Activities of lipase and trypsin in duodenal juice of infants small for gestational age

Preweaning performance in intrauterine growth-restricted piglets: Characteristics and interventions

Intrauterine growth restriction (IUGR) is frequently observed in pig production, especially when using highly prolific sows. IUGR piglets are born with low body weight and shape indicative of differences in organ growth. Insufficient uteroplacental nutrient transfer to the fetuses is the leading cause of growth restriction in the pig. Supplementing the sow's gestation diet with arginine and/or glutamine improves placenta growth and functionality and consequently is able to reduce IUGR incidence. IUGR piglets are at higher risk of dying preweaning and face higher morbidity than their normal-weight littermates. A high level of surveillance during farrowing and individual nutrient supplementation can reduce the mortality rates. Still, these do not reverse the long-term consequences of IUGR, which are induced by persistent structural deficits in different organs. Dietary interventions peri-weaning can optimize performance but these are less effective in combating the metabolic changes that occurred in IUGR, which affect reproductive performance later in life. IUGR piglets share many similarities with IUGR infants, such as a poorer outcome of males. Using the IUGR piglet as an animal model to further explore the structural and molecular basis of the long-term consequences of IUGR and the potential sex bias could aid in fully understanding the impact of prenatal undernutrition and finding solutions for both species and sexes.

Review of paediatric gastrointestinal physiology relevant to the absorption of orally administered medicines

Despite much progress in regulations to improve paediatric drug development, there remains a significant need to develop better medications for children. For the design of oral dosage forms, a detailed understanding of the specific gastrointestinal (GI) conditions in children of different age categories and how they differ from GI conditions in adults is essential. Several review articles have been published addressing the ontogeny of GI characteristics, including luminal conditions in the GI tract of children. However, the data reported in most of these reviews are of limited quality because (1) information was cited from very old publications and sometimes low quality sources, (2) data gaps in the original data were filled with textbook knowledge, (3) data obtained on healthy and sick children were mixed, (4) average data obtained on groups of patients were mixed with data obtained on individual patients, and (5) results obtained using investigative techniques that may have altered the outcome of the respective studies were considered. Consequently, many of these reviews draw conclusions that may be incorrect. The aim of the present review was to provide a comprehensive and updated overview of the available original data on the ontogeny of GI luminal conditions relevant to oral drug absorption in the paediatric population. To this end, the PubMed and Web of Science metadatabases were searched for appropriate studies that examined age-related conditions in the oral cavity, esophagus, stomach, small intestine, and colon. Maturation was observed for several GI parameters, and corresponding data sets were identified for each paediatric age group. However, it also became clear that the ontogeny of several GI traits in the paediatric population is not yet known. The review article provides a robust and valuable data set for the development of paediatric in vitro and in silico biopharmaceutical tools to support the development of age-appropriate dosage forms. In addition, it provides important information on existing data gaps and should provide impetus for further systematic and well-designed in vivo studies on GI physiology in children of specific age groups in order to close existing knowledge gaps and to sustainably improve oral drug therapy in children.

Exocrine Pancreatic Maturation in Pre-term and Term Piglets Supplemented With Bovine Colostrum

Pre-term infants have an immature digestive system predisposing to short- and long-term complications including feeding intolerance, maldigestion and necrotizing enterocolitis (NEC). Optimal feeding strategies are required to promote maturation of the gut including the exocrine pancreas. Little is known about age- and diet-related development of pancreatic exocrine enzymes following pre-term birth. Currently, bovine colostrum supplementation is investigated in clinical trials on pre-term infants. Using pigs as models for infants, we hypothesized that pancreatic enzyme content is (1) immature following pre-term birth, (2) stimulated by early colostrum supplementation, and (3) stimulated by later colostrum fortification. Thus, using piglets as models for infants, we measured trypsin, amylase, lipase and total protein in pancreatic tissue collected from piglets delivered by cesarean section either pre-term (90% gestation) or close to term. Experiment 1:Pre-term and term pigs were compared at birth and 11 days. Experiment 2: Pre-term and term pigs were either enterally supplemented with bovine colostrum or fed total parenteral nutrition for 5 days, followed by exclusive milk feeding until day 26. Experiment 3: Pre-term pigs were fed bovine's milk with or without colostrum fortification until 19 days. The results showed that pancreatic trypsin, amylase and total protein contents were reduced in pre-term vs. term pigs. Trypsin mainly increased with advancing post-conceptional age (2-fold), while amylase was affected predominantly by advancing post-natal age, and mostly in pre-term pigs from birth to 11 or 26 days. Colostrum feeding in both term and pre-term piglets decreased trypsin and increased amylase contents. Lipase activity decreased with advancing gestational age at birth and post-natal age, with no consistent responses to colostrum feeding, with lipase activities decreasing relative to total pancreatic protein content. In summary, key pancreatic enzymes, amylase and trypsin, are immature following pre-term birth, potentially contributing to reduced digestive capacity in pre-term neonates. Rapid post-natal increases occurs within few weeks of pre-term birth, partly stimulated by enteral colostrum intake, reflecting a marked adaptation capacity. Alternatively, lipase is less affected by pre-/post-natal age and feeding. Thus, there is a highly enzyme-specific and asymmetric perinatal development of the exocrine pancreas.

Characterisation of fasted state gastric and intestinal fluids collected from children

Fundamental knowledge about the composition of intestinal fluids in paediatric populations is currently unavailable. This study aimed to characterise gastric and intestinal fluid from paediatric populations. Gastric and intestinal fluid samples were obtained during routine clinical endoscopy from paediatric patients at a large teaching hospital. These fluids were characterised to measure the pH; buffer capacity; osmolality; bile acid concentration and composition. A total of 55 children were recruited to the study aged from 11 months to 15 years of age where 53 gastric fluid samples and 40 intestinal fluid samples were obtained. pH values recorded ranged from pH 0.57 to 11.05 (median: 2.50) in gastric fluids and from 0.89 to 8.97 (median: 3.27) in intestinal fluids. The buffer capacity did not change significantly between gastric and intestinal fluids with median values of 12 mM/L/ΔpH for both fluids. Gastric fluid osmolality values ranged from 1 to 615 mOsm/kg, while intestinal fluid values ranged from 35 to 631 mOsm/kg. Gastric fluid bile acid concentrations ranged from 0.002 to 2.3 mM with a median value of 0.017 mM whilst intestinal fluid bile acid concentrations ranged from 0.0008 to 3.3 mM with a median value of 0.178 mM. Glycocholate; taurocholic acid; glycochenodeoxycholate and taurochenodeoxycholate were the most commonly identified bile acids within paediatric intestinal fluids. All compositional components were associated with large inter-individual variability. Further work is required to develop simulated paediatric media and to explore the impact of these media on drug solubility and dissolution.

Catch-up growth in intrauterine growth-restricted piglets associated with the restore of pancreatic and intestinal functions via porcine glucagon-like peptide-2 microspheres

Intrauterine growth restriction (IUGR) results in abnormal morphology and gastrointestinal function, such as reduced villi height and crypt depth, thinner mucosa and muscle layers, and reduced brush border enzyme activities, delayed gastric emptying, increased stress response. As a gastrointestinal growth factor, the manner by which the porcine glucagon-like peptide-2 (pGLP-2) microsphere administration restored the gastrointestinal function and growth performance of IUGR piglets was investigated. Fourteen newborn Duroc × (Yorkshire × Landrace) IUGR piglets (0.92 ± 0.113 kg) were assigned into the IUGR (negative control group) and pGLP-2 microsphere groups. The piglets in group pGLP-2 were intraperitoneally administered with 100 mg pGLP-2 microspheres on day 1 after birth. From days 15 to 26 of trial, the body weight of the pGLP-2 group was significantly higher than that of the control. IUGR piglets of group pGLP-2 showed a significantly increased pancreas weight, serum insulin content and activity of lipase and amylase. Injection of pGLP-2 microspheres restored the intestinal absorptive capacity by significantly increasing the mRNA expression of the sodium-glucose cotransporter 1 in the jejunum and the peptide transporter 1 in the jejunum. It also restored the redox balance by increasing the catalase mRNA expression and decreasing the heat shock protein 70 mRNA expression. In addition, this improvement was associated with the significant increase in gut diameter, length and weight. Therefore, it was concluded that the injection of pGLP-2 microspheres was a suitable therapeutic strategy for compensatory growth in low birth weight IUGR piglets.

Changes in Faecal Microbiota Profiles Associated With Performance and Birthweight of Piglets

The gastrointestinal tract microbiota interacts with the host to modulate metabolic phenotype. This interaction could provide insights into why some low birthweight pigs can exhibit compensatory growth whilst others remain stunted. This study aimed to identify microbiota markers associated with birthweight [low birthweight (n = 13) or normal birthweight pigs (n = 13)] and performance ["good" or "poor" average daily gain (ADG) class]. Furthermore, the study determined whether the taxonomic markers were longitudinal, or time point specific in their ability to identify low birthweight pigs who could exhibit compensatory growth. Faecal samples were collected and liveweight recorded at 10 different time points from birth to 56 days of age. No consistent associations between birthweight, performance and gut microbiota were found across all time points. However, there was a significant (P < 0.05) effect of birthweight on microbiota richness at 21, 27, 32 and 56 days of age. Significant differences (P < 0.05) in genera abundance according to birthweight and performance were also identified. Low birthweight pigs had a significantly (P < 0.05) lower abundance of Ruminococcaceae UCG-005, but a significantly (P < 0.05) higher abundance of Ruminococcaceae UCG-014 on days 21 and 32, respectively. Piglets classified as having a "good" ADG class had a significantly (P < 0.05) higher abundance of Lactobacillus, unclassified Prevotellaceae and Ruminococcaceae UCG-005 on days 4, 8 and 14, respectively. Furthermore, Ruminococcaceae UCG-005 was significantly more abundant at 14 days of age in normal birthweight pigs with a "good" ADG class compared to those classified as "poor." The results of this study indicate that there are time point-specific differences in the microbiota associated with birthweight and performance, corresponding to the period in which solid feed intake first occurs. Identifying early-life microbiota markers associated with performance emphasises the importance of the neonatal phase when considering intervention strategies aimed at promoting performance.

Design, characterization and in vivo evaluation of nanostructured lipid carriers (NLC) as a new drug delivery system for hydrochlorothiazide oral administration in pediatric therapy

The hydrochlorothiazide (HCT) low solubility and permeability give rise to limited and variable bioavailability; its low stability makes it difficult to develop stable aqueous liquid formulations; its low dose makes the achievement of a homogeneous drug distribution very difficult. Thus, the aim of this study was to investigate the effectiveness of a strategy based on the development of nanostructured lipid carriers (NLC) as an innovative oral pediatric formulation of HCT with improved therapeutic efficacy. The performance of various synthetic and natural liquid lipids was examined and two different preparation methods were employed, i.e. homogenization-ultrasonication (HU) and microemulsion (ME), in order to evaluate their influence on the NLC properties in terms of size, polydispersity index, ζ-potential, entrapment efficiency, gastric stability, and drug release properties. Precirol®ATO5 was used as solid lipid and Tween^®80 and Pluronic^®F68 as surfactants, formerly selected in a previous study focused on the development of HCT-solid lipid nanoparticles (SLNs). The presence of Pluronic^®F68 did not allow ME formation. On the contrary, using Tween^®80, the ME method enabled a higher entrapment efficiency than the HU. Regardless of the preparation method, NLCs exhibited great entrapment efficiency values clearly higher than previous SLNs. Moreover, NLC-ME formulations provided a prolonged release, which lasted for 6 h. In particular, NLC-ME containing Tween^®20 as Co-Surfactant showed the best performances, giving rise to a complete drug release, never achieved with previous SLN formulations, despite their successful results. In vivo studies on rats confirmed these results, displaying their best diuretic profile. Moreover, all HCT-loaded NLC formulations showed higher stability than the corresponding SLNs.

Infant digestion physiology and the relevance of in vitro biochemical models to test infant formula lipid digestion

Lipids play an important role in the diet of preterm and term infants providing a key energy source and essential lipid components for development. While a lot is known about adult lipid digestion, our understanding of infant digestion physiology is still incomplete, the greatest gap being on the biochemistry of the small intestine, particularly the activity and relative importance of the various lipases active in the intestine. The literature has been reviewed to identify the characteristics of lipid digestion of preterm and term infants, but also to better understand the physiology of the infant gastrointestinal tract compared to adults that impacts the absorption of lipids. The main differences are a higher gastric pH, submicellar bile salt concentration, a far more important role of gastric lipases as well as differences at the level of the intestinal barrier. Importantly, the consequences of improper in vitro replication of gastric digestions conditions (pH and lipase specificity) are demonstrated using examples from the most recent of studies. It is true that some animal models could be adapted to study infant lipid digestion physiology, however the ethical relevance of such models is questionable, hence the development of accurate in vitro models is a must. In vitro models that combine up to date knowledge of digestion biochemistry with intestinal cells in culture are the best choice to replicate digestion and absorption in infant population, this would allow the adaptation of infant formula for a better digestion and absorption of dietary lipids by preterm and term infants.

In Vitro Model Simulating Gastro-Intestinal Digestion in the Pediatric Population (Neonates and Young Infants)

The focus on drug delivery for the pediatric population has been steadily increasing in the last decades. In terms of developing in vitro models simulating characteristics of the targeted pediatric population, with the purpose of predicting drug product performance after oral administration, it is important to simulate the gastro-intestinal conditions and processes the drug will encounter upon oral administration. When a drug is administered in the fed state, which is commonly the case for neonates, as they are typically fed every 3 h, the digestion of the milk will affect the composition of the fluid available for drug dissolution/solubilization. Therefore, in order to predict the solubilized amount of drug available for absorption, an in vitro model simulating digestion in the gastro-intestinal tract should be utilized. In order to simulate the digestion process and the drug solubilization taking place in vivo, the following aspects should be considered; physiologically relevant media, media volume, use of physiological enzymes in proper amounts, as well as correct pH and addition of relevant co-factors, e.g., bile salts and co-enzymes. Furthermore, physiological transit times and appropriate mixing should be considered and mimicked as close as possible. This paper presents a literature review on physiological factors relevant for digestion and drug solubilization in neonates. Based on the available literature data, a novel in vitro digestion model simulating digestion and drug solubilization in the neonate and young infant pediatric population (2 months old and younger) was designed.

Intrauterine growth retarded piglet as a model for humans--studies on the perinatal development of the gut structure and function

The overall acceptance of pig models for human biomedical studies is steadily growing. Results of rodent studies are usually confirmed in pigs before extrapolating them to humans. This applies particularly to gastrointestinal and metabolism research due to similarities between pig and human physiology. In this context, intrauterine growth retarded (IUGR) pig neonate can be regarded as a good model for the better understanding of the IUGR syndrome in humans. In pigs, the induction of IUGR syndrome may include maternal diet intervention, dexamethasone treatment or temporary reduction of blood supply. However, in pigs, like in humans, circa 8% of neonates develop IUGR syndrome spontaneously. Studies on the pig model have shown changes in gut structure, namely a reduced thickness of mucosa and muscle layers, and delayed kinetic of disappearance of vacuolated enterocytes were found in IUGR individuals in comparison with healthy ones. Functional changes include reduced dynamic of gut mucosa rebuilding, decreased activities of main brush border enzymes, and changes in the expression of proteins important for carbohydrate, amino acids, lipid, mineral and vitamin metabolism. Moreover, profiles of intestinal hormones are different in IUGR and non-IUGR piglets. It is suggested that supplementation of the mothers during the gestation and/or the IUGR offspring after birth can help in restoring the development of the gastrointestinal tract. The pig provides presumably the optimal animal model for humans to study gastrointestinal tract structure and function development in IUGR syndrome.

Pancreatic lipase-related protein 2 digests fats in human milk and formula in concert with gastric lipase and carboxyl ester lipase

BACKGROUND

Dietary fats must be digested into fatty acids and monoacylglycerols prior to absorption. In adults, colipase-dependent pancreatic triglyceride lipase (PTL) contributes significantly to fat digestion. In newborn rodents and humans, the pancreas expresses low levels of PTL. In rodents, a homologue of PTL, pancreatic lipase-related protein 2 (PLRP2), and carboxyl ester lipase (CEL) compensate for the lack of PTL. In human newborns, the role of PLRP2 in dietary fat digestion is unclear. To clarify the potential of human PLRP2 to influence dietary fat digestion in newborns, we determined PLRP2 activity against human milk and infant formula.

METHODS

The activity of purified recombinant PLRP2, gastric lipase (GL), and CEL against fats in human milk and formula was measured with each lipase alone and in combination with a standard pH-stat assay.

RESULTS

Colipase added to human milk stimulated fat digestion. PLRP2 and CEL had activity against human milk and formula. Predigestion with GL increased PLRP2 activity against both substrates. Together, CEL and PLRP2 activity was additive with formula and synergistic with human milk.

CONCLUSION

PLRP2 can digest fats in human milk and formula. PLRP2 acts in concert with CEL and GL to digest fats in human milk in vitro.

Postnatal leptin promotes organ maturation and development in IUGR piglets

Babies with intra-uterine growth restriction (IUGR) are at increased risk for experiencing negative neonatal outcomes due to their general developmental delay. The present study aimed to investigate the effects of a short postnatal leptin supply on the growth, structure, and functionality of several organs at weaning. IUGR piglets were injected from day 0 to day 5 with either 0.5 mg/kg/d leptin (IUGRLep) or saline (IUGRSal) and euthanized at day 21. Their organs were collected, weighed, and sampled for histological, biochemical, and immunohistochemical analyses. Leptin induced an increase in body weight and the relative weights of the liver, spleen, pancreas, kidneys, and small intestine without any changes in triglycerides, glucose and cholesterol levels. Notable structural and functional changes occurred in the ovaries, pancreas, and secondary lymphoid organs. The ovaries of IUGRLep piglets contained less oogonia but more oocytes enclosed in primordial and growing follicles than the ovaries of IUGRSal piglets, and FOXO3A staining grade was higher in the germ cells of IUGRLep piglets. Within the exocrine parenchyma of the pancreas, IUGRLep piglets presented a high rate of apoptotic cells associated with a higher trypsin activity. In the spleen and the Peyer's patches, B lymphocyte follicles were much larger in IUGRLep piglets than in IUGRSal piglets. Moreover, IUGRLep piglets showed numerous CD79(+) cells in well-differentiated follicle structures, suggesting a more mature immune system. This study highlights a new role for leptin in general developmental processes and may provide new insight into IUGR pathology.

Ontogeny of oral drug absorption processes in children

INTRODUCTION

A large proportion of prescribed drugs to children are administered orally. Age-related change in factors affecting oral absorption can have consequences for drug dosing.

AREAS COVERED

For each process affecting oral drug absorption, a systematic search has been performed using Medline to identify relevant articles (from inception till February 2012) in humans. This review presents the findings on age-related changes of the following processes affecting oral drug absorption: gastric pH, gastrointestinal motility, bile salts, pancreatic function, intestinal pH, intestinal drug-metabolizing enzymes and transporter proteins.

EXPERT OPINION

Clinicians should bear in mind the ontogeny of oral drug absorption processes when prescribing oral drugs to children. The authors' review shows large information gaps on almost all drug absorption processes. It is important that more knowledge is acquired on intestinal transit time, intestinal pH and the ontogeny of intestinal drug-metabolizing enzymes and drug transporter proteins. Furthermore, the ultimate goal in this field should be to predict more precisely the oral disposition of drugs in children across the entire pediatric age range.

Pharmacology and safety of glycerol phenylbutyrate in healthy adults and adults with cirrhosis

Phenylbutyric acid (PBA), which is approved for treatment of urea cycle disorders (UCDs) as sodium phenylbutyrate (NaPBA), mediates waste nitrogen excretion via combination of PBA-derived phenylacetic acid with glutamine to form phenylactylglutamine (PAGN) that is excreted in urine. Glycerol phenylbutyrate (GPB), a liquid triglyceride pro-drug of PBA, containing no sodium and having favorable palatability, is being studied for treatment of hepatic encephalopathy (HE). In vitro and clinical studies have been performed to assess GPB digestion, safety, and pharmacology in healthy adults and individuals with cirrhosis. GPB hydrolysis was measured in vitro by way of pH titration. Twenty-four healthy adults underwent single-dose administration of GPB and NaPBA and eight healthy adults and 24 cirrhotic subjects underwent single-day and multiple-day dosing of GPB, with metabolites measured in blood and urine. Simulations were performed to assess GPB dosing at higher levels. GPB was hydrolyzed by human pancreatic triglyceride lipase, pancreatic lipase-related protein 2, and carboxyl-ester lipase. Clinical safety was satisfactory. Compared with NaPBA, peak metabolite blood levels with GPB occurred later and were lower; urinary PAGN excretion was similar but took longer. Steady state was achieved within 4 days for both NaPBA and GPB; intact GPB was not detected in blood or urine. Cirrhotic subjects converted GPB to PAGN similarly to healthy adults. Simulations suggest that GPB can be administered safely to cirrhotic subjects at levels equivalent to the highest approved NaPBA dose for UCDs.

CONCLUSION

GPB exhibits delayed release characteristics, presumably reflecting gradual PBA release by pancreatic lipases, and is well tolerated in adults with cirrhosis, suggesting that further clinical testing for HE is warranted.

Nutritional programming of gastrointestinal tract development. Is the pig a good model for man?

The consequences of early-life nutritional programming in man and other mammalian species have been studied chiefly at the metabolic level. Very few studies, if any, have been performed in the gastrointestinal tract (GIT) as the target organ, but extensive GIT studies are needed since the GIT plays a key role in nutrient supply and has an impact on functions of the entire organism. The possible deleterious effects of nutritional programming at the metabolic level were discovered following epidemiological studies in human subjects, and confirmed in animal models. Investigating the impact of programming on GIT structure and function would need appropriate animal models due to ethical restrictions in the use of human subjects. The aim of the present review is to discuss the use of pigs as an animal model as a compromise between ethically acceptable animal studies and the requirement of data which can be interpolated to the human situation. In nutritional programming studies, rodents are the most frequently used model for man, but GIT development and digestive function in rodents are considerably different from those in man. In that aspect, the pig GIT is much closer to the human than that of rodents. The swine species is closely comparable with man in many nutritional and digestive aspects, and thus provides ample opportunity to be used in investigations on the consequences of nutritional programming for the GIT. In particular, the 'sow-piglets' dyad could be a useful tool to simulate the 'human mother-infant' dyad in studies which examine short-, middle- and long-term effects and is suggested as the reference model.

Selective growth of mucolytic bacteria including Clostridium perfringens in a neonatal piglet model of total parenteral nutrition

BACKGROUND

Compromised barrier function and intestinal inflammation are common complications of total parenteral nutrition (TPN).

OBJECTIVE

We tested the hypothesis that the lack of enteral nutrients in TPN might select commensal or pathogenic bacteria that use mucus as a substrate, thereby weakening the protection provided by the intestinal mucus layer.

DESIGN

Ileal microbiota profiles of piglets fed by total enteral nutrition (TEN; n = 6) or TPN (n = 5) were compared with the use of 16S ribosomal DNA polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis and with a PCR-based method developed to specifically measure Clostridium perfringens concentrations. Ileal bacteria from TEN and TPN piglets were also examined for their ability to grow on mucin or sulfated monosaccharides.

RESULTS

Bacterial community structure was equally complex in the ileum of TEN and TPN piglets, but profiles clustered according to mode of nutrition. Sixty-two percent of total mucus-associated bacteria (100 colonies tested) in TPN compared with 33% of mucus-associated bacteria (100 colonies tested) in TEN ileal samples grew on mucin. Bacteria capable of using sulfated monosaccharides were also enriched in TPN samples. C. perfringens, an opportunistic pathogen, was specifically enriched in the TPN ileum (P < 0.05). These results were corroborated by cultivation-based studies that showed rapid growth of C. perfringens on mucin-based substrates.

CONCLUSIONS

Mucolytic potential is widespread among intestinal bacteria. Mucolytic bacteria in general and C. perfringens in particular were selected when enteral nutrients were withheld in this TPN piglet model. Similar enrichment processes may occur in humans nourished by TPN and may thereby contribute to intestinal dysfunction.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Functional development of fat absorption in term and preterm neonates strongly correlates with ability to absorb long-chain Fatty acids from intestinal lumen

Our goal for this study was to determine whether the maturation of fat absorption in neonatal life is functionally related to an increased ability to hydrolyze dietary fat, to absorb long-chain fatty acids, or to do both. In 16 preterm and in eight term neonates, the intestinal ability to hydrolyze triacylglycerols and the capacity to absorb long-chain fatty acids were determined at several times between birth and 5 mo after the term age. These processes were compared with the percentage of fat absorption (formula-fed infants) or with fecal fat excretion (breast-fed infants). The functional capacity to digest triacylglycerols and to absorb the lipolytic products was evaluated by measuring serum concentrations of the lipolytic product [1-(13)C]palmitate after the enteral administration of tri-1-(13)C palmitoyl-glycerol. Long-chain fatty acids absorption (i.e. independent of lipolysis) was determined by measuring serum concentrations of [1-(13)C]stearate after its enteral administration. The efficacy of fat absorption increased in preterm infants (formula-fed) from 91.2 +/- 1.1% (mean +/- SEM) at 32.3 wk postconceptional age (PCA) to 97.3 +/- 0.6% at 53.6 wk PCA (p < 0.001), and in term infants from 91.7 +/- 1.8% (40.0 wk PCA) to 97.4 +/- 1.3% (58.9 wk PCA, p = 0.07). Both the serum concentration of [1-(13)C]stearate and that of [1-(13)C]palmitate appeared highly correlated with the efficacy of fat absorption (r = 0.82, p = 0.02; and r = 0.91, p = 0.004; respectively) and with PCA (r = 0.99, p < 0.001; and r = 0.85, p < 0.02; respectively). These results indicate that the functional development of fat absorption in preterm and term infants is related to the capacity to absorb long-chain fatty acids from the intestine.

Discoordinate expression of pancreatic lipase and two related proteins in the human fetal pancreas

The lipase gene family contains a large number of members. Among the most closely related are pancreatic triglyceride lipase (PTL) and two pancreatic lipase-related proteins (PLRP1 and PLRP2). Previous studies in rodents demonstrated divergent temporal expression of the genes encoding these proteins. PLRP1 and PLRP2 were expressed in fetal pancreas, whereas PTL was not expressed until pups were several weeks old. To determine whether the human pancreas has a similar expression pattern for these genes, we determined the levels of each mRNA in fetal pancreas at various ages. A reverse transcriptase-PCR method was developed and used to quantify the mRNA levels for the three species normalized to the mRNA encoding cyclophillin. The mRNA encoding PLRP1 and PLRP2 was present by 16 wk in the fetal pancreas. In contrast, the mRNA encoding PTL was not present in the fetal pancreas. This pattern of expression suggests that the genes encoding theses proteins have different regulatory elements controlling temporal expression and provides another example of nonparallel expression of genes encoding pancreatic exocrine proteins.

Increased energy expenditure and fecal fat excretion do not impair weight gain in small-for-gestational-age preterm infants

In order to optimize the nutrition of high-risk premature infants beyond the early postnatal period, a more precise knowledge of individual nutritional requirements is needed. We therefore studied the influence of intrauterine growth retardation on energy expenditure and nutrient utilization determined by indirect calorimetry and fecal fat excretion (steatocrit) in nineteen premature infants who were appropriate-for-gestational-age (AGA; mean gestational age 29.9+/-0.3 weeks, mean birth weight 1.30+/-0.05 kg) and thirteen small-for-gestational-age (SGA) premature infants [mean gestational age 32.4+/-0.5 weeks, mean birth weight 1.024+/-0.07 kg (i.e., below the 10th percentile)] during the first and second month of life. All infants were clinically stable during the study period. In nine SGA infants we observed a significantly higher steatocrit compared to twelve AGA infants (29+/-1 vs. 17+/-1% p = 0.0001). SGA infants (n = 12) also showed a slightly (albeit statistically not significantly) higher energy expenditure than AGA infants (n = 15) (58.7+/-1.9 vs. 53.6+/-1.5 kcal/kg per day, p = 0.054). Despite the increased fat excretion and higher energy expenditure, SGA infants gained weight more rapidly during the study period than AGA infants (20+/-1 vs. 17+/-1 g/kg per day, p = 0.026). We conclude that influences of intrauterine growth retardation on energy expenditure and nutrient utilization persist during the first weeks of extrauterine life. However, these metabolic changes do not impair the capability of SGA infants for extrauterine catch-up growth if adequate nutrition is provided.

Bile salt-stimulated lipase and digestion of non-breast milk fat

BACKGROUND

13 Carbon (13C)-lipid breath tests are an effective, noninvasive way of repeatedly measuring fat digestion. The purpose of this study was to assess the contribution of bile salt-stimulated lipase (BSSL) in human milk to the digestion of non-breast-milk fat in Gambian infants.

METHODS

Twelve Gambian infants (aged 3-8 months) were studied on 4 days. 13C-Trioctanoin (7.5 mg/kg, digested by BSSL preduodenal and pancreatic lipases) and 13C-cholesteryl octanoate (25 mg/kg, digested by BSSL and pancreatic lipases) were used as substrates. The percentage dose recovery (PDR) of 13C in breath during 5 hours was compared after ingestion of each substrate with fresh, expressed breast milk (FBM) or heated, expressed breast milk (HBM). Gas isotope ratio-mass spectrometry was used to measure 13C enrichment, and breast milk samples were analysed for esterase activity.

RESULTS

Heating breast milk significantly decreased esterase activity (mean +/- SD values: FBM = 12.2 +/- 2.9 IU/ml; HBM = 0.5 +/- 0.3 IU/ml), and there was no difference in the volumes of milk ingested on each test day (approximately 50 ml). The PDR of 13C was comparable to that previously described in healthy English infants and was not increased by BSSL. The mean +/- SD PDR of 13C from trioctanoin was 36.3 +/- 8.4% for FBM and 34.6 +/- 6.3% for HBM (NS). From cholesteryl octanoate, the mean +/- SD PDR of 13C was 24.3 +/- 8.7% for FBM and 27.1 +/- 7.5% for HBM (NS).

CONCLUSIONS

Bile salt-stimulated lipase may enhance fat digestion in younger or malnourished infants who have a greater degree of pancreatic enzyme deficiency. However, this study suggests that it does not increase the digestion of non-breast-milk fat in healthy, well-nourished infants aged 3 to 8 months from an underprivileged background, who typically ingest frequent small quantities of breast milk.

Postnatal growth patterns of full-term low birth weight infants in Northeast Brazil are related to socioeconomic status

Low birth weight has many adverse consequences, some of which might be ameliorated if there is good postnatal compensatory, or catch-up, growth. We monitored growth, morbidity and feeding patterns in a cohort of 133 full-term, low birth weight infants from poor families in Pernambuco, Brazil, and investigated the relative contributions of a number of socioeconomic, maternal and infant variables to postnatal growth. Growth was measured at 4, 8, 17, 26 and 52 wk of age. Differential growth patterns were most marked during the first 8 wk of life, and the gains in z-score during this interval were strongly associated with attained z-scores at 12 months (r = 0.62 for weight and 0.64 for length). In a multivariate model, socioeconomic variables explained 21.4% of the variation in maximum gain in weight-for-age z-score achieved during the 12-month period, maternal weight explained a further 4.4%, infant birth length 4.7% and neonatal illness 5.4%. For maximum gain in length-for-age z-score, socioeconomic variables accounted for 24.4% of the variance, maternal height 4.9%, maternal smoking 3.3% and neonatal illness 3.1%. We surmise that the early differential growth patterns are set in utero and are indirectly affected prenatally by socioeconomic status.

Faecal chymotrypsin in small for gestational age infants: effects of nucleotides and breast feeding

The effect of diet on pancreatic exocrine function, measured by faecal chymotrypsin activity (FCA), was studied longitudinally in three groups of small for gestational age (SGA) infants in the first six months of life. The three groups comprised breastfed infants (group B), those randomly allocated to receive a standard infant formula (group S), or the same formula supplemented with nucleotides (group N). The three groups did not differ in their birthweight or gestational age. Nucleotide supplementation of infant formula improves catchup growth in SGA infants but whether this is due to effects on the gastrointestinal mucosa or the exocrine pancreas is not known. There were no differences in FCA at study entry but by one month group B had significantly lower values than the other groups, and this was maintained at 2, 4, and 6 months. Groups N and S did not differ significantly at any time point. Nucleotide supplementation of infant formula does not influence pancreatic exocrine function and its effect on growth is unlikely, therefore, to be mediated through the pancreas. This study shows that breast feeding is associated with lower FCA which may be related to the lower protein content of human milk. Reliable interpretation of FCA in young infants requires information about their diet.

Digestive enzymes in human milk: stability at suboptimal storage temperatures

BACKGROUND

Women who return to work outside of the home while still breastfeeding must often store the expressed milk at less than optimal temperatures. Human milk provides digestive enzymes (amylase and lipase) that compensate in the newborn for immature pancreatic function.

METHODS

We have assessed the stability of amylase and bile salt-dependent lipase after storage for 1-24 h at 15, 25, and 38 degrees C.

RESULTS

Both enzymes were stable at 15 and 25 degrees C for 24 h, whereas at 38 degrees C there was a 15 and 20% decrease in lipase and amylase activity, respectively. The stability of milk lipoprotein lipase was also tested. This very labile enzyme was more stable in milk than previously reported for blood and tissues, i.e., 20 and 50% decrease in activity after storage at 15 or 25 degrees C for 24 h, respectively. A two-unit drop in milk pH by 24 h of storage would not affect the activity of digestive enzymes, which are stable at pH > 3.5.

CONCLUSIONS

We conclude that milk provides the same compensatory digestive activity after short-term storage, even at relatively high temperature, as when fed fresh to the infant.

Effect of human milk or formula on gastric function and fat digestion in the premature infant

The effect of diet, human milk or formula, on gastric function (lipase and pepsin activity, pH, and volume) and intragastric digestion of fat was assessed in 28 appropriate for gestational age preterm infants (gestational age, 28.9 +/- 1.4, 29.1 +/- 0.9, 29.5 +/- 0.6 wk; birth weight, 1.00 +/- 0.14 to 1.18 +/- 0.07 kg). The infants were fed either human milk (n = 11), SMA Super Preemie formula (n = 9), or Similac, Special Care formula (n = 8). Fasting and postprandial activity of digestive enzymes, pH, and gastric volume (measured before or during 50 min after gavage feeding) did not differ as a function of diet among the three groups of infants. Gastric lipase output, 23.1 +/- 5.1, 28.3 +/- 6.6, and 22.5 +/- 6.4 (U/kg of body weight) in human milk-, SMA SP-, or Similac SC-fed infants was comparable to the gastric lipase output of healthy adults fed a high fat diet (22.6 +/- 3.0). Pepsin output was, however, significantly lower (597 +/- 77, 743 +/- 97, and 639 +/- 142 U/kg of body weight) in human milk-, SMA SP-, and Similac SC-fed infants) than in healthy adults (3352 +/- 753 U/kg). The hydrolysis of dietary fat was 1.7-2.5-fold higher (p < 0.01) in human milk-fed infants than in infants fed either formula. We conclude that differences in type of feeding, i.e. different fatty acid profiles (long chain or medium chain triglycerides), different emulsions (natural or artificial), and different fat particle sizes do not affect the level of activity of gastric enzymes. However, the triglyceride within milk fat globules appears to be more accessible to gastric lipase than that within formula fat particles. We suggest that the contribution of gastric lipase to overall fat digestion might be greater in the newborn (a period of pancreatic insufficiency) than in the adult.

Nucleotide supplementation and the growth of term small for gestational age infants

A double blind randomised controlled trial in small for gestational age (SGA) infants, whose intestinal mucosa was shown to be functionally impaired as a result of intrauterine undernutrition, was carried out to investigate the hypothesis that nucleotide supplementation of a milk formula could improve catchup growth. Anthropometric data were collected on 74 infants, 39 randomly allocated to the nucleotide supplemented group (group N) and 35 to a standard formula group (group S). From study entry to 2 months of age, infants in group N had significantly higher mean rates of weight gain (106.3 compared with 94.7 g/kg baseline weight/week) and length gain (21.8 v 19.7 mm/m baseline length/week). Over the whole six months for which the trial formula was provided group N had significantly higher mean rates of gain of weight (80.1 compared with 71.8 g/kg baseline weight/week), length (16.2 compared with 15.0 mm/m baseline length/week), and head circumference (11.8 compared with 10.8 mm/m baseline head circumference/week). Catchup growth in SGA infants is therefore improved by nucleotide supplementation of infant formula.

Limited fat digestion in infants with bronchopulmonary dysplasia

In 10 hyaline membrane disease patients with development of bronchopulmonary dysplasia, 16 hyaline membrane disease patients without development of bronchopulmonary dysplasia, and 12 very-low-birthweight infants without major medical problems, we measured the lipase and trypsin activity as well as the bile acids concentrations in preprandially aspirated duodenal juice. In addition, fat and nitrogen balances were performed during the 5th and 6th weeks of postnatal life. The mean duodenal lipase activity in the patients with bronchopulmonary dysplasia was significantly lower than those of the patients without bronchopulmonary dysplasia (4.41 +/- 3.0 versus 9.95 +/- 3.0 U/ml, p < 0.05) and of the controls (19.94 +/- 6.8 U/ml). The mean total bile acid concentration was below the critical micellar concentration of 4 mmol/L only in the patients with bronchopulmonary dysplasia. The fecal fat excretion rate in the patients with bronchopulmonary dysplasia was significantly higher than in the patients without bronchopulmonary dysplasia (21.4 +/- 4.6% versus 11.3 +/- 3.4% of intake, p < 0.01) as well as that of the controls (7.9 +/- 2.8% of intake). The serum urea concentrations were similar in the patients without bronchopulmonary dysplasia and in the controls (1.97 +/- 0.6 and 1.89 +/- 0.4 mmol/L, respectively) but significantly higher in the patients with bronchopulmonary dysplasia (2.54 +/- 0.5 mmol/L). The lowest weight gain was found in the patients with bronchopulmonary dysplasia (8.2 +/- 4.7 g/kg/day). It was significantly lower than one of the patients without bronchopulmonary dysplasia or the controls (13.5 +/- 4.0 and 16.2 +/- 3.7 g/kg/day, respectively). The data indicate that patients who develop bronchopulmonary dysplasia have a limited fat absorption, which may help to explain the inadequate weight gain.

Catch up growth and pancreatic function in growth retarded neonates

To test the hypothesis that relative pancreatic dysfunction is a determinant of catch up growth in small for gestational age (SGA) babies, 47 such babies (median gestation 38 weeks; range 27-41) and 41 appropriate for gestational age (AGA) babies matched for sex, race, and gestational age were recruited. Anthropometry was performed within 48 hours of birth and at 6 months. Faecal chymotrypsin activities were measured at 0-2 days, 14 days, 6 weeks and 6 months. At 6 months 30 SGA infants and 25 AGA infants were remeasured. In each group, median stool chymotrypsin activities doubled between 0-2 days and 6 months (9.0-25.5 IU/g SGA group; 11.6-25.3 IU/g AGA group). SGA babies had significantly lower chymotrypsin activities at 14 days (10.9 U/g) than AGA babies (15.5 U/g). In the SGA group faecal chymotrypsin activities at 0-2 days were strongly correlated with both catch up weight and with catch up length when corrected for the effects of birthweight. These data show that impaired pancreatic exocrine function at birth is associated with severe intrauterine malnutrition and with impaired catch up growth during the first 6 months of life.

Lipid metabolism in pediatric nutrition

The abrupt transition from carbohydrate to fat as the main energy source that occurs at birth is not matched by commensurate endogenous fat-digesting capacity in the newborn. Newborn infants are, however, able to digest fat efficiently through the activities of gastric lipase and the exogenous digestive lipase of human milk, which compensate for the low activity of pancreatic lipase. Fat absorption is well-developed at birth and is commensurate with the high fat intake of the infant. Tissue uptake of dietary fat is also adequate, based on sufficient lipoprotein lipase (above 26 to 27 weeks' gestation) and rapid postnatal increase of lecithin:cholesterol acyl transferase, the enzymes that regulate tissue uptake of circulatory lipoprotein triglyceride and cholesterol.