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Cyst(e)ine requirements in enterally fed very low birth weight preterm infants

Maaike A Riedijk1, Gardi Voortman, Ron H T van Beek

  • 1Erasmus MC-Sophia Children's Hospital, Department of Pediatrics, Division of Neonatology, Dr Molewaterplein 60, 3015 GJ, Rotterdam, The Netherlands.

Pediatrics
|February 20, 2008
PubMed

Insights

Cystine is likely not essential for preterm infants fed enterally with adequate methionine. Studies show no increased need for cystine, suggesting it

Area of Science:

  • Nutritional biochemistry and metabolism in neonates.
  • Pediatric gastroenterology and clinical nutrition.
  • Amino acid metabolism in preterm infants.

Background:

  • Optimal nutrition is critical for preterm infant development.
  • Amino acid requirements differ in preterm infants due to growth rates.
  • Cystine may be conditionally essential for preterm infants.

Purpose of the Study:

  • To determine cystine requirements in enterally fed preterm infants (<29 weeks gestational age).
  • To assess cystine needs at 32 and 35 weeks postmenstrual age.
  • To investigate if cystine is conditionally essential in this population.

Main Methods:

  • Randomized controlled trial with 5 graded cystine diets (adequate methionine).
  • Indicator amino acid oxidation technique using [1-(13)C]phenylalanine.
  • 24-hour adaptation period before measurement.

Main Results:

  • 47 very low birth weight preterm infants (gestational age <29 weeks) were studied.
  • Increased dietary cystine did not decrease [1-(13)C]phenylalanine oxidation.
  • No evidence of limited endogenous cystine synthesis was found.

Conclusions:

  • Cystine is likely not conditionally essential in preterm infants >32 weeks postmenstrual age with adequate methionine.
  • Estimated cystine requirement is <18 mg/kg/day in this group.
  • Findings do not support the hypothesis of limited endogenous cystine synthesis.
Abstract

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