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Background and aimsGut transit time is a key modulator of host–microbiome interactions, yet this is often overlooked, partly because reliable methods are typically expensive or burdensome. The aim of this single-arm, single-blinded intervention study is to assess (1) the relationship between gut transit time and the human gut microbiome, and (2) the utility of the ‘blue dye’ method as an inexpensive and scalable technique to measure transit time.MethodsWe assessed interactions between the taxonomic and functional potential profiles of the gut microbiome (profiled via shotgun metagenomic sequencing), gut transit time (measured via the blue dye method), cardiometabolic health and diet in 863 healthy individuals from the PREDICT 1 study.ResultsWe found that gut microbiome taxonomic composition can accurately discriminate between gut transit time classes (0.82 area under the receiver operating characteristic curve) and longer gut transit time is linked with specific microbial species such as Akkermansia muciniphila, Bacteroides spp and Alistipes spp (false discovery rate-adjusted p values <0.01). The blue dye measure of gut transit time had the strongest association with the gut microbiome over typical transit time proxies such as stool consistency and frequency.ConclusionsGut transit time, measured via the blue dye method, is a more informative marker of gut microbiome function than traditional measures of stool consistency and frequency. The blue dye method can be applied in large-scale epidemiological studies to advance diet-microbiome-health research. Clinical trial registry website https://clinicaltrials.gov/ct2/show/NCT03479866 and trial number NCT03479866.

BackgroundColonic motility in constipation can be assessed non-invasively using MRI.ObjectiveTo compare MRI with high-resolution colonic manometry (HRCM) for predicting treatment response.DesignPart 1: 44 healthy volunteers (HVs), 43 patients with irritable bowel syndrome with constipation (IBS-C) and 37 with functional constipation (FC) completed stool diaries and questionnaires and underwent oral macrogol (500–1000 mL) challenge. Whole gut transit time (WGTT), segmental colonic volumes (CV), MRI-derived Motility Index and chyme movement by ‘tagging’ were assessed using MRI and time to defecation after macrogol recorded. Left colonic HRCM was recorded before and after a 700 kcal meal. Patients then proceeded to Part 2: a randomised cross-over study of 10-days bisacodyl 10 mg daily versus hyoscine 20 mg three times per day, assessing daily pain and constipation.ResultsPart 1: Total CVs median (range) were significantly greater in IBS-C (776 (595–1033)) and FC (802 (633–951)) vs HV (645 (467–780)), p<0.001. Patients also had longer WGTT and delayed evacuation after macrogol. IBS-C patients showed significantly reduced tagging index and less propagated pressure wave (PPW) activity during HRCM versus HV. Compared with FC, IBS-C patients were more anxious and reported more pain. Abnormally large colons predicted significantly delayed evacuation after macrogol challenge (p<0.02), impaired manometric meal response and reduced pain with bisacodyl (p<0.05).Part 2: Bisacodyl compared with hyoscine increased bowel movements but caused more pain in both groups (p<0.03).ConclusionAn abnormally large colon is an important feature in constipation which predicts impaired manometric response to feeding and treatment responses. HRCM shows that IBS-C patients have reduced PPW activity.Trial registration numberThe study was preregistered on ClinicalTrials.gov, Reference: NCT03226145.

Background: The relationship between gut microbiota composition, lifestyles, and colonic transit time (CTT) remains poorly understood. This study investigated associations among gut microbiota profiles, diet, lifestyles, and CTT in individuals with subjective constipation. Methods: We conducted a secondary analysis of data from our randomized clinical trial, examining gut microbiota composition, CTT, and dietary intake in baseline and final assessments of 94 participants with subjective constipation. Participants were categorized into normal-transit (<36 h) and slow-transit (≥36 h) groups based on CTT at baseline. Gut microbiota composition was measured using 16S rRNA sequencing, and dietary patterns were assessed through semi-quantitative food frequency questionnaires. Enterotype analysis, machine learning approaches, and metabolic modeling were employed to investigate microbiota–diet interactions. The constipated participants primarily belonged to Lachnospiraceae (ET-L). Results: The slow-transit group showed higher alpha diversity than the normal-transit group. Butyricicoccus faecihominis was abundant in the normal-transit group, while Neglectibacter timonensis, Intestinimonas massiliensis, and Intestinibacter bartlettii were abundant in the slow-transit group, which also had a higher abundance of mucin-degrading bacteria. Metabolic modeling predicted increased N-acetyl-D-glucosamine (GlcNAc), a mucin-derived metabolite, in the slow-transit group. Network analysis identified two microbial co-abundance groups (CAG3 and CAG9) significantly associated with transit time and dietary patterns. Six mucin-degrading species showed differential correlations with GlcNAc and a plant-based diet, particularly, including rice, bread, fruits and vegetables, and fermented beans. In conclusion, an increased abundance of mucin-degrading bacteria and their predicted metabolic products were associated with delayed CTT. Conclusion: These findings suggest dietary modulation of these bacterial populations as a potential therapeutic strategy for constipation. Moreover, our results reveal a potential immunometabolic mechanism where mucin-degrading bacteria and their metabolic interactions may influence intestinal transit, mucosal barrier function, and immune response.

Lactulose mannitol ratio tests are clinically useful for assessing disorders characterised by changes in gut permeability and for assessing mixing in the intestinal lumen. Variations between currently used test protocols preclude meaningful comparisons between studies. We determined the optimal sampling period and related this to intestinal residence. Half-hourly lactulose and mannitol urinary excretions were determined over 6 hours in 40 healthy female volunteers after administration of either 600 mg aspirin or placebo, in randomised order at weekly intervals. Gastric and small intestinal transit times were assessed by the SmartPill in 6 subjects from the same population. Half-hourly percentage recoveries of lactulose and mannitol were grouped on a basis of compartment transit time. The rate of increase or decrease of each sugar within each group was explored by simple linear regression to assess the optimal period of sampling. The between subject standard errors for each half-hourly lactulose and mannitol excretion were lowest, the correlation of the quantity of each sugar excreted with time was optimal and the difference between the two sugars in this temporal relationship maximal during the period from 2½-4 h after ingestion. Half-hourly lactulose excretions were generally increased after dosage with aspirin whilst those of mannitol were unchanged as was the temporal pattern and period of lowest between subject standard error for both sugars. The results indicate that between subject variation in the percentage excretion of the two sugars would be minimised and the differences in the temporal patterns of excretion would be maximised if the period of collection of urine used in clinical tests of small intestinal permeability were restricted to 2½-4 h post dosage. This period corresponds to a period when the column of digesta column containing the probes is passing from the small to the large intestine.

Despite a lack of supportive data, stool form and stool frequency are often used as clinical surrogates for gut transit in constipated patients. The aim of this study was to assess the correlation between stool characteristics (form and frequency) and gut transit in constipated and healthy adults. A post hoc analysis was performed on 110 subjects (46 chronic constipation) from nine US sites recording stool form (Bristol Stool Scale) and frequency during simultaneous assessment of whole-gut and colonic transit by wireless motility capsule (WMC) and radio-opaque marker (ROM) tests. Stool form and frequency were correlated with transit times using Spearman's rank correlation. Accuracy of stool form in predicting delayed transit was assessed by receiver operating characteristic analysis. In the constipated adults (42 females, 4 males), moderate correlations were found between stool form and whole-gut transit measured by WMC (r=-0.61, P<0.0001) or ROM (-0.45, P=0.0016), as well as colonic transit measured by WMC (-0.62, P<0.0001). A Bristol stool form value <3 predicted delayed whole-gut transit with a sensitivity of 85% and specificity of 82% and delayed colonic transit with a sensitivity of 82% and specificity of 83%. No correlation between stool form and measured transit was found in healthy adults, regardless of gender. No correlation was found between stool frequency and measured transit in constipated or healthy adults. The correlation between stool frequency and measured transit remained poor in constipated adults with <3 bowel movements per week. Stool form predicts delayed vs. normal transit in adults. However, only a moderate correlation exists between stool form and measured whole-gut or colonic transit time in constipated adults. In contrast, stool frequency is a poor surrogate for transit, even in those with reduced stool frequency.

Aims/hypothesis We hypothesised that type 1 diabetic patients with established diabetic sensorimotor polyneuropathy (DSPN) would have segmental and/or pan-enteric dysmotility in comparison to healthy age-matched controls. We aimed to investigate the co-relationships between gastrointestinal function, degree of DSPN and clinical symptoms. Methods An observational comparison was made between 48 patients with DSPN (39 men, mean age 50 years, range 29–71 years), representing the baseline data of an ongoing clinical trial (representing a secondary analysis of baseline data collected from an ongoing double-blind randomised controlled trial investigating the neuroprotective effects of liraglutide) and 41 healthy participants (16 men, mean age 49 years, range 30–78) who underwent a standardised wireless motility capsule test to assess gastrointestinal transit. In patients, vibration thresholds, the Michigan Neuropathy Screening Instrument and Patient Assessment of Upper Gastrointestinal Symptom questionnaires were recorded. Results Compared with healthy controls, patients showed prolonged gastric emptying (299 ± 289 vs 179 ± 49 min; p =  0.01), small bowel transit (289 ± 107 vs 224 ± 63 min; p  = 0.001), colonic transit (2140, interquartile range [IQR] 1149–2799 min vs 1087, IQR 882–1650 min; p  = 0.0001) and whole-gut transit time (2721, IQR 1196–3541 min vs 1475 (IQR 1278–2214) min; p  < 0.0001). Patients also showed an increased fall in pH across the ileocaecal junction (−1.8 ± 0.4 vs −1.3 ± 0.4 pH; p  < 0.0001), which was associated with prolonged colonic transit ( r  = 0.3, p  = 0.001). Multivariable regression, controlling for sex, disease duration and glycaemic control, demonstrated an association between whole-gut transit time and total GCSI ( p =  0.02). Conclusions/interpretation Pan-enteric prolongation of gastrointestinal transit times and a more acidic caecal pH, which may represent heightened caecal fermentation, are present in patients with type 1 diabetes. The potential implication of delayed gastrointestinal transit on the bioavailability of nutrition and on pharmacotherapeutic and glycaemic control warrants further investigation. Trial registration EUDRA CT: 2013-004375-12

Objective: To determine the efficacy, impact on quality of life (QOL) and safety of prucalopride, a selective, high-affinity 5-HT4 receptor agonist, in patients with chronic constipation. Methods: In this multicentre, randomised, placebo controlled, parallel-group, phase III study, patients with chronic constipation (two or fewer spontaneous complete bowel movements (SCBM)/week) received 2 mg or 4 mg prucalopride or placebo, once daily, for 12 weeks. The primary efficacy endpoint was the proportion of patients reaching three or more SCBM/week. The key secondary efficacy endpoint was the proportion of patients having an increase of one or more SCBM/week. The primary QOL endpoint was the patient assessment of constipation QOL satisfaction subscale score. Safety parameters included adverse events, laboratory values and cardiovascular events. Results: Efficacy was evaluated over 713 patients. Averaged over 12 weeks, higher proportions of patients on prucalopride 2 mg (19.5%; p<0.01), 4 mg (23.6%; p<0.001) had three or more SCBM/week (or normalisation of bowel function) compared with placebo (9.6%). Similar results were seen in the subgroup (83%) of patients dissatisfied with previous laxative treatment. Both doses of prucalopride also significantly improved secondary efficacy and QOL endpoints, including the proportion of patients with an increase of one or more SCBM/week, evacuation completeness, perceived disease severity and treatment effectiveness and QOL. Prucalopride 4 mg significantly reduced the need for straining versus placebo (p<0.05). The most frequent treatment-related adverse events were headache and diarrhoea. Both doses of prucalopride were safe and well tolerated. Conclusion: Prucalopride significantly and consistently improved bowel function, associated symptoms and satisfaction in chronically constipated patients. Trial registration number: NCT00488137.

Objective:This study evaluated gastric emptying (GE) and small intestinal (SI) transit in people with morbid obesity and their relationships to glycaemia, incretin hormones, and glucose absorptionMethods:GE and caecal arrival time (CAT) of a mixed meal were assessed in 22 morbidly obese (50.2 ± 2.5 years; 13 F:9 M; BMI: 48.6 ± 1.8 kg/m2) and 10 lean (38.6 ± 8.4 years; 5 F:5 M; BMI: 23.9 ± 0.7 kg/m2) subjects, using scintigraphy. Blood glucose, plasma 3-O-methylglucose, insulin, glucagon, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were measured. Insulin sensitivity and resistance were also quantifiedResults:When compared with lean subjects, GE (t50: 60.7 ± 6.5 vs. 41.1 ± 7.3 min; P  = 0.04) and CAT (221.5 ± 9.8 vs. 148.0 ± 7.1 min; P =  0.001) of solids were prolonged in morbid obesity. Postprandial rises in GIP (P = 0.001), insulin (P  = 0.02), glucose (P = 0.03) and 3-O-methylglucose (P = 0.001) were less. Whereas GLP-1 increased at 45 mins post-prandially in lean subjects, there was no increase in the obese (P  = 0.04). Both fasting (P = 0.045) and postprandial (P = 0.012) plasma glucagon concentrations were higher in the obeseConclusions:GE and SI transit are slower in the morbidly obese, and associated with reductions in postprandial glucose absorption, and glycaemic excursions, as well as plasma GIP and GLP-1

BackgroundConstipation is one of the most common gastrointestinal complaints. Although the causes of constipation are varied, dietary habits have a significant influence. Excessive fat intake is suggested as one of the main causes of constipation; however, the exact mechanism is unknown.AimsTo investigate whether a high-fat diet (HFD) causes constipation in mice and to clarify the underlying mechanism, focusing on the amount of colonic mucus.MethodsSix-week-old male C57BL/6 mice were randomly divided into two groups: mice fed with HFD and those with normal chow diet (NCD). Fecal weight, water content, total gastrointestinal transit time, and colon transit time were measured to determine whether the mice were constipated. The colonic mucus was evaluated by immunostaining and quantified by spectrometry. Malondialdehyde (MDA) was measured using the thiobarbituric acid (TBA) test as a marker for oxidative stress.ResultsCompared to the NCD group, the weight of feces was less in the HFD group. In the functional experiment, the total gastrointestinal transit time and colon transit time were longer in the HFD group. Furthermore, HFD significantly reduced the amount of colonic mucus. In addition, the reduction in colonic mucus caused by surfactant resulted in constipation in the NCD group.ConclusionsHFD causes constipation with delayed colon transit time possibly via the reduction in colonic mucus in mice.

Constipation is often characterized by slow colonic transit, but the relationship between colonic transit time (CTT) and symptoms is unclear. The aims of this study were to investigate the effect of prucalopride, a 5-hydroxytryptamine receptor-4 agonist, on CTT and assess the relationship between CTT and symptoms. This was an integrated analysis of three randomized, placebo-controlled, phase 2 dose-finding trials of prucalopride in patients with chronic constipation (ClinicalTrials.gov identifiers: NCT00617513; NCT00631813; and NCT00596596). Measurements of CTT were analyzed using radio-opaque markers at the start and end (4 or 12 weeks) of treatment. At these visits, patients assessed the presence and severity of their symptoms. In total, 280 patients had CTT measurements before and at the end of treatment and were included in the analysis. Their mean age was 43 years, 93% were women, and mean duration of constipation was 19 years. After a once daily treatment with prucalopride 2 mg (n=98) and 4 mg (n=70), CTT was reduced by 12.0 h (95% confidence interval (CI): -18.9, -5.1) and 13.9 h (95% CI: -20.5, -7.4), respectively; CTT increased by 0.5 h (95% CI: -4.5, 5.5) with placebo (n=112). At the end of the trial, symptoms including bloating/flatulence/distension and straining were rated as severe or very severe by a higher proportion of patients with slow or very slow CTT (>48 h) than by those with normal CTT. There was a clear relationship between increased CTT and increased symptom severity in patients with chronic constipation. Treatment with prucalopride accelerated CTT in these individuals.