Tryptophan metabolism in health and disease

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.

Detection of Exchangeable Protons in NMR Metabolomic Analysis Using AI-Designed Water Irradiation Devoid Pulses

1H NMR spectroscopy has enabled the quantitative profiling of metabolites in various biofluids, emerging as a possible diagnostic tool for metabolic disorders and other diseases. To boost the signal-to-noise ratio and detect proton resonances near the water signal, current 1H NMR experiments require solvent suppression schemes (e.g., presaturation, jump-and-return, WATERGATE, excitation sculpting, etc.). Unfortunately, these techniques affect the quantitative assessment of analytes containing exchangeable protons. To address this issue, we introduce two new one-dimensional (1D) 1H NMR techniques that eliminate the water signal, preserving the intensities of exchangeable protons. Using GENETICS-AI, a software that combines an evolutionary algorithm and artificial intelligence, we tailored new water irradiation devoid (WADE) pulses and optimized the 1D 1H NOESY sequence for metabolomic analysis. When applied to human urine samples, kidney tissue extract, and plasma, the WADE technique allowed for accurate measurement of typical metabolites and direct quantification of urea, which is usually challenging to measure using standard NMR experiments. We anticipate that these new NMR techniques will significantly improve the accuracy and reliability of metabolite quantitative assessment for a wide range of biological fluids.

Association of dietary water intake with body composition and the potential mechanism based on urinary metabolic signatures in Chinese elderly individuals aged 75 years and above

With the rising global aging rate, elderly nutrition and health issues are major concerns. Current research focuses on nutrients such as protein and vitamins, while there are limited studies on water intake in the elderly. The aim of this study was to assess whether Chinese people aged over 75 years are meeting the recommended adequate intake (AI) for total water intake and its relationship with body composition. This was done by exploring potential mechanisms through the analysis of urinary metabolites. Water intake and dietary status were collected from 456 community seniors aged over 75 years using a 24-hour water intake and dietary record form. Body composition was determined by bioelectrical impedance analysis (BIA). We found that 16.01% of community seniors reached the AI. The protein, fat-free mass (FFM) and skeletal muscle mass (SMM) levels were all increased in the AI group compared to the Collapse

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MESH Headings

• Humans
• Aged
• Body Composition
• Male
• Female
• Aged, 80 and over
• China
• Drinking
• Diet
• East Asian People

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Affiliation(s)

Sai Yao Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.
Tianlin Gao Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.
Yajun Liu Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.
Ying Zhou Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.
Zhixuan Zhao Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.
Yinkun Wang Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.
Xincen Wang Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.
Aiguo Ma Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.
Feng Zhong Institute of Nutrition and Health, School of Public Health, Qingdao University, Qingdao, Shandong, 266000, China.

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Molecular mechanisms underlying the beneficial effects of fermented yoghurt prepared by nano-exopolysaccharide-producing Lactiplantibacillus plantarum LCC-605 based on untargeted metabolomic analysis

Following our previous discovery that Lactiplantibacillus plantarum LCC-605 secreted spherical exopolysaccharide nanoparticles (EPS-605 NPs), which may contribute to the quality, function, and stability of the fermented yoghurt. We thus prepared the fermented skim milk with strain LCC-605 (Y-605) and investigated the functions and metabolic changes of Y-605. Y-605 showed excellent antioxidant activities with DPPH, ABTS+, and hydroxyl scavenging ability of 90.6 ± 0.1 %, 96.1 ± 0.2 %, and 99.3 ± 0.4 %, respectively, and cholesterol-lowering ability up to 39.9 %. After storage for 7 days, the bacterial count reached 10.9 log CFU/mL. EPS production significantly improved the water holding capacity (71.7 ± 0.5 %), and the texture of the yoghurt. Untargeted metabolomic analysis further revealed significant metabolomic differences between skim milk and Y-605, validating the beneficial mechanism of Y-605. This study develops a novel probiotic for producing functional yoghurts and provides the basis for understanding the beneficial mechanism of Y-605.

Characterizing metabolomic and proteomic changes in depression: a systematic analysis

Despite the widespread use of metabolomics and proteomics to explore the molecular landscape of depression, there is a lack of consensus regarding dysregulated molecules with replicable evidence. Thus, this study aimed to identify robust metabolomic and proteomic features in depression by integrating evidence from large-scale studies. In this study, a knowledge base-mining approach was adopted to compile a list of dysregulated molecules derived from metabolomic and proteomic studies. A vote-counting approach was performed to identify consistently altered molecules in the blood and urine samples of patients with depression. A total of 2398 molecular entries were selected, comprising 857 unique metabolites and 468 unique proteins from 143 metabolomic and 23 proteomic studies in depression. The results of vote-counting analyses revealed that 11 metabolites in blood and 5 metabolites in urine exhibited consistent disturbances across studies. Circulating levels of glutamic acid and phosphatidylcholine (32:0) were elevated in depressive patients, whereas the levels of tryptophan, kynurenic acid, kynurenine, acetylcarnitine, serotonin, creatinine, inosine, phenylalanine, and valine were lower. Urinary levels of isobutyric acid, alanine, and nicotinic acid were higher, whereas the levels of N-methylnicotinamide and tyrosine were lower. Moreover, analysis of the proteomic dataset identified only one circulating protein, ceruloplasmin, that was consistently dysregulated. Convergence comparison prioritized tryptophan as the top-ranked circulating metabolite, followed by kynurenic acid, acetylcarnitine, creatinine, serotonin, and valine. Collectively, robust evidence of metabolomic changes was observed in patients with depression, pointing to a role as potential biomarkers. Further investigation of consensus proteomic features for depression is necessitated.

3-Indoleacetic Acid-Modified Chondroitin Sulfate-Mediated Paclitaxel Nanocrystal Assembly for the Treatment of Pancreatic Cancer

High drug-loading nanocrystals show significant advantages in delivering hydrophobic small-molecule drugs. However, these nanocrystals face challenges, including inherent instability and limited targetability. In this study, we developed a paclitaxel nanocrystal delivery platform based on chondroitin sulfate modified with 3-indoleacetic acid (CS-IAA). Paclitaxel and CS-IAA assembled into stable nanocrystals (PTX@CS-IAA, PC) with a high drug loading (up to 46.6%), facilitated by π-π stacking and hydrophobic interactions. CS-IAA targets tumors through CD44 receptors, which helps to minimize off-target effects. Additionally, CS-IAA, serving as a functional delivery vehicle, can significantly increase reactive oxygen species (ROS) levels at the tumor site. In an orthotopic pancreatic cancer mouse model, PTX@CS-IAA nanocrystals showed significantly enhanced antitumor effects. When PTX@CS-IAA was combined with the αPD-L1 antibody, the survival of mice with pancreatic tumors was further prolonged. This study provides valuable insights into alternative treatment options for pancreatic cancer, with the potential to improve patient prognosis and survival.

Potential Biomarkers of Fatal Hypothermia Revealed by UHPLC-MS Metabolomics in Mice

BACKGROUND

The postmortem diagnosis of fatal hypothermia presents a considerable challenge in forensic medicine. Metabolomics, a powerful tool reflecting comprehensive changes in endogenous metabolites, offers significant potential for exploring disease mechanisms and identifying diagnostic markers.

METHODS

In this study, we employed ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) to perform a non-targeted metabolomic analysis of liver, stomach, spleen, and musculus gastrocnemius tissues from mice subjected to fatal hypothermia.

RESULT

A substantial number of differential metabolites were identified in each tissue: 1601 in the liver, 420 in the stomach, 732 in the spleen, and 668 in the gastrocnemius muscle. The most significantly altered metabolites were as follows: magnoflorine (liver, upregulated, ranked first in fold-change), gibberellic acid (stomach, downregulated, ranked first in fold-change), nitrofurantoin (spleen, upregulated, ranked first in fold-change), and isoreserpin (gastrocnemius muscle, downregulated, ranked first in fold-change). Glycerophospholipid metabolism exhibited notable enrichment in all tissues (spleen: second, liver: tenth, stomach: eleventh, gastrocnemius muscle: twenty-first), as did tryptophan metabolism (spleen: thirteenth, liver: eighth, stomach: third, gastrocnemius muscle: seventeenth).

CONCLUSIONS

Our findings provide insights into the metabolic perturbations associated with fatal hypothermia in different tissues and lay a foundation for the identification of potential tissue biomarkers for forensic diagnosis.

The Inflammatory Mechanism of Parkinson's Disease: Gut Microbiota Metabolites Affect the Development of the Disease Through the Gut-Brain Axis

Parkinson's disease is recognized as the second most prevalent neurodegenerative disorder globally, with its incidence rate projected to increase alongside ongoing population growth. However, the precise etiology of Parkinson's disease remains elusive. This article explores the inflammatory mechanisms linking gut microbiota to Parkinson's disease, emphasizing alterations in gut microbiota and their metabolites that influence the disease's progression through the bidirectional transmission of inflammatory signals along the gut-brain axis. Building on this mechanistic framework, this article further discusses research methodologies and treatment strategies focused on gut microbiota metabolites, including metabolomics detection techniques, animal model investigations, and therapeutic approaches such as dietary interventions, probiotic treatments, and fecal transplantation. Ultimately, this article aims to elucidate the relationship between gut microbiota metabolites and the inflammatory mechanisms underlying Parkinson's disease, thereby paving the way for novel avenues in the research and treatment of this condition.

Metabolites Discovery from Streptomyces xanthus: Exploring the Potential of Desert Microorganisms

The Taklamakan Desert is an extreme environment supporting a unique and diverse microbial community with significant potential for exploration. Strain TRM70308T, isolated from desert soil, shares 98.43% 16S rRNA gene sequence similarity with Streptomyces alkaliterrae OF1T. Polyphasic taxonomy confirmed TRM70308T as a novel species, named Streptomyces xanthus. Genomic analysis revealed that only one of the strain's 25 biosynthetic gene clusters (BGCs) formed a cluster of gene families (CGFs) within the MIBiG database, emphasizing its genomics uniqueness. LC-MS/MS and Feature-Based Molecular Networking (FBMN) identified 33 metabolites across various categories, including alkaloids, saponins, benzoic acids, and benzofurans, most of which remain uncharacterized. Further chemical investigation led to the isolation of one novel compound, aconicarpyrazine C, and four known compounds: thiolutin, dibutyl phthalate, bis(2-ethylhexyl) phthalate, and N-acetyltryptamine. Thiolutin exhibited strong activity against five local fungal pathogens that cause plant diseases, with a production yield of 270 mg/L. These results establish a foundation for pilot-scale thiolutin production and its potential development as an antifungal agent for agricultural applications. Our findings highlight deserts as a valuable source of novel actinomycetes and bioactive natural products with immense potential for future research and development.

Harnessing amino acid pathways to influence myeloid cell function in tumor immunity

Amino acids are pivotal regulators of immune cell metabolism, signaling pathways, and gene expression. In myeloid cells, these processes underlie their functional plasticity, enabling shifts between pro-inflammatory, anti-inflammatory, pro-tumor, and anti-tumor activities. Within the tumor microenvironment, amino acid metabolism plays a crucial role in mediating the immunosuppressive functions of myeloid cells, contributing to tumor progression. This review delves into the mechanisms by which specific amino acids-glutamine, serine, arginine, and tryptophan-regulate myeloid cell function and polarization. Furthermore, we explore the therapeutic potential of targeting amino acid metabolism to enhance anti-tumor immunity, offering insights into novel strategies for cancer treatment.

Gut Bacteria-Derived Tryptamine Ameliorates Diet-Induced Obesity and Insulin Resistance in Mice

Tryptophan is an essential amino acid that is metabolized in the intestine by gut bacteria into indole derivatives, including tryptamine. However, little is known about which bacterial tryptophan metabolites directly influence obesity. In this study, we identified tryptamine as a bacterial metabolite that significantly reduced fat mass following the intraperitoneal injection of five bacterial tryptophan end-products in a diet-induced obese mouse model. Interestingly, tryptamine, a serotonin analog, inhibited both lipogenesis and lipolysis in adipose tissue, which was further confirmed in a 3T3-L1 adipocyte cell culture study. Moreover, oral tryptamine supplementation markedly reduced fat mass and improved insulin sensitivity in a long-term, high-fat-diet, pair-feeding model. These studies demonstrate the therapeutic potential of tryptamine, a bacterial tryptophan metabolite, in ameliorating obesity and insulin resistance by directly regulating lipogenesis and lipolysis in white adipose tissue.

Dysbiotic oral microbiota-derived kynurenine, induced by chronic restraint stress, promotes head and neck squamous cell carcinoma by enhancing CD8+ T cell exhaustion

BACKGROUND

Chronic restraint stress (CRS) is a tumour-promoting factor. However, the underlying mechanism is unknown.

OBJECTIVE

We aimed to investigate whether CRS promotes head and neck squamous cell carcinoma (HNSCC) by altering the oral microbiota and related metabolites and whether kynurenine (Kyn) promotes HNSCC by modulating CD8+ T cells.

DESIGN

4-nitroquinoline-1-oxide (4NQO)-treated mice were exposed to CRS. Germ-free mice treated with 4NQO received oral microbiota transplants from either CRS or control mouse donors. 16S rRNA gene sequencing and liquid chromatography-mass spectrometry were performed on mouse saliva, faecal and plasma samples to investigate alterations in their microbiota and metabolites. The effects of Kyn on HNSCC were studied using the 4NQO-induced HNSCC mouse model.

RESULTS

Mice subjected to CRS demonstrated a higher incidence of HNSCC and oral microbial dysbiosis than CRS-free control mice. Pseudomonas and Veillonella species were enriched while certain oral bacteria, including Corynebacterium and Staphylococcus species, were depleted with CRS exposure. Furthermore, CRS-altered oral microbiota promoted HNSCC formation, caused oral and gut barrier dysfunction, and induced a host metabolome shift with increased plasma Kyn in germ-free mice exposed to 4NQO treatment. Under stress conditions, we also found that Kyn activated aryl hydrocarbon receptor (AhR) nuclear translocation and deubiquitination in tumour-reactive CD8+ T cells, thereby promoting HNSCC tumourigenesis.

CONCLUSION

CRS-induced oral microbiota dysbiosis plays a protumourigenic role in HNSCC and can influence host metabolism. Mechanistically, under stress conditions, Kyn promotes CD8+ T cell exhaustion and HNSCC tumourigenesis through stabilising AhR by its deubiquitination.

Farfarae Flos Mitigates Cigarette Smoking-Induced Lung Inflammation by Regulating the Lysophosphatidylcholine Biosynthesis and Tryptophan Metabolism

An increased risk of developing respiratory diseases has been linked to exposure to cigarette smoking (CS). The flower buds of Tussilago farfara L., also known as Farfarae Flos (FF), can be used for the treatment of cough, bronchitis, and asthmatic disorders in China. In the present study, we used lung and fecal metabolomics, as well as the intestinal flora analysis, aimed to investigate the protective effect of FF against the CS exposure induced lung inflammation on mice. The results showed that FF administration could relieve the lung inflammation as demonstrated by lung index, interleukin-6 (IL-6), and interleukin-1β (IL-1β) levels, as well as the pulmonary pathological change. The lung metabolomics coupled with molecular docking showed that FF could alleviate lung inflammation by regulating lysophosphatidylcholine biosynthesis through the caffeoyl quinic acids distributed in the lung tissue. In addition, fecal metabolome coupled with 16S rRNA gene sequencing showed that FF could regulate the tryptophan metabolism by regulating the intestinal flora disorders. This study provided new insights of FF to relieve CS-induced pulmonary inflammation with the multimechanism.

Circulating tryptophan-kynurenine pathway metabolites are associated with all-cause mortality among patients with stage I-III colorectal cancer

Alterations within the tryptophan-kynurenine metabolic pathway have been linked to the etiology of colorectal cancer (CRC), but the relevance of this pathway for prognostic outcomes in CRC patients needs further elucidation. Therefore, we investigated associations between circulating concentrations of tryptophan-kynurenine pathway metabolites and all-cause mortality among CRC patients. This study utilizes data from 2102 stage I-III CRC patients participating in six prospective cohorts involved in the international FOCUS Consortium. Preoperative circulating concentrations of tryptophan, kynurenine, kynurenic acid (KA), 3-hydroxykynurenine (HK), xanthurenic acid (XA), 3-hydroxyanthranilic acid (HAA), anthranilic acid (AA), picolinic acid (PA), and quinolinic acid (QA) were measured by liquid chromatography-tandem mass spectrometry. Using Cox proportional hazards regression, we examined associations of above-mentioned metabolites with all-cause mortality, adjusted for potential confounders. During a median follow-up of 3.2 years (interquartile range: 2.2-4.9), 290 patients (13.8%) deceased. Higher blood concentrations of tryptophan, XA, and PA were associated with a lower risk of all-cause mortality (per doubling in concentrations: tryptophan: HR = 0.56; 95%CI:0.41,0.76, XA: HR = 0.74; 95%CI:0.64,0.85, PA: HR = 0.76; 95%CI:0.64,0.92), while higher concentrations of HK and QA were associated with an increased risk of death (per doubling in concentrations: HK: HR = 1.80; 95%CI:1.47,2.21, QA: HR = 1.31; 95%CI:1.05,1.63). A higher kynurenine-to-tryptophan ratio, a marker of cell-mediated immune activation, was associated with an increased risk of death (per doubling: HR = 2.07; 95%CI:1.52,2.83). In conclusion, tryptophan-kynurenine pathway metabolites may be prognostic markers of survival in CRC patients.

Cadmium alters the cellular metabolome of human ovarian granulosa cells

Cadmium (Cd) is a toxic heavy metal that has been extensively implicated in disordered folliculogenesis, but the mechanisms underlying the ovarian toxicity of Cd remain to be explored fully. Granulosa cells are key players in ovarian follicular development and are the primary cells affected by Cd exposure-induced damage and dysfunction. In this study, we investigated how various levels of exposure of Cd (3 and 10 μM) to human granulosa cells (KGN cells) impacted the metabolism of the KGN cells utilizing a non-targeted metabolomics methodology. In vitro cell experiments revealed that Cd exposure dose-dependently diminished the viability of KGN cells. Metabolomics analysis revealed the presence of 296 (182 elevated and 114 reduced) and 397 (244 elevated and 153 reduced) differentially expressed metabolites after exposure to 3 and 10 μM, respectively. Cd exposure was found to significantly enrich nucleotide metabolism, sphingolipid metabolism, and ABC transporters in both groups. Although amino acid metabolic pathways exhibited significant enrichment across all groups, only glutathione, cysteine, and methionine metabolism were notably enriched in KGN cells exposed to 3 μM Cd, while glutathione and tryptophan metabolism were significantly enriched in the 10 μM Cd exposure cohort. The outcomes of this study provide mechanistic clues for elucidating Cd's cytotoxic impact on granulosa cells, and deepen our understanding of the ovarian toxicity of Cd.

3-Hydroxyanthranic acid inhibits growth of oral squamous carcinoma cells through growth arrest and DNA damage inducible alpha

OBJECTIVES

The specific role of 3-hydroxyanthranilic acid(3-HAA) in oral squamous cell carcinoma (OSCC) remains unclear. This study investigated the roles of 3-HAA in OSCC and the underlying mechanism.

MATERIALS AND METHODS

The effects of 3-HAA on OSCC were examined using CCK-8, colony formation, EdU incorporation assays and xenograft mouse model. The underlying mechanisms were investigated with RNA-seq, apoptosis array and cell cycle array. Short hairpin RNAs (shRNAs) were used to knockdown the expression of growth arrest and DNA damage inducible alpha (GADD45A) in OSCC cells. CCK-8 and xenograft mouse model were employed to elucidate the role of GADD45A. The binding sites between GADD45A and Yin Yang 1(YY1) were determined using luciferase reporter assay.

RESULTS

3-HAA was selectively down-regulated in OSCC patients and the decreasing level intensified with pathological progression. Higher expression of kynurenine 3-monooxygenase (KMO) and kynureninase (KYNU), which can increase the content of 3-HAA, was associated with poorer prognosis of OSCC patients. Exogenous 3-HAA hampered growth of OSCC cells both in vitro and in vivo. 3-HAA induced growth arrest, G2/M-phase arrest, and apoptosis of OSCC cells. RNA-seq indicated that 3-HAA significantly increased GADD45A expression. 3-HAA promoted transcription of GADD45A by transcription factor YY1. Knockdown of GADD45A significantly reversed 3-HAA-induced growth inhibition of OSCC cells in vivo and in vitro.

DISCUSSION

3-HAA induced apoptosis and cell cycle arrest of OSCC cells via GADD45A, indicating that 3-HAA and GADD45A are potential therapeutic targets for OSCC.

Achieving healthy aging through gut microbiota-directed dietary intervention: Focusing on microbial biomarkers and host mechanisms

BACKGROUND

Population aging has become a primary global public health issue, and the prevention of age-associated diseases and prolonging healthy life expectancies are of particular importance. Gut microbiota has emerged as a novel target in various host physiological disorders including aging. Comprehensive understanding on changes of gut microbiota during aging, in particular gut microbiota characteristics of centenarians, can provide us possibility to achieving healthy aging or intervene pathological aging through gut microbiota-directed strategies.

AIM OF REVIEW

This review aims to summarize the characteristics of the gut microbiota associated with aging, explore potential biomarkers of aging and address microbiota-associated mechanisms of host aging focusing on intestinal barrier and immune status. By summarizing the existing effective dietary strategies in aging interventions, the probability of developing a diet targeting the gut microbiota in future is provided.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review is focused on three key notions: Firstly, gut microbiota has become a new target for regulating health status and lifespan, and its changes are closely related to age. Thus, we summarized aging-associated gut microbiota features at the levels of key genus/species and important metabolites through comparing the microbiota differences among centenarians, elderly people and younger people. Secondly, exploring microbiota biomarkers related to aging and discussing future possibility using dietary regime/components targeted to aging-related microbiota biomarkers promote human healthy lifespan. Thirdly, dietary intervention can effectively improve the imbalance of gut microbiota related to aging, such as probiotics, prebiotics, and postbiotics, but their effects vary among.

Supplementation with L-kynurenine during in vitro maturation improves bovine oocytes developmental competence through its antioxidative action

Oxidative stress impairs the developmental potential of oocytes during in vitro maturation (IVM). L-kynurenine (L-KYN), an endogenous metabolite, exhibits antioxidant, anti-inflammatory and neuroprotective effects. This work aimed to evaluate the potential effects of L-KYN on bovine oocyte IVM and its mechanisms. Different concentrations of L-KYN (0, 10, 50, 100, and 200 μmol/L) were supplemented to bovine oocyte IVM medium. Results shown a notable enhancement in the oocyte maturation rate and the subsequent zygote cleavage and blastocyst formation rate when the L-KYN concentration reached 100 μmol/L. Further analysis revealed that this treatment effectively down-regulated expression levels of genes to cumulus cell apoptosis (Bax and Caspase3), up-regulated expression levels of genes to cumulus cell expansion (HAS2, PTX3, and PTGS2) and oocyte antioxidant (GPX4 and CAT). L-KYN supplementation also effectively increased glutathione (GSH) levels, promoted oocytes mitochondrial activity, enhanced DNA repairability, deceased reactive oxygen species (ROS) levels, and reduced apoptosis. In conclusion, adding 100 μmol/L of L-KYN to IVM medium could enhance bovine oocyte quality and the subsequent embryonic development. L-KYN could be a potential antioxidant supplement for bovine oocyte maturation in vitro.

Biomimetic nanoplatform with microbiome modulation and antioxidant functions ameliorating insulin resistance and pancreatic β-cell dysfunction for T2DM management

Insulin resistance and pancreatic β-cell dysfunction are the main pathogenesis of type 2 diabetes mellitus (T2DM). However, insulin therapy and diabetes medications do not effectively solve the two problems simultaneously. In this study, a biomimetic oral hydrogen nanogenerator that leverages the benefits of edible plant-derived exosomes and hydrogen therapy was constructed to overcome this dilemma by modulating gut microbiota and ameliorating oxidative stress and inflammatory responses. Hollow mesoporous silica (HMS) nanoparticles encapsulating ammonia borane (A) were used to overcome the inefficiency of H2 delivery in traditional hydrogen therapy, and exosomes originating from ginger (GE) were employed to enhance biocompatibility and regulate intestinal flora. Our study showed that HMS/A@GE not only considerably ameliorated insulin resistance and liver steatosis, but inhibited the dedifferentiation of islet β-cell and enhanced pancreatic β-cell proportion in T2DM model mice. In addition to its antioxidant and anti-inflammatory effects, HMS/A@GE augmented the abundance of Lactobacilli spp. and tryptophan metabolites, such as indole and indole acetic acid, which further activated the AhR/IL-22 pathway to improve intestinal-barrier function and metabolic impairments. This study offers a potentially viable strategy for addressing the current limitations of diabetes treatment by integrating gut-microbiota remodelling with antioxidant therapies.

Development of a liquid chromatography-mass spectrometry based targeted metabolomics method for discovering diagnostic biomarkers in Kawasaki disease

Kawasaki disease (KD) has emerged as the leading cause of acquired heart disease in children, primarily due to the absence of highly sensitive and specific biomarkers for early and accurate diagnosis. To address this issue, a simple and comprehensive targeted metabolomics method employing ultra high-performance liquid chromatography coupled with Q-TRAP mass spectrometry has been developed to identify new metabolite biomarkers for KD. This method enables the simultaneous quantification of 276 metabolites, covering 60 metabolic pathways, with a particular emphasis on metabolites relevant to KD. The use of nine ISs and commercial quality control samples significantly enhances both accuracy and precision. Through validation and application to serum samples from patients with KD, seventeen differential serum metabolites were identified. The altered metabolites are primarily associated with three functional metabolic pathways: tricarboxylic acid cycle, tryptophan metabolism, and bile acid metabolism, all of which are believed to be involved in the inflammatory and immune responses in KD patients. Ultimately, eight differential metabolites (indole-3-propionic acid, thiamine, indolepyruvic acid, levodopa, l-selenomethionine, isocitric acid, trans-aconitate, and N-acetylasparagine) were identified that could potentially serve as diagnostic biomarkers with the area under the curve values exceeding 0.9. Our targeted metabolomics approach demonstrates applicability in identifying potential metabolite biomarkers for KD and holds great promise in unraveling the intricate pathophysiology of the disease.

Studies on the alleviating effect of Bifidobacterium lactis V9 on dextran sodium sulfate-induced colitis in mice

Background

Inflammatory bowel disease (IBD) has become a global public health problem with complex pathogenesis and limited therapeutic options. We aimed to investigate the potential mechanisms by which Bifidobacterium lactis V9 (V9) alleviated colitis in a dextran sodium sulfate-induced colitis model mice.

Methods

Mice were induced to develop colitis by drinking DSS solution to induce colitis. The expression of the relevant factors in the blood supernatant of the mice was determined by ELISA. RT-qPCR and Western blotting were used to detect mRNA and protein expression of target genes. The fecal microbiota was analyzed by 16S rRNA sequencing. Intestinal metabolites were analyzed by untargeted metabolomics.

Results

V9 effectively improved the overall symptoms of the colitis model mice. H&E showed that V9 re-stored the intestinal tissue structure. ELISA showed that V9 decreased the levels of IL-6, IL-22, and TNF-α and increased IL-10, SP, VIP, and 5-HT. V9 increased the expression of AHR, CYP1A1, MUC2, Claudin-3, Occludin, and ZO-1, and decreased 5-hydroxytryptamine transporter and Claudin-2. V9 increased the abundance of gut microbiota in colitis mice to promote the growth of beneficial bacteria. V9 increased tryptophan metabolites, and short-chain fatty acids, and improved gut inflammation.

Conclusion

V9 attenuates intestinal inflammation, improves the mucosal barrier, modulates intestinal microecology and exerts a protective effect in a mouse model of DSS-induced colitis.

Circadian metabolic adaptations to infections

Circadian clocks are biological oscillators that evolved to coordinate rhythms in behaviour and physiology around the 24-hour day. In mammalian tissues, circadian rhythms and metabolism are highly intertwined. The clock machinery controls rhythmic levels of circulating hormones and metabolites, as well as rate-limiting enzymes catalysing biosynthesis or degradation of macromolecules in metabolic tissues, such control being exerted both at the transcriptional and post-transcriptional level. During infections, major metabolic adaptation occurs in mammalian hosts, at the level of both the single immune cell and the whole organism. Under these circumstances, the rhythmic metabolic needs of the host intersect with those of two other players: the pathogen and the microbiota. These three components cooperate or compete to meet their own metabolic demands across the 24 hours. Here, we review findings describing the circadian regulation of the host response to infection, the circadian metabolic adaptations occurring during host-microbiota-pathogen interactions and how such regulation can influence the immune response of the host and, ultimately, its own survival.This article is part of the Theo Murphy meeting issue 'Circadian rhythms in infection and immunity'.

Neurological mechanism-based analysis of the role and characteristics of physical activity in the improvement of depressive symptoms

Depression is a common mental disorder characterized by a high prevalence and significant adverse effects, making the searching for effective interventions an urgent priority. In recent years, physical activity (PA) has increasingly been recognized as a standard adjunctive treatment for mental disorders owing to its low cost, easy application, and high efficiency. Epidemiological data shows positive preventive and therapeutic effects of PA on mental illnesses such as depression. This article systematically describes the prophylactic and therapeutic effects of PA on depression and its biological basis. A comprehensive literature analysis reveals that PA significantly improves depressive symptoms by upregulating the expression of "exerkines" such as irisin, adiponectin, and BDNF to positively impacting neuropsychiatric conditions. In particular, lactate could also play a critical role in the ameliorating effects of PA on depression due to the findings about protein lactylation as a novel protein post-transcriptional modification. The literature also suggests that in terms of brain structure, PA may improve hippocampal volume, basal ganglia (neostriatum, caudate-crustal nucleus) and PFC density in patients with MDD. In summary, this study elucidates the multifaceted positive effects of PA on depression and its potential biological mechanisms with a particular emphasis on the roles of various exerkines. Future research may further investigate the effects of different types, intensities, and durations of PA on depression, as well as how to better integrate PA interventions into existing treatment strategies to achieve optimal outcomes in mental health interventions.

Impact of astaxanthin on the capacity of gut microbiota to produce tryptophan catabolites

This study utilized in vitro colonic fermentation to examine the impact of astaxanthin on the microbial catabolism of tryptophan. Astaxanthin significantly altered the gut microbiota and raised the tryptophan catabolism metabolite levels in an in vitro human colonic fermentation system. To eliminate the influence of substrate availability, we conducted in vitro colonic fermentation of the gut microbiota of astaxanthin-domesticated mice. We observed that the capacity of astaxanthin-domesticated gut microbiota to catalyze the conversion of tryptophan to indole and derivatives was considerably augmented. Astaxanthin significantly increased the relative abundance of Akkermansia, Ruminococcus, Bacteroides and Lactobacillus and elevated the levels of indole-3-lactic acid and indole-3-propionic acid. These results demonstrated that astaxanthin regulates tryptophan metabolism by modifying gut microbiota and increasing the levels of indole metabolites, such as indole-3-lactic acid and indole-3-propionic acid. This study provides insights into the physiological activity of astaxanthin and sheds light on the potential for enhancing tryptophan metabolism through dietary manipulation of the gut microbiota.

The immunological perspective of major depressive disorder: unveiling the interactions between central and peripheral immune mechanisms

Major depressive disorder is a prevalent mental disorder, yet its pathogenesis remains poorly understood. Accumulating evidence implicates dysregulated immune mechanisms as key contributors to depressive disorders. This review elucidates the complex interplay between peripheral and central immune components underlying depressive disorder pathology. Peripherally, systemic inflammation, gut immune dysregulation, and immune dysfunction in organs including gut, liver, spleen and adipose tissue influence brain function through neural and molecular pathways. Within the central nervous system, aberrant microglial and astrocytes activation, cytokine imbalances, and compromised blood-brain barrier integrity propagate neuroinflammation, disrupting neurotransmission, impairing neuroplasticity, and promoting neuronal injury. The crosstalk between peripheral and central immunity creates a vicious cycle exacerbating depressive neuropathology. Unraveling these multifaceted immune-mediated mechanisms provides insights into major depressive disorder's pathogenic basis and potential biomarkers and targets. Modulating both peripheral and central immune responses represent a promising multidimensional therapeutic strategy.

Peripheral tryptophan-kynurenine pathway dysfunction in first-episode schizophrenia

The tryptophan (TRP)-kynurenine (KYN) pathway is involved in the pathogenesis of schizophrenia. This study aimed to investigate the levels of TRP-KYN metabolites in serum and urine of patients with first-episode schizophrenia (FES) and their association with clinical manifestations. This study included 38 drug-naive patients with FES and 43 healthy controls (HCs). Clinical symptoms were evaluated using the Positive and Negative Syndrome Scale (PANSS). Levels of TRP-KYN metabolites in serum and urine were quantified. Patients with FES showed significantly higher serum quinolinic acid/kynurenic acid (QUIN/KYNA) ratio and urine KYN/TRP ratio compared to HCs, while neuroprotective metabolites, including serum KYNA, xanthurenic acid (XA), and urine picolinic acid (PIC) levels, were significantly reduced, along with a decreased urine PIC/QUIN ratio (p < 0.05). The urine KYNA/KYN ratio was negatively correlated with PANSS general psychopathology scores (r = -0.35, p = 0.04) and with PANSS total scores (r = -0.35, p = 0.046). Patients with FES exhibited dysregulation of the peripheral TRP-KYN pathway, characterized by an increased neurotoxic-to-neuroprotective QUIN/KYNA ratio and reduced levels of neuroprotective metabolites. This shift towards increased neurotoxic product generation suggests that the dysregulation of the TRP-KYN pathway could play a role in the pathophysiology of schizophrenia.

GRP78 as a potential therapeutic target in cancer treatment: an updated review of its role in chemoradiotherapy resistance of cancer cells

GRP78 (Glucose-related protein 78, BiP/HSPA5) is commonly overexpressed in cancer cells. Acting as an activator of endoplasmic reticulum stress, GRP78 is involved in the resistance of cancer cells to injury. Current evidence suggests that GRP78 plays a significant role in the radiotherapy resistance and chemotherapy resistance of cancers, which is accomplished through a variety of complex pathways. These include the promotion of tumor stemness, inhibition of apoptosis, regulation of autophagy, maintenance of tumor microenvironment homeostasis, protection of dormant cells, evasion of senescence, counteraction of autoantibodies against GRP78, facilitation of DNA damage repair, suppression of ferroptosis, and modulation of metabolic reprogramming in tumor cells. Importantly, chemoradiotherapy resistance in cancers are the main reasons for treatment failure in patients, severely affecting their survival. Investigating the mechanisms of GRP78 in tumor therapeutic resistance is essential. In this article, we review the mechanisms by which GRP78 mediates cell survival and chemoradiotherapy resistance in cancers and provide an overview of clinical trials targeting GRP78 therapy.

Indole-3-lactic acid derived from tryptophan metabolism alleviates the sFlt-1-induced preeclampsia-like phenotype via the activation of aryl hydrocarbon receptor

AIMS

Preeclampsia (PE) is an unusual multisystem condition that occurs during pregnancy and is characterized by maternal endothelial dysfunction and damage to various organs. The catabolism of L-tryptophan (Trp) is involved in various biological activities, including healthy pregnancy. Our previous work revealed that PE significantly elevated the concentration of indole-3-lactic acid (ILA), a Trp derivative, during the third trimester of pregnancy. However, the effects of ILA on the occurrence of PE and its influence on fetoplacental vascular functionality remain unknown.

MATERIALS AND METHODS

Twenty-five Trp metabolites were detected in maternal serum. The effects of ILA on the functions of human umbilical vein endothelial cells (HUVECs) were examined. Furthermore, a soluble fms-like tyrosine kinase-1 (sFlt-1) induced PE-like mouse model was established and treated with ILA.

KEY FINDINGS

We found that the ratio of ILA to Trp gradually increased as pregnancy progressed. PE did not significantly change the concentration of ILA during either the first or second trimester. Moreover, as an aryl hydrocarbon receptor (AhR) ligand, ILA promoted HUVEC proliferation, migration and tube formation through the PI3K/AKT signaling pathway after AhR activation. Importantly, ILA administration alleviated sFlt-1-induced PE-like symptoms in mice. Similarly, our in vitro study demonstrated that ILA significantly relieved sFlt-1-induced HUVEC dysfunction by increasing the VEGFA and PIGF levels.

SIGNIFICANCE

These data strongly suggest that PE-elevated ILA in the third trimester is a protective mechanism against vascular dysfunction. Therefore, we propose that ILA is a novel and promising therapeutic approach for the treatment of PE that promotes endothelial cell functions.

Metabolomics Signatures of Exposure to Ambient Air Pollution: A Large-Scale Metabolome-Wide Association Study in the Cancer Prevention Study-II Nutrition Cohort

Existing air pollution metabolomics studies showed inconsistent results, often limited by small sample size and individual air pollutants effects. We conducted a metabolome-wide association study among 1096 women (68.2 ± 5.7 years) who provided blood samples (1998-2001) within the Cancer Prevention Study-II Nutrition Cohort. Annual average individual exposures to particulate matter, nitrogen dioxide, ozone, sulfur dioxide, and carbon monoxide in the year of blood draw were used. Metabolomics profiling was conducted on serum samples by Metabolon. We evaluated the individual air pollutants effects using multiple linear regression and the mixture effect using quantile g-computation, adjusting for confounders and false discovery rate (FDR). Ninety-five metabolites were significantly associated with at least one air pollutant or mixture (FDR < 0.05). These metabolites were enriched in pathways related to oxidative stress, systemic inflammation, energy metabolism, signals transduction, nucleic acid damage and repair, and xenobiotics. Sixty metabolites were confirmed with level 1 or 2 evidence, among which 21 have been previously linked to air pollution exposure, including taurine, creatinine, and sebacate. Overall, our results replicate prior findings in a large sample and provide novel insights into biological responses to long-term air pollution exposure using mixture analysis.

Investigating the biological significance of the TCM principle "promoting urination to regulate bowel movements" through the influence of the intestinal microbiota and their metabolites on the renal-intestinal axis

Treatment methods in traditional Chinese medicine (TCM) are foundational to their theoretical, methodological, formulaic, and pharmacological systems, significantly contributing to syndrome differentiation and therapy. The principle of "promoting urination to regulate bowel movements" is a common therapeutic approach in TCM. The core concept is "promoting the dispersion and drainage of water dampness, regulating urination to relieve diarrhea," yet its scientific underpinning remains unclear. Modern medical treatment for watery diarrhea primarily focuses on electrolyte replenishment, as diuretics may lead to dehydration and other side effects. Some reports suggest that this TCM approach lacks scientific validity. Microecology, an area associated with the origins of TCM, is closely related to the development, diagnosis, and treatment of diarrhea. The renal-intestinal axis offers a molecular biological basis for examining associated pathological mechanisms, advancing therapeutic targets such as "treating the intestine to address kidney issues" and highlighting the interactions within the "renal-intestinal microbiota-liquid metabolism" framework, thus providing an endogenous mechanism to support "treating the intestine through the kidney." An increasing number of studies have shown that the intestinal microbiota and its metabolites, as unique mediators, are involved in the physiological and pathological changes of the body. Therefore, this study explores the relationship between fluid metabolism and diarrhea from the perspective of the intestinal microbiota and its metabolites, aiming to elucidate the biological mechanisms underlying the "promoting urination to regulate bowel movements" therapeutic approach and to clarify the scientific basis for treating diarrhea via the renal-intestinal axis. This research provides new insights for the study of TCM microbiology.

Rat models of postintracerebral hemorrhage pneumonia induced by nasal inoculation with Klebsiella pneumoniae or intratracheal inoculation with LPS

Background

A stable and reproducible experimental bacterial pneumonia model postintracerebral hemorrhage (ICH) is necessary to help investigating the pathogenesis and novel treatments of Stroke-associated pneumonia (SAP).

Aim

To establish a Gram-negative bacterial pneumonia-complicating ICH rat model and an acute lung injury (ALI)-complicating ICH rat model.

Methods

We established two standardized models of post-ICH pneumonia by nasal inoculation with Klebsiella pneumoniae (Kp) or intratracheal inoculation with lipopolysaccharide (LPS). Survival and neurological scores were monitored. Magnetic resonance imaging was performed to evaluate hematoma volume. Abdominal aortic blood was collected for leukocyte counting, serum was isolated to determine concentrations of S100β and proinflammatory cytokines using ELISAs. Histopathological changes of brain, lung and gut were assessed using hematoxylin-eosin staining. Lung was isolated for immunofluorescence staining for myeloperoxidase (MPO). Bronchoalveolar lavage fluid was collected for leukocyte counting, and supernatant was prepared to measure MPO activity. Ileum was isolated for immunofluorescence staining for tight junction proteins ZO-1 and γδ TCRs/IL-17A and for Alcian blue-nuclear fast red staining of acidic mucins. Feces were collected, 16S rRNA sequencing, untargeted metabolomics and Spearman's correlation analyses were performed to explore changes of gut microbiota, metabolites and their interactions.

Results

In Kp-induced bacterial pneumonia-complicating ICH rats, we demonstrated that Kp challenge caused more severe neurological deficits, brain damage, neuroinflammation, and aggravated pneumonia and lung injury. Disruptions of the intestinal structure and gut barrier and the reductions of the protective intestinal IL-17A-producing γδT cells were also observed. Kp challenge exacerbated the gut microbiota dysbiosis and fecal metabolic profile disorders, which were characterized by abnormal sphingolipid metabolism especially elevated ceramide levels; increased levels of neurotoxic quinolinic acid and an upregulation of tryptophan (Trp)-serotonin-melatonin pathway. Spearman's correlation analyses further revealed that the reduction or depletion of some beneficial bacteria, such as Allobaculum and Faecalitalea, and the blooming of some opportunistic pathogens, such as Turicibacter, Dietzia, Corynebacterium and Clostridium_sensu_stricto_1 in Kp-induced SAP rats were associated with the disordered sphingolipid and Trp metabolism. Using an LPS-induced ALI complicating ICH model, we also characterized SAP-induced brain, lung and gut histopathology injuries; peripheral immune disorders and intense pulmonary inflammatory responses.

Conclusions

These two models may be highly useful for investigating the pathogenesis and screening and optimizing potential treatments for SAP. Moreover, the differential genera and sphingolipid or Trp metabolites identified above seem to be promising therapeutic targets.

Tryptophan metabolism-related gene CYP1B1 serves as a shared biomarker for both Parkinson's disease and insomnia

Parkinson's disease (PD) and insomnia are prevalent neurological disorders, with emerging evidence implicating tryptophan (TRP) metabolism in their pathogenesis. However, the precise mechanisms by which TRP metabolism contributes to these conditions remain insufficiently elucidated. This study explores shared tryptophan metabolism-related genes (TMRGs) and molecular mechanisms underlying PD and insomnia, aiming to provide insights into their shared pathogenesis. We analyzed datasets for PD (GSE100054) and insomnia (GSE208668) obtained from the Gene Expression Omnibus (GEO) database. TMRGs were obtained from the Molecular Signatures Database (MSigDB) and the Genecards database. Tryptophan metabolism-related differentially expressed genes (TM-DEGs) were identified by intersecting TMRGs with shared differentially expressed genes (DEGs) from these datasets. Through Protein-Protein Interaction (PPI) network analysis, Support Vector Machine-Recursive Feature Elimination (SVM-RFE) , and Extreme Gradient Boosting (XGBoost) machine learning, we identified Cytochrome P4501B1 (CYP1B1) and Electron Transfer Flavoprotein Alpha (ETFA) as key hub genes. Subsequently, we employed CIBERSORT and single-sample gene set enrichment analysis (ssGSEA) to further investigate the association between hub genes and peripheral immune activation and inflammatory response. Additionally, gene interaction, Drug-mRNA, Transcription Factor (TF)-mRNA, and competing endogenous RNA (ceRNA) networks centered on these hub genes were constructed to explore regulatory mechanisms and potential drug interactions. Finally, validation through bioinformatics and animal experiments identified CYP1B1 as a promising biomarker associated with both PD and insomnia.

Dysregulated tryptophan metabolism contributes to metabolic syndrome in Chinese community-dwelling older adults

BACKGROUND

As the prevalence of metabolic syndrome (MetS) rises among older adults, the associated risks of cardiovascular diseases and diabetes significantly increase, and it is closely linked to various metabolic processes in the body. Dysregulation of tryptophan (TRP) metabolism, particularly alterations in the kynurenine (KYN) and serotonin pathways, has been linked to the onset of chronic inflammation, oxidative stress, and insulin resistance, key contributors to the development of MetS. We aim to investigate the relationship between the TRP metabolites and the risk of MetS in older adults.

METHODS

Ultra-performance liquid chromatography tandem mass spectrometry was used to detect TRP and its seven metabolites in a study involving 986 participants. Physical examination included the following indicators: blood pressure, body mass index, triglyceride levels, and high-density lipoprotein cholesterol (HDL-C) levels. Multiple linear regression, restricted cubic spline curve, binary logistic analysis, and sex-stratified analysis were used to explore the relationship between the metabolites and the risk of MetS in older adults.

RESULTS

The results indicated that, after adjusting for covariates, higher levels of TRP, KYN, kynurenic acid (KA), and xanthurenic acid (XA) were risk factors for MetS (P for trend < 0.05). By contrast, higher ratios of 5-hydroxytryptamine to TRP and indole-3-propionic acid to TRP were protective factors against MetS (P for trend < 0.05).

CONCLUSIONS

TRP and its metabolites may serve as potential indicators for assessing and managing MetS in older adults, complementing existing biomarkers.

CLINICAL TRIAL NUMBER

Not applicable.

Characteristic alterations of gut microbiota and serum metabolites in patients with chronic tinnitus: a multi-omics analysis

Chronic tinnitus is a central nervous system disorder. Currently, the effects of gut microbiota on tinnitus remain unexplored. To explore the connection between gut microbiota and tinnitus, we conducted 16S rRNA sequencing of fecal microbiota and serum metabolomic analysis in a cohort of 70 patients with tinnitus and 30 healthy volunteers. We used the weighted gene co-expression network method to analyze the relationship between the gut microbiota and the serum metabolites. The random forest technique was utilized to select metabolites and gut taxa to construct predictive models. A pronounced gut dysbiosis in the tinnitus group, characterized by reduced bacterial diversity, an increased Firmicutes/Bacteroidetes ratio, and some opportunistic bacteria including Aeromonas and Acinetobacter were enriched. In contrast, some beneficial gut probiotics decreased, including Lactobacillales and Lactobacillaceae. In serum metabolomic analysis, serum metabolic disturbances in tinnitus patients and these differential metabolites were enriched in pathways of neuroinflammation, neurotransmitter activity, and synaptic function. The predictive models exhibited great diagnostic performance, achieving 0.94 (95% CI: 0.85-0.98) and 0.96 (95% CI: 0.86-0.99) in the test set. Our study suggests that changes in gut microbiota could potentially influence the occurrence and chronicity of tinnitus, and exert regulatory effects through changes in serum metabolites. Overall, this research provides new perceptions into the potential role of gut microbiota and serum metabolite in the pathogenesis of tinnitus, and proposes the "gut-brain-ear" concept as a pathomechanism underlying tinnitus, with significant clinical diagnostic implications and therapeutic potential.IMPORTANCETinnitus affects millions of people worldwide. Severe cases may lead to sleep disorders, anxiety, and depression, subsequently impacting patients' lives and increasing societal healthcare expenditures. However, tinnitus mechanisms are poorly understood, and effective therapeutic interventions are currently lacking. We discovered the gut microbiota and serum metabolomics changes in patients with tinnitus, and provided the potential pathological mechanisms of dysregulated gut flora in chronic tinnitus. We proposed the innovative concept of the "gut-brain-ear axis," which underscores the exploration of gut microbiota impact on susceptibility to chronic tinnitus through serum metabolic profile modulation. We also reveal novel biomarkers associated with chronic tinnitus, offering a new conceptual framework for further investigations into the susceptibility of patients, potential treatment targets for tinnitus, and assessing patient prognosis. Subsequently, gut microbiota and serum metabolites can be used as molecular markers to assess the susceptibility and prognosis of tinnitus.Furthermore, fecal transplantation may be used to treat tinnitus.

TGM2-mediated histone serotonylation promotes HCC progression via MYC signalling pathway

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is an aggressive malignancy for which there are few effective treatment options. H3Q5ser, a serotonin-based histone modification mediated by transglutaminase 2 (TGM2), affects diverse biological processes, such as neurodevelopment. The role of TGM2-mediated H3Q5ser in HCC progression remains unclear. This study investigated the role of TGM2 in promoting HCC progression and evaluated its potential as a therapeutic target for HCC treatment.

METHODS

Adeno-associated virus-mediated liver-specific overexpression models of Tgm2 or H3.3 were adopted to validate the effects of H3Q5ser on HCC progression. CUT&Tag and RNA sequencing was employed to investigate the underlying mechanisms. HCC organoids, subcutaneous xenograft models, and hydrodynamic tail vein injection models were used to evaluate the treatment efficiency of TGM2 inhibitors.

RESULTS

TMG2 expression positively correlated with higher alpha-fetoprotein levels, poor differentiation, and a later BCLC stage. Tgm2 deficiency or H3Q5ser inhibition notably inhibited HCC progression. CUT&Tag and RNA sequencing analyses revealed that downregulated genes were enriched in the MYC pathway following treatment with the TGM2 inhibitors. Furthermore, transcriptional intermediary factor 1 β mediated the recruitment of TGM2 to MYC, facilitating H3Q5ser modifications on MYC target genes. Finally, targeting the transglutaminase activity of TGM2 significantly suppressed HCC progression and showed synergy with sorafenib treatment in preclinical models. TGM2 inhibitors did not cause significant myelosuppression or tissue damage.

CONCLUSIONS

TGM2 serves as a prognostic biomarker and targeting its transglutaminase activity may be an effective strategy for inhibiting HCC progression.

IMPACT AND IMPLICATIONS

Transglutaminase 2 (TGM2)-mediated H3Q5ser modifications promote hepatocellular carcinoma (HCC) progression via MYC pathway signalling. Targeting the transglutaminase activity of TGM2 markedly inhibited HCC progression. TGM2 inhibitors did not induce significant myelosuppression or tissue damage. This preclinical study provides a theoretical basis to explore new strategies for HCC therapy.

Metabolomics Revealed Cadmium Exposure Associated with Alterations in Serum Metabolism in Children

Cadmium is a heavy metal contaminant known to cause various health issues. However, limited research exists on the serum metabolomic effects of cadmium exposure in children. In this study, we recruited 42 children to analyze their serum metabolomic profiles, along with measuring urinary cadmium and creatinine concentrations, to evaluate the impact of environmental cadmium exposure on serum metabolism. We also screened for potential biomarkers. The findings revealed that environmental cadmium exposure led to disruptions in amino acid metabolism, biosynthesis of secondary metabolites, endocrine function, lipid metabolism, nervous system function, sensory processes, and the metabolism of cofactors and vitamins in children. Lansioside C, Hydroxytanshinone, and 1-Methylinosine were identified as potential biomarkers. In conclusion, environmental cadmium exposure negatively impacts children's neurological development by inducing metabolic disturbances and increasing the risk of oxidative stress-related disorders. This study provides a valuable theoretical foundation for future efforts to prevent the harmful effects of cadmium exposure in children and mitigate associated health risks.

Metabolomics analysis of anaphylactoid reactions induced by Xueshuantong injection in normal and immunocompromised mice

Background

Xueshuantong injection (Lyophilized) (XSTI) is widely used to treat cardiovascular and cerebrovascular diseases. However, anaphylactoid reactions (ARs) are frequently reported as one of its side effects, and the mechanisms of ARs and their relationship with the different immune status are still not well understood.

Purpose

This article aims to examine the sensitizing effect of XSTI, explore the impact of normal and immunocompromised states on ARs, and analyze AR-related metabolic pathways by metabolomics.

Methods

An immunocompromised mouse model was established through intraperitoneal injection of cyclophosphamide (CTX). Normal and immunocompromised mice were then treated with normal saline (NS), histamine (HIS), and XSTI, respectively. Behavioral responses, auricle blue staining, and Evans blue (EB) exudation were used as indices to evaluate the sensitization of XSTI on both normal and immunocompromised mice. Subsequently, ARs models with different immune statuses were established, and validated by measuring four serum indicators using enzyme-linked immunosorbent assay (ELISA). Finally, LC-MS metabolomics analysis was performed on mouse serum to evaluate the metabolic pathways.

Results

The intensity of ARs induced by XSTI in mice was found to increase with the administered dose, with normal mice exhibiting higher AR intensities compared to immunocompromised mice. Metabolomic analysis revealed significant metabolic changes in XSTI-treated mice. The metabolic pathways predicted from these different metabolites include biotin metabolism, histidine metabolism, glycerolipid metabolism, bile secretion, arachidonic acid metabolism, sphingolipid metabolism, niacin and nicotinamide metabolism, tryptophan metabolism, steroid biosynthesis, and arginine and proline metabolism.

Conclusion

Research indicated that the sensitization of XSTI is dose-dependent, and mice with weakened immune functions exhibit lower sensitivity. Through metabolomics research, the differential metabolites in mice were analyzed, and the metabolic pathways inducing ARs were predicted. This study offers guidance on safe medication from the perspective of organism susceptibility and lays a foundation for research on the potential mechanisms of ARs.

Tear Fluid-Based Metabolomics Profiling in Chronic Dacryocystitis Patients

Chronic dacryocystitis (CD) can result in severe complications and vision impairment due to ongoing microbial infections and persistent tearing. Tear fluid, which contains essential components vital for maintaining ocular surface health, has been investigated for its potential in the noninvasive identification of ocular biomarkers through metabolomics analysis. In this study, we employed UHPLC-MS/MS to analyze the tear metabolome of CD patients. UHPLC-MS/MS analysis of tear samples from CD patients revealed significant metabolic alterations. Compared with the control group, 298 metabolites were elevated, while 142 were decreased. KEGG pathway analysis suggested that these changes primarily affected arginine and proline metabolism, biosynthesis of amino acids, and phenylalanine biosynthesis in CD. Notably, 3-dehydroquinic acid, anthranilic acid, citric acid, and l-isoleucine emerged as potential biomarker candidates of CD with high diagnostic accuracy (AUC = 0.94). These findings suggest that tear fluid metabolism, particularly amino acid biosynthesis, plays a significant role in the pathogenesis of CD. Uncovering these metabolic products and pathways provides valuable insights into the mechanisms underlying CD and paves the way for the development of diagnostic tools and targeted therapies.

Oxidative imbalance as a co-player in jaw functional limitations and biopsychosocial profile in patients with temporomandibular disorder-myofascial pain with referral

Introduction

Temporomandibular disorders have a multifactorial etiology including biological, biomechanical, neuromuscular, and biopsychosocial factors. Current research on temporomandibular disorders focuses on identifying clinically relevant biomarkers thus creating a new way of thinking about this dysfunction. The aim of the study was to determine the relationship between salivary/blood concentrations of oxidative/nitrosative stress biomarkers and biopsychosocial findings in patients with temporomandibular disorder-myofascial pain with referral.

Methods

The sample enrolled a total of 26 individuals with temporomandibular myofascial pain with referral (twenty women, six men). The procedure included clinical examination according to the Diagnostic Criteria for Temporomandibular Disorders, saliva and blood collection. Biochemical analysis concerned, among others, the content of reduced glutathione, uric acid, total antioxidant capacity, advanced glycation end products, malondialdehyde, total lipid hydroperoxides, kynurenine, N-formylkynurenine, and peroxynitrite. All determinations were considered with respect to the Patient Health Questionnaire-4 (PHQ-4), Patient Health Questionnaire-9 (PHQ-9), Patient Health Questionnaire-15 (PHQ-15), Generalized Anxiety Disorder-7 (GAD-7), Jaw Functional Limitation Scale-20 (JFLS-20), Perceived Stress Scale-10 (PSS-10), and Beck Depression Inventory (BDI).

Results and discussion

The average age of participants was 24.2 ± 1.23. High content of kynurenine and N-formylkynurenine in plasma was related to intensified psychological distress (PHQ-4) and anxiety (GAD-7). Low concentration of plasma malondialdehyde and total lipid hydroperoxides was linked with severe somatization (PHQ-15) and stress (PSS-10), respectively. Reduced levels of non-enzymatic antioxidants were associated with greater jaw functional mobility restrictions as well as limited mastication and communication factor with respect to JFLS-20. These findings indicate that oxidative stress biomarkers are significantly related to the biopsychosocial profile in patients with temporomandibular disorder.

Tryptophan Kynurenine Pathway-Based Imaging Agents for Brain Disorders and Oncology-From Bench to Bedside

Tryptophan (Trp)-based radiotracers have excellent potential for imaging many different types of brain pathology because of their involvement with both the serotonergic and kynurenine (KYN) pathways. However, radiotracers specific to the kynurenine metabolism pathway are limited. In addition, historically Trp-based radiopharmaceuticals were synthesized with the short-lived isotope carbon-11. A newer generation of Trp-based imaging agents using the longer half-lived and commercially available isotopes, such as fluorine-18 and iodine-124, are being developed. The newly developed amino acid-based tracers have been demonstrated to have favorable radiochemical and imaging characteristics in pre-clinical studies. However, many barriers still exist in the clinical translation of KYN pathway-specific radiotracers.

Topical application of magnolol ameliorates psoriasis-like dermatitis by inhibiting NLRP3/Caspase-1 pathway and regulating tryptophan metabolism

Psoriasis (PSO) is a common inflammatory skin disease caused by multiple factors. Magnolia officinalis is an important medicinal plant in China, with various values such as ecology, medicine, food, and daily chemicals. However, its diverse application potential has not been fully explored. Magnolol (MGO) is the main active compound of Magnolia officinalis with significant anti-inflammatory effect. To investigate the application potential of MGO in inflammatory skin disease, the effects and underlying mechanisms of topical MGO treating psoriasis were explored in this study. Network pharmacology and molecular docking firstly predicted that topical MGO may treat psoriasis by regulating pyroptosis pathway and acting on caspase-1 (CASP1). In vitro experiments then demonstrated that MGO could inhibit the level of inflammatory cytokines and the key protein expression of NOD-like receptor protein 3 (NLRP3)/Caspase-1 pathway in lipopolysaccharide (LPS)-stimulated phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 cells. Meanwhile, MGO could inhibit CuSO4-induced neutrophils migration in Tg (mpx:EGFP) zebrafish by suppressing inflammation and pyroptosis. This study further indicated that topical application of MGO ameliorated imiquimod (IMQ)-induced psoriasis-like dermatitis by reducing the release of inflammatory factors and decreasing the key protein expression of pyroptosis-related NLRP3/Caspase-1 pathway. Metabolomics analysis revealed that topical application of MGO could significantly regulate tryptophan metabolism and affect the level of tryptophan in skin lesions. Tryptophan could also regulate inflammation-related genes and inhibit pyroptosis-related NLRP3/Caspase-1 pathway in LPS-stimulated PMA-differentiated THP-1 cells. In conclusion, this study suggested that topical MGO may ameliorate psoriasis-like dermatitis by inhibiting NLRP3/Caspase-1 pathway and regulating tryptophan metabolism.

Study on the mechanism of brain injury caused by acute diquat poisoning based on metabolomics

Brain injury following acute diquat poisoning has become increasingly common in moderate to severe cases, with unclear pathogenesis and high mortality. To investigate this, we conducted metabolomics on brain tissue from poisoned rats, combined with clinical biochemical and pathological analyses. In the high-dose group, 24 metabolites showed significant differences compared to the control group: 18 were upregulated, including cytosine, sedoheptulose-7-phosphate, indole, 3-dehydroshikimate, etc.; 6 were downregulated, including 6-phosphogluconic acid, 3-hydroxybenzoic acid, dAMP, etc. In the low-dose group, 10 metabolites showed significant differences: 4 were upregulated, including pentamidine, γ-tocotrienol, benzoylecgonine, etc.; and 6 were downregulated, including dAMP, glutathione, 3-hydroxybenzoic acid, etc. Enrichment analysis identified two key pathways-phenylalanine, tyrosine, and tryptophan biosynthesis, and the pentose phosphate pathway-as involved in brain injury. ROC analysis of six differential metabolites showed that sedoheptulose-7-phosphate, (2R)-2-hydroxy-3-(phosphonatooxy)propanoate, and 3-hydroxybenzoic acid had AUC values above 0.8. These findings suggest that these three metabolites demonstrate strong diagnostic potential for brain injury induced by diquat poisoning. Correlation analysis linked these biomarkers to clinical indicators such as neutrophil count and the eutrophil to lymphocyte ratio, supporting their relevance. This study provides insights into the mechanisms and biomarkers of diquat-induced brain injury, offering a foundation for future treatment and rapid detection.

Microbiome and bladder cancer: the role of probiotics in treatment

Bladder cancer (BCa) remains a significant global health challenge, with increasing interest in the role of the bladder microbiome in its pathogenesis, progression and treatment outcomes. The complex relationship between bladder cancer and the microbiome, as well as the potential impact of probiotics on treatment effectiveness, is currently under investigation. Research suggests that the microbiota may influence BCa recurrence prevention and enhance the efficacy of the Bacillus Calmette-Guérin (BCG) vaccine. Recent studies reveal differences in the bladder microbiome between individuals without bladder cancer and those with the disease. In the healthy bladder, Streptococcus and Lactobacillus are consistently identified as the most prevalent genera. However, in men, the predominant bacterial genera are Staphylococcus, Corynebacterium and Streptococcus, while in women with bladder cancer, Gardnerella and Lactobacillus are dominant. Probiotics, particularly Lactobacillus spp., can exhibit anti-tumor properties by competing with pathogenic strains involved in carcinogenesis or by producing regulatory substances. They regulate cancer signaling, induce apoptosis, inhibit mutagenic activity, downregulate oncogene expression, induce autophagy, inhibit kinases, reactivate tumor suppressors and prevent metastasis. These mechanisms have shown promising results in both preclinical and some clinical studies.

Causal Relationship Between Intestinal Microbiota, Inflammatory Cytokines, Peripheral Immune Cells, Plasma Metabolome and Parkinson's Disease: A Mediation Mendelian Randomization Study

Parkinson's disease (PD) is a neurodegenerative disease involving multiple factors. We explored the connection between intestinal microbiome levels and PD by examining inflammatory cytokines, peripheral immune cell counts and plasma metabolomics as potential factors. By obtaining the Genome-Wide Association Study (GWAS) data needed for this study from GWAS Catalog, including summary data for 473 intestinal microbiota traits (N = 5959), 91 inflammatory cytokine traits (N = 14,824), 118 peripheral immune cell count traits (N = 3757), 1400 plasma metabolite traits (N = 8299) and PD traits (N = 482,730). We used two-step Mendelian randomization (MR) mediated analysis to investigate possible pathways from intestinal microbiota to PD mediated by inflammatory cytokines, peripheral immune cells and plasma metabolites. MR has revealed the causal effects of 19 intestinal microbiota, 1 inflammatory cytokine and 12 plasma metabolites on PD, whereas there is no significant causal relationship between immune cell count characteristics and the occurrence of PD. Mediation analysis showed that the associations between the genus Demequina and PD were mediated by tryptophan with mediated proportions of 17.51% (p = 0.0393). Our study demonstrates that genus Demequina may promote the occurrence of PD by reducing the levels of tryptophan.

Host-microbe serotonin metabolism

As a result of a long evolutionary history, serotonin plays a variety of physiological roles, including neurological, cardiovascular, gastrointestinal, and endocrine functions. While many of these activities can be accommodated within the serotoninergic activity, recent findings have revealed an unsuspected role of serotonin in orchestrating host and microbial dialogue at the tryptophan dining table, to the benefit of local and systemic homeostasis. Herein we review the dual role of serotonin at the host-microbe interface and discuss how unraveling the interconnections among the host and microbial pathways of tryptophan degradation may help to accommodate the versatility of serotonin in physiology and pathology.

Calcium Channel Blocker Lacidipine Promotes Antitumor Immunity by Reprogramming Tryptophan Metabolism

Dysfunction of calcium channels is involved in the development and progression of some cancers. However, it remains unclear the role of calcium channel inhibitors in tumor immunomodulation. Here, calcium channel blocker lacidipine is identified to potently inhibit the enzymatic activity and expression of indoleamine 2,3-dioxygenase 1 (IDO1), a rate-limiting enzyme in tryptophan metabolism. Lacidipine activates effector T cells and incapacitates regulatory T cells (Tregs) to augment the anti-tumor effect of chemotherapeutic agents in breast cancer by converting immunologically "cold" into "hot" tumors. Mechanistically, lacidipine targets calcium channels (CaV1.2/1.3) to inhibit Pyk2-JAK1-calmodulin complex-mediated IDO1 transcription suppression, which suppresses the kynurenine pathway and maintains the total nicotinamide adenine dinucleotide (NAD) pool by regulating NAD biosynthesis. These results reveal a new function of calcium channels in IDO1-mediated tryptophan metabolism in tumor immunity and warrant further development of lacidipine for the metabolic immunotherapy in breast cancer.

Rewiring Tryptophan Metabolism via Programmable Probiotic Integrated by Dual-Layered Microcapsule Protects against Inflammatory Bowel Disease in Mice

Intestinal dysbiosis and the associated l-tryptophan metabolic disorder are pivotal in inflammatory bowel disease progression, leading to a compromised intestinal barrier integrity. Remedying the dysfunction in tryptophan metabolism has emerged as a promising therapeutic strategy. Herein, we reprogram the tryptophan metabolism in situ by EcN-TRP@A/G, encapsulating the engineered probiotic, EcN-TRP, with enhanced tryptophan synthesis capacity, for sustained modulation, thereby restoring intestinal barrier function and microbial homeostasis. The pH-responsive dual-layered EcN-TRP@A/G microcapsule developed via high-voltage electrospraying and liquid interface self-assembly, preserved probiotic viability in the harsh gastrointestinal milieu, and facilitated targeted colon release. Bioluminescent tracking in mice reveals a 22.84-fold increase in EcN-TRP@A/G viability and distribution compared to naked EcN-TRP. Targeted metabolomics highlights EcN-TRP@A/G's modulation of the tryptophan-indole pathway. Oral administration of EcN-TRP@A/G sustained elevates indole metabolites, particularly indole-3-acetic acid and indole-3-propionic acid, in colon tissue for up to 7 days. In IBD mice, EcN-TRP@A/G improves intestinal permeability, reduces inflammation, and recovers the gut microbiome by enhancing beneficial bacteria abundance like Prevotellaceae_UCG-001 and Anaerostipes while suppressing pathogenic strains like Escherichia-Shigella. Our findings offer a cost-effective approach, harnessing the probiotic metabolic potential in situ through engineered modifications for effective IBD treatment.

Tryptophan metabolite atlas uncovers organ, age, and sex-specific variations

Although tryptophan (Trp) is the largest and most structurally complex amino acid, it is the least abundant in the proteome. Its distinct indole ring and high carbon content enable it to generate various biologically active metabolites such as serotonin, kynurenine (Kyn), and indole-3-pyruvate (I3P). Dysregulation of Trp metabolism has been implicated in diseases ranging from depression to cancer. Investigating Trp and its metabolites in healthy tissues offers pathways to target disease-associated disruptions selectively, while preserving essential functions. In this study, we comprehensively mapped Trp metabolites across the Kyn, serotonin, and I3P pathways, as well as the microbiome-derived metabolite tryptamine, in C57BL/6 mice. Our comprehensive analysis covered 12 peripheral organs, the central nervous system, and serum in both male and female mice at three life stages: young (3 weeks), adult (54 weeks), and aged (74 weeks). We found significant tissue-, sex-, and age-specific variations in Trp metabolism, with notably higher levels of the oncometabolites I3P and Kyn in aging males. These findings emphasize the value of organ-specific analysis of Trp metabolism for understanding its role in disease progression and identifying targeted therapeutic opportunities.

Integrated machine learning reveals the role of tryptophan metabolism in clear cell renal cell carcinoma and its association with patient prognosis

BACKGROUND

Precision oncology's implementation in clinical practice faces significant constraints due to the inadequacies in tools for detailed patient stratification and personalized treatment methodologies. Dysregulated tryptophan metabolism has emerged as a crucial factor in tumor progression, encompassing immune suppression, proliferation, metastasis, and metabolic reprogramming. However, its precise role in clear cell renal cell carcinoma (ccRCC) remains unclear, and predictive models or signatures based on tryptophan metabolism are conspicuously lacking.

METHODS

The influence of tryptophan metabolism on tumor cells was explored using single-cell RNA sequencing data. Genes involved in tryptophan metabolism were identified across both single-cell and bulk-cell dimensions through weighted gene co-expression network analysis (WGCNA) and its single-cell data variant (hdWGCNA). Subsequently, a tryptophan metabolism-related signature was developed using an integrated machine-learning approach. This signature was then examined in multi-omics data to assess its associations with patient clinical features, prognosis, cancer malignancy-related pathways, immune microenvironment, genomic characteristics, and responses to immunotherapy and targeted therapy. Finally, the genes within the signature were validated through experiments including qRT-PCR, Western blot, CCK8 assay, and transwell assay.

RESULTS

Dysregulated tryptophan metabolism was identified as a potential driver of the malignant transformation of normal epithelial cells. The tryptophan metabolism-related signature (TMRS) demonstrated robust predictive capability for overall survival (OS) and progression-free survival (PFS) across multiple datasets. Moreover, a high TMRS risk score correlated with increased tumor malignancy, significant metabolic reprogramming, an inflamed yet dysfunctional immune microenvironment, heightened genomic instability, resistance to immunotherapy, and increased sensitivity to certain targeted therapeutics. Experimental validation revealed differential expression of genes within the signature between RCC and adjacent normal tissues, with reduced expression of DDAH1 linked to enhanced proliferation and metastasis of tumor cells.

CONCLUSION

This study investigated the potential impact of dysregulated tryptophan metabolism on clear cell renal cell carcinoma, leading to the development of a tryptophan metabolism-related signature that may provide insights into patient prognosis, tumor biological status, and personalized treatment strategies. This signature serves as a valuable reference for further exploring the role of tryptophan metabolism in renal cell carcinoma and for the development of clinical applications based on this metabolic pathway.

Amitriptyline revitalizes ICB response via dually inhibiting Kyn/Indole and 5-HT pathways of tryptophan metabolism in ovarian cancer

Reprogramming tryptophan metabolism (TRP) may be able to overcome immunosuppression and restore the immune checkpoint blockade (ICB) response in patients with epithelial ovarian cancer (EOC) resistant to ICB therapy because TRP metabolism is involved in the kynurenine/indole and serotonin pathways of tryptophan metabolism. Herein, employing amitriptyline (AMI), an antagonist of TLR4 and serotonin transporter (SERT), we revealed that AMI remodels the immunological landscape of EOC. In particular, AMI lowered the expression of IDO1, IL-4I1, and PD-L1, the quantity of KYN and indoles, and the level of immunosuppressive immune cells MDSC, Tregs, and CD8+CD39+/PD-1+ T cell. AMI boosted the killing potential of anti-PD-1-directed CD8+T cells and worked in concert with PD-1 inhibitors to suppress tumor growth and to prolong the survival of EOC-bearing mice. This work highlights AMI as an effective regulator of ICB response by manipulating EOC cell TRP metabolism, indicating it could be a potential strategy for improving EOC ICB therapy.