Intestinal Dysbiosis and the Developing Lung: The Role of Toll-Like Receptor 4 in the Gut-Lung Axis

Background

In extremely premature infants, postnatal growth restriction (PNGR) is common and increases the risk of developing bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH). Mechanisms by which poor nutrition impacts lung development are unknown, but alterations in the gut microbiota appear to play a role. In a rodent model, PNGR plus hyperoxia causes BPD and PH and increases intestinal Enterobacteriaceae, Gram-negative organisms that stimulate Toll-like receptor 4 (TLR4). We hypothesized that intestinal dysbiosis activates intestinal TLR4 triggering systemic inflammation which impacts lung development.

Methods

Rat pups were assigned to litters of 17 (PNGR) or 10 (normal growth) at birth and exposed to room air or 75% oxygen for 14 days. Half of the pups were treated with the TLR4 inhibitor TAK-242 from birth or beginning at day 3. After 14 days, pulmonary arterial pressure was evaluated by echocardiography and hearts were examined for right ventricular hypertrophy (RVH). Lungs and serum samples were analyzed by western blotting and immunohistochemistry.

Results

Postnatal growth restriction + hyperoxia increased pulmonary arterial pressure and RVH with trends toward increased plasma IL1β and decreased IκBα, the inhibitor of NFκB, in lung tissue. Treatment with the TLR4 inhibitor attenuated PH and inflammation.

Conclusion

Postnatal growth restriction induces an increase in intestinal Enterobacteriaceae leading to PH. Activation of the TLR4 pathway is a promising mechanism by which intestinal dysbiosis impacts the developing lung.

The developing gut-lung axis: postnatal growth restriction, intestinal dysbiosis, and pulmonary hypertension in a rodent model

BACKGROUND

Postnatal growth restriction (PNGR) in premature infants increases risk of pulmonary hypertension (PH). In a rodent model, PNGR causes PH, while combining PNGR and hyperoxia increases PH severity. We hypothesized that PNGR causes intestinal dysbiosis and that treatment with a probiotic attenuates PNGR-associated PH.

METHOD

Pups were randomized at birth to room air or 75% oxygen (hyperoxia), to normal milk intake (10 pups/dam) or PNGR (17 pups/dam), and to probiotic Lactobacillus reuteri DSM 17938 or phosphate-buffered saline. After 14 days, PH was assessed by echocardiography and right ventricular hypertrophy (RVH) was assessed by Fulton's index (right ventricular weight/left ventricle + septal weight). The small bowel and cecum were analyzed by high-throughput 16S ribosomal RNA gene sequencing.

RESULTS

PNGR with or without hyperoxia (but not hyperoxia alone) altered the microbiota of the distal small bowel and cecum. Treatment with DSM 17938 attenuated PH and RVH in pups with PNGR, but not hyperoxia alone. DSM 17938 treatment decreased α-diversity. The intestinal microbiota differed based on oxygen exposure, litter size, and probiotic treatment.

CONCLUSION

PNGR causes intestinal dysbiosis and PH. Treatment with DSM 17938 prevents PNGR-associated RVH and PH. Changes in the developing intestine and intestinal microbiota impact the developing lung vasculature and RV.

Neonatal intestinal dysbiosis

The initial colonization of the neonatal intestinal tract is influenced by delivery mode, feeding, the maternal microbiota, and a host of environmental factors. After birth, the composition of the infant's microbiota undergoes a series of significant changes particularly in the first weeks and months of life ultimately developing into a more stable and diverse adult-like population in childhood. Intestinal dysbiosis is an alteration in the intestinal microbiota associated with disease and appears to be common in neonates. The consequences of intestinal dysbiosis are uncertain, but strong circumstantial evidence and limited confirmations of causality suggest that dysbiosis early in life can influence the health of the infant acutely, as well as contribute to disease susceptibility later in life.

Change in neonatal resuscitation guidelines and trends in incidence of meconium aspiration syndrome in California

OBJECTIVE

To describe trends in the incidence and severity of meconium aspiration syndrome (MAS) around the release of revised Neonatal Resuscitation Program (NRP) guidelines in 2016.

STUDY DESIGN

The California Perinatal Quality Care Collaborative database was queried for years 2013-2017 to describe the incidence and outcomes of infants with MAS. Results were analyzed based on both individual years and pre- vs. post-guideline epochs (2013-15 vs. 2017).

RESULT

Incidence of MAS decreased significantly from 2013-15 to 2017 (1.02 to 0.78/1000 births, p < 0.001). Among infants with MAS, delivery room intubations decreased from 2013-15 to 2017 (44.3 vs. 35.1%; p = 0.005), but similar proportion of infants required invasive respiratory support (80.1 vs. 80.8%), inhaled nitric oxide (28.8 vs. 28.4%) or extracorporeal membrane oxygenation (0.81 vs. 0.35%).

CONCLUSION

While the study design precludes confirmation of implementation of the recent NRP recommendation, there was no increase in the incidence or severity of MAS following its release.

Fetal exposure to maternal inflammation interrupts murine intestinal development and increases susceptibility to neonatal intestinal injury

Fetal exposure to chorioamnionitis can impact the outcomes of the developing fetus both at the time of birth and in the subsequent neonatal period. Infants exposed to chorioamnionitis have a higher incidence of gastrointestinal (GI) pathology, including necrotizing enterocolitis (NEC); however, the mechanism remains undefined. To simulate the fetal exposure to maternal inflammation (FEMI) induced by chorioamnionitis, pregnant mice (C57BL/6J, IL-6 ^-/-, RAG ^-/- or TNFR1 ^-/-) were injected intraperitoneally on embryonic day (E)15.5 with lipopolysaccharide (LPS; 100 µg/kg body weight). Pups were delivered at term, and reared to postnatal day (P)0, P7, P14, P28 or P56. Serum and intestinal tissue samples were collected to quantify growth, inflammatory markers, histological intestinal injury, and goblet and Paneth cells. To determine whether FEMI increased subsequent susceptibility to intestinal injury, a secondary dose of LPS (100 µg/kg body weight) was given on P5, prior to tissue harvesting on P7. FEMI had no effect on growth of the offspring or their small intestine. FEMI significantly decreased both goblet and Paneth cell numbers while simultaneously increasing serum levels of IL-1β, IL-10, KC/GRO (CXCL1 and CXCL2), TNF and IL-6. These alterations were IL-6 dependent and, importantly, increased susceptibility to LPS-induced intestinal injury later in life. Our data show that FEMI impairs normal intestinal development by decreasing components of innate immunity and simultaneously increasing markers of inflammation. These changes increase susceptibility to intestinal injury later in life and provide novel mechanistic data to potentially explain why preterm infants exposed to chorioamnionitis prior to birth have a higher incidence of NEC and other GI disorders.

Early-life gut microbiome modulation reduces the abundance of antibiotic-resistant bacteria

Background

Antibiotic-resistant (AR) bacteria are a global threat. AR bacteria can be acquired in early life and have long-term sequelae. Limiting the spread of antibiotic resistance without triggering the development of additional resistance mechanisms is of immense clinical value. Here, we show how the infant gut microbiome can be modified, resulting in a significant reduction of AR genes (ARGs) and the potentially pathogenic bacteria that harbor them.

Methods

The gut microbiome was characterized using shotgun metagenomics of fecal samples from two groups of healthy, term breastfed infants. One group was fed B. infantis EVC001 in addition to receiving lactation support (n = 29, EVC001-fed), while the other received lactation support alone (n = 31, controls). Coliforms were isolated from fecal samples and genome sequenced, as well as tested for minimal inhibitory concentrations against clinically relevant antibiotics.

Results

Infants fed B. infantis EVC001 exhibited a change to the gut microbiome, resulting in a 90% lower level of ARGs compared to controls. ARGs that differed significantly between groups were predicted to confer resistance to beta lactams, fluoroquinolones, or multiple drug classes, the majority of which belonged to Escherichia, Clostridium, and Staphylococcus. Minimal inhibitory concentration assays confirmed the resistance phenotypes among isolates with these genes. Notably, we found extended-spectrum beta lactamases among healthy, vaginally delivered breastfed infants who had never been exposed to antibiotics.

Conclusions

Colonization of the gut of breastfed infants by a single strain of B. longum subsp. infantis had a profound impact on the fecal metagenome, including a reduction in ARGs. This highlights the importance of developing novel approaches to limit the spread of these genes among clinically relevant bacteria. Future studies are needed to determine whether colonization with B. infantis EVC001 decreases the incidence of AR infections in breastfed infants.

Trial registration

This clinical trial was registered at ClinicalTrials.gov, NCT02457338.

Neonatal Vitamin A Supplementation and Vitamin A Status Are Associated with Gut Microbiome Composition in Bangladeshi Infants in Early Infancy and at 2 Years of Age

BACKGROUND

Infancy is a crucial period for establishing the intestinal microbiome. This process may be influenced by vitamin A (VA) status because VA affects intestinal immunity and epithelial integrity, factors that can, in turn, modulate microbiome development.

OBJECTIVES

The aim of this study was to determine if neonatal VA supplementation (VAS) affected the abundance of Bifidobacterium, a beneficial commensal, or of Proteobacteria, a phylum containing enteric pathogens, in early (6-15 wk) or late (2 y) infancy. Secondary objectives were to determine if VAS affected the abundance of other bacterial taxa, and to determine if VA status assessed by measuring plasma retinol was associated with bacterial abundance.

METHODS

Three hundred and six Bangladeshi infants were randomized by sex and birthweight status (above/below median) to receive 1 VA dose (50,000 IU) or placebo within 48 h of birth. Relative abundance at the genus level and above was assessed by 16S rRNA gene sequencing. A terminal restriction fragment-length polymorphism assay was used to identify Bifidobacterium species and subspecies at 6 wk.

RESULTS

Linear regression showed that Bifidobacterium abundance in early infancy was lower in boys (median, 1st/3rd quartiles; 0.67, 0.52/0.78) than girls (0.73, 0.60/0.80; P = 0.003) but that boys receiving VAS (0.69, 0.55/0.78) had higher abundance than boys receiving placebo (0.65, 0.44/0.77; P = 0.039). However this difference was not seen in girls (VAS 0.71, 0.54/0.80; placebo 0.75, 0.63/0.81; P = 0.25). VAS did not affect Proteobacteria abundance. Sex-specific associations were also seen for VA status, including positive associations of plasma retinol with Actinobacteria (the phylum containing Bifidobacterium) and Akkermansia, another commensal with possible health benefits, for girls in late infancy.

CONCLUSIONS

Better VA status in infancy may influence health both in infancy and later in life by promoting the establishment of a healthy microbiota. This postulated effect of VA may differ between boys and girls. This trial was registered at clinicaltrials.gov as NCT02027610.

Bacterial colonization and antimicrobial resistance genes in neonatal enteral feeding tubes

Enteral feeding is a key component of care in neonatal intensive care units (NICUs); however, feeding tubes harbor microbes. These microbes have the potential to cause disease, yet their source remains controversial and clinical recommendations to reduce feeding tube colonization are lacking. This study aims to improve our understanding of the bacteria in neonatal feeding tubes and to evaluate factors that may affect these bacteria. 16S rRNA gene sequencing was used to characterize the bacteria present in pharyngeal, esophageal, and gastric portions of feeding tubes, residual fluid of the tubes, and infant stool using samples from 47 infants. Similar distributions of taxa were observed in all samples, although beta diversity differed by sample type. Feeding tube samples had lower alpha diversity than stool samples, and alpha diversity increased with gestational age, day of life, and tube dwell time. In a subset of samples from 6 infants analyzed by whole metagenome sequencing, there was greater overlap in transferable antimicrobial resistance genes between tube and fecal samples in breast milk fed infants than in formula fed infants. These findings develop our understanding of neonatal feeding tube colonization, laying a foundation for research into methods for minimizing NICU patients' exposure to antimicrobial resistant microbes.

A review on the interactions between the tumor microenvironment and androgen receptor signaling in prostate cancer

Prostate cancer growth is controlled by androgen receptor signaling via both androgen-dependent and androgen-independent pathways. Furthermore, the prostate is an immune competent organ with inflammatory changes both within the systemic and local environment contributing to the reprogramming of the prostatic epithelium with consistently elevated lymphocyte infiltration and proinflammatory cytokines being found in prostate cancer. The crosstalk between the tumor microenvironment and androgen receptor signaling is complex with both protumorigenic and antitumorigenic roles observed. However, despite an increase in immune checkpoint inhibitors and inflammatory signaling blockades available for a range of cancer types, we are yet to see substantial progress in the treatment of prostate cancer. Therefore, this review aims to summarize the tumor microenvironment and its impact on androgen receptor signaling in prostate cancer.

Effect of withholding feeds on transfusion-related acute gut injury in preterm infants: a pilot randomized controlled trial

Background: Several retrospective studies have reported an increase in necrotizing enterocolitis (NEC) during the 48 h following red blood cell (RBC) transfusion. Whether withholding enteral feeding during transfusion decreases the risk of transfusion-associated acute gut injury (TRAGI) in preterm infants is unclear.Study design and methods: In this pilot study, 112 preterm infants with gestational age ≤32 weeks and/or birth weight ≤1500 g were randomly assigned to withholding (NPO) or continuance of feeding (FED) during RBC transfusion. Primary outcome measure was development of NEC (stage ≥ 2) within 72 h of a transfusion and the change in abdominal circumference.Results: One hundred fifty-four transfusion episodes (74 NPO and 80 FED) were analyzed. Demographic characteristics were found to be similar in both groups. There was no difference in rates of NEC (0 versus 3.4%; p = .49) between the NPO and FED groups. The incidence of feeding intolerance was higher in the FED group; however, it was statistically insignificant (1.9 versus 6.8%, p = .36). Abdominal circumference remained similar in both groups in all three consecutive days following transfusion (p>.05).Conclusion: This pilot study does not support withholding feedings during transfusion but is not adequately powered to test the hypothesis that NPO decreases NEC rates. Adequately powered well-designed multicenter trials are still required.

Probiotics and the prevention of necrotizing enterocolitis

BACKGROUND

Immaturity of the host immune system and alterations in the intestinal microbiome appear to be key factors in the pathogenesis of necrotizing enterocolitis (NEC). The aim of this paper is to weigh the evidence for the use of probiotics to prevent NEC in premature infants.

METHODS

Animal studies, randomized controlled trials, observational cohort studies and meta-analyses involving administration of probiotic products for the prevention of NEC were reviewed. This review of the evidence summarizes the available preclinical and clinical data.

RESULTS

In animal models probiotic microbes alter the intestinal microbiome, decrease inflammation and intestinal permeability and decrease the incidence and severity of experimental NEC. In randomized, placebo-controlled trials and cohort studies of premature infants, probiotic microbes decrease the risk of NEC, death and sepsis.

CONCLUSION

Evidence is strong for the prevention of NEC with the use of combination probiotics in premature infants who receive breast milk. The potential risks and benefits of probiotic administration to premature infants should be carefully reviewed with parents.

TYPE OF STUDY

Therapeutic.

LEVEL OF EVIDENCE

I.

Bifidobacterium Abundance in Early Infancy and Vaccine Response at 2 Years of Age

BACKGROUND

The intestinal microbiome in early infancy affects immunologic development and thus may affect vaccine memory, though few prospective studies have examined such associations. We examined the association of Bifidobacterium levels in early infancy with memory responses to early vaccination measured at 2 years of age.

METHODS

In this prospective observational study, we examined the association of Bifidobacterium abundance in the stool of healthy infants at 6 to 15 weeks of age, near the time of vaccination, with T-cell and antibody responses measured at 6 weeks, 15 weeks, and 2 years of age. Infants were vaccinated with Bacillus Calmette-Guérin (BCG) (at birth), oral polio virus (at birth and at 6, 10, and 14 weeks), tetanus toxoid (TT) (at 6, 10, and 14 weeks), and hepatitis B virus (at 6, 10, and 14 weeks). Fecal Bifidobacterium was measured at 6, 11, and 15 weeks. Bifidobacterium species and subspecies were measured at 6 weeks.

RESULTS

Mean Bifidobacterium abundance in early infancy was positively associated with the CD4 T-cell responses to BCG, TT, and hepatitis B virus at 15 weeks, with CD4 responses to BCG and TT at 2 years, and with plasma TT-specific immunoglobulin G and stool polio-specific immunoglobulin A at 2 years. Similar associations were seen for the predominant subspecies, Bifidobacterium longum subspecies infantis.

CONCLUSIONS

Bifidobacterium abundance in early infancy may increase protective efficacy of vaccines by enhancing immunologic memory. This hypothesis could be tested in clinical trials of interventions to optimize Bifidobacterium abundance in appropriate populations.

Peptidomics Analysis of Milk Protein-Derived Peptides Released over Time in the Preterm Infant Stomach

Over the course of milk digestion, native milk proteases and infant digestive proteases fragment intact proteins into peptides with potential bioactivity. This study investigated the release of peptides over 3 h of gastric digestion in 14 preterm infant sample sets. The peptide content was extracted and analyzed from milk and gastric samples via Orbitrap tandem mass spectrometry. The relative ion intensity (abundance) and count of peptides in each sample were compared over time and between infants fed milk fortified with bovine milk fortifier and infants fed unfortified milk. Bioactivity of the identified peptides was predicted by sequence homology to known bioactive milk peptides. Both total and bioactive peptide abundance and count continuously increased over 3 h of gastric digestion. After accounting for infant weight, length, and postconceptual age, fortification of milk limited the release of peptides from human milk proteins. Peptides that survived further gastric digestion after their initial release were structurally more similar to bioactive peptides than nonsurviving peptides. This work is the first to provide a comprehensive profile of milk peptides released during gastric digestion over time, which is an essential step in determining which peptides are most likely to be biologically relevant in the infant. Data are available via ProteomeXchange with identifier PXD012192.

Colonization by B. infantis EVC001 modulates enteric inflammation in exclusively breastfed infants

BACKGROUND

Infant gut dysbiosis, often associated with low abundance of bifidobacteria, is linked to impaired immune development and inflammation-a risk factor for increased incidence of several childhood diseases. We investigated the impact of B. infantis EVC001 colonization on enteric inflammation in a subset of exclusively breastfed term infants from a larger clinical study.

METHODS

Stool samples (n = 120) were collected from infants randomly selected to receive either 1.8 × 10¹⁰ CFU B. infantis EVC001 daily for 21 days (EVC001) or breast milk alone (controls), starting at day 7 postnatal. The fecal microbiome was analyzed using 16S ribosomal RNA, proinflammatory cytokines using multiplexed immunoassay, and fecal calprotectin using ELISA at three time points: days 6 (Baseline), 40, and 60 postnatal.

RESULTS

Fecal calprotectin concentration negatively correlated with Bifidobacterium abundance (P < 0.0001; ρ = -0.72), and proinflammatory cytokines correlated with Clostridiaceae and Enterobacteriaceae, yet negatively correlated with Bifidobacteriaceae abundance. Proinflammatory cytokines were significantly lower in EVC001-fed infants on days 40 and 60 postnatally compared to baseline and compared to control infants.

CONCLUSION

Our findings indicate that gut dysbiosis (absence of B. infantis) is associated with increased intestinal inflammation. Early addition of EVC001 to diet represents a novel strategy to prevent enteric inflammation during a critical developmental phase.

Somatic growth and the risks of bronchopulmonary dysplasia and pulmonary hypertension: connecting epidemiology and physiology 1

In the premature infant, poor growth in utero (fetal growth restriction) and in the first weeks of life (postnatal growth restriction) are associated with increased risk for bronchopulmonary dysplasia and pulmonary hypertension. In this review, we summarize the epidemiologic data supporting these associations, present a novel rodent model of postnatal growth restriction, and review 5 promising mechanisms by which poor nutrition may affect the developing lung. These observations support the hypothesis that nutritional and (or) pharmacologic interventions early in life may be able to decrease risk of the pulmonary complications of extreme prematurity.

The Use of Telemedicine to Address Disparities in Access to Specialist Care for Neonates

Introduction: Outcomes for premature and critically ill neonates are improved with care provided by neonatologists in a neonatal intensive care unit (NICU). For smaller hospitals, maintaining the personnel and equipment necessary for the delivery and care of unexpectedly high-risk neonates is a significant challenge. To address this disparity in access, telemedicine has been increasingly used to support providers, patients, and their families in community newborn nurseries and NICUs. The purpose of this review is to present the current state of the use of telemedicine by regional NICUs to support community newborn nurseries, NICUs, and families. Methods: A literature review was conducted by two independent reviewers. Articles were selected for inclusion if they described the use of telemedicine with neonates or in the NICU. Two reviewers assessed the quality of the articles using the National Heart, Lung, and Blood Institute Study Quality Assessment Tools. Results: Fourteen articles were identified. After consensus discussion, eight of the articles were rated good and six were rated fair by the two reviewers. Many of the articles suggested improvements in quality of care, family satisfaction, and reductions in the cost of care. Unfortunately, a majority of the studies to date have had small sample sizes or were performed in a single institution and lacked robust evaluations of patient- and family-centered outcomes and provider decision making. Conclusions: While these early studies are promising, more robust studies involving more patients and more institutions are needed to identify opportunities where telemedicine can impact health outcomes, patient-centeredness, or costs of care of neonates.

Umbilical cord blood metabolomics reveal distinct signatures of dyslipidemia prior to bronchopulmonary dysplasia and pulmonary hypertension

Pulmonary hypertension (PH) is a common consequence of bronchopulmonary dysplasia (BPD) and remains a primary contributor to increased morbidity and mortality among preterm infants. Unfortunately, at the present time, there are no reliable early predictive markers for BPD-associated PH. Considering its health consequences, understanding in utero perturbations that lead to the development of BPD and BPD-associated PH and identifying early predictive markers is of utmost importance. As part of the discovery phase, we applied a multiplatform metabolomics approach consisting of untargeted and targeted methodologies to screen for metabolic perturbations in umbilical cord blood (UCB) plasma from preterm infants that did ( n = 21; cases) or did not ( n = 21; controls) develop subsequent PH. A total of 1,656 features were detected, of which 407 were annotated by metabolite structures. PH-associated metabolic perturbations were characterized by reductions in major choline-containing phospholipids, such as phosphatidylcholines and sphingomyelins, indicating altered lipid metabolism. The reduction in UCB abundances of major choline-containing phospholipids was confirmed in an independent validation cohort consisting of UCB plasmas from 10 cases and 10 controls matched for gestational age and BPD status. Subanalyses in the discovery cohort indicated that elevations in the oxylipins PGE1, PGE2, PGF2a, 9- and 13-HOTE, 9- and 13-HODE, and 9- and 13-KODE were positively associated with BPD presence and severity. This expansive evaluation of cord blood plasma identifies compounds reflecting dyslipidemia and suggests altered metabolite provision associated with metabolic immaturity that differentiate subjects, both by BPD severity and PH development.

Loss of murine Paneth cell function alters the immature intestinal microbiome and mimics changes seen in neonatal necrotizing enterocolitis

Necrotizing enterocolitis (NEC) remains the leading cause of gastrointestinal morbidity and mortality in premature infants. Human and animal studies suggest a role for Paneth cells in NEC pathogenesis. Paneth cells play critical roles in host-microbial interactions and epithelial homeostasis. The ramifications of eliminating Paneth cell function on the immature host-microbial axis remains incomplete. Paneth cell function was depleted in the immature murine intestine using chemical and genetic models, which resulted in intestinal injury consistent with NEC. Paneth cell depletion was confirmed using histology, electron microscopy, flow cytometry, and real time RT-PCR. Cecal samples were analyzed at various time points to determine the effects of Paneth cell depletion with and without Klebsiella gavage on the microbiome. Deficient Paneth cell function induced significant compositional changes in the cecal microbiome with a significant increase in Enterobacteriacae species. Further, the bloom of Enterobacteriaceae species that occurs is phenotypically similar to what is seen in human NEC. This further strengthens our understanding of the importance of Paneth cells to intestinal homeostasis in the immature intestine.

The preterm infant stomach actively degrades milk proteins with increasing breakdown across digestion time

AIM

This study investigated the effect of time post-ingestion on gastric digestion and gastric hormones after feeding preterm infants unfortified and fortified human milk.

METHODS

Human milk and infant gastric samples were collected from 14 preterm (23-32 weeks birth gestational age) mother-infant pairs within 7-98 days postnatal age. Gastric samples were collected one, two and three hours after beginning of feeding. Samples were analysed for pH, proteolysis, general protease activity and the concentrations of pepsin, gastrin and gastrin-releasing peptide (GRP). One-way ANOVA with repeated measures followed by Tukey's multiple comparisons test was used.

RESULTS

Gastric pH was significantly decreased after each hour in the preterm infant stomach from one to three hours postprandial. Proteolysis increased significantly from human milk to gastric contents at one, two and three hours postprandial (by 62, 131% and 181%, p < 0.05). General protease activity increased significantly by 58% from human milk to the gastric contents at two hours postprandial. GRP was present in human milk, whereas gastrin was produced in the infant stomach.

CONCLUSION

Although preterm infants may digest human milk proteins to a lesser extent than term infants, we demonstrated that the preterm infant stomach actively degrades milk proteins with increasing breakdown over digestion time.

Comparison of Human Milk Immunoglobulin Survival during Gastric Digestion between Preterm and Term Infants

Human milk provides immunoglobulins (Igs) that supplement the passive immune system of neonates; however, the extent of survival of these Igs during gastric digestion and whether this differs between preterm and term infants remains unknown. Human milk, and infant gastric samples at 2 h post-ingestion were collected from 15 preterm (23⁻32 week gestational age (GA)) mother-infant pairs and from 8 term (38⁻40 week of GA) mother-infant pairs within 7⁻98 days postnatal age. Samples were analyzed via ELISA for concentration of total IgA (secretory IgA (SIgA)/IgA), total secretory component (SC/SIgA/SIgM), total IgM (SIgM/IgM), and IgG as well as peptidomics. Total IgA concentration decreased by 60% from human milk to the preterm infant stomach and decreased by 48% in the term infant stomach. Total IgM and IgG concentrations decreased by 33% and 77%, respectively, from human milk to the term infant stomach but were stable in the preterm infant stomach. Release of peptides from all Ig isotypes in the term infant stomach was higher than in the preterm stomach. Overall, the stability of human milk Igs during gastric digestion is higher in preterm infant than in term infants, which could be beneficial for assisting the preterm infants' immature immune system.

Lipopolysaccharide-induced maternal inflammation induces direct placental injury without alteration in placental blood flow and induces a secondary fetal intestinal injury that persists into adulthood

PROBLEM

Premature birth complicates 10%-12% of deliveries. Infection and inflammation are the most common etiologies and are associated with increased offspring morbidity and mortality. We hypothesize that lipopolysaccharide (LPS)-induced maternal inflammation causes direct placenta injury and subsequent injury to the fetal intestine.

METHOD OF STUDY

Pregnant C57Bl6 mice were injected intraperitoneally on day 15.5 with 100 μg/kg LPS or saline. Maternal serum, amniotic fluid, placental samples, and ileal samples of offspring were obtained assessed for inflammation and/or injury. Maternal placental ultrasounds were performed. Placental DNA was isolated for microbiome analysis.

RESULTS

Maternal injection with LPS caused elevated IL-1β, IL-10, IL-6, KC-GRO, and TNF. Placental tissue showed increased IL-1β, IL-6, and KC-GRO and decreased IL-10, but no changes were observed in amniotic fluid. Placental histology demonstrated LPS-induced increases in mineralization and necrosis, but no difference in placental blood flow. Most placentas had no detectable microbiome. Exposure to maternal LPS induced significant injury to the ilea of the offspring.

CONCLUSION

Lipopolysaccharide causes a maternal inflammatory response that is mirrored in the placenta. Placental histology demonstrates structural changes; however, placental blood flow is preserved. LPS also induces an indirect intestinal injury in the offspring that lasts beyond the neonatal period.

Plasma Lipoprotein Particle Subclasses in Preterm Infants

OBJECTIVE

 A pilot study to determine lipoprotein classes and subclasses in premature infants and examine associations with nutritional intake, gestational age (GA), and morbidity.

STUDY DESIGN

 Plasma lipoprotein particle concentrations were analyzed in a cohort of 15 premature infants in the first 5 days of life and again at 2 weeks. Breast milk samples were analyzed for fatty acid content. Associations between lipoprotein particle subclasses and GA, breast milk intake, milk fatty acid intake, and chronic lung disease (CLD) were determined.

RESULTS

 At 2 weeks of age, more premature infants had higher concentrations of total very low-density lipoprotein and lower concentrations of total high-density lipoprotein (HDL) and large HDL particles (similar to profiles seen in adults and children with infectious disease, cardiometabolic disease, and diabetes). Lower total HDL, large HDL, and medium HDL and a higher small HDL:total HDL ratio at 2 weeks were each associated with CLD with GA a likely confounder. Intake of human milk C18 and C20 fatty acids was inversely correlated with plasma total LDL concentration at 2 weeks of age.

CONCLUSION

 Dyslipidemia was common in extremely premature infants and was associated with CLD and with lower intake of specific long chain fatty acids.

Probiotics and necrotizing enterocolitis

In this review, we summarize existing knowledge regarding the effects of probiotics on necrotizing enterocolitis (NEC). We review the role of the microbiome in NEC and pre-clinical data on mechanisms of probiotic action. Next, we summarize existing randomized controlled trials and observational studies of probiotics to prevent NEC. We also summarize findings from several recent meta-analyses and report a new cumulative meta-analysis of probiotic trials. Finally, we review data from cohorts routinely using commercially available probiotics. Our goal is to inform clinicians about the risks and benefits of probiotics, which may be helpful for those considering use in preterm infants to prevent NEC, death, or sepsis.