Association between duodenal bile salts and gastric emptying in patients with functional dyspepsia

Targeted metabolomics revealed the mechanisms underlying the role of Liansu capsule in ameliorating functional dyspepsia

ETHNOPHARMACOLOGICAL RELEVANCE

Liansu capsule could alleviate dyspeptic symptoms; however, the mechanisms underlying its role in treating functional dyspepsia (FD) remain unclear.

AIM OF THE STUDY

To elucidate the mechanism underlying the efficacy of Liansu capsule in alleviating FD symptoms.

MATERIALS AND METHODS

Thirty-six male mice were randomly divided into the following six groups: control, model, low-strength Liansu, moderate-strength Liansu, high-strength Liansu, and domperidone groups. Small intestine propulsion rate, gastric residual rate and histopathological analysis were performed to evaluate efficacy of Liansu capsule. Levels of interleukin-1β, interleukin-6, tumor necrosis factor α, phosphorylation of p65, ghrelin and gastrin were verified by real-time quantitative polymerase chain reaction and immunofluorescence assays. Targeted metabolomic analyses, western blotting and immunofluorescence assays were used to explore the mechanism of Liansu capsule in ameliorating FD.

RESULTS

The Liansu capsule significantly ameliorated the symptoms of FD, and markedly increased the levels of ghrelin and gastrin. Moreover, Liansu capsule significantly downregulated the levels of the proinflammatory cytokine interleukin-1β, interleukin-6, tumor necrosis factor α, and inhibited the phosphorylation of p65. Targeted metabolomic analyses showed that Liansu capsule significantly reduced the levels of deoxycholic acid and hyodeoxycholic acid, which were significantly elevated in the model group. Furthermore, these results showed that deoxycholic acid and hyodeoxycholic acid markedly promoted the levels of Takeda G-protein-coupled receptor 5 (TGR5), phosphorylated signal transducer and activator of transcription 3 (STAT3), and Kruppel-like factor 5 (KLF5) in vitro. whereas, Liansu capsule significantly reduced the levels of TGR5, phosphorylated STAT3, and KLF5.

CONCLUSION

Our findings indicated that Liansu capsule improved FD by regulating the deoxycholic acid/hyodeoxycholic acid-TGR5-STAT3-KLF5 axis. The findings reveal a novel mechanism underlying the role of Liansu capsule, which may be a promising therapeutic strategy for FD.

Review article: Functional dyspepsia-a gastric disorder, a duodenal disorder or a combination of both?

BACKGROUND

Functional dyspepsia (FD) is one of the most frequent conditions in gastroenterological outpatient health care. Most recent research in FD has shifted its focus to duodenal pathophysiological mechanisms, although current treatments still focus mainly the stomach.

AIM

The aim of the study was to provide a comprehensive overview of the pathophysiology of FD focusing on a paradigm shift from gastric towards duodenal mechanisms.

METHODS

We conducted a literature search in PubMed for studies describing mechanisms that could possibly cause FD.

RESULTS

The pathophysiology of FD remains incompletely understood. Recent studies show that duodenal factors such as acid, bile salt exposure and eosinophil and mast cell activation correlate with symptom pattern and burden and can be associated with gastric sensorimotor dysfunction. The evolving data identify the duodenum an interesting target for new therapeutic approaches. Furthermore, the current first-line treatment, that is proton pump inhibitors, reduces duodenal low-grade inflammation and FD symptoms.

CONCLUSION

Future research for the treatment of FD should focus on the inhibition of duodenal mast cell activation, eosinophilia and loss of mucosal integrity.

Gastroparesis and Functional Dyspepsia: Spectrum of Gastroduodenal Neuromuscular Disorders or Unique Entities?

Gastroparesis is defined by delayed gastric emptying in the absence of mechanical obstruction of the stomach. Patients experience symptoms of nausea, vomiting, abdominal pain, fullness, and early satiety. The recognition of the disorder has progressed due to availability of gastric emptying scintigraphy and advancements made in understanding its pathophysiology and treatment options. The clinical presentation and treatment of gastroparesis overlap with a more commonly recognized disorder of gut-brain interaction, functional dyspepsia. Recent studies have reenergized the discussion whether these two are separate entities or perhaps reflect a spectrum of gastroduodenal neuromuscular disorders. The societal guidelines conflict on the utility of gastric emptying scintigraphy in assessment of patients with upper gastrointestinal symptoms. A better appraisal of similarities and differences between gastroparesis and functional dyspepsia will allow targeted treatment for these disorders. This is particularly important as specific pharmacological and endoscopic treatment options are being developed for gastroparesis which are unlikely to be helpful for functional dyspepsia. This review makes the case for considering these disorders in a spectrum where identification of both would most ideally position us toward providing the optimal clinical care.

Role of the duodenal microbiota in functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is a common and debilitating gastrointestinal disorder attributed to altered gut-brain interactions. While the etiology of FD remains unknown, emerging research suggests the mechanisms are likely multifactorial and heterogenous among patient subgroups. Small bowel motor disturbances, visceral hypersensitivity, chronic microinflammation, and increased intestinal tract permeability have all been linked to the pathogenesis of FD. Recently, alterations to the gut microbiome have also been implicated to play an important role in the disease. Changes to the duodenal microbiota may either trigger or be a consequence of immune and neuronal disturbances observed in the disease, but the mechanisms of influence of small intestinal flora on gastrointestinal function and symptomatology are unknown.

PURPOSE

This review summarizes and synthesizes the literature on the link between the microbiota, low-grade inflammatory changes in the duodenum and FD. This review is not intended to provide a complete overview of FD or the small intestinal microbiota, but instead outline some of the key conceptual advances in understanding the interactions between altered gastrointestinal bacterial communities; dietary factors; host immune activation; and stimulation of the gut-brain axes in patients with FD versus controls. Current and emerging treatment approaches such as dietary interventions and antibiotic or probiotic use that have demonstrated symptom benefits for patients are reviewed, and their role in modulating the host-microbiota is discussed. Finally, suggested opportunities for diagnostic and therapeutic improvements for patients with this condition are presented.

Immune Activation in Functional Dyspepsia: Bystander Becoming the Suspect

Disorders of gut-brain interaction (DGBI), formerly termed functional gastrointestinal disorders (FGID), are highly prevalent although exact pathophysiological mechanisms remain unclear. Intestinal immune activation has been recognized, but increasing evidence supports a pivotal role for an active inflammatory state in these disorders. In functional dyspepsia (FD), marked eosinophil and mast cell infiltration has been repeatedly demonstrated and associations with symptoms emphasize the relevance of an eosinophil-mast cell axis in FD pathophysiology. In this Review, we highlight the importance of immune activation in DGBI with a focus on FD. We summarize eosinophil biology in both homeostasis and inflammatory processes. The evidence for immune activation in FD is outlined with attention to alterations on both cellular and molecular level, and how these may contribute to FD symptomatology. As DGBI are complex and multifactorial conditions, we shed light on factors associated to, and potentially influencing immune activation, including bidirectional gut-brain interaction, allergy and the microbiota. Crucial studies reveal a therapeutic benefit of treatments targeting immune activation, suggesting that specific anti-inflammatory therapies could offer renewed hope for at least a subset of DGBI patients. Lastly, we explore the future directions for DGBI research that could advance the field. Taken together, emerging evidence supports the recognition of FD as an immune-mediated organic-based disorder, challenging the paradigm of a strictly functional nature.

The Role of Leaky Gut in Functional Dyspepsia

Patients with functional dyspepsia (FD) complain of epigastric symptoms with no identifiable cause. Increased intestinal permeability has been described in these patients, especially in the proximal small bowel or duodenum, and was associated with mucosal immune activation and symptoms. In this review, we discuss duodenal barrier function, including techniques currently applied in FD research. We summarize the available data on duodenal permeability in FD and factors associated to increased permeability, including mucosal eosinophils, mast cells, luminal and systemic factors. While the increased influx of antigens into the duodenal mucosa could result in local immune activation, clinical evidence for a causal role of permeability is lacking in the absence of specific barrier-protective treatments. As both existing and novel treatments, including proton pump inhibitors (PPI) and pre- or probiotics may impact duodenal barrier function, it is important to recognize and study these alterations to improve the knowledge and management of FD.

Efficacy and safety of spore-forming probiotics in the treatment of functional dyspepsia: a pilot randomised, double-blind, placebo-controlled trial

BACKGROUND

Current treatments for functional dyspepsia have limited efficacy or present safety issues. We aimed to assess spore-forming probiotics in functional dyspepsia as monotherapy or add-on therapy to long-term treatment with proton-pump inhibitors.

METHODS

In this single-centre, randomised, double-blind, placebo-controlled pilot trial that took place at University Hospitals Leuven (Leuven, Belgium), adult patients (≥18 years) with functional dyspepsia (as defined by Rome IV criteria, on proton-pump inhibitors or off proton-pump inhibitors) were randomly assigned (1:1) via computer-generated blocked lists, stratified by proton-pump inhibitor status, to receive 8 weeks of treatment with probiotics (Bacillus coagulans MY01 and Bacillus subtilis MY02, 2·5 × 10⁹ colony-forming units per capsule) or placebo consumed twice per day, followed by an open-label extension phase of 8 weeks. Individuals with a history of abdominal surgery, diabetes, coeliac or inflammatory bowel disease, active psychiatric conditions, and use of immunosuppressant drugs, antibiotics, or probiotics in the past 3 months were excluded. All patients and on-site study personnel were masked to treatment allocation in the first 8 weeks. Symptoms, immune activation, and faecal microbiota were assessed and recorded. The primary endpoint was a decrease of at least 0·7 in the postprandial distress syndrome (PDS) score of the Leuven Postprandial Distress Scale in patients with a baseline PDS score of 1 or greater (at least mild symptoms), assessed in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT04030780.

FINDINGS

Between June 3, 2019, and March 11, 2020, of 93 individuals assessed for eligibility, we included 68 patients with functional dyspepsia (51 [75%] women, mean age 40·1 years [SD 14·4], 34 [50%] on proton-pump inhibitors). We randomly assigned 32 participants to probiotics and 36 to placebo. The proportion of clinical responders was higher with probiotics (12 [48%] of 25) than placebo (six [20%] of 30; relative risk 1·95 [95% CI 1·07-4·11]; p=0·028). The number of patients with adverse events was similar with probiotics (five [16%] of 32) and placebo (12 [33%] of 36). Two serious adverse events occurring during the open-label phase (appendicitis and syncope in two separate patients) were assessed as unlikely to be related to the study product.

INTERPRETATION

In this exploratory study, B coagulans MY01 and B subtilis MY02 were efficacious and safe in the treatment of functional dyspepsia. Participants had potentially beneficial immune and microbial changes, which could provide insights into possible underlying mechanisms as future predictors or treatment targets.

FUNDING

MY HEALTH.