Association between H. pylori, duodenal mechanosensory thresholds, and small intestinal motility in chronic unexplained dyspepsia

The stomach-brain axis

The stomach has distinct functions in relation to the ingestion and handling of solids and liquids. These functions include storage of the food before it is gradually emptied into the duodenum, mechanical crushing of larger food particles to increase the surface area, secretion of an acidic enzyme rich gastric juice and mixing the ingested food with the gastric juice. In addition, the stomach 'senses' the composition of the gastric content and this information is passed via the vagal nerve to the lateral hypothalamus and the limbic system, most likely as palatability signals that influence eating behaviour. Other sensory qualities related to the stimulation of gastric tension receptors are satiety and fullness. Receptors that respond to macronutrient content or gastric wall tension influence appetite and meal related hormone responses. The ingestion of food - in contrast to an infusion of nutrients into the stomach - has distinct effects on the activation of specific brain regions. Brain areas such as thalamus, amygdala, putamen and praecuneus are activated by the ingestion of food. Gastric nutrient infusion evokes greater activation in the hippocampus and anterior cingulate. The brain integrates these interrelated neural and hormonal signals arising from the stomach as well as visual, olfactory and anticipatory stimuli that ultimately influence eating and other behavioural patterns. Furthermore, there is now good evidence from experimental studies that gastric afferents influence mood, and animal studies point towards the possibility that gastric dysfunction may be a risk factor for mood disorders such as anxiety and depression. The stomach is also not only colonised by Helicobacter pylori but a large array of bacteria. While there is sufficient evidence to suggest that H. pylori may alter caloric intake and mood, the role of other gastric microbiome for the brain function is unknown. To address this appropriate targeted gastric microbiome studies would be required instead of widely utilised opportunistic stool microbiome studies. In summary, it is now well established that there are important links between the brain and the stomach that have significant effects on gastric function. However, the stomach also influences the brain. Disturbances in the crosstalk between the stomach and the brain may manifest as functional GI disorders while disturbances in the stomach-brain communication may also result in an altered regulation of satiety and as a consequence may affect eating behaviour and mood. These observations may enable the identification of novel therapies targeted at the gastroduodenum that positively alter brain function and treat or prevent conditions such as obesity or functional gastrointestinal disorders.

Relationship between symptom pattern, assessed by the PAGI-SYM questionnaire, and gastric sensorimotor dysfunction in functional dyspepsia

The patient assessment of upper gastrointestinal symptom severity index (PAGI-SYM) questionnaire was recently developed and validated for the evaluation of therapeutic responsiveness in functional dyspepsia (FD). Functional dyspepsia is a heterogeneous disorder, with different pathophysiological mechanisms underlying the symptom pattern. The relationship between PAGI-SYM scores and putative pathophysiological mechanisms has not been studied. The aim of this study was to evaluate the relationship between PAGI-SYM subscales and gastric emptying, gastric sensitivity and gastric accommodation in FD. A total of 161 consecutive FD patients underwent Helicobacter pylori (HP), gastric barostat and standardized gastric emptying testing (n = 126), and completed the PAGI-SYM questionnaire. Relationships between scores for the six subscales (heartburn/regurgitation, nausea/vomiting, fullness/satiety, bloating, upper abdominal pain, lower abdominal pain) and gastric function were analysed using Pearson's linear correlation, multiple regression analysis, chi-square and Student's t-tests. Gastric emptying was significantly correlated with scores for heartburn/regurgitation (r = 0.26), nausea/vomiting (r = 0.19), fullness/satiety (r = 0.20), bloating (r = 0.21) and lower abdominal pain (r = 0.22; all P < 0.05). Patients with delayed emptying had significantly higher scores for each of these subscales (all P < 0.05). Discomfort volume during gastric distension was significantly correlated with scores for fullness/satiety (r = -0.27), bloating (r = -0.23), heartburn/regurgitation (r = -0.21), and upper abdominal pain (r = -0.20). Patients with hypersensitivity to distension had significantly higher scores for fullness/satiety (P < 0.05). At different cut-off levels of symptom severities, consistent associations were found between fullness/satiety and gastric discomfort volume, between preprandial volumes and upper abdominal pain, compliance and upper abdominal pain, and between bloating and gastric discomfort volume. Multiple regression analysis revealed that gastric emptying rate contributed significantly to models for the severity of these subscales. The importance of discomfort volume disappeared in favour of gender when sex was included in the model. No significant correlations were found with HP status or with gastric accommodation. PAGI-SYM scores are mainly correlated with gastric emptying rate and with gastric hypersensitivity. Multivariate analysis suggests that the questionnaire may be useful in the evaluation of gastroprokinetics. Its role in the evaluation of drugs that alter gastric sensitivity is less clear.

Gastric emptying of solids in children with H. pylori-positive and H. pylori-negative non-ulcer dyspepsia

OBJECTIVE

There is currently no data available in children on possible relationships among Helicobacter pylori, gastric motility and gastric inflammation. This is a prospective study of gastric emptying (GE) in symptomatic children with and without H. pylori who met symptom-based criteria for non-ulcer dyspepsia (NUD).

METHODS

47 consecutive dyspeptic patients (23 males; age range, 7 to 18 years) were enrolled. All patients had extensive negative diagnostic investigations. Scintigraphic solid-phase gastric emptying was assessed.

RESULTS

21 H. pylori-positive and 26 H. pylori-negative patients were identified with non-ulcer dyspepsia. The groups were not different in clinical symptoms except that pain related to feeding was more frequent in infected children (P < 0.03). Nodular antral gastritis was found more frequently in the H. pylori positive group (P < 0.0001). The gastritis score was more severe in H. pylori infected than H. pylori negative patients in both fundic and body mucosa (P < 0.001). Within the H. pylori-positive NUD group, the mean half-time GE of a solid meal was significantly accelerated compared to the non-infected group (P < 0.05). There was no difference in the intragastric food distribution and curves of gastric emptying of both groups. A significant relationship was found between the degree of gastric body inflammation gastric emptying, but not antral inflammation. Gastric emptying rate did not differ by sex or age of the subjects in either group.

CONCLUSIONS

In dyspeptic children with H. pylori, gastric emptying of a solid was significantly accelerated compared with symptomatic H. pylori uninfected patients. This suggests that H. pylori is able to induce gastric emptying acceleration. Our findings add more information on H. pylori infection and gastroduodenal disease.

Electrogastrography as a diagnostic tool for delayed gastric emptying in functional dyspepsia and irritable bowel syndrome

Several pathophysiological mechanisms have been proposed in functional gastrointestinal (GI) disorders, e.g. altered GI motility and sensitivity. The aim of this study was to investigate gastric electrical activity (GEA) in patients with functional dyspepsia (FD) or irritable bowel syndrome (IBS) compared with healthy controls (HC), and to assess if abdominal symptoms and delayed gastric emptying are associated with alterations in GEA, as determined by electrogastrography (EGG). Forty patients with FD, IBS or both were compared with 22 HC. EGG was performed before and after a standard meal. Frequencies and amplitudes pre- and post-prandially were analysed. Furthermore, gastric emptying and symptom scores were assessed. Eight of 40 patients (20%; three FD, three IBS, two FD and IBS) had delayed gastric emptying. Disturbed gastric emptying and lack of a postprandial increase in the EGG amplitude were significantly correlated (r = 0.8; P < 0.005). No differences between controls and patients were observed in the distribution of EGG frequencies. Treatment with the prokinetically active macrolide erythromycin improved gastric emptying, GEA and symptoms (n = 4). The data suggest that EGG could be useful as a diagnostic tool in patients with FD and IBS to identify a subgroup of patients with delayed gastric emptying.

Acid infusion enhances duodenal mechanosensitivity in healthy subjects

Duodenal acid has been suggested to be of importance for dyspeptic symptoms. We investigated the effects of acid on duodenal mechanosensitivity and antroduodenal motility in 10 healthy subjects before and during duodenal infusion of acid (0.1 N HCl) or water by using a combined barostat-manometry assembly. During acid infusion, increased sensitivity to balloon distension was seen, with reduced perception (P = 0.04) and discomfort thresholds (P = 0.06) and higher intensity of discomfort (P = 0.02) compared with water. Higher balloon volumes were seen during acid infusion, indicating decreased tone (P = 0.05). Large volume waves were more prevalent during acid than water infusion (P = 0.009). The acid infusion suppressed antral contractions (P = 0.04) and increased the number of contractions in the proximal duodenum (P = 0.02) compared with before the infusion. In conclusion, duodenal acid enhances mechanical sensitivity in the duodenum, affects gastroduodenal motor function, and might be of importance for dyspeptic symptoms.

Functional dyspepsia: evaluation and treatment

Functional dyspepsia is one of the most common disorders seen in general practice and by gastroenterologists. New concepts regarding the pathophysiology and its role for the symptom pattern have emerged during the last few years. This is of importance for development of new treatment alternatives in the near future. At the moment, however, empirical treatment with acid-suppressive agents and prokinetics is the recommended therapeutic approach in the management of these patients, despite limited efficacy. Identification and treatment of H pylori infection has been recommended for uninvestigated dyspepsia, because it may cure underlying peptic ulcer disease, but is unlikely to provide symptomatic benefit to patients with functional dyspepsia. Refractory patients may respond to antidepressants or to psychologic treatments, but proof of efficacy is limited. New and more effective approaches are badly needed for functional dyspepsia.

Immune-mediated neural dysfunction in a murine model of chronic Helicobacter pylori infection

BACKGROUND & AIMS

Neuromuscular changes producing dysmotility and hyperalgesia may underlie symptom generation in functional gastrointestinal disorders. We investigated whether chronic Helicobacter pylori-induced gastritis causes neuromuscular dysfunction.

METHODS

In vitro muscle contractility and acetylcholine release were evaluated in mice before and after H. pylori eradication. H. pylori colonization and gastritis were graded histologically. Substance P (SP)-, vasoactive intestinal polypeptide (VIP)-, and calcitonin gene-related peptide (CGRP) immunoreactivity (IR) and macrophages were studied by immunohistochemistry.

RESULTS

In Balb/c mice, chronic H. pylori infection did not affect muscle function but augmented antral relaxation after nerve electric field stimulation. Infected mice had lower acetylcholine release by electric field stimulation and had higher density of SP-, CGRP-, and VIP-IR nerves in the stomach and of SP- and CGRP-IR in the spinal cord. Cholinergic nerve dysfunction worsened progressively and was associated with increasing macrophage and mononuclear but not polymorphonuclear infiltrate or bacterial colonization. SCID mice had unchanged acetylcholine release despite high H. pylori colonization and macrophage infiltration. Eradication of H. pylori normalized functional and morphologic abnormalities except for increased density of gastric SP- and CGRP-IR nerves.

CONCLUSIONS

H. pylori infection induces functional and morphologic changes in the gastric neural circuitry that are progressive and lymphocyte dependent, and some persist after H. pylori eradication. The data have direct implications regarding the role of H. pylori infection in functional dyspepsia.

Dyspeptic symptoms in middle-aged to old adults: the role of Helicobacter pylori infection, and various demographic and lifestyle factors

OBJECTIVES

To evaluate the role of factors supposed to interfere with the gastric mucosa like Helicobacter pylori, smoking and analgesics in symptom generation in a population-based sample of middle-aged to old.

SUBJECTS

A total of 288 subjects aged 50-85 (mean 65 +/- 7.2) attending a General Science-orientated Continuing Education Programme at the University of Ulm.

METHODS

Helicobacter pylori infection was determined by the 13C-urea breath test. Demographic data, gastrointestinal symptoms and factors supposed to be involved in symptom generation were collected by a standardized questionnaire. The association between various demographic and lifestyle factors with a gastrointestinal symptom score was quantified by odds ratios (ORs) using multiple logistic regression.

RESULTS

Use of nonsteroidal anti-inflammatory drugs (OR=1.2; 95% CI=0.7-2.1) was no risk factor for abdominal symptoms, whereas female sex (OR= 1.6; 95% CI=0.9-2.9) and current smoking (OR= 3.7; 95% CI=0.9-15.4) were associated with a high symptom score. Age 70 years and over was significantly associated with a lower symptom score (OR=0.4; 95% CI=0.2-0.9). However, H. pylori infection was a risk factor for a high symptom score in that age group (OR=4.3; 95% CI=1.2-14.8), whereas no such association (and even a tendency to reduced symptom levels in infected subjects) was observed in younger age groups.

CONCLUSION

The role of H. pylori infection in symptoms may vary by age. The loss of symptoms in the elderly may delay detection of gastroduodenal pathology and appropriate treatment in older adults.

Review article: Helicobacter pylori and nonulcer dyspepsia

Although up to 50% of patients diagnosed with nonulcer dyspepsia (NUD) have Helicobacter pylori infection and underlying chronic gastritis, it remains controversial whether any causal relationship exists. The results of worldwide epidemiological studies have been unconvincing. No clear-cut link has been documented between H. pylori and any specific symptom profile or pathophysiological mechanism in NUD. In the randomized controlled trials, methodological weaknesses may explain in part the conflicting results, but even in the well-conducted trials controversy persists. Although meta-analyses have attempted to resolve the issue, inherent methodological difficulties with meta-analysis remain a problem. Moreover, even the methodologically sound meta-analyses have reported conflicting results. In addition, predictors of treatment response remain obscure, and there continue to be theoretical concerns about the treatment of H. pylori infection in all patients with NUD. Hence, the management of these patients is challenging, but eradication of H. pylori infection may be beneficial in a small subgroup of cases with NUD that cannot be identified before treatment.

Helicobacter pylori eradication in patients with non-ulcer dyspepsia

Epidemiological and pathophysiological studies, as well as clinical trials, attempting to identify a relationship between Helicobacter pylori infection and non-ulcer dyspepsia (NUD), or a subset of NUD, have produced inconsistent and confusing results. While it is possible that H. pylori eradication may be beneficial for symptom relief in a small proportion of patients, routine H. pylori testing and treatment in documented NUD is not currently widely accepted. Despite the lack of convincing evidence, the European Helicobacter pylori Study Group, an Asian Pacific Consensus Meeting, the American Digestive Health Foundation and the American Gastroenterology Association have all recommended considering H. pylori eradication in patients with NUD on a patient-by-patient basis. Recently, large prospective, randomised, double-blind, controlled clinical trials applying highly effective antimicrobial therapy have been conducted with 12 months follow-up. Although these well-designed studies have reached differing conclusions, the results have been largely negative. H. pylori eradication therapy in NUD will fail to relieve symptoms in most patients in the long term.

Functional dyspepsia: New insights into the pathophysiology

The pathogenesis of functional dyspepsia remains poorly understood. There is increasing evidence pointing to a predominant role of gastroduodenal visceral hypersensitivity in the pathogenesis, where patients have abnormally reduced gastric and small intestinal sensory thresholds. Motor abnormalities observed in subgroups of patients include delayed gastric emptying, antral hypomotility, gastric dysrhythmias, abnormal gastrointestinal reflexes and small intestinal dysmotility, but these may be secondary pheno nena. The central nervous system modifies peripheral visceral afferent pathways and, hente, psychological factors may possibly alter symptom status. Other putative mechanisms include Helicobacter pylori gastritis and gastric acid hypersecretion or sensitivity, but the role of these remain controversial.

Helicobacter pylori and functional dyspepsia: a real causal link?

This chapter reviews the evidence for a link between functional dyspepsia and Helicobacter pylori infection from three angles. In the section on pathophysiology, we evaluate how H. pylori could theoretically produce dyspeptic symptoms: many mechanisms can be proposed. In the discussion on epidemiology, we evaluate possible associations between the occurrence of symptoms and infection. Here, many studies claiming a coincidence or chronological sequence of infection and symptoms are criticized because of their poor design. In the section on the improvement of functional dyspepsia by the treatment of H. pylori infection, the conclusion is reached that if such an effect occurs at all--which is unlikely--it is very weak. The controversy on the link between H. pylori infection and functional dyspepsia is presently ongoing. Some authors are still trying to save an elegant concept that once looked so plausible but now has the facts against it.

Is functional dyspepsia just a subset of the irritable bowel syndrome?

To determine whether functional dyspepsia and irritable bowel syndrome are different entities, epidemiological data, factor analysis studies, physiological data and associated psychological symptoms were reviewed. Between 30% and 60% of patients with either diagnosis also meet the criteria for the other diagnosis, a level greater than expected to occur by chance but not sufficient to infer an identity. Most factor analysis studies identify independent clusters of symptoms corresponding to functional dyspepsia and irritable bowel syndrome. Visceral hypersensitivity is seen throughout the gastrointestinal tract in both disorders, but the motility patterns seen in association with functional dyspepsia (principally antral hypomotility and delayed gastric emptying) differ from the motility patterns seen in irritable bowel syndrome. Psychological symptoms are similar in these two disorders but are not believed to be aetiological for either of them. Thus, based on a factor analysis of gastrointestinal symptoms and differences in intestinal motility, functional dyspepsia and irritable bowel syndrome appear to be different entities.

Gastrointestinal sensory abnormalities in functional dyspepsia

Symptoms of functional dyspepsia, such as epigastric pain, bloating or early satiety and nausea, are non-specific and are likely to arise from different mechanisms. Current evidence suggests the presence of at least two subgroups: patients who respond to a prolonged course of acid suppression and patients who show a significant overlap of symptoms with other functional gastrointestinal disorders such as irritable bowel syndrome. An enhanced sensitivity of visceral afferent pathways with or without associated autonomic dysregulation appears to play an important role in the aetiology of symptoms in the second group. In the absence of visceral hypersensitivity, neither the slowing of gastric emptying nor the presence of chronic gastritis appears to be sufficient to cause symptoms of functional dyspepsia. The mechanisms and aetiology of visceral hypersensitivity are incompletely understood. An alteration in the interplay between vagal and spinal afferents, and the inadequate activation of antinociceptive systems in response to tissue irritation, may play a role in symptom generation.

Antibody response to specific H. pylori antigens in functional dyspepsia, duodenal ulcer disease, and health

OBJECTIVE

The relationship between H. pylori and functional dyspepsia remains controversial. The aim of this study was to identify a potential link between the antibody response to specific H. pylori antigens and functional dyspepsia.

METHODS

A total of 50 consecutive patients with functional dyspepsia, 50 patients with duodenal ulcer (DU), and 150 healthy blood donor control subjects with no history of peptic ulceration were studied. H. pylori status was determined by IgG antibodies using a validated ELISA. In H. pylori-positive subjects, antibodies against specific H. pylori antigens were identified by Western blot.

RESULTS

All DU patients (100%; 95%; CI, 93-100), 30 of 50 patients with functional dyspepsia (60%; 95% CI, 45-74) and 65 of 150 (43.3%; 95% CI, 34.3-51) blood donor controls tested positive for H. pylori. Forty-six of 50 (92%; 95% CI, 81-98) DU patients tested positive for the 91 kDa antigen (vacA) compared with 46 of 65 (69%; 95% CI, 58-81) control subjects and 22 of 30 (73%; 95% CI, 54-88) functional dyspepsia patients (p < 0.01 DU versus controls). Similarly, the 120 kDa antigen (cagA) tended (p < 0.15) to be more prevalent in DU patients (82%; 95% CI, 69-91) compared with controls (69%; 95% CI, 57-80) but not functional dyspepsia (77%; 95% CI, 57-90). No specific H. pylori antigens were associated with dyspepsia subgroups.

CONCLUSION

No specific H. pylori antigens are linked to functional dyspepsia.

What role does Helicobacter pylori play in dyspepsia and nonulcer dyspepsia? Arguments for and against H. pylori being associated with dyspeptic symptoms

A major role for Helicobacter pylori gastritis in nonulcer dyspepsia (NUD) is controversial. Gastroduodenal dysfunction may be associated with H. pylori infection, but there is little evidence for a causal link with dyspepsia. Population-based studies with appropriate methodology have generally failed to confirm an association between H. pylori and NUD. Furthermore, no definite association between subgroups of NUD (ulcer-like, dysmotility-like, reflux-like, and nonspecific) and H. pylori has been identified however the subgroups have been defined, and no specific symptom pattern characterizes patients with H. pylori infection. Whether H. pylori-induced alterations of gastric physiology can explain NUD remains open to debate while we await the results of more specific experiments. Although acid secretion in response to gastrin-releasing peptide may be increased in a subset of NUD patients who are infected with H. pylori, uninfected patients with NUD have not been assessed and the results require confirmation. Most studies suggest no association between H. pylori and gastroduodenal motor or sensory dysfunction in NUD. Treatment trials have been unconvincing. The trials with bismuth therapy have not been adequately blinded. Furthermore, some studies suggest that H. pylori-negative patients with NUD may respond to bismuth treatment, although the results have not been uniform. Therapies aimed at curing H. pylori infection have produced mixed results, with small positive and negative trials. The trials that have used adequate outcome measures have more often than not been negative. Based on current evidence, H. pylori is not established to be of causal importance in NUD.