Impact of oral L-glutamine on glutathione, glutamine, and glutamate blood levels in volunteers.
OBJECTIVE
We investigated the effect of glutamine supplementation on plasma glutamine (Gln), glutamate (Glu), and whole-blood glutathione (GSH) concentrations in human volunteers.


METHODS
Subjects first adapted to a standard diet with known intakes of protein, total GSH, cysteine, methionine, and total Glu (Glu values include Glu and Gln) for 3 d. Plasma Gln, Glu, and whole-blood GSH levels were then measured at 4-h intervals over 24 h. Supplemental oral Gln (0.3 g x kg(-1) x d(-1)) was ingested for 10 d and then 24-h plasma levels of Gln, Glu, and whole-blood GSH were measured.


RESULTS
The plasma concentrations of Glu (116%; P = 0.006) and Gln (20%; P = 0.046) were significantly higher, whereas concentrations of GSH were significantly lower (37%; P = 0.00091) after oral Gln supplementation.


CONCLUSIONS
Oral Gln increases Glu and Gln levels in plasma of healthy subjects but does not increase GSH red cell (whole-blood) levels. Thus, GSH biosynthesis and preservation of GHS stores in red blood cells may involve rate-limiting substrates other than Gln.
Valencia
Erick
E
Pharmaceutical Nutrition Group, School of Biological and Molecular Sciences, Oxford Brookes University, Oxford, United Kingdom.evalencia@brookes.ac.uk
Marin
Angela
A
Hardy
Gil
G
D000284:Administration, Oral; D000328:Adult; D000975:Antioxidants / Q000032:analysis; D002940:Circadian Rhythm; D019587:Dietary Supplements; D004912:Erythrocytes / Q000737:chemistry; D005260:Female; D018698:Glutamic Acid / Q000097:blood*; D005973:Glutamine / Q000008:administration & dosage* / Q000097:blood* / Q000494:pharmacology; D005978:Glutathione / Q000096:biosynthesis / Q000097:blood* / Q000493:pharmacokinetics; D006801:Humans; D007536:Isomerism; D008297:Male
D000975:Antioxidants; D005973:Glutamine; D018698:Glutamic Acid; D005978:Glutathione