Metabolome-associated psychological comorbidities improvement in irritable bowel syndrome patients receiving a probiotic.

Our recent randomized, placebo-controlled study in Irritable Bowel Syndrome (IBS) patients with diarrhea or alternating bowel habits showed that the probiotic Bifidobacterium longum (BL) NCC3001 improves depression scores and decreases brain emotional reactivity. However, the involved metabolic pathways remain unclear. This analysis aimed to investigate the biochemical pathways underlying the beneficial effects of BL NCC3001 using metabolomic profiling. Patients received probiotic (1x 1010CFU, n=16) or placebo (n=19) daily for 6 weeks. Anxiety and depression were measured using the Hospital Anxiety and Depression Scale. Brain activity in response to negative emotional stimuli was assessed by functional Magnetic Resonance Imaging. Probiotic fecal abundance was quantified by qPCR. Quantitative measurement of specific panels of plasma host-microbial metabolites was performed by mass spectrometry-based metabolomics. Probiotic abundance in feces was associated with improvements in anxiety and depression scores, and a decrease in amygdala activation. The probiotic treatment increased the levels of butyric acid, tryptophan, N-acetyl tryptophan, glycine-conjugated bile acids, and free fatty acids. Butyric acid concentration correlated with lower anxiety and depression scores, and decreased amygdala activation. Furthermore, butyric acid concentration correlated with the probiotic abundance in feces. In patients with non-constipation IBS, improvements in psychological comorbidities and brain emotional reactivity were associated with an increased abundance of BL NCC3001 in feces and specific plasma metabolites, mainly butyric acid. These findings suggest the importance of a probiotic to thrive in the gut and highlight butyric acid as a potential biochemical marker linking microbial metabolism with beneficial effects on the gut-brain axis.

Oral tryptophan activates duodenal aryl hydrocarbon receptor in healthy subjects: a crossover randomized controlled trial.

Background and Aims: Tryptophan is an essential amino acid transformed by host and gut microbial enzymes into metabolites that regulate mucosal homeostasis through Aryl hydrocarbon receptor (AhR) activation. Alteration of tryptophan metabolism has been associated with chronic inflammation, however whether tryptophan supplementation affects the metabolite repertoire and AhR activation under physiologic conditions in humans, is unknown. Methods: We performed a randomized, double blind, placebo-controlled, crossover study in 20 healthy volunteers. Subjects on a low tryptophan background diet were randomly assigned to a 3-week L-tryptophan supplementation (3 g/day) or placebo, and after a 2-week washout switched to opposite interventions. We assessed gastrointestinal and psychological symptoms by validated questionnaires, AhR activation by cell reporter assay, tryptophan metabolites by liquid chromatography and high-resolution mass spectrometry, cytokine production in isolated monocytes by ELISA and microbiota profile by 16S rRNA Illumina technique. Results: Oral tryptophan supplementation was well tolerated, with no changes in gastrointestinal or psychological scores. Compared with placebo, tryptophan increased AhR activation capacity by duodenal contents, but not by feces. This was paralleled by higher urinary and plasma kynurenine metabolites and indoles. Tryptophan had a modest impact on fecal microbiome profiles, and no significant effect on cytokine production. Conclusions: At the doses used in this study, oral tryptophan supplementation in humans induces microbial indole and host kynurenine metabolic pathways in the small intestine, known to be immunomodulatory. The results should prompt tryptophan intervention strategies in inflammatory conditions of the small intestine where the AhR pathway is impaired.

Review and Critical Appraisal of Clinical Practice Guidelines of Modalities Used in the Diagnosis of Celiac Disease.

Background: There is controversy over the recommendations for specific serological strategies implemented and the need for a biopsy to confirm celiac disease (CeD). We reviewed and appraised the current clinical practice guidelines (CPGs) to assess the quality and reliability of recommendations for CeD diagnosis in pediatric and adult populations. Methods: We searched databases, including MEDLINE, EMBASE, Web of Science, and CINAHL, between December 2010 and January 2021 for CPGs. Four independent reviewers extracted data. Appraisal of Guidelines Research and Evaluation (AGREE II) criteria were applied by two reviewers, and a standardized score was calculated for each of the six domains. A cut-off of 60% was used to identify high-quality guidelines. Results: A total of 654 records were identified, 10 of which were eligible for data extraction. Both adult and pediatric CPGs averaged above 70% for the domains of 'scope and purpose' and 'clarity and presentation'. For 'stakeholder involvement', the mean adult and pediatric CPG scores were below the cut-off. Only one adult-focused guideline exceeded the cut-off for the 'rigour of development' domain. 'Applicability' scores were most alarming, with adult CPGs averaging 21% and pediatric CPGs averaging 23%. Conclusion: Our review and appraisal of the CPGs for the diagnosis of CeD highlight significant discrepancies in clinical recommendations and some concerns regarding methodological rigour, particularly in stakeholder engagement, rigour, and applicability. Creating a Canadian guideline of high methodological quality that overcomes these weaknesses is critical to optimize patient care and ensuring accurate diagnoses in CeD.

Nutritional Considerations in Celiac Disease and Non-Celiac Gluten/Wheat Sensitivity.

A gluten-free diet (GFD) is the only available treatment for celiac disease (CeD), and it may also improve symptoms in non-celiac gluten/wheat sensitivity (NCGWS). In CeD, gluten triggers an immune reaction leading to enteropathy, malabsorption, and symptoms; in NCGWS, the mechanism leading to symptoms is unknown, and neither wheat nor gluten triggers enteropathy or malabsorption. A strict GFD is, therefore, necessary for CeD, but a gluten-restricted diet (GRD) may suffice to achieve symptom control for NCGWS. Regardless of this distinction, the risk of malnutrition and macro- and micronutrient deficiencies is increased by the adoption of a GFD or GRD. Thus, patients with CeD or NCGWS should undergo nutritional assessment and subsequent monitoring, based on evidence-based tools, under the care of a multidisciplinary team involving physicians and dietitians, for the long-term management of their nutrition. This review gives an overview of available nutrition assessment tools and considerations for the nutritional management of CeD and NCGWS populations.

Comment on Chao, H.-C. Zinc Deficiency and Therapeutic Value of Zinc Supplementation in Pediatric Gastrointestinal Diseases. Nutrients 2023, 15, 4093.

We appreciate the recent review article by Chao H.-C. [...].

Biogeographic Variation and Functional Pathways of the Gut Microbiota in Celiac Disease.

BACKGROUND & AIMS: Genes and gluten are necessary but insufficient to cause celiac disease (CeD). Altered gut microbiota has been implicated as an additional risk factor. Variability in sampling site may confound interpretation and mechanistic insight, as CeD primarily affects the small intestine. Thus, we characterized CeD microbiota along the duodenum and in feces and verified functional impact in gnotobiotic mice. METHODS: We used 16S rRNA gene sequencing (Illumina) and predicted gene function (PICRUSt2) in duodenal biopsies (D1, D2 and D3), aspirates, and stool from patients with active CeD and controls. CeD alleles were determined in consented participants. A subset of duodenal samples stratified according to similar CeD risk genotypes (controls DQ2-/- or DQ2+/- and CeD DQ2+/-) were used for further analysis and to colonize germ-free mice for gluten metabolism studies. RESULTS: Microbiota composition and predicted function in CeD was largely determined by intestinal location. In the duodenum, but not stool, there was higher abundance of Escherichia coli (D1), Prevotella salivae (D2), and Neisseria (D3) in CeD vs controls. Predicted bacterial protease and peptidase genes were altered in CeD and impaired gluten degradation was detected only in mice colonized with CeD microbiota. CONCLUSIONS: Our results showed luminal and mucosal microbial niches along the gut in CeD. We identified novel microbial proteolytic pathways involved in gluten detoxification that are impaired in CeD but not in controls carrying DQ2, suggesting an association with active duodenal inflammation. Sampling site should be considered a confounding factor in microbiome studies in CeD.

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.

Association of Celiac Disease and Inflammatory Bowel Disease: A Nationwide Register-Based Cohort Study.

INTRODUCTION: To determine the risk of inflammatory bowel disease (IBD) in patients with celiac disease (CeD) (and vice versa ) compared with general-population comparators. METHODS: Using Swedish histopathology and healthcare register data, we identified 48,551 patients with CeD and 83,529 with IBD diagnosed in 1969-2016. Each patient was compared with age- and sex-matched general-population comparators (CeD: n = 240,136; IBD: n = 408,195). Cox regression estimated hazard ratios (HRs) for IBD in patients with CeD and vice versa . Our main analyses were limited to events beyond the first year of follow-up to reduce potential surveillance bias. RESULTS: During follow-up, 784 (1.6%) patients with CeD were diagnosed with IBD compared with 1,015 (0.4%) matched comparators. In patients with CeD, the HR for IBD was 3.91 (95% confidence interval [CI] 3.56-4.31), with largely similar HRs for Crohn's disease (4.36; 3.72-5.11) and ulcerative colitis (3.40; 3.00-3.85). During follow-up, 644 (0.8%) patients with IBD and 597 (0.1%) comparators were diagnosed with CeD. The HR for CeD in patients with IBD was 5.49 (95% CI 4.90-6.16), with the highest risk estimates seen in ulcerative colitis (HR = 6.99; 6.07-8.05), and the HR for Crohn's disease was 3.31 (2.69-4.06). In patients with CeD and IBD, the diagnostic interval was usually <1 year; however, HRs of 3-4 were seen even after 10 years of follow-up. During 20 years of follow-up, 2.5% of patients with CeD developed incident IBD, and 1.3% of patients with IBD developed CeD. DISCUSSION: The bidirectional association between CeD diagnosis and IBD warrants attention in the initial assessment and follow-up of these conditions. Their co-occurrence, independent of temporal sequence, suggests shared etiology.

Perioperative optimization with nutritional supplements in patients undergoing gastrointestinal surgery for cancer: A randomized, placebo-controlled feasibility clinical trial.

BACKGROUND: Perioperative nutritional supplementation may improve outcomes. Trials have not investigated the role of combination strategy using different types of nutritional supplements. METHODS: We conducted a single-site randomized pilot trial, among gastrointestinal cancer patients undergoing surgery, comparing perioperative nutritional supplements versus placebo (1 placebo to each supplement), to determine feasibility of a larger trial. Intervention, administered in sequence, included: protein supplementation (preoperative day 30-6), protein supplementation rich in arginine and omega-6 (preoperative day 5-1, and postoperative day 1-5), and carbohydrate loading (surgery day). Primary outcome was enrollment. Secondary outcomes included participant compliance with study supplements (target ≥70% of total packets). We planned protocol modifications to improve enrollment and compliance. Postoperative complications were described. RESULTS: Over 18 months, 495 patients were screened, 144 were deemed eligible, and 71 consented to participate, resulting in an enrollment fraction of 71/144 (49%, 95% confidence interval: 41%-57%). 'Too much burden' was the most common reason for refusal to participate (34%). Participants' median overall compliance with study packets was 80%. Protocol modifications (decreasing the interval from enrollment to surgery from 4 to 2 weeks and decreasing length of baseline assessment) did not impact enrollment or compliance. Postoperative complications were similar between control (18/31 [58%, 95% confidence interval: 4-74]), and intervention (22/34 [65%, 95% confidence interval: 48-79]) arms, with a higher proportion of infectious complications in the control arm (16/31, 52% vs 12/34, 35%). CONCLUSION: Results from this pilot suggest a larger phase III trial is feasible. Postoperative infectious complications were common, making this a suitable outcome of interest.

Reduction in Anxiety and Depression Scores Associated with Improvement in Quality of Life in Patients with Inflammatory Bowel Disease.

BACKGROUND: The aim of this study was to examine the associations among depression, anxiety and health-related quality of life and predictors of improvement of quality of life in patients with inflammatory bowel disease. METHODS: This was a prospective cohort study conducted in the gastroenterology clinic at McMaster University Medical Center in Hamilton, Ontario, Canada from May 2014 to March 2015. We included 60 adult patients above the age of 18 years old with a diagnosis of inflammatory bowel disease. We assessed anxiety and depression using the Hospital Anxiety and Depression Scale (HADS) and Health Related Quality of Life (HRQoL) using the Short Inflammatory Bowel Disease questionnaire (SIBDQ) at baseline and after 6 months. Linear regression was performed to estimate the associations among depression, anxiety and predictors of improvement in health-related quality of life. RESULTS: The anxiety scores decreased over the span of 6 months (median HADS-A baseline 9.00 [interquartile range {IQR} 6 to 12], and median HADS-A 6 months 7.00 [IQR 3.75 to 7.00]). There was a moderate negative correlation between anxiety (baseline r = -0.510, and 6-month r = -0.620; P < 0.001), depression (baseline r = -0.630, and 6-month r = -0.670; P < 0.001) and HRQoL scores. Using a multivariate linear regression model, elevated HADS score were associated with lower SIBDQ scores at baseline (Beta coefficient -0.696 [95% confidence interval {CI} -1.51 to -0.842]; P < 0.001). Lower SIBDQ score at baseline predicted decreased SIBDQ at 6 months (Beta coefficient 0.712 [95% CI 0.486 to 1.02]; P < 0.001). CONCLUSION: Anxiety and depression are frequently seen in inflammatory bowel disease patients and lead to poor HRQoL. Psychological comorbidities may contribute to maladaptive behaviours and difficult disease management.

The complexities of approaching nutrition in inflammatory bowel disease: current recommendations and future directions.

Inflammatory bowel diseases (IBDs), including Crohn's disease and ulcerative colitis predispose patients to malnutrition due to a combination of increased basal metabolic rate, decreased oral intake, and increased nutritional losses and malabsorption. Malnutrition is common, affecting up to 75% of patients with Crohn's disease and 62% of patients with ulcerative colitis, and is associated with worse disease prognosis, higher complication rates, decreased quality of life, and increased mortality risk. It is imperative to screen patients with IBD for malnutrition to assess those at increased risk and treat accordingly to prevent progression and complications. This literature review provides an overall approach to optimizing nutrition in IBD, focusing on the assessment for the diagnosis of malnutrition, management of macro- and micronutrient deficiencies, and identification of areas for future study.

Fecal microbiome differs between patients with systemic sclerosis with and without small intestinal bacterial overgrowth.

Introduction: Gastrointestinal manifestations of systemic sclerosis affect up to 90% of patients, with symptoms including diarrhea and constipation. Small intestinal bacterial overgrowth is a condition associated with increased numbers of pathogenic bacteria in the small bowel. While currently unknown, it has been suggested that dysregulation of the fecal microbiota may play a role in the development of systemic sclerosis and small intestinal bacterial overgrowth. Objectives: Our study aimed to describe the fecal microbiota of patients with systemic sclerosis and compare it between those with and without a diagnosis of small intestinal bacterial overgrowth. We also compared the fecal microbiota of systemic sclerosis patients with that of healthy controls to understand the association between particular bacterial taxa and clinical gastrointestinal manifestations of systemic sclerosis. Methods: A total of 29 patients with systemic sclerosis underwent breath testing to assess for small intestinal bacterial overgrowth, provided stool samples to determine taxonomic assignments, and completed the University of California Los Angeles Scleroderma Clinical Trial Consortium Gastrointestinal Tract 2.0, which details symptoms and quality-of-life factors. Stool samples were compared between systemic sclerosis patients with and without small intestinal bacterial overgrowth, and between patients with systemic sclerosis and a healthy control cohort (n = 20), aged 18-80 years. Results: Fecal microbiome analyses demonstrated differences between systemic sclerosis patients with and without small intestinal bacterial overgrowth and differences in the diversity of species between healthy controls and patients with systemic sclerosis. Trends were also observed in anticentromere antibody systemic sclerosis patients, including higher Alistipies indistincus spp. levels associated with increased methane levels of breath gas testing and higher Slakia spp. levels associated with increased rates of fecal soiling. Conclusions: Our results suggest that changes to the fecal microbiome occur in patients with small intestinal bacterial overgrowth and systemic sclerosis when compared to healthy controls. As a cross-sectional study, the potential pathophysiologic role of an altered microbiome in the development of systemic sclerosis was not considered and hence needs to be further investigated.

Real-World Gluten Exposure in Patients With Celiac Disease on Gluten-Free Diets, Determined From Gliadin Immunogenic Peptides in Urine and Fecal Samples.

BACKGROUND & AIMS: It is not clear how often patients who are on gluten-free diets (GFDs) for treatment of celiac disease still are exposed to gluten. We studied levels of gluten immunogenic peptides (GIP) in fecal and urine samples, collected over 4 weeks, from patients with celiac disease on a long-term GFD. METHODS: We performed a prospective study of 53 adults with celiac disease who had been on a GFD for more than 2 years (median duration, 8 y; interquartile range, 5-12 y) in Argentina. At baseline, symptoms were assessed by the celiac symptom index questionnaire. Patients collected stool each Friday and Saturday and urine samples each Sunday for 4 weeks. We used a commercial enzyme-linked immunosorbent assay to measure GIP in stool and point-of-care tests to measure GIP in urine samples. RESULTS: Overall, 159 of 420 stool and urine samples (37.9%) were positive for GIP; 88.7% of patients had at least 1 fecal or urine sample that was positive for GIP (median, 3 excretions). On weekends (urine samples), 69.8% of patients excreted GIP at least once, compared with 62.3% during weekdays (stool). The number of patients with a sample that was positive for GIP increased over the 4-week study period (urine samples in week 1 vs week 4: P < .05). Patients with symptoms had more weeks in which GIP was detected in stool than patients without symptoms (P < .05). The number of samples that were positive for GIP correlated with titers of deamidated gliadin peptide IgA in patients' blood samples, but not with levels of tissue transglutaminase. CONCLUSIONS: Patients with celiac disease on a long-term GFD still frequently are exposed to gluten. Assays to detect GIP in stool and urine might be used to assist dietitians in assessment of GFD compliance.

Gluten-Free Diet Reduces Symptoms, Particularly Diarrhea, in Patients With Irritable Bowel Syndrome and Antigliadin IgG.

BACKGROUND & AIMS: Many patients with irritable bowel syndrome (IBS) perceive that their symptoms are triggered by wheat-containing foods. We assessed symptoms and gastrointestinal transit before and after a gluten-free diet (GFD) in unselected patients with IBS and investigated biomarkers associated with symptoms. METHODS: We performed a prospective study of 50 patients with IBS (ROME III, all subtypes), with and without serologic reactivity to gluten (antigliadin IgG and IgA), and 25 healthy subjects (controls) at a university hospital in Hamilton, Ontario, Canada, between 2012 and 2016. Gastrointestinal transit, gut symptoms, anxiety, depression, somatization, dietary habits, and microbiota composition were studied before and after 4 weeks of a GFD. HLA-DQ2/DQ8 status was determined. GFD compliance was assessed by a dietitian and by measuring gluten peptides in stool. RESULTS: There was no difference in symptoms among patients at baseline, but after the GFD, patients with antigliadin IgG and IgA reported less diarrhea than patients without these antibodies (P = .03). Compared with baseline, IBS symptoms improved in 18 of 24 patients (75%) with antigliadin IgG and IgA and in 8 of 21 patients (38%) without the antibodies. Although constipation, diarrhea, and abdominal pain were reduced in patients with antigliadin IgG and IgA, only pain decreased in patients without these antibodies. Gastrointestinal transit normalized in a higher proportion of patients with antigliadin IgG and IgA. Anxiety, depression, somatization, and well-being increased in both groups. The presence of antigliadin IgG was associated with overall reductions in symptoms (adjusted odds ratio compared with patients without this antibody, 128.9; 95% CI, 1.16-1427.8; P = .04). Symptoms were reduced even in patients with antigliadin IgG and IgA who reduced gluten intake but were not strictly compliant with the GFD. In controls, a GFD had no effect on gastrointestinal symptoms or gut function. CONCLUSIONS: Antigliadin IgG can be used as a biomarker to identify patients with IBS who might have reductions in symptoms, particularly diarrhea, on a GFD. Larger studies are needed to validate these findings. ClinicalTrials.gov: NCT03492333.

The Risk of Contracting COVID-19 Is Not Increased in Patients With Celiac Disease.

The World Health Organization declared coronavirus disease-2019 (COVID-19) a global pandemic in March 2020. Since then, there are more than 34 million cases of COVID-19 leading to more than 1 million deaths worldwide. Numerous studies suggest that celiac disease (CeD), a chronic immune-mediated gastrointestinal condition triggered by gluten, is associated with an increased risk of respiratory infections.1-3 However, how it relates to the risk of COVID-19 is unknown. To address this gap, we conducted a cross-sectional study to evaluate whether patients with self-reported CeD are at an increased risk of contracting COVID-19.

Current and emerging therapies for coeliac disease.

Coeliac disease is a common enteropathy that occurs in genetically susceptible individuals in response to the ingestion of gluten proteins present in wheat, rye and barley. Currently, the only available treatment for the condition is a strict, life-long gluten-free diet that, despite being safe and often effective, is associated with several challenges. Due to the high cost, particularly restrictive nature and perception of decreased quality of life associated with the diet, some patients are continuously exposed to gluten, which prevents an adequate disease control. Moreover, a subgroup of patients does not respond to the diet adequately, and healing of the small-bowel mucosa can be incomplete. Thus, there is a need for alternative treatment forms. The increasingly understood pathogenetic process of coeliac disease has enabled the identification of various targets for future therapies. Multiple investigational therapies ranging from tolerogenic to immunological approaches are in the pipeline, and several drug candidates have entered phase II/III clinical trials. This Review gives a broad overview of the different investigative treatment modalities for coeliac disease and summarizes the latest advances in this field.

Derivation and validation of a novel method to subgroup patients with functional dyspepsia: beyond upper gastrointestinal symptoms.

BACKGROUND: Conventionally, patients with functional dyspepsia are subgrouped based on upper gastrointestinal symptoms, according to the Rome criteria. However, psychological co-morbidity and extraintestinal symptoms are also relevant to functional gastrointestinal disorders. AIM: To investigate whether it is possible to subgroup people with functional dyspepsia using factors beyond upper gastrointestinal symptoms. METHODS: We collected demographic, symptom and psychological health data from adult subjects meeting the Rome III criteria for functional dyspepsia in two secondary care cross-sectional surveys in Canada and the UK. We performed latent class analysis, a method of model-based clustering, to identify specific subgroups (clusters). For each cluster, we drew a radar plot, and compared these by visual inspection, describing cluster characteristics. RESULTS: In total, 400 individuals met Rome III criteria for functional dyspepsia in the Canadian cohort, and 262 the UK cohort. A four-cluster model was the optimum solution and the characteristics of the clusters were almost identical between the two cohorts. The clusters were defined by a pattern of gastrointestinal symptoms and were further differentiated by the extent of extraintestinal and psychological co-morbidity. Cluster 1 (mean age 46.7 years, 66.7% female) consisted of epigastric pain and nausea with high psychological burden, cluster 2 (mean age 41.5 years, 77.7% female) high overall gastrointestinal symptom severity with high psychological burden, cluster 3 (45.8 years, 67.2% female) oesophageal symptoms and early satiety with low psychological burden, and cluster 4 (mean age 40.4 years, 71.5% female) postprandial fullness with low psychological burden. We validated the model derived using the Canadian study population externally by applying it to the UK dataset. We demonstrated reproducibility; it would perform similarly when applied to a different dataset. CONCLUSIONS: Latent class analysis identified four distinct functional dyspepsia subgroups characterised by varying degrees of gastrointestinal symptoms, extraintestinal symptoms and psychological co-morbidity. Further research is needed to assess whether they might be used to direct treatment.

Probiotics for Celiac Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

INTRODUCTION: Many patients with celiac disease (CD) experience persistent symptoms despite adhering to the gluten-free diet. Different studies have assessed the use of probiotics as an adjuvant treatment for CD. We performed a systematic review and meta-analysis to evaluate the efficacy of probiotics in improving gastrointestinal (GI) symptoms and quality of life (QOL) in patients with CD. METHODS: We searched EMBASE, MEDLINE, CINAHL, Web of Science, CENTRAL, and DARE databases up to February 2019 for randomized controlled trials (RCTs) evaluating probiotics compared with placebo for treating CD. We collected data on GI symptoms, QOL, adverse events, serum tumor necrosis factor-α, intestinal permeability, and microbiota composition. RESULTS: We screened 2,831 records and found that 7 articles describing 6 RCTs (n = 279 participants) were eligible for quantitative analysis. Probiotics improved GI symptoms when assessed by the GI Symptoms Rating Scale (mean difference symptom reduction: -28.7%; 95% confidence interval [CI] -43.96 to -13.52; P = 0.0002). There was no difference in GI symptoms after probiotics when different questionnaires were pooled. The levels of Bifidobacteria increased after probiotics (mean difference: 0.85 log colony-forming units (CFU) per gram; 95% CI 0.38-1.32 log CFU per gram; P = 0.0003). There were insufficient data on tumor necrosis factor-a levels or QOL for probiotics compared with placebo. No difference in adverse events was observed between probiotics and placebo. The overall certainty of the evidence ranged from very low to low. DISCUSSION: Probiotics may improve GI symptoms in patients with CD. High-quality clinical trials are needed to improve the certainty in the evidence (see Visual abstract, Supplementary Digital Content 2, http://links.lww.com/AJG/B595).