A placebo-controlled trial of an oral capsaicin load in patients with functional dyspepsia

The regulatory effects of fucoidan and laminarin on functional dyspepsia mice induced by loperamide

Gastrointestinal dysmotility is a common cause of functional dyspepsia. As two kinds of polysaccharides derived from brown algae, fucoidan and laminarin possess many physiological properties; however, their relative abilities in regulating gastrointestinal motility have not been illustrated yet. In this study, we aimed to investigate the regulatory effect of fucoidan and laminarin on functional dyspepsia mice induced by loperamide. Mice with gastrointestinal dysmotility were treated with fucoidan (100 and 200 mg per kg bw) and laminarin (50 and 100 mg per kg bw). As a result, fucoidan and laminarin reversed the dysfunction mainly through regulating gastrointestinal hormones (motilin and ghrelin), the cholinergic pathway, the total bile acid level, c-kit protein expression, and gastric smooth muscle contraction-related gene expression (ANO1 and RYR3). Moreover, fucoidan and laminarin intervention modulated the gut microbiota profile including the altered richness of Muribaculaceae, Lachnospiraceae, and Streptococcus. The results indicated that fucoidan and laminarin may restore the rhythm of the migrating motor complex and regulate gut microecology. In conclusion, we provided evidence to support that fucoidan and laminarin might have potential abilities to regulate gastrointestinal motility.

Non-Chinese herbal medicines for functional dyspepsia

BACKGROUND

One-third of people with gastrointestinal disorders, including functional dyspepsia, use some form of complementary and alternative medicine, including herbal medicines.

OBJECTIVES

The primary objective is to assess the effects of non-Chinese herbal medicines for the treatment of people with functional dyspepsia.

SEARCH METHODS

We searched the following electronic databases on 22 December 2022: Cochrane Central Register of Controlled Trials, MEDLINE, Embase, Allied and Complementary Medicine Database, Latin American and Caribbean Health Sciences Literature, among other sources, without placing language restrictions.

SELECTION CRITERIA

We included RCTs comparing non-Chinese herbal medicines versus placebo or other treatments in people with functional dyspepsia.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened references, extracted data and assessed the risk of bias from trial reports. We used a random-effects model to calculate risk ratios (RRs) and mean differences (MDs). We created effect direction plots when meta-analysis was not possible, following the reporting guideline for Synthesis without Meta-analysis (SWiM). We used GRADE to assess the certainty of the evidence (CoE) for all outcomes.

MAIN RESULTS

We included 41 trials with 4477 participants that assessed 27 herbal medicines. This review evaluated global symptoms of functional dyspepsia, adverse events and quality of life; however, some studies did not report these outcomes. STW5 (Iberogast) may moderately improve global symptoms of dyspepsia compared with placebo at 28 to 56 days; however, the evidence is very uncertain (MD -2.64, 95% CI -4.39 to -0.90; I2 = 87%; 5 studies, 814 participants; very low CoE). STW5 may also increase the improvement rate compared to placebo at four to eight weeks' follow-up (RR 1.55, 95% CI 0.98 to 2.47; 2 studies, 324 participants; low CoE). There was little to no difference in adverse events for STW5 compared to placebo (RR 0.92, 95% CI 0.52 to 1.64; I2 = 0%; 4 studies, 786 participants; low CoE). STW5 may cause little to no difference in quality of life compared to placebo (no numerical data available, low CoE). Peppermint and caraway oil probably result in a large improvement in global symptoms of dyspepsia compared to placebo at four weeks (SMD -0.87, 95% CI -1.15 to -0.58; I2 = 0%; 2 studies, 210 participants; moderate CoE) and increase the improvement rate of global symptoms of dyspepsia (RR 1.53, 95% CI 1.30 to 1.81; I2 = 0%; 3 studies, 305 participants; moderate CoE). There may be little to no difference in the rate of adverse events between this intervention and placebo (RR 1.56, 95% CI 0.69 to 3.53; I2 = 47%; 3 studies, 305 participants; low CoE). The intervention probably improves the quality of life (measured on the Nepean Dyspepsia Index) (MD -131.40, 95% CI -193.76 to -69.04; 1 study, 99 participants; moderate CoE). Curcuma longa probably results in a moderate improvement global symptoms of dyspepsia compared to placebo at four weeks (MD -3.33, 95% CI -5.84 to -0.81; I2 = 50%; 2 studies, 110 participants; moderate CoE) and may increase the improvement rate (RR 1.50, 95% CI 1.06 to 2.11; 1 study, 76 participants; low CoE). There is probably little to no difference in the rate of adverse events between this intervention and placebo (RR 1.26, 95% CI 0.51 to 3.08; 1 study, 89 participants; moderate CoE). The intervention probably improves the quality of life, measured on the EQ-5D (MD 0.05, 95% CI 0.01 to 0.09; 1 study, 89 participants; moderate CoE). We found evidence that the following herbal medicines may improve symptoms of dyspepsia compared to placebo: Lafonesia pacari (RR 1.52, 95% CI 1.08 to 2.14; 1 study, 97 participants; moderate CoE), Nigella sativa (SMD -1.59, 95% CI -2.13 to -1.05; 1 study, 70 participants; high CoE), artichoke (SMD -0.34, 95% CI -0.59 to -0.09; 1 study, 244 participants; low CoE), Boensenbergia rotunda (SMD -2.22, 95% CI -2.62 to -1.83; 1 study, 160 participants; low CoE), Pistacia lenticus (SMD -0.33, 95% CI -0.66 to -0.01; 1 study, 148 participants; low CoE), Enteroplant (SMD -1.09, 95% CI -1.40 to -0.77; 1 study, 198 participants; low CoE), Ferula asafoetida (SMD -1.51, 95% CI -2.20 to -0.83; 1 study, 43 participants; low CoE), ginger and artichoke (RR 1.64, 95% CI 1.27 to 2.13; 1 study, 126 participants; low CoE), Glycyrrhiza glaba (SMD -1.86, 95% CI -2.54 to -1.19; 1 study, 50 participants; moderate CoE), OLNP-06 (RR 3.80, 95% CI 1.70 to 8.51; 1 study, 48 participants; low CoE), red pepper (SMD -1.07, 95% CI -1.89 to -0.26; 1 study, 27 participants; low CoE), Cuadrania tricuspidata (SMD -1.19, 95% CI -1.66 to -0.72; 1 study, 83 participants; low CoE), jollab (SMD -1.22, 95% CI -1.59 to -0.85; 1 study, 133 participants; low CoE), Pimpinella anisum (SMD -2.30, 95% CI -2.79 to -1.80; 1 study, 107 participants; low CoE). The following may provide little to no difference compared to placebo: Mentha pulegium (SMD -0.38, 95% CI -0.78 to 0.02; 1 study, 100 participants; moderate CoE) and cinnamon oil (SMD 0.38, 95% CI -0.17 to 0.94; 1 study, 51 participants; low CoE); moreover, Mentha longifolia may increase dyspeptic symptoms (SMD 0.46, 95% CI 0.04 to 0.88; 1 study, 88 participants; low CoE). Almost all the studies reported little to no difference in the rate of adverse events compared to placebo except for red pepper, which may result in a higher risk of adverse events compared to placebo (RR 4.31, 95% CI 1.56 to 11.89; 1 study, 27 participants; low CoE). With respect to the quality of life, most studies did not report this outcome. When compared to other interventions, essential oils may improve global symptoms of dyspepsia compared to omeprazole. Peppermint oil/caraway oil, STW5, Nigella sativa and Curcuma longa may provide little to no benefit compared to other treatments.

AUTHORS' CONCLUSIONS

Based on moderate to very low-certainty evidence, we identified some herbal medicines that may be effective in improving symptoms of dyspepsia. Moreover, these interventions may not be associated with important adverse events. More high-quality trials are needed on herbal medicines, especially including participants with common gastrointestinal comorbidities.

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 and Food: Immune Overlap with Food Sensitivity Disorders

PURPOSE OF REVIEW

Functional dyspepsia (FD) is a chronic functional gastrointestinal disorder characterised by upper gastrointestinal symptoms. Here, we aimed to examine the evidence for immune responses to food in FD and overlap with food hypersensitivity conditions.

RECENT FINDINGS

A feature of FD in a subset of patients is an increase in mucosal eosinophils, mast cells, intraepithelial cytotoxic T cells and systemic gut-homing T cells in the duodenum, suggesting that immune dysfunction is characteristic of this disease. Rates of self-reported non-celiac wheat/gluten sensitivity (NCW/GS) are higher in FD patients. FD patients commonly report worsening symptoms following consumption of wheat, fermentable oligosaccharides, disaccharides, monosaccharides, or polyols (FODMAPs), high-fat foods and spicy foods containing capsaicin. Particularly, wheat proteins and fructan in wheat may drive symptoms. Immune mechanisms that drive responses to food in FD are still poorly characterised but share key effector cells to common food hypersensitivities including non-IgE-mediated food allergy and eosinophilic oesophagitis.

Effects and mechanisms of acupuncture and electroacupuncture for functional dyspepsia: A systematic review

BACKGROUND

Functional dyspepsia (FD) is a common digestive disease with limited therapeutic options. According to evidence-based clinical practice, acupuncture or electroacupuncture (EA) seems to be a promising therapy for patients with FD. However, there is still a lack of systematic reviews that have analyzed current clinical trials for a better understanding of mechanisms involved in the ameliorating effect of acupuncture and EA on FD.

AIM

To evaluate the results and qualities of existing clinical evidence for researching the underlying mechanisms of acupuncture/EA in treating FD.

METHODS

A systematic search of the literature was performed to identify randomized controlled trials in which research on the mechanism of acupuncture or EA was conducted in FD patients. Databases searched included PubMed, EMBASE, Cochrane Library, and Web of Science. Data extraction and quality assessment were completed by two investigators independently and the results of quality evaluation were exported through Review Manager V5.3.

RESULTS

Eight studies were included in this review with a total of 17 items for detecting techniques for mechanistic research. Positive effects of acupuncture and EA were observed in regulating gastric motility, gastric accommodation, mental status, gastrointestinal hormones, and central and autonomic functions while improving dyspeptic symptoms and quality of life.

CONCLUSION

The key findings of this systematic review support the potential of acupuncture and EA in altering the heterogeneous pathophysiology in patients with FD. However, high-quality studies with well-planned designs are necessary to provide more credible evidence.

Insights into the evaluation and management of dyspepsia: recent developments and new guidelines

Dyspepsia is a very common gastrointestinal (GI) condition worldwide. We critically examine the recommendations of recently published guidelines for the management of dyspepsia, including those produced jointly by the American College of Gastroenterology and the Canadian Association of Gastroenterology, and those published by the UK National Institute for Health and Care Excellence. Dyspepsia is a symptom complex, characterized by a range of upper GI symptoms including epigastric pain or burning, early satiety, and post-prandial fullness. Although alarm features are used to help prioritize access to upper GI endoscopy, they are of limited utility in predicting endoscopic findings, and the majority of patients with dyspepsia will have no organic pathology identified at upper GI endoscopy. These patients are labelled as having functional dyspepsia (FD). The Rome IV criteria, which are used to define FD, further subclassify patients with FD as having either epigastric pain syndrome or post-prandial distress syndrome, depending on their predominant symptoms. Unfortunately, the Rome criteria perform poorly at identifying FD without the need for upper GI endoscopy. This has led to the investigation of alternative diagnostic approaches, including whether a capsaicin pill or combined serum biomarkers can accurately identify patients with FD. However, there is insufficient evidence to support either of these approaches at the present time. Patients with FD should be tested for H. pylori infection and be prescribed eradication therapy if they test positive. If they continue to have symptoms following this, then a trial of treatment with a proton pump inhibitor (PPI) should be given for up to 8 weeks. In cases where symptoms fail to adequately respond to PPI treatment, a tricyclic antidepressant may be of benefit, and should be continued for 6 to 12 months in patients who respond. Prokinetics demonstrate limited efficacy for treating FD, but could be considered if other strategies have failed. However, there are practical difficulties due to their limited availability in some countries and the risk of serious side effects. Patients with FD who fail to respond to drug treatments should be offered psychological therapy, where available. Overall, with the exception of recommendations relating to H. pylori testing and the prescription of PPIs, which are made on the basis of high-quality evidence, the evidence underpinning other elements of dyspepsia management is largely of low-quality. Consequently, there are still many aspects of the evaluation and management of dyspepsia that require further research.

Relationship Between Abdominal Symptoms and Fructose Ingestion in Children with Chronic Abdominal Pain

BACKGROUND

Limited valid data are available regarding the association of fructose-induced symptoms, fructose malabsorption, and clinical symptoms.

AIM

To develop a questionnaire for valid symptom assessment before and during a carbohydrate breath test and to correlate symptoms with fructose breath test results in children/adolescents with functional abdominal pain.

METHODS

A Likert-type questionnaire assessing symptoms considered relevant for hydrogen breath test in children was developed and underwent initial validation. Fructose malabsorption was determined by increased breath hydrogen in 82 pediatric patients with functional abdominal pain disorders; fructose-induced symptoms were quantified by symptom score ≥2 and relevant symptom increase over baseline. The results were correlated with clinical symptoms. The time course of symptoms during the breath test was assessed.

RESULTS

The questionnaire exhibited good psychometric properties in a standardized assessment of the severity of carbohydrate-related symptoms. A total of 40 % (n = 33) had malabsorption; symptoms were induced in 38 % (n = 31), but only 46 % (n = 15) with malabsorption were symptomatic. There was no significant correlation between fructose malabsorption and fructose-induced symptoms. Clinical symptoms correlated with symptoms evoked during the breath test (p < 0.001, r2 = 0.21) but not with malabsorption (NS). Malabsorbers did not differ from non-malabsorbers in terms of symptoms during breath test. Symptomatic patients had significantly higher pain and flatulence scores over the 9-h observation period (p < 0.01) than did nonsymptomatic patients; the meteorism score was higher after 90 min.

CONCLUSIONS

Fructose-induced symptoms but not fructose malabsorption are related to increased abdominal symptoms and have distinct timing patterns.

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.

Food Therapy in Sinosphere Asia

Traditional Chinese Food Therapy has long been an integral part of dietary practices in Sinosphere Asia. This therapy is defined by the classification of foods into cooling (Yin) and heaty (Yang) and the manipulation of dietary intake of these foods as a therapeutic strategy for chronic diseases. Both functional dyspepsia (FD) and irritable bowel syndrome (IBS) are chronic, functional gut disorders widely prevalent in Sinosphere Asia. Diet is increasingly recognized as a symptom trigger in FD and IBS, and the evidence suggesting the utility of diet therapies as front-line management is growing, particularly in the West. Specifically, a diet low in Fermentable, Oligosaccharides, Disaccharides, Monosaccharides, and Polyols is an efficacious therapy for patients with IBS. In contrast, a proportion of patients with IBS in Sinosphere Asia utilize Chinese Food Therapy for symptom management. Chinese Food Therapy provides an attractive target for integration with evidence-based Western dietary therapies as a management strategy in FD and IBS. However, significant gaps in research exist with the utility of Chinese Food Therapy that first need to be addressed. This includes a lack of standardization for heaty and cooling classification, limited mechanistic rationale or clinical studies supporting its efficacy in FD and IBS, and the lack of an ideal practitioner for implementation of Chinese Food Therapy. Hence, the review provides a summary of the role of diet and nutrition in Sinosphere Asia with an emphasis on FD and IBS, and an examination of how modern dietary practices may be able to be integrated into practices in this region.

Clinical characteristics of functional dyspepsia depending on chemosensitivity to capsaicin

BACKGROUND

Augmented chemosensitivity to capsaicin has been demonstrated in approximately half of functional dyspepsia (FD) patients.

AIM

We determined clinical characteristics of FD patients with and without chemical hypersensitivity at baseline and after capsaicin ingestion for 4 weeks.

METHODS

N=49 outpatients with confirmed FD received an oral sensitivity test with 0.75 mg capsaicin at three occasions, before and after ingesting 0.25 mg capsaicin tid for 4 weeks. Symptomatic response to capsaicin allowed stratification to a capsaicin positive (chemosensitive) and a capsaicin negative (not chemosensitive) patient group. Symptom diaries were completed in the week before and during capsaicin ingestion.

RESULTS

A total of 53% FD had a positive capsaicin test, Crohnbach alpha was 0.85. Basic clinical characteristics were comparable in capsaicin positive and negative FD, but median daily aggregate upper gastrointestinal symptoms scores were significantly higher in capsaicin positive (median: 9.4; 5.4/11.7) than in capsaicin negative patients (6.6; 4.1/8.1) (P<.05). After capsaicin ingestion, upper gastrointestinal symptoms scores were reduced by -3.3 (-4.9/-1.9; P<.001) in capsaicin positive and -2.6 (-3.8/-0.3; P<.05) in capsaicin negative patients. Lower abdominal symptoms were comparable in capsaicin positive and negative patients at baseline (NS). After capsaicin ingestion lower gastrointestinal symptoms scores were reduced by -1.0 (-1.8/-0.1; P<.05) in capsaicin positive but not significantly altered (-0.6; -1.7/+0.9; NS) in capsaicin negative patients. After long-term capsaicin ingestion, the capsaicin test turned negative in 53% of chemosensitive patients (P<.01).

CONCLUSIONS

Differences in upper GI symptoms distinguished capsaicin positive and negative patients. Symptom improvement after long-term capsaicin ingestion was indirect proportional to the capsaicin test result.

Mexican consensus on dyspepsia

Since the publication of the 2007 dyspepsia guidelines of the Asociación Mexicana de Gastroenterología, there have been significant advances in the knowledge of this disease. A systematic search of the literature in PubMed (01/2007 to 06/2016) was carried out to review and update the 2007 guidelines and to provide new evidence-based recommendations. All high-quality articles in Spanish and English were included. Statements were formulated and voted upon using the Delphi method. The level of evidence and strength of recommendation of each statement were established according to the GRADE system. Thirty-one statements were formulated, voted upon, and graded. New definition, classification, epidemiology, and pathophysiology data were provided and include the following information: Endoscopy should be carried out in cases of uninvestigated dyspepsia when there are alarm symptoms or no response to treatment. Gastric and duodenal biopsies can confirm Helicobacter pylori infection and rule out celiac disease, respectively. Establishing a strong doctor-patient relationship, as well as dietary and lifestyle changes, are useful initial measures. H2-blockers, proton-pump inhibitors, prokinetics, and antidepressants are effective pharmacologic therapies. H.pylori eradication may be effective in a subgroup of patients. There is no evidence that complementary and alternative therapies are beneficial, with the exception of Iberogast and rikkunshito, nor is there evidence on the usefulness of prebiotics, probiotics, or psychologic therapies. The new consensus statements on dyspepsia provide guidelines based on up-to-date evidence. A discussion, level of evidence, and strength of recommendation are presented for each statement.

Chili Peppers, Curcumins, and Prebiotics in Gastrointestinal Health and Disease

There is growing evidence for the role of several natural products as either useful agents or adjuncts in the management of functional GI disorders (FGIDs). In this review, we examine the medical evidence for three such compounds: chili, a culinary spice; curcumin, another spice and active derivative of a root bark; and prebiotics, which are nondigestible food products. Chili may affect the pathogenesis of abdominal pain especially in functional dyspepsia and cause other symptoms. It may have a therapeutic role in FGIDs through desensitization of transient receptor potential vanilloid-1 receptor. Curcumin, the active ingredient of turmeric rhizome, has been shown in several preclinical studies and uncontrolled clinical trials as having effects on gut inflammation, gut permeability and the brain-gut axis, especially in FGIDs. Prebiotics, the non-digestible food ingredients in dietary fiber, may serve as nutrients and selectively stimulate the growth and/or activity of certain colonic bacteria. The net effect of this change on colonic microbiota may lead to the production of acidic metabolites and other compounds that help to reduce the production of toxins and suppress the growth of harmful or disease-causing enteric pathogens. Although some clinical benefit in IBS has been shown, high dose intake of prebiotics may cause more bloating from bacterial fermentation.

A prospective study on symptom generation according to spicy food intake and TRPV1 genotypes in functional dyspepsia patients

BACKGROUND

Capsaicin is an ingredient of red peppers that binds to transient receptor potential vanilloid subtype 1 (TRPV1), and Koreans eat more capsaicin-rich food than do Japanese. This study aimed to compare symptom generation according to TRPV1 genotypes and the intake of spicy foods.

METHODS

Consecutive functional dyspepsia (FD) patients who were evaluated at Konkuk University Medical Centre (Korea) and Keio University Hospital (Japan) were included. Questionnaires on spicy food intake, patient assessment of gastrointestinal symptoms (PAGI-SYM), patient assessment of quality of life, and hospital anxiety and depression scale were provided. Blood was sampled for the detection of TRPV1 polymorphisms, and upper gastrointestinal endoscopy was performed with biopsies.

KEY RESULTS

Of 121 included subjects, 35 and 28 carried the TRPV1 CC and GG genotypes, respectively, with the prevalence rates not differing between Japan and Korea. The prevalence of FD subtypes did not differ with the spicy food intake, TRPV1 genotypes, or Helicobacter pylori infection. Neither TRPV1 polymorphisms nor H. pylori infections were related to scores on the PAGI-SYM questionnaires, but spicy food intake was positively correlated with the scores for stomach fullness (p = 0.001) and retching (p = 0.001). Using the linear regression analysis, stomach fullness was associated with spicy food intake (p = 0.007), whereas retching was related to younger age (p < 0.001) and female gender (p = 0.014).

CONCLUSIONS & INFERENCES

Upper gastrointestinal symptoms are more common in subjects with a higher consumption of spicy foods, younger age and female gender, regardless of TRPV1 genotypes and the H. pylori infection status. Capsaicin-rich foods may induce stomach fullness.

Visceral hypersensitivity and electromechanical dysfunction as therapeutic targets in pediatric functional dyspepsia

Functional gastrointestinal disorders (FGID) are common clinical syndromes diagnosed in the absence of biochemical, structural, or metabolic abnormalities. They account for significant morbidity and health care expenditures and are identifiable across variable age, geography, and culture. Etiology of abdominal pain associated FGIDs, including functional dyspepsia (FD), remains incompletely understood, but growing evidence implicates the importance of visceral hypersensitivity and electromechanical dysfunction. This manuscript explores data supporting the role of visceral hypersensitivity and electromechanical dysfunction in FD, with focus on pediatric data when available, and provides a summary of potential therapeutic targets.

Dyspepsia

Dyspepsia is a complex disorder with several distinct pathophysiologic mechanisms that are still poorly understood. Patients who experience dyspepsia have a high burden of disease, with significant personal and economic costs. Although serious pathology presenting as dyspepsia is rare, clinicians need to be aware of alarm features that should trigger prompt referral for subspecialty care. Those without alarm features can be managed in a rational way with either empiric antisecretory therapy, test-and-treat for H pylori eradication, antidepressants, and psychotherapy, or a combination of these. Given the heterogeneity of symptoms and large variability in response to different treatments, more research into specific pathophysiologic mechanisms will likely help guide diagnosis and treatment choices in the future.

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.

Capsaicin receptor as target of calcitonin gene-related peptide in the gut

Calcitonin gene-related peptide (CGRP), a 37 aminoacid-residue peptide, is a marker of afferent fibers in the upper gastrointestinal tract, being almost completely depleted following treatment with the selective neurotoxin capsaicin that targets these fibers via transient receptor potential vanilloid type-1 (TRPV-1). It is widely distributed in the peripheral nervous system of mammals where it is present as alpha isoform, while intrinsic neurons of the enteric nervous systems express predominantly CGRP-beta. Many gastrointestinal functions involve CGRP-containing afferent fibers of the enteric nervous system such as defense against irritants, intestinal nociception, modulation of gastrointestinal motility and secretion, and healing of gastric ulcers. The main effects on stomach homeostasis rely on local vasodilator actions during increased acid-back diffusion. In humans, release of CGRP through the activation of TRPV-1 has been shown to protect from gastric damage induced by several stimuli and to be involved in gastritis. In both dyspepsia and irritable bowel syndrome the repeated stimulation of TRPV-1 induced an improvement in epigastric pain of these patients. The TRPV-1/CGRP pathway might be a novel target for therapeutics in gastric mucosal injury and visceral sensitivity.

Changes in gastrointestinal tract function and structure in functional dyspepsia

Functional dyspepsia is an extremely common disorder of gastrointestinal function. The disorder is thought to be heterogeneous, with different pathophysiological mechanisms underlying varied symptom patterns. A diversity of changes in gastrointestinal tract function and structure has been described in functional dyspepsia. These involve alterations in the stomach, such as impaired accommodation, delayed gastric emptying and hypersensitivity, and alterations in the duodenum, such as increased sensitivity to duodenal acid and/or lipids and low-grade inflammation. In this Review, we summarize all these abnormalities in an attempt to provide an integrated overview of the pathophysiological mechanisms in functional dyspepsia.

Visceral and somatic sensory function in functional dyspepsia

BACKGROUND

Visceral hypersensitivity is one of the proposed underlying mechanisms in functional dyspepsia (FD). It is not clear whether visceral hypersensitivity in FD is a manifestation of a central sensitization also encompassing somatic sensitization. Transient receptor potential vanilloid-1 (TRPV(1)) pathways are involved in gastric mechanosensory physiology and the TRPV(1) receptor agonist, capsaicin, has been used as a chemical stimulant.

METHODS

In this double-blind, randomized study we evaluated both visceral and somatic sensory function in 34 FD patients and 42 healthy controls using quantitative sensory testing. Visceral pain sensitivity was assessed using a validated gastric pain model with oral capsaicin capsule titration and somatic pain sensitivity was determined by foot heat and hand electric stimulation.

KEY RESULTS

The median capsaicin dose required to attain moderate pain was 0.5mg in FD and 1mg in controls (P = 0.03). At these doses, mean pain intensities on a 0-100 visual analog scale were greater for FD than controls [56.9 (95% confidence intervals, 52.2-61.5) vs 45.1 (41.6-48.6), resp.] (P = 0.005). Overall, mean somatic sensory and pain thresholds were similar in FD and control groups, but in a subgroup of FD pain hypersensitivity was seen on the hand and on the foot at different stimulation thresholds.

CONCLUSIONS & INFERENCES

A majority of patients with FD have visceral chemo-hypersensitivity involving TRPV(1) pathways. A substantial subgroup also has somatic hypersensitivity as evidence of central sensitization.

Irritable bowel syndrome: methods, mechanisms, and pathophysiology. Methods to assess visceral hypersensitivity in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder, characterized by recurrent abdominal pain or discomfort in combination with disturbed bowel habits in the absence of identifiable organic cause. Visceral hypersensitivity has emerged as a key hypothesis in explaining the painful symptoms in IBS and has been proposed as a "biological hallmark" for the condition. Current techniques of assessing visceral perception include the computerized barostat using rectal distensions, registering responses induced by sensory stimuli including the flexor reflex and cerebral evoked potentials, as well as brain imaging modalities such as functional magnetic resonance imaging and positron emission tomography. These methods have provided further insight into alterations in pain processing in IBS, although the most optimal method and condition remain to be established. In an attempt to give an overview of these methods, a literature search in the electronic databases PubMed and MEDLINE was executed using the search terms "assessment of visceral pain/visceral nociception/visceral hypersensitivity" and "irritable bowel syndrome." Both original articles and review articles were considered for data extraction. This review aims to discuss currently used modalities in assessing visceral perception, along with advantages and limitations, and aims also to define future directions for methodological aspects in visceral pain research. Although novel paradigms such as brain imaging and neurophysiological recordings have been introduced in the study of visceral pain, confirmative studies are warranted to establish their robustness and clinical relevance. Therefore, subjective verbal reporting following rectal distension currently remains the best-validated technique in assessing visceral perception in IBS.

Investigating functional dyspepsia in Asia

The diagnosis of functional dyspepsia (FD) is challenging since it depends largely on symptoms which are often heterogeneous and overlapping. This is particularly so in Asia with many different cultures and languages. Symptom-based diagnosis of FD based on Rome III criteria has not been fully validated and it may not be suitable in some Asian populations. Clinicians often assume that investigations in FD are not rewarding and physiological tests are often not available unless in the research setting. Investigation of alarm features and role of Helicobacter pylori in FD remain controversial but experts agreed that both should be tested. Physiological tests including gastric accommodation and chemical hypersensitivity tests are underutilized in Asia and available studies were few. While experts do not recommend routine clinical use of gastric accommodation tests but they agree that these tests can be advocated if clinically indicated. Empiric therapeutic trial is not currently a diagnostic option. The pathogenesis of FD is still poorly understood and there is a substantial placebo response. As a conclusion, a diagnosis of FD is challenging especially so in the context of Asia and despite the limitations of available physiological tests experts agreed that these tests can be advocated if and when clinically indicated.