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

New Role of the Serotonin as a Biomarker of Gut-Brain Interaction

Serotonin (5-hydroxytryptamine: 5-HT), a neurotransmitter that regulates mood in the brain and signaling in the gut, has receptors throughout the body that serve various functions, especially in the gut and brain. Selective serotonin reuptake inhibitors (SSRIs) are used to treat depression, but their efficacy is uncertain. Depression is often associated with early gastrointestinal symptoms. Gut disorders such as functional dyspepsia (FD), irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), are linked to elevated serotonin levels. In this review, we would like to discuss the approach of using serotonin as a biomarker for gut-brain, and body-wide organ communication may lead to the development of preventive and innovative treatments for gut-brain disorders, offering improved visibility and therapeutic monitoring. It could also be used to gauge stress intensity for self-care and mental health improvement.

Prokinetics for the treatment of functional dyspepsia: an updated systematic review and network meta-analysis

BACKGROUND

Since the previous network meta-analysis assessing the efficacy of prokinetics for functional dyspepsia (FD), there have been a number of new studies and cinitapride is a new prokinetic agent for FD. This updated meta-analysis aimed to explore the efficacy and safety of prokinetics for FD.

METHODS

An updated study search in Pubmed, EMBASE, Cochrane Library and Web of Science was conducted in literatures published from July 2015 to March 2023. Randomized controlled trials investigating the use of prokinetics in adult FD patients were included. The primary outcome was the total efficacy rate and the secondary outcome was adverse events. A Bayesian network meta-analysis was performed using R software.

RESULTS

A total of 28 studies were included. Network meta-analysis showed that metoclopramide had a higher total efficacy rate than mosapride (OR: 3.53, 95%CI: 1.70-7.47), domperidone (OR: 2.29, 95%CI: 1.16-4.63), itopride(OR: 2.77, 95%CI: 1.41-5.59), acotiamide(OR: 2.63, OR: 1.33-5.36), and placebo(OR: 5.68, 95%CI: 2.98-11.10), however similar to cinitapride (OR: 1.62, 95%CI: 0.75-3.53). Cinitapride had a higher total efficacy rate than mosapride (OR: 2.18, 95%CI: 1.16-4.14) and placebo (OR: 3.52, 95%CI: 2.01-6.24). Cinitapride had lower risk of total adverse events than domperidone. There was no difference in the risk of drug-related adverse events between the prokinetics.

CONCLUSIONS

Metoclopramide and cinitapride may have a better efficacy than other prokinetics in the treatment of FD, and cinitapride may have a lower risk of total adverse events. Further studies using uniform definitions or validated tools to measure the total efficacy rate are needed.

Gastrointestinal hormones and regulation of gastric emptying

PURPOSE OF REVIEW

In this review, we evaluate recent findings related to the association between gastrointestinal hormones and regulation of gastric emptying.

RECENT FINDINGS

Motilin and ghrelin, which act during fasting, promote gastric motility, whereas most of the hormones secreted after a meal inhibit gastric motility. Serotonin has different progastric or antigastric motility effects depending on the receptor subtype. Serotonin receptor agonists have been used clinically to treat dyspepsia symptoms but other hormone receptor agonists or antagonists are still under development. Glucagon-like peptide 1 agonists, which have gastric motility and appetite-suppressing effects are used as a treatment for obesity and diabetes.

SUMMARY

Gastrointestinal hormones play an important role in the regulation of gastric motility. Various drugs have been developed to treat delayed gastric emptying by targeting gastrointestinal hormones or their receptors but few have been commercialized.

Comparative Efficacy of Various Pharmacological Interventions in the Treatment of Functional Dyspepsia: A Network Meta-Analysis

BACKGROUND AND AIM

Patients with functional dyspepsia often select different pharmacological treatments. We aimed to compare and rank the efficacy of different pharmacological interventions in treating functional dyspepsia.

METHODS

We searched EMBASE, PubMed, Cochrane, Web of Science and MEDLINE from the date of database inception to March 28, 2019. A random-effects model was selected to conduct traditional meta-analysis to directly examine the efficacy of different pharmacological interventions. The consistency model was selected to conduct a network meta-analysis to evaluate the relative effects and rank probability of different pharmacological interventions.

RESULTS

We included 58 trials (15,629 participants and 21 pharmacological treatments). Network meta-analysis showed that cisapride, domperidone, itopride, and levosulpiride were better than placebo, especially in short term (< 4 weeks). And levosulpiride was significantly more effective than 15 other drugs and placebo (ORs ranging between 0.05 and 0.15). Cisapride was significantly more effective than lansoprazole (OR 0.30, 95% CrI 0.09-0.99) and tegaserod (OR 0.26, 95% CrI 0.07-0.98). The rank probability showed that levosulpiride was most likely to be rank 1 (77%), cinitapride rank 2 (17%), and cisapride rank 3 (23%).

CONCLUSIONS

Our study confirmed the effectiveness of several pharmacological treatments for ameliorating functional dyspepsia. Furthermore, levosulpiride relatively ranked the best in managing FD. Physicians should be encouraged to apply promising pharmacological interventions (e.g., levosulpiride and cisapride). However, the results should be interpreted with caution due to small study effects.

Physiological mechanisms of unexplained (functional) gastrointestinal disorders

Functional gastrointestinal disorders (FGIDs) encompass a range of complex conditions with similar clinical characteristics and no overt pathology. Recent recognition of sub-clinical pathologies in FGIDs, in conjunction with physiological and biochemical abnormalities including increased intestinal permeability, microbial profile alterations, differences in metabolites and extra-intestinal manifestations of disease, call into question the designation of these conditions as 'functional'. This is despite significant heterogeneity in both symptom profile and specifics of reported physiological abnormalities hampering efforts to determine defined mechanisms that drive onset and chronicity of symptoms. Instead, the literature demonstrates these conditions are disorders of homeostatic imbalance, with disruptions in both host and microbial function and metabolism. This imbalance is also associated with extraintestinal abnormalities including psychological comorbidities and fatigue that may be a consequence of gastrointestinal disruption. Given the exploitation of such abnormalities will be crucial for improved therapeutic selection, an enhanced understanding of the relationship between alterations in function of the gastrointestinal tract and the response of the immune system is of interest in identifying mechanisms that drive FGID onset and chronicity. Considerations for future research should include the role of sex hormones in regulating physiological functions and treatment responses in patients, as well as the importance of high-level phenotyping of clinical, immune, microbial and physiological parameters in study cohorts. There is opportunity to examine the functional contribution of the microbiota and associated metabolites as a source of mechanistic insight and targets for therapeutic modulation.

Effectiveness of Buspirone in Patients with Functional Dyspepsia: A Randomized, Double-Blind, Placebo-Controlled Study

BACKGROUND Functional dyspepsia (FD) is a relatively common disorder whose pathogenesis has yet been poorly understood. There are still debates concerning definitions and the best possible treatments for this disorder. We aimed to assess the effectiveness of buspirone, a 5-hydroxytryptamine (HT)1A agonist, in improving the symptoms and quality of life (QoL) as well as psychological dimensions in patients with FD. METHODS This study was a randomized, double-blinded, placebo-controlled trial performed on 30 patients with FD, residing in the city of Sari, northern Iran, from December 2017 to October 2018. Consecutive patients referring to a tertiary hospital with a clinical diagnosis of FD, according to the Rome IV criteria, were recruited. All patients were ethnically Persian and had normal upper endoscopy and negative histological evaluation results for any gastrointestinal disease or helicobacter pylori (H. pylori) infection while evaluating biopsy samples endoscopically. Exclusion criteria were being diagnosed with major psychiatric disorders, suicidal thoughts, recent treatments with psychoactive drugs, as well as major cognitive impairments. Patients were randomly assigned to receive either buspirone (n=18) or placebo (n=12) for two months. The first group received buspirone 5mg three times a day for the first month and 10mg three times a day for the second month. During the treatment course, the patients were advised to report any adverse reactions. Also, both groups were evaluated by three questionnaires [demographic characteristics form, the 36-Item Short-Form Health Survey (SF-36), The Short-Form Leeds Dyspepsia Questionnaire (SF-LDQ) and Hospital Anxiety and Depression Scale(HADS)] at the baseline and at the end of the 8th week by a blinded psychologist. Finally, data were analyzed using SPSS software (version 18). P values <0.05 were considered statistically significant. RESULTS The most common symptoms of the patients were FD followed by heartburn. No significant differences were observed between buspirone and placebo groups regarding QoL (p=0.58), anxiety and depression (p =0.36), and severity and frequency of FD symptoms (p =0.22) before and after the intervention. In both groups, the overall QoL as well as HADS and SF-LDQ scores had significantly improved at the end of the study compared with the baseline. CONCLUSION Our findings indicate no significant effects associated with buspirone on the clinical course of FD, compared with placebo. More studies are needed to introduce effective therapies according to the pathophysiology of FD.

Tegaserod for the Treatment of Irritable Bowel Syndrome

Background: Tegaserod (Zelnorm®) is a 5-hydroxytryptamine (serotonin) type 4 receptor agonist for the treatment of hypomotility disorders of the lower gastrointestinal tract associated with the irritable bowel syndrome with constipation (IBS-C).

Objective: The authors provide the reader with a better understanding on tegaserod mechanism of action, on its pharmacodynamics and pharmacokinetic properties, on safety and tolerability, with a summary of the key published clinical trials conducted in patients with irritable bowel syndrome (IBS). Its effects on colon inflammation have also been described.

Results: Tegaserod was withdrawn in 2007 due to increased risks of cardiovascular adverse effects. The manufacturer denied this, because pre-existing cardiovascular disease or risk factors were attributed to all affected patients. Thus, no causal relationship between tegaserod use and cardiovascular events was clearly shown. A matched case-control study of tegaserod-treated with untreated patients found no association between tegaserod and adverse cardiovascular outcomes. Despite its adverse effects, tegaserod resulted to be effective in treating chronic constipation in adult women aged < 65 years with IBS-C, while the safety and effectiveness of tegaserod in men with IBS-C have not been established.

Conclusion: Tegaserod was resubmitted to the Food and Drug Administration in 2018 for use in a low-risk population. Moreover, tegaserod has also been shown to improve symptoms, enhance gastric accommodation and significantly attenuate visceral pain arising from the colon in functional dyspepsia patients. Treatment with tegaserod seems also to exert a protective effect in inflamed colons, reducing the severity of colitis in animal models.

Inflammation and Overlap of Irritable Bowel Syndrome and Functional Dyspepsia

Irritable bowel syndrome (IBS) and functional dyspepsia (FD) are common functional gastrointestinal disorders (FGIDs) and account for a large proportion of consulting patients. These 2 disorders overlap with each other frequently. The pathogenesis of IBS or FD is complicated and multi-factors related, in which infectious or non-infectious inflammation and local or systemic immune response play significant roles. There are few studies focusing on the mechanism of inflammation in patients with overlap syndrome of irritable bowel syndrome and functional dyspepsia (IBS-FD). This review focuses on current advances about the role of inflammation in the pathogenesis of IBS and FD and the possible mechanism of inflammation in IBS-FD.

Management of Dyspepsia and Gastroparesis in Patients with Diabetes. A Clinical Point of View in the Year 2021

Diabetes mellitus is a widespread disease, and represents an important public health burden worldwide. Together with cardiovascular, renal and neurological complications, many patients with diabetes present with gastrointestinal symptoms, which configure the so-called diabetic enteropathy. In this review, we will focus on upper gastrointestinal symptoms in patients with diabetes, with particular attention to dyspepsia and diabetic gastroparesis (DG). These two clinical entities share similar pathogenetic mechanisms, which include autonomic neuropathy, alterations in enteric nervous system and histological abnormalities, such as interstitial cells of Cajal depletion. Moreover, the differential diagnosis may be challenging because of overlapping clinical features. Delayed gastric emptying should be documented to differentiate between DG and dyspepsia and it can be assessed through radioactive or non-radioactive methods. The clinical management of dyspepsia includes a wide range of different approaches, above all Helicobacter pylori test and treat. As regards DG treatment, a central role is played by dietary modification and glucose control and the first-line pharmacological therapy is represented by the use of prokinetics. A minority of patients with DG refractory to medical treatment may require more invasive therapeutic approaches, including supplemental nutrition, gastric electric stimulation, pyloromyotomy and gastrectomy.

Management of functional dyspepsia in 2020: a clinical point of view

Dyspepsia is a disorder that refers mainly to central upper abdominal pain or discomfort. When a cause of this symptom is not identified the condition is termed functional dyspepsia (FD), that affects a large part of the general population. The relevance of FD is due to its high prevalence, but also to its chronic or intermittent course. This induces a significant burden for each national healthcare system. The pathogenesis of FD is complex and multifactorial, depending on cultural, environmental, and biological factors. Although considered of main importance in the pathophysiology of several gastroduodenal diseases, in the context of FD Helicobacter pylori (H. pylori) infection plays a limited role. The diagnosis of FD requires the exclusion of organic gastroduodenal diseases as well as H. pylori infection. Thus, the diagnostic workup includes a complete anamnesis, biochemical tests, and endoscopy with biopsy (when requested), and the satisfaction of clinic criteria recommended by the Rome IV consensus. The treatment of FD is also challenging, in fact more and more studies focused on a wide range of different therapies, with a multitude of results. The aim of this literature review is to provide an update of the new evidences useful for diagnosis and management of FD.

Modified Liu-Jun-Zi decoction alleviates visceral hypersensitivity in functional dyspepsia by regulating EC cell-5HT3r signaling in duodenum

ETHNOPHARMACOLOGICAL RELEVANCE

Modified Liu-Jun-Zi (MLJZ) is derived from one of the most famous traditional Chinese prescription Liu-Jun-Zi. It exhibits therapeutic effects in functional dyspepsia (FD), but the underlying mechanisms remain not well understood. Enterochromaffin (EC) cells contribute to the pathogeneses of visceral hypersensitivity in functional gastrointestinal disorders. But whether and how EC cells in duodenum participate in the mechanism of FD remain unsettled.

AIM OF THE STUDY

To detect the crucial factors related to EC cells, and to evaluate the therapeutic effect of MLJZ and to determine whether MLJZ relieves visceral hypersensitivity in FD by regulating EC cell-5-hydroxytryptamine 3 receptor (5HT3r) signaling.

MATERIALS AND METHODS

FD rats were established by iodoacetamide gavage combined with tail clamping method. The verification of FD model and the evaluation of the therapeutic effect of MLJZ was taken place by hematoxylin-eosin (HE) staining and visceral sensitivity measurement. The expression of EC cells and 5-hydroxytryptamine (5HT) in duodenum was detected by Immunohistochemistry (IHC) staining and enzyme-linked immunosorbent assay (ELISA). IHC staining and quantitative polymerase chain reaction (qPCR) were applied to measure the expression of tryptophan hydroxylase-1 (TPH1), paired box gene 4 (PAX4), transient receptor potential A1 (TRPA1), transient receptor potential C4 (TRPC4) and 5HT3r. Duodenum sections were stained by double immunofluorescence (IF) to study the synthesis of 5HT in EC cells.

RESULTS

The gastric sensitivity increased in FD rats while MLJZ decoction significantly attenuated visceral hypersensitivity. The duodenum of FD rats displayed increased expressions of EC cells, 5HT, TPH1, PAX4 and 5HT3r. And the overexpression was reduced in response to MLJZ decoction treatment.

CONCLUSIONS

EC cell-5HT3r signaling pathway is abnormally active in FD with visceral hypersensitivity. And MLJZ decoction can alleviates visceral hypersensitivity in FD by regulating EC cell-5HT3r signaling in duodenum.

The Role of GI Peptides in Functional Dyspepsia and Gastroparesis: A Systematic Review

Functional dyspepsia (FD) and gastroparesis (GP) are common disorders of the upper gastrointestinal tract. The pathophysiology of these conditions is likely to be heterogenous, and factors such as altered motility, sensitivity and response to nutrition have been identified as putative underlying mechanisms. Motility, sensitivity as well as responses to nutrition can be influenced or mediated by peptide hormones and serotonin released from the gastrointestinal mucosa. This review summarizes the role of GI peptides in functional dyspepsia and gastroparesis. In most studies, the levels of somatostatin, ghrelin, and motilin did not differ between healthy volunteers and FD or GP patients, but higher symptom burden was often correlated with higher peptide levels. Ghrelin and motilin receptor agonists showed promising results in improvement of the gastric emptying, but the link with improvement of symptoms is less predictable. Serotonin agonists have a potential to improve symptoms in both FD and idiopathic gastroparesis. Drugs acting on the GLP-1 and on the PYY receptors deserve further investigation. There is a need for systematic large scale studies.