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. DESIGN: Eight preterm infants (x +/- SD birth weight: 1.1 +/- 0.1 kg; gestational age: 29 +/- 2 wk) were studied during 2 periods. During period A, 40% of total intake was administered enterally and 60% was administered parenterally. Total threonine intake was 58 +/- 6 micromol kg(-1) h(-1). During period B, the infants received full enteral feeding, and the total threonine intake was 63 +/- 6 micromol kg(-1) h(-1). Dual stable-isotope tracer techniques were used to assess splanchnic and whole-body threonine kinetics. RESULTS: The fractional first-pass threonine uptake by the intestine was remarkably high in both periods: 82 +/- 6% during partial enteral feeding and 70 +/- 6% during full enteral feeding. Net threonine retention was not affected by the route of feeding. CONCLUSION: In preterm infants, the splanchnic tissues extract a very large amount of the dietary threonine intake, which indicates a high obligatory visceral need for threonine, presumably for the purposes of synthesis.

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. DESIGN: Eight preterm infants [birth weight ( +/- SD): 1.19 +/- 0.22 kg, gestational age: 29 +/- 1 wk] were studied while they received 2 different enteral intakes (A: 40% enteral, 60% parenteral, total glucose intake = 7.5 +/- 0.5 mg. kg(-1). min(-1), and B: 100% enteral, total glucose intake = 7.8 +/- 0.4 mg. kg(-1). min(-1)). Splanchnic and whole-body glucose kinetics were measured by use of dual-tracer techniques. RESULTS: During both feeding periods, approximately one-third of dietary glucose intake was utilized during the first pass by the splanchnic tissues. More than three-quarters of this utilized glucose was oxidized in both periods (79 +/- 36% with A and 84 +/- 45% with B). Whole-body glucose oxidation was substantial under both circumstances: 72 +/- 5% and 77% +/- 6% of the glucose flux was oxidized during partial (A) and full (B) enteral feeding, respectively. CONCLUSIONS: Approximately one-third of dietary glucose is utilized during the first pass by the splanchnic tissues, irrespective of the dietary intake. Most of the utilized glucose is used for energy generation.

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. The aim of this study was to evaluate systemic availability of dietary amino acids (leucine) during chemotherapy-induced mucositis. We studied eight childhood cancer patients (age 1.5-16 y) on 2 d, i.e. the day before chemotherapy and 3-5 d after. Chemotherapy-induced oral mucositis and diarrhea were scored on a World Health Organization toxicity scale. Stable isotope tracers were used to measure first-pass splanchnic leucine uptake and whole-body leucine kinetics. Patients showed increased mucositis and/or diarrhea toxicity scores (p < 0.0001) after chemotherapy. Systemic availability of enterally administered leucine was not significantly affected by chemotherapy (before 60%, after 90%, p = 0.46). Interestingly, five patients already showed a negative leucine balance before chemotherapy. In conclusion, most children receiving chemotherapy are already catabolic before start of a new cycle of chemotherapy. Amino acid transport as measured by leucine uptake in the intestine is not affected by chemotherapy-induced mucositis.

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. We present a method that simplifies the collection of breath samples in preterm infants. Seven preterm infants with a gestational age of 26-29 wk were studied on different postnatal days (range, 8-52 d) while receiving full enteral feeding. A primed constant 3-h intragastric infusion of [13C]bicarbonate was given, and breath samples were collected by means of direct nasopharyngeal sampling and by a sodium hydroxide trap simultaneously. Breath CO2 isotopic enrichments rose rapidly to reach a plateau by 120 min with <5% variation of plateau in both methods. 13CO2 breath isotopic enrichments obtained by the direct nasopharyngeal sampling method correlated highly (r2 = 0.933; p < 0.0001) with the trapping method. The Bland-Altman analysis showed no significant variability between the two methods and demonstrated that the 95% confidence interval is within +/- 4.68 delta per thousand. These findings validate the simple method of direct nasopharyngeal sampling of expired air in neonates.