Levels Of Tryptophan Metabolites Research Articles

Herpes simplex reactivation triggers symptom exacerbation in patients with major depressive disorder

BackgroundHerpes Simplex Virus (HSV) infection has been linked to depression, but the underlying mechanism remains largely unknown. We hypothesized that recurring HSV infection could exacerbate depressive symptomatology via activation of the immune response and the kynurenine pathway in patients with Major Depressive Disorder (MDD). Methods32 MDD patients and 17 psychiatrically healthy individuals with a history of HSV recurrence were enrolled into the study. Blood samples were obtained, and psychiatric symptom severity was assessed at three separate visits- asymptomatic, active infection, and follow-up. Plasma levels of tryptophan metabolite levels were measured using ultra-high performance liquid chromatography-mass spectrometry (LC-MS), and inflammation-associated proteins were measured using high sensitivity electrochemiluminescence. ResultsThere was a significant effect of infection recurrence on IFN-γ and sICAM-1 levels, the latter being influenced by MDD diagnosis. This indicates that the effect of infection on sICAM-1 levels differs between control and depressed groups, although post hoc analysis suggests that interaction effect might be subtle. Infection recurrence had a significant effect on the reactivity of psychiatric symptoms. Finally, there was a positive correlation between levels of anti-inflammatory cytokines IL-10 and IL-13 and depression severity in the cohort during infection recurrence. LimitationsRelatively small sample size, limited number of male participants, and the relatively weak inflammatory stimuli studied. ConclusionsMDD patients might react with an exacerbation of symptoms along with elevations of inflammatory markers during HSV recurrence. Further, the association with symptom severity indicates that therapeutic modulation of inflammation may be beneficial in patients with MDD, especially during active infections.

Baitouweng decoction alleviates ulcerative colitis by regulating tryptophan metabolism through DOPA decarboxylase promotion.

Baitouweng decoction (BTW) is a classic botanical drugs formula that has been widely used clinically for the treatment of gut-related disorders in China. However, its role in ameliorating ulcerative colitis (UC) remains to be explored. The study aimed to determine the therapeutic efficacy and potential mechanism of action of BTW on dextran sodium sulfate (DSS)-induced colitis mice. In vivo: 3.5% DSS-induced experimental colitis mice were treated with BTW (Pulsatilla chinensis (Bunge) Regel, Phellodendron chinense C. K. Schneid, Coptis chinensis Franch and Fraxinus chinensis Roxb), kynurenine or DOPA decarboxylase (DDC) inhibitor (carbidopa). In vitro: Caco-2 cells were stimulated with TNF-α to activate inflammation and later treated with various concentrations of BTW and carbidopa. Model evaluation included body weight, disease activity index (DAI) score, colon length and histopathology. Cytokine levels were measured by flow cytometry. Protein levels were analyzed by proteomics and functionally annotated. The levels of tryptophan metabolites in mouse serum and colon were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Alcian Blue/Phosphate Acid Schiff (AB/PAS) staining, immunohistochemistry and western blot were used to assess the intestinal barrier function and detect the protein expression levels. BTW significantly reduced the DAI, ameliorated colonic injury and regulated inflammatory cytokines in DSS-induced colitis mice. The botanical drugs formula also promoted intestinal epithelial barrier repair by enhancing the expression of the tight junction (TJ) proteins. Tryptophan metabolic signaling pathway was significantly enriched in DSS-induced UC mice, and BTW decreased the level of kynurenine, increased indole metabolites. The therapeutic effect of BTW was evidently reduced when kynurenine was given to mice. Also, BTW promoted DDC protein expression and activated the aryl hydrocarbon receptor (AHR)/IL-22 signaling pathway. BTW improves ulcerative colitis by promoting DDC expression, regulating the conversion of tryptophan metabolism from the kynurenine pathway to the indole metabolism pathway, thereby modulating tryptophan metabolism to increase indole metabolites, and activating AHR receptors to restore intestinal barrier function.

BICC1 drives pancreatic cancer stemness and chemoresistance by facilitating tryptophan metabolism.

Pancreatic adenocarcinoma is the fourth leading cause of malignancy-related deaths, with rapid development of drug resistance driven by pancreatic cancer stem cells. However, the mechanisms sustaining stemness and chemotherapy resistance in pancreatic ductal adenocarcinoma (PDAC) remain unclear. Here, we demonstrate that Bicaudal C homolog 1 (BICC1), an RNA binding protein regulating numerous cytoplasmic mRNAs, facilitates chemoresistance and stemness in PDAC. Mechanistically, BICC1 activated tryptophan catabolism in PDAC by up-regulating indoleamine 2,3-dioxygenase-1 (IDO1) expression, a tryptophan-catabolizing enzyme. Increased levels of tryptophan metabolites contribute to NAD+ synthesis and oxidative phosphorylation, leading to a stem cell-like phenotype. Blocking BICC1/IDO1/tryptophan metabolism signaling greatly improves the gemcitabine (GEM) efficacy in several PDAC models with high BICC1 level. These findings indicate that BICC1 is a critical tryptophan metabolism regulator that drives the stemness and chemoresistance of PDAC and thus a potential target for combinatorial therapeutic strategy against chemoresistance.

Vertical Transfer of Maternal Gut Microbes to Offspring of Western Diet-Fed Dams Drives Reduced Levels of Tryptophan Metabolites and Postnatal Innate Immune Response.

Maternal obesity and/or Western diet (WD) is associated with an increased risk of metabolic dysfunction-associated steatotic liver disease (MASLD) in offspring, driven, in part, by the dysregulation of the early life microbiome. Here, using a mouse model of WD-induced maternal obesity, we demonstrate that exposure to a disordered microbiome from WD-fed dams suppressed circulating levels of endogenous ligands of the aryl hydrocarbon receptor (AHR; indole, indole-3-acetate) and TMAO (a product of AHR-mediated transcription), as well as hepatic expression of Il10 (an AHR target), in offspring at 3 weeks of age. This signature was recapitulated by fecal microbial transfer from WD-fed pregnant dams to chow-fed germ-free (GF) lactating dams following parturition and was associated with a reduced abundance of Lactobacillus in GF offspring. Further, the expression of Il10 was downregulated in liver myeloid cells and in LPS-stimulated bone marrow-derived macrophages (BMDM) in adult offspring, suggestive of a hypo-responsive, or tolerant, innate immune response. BMDMs from adult mice lacking AHR in macrophages exhibited a similar tolerogenic response, including diminished expression of Il10. Overall, our study shows that exposure to maternal WD alters microbial metabolites in the offspring that affect AHR signaling, potentially contributing to innate immune hypo-responsiveness and progression of MASLD, highlighting the impact of early life gut dysbiosis on offspring metabolism. Further investigations are warranted to elucidate the complex interplay between maternal diet, gut microbial function, and the development of neonatal innate immune tolerance and potential therapeutic interventions targeting these pathways.

Circulating bacterial peptides and linked metabolomic signatures are indicative of early mortality in pediatric cirrhosis.

Patients with pediatric cirrhosis-sepsis (PC-S) attain early mortality. Plasma bacterial composition, the cognate metabolites, and their contribution to the deterioration of patients with PC-S to early mortality are unknown. We aimed to delineate the plasma metaproteome-metabolome landscape and identify molecular indicators capable of segregating patients with PC-S predisposed to early mortality in plasma, and we further validated the selected metabolite panel in paired 1-drop blood samples using untargeted metaproteomics-metabolomics by UHPLC-HRMS followed by validation using machine-learning algorithms. We enrolled 160 patients with liver diseases (cirrhosis-sepsis/nonsepsis [n=110] and noncirrhosis [n=50]) and performed untargeted metaproteomics-metabolomics on a training cohort of 110 patients (Cirrhosis-Sepsis/Nonsepsis, n=70 and noncirrhosis, n=40). The candidate predictors were validated on 2 test cohorts-T1 (plasma test cohort) and T2 (1-drop blood test cohort). Both T1 and T2 had 120 patients each, of which 70 were from the training cohort. Increased levels of tryptophan metabolites and Salmonella enterica and Escherichia coli-associated peptides segregated patients with cirrhosis. Increased levels of deoxyribose-1-phosphate, N5-citryl-d-ornithine, and Herbinix hemicellulolytic and Leifsonia xyli segregated patients with PC-S. MMCN-based integration analysis of WMCNA-WMpCNA identified key microbial-metabolic modules linked to PC-S nonsurvivors. Increased Indican, Staphylobillin, glucose-6-phosphate, 2-octenoylcarnitine, palmitic acid, and guanidoacetic acid along with L. xyli, Mycoplasma genitalium, and Hungateiclostridium thermocellum segregated PC-S nonsurvivors and superseded the liver disease severity indices with high accuracy, sensitivity, and specificity for mortality prediction using random forest machine-learning algorithm. Our study reveals a novel metabolite signature panel capable of segregating patients with PC-S predisposed to early mortality using as low as 1-drop blood.

Metabolomic profiling reveals altered phenylalanine metabolism in Parkinson's disease in an Egyptian cohort.

Introduction: Parkinson's disease (PD) is the most common motor neurodegenerative disease worldwide. Given the complexity of PD etiology and the different metabolic derangements correlated to the disease, metabolomics profiling of patients is a helpful tool to identify patho-mechanistic pathways for the disease development. Dopamine metabolism has been the target of several previous studies, of which some have reported lower phenylalanine and tyrosine levels in PD patients compared to controls. Methods: In this study, we have collected plasma from 27 PD patients, 18 reference controls, and 8 high-risk controls to perform a metabolomic study using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Results: Our findings revealed higher intensities of trans-cinnamate, a phenylalanine metabolite, in patients compared to reference controls. Thus, we hypothesize that phenylalanine metabolism has been shifted to produce trans-cinnamate via L-phenylalanine ammonia lyase (PAL), instead of producing tyrosine, a dopamine precursor, via phenylalanine hydroxylase (PAH). Discussion: Given that these metabolites are precursors to several other metabolic pathways, the intensities of many metabolites such as dopamine, norepinephrine, and 3-hydroxyanthranilic acid, which connects phenylalanine metabolism to that of tryptophan, have been altered. Consequently, and in respect to Metabolic Control Analysis (MCA) theory, the levels of tryptophan metabolites have also been altered. Some of these metabolites are tryptamine, melatonin, and nicotinamide. Thus, we assume that these alterations could contribute to the dopaminergic, adrenergic, and serotonergic neurodegeneration that happen in the disease.

Relationship of tryptophan metabolites with the type and severity of multiple sclerosis.

Tryptophan is an essential amino acid primarily metabolized by the kynurenine pathway in mammals. Intermediate metabolites emerging in this pathway have been associated with many neurogenerative diseases. This study aimed to compare tryptophan pathway metabolite levels in patients with multiple sclerosis (MS) and healthy controls and reveal the relationship of tryptophan metabolites with disease subtype and the Expanded Disability Status Scale (EDSS) score. The study included a total of 80 MS cases [53 with relapsing remitting MS (RRMS) and 27 with secondary progressive MS (SPMS)] and 41 healthy volunteers. The patients with RRMS were further divided into relapse (RRMS-attack) and non-attack (RRMS-stable) groups. Using liquid chromatography mass spectrometry, tryptophan, kynurenine, kynurenic acid, quinolinic acid, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid levels were measured. The serum metabolite levels of the patient and control groups were compared. In addition, the link and relationship between the EDSS score and disease duration of the patients and their plasma tryptophan metabolite levels were examined. The tryptophan level of the patient group was significantly lower than that of the healthy controls (p<0.05). The kynurenine (105.38±65.43), quinolinic acid (10.42±3.56), kynurenine/tryptophan ratio (0.0218±0.019), and quinolinic acid/kynurenic acid ratio (1.7054±0.96141) of the patients with MS were significantly higher compared to the controls (p<0.05). In the receiver operating characteristic analysis of the power of kynurenine/tryptophan and quinolinic acid/kynurenic acid ratios in predicting the disease, both ratios predicted the diagnosis of MS (area under the curve: 0.793 and 0.645, respectively; p<0.05), albeit at low sensitivity and specificity. The parameters were similar between the RRMS-attack and RRMS-stable patient groups (p>0.05). There was also no significant difference between the RRMS and SPMS patient groups in terms of tryptophan metabolites (p>0.05). Lastly, no significant relationship was observed between tryptophan metabolites and MS subtype and the EDSS score. Our findings revealed that the kynurenine pathway involved in the tryptophan metabolism differed between the patients with MS and healthy controls, and this difference may be a limited guide in the diagnosis of MS, due to major overlaps in values for MS versus Controls, and is insufficient to determine the disease subtype.

Treatment of ankylosing spondylitis with TNFα inhibitors does not affect serum levels of tryptophan metabolites.

The imbalance between the kynurenine and serotonin pathways can have serious consequences, e.g., depression. One of the factors leading to the imbalance between the pathways of tryptophan metabolism is inflammation. The aim of our study was to assess the impact of treatment with tumor necrosis factor-alpha (TNFα)-inhibitors on tryptophan metabolism in patients with ankylosing spondylitis (AS). Forty patients with AS (twenty-eight males, twelve females; mean age 40 ± 11years), qualified to receive anti-TNF-α treatment, were prospectively assessed. As a control group, 20 healthy volunteers (7 males and 13 females, mean age 38 ± 5years) were recruited from the general population. Patients underwent full clinical and biochemical assessment before and after 6months of therapy. Disease activity was assessed by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). The presence of depressive disorders was assessed with Beck's Depression Inventory (BDI) scale. Serum concentrations of tryptophan, serotonin, kynurenine, and quinolinic acid were measured. The predominance of the kynurenine pathway in AS patients (compared to the control group) was demonstrated (p < 0.001). Surprisingly, no significant changes in serum levels of tryptophan and its metabolites in AS patients after treatment were found, despite clinical improvement. Moreover, the components of tryptophan metabolism did not correlate significantly with the clinical activity of AS, depression nor laboratory inflammatory markers. Probably some other factors influence the pathways of tryptophan metabolism in patients with ankylosing spondylitis.

Pathogenetic associations of anti-ribosomal P protein antibody titres and their subclasses in patients with systemic lupus erythematosus.

We evaluated the association between anti-ribosomal P antibody (anti-RibP) titres and disease activity in Japanese SLE patients. Eighty patients admitted and treated in Niigata University Hospital for new-onset or flare-up of SLE were included in this retrospective cross-sectional study. Clinical data were obtained from medical records at admission. The anti-RibP index, and cytokine and tryptophan metabolite levels were determined by ELISA. Of the 80 SLE patients, 30 had anti-RibP. Anti-RibP presence was associated with a greater prevalence of skin rash and more severe inflammatory responses, demonstrated by higher inflammatory cytokine levels, hypocomplementemia, and accelerated tryptophan metabolism, in younger patients. The serum anti-RibP index was correlated with age at diagnosis, clinical indicators, initial prednisolone dose, and cytokines and tryptophan metabolite levels in univariate analysis. Multivariate analysis showed that the anti-RibP index was independently associated with the initial prednisolone dose and the prevalence of skin rash. The anti-RibP IgGs were mainly the IgG2 and IgG3 subclasses, and anti-RibP IgG3 was associated with hypocomplementemia, higher DAS, accelerated kynurenine pathway activity, and higher proinflammatory cytokine production. The coexistence of anti-dsDNA IgG and anti-RibP IgG2 or IgG3 accompanied higher IL-10 and IFN-α2 levels; furthermore, anti-RibP IgG3 coexistence with anti-dsDNA antibody contributed to the requirement for higher initial prednisolone doses and accelerated kynurenine pathway activity. Anti-RibP was associated with clinical manifestations and parameters in SLE, and its index might be a useful indicator of disease severity. Anti-RibP IgG3 was the IgG subclass most strongly associated with the pathogenesis of SLE.

Integrative analysis of the gut microbiota and faecal and serum short-chain fatty acids and tryptophan metabolites in patients with cirrhosis and hepatic encephalopathy

ObjectiveThe purpose of this study was to describe the changes in the gut microbiome of patients with cirrhosis and hepatic encephalopathy (HE), as well as quantify the variations in short-chain fatty acid (SCFA) and tryptophan metabolite levels in serum and faeces.MethodsFresh faeces and serum were collected from 20 healthy volunteers (NC group), 30 cirrhosis patients (Cir group), and 30 HE patients (HE group). Then, 16S rRNA sequencing and metabolite measurements were performed using the faeces. Gas chromatography‒mass spectrometry and ultrahigh-performance liquid chromatography-tandem mass spectrometry were used to measure SCFA and tryptophan levels, respectively. The results were analysed by SIMCA16.0.2 software. Differences in species were identified using MetaStat and t tests. The correlations among the levels of gut microbes and metabolites and clinical parameters were determined using Spearman correlation analysis.ResultsPatients with cirrhosis and HE had lower microbial species richness and diversity in faeces than healthy volunteers; these patients also had altered β-diversity. Serum valeric acid levels were significantly higher in the HE group than in the Cir group. Serum SCFA levels did not differ between the Cir and NC groups. Serum melatonin and 5-HTOL levels were significantly higher in the HE group than in the Cir group. The Cir and NC groups had significant differences in the levels of eight serum tryptophan metabolites. Furthermore, the levels of faecal SCFAs did not differ between the HE and Cir groups. Faecal IAA-Ala levels were significantly lower in the HE group than in the Cir group. There were significant differences in the levels of 6 faecal SCFAs and 7 faecal tryptophan metabolites between the Cir and NC groups. Certain gut microbes were associated with serum and faecal metabolites, and some metabolites were associated with certain clinical parameters.ConclusionReduced microbial species richness and diversity were observed in patients with HE and cirrhosis. In both serum and faeces, the levels of different SCFAs and tryptophan metabolites showed varying patterns of change. In HE patients, the levels of some serum tryptophan metabolites, and not SCFAs, were correlated with liver function and systemic inflammation. Systemic inflammation in patients with cirrhosis was correlated with faecal acetic acid levels. In summary, this study identified metabolites important for HE and cirrhosis.

Serum tryptophan metabolites are associated with erosive hand osteoarthritis and pain: results from the DIGICOD cohort

To investigate host and gut-microbiota related Tryptophan metabolism in hand osteoarthritis (HOA). The baseline serum concentration of 20 Tryptophan metabolites was measured in 416 HOA patients in a cross-sectional analysis of the DIGICOD cohort. Tryptophan metabolites levels, metabolite-ratios and metabolism pathway activation were compared between erosive (N=141) and non-erosive HOA (N=275) by multiple logistic regressions adjusted on age, BMI and sex. The association between Tryptophan metabolite levels and HOA symptoms was investigated by a Spearman's rank correlation analysis. Four serum Tryptophan metabolites, eight metabolite ratios and one metabolism pathway were associated with erosive HOA. Erosive HOA was negatively associated with Tryptophan (odds ratio (OR)=0.41, 95% confidence interval [0.24-0.70]), indole-3-aldehyde (OR=0.67 [0.51-0.90]) and 3-OH-anthranilic acid (OR=1.32 [1.13-1.54]) and positively with 5-OH-Tryptophan levels (OR=1.41 [1.13-1.77]). The pro-inflammatory kynurenine-indoleamine 2,3-dioxygenase pathway was upregulated in erosive HOA (OR=1.60 [1.11-2.29]). Eleven metabolites were correlated with HOA symptoms and were mostly pain-related. Serotonin and N-acetyl serotonin levels were negatively correlated with number of tender joints. Indole-3-aldehyde level was negatively correlated and 3-OH-anthranilic acid, 3-OH-kynurenine and 5-OH-Tryptophan levels were positively correlated with number of patients-reported painful joints. Quinolinic acid and 3-OH-kynurenine levels correlated positively with AUSCAN pain. Tryptophan metabolites disturbance is associated with erosive HOA and pain and emphasize the role of low-grade inflammation and gut dysbiosis in HOA.

Abstract 1004: Higher circulating tryptophan metabolites are associated with improved survival among patients with stage I-III colorectal cancer: results from the FOCUS consortium

Abstract Introduction: Dysregulation of the tryptophan metabolic pathway has been linked to colorectal cancer (CRC) development. While circulating levels of tryptophan metabolites have been associated with a decreased risk of CRC, epidemiological studies assessing tryptophan metabolites in relation to CRC outcomes are limited. In this study, we investigated associations between biomarkers of the tryptophan metabolism and clinical outcomes in prospectively followed, non-metastatic CRC patients. Materials and Methods: A total of 2,102 patients with stage I-III CRC participated in six cohorts in the international FOCUS (folate dependent 1-carbon metabolism in colorectal cancer recurrence and survival) consortium. Preoperative circulating concentrations of tryptophan and its metabolites (kynurenine, kynurenic acid (KA), xanthurenic acid (XA), 3-hydroxy-anthralinic acid (HAA), anthranilic acid (AA), and picolinic acid (PA)) were measured by liquid chromatography-tandem mass spectrometry. Using Cox proportional hazards regression, we examined associations of tryptophan metabolites with overall survival (OS) and disease-free survival (DFS). Models were adjusted for patient age, sex, circulating creatinine levels, tumor site, tumor stage, and study site. Results: After a median follow-up of 3.2 years for OS, higher tryptophan levels were associated with a 25-44% better overall and disease-free survival (hazard ratio, HROS, 0.56; 95% confidence interval (CI), 0.41-0.76, HRDFS, 0.75; 95% CI, 0.57-0.99). Furthermore, the tryptophan metabolites XA and PA were associated with a better OS and DFS (XA: HROS, 0.74; 95% CI, 0.64-0.85, HRDFS, 0.84; 95% CI, 0.75-0.94; PA: HROS, 0.76; 95% CI, 0.64-0.92, HRDFS, 0.86; 95% CI, 0.75-0.99). No statistically significant associations were found between kynurenine, KA, HAA, and AA concentrations and OS and DFS. The kynurenine-to-tryptophan ratio was positively associated with worse CRC survival (HROS, 2.12; 95% CI, 1.57-2.88, HRDFS, 1.32; 95% CI, 1.01-1.73). Conclusion: Higher preoperative circulating tryptophan and its metabolites XA and PA are associated with improved OS and DFS. Furthermore, the kynurenine-to-tryptophan ratio may represent a promising predictor for survival among stage I-III CRC patients. Citation Format: Victoria Damerell, Stefanie Brezina, Jennifer Ose, Anne JMR Geijsen, Arve Ulvik, Eline H. van Roekel, Andreana N. Holowatyj, Dieuwertje E. Kok, Fränzel JB van Duijnhoven, Christopher I. Li, Nina Habermann, Alexis B. Ulrich, Ellen Kampman, Matty P. Weijenberg, Andrea Gsur, Per M. Ueland, Martin Schneider, Cornelia M. Ulrich, Biljana Gigic, FOCUS Consortium. Higher circulating tryptophan metabolites are associated with improved survival among patients with stage I-III colorectal cancer: results from the FOCUS consortium [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 1004.

Investigation of Genetic Variants Associated with Tryptophan Metabolite Levels via Serotonin and Kynurenine Pathways in Patients with Bipolar Disorder.

The kynurenine pathway (KP) may play a role in the pathophysiology of bipolar disorder (BD). We conducted a genome-wide association study (GWAS) to identify genetic variants associated with the plasma levels of the metabolites of tryptophan (TRP) via the serotonin (5-HT) and kynurenine (KYN) pathways in 44 patients with BD and 45 healthy controls. We assessed whether variants that were differentially associated with metabolite levels based on the diagnostic status improved the prediction accuracy of BD using penalized regression approaches. We identified several genetic variants that were significantly associated with metabolites (5-HT, 5-hydroxytryptophan (5-HTP), TRP, and quinolinic acid (QA) or metabolite ratios (5-HTP/TRP and KYN/TRP) and for which the diagnostic status exerted a significant effect. The inclusion of genetic variants led to increased accuracy in the prediction of the BD diagnostic status. Specifically, we obtained an accuracy of 0.77 using Least Absolute Shrinkage and Selection Operator (LASSO) regression. The predictors retained as informative in this model included body mass index (BMI), the levels of TRP, QA, and 5-HT, the 5-HTP/TRP ratio, and genetic variants associated with the levels of QA (rs6827515, rs715692, rs425094, rs4645874, and rs77048355) and TRP (rs292212) or the 5-HTP/TRP ratio (rs7902231). In conclusion, our study identified statistically significant associations between metabolites of TRP via the 5-HT and KYN pathways and genetic variants at the genome-wide level. The discriminative performance of penalized regression models incorporating clinical, genetic, and metabolic predictors warrants a follow-up analysis of this panel of determinants.

Berberine alleviates intestinal barrier dysfunction in glucolipid metabolism disorder hamsters by modulating gut microbiota and gut-microbiota-related tryptophan metabolites.

Barberry plants can be considered as useful additives and functional compounds in various industries, especially in the food industry. Berberine (BBR), the most important functional compound in the barberry roots, has recently been used to treat obesity, diabetes, and atherosclerosis. Gut microbiota and the intestinal barrier play an important role in the development of glucolipid metabolism disorders (GLMDs). However, the association of gut microbiota metabolism disorder and the intestinal barrier dysfunction effect of BBR in GLMDs remains elusive. The results showed that administration of BBR could increase the number of colonic glands and goblet cell mucus secretion, improve the intestinal barrier function, and reduce the serum glycolipid level in GLMD hamsters. Interestingly, BBR was metabolized into 12 metabolites by gut microbiota, and the main metabolic pathways were oxidation, demethylation, and hydrogenation. In addition, BBR significantly improved the species diversity and uniformity of gut microbiota and promoted the proliferation of beneficial microbiota. Furthermore, the levels of tryptophan metabolites, such as indole, indole-3-acetamide, indole-3-acetaldehyde, indole-3-pyruvic acid, and indole-3-acetic acid were significantly altered by BBR. Both the intestinal tight junction proteins and intestinal immune factors were altered by BBR. BBR could alleviate intestinal barrier dysfunction of GLMDs by modulating gut microbiota and gut-microbiota-related tryptophan metabolites, which may be one of the pharmacological mechanisms for the treatment of GLMDs. © 2022 Society of Chemical Industry.

Jian-Pi-Yi-Shen Formula Improves Adenine-Induced Chronic Kidney Disease via Regulating Tryptophan Metabolism and Aryl Hydrocarbon Receptor Signaling.

Traditional Chinese medicine (TCM) is an important complementary and alternative branch of chronic kidney disease (CKD) therapy. Jian-Pi-Yi-Shen formula (JPYSF) is a TCM formula used for treating CKD with good efficacy. However, the underlying mechanisms of JPYSF in treating CKD remain to be elucidated. The purpose of the present study was to investigate the renoprotective effect and potential mechanism of JPYSF in treating CKD. CKD rat model was induced by feeding a diet containing 0.75% w/w adenine for 4 weeks. JPYSF was given by gavage every day, starting from the 3rd week of the adenine-containing diet and continuing for 4 weeks at the dose of 10.89 g/kg. Renal injury was evaluated by serum creatinine (Scr), blood urea nitrogen (BUN), histopathology, and fibrotic markers expression. Serum levels of tryptophan metabolites were detected by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Aryl hydrocarbon receptor (AHR) signaling was tested by Western blot analysis. The results found that JPYSF treatment significantly lowered Scr and BUN levels, improved renal pathological injury, and down-regulated fibrotic markers expression in CKD rats. Furthermore, JPYSF significantly reduced the levels of 10 tryptophan metabolites in the serum of CKD rats and restored the level of tryptophan. Additionally, the kidney expression of AHR signaling was enhanced in CKD rats and was further suppressed in JPYSF treated rats. These results suggested that JPYSF protected against adenine-induced CKD via modulating tryptophan metabolism and AHR activation.

Abnormal Activation of Tryptophan-Kynurenine Pathway in Women With Polycystic Ovary Syndrome.

BackgroundWomen with polycystic ovary syndrome (PCOS) suffer from dysfunctional metabolism and studies have reported increased levels of tryptophan in patients with PCOS. However, the changes of downstream metabolites in tryptophan catabolism pathways remain unclear.MethodsThis is a cross-sectional study that included 200 PCOS patients and 200 control women who were recruited from the Reproductive Medicine Center of Peking University Third Hospital from October 2017 to June 2019. The PCOS patients and the control group were further divided into subtypes of normal weight and overweight/obesity. Fasting blood samples from all subjects were collected on days 2~3 of a natural menstrual cycle or when amenorrhea for over 40 days with follicle diameter not exceeding 10 mm. The plasma levels of tryptophan metabolites were quantitatively determined by the liquid chromatograph mass spectrometer, including tryptophan, serotonin, kynurenine, kynurenic acid, 3-hydroxykynurenine, and quinolinic acid.ResultsThe tryptophan-kynurenine pathway was dysregulated in women with PCOS, along with significantly elevated levels of tryptophan, serotonin, kynurenine, kynurenic acid, and quinolinic acid. Moreover, levels of tryptophan, kynurenine, and kynurenic acid were positively correlated with luteinizing hormone, anti-Müllerian hormone, fasting insulin, HOMA-IR. tryptophan, and kynurenine and quinolinic acid had an obvious association with C-reactive protein levels. Furthermore, logistic regression showed that tryptophan, serotonin, kynurenine, kynurenic acid and quinolinic acid were all associated significantly with the increased risk of PCOS with the adjustment for potential confounding factors. Additionally, tryptophan, kynurenine, and kynurenic acid had good diagnostic performances for PCOS, and their combination exhibited higher sensitivity and specificity to diagnostic efficiency, with the area under the ROC curve of 0.824 (95% CI 0.777-0.871), which was comparable to the endocrine indicators.Conclusion (s)The tryptophan-kynurenine pathway was abnormally activated in PCOS patients.

Ginsenoside Rg1 Alleviates Acute Ulcerative Colitis by Modulating Gut Microbiota and Microbial Tryptophan Metabolism.

Ulcerative colitis (UC) is a chronic and recurrent inflammatory disorder in the gastrointestinal tract. Here, we examined the pharmacological effects of ginsenoside Rg1, a natural compound with low bioavailability, on the acute experimental colitis mice induced by dextran sulfate sodium (DSS) and explored underlying mechanisms. Acute UC was induced in C57BL/6 mice by 2.5% DSS for 7 days, meanwhile, 2 mg/10 g b.w. ginsenoside Rg1 was administrated to treat the mice. Body weight, colon length, colon tissue pathology, and colon tissue inflammatory cytokines were assessed. The composition structure of gut microbiota was profiled using 16s rRNA sequencing. Global metabolomic profiling of the feces was performed, and tryptophan and its metabolites in the serum were detected. The results showed that Rg1 significantly ameliorated DSS-induced colonic injury and colonic inflammation. In addition, Rg1 also partly reversed the imbalance of gut microbiota composition caused by DSS. Rg1 intervention can regulate various metabolic pathways of gut microbiota such as valine, leucine, and isoleucine biosynthesis and vitamin B6 metabolism and the most prominent metabolic alteration was tryptophan metabolism. DSS decreased the levels of tryptophan metabolites in the serum, including indole-3-carboxaldehyde, indole-3-lactic acid, 3-indolepropionic acid, and niacinamide and Rg1 can increase the levels of these metabolites. In conclusion, the study discovered that Rg1 can protect the intestinal barrier and alleviate colon inflammation in UC mice, and the underlying mechanism is closely related to the regulation of gut microbiota composition and microbial tryptophan metabolism.

A review of chromatographic methods for bioactive tryptophan metabolites, kynurenine, kynurenic acid, quinolinic acid, and others, in biological fluids.

Kynurenine (KYN) is synthesized from an essential amino acid, tryptophan, by tryptophan 2,3-dioxygenase or indoleamine 2,3-dioxygenase via N-formyl-KYN in vivo. Subsequently, KYN acts as a precursor of some neuroactive metabolites such as kynurenic acid, quinolinic acid, and an important enzyme co-factor, nicotine adenine dinucleotide. These metabolites of tryptophan are a part of the 'kynurenine pathway.' In addition, KYN functions as an endogenous ligand for the aryl hydrocarbon receptor, which acts as a transcription factor. The levels of tryptophan metabolites are important for the assessment of the stage of neurological disorders, and therefore have garnered significant interest for clinical diagnosis. In this review, the detection of kynurenine, kynurenic acid, quinolinic acid, and other tryptophan metabolites performed via chromatographic methods such as HPLC using UV absorbance, fluorescence, and chromatographic-mass spectrometric detection is summarized.

Shenling Baizhu San ameliorates ulcerative colitis by regulating the gut microbiota and its tryptophan metabolites: A complementary medicine to mesalamine

Ethnopharmacological relevanceShenling Baizhu San (SBS) is commonly employed to improve gastrointestinal dysfunction in patients with ulcerative colitis (UC) in China. SBS combined with mesalamine has been demonstrated to result in improve its curative effects without increasing any adverse reactions, but the underlying mechanism remains unclarified. Aim of the studyOur study aimed to illuminate the potential therapeutic effects and mechanisms of SBS, which is a medicine complementary to mesalamine, in the treatment of UC. Materials and methodsA prospective cohort study was conducted to evaluate the efficacy of SBS as a complementary medicine to mesalamine for patients with UC (n = 48). The patients in the control group (n = 24) were given mesalamine alone, whereas those in the experimental group were administered mesalamine combined with SBS. The therapeutic outcome was assessed at 8 weeks. The structures of the gut microbiota (GMB) were characterized by 16S rRNA sequencing, and the microbial tryptophan metabolites were analyzed by UPLC–MS/MS to investigate the mechanism through which SBS achieves its effects. ResultsOur results showed that the combination of SBS and mesalamine could significantly improve the clinical signs of UC by achieving mucosal healing and relieving colon damage. Interestingly, the combination of SBS and mesalamine could alter the GMB structures and increase the microbial levels of tryptophan metabolites, including indole-3-propionic acid and indole-3-acetic acid. ConclusionSBS combined with mesalamine is effective in improving the clinical and endoscopic outcomes of patients with UC. SBS, as a complementary therapy to conventional treatment, alleviates UC via the GMB-tryptophan metabolite axis.

Tryptophan metabolites suppress the Wnt pathway and promote adverse limb events in chronic kidney disease.

Chronic kidney disease (CKD) imposes a strong and independent risk for peripheral artery disease (PAD). While solutes retained in CKD patients (uremic solutes) inflict vascular damage, their role in PAD remains elusive. Here, we show that the dietary tryptophan-derived uremic solutes including indoxyl sulfate (IS) and kynurenine (Kyn) at concentrations corresponding to those in CKD patients suppress β-catenin in several cell types, including microvascular endothelial cells (ECs), inhibiting Wnt activity and proangiogenic Wnt targets in ECs. Mechanistic probing revealed that these uremic solutes downregulated β-catenin in a manner dependent on serine 33 in its degron motif and through the aryl hydrocarbon receptor (AHR). Hindlimb ischemia in adenine-induced CKD and IS solute–specific mouse models showed diminished β-catenin and VEGF-A in the capillaries and reduced capillary density, which correlated inversely with blood levels of IS and Kyn and AHR activity in ECs. An AHR inhibitor treatment normalized postischemic angiogenic response in CKD mice to a non-CKD level. In a prospective cohort of PAD patients, plasma levels of tryptophan metabolites and plasma’s AHR-inducing activity in ECs significantly increased the risk of future adverse limb events. This work uncovers the tryptophan metabolite/AHR/β-catenin axis as a mediator of microvascular rarefaction in CKD patients and demonstrates its targetability for PAD in CKD models.