title: Lysine requirement of the enterally fed term infant in the first month of life.
abstract: BACKGROUND
  Infant nutrition has a major impact on child growth and functional development. Low and high intakes of protein or amino acids could have a detrimental effect.
  
  
  OBJECTIVE
  The objective of the study was to determine the lysine requirement of enterally fed term neonates by using the indicator amino acid oxidation (IAAO) method. L-[1-(13)C]phenylalanine was used as an indicator amino acid.
  
  
  METHODS
  Twenty-one neonates were randomly assigned to lysine intakes that ranged from 15 to 240 mg · kg(-1) · d(-1). Breath, urine, and blood samples were collected at baseline and during the plateau. The mean lysine requirement was determined by using biphasic linear regression crossover analysis on the fraction of (13)CO(2) recovery from L-[1-(13)C]phenylalanine oxidation (F(13)CO(2)) and phenylalanine oxidation rates calculated from the L-[1-(13)C]phenylalanine enrichment of urine and plasma.
  
  
  RESULTS
  The mean (±SD) phenylalanine flux calculated from urine and plasma L-[1-(13)C]phenylalanine enrichment data were 88.3 ± 6.9 and 84.5 ± 7.4 μmol · kg(-1) · h(-1), respectively. Graded intakes of lysine had no effect on phenylalanine fluxes. The mean lysine requirement determined by F(13)CO(2) was 130 mg · kg(-1) · d(-1) (upper and lower CIs: 183.7 and 76.3 mg · kg(-1) · d(-1), respectively). The mean requirement was identical to the requirement determined by using phenylalanine oxidation rates in urine and plasma.
  
  
  CONCLUSIONS
  The mean lysine requirement of enterally fed term neonates was determined by using F(13)CO(2) and phenylalanine oxidation rates calculated from the L-[1-(13)C]phenylalanine enrichment of urine and plasma. These methods yielded a similar result of 130 mg lysine · kg(-1) · d(-1). This study demonstrates that sampling of (13)CO(2) in expired air is sufficient to estimate the lysine requirement by using the IAAO method in infants. This trial was registered at www.trialregister.nl as NTR1610.
authors: Department of Pediatrics, Division of Neonatology, Erasmus Medical Centre-Sophia Children's Hospital, Rotterdam, Netherlands.
authors: Lisha
authors: L
authors: Huang
authors: Jacomine E
authors: JE
authors: Hogewind-Schoonenboom
authors: Femke
authors: F
authors: de Groof
authors: Jos W R
authors: JW
authors: Twisk
authors: Gardi J
authors: GJ
authors: Voortman
authors: Kristien
authors: K
authors: Dorst
authors: Henk
authors: H
authors: Schierbeek
authors: Günther
authors: G
authors: Boehm
authors: Ying
authors: Y
authors: Huang
authors: Chao
authors: C
authors: Chen
authors: Johannes B
authors: JB
authors: van Goudoever
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D018592:Cross-Over Studies; D004750:Enteral Nutrition; D005260:Female; D006801:Humans; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D007553:Isotope Labeling; D008239:Lysine / Q000008:administration & dosage* / Q000378:metabolism; D008297:Male; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide; D010649:Phenylalanine; D008239:Lysine