First 1000 Days and Beyond After Birth: Gut Microbiota and Necrotizing Enterocolitis in Preterm Infants

Digging deeper into necrotizing enterocolitis: bridging clinical, microbial, and molecular perspectives

Necrotizing Enterocolitis (NEC) is a severe, life-threatening inflammatory condition of the gastrointestinal tract, especially affecting preterm infants. This review consolidates evidence from various biomedical disciplines to elucidate the complex pathogenesis of NEC, integrating insights from clinical, microbial, and molecular perspectives. It emphasizes the modulation of NEC-associated inflammatory pathways by probiotics and novel biologics, highlighting their therapeutic potential. We further critically examine dysbiotic alterations within the gut microbiota, with a particular focus on imbalances in bacterial and viral communities, which may contribute to the onset of NEC. The intricate interactions among toll-like receptor 4 (TLR4), microvascular integrity, immune activation, and the inflammatory milieu are meticulously summarized, offering a sophisticated understanding of NEC pathophysiology. This academic review aims to enhance the etiological comprehension of NEC, promote the development of targeted therapeutic interventions, and impart the significant impact of perinatal factors on the formulation of preventive and curative strategies for the disease.

Human milk peptide MAMP-1 alleviates necrotizing enterocolitis via inhibition of the TLR4-mediated PI3K-AKT-NF-κB signaling pathway

Background: Necrotizing enterocolitis (NEC) is a disease with prevalent and serious intestinal inflammation that poses a significant threat to the lives of newborns. Human milk has been shown to prevent and treat the occurrence of NEC; however, the underlying mechanisms remain unclear. MAMP-1 is a significantly overexpressed endogenous peptide derived from β-casein extracted from the human milk of premature mothers, which is resistant to gastrointestinal conditions and exhibits favorable physicochemical properties. This study aims to investigate the mechanism by which the human milk-derived peptide MAMP-1 mitigates NEC in mice, offering new insights for clinical treatment. Methods: The C57BL/6 mice were categorized into three distinct groups randomly on the 7th day after birth, with 40 mice in each group. The NEC model was established using "artificial feeding + hypoxia + cold", and the MAMP-1 group received daily MAMP-1 gavage during NEC modeling. Ileum tissues and feces were collected. Pathological damage in the intestines was evaluated by H&E staining. ZO-1 expression was analyzed through immunofluorescence staining and western blot. Apoptosis in the intestine was assessed using western blot and TUNEL staining. The effects of signaling pathways were confirmed through western blot and RNA sequencing. The expression of inflammatory factors was assessed using RT-PCR. 16S high-throughput sequencing was used to determine the diversity and abundance of the gut microbiota. Results: MAMP-1 reduced the mortality rate of NEC mice, alleviated ileum injury, increased the ZO-1 expression of the intestinal barrier, reduced the apoptotic protein expression, lowered the TUNEL positive area, increased anti-apoptotic protein expression, and reduced the levels of TLR4, P-PI3K, P-AKT, and NF-κB, leading to a reduction in the release of inflammatory cytokines. Furthermore, MAMP-1 decreased the abundance of harmful bacteria and increased the abundance of beneficial bacteria at both the phylum and genus levels. Conclusion: MAMP-1 might inhibit the TLR4-PI3K-AKT-NF-κB signaling pathways, further reducing inflammation factor release, and might decrease intestinal cell apoptosis. Results indicated that MAMP-1 might alleviate intestinal damage in NEC mice. Meanwhile, MAMP-1 might positively modulate the composition of the microbiota of NEC mice and further achieve the preventive and therapeutic effect of MAMP-1 on NEC.

Therapeutic potential of human breast milk-derived exosomes in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe inflammatory and necrotizing disease of the intestine that primarily affects the neonates, particularly premature infants. It has a high incidence of approximately 8.9% in extremely preterm infants, with a mortality rate ranging from 20 to 30%. In recent years, exosomes, particularly those derived from breast milk, have emerged as potential candidates for NEC therapy. Human breast milk-derived exosomes (BME) have been shown to enhance intestinal barrier function, protect intestinal epithelial cells from oxidative stress, promote the proliferation and migration of intestinal epithelial cells, and reduce the severity of experimental NEC models. As a subset of extracellular vesicles, BME possess the membrane structure, low immunogenicity, and high permeability, making them ideal vehicles for the treatment of NEC. Additionally, exosomes derived from various sources, including stem cells, intestinal epithelial cells, plants, and bacteria, have been implicated in the development and protection of intestinal diseases. This article summarizes the mechanisms through which exosomes, particularly BME, exert their effects on NEC and discusses the feasibility and obstacles associated with this novel therapeutic strategy.

Unveiling the dynamics of the breast milk microbiome: impact of lactation stage and gestational age

BACKGROUND

Breast milk (BM) provides complete nutrition for infants for the first six months of life and is essential for the development of the newborn's immature immune and digestive systems. While BM was conventionally believed to be sterile, recent advanced high throughput technologies have unveiled the presence of diverse microbial communities in BM. These insights into the BM microbiota have mainly originated from uncomplicated pregnancies, possibly not reflecting the circumstances of mothers with pregnancy complications like preterm birth (PTB).

METHODS

In this article, we investigated the BM microbial communities in mothers with preterm deliveries (before 37 weeks of gestation). We compared these samples with BM samples from healthy term pregnancies across different lactation stages (colostrum, transitional and mature milk) using 16S rRNA gene sequencing.

RESULTS

Our analysis revealed that the microbial communities became increasingly diverse and compositionally distinct as the BM matured. Specifically, mature BM samples were significantly enriched in Veillonella and lactobacillus (Kruskal Wallis; p < 0.001) compared to colostrum. The comparison of term and preterm BM samples showed that the community structure was significantly different between the two groups (Bray Curtis and unweighted unifrac dissimilarity; p < 0.001). Preterm BM samples exhibited increased species richness with significantly higher abundance of Staphylococcus haemolyticus, Propionibacterium acnes, unclassified Corynebacterium species. Whereas term samples were enriched in Staphylococcus epidermidis, unclassified OD1, and unclassified Veillonella among others.

CONCLUSION

Our study underscores the significant influence of pregnancy-related complications, such as preterm birth (before 37 weeks of gestation), on the composition and diversity of BM microbiota. Given the established significance of the maternal microbiome in shaping child health outcomes, this investigation paves the way for identifying modifiable factors that could optimize the composition of BM microbiota, thereby promoting maternal and infant health.

Araújo J, Marques C, Sousa L, Morais J, Castela I, Faria A, Neto MT, Cordeiro-Ferreira G, Virella D, Pita A, Pereira-da-Silva L, Calhau C. Changes in Microbiota Profile in the Proximal Remnant Intestine in Infants Undergoing Surgery Requiring Enterostomy

Early-life gut dysbiosis has been associated with an increased risk of inflammatory, metabolic, and immune diseases later in life. Data on gut microbiota changes in infants undergoing intestinal surgery requiring enterostomy are scarce. This prospective cohort study examined the enterostomy effluent of 29 infants who underwent intestinal surgery due to congenital malformations of the gastrointestinal tract, necrotizing enterocolitis, or spontaneous intestinal perforation. Initial effluent samples were collected immediately after surgery and final effluent samples were collected three weeks later. Gut microbiota composition was analysed using real-time PCR and 16S rRNA gene sequencing. Three weeks after surgery, an increase in total bacteria number (+21%, p = 0.026), a decrease in Staphylococcus (-21%, p = 0.002) and Candida spp. (-16%, p = 0.045), and an increase in Lactobacillus (+3%, p = 0.045) and in less abundant genera belonging to the Enterobacteriales family were found. An increase in alpha diversity (Shannon's and Simpson's indexes) and significant alterations in beta diversity were observed. A correlation of necrotizing enterocolitis with higher Staphylococcus abundance and higher alpha diversity was also observed. H2-blockers and/or proton pump inhibitor therapy were positively correlated with a higher total bacteria number. In conclusion, these results suggest that positive changes occur in the gut microbiota profile of infants three weeks after intestinal surgery.

Gut microbe metabolism of small molecules supports human development across the early stages of life

From birth to adulthood, the human gut-associated microbial communities experience profound changes in their structure. However, while the taxonomical composition has been extensively explored, temporal shifts in the microbial metabolic functionalities related to the metabolism of bioactive small molecules are still largely unexplored. Here, we collected a total of 6,617 publicly available human fecal shotgun metagenomes and 42 metatranscriptomes from infants and adults to explore the dynamic changes of the microbial-derived small molecule metabolisms according to the age-related development of the human gut microbiome. Moreover, by selecting metagenomic data from 250 breastfed and 217 formula-fed infants, we also investigated how feeding types can shape the metabolic functionality of the incipient gut microbiome. From the small molecule metabolism perspective, our findings suggested that the human gut microbial communities are genetically equipped and prepared to metabolically evolve toward the adult state as early as 1 month after birth, although at the age of 4 years, it still appeared functionally underdeveloped compared to adults. Furthermore, in respect of formula-fed newborns, breastfed infants showed enrichment in microbial metabolic functions related to specific amino acids present at low concentrations in human milk, highlighting that the infant gut microbiome has specifically evolved to synthesize bioactive molecules that can complement the human breast milk composition contributing to complete nutritional supply of infant.