Roles and action mechanisms of bile acid-induced gastric intestinal metaplasia: a review

GATA4 Forms a Positive Feedback Loop with CDX2 to Transactivate MUC2 in Bile Acids-Induced Gastric Intestinal Metaplasia

Background/Aims

Gastric intestinal metaplasia (GIM), a common precancerous lesion of gastric cancer, can be caused by bile acid reflux. GATA binding protein 4 (GATA4) is an intestinal transcription factor involved in the progression of gastric cancer. However, the expression and regulation of GATA4 in GIM has not been clarified.

Methods

The expression of GATA4 in bile acid-induced cell models and human specimens was examined. The transcriptional regulation of GATA4 was investigated by chromatin immunoprecipitation and luciferase reporter gene analysis. An animal model of duodenogastric reflux was used to confirm the regulation of GATA4 and its target genes by bile acids.

Results

GATA4 expression was elevated in bile acid-induced GIM and human specimens. GATA4 bound to the promoter of mucin 2 (MUC2) and stimulate its transcription. GATA4 and MUC2 expression was positively correlated in GIM tissues. Nuclear transcription factor-κB activation was required for the upregulation of GATA4 and MUC2 in bile acid-induced GIM cell models. GATA4 and caudal-related homeobox 2 (CDX2) reciprocally transactivated each other to drive the transcription of MUC2. In chenodeoxycholic acid-treated mice, MUC2, CDX2, GATA4, p50, and p65 expression levels were increased in the gastric mucosa.

Conclusions

GATA4 is upregulated and can form a positive feedback loop with CDX2 to transactivate MUC2 in GIM. NF-κB signaling is involved in the upregulation of GATA4 by chenodeoxycholic acid.

Effect of bile reflux on gastric juice microbiota in patients with different histology phenotypes

BACKGROUND/AIMS

Bile reflux (BR) can influence the gastric environment by altering gastric acidity and possibly the gastric microbiota composition. This study investigated the correlation between bile acids and microbial compositions in the gastric juice of 50 subjects with differing gastric pathologies.

METHODS

This study included 50 subjects, which were categorized into three groups based on the endoscopic BR grading system. The primary and secondary bile acid concentrations in gastric juice samples were measured, and microbiota profiling was conducted using 16 S rRNA gene sequencing.

RESULTS

Significant differences were observed in each bile acid level in the three endoscopic BR groups (P < 0.05). The Shannon index demonstrated a significant decrease in the higher BR groups (P < 0.05). Analysis of the β-diversity revealed that BR significantly altered the gastric microbiota composition. The presence of neoplastic lesions and the presence of H. pylori infection impacted the β-diversity of the gastric juice microbiota. The abundance of the Streptococcus and Lancefielfdella genera exhibited positive correlations for almost all bile acid components(P < 0.05). In addition, the abundance of Slobacterium, Veillonella, and Schaalia showed positive correlations with primary unconjugated bile acids (P < 0.05).

CONCLUSION

Changes in microbial diversity in the gastric juice were associated with BR presence in the stomach. This result suggests that the degree of BR should be considered when studying the gastric juice microbiome.

Exploration of gastric carcinogenesis from the relationship between bile acids and intestinal metaplasia and intragastric microorganisms (H. pylori and non-H. pylori)

Gastric cancer (GC) is a prevalent form of cancer, with Helicobacter pylori (H. pylori) infection being the most common risk factor. Recent studies have highlighted the role of long-term irritation of the gastric mucosa caused by bile reflux in the development of cancer. Bile acids (BAs), which are a significant component in bile reflux, have the potential to promote gastric carcinogenesis through various mechanisms. These mechanisms include the induction of intestinal metaplasia (IM), inhibition of H. pylori activity, modification of H. pylori colonization, and alteration of the abundance and composition of microorganisms in the stomach. Defining the mechanism of bile acid-induced gastric carcinogenesis could potentially be an effective approach to prevent GC. Hence, this paper aims to review the mechanism of bile acid-induced IM, the association between BAs and H. pylori infection as well as microorganisms in the stomach, and the correlation between BAs and gastric carcinogenesis. The ultimate goal is to elucidate the role of BAs in the development of GC.

Bile Acid Sequestrant Use and Gastric Cancer: A National Retrospective Cohort Analysis

INTRODUCTION

Bile acids have been implicated in gastric carcinogenesis. We hypothesized that bile acid sequestrant medication (BAM) use is associated with a lower gastric cancer (GC) incidence.

METHODS

We assembled a cohort of veterans receiving longitudinal care within the Veterans Health Administration between 2000 and 2020 who completed testing for Helicobacterpylori . The index date was the date of completed H. pylori testing. The primary exposure was the number of filled BAM prescription(s) in the 5 years before the index date. The primary outcome was incident GC, stratified by anatomic subsite. Follow-up began at the index date and ended at the earliest of GC, death, after 2 years of follow-up, or the study end (May 31, 2020). We used Kaplan-Meier curves to visualize differences in GC incidence by exposure group and multivariable Cox proportional hazards models to estimate the association between BAM exposure and anatomic site-specific GC.

RESULTS

Among 417,239 individuals (89% male, mean age 54 years, 63% non-Hispanic White), 4,916 (1.2%) filled at least one BAM prescription, 2,623 of whom filled ≥4. Compared with unexposed individuals, those with ≥4 BAM fills before entry had a lower incidence (adjusted hazard ratio 0.71; 95% confidence interval, 0.37-1.36) of GC, but confidence intervals were wide. Results were consistent irrespective of GC anatomic site.

DISCUSSION

BAMs may have a protective effect against both cardia and noncardia GC. Further research and external validation are needed to confirm these findings.

Role of exosomes in metastasis and therapeutic resistance in esophageal cancer

Esophageal cancer (EC) has a high incidence and mortality rate and is emerging as one of the most common health problems globally. Owing to the lack of sensitive detection methods, uncontrollable rapid metastasis, and pervasive treatment resistance, EC is often diagnosed in advanced stages and is susceptible to local recurrence. Exosomes are important components of intercellular communication and the exosome-mediated crosstalk between the cancer and surrounding cells within the tumor microenvironment plays a crucial role in the metastasis, progression, and therapeutic resistance of EC. Considering the critical role of exosomes in tumor pathogenesis, this review focused on elucidating the impact of exosomes on EC metastasis and therapeutic resistance. Here, we summarized the relevant signaling pathways involved in these processes. In addition, we discussed the potential clinical applications of exosomes for the early diagnosis, prognosis, and treatment of EC.

Endoscopic Transoral Outlet Reduction for the Treatment of Biliary Reflux Symptoms in Patients After One-Anastomosis Gastric Bypass-a Case Series

PURPOSE

OAGB is the third most common bariatric surgery. Biliary reflux (BR) is an inherent complication of this unique anatomy, although there is still controversy regarding its significance and long-term risks including carcinogenesis. To date, there is no effective treatment for BR with conversion to RYGB reserved for refractory patients. TORe is an effective treatment for weight-regain and dumping syndrome after RYGB. We hypothesized that narrowing the anastomosis would decrease the amount of bile refluxate entering the stomach and esophagus in patients with BR symptoms after OAGB and alleviate symptoms. The purpose of this study is to evaluate the efficacy of TORe for the treatment of BR symptoms after OAGB.

MATERIALS AND METHODS

BR was diagnosed clinically in patients after OAGB using the gastroesophageal reflux disease health-related quality of life (GERD-HRQL) instrument after treatment with high-dose proton pump inhibitor (PPI) excluded possible acid reflux. TORe was carried out using a suture pattern that narrowed and elongated the anastomosis. All patients were prospectively followed.

RESULTS

Twelve patients, post-OAGB, underwent TORe for BR. Symptoms resolved in 9 (75%) patients. GERD-HRQL score at 6 months declined from an average of 33.7 (SD 1.9) before the procedure to 16.1 (SD 10, p < 0.001). In one case, a small perforation was identified during the procedure and was immediately sutured with no further sequela.

DISCUSSION

TORe appears a safe and effective treatment for BR symptoms after OAGB, at least in the short term. Accurate tools for BR diagnosis, a larger cohort, and longer follow-up periods are needed to better show the effectiveness and durability of this treatment option.

Diagnostic Principles for Chronic Gastritis Associated with Duodenogastric Reflux

This article systematizes available data from the literature on biliary gastritis (BG) in order to increase the awareness of specialists about the latest possibilities for diagnosing the disease. BG occurs as a result of pathological duodenogastric reflux. In patients with a preserved duodenogastric junction, the dominant factor is represented by motor disorders of the upper digestive tract (primary biliary gastritis), while in patients recovering from surgical interventions it is represented by structural changes (secondary biliary gastritis). Progressive BG can lead to atrophy of the gastric mucosa, intestinal metaplasia, epithelial dysplasia, and eventually to gastric cancer. Diagnostic methods for BG are carried out to identify risk factors, exclude alarm symptoms and identify persistent motor disorders and pathological reflux (24 h pH-impedancemetry, hepatobiliary scintigraphy, 24 h monitoring of bilirubin content in the reflux using a Bilitec 2000 photometer), as well as to diagnose gastritis itself (esophagogastroduodenoscopy, morphological gastrobiopsy examination). The diagnosis of BG should be based on a multidisciplinary approach that combines a thorough analysis of a patient’s complaints, an anamnesis of the disease, and the results of endoscopic and histological research methods.

Diagnostic Principles for Chronic Gastritis Associated with Duodenogastric Reflux

This article systematizes available data from the literature on biliary gastritis (BG) in order to increase the awareness of specialists about the latest possibilities for diagnosing the disease. BG occurs as a result of pathological duodenogastric reflux. In patients with a preserved duodenogastric junction, the dominant factor is represented by motor disorders of the upper digestive tract (primary biliary gastritis), while in patients recovering from surgical interventions it is represented by structural changes (secondary biliary gastritis). Progressive BG can lead to atrophy of the gastric mucosa, intestinal metaplasia, epithelial dysplasia, and eventually to gastric cancer. Diagnostic methods for BG are carried out to identify risk factors, exclude alarm symptoms and identify persistent motor disorders and pathological reflux (24 h pH-impedancemetry, hepatobiliary scintigraphy, 24 h monitoring of bilirubin content in the reflux using a Bilitec 2000 photometer), as well as to diagnose gastritis itself (esophagogastroduodenoscopy, morphological gastrobiopsy examination). The diagnosis of BG should be based on a multidisciplinary approach that combines a thorough analysis of a patient's complaints, an anamnesis of the disease, and the results of endoscopic and histological research methods.

Alteration of gastric microbiota and transcriptome in a rat with gastric intestinal metaplasia induced by deoxycholic acid

Objective

Bile reflux plays a key role in the development of gastric intestinal metaplasia (GIM), an independent risk factor of gastric cancer. Here, we aimed to explore the biological mechanism of GIM induced by bile reflux in a rat model.

Methods

Rats were treated with 2% sodium salicylate and allowed to freely drink 20 mmol/L sodium deoxycholate for 12 weeks, and GIM was confirmed by histopathological analysis. Gastric microbiota was profiled according to the 16S rDNA V3-V4 region, gastric transcriptome was sequenced, and serum bile acids (BAs) were analyzed by targeted metabolomics. Spearman's correlation analysis was used in constructing the network among gastric microbiota, serum BAs, and gene profiles. Real-time polymerase chain reaction (RT-PCR) measured the expression levels of nine genes in the gastric transcriptome.

Results

In the stomach, deoxycholic acid (DCA) decreased the microbial diversity but promoted the abundances of several bacterial genera, such as Limosilactobacillus, Burkholderia-Caballeronia-Paraburkholderia, and Rikenellaceae RC9 gut group. Gastric transcriptome showed that the genes enriched in gastric acid secretion were significantly downregulated, whereas the genes enriched in fat digestion and absorption were obviously upregulated in GIM rats. The GIM rats had four promoted serum BAs, namely cholic acid (CA), DCA, taurocholic acid, and taurodeoxycholic acid. Further correlation analysis showed that the Rikenellaceae RC9 gut group was significantly positively correlated with DCA and RGD1311575 (capping protein-inhibiting regulator of actin dynamics), and RGD1311575 was positively correlated with Fabp1 (fatty acid-binding protein, liver), a key gene involved in fat digestion and absorption. Finally, the upregulated expression of Dgat1 (diacylglycerol acyltransferase 1) and Fabp1 related to fat digestion and absorption was identified by RT-PCR and IHC.

Conclusion

DCA-induced GIM enhanced gastric fat digestion and absorption function and impaired gastric acid secretion function. The DCA-Rikenellaceae RC9 gut group-RGD1311575/Fabp1 axis might play a key role in the mechanism of bile reflux-related GIM.

Differences in gastric microbiota and mucosal function between patients with chronic superficial gastritis and intestinal metaplasia

Chronic superficial gastritis (CSG) and intestinal metaplasia (IM) can further develop into gastric cancer, which seriously endangers the health of people all over the world. In this study, the differences in gastric microbiota between CSG patients and IM patients were detected by 16S rRNA gene sequencing. As the expression levels of mucin and CDX2 are closely related to IM, the expression differences of mucin (MUC2 and MUC5AC) and CDX2 in the gastric mucosa of CSG patients and IM patients were detected by Western blot and qRT-PCR. The results showed that both Faith_pd and Observed_species indexes of microbiota in the gastric juice of CSG patients were significantly higher than those of IM patients. At the genus level, Thermus and Anoxybacillus were dominant in the gastric juice of IM patients, and Helicobacter was dominant in the gastric juice of CSG patients. Non-metric multidimensional scaling (NMDS) demonstrated that the dispersion of samples in the CSG group is greater than that in the IM group, and some samples in the CSG group are clustered with samples in the IM group. The KEGG metabolic pathway difference analysis of gastric juice microbiota in CSG and IM patients revealed that the gastric juice microbiota in the CSG and IM patients were significantly enriched in the amino acid metabolism, carbohydrate metabolism, and metabolism of cofactors and vitamins, and the functional differences between the two groups were mainly concentrated in the bacterial secretion system (VirB1, VirB2, VirB3, VirD2, and VirD4). In conclusion, there are significant differences in gastric microbiota and mucosal function between the CSG and IM patients. Moreover, the results of this study may provide a new means for the detection of CSG and IM and a new direction for the prevention and treatment of CSG and IM.

Bile reflux alters the profile of the gastric mucosa microbiota

Background

Bile reflux can cause inflammation, gastric mucosa atrophy, and diseases such as stomach cancer. Alkaline bile flowing back into the stomach affects the intragastric environment and can alter the gastric bacterial community. We sought to identify the characteristics of the stomach mucosal microbiota in patients with bile reflux.

Methods

Gastric mucosal samples were collected from 52 and 40 chronic gastritis patients with and without bile reflux, respectively. The bacterial profile was determined using 16S rRNA gene analysis.

Results

In the absence of H. pylori infection, the richness (based on the Sobs and Chao1 indices; P <0.05) and diversity (based on Shannon indices; P <0.05) of gastric mucosa microbiota were higher in patients with bile reflux patients than in those without. There was a marked difference in the microbiota structure between patients with and without bile reflux (ANOSIM, R=0.058, P=0.011). While the genera, Comamonas, Halomonas, Bradymonas, Pseudomonas, Marinobacter, Arthrobacter, and Shewanella were enriched in patients with bile reflux, the genera, Haemophilus, Porphyromonas, and Subdoligranulum, were enriched in those without bile reflux.

Conclusion

Our results demonstrate that bile reflux significantly alters the composition of the gastric microbiota.

Deoxycholic acid induces gastric intestinal metaplasia by activating STAT3 signaling and disturbing gastric bile acids metabolism and microbiota

Intestinal metaplasia (IM) is the inevitable precancerous stage to develop intestinal-type gastric cancer (GC). Deoxycholic acid (DCA) is the main bile acid (BA) component of duodenogastric reflux and has shown an increased concentration during the transition from chronic gastritis to IM associated with continued STAT3 activation. However, the mechanisms underlying how DCA facilitates IM in the gastric epithelium need exploration. We evaluated IM and bile reflux in corpus tissues from 161 subjects undergoing GC screening. Cell survival and proliferation, proinflammatory cytokine expression and TGR5/STAT3/KLF5 axis activity were measured in normal human gastric cells, cancer cells, and organoid lines derived from C57BL/6, FVB/N and insulin-gastrin (INS-GAS) mice treated with DCA. The effects of DCA on IM development were determined in INS-GAS mice with long-term DCA supplementation, after which the gastric bacterial and BA metabolic profiles were measured by 16S rRNA gene sequencing and LC-MS. We revealed a BA-triggered TGR5/STAT3/KLF5 pathway in human gastric IM tissues. In gastric epithelial cells, DCA promoted proliferation and apoptotic resistance, upregulated proinflammatory cytokines and IM markers, and facilitated STAT3 phosphorylation, nuclear accumulation and DNA binding to the KLF5 promoter. DCA triggered STAT3 signaling and the downstream IM marker KLF5 in mouse gastric organoids in vitro and in vivo. In INS-GAS mice, DCA promoted the accumulation of serum total BAs and accelerated the stepwise development of gastric IM and dysplasia. DCA induced gastric environmental alterations involving abnormal BA metabolism and microbial dysbiosis, in which the Gemmobacter and Lactobacillus genera were specifically enriched. Lactobacillus genus enrichment was positively correlated with increased levels of GCA, CA, T-α-MCA, TCA and β-MCA in DCA-administrated INS-GAS mice. DCA promotes nuclear STAT3 phosphorylation, which mediates KLF5 upregulation associated with gastric inflammation and IM development. DCA disturbs the gastric microbiome and BA metabolism homeostasis during IM induction.