The threonine requirement in preterm neonates. De behoefte aan threonine in de voeding van de preterm geboren neonaat.

The exact requirement of essential amino acids for term and preterm neonates is not known. So far, requirements have been estimated either from the composition of human milk or are derived using nitrogen balance studies which are known to be imprecise. By using a new method, the indicator amino acid oxidation (IAAO), we are able to determine the exact individual requirement for all essential amino acids in both term and preterm infants. This will improve our knowledge on how to feed infants and might improve functional outcome in these vulnerable patient groups.

The aim of the study is to quantify the mean requirement of threonine in preterm infants. We hypothesize that the current estimations for preterms are too high.

Baseline samples will be obtained 15 and 5 minutes before starting tracer infusion. During the experiment duplicate 13C-enriched breath samples will be collected every 10 minutes during the last 45 minutes of the [13C]bicarbonate infusion and the last hour of the [1-13C]lysine infusion.

The subjects will adapt 24 hours to the study diet. An elemental diet (Neocate®, Danone) will be used to provide the infants with different amino acid intakes.

On the study day subjects will receive a primed (15 µmol/(kg) continuous (10 µmol/(kg•h)) enteral infusion of [13C]bicarbonate by the nasogastric tube for 2.5 h to quantify individual CO2 production. The labeled sodium bicarbonate infusion will be directly followed by a primed (40 µmol/(kg)) continuous (30 µmol/(kg•h)) enteral infusion of [1-13C]-lysine for four hours. 30 minutes before start of the oxidation study the feeding regimen will be changed into continuous drip-feeding. Enterally infused tracer will be mixed with the study formula and infused continuously by an infusion pump via the nasogastric tube. Breath samples will be obtained using the direct sampling method described by Van der Schoor et al.