Metabolic effects of glutamine and glutamate ingestion in healthy subjects and in persons with chronic obstructive pulmonary disease.
BACKGROUND
Because low plasma glutamate and glutamine concentrations are often seen in chronic obstructive pulmonary disease (COPD), glutamine or glutamate supplementation may be a good option for preventing further metabolic disturbances in COPD patients. However, the metabolic effects of glutamate supplementation have never been compared with those of glutamine supplementation.


OBJECTIVE
We compared the metabolic effects of repeated ingestion of glutamine and glutamate in COPD patients and in age-matched healthy control subjects.


METHODS
On 3 d separated by intervals of > or = 2 d, a protocol of primed constant and continuous infusion of [2H5]phenylalanine and [2H2]tyrosine was performed for 3 h in 8 stable male COPD patients and 8 healthy control subjects. After a 90-min tracer infusion, all subjects ingested a glutamine or glutamate drink or the same amount of water every 20 min for 80 min. Blood samples were taken at the end of the postabsorptive and ingestion periods to test for effects on plasma amino acid and substrate concentrations and whole-body protein turnover.


RESULTS
Glutamate but not glutamine ingestion resulted in higher plasma ornithine concentrations than did water ingestion (P < 0.01). The change in plasma arginine, citrulline, and urea concentrations was significantly (P < 0.01) higher after glutamine ingestion than after water or glutamate ingestion. Whole-body protein turnover decreased overall, independent of the drink consumed.


CONCLUSIONS
Repeated ingestion of glutamine and glutamate resulted in different effects on the plasma amino acid concentration. In both groups, ingestion of glutamine but not of glutamate increased the plasma concentrations of citrulline and arginine, substrates produced in the intestine and the liver.
Rutten
Erica P A
EP
Department of Respiratory Medicine, University of Maastricht, Maastricht, The Netherlands. e.rutten@pul.unimaas.nl
Engelen
Marielle P K J
MP
Wouters
Emiel F M
EF
Schols
Annemie M W J
AM
Deutz
Nicolaas E P
NE
D000368:Aged; D000596:Amino Acids / Q000097:blood* / Q000378:metabolism; D016022:Case-Control Studies; D003903:Deuterium; D019587:Dietary Supplements; D018698:Glutamic Acid / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism; D005973:Glutamine / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D019518:Postprandial Period; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000378:metabolism*; D012129:Respiratory Function Tests
D000596:Amino Acids; D005973:Glutamine; D018698:Glutamic Acid; D003903:Deuterium