Protective effects of tryptophan on neuro-inflammation in rats after administering lipopolysaccharide

The Tryptophan Catabolite or Kynurenine Pathway in Alzheimer's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Alzheimer's disease (AD), which is characterized by progressive brain dysfunction and memory loss, is one of the most significant global health concerns for older adults. Neuroinflammation and increased oxidative stress contribute to the pathophysiology of AD, thereby presumably inducing tryptophan (TRP) degradation through the TRP catabolite (TRYCAT) pathway.

OBJECTIVE

To delineate the activity of the TRYCAT pathway along with levels of TRP and tryptophan catabolites (TRYCATs) in AD patients.

METHODS

We used PubMed, Google Scholar, Web of Science, and SciFinder during the month of January 2022 to gather the pertinent publications. We found 19 eligible articles which involved 738 patients and 665 healthy controls.

RESULTS

Our results revealed a significant difference (p = 0.008) in the kynurenine (KYN)/TRP ratio (standardized mean difference, SMD = 0.216, 95% confidence interval, CI: 0.057; 0.376), and a significant decrease in TRP in AD patients (SMD = -0.520, 95% CI: -0.738; -0.302, p < 0.0001). Moreover, we also found a significant increase in the central nervous system (CNS), brain, and cerebrospinal fluid kynurenic acid (KA)/KYN ratio but not in peripheral blood, as well as a significant decrease in plasma KA and xanthurenic acid in the CNS and blood.

CONCLUSION

AD is characterized by TRP depletion but not by an overactivity of the TRYCAT pathway. IDO-induced production of neurotoxic TRYCATs is not a key factor in the pathophysiology of AD.

Role of indoleamine 2,3-dioxygenase 1 (IDO1) and kynurenine pathway in the regulation of the aging process

Indoleamine 2,3-dioxygenase 1 (IDO1) is activated in chronic inflammatory states, e.g., in the aging process and age-related diseases. IDO1 enzyme catabolizes L-tryptophan (L-Trp) into kynurenine (KYN) thus stimulating the KYN pathway. The depletion of L-Trp inhibits the proliferation of immune cells in inflamed tissues and it also reduces serotonin synthesis predisposing to psychiatric disorders. Interestingly, IDO1 protein contains two immunoreceptor tyrosine-based inhibitory motifs (ITIM) which trigger suppressive signaling through the binding of PI3K p110 and SHP-1 proteins. This immunosuppressive activity is not dependent on the catalytic activity of IDO1. KYN and its metabolite, kynurenic acid (KYNA), are potent activators of the aryl hydrocarbon receptor (AhR) which can enhance immunosuppression. IDO1-KYN-AhR signaling counteracts excessive pro-inflammatory responses in acute inflammation but in chronic inflammatory states it has many harmful effects. A chronic low-grade inflammation is associated with the aging process, a state called inflammaging. There is substantial evidence that the activation of the IDO1-KYN-AhR pathway robustly increases with the aging process. The activation of IDO1-KYN-AhR signaling does not only suppress the functions of effector immune cells, probably promoting immunosenescence, but it also impairs autophagy, induces cellular senescence, and remodels the extracellular matrix as well as enhancing the development of osteoporosis and vascular diseases. I will review the function of IDO1-KYN-AhR signaling and discuss its activation with aging as an enhancer of the aging process.

Lizhong Decoction () Ameliorates Ulcerative Colitis in Mice via Regulation of Plasma and Urine Metabolic Profiling

OBJECTIVE

To elucidate the mechanism of Lizhong Decoction (LZD, ) in treating dextran sodium sulfate (DSS)-induced colitis in mice based on metabonomics.

METHODS

Thirty-six mice were randomly divided into 6 groups, including normal, model, low- (1.365 g/kg), medium- (4.095 g/kg) and high dose (12.285 g/kg) LZD and salazosulfadimidine (SASP) groups, 6 mice in each group. Colitis model mice were induced by DSS admistration for 7 days, and treated with low, medium and high dose LZD extract and positive drug SASP. Metabolic comparison of DSS-induced colitis and normal mice was investigated by using ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass (UPLC-Q-TOF/MS) combined with Metabolynx™ software.

RESULTS

The metabolic profiles of plasma and urine in colitis mice were distinctly ameliorated after LZD treatment (P<0.05). Potential biomarkers (9 in serum and 4 in urine) were screened and tentatively identified. The endogenous metabolites were mainly involved in primary bile acid, sphingolipid, linoleic acid, arachidonic acid, amino acids (alanine, aspartate, and glutamate), butanoate and glycerophospholipid metabolism in plasma, and terpenoid backbone biosynthesis, glycerophospholipid and tryptophan metabolism in urine. After LZD treatment, these markers notably restored to normal levels.

CONCLUSIONS

The study revealed the underlying mechanism of LZD on amelioration of ulcerative colitis based on metabonomics, which laid a foundation for further exploring the pathological and physiological mechanism, early diagnosis, and corresponding drug development of colitis.

Role of microbes in the pathogenesis of neuropsychiatric disorders

Microbes inhabit different anatomical sites of the human body including oral cavity, gut, and skin. A growing literature highlights how microbiome variation is associated with human health and disease. There is strong evidence of bidirectional communication between gut and brain mediated by neurotransmitters and microbial metabolites. Here, we review the potential involvement of microbes residing in the gut and in other body sites in the pathogenesis of eight neuropsychiatric disorders, discussing findings from animal and human studies. The data reported provide a comprehensive overview of the current state of the microbiome research in neuropsychiatry, including hypotheses about the mechanisms underlying the associations reported and the translational potential of probiotics and prebiotics.

Tryptophan-tagged peptide from serine threonine-protein kinase of Channa striatus improves antioxidant defence in L6 myotubes and attenuates caspase 3-dependent apoptotic response in zebrafish larvae

This study reports the antioxidant property and molecular mechanism of a tryptophan-tagged peptide derived from a teleost fish Channa striatus of serine threonine-protein kinase (STPK). The peptide was tagged with tryptophan to enhance the antioxidant property of STPK and named as IW13. The antioxidant activity of IW13 peptide was investigated using in vitro methods such as DPPH, ABTS, superoxide anion radical scavenging and hydrogen peroxide scavenging assay. Furthermore, to investigate the toxicity and dose response of IW13 peptide on antioxidant defence in vitro, L6 myotubes were induced with generic oxidative stress due to exposure of hydrogen peroxide (H₂O₂). IW13 peptide exposure was found to be non-cytotoxic to L6 cells in the tested concentration (10, 20, 30, 40 and 50 μM). Also, the pre-treatment of IW13 peptide decreased the lipid peroxidation level and increased glutathione enzyme activity. IW13 peptide treatment upregulated the antioxidant enzyme genes: GPx (glutathione peroxidase), GST (glutathione S transferase) and GCS (glutamine cysteine synthase), in vitro in L6 myotubes and in vivo in zebrafish larvae against the H₂O₂-induced oxidative stress. The results demonstrated that IW13 renders protection against the H₂O₂-induced oxidative stress through a cellular antioxidant defence mechanism by upregulating the gene expression, thus enhancing the antioxidant activity in the cellular or organismal level. The findings exhibited that the tryptophan-tagged IW13 peptide from STPK of C. striatus could be a promising candidate for the treatment of oxidative stress-associated diseases.

Tryptophan pathway catabolites (serotonin, 5-hydroxyindolacetic acid, kynurenine) and enzymes (monoamine oxidase and indole amine 2,3 dioxygenase) in patients with septic shock: A prospective observational study versus healthy controls

Septic shock is associated with a strong inflammatory response that induces vasodilation and vascular hyporeactivity. We investigated the role for tryptophan-pathway catabolites of proinflammatory cytokines in septic shock.We prospectively included 30 patients with very recent-onset septic shock and 30 healthy volunteers. The following were assayed once in the controls and on days 1, 2, 3, 7, and 14 in each patient: plasma free and total tryptophan, platelet and plasma serotonin, total blood serotonin, urinary serotonin, plasma and urinary 5-hydroxyindolacetic acid, plasma kynurenine, monoamine oxidase activity, and total indole amine 2,3-dioxygenase activity. Organ-system failure and mortality were recorded.Compared with the healthy controls, the patients with septic shock had 2-fold to 3-fold lower total tryptophan levels throughout the 14-day study period. Platelet serotonin was substantially lower, while monoamine oxidase activity and 5-hydroxyindolacetic acid were markedly higher in the patients than in the controls, consistent with the known conversion of tryptophan to serotonin, which is then promptly and largely degraded to 5-hydroxyindolacetic acid. Plasma kynurenine was moderately increased and indole amine 2,3-dioxygenase activity markedly increased in the patients versus the volunteers, reflecting conversion of tryptophan to kynurenine. Changes over time in tryptophan metabolites were not associated with survival in the patients but were associated with the Sequential Organ Failure Assessment score and hemodynamic variables including hypotension and norepinephrine requirements.Our results demonstrate major tryptophan pathway alterations in septic shock. Marked alterations were found compared with healthy volunteers, and tryptophan metabolite levels were associated with organ failure and hemodynamic alterations. Tryptophan metabolite levels were not associated with surviving septic shock, although this result might be ascribable to the small sample size.Trial registration: ClinicalTrials.gov; No: NCT00684736; URL: www.clinicaltrials.gov.

Treatment with the essential amino acid L-tryptophan reduces masticatory impairments in experimental cerebral palsy

Purpose Children with cerebral palsy (CP) often exhibit difficulties in feeding resulting from deficits in chewing. This study investigates the therapeutic potential of L-tryptophan (TRI) to reduce deficits in chewing in rats subjected to an experimental model of CP.Methods A total of 80 Wistar albino rats were used. Pups were randomly assigned to 4 experimental groups: Control Saline, Control TRI, CP Saline, and CP TRI groups. The experimental model of CP was based on the combination of perinatal anoxia associated with postnatal sensorimotor restriction of the hind limbs. TRI was administered subcutaneously during the lactation period. Anatomical and behavioral parameters were evaluated during maturation, including body weight gain, food intake, chewing movements, relative weight and the distribution of the types of masseter muscle fibers.Results The induction of CP limited body weight gain, decreased food intake and led to impairment in the morphological and functional parameters of chewing. Moreover, for a comparable amount of food ingested, CP TRI animals grew the most. In addition, supplementation with TRI improved the number of chewing movements, and increased the weight and proportion of type IIB fibers of the masseter in rats subjected to CP.Conclusion These results demonstrate that experimental CP impaired the development of mastication and that TRI supplementation increased masticatory maturation in animals subjected to CP.

Serum-based metabolomics characterization of patients with reticular oral lichen planus

OBJECTIVE

Oral lichen planus (OLP) is a chronic inflammatory mucosal lesion and systemic disease. In OLP, reticular type is the most common presentation of the disease. However, little is known about it. The aim of this study was to analyze the pathogenesis of reticular OLP and its possible associations with the pathological changes in other organ systems through serum-based metabolomics.

METHODS

Blood samples were obtained from 16 reticular OLP patients and 24 control subjects. Liquid chromatography (LC)-mass spectrometry (MS) system was used to identify differentially expressed metabolites. The pathways analysis was performed by MetaboAnalyst. Pathological network was constructed by Cytoscape software.

RESULTS

Totally, 31 modulated metabolites were identified, whose dysregulations affected 25 metabolic pathways and 7 pathological processes in the disease. Through an impact-value screen (impact-value＞0.1), 6 pathways were selected as the significantly dysregulated pathways. Pathological network showed that these metabolites participated in 7 pathological processes, that is, apoptosis process, DNA damage and repair disorder, oxidative stress injury, carbohydrate metabolism disorder, mood dysfunction, inflammatory lesion, and other pathological process.

CONCLUSION

The study demonstrated that reticular OLP could cause the dysregulations of the metabolites in serum, which might be also further linked to other organ and systemic diseases through the blood system, such as diabetes, sleep disorders, and depression, etc.

Metabolomics analysis of oral mucosa reveals profile perturbation in reticular oral lichen planus

BACKGROUND

Oral lichen planus (OLP) is a chronic inflammatory mucosal disorder and potentially oral premalignant lesion affecting the stratified squamous epithelia. In OLP, reticular type is the most common clinical form of the disease. However, little is known about it. Metabolomics analysis may help to investigate the disease pathogenesis and to improve clinical treatment.

METHODS

Liquid chromatography (LC)-mass spectrometry (MS) system, XCMS software, SIMCA software, and OSI / SMMS software were integrated to identify differentially expressed metabolites for the pathways and pathology analysis.

RESULTS

Totally, 21 modulated metabolites were identified, whose dysregulations affected 30 metabolic pathways. Through an impact-value screen (impact-value>0.1), 8 pathways were selected as the significantly dysregulated pathways. Pathological network showed that these metabolites participated in 5 pathological processes, that is, inflammatory lesion, DNA damage and repair disorder, apoptosis process, oxidative stress injury, and abnormal energy expenditure.

CONCLUSION

The study revealed the metabolic perturbation of oral mucosa in reticular OLP, which may provide an important reference for the understanding of the pathogenesis of the disease and the discovery of therapeutic targets.

Pretreatment With Risperidone Ameliorates Systemic LPS-Induced Oxidative Stress in the Cortex and Hippocampus

Risperidone (RIS), an atypical antipsychotic has been found to show anti-inflammatory effect against lipopolysaccharide (LPS)-induced inflammation. In vitro study has revealed that RIS inhibits the LPS-induced reactive oxygen species (ROS) formation. We investigated the antioxidant effects of RIS on LPS-induced oxidative stress markers in Swiss albino mice. Ten weeks old male Swiss albino mice (30 ± 2 g) were pretreated with either distilled water (control) or RIS (3 mg/kg) for 7 days. On day 8, animals were challenged with a single dose of LPS (0.8 mg/kg) while control animals received distilled water only. The animals were sacrificed after 24 h of LPS administration and tissue samples were collected. RIS administration significantly (p < 0.05) reduced the LPS-induced elevated levels of lipid peroxidation product malondialdehyde (MDA), advanced protein oxidation products, and nitric oxide (NO) in the cortex. Catalase (CAT) and superoxide dismutase (SOD) levels were also diminished while the level of glutathione (GSH) was enhanced. Hippocampus data showed that RIS significantly (p < 0.05) reduced the LPS-induced increased levels of MDA and NO, and SOD activity. Our results suggest that LPS-induced neuronal oxidative damage can be alleviated by the pretreatment with RIS and the effect is shown presumably by scavenging of the ROS by risperidone as an antioxidant.

Therapeutic effects of dietary intervention on neuroinflammation and brain metabolism in a rat model of photothrombotic stroke

INTRODUCTION

A possible target for stroke management is modulation of neuroinflammation. Evidence suggests that food components may exert anti-inflammatory properties and thus may reduce stroke-induced brain damage.

AIM

To investigate the efficacy of a diet, containing anti-inflammatory ingredients, as treatment for focal ischemic brain damage induced by photothrombotic stroke in the somatosensory cortex of rats.

RESULTS

Brain lesions were surrounded by strong astrogliosis on both day 7 and day 21 after stroke and were accompanied by a trend toward globally decreased glucose metabolism on day 7. The investigational diet applied 2 weeks before the ischemia did not affect astrocyte activation on day 7, but reduced it at day 21. The investigational diet applied immediately after the ischemia, increased astrocyte activation on day 7 and completely reversed this effect on day 21. Moreover, postischemic intervention increased glucose metabolism in somatosensory cortex ipsilateral to the lesion on day 7.

CONCLUSION

This study reveals potentially beneficial effects of a diet containing elevated amounts of anti-inflammatory nutrients on the recovery from ischemic brain damage. Therefore, dietary intervention can be considered as an adjuvant therapy for recovery from this brain pathology.

Patchouli oil ameliorates acute colitis: A targeted metabolite analysis of 2,4,6-trinitrobenzenesulfonic acid-induced rats

The incidence of inflammatory bowel disease (IBD), characterized by chronic, relapsing intestinal inflammation, has continually increased in recent years. A previous study by our group identified five potential metabolic markers possibly associated with the pathology of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced IBD in rats. The present study aimed to examine the potential therapeutic effects of the essential oil of Pogostemon cablin (also known as patchouli; PO) on TNBS-induced rats and investigate the concomitant metabolic changes by targeting the previously identified potential markers. Pogostemon cablin is widely used to treat gastrointestinal diseases, including IBD, in China. The results of the present study showed that PO (270 mg/kg, rectal instillation) significantly alleviated colonic damage and reduced disease activity indicators and colonic myeloperoxidase in TNBS-induced rats. In addition, a targeted metabolic profiling study identified that four metabolites were elevated in the urine of the animals in the TNBS group, which were significantly inhibited by treatment with PO: Two tryptophan metabolites [4-(2-aminophenyl)-2,4-dioxobutanoic acid and 4,6-cihydroxyquinoline] and two gut microbial metabolites (phenylacetylglycine and p-cresol glucuronide). Taken together, these findings suggested that PO ameliorated the symptoms of TNBS-induced IBD and reversed the metabolic changes potentially associated with TNBS-induced IBD in rats.

Dioscin relieves endotoxemia induced acute neuro-inflammation and protect neurogenesis via improving 5-HT metabolism

Sepsis, in addition to causing fatality, is an independent risk factor for cognitive impairment among sepsis survivors. The pathologic mechanism of endotoxemia induced acute neuro-inflammation still has not been fully understood. For the first time, we found the disruption of neurotransmitters 5-HT, impaired neurogenesis and activation of astrocytes coupled with concomitant neuro-inflammation were the potential pathogenesis of endotoxemia induced acute neuro-inflammation in sepsis survivors. In addition, dioscin a natural steroidal saponin isolated from Chinese medicinal herbs, enhanced the serotonergic system and produced anti-depressant effect by enhancing 5-HT levels in hippocampus. What is more, this finding was verified by metabolic analyses of hippocampus, indicating 5-HT related metabolic pathway was involved in the pathogenesis of endotoxemia induced acute neuro-inflammation. Moreover, neuro-inflammation and neurogenesis within hippocampus were indexed using quantitative immunofluorescence analysis of GFAP DCX and Ki67, as well as real-time RT-PCR analysis of some gene expression levels in hippocampus. Our in vivo and in vitro studies show dioscin protects hippocampus from endotoxemia induced cascade neuro-inflammation through neurotransmitter 5-HT and HMGB-1/TLR4 signaling pathway, which accounts for the dioscin therapeutic effect in behavioral tests. Therefore, the current findings suggest that dioscin could be a potential approach for the therapy of endotoxemia induced acute neuro-inflammation.

Baseline acetylcholinesterase activity and serotonin plasma levels are not associated with delirium in critically ill patients

Objective

The aim of this study was to investigate whether plasma serotonin levels or acetylcholinesterase activities determined upon intensive care unit admission could predict the occurrence of acute brain dysfunction in intensive care unit patients.

Methods

A prospective cohort study was conducted with a sample of 77 non-consecutive patients observed between May 2009 and September 2010. Delirium was determined using the Confusion Assessment Method for the Intensive Care Unit tool, and the acetylcholinesterase and serotonin measurements were determined from blood samples collected up to a maximum of 24 h after the admission of the patient to the intensive care unit.

Results

In the present study, 38 (49.6%) patients developed delirium during their intensive care unit stays. Neither serum acetylcholinesterase activity nor serotonin level was independently associated with delirium. No significant correlations of acetylcholinesterase activity or serotonin level with delirium/coma-free days were observed, but in the patients who developed delirium, there was a strong negative correlation between the acetylcholinesterase level and the number of delirium/coma-free days, indicating that higher acetylcholinesterase levels are associated with fewer days alive without delirium or coma. No associations were found between the biomarkers and mortality.

Conclusions

Neither serum acetylcholinesterase activity nor serotonin level was associated with delirium or acute brain dysfunction in critically ill patients. Sepsis did not modify these relationships.

The combination of vitamins and omega-3 fatty acids has an enhanced anti-inflammatory effect on microglia

Neuroinflammation is a common phenomenon in the pathology of many brain diseases. In this paper we explore whether selected vitamins and fatty acids known to modulate inflammation exert an effect on microglia, the key cell type involved in neuroinflammation. Previously these nutrients have been shown to exert anti-inflammatory properties acting on specific inflammatory pathways. We hypothesized that combining nutrients acting on converging anti-inflammatory pathways may lead to enhanced anti-inflammatory properties as compared to the action of a single nutrient. In this study, we investigated the anti-inflammatory effect of combinations of nutrients based on the ability to inhibit the LPS-induced release of nitric oxide and interleukin-6 from BV-2 cells. Results show that omega-3 fatty acids, vitamins A and D can individually reduce the LPS-induced secretion of the pro-inflammatory cytokines by BV-2 cells. Moreover, we show that vitamins A, D and omega-3 fatty acids (docosahexaenoic and eicosapentaenoic) at concentrations where they individually had little effect, significantly reduced the secretion of the inflammatory mediator, nitric oxide, when they were combined. The conclusion of this study is that combining different nutrients acting on convergent anti-inflammatory pathways may result in an increased anti-inflammatory efficacy.

Effects of tryptophan supplementation on growth performance, antioxidative activity, and meat quality of ducks under high stocking density

High stocking density (STD) could affect duck welfare and production. The objective of our study was to investigate whether dietary tryptophan (TRP) supplementation could alleviate the detrimental effects of high STD on ducks. White Pekin ducks at 4 to 6 wk of age were raised at 11 birds/m(2) and fed diets containing 0.18, 0.48, 0.78, or 1.08% TRP for 21 d. Growth performance, concentrations of TRP and metabolites in the blood and hypothalamus, antioxidative activities in serum and tissue, meat quality, serum uric acid, and urea nitrogen were measured. Weight gain and feed efficiency were significantly improved by TRP supplementation at ≥ 0.48 and ≥ 0.78% (P < 0.05 and P < 0.001, respectively). Serum TRP, hypothalamic TRP, 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacitic acid (5-HIAA), and 5-HIAA/5-HT were also increased significantly (P < 0.01). These increases plateaued at 0.48% TRP, and no further improvement was obtained by adding more TRP to the diet. Dietary TRP supplementation significantly increased levels of total antioxidant capacity, glutathione peroxidase (GSH-Px), and catalase (CAT) in serum; GSH-Px in liver; and GSH-Px and CAT in breast muscle (P < 0.05). Malondialdehyde levels in breast muscle decreased (P < 0.001). Drip loss of breast muscle and pH decline at 45 min postmortem were reduced by TRP supplementation (P < 0.01 and P < 0.05, respectively). Meat color was similar among different treatments (P > 0.05). Breast muscle shear force was increased significantly when dietary TRP level increased to 1.08% (P < 0.01). For ducks raised at 11 birds/m², dietary TRP supplementation could alleviate stress and improve growth performance, antioxidative activity, and meat quality.

Immune stimulation by exogenous melatonin during experimental endotoxemia

Melatonin has been shown to enhance the immune response under immune-compromised conditions. However, its immune-modulatory effects under inflammatory conditions are unclear at present. Both pro- and anti-inflammation has been reported. To study time-dependent effects of melatonin on the general immune response during endotoxemia in more detail, we used two models in male rats: per-acute endotoxemia was induced by lipopolysaccharide (LPS) bolus injection (2.5 mg/kg), sub-acute endotoxemia by LPS infusion (2.5 mg/kg × h). Melatonin was applied directly before and 2 h after LPS administration (3 mg/kg, each). The LPS-induced formation of the pro-inflammatory cytokines tumor necrosis factor alpha, interferon-gamma, interleukin (IL)-1α/β, IL-5, and IL-6 and of the anti-inflammatory cytokine IL-10 was further amplified by melatonin, although it was only significant during per-acute endotoxemia. In both models, melatonin had no effect on the LPS-induced nitric oxide release. These findings show that exogenous melatonin is capable of enhancing the general immune response under inflammatory conditions.

Metabolite profiling of plasma and urine from rats with TNBS-induced acute colitis using UPLC-ESI-QTOF-MS-based metabonomics--a pilot study

The incidence of inflammatory bowel disease, a relapsing intestinal condition whose precise etiology is still unclear, has continually increased over recent years. Metabolic profiling is an effective method with high sample throughput that can detect and identify potential biomarkers, and thus may be useful in investigating the pathogenesis of inflammatory bowel disease. In this study, using a metabonomics approach, a pilot study based on ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS) was performed to characterize the metabolic profile of plasma and urine samples of rats with experimental colitis induced by 2,4,6-trinitrobenzene sulfonic acid. Acquired metabolic profile data were processed by multivariate data analysis for differentiation and screening of potential biomarkers. Five metabolites were identified in urine: two tryptophan metabolites [4-(2-aminophenyl)-2,4-dioxobutanoic acid and 4,6-cihydroxyquinoline], two gut microbial metabolites (phenyl-acetylglycine and p-cresol glucuronide), and the bile acid 12α-hydroxy-3-oxocholadienic acid. Seven metabolites were identified in plasma: three members of the bile acid/alcohol group (cholic acid, 12α-hydroxy-3-oxocholadienic acid and cholestane-3,7,12,24,25-pentol) and four lysophosphatidylcholines [LysoPC(20:4), LysoPC(16:0), LysoPC(18:1) and LysoPC(18:0)]. These metabolites are associated with damage of the intestinal barrier function, microbiota homeostasis, immune modulation and the inflammatory response, and play important roles in the pathogenesis of inflammatory bowel disease. Our results positively support application of the metabonomic approach in study of the pathophysiological mechanism of inflammatory bowel disease.