Local immune response as novel disease mechanism underlying abdominal pain in patients with irritable bowel syndrome

OBJECTIVES

Irritable bowel syndrome (IBS) is the most frequently diagnosed functional gastrointestinal disorder, with a prevalence of up to 25% of the global population. IBS patients suffer from abnormal abdominal pain, or visceral hypersensitivity (VHS), associated with altered bowel habits in the absence of an organic detectable cause. The pathophysiology of the disease is incompletely understood, but the dysregulation of the brain-gut axis is well established in IBS.

METHODS

IBS onset is mainly triggered by infectious gastroenteritis, psychological factors, and dietary factors, but genetic predispositions and intestinal dysbiosis might also play a role. Additionally, immune activation, and particularly chronic mast cell activation, have been shown to underlie the development of abdominal pain in IBS.

RESULTS

By releasing increased levels of mediators, including histamine, mast cells sensitize enteric nociceptors and lead to VHS development. The mechanisms underlying aberrant mast cell activation in IBS are still under investigation, but we recently showed that a local break in oral tolerance to food antigens led to IgE-mediated mast cell activation and food-induced abdominal pain in preclinical models and in IBS patients.

CONCLUSION

The concept of food-mediated VHS highlights the potential of therapies targeting upstream mechanisms of mast cell sensitization to treat IBS.

The 2018 ISDE achalasia guidelines

Achalasia is a relatively rare primary motor esophageal disorder, characterized by absence of relaxations of the lower esophageal sphincter and of peristalsis along the esophageal body. As a result, patients typically present with dysphagia, regurgitation and occasionally chest pain, pulmonary complication and malnutrition. New diagnostic methodologies and therapeutic techniques have been recently added to the armamentarium for treating achalasia. With the aim to offer clinicians and patients an up-to-date framework for making informed decisions on the management of this disease, the International Society for Diseases of the Esophagus Guidelines proposed and endorsed the Esophageal Achalasia Guidelines (I-GOAL). The guidelines were prepared according the Appraisal of Guidelines for Research and Evaluation (AGREE-REX) tool, accredited for guideline production by NICE UK. A systematic literature search was performed and the quality of evidence and the strength of recommendations were graded according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE). Given the relative rarity of this disease and the paucity of high-level evidence in the literature, this process was integrated with a three-step process of anonymous voting on each statement (DELPHI). Only statements with an approval rate >80% were accepted in the guidelines. Fifty-one experts from 11 countries and 3 representatives from patient support associations participated to the preparations of the guidelines. These guidelines deal specifically with the following achalasia issues: Diagnostic workup, Definition of the disease, Severity of presentation, Medical treatment, Botulinum Toxin injection, Pneumatic dilatation, POEM, Other endoscopic treatments, Laparoscopic myotomy, Definition of recurrence, Follow up and risk of cancer, Management of end stage achalasia, Treatment options for failure, Achalasia in children, Achalasia secondary to Chagas' disease.

Economic evaluation of the randomized European Achalasia trial comparing pneumodilation with Laparoscopic Heller myotomy

BACKGROUND

A recent multicenter randomized trial in achalasia patients has shown that pneumatic dilation resulted in equivalent relief of symptoms compared to laparoscopic Heller myotomy. Additionally, the cost of each treatment should be also taken in consideration. Therefore, the aim of the present study was to perform an economic analysis of the European achalasia trial.

METHODS

Patients with newly diagnosed achalasia were enrolled from to 2003 to 2008 in 14 centers in five European countries and were randomly assigned to either pneumatic dilation (PD) or laparoscopic Heller (LHM). The economic analysis was performed in the three centers in three different countries where most patients were enrolled (Amsterdam [NL], Leuven, [B] and Padova [I]) and then applied to all patients included in the study. The total raw costs of the two treatments per patient include the initial costs, the costs of complications, and the costs of retreatments.

RESULTS

Two hundred and one patients, 107 (57 males and 50 females, mean age 46 CI: 43-49 years) were randomized to LHM and 94 (59 males and 34 females, mean age 46 CI 43-50 years) to PD. The total cost of PD per patient was quite comparable in the three different centers; €3397 in Padova, €3259 in Amsterdam and €3792 in Leuven. For LHM, the total costs per patient were highest in Amsterdam: €4488 in Padova, €6720 in Amsterdam, and €5856 in Leuven.

CONCLUSION

In conclusion, the strategy of treating achalasia starting with PD appears the most economic approach, independent of the health system.

Restoring airway epithelial barrier dysfunction: a new therapeutic challenge in allergic airway disease

An intact functional mucosal barrier is considered to be crucial for the maintenance of airway homeostasis as it protects the host immune system from exposure to allergens and noxious environmental triggers. Recent data provided evidence for the contribution of barrier dysfunction to the development of inflammatory diseases in the airways, skin and gut. A defective barrier has been documented in chronic rhinosinusitis, allergic rhinitis, asthma, atopic dermatitis and inflammatory bowel diseases. However, it remains to be elucidated to what extent primary (genetic) versus secondary (inflammatory) mechanisms drive barrier dysfunction. The precise pathogenesis of barrier dysfunction in patients with chronic mucosal inflammation and its implications on tissue inflammation and systemic absorption of exogenous particles are only partly understood. Since epithelial barrier defects are linked with chronicity and severity of airway inflammation, restoring the barrier integrity may become a useful approach in the treatment of allergic diseases. We here provide a state-of-the-art review on epithelial barrier dysfunction in upper and lower airways as well as in the intestine and the skin and on how barrier dysfunction can be restored from a therapeutic perspective.

Incidence of prolonged postoperative ileus after colorectal surgery: a systematic review and meta-analysis

AIM

Prolonged postoperative ileus (PPOI) after colorectal surgery remains a leading cause of delayed postoperative recovery and prolonged hospital stay. Its exact incidence is unknown. The aim of this systematic review is to investigate the definitions and incidence of PPOI previously described.

METHOD

MEDLINE, Embase and the Cochrane Database of Systematic Reviews (up to July 2014) were searched. Two authors independently reviewed citations using predefined inclusion and exclusion criteria.

RESULTS

The search strategy yielded 3233 citations; 54 were eligible, comprising 18 983 patients. Twenty-six studies were prospective [17 of these being randomized controlled trials (RCTs)] and 28 were retrospective. Meta-analysis revealed an incidence of PPOI of 10.3% (95% CI 8.4-12.5) and 10.2% (95% CI 5.6-17.8) for non-RCTs and RCTs, respectively. Significant heterogeneity was observed for both non-RCTs and for RCTs. The used definition of PPOI, the type of surgery and access (laparoscopic, open) and the duration of surgery lead to significant variability of reported PPOI incidence between studies. The incidence of PPOI is lower after laparoscopic colonic resection.

CONCLUSION

There is a large variation in the reported incidence of PPOI. A uniform definition of PPOI is needed to allow meaningful inter-study comparisons and to evaluate strategies to prevent PPOI.

A meta-analysis of immunogenetic Case-Control Association Studies in irritable bowel syndrome

BACKGROUND

To date, genetic-association studies of single nucleotide polymorphisms (SNP) in selected candidate genes with the symptom phenotype of irritable bowel syndrome (IBS) have typically involved hundreds to 2000 patients. SNPs in immune-related genes, such as cytokine and cytokine receptor encoding genes, have been reported to associate with IBS risk.

METHODS

We conducted two independent case-control studies on 16 SNPs in IL1R1, IL4, IL6, IL8, IL10, IL23R, TNFA, and TNFSF15, one from the UK (194 patients and 92 healthy volunteers) and one from the USA (137 patients and 96 healthy volunteers). The main aim was to examine the relationship between inherited immunological diversity and IBS risk in a meta-analysis which included 12 additional, earlier studies. The meta-analysis comprised a total of 2894 patients (839 IBS-C, 1073 IBS-D, 502 IBS-M), and 3138 healthy volunteers with self-reported Caucasian ancestry.

KEY RESULTS

The association of SNP rs4263839 (TNFSF15) was investigated in four studies and confirmed in the meta-analysis: IBS (OR 1.19, 95% CI 1.08-1.31), and IBS-C (OR 1.24, 95% CI 1.08-1.42). No additional SNPs residing in immunogenes associated with IBS symptom phenotypes.

CONCLUSIONS & INFERENCES

Our meta-analysis could not confirm a major role of most investigated SNPs, but a moderate association between rs4263839 TNFSF15 and IBS, in particular IBS-C. The analysis emphasizes the importance of definition and phenotype homogeneity, adequate study size and representativeness of the patient and control collective.

In-hospital costs associated with chronic constipation in Belgium: a retrospective database study

BACKGROUND

Real-life data on the economic burden of chronic idiopathic constipation are scarce. The objectives of this study were to assess hospitalization resource use and costs associated with chronic constipation and its complications in Belgium.

METHODS

This was a single country, retrospective study using the IMS Hospital Disease Database (2008), which comprises data on 34% of acute hospital beds in Belgium and contains information on patient demographics, length of stay (LOS), billed costs, drug use, diagnoses, and procedures. Stays with a primary diagnosis of constipation, or a secondary diagnosis of constipation and a concomitant diagnosis of a constipation-related complication, were selected. Patients with diagnoses of colorectal cancer, ulcerative colitis or Crohn's disease, or who had stays involving potentially constipation-inducing procedures, were excluded as having secondary constipation. Patients receiving opioids, calcium-antagonists, antipsychotics or antidepressants were excluded as having drug-induced constipation.

KEY RESULTS

In total, 1541 eligible patients were identified. The average unadjusted cost per day in hospital for idiopathic constipation was €441 (€311 ± 1.4 in day clinic visits without overnight stays; €711 ± 14.0 in full hospitalizations with complications). The average LOS in a full hospitalization setting was 7.0 and 4.0 days in stays with and without complications, respectively. The most frequent drug and procedural treatments were osmotically acting laxatives (with complications: 42.61%; without complications: 35.69%), and transanal enema (2.32% and 2.03%), respectively.

CONCLUSIONS & INFERENCES

The burden of constipation is often underestimated; it is a condition reflected by hospital-related costs comparable to such indications as migraine, which increase when associated with complications.

Balloon dilation of the esophago-gastric junction affects lower and upper esophageal sphincter function in achalasia

BACKGROUND

Pneumatic dilation of the lower esophageal sphincter (LES) in achalasia has an unappreciated effect on upper esophageal sphincter (UES) function. We studied UES pressure patterns at baseline and alterations in UES parameters resulting from therapy.

METHODS

High-resolution manometry (HRM) tracings from 50 achalasia patients, seen at a tertiary center between January 2009 and July 2011, were reviewed. Manometric parameters studied were (i) LES: resting pressure (restP), 4-second integrated relaxation pressure (IRP4); (ii) UES: resting pressure (restP), minimal relaxation pressure (MRP), peak pressure (PP), relaxation interval (RI), intrabolus pressure (IBP), and deglutitive sphincter resistance (DSR). Mixed models analyses with LES and UES parameters as dependent variables and treatment stage as within-subject independent variable of interest were used. Correlations between treatment-induced changes in LES, UES, and esophageal body (EB) parameters were performed.

KEY RESULTS

Pre- and posttreatment HRM tracings were available from 50 patients (mean age 52.7 ± 18.6 years, 29 men). Upper esophageal sphincter parameters MRP (17.9 ± 1.2 vs 15.2 ± 0.9 mmHg; p = 0.02) and IBP (31.5 ± 1.5 vs 27.4 ± 1.2 mmHg; p = 0.009) were significantly reduced after initial balloon dilation and this effect was significant in type II achalasia (p = 0.002 and p = 0.0006). Peak pressure, RI, and DSR were not. The therapeutic effect on LES IRP4 correlated significantly with the change in UES MRP, statistically mediated by the change in EB deglutitive pressure (p = 0.004 and p = 0.0002).

CONCLUSIONS & INFERENCES

We present the first HRM study demonstrating that pneumatic dilation of the LES affects intraesophageal and UES pressures in patients with achalasia.

Up-date on neuro-immune mechanisms involved in allergic and non-allergic rhinitis

Non-allergic rhinitis (NAR) is a common disorder, which can be defined as chronic nasal inflammation, independent of systemic IgE-mediated mechanisms. Symptoms of NAR patients mimic those of allergic rhinitis (AR) patients. However, AR patients can easily be diagnosed with skin prick test or allergen-specific IgE measurements in the serum, whereas NAR patients form a heterogeneous group and are difficult to diagnose because of an extensive list of different phenotypes, all varying in severity, underlying etiology and type of inflammation. Characterization of those phenotypes, mechanisms and management of NAR represents one of the major unmet needs in the field of allergic and non-allergic diseases. This review aims at providing a comprehensive overview of the state of the art in classifying the NAR patients and focuses on the neuro-immune mechanisms involved in allergic and non-allergic rhinitis, including reflections on the pathophysiology and the currently available treatment options.

The clinical importance of the anti-inflammatory vagovagal reflex

Excessive activation of the immune system is prevented by anti-inflammatory mediators such as corticosteroids and anti-inflammatory cytokines. Recently, it became clear that the brain not only senses peripheral inflammation through vagal afferent nerve fibers, but also provides an integrated response dampening the immune system through vagal efferents. This so-called anti-inflammatory pathway has been introduced as a third system by which the immune system is modulated. In sepsis, the anti-inflammatory effect is mediated by modulation of splenic macrophages, whereas in the gut, vagal nerve fibers synapse with enteric cholinergic neurons interacting with resident intestinal macrophages. In this chapter, the preclinical data underscoring the importance of this pathway are summarized, and its clinical significance is reviewed. Finally, the current data supporting its relevance to human disease and its therapeutic potential will be discussed. Insight in the mechanisms underlying these crucial properties will lead to better understanding of immune-mediated diseases and ultimately to improved anti-inflammatory therapies.

Up-date on neuro-immune mechanisms involved in allergic and non-allergic rhinitis

Non-allergic rhinitis (NAR) is a common disorder, which can be defined as chronic nasal inflammation, independent of systemic IgE-mediated mechanisms. Symptoms of NAR patients mimic those of allergic rhinitis (AR) patients. However, AR patients can easily be diagnosed with skin prick test or allergen-specific IgE measurements in the serum, whereas NAR patients form a heterogeneous group and are difficult to diagnose because of an extensive list of different phenotypes, all varying in severity, underlying etiology and type of inflammation. Characterization of those phenotypes, mechanisms and management of NAR represents one of the major unmet needs in the field of allergic and non-allergic diseases. This review aims at providing a comprehensive overview of the state of the art in classifying the NAR patients and focuses on the neuro-immune mechanisms involved in allergic and non-allergic rhinitis, including reflections on the pathophysiology and the currently available treatment options.

Altered brain activation to colorectal distention in visceral hypersensitive maternal-separated rats

BACKGROUND

Early life trauma can predispose to increased visceral pain perception. Human neuroimaging studies emphasize that altered brain processing may contribute to increased visceral sensitivity. The aim of our study was to evaluate brain responses to painful visceral stimuli in maternal-separated rats before and after acute stress exposure in vivo.

METHODS

H(2)(15)O microPET scanning was performed during colorectal distention in maternal-separated rats before and after water avoidance stress. Brain images were anatomically normalized to Paxinos space and analyzed by voxel-based statistical parametric mapping (SPM2). Colorectal induced visceral pain was assessed by recording of the visceromotor response using abdominal muscle electromyography.

KEY RESULTS

Colorectal distention (1.0-2.0 mL) evoked a volume-dependent increase in visceromotor response in maternal-separated rats. Stress [water avoidance (WA)] induced an increased visceromotor response to colorectal distention in awake and anesthetized rats. In pre-WA rats, colorectal distention evoked significant increases in regional blood flow in the cerebellum and periaquaductal gray (PAG). Colorectal distention post-WA revealed activation clusters covering the PAG as well as somatosensory cortex and hippocampus. At maximal colorectal distention, the frontal cortex was significantly deactivated.

CONCLUSIONS & INFERENCES

WA stress induced increased pain perception as well as activation of the somatosensory cortex, PAG, and hippocampus in maternal-separated rats. These findings are in line with human studies and provide indirect evidence that the maternal separation model mimics the cerebral response to visceral hypersensitivity in humans.

Achalasia and esophago-gastric junction outflow obstruction: focus on the subtypes

BACKGROUND

The choice between pneumatic dilation and surgical myotomy is mainly determined by the preference and expertise of the treating physician. Ideally, however, treatment should be personalized to provide the optimal clinical outcome. The introduction of high resolution manometry has not only improved the specificity to diagnose achalasia, but also identified three different manometric subclasses.

PURPOSE

To review, the data suggesting differences in clinical response to treatment depending on the manometric profile.

Increasing body weight enhances prevalence and proximal extent of reflux in GERD patients 'on' and 'off' PPI therapy

BACKGROUND

Increased body weight is associated with higher intragastric pressure. Proximal extent of reflux is a determinant of symptoms in patients with gastro-esophageal reflux disease (GERD). We aimed to investigate the association between body mass index (BMI) and abdominal circumference on the incidence and proximal extent of reflux.

METHODS

A total of 95 patients [37 men, age 51(16-82) years] with typical and/or atypical GERD symptoms underwent 24 h impedance-pH monitoring. Forty-nine patients were studied 'off' and 46 'on' proton pump inhibitors (PPI) treatment. Reflux was classified as acid (pH < 4) or weakly acidic (pH 4-7). Proximal extent was defined as the number of reflux events reaching ≥15 cm above the lower esophageal sphincter. Body mass index and abdominal circumference (cm) were assessed.

KEY RESULTS

In patients 'off' PPI, there was a correlation between BMI and esophageal acid exposure (ρ = 0.53, P < 0.001), volume exposure (ρ = 0.48, P < 0.001), total number of reflux events (ρ = 0.47, P < 0.001) and number of acid reflux events (ρ = 0.49, P < 0.001). In patients 'on' PPI there was a correlation between BMI and esophageal acid exposure (ρ = 0.32, P = 0.03), volume exposure (ρ = 0.46, P < 0.01) and total number of reflux events (ρ = 0.33, P = 0.03). Similar correlations were found between abdominal circumference and reflux. A correlation between BMI and proximal extent of reflux was present in patients 'off' PPI (ρ = 0.32, P = 0.03). In patients 'on' PPI, we found a correlation between abdominal circumference and proximal extent (ρ = 0.31, P = 0.03).

CONCLUSIONS & INFERENCES

Body mass index and abdominal circumference may contribute to GER and its proximal extent, in patients 'on and 'off' PPI. Further studies investigating the role of weight reduction in the control of GERD symptoms are warranted.

Diagnosis and treatment of chronic constipation--a European perspective

BACKGROUND

Although constipation can be a chronic and severe problem, it is largely treated empirically. Evidence for the efficacy of some of the older laxatives from well-designed trials is limited. Patients often report high levels of dissatisfaction with their treatment, which is attributed to a lack of efficacy or unpleasant side-effects. Management guidelines and recommendations are limited and are not sufficiently current to include treatments that became available more recently, such as prokinetic agents in Europe.

PURPOSE

We present an overview of the pathophysiology, diagnosis, current management and available guidelines for the treatment of chronic constipation, and include recent data on the efficacy and potential clinical use of the more newly available therapeutic agents. Based on published algorithms and guidelines on the management of chronic constipation, secondary pathologies and causes are first excluded and then diet, lifestyle, and, if available, behavioral measures adopted. If these fail, bulk-forming, osmotic, and stimulant laxatives can be used. If symptoms are not satisfactorily resolved, a prokinetic agent such as prucalopride can be prescribed. Biofeedback is recommended as a treatment for chronic constipation in patients with disordered defecation. Surgery should only be considered once all other treatment options have been exhausted.

Diagnosis and treatment of chronic constipation--a European perspective

BACKGROUND

Although constipation can be a chronic and severe problem, it is largely treated empirically. Evidence for the efficacy of some of the older laxatives from well-designed trials is limited. Patients often report high levels of dissatisfaction with their treatment, which is attributed to a lack of efficacy or unpleasant side-effects. Management guidelines and recommendations are limited and are not sufficiently current to include treatments that became available more recently, such as prokinetic agents in Europe.

PURPOSE

We present an overview of the pathophysiology, diagnosis, current management and available guidelines for the treatment of chronic constipation, and include recent data on the efficacy and potential clinical use of the more newly available therapeutic agents. Based on published algorithms and guidelines on the management of chronic constipation, secondary pathologies and causes are first excluded and then diet, lifestyle, and, if available, behavioral measures adopted. If these fail, bulk-forming, osmotic, and stimulant laxatives can be used. If symptoms are not satisfactorily resolved, a prokinetic agent such as prucalopride can be prescribed. Biofeedback is recommended as a treatment for chronic constipation in patients with disordered defecation. Surgery should only be considered once all other treatment options have been exhausted.

Review article: endpoints used in functional dyspepsia drug therapy trials

BACKGROUND

The measurement of patient-reported outcomes (PRO) in treatment trials for functional gastrointestinal disorders is a matter of controversy.

AIM

To focus on instruments and endpoints that have been used to evaluate the efficacy of therapeutic agents in functional dyspepsia (FD) trials, also considering the newly defined Rome III FD criteria.

METHODS

A Medline search was conducted to identify relevant studies pertaining to FD treatment, with particular emphasis on the studies to date which have used validated outcome measures.

RESULTS

Currently available outcome measures are heterogeneous across studies. They include global binary endpoints, analogue or categorical scoring scales, uni- or multi-dimensional disease specific questionnaires, global outcome evaluations and quality of life questionnaires. Across the available outcome measures, substantial heterogeneity is found, not only in the type of endpoint measure, but also in the number and types of symptoms that are considered to be part of the FD symptom complex. Especially based on content validity, none of the existing questionnaires or endpoints can be considered sufficiently validated to be recommended unequivocally as the primary outcome measure for FD trials according to the Rome III criteria. On the other hand, existing well-validated multi-dimensional questionnaires that include many non-FD symptoms can be narrowed down to evaluate only the cardinal symptoms according to Rome III.

CONCLUSIONS

There is an urgent need to develop Rome III-based patient-reported outcomes for functional dyspepsia. Well-validated multi-dimensional questionnaires may serve as a guidance for this purpose, and could also be considered for use in ongoing clinical trials.

The GABA(B) receptor agonist AZD9343 inhibits transient lower oesophageal sphincter relaxations and acid reflux in healthy volunteers: a phase I study

BACKGROUND

Transient lower oesophageal sphincter relaxations (TLESRs) represent an interesting target for the treatment of gastro-oesophageal reflux. Baclofen reduces TLESRs and reflux episodes, but is not optimal for clinical application because of its central side effects. Therefore, new agents are required.

AIM

To study the effect of AZD9343, a new selective GABA(B) receptor agonist, in healthy volunteers.

METHODS

A total of 27 subjects participated in a placebo-controlled, randomized, two-centre phase I study. Subjects underwent oesophageal manometry and pH-metry for 3 h postprandially. Before meal ingestion, a single oral dose of placebo, 60 and 320 mg AZD9343 or 40 mg baclofen was given on four separate days.

RESULTS

Somnolence was reported after 320 mg AZD9343 and baclofen. Reversible short-lasting paraesthesia was reported after AZD9343. AZD9343 320 mg and baclofen significantly reduced the number of TLESRs with 32% and 40% respectively. Acid reflux was significantly decreased by AZD9343 and baclofen. Like baclofen, AZD9343 increased LES pressure before meal intake. AZD9343 320 mg and baclofen significantly reduced the swallowing rate.

CONCLUSIONS

Like baclofen, AZD9343 dose-dependently decreases the number of TLESRs and acid reflux episodes, increases LES pressure and reduces swallowing, extending the concept that GABA(B) agonists are potent reflux inhibitors. However, discovery of analogues with an improved side effect profile is warranted.

A placebo-controlled trial of the 5-HT1A agonist R-137696 on symptoms, visceral hypersensitivity and on impaired accommodation in functional dyspepsia

Acute studies suggested a therapeutic benefit for fundus-relaxing drugs in functional dyspepsia (FD) with visceral hypersensitivity (VH) to gastric distention or impaired accommodation (IA), but long-term studies are lacking. R-137696 is a serotonin-1A (5-HT(1A)) receptor agonist which relaxes the proximal stomach in man. Our aim was to investigate the influence of R-137696 on symptoms in FD with VH or IA. Randomized, double-blind, placebo-controlled, parallel group study of 4 weeks R-137696 2 mg t.i.d. in FD with VH or IA. Symptoms were assessed using the patient assessment of upper gastrointestinal symptom severity index (PAGI-SYM) total score and individual symptom subscales. Barostat studies were performed before and after 4 weeks of treatment. Fifty-three patients (33 VH and 20 IA), 18 men, mean age 40 +/- 13 years were recruited. Twenty-four received placebo and 29 received R-137696. In VH patients, both placebo and R-137696 improved total symptom scores, with a tendency for superiority of placebo (-1.12 vs-0.51, P = 0.07). Placebo was superior for the subscales of early satiety, bloating, fullness and discomfort (all P < 0.05). In IA, both placebo and R-137696 had no significant influence on total or individual symptom scores (-0.08 and -0.27). In VH, both placebo and R-137696 increased the discomfort volume, without a statistical difference between both arms (+120 and +164 mL). In IA, both placebo and R-137696 enhanced accommodation, without a statistical difference between both (+77 and +159 mL). Adverse events were similar for drug and placebo. A 4-week administration of the fundus-relaxing 5-HT(1A) agonist R-137696 failed to significantly improve symptoms, VH or gastric accommodation compared to placebo.

Evidence that nitric oxide mechanisms regulate small intestinal motility in humans

BACKGROUND

Non-cholinergic non-adrenergic neural mechanisms involving nerves containing NO have been shown to modulate smooth muscle in the gastrointestinal tract, and it has been suggested that release from tonic NO inhibition may be important in the regulation of cyclical fasting small intestinal motility.

AIMS

To evaluate the role of NO mechanisms in the regulation of fasting small intestinal motor activity in humans using a specific NO synthase inhibitor, NG-monomethyl-L-arginine ( L-NMMA).

METHODS

In seven healthy male volunteers, duodenal and jejunal pressures were measured for four hours with a nine lumen manometric catheter. Volunteers attended on four separate days on which they received an intravenous infusion either saline or L-NMMA (0.5, 2, or 4 mg/kg/h) in random order. Intravenous infusions began 10 minutes after completion of phase III of the migrating motor complex (MMC).

RESULTS

The first episode of phase III activity occurred earlier after infusion of 2 and 4 mg/kg/h L-NMMA than after infusion of 0.5 mg/kg/h L-NMMA or saline (mean (95% confidence interval) 52 (36-68) and 57 (18-97) v 116 (69-193) and 145 (64-226) minutes respectively) with a resultant MMC cycle length of 82 (59-105) and 86 (46-126) v 132 (49-198) and 169 (98-240) minutes respectively. The total number of phase III activities during the four hour recording was increased (p<0.05) by L-NMMA at a dose of 4 mg/kg/h (2 (1-3)) but not at 2 mg/kg/h (1.5 (1-2)) or 0.5 mg/kg/h (1.3 (1-2)) compared with saline (1.3 (0.6-2)). L-NMMA had no effect on the duration, velocity, number of contractions per minute, length of migration, or site of origin of phase III of the MMC. The duration of phase I activity was shorter (p<0.05) with 4 mg/kg/h L-NMMA than with saline (12 (1-23) v 31 (19-44) minutes).

CONCLUSIONS

These observations suggest that NO mechanisms play a role in the regulation of fasting small intestinal motor activity in humans.

Effects of nitroglycerin on liquid gastric emptying and antropyloroduodenal motility

The effects of the nitric oxide donor nitroglycerin on gastric emptying and antropyloroduodenal motility were evaluated in nine healthy male subjects (ages 19-36 yr). Antropyloroduodenal pressures were recorded with a manometric assembly that had nine side holes spanning the antrum and proximal duodenum and a pyloric sleeve sensor; gastric emptying was quantified scintigraphically. In each subject, the emptying of 300 ml of 25% glucose labeled with 99mTc was assessed on two separate days during intravenous infusion of either nitroglycerin (5 micrograms/min in 5% dextrose) or 5% dextrose (control). Studies were performed with the subject in the supine position; blood pressure and heart rate were monitored. Nitroglycerin had no significant effect on blood pressure or heart rate. Nitroglycerin slowed gastric emptying (P < 0.02), and this was associated with greater retention of the drink in the proximal stomach (P < 0.05). In both nitroglycerin and control studies, ingestion of the drink was associated with an increase in the number of isolated pyloric pressure waves (P < 0.05) and antral pressure wave sequences (P < 0.05). Nitroglycerin reduced the number of isolated pyloric pressure waves (P < 0.05), basal pyloric pressure (P < 0.05), and the number of antral pressure wave sequences (P < 0. 05), but not the total number of antral pressure waves. The rate of gastric emptying and the number of isolated pyloric pressure waves were inversely related during control (P = 0.03) and nitroglycerin (P < 0.05) infusions. We conclude that in normal subjects, 1) gastric emptying of 300 ml of 25% glucose is inversely related to the frequency of phasic pyloric pressure waves, and 2) nitroglycerin in a dose of 5 micrograms/min inhibits pyloric motility, alters the organization but not the number of antral pressure waves, and slows gastric emptying and intragastric distribution of 25% glucose.