High Tryptophan Research Articles

Integrated analysis of bulk and single-cell RNA sequencing reveals the impact of nicotinamide and tryptophan metabolism on glioma prognosis and immunotherapy sensitivity

BackgroundNicotinamide and tryptophan metabolism play important roles in regulating tumor synthesis metabolism and signal transduction functions. However, their comprehensive impact on the prognosis and the tumor immune microenvironment of glioma is still unclear. The purpose of this study was to investigate the association of nicotinamide and tryptophan metabolism with prognosis and immune status of gliomas and to develop relevant models for predicting prognosis and sensitivity to immunotherapy in gliomas.MethodsBulk and single-cell transcriptome data from TCGA, CGGA and GSE159416 were obtained for this study. Gliomas were classified based on nicotinamide and tryptophan metabolism, and PPI network associated with differentially expressed genes was established. The core genes were identified and the risk model was established by machine learning techniques, including univariate Cox regression and LASSO regression. Then the risk model was validated with data from the CGGA. Finally, the effects of genes in the risk model on the biological behavior of gliomas were verified by in vitro experiments.ResultsThe high nicotinamide and tryptophan metabolism is associated with poor prognosis and high levels of immune cell infiltration in glioma. Seven of the core genes related to nicotinamide and tryptophan metabolism were used to construct a risk model, and the model has good predictive ability for prognosis, immune microenvironment, and response to immune checkpoint therapy of glioma. We also confirmed that high expression of TGFBI can lead to an increased level of migration, invasion, and EMT of glioma cells, and the aforementioned effect of TGFBI can be reduced by FAK inhibitor PF-573,228.ConclusionsOur study evaluated the effects of nicotinamide and tryptophan metabolism on the prognosis and tumor immune microenvironment of glioma, which can help predict the prognosis and sensitivity to immunotherapy of glioma.

Tryptophan Metabolites Improve Intestinal Mucosal Barrier via the Aryl Hydrocarbon Receptor-Interleukin-22 Pathway in Murine Dextran Sulfate Sodium-Induced Pouchitis.

Pouchitis is the commonest complication after ileal pouch-anal anastomosis for ulcerative colitis. The protective effect of tryptophan metabolites on the mucosal barrier may be an effective method for treating pouchitis. The role of tryptophan metabolites on pouchitis remained unclear. We aimed to establish a murine model of dextran sulfate sodium-induced pouchitis to examine the roles of tryptophan metabolites in its pathogenesis. This is a study combined clinical patient data and animal research. A total of 22 patients were enrolled: 5 with familial adenomatous polyposis after ileal pouch-anal anastomosis, eight ulcerative colitis patients after ileal pouch-anal anastomosis patients with pouchitis, and 9 ulcerative colitis patients after ileal pouch-anal anastomosis with normal pouch. The demographic data and fecal samples of patients were collected. Male C57BL/6 mice were purchased from a licensed breeder and underwent ileal pouch-anal anastomosis to establish murine model of pouch. The bloods, feces, tissues of mice were collected. This study was performed in an academic medical center in China. The demographic data of patients were observational collected. The mice underwent ileal pouch-anal anastomosis were divided into six groups: control group with chow diet, dextran sulfate sodium, 6-formylindolo[3,2-b] carbazole + dextran sulfate sodium, high tryptophan diet + dextran sulfate sodium, CH-223191 + dextran sulfate sodium, indole-3-carboxaldehyde + dextran sulfate sodium. Animals were sacrificed after dextran sulfate sodium for 7 days. Fecal tryptophan metabolite level and microbiome composition, the severity of pouchitis, intestinal mucosal barrier function, and activation of the aryl hydrocarbon receptor-interleukin 22 pathway were assessed. Patients with pouchitis had lower fecal microbial diversity and indole-3-acetic acid levels. In murine pouchitis model, high-tryptophan diet increased fecal levels of 3-indoleglyoxylic acid, indole-3-aldehyde, and indole. A high-tryptophan diet and intraperitoneal aryl hydrocarbon receptor ligand 6-formylindolo[3,2-b] carbazole injection alleviated pouchitis. Tryptophan metabolites improved pouch mucosal barriers. aryl hydrocarbon receptor inhibitors exacerbated experimental pouchitis and disrupted the mucosal barrier; however, the aryl hydrocarbon receptor ligand indole-3-carboxaldehyde reversed this effect. This study was limited by small human sample size and lacking an Aryl hydrocarbon receptor knockout mouse model. A high-tryptophan diet and aryl hydrocarbon receptor ligand alleviated dextran sulfate sodium-induced pouchitis in murine ileal pouch-anal anastomosis model, which might be through regulating epithelial tight junctions and promoting goblet-cell differentiation, as well as maintaining the integrity and function of the mucosal barrier. This study provides a rationale for the clinical application of Aryl hydrocarbon receptor ligands in the treatment of pouchitis. See Video Abstract.

Longitudinal associations of plasma kynurenines and ratios with fatigue and quality of life in colorectal cancer survivors up to 12 months post-treatment.

Fatigue is prevalent in colorectal cancer (CRC) survivors, impacting their health-related quality of life (HRQoL). Inflammation-induced activation of the kynurenine pathway may play a role in cancer-related fatigue and HRQoL, but evidence is scarce. Therefore, we aimed to investigate longitudinal associations of plasma tryptophan, kynurenines, and ratios with fatigue and HRQoL in CRC survivors up to 12 months post-treatment. Repeated measurements at 6 weeks, 6 months, and 12 months post-treatment were performed in 249 stage I-III CRC survivors. Plasma tryptophan and eight kynurenines were analyzed using liquid chromatography-tandem mass spectrometry (LC/MS-MS). Fatigue and HRQoL outcomes were evaluated using validated questionnaires. Confounder-adjusted linear mixed models were conducted to analyze longitudinal associations, with false discovery rate (FDR) correction. Higher tryptophan (Trp), kynurenic acid (KA), and xanthurenic acid (XA) concentrations, as well as a higher kynurenic acid-to-quinolinic acid ratio (KA/QA), were associated with less fatigue and better functioning, while a higher kynurenine-to-tryptophan ratio (KTR) and 3-hydroxykynurenine ratio (HKr) were associated with more fatigue and worse functioning. Finally, higher KA and XA concentrations and a higher KA/QA ratio were associated with a higher overall HRQoL summary score, while a higher HKr was associated with a lower overall HRQoL summary score. In conclusion, we observed that tryptophan and several kynurenines were longitudinally associated with fatigue and HRQoL in CRC survivors up to 12 months post-treatment. Future research is needed to validate our findings and explore the potential of the kynurenine pathway as intervention target for reducing fatigue and enhancing HRQoL after CRC treatment.

Tryptophanyl-tRNA synthetase-1 (WARS-1) depletion and high tryptophan concentration lead to genomic instability in Caenorhabditis elegans

The fidelity of translation is ensured by a family of proteins named aminoacyl-tRNA synthetases (ARSs), making them crucial for development and survival. More recently, mutations in the tryptophanyl-tRNA synthetase 1 (WARS1) have been linked to various human diseases, from intellectual disability to various types of cancer. To understand the function of WARS1, we investigated the effect of WARS-1 depletion during the mitotic and meiotic cell cycle in the developing germline of Caenorhabditis elegans (C. elegans) and demonstrated the role of WARS-1 in genome integrity. wars-1 knockdown results in cell cycle arrest of the mitotically active germ cells. Such mitotic arrest is also associated with canonical DNA damage-induced checkpoint signaling in mitotic and meiotic germ cells. Significantly, such DNA checkpoint activation is associated with the morphological anomalies in chromatin structures that are the hallmarks of genome instability, such as the formation of chromatin bridges, micronuclei, and chromatin buds. We demonstrated that knocking down wars-1 results in an elevation of the intracellular concentration of tryptophan and its catabolites, a surprising finding emphasizing the impact of cellular amino acid availability and organismal/individual dietary uptake on genome integrity. Our result demonstrates that exposing C. elegans to a high tryptophan dosage leads to DNA damage checkpoint activation and a significant increase in the tryptophan metabolites. Targeting tryptophan catabolism, the least utilized amino acid in nature, can be important in developing new cancer therapeutic approaches. All in all, we have strong evidence that knocking down wars-1 results in defects in genomic integrity.

Nitrogen Nutrition Modulates the Response to Alternaria brassicicola Infection via Metabolic Modifications in Arabidopsis Seedlings.

Little is known about the effect of nitrogen nutrition on seedling susceptibility to seed-borne pathogens. We have previously shown that seedlings grown under high nitrate (5 mM) conditions are less susceptible than those grown under low nitrate (0.1 mM) and ammonium (5 mM) in the Arabidopsis-Alternaria brassicicola pathosystem. However, it is not known how seedling metabolism is modulated by nitrogen nutrition, nor what is its response to pathogen infection. Here, we addressed this question using the same pathosystem and nutritive conditions, examining germination kinetics, seedling development, but also shoot ion contents, metabolome, and selected gene expression. Nitrogen nutrition clearly altered the seedling metabolome. A similar metabolomic profile was observed in inoculated seedlings grown at high nitrate levels and in not inoculated-seedlings. High nitrate levels also led to specific gene expression patterns (e.g., polyamine metabolism), while other genes responded to inoculation regardless of nitrogen supply conditions. Furthermore, the metabolites best correlated with high disease symptoms were coumarate, tyrosine, hemicellulose sugars, and polyamines, and those associated with low symptoms were organic acids (tricarboxylic acid pathway, glycerate, shikimate), sugars derivatives and β-alanine. Overall, our results suggest that the beneficial effect of high nitrate nutrition on seedling susceptibility is likely due to nutritive and signaling mechanisms affecting developmental plant processes detrimental to the pathogen. In particular, it may be due to a constitutively high tryptophan metabolism, as well as down regulation of oxidative stress caused by polyamine catabolism.

Association of tryptophan pathway metabolites with mortality and effectiveness of nutritional support among patients at nutritional risk: secondary analysis of a randomized clinical trial.

Tryptophan is an essential amino acid and is the precursor of many important metabolites and neurotransmitters. In malnutrition, the availability of tryptophan is reduced, potentially putting patients at increased risks. Herein, we investigated the prognostic implications of the tryptophan metabolism in a secondary analysis of the Effect of Early Nutritional Support on Frailty, Functional Outcomes, and Recovery of Malnourished Medical Inpatients Trial (EFFORT), a randomized, controlled trial comparing individualized nutritional support to usual care in patients at risk for malnutrition. Among 238 patients with available measurements, low plasma levels of metabolites were independently associated with 30-day mortality with adjusted hazard ratios (HR) of 1.77 [95% CI 1.05-2.99, p 0.034] for tryptophan, 3.49 [95% CI 1.81-6.74, p < 0.001] for kynurenine and 2.51 [95% CI 1.37-4.63, p 0.003] for serotonin. Nutritional support had more beneficial effects on mortality in patients with high tryptophan compared to patients with low tryptophan levels (adjusted HR 0.61 [95% CI 0.29-1.29] vs. HR 1.72 [95% CI 0.79-3.70], p for interaction 0.047). These results suggest that sufficient circulating levels of tryptophan might be a metabolic prerequisite for the beneficial effect of nutritional interventions in this highly vulnerable patient population.

A188 ENHANCED MICROBIAL TRYPTOPHAN METABOLISM ACTIVATES THE ARYL HYDROCARBON RECEPTOR AND AMELIORATES INTESTINAL INFLAMMATION

Abstract Background Intestinal microbiota, diet, and the immune system have been proposed to contribute to the development of inflammatory bowel diseases (IBD). The aryl hydrocarbon receptor (AhR) is a critical regulator of intestinal immunity and mucosal barrier homeostasis that is activated by agonists such as host and microbial tryptophan metabolites. IBD patients have altered microbiota and reduced AhR agonists in intestinal content resulting in downregulation of AhR. Our recent findings indicate that mice harbouring microbiota with impaired tryptophan metabolism and AhR agonist production develop more severe inflammation during colitis. Aims To study the influence of diet-microbe interventions on AhR activation and intestinal inflammation in mice with impaired microbial tryptophan metabolism. Methods Germ-free C57BL/6 mice from McMaster’s Axenic Gnotobiotic Unit were colonized with cecal content of mice harbouring reduced microbiota with impaired tryptophan metabolism with and without tryptophan metabolizing Clostridium sporogenes. Following three weeks of microbial stabilization, mice were provided a high tryptophan (HT) diet or a low tryptophan (LT) diet as a control. Experimental colitis was induced using dextran sulfate sodium in drinking water (DSS; 2.5% w/v). Briefly, DSS was provided ad libitum for five days, followed by two days of recovery before tissue collection. Activation of AhR was measured in stool and C. sporogenes cultures using an in vitro AhR luciferase reporter assay. AhR agonists were quantified by capillary-electrophoresis-mass spectrometry. Colonic expression of AhR pathway genes was evaluated by RT-qPCR. Susceptibility to colitis was assessed by histologic analysis of distal colon sections, fecal lipocalin-2, weight loss, and clinical scores. Inflammatory gene transcripts were quantified in colon tissue by Nanostring. Results C. sporogenes efficiently produces AhR agonists in vitro and in vivo. In mice with impaired tryptophan metabolism, the HT diet increased AhR agonists in intestinal content and colonic AhR pathway gene expression, which was further enhanced in mice colonized with C. sporogenes. Compared to mice fed LT and HT diets, mice colonized with C. sporogenes and fed HT were most protected from weight loss, tissue damage, and immune cell infiltration. Conclusions These findings highlight the potential of tryptophan-rich diets and targeted microbe interventions as a novel approach to enhance AhR activation and mitigate inflammation during colitis. Consequently, exploring methods to improve tryptophan metabolism through diet and manipulation of the microbiota could be a promising therapeutic avenue for IBD patients with impaired AhR activation. Funding Agencies CCC, CIHR

The effects of tryptophan loading on Attention Deficit Hyperactivity in adults: A remote double blind randomised controlled trial.

Despite the impact and prevalence of Attention Deficit Hyperactivity Disorder (ADHD), current treatment options remain limited and there is a drive for alternative approaches, including those building on evidence of a role for tryptophan (TRP) and serotonin (5-HT). This study aimed to evaluate the effect of acute TRP loading on attention and impulsivity in adults with ADHD. We conducted a remote double blind randomised controlled trial (RCT) using TRP loading to examine the effects of a balanced amino acid load in comparison to low and high TRP loading in individuals with ADHD (medicated, N = 48, and unmedicated, N = 46) and controls (N = 50). Participants were randomised into one of three TRP treatment groups using stratified randomisation considering participant group and gender using a 1:1:1 ratio. Baseline testing of attention and impulsivity using the Test of Variables of Attention Task, Delay Discounting Task, and Iowa Gambling Task was followed by consumption of a protein drink (BAL, LOW, or HIGH TRP) before repeated testing. No effects of TRP were observed for any of the measures. In the present study, TRP loading did not impact on any measure of attention or impulsivity in those with ADHD or Controls. The findings need to be confirmed in another trial with a larger number of patients that also considers additional measures of dietary protein, plasma TRP and aggression. (Registration ID ISRCTN15119603).

Indole-3-Lactic Acid, a Tryptophan Metabolite of Lactiplantibacillus plantarum DPUL-S164, Improved Intestinal Barrier Damage by Activating AhR and Nrf2 Signaling Pathways.

A growing body of evidence suggests that microbial tryptophan metabolites play a crucial role in maintaining intestinal barrier stability and modulating host immunity. Our previous study showed that the Lactiplantibacillus plantarum (L. plantarum ) DPUL-S164 intervention in mice with a high tryptophan (Trp) diet promotes indole-3-lactic acid (ILA) production in the mice's intestinal tract and ameliorates dextran sodium sulfate(DSS)-induced intestinal barrier damage in mice. In this study, we used the HT-29 cell monolayer model to evaluate the effect of the L. plantarum DPUL-S164 Trp metabolites (DPUL-S164-TM) on the intestinal barrier. We found that L. plantarum DPUL-S164-TM alleviated lipopolysaccharide (LPS)-induced intestinal barrier damage and inflammation of the HT-29 cell monolayer by promoting the expression of tight junction proteins (ZO-1, occludin, claudin1), activating the AhR and Nrf2 signaling pathways, and inhibiting the NF-κB signaling pathway. We found that the promotion of tight junction protein expression and the activation of the Nrf2 signaling pathway by L. plantarum DPUL-S164-TM were dependent on the AhR expression of HT-29 cells. Additionally, L. plantarum DPUL-S164-TM showed a dramatic increase in the ILA content. Therefore, we inferred that ILA in L. plantarum DPUL-S164-TM plays a key role in improving the intestinal barrier function and alleviating inflammation.

Tryptophan metabolism regulates inflammatory macrophage polarization as a predictive factor for breast cancer immunotherapy

Metabolic reprogramming plays a pivotal role in regulating macrophage polarization and function. However, the impact of macrophage tryptophan metabolism on polarization within the breast cancer microenvironment remains elusive. In this study, we used single-cell transcriptome analysis and found that macrophages had the highest tryptophan metabolic activity in breast cancer, melanoma, and head and neck squamous cell carcinoma (HNSC). Further analysis revealed that the tryptophan metabolic activity of macrophages was positively correlated with the M1 macrophage scores in breast cancer. Pancancer analysis found positive correlations between tryptophan metabolism and the M1 macrophage score in almost all tumor types. Spatial transcriptome analysis revealed higher tryptophan metabolism in regions with higher M1 macrophage score in breast cancer tissues. Immune infiltration analysis revealed that the high tryptophan metabolism group exhibited a higher immune score, an increased proportion of CD8+ T cells, augmented cytolytic activity mediated by CD8+ T cells, and elevated expression of immune checkpoint molecules. Spatial immunophenotype cohort analysis exhibited that breast cancer patients expected to respond to immunotherapy had stronger tryptophan metabolism, with a 73.8 % area under the ROC curve. Single-cell transcriptome analysis of the immunotherapy cohort found that patients responding to immunotherapy had higher macrophage tryptophan metabolism prior to treatment initiation. Finally, in vitro experiments demonstrated elevated expression of tryptophan metabolic enzymes in M1 macrophages. Moreover, tryptophan facilitated the expression of M1 polarization markers, whereas inhibitors of tryptophan metabolic enzymes, such as NLG919, LM10, and Ro 61–8048, inhibited the expression of M1 polarization markers. In conclusion, this study identified a dual role for macrophage tryptophan metabolism in breast cancer; on the one hand, it promotes macrophage M1 polarization, while on the other hand, it serves as a promising predictor for the effectiveness of immunotherapy in breast cancer.

Longitudinal associations of macronutrient and micronutrient intake with plasma kynurenines in colorectal cancer survivors up to 12 months posttreatment

BackgroundThe tryptophan-kynurenine pathway is increasingly recognized to play a role in health-related quality of life (HRQoL) after cancer. Because tryptophan is an essential amino acid, and vitamins and minerals act as enzymatic cofactors in the tryptophan-kynurenine pathway, a link between diet and kynurenines is plausible. ObjectivesThis study aimed to investigate the longitudinal associations of macronutrient and micronutrient intake with metabolites of the kynurenine pathway in colorectal cancer (CRC) survivors up to 12 mo posttreatment. MethodsIn a prospective cohort of stage I–III CRC survivors (n = 247), repeated measurements were performed at 6 wk, 6 mo, and 12 mo posttreatment. Macronutrient and micronutrient intake was measured by 7-d dietary records. Plasma concentrations of tryptophan and kynurenines were analyzed using liquid chromatography tandem mass spectrometry (LC/MS-MS). Longitudinal associations were analyzed using linear mixed models adjusted for sociodemographic, clinical, and lifestyle factors. ResultsAfter adjustment for multiple testing, higher total protein intake was positively associated with kynurenic acid (KA) (β as standard deviation [SD] change in KA concentration per 1 SD increase in total protein intake: 0.12; 95% CI: 0.04, 0.20), xanthurenic acid (XA) (standardized β: 0.22; 95% CI: 0.11, 0.33), 3-hydroxyanthranilic acid (HAA) (standardized β: 0.15; 95% CI: 0.04, 0.27) concentrations, and the kynurenic acid-to-quinolinic acid ratio (KA/QA) (standardized β: 0.12; 95% CI: 0.02,0.22). In contrast, higher total carbohydrate intake was associated with lower XA concentrations (standardized β: −0.18; 95% CI: −0.30, −0.07), a lower KA/QA (standardized β: −0.23; 95% CI: −0.34, −0.13), and a higher kynurenine-to-tryptophan ratio (KTR) (standardized β: 0.20; 95% CI: 0.10, 0.30). Higher fiber intake was associated with a higher KA/QA (standardized β: 0.11; 95% CI: 0.02, 0.21) and a lower KTR (standardized β: −0.12; 95% CI: −0.20, −0.03). Higher total fat intake was also associated with higher tryptophan (Trp) concentrations (standardized β: 0.18; 95% CI: 0.06, 0.30) and a lower KTR (standardized β: −0.13; 95% CI: −0.22, −0.03). For micronutrients, positive associations were observed for zinc with XA (standardized β: 0.13; 95% CI: 0.04, 0.21) and 3-hydroxykynurenine (HK) (standardized β: 0.12; 95% CI: 0.03, 0.20) concentrations and for magnesium with KA/QA (standardized β: 0.24; 95% CI: 0.13, 0.36). ConclusionsOur findings show that intake of several macronutrients and micronutrients is associated with some metabolites of the kynurenine pathway in CRC survivors up to 12 mo posttreatment. These results may be relevant for enhancing HRQoL after cancer through potential diet-induced changes in kynurenines. Further studies are necessary to confirm our findings.

Persistent Symptoms and IFN-γ-Mediated Pathways after COVID-19.

After COVID-19, patients have reported various complaints such as fatigue, neurological symptoms, and insomnia. Immune-mediated changes in amino acid metabolism might contribute to the development of these symptoms. Patients who had had acute, PCR-confirmed COVID-19 infection about 60 days earlier were recruited within the scope of the prospective CovILD study. We determined the inflammatory parameters and alterations in tryptophan and phenylalanine metabolism in 142 patients cross-sectionally. Symptom persistence (pain, gastrointestinal symptoms, anosmia, sleep disturbance, and neurological symptoms) and patients' physical levels of functioning were recorded. Symptoms improved in many patients after acute COVID-19 (n = 73, 51.4%). Still, a high percentage of patients had complaints, and women were affected more often. In many patients, ongoing immune activation (as indicated by high neopterin and CRP concentrations) and enhanced tryptophan catabolism were found. A higher phenylalanine to tyrosine ratio (Phe/Tyr) was found in women with a lower level of functioning. Patients who reported improvements in pain had lower Phe/Tyr ratios, while patients with improved gastrointestinal symptoms presented with higher tryptophan and kynurenine values. Our results suggest that women have persistent symptoms after COVID-19 more often than men. In addition, the physical level of functioning and the improvements in certain symptoms appear to be associated with immune-mediated changes in amino acid metabolism.

Aromatic Amino Acids and Their Interactions with Gut Microbiota-Related Metabolites for Risk of Gestational Diabetes: A Prospective Nested Case-Control Study in a Chinese Cohort

Introduction: The aim of this study was to explore associations of aromatic amino acids (AAA) in early pregnancy with gestational diabetes mellitus (GDM), and whether high AAA and gut microbiota-related metabolites had interactive effects on GDM risk. Methods: We conducted a 1:1 case-control study (n = 486) nested in a prospective cohort of pregnant women from 2010 to 2012. According to the International Association of Diabetes and Pregnancy Study Group’s criteria, 243 women were diagnosed with GDM. Binary conditional logistic regression was performed to examine associations of AAA with GDM risk. Interactions between AAA and gut microbiota-related metabolites for GDM were examined using additive interaction measures. Results: High phenylalanine and tryptophan were associated with increased GDM risk (OR: 1.72, 95% CI: 1.07–2.78 and 1.66, 1.02–2.71). The presence of high trimethylamine (TMA) markedly increased the OR of high phenylalanine alone up to 7.95 (2.79–22.71), while the presence of low glycoursodeoxycholic acid (GUDCA) markedly increased the OR of high tryptophan alone up to 22.88 (5.28–99.26), both with significant additive interactions. Furthermore, high lysophosphatidylcholines (LPC18:0) mediated both interactive effects. Conclusions: High phenylalanine may have an additive interaction with high TMA, while high tryptophan may have an additive interaction with low GUDCA toward increased risk of GDM, both being mediated via LPC18:0.

Tryptophan metabolism determines outcome in tuberculous meningitis: a targeted metabolomic analysis.

Cellular metabolism is critical for the host immune function against pathogens, and metabolomic analysis may help understand the characteristic immunopathology of tuberculosis. We performed targeted metabolomic analyses in a large cohort of patients with tuberculous meningitis (TBM), the most severe manifestation of tuberculosis, focusing on tryptophan metabolism. We studied 1069 Indonesian and Vietnamese adults with TBM (26.6% HIV-positive), 54 non-infectious controls, 50 with bacterial meningitis, and 60 with cryptococcal meningitis. Tryptophan and downstream metabolites were measured in cerebrospinal fluid (CSF) and plasma using targeted liquid chromatography-mass spectrometry. Individual metabolite levels were associated with survival, clinical parameters, CSF bacterial load and 92 CSF inflammatory proteins. CSF tryptophan was associated with 60-day mortality from TBM (hazard ratio [HR] = 1.16, 95% confidence interval [CI] = 1.10-1.24, for each doubling in CSF tryptophan) both in HIV-negative and -positive patients. CSF tryptophan concentrations did not correlate with CSF bacterial load nor CSF inflammation but were negatively correlated with CSF interferon-gamma concentrations. Unlike tryptophan, CSF concentrations of an intercorrelating cluster of downstream kynurenine metabolites did not predict mortality. These CSF kynurenine metabolites did however correlate with CSF inflammation and markers of blood-CSF leakage, and plasma kynurenine predicted death (HR 1.54, 95% CI = 1.22-1.93). These findings were mostly specific for TBM, although high CSF tryptophan was also associated with mortality from cryptococcal meningitis. TBM patients with a high baseline CSF tryptophan or high systemic (plasma) kynurenine are at increased risk of death. These findings may reveal new targets for host-directed therapy. This study was supported by National Institutes of Health (R01AI145781) and the Wellcome Trust (110179/Z/15/Z and 206724/Z/17/Z).

Ruminococcus gnavusis a pathobiont expanded by genetic susceptibility and dietary tryptophan in a lupus-prone mouse model

Abstract Gut microbial dysbiosis has been associated with the development of systemic lupus erythematosus (SLE). Dietary tryptophan modifies the composition of gut microbiota as well as disease activity in a lupus-prone mouse (TC). To directly test the modulatory function of tryptophan on the gut microbiota, we transplanted the gut microbiota from TC and B6 control mice into germ-free or antibiotic treated B6 recipients fed with high or low dietary tryptophan. Interestingly, a putative human lupus pathobiont Ruminococcus gnavus (Rg) was only enriched in the recipients of TC microbiota fed with high dietary tryptophan, which produced anti-dsDNA IgA and presented T cell infiltration in the kidney. A higher level of Rg was detected in untouched TC mice as compared to B6 controls, in correlation with the levels of lupus signature cytokines. Depletion of this bacterium from the gut of TC mice decreased autoantibody production and increased the frequency of regulatory T cells. Conversely, monocolonization of antibiotic-treated TC mice with Rg induced the production of autoantibody as well as increased the frequency of IFN-γ+ T cells, IL-10+ non-T regulatory cells and GC B cells as compared to age-matched TC mice. These results indicate that monocolonization with Rg is sufficient to induce the autoimmune activation in lupus mouse model and that this bacterium is expanded by the combination of lupus genetic susceptibility and tryptophan. This project is supported by grant RO1 AI143313 from the NIH to LMo.

Increased tryptophan, but not increased glucose metabolism, predict resistance of pembrolizumab in stage III/IV melanoma

ABSTRACT Clinical trials of combined IDO/PD1 blockade in metastatic melanoma (MM) failed to show additional clinical benefit compared to PD1-alone inhibition. We reasoned that a tryptophan-metabolizing pathway other than the kynurenine one is essential. We immunohistochemically stained tissues along the nevus-to-MM progression pathway for tryptophan-metabolizing enzymes (TMEs; TPH1, TPH2, TDO2, IDO1) and the tryptophan transporter, LAT1. We assessed tryptophan and glucose metabolism by performing baseline C11-labeled α-methyl tryptophan (C11-AMT) and fluorodeoxyglucose (FDG) PET imaging of tumor lesions in a prospective clinical trial of pembrolizumab in MM (clinicaltrials.gov, NCT03089606). We found higher protein expression of all TMEs and LAT1 in melanoma cells than tumor-infiltrating lymphocytes (TILs) within MM tumors (n = 68). Melanoma cell-specific TPH1 and LAT1 expressions were significantly anti-correlated with TIL presence in MM. High melanoma cell-specific LAT1 and low IDO1 expression were associated with worse overall survival (OS) in MM. Exploratory optimal cutpoint survival analysis of pretreatment ‘high’ vs. ‘low’ C11-AMT SUVmax of the hottest tumor lesion per patient revealed that the ‘low’ C11-AMT SUVmax was associated with longer progression-free survival in our clinical trial (n = 26). We saw no such trends with pretreatment FDG PET SUVmax. Treatment of melanoma cell lines with telotristat, a TPH1 inhibitor, increased IDO expression and kynurenine production in addition to suppression of serotonin production. High melanoma tryptophan metabolism is a poor predictor of pembrolizumab response and an adverse prognostic factor. Serotoninergic but not kynurenine pathway activation may be significant. Melanoma cells outcompete adjacent TILs, eventually depriving the latter of an essential amino acid.

Amino acid content in spring common wheat grain

The aim of the study was to determine the differences in the content of amino acids in wheat grains of the world collection of VIR in the agro-climatic conditions of the Republic of Tatarstan and to search for sources of increased content of essential amino acids for the use of these data in breeding. The study was conducted in 2021-2022 at the experimental base of the Tatar Research Institute of Agriculture of the Kazan Scientific Center of the Russian Academy of Sciences, located 15 km away from Kazan, the soil of the experimental site is gray forest. 354 samples of spring wheat were studied. The determination of the content of seventeen amino acids and protein in wheat grain was carried out using the near-infrared spectroscopy method on the DS 2500F device from FOSS. The protein content in the grain has a significant effect on the amount of essential acids. The correlation between the protein content and the amount of essential acids in wheat grain is high in 2021. r = 0.91 ± 0.02 and average in 2022. r = 0.69± 0.04. The highest content of glutamine in wheat grain was noted - up to 2.22 % and proline - up to 1.55 %. The source of high grain content of histidine 0.38- 0.40 %, isoleucine 0.53-0.54 %, lysine 0.61-0.62 %, methionine 0.28-0.30 %, phenylalanine 0.66-0.67 %, threonine 0.52-0.56 % and tyrosine 0.31-0.36 % was the Ranee sample (k-26982). The Panifor sample was a source of high grain content of cysteine 0.58-0.63 %, histidine 0.39 % and threonine 0.51-0.58 %. The Arrino sample (k-65995) is a source of high grain content of leucine 0.82-0.91 %, tyrosine 0.31-0.34 % and valine 0.75-0.78 %. According to the lysine content in protein (grams of amino acid per 100 grams of protein), samples Ranee (k-26982) - 3.63-3.66 and NIL Avocet Yr15 (k-66241) - 2.86-4.52 were isolated. According to the content of methionine in the protein, samples of Uffo (k- 66798) - 1.80-1.8 and Fiorina (k-66034) - 1.70-1.91 were isolated. According to the threonine content, three samples Ranee (k-26982) - 3.04-3.36, Panifor (k-66039) - 3.09-3.20 and Cub (k- 62510) - 3.07-3.20 were distinguished. The source of the high tryptophan content in the protein were samples Ethos (k- 65002) - 2.00-2.27, Tulaykovskaya 108 (k- 65452) - 2.01-2.26 and Ekada 109 (k-66239) - 2.07-2.14.

Tryptophan intake, not always the more the better.

To investigate the effects of excessive tryptophan intake on the body and the effects of tryptophan metabolism-related aryl hydrocarbon receptor (AhR) pathway in healthy rats and chronic kidney disease rats, to study the adverse effects of excess tryptophan. In Part I Experiment, the healthy rats were fed with diet containing 0.6, 1.2 and 1.8% tryptophan for 12 weeks. After the intervention, the blood and kidney tissues were collected. Serum creatinine and blood urea nitrogen were detected. Hematoxylin-eosin (H&E) staining was used to observe renal pathological changes. Enzyme-linked immunosorbent assay was used to detect serum kynurenic acid and AhR levels. The kidney levels of AhR, CyP1A1 and CyP1B1 were detected by western-blot. In Part II Experiment, the chronic kidney disease (CKD) model was induced by intra-gastric gavage with adenine for 4 weeks. Then the CKD rats were given tryptophan at a dose of 100 mg/kg or 500 mg/kg for eight weeks. Rat survival curve, renal function, renal tissue pathology and serum AhR were detected. Tryptophan-targeted ultra-high-performance liquid chromatography coupled with multiple reaction monitoring mass spectrometry (UHPLC-MRM-MS) was employed to quantitatively access the tryptophan-targeted metabolites in two parts experiments. In part I experiment, high tryptophan diet can increase the level of blood urea nitrogen (BUN) in healthy rats and induce focal renal tubulointerstitial injury. Tryptophan-targeted analyzes showed that high tryptophan diet feeding can significantly increase the concentration of kynurenine and indole metabolites. The serum AhR level and kidney AhR, CyP1A1 and CyP1B1 were also significantly increased in high tryptophan diet rats. In part II experiment, high tryptophan intervention induced a significant increase in mortality, serum creatinine, urea nitrogen levels, and renal pathological damage in CKD rats. The levels of tryptophan-targeted metabolites, kynurenine, xanthurenate, picolinic acid, 5-hydroxyindole-3-acetic acid, indole-3-lactic acid, indoleacetate and indoxyl sulfate, showed an upward trend in the high-dose tryptophan group (Ade + Trp-H) compared with the adenine group. The serum AhR of Ade + Trp-H rats was significantly higher than those of adenine rats. Moderate tryptophan intake may be beneficial, but excessive tryptophan can lead to accumulation of kynurenine and indole metabolites, activate AhR pathway and induce kidney injury.

Abstract 4705: Profiling of immune cell components and soluble factors in ovarian cancer ascites highlights impaired immune environment

Abstract Background: It’s now increasingly recognized that ovarian cancer (OC) ascites play a significant role in OC progression - behavior of tumor cells is influenced by the nature of their surrounding microenvironment. Thus, characterization of ascites composition is essential to understand how this milieu affects tumor progression and particularly the immunosuppressive pathways that would underlie immune response dysfunctions and, in turn, how biological ascites effects can be influenced by that composition. Methods: Ascites samples were collected from advanced OC patients. Through respective multiplexed approaches of flow cytometry-based marker expression analysis and quantitation of mediators, immune context was profiled by investigating immune cell composition and levels of a plethora of soluble factors, including cytokines/chemokines, and metabolic pathways of some amino acids known to be involved in immunosuppression. Furthermore, ascites fluids were functionally screened for their biological effects on healthy monocytes, either undifferentiated or undergoing M1 polarization. Results: Unlike healthy PBMCs, OC ascites were mostly “enriched” in regulatory/immunosuppressive immune cell subsets including T and myeloid populations. Also, T cells were shown to highly express immune checkpoints such as PD1 in T cells and TIGIT in Tregs. Intriguingly, a high CD4/CD8 ratio was seen. Also, CD163+ tumor-associated macrophages were shown to express CSF1R, CCR8 and CCR2, and to even display a mixed phenotype since also expressing Arg1, CD80, and iNOS. On acellular fractions, most ascites demonstrated elevated CCL18, IL6, LIF, VEGF, and CCL2 levels, and low IL2, IL4, and IL17 levels. Interestingly, unlike healthy plasmas, these ascites appeared to harbor a metabolically-immunosuppressive profile characterized by high glutaminolysis and tryptophan (Trp) degradation in kynurenine (Kyn). Functionally, we demonstrated that not only ascites basically polarized monocytes into M2 macrophages, but even antagonized with their M1 polarization to ultimately tilt to M2 status. Conclusions: Taken together, our data show that ascites fluids most favorable to the M2 phenotype were associated with high LIF, VEGF, IL6, CCL2, and CCL18 levels, and with elevated Kyn to Trp ratios - Kyn levels being strongly higher than in healthy plasmas. Our results thus highlight a peculiar altered environment of OC ascites where a mixture of suppressive cells and signaling factors mediate extracellular cues leading to immune cell activity dysfunction. Altogether, these translational findings highlight OC ascites as a valuable tool to understand the mechanisms of suppression and develop predictive profiles, and to provide new insights for the identification of new targets and development of targeted-therapies. Citation Format: Assia Chaibi, Coriolan Lebreton, Dominique Bodet, Jean-Philippe Guegan, Guillaume Babin, Antoine Italiano, Alban Bessede, Imane Nafia. Profiling of immune cell components and soluble factors in ovarian cancer ascites highlights impaired immune environment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4705.

Genetic risk of depression is different in subgroups of dietary ratio of tryptophan to large neutral amino acids

Manipulation of intake of serotonin precursor tryptophan has been exploited to rapidly induce and alleviate depression symptoms. While studies show that this latter effect is dependent on genetic vulnerability to depression, the effect of habitual tryptophan intake in the context of predisposing genetic factors has not been explored. Our aim was to investigate the effect of habitual tryptophan intake on mood symptoms and to determine the effect of risk variants on depression in those with high and low tryptophan intake in the whole genome and specifically in serotonin and kynurenine pathways. 63,277 individuals in the UK Biobank with data on depressive symptoms and tryptophan intake were included. We compared two subpopulations defined by their habitual diet of a low versus a high ratio of tryptophan to other large amino acids (TLR). A modest protective effect of high dietary TLR against depression was found. NPBWR1 among serotonin genes and POLI in kynurenine pathway genes were significantly associated with depression in the low but not in the high TLR group. Pathway-level analyses identified significant associations for both serotonin and kynurenine pathways only in the low TLR group. In addition, significant association was found in the low TLR group between depressive symptoms and biological process related to adult neurogenesis. Our findings demonstrate a markedly distinct genetic risk profile for depression in groups with low and high dietary TLR, with association with serotonin and kynurenine pathway variants only in case of habitual food intake leading to low TLR. Our results confirm the relevance of the serotonin hypothesis in understanding the neurobiological background of depression and highlight the importance of understanding its differential role in the context of environmental variables such as complexity of diet in influencing mental health, pointing towards emerging possibilities of personalised prevention and intervention in mood disorders in those who are genetically vulnerable.