The microbial metabolites, short-chain fatty acids, regulate colonic Treg cell homeostasis

Interplay of m6A RNA methylation and gut microbiota in modulating gut injury

The gut microbiota undergoes continuous variations among individuals and across their lifespan, shaped by diverse factors encompassing diet, age, lifestyle choices, medication intake, and disease states. These microbial inhabitants play a pivotal role in orchestrating physiological metabolic pathways through the production of metabolites like bile acids, choline, short-chain fatty acids, and neurotransmitters, thereby establishing a dynamic "gut-organ axis" with the host. The intricate interplay between the gut microbiota and the host is indispensable for gut health, and RNA N6-methyladenosine modification, a pivotal epigenetic mark on RNA, emerges as a key player in this process. M6A modification, the most prevalent internal modification of eukaryotic RNA, has garnered significant attention in the realm of RNA epigenetics. Recent findings underscore its potential to influence gut microbiota diversity and intestinal barrier function by modulating host gene expression patterns. Conversely, the gut microbiota, through its impact on the epigenetic landscape of host cells, may indirectly regulate the recruitment and activity of RNA m6A-modifying enzymes. This review endeavors to delve into the biological functions of m6A modification and its consequences on intestinal injury and disease pathogenesis, elucidating the partial possible mechanisms by which the gut microbiota and its metabolites maintain host intestinal health and homeostasis. Furthermore, it also explores the intricate crosstalk between them in intestinal injury, offering a novel perspective that deepens our understanding of the mechanisms underlying intestinal diseases.

Gut microbiota in hepatocellular carcinoma immunotherapy: immune microenvironment remodeling and gut microbiota modification

Hepatocellular carcinoma (HCC) remains a leading cause of cancer-related mortality, with limited treatment options at advanced stages. The gut microbiota, a diverse community of microorganisms residing in the gastrointestinal tract, plays a pivotal role in regulating immune responses through the gut-liver axis. Emerging evidence underscores its impact on HCC progression and the efficacy of immunotherapy. This review explores the intricate interactions between gut microbiota and the immune system in HCC, with a focus on key immune cells and pathways involved in tumor immunity. Additionally, it highlights strategies for modulating the gut microbiota - such as fecal microbiota transplantation, dietary interventions, and probiotics - as potential approaches to enhancing immunotherapy outcomes. A deeper understanding of these mechanisms could pave the way for novel therapeutic strategies aimed at improving patient prognosis.

Immunopathological and microbial signatures of inflammatory bowel disease in partial RAG deficiency

Partial RAG deficiency (pRD) can manifest with systemic and tissue-specific immune dysregulation, with inflammatory bowel disease (IBD) in 15% of the patients. We aimed at identifying the immunopathological and microbial signatures associated with IBD in patients with pRD and in a mouse model of pRD (Rag1w/w) with spontaneous development of colitis. pRD patients with IBD and Rag1w/w mice showed a systemic and colonic Th1/Th17 inflammatory signature. Restriction of fecal microbial diversity, abundance of pathogenic bacteria, and depletion of microbial species producing short-chain fatty acid were observed, which were associated with impaired induction of lamina propria peripheral Treg cells in Rag1w/w mice. The use of vedolizumab in Rag1w/w mice and of ustekinumab in a pRD patient were ineffective. Antibiotics ameliorated gut inflammation in Rag1w/w mice, but only bone marrow transplantation (BMT) rescued the immunopathological and microbial signatures. Our findings shed new light in the pathophysiology of gut inflammation in pRD and establish a curative role for BMT to resolve the disease phenotype.

Unraveling the potential of bioengineered microbiome-based strategies to enhance cancer immunotherapy

The human microbiome plays a pivotal role in the field of cancer immunotherapy. The microbial communities that inhabit the gastrointestinal tract, as well as the bacterial populations within tumors, have been identified as key modulators of therapeutic outcomes, affecting immune responses and reprogramming the tumor microenvironment. Advances in synthetic biology have made it possible to reprogram and engineer these microorganisms to improve antitumor activity, enhance T-cell function, and enable targeted delivery of therapies to neoplasms. This review discusses the role of the microbiome in modulating both innate and adaptive immune mechanisms-ranging from the initiation of cytokine production and antigen presentation to the regulation of immune checkpoints-and discusses how these mechanisms improve the efficacy of immune checkpoint inhibitors. We highlight significant advances with bioengineered strains like Escherichia coli Nissle 1917, Lactococcus lactis, Bifidobacterium, and Bacteroides, which have shown promising antitumor efficacy in preclinical models. These engineered microorganisms not only efficiently colonize tumor tissues but also help overcome resistance to standard therapies by reprogramming the local immune environment. Nevertheless, several challenges remain, such as the requirement for genetic stability, effective tumor colonization, and the control of potential safety issues. In the future, the ongoing development of genetic engineering tools and the optimization of bacterial delivery systems are crucial for the translation of microbiome-based therapies into the clinic. This review highlights the potential of bioengineered microbiota as an innovative, personalized approach in cancer immunotherapy, bringing hope for more effective and personalized treatment options for patients with advanced malignancies.

Modulation of Intestinal Flora: a Novel Immunotherapeutic Approach for Enhancing Thyroid Cancer Treatment

Over the past 3 years, there has been a growing interest in clinical research regarding the potential involvement of intestinal flora in thyroid cancer (TC). This review delves into the intricate connection between intestinal flora and TC, focusing on the particular intestinal flora that is directly linked to the disease and identifying which may be able to predict potential microbial markers of TC. In order to shed light on the inflammatory pathways connected to the onset of TC, we investigated the impact of intestinal flora on immune modulation and the connection between chronic inflammation when investigating the role of intestinal flora in the pathogenesis of TC. Furthermore, the potential role of intestinal flora metabolites in the regulation of thyroid function was clarified by exploring the effects of short-chain fatty acids and lipopolysaccharide on thyroid hormone synthesis and metabolism. Based on these findings, we further explore the effects of probiotics, prebiotics, postbiotics, vitamins, and trace elements.

Therapeutic potential of gut microbiota modulation in epilepsy: A focus on short-chain fatty acids

According to the criteria established by the International League Against Epilepsy (ILAE), epilepsy is defined as a disorder characterized by at least two unprovoked seizures occurring more than 24 h apart. Its pathogenesis is closely related to various physiological and pathological factors. Advances in high-throughput metagenomic sequencing have increasingly highlighted the role of gut microbiota dysbiosis in epilepsy. Short-chain fatty acids (SCFAs), the major metabolites of the gut microbiota and key regulators of the gut-brain axis, support physiological homeostasis through multiple mechanisms. Recent studies have indicated that SCFAs not only regulate seizures by maintaining intestinal barrier integrity and modulating intestinal immune responses, but also affect the structure and function of the blood-brain barrier (BBB) and regulate neuroinflammation. This review, based on current literatures, explores the relationship between SCFAs and epilepsy, emphasizing how SCFAs affect epilepsy by modulating the intestinal barrier and BBB. In-depth studies on SCFAs may reveal their therapeutic potential and inform the development of gut microbiota-targeted epilepsy treatments.

Oleic acid regulates CD4+ T cells differentiation by targeting ODC1-mediated STAT5A phosphorylation in Vogt-Koyanagi-Harada disease

BACKGROUND

Vogt-Koyanagi-Harada (VKH) is a multisystemic autoimmune disorder characterized by bilateral panuveitis frequently accompanied by neurologic manifestations. While metabolic dysregulation is increasingly recognized in the context of autoimmune diseases, the role of specific metabolites in VKH disease remains unexplored.

METHODS

Non-targeted and targeted metabolomics analysis, phospho-antibody array, proteome microarray, surface plasmon resonance, and molecular simulation were used to identify molecular target of OA.

RESULTS

We investigated metabolic profile of VKH disease and found that oleic acid (OA) was enriched in this disease. A series of functional assays showed that OA could exacerbate experimental autoimmune uveitis (EAU) in association with increased frequency of Th1 and Th17 cells and decreased proportion of Treg cells in vitro. However, the specific molecular target of OA remains elusive. Through proteome microarrays, molecular simulations and surface plasmon resonance assays, Ornithine decarboxylase 1 (ODC1) was identified as target protein of OA. OA could bind to ODC1, increase ODC1 protein expression in both a time- and concentration-dependent manner and promote subsequently putrescine production. Phospho-antibody array analysis revealed that OA inhibited phosphorylation of STAT5A (Y694) in CD4+T cells, leading to imbalance of Th1/Th17 and Treg cells and decreased transcription of IL-10. OA upregulated ODC1 protein and putrescine levels through binding to LYS-78, inhibited phosphorylation of STAT5A protein and subsequently decreased binding of STAT5A at IL-10 promoter.

CONCLUSION

These results reveals that OA could be a crucial metabolite for modulation of CD4+T cell differentiation and that ODC1-mediated phosphorylation and transcriptional activity of STAT5A contributes to development of VKH disease progression, highlighting ODC1 as a novel therapeutic target in VKH disease.

Impact of gut microbiota on colorectal anastomotic healing (Review)

Intestinal anastomosis is a critical procedure in both emergency and elective surgeries to maintain intestinal continuity. However, the incidence of anastomotic leakage (AL) has recently increased, reaching up to 20%, imposing major clinical and economic burdens. Substantial perioperative alterations in the intestinal microbiota composition may contribute to AL, particularly due to disruptions in key microbial populations essential for intestinal health and healing. The intricate interplay between the intestinal microbiota and the host immune system, along with microbial changes before and during surgery, significantly influences anastomotic integrity. Notably, specific pathogens such as Enterococcus and Pseudomonas aeruginosa have been implicated in AL pathogenesis. Preventive strategies including dietary regulation, personalized intestinal preparation, microbiota restoration and enhanced recovery after surgery protocols, may mitigate AL risks. Future research should focus on elucidating the precise mechanisms linking intestinal microbiota alterations to anastomotic healing and developing targeted interventions to improve surgical outcomes.

The Microbial Metabolite δ-Valerobetaine Strengthens the Gut Epithelial Barrier

Metabolic processes within gut microbes generate bioactive metabolites that impact intestinal epithelial barrier function. Herein, gnotobiotic mice and mass spectrometry-based metabolomics were used to identify novel metabolites in host tissues of microbial origin. Of those detected, the gut microbe-generated metabolite δ-valerobetaine (δ-VB) is a potent inhibitor of l-carnitine biosynthesis and a modulator of fatty acid oxidation by mitochondria in liver cells. The bioactivity of δ-VB toward gut epithelial barrier function was assessed. Germ-free mice are devoid of δ-VB, and administration of δ-VB to germ-free mice induced the enrichment of transcript sets associated with gut mitochondrial respiration and fatty acid oxidation in colonic tissue. Furthermore, δ-VB induced the differential expression of genes that function in barrier function in germ-free and conventionally raised mice. Functionally, δ-VB decreased gut barrier permeability and augmented wound healing in cultured gut epithelial cells and elicited cytoprotective and prorestitutive effects in a mouse model of colonic injury. These data indicate that the microbial-derived metabolite δ-VB is a modulator of gut epithelium function, and thus is a molecular target to potentially manage microbiome-host dysbiosis in intestinal health and disease.

Interaction between gut microbiota and T cell immunity in colorectal cancer

This review delves into the complex and multi-layered mechanisms that govern the interaction between gut microbiota and T cells in the context of colorectal cancer (CRC), revealing a novel "microbiota-immune regulatory landscape" within the tumor microenvironment. As CRC progresses, the gut microbiota experiences a significant transformation in both its composition and metabolic patterns. On one hand, specific microbial entities within the gut microbiota can directly engage with T cells, functioning as "immunological triggers" that shape T-cell behavior. Simultaneously, microbial metabolites, such as short-chain fatty acids and bile acids, serve as "molecular regulators" that intricately govern T-cell function and differentiation, fine-tuning the immune response. On the other hand, the quorum-sensing mechanism, a recently recognized communication network among bacteria, also plays a pivotal role in orchestrating T-cell immunity. Additionally, the gut microbiota forms an intriguing connection with the neuro-immune regulatory axis, a largely unexplored "territory" in CRC research. Regarding treatment strategies, a diverse array of intervention approaches-including dietary modifications, the utilization of probiotics, bacteriophages, and targeted antibiotic therapies-offer promising prospects for restoring the equilibrium of the gut microbiota, thereby acting as "ecosystem renovators" that impede tumor initiation and progression. Nevertheless, the current research landscape in this field is fraught with challenges. These include significant variations in microbial composition, dietary preferences, and tumor microenvironments among individuals, a lack of large-scale cohort studies, and insufficient research that integrates tumor mutation analysis, gut microbiota investigations, and immune microenvironment evaluations. This review emphasizes the necessity for future research efforts to seamlessly incorporate multiple factors and utilize bioinformatics analysis to construct a more comprehensive "interactive map" of the gut microbiota-T cell relationship in CRC. The aim is to establish a solid theoretical basis for the development of highly effective and personalized treatment regimens, ultimately transforming the therapeutic approach to CRC.

Fueling the fire: colonocyte metabolism and its effect on the colonic epithelia

Colonic permeability is a major consequence of dysbiosis and diseases affecting the colon, further contributing to inflammation and extraintestinal diseases. Recent advances have shed light on the association between colonocyte energy utilization and the mechanisms that support epithelial function and homeostasis. One unifying theme is the induction of colonocyte hypoxia, driven by the aerobic oxidation of microbial-derived butyrate, as a critical factor promoting multiple cellular processes that support intestinal barrier function, mucus secretion, and the maintenance of synergistic luminal microbes. Particular attention will be focused on experimental evidence supporting beta-oxidation via activation of peroxisome proliferators-activated receptor-γ (PPAR) and upregulation and activation of processes that promote barrier function by hypoxia-inducible factor (HIF) signaling. Growing evidence suggests that colonocyte energy utilization is tightly regulated and switches between beta-oxidation of butyrate and anaerobic glycolysis, the latter being associated with several disease states. As most of the primary literature associated with colonocyte energy utilization has focused on adult models, evidence supporting butyrate oxidation in the neonatal gut is lacking. Thus, this review details the current state of knowledge linking colonocyte substrate utilization to mechanisms supporting gut health, but also highlights the counterindications of colonic butyrate availability and utilization in developmental periods.

Gut microbiota mediates semaglutide attenuation of diabetes-associated cognitive decline

Diabetes-associated cognitive decline (DACD), characterized by cognitive impairment, is a serious complication of diabetes mellitus (DM). Research has shown that semaglutide, a novel glucagon-like peptide-1 receptor agonist, has neurotrophic and neuroprotective properties. However, a comprehensive understanding of the specific effects and underlying mechanisms of semaglutide treatment in patients with DACD remains lacking. In this study, we evaluated the potential of semaglutide to alleviate DACD in mice with DM. Eight-week-old mice fed a high-fat diet with streptozotocin-induced DM were subcutaneously injected with semaglutide (30 ​nmol/kg qd) for 12 weeks. Semaglutide administration significantly alleviated cognitive impairment, inhibited hippocampal neuron loss, improved the hippocampal synaptic ultrastructure, and effectively mitigated neuroinflammation. Furthermore, semaglutide treatment increased the relative abundances of g_Alistipes, g_norank_f_Eubacterium_coprostanoligenes, g_Bacteroides, and g_Parabacteroides, while decreasing the relative abundances of g_ faecalibaculum, g_Colodertribacter, g_GCA-900066575, g_Erysipelatoclostridium, and g_norank_f_Lachnospiraceae. Semaglutide also induced alterations in fecal and serum metabolites, as well as transcriptomic changes in brain tissue, with significant common enrichment in neuroactive ligand-receptor interactions. Furthermore, strong correlations were observed among semaglutide-affected genes, metabolites, and microbiota, as assessed by correlation analysis and integrative modeling. In conclusion, these findings suggest a correlation between the protective effects of semaglutide against DACD and the microbiota-gut-brain axis.

Sialic Acid (Neu5Ac)-Driven Modulation of Intestinal Sialylation as a Novel Approach to Mitigating Allergic Reactions to Shrimp Tropomyosin

Sialic acids are crucial for maintaining intestinal homeostasis, but their role in food allergies remains poorly understood. This study investigates the regulatory function of sialic acid (Neu5Ac) in tropomyosin-induced allergic responses, with the aim of identifying potential therapeutic targets. In a C57BL/6N mouse model sensitized with shrimp tropomyosin, Neu5Ac treatment alleviated allergic symptoms, as evidenced by reduced anaphylaxis scores, lower levels of allergen-specific antibodies and Th2 cytokines, enhanced gut microbiota composition, and increased short-chain fatty acid production. To validate these findings, we used the sialyltransferase inhibitor 3Fax-Peracetyl Neu5Ac to inhibit sialylation in both the mouse and CMT93 cell models. Mice with reduced sialylation displayed more severe allergic symptoms, including diarrhea, elevated anaphylaxis scores, increased antibody levels, a Th2-skewed immune response, compromised intestinal barriers, and higher mortality rates. Similarly, in CMT93 cells, sialylation inhibition led to increased secretion of inflammatory markers and greater cellular permeability. These findings underscore the protective effects of Neu5Ac in alleviating food allergies and suggest that enhancing sialylation could provide a novel therapeutic strategy for managing allergic responses.

Links between short-chain fatty acids and osteoarthritis from pathology to clinic via gut-joint axis

Short-chain fatty acids (SCFAs), the primary metabolites produced by the microbial fermentation of dietary fibers in the gut, have a key role in protecting gut health. Increasing evidence indicates SCFAs can exert effects on distant tissues and organs beyond the gut via blood circulation. Osteoarthritis (OA) is a chronic inflammatory joint disease that severely diminishes the physical function and quality of life. However, effective clinical treatments for OA remain elusive. Recent studies have shown that SCFAs can exert beneficial effects on damaged joints in OA. SCFAs can mitigate OA progression by preserving intestinal barrier function and maintaining the integrity of cartilage and subchondral bone, suggesting that they have substantial potential to be the adjunctive treatment strategy for OA. This review described the SCFAs in the human body and their cellular signaling mechanism, and summarized the multiple effects of SCFAs (especially butyrate, propionate, and acetate) on the prevention and treatment of OA by regulating the gut-joint axis, providing novel insights into their promising clinical applications.

The free fatty acid receptor 2 (FFA2): Mechanisms of action, biased signaling, and clinical prospects

Free Fatty Acid Receptor 2 (FFA2), also known as GPR43, is a receptor activated by short-chain fatty acids (SCFAs) with fewer than six carbons in their aliphatic chains. This receptor is expressed in immune cells, adipose tissue, the gastrointestinal tract, and pancreatic islet cells, where it plays a crucial role in the modulation of inflammation, lipid metabolism, insulin secretion, and appetite regulation. Extensive research has been conducted to elucidate the structural attributes and physiological functions of FFA2. Furthermore, several synthetic agonists have been developed for FFA2 that can preferentially activate certain G-proteins, demonstrating potential pharmacological advantages in both in vivo and in vitro studies. Herein, we review the structure and physiological functions of FFA2 and its synthetic ligands, discussing the structural basis of FFA2's biased signaling and the potential role of biased ligands targeting this receptor in the treatment of metabolic and neurodegenerative diseases.

The Role of G Protein-Coupled Receptors in the Regulation of Orthopaedic Diseases by Gut Microbiota

Exercise and diet modulate the gut microbiota, which is involved in the regulation of orthopaedic diseases and synthesises a wide range of metabolites that modulate cellular function and play an important role in bone development, remodelling and disease. G protein-coupled receptors (GPCRs), the largest family of transmembrane receptors in the human body, interact with gut microbial metabolites to regulate relevant pathological processes. This paper provides a review of different dietary and exercise effects on the pathogenic gut microbiota and their metabolites associated with GPCRs in orthopaedic diseases. RESULTS: Generally, metabolites produced by gut microbiota contribute to the maintenance of bone health by activating the corresponding GPCRs, which are involved in bone metabolism, regulation of immune response, and maintenance of gut flora homeostasis. Exercise and diet can influence gut microbiota, and an imbalance in gut microbiota homeostasis can trigger a series of adverse immune and metabolic responses by affecting GPCR function, ultimately leading to the onset and progression of various orthopaedic diseases. Understanding these relationships is crucial for elucidating the pathogenesis of orthopaedic diseases and developing personalised probiotic-based therapeutic strategies. In the future, we should further explore how to prevent and treat orthopaedic diseases through GPCR-based modulation of gut microbes and their interactions. The development of substances that precisely modulate gut microbes through different exercises and diets will provide more effective interventions to improve bone health in patients.

The mechanism of disease progression by aging and age-related gut dysbiosis in multiple sclerosis

Multiple sclerosis (MS) is the most common demyelinating disease caused by a multifaceted interplay of genetic predispositions and environmental factors. Most patients initially experience the relapsing-remitting form of the disease (RRMS), which is characterized by episodes of neurological deficits followed by periods of symptom resolution. However, over time, many individuals with RRMS advance to a progressive form of the disease, known as secondary progressive MS (SPMS), marked by a gradual worsening of symptoms without periods of remission. The mechanisms underlying this transition remain largely unclear, and current disease-modifying therapies (DMTs) are partially effective in treating SPMS. Age is widely acknowledged as a risk factor for the transition from RRMS to SPMS. One factor associated with aging that may influence the progression of MS is gut dysbiosis. This review discusses how aging and age-related gut dysbiosis affect the progression of MS.

Advancements in the study of short-chain fatty acids and their therapeutic effects on atherosclerosis

Atherosclerosis (AS) remains a leading cause of cardiovascular disease and mortality globally. This chronic condition is characterized by inflammation, lipid accumulation, and the deposition of cellular components within arterial walls. Emerging evidence has highlighted the multifaceted therapeutic potential of short-chain fatty acids (SCFAs) in mitigating AS progression. SCFAs have demonstrated anti-inflammatory properties and the ability to regulate immune responses, metabolic pathways, vascular integrity, and intestinal barrier function in animal models of AS. Consequently, SCFAs have garnered significant attention as a promising approach for the prevention and treatment of AS. However, further clinical trials and studies are necessary to fully elucidate the underlying mechanisms and effects of SCFAs. Additionally, different types of SCFAs may exert distinct impacts, necessitating more in-depth investigation into their specific roles and mechanisms. This review provides an overview of the diverse cellular mechanisms contributing to AS formation, as well as a discussion of the significance of SCFAs in AS pathogenesis and their multifaceted therapeutic potential. Nonetheless, additional research is warranted to comprehensively understand and harness the potential of various SCFAs in the context of AS.

Diet-pathobiont interplay in health and inflammatory bowel disease

The intestinal microbiota plays a crucial role in maintaining host health by participating in various beneficial functions. However, under certain conditions, it can contribute to the development of inflammatory bowel disease (IBD) and other chronic inflammatory conditions. Importantly, not all commensal microbiota members are drivers of inflammation. A specific subset of commensal bacteria, known as pathobionts, can exhibit pathogenic potential under specific circumstances. Their inflammatory potential is modulated by several factors, including the host's genetic background and the surrounding microbiota. Furthermore, diet has emerged as a critical factor influencing the gut microbiota, with some studies highlighting its role in modulating pathobionts. This review will delve into the role played by pathobionts in chronic intestinal inflammation, in both mouse models as well as in humans, with a focus on the interplay between dietary factors and pathobiont members of the intestinal microbiota. Understanding the complex relationships between diet, pathobionts, and chronic inflammation could pave the way for diet-based therapeutic strategies aimed at managing chronic inflammatory conditions.

Targeting symbionts by apolipoprotein L proteins modulates gut immunity

The mammalian gut harbours trillions of commensal bacteria that interact with their hosts through various bioactive molecules1,2. However, the mutualistic strategies that hosts evolve to benefit from these symbiotic relationships are largely unexplored. Here we report that mouse enterocytes secrete apolipoprotein L9a and b (APOL9a/b) in the presence of microbiota. By integrating flow cytometry sorting of APOL9-binding bacterial taxa with 16S ribosomal RNA gene sequencing (APOL9-seq), we identify that APOL9a/b, as well as their human equivalent APOL2, coat gut bacteria belonging to the order of Bacteroidales with a high degree of specificity through commensal ceramide-1-phosphate (Cer1P) lipids. Genetic abolition of ceramide-1-phosphate synthesis pathways in gut-dominant symbiote Bacteroides thetaiotaomicron significantly decreases the binding of APOL9a/b to the bacterium. Instead of lysing the bacterial cells, coating of APOL9a/b induces the production of outer membrane vesicles (OMVs) from the target bacteria. Subsequently, the Bacteroides-elicited outer membrane vesicles enhance the host's interferon-γ signalling to promote major histocompatibility complex class II expression in the intestinal epithelial cells. In mice, the loss of Apol9a/b compromises the gut major histocompatibility complex class II-instructed immune barrier function, leading to early mortality from infection by intestinal pathogens. Our data show how a host-elicited factor benefits gut immunological homeostasis by selectively targeting commensal ceramide molecules.

Roles of the gut microbiota in immune-related adverse events: mechanisms and therapeutic intervention

Immune checkpoint inhibitors (ICIs) constitute a major breakthrough in the field of cancer therapy; their use has resulted in improved outcomes across various tumour types. However, ICIs can cause a diverse range of immune-related adverse events (irAEs) that present a considerable challenge to the efficacy and safety of these treatments. The gut microbiota has been demonstrated to have a crucial role in modulating the tumour immune microenvironment and thus influences the effectiveness of ICIs. Accumulating evidence indicates that alterations in the composition and function of the gut microbiota are also associated with an increased risk of irAEs, particularly ICI-induced colitis. Indeed, these changes in the gut microbiota can contribute to the pathogenesis of irAEs. In this Review, we first summarize the current clinical challenges posed by irAEs. We then focus on reported correlations between alterations in the gut microbiota and irAEs, especially ICI-induced colitis, and postulate mechanisms by which these microbial changes influence the occurrence of irAEs. Finally, we highlight the potential value of gut microbial changes as biomarkers for predicting irAEs and discuss gut microbial interventions that might serve as new strategies for the management of irAEs, including faecal microbiota transplantation, probiotic, prebiotic and/or postbiotic supplements, and dietary modulations.

Unveiling the role of the upper respiratory tract microbiome in susceptibility and severity to COVID-19

It is argued that commensal bacteria in the upper respiratory tract (URT) protect against pathogen colonization and infection, including respiratory viruses. Given that the microbiome can mediate immune modulation, a link between the URT microbiome (URTM) and COVID-19 susceptibility and severity is expected. This 16S metagenomics cross-sectional study assessed URTM composition, metabolic prediction, and association with laboratory biomarkers in non-COVID-19 pneumonia (NO-CoV), moderate (M-CoV), severe (S-CoV) COVID-19 patients, as well as COVID-19-negative, asymptomatic (NC) patients. The S-CoV group exhibited reduced URTM diversity, primarily due to a decreased abundance of eubiotic taxa. Some of these taxa (e.g., Haemophilus sp., Neisseria sp.) were also associated with inflammatory biomarkers. Multiple metabolic pathways (e.g., short-chain fatty acids, vitamin B12) linked to immune response, antiviral activity, and host susceptibility showed decreased abundance in S-CoV. These pathways could suggest potential alternatives for the therapeutic arsenal against COVID-19, providing reassurance about the progress in understanding and treating this disease.

Prebiotics for Induction and Maintenance of Remission in Inflammatory Bowel Disease: Systematic Review and Meta-Analysis

BACKGROUND

Prebiotics are nondigestible carbohydrates fermented by gut bacteria into metabolites that confer health benefits. However, evidence on their role for inflammatory bowel disease (IBD) is unclear. This study systematically evaluated the research on prebiotics for treatment of IBD.

METHODS

A search was performed in PubMed, Embase, Cochrane, and Web of Science. Eligible articles included randomized controlled trials or prospective observational studies that compared a prebiotic with a placebo or lower-dose control in patients with IBD. Meta-analyses were performed using random-effects models for the outcomes of clinical remission, clinical relapse, and adverse events.

RESULTS

Seventeen studies were included. For induction of clinical remission in ulcerative colitis (UC), the fructooligosaccharide (FOS) kestose was effective (relative risk, 2.75, 95% confidence interval, 1.05-7.20; n = 40), but oligofructose-enriched inulin (OF-IN) and lactulose were not. For maintenance of remission in UC, germinated barley foodstuff trended toward preventing clinical relapse (relative risk, 0.40; 95% confidence interval, 0.15-1.03; n = 59), but OF-IN, oat bran, and Plantago ovata did not. For Crohn's disease, OF-IN and lactulose were no different than controls for induction of remission, and FOS was no different than controls for maintenance of remission. Flatulence and bloating were more common with OF-IN; reported adverse events were otherwise similar to controls for other prebiotics.

CONCLUSION

Prebiotics, particularly FOS and germinated barley foodstuff, show potential as effective and safe dietary supplements for induction and maintenance of remission in UC, respectively. The overall certainty of evidence was very low. There would be benefit in further investigation on the role of prebiotics as treatment adjuncts for IBD.

Butyrate-producing bacteria in pregnancy maintenance: mitigating dysbiosis-induced preterm birth

BACKGROUND

Preterm birth (PTB) is a major contributor to neonatal morbidity, mortality, and long-term health complications. Despite advances in perinatal care, PTB rates remain high, and its multifactorial etiology is not fully understood. Increasing evidence suggests that maternal gut microbiota plays a critical role in pregnancy maintenance, potentially through modulation of immune responses. However, the underlying causal mechanisms remain unclear. We hypothesized that dysbiosis disrupts immune tolerance and promotes PTB, and that butyrate (short-chain fatty acid produced by specific gut bacteria) may counteract this effect by enhancing regulatory T cell (Treg)-mediated immune regulation.

METHODS

We established a dysbiosis-induced PTB mouse model using vancomycin treatment combined with subclinical immune activation via anti-CD3ε antibody. Pregnant mice were fed either a standard or butyrate-enriched diet. Outcomes included gestational length, PTB incidence, live pup rates, and Treg cell levels assessed by flow cytometry. Parallelly, 16S rRNA gene sequencing was performed on fecal samples from 32 pregnant women to compare gut microbial composition between spontaneous PTB and term birth groups. Multivariate logistic regression and correlation analyses were conducted to assess associations with gestational outcomes.

RESULTS

Vancomycin-induced dysbiosis in mice significantly reduced Treg cell populations and increased PTB rates (43.3% in dysbiosis vs. 0% in controls; p < 0.05), while butyrate supplementation reduced PTB incidence (p = 0.03), prolonged gestation (p = 0.01), and restored Treg counts (p < 0.001). In human samples, significant reductions in Lachnospiraceae and Ruminococcaceae, representative butyrate-producing bacteria, were seen in PTB cases. Their combined abundance was independently associated with sPTB risk (p = 0.019) and positively correlated with gestational age (r = 0.59, p < 0.001).

CONCLUSIONS

Our findings demonstrate that maternal dysbiosis increases PTB risk via impaired immune tolerance, and that butyrate supplementation effectively reverses this effect in vivo. Human data support the translational relevance of butyrate-producing microbiota in pregnancy maintenance. These results highlight butyrate as a promising target for dietary interventions aimed at reducing PTB incidence by restoring immune homeostasis. Trial registration Not applicable.

Progress of research on the gut microbiome and its metabolite short-chain fatty acids in postmenopausal osteoporosis: a literature review

Postmenopausal osteoporosis (PMOP) is a systemic metabolic bone disease caused by the decrease in estrogen levels after menopause. It leads to bone loss, microstructural damage, and an increased risk of fractures. Studies have found that the gut microbiota and its metabolites can regulate bone metabolism through the gut-bone axis and the gut-brain axis. As research progresses, PMOP has been found to be associated with gut microbiota dysbiosis and Th17/Treg imbalance. The gut microbiota is closely related to the development and differentiation of Treg and Th17 cells. Among them, the metabolites of the gut microbiota such as short-chain fatty acids (SCFAs) can regulate the differentiation of effector T cells by acting on molecular receptors on immune cells, thereby regulating the bone immune process. The multifaceted relationship among the gut microbiota, SCFAs, Th17/Treg cell-mediated bone immunity, and bone metabolism is eliciting attention from researchers. Through a review of existing literature, we have comprehensively summarized the effects of the gut microbiota and SCFAs on PMOP, especially from the perspective of Th17/Treg balance. Regulating this balance may provide new opportunities for PMOP treatment.

Lizhong decoction alleviates experimental ulcerative colitis via regulating gut microbiota-SCFAs-Th17/Treg axis

ETHNOPHARMACOLOGICAL RELEVANCE

Lizhong decoction (LZD), a Traditional Chinese Medicine formula, is widely utilized to treat gastrointestinal diseases, including ulcerative colitis in China for thousands of years.

AIM OF THE STUDY

To investigate whether the protective effect of LZD on ulcerative colitis is dependent on gut microbiota and T-cell immune homeostasis.

MATERIAL AND METHODS

The preventive effects of LZD on dextran sodium sulfate (DSS)-induced colitis mice were evaluated through the measurement of body weight, disease activity index, colon length and hematoxylin-eosin staining. Flow cytometry was used to detect the ratio of Th17/Treg cells. Pseudo sterile mice and fecal transplantation experiments were used to investigate whether the preventive effect of LZD was dependent on the gut microbiota. The alterations of gut microbiota were identified by the 16S rDNA sequencing. The content of intestinal short-chain fatty acids (SCFAs) was detected by LC-MS/MS analysis. The downstream signal pathways of SCFAs were detected by the immunoblotting.

RESULTS

LZD administration significantly alleviated weight loss and intestinal injury in DSS-induced colitis mice. LZD administration also promotes the balance of Th17/Treg cells. Moreover, LZD administration relies on gut microbiota to alleviate ulcerative colitis and regulate Th17/Treg cell balance. LZD administration significantly improves gut microbial composition in colitis mice, elevating the abundance of SCFAs producing bacterium such as lachnospiraceae_nk4a136_group and Akkermansia. LZD treatment further increases the abundance of SCFAs and promotes activation of free fatty acid activated receptor 2 (FFAR2).

CONCLUSION

LZD administration promotes Th17/Treg cell balance in a gut microbiota-SCFAs dependent manner, which in turn ameliorates ulcerative colitis.

Gut microbiome and blood biomarkers reveal differential responses to aerobic and anaerobic exercise in collegiate men of diverse training backgrounds

The gut microbiome influences physiological responses to exercise by modulating inflammatory markers and metabolite production. Athletes typically exhibit greater microbial diversity, which may be associated with improved performance, but the mechanisms linking different exercise modalities to the gut microbiome are not fully understood. In this study, blood and stool samples were collected from endurance athletes, strength athletes, and non-athletic controls performing two maximal exercise tests (the anaerobic Wingate test and the aerobic Bruce Treadmill Test) to integrate serum biomarker data with gut bacterial metagenomic profiles. While most biochemical markers showed similar post-exercise trends across groups, SPARC (secreted protein acidic and rich in cysteine) and adiponectin levels showed modality-specific responses. Strength-trained participants showed unique microbiome-biomarker associations after the Wingate test. In addition, baseline enrichment of certain bacterial taxa, including Clostridium phoceensis and Catenibacterium spp., correlated with reduced Bruce Treadmill test response in strength-trained individuals. These findings, while requiring further validation, indicate the complex interplay between exercise type, training background, and the gut microbiome, and suggest that specific microbial species may help shape recovery and adaptation.

The Role of Gut Microbiota on Intestinal Fibrosis in Inflammatory Bowel Disease and Traditional Chinese Medicine Intervention

Inflammatory bowel disease (IBD) is a chronic, relapsing inflammatory disorder of the intestine, frequently complicated by intestinal fibrosis. As fibrosis progresses, it can result in luminal stricture and compromised intestinal function, significantly diminishing patients' quality of life. Emerging evidence suggests that gut microbiota and their metabolites contribute to the pathogenesis of IBD-associated intestinal fibrosis by influencing inflammation and modulating immune responses. This review systematically explores the mechanistic link between gut microbiota and intestinal fibrosis in IBD and evaluates the therapeutic potential of traditional Chinese medicine (TCM) interventions. Relevant studies were retrieved from PubMed, Web of Science, Embase, Scopus, CNKI, Wanfang, and VIP databases. Findings indicate that TCM, including Chinese herbal prescriptions and bioactive constituents, can modulate gut microbiota composition and microbial metabolites, ultimately alleviating intestinal fibrosis through anti-inflammatory, immunemodulatory, and anti-fibrotic mechanisms. These insights highlight the potential of TCM as a promising strategy for targeting gut microbiota in the management of IBD-associated fibrosis.

In utero human intestine contains maternally derived bacterial metabolites

BACKGROUND

Understanding when host-microbiome interactions are first established is crucial for comprehending normal development and identifying disease prevention strategies. Furthermore, bacterially derived metabolites play critical roles in shaping the intestinal immune system. Recent studies have demonstrated that memory T cells infiltrate human intestinal tissue early in the second trimester, suggesting that microbial components such as peptides that can prime adaptive immunity and metabolites that can influence the development and function of the immune system are also present in utero. Our previous study reported a unique fetal intestinal metabolomic profile with an abundance of several bacterially derived metabolites and aryl hydrocarbon receptor (AHR) ligands implicated in mucosal immune regulation.

RESULTS

In the current study, we demonstrate that a number of microbiome-associated metabolites present in the fetal intestines are also present in the placental tissue, and their abundance is different across the fetal intestine, fetal meconium, fetal placental villi, and the maternal decidua. The fetal gastrointestinal samples and maternal decidua samples show substantially higher positive correlation on the abundance of these microbial metabolites than the correlation between the fetal gastrointestinal samples and meconium samples. The expression of genes associated with the transport and signaling of some microbial metabolites is also detectable in utero.

CONCLUSIONS

We suggest that the microbiome-associated metabolites are maternally derived and vertically transmitted to the fetus. Notably, these bacterially derived metabolites, particularly short-chain fatty acids and secondary bile acids, are likely biologically active and functional in regulating the fetal immune system and preparing the gastrointestinal tract for postnatal microbial encounters, as the transcripts for their various receptors and carrier proteins are present in second trimester intestinal tissue through single-cell transcriptomic data. Video Abstract.

Function and therapeutic potential of Amuc_1100, an outer membrane protein of Akkermansia muciniphila: A review

The gut microbiota-derived protein Amuc_1100, a key outer membrane component of Akkermansia muciniphila, has emerged as a groundbreaking therapeutic agent with unique structural and functional properties. Amuc_1100 exerts multifaceted immune-metabolic effects through novel mechanisms, including modulation of TLR2/4 and JAK/STAT pathways. This review highlights its unique multi-component structure that enables synergistic biological activity, and its pharmacological properties, which underlies its ability to enhance intestinal barrier integrity, restore microbiota balance, and suppress systemic inflammation. Crucially, Amuc_1100 demonstrates unprecedented therapeutic versatility across both intestinal disorders (e.g., inflammatory bowel disease, antibiotic-associated diarrhea) and extraintestinal conditions-notably improving neuropsychiatric symptoms via gut-serotonin axis regulation, combating cancer through CD8+ T cell activation, and mitigating cardiotoxicity via gut-heart immune crosstalk. Emerging innovations in targeted delivery systems, including gut-retentive nano-formulations and engineered probiotic vectors, further amplify its clinical potential. We critically evaluate recent advances distinguishing Amuc_1100's mechanisms from live bacterial interventions. By synthesizing evidence from preclinical models, this work positions Amuc_1100 as a prototype for next-generation microbiome-derived therapeutics, bridging microbial ecology with precision medicine.

Nervous system-gut microbiota-immune system axis: future directions for preventing tumor

Tumor is one of the leading causes of death worldwide. The occurrence and development of tumors are related to multiple systems and factors such as the immune system, gut microbiota, and nervous system. The immune system plays a critical role in tumor development. Studies have also found that the gut microbiota can directly or indirectly affect tumorigenesis and tumor development. With increasing attention on the tumor microenvironment in recent years, the nervous system has emerged as a novel regulator of tumor development. Some tumor therapies based on the nervous system have also been tested in clinical trials. However, the nervous system can not only directly interact with tumor cells but also indirectly affect tumor development through the gut microbiota. The nervous system-mediated gut microbiota can regulate tumorigenesis, growth, invasion, and metastasis through the immune system. Here, we mainly explore the potential effects of the nervous system-gut microbiota-immune system axis on tumorigenesis and tumor development. The effects of the nervous system-gut microbiota-immune system axis on tumors involve the nervous system regulating immune cells through the gut microbiota, which can prevent tumor development. Meanwhile, the direct effects of the gut microbiota on tumors and the regulation of the immune system by the nervous system, which can affect tumor development, are also reviewed.

Structural characterization of the exopolysaccharide produced by Bacillus amyloliquefaciens JM033 and evaluation of its ability to regulate immunity and intestinal flora

The probiotic strain Bacillus amyloliquefaciens JM033 (B. amyloliquefaciens JM033), isolated from the traditional Chinese fermented food Sufu (also known as Fu-ru or fermented bean curd), is distinguished by its high production of exopolysaccharides (EPS). The EPS (BAP-1) produced by this strain was purified and its structure analyzed. BAP-1 is a novel hybrid fructan with a molecular weight of 17.6 kDa. It is composed of →6)-β-D-Fruf-(2 → and →1,6)-β-D-Fruf-(2→, which form the backbone, with a branched chain of β-D-Fruf-(2 → attached at the 1-position of residue B. In vivo studies on mice indicated that BAP-1 improves immunity in immunosuppressed mice by enhancing humoral immunity (P < 0.01), monocyte-macrophage phagocytosis (P < 0.01), and NK cell killing activity (P < 0.05). Additionally, BAP-1 was found to improve the composition of the intestinal microbiota and stimulate the production of short-chain fatty acids. Notably, BAP-1 exhibited a significant effect on the proliferation of Akkermansia. Therefore, BAP-1 shows promise as a prebiotic and may contribute to the development of new immunomodulatory agents.

AMPK is necessary for Treg functional adaptation to microenvironmental stress during malignancy and viral pneumonia

CD4+FOXP3+ Treg cells maintain self tolerance, suppress the immune response to cancer, and protect against tissue injury during acute inflammation. Treg cells require mitochondrial metabolism to function, but how Treg cells adapt their metabolic programs to optimize their function during an immune response occurring in a metabolically stressed microenvironment remains unclear. Here, we tested whether Treg cells require the energy homeostasis-maintaining enzyme AMPK to adapt to metabolically aberrant microenvironments caused by malignancy or lung injury, finding that AMPK is dispensable for Treg cell immune-homeostatic function but is necessary for full Treg cell function in B16 melanoma tumors and during influenza virus pneumonia. AMPK-deficient Treg cells had lower mitochondrial mass and exhibited an impaired ability to maximize aerobic respiration. Mechanistically, we found that AMPK regulates DNA methyltransferase 1 to promote transcriptional programs associated with mitochondrial function in the tumor microenvironment. During viral pneumonia, we found that AMPK sustains metabolic homeostasis and mitochondrial activity. Induction of DNA hypomethylation was sufficient to rescue mitochondrial mass in AMPK-deficient Treg cells, linking AMPK function to mitochondrial metabolism via DNA methylation. These results define AMPK as a determinant of Treg cell adaptation to metabolic stress and offer potential therapeutic targets in cancer and tissue injury.

The Critical Role of Regulatory T Cells in Immune Tolerance and Rejection Following Liver Transplantation: Interactions With the Gut Microbiome

Liver transplantation (LT) is the ultimate treatment for patients with end-stage liver disease or early hepatocellular carcinoma. In the context of LT, because of the unique immunological characteristics of human liver allograft, 5%-20% of selected LT recipients can achieve operational tolerance. Nonetheless, there remains a risk of rejection in LT patients. Maintaining immune homeostasis is thus crucial for improving clinical outcomes in these patients. In mechanism, several immune cells, including dendritic cells, Kupffer cells, myeloid-derived suppressor cells, hepatic stellate cells, regulatory B cells, and CD4 + regulatory T cells (Treg), contribute to achieving tolerance following LT. In terms of Treg, it plays a role in successfully minimizing immunosuppression or achieving tolerance post-LT while also reducing the risk of rejection. Furthermore, the gut microbiome modulates systemic immune functions along the gut-liver axis. Recent studies have explored changes in the microbiome and its metabolites under various conditions, including post-LT, acute rejection, and tolerance. Certain functional microbiomes and metabolites exhibit immunomodulatory functions, such as the augmentation of Treg, influencing immune homeostasis. Therefore, understanding the mechanisms of tolerance in LT, the role of Treg in tolerance and rejection, as well as their interactions with gut microbiome, is vital for the management of LT patients.

Short-chain fatty acids as a novel intervention for high-fat diet-induced metabolic syndrome

Metabolic syndrome (MetS) is driven by a complex interplay of genetic, lifestyle, and dietary factors, leading to weight gain, insulin resistance, dyslipidemia, and chronic inflammation. Gut microbiota dysbiosis has been recently recognized as a key contributor to MetS, leading to advancements in gut microbiome-based interventions to improve health outcomes. Considering the unique challenges associated with the use of pre/probiotics, short-chain fatty acids (SCFA), also known as postbiotics, have emerged as promising therapeutic agents due to their role in modulating host metabolism and physiology. Considering this, the aim of the current study was to explore the therapeutic potential of SCFA (butyrate, propionate, and acetate) supplementation against a high-fat diet (HFD)-induced experimental model of MetS in male Wistar rats. Alterations in body weight, lipid profile, histopathology, and adipose tissue accumulation were assessed to establish SCFA-mediated amelioration of experimental MetS. Further, the enzymatic (GPx, Catalase, GR, and GST) and non-enzymatic (LPO, total ROS, and Redox ratio were evaluated. The results indicated that SCFA supplementation could effectively mitigate key features of MetS. A significant reduction in body weight gain and fasting blood glucose levels, along with markedly lowered triglycerides, total cholesterol, and LDL levels, with partial restoration of HDL levels was observed following SCFA supplementation. SCFA administration also attenuated MetS-associated hepatic damage as studied by histopathological investigation and analysis of liver function marker enzyme activities. Such ameliorative effects of SCFA against HFD-induced MetS were owed to potential redox modulation studied using enzymatic and non-enzymatic oxidative stress markers. In conclusion, the study's outcomes show that SCFA supplementation could potentially be used against managing MetS. It underscores the therapeutic potential of SCFA by placing them as a novel gut microbiome-based dietary approach to improve metabolic health and reduce the risk of MetS-associated complications. However, more detailed mechanistic explorations are warranted in the future, leading to their beneficial role in MetS contributing to holistic health outcomes.

Tissue-Resident Memory T Cells in Tumor Immunity and Immunotherapy of Digestive System Tumors

BACKGROUND

Tissue-resident memory T (TRM) cells possess unique abilities to migrate, establish themselves in tissues, and monitor peripheral tissues without circulating. They are crucial in providing long-lasting and local immune protection against surface infections. TRMs demonstrate distinct phenotypic and functional characteristics compared to central memory T (Tcm) cells and effector memory T (Tem) cells.

METHODS

We reviewed a large number of literature to explore the physiological and functional roles of tissue-resident memory T cells, as well as the link between TRM cells and the development and prognosis of digestive tract tumors. We also investigated the association between TRM cells, intestinal flora, and metabolites.

RESULTS

Recent studies have implicated TRMs in the immune response against tumors, making them a potential target for cancer therapy. However, research specifically focused on gastrointestinal tumors is limited.

CONCLUSION

This review aims to compile and assess the most recent data on the role of TRM cells in gastrointestinal tumor immunity. Additionally, it explores recent advancements in immunotherapy and investigates how TRMs may influence intestinal flora and metabolites.

The gut microbiome and cancer: from tumorigenesis to therapy

The gut microbiome has a crucial role in cancer development and therapy through its interactions with the immune system and tumour microenvironment. Although evidence links gut microbiota composition to cancer progression, its precise role in modulating treatment responses remains unclear. In this Review, we summarize current knowledge on the gut microbiome's involvement in cancer, covering its role in tumour initiation and progression, interactions with chemotherapy, radiotherapy and targeted therapies, and its influence on cancer immunotherapy. We discuss the impact of microbial metabolites on immune responses, the relationship between specific bacterial species and treatment outcomes, and potential microbiota-based therapeutic strategies, including dietary interventions, probiotics and faecal microbiota transplantation. Understanding these complex microbiota-immune interactions is critical for optimizing cancer therapies. Future research should focus on defining microbial signatures associated with treatment success and developing targeted microbiome modulation strategies to enhance patient outcomes.

The gut microbiota in spondyloarthritis: an update

PURPOSE OF REVIEW

This review provides an updated overview of the gut microbiota's involvement in spondyloarthritis (SpA) from a clinical perspective. It explores mechanisms by which the gut microbiota may influence SpA pathogenesis and considers the therapeutic implications of targeting the microbiome in SpA treatment.

RECENT FINDINGS

The pathogenesis of SpA is multifactorial, involving genetic predisposition, external factors and dysregulation of the immune system. Recent studies have identified alterations in the gut microbiome of patients with SpA, including changes in microbial diversity and specific taxa linked to disease activity. HLA-B27 status seems to influence gut microbiota composition, potentially impacting disease progression. In HLA-B27 transgenic rats, the association between gut microbiota and SpA development has been confirmed, supporting findings from human studies. A compromised gut barrier, influenced by proteins like zonulin, may allow microbial antigens to translocate, triggering immune responses associated with SpA.

SUMMARY

These findings highlight the potential for microbiota-modulating therapies, such as probiotics, prebiotics, diet and exercise, in managing SpA. However, methodological variability in human studies exposes the need for more rigorous research to better understand these associations. This may offer the opportunity to refine treatment strategies, offering a personalized approach to managing the disease.

Inflammatory bowel disease and neuropsychiatric disorders: Mechanisms and emerging therapeutics targeting the microbiota-gut-brain axis

Crohn's disease (CD) and ulcerative colitis (UC) are the two major entities of inflammatory bowel disease (IBD). These disorders are known for their relapsing disease course and severe gastrointestinal symptoms including pain, diarrhoea and bloody stool. Accumulating evidence suggests that IBD is not only restricted to the gastrointestinal tract and that disease processes are able to reach distant organs including the brain. In fact, up to 35 % of IBD patients also suffer from neuropsychiatric disorders such as generalized anxiety disorder and major depressive disorder. Emerging research in this area indicates that in many cases these neuropsychiatric disorders are a secondary condition as a consequence of the disturbed communication between the gut and the brain via the microbiota-gut-brain axis. In this review, we summarise the current knowledge on IBD-associated neuropsychiatric disorders. We examine the role of different pathways of the microbiota-gut-brain axis in the development of CNS disorders highlighting altered neural, immunological, humoral and microbial communication. Finally, we discuss emerging therapies targeting the microbiota-gut-brain axis to alleviate IBD and neuropsychiatric symptoms including faecal microbiota transplantation, psychobiotics, microbial metabolites and vagus nerve stimulation.

Cyclosporine combined with dexamethasone regulates hepatic Abca1 and PPARα expression and lipid metabolism via butyrate derived from the gut microbiota

Immunosuppression often leads to drastic metabolic, hormonal, and physiological disorders. Changes in the gut microbiota are believed to be one of the factors contributing to these disorders, but the association remains uncertain. Clinical studies can be complicated by confounding variables, such as diet and other drivers of heterogeneity in human microbiomes. In this study, we identified pronounced gut microbiome signatures in rhesus macaques (RMs) with immunosuppression-induced lipid metabolism disorders following cyclosporine combined with dexamethasone. Furthermore, we observed similar changes in the gut microbiota of mice with immunosuppression-induced lipid metabolism disorders, which were associated with short-chain fatty acid metabolism. ELISA showed that immunosuppression significantly reduced the levels of butyric acid in both feces and serum of mice. Spearman correlation analysis identified a significant correlation between serum butyric acid levels and gut microbial dysbiosis induced by immunosuppression, particularly in relation to f_Lachnospiraceae, g_unidentified_Ruminococcaceae, and s_Clostridium leptum. Additionally, mice transplanted with gut microbiota from immunosuppressed mice exhibited hepatic lipid metabolism disorders, and RNA sequencing revealed significant downregulation of ABC transporters and PPARα in the liver, which was closely associated with lipid transport and metabolism, particularly Abca1. Moreover, butyric acid supplementation alleviated hepatic lipid metabolism disorders and upregulated the expression of Abca1 and PPARα in mice transplanted with immunosuppression-induced gut microbiota. Thus, we propose that the combination of cyclosporine and dexamethasone regulates the expression of hepatic Abca1 and PPARα by modulating the gut microbiota and its derived butyrate, particularly Lachnospiraceae and Clostridium leptum, further regulating hepatic lipid metabolism.

Fecal microbiota transplantation against moderate-to-severe atopic dermatitis: A randomized, double-blind controlled explorer trial

BACKGROUND

Fecal microbiota transplantation (FMT) is a novel treatment for inflammatory diseases. Herein, we assess its safety, efficacy, and immunological impact in patients with moderate-to-severe atopic dermatitis (AD).

METHODS

In this randomized, double-blind, placebo-controlled clinical trial, we performed the efficacy and safety assessment of FMT for moderate-to-severe adult patients with AD. All patients received FMT or placebo once a week for 3 weeks, in addition to their standard background treatments. Patients underwent disease severity assessments at weeks 0, 1, 2, 4, 8, 12, and 16, and blood and fecal samples were collected for immunologic analysis and metagenomic shotgun sequencing, respectively. Safety was monitored throughout the trial.

RESULTS

Improvements in eczema area and severity index (EASI) scores and percentage of patients achieving EASI 50 (50% reduction in EASI score) were greater in patients treated with FMT than in placebo-treated patients. No serious adverse reactions occurred during the trial. FMT treatment decreased the Th2 and Th17 cell proportions among the peripheral blood mononuclear cells, and the levels of TNF-α, and total IgE in serum. By contrast, the expression levels of IL-12p70 and perforin on NK cells were increased. Moreover, FMT altered the abundance of species and functional pathways of the gut microbiota in the patients, especially the abundance of Megamonas funiformis and the pathway for 1,4-dihydroxy-6-naphthoate biosynthesis II.

CONCLUSION

FMT was a safe and effective therapy in moderate-to-severe adult patients with AD; the treatment changed the gut microbiota compositions and functions.

Therapeutic targeting of the host-microbiota-immune axis: implications for precision health

The human body functions as a complex ecosystem, hosting trillions of microbes that collectively form the microbiome, pivotal in immune system regulation. The host-microbe immunological axis maintains homeostasis and influences key physiological processes, including metabolism, epithelial integrity, and neural function. Recent advancements in microbiome-based therapeutics, including probiotics, prebiotics and fecal microbiota transplantation, offer promising strategies for immune modulation. Microbial therapies leveraging microbial metabolites and engineered bacterial consortia are emerging as novel therapeutic strategies. However, significant challenges remain, including individual microbiome variability, the complexity of host-microbe interactions, and the need for precise mechanistic insights. This review comprehensively examines the host microbiota immunological interactions, elucidating its mechanisms, therapeutic potential, and the future directions of microbiome-based immunomodulation in human health. It will also critically evaluate challenges, limitations, and future directions for microbiome-based precision medicine.

Tuo-Min-Ding-Chuan Decoction Alleviates Asthma via Spatial Regulation of Gut Microbiota and Treg Cell Promotion

Objective: Tuo-Min-Ding-Chuan decoction (TMDC), a traditional Chinese prescription, has demonstrated significant clinical efficacy in treating allergic asthma. This study aimed to investigate the mechanism of TMDC in treating asthma from the perspective of Treg cells and gut microbiota across distinct gut segments (jejunum, ileum, cecum, and colon). Methods: An ovalbumin (OVA)-induced asthma model was established in mice, followed by oral administration of TMDC at high, medium, and low dose. Immune cells and lung inflammation were examined to assess asthma severity. Microbial composition was determined by 16S rRNA sequencing. Antibiotic cocktail and Lactobacillus rhamnosus GG (LGG) were administrated to confirm the key role of specific bacteria. Results: TMDC attenuated lung inflammation (p < 0.01) and eosinophilic infiltration (p < 0.01) as well as IL-4 and IL-5 secretion (p < 0.01); it was also associated with an increase in Treg cells in the lung, small intestine (SI), and colon (p < 0.05). Meanwhile, TMDC restored the number of microbiota species and the Shannon index in the hindgut and reinstated beneficial bacteria, such as Allobaculum and Turicibacter, which were diminished in asthmatic mice. Notably, TMDC significantly enriched Bifidobacterium and Lactobacillus, particularly in the hindgut. Lactobacillus abundance was significantly correlated (p < 0.05) with Treg cells, IL-4, IL-5, and eosinophils. Furthermore, LGG supplementation restored elevated lung inflammation (p < 0.05) and decreased Treg cells (p < 0.01) due to antibiotic-induced microbiota depletion. Conclusion: TMDC alleviated asthma by promoting Treg cell expansion in a Lactobacillus-dependent manner across different gut segments, providing new insights into its therapeutic mechanisms.

Exploring the Therapeutic and Gut Microbiota-Modulating Effects of Qingreliangxuefang on IMQ-Induced Psoriasis

Purpose

To investigate the therapeutic and gut microbiota-modulating effects of Qingreliangxuefang (QRLXF) on psoriasis.

Materials and Methods

We used network pharmacology, a computational approach, to identify key bioactive compounds and biological targets, and explored the molecular mechanisms of QRLXF. The effects of QRLXF on keratinocyte proliferation and inflammation were evaluated using a mouse model of psoriasis. Changes in the gut microbiota were analyzed via 16SrDNA sequencing, and T cell subsets were assessed using flow cytometry.

Results

Network pharmacology analysis suggested that QRLXF ameliorated psoriasis by modulating Th17 cell differentiation. Further experiments confirmed the anti-inflammatory effects and relief of psoriatic lesions in IMQ-induced mice. 16SrDNA sequencing revealed significant shifts in the gut microbiota, notably increases in Ligilactobacillus and Lactobacillus genera and decreases in Anaerotruncus, Negativibacillus, Bilophila, and Mucispirillum, suggesting a potential relationship between specific microbiota changes and Th17 cell differentiation.

Conclusion

QRLXF alleviated psoriatic dermatitis by regulating Th17 cell responses and modifying gut microbiota profiles, highlighting its therapeutic potential for psoriasis treatment.

Differences in the gut and pharyngeal microbiomes before and after treatment of an acute exacerbation of chronic obstructive pulmonary disease

This study investigated the gut microbiota and pharyngeal microbiome before and after treatment of an acute exacerbation of chronic obstructive pulmonary disease (AECOPD). The abundance and diversity of microorganisms in the gut and pharynx were examined in 24 patients before and after treatment of AECOPD. Enzyme-linked immunosorbent assay was used to detect inflammatory factors in venous blood and 16S rDNA sequencing was performed. The concentration of short-chain fatty acids (SCFAs) in fecal samples was measured by chromatography-mass spectrometry. The results indicated that the diversity and richness of the gut microbiota decreased post-treatment. The linear discriminant analysis effect size (LEfSe) algorithm revealed an increase in the abundance of f_Dietziaceae, g_Dietzia, g_Megasphaera, g_Robinsoniella, s_Salivarius, and s_Peoriensis in the gut after treatment. There was also a post-treatment decrease in the richness of the pharyngeal microbiome. LEfSe revealed a high abundance of p_Actinobacteria, f_Bacteriodaceae, o_Thermales, g_Bacteroides, and g_Thermus in the pharynx before treatment, and an increased abundance of o_Enterobacterales, f_Enterobacteriaceae, f_Ruminococcaceae, and g_Faecalibacterium after treatment. There were no post-treatment changes in SCFA levels. However, the serum C-reactive protein level decreased after treatment. Levels of other inflammatory factors, including tumor necrosis factor-alpha, interleukin (IL)-1β, IL-6, IL-10, transforming growth factor-beta, IL-23, IL-17, and interferon-gamma, were consistent before and after treatment. In this study, changes in the gut microbiota and pharyngeal microbiome occurred after treatment for AECOPD, with no changes in levels of SCFAs or inflammatory factors, except for a decrease in the C-reactive protein level.

A Literature Review on the Impact of the Gut Microbiome on Cancer Treatment Efficacy, Disease Evolution and Toxicity: The Implications for Hematological Malignancies

The gut microbiome plays a crucial role in modulating the efficacy and toxicity of cancer therapies, particularly in hematological malignancies. This review examines the dynamic interplay between gut microbiota and cancer treatments, such as chemotherapy, immunotherapy, and hematopoietic stem cell transplantation (HSCT). Disruptions in the gut microbiome, known as dysbiosis, are associated with adverse effects like gastrointestinal toxicity, neutropenia and cardiotoxicity during chemotherapy. Conversely, the supplementation of probiotics has shown potential in mitigating these side effects by enhancing gut barrier function and regulating immune responses. In HSCT, a higher diversity of gut microbiota is linked to better patient outcomes, including reduced graft-versus-host disease (GVHD) and improved survival rates. The microbiome also influences the efficacy of immunotherapies, such as immune checkpoint inhibitors and CAR-T cell therapy, by modulating immune pathways. Research suggests that certain bacteria, including Bifidobacterium and Akkermansia muciniphila, enhance therapeutic responses by promoting immune activation. Given these findings, modulating the gut microbiome could represent a novel strategy for improving cancer treatment outcomes. The growing understanding of the microbiome's impact on cancer therapy underscores its potential as a target for personalized medicine and offers new opportunities to optimize treatment efficacy while minimizing toxic side effects.

Mapping the global research landscape on psoriasis and the gut microbiota: visualization and bibliometric analysis

Background

Psoriasis is a common chronic inflammatory skin disease with a complex pathogenesis. Recently, the role of gut microbiota in psoriasis has attracted increasing attention. A systematic bibliometric analysis of relevant literature is necessary to understand better the current state and development trends in this field.

Materials and methods

The Web of Science Core Collection database was searched for literature indexed from 2004 to October 15, 2024. Bibliometric analysis was conducted using Bibliometrix, CiteSpace (version 6.3.R1), R 4.2.2 with the Bibliometrix package, Scimago Graphica 1.0.45, and VOSviewer (version 1.6.20.0) to visualize publication types, years, authors, countries, institutions, journal sources, references, and keywords.

Results

The development of psoriasis and gut microbiota research can be divided into two phases: slow growth (2004-2014) and rapid development (2014-2024). Lidia Rudnicka is the most active and influential author. China produced the highest number of publications, followed by the United States, which had the highest number of citations per article. The International Journal of Molecular Sciences published the most articles. In contrast, articles in the Journal of Investigative Dermatology, British Journal of Dermatology, and Journal of Allergy and Clinical Immunology were cited over 1,000 times. Keyword and co-citation analyses identified evolving research hotspots. Early studies focused on the association between gut microbiota and comorbid inflammatory diseases. Recent research has delved into specific mechanisms, such as disruption of gut barrier function, short-chain fatty acid metabolism alterations, impaired regulatory T-cell function, and excessive activation of Th17 cells. These mechanisms highlight how gut dysbiosis exacerbates psoriasis patients' systemic inflammation and skin lesions.

Conclusion

The field of psoriasis and gut microbiota research is developing rapidly despite uneven research distribution. This bibliometric evaluation assesses the current state of research and provides new perspectives for understanding the complex interactions between microbes and the host. Future efforts should strengthen international collaboration to deeply explore the mechanisms of gut microbiota's role in psoriasis, especially its potential applications in disease diagnosis and treatment.

Efficacy and safety of probiotic and synbiotic supplementation in metabolic syndrome: a systematic review and meta-analysis

AIMS

This review aims to address current research gaps and evaluate the effectiveness and safety of probiotic and synbiotic supplementation in patients with metabolic syndrome (MetS).

DATA SYNTHESIS

Four databases (PubMed, Cochrane, Embase, and Web of Science) were searched to find the randomized controlled trials published up to October 20, 2023. Anthropometric measurements, glucose, blood pressure and lipid metabolism were main outcomes, inflammatory markers, liver function, and etc. were the secondary outcomes. A meta-analysis was conducted by Review Manager 5.4 and STATA 15.0. In addition, sensitivity analysis and subgroup analysis were conducted to assess the stability of outcomes and potential sources of heterogeneity. Twenty-four full-text articles met the inclusion criteria, involving 1186 patients. The pooled analysis demonstrated significant reductions in body weight (WMD: -0.79 kg; p = 0.001), waist circumference (WMD: -1.04 cm; p = 0.0007), total cholesterol (SMD: -0.14; p = 0.03), triglyceride (SMD: -0.25; p = 0.0001), fasting blood glucose (SMD: -0.20; p = 0.003), and insulin levels (SMD: -0.17; p = 0.03). Additionally, the probiotic and synbiotic group showed increased high-density lipoprotein cholesterol (SMD: 0.15; p = 0.02). Subgroup analysis implied that age <50 years, intervention duration <12 weeks, and Asian patients may have better curative effects. No significant increase in adverse reactions was reported.

CONCLUSIONS

Probiotic and synbiotic supplementation can effectively improve body composition, lipid metabolism, and glucose metabolism in MetS patients without increasing adverse reactions. Further rigorous and long-term trials are required to validate these results and refine intervention details.

RSV infection in neonatal mice and gastrointestinal microbiome alteration contribute to allergic predisposition

Severe respiratory syncytial virus (RSV) infection during infancy is associated with a 2 to 4-fold increased risk for the development of wheezing and asthma. Recent studies have implicated microbiome changes, either within the lung or gut, during early life can also affect the development of pulmonary disease. Our studies demonstrate long-term gastrointestinal and lung microbiome changes following early life (EL) RSV infection. To determine the respective roles of ELRSV infection and the gut microbiome, we performed germ-free neonatal infection and microbiome colonization using a microbiome from an uninfected animal followed by cockroach allergen (CRA)-induced asthma 4 weeks later. Germ-free animals with ELRSV infection displayed increased airway disease that was diminished by microbiome colonization, including airway hyperreactivity (AHR), mucus, and eosinophil infiltration. To address the role of virus induced gastrointestinal microbiome alterations, we utilized GF mice conventionalized with RSV-associated or naive microbiomes followed by CRA-induced disease. Transfer of neonatal microbiome taken during acute RSV infection did not alter the allergic response to CRA. However, the transfer of a naive adult microbiome conferred protection from enhanced AHR in response to CRA whereas an RSV associated microbiome did not. Taken together, our data indicate that microbiome alteration and early life RSV infection both contribute to allergic predisposition.

Fatty acid metabolism: The crossroads in intestinal homeostasis and tumor

Fatty acids (FAs) have various functions on cell regulation considering their abundant types and metabolic pathways. In addition, the relation between FA and other nutritional metabolism makes their functions more complex. As the first place for diet-derived FA metabolism, intestine is significantly influenced despite lack of clear conclusions due to the inconsistent findings. In this review, we discuss the regulation of fatty acid metabolism on the fate of intestinal stem cells in homeostasis and disorders, and also focus on the intestinal tumor development and treatment from the aspect of gut microbiota-epithelium-immune interaction. We summarize that the balances between FA oxidation and glycolysis, between oxidative phosphorylation and ketogenesis, between catabolism and anabolism, and the specific roles of individual FA types determine the diverse effects of intestinal FA metabolism in different cases. We hope this will inspire further dissection and suggest precise dietary/metabolic intervention for different demands related to intestinal health.