Nutrient Fortification of Human Donor Milk Affects Intestinal Function and Protein Metabolism in Preterm Pigs

Gut microbiota development in very preterm infants following fortification of human milk

Very preterm infants (VPIs) are born with an immature gut and predisposed to gut microbiota dysbiosis-related diseases, for example, necrotizing enterocolitis. Although fortification of human milk is required for these infants, the optimal fortifier remains uncertain. Bovine colostrum (BC), rich in protein and bioactive components, could serve as an alternative to conventional fortifiers (CF). The gut microbiota (GM) of 225 VPIs fed human milk fortified with either BC or CF (FortiColos study, NCT03537365) was profiled by 16S rRNA gene amplicon sequencing of fecal samples collected before, and after 1 and 2 weeks of fortification. Birth mode exhibited transient effects on the microbial community structure shortly after birth, with cesarean section-born VPIs dominated by Firmicutes, whereas vaginally born VPIs were dominated by Proteobacteria. This birth mode-derived difference diminished with age and disappeared around 1 month after birth. Fortifier type affected the microbial community structure to a modest extent, but no specific taxa significantly differed between the BC and CF groups. Fecal pH, increased by BC, was positively correlated with Staphylococcus and Corynebacterium and negatively with Bifidobacterium abundance. Change in the relative abundance of Staphylococcus was negatively correlated with body weight gain. Collectively, fortification of human milk with BC or CF does influence the GM of VPIs but only to a modest extent during early life. Birth mode appears to have a significant, but temporary influence on the GM during this period.IMPORTANCEEarly life is a key period for gut microbiota (GM) establishment, where enteral feeding plays a significant role. This is also the case for infants born preterm, who, due to their immature gut, are at a high risk of developing GM dysbiosis-related diseases. Human milk is the optimal feed for preterm infants, but it requires fortification to reach adequate levels of especially protein. Only a few studies have investigated the impact of fortifiers on GM development in preterm infants. Here, we demonstrate that two different bovine milk-based fortifiers, bovine colostrum and a conventional fortifier based on mature bovine milk, exhibit limited effects on the microbial community structure of very preterm infants. These findings suggest that although great care in terms of optimally maturing the preterm infant GM should be taken, the choice of fortifier only has limited impact. In clinical practice, the choice of fortifier can thus be fully focussed on optimizing preterm infant nutrition.CLINICAL TRIALSThis study is registered with ClinicalTrials.gov as NCT03537365.

Enteral plasma feeding improves gut function and immunity in piglets after birth asphyxia

INTRODUCTION

Birth asphyxia may negatively affect gut function and immunity in newborns. Conversely, immunomodulatory milk diets may protect the gut and immune system against damage caused by asphyxia. Using caesarean-derived pigs as models, we hypothesised that enteral feeding with plasma improves gut and immune functions in asphyxiated newborns.

METHODS

Near-term pig fetuses (98% gestation,) were delivered by caesarean section after 8 min umbilical cord occlusion, leading to transient birth asphyxia (ASP, n = 75) and compared with non-occluded controls (CON, n = 69). Piglets were further randomised to supplementation with/without porcine plasma (plasma, PLA/vehicle, VEH), into bovine colostrum (first 24 h) or formula (until 72 h).

RESULTS

Compared with CON, ASP piglets took longer to achieve stable respiration and showed reduced blood pH, weight gain and survival. Independent of asphyxia, plasma supplementation reduced gut haemorrhagic lesions, permeability and inflammatory cytokines together with improved villous morphology and brush-border enzyme activities. Asphyxia reduced blood cytokine responses to ex vivo bacterial stimulation, whereas plasma supplementation ameliorated this effect.

CONCLUSION

Dietary plasma supplementation improves survival, gut functions and immunity in both normal and asphyxiated newborns. The components in plasma that mediate gut-protective effects in piglets remain to be identified, but may benefit also birth-compromised newborn infants.

IMPACT

Complicated deliveries leading to birth asphyxia, may negatively affect gut, liver and immune adaptation in the first days after birth. Using a model of birth asphyxia in caesarean-derived piglets, we show that enteral feeding with maternal plasma exerts gut maturational and immunomodulatory effects in both control and asphyxiated animals in the first days of life. The mechanisms behind the gut-protective effects of plasma are unknown, but plasma components hold potential for new oral therapies for compromised newborn infants as well as piglets.

Systemic immune markers and infection risk in preterm infants fed human milk fortified with bovine colostrum or conventional fortifier, a secondary analysis of the FortiColos trial

BACKGROUND

For very preterm infants, human milk is often fortified with formula products based on processed bovine milk. Intact bovine colostrum (BC), rich in anti-inflammatory milk factors, is considered an alternative. We investigated if BC affects anti-inflammatory/TH2 immunity and infection risk in very preterm infants.

METHODS

For a secondary analysis of a multicenter, randomized controlled trial (NCT03537365), very preterm infants (26-31 weeks gestation, 23% small for gestational age, SGA) were randomized to receive BC (ColoDan, Biofiber, Denmark, n = 113) or conventional fortifier (PreNAN, Nestlé, Switzerland, n = 116). Infection was defined as antibiotic treatment for five or more consecutive days and 29 cytokines/chemokines were measured in plasma before and after start of fortification.

RESULTS

In general, infection risk after start of fortification was associated with low gestational age, SGA status and antibiotics use prior to fortification. Adjusted for confounders, infants fortified with BC showed more infection episodes (20 vs 12%, P < 0.05) and higher cumulative infection risk (hazard ratio, HR 1.9, P = 0.06), particularly for SGA infants (HR 3.6, P < 0.05). Additionally, BC-fortified infants had higher levels of TH2-related cytokines/chemokines (IL-10, MDC, MCP4) and reduced levels of cytokines related to TH1/TH17-responses (IL-15, IL-17, GM-CSF). The differences were most pronounced in SGA infants, displaying higher levels of TH2-related IL-4, IL-6, and IL-13, and lower interferon-γ and IL-1α levels in the BC group.

CONCLUSION

Infants fortified with BC displayed a delayed shift from TH2- to TH1-biased systemic immunity, notably in SGA infants, possibly influenced by multiple confounding factors, alongside elevated antibiotic use, suggesting increased susceptibility to infection.

Nutritional and health effects of bovine colostrum in neonates

High concentrations of immunoglobulins, bioactive peptides, and growth factors are found in bovine colostrum (BC), the milk produced by cows in the first few days after parturition. Various biological functions make it increasingly used to provide nutritional support and immune protection to the offspring of many species, including humans. These biological functions include cell growth stimulation, anti-infection, and immunomodulation. The primary components and biological functions of colostrum were reviewed in the literature, and the authors also looked at its latent effects on the growth and development of neonates as well as on conditions such as infections, necrotizing enterocolitis, short bowel syndrome, and feeding intolerance. The importance of BC in neonatal nutrition, immune support, growth and development, and gut health has been demonstrated in a number of experimental and animal studies. BC has also been shown to be safe at low doses without adverse effects in newborns. BC supplementation has been shown to be efficient in preventing several disorders, including rotavirus diarrhea, necrotizing enterocolitis, and sepsis in animal models of prematurity and some newborn studies. Therefore, BC supplementation should be considered in cases where maternal milk is insufficient or donor milk is unavailable. The optimal age, timing, dosage, and form of BC administration still require further investigation.

Glucose-regulatory hormones and growth in very preterm infants fed fortified human milk

BACKGROUND

Bovine colostrum (BC) contains a range of milk bioactive components, and it is unknown how human milk fortification with BC affects glucose-regulatory hormones in very preterm infants (VPIs). This study aimed to investigate the associations between hormone concentrations and fortification type, birth weight (appropriate/small for gestational age, AGA/SGA), milk intake, postnatal age, and body growth.

METHODS

225 VPIs were randomized to fortification with BC or conventional fortifier (CF). Plasma hormones were measured before, one and two weeks after start of fortification. ΔZ-scores from birth to 35 weeks postmenstrual age were calculated.

RESULTS

Compared with CF, infants fortified with BC had higher plasma GLP-1, GIP, glucagon, and leptin concentrations after start of fortification. Prior to fortification, leptin concentrations were negatively associated with growth, while IGF-1 concentrations associated positively with growth during fortification. In AGA infants, hormone concentrations generally increased after one week of fortification. Relative to AGA infants, SGA infants showed reduced IGF-1 and leptin concentrations.

CONCLUSION

Fortification with BC increased the plasma concentrations of several glucose-regulatory hormones. Concentrations of IGF-1 were positively, and leptin negatively, associated with growth. Glucose-regulatory hormone levels were affected by birth weight, milk intake and postnatal age, but not closely associated with growth in VPIs.

IMPACT

Little is known about the variation in glucose-regulatory hormones in the early life of very preterm infants (VPIs). This study shows that the levels of glucose-regulatory hormones in plasma of VPIs are highly variable and modified by birth weight (appropriate or small for gestational age, AGA or SGA), the type of fortifier, enteral nutritional intake, and advancing postnatal age. The results confirm that IGF-1 levels are positively associated with early postnatal growth in VPIs, yet the levels of both IGF-1 and other glucose-regulatory hormones appeared to explain only a small part of the overall variation in growth rates.

Osmolality of fortified donor human milk: An experimental study

BACKGROUND

We quantify the osmolality of human milk fortified with human milk fortifiers (HMFs), powder infant formulas and protein additives.

METHODS

Commercial liquid HMFs and powder infant formulas were added to pasteurized pooled donor human milk in triplicate and stirred. The osmolality of unfortified and fortified human milk at 22, 24, 26, 27, 28, and 30 kcal/oz (0.73, 0.8, 0.87, 0.9, 0.93, and 1 kcal/ml, respectively) was determined using freezing-point depression.

RESULTS

The osmolality of fortified human milk associated with energy density in a linear relationship regardless of the fortification strategies. Multiple liquid HMFs and every powder infant formula exceeded the osmolality threshold of 450 mOsm/kg H2 O within the energy densities tested.

CONCLUSION

The osmolality of fortified human milk is highly variable and should be considered when selecting a fortifying agent for human milk.

Ultra-High Temperature Treatment of Liquid Infant Formula, Systemic Immunity, and Kidney Development in Preterm Neonates

SCOPE

Ready-to-feed liquid infant formulas (IFs) are increasingly being used for newborn preterm infants when human milk is unavailable. However, sterilization of liquid IFs by ultra-high temperature (UHT) introduces Maillard reaction products (MRPs) that may negatively affect systemic immune and kidney development.

METHODS AND RESULTS

UHT-treated IF without and with prolonged storage (SUHT) are tested against pasteurized IF (PAST) in newborn preterm pigs as a model for preterm infants. After 5 days, blood leukocytes, markers of systemic immunity and inflammation, kidney structure and function are evaluated. No consistent differences between UHT and PAST pigs are observed. However, SUHT increases plasma TNFα and IL-6 and reduces neutrophils and in vitro response to LPS. In SUHT pigs, the immature kidneys show minor upregulation of gene expressions related to inflammation (RAGE, MPO, MMP9) and oxidative stress (CAT, GLO1), together with glomerular mesangial expansion and cell injury. The increased inflammatory status in SUHT pigs appears unrelated to systemic levels of MRPs.

CONCLUSION

SUHT feeding may impair systemic immunity and affect kidney development in preterm newborns. The systemic effects may be induced by local gut inflammatory effects of MRPs. Optimal processing and length of storage are critical for UHT-treated liquid IFs for preterm infants.

Preterm pigs for preterm birth research: reasonably feasible

Preterm birth will disrupt the pattern and course of organ development, which may result in morbidity and mortality of newborn infants. Large animal models are crucial resources for developing novel, credible, and effective treatments for preterm infants. This review summarizes the classification, definition, and prevalence of preterm birth, and analyzes the relationship between the predicted animal days and one human year in the most widely used animal models (mice, rats, rabbits, sheep, and pigs) for preterm birth studies. After that, the physiological characteristics of preterm pig models at different gestational ages are described in more detail, including birth weight, body temperature, brain development, cardiovascular system development, respiratory, digestive, and immune system development, kidney development, and blood constituents. Studies on postnatal development and adaptation of preterm pig models of different gestational ages will help to determine the physiological basis for survival and development of very preterm, middle preterm, and late preterm newborns, and will also aid in the study and accurate optimization of feeding conditions, diet- or drug-related interventions for preterm neonates. Finally, this review summarizes several accepted pediatric applications of preterm pig models in nutritional fortification, necrotizing enterocolitis, neonatal encephalopathy and hypothermia intervention, mechanical ventilation, and oxygen therapy for preterm infants.

State-of-the-art review and update of in vivo models of necrotizing enterocolitis

NEC remains one of the most common causes of mortality and morbidity in preterm infants. Animal models of necrotizing enterocolitis (NEC) have been crucial in improving our understanding of this devastating disease and identifying biochemical pathways with therapeutic potential. The pathogenesis of NEC remains incompletely understood, with no specific entity that unifies all infants that develop NEC. Therefore, investigators rely on animal models to manipulate variables and provide a means to test interventions, making them valuable tools to enhance our understanding and prevent and treat NEC. The advancements in molecular analytic tools, genetic manipulation, and imaging modalities and the emergence of scientific collaborations have given rise to unique perspectives and disease correlates, creating novel pathways of investigation. A critical review and understanding of the current phenotypic considerations of the highly relevant animal models of NEC are crucial to developing novel therapeutic and preventative strategies for NEC.

A Randomized, Controlled Study to Investigate How Bovine Colostrum Fortification of Human Milk Affects Bowel Habits in Preterm Infants (FortiColos Study)

Background: Human milk does not meet the nutritional needs to support optimal growth of very preterm infants during the first weeks of life. Nutrient fortifiers are therefore added to human milk, though these products are suspected to increase gut dysmotility. The objective was to evaluate whether fortification with bovine colostrum (BC) improves bowel habits compared to a conventional fortifier (CF) in very preterm infants. Methods: In an unblinded, randomized study, 242 preterm infants (26−31 weeks of gestation) were randomized to receive BC (BC, Biofiber Damino, Gesten, Denmark) or CF (FM85 PreNAN, Nestlé, Vevey, Switzerland) as a fortifier. Stools (Amsterdam Stool Scale), bowel gas restlessness, stomach appearance score, volume, and frequency of gastric residuals were recorded before each meal until 35 weeks post-menstrual age. Results: As intake of fortifiers increased, stools became harder in both groups (p < 0.01) though less in BC infants (p < 0.05). The incidence of bowel gas restlessness increased with laxative treatments and days of fortification in both groups (p < 0.01), but laxatives were prescribed later in BC infants (p < 0.01). With advancing age, stomach appearance scores improved, but more so in BC infants (p < 0.01). Conclusions: Although there are limitations, a minimally processed, bioactive milk product such as BC induced similar or slightly improved bowel habits in preterm infants.

Clinical outcome and gut development after insulin-like growth factor-1 supplementation to preterm pigs

BACKGROUND

Elevation of circulating insulin-like growth factor-1 (IGF-1) within normal physiological levels may alleviate several morbidities in preterm infants but safety and efficacy remain unclear. We hypothesized that IGF-1 supplementation during the first 1-2 weeks after preterm birth improves clinical outcomes and gut development, using preterm pigs as a model for infants.

METHODS

Preterm pigs were given vehicle or recombinant human IGF-1/binding protein-3 (rhIGF-1, 2.25 mg/kg/d) by subcutaneous injections for 8 days (Experiment 1, n = 34), or by systemic infusion for 4 days (Experiment 2, n = 19), before collection of blood and organs for analyses.

RESULTS

In both experiments, rhIGF-1 treatment increased plasma IGF-1 levels 3-4 fold, reaching the values reported for term suckling piglets. In Experiment 1, rhIGF-1 treatment increased spleen and intestinal weights without affecting clinical outcomes like growth, blood biochemistry (except increased sodium and gamma-glutamyltransferase levels), hematology (e.g., red and white blood cell populations), glucose homeostasis (e.g., basal and glucose-stimulated insulin and glucose levels) or systemic immunity variables (e.g., T cell subsets, neutrophil phagocytosis, LPS stimulation, bacterial translocation to bone marrow). The rhIGF-1 treatment increased gut protein synthesis (+11%, p < 0.05) and reduced the combined incidence of all-cause mortality and severe necrotizing enterocolitis (NEC, p < 0.05), but had limited effects on intestinal morphology, cell proliferation, cell apoptosis, brush-border enzyme activities, permeability and levels of cytokines (IL-1β, IL-6, IL-8). In Experiment 2, rhIGF-1 treated pigs had reduced blood creatine kinase, creatinine, potassium and aspartate aminotransferase levels, with no effects on organ weights (except increased spleen weight), blood chemistry values, clinical variables or NEC.

CONCLUSION

Physiological elevation of systemic IGF-1 levels for 8 days after preterm birth increased intestinal weight and protein synthesis, spleen weight and potential overall viability of pigs, without any apparent negative effects on recorded clinical parameters. The results add further preclinical support for safety and efficacy of supplemental IGF-1 to hospitalized very preterm infants.

Potential Benefits of Bovine Colostrum in Pediatric Nutrition and Health

Bovine colostrum (BC), the first milk produced from cows after parturition, is increasingly used as a nutritional supplement to promote gut function and health in other species, including humans. The high levels of whey and casein proteins, immunoglobulins (Igs), and other milk bioactives in BC are adapted to meet the needs of newborn calves. However, BC supplementation may improve health outcomes across other species, especially when immune and gut functions are immature in early life. We provide a review of BC composition and its effects in infants and children in health and selected diseases (diarrhea, infection, growth-failure, preterm birth, necrotizing enterocolitis (NEC), short-bowel syndrome, and mucositis). Human trials and animal studies (mainly in piglets) are reviewed to assess the scientific evidence of whether BC is a safe and effective antimicrobial and immunomodulatory nutritional supplement that reduces clinical complications related to preterm birth, infections, and gut disorders. Studies in infants and animals suggest that BC should be supplemented at an optimal age, time, and level to be both safe and effective. Exclusive BC feeding is not recommended for infants because of nutritional imbalances relative to human milk. On the other hand, adverse effects, including allergies and intolerance, appear unlikely when BC is provided as a supplement within normal nutrition guidelines for infants and children. Larger clinical trials in infant populations are needed to provide more evidence of health benefits when patients are supplemented with BC in addition to human milk or formula. Igs and other bioactive factors in BC may work in synergy, making it critical to preserve bioactivity with gentle processing and pasteurization methods. BC has the potential to become a safe and effective nutritional supplement for several pediatric subpopulations.

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.

Developing a Reference Database for Typical Body and Organ Growth of the Artificially Reared Pig as a Biomedical Research Model

Objectives: The pig is a common model utilized to support substantiation of novel bioactive components in infant formula. However, reference ranges for outcomes to determine safety are unclear. Our objective was to use historical data to objectively define typical body and organ growth metrics of the domesticated pig in research. Methods: Twenty-two studies were compiled to assess typical growth of body and organ weights in young pigs. Metadata were organized to include milk replacer sources, bioactive components, sex, breed, source of herd, feeding regimen, and rearing environment. A combination of statistical models including simple linear regression and linear mixed effect models were used to assess typical growth patterns. Results: Over 18,000 data points from 786 animals were available. In general, minimal differences in the growth of pigs who were male and female, artificially- or sow-reared, or fed ad libitum- or by scheduled-feeding, were observed in the first 30 days of life (P > 0.05). A weight-for-age chart from reference pigs was developed to compare body weights of pigs demonstrating growth characterized as accelerated, typical, reduced, and failure to thrive to illustrate effects of dietary interventions. Distributions of relative brain, liver, and intestine weights (as % of total body weight) were similar between rearing environments and sexes. An alternative bivariate level approach was utilized for the analysis of organ weights. This approach revealed significant biologically-relevant insights into how deficient diets can affect organ weight that a univariate level assessment of weight distribution was unable to detect. Conclusions: Ultimately, these data can be used to better interpret whether bioactive ingredients tested in the pig model affect growth and development within typical reference values for pigs in the first 30 days of life.

Gut transit time, using radiological contrast imaging, to predict early signs of necrotizing enterocolitis

BACKGROUND

Immature gut motility in preterm neonates may be a risk factor for necrotizing enterocolitis (NEC). Using preterm pigs as a model for infants, we hypothesized that intestinal dysmotility precedes NEC development.

METHODS

Eighty-five preterm pigs were fed increasing amounts of milk diets to induce NEC lesions, as detected at autopsy on day 5. Gut transit time was determined on day 4 by x-ray imaging after oral intake of contrast solution.

RESULTS

No clinical or radiological signs of NEC were detected on day 4, but macroscopic NEC lesions were recorded in 59% of pigs (n = 50) on day 5. Relative to pigs without NEC (noNEC, n = 35), pigs with small intestinal lesions (siNEC, n = 18) showed delayed stomach emptying time (StEmpty) and time for contrast to reach cecum (ToCecum) already on day 4. Pigs with lesions only in colon (coNEC, n = 20) showed more diarrhea, shorter ToCecum time, but longer small intestinal emptying time (SiEmpty). ToCecum time predicted siNEC and coNEC lesions with a receiver-operator characteristic area under the curve of 78-81%.

CONCLUSIONS

Region-dependent changes in gut transit time is associated with early NEC development in preterm pigs. How gut dysmotility is related to NEC in preterm infants requires further investigations.

IMPACT

Using preterm pigs as a model for preterm infants, we show that gut transit time, using serial x-ray contrast imaging, was changed in individuals with NEC-like lesions before they showed the typical radiological signs of NEC. Thus prolonged transit time across the entire gut was recorded when NEC lesions appeared in the small intestine but not when lesions were detected only in the colon. Until now, recordings of food transit have mainly investigated changes in the upper gut. Using serial x-rays, this study describes food transit across the entire gut and documents a region-dependent effect of NEC lesions on gut transit changes in preterm individuals. The findings provide proof of concept for use of x-ray contrast imaging as a tool to monitor gut transit in preterm pigs as models for infants. Delayed passage across the entire gut may be an early sign of small intestinal NEC, at least in pigs. More studies are needed to confirm relations in infants. In the future, it might be possible to use x-ray contrast imaging in preterm infants to better understand gut motility in relation to early NEC progression and need for medical NEC treatment.

Low Splanchnic Oxygenation and Risk for Necrotizing Enterocolitis in Extremely Preterm Newborns

OBJECTIVE

The aim of the study was to investigate whether splanchnic oxygenation (SrSO2), measured with near-infrared spectroscopy (NIRS), during the first week of life is associated with the risk of developing necrotizing enterocolitis (NEC) in extremely preterm infants.

METHODS

This was a prospective observational cohort study including extremely preterm infants (<28 weeks of gestation) born at Karolinska University Hospital from September 2014 to December 2016. Using 1-hour NIRS monitoring during enteral feeding, mainly continuous enteral feeding, in the first week of life we measured both cerebral and splanchnic oxygenation. Primary outcome was risk of developing NEC (Bell stage ≥ II). Secondary outcome was the association between low mean SrSO2 during the first week of life and postnatal age at full enteral nutrition.

RESULTS

We enrolled 52 extremely preterm newborns, but only 45 infants had complete NIRS data. One infant developed NEC within 1 day of NIRS monitoring and was excluded from the study. Median gestational age was 25.6 weeks (range 23.0-27.9) and median birth weight 698 g (range 485-1353). Eight infants developed NEC at the median postnatal age of 15 days (range 6-35). Median postnatal age at full enteral nutrition was 10 days (range 6-23). Infants with mean SrSO2 <30% had a higher risk for developing NEC compared with those with SrSO2 >30% (crude risk ratio 5.25; 95% CI [1.19-23.01]). Small for gestational age, gestational age, birth weight, postnatal age did not affect the results. We found no association between SrSO2 and age at full enteral nutrition.

CONCLUSIONS

Low mean SrSO2 (<30%) during the first week of life is associated with an increased risk for developing NEC in extremely preterm infants on mainly continuous enteral nutrition.

Diet Modulates the High Sensitivity to Systemic Infection in Newborn Preterm Pigs

Background: Preterm infants are born with an immature immune system, limited passive immunity, and are at risk of developing bacteremia and sepsis in the postnatal period. We hypothesized that enteral feeding, with or without added immunoglobulins, improves the clinical response to systemic infection by coagulase negative staphylococci.

Methods: Using preterm cesarean delivered pigs as models for preterm infants, we infused live Staphylococcus epidermidis (SE, 5 × 10⁹ colony forming units per kg) systemically 0–3 days after birth across five different experiments. SE infection responses were assessed following different gestational age at birth (preterm vs. term), enteral milk diets (bovine colostrum, infant formula with or without added porcine plasma) and with/without systemic immunoglobulins. Pigs infected with SE were assessed 12–48 h for clinical variables, blood bacteriology, chemistry, hematology, and gut dysfunction (intestinal permeability, necrotizing enterocolitis lesions).

Results: Adverse clinical responses and increased mortality were observed in preterm vs. term pigs, when infected with SE just after birth. Feeding bovine colostrum just after birth improved blood SE clearance and clinical status (improved physical activity and intestinal structure, fewer bone marrow bacteria), relative to pigs fed infant formula. A few days later, clinical responses to SE bacteremia (hematology, neutrophil phagocytic capacity, T cell subsets) were less severe, and less affected by different milk diets, with or without added immunoglobulins.

Conclusion: Prematurity increases the sensitivity of newborn pigs to SE bacteremia, potentially causing sepsis. Sensitivity to systemic SE infection decreases rapidly in the days after preterm birth. Both age and diet (parenteral nutrition, colostrum, milk, formula) may influence gut inflammation, bacterial translocation and systemic immune development in the days after birth in preterm newborns.

Nutrient Restriction has Limited Short-Term Effects on Gut, Immunity, and Brain Development in Preterm Pigs

BACKGROUND

Extrauterine growth restriction (EUGR) in preterm infants is associated with higher morbidity and impaired neurodevelopment. Early nutrition support may prevent EUGR in preterm infants, but it is not known if this improves organ development and brain function in the short and long term.

OBJECTIVE

Using pigs as models for infants, we hypothesized that diet-induced EUGR impairs gut, immunity, and brain development in preterm neonates during the first weeks after birth.

METHODS

Forty-four preterm caesarean-delivered pigs (Danish Landrace × Large White × Duroc, birth weight 975 ± 235 g, male:female ratio 23:21) from 2 sows were fed increasing volumes [32-180 mL/(kg·d)] of dilute bovine milk (EUGR group) or the same diet fortified with powdered bovine colostrum for 19 d (CONT group, 50-100% higher protein and energy intake than the EUGR group).

RESULTS

The EUGR pigs showed reduced body growth (-39%, P < 0.01), lower plasma albumin, phosphate, and creatine kinase concentrations (-35 to 14%, P < 0.05), increased cortisol and free iron concentrations (+130 to 700%, P < 0.05), and reduced relative weights of the intestine, liver, and spleen (-38 to 19%, all P < 0.05). The effects of EUGR on gut structure, function, microbiota, and systemic immunity were marginal, although EUGR temporarily increased type 1 helper T cell (Th1) activity (e.g. more blood T cells and higher Th1-related cytokine concentrations on day 8) and reduced colon nutrient fermentation (lower SCFA concentration; -45%, P < 0.01). Further, EUGR pigs showed increased relative brain weights (+19%, P < 0.01), however, memory and learning, as tested in a spatial T-maze, were not affected.

CONCLUSION

Most of the measured organ growth, and digestive, immune, and brain functions showed limited effects of diet-induced EUGR in preterm pigs during the first weeks after birth. Likewise, preterm infants may show remarkable physiological adaptation to deficient nutrient supply during the first weeks of life although early life malnutrition may exert negative consequences later.

Gastric Residual to Predict Necrotizing Enterocolitis in Preterm Piglets As Models for Infants

BACKGROUND

Necrotizing enterocolitis (NEC) is a serious intestinal inflammatory disease in preterm infants. High volume of gastric residual (GR) after oral feedings is often used as a predictor of NEC, but evidence is limited. Using NEC-sensitive preterm piglets as models, we hypothesized that GR mass and related plasma biomarkers predict early onset of NEC.

METHODS

In total, 258 newborn preterm piglets were fed bovine milk-based formulas for 5 days. At euthanasia, the stomach, small intestine, and colon were evaluated for NEC lesions. Mass, acidity, gastrin, and bile acid levels were determined for GR content, together with gastrin, glucagon-like peptide 2 (GLP-2), and gastric inhibitory polypeptide (GIP) levels in plasma.

RESULTS

In total, 48% of piglets had NEC lesions in the small intestine and/or colon. These piglets had higher GR mass (+32%, P < 0.001) and lower gastric bile acid concentrations (-22%, P < 0.05) than piglets without NEC lesions. The positive and negative predictive values for these markers were 34%-61%. Gastric acidity, gastrin, GLP-2, and GIP levels were similar for piglets with and without NEC lesions.

CONCLUSION

Elevated GR mass correlates positively with NEC lesions but may be a poor predictor of NEC, even when combined with other biomarkers. More knowledge about gastric emptying and gut transit in preterm neonates is required to understand how GR volume and composition relate to morbidities, such as NEC, in preterm neonates.

Translational Advances in Pediatric Nutrition and Gastroenterology: New Insights from Pig Models

Pigs are increasingly important animals for modeling human pediatric nutrition and gastroenterology and complementing mechanistic studies in rodents. The comparative advantages in size and physiology of the neonatal pig have led to new translational and clinically relevant models of important diseases of the gastrointestinal tract and liver in premature infants. Studies in pigs have established the essential roles of prematurity, microbial colonization, and enteral nutrition in the pathogenesis of necrotizing enterocolitis. Studies in neonatal pigs have demonstrated the intestinal trophic effects of akey gut hormone, glucagon-like peptide 2 (GLP-2), and its role in the intestinal adaptation process and efficacy in the treatment of short bowel syndrome. Further, pigs have been instrumental in elucidating the physiology of parenteral nutrition-associated liver disease and the means by which phytosterols, fibroblast growth factor 19, and a new generation of lipid emulsions may modify disease. The premature pig will continue to be a valuable model in the development of optimal infant diets (donor human milk, colostrum), specific milk bioactives (arginine, growth factors), gut microbiota modifiers (pre-, pro-, and antibiotics), pharmaceutical drugs (GLP-2 analogs, FXR agonists), and novel diagnostic tools (near-infrared spectroscopy) to prevent and treat these pediatric diseases.

Bovine Colostrum Before or After Formula Feeding Improves Systemic Immune Protection and Gut Function in Newborn Preterm Pigs

Objectives: Maternal milk is often absent or in limited supply just after preterm birth. Many preterm infants are therefore fed infant formula as their first enteral feed despite an increased risk of feeding intolerance, necrotizing enterocolitis (NEC), and infection. Using preterm pigs as a model for preterm infants, we hypothesized that bovine colostrum given before or after formula feeding would alleviate formula-induced detrimental effects during the first days after preterm birth.

Methods: A total of 74 preterm pigs received gradually increasing volumes of formula (F) or bovine colostrum (C) until day 5, when they were euthanized or transitioned to either C or F for another 4 days, resulting in six groups: C or F until day 5 (C5, F5, n = 11 each), C or F until day 9 (CC, FF n = 12–13 each), C followed by F (CF, n = 14), and F followed by C (FC, n = 13).

Results: Systemically, colostrum feeding stimulated circulating neutrophil recruitment on day 5 (C5 vs. F5, P < 0.05). Relative to initial formula feeding, initial colostrum feeding promoted the development of systemic immune protection as indicated by a decreased T-helper cell population and an increased regulatory T-cell population (CC + CF vs. FC + FF, P < 0.01). In the gut, colostrum feeding improved intestinal parameters such as villus heights, enzymes, hexose absorption, colonic goblet cell density, and decreased the incidence of severe NEC (27 vs. 64%), diarrhea (16 vs. 49%), and gut permeability on day 5, coupled with lowered expression of LBP, MYD88, IL8, HIF1A, and CASP3 (C5 vs. F5, all P < 0.05). On day 9, the incidence of severe NEC was similarly low across groups (15–21%), but diarrhea resistance and intestinal parameters were further improved by colostrum feeding, relative to exclusive formula feeding (CC, CF, or FC vs. FF, respectively, all P < 0.05). The expression of MYD88 and CASP3 remained downregulated by exclusive colostrum feeding (CC vs. FF, P < 0.01) and colostrum before or after formula feeding down regulated HIF1A and CASP3 expression marginally.

Conclusion: Colostrum feeding ameliorated detrimental effects of formula feeding on systemic immunity and gut health in preterm newborns, especially when given immediately after birth.

Alpha-Lactalbumin Enriched Whey Protein Concentrate to Improve Gut, Immunity and Brain Development in Preterm Pigs

Human milk is rich in nutritional factors, such as alpha-lactalbumin (α-Lac), and important for neonatal development, but nutrient supplementation may be required for optimal growth. Using a pig model, we hypothesized that α-Lac-enriched whey protein concentrate (WPC) supplementation improves neonatal development. Cesarean-delivered preterm pigs were fed either dilute bovine milk (REF) or REF milk supplemented with WPC with normal (STANDARD-ALPHA) or high (HIGH-ALPHA) α-Lac. Clinical, gut, immune and cognitive endpoints (open field, T-maze) were assessed and tissues collected at Day 19. The growth of STANDARD-ALPHA and HIGH-ALPHA were higher than REF (31 vs. 19 g/kg/d). Most organ weights, gut, immunity and brain variables were similar between WPC groups. HIGH-ALPHA had a higher bone mineral content, colon microbial diversity and an abundance of specific bacteria and microbial metabolites, and tended to show a faster food transit time (p = 0.07). Relative to REF, WPC pigs showed higher relative organ weights, blood amino acids, blood neutrophil function, and microbial metabolites, but lower brush-border enzyme activities and plasma cortisol. Cognition outcomes did not differ among the groups. In conclusion, WPC supplementation of milk improved some growth, gut and immunity parameters in preterm pigs. However, increasing the α-Lac content beyond human milk levels had limited effects on the immature gut and developing brain.

Supplemental Insulin-Like Growth Factor-1 and Necrotizing Enterocolitis in Preterm Pigs

Background: Recombinant human IGF-1/binding protein-3 (rhIGF-1/BP-3) is currently tested as a therapy in preterm infants but possible effects on the gut, including necrotizing enterocolitis (NEC), have not been tested. The aim of this study was to evaluate if rhIGF-1/BP-3 supplementation in the first days after birth negatively affects clinical variables like growth, physical activity, blood chemistry and hematology and gut maturation (e.g., intestinal permeability, morphology, enzyme activities, cytokine levels, enterocyte proliferation, NEC lesions), using NEC-sensitive preterm pigs as a model for preterm infants. Methods: Preterm pigs were given twice daily subcutaneous injections of rhIGF-1/BP-3 or vehicle. Blood was collected for IGF-1 measurements and gut tissue for NEC evaluation and biochemical analyses on day 5. Results: Baseline circulating IGF-1 levels were low in preterm pigs compared with near-term pigs reared by their mother (<20 vs. 70 ng/ml). Injection with rhIGF-1/BP-3 resulted in increased plasma IGF-1 levels for up to 6 h after injection (>40 ng/mL). rhIGF-1/BP-3 treatment reduced the incidence of severe NEC lesions (7/24 vs.16/24, p = 0.01) and overall NEC severity (1.8 ± 0.2 vs. 2.6 ± 0.3, p < 0.05, with most lesions occurring in colon). In the small intestine, villi length (405 ± 25 vs. 345 ± 33 μm) and activities of the brush border peptidases aminopeptidase N and dipeptidylpeptidase IV were increased in rhIGF-1/BP-3 treated pigs, relative to control pigs (+31-44%, both p < 0.05). The treatment had no effects on body weight, blood chemistry or hematology, except for an increase in blood leucocyte and neutrophil counts (p < 0.05, i.e., reduced neonatal neutropenia). Likewise, rhIGF-1/BP-3 treatment did not affect intestinal tissue cytokine levels (IL-1β, IL-6, IL-8, TNFα,), enterocyte proliferation, goblet cell density, permeability or bacterial translocation to the bone marrow. Conclusion: Supplemental rhIGF-1/BP-3 did not negatively affect any of the measured variables of clinical status or gut maturation in preterm pigs. Longer-term safety and efficacy of exogenous rhIGF-1/BP-3 to support maturation of the gut and other critical organs in preterm newborns remain to be investigated in both pigs and infants.

Protein intakes to optimize outcomes for preterm infants

Proteins are key structural components of all human cells and are also involved in key physiologic processes through their roles as enzymes, hormones and transport proteins. Protein requirements are substantially higher in preterm infants than those born at term, yet inadequate protein intakes are a common problem on many neonatal units. Very preterm infants (VPT, <32 weeks) commonly receive parenteral amino acid solutions which are typically commenced on admission, and increased over the next few days. Several recent studies have explored differing parenteral amino acid intakes in the first few days, and recommendations have recently been updated. Parenteral nutrition intakes are decreased as enteral feeds are tolerated, but human milk alone will not meet protein needs in most VPT and supplementation or fortification will be required. This review paper considers basic protein and amino acid physiology in the newborn period, and the evidence base for current recommendations.

FortiColos - a multicentre study using bovine colostrum as a fortifier to human milk in very preterm infants: study protocol for a randomised controlled pilot trial

BACKGROUND

Very preterm infants (< 32 weeks gestation) have a relatively high nutrient requirement for growth and development. The composition of human milk is often inadequate to ensure optimal growth so it is common to fortify human milk for very preterm infants with nutrient fortifiers based on bovine milk. However, there are concerns that bovine milk-based fortifiers may increase the risk of feeding intolerance, necrotizing enterocolitis and late-onset sepsis. We hypothesize that a bovine colostrum-based product is a suitable alternative to bovine milk-based products when used as a fortifier to human milk in very preterm infants.

METHODS/DESIGN

In an open-label multicentre randomised controlled pilot trial, 200 very preterm infants (26 + 0 to 30 + 6 weeks gestation at birth) will be randomly allocated to a bovine colostrum-based or a bovine milk-based fortifier added to mother's own milk and/or human donor milk. Outcomes are growth rate, incidence of necrotizing enterocolitis and late-onset sepsis, a series of paraclinical endpoints, and practical feasibility of using the novel fortifier for very preterm infants.

DISCUSSION

The optimal enteral diet and feeding regimen for very preterm infants remain debated; this clinical trial will document the feasibility, safety and preliminary efficacy of using bovine colostrum, rich in nutrients and bioactive factors, as a novel fortifier for human milk to very preterm infants. Data on infant growth, metabolism, gut function and immunity will be assessed from clinical data as well as blood and stool samples.

TRIAL REGISTRATION

Registered retrospectively 25 May 2018 at ClinicalTrials.gov: NCT03537365 .

Milk feed osmolality and adverse events in newborn infants and animals: a systematic review

BACKGROUND

High feed osmolality (or osmolarity) is often suggested to be linked with adverse gastrointestinal events in preterm infants.

AIM

To systematically review the literature on milk feed osmolality and adverse gastrointestinal events in newborn and low birthweight infants and animals.

METHODS

MEDLINE, Embase, CAB Abstracts, Current Contents, BIOSIS Previews and SciSearch were searched from inception to May 2018 to identify potentially relevant studies.

INCLUSION CRITERIA

randomised controlled or observational studies of newborn and low birthweight infants or animals investigating the effects of milk-based feeds with different osmolalities. Only full-text, English-language papers were included.

RESULTS

Ten human and six animal studies met the inclusion criteria. Of human studies, seven reported no differences in adverse events with varying feed osmolalities; one reported delayed gastric emptying with feed osmolarity of 539 mOsm/L compared with lower levels; one reported higher necrotising enterocolitis (NEC) incidence with feed osmolarity of 650 mOsm/L compared with 359 mOsm/L; one found higher NEC incidence with the lowest feed osmolality (326 mOsm/kg compared with 385 mOsm/kg). Of animal studies, two reported delayed gastric emptying with feed osmolarity >624 mOsm/L, one reported decreased survival due to dehydration with dietary osmolarities ≥765 mOsmol/L and none reported increased NEC incidence with differing feed osmolalities. No clear mechanisms were found, and diet composition differences limited the interpretations regarding the independent impact of osmolality.

CONCLUSIONS

There is no consistent evidence that differences in feed osmolality in the range 300-500 mOsm/kg are associated with adverse gastrointestinal symptoms in neonates.

Neonatal gut and immune maturation is determined more by postnatal age than by postconceptional age in moderately preterm pigs

Preterm infants have immature organ functions that predispose them to gut and immune disorders. Developmental delays at preterm birth may affect various organs differently at term-corrected age. We hypothesized that gut and immune maturation in moderately preterm neonates depends more on birth and postnatal factors than on advancing postconceptional age (PCA). Using preterm pigs as models, we investigated how gut and immune parameters develop until term-corrected age and how these differ from those in term counterparts. Preterm ( n = 43, 106 days of gestation) and term pigs ( n = 41, 116 days of gestation) were delivered by caesarean section and euthanized at birth ( day 1) or postnatal day 11 (term-corrected age for preterm pigs) using identical rearing conditions. Relative to term pigs, preterm pigs had lower blood oxygenation, glucose, and cortisol levels, lower gut lactase activity, villus height, and goblet cell density, and lower blood neutrophil, helper T, and cytotoxic T cell numbers at birth. Despite slower growth in preterm pigs, most intestinal and immune parameters increased markedly after birth in both groups. However, some parameters remained negatively affected by preterm birth until postnatal day 11 (goblet cells, gut permeability, and cytotoxic T cells). The colon microbiota showed limited differences between preterm and term pigs at this time. At the same PCA, preterm 11-day-old pigs had higher blood leukocyte numbers and gut enzyme activities but lower villus height and blood cytotoxic T cell numbers relative to newborn term pigs. Birth and postnatal factors, not advancing PCA, are key determinants of gut and immune maturation in moderately preterm neonates. NEW & NOTEWORTHY Postnatally, preterm infants are often considered to reach a physiological maturation similar to that in term infants when they reach term-corrected postconceptional age (PCA). Using preterm pigs as models, we show that PCA may be a poor measure of gut and immune maturation because environmental triggers (regardless of PCA at birth) are critical. Possibly, PCA is only relevant to evaluate physiological maturation of organs that develop relatively independent of the external environment (e.g., the brain).

Human Milk Fortification with Bovine Colostrum Is Superior to Formula-Based Fortifiers to Prevent Gut Dysfunction, Necrotizing Enterocolitis, and Systemic Infection in Preterm Pigs

BACKGROUND

Fortification of donor human milk (DHM) is required for optimal growth of very preterm infants, but there are concerns of more gut dysfunction and necrotizing enterocolitis (NEC) when using formula-based fortifiers (FFs), especially soon after birth. Intact bovine colostrum (BC) is rich in nutrients and bioactive factors, and protects against NEC in preterm pigs. We hypothesized that fortification of DHM with BC is superior to FFs to prevent gut dysfunction and infections when provided shortly after preterm birth.

METHODS

Two FF products, Enfamil (ENF; intact protein, vegetable oil) and PreNAN+Nutrilon (NAN; extensively hydrolyzed protein, maltodextrin), were compared with BC as fortifier to DHM fed to preterm pigs for 5 days.

RESULTS

Relative to the DHM+BC group, DHM+FF groups had higher diarrhea score and lower hexose uptake and lactase activity, and specifically the DHM+NAN group showed higher gut permeability, NEC score, more mucosa-adherent bacteria with altered gut microbiota structure (ie, lower diversity, increased Enterococcus, decreased Staphylococcus abundance). Both DHM+FF groups showed higher expression of intestinal cytokine and inflammation-related genes, more gut-derived bacteria in the bone marrow, lower density of mucin-containing goblet cells, and slightly higher colon lactate, stomach pH and acetate, and blood neutrophil-to-lymphocyte levels than the DHM+BC group.

CONCLUSIONS

Used as a fortifier to DHM, BC is superior to FFs to support gut function, nutrient absorption, and bacterial defense mechanisms in preterm pigs. It is important to optimize the composition of nutrient fortifiers for preterm infants fed human milk.

Necrotizing enterocolitis is associated with acute brain responses in preterm pigs

Background

Necrotizing enterocolitis (NEC) is an acute gut inflammatory disorder that occurs in preterm infants in the first weeks after birth. Infants surviving NEC often show impaired neurodevelopment. The mechanisms linking NEC lesions with later neurodevelopment are poorly understood but may include proinflammatory signaling in the immature brain. Using preterm pigs as a model for preterm infants, we hypothesized that severe intestinal NEC lesions are associated with acute effects on the developing hippocampus.

Methods

Cesarean-delivered preterm pigs (n = 117) were reared for 8 days and spontaneously developed variable severity of NEC lesions. Neonatal arousal, physical activity, and in vitro neuritogenic effects of cerebrospinal fluid (CSF) were investigated in pigs showing NEC lesions in the colon (Co-NEC) or in the small intestine (Si-NEC). Hippocampal transcriptome analysis and qPCR were used to assess gene expressions and their relation to biological processes, including neuroinflammation, and neural plasticity. Microglia activation was quantified by stereology. The neuritogenic response to selected proteins was investigated in primary cultures of hippocampal neurons.

Results

NEC development rapidly reduced the physical activity of pigs, especially when lesions occurred in the small intestine. Si-NEC and Co-NEC were associated with 27 and 12 hippocampal differentially expressed genes (DEGs), respectively. These included genes related to neuroinflammation (i.e., S100A8, S100A9, IL8, IL6, MMP8, SAA, TAGLN2) and hypoxia (i.e., PDK4, IER3, TXNIP, AGER), and they were all upregulated in Si-NEC pigs. Genes related to protection against oxidative stress (HBB, ALAS2) and oligodendrocytes (OPALIN) were downregulated in Si-NEC pigs. CSF collected from NEC pigs promoted neurite outgrowth in vitro, and the S100A9 and S100A8/S100A9 proteins may mediate the neuritogenic effects of NEC-related CSF on hippocampal neurons. NEC lesions did not affect total microglial cell number but markedly increased the proportion of Iba1-positive amoeboid microglial cells.

Conclusions

NEC lesions, especially when present in the small intestine, are associated with changes to hippocampal gene expression that potentially mediate neuroinflammation and disturbed neural circuit formation via enhanced neuronal differentiation. Early brain-protective interventions may be critical for preterm infants affected by intestinal NEC lesions to reduce their later neurological dysfunctions.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1201-x) contains supplementary material, which is available to authorized users.