Management of upper gastrointestinal symptoms in patients with autoimmune gastritis

PURPOSE OF REVIEW

Autoimmune gastritis is characterized by atrophy of acid secreting parietal cells resulting in achlorhydria. Upper gastrointestinal symptoms are common in autoimmune gastritis and frequently result in prescriptions for acid suppressant medications despite the inability of the stomach to secrete acid. Evidence-based recommendations for management of gastrointestinal symptoms in autoimmune gastritis are lacking.

RECENT FINDINGS

The most common symptoms in patients with autoimmune gastritis are dyspepsia, heartburn, and regurgitation. Gastroesophageal reflux should be confirmed by pH-impedance testing and is typically weakly acid or alkaline. Therapy for reflux focuses on mechanical prevention of reflux (i.e., elevation of the head of the bed and alginates) or when severe, antireflux surgery. The etiology of dyspepsia in autoimmune gastritis is unclear and largely unstudied. In the first half of the 20th century, oral administration of acid to "aid digestion" was widely used with reported success. However, randomized, placebo-controlled trials are lacking. Here, we provide suggestions for attempting gastric acidification therapy.

SUMMARY

Upper GI symptoms are common in autoimmune gastritis. Their pathogenesis and therapy remain incompletely understood. Acid suppressant medications are useless and should be discontinued. A trial of acid replacement therapy is recommended especially in the form of placebo-controlled trials.

Parietal Cell Dysfunction: A Rare Cause of Gastric Neuroendocrine Neoplasm with Achlorhydria and Extreme Hypergastrinemia

A 69-year-old woman with multiple neuroendocrine neoplasms (NENs) was referred to our hospital. Although she had extreme hypergastrinemia (11,675 pg/mL), no findings that indicated types I to III gastric NENs were found. Although gastric corpus atrophy was suspected on conventional white-light imaging, findings on magnifying endoscopy with narrow-band imaging indicated no severe atrophy. A biopsy from the background fundic gland mucosa revealed no atrophic changes, parietal cells with vacuolated cytoplasm and negative findings for H⁺K⁺-ATPase. Thus, this case was diagnosed as multiple NENs with parietal cell dysfunction. Neither progression nor metastasis has been confirmed during two-year follow-up.

Alterations in SLC4A2, SLC26A7 and SLC26A9 Drive Acid-Base Imbalance in Gastric Neuroendocrine Tumors and Uncover a Novel Mechanism for a Co-Occurring Polyautoimmune Scenario

Autoimmune polyendocrine syndrome (APS) is assumed to involve an immune system malfunction and entails several autoimmune diseases co-occurring in different tissues of the same patient; however, they are orphans of its accurate diagnosis, as its genetic basis and pathogenic mechanism are not understood. Our previous studies uncovered alterations in the ATPase H+/K+ Transporting Subunit Alpha (ATP4A) proton pump that triggered an internal cell acid-base imbalance, offering an autoimmune scenario for atrophic gastritis and gastric neuroendocrine tumors with secondary autoimmune pathologies. Here, we propose the genetic exploration of APS involving gastric disease to understand the underlying pathogenic mechanism of the polyautoimmune scenario. The whole exome sequencing (WES) study of five autoimmune thyrogastric families uncovered different pathogenic variants in SLC4A2, SLC26A7 and SLC26A9, which cotransport together with ATP4A. Exploratory in vitro studies suggested that the uncovered genes were involved in a pathogenic mechanism based on the alteration of the acid-base balance. Thus, we built a custom gene panel with 12 genes based on the suggested mechanism to evaluate a new series of 69 APS patients. In total, 64 filtered putatively damaging variants in the 12 genes of the panel were found in 54.17% of the studied patients and none of the healthy controls. Our studies reveal a constellation of solute carriers that co-express in the tissues affected with different autoimmune diseases, proposing a unique genetic origin for co-occurring pathologies. These results settle a new-fangled genetics-based mechanism for polyautoimmunity that explains not only gastric disease, but also thyrogastric pathology and disease co-occurrence in APS that are different from clinical incidental findings. This opens a new window leading to the prediction and diagnosis of co-occurring autoimmune diseases and clinical management of patients.

A Case of Severe Hypocalcemia Caused by Malabsorption Due to Partial Gastrectomy and Small Bowel Resection

Objective

Calcium is an essential mineral involved in the functioning of nearly every human cell. Calcium levels are regulated by dietary absorption, vitamin D status, and parathyroid hormone (PTH). This report describes a patient in whom childhood bowel resection and partial gastrectomy resulted in malabsorptive hypocalcemia in adulthood.

Case Report

A 21-year-old man presented with syncope and a fall resulting in a right femoral neck fracture. His medical history included small bowel obstructions at age 9 requiring bowel resection, and at age 12 with gastric perforation and partial gastrectomy. Laboratory values showed calcium level of 4.9 mg/dL (8.9-10.3 mg/dL). PTH level was 273 pg/mL (12.0-88.0 pg/mL), 25-hydroxy-vitamin D was 28 ng/dL (30-100 ng/mL), and 1,25-dihydroxy-vitamin D was 54 pg/dL (18-72 pg/mL). Furthermore, magnesium and phosphorus levels were 2.1 mg/dL (1.5-2.6 mg/dL) and 4.4 mg/dL (2.4-4.7 mg/dL), respectively. Calcium levels improved to 9.5 mg/dL on 10% calcium gluconate drip but could not be maintained above 7 mg/dL on oral calcium carbonate supplementation, despite doses as high as 3750 mg three times daily with calcitriol 0.75 mcg twice daily. After switching from calcium carbonate to calcium citrate 3500 mg three times daily, the calcium level improved and was maintained between 8.3 and 9.0 mg/dL.

Discussion

High calcium needs, other nutrient deficiencies, and response to calcium citrate versus calcium carbonate suggest malabsorption from achlorhydria and small bowel resection.

Conclusion

This case emphasizes the gastrointestinal physiology in calcium homeostasis and highlights the recognition of hypocalcemia as a complication of gastric and bowel resection.

Improving Dissolution Behavior and Oral Absorption of Drugs with pH-Dependent Solubility Using pH Modifiers: A Physiologically Realistic Mass Transport Analysis

Orally dosed drugs must dissolve in the gastrointestinal (GI) tract before being absorbed through the epithelial cell membrane. In vivo drug dissolution depends on the GI tract's physiological conditions such as pH, residence time, luminal buffers, intestinal motility, and transit and drug properties under fed and fasting conditions (Paixão, P. et al. Mol. Pharm. 2018 and Bermejo, et al. M. Mol. Pharm. 2018). The dissolution of an ionizable drug may benefit from manipulating in vivo variables such as the environmental pH using pH-modifying agents incorporated into the dosage form. A successful example is the use of such agents for dissolution enhancement of BCS class IIb (high-permeability, low-solubility, and weak base) drugs under high gastric pH due to the disease conditions or by co-administration of acid-reducing agents (i.e., proton pump inhibitors, H2-antagonists, and antacids). This study provides a rational approach for selecting pH modifiers to improve monobasic and dibasic drug compounds' dissolution rate and extent under high-gastric pH dissolution conditions, since the oral absorption of BCS class II drugs can be limited by either the solubility or the dissolution rate depending on the initial dose number. Betaine chloride, fumaric acid, and tartaric acid are examples of promising pH modifiers that can be included in oral dosage forms to enhance the rate and extent of monobasic and dibasic drug formulations. However, selection of a suitable pH modifier is dependent on the drug properties (e.g., solubility and pK_a) and its interplay with the pH modifier pK_a or pK_as. As an example of this complex interaction, for basic drugs with high pK_a and intrinsic solubility values and large doses, a polyprotic pH modifier can be expected to outperform a monoacid pH modifier. We have developed a hierarchical mass transport model to predict drug dissolution of formulations under varying pH conditions including high gastric pH. This model considers the effect of physical and chemical properties of the drug and pH modifiers such as pK_a, solubility, and particle size distribution. This model also considers the impact of physiological conditions such as stomach emptying rate, stomach acid and buffer secretion, residence time in the GI tract, and aqueous luminal volume on drug dissolution. The predictions from this model are directly applicable to in vitro multi-compartment dissolution vessels and are validated by in vitro experiments in the gastrointestinal simulator. This model's predictions can serve as a potential data source to predict plasma concentrations for formulations containing pH modifiers administered under the high-gastric pH conditions. This analysis provides an improved formulation design procedure using pH modifiers by minimizing the experimental iterations under both in vitro and in vivo conditions.

Marked Hypergastrinemia with G-cell Hyperplasia in Two Autoimmune Gastritis Patients

Gastrin regulates gastric acid secretion, and gastrin secretion itself is regulated by the negative feedback system of gastric acidity. Autoimmune gastritis (AG) is a disease where parietal cells are destroyed, resulting in decreased acid production and an elevated serum gastrin level. We herein report 2 AG cases with marked hypergastrinemia (>5,000 pg/mL). In both cases, 24-hour gastric pH monitoring showed no time when gastric pH was <2, and immunohistochemistry revealed more than 140 gastrin-positive cells per linear millimeter at the antral mucosa. This is the first report to confirm the relationship between marked hypergastrinemia and G-cell hyperplasia with AG.

Physiologically Based Absorption Modeling of Salts of Weak Bases Based on Data in Hypochlorhydric and Achlorhydric Biorelevant Media

Physiologically based absorption modeling has been attracting increased attention to study the interactions of weakly basic drug compounds with acid-reducing agents like proton-pump inhibitors and H2 blockers. Recently, standardized gastric and intestinal biorelevant media to simulate the achlorhydric and hypochlorhydric stomach were proposed and solubility and dissolution data for two model compounds were generated. In the current manuscript, for the first time, we report the utility of these recently proposed biorelevant media as input into physiologically based absorption modeling. Where needed, data collected with the biorelevant gastrointestinal transfer (BioGIT) system were used for informing the simulations in regard to the precipitation kinetics. Using two model compounds, a HCl salt and a semi-fumarate co-crystal which as expected dissolve to a greater extent in these media (and in gastric and intestinal human aspirates) compared to what the pH-solubility profile of the free form would suggest, we demonstrate successful description of the plasma concentration profiles and correctly predicted the lack of significant interaction after administration with pantoprazole or famotidine, respectively. Thus, the data reported in this manuscript represent an initial step towards defining biorelevant input for such simulations on interactions with acid-reducing agents.

The risk of Clostridium difficile infection in patients with pernicious anaemia: a retrospective cohort study using primary care database

Background

Studies have found an association between proton pump inhibitor (PPI) use and Clostridium difficile infection. The purpose of this study was to determine whether the mechanism by which PPIs induce an increased risk of C. difficile infection is supported by the same mechanism acting in another cause of achlorhydria, pernicious anaemia.

Methods

Using a database of anonymised primary care records between 1990 and 2013, we selected exposed patients with a diagnosis of pernicious anaemia treated with vitamin B12 therapy. Each exposed patient was matched by age, gender and general practice to up to 10 controls. Cox regression analysis was used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for C. difficile infection with pernicious anaemia, adjusted for potential confounders.

Results

We identified 45,467 exposed patients matched to 449,635 controls. The crude incidence rate of C. difficile infection was 1.85/1000 person-years for the exposed cohort and 1.09/1000 person-years for controls. Patients with pernicious anaemia had a greater risk of C. difficile infection than the controls (adjusted HR 1.57, 95% CI 1.40-1.76).

Conclusions

Pernicious anaemia patients have an increased risk of C. difficile infection. This supports the theory that severe achlorhydria is the mechanism that increases the risk of C. difficile infection in long-term PPI users.

Risk of community-acquired pneumonia in patients with a diagnosis of pernicious anemia: a population-based retrospective cohort study

OBJECTIVE

Pernicious anemia (PA) is an autoimmune disease that causes achlorhydria or profound hypochlorhydria. We conducted a population-based study to determine whether individuals with PA are at an increased risk for community-acquired pneumonia (CAP).

METHODS

We performed a retrospective cohort study using The Health Improvement Network (THIN) from the UK (1993-2009). The eligible study cohort included individuals 18 years of age or older, with at least 1 year of THIN follow-up. The exposed group consisted of individuals with a diagnosis code for PA. The unexposed group consisted of individuals without a diagnosis of PA and was frequency matched with the exposed group with respect to age, sex, and practice site. Cox regression analysis was used to determine the hazard ratio with the 95% confidence interval for CAP associated with PA, accounting for a comprehensive list of potential confounders.

RESULTS

The study included 13,605 individuals with PA and 50,586 non-PA individuals. The crude incidence rate of CAP was 9.4/1000 person-years for those with PA, versus 6.4/1000 person-years for those without PA. The multivariable adjusted hazard ratio for CAP associated with PA was 1.18 (95% confidence interval 1.08-1.29).

CONCLUSION

In this large population-based cohort study, individuals with PA and presumed chronic achlorhydria were at an increased risk for CAP.

Is achlorhydria a cause of iron deficiency anemia?

We re-evaluated the old hypothesis that gastritis-induced achlorhydria is a cause of iron deficiency anemia (IDA) in humans. First, we analyzed the currently available research on the association between achlorhydria and IDA. When gastric acid secretion was measured after maximal stimulation, the frequency of achlorhydria (or severe hypochlorhydria) was 44% in patients with idiopathic IDA and 1.8% in healthy controls. In some patients with pernicious anemia, presumed achlorhydria preceded the development of IDA in time. However, we found no credible evidence that IDA caused gastritis or that IDA preceded the development of achlorhydria. Thus, correlational results favor achlorhydria as the causal factor in the association between achlorhydria and IDA. Second, we sought to determine whether gastritis and achlorhydria cause negative iron balance. When biosynthetic methods were used to isotopically label iron in food, achlorhydric patients were found to have severe malabsorption of nonheme iron, which persisted after the development of IDA. In 1 study, achlorhydria reduced the normal increase in heme-iron absorption from hemoglobin in response to iron deficiency. After an injection of isotopic iron into normal men, the physiologic loss of iron from the body was found to be 1 mg/d. Patients with chronic gastritis had excess fecal loss of isotopically tagged plasma iron. Calculations based on these results indicate that the absorption of iron from a typical Western diet by achlorhydric patients would be less than physiologic iron losses, creating a negative iron balance that could not be overcome by the adaptive increase in duodenal iron absorptive capacity that occurs in response to iron deficiency. The combination of results from these correlational and pathophysiologic studies supports the hypothesis that gastritis-induced achlorhydria can be an independent cause of IDA.

Prevalence of H. pylori infection and atrophic gastritis among symptomatic and dyspeptic adults in Kazakhstan. A hospital-based screening study using a panel of serum biomarkers

BACKGROUND

Health authorities of Kazakhstan are seeking for effective measures to interrupt the untoward trend, projected to increase the current number of gastric cancer (GC) cases (n=3,316) by 50% until the year 2030.

OBJECTIVE

Use of a non-invasive blood test with four stomach-specific biomarkers [Pepsinogen-I (PG-I) and -II (PG-II), amidated gastrin-17 (G-17), and Helicobacter pylori (HP) IgG antibodies], to assess for the prevalence of stomach conditions: Helicobacter pylori (HP) infection and atrophic gastritis (AG), both known to increase GC risk of in Kazakhstan.

MATERIALS AND METHODS

A cohort of 835 (symptomatic and asymptomatic) cases (473 women and 362 men)(median age 46.8 years; range 13.6-74.8) was examined with a panel of biomarkers. Results were assigned in five categories: 1) Healthy stomach, 2) HP infection, 3) atrophic gastritis (AG) of the antrum, 4) AG of the corpus, and 5) AG of both antrum and corpus (pangastritis).

RESULTS

The distribution in these five categories was identical in both sexes (p=0.259). Healthy stomach was detected only in 196 (23.5%) subjects, whereas the vast majority, 62.3% (n=519) had HP infection (with no AG). In 118 (14.1%) subjects, results were consistent with AG; in antrum (n=72), corpus (n=42) or pangastritis (n=4). Prevalence of AG increased with patient's age in both sexes. There was no age-related pattern in biomarker levels, and only slight differences between the genders.

CONCLUSION

While capable of detecting the subjects at risk for GC (HP or AG), GP seems to be a cost-effective means to intervene the current ominous trend in GC incidence in Kazakhstan.

Hypochlorhydria and achlorhydria are associated with false-positive secretin stimulation testing for Zollinger-Ellison syndrome

OBJECTIVES

Secretin stimulation testing (SST) is used to evaluate patients with hypergastrinemia in the diagnosis of Zollinger-Ellison syndrome. Case series have documented false-positive SST in patients with achlorhydria. This study reviews our experience with SST in hypochlorhydric and achlorhydric patients.

METHODS

We examined 27 patients with hypochlorhydria or achlorhydria based on a predefined basal acid output (BAO) measurement of less than 5.0 mEq/h who also underwent SST for diagnosis of Zollinger-Ellison syndrome. We report the frequency of false-positive SST results in this setting.

RESULTS

Three hundred thirty patients underwent gastric analysis of which 27 had BAO of less than 5.0 mEq/h and SST conducted. The mean (SD) fasting gastrin level was 247 (304) pg/mL, and the mean (SD) BAO measurement was 1.6 (1.8) mEq/h. Twenty patients were off, and 7 were on antisecretory therapy at time of testing. Four patients had false-positive SST results: 3 with gastric atrophy (BAO = 0 mEq/h) and 1 with drug-induced hypochlorhydria (BAO = 0.5 mEq/hr). These false-positive test results were confirmed by structural and functional imaging studies.

CONCLUSIONS

We have identified a 14.8% false-positive rate in SST in patients with hypochlorhydria or achlorhydria. Growing literature has identified severe consequences associated with discontinuing antisecretory treatment for testing; therefore, SST will require interpretation in the setting of gastric acid suppression and needs to be interpreted in this context.

Rationale in diagnosis and screening of atrophic gastritis with stomach-specific plasma biomarkers

BACKGROUND AND AIMS

Atrophic gastritis (AG) results most often from Helicobacter pylori (H. pylori) infection. AG is the most important single risk condition for gastric cancer that often leads to an acid-free or hypochlorhydric stomach. In the present paper, we suggest a rationale for noninvasive screening of AG with stomach-specific biomarkers.

METHODS

The paper summarizes a set of data on application of the biomarkers and describes how the test results could be interpreted in practice.

RESULTS

In AG of the gastric corpus and fundus, the plasma levels of pepsinogen I and/or the pepsinogen I/pepsinogen II ratio are always low. The fasting level of gastrin-17 is high in AG limited to the corpus and fundus, but low or non-elevated if the AG occurs in both antrum and corpus. A low fasting level of G-17 is a sign of antral AG or indicates high intragastric acidity. Differentiation between antral AG and high intragastric acidity can be done by assaying the plasma G-17 before and after protein stimulation, or before and after administration of the proton pump inhibitors (PPI). Amidated G-17 will rise if the antral mucosa is normal in structure. H. pylori antibodies are a reliable indicator of helicobacter infection, even in patients with AG and hypochlorhydria.

CONCLUSIONS

Stomach-specific biomarkers provide information about the stomach health and about the function of stomach mucosa and are a noninvasive tool for diagnosis and screening of AG and acid-free stomach.

Does high gastric cancer risk associated with low serum ferritin level reflect achlorhydria? An examination via cross-sectional study

With respect to the inverse association of serum ferritin level (SFL) with the risk of gastric cancer (GC) observed in some recent epidemiologic studies, possible mediation by achlorhydria as well as atrophic gastritis (AG), both of which are strongly associated with GC risk at not only the individual but also the population level, was examined in a cross-sectional study of 634 men aged 40 to 49 years randomly selected from 5 populations in Okinawa, Iwate, Nagano, Akita and Tokyo. AG and achlorhydria were serologically diagnosed based on the criteria of pepsinogen (Pep) I level < 70 ng/ml and Pep I/Pep II ratio < 3.0, as described previously, and a serum gastrin level of over 140 pg/ml, respectively. In the results, while the mean SFL for all the subjects differed significantly by area, similar areal differences in SFL were also found even when only the non-AG cases were considered. However, both of the above differences were eliminated with the exception of those between Okinawa and each of the other 4 areas, when adjustments were made for medical histories of diabetes mellitus, ulcers and liver disease, body mass index and gamma-glutamyltranspeptidase level. Therefore, no correlation among the 5 areas was observed between the adjusted areal mean SFLs and GC mortality in either case.(ABSTRACT TRUNCATED AT 250 WORDS)