Amino acids do not suppress proteolysis in premature neonates

Brenda B. Poindexter, Cheryl A. Karn, Catherine A. Leitch, Edward A. Liechty, Scott C. Denne

Research output: Contribution to journalArticle

41 Scopus citations


To determine whether increased amino acid availability can reduce proteolysis in premature neonates and to assess the capacity of infants born prematurely to acutely increase the irreversible catabolism of the essential amino acids leucine (via oxidation) and phenylalanine (via hydroxylation to form tyrosine), leucine and phenylalanine kinetics were measured under basal conditions and in response to a graded infusion of intravenous amino acids (1.2 and 2.4 g·kg-1·day-1) in clinically stable premature (∼32 wk gestation) infants in the 1st wk of life. In contrast to the dose-dependent suppression of proteolysis seen in healthy full-term neonates, the endogenous rates of appearance of leucine and phenylalanine (reflecting proteolysis) were unchanged in response to amino acids (297 ± 21, 283 ± 19, and 284 ± 31 μmol·kg-1·-1 for leucine and 92 ± 6, 92 ± 4, and 84 ± 7 μmol·kg-1·h-1 for phenylalanine). Similar to full-term neonates, leucine oxidation (40 ± 5, 65 ± 6, and 99 ± 7 μmol·kg-1·h-1 and phenylalanine hydroxylation (12 ± 1, 16 ± 1, and 20 ± 2 μmol·kg-1·h-1) increased in a stepwise fashion in response to graded amino acids, This capacity to increase phenylalanine hydroxylation may be crucial to meet tyrosine needs when exogenous supply is limited. Finally, to determine whether amino acids stimulate glucose production in premature neonates, glucose rate of appearance was measured during each study period. In response to amino acid infusion, rates of endogenous glucose production were unchanged (and near zero).

Original languageEnglish (US)
Pages (from-to)E472-E478
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number3 44-3
StatePublished - Oct 1 2001


  • Leucine
  • Phenylalanine
  • Premature newborns
  • Protein turn-over
  • Stable isotope tracers

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry
  • Physiology (medical)

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  • Cite this

    Poindexter, B. B., Karn, C. A., Leitch, C. A., Liechty, E. A., & Denne, S. C. (2001). Amino acids do not suppress proteolysis in premature neonates. American Journal of Physiology - Endocrinology and Metabolism, 281(3 44-3), E472-E478.