Suppression of Helicobacter pylori reduces gastrin releasing peptide stimulated gastrin release in duodenal ulcer patients

Low circulating levels of gastrin-17 in patients with Barrett's esophagus

AIM: To examine whether the fasting levels of serum gastrin-17 (G-17) are lower in Barrett's esophagus (BE) patients than in non-Barrett controls.

METHODS: Nineteen patients with BE (presenting with a tubular segment ≥2 cm long in lower esophagus and intestinal metaplasia of incomplete type ("pecialized columnar epithelium") in endoscopic biopsies from the tubular segment below the squamocolumnar junction were collected prospectively from outpatients referred to diagnostic gastroscopy. The controls comprised 199 prospectively collected dyspeptic outpatients without BE or any endoscopically visible lesions in the upper GI tract. Fasting levels of serum G-17 (G-17fast) were assayed with an EIA test using a Mab highly specific to amidated G-17. None of the patients and controls received therapy with PPIs or other antisecretory agents.

RESULTS: The mean and median levels of G-17fast in serum were significantly lower (P = 0.001) in BE patients than in controls. The positive likelihood ratios (LR+) of low G-17fast to predict BE in the whole study population at G-17fast levels <0.5, <1, or <1.5 pmol/L were 3.5, 3.0, and 2.8, respectively. Among patients and controls with healthy stomach mucosa, the LR+ were 5.6, 3.8, and 2.6, respectively. In the whole study population, serum G-17 was below 2 pmol/L in 15 of 19 BE patients (79%). The corresponding prevalence was 66 of 199 (33%) in controls (P<0.001). The G-17fast was 5 pmol/L or more in only one of the 19 BE patients (5%). In controls, 76 of the 199 patients (38%) had such high serum G-17fast levels (P<0.01).

CONCLUSION: Serum levels of G-17fast tend to be lower in native patients with BE than in healthy controls.

Tumour Necrosis Factor Alpha Antibody Affects Gastrin Release in Crohn Disease

BACKGROUND

Gastrin plays an important role in the regulation of gastric acid secretion in humans. Tumour necrosis factor alpha (TNF-α) stimulates gastrin release from antral G cells in vitro. The aim was to determine whether gastrin release decreases in patients with Crohn disease treated with monoclonal antibody to TNF-α.

METHODS

Twenty-five consecutive patients with Crohn disease (10 M, 15 F; 18 with fistulas) were treated with a single intravenous infusion of the monoclonal antibody to TNF-α, infliximab, at a dose of 5 mg/kg. Basal and bombesin stimulated gastrin was measured after an overnight fast immediately before and 2 weeks after infliximab. Helicobacter pylori status was determined by serology.

RESULTS

Twenty-two patients were H. pylori-negative. Basal plasma gastrin was 21 (16-26) pmol/L before and 19 (15-25) pmol/L after infliximab (NS). Bombesin stimulated gastrin decreased from 49 (40-62) pmol/L before to 36 (33-59) pmol/L (P &lt; 0.005) 2 weeks after infliximab.

CONCLUSION

Gastrin release in response to bombesin decreases in patients with Crohn disease treated with infliximab.

Increase of arterial thrombosis parameters in chronic Helicobacter pylori infection in mice

An animal model was developed to study arterial thrombosis and determine if animals infected with Helicobacter pylori behave differently after induction of direct damage to blood vessels. Twenty-one C56/BL6 mice inoculated with the "Sydney strain" of H. pylori and 19 uninfected animals were kept for 1 year before testing. Vascular lesions were induced to mesenteric arterioles (15-25 microm diameter) by Argon laser. The dynamic course of thrombus formation was continuously monitored by a video camera for 10 min. Three parameters were assessed: (1) the number of laser pulses required to induce thrombus formation, (2) the number of platelet emboli removed by the blood flow and, (3) the duration of embolization. Additionally, blood was tested for platelet aggregation, fibrinogen, and cell count. Of the parameters measured, statistical differences between infected and uninfected mice concerned the number of emboli formed (6.00+/-2.18 infected vs. 3.89+/-1.37 non-infected, p=.0006) and the duration of embolization (2.41+/-0.73 min infected vs. 1.47+/-0.61 min non-infected p>.0001). A significant difference was also found in the fibrinogen levels between infected and uninfected mice. Chronic infection of mice with H. pylori leads to increased platelet embolization after damage to arterioles. These results are in favor of the possible involvement of H. pylori infection in the acute phase of coronary heart disease (CHD).

Circulating cytokines and gastrin levels in asymptomatic subjects infected by Helicobacter pylori (H. pylori)

The pathophysiology of hypergastrinemia in H. pylori infection has been largely investigated and different reports clearly show that the infected antrum has a marked inflammatory response with a suggestive local production of cytokines. Notwithstanding, a few data are available on the circulating levels of cytokines and gastrin in the asymptomatic people carrying H. pylori infection. Thus, aim of the study was to evaluate circulating proinflammatory cytokines [Interleukin (IL)-8, Interleukin (IL)-10, Interferon (IFN)-gamma, and Tumor Necrosis Factor (TNF)-alpha] and gastrin levels in H. pylori positive asymptomatic subjects vs. H. pylori negative ones. To this end, thirty healthy volunteers with no digestive symptoms or systemic disease were enrolled and H. pylori infection was identified by a 13C-urea breath test. Plasma levels of gastrin were determined using the RIA kit whereas IL-8, TNF-alpha, IL-10, and IFN-gamma levels in serum were measured with a solid-phase ELISA. Fifteen infected people showed significantly higher gastrin and TNF-alpha levels than uninfected subjects. On the contrary, IL-8 levels were significantly higher in the uninfected subjects than in H. pylori positive ones (P < 0.0422). IFN-gamma and IL-10 circulating levels were not affected by H. pylori presence, being not significantly different in the two groups.

Review article: gastrin and colorectal cancer

The polypeptide hormone gastrin was identified nearly a hundred years ago and its role in the regulation of acid secretion is well established. Gastrin also acts as a growth factor and is trophic for the normal gastric oxyntic mucosa. This growth promoting action has led to the extensive investigation of its role in carcinogenesis, in particular colorectal neoplasia. The relationship between gastrin and colorectal adenocarcinoma has been subject to controversy, however the findings from several recent studies have resulted in a clearer understanding of the mechanism of action of gastrin in this is common cancer. The majority of colorectal cancers produce their own gastrin, which may act in an autocrine manner. The tumour cells also express gastrin/CCKB receptors (and/or a combination of isoforms) which mediate the proliferative action. This locally produced gastrin gives rise to a small increase in systemic gastrin levels. Autocrine gastrin may also have a role in tumour development, as expression occurs early in the adenoma-carcinoma sequence. In addition, several studies using animal models have shown that systemic hypergastrinaemia promotes the proliferation of both normal and neoplastic colonic epithelium. Hyperproliferative colonic epithelium in the presence of hypergastrinaemia has been recorded in humans and a well-designed epidemiological study has demonstrated an increased incidence of colorectal cancer. Gastrin is a potential therapeutic target in the treatment of colorectal cancer and several approaches have been assessed. Receptor antagonists and antisecretory agents have been demonstrated to be ineffectual. Novel methods of inhibition, including the use of anti-gastrin antibodies, are currently being evaluated.

Expression of progastrin-derived peptides and somatostatin in fundus and antrum of nonulcer dyspepsia subjects with and without Helicobacter pylori infection

The hypergastrinemia and hyperacidity associated with Helicobacter pylori infection has been explained by either a primary excess of gastrin or a lack of inhibitory influence by somatostatin (SOM). The objective of the present study was to compare the concentrations of fundic and antral SOM- and antral progastrin-derived peptides in nonulcer dyspepsia (NUD) subjects with and without H. pylori infection. Antral and fundic mucosal biopsies were extracted and assayed for SOM and gastrin amide, glycine-extended gastrin (gastrin gly), progastrin, and total gastrin. There was a significant sixfold reduction in antral SOM but no change in fundic SOM content in H. pylori-infected subjects compared to uninfected subjects. Antral gastrin amide concentrations were significantly higher in infected subjects. However, the concentrations of the nonamidated gastrin forms (progastrin and glycine-extended gastrin) were significantly lower in the infected subjects, indicating an increased conversion of the precursor forms of gastrin to amidated gastrin, the type known to stimulate gastric acidity. The present study demonstrates that the elevated gastrin concentrations associated with H. pylori infection may be due to a reduction in the paracrine inhibitory effect of SOM on antral gastrin release. In addition, the posttranslational processing of gastrin to the amidated forms is increased in infected subjects, explaining why the elevation in antral gastrin is confined to the amidated form.

[Effect of Helicobacter pylori eradication on histological lesions of gastric mucosa. An 18-month follow-up study]

OBJECTIVE

To evaluate the effect of Helicobacter pylori eradication on pathologic lesions over the gastric mucosa during an 18-month follow-up period.

PATIENTS AND METHODS

A total of 122 duodenal ulcer patients infected with H. pylori were prospectively studied. Patients were randomized to receive: ranitidine alone, ranitidine plus antibiotics, or bismuth plus antibiotics. An endoscopy was performed at 3, 6, 12 and 18 months. Haematoxylin-eosin, Giemsa, and Warthin-Starry staining methods were used. Histologic lesions were classified according to the following score: normal (0); superficial chronic gastritis (CG): mild (0.5), moderate (1) and severe (1.5); atrophic CG: mild (2), moderate (3) and severe (4); intestinal metaplasia: absence (0), mild (1), moderate (2) and severe (3). The acute inflammatory activity (active CG) was scored from 0 to 3 (absence, mild, moderate, severe) regarding: inflammatory density in the lamina propria, density of plymorphonuclear leukocytes in the lamina propria, density of intra-epithelial polymorphonuclear leukocytes and superficial erosions.

RESULTS

H. pylori eradication was achieved in 31% of patients (0% in the group of ranitidine alone and 48% in patients who received antibiotics). The score corresponding to CG declined progressively after H. pylori eradication, with average values of 2.1 +/- 1.3, 1.98 +/- 1.4, 1.73 +/- 1.6, 1.43 +/- 1.9 and 1.38 +/- 1.9 (p < 0.0001) at 0, 3, 6, 12 and 18 months, respectively. The corresponding score for active CG also improved progressively after eradication: 7.82 +/- 1, 2.51 +/- 0.7, 1.24 +/- 0.6, 0.45 +/- 1.6 and 0.12 +/- 0.5 (p < 0.0001). Nevertheless, no changes were observed regarding atrophia or intestinal metaplasia conditions.

CONCLUSIONS

H. pylori eradication is associated with a histologic improvement of gastric mucosa. It begins early and continues for the 18 months after therapy. The improvement in the overall inflammatory component is slow and progressive. In contrast, improvement of the acute component in gastritis is more marked early, and is observed immediately after eradication. Nevertheless, H. pylori eradication is not followed by an improvement in atrophy or intestinal metaplasia.

Conceivable mechanisms by which Helicobacter pylori provokes duodenal ulcer disease

A conceivable concept for the development of duodenal ulcers in Helicobacter pylori (H. pylori) infected subjects is presented in this chapter. The concept includes an explanation of the fact that only a minority of all H. pylori-infected subjects will develop a duodenal ulcer. Helicobacter pylori infection of the antrum induces a hypersecretion of gastric acid secretion, giving rise to gastric metaplasia in the duodenal bulb. This gastric metaplasia is a prerequisite for H. pylori colonization of the bulb. These events are common to all H. pylori-infected subjects. However, a much higher density of H. pylori bacteria and colonization with virulent organisms has been found in the bulb of duodenal ulcer patients, resulting in a much stronger inflammatory reaction with active duodenitis and an impaired bicarbonate secretion. These characteristics, together with acid hypersecretion, seem to be the important factors in evoking a duodenal ulcer.

Hypotheses on the role of cytokines in peptic ulcer disease

Helicobacter pylori is the cause of chronic type B gastritis and occurs in almost all patients with duodenal ulcers. Infection with H. pylori is characterized by an increased production of several inflammatory cytokines. Increasing evidence suggests a central role of these cytokines in the pathogenesis of H. pylori-associated gastritis and peptic ulcer disease. Cytokines may be crucial in the recruitment and activation of inflammatory cells and in stimulation of gastrin release. In addition to their proinflammatory properties, cytokines may also inhibit the ulcer occurrence by stimulation of prostaglandins and somatostatin release and by direct impairment of acid secretion. The balance of these factors may determine the clinical outcome of H. pylori infection.

H. pylori stimulates gastrin release from canine antral cells in primary culture

Patients chronically infected with Helicobacter pylori are known to have hypergastrinemia. Previous studies have demonstrated the stimulation of gastrin from isolated G cells by monocytes and cytokines. The aim of this study was to determine if H. pylori can directly stimulate gastrin secretion. The secretion of gastrin from canine G cells in 48-h primary cultures was investigated using either live H. pylori bacteria or various bacterial extracts from three well-characterized strains. Whole bacterial sonic extracts and water-extracted surface proteins, but not PBS extracts, from strains 43579 (CagA+/VacA+), 60190 (CagA+/VacA+), and 60190:v1 (CagA+/VacA-) significantly stimulated gastrin release. Controls demonstrated that gastrin stimulation by the sonic extracts was not due to a direct toxic effect on G cells. We conclude that H. pylori produces a soluble factor(s), which can directly stimulate gastrin release in enriched canine G cell cultures. This stimulatory effect may play an important role in the H. pylori-associated hypergastrinemia and subsequent development of peptic ulcer disease.

Gastrin release and gastric acid secretion in the rat infected with either Helicobacter felis or Helicobacter heilmannii

Helicobacter pylori infection in humans has been shown to be associated with changes in gastric physiology, including exaggerated basal and meal-stimulated gastrin levels. This has been suggested to be due to the direct effects of the bacterium through inflammation and its urease enzyme. The gastric bacteria Helicobacter felis and Helicobacter heilmannii colonize the antrum of rats in large numbers and induce no significant inflammatory response. Thus, the direct effect of Helicobacter infection on gastric physiology, independent of gastritis, could be studied. Basal, freely fed and stimulated acid and gastrin levels were recorded from animals infected with H. felis, H. heilmannii or uninfected controls over a 30 week period. No significant difference was found between freely fed gastrin over 7 weeks or fasting gastrin over 24 weeks or basal and stimulated acid over 30 weeks between all three groups. Triple therapy did not alter gastrin or acid output. The antrum of all Helicobacter-infected rats was well colonized; triple therapy cleared H. felis but not H. heilmannii. Very little inflammation was seen in control or Helicobacter-infected animals. In conclusion, Helicobacter-induced effects on gastric physiology are unlikely to be due to direct bacterial effects, but are best explained by other factors (i.e. inflammatory damage).

How does Helicobacter pylori cause mucosal damage? Its effect on acid and gastrin physiology

Helicobacter pylori infection increases gastric acid secretion in patients with duodenal ulcers but diminishes acid output in patients with gastric cancer and their relatives. Investigation of the basic mechanisms may show how H. pylori causes different diseases in different persons. Infection of the gastric antrum increases gastrin release. Certain cytokines released in H. pylori gastritis, such as tumor necrosis factor alpha and specific products of H. pylori, such as ammonia, release gastrin from G cells and might be responsible. The infection also diminishes mucosal expression of somatostatin. Exposure of canine D cells to tumor necrosis factor alpha in vitro reproduces this effect. These changes in gastrin and somatostatin increase acid secretion and lead to duodenal ulceration. But the acid response depends on the state of the gastric corpus mucosa. The net effect of corpus gastritis is to decrease acid secretion. Specific products of H. pylori inhibit parietal cells. Also, interleukin 1 beta, which is overexpressed in H. pylori gastritis, inhibits both parietal cells and histamine release from enterochromaffin-like cells. H. pylori also promotes gastric atrophy, leading to loss of parietal cells. Factors such as a high-salt diet and a lack of dietary antioxidants, which also increase corpus gastritis and atrophy, may protect against duodenal ulcers by decreasing acid output. However, the resulting increase of intragastric pH may predispose to gastric cancer by allowing other bacteria to persist and produce carcinogens in the stomach.

Reduced secretion of epidermal growth factor in duodenal ulcer patients with Helicobacter pylori infection

AIM: To investigate the concentration changes of epidermal growth factor (EGF) in duodenal ulcer patients with Helicobacter pylori (H. pylori) infection.

METHODS: Immunoreactive concentration of somatostatin, gastrin and epidermal growth factor of gastric and saliva juice in healthy volunteers, and chronic gastritis and duodenal ulcer patients with H. pylori infection were measured by radioimmunoassay.

RESULTS: Gastrin concentration of gastric juice in H. pylori-positive chronic gastritis (P > 0.05) and duodenal ulcer patients (P < 0.01) was higher than that of healthy volunteers (P < 0.05), whereas som atostatin concentration of gastric juice in chronic gastritis (P < 0.05) and duodenal ulcer patients (P < 0.01) was lower than that in healthy volunteers. Furthermore, EGF levels of gastric and saliva juice in duodenal ulcer patients with H. pylori infection (n = 10, 272.0 ng/L ± 96.3 ng/L and 8.3 ng/L ± 2.4 ng/L, respectively) were significantly lower than that in healthy volunteers (n = 12, 405.6 ng/L ± 35.6 ng/mL and 22.0 ng/L ± 17.0 ng/L, respectively) and in H. pylori-positive chronic gastritis patients (n = 25, 423.0 ng/L ± 104.0 ng/L and 22.0 ng/L ± 11.1 ng/L, respectively (P < 0.05).

CONCLUSION: A lower secretion of EGF may be a causative factor in the pathogenesis of H. pylori-positive duodenal ulcer.

Basal and stimulated gastrin levels and gastric acid output five months after therapy for Helicobacter pylori eradication in duodenal ulcer patients

The aim of our study was to demonstrate the effect of Helicobacter pylori eradication on basal and stimulated serum gastrin levels and gastric acid output 5 months after therapy of patients with duodenal ulcer. Thirty-two patients (24 men and eight women with a mean age of 45 years) who had had endoscopy and were diagnosed as having duodenal ulcer entered the study. In all patients three biopsy specimens were taken from the duodenal bulb, gastric antrum, body, and fundus. These specimens were then sent for microbiological and histological examination. Triple therapy consisting of bismuth, metronidazole, and tetracycline was administered. Endoscopy was repeated 1 and 5 months after therapy, and biopsy specimens were again taken from the gastric antrum and body. Before treatment, serum samples were taken to measure basal and stimulated (90 min) gastrin levels after ingestion of two beef cubes, and basal and stimulated acid outputs (after pentagastrin) were studied. Measurements of gastrin and gastric acid output were repeated 5 months after therapy. H. pylori was eradicated in 26 patients (81.3%). Basal gastrin levels (mean +/- SD) at diagnosis and after eradication were 44 +/- 12 and 35.8 +/- 2 pg/ml, respectively (p < 0.05). Similarly, stimulated gastrin levels (integrated values) decreased from 5,303 +/- 1,526 pg/ml/min before therapy to 3,779 +/- 1,204 pg/ml/min after eradication (p < 0.001). However, basal (4.9 +/- 4mEq/h) and stimulated (28.5 +/- 10mEq/h) acid output did not vary after eradication (3.9 +/- 4 mEq/h and 26.2 +/- 12 mEq/h, respectively). We conclude that basal and stimulated gastric acid output are not changed by H. pylori eradication in duodenal ulcer patients 5 months after therapy, in spite of its association with a significant decrease in basal and stimulated gastrin levels.

Helicobacter pylori and disturbance of gastric function associated with duodenal ulcer disease and gastric cancer

Helicobacter pylori is now recognized as the major acquired factor in the pathogenesis of duodenal ulcer disease (DU). There is also an association between H. pylori infection and the subsequent development of gastric cancer. The mechanisms by which such infection predisposes the host to these diseases are incompletely understood, but disorders induced by the bacterium in gastric function play a pivotal role. In most patients, H. pylori infection stimulates acid secretion, leading to a predisposition to DU development. However, in some patients, the infection is associated with a significant decrease in acid secretion, a predisposition to gastric cancer. These divergent effects of H. pylori on gastric acid secretion explain the early conflicting reports on changes in acid secretion associated with the infection. The reason why H. pylori infection produces divergent effects on gastric acid secretion is unclear, but may be related to differences in bacterial strains or genetic, dietary or other environmental factors.

Helicobacter pylori and hormones

Helicobacter pylori affects gastric acid secretion via several mechanisms. One of these is by changing gastric regulatory physiology. The infection elevates plasma gastrin levels and decreases gastric mucosal expression of the inhibitory peptide somatostatin. These changes may be due to products of H. pylori itself or inflammatory cytokines released in H. pylori infection: acid secretion is inhibited less by a low intra-gastric pH, infusions of cholecystokinin and gastric distention in infected persons. Eradication of H. pylori rapidly decreases basal acid secretion and gastrin-releasing, peptide-stimulated acid secretion. There are now reports that maximally-stimulated acid secretion, a measure of the parietal cell mass, falls significantly six and 12 months after eradication of H. pylori from duodenal ulcer patients. This might be due to withdrawal of the trophic effect of gastrin. However H. pylori can also decrease gastric acid secretion, both through the mechanisms described in Dr. Cave's paper and by causing gastric mucosal atrophy with loss of parietal cells. The net effect on acid presumably depends on which mechanism predominates. The processes involved may be crucial determinants of clinical outcome. For example, infection with little atrophy and high acid secretion is associated with duodenal ulcers, while infection with atrophy and low acid secretion increases the risk of gastric cancer of the intestinal-type.

Eradication of Helicobacter pylori infection in patients with non-ulcer dyspepsia. Effects on basal and bombesin-stimulated serum gastrin and gastric acid secretion

BACKGROUND

This study evaluates the effect of eradicating Helicobacter pylori on basal and bombesin-stimulated gastric acid secretion and serum gastrin in non-ulcer dyspepsia.

METHODS

Before and 1 month after an attempt to eradicate H. pylori basal and bombesin-stimulated gastric acid outputs were measured in 23 patients. H. pylori was eradicated in 15 patients (group A) but not in the other 8 (group B). Incremental gastric acid output was calculated by subtracting basal from bombesin-stimulated values.

RESULTS

Basal acid output increased significantly (p = 0.01) after therapy in group A (delta 1.6 +/- 0.6 mmol/h) but not in group B (delta 0.2 +/- 0.5 mmol/h). Incremental gastric acid output decreased distinctly (delta-3.9 +/- 1.4 mmol/h) after therapy in group A (p = 0.02) but not in group B (delta-2.2 +/- 1.7 mmol/h). Basal serum gastrin decreased significantly (p < 0.005) after therapy in group A (delta-9 +/- 4 pM) but not in group B (delta-1 +/- 2 pM). Integrated serum gastrin responses to bombesin decreased markedly (p < 0.001) after therapy in group A (delta-5.0 +/- 1.6 nM*60 min) but slightly in group B (delta-0.9 +/- 1.3 nM*60 min) (p < 0.05).

CONCLUSIONS

In patients with non-ulcer dyspepsia basal serum gastrin concentrations decrease but basal gastric acid outputs increase after eradication of H. pylori. Bombesin-induced increments in gastric acid output, however, decrease in parallel with gastrin release.

The somatostatin-gastrin link of Helicobacter pylori infection

Helicobacter pylori is the new-found cause of duodenal ulcers (DU), but acid secretion remains necessary and is elevated in DU patients. My group and others have asked whether H. pylori itself alters gastric physiology. This infection has been found to decrease local expression of the inhibitory peptide somatostatin, and to increase release of the acid-stimulating hormone gastrin. H. pylori infection can alter acid secretion in both directions. Acid disappears temporarily on first infection, and may dwindle later if H. pylori causes gastric atrophy. DU patients have approximately twice the normal parietal cell mass, which increases their maximal secretory capacity, but it is not clear whether or not this is due to H. pylori. However, the infection certainly does change physiological control of acid secretion, as expected from the endocrine changes. Acid secretion is elevated during fasting, during stimulation with an acidic meal and during infusions of gastrin-releasing peptide. The balance between these opposing effects of H. pylori on acid may be crucial in determining the clinical outcome of H. pylori infection. High-acid secretion leads to DUs whilst low acid secretion is found in patients with gastric ulcers and gastric cancer. Inflammatory cytokines released in H. pylori gastritis may cause some of these changes in gastric physiology.

Pathogenic mechanisms

Research is asking how H. pylori causes diseases, and also why the same bacteria produces different conditions in different persons. The process involves bacterial factors and the host's response. Some bacterial factors such as urease are produced by all strains of H. pylori. This enzyme may damage the gastric epithelium by practically releasing ammonia. Other bacterial factors such as vacuolating toxin are only produced by some strains, and these strains are more likely to cause ulcers or cancer. The host's response has been studied by physiologists, immunologists, and histologists, but the separation of systems is artificial. For example, physiologists find that H. pylori stops gastric D-cells from expressing somatostatin normally, which impairs reflex inhibition of acid secretion, but the D-cell malfunction is probably due to inflammatory factors. In H. pylori gastritis, the gastric epithelial cells behave like immunocytes and express class II molecules and cytokines such as interleukin-8. The patient's histological response to H. pylori is quite closely related to the disease outcome. Patients who respond by developing gastric atrophy are more likely to get gastric ulcers or stomach cancer, but patients whose gastric corpus remains healthy tend to secrete more acid and develop duodenal ulcers, particularly if they have gastric metaplasia in their duodenum. Studies of disease mechanisms provide a valuable insight into the development of these common diseases, and may enable us to identify at-risk groups who particularly merit eradication therapy.

A substantial proportion of non-ulcer dyspepsia patients have the same abnormality of acid secretion as duodenal ulcer patients

Acid secretion in response to gastrin releasing peptide (GRP) is increased six-fold in Helicobacter pylori positive duodenal ulcer (DU) patients and threefold in H pylori positive healthy volunteers, and this fully resolves after eradication of the infection. This study was undertaken to determine whether a proportion of H pylori positive patients with non-ulcer dyspepsia (NUD) have an acid secretion disturbance similar to DU patients. Basal and GRP stimulated gastrin concentrations and acid output were examined in 25 H pylori positive NUD patients and the results compared with those of 25 H pylori positive healthy volunteers, 25 H pylori negative healthy volunteers, and 25 H pylori positive DU patients. Compared with the H pylori negative healthy volunteers, GRP stimulated gastrin was increased approximately three fold in each of the three infected groups. GRP stimulated acid secretion (median, range) was higher in the H pylori positive NUD patients (29.6 mmol/h (5.2-46.5)) (p < 0.005) than in the H pylori positive healthy volunteers (19.0 (1.0-38.3)) (p < 0.001) or H pylori negative healthy volunteers (6.3 (2.8-20.9)) (p < 0.0001). The H pylori positive NUD patients, however, had lower acid output than the DU patients (39.1 (17.9-64)) (p < 0.005). These findings are consistent with approximately 50% of the NUD patients having a similar disturbance of GRP stimulated acid secretion to DU patients.

Helicobacter pylori infection: physiopathologic implication of N alpha-methyl histamine

BACKGROUND/AIMS

In the gastric mucosa of Helicobacter pylori-infected subjects, we previously detected N alpha-methyl histamine (N alpha-MeHA), a minor catabolite of histamine and a potent agonist of histamine H3 receptors. The origin of N alpha-MeHA and its effects on gastric histamine and somatostatin in infected subjects were investigated.

METHODS

Ten noninfected patients and 13 patients with intense colonization were compared. N alpha-MeHA content and its synthetic enzyme activity, N alpha-histamine methyltransferase, binding of [3H]N alpha-MeHA, histamine and somatostatin contents, and histidine decarboxylase activity were assayed in antral and fundic biopsy specimens and in cultured H. pylori strains.

RESULTS

Gastric histamine and somatostatin contents as well as histidine decarboxylase activity were decreased in infected patients and were restored to normal after antimicrobial treatment. Both N alpha-MeHA and N alpha-histamine methyltransferase activity were present in the mucosa of infected patients and in cultured strains and were very low in noninfected patients or after eradication of H. pylori. [3H]N alpha-MeHA bound to gastric mucosa but not to cultured strains. The [3H]N alpha-MeHA specific binding sites were characterized as H3 receptors. The amount of bound [3H]N alpha-MeHA seemed correlated positively with somatostatin content and histidine decarboxylase activity and negatively with N alpha-MeHA content and N alpha-histamine methyltransferase activity.

CONCLUSIONS

H. pylori is the main source of gastric N alpha-MeHA that may lower histidine decarboxylase activity and somatostatin content through H3 receptors.

Basal serum gastrin concentrations before and after eradication of Helicobacter pylori infection measured by sequence specific radioimmunoassays

BACKGROUND

Helicobacter pylori infection of the antral mucosa is responsible for an increase in basal and stimulated serum gastrin. In the present study we have investigated whether gastritis induced by H. pylori is responsible for abnormalities in the processing of gastrin in dyspeptic patients.

METHODS

Basal serum gastrin was measured by radioimmunoassay before, 5 weeks, and 1 year after anti-H. pylori therapy in 73 H. pylori positive functional dyspeptic patients. Three region-specific antisera were used, specific for the biologically active carboxy-terminal part, the biologically inactive amino-terminal part of gastrin 1-17, and for the non-sulphated tyrosyl residue in gastrin 1-17.

RESULTS

Basal serum gastrin levels were markedly (P < 0.01) decreased 5 weeks and 1 year after successful eradication of H. pylori (n = 39) but not in the patients in whom treatment failed (n = 34). A decline of gastrin was observed for each of the three radioimmunoassays.

CONCLUSION

The decrease of serum gastrin levels in all three radioimmunoassays after a successful eradication of H. pylori does not point to major changes in the processing of gastrin. These results suggest that G-cells in the antral mucosa are not functionally affected by the inflammation.

Treatment of peptic ulcers from now to the millennium

The present strategies for the management of peptic ulceration are well tolerated and clinically effective. Histamine H2-receptor antagonists can be used for mild to moderate disease, and proton pump inhibitors are of particular benefit for patients with severe peptic ulceration and the Zollinger-Ellison syndrome. However, none of these treatments provides protection against recurrent ulceration, except when taken as long-term continuous treatment. Long-term exposure to pharmacological agents raises problems of safety, particularly relating to a lack of intragastric acidity. In addition, the accelerated development of atrophic gastritis in patients receiving omeprazole requires investigation and assessment. It is unlikely that there will be any major development in the area of control of gastric acid secretion, except perhaps the introduction of specific immunization against gastrin. However, the clinical benefit of this strategy awaits assessment. The main area for development must be the introduction of convenient and effective regimens for the eradication of Helicobacter pylori infection. Existing regimens are either simpler and relatively ineffective, or too complicated for widespread application. Bearing in mind the long gestation period of any new drug, it seems likely that the only innovative drug that will be introduced for the management of peptic ulceration before the millennium will be ranitidine bismuth citrate, an antisecretory anti-H. pylori drug that will usually be used in combination with an antibiotic.

Gastrin and somatostatin in Helicobacter pylori infected antral mucosa

Helicobacter pylori infection is associated with increased meal stimulated gastrin secretion, but the reason for this is unknown. Sequence specific radioimmunoassays were used to measure the concentration of alpha-amidated gastrin, the total progastrin product, and somatostatin in biopsy specimens of human antral mucosa. The antral concentrations of alpha-amidated gastrin and of total progastrin products were significantly higher in H pylori infected patients than in those not infected by this organism. In contrast, the antral somatostatin concentration was significantly decreased in infected patients. Progastrin processing, determined by gel chromatography, seemed unaffected by H pylori infection. The results suggest that the finding of increased gastrin secretion from the antral G cells in H pylori infected patients may be a result of reduced inhibition of G-cell secretion by somatostatin.

Gut hormones in gastric function

This chapter has focused on many of the gut hormones that regulate gastric function. Gastrin remains the principal, and only, gastric hormone controlling gastric acid secretion during the cephalic, gastric and intestinal phases of secretion. Several other hormones, including cholecystokinin, peptide YY and secretin, released from intestinal endocrine cells in response to food substrates, have significant inhibitory effects on gastric acid secretion. Many of these hormones, including enteroglucagon and glucagon-like peptide, may act through paracrine release of somatostatin, which in turn acts as the final mediator of acid inhibition. In addition, several peptides contained in nerves, including gastrin releasing peptide and vasoactive intestinal peptide, have been shown to regulate gastric acid secretion and motor function. With the creation of specific monoclonal antibodies for use in in vivo immunoneutralization studies, and the development of selective chemical antagonists for use in receptor blockade experiments, the specific contributions of the different gut hormones in the regulation of gastric function, can be assessed.

Helicobacter pylori infection and exaggerated gastrin release. Effects of inflammation and progastrin processing

Helicobacter pylori infection is associated with exaggerated gastrin release. We investigated whether this abnormality was due to the bacteria or the immune response. Fasting and meal-stimulated 'total' and amidated gastrin were measured in 10 H. pylori-infected volunteers before eradication therapy, after 2 and 14 days of therapy, and 4 weeks after completion of therapy. The exaggerated meal-stimulated gastrin concentration remained unchanged after 2 days of therapy, although the polymorphonuclear cell infiltrate and H. pylori bacteria were no longer evident. The expected fall in gastrin concentration after 14 days of therapy was associated with a reduction in the density of mucosal mononuclear cells, suggesting exaggerated gastrin release was related to chronic inflammation or to H. pylori or its products. The effect of H. pylori on normal progastrin processing was also assessed; 2 control groups were included: 10 H. pylori-uninfected volunteers and 13 patients with H. pylori peptic ulcers. There was a significant difference in the proportion of circulating gastrins that were biologically active amidated gastrins between ulcer patients and uninfected controls (56.7 +/- 4% versus 33.8 +/- 4%, p < 0.001). The proportion of amidated to total gastrins did not increase after successful eradication.

Eradicating Helicobacter pylori infection lowers gastrin mediated acid secretion by two thirds in patients with duodenal ulcer

Helicobacter pylori (H pylori) raises serum gastrin but it is unclear whether this stimulates increased acid secretion. Gastrin mediated acid secretion and plasma gastrin after the intravenous infusion of gastrin releasing peptide was studied in nine H pylori negative and nine H pylori positive healthy volunteers, and in 11 duodenal ulcer patients. Nine of the last group were re-examined one month after eradication of H pylori. The median acid output (mmol/h) to gastrin releasing peptide (40 pmol/kg/h) in the H pylori positive healthy volunteers was 15.1 (range 3.3-38.3), which was three times that of the H pylori negative healthy volunteers (median = 5.5, range 1.0-9.0) (p < 0.02). The median acid output in the duodenal ulcer patients with H pylori was 37 (range 8.5-57), which was > six times that of the H pylori negative healthy volunteers. Eradication of H pylori in the duodenal ulcer patients lowered their acid secretion by a median of 66% (range 30%-80%) (p < 0.01) and to values equivalent to the H pylori positive healthy volunteers. The pepsin output in response to gastrin releasing peptide followed the same pattern as the acid output. The median plasma gastrin concentrations during gastrin releasing peptide were similar in the H pylori positive duodenal ulcer patients (150 ng/l, range 95-400) and H pylori positive healthy volunteers (129 ng/l, range 23-420) and both were appreciably higher than H pylori negative healthy volunteers (60 ng/l, range 28-135) (p < 0.005 for each). Eradication of H pylori lowered the plasma gastrin in the duodenal ulcer patients to values equivalent to the H pylori negative healthy volunteers. These findings show a threefold increase in acid secretion in H pylori positive healthy volunteers that is explained by H pylori induced hypergastrinaemia and a sixfold increase in acid secretion in the duodenal ulcer patients that is explained by the combination of H pylori induced hypergastrinaemia and an exaggerated acid response to stimulation by gastrin. Eradicating H pylori lowers gastrin mediated acid secretion by 66% in duodenal ulcer patients as a result of the resolution of the hypergastrinaemia. Increased gastrin mediated acid secretion seems to be the key factor in the pathophysiology of duodenal ulceration and explains the role of H pylori infection in the disorder.

Acid secretion and sensitivity to gastrin in patients with duodenal ulcer: effect of eradication of Helicobacter pylori

The effect of ulcer healing with eradication of Helicobacter pylori (H pylori) on gastric function was investigated in nine patients with duodenal ulcer disease. One month after eradication there were significant reductions in both basal plasma gastrin concentration, from a median (range) of 19 (1-22) to 6 (2-15) pmol/l (p < 0.05), and of basal acid secretion from 8.3 (2.4-24) to 2.6 (1.4-8.1) mM H+/h, (p < 0.01). The peak acid secretion rate was unchanged from 37 (16-59) to 37 (21-59) mM H+/h. After treatment there was no change in the parietal cell sensitivity to stepped infusions of gastrin heptadecapeptide: the median concentration of gastrin required for 50% of maximal acid secretion (EC50) was 41 (14.8-126) before and 33 (23-125) pmol/l after eradication of H pylori. The metabolic clearance rate of gastrin was also unaffected by the eradication of H pylori. Thus eradication of H pylori infection from patients with active duodenal ulcers is accompanied by falls in both basal gastrin release and basal acid secretion without a change in the parietal cell sensitivity to gastrin. Cyclical changes in H pylori infection may cause the variations in basal acid secretion that are seen in duodenal ulcer disease.

Helicobacter pylori related hypergastrinaemia is the result of a selective increase in gastrin 17

Helicobacter pylori infection increases the serum concentration of gastrin, and this may be one of the mechanisms by which it predisposes to duodenal ulceration. Different forms of circulating gastrin were studied both basally and postprandially in 13 duodenal ulcer patients before and one month after eradication of H pylori. Three antisera that are specific for particular regions of the gastrin molecules were used. Gel chromatography indicated that > 90% of the circulating gastrin consisted of gastrin (G) 17 and G34 both before and after eradicating the infection. The basal median total immunoreactive gastrin concentration fell from 26 pmol/l (range 11-43) to 19 pmol/l (8-39) (p < 0.05), entirely because of a fall in G17 from 6 pmol/l (< 2.4-25) to < 2.4 pmol/l (< 2.4-23) (p < 0.001). The median (range) basal G34 values were similar before (15 pmol (2-36)) and after (10 pmol (2-30)) eradication. The median total immunoreactive gastrin concentration determined 20 minutes postprandially fell from 59 pmol/l (38-114) to 33 pmol/l (19-88) (p < 0.005), and again this was entirely the result of a fall in G17 from 43 pmol/l (9-95) to 17 pmol/l (< 2.4-52) (p < 0.001). The median postprandial G34 values were similar before (13 pmol/l, range 6-42) and after (15 pmol/l, range 6-30) eradication. Eating stimulated a noticeable rise in G17 but little change in G34, both in the presence and absence of H pylori. The finding that H pylori infection selectively increases G17 explains why the infection causes mainly postprandial hypergastrinaemia. G17 is increased selectively because H pylori predominantly affects the antral mucosa which is the main source of G17 whereas G34 is mainly duodenal in origin. This study also indicates that the increased concentration of gastrin in H pylori infection is the result of an increase in one of the main biologically active forms of the hormone.

Influence of Helicobacter pylori, sex, and age on serum gastrin and pepsinogen concentrations in subjects without symptoms and patients with duodenal ulcers

The relation between Helicobacter pylori (H pylori) infection and fasting gastrin and pepsinogen-I and -II concentrations was evaluated in 278 volunteers without symptoms and the results were compared with the values obtained in 35 patients with duodenal ulcers. H pylori infection was determined with the 13C-urea breath test in subjects without symptoms and with endoscopy, biopsy (histology and culture), and quick urease test (CLO-test) in patients with duodenal ulcers. Gastrin and pepsinogen-I and -II concentrations were assayed with specific radioimmunoassay systems. The results clearly indicate that fasting gastrin and pepsinogen-I and -II concentrations were significantly higher in H pylori positive compared with H pylori negative subjects. Neither age nor sex affected basal gastrin and pepsinogen concentrations in H pylori negative subjects. Fasting gastrin, pepsinogen-I and -II concentrations in serum samples were similar in H pylori positive persons with no symptoms and those with duodenal ulcers suggesting that similar mechanisms are involved in increasing plasma concentrations of these variables in both populations. Hypergastrinaemia and hyperpepsinogenaemia are therefore probably secondary to active H pylori infection.

Antral Helicobacter pylori infection, hypergastrinemia and peptic ulcers: effect of eradicating the organism

BACKGROUND

A randomized prospective study on the response of fasting serum gastrin concentrations in peptic ulcer patients was performed in order to test the hypothesis that H. pylori infection in the gastric antrum increases gastrin release, and to examine whether the high fasting serum gastrin concentrations respond to treatment that eradicates H. pylori.

METHODS

One hundred and twenty-seven patients with gastric or duodenal ulcer were included in this study. Patients were divided into three groups on the basis of antral H. pylori status and therapeutic modalities. The first group, 58 patients infected by H. pylori, was treated with metronidazole and tripotassium dicitrato bismuthate combined with ranitidine and mylanta. The second group, 40 patients also infected by H. Pylori, was treated with ranitidine and mylanta. The third group, 29 patients, free of H. pylori infection, was designed to evaluate the influence of H2-receptor antagonist on the change of gastrin. When ulcers were completely healed, changes of gastrin concentrations and H. pylori status were re-examined.

RESULTS

H. pylori was eradicated in all patients who have received antibacterial therapy in 4 weeks, and serum gastrin concentrations were significantly decreased after eradication of the organism both in gastric and in duodenal ulcer diseases. (Gastric ulcer: 129.3 +/- 47.0 pg/ml before and 63.7 +/- 21.6 pg/ml after treatment. Duodenal ulcer: 108.3 +/- 35.0 pg/ml and 66.5 +/- 21.9 pg/ml, respectively. Total: 112.7 +/- 38.2 pg/ml vs 66.0 +/- 21.6 pg/ml) (p < 0.01). In contrast, H. pylori-positive patients who have not received antibacterial therapy were still infected at the completion of the study, and serum gastrin concentrations increased even though the difference was not significant. (Gastric ulcer: 118.4 +/- 51.2 pg/ml vs 124.0 +/- 56.5 pg/ml. Duodenal ulcer: 85.4 +/- 35.1 pg/ml vs 104.6 +/- 43.5. Total: 99.5 +/- 45.3 vs 112.9 +/- 48.7 pg/ml.) (p > 0.05). None of the patients who were initially H. pylori-negative has been reinfected during the period of the study, and their serum gastrin concentrations were not changed. (Gastric ulcer: 69.8 +/- 38.0 pg/ml. Total: 63.2 +/- 31.1 pg/ml. Duodenal ulcer: 55.1 +/- 17.6 pg/ml vs 55.8 +/- 13.8 pg/ml. Total: 63.2 +/- 31.1 pg/ml vs 63.4 +/- 30.0 pg/ml). Four- to six-week therapy of H2-receptor antagonist and antacid had no influence on serum gastrin concentrations.

CONCLUSIONS

On the basis of the above results, we confirmed that the chronic infection of H. pylori of gastric antrum in peptic ulcer patients causes increased release of serum gastrin, and eradication of the organism results in a significant fall in serum gastrin concentrations.