Predicting the response to Ondansetron, a 5HT3 receptor antagonist, in irritable bowel syndrome with diarrhoea: the utility of clinical features and objective biomarkers

Background: Patients with diarrhoea predominant irritable bowel syndrome (IBS-D) suffer from loose frequent stools with associated urgency and fear of incontinence. Relief from these symptoms is an important unmet need. The 5-HT3 receptor antagonist Alosetron has been shown to increase stool consistency, decrease urgency and reduce abdominal pain leading to a global increase in satisfaction with treatment [1]. Its use is restricted following an increased incidence of ischaemic colitis and this agent is not available in Europe. The serine proteases family of proteolytic enzymes have been identified as the source of increased faecal proteolytic activity in patients with IBS. These enzymes may be mechanistically important via their action on the Protease activated receptor (PAR) -2, inducing increases in permeability and hypersensitivity. Aims: To assess the efficacy of the commonly prescribed 5-HT3 antagonist Ondansetron, in patients with IBS-D and to identify biomarkers that might allow us to predict response defining an Ondansetron responsive endophenotype of IBS. To structurally characterise faecal serine proteases and define the impact of treatment with Ondansetron. Methods: 120 patients meeting Rome III criteria for IBS-D entered a randomised, double-blind, placebo controlled, cross-over study of 5 weeks of Ondansetron 4mg versus placebo with dose titration allowed up to two tablets thrice daily in the first 3 weeks. Patients completed daily bowel symptom diaries documenting stool consistency using the Bristol Stool Form Score (BSFS). Gut transit and small bowel water content were measured in the last week of each treatment. The primary endpoint was average stool consistency in the last 2 weeks of treatment. Faecal samples were obtained from 30 healthy volunteers (HV) and 79 IBS-D patients participating in a trial of Ondansetron versus placebo. Colonic transit was measured using radio-opaque markers. Faecal serine proteases (FSP) were purified from faecal extracts using Benzamidine-Sepharose affinity chromatography. SDS-PAGE profiled components were identified using trypsinolysis and tandem-mass-spectrometry. Functional protease activity in faecal extracts was measured using a colourimetric assay based upon the proteolysis of azo-casein. Results: Ondansetron significantly improved stool consistency In the intention to treat analysis n= 101, with a 1.39 (95% CI1.20-1.58)point decrease on the Bristol stool form scale whilst taking Ondansetron compared to a 0.51 (95% CI 0.32-0.72) point reduction whilst taking placebo p=<0.0001. Compared to placebo patients on Ondansetron experienced fewer days with urgency (p=0.01), lower urgency scores (P<0.001), reduced frequency of defecation (p=0.001) and less bloating (p=0. 25) although pain scores did not change significantly. Protein analysis identified the most abundant FSPs as being of human origin and likely pancreatic juice derived. Functional assays showed increased FSP and faecal amylase in IBS-D compared to HV. Those with higher amylase had significantly higher FSP and greater anxiety. FSP activity correlated negatively with whole gut transit in IBS-D (Spearman r=-0.32, p=0.005) and HV (r=-0.55, p=0.014), but was not affected by treatment with Ondansetron. Conclusions: Ondansetron is an effective and well tolerated treatment in patients with IBS-D with a low number of side effects. It slows whole gut transit, but without a demonstrable difference in small bowel water content. Clinical rather than biochemical indicators predicted responsiveness to Ondansetron best. Patients with less severe symptoms are more likely to respond well to Ondansetron which should prove a useful addition to the current rather limited therapies available for this important group of patients. Previous reports that FSP activity is elevated in some patients with IBS-D has been confirmed. We have increased our understanding of this phenomenon by characterising the proteins responsible for the serine protease activity, showing that most of this activity is likely due to human pancreatic enzymes

Predicting the response to Ondansetron, a 5HT3 receptor antagonist, in irritable bowel syndrome with diarrhoea: the utility of clinical features and objective biomarkers

Background: Patients with diarrhoea predominant irritable bowel syndrome (IBS-D) suffer from loose frequent stools with associated urgency and fear of incontinence. Relief from these symptoms is an important unmet need. The 5-HT3 receptor antagonist Alosetron has been shown to increase stool consistency, decrease urgency and reduce abdominal pain leading to a global increase in satisfaction with treatment [1]. Its use is restricted following an increased incidence of ischaemic colitis and this agent is not available in Europe. The serine proteases family of proteolytic enzymes have been identified as the source of increased faecal proteolytic activity in patients with IBS. These enzymes may be mechanistically important via their action on the Protease activated receptor (PAR) -2, inducing increases in permeability and hypersensitivity. Aims: To assess the efficacy of the commonly prescribed 5-HT3 antagonist Ondansetron, in patients with IBS-D and to identify biomarkers that might allow us to predict response defining an Ondansetron responsive endophenotype of IBS. To structurally characterise faecal serine proteases and define the impact of treatment with Ondansetron. Methods: 120 patients meeting Rome III criteria for IBS-D entered a randomised, double-blind, placebo controlled, cross-over study of 5 weeks of Ondansetron 4mg versus placebo with dose titration allowed up to two tablets thrice daily in the first 3 weeks. Patients completed daily bowel symptom diaries documenting stool consistency using the Bristol Stool Form Score (BSFS). Gut transit and small bowel water content were measured in the last week of each treatment. The primary endpoint was average stool consistency in the last 2 weeks of treatment. Faecal samples were obtained from 30 healthy volunteers (HV) and 79 IBS-D patients participating in a trial of Ondansetron versus placebo. Colonic transit was measured using radio-opaque markers. Faecal serine proteases (FSP) were purified from faecal extracts using Benzamidine-Sepharose affinity chromatography. SDS-PAGE profiled components were identified using trypsinolysis and tandem-mass-spectrometry. Functional protease activity in faecal extracts was measured using a colourimetric assay based upon the proteolysis of azo-casein. Results: Ondansetron significantly improved stool consistency In the intention to treat analysis n= 101, with a 1.39 (95% CI1.20-1.58)point decrease on the Bristol stool form scale whilst taking Ondansetron compared to a 0.51 (95% CI 0.32-0.72) point reduction whilst taking placebo p=<0.0001. Compared to placebo patients on Ondansetron experienced fewer days with urgency (p=0.01), lower urgency scores (P<0.001), reduced frequency of defecation (p=0.001) and less bloating (p=0. 25) although pain scores did not change significantly. Protein analysis identified the most abundant FSPs as being of human origin and likely pancreatic juice derived. Functional assays showed increased FSP and faecal amylase in IBS-D compared to HV. Those with higher amylase had significantly higher FSP and greater anxiety. FSP activity correlated negatively with whole gut transit in IBS-D (Spearman r=-0.32, p=0.005) and HV (r=-0.55, p=0.014), but was not affected by treatment with Ondansetron. Conclusions: Ondansetron is an effective and well tolerated treatment in patients with IBS-D with a low number of side effects. It slows whole gut transit, but without a demonstrable difference in small bowel water content. Clinical rather than biochemical indicators predicted responsiveness to Ondansetron best. Patients with less severe symptoms are more likely to respond well to Ondansetron which should prove a useful addition to the current rather limited therapies available for this important group of patients. Previous reports that FSP activity is elevated in some patients with IBS-D has been confirmed. We have increased our understanding of this phenomenon by characterising the proteins responsible for the serine protease activity, showing that most of this activity is likely due to human pancreatic enzymes

Treatment of irritable bowel syndrome with diarrhoea using titrated ondansetron (TRITON): study protocol for a randomised controlled trial

Background: Irritable bowel syndrome with diarrhoea (IBS-D) affects up to 4% of the general population. Symptoms include frequent, loose, or watery stools with associated urgency, resulting in marked reduction of quality of life and loss of work productivity. Ondansetron, a 5HT3 receptor antagonist, has had an excellent safety record for over 20 years as an antiemetic, yet is not widely used in the treatment of IBS-D. It has, however, been shown to slow colonic transit and in a small randomised, placebo-controlled, cross-over pilot study, benefited patients with IBS-D. Methods: This trial is a phase III, parallel group, randomised, double-blind, multi-centre, placebo-controlled trial, with embedded mechanistic studies. Participants (n = 400) meeting Rome IV criteria for IBS-D will be recruited from outpatient and primary care clinics and by social media to receive either ondansetron (dose titrated up to 24 mg daily) or placebo for 12 weeks. Throughout the trial, participants will record their worst abdominal pain, worst urgency, stool frequency, and stool consistency on a daily basis. The primary endpoint is the proportion of “responders” in each group, using Food and Drug Administration (FDA) recommendations. Secondary endpoints include pain intensity, stool consistency, frequency, and urgency. Mood and quality of life will also be assessed. Mechanistic assessments will include whole gut transit, faecal tryptase and faecal bile acid concentrations at baseline and between weeks 8 and 11. A subgroup of participants will also undergo assessment of sensitivity (n = 80) using the barostat, and/or high-resolution colonic manometry (n = 40) to assess motor patterns in the left colon and the impact of ondansetron. Discussion: The TRITON trial aims to assess the effect of ondansetron across multiple centres. By defining ondansetron’s mechanisms of action we hope to better identify patients with IBS-D who are likely to respond

Faecal microbiota composition and host–microbe cross-talk following gastroenteritis and in postinfectious irritable bowel syndrome

Background: About 10% of patients with IBS report the start of the syndrome after infectious enteritis. The clinical features of postinfectious IBS (PI-IBS) resemble those of diarrhoea-predominant IBS (IBS-D). While altered faecal microbiota has been identified in other IBS subtypes, composition of the microbiota in patients with PI-IBS remains uncharacterised.Objective: To characterise the microbial composition of patients with PI-IBS, and to examine the associations between the faecal microbiota and a patient's clinical features.Design: Using a phylogenetic microarray and selected qPCR assays, we analysed differences in the faecal microbiota of 57 subjects from five study groups: patients with diagnosed PI-IBS, patients who 6 months after gastroenteritis had either persisting bowel dysfunction or no IBS symptoms, benchmarked against patients with IBS-D and healthy controls. In addition, the associations between the faecal microbiota and health were investigated by correlating the microbial profiles to immunological markers, quality of life indicators and host gene expression in rectal biopsies.Results: Microbiota analysis revealed a bacterial profile of 27 genus-like groups, providing an Index of Microbial Dysbiosis (IMD), which significantly separated patient groups and controls. Within this profile, several members of Bacteroidetes phylum were increased 12-fold in patients, while healthy controls had 35-fold more uncultured Clostridia. We showed correlations between the IMD and expression of several host gene pathways, including amino acid synthesis, cell junction integrity and inflammatory response, suggesting an impaired epithelial barrier function in IBS.Conclusions :The faecal microbiota of patients with PI-IBS differs from that of healthy controls and resembles that of patients with IBS-D, suggesting a common pathophysiology. Moreover, our analysis suggests a variety of host–microbe associations that may underlie intestinal symptoms, initiated by gastroenteritis

Colon wall motility: comparison of novel quantitative semi-automatic measurements using cine MRI

Background Recently, cine magnetic resonance imaging (MRI) has shown promise for visualizing movement of the colonic wall, although assessment of data has been subjective and observer dependent. This study aimed to develop an objective and semi-automatic imaging metric of ascending colonic wall movement, using image registration techniques. Methods Cine balanced turbo field echo MRI images of ascending colonic motility were acquired over 2 min from 23 healthy volunteers (HVs) at baseline and following two different macrogol stimulus drinks (11 HVs drank 1 L and 12 HVs drank 2 L). Motility metrics derived from large scale geometric and small scale pixel movement parameters following image registration were developed using the post ingestion data and compared to observer grading of wall motion. Inter and intra-observer variability in the highest correlating metric was assessed using Bland–Altman analysis calculated from two separate observations on a subset of data. Key Results All the metrics tested showed significant correlation with the observer rating scores. Line analysis (LA) produced the highest correlation coefficient of 0.74 (95% CI: 0.55–0.86), p < 0.001 (Spearman Rho). Bland–Altman analysis of the inter- and intra-observer variability for the LA metric, showed almost zero bias and small limits of agreement between observations (−0.039 to 0.052 intra-observer and −0.051 to 0.054 inter-observer, range of measurement 0–0.353). Conclusions & Inferences The LA index of colonic motility derived from cine MRI registered data provides a quick, accurate and non-invasive method to detect wall motion within the ascending colon following a colonic stimulus in the form of a macrogol drink

Impaired uptake of serotonin by platelets from patients with irritable bowel syndrome correlates with duodenal immune activation

Background &amp; AimsPatients with irritable bowel syndrome with diarrhea (IBS-D) have increased mucosal serotonin (5-hydroxytryptamine [5-HT]) availability, possibly because immune activation reduces activity of the 5-HT transporter (SERT). We investigated the relationship between mucosal and platelet SERT and immune activation of the duodenal mucosa in patients with IBS-D.MethodsWe quantified mucosal intraepithelial lymphocytes (IELs), mast cells, and enterochromaffin cells in blood samples, measured levels of SERT messenger RNA (mRNA) in mucosal samples, and assessed platelet uptake of 5-HT and platelet membrane binding of 3H-paroxetine in samples from 29 healthy volunteers (HVs), 20 patients with IBS-D, and 20 untreated patients with celiac disease.ResultsPatients with IBS-D or celiac disease had increased numbers of IELs and mast cells compared with HVs (both P &lt; .001). Levels of SERT mRNA were reduced in the mucosa of patients with IBS-D or celiac disease and were inversely correlated with numbers of IELs (r = ?0.72, P &lt; .0001). Uptake of 5-HT by platelets from patients with IBS-D or celiac disease was reduced (mean, 17.1 ± 3.5 and 28.3 ± 4.1 nmol • min?1 • mg?1, respectively) compared with HVs (50.8 ± 8.0 nmol • min?1 • mg?1, P &lt; .01 and P = .05, respectively). Binding of paroxetine to membranes of platelets from patients with IBS-D (median [interquartile range], 226 [92–405] fmol/mg protein) was significantly greater than that from HVs (109 [69–175] fmol/mg protein) and correlated inversely with platelet uptake of 5-HT (r = ?0.62, P = .03). Tryptase release from incubated biopsy samples was significantly increased in patients with IBS-D (2.2 [0.42–3.5] vs 0.50 [0.25–0.86] ng • mL?1 • mg?1 for HVs; P = .03).ConclusionsPlatelet SERT is reduced in IBS-D and associated with reduced levels of SERT mRNA and duodenal immune activation.<br/

Follow-on rifaximin for the prevention of recurrence following standard treatment of infection with clostridium fifficile (RAPID): a randomised placebo controlled trial

©2018 The Authors. Published by BMJ. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: http://dx.doi.org/10.1136/gutjnl-2018-316794Background Clostridium difficile infection (CDI) recurs after initial treatment in approximately one in four patients. A single-centre pilot study suggested that this could be reduced using ’follow-on’ rifaximin treatment. We aimed to assess the efficacy of rifaximin treatment in preventing recurrence. Methods A multisite, parallel group, randomised, placebo controlled trial recruiting patients aged ≥18 years immediately after resolution of CDI through treatment with metronidazole or vancomycin. Participants received either rifaximin 400mg three times a day for 2weeks, reduced to 200mg three times a day for a further 2weeks or identical placebo. The primary endpoint was recurrence of CDI within 12 weeks of trial entry. Results Between December 2012 and March 2016, 151 participants were randomised to either rifaximin or placebo. Primary outcome data were available on 130. Mean age was 71.9 years (SD 15.3). Recurrence within 12 weeks was 29.5% (18/61) among participants allocated to placebo compared with 15.9% (11/69) among those allocated to rifaximin, a difference between groups of 13.7% (95% CI −28.1% to 0.7%, p=0.06). The risk ratio was 0.54 (95% CI 0.28 to 1.05, p=0.07). During 6-month safety follow-up, nine participants died in each group (12%). Adverse event rates were similar between groups. Conclusion While ’follow-on’ rifaximin after CDI appeared to halve recurrence rate, we failed to reach our recruitment target in this group of frail elderly patients, so the estimated effect of rifaximin lacks precision. A meta-analysis including a previous trial suggests that rifaximin may be effective; however, further, larger confirmatory studies are needed.The trial was sponsored by the University of Nottingham, was coordinated from the Nottingham Clinical Trials Unit and was supported by the National Institute for Health Research Clinical Research Network