A tryptophan metabolite made by a gut microbiome eukaryote induces pro-inflammatory T cells

Decoding Blastocystis-Driven Mechanisms in Gut Microbiota and Host Metabolism

Blastocystis, a prevalent eukaryotic microorganism in the gut microbiota, has emerged as a potential link between healthy diets and improved cardiometabolic health. Despite its genetic diversity and varied host interactions, Blastocystis is consistently associated with healthier dietary patterns and reduced risk of cardiometabolic diseases. Current evidence suggests that Blastocystis may influence host metabolism by modulating gut microbial composition, short-chain fatty acids (SCFAs) production, and immune cell differentiation. Moreover, its role in tryptophan metabolism provides intriguing insights into its potential impact on host signaling pathways. However, mechanistic evidence connecting Blastocystis to improved metabolic health remains limited. This perspective explores plausible pathways, including SCFAs-mediated signaling, tryptophan metabolism, and immune modulation, through which Blastocystis may exert its effects. A systematic research framework integrating axenic cultivation, in vitro co-culture systems, animal models, and multi-omics approaches is proposed to further elucidate these mechanisms and expand the understanding of Blastocystis in gut health and disease.

Gut commensal Lachnospiraceae bacteria contribute to anti-colitis effects of Lactiplantibacillus plantarum exopolysaccharides

The probiotic Lactiplantibacillus plantarum (L. plantarum) could ameliorate colitis. Alterations in the composition of gut microbiota (GM) have been proved in cases of colitis. The exopolysaccharides from L. plantarum HMPM2111 (LPE) could be effective in colitis through altering the composition of the GM. These effects were linked to inhibiting intestinal inflammation, regulating the TXNIP/NLRP3 inflammasome axis, and attenuating colonic barrier dysfunction. The combination of fecal microbiota transplantation (FMT) and antibiotic inducement showed that gut bacteria susceptible to vancomycin were inversely associated with colitis features and were necessary for the anti-inflammatory effects of LPE. The elevated abundances of gut commensal Lachnospiraceae bacteria were associated with the restoration of colitis treated by LPE. Metabolomics analysis showed that colitis mice treated with LPE had higher levels of propionate and tryptophan metabolites generated from gut bacteria. The administration of these metabolites protected colitis and resulted in a reduction in inflammatory responses. The outcomes of our investigation emerge the significance of the GM in controlling the protective implications of LPE against colitis. Lachnospiraceae bacteria, together with downstream metabolites, contribute substantially to protection. This work elucidates the essential function of the GM-metabolite axis in producing comprehensive protection versus colitis and identifies prospective treatment targets.

Exploring effects of gut microbiota on tertiary lymphoid structure formation for tumor immunotherapy

Anti-tumor immunity, including innate and adaptive immunity is critical in inhibiting tumorigenesis and development of tumor. The adaptive immunity needs specific lymph organs such as tertiary lymphoid structures (TLSs), which are highly correlated with improved survival outcomes in many cancers. In recent years, with increasing attention on the TLS in tumor microenvironment, TLSs have emerged as a novel target for anti-tumor therapy. Excitingly, studies have shown the contribution of TLSs to the adaptive immune responses. However, it is unclear how TLSs to form and how to more effectively defense against tumor through TLS formation. Recent studies have shown that the inflammation plays a critical role in TLS formation. Interestingly, studies have also found that gut microbiota can regulate the occurrence and development of inflammation. Therefore, we here summarize the potential effects of gut microbiota- mediated inflammation or immunosuppression on the TLS formation in tumor environments. Meanwhile, this review also explores how to manipulate mature TLS formation through regulating gut microbiota/metabolites or gut microbiota associated signal pathways for anti-tumor immunity, which potentially lead to a next-generation cancer immunotherapy.

Metabolism of Tryptophan, Glutamine, and Asparagine in Cancer Immunotherapy-Synergism or Mechanism of Resistance?

Amino acids are crucial components of proteins, key molecules in cellular physiology and homeostasis. However, they are also involved in a variety of other mechanisms, such as energy homeostasis, nitrogen exchange, further synthesis of bioactive compounds, production of nucleotides, or activation of signaling pathways. Moreover, amino acids and their metabolites have immunoregulatory properties, significantly affecting the behavior of immune cells. Immunotherapy is one of the oncological treatment methods that improves cytotoxic properties of one's own immune system. Thus, enzymes catalyzing amino acid metabolism, together with metabolites themselves, can affect immune antitumor properties and responses to immunotherapy. In this review, we will discuss the involvement of tryptophan, glutamine, and asparagine metabolism in the behavior of immune cells targeted by immunotherapy and summarize results of the most recent investigations on the impact of amino acid metabolites on immunotherapy.

Gut microbiota contributes to the intestinal and extraintestinal immune homeostasis by balancing Th17/Treg cells

Gut microbiota is generally considered to play an important role in host health due to its extensive immunomodulatory activities. Th17 and Treg cells are two important CD4+ T cell subsets involved in immune regulation, and their imbalance is closely tied to many immune diseases. Recently, abundant researches have highlighted the importance of gut microbiota in supporting intestinal and extraintestinal immunity through the balance of Th17 and Treg cells. Here, we presented a comprehensive review of these findings. This review first provided an overview of gut microbiota, along with Th17/Treg cell differentiation and cytokine production. Subsequently, the review summarized the regulatory effects of gut microbiota (in terms of species, components, and metabolites) on the Th17/Treg cell balance in the local intestines and extraintestinal organs, such as lung, liver, brain, kidney, and bone. Specifically, the Th17 and Treg cells that can be modulated by gut microbiota originate not only from the gut and extraintestinal organs, but also from peripheral blood and spleen. Then, the microbial therapeutics, including probiotics, prebiotics, postbiotics, and fecal microbiota transplantation (FMT), were also reviewed because of their therapeutic potentials in addressing intestinal and extraintestinal diseases via the Th17/Treg axis. Finally, the review discussed the clinical applications and future study prospects of microbial therapeutics by targeting the Th17/Treg cell balance. In conclusion, this review focused on elucidating the regulatory effects of gut microbiota in balancing Th17/Treg cells to maintain intestinal and extraintestinal immune homeostasis, contributing to the further development and promotion of microbial therapeutics.

Serum metabolic alterations in chickens upon infectious bursal disease virus infection

BACKGROUND

Infectious bursal disease virus (IBDV) is a highly contagious immunosuppressive virus of chickens. Chickens acquire infection by the oral route under natural conditions. Although the histological and pathological changes after IBDV infection are well described, the alterations in serum metabolome have not been reported. In this study, SPF chickens were infected with attenuated IBDV (atIBDV) strain LM and very virulent IBDV (vvIBDV) strain LX, respectively. On the seventh day after oral infection, serum samples of experimental chickens were identified using ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS). The serum metabolic profiles were analyzed by multivariate statistical methods. KEGG enrichment analysis was performed to evaluate the dysregulated biological pathways.

RESULTS

We identified 368 significantly altered metabolites in response to both atIBDV and vvIBDV infection. The metabolic disorder of amino acid and lipid was associated with IBDV infection, especially tryptophan, glycerophospholipid, lysine, and tyrosine metabolism. The differential metabolites enriched in the four metabolic pathways were PC(20:4(5Z,8Z,11Z,14Z)/18:0), PE(16:0/18:2(9Z,12Z)), PE(16:0/22:6(4Z,7Z,10Z,13Z,16Z,19Z)), PE(18:0/20:4(5Z,8Z,11Z,14Z)), PE(18:0/20:4(8Z,11Z,14Z,17Z)), PE(18:0/22:6(4Z,7Z,10Z,13Z,16Z,19Z)), PE(20:3(8Z,11Z,14Z)/16:0), PE(22:6(4Z,7Z,10Z,13Z,16Z,19Z)/16:0), PE-NMe(20:5(5Z,8Z,11Z,14Z,17Z)/18:0), PS(20:3(5Z,8Z,11Z)/18:2(9Z,12Z)), 2-aminobenzoic acid, 4-(2-aminophenyl)-2,4-dioxobutanoic acid, N-acetylserotonin, 5-hydroxyindoleacetate, indole-3-acetaldehyde, indole-3-acetate, p-coumaric acid, L-tyrosine, homovanillin, and S-glutaryldihydrolipoamide.

CONCLUSION

The atIBDV and vvIBDV infection causes metabolic changes in chicken serum. The differential metabolites and dysregulated metabolic pathways reflect the host response to the IBDV infection.

Intestinal Microbiota and Aging in People with HIV-What We Know and What We Don't

PURPOSE OF REVIEW

People with HIV (PWH) experience premature aging and an elevated risk of age-related comorbidities, even with viral suppression through antiretroviral therapy (ART). We examine gastrointestinal disruptions, specifically impaired intestinal barrier integrity and microbial dysbiosis, as contributors to these comorbidities.

RECENT FINDINGS

HIV infection compromises the intestinal epithelial barrier, increasing permeability and microbial translocation, which trigger inflammation and cellular stress. ART does not fully restore gut barrier integrity, leading to persistent inflammation and cellular stress. Additionally, HIV-associated microbial dysbiosis favors pro-inflammatory bacteria, intensifying inflammation and tissue damage, which may contribute to premature aging in PWH. Understanding the interactions between intestinal microbiota, chronic inflammation, cellular stress, and aging is essential to developing therapies aimed at reducing inflammation and slowing age-related diseases in PWH. In this review, we discuss critical knowledge gaps and highlight the therapeutic potential of microbiota-targeted interventions to mitigate inflammation and delay age-associated pathologies in PWH.

Supplementation with Chinese herbal preparations protect the gut-liver axis of Hu sheep, promotes gut-liver circulation, regulates intestinal flora and immunity

The gut-liver axis in ruminants can explain nutrient regulation, the gut-liver cycle, and immune function in ruminant biology through the gut microbe-gut metabolite-liver metabolite relationship. to investigate the effects of herbal feed additives on the gut-liver axis of Hu sheep. In this study, a broadly targeted UPLC-MS/MS metabolomics approach and 16s sequencing of gut microorganisms were used to detect, identify and quantify changes in ileal microorganisms, liver metabolites and ileal metabolites following the addition of Chinese herbal preparations. The addition of a 0.5% herbal feed additive increased ileal IgA, IgG and complement C3 levels. The addition of Chinese herbal preparations can increase the abundance of Firmicutes, Actinobacteriota, Bacteroidota, at the portal level of the ileum, increase the metabolism of organic matter and its derivatives, bile acids, amino acids and their metabolites, coenzymes, and vitamins in the liver and ileum, enhance nutrient absorption and waste metabolism, accelerate liver metabolism, promote gut-liver circulation, and improve ileal and liver immunity. This study provides a theoretical basis for understanding the effects of herbal feed additives on the gut-liver axis in ruminants.

Molecular mechanisms and therapeutic significance of Tryptophan Metabolism and signaling in cancer

Tryptophan (Trp) metabolism involves three primary pathways: the kynurenine (Kyn) pathway (KP), the 5-hydroxytryptamine (serotonin, 5-HT) pathway, and the indole pathway. Under normal physiological conditions, Trp metabolism plays crucial roles in regulating inflammation, immunity, and neuronal function. Key rate-limiting enzymes such as indoleamine-2,3-dioxygenase (IDO), Trp-2,3-dioxygenase (TDO), and kynurenine monooxygenase (KMO) drive these metabolic processes. Imbalances in Trp metabolism are linked to various cancers and often correlate with poor prognosis and adverse clinical characteristics. Dysregulated Trp metabolism fosters tumor growth and immune evasion primarily by creating an immunosuppressive tumor microenvironment (TME). Activation of the KP results in the production of immunosuppressive metabolites like Kyn, which modulate immune responses and promote oncogenesis mainly through interaction with the aryl hydrocarbon receptor (AHR). Targeting Trp metabolism therapeutically has shown significant potential, especially with the development of small-molecule inhibitors for IDO1, TDO, and other key enzymes. These inhibitors disrupt the immunosuppressive signals within the TME, potentially restoring effective anti-tumor immune responses. Recently, IDO1 inhibitors have been tested in clinical trials, showing the potential to enhance the effects of existing cancer therapies. However, mixed results in later-stage trials underscore the need for a deeper understanding of Trp metabolism and its complex role in cancer. Recent advancements have also explored combining Trp metabolism inhibitors with other treatments, such as immune checkpoint inhibitors, chemotherapy, and radiotherapy, to enhance therapeutic efficacy and overcome resistance mechanisms. This review summarizes the current understanding of Trp metabolism and signaling in cancer, detailing the oncogenic mechanisms and clinical significance of dysregulated Trp metabolism. Additionally, it provides insights into the challenges in developing Trp-targeted therapies and future research directions aimed at optimizing these therapeutic strategies and improving patient outcomes.

An Update on Blastocystis: Possible Mechanisms of Blastocystis-Mediated Colorectal Cancer

Blastocystis is an anaerobic parasite that colonizes the intestinal tract of humans and animals. When it was first discovered, Blastocystis was considered to be a normal flora with beneficial effects on human health, such as maintaining gut hemostasis and improving intestinal barrier integrity. Later, with increasing research on Blastocystis, reports showed that Blastocystis sp. is associated with gastrointestinal disorders, colorectal cancer (CRC), and neurological disorders. The association between Blastocystis sp. and CRC has been confirmed in several countries. Blastocystis sp. can mediate CRC via similar mechanisms to CRC-associated bacteria, including infection-mediated inflammation, increased oxidative stress, induced gut dysbiosis, and damage to intestinal integrity, leading to a leaky gut. IL-8 is the main inflammatory cytokine released from epithelial cells and can promote CRC development. The causal association of Blastocystis sp. with other diseases needs further investigation. In this review, we have provided an update on Blastocystis sp. and summarized the debate about the beneficial and harmful effects of this parasite. We have also highlighted the possible mechanisms of Blastocystis-mediated CRC.

Metabolic Pathways Affected in Patients Undergoing Hemodialysis and Their Relationship with Inflammation

Worldwide, 3.9 million individuals rely on kidney replacement therapy. They experience heightened susceptibility to cardiovascular diseases and mortality, alongside an increased risk of infections and malignancies, with inflammation being key to explaining this intensified risk. This study utilized semi-targeted metabolomics to explore novel metabolic pathways related to inflammation in this population. We collected pre- and post-session blood samples of patients who had already undergone one year of chronic hemodialysis and used liquid chromatography and high-resolution mass spectrometry to perform a metabolomic analysis. Afterwards, we employed both univariate (Mann-Whitney test) and multivariate (logistic regression with LASSO regularization) to identify metabolites associated with inflammation. In the univariate analysis, indole-3-acetaldehyde, 2-ketobutyric acid, and urocanic acid showed statistically significant decreases in median concentrations in the presence of inflammation. In the multivariate analysis, metabolites positively associated with inflammation included allantoin, taurodeoxycholic acid, norepinephrine, pyroglutamic acid, and L-hydroorotic acid. Conversely, metabolites showing negative associations with inflammation included benzoic acid, indole-3-acetaldehyde, methionine, citrulline, alphaketoglutarate, n-acetyl-ornithine, and 3-4-dihydroxibenzeneacetic acid. Non-inflamed patients exhibit preserved autophagy and reduced mitochondrial dysfunction. Understanding inflammation in this group hinges on the metabolism of arginine and the urea cycle. Additionally, the microbiota, particularly uricase-producing bacteria and those metabolizing tryptophan, play critical roles.

Tryptophan As a New Member of RNA-Induced Silencing Complexes Prevents Colon Cancer Liver Metastasis

Essential amino acids (EAA) and microRNAs (miRs) control biological activity of a cell. Whether EAA regulates the activity of miR has never been demonstrated. Here, as proof-of-concept, a tryptophan (Trp, an EAA) complex containing Argonaute 2 (Ago2) and miRs including miR-193a (Trp/Ago2/miR-193a) is identified. Trp binds miR-193a-3p and interacts with Ago2. Trp/Ago2/miR-193a increases miR-193a-3p activity via enhancing Argonaute 2 (Ago2) RNase activity. Other miRs including miR-103 and miR-107 in the Trp complex enhance miR-193a activity by targeting the same genes. Mechanistically, the Trp/Ago2/miR-193a complex interacts with Trp-binding pockets of the PIWI domain of Ago2 to enhance Ago2 mediated miR activity. This newly formed Ago2/Trp/miR-193a-3p complex is more efficient than miR-193a-3p alone in inhibiting the expression of targeted genes and inhibiting colon cancer liver metastasis. The findings show that Trp regulates miR activity through communication with the RNA-induced silencing complexes (RISC), which provides the basis for tryptophan based miR therapy.

Aryl Hydrocarbon Receptor Signalling in the Control of Gut Inflammation

Aryl hydrocarbon receptor (AHR), a transcription factor activated by many natural and synthetic ligands, represents an important mediator of the interplay between the environment and the host's immune responses. In a healthy gut, AHR activation promotes tolerogenic signals, which help maintain mucosal homeostasis. AHR expression is defective in the inflamed gut of patients with inflammatory bowel diseases (IBD), where decreased AHR signaling is supposed to contribute to amplifying the gut tissue's destructive immune-inflammatory responses. We here review the evidence supporting the role of AHR in controlling the "physiological" intestinal inflammation and summarize the data about the therapeutic effects of AHR activators, both in preclinical mouse models of colitis and in patients with IBD.

Commensal protist Tritrichomonas musculus exhibits a dynamic life cycle that induces extensive remodeling of the gut microbiota

Commensal protists and gut bacterial communities exhibit complex relationships, mediated at least in part through host immunity. To improve our understanding of this tripartite interplay, we investigated community and functional dynamics between the murine protist Tritrichomonas musculus and intestinal bacteria in healthy and B-cell-deficient mice. We identified dramatic, protist-driven remodeling of resident microbiome growth and activities, in parallel with Tritrichomonas musculus functional changes, which were accelerated in the absence of B cells. Metatranscriptomic data revealed nutrient-based competition between bacteria and the protist. Single-cell transcriptomics identified distinct Tritrichomonas musculus life stages, providing new evidence for trichomonad sexual replication and the formation of pseudocysts. Unique cell states were validated in situ through microscopy and flow cytometry. Our results reveal complex microbial dynamics during the establishment of a commensal protist in the gut, and provide valuable data sets to drive future mechanistic studies.

Houttuynia cordata thunb. alleviates inflammatory bowel disease by modulating intestinal microenvironment: a research review

Inflammatory bowel disease (IBD) is a complex group of chronic intestinal diseases, the cause of which has not yet been clarified, but it is widely believed that the disorder of the intestinal microenvironment and its related functional changes are key factors in the development of the disease. Houttuynia cordata thunb. is a traditional plant with abundant resources and long history of utilization in China, which has attracted widespread attention in recent years due to its potential in the treatment of IBD. However, its development and utilization are limited owing to the aristolochic acid alkaloids contained in it. Therefore, based on the relationship between the intestinal microenvironment and IBD, this article summarizes the potential mechanisms by which the main active ingredients of Houttuynia cordata thunb., such as volatile oils, polysaccharides, and flavonoids, and related traditional Chinese medicine preparations, such as Xiezhuo Jiedu Formula, alleviate IBD by regulating the intestinal microenvironment. At the same time, combined with current reports, the medicinal and edible safety of Houttuynia cordata thunb. is explained for providing ideas for further research and development of Houttuynia chordate thunb. in IBD disease, more treatment options for IBD patients, and more insights into the therapeutic potential of plants with homology of medicine and food in intestinal diseases, and even more diseases.

Distinct Intestinal Microbial Signatures Linked to Accelerated Biological Aging in People with HIV

Background

People with HIV (PWH), even with controlled viral replication through antiretroviral therapy (ART), experience persistent inflammation. This is partly due to intestinal microbial dysbiosis and translocation. Such ongoing inflammation may lead to the development of non-AIDS-related aging-associated comorbidities. However, there remains uncertainty regarding whether HIV affects the biological age of the intestines and whether microbial dysbiosis and translocation influence the biological aging process in PWH on ART. To fill this knowledge gap, we utilized a systems biology approach, analyzing colon and ileal biopsies, blood samples, and stool specimens from PWH on ART and their matched HIV-negative counterparts.

Results

Despite having similar chronological ages, PWH on ART exhibit accelerated biological aging in the colon, ileum, and blood, as measured by various epigenetic aging clocks, compared to HIV-negative controls. Investigating the relationship between microbial translocation and biological aging, PWH on ART had decreased levels of tight junction proteins in the colon and ileum, along with increased microbial translocation. This increased intestinal permeability correlated with faster intestinal and systemic biological aging, as well as increased systemic inflammation. When investigating the relationship between microbial dysbiosis and biological aging, the intestines of PWH on ART had higher abundance of specific pro-inflammatory bacterial genera, such as Catenibacterium and Prevotella. These bacteria significantly correlated with accelerated local and systemic biological aging. Conversely, the intestines of PWH on ART had lower abundance of bacterial genera known for producing short-chain fatty acids and exhibiting anti-inflammatory properties, such as Subdoligranulum and Erysipelotrichaceae, and these bacteria taxa were associated with slower biological aging. Correlation networks revealed significant links between specific microbial genera in the colon and ileum (but not in feces), increased aging, a rise in pro-inflammatory microbial-related metabolites (e.g., those in the tryptophan metabolism pathway), and a decrease in anti-inflammatory metabolites like hippuric acid and oleic acid.

Conclusions

We identified a specific microbial composition and microbiome-related metabolic pathways that are intertwined with both intestinal and systemic biological aging in PWH on ART. A deeper understanding of the mechanisms underlying these connections could potentially offer strategies to counteract premature aging and its associated health complications in PWH.