Proline ameliorates arginine deficiency during enteral but not parenteral feeding in neonatal piglets.

The indispensability of arginine has not been conclusively established in newborns. Because parenteral feeding bypasses the gut (where de novo synthesis of arginine occurs from proline), a dietary supply of arginine that is sufficient to maintain urea cycle function may be of greater importance during intravenous compared with enteral feeding. Two-day-old piglets (n = 12) were fed nutritionally complete diets for 5 days via either a central vein catheter (IV pigs, n = 6) or a gastric catheter (IG pigs, n = 6).

A randomized trial of 72- versus 24-hour intravenous tubing set changes in newborns receiving lipid therapy.

Objective: To compare the microbial contamination rate of infusate in the intravenous tubing of newborns receiving lipid therapy, replacing the intravenous delivery system at 72-hour versus 24-hour intervals.

Design: Infants requiring intravenous lipid therapy were randomly assigned to have intravenous sets changed on a 72- or a 24-hour schedule, in a 3:1 ratio, in order to compare the infusate contamination rates in an equivalent number of tubing sets.

Setting: A 35-bed, teaching, referral, neonatal intensive-care unit (NICU).

Isotopic enrichment of amino acids in urine following oral infusions of L-[1-(13)C]phenylalanine and L-[1-(13)C]lysine in humans: confounding effect of D-[13C]amino acids.

Urine sampling of the free amino acid pool serves to reflect plasma enrichment and is used as a noninvasive means to determine isotope enrichment in studies of amino acid metabolism. We determined the effect of D-[13C]phenylalanine and D-[13C]lysine content of tracers on urinary amino acid enrichment following oral infusion of L-[13C]phenylalanine in 18 preterm infants and L-[1-(13)C]lysine in seven healthy adult females. Urinary [13C]phenylalanine enrichment was higher (P < .

Intestinal atrophy has a greater impact on nitrogen metabolism than liver by-pass in piglets fed identical diets via gastric, central venous or portal venous routes.

Whole-body nitrogen metabolism is altered during parenteral feeding as a result of gut atrophy and/or lack of splanchnic first-pass metabolism. We developed in vivo models to describe the metabolic and physiologic effects of first-pass metabolism by the small intestine/liver, liver or non-splanchnic tissues. Fifteen 2- to 4-d-old piglets were fed identical diets continuously for 8 d via gastric (IG), portal (IP) or central venous (IV) catheters.

A comparison of parenteral and enteral feeding in neonatal piglets, including an assessment of the utilization of a glutamine-rich, pediatric elemental diet.

Background: The amino acid requirement profile for infants is different than that for adults and needs to be established; this profile also is different for infants receiving total parenteral nutrition. We used the neonatal piglet as a model for the infant to address (1) the metabolic and physiologic changes due to route of feeding and (2) the adequacy of the amino acid pattern in a pediatric elemental diet.

Methods: Diets differed only in their amino acid pattern (modified human milk [MHM] and a commercial pediatric elemental diet [PED]) and were fed continuously for 8 days.

Prior protein intake may affect phenylalanine kinetics measured in healthy adult volunteers consuming 1 g protein. kg-1. d-1.

Study of the amino acid metabolism of vulnerable groups, such as pregnant women, children and patients, is needed. Our existing protocol is preceded by 2 d of adaptation to a low 13C formula diet at a protein intake of 1 g. kg-1.

Threonine kinetics in preterm infants fed their mothers' milk or formula with various ratios of whey to casein.

Background: Plasma threonine concentrations are elevated in infants fed formula containing a whey-to-casein protein ratio of 60:40 compared with concentrations in infants fed formula containing a ratio of 20:80 or human milk (60:40).

Objective: We studied whether degradation of excess threonine was lower in formula-fed infants than in infants fed their mothers' milk.

Design: Threonine kinetics were examined in 17 preterm infants (gestational age: 31+/-2 wk: birth weight: 1720+/-330 g) by using an 18-h oral infusion of [1-13C]threonine at a postnatal age of 21+/-11 d and weight of 1971+/-270 g.

Aggressive oral, enteral or parenteral nutrition: prescriptive decisions in children with cancer.

Over the past 18 years, our laboratory has been interested in the pathogenesis of energy imbalance caused by a variety of diseases. Our view is that a clear understanding of the various factors causing negative energy balance, which in turn results in malnutrition, is the most effective way of designing preventive and therapeutic nutritional strategies. Thus, in cancer, one of the common factors is anorexia, due either to the primary tumor or to the effects of cancer therapy.

Phenylalanine and tyrosine metabolism in neonates receiving parenteral nutrition differing in pattern of amino acids.

Tyrosine is considered to be an indispensable dietary amino acid in the neonate, yet achieving adequate parenteral tyrosine intake is difficult due to its poor solubility. Increasing the supply of phenylalanine is the most common means of compensating for low tyrosine levels. Unfortunately, plasma phenylalanine concentrations are sometimes elevated in infants receiving high phenylalanine intake.

Development of a minimally invasive protocol for the determination of phenylalanine and lysine kinetics in humans during the fed state.

The primed, continuous intravenous infusion of amino acids labeled with 13C together with measurement of isotopic enrichment in plasma is commonly used to study amino acid metabolism. However, a less invasive, oral infusion that also produces an isotopic steady state in CO2 and urine would be useful, particularly for pediatric studies. We measured the 13C enrichments of expired CO2, plasma and urine free phenylalanine and lysine and estimated flux and oxidation rates in adult humans (n = 12) who received a 4-h oral, primed, equal dose infusion of either L-[1-13C]phenylalanine, L-[1-13C]lysine (D-lysine = 1.

Nutrition and cystic fibrosis.

Cystic fibrosis is commonly associated with energy deficiency in children and adults. Chronic undernutrition will lead to failure to thrive, wasting, and stunting of linear growth; nutrition and survival are intimately related in cystic fibrosis. These problems can simply be considered as energy imbalance, and management centers on restoration of energy balance.

Threonine requirement of neonatal piglets receiving total parenteral nutrition is considerably lower than that of piglets receiving an identical diet intragastrically.

Evidence is accumulating that the amino acid requirements for neonates receiving total parenteral nutrition (TPN) are significantly different than those for oral feeding and need to be determined. The parenteral threonine requirement was determined in 3-d-old male Yorkshire piglets (n = 25) by examining the effect of varying dietary threonine intakes [0.05-0.

Tryptophan requirement in young adult women as determined by indicator amino acid oxidation with L-[13C]phenylalanine.

To determine tryptophan requirements with use of the indicator amino acid oxidation technique, we studied 5 healthy, premenopausal women who each consumed 6 different intakes of tryptophan. The energy-sufficient diet contained 1.0 g x kg(-1) x d(-1) of an L-amino acid mixture patterned after egg protein, with adequate phenylalanine (14 mg x kg(-1) x d(-1)) and excess tyrosine (40 mg x kg(-1) x d(-1)).

Empirical examination of the ability of children to consent to clinical research.

This study examined the quality of children's assent to a clinical trial. In subjects younger than 9 years of age, understanding of most aspects of the study was found to be poor to non-existent. Understanding of procedures was poor in almost all subjects.

Evidence that phenylalanine hydroxylation rates are overestimated in neonatal subjects receiving total parenteral nutrition with a high phenylalanine content.

Recent publications have indicated that the parenterally fed neonate has a substantial ability to hydroxylate phenylalanine. Examination of these data suggests that, at high phenylalanine intakes, estimated rates of hydroxylation exceed rates of intake. This implies significant net tissue breakdown.

Effect of exogenous insulin on protein metabolism with differing nonprotein energy intakes in Type 2 diabetes mellitus.

Objective: To determine if insulin treatment combined with a generous protein intake would normalize whole-body protein kinetics and nitrogen balance in obese subjects with Type 2 diabetes mellitus when compared to obese nondiabetic subjects: 1) during weight-maintenance and 2) after a very low energy diet (VLED).

Design: Clinical intervention study of iso- followed by hypoenergetic feedings with or without exogenous insulin.

Subjects: Sixteen obese subjects with a body mass index (BMI) of 39+/-4 kg/m2, with Type 2 diabetes mellitus (three men, six women) or without (one man, six women).

Free amino acids in milks of human subjects, other primates and non-primates.

Preterm and term transitional milks of human subjects and mature milks of human subjects, non-human primates and non-primates were analysed for free amino acids (AA) using precolumn phenylisothiocyanate derivatization and liquid chromatography. Differences in free AA between three types of human milk were small. Milks of pinnipeds (seals and sea lions) contained the highest levels of total free AA (8634-20,862 mumol/l), while the milks of cows and sheep had the lowest levels of total free AA (1061-1357 mumol/l).

Do infants with cystic fibrosis need a protein hydrolysate formula? A prospective, randomized, comparative study.

Objectives: We compared the nutritional benefits of a protein hydrolysate and a conventional infant formula in infants newly diagnosed with cystic fibrosis (CF).

Study Design: Twenty-three infants with CF (<6 months of age) and pancreatic insufficiency were randomized to receive a hydrolysate formula (Alimentum) or a cow's milk-based formula (Similac). Each patient was monitored at 1 month and then every 3 months for 1 year.

Lysine requirement of neonatal piglets receiving total parenteral nutrition as determined by oxidation of the indicator amino acid L-[1-14C]phenylalanine.

The indicator amino acid oxidation technique was adapted for use during total parenteral nutrition. Twenty-one male Yorkshire piglets (3 d of age) fitted with jugular and femoral vein catheters, received total parenteral nutrition for 6 d. Total parenteral nutrition included 15 g amino acids .

Whole-body protein turnover in the healthy elderly.

We tested the hypothesis that aging affects whole-body protein turnover via altered fat-free mass (FFM). Whole-body protein kinetics were estimated by the 60-h oral [15N]glycine method. Results from 16 healthy, elderly subjects (8 men and 8 women with a mean age of 72.

Energy expenditure and body composition in children with Crohn's disease: effect of enteral nutrition and treatment with prednisolone.

Background: Malnutrition and growth retardation are common complications of Crohn's disease in children. The contribution of resting energy expenditure (REE) to malnutrition is unclear.

Aims: To characterise the REE and body composition in children with Crohn's disease and compare them with normal controls and patients with anorexia nervosa; to compare the effects of prednisolone and enteral nutrition on energy expenditure and body composition.

Ability of the Higgins Nutrition Intervention Program to improve adolescent pregnancy outcome.

Objectives: To determine the extent to which birth weight can be increased and the risk for adverse pregnancy outcome decreased when pregnant adolescents participated in the Higgins Nutrition Intervention Program; and to describe the dietary components of the program, including their variation as a function of diagnosed risk for adverse pregnancy outcome.

Design: Retrospective cohort study involving review of medical charts.

Subjects/setting: Developed as an adjunct to routine prenatal care, the Higgins Nutrition Intervention Program consists of an assessment of each pregnant adolescent's risk profile for adverse pregnancy outcomes and an individualized nutritional rehabilitation program based on that profile.

Tyrosine kinetics and requirements during total parenteral nutrition in the neonatal piglet: the effect of glycyl-L-tyrosine supplementation.

Tyrosine may be a conditionally indispensable amino acid in the neonate; however, the provision of aromatic amino acids to neonates receiving total parenteral nutrition (TPN) is complicated by the poor solubility of crystalline tyrosine. In the present study, we investigated tyrosine kinetics and requirements during TPN, when tyrosine was supplied as the soluble dipeptide, glycyl-L-tyrosine in a neonatal piglet model. Fifteen 3-d-old male Yorkshire piglets were fitted with external jugular and femoral catheters and randomized to one of five tyrosine intakes: 0.

Phenylalanine requirements determined by using L-[1-14C]phenylalanine in neonatal piglets receiving total parenteral nutrition supplemented with tyrosine.

The definition of amino acid requirements for neonates receiving total parenteral nutrition (TPN) is critical for the further improvement of this nutritional regimen. In the present study we investigated the kinetics and requirements of phenylalanine and tyrosine in neonatal piglets receiving TPN. Twenty-four 3-d-old male Yorkshire piglets were fitted with external jugular and femoral catheters and maintained on identical TPN formulations for 5 d.

Effect of glycemic control on the kinetics of whole-body protein metabolism in obese subjects with non-insulin-dependent diabetes mellitus during iso- and hypoenergetic feeding.

We postulated whether interventions capable of restoring euglycemia would correct whole-body protein metabolism, shown previously to be elevated in hyperglycemic persons with non-insulin-dependent diabetes (NIDDM). The kinetics of protein metabolism were estimated in obese subjects with NIDDM in the hyper- and normoglycemic states during isoenergetic feeding and in the normoglycemic state induced by 4 wk of a very-low-energy diet (VLED) with constant protein intake. Seven NIDDM subjects [three males and four females with a body mass index (in kg/m2) of 39 +/- 2] were given a weight-maintaining, liquid formula providing 95 g protein/d for 15 d, followed in six subjects (two males and four females) for 27 d by a diet providing 1.