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Phenylalanine and tyrosine metabolism in neonates receiving parenteral nutrition differing in pattern of amino acids.
Pediatr Res 1998; 44(6):907-14PR

Abstract

Tyrosine is considered to be an indispensable dietary amino acid in the neonate, yet achieving adequate parenteral tyrosine intake is difficult due to its poor solubility. Increasing the supply of phenylalanine is the most common means of compensating for low tyrosine levels. Unfortunately, plasma phenylalanine concentrations are sometimes elevated in infants receiving high phenylalanine intake. This led us to study the phenylalanine and tyrosine metabolism in 16 neonates randomized to receive total parenteral nutrition with either a high or a moderate phenylalanine-containing amino acid solution. A primed, 24-h continuous stable isotope infusion of L-[1-13C]phenylalanine and L-[3,3-2H2]tyrosine was given to enable the measurement of phenylalanine and tyrosine kinetics. Results demonstrated that 1) phenylalanine hydroxylation was significantly greater in infants receiving high phenylalanine, 2) phenylalanine oxidation and percent dose oxidized was also significantly greater in infants receiving high phenylalanine, 3) apparent phenylalanine retention was greater in neonates receiving high phenylalanine, and 4) alternate catabolites of phenylalanine and tyrosine metabolism were significantly greater in infants receiving high phenylalanine compared with moderate phenylalanine. We conclude that neonates respond to increased parenteral phenylalanine intake by increasing their hydroxylation and oxidation rates. The greater oxidation of phenylalanine in infants receiving high phenylalanine in conjunction with the urinary excretion of alternate catabolites of phenylalanine and tyrosine suggests that the high phenylalanine intake may be in excess of needs. However, the lower apparent phenylalanine retention observed in infants receiving moderate phenylalanine suggests that the total aromatic amino acid level of moderate phenylalanine may be deficient for neonatal needs.

Authors+Show Affiliations

Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Comparative Study
Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

9853926

Citation

Roberts, S A., et al. "Phenylalanine and Tyrosine Metabolism in Neonates Receiving Parenteral Nutrition Differing in Pattern of Amino Acids." Pediatric Research, vol. 44, no. 6, 1998, pp. 907-14.
Roberts SA, Ball RO, Filler RM, et al. Phenylalanine and tyrosine metabolism in neonates receiving parenteral nutrition differing in pattern of amino acids. Pediatr Res. 1998;44(6):907-14.
Roberts, S. A., Ball, R. O., Filler, R. M., Moore, A. M., & Pencharz, P. B. (1998). Phenylalanine and tyrosine metabolism in neonates receiving parenteral nutrition differing in pattern of amino acids. Pediatric Research, 44(6), pp. 907-14.
Roberts SA, et al. Phenylalanine and Tyrosine Metabolism in Neonates Receiving Parenteral Nutrition Differing in Pattern of Amino Acids. Pediatr Res. 1998;44(6):907-14. PubMed PMID: 9853926.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Phenylalanine and tyrosine metabolism in neonates receiving parenteral nutrition differing in pattern of amino acids. AU - Roberts,S A, AU - Ball,R O, AU - Filler,R M, AU - Moore,A M, AU - Pencharz,P B, PY - 1998/12/16/pubmed PY - 1998/12/16/medline PY - 1998/12/16/entrez SP - 907 EP - 14 JF - Pediatric research JO - Pediatr. Res. VL - 44 IS - 6 N2 - Tyrosine is considered to be an indispensable dietary amino acid in the neonate, yet achieving adequate parenteral tyrosine intake is difficult due to its poor solubility. Increasing the supply of phenylalanine is the most common means of compensating for low tyrosine levels. Unfortunately, plasma phenylalanine concentrations are sometimes elevated in infants receiving high phenylalanine intake. This led us to study the phenylalanine and tyrosine metabolism in 16 neonates randomized to receive total parenteral nutrition with either a high or a moderate phenylalanine-containing amino acid solution. A primed, 24-h continuous stable isotope infusion of L-[1-13C]phenylalanine and L-[3,3-2H2]tyrosine was given to enable the measurement of phenylalanine and tyrosine kinetics. Results demonstrated that 1) phenylalanine hydroxylation was significantly greater in infants receiving high phenylalanine, 2) phenylalanine oxidation and percent dose oxidized was also significantly greater in infants receiving high phenylalanine, 3) apparent phenylalanine retention was greater in neonates receiving high phenylalanine, and 4) alternate catabolites of phenylalanine and tyrosine metabolism were significantly greater in infants receiving high phenylalanine compared with moderate phenylalanine. We conclude that neonates respond to increased parenteral phenylalanine intake by increasing their hydroxylation and oxidation rates. The greater oxidation of phenylalanine in infants receiving high phenylalanine in conjunction with the urinary excretion of alternate catabolites of phenylalanine and tyrosine suggests that the high phenylalanine intake may be in excess of needs. However, the lower apparent phenylalanine retention observed in infants receiving moderate phenylalanine suggests that the total aromatic amino acid level of moderate phenylalanine may be deficient for neonatal needs. SN - 0031-3998 UR - https://www.unboundmedicine.com/medline/citation/9853926/Phenylalanine_and_tyrosine_metabolism_in_neonates_receiving_parenteral_nutrition_differing_in_pattern_of_amino_acids_ L2 - http://dx.doi.org/10.1203/00006450-199812000-00014 DB - PRIME DP - Unbound Medicine ER -