Maternal aryl hydrocarbon receptor activation protects newborns against necrotizing enterocolitis

Blocking OLFM4/galectin-3 axis in placental polymorphonuclear myeloid-derived suppressor cells triggers intestinal inflammation in newborns

Fetal growth restriction (FGR) is a major cause of premature and low-weight births, which increases the risk of necrotizing enterocolitis (NEC); however, the association remains unclear. We report a close correlation between placental polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) and NEC. Newborns with previous FGR exhibited intestinal inflammation and more severe NEC symptoms than healthy newborns. Placental PMN-MDSCs are vital regulators of fetal development and neonatal gut inflammation. Placental single-cell transcriptomics revealed that PMN-MDSCs populations and olfactomedin-4 gene (Olfm4) expression levels were significantly increased in PMN-MDSCs in later pregnancy compared to those in early pregnancy and non-pregnant females. Female mice lacking Olfm4 in myeloid cells mated with wild-type males showed FGR during pregnancy, with a decreased placental PMN-MDSCs population and expression of growth-promoting factors (GPFs) from placental PMN-MDSCs. Galectin-3 (Gal-3) stimulated the OLFM4-mediated secretion of GPFs by placental PMN-MDSCs. Moreover, GPF regulation via OLFM4 in placental PMN-MDSCs was mediated via hypoxia inducible factor-1α (HIF-1α). Notably, the offspring of mothers lacking Olfm4 exhibited intestinal inflammation and were susceptible to NEC. Additionally, OLFM4 expression decreased in placental PMN-MDSCs from pregnancies with FGR and was negatively correlated with neonatal morbidity. These results revealed that placental PMN-MDSCs contributed to fetal development and ameliorate newborn intestinal inflammation.

Exploring the Immunomodulatory Potential of Human Milk: Aryl Hydrocarbon Receptor Activation and Its Impact on Neonatal Gut Health

Several metabolites of the essential amino acid tryptophan have emerged as key players in gut homeostasis through different cellular pathways, particularly through metabolites which can activate the aryl hydrocarbon receptor (AHR). This study aimed to map the metabolism of tryptophan in early life and investigate the effects of specific metabolites on epithelial cells and barrier integrity. Twenty-one tryptophan metabolites were measured in the feces of full-term and preterm neonates as well as in human milk and formula. The ability of specific AHR metabolites to regulate cytokine-induced IL8 expression and maintain barrier integrity was assessed in Caco2 cells and human fetal organoids (HFOs). Overall, higher concentrations of tryptophan metabolites were measured in the feces of full-term neonates compared to those of preterm ones. Within AHR metabolites, indole-3-lactic acid (ILA) was significantly higher in the feces of full-term neonates. Human milk contained different levels of several tryptophan metabolites compared to formula. Particularly, within the AHR metabolites, indole-3-sulfate (I3S) and indole-3-acetic acid (IAA) were significantly higher compared to formula. Fecal-derived ILA and milk-derived IAA were capable of reducing TNFα-induced IL8 expression in Caco2 cells and HFOs in an AHR-dependent manner. Furthermore, fecal-derived ILA and milk-derived IAA significantly reduced TNFα-induced barrier disruption in HFOs.

Protective Effects of Lactobacillus reuteri on Intestinal Barrier Function in a Mouse Model of Neonatal Necrotizing Enterocolitis

OBJECTIVE

 The intestinal mucosal and immune barriers play considerable roles in the pathogenesis of necrotizing enterocolitis (NEC). The present research was designed to assess the protective effects of Lactobacillus reuteri (LR) DSM 17938 (LR 17938) on the intestinal barriers and its beneficial effects on inflammation in a neonatal mouse model of NEC.

STUDY DESIGN

 Overall, 7-day-old 75 C57BL/6 neonatal mice were separated into three groups (n = 25) as follows: (1) control, (2) NEC, and (3) NEC + LR17938 (LR group). NEC mice were administered a hypertonic feeding formula and subjected to asphyxia and hypothermia. Hematoxylin and eosin (HE) staining and pathological scores were used to assess the pathological changes in the intestine. Oxidative stress was evaluated based on the levels of superoxide dismutase (SOD) and malondialdehyde (MDA). Tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels were detected to assess inflammation. Gut permeability levels, bacterial translocation, and the levels of secretory idioglobulin A (sIgA), β-defensin, and tight junction (TJ) proteins were detected to evaluate gut mucosal and immune barrier function, and gut microbial diversity was detected to assess the composition of the gut flora.

RESULTS

 LR 17938 administration decreased the NEC-induced increase in intestinal scores, mortality rate, gut damage, the MDA level, and TNF-α and IL-1β expressions. Besides, LR 17938 improved the survival rate of NEC mice. Moreover, LR 17938 administration improved gut permeability levels, SOD activity and the bacterial translocation, ameliorated the expression of TJ proteins, and improved the gut microbiota compared with those of NEC mice.

CONCLUSION

 LR 17938 reduced intestinal inflammation and played a protective role in a neonatal animal model of NEC, possibly by regulating oxidative stress and exerting a protective effect on the gut mucosal and immune barriers.

KEY POINTS

· Our research indicated a protective effect of LR 17938 on gut barrier function in NEC mice.. · LR 17938may affect the diversity of gut flora, which are known to target beneficial bacteria.. · LR 17938 protected gut barrier function in the NEC pups by improving gut permeability..

Extracellular Nicotinamide Phosphoribosyltransferase Is a Therapeutic Target in Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency of prematurity. Postulated mechanisms leading to inflammatory necrosis of the ileum and colon include activation of the pathogen recognition receptor Toll-like receptor 4 (TLR4) and decreased levels of transforming growth factor beta (TGFβ). Extracellular nicotinamide phosphoribosyltransferase (eNAMPT), a novel damage-associated molecular pattern (DAMP), is a TLR4 ligand and plays a role in a number of inflammatory disease processes. To test the hypothesis that eNAMPT is involved in NEC, an eNAMPT-neutralizing monoclonal antibody, ALT-100, was used in a well-established animal model of NEC. Preterm Sprague-Dawley pups delivered prematurely from timed-pregnant dams were exposed to hypoxia/hypothermia and randomized to control-foster mother dam-fed rats, injected IP with saline (vehicle) 48 h after delivery; control + mAB-foster dam-fed rats, injected IP with 10 µg of ALT-100 at 48 h post-delivery; NEC-orally gavaged, formula-fed rats injected with saline; and NEC + mAb-formula-fed rats, injected IP with 10 µg of ALT-100 at 48 h. The distal ileum was processed 96 h after C-section delivery for histological, biochemical, molecular, and RNA sequencing studies. Saline-treated NEC pups exhibited markedly increased fecal blood and histologic ileal damage compared to controls (q < 0.0001), and findings significantly reduced in ALT-100 mAb-treated NEC pups (q < 0.01). Real-time PCR in ileal tissues revealed increased NAMPT in NEC pups compared to pups that received the ALT-100 mAb (p < 0.01). Elevated serum levels of tumor necrosis factor alpha (TNFα), interleukin 6 (IL-6), interleukin-8 (IL-8), and NAMPT were observed in NEC pups compared to NEC + mAb pups (p < 0.01). Finally, RNA-Seq confirmed dysregulated TGFβ and TLR4 signaling pathways in NEC pups that were attenuated by ALT-100 mAb treatment. These data strongly support the involvement of eNAMPT in NEC pathobiology and eNAMPT neutralization as a strategy to address the unmet need for NEC therapeutics.

Bioluminescence imaging of Cyp1a1-luciferase reporter mice demonstrates prolonged activation of the aryl hydrocarbon receptor in the lung

Aryl hydrocarbon receptor (AHR) signalling integrates biological processes that sense and respond to environmental, dietary, and metabolic challenges to ensure tissue homeostasis. AHR is a transcription factor that is inactive in the cytosol but upon encounter with ligand translocates to the nucleus and drives the expression of AHR targets, including genes of the cytochrome P4501 family of enzymes such as Cyp1a1. To dynamically visualise AHR activity in vivo, we generated reporter mice in which firefly luciferase (Fluc) was non-disruptively targeted into the endogenous Cyp1a1 locus. Exposure of these animals to FICZ, 3-MC or to dietary I3C induced strong bioluminescence signal and Cyp1a1 expression in many organs including liver, lung and intestine. Longitudinal studies revealed that AHR activity was surprisingly long-lived in the lung, with sustained Cyp1a1 expression evident in discrete populations of cells including columnar epithelia around bronchioles. Our data link diet to lung physiology and also reveal the power of bespoke Cyp1a1-Fluc reporters to longitudinally monitor AHR activity in vivo.

Indoxyl sulphate-initiated activation of cardiac fibroblasts is modulated by aryl hydrocarbon receptor and nuclear factor-erythroid-2-related factor 2

In the last decade, extensive attention has been paid to the uremic toxin indoxyl sulphate (IS) as an inducer of cardiac fibroblast (cFib) activation and cardiac fibrosis in chronic kidney disease. At cellular level, IS engages aryl hydrocarbon receptor (AhR) and regulates many biological functions. We analysed how AhR inhibition by CH-223191 (CH) and overexpression of non-functional (dominant negative, DN) nuclear factor-erythroid-2-related factor 2 (NRF2), a transcription factor recruited by AhR, modulate the response of neonatal mouse (nm) cFib to IS. We also evaluated nm-cardiomyocytes after incubation with the conditioned medium (CM) of IS±CH-treated nm-cFib. IS induced activation, collagen synthesis, TLR4 and-downstream-MCP-1, and the genes encoding angiotensinogen, angiotensin-converting enzyme, angiotensin type 1 receptor (AT1r) and neprilysin (Nepr) in nm-cFib. CH antagonized IS-initiated nm-cFib activation, but did not affect or even magnified the other features. IS promoted NRF2 nuclear translocation and expression the NRF2 target Nqo1. Both pre-incubation with CH and transfection of DN-NRF2 resulted in loss of NRF2 nuclear localization. Moreover, DN-NRF2 overexpression led to greater TLR4 and MCP-1 levels following exposure to IS. The CM of IS-primed nm-cFib and to a larger extent the CM of IS+CH-treated nm-cFib upregulated AT1r, Nepr and TNFα and myostatin genes in nm-cardiomyocytes. Hence, IS triggers pro-inflammatory activation of nm-cFib partly via AhR, and AhR-NRF2 counteract it. Strategies other than AhR inhibition are needed to target IS detrimental actions on cardiac cells.

A high fiber diet or supplementation with Lactococcus lactis subspecies cremoris to pregnant mice confers protection against intestinal injury in adult offspring

The diet during pregnancy, or antenatal diet, influences the offspring's intestinal health. We previously showed that antenatal butyrate supplementation reduces injury in adult murine offspring with dextran sulfate sodium (DSS)-induced colitis. Potential modulators of butyrate levels in the intestine include a high fiber diet or dietary supplementation with probiotics. To test this, we supplemented the diet of pregnant mice with high fiber, or with the probiotic bacteria Lactococcus lactis subspecies cremoris or Lactobacillus rhamnosus GG. We then induced chronic colitis with DSS in their adult offspring. We demonstrate that a high fiber antenatal diet, or supplementation with Lactococcus lactis subspecies cremoris during pregnancy diminished the injury from DSS-induced colitis in offspring. These data are evidence that antenatal dietary interventions impact offspring gut health and define the antenatal diet as a therapeutic modality to enhance offspring intestinal health.

The Bern Birth Cohort (BeBiCo) to study the development of the infant intestinal microbiota in a high-resource setting in Switzerland: rationale, design, and methods

BACKGROUND

Microbiota composition is fundamental to human health with the intestinal microbiota undergoing critical changes within the first two years of life. The developing intestinal microbiota is shaped by maternal seeding, breast milk and its complex constituents, other nutrients, and the environment. Understanding microbiota-dependent pathologies requires a profound understanding of the early development of the healthy infant microbiota.

METHODS

Two hundred and fifty healthy pregnant women (≥20 weeks of gestation) from the greater Bern area will be enrolled at Bern University hospital's maternity department. Participants will be followed as mother-baby pairs at delivery, week(s) 1, 2, 6, 10, 14, 24, 36, 48, 96, and at years 5 and 10 after birth. Clinical parameters describing infant growth and development, morbidity, and allergic conditions as well as socio-economic, nutritional, and epidemiological data will be documented. Neuro-developmental outcomes and behavior will be assessed by child behavior checklists at and beyond 2 years of age. Maternal stool, milk, skin and vaginal swabs, infant stool, and skin swabs will be collected at enrolment and at follow-up visits. For the primary outcome, the trajectory of the infant intestinal microbiota will be characterized by 16S and metagenomic sequencing regarding composition, metabolic potential, and stability during the first 2 years of life. Secondary outcomes will assess the cellular and chemical composition of maternal milk, the impact of nutrition and environment on microbiota development, the maternal microbiome transfer at vaginal or caesarean birth and thereafter on the infant, and correlate parameters of microbiota and maternal milk on infant growth, development, health, and mental well-being.

DISCUSSION

The Bern birth cohort study will provide a detailed description and normal ranges of the trajectory of microbiota maturation in a high-resource setting. These data will be compared to data from low-resource settings such as from the Zimbabwe-College of Health-Sciences-Birth-Cohort study. Prospective bio-sampling and data collection will allow studying the association of the microbiota with common childhood conditions concerning allergies, obesity, neuro-developmental outcomes , and behaviour. Trial registration The trial has been registered at www.

CLINICALTRIALS

gov , Identifier: NCT04447742.

Early-life interactions between the microbiota and immune system: impact on immune system development and atopic disease

Prenatal and early postnatal life represent key periods of immune system development. In addition to genetics and host biology, environment has a large and irreversible role in the immune maturation and health of an infant. One key player in this process is the gut microbiota, a diverse community of microorganisms that colonizes the human intestine. The diet, environment and medical interventions experienced by an infant determine the establishment and progression of the intestinal microbiota, which interacts with and trains the developing immune system. Several chronic immune-mediated diseases have been linked to an altered gut microbiota during early infancy. The recent rise in allergic disease incidence has been explained by the 'hygiene hypothesis', which states that societal changes in developed countries have led to reduced early-life microbial exposures, negatively impacting immunity. Although human cohort studies across the globe have established a correlation between early-life microbiota composition and atopy, mechanistic links and specific host-microorganism interactions are still being uncovered. Here, we detail the progression of immune system and microbiota maturation in early life, highlight the mechanistic links between microbes and the immune system, and summarize the role of early-life host-microorganism interactions in allergic disease development.

Impacts of maternal microbiota and microbial metabolites on fetal intestine, brain, and placenta

BACKGROUND

The maternal microbiota modulates fetal development, but the mechanisms of these earliest host-microbe interactions are unclear. To investigate the developmental impacts of maternal microbial metabolites, we compared full-term fetuses from germ-free and specific pathogen-free mouse dams by gene expression profiling and non-targeted metabolomics.

RESULTS

In the fetal intestine, critical genes mediating host-microbe interactions, innate immunity, and epithelial barrier were differentially expressed. Interferon and inflammatory signaling genes were downregulated in the intestines and brains of the fetuses from germ-free dams. The expression of genes related to neural system development and function, translation and RNA metabolism, and regulation of energy metabolism were significantly affected. The gene coding for the insulin-degrading enzyme (Ide) was most significantly downregulated in all tissues. In the placenta, genes coding for prolactin and other essential regulators of pregnancy were downregulated in germ-free dams. These impacts on gene expression were strongly associated with microbially modulated metabolite concentrations in the fetal tissues. Aryl sulfates and other aryl hydrocarbon receptor ligands, the trimethylated compounds TMAO and 5-AVAB, Glu-Trp and other dipeptides, fatty acid derivatives, and the tRNA nucleobase queuine were among the compounds strongly associated with gene expression differences. A sex difference was observed in the fetal responses to maternal microbial status: more genes were differentially regulated in male fetuses than in females.

CONCLUSIONS

The maternal microbiota has a major impact on the developing fetus, with male fetuses potentially more susceptible to microbial modulation. The expression of genes important for the immune system, neurophysiology, translation, and energy metabolism are strongly affected by the maternal microbial status already before birth. These impacts are associated with microbially modulated metabolites. We identified several microbial metabolites which have not been previously observed in this context. Many of the potentially important metabolites remain to be identified.

The Effect of Maternal Probiotic or Synbiotic Supplementation on Sow and Offspring Gastrointestinal Microbiota, Health, and Performance

The increasing prevalence of antimicrobial-resistant pathogens has prompted the reduction in antibiotic and antimicrobial use in commercial pig production. This has led to increased research efforts to identify alternative dietary interventions to support the health and development of the pig. The crucial role of the GIT microbiota in animal health and performance is becoming increasingly evident. Hence, promoting an improved GIT microbiota, particularly the pioneer microbiota in the young pig, is a fundamental focus. Recent research has indicated that the sow's GIT microbiota is a significant contributor to the development of the offspring's microbiota. Thus, dietary manipulation of the sow's microbiota with probiotics or synbiotics, before farrowing and during lactation, is a compelling area of exploration. This review aims to identify the potential health benefits of maternal probiotic or synbiotic supplementation to both the sow and her offspring and to explore their possible modes of action. Finally, the results of maternal sow probiotic and synbiotic supplementation studies are collated and summarized. Maternal probiotic or synbiotic supplementation offers an effective strategy to modulate the sow's microbiota and thereby enhance the formation of a health-promoting pioneer microbiota in the offspring. In addition, this strategy can potentially reduce oxidative stress and inflammation in the sow and her offspring, enhance the immune potential of the milk, the immune system development in the offspring, and the sow's feed intake during lactation. Although many studies have used probiotics in the maternal sow diet, the most effective probiotic or probiotic blends remain unclear. To this extent, further direct comparative investigations using different probiotics are warranted to advance the current understanding in this area. Moreover, the number of investigations supplementing synbiotics in the maternal sow diet is limited and is an area where further exploration is warranted.

Building better barriers: how nutrition and undernutrition impact pediatric intestinal health

Chronic undernutrition is a major cause of death for children under five, leaving survivors at risk for adverse long-term consequences. This review focuses on the role of nutrients in normal intestinal development and function, from the intestinal epithelium, to the closely-associated mucosal immune system and intestinal microbiota. We examine what is known about the impacts of undernutrition on intestinal physiology, with focus again on the same systems. We provide a discussion of existing animal models of undernutrition, and review the evidence demonstrating that correcting undernutrition alone does not fully ameliorate effects on intestinal function, the microbiome, or growth. We review efforts to treat undernutrition that incorporate data indicating that improved recovery is possible with interventions focused not only on delivery of sufficient energy, macronutrients, and micronutrients, but also on efforts to correct the abnormal intestinal microbiome that is a consequence of undernutrition. Understanding of the role of the intestinal microbiome in the undernourished state and correction of the phenotype is both complex and a subject that holds great potential to improve recovery. We conclude with critical unanswered questions in the field, including the need for greater mechanistic research, improved models for the impacts of undernourishment, and new interventions that incorporate recent research gains. This review highlights the importance of understanding the mechanistic effects of undernutrition on the intestinal ecosystem to better treat and improve long-term outcomes for survivors.

Human Cytomegalovirus in breast milk is associated with milk composition, the infant gut microbiome, and infant growth

Human cytomegalovirus (CMV) is a highly prevalent herpesvirus that is often transmitted to the neonate via breast milk. Postnatal CMV transmission can have negative health consequences for preterm and immunocompromised infants, but any effects on healthy term infants are thought to be benign. Furthermore, the impact of CMV on the composition of the hundreds of bioactive factors in human milk has not been tested. Here, we utilize a cohort of exclusively breastfeeding full term mother-infant pairs to test for differences in the milk transcriptome and metabolome associated with CMV, and the impact of CMV in breast milk on the infant gut microbiome and infant growth. We find upregulation of the indoleamine 2,3- dioxygenase (IDO) tryptophan-to-kynurenine metabolic pathway in CMV+ milk samples, and that CMV+ milk is associated with decreased Bifidobacterium in the infant gut. Our data indicate a complex relationship between milk CMV, milk kynurenine, and infant growth; with kynurenine positively correlated, and CMV viral load negatively correlated, with infant weight-for-length at 1 month of age. These results suggest CMV transmission, CMV-related changes in milk composition, or both may be modulators of full term infant development.

Human milk oligosaccharides reduce necrotizing enterocolitis-induced neuroinflammation and cognitive impairment in mice

Necrotizing enterocolitis (NEC) is the leading cause of morbidity and mortality in premature infants. One of the most devastating complications of NEC is the development of NEC-induced brain injury, which manifests as impaired cognition that persists beyond infancy and which represents a proinflammatory activation of the gut-brain axis. Given that oral administration of the human milk oligosaccharides (HMOs) 2'-fucosyllactose (2'-FL) and 6'-sialyslactose (6'-SL) significantly reduced intestinal inflammation in mice, we hypothesized that oral administration of these HMOs would reduce NEC-induced brain injury and sought to determine the mechanisms involved. We now show that the administration of either 2'-FL or 6'-SL significantly attenuated NEC-induced brain injury, reversed myelin loss in the corpus callosum and midbrain of newborn mice, and prevented the impaired cognition observed in mice with NEC-induced brain injury. In seeking to define the mechanisms involved, 2'-FL or 6'-SL administration resulted in a restoration of the blood-brain barrier in newborn mice and also had a direct anti-inflammatory effect on the brain as revealed through the study of brain organoids. Metabolites of 2'-FL were detected in the infant mouse brain by nuclear magnetic resonance (NMR), whereas intact 2'-FL was not. Strikingly, the beneficial effects of 2'-FL or 6'-SL against NEC-induced brain injury required the release of the neurotrophic factor brain-derived neurotrophic factor (BDNF), as mice lacking BDNF were not protected by these HMOs from the development of NEC-induced brain injury. Taken in aggregate, these findings reveal that the HMOs 2'-FL and 6'-SL interrupt the gut-brain inflammatory axis and reduce the risk of NEC-induced brain injury.NEW & NOTEWORTHY This study reveals that the administration of human milk oligosaccharides, which are present in human breast milk, can interfere with the proinflammatory gut-brain axis and prevent neuroinflammation in the setting of necrotizing enterocolitis, a major intestinal disorder seen in premature infants.

Fecal microbiota transplantation improves chicken growth performance by balancing jejunal Th17/Treg cells

BACKGROUND

Intestinal inflammation has become a threatening concern in chicken production worldwide and is closely associated with Th17/Treg cell imbalance. Several studies described that gut microbiota is significantly implicated in chicken growth by modulating intestinal immune homeostasis and immune cell differentiation. Whether reshaping gut microbiota by fecal microbiota transplantation (FMT) could improve chicken growth by balancing Th17/Treg cells is an interesting question.

RESULTS

Here, the chickens with significantly different body weight from three different breeds (Turpan cockfighting × White Leghorn chickens, white feather chickens, and yellow feather chickens) were used to compare Th17 and Treg cells. qPCR and IHC staining results indicated that Th17 cell-associated transcriptional factors Stat3 and rorγt and cytokines IL-6, IL-17A, and IL-21 were significantly (P < 0.05) higher in the jejunum of low body weight chickens, while Treg cell-associated transcriptional factor foxp3 and cytokines TGF-β and IL-10 were significantly (P < 0.05) lower in the jejunum of low body weight chickens, indicating imbalanced Th17/Treg cells were closely related to chicken growth performance. Transferring fecal microbiota from the healthy donor with better growth performance and abundant Lactobacillus in feces to 1-day-old chicks markedly increased growth performance (P < 0.001), significantly decreased Th17 cell-associated transcriptional factors and cytokines, and increased Treg cell-associated transcriptional factors and cytokines in the jejunum (P < 0.05). Furthermore, FMT increased the abundance of Lactobacillus (FMT vs Con; 84.98% vs 66.94%). Besides, the metabolites of tryptophan including serotonin, indole, and 5-methoxyindoleacetate were increased as well, which activated their receptor aryl-hydrocarbon-receptor (AhR) and expressed more CYP1A2 and IL-22 to maintain Th17/Treg cell balance and immune homeostasis.

CONCLUSION

These findings suggested that imbalanced Th17/Treg cells decreased chicken growth performance, while FMT-reshaped gut microbiota, i.e., higher Lactobacilli, increased chicken growth performance by balancing Th17/Treg cells. Video Abstract.

The role of human milk nutrients in preventing necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an intestinal disease that primarily impacts preterm infants. The pathophysiology of NEC involves a complex interplay of factors that result in a deleterious immune response, injury to the intestinal mucosa, and in its most severe form, irreversible intestinal necrosis. Treatments for NEC remain limited, but one of the most effective preventative strategies for NEC is the provision of breast milk feeds. In this review, we discuss mechanisms by which bioactive nutrients in breast milk impact neonatal intestinal physiology and the development of NEC. We also review experimental models of NEC that have been used to study the role of breast milk components in disease pathophysiology. These models are necessary to accelerate mechanistic research and improve outcomes for neonates with NEC.

New insights into the pathogenesis of necrotizing enterocolitis and the dawn of potential therapeutics

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disorder in premature infants that causes significant morbidity and mortality. Research efforts into the pathogenesis of NEC have discovered a pivotal role for the gram-negative bacterial receptor, Toll-like receptor 4 (TLR4), in its development. TLR4 is activated by dysbiotic microbes within the intestinal lumen, which leads to an exaggerated inflammatory response within the developing intestine, resulting in mucosal injury. More recently, studies have identified that the impaired intestinal motility that occurs early in NEC has a causative role in disease development, as strategies to enhance intestinal motility can reverse NEC in preclinical models. There has also been broad appreciation that NEC also contributes to significant neuroinflammation, which we have linked to the effects of gut-derived pro-inflammatory molecules and immune cells which activate microglia in the developing brain, resulting in white matter injury. These findings suggest that the management of the intestinal inflammation may secondarily be neuroprotective. Importantly, despite the significant burden of NEC on premature infants, these and other studies have provided a strong rationale for the development of small molecules with the capability of reducing NEC severity in pre-clinical models, thus guiding the development of specific anti-NEC therapies. This review summarizes the roles of TLR4 signaling in the premature gut in the pathogenesis of NEC, and provides insights into optimal clinical management strategies based upon findings from laboratory studies.

Tumor-Suppressive Functions of the Aryl Hydrocarbon Receptor (AhR) and AhR as a Therapeutic Target in Cancer

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor involved in regulating a wide range of biological responses. A diverse array of xenobiotics and endogenous small molecules bind to the receptor and drive unique phenotypic responses. Due in part to its role in mediating toxic responses to environmental pollutants, AhR activation has not been traditionally viewed as a viable therapeutic approach. Nonetheless, the expression and activation of AhR can inhibit the proliferation, migration, and survival of cancer cells, and many clinically approved drugs transcriptionally activate AhR. Identification of novel select modulators of AhR-regulated transcription that promote tumor suppression is an active area of investigation. The development of AhR-targeted anticancer agents requires a thorough understanding of the molecular mechanisms driving tumor suppression. Here, we summarized the tumor-suppressive mechanisms regulated by AhR with an emphasis on the endogenous functions of the receptor in opposing carcinogenesis. In multiple different cancer models, the deletion of AhR promotes increased tumorigenesis, but a precise understanding of the molecular cues and the genetic targets of AhR involved in this process is lacking. The intent of this review was to synthesize the evidence supporting AhR-dependent tumor suppression and distill insights for development of AhR-targeted cancer therapeutics.

Impact of maternal factors, environmental factors, and race on necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a complex disease with a multifactorial etiology. As the leading cause of intestinal morbidity and mortality among premature infants, many resources are being dedicated to neonatal care and molecular targets in the newborn intestine. However, NEC is heavily influenced by maternal and perinatal factors as well. Given its nature, preventive approaches to NEC are more likely to improve outcomes than new treatment strategies. Therefore, this review focuses on maternal, environmental, and racial factors associated with the development of NEC, with an emphasis on those that may be modifiable to decrease the incidence of the disease.

Gestational Development of the Human Immune System

Building an immune system is a monumental task critical to the survival of the fetus and newborn. A functional fetal immune system must complement the maternal immune system in handling in utero infection; abstain from damaging non-self-reactions that would compromise the materno-fetal interface; mobilize in response to infection and equip mucosal tissues for pathogen exposure at birth. There is growing appreciation that immune cells also have noncanonical roles in development and specifically may contribute to tissue morphogenesis. In this review we detail how hematopoietic and lymphoid organs jointly establish cellular constituents of the immune system; how these constituents are organized in 2 mucosal sites-gut and lung-where early life immune function has long-term consequences for health; and how exemplar diseases of prematurity and inborn errors of immunity reveal dominant pathways in prenatal immunity.

β-glucan protects against necrotizing enterocolitis in mice by inhibiting intestinal inflammation, improving the gut barrier, and modulating gut microbiota

BACKGROUND

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease with high morbidity and mortality, affecting preterm infants especially those with very low and extremely low birth weight. β-glucan has manifested multiple biological effects including anti-inflammatory, regulation of gut microbiota, and immunomodulatory activities. This study aimed to investigate the effects of β-glucan on NEC.

METHODS

Neonatal C57BL/6 mice were randomly divided into three groups: Control group, NEC group and β-glucan group. Newborn 3-day-old mice were gavaged with either 1 mg/ml β-glucan or phosphate buffer saline at 0.03 ml/g for 7 consecutive days before NEC induction and a NEC model was established with hypoxia combined with cold exposure and formula feeding. All the pups were killed after 72-h modeling. Hematoxylin-eosin staining was performed to assess the pathological injury to the intestines. The mRNA expression levels of inflammatory factors in intestinal tissues were determined using quantitative real-time PCR. The protein levels of TLR4, NF-κB and tight junction proteins in intestinal tissues were evaluated using western blotting and immunohistochemistry. 16S rRNA sequencing was performed to determine the structure of the gut microbiota.

RESULTS

β-glucan administration ameliorated intestinal injury of NEC mice; reduced the intestinal expression of TLR4, NF-κB, IL-1β, IL-6, and TNF-α; increased the intestinal expression of IL-10; and improved the expression of ZO-1, Occludin and Claudin-1 within the intestinal barrier. Pre-treatment with β-glucan also increased the proportion of Actinobacteria, Clostridium butyricum, Lactobacillus johnsonii, Lactobacillus murinus, and Lachnospiraceae bacterium mt14 and reduced the proportion of Klebsiella oxytoca g Klebsiella in the NEC model.

CONCLUSION

β-glucan intervention prevents against NEC in neonatal mice, possibly by suppressing the TLR4-NF-κB signaling pathway, improving intestinal barrier function, and partially regulating intestinal microbiota.

Current and future methods of probiotic therapy for necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a complex intestinal disease that primarily affects premature neonates. Given its significant mortality and morbidity, there is an urgent need to develop improved prophylactic measures against the disease. One potential preventative strategy for NEC is the use of probiotics. Although there has been significant interest for decades in probiotics in neonatal care, no clear guidelines exist regarding which probiotic to use or for which patients, and no FDA-approved products exist on the market for NEC. In addition, there is lack of agreement regarding the benefits of probiotics in neonates, as well as some concerns about the safety and efficacy of available products. We discuss currently available probiotics as well as next-generation probiotics and novel delivery strategies which may offer an avenue to capitalize on the benefits of probiotics, while minimizing the risks. Thus, probiotics may still prove to be an effective prevention strategy for NEC, although further product development and research is needed to support use in the preterm population.

Prebiotic activity of chitooligosaccharides and their ability to alleviate necrotizing enterocolitis in newborn rats

Chitooligosaccharides (COS) have many bioactive functions and favorable prospects in the fields of biomedicine and functional foods. In this study, COS was found to significantly improve the survival rate of neonatal necrotizing enterocolitis (NEC) model rats, alter the composition of the intestinal microbiota, inhibit the expression of inflammatory cytokines, and alleviate intestinal pathological injury. In addition, COS also increased the abundance of Akkermansia, Bacteroides, and Clostridium sensu stricto 1 in the intestines of normal rats (the normal rat model is more universal). The in vitro fermentation results found that COS was degraded by the human gut microbiota to promote the abundance of Clostridium sensu stricto 1 and produced numerous short-chain fatty acids (SCFAs). In vitro metabolomic analysis revealed that COS catabolism was associated with significant increases in 3-hydroxybutyrate acid and γ-aminobutyric acid. This study provides evidence for the potential of COS as a prebiotic in food products and to ameliorate NEC development in neonatal rats.

Microbial regulation of offspring diseases mediated by maternal-associated microbial metabolites

The microbiota plays a crucial role in individuals’ early and long-term health. Previous studies indicated that the microbial regulation of health may start before birth. As the in utero environment is (nearly) sterile, the regulation is probably be originated from maternal microbiota and mediated by their metabolites transferred across the placenta. After the birth, various metabolites are continuously delivered to offspring through human milk feeding. Meanwhile, some components, for example, human milk oligosaccharides, in human milk can only be fermented by microbes, which brings beneficial effects on offspring health. Hence, we speculated that human milk-derived metabolites may also play roles in microbial regulation. However, reports between maternal-associated microbial metabolites and offspring diseases are still lacking and sparsely distributed in several fields. Also, the definition of the maternal-associated microbial metabolite is still unclear. Thus, it would be beneficial to comb through the current knowledge of these metabolites related to diseases for assisting our goals of early prediction, early diagnosis, early prevention, or early treatment through actions only on mothers. Therefore, this review aims to present studies showing how researchers came to the path of investigating these metabolites and then to present studies linking them to the development of offspring asthma, type 1 diabetes mellitus, food allergy, neonatal necrotizing enterocolitis, or autism spectrum disorder. Potential English articles were collected from PubMed by searching terms of disease(s), maternal, and a list of microbial metabolites. Articles published within 5 years were preferred.

The administration of a pre-digested fat-enriched formula prevents necrotising enterocolitis-induced lung injury in mice

Necrotising enterocolitis (NEC) is a devastating gastrointestinal disease of prematurity that typically develops after the administration of infant formula, suggesting a link between nutritional components and disease development. One of the most significant complications that develops in patients with NEC is severe lung injury. We have previously shown that the administration of a nutritional formula that is enriched in pre-digested Triacylglyceride that do not require lipase action can significantly reduce the severity of NEC in a mouse model. We now hypothesise that this 'pre-digested fat (PDF) system' may reduce NEC-associated lung injury. In support of this hypothesis, we now show that rearing newborn mice on a nutritional formula based on the 'PDF system' promotes lung development, as evidenced by increased tight junctions and surfactant protein expression. Mice that were administered this 'PDF system' were significantly less vulnerable to the development of NEC-induced lung inflammation, and the administration of the 'PDF system' conferred lung protection. In seeking to define the mechanisms involved, the administration of the 'PDF system' significantly enhanced lung maturation and reduced the production of reactive oxygen species (ROS). These findings suggest that the PDF system protects the development of NEC-induced lung injury through effects on lung maturation and reduced ROS in the lung and also increases lung maturation in non-NEC mice.

The administration of amnion-derived multipotent cell secretome ST266 protects against necrotizing enterocolitis in mice and piglets

Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in premature infants and is steadily rising in frequency. Patients who develop NEC have a very high mortality, illustrating the importance of developing novel prevention or treatment approaches. We and others have shown that NEC arises in part from exaggerated signaling via the bacterial receptor, Toll-like receptor 4 (TLR4) on the intestinal epithelium, leading to widespread intestinal inflammation and intestinal ischemia. Strategies that limit the extent of TLR4 signaling, including the administration of amniotic fluid, can reduce NEC development in mouse and piglet models. We now seek to test the hypothesis that a secretome derived from amnion-derived cells can prevent or treat NEC in preclinical models of this disease via a process involving TLR4 inhibition. In support of this hypothesis, we show that the administration of this secretome, named ST266, to mice or piglets can prevent and treat experimental NEC. The protective effects of ST266 occurred in the presence of marked TLR4 inhibition in the intestinal epithelium of cultured epithelial cells, intestinal organoids, and human intestinal samples ex vivo, independent of epidermal growth factor. Strikingly, RNA-seq analysis of the intestinal epithelium in mice reveals that the ST266 upregulates critical genes associated with gut remodeling, intestinal immunity, gut differentiation. and energy metabolism. These findings show that the amnion-derived secretome ST266 can prevent and treat NEC, suggesting the possibility of novel therapeutic approaches for patients with this devastating disease.NEW & NOTEWORTHY This work provides hope for children who develop NEC, a devastating disease of premature infants that is often fatal, by revealing that the secreted product of amniotic progenitor cells (called ST266) can prevent or treat NEC in mice, piglet, and "NEC-in-a-dish" models of this disease. Mechanistically, ST266 prevented bacterial signaling, and a detailed transcriptomic analysis revealed effects on gut differentiation, immunity, and metabolism. Thus, an amniotic secretome may offer novel approaches for NEC.

Luteolin alleviates methionine-choline-deficient diet-induced non-alcoholic steatohepatitis by modulating host serum metabolome and gut microbiome

Background and purpose

Previous studies have indicated the protective effects of luteolin against non-alcoholic steatohepatitis (NASH), but the definite underlying mechanism still remains unclear. This study aimed to explore the metabolomic and metagenomic signatures of NASH with luteolin supplementation.

Experimental approach

Mice were fed with a methionine–choline-deficient (MCD) diet containing 0.05% luteolin for 6 weeks. NASH severity was determined based on the liver histological observations, serum and hepatic biochemical measurements. Targeted metabolomics was conducted to identify differential metabolites in mice serum. 16S rRNA sequencing was conducted to assess the gut microbiota composition and function in mice colon.

Results

In detail, luteolin treatment significantly alleviated MCD diet-induced hepatic lipid deposition, liver function damage, and oxidative stress. Targeted plasma metabolomics revealed that 5-hydroxyindole, LPE (0:0/22:5), indole 3-phosphate, and N-phenylacetylphenylalanine were remarkably elevated, and homogentisic acid, thiamine, KN-93, PC (16:1e/8, 9-EpETE), carnitine C9:1-OH, FFA (18:4) and carnitine C8:1 were significantly decreased in NASH group as compared to normal group, which could be profoundly reversed after luteolin treatment. 16S rRNA sequencing indicated that luteolin supplementation significantly increased Erysipelatoclostridium and Pseudomonas as well as decreased Faecalibaculum at genus level. Most importantly, a negative association between thiamine and Faecalibaculum was observed based on Spearman's correlation analysis, which may play an important role in the preventive effects of luteolin against NASH.

Conclusion

Collectively, luteolin may alleviate the NASH by modulating serum metabolome and gut microbiome, which supports its use as a dietary supplement for NASH prevention.

Butyrate supplementation to pregnant mice elicits cytoprotection against colonic injury in the offspring

BACKGROUND

Maternal diet during pregnancy can impact progeny health and disease by influencing the offspring's gut microbiome and immune development. Gut microbial metabolism generates butyrate, a short-chain fatty acid that benefits intestinal health. Here we assess the effects of antenatal butyrate on the offspring's gastrointestinal health. We hypothesized that antenatal butyrate supplementation will induce protection against colitis in the offspring.

METHODS

C57BL/6 mice received butyrate during pregnancy and a series of experiments were performed on their offspring. RNA sequencing was performed on colonic tissue of 3-week-old offspring. Six-8-week-old offspring were subjected to dextran sulfate sodium-induced colitis. Fecal microbiome analysis was performed on the 6-8-week-old offspring.

RESULTS

Antenatal butyrate supplementation dampened transcript enrichment of inflammation-associated colonic genes and prevented colonic injury in the offspring. Antenatal butyrate increased the offspring's stool microbiome diversity and expanded the prevalence of specific gut microbes.

CONCLUSIONS

Antenatal butyrate supplementation resulted in downregulation of genes in the offspring's colon that function in inflammatory signaling. In addition, antenatal butyrate supplementation was associated with protection against colitis and an expanded fecal microbiome taxonomic diversity in the offspring.

IMPACT

Dietary butyrate supplementation to pregnant mice led to downregulation of colonic genes involved in inflammatory signaling and cholesterol synthesis, changes in the fecal microbiome composition of the offspring, and protection against experimentally induced colitis in the offspring. These data support the mounting evidence that the maternal diet during pregnancy has enduring effects on the offspring's long-term health and disease risk. Although further investigations are needed to identify the mechanism of butyrate's effects on fetal gut development, the current study substantiates the approach of dietary intervention during pregnancy to optimize the long-term gastrointestinal health of the offspring.

Bench to bedside - new insights into the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death and disability from gastrointestinal disease in premature infants. Recent discoveries have shed light on a unifying theorem to explain the pathogenesis of NEC, suggesting that specific treatments might finally be forthcoming. A variety of experiments have highlighted how the interaction between bacterial signalling receptors on the premature intestine and an abnormal gut microbiota incites a pro-inflammatory response in the intestinal mucosa and its underlying endothelium that leads to NEC. Central amongst the bacterial signalling receptors implicated in NEC development is the lipopolysaccharide receptor Toll-like receptor 4 (TLR4), which is expressed at higher levels in the premature gut than in the full-term gut. The high prenatal intestinal expression of TLR4 reflects the role of TLR4 in the regulation of normal gut development, and supports additional studies indicating that NEC develops in response to signalling events that occur in utero. This Review provides new evidence explaining the pathogenesis of NEC, explores new findings indicating that NEC development has origins before birth, and discusses future questions and opportunities for discovery in this field.

Bifidobacteriumlongum subsp. infantis EVC001 Administration Is Associated with a Significant Reduction in the Incidence of Necrotizing Enterocolitis in Very Low Birth Weight Infants

OBJECTIVE

To assess the effects of Bifidobacteriumlongum subsp. infantis EVC001 (Binfantis EVC001) administration on the incidence of necrotizing enterocolitis (NEC) in preterm infants in a single level IV neonatal intensive care unit (NICU).

STUDY DESIGN

Nonconcurrent retrospective analysis of 2 cohorts of very low birth weight (VLBW) infants not exposed and exposed to Binfantis EVC001 probiotic at Oregon Health & Science University from 2014 to 2020. Outcomes included NEC incidence and NEC-associated mortality, including subgroup analysis of extremely low birth weight (ELBW) infants. Log-binomial regression models were used to compare the incidence and risk of NEC-associated outcomes between the unexposed and exposed cohorts.

RESULTS

The cumulative incidence of NEC diagnoses decreased from 11.0% (n = 301) in the no EVC001 (unexposed) cohort to 2.7% (n = 182) in the EVC001 (exposed) cohort (P < .01). The EVC001 cohort had a 73% risk reduction of NEC compared with the no EVC001 cohort (adjusted risk ratio, 0.27; 95% CI, 0.094-0.614; P < .01) resulting in an adjusted number needed to treat of 13 (95% CI, 10.0-23.5) for Binfantis EVC001. NEC-associated mortality decreased from 2.7% in the no EVC001 cohort to 0% in the EVC001 cohort (P = .03). There were similar reductions in NEC incidence and risk for ELBW infants (19.2% vs 5.3% [P < .01]; adjusted risk ratio, 0.28; 95% CI, 0.085-0.698 [P = .02]) and mortality (5.6% vs 0%; P < .05) in the 2 cohorts.

CONCLUSIONS

In this observational study of 483 VLBW infants, Binfantis EVC001 administration was associated with significant reductions in the risk of NEC and NEC-related mortality. Binfantis EVC001 supplementation may be considered safe and effective for reducing morbidity and mortality in the NICU.

Necrotizing enterocolitis: Bench to bedside approaches and advancing our understanding of disease pathogenesis

Necrotizing enterocolitis (NEC) is a devastating, multifactorial disease mainly affecting the intestine of premature infants. Recent discoveries have significantly enhanced our understanding of risk factors, as well as, cellular and genetic mechanisms of this complex disease. Despite these advancements, no essential, single risk factor, nor the mechanism by which each risk factor affects NEC has been elucidated. Nonetheless, recent research indicates that maternal factors, antibiotic exposure, feeding, hypoxia, and altered gut microbiota pose a threat to the underdeveloped immunity of preterm infants. Here we review predisposing factors, status of unwarranted immune responses, and microbial pathogenesis in NEC based on currently available scientific evidence. We additionally discuss novel techniques and models used to study NEC and how this research translates from the bench to the bedside into potential treatment strategies.

Identification and Validation of Autophagy-Related Genes in Necrotizing Enterocolitis

BACKGROUND

Autophagy plays an essential role in the occurrence and progression of necrotizing enterocolitis (NEC). We intend to carry out the identification and validation of the probable autophagy-related genes of NEC via bioinformatics methods and experiment trials.

METHODS

The autophagy-related differentially expressed genes (arDEGs) of NEC were identified by analyzing the RNA sequencing data of the experiment neonatal mouse model and dataset GSE46619. Protein-protein interactions (PPIs), Gene Ontology (GO) enrichment analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were used for the arDEGs. Then, co-expressed autophagy-related genes in two datasets were identified by Venn analysis and verified by qRT-PCR in experimental NEC.

RESULTS

Autophagy increased in experimental NEC and 47 arDEGs were identified in experimental NEC by RNA-sequencing. The PPI results proclaimed those genes interplayed with each other. The GO and KEGG enrichment results of arDEGs reported certain enriched pathways related to autophagy and macroautophagy. Furthermore, 22 arDEGs were identified in human NEC from dataset GSE46619. The GO and KEGG enrichment analysis of these genes showed similar enriched terms with the results of experimental NEC. Finally, HIF-1a, VEGFA, ITGA3, ITGA6, ITGB4, and NAMPT were identified as co-expressed autophagy-related genes by Venn analysis in human NEC from dataset GSE46619 and experimental NEC. The result of quantified real-time PCR (qRT-PCR) revealed that the expression levels of HIF-1a and ITGA3 were upregulated, while VEGFA and ITGB4 were downregulated in experimental NEC.

CONCLUSION

We identified 47 arDEGs in experimental NEC and 22 arDEGs in human NEC via bioinformatics analysis. HIF-1a, ITGA3, VEGFA, and ITGB4 may have effects on the progression of NEC through modulating autophagy.

Lactobacillus lactis and Pediococcus pentosaceus-driven reprogramming of gut microbiome and metabolome ameliorates the progression of non-alcoholic fatty liver disease

BACKGROUND

Although microbioa-based therapies have shown putative effects on the treatment of non-alcoholic fatty liver disease (NAFLD), it is not clear how microbiota-derived metabolites contribute to the prevention of NAFLD. We explored the metabolomic signature of Lactobacillus lactis and Pediococcus pentosaceus in NAFLD mice and its association in NAFLD patients.

METHODS

We used Western diet-induced NAFLD mice, and L. lactis and P. pentosaceus were administered to animals in the drinking water at a concentration of 109 CFU/g for 8 weeks. NAFLD severity was determined based on liver/body weight, pathology and biochemistry markers. Caecal samples were collected for the metagenomics by 16S rRNA sequencing. Metabolite profiles were obtained from caecum, liver and serum. Human stool samples (healthy control [n = 22] and NAFLD patients [n = 23]) were collected to investigate clinical reproducibility for microbiota-derived metabolites signature and metabolomics biomarker.

RESULTS

L. lactis and P. pentosaceus supplementation effectively normalized weight ratio, NAFLD activity score, biochemical markers, cytokines and gut-tight junction. While faecal microbiota varied according to the different treatments, key metabolic features including short chain fatty acids (SCFAs), bile acids (BAs) and tryptophan metabolites were analogously restored by both probiotic supplementations. The protective effects of indole compounds were validated with in vitro and in vivo models, including anti-inflammatory effects. The metabolomic signatures were replicated in NAFLD patients, accompanied by the comparable levels of Firmicutes/Bacteroidetes ratio, which was significantly higher (4.3) compared with control (0.6). Besides, the consequent biomarker panel with six stool metabolites (indole, BAs, and SCFAs) showed 0.922 (area under the curve) in the diagnosis of NAFLD.

CONCLUSIONS

NAFLD progression was robustly associated with metabolic dys-regulations in the SCFAs, bile acid and indole compounds, and NAFLD can be accurately diagnosed using the metabolites. L. lactis and P. pentosaceus ameliorate NAFLD progression by modulating gut metagenomic and metabolic environment, particularly tryptophan pathway, of the gut-liver axis.

Sodium Butyrate Alleviates Intestinal Inflammation in Mice with Necrotizing Enterocolitis

Objective

To determine the role of sodium butyrate in intestinal inflammation via regulation of high-mobility group box-1 (HMGB1), we analyzed the potential mechanism in necrotizing enterocolitis (NEC) in a neonatal mouse model.

Methods

A NEC model was created with hypoxia and cold exposure and artificial overfeeding. C57BL/6 neonatal mice were randomized into three groups: the control, untreated NEC, and sodium butyrate (150 mM)-pretreated NEC groups. Pathological variations in ileocecal intestinal tissue were observed by HE staining and scored in a double-blind manner. The mRNA expression levels of HMGB1, Toll-like receptor 4 (TLR4), nuclear factor-κB (NF-κB), and inflammatory cytokines in intestinal tissues were determined by quantitative real-time PCR. The protein levels of HMGB1 and associated cytokines in intestinal tissues were evaluated using ELISA. The relative protein expression levels of TLR4 and NF-κB in intestinal tissues were quantified by western blot.

Results

Sodium butyrate administration improved the body weight and survival rate of NEC mice; relieved intestinal pathological injury; reduced the intestinal expression of HMGB1, TLR4, NF-κB, interleukin- (IL-) 1β, IL-6, IL-8, and TNF-α; and increased the intestinal expression of IL-10 (P < 0.05). Treatment with butyrate decreased the proportion of opportunistic Clostridium_sensu_stricto_1 and Enterococcus and increased the proportion of beneficial Firmicutes and Lactobacillus in the NEC model.

Conclusions

Sodium butyrate intervention relieves intestinal inflammation and partially corrects the disrupted intestinal flora in mice with NEC.

Untargeted Metabolomic Analysis of Human Milk from Mothers of Preterm Infants

The application of metabolomics in neonatology offers an approach to investigate the complex relationship between nutrition and infant health. Characterization of the metabolome of human milk enables an investigation into nutrients that affect the neonatal metabolism and identification of dietary interventions for infants at risk of diseases such as necrotizing enterocolitis (NEC). In this study, we aimed to identify differences in the metabolome of breast milk of 48 mothers with preterm infants with NEC and non-NEC healthy controls. A minimum significant difference was observed in the human milk metabolome between the mothers of infants with NEC and mothers of healthy control infants. However, significant differences in the metabolome related to fatty acid metabolism, oligosaccharides, amino sugars, amino acids, vitamins and oxidative stress-related metabolites were observed when comparing milk from mothers with control infants of ≤1.0 kg birth weight and >1.5 kg birth weight. Understanding the functional biological features of mothers’ milk that may modulate infant health is important in the future of tailored nutrition and care of the preterm newborn.

Nurturing the Early Life Gut Microbiome and Immune Maturation for Long Term Health

Early life is characterized by developmental milestones such as holding up the head, turning over, sitting up and walking that are typically achieved sequentially in specific time windows. Similarly, the early gut microbiome maturation can be characterized by specific temporal microorganism acquisition, colonization and selection with differential functional features over time. This orchestrated microbial sequence occurs from birth during the first years of age before the microbiome reaches an adult-like composition and function between 3 and 5 years of age. Increasingly, these different steps of microbiome development are recognized as crucial windows of opportunity for long term health, primarily linked to appropriate immune and metabolic development. For instance, microbiome disruptors such as preterm and Cesarean-section birth, malnutrition and antibiotic use are associated with increased risk to negatively affect long-term immune and metabolic health. Different age discriminant microbiome taxa and functionalities are used to describe age-appropriate microbiome development, and advanced modelling techniques enable an understanding and visualization of an optimal microbiome maturation trajectory. Specific microbiome features can be related to later health conditions, however, whether such features have a causal relationship is the topic of intense research. Early life nutrition is an important microbiome modulator, and 'Mother Nature' provides the model with breast milk as the sole source of nutrition for the early postnatal period, while dietary choices during the prenatal and weaning period are to a large extent guided by tradition and culture. Increasing evidence suggests prenatal maternal diet and infant and child nutrition impact the infant microbiome trajectory and immune competence development. The lack of a universal feeding reference for such phases represents a knowledge gap, but also a great opportunity to provide adequate nutritional guidance to maintain an age-appropriate microbiome for long term health. Here, we provide a narrative review and perspective on our current understanding of age-appropriate microbiome maturation, its relation to long term health and how nutrition shapes and influences this relationship.

Microbiota Signals during the Neonatal Period Forge Life-Long Immune Responses

The microbiota regulates immunological development during early human life, with long-term effects on health and disease. Microbial products include short-chain fatty acids (SCFAs), formyl peptides (FPs), polysaccharide A (PSA), polyamines (PAs), sphingolipids (SLPs) and aryl hydrocarbon receptor (AhR) ligands. Anti-inflammatory SCFAs are produced by Actinobacteria, Bacteroidetes, Firmicutes, Spirochaetes and Verrucomicrobia by undigested-carbohydrate fermentation. Thus, fiber amount and type determine their occurrence. FPs bind receptors from the pattern recognition family, those from commensal bacteria induce a different response than those from pathogens. PSA is a capsular polysaccharide from B. fragilis stimulating immunoregulatory protein expression, promoting IL-2, STAT1 and STAT4 gene expression, affecting cytokine production and response modulation. PAs interact with neonatal immunity, contribute to gut maturation, modulate the gut–brain axis and regulate host immunity. SLPs are composed of a sphingoid attached to a fatty acid. Prokaryotic SLPs are mostly found in anaerobes. SLPs are involved in proliferation, apoptosis and immune regulation as signaling molecules. The AhR is a transcription factor regulating development, reproduction and metabolism. AhR binds many ligands due to its promiscuous binding site. It participates in immune tolerance, involving lymphocytes and antigen-presenting cells during early development in exposed humans.

Indole-3-Carbinol-Dependent Aryl Hydrocarbon Receptor Signaling Attenuates the Inflammatory Response in Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) causes significant morbidity and mortality in premature infants; therefore, the identification of therapeutic and preventative strategies against NEC remains a high priority. The ligand-dependent transcription factor aryl hydrocarbon receptor (AhR) is well known to contribute to the regulation of intestinal microbial communities and amelioration of intestinal inflammation. However, the role of AhR signaling in NEC is unclear. Experimental NEC was induced in 4-d-old wild-type mice or mice lacking AhR expression in the intestinal epithelial cells or AhR expression in CD11c⁺ cells (AhR^ΔCD11c) by subjecting animals to twice daily hypoxic stress and gavage feeding with formula supplemented with LPS and enteric bacteria. During NEC, compared with wild-type mice treated with vehicle, littermates treated with an AhR proligand, indole-3-carbinol, had reduced expression of Il1b and Marco, a scavenger receptor that mediates dendritic cell activation and the recognition and clearance of bacterial pathogens by macrophages. Furthermore, indole-3-carbinol treatment led to the downregulation of genes involved in cytokine and chemokine, as revealed by pathway enrichment analysis. AhR expression in the intestinal epithelial cells and their cre-negative mouse littermates were similarly susceptible to experimental NEC, whereas AhR^ΔCD11c mice with NEC exhibited heightened inflammatory responses compared with their cre-negative mouse littermates. In seeking to determine the mechanisms involved in this increased inflammatory response, we identified the Tim-4^- monocyte-dependent subset of macrophages as increased in AhR^ΔCD11c mice compared with their cre-negative littermates. Taken together, these findings demonstrate the potential for AhR ligands as a novel immunotherapeutic approach to the management of this devastating disease.