Acute depletion of plasma glutamine increases leucine oxidation in prednisone-treated humans

Clin Nutr. 2007 Apr;26(2):231-8. doi: 10.1016/j.clnu.2006.09.010. Epub 2006 Nov 13.

Abstract

Background, aims & methods: To determine whether depletion in plasma glutamine worsens the catabolic response to corticosteroids, seven healthy volunteers received oral prednisone for 6 days on two separate occasions, at least 2 weeks apart, and in random order. On the sixth day of each treatment course, they received 5 h intravenous infusions of L-[1-(14)C]-leucine and L-[1-(13)C]-glutamine in the postabsorptive state (1) under baseline conditions (prednisone only day) and (2) after 24h of treatment with phenylbutyrate (prednisone+phenylbutyrate day), a glutamine chelating agent.

Results: Phenylbutyrate treatment was associated with (1) an approximately 15% decline in plasma glutamine concentration (627+/-39 vs. 530+/-31 micromol l(-1); P<0.05), (2) no change in leucine appearance rate, an index of protein breakdown (124+/-9 vs. 128+/-9 micromol kg(-1) h(-1); NS) nor in non-oxidative leucine disposal, an index of whole body protein synthesis (94+/-9 vs. 91+/-7 micromol kg(-1) h(-1); NS), and (3) a approximately 25% rise in leucine oxidation (30+/-1 vs. 38+/-2 micromol kg(-1) h(-1), P<0.05), despite an approximately 25% decline (P<0.05) in leucine concentration.

Conclusions: In a model of mild, stress-induced protein catabolism, depletion of plasma glutamine per se may worsen branched chain amino acid and protein wasting.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Carbon Isotopes
  • Cross-Over Studies
  • Female
  • Glucocorticoids / administration & dosage
  • Glucocorticoids / metabolism*
  • Glutamine / blood*
  • Glutamine / metabolism
  • Humans
  • Kinetics
  • Leucine / metabolism*
  • Male
  • Oxidation-Reduction
  • Phenylbutyrates / pharmacology*
  • Prednisone / administration & dosage
  • Prednisone / metabolism*
  • Protein Biosynthesis
  • Proteins / metabolism*

Substances

  • Carbon Isotopes
  • Glucocorticoids
  • Phenylbutyrates
  • Proteins
  • Glutamine
  • Leucine
  • Prednisone