Cultivated human intestinal fungus Candida metapsilosis M2006B attenuates colitis by secreting acyclic sesquiterpenoids as FXR agonists

Insights into gut fungi in pigs: A comprehensive review

Fungi in the gut microbiota of mammals play a crucial role in host physiological regulation, including intestinal homeostasis and host immune regulation. However, our understanding of gut fungi in mammals remains limited, especially in economically valuable animals, such as pigs. Therefore, this review first describes the classification and characterisation of fungi, provides insights into the methods used to study gut fungi, and summarises the recent progress on pig gut fungi. Additionally, it discusses the challenges in the study of pig gut fungi and highlights potential perspectives. The aim of this review is to serve as a valuable reference for advancing our knowledge of gut fungi in animals.

Role of Candida species in pathogenesis, immune regulation, and prognostic tools for managing ulcerative colitis and Crohn's disease

The gut microbiome plays a key role in the pathogenesis and disease activity of inflammatory bowel disease (IBD). While research has focused on the bacterial microbiome, recent studies have shifted towards host genetics and host-fungal interactions. The mycobiota is a vital component of the gastrointestinal microbial community and plays a significant role in immune regulation. Among fungi, Candida species, particularly Candida albicans (C. albicans), have been extensively studied due to their dual role as gut commensals and invasive pathogens. Recent findings indicate that various strains of C. albicans exhibit considerable differences in virulence factors, impacting IBD's pathophysiology. Intestinal fungal dysbiosis and antifungal mucosal immunity may be associated to IBD, especially Crohn's disease (CD). This article discusses intestinal fungal dysbiosis and antifungal immunity in healthy individuals and CD patients. It discusses factors influencing the mycobiome's role in IBD pathogenesis and highlights significant contributions from the scientific community aimed at enhancing understanding of the mycobiome and encouraging further research and targeted intervention studies on specific fungal populations. Our article also provided insights into a recent study by Wu et al in the World Journal of Gastroenterology regarding the role of the gut microbiota in the pathogenesis of CD.

Unveiling the overlooked fungi: the vital of gut fungi in inflammatory bowel disease and colorectal cancer

The fungi of the human microbiota play important roles in the nutritional metabolism and immunological balance of the host. Recently, research has increasingly emphasised the role of fungi in modulating inflammation in intestinal diseases and maintaining health in this environment. It is therefore necessary to understand more clearly the interactions and mechanisms of the microbiota/pathogen/host relationship and the resulting inflammatory processes, as well as to offer new insights into the prevention, diagnosis and treatment of inflammatory bowel disease (IBD), colorectal cancer (CRC) and other intestinal pathologies. In this review, we comprehensively elucidate the fungal-associated pathogenic mechanisms of intestinal inflammation in IBD and related CRC, with an emphasis on three main aspects: the direct effects of fungi and their metabolites on the host, the indirect effects mediated by interactions with other intestinal microorganisms and the immune regulation of the host. Understanding these mechanisms will enable the development of innovative approaches based on the use of fungi from the resident human microbiota such as dietary interventions, fungal probiotics and faecal microbiota transplantation in the prevention, diagnosis and treatment of intestinal diseases.

TNF compromises intestinal bile-acid tolerance dictating colitis progression and limited infliximab response

The intestine constantly encounters and adapts to the external environment shaped by diverse dietary nutrients. However, whether and how gut adaptability to dietary challenges is compromised in ulcerative colitis is incompletely understood. Here, we show that a transient high-fat diet exacerbates colitis owing to inflammation-compromised bile acid tolerance. Mechanistically, excessive tumor necrosis factor (TNF) produced at the onset of colitis interferes with bile-acid detoxification through the receptor-interacting serine/threonine-protein kinase 1/extracellular signal-regulated kinase pathway in intestinal epithelial cells, leading to bile acid overload in the endoplasmic reticulum and consequent apoptosis. In line with the synergy of bile acids and TNF in promoting gut epithelial damage, high intestinal bile acids correlate with poor infliximab response, and bile acid clearance improves infliximab efficacy in experimental colitis. This study identifies bile acids as an "opportunistic pathogenic factor" in the gut that would represent a promising target and stratification criterion for ulcerative colitis prevention/therapy.

Biotransformation of chenodeoxycholic acid by human intestinal fungi and the agonistic effects on FXR

Bile acids play a vital role in modulating host metabolism, with chenodeoxycholic acid (CDCA) standing out as a primary bile acid that naturally activates farnesoid X receptor (FXR). In this study, we investigated the microbial transformations of CDCA by seven human intestinal fungal species. Our findings revealed that hydroxylation and dehydrogenation were the most prevalent metabolic pathways. Incubation of CDCA with Rhizopus microspores (PT2906) afforded eight undescribed compounds (6-13) alongside five known analogs (1-5) which were elucidated by HRESI-MS and NMR data. Notably, compounds 8, 12 and 13 exhibited an inhibitory effect on FXR in contrast to the FXR activation observed with CDCA in vitro assays. This study shone a light on the diverse transformations of CDCA by intestinal fungi, unveiling potential modulators of FXR activity with implications for host metabolism.

Gut virome-wide association analysis identifies cross-population viral signatures for inflammatory bowel disease

BACKGROUND

The gut virome has been implicated in inflammatory bowel disease (IBD), yet a full understanding of the gut virome in IBD patients, especially across diverse geographic populations, is lacking.

RESULTS

In this study, we conducted a comprehensive gut virome-wide association study in a Chinese cohort of 71 IBD patients (15 with Crohn's disease and 56 with ulcerative colitis) and 77 healthy controls via viral-like particle (VLP) and bulk virome sequencing of their feces. By utilizing an integrated gut virus catalog tailored to the IBD virome, we revealed fundamental alterations in the gut virome in IBD patients. These characterized 139 differentially abundant viral signatures, including elevated phages predicted to infect Escherichia, Klebsiella, Enterococcus_B, Streptococcus, and Veillonella species, as well as IBD-depleted phages targeting Prevotella, Ruminococcus_E, Bifidobacterium, and Blautia species. Remarkably, these viral signatures demonstrated high consistency across diverse populations such as those in Europe and the USA, emphasizing their significance and broad relevance in the disease context. Furthermore, fecal virome transplantation experiments verified that the colonization of these IBD-characterized viruses can modulate experimental colitis in mouse models.

CONCLUSIONS

Building upon these insights into the IBD gut virome, we identified potential biomarkers for prognosis and therapy in IBD patients, laying the foundation for further exploration of viromes in related conditions. Video Abstract.

A genomic compendium of cultivated human gut fungi characterizes the gut mycobiome and its relevance to common diseases

The gut fungal community represents an essential element of human health, yet its functional and metabolic potential remains insufficiently elucidated, largely due to the limited availability of reference genomes. To address this gap, we presented the cultivated gut fungi (CGF) catalog, encompassing 760 fungal genomes derived from the feces of healthy individuals. This catalog comprises 206 species spanning 48 families, including 69 species previously unidentified. We explored the functional and metabolic attributes of the CGF species and utilized this catalog to construct a phylogenetic representation of the gut mycobiome by analyzing over 11,000 fecal metagenomes from Chinese and non-Chinese populations. Moreover, we identified significant common disease-related variations in gut mycobiome composition and corroborated the associations between fungal signatures and inflammatory bowel disease (IBD) through animal experimentation. These resources and findings substantially enrich our understanding of the biological diversity and disease relevance of the human gut mycobiome.

Characterizations of gut bacteriome, mycobiome, and virome of healthy individuals living in sea-level and high-altitude areas

BACKGROUND

The contribution of gut microbiota to human high-altitude adaptation remains inadequately understood.

METHODS

Here a comparative analysis of gut microbiota was conducted between healthy individuals living at sea level and high altitude using deep whole-metagenome shotgun sequencing, to investigate the adaptive mechanisms of gut microbiota in plateau inhabitants.

RESULTS

The results showed the gut bacteriomes in high-altitude individuals exhibited greater within-sample diversity and significant alterations in both bacterial compositional and functional profiles when compared to those of sea-level individuals, indicating the potential selection of unique bacteria associated with high-altitude environments. The strain-level investigation revealed enrichment of Collinsella aerofaciens and Akkermansia muciniphila in high-altitude populations. The characteristics of gut virome and gut mycobiome were also investigated. Compared to sea-level subjects, high-altitude subjects exhibited a greater diversity in their gut virome, with an increased number of viral operational taxonomic units (vOTUs) and unique annotated genes. Finally, correlation analyses revealed 819 significant correlations between 42 bacterial species and 375 vOTUs, while no significant correlations were observed between bacteria and fungi or between fungi and viruses.

CONCLUSION

The findings have significantly contributed to an enhanced comprehension of the mechanisms underlying the high-altitude geographic adaptation of the human gut microbiota.

Discovery of antifungal secondary metabolites from an intestinal fungus Fusarium sp

Intestinal fungi, which are important parts of the gut microbiota, have the ability to produce specialized metabolites that significantly contribute to maintaining the balance of the gut microbiota and promoting the health of the host organism. In the present study, two new glycosides, including fusintespyrone A (1) and cerevisterolside A (4), as well as ten known compounds were isolated from the intestinal fungus Fusarium sp. LE06. The structures of the new compounds were elucidated by a combination of spectroscopic methods, such as mass spectrometry (MS) and nuclear magnetic resonance (NMR), along with chemical reactions and calculations of NMR and ECD spectra. Compounds 1-3 showed significant growth inhibition against Aspergillus fumigatus, Fusarium oxysporum, and Verticillium dahliae with MIC values in the range of 1.56-6.25 μg ml-1.

A comprehensive guide to assess gut mycobiome and its role in pathogenesis and treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is an immune mediated chronic inflammatory disorder of gastrointestinal tract, which has underlying multifactorial pathogenic determinants such as environmental factors, susceptibility genes, gut microbial dysbiosis and a dysregulated immune response. Human gut is a frequent inhabitant of complex microbial ecosystem encompassing bacteria, viruses, parasites, fungi and other microorganisms that have an undisputable role in maintaining balanced homeostasis. All of these microbes interact with immune system and affect human gut physiology either directly or indirectly with interaction of each other. Intestinal fungi represent a smaller but crucial component of the human gut microbiome. Besides interaction with bacteriome and virome, it helps in balancing homoeostasis between pathophysiological and physiological processes, which is often dysregulated in patients with IBD. Understanding of gut mycobiome and its clinical implications are still in in its infancy as opposed to bacterial component of gut microbiome, which is more often focused. Modulation of gut mycobiome represents a novel and promising strategy in the management of patients with IBD. Emerging mycobiome-based therapies such as diet interventions, fecal microbiota transplantation (FMT), probiotics (both fungal and bacterial strains) and antifungals exhibit substantial effects in calibrating the gut mycobiome and restoring dysbalanced immune homeostasis by restoring the core gut mycobiome. In this review, we summarized compositional and functional diversity of the gut mycobiome in healthy individuals and patients with IBD, gut mycobiome dysbiosis in patients with IBD, host immune-fungal interactions and therapeutic role of modulation of intestinal fungi in patients with IBD.

The mycobiome as integral part of the gut microbiome: crucial role of symbiotic fungi in health and disease

The gut mycobiome significantly affects host health and immunity. However, most studies have focused on symbiotic bacteria in the gut microbiome, whereas less attention has been given to symbiotic fungi. Although fungi constitute only 0.01%-0.1% of the gut microbiome, their larger size and unique immunoregulatory functions make them significant. Factors like diet, antimicrobials use, and age can disrupt the fungal community, leading to dysbiosis. Fungal-bacterial-host immune interactions are critical in maintaining gut homeostasis, with fungi playing a role in mediating immune responses such as Th17 cell activation. This review highlights methods for studying gut fungi, the composition and influencing factors of the gut mycobiome, and its potential in therapeutic interventions for intestinal and hepatic diseases. We aim to provide new insights into the underexplored role of gut fungi in human health.

Unveiling the hidden players: exploring the role of gut mycobiome in cancer development and treatment dynamics

The role of gut fungal species in tumor-related processes remains largely unexplored, with most studies still focusing on fungal infections. This review examines the accumulating evidence suggesting the involvement of commensal and pathogenic fungi in cancer biological process, including oncogenesis, progression, and treatment response. Mechanisms explored include fungal influence on host immunity, secretion of bioactive toxins/metabolites, interaction with bacterial commensals, and migration to other tissues in certain types of cancers. Attempts to utilize fungal molecular signatures for cancer diagnosis and fungal-derived products for treatment are discussed. A few studies highlight fungi's impact on the responsiveness and sensitivity to chemotherapy, radiotherapy, immunotherapy, and fecal microbiota transplant. Given the limited understanding and techniques in fungal research, the studies on gut fungi are still facing great challenges, despite having great potentials.

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

Gut mycobiome: A "black box" of gut microbiome-host interactions

Fungi, being a necessary component of the gut microbiome, potentially have direct or indirect effects on the health and illness status of the host. The gut mycobiome is an inducer of the host's immunity, maintaining intestinal homeostasis, and protecting against infections, as well as a reservoir of opportunistic microorganisms and a potential cofactor when the host is immunocompromised. In addition, gut fungi interact with a diverse range of microbes in the intestinal niches. In this article, we reviewed the composition of gut mycobiome, their association with host health and illness, and summarized the specific Candida albicans-host interactions, in order to provide insights and directions for the ongoing study of fungi. This article is categorized under: Infectious Diseases > Molecular and Cellular Physiology.

Beneficial herb-drug interaction of rhein in Jinhongtang and Imipenem/Cilastatin mediated by organic anion transporters

ETHNOPHARMACOLOGICAL RELEVANCE

Jinhongtang as a traditional Chinese medicine (TCM) formula, has been widely used as a clinical adjuvant in the treatment of acute abdominal diseases and sepsis. Clinical benefits of the concurrent use of Jinhongtang and antibiotics have been observed, however, the mechanism has not been fully understood.

AIM OF THE STUDY

The present study aimed to explore the effect of Jinhongtang on the antibacterial activity of Imipenem/Cilastatin and to clarify the underlying mechanism of herb-drug interaction (HDI).

MATERIALS AND METHODS

A mouse model of sepsis induced by Staphylococcus aureus (S. aureus) was used to evaluate the pharmacodynamic interaction in vivo. In vitro antibacterial activity of Imipenem/Cilastatin was studied by determining minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Pharmacokinetic interaction was investigated by pharmacokinetic studies in rats and uptake assays using OAT1/3-HEK293 cells. The main constituents ingested into blood of rats were qualitatively identified by UHPLC-Q-TOF-MS.

RESULTS

Mice treated by Imipenem/Cilastatin and Jinhongtang exhibited higher survival rate, lower bacteria load and less inflammation in blood and lung tissues, compared with those treated by Imipenem/Cilastatin alone after injection of S. aureus. However, MIC and MBC of Imipenem/Cilastatin against S. aureus in vitro were not significantly changed in the presence of Jinhongtang. On the contrary, Jinhongtang increased the plasma concentration of Imipenem and decreased its urinary excretion in rats. CL_r of Imipenem was reduced by 58.5%, while its half-life (t_1/2) was prolonged for approximate 1.2 times after coadministered Jinhongtang. Furthermore, the extracts of Jinhongtang, single herb in the prescription, and main absorbable constituents inhibited cellular uptake of probe substrates and Imipenem by OAT1/3-HEK293 cells to different extents. Among them, rhein exhibited the strongest inhibition capacity with IC₅₀ values of 0.08 ± 0.01 μM (OAT1) and 2.86 ± 0.28 μM (OAT3). Moreover, coadministration of rhein also significantly enhanced the antibacterial activity of Imipenem/Cilastatin in sepsis mice.

CONCLUSION

Concomitant administration of Jinhongtang enhanced antibacterial activity of Imipenem/Cilastatin in sepsis mice induced by S. aureus through reducing renal elimination of Imipenem via inhibition of OATs. Our investigation provided the insight of Jinhongtang as an effective supplement to enhance the antibacterial activity of Imipenem/Cilastatin and can be useful for future clinical studies.

Bile acids and their receptors: Potential therapeutic targets in inflammatory bowel disease

Chronic and recurrent inflammatory disorders of the gastrointestinal tract caused by a complex interplay between genetics and intestinal dysbiosis are called inflammatory bowel disease. As a result of the interaction between the liver and the gut microbiota, bile acids are an atypical class of steroids produced in mammals and traditionally known for their function in food absorption. With the development of genomics and metabolomics, more and more data suggest that the pathophysiological mechanisms of inflammatory bowel disease are regulated by bile acids and their receptors. Bile acids operate as signalling molecules by activating a variety of bile acid receptors that impact intestinal flora, epithelial barrier function, and intestinal immunology. Inflammatory bowel disease can be treated in new ways by using these potential molecules. This paper mainly discusses the increasing function of bile acids and their receptors in inflammatory bowel disease and their prospective therapeutic applications. In addition, we explore bile acid metabolism and the interaction of bile acids and the gut microbiota.

Bile Acids, Intestinal Barrier Dysfunction, and Related Diseases

The intestinal barrier is a precisely regulated semi-permeable physiological structure that absorbs nutrients and protects the internal environment from infiltration of pathological molecules and microorganisms. Bile acids are small molecules synthesized from cholesterol in the liver, secreted into the duodenum, and transformed to secondary or tertiary bile acids by the gut microbiota. Bile acids interact with bile acid receptors (BARs) or gut microbiota, which plays a key role in maintaining the homeostasis of the intestinal barrier. In this review, we summarize and discuss the recent studies on bile acid disorder associated with intestinal barrier dysfunction and related diseases. We focus on the roles of bile acids, BARs, and gut microbiota in triggering intestinal barrier dysfunction. Insights for the future prevention and treatment of intestinal barrier dysfunction and related diseases are provided.

Bile acid alterations associated with indolent course of inflammatory bowel disease

BACKGROUND

The indolent course of treatment-naive patients with inflammatory bowel disease (IBD) is confirmed predictable based on clinical characteristics. Current evidences supported that bile acids (BAs) alteration might be promising biomarkers in the field of IBD. We aimed to analyze the alterations of BAs as the disease progresses and explore their predictive value for indolent course of IBD.

METHODS

The indolent course of IBD was defined as a disease course without need for strict interventions throughout the entire follow-up. A targeted metabolomics method was used to detect the concentration of 27 BAs from serum sample in treatment-naive patients with IBD (Crohn's disease [CD], n = 27; ulcerative colitis [UC], n = 50). Patients with CD and UC were individually divided into two groups for further study according to the median time of indolent course. The overall BAs profile and the clinical value of BAs in predicting indolent course of IBD were identified between different groups.

RESULTS

For CD, the levels of deoxycholic acid, glycodeoxycholic acid, taurodeoxycholic acid, glycolithocholic acid-3-sulfate disodium salt and iso-lithocholic acid were significantly increased in patients with indolent course > 18 M (p < 0.05). These five BAs owned 83.5% accuracy for predicting indolent course over 18 months in CD. For UC, the concentration of deoxycholic acid and glycodeoxycholic acid were significantly higher, while dehydrocholic acid were lower in patients with indolent course > 48 M (p < 0.05). These three BAs predicted indolent course over 48 months of 69.8% accuracy in UC.

CONCLUSION

The specific BAs alterations might be potential biomarkers in predicting disease course of IBD patients.

Fungal gut microbiota dysbiosis in systemic lupus erythematosus

Introduction

Despite recent developments in our comprehension of how the gut microbiota and systemic lupus erythematosus (SLE) are related. The mycobiome: which is a small but crucial part of the gut microbiota and is involved in hosts’ homeostasis and physiological processes, remained unexplored in SLE.

Methods

We profiled the gut fungal mycobiota based on internal transcribed spacer region 1 (ITS1) sequencing for the gut microbial DNA from the SLE individuals with lupus nephritis (LN) (n = 23), SLE without LN (n = 26) and healthy controls (n = 14) enrolled in Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School.

Results

The ITS sequencing generated a total of 4.63 million valid tags which were stratified into 4,488 operational taxonomic units (OTUs) and identified about 13 phyla and 262 genera. Patients with SLE were characterized with unique fungal flora feature. The fungal microbiomes of the three groups displayed distinct beta diversity from each other. Compared with HC group, the abundance of fungal dysbiosis was reflected in a higher ratio of opportunistic fungi in SLE or LN group, as well as the loss of Rhizopus and Malassezia. The main principal components of the flora between the SLE and LN group were generally consistent. The relative abundance of Vanrija in the fecal fungal community was higher in LN group, while the relative abundance of Fusarium was higher in SLE group. Moreover, our data revealed superior diagnostic accuracy for SLE with the fungal species (e.g. Candida, Meyerozyma). Correlations between gut fungi and clinical parameters were identified by Spearman’s correlation analysis. Interestingly, Aspergillus in SLE patients was positively correlated with ACR, 24 h proteinuria, proteinuria, anti-dsDNA, ANA, and SLEDAI, while Rhizopus was negatively correlated with lymphocytes and Hb. Finally, we successfully cultured the fungi and identified it as Candida glabrata by microscopic observation and mass spectrometry.

Discussion

We first explored the highly significant gut fungal dysbiosis and ecology in patients with SLE, and demonstrated the applicability of fungal species as SLE diagnostic tools, signifying that the gut fungal mycobiome-host interplay can potentially contribute in disease pathogenesis.

Mycobiome and Inflammatory Bowel Disease: Role in Disease Pathogenesis, Current Approaches and Novel Nutritional-based Therapies

Inflammatory bowel disease (IBD), a disorder characterized by chronic inflammation of the gastrointestinal (GI) tract and a range of adverse health effects including diarrhea, abdominal pain, vomiting, and bloody stools, affects nearly 3.1 million genetically susceptible adults in the United States today. Although the etiology of IBD remains unclear, genetics, stress, diet, and gut microbiota dysbiosis- especially in immunocompromised individuals- have been identified as possible causes of disease. Although previous research has largely focused on the role of bacteria in IBD pathogenesis, recently observed alterations of fungal load and biodiversity in the GI tract of afflicted individuals suggest interkingdom interactions amongst different gut microbial communities, particularly between bacteria and fungi. These discoveries point to the potential utilization of treatment approaches such as antibiotics, antifungals, probiotics, and postbiotics that target both bacteria and fungi in managing IBD. In this review, we discuss the impact of specific fungi on disease pathogenesis, with a focus on the highly virulent genus Candida and how the presence of certain co-enzymes impacts its virulence. In addition, we evaluate current gut microbiome-based therapeutic approaches with the intention of better understanding the mechanisms behind novel therapies.

Therapeutic role of ursodeoxycholic acid in colitis-associated cancer via gut microbiota modulation

Inflammatory bowel disease (IBD) is a predisposing factor for colitis-associated cancer (CAC). The association between bile acids and the gut microbiota has been demonstrated in colon neoplasia; however, the effect of ursodeoxycholic acid (UDCA) on gut microbiota alteration in development of colitis and CAC is unknown. Our analysis of publicly available datasets demonstrated the association of UDCA treatment and accumulation of Akkermansia. UDCA-mediated alleviation of DSS-induced colitis was microbially dependent. UDCA treatment significantly upregulated Akkermansia colonization in a mouse model. Colonization of Akkermansia was associated with enhancement of the mucus layer upon UDCA treatment as well as activation of bile acid receptors in macrophages. UDCA played a role in CAC prevention and treatment in the AOM-DSS and ApcMin/+-DSS models through downregulation of inflammation and accumulation of Akkermansia. This study suggests that UDCA intervention could reshape intestinal gut homeostasis, facilitating colonization of Akkermansia and preventing and treating colitis and CAC.

Farnesoid-X receptor as a therapeutic target for inflammatory bowel disease and colorectal cancer

Farnesoid-X receptor (FXR), as a nuclear receptor activated by bile acids, is a vital molecule involved in bile acid metabolism. Due to its expression in immune cells, FXR has a significant effect on the function of immune cells and the release of chemokines when immune cells sense changes in bile acids. In addition to its regulation by ligands, FXR is also controlled by post-translational modification (PTM) activities such as acetylation, SUMOylation, and methylation. Due to the high expression of FXR in the liver and intestine, it significantly influences intestinal homeostasis under the action of enterohepatic circulation. Thus, FXR protects the intestinal barrier, resists bacterial infection, reduces oxidative stress, inhibits inflammatory reactions, and also acts as a tumor suppressor to impair the multiplication and invasion of tumor cells. These potentials provide new perspectives on the treatment of intestinal conditions, including inflammatory bowel disease (IBD) and its associated colorectal cancer (CRC). Moreover, FXR agonists on the market have certain organizational heterogeneity and may be used in combination with other drugs to achieve a greater therapeutic effect. This review summarizes current data on the role of FXR in bile acid metabolism, regulation of immune cells, and effects of the PTM of FXR. The functions of FXR in intestinal homeostasis and potential application in the treatment of IBD and CRC are discussed.

Microbial transformation of capsaicin by several human intestinal fungi and their inhibitory effects against lysine-specific demethylase 1

Capsaicin widely exists in the Capsicum genus (e.g., hot peppers) and is commonly used as a food additive or medicinal material. In this work, microbial transformation of capsaicin was performed based on the three cultivated human intestinal fungi. Fourteen metabolites were obtained, and their chemical structures were elucidated by spectroscopic data analysis, including 13 compounds with undescribed structures. Hydroxylation, lactylation, succinylation, citric acylation, and acetylation were observed for these microbial metabolites derived from capsaicin, which indicated diverse catalytic characteristics of human intestinal fungi. In an in vitro bioassay, four metabolites and capsaicin inhibited the activity of lysine-specific demethylase 1 (LSD1) with a more than 70% inhibitory rate at 10 μM. In particular, 9,5'-dihydroxycapsaicin displayed the strongest inhibitory effect with an IC₅₀ of 1.52 μM. Therefore, capsaicin analogs displayed potential application as LSD1 inhibitors against the invasion and migration of cancer cells.