Acute depletion of plasma glutamine increases leucine oxidation in prednisone-treated humans.
OBJECTIVE
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.
Le Bacquer
Olivier
O
INSERM U.539, Centre de Recherche en Nutrition Humaine, Nantes, France.
Mauras
Nelly
N
Welch
Susan
S
Haymond
Morey
M
Darmaun
Dominique
D
D000293:Adolescent; D000328:Adult; D002247:Carbon Isotopes; D018592:Cross-Over Studies; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage / Q000378:metabolism*; D005973:Glutamine / Q000097:blood* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007930:Leucine / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D010654:Phenylbutyrates / Q000494:pharmacology*; D011241:Prednisone / Q000008:administration & dosage / Q000378:metabolism*; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*
D002247:Carbon Isotopes; D005938:Glucocorticoids; D010654:Phenylbutyrates; D011506:Proteins; D005973:Glutamine; D007930:Leucine; D011241:Prednisone