title: An isotopic study of the effect of dietary carbohydrate on the metabolic fate of dietary leucine and phenylalanine.
abstract: The fate of dietary leucine and phenylalanine was studied in five healthy, young adult men, by using a dual, stable isotope-tracer infusion approach to estimate amino acid fluxes, splanchnic (Sp) uptake, and dietary of absorbed amino acid to the peripheral circulation. Subject received two, 4-h tracer infusions of [1-13C]leucine and [15N]phenylalanine infused through a feeding tube placed in the duodenum, and [5,5,5-2H3]leucine, [ring-2H5]phenylalanine, and [6,6-2H2]glucose infused simultaneously by vein. In one experiment subjects received an amino acid mixture (83 mg amino acid.kg-1.h-1) via the feeding tube and in the other experiment amino acids were supplied with carbohydrate (CHO) (167 mg.kg-1.h-1). Sp uptake of dietary leucine decreased with added dietary CHO (29% of ingested leucine for amino acids alone vs 20% with CHO; P < 0.05) but was not different for phenylalanine (P > 0.05). Addition of CHO decreased both release of leucine via protein breakdown and leucine oxidation and increased body leucine balance (P < 0.05).
authors.affiliation: Clinical Research Center and School of Science, Massachusetts Institute of Technology, Cambridge 02142.
authors.forename: M
authors.initials: M
authors.lastname: Krempf
authors.forename: R A
authors.initials: RA
authors.lastname: Hoerr
authors.forename: V A
authors.initials: VA
authors.lastname: Pelletier
authors.forename: L M
authors.initials: LM
authors.lastname: Marks
authors.forename: R
authors.initials: R
authors.lastname: Gleason
authors.forename: V R
authors.initials: VR
authors.lastname: Young
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002247:Carbon Isotopes; D003903:Deuterium; D004032:Diet; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D006801:Humans; D007651:Keto Acids / Q000378:metabolism; D007930:Leucine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D009587:Nitrogen Isotopes; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D013152:Splanchnic Circulation
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D004040:Dietary Carbohydrates; D007651:Keto Acids; D009587:Nitrogen Isotopes; D010649:Phenylalanine; C013082:alpha-ketoisocaproic acid; D003903:Deuterium; D007930:Leucine