Bile acid malabsorption in chronic diarrhea: pathophysiology and treatment. Can J Gastroenterol. 2013;27:653-659. [PMID: 24199211 DOI: 10.1155/2013/485631]

European Consensus on Malabsorption-UEG & SIGE, LGA, SPG, SRGH, CGS, ESPCG, EAGEN, ESPEN, and ESPGHAN. Part 1: Definitions, Clinical Phenotypes, and Diagnostic Testing for Malabsorption

Malabsorption is a complex and multifaceted condition characterised by the defective passage of nutrients into the blood and lymphatic streams. Several congenital or acquired disorders may cause either selective or global malabsorption in both children and adults, such as cystic fibrosis, exocrine pancreatic insufficiency (EPI), coeliac disease (CD) and other enteropathies, lactase deficiency, small intestinal bacterial overgrowth (SIBO), autoimmune atrophic gastritis, Crohn's disease, and gastric or small bowel resections. Early recognition of malabsorption is key for tailoring a proper diagnostic work-up for identifying the cause of malabsorption. A patient's medical and pharmacological history is essential for identifying risk factors. Several examinations such as endoscopy with small intestinal biopsies, non-invasive functional tests and radiological imaging are useful in diagnosing malabsorption. Because of its high prevalence, CD should always be looked for in cases of malabsorption with no other obvious explanations and in high-risk individuals. Nutritional support is key in the management of patients with malabsorption; different options are available, including oral supplements, enteral or parenteral nutrition. In patients with short bowel syndrome, teduglutide proved effective in reducing the need for parenteral nutrition, thus improving the quality of life of these patients. Primary care physicians play a central role in the early detection of malabsorption and should be involved in multidisciplinary teams for improving the overall management of these patients. In this European consensus, involving ten scientific societies and several experts, we have dissected all the issues around malabsorption, including the definitions and diagnostic testing (Part 1), high-risk categories and special populations, nutritional assessment and management, and primary care perspective (Part 2).

Influence of gut bile acid composition on the glucose-lowering effect and safety of metformin

AIMS

This study evaluates how changes in intestinal bile acid composition, induced by cholestyramine, a bile acid sequestrant, affect metformin's pharmacodynamics (PD).

METHODS

An open-label, 2-period 1-sequence crossover study was conducted with healthy male adults. Each period consisted of both before and after metformin treatments. Cholestyramine was administered during the second period to change the bile acid pool. For, PD assessment, an oral glucose tolerance test was conducted at each treatment in both periods. Metformin was administered 3 times during each period, and cholestyramine was administered 3 times per day for 7 days during the second period. Maximum serum glucose concentration, area under the glucose concentration curve and homeostatic model assessment of insulin resistance were calculated. Baseline-corrected PD parameters were derived by subtracting pre-metformin values from post-metformin values. Lipid and panels and bile acid profiles in stool were measured. Adverse events were monitored throughout the study.

RESULTS

Fourteen subjects completed the study. The mean values of 3 PD parameters were all decreased after metformin administration in both periods. Cholestyramine administration led to a further decrease in baseline-corrected PD parameters, significantly reducing the area under the glucose concentration curve by 44.7%. Diarrhoea, the most common adverse event, was reported in 10 subjects during the metformin alone treatment and in 1 subject during the cholestyramine combined treatment (P < .01).

CONCLUSION

Cholestyramine affected the glucose-lowering effect of metformin by the possible change in the bile acid pool in the gut, and metformin-associated diarrhoea was improved by cholestyramine.

Bile acid diarrhea in patients with chronic diarrhea. Current appraisal and recommendations for clinical practice

Bile Acid Diarrhea (BAD) is a common cause of chronic diarrhea, often accompanied by urgency, occasional fecal incontinence, abdominal pain, and fatigue. A nationwide survey has shown limited awareness of BAD within the Italian medical community, prompting a panel of experts to develop a Position Paper that outlines the most practical and cost-saving diagnostic investigations and treatments for this frequently overlooked condition. The document provides an overview of the epidemiology, pathophysiology, clinical manifestations, and classification of the different types of Bile Acid Diarrhea (BAD). A key focus is the diagnostic approach to identifying and managing the many undiagnosed BAD patients in both primary care and specialized medical settings. Finally, the paper addresses the optimal therapeutic strategies for BAD, including traditional bile acid sequestrants and newer, promising treatments.

Advances in the pathophysiology, diagnosis and management of chronic diarrhoea from bile acid malabsorption: a systematic review

Bile acid malabsorption (BAM) is an important disorder of digestive pathophysiology as it generates chronic diarrhoea. This condition originates from intricate pathways involving bile acid synthesis and metabolism in the liver and gut, the composition of gut microbiota, enterohepatic circulation and key receptors as farnesoid X receptor (FXR), fibroblast growth factor receptor 4 (FGFR4), and the G-protein bile acid receptor-1 (GPBAR-1). Although symptoms can resemble those related to disorders of gut brain interaction, accurate diagnosis of BAM may greatly benefit the patient. The empiric diagnosis of BAM is primarily based on the clinical response to bile acid sequestrants. Specific tests including the 48-hour fecal bile acid test, serum levels of 7α-hydroxy-4-cholesten-3-one (C4) and fibroblast growth factor 19 (FGF19), and the 75Selenium HomotauroCholic Acid Test (SeHCAT) are not widely available. Nevertheless, lack of diagnostic standardization of BAM may account for poor recognition and delayed management. Beyond bile acid sequestrants, therapeutic approaches include the use of FXR agonists, FGF19 analogues, glucagon-like peptide-1 (GLP-1) receptor agonists, and microbiota modulation. These novel agents can best make their foray into the therapeutic armamentarium if BAM does not remain a diagnosis of exclusion. Ignoring BAM as a specific condition may continue to contribute to increased healthcare costs and reduced quality of life. Here, we aim to provide a comprehensive review of the pathophysiology, diagnosis, and management of BAM.

Evidence-Based Clinical Guidelines for Chronic Diarrhea 2023

The Japan Gastroenterological Association (JGA) published the first version of clinical guidelines for chronic diarrhea 2023. These guidelines describe the definition, classification, diagnostic criteria, diagnostic testing methods, epidemiology, pathophysiology, and treatment of chronic diarrhea, and provide flowcharts for the diagnosis and treatment of chronic diarrhea based on the latest evidence. Treatment for chronic diarrhea begins by distinguishing secondary chronic constipation with a clear etiology, such as drug-induced diarrhea, food-induced diarrhea, systemic disease-associated diarrhea, infection-associated diarrhea, organic disease-associated diarrhea, and bile acid diarrhea. The first line of treatment for chronic diarrhea in the narrow sense, defined in these guidelines as functional diarrhea in routine medical care, is lifestyle modification and dietary therapy. The first medicines to be considered for oral treatment are probiotics for regulating the gut microbiome and anti-diarrheals. Other medications, such as 5HT3 receptor antagonists, anticholinergics, Kampo medicine, psychotherapy, antibiotics, bulking agents, adrenergic agonists, and somatostatin analogs, lack sufficient evidence for their use, highlighting a challenge for future research. This Clinical Guidelines for Chronic Diarrhea 2023, which provides the best clinical strategies for treating chronic diarrhea in Japan, will also be useful for medical treatment worldwide.

Cholestyramine alleviates bone and muscle loss in irritable bowel syndrome via regulating bile acid metabolism

Irritable bowel syndrome (IBS) is a widespread gastrointestinal disorder known for its multifaceted pathogenesis and varied extraintestinal manifestations, yet its implications for bone and muscle health are underexplored. Recent studies suggest a link between IBS and musculoskeletal disorders, but a comprehensive understanding remains elusive, especially concerning the role of bile acids (BAs) in this context. This study aimed to elucidate the potential contribution of IBS to bone and muscle deterioration via alterations in gut microbiota and BA profiles, hypothesizing that cholestyramine could counteract these adverse effects. We employed a mouse model to characterize IBS and analysed its impact on bone and muscle health. Our results revealed that IBS promotes bone and muscle loss, accompanied by microbial dysbiosis and elevated BAs. Administering cholestyramine significantly mitigated these effects, highlighting its therapeutic potential. This research not only confirms the critical role of BAs and gut microbiota in IBS-associated bone and muscle loss but also demonstrates the efficacy of cholestyramine in ameliorating these conditions, thereby contributing significantly to the field's understanding and offering a promising avenue for treatment.

Review article: A practical approach to persistent gastrointestinal symptoms in inflammatory bowel disease in remission

BACKGROUND

Persistent gastrointestinal symptoms are prevalent in adult patients with inflammatory bowel disease (IBD), even when endoscopic remission is reached. These symptoms can have profound negative effects on the quality of life of affected patients and can be difficult to treat. They may be caused by IBD-related complications or comorbid disorders, but they can also be explained by irritable bowel syndrome (IBS)-like symptoms.

AIMS

To provide a practical step-by-step guide to diagnose and treat persistent gastrointestinal symptoms in patients with IBD in remission via a personalised approach.

METHODS

We scrutinised relevant literature on causes, diagnostics and treatment of persistent gastrointestinal symptoms (abdominal pain or discomfort, bloating, abdominal distension, diarrhoea, constipation and faecal incontinence) in patients with IBD in remission.

RESULTS

A graphical practical guide for several steps in diagnosing, identifying potential triggers and adequate treatment of persistent gastrointestinal symptoms in IBD in remission is provided based on supporting literature. The first part of this review focuses on the diagnostic and treatment approaches for potential IBD-related complications and comorbidities. The second part describes the approach to IBS-like symptoms in IBD in remission.

CONCLUSIONS

Persistent gastrointestinal symptoms in IBD in remission can be traced back to potential pathophysiological mechanisms in individual patients and can be treated adequately. For both IBD-related complications and comorbidities and IBS-like symptoms in IBD in remission, pharmacological, dietary, lifestyle or psychological treatments can be effective. A systematic and personalised approach is required to reduce the burden for patients, healthcare systems, and society.

[Bile Acid Diarrhea]

Diarrhea is a very common gastrointestinal symptom, and the presence of higher concentrations of bile acid in the colon leads to bile acid diarrhea (BAD). In BAD patients, a portion of bile from the small intestine that is normally controlled by enterohepatic circulation is present at a high concentration in the lumen of the large intestine, resulting in increased motility and secretion of the large intestine. The prevalence of BAD is estimated to be 1-2% of the general population, and it comprises one-third of the instances of diarrhea-predominant irritable bowel syndrome. The clinical symptoms of BAD include chronic diarrhea, increased frequency of defecation, urgency to defecate, fecal incontinence, and cramping abdominal pain. The pathophysiology of BAD has not yet been fully elucidated. However, recent studies have reported increased intestinal permeability, shortened intestinal transit time, and changes in the intestinal microbial community to be the possible causes of BAD. Although fecal and serum bile acid tests are widely used for diagnosis, new test methods that are non-invasive, inexpensive, and have high sensitivity and specificity are needed at various institutions to facilitate the diagnosis. The selenium homo-tauro-cholic acid (SeHCAT) test is the gold standard for BAD diagnosis and severity assessment. The validation of several other serum markers, such as 7-hydroxy-4-cholesten-3-one (serum 7αC4) and the fibroblast growth factor 19 (FGF19) for use in clinical practice is ongoing. Although bile acid sequestrants are the mainstay of treatment, the development of drugs that are more effective and have better compliance is required. Farnesoid X receptor (FXR) agonists are showing promising results.

Influence of the bile acid/microbiota axis in ileal surgery: a systematic review

AIM

The gastrointestinal bile acid (BA)/microbiota axis has emerged as a potential mediator of health and disease, particularly in relation to pathologies such as inflammatory bowel disease (IBD) and colorectal cancer. Whilst it presents an exciting new avenue for therapies, it has not yet been characterized in surgical resection of the ileum, where BA reabsorption occurs. The identification of BA/microbiota signatures may provide future therapies with perioperative personalized medicine. In this work we conduct a systematic review with the aim of investigating the microbiome and BA changes that are associated with resection of the ileum.

METHOD

The databases included were MEDLINE, EMBASE, Web of Science and Cochrane libraries. The outcomes of interest were faecal microbiome and BA signatures after ileal resection.

RESULTS

Of the initial 3106 articles, three studies met the inclusion/exclusion criteria for data extraction. A total of 257 patients (46% surgery, 54% nonsurgery controls) were included in the three studies. Two studies included patients with short bowel syndrome and the other included patients with IBD. Large-scale microbiota changes were reported. In general, alpha diversity had decreased amongst patients with ileal surgery. Phylum-level changes included decreased Bacteroidetes and increased Proteobacteria and Fusobacteria in patients with an intestinal resection. Surgery was associated with increased total faecal BAs, cholic acid and chenodeoxycholic acid. There were decreases in deoxycholic acid and glycine and taurine conjugated bile salts. Integrated BA and microbiota data identified correlations with several bacterial families and BA.

CONCLUSION

The BA/microbiota axis is still a novel area with minimal observational data in surgery. Further mechanistic research is necessary to further explore this and identify its role in improving perioperative outcomes.

Bile Acid Diarrhea: From Molecular Mechanisms to Clinical Diagnosis and Treatment in the Era of Precision Medicine

Bile acid diarrhea (BAD) is a multifaceted intestinal disorder involving intricate molecular mechanisms, including farnesoid X receptor (FXR), fibroblast growth factor receptor 4 (FGFR4), and Takeda G protein-coupled receptor 5 (TGR5). Current diagnostic methods encompass bile acid sequestrants (BAS), 48-h fecal bile acid tests, serum 7α-hydroxy-4-cholesten-3-one (C4), fibroblast growth factor 19 (FGF19) testing, and 75Selenium HomotauroCholic acid test (75SeHCAT). Treatment primarily involves BAS and FXR agonists. However, due to the limited sensitivity and specificity of current diagnostic methods, as well as suboptimal treatment efficacy and the presence of side effects, there is an urgent need to establish new diagnostic and treatment methods. While prior literature has summarized various diagnostic and treatment methods and the pathogenesis of BAD, no previous work has linked the two. This review offers a molecular perspective on the clinical diagnosis and treatment of BAD, with a focus on FXR, FGFR4, and TGR5, emphasizing the potential for identifying additional molecular mechanisms as treatment targets and bridging the gap between diagnostic and treatment methods and molecular mechanisms for a novel approach to the clinical management of BAD.

Diagnosis and treatment of post-cholecystectomy diarrhoea

The incidence of cholecystitis is relatively high in developed countries and may usually be attributed to gallstones, the treatment for which involves complete surgical removal of the gallbladder (cholecystectomy). Bile acids produced following cholecystectomy continue to flow into the duodenum but are poorly absorbed by the colon. Excessive bile acids in the colon stimulate mucosal secretion of water and electrolytes leading, in severe cases, to diarrhoea. Bile acid diarrhoea (BAD) is difficult to diagnose, requiring a comprehensive medical history and physical examination in combination with laboratory evaluation. The current work reviews the diagnosis and treatment of BAD following cholecystectomy.

Combined, elobixibat, and colestyramine reduced cholesterol toxicity in a mouse model of metabolic dysfunction-associated steatotic liver disease

BACKGROUND

Cholesterol levels and bile acid metabolism are important drivers of metabolic dysfunction-associated steatohepatitis (MASH) progression. Using a mouse model, we investigated the mechanism by which cholesterol exacerbates MASH and the effect of colestyramine (a bile acid adsorption resin) and elobixibat (an apical sodium-dependent bile acid transporter inhibitor) concomitant administration on bile acid adsorption and MASH status.

METHODS

Mice were fed a high-fat high-fructose diet with varying concentrations of cholesterol to determine changes in fatty liver according to liver status, water intake, defecation status, insulin resistance, bile acid levels, intestinal permeability, atherosclerosis (in apolipoprotein E knockout mice), and carcinogenesis (in diethylnitrosamine mice). Using small interfering ribonucleic acid (siRNA), we evaluated the effect of sterol regulatory element binding protein 1c (SREBP1c) knockdown on triglyceride synthesis and fatty liver status following the administration of elobixibat (group E), colestyramine (group C), or both (group EC).

RESULTS

We found greater reductions in serum alanine aminotransferase levels, serum lipid parameters, serum primary bile acid concentrations, hepatic lipid levels, and fibrosis area in EC group than in the monotherapy groups. Increased intestinal permeability and watery diarrhea caused by elobixibat were completely ameliorated in group EC. Group EC showed reduced plaque formation rates in the entire aorta and aortic valve of the atherosclerosis model, and reduced tumor counts and tumor burden in the carcinogenesis model.

CONCLUSIONS

Excessive free cholesterol in the liver can promote fatty liver disease. Herein, combination therapy with EC effectively reduced free cholesterol levels in MASH model mice. Our study provides strong evidence for combination therapy as an effective treatment for MASH.

Emerging role of the gut microbiome in post-infectious irritable bowel syndrome: A literature review

Post-infectious irritable bowel syndrome (PI-IBS) is a particular type of IBS, with symptom onset after an acute episode of infectious gastroenteritis. Despite infectious disease resolution and clearance of the inciting pathogen agent, 10% of patients will develop PI-IBS. In susceptible individuals, the exposure to pathogenic organisms leads to a marked shift in the gut microbiota with prolonged changes in host-microbiota interactions. These changes can affect the gut-brain axis and the visceral sensitivity, disrupting the intestinal barrier, altering neuromuscular function, triggering persistent low inflammation, and sustaining the onset of IBS symptoms. There is no specific treatment strategy for PI-IBS. Different drug classes can be used to treat PI-IBS similar to patients with IBS in general, guided by their clinical symptoms. This review summarizes the current evidence for microbial dysbiosis in PI-IBS and analyzes the available data regarding the role of the microbiome in mediating the central and peripheral dysfunctions that lead to IBS symptoms. It also discusses the current state of evidence on therapies targeting the microbiome in the management of PI-IBS. The results of microbial modulation strategies used in relieving IBS symptomatology are encouraging. Several studies on PI-IBS animal models reported promising results. However, published data that describe the efficacy and safety of microbial targeted therapy in PI-IBS patients are scarce. Future research is required.

The analysis of gut microbiota in patients with bile acid diarrhoea treated with colesevelam

Introduction

Bile acid diarrhoea (BAD) is a common disorder that results from an increased loss of primary bile acids and can result in a change in microbiome. The aims of this study were to characterise the microbiome in different cohorts of patients with BAD and to determine if treatment with a bile acid sequestrant, colesevelam, can alter the microbiome and improve microbial diversity.

Materials and methods

Patients with symptoms of diarrhoea underwent 75-selenium homocholic acid (75SeHCAT) testing and were categorised into four cohorts: idiopathic BAD, post-cholecystectomy BAD, post-operative Crohn’s disease BAD and 75SeHCAT negative control group. Patients with a positive 75SeHCAT (&lt;15%) were given a trial of treatment with colesevelam. Stool samples were collected pre-treatment, 4-weeks, 8-weeks and 6–12 months post-treatment. Faecal 16S ribosomal RNA gene analysis was undertaken.

Results

A total of 257 samples were analysed from 134 patients. α-diversity was significantly reduced in patients with BAD and more specifically, in the idiopathic BAD cohort and in patients with severe disease (SeHCAT &lt;5%); p &lt; 0.05. Colesevelam did not alter bacterial α/β-diversity but patients who clinically responded to treatment had a significantly greater abundance of Fusobacteria and Ruminococcus, both of which aid in the conversion of primary to secondary bile acids.

Conclusion

This is the first study to examine treatment effects on the microbiome in BAD, which demonstrated a possible association with colesevelam on the microbiome through bile acid modulation in clinical responders. Larger studies are now needed to establish a causal relationship with colesevelam and the inter-crosstalk between bile acids and the microbiome.

Exocrine pancreatic insufficiency after bariatric surgery: a bariatric surgery center of excellence experience

INTRODUCTION

Gastrointestinal symptoms such as diarrhea, bloating, abdominal pain, and nausea are common after bariatric surgery (BS) and can lead to significant morbidity. While many diagnoses can explain these symptoms, post-bariatric exocrine pancreatic insufficiency (EPI) is becoming increasingly recognized as contributor to gastrointestinal symptoms. The frequency and outcomes of EPI after BS are not well understood. We investigated the prevalence and outcomes of EPI over 18 years at a tertiary bariatric referral center.

METHODS

A retrospective review of patients who underwent primary or revisional BS from 2002 to 2020 was performed. Patients were included if they were suspected of having EPI or underwent fecal elastase testing (FE-1). EPI diagnosis was defined as positive FE-1 testing or improvement with empiric pancreatic enzyme replacement therapy (PERT).

RESULTS

EPI was suspected in 261 patients, and 190 were tested via FE-1 (89.5%) or empirically treated (10.5%). EPI was diagnosed in 79 (41.6%) patients and was associated with older age and lower BMI. Therapeutic PERT was given to 65 patients diagnosed with EPI, and 56 (86.2%) patients reported improved symptoms. Patients who underwent RYGB and BPD-DS were more likely to have EPI than those after SG (47.9% and 70.0% vs 17.4%, p < 0.01). EPI diagnosis was associated with a history chronic pancreatitis. While diarrhea and abdominal pain were the most common symptoms prompting FE-1 testing, no symptoms were significantly associated with EPI. EPI was also associated with abnormal fecal fat results and treatment with bile acid sequestrants, but not small intestinal bacterial overgrowth.

CONCLUSION

This study highlights that exocrine pancreatic insufficiency can account to for previously unexplained GI complaints after bariatric surgery. Therefore, bariatric surgery programs should consider this diagnosis in symptomatic patients, especially following RYGB and BPD-DS. Further work to define patient factors that should prompt evaluation, optimal treatment, and prevention is necessary.

Postoperative diarrhea in Crohn's disease: Pathogenesis, diagnosis, and therapy

Diarrhea is a frequent symptom in postoperative patients with Crohn's diseases (CD), and several different mechanisms likely account for postoperative diarrhea in CD. A targeted strategy based on a comprehensive understanding of postoperative diarrhea is helpful for better postoperative recovery.

Novel technologies to characterize and engineer the microbiome in inflammatory bowel disease

We present an overview of recent experimental and computational advances in technology used to characterize the microbiome, with a focus on how these developments improve our understanding of inflammatory bowel disease (IBD). Specifically, we present studies that make use of flow cytometry and metabolomics assays to provide a functional characterization of microbial communities. We also describe computational methods for strain-level resolution, temporal series, mycobiome and virome data, co-occurrence networks, and compositional data analysis. In addition, we review novel techniques to therapeutically manipulate the microbiome in IBD. We discuss the benefits and drawbacks of these technologies to increase awareness of specific biases, and to facilitate a more rigorous interpretation of results and their potential clinical application. Finally, we present future lines of research to better characterize the relation between microbial communities and IBD pathogenesis and progression.

Bacillus Subtilis Promotes the Release of 5-HT to Regulate Intestinal Peristalsis in STC Mice via Bile Acid and Its Receptor TGR5 Pathway

BACKGROUND

Slow transit constipation (STC) is caused by intestinal peristalsis dysfunction and is closely associated with disturbance of the intestinal microecological balance. Bacillus subtilis plays a positive role in the treatment of STC, but its mechanism needs to be further explored.

AIMS

The purpose of the present study was to explore the effects and mechanism of B. subtilis on the pathophysiology of STC.

METHODS

A STC mouse model was established with compound diphenoxylate, following which B. subtilis was used to treat STC. The effects and possible mechanism of B. subtilis on STC were investigated by assessing intestinal motility, histology of the colon, release of 5-HT in enterochromaffin cells (ECs) and the TGR5/TRPA1 pathway. Moreover, LC-MS targeted metabolomics was used to analyze the regulation of Bacillus subtilis on bile acid metabolisms in STC mice.

RESULTS

Bacillus subtilis significantly increased 24 h defecations, fecal moisture and intestinal transport rate of STC mice, improved pathological damage of the colon and showed protective effects on the intestinal tract. The release of 5-HT from ECs and the bile acid receptor TGR5/TRPA1 pathway were significantly increased in STC mice treated with B. subtilis. In addition, the metabolomics results showed that the bile acid contents of STC mice were significantly decreased, and B. subtilis could increase the bile acid composition and content of STC mice.

CONCLUSION

Bacillus subtilis regulates intestinal peristalsis of STC by promoting the release of 5-HT from ECs through bile acid metabolism and its receptor TGR5 pathway and plays a positive role in the treatment of STC.

Impact of Bile Acid Diarrhea in Patients With Diarrhea-Predominant Irritable Bowel Syndrome on Symptoms and Quality of Life

BACKGROUND & AIMS

Bile acid diarrhea (BAD) affects approximately a quarter of patients with irritable bowel syndrome with diarrhea (IBS-D). We aimed to compare the demographics, bowel and somatic symptoms, and quality of life of patients with IBS-D, with or without BAD.

METHODS

On one occasion, patients with IBS-D (positive for Rome III criteria) completed the following questionnaires: bowel disease questionnaire, Hospital Anxiety and Depression inventory, general quality of life (Symptom Checklist-90), and IBS-specific quality of life. A fasting serum C4 level higher than 52.5 ng/mL was used as a biomarker for BAD. Statistical analysis included a multiple variable logistic model to identify strong predictors of BAD in IBS-D.

RESULTS

Among 219 patients (79% female) with IBS-D, 44 had BAD; the BAD group was significantly older and had a higher body mass index than the patients without BAD. Patients with BAD had more severe bowel dysfunction and impact on IBS-specific quality of life (need of toilet proximity) compared with patients with IBS-D without BAD. Patients with BAD were more likely than other IBS-D groups to receive antidiarrheals, bile acid binders, and antacid secretory agents. The severity of diarrhea and need of toilet proximity were predictors of BAD in IBS-D (P < .01). Patients with BAD were more likely to have a depression score higher than 8 on the Hospital Anxiety and Depression inventory.

CONCLUSIONS

There is a greater impact on bowel and somatic symptoms and quality of life in IBS-D with BAD compared with IBS-D without BAD. Screening for BAD in IBS-D is especially relevant, with more severe and frequent diarrhea along with urgency.

Mesalamine and cholestyramine for immune checkpoint inhibitor-mediated diarrhea and colitis

PURPOSE

Immune checkpoint inhibitors (ICI) are effective against various malignancies. However, adverse events including diarrhea and colitis can lead to significant morbidity and mortality. Recommendations for the management of ICI mediated diarrhea and colitis include steroids and biologics. Given their associated risks, this study evaluated the role of the non-immunosuppressive agents, mesalamine and or cholestyramine.

METHODS

This is a retrospective, descriptive, single-center study of adults who developed ICI diarrhea and colitis between 2010 and 2020 at MD Anderson Cancer Center. Clinical data and outcomes were compared between those treated with the non-immunosuppressive therapies mesalamine and/or cholestyramine alone versus those who received additional immunosuppression with steroids and biologics.

RESULTS

Our sample comprised 66 patients wherein, the mean age was 63 years, 71% were males, and 97% had stage III/IV cancers. Fourteen patients were treated successfully with non-immunosuppressive therapy. They had grade 1-3 diarrhea and 1-2 colitis with no difference in the rate of histologic colitis compared to those who received immunosuppressive therapy. They had less CTLA-4 inhibitor-based therapy (36% vs. 73%, p = 0.034), delayed onset of symptoms (159 vs. 64 days, p = 0.011), lower fecal calprotectin levels (56 vs. 234, p = 0.012) and were more likely to resume ICI therapy (64% vs. 25%, p = 0.006).

CONCLUSION

Mesalamine and/or cholestyramine may be effective for mild ICI diarrhea and colitis among patients with delayed symptom onset with lower colonic inflammatory burden. Prospective studies randomizing patients with mild colitis between mesalamine/cholestyramine and immunosuppressive treatment are warranted to assess their efficacy and safety.

Usefulness of colestimide for diarrhea in postoperative Crohn's disease

Background and Aim

Crohn's disease (CD) often causes intractable diarrhea after intestinal resection. Anion exchange resins have been reported to be effective in patients with bile acid diarrhea after distal ileectomy; furthermore, bile acid metabolism has been implicated in the pathogenesis of CD. Therefore, we aimed to examine the effectiveness of colestimide in the management of postoperative CD, and to compare its impact between patients with and those without ileocecal resection.

Methods

Postoperative CD patients prescribed colestimide for diarrhea between April 2017 and December 2020 were retrospectively evaluated for changes in the total Crohn's disease activity index (CDAI), each CDAI component including diarrhea frequency/week, albumin, and C‐reactive protein (CRP) was evaluated before and after the administration of colestimide. Furthermore, comprehensive patient and physician assessments were reviewed from medical records during the first outpatient visit as a global clinical judgment after the initiation of colestimide therapy.

Results

A total of 24 patients were included, of whom 17 had a previous history of ileocecal resection. Significant improvement was noted in CDAI and diarrhea frequency only in the ileocecal resection group (CDAI: 114.5 ± 52.7 and 95.4 ± 34.8, P < 0.05; diarrhea frequency/week 23.8 ± 14.1 and 15.4 ± 11.2, P < 0.05, respectively). There was no significant improvement in other CDAI components, albumin level, or CRP level in either group. In the global clinical judgment, 13 and 4 patients in the ileocecal and non‐ileocecal resection groups, respectively, were judged as “effective,” with an overall efficacy rate of 70.8%.

Conclusion

Colestimide is effective for diarrhea in patients with postoperative CD, especially after ileocecal resection.

Functional, Diagnostic and Therapeutic Aspects of Bile

Bile is a unique body fluid synthesized in our liver. Enterohepatic circulation preserves bile in our body through its efficient synthesis, transport, absorption, and reuptake. Bile is the main excretory route for bile salts, bilirubin, and potentially harmful exogenous lipophilic substances. The primary way of eliminating cholesterol is bile. Although bile has many organic and inorganic contents, bile acid is the most physiologically active component. Bile acids have a multitude of critical physiologic functions in our body. These include emulsification of dietary fat, absorption of fat and fat-soluble vitamins, maintaining glucose, lipid, and energy homeostasis, sustenance of intestinal epithelial integrity and epithelial cell proliferation, reducing inflammation in the intestine, and prevention of enteric infection due to its antimicrobial properties. But bile acids can be harmful in certain altered conditions like cholecystectomy, terminal ileal disease or resection, cholestasis, duodenogastric bile reflux, duodenogastroesophageal bile reflux, and bile acid diarrhea. Bile acids can have malignant potentials as well. There are also important diagnostic and therapeutic roles of bile acid and bile acid modulation.

Bile Acid-Related Regulation of Mucosal Inflammation and Intestinal Motility: From Pathogenesis to Therapeutic Application in IBD and Microscopic Colitis

Inflammatory bowel diseases (IBD) and microscopic colitis are chronic immune-mediated inflammatory disorders that affect the gastroenterological tract and arise from a complex interaction between the host’s genetic risk factors, environmental factors, and gut microbiota dysbiosis. The precise mechanistic pathways interlinking the intestinal mucosa homeostasis, the immunological tolerance, and the gut microbiota are still crucial topics for research. We decided to deeply analyze the role of bile acids in these complex interactions and their metabolism in the modulation of gut microbiota, and thus intestinal mucosa inflammation. Recent metabolomics studies revealed a significant defect in bile acid metabolism in IBD patients, with an increase in primary bile acids and a reduction in secondary bile acids. In this review, we explore the evidence linking bile acid metabolites with the immunological pathways involved in IBD pathogenesis, including apoptosis and inflammasome activation. Furthermore, we summarize the principal etiopathogenetic mechanisms of different types of bile acid-induced diarrhea (BAD) and its main novel diagnostic approaches. Finally, we discuss the role of bile acid in current and possible future state-of-the-art therapeutic strategies for both IBD and BAD.

Pathophysiology and Clinical Management of Bile Acid Diarrhea

Bile acid malabsorption (BAM) represents a common cause of chronic diarrhea whose prevalence is under-investigated. We reviewed the evidence available regarding the pathophysiology and clinical management of bile acid diarrhea (BAD). BAD results from dysregulation of the enterohepatic recirculation of bile acids. It has been estimated that 25–33% of patients with functional diarrhea and irritable bowel syndrome with diarrhea have BAM. Currently, the selenium homotaurocholic acid test is the gold standard for BAD diagnosis and severity assessment. However, it is an expensive method and not widely available. The validation of the utility in the clinical practice of several other serum markers, such as 7α-hydroxy-4-cholesten-3-one (C4) and the fibroblast growth factor 19 (FGF19) is ongoing. The first-line treatment of patients with BAD is bile acid sequestrants. Patients that are refractory to first-line therapy should undergo further diagnostics to confirm the diagnosis and to treat the underlying cause of BAD. An early and correct diagnosis of BAD would improve patient’s quality of life, avoiding additional diagnostic tests that burden health care systems. Considering the limited availability and tolerability of specific medications for BAD treatment, future research is awaited to identify other therapeutic approaches, such as gut microbiota modulating therapies.

Bile Acid Diarrhea in Adults and Adolescents

BACKGROUND

Bile acids are central to enterohepatic signaling pathways activated through natural receptors, farnesoid X receptor [FXR mediates synthesis of fibroblast growth factor-19 (FGF-19)], and G protein-coupled bile acid receptor 1 (GPBAR1, also known as TGR5). Although bile acid diarrhea (BAD) is more commonly encountered in ileal resection or disease, there is evidence documenting "idiopathic" BAD in about 20% of adolescents and 30% of adults presenting with chronic, non-bloody diarrhea often attributed to irritable bowel syndrome. Mechanism(s) leading to increased hepatic synthesis and colonic bile acid levels in "idiopathic" BAD include reduced synthesis of FGF-19 by the ileal mucosa, or genetic variation in hepatocyte proteins klotho β and FGF receptor 4 (FGFR4) that mediate negative feedback of bile acid synthesis.

PURPOSE

The objective of this review is to summarize the diagnosis of BAD in adults and adolescents. In addition to ⁷⁵ SeHCAT retention for diagnosis of BAD, studies have validated fasting serum 7αC4 and FGF-19, respectively, by-product and inhibitor of hepatic bile acid synthesis, as well as fecal bile acid measurements. These assays are widely available through reference laboratories, and they are being simplified (eg, measurement of primary fecal bile acids in a random stool sample). BAD has also been identified as a co-factor contributing to persistent diarrhea in other diseases in remission including inflammatory bowel disease, microscopic colitis, celiac disease, and neuroendocrine tumors. In summary, advances in diagnosis of BAD provide opportunities for generalists and pediatric and adult gastroenterologists to provide targeted treatment for BAD presenting as chronic non-bloody diarrhea.

Bile Acid Sequestrants for Hypercholesterolemia Treatment Using Sustainable Biopolymers: Recent Advances and Future Perspectives

Bile acids, the endogenous steroid nucleus containing signaling molecules, are responsible for the regulation of multiple metabolic processes, including lipoprotein and glucose metabolism to maintain homeostasis. Within our body, they are directly produced from their immediate precursors, cholesterol C (low-density lipoprotein C, LDL-C), through the enzymatic catabolic process mediated by 7-α-hydroxylase (CYP7A1). Bile acid sequestrants (BASs) or amphiphilic resins that are nonabsorbable to the human body (being complex high molecular weight polymers/electrolytes) are one of the classes of drugs used to treat hypercholesterolemia (a high plasma cholesterol level) or dyslipidemia (lipid abnormalities in the body); thus, they have been used clinically for more than 50 years with strong safety profiles as demonstrated by the Lipid Research Council-Cardiovascular Primary Prevention Trial (LRC-CPPT). They reduce plasma LDL-C and can slightly increase high-density lipoprotein C (HDL-C) levels, whereas many of the recent clinical studies have demonstrated that they can reduce glucose levels in patients with type 2 diabetes mellitus (T2DM). However, due to higher daily dosage requirements, lower efficacy in LDL-C reduction, and concomitant drug malabsorption, research to develop an "ideal" BAS from sustainable or natural sources with better LDL-C lowering efficacy and glucose regulations and lower side effects is being pursued. This Review discusses some recent developments and their corresponding efficacies as bile removal or LDL-C reduction of natural biopolymer (polysaccharide)-based compounds.

Emerging therapies in the management of Irritable Bowel Syndrome (IBS)

INTRODUCTION

Irritable bowel syndrome (IBS) is a common, symptom-based disorder of chronic abdominal pain and altered bowel habits. The pathogenesis of IBS is multifactorial, leading to the potential for the development of multiple, diverse treatment strategies. This mechanistic heterogeneity also leads to the realization that available therapies are only effective in a subset of IBS suffers. Current US Food and Drug Administration (FDA) approved therapies for IBS with diarrhea (IBS-D) and IBS with constipation (IBS-C) are reviewed. Limited symptom responses and side effect experiences lead to considerable patient dissatisfaction with currently available IBS treatments. Only a small percentage of IBS patients are on prescription therapies underscoring the potential market and need for additional therapeutic options.

AREAS COVERED

: Expanding on currently available therapies, the serotonergic and endogenous opioid receptor systems continue to be a focus of future IBS treatment development. Additional novel emerging therapies include the endogenous cannabinoid system, bile acid secretion and sequestration, and exploit our enhanced understanding of visceral sensory signaling and intestinal secretomotor function.

EXPERT OPINION

While challenges remain for the future development of IBS therapies, the diverse etiologies underlying the disorder present an opportunity for novel therapies. Hence, great potential is anticipated for future IBS treatment options.

Intestinal and Mucosal Microbiome Response to Oral Challenge of Enterotoxigenic Escherichia coli in Weaned Pigs

Enterotoxigenic Escherichia coli (ETEC) is closely associated with diarrhoea in children in resource-limited countries. This study aims to investigate the change of the mucosal microbiome and protein expression in the ileum induced by E. coli K88 (ETEC) using pigs as a model. Seven weaned male pigs were orally given ETEC (1 × 10⁹ CFU, n = 7), and the other seven received saline (CON, n = 7). Ileal tissues were obtained 48 hours after the ETEC challenge for both proteomic and mucosal microbiome analyses. Nine proteins were found with altered abundance between the two groups, including a decrease in FABP1 and FABP6, involved in bile acid circulation. The TLR-9 mediated pathway was also affected showing increased transcription of genes SIGIRR and MyD88. Correlations between the ileal proteins and mucosal bacterial taxa found included a positive correlation between Lactobacilllus and PPP3CA (r = 0.9, p < 0.001) and a negative correlation between Prevotella with CTNND1 (r = −0.7, p < 0.01). In conclusion, ETEC infection caused inflammation and impaired the circulation of bile acids and the mucosal microbiome may affect the expression of intestinal proteins. Further studies are needed to explain the exact roles of these affected processes in the pathogenesis of ETEC-triggered diarrhoea.

Interplay between gut microbiota and bile acids in diarrhoea-predominant irritable bowel syndrome: a review

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disease that disturbs the physiology and psychology of patients and increases the burden on families, the healthcare system, society, and economic development, affecting more and more people around the world. Despite the multiple factors that account for IBS remaining incompletely studied, emerging evidence demonstrated the abnormal changes in gut microbiota and bile acids (BAs) metabolism closely associated with IBS. Moreover, microbiota drives significant modifications for BAs, consisting of deconjugation, 7α-dehydroxylation, oxidation, epimerization, desulfation, esterification, and so on, while BAs, in turn, affect the microbiota directly or indirectly. In light of the complex connection among gut microbiota, BAs, and IBS, it is urgent to review the latest research progress in this field. In this review, we described the disorders of intestinal microecology and BAs profiles in IBS-D and also highlighted the cross-talk between gut microbiota and BAs in the context of IBS-D. Integrating these, we suggest that new therapeutic strategies targeting the microbiota-BAs axis for IBS-D, even for other related diseases caused by bacteria-bile acid dysbiosis should be expected.

Bile Acid Malabsorption as a Consequence of Cancer Treatment: Prevalence and Management in the National Leading Centre

The aim was to establish prevalence of bile acid malabsorption (BAM) and management in patients who underwent treatment for malignancy. Retrospective evaluation of data in patients seen within six months (August 2019-January 2020) was carried out. Demographic, nuclear medicine (Selenium Homocholic Acid Taurine (SeHCAT) scan result), clinical (previous malignancy, type of intervention (medication, diet), response to intervention) and laboratory (vitamin D, vitamin B12 serum levels) data were searched. In total, 265 consecutive patients were reviewed. Out of those, 87/265 (33%) patients (57 females, 66%) were diagnosed with BAM. Mean age was 59 +/- 12 years. The largest group were females with gynaecological cancer (35), followed by haematology group (15), colorectal/anal (13), prostate (9), upper gastrointestinal cancer (6), another previous malignancy (9). Severe BAM was most common in haematology (10/15; 67%) and gynaecological group (21/35; 60%). Medication and low-fat diet were commenced in 65/87 (75%), medication in 10/87 (11%), diet in 6/87 (7%). Colesevelam was used in 71/75 (95%). Symptoms improved in 74/87 (85%) patients. Vitamin D insufficiency/deficiency was diagnosed in 62/87 (71%), vitamin B12 deficiency in 39/87 (45%). BAM is a common condition in this cohort however treatments are highly effective.

Aqueous Tuber Extracts of Tylosema fassoglense (Kotschy ex Schweinf.) Torre and Hillc. (Fabaceae). Possess Significant In-Vivo Antidiarrheal Activity and Ex-Vivo Spasmolytic Effect Possibly Mediated by Modulation of Nitrous Oxide System, Voltage-Gated Calcium Channels, and Muscarinic Receptors

Tylosema fassoglense (TFG) is used as an antidiarrheal traditional medicine in Western Kenya. This study aimed to investigate the antidiarrheal activity of its aqueous extracts in-vivo and the putative mechanism (s) of action ex-vivo using Sprague-Dawley rats and New Zealand white rabbits respectively. The in-vivo antidiarrheal effects of the extract were evaluated in castor oil-induced diarrhea, the castor oil-induced enteropooling, and phenol red gastric motility tests. On the other hand, isolated rabbit's jejunal segments were used to evaluate the spasmolytic effect of TFG on spontaneous contraction, in acetylcholine-induced contraction, in presence of 80mMK⁺, calcium chloride-induced contraction as well as in presence of the following antagonists: naloxone, methylene blue, L-NAME, prazosin, and propranolol in the ex-vivo studies. The data were express as Mean ± S.E.M and analyzed by one-way ANOVA and Tukey's post hoc test in cases of significance which was set at p < 0.05. The extract was phytochemically characterized using Liquid chromatography Mass spectroscopy (LC-MS).The extract possessed significant inhibitory effect in the in-vivo experiments. The extract exhibited significant spasmolytic effect on both spontaneous contraction and in jejunal segment pre-contracted acetylcholine as well as in presence of 80mMK⁺ solution. It also attenuated the spasmogenic effect of various concentration of calcium chloride. The extract's spasmolytic effect was, however, significantly attenuated in presence of several antagonists (methylene blue and L-NAME) but the adrenergic blockers (prazosin and propranolol) had no significant effect in the ex-vivo studies. LC-MS identified thirty compounds where Proathocyanidin (11.54%), Syringic acid (7.30%), and 4-Hydroxybenzoic acid (6.19%) had the highest percentage abundance. In conclusion, the results obtained in this study partially validate the traditional uses of the tubers of this plant species as an antidiarrheal. These antidiarrheal effects are probably mediated via modulation of nitrous oxide pathway, voltage gated calcium channels, and muscarinic receptors.

Pharmacological and Parenteral Nutrition-Based Interventions in Microvillus Inclusion Disease

Microvillus inclusion disease (MVID) is a rare inherited and invariably fatal enteropathy, characterized by severe intractable secretory diarrhea and nutrient malabsorption. No cure exists, and patients typically die during infancy because of treatment-related complications. The need for alternative treatment strategies is evident. Several pharmacological interventions with variable successes have been tried and reported for individual patients as part of their clinical care. Unfortunately, these interventions and their outcomes have remained hidden in case reports and have not been reviewed. Further, recent advances regarding MVID pathogenesis have shed new light on the outcomes of these pharmacological interventions and offer suggestions for future clinical research and trials. Hence, an inventory of reported pharmacological interventions in MVID, their rationales and outcomes, and a discussion of these in the light of current knowledge is opportune. Together with a discussion on MVID-specific pharmacokinetic, -dynamic, and -genetic concerns that pose unique challenges regarding pharmacological strategies, we envision that this paper will aid researchers and clinicians in their efforts to develop pharmacological interventions to combat this devastating disease.

Antifungal activity and antidiarrheal activity via antimotility mechanisms of (-)-fenchone in experimental models

BACKGROUND

(-)-Fenchone is a bicyclic monoterpene present in essential oils of plant species, such as Foeniculum vulgare and Peumus boldus, used to treatment of gastrointestinal diseases. Pharmacological studies report its anti-inflammatory, antioxidant, and antinociceptive activity.

AIM

To investigate antidiarrheal activity related to gastrointestinal motility, intestinal secretion and antimicrobial activity.

METHODS

A castor oil-induced diarrhea model was used to evaluate antidiarrheal activity. Intestinal transit and gastric emptying protocols were used to assess a possible antimotility effect. Muscarinic receptors, presynaptic α₂-adrenergic and tissue adrenergic receptors, K_ATP channels, nitric oxide were investigated to uncover antimotility mechanisms of action and castor oil-induced enteropooling to elucidate antisecretory mechanisms. The antimicrobial activity was evaluated in the minimum inhibitory concentration model, the fractional inhibitory concentration index using the (-)-fenchone association method with standard antifungal agents.

RESULTS

(-)-Fenchone (75, 150 and 300 mg/kg) showed antidiarrheal activity, with a significant decrease in the evacuation index. This activity is possibly related to a percentage of reduced intestinal transit (75, 150 and 300 mg/kg). The antimotility effect of (-)-fenchone decreased in the presence of pilocarpine, yohimbine, propranolol, L-NG-nitroarginine methyl ester or glibenclamide. In the enteropooling model, no reduction in intestinal fluid weight was observed. (-)- Fenchone did not show antibacterial activity; on the other hand, inhibits the growth of strains of fungi with a minimum fungicide concentration of 32 μg/mL. However, when it was associated with amphotericin B, no synergism was observed.

CONCLUSION

The antidiarrheal effect of (-)-fenchone in this study involves antimotility effect and not involve antisecretory mechanisms. (-)-Fenchone presents antifungal activity; however, it did not show antibacterial activity.

Huangjinya Black Tea Alleviates Obesity and Insulin Resistance via Modulating Fecal Metabolome in High-Fat Diet-Fed Mice

SCOPE

Huangjinya is a light-sensitive tea mutant containing low levels of tea polyphenols. Currently, most studies focused on characteristics formation, free amino acid metabolism and phytochemical purification. The biological activity of Huangjinya black tea (HJBT) on metabolic syndrome regarding fecal metabolome modulation is unavailable and is studied herein.

METHODS AND RESULTS

High-fat diet (HFD)-fed mice are treated with HJBT for 9 weeks, various metabolic biomarkers and fecal metabolites are determined. HJBT reduces adipogenic and lipogenic gene expression, enhances lipolytic gene expression, decreases adipocyte expansion, and prevents the development of obesity. HJBT reduces lipogenic gene expression, increases fatty acid oxidation-related genes expression, which alleviates liver steatosis. HJBT enhances glucose/insulin tolerance, increases insulin/Akt signaling, attenuates hyperlipidemia and hyperglycemia, prevents the onset of insulin resistance. HJBT modulates bile acid metabolism, promotes secondary/primary bile acid ratio; increases short-chain fatty acids production, promotes saturated and polyunsaturated fatty acids content; reduces carnitines and phosphocholines, but increases myo-inositol content; decreases branched-chain and aromatic amino acids content; increases the metabolite content related to pentose phosphate pathway.

CONCLUSION

This study reported the association between fecal metabolome modulation and metabolism improvement due to HJBT administration, proposes HJBT as a dietary intervention for preventing obesity and metabolic disorders.

Bile acid diarrhoea: Current and potential methods of diagnosis

Chronic diarrhoea is common and mostly due to diarrhoea predominant irritable bowel syndrome. Diarrhoea predominant irritable bowel syndrome affects about 11% of the population; however, up to a third of these patients actually have bile acid diarrhoea. There are, therefore, more than one million sufferers of bile acid diarrhoea in the UK. Bile acid diarrhoea is caused by small bowel malabsorption of bile acids and the increased bile acids in the large intestine cause diarrhoea. Once diagnosed, the treatment of bile acid diarrhoea is simple and effective. Bile acid diarrhoea , however, is often not diagnosed because of a lack of easily available and reliable diagnostic methods. In the United Kingdom, the radiolabelled 23-seleno-25-homotaurocholic acid test is the gold-standard method of diagnosis. 23-seleno-25-homotaurocholic acid test, however, is expensive, inconvenient to the patient, involves radiation exposure and has limited availability. As such, a laboratory biomarker is desirable. This review briefly discusses the pathophysiology and management of bile acid diarrhoea and critically evaluates methods for its diagnosis, including serum 7α-hydroxy-4-cholesten-3-one, faecal bile acid measurement, serum fibroblast growth factor 19, urine-2-propanol, and the ¹⁴C-glycocholate breath and stool test.

The Role of Bile Acids in Chronic Diarrhea

Bile acids (BAs) are the central signals in enterohepatic communication, and they also integrate microbiota-derived signals into enterohepatic signaling. The tissue distribution and signaling pathways activated by BAs through natural receptors, farsenoid X receptor and G protein-coupled BA receptor 1 (GPBAR1, also known as Takeda G-coupled receptor 5), have led to a greater understanding of the mechanisms and potential therapeutic agents. BA diarrhea is most commonly encountered in ileal resection or disease, in idiopathic disorders (with presentation similar to functional diarrhea or irritable bowel syndrome with diarrhea), and in association with malabsorption such as chronic pancreatitis or celiac disease. Diagnosis of BA diarrhea is based on Se-homocholic acid taurine retention, 48-hour fecal BA excretion, or serum 7αC4; the latter being a marker of hepatic BA synthesis. BA diarrhea tends to be associated with higher body mass index, increased stool weight and stool fat, and acceleration of colonic transit. Biochemical markers of increased BA synthesis or excretion are available through reference laboratories. Current treatment of BA diarrhea is based on BA sequestrants, and, in the future, it is anticipated that farsenoid X receptor agonists may also be effective. The optimal conditions for an empiric trial with BA sequestrants as a diagnostic test are still unclear. However, such therapeutic trials are widely used in clinical practice. Some national guidelines recommend definitive diagnosis of BA diarrhea over empirical trial.

A Clostridia-rich microbiota enhances bile acid excretion in diarrhea-predominant irritable bowel syndrome

An excess of fecal bile acids (BAs) is thought to be one of the mechanisms for diarrhea-predominant irritable bowel syndrome (IBS-D). However, the factors causing excessive BA excretion remain incompletely studied. Given the importance of gut microbiota in BA metabolism, we hypothesized that gut dysbiosis might contribute to excessive BA excretion in IBS-D. By performing BA-related metabolic and metagenomic analyses in 290 IBS-D patients and 89 healthy volunteers, we found that 24.5% of IBS-D patients exhibited excessive excretion of total BAs and alteration of BA-transforming bacteria in feces. Notably, the increase in Clostridia bacteria (e.g., C. scindens) was positively associated with the levels of fecal BAs and serum 7α-hydroxy-4-cholesten-3-one (C4), but negatively correlated with serum fibroblast growth factor 19 (FGF19) concentration. Furthermore, colonization with Clostridia-rich IBS-D fecal microbiota or C. scindens individually enhanced serum C4 and hepatic conjugated BAs but reduced ileal FGF19 expression in mice. Inhibition of Clostridium species with vancomycin yielded opposite results. Clostridia-derived BAs suppressed the intestinal FGF19 expression in vitro and in vivo. In conclusion, this study demonstrates that the Clostridia-rich microbiota contributes to excessive BA excretion in IBS-D patients, which provides a mechanistic hypothesis with testable clinical implications.

IBD and Bile Acid Absorption: Focus on Pre-clinical and Clinical Observations

Inflammatory bowel disease (IBD) causes chronic inflammation affecting the GI tract. It is classified as consisting of Crohn’s Disease (CD) and Ulcerative Colitis (UC). Bile Acid absorption is altered in both pre-clinical models of Inflammatory Bowel Disease (IB) and in human IBD. The bile acid transporter apical sodium dependent bile acid transporter (ASBT) showed decreased expression in rats with TNBS colitis. Decreased ASBT expression has also been described in murine, canine and rabbit models of intestinal inflammation. Human IBD studies have shown that an inflamed ileum can interrupt enterohepatic recirculation of bile acid, which could be due to inflammatory cytokine induced repression of the ASBT promoter. There are different hypotheses as to why ASBT is downregulated during CD. In addition, one study has demonstrated the beneficial effect of a glucocorticoid on ASBT expression, when treating IBD. Our aim in this paper was to systematically review various aspects of bile acid malabsorption in animal models of intestinal inflammation, as well as in IBD.

Mechanism of Asbt (Slc10a2)-related bile acid malabsorption in diarrhea after pelvic radiation

Background: Radiation is a mode of treatment for many pelvic malignancies, most of which originate in the gynecologic, gastrointestinal, and genitourinary systems. However, the healthy gut is unavoidably included in the irradiation volume, resulting in undesirable results that manifest as radiation-induced diarrhea (RID), which is the most common side effect of radiation therapy and significantly affects the patients' quality of life. This study aimed to investigate the potential mechanism of diarrhea after pelvic radiotherapy in rats based on the effect of radiation on bile acid homeostasis and sodium-dependent bile acid transporter (Asbt).Methods: In this experimental study, male Sprague-Dawley rats were divided into the following groups - pelvic irradiation, cholestyramine-concurrent radiation, and control groups. The rats in the pelvic irradiation group were irradiated in the pelvic region with 2 Gy per day for five consecutive days. The total bile acid (TBA) levels in the ileum, colon, and feces were measured using automatic biochemical analyzer, and the levels of individual bile acids were evaluated by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). The mRNA and protein expression of Asbt in ileum were assessed by qRT-PCR and Western blot assay. The rats in the cholestyramine-concurrent radiation group were administered with cholestyramine, a bile acid-chelating resin, and concurrent radiation for 5 days. The body weight of rats was monitored daily, and the degree of diarrhea was scored.Results: Diarrhea was observed at 2 and 3 days post-pelvic radiation. The TBA levels were significantly decreased at 4 and 5 days post-radiation in the ileum (p < .01, p < .01) and increased at 4 and 5 days post-radiation in the colon (p < .05, p < .05). The fecal excretions of TBA were significantly increased at 3, 4, and 5 days post-radiation (p < .05). The levels of individual bile acids were significantly decreased in the ileum and increased in the colon and feces, post-radiation. The mRNA and protein expression of Asbt in the ileum gradually decreased with increasing days of pelvic radiation and significantly decreased at 3 and 5 days post-radiation, respectively. Furthermore, a significant decrease in body weight was observed post-pelvic radiation, and cholestyramine administration did not reverse the weight loss. However, the incidence of RID was decreased after administration of cholestyramine.Conclusions: Bile acid malabsorption is partially responsible for RID post-pelvic radiation in rats, and the potential mechanism is related to the downregulation of the ileal Asbt.

Canadian Association of Gastroenterology Clinical Practice Guideline on the Management of Bile Acid Diarrhea

BACKGROUND & AIMS

Chronic diarrhea affects about 5% of the population overall. Altered bile acid metabolism is a common but frequently undiagnosed cause.

METHODS

We performed a systematic search of publication databases for studies of assessment and management of bile acid diarrhea (BAD). The certainty (quality) of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation approach. Patient population, intervention, comparator, and outcome questions were developed through an iterative process and were voted on by a group of specialists.

RESULTS

The certainty of evidence was generally rated as very low. Therefore, 16 of 17 recommendations are conditional. In patients with chronic diarrhea, consideration of risk factors (terminal ileal resection, cholecystectomy, or abdominal radiotherapy), but not additional symptoms, was recommended for identification of patients with possible BAD. The group suggested testing using ⁷⁵selenium homocholic acid taurine (where available) or 7α-hydroxy-4-cholesten-3-one, including patients with irritable bowel syndrome with diarrhea, functional diarrhea, and Crohn's disease without inflammation. Testing was suggested over empiric bile acid sequestrant therapy (BAST). Once remediable causes are managed, the group suggested cholestyramine as initial therapy, with alternate BAST when tolerability is an issue. The group suggested against BAST for patients with extensive ileal Crohn's disease or resection and suggested alternative antidiarrheal agents if BAST is not tolerated. Maintenance BAST should be given at the lowest effective dose, with a trial of intermittent, on-demand administration, concurrent medication review, and reinvestigation for patients whose symptoms persist despite BAST.

CONCLUSIONS

Based on a systematic review, BAD should be considered for patients with chronic diarrhea. For patients with positive results from tests for BAD, a trial of BAST, initially with cholestyramine, is suggested.

Canadian Association of Gastroenterology Clinical Practice Guideline on the Management of Bile Acid Diarrhea

Background and Aims

Chronic diarrhea affects about 5% of the population overall. Altered bile acid metabolism is a common but frequently undiagnosed cause.

Methods

We performed a systematic search of publication databases for studies of assessment and management of bile acid diarrhea (BAD). The certainty (quality) of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation approach. Patient population, intervention, comparator and outcome questions were developed through an iterative process and were voted on by a group of specialists.

Results

The certainty of evidence was generally rated as very low. Therefore, 16 of 17 recommendations are conditional. In patients with chronic diarrhea, consideration of risk factors (terminal ileal resection, cholecystectomy or abdominal radiotherapy), but not additional symptoms, was recommended for identification of patients with possible BAD. The group suggested testing using ⁷⁵selenium homocholic acid taurine (where available) or 7α-hydroxy-4-cholesten-3-one, including patients with irritable bowel syndrome with diarrhea, functional diarrhea and Crohn's disease without inflammation. Testing was suggested over empiric bile acid sequestrant therapy (BAST). Once remediable causes are managed, the group suggested cholestyramine as initial therapy, with alternate BAST when tolerability is an issue. The group suggested against BAST for patients with extensive ileal Crohn's disease or resection and suggested alternative antidiarrheal agents if BAST is not tolerated. Maintenance BAST should be given at the lowest effective dose, with a trial of intermittent, on-demand administration, concurrent medication review and reinvestigation for patients whose symptoms persist despite BAST.

Conclusions

Based on a systematic review, BAD should be considered for patients with chronic diarrhea. For patients with positive results from tests for BAD, a trial of BAST, initially with cholestyramine, is suggested.

Etiologies of Long-Term Postcholecystectomy Symptoms: A Systematic Review

BACKGROUND

Cholecystectomy does not relieve abdominal symptoms in up to 40% of patients. With 700,000 cholecystectomies performed in the US, annually, about 280,000 patients are left with symptoms, making this a serious problem. We performed a systematic review to determine the different etiologies of long-term postcholecystectomy symptoms with the aim to provide guidance for clinicians treating these patients.

METHODS

A systematic search of the literature was performed using MEDLINE, EMBASE, and Web of Science. Articles describing at least one possible etiology of long-term symptoms after a laparoscopic cholecystectomy were included in this review. Long-term symptoms were defined as abdominal symptoms that were present at least four weeks after cholecystectomy, either persistent or incident. The etiologies of persistent and incident symptoms after LC and the mechanism or hypothesis behind the etiologies are provided. If available, the prevalence of the discussed etiology is provided.

RESULTS

The search strategy identified 3320 articles of which 130 articles were included. Etiologies for persistent symptoms were residual and newly formed gallstones (41 studies, prevalence ranged from 0.2 to 23%), coexistent diseases (64 studies, prevalence 1-65%), and psychological distress (13 studies, no prevalence provided). Etiologies for incident symptoms were surgical complications (21 studies, prevalence 1-3%) and physiological changes (39 studies, prevalence 16-58%). Sphincter of Oddi dysfunction (SOD) was reported as an etiology for both persistent and incident symptoms (21 studies, prevalence 3-40%).

CONCLUSION

Long-term postcholecystectomy symptoms vary amongst patients, arise from different etiologies, and require specific diagnostic and treatment strategies. Most symptoms after cholecystectomy seem to be caused by coexistent diseases and physiological changes due to cholecystectomy. The outcome of this research is summarized in a decision tree to give clinical guidance on the treatment of patients with symptoms after cholecystectomy.

Post-infectious Irritable Bowel Syndrome: A Narrative Review

The Irritable bowel syndrome (IBS) is a functional disorder of alimentary system, which may be caused by infectious gastroenteritis determined as post infectious irritable bowel syndrome (PI-IBS). The prevalence of PI-IBS is reported to be 4-36% in patients with infectious gastroenteritis. The exact mechanism leading to PI-IBS is not fully understood and some factors pertaining to infectious agent and host response may have a role. Rome IV diagnostic criteria provided new definition for PI-IBS. Though it is now considered a well-defined functional disorder of gastrointestinal system, no specific treatment is yet available for PI-IBS. This article reviews the latest issues on these heading about PI-IBS.

Gut Movements: A Review of the Physiology of Gastrointestinal Transit

The well-regulated mechanisms of intestinal transit favor aboral movement of intestinal contents during the formation of normal stool. Electrical pacemakers initiate mechanical smooth muscular propulsion under regulation by the enteric nervous system-a function of the "brain-gut axis." Several unique intestinal motor patterns function in concert to enhance the activities of intestinal transit. Development of pharmacologic targets of intestinal transit mechanisms afford clinicians control in the management of functional gastrointestinal disorders. This review highlights the important physiologic events of intestinal transit, discusses selected pharmacologic and neuromodulators involved in these processes, and provides relevant clinical correlates to physiologic events.

Impact of gastrointestinal disease states on oral drug absorption – implications for formulation design – a PEARRL review

Objectives

Drug product performance in patients with gastrointestinal (GI) diseases can be altered compared to healthy subjects due to pathophysiological changes. In this review, relevant differences in patients with inflammatory bowel diseases, coeliac disease, irritable bowel syndrome and short bowel syndrome are discussed and possible in vitro and in silico tools to predict drug product performance in this patient population are assessed.

Key findings

Drug product performance was altered in patients with GI diseases compared to healthy subjects, as assessed in a limited number of studies for some drugs. Underlying causes can be observed pathophysiological alterations such as the differences in GI transit time, the composition of the GI fluids and GI permeability. Additionally, alterations in the abundance of metabolising enzymes and transporter systems were observed. The effect of the GI diseases on each parameter is not always evident as it may depend on the location and the state of the disease. The impact of the pathophysiological change on drug bioavailability depends on the physicochemical characteristics of the drug, the pharmaceutical formulation and drug metabolism. In vitro and in silico methods to predict drug product performance in patients with GI diseases are currently limited but could be a useful tool to improve drug therapy.

Summary

Development of suitable in vitro dissolution and in silico models for patients with GI diseases can improve their drug therapy. The likeliness of the models to provide accurate predictions depends on the knowledge of pathophysiological alterations, and thus, further assessment of physiological differences is essential.