Non-invasive method for the assessment of gastric acid secretion.

Methods for the measure of gastric acid secretion include invasive and non-invasive tests. The gold-standard to measure the acid output is the collection of gastric after in basal condition (Basal Acid Output, B.A.O.) and after an i.m. injection of pentagastrin (Maximal Acid Output, M.A.O.). However, direct measurement of gastric acid production is out of order in clinical practice, but many GI symptoms are claimed to be related with acid disorders and empirically cured. Hypochlorhydria is associated with precancerous conditions such as chronic atrophic gastritis (CAG). Acid measurement with non-invasive methods (pepsinogens) is supported by international guidelines.

Mutation of the gastric hydrogen-potassium ATPase alpha subunit causes iron-deficiency anemia in mice.

Iron is an essential component of heme and hemoglobin, and therefore restriction of iron availability directly limits erythropoiesis. In the present study, we report a defect in iron absorption that results in iron-deficiency anemia, as revealed by an N-ethyl-N-nitrosourea-induced mouse phenotype called sublytic. Homozygous sublytic mice develop hypochromic microcytic anemia with reduced osmotic fragility of RBCs. The sublytic phenotype stems from impaired gastrointestinal iron absorption caused by a point mutation of the gastric hydrogen-potassium ATPase α subunit encoded by Atp4a, which results in achlorhydria. The anemia of sublytic homozygotes can be corrected by feeding with a high-iron diet or by parenteral injection of iron dextran; rescue can also be achieved by providing acidified drinking water to sublytic homozygotes. These findings establish the necessity of the gastric proton pump for iron absorption and effective erythropoiesis.

[Chronic use of proton pump inhibitors: is the risk of osteoporosis and fractures real?]. / ¿Es real el riesgo de osteoporosis y riesgo de fracturas con el uso crónico de inhibidores de la bomba de protones?

Proton pump inhibitors (PPI) are one of the most widely used groups of drugs and their potential toxicity is periodically reviewed, emphasizing aspects originally considered secondary. The present review analyzes the physiological and pharmacological bases and the scarce clinical evidence for a potential association between the continued administration of PPI and the development of osteoporosis and bone fractures. Both disorders are clearly related to calcium homeostasis and are highly important in elderly patients due to their poor general prognosis and disabling consequences.

A role for the Ca2+ channel TRPML1 in gastric acid secretion, based on analysis of knockout mice.

BACKGROUND & AIMS: Mutations in TRPML1, a lysosomal Ca(2+)-permeable TRP channel, lead to mucolipidosis type IV, a neurodegenerative lysosomal storage disease. An unusual feature of mucolipidosis type IV is constitutive achlorhydria. We produced Trpml1(-/-) (null) mice to investigate the requirement for this protein in gastric acid secretion. METHODS: Trpml1-null mice were generated by gene targeting. The expression of Trpml1 and its role in acid secretion by gastric parietal cells were analyzed using biochemical, histologic, and ultrastructural approaches. RESULTS: Trpml1 is expressed by parietal cells and localizes predominantly to the lysosomes; it was dynamically palmitoylated and dephosphorylated in vivo following histamine stimulation of acid secretion. Trpml1-null mice had significant impairments in basal and histamine-stimulated gastric acid secretion and markedly reduced levels of the gastric proton pump. Histologic and ultrastructural analyses revealed that Trpml1(-/-) parietal cells were enlarged, had multivesicular and multi-lamellated lysosomes, and maintained an abnormal intracellular canalicular membrane. The intralysosomal Ca(2+) content and receptor-mediated Ca(2+) signaling were, however, unaffected in Trpml1(-/-) gastric glands, indicating that Trpml1 does not function in the regulation of lysosomal Ca(2+). CONCLUSIONS: Loss of Trpml1 causes reduced levels and mislocalization of the gastric proton pump and alters the secretory canaliculi, causing hypochlorhydria and hypergastrinemia. The lysosomal enlargement and defective intracellular canaliculi formation observed in Trpml1(-/-) parietal cells indicate that Trpml1 functions in the formation and trafficking of the tubulovesicles. This study provides direct evidence for the regulation of gastric acid secretion by a TRP channel; TRPML1 is an important protein in parietal cell apical membrane trafficking.

Intracellular calcium release and protein kinase C activation stimulate sonic hedgehog gene expression during gastric acid secretion.

BACKGROUND & AIMS: Hypochlorhydria during Helicobacter pylori infection inhibits gastric Sonic Hedgehog (Shh) expression. We investigated whether acid-secretory mechanisms regulate Shh gene expression through intracellular calcium (Ca2(+)(i))-dependent protein kinase C (PKC) or cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) activation. METHODS: We blocked Hedgehog signaling by transgenically overexpressing a secreted form of the Hedgehog interacting protein-1, a natural inhibitor of hedgehog ligands, which induced hypochlorhydria. Gadolinium, ethylene glycol-bis(ß-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) + 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), PKC-overexpressing adenoviruses, and PKC inhibitors were used to modulate Ca(2+)(i)-release, PKC activity, and Shh gene expression in primary gastric cell, organ, and AGS cell line cultures. PKA hyperactivity was induced in the H(+)/K(+)-ß-cholera-toxin-overexpressing mice. RESULTS: Mice that expressed secreted hedgehog-interacting protein-1 had lower levels of gastric acid (hypochlorhydria), reduced production of somatostatin, and increased gastrin gene expression. Hypochlorhydria in these mice repressed Shh gene expression, similar to the levels obtained with omeprazole treatment of wild-type mice. However, Shh expression also was repressed in the hyperchlorhydric H(+)/K(+)-ß-cholera-toxin model with increased cAMP, suggesting that the regulation of Shh was not solely acid-dependent, but pertained to specific acid-stimulatory signaling pathways. Based on previous reports that Ca(2+)(i) release also stimulates acid secretion in parietal cells, we showed that gadolinium-, thapsigargin-, and carbachol-mediated release of Ca(2+)(i) induced Shh expression. Ca(2+)-chelation with BAPTA + EGTA reduced Shh expression. Overexpression of PKC-α, -ß, and -δ (but not PKC-ϵ) induced an Shh gene expression. In addition, phorbol esters induced a Shh-regulated reporter gene. CONCLUSIONS: Secretagogues that stimulate gastric acid secretion induce Shh gene expression through increased Ca(2+)(i)-release and PKC activation. Shh might be the ligand transducing changes in gastric acidity to the regulation of G-cell secretion of gastrin.

Loss of parietal cell expression of Sonic hedgehog induces hypergastrinemia and hyperproliferation of surface mucous cells.

BACKGROUND & AIMS: Sonic Hedgehog (Shh) is expressed in the adult stomach, but its role as a gastric morphogen is unclear. We sought to identify mechanisms by which Shh might regulate gastric epithelial cell function and differentiation. METHODS: Mice with a parietal cell-specific deletion of Shh (HKCre/Shh(KO)) were created. Gastric morphology and function were studied in control and HKCre/Shh(KO) mice between 1 and 8 months of age. RESULTS: In contrast to control mice, HKCre/Shh(KO) mice developed gastric hypochlorhydria, hypergastrinemia, and a phenotype that resembled foveolar hyperplasia. The fundic mucosa of HKCre/Shh(KO) mice had an expanded surface pit cell lineage that was documented by increased incorporation of bromodeoxyuridine and was attributed to the hypergastrinemia. Compared with controls, numbers of total mucous neck and zymogen cells were significantly decreased in stomachs of HKCre/Shh(KO) mice. In addition, zymogen and neck cell markers were coexpressed in the same cell populations, indicating disrupted differentiation of the zymogen cell lineage from the mucous neck cells in the stomachs of HKCre/Shh(KO) mice. Laser capture microdissection of the surface epithelium, followed by quantitative reverse-transcription polymerase chain reaction, revealed a significant increase in expression of Indian Hedgehog, glioma-associated oncogene homolog 1, Wnt, and cyclin D1. Laser capture microdissection analysis also showed a significant increase in Snail with a concomitant decrease in E-cadherin. CONCLUSIONS: In the stomachs of adult mice, loss of Shh from parietal cells results in hypochlorhydria and hypergastrinemia. Hypergastrinemia might subsequently induce increased Hedgehog and Wnt signaling in the surface pit epithelium, resulting in hyperproliferation.

The ghrelin system in acinar cells: localization, expression, and regulation in the exocrine pancreas.

OBJECTIVES: Ghrelin and its receptor are expressed abundantly in the stomach and pituitary. Recently, a ghrelin system, consisting of both ligand and receptor, has also been found to exist in the endocrine cells of pancreatic islets. This ghrelin system may play a role in regulating insulin secretion and glucose homeostasis. The aim of the present study was to investigate whether a functional ghrelin system also exists in the exocrine pancreas. METHODS: Precise localization and expression of ghrelin and its receptor in rat pancreatic acinar cells were examined by immunocytochemistry and Western blot, whereas messenger RNA levels were examined by semiquantitative reverse transcription-polymerase chain reaction. The roles of physiological and pathophysiological conditions, such as gastric acid inhibition, starvation, and acute pancreatitis, in regulation of ghrelin and its receptor were also examined. RESULTS: Both ghrelin and its receptor were detected, at both protein and messenger RNA levels, in the acinar cells of the exocrine pancreas. Ghrelin receptor expression was up-regulated by gastric acid inhibition and down-regulated by acute pancreatitis, whereas levels remained unchanged after food deprivation. In contrast, ghrelin expression did not exhibit significant changes in any condition. CONCLUSIONS: Our data indicate that a ghrelin system exists in the acinar cells of the exocrine pancreas. This system is subject to regulation by physiological and pathophysiological stimuli and may thus regulate exocrine functions by paracrine and/or autocrine mechanisms.

Lessons from the gastrin knockout mice.

The gastrointestinal hormone, gastrin, was discovered a century ago as the second hormone in history. Subsequently, gastrin peptides have been identified and the genes encoding the hormone as well as its receptor have been cloned in several mammalian species including the mouse. This has facilitated the development of gastrin and gastrin receptor deficient mice as models for genetic dissection of the role of gastrins in maintaining gastric homeostasis and control of acid secretion. The gastrin knockout mice are achlorhydric due to inactivation of the ECL and parietal cells. Moreover, this achlorhydria is associated with the development of intestinal metaplasia and bacterial overgrowth, which ultimately lead to development of gastric tumors. Outside the stomach, gastrin deficiency alters pancreatic islet physiology and is associated with a moderate fasting hypoglycemia in the fasting state. But lack of gastrin does not impair islet regeneration. The association between progastrin, progastrin-derived processing intermediates and colorectal carcinogenesis has also been examined through genetic or chemical cancer induction in several mouse models, although the clinical relevance of these studies still remains to be proven. While others have focused on models of increased gastrin production, the present review will describe the lessons learned from the gastrin deficient mice. These mice help understand how dysregulation of gastrin secretion may be implicated in human disease.

Expanded parietal cell pool in transgenic mice unable to synthesize histamine.

BACKGROUND: The histidine decarboxylase enzyme (HDC) is responsible for the synthesis of histamine in mammals. Histidine decarboxylase-deficient (HDC-/-) mice have recently been developed by targeted mutation of the HDC gene. METHODS: The impact of prolonged histamine deficiency was studied on gastric morphology (by immunohistochemistry and morphometry), gastric acid secretion (by a wash-through method for basal gastric acid secretion and by pylorus ligation for stimulated gastric acid secretion) and gastrin levels (by radioimmunoassay) in homozygous HDC-/- mice kept on a low-histamine diet. RESULTS: A double maximal gastric acid secretory response was found in knockouts after exogenous histamine administration. In contrast, the gastric acid secretion was significantly reduced after gastrinergic and cholinergic stimulation in the absence of histamine. The oxynthic gland area of HDC-/- mice was thickened with an increased parietal cell count compared to wild types. Substantially elevated serum and antral tissue gastrin levels of HDC-/- mice could be possible indications of both an expanded parietal cell mass and/or an increased histamine-induced maximal gastric acid secretory capacity of this genotype. CONCLUSIONS: These data suggest that not enough compensatory mechanisms develop in HDC-/- mice during a prolonged low-histamine diet to maintain/restore normal gastric acid secretion. An expanded parietal cell pool was also demonstrated in HDC-/- mice kept on a low-histamine diet, probably caused by a trophic effect of sustained hypergastrinaemia. The HDC-/- strain is a suitable model for studying the effects of achlorhydria and consequent hypergastrinaemia as an approach to human conditions such as atrophic gastritis or long-term antisecretory therapies.

Occurrence and significance of gastric colonization during acid-inhibitory therapy.

There are now a wide variety of drugs available that are able profoundly to reduce the production of gastric acid. These drugs are currently widely prescribed for the treatment of peptic ulceration and gastro-oesophageal reflux disease. One of the main functions of gastric acid is to kill ingested bacteria. Colonization of the gastric lumen occurs in patients on anti-secretory medication, the degree of bacterial overgrowth depending upon the degree of elevation of the pH. There have been concerns that these bacteria may produce carcinogenic nitrosamines and increase the risk of gastric cancer, but there is at present no definitive evidence in support of this. A profound suppression of gastric acid may also facilitate the colonization of the upper small intestine, leading to deconjugation of the bile salts and malabsorption. There is some evidence that profound gastric acid suppression may decrease the number of ingested pathogens required to produce enteric disease. This chapter discusses these potential bacterial complications of therapeutic acid suppression and the evidence for them.

Gastric emptying and dyspeptic symptoms in patients with nonautoimmune fundic atrophic gastritis.

Our aim was to evaluate the relationship between gastric emptying and demographic, clinical, histological, and secretory features in patients with nonautoimmune fundic atrophic gastritis. Only 31% of 45 patients with fundic atrophic gastritis presented with achlorhydria. Scintigraphic gastric emptying of solids was delayed compared to healthy controls. Patients with achlorhydria showed gastric emptying rates lower than those with preserved acid secretion. Significant, but weak, correlations were observed between emptying rates and both peak acid output (Rs = 0.33) and serum gastrin levels (Rs = -0.36), but not with grading of mucosal atrophy. No symptom differences were observed between patients with or without achlorhydria, but a weak correlation was detected between peak acid output and the severity of epigastric pain (Rs = 0.40). In conclusion, patients with fundic atrophic gastritis present delayed gastric emptying that is weakly related to the reduction of the acid secretion and the raising of serum gastrin levels rather than to the severity of the atrophy.

Impaired feedback of gastric functions in carboxypeptidase E-deficient mice.

Carboxypeptidase E deficiency as seen in the fat/fat mice is associated with reduced antral somatostatin content but tripling of the progastrin product. Thus, fat/fat mice are able to maintain normal tissue concentrations of bioactive alpha-amidated gastrin in spite of grossly attenuated progastrin processing. After induction of achlorhydria, however, neither the amount of alpha-amidated gastrin nor the total progastrin product increased in the fat/fat mice. This is contrary to what is seen in wild-type mice. Furthermore, the synthesis of antral somatostatin and fundic chromogranin A is also abnormal. Hence the results suggest a breakdown in the feedback loop that regulates gastric acid secretion.

Enfermedad de ménétrier: presentación de un caso infantil con diez años de seguimiento y degeneración maligna / Gastric adenocarcinoma in a patient with ménétrier disease after ten years of follow-up

Introducción. La enfermedad de Ménétrier ocurre con menor frecuencia en los niños que en los adultos. En los niños se reconoce como una enfermedad benigna, autolimitada, de buen pronóstico; en adultos por el contrario, puede malignizarse y degenerar en linfoma gástrico o adenocarcinoma. Se caracteriza por hipertrofia de los pliegues gástricos, hipoproteinemia con hipoalbuminemia e hipersecreción gástrica, con hipoclorhidria o aclorhidria. Caso clínico. Se presenta el caso de una niña con enfermedad de Ménétrier diagnosticada a los 12 años de edad con evolución atípica y seguimiento durante 10 años. Se describen los hallazgos clínicos, bioquímicos, endoscópicos e histológicos durante su evolución, así como tratamientos recibidos y su respuesta. Se describe la evolución atípica, degeneración maligna de la enfermedad. Se hace una revisión de la literatura en cuanto a las causas de la enfermedad, su fisiopatología, evolución natural y las posibilidades terapéuticas existentes. Conclusión. En este caso se demuestra la degeneración maligna de la enfermedad de Ménétier, con evolución a adenocarcinoma gástrico intramucoso, después de diez años de evolución, en una niña de doce años de edad, este tipo de evolución se ha descrito solamente en adultos.

Drug-induced hypochlorhydria causes high duodenal bacterial counts in the elderly.

BACKGROUND: Small bowel bacterial overgrowth secondary to drug-induced hypochlorhydria may be of particular importance in the elderly, in whom anti-ulcer drugs are commonly prescribed and the consequences of malabsorption may be severe. METHODS: Duodenal aspirates were obtained from elderly individuals before (n = 24) and during a 2-month treatment course with either omeprazole (20 mg daily; n = 8) or ranitidine (300 mg b.d.; n = 6), and from six patients with small bowel bacterial overgrowth who had diarrhoea and malabsorption. RESULTS: Before treatment, duodenal bacterial counts were normal (< 10(4) colony forming units/mL) in 23 elderly subjects (96%). However, six of 14 patients (43%) treated with omeprazole (5 of 8) or ranitidine (1 of 6) developed bacterial counts > 10(5) cfu/mL. All remained asymptomatic and had normal lactulose breath H2 profiles during treatment. CONCLUSION: Drug-induced hypochlorhydria causes high duodenal bacterial counts in the elderly but, in the short term, this bacterial overgrowth is not associated with malabsorption.

Hypochlorhydria from short-term omeprazole treatment does not inhibit intestinal absorption of calcium, phosphorus, magnesium or zinc from food in humans.

OBJECTIVE: Low gastric pH is generally believed to be an important factor in intestinal mineral absorption. Thus, hypochlorhydria could be an important risk factor for mineral malabsorption and the development of marginal mineral status. We studied whether the hypochlorhydria associated with treatment with the anti-ulcer medication omeprazole, a potent gastric proton pump inhibition, would affect intestinal calcium, phosphorus, magnesium, or zinc absorption from food. METHODS: Thirteen normal, healthy adults were assigned to either a control group (n = 5) receiving no drug treatment or an omeprazole treatment group (n = 8) to produce increased gastric pH. Omeprazole treatment of normal volunteers resulted in a significant change in postprandial gastric pH (pH 6.4 +/- 0.3 vs. 3.6 +/- 0.5 in control subjects, p < 0.01) and baseline fasting pH (pH 5.8 +/- 0.5 vs. pH 1.8 +/- 0.3 in controls, p < 0.01) after an overnight fast. Net mineral absorption from a standard test meal was measured using a whole gut lavage technique. Mineral absorption was measured twice in each subject, once with 120 mL of 0.1 mol/liter hydrochloric acid and a second time with 120 mL of distilled water alone. RESULTS: We found that despite marked changes in gastric pH due to drug treatment or administration of exogenous HCl, no change in the intestinal absorption of calcium, phosphorus, magnesium or zinc from a standard test meal was evident. CONCLUSIONS: These findings suggest that changing the gastric pH alone does not modify the net intestinal absorption of several minerals from food. Therefore, it is unlikely that moderate hypochlorhydria resulting from short-term omeprazole treatment substantially increases the risk for developing calcium, phosphorus, magnesium, or zinc deficiencies due to mineral malabsorption.

Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein-bound vitamin B12 absorption.

OBJECTIVE: To investigate the effects of hypochlorhydria and acidic drink ingestion on protein-bound vitamin B12 absorption in elderly subjects. METHODS: Absorption of protein-bound vitamin B12 was examined in elderly normal subjects (n = 8), and in hypochlorhydric subjects due to omeprazole treatment (n = 8) or with atrophic gastritis (n = 3). Subjects underwent absorption tests of protein-bound vitamin B12 ingested with water, cranberry juice and 0.1 N hydrochloric acid. RESULTS: Protein-bound vitamin B12 absorption was lower in the omeprazole-treated group (0.50%) compared to the normal group (1.21%; p < 0.001). With cranberry juice ingestion, the omeprazole-treated group showed an increase in absorbed protein-bound vitamin B12 (p = 0.025). With dilute hydrochloric acid ingestion, there was a further increase in vitamin B12 absorption (p < 0.001). CONCLUSION: Omeprazole causes protein-bound vitamin B12 malabsorption, and ingestion of an acidic drink improves protein-bound vitamin B12 absorption.

Achlorhydria does not protect against benign upper gastrointestinal ulcers during NSAID use.

It is widely accepted that the absence of acid-peptic activity excludes the presence of a benign upper gastrointestinal ulcer. We assessed the frequency of a history of benign upper gastrointestinal ulcer disease in patients with and without serological evidence of achlorhydria with reference to the use of nonsteroidal antiinflammatory drugs (NSAIDs). In total 857 patients were interviewed, using a standard questionnaire with emphasis on demographic data, chronic use of NSAID, and history of upper gastrointestinal ulcers. The frequency of achlorhydria was determined by extremely low serum levels of pepsinogen A (PgA < 17 micrograms/liter). Of the total group of patients, 36 patients (4.2%; 95% CI 2.9-5.5) had a PgA lower than 17 micrograms/liter. A history of benign upper gastrointestinal ulcer was found in 57/827 (6.9%) of patients with serum PgA higher than 17 micrograms/liter and in 3/36 (8.3%) of patients with serum PgA lower than 17 micrograms/liter (NS). The three patients with upper gastrointestinal ulcer and PgA lower than 17 micrograms/liter were known to have pernicious anemia (PA) before (two patients) or simultaneously (one patient) with the diagnosis of the upper gastrointestinal ulcer and were using NSAIDs at that time. The presence of gastric acid is not obligatory for the development of ulcers during NSAID use.