Comparison of the metabolomic profiles of irritable bowel syndrome patients with ulcerative colitis patients and healthy controls: new insights into pathophysiology and potential biomarkers

Urinary metabolome of infants with colic treated with Lactobacillus reuteri DSM 17938: a pilot randomized trial

BACKGROUND

Lactobacillus reuteri DSM 17938 is the only probiotic recommended for treatment of colicky infants, but its mechanism of action is not clear. The study aim was to examine urinary metabolomic fingerprint of colicky breastfed infants before and after 1 month of orally administered Lactobacillus reuteri DSM 17938 or placebo.

METHODS

This randomized, blinded, placebo-controlled clinical trial was carried out with a well-documented probiotic. Thirty-two infants were enrolled, 16 in the probiotic group and 16 in the placebo group. Urine samples were collected from each subject before starting supplementation and at the end of the study period. Metabolomic profiles were obtained using a gas chromatography/mass spectrometry instrument. Subsequently, to compare groups before and after probiotic supplementation, univariate and multivariate statistical analysis were performed.

RESULTS

In the L. reuteri treated group all metabolites for all class of nutrients (sugars, amino acids, carboxylic acids) resulted more abundant after the study period. The comparison with a control group (placebo treated), confirmed this effect on urines.

CONCLUSIONS

The metabolomic analysis of urine samples from infants treated with L. reuteri DSM 17938 allowed to detect some interesting features related to the effect of this treatment on urinary metabolome. To validate the results, a test on a larger cohort is required.

Metabolic biomarkers in irritable bowel syndrome diagnosis

Irritable bowel syndrome (IBS) is a chronic gastrointestinal (GI) disorder characterized by altered bowel habits and abdominal discomfort during defecation. It significantly impacts life quality and work productivity for those affected. Global data suggests a slightly higher prevalence in females than in males. Today, unambiguous diagnosis of IBS remains challenging due to the absence of a specific biochemical, histopathological, or radiological test. Current diagnosis relies heavily on thorough symptom evaluation. Efforts by the Rome committees have established standardized diagnostic criteria (Rome I-IV), improving consistency and clinical applicability. Recent studies in this framework, seem to have successfully employed metabolomics techniques to identify distinct metabolite profiles in breath and stool samples of IBS patients, differentiating them from healthy controls and those with other functional GI disorders, such as inflammatory bowel disease (IBD). Building on this success, researchers are investigating the presence of similar metabolites in easily accessible biofluids such as urine, potentially offering a less invasive diagnostic approach. Accordingly, this review focuses on key metabolites specifically detected in IBS patients' biological specimens, with a focus on urinary metabolites, using various methods, particularly mass spectrometry (MS)-based techniques, including gas chromatography-MS (GC-MS), liquid chromatography-tandem MS (LC-MS/MS), and capillary electrophoresis-MS (CE-MS) metabolomics assays. These findings may make provision for a new set of non-invasive biomarkers for IBS diagnosis and management.

Serum and Urine Metabolomic Profiling of Newly Diagnosed Treatment-Naïve Inflammatory Bowel Disease Patients

BACKGROUND AND AIMS

Inflammatory bowel disease (IBD) is a prevalent chronic noncurable disease associated with profound metabolic changes. The discovery of novel molecular indicators for unraveling IBD etiopathogenesis and the diagnosis and prognosis of IBD is therefore pivotal. We sought to determine the distinctive metabolic signatures from the different IBD subgroups before treatment initiation.

METHODS

Serum and urine samples from newly diagnosed treatment-naïve IBD patients and age and sex-matched healthy control (HC) individuals were investigated using proton nuclear magnetic resonance spectroscopy. Metabolic differences were identified based on univariate and multivariate statistical analyses.

RESULTS

A total of 137 Crohn's disease patients, 202 ulcerative colitis patients, and 338 HC individuals were included. In the IBD cohort, several distinguishable metabolites were detected within each subgroup comparison. Most of the differences revealed alterations in energy and amino acid metabolism in IBD patients, with an increased demand of the body for energy mainly through the ketone bodies. As compared with HC individuals, differences in metabolites were more marked and numerous in Crohn's disease than in ulcerative colitis patients, and in serum than in urine. In addition, clustering analysis revealed 3 distinct patient profiles with notable differences among them based on the analysis of their clinical, anthropometric, and metabolomic variables. However, relevant phenotypical differences were not found among these 3 clusters.

CONCLUSIONS

This study highlights the molecular alterations present within the different subgroups of newly diagnosed treatment-naïve IBD patients. The metabolomic profile of these patients may provide further understanding of pathogenic mechanisms of IBD subgroups. Serum metabotype seemed to be especially sensitive to the onset of IBD.

Application of metabolomics in irritable bowel syndrome in recent 5 years

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders worldwide, characterized by chronic abdominal pain or discomfort and altered bowel habits. To date, the exact pathogenesis of IBS remains elusive, but is clearly multifactorial, including environmental and host factors. However, the management of patients with IBS is challenging and the current diagnostic and therapeutic modalities have unsatisfactory outcomes. Therefore, it is important to develop more effective methods to diagnose IBS early. Metabolomics studies the metabolites most closely related to patient characteristics, which can provide useful clinical biomarkers that can be applied to IBS and may open up new diagnostic approaches. Traditional Chinese medicine (TCM) can play a role in improving symptoms and protecting target organs, but its mechanism needs to be studied in depth. In this review, based on PubMed/MEDLINE and other databases, we searched metabolomics studies related to IBS in the past 5 years, including those related to clinical studies and animal studies, as well as literatures on TCM interventions in IBS, to provide an updated overview of the application of metabolomics to the diagnosis and treatment of IBS and the improvement of IBS by TCM.

Histamine-producing bacteria and their role in gastrointestinal disorders

INTRODUCTION

Gut microbiota produces thousands of metabolites, which have a huge impact on the host health. Specific microbial strains are able to synthesize histamine, a molecule with a crucial role in many physiologic and pathologic mechanisms of the host. This function is mediated by the histidine decarboxylase enzyme (HDC) that converts the amino acid histidine to histamine.

AREAS COVERED

This review summarizes the emerging data on histamine production by gut microbiota, and the effect of bacterial-derived histamine in different clinical contexts, including cancer, irritable bowel syndrome, and other gastrointestinal and extraintestinal pathologies. This review will also outline the impact of histamine on the immune system and the effect of probiotics that can secrete histamine. Search methodology: we searched the literature on PubMed up to February 2023.

EXPERT OPINION

The potential of modulating gut microbiota to influence histamine production is a promising area of research, and although our knowledge of histamine-secreting bacteria is still limited, recent advances are exploring their diagnostic and therapeutical potential. Diet, probiotics, and pharmacological treatments directed to the modulation of histamine-secreting bacteria may in the future potentially be employed in the prevention and management of several gastrointestinal and extraintestinal disorders.

Systematic Review: Urine Biomarker Discovery for Inflammatory Bowel Disease Diagnosis

Inflammatory bowel diseases (IBDs) are chronic, heterogeneous, and inflammatory conditions mainly affecting the gastrointestinal tract. Currently, endoscopy is the gold standard test for assessing mucosal activity and healing in clinical practice; however, it is a costly, time-consuming, invasive, and uncomfortable procedure for the patients. Therefore, there is an urgent need for sensitive, specific, fast and non-invasive biomarkers for the diagnosis of IBD in medical research. Urine is an excellent biofluid for discovering biomarkers because it is non-invasive to sample. In this review, we aimed to summarize proteomics and metabolomics studies performed in both animal models of IBD and humans that identify urinary biomarkers for IBD diagnosis. Future large-scale multi-omics studies should be conducted in collaboration with clinicians, researchers, and industry to make progress toward the development of sensitive and specific diagnostic biomarkers, thereby making personalized medicine possible.

Understanding neuroimmune interactions in disorders of gut-brain interaction: from functional to immune-mediated disorders

Functional gastrointestinal disorders-recently renamed into disorders of gut-brain interaction-such as irritable bowel syndrome and functional dyspepsia are highly prevalent conditions with bothersome abdominal symptoms in the absence of structural abnormalities. While traditionally considered as motility disorders or even psychosomatic conditions, our understanding of the pathophysiology has evolved significantly over the last two decades. Initial observations of subtle mucosal infiltration with immune cells, especially mast cells and eosinophils, are since recently being backed up by mechanistic evidence demonstrating increased release of nociceptive mediators by immune cells and the intestinal epithelium. These mediators can activate sensitised neurons leading to visceral hypersensitivity with bothersome symptoms. The interaction between immune activation and an impaired barrier function of the gut is most likely a bidirectional one with alterations in the microbiota, psychological stress and food components as upstream players in the pathophysiology. Only few immune-targeting treatments are currently available, but an improved understanding through a multidisciplinary scientific approach will hopefully identify novel, more precise treatment targets with ultimately better outcomes.

Concentrations of Plasma Amino Acids and Neurotransmitters in Participants with Functional Gut Disorders and Healthy Controls

Amino acids are important in several biochemical pathways as precursors to neurotransmitters which impact biological processes previously linked to functional gastrointestinal disorders (FGIDs). Dietary protein consumption, metabolic host processes, and the gut microbiome can influence the plasma concentration of amino acids and neurotransmitters, and their uptake by tissues. The aim of this analysis was to quantify 19 proteogenic and 4 non-proteogenic amino acids and 19 neurotransmitters (including precursors and catabolites, herein referred to as neurotransmitters) to ascertain if their circulating concentrations differed between healthy participants and those with FGIDs. Plasma proteogenic and non-proteogenic amino acids and neurotransmitters were measured using ultra-performance liquid chromatography and liquid chromatography-mass spectrometry, respectively, from 165 participants (Rome IV: irritable bowel syndrome (IBS-constipation, IBS-diarrhea), functional constipation, functional diarrhea, and healthy controls). There were significant differences (p < 0.05) in pairwise comparisons between healthy controls and specific FGID groups for branched-chain amino acids (BCAAs), ornithine, and alpha-aminobutyric acid. No other significant differences were observed for the neurotransmitters or any other amino acids analyzed. Multivariate and bivariate correlation analyses between proteogenic and non-proteogenic amino acids and neurotransmitters for constipation (constipation (IBS-C and functional constipation) and phenotypes diarrhea (IBS-D and functional diarrhea)) and healthy controls suggested that associations between BCAAs, 5-hydroxytryptophan, and kynurenine in combination with tyrosine, 3,4-dihydroxyphenylalanine, and 3,4-dihydroxyphenylacetic acid and associations with gamma-aminobutyric acid, glutamate, asparagine, and serine are likely disrupted in FGID phenotypes. In conclusion, although correlations were evident between some proteogenic and non-proteogenic amino acids and neurotransmitters, the results showed minor concentration differences in plasma proteogenic and non-proteogenic amino acids, amino acid-derived metabolites, and neurotransmitters between FGID phenotypes and healthy controls.

Immunometabolism and microbial metabolites at the gut barrier: Lessons for therapeutic intervention in inflammatory bowel disease

The concept of immunometabolism has emerged recently whereby the repolarizing of inflammatory immune cells toward anti-inflammatory profiles by manipulating cellular metabolism represents a new potential therapeutic approach to controlling inflammation. Metabolic pathways in immune cells are tightly regulated to maintain immune homeostasis and appropriate functional specificity. Because effector and regulatory immune cell populations have different metabolic requirements, this allows for cellular selectivity when regulating immune responses based on metabolic pathways. Gut microbes have a major role in modulating immune cell metabolic profiles and functional responses through extensive interactions involving metabolic products and crosstalk between gut microbes, intestinal epithelial cells, and mucosal immune cells. Developing strategies to target metabolic pathways in mucosal immune cells through the modulation of gut microbial metabolism has the potential for new therapeutic approaches for human autoimmune and inflammatory diseases, such as inflammatory bowel disease. This review will give an overview of the relationship between metabolic reprogramming and immune responses, how microbial metabolites influence these interactions, and how these pathways could be harnessed in the treatment of inflammatory bowel disease.

Changes in signalling from faecal neuroactive metabolites following dietary modulation of IBS pain

OBJECTIVE

Dietary therapies for irritable bowel syndrome (IBS) have received increasing interest but predicting which patients will benefit remains a challenge due to a lack of mechanistic insight. We recently found evidence of a role for the microbiota in dietary modulation of pain signalling in a humanised mouse model of IBS. This randomised cross-over study aimed to test the hypothesis that pain relief following reduced consumption of fermentable carbohydrates is the result of changes in luminal neuroactive metabolites.

DESIGN

IBS (Rome IV) participants underwent four trial periods: two non-intervention periods, followed by a diet low (LFD) and high in fermentable carbohydrates for 3 weeks each. At the end of each period, participants completed questionnaires and provided stool. The effects of faecal supernatants (FS) collected before (IBS FS) and after a LFD (LFD FS) on nociceptive afferent neurons were assessed in mice using patch-clamp and ex vivo colonic afferent nerve recording techniques.

RESULTS

Total IBS symptom severity score and abdominal pain were reduced by the LFD (N=25; p<0.01). Excitability of neurons was increased in response to IBS FS, but this effect was reduced (p<0.01) with LFD FS from pain-responders. IBS FS from pain-responders increased mechanosensitivity of nociceptive afferent nerve axons (p<0.001), an effect lost following LFD FS administration (p=NS) or when IBS FS was administered in the presence of antagonists of histamine receptors or protease inhibitors.

CONCLUSIONS

In a subset of IBS patients with improvement in abdominal pain following a LFD, there is a decrease in pronociceptive signalling from FS, suggesting that changes in luminal mediators may contribute to symptom response.

Anti-Inflammatory Diet Prevents Subclinical Colonic Inflammation and Alters Metabolomic Profile of Ulcerative Colitis Patients in Clinical Remission

A relationship between ulcerative colitis (UC) and diet has been shown in epidemiological and experimental studies. In a 6-month, open-label, randomized, placebo-controlled trial, adult UC patients in clinical remission were randomized to either an “Anti-inflammatory Diet (AID)” or “Canada’s Food Guide (CFG)”. Menu plans in the AID were designed to increase the dietary intake of dietary fiber, probiotics, antioxidants, and omega-3 fatty acids and to decrease the intake of red meat, processed meat, and added sugar. Stool was collected for fecal calprotectin (FCP) and microbial analysis. Metabolomic analysis was performed on urine, serum, and stool samples at the baseline and study endpoint. In this study, 53 patients were randomized. Five (19.2%) patients in the AID and 8 (29.6%) patients in the CFG experienced a clinical relapse. The subclinical response to the intervention (defined as FCP < 150 µg/g at the endpoint) was significantly higher in the AID group (69.2 vs. 37.0%, p = 0.02). The patients in the AID group had an increased intake of zinc, phosphorus, selenium, yogurt, and seafood versus the control group. Adherence to the AID was associated with significant changes in the metabolome, with decreased fecal acetone and xanthine levels along with increased fecal taurine and urinary carnosine and p-hydroxybenzoic acid levels. The AID subjects also had increases in fecal Bifidobacteriaceae, Lachnospiraceae, and Ruminococcaceae. In this study, we found thatdietary modifications involving the increased intake of anti-inflammatory foods combined with a decreased intake of pro-inflammatory foods were associated with metabolic and microbial changes in UC patients in clinical remission and were effective in preventing subclinical inflammation.

Histamine production by the gut microbiota induces visceral hyperalgesia through histamine 4 receptor signaling in mice

The gut microbiota has been implicated in chronic pain disorders, including irritable bowel syndrome (IBS), yet specific pathophysiological mechanisms remain unclear. We showed that decreasing intake of fermentable carbohydrates improved abdominal pain in patients with IBS, and this was accompanied by changes in the gut microbiota and decreased urinary histamine concentrations. Here, we used germ-free mice colonized with fecal microbiota from patients with IBS to investigate the role of gut bacteria and the neuroactive mediator histamine in visceral hypersensitivity. Germ-free mice colonized with the fecal microbiota of patients with IBS who had high but not low urinary histamine developed visceral hyperalgesia and mast cell activation. When these mice were fed a diet with reduced fermentable carbohydrates, the animals showed a decrease in visceral hypersensitivity and mast cell accumulation in the colon. We observed that the fecal microbiota from patients with IBS with high but not low urinary histamine produced large amounts of histamine in vitro. We identified Klebsiella aerogenes, carrying a histidine decarboxylase gene variant, as a major producer of this histamine. This bacterial strain was highly abundant in the fecal microbiota of three independent cohorts of patients with IBS compared with healthy individuals. Pharmacological blockade of the histamine 4 receptor in vivo inhibited visceral hypersensitivity and decreased mast cell accumulation in the colon of germ-free mice colonized with the high histamine-producing IBS fecal microbiota. These results suggest that therapeutic strategies directed against bacterial histamine could help treat visceral hyperalgesia in a subset of patients with IBS with chronic abdominal pain.

Alpha-Ketoglutarate Promotes Goblet Cell Differentiation and Alters Urea Cycle Metabolites in DSS-Induced Colitis Mice

The metabolite, alpha-ketoglutarate (aKG), shows promise as an approach for ameliorating colitis, but much remains unknown about the full extent of its effects on the metabolome and mucosal barrier. To further elucidate this matter, C57BL/6 male mice received drinking water with or without 1% aKG for three weeks, then were subjected to 2.5% dextran sulfate sodium (DSS) induction for 7 days followed by 7 days of recovery. Cecal content and intestinal tissue samples were analyzed for changes in metabolite profile and signaling pathways. Gas chromatography-mass spectrometry (GC-MS) metabolomics revealed a separation between the metabolome of mice treated with or without aKG; putrescine and glycine were significantly increased; and ornithine and amide products, oleamide and urea were significantly decreased. Based on a pathway analysis, aKG treatment induced metabolite changes and enriched glutathione metabolism and the urea cycle. Additionally, signaling pathways committing epithelial cells to the secretory lineage were elevated in aKG-treated mice. Consistently, aKG supplementation increased goblet cells staining, mRNA expression of mucin 2, and, trefoil factor 3 and Krüppel-like factor 4, markers of goblet cell differentiation. These data suggest the ameliorating the effects of aKG against chemically induced colitis involves a reduction in harmful metabolites and the promotion of goblet cell differentiation, resulting in a more-fortified mucus layer.

Diallyl Disulfide (DADS) Ameliorates Intestinal Candida albicans Infection by Modulating the Gut microbiota and Metabolites and Providing Intestinal Protection in Mice

Diallyl disulfide (DADS), a garlic extract also known as allicin, has been reported to have numerous biological activities, including anticancer, antifungal, and inflammation-inhibiting activities, among others. Although many studies have assessed whether DADS can treat Candida albicans infection in vitro, its in vivo function and the underlying mechanism are still not clear. Accumulated evidence has implicated the gut microbiota as an important factor in the colonization and invasion of C. albicans. Thus, this study aimed to identify the mechanism by which DADS ameliorates dextran sulfate (DSS)-induced intestinal C. albicans infection based on the systematic analysis of the gut microbiota and metabolomics in mice. Here, we determined the body weight, survival, colon length, histological score, and inflammatory cytokine levels in the serum and intestines of experimental mice. Fecal samples were collected for gut microbiota and metabolite analysis by 16S rRNA gene sequencing and LC-MS metabolomics, respectively. DADS significantly alleviated DSS-induced intestinal C. albicans infection and altered the gut microbial community structure and metabolic profile in the mice. The abundances of some pathogenic bacteria, such as Proteobacteria, Escherichia-Shigella, and Streptococcus, were notably decreased after treatment with DADS. In contrast, SCFA-producing bacteria, namely, Ruminiclostridium, Oscillibacter, and Ruminococcaceae_UCG-013, greatly increased in number. The perturbance of metabolites in infectious mice was improved by DADS, with increases in secondary bile acids, arachidonic acid, indoles and their derivatives, which were highly related to the multiple differentially altered metabolic pathways, namely, bile secretion, arachidonic acid metabolism, and tryptophan metabolism. This study indicated that DADS could modulate gut microbiota and metabolites and protect the gut barrier to alleviate DSS-induced intestinal C. albicans infection in mice. Moreover, this work might also provide novel insight into the treatment of C. albicans infection using DADS.

Neurotransmitter and Intestinal Interactions: Focus on the Microbiota-Gut-Brain Axis in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder of unknown etiology. IBS is caused by a disruption in the gut-brain axis. Given the importance of the gut microbiota in maintaining local and systemic homeostasis of immunity, endocrine, and other physiological processes, the microbiota-gut-brain axis has been proposed as a key regulator in IBS. Neurotransmitters have been shown to affect blood flow regulation, intestinal motility, nutrient absorption, the gastrointestinal immune system, and the microbiota in recent studies. It has the potential role to play a function in the pathophysiology of the gastrointestinal and neurological systems. Transmitters and their receptors, including 5-hydroxytryptamine, dopamine, γ-aminobutyric acid, and histamine, play an important role in IBS, especially in visceral sensitivity and gastrointestinal motility. Studies in this field have shed light on revealing the mechanism by which neurotransmitters act in the pathogenesis of IBS and discovering new therapeutic strategies based on traditional pharmacological approaches that target the nervous system or novel therapies that target the microbiota.

Identification of diagnostic signatures in ulcerative colitis patients via bioinformatic analysis integrated with machine learning

Ulcerative colitis (UC) is an immune-related disorder with enhanced prevalence globally. Early diagnosis is critical for the effective treatment of UC. However, it still lacks specific diagnostic signatures. The aim of our study was to explore efficient signatures and construct the diagnostic model for UC. Microarray data of GSE87473 and GSE48634, which were obtained from tissue biopsy samples, were downloaded from the Gene Expression Omnibus (GEO), and differently expressed genes (DEGs), GO, and KEGG analyses were performed. We constructed the PPI network via STRING database. The immune infiltration of the samples was evaluated using CIBERSORT methods combined with the LM22 feature matrix. The logistic regression model was constructed, with the expression of selected genes as the predictor variable, and the UC occurrence as the responsive variable. As a result, a total of 126 DEGs between the UC patients and normal counterparts were identified. The GO and KEGG analysis revealed that multiple biological processes, such as antimicrobial humoral immune response mediated by antimicrobial peptide and IL-17 signaling pathway, were enriched. The infiltration of eight immune cell types (B cells naive, Dendritic.cells.activated, Macrophages.M0, Macrophages.M2, Mast.cells.resting, Neutrophils, Plasma.cells, and T.cells.follicular.helper) was significantly different between patients with UC and normal counterparts. The top 50 most significant DEGs were selected for the construction of the PPI network. The average AUC of the logistic regression model in the fivefold cross-validation was 0.8497 in the training set, GSE87473. The AUC of another independent verification set of GSE48634 from the GEO database was 0.7208. In conclusion, we identified potential hub genes, including REG3A, REG1A, DEFA6, REG1B, and DEFA5, which might be significantly associated with UC progression. The logistic regression model based on the five genes could reliably diagnose UC patients.

Metabolomics Insights into Inflammatory Bowel Disease: A Comprehensive Review

Inflammatory bowel disease (IBD) is a chronic, complex relapsing disorder characterised by immune dysregulation, gut microbiota alteration, and disturbed intestinal permeability. The diagnosis and the management of IBD are challenging due to the recurrent nature and complex evolution of the disease. Furthermore, the molecular mechanism underlying the aetiology and pathogenesis of IBD is still poorly understood. There is an unmet need for novel, reliable, and noninvasive tools for diagnosing and monitoring IBD. In addition, metabolomic profiles may provide a priori determination of optimal therapeutics and reveal novel targets for therapies. This review tries to gather scientific evidence to summarise the emerging contribution of metabolomics to elucidate the mechanisms underlying IBD and changes associated with disease phenotype and therapies, as well as to identify biomarkers with metabolic imbalance in those patients. Metabolite changes during health and disease could provide insights into the disease pathogenesis and the discovery of novel indicators for the diagnosis and prognosis assessment of IBD. Metabolomic studies in IBD have shown changes in tricarboxylic acid cycle intermediates, amino-acid and fatty-acid metabolism, and oxidative pathways. Metabolomics has made progress towards identifying metabolic alterations that may provide clinically useful biomarkers and a deeper understanding of the disease. However, at present, there is insufficient evidence evaluating the predictive accuracy of these molecular signatures and their diagnostic ability, which is necessary before metabolomic data can be translated into clinical practice.

Gut Microbiota-Derived Metabolites in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is the most common functional bowel disorder worldwide and is associated with visceral hypersensitivity, gut motility, immunomodulation, gut microbiota alterations, and dysfunction of the brain-gut axis; however, its pathophysiology remains poorly understood. Gut microbiota and its metabolites are proposed as possible etiological factors of IBS. The aim of our study was to investigate specific types of microbiota-derived metabolites, especially bile acids, short-chain fatty acids, vitamins, amino acids, serotonin and hypoxanthine, which are all implicated in the pathogenesis of IBS. Metabolites-focused research has identified multiple microbial targets relevant to IBS patients, important roles of microbiota-derived metabolites in the development of IBS symptoms have been established. Thus, we provide an overview of gut microbiota and their metabolites on the different subtypes of IBS (constipation-predominant IBS-C, diarrhea-predominant IBS-D) and present controversial views regarding the role of microbiota in IBS.

Gastrointestinal disorders in hyperkinetic movement disorders and ataxia

BACKGROUND

Gastrointestinal (GI) disorders have been thoroughly investigated in hypokinetic disorders such as Parkinson's disease, but much less is known about GI disorders in hyperkinetic movement disorders and ataxia. The aim of this review is to draw attention to the GI disorders that are associated with these movement disorders.

METHODS

References for this systematic review were identified by searches of PubMed through May 2020. Only publications in English were reviewed.

RESULTS

Data from 249 articles were critically reviewed, compared, and integrated. The most frequently reported GI symptoms overall in hyperkinetic movement disorders and ataxia are dysphagia, sialorrhea, weight changes, esophago-gastritis, gastroparesis, constipation, diarrhea, and malabsorption. We report in detail on the frequency, characteristics, pathophysiology, and management of GI symptoms in essential tremor, restless legs syndrome, chorea, and spinocerebellar ataxias. The limited available data on GI disorders in dystonias, paroxysmal movement disorders, tardive dyskinesias, myoclonus, and non-SCA ataxias are also summarized.

CONCLUSION

The purpose of our systematic review is to draw attention that, although primarily motor disorders, hyperkinetic movement disorders and ataxia can involve the GI system. Raising awareness about the GI symptom burden in hyperkinetic movement disorders and ataxia could contribute to a new research interest in that field, as well as improved patient care.

Neurotransmitter Dysfunction in Irritable Bowel Syndrome: Emerging Approaches for Management

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder whose aetiology is still unknown. Most hypotheses point out the gut-brain axis as a key factor for IBS. The axis is composed of different anatomic and functional structures intercommunicated through neurotransmitters. However, the implications of key neurotransmitters such as norepinephrine, serotonin, glutamate, GABA or acetylcholine in IBS are poorly studied. The aim of this review is to evaluate the current evidence about neurotransmitter dysfunction in IBS and explore the potential therapeutic approaches. IBS patients with altered colorectal motility show augmented norepinephrine and acetylcholine levels in plasma and an increased sensitivity of central serotonin receptors. A decrease of colonic mucosal serotonin transporter and a downregulation of α2 adrenoceptors are also correlated with visceral hypersensitivity and an increase of 5-hydroxyindole acetic acid levels, enhanced expression of high affinity choline transporter and lower levels of GABA. Given these neurotransmitter dysfunctions, novel pharmacological approaches such as 5-HT₃ receptor antagonists and 5-HT₄ receptor agonists are being explored for IBS management, for their antiemetic and prokinetic effects. GABA-analogous medications are being considered to reduce visceral pain. Moreover, agonists and antagonists of muscarinic receptors are under clinical trials. Targeting neurotransmitter dysfunction could provide promising new approaches for IBS management.

Systematic Metabolic Profiling of Mice with Dextran Sulfate Sodium-Induced Colitis

Purpose

Inflammatory bowel diseases (IBD) are a chronic inflammatory disease, which affects almost all tissues in the body. Previous studies mainly focused on breathing, fecal, and urine samples of patients with IBD. However, there is no comprehensive metabolomic analysis of the serum, colon, heart, liver, kidney, cortex, hippocampus, and brown fat tissues. Therefore, the aim of our study is to evaluate the utility metabolomic analysis of target tissues in the pathogenesis of IBD in exploring new biomarkers for early diagnosis and treatment.

Methods

Male Sprague–Dawley rats were randomly allocated to control and DSS-treated groups (n = 7). Dextran sulfate sodium (DSS) was orally administered for 6 weeks. Gas chromatography-mass spectrometry (GC-MS) was used for metabolite determination, multivariate statistical analysis was used to identify metabolites that were differentially expressed in two groups.

Results

Our results showed that 3, 11, 12, 6, 5, 13, 13, and 11 metabolites were differentially expressed between the DSS treatment group and the control group in the serum, colon, heart, liver, kidney, cortex, hippocampus, and brown fat tissues, respectively. The most significant change of metabolites in the study was amino acid (L-alanine, L-glutamic acid, L-phenylalanine, L-proline, L-lysine, L-isoleucine, L-tryptophan, L-norleucine, L-valine, glycine, serine, L-threonine), organic acid (citric acid, 3-hydroxybutyric acid, propanoic acid), glucide (D-arabinose, D-fructose) and purine (9H-purin-6-ol, D-ribose) profiles. Several pathways were affected according to the integrated pathway analysis. These pathways ranged from amino acid metabolism (such as alanine, aspartate, and glutamate metabolism, glutathione metabolism) to purine metabolism (aminoacyl-tRNA biosynthesis).

Conclusion

Using GC-MS-based profiling of metabolite changes, these results may provide a more comprehensive view for IBD and IBD-related diseases and improve the understanding of IBD pathogenesis.

Proteomic and molecular evidences of Il1rl2, Ric8a, Krt18 and Hsp90b1 modulation during experimental hepatic fibrosis and pomegranate supplementation

The inspection of variations in the proteomic aspects conspire the biomarker discovery in diagnostics of peculiar diseases. Recent developments in high-throughput proteomic techniques have provided leverage in the discovery of biomarkers during the etiology of various diseases. We identified potential biomarkers by utilizing proteomics, bioinformatics and gene expression studies. Meticulous assessment of collagen and hydroxyproline levels along with the glycogen and protein carbonyl levels exhibited deterioration in the N' - Nitrosodiethylamine (NDEA) administered rat livers and subsequent salubrious effect of pomegranate juice. The immunohistochemical inspection of iNOS and nitrite estimation indicated the peccant fibrotic alterations. 2D proteome profiling and MALDI-TOF MS/MS furthered the significant biomarkers to be analyzed for the gene ontology by PANTHER, cluster analysis by DAVID and network simulation by STRING 10.0. Several genes found relevant after MALDI analysis were evaluated by real-time PCR (RTPCR). Our data revealed CYP2b15, HSP70, TRFE, HPT, Il1rl2, Ric8a, Krt18, Hsp90b1 and iNOS as novel biomarkers for the mechanism of pomegranate against liver fibrosis. It can be inferred that NDEA-induced liver fibrosis actuates various biological pathways by the identified biomarkers and pomegranate juice modifies them.

Are Volatile Organic Compounds Accurate Markers in the Assessment of Colorectal Cancer and Inflammatory Bowel Diseases? A Review

Simple Summary

Early diagnosis is crucial for reducing colorectal cancer-related mortality in both the general population and inflammatory bowel disease. Volatile organic compound (VOC) analysis is a promising alternative to the gold standard procedure, endoscopy, for early detection and surveillance of colorectal diseases. This review aimed to provide a general overview of the most recent evidence in this area on VOC testing in breath, stool, and urine samples.

Abstract

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the Western world. Early detection decreases incidence and mortality. Screening programs based on fecal occult blood testing help identify patients requiring endoscopic examination, but accuracy is far from optimal. Among the alternative strategies, volatile organic compounds (VOCs) represent novel potentially useful biomarkers of colorectal cancer. They also represent a promising tool for the screening of both intestinal inflammation and related CRC. The review is focused on the diagnostic potential of VOCs in sporadic CRC and in inflammatory bowel diseases (IBD), which increase the risk of CRC, analyzing future clinical applications. Despite limitations related to inadequate strength of evidence, differing analytical platforms identify different VOCs, and this unconventional approach for diagnosing colorectal cancer is promising. Some VOC profiles, besides identifying inflammation, seem disease-specific in inflammatory bowel diseases. Thus, breath, urine, and fecal VOCs provide a new and promising clinical approach to differential diagnosis, evaluation of the inflammatory status, and possibly the assessment of treatment efficacy in IBD. Conversely, specific VOC patterns correlating inflammatory bowel disease and cancer risk are still lacking, and studies focused on this issue are strongly encouraged. No prospective studies have assessed the risk of CRC development by using VOCs in samples collected before the onset of disease, both in the general population and in patients with IBD.

Urinary Metabolites Enable Differential Diagnosis and Therapeutic Monitoring of Pediatric Inflammatory Bowel Disease

Rates of pediatric Crohn's disease (CD) and ulcerative colitis (UC) are increasing globally. Differentiation of these inflammatory bowel disease (IBD) subtypes however can be challenging when relying on invasive endoscopic approaches. We sought to identify urinary metabolic signatures of pediatric IBD at diagnosis, and during induction treatment. Nontargeted metabolite profiling of urine samples from CD (n = 18) and UC (n = 8) in a pediatric retrospective cohort study was performed using multisegment injection-capillary electrophoresis-mass spectrometry. Over 122 urinary metabolites were reliably measured from pediatric IBD patients, and unknown metabolites were identified by tandem mass spectrometry. Dynamic changes in sum-normalized urinary metabolites were also monitored following exclusive enteral nutrition (EEN) or corticosteroid therapy (CS) in repeat urine samples collected over 8 weeks. Higher urinary excretion of indoxyl sulfate, hydroxyindoxyl sulfate, phenylacetylglutamine, and sialic acid were measured in CD as compared to UC patients, but lower threonine, serine, kynurenine, and hypoxanthine (p < 0.05). Excellent discrimination of CD from UC was achieved based on the urinary serine:indoxylsulfate ratio (AUC = 0.972; p = 3.21 × 10^-5). Urinary octanoyl glucuronide, pantothenic acid, and pyridoxic acid were also identified as specific dietary biomarkers of EEN in pediatric IBD patients who achieved clinical remission. This work may complement or replace existing strategies in the diagnosis and early management of children with IBD.

Dopa responsive irritable bowel syndrome: restless bowel syndrome or a gastrointestinal variant of restless legs syndrome?

In addition to the legs, restless legs syndrome (RLS) affects various other parts of the body, including the arms, abdomen, face, head-neck, oral cavity, genital area and bladder. RLS is also associated with several comorbid conditions, including irritable bowel syndrome (IBS). We are reporting two cases of RLS who also had IBS, fulfilling the Rome IV criteria. The administration of levodopa and dopamine agonists provided a complete improvement in both IBS and RLS. Review of the literature suggest that the clinical semiology and clinical pattern of IBS (urge to defaecate, abdominal pain, abdominal distension, bloating, disturbed sleep and circadian rhythm) simulate the semiology and pattern of RLS. Similarities are also noted in the associated comorbid conditions, effective drugs and proposed hypotheses for both clinical syndromes. We hypothesise that RLS may affect intestine, and IBS-like symptoms in a subset of patients with RLS may be the part of RLS symptoms complex.

Alterations in the gut microbiota and metabolic profiles coincide with intestinal damage in mice with a bloodborne Candida albicans infection

Candida albicans is an opportunistic fungus that can threaten life especially in patients with candidemia. The morbidity and mortality of candidemia originating from a central venous catheter (CVC) and illicit intravenous drug use (IVDU) are increasing. However, the mechanism underlying the bloodborne C. albicans infection remains unclear. Herein, we evaluated the gut microbiome, metabolites and intestinal mucosa by constructing the mouse models with candidemia. Model mice were injected with C. albicans via tail vein. Control mice underwent sham procedures. We observed basic life characteristics, intestinal damage-related alterations using hematoxylin and eosin (H&E) staining, intestinal tight junction protein levels, and intestinal permeability in these mice. Fecal samples were analyzed by performing 16S rRNA gene sequencing of the microbiota and LC-MS metabolomics to reveal the perturbations in intestinal flora and metabolism exacerbating intestinal damage. Weight loss, a decreased survival rate, C. albicans infection spread, and colonic epithelial damage occurred in the model group. Furthermore, the intestinal flora abundance was reduced. Several probiotics, such as Lactobacillus, and butyrate-producing bacteria, including Roseburia, Lachnospiraceae, and Clostridia, were depleted, and some pathogenic bacteria, such as Escherichia-Shigella and Proteus, belonging to the Proteobacteria phylum, and the inflammation mediators Ruminococcus and Parabacteroides were enriched in model mice. Multiple differentially altered metabolic pathways were observed and mainly related to bile acid, arachidonic acid, bile secretion, and arachidonic acid metabolism. This study illustrated the effects of a bloodborne C. albicans on the intestinal microbiota, metabolites, and intestinal barrier, which may provide new insights into tests or treatments for candidemia originating from CVC or IVDU.

Characteristics of immune cell infiltration and associated diagnostic biomarkers in ulcerative colitis: results from bioinformatics analysis

Ulcerative colitis (UC) is a type of refractory and recurrent inflammatory disorder that occurs in colon and rectum. Immune cell infiltration plays a critical role in UC progression; therefore, this study aims to explore potential biomarkers for UC and to analyze characteristics of immune cell infiltration based on the bioinformatic analysis. In this study, 248 differentially expressed genes (DEGs) were screened, and the top 20 immune-related hub genes and pathways were assessed. Moreover, four candidate diagnostic biomarkers (DPP10, S100P, AMPD1, and ASS1) were identified and validated. Immune cell infiltration analysis identified 13 differentially infiltrated immune cells (IICs) in UC samples compared to normal samples, and the result showed that two IICs only expressed in UC samples. In addition, the present research found that DPP10 was negatively correlated with neutrophils, S100P exhibited a positive correlation with resting CD4 memory T cells, AMPD1 was positively correlated with M2 macrophages, and ASS1 was inversely associated with neutrophils and positively related to CD8 T cells. Taken together, these findings indicated that DPP10, S100P, AMPD1, and ASS1 may act as diagnostic biomarkers for UC, and that differential IICs may help to illustrate the progression of UC.

Serum levels of high sensitive C-reactive protein and tumor necrosis factor-alpha in different subtypes of irritable bowel syndrome and their correlation

BACKGROUND

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder, and the pathogenetic mechanism is still not clear at present. Recent studies have shown that low-grade inflammation plays important roles in the occurrence and progression of IBS. However, the exact inflammatory markers of IBS and the relationship between the non-specific inflammatory marker hypersensitive C-reactive protein (hs-CRP) and the diagnosis and classification of IBS are not clear.

AIM

To investigate the serum levels of hs-CRP, a non-specific inflammatory marker, and tumor necrosis factor-alpha (TNF-α) in different subtypes of IBS and their correlation under Rome IV criteria.

METHODS

One hundred and seventy-seven IBS patients who were treated at the Affiliated Hospital of Yangzhou University and Subei People's Hospital and 174 normal controls who received physical examinations at the same hospitals from January 2017 to January 2019 were selected as subjects in this study. The levels of hs-CRP and TNF-α in serum of the subjects were detected by transmittance turbidity method and enzyme-linked immunosorbent assay, respectively.

RESULTS

The serum levels of TNF-α and hs-CRP in IBS patients were significantly higher than those in healthy controls (P < 0.001). Among five different IBS subtypes, the levels of TNF-α and hs-CRP in the postinfectious irritable bowel syndrome (PI-IBS) and diarrhea-predominant irritable bowel syndrome (IBS-D) groups were significantly higher than those in the other three subtypes (P < 0.001). Hs-CRP levels were positively correlated with the levels of TNF-α in the IBS-D (P < 0.001) and PI-IBS groups (P < 0.05), and the correlation coefficients were 0.814 and 0.432, respectively.

CONCLUSION

Hs-CRP may be used as a potential inflammatory marker for the diagnosis and treatment of IBS-D and PI-IBS.

Application of metabolomics to the study of irritable bowel syndrome

The pathophysiology of irritable bowel syndrome and the detection of biomarkers of specific mechanisms and/or predictors of therapeutic response remain elusive. This roadblock reflects, in large part, the complexity and heterogeneity of the disorder. Recently, there has been growing evidence of a dietary and/or microbiome interaction with the host that may trigger symptoms in a subset of patients. While a number of techniques are available to examine these potential interactions, "omic" approaches such as metabolomics are becoming more widely used. Metabolomics measures hundreds and potentially thousands of known and unknown small molecule chemicals (metabolites) to provide a unique look into mechanisms that underlie symptom generation and potential predictors of therapeutic response. In this issue of the journal, Lee et al use nuclear magnetic resonance (NMR) to demonstrate the value of this approach to study IBS. This review examines the use of metabolomics to better understand IBS, focusing on what has been learned to date, practical and technical considerations, its potential for future research and how the study by Lee et al have contributed to these concepts.

Gut Microbial Metabolites and Biochemical Pathways Involved in Irritable Bowel Syndrome: Effects of Diet and Nutrition on the Microbiome

The food we consume and its interactions with the host and their gut microbiota affect normal gut function and health. Functional gut disorders (FGDs), including irritable bowel syndrome (IBS), can result from negative effects of these interactions, leading to a reduced quality of life. Certain foods exacerbate or reduce the severity and prevalence of FGD symptoms. IBS can be used as a model of perturbation from normal gut function with which to study the impact of foods and diets on the severity and symptoms of FGDs and understand how critical processes and biochemical mechanisms contribute to this impact. Analyzing the complex interactions between food, host, and microbial metabolites gives insights into the pathways and processes occurring in the gut which contribute to FGDs. The following review is a critical discussion of the literature regarding metabolic pathways and dietary interventions relevant to FGDs. Many metabolites, for example bile acids, SCFAs, vitamins, amino acids, and neurotransmitters, can be altered by dietary intake, and could be valuable for identifying perturbations in metabolic pathways that distinguish a "normal, healthy" gut from a "dysfunctional, unhealthy" gut. Dietary interventions for reducing symptoms of FGDs are becoming more prevalent, but studies investigating the underlying mechanisms linked to host, microbiome, and metabolite interactions are less common. Therefore, we aim to evaluate the recent literature to assist with further progression of research in this field.

Peroxiredoxin 1 as an inflammatory marker in diarrhea-predominant and postinfectious irritable bowel syndrome

BACKGROUND

Low-grade inflammation occurs in some patients with irritable bowel syndrome (IBS). However, the exact inflammatory markers of IBS and the relationship of these markers with IBS subtypes and symptoms are poorly defined. Peroxiredoxin 1 (PRDX1) plays an important role in inflammatory responses, including intestinal inflammation. We investigated whether PRDX1 is associated with the diagnosis, subtypes, and symptom severity of IBS.

METHODS

A total of 177 IBS patients and 174 sex- and age-matched healthy controls (HCs) were recruited. The PRDX1 levels in the sera and colonic mucosa of the participants were detected by enzyme-linked immunosorbent assays and immunohistochemistry. The severity of IBS symptoms was assessed using the IBS Severity Scoring System (SSS) questionnaire.

RESULTS

The PRDX1 levels in the sera (F = 71.81, P < .001) and colonic mucosa (F = 5.359, P < .001) of postinfectious (PI-IBS) and diarrhea-predominant IBS (IBS-D) groups were significantly higher than those of the other three IBS subtypes and HC group. The PRDX1 level in the serum and colonic mucosa of IBS-D (serum, P < .01, mucosa, P < .001) and PI-IBS (serum, P < .05, mucosa, P < .001) groups with the most severe symptoms was significantly higher than that in the groups with mild and moderate symptoms. Correlation analysis revealed that in patients with IBS-D (P < .001) and PI-IBS (P < .05), the levels of PRDX1 and TNF-α in sera had a significant positive correlation with IBS-SSS.

CONCLUSION

Elevated PRDX1 in the serum and colon mucosa may be closely related to the progression of IBS (especially IBS-D and PI-IBS) and the expression of gastrointestinal symptoms.

Symptoms of mast cell activation syndrome in functional gastrointestinal disorders

Objectives: Mast cell involvement is evident in functional gastrointestinal disorders (FGID). FGID and mast cell activation syndrome (MCAS) are associated with multi-organ symptoms. An overlap has not been assessed.Methods: MCAS symptoms were determined by questionnaires in 2083 FGID patients.Results: The median number of MCAS symptoms ([IQR] (range 0-16)) was 6 [4-8] in all FGID, and in functional dyspepsia (FD) patients, 7 [5-9] in overlapping irritable bowel syndrome and FD (IBS+FD), 5 [3-8] in IBS and 5 [3-6] in non-IBS/non-FD (p < .001 vs. FD and IBS + FD) patients. MCAS symptoms in ≥2 organ-systems existed in 1773 (85%) of all patients.Conclusions: MCAS symptoms are common in FGID warranting further mechanistic investigation.

Multi-omics Analysis of Gut Microbiota and Metabolites in Rats With Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal dysfunctional disease. The pathophysiology of IBS is, however, largely unknown. This study aimed to determine whether evaluation of fecal metabolite and microbiota profiles may offer an opportunity to identify a novel pathophysiological target for IBS, and to reveal possible gut microbe–metabolite associations. By using gas chromatography coupled to time-of-flight mass spectrometry (GC-TOFMS) and 16S rRNA gene sequencing, we measured fecal metabolites and microbiota of the control and water avoidance stress (WAS)-induced IBS rats. We found a significantly differential metabolite profile between the IBS and control groups; a cluster of metabolites was also found to be significantly associated with the amount of defecations. Moreover, the WAS group exhibited a decreased alpha diversity of the microbial population as compared to the control group. However, the characteristics of gut microbiota could not differentiate the IBS group from the control group. Correlation of the metabolite level with the number of microbial genera showed no significant association between the control and IBS groups. This study provides a global perspective on metabolomics and microbiota profiling in WAS-induced IBS model and a theoretical basis for research on the pathophysiology of IBS.