Microbiota-activated PPAR-γ signaling inhibits dysbiotic Enterobacteriaceae expansion

An early-life microbiota metabolite protects against obesity by regulating intestinal lipid metabolism

The mechanisms by which the early-life microbiota protects against environmental factors that promote childhood obesity remain largely unknown. Using a mouse model in which young mice are simultaneously exposed to antibiotics and a high-fat (HF) diet, we show that Lactobacillus species, predominant members of the small intestine (SI) microbiota, regulate intestinal epithelial cells (IECs) to limit diet-induced obesity during early life. A Lactobacillus-derived metabolite, phenyllactic acid (PLA), protects against metabolic dysfunction caused by early-life exposure to antibiotics and a HF diet by increasing the abundance of peroxisome proliferator-activated receptor γ (PPAR-γ) in SI IECs. Therefore, PLA is a microbiota-derived metabolite that activates protective pathways in the small intestinal epithelium to regulate intestinal lipid metabolism and prevent antibiotic-associated obesity during early life.

The role of microbiome-based therapeutics for the reduction and prevention of antimicrobial-resistant organism colonization

The gut is host to a diverse array of microbiota that constitute a complex ecological system crucial to human physiology. Disruptors to the normal host microbiota, such as antimicrobials, can cause a loss of species diversity in the gut, reducing its ability to resist colonization by invading pathogens and potentially leading to colonization with antimicrobial resistant organisms (AROs). ARO negatively impact gut health by disrupting the usual heterogeneity of gut microbiota and have the potential to cause systemic disease. In recent years, fecal microbiota transplantation (FMT) has been increasingly explored in the management of specific disease states such as Clostridioides difficile infection (CDI). Promising data from management of CDI has led to considerable interest in understanding the role of therapeutics to restore the gut microbiota to a healthy state. This review aims to discuss key studies that highlight the current landscape, and explore existing clinical evidence, for the use of FMT and microbiome-based therapeutics in combating intestinal colonization with ARO. We also explore potential future directions of such therapeutics and discuss unaddressed needs in this field that merit further investigation.

Mitochondria of intestinal epithelial cells in depression: Are they at a crossroads of gut-brain communication?

The role of gut dysbiosis in depression is well established. However, recent studies have shown that gut microbiota is regulated by intestinal epithelial cell (IEC) mitochondria, which has yet to receive much attention. This review summarizes the recent developments about the critical role of IEC mitochondria in actively maintaining gut microbiota, intestinal metabolism, and immune homeostasis. We propose that IEC mitochondrial dysfunction alters gut microbiota composition, participates in cell fate, mediates oxidative stress, activates the peripheral immune system, causes peripheral inflammation, and transmits peripheral signals through the vagus and enteric nervous systems. These pathological alterations lead to brain inflammation, disruption of the blood-brain barrier, activation of the hypothalamic-pituitary-adrenal axis, activation of microglia and astrocytes, induction of neuronal loss, and ultimately depression. Furthermore, we highlight the prospect of treating depression through the mitochondria of IECs. These new findings suggest that the mitochondria of IECs may be a newly found important factor in the pathogenesis of depression and represent a potential new strategy for treating depression.

Gut microbiome and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent chronic liver disease globally and imposed a heavy economic burden on society and individuals. To date, the pathological process of NAFLD is not yet fully elucidated. Compelling evidences have demonstrated the pivotal role of gut microbiota in the pathogenesis of NAFLD, and gut dysbiosis has been commonly observed in patients with NAFLD. Gut dysbiosis impairs gut permeability, allowing the translocation of bacterial products such as lipopolysaccharides (LPS), short-chain fatty acids (SCFAs), and ethanol to the liver via portal blood flow. This review aimed to shed light on the underlying mechanisms by which gut microbiota influences the development and progression of NAFLD. In addition, the potential application of gut microbiome as a non-invasive diagnostic tool and a novel therapeutical target was reviewed.

Polysaccharides from Platycodon grandiflorus attenuates high-fat diet induced obesity in mice through targeting gut microbiota

The root of Platycodon grandiflorus (PG), abundant in soluble polysaccharides, has a long history in traditional Asian diets and herbal medicine due to its anti-inflammatory activity and anti-obesity effects. Our previous study was the first to establish a link between the beneficial effects of PG and changes in the gut microbiota, and suggested potential roles that the polysaccharide components play. However, more evidence was needed to understand the anti-obesity functions of polysaccharides from PG (PS) and their relationship with the regulation of the gut microbiota. In this study, we first performed an experiment to explore the anti-obesity activities of PS: Male C57BL/6 mice (six-weeks-old) were fed either a standard control diet (CON), or a high-fat diet (HFD) to induce obesity, or a HFD supplemented with PS (HFPS) for 8 weeks. Body weight and food intake were monitored throughout. Lipid metabolism were determined and related gene expression changes in adipose tissues were analyzed by RNA-seq. Amplicon sequencing of the bacterial 16 S rRNA gene was used to explore gut microbiota structure in fecal samples. Then, we performed the second experiment to explore whether the anti-obesity activities of PS were dependent on the regulation of the gut microbiota: Male C57BL/6 mice (six-weeks-old), treated with an antibiotic cocktail to reduce the gut microbial load, were fed either a HFD (A-HFD) or a HFPS (A-HFPS) diet for 8 weeks. Finally, we used in vitro fermentation experiments to verify the effects of PS on the growth and metabolic activities of the gut microbes. We found that PS significantly reduced HFD-induced weight gain and excessive fat accumulation, changed the expression of key genes involved in lipid metabolism, and attenuated HFD-induced changes in the gut microbiota. However, PS did not affect fat accumulation or lipid metabolism in the gut microbiota depleted mice. Overall, our results show that PS has significant effects on the gut microbiota in the mouse model, and the anti-obesity effects of PS are mediated via changes in the gut microbiota composition and metabolic activity.

Blocked conversion of Lactobacillus johnsonii derived acetate to butyrate mediates copper-induced epithelial barrier damage in a pig model

BACKGROUND

High-copper diets have been widely used to promote growth performance of pigs, but excess copper supplementation can also produce negative effects on ecosystem stability and organism health. High-copper supplementation can damage the intestinal barrier and disturb the gut microbiome community. However, the specific relationship between high-copper-induced intestinal damage and gut microbiota or its metabolites is unclear.

OBJECTIVE

Using fecal microbiota transplantation and metagenomic sequencing, responses of colonic microbiota to a high-copper diet was profiled. In addition, via comparison of specific bacteria and its metabolites rescue, we investigated a network of bacteria-metabolite interactions involving conversion of specific metabolites as a key mechanism linked to copper-induced damage of the colon.

RESULTS

High copper induced colonic damage, Lactobacillus extinction, and reduction of SCFA (acetate and butyrate) concentrations in pigs. LefSe analysis and q-PCR results confirmed the extinction of L. johnsonii. In addition, transplanting copper-rich fecal microbiota to ABX mice reproduced the gut characteristics of the pig donors. Then, L. johnsonii rescue could restore decreased SCFAs (mainly acetate and butyrate) and colonic barrier damage including thinner mucus layer, reduced colon length, and tight junction protein dysfunction. Given that acetate and butyrate concentrations exhibited a positive correlation with L. johnsonii abundance, we investigated how L. johnsonii exerted its effects by supplementing acetate and butyrate. L. johnsonii and butyrate administration but not acetate could correct the damaged colonic barrier. Acetate administration had no effects on butyrate concentration, indicating blocked conversion from acetate to butyrate. Furthermore, L. johnsonii rescue enriched a series of genera with butyrate-producing ability, mainly Lachnospiraceae NK4A136 group.

CONCLUSIONS

For the first time, we reveal the microbiota-mediated mechanism of high-copper-induced colonic damage in piglets. A high-copper diet can induce extinction of L. johnsonii which leads to colonic barrier damage and loss of SCFA production. Re-establishment of L. johnsonii normalizes the SCFA-producing pathway and restores colonic barrier function. Mechanistically, Lachnospiraceae NK4A136 group mediated conversion of acetate produced by L. johnsonii to butyrate is indispensable in the protection of colonic barrier function. Collectively, these findings provide a feasible mitigation strategy for gut damage caused by high-copper diets. Video Abstract.

Vegetarian Diets and Cardiovascular Risk Reduction: Pros

There is an ongoing need for public health interventions aimed at further mitigating the risk of cardiovascular disease (CVD) through changes in dietary patterns and other lifestyle habits. Plant-based diets (PBDs) are effective in reducing CVD risk factors, a benefit evidenced by the favorable cardio-metabolic profiles observed in vegetarians who abstain from consuming meat, fish, and poultry compared to omnivores. Numerous studies have demonstrated that PBDs, particularly when rich in high-quality plant foods such as whole grains, fruits, vegetables, and nuts, are associated with a lower risk of adverse cardiovascular outcomes. Herein, we briefly review the current evidence regarding the relationship between CVD and PBDs, as well as the potential underlying biological mechanisms.

Natural compounds targeting nuclear receptors for effective cancer therapy

Human nuclear receptors (NRs) are a family of forty-eight transcription factors that modulate gene expression both spatially and temporally. Numerous biochemical, physiological, and pathological processes including cell survival, proliferation, differentiation, metabolism, immune modulation, development, reproduction, and aging are extensively orchestrated by different NRs. The involvement of dysregulated NRs and NR-mediated signaling pathways in driving cancer cell hallmarks has been thoroughly investigated. Targeting NRs has been one of the major focuses of drug development strategies for cancer interventions. Interestingly, rapid progress in molecular biology and drug screening reveals that the naturally occurring compounds are promising modern oncology drugs which are free of potentially inevitable repercussions that are associated with synthetic compounds. Therefore, the purpose of this review is to draw our attention to the potential therapeutic effects of various classes of natural compounds that target NRs such as phytochemicals, dietary components, venom constituents, royal jelly-derived compounds, and microbial derivatives in the establishment of novel and safe medications for cancer treatment. This review also emphasizes molecular mechanisms and signaling pathways that are leveraged to promote the anti-cancer effects of these natural compounds. We have also critically reviewed and assessed the advantages and limitations of current preclinical and clinical studies on this subject for cancer prophylaxis. This might subsequently pave the way for new paradigms in the discovery of drugs that target specific cancer types.

Microbes, metabolites and muscle: Is the gut-muscle axis a plausible therapeutic target in Duchenne muscular dystrophy?

NEW FINDINGS

What is the topic of this review? The contribution of gut microbial signalling to skeletal muscle maintenance and development and identification of potential therapeutic targets in progressive muscle degenerative diseases such as Duchenne muscular dystrophy. What advances does it highlight? Gut microbe-derived metabolites are multifaceted signalling molecules key to muscle function, modifying pathways contributing to skeletal muscle wasting, making them a plausible target for adjunctive therapy in muscular dystrophy.

ABSTRACT

Skeletal muscle is the largest metabolic organ making up ∼50% of body mass. Because skeletal muscle has both metabolic and endocrine properties, it can manipulate the microbial populations within the gut. In return, microbes exert considerable influence on skeletal muscle via numerous signalling pathways. Gut bacteria produce metabolites (i.e., short chain fatty acids, secondary bile acids and neurotransmitter substrates) that act as fuel sources and modulators of inflammation, influencing host muscle development, growth and maintenance. The reciprocal interactions between microbes, metabolites and muscle establish a bidirectional gut-muscle axis. The muscular dystrophies constitute a broad range of disorders with varying disabilities. In the profoundly debilitating monogenic disorder Duchenne muscular dystrophy (DMD), skeletal muscle undergoes a reduction in muscle regenerative capacity leading to progressive muscle wasting, resulting in fibrotic remodelling and adipose infiltration. The loss of respiratory muscle in DMD culminates in respiratory insufficiency and eventually premature death. The pathways contributing to aberrant muscle remodelling are potentially modulated by gut microbial metabolites, thus making them plausible targets for pre- and probiotic supplementation. Prednisone, the gold standard therapy for DMD, drives gut dysbiosis, inducing a pro-inflammatory phenotype and leaky gut barrier contributing to several of the well-known side effects associated with chronic glucocorticoid treatment. Several studies have observed that gut microbial supplementation or transplantation exerts positive effects on muscle, including mitigating the side effects of prednisone. There is growing evidence in support of the potential for an adjunctive microbiota-directed regimen designed to optimise gut-muscle axis signalling, which could alleviate muscle wasting in DMD.

Gut microbiota bridges the iron homeostasis and host health

The gut microbiota acts as a symbiotic microecosystem that plays an indispensable role in the regulation of a number of metabolic processes in the host by secreting secondary metabolites and impacting the physiology and pathophysiology of numerous organs and tissues through the circulatory system. This relationship, referred to as the "gut-X axis", is associated with the development and progression of disorders, including obesity, fatty liver and Parkinson's disease. Given its importance, the gut flora is a vital research area for the understanding and development of the novel therapeutic approaches for multiple disorders. Iron is a common but necessary element required by both mammals and bacteria. As a result, iron metabolism is closely intertwined with the gut microbiota. The host's iron homeostasis affects the composition of the gut microbiota and the interaction between host and gut microbiota through various mechanisms such as nutrient homeostasis, intestinal peaceability, gut immunity, and oxidative stress. Therefore, understanding the relationship between gut microbes and host iron metabolism is not only of enormous significance to host health but also may offer preventative and therapeutic approaches for a number of disorders that impact both parties. In this review, we delve into the connection between the dysregulation of iron metabolism and dysbiosis of gut microbiota, and how it contributes to the onset and progression of metabolic and chronic diseases.

A microbial consortium alters intestinal Pseudomonadota and antimicrobial resistance genes in individuals with recurrent Clostridioides difficile infection

Intestinal colonization with pathogens and antimicrobial-resistant organisms (AROs) is associated with increased risk of infection. Fecal microbiota transplant (FMT) has successfully been used to cure recurrent Clostridioides difficile infection (rCDI) and to decolonize intestinal AROs. However, FMT has significant practical barriers to safe and broad implementation. Microbial consortia represent a novel strategy for ARO and pathogen decolonization, with practical and safety advantages over FMT. We undertook an investigator-initiated analysis of stool samples collected from previous interventional studies of a microbial consortium, microbial ecosystem therapeutic (MET-2), and FMT for rCDI before and after treatment. Our aim was to assess whether MET-2 was associated with decreased Pseudomonadota (Proteobacteria) and antimicrobial resistance gene (ARG) burden with similar effects to FMT. Participants were selected for inclusion if baseline stool had Pseudomonadota relative abundance ≥10%. Pre- and post-treatment Pseudomonadota relative abundance, total ARGs, and obligate anaerobe and butyrate-producer relative abundances were determined by shotgun metagenomic sequencing. MET-2 administration had similar effects to FMT on microbiome outcomes. The median Pseudomonadota relative abundance decreased by four logs after MET-2 treatment, a greater decrease than that observed after FMT. Total ARGs decreased, while beneficial obligate anaerobe and butyrate-producer relative abundances increased. The observed microbiome response remained stable over 4 months post-administration for all outcomes. IMPORTANCE Overgrowth of intestinal pathogens and AROs is associated with increased risk of infection. With the rise in antimicrobial resistance, new therapeutic strategies that decrease pathogen and ARO colonization in the gut are needed. We evaluated whether a microbial consortium had similar effects to FMT on Pseudomonadota abundances and ARGs as well as obligate anaerobes and beneficial butyrate producers in individuals with high Pseudomonadota relative abundance at baseline. This study provides support for a randomized, controlled clinical trial of microbial consortia (such as MET-2) for ARO decolonization and anaerobe repletion.

Formate oxidation in the intestinal mucus layer enhances fitness of Salmonella enterica serovar Typhimurium

Salmonella enterica serovar Typhimurium induces intestinal inflammation to create a niche that fosters the outgrowth of the pathogen over the gut microbiota. Under inflammatory conditions, Salmonella utilizes terminal electron acceptors generated as byproducts of intestinal inflammation to generate cellular energy through respiration. However, the electron donating reactions in these electron transport chains are poorly understood. Here, we investigated how formate utilization through the respiratory formate dehydrogenase-N (FdnGHI) and formate dehydrogenase-O (FdoGHI) contribute to gut colonization of Salmonella. Both enzymes fulfilled redundant roles in enhancing fitness in a mouse model of Salmonella-induced colitis, and coupled to tetrathionate, nitrate, and oxygen respiration. The formic acid utilized by Salmonella during infection was generated by its own pyruvate-formate lyase as well as the gut microbiota. Transcription of formate dehydrogenases and pyruvate-formate lyase was significantly higher in bacteria residing in the mucus layer compared to the lumen. Furthermore, formate utilization conferred a more pronounced fitness advantage in the mucus, indicating that formate production and degradation occurred predominantly in the mucus layer. Our results provide new insights into how Salmonella adapts its energy metabolism to the local microenvironment in the gut. IMPORTANCE Bacterial pathogens must not only evade immune responses but also adapt their metabolism to successfully colonize their host. The microenvironments encountered by enteric pathogens differ based on anatomical location, such as small versus large intestine, spatial stratification by host factors, such as mucus layer and antimicrobial peptides, and distinct commensal microbial communities that inhabit these microenvironments. Our understanding of how Salmonella populations adapt its metabolism to different environments in the gut is incomplete. In the current study, we discovered that Salmonella utilizes formate as an electron donor to support respiration, and that formate oxidation predominantly occurs in the mucus layer. Our experiments suggest that spatially distinct Salmonella populations in the mucus layer and the lumen differ in their energy metabolism. Our findings enhance our understanding of the spatial nature of microbial metabolism and may have implications for other enteric pathogens as well as commensal host-associated microbial communities.

Red cabbage juice-mediated gut microbiota modulation improves intestinal epithelial homeostasis and ameliorates colitis

Gut microbiota plays a crucial role in inflammatory bowel disease (IBD) and has therapeutic benefits. Thus, targeting the gut microbiota is a promising therapeutic approach for IBD treatment. We recently found that red cabbage juice (RCJ) ameliorates dextran sulfate sodium (DSS)-induced colitis in mice. However, the underlying mechanisms remain unknown. The current study investigated the modulation of gut microbiota in response to treatment with RCJ to ameliorate the DSS colitis. The initial results demonstrated that mice treated with DSS + RCJ showed increased body weight and decreased diarrhea and blood in feces compared to the DSS alone group. RCJ ameliorated colitis by regulating the intestinal barrier function by reducing the number of apoptotic cells, improving colonic protective mucin, and increasing tight junction protein in RCJ + DSS groups compared to the DSS group. Short-gun metagenomic analysis revealed significant enrichment of short-chain fatty acid (SCFAs)-producing bacteria (Butyrivibrio, Ruminococcaceae, Acetatifactor muris, Rosburia Sp. CAG:303 , Dorea Sp. 5-2) increased PPAR-© activation, leading to repression of the nuclear factor κB (NFκB) signaling pathway, thus decreasing the production of crucial inflammatory cytokines and chemokines in the RCJ + DSS groups compared to the DSS group. Pathway abundance analysis showed an increased abundance of the SCFA pathway, reduced histidine degradation ( Bacteroides sartorii, and Bacteroides caecimuris ), and LCFA production in the RCJ+DSS treated group, suggesting the promotion of good colonic health. Furthermore, increased T-reg (FOXP3+) cells in the colon were due to SCFAs produced by the gut microbiota, which was corroborated by an increase in IL-10, a vital anti-inflammatory cytokine. Thus, our study provides the first evidence that RCJ ameliorates colonic inflammation by modulating the gut microbiota.

Probiotic Escherichia coli Nissle 1917-derived outer membrane vesicles modulate the intestinal microbiome and host gut-liver metabolome in obese and diabetic mice

Introduction

Obesity and diabetes are common chronic metabolic disorders which can cause an imbalance of the intestinal flora and gut-liver metabolism. Several studies have shown that probiotics, including Escherichia coli Nissle 1917 (EcN), promote microbial balance and metabolic health. However, there are no studies on how EcN outer membrane vesicles (EcN-OMVs) influence the intestinal microflora and affect the metabolic disorders of obesity and diabetes.

Methods

In this study, we evaluated the effects of EcN-OMVs on high-fat diet (HFD)-induced obesity and HFD + streptozotocin (STZ)-induced diabetes.

Results

EcN-OMVs could reduce body weight, decrease blood glucose, and increase plasma insulin in obese mice. Similarly, EcN-OMVs treatment could modify the ratio of Firmicutes/Bacteroidetes in the gut, elevate intestinal short-chain fatty acid (SCFA)-producing flora, and influence the SCFA content of the intestine. Furthermore, the intestinal metabolites ornithine and fumaric acid, hepatic ω-6 unsaturated fatty acids, and SCFAs were significantly increased after administering EcN-OMVs.

Discussion

Overall, this study showed that EcN-OMVs might act as post-biotic agents that could modulate gut-liver metabolism and ameliorate the pathophysiology of obesity and diabetes.

FG-4592 relieves diabetic kidney disease severity by influencing metabolic profiles via gut microbiota reconstruction in both human and mouse models

Objective: Diabetic kidney disease (DKD) is one of the most prevalent complications of diabetes mellitus (DM) and is highly associated with devastating outcomes. Hypoxia-inducible factor (HIF), the main transcription factor that regulates cellular responses to hypoxia, plays an important role in regulating erythropoietin (EPO) synthesis. FG-4592 is the HIF stabilizer that is widely used in patients with renal anemia. We investigated the effect of FG-4592 on DKD phenotypes and the pharmacologic mechanism from the perspective of gut microbiota and systemic metabolism. Design: We collected the clinical data of 73 participants, including 40 DKD patients with combined renal anemia treated with FG-4592, and 33 clinical index-matched DKD patients without FG-4592 treatment from The First Affiliated Hospital of Zhengzhou University at the beginning and after a 3-6-month follow-up period. We established DKD mouse models treated by FG-4592 and performed fecal microbiota transplantation from FG-4592-treated DKD mice to investigate the effects of FG-4592 on DKD and to understand this mechanism from a microbial perspective. Untargeted metabolome-microbiome combined analysis was implemented to globally delineate the mechanism of FG-4592 from both microbial and metabolomic aspects. Result: DKD phenotypes significantly improved after 3-6 months of FG-4592 treatment in DKD patients combined with renal anemia, including a decreased level of systolic blood pressure, serum creatinine, and increased estimated glomerular infiltration rate. Such effects were also achieved in the DKD mouse model treated with FG-4592 and can be also induced by FG-4592-influenced gut microbiota. Untargeted plasma metabolomics-gut microbiota analysis showed that FG-4592 dramatically altered both the microbial and metabolic profiles of DKD mice and relieved DKD phenotypes via upregulating beneficial gut microbiota-associated metabolites. Conclusion: FG-4592 can globally relieve the symptoms of DKD patients combined with renal anemia. In the animal experiment, FG-4592 can reconstruct the intestinal microbial profiles of DKD to further upregulate the production of gut-associated beneficial metabolites, subsequently improving DKD phenotypes.

The alleviating effect of ellagic acid on DSS-induced colitis via regulating gut microbiomes and gene expression of colonic epithelial cells

The anti-inflammatory effect of ellagic acid (EA) and its possible underlying mechanism in dextran sulfate sodium (DSS)-induced mouse chronic colonic inflammation were studied. It was observed that EA administration significantly alleviated the colonic inflammation phenotypes, including decreasing the disease activity index (DAI), enhancing the body weight loss, and improving the shortened length of the colon and pathological damage of colon tissue. Additionally, EA reshaped the constitution of the gut microbiota by elevating the ratio of Bacteroidetes along with Bacteroides and Muribaculaceae, while decreasing the proportion of Firmicutes. The Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2) revealed that the metabolic function of the gut microbiota was also changed. Furthermore, mouse colon transcriptome analysis showed that the tight junction and peroxisome proliferator-activated receptor (PPAR) signaling pathways were activated and the expressions of related genes were upregulated after EA intervention. These results showed that EA could remodel the gut bacterial composition, change the intestinal epithelial cell gene expressions in mice, and consequently improve the colonic inflammatory symptoms.

Gut Microbiota and Critically Ill Patients: Immunity and Its Modulation via Probiotics and Immunonutrition

Critically ill patients have a hyper-inflammatory response against various offending injuries that can result in tissue damage, organ failure, and fatal prognosis. The origin of this detrimental, uncontrolled inflammatory cascade can be found also within our gut. In detail, one of the main actors is our gut microbiota with its imbalance, namely gut dysbiosis: learning about the microbiota's dysfunction and pathophysiology in the frame of critical patients is of crucial and emerging importance in the management of the systemic inflammatory response syndrome (SIRS) and the multiple organ dysfunction syndrome (MODS). Multiple pieces of evidence indicate that the bacteria that populate our gut efficiently modulate the immune response. Treatment and pretreatment with probiotics have shown promising preliminary results to attenuate systemic inflammation, especially in postoperative infections and ventilation performance. Finally, it is emerging how immunonutrition may exert a possible impact on the health status of patients in intensive care. Thus, this manuscript reviews evidence from the literature on gut microbiota composition, its derangement in critically ill patients, its pathophysiological role, and the described and emerging opportunities arising from its modulation.

Role of Hydrogen Sulfide in Inflammatory Bowel Disease

Hydrogen sulfide (H2S), originally known as toxic gas, has now attracted attention as one of the gasotransmitters involved in many reactions in the human body. H2S has been assumed to play a role in the pathogenesis of many chronic diseases, of which the exact pathogenesis remains unknown. One of them is inflammatory bowel disease (IBD), a chronic intestinal disease subclassified as Crohn's disease (CD) and ulcerative colitis (UC). Any change in the amount of H2S seems to be linked to inflammation in this illness. These changes can be brought about by alterations in the microbiota, in the endogenous metabolism of H2S and in the diet. As both too little and too much H2S drive inflammation, a balanced level is needed for intestinal health. The aim of this review is to summarize the available literature published until June 2023 in order to provide an overview of the current knowledge of the connection between H2S and IBD.

Exploring the Plasticity of Diet on Gut Microbiota and Its Correlation with Gut Health

Dietary habits have been proven to help alter the composition of gut microbiota, and exploring the impact of nutritional patterns on gut microbiota changes can help protect gut health. However, few studies have focused on the dietary impact on the gut microbiota over an experimental timeframe. In this study, 16S rRNA gene sequencing was employed to investigate the gut microbiota of mice under different dietary patterns, including AIN-93G diet (Control), high protein diet (HPD), high fiber diet (HFD), and switch diet (Switch). The alpha diversity of the HPD group significantly decreased, but HFD can restore this decline. During HPD, some genera were significantly upregulated (e.g., Feacalibaculum) and downregulated (e.g., Parabacteroides). However, after receiving HFD, other genera were upregulated (e.g., Akkermansia) and downregulated (e.g., Lactobacillus). In addition, the interaction between pathogenic bacteria was more pronounced during HPD, while the main effect was probiotics during HFD. In conclusion, the plasticity exhibited by the gut microbiota was subject to dietary influences, wherein disparate dietary regimens hold pivotal significance in upholding the well-being of the host. Therefore, our findings provide new ideas and references for the relationship between diets and gut microbiota.

Role of the gut microbiota in nutrient competition and protection against intestinal pathogen colonization

The human gut microbiota can restrict the growth of pathogens to prevent them from colonizing the intestine ('colonization resistance'). However, antibiotic treatment can kill members of the gut microbiota ('gut commensals') and reduce competition for nutrients, making these nutrients available to support the growth of pathogens. This disturbance can lead to the growth and expansion of pathogens within the intestine (including antibiotic-resistant pathogens), where these pathogens can exploit the absence of competitors and the nutrient-enriched gut environment. In this review, we discuss nutrient competition between the gut microbiota and pathogens. We also provide an overview of how nutrient competition can be harnessed to support the design of next-generation microbiome therapeutics to restrict the growth of pathogens and prevent the development of invasive infections.

High-fat diet-disturbed gut microbiota-colonocyte interactions contribute to dysregulating peripheral tryptophan-kynurenine metabolism

BACKGROUND

Aberrant tryptophan (Trp)-kynurenine (Kyn) metabolism has been implicated in the pathogenesis of human disease. In particular, populations with long-term western-style diets are characterized by an excess of Kyn in the plasma. Host-gut microbiota interactions are dominated by diet and are essential for maintaining host metabolic homeostasis. However, the role of western diet-disturbed gut microbiota-colonocyte interactions in Trp metabolism remains to be elucidated.

RESULTS

Here, 4-week-old mice were fed with a high-fat diet (HFD), representing a typical western diet, for 4 weeks, and multi-omics approaches were adopted to determine the mechanism by which HFD disrupted gut microbiota-colonocyte interplay causing serum Trp-Kyn metabolism dysfunction. Our results showed that colonocyte-microbiota interactions dominated the peripheral Kyn pathway in HFD mice. Mechanistically, persistent HFD-impaired mitochondrial bioenergetics increased colonic epithelial oxygenation and caused metabolic reprogramming in colonites to support the expansion of Proteobacteria in the colon lumen. Phylum Proteobacteria-derived lipopolysaccharide (LPS) stimulated colonic immune responses to upregulate the indoleamine 2,3-dioxygenase 1 (IDO1)-mediated Kyn pathway, leading to Trp depletion and Kyn accumulation in the circulation, which was further confirmed by transplantation of Escherichia coli (E.coli) indicator strains and colonic IDO1 depletion. Butyrate supplementation promoted mitochondrial functions in colonocytes to remodel the gut microbiota in HFD mice, consequently ameliorating serum Kyn accumulation.

CONCLUSIONS

Our results highlighted that HFD disrupted the peripheral Kyn pathway in a gut microbiota-dependent manner and that the continuous homeostasis of gut bacteria-colonocytes interplay played a central role in the regulation of host peripheral Trp metabolism. Meanwhile, this study provided new insights into therapies against western diet-related metabolic disorders. Video Abstract.

Gut microbial metabolites and its impact on human health

One of the primary methods by which the gut microbiome interacts with its host is through the interactions that occur through the production of the metabolites produced, either directly, or indirectly, through microbial metabolism. Decades of research has demonstrated that these metabolic products play a vital role in human health, either for its benefit or detriment. This review article highlights the main metabolites produced by the interactions between diet and the gut microbiome, bile acids and the gut microbiome, and products produced by the gut microbiome alone. Additionally, this article reviews the literature on the effects that these metabolites play on human health.

Murine Models of Salmonella Infection

The pathogen Salmonella enterica encompasses a range of bacterial serovars that cause intestinal inflammation and systemic infections in humans. Mice are a widely used infection model due to their relative simplicity and versatility. Here, we provide standardized protocols for culturing the prolific zoonotic pathogen S. enterica serovar Typhimurium for intragastric inoculation of mice to model colitis or systemic dissemination, along with techniques for direct extraintestinal infection. Furthermore, we present procedures for quantifying pathogen burden and for characterizing the immune response by analyzing tissue pathology, inflammatory markers, and immune cells from intestinal tissues. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Murine colitis model utilizing oral streptomycin pretreatment and oral S. Typhimurium administration Basic Protocol 2: Intraperitoneal injection of S. Typhimurium for modeling extraintestinal infection Support Protocol 1: Preparation of S. Typhimurium inoculum Support Protocol 2: Preparation of mixed S. Typhimurium inoculum for competitive infection Basic Protocol 3: Assessment of S. Typhimurium burden Support Protocol 3: Preservation and pathological assessment of S. Typhimurium-infected tissues Support Protocol 4: Measurement of inflammatory marker expression in intestinal tissues by qPCR Support Protocol 5: Preparation of intestinal content for inflammatory marker quantification by ELISA Support Protocol 6: Immune cell isolation from Salmonella-infected intestinal tissues.

Talk to Me-Interplay between Mitochondria and Microbiota in Aging

The existence of mitochondria in eukaryotic host cells as a remnant of former microbial organisms has been widely accepted, as has their fundamental role in several diseases and physiological aging. In recent years, it has become clear that the health, aging, and life span of multicellular hosts are also highly dependent on the still-residing microbiota, e.g., those within the intestinal system. Due to the common evolutionary origin of mitochondria and these microbial commensals, it is intriguing to investigate if there might be a crosstalk based on preserved common properties. In the light of rising knowledge on the gut-brain axis, such crosstalk might severely affect brain homeostasis in aging, as neuronal tissue has a high energy demand and low tolerance for according functional decline. In this review, we summarize what is known about the impact of both mitochondria and the microbiome on the host's aging process and what is known about the aging of both entities. For a long time, bacteria were assumed to be immortal; however, recent evidence indicates their aging and similar observations have been made for mitochondria. Finally, we present pathways by which mitochondria are affected by microbiota and give information about therapeutic anti-aging approaches that are based on current knowledge.

IEC-intrinsic IL-1R signaling holds dual roles in regulating intestinal homeostasis and inflammation

Intestinal epithelial cells (IECs) constitute a critical first line of defense against microbes. While IECs are known to respond to various microbial signals, the precise upstream cues regulating diverse IEC responses are not clear. Here, we discover a dual role for IEC-intrinsic interleukin-1 receptor (IL-1R) signaling in regulating intestinal homeostasis and inflammation. Absence of IL-1R in epithelial cells abrogates a homeostatic antimicrobial program including production of antimicrobial peptides (AMPs). Mice deficient for IEC-intrinsic IL-1R are unable to clear Citrobacter rodentium (C. rodentium) but are protected from DSS-induced colitis. Mechanistically, IL-1R signaling enhances IL-22R-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation in IECs leading to elevated production of AMPs. IL-1R signaling in IECs also directly induces expression of chemokines as well as genes involved in the production of reactive oxygen species. Our findings establish a protective role for IEC-intrinsic IL-1R signaling in combating infections but a detrimental role during colitis induced by epithelial damage.

Interaction of beta-glucans with gut microbiota: Dietary origins, structures, degradation, metabolism, and beneficial function

Beta-glucan (BG), a polysaccharide comprised of interfacing glucose monomers joined via beta-glycosidic linkages, can be defined as a type of dietary fiber with high specificity based on its interaction with the gut microbiota. It can induce similar interindividual microbiota responses, thereby having beneficial effects on the human body. In this paper, we review the four main sources of BG (cereals, fungi, algae, and bacteria) and their differences in structure and content. The interaction of BG with gut microbiota and the resulting health effects have been highlighted, including immune enhancement, regulation of serum cholesterol and insulin levels, alleviation of obesity and improvement of cognitive disorders. Finally, the application of BG in food products and its beneficial effects on the gut microbiota of consumers were discussed. Although some of the mechanisms of action remain unclear, revealing the beneficial functions of BG from the perspective of gut microbiota can help provide theoretical support for the development of diets that target the regulation of microbiota.

In Vivo Tissue Distribution of Microplastics and Systemic Metabolomic Alterations After Gastrointestinal Exposure

Global plastic use has consistently increased over the past century with several different types of plastics now being produced. Much of these plastics end up in oceans or landfills leading to a substantial accumulation of plastics in the environment. Plastic debris slowly degrades into microplastics (MPs) that can ultimately be inhaled or ingested by both animals and humans. A growing body of evidence indicates that MPs can cross the gut barrier and enter into the lymphatic and systemic circulation leading to accumulation in tissues such as the lungs, liver, kidney, and brain. The impacts of mixed MPs exposure on tissue function through metabolism remains largely unexplored. To investigate the impact of ingested MPs on target metabolomic pathways, mice were subjected to either polystyrene microspheres or a mixed plastics (5 µm) exposure consisting of polystyrene, polyethylene and the biodegradability and biocompatible plastic, poly-(lactic-co-glycolic acid). Exposures were performed twice a week for four weeks at a dose of either 0, 2, or 4 mg/week via oral gastric gavage. Our findings demonstrate that, in mice, ingested MPs can pass through the gut barrier, be translocated through the systemic circulation, and accumulate in distant tissues including the brain, liver, and kidney. Additionally, we report on the metabolomic changes that occur in the colon, liver and brain which show differential responses that are dependent on dose and type of MPs exposure. Lastly, our study provides proof of concept for identifying metabolomic alterations associated with MPs exposure and adds insight into the potential health risks that mixed MPs contamination may pose to humans.

Microbiota-mediated colonization resistance: mechanisms and regulation

A dense and diverse microbial community inhabits the gut and many epithelial surfaces. Referred to as the microbiota, it co-evolved with the host and is beneficial for many host physiological processes. A major function of these symbiotic microorganisms is protection against pathogen colonization and overgrowth of indigenous pathobionts. Dysbiosis of the normal microbial community increases the risk of pathogen infection and overgrowth of harmful pathobionts. The protective mechanisms conferred by the microbiota are complex and include competitive microbial-microbial interactions and induction of host immune responses. Pathogens, in turn, have evolved multiple strategies to subvert colonization resistance conferred by the microbiota. Understanding the mechanisms by which microbial symbionts limit pathogen colonization should guide the development of new therapeutic approaches to prevent or treat disease.

Altered gut microbiota in temporal lobe epilepsy with anxiety disorders

Introduction

Patients with epilepsy are particularly vulnerable to the negative effects of anxiety disorders. In particular, temporal lobe epilepsy with anxiety disorders (TLEA) has attracted more attention in epilepsy research. The link between intestinal dysbiosis and TLEA has not been established yet. To gain deeper insight into the link between gut microbiota dysbiosis and factors affecting TLEA, the composition of the gut microbiome, including bacteria and fungi, has been examined.

Methods

The gut microbiota from 51 temporal lobe epilepsy patients has been subjected to sequencing targeting 16S rDNA (Illumina MiSeq) and from 45 temporal lobe epilepsy patients targeting the ITS-1 region (through pyrosequencing). A differential analysis has been conducted on the gut microbiota from the phylum to the genus level.

Results

TLEA patients' gut bacteria and fungal microbiota exhibited distinct characteristics and diversity as evidenced by high-throughput sequencing (HTS). TLEA patients showed higher abundances of Escherichia-Shigella (genus), Enterobacterales (order), Enterobacteriaceae (family), Proteobacteria (phylum), Gammaproteobacteria (class), and lower abundances of Clostridia (class), Firmicutes, Lachnospiraceae (family), Lachnospirales (order), and Ruminococcus (genus). Among fungi, Saccharomycetales fam. incertae sedis (family), Saccharomycetales (order), Saccharomycetes (class), and Ascomycota (phylum) were significantly more abundant in TLEA patients than in patients with temporal lobe epilepsy but without anxiety. Adoption and perception of seizure control significantly affected TLEA bacterial community structure, while yearly hospitalization frequency affected fungal community structures in TLEA patients.

Conclusion

Here, our study validated the gut microbiota dysbiosis of TLEA. Moreover, the pioneering study of bacterial and fungal microbiota profiles will help in understanding the course of TLEA and drive us toward preventing TLEA gut microbiota dysbiosis.

Targeting PPARs for therapy of atherosclerosis: A review

Atherosclerosis, a chief pathogenic factor of cardiovascular disease, is associated with many factors including inflammation, dyslipidemia, and oxidative stress. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors and are widely expressed with tissue- and cell-specificity. They control multiple genes that are involved in lipid metabolism, inflammatory response, and redox homeostasis. Given the diverse biological functions of PPARs, they have been extensively studied since their discovery in 1990s. Although controversies exist, accumulating evidence have demonstrated that PPAR activation attenuates atherosclerosis. Recent advances are valuable for understanding the mechanisms of action of PPAR activation. This article reviews the recent findings, mainly from the year of 2018 to present, including endogenous molecules in regulation of PPARs, roles of PPARs in atherosclerosis by focusing on lipid metabolism, inflammation, and oxidative stress, and synthesized PPAR modulators. This article provides information valuable for researchers in the field of basic cardiovascular research, for pharmacologists that are interested in developing novel PPAR agonists and antagonists with lower side effects as well as for clinicians.

Modulation of Host-Microbe Metabolism by Cholera Toxin

In order for successful fecal-oral transmission, enteric bacterial pathogens have to successfully compete with the intestinal microbiota and reach high concentrations during infection. Vibrio cholerae requires cholera toxin (CT) to cause diarrheal disease, which is thought to promote the fecal-oral transmission of the pathogen. Besides inducing diarrheal disease, the catalytic activity of CT also alters host intestinal metabolism, which promotes the growth of V. cholerae during infection through the acquisition of host-derived nutrients. Furthermore, recent studies have found that CT-induced disease activates a niche-specific suite of V. cholerae genes during infection, some of which may be important for fecal-oral transmission of the pathogen. Our group is currently exploring the concept that CT-induced disease promotes the fecal-oral transmission of V. cholerae by modulating both host and pathogen metabolism. Furthermore, the role of the intestinal microbiota in pathogen growth and transmission during toxin-induced disease merits further investigation. These studies open the door to investigating whether other bacterial toxins also enhance pathogen growth and transmission during infection, which may shed light on the design of novel therapeutics for intervention or prevention of diarrheal diseases.

Dysregulation along the gut microbiota-immune system axis after oral exposure to titanium dioxide nanoparticles: A possible environmental factor promoting obesity-related metabolic disorders

Food additives are one major hallmark of ultra-processed food in the Western-diet, a food habit often associated with metabolic disorders. Among these additives, the whitener and opacifying agent titanium dioxide (TiO₂) raises public health issues due to the ability of TiO₂ nanoparticles (NPs) to cross biological barriers and accumulate in different systemic organs like spleen, liver and pancreas. However before their systemic passage, the biocidal properties of TiO₂ NPs may alter the composition and activity of the gut microbiota, which play a crucial role for the development and maintenance of immune functions. Once absorbed, TiO₂ NPs may further interact with immune intestinal cells involved in gut microbiota regulation. Since obesity-related metabolic diseases such as diabetes are associated with alterations in the microbiota-immune system axis, this raises questions about the possible involvement of long-term exposure to food-grade TiO₂ in the development or worsening of these diseases. The current purpose is to review the dysregulations along the gut microbiota-immune system axis after oral TiO₂ exposure compared to those reported in obese or diabetic patients, and to highlight potential mechanisms by which foodborne TiO₂ NPs may increase the susceptibility to develop obesity-related metabolic disorders.

Gut microbiota in colorectal cancer development and therapy

Colorectal cancer (CRC) is one of the commonest cancers globally. A unique aspect of CRC is its intimate association with the gut microbiota, which forms an essential part of the tumour microenvironment. Research over the past decade has established that dysbiosis of gut bacteria, fungi, viruses and Archaea accompanies colorectal tumorigenesis, and these changes might be causative. Data from mechanistic studies demonstrate the ability of the gut microbiota to interact with the colonic epithelia and immune cells of the host via the release of a diverse range of metabolites, proteins and macromolecules that regulate CRC development. Preclinical and some clinical evidence also underscores the role of the gut microbiota in modifying the therapeutic responses of patients with CRC to chemotherapy and immunotherapy. Herein, we summarize our current understanding of the role of gut microbiota in CRC and outline the potential translational and clinical implications for CRC diagnosis, prevention and treatment. Emphasis is placed on how the gut microbiota could now be better harnessed by developing targeted microbial therapeutics as chemopreventive agents against colorectal tumorigenesis, as adjuvants for chemotherapy and immunotherapy to boost drug efficacy and safety, and as non-invasive biomarkers for CRC screening and patient stratification. Finally, we highlight the hurdles and potential solutions to translating our knowledge of the gut microbiota into clinical practice.

Excess Dietary Sugar Alters Colonocyte Metabolism and Impairs the Proliferative Response to Damage

BACKGROUND & AIMS

The colonic epithelium requires continuous renewal by crypt resident intestinal stem cells (ISCs) and transit-amplifying (TA) cells to maintain barrier integrity, especially after inflammatory damage. The diet of high-income countries contains increasing amounts of sugar, such as sucrose. ISCs and TA cells are sensitive to dietary metabolites, but whether excess sugar affects their function directly is unknown.

METHODS

Here, we used a combination of 3-dimensional colonoids and a mouse model of colon damage/repair (dextran sodium sulfate colitis) to show the direct effect of sugar on the transcriptional, metabolic, and regenerative functions of crypt ISCs and TA cells.

RESULTS

We show that high-sugar conditions directly limit murine and human colonoid development, which is associated with a reduction in the expression of proliferative genes, adenosine triphosphate levels, and the accumulation of pyruvate. Treatment of colonoids with dichloroacetate, which forces pyruvate into the tricarboxylic acid cycle, restored their growth. In concert, dextran sodium sulfate treatment of mice fed a high-sugar diet led to massive irreparable damage that was independent of the colonic microbiota and its metabolites. Analyses on crypt cells from high-sucrose-fed mice showed a reduction in the expression of ISC genes, impeded proliferative potential, and increased glycolytic potential without a commensurate increase in aerobic respiration.

CONCLUSIONS

Taken together, our results indicate that short-term, excess dietary sucrose can directly modulate intestinal crypt cell metabolism and inhibit ISC/TA cell regenerative proliferation. This knowledge may inform diets that better support the treatment of acute intestinal injury.

Comprehensive Analysis of Microbiome, Metabolome, and Transcriptome Revealed the Mechanisms of Intestinal Injury in Rainbow Trout under Heat Stress

Global warming is one of the most common environmental challenges faced by cold-water fish farming. Intestinal barrier function, gut microbiota, and gut microbial metabolites are significantly altered under heat stress, posing serious obstacles to the healthy artificial culture of rainbow trout. However, the molecular mechanisms underlying intestinal injury in rainbow trout under heat stress remain unclear. In the present study, the optimal growth temperature for rainbow trout (16 °C) was used for the control group, and the maximum temperature tolerated by rainbow trout (24 °C) was used for the heat stress group, which was subjected to heat stress for 21 days. The mechanism of intestinal injury in rainbow trout under heat stress was explored by combining animal histology, 16S rRNA gene amplicon sequencing, ultra-high performance liquid chromatography-mass spectrometry, and transcriptome sequencing. The results showed that the antioxidant capacity of rainbow trout was enhanced under heat stress, the levels of stress-related hormones were significantly increased, and the relative expression of genes related to heat stress proteins was significantly increased, indicating that the heat stress model of rainbow trout was successfully established. Secondly, the intestinal tract of rainbow trout showed inflammatory pathological characteristics under heat stress, with increased permeability, activation of the inflammatory factor signaling pathway, and increased relative expression of inflammatory factor genes, suggesting that the intestinal barrier function was impaired. Thirdly, heat stress caused an imbalance of intestinal commensal microbiota and changes in intestinal metabolites in rainbow trout, which participated in the stress response mainly by affecting lipid metabolism and amino acid metabolism. Finally, heat stress promoted intestinal injury in rainbow trout by activating the peroxisome proliferator-activated receptor-α signaling pathway. These results not only expand the understanding of fish stress physiology and regulation mechanisms, but also provide a scientific basis for healthy artificial culture and the reduction of rainbow trout production costs.

Gut taste receptor type 1 member 3 is an intrinsic regulator of Western diet-induced intestinal inflammation

BACKGROUND

Long-term intake of a Western diet (WD), characterized by a high-fat content and sugary drinks, is hypothesized to contribute to the development of inflammatory bowel disease (IBD). Despite the identified clinical association, the molecular mechanisms by which dietary changes contribute to IBD development remain unknown. Therefore, we examined the influence of long-term intake of a WD on intestinal inflammation and the mechanisms by which WD intake affects IBD development.

METHODS

Mice fed normal diet or WD for 10 weeks, and bowel inflammation was evaluated through pathohistological and infiltrated inflammatory cell assessments. To understand the role of intestinal taste receptor type 1 member 3 (TAS1R3) in WD-induced intestinal inflammation, cultured enteroendocrine cells harboring TAS1R3, subjected to RNA interference or antagonist treatment, and Tas1r3-deficient mice were used. RNA-sequencing, flow cytometry, 16S metagenomic sequencing, and bioinformatics analyses were performed to examine the involved mechanisms. To demonstrate their clinical relevance, intestinal biopsies from patients with IBD and mice with dextran sulfate sodium-induced colitis were analyzed.

RESULTS

Our study revealed for the first time that intestinal TAS1R3 is a critical mediator of WD-induced intestinal inflammation. WD-fed mice showed marked TAS1R3 overexpression with hallmarks of serious bowel inflammation. Conversely, mice lacking TAS1R3 failed to exhibit inflammatory responses to WD. Mechanistically, intestinal transcriptome analysis revealed that Tas1r3 deficiency suppressed mTOR signaling, significantly increasing the expression of PPARγ (a major mucosal defense enhancer) and upregulating the expression of PPARγ target-gene (tight junction protein and antimicrobial peptide). The gut microbiota of Tas1r3-deficient mice showed expansion of butyrate-producing Clostridia. Moreover, an increased expression of host PPARγ-signaling pathway proteins was positively correlated with butyrate-producing microbes, suggesting that intestinal TAS1R3 regulates the relationship between host metabolism and gut microflora in response to dietary factors. In cultured intestinal cells, regulation of the TAS1R3-mTOR-PPARγ axis was critical for triggering an inflammatory response via proinflammatory cytokine production and secretion. Abnormal regulation of the axis was observed in patients with IBD.

CONCLUSIONS

Our findings suggest that the TAS1R3-mTOR-PPARγ axis in the gut links Western diet consumption with intestinal inflammation and is a potential therapeutic target for IBD.

5-ASA can functionally replace Clostridia to prevent a post-antibiotic bloom of Candida albicans by maintaining epithelial hypoxia

Antibiotic prophylaxis sets the stage for an intestinal bloom of Candida albicans , which can progress to invasive candidiasis in patients with hematologic malignancies. Commensal bacteria can reestablish microbiota-mediated colonization resistance after completion of antibiotic therapy, but they cannot engraft during antibiotic prophylaxis. Here we use a mouse model to provide a proof of concept for an alternative approach, which replaces commensal bacteria functionally with drugs to restore colonization resistance against C. albicans . Streptomycin treatment, which depletes Clostridia from the gut microbiota, disrupted colonization resistance against C. albicans and increased epithelial oxygenation in the large intestine. Inoculating mice with a defined community of commensal Clostridia species reestablished colonization resistance and restored epithelial hypoxia. Notably, these functions of commensal Clostridia species could be replaced functionally with the drug 5-aminosalicylic acid (5-ASA), which activates mitochondrial oxygen consumption in the epithelium of the large intestine. When streptomycin-treated mice received 5-ASA, the drug reestablished colonization resistance against C. albicans and restored physiological hypoxia in the epithelium of the large intestine. We conclude that 5-ASA treatment is a non-biotic intervention that restores colonization resistance against C. albicans without requiring the administration of live bacteria.

Sialic acid exacerbates gut dysbiosis-associated mastitis through the microbiota-gut-mammary axis by fueling gut microbiota disruption

BACKGROUND

Mastitis is one of the most severe diseases in humans and animals, especially on dairy farms. Mounting evidence indicates that gastrointestinal dysbiosis caused by induction of subacute ruminal acidosis (SARA) by high-grain diet consumption and low in dietary fiber is associated with mastitis initiation and development, however, the underlying mechanism remains unknown.

RESULTS

In the present study, we found that cows with SARA-associated mastitis have altered metabolic profiles in the rumen, with increased sialic acids level in particular. Consumption of sialic acid (SA) in antibiotic-treated mice, but not healthy mice, induced marked mastitis. SA treatment of antibiotic-treated mice also induced mucosal and systemic inflammatory responses, as evidenced by increased colon and liver injuries and several inflammatory markers. In addition, gut dysbiosis caused by antibiotic impaired gut barrier integrity, which was aggravated by SA treatment. SA potentiated serum LPS level caused by antibiotic treatment, leading to increased activation of the TLR4-NF-κB/NLRP3 pathways in the mammary gland and colon. Moreover, SA facilitated gut dysbiosis caused by antibiotic, and especially enhanced Enterobacteriaceae and Akkermansiaceae, which correlated with mastitis parameters. Fecal microbiota transplantation from SA-antibiotic-treated mice mimicked mastitis in recipient mice. In vitro experiments showed that SA prompted Escherichia coli growth and virulence gene expression, leading to higher proinflammatory cytokine production in macrophages. Targeting the inhibition of Enterobacteriaceae by sodium tungstate or treating with the commensal Lactobacillus reuteri alleviated SA-facilitated mastitis. In addition, SARA cows had distinct ruminal microbial structure by the enrichment of SA-utilizing opportunistic pathogenic Moraxellaceae and the depletion of SA-utilizing commensal Prevotellaceae. Treating mice with the specific sialidase inhibitor zanamivir reduced SA production and Moraxellaceae abundance, and improved mastitis in mice caused by ruminal microbiota transplantation from cows with SARA-associated mastitis.

CONCLUSIONS

This study, for the first time, indicates that SA aggravates gut dysbiosis-induced mastitis by promoting gut microbiota disturbance and is regulated by commensal bacteria, indicating the important role of the microbiota-gut-mammary axis in mastitis pathogenesis and suggesting a potential strategy for mastitis intervention based on gut metabolism regulation. Video Abstract.

The potential of tailoring the gut microbiome to prevent and treat cardiometabolic disease

Despite milestones in preventive measures and treatment, cardiovascular disease (CVD) remains associated with a high burden of morbidity and mortality. The protracted nature of the development and progression of CVD motivates the identification of early and complementary targets that might explain and alleviate any residual risk in treated patients. The gut microbiota has emerged as a sentinel between our inner milieu and outer environment and relays a modified risk associated with these factors to the host. Accordingly, numerous mechanistic studies in animal models support a causal role of the gut microbiome in CVD via specific microbial or shared microbiota-host metabolites and have identified converging mammalian targets for these signals. Similarly, large-scale cohort studies have repeatedly reported perturbations of the gut microbial community in CVD, supporting the translational potential of targeting this ecological niche, but the move from bench to bedside has not been smooth. In this Review, we provide an overview of the current evidence on the interconnectedness of the gut microbiome and CVD against the noisy backdrop of highly prevalent confounders in advanced CVD, such as increased metabolic burden and polypharmacy. We further aim to conceptualize the molecular mechanisms at the centre of these associations and identify actionable gut microbiome-based targets, while contextualizing the current knowledge within the clinical scenario and emphasizing the limitations of the field that need to be overcome.

Complex regulatory effects of gut microbial short-chain fatty acids on immune tolerance and autoimmunity

Immune tolerance deletes or suppresses autoreactive lymphocytes and is established at multiple levels during the development, activation and effector phases of T and B cells. These mechanisms are cell-intrinsically programmed and critical in preventing autoimmune diseases. We have witnessed the existence of another type of immune tolerance mechanism that is shaped by lifestyle choices, such as diet, microbiome and microbial metabolites. Short-chain fatty acids (SCFAs) are the most abundant microbial metabolites in the colonic lumen and are mainly produced by the microbial fermentation of prebiotics, such as dietary fiber. This review focuses on the preventive and immunomodulatory effects of SCFAs on autoimmunity. The tissue- and disease-specific effects of dietary fiber, SCFAs and SCFA-producing microbes on major types of autoimmune diseases, including type I diabetes, multiple sclerosis, rheumatoid arthritis and lupus, are discussed. Additionally, their key regulatory mechanisms for lymphocyte development, tissue barrier function, host metabolism, immunity, autoantibody production, and inflammatory effector and regulatory lymphocytes are discussed. The shared and differential effects of SCFAs on different types and stages of autoimmune diseases are discussed.

Metabolite interactions between host and microbiota during health and disease: Which feeds the other?

Metabolites produced by the host and microbiota play a crucial role in how human bodies develop and remain healthy. Most of these metabolites are produced by microbiota and hosts in the digestive tract. Metabolites in the gut have important roles in energy metabolism, cellular communication, and host immunity, among other physiological activities. Although numerous host metabolites, such as free fatty acids, amino acids, and vitamins, are found in the intestine, metabolites generated by gut microbiota are equally vital for intestinal homeostasis. Furthermore, microbiota in the gut is the sole source of some metabolites, including short-chain fatty acids (SCFAs). Metabolites produced by microbiota, such as neurotransmitters and hormones, may modulate and significantly affect host metabolism. The gut microbiota is becoming recognized as a second endocrine system. A variety of chronic inflammatory disorders have been linked to aberrant host-microbiota interplays, but the precise mechanisms underpinning these disturbances and how they might lead to diseases remain to be fully elucidated. Microbiome-modulated metabolites are promising targets for new drug discovery due to their endocrine function in various complex disorders. In humans, metabolotherapy for the prevention or treatment of various disorders will be possible if we better understand the metabolic preferences of bacteria and the host in specific tissues and organs. Better disease treatments may be possible with the help of novel complementary therapies that target host or bacterial metabolism. The metabolites, their physiological consequences, and functional mechanisms of the host-microbiota interplays will be highlighted, summarized, and discussed in this overview.

Impact of childhood malnutrition and intestinal microbiota on MDR infections

The global burden of infection from MDR organisms (MDROs) disproportionately affects children residing in low- and middle-income countries and those with increased healthcare exposure. These populations have high rates of malnutrition making them increasingly vulnerable to infection with intestinal-derived pathogens. Malnourished children experience increased incidence of intestinal carriage and invasive infection with intestinal-derived MDROs including ESBL- and carbapenemase-producing Enterobacterales. However, the relationship between malnutrition and MDRO infection remains to be clearly defined. Impairment in intestinal barrier function and innate and adaptive immunity in malnutrition increases the risk for infection with intestinal-derived pathogens, and there is an increasing appreciation of the role of the intestinal microbiota in this process. Current evidence from human studies and animal models suggests that diet and the intestinal microbiota influence each other to determine nutritional status, with important implications for infectious outcomes. These insights are crucial to developing microbiota-targeted strategies aimed at reversing the growing burden of MDRO infections in malnourished populations worldwide.

Dysbiome and Its Role in Surgically Relevant Medical Disease

Several surgically relevant conditions are directly or indirectly influenced by the human microbiome. Different microbiomes may be found within, or along, specific organs and intra-organ variation is common. Such variations include those found along the course of the gastrointestinal tract as well as those on different regions of the skin. A variety of physiologic stressors and care interventions may derange the native microbiome. A deranged microbiome is termed a dysbiome and is characterized by decreased diversity and an increase in the proportion of potentially pathogenic organisms; the elaboration of virulence factors coupled with clinical consequences defines a pathobiome. Specific conditions such as Clostridium difficile colitis, inflammatory bowel disease, obesity, and diabetes mellitus are tightly linked to a dysbiome or pathobiome. Additionally, massive transfusion after injury appears to derange the gastrointestinal microbiome as well. This review explores what is known about these surgically relevant clinical conditions to chart how non-surgical interventions may support surgical undertakings or potentially reduce the need for operation.

Poultry gut health and beyond

Intestinal health is critically important for the digestion and absorption of nutrients and thus is a key factor in determining performance. Intestinal health issues are very common in high performing poultry lines due to the high feed intake, which puts pressure on the physiology of the digestive system. Excess nutrients which are not digested and absorbed in the small intestine may trigger dysbiosis, i.e. a shift in the microbiota composition in the intestinal tract. Dysbiosis as well as other stressors elicit an inflammatory response and loss of integrity of the tight junctions between the epithelial cells, leading to gut leakage. In this paper, key factors determining intestinal health and the most important nutritional tools which are available to support intestinal health are reviewed.

Leveraging the microbiome in the treatment of sepsis: potential pitfalls and new perspectives

PURPOSE OF REVIEW

This review aims to provide an overview of the current knowledge about microbiota-targeted therapies in sepsis, and calls out - despite recent negative studies - not to halt our efforts of translating these tools into regular medical practice.

RECENT FINDINGS

The intestinal microbiome has an important role in shaping our immune system, and microbiota-derived metabolites prime innate and adaptive inflammatory responses to infectious pathogens. Microbiota composition is severely disrupted during sepsis, which has been linked to increased risk of mortality and secondary infections. However, efforts of using these microbes as a tool for prognostic or therapeutic purposes have been unsuccessful so far, and recent trials studying the impact of probiotics in critical illness did not improve patient outcomes. Despite these negative results, researchers must continue their attempts of harnessing the microbiome to improve sepsis survival in patients with a high risk of clinical deterioration. Promising research avenues that could potentially benefit sepsis patients include the development of next-generation probiotics, use of the microbiome as a theranostic tool to direct therapy, and addressing the restoration of microbial communities following ICU discharge.

SUMMARY

Although research focused on microbiome-mediated therapy in critically ill patients has not yielded the results that were anticipated, we should not abandon our efforts to translate promising preclinical findings into clinical practice.

Microbiome in Behcet's syndrome

This review will discuss the current understanding of the role of microbiomes in Behcet's Syndrome, their influence on immune response and disease and potential future studies.

Altered intestinal microbiome and metabolome correspond to the clinical outcome of sepsis

BACKGROUND

The gut microbiome plays a pivotal role in the progression of sepsis. However, the specific mechanism of gut microbiota and its metabolites involved in the process of sepsis remains elusive, which limits its translational application.

METHOD

In this study, we used a combination of the microbiome and untargeted metabolomics to analyze stool samples from patients with sepsis enrolled at admission, then microbiota, metabolites, and potential signaling pathways that might play important roles in disease outcome were screened out. Finally, the above results were validated by the microbiome and transcriptomics analysis in an animal model of sepsis.

RESULTS

Patients with sepsis showed destruction of symbiotic flora and elevated abundance of Enterococcus, which were validated in animal experiments. Additionally, patients with a high burden of Bacteroides, especially B. vulgatus, had higher Acute Physiology and Chronic Health Evaluation II scores and longer stays in the intensive care unit. The intestinal transcriptome in CLP rats illustrated that Enterococcus and Bacteroides had divergent profiles of correlation with differentially expressed genes, indicating distinctly different roles for these bacteria in sepsis. Furthermore, patients with sepsis exhibited disturbances in gut amino acid metabolism compared with healthy controls; namely, tryptophan metabolism was tightly related to an altered microbiota and the severity of sepsis.

CONCLUSION

Alterations in microbial and metabolic features in the gut corresponded with the progression of sepsis. Our findings may help to predict the clinical outcome of patients in the early stage of sepsis and provide a translational basis for exploring new therapies.

Obesity and the microbiome in atopic dermatitis: Therapeutic implications for PPAR-γ agonists

Atopic dermatitis (AD) is an inflammatory skin disease characterized by epidermal barrier disruption, Th2 immune responses to skin allergens and microbial dysbiosis within affected lesions. Studies within the past decade have revealed genetic and environmental factors contributing to AD in children. Obesity is a metabolic disorder that often manifests early in life and is associated with reduced bacterial diversity, leading to skin colonization with lipophilic bacteria and intestinal colonization with pro-inflammatory species. These changes impair epithelial barriers and promote Th17 responses, which may worsen the severity of AD symptoms. While few studies have examined the contribution of microbiota in obesity-induced allergies, there is emerging evidence that PPAR-γ may be an effective therapeutic target. This review discusses the microbiome in pediatric AD, treatment with probiotics, how disease is altered by obesity and potential therapeutic effects of PPAR-γ agonists. While healthy skin contains diverse species adapted for specific niches, lesional skin is highly colonized with Staphylococcus aureus which perpetuates the inflammatory reaction. Treatments for AD should help to restore microbial diversity in the skin and intestine, as well as epithelial barrier function. Pre-clinical models have shown that PPAR-γ agonists can suppress Th17 responses, IgE production and mast cell function, while improving the epidermal barrier and microbial homeostasis. Overall, PPAR-γ agonists may be effective in a subset of patients with AD, and future studies should distinguish their metabolic and anti-inflammatory effects in order to inform the best therapies.

A review of probiotics in the treatment of autism spectrum disorders: Perspectives from the gut–brain axis

Autism spectrum disorders (ASD) are a class of neurodevelopmental conditions with a large societal impact. Despite existing evidence suggesting a link between ASD pathogenesis and gut–brain axis dysregulation, there is no systematic review of the treatment of probiotics on ASD and its associated gastrointestinal abnormalities based on the gut–brain axis. Therefore, we performed an analysis for ASD based on preclinical and clinical research to give a comprehensive synthesis of published evidence of a potential mechanism for ASD. On the one hand, this review aims to elucidate the link between gastrointestinal abnormalities and ASD. Accordingly, we discuss gut microbiota dysbiosis regarding gut–brain axis dysfunction. On the other hand, this review suggests that probiotic administration to regulate the gut–brain axis might improve gastrointestinal symptoms, restore ASD-related behavioral symptoms, restore gut microbiota composition, reduce inflammation, and restore intestinal barrier function in human and animal models. This review suggests that targeting the microbiota through agents such as probiotics may represent an approach for treating subsets of individuals with ASD.