Threonine requirement of parenterally fed postsurgical human neonates.
BACKGROUND
The threonine requirement of human neonates who receive parenteral nutrition (PN) has not been determined experimentally.


OBJECTIVE
The objective was to determine the parenteral threonine requirement for human neonates by using the minimally invasive indicator amino acid oxidation technique with L-[1-(13)C]phenylalanine as the indicator amino acid.


METHODS
Nine postsurgical neonates were randomly assigned to 16 threonine intakes ranging from 10 to 100 mg . kg(-1) . d(-1). Breath and urine samples were collected at baseline and at plateau for (13)CO(2) and amino acid enrichment, respectively. The mean threonine requirement was determined by applying a 2-phase linear regression crossover analysis to the measured rates of (13)CO(2) release (F(13)CO(2)) and L-[1-(13)C]phenylalanine oxidation.


RESULTS
The mean threonine parenteral requirement determined by using phenylalanine oxidation was 37.6 mg . kg(-1) . d(-1) (upper and lower confidence limits, respectively: 29.9 and 45.2 mg . kg(-1) . d(-1)) and by using F(13)CO(2) oxidation was 32.8 mg . kg(-1) . d(-1) (upper and lower confidence limits, respectively: 29.7 and 35.9 mg . kg(-1) . d(-1)). Graded intakes of threonine had no effect on phenylalanine flux.


CONCLUSIONS
This is the first study to report on the threonine requirement for human neonates receiving PN. We found that the threonine requirement for postsurgical PN-fed neonates is 22-32% of the content of threonine that is presently found in commercial PN solutions (111-165 mg . kg(-1) . d(-1)).
Chapman
Karen P
KP
Research Institute, The Hospital for Sick Children, Toronto, ON, Canada.
Courtney-Martin
Glenda
G
Moore
Aideen M
AM
Ball
Ronald O
RO
Pencharz
Paul B
PB
D000222:Adaptation, Physiological; D001944:Breath Tests; D002247:Carbon Isotopes / Q000032:analysis / Q000652:urine; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007227:Infant Nutritional Physiological Phenomena / Q000502:physiology*; D007231:Infant, Newborn; D008297:Male; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D010288:Parenteral Nutrition; D010649:Phenylalanine / Q000378:metabolism; D011182:Postoperative Care; D013912:Threonine / Q000008:administration & dosage* / Q000378:metabolism* / Q000652:urine; D016482:Urinalysis
D002247:Carbon Isotopes; D013912:Threonine; D010649:Phenylalanine