Elsevier

Metabolism

Volume 46, Issue 2, February 1997, Pages 164-167
Metabolism

Splanchnic versus whole-body production of α-ketoisocaproate from leucine in the fed state

https://doi.org/10.1016/S0026-0495(97)90296-1Get rights and content

Abstract

The extent to which dietary branched-chain amino acids are deaminated by the splanchnic tissues (ie, the liver and gut) in the fed state and released as ketoacids into the systemic circulation is not known. To determine this, we combined the oral (L-[1-13C]-leucine, [13C]-Leu) and intravenous (l-[5,5,5-2H3]leucine, [2H3]-Leu) leucine tracer infusion with the intravenous administration of an independent isotope of the leucine ketoanalog α-ketoisocaproic acid (KIC) ([4,5-3H]KIC). The study was conducted during constant administration of a complete mixed meal. We found that 26% ± 5% of the orally administered leucine was taken up by the splanchnic organs at first pass, whereas 74% ± 5% appeared in the systemic circulation. The rate of splanchnic KIC release from deamination of dietary leucine accounted for 3% ± 0.2% of the oral leucine administration rate and 13% ± 2% of leucine splanchnic uptake (fractional splanchnic deamination). The fraction of whole-body total leucine uptake that was deaminated to KIC was 41% ± 5% (P < .05 v fractional splanchnic deamination of dietary leucine uptake). We conclude that (1) the release of KIC from leucine deamination within splanchnic tissues constitutes a minimal fraction of first-pass dietary leucine uptake, and (2) splanchnic tissues are relatively less efficient than the whole body in KIC production from leucine deamination.

References (15)

  • J Cortiella et al.

    Leucine kinetics at graded intakes in young man: Quantitative fate of dietary leucine

    Am J Clin Nutr

    (1988)
  • FL Shinnick et al.

    Branched-chain amino acid oxidation by isolated rat tissue preparation

    Biochim Biophys Acta

    (1976)
  • G Biolo et al.

    Leucine and phenylalanine kinetics during mixed meal ingestion: A multiple tracer approach

    Am J Physiol

    (1992)
  • P Tessari et al.

    Fasting and postprandial phenylalanine and leucine kinetics in liver cirrhosis

    Am J Physiol

    (1994)
  • G Biolo et al.

    Regulation of postprandial whole-body proteolysis in insulin deprived IDDM

    Diabetes

    (1994)
  • FF Horber et al.

    Human growth hormone prevents the protein catabolic side effects of prednisone in humans

    J Clin Invest

    (1990)
  • RA Hoerr et al.

    Leucine kinetics from [2H3]- and [13C]-leucine infused simultaneously by gut and vein

    Am J Physiol

    (1991)
There are more references available in the full text version of this article.

Cited by (23)

View all citing articles on Scopus
1

Present address for G.B.: Institute of Clinica Medica, Hospital of Cattinara, 34149 Trieste, Italy.

View full text