Leucine kinetics after a brief fast and in response to feeding in premature infants

Scott C. Denne, Cheryl A. Karn, Edward A. Liechty

Research output: Contribution to journalArticle

24 Scopus citations


To examine how feeding affects changes in leucine and protein metabolism, leucine kinetics were determined in nine preterm infants (32 ± 2 wk gestation: x̄ ± SD) after a brief fast and again during hourly feedings. Rates of leucine oxidation were similar during the lasting and feeding periods (31 ± 4 vs 37 ± 6 μmol·kg-1·h-1; x̄ ± SE). The nonoxidative disposal rates of leucine (a reflection of protein synthesis) were also similar during both periods (228 ± 20 vs 205 ± 10 μmol·kg-1·h-1; x̄ ± SE). In contrast, the rates of leucine release from endogenous protein (an indication of protein breakdown) were significantly reduced by feeding (259 ± 23 vs 185 ± 11 μmol·kg-1·h-1; x̄ ± SE, P = 0.02). A significant positive correlation was demonstrated between the fasting rate of leucine release from endogenous protein and the degree of suppression produced by feeding (r2 = 0.796, P = 0.001). Conversely, a significant inverse correlation was shown between the nonoxidative disposal rate of leucine during fasting and the increase in response to feeding (r2 = 0.848, P < 0.001). These data suggest that premature infants respond to feeding after a brief fast by suppressing protein breakdown, rather than by increasing protein synthesis, and changes in protein metabolism produced by feeding in premature newborns may be influenced by the prevailing rates of protein breakdown and synthesis during fasting.

Original languageEnglish (US)
Pages (from-to)899-904
Number of pages6
JournalAmerican Journal of Clinical Nutrition
Issue number5
StatePublished - 1992


  • Essential amino acid metabolism
  • Leucine
  • Premature infants
  • Protein synthesis
  • Protein turnover
  • Stable-isotope tracers

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Food Science

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