TY - JOUR
T1 - Decreased cysteine and proline synthesis in parenterally fed, premature infants
AU - Miller, Ronna G.
AU - Jahoor, Farook
AU - Jaksic, Tom
N1 - Funding Information:
From the Corn and Webb Mading Department of Surgery, and the USDAIARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine and Texas Children’s Hospital, Houston, TX. Presented at the 1994 Annual Meeting of the Section on Surgery of the American Academy of Pediatrics, Dallas, Texas, October 21-23, 1994. Funding has been provided by the US Department Agriculture Research Service, under Cooperative 58-6250-1-003. The contents of this article do not necessarily reflect the vtews or policies of the US Department of Agriculture, nor does mention of trade names, commercial products, or organizations imply endorsement by the US government. Address reprint requests to Tom Jaksic, MD, PhD, Depatiment of Pediatric Surgery, Texas Children’s Hospital, Clinical Care Center, Suite 245, 6621 Fannin, MC 3-2325, Houston, TX 77030-2399. Copyright o 1995 by W.B. Saunders Company 0022-3468/95/300?-0010$03.00/0
PY - 1995/7
Y1 - 1995/7
N2 - Little is known about the amino acid (AA) biosynthetic capacity and requirements of premature infants. This study assessed the synthesis of seven biochemically nonessential AA from a universal precursor, glucose, in stable, parenterally fed, premature neonates. Seven infants (six boys, one girl) were studied at a mean age of 6.3 ± 0.6 (SEM) days; mean gestational age was 29.7 ± 1.3 (SEM) weeks, and mean birth weight was 1,222.8 ± 176.5 (SEM) grams. All infants were parenterally fed a mixture of 7.5% to 12.5% dextrose and 2.2% Trophamine, with or without lipid. Mean caloric intake was 93 ± 8.4 (SEM) kcal/kg/d, and total AA intake was standardized at 2.86 g/kg/d AA, plus supplemental cysteine (30 mg/g AA/d). Each infant received a 4-hour continuous, unprimed intravenous infusion of a stable isotope tracer of D-[U13C] glucose (200 mg/kg). Blood samples were obtained before and at the end of the infusion. Conversion of the glucose tracer into seven biochemically nonessential AA (cysteine [Cys], proline [Pro], aspartate [Asp], serine [Ser], glutamate [Glu], alanine [Ala], and glycine [Gly]) was assessed by measuring their isotopic enrichment in plasma, using gas chromatography/mass spectrometry ( GC MS), and expressed as mole percent excess (MPE) (mean ± SEM). The isotopic enrichment of plasma glucose was also measured using GC MS. Free plasma AA concentrations (mean ± SD) were measured using an automated amino acid analyzer. Mean MPE for M + 1, M + 2 and M + 3 Cys, and for M + 1 and M + 3 Pro were not significantly different from 0; M + 2 Pro barely achieved statistical significance (P = .048). In contrast, there was significant (P < .05) enrichment of all isotopomers of all the other test AA except M + 2 Ala (P = .06). The mean free plasma Cys concentration (29.2 ± 13.4 μmol/L) was five-fold lower than the published value for term infants (153 ± 25.5 μmol/L), despite supplementation. Detectable enrichment of all glucose isotopomers confirmed precursor incorporation into the glycolytic/gluconeogenic pathways; the M + 6 isotopomer (precursor) enrichment was 6.87 ± 0.53 MPE. These results provide in vivo evidence to suggest that Cys and Pro are essential amino acids in parenterally fed, premature neonates.
AB - Little is known about the amino acid (AA) biosynthetic capacity and requirements of premature infants. This study assessed the synthesis of seven biochemically nonessential AA from a universal precursor, glucose, in stable, parenterally fed, premature neonates. Seven infants (six boys, one girl) were studied at a mean age of 6.3 ± 0.6 (SEM) days; mean gestational age was 29.7 ± 1.3 (SEM) weeks, and mean birth weight was 1,222.8 ± 176.5 (SEM) grams. All infants were parenterally fed a mixture of 7.5% to 12.5% dextrose and 2.2% Trophamine, with or without lipid. Mean caloric intake was 93 ± 8.4 (SEM) kcal/kg/d, and total AA intake was standardized at 2.86 g/kg/d AA, plus supplemental cysteine (30 mg/g AA/d). Each infant received a 4-hour continuous, unprimed intravenous infusion of a stable isotope tracer of D-[U13C] glucose (200 mg/kg). Blood samples were obtained before and at the end of the infusion. Conversion of the glucose tracer into seven biochemically nonessential AA (cysteine [Cys], proline [Pro], aspartate [Asp], serine [Ser], glutamate [Glu], alanine [Ala], and glycine [Gly]) was assessed by measuring their isotopic enrichment in plasma, using gas chromatography/mass spectrometry ( GC MS), and expressed as mole percent excess (MPE) (mean ± SEM). The isotopic enrichment of plasma glucose was also measured using GC MS. Free plasma AA concentrations (mean ± SD) were measured using an automated amino acid analyzer. Mean MPE for M + 1, M + 2 and M + 3 Cys, and for M + 1 and M + 3 Pro were not significantly different from 0; M + 2 Pro barely achieved statistical significance (P = .048). In contrast, there was significant (P < .05) enrichment of all isotopomers of all the other test AA except M + 2 Ala (P = .06). The mean free plasma Cys concentration (29.2 ± 13.4 μmol/L) was five-fold lower than the published value for term infants (153 ± 25.5 μmol/L), despite supplementation. Detectable enrichment of all glucose isotopomers confirmed precursor incorporation into the glycolytic/gluconeogenic pathways; the M + 6 isotopomer (precursor) enrichment was 6.87 ± 0.53 MPE. These results provide in vivo evidence to suggest that Cys and Pro are essential amino acids in parenterally fed, premature neonates.
KW - Stable isotope
KW - amino acid
KW - metabolism
KW - newborn
KW - nutrition
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U2 - 10.1016/0022-3468(95)90320-8
DO - 10.1016/0022-3468(95)90320-8
M3 - Article
C2 - 7472952
AN - SCOPUS:0029164213
SN - 0022-3468
VL - 30
SP - 953
EP - 958
JO - Journal of Pediatric Surgery
JF - Journal of Pediatric Surgery
IS - 7
ER -