TY - JOUR
T1 - Compartmentation of endogenously synthesized amino acids in neonates
AU - Miller, Ronna G.
AU - Keshen, Tamir H.
AU - Jahoor, Farook
AU - Shew, Stephen B.
AU - Jaksic, Tom
N1 - Funding Information:
The authors would like to thank Melanie del Rosario, Elizabeth Frazer, and Dan Liu for technical assistance, Adam Gillum for illustrations, E. O'Brian Smith, Ph.D. for statistical support, and Leslie Loddeke for editorial assistance. This work is a publication of the USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine and Texas Children's Hospital, Houston, Texas. Funding has been provided from the U.S. Department of Agriculture, Agricultural Research Service under Cooperative Agreement No. 58-6250-1-003. The contents of this publication do not necessarily re¯ect the views or policies of the U.S. Department of Agriculture, nor does the mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.
PY - 1996/6
Y1 - 1996/6
N2 - The conversion of D-[U-13C]glucose to proline (Pro), aspartate (Asp), and cysteine (Cys) is limited in premature neonates, implying that these amino acids (AA) are conditionally essential. This study was performed to determine whether these findings resulted from an insufficient precursor dose or intracellular compartmentation of newly synthesized amino acids, rather than inadequate synthesis. In the first phase of this study, seven total parenteral nutrition-fed, premature neonates received IV D-[U13C]glucose at 5 mg/kg/min for 4 hr. In the second phase, a separate cohort of eight patients received an identical infusion. Blood was obtained before and at the end of the infusion. Isotopic enrichments of the free plasma AA and glucose were measured using gas chromatography/mass spectrometry in both studies. In phase 2, the isotopic enrichments of the AA bound to the hepatically synthesized proteins, fibrinogen and VLDL-apolipoprotein B-100 (apo B-100), were measured. In phase 1, despite a glucose precursor enrichment greater than 66%, Pro, Asp, and Cys remained the least enriched of all amino acids studied (P < 0.05). Asp, but not Pro, demonstrated very high enrichments in apo B-100 (P < 0.001), reflecting distinct intracellular compartmentation. We conclude that the limited conversion of D-[U-13C]glucose to Pro, Asp, and Cys did not result from low precursor glucose enrichment and that there is evidence of Asp compartmentation (intracellular) in premature neonates. However, the low Pro enrichment in the free plasma AA pool and the absence of intracellular Pro compartmentation suggest that Pro may be a conditionally essential AA for premature neonates.
AB - The conversion of D-[U-13C]glucose to proline (Pro), aspartate (Asp), and cysteine (Cys) is limited in premature neonates, implying that these amino acids (AA) are conditionally essential. This study was performed to determine whether these findings resulted from an insufficient precursor dose or intracellular compartmentation of newly synthesized amino acids, rather than inadequate synthesis. In the first phase of this study, seven total parenteral nutrition-fed, premature neonates received IV D-[U13C]glucose at 5 mg/kg/min for 4 hr. In the second phase, a separate cohort of eight patients received an identical infusion. Blood was obtained before and at the end of the infusion. Isotopic enrichments of the free plasma AA and glucose were measured using gas chromatography/mass spectrometry in both studies. In phase 2, the isotopic enrichments of the AA bound to the hepatically synthesized proteins, fibrinogen and VLDL-apolipoprotein B-100 (apo B-100), were measured. In phase 1, despite a glucose precursor enrichment greater than 66%, Pro, Asp, and Cys remained the least enriched of all amino acids studied (P < 0.05). Asp, but not Pro, demonstrated very high enrichments in apo B-100 (P < 0.001), reflecting distinct intracellular compartmentation. We conclude that the limited conversion of D-[U-13C]glucose to Pro, Asp, and Cys did not result from low precursor glucose enrichment and that there is evidence of Asp compartmentation (intracellular) in premature neonates. However, the low Pro enrichment in the free plasma AA pool and the absence of intracellular Pro compartmentation suggest that Pro may be a conditionally essential AA for premature neonates.
UR - http://www.scopus.com/inward/record.url?scp=0029977679&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0029977679&partnerID=8YFLogxK
U2 - 10.1006/jsre.1996.0247
DO - 10.1006/jsre.1996.0247
M3 - Article
C2 - 8661197
AN - SCOPUS:0029977679
SN - 0022-4804
VL - 63
SP - 199
EP - 203
JO - Journal of Surgical Research
JF - Journal of Surgical Research
IS - 1
ER -