Influence of tegaserod on proximal gastric tone and on the perception of gastric distention in functional dyspepsia

Nocebo response intensity and influencing factors in the randomized clinical trials of functional dyspepsia: A systematic review and meta-analysis

OBJECTIVES

In this study we aimed to evaluate the nocebo response rate in patients with functional dyspepsia (FD) and to explore its influencing factors.

METHODS

A literature search of the EMBASE, PubMed, and Cochrane Library databases was conducted for all articles published up to March 2021. Randomized, parallel-designed, placebo-controlled trials on pharmacological interventions for patients with FD were included. A meta-analysis that utilized random effects to analyze the incidence of adverse events (AEs) among participants who were given placebo was conducted, and the correlation between trial characteristics and the magnitude of the nocebo response rate was analyzed.

RESULTS

Altogether, 27 studies including 1866 paitents were deemed eligible and included in the analysis. The total nocebo response rate was 26% (95% confidence interval [CI] 18%-33%). The most frequently reported AEs included nasopharyngitis (9%), constipation (6%), headache (5%), and diarrhea (3%). There were significant differences in nocebo response rates among studies conducted in different country or region, treatment duration, types of medication, sponsorship and different versions of the Rome criteria used for FD diagnosis. While number of centers engaged in the study, types of FD diagnosis and dosing frequency were not significantly associated with the nocebo response rate.

CONCLUSIONS

Patients with FD exhibit notable nocebo response strength in clinical trials. The researchers should adopt a more careful approach when analyzing the relationships between AEs and interventions in such trials.

A randomized, double-blind, placebo-controlled, phase 2b study of the efficacy and safety of velusetrag in subjects with diabetic or idiopathic gastroparesis

BACKGROUND

This study assessed the efficacy and safety of velusetrag-a 5-HT₄ agonist with pan-gastrointestinal prokinetic activity-for gastroparesis symptom management and gastric emptying (GE).

METHODS

In this multicenter, double-blind, randomized, placebo-controlled study, subjects with diabetic or idiopathic gastroparesis received velusetrag 5, 15, or 30 mg or placebo for 12 weeks. The primary efficacy outcome was a 7-day mean Gastroparesis Cardinal Symptom Index 24-h composite score (GCSI-24H) change from baseline at week 4; GE was evaluated using scintigraphy (GES) and breath tests, and safety from adverse events (AEs).

KEY RESULTS

232 subjects (183 females; 113 idiopathic gastroparesis) received treatment from February 2015 through June 2017. Least-squares mean improvement from baseline GCSI-24H (primary endpoint) at week 4 was -1.5 following velusetrag 5 mg vs -1.1 following placebo (treatment difference, -0.4; 95% confidence interval, -0.75 to -0.03; nominal p = 0.0327; Hochberg-adjusted p = 0.0980 [not significant]). Symptom improvement from baseline was achieved only with velusetrag 5 mg, which resulted in greater improvement from baseline vs placebo in all gastroparesis core symptoms, especially in subjects with idiopathic gastroparesis. Improvement from baseline GE by GES was greater in subjects receiving velusetrag (all doses) vs placebo; >70% of subjects receiving velusetrag 30 mg had GE normalization at 4 h. Treatment-emergent AEs were generally mild.

CONCLUSIONS AND INFERENCES

Velusetrag treatment was generally well-tolerated and associated with improved GE vs placebo in subjects with diabetic or idiopathic gastroparesis; however, only the lowest dose, velusetrag 5 mg, was associated with short-term improvement in gastroparesis symptoms.

CLINICALTRIALS

GOV: NCT02267525.

Tegaserod: What's Old Is New Again

Irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) are common gastrointestinal disorders imposing considerable impact on the quality of life and well-being of affected individuals. A paucity of evidence-based treatment options exist for CIC and IBS-C sufferers. Tegaserod, a 5-HT₄ agonist, has a substantial body of preclinical and clinical study evidence to support its beneficial role in modulating sensorimotor function of the luminal gastrointestinal tract. Tegaserod was first approved for use by the U.S. Food and Drug Administration for the management of IBS-C and CIC in 2002 and 2004, respectively. Tegaserod enjoyed a successful uptake in the management of these disorders during its first several years of availability in the United States, but was later withdrawn from the market in 2007 over concerns related to adverse cardiovascular events. Since then, additional safety data has been generated, and following a resubmission and review by the Food and Drug Administration, in April 2019, tegaserod was once again approved for use in IBS-C under a more restricted labeling, confining use to women under 65 years of age without heart disease or additional cardiovascular risk factors. This review summarizes the regulatory journey of tegaserod and details the existing pharmacokinetic, physiologic, clinical, and safety data of tegaserod generated over the last 2 decades. The discussion also examines the future of tegaserod in the treatment of these constipation disorders, as well as its potential role in other related disorders of brain-gut interaction.

New Developments in Prokinetic Therapy for Gastric Motility Disorders

Prokinetic agents amplify and coordinate the gastrointestinal muscular contractions to facilitate the transit of intra-luminal content. Following the institution of dietary recommendations, prokinetics are the first medications whose goal is to improve gastric emptying and relieve symptoms of gastroparesis. The recommended use of metoclopramide, the only currently approved medication for gastroparesis in the United States, is for a duration of less than 3 months, due to the risk of reversible or irreversible extrapyramidal tremors. Domperidone, a dopamine D2 receptor antagonist, is available for prescription through the FDA's program for Expanded Access to Investigational Drugs. Macrolides are used off label and are associated with tachyphylaxis and variable duration of efficacy. Aprepitant relieves some symptoms of gastroparesis. There are newer agents in the pipeline targeting diverse gastric (fundic, antral and pyloric) motor functions, including novel serotonergic 5-HT₄ agonists, dopaminergic D_2/3 antagonists, neurokinin NK₁ antagonists, and ghrelin agonist. Novel targets with potential to improve gastric motor functions include the pylorus, macrophage/inflammatory function, oxidative stress, and neurogenesis. In the current review, we discuss the use of pharmacological approaches with potential to enhance motor functions in the management of gastroparesis.

The effect of prucalopride on gastric sensorimotor function and satiation in healthy volunteers

BACKGROUND

Gastric motor function alterations have been implicated in the pathogenesis of functional dyspepsia with postprandial distress syndrome (PDS). Prucalopride, a 5-TH4 agonist, is known to stimulate gastrointestinal motility. We aimed to evaluate the effect of prucalopride on gastric sensorimotor function in healthy subjects (HV).

METHODS

Barostat and intragastric pressure (IGP) measurements were performed in 17 HV (59% females, age 29.4 ± 2.7 y) after treatment with placebo or prucalopride (2 mg) (single-blind cross-over). Isobaric stepwise distensions and gastric sensations were assessed to determine gastric compliance and sensitivity. Gastric accommodation (GA) with the barostat was quantified before and after ingestion of 200 ml of a nutrient drink (ND). GA measured by IGP was quantified as the drop of IGP from baseline during the intragastric infusion of ND until maximal satiation (60 ml/min).

KEY RESULTS

Prucalopride did not affect barostat assessed gastric compliance or sensitivity. No differences were observed in GA after prucalopride. During the barostat study, 10 min after the meal, 7 HVs reported significantly higher ratings for nausea after prucalopride (p < 0.001), and vomiting was induced in 4 of the HVs. A positive correlation was observed between the delta mean perception of nausea with the delta mean increase of intra-balloon volume before and after meal ingestion (r = 0.37, p = 0.03). During IGP measurements, no effect on nutrient tolerance was observed and increased cramp severity scores were observed which were associated with a significant increase of distal IGP (r = 0.78, p < 0.0001).

CONCLUSIONS & INFERENCES

Prucalopride does not enhances gastric accommodation but it might increase sensitivity to gastric distention. Furthermore, the increase in sensitivity seems to be related to an increase in nausea with distension. Clinicaltrials.gov: NCT04429802.

Gastric accommodation influences proximal gastric and total gastric emptying in concurrent measurements conducted in healthy volunteers

Gastric emptying and gastric accommodation play a role in generation of upper gastrointestinal symptoms. Although both functions have been measured simultaneously using MRI or ^99mTc SPECT methodology, the correlation of these two functions has not been evaluated simultaneously using a solid and liquid meal. To study relationships of whole or proximal stomach volumes to emptying, we concurrently measured postprandial gastric accommodation and emptying (over 4 h) of a ¹¹¹In-labeled mixed solid and liquid meal. A semiautomated method allowing selection of a segmentation threshold based on a grayscale image was used to measure volume of the proximal half of the stomach, defined as the top half of axial slices along the vertical length of the stomach. A correction factor derived from phantom studies was applied for upscatter from the ^99mTc to the ¹¹¹In window. Relationships of time to emptying 10%, 25%, 50%, and 75% of the meal to fasting and postprandial gastric volumes were evaluated using Spearman correlation. Whole stomach fed and accommodation volumes were significantly correlated with all gastric emptying times (10%, 25%, and 50%). Proximal stomach fed volumes were similarly associated with 50% and 75% proximal gastric emptying. Fed proximal gastric volume was associated with 50% and 75% whole gastric emptying. Fed proximal accommodation volume was associated with 50% gastric emptying. Fasting gastric volumes were not significant determinants of emptying rates. In conclusion, postprandial gastric accommodation is significantly associated with the rate of gastric emptying, with higher gastric volumes associated with prolongation of emptying. Novel methods to measure proximal gastric accommodation and correct for radioisotope upscatter are described.NEW & NOTEWORTHY In vivo human studies evaluated concurrently the volume of the stomach during fasting and after a solid and liquid meal using a new SPECT-based method. Although fasting gastric volumes did not impact the rates of gastric emptying, both postprandial and accommodation volumes of the whole and proximal stomach were significantly correlated with gastric emptying. Larger stomach volumes were associated with slower gastric emptying.

Clinical Practice Guidelines for Functional Dyspepsia in Korea

Functional dyspepsia (FD) is a chronic upper gastrointestinal (GI) symptom complex that routine diagnostic work-up, such as endoscopy, blood laboratory analysis, or radiological examination, fails to identify a cause. It is highly prevalent in the World population, and its response to the various available therapeutic strategies is only modest because of the heterogenous nature of its pathogenesis. Therefore, FD represents a heavy medical burden for healthcare systems. We constituted a guideline development committee to review the existing guidelines on the management of functional dyspepsia. This committee drafted statements and conducted a systematic review and meta-analysis of various studies, guidelines, and randomized control trials. External review was also conducted by selected experts. These clinical practice guidelines for FD were developed based on evidence recently accumulated with the revised version of FD guidelines released in 2011 by the Korean Society of Neurogastroenterology and Motility. These guidelines apply to adults with chronic symptoms of FD and include the diagnostic role of endoscopy, Helicobacter pylori screening, and systematic review and meta-analyses of the various treatment options for FD (proton pump inhibitors, H.pylori eradication, and tricyclic antidepressants), especially according to the FD subtype. The purpose of these new guidelines is to aid the understanding, diagnosis, and treatment of FD, and the targets of the guidelines are clinicians, healthcare workers at the forefront of patient care, patients, and medical students. The guidelines will continue to be revised and updated periodically.

Review article: treatment options for functional dyspepsia

BACKGROUND

Functional dyspepsia, consisting of epigastric pain syndrome and postprandial distress syndrome, is a prevalent functional gastrointestinal disorder. To date, only limited treatment options are available and conflicting results in terms of efficacy have been reported. Consequently, nonpharmacological treatment options are increasingly being explored for functional dyspepsia.

AIM

To provide an overview of current pharmacological and nonpharmacological treatment options for functional dyspepsia.

METHODS

A literature search was conducted on Pubmed and other sources to identify relevant studies.

RESULTS

Acid suppressive therapy reduced symptoms in 30%-70% of the patients, with higher benefit in epigastric pain syndrome and superior effectiveness for proton pump inhibitors compared to H₂ -antagonists. Prokinetic agents, primarily used to treat postprandial distress syndrome, showed variable efficiency: 59%-81% responder rate for dopamine receptor antagonists, 32%-91% for serotonin-4-receptor agonists and 31%-80% for muscarinic receptor antagonists. H Pylori eradication, recommended in infected patients, was effective in 24%-82%. Refractory symptoms are addressed with neuromodulators. However, their efficacy in functional dyspepsia remains incompletely elucidated, available data showing symptom reduction in 27%-71% of the patients. Regarding herbal agents, peppermint oil reduced symptoms in 66%-91%, rikkunshito in 29%-34% and iberogast in 20%-95%. Lastly, acupuncture, cognitive behavioural therapy and hypnotherapy may help to provide symptom control, but research on their efficacy remains sparse.

CONCLUSIONS

None of the available therapies is effective in the majority of patients without being associated with major side effects. Developing new treatment options is challenging due to the heterogeneity of functional dyspepsia, the lack of readily identified target mechanisms and the poor association between pathophysiological disturbances and symptoms.

Efficacy of serotonin receptor agonists in the treatment of functional dyspepsia: a meta-analysis

INTRODUCTION

Functional dyspepsia (FD) is typically treated with serotonin receptor (5-HT) agonists such as cisapride, mosapride, tegaserod and tandospirone citrate. However, there are conflicting efficacy data, possibly due to significant heterogeneity between studies. In this meta-analysis, we analyzed the efficacy and safety data from studies evaluating the efficacy of serotonin receptor agonists in patients with FD.

MATERIAL AND METHODS

Relevant studies were selected from the Medline, Cochrane, EMBASE, and Google Scholar databases. The meta-analysis included 10 RCTs which evaluated the efficacy of serotonin receptor agonists in patients with FD (final total of 892 patients in the serotonin receptor agonist group, and 640 participants in the placebo group). The primary outcomes were the response rates and abdominal symptoms score. The Cochrane Collaboration's tool was used to assess risk. Sensitivity analysis was carried out using the leave-one-out approach.

RESULTS

Patients treated with serotonin receptor agonists had a significantly higher response rate compared to placebo-treated patients (pooled OR = 2.99; 95% CI: 1.15-7.77; p = 0.025). Patients treated with serotonin receptor agonists had a significant improvement in symptom scores compared to the placebo group (pooled standardized mean difference = -0.43; 95% CI: -0.83 to -0.04; p = 0.031). Sensitivity analysis indicated that the pooled estimates for abdominal symptom score might be affected by the Yeoh et al. (1997) study.

CONCLUSIONS

Serotonin receptor agonists had a significantly higher efficacy compared to placebo in the treatment of FD.

Effect of prucalopride on intestinal gas tolerance in patients with functional bowel disorders and constipation

BACKGROUND AND AIM

Patients with functional bowel disorders develop gas retention and symptoms in response to intestinal gas loads that are well tolerated by healthy subjects. Stimulation of 5HT-4 receptors in the gut has both prokinetic and antinociceptive effects. The aim of this study is to determine the effect of prucalopride, a highly selective 5HT-4 agonist, on gas transit and tolerance in women with functional bowel disorders complaining of constipation.

METHODS

Twenty-four women with functional bowel disorders complaining of constipation were included in the study. Patients were studied twice on separate days in a cross-over design. On each study day, an intestinal gas challenge test was performed. During the five previous days, prucalopride (2 mg/day) or placebo was administered. Abdominal symptoms, stool frequency, and stool consistency were recorded during the treatment period on daily questionnaires.

RESULTS

During the gas challenge test, prucalopride did not decrease the volume of gas retained in the subset of patients who had significant gas retention (≥ 200 mL) while on placebo. However, in those patients who had increased symptoms during the gas test (≥ 3 on a 0 to 6 scale) when on placebo, prucalopride did significantly reduce the perception of symptoms (2.3 ± 0.5 mean score vs 3.5 ± 0.3 on placebo; P = 0.045). During the treatment period with prucalopride, patients exhibited an increase in the total number of bowel movements and decreased stool consistency compared with placebo.

CONCLUSION

Prucalopride reduces abdominal symptoms without modifying gas retention when patients with functional bowel disorders are challenged with the gas transit and tolerance test. European Clinical Trials Database (EudraCT2011-006354-86).

Granisetron Transdermal System for Treatment of Symptoms of Gastroparesis: A Prescription Registry Study

Background/Aims

Serotonin receptor (eg, 5-HT₃) antagonists are used to treat nausea and vomiting from a variety of causes. Granisetron transdermal system (GTS) is an appealing delivery system for patients with gastroparesis. To assess if GTS improves nausea and vomiting and other gastroparesis symptoms in patients with gastroparesis.

Methods

Patients with gastroparesis and symptoms of nausea and vomiting refractory to conventional treatment were treated with GTS. Symptoms of gastroparesis were assessed using a modified Gastroparesis Cardinal Symptom Index (GCSI). Following 2 weeks of treatment, patients were asked to assess their symptoms and indicate their therapeutic response using the Clinical Patient Grading Assessment Scale (CPGAS) reporting if symptoms of nausea and vomiting improved on a scale: 0 = no change to +7 = completely better.

Results

Fifty-one patients received GTS by prescription: average age was 40 ± 17 years, 44 female, 11 diabetics, 23 ± 20% retention at 4 hours on gastric emptying scintigraphy. Thirty-nine of the 51 (76%) patients stated improvement with GTS. There was significant improvement in nausea and vomiting as assessed with CPGAS at 2 weeks (2.28 ± 2.53; P < 0.05). Symptoms of nausea and vomiting significantly improved. Other symptoms including postprandial fullness, loss of appetite, upper abdominal pain, and early satiety improved. Side effects reported included redness at the site of the patch in 7 patients, pruritus in 5, and constipation in 5.

Conclusions

GTS was moderately effective in reducing nausea and/or vomiting in 76% of gastroparesis patients. In addition to nausea and vomiting, symptoms of postprandial fullness, loss of appetite, upper abdominal pain, and early satiety also improved.

The Role of Visceral Hypersensitivity in Irritable Bowel Syndrome: Pharmacological Targets and Novel Treatments

Irritable bowel syndrome (IBS) is the most common disorder referred to gastroenterologists and is characterized by altered bowel habits, abdominal pain, and bloating. Visceral hypersensitivity (VH) is a multifactorial process that may occur within the peripheral or central nervous systems and plays a principal role in the etiology of IBS symptoms. The pharmacological studies on selective drugs based on targeting specific ligands can provide novel therapies for modulation of persistent visceral hyperalgesia. The current paper reviews the cellular and molecular mechanisms underlying therapeutic targeting for providing future drugs to protect or treat visceroperception and pain sensitization in IBS patients. There are a wide range of mediators and receptors participating in visceral pain perception amongst which substances targeting afferent receptors are attractive sources of novel drugs. Novel therapeutic targets for the management of VH include compounds which alter gut-brain pathways and local neuroimmune pathways. Molecular mediators and receptors participating in pain perception and visceroperception include histamine-1 receptors, serotonin (5-hydrodytryptamine) receptors, transient receptor potential vanilloid type I, tachykinins ligands, opioid receptors, voltage-gated channels, tyrosine receptor kinase receptors, protease-activated receptors, adrenergic system ligands, cannabinoid receptors, sex hormones, and glutamate receptors which are discussed in the current review. Moreover, several plant-derived natural compounds with potential to alleviate VH in IBS have been highlighted. VH has an important role in the pathology and severity of complications in IBS. Therefore, managing VH can remarkably modulate the symptoms of IBS. More preclinical and clinical investigations are needed to provide efficacious and targeted medicines for the management of VH.

Efficacy of Mirtazapine in Patients With Functional Dyspepsia and Weight Loss

BACKGROUND & AIMS

A subset of patients with functional dyspepsia (FD) present with early satiation and weight loss, for which there are no established therapeutic options. We investigated the efficacy of mirtazapine (an antidepressant and antagonist of the histamine receptor H1, the α2 adrenergic receptor, and the serotonin receptors 5-HT2C and 5-HT-3) in patients with FD and weight loss.

METHODS

We conducted a randomized, placebo-controlled pilot trial that studied 34 patients with FD (29 women; mean age, 35.9 ± 2.3 years) with weight loss >10% of original body weight (mean loss, 12.4 ± 2.3 kg) without depression or anxiety. After a run-in period, patients were randomly assigned to groups given placebo (n = 17) or mirtazapine 15 mg each day for 8 weeks (n = 17) in a double-blind manner. Subjects were evaluated during a 2-week baseline and 8-week treatment for dyspepsia symptom severity, quality of life (on the basis of the Nepean Dyspepsia Index), and gastrointestinal-specific anxiety; they were given a nutrient challenge test and weighed. Data were analyzed by using linear mixed models, followed by planned contrasts with adaptive step-down Bonferroni multiple testing correction.

RESULTS

Two patients in each group dropped out. At weeks 4 and 8, mirtazapine significantly reduced mean dyspepsia symptom severity scores compared with week 0 (P = .003 and P = .017, respectively); there was no significant reduction in the placebo group (P > .37 for weeks 4 and 8). The difference in change from week 0 between mirtazapine and placebo showed a trend with a large effect size at week 4 (P = .059) that was not significant at week 8 (P = .55). However, improvements from week 0 to weeks 4 and 8 were significantly larger in the mirtazapine group than placebo group for early satiation, quality of life, gastrointestinal-specific anxiety, weight, and nutrient tolerance (mostly with large effect sizes).

CONCLUSIONS

In a randomized, placebo-controlled trial, mirtazapine significantly improved early satiation, quality of life, gastrointestinal-specific anxiety, nutrient tolerance, and weight loss in patients with FD. ClinicalTrials.gov number: NCT01240096.

Current and Emerging Medical Therapies for Gastroparesis

OPINION STATEMENT

Gastroparesis likely involves various pathophysiological disorders and is increasingly prevalent as complications of surgeries, medications, and chronic diabetes. Key to diagnosis is evidence of delayed gastric emptying, generally based on standardized scintigraphy, and ruling out distal obstruction or other dysmotilities. Initial medical management includes reviewing potentially exacerbating medications and ruling out other reversible causes, achieving tighter glucose control in diabetics, and implementing dietary and lifestyle changes. While current available medications are limited, symptomatic control is aimed at improving gastric emptying, alleviating nausea and vomiting, and treating associated abdominal pain. Other potential therapies are aimed at reducing acid production, improving gastric accommodation or pyloric dysfunction, and treating bacterial overgrowth. Future studies should be aimed toward identification of subpopulations of gastroparetics who are better responders to the various medications based on differences in underlying pathophysiology and adopting standardized study end point measures that may allow for comparisons across trials. This chapter will review current treatment options, upcoming promising medications, and some of the hurdles in advancing the field forward.

Effect of 5-hydroxytryptamine receptor 4 agonist mosapride on human gastric accommodation

BACKGROUND

Impaired gastric accommodation is one of the major features of functional dyspepsia. Mosapride citrate is a 5-hydroxytryptamine receptor 4 (5-HT4) agonist, which is shown to improve upper abdominal symptoms. However, effect of mosapride on gastric accommodation was not clear. We tested the hypothesis that mosapride enhances the gastric accommodation in normal individuals.

METHODS

Fourteen male healthy volunteers completed this study. Single administration of mosapride or placebo was performed randomly with more than 1-week interval. Subjects swallowed a triple-lumen polyvinyl tube with a polyethylene bag. The bag was positioned in the proximal stomach and the minimal distending pressure (MDP) was determined. The ramp distension starting from the MDP was then performed and subjects were instructed to score their perception using ordinate scales. Next the intra-bag pressure was set at MDP + 2 mmHg and a liquid meal was administered 30 min later, and the intra-bag volume was recorded for 60 min. We compared the MDP, perception scores, and the intra-bag volume changes by administering placebo and mosapride.

KEY RESULTS

Minimal distending pressure was not significantly different in subjects receiving mosapride or placebo. Treatment with mosapride had no effect on intra-bag pressures or volumes inducing first sensation or discomfort. Gastric accommodation, expressed as the difference between pre- and postmeal intra-bag volumes, and the percent change of the intra-bag volumes by the meal was significantly enhanced by mosapride compared with placebo.

CONCLUSIONS & INFERENCES

This is the first study clearly demonstrating that single administration of 5-HT4 agonist can enhance gastric accommodation in humans. (Umin.ac.jp, number UMIN000014063).

Clinical presentation and pathophysiology of gastroparesis

Gastroparesis is a heterogeneous disorder defined by delay in gastric emptying. Symptoms of gastroparesis are nonspecific, including nausea, vomiting, early satiety, bloating, and/or abdominal pain. Normal gastric motor function and sensory function depend on a complex coordination between the enteric and central nervous system. This article discusses the pathophysiology of delayed gastric emptying and the symptoms of gastroparesis, including antropyloroduodenal dysmotility, impaired gastric accommodation, visceral hypersensitivity, and autonomic dysfunction. The underlying pathophysiology of gastroparesis is complex and multifactorial. The article discusses how a combination of these factors leads to symptoms of gastroparesis.

Gastroduodenal mechanisms underlying functional gastric disorders

Functional dyspepsia (FD), a disorder thought to originate from the gastroduodenum, is one of the most prevalent functional gastrointestinal disorders. In this review, we focused on gastroduodenal mechanisms involved in the pathophysiology of FD. The roles of impaired gastric accommodation, delayed gastric emptying, hypersensitivity to gastric distention and to luminal agents, altered mucosal integrity, low-grade inflammation and psychological stress are reviewed. The underlying pathophysiology in FD is probably multifactorial, involving a combination of several of these factors, ultimately leading to symptom pattern and severity.

5-Hydroxytryptamine (serotonin) in the gastrointestinal tract

PURPOSE OF REVIEW

Although the gut contains most of the body's 5-hydroxytryptamine (5-HT), many of its most important functions have recently been discovered. This review summarizes and directs attention to this new burst of knowledge.

RECENT FINDINGS

Enteroendocrine cells have classically been regarded as pressure sensors, which secrete 5-HT to initiate peristaltic reflexes; nevertheless, recent data obtained from studies of mice that selectively lack 5-HT either in enterochromaffin cells (deletion of tryptophan hydroxylase 1 knockout; TPH1KO) or neurons (TPH2KO) imply that neuronal 5-HT is more important for constitutive gastrointestinal transit than that of enteroendocrine cells. The enteric nervous system of TPH2KO mice, however, also lacks a full complement of neurons; therefore, it is not clear whether slow transit in TPH2KO animals is due to their neuronal deficiency or absence of serotonergic neurotransmission. Neuronal 5-HT promotes the growth/maintenance of the mucosa as well as neurogenesis. Enteroendocrine cell derived 5-HT is an essential component of the gastrointestinal inflammatory response; thus, deletion of the serotonin transporter increases, whereas TPH1KO decreases the severity of intestinal inflammation. Enteroendocrine cell derived 5-HT, moreover, is also a hormone, which inhibits osteoblast proliferation and promotes hepatic regeneration.

SUMMARY

New studies show that enteric 5-HT is a polyfunctional signalling molecule, acting both in developing and mature animals as a neurotransmitter paracrine factor, endocrine hormone and growth factor.

Relationship between symptoms and proximal stomach function in patients with functional dyspepsia

AIM: To investigate the prevalence of impaired proximal stomach function and its relationship to symptoms in patients with functional dyspepsia (FD).

METHODS: Fifty-nine patients with FD and 32 healthy subjects (HS) were enrolled in this study. After an overnight fast of at least 12 h, a double-lumen polyvinyl tube with an adherent plastic bag that was finely folded was introduced through the patient's mouth. A gastric barostat was used to evaluate proximal stomach function (sensitivity, accommodation and compliance). After an overnight fast, gastric emptying was measured by single photon emission computerized tomography (SPECT). The gastric emptying curve was plotted to calculate the gastric emptying half-time. Individual dyspepsia symptom scores were obtained for all patients and their relationship with proximal stomach function was assessed. Logistic regression analysis and χ² statistics were used to identify the association between proximal stomach function and symptoms.

RESULTS: Visceral hypersensitivity to gastric distention was found in 44.07% of the patients, and their gastric emptying half-time did not significantly differ from that of patients with normal sensitivity. Epigastric pain was significantly more prevalent in patients with visceral hypersensitivity than in those with normal sensitivity (P < 0.01). Epigastric pain was independently and significantly associated with hypersensitivity to gastric distention (OR = 4.430, P < 0.05). Impaired gastric accommodation was found in 37.29% of the patients, and their gastric emptying half-time did not differ from that of other patients. Impaired gastric accommodation to gastric distention was associated with a higher prevalence of early satiety (P < 0.05). The presence of early satiety was the only symptom that was independently associated with impaired accommodation to gastric distention (OR = 3.231, P < 0.05). Reduced compliance was found in 54.24% of the patients; however, no relationship was found between reduced compliance and dyspeptic symptoms.

CONCLUSION: Symptoms are associated with impaired proximal stomach function in patients with FD. Epigastric pain and early satiety can be used to predict the presence of hypersensitivity and impaired accommodation, respectively.

Functional dyspepsia

PURPOSE OF REVIEW

This review summarizes the recent progress in the epidemiology, pathophysiology and treatment of functional dyspepsia.

RECENT FINDINGS

Epidemiological, pathophysiological and therapeutic studies continue to examine the Rome III-proposed subdivision of functional dyspepsia into epigastric pain syndrome and postprandial distress syndrome. Although epidemiological studies support the subdivision, studies in patient samples show major overlap. Several studies identified overlapping functional disorders and psychosocial comorbidity as major contributors to the severity of functional dyspepsia and its impact on quality of life. Central processing of visceral stimuli, and its role in the pathogenesis of functional dyspepsia, as well as low-grade inflammation in the duodenum are important emerging topics in pathophysiology research. Therapeutic studies have reported on prokinetic and fundus-relaxing drugs. Acotiamide is a first-in-class drug with both prokinetic and fundus-relaxing properties that was evaluated in the recent phase 2 and phase 3 trials in functional dyspepsia.

SUMMARY

There is gradual progress in our understanding of the symptom pattern, impact and pathophysiology of functional dyspepsia. The areas of recent advances including the recognition of low-grade duodenal inflammation, central nervous system processing and the exploration of novel pharmacotherapeutic approaches are summarized in this review.