Effect of the Microbiome on Intestinal Innate Immune Development in Early Life and the Potential Strategy of Early Intervention

Chronic Arsenic Exposure Causes Alzheimer's Disease Characteristic Effects and the Intervention of Fecal Microbiota Transplantation in Rats

Arsenic exposure and intestinal microbiota disorders may be related with Alzheimer's disease (AD), but the mechanism has not been elucidated. This study conducted chronic arsenic exposure from rat's maternal body to adult offspring to investigate the mechanisms of the characteristic effects of chronic arsenic exposure on AD, and further explored the intervention effect of fecal microbiota transplantation (FMT) on arsenic-mediated neurotoxicity. Transmission electron microscopy, HE staining, and related indicators were measured in the control group, the exposed group, and the FMT intervention group. Western blot was used to determine microtubule-associated proteins Tau and p-Tau396, intestinal-brain barrier-related proteins Claudin-1 and Occludin, ELISA was used to detect the content of Aβ1-42, and 16S rRNA sequencing was used to detect the intestinal flora of feces. Results showed that chronic arsenic exposure could lead to neurobehavioral defects in rats, increase the expression levels of Tau, p-Tau396, and Aβ1-42 in hippocampus (p < 0.05), increase the abundance of Clostridium _ UCG-014, decrease the abundance of Roseburia, and decrease the expression levels of Claudin-1 and Occludin in colon and hippocampus (p < 0.05). After FMT intervention, the expression levels of Tau and p-Tau396 were decreased (p < 0.05), and the abundance of Roseburia was increased. In summary, chronic arsenic exposure caused intestinal flora disorder by changing the abundance of inflammation-related flora, thereby destroying the gut-brain barrier and causing AD characteristic effects in rats. Although the bacterial specific genus was improved and the expression of AD-related proteins was reduced after transplantation, it could not alleviate the neurobehavioral defects and neurotoxicity caused by arsenic exposure.

Effects of pectin-type polysaccharides derived from Houttuynia cordata on the intestinal immune system in native C3H/HeN mice

Dietary polysaccharides have attracted considerable attention because of their species-specific chemical composition and diverse biological activities. Polysaccharides derived from Houttuynia cordata (HC) exhibit broad pharmacological activities, emphasizing their diverse roles in biological processes. This study investigated the effects of HC-derived polysaccharides on Peyer's patch (PP)-mediated intestinal immune response. The crude polysaccharide (HCP) isolated from HC extract (HCE) was identified as a pectin-type polysaccharide rich in the homogalacturonan (HG) domain, which was further hydrolyzed by endo-polygalacturonase to produce HCPE. In vitro, HCPE significantly enhanced PP-mediated cytokine secretion and bone marrow cell (BMC) proliferation compared with HCP. In vivo, a 4-week treatment with oral HCPE stimulated PP-mediated secretion of hematopoietic growth factors and promoted BMC proliferation. Additionally, HCPE upregulated IgA-associated factors, leading to increased IgA levels in the small intestine, serum, and feces, while also significantly elevating short-chain fatty acid levels, potentially improving the gut environment. To the best of our knowledge, this is the first study to systematically analyze PP-mediated intestinal immunostimulatory activity of HC-derived polysaccharides both in vitro and in vivo. These findings provide valuable insights into the potential of HCPE as an intestinal immunostimulatory agent and establish a foundation for future research on the immunological effects of HC-derived polysaccharides.

Gut Microbiota-Derived Hyocholic Acid Enhances Type 3 Immunity and Protects Against Salmonella enterica Serovar Typhimurium in Neonatal Rats

This study investigates how microbiome colonization influences the development of intestinal type 3 immunity in neonates. The results showed that reduced oxygen levels in the small intestine of neonatal rats induced by Saccharomyces boulardii accelerated microbiome colonization and type 3 immunity development, which protected against Salmonella enterica serovar Typhimurium infection. Microbiome maturation increased the abundance of microbiome-encoded bile salt hydrolase (BSH) genes and hyocholic acid (HCA) levels. Furthermore, reducing oxygen levels in the intestine increased the abundance of Limosilactobacillus reuteri, a bacterium encoding BSH, and promoted intestinal type 3 immunity. However, inhibition of BSH blocked the L. reuteri-induced development of intestinal type 3 immunity. Mechanistically, HCA promoted the development of gamma-delta T cells and type 3 innate lymphoid cells by stabilizing the mRNA expression of RAR-related orphan receptor C via the farnesoid X receptor-WT1-associated protein-N6-methyl-adenosine axis. These results reveal that gut microbiota-derived HCA plays a crucial role in promoting the development of intestinal type 3 immunity in neonates. This discovery introduces potential therapeutic avenues for strengthening intestinal immunity in early life or treating bacterial infections by targeting microbial metabolites.

Yeast cell wall polysaccharides accelerate yet in-feed antibiotic delays intestinal development and maturation via modulating gut microbiome in chickens

BACKGROUND

It is important to promote intestinal development and maturation of chicks for feed digestion and utilization, intestinal health, and disease resistance. This study aimed to investigate the effects of dietary yeast cell wall polysaccharides (YCWP) addition on intestinal development and maturation of chickens and its potential action mechanism.

METHODS

180 one-day-old male Arbor Acres broilers were randomly assigned to three groups containing control (basal diets without any antibiotics or anticoccidial drug), bacitracin methylene disalicylate (BMD)-treated group (50 mg/kg) and YCWP-supplemented group (100 mg/kg).

RESULTS

Compared with control group, in-feed antibiotic BMD continuous administration significantly decreased crypt depth (d 21) and villus height (d 42) along with mucosal maltase activity (d 42) in the ileum (P < 0.05). Also, BMD markedly downregulated gene expression levels of β-catenin, lysozyme, occludin and FABP-2 (d 21) and innate immune related genes CD83 and MHC-I mRNA levels (d 42, P < 0.05), and decreased goblet cell counts in the ileum of chickens (d 21 and d 42, P < 0.05). While, TLR-2, TLR-6 and iNOS mRNA abundances were notably upregulated by BMD treatment (d 42, P < 0.05). Nevertheless, dietary YCWP addition significantly increased the ratio of villus height to crypt depth (d 21), villus surface area (d 21 and d 42), ileal alkaline phosphatase and maltase activities as well as goblet cell (d 21 and d 42) and IgA-producing plasma cell numbers as compared to BMD treatment (d 21, P < 0.05). YCWP addition also upregulated gene expression levels of Lgr5, Wnt/β-catenin signaling pathway related gene (Wnt3, β-catenin, d 21; β-catenin, d 42), intestinal cells proliferation marker Ki-67 and barrier function related genes (occludin, d 21 and d 42, P < 0.05). Moreover, YCWP significantly increased antigen presenting cell marker related genes (MHC-II, d 21; CD83 and MHC-I, d 42), TLR-1, TLR-2 and TLR-6 mRNA levels (d 21, P < 0.05). Cecal microbiome analysis showed that YCWP addition obviously improved cecal microbial composition, as indicated by increasing relative abundance of Fournierella, Psychrobacter and Ruminiclostridium on d 21, and Alistipes and Lactobacillus on d 42, which were positively related with gut development and maturation related indexes (P < 0.05).

CONCLUSION

Collectively, YCWP promoted yet antibiotic BMD delayed intestinal morphological and immunological development linked with modulating gut microbiome in chickens.

Effect of different delivery modes on intestinal microbiota and immune function of neonates

Different delivery methods can cause variations in the composition and structure of intestinal microbiota in neonates. However, the impact of the microecological environment on host immune function requires further investigation. In this study, 75 healthy neonates were divided into two groups: vaginal delivery group (n = 36) and cesarean section group (n = 39). Fecal and peripheral blood samples were collected from the 7th to the 10th day. 16S rRNA sequencing technique was performed to investigate the gut microbiota on fecal samples. Levels of immunoglobulins and Th1 and Th2 cells in the peripheral blood of neonates were measured. The abundance of Escherichia, Bifidobacterium, and Bacteroides in neonates in the cesarean section group was significantly lower than that in the vaginal delivery group. Metabolic pathway analysis showed three significantly up-regulated metabolic pathways in the intestinal microbiota of neonates in the cesarean section group. The levels of serum IgG and IL-12p70 in the cesarean section group were lower than those in the vaginal delivery group, and the proportion of IFN-γ/IL-4 was significantly lower in the cesarean section group compared to the vaginal delivery group. The mode of delivery has potential impact on the intestinal microbiota and immune functions of neonates, potentially leading to an imbalance of Th1/Th2 cells in neonates delivered by cesarean section.

From Birth to Weaning: A Window of Opportunity for Microbiota

(1) Background: The first 1000 days of life constitute a critical window of opportunity for microbiota development. Nutrients play a crucial role in enriching and diversifying the microbiota, derived not only from solid food but also from maternal dietary patterns during gestation. (2) Methods: We conducted a comprehensive literature review using the PubMed database, covering eleven years (2013-2023). We included English-language reviews, original research papers, and meta-analyses, while excluding case reports and letters. (3) Results: Consensus in the literature emphasizes that our interaction with a multitude of microorganisms begins in the intrauterine environment and continues throughout our lives. The existing data suggest that early nutritional education programs, initiated during pregnancy and guiding infant diets during development, may influence the shaping of the gut microbiota, promoting long-term health. (4) Conclusions: Further research is necessary in the coming years to assess potential interventions and early nutritional models aimed at modulating the pediatric microbiota, especially in vulnerable populations such as premature newborns.

Treatment of preterm brain injury via gut-microbiota-metabolite-brain axis

BACKGROUND

Brain injury in preterm infants potentially disrupts critical structural and functional connective networks in the brain. It is a major cause of neurological sequelae and developmental deficits in preterm infants. Interesting findings suggest that the gut microbiota (GM) and their metabolites contribute to the programming of the central nervous system (CNS) during developmental stages and may exert structural and functional effects throughout the lifespan.

AIM

To summarize the existing knowledge of the potential mechanisms related to immune, endocrine, neural, and blood-brain barrier (BBB) mediated by GM and its metabolites in neural development and function.

METHODS

We review the recent literature and included 150 articles to summarize the mechanisms through which GM and their metabolites work on the nervous system. Potential health benefits and challenges of relevant treatments are also discussed.

RESULTS

This review discusses the direct and indirect ways through which the GM may act on the nervous system. Treatment of preterm brain injury with GM or related derivatives, including probiotics, prebiotics, synbiotics, dietary interventions, and fecal transplants are also included.

CONCLUSION

This review summarizes mechanisms underlying microbiota-gut-brain axis and novel therapeutic opportunities for neurological sequelae in preterm infants. Optimizing the initial colonization and microbiota development in preterm infants may represent a novel therapy to promote brain development and reduce long-term sequelae.

A comprehensive review on infant formula: nutritional and functional constituents, recent trends in processing and its impact on infants' gut microbiota

Human milk is considered the most valuable form of nutrition for infants for their growth, development and function. So far, there are still some cases where feeding human milk is not feasible. As a result, the market for infant formula is widely increasing, and formula feeding become an alternative or substitute for breastfeeding. The nutritional value of the formula can be improved by adding functional bioactive compounds like probiotics, prebiotics, human milk oligosaccharides, vitamins, minerals, taurine, inositol, osteopontin, lactoferrin, gangliosides, carnitine etc. For processing of infant formula, diverse thermal and non-thermal technologies have been employed. Infant formula can be either in powdered form, which requires reconstitution with water or in ready-to-feed liquid form, among which powder form is readily available, shelf-stable and vastly marketed. Infants' gut microbiota is a complex ecosystem and the nutrient composition of infant formula is recognized to have a lasting effect on it. Likewise, the gut microbiota establishment closely parallels with host immune development and growth. Therefore, it must be contemplated as an important factor for consideration while developing formulas. In this review, we have focused on the formulation and manufacturing of safe and nutritious infant formula equivalent to human milk or aligning with the infant's needs and its ultimate impact on infants' gut microbiota.

The ratios of dietary non-fibrous carbohydrate (NFC) to neutral detergent fiber (NDF) influence intestinal immunity of rabbits by regulating gut microbiota composition and metabolites

Carbohydrate is the most common macronutrient consumed across all phases of the diet and acts as a potential regulator in modulating the gut microbiota in animals. However, the influences of dietary non-fibrous carbohydrate (NFC) to neutral detergent fiber (NDF) in different ratios on gut microbiota, metabolites, intestinal immunity, and growth performance have not been fully explored. A total of 135 healthy weaned rabbits (45.1 ± 0.7 d of age) with an average body weight of 1.08 ± 0.07 kg were randomly divided into five groups. Under the same other nutrient levels, rabbits were fed diets with NFC/NDF ratios of 0.7 (T1), 1.0 (T2), 1.3 (T3), 1.6 (T4), and 1.9 (T5). During the 28-day experiment, T3 rabbits showed the highest final body weight and the lowest feed-to-weight ratio than T5 rabbits (P < 0.05) but no significant difference with T1 or T2 rabbits. The expression of cecal pro-inflammatory factors IL-1β and TNF-α was increased in the T4 and T5 than in those of other groups (P < 0.05). Conversely, the tight junction proteins (ZO-1, Claudin-1, and Occludin) were decreased to varying degrees in the T4 and T5 groups. The pH value in the cecal digesta of T5 rabbits was lower than that of T1, T2, and T3 (P < 0.05), while the concentration of volatile fatty acids and propionate was higher than those of T1, T2, and T3 rabbits (P < 0.05). In terms of gut microbiota, at the phylum level, the relative burden of Firmicutes and Actinobacteria in T2 rabbits was the highest (P < 0.05), and the relative burden of Proteobacteria in T5 rabbits was higher than that of other groups (P < 0.05). At the genus level, the relative burden of Ruminococcus was higher in T2 and T3 rabbits than that of other groups, and T5 rabbits have the lowest relative burden of Ruminococcus. Combination analysis showed that cecal metabolites were positively associated with fermentation-related phenotypes and the burden of Firmicutes (P < 0.05). In conclusion, different dietary NFC/NDF ratios can affect the intestinal immune response and growth performance of rabbits, and there was a positive effect when dietary NFC/NDF = 1.0-1.3.

Microbiota-Derived Extracellular Vesicles Detected in Human Blood from Healthy Donors

The microbiota constitutes an important part of the holobiont in which extracellular vesicles (EVs) are key players in health, especially regarding inter- and intra-kingdom communications. Analysis of EVs from the red blood cell concentrates of healthy donors revealed variable amounts of OmpA and LPS in 12 of the 14 analyzed samples, providing indirect experimental evidence of the presence of microbiota EVs in human circulating blood in the absence of barrier disruption. To investigate the role of these microbiota EVs, we tracked the fusion of fluorescent Escherichia coli EVs with blood mononuclear cells and showed that, in the circulating blood, these EVs interacted almost exclusively with monocytes. This study demonstrates that bacterial EVs constitute critical elements of the host-microbiota cellular communication. The analysis of bacterial EVs should thus be systematically included in any characterization of human EVs.

Gut Microbiota and Therapy in Metastatic Melanoma: Focus on MAPK Pathway Inhibition

Gut microbiome (GM) and its either pro-tumorigenic or anti-tumorigenic role is intriguing and constitutes an evolving landscape in translational oncology. It has been suggested that these microorganisms may be involved in carcinogenesis, cancer treatment response and resistance, as well as predisposition to adverse effects. In melanoma patients, one of the most immunogenic cancers, immune checkpoint inhibitors (ICI) and MAPK-targeted therapy—BRAF/MEK inhibitors—have revolutionized prognosis, and the study of the microbiome as a modulating factor is thus appealing. Although BRAF/MEK inhibitors constitute one of the main backbones of treatment in melanoma, little is known about their impact on GM and how this might correlate with immune re-induction. On the contrary, ICI and their relationship to GM has become an interesting field of research due to the already-known impact of immunotherapy in modulating the immune system. Immune reprogramming in the tumor microenvironment has been established as one of the main targets of microbiome, since it can induce immunosuppressive phenotypes, promote inflammatory responses or conduct anti-tumor responses. As a result, ongoing clinical trials are evaluating the role of fecal microbiota transplant (FMT), as well as the impact of using dietary supplements, antibiotics and probiotics in the prediction of response to therapy. In this review, we provide an overview of GM’s link to cancer, its relationship with the immune system and how this may impact response to treatments in melanoma patients. We also discuss insights about novel therapeutic approaches including FMT, changes in diet and use of probiotics, prebiotics and symbiotics. Finally, we hypothesize on the possible pathways through which GM may impact anti-tumor efficacy in melanoma patients treated with targeted therapy, an appealing subject of which little is known.