The role of bile acids in functional GI disorders

Unravelling the therapeutic landscape of bile acid-based therapies in gastrointestinal disorders

ABSTRACT

Bile acids serve as endogenous ligands for nuclear and cell membrane receptors and play a crucial role in bile acid and lipid metabolism. These detergent-like compounds promote bile flow and aid in the absorption of dietary fats and fat-soluble vitamins in the intestine. Synthesized in the liver as end products of cholesterol catabolism, bile acids exhibit a chemical structure comprising a nucleus and a side chain featuring a carboxyl group, with diverse steric arrangements and potential polar substituents. Critical interactions occur between bile acid species and various nuclear and cell membrane receptors, including the farnesoid X receptor and G-protein-coupled bile acid receptor 1. This research aimed to review the literature on bile acids and their roles in treating different diseases. Currently, numerous investigations are concentrating on specific bile acid species that target nuclear receptors in the gastrointestinal system, aiming to improve the treatment of conditions such as nonalcoholic fatty liver disease. Given the global attention this topic has garnered from research groups, it is considered relatively new, thus anticipating some gaps or incomplete data. Bile acid species have a significant therapeutic promise, especially in their ability to activate or inhibit nuclear receptors, such as farnesoid X receptor. This research provides to offer essential information for scientists and medical practitioners interested in discovering new studies that underscore the importance of bile acids in ameliorating and impeding the progression of disorders. Furthermore, it opens avenues for previously overlooked bile acid-based therapies.

Efficacy and Safety of Elobixibat in Parkinson's Disease with Chronic Constipation: CONST-PD Study

BACKGROUND

Chronic constipation is a common digestive complication of Parkinson's disease (PD).

OBJECTIVES

To verify the usefulness of elobixibat, an ileal bile acid transporter inhibitor, for chronic constipation in PD.

METHODS

This double-blind, placebo-controlled study consisted of a 2-week observation/washout period and a 4-week treatment period. All patients received a Bowel Movement Diary at Week -2 and were allocated to elobixibat (10 mg) or placebo at Week 0. Patients visited at Weeks 2 and 4 to report daily spontaneous bowel movements (SBM), stool form, drug use, quality of life (QOL), and safety. Changes in these parameters were assessed.

RESULTS

The study included 38 patients in the elobixibat group and 39 in the placebo group, and 37 each completed the study. SBM frequency/week (mean ± standard deviation) increased significantly from 4.2 ± 2.6 at baseline to 5.9 ± 3.2 at Week 4 in the elobixibat group (P = 0.0079), but not in the placebo group (4.5 ± 2.7 to 5.3 ± 3.5; P = 0.0889). On analysis of covariance, the between-group difference in frequency changes at Week 4 (primary endpoint) was not significant after adjustment by baseline and sex (point estimate = 0.8; 95% confidence interval = -0.57 to 2.09, P = 0.2601), although a significant difference (P = 0.0011) was evidenced at Week 1 by a similar analysis. Stool form and scores of satisfaction and stigma were improved by elobixibat. Adverse events were as previously reported.

CONCLUSIONS

Elobixibat improved the SBM frequency, though the defined primary endpoint was not evidenced. QOL parameters (stool consistency and treatment satisfaction) were also improved. Elobixibat may have therapeutic benefits in PD patients suffering from chronic constipation.

TRIAL REGISTRATION INFORMATION

Trial Registration Number: JPRN-jRCTs031200172 (submitted: October 26, 2020; first patient enrolment: December 23, 2020; https://jrct.niph.go.jp/en-latest-detail/jRCTs031200172).

Effects of Prebiotic Yeast Mannan on Gut Health and Sleep Quality in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Study

Human gut health is closely related to sleep. We aimed to evaluate the efficacy of yeast mannan (YM) in improving bowel habits and sleep quality, along with metabolomics in fecal samples. A total of 40 healthy adults (age range, 22-64 years) with discomfort in defecation were enrolled and randomly allocated to receive either YM (n = 20; 1.1 g/day) or placebo (n = 20) for four weeks. Participants recorded their defecation habits throughout the test periods. Sleep electroencephalogram (EEG) recording using an EEG device and fecal sampling were performed pre- and post-treatment. The YM group significantly increased defecation frequency and stool volumes compared to the placebo group. After 4 weeks of treatment, the non-REM sleep stage 3 (N3) duration in the YM group was significantly higher than that in the placebo group. YM ingestion significantly lengthened total time in bed (TIB) and significantly shortened N3 latency compared to placebo intake during the trial. The metabolomics analysis found a total of 20 metabolite differences between the YM and placebo groups. As a result of stepwise linear regression, changes in fecal propionate and gamma-aminobutyric acid (GABA) levels were identified as the primary factors explaining changes in TIB and N3 latency, respectively. Our findings suggest that the prebiotic YM could be beneficial to gut health and sleep quality.

Elobixibat improves rectal sensation in patients with chronic constipation aged ≥60 years: a randomised placebo-controlled study

OBJECTIVE

High rectal sensory thresholds (RSTs) are associated with chronic constipation (CC), especially in older patients. Bile acids (BAs) affect the RSTs of healthy individuals. Here, we aimed to investigate the effects of the BA transporter inhibitor elobixibat in patients with CC aged ≥60 years.

DESIGN

We prospectively compared the RSTs of 17 patients with CC aged ≥60 years with those of 9 healthy individuals of the same age range. We next performed a prospective, randomised, parallel-group, double-blind, placebo-controlled clinical trial of 17 patients with CC who administered elobixibat or placebo daily for 1 week. Using barostat methodology, their first constant sensation volume (FCSV), defaecatory desire volume (DDV), and maximum tolerable volume (MTV) thresholds; their rectal compliance; and their faecal BA concentrations were measured before and after treatment.

RESULTS

There were no significant differences in the RSTs of healthy individuals and patients with CC, but all of these tended to be higher in the latter group. Elobixibat increased the desire to defaecate, significantly reduced the threshold for FCSV (p=0.0018), and tended to reduce the threshold for DDV (p=0.0899) versus placebo. However, there were no differences in the MTV or rectal compliance of the two groups. The total faecal BA concentration increased, and particularly that of secondary BAs in the elobixibat group. Elobixibat was most efficacious in participants with a longer duration of CC and a history of treatment for CC.

CONCLUSION

Elobixibat reduces the RSTs of patients with CC aged ≥60 years, which may be important for its therapeutic effects.

TRIAL REGISTRATION NUMBER

jRCTs061200030.

Treatment of Chronic Constipation using Elobixibat in a Real-World Setting: A Retrospective Cohort Study using an Electronic Medical Records Database in Japan

Background

Chronic constipation is a common condition affecting people of all ages; therefore, the socioeconomic burden of chronic constipation is nonnegligible. Elobixibat (ELO), an ileal bail acid transport inhibitor, was launched in Japan in 2018. However, evidence of its use in diverse populations is limited.

Objectives

This study aimed to evaluate the prescription of ELO, risk factors associated with ELO discontinuation, and the continuation of stimulants or saline laxatives during ELO treatment in a real-world setting using an extensive electronic medical records database that primarily includes data from acute-care hospitals.

Methods

Data of patients prescribed for ELO from April 1, 2018, to March 31, 2022, were extracted from the database. The discontinuation of ELO and stimulant or saline laxatives during ELO treatment was evaluated using the Kaplan-Meier method. The Cox proportional hazards model evaluated risk factors associated with laxative discontinuation.

Results

In total, 11,062 patients were evaluated. The rate of ELO discontinuation within 360 days of initiation was 78.7%. Hospitalized at the ELO initiation, stage 5 chronic kidney disease, and diagnosis of constipation by departments of obstetrics and gynecology or by departments of malignant neoplasm were identified as risk factors for discontinuation. Diagnosis of constipation, diabetes mellitus, Parkinson's disease, and previous laxative treatment was associated with a lower risk of ELO discontinuation. The prescription rate of stimulants and saline laxatives markedly decreased after ELO initiation; furthermore, nearly half of patients who were continuously prescribed ELO discontinued these laxatives within 360 days.

Conclusions

The discontinuation of ELO was associated with various factors and using ELO may be beneficial in the withdrawal of concurrent stimulants and saline laxatives. These findings may help effectively manage chronic constipation.

Development of functional gastrointestinal disorder symptoms following laparoscopic cholecystectomy: a prospective cohort study

Background

The casual relationship between the role of cholecystectomy and functional gastrointestinal disorders (FGIDs) are a controversial clinical challenge. This study aimed to investigate: (1) the overlap of FGIDs before cholecystectomy and its long-term outcome after surgery in patients with symptomatic cholelithiasis, and (2) the incidence of new-onset FGIDs after cholecystectomy.

Methods

Patients with symptomatic gallstone disease who underwent elective, laparoscopic cholecystectomy were prospectively enrolled. Healthy populations who underwent medical check-ups were selected as age- and sex-matched controls. Questionnaires regarding sociodemographic characteristics, gastrointestinal symptoms and a somatization symptom checklist (SSC) were completed at baseline and 12 months thereafter.

Results

The prevalence of all FGID symptoms before cholecystectomy were significantly higher in the group of patients with symptomatic cholecystolithiasis compared to the control group. In cholecystectomy group, the preoperative FGID symptoms improved after surgery, except for chronic diarrhea. Compared to the controls, the new-onset FGIDs, including functional dyspepsia (14.8% vs. 6.9%; p = 0.040), functional diarrhea (6.6% vs. 0.2%; p < 0.001), and chronic abdominal pain (11.9% vs. 4.4%; p = 0.024), were more common at 1 year after cholecystectomy. Somatization was independent predictors of new-onset dyspepsia and abdominal pain, while newly occurring diarrhea was not realted to somatization.

Conclusion

Overlap of FGIDs was common in patients with symptomatic cholelithiasis before surgery and at follow-up 1 year after cholecystectomy. Furthermore, new-onset FGIDs could be occurred after cholecystectomy. Therefore, a delicate diagnostic approaches and appropriate treatments about co-existent FGIDs should be given in patients with cholelithiasis before and after cholecystectomy.

The regulatory effects of fucoidan and laminarin on functional dyspepsia mice induced by loperamide

Gastrointestinal dysmotility is a common cause of functional dyspepsia. As two kinds of polysaccharides derived from brown algae, fucoidan and laminarin possess many physiological properties; however, their relative abilities in regulating gastrointestinal motility have not been illustrated yet. In this study, we aimed to investigate the regulatory effect of fucoidan and laminarin on functional dyspepsia mice induced by loperamide. Mice with gastrointestinal dysmotility were treated with fucoidan (100 and 200 mg per kg bw) and laminarin (50 and 100 mg per kg bw). As a result, fucoidan and laminarin reversed the dysfunction mainly through regulating gastrointestinal hormones (motilin and ghrelin), the cholinergic pathway, the total bile acid level, c-kit protein expression, and gastric smooth muscle contraction-related gene expression (ANO1 and RYR3). Moreover, fucoidan and laminarin intervention modulated the gut microbiota profile including the altered richness of Muribaculaceae, Lachnospiraceae, and Streptococcus. The results indicated that fucoidan and laminarin may restore the rhythm of the migrating motor complex and regulate gut microecology. In conclusion, we provided evidence to support that fucoidan and laminarin might have potential abilities to regulate gastrointestinal motility.

Serum total bile acid levels assist in the prediction of acute intussusception with abdominal type Henoch-Schonlein purpura in children

Background

The severe acute abdomen associated with Henoch-Schonlein purpura (HSP) is an acute intussusception (AI). There is no reliable specific marker for AI with abdominal-type HSP. The serum total bile acid (TBA) level is a new prognostic marker associated with the severity of intestinal inflammation. The purpose of this study was to identify the prognostic value of serum TBA levels for the diagnosis of AI in children with abdominal-type HSP.

Methods

A retrospective study of 708 patients with abdominal-type HSP was conducted, with demographic data, clinical symptoms, hepatic function index, immune function markers, and clinical outcomes assessed. Patients were divided into two groups: HSP (613 patients) and HSP with AI (95 patients). The data were analysed using SPSS 22.0.

Results

Of the 708 patients, the serum TBA levels were higher in the HSP with AI group than in the HSP group (P < 0.05). Logistic regression analysis showed that vomiting (OR = 396.492, 95% CI = 14.93-10,529.67, P < 0.001), haematochezia (OR = 87.436, 95% CI = 5.944-1,286.214, P = 0.001), TBA (OR = 16.287, 95% CI = 4.83-54.922, P < 0.001), and D-dimer (OR = 5.987, 95% CI = 1.892-15.834, P = 0.003) were independent risk factors for abdominal-type HSP with AI. Receiver operating characteristic (ROC) curve analysis showed that the optimal cut-off serum TBA value (sensitivity = 91.58%, specificity = 84.67%, AUC = 93.6524%) was >3 μmol/L for predicting AI in children with abdominal-type HSP. In this group of HSP patients with AI, a serum TBA level ≥6.98 μmol/L was significantly associated with an increased incidence of operative treatment (51.85% vs. 75.61%, P = 0.0181), intestinal necrosis (9.26% vs. 29.27%, P = 0.0117), and length of hospital stay [15.76 ± 5.31 vs. 10.98 ± 2.83 (days), P < 0.0001].

Conclusion

In children with HSP and AI, the serum TBA level was significantly higher. A novel but promising haematological indicator, the serum TBA level, helps identify HSP with and without AI and predicts intestinal necrosis in HSP with AI.

Gut microbiota: a new avenue to reveal pathological mechanisms of constipation

Constipation is very pervasive all over the world. It is a common multifactorial gastrointestinal disease, and its etiology and pathomechanism are not completely clear. Now, increasing evidence shows that intestinal flora is closely related to constipation. Intestinal flora is the largest microbiota in the human body and has powerful metabolic functions. Intestinal flora can produce a variety of metabolites, such as bile acids, short-chain fatty acids, tryptophan metabolites, and methane, which have important effects on intestinal motility and secretion. The host can also monitor the intestinal flora and regulate gut dysbacteriosis in constipation. To explore the relationship between intestinal flora and host, the combination of multiomics technology has become the powerful and effective method. Furthermore, the homeostasis restoration of intestinal flora also provides a new strategy for the treatment of constipation. This review aims to explore the interaction between intestinal flora and host in constipation, which contributes to disclose the pathogenesis of constipation and the development of novel drugs for the treatment of constipation from the perspective of intestinal flora. KEY POINTS: • This review highlights the regulation of gut microbiota on the intestinal motility and secretion of host. • The current review gives an insight into the role of the host on the recognition and regulation of intestinal ecology under constipation. • The article also introduces some novel methods of current gut microbiota research and gut microbiota-based constipation therapies.

Abnormal bile acid metabolism is an important feature of gut microbiota and fecal metabolites in patients with slow transit constipation

Destructions in the intestinal ecosystem are implicated with changes in slow transit constipation (STC), which is a kind of intractable constipation characterized by colonic motility disorder. In order to deepen the understanding of the structure of the STC gut microbiota and the relationship between the gut microbiota and fecal metabolites, we first used 16S rRNA amplicon sequencing to evaluate the gut microbiota in 30 STC patients and 30 healthy subjects. The α-diversity of the STC group was changed to a certain degree, and the β-diversity was significantly different, which indicated that the composition of the gut microbiota of STC patients was inconsistent with healthy subjects. Among them, Bacteroides, Parabacteroides, Desulfovibrionaceae, and Ruminiclostridium were significantly upregulated, while Subdoligranulum was significantly downregulated. The metabolomics showed that different metabolites between the STC and the control group were involved in the process of bile acids and lipid metabolism, including taurocholate, taurochenodeoxycholate, taurine, deoxycholic acid, cyclohexylsulfamate, cholic acid, chenodeoxycholate, arachidonic acid, and 4-pyridoxic acid. We found that the colon histomorphology of STC patients was significantly disrupted, and TGR5 and FXR were significantly downregulated. The differences in metabolites were related to changes in the abundance of specific bacteria and patients’ intestinal dysfunction. Analysis of the fecal genomics and metabolomics enabled separation of the STC from controls based on random forest model prediction [STC vs. control (14 gut microbiota and metabolite biomarkers)—Sensitivity: 1, Specificity: 0.877]. This study provided a perspective for the diagnosis and intervention of STC related with abnormal bile acid metabolism.

Role of gut microbiota-derived signals in the regulation of gastrointestinal motility

The gastrointestinal (GI) tract harbors trillions of commensal microbes, called the gut microbiota, which plays a significant role in the regulation of GI physiology, particularly GI motility. The GI tract expresses an array of receptors, such as toll-like receptors (TLRs), G-protein coupled receptors, aryl hydrocarbon receptor (AhR), and ligand-gated ion channels, that sense different gut microbiota-derived bioactive substances. Specifically, microbial cell wall components and metabolites, including lipopeptides, peptidoglycan, lipopolysaccharides (LPS), bile acids (BAs), short-chain fatty acids (SCFAs), and tryptophan metabolites, mediate the effect of gut microbiota on GI motility through their close interactions with the enteroendocrine system, enteric nervous system, intestinal smooth muscle, and immune system. In turn, GI motility affects the colonization within the gut microbiota. However, the mechanisms by which gut microbiota interacts with GI motility remain to be elucidated. Deciphering the underlying mechanisms is greatly important for the prevention or treatment of GI dysmotility, which is a complication associated with many GI diseases, such as irritable bowel syndrome (IBS) and constipation. In this perspective, we overview the current knowledge on the role of gut microbiota and its metabolites in the regulation of GI motility, highlighting the potential mechanisms, in an attempt to provide valuable clues for the development of gut microbiota-dependent therapy to improve GI motility.

Colonic bacterial diversity and dysbiosis in active microscopic colitis as compared to chronic diarrhoea and healthy controls: effect of polyethylene glycol after bowel lavage for colonoscopy

Background

Most microbiota studies in microscopic colitis patients are performed after diagnostic colonoscopy without considering the potential effect of colonic lavage. Patients may achieve clinical remission after colonoscopy and it is unknown whether lavage-induced changes play a role.

Aim

To assess the effect of polyethylene glycol (PEG) colonic lavage on clinical remission rate, microbial diversity, microbial dysbiosis index and specific microbial changes in patients with active microscopic colitis as compared to other diarrhoeal diseases and healthy controls.

Methods

Fifty-five consecutive patients presenting chronic watery diarrhoea and 12 healthy controls were included. Faecal samples were collected three days before and 30 days after PEG in patients and controls for microbiome analysis.

Results

Clinical remission was observed in 53% of microscopic colitis patients, and in 32% of non-microscopic colitis patients (p = 0.16). Considering patients with persisting diarrhoea after colonoscopy, 71% of non-microscopic colitis patients had bile acid diarrhoea. Baseline Shannon Index was lower in diarrhoea groups than in healthy controls (p = 0.0025); there were no differences between microscopic colitis, bile-acid diarrhoea and functional diarrhoea. The microbial dysbiosis index was significantly higher in microscopic colitis than in bile acid diarrhoea plus functional diarrhoea (p = 0.0095), but no bacterial species showed a significantly different relative abundance among the diarrheal groups.

Conclusions

Dysbiosis is a feature in active microscopic colitis, but loss of microbial diversity was similar in all diarrheal groups, suggesting that faecal microbial changes are not due to microscopic colitis itself but associated with stool form. A considerable number of microscopic colitis patients achieved clinical remission after colonoscopy, but we were unable to demonstrate related PEG-induced changes in faecal microbiome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02392-w.

Late-Stage Glioma Is Associated with Deleterious Alteration of Gut Bacterial Metabolites in Mice

Brain-gut axis refers to the bidirectional functional connection between the brain and the gut, which sustains vital functions for vertebrates. This connection also underlies the gastrointestinal (GI) comorbidities associated with brain disorders. Using a mouse model of glioma, based on the orthotopic injection of GL261 cell line in syngeneic C57BL6 mice, we show that late-stage glioma is associated with GI functional alteration and with a shift in the level of some bacterial metabolites in the cecum. By performing cecal content transfer experiments, we further show that cancer-associated alteration in cecal metabolites is involved in end-stage disease progression. Antibiotic treatment results in a slight but significant delay in mice death and a shift in the proportion of myeloid cells in the brain tumor environment. This work rationally considers microbiota modulating strategies in the clinical management of patients with late-stage glioma.

Investigating the efficacy and safety of elobixibat, an ileal bile acid transporter inhibitor, in patients with Parkinson's disease with chronic constipation: a multicentre, placebo-controlled, randomised, double-blind, parallel-group stud (CONST-PD)

INTRODUCTION

Chronic constipation worsens the quality of life (QOL) of patients with Parkinson's disease (PD). Elobixibat, an ileal bile acid transporter inhibitor, is a useful laxative, but its effect on chronic constipation in patients with PD remains unclear. Therefore, we designed a placebo-controlled, randomised, double-blind study to investigate the efficacy and safety of elobixibat in patients with PD with chronic constipation.

METHODS AND ANALYSIS

The study will consist of 2-week observation and 4-week treatment periods. Patients with clinically established PD will record the status of spontaneous bowel movements and use of rescue medications/concomitant medications in a Bowel Movement Diary from the start of the observation period at visit 1 (week -2). At visit 2 (week 0), patients will be assessed for final registration based on the diary records and physical examinations, and allocated to either the elobixibat or placebo group. Daily intake of the investigational drug will be recorded in the diary. Patients will undergo laboratory tests and answer constipation-related, PD-related and QOL-related questionnaires at visits 2 and 4 (week 4). Subjective symptoms and objective findings will be collected at visits 2, 3 (week 2) and 4. Since patients' motor function might be improved by treatment of constipation, the use of dopamine preparations will also be monitored. Bowel movement data and other parameters will be compared between groups.Safety information will be collected as adverse events, specifically focusing on those occurring in association with study conduct.

ETHICS AND DISSEMINATION

This study will be conducted in accordance with the Helsinki Declaration, the Clinical Trials Act of the Japan Ministry of Health, Labour and Welfare, and related laws and regulations. The study was approved by the Juntendo University Certified Review Board. The results will be disseminated through an online study registry (Japan Registry of Clinical Trials), presented at scientific conferences, and published in medical journals.

TRIAL REGISTRATION NUMBER

JPRN-jRCTs031200172; Pre-results.

Paeoniflorin Improved Constipation in the Loperamide-Induced Rat Model via TGR5/TRPA1 Signaling-Mediated 5-Hydroxytryptamine Secretion

Slow transit constipation (STC) is a common type of constipation with a high incidence rate and a large number of patients. We aimed to investigate the therapeutic effects and potential mechanism of paeoniflorin (PAE) on loperamide-induced Sprague Dawley (SD) rat constipation models. Rats with loperamide-induced constipation were orally administered different concentrations of PAE (10, 20, or 40 mg/kg). In vitro, enterochromaffin (EC)-like RIN-14B cells were treated with 20, 40, or 80 μg/ml PAE. We found that PAE treatment significantly improved the symptoms of constipation and increased the intestinal transit rate. Hematoxylin and eosin (H&E) staining showed that PAE alleviated colonic tissue pathological damage. Besides, our results implied that PAE concentration-dependently promoted the content of 5-hydroxytryptamine (5-HT) catalyzed by tryptophan hydroxylase (Tph)-1 in the serum of loperamide-induced rats and in RIN-14B cells. Western blot and immunofluorescence (IF) stain indicated that PAE also promoted the expression of G protein-coupled BA receptor 1 (TGR5), transient receptor potential ankyrin 1 (TRPA1), phospholipase C (PLC)-γ1, and phosphatidylinositol 4,5-bisphosphate (PIP2) in vivo and in vitro. RIN-14B cells were cotreated with a TGR5 inhibitor (SBI-115) to explore the mechanism of PAE in regulating the 5-HT secretion. We observed inhibition of TGR5 reversed the increase of 5-HT secretion induced by PAE in RIN-14B cells. We provided evidence that PAE could promote 5-HT release from EC cells and improve constipation by activating the TRPA1 channel and PLC-γ1/PIP2 signaling. Thus, PAE may provide therapeutic effects for patients with STC.

Role of gut microbiota in functional constipation

Functional constipation (FC) is common, yet the etiology is not clear. Accumulating evidence suggests an association between FC and abnormal gut microbiota. The relationship between the gut microbiota and the gut transit is likely bidirectional. This review summarizes the current evidence regarding the impact of gut microbiota on the pathogenesis of FC. By modulating the colonic motility, secretion, and absorption, gut microbiota may contribute to the development of FC through microbial metabolic activities involving bile acids, short-chain fatty acids, 5-hydroxytryptamine, and methane. In support of the key roles of the gut microbiota in FC, treatment with probiotics, prebiotics, synbiotics, and traditional Chinese medicine often result in compositional and functional changes in the gut microbiota. Further studies on the pathogenesis of FC and the therapeutic mechanism of microecological agents will provide a knowledge base for better management of FC.

Roles of Gut Microbiota and Metabolites in Pathogenesis of Functional Constipation

Functional constipation (FC), a condition characterized by heterogeneous symptoms (infrequent bowel movements, hard stools, excessive straining, or a sense of incomplete evacuation), is prevalent over the world. It is a multifactorial disorder and can be categorized into four subgroups according to different pathological mechanisms: normal transit constipation (NTC), slow transit constipation (STC), defecatory disorders (DD), and mixed type. Recently, growing evidence from human and animals has pointed that there was a strong association between gut microbiota and FC based on the brain-gut-microbiome axis. Studies have reported that the main characteristics of gut microbiota in FC patients were the relative decrease of beneficial bacteria such as Lactobacillus and Bifidobacterium, the relative increase of potential pathogens, and the reduced species richness. Gut microbiota can modulate gut functions through the metabolites of bacterial fermentation, among which short-chain fatty acids (SCFAs), secondary bile salts (BAs), and methane occupied more important positions and could trigger the release of gut hormones from enteroendocrine cells (EECs), such as 5-hydroxytryptamine (5-HT), peptide YY (PYY), and glucagon-like peptide-1 (GLP-1). Subsequently, these gut hormones can influence gut sensation, secretion, and motility, primarily through activating specific receptors distributed on smooth muscle cells, enteric neurons, and epithelial cells. However, research findings were inconsistent and even conflicting, which may be partially due to various confounding factors. Future studies should take the associated confounders into consideration and adopt multiomics research strategies to obtain more complete conclusions and to provide reliable theoretical support for exploring new therapeutic targets.

Approach to the adult patient with chronic diarrhea: A literature review

Chronic diarrhea is defined by symptoms lasting longer than 4 weeks. It is a common problem that affects up to 5% of the adult population. Different pathophysiologic mechanisms involve numerous causes, including drug side effects, postoperative anatomic and physiologic alterations, intestinal and colonic wall abnormalities, inflammatory or malabsorption causes, pancreatobiliary diseases, and functional or gut-brain axis disorders associated with dysbiosis or gastrointestinal motility alterations. Due to such a broad differential diagnosis, it is important to categorize chronic diarrhea into five main groups: drug side effect, postoperative, postinfectious, malabsorptive, inflammatory, and functional. The present review is a narrative analysis of the diagnostic approach, emphasizing key aspects of the clinical history, the utility of biomarkers (in breath, stool, urine, and serology) and malabsorption and motility tests, the role of radiologic and endoscopic studies, and the most common histologic findings. A diagnostic algorithm aimed at determining etiology and personalizing therapy is also proposed.

Approach to the adult patient with chronic diarrhea: a literature review

Chronic diarrhea is defined by symptoms lasting longer than 4 weeks. It is a common problem that affects up to 5% of the adult population. Different pathophysiologic mechanisms involve numerous causes, including drug side effects, postoperative anatomic and physiologic alterations, intestinal and colonic wall abnormalities, inflammatory or malabsorption causes, pancreatobiliary diseases, and functional or gut-brain axis disorders associated with dysbiosis or gastrointestinal motility alterations. Due to such a broad differential diagnosis, it is important to categorize chronic diarrhea into five main groups: drug side effect, postoperative, postinfectious, malabsorptive, inflammatory, and functional. The present review is a narrative analysis of the diagnostic approach, emphasizing key aspects of the clinical history, the utility of biomarkers (in breath, stool, urine, and serology) and malabsorption and motility tests, the role of radiologic and endoscopic studies, and the most common histologic findings. A diagnostic algorithm aimed at determining etiology and personalizing therapy is also proposed.

[Use of antimicrobials in acute canine diarrhea - overview of potential risks, indications and alternatives]

In Germany, antibiotics are frequently used in dogs with gastrointestinal disorders such as acute diarrhea. In line with global efforts to limit antibiotic use, this literature review aims to provide a guideline for the rational and judicious use of antibiotics in acute canine diarrhea. Antibiotics can lead to gastrointestinal side effects and may exert a negative influence on the intestinal microbiota in addition to increasing the occurrence of resistant bacteria. There is also evidence that chronic immunological diseases may be triggered by the administration of antibiotics. Therefore, these should not be administered in uncomplicated acute diarrhea without signs of sepsis or systemic inflammatory reaction. In addition, enteropathogenic bacteria usually do not play a role in the etiology of acute diarrhea. For select clinical entities such as acute hemorrhagic diarrhea syndrome, antibiotic therapy should only be recommended in cases displaying signs of bacterial translocation with subsequent sepsis. In the case of parvovirosis, on the other hand, the administration of antibiotics is unavoidable due to the immunological incompetence of the dog caused by the accompanying severe neutropenia.

Sex- and Gender-Related Differences in Common Functional Gastroenterologic Disorders

Functional gastrointestinal (GI) disorders (FGIDs) result from central and peripheral mechanisms, cause chronic remitting-relapsing symptoms, and are associated with comorbid conditions and impaired quality of life. This article reviews sex- and gender-based differences in the prevalence, pathophysiologic factors, clinical characteristics, and management of functional dyspepsia (FD) and irritable bowel syndrome (IBS) that together affect approximately 1 in 4 people in the United States. These conditions are more common in women. Among patients with IBS, women are more likely to have severe symptoms and coexistent anxiety or depression; constipation or bloating and diarrhea are more common in women and men, respectively, perhaps partly because defecatory disorders, which cause constipation, are more common in women. Current concepts suggest that biological disturbances (eg, persistent mucosal inflammation after acute gastroenteritis) interact with other environmental factors (eg, abuse) and psychological stressors, which influence the brain and gut to alter GI tract motility or sensation, thereby causing symptoms. By comparison to a considerable understanding of sex-based differences in the pathogenesis of visceral hypersensitivity in animal models, we know less about the contribution of these differences to FGID in humans. Slow gastric emptying and colon transit are more common in healthy women than in men, but effects of gonadal hormones on colon transit are less important than in rodents. Although increased visceral sensation partly explains symptoms, the effects of sex on visceral sensation, colonic permeability, and the gut microbiome are less prominent in humans than rodents. Whether sex or gender affects response to medications or behavioral therapy in FD or IBS is unclear because most patients in these studies are women.

Vitamin D receptor is overexpressed in the duodenum of patients with irritable bowel syndrome

BACKGROUND AND AIM

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, and bile acids are thought to be associated with the pathogenesis of IBS. Bile acid receptors are expressed on intestinal epithelial cells. However, no study has assessed bile acid receptor proteins in IBS. Therefore, we examined the intestinal mucosal expression of bile acid receptors in patients with IBS.

METHODS

Intestinal biopsies were performed in patients with IBS and controls. Mast cells, vitamin D receptor (VDR), and somatostatin were stained with specific antibodies. Levels of VDR, farnesoid X receptor (FXR), takeda-G-protein-receptor-5 (TGR5), claudins, and transient-receptor-potential-cation-channel-subfamily-V-member 6 (TRPV6) were assessed by western blotting.

RESULTS

3Mast cell counts in the second part of the duodenum were significantly higher in patients with IBS than in controls. VDR protein levels were significantly elevated in the duodenum and terminal ileum of patients with IBS compared with controls, although this difference was not seen in the cecum or rectum. FXR and TGR5 protein levels did not differ in any part of the intestine. VDR-positive cryptal epithelia in IBS were distributed not only at basal crypt but also along the upper part of the basal crypt epithelial cells. In contrast, the pattern of gut somatostatin-positive cells, claudins, and TRPV6 levels did not differ.

CONCLUSIONS

The number of mast cells in the duodenum was significantly increased, and the protein expression levels of VDR, but not those of FXR or TGR5, were elevated in the duodenal epithelial crypt in patients with IBS.

Bile Acids as Key Modulators of the Brain-Gut-Microbiota Axis in Alzheimer's Disease

Recently, the concept of the brain-gut-microbiota (BGM) axis disturbances in the pathogenesis of Alzheimer's disease (AD) has been receiving growing attention. At the same time, accumulating data revealing complex interplay between bile acids (BAs), gut microbiota, and host metabolism have shed new light on a potential impact of BAs on the BGM axis. The crosstalk between BAs and gut microbiota is based on reciprocal interactions since microbiota determines BA metabolism, while BAs affect gut microbiota composition. Secondary BAs as microbe-derived neuroactive molecules may affect each of three main routes through which interactions within the BGM axis occur including neural, immune, and neuroendocrine pathways. BAs participate in the regulation of multiple gut-derived molecule release since their receptors are expressed on various cells. The presence of BAs and their receptors in the brain implies a direct effect of BAs on the regulation of neurological functions. Experimental and clinical data confirm that disturbances in BA signaling are present in the course of AD. Disturbed ratio of primary to secondary BAs as well as alterations in BA concertation in serum and brain samples have been reported. An age-related shift in the gut microbiota composition associated with its decreased diversity and stability observed in AD patients may significantly affect BA metabolism and signaling. Given recent evidence on BA neuroprotective and anti-inflammatory effects, new therapeutic targets have been explored including gut microbiota modulation by probiotics and dietary interventions, ursodeoxycholic acid supplementation, and use of BA receptor agonists.

Altered metabolism of bile acids correlates with clinical parameters and the gut microbiota in patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND

Bile acids (BAs) have attracted attention in the research of irritable bowel syndrome with predominant diarrhea (IBS-D) due to their ability to modulate bowel function and their tight connection with the gut microbiota. The composition of the fecal BA pool in IBS-D patients is reportedly different from that in healthy populations. We hypothesized that BAs may participate in the pathogenesis of IBS-D and the altered BA profile may be correlated with the gut microbiome.

AIM

To investigate the role of BAs in the pathogenesis of IBS-D and the correlation between fecal BAs and gut microbiota.

METHODS

Fifty-five IBS-D patients diagnosed according to the Rome IV criteria and twenty-eight age-, sex-, and body mass index-matched healthy controls (HCs) were enrolled in this study at the gastroenterology department of China-Japan Friendship Hospital. First, clinical manifestations were assessed with standardized questionnaires, and visceral sensitivity was evaluated via the rectal distension test using a high-resolution manometry system. Fecal primary BAs including cholic acid (CA) and chenodeoxycholic acid (CDCA), secondary BAs including deoxycholic acid (DCA), lithocholic acid (LCA), and ursodeoxycholic acid (UDCA) as well as the corresponding tauro- and glyco-BAs were examined by ultraperformance liquid chromatography coupled to tandem mass spectrometry. The gut microbiota was analyzed using 16S rRNA gene sequencing. Correlations between fecal BAs with clinical features and gut microbiota were explored.

RESULTS

Fecal CA (IBS-D: 3037.66 [282.82, 6917.47] nmol/g, HC: 20.19 [5.03, 1304.28] nmol/g; P < 0.001) and CDCA (IBS-D: 1721.86 [352.80, 2613.83] nmol/g, HC: 57.16 [13.76, 1639.92] nmol/g; P < 0.001) were significantly increased, while LCA (IBS-D: 1621.65 [58.99, 2396.49] nmol/g, HC: 2339.24 [1737.09, 2782.40]; P = 0.002] and UDCA (IBS-D: 8.92 [2.33, 23.93] nmol/g, HC: 17.21 [8.76, 33.48] nmol/g; P = 0.025) were significantly decreased in IBS-D patients compared to HCs. Defecation frequency was positively associated with CA (r = 0.294, P = 0.030) and CDCA (r = 0.290, P = 0.032) and negatively associated with DCA (r = -0.332, P = 0.013) and LCA (r = -0.326, P = 0.015) in IBS-D patients. In total, 23 of 55 IBS-D patients and 15 of 28 HCs participated in the visceral sensitivity test. The first sensation threshold was negatively correlated with CDCA (r = -0.459, P = 0.028) in IBS-D patients. Furthermore, the relative abundance of the family Ruminococcaceae was significantly decreased in IBS-D patients (P < 0.001), and 12 genera were significantly lower in IBS-D patients than in HCs (P < 0.05), with 6 belonging to Ruminococcaceae. Eleven of these genera were negatively correlated with primary BAs and positively correlated with secondary BAs in all subjects.

CONCLUSION

The altered metabolism of BAs in the gut of IBS-D patients was associated with diarrhea and visceral hypersensitivity and might be ascribed to dysbiosis, especially the reduction of genera in Ruminococcaceae.

Gut Microbiota-Bile Acid Crosstalk in Diarrhea-Irritable Bowel Syndrome

The occurrence of diarrhea-predominant irritable bowel syndrome (IBS-D) is the result of multiple factors, and its pathogenesis has not yet been clarified. Emerging evidence indicates abnormal changes in gut microbiota and bile acid (BA) metabolism have a close relationship with IBS-D. Gut microbiota is involved in the secondary BA production via deconjugation, 7α-dehydroxylation, oxidation, epimerization, desulfation, and esterification reactions respectively. Changes in the composition and quantity of gut microbiota have an important impact on the metabolism of BAs, which can lead to the occurrence of gastrointestinal diseases. BAs, synthesized in the hepatocytes, play an important role in maintaining the homeostasis of gut microbiota and the balance of glucose and lipid metabolism. In consideration of the complex biological functional connections among gut microbiota, BAs, and IBS-D, it is urgent to review the latest research progress in this field. In this review, we summarized the alterations of gut microbiota in IBS-D and discussed the mechanistic connections between gut microbiota and BA metabolism in IBS-D, which may be involved in activating two important bile acid receptors, G-protein coupled bile acid receptor 1 (TGR5) and farnesoid X receptor (FXR). We also highlight the strategies of prevention and treatment of IBS-D via regulating gut microbiota-bile acid axis, including probiotics, fecal microbiota transplantation (FMT), cholestyramine, and the cutting-edge technology about bacteria genetic engineering.

An Inverse Correlation of Serum Fibroblast Growth Factor 19 with Abdominal Pain and Inflammatory Markers in Patients with Ulcerative Colitis

Background and Aims

Bile acids (BA) play an important role in the modulation of numerous gut functions. Fibroblast growth factor 19 (FGF19) is the ileal hormone regulating BA homeostasis. The aim of the study was to evaluate serum FGF19 level and its correlation with clinical and endoscopic disease activity indices along with inflammatory biomarkers including serum CRP and fecal calprotectin levels in patients with ulcerative colitis (UC).

Methods

Fasting serum FGF19 level was measured using ELISA test in 16 patients with active UC (7 F, 9 M), 15 patients with nonactive UC (8 F, 7 M), and 19 healthy controls (11 F, 8 M). The disease activity was assessed based on the clinical and endoscopic evaluations as well as serum CRP and fecal calprotectin level measurement.

Results

The median serum FGF19 level was higher in patients with nonactive UC (175.3 pg/ml (108.7-342.3)) than in patients with active UC (114.3 pg/ml (68.9-155.3), p = 0.093). The median FGF19 level in healthy controls amounted to 151.6 pg/ml (90.6-224.2), and there were no statistically significant differences between the patients with active and nonactive UC compared to the healthy controls. An inverse correlation was observed between FGF19 level and abdominal pain intensity (R = –0.48, p = 0.007) as well as fecal calprotectin (R = –0.38, p = 0.036) and CRP levels (R = –0.36, p = 0.045). The serum FGF19 level was not correlated neither with clinical nor endoscopic disease activity indices.

Conclusions

The inverse correlations between FGF19 level and abdominal pain as well as inflammatory markers in UC may imply its potential analgesic and anti-inflammatory effects.

What Is the Impact of Diet on Nutritional Diarrhea Associated with Gut Microbiota in Weaning Piglets: A System Review

Piglets experience severe growth challenges and diarrhea after weaning due to nutritional, social, psychological, environmental, and physiological changes. Among these changes, the nutritional factor plays a key role in postweaning health. Dietary protein, fibre, starch, and electrolyte levels are highly associated with postweaning nutrition diarrhea (PWND). In this review, we mainly discuss the high protein, fibre, resistant starch, and electrolyte imbalance in diets that induce PWND, with a focus on potential mechanisms in weaned piglets.

New insights into irritable bowel syndrome: from pathophysiology to treatment

Irritable bowel syndrome (IBS) is the most common reason to visit a gastroenterologist. IBS was believed to be a functional disease, but many possible pathophysiologic mechanisms can now explain the symptoms. IBS patients are classified into subtypes according to their predominant bowel habit, based on the Rome IV criteria. These include diarrhea-predominant and constipation-predominant IBS, as well as the mixed type, a combination of the two. Usually, IBS treatment is based on the predominant symptoms, with many options for each subtype. A new promising treatment option, fecal microbiota transplantation, seems to have beneficial effects on IBS. However, treating the pathophysiological causative agent responsible for the symptoms is an emerging approach. Therefore, before the appropriate therapeutic option is chosen for treating IBS, a clinical evaluation of its pathophysiology should be performed.

Altered duodenal bile salt concentration and receptor expression in functional dyspepsia

Background

Functional dyspepsia is a common functional gastrointestinal disorder in which a variety of pathophysiological mechanisms such as increased intestinal permeability and low-grade inflammation are involved. The factor causing these alterations, however, has not been identified.

Objective

We aimed to evaluate the luminal bile salt content and receptor expression in patients with functional dyspepsia and healthy volunteers.

Methods

Gastroduodenoscopy was performed to obtain duodenal biopsies from 25 healthy volunteers and 25 patients with functional dyspepsia (Rome III) to measure duodenal bile salt receptor expression with Western blot. Duodenal fluid aspirates were collected at fixed time points during fasted and fed state conditions and bile salt composition analysis was performed by liquid chromatography-mass spectrometry/mass spectrometry.

Results

Patients (N = 17) displayed decreased fasted bile salt concentrations compared to healthy volunteers (N = 20) over time (1.8 ± 0.3 mM vs 3.6 ± 0.5 mM; p = 0.03). In addition, an increased expression of duodenal bile salt sensor vitamin D receptor was found in patients (3.7 ± 1.0-fold; p < 0.0005; N = 24 for both groups).

Conclusion

Patients with functional dyspepsia are characterized by a decreased duodenal bile salt concentration in fasted state and an increased duodenal vitamin D receptor expression.

Novel associations of bile acid diarrhoea with fatty liver disease and gallstones: a cohort retrospective analysis

Background

Bile acid diarrhoea (BAD) is a common cause of chronic diarrhoea with a population prevalence of primary BAD around 1%. Previous studies have identified associations with low levels of the ileal hormone fibroblast growth factor 19 (FGF19), obesity and hypertriglyceridaemia. The aim of this study was to identify further associations of BAD.

Methods

A cohort of patients with chronic diarrhoea who underwent ⁷⁵selenohomocholic acid taurate (SeHCAT) testing for BAD was further analysed retrospectively. Additional clinical details available from the electronic patient record, including imaging, colonoscopy, chemistry and histopathology reports were used to calculate the prevalence of fatty liver disease, gallstones, colonic neoplasia and microscopic colitis, which was compared for BAD, the primary BAD subset and control patients with diarrhoea.

Findings

Of 578 patients, 303 (52%) had BAD, defined as a SeHCAT 7d retention value <15%, with 179 (31%) having primary BAD. 425 had an alanine aminotransferase (ALT) recorded, 184 had liver imaging and 176 had both. Overall, SeHCAT values were negatively associated with ALT (r_s=−0.19, p<0.0001). Patients with BAD had an OR of 3.1 for an ALT >31 ng/mL with imaging showing fatty liver (p<0.001); similar figures occurred in the primary BAD group. FGF19 was not significantly related to fatty liver but low levels were predictive of ALT >40 IU/L. In 176 subjects with gallbladder imaging, 27% had gallstones, 7% had a prior cholecystectomy and 34% either of these. The median SeHCAT values were lower in those with gallstones (3.8%, p<0.0001), or gallstones/cholecystectomy (7.2%, p<0.001), compared with normal gallbladder imaging (14%). Overall, BAD had an OR of 2.0 for gallstones/cholecystectomy (p<0.05). BAD was not significantly associated with colonic adenoma/carcinoma or with microscopic colitis.

Interpretation

The diagnosis of BAD is associated with fatty liver disease and with gallstones. The reasons for these associations require further investigation into potential metabolic causes.

Linking Gut Microbiota to Colorectal Cancer

Pre-clinical and clinical data produce mounting evidence that the microbiota is strongly associated with colorectal carcinogenesis. Dysbiosis may change the course of carcinogenesis as microbial actions seem to impact genetic and epigenetic alterations leading to dysplasia, clonal expansion and malignant transformation. Initiation and promotion of colorectal cancer may result from direct bacterial actions, bacterial metabolites and inflammatory pathways. Newer aspects of microbiota and colorectal cancer include quorum sensing, biofilm formation, sidedness and effects/countereffects of microbiota and probiotics on chemotherapy. In the future, targeting the microbiota will probably be a powerful weapon in the battle against CRC as gut microbiology, genomics and metabolomics promise to uncover important linkages between microbiota and intestinal health.

Bacterial bile salt hydrolase: an intestinal microbiome target for enhanced animal health

To effectively mitigate antimicrobial resistance in the agricultural ecosystem, there is an increasing pressure to reduce and eliminate the use of in-feed antibiotics for growth promotion and disease prevention in food animals. However, limiting antibiotic use could compromise animal production efficiency and health. Thus, there is an urgent need to develop effective alternatives to antibiotic growth promoters (AGPs). Increasing evidence has shown that the growth-promoting effect of AGPs was highly correlated with the reduced activity of bile salt hydrolase (BSH), an intestinal bacterial enzyme that has a negative impact on host fat digestion and energy harvest; consistent with this finding, the population of Lactobacillus species, the major intestinal BSH-producer, was significantly reduced in response to AGP use. Thus, BSH is a key mechanistic microbiome target for developing novel alternatives to AGPs. Despite recent significant progress in the characterization of diverse BSH enzymes, research on BSH is still in its infancy. This review is focused on the function of BSH and its significant impacts on host physiology in human beings, laboratory animals and food animals. The gaps in BSH-based translational microbiome research for enhanced animal health are also identified and discussed.

The Ameliorating Effect of Lactobacillus gasseri OLL2716 on Functional Dyspepsia in Helicobacter pylori-Uninfected Individuals: A Randomized Controlled Study

BACKGROUND/AIMS

Probiotics appear to improve Helicobacter pylori-associated dyspepsia via an inhibitory effect on H. pylori; however, uncertainty exists regarding their effects in H. pylori-uninfected individuals. We evaluated the efficacy of Lactobacillus gasseri OLL2716 (L. gasseri OLL2716) on H. pylori-uninfected individuals with functional dyspepsia (FD).

METHODS

A double-blind, parallel-group, placebo-controlled, randomized, controlled trial was performed. Participants were randomly assigned to ingest L. gasseri OLL2716-containing yogurt (L. gasseri OLL2716 group) or L. gasseri OLL2716-free yogurt (placebo group) for 12 weeks. Participants completed questionnaires that dealt with a global assessment as well as symptom severity. The per-protocol (PP) population was evaluated for efficacy in accordance with a plan prepared beforehand.

RESULTS

Randomization was performed on 116 individuals; the PP population consisted of 106 individuals (mean age 42.8 ± 9.0). The impressions regarding the overall effect on gastric symptoms were more positive in the L. gasseri OLL2716 group compared to that in the placebo group (statistical trend; p = 0.073). The elimination rate for major FD symptoms was 17.3 and 35.3% in the placebo and L. gasseri OLL2716 groups respectively (p = 0.048).

CONCLUSION

L. gasseri OLL2716 has beneficial effects on FD without H. pylori involvement.

Potential role of fecal microbiota from patients with slow transit constipation in the regulation of gastrointestinal motility

The gut microbiota is involved in various physiological functions, and disturbances in the host-microbiome have been proven to contribute to the dysfunction of gut; however, whether microbiota participates in the pathogenesis of constipation remains unclear. In this study, we extracted and analyzed microbiota in feces from constipated donors who had undergone effective therapy with fecal microbiota transplantation, transplanted microbiota into pseudo-germ-free mice, and measured gut motility. These mice presented with lower pellet frequency and water percentage, smaller pellet size, delayed gastrointestinal transit time, and weaker spontaneous contractions of colonic smooth muscle. To determine the mechanism underlying delayed gut motility, microbial metabolites were measured. Short chain fatty acids and secondary bile acids were decreased in mice receiving microbiota from constipated donors. Moreover, the compositional changes of gut microbiota in constipated patients were identified, including the operational taxonomic unit, and the species richness and α diversity were much greater than those in healthy volunteers. These findings suggest that alterations of the microbiome might affect gut motility via altered microbial-derived metabolites in the development of constipation, and the restoration of disturbed microbiota might improve the clinical phenotype. This study indicates that regulating the intestinal environment may be a novel therapy strategy for constipation.

Therapeutic Modulation of Gut Microbiota in Functional Bowel Disorders

Functional bowel disorders (FBDs) are functional gastrointestinal disorders with symptoms attributable to the middle or lower gastrointestinal tract. These include irritable bowel syndrome, functional bloating, functional constipation, functional diarrhea, and unspecified FBD. Increasing evidence has emerged of late that intestinal microbiota is involved in the pathogenesis of FBDs. In this review, the therapeutic benefits and future perspectives of the currently available strategies for modifying the gut microbiota in FBDs are described, focusing primarily on irritable bowel syndrome and functional constipation.

Underlying molecular and cellular mechanisms in childhood irritable bowel syndrome

Irritable bowel syndrome (IBS) affects a large number of children throughout the world. The symptom expression of IBS is heterogeneous, and several factors which may be interrelated within the IBS biopsychosocial model play a role. These factors include visceral hyperalgesia, intestinal permeability, gut microbiota, psychosocial distress, gut inflammation, bile acids, food intolerance, colonic bacterial fermentation, and genetics. The molecular and cellular mechanisms of these factors are being actively investigated. In this mini-review, we present updates of these mechanisms and, where possible, relate the findings to childhood IBS. Mechanistic elucidation may lead to the identification of biomarkers as well as personalized childhood IBS therapies.

Irritable bowel syndrome, the microbiota and the gut-brain axis

Irritable bowel syndrome is a common functional gastrointestinal disorder and it is now evident that irritable bowel syndrome is a multi-factorial complex of changes in microbiota and immunology. The bidirectional neurohumoral integrated communication between the microbiota and the autonomous nervous system is called the gut-brain-axis, which integrates brain and GI functions, such as gut motility, appetite and weight. The gut-brain-axis has a central function in the perpetuation of irritable bowel syndrome and the microbiota plays a critical role. The purpose of this article is to review recent research concerning the epidemiology of irritable bowel syndrome, influence of microbiota, probiota, gut-brain-axis, and possible treatment modalities on irritable bowel syndrome.

Effects of conventional and a novel colonic-release bile acid sequestrant, A3384, on fibroblast growth factor 19 and bile acid metabolism in healthy volunteers and patients with bile acid diarrhoea

BACKGROUND

Primary bile acid diarrhoea (BAD) is associated with increased bile acid synthesis and low fibroblast growth factor 19 (FGF19). Bile acid sequestrants are used as therapy, but are poorly tolerated and may exacerbate FGF19 deficiency.

AIM

The purpose of this study was to evaluate the pharmacological effects of conventional sequestrants and a colonic-release formulation preparation of colestyramine (A3384) on bile acid metabolism and bowel function in patients with BAD.

METHODS

Patients with seven-day ⁷⁵selenium-homocholic acid taurine (SeHCAT) scan retention <10% were randomised in a double-blind protocol to two weeks treatment with twice-daily A3384 250 mg (n = 6), 1 g (n = 7) or placebo (n = 6). Thirteen patients were taking conventional sequestrants at the start of the study. Symptoms were recorded and serum FGF19 and 7α-hydroxy-4-cholesten-3-one (C4) measured.

RESULTS

Median serum FGF19 on conventional sequestrant treatment was 28% lower than baseline values in BAD (p < 0.05). C4 on conventional sequestrant treatment was 58% higher in BAD (p < 0.001). No changes were seen on starting or withdrawing A3384. A3384 improved diarrhoeal symptoms, with a median reduction of 2.2 points on a 0-10 Likert scale compared to placebo, p < 0.05.

CONCLUSIONS

Serum FGF19 was suppressed and bile acid production up-regulated on conventional bile acid sequestrants, but not with A3384. This colonic-release formulation of colestyramine produced symptomatic benefit in patients with BAD.

Glucose and lipid effects of the ileal apical sodium-dependent bile acid transporter inhibitor GSK2330672: double-blind randomized trials with type 2 diabetes subjects taking metformin

AIMS

To investigate the pharmacodynamics, pharmacokinetics and safety/tolerability of blocking reuptake of bile acids using the inhibitor GSK2330672 (GSK672) in patients with type 2 diabetes (T2D).

METHODS

Subjects with T2D taking metformin were enrolled in two studies in which they took metformin 850 mg twice daily for 2 weeks prior to and during the randomized treatment periods. In the first crossover study (n = 15), subjects received GSK672 45 mg, escalating to 90 mg, twice daily, or placebo for 7 days. The second parallel-group study (n = 75) investigated GSK672 10-90 mg twice daily, placebo or sitagliptin for 14 days.

RESULTS

In both studies, GSK672 reduced circulating bile acids and increased serum 7-α-hydroxy-4-cholesten-3-one (C4), an intermediate in the hepatic synthesis of bile acids. Compared with placebo, in the parallel-group study 90 mg GSK672 twice daily reduced fasting plasma glucose [FPG; -1.21 mmol/l; 95% confidence interval (CI) -2.14, -0.28] and weighted-mean glucose area under the curve (AUC)0-24 h (-1.33 mmol/l; 95% CI -2.30, -0.36), as well as fasting and weighted-mean insulin AUC0 -24 h . GSK672 also reduced cholesterol (LDL, non-HDL and total cholesterol) and apolipoprotein B concentrations; the maximum LDL cholesterol reduction was ∼40%. There was no change in HDL cholesterol but there was a trend towards increased fasting triglyceride levels in the GSK672 groups compared with placebo. In both studies, the most common adverse events associated with GSK672 were gastrointestinal, mostly diarrhoea (22-100%), which appeared to be independent of dose.

CONCLUSIONS

In subjects with T2D on metformin, GSK672 improved glucose and lipids, but there was a high incidence of gastrointestinal adverse events.

The Intestinal Microenvironment and Functional Gastrointestinal Disorders

For decades, interactions between the enteric neuromuscular apparatus and the central nervous system have served as the primary focus of pathophysiological research in the functional gastrointestinal disorders. The accumulation of patient reports, as well as clinical observations, has belatedly led to an interest in the role of various luminal factors and their interactions with each other and the host in functional gastrointestinal disorders. Most prominent among these factors has been the role of food. As a consequence, while not always evidence-based, dietary interventions are enjoying a renaissance in irritable bowel syndrome management. Not surprisingly, given its exploration in many disease states, the gut microbiota has also been studied in functional gastrointestinal disorders; data remain inconclusive. Likewise, there is also a considerable body of experimental and some clinical data to link functional gastrointestinal disorders pathogenesis to disturbances in epithelial barrier integrity, abnormal entero-endocrine signaling and immune activation. These data provide growing evidence supporting the existence of micro-organic changes, particularly in subgroups of patients with functional dyspepsia and IBS. However, their exact role in the complex pathophysiology and symptom generation of functional gastrointestinal disorders needs to be further studied and elucidated particularly with longitudinal and interventional studies.

Pharmacological, Pharmacokinetic, and Pharmacogenomic Aspects of Functional Gastrointestinal Disorders

This article reviews medications commonly used for the treatment of patients with functional gastrointestinal disorders. Specifically, we review the animal models that have been validated for the study of drug effects on sensation and motility; the preclinical pharmacology, pharmacokinetics, and toxicology usually required for introduction of new drugs; the biomarkers that are validated for studies of sensation and motility endpoints with experimental medications in humans; the pharmacogenomics applied to these medications and their relevance to the FGIDs; and the pharmacology of agents that are applied or have potential for the treatment of FGIDs, including psychopharmacologic drugs.

Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis

The gastrointestinal (GI) tract contains much of the body's serotonin (5-hydroxytryptamine, 5-HT), but mechanisms controlling the metabolism of gut-derived 5-HT remain unclear. Here, we demonstrate that the microbiota plays a critical role in regulating host 5-HT. Indigenous spore-forming bacteria (Sp) from the mouse and human microbiota promote 5-HT biosynthesis from colonic enterochromaffin cells (ECs), which supply 5-HT to the mucosa, lumen, and circulating platelets. Importantly, microbiota-dependent effects on gut 5-HT significantly impact host physiology, modulating GI motility and platelet function. We identify select fecal metabolites that are increased by Sp and that elevate 5-HT in chromaffin cell cultures, suggesting direct metabolic signaling of gut microbes to ECs. Furthermore, elevating luminal concentrations of particular microbial metabolites increases colonic and blood 5-HT in germ-free mice. Altogether, these findings demonstrate that Sp are important modulators of host 5-HT and further highlight a key role for host-microbiota interactions in regulating fundamental 5-HT-related biological processes.