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Background: Both the Crohn's disease exclusion diet combined with partial enteral nutrition (CDED+PEN) and exclusive enteral nutrition (EEN) can induce remission in mild-to-moderate pediatric Crohn's disease and are associated with a marked decrease in fecal kynurenine levels. This suggests a link between clinical outcome of dietary therapy and changes in tryptophan metabolism pathways. Here, we characterize the changes in several fecal tryptophan metabolites induced by CDED+PEN or EEN and their association with remission., Methods: A total of 21 tryptophan metabolites were quantified in fecal samples from a 12-week prospective randomized trial with CDED+PEN or EEN for induction of remission in mild to moderate pediatric Crohn's disease. Tryptophan metabolites at week 0 (W0), W6, and W12 of 73 samples were quantitatively measured by liquid chromatography coupled with triple quadrupole mass spectrometry, and data were analyzed according to clinical groups of baselines (W0), induced remission at W6, no remission, sustained remission at W12, and nonsustained remission., Results: Reduction in components of the kynurenine pathway, such as kynurenine and quinolinic acid, were strongly associated with induced remission with both CDED+PEN and EEN, which were maintained in sustained remission. Specific serotonin pathway metabolites, such as melatonin, N-acetylserotonin, and 5-OH-tryptophan, were significantly increased in fecal samples from patients maintaining remission at W12 with both CDED+PEN and EEN. Importantly, in samples from patients failing to sustain remission, no changes were observed. Remission induction with EEN differs from CDED+PEN, particularly the moderate effects on indole pathway metabolites. The ratios of kynurenine and melatonin and quinolinic acid and melatonin perform well as markers for sustained remission., Conclusions: The reduction in specific kynurenine pathway compounds and the increase in serotonin pathway compounds are associated with diet-induced and sustained remission. Further studies are warranted to assess causality and the association of these metabolites with specific diet and lifestyle factors, affecting sustained clinical remission., (© 2023 Crohn’s & Colitis Foundation. Published by Oxford University Press on behalf of Crohn’s & Colitis Foundation.)

Introduction: Early relapse in Crohn's disease (CD) is associated with a more severe disease course. The microbiome plays a crucial role, yet strategies targeting the microbiome are underrepresented in current guidelines. We hypothesise that early manipulation of the microbiome will improve clinical response to standard-of-care (SOC) induction therapy in patients with a relapse-associated microbiome profile. We describe the protocol of a pilot study assessing feasibility of treatment allocation based on baseline faecal microbiome profiles., Methods and Analysis: This is a 52-week, multicentre, randomised, controlled, open-label, add-on pilot study to test the feasibility of a larger multicontinent trial evaluating the efficacy of adjuvant antibiotic therapy in 20 paediatric patients with mild-to-moderate-CD (10

Background and Aims: Nutritional therapy with the Crohn's Disease Exclusion Diet + Partial Enteral Nutrition [CDED+PEN] or Exclusive Enteral Nutrition [EEN] induces remission and reduces inflammation in mild-to-moderate paediatric Crohn's disease [CD]. We aimed to assess if reaching remission with nutritional therapy is mediated by correcting compositional or functional dysbiosis., Methods: We assessed metagenome sequences, short chain fatty acids [SCFA] and bile acids [BA] in 54 paediatric CD patients reaching remission after nutritional therapy [with CDED + PEN or EEN] [NCT01728870], compared to 26 paediatric healthy controls., Results: Successful dietary therapy decreased the relative abundance of Proteobacteria and increased Firmicutes towards healthy controls. CD patients possessed a mixture of two metabotypes [M1 and M2], whereas all healthy controls had metabotype M1. M1 was characterised by high Bacteroidetes and Firmicutes, low Proteobacteria, and higher SCFA synthesis pathways, and M2 was associated with high Proteobacteria and genes involved in SCFA degradation. M1 contribution increased during diet: 48%, 63%, up to 74% [Weeks 0, 6, 12, respectively.]. By Week 12, genera from Proteobacteria reached relative abundance levels of healthy controls with the exception of E. coli. Despite an increase in SCFA synthesis pathways, remission was not associated with increased SCFAs. Primary BA decreased with EEN but not with CDED+PEN, and secondary BA did not change during diet., Conclusion: Successful dietary therapy induced correction of both compositional and functional dysbiosis. However, 12 weeks of diet was not enough to achieve complete correction of dysbiosis. Our data suggests that composition and metabotype are important and change quickly during the early clinical response to dietary intervention. Correction of dysbiosis may therefore be an important future treatment goal for CD., (© The Author(s) 2022. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation.)

Background and Aims: Paediatric inflammatory bowel disease [IBD] is characterized by altered immunological and metabolic pathways. Metabolomics may therefore increase pathophysiological understanding and could develop into characterization of biomarkers for diagnosis and IBD treatment response. However, no uniform metabolomic profiles have been identified to date. This systematic review aimed to identify faecal metabolomic signatures in paediatric IBD vs controls, and to describe metabolites associated with disease activity and treatment response., Methods: A literature search was performed in Embase, Medline, Web of Science and Cochrane Library. Studies assessing faecal metabolomics in paediatric patients < 18 years with IBD [de novo, active, inactive] with comparative groups [IBD vs non-IBD; responders vs non-responders] were included. The quality of included studies was assessed according to the Newcastle-Ottawa Scale., Results: Nineteen studies were included [540 patients with IBD, 386 controls], assessing faecal short-chain fatty acids [SCFA] [five studies], amino acids [AA] [ten studies], bile acids [BA] [eight studies] and other metabolites [nine studies] using various methodologies. Significantly increased levels of AA [particularly phenylalanine], primary BA and lower levels of secondary BA were described in paediatric IBD compared to controls. Faecal SCFA results varied across studies. Additionally, responders and non-responders to exclusive enteral nutrition and infliximab showed differences in baseline faecal metabolites [based on BA, AA]., Conclusions: This systematic review provides evidence for distinct faecal metabolomic profiles in paediatric IBD. However, results varied across studies, possibly due to differences in study design and applied analytical techniques. Faecal metabolomics could provide more insight into host-microbial interactions in IBD, but further studies with standardized methodologies and reporting are needed., (© The Author(s) 2022. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation.)

Background & Aims: The Crohn's disease (CD) exclusion diet (CDED) plus partial enteral nutrition (PEN) and exclusive enteral nutrition (EEN) both induce remission in pediatric CD. CDED+PEN is better tolerated and able to sustain remission. We characterized the changes in fecal metabolites induced by CDED+PEN and EEN and their relationship with remission., Methods: A total of 216 fecal metabolites were measured in 80 fecal samples at week (W) 0, W6, and W12, of children with mild to moderate CD in a prospective randomized trial comparing CDED+PEN vs EEN. The metabolites were measured using liquid chromatography coupled to mass spectrometry. Metagenome Kyoto Encyclopedia of Genes and Genomes Orthology analysis was performed to investigate the differential functional gene abundance involved in specific metabolic pathways. Data were analyzed according to clinical outcome of remission (W6&#95;rem), no remission (W6&#95;nr), sustained remission (W12&#95;sr), and nonsustained (W12&#95;nsr) remission., Results: A decrease in kynurenine and succinate synthesis and an increase in N-α-acetyl-arginine characterized CDED+PEN W6&#95;rem, whereas changes in lipid metabolism characterized EEN W6&#95;rem, especially reflected by lower levels in ceramides. In contrast, fecal metabolites in EEN W6&#95;nr were comparable to baseline/W0 samples. CDED+PEN W6&#95;rem children maintained metabolome changes through W12. In contrast, W12&#95;nsr children in the EEN group, who resumed a free diet after week 6, did not. The metabolome of CDED+PEN differed from EEN in the purine, pyrimidine, and sphingolipid pathways. A significant differential abundance in several genes involved in these pathways was detected., Conclusion: CDED+PEN- and EEN-induced remission are associated with significant changes in inflammatory bowel disease-associated metabolites such as kynurenine, ceramides, amino acids, and others. Sustained remission with CDED+PEN, but not EEN, was associated with persistent changes in metabolites., Clinicaltrials: gov, Number NCT01728870., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Inflammatory bowel disease (IBD) is a chronic, autoimmune disorder of the gastrointestinal tract with numerous genetic and environmental risk factors. Patients with Crohn's disease (CD) or ulcerative colitis (UC) often demonstrate marked disruptions of their gut microbiome. The intestinal microbiota is strongly influenced by diet. The association between the increasing incidence of IBD worldwide and increased consumption of a westernized diet suggests host nutrition may influence the progression or treatment of IBD via the microbiome. Several nutritional therapies have been studied for the treatment of CD and UC. While their mechanisms of action are only partially understood, existing studies do suggest that diet-driven changes in microbial composition and function underlie the diverse mechanisms of nutritional therapy. Despite existing therapies for IBD focusing heavily on immune suppression, nutrition is an important treatment option due to its superior safety profile, potentially low cost, and benefits for growth and development. These benefits are increasingly important to patients. In this review, we will describe the clinical efficacy of the different nutritional therapies that have been described for the treatment of CD and UC. We will also describe the effects of each nutritional therapy on the gut microbiome and summarize the strength of the literature with recommendations for the practicing clinician.

Introduction: Current therapies in pediatric Inflammatory Bowel Diseases (IBD) target the immune system and often fail to sustain long-term remission. There is a high need for development of alternative treatment strategies such as antibiotics in pediatric IBD. Areas covered: This study systematically assessed efficacy and safety of antibiotics in pediatric IBD. CENTRAL, EMBASE, and Medline were searched for Randomized Controlled Trials (RCTs). Quality assessment was conducted with the Cochrane risk-of-bias tool. Expert opinion : Two RCTs (n = 101, 4.4-18 years, 43% male) were included. Both studies had overall low risk of bias. In mild-to-moderate Crohn's disease, azithromycin+metronidazole (AZ+MET) (n = 35) compared to metronidazole (MET) alone (n = 38) did not induce a significantly different response (PCDAI drop ≥12.5 or remission) (p = 0.07). For induction of remission (PCDAI≤10), AZ+MET was more effective than MET (p = 0.025). In Acute Severe Colitis, mean 5-day-PUCAI was significantly lower in the antibiotic (vancomycin, amoxicillin, metronidazole, doxycycline)+intravenous-corticosteroids group (AB+IVCS) (n = 16) compared to IVCS alone (n=12) (p = 0.037), whereas remission (PUCAI<10) did not differ (p = 0.61). No significant drug-related adverse events were reported. Results of this systematic review of antibiotic use highlight the lack of evidence in pediatric IBD. More evidence is needed before widespread implementation in daily practice.

The increase in incidences of pediatric Crohn's Disease (CD) worldwide has been strongly linked with dietary shifts towards a Westernized diet, ultimately leading to altered gut microbiota and disturbance in intestinal immunity and the metabolome. Multiple clinical studies in children with CD have demonstrated the high efficacy of nutritional therapy with exclusive enteral nutrition (EEN) to induce remission with an excellent safety profile. However, EEN is poorly tolerated, limiting its compliance and clinical application. This has spiked an interest in the development of alternative and better-tolerated nutritional therapy strategies. Several nutritional therapies have now been designed not only to treat the nutritional deficiencies seen in children with active CD but also to correct dysbiosis and reduce intestinal inflammation. In this review, we report the most recent insights regarding nutritional strategies in children with active CD: EEN, partial enteral nutrition (PEN), Crohn's disease exclusive diet (CDED), and CD treatment-with-eating diet (CD-TREAT). We describe their setup, efficacy, safety, and (dis)advantages as well as some of their potential mechanisms of action and perspectives. A better understanding of different nutritional therapeutic options and their mechanisms will yield better and safer management strategies for children with CD and may address the barriers and limitations of current strategies in children.

The aryl hydrocarbon receptor (AhR) is a nuclear protein which, upon association with certain endogenous and exogenous ligands, translocates into the nucleus, binds DNA and regulates gene expression. Tryptophan (Trp) metabolites are one of the most important endogenous AhR ligands. The intestinal microbiota is a critical player in human intestinal homeostasis. Many of its effects are mediated by an assembly of metabolites, including Trp metabolites. In the intestine, Trp is metabolized by three main routes, leading to kynurenine, serotonin, and indole derivative synthesis under the direct or indirect involvement of the microbiota. Disturbance in Trp metabolism and/or AhR activation is strongly associated with multiple gastrointestinal, neurological and metabolic disorders, suggesting Trp metabolites/AhR signaling modulation as an interesting therapeutic perspective. In this review, we describe the most recent advances concerning Trp metabolism and AhR signaling in human health and disease, with a focus on nutrition as a potential therapy to modulate Trp metabolites acting on AhR. A better understanding of the complex balance between these pathways in human health and disease will yield therapeutic opportunities.