Clinical NEC prevention practices drive different microbiome profiles and functional responses in the preterm intestine

Necrotizing enterocolitis: specific human milk oligosaccharides prevent enteric glia loss and hypomotility

BACKGROUND

Necrotizing enterocolitis (NEC) is mediated by toll-like receptor 4 (TLR4)-induced inflammation and is preceded by reduced intestinal motility. Human milk oligosaccharides (HMOs) are non-digestible components of breast milk that prevent NEC in preclinical models. We now hypothesize that HMOs can reduce the risk of NEC through restoration of intestinal motility and reduced TLR4-mediated inflammation.

METHODS

NEC was induced in C57-BL/6 mice through the combination of formula gavage, hypoxia, and oral administration of NEC stool. Mice were administered either 2'-FL (5 g/L), 6'-SL (5 g/L), or a blend of 5 specific HMOs (5 g/L) containing 2'-FL (2.606 g/L), 3'-FL (0.652 g/L), LNT (1.304 g/L), 3'-SL (0.174 g/L), and 6'-SL (0.260 g/L). Gastrointestinal motility was assessed by 70 Kd FITC-dextran transit time. Enteric glia were quantified by immunohistochemistry and qRT-PCR expression.

RESULTS

Administration of either 2'-FL, 6'-SL, or HMO blend significantly attenuated NEC severity and reversed intestinal hypomotility. HMOs prevented enteric glia loss and regulated key genes critical for enteric glia maintenance, attenuated pro-apoptotic genes, and increased anti-apoptotic genes in vitro, resulting in a reduction in apoptosis. Strikingly, HMOs reduced LPS-TLR4-induced NFκB signaling and ROS generation in enteric glia.

CONCLUSIONS

HMOs protect against NEC at least in part through protective effects on inflammation and the enteric nervous system.

IMPACT

This study sheds light on the role of certain human milk oligosaccharides in a clinically relevant mouse model of NEC and adds additional insights into their underlying mechanism of action by revealing a protective effect on the enteric nervous system. These results reveal that HMOs prevent the loss of enteric glia in NEC and influence the expression of genes that regulate enteric glia maintenance. HMOs also limit TLR4-NFkB signaling, providing an additional mechanism of enteric glia maintenance.

Impact of probiotics on gut microbiome of extremely preterm or extremely low birthweight infants

IMPACT

Meta-analysis of probiotic administration to very preterm or very low birthweight (VP/VLBW) infants shows reduced risk of necrotising enterocolitis (NEC). Separately reported outcomes for extremely preterm infants (<28 weeks) or extremely low birth weight infants (<1000 g) (EP/ELBW) are lacking meaning some clinicians do not administer probiotics to EP/ELBW infants despite their high risk of NEC. We present data showing the gut microbiome is impacted in EP/ELBW infants in a similar manner to VP/VLBW infants, suggesting that risk reduction for necrotising enterocolitis that is microbiome driven will also be seen in EP/ELBW infants, making probiotic administration beneficial.

Role of Human Milk Microbiota in Infant Neurodevelopment: Mechanisms and Clinical Implications

BACKGROUND

Human milk (HM) is recognized as an ideal source of nutrition for newborns; as a result, its multiple bioactive molecules can support the growth of healthy newborns and reduce the risk of mortality and diseases such as asthma, respiratory infections, diabetes (type 1 and 2), and gastrointestinal disorders such as ulcerative colitis and Crohn's disease. Furthermore, it can reduce the severity of necrotizing enterocolitis (NEC) in preterm infants. Moreover, human milk oligosaccharides (HMOs) present in breast milk show an immunomodulatory, prebiotic, and neurodevelopmental effect that supports the microbiota-gut-brain axis.

MATERIAL AND METHODS

This study examined the state-of-the-art research, using keywords such as "breastfeeding", "human milk oligosaccharides", "microbiota-gut-brain axis", "infants", and "malnutrition". The literature review was conducted by selecting articles between 2013 and 2024, as the most recent ones. The databases used were Web Science, PubMed, and Scopus.

RESULTS

We found multiple studies examining the composition of HM and infant formula (IF). However, further longitudinal studies and randomized control trials (RCTs) are needed to better understand the clinical outcomes that bioactive components exert on healthy and hospitalized children and how, in conditions of malnutrition, it is necessary to support the growth of the newborn.

CONCLUSIONS

In this review, we affirm the importance of human milk and, through it, the modulation of the microbiota and the neuroprotective role in newborns, determining the health of the following years of life.

Diagnosing and engineering gut microbiomes

The microbes, nutrients and toxins that we are exposed to can have a profound effect on the composition and function of the gut microbiome. Thousands of peer-reviewed publications link microbiome composition and function to health from the moment of birth, right through to centenarians, generating a tantalizing glimpse of what might be possible if we could intervene rationally. Nevertheless, there remain relatively few real-world examples where successful microbiome engineering leads to beneficial health effects. Here we aim to provide a framework for the progress needed to turn gut microbiome engineering from a trial-and-error approach to a rational medical intervention. The workflow starts with truly understanding and accurately diagnosing the problems that we are trying to fix, before moving on to developing technologies that can achieve the desired changes.

Unlocking the potential for microbiome-based therapeutics to address the sustainable development goal of good health and wellbeing

Recent years have witnessed major advances and an ever-growing list of healthcare applications for microbiome-based therapeutics. However, these advances have disproportionately targeted diseases common in high-income countries (HICs). Within low- to middle-income countries (LMIC), opportunities for microbiome-based therapeutics include sexual health epidemics, maternal health, early life mortality, malnutrition, vaccine response and infectious diseases. In this review we detail the advances that have been achieved in microbiome-based therapeutics for these areas of healthcare and identify where further work is required. Current efforts to characterise microbiomes from LMICs will aid in targeting and optimisation of therapeutics and preventative strategies specifically suited to the unmet needs within these populations. Once achieved, opportunities from disease treatment and improved treatment efficacy through to disease prevention and vector control can be effectively addressed using probiotics and live biotherapeutics. Together these strategies have the potential to increase individual health, overcome logistical challenges and reduce overall medical, individual, societal and economic costs.

Lilja H. Risk of neurodevelopmental impairment in Swedish preterm children treated for necrotizing enterocolitis: retrospective cohort study

BACKGROUND

As the survival of preterm infants has increased, the management of long-term complications, especially neurodevelopmental impairment, becomes increasingly important. The aim of this study was to investigate the risk of neurodevelopmental disorders in preterm babies receiving medical or surgical treatment for necrotizing enterocolitis, compared with other preterm babies and preterm babies who received abdominal surgery for other indications.

METHODS

In this nationwide Swedish cohort study, including all liveborn preterm babies born between 1998 and 2019, the risk of attention deficit (and hyperactivity) disorder, autism spectrum disorders, cerebral palsy and intellectual disability was assessed by multivariable Cox regression, expressed as hazard ratios and 95% confidence intervals (c.i.).

RESULTS

Of the surgically (n = 384) and medically (n = 709) treated preterm infants with necrotizing enterocolitis, neurodevelopmental disorders were present in 32% (HR 2.24, 95% c.i. 1.86 to 2.69) and 22% respectively (HR 1.40, 95% c.i. 1.19 to 1.65), compared with 21% (HR 1.63, 95% c.i. 1.40 to 1.91) in the abdominal surgery group (n = 844) and 13% (reference) among other preterm infants (n = 78 972). The highest relative increases were for intellectual disability (HR 3.60, 95% c.i. 2.65 to 4.89) in the surgical necrotizing enterocolitis group and abdominal surgery group (HR 2.84, 95% c.i. 2.12 to 3.80) compared with the control preterm group, and for cerebral palsy (respectively HR 2.74, 95% c.i. 2.04 to 3.68 and HR 2.54, 95% c.i. 1.87 to 3.44). Medically treated necrotizing enterocolitis was associated with autism (HR 1.67, 95% c.i. 1.34 to 2.08), without significant increases for the other specific outcomes. Both surgically treated groups were also strongly associated with both attention deficit (and hyperactivity) disorder and autism.

CONCLUSION

Surgically treated necrotizing enterocolitis, medically treated necrotizing enterocolitis and abdominal surgery for other indications in preterm infants were all associated with an increased risk of impaired neurodevelopmental outcomes, compared with other preterm infants.

Gut Microbiota-Derived Metabolites and Their Role in the Pathogenesis of Necrotizing Enterocolitis in Preterm Infants: A Narrative Review

Background: Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease that occurs predominantly in premature infants and is characterized by the inflammation and necrosis of the intestine, showing high morbidity and mortality rates. Despite decades of research efforts, a specific treatment is currently lacking, and preventive strategies are the mainstays of care. This review aims to help understand the complex interplay between gut microbiota and their metabolites in NEC pathogenesis. In particular, we focused on how these factors can influence gut health, immune responses, and intestinal barrier integrity. Discussion: Current research has increasingly focused on the role of the gut microbiota and their metabolites in NEC pathogenesis, thanks to their involvement in modulating gut health, immune responses, and intestinal barrier integrity. Conclusions: A deeper understanding of the interplay between gut microbiota and their metabolites is essential for developing personalized strategies to prevent NEC. By targeting these microbial interactions, new therapeutic approaches may emerge that offer improved outcomes for preterm infants at a high risk of NEC.

Clinical sequelae of gut microbiome development and disruption in hospitalized preterm infants

Aberrant preterm infant gut microbiota assembly predisposes to early-life disorders and persistent health problems. Here, we characterize gut microbiome dynamics over the first 3 months of life in 236 preterm infants hospitalized in three neonatal intensive care units using shotgun metagenomics of 2,512 stools and metatranscriptomics of 1,381 stools. Strain tracking, taxonomic and functional profiling, and comprehensive clinical metadata identify Enterobacteriaceae, enterococci, and staphylococci as primarily exploiting available niches to populate the gut microbiome. Clostridioides difficile lineages persist between individuals in single centers, and Staphylococcus epidermidis lineages persist within and, unexpectedly, between centers. Collectively, antibiotic and non-antibiotic medications influence gut microbiome composition to greater extents than maternal or baseline variables. Finally, we identify a persistent low-diversity gut microbiome in neonates who develop necrotizing enterocolitis after day of life 40. Overall, we comprehensively describe gut microbiome dynamics in response to medical interventions in preterm, hospitalized neonates.

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.

Gut Microbiota and Immune System in Necrotizing Enterocolitis and Related Sepsis

A severe condition of sepsis can be a complication of necrotizing enterocolitis (NEC), which can occur in premature infants and becomes a medical challenge in the neonatal intensive care unit (NICU). It is a multifactorial intestinal disease (can affect both the small and large intestine) that can lead to ischemia of the intestinal tissues that evolves into acute organ necrosis. One of these factors is that different types of nutrition can influence the onset or the progression of the disease. Cow-milk-based infant formulas have been shown to cause it in premature infants more frequently than human milk. Recently, nutrition has been shown to be beneficial after surgery. Several issues still under study, such as the pathogenesis and the insufficient and often difficult therapeutic approach, as well as the lack of a common and effective prevention strategy, make this disease an enigma in daily clinical practice. Recent studies outlined the emerging role of the host immune system and resident gut microbiota, showing their close connection in NEC pathophysiology. In its initial stages, broad-spectrum antibiotics, bowel rest, and breastfeeding are currently used, as well as probiotics to help the development of the intestinal microbiota and its eubiosis. This paper aims to present the current knowledge and potential fields of research in NEC pathophysiology and therapeutic assessment.

More than nutrition: Therapeutic potential and mechanism of human milk oligosaccharides against necrotizing enterocolitis

Human milk is the most valuable source of nutrition for infants. The structure and function of human milk oligosaccharides (HMOs), which are key components of human milk, have long been attracting particular research interest. Several recent studies have found HMOs to be efficacious in the prevention and treatment of necrotizing enterocolitis (NEC). Additionally, they could be developed in the future as non-invasive predictive markers for NEC. Based on previous findings and the well-defined functions of HMOs, we summarize potential protective mechanisms of HMOs against neonatal NEC, which include: modulating signal receptor function, promoting intestinal epithelial cell proliferation, reducing apoptosis, restoring intestinal blood perfusion, regulating microbial prosperity, and alleviating intestinal inflammation. HMOs supplementation has been demonstrated to be protective against NEC in both animal studies and clinical observations. This calls for mass production and use of HMOs in infant formula, necessitating more research into the safety of industrially produced HMOs and the appropriate dosage in infant formula.

Gut microbiome derived short chain fatty acids: Promising strategies in necrotising enterocolitis

Necrotising enterocolitis (NEC) is a devastating condition that poses a significant risk of morbidity and mortality, particularly among preterm babies. Extensive research efforts have been directed at identifying optimal treatment and diagnostic strategies but results from such studies remain unclear and controversial. Among the most promising candidates are prebiotics, probiotics and their metabolites, including short chain fatty acids (SCFAs). Such metabolites have been widely explored as possible biomarkers of gut health for different clinical conditions, with overall positive effects on the host observed. This review aims to describe the role of gut microbiome derived SCFAs in necrotising enterocolitis. Until now, information has been conflicting, with the primary focus on the main three SCFAs (acetic acid, propionic acid, and butyric acid). While numerous studies have indicated the relationship between SCFAs and NEC, the current evidence is insufficient to draw definitive conclusions about the use of these metabolites as NEC biomarkers or their potential in treatment strategies. Ongoing research in this area will help enhance both our understanding of SCFAs as valuable indicators of NEC and their practical application in clinical settings.

Human milk oligosaccharides combine with Bifidobacterium longum to form the "golden shield" of the infant intestine: metabolic strategies, health effects, and mechanisms of action

Human milk oligosaccharides (HMOs) are the third most important nutrient in human milk and are the gold standard for infant nutrition. Due to the lack of an enzyme system capable of utilizing HMOs in the infant intestine, HMOs cannot be directly utilized. Instead, they function as natural prebiotics, participating in the establishment of the intestinal microbiota as a "bifidus factor." A crucial colonizer of the early intestine is Bifidobacterium longum (B. longum), particularly its subspecies B. longum subsp. infantis, which is the most active consumer of HMOs. However, due to the structural diversity of HMOs and the specificity of B. longum strains, studies on their synergy are limited. An in-depth investigation into the mechanisms of HMO utilization by B. longum is essential for applying both as synbiotics to promote early intestinal development in infants. This review describes the colonization advantages of B. longum in the infant intestinal tract and its metabolic strategies for HMOs. It also summarizes recent studies on the effect and mechanism of B. longum and HMOs in infant intestinal development directly or indirectly through the action of metabolites. In conclusion, further structural analysis of HMOs and a deeper understanding of the interactions between B. longum and HMOs, as well as clinical trials, are necessary to lay the foundation for future practical applications as synbiotics.

Changes in Gut Microbiota at 1-60 Days in 92 Preterm Infants in a Neonatal Intensive Care Unit Using 16S rRNA Gene Sequencing

BACKGROUND Neonatal gut diversity is influenced by birth conditions and probiotic/antibiotic use. The gut microbiota affects brain development, immunity, and risk of diseases. Preterm infants, especially in neonatal intensive care units (NICUs), have different gut flora from full-term infants, suggesting in utero microbial colonization. This study examined gut microbiota changes in 92 NICU preterm infants in China. MATERIAL AND METHODS We collected data on 92 preterm infants admitted to the NICU immediately after birth, and fecal samples were collected on days 1, 3, 7, 14, 21, 28, and 60. We analyzed changes in intestinal bacteria through 16S rRNA sequencing, predicted the change in gut microbiota function over time, and compared the effects of main feeding modality on the intestinal bacteria of preterm infants. RESULTS At the phylum level, the top 5 phyla in total accounted for 99.69% of the abundance, in decreasing order of abundance: Proteobacteria, Firmicutes, Actinobacteria, Tenericutes, and Bacteroidetes. At the genus level, the top 10 genera in terms of abundance accounted for a total of 90.90%, in decreasing order of abundance: Pseudomonas, Staphylococcus, Klebsiella, Escherichia-Shigella, unclassified Enterobacteriaceae, Staphylococcus, Clostridium-sensu-stricto-1, Streptococcus, Sphingomonas, and Ureaplasma. The abundance of Proteobacteria and Pseudomonas showed a decreasing trend at first, reached a minimum at day 14, and then an increasing trend, while the opposite trend was observed for Firmicutes. The metabolic function of the bacterial community changed greatly at different time points. The abundance of Proteobacteria at the phylum level and Streptococcus at the genus level in formula-fed infants were significantly higher than in breast-fed infants. CONCLUSIONS Between 1 and 60 days, the gut microbiome in preterm infants in the NICU changed with changes in feeding patterns, with the main gut bacteria being from the phyla, Proteobacteria, and Pseudomonas.