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AbstractBackgroundSynthetic human ghrelin accelerates gastric emptying, reduces gastric accommodation, and results in numerical increases in postprandial symptom scores. The ghrelin receptor agonist, relamorelin, accelerates gastric emptying in patients with diabetic gastroparesis.AimTo measure pharmacological effects of relamorelin on gastric accommodation, distal antral motility, and satiation in healthy volunteers.MethodsIn a placebo‐controlled, double‐blind, randomized study of 16 healthy volunteers, we compared effects of 30 μg subcutaneous (s.c.) relamorelin to placebo on: (i) gastric volumes measured by single photon emission computed tomography, (ii) 1‐h postprandial distal antral motility index (MI) by 15‐lumen perfusion gastroduodenal manometry, and (iii) satiation tested by Ensure nutrient drink test. Primary endpoints were: fasting and postprandial gastric volumes, distal antral phasic pressure activity (number of contractions, mean amplitude, and MI), and maximum tolerated volume. Results were normally distributed and the two treatment groups were compared using t‐test.Key ResultsRelamorelin, 30 μg s.c., significantly increased the number of contractions in the distal antrum during 0–60 min postmeal when compared to placebo (p = 0.022); this was also observed in the first two 15‐min periods (p = 0.005 and 0.015 for number of contractions 0–15 and 16–30). There was borderline increase in MI0‐15 (p = 0.055) and numerically increased MI0‐60 (p = 0.139) and MI16‐30 (p = 0.116). The amplitude of contractions was not significantly increased. Relamorelin did not significantly alter fasting or postprandial gastric volumes, gastric accommodation, or satiation volumes and symptoms.Conclusions & InferencesRelamorelin increases frequency of distal antral motility contractions without significant effects on amplitude of contractions. The lack of inhibition of accommodation and absence of increase in satiation symptoms support relamorelin for the treatment of symptomatic gastroparesis (ClinicalTrials.gov NCT02466711).

The mucosal gene expression in rectosigmoid mucosa (RSM) in irritable bowel syndrome with diarrhea (IBS-D) is unknown. Our objectives were, first, to study mRNA expression [by RT2 PCR of 19 genes pertaining to tight junctions, immune activation, intestinal ion transport and bile acid (BA) homeostasis] in RSM in IBS-D patients ( n = 47) and healthy controls ( n = 17) and study expression of a selected protein (PDZD3) in 10 IBS-D patients and 4 healthy controls; second, to assess RSM mRNA expression according to genotype and fecal BA excretion (high ≥2,337 μmol/48 h); and third, to determine whether genotype or mucosal mRNA expression is associated with colonic transit or BA parameters. Fold changes were corrected for false detection rate for 19 genes studied ( P < 0.00263). In RSM in IBS-D patients compared with controls, mRNA expression of GUC2AB, PDZD3, and PR2Y4 was increased, whereas CLDN1 and FN1 were decreased. One immune-related gene was upregulated (C4BP4) and one downregulated (CCL20). There was increased expression of a selected ion transport protein (PDZD3) on immunohistochemistry and Western blot in IBS-D compared with controls ( P = 0.02). There were no significant differences in mucosal mRNA in 20 IBS-D patients with high compared with 27 IBS-D patients with normal BA excretion. GPBAR1 ( P < 0.05) was associated with colonic transit. We concluded that mucosal ion transport mRNA (for several genes and PDZD3 protein) is upregulated and barrier protein mRNA downregulated in IBS-D compared with healthy controls, independent of genotype. There are no differences in gene expression in IBS-D with high compared with normal fecal BA excretion.

Summary Background About one‐third of patients with IBS ‐diarrhoea (irritable bowel syndrome‐D) have evidence of increased bile acid synthesis or excretion. Aims To assess effects of the bile acid sequestrant, colesevelam, on faecal excretion of BA s, hepatic BA synthesis and diarrhoea in IBS ‐D; to appraise whether individual or random stool samples accurately reflect 48‐h total faecal bile acid excretion and proportions of the main bile acids excreted and to study the faecal fat excretion in response to colesevelam. Methods A single‐centre, unblinded, single‐dose trial of effects of colesevelam, 1875 mg [3 tablets (625 mg tablets)] orally, twice daily, for 10 days on total 48‐h faecal bile acid excretion and fasting serum C4 (7α‐hydroxy‐4‐cholesten‐3‐one; surrogate of hepatic bile acid synthesis). Stool diaries documented bowel functions for 8 days prior and 8 days during colesevelam treatment. Stool 48‐h samples and fasting serum were collected for faecal fat, faecal bile acid and serum C4. Results Colesevelam was associated with significantly increased faecal total bile acid excretion and deoxycholic acid excretion, increased serum C4 and more solid stool consistency. There was a significant inverse correlation between number of bowel movements per week and the total bile acid sequestered into stool during the last 48 h of treatment. Random stool samples did not accurately reflect 48‐h total or individual faecal bile acid excretion. Sequestration of bile acids by colesevelam did not increase faecal fat. Conclusions Colesevelam increases delivery of bile acids to stool while improving stool consistency, and increases hepatic bile acid synthesis, avoiding steatorrhoea in patients with IBS ‐D. Overall effects are consistent with luminal bile acid sequestration by colesevelam.

AbstractBackgroundA valid biomarker is ‘an indicator of normal biologic or pathogenic processes, or pharmacological responses to a therapeutic intervention’. There is no validated biomarker for irritable bowel syndrome (IBS). The aim of the study was to assess ability of three quantitative traits to identify treatable processes to discriminate between IBS‐diarrhea (IBS‐D) patients, IBS‐constipation (IBS‐C) patients and healthy volunteers (HV).MethodsIn 30 HV, 30 IBS‐C patients and 64 IBS‐D patients, we characterized bowel symptoms and quantitated pathophysiological mechanisms: bile acid (BA) synthesis (serum C4 and FGF19), fecal BA and fat, colonic transit (CT), and intestinal permeability (IP). We used multiple logistic regression and receiver‐operating characteristic (ROCAUC) to appraise three factors (fecal BA, CT, and IP) individually and in combination to identify discriminant targets for treatment in IBS.Key ResultsThere were significant associations between the three subgroups and symptoms reflecting bowel function and the quantitative traits. There were significant associations between fecal BA and CT at 48 h (r = 0.43; p < 0.001) and between fecal BA and IP (r = 0.23; p = 0.015). Individually, fecal BA and CT48 (but not IP) were significant independent predictors for distinguishing HV from IBS. In combination, they discriminated HV from IBS‐D patients (ROCAUC 0.70), HV from IBS‐C patients (ROCAUC 0.73), and IBS‐C patients from IBS‐D patients (ROCAUC 0.86). Colonic transit and fecal BA excretion together discriminate between healthy volunteers and IBS‐C patients or IBS‐D patients, or between the IBS subgroups with 75–90% specificity at 60% sensitivity.Conclusions & InferencesColonic transit and fecal BA individually and together constitute useful biomarkers to identify treatable mechanisms in IBS and to differentiate subgroups of IBS.

The pathobiology of irritable bowel syndrome (IBS) is multifaceted. We aimed to identify candidate genes predisposing to quantitative traits in IBS. In 30 healthy volunteers, 30 IBS-constipation, and 64 IBS-diarrhea patients, we measured bowel symptoms, bile acid (BA) synthesis (serum 7α-hydroxy-4-cholesten-3-one and FGF19), fecal BA and fat, colonic transit (CT by scintigraphy), and intestinal permeability (IP by 2-sugar excretion). We assessed associations of candidate genes controlling BA metabolism ( KLB rs17618244 and FGFR4 rs351855), BA receptor ( GPBAR1 rs11554825), serotonin (5-HT) reuptake ( SLC6A4 through rs4795541 which encodes for the 44-bp insert in 5HTTLPR), or immune activation ( TNFSF15 rs4263839) with three primary quantitative traits of interest: colonic transit, BA synthesis, and fecal BA excretion. There were significant associations between fecal BA and CT at 48 h ( r = 0.43; P < 0.001) and IP ( r = 0.23; P = 0.015). GPBAR1 genotype was associated with CT48 ( P = 0.003) and total fecal BA [ P = 0.030, false detection rate (FDR) P = 0.033]. Faster CT48 observed with both CC and TT GPBAR1 genotypes was due to significant interaction with G allele of KLB, which increases BA synthesis and excretion. Other univariate associations ( P < 0.05, without FDR correction) observed between GPBAR1 and symptom phenotype and gas sensation ratings support the role of GPBAR1 receptor. Associations between SLC6A4 and stool consistency, ease of passage, postprandial colonic tone, and total fecal BA excretion provide data in support of future hypothesis-testing studies. Genetic control of GPBAR1 receptor predisposing to pathobiological mechanisms in IBS provides evidence from humans in support of the importance of GPBAR1 to colonic motor and secretory functions demonstrated in animal studies.

Our aim was to conduct a pilot case-control study of RNA expression profile using RNA sequencing of rectosigmoid mucosa of nine females with -diarrhea-predominant irritable bowel syndrome (IBS-D) with accelerated colonic transit and nine female healthy controls. Mucosal total RNA was isolated and purified, and next-generation pair-end sequencing was performed using Illumina TruSeq. Analysis was carried out using a targeted approach toward 12 genes previously associated with IBS and a hypothesis-generating approach. Of the 12 targeted genes tested, patients with IBS-D had decreased mRNA expression of TNFSF15 (fold change controls to IBS-D: 1.53, P = 0.01). Overall, up- and downregulated mRNA expressions of 21 genes ( P = 10−5 to 10−8; P values with false detection rates are shown) were potentially relevant to IBS-D including the following: neurotransmitters [ P2RY4 ( P = 0.001), vasoactive intestinal peptide ( VIP, P = 0.02)]; cytokines [ CCL20 ( P = 0.019)]; immune function [ C4BPA complement cascade ( P = 0.0187)]; interferon-related [ IFIT3 ( P = 0.016)]; mucosal repair and cell adhesion [trefoil protein ( TFF1, P = 0.012)], retinol binding protein [ RBP2 ( P = 0.017)]; fibronectin ( FN1, P = 0.009); and ion channel functions [guanylate cyclase ( GUCA2B, P = 0.017), PDZ domain-containing protein 3 ( PDZD3, P = 0.029)]. Ten genes associated with functions related to pathobiology of IBS-D were validated by RT-PCR. There was significant correlation in fold changes of the selected genes ( Rs = 0.73, P = 0.013). Up- or downregulation of P2RY4, GUC2AB, RBP2, FNI, and C4BPA genes were confirmed on RT-PCR, which also revealed upregulation of farnesoid X receptor ( FXR) and apical sodium-coupled bile acid transporter ( IBAT/ASBT). RNA-Seq and RT-PCR analysis of rectosigmoid mucosa in IBS-D show transcriptome changes that provide the rationale for validation studies to explore the role of mucosal factors in the pathobiology of IBS-D.

OBJECTIVE To investigate the pharmacokinetics (PK), pharmacodynamics, and safety of single-dose RM-131 in type 2 diabetic patients with gastrointestinal cardinal symptoms (GCSI) and previously documented delayed gastric emptying (DGE). RESEARCH DESIGN AND METHODS In a randomized crossover study, 10 female patients received RM-131 (100 μg s.c.) or placebo and underwent scintigraphic gastric emptying (GE) and colonic filling at 6 h (CF6) of a solid-liquid meal administered 30 min postdosing. Adverse events, plasma glucose, and hormonal levels were assessed. GCSI daily diary (GCSI-DD) was completed during treatments. PK was assessed in this cohort and healthy volunteers (HVs). RESULTS At screening, HbA1c was 7.2 ± 0.4% (SEM) and total GCSI-DD score was 1.32 ± 0.21. RM-131 accelerated GE t1/2 of solids (P = 0.011); mean difference (Δ) in solid GE t1/2 was 68.3 min (95% CI 20–117) or 66.1%. There were numerical differences in GE lag time, CF6 solids, and GE t1/2 liquids (all P &lt; 0.14). With a significant (P &lt; 0.014) order effect, further analysis of the first treatment period (n = 5 per group) confirmed significant RM-131 effects on GE t1/2 (solids, P = 0.016; liquids, P = 0.024; CF6, P = 0.013). PK was similar in DGE patients and HVs. There were increases in 120-min blood glucose (P = 0.07) as well as 30–90-min area under the curve (AUC) levels of growth hormone, cortisol, and prolactin (all P &lt; 0.02) with single-dose RM-131. Only light-headedness was reported more on RM-131. CONCLUSIONS RM-131 greatly accelerates the GE of solids in patients with type 2 diabetes and documented DGE. PK is similar in diabetic patients and HVs.

SummaryBackgroundTapentadol is a mu‐opioid receptor agonist and norepinephrine reuptake inhibitor. In clinical trials, tapentadol provided somatic pain relief comparable to mu‐opioids such as oxycodone, with significantly less gastrointestinal adverse effects. The acute effects of tapentadol on gastrointestinal and colonic transit are unclear.AimTo compare acute effects of oral tapentadol and oxycodone on gastric, small bowel and colonic transit of solids in 38 healthy human subjects.MethodsIn a randomised, parallel‐group, double‐blind, placebo‐controlled study of the effects of identical‐appearing tapentadol immediate release (IR), 75 mg t.d.s., or oxycodone IR, 5 mg t.d.s., for 48 h, we measured gastric (GE), small bowel (SBT measured as colonic filling at 6 h) and colonic transit by validated scintigraphy. Drug was commenced on the evening before the start of the transit test. The primary endpoints were overall colonic transit (geometric centre, GC) at 24 h and GE half‐time (t1/2). ancova of transit data included gender or BMI as covariates. Adverse effects were summarised.ResultsAt the doses tested, oxycodone and tapentadol significantly delayed GE t1/2 and SBT, but not overall colonic transit, compared to placebo. Transit profiles in all regions were not significantly different between oxycodone and tapentadol at the doses tested. Both oxycodone and tapentadol were associated with nausea and central effects attributable to central opiate effects.ConclusionsTapentadol significantly delayed gastric emptying t1/2 and small bowel transit, similar to oxycodone. These data suggest that acute administration of tapentadol may not have significant advantages over standard mu‐opioids, in terms of the potential to avoid upper gastrointestinal motor dysfunction.