Threonine requirement of parenterally fed postsurgical human neonates

Abstract

BackgroundThe threonine requirement of human neonates who receive parenteral nutrition (PN) has not been determined experimentally. ObjectiveThe objective was to determine the parenteral threonine requirement for human neonates by using the minimally invasive indicator amino acid oxidation technique with l-[1-13C]phenylalanine as the indicator amino acid. DesignNine 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 13CO2 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 13CO2 release (F13CO2) and l-[1-13C]phenylalanine oxidation. ResultsThe 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 F13CO2 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. ConclusionThis 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).