Effects of leucine, isoleucine, or threonine infusion on leucine metabolism in humans

Journal Article · Thu Oct 01 04:00:00 EDT 1987 · American Journal of Physiology; (USA)

OSTI ID:7266834

Schwenk, W F; Haymond, M W ^[1]

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1. Mayo Clinic and Foundation, Rochester, MN (USA)

Leucine and/or its {alpha}-keto acid, {alpha}-ketoisocaproate (KIC), have been reported to spare protein in humans. To determine whether specific amino acid infusions affect whole-body protein metabolism as estimated by changes in leucine flux and oxidation, five groups of normal subjects were infused with saline, leucine, isoleucine, or threonine. Independent estimates of leucine metabolism were obtained using simultaneous infusions of ({sup 3}H)-leucine and {alpha}-({sup 14}C)ketoisocaproate. Nearly identical results were obtained using either tracer compared with the saline controls. Compared with the saline controls, leucine infusion (1) had no effect on estimated rates of appearance of endogenous leucine, (2) stimulated leucine oxidation, (3) decreased plasma concentrations of other amino acids, and (4) stimulated nonoxidized leucine disappearance in a dose-dependent fashion. In contrast, isoleucine and threonine infusions had no effect on leucine metabolism. Assuming the validity of the isotope model employed, these data suggest that the purported anabolic effect of leucine infusion on whole-body protein metabolism is mediated via stimulation of protein synthesis rather than decreased proteolysis.

• OSTI ID: 7266834
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 253:4; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BIOASSAY
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
DIAGNOSTIC TECHNIQUES
GLUCAGON
HORMONES
HYDROGEN COMPOUNDS
HYDROXY ACIDS
IMMUNOASSAY
IMMUNOLOGY
INSULIN
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEUCINE
METABOLISM
ORGANIC ACIDS
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PEPTIDES
PITUITARY HORMONES
POLYPEPTIDES
PROTEINS
RADIOASSAY
RADIOIMMUNOASSAY
RADIOIMMUNODETECTION
RADIOIMMUNOLOGY
STH
SYNTHESIS
THREONINE
TRACER TECHNIQUES
TRITIUM COMPOUNDS