plasma with the baseline diet; these values were 37.7% (P < 0.001) and 19.4% (P < 0.01) lower with the Step II diet. Similar changes were observed in the fasting state between the 2 diets. The mean apo A-IV secretion rate decreased significantly from baseline by 59.6% in TRLs and by 40.2% in plasma. Significant correlations were observed between TRL apo A-IV concentrations and the secretion rate (r = 0.94, P < 0.001) and between TRL apo A-IV pool size and TRL-cholesterol concentrations (r = 0.48, P < 0.01).
  
  
  CONCLUSIONS
  Our data indicate that the National Cholesterol Education Program Step II diet significantly decreases TRL and plasma apo A-IV concentrations compared with the average US diet and that this decrease is due to a decreased secretion rate.
authors.affiliation: Lipid Metabolism Laboratory and the Mass Spectrometry Laboratory, Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Sun
authors.forename: F K
authors.initials: FK
authors.lastname: Welty
authors.forename: G G
authors.initials: GG
authors.lastname: Dolnikowski
authors.forename: A H
authors.initials: AH
authors.lastname: Lichtenstein
authors.forename: E J
authors.initials: EJ
authors.lastname: Schaefer
mesh_terms: D000328:Adult; D000975:Antioxidants; D001054:Apolipoproteins A / Q000097:blood / Q000378:metabolism*; D002791:Cholesterol, Dietary / Q000008:administration & dosage* / Q000378:metabolism; D018752:Diet, Fat-Restricted; D004041:Dietary Fats / Q000008:administration & dosage* / Q000378:metabolism; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007553:Isotope Labeling; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D001054:Apolipoproteins A; D002791:Cholesterol, Dietary; D004041:Dietary Fats; D014280:Triglycerides; C022205:apolipoprotein A-IV