Clinical characteristics of functional dyspepsia depending on chemosensitivity to capsaicin

[Guideline on functional dyspepsia, a disorder of gut-brain-interaction (DGBI): S1 Guideline of the German Society for Neurogastroenterology and Motility (DGNM)]

Functional dyspepsia is common and classified as a disorder of gut-brain interaction (DGBI). The prevalence is estimated around 10 % of the population. Diagnosis is based on symptoms, which are based on the Rome IV criteria, in combination with diagnostic procedures that may include laboratory testing, Helicobacter pylori testing, upper gastrointestinal endoscopy, abdominal ultrasound, and other examinations, depending on the severity, duration and presence of alarming symptoms. Therapeutic procedures include psychoeducation, dietary counseling, mind-body procedures, psychotherapy and medication. The S1 guideline summarizes the current state of knowledge and allows a targeted approach based on the currently available medical evidence.

Nonallergic Diseases Associated With Foods

Clinicians are faced with evaluating real and alleged reactions to foods that may be allergic or nonallergic. Pathogenesis, diagnosis, and treatment of various non-IgE-mediated diseases are discussed in this review. These food-related conditions range from mild to severe. Referral for an allergy workup may be pursued despite the lack of IgE-mediated symptoms. Diagnostic testing is available for defined non-IgE-mediated food diseases that are either immunologic or nonimmunologic. These include celiac disease and related disorders, carbohydrate maldigestion, pancreatic insufficiency, and histamine intolerance. In contrast, there is a paucity of definitive studies to prove food intolerance diseases. There are no definitive diagnostic criteria or testing for nonceliac gluten sensitivity. Functional gastrointestinal disorders, such as irritable bowel syndrome, are better stratified diagnostically but still lack reliable testing. Both nonceliac gluten sensitivity and irritable bowel syndrome are linked to dietary triggers including fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. Therefore, dietary alteration alone may be diagnostic and therapeutic when all other conditions are ruled out. These conditions are important considerations when evaluating a patient with history of a food reaction. There is little evidence that foods are causative in other ailments such as acne, migraines, and nasal congestion and hypersecretion.

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.

British Society of Gastroenterology guidelines on the management of functional dyspepsia

Functional dyspepsia (FD) is a common disorder of gut-brain interaction, affecting approximately 7% of individuals in the community, with most patients managed in primary care. The last British Society of Gastroenterology (BSG) guideline for the management of dyspepsia was published in 1996. In the interim, substantial advances have been made in understanding the complex pathophysiology of FD, and there has been a considerable amount of new evidence published concerning its diagnosis and classification, with the advent of the Rome IV criteria, and management. The primary aim of this guideline, commissioned by the BSG, is to review and summarise the current evidence to inform and guide clinical practice, by providing a practical framework for evidence-based diagnosis and treatment of patients. The approach to investigating the patient presenting with dyspepsia is discussed, and efficacy of drugs in FD summarised based on evidence derived from a comprehensive search of the medical literature, which was used to inform an update of a series of pairwise and network meta-analyses. Specific recommendations have been made according to the Grading of Recommendations Assessment, Development and Evaluation system. These provide both the strength of the recommendations and the overall quality of evidence. Finally, in this guideline, we consider novel treatments that are in development, as well as highlighting areas of unmet need and priorities for future research.

Altered Vagal Signaling and Its Pathophysiological Roles in Functional Dyspepsia

The vagus nerve is crucial in the bidirectional communication between the gut and the brain. It is involved in the modulation of a variety of gut and brain functions. Human studies indicate that the descending vagal signaling from the brain is impaired in functional dyspepsia. Growing evidence indicate that the vagal signaling from gut to brain may also be altered, due to the alteration of a variety of gut signals identified in this disorder. The pathophysiological roles of vagal signaling in functional dyspepsia is still largely unknown, although some studies suggested it may contribute to reduced food intake and gastric motility, increased psychological disorders and pain sensation, nausea and vomiting. Understanding the alteration in vagal signaling and its pathophysiological roles in functional dyspepsia may provide information for new potential therapeutic treatments of this disorder. In this review, we summarize and speculate possible alterations in vagal gut-to-brain and brain-to-gut signaling and the potential pathophysiological roles in functional dyspepsia.

An Update on the Assessment and Management of Pediatric Abdominal Pain

Chronic abdominal pain is very common in children and adolescent and results in high personal and social costs. Most youth with chronic abdominal pain fulfill criteria for a functional abdominal pain disorder (FAPD) as defined by Rome criteria. These are complex conditions with a wide array of biological, psychological, and social factors contributing to the experience of pain. The purpose of the current review is to provide an overview of the pathophysiology of FAPDs and an up-to-date summary of the literature related to FAPDs in children and adolescents, with additional focus on several areas (eg, diet and probiotics) where patients and families frequently have questions or implement self-directed care. We also provide an approach to the assessment and treatment of pediatric FAPDs focusing on the robust literature regarding psychological interventions and much sparser literature regarding medication treatment.

Functional dyspepsia

Dyspepsia is a complex of symptoms referable to the gastroduodenal region of the gastrointestinal tract and includes epigastric pain or burning, postprandial fullness, or early satiety. Approximately 80% of individuals with dyspepsia have no structural explanation for their symptoms and have functional dyspepsia. Functional dyspepsia affects up to 16% of otherwise healthy individuals in the general population. Risk factors include psychological comorbidity, acute gastroenteritis, female sex, smoking, use of non-steroidal anti-inflammatory drugs, and Helicobacter pylori infection. The pathophysiology remains incompletely understood, but it is probably related to disordered communication between the gut and the brain, leading to motility disturbances, visceral hypersensitivity, and alterations in gastrointestinal microbiota, mucosal and immune function, and CNS processing. Although technically a normal endoscopy is required to diagnose functional dyspepsia, the utility of endoscopy in all patients with typical symptoms is minimal; its use should be restricted to people aged 55 years and older, or to those with concerning features, such as weight loss or vomiting. As a result of our incomplete understanding of its pathophysiology, functional dyspepsia is difficult to treat and, in most patients, the condition is chronic and the natural history is one of fluctuating symptoms. Eradication therapy should be offered to patients with functional dyspepsia who test positive for Helicobacter pylori. Other therapies with evidence of effectiveness include proton pump inhibitors, histamine-2 receptor antagonists, prokinetics, and central neuromodulators. The role of psychological therapies is uncertain. As our understanding of the pathophysiology of functional dyspepsia increases, it is probable that the next decade will see the emergence of truly disease-modifying therapies for the first time.

Predictive value of alarm symptoms in patients with Rome IV dyspepsia: A cross-sectional study

BACKGROUND

No studies have evaluated the predictive value of alarm symptoms for organic dyspepsia and organic upper gastrointestinal (GI) diseases based on Rome IV criteria in the Chinese population.

AIM

To evaluate the predictive value of alarm symptoms for dyspeptic patients based on Rome IV criteria.

METHODS

We performed a cross-sectional study of dyspepsia patients who met the inclusion and exclusion criteria at two academic urban tertiary-care centers from March 2018 to January 2019. Basic demographic data, dyspeptic information, alarm symptoms, lifestyle, examination results, family history and outpatient cost information were collected. Dyspepsia patients with normal findings on upper GI endoscopy, epigastric ultrasound and laboratory examination and without Helicobacter pylori-associated dyspepsia were classified as functional dyspepsia.

RESULTS

A total of 381 patients were enrolled in the study, including 266 functional dyspepsia patients and 115 organic dyspepsia patients. There were 24 patients with organic upper GI disease among patients with organic dyspepsia. We found that based on the Rome IV criteria, alarm symptoms were of limited value in differentiating organic dyspepsia and organic upper GI diseases from functional dyspepsia. Age (odds ratio (OR) = 1.056, P = 0.012), smoking (OR = 4.714, P = 0.006) and anemia (OR = 88.270, P < 0.001) were independent predictors for organic upper GI diseases. For the comparison of epigastric pain syndrome, postprandial distress syndrome and epigastric pain syndrome combined with postprandial distress syndrome, the results showed that there were statistically significant differences in anorexia (P = 0.021) and previous visits (P = 0.012). The ClinicalTrials.gov number is NCT03479528.

CONCLUSION

Most alarm symptoms had poor predictive value for organic dyspepsia and organic upper GI diseases based on Rome IV criteria. Gastroscopic screening should not be based solely on alarm symptoms.

The Role of Diet in Functional Dyspepsia Management

Functional dyspepsia is a common functional gastrointestinal disease that is characterized by postprandial fullness, early satiation, epigastric pain, and/or epigastric burning. Eating a meal is a key factor in the occurrence of symptoms during functional dyspepsia, and patients frequently request dietary advice that could relieve these symptoms. Eating behaviors, irregular meal patterns, and moderate-to-fast eating rates are significantly associated with functional dyspepsia. The role of diet is complex; fat ingestion increases the occurrence of symptoms in dyspeptic patients, which might be affected by cognitive factors and palatability. Data concerning the role of carbohydrates are conflicting. Wheat may induce symptoms in patients with nonceliac gluten/wheat sensitivity, and gluten-free diets might be beneficial. Data concerning the role of FODMAPs (Fructo, Oligo, Di-, Monosaccharides, And Polyols) in functional dyspepsia are lacking; however, as there is a frequent overlap between functional dyspepsia and irritable bowel syndrome, a diet that is low in FODMAPs might be useful in relieving some symptoms. Data concerning alcohol are also conflicting. Adherence to a Mediterranean diet seems to be associated with a decrease in dyspepsia symptoms. Finally, data concerning diet modifications are conflicting, and the impact of diet modifications on symptom intensity or frequency has never been reported in randomized prospective studies. Common sense dietary recommendations, such as eating slowly and regularly, as well as decreasing the fat content of meals, can be provided in daily clinical practice.

The Altered Mucosal Barrier Function in the Duodenum Plays a Role in the Pathogenesis of Functional Dyspepsia

BACKGROUND

An altered gastrointestinal barrier function is reportedly associated with the pathogenesis of functional dyspepsia (FD); however, the pathogenesis of FD has not yet been fully elucidated.

AIMS

The objective of the present study was to determine whether the mucosal barrier function is impaired in patients with FD and to investigate the mechanisms underlying FD.

METHODS

The present study included patients with FD (FD group, n = 24), non-FD patients with abdominal symptoms (symptomatic control group, n = 14), and patients with no abdominal symptoms (asymptomatic control group, n = 20). The groups were compared regarding the mucosal electrical impedance (MI) values of the stomach and duodenum, which were measured using a tissue conductance meter during esophagogastroduodenoscopy.

RESULTS

There were no significant differences between the three groups in the MI of the stomach. In contrast, the duodenal MI of the FD group (17.8 ± 4.3 Ω) was significantly lower than those of the symptomatic control group (27.2 ± 6.4 Ω, p < 0.0001) and asymptomatic control group (23.0 ± 7.4 Ω, p = 0.016). The expression of zonula occludens-1 (ZO-1) was significantly lower in the FD group than in the symptomatic control group (p = 0.011), where ZO-1 was positively correlated with the duodenal MI (β = 0.513, p = 0.017). The interleukin (IL)-1β expression was significantly higher in the FD group than in the symptomatic control group (p = 0.041), where IL-1β was inversely correlated with the duodenal MI (β = - 0.600, p = 0.004).

CONCLUSIONS

The mucosal barrier function of the duodenum was altered in patients with FD. Both a decreased ZO-1 and increased IL-1β may play a role in the pathogenesis of FD.

Postprandial distress syndrome: stratification and management

Functional dyspepsia (FD), defined by the Rome consensus as the presence of functional symptoms originating from the gastroduodenum, is one of the most common functional gastrointestinal disorders. FD is subdivided into postprandial distress syndrome (PDS), with meal-related symptoms such as postprandial fullness and early satiation, and epigastric pain syndrome (EPS), with meal-unrelated symptoms such as epigastric pain or burning. We used a literature search for a narrative review on the current state of knowledge regarding PDS. Areas covered: Epidemiological studies support PDS as a separate entity and the biggest FD subgroup. The pathophysiology of PDS is heterogeneous, and disorders of gastric sensorimotor function as well as low grade duodenal inflammation have been implicated. Although prokinetic agents may provide the most pathophysiology-oriented treatment option, there is a paucity of suitable agents, and proton pump inhibitors are the traditional first-line therapy. Other options include agents that enhance gastric accommodation, such as acotiamide and 5-HT_1A agonists, neuromodulators such as mirtazapine, and traditional medicine approaches. Expert commentary: PDS is highly prevalent, with probably heterogeneous underlying pathophysiology. Motility modifying agents and neuromodulators are the cornerstone of PDS therapy, but there is a need for high quality studies of new therapeutic approaches.

Gastric administration of garlic powder containing the trpa1- agonist allicin induces specific epigastric symptoms and gastric relaxation in healthy subjects

BACKGROUND

TRPA1 is an excitatory ion channel and is involved in sensory processes including thermal nociception and inflammatory pain. The allicin in garlic is a strong activator of the TRPA1 channel.

AIM

To evaluate the effect of intragastric garlic powder containing allicin on perception, gastric tone, and mechanosensitivity.

METHODS

An infusion-barostat balloon assembly was used for infusion of test solutions, for distension, and to measure proximal gastric compliance and tone. After an initial open label dose finding with 1 g, 2 g, 3.75 g, and 7.5 g commercially available garlic powder, a bolus of 2 g garlic powder (11 mg allicin)/60 mL H₂ O was considered to induce moderate but constant sensation and was used hereafter in a placebo-controlled, single-dose, double-blind, randomized study in 7 volunteers to evaluate gastric sensation, tone, and mechanosensitivity.

KEY RESULTS

Bolus injection of garlic caused immediate epigastric symptoms, mean aggregate symptom scores (AUC in 15 minutes) were 106 ± 49 vs. 35 ± 30 after placebo (P = 0.01). Garlic induced significant epigastric pressure, stinging, and warmth (P < 0.01 vs. placebo), while intensity of cramps, satiety, nausea, and pain was not significantly different to placebo (P > 0.05). Garlic induced an immediate, short lived fundic relaxation (balloon volume 627 ± 349 mL vs. -145 ± 120 mL; P < 0.02). No effect of allicin on proximal gastric mechanosensitivity and compliance was observed (NS).

CONCLUSION AND INFERENCES

Garlic containing allicin induces immediate epigastric symptoms of pressure, stinging, and warmth and induces fundic relaxation but does not influence mechanosensitivity or compliance. TRPA1 is a receptor that is involved in gastric sensation and motility.

Gastroduodenal motility disorders

PURPOSE OF REVIEW

This review summarizes recent progress in the epidemiology, pathophysiology and treatment of gastroduodenal motility disorders with an emphasis on functional dyspepsia and gastroparesis.

RECENT FINDINGS

Pathophysiological research has focused on the association of delayed emptying and impaired accommodation with symptom pattern. Studies also confirmed the presence of altered mucosal integrity and low-grade immune activation in the duodenum in functional dyspepsia, while changes in numbers of interstitial cells of Cajal and myenteric neurons were confirmed in gastroparesis. Treatment advances in gastroparesis include new prokinetics such as the ghrelin receptor agonist relamorelin and the antiemetic agent aprepitant. The efficacy and use of neuromodulators were reviewed and new management guidelines for functional dyspepsia were published.

SUMMARY

Pathophysiological research has focused on cellular changes in gastroparesis and gastroduodenal motility disorders. New treatments include relamorelin and aprepitant for gastroparesis.

Identification of Individuals with Functional Dyspepsia With a Simple, Minimally Invasive Test: A Single Center Cohort Study of the Oral Capsaicin Test

OBJECTIVES

The diagnosis of functional dyspepsia (FD) is challenging due to the lack of reliable biological markers to support the diagnosis. We assessed the relevance of a previously validated simple test for chemical hypersensitivity in the setting of a gastrointestinal outpatient department.

METHODS

A total of 224 outpatients who were referred for evaluation of gastrointestinal symptoms in the absence of alarm symptoms swallowed a capsule containing 0.75 mg capsaicin. Severity of symptoms before and after capsule ingestion was assessed by a graded questionnaire and the difference in aggregate symptom scores (delta) was calculated.

RESULTS

Sensitivity of the test was between 0.51-0.59, specificity was 0.84-0.89 and positive predictive value for the diagnosis of FD 70-71%. FD patients had significantly higher median delta symptom scores (10.0; 25% quartile: 3.0; 75% quartile: 16.0) as compared to inflammatory bowel disease (2.5; 1.0/8.5)(P=0.003), peptic ulcer disease (0.0; -1.5/4.5) (P<0.001), irritable bowel syndrome (3.0;0.5/8.5)(P=0.001), and patients classified with "other disease" (2.5;0.0/5.0)(P<0.001). Patients with gastroesophageal reflux disease had significantly lower symptom scores if FD was not concomitantly diagnosed (2.0; 0.0/6.0) than if FD was present (10.0; 4.0/15.0).

CONCLUSIONS

Hypersensitivity for capsaicin discriminates functional dyspepsia from patients with other GI disorders. The capsaicin test is a simple and non invasive method to detect a large subgroup of functional dyspepsia with chemical hypersensitivity. These findings might open new diagnostic options in functional dyspepsia and possibly new therapeutic options by targeting the specific capsaicin receptor TRPV1.

Lack of an Effect of Gastric Capsaicin on the Rectal Component of the Gastrocolonic Response

Luminal capsaicin induces local and distant reflexes in the upper gastrointestinal tract and stimulates lower gastrointestinal symptoms in susceptible persons. We aimed to evaluate the effect of gastric capsaicin on rectal motor function and sensation.

METHODS

Eighteen healthy volunteers participated twice, at least 1 week apart, in this double-blind, placebo-controlled crossover study. Participants swallowed a gastric tube for capsaicin or saline infusion. A barostat tube was placed in the rectum to measure rectal tone before and during gastric capsaicin (40 µg/ml, 2.5 ml/min) or placebo infusion and to conduct distension experiments before and after gastric infusions. Gastric infusions were terminated after 60 min or when epigastric discomfort occurred. Differences in rectal tone, compliance, and sensitivity between gastric placebo and gastric capsaicin were determined.

RESULTS

On both study days, basal rectal volumes, compliance, and sensitivity parameters were comparable (NS) before gastric infusions. Gastric capsaicin infusion induced epigastric discomfort that necessitated termination of infusion after 29.6 ± 12.3 min (saline: 54.7 ± 8.9 min; p < 0.01). Rectal tone, aggregate perception scores, and rectal compliance did not differ between placebo and capsaicin trials (p > 0.05). Rectal tone increased significantly only when capsaicin induced epigastric discomfort (p < 0.05). The reproducibility of the barostat trial was acceptable with significant correlations of volumes, pressures (< 0.05; r ² from 0.41 to 0.55), rectal compliance (p < 0.01; r ² = 0.44), and aggregate perception scores (p values all < 0.05; r ² from 0.44 to 0.0.65) between the two barostat trials.

CONCLUSION

Gastric perfusion with capsaicin does not directly influence rectal physiology through a reflex arc.