Necrotizing enterocolitis: The intestinal microbiome, metabolome and inflammatory mediators

Chorioamnionitis induces enteric nervous system injury: effects of timing and inflammation in the ovine fetus

BACKGROUND

Chorioamnionitis, inflammation of the chorion and amnion, which often results from intrauterine infection, is associated with premature birth and contributes to significant neonatal morbidity and mortality, including necrotizing enterocolitis (NEC). Recently, we have shown that chronic chorioamnionitis is associated with significant structural enteric nervous system (ENS) abnormalities that may predispose to later NEC development. Understanding time point specific effects of an intra-amniotic (IA) infection on the ENS is important for further understanding the pathophysiological processes and for finding a window for optimal therapeutic strategies for an individual patient. The aim of this study was therefore to gain insight in the longitudinal effects of intrauterine LPS exposure (ranging from 5 h to 15 days before premature delivery) on the intestinal mucosa, submucosa, and ENS in fetal lambs by use of a well-established translational ovine chorioamnionitis model.

METHODS

We used an ovine chorioamnionitis model to assess outcomes of the fetal ileal mucosa, submucosa and ENS following IA exposure to one dose of 10 mg LPS for 5, 12 or 24 h or 2, 4, 8 or 15 days.

RESULTS

Four days of IA LPS exposure causes a decreased PGP9.5- and S100β-positive surface area in the myenteric plexus along with submucosal and mucosal intestinal inflammation that coincided with systemic inflammation. These changes were preceded by a glial cell reaction with early systemic and local gut inflammation. ENS changes and inflammation recovered 15 days after the IA LPS exposure.

CONCLUSIONS

The pattern of mucosal and submucosal inflammation, and ENS alterations in the fetus changed over time following IA LPS exposure. Although ENS damage seemed to recover after prolonged IA LPS exposure, additional postnatal inflammatory exposure, which a premature is likely to encounter, may further harm the ENS and influence functional outcome. In this context, 4 to 8 days of IA LPS exposure may form a period of increased ENS vulnerability and a potential window for optimal therapeutic strategies.

Assessment of Neonatal Intensive Care Unit Practices and Preterm Newborn Gut Microbiota and 2-Year Neurodevelopmental Outcomes

IMPORTANCE

In very preterm newborns, gut microbiota is highly variable with major dysbiosis. Its association with short-term health is widely studied, but the association with long-term outcomes remains unknown.

OBJECTIVE

To investigate in preterm newborns the associations among practice strategies in neonatal intensive care units (NICUs), gut microbiota, and outcomes at 2 years.

DESIGN, SETTING, AND PARTICIPANTS

EPIFLORE is a prospective observational cohort study that includes a stool sample collection during the fourth week after birth. Preterm newborns of less than 32 weeks of gestational age (GA) born in 2011 were included from 24 NICUs as part of the French nationwide population-based cohort, EPIPAGE 2. Data were collected from May 2011 to December 2011 and analyzed from September 2016 to December 2018.

EXPOSURES

Eight NICU strategies concerning sedation, ventilation, skin-to-skin practice, antibiotherapy, ductus arteriosus, and breastfeeding were assessed. A NICU was considered favorable to a practice if the percentage of that practice in the NICU was more than the expected percentage.

MAIN OUTCOMES AND MEASURES

Gut microbiota was analyzed by 16S ribosomal RNA gene sequencing and characterized by a clustering-based method. The 2-year outcome was defined by death or neurodevelopmental delay using a Global Ages and Stages questionnaire score.

RESULTS

Of 577 newborns included in the study, the mean (SD) GA was 28.3 (2.0) weeks, and 303 (52.5%) were male. Collected gut microbiota was grouped into 5 discrete clusters. A sixth cluster included nonamplifiable samples owing to low bacterial load. Cluster 4 (driven by Enterococcus [n = 63]), cluster 5 (driven by Staphylococcus [n = 52]), and cluster 6 (n = 93) were significantly associated with lower mean (SD) GA (26.7 [1.8] weeks and 26.8 [1.9] weeks, respectively) and cluster 3 (driven by Escherichia/Shigella [n = 61]) with higher mean (SD) GA (29.4 [1.6] weeks; P = .001). Cluster 3 was considered the reference. After adjustment for confounders, no assisted ventilation at day 1 was associated with a decreased risk of belonging to cluster 5 or cluster 6 (adjusted odds ratio [AOR], 0.21 [95% CI, 0.06-0.78] and 0.19 [95% CI, 0.06-0.62], respectively) when sedation (AOR, 10.55 [95% CI, 2.28-48.87] and 4.62 [1.32-16.18], respectively) and low volume of enteral nutrition (AOR, 10.48 [95% CI, 2.48-44.29] and 7.28 [95% CI, 2.03-26.18], respectively) was associated with an increased risk. Skin-to-skin practice was associated with a decreased risk of being in cluster 5 (AOR, 0.14 [95% CI, 0.04-0.48]). Moreover, clusters 4, 5, 6 were significantly associated with 2-year nonoptimal outcome (AOR, 6.17 [95% CI, 1.46-26.0]; AOR, 4.53 [95% CI, 1.02-20.1]; and AOR, 5.42 [95% CI, 1.36-21.6], respectively).

CONCLUSIONS AND RELEVANCE

Gut microbiota of very preterm newborns at week 4 is associated with NICU practices and 2-year outcomes. Microbiota could be a noninvasive biomarker of immaturity.

New directions in necrotizing enterocolitis with early-stage investigators

The 2019 Necrotizing Enterocolitis (NEC) Symposium expanded upon the NEC Society's goals of bringing stakeholders together to discuss cutting-edge science, potential therapeutics and preventative measures, as well as the patient-family perspectives of NEC. The Symposium facilitated discussions and shared knowledge with the overarching goal of creating "A World Without NEC." To accomplish this goal, new research to advance the state of the science is necessary. Over the last decade, several established investigators have significantly improved our understanding of the pathophysiology of NEC and they have paved the way for the next generation of clinician-scientists funded to perform NEC research. This article will serve to highlight the contributions of these young clinician-scientists that seek to elucidate how immune, microbial and nervous system dysregulation contributes to the pathophysiology of NEC.

Challenges in diagnosing necrotizing enterocolitis

One of the many challenges with necrotizing enterocolitis (NEC) remains our inability to make an accurate diagnosis of NEC. The lack of a unifying cause and multiple variations in presentations lead to great uncertainty with NEC. Separating out the needs of the researcher wanting to define NEC from the clinician and patient family's perspectives who want an accurate diagnosis for NEC is important. The need to augment and/or replace the outdated modified Bell staging criteria is crucial to improving NEC management. Emerging literature suggests that genetic susceptibility and stool microbiota signatures may help identify preterm infants at increased risk of the disease. Ongoing studies using single or multi-omic approaches may help to characterize biomarkers that will aid in the prediction or early diagnosis of NEC, as well as differentiate other causes of severe bowel injury. Bowel ultrasound shows promise in improving our diagnostic accuracy for NEC but has been slow in adoption. Patient family perspectives are key in accelerating our efforts to integrate newer diagnostic methods into practice.

Evidence from systematic reviews of randomized trials on enteral lactoferrin supplementation in preterm neonates

In this commentary, we summarize the current evidence from randomized controlled trials on enteral lactoferrin supplementation in preterm neonates. Our recently completed systematic review includes 12 randomized controlled trials performed all over the world. Our meta-analysis suggests clinical benefit in decreasing late-onset sepsis, late-onset fungal sepsis, length of stay in the hospital and urinary tract infections. There were no adverse effects. There was no statistically significant decrease in necrotizing enterocolitis, mortality or neurodevelopmental impairment in lactoferrin supplemented preterm infants. There was significant statistical heterogeneity in the effects of lactoferrin on late-onset sepsis between larger and smaller studies, which may reflect either small study biases, differences in the effectiveness, dose or duration of supplemental lactoferrin products, or differences in underlying population risk, or any or all of these.

Beneficial effects of butyrate in intestinal injury

PURPOSE

Butyrate is a short-chain fatty acid produced in the intestine. It is controversial whether butyrate is protective or destructive for the intestinal epithelium in the development of diseases like necrotizing enterocolitis (NEC), and its mechanism of action remains unclear. We aimed to determine the effect of butyrate on the intestinal epithelium by studying its effects on intestinal epithelial cells (IEC-18) exposed to injury and in vivo by investigating the effects on the intestine in an experimental model of NEC.

METHODS

A) In vitro study: Butyrate was given to normal IEC-18 to determine the dose triggering injury. Based on above results, low dose butyrate (1 mM) was given to H₂O₂-injured cells to determine its effect against inflammation. B) In vivo study: NEC was induced by hypoxia and gavage feeding between postnatal day P5 and P9 (n = 8). Breastfed mice were used as control (n = 7). Butyrate (150 mM) was administered by enema on P6 in NEC (n = 6). Distal ileum was harvested on P9.

RESULTS

High dose (16 mM) butyrate upregulated inflammatory marker IL-6, while low dose butyrate protected cells from injury by reducing IL-6 expression. Similarly, compared with NEC alone, NEC mice who received butyrate had reduced intestinal damage, reduced IL-6 and NF-ĸB expression, and increased intestinal tight junction marker Claudin-7.

CONCLUSION

Butyrate has opposite effects depending on the dose administered. Butyrate can protect cells from H₂O₂-induced injury and can in vivo protect the intestine from NEC. This beneficial effect is because of downregulation of inflammation and enhancement of intestinal barrier.

The Role of Glycosaminoglycans in Protection from Neonatal Necrotizing Enterocolitis: A Narrative Review

Necrotizing enterocolitis, a potentially fatal intestinal inflammatory disorder affecting primarily premature infants, is a significant cause of morbidity and mortality in neonates. While the etiology of the disease is, as yet, unknown, a number of risk factors for the development of necrotizing enterocolitis have been identified. One such risk factor, formula feeding, has been shown to contribute to both increased incidence and severity of the disease. The protective influences afforded by breastfeeding are likely attributable to the unique composition of human milk, an extremely potent, biologically active fluid. This review brings together knowledge on the pathogenesis of necrotizing enterocolitis and current thinking on the instrumental role of one of the more prominent classes of bioactive components in human breast milk, glycosaminoglycans.

Nutrients and Microbiota in Lung Diseases of Prematurity: The Placenta-Gut-Lung Triangle

Cardiorespiratory function is not only the foremost determinant of life after premature birth, but also a major factor of long-term outcomes. However, the path from placental disconnection to nutritional autonomy is enduring and challenging for the preterm infant and, at each step, will have profound influences on respiratory physiology and disease. Fluid and energy intake, specific nutrients such as amino-acids, lipids and vitamins, and their ways of administration -parenteral or enteral-have direct implications on lung tissue composition and cellular functions, thus affect lung development and homeostasis and contributing to acute and chronic respiratory disorders. In addition, metabolomic signatures have recently emerged as biomarkers of bronchopulmonary dysplasia and other neonatal diseases, suggesting a profound implication of specific metabolites such as amino-acids, acylcarnitine and fatty acids in lung injury and repair, inflammation and immune modulation. Recent advances have highlighted the profound influence of the microbiome on many short- and long-term outcomes in the preterm infant. Lung and intestinal microbiomes are deeply intricated, and nutrition plays a prominent role in their establishment and regulation. There is an emerging evidence that human milk prevents bronchopulmonary dysplasia in premature infants, potentially through microbiome composition and/or inflammation modulation. Restoring antibiotic therapy-mediated microbiome disruption is another potentially beneficial action of human milk, which can be in part emulated by pre- and probiotics and supplements. This review will explore the many facets of the gut-lung axis and its pathophysiology in acute and chronic respiratory disorders of the prematurely born infant, and explore established and innovative nutritional approaches for prevention and treatment.

The Epigenetic Connection Between the Gut Microbiome in Obesity and Diabetes

Metabolic diseases are becoming an alarming health issue due to elevated incidences of these diseases over the past few decades. Various environmental factors are associated with a number of metabolic diseases and often play a crucial role in this process. Amongst the factors, diet is the most important factor that can regulate these diseases via modulation of the gut microbiome. The gut microbiome participates in multiple metabolic processes in the human body and is mainly responsible for regulation of host metabolism. The alterations in function and composition of the gut microbiota have been known to be involved in the pathogenesis of metabolic diseases via induction of epigenetic changes such as DNA methylation, histone modifications and regulation by noncoding RNAs. These induced epigenetic modifications can also be regulated by metabolites produced by the gut microbiota including short-chain fatty acids, folates, biotin and trimethylamine-N-oxide. In addition, studies have elucidated the potential role of these microbial-produced metabolites in the pathophysiology of obesity and diabetes. Hence, this review focuses on the interactions between the gut microbiome and epigenetic processes in the regulation and development of obesity and diabetes, which may have potential as a novel preventive or therapeutic approach for several metabolic and other human diseases.

Risk of Necrotizing Enterocolitis Associated With the Single Nucleotide Polymorphisms VEGF C-2578A, IL-18 C-607A, and IL-4 Receptor α-Chain A-1902G: A Validation Study in a Prospective Multicenter Cohort

The etiology of necrotizing enterocolitis (NEC) is multifactorial and an underlying genetic predisposition to NEC is increasingly being recognized. A growing number of studies identified single nucleotide polymorphisms (SNPs) of selected genes with potential biological relevance in the development of NEC. However, few of these genetic studies have been replicated in validation cohorts. We aimed to confirm in a cohort of 358 preterm newborns (gestational age <30 weeks, 26 cases of NEC ≥ Bell stage II) the association with NEC of three candidate SNPs: the vascular endothelium growth factor (VEGF) C-2578A polymorphism (rs699947), the interleukin (IL)-18 C-607A polymorphism (rs1946518), and the IL-4 receptor α-chain (IL-4Rα) A-1902G polymorphism (rs1801275). We observed that allele and genotype frequencies of the three SNPs did not significantly differ between the infants with and without NEC. In contrast, the minor G-allele of the IL-4Rα A-1902G polymorphism was significantly less frequent in the group of 51 infants with the combined outcome NEC or death before 34 weeks postmenstrual age than in the infants without the outcome (0.206 vs. 0.331, P = 0.01). In addition, a significant negative association of the G-allele with the combined outcome NEC or death was found using the dominant (adjusted odds ratio, aOR: 0.44, 95% CI 0.21-0.92), recessive (aOR 0.15, 95% CI 0.03-0.74), and additive (aOR 0.46, 95% CI 0.26-0.80) genetic models. In conclusion our study provides further evidence that a genetic variant of the IL-4Rα gene may contribute to NEC.

[Clinical features and outcomes of neonatal necrotizing enterocolitis]

OBJECTIVE

To study the clinical features of neonatal necrotizing enterocolitis (NEC) and risk factors for poor outcomes.

METHODS

A retrospective analysis was performed for the clinical data of 121 preterm infants diagnosed with NEC. According to the treatment method, they were divided into a non-surgical group (n=66) and a surgical group (n=55). According to the outcome, they were divided into a survival group (n=76) and a death group (n=45). Clinical features were compared between these groups. Risk factors for poor outcomes were analyzed by multivariate logistic regression analysis.

RESULTS

Compared with the non-surgical group, the surgical group had significantly lower corrected gestational age, minimum platelet count, and incidence rate of bloody stool at the onset of NEC (P<0.05). The maximum C-reactive protein (CRP) and mortality rate in the surgical group were significantly higher than those in the non-surgical group (P<0.05). Compared with the survival group, the death group had significantly lower gestational age at birth, birth weight, proportion of small-for-gestational-age infants, and corrected gestational age, body weight and minimum platelet count at the onset of NEC (P<0.05). The incidence of patent ductus arteriosus, rate of use of ibuprofen, maximum CRP and rate of surgical treatment in the death group were significantly higher than those in the survival group (P<0.05). The multivariate logistic regression analysis showed that ibuprofen treatment was a risk factor for death in infants with NEC (OR=9.149, P<0.05).

CONCLUSIONS

Ibuprofen treatment increases the risk for death in preterm infants with NEC.

Abdominal ultrasound should become part of standard care for early diagnosis and management of necrotising enterocolitis: a narrative review

Necrotising enterocolitis (NEC) is a leading cause of death and disability in preterm newborns. Early diagnosis through non-invasive investigations is a crucial strategy that can significantly improve outcomes. Hence, this review gives particular attention to the emerging role of abdominal ultrasound (AUS) in the early diagnosis of NEC, its performance against abdominal radiograph and the benefits of AUS use in daily practice. AUS has been used in the diagnosis and management of NEC for a couple of decades. However, its first-line use has been minimal, despite growing evidence demonstrating AUS can be a critical tool in the early diagnosis and management of NEC. In 2018, the NEC group of the International Neonatal Consortium recommended using AUS to detect pneumatosis and/or portal air in preterm NEC as part of the 'Two out of three' model. To facilitate widespread adoption, and future improvement in practice and outcomes, collaboration between neonatologists, surgeons and radiologists is needed to generate standard operating procedures and indications for use for AUS. The pace and scale of the benefit generated by use of AUS can be amplified through use of computer-aided detection and artificial intelligence.

Exploring the Science behind Bifidobacterium breve M-16V in Infant Health

Probiotics intervention has been proposed as a feasible preventative approach against adverse health-related complications in infants. Nevertheless, the umbrella concept of probiotics has led to a massive application of probiotics in a range of products for promoting infant health, for which the strain-specificity, safety and efficacy findings associated with a specific probiotics strain are not clearly defined. Bifidobacterium breve M-16V is a commonly used probiotic strain in infants. M-16V has been demonstrated to offer potential in protecting infants from developing the devastating necrotising enterocolitis (NEC) and allergic diseases. This review comprehends the potential beneficial effects of M-16V on infant health particularly in the prevention and treatment of premature birth complications and immune-mediated disorders in infants. Mechanistic studies supporting the use of M-16V implicated that M-16V is capable of promoting early gut microbial colonisation and may be involved in the regulation of immune balance and inflammatory response to protect high-risk infants from NEC and allergies. Summarised information on M-16V has provided conceptual proof of the use of M-16V as a potential probiotics candidate aimed at promoting infant health, particularly in the vulnerable preterm population.

Differential Immune Activation in Fetal Macrophage Populations

Distinct macrophage subsets populate the developing embryo and fetus in distinct waves. However little is known about the functional differences between in utero macrophage populations or how they might contribute to fetal and neonatal immunity. Here we tested the innate immune response of mouse macrophages derived from the embryonic yolk sac and from fetal liver. When isolated from liver or lung, CD11bHI fetal liver derived macrophages responded to the TLR4 agonist LPS by expressing and releasing inflammatory cytokines. However F4/80HI macrophages from the yolk sac did not respond to LPS treatment. While differences in TLR4 expression did not appear to explain these data, F4/80HI macrophages had much lower NLRP3 inflammasome expression compared to CD11bHI macrophages. Gene expression profiling also demonstrated LPS-induced expression of inflammatory genes in CD11bHI macrophages, but not in F4/80HI cells. Genes expressed in LPS-treated CD11bHI macrophages were more likely to contain predicted NF-κB binding sites in their promoter regions. Our data show that CD11bHI macrophages derived from fetal liver are the major pro-inflammatory cells in the developing fetus. These findings could have important implications in better understanding the fetal inflammatory response and the unique features of neonatal immunity.

Necrotizing Enterocolitis, Gut Microbiota, and Brain Development: Role of the Brain-Gut Axis

Necrotizing enterocolitis (NEC) is a relatively common disease in very-low-birth-weight infants and is associated with high mortality and morbidity. In survivors, neurodevelopmental impairment is frequently seen. The exact etiology remains largely to be elucidated, but microbiota are considered to play a major role in the development of NEC. Furthermore, emerging evidence exists that the microbiota is also of importance in brain function and development. Therefore, microbiota characterization has not only potential as a diagnostic or even preventive tool to predict NEC, but may also serve as a biomarker to monitor and possibly even as a target to manipulate brain development. Analysis of fecal volatile organic compounds, which shape the volatile metabolome and reflect microbiota function and host interaction, has been shown to be of interest in the diagnosis of NEC and late-onset sepsis. In this review, we discuss evidence of the role of the complex interplay between microbiota, NEC, and brain development, including the brain-gut axis in preterm infants.