Necrotizing enterocolitis in premature infants-A defect in the brakes? Evidence from clinical and animal studies

Recent advances in understanding pathophysiology of non-nutritional stunting in very preterm infants

Very preterm infants (VPIs) often experience extrauterine growth failure. Therefore, aggressive nutritional management of VPIs is recommended with the goal of achieving the postnatal growth of an equivalent fetus. However, VPIs frequently present postnatal length growth restriction at term-corrected age that remains lower than the standard weight and have greater fat mass and lower lean and bone mass than term-born infants. This condition differs from the classic pattern of infant undernutrition defined as a significantly lower weight for a given length. Moreover, it suggests that nonnutritional factors play a key role in length growth restriction. While weight faltering has been extensively studied, the significance of length growth failure in VPIs has only recently emerged. The nonnutritional factors underlying poor length growth in VPIs are currently not fully understood. In this review, we address recent advances in our understanding of the pathophysiology of length growth restriction, which has been identified as a major predictor of adverse neurodevelopmental and cognitive outcomes in VPIs. First, we review the shortand long-term consequences of poor length growth in VPIs; next, we highlight the effects of nonnutritional factors on postnatal length growth with focus on sustained neonatal inflammation; and finally, we discuss hypothesis and future lines of research attempting to understand the complex inflammatory-endocrine interactions and pathophysiological changes during early postnatal life, appropriately guide and apply clinical strategies aimed at optimizing length growth of VPIs, and identify evidence of the associations between sustained neonatal inflammation, stunting, and long-term health risks and the potential implications thereof.

Cytomegalovirus Worsens Necrotizing Enterocolitis Severity in Mice via Increased Toll-Like Receptor 4 Signaling

BACKGROUND AND AIMS

Necrotizing enterocolitis (NEC) is a life-threatening condition in premature infants, marked by acute intestinal necrosis. NEC develops in part after activation of the lipopolysaccharide receptor toll-like receptor 4 (TLR4) by intestinal microbes in the intestinal epithelium. Previous authors have shown an increased risk of NEC in human infants after cytomegalovirus (CMV) infection, which can affect mitochondrial function. We now seek to explore the impact and the mechanisms of CMV infection on NEC severity and its relationship with TLR4 signaling and mitochondria function.

METHODS

NEC was induced in newborn mice with and without CMV infection. RNA sequencing and gene set enrichment analysis were performed to identify effects on inflammatory and metabolic pathways. The role of TLR4 signaling and mitochondrial function were investigated in wild-type and Tlr4-deficient mice. The adenosine receptor agonist 5'-N-ethylcarboxamido adenosine was tested for its ability to reduce CMV-induced effects on NEC severity.

RESULTS

CMV infection significantly increased NEC severity in wild-type mice. Mechanistically, CMV infection triggered proinflammatory pathways, disrupted cellular metabolism, and upregulated Tlr4 expression, leading to mitochondrial dysfunction and nuclear factor-kB translocation. These effects were notably absent in Tlr4-deficient mice. 5'-N-ethylcarboxamido adenosine treatment reversed CMV-induced NEC severity by reducing mitochondrial dysfunction and TLR4-driven nuclear factor-kB activation.

CONCLUSIONS

CMV infection worsens NEC severity in mice by amplifying TLR4 signaling, inflammation, and mitochondrial dysfunction. Targeting CMV and its influence on TLR4 may offer novel therapeutic approaches for NEC.

Vitamin A enhances PI3K/Akt signaling and mitigates enterocyte apoptosis in a mouse model of necrotizing enterocolitis

PURPOSE

This study aims to elucidate the roles of the PI3K-Akt signaling pathway and enterocyte apoptosis in necrotizing enterocolitis (NEC) pathogenesis and investigate the impact of vitamin A intervention on these factors.

METHODS

We employed an NEC mouse model and administered vitamin A treatment. Retinol levels in mouse blood were quantified using ELISA. Intestinal cell apoptosis in NEC mice was assessed via the TUNEL assay. We evaluated mRNA and protein expressions of Bcl-2, Bax, cytochrome C (CytoC), Caspase 3, and PI3K/Akt signaling pathway components using qPCR and western blotting.

RESULTS

In NEC models, PI3K, Akt, and Bcl-2 were downregulated, accompanied by upregulated Bax, CytoC, and Caspase 3 at both mRNA and protein levels. These molecular changes were associated with an increase in enterocyte apoptosis in the NEC models. Vitamin A supplementation increased PI3K, Akt, and Bcl-2 expression while decreasing Bax, CytoC, and Caspase 3 levels in the NEC models, resulting in reduced apoptosis.

CONCLUSION

Vitamin A has the potential to mitigate enterocyte apoptosis in NEC by upregulating the PI3K/Akt signaling pathway and modulating apoptotic signals, providing new insights into the inhibitory effect of vitamin A on enterocyte apoptosis in NEC.

Bedside Utilization of Intestinal Pathology in Preterm Infants with Surgical Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is one of the most common conditions requiring emergency surgery in the neonatal intensive care unit and is associated with multiorgan dysfunction, multiple systemic morbidities, and mortality. The resected bowel commonly shows evidence of coagulative necrosis, inflammation, interstitial hemorrhages, and reparative changes on the pathology examination. The severity of these pathological abnormalities may correlate with the disease's severity and pace of progression and may assist in the prediction of clinical outcomes. This review presents current evidence about the clinical utility of intestinal pathology in bedside decision-making, accurate diagnosing, prediction of outcomes, and the prognostication of preterm infants with surgical NEC. Developing refined and validated noninvasive methods to diagnose the extent of bowel injury and monitoring tissue repair throughout disease progression is paramount to mitigate the long-term morbidities in preterm infants with surgical NEC. Improved imaging methods such as targeted bowel ultrasound capable of assessing the inflammation and necrosis in real time will greatly advance care and provide focus for the temporal framework of surgical interventions. KEY POINTS: · The degree and severity of intestinal pathological changes are associated with different outcomes.. · Bedside utilization of the intestinal pathological changes may help improve outcomes.. · Targeted noninvasive methods to diagnose the extent of bowel injury in real time are greatly needed..

Different infant formulas can activate toll-like receptor 9 in vitro and inhibit interleukin 6 in human primary intestinal epithelial cells

PURPOSE

Necrotizing enterocolitis (NEC) is the most severe gastrointestinal disease in preterm infants caused by an exaggerated intestinal epithelial immune activation. Several studies show that modulation of toll-like receptor 9 (TLR9) activity may have positive effects on preventing intestinal inflammatory mechanisms ultimately resulting in NEC development. In this study, the effect of various infant formulas (IF) and the probiotic strain Limosilactobacillus fermentum CECT5716 on TLR9 activation were analyzed in vitro.

METHODS

First, TLR4 and TLR9 expression was analyzed on human primary intestinal epithelial cells (P-IECs) by qPCR and Western blot analysis. Then genetically designed HEK-Dual™ hTLR9 (NF/IL8) reporter cells (HEK-Dual) were treated with different IFs, L. fermentum CECT5716, and different functional components to measure TLR9 activation via luminescence. Finally, the IFs were investigated in P-IECs to analyze TLR downstream signaling by Western blot analysis.

RESULTS

IFs containing intact protein and L. fermentum CECT5716 activated TLR9 in HEK-Dual cells, but the functional components lactoferrin, L-5-methyltetrahydrofolate, and hydrolyzed whey proteins failed to activate TLR9. In P-IECs, the IFs induced increased phosphorylation of MAPK8/9 of the TLR signaling pathway and significantly reduced IL6 levels. Consistently, IL6 levels were increased in P-IECs when TLR9-signaling was inhibited. Interestingly, L. fermentum CECT5716 enhanced TLR9-signaling and increased NF-kappa-B inhibitor alpha-phosphorylation.

CONCLUSION

We found out that the used control formula, prebiotic formula, prebiotic formula with hydrolyzed-protein, and L. fermentum CECT5716 reduce IL6 levels in human P-IECs through TLR9 activation. L. fermentum CECT5716 and the here tested IFs could be a promising approach for modulation of gut health in infants.

Understanding necrotizing enterocolitis endotypes and acquired intestinal injury phenotypes from a historical and artificial intelligence perspective

Necrotizing enterocolitis (NEC) remains a devastating disease in preterm and term neonates. Despite significant progress made in understanding NEC pathogenesis over the last 50 years, the inability of current definitions to discriminate the various pathophysiological processes underlying NEC has led to an umbrella term that limits clinical and research progress. In this mini review, we provide a historical perspective on how NEC definitions and pathogenesis have evolved to our current understanding of NEC endotypes. We also discuss how artificial intelligence-based approaches are influencing our knowledge of risk-factors, classification and prognosis of NEC and other neonatal intestinal injury phenotypes.

The conundrum of intestinal injury in preterm infants receiving mother's own milk

"Necrotizing enterocolitis" ("NEC") is a heterogeneous group of intestinal injuries experienced primarily in preterm infants. Risk factors include among others preterm gut microbiome alterations. Maternal milk (MM), or otherwise parent milk, is protective for the developing intestine due to its constituents, which include bioactive antimicrobials, immunomodulatory molecules, human milk oligosaccharides (HMOs), secretory immunoglobulin A (sIgA), and microorganisms. However, some preterm infants receiving exclusively mother's own milk (MOM) develop intestinal injuries. Studies showed predisposition to increased risk for "NEC", when a decreased MM HMO, disialyllacto-N-tetraose, is combined with an altered infant's gut microbiome. The intestine may also become more prone to injury with a greater amount of bacteria not bound to IgA. Variations in MM composition may alter the offspring gut microbiome, depriving protection. The different "NEC" entities should be considered to play a role as to why, in many studies, MOM does not provide absolute protection against preterm intestinal injury.

Impact of Clinical Use of Probiotics on Preterm-Related Outcomes in Infants with Extremely Low Birth Weight

Background: Preterm birth significantly contributes to mortality and morbidities, with recent studies linking these issues to gut microbiota imbalances. Probiotic supplementation shows promise in mitigating adverse outcomes in preterm infants, but optimal timing and guidelines remain unclear. This study assesses the benefits of probiotic supplementation for preterm infants without consistent guidelines. Methods: This retrospective study examined extremely low-birth-weight (ELBW) infants in neonatal intensive care units from 2017 to 2021. Mortality and preterm-related outcomes were compared between infants receiving probiotics and those not. Subgroup analyses based on probiotic initiation timing were conducted: early (≤14 days), late (>14 days), and non-probiotic groups. Results: The study included 330 ELBW infants: 206 received probiotics (60 early, 146 late), while 124 did not. Probiotic supplementation was associated with lower overall mortality (adjusted OR 0.22, 95% CI 0.09-0.48) and decreased mortality from necrotizing enterocolitis (NEC) or late-onset sepsis (LOS) (adjusted OR 0.12, 95% CI 0.03-0.45). Early probiotics reduced overall mortality, NEC/LOS-related mortality, and NEC/LOS-unrelated mortality. Late probiotics decreased overall mortality and NEC/LOS-related mortality. Early probiotic use also expedited full enteral feeding achievement. Conclusions: Probiotic supplementation reduces mortality and improves feeding tolerance in preterm infants. Establishing guidelines for probiotic use in this population is crucial.

Gut microbiota differences in five-year-old children that were born preterm with a history of necrotizing enterocolitis: A pilot trial

The study explores the long-term effects of necrotizing enterocolitis (NEC) on gut microbiota in preterm infants by analyzing stool samples from 5-year-old children using shotgun metagenomic sequencing. It compares children with a history of NEC, treated surgically or medically, to preterm controls without NEC. Findings reveal persistent gut microbiota dysbiosis in NEC children, with reduced species diversity and evenness, especially in those treated surgically. The surgical NEC group had a lower Shannon index, indicating less microbial diversity. Significant differences in taxonomic profiles were observed, mainly influenced by surgical treatment. These results underscore the lasting impact of NEC and its treatment on gut microbiota, suggesting a need for strategies addressing long-term dysbiosis.

Role of innate T cells in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a destructive gastrointestinal disease primarily affecting preterm babies. Despite advancements in neonatal care, NEC remains a significant cause of morbidity and mortality in neonatal intensive care units worldwide and the etiology of NEC is still unclear. Risk factors for NEC include prematurity, very low birth weight, feeding with formula, intestinal dysbiosis and bacterial infection. A review of the literature would suggest that supplementation of prebiotics and probiotics prevents NEC by altering the immune responses. Innate T cells, a highly conserved subpopulation of T cells that responds quickly to stimulation, develops differently from conventional T cells in neonates. This review aims to provide a succinct overview of innate T cells in neonates, encompassing their phenotypic characteristics, functional roles, likely involvement in the pathogenesis of NEC, and potential therapeutic implications.

Butyrate suppresses experimental necrotizing enterocolitis-induced brain injury in mice

Background

Necrotizing enterocolitis (NEC) is a devastating disease in premature infants, and 50% of infants with surgical NEC develop neurodevelopmental defects. The mechanisms by which NEC-induced cytokine release and activation of inflammatory cells in the brain mediate neuronal injury, and whether enteral immunotherapy attenuates NEC-associated brain injury remain understudied. Based on our prior work, which demonstrated that experimental NEC-like intestinal injury is attenuated by the short-chain fatty acid, butyrate, in this study, we hypothesize that NEC-induced brain injury would be suppressed by enteral butyrate supplementation.

Methods

A standardized NEC mouse model [enteral formula feeding, lipopolysaccharide (LPS), and hypoxia] was used. Mice were randomized into the following groups: control, NEC, butyrate pretreated NEC, and butyrate control. NEC scoring (1-4 with 4 representing severe injury) was performed on ileal sections using a validated scoring system. Intestinal and brain lysates were used to assess inflammation, proinflammatory signaling, and apoptosis.

Results

NEC-induced intestinal injury was attenuated by butyrate supplementation. NEC-induced microglial activation in the cerebral cortex and hippocampus was suppressed with butyrate. NEC increased the number of activated microglial cells but decreased the number of oligodendrocytes. Butyrate pretreatment attenuated these changes. Increased activation of proinflammatory Toll-like receptor signaling, cytokine expression, and induction of GFAP and IBA1 in the cerebral cortex observed with NEC was suppressed with butyrate.

Conclusion

Experimental NEC induced inflammation and activation of microglia in several regions of the brain, most prominently in the cortex. NEC-induced neuroinflammation was suppressed with butyrate pretreatment. The addition of short-chain fatty acids to diet may be used to attenuate NEC-induced intestinal injury and neuroinflammation in preterm infants.

The Detrimental Effects of Peripartum Antibiotics on Gut Proliferation and Formula Feeding Injury in Neonatal Mice Are Alleviated with Lactobacillus rhamnosus GG

Peripartum antibiotics can negatively impact the developing gut microbiome and are associated with necrotizing enterocolitis (NEC). The mechanisms by which peripartum antibiotics increase the risk of NEC and strategies that can help mitigate this risk remain poorly understood. In this study, we determined mechanisms by which peripartum antibiotics increase neonatal gut injury and evaluated whether probiotics protect against gut injury potentiated by peripartum antibiotics. To accomplish this objective, we administered broad-spectrum antibiotics or sterile water to pregnant C57BL6 mice and induced neonatal gut injury to their pups with formula feeding. We found that pups exposed to antibiotics had reduced villus height, crypt depth, and intestinal olfactomedin 4 and proliferating cell nuclear antigen compared to the controls, indicating that peripartum antibiotics impaired intestinal proliferation. When formula feeding was used to induce NEC-like injury, more severe intestinal injury and apoptosis were observed in the pups exposed to antibiotics compared to the controls. Supplementation with the probiotic Lactobacillus rhamnosus GG (LGG) reduced the severity of formula-induced gut injury potentiated by antibiotics. Increased intestinal proliferating cell nuclear antigen and activation of the Gpr81-Wnt pathway were noted in the pups supplemented with LGG, suggesting partial restoration of intestinal proliferation by probiotics. We conclude that peripartum antibiotics potentiate neonatal gut injury by inhibiting intestinal proliferation. LGG supplementation decreases gut injury by activating the Gpr81-Wnt pathway and restoring intestinal proliferation impaired by peripartum antibiotics. Our results suggest that postnatal probiotics may be effective in mitigating the increased risk of NEC associated with peripartum antibiotic exposure in preterm infants.