Tryptophan metabolism in health and disease

Tryptophan metabolism and ischemic stroke: An intricate balance

Ischemic stroke, which is characterized by hypoxia and ischemia, triggers a cascade of injury responses, including neurotoxicity, inflammation, oxidative stress, disruption of the blood-brain barrier, and neuronal death. In this context, tryptophan metabolites and enzymes, which are synthesized through the kynurenine and 5-hydroxytryptamine pathways, play dual roles. The delicate balance between neurotoxic and neuroprotective substances is a crucial factor influencing the progression of ischemic stroke. Neuroprotective metabolites, such as kynurenic acid, exert their effects through various mechanisms, including competitive blockade of N-methyl-D-aspartate receptors, modulation of α7 nicotinic acetylcholine receptors, and scavenging of reactive oxygen species. In contrast, neurotoxic substances such as quinolinic acid can hinder the development of vascular glucose transporter proteins, induce neurotoxicity mediated by reactive oxygen species, and disrupt mitochondrial function. Additionally, the enzymes involved in tryptophan metabolism play major roles in these processes. Indoleamine 2,3-dioxygenase in the kynurenine pathway and tryptophan hydroxylase in the 5-hydroxytryptamine pathway influence neuroinflammation and brain homeostasis. Consequently, the metabolites generated through tryptophan metabolism have substantial effects on the development and progression of ischemic stroke. Stroke treatment aims to restore the balance of various metabolite levels; however, precise regulation of tryptophan metabolism within the central nervous system remains a major challenge for the treatment of ischemic stroke. Therefore, this review aimed to elucidate the complex interactions between tryptophan metabolites and enzymes in ischemic stroke and develop targeted therapies that can restore the delicate balance between neurotoxicity and neuroprotection.

Gut-derived lactic acid enhances tryptophan to 5-hydroxytryptamine in regulation of anxiety via Akkermansia muciniphila

The gut microbiota plays a pivotal role in anxiety regulation through pathways involving neurotransmitter production, immune signaling, and metabolic interactions. Among these, gut-derived serotonin (5-hydroxytryptamine, 5-HT), synthesized from tryptophan metabolism, has been identified as a key mediator. However, it remains unclear whether specific microbial factors regulate tryptophan metabolism to influence 5-HT production and anxiety regulation. In this study, we analyzed 110 athletes undergoing closed training and found that fecal lactate levels were significantly associated with anxiety indicators. We observed a significant negative correlation between Akkermansia abundance and anxiety levels in athletes. Co-supplementation with lactate and Akkermansia muciniphila (A. muciniphila) modulated tryptophan metabolism by increasing key enzyme TPH1 and reducing IDO1, thus shifting metabolism from kynurenine (Kyn) to 5-HT. In addition, lactate enhanced the propionate production capacity of A. muciniphila, potentially contributing to anxiety reduction in mice. Taken together, these findings suggest that enteric lactate and A. muciniphila collaboratively restore the imbalance in tryptophan metabolism, leading to increased 5-HT activity and alleviating anxiety phenotypes. This study highlights the intricate interplay between gut metabolites and anxiety regulation, offering potential avenues for microbiota-targeted therapeutic strategies for anxiety.

Interkingdom signaling between gastrointestinal hormones and the gut microbiome

The interplay between the gut microbiota and gastrointestinal hormones plays a pivotal role in the health of the host and the development of diseases. As a vital component of the intestinal microecosystem, the gut microbiota influences the synthesis and release of many gastrointestinal hormones through mechanisms such as modulating the intestinal environment, producing metabolites, impacting mucosal barriers, generating immune and inflammatory responses, and releasing neurotransmitters. Conversely, gastrointestinal hormones exert feedback regulation on the gut microbiota by modulating the intestinal environment, nutrient absorption and utilization, and the bacterial biological behavior and composition. The distributions of the gut microbiota and gastrointestinal hormones are anatomically intertwined, and close interactions between the gut microbiota and gastrointestinal hormones are crucial for maintaining gastrointestinal homeostasis. Interventions leveraging the interplay between the gut microbiota and gastrointestinal hormones have been employed in the clinical management of metabolic diseases and inflammatory bowel diseases, such as bariatric surgery and fecal microbiota transplantation, offering promising targets for the treatment of dysbiosis-related diseases.

Microbiota-derived IPA alleviates intestinal mucosal inflammation through upregulating Th1/Th17 cell apoptosis in inflammatory bowel disease

The gut microbiota-derived metabolite indole-3-propionic acid (IPA) plays an important role in maintaining intestinal mucosal homeostasis, while the molecular mechanisms underlying IPA regulation on mucosal CD4+ T cell functions in inflammatory bowel disease (IBD) remain elusive. Here we investigated the roles of IPA in modulating mucosal CD4+ T cells and its therapeutic potential in treatment of human IBD. Leveraging metabolomics and microbial community analyses, we observed that the levels of IPA-producing microbiota (e.g. Peptostreptococcus, Clostridium, and Fournierella) and IPA were decreased, while the IPA-consuming microbiota (e.g. Parabacteroides, Erysipelatoclostridium, and Lachnoclostridium) were increased in the feces of IBD patients than those in healthy donors. Dextran sulfate sodium (DSS)-induced acute colitis and CD45RBhighCD4+ T cell transfer-induced chronic colitis models were then established in mice and treated orally with IPA to study its role in intestinal mucosal inflammation in vivo. We found that oral administration of IPA attenuated mucosal inflammation in both acute and chronic colitis models in mice, as characterized by increased body weight, and reduced levels of pro-inflammatory cytokines (e.g. TNF-α, IFN-γ, and IL-17A) and histological scores in the colon. We further utilized RNA sequencing, molecular docking simulations, and surface plasmon resonance analyses and identified that IPA exerts its biological effects by interacting with heat shock protein 70 (HSP70), leading to inducing Th1/Th17 cell apoptosis. Consistently, ectopic expression of HSP70 in CD4+ T cells conferred resistance to IPA-induced Th1/Th17 cell apoptosis. Therefore, these findings identify a previously unrecognized pathway by which IPA modulates intestinal inflammation and provide a promising avenue for the treatment of IBD.

2,3,7,8-tetrachlorodibenzofuran modulates intestinal microbiota and tryptophan metabolism in mice

Persistent organic pollutants (POPs) are known to disrupt gut microbiota composition and host metabolism, primarily through dietary exposure. In this study, we investigate the impact of 2,3,7,8-tetrachlorodibenzofuran (TCDF) on gut microbiota and host metabolic processes. RNA-seq analysis revealed that TCDF exposure significantly affected tryptophan metabolism, lipid metabolic pathways, and immune system function. Metagenomic and metabolomic analyses further showed that TCDF reduced the abundance of Mucispirillum schaedleri and levels of two key tryptophan metabolites, indole-3-carboxaldehyde (3-IAld) and Indole acrylic acid (IA). Supplementation with 3-IAld and IA alleviated TCDF-induced liver toxicity in mouse, as evidenced by reduced Cyp1a1 expression, and mitigated intestinal inflammation, reflected by lower pro-inflammatory cytokines (Ifn-γ and Il-1β) in the colon. Additionally, 3-IAld and IA supplementation enhanced intestinal barrier function, as demonstrated by increased Mucin 2 (MUC2) expression in the gut mucosa of mouse. These findings suggest that TCDF exposure disrupts the gut microbiome and host metabolic balance, and highlight the potential therapeutic role of tryptophan-derived metabolites in mitigating environmental pollutant-induced damage.

Proof of concept study for developing 1-thienyl-β-carboline derivatives as IDO1 and TDO dual inhibitors to treat Parkinson's disease complicating depression

Depressive symptoms are the most common neuropsychiatric disorders at all stages of Parkinson's disease (PD). Imbalances of the kynurenine pathway of tryptophan metabolism have been closely linked to the pathogenesis of PD and depression. Herein, we designed and synthesized a series of 1-thienyl-β-carboline derivatives as IDO1 and TDO dual inhibitors; among them, compound CZ-17 manifested moderate inhibitory activities to IDO1 and TDO with IC50 values of 0.33 and 1.78 μM, respectively. CZ-17 inhibited the kynurenine pathway of tryptophan degradation at the cellular level, and remarkably reduced the kynurenine/tryptophan ratio. CZ-17 displayed directly neuroprotective effect in corticosterone-induced PC12 neural cell injury model. In vivo experiments demonstrated that CZ-17 significantly increased dopamine and serotonin levels, improved MPTP-induced motor disability and rescued LPS-induced depressive behavior in zebrafish model. Acute toxicity tests of CZ-17 in zebrafish embryos showed no toxicity within the effective dose range. Additionally, CZ-17 displayed the potential to cross the BBB via passive diffusion according to ADMET prediction and Caco-2 permeability assay. Thus, CZ-17 may be a promising drug candidate for PD complicating depression.

L-Kynurenine activates the AHR-PCSK9 pathway to mediate the lipid metabolic and ovarian dysfunction in polycystic ovary syndrome

Dysregulated amino acid metabolism is a key contributor to polycystic ovary syndrome (PCOS). This cross-sectional study revealed that serum levels of L-kynurenine (L-Kyn) were significantly elevated in women with PCOS, whereas pyridoxal 5'-phosphate (PLP) levels were markedly reduced. Moreover, human serum L-Kyn levels exhibited a positive correlated with low-density lipoprotein cholesterol (LDL-C) and a negative correlation with high-density lipoprotein cholesterol (HDL-C). Additionally, letrozole (LET) induced PCOS-like mice displayed increased hepatic L-Kyn levels. Mechanistically, both in vivo and in vitro experiments demonstrated that the upregulation of indoleamine 2,3-dioxygenase (IDO1) activates the aryl hydrocarbon receptor (AHR) - proprotein convertase subtilisin/kexin type 9 (PCSK9) pathway in the liver of PCOS-like mice, thereby contributing to dyslipidemia. Treatment with epacadostat, an inhibitor of the enzyme IDO1, or PLP, a cofactor for L-Kyn catabolism, effectively restored ovarian function, improved glucose tolerance, and ameliorated lipid profile abnormalities in PCOS-like mice.

Metabolic reprogramming of tumor microenviroment by engineered bacteria

The tumor microenvironment (TME) is a complex ecosystem that plays a crucial role in tumor progression and response to therapy. The metabolic characteristics of the TME are fundamental to its function, influencing not only cancer cell proliferation and survival but also the behavior of immune cells within the tumor. Metabolic reprogramming-where cancer cells adapt their metabolic pathways to support rapid growth and immune evasion-has emerged as a key factor in cancer immunotherapy. Recently, the potential of engineered bacteria in cancer immunotherapy has gained increasing recognition, offering a novel strategy to modulate TME metabolism and enhance antitumor immunity. This review summarizes the metabolic properties and adaptations of tumor and immune cells within the TME and summarizes the strategies by which engineered bacteria regulate tumor metabolism. We discuss how engineered bacteria can overcome the immunosuppressive TME by reprogramming its metabolism to improve antitumor therapy. Furthermore, we examine the advantages, potential challenges, and future clinical translation of engineered bacteria in reshaping TME metabolism.

Bacillus paralicheniformis-mediated gut microbiota promotes M2 macrophage polarization by inhibiting P38 MAPK signaling to alleviate necrotizing enterocolitis and apoptosis in mice

Clostridial necrotizing enterocolitis is a severe gastrointestinal disease induced by Clostridium, strongly associated with intestinal dysbiosis. Fecal microbiota transplantation (FMT) has proven effective in treating gastrointestinal diseases by remodeling intestinal microbial homeostasis. However, it remains unclear whether FMT from donors with beneficial microbiota can improve the recipient's intestinal function more efficiently. This study found that probiotic Bacillus paralicheniformis SN-6-mediated gut microbiota effectively prevent Clostridial necrotizing enteritis and explored the underlying molecular mechanisms. Data demonstrated that SN-6 altered gut microbiota composition, ameliorated Clostridium perfringens-induced intestinal microbiota dysbiosis and metabolic reprogramming, particularly enhancing tryptophan metabolism. This led to a marked reduction in intestinal barrier damage and inflammation. FMT from SN-6-treated mice reduced jejunal inflammation in Clostridium perfringens-infected mice, strengthened jejunal barrier and enriched beneficial bacteria, such as Lactobacillus, Blautia, Akkermansia. Furthermore, 3-indoleacetic acid (IAA), a metabolite enriched by SN-6, activated aryl hydrocarbon receptor (AhR), suppressed the P38 mitogen-activated protein kinase (P38 MAPK) signaling, and drove macrophage polarization from M0 to M2-type, thereby reducing apoptosis and excessive inflammation. This study highlights Bacillus paralicheniformis SN-6 as a key modulator of intestinal immunomodulation via the gut microbiota-IAA-AhR-P38 MAPK axis, offering a potential therapeutic target for preventing and controlling clostridial necrotizing enteritis.

An ultra-high-performance tandem mass spectrometry method to quantify tryptophan metabolites in aqueous humor of primary angle-closure glaucoma patients

This study presented the development and validation of a robust ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantification of tryptophan (TRP) and its nine metabolites in aqueous humor (AH) to explore the regulation of the TRP metabolic pathway in primary angle-closure glaucoma (PACG). The optimized UPLC-MS/MS method demonstrated good linearity (R² > 0.99), sensitivity (LLMI: 0.11 - 1.31 ng/mL), precision (CVs: 2.18 % and 12.88 %), recovery rates (85.06 % - 105.74 %), bench-top, long-term and on-instrument stabilities (CVs: 2.35 % - 6.88 %). The validated UPLC-MS/MS method was applied to AH samples from PACG patients with cataract and cataract-alone patients. The results showed that kynurenine and 3-hydroxykynurenine concentrations were significantly increased in the AH of the PACG group, indicating up-regulated indoleamine 2,3-dioxygenase activity and a metabolic shift towards the production of the neurotoxic metabolites within the kynurenine pathway. These findings underscore the potential involvement of TRP metabolism in PACG pathogenesis.

Serum metabolic profiling in diabetic kidney disease patients using ultra-high performance liquid chromatography-tandem mass spectrometry

Background

Diabetic kidney disease (DKD) remains one of the leading causes of end-stage renal failure. The currently available diagnostic and classification markers, such as the urinary albumin-to-creatinine ratio and estimated glomerular filtration rate, demonstrate inadequate precision in forecasting the onset and progression of DKD. This study aims to investigate the serum metabolic profile of patients with DKD, with the objective of identifying reliable biomarkers that can enhance the prediction of the transition from diabetes mellitus (DM) to DKD and distinguishing DKD from nondiabetic kidney disease (NDKD).

Methods

Untargeted metabolomic analysis was performed on serum samples obtained from 53 DKD patients, 54 NDKD patients, 59 individuals diagnosed with simple diabetes mellitus (SDM), and 56 healthy controls utilizing ultra-high performance liquid chromatography-tandem mass spectrometry. Differential metabolites among the groups were identified, metabolic pathways were investigated, and the diagnostic efficacy of selected metabolites was evaluated.

Results

The metabolic enrichment pathways shared between DKD and NDKD encompassed glycerophospholipid metabolism, glycerolipid metabolism, and tryptophan metabolism. In contrast, pyrimidine metabolism and arginine biosynthesis were uniquely enriched in DKD. Compared to the NDKD group, significantly elevated levels of phosphatidylglycerol (PG, 14:0) and D-Maltose were observed in DKD patients. Additionally, in comparison to the SDM group, the DKD group exhibited significant increases in lysophosphatidic acid (LPA, 16:3), LPA (18:5), LPA (22:5), phosphatidic acid (PA, 18:3), PG (26:4), L-Glutamine, Uridine, Cytidine, Formyl-N-acetyl-5-methoxykynurenamine, 2-Oxoadipate, Thymidine, L-Citrulline, and 5-Hydroxy-L-tryptophan, while PG (28:4) levels were markedly reduced. Among these, Uridine, Cytidine, Thymidine, and L-Citrulline were associated with pyrimidine metabolism, whereas L-Glutamine and L-Citrulline participated in the arginine biosynthesis pathway. Furthermore, the differential metabolites exhibited varying degrees of correlation with renal function indicators in DKD patients.

Conclusions

PG (14:0) and D-Maltose may help distinguish DKD from NDKD, while L-Glutamine, Uridine, Cytidine, Thymidine, and L-Citrulline are linked to the progression from DM to DKD. Larger studies are needed to validate these findings and assess their diagnostic and causal significance.

IDO1 inhibitors block septic cytokine storm by suppressing the IDO1-AHR-CYP1A1 axis

Indoleamine-2,3-dioxygenase 1 (IDO1) is the rate-limiting enzyme in tryptophan (Trp) catabolism along kynurenine (Kyn) pathway. Increased IDO1 activity has been noticed in patients with sepsis, while IDO1's involvement in sepsis, especially in the initial cytokine storm phase is not yet completely understood. Using the GEO database and clinical samples of sepsis, current study revealed that IDO1-AHR-CYP1A1 axis was significantly upregulated and closely related to cytokine storm in septic patients. With cell models of cytokine storm, it was found that IDO1 promoted cytokine storm and the apoptosis of model cells via AHR-CYP1A1, and IDO1-AHR-CYP1A1 axis correlated classic cytokine storm signal pathway including STAT3, NF-κB/STAT1, JNK/p38. With mouse models of septic cytokine storm, it was shown that IDO1 inhibitors could block the upregulated IDO1-AHR-CYP1A1 axis, reduce the enhanced inflammatory cytokine levels, decrease the phosphorylation of classic cytokine storm signal pathway, rescue organ damage, and increase survival rate. It was also found that IDO1 activation occurred after the increase of inflammatory cytokine levels. Therefore, classic cytokine storm signal pathways, inflammatory cytokines and IDO1-AHR-CYP1A1 axis form a tripartite interaction loop to promote cytokine storm. IDO1 inhibitors were able to block this process.

Effects of short-term tryptophan supplementation in late-pregnant sows on reproductive performance and piglet growth

Proper nutrition in late pregnancy is crucial for postpartum recovery and piglet growth. Improper management can lead to various physiological stresses in sows, resulting in reduced reproductive performance. This study aimed to assess the potential benefits of short-term supplementation with tryptophan on late-pregnant sows, fed from day 99 to day 114 of gestation. We divided 21 Landrace hybrid sows into three groups. The control group was fed a basal diet, while the experimental groups were fed basal diets supplemented with 0.1 % and 0.2 % tryptophan, respectively. Results indicated that feeding 0.1-0.2 % tryptophan had no significant effect on sows' glucose and lipid metabolism. However, compared to the control group, tryptophan supplementation significantly increased reproductive hormone (E2) levels in sows, with no significant impact on immune function and oxidative status. Furthermore, sows showed significant improvements in reproductive performance after tryptophan supplementation, particularly in weaning survival rate, and average litter weight at birth,. Further investigation revealed that tryptophan supplementation significantly increased melatonin levels in sows. Given melatonin's beneficial effects on mammalian reproductive activity, it is inferred that these effects are partly mediated by tryptophan derived melatonin. In conclusion, supplementation with tryptophan in late pregnancy positively influences reproductive activity in sows and the growth of newborn piglets. Due to the limitation of sample size, these effects are only preliminary assessments. In the future, we will expand the sample size and further explore its mechanism.

The Tryptophan-Kynurenine pathway in people living with HIV: a systematic review

PURPOSE

HIV-1 disrupts the metabolic profile of people living with HIV (PLWH), including the Tryptophan-Kynurenine (Trp-Kyn) pathway, linked to disease outcomes and comorbidities. Despite numerous studies, consensus on key dysregulated metabolites in antiretroviral therapy (ART)-treated PLWH is lacking. This systematic review compiles data to identify and highlight the most noteworthy Trp-Kyn metabolites.

METHODS

PubMed, Scopus, and Web of Science databases were searched using a search protocol specifically designed for this study. Studies that investigated the levels of metabolites in the Trp-Kyn pathway in the peripheral blood of PLWH on ART, as well as in healthy control groups were included.

RESULTS

Thirteen metabolomic studies that investigated this pathway met our inclusion criteria. The findings revealed that Trp, Kyn, and the Kyn/Trp ratio (indicative of indoleamine 2,3-dioxygenase IDO activity) were the most investigated metabolites in this metabolic pathway. Evidence consistently demonstrated that Trp levels were lower in PLWH, while predicted IDO activity was consistently higher. Despite the widespread investigation of Kyn, there was no clear consensus on its levels in PLWH, with some studies reporting higher levels and others finding no significant differences compared to HIV-negative controls.

CONCLUSION

In the modern ART era, Trp metabolism and IDO activity may play key regulatory roles in HIV-1 pathogenesis, as evidenced by the consistent patterns observed across various studies. These metabolites and related pathways warrant further investigation as potential targets for improved diagnostics, prognostics, and therapeutics in the context of HIV-1.

Decoding tryptophan: Pioneering new frontiers in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease that affects multiple organ systems, with its pathogenesis intricately tied to genetic, environmental, and immune regulatory factors. In recent years, the aberration of tryptophan metabolism has emerged as a key player in the disease, particularly through the activation of the kynurenine pathway and its influence on immune regulation. This review delves into the critical pathways of tryptophan metabolism and its profound impact on the multi-system manifestations of SLE, including its connections to the nervous system, kidneys, skin, and other organs. Additionally, it examines how tryptophan metabolism modulates the function of various immune cell types. The review also explores potential therapeutic avenues targeting tryptophan metabolism, such as dietary interventions, probiotic modulation, IDO expression inhibition, and immunoadsorption techniques. While current research has underscored the pivotal role of tryptophan metabolism in the onset and progression of SLE, its full therapeutic potential remains to be fully elucidated. This review aims to provide a solid scientific foundation for therapeutic strategies based on modulating tryptophan metabolism in SLE, offering a comprehensive overview of both clinical and basic research in this rapidly evolving field.

L-Kynurenine regulates immune response in ICIs-associated myocarditis via JAK/STAT pathway

BACKGROUND

Immune checkpoint inhibitor associated myocarditis (ICIAM) is a drug-induced myocarditis characterized by the infiltration of immune cells into cardiac. However, the mechanisms are unknown and effective drug therapies are lacking in clinical practice. This study aims to explore the relationship between plasma metabolites and the treatment of ICIAM.

METHODS

Human plasma metabolites were analyzed using untargeted metabolomics for characteristic metabolites. For in vivo experiments, Male Balb/c mice were divided into six groups: PBS, L-Kynurenine, cTNI+PD-1 inhibitor (ICIs), ICIs+L-Kynurenine, ICIs+RO8191, ICIs+RO8191+L-Kynurenine. On day 21 post-modeling, echocardiography, ELISA and histopathology were employed to evaluate the therapeutic effect of L-Kynurenine. Flow cytometry was used to determine the proportion of immune cells in the heart and spleen. Bulk-RNAseq was conducted to analyze differential genes, and q-PCR, immunofluorescence and western blot were performed for validation experiments.

RESULTS

Untargeted metabolomics verified that indoleamine 2,3 dioxygenase-1 (IDO1)-derived L-Kynurenine level was higher in the serum of ICIAM compared to non-ICIAM patients. Meanwhile, in vitro and in vivo experiments showed that L-Kynurenine exhibited a therapeutic ability in ICIAM by inhibiting the pro-inflammatory polarization of immune cells and the secretion of pro-inflammatory cytokines. Mechanistically, L-Kynurenine improved cardiac functions majorly by the inhibition of the JAK1/STAT3 signaling pathway.

CONCLUSION

L-Kynurenine exhibits significant therapeutic potential in ICIAM. The multi-roles of L-Kynurenine in regulating immune responses make it possible to be used as a targeted drug for ICIAM therapy.

Tryptophan metabolites exert potential therapeutic activity in graves' orbitopathy by ameliorating orbital fibroblasts inflammation and proliferation

PURPOSE

Graves' orbitopathy (GO) is a sight-threatening organ-specific autoimmune disease with complicated pathogenesis. Gut microbiota-derived tryptophan (Trp) metabolites play important roles in immune-related diseases, but their role in GO remains unknown.

METHODS

Trp metabolism-associated gut flora was analyzed by 16 S sequencing in GO patients and controls. Serum metabolomics profiling was performed to assess Trp metabolic pathway. Trp metabolites levels were measured by ELISA in 401 serum samples from a case-control study, and their effects on inflammation and proliferation in orbital fibroblasts were evaluated in vitro.

RESULTS

Trp metabolism-associated gut flora, including phylum Firmicutes and genus Anaerostipes, were significantly down-regulated in GO patients. Serum metabolomics revealed significant enrichment of Trp metabolic pathway in both GO and Graves' disease (GD) groups. Serum levels of indolepropionic acid (IPA), indole-3-lactate (ILA), and indoleacetic acid (IAA) were significantly decreased in both GD and GO patients compared to controls, with IAA levels further reduced in GO compared to GD patients. Notably, active GO patients had significantly lower IAA levels compared to inactive ones. Moreover, the levels of IAA were negatively correlated with clinical activity score and serum thyrotropin receptor antibody (TRAb) in GO patients. In vitro, IPA, ILA, and IAA mitigated TNFα-induced inflammation and proliferation in orbital fibroblasts by suppressing the Akt signaling pathway.

CONCLUSION

Trp metabolites IAA maybe a novel biomarker for GO progression. And IPA, ILA and IAA may play a protective role in GO by regulating inflammation and proliferation in orbital fibroblasts, suggesting their potential as therapeutic targets for GO treatment.

Neurodevelopmental effects of exposure to environmentally relevant concentrations of perfluorooctane sulfonic acid (PFOS), perfluorobutanesulfonic acid (PFBS) and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) on larval zebrafish: Multi-omics and neuropathology perspective

Previous studies have shown that perfluorooctane sulfonic acid (PFOS) and its new substitutes perfluorobutanesulfonic acid (PFBS) and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) were associated with neurological abnormalities. However, many of these were conducted at concentrations higher than environmental levels, thus causing overt toxicity. This study employed multi-omics (transcriptomics and targeted metabolomics), morphological, behavioral and neuropathological methods to assess zebrafish embryos exposed to environmentally relevant concentrations (ERC) (10 and 100 ng/L), aiming to better elucidate the key molecular mechanisms that induce neurotoxic effects at ERC. Early development indicators and behavioral analyses showed that these three substances negatively impacted zebrafish development and inhibited locomotor behavior. Neuropathology and transcriptomics indicated that they disrupted visual phototransduction and lysosomal pathways, leading to the destruction of Nissl bodies, myelin sheaths and retinal structures, which were related to the abnormal transcription of relevant genes. Furthermore, targeted metabolomics demonstrated that they caused neurotoxicity by increasing the content of kynurenine and decreasing the content of asparagine and histidine. These findings indicated that they had similar neurotoxic effects, but the mechanisms may differ slightly. Collectively, this study will provide novel insights into understanding the mechanisms by which ERC of PFOS and its substitutes produce neurodevelopmental toxicity.

Circulating metabolic biomarkers mediated causal relationship between gut microbiota and bladder cancer: a two-step mendelian randomization study

BACKGROUND

Dysbiosis of the gut microbiota (GM) has been reported to be associated with cancers, including bladder cancer (BLCA). However, the specific causal relationship between GM and BLCA, as well as the mediating role of circulating metabolic biomarkers (CMBs), has remained unclear. Therefore, we aimed to elucidate the causal relationship among GM, CMBs, and BLCA, through a mendelian randomization (MR) approach.

METHOD

The summary statistics of 473 GM (n = 5959) and 233 CMBs (n = 136,016) from the NHGRI-EBI GWAS Catalog, and BLCA (cases n = 2053 and controls n = 287,137) from the FinnGen study were leveraged for our research. Bidirectional MR analysis was conducted to investigate the causal link between GM and BLCA, and two-step MR (TSMR) was employed to identified potential mediating CMBs. The inverse-variance weighted (IVW) was primarily utilized for effect estimation. Additionally, the Cochrane's Q test was used to evaluate heterogeneity, and the MR-Egger method was employed to evaluate pleiotropy.

RESULT

The study revealed that 15 GM and 12 CMBs were causally associated with BLCA (p < 0.05). Specially, dorea was found to significantly increase the risk of developing BLCA (OR = 2.20, 95% CI: 1.29-3.75). Furthermore, TSMR analysis indicated that total cholesterol levels in small HDL and cholesterol esters in small HDL mediate the causal relationship between dorea and BLCA, with mediated proportions of 2.46% and 2.14%, respectively.

CONCLUSION

The findings of this study provide compelling evidence supporting the mediating role of CMBs in the causal relationship on GM and BLCA.

Indole-3-lactic acid derived from tryptophan metabolism promotes trophoblast migration and invasion by activating the AhR/VCAN pathway

BACKGROUND

Preeclampsia (PE) is a life-threatening condition that is unique to human pregnancy, and it is a leading cause of maternal and neonatal morbidity and mortality. Currently, the only definitive treatment for PE is delivery of the placenta. Several studies have suggested that the gut microbiota and its derived metabolites may be associated with PE. Our previous work indicated that the level of indole-3-lactic acid (ILA), which is a metabolite derived from tryptophan (Trp) metabolism in the gut, is increased in PE patients. However, the effects of ILA on trophoblast function and its underlying mechanisms remain largely unknown.

METHODS

Transwell assays were conducted to assess the effects of ILA on trophoblast migration and invasion. Moreover, the aryl hydrocarbon receptor (AhR) signaling pathway was examined by qRT-PCR, western blotting and siRNA transfection. Additionally, RNA-seq analysis was performed to explore the mechanism underlying the ILA-mediated effects on trophoblast function. Finally, in vivo trophoblast invasion was evaluated through immunohistochemical analysis.

RESULTS

Our data demonstrated that ILA promoted HTR-8/SVneo cell migration and invasion through AhR signaling pathway activation. Mechanistically, VCAN upregulation played a key role in mediating the effects of ILA on trophoblasts after AhR activation. Notably, ILA supplementation improved spiral artery remodeling and increased trophoblast invasion in PE-like mice, primarily by increasing VCAN levels.

CONCLUSIONS

These data strongly suggest that elevated ILA in PE serve as a protective mechanism against trophoblast dysfunction. Therefore, we propose that ILA may be a novel and promising therapeutic approach for treating PE by enhancing trophoblast functions.

Theabrownin Alleviates Type 2 Diabetes Mellitus in db/db Mice via Modulating LPS/GLP-1 Levels and Restoring Islet Cells: Evidence from Gut-Pancreas Axis

Theabrownin has demonstrated metabolic-modulating effects, but the doses used in previous studies are difficult to achieve through regular tea consumption. This study reassesses its hypoglycemic effects at physiologically relevant doses in the db/db mouse model of type 2 diabetes mellitus (T2DM), with a focus on intestinal microbiota and metabolic pathways. The findings show that theabrownin delays glucose absorption by inhibiting α-glucosidase in the duodenum. It also reduces lipopolysaccharide (LPS)-producing bacteria, increases Akkermansia muciniphila abundance, lowers serum LPS levels, and alleviates β-cell dysfunction due to oxidative stress. Additionally, theabrownin promotes the microbial indole pathway of tryptophan metabolism, enhancing glucagon-like peptide-1 (GLP-1) secretion, which helps mitigate β-cell dysfunction. In conclusion, theabrownin shows potential as a dietary supplement for T2DM treatment, primarily regulating LPS/GLP-1 levels and restoring pancreatic islet function. These findings highlight the potential role of fermented tea in glucose metabolism regulation.

Edwardsiella piscicida infection-induced tryptophan-kynurenine metabolic pathway impairs Th17 cells to drive intestinal inflammation in teleost

Enteric pathogens exacerbate intestinal inflammation by disrupting microbiota-host metabolic interactions. While T helper 17 (Th17) cells are critical for maintaining intestinal homeostasis, the mechanisms through which enteric pathogens manipulate the function of Th17 cells to drive inflammation remain poorly understood. In this study, we established an immersion infection model using Edwardsiella piscicida in turbot (Scophthalmus maximus) to investigate the mechanism about enteric pathogen-induced intestinal inflammation, and found that E. piscicida infection significantly impairs the function of intestinal Th17 cells. By analyzing changes in the intestinal microbiota and metabolites, we observed a marked increase in the abundance of Proteobacteria phylum, which positively correlated with elevated levels of tryptophan-kynurenine (Trp-Kyn) pathway metabolites. Further investigation revealed that the enhanced Trp-Kyn pathway inhibits the function of intestinal Th17 cells. Importantly, pharmacological inhibition of the Trp-Kyn pathway could restore the function of Th17 cells and alleviate the infection-induced intestinal inflammation. Taken together, these findings uncover a critical link between microbiota-mediated tryptophan metabolism and Th17 cell's dysregulation during enteric pathogen infection in teleost, which provide novel insights into the metabolic reprogramming of host immunity and to identify potential therapeutic targets for mitigating intestinal inflammation.

The relationship between tryptophan metabolism and gut microbiota: Interaction mechanism and potential effects in infection treatment

Human health is influenced by the gut microbiota, particularly in aspects of host immune homeostasis and intestinal immune response. Tryptophan (Trp) not only acts as a nutrient enhancer but also plays a critical role in the balance between host immune tolerance and gut microbiota maintenance. Both endogenous and bacterial metabolites of Trp, exert significant effects on gut microbial composition, microbial metabolism, the host immunity and the host-microbiome interface. Trp metabolites regulate host immunity by activating aryl hydrocarbon receptor (AhR), thereby contributing to immune homeostasis. Among Trp metabolites, AhR ligands include endogenous metabolites (such as kynurenine), and bacterial metabolites (such as indole and its derivatives). Here, we present a comprehensive analysis of the relationships between Trp metabolism and 14 key microbiota, encompassing fungi (e.g., Candida albicans, Aspergillus), bacteria (e.g., Ruminococcus gnavus, Bacteroides, Prevotella copri, Clostridium difficile, Escherichia coli, lactobacilli, Mycobacterium tuberculosis, Pseudomonas aeruginosa, Staphylococcus aureus, Helicobacter. Pylori), and viruses (e.g., SARS-CoV-2, influenza virus). This review clarifies how the gut microbiota regulates Trp metabolism and uncovers the underlying mechanisms of these interactions. And increased mechanistic insight into how the microbiota modulate the host immune system through Trp metabolism may allow for the identification of innovative therapies that are specifically designed to target Trp absorption, Trp metabolites, the gut microbiota, or interactions between Trp and gut microbiota to treat both intestinal and extra-intestinal inflammation as well as microbial infections.

1, 8-Cineole Ameliorated Staphylococcus aureus-Induced Pneumonia through Modulation of TRP-KYN and Arginine-NO Reprogramming

1, 8-Cineole (Cin), a cyclic monoterpenoid derived from tea trees and eucalyptus species, exhibits diverse pharmacological properties. Yet, its therapeutic impact and underlying mechanism against Staphylococcus aureus (S. aureus) pneumonia remain to be elucidated. In this study, metabolomics based on UPLC-MS/MS was integrated with network pharmacology, molecular biology, and molecular docking to investigate the effects of Cin. The findings demonstrated that Cin markedly reduced mortality and lung bacterial load, lessened pulmonary damage while suppressing the levels of proinflammatory factors, including tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in the bronchoalveolar lavage fluid (BALF) of infected mice. Additionally, 19 metabolites, primarily involved in tryptophan metabolism and arginine biosynthesis, were notably modified by Cin via suppressing the enzymatic activity of indoleamine 2, 3-dioxygenase 1 (IDO1) and inducible nitric oxide synthase (iNOS), thereby attenuating the inflammatory response. Notably, knockdown of IDO1 or iNOS significantly diminished the anti-inflammation effect of Cin. In conclusion, our study validates the therapeutic potential of Cin against S. aureus pneumonia via anti-inflammation by downregulating IDO1 and iNOS. Our results provide a theoretical basis of natural substances applied in bacterial pneumonia treatment.

Equol neutralizes toxin B to combat Clostridioides difficile infection without disrupting the gut microbiota

Clostridioides difficile (C. difficile) toxin B (TcdB) is essential for C. difficile pathogenicity. TcdB induces apoptosis in host cells by internalizing and utilizing its glycosyltransferase activity to modify members of the small GTPase protein family through glycosylation. The intestinal environment is critical for the colonization of C. difficile, and the use of broad-spectrum antibiotics disrupts the balance of the gut microbiota, leading to increased susceptibility of the host to C. difficile. At present, the mainstream clinical approach for treating C. difficile infection (CDI) involves antibiotic therapies such as vancomycin, which disrupt the gut microbiota and are associated with a considerable risk of infection recurrence. Therefore, there is an urgent clinical need to develop new strategies to combat CDI. Here, we have identified a natural compound, equol, which inhibits the TcdB-mediated glycosylation of Rac1 through direct interaction, thereby reducing TcdB-induced cell death. Equol functions as an inhibitor of indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO), effectively suppressing the conversion of tryptophan to kynurenine in the intestinal tract while preserving the integrity of the gut microbiota. Concurrently, equol exhibits robust antioxidant properties, which markedly reduced TcdB-mediated oxidative damage and subsequent cell death. These findings suggest that equol holds therapeutic potential for the treatment of CDI.

Synergistic Toxicity of Combined Exposure to Acrylamide and Polystyrene Nanoplastics on the Gut-Liver Axis in Mice

Acrylamide (AA) and nanoplastics (NPs) are common food toxicants. However, their combined toxicity and health risks call for further studies. This study aimed to investigate the combined toxicity of AA and polystyrene NPs (PS-NPs) in mice through drinking water exposure. Co-exposure to AA and PS-NPs aggravated colon and liver damage, including more severe inflammatory infiltration, higher levels of colonic and hepatic pro-inflammatory cytokines, and elevated serum content of lipopolysaccharide and activities of diamine oxidase, alanine aminotransferase, and aspartate aminotransferase compared to single exposures. Co-exposure also significantly downregulated the expression of colonic tight-junction genes ZO-1 and Claudin-5. Metabolomics revealed that co-exposure induced more profound metabolic disorders in the liver, particularly affecting amino acid and carbohydrate metabolism. 16S amplicon sequencing showed that co-exposure caused more drastic gut microbiota dysbiosis, characterized by a decrease in beneficial bacteria (unclassified_f__Oscillospiraceae, Roseburia, UCG-005, Ruminiclostridium, unclassified_o__Clostridia_UCG-014, Fournierella, and Acetatifactor) and an increase in pathogenic bacteria (Eubacterium_xylanophilum_group and Eubacterium_nodatum_group). Correlation analysis indicated a negative correlation between beneficial bacteria and intestinal-liver toxicity indicators and a positive correlation between pathogenic bacteria and these indicators. Overall, our findings showed that AA and PS-NPs exerted synergistic toxicity to the gut-liver axis in mammals, highlighting the higher health risks of their combined ingestion.

Weissella viridescens Attenuates Hepatic Injury, Oxidative Stress, and Inflammation in a Rat Model of High-Fat Diet-Induced MASLD

Background: Metabolic-dysfunction-associated steatotic liver disease (MASLD) is the most prevalent chronic liver disorder globally. Probiotic supplementation has shown promise in its prevention and treatment. Although Weissella viridescens, a lactic acid bacterium with immunomodulatory effects, has antibacterial and anti-inflammatory activities, there is a lack of direct evidence for its role in alleviating MASLD. This study aimed to investigate the protective effects of W. viridescens strain Wv2365, isolated from healthy human feces, in a high-fat diet (HFD)-induced rat model of MASLD. Methods: Rats were randomly assigned to a normal chow diet (NC), high-fat diet (HFD), and HFD supplemented with W. viridescens Wv2365 (Wv2365) groups. All groups were fed their respective diets for 8 weeks. During this period, the NC and HFD groups received a daily oral gavage of PBS, while the Wv2365 group received a daily oral gavage of Wv2365. Results: Wv2365 supplementation significantly reduced HFD-induced body weight gain, improved NAFLD activity scores, alleviated hepatic injury, and restored lipid metabolism. A liver transcriptomic analysis revealed the downregulation of inflammation-related pathways, along with decreased serum levels of TNF-α, IL-1β, IL-6, MCP-1, and LPS. Wv2365 also activated the Nrf2/HO-1 antioxidant pathway, enhanced hepatic antioxidant enzyme activities and reduced malondialdehyde levels. A gut microbiota analysis showed the enrichment of beneficial genera, including Butyricicoccus, Akkermansia, and Blautia. Serum metabolomic profiling revealed increased levels of metabolites including indole-3-propionic acid, indoleacrylic acid, and glycolithocholic acid. Conclusions: Wv2365 attenuates hepatic injury, oxidative stress, and inflammation in a rat model of high-fat-diet-induced MASLD, supporting its potential as a probiotic candidate for the modulation of MASLD.

The gut-brain axis mechanism of normal appetite induced by kynurenic acid

Feeding is essential for both host-organism survival and gut-microbiota maintenance. Our research focuses on how kynurenic acid (KYNA), a gut-microbiota metabolite, regulates appetite during fasting. We find that fasting significantly raises KYNA levels in the intestine, which increases short-term food intake by inhibiting vagal afferent nerve in the nodose ganglion (NG) and activating AgRP neurons in arcuate nucleus (ARCAgRP). The orexigenic effects of KYNA are abolished by subdiaphragmatic vagotomy (sdVx), chemogenetic activation/inhibition of glutamatergic NG/ARCAgRP neurons, inhibiting the nucleus of the solitary tract (NTS) to ARCAgRP inputs, or knockdown of GPR35 (a KYNA receptor) in the intestinal vagal afferent nerve. Our data support a model in which KYNA acts through the GPR35 receptor to inhibit vagal afferent signaling and subsequently activate ARCAgRP neurons, which leads to increased food intake. These findings reveal a mechanism by which gut microbiota controls appetite during fasting, highlighting the complex relationship between microbial and host feeding behavior.

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.

The roles of enhancer, especially super-enhancer-driven genes in tumor metabolism and immunity

Abnormal metabolism is a characteristic of malignant tumors. Numerous factors play roles in the regulation of tumor metabolism. As epigenetic regulators, enhancers, especially the super-enhancers (SEs), serve as platforms for transcription factors that regulate the expression of metabolism-related enzymes or transporters at the gene level. In this study, we review the effects of enhancer/ SE-driven genes on tumor metabolism and immunity. Enhancers/SEs play regulatory roles in glucose metabolism (glycolysis, gluconeogenesis, tricarboxylic acid (TCA) cycle, pyruvate, and pentose phosphate pathway, lipid metabolism (cholesterol, fatty acid, phosphatide, and sphingolipid), and amino acid metabolism (glutamine, tryptophan, arginine, and cystine). By regulating tumor metabolism, enhancers and SEs can reprogram tumor microenvironment, especially the status of various immune cells. Therefore, interfering enhancers/SEs that regulate the tumor metabolism is likely to enhance the effectiveness of immunotherapy.

Plasma metabolomics differentiating and predicting prognosis of coronary artery disease patients with distinct nutritional status

This study investigated the metabolic mechanisms underlying the association between malnutrition and poor prognosis in coronary artery disease (CAD). We hypothesized that specific metabolites associated with nutritional status impact all-cause mortality and Major Adverse Cardiovascular Events in CAD patients. To test this hypothesis, we evaluated the nutritional status of 5182 CAD patients from multiple centers using three nutritional risk screening tools and analyzed the impact on CAD outcomes with restricted cubic splines and Cox regression. Poor nutritional status was found to be linked to increased adverse outcomes. Further analysis using multiple linear regression and mediation analysis identified elevated concentrations of β-pseudouridine and dulcitol, and decreased concentrations of l-tryptophan and LPC (18:2/0:0), among other metabolites, as mediators of this association. Employing Least Absolute Shrinkage and Selection Operator for variable selection, we integrated these metabolites with clinical variables, which significantly improved the predictive accuracy for adverse outcomes. Our results highlight significant metabolic disparities in CAD patients based on nutritional status and provide novel insights into the role of nutrition-associated metabolites in CAD prognosis. These findings suggest that customized nutritional interventions targeting these metabolites could positively influence the progression of CAD.

Virtual screening and characterization of novel myogenic peptides from bovine collagen hydrolysates: Targeting myomaker

The increasing prevalence of muscle aging, exacerbated by an aging population, poses a significant threat to public health, necessitating the development of more effective interventions. This study primarily aimed to elucidate the mechanism by which bovine bone collagen facilitates muscle differentiation and regeneration. Initially, peptide sequences within bovine bone collagen hydrolysate were identified using peptidomics. Molecular docking and dynamics simulations subsequently demonstrated that the peptide AGPPGPPGPAGK could form a stable complex with Myomaker, suggesting its potential to regulate myoblast differentiation by targeting Myomaker. The physicochemical properties of AGPPGPPGPAGK were predicted using various deep learning tools, providing insight into its functional capabilities. Further molecular and cellular experiments confirmed that the peptide could enhance myoblast differentiation by regulating energy metabolism. Transcriptome analysis further supported these findings, revealing that the peptide modulated energy metabolism during myoblast differentiation. Finally, a combined bioinformatic and transcriptomic analysis indicated a potential regulatory role of Hrh1 in energy metabolism during cell differentiation, a finding that warrants further investigation.

Shenqi granules enhance recovery from cerebral ischemia-reperfusion injury by modulating tryptophan and tyrosine metabolism and activating NFE2L2/NRF2

BACKGROUND

Stroke is a multifaceted physiological event linked to imbalances in gut microbiota and disruptions in metabolic pathways. Traditional Chinese medicines, leveraging the gut-brain axis, have been shown to significantly ameliorate ischemic stroke. However, the specific role and molecular mechanism of Shenqi granules (SQF) in enhancing the recovery from ischemic stroke remain to be elucidated.

PURPOSE

This study aims to explore the therapeutic effects of SQF on rats with cerebral ischemia-reperfusion injury (CIRI) and its regulatory effects on the gut microbiota, providing a basis for the clinical rational use of drugs in ischemic stroke.

METHODS

The study conducted a comprehensive biological assessment of SQF's role in improving CIRI at the whole-animal level. Subsequently, Weighted Gene Co-expression Network Analysis (WGCNA) and network pharmacology analysis were used for component analysis and target prediction. Then, the therapeutic targets of SQF were further validated through molecular docking and molecular experiments. Finally, an integrated omics approach combining fecal untargeted metabolome and 16S rRNA sequencing was employed to state the anti-CIRI effects of SQF and its potential mechanisms.

RESULTS

SQF alleviates cerebral infarct volume and improves cognitive functions in MCAO rats. Network pharmacology analysis shows 20 potential active ingredients of SQF could target 13 target proteins. Further employing WGCNA, our study identified four key targets of SQF in the treatment of ischemic stroke. Based on molecular docking and molecular experiments, SQF improves CIRI by activating NFE2L2/NRF2. Serum metabolomics analysis identified six metabolites related to the tryptophan and tyrosine metabolic pathways, which interact with NFE2L2/NRF2 protein. Fecal metabolome and microbiome reveal that SQF's protective effect on CIRI is linked to the tryptophan metabolism and tyrosine metabolism and gut microbiome modulation. In particular, metabolites related to tryptophan and tyrosine metabolism, such as kynurenic acid and dopamine, may exert their protective effects by interacting with NFE2L2/NRF2.

CONCLUSION

This pioneering study unveils the therapeutic potential of SQF in addressing CIRI, highlighting the pivotal role of NFE2L2/NRF2 upregulation in its mechanism of action. Furthermore, SQF demonstrates its efficacy in restoring gut microbiota balance by modulating the metabolism of tryptophan and tyrosine in CIRI. By elucidating the intricate interplay among constituents, targets, metabolites, and gut microbiota, this research offers novel insights into the multifaceted mechanisms underlying SQF's therapeutic impact on CIRI.

Mass spectrometric monitoring of redox transformation and arylation of tryptophan

Tryptophan (Trp) is an essential amino acid obtained from human diet. It is involved not only in de novo biosynthesis of proteins but also in complex metabolic pathways. Redox transformation of tryptophan is under-explored in comparison with kynurenine, serotonin and indole pyruvate pathways. We described herein a mass spectrometric approach that can not only detect electron transfer-associated changes in masses and charges, but also identify electron-directed bond cleavages and radical-radical cross-coupling reactions in redox transformation of tryptophan. Photoactive TiO2 that is widely applied in cosmetic products is used as electron donor and receptor because of the capability to generate photoelectrons and holes. It was demonstrated tryptophan undergoes redox transformation through the removal of an electron from amino nitrogen atom by hole oxidization along with an electron capture in the indole ring. The back and forth electron-shuttle converts electric energy into chemical energy that enforces bond cleavages. Sodium-coupled electron transfer (SCET) was found in complementary with proton-coupled electron transfer in tryptophan. The movement of sodium ions avoids electric charge buildup caused by electron transfer. Various redox products were detected on both light irradiated TiO2 and skins, among which β-carboline shows extensive radical scavenging ability for diverse cross-coupling with indole derivatives. Light-independent redox products have been detected in vivo such as in mouse brain, indicating the presence of in vivo electron transfer-directed redox transformation. It has also been revealed that tryptophan can be arylated on Cα and Cβ atoms in response to the exposure of halogenated aromatics.

The tryptophan metabolite 3-hydroxyanthranilic acid alleviates hyperoxia-induced bronchopulmonary dysplasia via inhibiting ferroptosis

Bronchopulmonary dysplasia (BPD) is a prevalent chronic respiratory condition in preterm infants with an increasing incidence, severely affecting their survival rate and quality of life. Exploring the underlying mechanisms of BPD helps to develop novel effective therapeutic strategies. In this study, integrated metabolomic analyses of tracheal aspirates (TAs) from BPD infants and non-BPD infants, along with lung tissues from hyperoxia-induced experimental BPD neonatal rats and control rats, demonstrated that BPD was associated with a significant reduction in 3-hydroxyanthranilic acid (3-HAA), which was confirmed to be partly caused by tryptophan-metabolizing enzyme disorders. In vivo and in vitro models were subsequently established to assess the efficacy and underlying mechanisms of 3-HAA in relation to BPD. Compared with the BPD group, 3-HAA nebulization improved lung development and suppressed inflammation in rats. Limited proteolysis-small molecule mapping (LiP-SMap) proteomic analysis revealed the involvement of the ferroptosis pathway in the underlying mechanism by which 3-HAA alleviated hyperoxia-induced BPD injury. Ferroptosis was identified by detecting Fe2+ levels, malondialdehyde (MDA), 4-HNE, total aldehydes, mitochondrial morphology, ferroptosis-associated protein and mRNA expression, and this dysregulation was indeed ameliorated by 3-HAA nebulization in vivo. Furthermore, a combination of LiP-SMap, molecular docking, SPR and Co-IP analyses confirmed that 3-HAA can bind directly to FTH1 and disrupt the nuclear receptor coactivator 4 (NCOA4)-FTH1 interaction. In conclusion, our study is the first to reveal that BPD is linked to the reduction of 3-HAA, and 3-HAA could inhibit the ferroptosis pathway by targeting FTH1, thereby alleviating hyperoxia-induced injury in rats and alveolar type II epithelial cells, highlighting the potential of targeting 3-HAA and ferroptosis for clinical applications in BPD.

Chronic Exposure to Fluxapyroxad Exacerbated Susceptibility to Colitis in Mice via a Gut Microbiota-Indole Derivatives-Th17/Treg Cell Balance Axis

Fluxapyroxad is the most commonly used succinate dehydrogenase inhibitor fungicide. This work investigated its adverse effects on colitis susceptibility and explored the underlying mechanisms based on a mouse model. After 13 weeks of exposure at the acceptable daily intake (ADI) level, fluxapyroxad exacerbated the susceptibility to colitis, impaired the intestinal barrier, and elevated proinflammatory cytokines and chemokines of the colon in mice. It was found that this toxic effect was caused by the disruption of the gut microbiome. Specifically, the abundance of Lachnospiraceae and Muribaculaceae decreased, while Desulfovibrionaceae and Eggerthellaceae increased. Altered microbiota reduced fecal indole derivatives, including indole-3-lactic acid (ILA), indole-3-acetic acid (IAA), and indole-3-acrylic acid (IArA), inhibiting aryl hydrocarbon receptor (AHR) activation, disrupting immune homeostasis by overactivating Th17 cells and insufficient Treg cell differentiation, and causing mild colonic inflammation. Oral antibiotic-treated mice and fecal transfer experiments validated the pathway. Susceptibility to colitis induced by fluxapyroxad was not detected in the oral antibiotic-treated mice. Fecal transfer of the disordered gut microbiota caused by fluxapyroxad could aggravate the severity of colitis in recipient oral antibiotic-treated mice that did not receive fluxapyroxad exposure. In conclusion, chronic fluxapyroxad exposure at the ADI level exacerbated colitis via a gut microbiota-indole derivatives-Treg/Th17 cell balance axis, offering a new risk assessment perspective of fluxapyroxad.

Risk Factors for Chronic Kidney Disease in Patients With Crohn's Disease

BACKGROUND

Patients with inflammatory bowel diseases (IBD), including Crohn's disease (CD), are at risk of complications, including kidney disease. It is important to identify IBD patients at higher risk of chronic kidney disease (CKD) to improve prevention and treatment. Here, we investigated the clinical and metabolomic characteristics of CD patients who develop CKD.

METHODS

We identified adult CD patients with (CD + CKD, n = 87) and selected CD patients without CKD (CD controls) matched by age, race, and gender. We collected data on demographic characteristics (age, smoking status, ethnicity, gender), IBD characteristics (diagnosis, Montreal classification, medication use, IBD-related surgeries, perianal disease), and kidney-related factors (primary sclerosing cholangitis, end-stage renal disease, hypertension, diabetes, organ transplantation, and nephrolithiasis). Univariate and multivariate analyses were conducted and odds ratios were calculated to identify risk factors for CKD. Serum samples were collected for untargeted metabolomic analysis.

RESULTS

Chronic kidney disease was far more common in CD patients than UC patients. Crohn's disease patients with kidney stones had a 10-fold higher risk of developing CKD than those without kidney stones. Crohn's disease patients with more than 2 IBD-related surgeries had a 7.3-fold higher risk of developing CKD than those who had not undergone surgery. There was no relationship between the number of biologics used or mesalamine use and the risk of CKD. The serum of CD + CKD patients had elevated levels of pro-inflammatory metabolites and those linked to kidney injury.

CONCLUSIONS

We recommend regular kidney function monitoring and ensuring proper hydration to prevent or manage potential kidney-related complications in CD patients. Patients with resections and kidney stones are particularly vulnerable.

Landscapes of gut microbiome and metabolic signatures in vitiligo patients with co-morbid emotional distress

BACKGROUND

Vitiligo is a depigmentation disorder frequently associated with emotional distress; however, the precise mechanisms underlying this co-morbidity remain unclear.

OBJECTIVE

This study aims to investigate whether gut dysbiosis and gut metabolites contributes to emotional distress in patients with vitiligo.

METHODS

Depression and anxiety were assessed using the Patient Health Questionnaire-9 and Generalized Anxiety Disorder-7, respectively. Totally enrolled 28 vitiligo patients were diagnosed with depression or anxiety (VWD), 44 without such conditions (VTD), and 37 healthy controls (HC). Stool samples were analyzed using 16S rRNA gene sequencing and liquid chromatography triple quadrupole tandem mass spectrometry.

RESULTS

The intestinal flora of VWD group changed significantly with reduced α-diversity. The β-diversity varied among groups. Megasphaera and Anaerostipes increased in the VWD group, whereas Bilophila etc. decreased. Linear Discriminant Analysis Effect Size revealed Lachnoclostridium as a representative flora in the VWD and Faecalibacterium as a representative flora in the VTD. Metabolites such as L-glutamic acid and indole were lower in the VWD group than in the HC, while oleamide, cuminaldehyde, and taurine were higher in the VWD with VTD group. Lachnoclostridium negatively correlated with indole and L-glutamic acid. This study identified notable variations in pathways involved in the biosynthesis of phenylalanine, tyrosine, and tryptophan bile secretion, GABAergic synapses, and taurine and hypotaurine metabolism between the VWD and HC groups.

CONCLUSION

Specific fecal microbes and metabolites may contribute to the pathogenesis of VWD. These findings provide a novel perspective for addressing emotional distress in patients with vitiligo by targeting the gut-brain-skin axis.

Serum Metabolomic Profiling in Healthy Dogs Supplemented with Increasing Levels of Purified Beta-1,3/1,6-Glucans

Metabolomics has proven to be an effective tool for elucidating mechanisms and assessing the effectiveness of dietary interventions in canine and feline nutrition. In this context, the present study aimed to perform a metabolomic analysis of the serum of dogs supplemented with increasing levels of beta-1,3/1,6-glucans to generate evidence and gain a deeper understanding of the metabolic responses associated with this supplementation. Eight dogs were evenly assigned to two balanced 4 × 4 Latin squares. Four diets were tested, differing only in beta-glucan content (0.0%, 0.07%, 0.14%, and 0.28%), and the dogs were fed according to their individual maintenance energy requirements. Each experimental period lasted 35 days. On day 35, 5 mL of blood was collected via jugular venipuncture to obtain serum for metabolomic analysis. Nuclear magnetic resonance analysis identified 12 key serum metabolites. Hierarchical heat map analysis revealed differences in metabolite intensity between treatments (p < 0.05). Additionally, the most relevant metabolic pathways were phenylalanine, tyrosine, and tryptophan metabolism; alanine, aspartate, and glutamate metabolism; and glyoxylate and dicarboxylate metabolism. This study demonstrated that increasing levels of purified beta-1,3/1,6-glucans from Saccharomyces cerevisiae modulated key metabolic pathways in dogs, particularly those related to amino acid, lipid and energy metabolisms, and gut microbiota. These findings provide insights into the mechanisms by which beta-glucans influence canine health.

The molecular signature of heat stress in sweat reveals non-invasive biomarker candidates for health monitoring

Heat stress is a significant public health challenge that leads to an increased risk of serious health deterioration, injuries, and loss of economic productivity. While the gold standard for monitoring heat stress continues to remain with population-based measurements, a straight-forward person-centered approach is lacking. Sweat can supply a wealth of molecular information, ranging from protein levels to levels of metabolites; it is thus a promising monitoring biofluid. A thorough investigation of sweat's molecular signature during heat stress is called for. We conducted a cross-over study on healthy participants with personalized heat-stress visits to investigate heat stress's proteomic and molecular signatures in sweat. Through mass-spectrometry analysis, we identified multiple candidate biomarkers ranging from amino acids to microbiome metabolites and proteins. To the best of our knowledge, these biomarker candidates represent the first successful approach to metabolically differentiate between various heat stressors thereby enabling their acute monitoring. While these biomarker candidates need further investigation to confirm their clinical value, many have already been identified as directly associated with heat stress in animals and plants. Once further investigated, next-generation wearable devices for person-centered, on-skin sweat-analysing platforms could be developed that would transform health management during exposure to heat stress.

Elevated brain manganese induces motor disease by upregulating the kynurenine pathway of tryptophan metabolism

Elevated brain levels of the essential metals manganese (Mn), copper, or iron induce motor disease. However, mechanisms of metal-induced motor disease are unclear and treatments are lacking. Elucidating the mechanisms of Mn-induced motor disease is particularly important because occupational and environmental Mn overexposure is a global public health problem. To address this, here we combined unbiased transcriptomics and metabolomics with functional studies in a mouse model of human environmental Mn exposure. Transcriptomics unexpectedly revealed that Mn exposure up-regulated expression of metabolic pathways in the brain and liver. Notably, genes in the kynurenine pathway of tryptophan metabolism, which produces neuroactive metabolites that impact neurological function, were up-regulated by Mn. Subsequent unbiased metabolomics revealed that Mn treatment altered kynurenine pathway metabolites in the brain and liver. Functional experiments then demonstrated that pharmacological inhibition of the first and rate-limiting step of the kynurenine pathway fully rescued Mn-induced motor deficits. Finally, elevated Mn directly activates hypoxia-inducible factor (HIF) transcription factors, and additional mechanistic assays identified a role for HIF1, but not HIF2, in regulating expression of hepatic kynurenine pathway genes under physiological or Mn exposure conditions, suggesting that Mn-induced HIF1 activation may contribute to the dysregulation of the kynurenine pathway in Mn toxicity. These findings (1) identify the upregulation of the kynurenine pathway by elevated Mn as a fundamental mechanism of Mn-induced motor deficits; (2) provide a pharmacological approach to treat Mn-induced motor disease; and (3) should broadly advance understanding of the general principles underlying neuromotor deficits caused by metal toxicity.

Metabolomic Associations With Fatigue and Physical Function in Children With Cancer: A Pilot Study

Background: Fatigue is a frequently reported symptom in children undergoing cancer treatment. Prior research shows an inverse relationship between fatigue and physical activity. Less is known about fatigue's relationship with physical function or the underlying biological mechanisms of fatigue. This study explored associations among fatigue, physical function, and associated metabolites. Methods: Children (7-18 years) provided serum samples and self-reports of fatigue and lower extremity physical function (mobility) using Pediatric Patient-Reported Outcomes Measurement Information System (PROMIS) surveys at two timepoints during cancer therapy. PROMIS scores were categorized as high/low per established cut points (high fatigue T >47.5; high physical function T >51.5). High-resolution liquid chromatography-mass spectrometry extracted 29 metabolites hypothesized a priori to be associated with fatigue or physical function. Descriptive statistics summarized PROMIS scores, and linear mixed effect models estimated metabolite associations adjusting for age, gender and steroid use. Results: Forty children participated (female, 53%; 7-12 years, 38%; 13-18 years 62%; Hodgkins Lymphoma, 33%; Acute Lymphoblastic/Lymphocytic Leukemia, 40%; Osteosarcoma, 10%; Other, 17%). Physical function and fatigue were inversely related: T1 (r = -0.64; p < .001) and T2 (r = -0.63; p < .001). One metabolite (indole-3-latic acid) differentiated between low and high fatigue. Five metabolites differentiated significantly between low and high physical function (4-Hydroxybenzoic acid, m-Coumaric acid, myoinositol, tryptophan, and tyrosine). Conclusions:These findings substantiate prior studies showing metabolites, particularly amino acids, significantly associated with fatigue and physical function. All significant metabolites were associated with the gut microbiome. Physical function was inversely corelated with fatigue providing another potential intervention for fatigue management.

Evaluating the impact of gut microbiota, circulating cytokines and plasma metabolites on febrile seizure risk in Mendelian randomization study

Febrile seizures (FS) is the most common type of convulsion in infants and preschool children. This study aimed to investigate the associations between gut microbiota abundance, plasma metabolites, circulating cytokines, and FS. Summary statistics of 211 gut microbiota traits, 1,400 plasma metabolite traits, 91 circulating cytokine traits, and FS were obtained from publicly available genome-wide association studies. Two-sample Mendelian randomization (MR) analysis and causality was inferred using Inverse variance-weighted (IVW), Weighted median, MR-Egger, simple mode-based estimate and weighted mode-based estimate 5 methods. Several sensitivity analyses were also used to ensure the robustness of the results. Furthermore, mediation analysis was used to determine the pathway from gut microbiota to FS mediated by plasma metabolites and circulating cytokines. MR revealed the associations of 1 gut microbiota (phylum Verrucomicrobia), 4 circulating cytokines and 50 plasma metabolites on FS. Based on the known pathogenic metabolites, we observed that the tryptophan, androgen, and sphingolipids pathways are associated with FS. Mediation analysis revealed 1 strongly documented plasma metabolite (Ascorbic acid 2-sulfate) as a mediator linking "gut microbiota to plasma metabolite to FS". Sensitivity analysis was represented no heterogeneity or pleiotropy in this study.Our study provides some causal evidence concerning the effects of the gut microbiota, circulating cytokines, and plasma metabolites on FS, which needs to be verified in randomized controlled trials. These biomarkers provide new insights into the underlying mechanisms of FS and contribute to its prevention, diagnosis, and treatment.

Multiple pathways through which the gut microbiota regulates neuronal mitochondria constitute another possible direction for depression

As a significant mental health disorder worldwide, the treatment of depression has long faced the challenges of a low treatment rate, significant drug side effects and a high relapse rate. Recent studies have revealed that the gut microbiota and neuronal mitochondrial dysfunction play central roles in the pathogenesis of depression: the gut microbiota influences the course of depression through multiple pathways, including immune regulation, HPA axis modulation and neurotransmitter metabolism. Mitochondrial function serves as a key hub that mediates mood disorders through mechanisms such as defective energy metabolism, impaired neuroplasticity and amplified neuroinflammation. Notably, a bidirectional regulatory network exists between the gut microbiota and mitochondria: the flora metabolite butyrate enhances mitochondrial biosynthesis through activation of the AMPK-PGC1α pathway, whereas reactive oxygen species produced by mitochondria counteract the flora composition by altering the intestinal epithelial microenvironment. In this study, we systematically revealed the potential pathways by which the gut microbiota improves neuronal mitochondrial function by regulating neurotransmitter synthesis, mitochondrial autophagy, and oxidative stress homeostasis and proposed the integration of probiotic supplementation, dietary fiber intervention, and fecal microbial transplantation to remodel the flora-mitochondrial axis, which provides a theoretical basis for the development of novel antidepressant therapies targeting gut-brain interactions.

Effects of Environmental Pollutants on Tryptophan Metabolism

Tryptophan (Trp) is an important essential amino acid that plays a variety of physiological functions in the human body, including being a precursor of neurotransmitter and participating in immune regulation. Currently, more and more studies show that some pollutants in the environment can affect the metabolism of Trp and consequently affect human health. The present paper offers a comprehensive overview of prior research investigating the impact of environmental pollutants, including inorganic and organic contaminants, microplastics, and nanoplastics on the nervous system, immune system, digestive system, and maternal-fetal pregnancy, revealing their detrimental effects on Trp metabolism and human well-being.

Steam explosion treatment for improving the quality of Xuehua pear soup: Components profile, antioxidant and anti-inflammatory activity in vitro, its flavor and metabolomics study

In this study, steam explosion (SE) was applied to produce Xuehua pear soup (XPS) at different steam explosion pressure. The results showed that 0.3-0.6 MPa was the optimal pressure to improve the XPS quality. After SE treatment, the titratable acid of XPS decreased whereas it became darker. 0.6 MPa was the optimal pressure to enhance total flavonoid content and concentrated catechin, protocatechuic and rutin, endowing XPS with good antioxidant activity. 0.3 MPa was conducive to enrich arbutin, caffeic acid and gallic acid, endowing XPS with good immunomodulatory effect in vitro. XPS possessed the cake and caramel flavor due to SE treatment and its green, sweet, caramel and herbal odor increased. Finally, 5 metabolic pathways were screened to clarify the formation mechanism involving 21 metabolites. These results proved steam explosion had the potential to concentrated nutrients and improve flavor during food processing.

Immunogenic Cell Death and Metabolic Reprogramming in Cancer: Mechanisms, Synergies, and Innovative Therapeutic Strategies

Immunogenic cell death (ICD) is a promising cancer therapy where dying tumor cells release damage-associated molecular patterns (DAMPs) to activate immune responses. Recent research highlights the critical role of metabolic reprogramming in tumor cells, including the Warburg effect, oxidative stress, and lipid metabolism, in modulating ICD and shaping the immune microenvironment. These metabolic changes enhance immune activation, making tumors more susceptible to immune surveillance. This review explores the molecular mechanisms linking ICD and metabolism, including mitochondrial oxidative stress, endoplasmic reticulum (ER) stress, and ferroptosis. It also discusses innovative therapeutic strategies, such as personalized combination therapies, metabolic inhibitors, and targeted delivery systems, to improve ICD efficacy. The future of cancer immunotherapy lies in integrating metabolic reprogramming and immune activation to overcome tumor immune evasion, with multi-omics approaches and microbiome modulation offering new avenues for enhanced treatment outcomes.

Metabolomics profiling identifies diagnostic metabolic signatures for pregnancy loss: a cross-sectional study from northwestern China

Objective

To identify potential diagnostic metabolic biomarkers for pregnancy loss (PL) by performing untargeted metabolomics analysis.

Methods

The present study performed untargeted metabolomics analysis on plasma samples from PL patients (n=70) and control subjects (n=122) using liquid chromatography‒mass spectrometry (LC‒MS). Metabolic profiles were evaluated using orthogonal partial least squares discriminant analysis (OPLS-DA), and pathway enrichment analysis was conducted via the KEGG database. LASSO regression was employed to identify significant metabolites, and their diagnostic performance was evaluated through receiver operating characteristic (ROC) curves. Pearson correlation analysis was used to explore the relationships between differentially abundant metabolites and clinical parameters.

Results

In total, 359 metabolites were identified, 57 of which were significantly altered between the control and PL group through OPLS-DA. Differential metabolites were significantly enriched in caffeine metabolism, tryptophan metabolism, and riboflavin metabolism pathways. Key metabolites, such as testosterone glucuronide, 6-hydroxymelatonin, and (S)-leucic acid, exhibited strong diagnostic potential, with AUC values of 0.991, 0.936 and 0.952, respectively, and the combined AUC was 0.993. Furthermore, Pearson correlation analysis revealed a significant negative correlation between the waist‒to‒hip ratio (WHR) and the abundance of testosterone glucuronide (r = -0.291, p = 0.0146), and a significant positive correlation between WHR and (S)-leucic acid (r = 0.248, p = 0.0381) in the PL group.

Conclusion

We identified a panel of plasma metabolites with significant diagnostic potential for PL. These biomarkers may facilitate early, noninvasive diagnosis and offer insights into metabolic dysregulation associated with pregnancy loss.

Integrating multi-omics data of Triple-Negative Breast Cancer to explore the role of Kynurenine pathway and KYNU as a therapeutic target

BACKGROUND

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer with poor prognosis. TNBC currently lacks effective therapeutic options, and its molecular mechanisms are still unclear. Thus, identifying novel molecular targets may offer insights to enhance treatment strategies. Accumulating evidence suggests the key role of the kynurenine pathway (KP) of the tryptophan metabolism in the pathogenesis of tumor diseases. The KP is the primary route of tryptophan metabolism, accounting for over 95 % of tryptophan catabolism. Genes within the KP have been implicated in tumor promotion, although their functional mechanisms remain to be elucidated.

METHODS

Bioinformatics approaches were employed to analyze the expression and function of all genes within the KP in TNBC.

RESULTS

Genes of the KP were found to be upregulated in TNBC and associated with adverse outcomes. These genes were predominantly involved in various biosynthetic functions. Correlation analyses revealed a close association between KP genes and markers of inflammatory pathways, as well as with chemoresistance in tumors. Immunofluorescence revealed that KYNU accumulated in the nucleus and at sites of nuclear chromatin in TNBC cells.

CONCLUSION

Genes of the KP are correlated with the progression and drug resistance of TNBC, but further research is needed to clarify the underlying molecular mechanisms.

Identification of potential shared gene signatures between periodontitis and breast cancer by integrating bulk RNA-seq and scRNA-seq data

Studies have shown that patients with periodontitis (PD) have an increased risk of breast cancer (BC). However, the exact mechanism remains to be further investigated. This study aimed to investigate the genes, pathways and immune cells that may interact with PD and BC. From the Gene Expression Omnibus (GEO) and TCGA databases, we retrieved the gene expression profiles of samples with PD and BC, respectively. Common genes between two diseases were found using differential expression analysis and weighted gene co-expression network analysis (WGCNA). Machine learning methods were used to find shared diagnostic genes. Single-sample GSEA (ssGSEA) was performed to study the expression profiles of 28 immune cells in PD and BC, and single-cell RNA sequencing (scRNA-seq) data was used to visualize localization of shared genes. Finally, we employed qRT-PCR and immunohistochemistry staining to confirm the expression of hub genes in two diseases. PD and BC had 21 shared crosstalk genes, which were primarily related to peptide hormone response, organic acid transmembrane transport, and carboxylic acid transmembrane transport. By using machine learning methods, ANKRD29 and TDO2 were the most efficient shared diagnostic biomarkers, which were confirmed by Immunohistochemical staining and qRT-PCR. ssGSEA showed that immunology was involved in both diseases and that ANKRD29 and TDO2 may be involved in both diseases by mediating immune cells. scRNA-seq further confirms the importance of these genes in regulating immunity in both diseases. In brief, our study identified 2 genes that may serve as biomarkers and targets for the diagnosis and treatment of PD and BC.