Amino acids and proteins.

Amino acids and protein are key factors for growth. The neonatal period requires the highest intake in life to meet the demands. Those demands include amino acids for growth, but proteins and amino acids also function as signalling molecules and function as neurotransmitters.

Amino acid homeostasis in the preterm infant.

Functional outcome of preterm infants is highly related to the quality and quantity of nutrients provided during the first few weeks of life. New guidelines, as published by the ESPGHAN in 2010, have provided means to prevent undernutrition in the NICU. Especially proteins and amino acids seem to play a pivotal role, and the optimal regimen has not yet been determined.

Majority of dietary glutamine is utilized in first pass in preterm infants.

Glutamine is a conditionally essential amino acid for very low-birth weight infants by virtue of its ability to play an important role in several key metabolic processes of immune cells and enterocytes. Although glutamine is known to be used to a great extent, the exact splanchnic metabolism in enterally fed preterm infants is unknown. We hypothesized that preterm infants show a high splanchnic first-pass glutamine metabolism and the primary metabolic fate of glutamine is oxidation.

Effect of enteral IGF-1 supplementation on feeding tolerance, growth, and gut permeability in enterally fed premature neonates.

Objectives: The gastrointestinal tract of the premature newborn functions suboptimally with regard to digestion, absorption, and feeding tolerance. Human milk contains trophic factors, such as insulin-like growth factor-1 (IGF-1), that are believed to stimulate gut growth and function. The objective of this double blind, randomized, controlled trial was to assess the effects of enteral IGF-1 supplementation on whole body growth measured by weight gain (in grams per kilogram per day), days to regain birth weight, and anthropometrical characteristics, and gut maturation and permeability (measured by sugar absorption tests).

The gut takes nearly all: threonine kinetics in infants.

Background: Threonine is an essential amino acid that is abundantly present in intestinally produced glycoproteins. Animal studies show that intestinal first-pass threonine metabolism is high, particularly during a restricted enteral protein intake.

Objective: The objective of the study was to quantify intestinal first-pass threonine metabolism in preterm infants during full enteral feeding and during restricted enteral intake.

Chemotherapy does not influence intestinal amino acid uptake in children.

Chemotherapy will frequently induce intestinal damage (mucositis). Enteral nutrition is then often withheld for fear of impaired intestinal absorption as shown in animal models. There is no clinical evidence, however, that absorption is indeed compromised during chemotherapy-induced mucositis.

Intestinal amino acid metabolism in neonates.

The portal-drained viscera (stomach, intestine, pancreas and spleen) have a much higher rate of both energy expenditure and protein synthesis than can be estimated on the basis of their weight. A high utilization rate of dietary nutrients by the portal-drained viscera might result in a low systemic availability which determines whole-body growth. From studies in our multiple catheterized piglet model, we conclude that more than half of the dietary protein intake is utilized within the portal-drained viscera and that amino acids are a major fuel source for the visceral organs.

Threonine utilization is high in the intestine of piglets.

The whole-body threonine requirement in parenterally fed piglets is substantially lower than that in enterally fed piglets, indicating that enteral nutrition induces intestinal processes in demand of threonine. We hypothesized that the percentage of threonine utilization for oxidation and intestinal protein synthesis by the portal-drained viscera (PDV) increases when dietary protein intake is reduced. Piglets (n = 18) received isocaloric normal or protein-restricted diets.

Splanchnic bed metabolism of glucose in preterm neonates.

Background: Glucose is a major oxidative substrate for intestinal energy generation in neonatal animals; however, few data in preterm infants are available. Early administration of enteral nutrition, including glucose, may be an effective strategy to support intestinal adaptation to extrauterine life in preterm neonates.

Objective: The purpose of the present study was to quantify the first-pass uptake and oxidation of glucose by the splanchnic tissues (intestine and liver) in human neonates.

Validation of the direct nasopharyngeal sampling method for collection of expired air in preterm neonates.

In clinical studies, the oxidation of 13C-labeled substrates to 13CO2 and the measurement of the appearance of excess 13CO2 in expiratory air has progressed to an increasingly common method as it is noninvasive and lacks the radiation exposure associated with the use of 14C. The collection of respiratory CO2 currently used occurs via trapping of CO2 in sodium hydroxide (trapping method), sometimes in conjunction with indirect calorimetry. The aim of the present study was to determine the accuracy of our direct nasopharyngeal sampling method for the collection of breath samples in preterm infants compared with the currently used trapping method.

The high metabolic cost of a functional gut.

Background & Aims: Animal studies have shown that more than half of the dietary protein intake is used by the gut and that a large proportion of this utilization is devoted to (glyco-)protein synthesis. Recycling of these secretions may play a critical role in the regulation of overall dietary amino acid bioavailability.

Methods: Four piglets (age 32 days, 8-10 kg) bearing portal, arterial, and duodenal catheters and a portal flow probe were infused with a complete diet via the duodenum for 12 hours, followed by 12 hours of fasting.