Bridging intestinal immunity and gut microbiota by metabolites

Integrative Analysis of Gut Microbiota and Fecal Metabolites in Rats after Prednisone Treatment

Prednisone (PRED) is a synthetic glucocorticoid (GC) widely used in immune-mediated diseases for its immunosuppressive and anti-inflammatory properties. The effects of GC are achieved by genomic and nongenomic mechanisms. However, the nongenomic effects are largely unknown. Thus, we aimed to investigate how long-term prednisone therapy changes the composition of the gut microbiota and fecal metabolites in rats. Male Sprague-Dawley rats were randomly assigned to a control (CON) group and a PRED group, which received prednisone treatment daily for 6 weeks by gavage. The V3 to V4 regions of bacterial 16S rRNA genes were amplified and sequenced after the total bacterial DNA was extracted from fecal samples. The alpha and beta diversities were calculated. The compositional alteration of the gut microbiota at different taxonomic levels was analyzed using the Metastats method. Meanwhile, the fecal metabolites were quantitated in an ultra-performance liquid chromatography system. Similar microbial richness and diversity between the CON and PRED groups were indicated by the alpha diversity results. The gut microbial communities differed significantly between two groups. The relative abundances of the genera Eisenbergiella, Alistipes, and Clostridium XIVb decreased, whereas that of Anaerobacterium increased significantly in rats after the 6-week prednisone treatment. In total, 11 downregulated and 10 upregulated fecal metabolites were identified. Differential fecal metabolites were enriched in the pathways, including phenylalanine metabolism, butanoate metabolism, and propanoate metabolism. The lowered production of short-chain fatty acids was associated with the decreased relative abundance of the genera Alistipes and Clostridium XIVb and increased abundance of the genus Anaerobacterium. The composition of the gut microbiota and fecal metabolites was changed after long-term prednisone treatment. This may help us to understand the pharmacology of prednisone. IMPORTANCE Prednisone is widely used in chronic glomerular diseases, immunological disorders, and rheumatic diseases for its anti-inflammatory and immunosuppressive properties. It is a synthetic glucocorticoid (GC) that shows therapeutic effects after conversion to prednisolone by the liver. Prolonged GC therapy causes anti-inflammatory effects; it also results in a variety of adverse events, including obesity, hypertension, psychiatric symptoms, and dyslipidemia. The therapeutic effects and adverse events of GCs may be associated with changes in the gut microbiota, as the host might be affected by the metabolites generated by the altered gut microbes. Thus, we investigated how long-term prednisone therapy changed the composition of the gut microbiota and fecal metabolites in rats. This study may shed new light on the pharmacology of prednisone.

Probiotics Treatment of Leg Diseases in Broiler Chickens: a Review

Normal development and growth of bones are critical for poultry. With the rapid growth experienced by broiler chickens, higher incidences of leg weakness and lameness are common problems in adolescent meat-type poultry that present huge economic and welfare issues. Leg disorders such as angular bone deformities and tibial dyschondroplasia have become common in broilers and are associated with poor growth, high mortality rates, increased carcass condemnation, and downgrading at slaughter. Probiotics have shown promise for a variety of health purposes, including preventing diarrhea, elevating carcass quality, and promoting growth of the poultry. In addition, recent studies have indicated that probiotics can maintain the homeostasis of the gut microbiota and improve the health of the gastrointestinal tract, which confers a potentially beneficial effect on bone health. This review mainly describes the occurrence of broiler leg disease and the role of probiotics in bone health through regulating the gut microbiota and improving intestinal function, thus providing a relevant theoretical basis for probiotics to hinder the development of skeletal disorders in broiler chickens.

Gut Microbiota-Derived Metabolites in Colorectal Cancer: The Bad and the Challenges

Accumulating evidence from studies in humans and animal models has elucidated that gut microbiota, acting as a complex ecosystem, contributes critically to colorectal cancer (CRC). The potential mechanisms often reported emphasize the vital role of carcinogenic activities of specific pathogens, but in fact, a series of metabolites produced from exogenous dietary substrates or endogenous host compounds occupy a decisive position similarly. Detrimental gut microbiota-derived metabolites such as trimethylamine-N-oxide, secondary bile acids, hydrogen sulfide and N-nitroso compounds could reconstruct the ecological composition and metabolic activity of intestinal microorganisms and formulate a microenvironment that opens susceptibility to carcinogenic stimuli. They are implicated in the occurrence, progression and metastasis of CRC through different mechanisms, including inducing inflammation and DNA damage, activating tumorigenic signaling pathways and regulating tumor immunity. In this review, we mainly summarized the intimate relationship between detrimental gut microbiota-derived metabolites and CRC, and updated the current knowledge about detrimental metabolites in CRC pathogenesis. Then, multiple interventions targeting these metabolites for CRC management were critically reviewed, including diet modulation, probiotics/prebiotics, fecal microbiota transplantation, as well as more precise measures such as engineered bacteria, phage therapy and chemopreventive drugs. A better understanding of the interplay between detrimental microbial metabolites and CRC would hold great promise against CRC.

Fecal Microbiota Transplantation Protects the Intestinal Mucosal Barrier by Reconstructing the Gut Microbiota in a Murine Model of Sepsis

The gastrointestinal (GI) tract has long been hypothesized to play an integral role in the pathophysiology of sepsis, and gut microbiota (GM) dysbiosis may be the key factor. Previous studies have shown that the gut flora was significantly altered in critically ill patients. This study aimed to observe what kind of GM dysbiosis is in the early stage of sepsis and whether the application of fecal microbiota transplantation (FMT) can reconstruct the GM of septic mice and restore its protective function on the intestinal mucosal barrier. The study investigated the effect of FMT on gut microbiota, mucosal barrier function, inflammatory response, and survival in a murine model of sepsis established by cecal ligation and puncture (CLP). It is found that FMT can not only reduce morbidity and mortality and restore the abundance and diversity of the gut flora in septic mice, but can also improve the intestinal barrier function by reducing epithelial cell apoptosis, improving the composition of the mucus layer, upregulating the expression of tight junction proteins, and reducing intestinal permeability and the inflammatory response. After FMT, Lachnospiraceae contributed the most to intestinal protection through enhancement of the L-lysine fermentation pathway. FMT offers a microbe-mediated survival advantage in a murine model of sepsis. Therefore, an improved understanding of the connection between microbiota, and systemic illness may yield new therapeutic strategies for patients with sepsis.

THE INTESTINAL COMMENSAL, Bacteroides fragilis, MODULATES HOST RESPONSES TO VIRAL INFECTION AND THERAPY: LESSONS FOR EXPLORATION DURING Mycobacterium tuberculosis INFECTION

The gut microbiota has emerged as a critical player in host health. Bacteroides fragilis is a prominent member of the gut microbiota within the phyla Bacteroidetes. This commensal bacterium produces unique capsular polysaccharides processed by antigen-presenting cells and activates CD4⁺ T cells to secrete inflammatory cytokines. Indeed, due to their immunomodulatory functions, B. fragilis and its capsular polysaccharide-A (PSA) are arguably the most explored single commensal microbiota/symbiotic factor. B. fragilis/PSA has been shown to protect against colitis, encephalomyelitis, colorectal cancer, pulmonary inflammation, and asthma. Here, we review (1) recent data on the immunomodulatory role of B. fragilis/PSA during viral infections and therapy, (2) B. fragilis PSA's dual ability to mediate pro-and anti-inflammatory processes, and the potential for exploring this unique characteristic during intracellular bacterial infections such as with Mycobacterium tuberculosis (3) discuss the protective roles of single commensal-derived probiotic species including B. fragilis in lung inflammation and respiratory infections that may provide essential cues for possible exploration of microbiota based/augmented therapies in tuberculosis (TB). Available data on the relationship between B. fragilis/PSA, the immune system, and disease suggest clinical relevance for developing B. fragilis into a next-generation probiotic or, possibly, the engineering of PSA into a potent carbohydrate-based vaccine.

Do Engineered Nanomaterials Affect Immune Responses by Interacting With Gut Microbiota?

Engineered nanomaterials (ENMs) have been widely exploited in several industrial domains as well as our daily life, raising concern over their potential adverse effects. While in general ENMs do not seem to have detrimental effects on immunity or induce severe inflammation, their indirect effects on immunity are less known. In particular, since the gut microbiota has been tightly associated with human health and immunity, it is possible that ingested ENMs could affect intestinal immunity indirectly by modulating the microbial community composition and functions. In this perspective, we provide a few pieces of evidence and discuss a possible link connecting ENM exposure, gut microbiota and host immune response. Some experimental works suggest that excessive exposure to ENMs could reshape the gut microbiota, thereby modulating the epithelium integrity and the inflammatory state in the intestine. Within such microenvironment, numerous microbiota-derived components, including but not limited to SCFAs and LPS, may serve as important effectors responsible of the ENM effect on intestinal immunity. Therefore, the gut microbiota is implicated as a crucial regulator of the intestinal immunity upon ENM exposure. This calls for including gut microbiota analysis within future work to assess ENM biocompatibility and immunosafety. This also calls for refinement of future studies that should be designed more elaborately and realistically to mimic the human exposure situation.

Rotundic acid ameliorates non-alcoholic steatohepatitis via SREBP-1c/ SCD1 signaling pathway and modulating gut microbiota

Non-alcoholic steatohepatitis (NASH) is a devastating form of non-alcoholic fatty liver disease (NAFLD) with distinguished hallmarks of steatosis and inflammation. Rotundic acid (RA) is a natural pentacyclic triterpene compound extracted from the bank of Ilex rotunda Thunb with a wide range of biological activities. The aim of the study is to evaluate the pharmacological effect and action mechanism of RA on NASH in vitro and in vivo. RA has weak lipid lowering ability in rat primary hepatocytes, significantly decreases serum LDL level, hepatic TG and TC levels and lipid droplets, reduces NAS compared with the NASH group, and alleviates hepatic inflammation. RA also enhances the recovery of intestinal bacterial community and intestinal-derived short-chain fatty acid caused by high food diet (HFD). Further investigation shows that RA protects against HFD-induced NASH via downregulating the expression of SREBP-1c/SCD1 signaling pathway and improving gut microbiota. These findings imply that RA might be helpful for the alleviation of NASH.

The role of microbiota and enteroendocrine cells in maintaining homeostasis in the human digestive tract

The microbiota is a heterogeneous ecosystem consisting of diverse microorganisms unique to an individual, playing a crucial role in maintaining human body homeostasis. The microbiota, as a suggested endocrine organ, is also capable of producing and regulating hormones, playing an important role in food processing, synthesis of vitamins, pathogen displacement, and influencing functions of distant systems and organs. The efficient connections between the brain and intestines and microbiota ensure the maintenance of the digestive tract homeostasis, with the bidirectional brain and gut axis playing an important role in the regulation of digestion. Enteroendocrine cells (EECs) are a fascinating example of highly specified cells scattered throughout the gastrointestinal (GI) tract. They produce and release signaling molecules (hormones), thus modulate homeostatic functions. EECs are believed to be crucial sensors of gut microbiota or/and microbial metabolites, secreting peptide hormones and cytokines in response to them. The diet, microbiota, and EECs are inevitably dependent on one another, thus together (nutrients, microbiota, enterohormones) affect metabolism. This manuscript reviews the role of various components of the brain-gut axis in digestive and absorption processes, as well as the maintenance of digestive tract homeostasis and the consequences of disturbances in the individual components of this axis.

Acetate decreases PVR/CD155 expression via PI3K/AKT pathway in cancer cells

In recent years, restoring anti-tumor immunity has garnered a growing interest in cancer treatment. As potential therapeutics, immune checkpoint inhibitors have demonstrated benefits in many clinical studies. Although various methods have been applied to suppress immune checkpoints to boost anti-tumor immunity, including the use of immune checkpoint inhibitors, there are still unmet clinical needs to improve the response rate of cancer treatment. Here, we show that acetate can suppress the expression of poliovirus receptor (PVR/CD155), a ligand for immune checkpoint, in colon cancer cells. We demonstrated that acetate treatment could enhance effector responses of CD8⁺ T cells by decreasing the expression of PVR/CD155 in cancer cells. We also found that acetate could reduce the expression of PVR/CD155 by deactivating the PI3K/AKT pathway. These results demonstrate that acetate-mediated expression of PVR/CD155 in cancer cells might potentiate the anti-tumor immunity in the microenvironment of cancer. Our findings indicate that maintaining particular acetate concentrations could be a complementary strategy in current cancer treatment.

Microbiome Metabolites and Thyroid Dysfunction

Thyroid diseases are common conditions that have a negative impact on the health of all populations. The literature sheds light on the differences in the composition of the intestinal microbiota in patients suffering from thyroid diseases compared to healthy individuals. The microbiome affects the proper functioning of the thyroid gland, and the existence of the gut–thyroid axis is discussed in the context of both thyroid diseases and intestinal dysbiosis. The purpose of this review is to describe associations between the microbiome and its metabolites and thyroid dysfunction. We try to explain the role of the microbiome in the metabolism of thyroid hormones and the impact of thyroid autoimmune diseases. In addition, we raise issues related to the influence of bacterial metabolites, such as short-chain fatty acids or secondary bile acids, in the functioning of the thyroid gland. Last but not least, we explored the interactions between the gut microbiota and therapeutics and supplements typically administered to patients with thyroid diseases.

Metabolites of intestinal microflora upregulate microRNA-200c-3p expression level to suppress airway epithelial inflammation via the IL6ST/JNK/STAT3 signaling pathway

Intestinal microfloras are involved in various types of cancer; however, there is a limited amount of research into the involvement of metabolites of intestinal microflora (MIM) in asthmatic airway epithelial cells (AECs). The present study was designed to reveal the functions and mechanisms of MIM in the asthmatic inflammation of AECs. House dust mite (HDM)-induced asthma cell models were established and treated with mouse MIM. A MTT assay was used to investigate AEC viability, while reverse transcription-quantitative PCR and western blot analysis were used to measure the expression levels of miR-200c-3p, IL6ST, JNK and STAT3 in asthmatic AECs. ELISA was used to measure the concentration of IL-5 and IL-6. Furthermore, the targeting relationship between microRNA(miR)-200c-3p and IL6ST was investigated using a luciferase reporter gene assay. Compared with normal human bronchial epithelial cells, HDM-induced AECs had lower expression level of miR-200c-3p, higher mRNA and protein expression levels of IL6ST and an increase in IL-5 and IL-6 concentration. Both MIM and miR-200c-3p mimics suppressed the secretion of IL-5 and L-6 and promoted the proliferation of HDM-induced AECs. MIM could also upregulate miR-200c-3p and downregulate IL6ST and proteins in the JNK/STAT3 pathway. IL6ST was found to be a downstream target of miR-200c-3p. Inhibition of miR-200c-3p reversed the suppression of asthmatic inflammation by MIM. In summary, MIM upregulated miR-200c-3p expression level to reduce the protein and mRNA expression levels of IL6ST and suppress its downstream JNK/STAT3 signaling pathway, therefore inhibiting the asthmatic inflammation of AECs.

Sublancin protects against methicillin-resistant Staphylococcus aureus infection by the combined modulation of innate immune response and microbiota

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen responsible for community and hospital bacterial infections. In the present study, the protective role of sublancin, an antimicrobial peptides, was explored in MRSA infection model. We report that sublancin directly induce macrophage migration through the chemotactic receptors. We further show that sublancin exhibits protection in a mouse MRSA infection model. This protection involved an immunomodulatory activity, but was blocked by depletion of monocyte/macrophages or neutrophils. Sublancin selectively up-regulates the levels of chemokines (C-X-C motif chemokine ligand 1, CXCL1 and monocyte chemoattractant protein-1, MCP-1) while reducing the production of pro-inflammatory cytokine (tumor necrosis factor-α, TNF-α). Meanwhile, sublancin regulated the microbiota composition disrupted by MRSA injection, increasing the abundance of Lactobacillus and decreasing that of Staphylococcus and Pseudomonas. Also, sublancin restored to normal levels of metabolic functional pathways, especially amino acid biosynthesis (e.g., branched amino acid, histidine and tryptophan), disrupted after injection, and this restoration was significantly correlated with neutrophils. These results demonstrates that sublancin stimulates the innate response and modulates the microbiota community to protect against MRSA infection.

Chronic Stress-Induced Depression and Anxiety Priming Modulated by Gut-Brain-Axis Immunity

Chronic stress manifests as depressive- and anxiety-like behavior while recurrent stress elicits disproportionate behavioral impairments linked to stress-induced immunological priming. The gut-brain-microbiota-axis is a promising therapeutic target for stress-induced behavioral impairments as it simultaneously modulates peripheral and brain immunological landscapes. In this study, a combination of probiotics and prebiotics, known as a synbiotic, promoted behavioral resilience to chronic and recurrent stress by normalizing gut microbiota populations and promoting regulatory T cell (Treg) expansion through modulation of ileal innate lymphoid cell (ILC)3 activity, an impact reflecting behavioral responses better than limbic brain region neuroinflammation. Supporting this conclusion, a multivariate machine learning model correlatively predicted a cross-tissue immunological signature of stress-induced behavioral impairment where the ileal Treg/T helper17 cell ratio associated to hippocampal chemotactic chemokine and prefrontal cortex IL-1β production in the context of stress-induced behavioral deficits. In conclusion, stress-induced behavioral impairments depend on the gut-brain-microbiota-axis and through ileal immune regulation, synbiotics attenuate the associated depressive- and anxiety-like behavior.

The Role of the Microbiota-Gut-Brain Axis in the Health and Illness Condition: A Focus on Alzheimer's Disease

Trillions of commensal microbes live in our body, the majority in the gut. This gut microbiota is in constant interaction with the homeostatic systems, the nervous, immune and endocrine systems, being fundamental for their appropriate development and function as well as for the neuroimmunoendocrine communication. The health state of an individual is understood in the frame of this communication, in which the microbiota-gut-brain axis is a relevant example. This bidirectional axis is constituted in early age and is affected by many environmental and lifestyle factors such as diet and stress, among others, being involved in the adequate maintenance of homeostasis and consequently in the health of each subject and in his/her rate of aging. For this, an alteration of gut microbiota, as occurs in a dysbiosis, and the associated gut barrier deterioration and the inflammatory state, affecting the function of immune, endocrine and nervous systems, in gut and in all the locations, is in the base of a great number of pathologies as those that involve alterations in the brain functions. There is an age-related deterioration of microbiota and the homeostatic systems due to oxi-inflamm-aging, and thus the risk of aging associated pathologies such as the neurodegenerative illness. Currently, this microbiota-gut-brain axis has been considered to have a relevant role in the pathogenesis of Alzheimer's disease and represents an important target in the prevention and slowdown of the development of this pathology. In this context, the use of probiotics seems to be a promising help.

PM2.5 induces intestinal damage by affecting gut microbiota and metabolites of rats fed a high-carbohydrate diet

PM_2.5 has a major impact on the gastrointestinal system, but the specific mechanism behind this action is not fully understood. Current studies have focused on the relationship between PM_2.5 and intestinal flora disorder, while ignoring the important influence of diet on gut microbes. In this study, SD rats were fed either a normal, high-fat, or high-carbohydrate diet for two months and exposed to PM_2.5 (7 mg/kg b.w.) by intratracheal instillation. The results showed that the body and kidney weights of the rats in the high-fat diet group were significantly increased relative to those with a normal diet, and changes in the intestinal microbes and metabolites induced by PM_2.5 were observed. Rats in the high-carbohydrate diet group had a significant response, and the diversity and richness indices of the flora were reduced (p < 0.05); additionally, intestinal Biffidobacterium and Lactobacillus were enriched, while many endogenous metabolites were found. Some amino acids derivatives and long-chain fatty acids were increased (p < 0.05). Both diet structure and PM_2.5 exposure can affect the composition of gut microbiota, and intestinal metabolites may be associated with cell membrane damage when a high-carbohydrate diet interacts with PM_2.5. This study considers multiple dietary factors to further supplement the evidence of intestinal damage via PM_2.5.

Acceleration of Small Intestine Development and Remodeling of the Microbiome Following Hyaluronan 35 kDa Treatment in Neonatal Mice

The beneficial effects of human milk suppressing the development of intestinal pathologies such as necrotizing enterocolitis in preterm infants are widely known. Human milk (HM) is rich in a multitude of bioactive factors that play major roles in promoting postnatal maturation, differentiation, and the development of the microbiome. Previous studies showed that HM is rich in hyaluronan (HA) especially in colostrum and early milk. This study aims to determine the role of HA 35 KDa, a HM HA mimic, on intestinal proliferation, differentiation, and the development of the intestinal microbiome. We show that oral HA 35 KDa supplementation for 7 days in mouse pups leads to increased villus length and crypt depth, and increased goblet and Paneth cells, compared to controls. We also show that HA 35 KDa leads to an increased predominance of Clostridiales Ruminococcaceae, Lactobacillales Lactobacillaceae, and Clostridiales Lachnospiraceae. In seeking the mechanisms involved in the changes, bulk RNA seq was performed on samples from the terminal ileum and identified upregulation in several genes essential for cellular growth, proliferation, and survival. Taken together, this study shows that HA 35 KDa supplemented to mouse pups promotes intestinal epithelial cell proliferation, as well as the development of Paneth cells and goblet cell subsets. HA 35 KDa also impacted the intestinal microbiota; the implications of these responses need to be determined.

The Interplay between Androgen and Gut Microbiota: Is There a Microbiota-Gut-Testis Axis

The gut microbiota, a large ecosystem interacting with the host, has been shown to affect the health and fitness of the host-microbial superorganism. Increasing evidence suggests that the gut microbiota communicates with distal organs of the host including the brain, liver, and muscle, as well as testis, through various complex mechanisms. So far, we know that the androgen can markedly remodel the gut microbiota and has initiated an interdisciplinary field termed "microgenderome." More recently, the gut microbiota has been found as a major regulator of androgen production and metabolism in turn and even could trespass the blood-testis barrier (BTB) to regulate spermatogenesis, which largely updates the current knowledge on male reproduction. In this review, we provided a brief overview of the context of the gender bias of diseases related to gut microbiota, the sex dimorphism of gut microbiota, and their relationships with androgen. We also summarized the known interaction between the testis and gut microbiota based on published animal studies and tentatively discussed the hypothesis of microbiota-gut-testis axis. Finally, we highlighted the opportunities and challenges underlying the ongoing research. This knowledge may extend our understanding of the role of gut microbiota in male health and microbiota-related diseases.

Binary Metabolic Phenotypes and Phenotype Diversity Metrics for the Functional Characterization of Microbial Communities

The profiling of 16S rRNA revolutionized the exploration of microbiomes, allowing to describe community composition by enumerating relevant taxa and their abundances. However, taxonomic profiles alone lack interpretability in terms of bacterial metabolism, and their translation into functional characteristics of microbiomes is a challenging task. This bottom-up approach minimally requires a reference collection of major metabolic traits deduced from the complete genomes of individual organisms, an accurate method of projecting these traits from a reference collection to the analyzed amplicon sequence variants (ASVs), and, ultimately, an approach to a microbiome-wide aggregation of predicted individual traits into physiologically relevant cumulative metrics to characterize and compare multiple microbiome samples. In this study, we extended a previously introduced computational approach for the functional profiling of complex microbial communities, which is based on the concept of binary metabolic phenotypes encoding the presence ("1") or absence ("0") of various measurable physiological properties in individual organisms that are termed phenotype carriers or non-carriers, respectively. Derived from complete genomes via metabolic reconstruction, binary phenotypes provide a foundation for the prediction of functional traits for each ASV identified in a microbiome sample. Here, we introduced three distinct mapping schemes for a microbiome-wide phenotype prediction and assessed their accuracy on the 16S datasets of mock bacterial communities representing human gut microbiome (HGM) as well as on two large HGM datasets, the American Gut Project and the UK twins study. The 16S sequence-based scheme yielded a more accurate phenotype predictions, while the taxonomy-based schemes demonstrated a reasonable performance to warrant their application for other types of input data (e.g., from shotgun metagenomics or qPCR). In addition to the abundance-weighted Community Phenotype Indices (CPIs) reflecting the fractional representation of various phenotype carriers in microbiome samples, we employ metrics capturing the diversity of phenotype carriers, Phenotype Alpha Diversity (PAD) and Phenotype Beta Diversity (PBD). In combination with CPI, PAD allows to classify the robustness of metabolic phenotypes by their anticipated stability in the face of potential environmental perturbations. PBD provides a promising approach for detecting the metabolic features potentially contributing to disease-associated metabolic traits as illustrated by a comparative analysis of HGM samples from healthy and Crohn's disease cohorts.

Effect of Vancomycin on the Gut Microbiome and Plasma Concentrations of Gut-Derived Uremic Solutes

Introduction

Declining renal function results in the accumulation of solutes normally excreted by healthy kidneys. Data suggest that some of the protein-bound solutes mediate accelerated cardiovascular disease. Many of the poorly dialyzable protein-bound uremic retention solutes are products of gut bacterial metabolism.

Methods

We performed a blinded-randomized controlled trial comparing the changes in plasma concentrations of a panel of protein-bound solutes and microbiome structure in response to the once-weekly oral administration of 250 mg of vancomycin or placebo over a period of 12 weeks in a cohort of stable patients with end-stage kidney disease. We also examined the pattern of recovery of the solutes and gut microbiome over 12 weeks of placebo administration following vancomycin.

Results

We enrolled 15 subjects. Ten subjects provided sufficient plasma and stool samples to permit us to examine the effect of vancomycin on plasma solute levels. We showed that a weekly dose of vancomycin resulted in a reduction in the plasma concentration of 7 colon-derived solutes. We described a significant effect of vancomycin on the microbiome structure with a decrease in alpha diversity and change in beta diversity. Multiple taxa decreased with vancomycin including genera Clostridium and Bacteroides. We demonstrated microbiome recovery after stopping vancomycin. However, recovery in the solutes was highly variable between subjects.

Conclusions

We demonstrated that microbiome suppression using vancomycin resulted in changes in multiple gut-derived uremic solutes. Future studies are needed to address whether reduction in those uremic solutes results in improvement of cardiovascular outcomes in ESKD patients.

The Intestinal Microbiome Primes Host Innate Immunity against Enteric Virus Systemic Infection through Type I Interferon

Intestinal microbiomes are of vital importance in antagonizing systemic viral infection. However, very little literature has shown whether commensal bacteria play a crucial role in protecting against enteric virus systemic infection from the aspect of modulating host innate immunity. In the present study, we utilized an enteric virus, encephalomyocarditis virus (EMCV), to inoculate mice treated with phosphate-buffered saline (PBS) or given an antibiotic cocktail (Abx) orally or intraperitoneally to examine the impact of microbiota depletion on virulence and viral replication in vivo. Microbiota depletion exacerbated the mortality, neuropathogenesis, viremia, and viral burden in brains following EMCV infection. Furthermore, Abx-treated mice exhibited severely diminished mononuclear phagocyte activation and impaired type I interferon (IFN) production and expression of IFN-stimulated genes (ISG) in peripheral blood mononuclear cells (PBMC), spleens, and brains. With the help of fecal bacterial 16S rRNA sequencing of PBS- and Abx-treated mice, we identified a single commensal bacterium, Blautia coccoides, that can restore mononuclear phagocyte- and IFNAR (IFN-α/β receptor)-dependent type I IFN responses to restrict systemic enteric virus infection. These findings may provide insight into the development of novel therapeutics for preventing enteric virus infection or possibly alleviating clinical diseases by activating host systemic innate immune responses via respective probiotic treatment using B. coccoides.

Metabolic regulation on the immune environment of glioma through gut microbiota

The gut-brain axis has paved our way in understanding varieties of disease. The gut microbiota especially the bacterial population plays critical roles in immune system development and function. Glioma comprises 80 percent of malignant brain cancer and glioblastoma (GBM) is the most malignant kind. GBM has a reputation for its suppressive immune environment and poor patient prognosis. Moreover, altered metabolites from gut microbiota affect both systemic immune and central nervous system (CNS) immunity. Here we will focus on the crosstalk between gut microbiota and GBM, and further explore how this communication contributes to glioma initiation and development. Finally, we highlight the latest insights on the metabolic regulation of immunity through gut microbiota, which provides a promising therapeutic strategy for GBM.

Effects of Pediococcus pentosaceus LI05 on immunity and metabolism in germ-free rats

Many Pediococcus spp. have health-promoting benefits, and Pediococcus pentosaceus LI05 is one such species that was proved to be beneficial in previous studies. Our research aimed to determine the immune and metabolic effects of P. pentosaceus LI05 on germ-free rats. Germ-free rats were gavaged with P. pentosaceus LI05 suspensions (1 × 10⁹ CFU) for 2 weeks, and 3 weeks later, blood, spleen, intestine and liver samples were gathered for metabolome, intestine morphology, immunity, and transcriptomics analyses. Oral gavage of P. pentosaceus LI05 reduced the bodyweight of rats, which manifested as increased fecal carbohydrate concentrations, decreased intestinal fat intake and the hepatic fat synthesis gene expression, and accelerated fat-to-glycogen conversion. In addition, P. pentosaceus LI05 exhibited an anti-inflammatory ability, reducing serum proinflammatory cytokine levels and increasing intestinal subepidermal CD4⁺ cell levels. Furthermore, administration of P. pentosaceus LI05 increased the antimicrobial ability and enhanced the liver detoxification function. These results indicate that as a probiotic, P. pentosaceus LI05 ameliorates the hampered immune response of GF animals and improves the metabolism of fat and toxic substances.

Mechanism of deoxynivalenol mediated gastrointestinal toxicity: Insights from mitochondrial dysfunction

Deoxynivalenol (DON) is a mycotoxin predominantly produced by Fusarium genus, and widely contaminates cereals and associated products all over the world. The intestinal toxicity of DON is well established. However, intestinal homeostasis involves mitochondria, which has rarely been considered in the context of DON exposure. We summarize the recent knowledge on mitochondria as a key player in maintaining intestinal homeostasis based on their functions in cellular energy metabolism, redox homeostasis, apoptosis, intestinal immune responses, and orchestrated bidirectional cross-talk with gut microbe. In addition, we discuss the pivotal roles of mitochondrial dysfunction in the intestinal toxicity of DON and highlight promising mitochondrial-targeted therapeutics for DON-induced intestinal injury. Recent studies support that the intestinal toxicity of DON is attributed to mitochondrial dysfunction as a critical factor. Mitochondrial dysfunction characterized by failure in respiratory capacities and ROS overproduction has been demonstrated in intestinal cells exposed to DON. Perturbation of mitochondrial respiration leading to ROS accumulation is implicated in the early initiation of apoptosis. DON-induced intestinal inflammatory response is tightly linked to the mitochondrial ROS, whereas immunosuppression is intimately associated with mitophagy inhibition. DON perturbs the orchestrated bidirectional cross-talk between gut microbe and host mitochondria, which may be involved in DON-induced intestinal toxicity.

Metabolomic Profiles in the Intestine of Shrimp Infected by White Spot Syndrome Virus and Antiviral Function of the Metabolite Linoleic Acid in Shrimp

White spot syndrome virus (WSSV) is a threatening pathogenic virus in shrimp culture, and at present, no effective strategy can prevent and control the disease. Intestinal flora and its metabolites are important for the resistance of shrimp to lethal pathogenic viruses. However, the changes of metabolites in the shrimp intestines after WSSV infection remain unclear. We established an artificial oral infection method to infect shrimp with WSSV and analyzed the metabolites in intestinal content of shrimp by HPLC and tandem mass spectrometry. A total of 78 different metabolites and five different metabolic pathways were identified. Among them, we found that the content of linoleic acid, an unsaturated fatty acid, increased significantly after WSSV infection, indicating that linoleic acid might be involved in antiviral immunity in shrimp. Further study showed that, after oral administration of linoleic acid, WSSV proliferation decreased evidently in the shrimp, and survival rate of the shrimp increased significantly. Mechanical analysis showed that linoleic acid directly bound to WSSV virions and inhibited the viral replication. Linoleic acid also promoted the expression of antimicrobial peptides and IFN-like gene Vago5 by activating the ERK-NF-κB signaling pathway. Our results indicated that WSSV infection caused metabolomic transformation of intestinal microbiota and that the metabolite linoleic acid participated in the immune response against WSSV in shrimp.

The Oral-Gut-Brain AXIS: The Influence of Microbes in Alzheimer's Disease

Alzheimer's disease (AD) is one of the most frequently diagnosed neurodegenerative disorders worldwide and poses a major challenge for both affected individuals and their caregivers. AD is a progressive neurological disorder associated with high rates of brain atrophy. Despite its durable influence on human health, understanding AD has been complicated by its enigmatic and multifactorial nature. Neurofibrillary tangles and the deposition of amyloid-beta (Aβ) protein are typical pathological features and fundamental causes of cognitive impairment in AD patients. Dysbiosis of oral and gut microbiota has been reported to induce and accelerate the formation of Aβ plaques and neurofibrillary tangles. For instance, some oral microbes can spread to the brain through cranial nerves or cellular infections, which has been suggested to increase the risk of developing AD. Importantly, the interaction between intestinal microbiota and brain cells has been recognized as influencing the development of AD as well as other neurodegenerative diseases. In particular, the metabolites produced by certain intestinal microorganisms can affect the activity of microglia and further mediate neuroinflammation, which is a leading cause of neuronal necrosis and AD pathogenesis. Which pathogens and associated pathways are involved in the development and progression of AD remains to be elucidated; however, it is well-known that gut microbiota and their metabolites can affect the brain by both direct and indirect means. Understanding the specific mechanisms involved in the interaction between these pathogens and the nervous system is vital for the early intervention in AD. In this review, we aim to comprehensively discuss the possible mechanistic pathways underlying the oral-brain, the gut-brain and the oral-gut-brain associations.

Direct and indirect effects of microbiota-derived metabolites on neuroinflammation in multiple sclerosis

Multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) are highly influenced by changes in the microbiota and of microbiota-derived metabolites, including short chain fatty acids, bile acids, and tryptophan derivatives. This review will discuss the effects of microbiota-derived metabolites on neuroinflammation driven by central nervous system-resident cells and peripheral immune cells, and their influence on outcomes of EAE and MS.

The Anti-Inflammatory Effect and Mucosal Barrier Protection of Clostridium butyricum RH2 in Ceftriaxone-Induced Intestinal Dysbacteriosis

This study aimed at determining the beneficial effect of Clostridium butyricum (CB) RH2 on ceftriaxone-induced dysbacteriosis. To this purpose, BALB/c mice were exposed to ceftriaxone (400 mg/ml) or not (control) for 7 days, and administered a daily oral gavage of low-, and high-dose CB RH2 (10⁸ and 10¹⁰ CFU/ml, respectively) for 2 weeks. CB RH2 altered the diversity of gut microbiota, changed the composition of gut microbiota in phylum and genus level, decreased the F/B ratio, and decreased the pro-inflammatory bacteria (Deferribacteres, Oscillibacter, Desulfovibrio, Mucispirillum and Parabacteroides) in ceftriaxone-treated mice. Additionally, CB RH2 improved colonic architecture and intestinal integrity by improving the mucous layer and the tight junction barrier. Furthermore, CB RH2 also mitigated intestinal inflammation through decreasing proinflammatory factors (TNF-α and COX-2) and increasing anti-inflammatory factors (IL-10). CB RH2 had direct effects on the expansion of CD4⁺ T cells in Peyer’s patches (PPs) in vitro, which in turn affected their immune response upon challenge with ceftriaxone. All these data suggested that CB RH2 possessed the ability to modulate the intestinal mucosal and systemic immune system in limiting intestinal alterations to relieve ceftriaxone-induced dysbacteriosis.

Immune activation by microbiome shapes the colon mucosa: Comparison between healthy rat mucosa under conventional and germ-free conditions

Germ-free animals (GF) are those without a microbiome since birth. This particular biological model has become one of special interest with the growing evidence of importance of the microbiome in the life, development, adaptation, and immunity of humans and animals in the environments in which they live. Anatomical differences observed in GF compared with conventionally-reared animals (CV) has given rise to the question of the influence of commensal microflora on the development of structure and function (even immunological) of the bowel. Only recently, thanks to achievements in microscopy and associated methods, structural differences can be better evaluated and put in perspective with the immunological characteristics of GF vs. CV animals. This study, using a GF rat model, describes for the first time the possible influence that the presence of commensal microflora, continuously stimulating mucosal immunity, has on the collagen scaffold organization of the colon mucosa. Significant differences were found between CV and GF mucosa structure with higher complexity in the CV rats associated to a more activated immune environment. The immunological data suggest that, in response to the presence of a microbiome, an effective homeostatic regulation in developed by the CV rats in healthy conditions to avoid inflammation and maintain cytokine levels near the spontaneous production found in the GF animals. The results indicated that collagen scaffold adapted to the immune microenvironment; therefore, it is apparent that the microbiome was able to condition the structure of the colon mucosa.

Complete genome sequencing of Peyer's patches-derived Lactobacillus taiwanensis CLG01, a potential probiotic with antibacterial and immunomodulatory activity

Background

The genus Lactobacillus is an important component of the gastrointestinal tract of human and animals and commonly considered as probiotic. L. taiwanensis has long been proposed to be a probiotic whereas understanding on this species is still in its infancy. Genomic information of L. taiwanensis is fairly limited. Extensive characterization of its beneficial traits is needed.

Results

A new strain CLG01 of L. taiwanensis was isolated from mouse Peyer’s patches. We established its probiotic profile through in vitro experiments. Complete genome of this strain was also sequenced and analyzed. L. taiwanensis CLG01 showed robust tolerance to acid and a degree of tolerance to bile salt with a promising antibacterial activity against a broad spectrum of pathogenic bacteria. In vitro treatment of mouse RAW 264.7 macrophage cells with heat-killed bacteria and bacterial supernatant of L. taiwanensis CLG01 resulted in enhancement of immune responses and upregulated expression of TNF-α and IL-6. The strain CLG01 also increased the IL-10 production of macrophages when co-treated with lipopolysaccharide (LPS). Complete genome of L. taiwanensis CLG01 contained a 1.89 Mb chromosome and two plasmids. Further genomic analysis revealed the presence of genes related to its resistance to different stresses and the beneficial effects mentioned above. Moreover, biosynthetic gene clusters (BGCs) encoding antimicrobial peptides, like bacteriocin, linear azol(in)e-containing peptide (LAP) and lanthipeptide, were also identified in the genome of L. taiwanensis CLG01.

Conclusions

L. taiwanensis CLG01, isolated from mouse Peyer’s patches, is the first L. taiwanensis strain with both phenotypes and genotypes systematically studied. These preliminary data confirmed the role of L. taiwanensis CLG01 as a potential probiotic candidate with antibacterial and immunomodulatory activity, which provide insight for further investigation to this species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02127-z.

Leptin Receptor q223r Polymorphism Influences Clostridioides difficile Infection-Induced Neutrophil CXCR2 Expression in an Interleukin-1β Dependent Manner

Neutrophils are key first-responders in the innate immune response to C. difficile infection (CDI) and play a central role in disease pathogenesis. Studies have clearly shown that tissue neutrophil numbers need to be tightly regulated for optimal CDI outcomes: while excessive colonic neutrophilia is associated with severe CDI, neutrophil depletion also results in worse outcomes. However, the biological mechanisms that control CDI-induced neutrophilia remain poorly defined. C-X-C chemokine receptor 2 (CXCR2) is a chemotactic receptor that is critical in neutrophil mobilization from bone marrow to blood and tissue sites. We have previously reported that a single nucleotide polymorphism (SNP) in leptin receptor (LEPR), present in up to 50% of people, influenced CDI-induced neutrophil CXCR2 expression and tissue neutrophilia. Homozygosity for mutant LEPR (i.e. RR genotype) was associated with higher CXCR2 expression and more tissue neutrophils. Here, we investigated the biological mechanisms that regulate neutrophil CXCR2 expression after CDI, and the influence of host genetics on this process. Our data reveal that: a) CXCR2 plays a key role in CDI-induced neutrophil extravasation from blood to colonic tissue; b) plasma from C. difficile-infected mice upregulated CXCR2 on bone marrow neutrophils; c) plasma from C. difficile-infected RR mice induced a higher magnitude of CXCR2 upregulation and had more IL-1β; and d) IL-1β neutralization reduced CXCR2 expression on bone marrow and blood neutrophils and their subsequent accrual to colonic tissue. In sum, our data indicate that IL-1β is a key molecular mediator that communicates between gastro-intestinal tract (i.e. site of CDI) and bone marrow (i.e. primary neutrophil reservoir) and regulates the intensity of CDI-induced tissue neutrophilia by modulating CXCR2 expression. Further, our studies highlight the importance of host genetics in affecting these innate immune responses and provide novel insights into the mechanisms by which a common SNP influences CDI-induced neutrophilia.

Linkage between the intestinal microbiota and residual feed intake in broiler chickens

Background

Intestinal microbiota plays a key role in nutrient digestion and utilization with a profound impact on feed efficiency of livestock animals. However, the intestinal microbes that are critically involved in feed efficiency remain elusive.

Methods

To identify intestinal bacteria associated with residual feed intake (RFI) in chickens, male Cobb broiler chicks were individually housed from day 14 to day 35. Individual RFI values were calculated for 56 chickens. Luminal contents were collected from the ileum, cecum, and cloaca of each animal on day 35. Bacterial DNA was isolated and subjected to 16S rRNA gene sequencing. Intestinal microbiota was classified to the feature level using Deblur and QIIME 2. High and low RFI groups were formed by selecting 15 and 17 chickens with the most extreme RFI values for subsequent LEfSe comparison of the difference in the microbiota. Spearman correlation analysis was further performed to identify correlations between the intestinal microbiota composition and RFI.

Results

No significant difference in evenness, richness, and overall diversity of the microbiota in the ileum, cecum, or cloaca was observed between high and low RFI chickens. However, LEfSe analysis revealed a number of bacterial features being differentially enriched in either high or low RFI chickens. Spearman correlation analysis further identified many differentially enriched bacterial features to be significantly correlated with RFI (P < 0.05). Importantly, not all short-chain fatty acid (SCFA) producers showed a positive association with RFI. While two novel members of Oscillibacter and Butyricicoccus were more abundant in low-RFI, high-efficiency chickens, several other SCFA producers such as Subdoligranulum variabile and two related Peptostreptococcaceae members were negatively associated with feed efficiency. Moreover, a few closely-related Lachnospiraceae family members showed a positive correlation with feed efficiency, while others of the same family displayed an opposite relationship.

Conclusions

Our results highlight the complexity of the intestinal microbiota and a need to differentiate the bacteria to the species, subspecies, and even strain levels in order to reveal their true association with feed efficiency. Identification of RFI-associated bacteria provides important leads to manipulate the intestinal microbiota for improving production efficiency, profitability, and sustainability of poultry production.

Different effects of probiotics and antibiotics on the composition of microbiota, SCFAs concentrations and FFAR2/3 mRNA expression in broiler chickens

AIMS

The aims of this study were to investigate the effects of probiotics and antibiotics on microbial composition, short chain fatty acids (SCFAs) concentration and free fatty acid receptor 2/3 (FFAR2/3) expression in boiler chickens.

METHODS AND RESULTS

A total of 150 1-day-old male broilers were randomly allocated into three groups, control (CON) group, probiotics (PB) group and antibiotics (ATB) group. Results indicated that PB improved the average body weight from 1 to 21 days and feed intake from 21 to 42 days (P < 0·05), while ATB improved the feed efficiency from 1 to 42 days (P < 0·05). Based on 16s rRNA sequencing, PB treatment increased the amount of kingdom bacteria, and the relative abundance of the main bacteria including acetate and butyrate producing bacteria of phylum Firmicutes, family Ruminococcaceae and genus Faecalibacterium. ATB treatment also increased the relative abundance of phylum Firmicutes, family Ruminococcaceae and Lachnospiraceae, however, it introduced some pathogenic bacteria, such as bacteria of family Rikenellaceae and Enterobacteriaceae. Gas chromatography and mass spectrometry (GC-MS) assay revealed that PB increased acetate and butyrate concentrations at both 21 and 42 days, and propionate at 42 days in the colorectum. Moreover qRT-PCR analysis showed PB treatment significantly activated the FFAR2/3 mRNA expressions. On the contrast, ATB treatment lowered the colorectal propionate at 21 days, and decreased acetate, propionate and butyrate concentrations at 42 days, accompanied with decreased FFAR2/3 mRNA expressions.

CONCLUSIONS

Compared to the CON birds, an enriched SCFAs producing bacteria with higher SCFAs contents and activated FFAR2/3 expressions are prominent features of PB birds. However, antibiotics treatment plays the reverse effect compared to PB treatment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study brings a significant idea that less SCFAs concentration may be another reason why the antibiotics inhibit the immune system development and immunity of the body.

Associations among Dietary Omega-3 Polyunsaturated Fatty Acids, the Gut Microbiota, and Intestinal Immunity

Omega-3 polyunsaturated fatty acids (omega-3 PUFAs), which are essential fatty acids that humans should obtain from diet, have potential benefits for human health. In addition to altering the structure and function of cell membranes, omega-3 PUFAs (docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), alpha-linolenic acid (ALA), and docosapentaenoic acid (DPA)) exert different effects on intestinal immune tolerance and gut microbiota maintenance. Firstly, we review the effect of omega-3 PUFAs on gut microbiota. And the effects of omega-3 PUFAs on intestinal immunity and inflammation were described. Furthermore, the important roles of omega-3 PUFAs in maintaining the balance between gut immunity and the gut microbiota were discussed. Additional factors, such as obesity and diseases (NAFLD, gastrointestinal malignancies or cancer, bacterial and viral infections), which are associated with variability in omega-3 PUFA metabolism, can influence omega-3 PUFAs–microbiome–immune system interactions in the intestinal tract and also play roles in regulating gut immunity. This review identifies several pathways by which the microbiota modulates the gut immune system through omega-3 PUFAs. Omega-3 supplementation can be targeted to specific pathways to prevent and alleviate intestinal diseases, which may help researchers identify innovative diagnostic methods.

Mucins, gut microbiota, and postbiotics role in colorectal cancer

An imbalance in the crosstalk between the host and gut microbiota affects the intestinal barrier function, which results in inflammatory diseases and colorectal cancer. The colon epithelium protects itself from a harsh environment and various pathogenic organisms by forming a double mucus layer, primarily comprising mucins. Recent studies are focusing on how dietary patterns alter the gut microbiota composition, which in turn regulates mucin expression and maintains the intestinal layers. In addition, modulation of gut microbiota by microbiotic therapy (involving fecal microbiota transplantation) has emerged as a significant factor in the pathologies associated with dysbiosis. Therefore, proper communication between host and gut microbiota via different dietary patterns (prebiotics and probiotics) is needed to maintain mucus composition, mucin synthesis, and regulation. Here, we review how the interactions between diet and gut microbiota and bacterial metabolites (postbiotics) regulate mucus layer functionalities and mucin expression in human health and disease.

Structure and predictive metabolic contribution of intestinal microbiota of Longfin yellowtail (Seriola rivoliana) juveniles in aquaculture systems

Seriola rivoliana intestinal microbiota (IM) was characterised under aquaculture conditions through 16S rRNA amplicon sequencing. Specimens of 30 days after hatching (DAH) were maintained in three tanks and fed under the same environmental conditions for characterisation 15 days prior to sampling. Three fish were randomly taken from each tank; total DNA extraction of the gut microbiota was performed to characterise microbial composition and its metabolic prediction. The V3 hypervariable region of the 16S rRNA was amplified and sequenced with Illumina pair-end technology. The prokaryotic components in the S. rivoliana intestine were dominated mainly by the phyla Proteobacteria, Firmicutes, Bacteroidetes, Cyanobacteria and Actinobacteria. No significant differences in beta diversity were detected in the three samples (tanks). However in alpha diversity, they were detected in juveniles of the same cohort within the same group, as exemplified by enrichment of certain bacterial groups, mainly of the Clostridia class, which were specific in each fish within the same tank. The metabolic prediction analyses suggested that S. rivoliana IM contribute to the metabolism of amino acids, carbohydrates, lipids, and immune system. This study provides the first IM characterisation under rearing conditions of S. rivoliana-a species with broad economic potential-and contributes to novel information for potential use of probiotics in future trials.

Interactions between host genetics and gut microbiota determine susceptibility to CNS autoimmunity

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system. The etiology of MS is multifactorial, with disease risk determined by genetics and environmental factors. An emerging risk factor for immune-mediated diseases is an imbalance in the gut microbiome. However, the identity of gut microbes associated with disease risk, their mechanisms of action, and the interactions with host genetics remain obscure. To address these questions, we utilized the principal autoimmune model of MS, experimental autoimmune encephalomyelitis (EAE), together with a genetically diverse mouse model representing 29 unique host genotypes, interrogated by microbiome sequencing and targeted microbiome manipulation. We identified specific gut bacteria and their metabolic functions associated with EAE susceptibility, implicating short-chain fatty acid metabolism as a key element conserved across multiple host genotypes. In parallel, we used a reductionist approach focused on two of the most disparate phenotypes identified in our screen. Manipulation of the gut microbiome by transplantation and cohousing demonstrated that transfer of these microbiomes into genetically identical hosts was sufficient to modulate EAE susceptibility and systemic metabolite profiles. Parallel bioinformatic approaches identified Lactobacillus reuteri as a commensal species unexpectedly associated with exacerbation of EAE in a genetically susceptible host, which was functionally confirmed by bacterial isolation and commensal colonization studies. These results reveal complex interactions between host genetics and gut microbiota modulating susceptibility to CNS autoimmunity, providing insights into microbiome-directed strategies aimed at lowering the risk for autoimmune disease and underscoring the need to consider host genetics and baseline gut microbiome composition.

Microbiota-Derived Short-Chain Fatty Acids Promote LAMTOR2-Mediated Immune Responses in Macrophages

ABSRTACTKlebsiella pneumoniae is a common cause of human-pneumonia-derived sepsis with high morbidity and mortality. The microbiota promotes and maintains host immune homeostasis. The mechanisms by which the gut microbiota affects the host defenses in the respiratory system systematically, however, remain poorly understood. Here, we show that gut microbiota depletion increases susceptibility to extracellular K. pneumoniae infections in terms of increased bacterial burdens in lung and decreased survival rates. Oral supplementation with gut microbiota-derived short-chain fatty acids (SCFAs), subsequently activating G protein-coupled receptor 43 (GPCR43), enhances a macrophage's capacity to phagocytose invading K. pneumoniae Furthermore, SCFAs and GPR43 increase macrophage bacterial clearance by upregulating LAMTOR2, which is further identified as an antibacterial effector and elucidated to facilitate phagosome-lysosome fusion and extracellular signal-regulated kinase (ERK) phosphorylation. Lastly, conditional ablation of Lamtor2 in macrophages decreases their antimicrobial activity, even though mice were pretreated with exogenous SCFA supplementation.IMPORTANCE These observations highlight that SCFAs promote macrophage elimination of K. pneumoniae via a LAMTOR2-dependent signal pathway and suggest that it is possible to intervene in K. pneumoniae pneumonia by targeting the gut microbiota.

Chitosan oligosaccharides attenuate loperamide-induced constipation through regulation of gut microbiota in mice

This study was designed to explore the improvement of chitosan oligosaccharides (COS) on constipation through regulation of gut microbiota. Here, we proved that COS treatment profoundly boosted intestinal motility, restrained inflammatory responses, improved water-electrolyte metabolism and prevented gut barrier damage in constipated mice induced by loperamide. By 16S rDNA gene sequencing, the disbalanced gut microbiota was observed in constipated mice, while COS treatment statistically reversed the abundance changes of several intestinal bacteria at either phylum, family and genus levels, which partly led to the balance in production of intestinal metabolites including bile acids, short-chain fatty acids and tryptophan catabolites. In addition, COS failed to relieve the constipation in mice with intestinal flora depletion, confirming the essentiality of gut microbiota in COS-initiated prevention against constipation. In summary, COS can ameliorate the development of loperamide-induced constipation in mice by remodeling the structure of gut microbial community.

MicroRNAs Regulate Intestinal Immunity and Gut Microbiota for Gastrointestinal Health: A Comprehensive Review

MicroRNAs are small non-coding RNAs regulating gene expression at the post-transcriptional level. The regulation of microRNA expression in the gut intestine is gradually recognized as one of the crucial contributors of intestinal homeostasis and overall health. Recent studies indicated that both the microRNAs endogenous in the gut intestine and exogenous from diets could play influential roles in modulating microbial colonization and intestinal immunity. In this review, we discuss the biological functions of microRNAs in regulating intestinal homeostasis by modulating intestinal immune responses and gut microbiota. We particularly focus on addressing the microRNA-dependent communication and interactions among microRNA, gut microbiota, and intestinal immune system. Besides, we also summarize the roles of diet-derived microRNAs in host-microbiome homeostasis and their benefits on intestinal health. A better understanding of the relationships among intestinal disorders, microRNAs, and other factors influencing intestinal health can facilitate the application of microRNA-based therapeutics for gastrointestinal diseases.

Amino Acid Metabolism in Rheumatoid Arthritis: Friend or Foe?

In mammals, amino acid metabolism has evolved to act as a critical regulator of innate and adaptive immune responses. Rheumatoid arthritis (RA) is the most common form of inflammatory arthropathy sustained by autoimmune responses. We examine here the current knowledge of tryptophan and arginine metabolisms and the main immunoregulatory pathways in amino acid catabolism, in both RA patients and experimental models of arthritis. We found that l-tryptophan (Trp) metabolism and, in particular, the kynurenine pathway would exert protective effects in all experimental models and in some, but not all, RA patients, possibly due to single nucleotide polymorphisms in the gene coding for indoleamine 2,3-dioxygenase 1 (IDO1; the enzyme catalyzing the rate-limiting step of the kynurenine pathway). The function, i.e., either protective or pathogenetic, of the l-arginine (Arg) metabolism in RA was less clear. In fact, although immunoregulatory arginase 1 (ARG1) was highly induced at the synovial level in RA patients, its true functional role is still unknown, possibly because of few available preclinical data. Therefore, our analysis would indicate that amino acid metabolism represents a fruitful area of research for new drug targets for a more effective and safe therapy of RA and that further studies are demanding to pursue such an important objective.

Intestinal Inflammation Alters the Expression of Hepatic Bile Acid Receptors Causing Liver Impairment

OBJECTIVES

The gut-liver axis has been recently investigated in depth in relation to intestinal and hepatic diseases. Key actors are bile acid (BA) receptors, as farnesoid-X-receptor (FXR), pregnane-X-receptor (PXR), and G-protein-coupled-receptor (GPCR; TGR5), that control a broad range of metabolic processes as well as inflammation and fibrosis. The present study aims to investigate the impact of intestinal inflammation on liver health with a focus on FXR, PXR, and TGR5 expression. The strategy to improve liver health by reducing gut inflammation is also considered. Modulation of BA receptors in the inflamed colonic tissues of inflammatory bowel disease (IBD) pediatric patients is analyzed.

METHODS

A dextran sodium sulphate (DSS) colitis animal model was built. Co-cultures with Caco2 and HepG2 cell lines were set up. Modulation of BA receptors in biopsies of IBD pediatric patients was assessed by real-time PCR and immunohistochemistry.

RESULTS

Histology showed inflammatory cell infiltration in the liver of DSS mice, where FXR and PXR were significantly decreased and oxidative stress was increased. Exposure of Caco2 to inflammatory stimuli resulted in the reduction of BA receptor expression in HepG2. Caco2 treatment with dipotassium glycyrrhizate (DPG) reduced these effects on liver cells. Inflamed colon of patients showed altered FXR, PXR, and TGR5 expression.

CONCLUSIONS

This study strongly suggests that gut inflammation affects hepatic cells by altering BA receptor levels as well as increasing the production of pro-inflammatory cytokines and oxidative stress. Hence, reducing gut inflammation is needed not only to improve the intestinal disease but also to protect the liver.

The Gut Microbiome as a Component of the Gut-Brain Axis in Cognitive Health

INTRODUCTION

The human microbiome, the microorganisms living in and on the body, plays a vital role in brain physiology and pathophysiology. The gut microbiome (GMB) has been identified as a link in the gut-brain axis moderating cognitive development and health.

OBJECTIVES

The objectives of this scoping review are to discuss mechanisms of the microbiome-gut-brain axis in cognition, review the existing literature on the GMB and cognition, and discuss implications for nursing research.

METHODS

We searched Pubmed using the terms "gut microbiome," "brain," and "cognition" and the terms "gut brain axis," "microbiome," and "cognition"; removed duplicates, studies not published in English, and unrelated publications; and added additional articles identified through references. We retained the 85 most relevant publications for this review.

RESULTS

Common themes in the current literature include GMB components; interactions on cognitive development; effects of GMB-gut-brain interactions on cognition, mild cognitive impairment and Alzheimer's disease; effects of GMB interactions with physiologic stress on cognition in critical care; and GMB modification for improved cognition. Review of the literature on each of these topics reveals multiple theoretical mechanisms of action for GMB-gut-brain interaction that modify cognitive development and function across the lifespan.

DISCUSSION

GMB components and dysbiosis have been implicated in many cognitive states, and specific microbiota constituents contribute to cognitive development, stability, and impairment. The study of these interactions is relevant to nursing research as it addresses the holistic human experience and microbiome constituents are modifiable, facilitating translation into the clinical setting.

Vitamin D and the Host-Gut Microbiome: A Brief Overview

There is a growing body of evidence for the effects of vitamin D on intestinal host-microbiome interactions related to gut dysbiosis and bowel inflammation. This brief review highlights the potential links between vitamin D and gut health, emphasizing the role of vitamin D in microbiological and immunological mechanisms of inflammatory bowel diseases. A comprehensive literature search was carried out in PubMed and Google Scholar using combinations of keywords "vitamin D," "intestines," "gut microflora," "bowel inflammation". Only articles published in English and related to the study topic are included in the review. We discuss how vitamin D (a) modulates intestinal microbiome function, (b) controls antimicrobial peptide expression, and (c) has a protective effect on epithelial barriers in the gut mucosa. Vitamin D and its nuclear receptor (VDR) regulate intestinal barrier integrity, and control innate and adaptive immunity in the gut. Metabolites from the gut microbiota may also regulate expression of VDR, while vitamin D may influence the gut microbiota and exert anti-inflammatory and immune-modulating effects. The underlying mechanism of vitamin D in the pathogenesis of bowel diseases is not fully understood, but maintaining an optimal vitamin D status appears to be beneficial for gut health. Future studies will shed light on the molecular mechanisms through which vitamin D and VDR interactions affect intestinal mucosal immunity, pathogen invasion, symbiont colonization, and antimicrobial peptide expression.

Transcriptomic microRNA Profiling of Dendritic Cells in Response to Gut Microbiota-Secreted Vesicles

The interconnection between nutrients, metabolites and microbes is a key factor governing the healthy/pathological status of an individual. Thus, microbiota-based research is essential in order to better understand human health and nutrition. Gut bacteria release membrane vesicles (MVs) as an intercellular communication mechanism that allows the direct delivery of factors that prime the host’s innate immune system. We have previously shown that MVs from intestinal E. coli activate dendritic cells (DCs) in a strain-specific manner. To gain insights into the regulatory mechanisms involved, here, we have used an RNA deep sequencing approach to identify differentially expressed miRNAs (microRNAs) in DCs which are challenged by the MVs of the probiotic Nissle 1917 (EcN) or the commensal ECOR12. MicroRNAs are post-transcriptional regulatory mediators that permit the fine tuning of signaling pathways. This approach allowed the identification of a common set of miRNAs which are modulated by MVs from both strains and miRNAs which are differentially expressed in response to EcN or ECOR12 MVs. Based on the differential expression of the target genes and subsequent validation experiments, we correlated some of the selected miRNAs with the reported cytokine profile and specific T cell responses. As far as we know, this is the first study to analyze the regulation of miRNAs in DCs by MVs released by gut microbiota.

Modulation of Anti-Tumour Immune Responses by Probiotic Bacteria

There is a growing amount of evidence to support the beneficial role of a balanced intestinal microbiota, or distinct members thereof, in the manifestation and progression of malignant tumours, not only in the gastrointestinal tract but also in distant tissues as well. Intriguingly, bacterial species have been demonstrated to be indispensable modulatory agents of widely-used immunotherapeutic or chemotherapeutic regiments. However, the exact contribution of commensal bacteria to immunity, as well as to neoplasia formation and response to treatment, has not been fully elucidated, and most of the current knowledge acquired from animal models has yet to be translated to human subjects. Here, recent advances in understanding the interaction of gut microbes with the immune system and the modulation of protective immune responses to cancer, either naturally or in the context of widely-used treatments, are reviewed, along with the implications of these observations for future therapeutic approaches. In this regard, bacterial species capable of facilitating optimal immune responses against cancer have been surveyed. According to the findings summarized here, we suggest that strategies incorporating probiotic bacteria and/or modulation of the intestinal microbiota can be used as immune adjuvants, aiming to optimize the efficacy of cancer immunotherapies and conventional anti-tumour treatments.

Predicted Metabolic Pathway Distributions in Stool Bacteria in Very-Low-Birth-Weight Infants: Potential Relationships with NICU Faltered Growth

Many very-low-birth-weight (VLBW) infants experience growth faltering in early life despite adequate nutrition. Early growth patterns can affect later neurodevelopmental and anthropometric potentials. The role of the dysbiotic gut microbiome in VLBW infant growth is unknown. Eighty-four VLBW infants were followed for six weeks after birth with weekly stool collection. DNA was extracted from samples and the V4 region of the 16S rRNA gene was sequenced with Illumina MiSeq. A similar microbiota database from full-term infants was used for comparing gut microbiome and predicted metabolic pathways. The class Gammaproteobacteria increased or remained consistent over time in VLBW infants. Out of 228 metabolic pathways that were significantly different between term and VLBW infants, 133 pathways were significantly lower in VLBW infants. Major metabolic differences in their gut microbiome included pathways involved in decreased glycan biosynthesis and metabolism, reduced biosynthetic capacity, interrupted amino acid metabolism, changes that could result in increased infection susceptibility, and many other system deficiencies. Our study reveals poor postnatal growth in a VLBW cohort who had dysbiotic gut microbiota and differences in predicted metabolic pathways compared to term infants. The gut microbiota in VLBW infants likely plays an important role in postnatal growth.

Can the microbiota predict response to systemic cancer therapy, surgical outcomes, and survival? The answer is in the gut

INTRODUCTION

The gut microbiota seems to play a key role in tumorigenesis, across various hallmarks of cancer. Recent evidence suggests its potential use as a biomarker predicting drug response and adding prognostic information, generally in the context of immuno-oncology.

AREAS COVERED

In this review, we focus on the modulating effects of gut microbiota dysbiosis on various anticancer molecules used in practice, including cytotoxic and immune-modulating agents, primarily immune-checkpoint inhibitors (ICI). Pubmed/Medline-based literature search was conducted to find potential original studies that discuss gut microbiota as a prognostic and predictive biomarker for cancer therapy. We also looked at the US ClinicalTrials.gov website to find additional studies particularly ongoing human clinical trials.

EXPERT COMMENTARY

Sequencing of stool-derived materials and tissue samples from cancer patients and animal models has shown a significant enrichment of various bacteria such as Fusobacterium nucleatum and Bacteroides fragilis were associated with resistant disease and poorer outcomes. Gut microbiota was also found to be associated with surgical outcomes and seems to play a significant role in anastomotic leak (ATL) after surgery mainly by collagen breakdown. However, this research field is just at the beginning and the current findings are not yet ready to change clinical practice.