Omeprazole and dietary nitrate independently affect levels of vitamin C and nitrite in gastric juice

Risk characterization of N-nitrosodimethylamine in pharmaceuticals

Since 2018, N-nitrosodimethylamine (NDMA) has been a reported contaminant in numerous pharmaceutical products. To guide the pharmaceutical industry, FDA identified an acceptable intake (AI) of 96 ng/day NDMA. The approach assumed a linear extrapolation from the Carcinogenic Potency Database (CPDB) harmonic-mean TD50 identified in chronic studies in rats. Although NDMA has been thought to act as a mutagenic carcinogen in experimental animals, it has not been classified as a known human carcinogen by any regulatory agency. Humans are exposed to high daily exogenous and endogenous doses of NDMA. Due to the likelihood of a threshold dose for NDMA-related tumors in animals, we believe that there is ample scientific basis to utilize the threshold-based benchmark dose or point-of-departure (POD) approach when estimating a Permissible Daily Exposure limit (PDE) for NDMA. We estimated that 29,000 ng/kg/day was an appropriate POD for calculating a PDE. Assuming an average bodyweight of 50 kg, we expect that human exposures to NDMA at doses below 5800 ng/day in pharmaceuticals would not result in an increased risk of liver cancer, and that there is little, if any, risk for any other type of cancer, when accounting for the mode-of-action in humans.

Is vitamin C a booster of the effects of dietary nitrate on endothelial function? Physiologic rationale and implications for research

Endothelial dysfunction (ED) is an early marker of vascular damage linked to the loss of integrity of the endothelial lining and represents a key step in the pathogenesis of atherosclerosis and cardiovascular diseases (CVDs). ED may be reversible, hence the development and testing of effective early interventions could be beneficial for the prevention and treatment of CVDs. Recent studies have demonstrated that the consumption of dietary nitrate (NO₃^-), an inorganic anion that serves as a substrate for the gas transmitter nitric oxide (NO), can lower blood pressure, improve endothelial function and, in observational studies, reduce the risk for CVD. We hypothesize that the co-consumption of NO₃^- with vitamin C, which is a potent antioxidant, could enhance the "yield" of NO produced from a given NO₃^- dose byThis could translate into greater NO-dependent effects on endothelial function (EF) and overall vascular health (than may be experienced with NO₃^- supplementation alone). This review presents evidence to suggest that the combination of vitamin C and dietary nitrate could represent a promising and effective approach to improve EF and reduce CVD risk, and discuss opportunities for future research.

In Vitro Analysis of N-Nitrosodimethylamine (NDMA) Formation From Ranitidine Under Simulated Gastrointestinal Conditions

Importance

A publication reported that N-nitrosodimethylamine (NDMA), a probable human carcinogen, was formed when ranitidine and nitrite were added to simulated gastric fluid. However, the nitrite concentrations used were greater than the range detected in acidic gastric fluid in prior clinical studies.

Objective

To characterize NDMA formation following the addition of ranitidine to simulated gastric fluid using combinations of fluid volume, pH levels, and nitrite concentrations, including physiologic levels.

Design, Setting, and Participants

One 150-mg ranitidine tablet was added to 50 or 250 mL of simulated gastric fluid with a range of nitrite concentrations from the upper range of physiologic (100 μmol/L) to higher concentrations (10 000 μmol/L) with a range of pH levels. NDMA amounts were assessed with a liquid chromatography-mass spectrometry method.

Main Outcomes and Measures

NDMA detected in simulated gastric fluid 2 hours after adding ranitidine.

Results

At a supraphysiologic nitrite concentration (ie, 10 000 μmol/L), the mean (SD) amount of NDMA detected in 50 mL simulated gastric fluid 2 hours after adding ranitidine increased from 222 (12) ng at pH 5 to 11 822 (434) ng at pH 1.2. Subsequent experiments with 50 mL of simulated gastric fluid at pH 1.2 with no added nitrite detected a mean (SD) of 22 (2) ng of NDMA, which is the background amount present in the ranitidine tablets. Similarly, at the upper range of physiologic nitrite (ie, 100 μmol/L) or at nitrite concentrations as much as 50-fold greater (1000 or 5000 μmol/L) only background mean (SD) amounts of NDMA were observed (21 [3] ng, 24 [2] ng, or 24 [3] ng, respectively). With 250 mL of simulated gastric fluid, no NDMA was detected at the upper physiologic range (100 μmol/L) or 10-fold physiologic (1000 μmol/L) nitrite concentrations, while NDMA was detected (mean [SD] level, 7353 [183] ng) at a 50-fold physiologic nitrite concentration (5000 μmol/L).

Conclusions and Relevance

In this in vitro study of ranitidine tablets added to simulated gastric fluid with different nitrite concentrations, ranitidine conversion to NDMA was not detected until nitrite was 5000 μmol/L, which is 50-fold greater than the upper range of physiologic gastric nitrite concentrations at acidic pH. These findings suggest that ranitidine is not converted to NDMA in gastric fluid at physiologic conditions.

Lost-in-Translation of Metabolic Effects of Inorganic Nitrate in Type 2 Diabetes: Is Ascorbic Acid the Answer?

Beneficial metabolic effects of inorganic nitrate (NO3-) and nitrite (NO2-) in type 2 diabetes mellitus (T2DM) have been documented in animal experiments; however, this is not the case for humans. Although it has remained an open question, the redox environment affecting the conversion of NO3- to NO2- and then to NO is suggested as a potential reason for this lost-in-translation. Ascorbic acid (AA) has a critical role in the gastric conversion of NO2- to NO following ingestion of NO3-. In contrast to AA-synthesizing species like rats, the lack of ability to synthesize AA and a lower AA body pool and plasma concentrations may partly explain why humans with T2DM do not benefit from NO3-/NO2- supplementation. Rats also have higher AA concentrations in their stomach tissue and gastric juice that can significantly potentiate gastric NO2--to-NO conversion. Here, we hypothesized that the lack of beneficial metabolic effects of inorganic NO3- in patients with T2DM may be at least in part attributed to species differences in AA metabolism and also abnormal metabolism of AA in patients with T2DM. If this hypothesis is proved to be correct, then patients with T2DM may need supplementation of AA to attain the beneficial metabolic effects of inorganic NO3- therapy.

Paradoxical relationship between proton pump inhibitors and COVID-19: A systematic review and meta-analysis

BACKGROUND

The proton pump inhibitors (PPIs), used to reduce gastric acid secretion, represent one of the most widely used pharmaceutical classes in the world. Their consumption as a risk factor for the evolution of severe forms of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been investigated as well as the mortality of these patients. These risks also appear to be linked to the duration and the dosage. On the other hand, several studies have emerged with regard to the protective or therapeutic effects of these drugs. More and more evidence underlines the immunomodulatory and anti-fibrotic role of PPIs. In addition, their ability to alkalize the contents of endosomes and lysosomes serves as an obstacle to the entry of the virus into the host cells.

AIM

To identify studies on the relationship between the intake of PPIs and coronavirus disease 2019 (COVID-19) in patients affected by SARS-CoV-2 infection, with the main objective of evaluating the outcomes related to severity and mortality.

METHODS

A literature review was performed in November 2020. The MEDLINE/PubMed, Cochrane Library, EMBASE and Google Scholar databases were searched for all relevant articles published in English on this topic. The search terms were identified by means of controlled vocabularies, such as the National Library of Medicine's MESH (Medical Subject Headings) and keywords. The MESH terms and keywords used were as follows: "COVID-19", "proton pump inhibitors", "PPIs", "SARS-CoV-2", "outcomes", "severity" and "mortality". The inclusion criteria regarding the studies considered in our analysis were: meta-analysis, case-control, hospital-based case-control, population-based case-control, retrospective studies, online survey, as well as cohort-studies, while articles not published as full reports, such as conference abstracts, case reports and editorials were excluded. We tried to summarize and pool all the data if available.

RESULTS

A total of 9 studies were found that described the use of PPIs, of which only 5 clearly reported the severity and mortality data in SARS-CoV-2 patients. Our pooled incidence analysis of severe events did not differ between patients with and without PPIs (odds ratio 1.65, 95% confidence interval: 0.62-4.35) (P = 0.314), or for mortality (odds ratio 1.77, 95% confidence interval: 0.62-5.03) (P = 0.286).

CONCLUSION

Detailed and larger case studies are needed to accurately understand the role of PPIs in this viral infection.

Long-term use of proton pump inhibitors as a risk factor for various adverse manifestations

The long-term use of proton pump inhibitors (PPIs) can lead to increased gastric pH, hypochlorhydria and in some cases to achlorhydria when compared to other acid-suppressing agents like histamine-2 (H2) receptor blockers and antacids. These consequences by the use of long-term PPIs may lead to significant vitamin (B₁₂ and C) and mineral (iron, calcium and magnesium) deficiencies which needs gastric acid for their absorption and bioavailability. Long-term use of PPIs by the pregnant patients may impose a potential risk of congenital malformations. Various studies have recommended the life style modifications and antacid use as first choice among pregnant womens by preserving PPIs (omeprazole as a safe choice of PPI) for severe conditions of gastroesophageal reflux disease. The long-term acid suppression by PPIs can also lead to enteric, respiratory and urinary tract infections. The hypochlorhydria by chronic PPIs use may induce hypergastrinemia, which ultimately mediates the gastric polyps, gastric carcinoids and gastric cancer. The concomitant use of PPIs with antiplatelet drugs like clopidogrel can impose the patients to major adverse cardiac events. This review has enlisted the comprehensive information regarding the adverse effects induced by long-term use of PPIs and their possible relations. Considerable studies like case-control, randomized trials, cohort studies and meta-analysis were reported in supporting these adverse effects. The clinicians and patients should be cautious about these effects so that they can avoid the serious outcomes. PPIs should be avoided for long-term use mainly in older adults unless there is a proper indication.

Effects of inorganic nitrate and vitamin C co-supplementation on blood pressure and vascular function in younger and older healthy adults: A randomised double-blind crossover trial

BACKGROUND

Vitamin C and inorganic nitrate have been linked to enhanced nitric oxide (NO) production and reduced oxidative stress. Vitamin C may also enhance the conversion of nitrite into NO.

AIMS

We investigated the potential acute effects of vitamin C and inorganic nitrate co-supplementation on blood pressure (BP) and peripheral vascular function. The secondary aim was to investigate whether age modified the effects of vitamin C and inorganic nitrate on these vascular outcomes.

METHODS

Ten younger (age 18-40 y) and ten older (age 55-70 y) healthy participants were enrolled in a randomised double-blind crossover clinical trial. Participants ingested a solution of potassium nitrate (7 mg/kg body weight) and/or vitamin C (20 mg/kg body weight) or their placebos. Acute changes in resting BP and vascular function (post-occlusion reactive hyperemia [PORH], peripheral pulse wave velocity [PWV]) were monitored over a 3-h period.

RESULTS

Vitamin C supplementation reduced PWV significantly (vitamin C: -0.70 ± 0.31 m/s; vitamin C placebo: +0.43 ± 0.30 m/s; P = 0.007). There were significant interactions between age and vitamin C for systolic, diastolic, and mean arterial BP (P = 0.02, P = 0.03, P = 0.02, respectively), with systolic, diastolic and mean BP decreasing in older participants and diastolic BP increasing in younger participants following vitamin C administration. Nitrate supplementation did not influence BP (systolic: P = 0.81; diastolic: P = 0.24; mean BP: P = 0.87) or vascular function (PORH: P = 0.05; PWV: P = 0.44) significantly in both younger and older participants. However, combined supplementation with nitrate and vitamin C reduced mean arterial BP (-2.6 mmHg, P = 0.03) and decreased PWV in older participants (PWV: -2.0 m/s, P = 0.02).

CONCLUSIONS

The co-administration of a single dose of inorganic nitrate and vitamin C lowered diastolic BP and improved PVW in older participants. Vitamin C supplementation improved PWV in both age groups but decreased systolic and mean BP in older participants only.

CLINICAL TRIAL REGISTRATION

Current Controlled Trials (ISRCTN98942199).

Ascorbic acid and retinol palmitate modulatory effect on omeprazole-induced oxidative damage, and the cytogenetic changes in S. cerevisiae and S180 cells

Omeprazole (OM), a prototype proton pump inhibitor, oxidizes thiol groups and induces DNA damage. The aim of this study was to evaluate the oxidative effects of omeprazole and its interactions with ascorbic acid (AA, 50 μM) and retinol palmitate (RP) in proficient and deficient Saccharomyces cerevisiae strains, as well as levels of cytogenetic damage in Sarcoma 180 (S180) cells. Omeprazole was tested at concentrations of 10, 20 and 40 μg/mL, whereas H₂O₂ (10 mM), cyclophosphamide (20 mg/mL), and saline (0.9% NaCl solution) were employed as stressor, positive control, and negative control, respectively. Results revealed that omeprazole concentration-dependently induces oxidative effects in S. cerevisiae strains. However, omeprazole co-treated with ascorbic acid (50 μM) and retinol palmitate (100 IU) significantly modulated the oxidative damage inflected on the S. cerevisiae strains. Furthermore, omeprazole did not produce micronucleus formation and chromosomal bridges in S180 cells, but induced shoots. Significant increase in karyolysis and karyorrhexis were also observed with the omeprazole treated groups, which was modulated by co-treatment with ascorbic acid and retinol palmitate. Taken all together, it is suggested that ascorbic acid and retinol palmitate can substantially modulate the oxidative damage caused by omeprazole on the S. cerevisiae strains, however, much precaution is recommended with omeprazole and antioxidant co-treatment.

Blockade of Cardiac Proton Pump Impairs Ventricular Remodeling Through a Superoxide-DDAH-Dependent Pathway in Infarcted Rats

Background

Proton pump inhibitors (PPIs) are frequently used to prevent or treat peptic ulcers. Recently, PPIs have been shown to increase the risk of myocardial infarction. The purpose of this study was to determine whether PPIs adversely affect ventricular remodeling in infarcted rats.

Methods

Male Wistar rats were randomly assigned to receive either vehicle, omeprazole, omeprazole + vitamin C, omeprazole + olmesartan, or famotidine treatment for 4 weeks starting 24 hours after inducing myocardial infarction by ligating coronary arteries.

Results

Compared with vehicle-treated infarcted rats, omeprazole-treated infarcted rats had significant changes with reduced myocardial vitamin C levels, increased oxidant production, and decreased dimethylarginine dimethylaminohydrolase 2 (DDAH2) activity, which in turn increased asymmetric dimethylarginine (ADMA) levels and impaired ventricular remodeling. With gastric protection similar to omeprazole, the H2 blocker famotidine had no effect on ventricular remodeling. In contrast to the in vivo results, the ex vivo study showed similar superoxide and DDAH2 protein levels between vehicle- and omeprazole-treated infarcted rats, suggesting involvement of gastric vitamin C uptake rather than myocardial vitamin C in mediating the impaired axis of vitamin C-superoxide-DDAH2 in the in vivo measurements. The administration of PPIs was associated with impaired DDAH2 expression and increased myocardial ADMA, which impaired ventricular remodeling after infarction. These effects were prevented by the coadministration of vitamin C or olmesartan.

Conclusions

Our results indicate that the administration of PPIs was associated with impaired DDAH2 expression and increased myocardial ADMA by reducing gastric vitamin C uptake, which impaired ventricular remodeling after infarction.

Dietary nitrate consumption and risk of CHD in women from the Nurses' Health Study

The consumption of nitrate-rich vegetables can acutely lower blood pressure and improve mediators shown to optimise vascular health. However, we do not yet understand the impact of long-term habitual dietary nitrate intake and its association with CVD. Therefore, the aim of this investigation was to examine the relationship between habitual dietary nitrate intakes and risk of CHD in women from the Nurses' Health Study. We prospectively followed 62 535 women who were free from diabetes, CVD and cancer at baseline in 1986. Information on diet was updated every 4 years with validated FFQ. The main outcome was CHD defined by the occurrence of non-fatal myocardial infarction or fatal CHD. Cox proportional hazard regression models were used to estimate the relative risks (RR) and 95 % CI. During 26 years of follow-up, 2257 cases of CHD were identified. When comparing the highest quintile of nitrate intake with the lowest quintile, in aged-adjusted analysis there was a protective association for CHD (RR=0·77, 95 % CI 0·68, 0·97; P=0·0002) which dissipated after further adjustment for smoking, physical activity, BMI and race (RR=0·91; 95 % CI 0·80, 1·04; P=0·27). This magnitude of association was further attenuated once we adjusted for the Alternative Healthy Eating Index excluding vegetable and fruit consumption (RR=1·04, 95 % CI 0·91, 1·20; P=0·34). Dietary nitrate intake was not related to the risk of CHD after adjustment for other lifestyle and non-vegetable dietary factors in a large group of US women.

Development of Paper-Based Analytical Devices for Minimizing the Viscosity Effect in Human Saliva

Rationale: Saliva as a sample matrix is rapidly gaining interest for disease diagnosis and point-of-care assays because it is easy to collect (non-invasive) and contains many health-related biomarkers. However, saliva poses particular problems relative to more common urine and blood matrices, which includes low analyte concentrations, lack of understanding of biomolecule transportation and inherent viscosity variability in human samples. While several studies have sought to improve assay sensitivity, few have addressed sample viscosity specifically. The goal of this study is to minimize the effect of sample viscosity on paper-based analytical devices (PADs) for the measurement of pH and nitrite in human saliva. Methods: PADs were used to measure salivary pH from 5.0 to 10.0 with a universal indicator consisting of chlorophenol red, phenol red and phenolphthalein. Nitrite determination was performed using the Griess reaction. Artificial saliva with viscosity values between 1.54 and 5.10 mPa∙s was tested on the proposed PAD. To ensure the proposed PADs can be tailored for use in-field analysis, the devices were shipped to Australia and tested with human specimens. Results: Initial experiments showed that viscosity had a significant impact on the calibration curve for nitrite; however, a more consistent curve could be generated when buffer was added after the sample, irrespective of sample viscosity. The linear range for nitrite detection was 0.1 to 2.4 mg/dL using the improved method. The nitrite measurement in artificial saliva also showed a good correlation with the standard spectrophotometry method (p=0.8484, paired sample t-test, n=20). Measured pH values from samples with varying viscosities correlated well with the results from our pH meter. Conclusions: The inherent variation of salivary viscosity that impacts nitrite and pH results can be addressed using a simple washing step on the PAD without the need for complex procedures.

Evidence of Drug-Nutrient Interactions with Chronic Use of Commonly Prescribed Medications: An Update

The long-term use of prescription and over-the-counter drugs can induce subclinical and clinically relevant micronutrient deficiencies, which may develop gradually over months or even years. Given the large number of medications currently available, the number of research studies examining potential drug-nutrient interactions is quite limited. A comprehensive, updated review of the potential drug-nutrient interactions with chronic use of the most often prescribed medications for commonly diagnosed conditions among the general U.S. adult population is presented. For the majority of the interactions described in this paper, more high-quality intervention trials are needed to better understand their clinical importance and potential consequences. A number of these studies have identified potential risk factors that may make certain populations more susceptible, but guidelines on how to best manage and/or prevent drug-induced nutrient inadequacies are lacking. Although widespread supplementation is not currently recommended, it is important to ensure at-risk patients reach their recommended intakes for vitamins and minerals. In conjunction with an overall healthy diet, appropriate dietary supplementation may be a practical and efficacious way to maintain or improve micronutrient status in patients at risk of deficiencies, such as those taking medications known to compromise nutritional status. The summary evidence presented in this review will help inform future research efforts and, ultimately, guide recommendations for patient care.

Omeprazole promotes carcinogenesis of fore-stomach in mice with co-stimulation of nitrosamine

Objectives

To investigate if oral omeprazole application induces cancers of fore and glandular stomach in mice.

Methods

A total of 66 eligible male mice were randomly divided into 6 groups, which were treated with control reagent, low (6 mg/kg) and high dose omeprazole (30 mg/kg), N-methyl-N’-nitro-N-nitrosoguanidine (MNNG, 100 mg/L water), and MNNG plus low and high dose omeprazole, respectively. After 24 weeks, concentrations of acid phosphatase (ACP) and N-acetyl-β-D-glucosaminidase(NAG) in serum and spleen was examined, and p21 and mTOR levels in stomach were detected.

Results

The mouse spleen weight index was smaller in the omeprazole group than the control group, and in the MNNG plus omeprazole groups than the MNNG group. In the fore-stomach, more carcinomas were observed in the MNNG plus omeprazole groups than in the MNNG group. In the glandular stomach, there existed more atypical hyperplasia cases in the MNNG plus omeprazole groups than the MNNG-treated group, and one carcinoma was induced in the MNNG plus high dose omeprazole group. Omeprazole alone caused minor gastric pathological changes. Omeprazole treatment lowered both serum and spleen ACP and NAG levels in both the non-MNNG-treated and MNNG-treated subgroups. In fore-stomach, there existed decreased p21 and mTOR levels in the omeprazole-treated groups than in the control group, and in the MNNG plus omeprazole groups than the MNNG-treated group.

Conclusion

Omeprazole promotes carcinogenesis of the mouse fore-stomach but not the glandular stomach following treatment with MNNG. Lysosomal hydrolase activity was inhibited and some cancer-associated proteins was dysregulated, which requires further explorations.

The role of inorganic nitrate and nitrite in CVD

CVD is the leading cause of death worldwide, a consequence of mostly poor lifestyle and dietary behaviours. Although whole fruit and vegetable consumption has been consistently shown to reduce CVD risk, the exact protective constituents of these foods are yet to be clearly identified. A recent and biologically plausible hypothesis supporting the cardioprotective effects of vegetables has been linked to their inorganic nitrate content. Approximately 60–80 % inorganic nitrate exposure in the human diet is contributed by vegetable consumption. Although inorganic nitrate is a relatively stable molecule, under specific conditions it can be metabolised in the body to produce NO via the newly discovered nitrate–nitrite–NO pathway. NO is a major signalling molecule in the human body, and has a key role in maintaining vascular tone, smooth muscle cell proliferation, platelet activity and inflammation. Currently, there is accumulating evidence demonstrating that inorganic nitrate can lead to lower blood pressure and improved vascular compliance in humans. The aim of this review is to present an informative, balanced and critical review of the current evidence investigating the role of inorganic nitrate and nitrite in the development, prevention and/or treatment of CVD. Although there is evidence supporting short-term inorganic nitrate intakes for reduced blood pressure, there is a severe lack of research examining the role of long-term nitrate intakes in the treatment and/or prevention of hard CVD outcomes, such as myocardial infarction and cardiovascular mortality. Epidemiological evidence is needed in this field to justify continued research efforts.

Nutritional consequences of long-term acid suppression; are they clinically important?

PURPOSE OF REVIEW

As acid suppression therapies with proton pump inhibitors are an extremely common practice for common acid-related diseases, there has been increased scrutiny on the safety of this class of therapy.

RECENT FINDINGS

There have been increasing reports of allegation of harm with the sustained use of proton pump inhibitors, in particular with potential adverse effects on vitamin and mineral absorption. This has prompted a number of product label changes directed by the US Food and Drug Administration, raising concerns for ongoing continued use among clinicians and patients.

SUMMARY

This review highlights the most recent information around these controversies and provides evidence summaries to help guide care providers in their care plans as well as discussions with patients.

Dietary Factors in Relation to Helicobacter pylori Infection

Background and Aim. Helicobacter pylori (HP) and diet are both risk factors for gastric cancer. The aim of this study was to evaluate the Helicobacter pylori infection and dietary habits common in Khuzestan province. Methods. This cross-sectional study was conducted in 2011–2013 on 374 patients. Participants were interviewed using a food frequency questionnaire and tissue sample of the antrum was sent for pathology lab. The histopathological major variables were graded on a scale of 3 (mild, moderate, and severe) and data analyzed using nonparametric tests. Results. In this study, of 160 patients (43%) that were determined, 8.1 percent had severe contamination. Among dietary patterns, relationship between energy intake and carbohydrate with H. pylori was significant. A direct association was found between mean daily intakes of sausage (P = 0.001) and burgers (P < 0.05) with HP infection. Low intake of fresh vegetables and fruits was the most significant risk factors (P < 0.05). Conclusion. There is a possibility that some dietary factors such as consumption of fast foods and low intake of fresh vegetables may increase the chance of HP and severity of this infection.

Water-soluble vitamin deficiencies in complicated peptic ulcer patients soon after ulcer onset in Japan

We investigated over time whether contemporary Japanese patients with complicated peptic ulcers have any water-soluble vitamin deficiencies soon after the onset of the complicated peptic ulcers. In this prospective cohort study, fasting serum levels of water-soluble vitamins (vitamins B1, B2, B6, B12, C, and folic acid) and homocysteine were measured at 3 time points (at admission, hospital discharge, and 3 mo after hospital discharge). Among the 20 patients who were enrolled in the study, 10 consecutive patients who completed measurements at all 3 time points were analyzed. The proportion of patients in whom any of the serum water-soluble vitamins that we examined were deficient was as high as 80% at admission, and remained at 70% at discharge. The proportion of patients with vitamin B6 deficiency was significantly higher at admission and discharge (50% and 60%, respectively, p<0.05) than at 3 mo after discharge (10%). In conclusion, most patients with complicated peptic ulcers may have a deficiency of one or more water-soluble vitamins in the early phase of the disease after the onset of ulcer complications, even in a contemporary Japanese population.

Involvement of luminal nitric oxide in the pathogenesis of the gastroesophageal reflux disease spectrum

Over the last 3 decades, the incidence of esophageal adenocarcinoma has dramatically increased in Western countries; a similar increase may be observed in Asian countries in the near future. Esophageal adenocarcinoma arises from a sequential gastroesophageal reflux disease (GERD) spectrum from reflux erosive esophagitis, to Barrett's esophagus, and finally to esophageal adenocarcinoma. At present, gastric acid and bile are assumed to be primarily involved in the etiology of the GERD spectrum. We reported in 2002 that, at the gastroesophageal junction in humans, abundant amounts of nitric oxide (NO) are generated luminally through the entero-salivary re-circulation of dietary nitrate. Since then, we have carried out a series of experiments to demonstrate that NO diffuses into the adjacent epithelium at cytotoxic levels. This diffusion results in disruption of the epithelial barrier function, exacerbation of inflammation, acceleration of columnar transformation in the esophagus (Barrett's esophagus) via the induction of caudal-type homeobox 2, and the shifting of carcinogenic N-nitroso compound formation from the luminal to epithelial compartment. These results suggest that, in addition to conventionally recognized causative factors, luminal NO could also be involved in the pathogenesis of the GERD spectrum. In addition, we recently showed that there is a prominent gender-related difference in NO-related cytotoxicity in the esophagus and that estrogen attenuated the esophageal tissue damage via the estrogen receptor in female rats. The role of estrogen in attenuating the esophageal tissue damage in NO-related esophageal damage could explain the well-recognized male predominance in the GERD spectrum in humans.

Qualitative analysis of anatomopathological changes of gastric mucosa due to long term therapy with proton pump inhibitors: experimental studies x clinical studies

INTRODUCTION

For a few decades the long-term use of proton pump inhibitors has had wide application in the treatment of several gastrointestinal diseases. Since then, however, several studies have called attention to the possible development of anatomical and pathological changes of gastric mucosa, resulting from the long term use of this therapeutic modality. Recent experimental and clinical studies suggest that these changes have connection not only to the development of precancerous lesions, but also of gastric tumors.

OBJECTIVE

To present a qualitative analysis of anatomical and pathological changes of gastric mucosa resulting from the long-term use of proton pump inhibitors.

METHOD

The headings used were: proton pump inhibitors, precancerous lesions and gastric neoplasms for a non systematic review of the literature, based on Medline, Lillacs and Scielo. Twelve articles were selected from clinical (9) and experimental (3) studies, for qualitative analysis of the results.

RESULTS

The gastric acid suppression by high doses of proton pump inhibitors induces hypergastrinemia and the consequent emergence of neuroendocrine tumors in animal models. Morphological changes most often found in these experimental studies were: enterochromaffin-like cell hyperplasia, neuroendocrine tumor, atrophy, metaplasia and adenocarcinoma. In the studies in humans, however, despite enterochromaffin-like cell hyperplasia, the other effects, neuroendocrine tumor and gastric atrophy, gastric metaplasia and or adenocarcinoma, were not identified.

CONCLUSION

Although it is not possible to say that the long-term treatment with proton pump inhibitors induces the appearance or accelerates the development of gastric cancer in humans, several authors have suggested that prolonged administration of this drug could provoke the development of gastric cancer. Thus, the evidence demonstrated in the animal model as well as the large number of patients who do or will do a long-term treatment with proton pump inhibitors, justifies the maintenance of this important line of research.

Effects of widely used drugs on micronutrients: a story rarely told

Vitamins and trace elements are essential to the body, however, deficiencies are frequently observed in the general population. Diet is mostly responsible for these deficiencies but drugs also may play a significant role by influencing their metabolism. These effects are rarely assessed in clinical practice, in part because of limited data available in the literature. Drug-induced micronutrient depletions, however, may be the origin of otherwise unexplained symptoms that might sometimes influence medication compliance. We present various examples of widely prescribed drugs that can precipitate micronutrient deficiencies. This review aims at sensitizing physicians on drug-micronutrient interactions. High-risk population groups also are presented and supplementation protocols are suggested.

Proton pump inhibitors and risk of vitamin and mineral deficiency: evidence and clinical implications

Proton pump inhibitors (PPIs) remain the superior choice worldwide in antisecretory therapy in the evidence-based treatment of upper gastrointestinal disorders including gastroesophageal reflux disease, erosive esophagitis, dyspepsia and peptic ulcer disease. PPI overutilization in ambulatory care settings is often a result of failure to re-evaluate the need for continuation of therapy, or insufficient use of on-demand and step-down therapy. Nonjudicious use of PPIs creates both preventable financial as well as medical concerns. PPIs have been associated with an increased risk of vitamin and mineral deficiencies impacting vitamin B12, vitamin C, calcium, iron and magnesium metabolism. While these risks are considered to be relatively low in the general population, they may be notable in elderly and malnourished patients, as well as those on chronic hemodialysis and concomitant PPI therapy. No current evidence recommends routine screening or supplementation for these potential vitamin and mineral deficiencies in patients on either short- or long-term PPI therapy. Reducing inappropriate prescribing of PPIs can minimize the potential risk of vitamin and mineral deficiencies.

Vitamin C, gastritis, and gastric disease: a historical review and update

The discovery of Helicobacter pylori as the cause of gastritis and peptic ulcers ushered in the modern era of research into gastritis and into acid-peptic diseases and rekindled interest in the role of ascorbic acid in the pathophysiology and treatment of gastritis and peptic ulcer disease. Here, we review historic and modern studies on ascorbic acid and gastric diseases with an emphasis on H. pylori gastritis and its sequelae. The relationship of ascorbic acid and gastritis and peptic ulcer and its complications was extensively studied during the 1930s through the 1950s. Much of this extensive literature has been effectively "lost." Ascorbic acid deficiency was associated with all forms of gastritis (e.g., autoimmune, chemical, and infectious) due in varying degrees to insufficient intake, increased metabolic requirements, and destruction within the GI tract. Importantly, gastritis-associated abnormalities in gastric ascorbic acid metabolism are reversed by H. pylori-eradication and potentially worsened by proton pump inhibitor therapy. Diets rich in naturally occurring ascorbic acid are associated with protection of the gastric corpus from atrophy and a reduction in the incidence of gastric cancer possibly through the ability of ascorbic acid to reduce oxidative damage to the gastric mucosa by scavenging carcinogenic N-nitroso compounds and free radicals and attenuating the H. pylori-induced inflammatory cascade. Ascorbic acid supplementation was possibly associated with a decreased incidence of bleeding from peptic ulcer disease. Pharmacologic doses of ascorbic acid also may improve the effectiveness of H. pylori-eradication therapy. Occasionally, looking back can help plot the way forward.

Micronutrients (Other than iron) and Helicobacter pylori infection: a systematic review

BACKGROUND

Many micronutrients depend on a healthy stomach for absorption. Helicobacter pylori chronic gastritis may alter gastric physiology affecting homeostasis of vitamins and minerals.

OBJECTIVES

Systematic review to assess whether H. pylori infection is associated with reduced micronutrient levels (other than iron) in the plasma or gastric juice and whether low micronutrient levels are modified by eradication treatment.

METHOD

Medline was searched for relevant publications from inception to June 2010. Studies describing micronutrient levels in H. pylori-infected and not-infected adults and/or the effect of eradication treatment on micronutrient levels were included.

FINDINGS

Fifty-two publications were selected: 46 investigated the association between H. pylori infection and reduced micronutrient levels and 14 the effect of eradication treatment on micronutrient levels. Sixty-four studies investigated vitamins (23 ascorbic acid, four ß-carotene, 21 cobalamin, 11 folate, and five α-tocopherol) and 10 addressed minerals (one calcium, one copper, one magnesium, one phosphorus, three selenium, and three zinc). Pooled standardized mean differences in micronutrient levels showed positive associations with H. pylori infection for ascorbic acid (gastric juice, -1.087) and cobalamin (-0.744), and a positive effect of eradication treatment, which increased ascorbic acid in the gastric juice (-1.408) and serum cobalamin (-1.910). No significant association between infection and low folate levels was observed. Meta-analyses for other micronutrients were not performed owing to insufficient data.

CONCLUSIONS

Meta-analyses indicate that H. pylori infection is associated with reduced levels of ascorbic acid and cobalamin, supported by the positive effect of eradication treatment. For other micronutrients, further studies are needed.

[Adverse effects of proton pump inhibitors: should we worry about long-term exposure?]

Long-term treatment with proton pump inhibitors (PPI) is becoming more prevalent. Although they are well tolerated in the short term, serious concerns about long-term use have arisen. Recent data suggest that the latter is associated with an increased risk for osteoporotic fracture (especially vertebral), Clostridium difficile infection and rebound acid hypersecretion after treatment discontinuation. Acute interstitial nephritis is rare but may progress to chronic renal failure. An increased risk of community-acquired pneumonia has not been established in the general population and seems limited to the most vulnerable patients. Consistent data are still missing to correctly assess the risk of iron deficiency, vitamin B12 deficiency or hypomagnesaemia and the risk of digestive malignant diseases, despite the pathophysiological basis that exists concerning gastric malignancy. Many drug interactions can occur on long-term treatment, including some that imply the cytochrome P450 enzymes. Finally, the risk-benefit balance for a chronic PPI use in children seems unfavorable in most cases.

Antioxidant pre-treatment prevents omeprazole-induced toxicity in an in vitro model of infectious gastritis

Omeprazole is a mainstay of therapy for gastroesophageal reflux disease (GERD) and gastritis, and is increasingly used as an over-the-counter remedy for dyspepsia. Omeprazole acts by selectively oxidizing thiol targets in the gastric proton pump, but it also appears to be toxic to the gastric mucosa. We hypothesized that omeprazole toxicity is due to non-specific oxidation of cell structures other than the proton pump, and tested the efficacy of antioxidants to prevent omeprazole-induced toxicity in isolated rabbit gastric glands. Toxicity was measured by uptake and converstion of calcein-AM, following three hours of exposure to omeprazole and a non-selective thiol-oxidant, monochloramine. Intracellular concentration of Zn(2+) and the capacity to maintain luminal acidity were monitored using the fluorescent reporters fluozin-3 and Lysosensor DND-160, respectively. Both omeprazole and monochloramine caused marked reduction in cell viability. The toxicity of omeprazole was independent of monochloramine toxicity. The thiol reducing agent dithiothreitol protected gastric glands from injury. The oxidant scavenger Vitamin C also protected, and did not impair the anti-secretory effects of omeprazole. Thus, omeprazole toxicity appears to be oxidative and preventable with antioxidant therapy, including Vitamin C. Vitamin C may be a safe and efficacious addition to treatments requiring the use of PPIs.

Adverse effects of proton pump inhibitors

Proton pump inhibitors (PPI) are very effective drugs used largely in acid related disorders. During the last years concern have been raised regarding their overutilisation in benign condition, such as gastroesophageal reflux disease. The debate focussed also on the risk of adverse events related to long term use of PPI. Apart of the case of Helicobacter Pylori (H. Pylori) positive patients, in whose long term acid suppression lead to the development of corpus predominant atrophic gastritis, precursor of cancer; the other assumed adverse events, have never been demonstrated in prospective studies. The attention should move towards the appropriate prescription of PPI, rather than the fear adverse effects of PPI. In fact, in clinical practise, PPI are often prescribed in patients without a specific acid related disease and continued long term based on their safety profile. This review focus on the main adverse events related to long term PPI use.

Exogenous luminal nitric oxide exacerbates esophagus tissue damage in a reflux esophagitis model of rats

OBJECTIVE

Cytotoxic concentrations of nitric oxide are generated luminally at the gastroesophageal junction through the entero-salivary recirculation of dietary nitrate in humans. The site of luminal nitric oxide generation shifts to the lower esophagus when gastric acid is refluxed into the esophagus. The aim of this study was to investigate the influence of persistent administration of exogenous nitric oxide on esophageal damage.

MATERIAL AND METHODS

0.1% sodium nitrite and/or 1% ascorbic acid was administered in an established rat acid-refluxed esophagitis model. Co-administration of both reactants in this model is thought to induce high concentrations of nitric oxide luminally in the esophagus by an acid-catalyzed chemical reaction when refluxed gastric acid is present. The tissue damage was evaluated by a macroscopic lesion index and myeloperoxidase activity. Nitrotyrosin was assessed immunohistochemically as a footprint of peroxynitrite formation.

RESULTS

Co-administration of sodium nitrite and ascorbic acid induced a 4- to 5-fold increase in the esophageal damage compared with baseline reflux esophagitis, while the damage was unchanged when either of the reagents alone was given. Nitrotyrosine was strongly stained in the tissue from the co-administration. Treatment of superoxide scavengers efficiently prevented the exacerbation of esophageal damage by exogenous nitric oxide exposure, suggesting an essential role of superoxide in esophageal damage.

CONCLUSIONS

Exogenous luminal nitric oxide greatly exacerbated the tissue damage of reflux esophagitis. Diffusion of the luminal nitric oxide into the adjacent superoxide-enriched inflamed tissue of the esophagus could lead to the production of the highly toxic agent peroxynitrite, thus causing exacerbation of the esophageal damage.

Effect of proton pump inhibitors on vitamins and iron

Vitamin C is actively secreted in human gastric juice. Proton pump inhibitor therapy lowers the concentration of vitamin C in gastric juice and the proportion of the vitamin in its active antioxidant form i.e., ascorbic acid. This has secondary effects on intragastric nitrite chemistry, resulting in a rise in gastric juice nitrite levels. There is also some evidence that proton pump inhibitors may reduce the bioavailability of ingested vitamin C. The effect of proton pump inhibitors on vitamin C and nitrite chemistry is more marked in Helicobacter pylori-infected subjects. Proton pump inhibitors also reduce the absorption of vitamin B(12) probably by inhibiting intragastric proteolysis and, thus, its release from food required prior to binding to R-proteins and gastric intrinsic factor. Under certain circumstances, the treatment may lower serum vitamin B(12) levels. Proton pump inhibitor therapy reduces the absorption of non-heme iron and this effect has been employed in the management of hemochromatosis. It may also retard clinical response to iron supplementation.

Formation of an adduct by clenbuterol, a beta-adrenoceptor agonist drug, and serum albumin in human saliva at the acidic pH of the stomach: evidence for an aryl radical-based process

Clenbuterol (CLB) is an antiasthmatic drug used also illegally as a lean muscle mass enhancer in both humans and animals. CLB and amine-related drugs in general are nitrosatable, thus raising concerns regarding possible genotoxic/carcinogenic activity. Oral administration of CLB raises the issue of its possible transformation by salivary nitrite at the acidic pH of gastric juice. In acidic human saliva CLB was rapidly transformed to the CLB arenediazonium ion. This suggests a reaction of CLB with salivary nitrite, as confirmed in aerobic HNO(2) solution by a drastic decrease in nitric oxide, nitrite, and nitrate. In human saliva, both glutathione and ascorbic acid were able to inhibit CLB arenediazonium formation and to react with preformed CLB arenediazonium. The effect of ascorbic acid is particularly pertinent because this vitamin is actively concentrated within the gastric juice. EPR spin trapping experiments showed that preformed CLB arenediazonium ion was reduced to the aryl radical by ascorbic acid, glutathione, and serum albumin, the major protein of saliva. As demonstrated by anti-CLB antibodies and MS, the CLB-albumin interaction leads to the formation of a covalent drug-protein adduct, with a preference for Tyr-rich regions. This study highlights the possible hazards associated with the use/abuse of this drug.

Changes in gene expression of gastric mucosa during therapeutic acid inhibition

BACKGROUND

Long-term therapy with potent acid inhibitors is a common treatment for gastro-esophageal reflux disease. Administration of proton pump inhibitors (PPIs) causes profound and continuous hypochlorhydria by inhibition of the proton pump in gastric parietal cells. Long-term hypergastrinaemia increases mucosal thickness and enterochromaffin-like cell density in oxyntic mucosa.

OBJECTIVE

The aim of this study was to see whether this very common clinical intervention induces significant changes in the gastric mucosal gene expression pattern.

METHODS

Seven patients suffering from gastro-esophageal reflux disease were included in this study. Endoscopic biopsies were taken from the corpus mucosa before and toward the end of a 3-month treatment with the PPI esomeprazole.

RESULTS

Microarray analysis identified 186 differentially expressed genes. A high proportion of genes with changed gene expression levels during PPI treatment are involved in proliferation, apoptosis, and stress response.

CONCLUSION

This study identified many genes that were not previously known to be affected by inhibition of gastric acid secretion. Further characterization of the functional roles of genes whose expression is modulated by potent acid inhibition may give new insight into the biological responses to potent acid inhibition, including the mucosal response to the moderately increased gastrin levels encountered in clinical practice.

Nitrogenous chemicals generated from acidification of saliva influence transient lower oesophageal sphincter relaxations

OBJECTIVE

Saliva contains high concentrations of nitrite derived from the enterosalivary recirculation of dietary nitrate and its reduction by buccal bacteria. Acidic gastric juice converts the swallowed nitrite to varying proportions ofnitrous acid and nitric oxide (NO) depending upon ascorbic acid availability. Neuronally generated NO is the key in the pathway of transient lower oesophageal sphincter relaxations in vivo. Furthermore, in vitro NO and nitrous acid relax the smooth muscle of the stomach, lower oesophageal sphincter (LOS) and oesophageal body. The objective of this article was to determine whether luminal administration of NO or nitrous acid affects the generation of transient LOS relaxations following a meal.

MATERIAL AND METHODS

Fifteen healthy subjects were studied on three separate days. A manometry catheter was used to record oesophageal, LOS and gastric pressures, and two oesophageal pH probes were used to record reflux. One of three solutions was infused each day into the cardia after a standardized meal: 1) control solution ofhydrochloric acid pH 1.0, 2) nitrous acid and 3) nitrous acid plus ascorbic acid to generate NO. The solutions were randomized and double-blinded.

RESULTS

The frequency of transient LOS relaxations was increased by the NO-generating solution at 5.2/h compared with both the control (3.5, p <0.01) and nitrous acid solution (3.1, p <0.0001). The NO-generating solution also increased oesophageal acid exposure to 62.2%, compared with both the control (37.5%, p <0.03) and nitrous acid solution (36.6%, p <0.002).

CONCLUSIONS

Luminal NO at the gastro-oesophageal junction increases the generation of transient LOS relaxations following a meal. Chemicals generated by the acidification of salivary nitrite may contribute to gastro-oesophageal motility disorders.

Red wine-dependent reduction of nitrite to nitric oxide in the stomach

Nitrite may be a source for nitric oxide (*NO), particularly in highly acidic environments, such as the stomach. Diet products contribute also with reductants that dramatically increase the production of *NO from nitrite. Red wine has been attributed health promoting properties largely on basis of the reductive antioxidant properties of its polyphenolic fraction. We show in vitro that wine, wine anthocyanin fraction and wine catechol (caffeic acid) dose- and pH-dependently promote the formation of *NO when mixed with nitrite, as measured electrochemically. The production of *NO promoted by wine from nitrite was substantiated in vivo in healthy volunteers by measuring *NO in the air expelled from the stomach, following consumption of wine, as measured by chemiluminescence. Mechanistically, the reaction involves the univalent reduction of nitrite, as suggested by the formation of *NO and by the appearance of EPR spectra assigned to wine phenolic radicals. Ascorbic and caffeic acids cooperate in the reduction of nitrite to *NO. Moreover, reduction of nitrite is critically dependent on the phenolic structure and nitro-derivatives of phenols are also formed, as suggested by caffeic acid UV spectral modifications. The reduction of nitrite may reveal previously unrecognized physiologic effects of red wine in connection with *NO bioactivity.

N-nitrosamine generation from ingested nitrate via nitric oxide in subjects with and without gastroesophageal reflux

BACKGROUND & AIMS

Nitrate ingestion leads to high luminal concentrations of nitric oxide being generated where saliva meets gastric acid. Nitric oxide generates N-nitrosative stress on reacting with oxygen at neutral pH. We aimed to ascertain if luminal nitric oxide exerts nitrosative stress in the human upper gastrointestinal tract, and to assess the influence of acid reflux on this phenomenon.

METHODS

A silicone tube, segmented every 15 mm and containing phosphate buffer pH 7.4 and the secondary amine morpholine, was inserted into the upper gastrointestinal tract of 16 healthy volunteers and 16 Barrett's esophagus patients. The tube wall has the same permeability properties as an epithelial lipid membrane, allowing passage of gases such as nitric oxide, but not hydrogen ions. After 2 hours, the tube was removed and the concentrations of nitrite and N-nitrosomorpholine in each segment were measured. Healthy volunteers were studied with and without ingestion of (15)N-enriched nitrate and Barrett's esophagus patients were studied with and without stimulation of acid reflux.

RESULTS

In healthy volunteers, N-nitrosomorpholine was generated in the tube sections exposed to gastric acid and increased 2-fold after nitrate. The N-nitrosomorpholine was 77% enriched with (15)N, confirming its source was the ingested nitrate. In the Barrett's patients, generation of N-nitrosomorpholine was shifted proximally with 80% of nitrosative stress occurring within the esophagus during periods of acid reflux.

CONCLUSIONS

This study demonstrates the in situ formation of N-nitrosamine from dietary nitrate via nitric oxide. During acid reflux, nitrosative stress occurs almost entirely within the esophagus and may contribute toward carcinogenesis at this site.

Role of the anion nitrite in ischemia-reperfusion cytoprotection and therapeutics

The anion nitrite (NO(2)(-)) constitutes a biochemical reservoir for nitric oxide (NO). Nitrite reduction to NO may be catalyzed by hemoglobin, myoglobin or other metal-containing enzymes and occurs at increasing rates under conditions of physiologic hypoxia or ischemia. A number of laboratories have now demonstrated in animal models the ability of nitrite to provide potent cytoprotection following focal ischemia-reperfusion (IR) injury of the heart, liver, brain, and kidney. While the mechanism of nitrite-mediated cytoprotection remains to be fully characterized, the release of nitrite-derived NO following IR appears to be central to this mechanism. The evidence of nitrite-mediated cytoprotection against IR injury in multiple animal models opens the door to potential therapeutic opportunities in human disease. Here we review the mechanisms for nitrite formation in blood and tissue, its metabolic equilibrium with NO, nitrate, and NO-modified proteins, the evidence supporting nitrite-mediated cytoprotection, and the potential mechanisms driving cytoprotection, and we explore the opportunities for the therapeutic application of nitrite for human disease.

Review article: proton pump inhibitors and bacterial overgrowth

Proton pump inhibitors are potent drugs producing profound suppression of gastric acid secretion. Consequently, they are highly effective at treating acid-related disorders. There have been concerns that the suppression of gastric acid will alter the bacterial flora of the upper gastrointestinal tract and lead to complications such as cancer, enteric or other infections and malabsorption. Studies have confirmed that proton pump inhibitors do alter the bacterial population but present evidence indicates that this only rarely leads to clinical disease. As with all drugs, proton pump inhibitors should only be used for disorders shown clearly to benefit from the therapy and where the benefits will outweigh the small risks associated with them. Further research to more fully quantify the risk associated with PPI therapy is required.

Cancer of the gastric cardia

Current evidence indicates that cardia cancers are of at least two distinct and disparate aetiologies. One type resembles cancer of the more distal stomach (Type A), being a consequence of atrophic gastritis due to Helicobacter pylori infection or more rarely autoimmune atrophic gastritis. Another type (Type B) resembles oesophageal adenocarcinoma and is likely to be a consequence of short-segment gastro-oesophageal reflux disease. The two cancers are themselves indistinguishable but examination of the gastric phenotype indicates the aetiology: Type A occurring in patients with evidence of atrophic gastritis whereas Type B occurs in subjects with healthy acid secreting stomachs. In subjects with healthy acid secreting stomachs the cardia has a specific luminal chemistry remaining highly acidic and unbuffered following a meal and having very active nitrosative chemistry due to the acidification of nitrite in saliva. This luminal chemistry may contribute to the high incidence of metaplasia and neoplasia at this anatomical site.

Gastric juice: a barrier against infectious diseases

All vertebrates produce gastric acid. Its main function is inactivation of ingested microorganisms. The majority of microbiological pathogens ingested never reaches the intestine because of the gastric barrier. Although gastric hypochlorhydria is fairly common due to atrophic gastritis, gastric surgery or use of inhibitors of gastric acid secretion, the resulting susceptibility to infection has not been studied extensively. Drug-induced blockade of acid secretion leads to gastrointestinal bacterial overgrowth; the clinical significance of this is still controversial. Gastric acidity is known to protect against non-typhoid salmonellosis and cholera and it is suspected that it protects against several parasitic diseases as giardiasis and strongyloides. There is a lack of studies focusing on the impact of the gastric acidic barrier on viral infections. Concerning prion infections only a single study has been performed, demonstrating a possible role of gastric acidity in the protection against foodborne prion disease in mice. The combination of malnutrition and hypochlorhydria may contribute to the high prevalence of gastrointestinal infections in developing countries. Further studies are needed to evaluate the clinical consequences of impaired gastric acidity with respect to susceptibility to infections.

Proton pump inhibitors reduce the bioavailability of dietary vitamin C

BACKGROUND

The gastric juice concentration of vitamin C is reduced in subjects with elevated intragastric pH. This is probably because of the fact that the vitamin is unstable at non-acidic pH and undergoes irreversible denaturation.

AIM

To determine whether elevation of intragastric pH reduces the bioavailability of dietary vitamin C.

METHODS

Plasma vitamin C was measured before and after a course of omeprazole 40 mg/day for 4 weeks in 14 Helicobacter pylori positive and 15 H. pylori negative subjects. Dietary intake of vitamin C was measured and intragastric pH monitored.

RESULTS

Compared with the H. pylori negative subjects, H. pylori positive subjects had a lower mean daily vitamin C intake (141.7 mg vs. 41.5 mg, P < 0.01) and also lower plasma vitamin C concentration (25.1 microg/mL vs. 17.4 microg/mL, P < 0.0001). After 28 days of 40 mg/day of omeprazole the mean plasma vitamin C level had fallen by 12.3% (P = 0.04). This fall affected both the H. pylori positive and negative subjects.

CONCLUSIONS

We have shown that a short course of omeprazole will cause a reduction in the plasma vitamin C level of healthy volunteers. This decrease in plasma vitamin C is independent of dietary intake of the vitamin and indicates reduced bioavailability. The clinical significance of this is unclear but any adverse effects will be most apparent in H. pylori infected subjects who have a low pre-treatment vitamin C status.

Efeito da administração de vitamina C sobre a colonização do estômago por Helicobacter pylori

RACIONAL: O tratamento convencional de Helicobacter pylori consiste na utilização de antimicrobianos, aos quais uma minoria expressiva de pacientes não responde. Tratamentos alternativos para a infecção têm sido propostos, incluindo o uso de antioxidantes. Destaque crescente tem sido atribuído à vitamina C ao se demonstrar que concentrações da mesma no estômago de indivíduos infectados com H. pylori são substancialmente menores do que as de indivíduos saudáveis. Doses farmacológicas de vitamina C foram investigadas na erradicação de H. pylori com resultados controversos. OBJETIVO: Avaliar o efeito da administração via oral de vitamina C sobre a colonização de estômago por H. pylori em pacientes infectados, com gastrite crônica ou com úlcera péptica cujos tratamentos convencionais não resultaram em erradicação. MATERIAL E MÉTODOS: Protocolo I: estudo aleatório, duplo-cego, controlado por placebo em pacientes com gastrite crônica, sem tratamento prévio para a infecção. Protocolo II: estudo aberto, não controlado em pacientes com úlcera péptica e pelo menos dois tratamentos prévios de erradicação. O tratamento consistiu em vitamina C 5 g/dia durante 28 dias consecutivos. Seu efeito foi avaliado pelo teste respiratório com 14C-uréia quanto à taxa de erradicação, à variação de radioatividade e à supressão da infecção. RESULTADOS: No protocolo I, 38 pacientes completaram o estudo, 21 recebendo vitamina C e 17 recebendo placebo durante 28 dias. A taxa de erradicação "por protocolo" com vitamina C foi zero, intervalo de confiança de 95%: 0%-15%. No protocolo II, oito pacientes completaram o tratamento. A taxa de erradicação foi zero, com intervalo de confiança de 95%: 05-32%. Não houve diminuição da carga bacteriana. CONCLUSÕES: A administração de vitamina C na dosagem diária de 5 g durante 28 dias não é eficaz na erradicação de infecção por H. pylori, nem altera quantitativamente sua carga no estômago dos pacientes infectados.

Apples increase nitric oxide production by human saliva at the acidic pH of the stomach: a new biological function for polyphenols with a catechol group?

Dietary inorganic nitrate is secreted in saliva and reduced to nitrite by bacterial flora. At the acidic pH of the stomach nitrite is present as nitrous acid in equilibrium with nitric oxide (*NO), and other nitrogen oxides with nitrating and nitrosating activity. *NO in the stomach exerts several beneficial effects, but nitrosating/nitrating species have been implicated as a possible cause of epithelial neoplasia at the gastroesophageal junction. We investigated the effects of apple extracts on *NO release by human saliva at pH 2. A water extract obtained from apple homogenate increased *NO release caused by acidification of saliva. Data show that polyphenols were responsible for this activity, with chlorogenic acid and (+)-catechin the most active and concentrated species. However, ferulic acid, a hydroxycinnamic acid with only one aromatic hydroxyl group, did not increase *NO release. Fructose, the most representative sugar in apples, was also inactive. Interestingly, ascorbic acid in saliva induced a SCN(-)-enhanced burst of *NO but, unlike apple, the release was transient. The simultaneous addition of ascorbic acid and apple extract caused a burst of *NO followed by the increased steady-state level characteristic of saliva containing apple extract. Chlorogenic acid and (+)-catechin, but not ferulic acid, formed o-semiquinone radicals and nitrated polyphenols, suggesting the scavenging of *NO(2) by o-semiquinones. Our results propose that some apple polyphenols not only inhibit nitrosation/nitration but also promote *NO bio-availabilty at the gastric level, a previously unappreciated function.

Nitrite is an alternative source of NO in vivo

In this study, we investigated whether orally administered nitrite is changed to NO and whether nitrite attenuates hypertension in a dose-dependent manner. We utilized a stable isotope of [15N]nitrite (15NO2−) as a source of nitrite to distinguish between endogenous nitrite and that exogenously administered and measured hemoglobin (Hb)-NO as an index of circulating NO in whole blood using electron paramagnetic resonance (EPR) spectroscopy. When 1 mg/kg Na15NO2was orally administered to rats, an apparent EPR signal derived from Hb15NO ( AZ= 23.4 gauss) appeared in the blood. The peak blood HbNO concentration occurred at the first measurement after intake (5 min) for treatment with 1 and 3 mg/kg (HbNO: 4.93 ± 0.52 and 10.58 ± 0.40 μM, respectively) and at 15 min with 10 mg/kg (HbNO: 38.27 ± 9.23 μM). In addition, coadministration of nitrite (100 mg/l drinking water) with Nω-nitro-l-arginine methyl ester (l-NAME; 1 g/l) for 3 wk significantly attenuated the l-NAME-induced hypertension (149 ± 10 mmHg) compared with l-NAME alone (170 ± 13 mmHg). Furthermore, this phenomenon was associated with an increase in circulating HbNO. Our findings clearly indicate that orally ingested nitrite can be an alternative to l-arginine as a source of NO in vivo and may explain, at least in part, the mechanism of the nitrite/nitrate-rich Dietary Approaches to Stop Hypertension diet-induced hypotensive effects.

Molecular characterization of rat gastric mucosal response to potent acid inhibition

Potent acid inhibition with proton pump inhibitors (PPIs) is widely used in clinical medicine, especially for gastroesophageal reflux disease. PPIs cause profound changes in the intragastric environment with near-neutral pH and increase serum concentration of the gastric secretagogue hormone gastrin. Long-term hypergastrinemia increases mucosal thickness and enterochromaffin-like cell density in gastric corpus mucosa and results in development of gastric carcinoids in experimental animals. Our aim was to study responses to potent acid inhibition by characterizing genome-wide gene expression changes in gastric corpus mucosa in rats dosed with the PPI omeprazole. Nine rats received 400 micromol/kg omeprazole daily for 10 wk. Seven rats received vehicle only. Analysis of gastric corpus with microarrays representing 11,848 genes identified 134 genes with changed gene expression levels in omeprazole-dosed rats. Several of the identified genes were previously known to be affected by potent acid inhibition. Of the 62 genes with known functions that changed gene expression levels after PPI dosing, 27 are known to be involved in proliferation and apoptosis and immune, inflammatory, and stress responses. Our study indicates that microarray analysis can detect relevant gene expression changes in the complex gastric tissue, and that cellular processes involved in cell growth and defense responses are strongly affected by PPI dosing. Many genes are identified that were not previously known to be affected by inhibition of gastric acid secretion or that have unknown biological functions. Characterization of the roles of these genes may give new insight into molecular responses to treatment with PPIs.

Effect of the H, K-ATPase inhibitor, esomeprazole magnesium, on gut total antioxidant capacity in mice

Antioxidant depletion is believed to be a mechanism involved in the pathophysiology of several upper gastrointestinal disorders, and H, K-ATPase inhibitors can alter free radical production by neutrophils. We hypothesized that the H, K-ATPase inhibitor esomeprazole magnesium would decrease gut free radical production with a concomitant increase in gut total antioxidant capacity. A/J mice (n = 10/group) received either vehicle (control) or one of three concentrations of esomeprazole magnesium in vehicle by once-daily gavage for 10 days. Using tissue extracts from stomach and colon, total antioxidant capacity, lipid peroxide levels, and constitutive Cu/Zn-superoxide dismutase were measured using validated assays. There was a dose-related increase in total antioxidant capacity (analysis of variance, P < 0.001) in stomach, but there was no change in the colon. In the assessment of free radical production, there was a trend toward decreased lipid peroxide levels in stomach from mice receiving esomeprazole. In stomach, Cu/Zn-superoxide dismutase activity was increased (ANOVA: p=.03) in mice receiving esomeprazole. In conclusion, gastric total antioxidant capacity and Cu/Zn-superoxide dismutase activity are increased by esomeprazole, and these changes may result in part from decreased free radical production. The present results support the notion that the pharmacological effects of this agent on upper intestinal tissue are more complex than previously thought, and appear to involve both enzymatic and nonenzymatic tissue antioxidants.

Effects of esomeprazole magnesium on nonsteroidal anti-inflammatory drug gastropathy

It has been proposed that tissue damage induced by nonsteroidal anti-inflammatory drugs is related to increased tissue free radical production with antioxidant depletion. We have shown that esomeprazole increases gastric total antioxidant capacity in mice and, therefore, hypothesized that the protective effect of esomeprazole during treatment with a nonsteroidal anti-inflammatory drug is related to increased gastric antioxidant capacity and decreased tissue free radical production. A/J mice received one of four treatments by daily gavage: saline in vehicle (control), indomethacin, esomeprazole, or indomethacin and esomeprazole. After 10 days, all mice were sacrificed and validated assays were used to measure gastric total antioxidant capacity, lipid peroxide levels, and myeloperoxidase activity. Indomethacin-treated mice developed weight loss and melena. No mice receiving indomethacin and esomeprazole died, but the death rate while receiving indomethacin was 38% (chi2, P = 0.05). Gastric lipid peroxide levels increased in mice receiving indomethacin treatment compared to treatment with esomeprazole and indomethacin (P = 0.03). There was a strong trend (P = 0.08) toward increased gastric total antioxidant capacity in mice receiving esomeprazole and indomethacin compared to mice receiving indomethacin. Gastric myeloperoxidase activities were not different among the four groups. Esomeprazole significantly improved survival in mice that received indomethacin, reduced free radical production, as estimated by lipid peroxide levels, and appeared to increase gastric total antioxidant capacity. The mechanisms for the beneficial effects of esomeprazole in the treatment of gastropathy are more complex than previously thought.

Helicobacter pylori infection and increased nitrite synthesis in the stomach. Inflammation and atrophy connections

BACKGROUND

We have previously shown that the nitrite content in the gastric juice of Helicobacter pylori-positive patients is significantly higher than that of H. pylori-negative patients and it decreases after eradication of H. pylori.

AIM

To examine the relationship between the nitric oxide synthesis in the gastric lumen and histological findings.

METHODS

Eighty-five middle aged Japanese patients were studied. Four specimens, each obtained from the greater and lesser curvature of antrum and gastric body were processed for the determination of histopathological scores using the updated Sydney System. Gastric juice was collected endoscopically to determine the concentration of nitrite using a modified Griess reaction.

RESULTS

There was a significant positive correlation between the nitrite and the pH levels (r = 0.81, P < 0.001) and between the pH levels and the histopathological scores in the corpus. The gastric juice pH and concentration of the nitrite increased in patients with histological diagnosis of normal, antral-predominant gastritis, pangastritis and corpus-predominant gastritis in due order.

CONCLUSIONS

H. pylori infection effects nitric oxide synthesis in the gastric lumen which is mainly connected with hypoacidity. The gastric juice pH is one of the useful markers for corpus dominant gastritis and probably for high-risk group of gastric cancer.

Intragastric formation and modulation of N-nitrosodimethylamine in a dynamic in vitro gastrointestinal model under human physiological conditions

Human exposure to carcinogenic N-alkylnitrosamines can occur exogenously via food consumption or endogenously by formation of these compounds through nitrosation of amine precursors. Information on the intragastric formation of NDMA from complex mixtures of precursors and inhibitors in humans is not available. In this study the formation of N-nitrosodimethylamine (NDMA) has been quantitatively analysed in a dynamic in vitro gastrointestinal model, in which gastric conditions can be modulated and closely simulates the physiological situation in humans. Substantial amounts of NDMA were produced when nitrite and dimethylamine or codfish were simultaneously introduced into the model. However, humans are gradually exposed to nitrite by the intake of nitrate-containing food. Nitrate secreted in saliva is converted to nitrite by oral bacteria. To mimic the human exposure to nitrite in a realistic way, nitrite was gradually added into the gastric compartment, simulating the swallowing of nitrite containing oral fluid after the intake of nitrate at the level of 0.1-10 times the ADI. Under these conditions, the cumulative amounts of NDMA formed were 2.3-422 microg NDMA and 1.8-42.7 microg NDMA at a rapid and slow gastric pH decrease, respectively. Beside codfish, various fish species and batches in combination with nitrite, simulating the intake of for times the ADI of nitrate, were investigated. Herring, pollack and plaice were also able to induce NDMA formation. Mackerel, salmon and pike perch did not result in increased NDMA formation. Furthermore, the effect of nitrosation modulators on NDMA formation was investigated. Thiocyanate (2 mM) increased NDMA formation, but the increase was not statistically significant. In contrast, orange jus and tea effectively, but not totally, reduced the amount of NDMA formed in the gastric compartment. These experiments show that (1). the dynamic in vitro gastrointestinal model is an appropriate tool for mechanistic studies on the intragastric formation of nitrosamines, and (2). that the results obtained with this model are helpful in evaluating human cancer risk for the combined intake of codfish-like fish species and nitrate-containing vegetables.