Contribution of proteolytic and metabolic sources to hepatic glutamine by 2H NMR analysis of urinary phenylacetylglutamine 2H-enrichment from 2H2O

Proteolytic and cataplerotic sources of hepatic glutamine were determined by H-2 NMR analysis of urinary phenylacetylglutamine (PAGN) H-2-enrichments in eight healthy subjects after (H2O)-H-2 and phenylbutyric acid ingestion. Body water enrichment was 0.49 +/- 0.03%. PAGN was enriched to lowerlevels with significant differences between the various glutamine positions. PAGN position 2 enrichment=0.33 +/- 0.02%; 3R=0.27 +/- 0.02%; 3S=0.27 +/- 0.02% and position 4=0.17 +/- 0.01%. Position 3R,S enrichments are conditional with the net conversion of citrate to glutamate and are therefore markers of cataplerosis. From the ratio of positions 3R,S to body water enrichment, 55 +/- 3% of hepatic glutamine was derived from cataplerosis and 45 +/- 3% from proteolysis. In conclusion, enrichment of PAGN 3R,S hydrogens relative to that of body water reflects the contribution of cataplerotic and proteolytic sources to hepatic glutamine. (C) 2009 Elsevier Inc. All rights reserved.