Multi-parametric approach to identify coffee components that regulate mechanisms of gastric acid secretion

Extracellular Vesicles and Particles Modulate Proton Secretion in a Model of Human Parietal Cells

The secretion of extracellular vesicles and particles (EVPs) is an important mechanism of cellular communication. In this work, we demonstrate a functional role of EVPs in mechanisms regulating gastric acid secretion. HGT-1 cells were used as a model system to assess proton secretion. First, in order to prove EVP secretion by HGT-1 cells, EVPs were isolated by size exclusion chromatography and characterized by nanoparticle tracking analysis, Western blot, and cryo transmission electron microscopy. For examination of the potential role of EVPs in proton secretion, HGT-1 cells were treated with pharmacological EV-inhibitors, resulting in a reduction of histamine-induced proton secretion. To demonstrate the functional role of EVPs in the mechanism of proton secretion, EVP-conditioned supernatant was collected after stimulation of HGT-1 cells with histamine, fractionated, and subjected to an activity screening. The results revealed constituents of the HGT-1-derived secretome with an MW of >100 kDa (including EVPs) to modulate proton secretion, while smaller constituents had no effect. Finally, a dose-dependent modulatory effect on proton secretion of HGT-1 cells was demonstrated by isolated HGT-1-derived EVPs. Hence, this study presents first results on the potential function of EVPs as a previously undiscovered mechanism of regulation of gastric acid secretion by parietal cells.

The magical smell and taste: Can coffee be good to patients with cardiometabolic disease?

Coffee is a beverage consumed globally. Although few studies have indicated adverse effects, it is typically a beneficial health-promoting agent in a range of diseases, including depression, diabetes, cardiovascular disease, and obesity. Coffee is rich in caffeine, antioxidants, and phenolic compounds, which can modulate the composition of the gut microbiota and mitigate both inflammation and oxidative stress, common features of the burden of lifestyle diseases. This review will discuss the possible benefits of coffee on complications present in patients with diabetes, cardiovascular disease and chronic kidney disease, outwith the social and emotional benefits attributed to caffeine consumption.

Effect of Dewaxed Coffee on Gastroesophageal Symptoms in Patients with GERD: A Randomized Pilot Study

Gastroesophageal Reflux Disease (GERD) is multifactorial pathogenesis characterized by the abnormal reflux of stomach contents into the esophagus. Symptoms are worse after the ingestion of certain foods, such as coffee. Hence, a randomized pilot study conducted on 40 Italian subjects was assessed to verify the effect of standard (SC) and dewaxed coffee (DC) consumption on gastroesophageal reflux symptoms and quality of life in patients with gastrointestinal diseases. The assessment of patient diaries highlighted a significant percentage reduction of symptoms frequency when consuming DC and a significant increase in both heartburn-free and regurgitation-free days. Consequentially, patients had a significant increase of antacid-free days during the DC assumption. Moreover, the polyphenolic profile of coffee pods was ascertained through UHPLC-Q-Orbitrap HRMS analysis. Chlorogenic acids (CGAs) were the most abundant investigated compounds with a concentration level ranging between 7.316 (DC) and 6.721 mg/g (SC). Apart from CGAs, caffeine was quantified at a concentration level of 5.691 mg/g and 11.091 for DC and SC, respectively. While still preliminary, data obtained from the present pilot study provide promising evidence for the efficacy of DC consumption in patients with GERD. Therefore, this treatment might represent a feasible way to make coffee more digestible and better tolerated.

Effects of Coffee on the Gastro-Intestinal Tract: A Narrative Review and Literature Update

The objective of the present research was to review the state of the art on the consequences of drinking coffee at the different levels of the gastrointestinal tract. At some steps of the digestive process, the effects of coffee consumption seem rather clear. This is the case for the stimulation of gastric acid secretion, the stimulation of biliary and pancreatic secretion, the reduction of gallstone risk, the stimulation of colic motility, and changes in the composition of gut microbiota. Other aspects are still controversial, such as the possibility for coffee to affect gastro-esophageal reflux, peptic ulcers, and intestinal inflammatory diseases. This review also includes a brief summary on the lack of association between coffee consumption and cancer of the different digestive organs, and points to the powerful protective effect of coffee against the risk of hepatocellular carcinoma. This review reports the available evidence on different topics and identifies the areas that would most benefit from additional studies.

Astringent Gallic Acid in Red Wine Regulates Mechanisms of Gastric Acid Secretion via Activation of Bitter Taste Sensing Receptor TAS2R4

Red wine is rich in phenolic compounds, which chiefly determine its characteristic taste. One of its major phenolic acid constituents for which an astringency, yet no clear contribution to bitter taste has been reported, is gallic acid (GA). In previous studies, we have demonstrated bitter-tasting constituents to regulate cellular proton secretion (PS) as a key mechanism of gastric acid secretion via activation of bitter taste sensing receptors (TAS2Rs). Here, we hypothesized a contributing role of GA to the red wine-stimulated effect on PS in human gastric tumor cells (HGT-1 cells). Sensory analyses revealed that 10 μM GA as the lowest concentration tested more bitter than tap water, with increasing bitter ratings up to 1000 μM. In HGT-1 cells, the concentration of 10 μM GA evoked the most pronounced effect on PS secretion, either when added to cells as in-water solution or when spiked to a red wine matrix. GA-spiking of Zweigelt and Blaufränkisch red wine samples up to a concentration of 10 μM resulted in an equally stimulated PS, whereas the non-GA-spiked wine samples demonstrated contrary effects on PS, indicating a functional role of GA on PS. Involvement of TAS2R4 in the GA-induced PS was verified by means of an HGT-1 homozygote CRISPR-Cas9 TAS2R4 knockout approach. Moreover, gene expression analyses revealed GA to increase TAS2R4. These results demonstrate a functional role of TAS2R4 in GA-evoked PS as a key mechanism of gastric acid secretion aiding digestion. Moreover, our data provide mechanistic insights, which will help to produce stomach-friendly red wines.

Effects of a non-caffeinated coffee substitute on functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is a debilitating functional gastrointestinal disorder characterized by early satiety, post-prandial fullness or epigastric pain related to meals. FD is diagnosed when organic etiology for the symptoms is not identified. It is widely believed that FD may be linked to the consumption of certain foods. In a clinical setting, it is often recommended that coffee be avoided in patients with FD. The lack of clinical research on non-caffeinated coffee substitute's effects on functional dyspepsia (FD) prompted the need to explore the topic clinically.

AIM

The purpose of this study is to investigate the effect of drinking non-caffeinated coffee substitute on FD symptoms in order to determine if recommending a non-caffeinated coffee substitute in patients with pre-existing FD relieves the patient's symptoms.

METHODS

This is a quantitative study with 51 patients diagnosed with FD. A patient-reported outcomes (PRO) instrument called the Gastrointestinal Symptom Rating Scale (GSRS) was used to determine the results. After the participants enrolled, they completed the pre-GSRS questionnaire. The participants were instructed to stop their daily consumption of caffeinated and/or decaffeinated coffee and replace it with the non-caffeinated coffee substitute. After one month, the participants returned to the physician's office to complete a post intervention GSRS questionnaire.

RESULTS

The Wilcoxon Signed Rank test was used to test for significant change across time. Our study showed a statistically significant decrease from pre-intervention to post-intervention for functional dyspepsia symptoms, (3.67-1.00), p < 0.001.

CONCLUSION

To our knowledge, this study is the first to evaluate whether removing coffee from a person's diet and replacing it with a non-caffeinated coffee substitute would result in the improvement of functional dyspepsia symptoms. Our results indicate that replacing a caffeinated or decaffeinated coffee with a non-caffeinated coffee substitute decreases FD symptoms.

Coffee and Yeasts: From Flavor to Biotechnology

Coffee is one of the most consumed beverages in the world, and its popularity has prompted the necessity to constantly increase the variety and improve the characteristics of coffee as a general commodity. The popularity of coffee as a staple drink has also brought undesired side effects, since coffee production, processing and consumption are all accompanied by impressive quantities of coffee-related wastes which can be a threat to the environment. In this review, we integrated the main studies on fermentative yeasts used in coffee-related industries with emphasis on two different directions: (1) the role of yeast strains in the postharvest processing of coffee, the possibilities to use them as starting cultures for controlled fermentation and their impact on the sensorial quality of processed coffee, and (2) the potential to use yeasts to capitalize on coffee wastes—especially spent coffee grounds—in the form of eco-friendly biomass, biofuel or fine chemical production.

Comprehensive lipid analysis of green Arabica coffee beans by LC-HRMS/MS

Lipids play an important role in coffee bean development, coffee brew and in the effects of coffee on human health. They account for around 17% of the dry bean weight and encompass different classes and subclasses, mostly triacylglycerols (TAG) and a minor quantity of phospholipids (PL) and ^βN-alkanoyl-5-hydroxytryptamides (C-5HT). To comprehensive profile these different lipids, it is important to evaluate extraction methods that provide high lipid coverage and to analyze the lipids in high-resolution techniques. In this work, liquid chromatography-high resolution tandem mass spectrometry (LC-HRMS/MS) was employed to comprehensive profile lipids from green Arabica coffee beans and to evaluate the extraction efficiency and lipid coverage of three methods: Bligh-Dyer (BD), Folch (FO), and Matyash (MA). The MA method yielded the greatest number of annotated compounds (131 lipids) compared to the other methods. In the positive electrospray ionization (ESI) mode, the main difference among extraction methods was observed for TAG and diacylglycerols, whereas for the negative ESI it was observed differences for phosphatidylinositol (PI), lysophosphatidylinositol and phosphatidic acid (p < 0.05). The analysis of coffees from different maturation stages and/or post-harvest processes were also performed using the MA method. Immature beans were discriminated from mature and overripe beans by its lower levels of C-5HT, PI, phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, and lysophosphatidylethanolamine. These results can help to better understand the coffee lipid composition and its association with coffee quality.

Hydrolysis of chlorogenic acid in apple juice using a p-coumaryl esterase of Rhizoctonia solani

BACKGROUND

Apple juice is rich in polyphenolic compounds, especially in chlorogenic acid. A sour and bitter taste has been attributed to the compound. Chlorogenic acid in coffee powder was quickly hydrolysed by a p-coumaryl esterase of Rhizoctonia solani (RspCAE) at its optimal pH of 6.0. It was unknown, however, if RspCAE would also degrade chlorogenic acid under the strongly acidic conditions (pH 3.3) present in apple juice.

RESULTS

Treatment of apple juice with RspCAE led to a chlorogenic acid degradation from 53.38 ± 0.94 mg L^-1 to 21.02 ± 1.47 mg L^-1 . Simultaneously, the caffeic acid content increased from 6.72 ± 0.69 mg L^-1 to 19.33 ± 1.86 mg/L^-1 . The aroma profile of the enzymatically treated sample and a control sample differed in only one volatile. Vitispirane had a higher flavour dilution factor in the treated juice. Sensory analysis showed no significant difference in the taste profile ( p < 0.05).

CONCLUSION

These results demonstrated a high stability and substrate specificity of RspCAE. An increase in caffeic acid and a concurrent decrease in chlorogenic acid concentration may exert a beneficial effect on human health. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Noncaloric Sweeteners Induce Peripheral Serotonin Secretion via the T1R3-Dependent Pathway in Human Gastric Parietal Tumor Cells (HGT-1)

The role of sweet taste in energy intake and satiety regulation is still controversial. Noncaloric artificial sweeteners (NCSs) are thought to help reduce energy intake, although little is known about their impact on the satiating neurotransmitter serotonin (5-HT). In the gastrointestinal (GI) tract, 5-HT regulates gastric acid secretion and gastric motility, both part of the complex network of mechanisms regulating food intake and satiety. This study demonstrated a stimulating impact compared to controls (100%) on 5-HT release in human gastric tumor cells (HGT-1) by the NCSs cyclamate (50 mM, 157% ± 6.3%), acesulfame potassium (Ace K, 50 mM, 197% ± 8.6%), saccharin (50 mM, 147% ± 6.7%), sucralose (50 mM, 194% ± 11%), and neohesperidin dihydrochalcone (NHDC, 1 mM, 201% ± 13%). Although these effects were not associated with the sweet taste intensity of the NCSs tested, involvement of the sweet receptor subunit T1R3 in the NCS-evoked response was demonstrated by mRNA expression of TAS1R3, co-incubation experiments using the T1R3 receptor antagonist lactisole, and a TAS1R3 siRNA knockdown approach. Analysis of the downstream signaling revealed activation of the cAMP/ERK/Ca²⁺ cascade. Co-treatment experiments with 10 mM glucose enhanced the 5-HT release induced by cyclamate, Ace K, saccharin, and sucralose, thereby supporting the enhancing effect of glucose on a NCS-mediated response. Overall, the results obtained identify NCSs as potent inducers of 5-HT release via T1R3 in human gastric parietal cells in culture and warrant in vivo studies to demonstrate their efficacy.

Identification of Bitter-Taste Intensity and Molecular Weight as Amino Acid Determinants for the Stimulating Mechanisms of Gastric Acid Secretion in Human Parietal Cells in Culture

Secretion of gastric acid, aimed at preventing bacterial growth and aiding the digestion of foods in the stomach, is chiefly stimulated by dietary intake of protein and amino acids (AAs). However, AAs' key structural determinants responsible for their effects on mechanisms regulating gastric acid secretion (GAS) have not been identified yet. In this study, AAs have been tested in the parietal cell model HGT-1 on GAS and on mRNA expression of genes regulating GAS. AAs' taste intensities from 0 (not bitter at all) to 10 (very bitter) were assessed in a sensory study, in which ARG (l: 6.42 ± 0.41; d: 4.62 ± 0.59) and ILE (l: 4.21 ± 0.43; d: 2.28 ± 0.33) were identified as bitter-tasting candidates in both isomeric forms. Pearson correlation showed that GAS in HGT-1 cells is directly associated with the bitter taste quality ( r: -0.654) in combination with the molecular weight of l-AA ( r: -0.685).

Human Sweet Receptor T1R3 is Functional in Human Gastric Parietal Tumor Cells (HGT-1) and Modulates Cyclamate and Acesulfame K-Induced Mechanisms of Gastric Acid Secretion

The noncaloric sweeteners (NCSs) cyclamate (Cycl) and acesulfame K (AceK) are widely added to foods and beverages. Little is known about their impact on gastric acid secretion (GAS), which is stimulated by dietary protein and bitter-tasting compounds. Since Cycl and AceK have a bitter off taste in addition to their sweet taste, we hypothesized they modulate mechanisms of GAS in human gastric parietal cells (HGT-1). HGT-1 cells were exposed to sweet tastants (50 mM of glucose, d-threonine, Cycl, or AceK) and analyzed for their intracellular pH index (IPX), as an indicator of proton secretion by means of a pH-sensitive dye, and for mRNA levels of GAS-associated genes by RT-qPCR. Since the NCSs act via the sweet taste-sensing receptor T1R2/T1R3, mRNA expression of the corresponding genes was analyzed in addition to immunocytochemical localization of the T1R2 and T1R3 receptor proteins. Exposure of HGT-1 cells to AceK or d-threonine increased the IPX to 0.60 ± 0.05 and 0.80 ± 0.04 ( P ≤ 0.05), respectively, thereby indicating a reduced secretion of protons, whereas Cycl demonstrated the opposite effect with IPX values of -0.69 ± 0.08 ( P ≤ 0.05) compared to controls (IPX = 0). Cotreatment with the T1R3-inhibitor lactisole as well as a TAS1R3 siRNA knock-down approach reduced the impact of Cycl, AceK, and d-thr on proton release ( P ≤ 0.05), whereas cotreatment with 10 mM glucose enhanced the NCS-induced effect ( P ≤ 0.05). Overall, we demonstrated Cycl and AceK as modulators of proton secretion in HGT-1 cells and identified T1R3 as a key element in this response.

Enzymatic mitigation of 5-O-chlorogenic acid for an improved digestibility of coffee

A p-coumaroyl esterase from Rhizoctonia solani was used to decrease 5-O-chlorogenic acid (5-CQA) content in coffee powder. HPLC-UV showed a decline of up to 98% of 5-CQA after the enzyme treatment. Effects on aroma were determined by means of aroma extract dilution analysis. Flavour dilution factors of treated and control extract differed in four volatile compounds only. Effect on aroma and taste was evaluated by sensory tests. No significant differences were perceived, and no off-flavour nor off-taste was noted. As chlorogenic acids are suspected to cause stomach irritating effects in sensitive people, the enzyme treatment offers a technically feasible approach to improve the quality of coffee beverages by reducing 5-CQA concentration without significantly affecting the aroma and taste profile.

Characterization of Bitter Compounds via Modulation of Proton Secretion in Human Gastric Parietal Cells in Culture

Humans perceive bitterness via around 25 different bitter receptors. Therefore, the identification of antagonists remains a complex challenge. We previously demonstrated several bitter-tasting compounds such as caffeine to induce acid secretion in the stomach and in a human gastric tumor cell line (HGT-1). Here, the results of a fluorescent-based in vitro assay using HGT-1 cells and a human sensory panel testing nine selected potential bitter modulators, with or without the bitter compounds caffeine or theobromine, were compared. Of the bitter-modulating compounds tested, eriodictyol, matairesinol, enterolacton, lariciresinol, and homoeriodictyol reduced the effect of caffeine on proton secretion by -163 ± 14.0, -152 ± 12.4, -74 ± 16.4, -58 ± 7.2, and -44.6 ± 16.5%, respectively, and reduced the bitter intensity of caffeine in the human sensory panel. In contrast, naringenin and 5,7-dihydroxy-4(4-hydroxyphenyl)chroman-2-one neither reduced the caffeine-induced proton secretion in HGT-1 cells nor showed an effect on bitter intensity perceived by the sensory panel. Results for theobromine were not as pronounced as those for caffeine, but followed a similar trend. The results demonstrate that the HGT-1 in vitro assay is a useful tool to identify potential bitter-masking compounds. Nevertheless, a sensory human panel is necessary to quantify the bitter-masking potency.

Acute effects of coffee consumption on self-reported gastrointestinal symptoms, blood pressure and stress indices in healthy individuals

Background

It has been suggested that coffee may affect the gut-brain axis with conflicting outcomes. Moreover, there is insufficient evidence to determine whether the type or temperature of coffee consumed will have a different impact on the gut-brain axis. The purpose of this study was to investigate the effects of acute coffee consumption on the following: 1. self-reported GI symptoms and salivary gastrin, 2. stress indices [salivary cortisol and alpha-amylase (sAA)] and psychometric measures, and 3. blood pressure (BP), in healthy, daily coffee consuming individuals in non-stressful conditions.

Methods

This was a randomized, double blind, crossover clinical trial, in which 40 healthy individuals (20 men, 20 women), 20–55 years of age, randomly consumed four 200 ml coffee beverages containing 160 mg caffeine (hot and cold instant coffee, cold espresso, hot filtered coffee), 1 week apart. Salivary samples and psychometric questionnaires were collected at baseline and post-coffee consumption at 15,30, and 60 min for salivary gastrin and sAA measurements and at 60,120, and 180 min for cortisol measurements. BP was measured at beginning and end of each intervention. ClinicalTrials.gov ID: NCT02253628

Results

Coffee consumption significantly increased sAA activity (P = 0.041), with significant differences only between cold instant and filter coffee at 15 and 30 min post-consumption (P < 0.05). Coffee temporarily increased salivary gastrin, without differences between coffee types. Coffee did not affect salivary cortisol or self-reported anxiety levels. Coffee consumption significantly increased BP, within the healthy physiological levels, in a gender specific manner at the end of the experimental periods, without differences between coffee types.

Conclusion

Acute coffee consumption in non-stressful conditions activated sAA and BP but not salivary cortisol, indicating activation of the sympathetic nervous system. Post-coffee sAA increase without a concomitant cortisol increase may also indicate that coffee may have some anti-stress properties.

Identification of Catechin, Syringic Acid, and Procyanidin B2 in Wine as Stimulants of Gastric Acid Secretion

Organic acids of wine, in addition to ethanol, have been identified as stimulants of gastric acid secretion. This study characterized the influence of other wine compounds, particularly phenolic compounds, on proton secretion. Forty wine parameters were determined in four red wines and six white wines, including the contents of organic acids and phenolic compounds. The secretory activity of the wines was determined in a gastric cell culture model (HGT-1 cells) by means of a pH-sensitive fluorescent dye. Red wines stimulated proton secretion more than white wines. Lactic acid and the phenolic compounds syringic acid, catechin, and procyanidin B2 stimulated proton secretion and correlated with the pro-secretory effect of the wines. Addition of the phenolic compounds to the least active white wine sample enhanced its proton secretory effect by 65 ± 21% (p < 0.05). These results indicate that not only malic and lactic acid but also bitter and astringent tasting phenolic compounds in wine contribute to its stimulatory effect on gastric acid secretion.

N(ε)-Carboxymethyllysine (CML), a Maillard reaction product, stimulates serotonin release and activates the receptor for advanced glycation end products (RAGE) in SH-SY5Y cells

Maillard reaction products, which are formed in highly thermally treated foods, are commonly consumed in a Western diet. In this study, we investigated the impact of N(ε)-carboxymethyllysine (CML), a well-characterized product of the Maillard reaction, on the gene regulation of the human neuroblastoma cell line SH-SY5Y. Pathway analysis of data generated from customized DNA microarrays revealed 3 h incubation with 50 μM and 500 μM CML to affect serotonin receptor expression. Further experiments employing qRT-PCR showed an up-regulation of serotonin receptors 2A, 1A and 1B after 0.25 h and 3 h. In addition, 500 μM CML increased serotonin release, thus showing effects of CML not only at a genetic, but also at a functional level. Intracellular calcium mobilization, which mediates serotonin release, was increased by CML at concentrations of 0.05-500 μM. Since calcium mobilization has been linked to the activation of the receptor for advanced glycation end products (RAGE), we further investigated the effects of CML on RAGE expression. RAGE was found to be up-regulated after incubation with 500 μM CML for 0.25 h. Co-incubation with the calcium blocker neomycin for 0.25 h blocked the up-regulation of RAGE and the serotonin receptors 2A, 1A and 1B. These results indicate a possible link between a CML-induced calcium-mediated serotonin release and RAGE.

Coffee polyphenols change the expression of STAT5B and ATF-2 modifying cyclin D1 levels in cancer cells

Background. Epidemiological studies suggest that coffee consumption reduces the risk of cancer, but the molecular mechanisms of its chemopreventive effects remain unknown. Objective. To identify differentially expressed genes upon incubation of HT29 colon cancer cells with instant caffeinated coffee (ICC) or caffeic acid (CA) using whole-genome microarrays. Results. ICC incubation of HT29 cells caused the overexpression of 57 genes and the underexpression of 161, while CA incubation induced the overexpression of 12 genes and the underexpression of 32. Using Venn-Diagrams, we built a list of five overexpressed genes and twelve underexpressed genes in common between the two experimental conditions. This list was used to generate a biological association network in which STAT5B and ATF-2 appeared as highly interconnected nodes. STAT5B overexpression was confirmed at the mRNA and protein levels. For ATF-2, the changes in mRNA levels were confirmed for both ICC and CA, whereas the decrease in protein levels was only observed in CA-treated cells. The levels of cyclin D1, a target gene for both STAT5B and ATF-2, were downregulated by CA in colon cancer cells and by ICC and CA in breast cancer cells. Conclusions. Coffee polyphenols are able to affect cyclin D1 expression in cancer cells through the modulation of STAT5B and ATF-2.

Identification of organic acids in wine that stimulate mechanisms of gastric acid secretion

Wine may cause stomach irritation due to its stimulatory effect on gastric acid secretion, although the mechanisms by which wine or components thereof activate pathways of gastric acid secretion are poorly understood. Gastric pH was measured with a noninvasive intragastric probe, demonstrating that administration of 125 mL of white or red wine to healthy volunteers stimulated gastric acid secretion more potently than the administration of equivalent amounts of ethanol. Between both beverages, red wine showed a clear trend for being more active in stimulating gastric acid secretion than white wine (p = 0.054). Quantification of the intracellular proton concentration in human gastric tumor cells (HGT-1), a well-established indicator of proton secretion and, in turn, stomach acid formation in vivo, confirmed the stronger effect of red wine as compared to white wine. RT-qPCR experiments on cells exposed to red wine also revealed a more pronounced effect than white wine on the fold change expression of genes associated with gastric acid secretion. Of the quantitatively abundant organic acids in wine, malic acid and succinic acid most actively stimulated proton secretion in vitro. However, addition of ethanol to individual organic acids attenuated the secretory effect of tartaric acid, but not that of the other organic acids. It was concluded that malic acid for white wine and succinic acid for red wine are key organic acids that contribute to gastric acid stimulation.

Identification of beer bitter acids regulating mechanisms of gastric acid secretion

Beer, one of the most consumed beverages worldwide, has been shown to stimulate gastric acid secretion. Although organic acids, formed by fermentation of glucose, are known to be stimulants of gastric acid secretion, very little is known about the effects of different types of beer or the active constituents thereof. In the present study, we compared the effects of different beers on mechanisms of gastric acid secretion. To investigate compound-specific effects on mechanisms of gastric acid secretion, organic acids and bitter compounds were quantified by HPLC-DAD and UPLC-MS/MS and tested in human gastric cancer cells (HGT-1) by means of a pH-sensitive fluorescent dye which determines the intracellular pH as an indicator of proton secretion. The expression of relevant genes, coding the H(+)/K(+)-ATPase, ATP4A, the histamine receptor, HRH2, the acetylcholine receptor, CHRM3, and the somatostatin receptor, SSTR2, was determined by qPCR. Ethanol and the organic acids succinic acid, malic acid, and citric acid were demonstrated to contribute to some extent to the effect of beer. The bitter acids comprising α-, β-, and iso-α-acids were identified as potential key components promoting gastric acid secretion and up-regulation of CHRM3 gene expression by a maximum factor of 2.01 compared to that of untreated control cells with a correlation to their respective bitterness.