An analysis of the role of the indigenous microbiota in cholesterol gallstone pathogenesis

The alteration of fecal microbial and metabolic profile of gallstone patients in Taiwan: Single-center study

BACKGROUND

Gallstone disease is a common health problem worldwide. The role of the gut microbiota in gallstone pathogenesis remains obscure. Our aim was to evaluate the association and crosstalk between gut microbiota, gut metabolomic, and metabolic parameters in cholesterol gallstone patients, pigmented gallstone patients, and controls.

METHODS

We collected stool samples from healthy individuals and patients with gallstones in our hospital from March 2019 to February 2021. 16s rRNA sequencing was performed, followed by differential abundance analyses. Measurement of bile acids and short-chain fatty acids was conducted via targeted metabolomics.

RESULT

Thirty healthy individuals and 20 gallstone patients were recruited. The intergroup difference of microbial composition was significant between control and gallstone patients. The control group had more abundant Faecalibacterium , Prevotella 9 , and Bacteroides plebeius DSM 17135 . The cholesterol stones group had higher Desulfovibrionaceae and Bacteroides uniformis than the other two groups, while the pigment stone group had more abundant Escherichia-Shigella . In the analysis of metabolites, only n-butyric acid had a significantly higher concentration in the controls than in the gallstone group ( p < 0.01). The level of 3α-hydroxy-12 ketolithocholic acid, deoxycholic acid, and cholic acid showed no intergroup differences but was correlated to the serum cholesterol level and bacterial richness and evenness.

CONCLUSION

Our study revealed the key taxa that can discriminate between individuals with or without gallstones. We also identified metabolites that are possibly associated with metabolic parameter and bacterial diversity. However, the correlation of the metabolites to certain clusters of bacteria should be analyzed in a larger cohort.

The role of bacteria in gallstone formation

Gallstones are a prevalent biliary system disorder that is particularly common in women. They can lead to various complications, such as biliary colic, infection, cholecystitis, and even gallbladder cancer. However, the etiology of gallstones remains incompletely understood. The significant role of bacteria in gallstone formation has been demonstrated in recent studies. Certain bacteria not only influence bile composition and the gallbladder environment but also actively participate in stone formation by producing enzymes such as β-glucuronidase and mucus. Therefore, this review aimed to analyze the mechanisms involving the types and quantities of bacteria involved in gallstone formation, providing valuable references for understanding the etiology and clinical treatment of gallstones.

Ganoderma lucidum polysaccharide ameliorates cholesterol gallstone formation by modulating cholesterol and bile acid metabolism in an FXR-dependent manner

BACKGROUND

Cholesterol gallstone (CG) disease is a worldwide common disease characterized by cholesterol supersaturation in gallbladder bile. Ganoderma lucidum polysaccharide (GLP) has been shown to possess various beneficial effects against metabolic disorders. However, the role and underlying mechanism of GLP in CG formation are still unknown. This study aimed to determine the role of GLP in ameliorating lithogenic diet (LD)-induced CG formation.

METHODS

Mice were fed either a normal chow diet, a LD, or LD supplemented with GLP. Real-time quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to detect the expression of genes involved in cholesterol and bile acid (BA) metabolism. The BA concentrations in the ileum were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The microbiota in cecal contents were characterized using 16S ribosomal RNA (16S rRNA) gene sequencing.

RESULTS

GLP effectively alleviated CG formation induced by LD. Specifically, GLP reduced the total cholesterol (TC) levels, increased the total BA levels, and decreased the cholesterol saturation index (CSI) in gallbladder bile. The protective effect of GLP was attributed to the inhibition of farnesoid X receptor (FXR) signaling, increased hepatic BA synthesis and decreased hepatic cholesterol synthesis and secretion. GLP also altered the BA composition in the ileum, reducing FXR-agonistic BAs and increasing FXR-antagonistic BAs, which may contribute to the inhibition of intestinal FXR signaling. Additionally, GLP improved dysbiosis of the intestinal flora and reduced the serum levels of hydrogen sulfide (H2S), a bacterial metabolite that can induce hepatic FXR, thereby inhibiting hepatic FXR signaling. Moreover, the protective effect of GLP against CG formation could be reversed by both the global and gut-restricted FXR agonists.

CONCLUSIONS

Taken together, GLP ameliorates CG formation by regulating cholesterol and BA metabolism in an FXR-dependent manner. Our study demonstrates that GLP may be a potential strategy for the prevention against CG disease.

Interplay between the Human Microbiome and Biliary Tract Cancer: Implications for Pathogenesis and Therapy

Biliary tract cancer, encompassing intrahepatic and extrahepatic cholangiocarcinoma as well as gallbladder carcinoma, stands as a prevalent malignancy characterized by escalating incidence rates and unfavorable prognoses. The onset of cholangiocarcinoma involves a multitude of risk factors and could potentially be influenced by microbial exposure. The human microbiome, encompassing the entirety of human microbial genetic information, assumes a pivotal role in regulating key aspects such as host digestion, absorption, immune responses, and metabolism. The widespread application of next-generation sequencing technology has notably propelled investigations into the intricate relationship between the microbiome and diseases. An accumulating body of evidence strongly suggests a profound interconnection between biliary tract cancer and the human microbiome. This article critically appraises the existing evidence pertaining to the microbiome milieu within patients afflicted by biliary tract cancer. Furthermore, it delves into potential mechanisms through which dysregulation of the human microbiome could contribute to the advancement of biliary tract cancer. Additionally, the article expounds on its role in the context of chemotherapy and immunotherapy for biliary tract cancer.

Identification of Intestinal Microbial Community in Gallstone Patients with Metagenomic Next-Generation Sequencing

Gallstone disease (GD) is one of the most common gastrointestinal diseases worldwide. Nowadays, intestinal microbiota are thought to play important roles in the formation of gallstones. In our study, human fecal samples were extracted for metagenomic next-generation sequencing (mNGS) on the Illumina HiSeq platform, followed by bioinformatics analyses. Our results showed that there was a particular intestinal micro-ecosystem in GD patients. In contrast to healthy people, the sequences of Bacteroidetes, Bacteroides and Thetaiotaomicron were obviously more abundant in GD patients at phylum, genus and species levels, respectively. On the other hand, the glycan metabolism and drug resistance, especially for the β-lactams, were the most profound functions of gut microbes in GD patients compared to those in normal subjects. Furthermore, a correlation analysis drew out that there existed a significant relationship between the serum levels of biochemical indicators and abundances of intestinal microbes in GD patients. Our results illuminate both the composition and functions of intestinal microbiota in GD patients. All in all, our study can broaden the insight into the potential mechanism of how gut microbes affect the progression of gallstones to some extent, which may provide potential targets for the prevention, diagnosis or treatment of GD.

The Role of the Bile Microbiome in Common Bile Duct Stone Development

INTRODUCTION

Common bile duct (CBD) stones are a health concern for 10-20% of individuals with symptomatic gallstones, leading to health complications and placing a burden on healthcare systems. This study was initiated to investigate the changes in microbiome compositions and the metabolic signature associated with CBD stones. The research approach integrated taxonomic and functional data with metabolomics data, complemented by in vivo experiments.

METHODS

In a single tertiary healthcare institution, a total of 25 patients were enrolled who had undergone endoscopic retrograde cholangiopancreatography (ERCP) between February 2019 and January 2021. We harvested DNA from bile samples acquired from these individuals. The amplification of the bacterial 16S rRNA gene V3-V4 region was conducted through polymerase chain reaction (PCR), followed by sequencing. We utilized QIIME2 for a comprehensive data analysis. Furthermore, we performed a metabolomic analysis of the bile samples using nuclear magnetic resonance (NMR) spectroscopy. For the assessment of functional gene enrichment, we employed MetaboAnalyst 5.0. Lastly, we executed in vivo experiments on C57BL/6 mice and undertook histological examinations of tissue samples.

RESULTS

Out of the 25 study subjects, 17 underwent ERCP due to CBD stones (the CBD stone group), while the remaining 8 had the procedure for different reasons (the non-CBD stone group). An alpha diversity analysis showed a significantly greater microbial diversity in the bile samples of the non-CBD stone group (p < 0.01), and a beta diversity analysis confirmed the greater microbial compositional abundance in the gut microbiomes in this group (p = 0.01). A taxonomic analysis revealed that the abundances of Enterococcaceae and Enterococcus were higher in the bile microbiomes of the CBD stone group. A metabolic profile analysis showed that the acetate, formate, and asparagine levels were higher in the CBD stone group. A pathway enrichment analysis showed the metabolic pathways (Arginine and Proline Metabolism, Aspartate Metabolism, Glycine, and Serine Metabolism, and Ammonia Recycling pathways) that were associated with these differences. Preclinical experiments demonstrated systemic inflammation and extracellular trap formation in the CBD stone group.

CONCLUSIONS

Our study highlights the importance of biliary dysbiosis and bile metabolites, specifically acetate and formate, in CBD stone development and progression. These findings have implications for the development of diagnostic and therapeutic strategies using microbiomes for CBD stones.

Gastrointestinal microbiome and cholelithiasis: Current status and perspectives

Cholelithiasis is a common digestive disease affecting 10% to 15% of adults. It imposes significant global health and financial burdens. However, the pathogenesis of cholelithiasis involves several factors and is incompletely elucidated. In addition to genetic predisposition and hepatic hypersecretion, the pathogenesis of cholelithiasis might involve the gastrointestinal (GI) microbiome, consisting of microorganisms and their metabolites. High-throughput sequencing studies have elucidated the role of bile, gallstones, and the fecal microbiome in cholelithiasis, associating microbiota dysbiosis with gallstone formation. The GI microbiome may drive cholelithogenesis by regulating bile acid metabolism and related signaling pathways. This review examines the literature implicating the GI microbiome in cholelithiasis, specifically gallbladder stones, choledocholithiasis, and asymptomatic gallstones. We also discuss alterations of the GI microbiome and its influence on cholelithogenesis.

Gastrointestinal microbiome and cholelithiasis: Current status and perspectives

Cholelithiasis is a common digestive disease affecting 10% to 15% of adults. It imposes significant global health and financial burdens. However, the pathogenesis of cholelithiasis involves several factors and is incompletely elucidated. In addition to genetic predisposition and hepatic hypersecretion, the pathogenesis of cholelithiasis might involve the gastrointestinal (GI) microbiome, consisting of microorganisms and their metabolites. High-throughput sequencing studies have elucidated the role of bile, gallstones, and the fecal microbiome in cholelithiasis, associating microbiota dysbiosis with gallstone formation. The GI microbiome may drive cholelithogenesis by regulating bile acid metabolism and related signaling pathways. This review examines the literature implicating the GI microbiome in cholelithiasis, specifically gallbladder stones, choledocholithiasis, and asymptomatic gallstones. We also discuss alterations of the GI microbiome and its influence on cholelithogenesis.

Association between the Dietary Inflammatory Index with gallstone disease: finding from Dena PERSIAN cohort

OBJECTIVE

The Dietary Inflammatory Index (DII) is a documented nutritional tool for assessing diet-induced inflammation that has been linked to various diseases/outcomes. The association between DII and gallstone disease (GSD) is yet to be explored. The objective of this study was to examine the association between DII and GSD.

DESIGN

This cross-sectional study was conducted using the baseline phase data of the Dena PERSIAN cohort. The analysed data included demographic information, lifestyle variables, body mass index, diabetes and fatty liver history, and laboratory test results. The 113-item Food Frequency Questionnaire was used to estimate the dietary intake of participants and quantify the inflammatory potential of the individual's diet. DII score was analysed as a continuous and quartiles variables. Univariable and multivariate logistic regressions were used to investigate the relationship between GSD and DII scores .

RESULTS

Out of 3626 individuals entering the study, 173 (4.77%) had GSD. The median DII was -0.08 (IQR=0.18). In the unadjusted model, the odds of having GSD were significantly higher in the first and second quartiles of DII (anti-inflammatory diet) than in higher quartiles (proinflammatory diet). In the adjusted model, the odds of having GSD in the third and fourth quartiles of DII scores compared with the first quartile were OR=0.59 (95% CI 0.36 to 0.95) and OR 0.51 (95% CI 0.30 to 0.84), respectively.

CONCLUSION

The results of this study suggest that a proinflammatory diet is associated with a reduced chance of GSD. However, longitudinal studies are needed to examine the causal association.

Curcumin Supplementation Ameliorates Bile Cholesterol Supersaturation in Hamsters by Modulating Gut Microbiota and Cholesterol Absorption

Curcumin is a polyphenol that has been shown to have prebiotic and cholesterol-lowering properties. This study aimed to investigate the impact of curcumin on bile cholesterol supersaturation and the potential mechanistic role of intestinal microbiota and cholesterol absorption. Male hamsters (n = 8) were fed a high-fat diet (HFD) supplemented with or without curcumin for 12 weeks. Results showed that curcumin significantly decreased cholesterol levels in the serum (from 5.10 to 4.10 mmol/L) and liver (from 64.60 to 47.72 nmol/mg protein) in HFD-fed hamsters and reduced the bile cholesterol saturation index (CSI) from 1.64 to 1.08 due to the beneficial modifications in the concentration of total bile acids (BAs), phospholipids and cholesterol (p < 0.05). Gut microbiota analysis via 16S rRNA sequencing revealed that curcumin modulated gut microbiota, predominantly increasing microbiota associated with BA metabolism and short-chain fatty acid production, which subsequently up-regulated the expression of hepatic cholesterol 7-alpha hydroxylase and increased the synthesis of bile acids (p < 0.05). Furthermore, curcumin significantly down-regulated the expression of intestinal Niemann−Pick C1-like protein 1(NPC1L1) in hamsters and reduced cholesterol absorption in Caco-2 cells (p < 0.05). Our results demonstrate that dietary curcumin has the potential to prevent bile cholesterol supersaturation through modulating the gut microbiota and inhibiting intestinal cholesterol absorption.

Factors Influencing Gallstone Formation: A Review of the Literature

Gallstone disease is a common pathology of the digestive system with nearly a 10–20% incidence rate among adults. The mainstay of treatment is cholecystectomy, which is commonly associated with physical pain and may also seriously affect a patient’s quality of life. Clinical research suggests that cholelithiasis is closely related to the age, gender, body mass index, and other basic physical characteristics of patients. Clinical research further suggests that the occurrence of cholelithiasis is related to obesity, diabetes, non-alcoholic fatty liver, and other diseases. For this reason, we reviewed the following: genetic factors; excessive liver cholesterol secretion (causing cholesterol supersaturation in gallbladder bile); accelerated growth of cholesterol crystals and solid cholesterol crystals; gallbladder motility impairment; and cardiovascular factors. Herein, we summarize and analyze the causes and mechanisms of cholelithiasis, discuss its correlation with the pathogenesis of related diseases, and discuss possible mechanisms.

Biliary Diseases from the Microbiome Perspective: How Microorganisms Could Change the Approach to Benign and Malignant Diseases

Recent evidence regarding microbiota is modifying the cornerstones on pathogenesis and the approaches to several gastrointestinal diseases, including biliary diseases. The burden of biliary diseases, indeed, is progressively increasing, considering that gallstone disease affects up to 20% of the European population. At the same time, neoplasms of the biliary system have an increasing incidence and poor prognosis. Framing the specific state of biliary eubiosis or dysbiosis is made difficult by the use of heterogeneous techniques and the sometimes unwarranted invasive sampling in healthy subjects. The influence of the microbial balance on the health status of the biliary tract could also account for some of the complications surrounding the post-liver-transplant phase. The aim of this extensive narrative review is to summarize the current evidence on this topic, to highlight gaps in the available evidence in order to guide further clinical research in these settings, and, eventually, to provide new tools to treat biliary lithiasis, biliopancreatic cancers, and even cholestatic disease.

The effect of Tauroursodeoxycholic acid (TUDCA) and gut microbiota on murine gallbladder stone formation

INTRODUCTION AND OBJECTIVES

The incidence of gallstone-related disease steadily increased in the last few years. Here, we aimed to investigate the effect of tauroursodeoxycholic acid¹ (TUDCA) on preventing cholesterol gallstones formation in high-fat fed (HFD) mice.

MATERIAL AND METHODS

Specific pathogen-free male C57Bl/6 mice were fed a lithogenic diet² (LD group) alone or in combination with TUDCA (5g/kg diet) for 8 weeks. Upon sacrifice, serum, gallbladder, liver and small intestine were collected and the formation of gallstones or crystals in the gallbladder was analyzed. Additionally, the intestinal microbiota, and bile acid composition, serum lipids and hepatic lipids were studied.

RESULTS

Cholesterol gallstones with cholesterol crystals formed in mice of the LD-fed group (15/15, 100%). However, only cholesterol crystals were found in three mice without the presence of any gallstone in the TUDCA-treated group. Both serum and hepatic total cholesterol levels in the TUDCA group were significantly decreased compared with the LD group. Concomitantly, mRNA expression of Abcg5 and Abcg8 was significantly lower in the liver of the TUDCA group whilst mRNA transcripts for Abcb11, Acat2, and Cyp27 were significantly increased compared with the LD group. Additionally, the gallbladder cholesterol saturation index (1.06±0.15) in the TUDCA group was significantly decreased compared with the LD group. Interestingly, the ratio of Firmicutes/Bacteroides in the TUDCA group was increased 3x fold.

CONCLUSIONS

TUDCA can inhibit the absorption and synthesis of lipids in the small intestine by improving the intestinal microbiota in HFD-fed mice, thus reducing gallstone formation.

Changes and Correlations of the Intestinal Flora and Liver Metabolite Profiles in Mice With Gallstones

There is increasing appreciation for the roles of the gut-liver axis in liver and gall diseases. Specific gut microbes are associated with susceptibility to gallstone diseases, while the relationship between intestinal flora and liver metabolism in the formation of gallstones remains unclear. In this study, an experimental group of model mice was given a lithogenic diet, and a control group was given a normal diet. Both groups were fed for 8 weeks. Integrating 16S rRNA gene sequencing and non-targeted metabolomics to explore the impact of the lithogenic diet on intestinal flora and liver metabolism, Spearman correlation analysis reveals the network of relationships between the intestine and liver. Our findings showed that the gut microbiome and liver metabolome compositions of the test group were significantly changed compared with those of the normal group. Through our research, biomarkers of gallstones were identified at the phylum (5), class (5), order (5), family (7), and genus levels. We predicted the function of the differential flora. We analyzed the liver metabolism of mice with gallstones paired with their flora, and the results showed that there were 138 different metabolites between the two groups. The metabolic pathways enriched by these differential metabolites are highly consistent with the functions of the disordered flora. We focused on an analysis of the relationship between deoxycholic acid, asymmetric dimethylarginine, glucosamine, tauroursodeoxycholic acid, and the disordered flora. This provides a basis for the establishment of the intestine-liver axis in gallstone disease. This research provides a theoretical basis for the research and development of probiotics and prebiotics.

Biliary microbiota and mucin 4 impact the calcification of cholesterol gallstones

BACKGROUND

Cholesterol gallstones account for over 80% of gallstones, and the pathogenesis of gallstone formation involves genetic and environmental factors. However, data on the evolution of cholesterol gallstones with various densities are limited. This study aimed to determine the roles of microbiota and mucins on the formation of calcified cholesterol gallstones in patients with cholelithiasis.

METHODS

Paired gallbladder tissues and bile specimens were obtained from cholelithiasis patients who were categorized into the isodense group and calcified group according to the density of gallstones. The relative abundance of microbiota in gallbladder tissues was detected. Immunohistochemistry and enzyme-linked immunosorbent assay were performed to detect the expression levels of MUC1, MUC2, MUC3a, MUC3b, MUC4, MUC5ac and MUC5b in gallbladder tissues and bile. The correlation of microbiota abundance with MUC4 expression was evaluated by linear regression.

RESULTS

A total of 23 patients with gallbladder stones were included. The density of gallstones in the isodense group was significantly lower than that of the calcified group (34.20 ± 1.50 vs. 109.40 ± 3.84 HU, P < 0.0001). Compared to the isodense group, the calcified group showed a higher abundance of gram-positive bacteria at the fundus, in the body and neck of gallbladder tissues. The concentrations of MUC1, MUC2, MUC3a, MUC3b, MUC5ac and MUC5b in the epithelial cells of gallbladder tissues showed no difference between the two groups, while the concentrations of MUC4 were significantly higher in the calcified group than that in the isodense group at the fundus (15.49 ± 0.69 vs. 10.23 ± 0.54 ng/mL, P < 0.05), in the body (14.54 ± 0.94 vs. 11.87 ± 0.85 ng/mL, P < 0.05) as well as in the neck (14.77 ± 1.04 vs. 10.85 ± 0.72 ng/mL, P < 0.05) of gallbladder tissues. Moreover, the abundance of bacteria was positively correlated with the expression of MUC4 (r = 0.569, P < 0.05) in the calcified group.

CONCLUSIONS

This study showed the potential clinical relevance among biliary microbiota, mucins and calcified gallstones in patients with gallstones. Gram-positive microbiota and MUC4 may be positively associated with the calcification of cholesterol gallstones.

Human bile microbiota: A retrospective study focusing on age and gender

AIMS

The emerging biliary colonization of microorganisms in patients with biliary diseases may be devastating. Recent evidence suggests that age and gender may influence changes in the microbial composition of gut microbiota. To study the relationship between these parameters on bile microbiota, we retrospectively reviewed positive bile cultures following an endoscopic retrograde cholangiopancreatography (ERCP) in a QA-certified academic surgical unit of a single institution.

METHODS

449 positive bile cultures from 172 Italian patients with diseases of the biliopancreatic system hospitalized from 2006 through 2017 were investigated for aerobic, anaerobic, and fungal organisms. The patients were stratified into four age intervals (22-66, 67-74, 75-81, and 82-93 years) and followed up for five years.

RESULTS

Gram-positive bacteria (GPB) was negatively associated with age only in multivariate analysis (R_partial = -0.114, p = 0.017), with younger patients prone to harbor GPB and older patients likely to have Gram-negative bacteria (GNB). There was a definite link with the male gender using both univariate and multivariate analysis (p < 0.001). Enterococcus spp. was the most common strain identified in patients with GPB except for patients aged 67-74 years for male (95.2%) and female (80.9%) patients. Escherichia coli and Klebsiella spp. were most frequent than others in every group analyzed. Analogous results were found for bacteria Non-fermenting Gram-negative bacilli (NFGNB), such as Pseudomonas spp. and Stenotrophomonas spp. apart of the 2nd quartile.

CONCLUSIONS

Our study strengthens the bond of age and gender with bile microbiota composition and suggests that further investigations may be required in targeting the aging microbiome. Other studies should also focus on Mediterranean epidemiological characteristics and antibiotic resistance surveillance system strategies.

Gallstone Disease, Obesity and the Firmicutes/Bacteroidetes Ratio as a Possible Biomarker of Gut Dysbiosis

Obesity is a major risk factor for developing gallstone disease (GSD). Previous studies have shown that obesity is associated with an elevated Firmicutes/Bacteroidetes ratio in the gut microbiota. These findings suggest that the development of GSD may be related to gut dysbiosis. This review presents and summarizes the recent findings of studies on the gut microbiota in patients with GSD. Most of the studies on the gut microbiota in patients with GSD have shown a significant increase in the phyla Firmicutes (Lactobacillaceae family, genera Clostridium, Ruminococcus, Veillonella, Blautia, Dorea, Anaerostipes, and Oscillospira), Actinobacteria (Bifidobacterium genus), Proteobacteria, Bacteroidetes (genera Bacteroides, Prevotella, and Fusobacterium) and a significant decrease in the phyla Bacteroidetes (family Muribaculaceae, and genera Bacteroides, Prevotella, Alistipes, Paludibacter, Barnesiella), Firmicutes (genera Faecalibacterium, Eubacterium, Lachnospira, and Roseburia), Actinobacteria (Bifidobacterium genus), and Proteobacteria (Desulfovibrio genus). The influence of GSD on microbial diversity is not clear. Some studies report that GSD reduces microbial diversity in the bile, whereas others suggest the increase in microbial diversity in the bile of patients with GSD. The phyla Proteobacteria (especially family Enterobacteriaceae) and Firmicutes (Enterococcus genus) are most commonly detected in the bile of patients with GSD. On the other hand, the composition of bile microbiota in patients with GSD shows considerable inter-individual variability. The impact of GSD on the Firmicutes/Bacteroidetes ratio is unclear and reports are contradictory. For this reason, it should be stated that the results of reviewed studies do not allow for drawing unequivocal conclusions regarding the relationship between GSD and the Firmicutes/Bacteroidetes ratio in the microbiota.

Alterations of the Bile Microbiome in Recurrent Common Bile Duct Stone

Objective

Common bile duct stone (CBDS) recurrence is associated with bile microbial structure. This study explored the structure of bile microbiome in patients with recurrent CBDS, and its relationship with the recurrence of CBDS.

Methods

Patients with recurrent CBDS (recurrence group) and controls without CBDS (control group) requiring endoscopic retrograde cholangiopancreatography (ERCP) were prospectively included. The control group was noncholelithiasis patients, mainly including benign and malignant biliary stenosis. Bile samples were collected, and bile microbiome structure was analyzed by the 16S rRNA encoding gene (V3-V4).

Results

A total of 27 patients in the recurrence group and 19 patients in the control group were included. The diversity of bile microbiome in the recurrence group was significantly lower than that in the control group (Shannon index: 2.285 vs. 5.612, P = 0.001). In terms of bile microbial distribution, patients with recurrent CBDS had significantly higher Proteobacteria (86.72% vs. 64.92%, P = 0.037), while Bacteroidetes (3.16% vs. 8.53%, P = 0.001) and Actinobacteria (0.29% vs. 6.74%, P = 0.001) are significantly lower compared with the control group at the phylum level. At the genus level, the recurrence group was mainly the Escherichia, and there was a variety of more evenly distributed microbiome in the control group, with significant differences between the two groups.

Conclusion

The diversity of bile microbiome in patients with recurrent CBDS is lower. Patients with recurrent CBDS may have bile microbial imbalance, which may be related to the repeated formation of CBDS.

Gallstone Disease and Microbiome

Gallstone disease (GSD) has, for many years, remained a high-cost, socially significant public health problem. Over the past decade, a number of studies have been carried out-both in humans and in animal models-confirming the role of the microbiota in various sections of the gastrointestinal tract as a new link in the etiopathogenesis of GSD. The microbiome of bile correlates with the bacterial composition of saliva, and the microbiome of the biliary tract has a high similarity with the microbiota of the duodenum. Pathogenic microflora of the oral cavity, through mechanisms of immunomodulation, can affect the motility of the gallbladder and the expression of mucin genes (MUC1, Muc3, MUC4), and represent one of the promoters of stone formation in the gallbladder. The presence of H. pylori infection contributes to the formation of gallstones and affects the occurrence of complications of GSD, including acute and chronic cholecystitis, cholangitis, pancreatitis. Intestinal bacteria (Clostridium, Bifidobacterium, Peptostreptococcus, Bacteroides, Eubacterium, and Escherichia coli) participating in the oxidation and epimerization of bile acids can disrupt enterohepatic circulation and lead to the formation of gallstones. At the same time, cholecystectomy due to GSD leads to the further transformation of the composition of the microbiota in various parts of the gastrointestinal tract, increasing the risk of developing stomach cancer and colorectal cancer. Further research is required to determine the possibility of using the evaluation of the composition of the microbiota of the gastrointestinal and biliary tracts as an early diagnostic marker of various gastroenterological diseases.

Transcriptomic profiles reveal differences in zinc metabolism, inflammation, and tight junction proteins in duodenum from cholesterol gallstone subjects

Cholesterol Gallstone Disease (GSD) is a common multifactorial disorder characterized by crystallization and aggregation of biliary cholesterol in the gallbladder. The global prevalence of GSD is ~10–20% in the adult population but rises to 28% in Chile (17% among men and 30% among women). The small intestine may play a role in GSD pathogenesis, but the molecular mechanisms have not been clarified. Our aim was to identify the role of the small intestine in GSD pathogenesis. Duodenal biopsy samples were obtained from patients with GSD and healthy volunteers. GSD status was defined by abdominal ultrasonography. We performed a transcriptome study in a discovery cohort using Illumina HiSeq. 2500, and qPCR, immunohistochemistry and immunofluorescence were used to validate differentially expressed genes among additional case-control cohorts. 548 differentially expressed genes between GSD and control subjects were identified. Enriched biological processes related to cellular response to zinc, and immune and antimicrobial responses were observed in GSD patients. We validated lower transcript levels of metallothionein, NPC1L1 and tight junction genes and higher transcript levels of genes involved in immune and antimicrobial pathways in GSD patients. Interestingly, serum zinc and phytosterol to cholesterol precursor ratios were lower in GSD patients. A significant association was observed between serum zinc and phytosterol levels. Our results support a model where proximal small intestine plays a key role in GSD pathogenesis. Zinc supplementation, modulation of proximal microbiota and/or intestinal barrier may be novel targets for strategies to prevent GSD.

Intestinal flora imbalance affects bile acid metabolism and is associated with gallstone formation

BACKGROUND

The gut microbiota participates in the metabolism of substances and energy, promotes the development and maturation of the immune system, forms the mucosal barrier, and protects the host from pathogen attacks. Although the pathogenesis of cholesterol gallstones is still not clear, studies have suggested that gut microbiota dysbiosis plays an important role in their formation.

METHODS

Microbial DNA from faeces of normal control patients and those of patients with calculi was subjected to 16S rRNA gene sequencing to detect gene expression changes in intestinal microbes. ELISA kits were used to measure free bile acids, secondary bile acids and coprostanol according to the manufacturer's instructions. The relationship between flora and their metabolites was then analysed.

RESULTS

In the gallstone group, the diversity of intestinal bacteria and the abundances of certain phylogroups were significantly decreased (p < 0.05), especially Firmicutes (p < 0.05), the largest phylum represented by the gut microbiota. This study found an increase in free bile acids (p < 0.001) and secondary bile acids (p < 0.01) in the enterohepatic circulation. Bile salt hydrolase activity was not related to the abundances of BSH-active bacteria. 7a-dehydroxylating gut bacteria were significantly increased (p < 0.01), whereas cholesterol-lowering bacteria were significantly reduced (p < 0.05). The Ruminococcus gnavus group could be used as a biomarker to distinguish the gallstone group from the control group.

CONCLUSION

We conclude that intestinal flora imbalance affects bile acid and cholesterol metabolism and is associated with gallstone formation.

Pioglitazone prevents cholesterol gallstone formation through the regulation of cholesterol homeostasis in guinea pigs with a lithogenic diet

Background

The cholesterol gallstones diseases (CGD) is highly correlated with metabolic syndrome and type 2 diabetes. The present study aimed to investigate preventive effects of pioglitazone (PIO), an antidiabetic drug, on the CGD in guinea pigs fed with a lithogenic diet (LD).

Methods

The guinea pigs were fed with the LD for 8 weeks. All guinea pigs were grouped as follows: low fat diet; LD; LD plus PIO (4 mg/kg); LD plus PIO (8 mg/kg); LD plus ezetimibe (EZE) (2 mg/kg). Gallbladder stones were observed using microscopy. The profile of biliary composition, and blood glucose, insulin and lipid were analyzed. The liver or ileum was harvested for determinations of hydroxyl-methyl-glutaryl-CoA reductase (HMGCR), sterol regulatory element-binding proteins 2 (SREBP2), 7α-hydroxylase (CYP7A1), adenosine triphosphate-binding cassette (ABC) sterol transporters G5 and G8 (ABCG5, ABCG8), bile salt export pump (BSEP), Niemann-Pick C1-Like 1 (NPC1L1) and acetyl-coenzyme A cholesterol acyltransferase (ACAT2) by Western blot. The gallbladders were used for histological examination.

Results

The LD successfully induced gallstone. Both pioglitazone and ezetimibe prevented gallstone formation, as well as hepatic and cholecystic damages. Pioglitazone significantly decreased HMGCR and SREBP2, but increased CYP7A1, ABCG5, ABCG8, and BSEP in the liver. Pioglitazone also remarkably decreased NPC1L1 and ACAT2, while increased ABCG5/8 in the intestine. The beneficial alterations of cholesterol and bile acids in the bile, as well as profile of glucose, insulin and lipid in the blood were found in the guinea pigs treated with pioglitazone.

Conclusion

Pioglitazone has a noticeable benefit towards the CGD, which is involved in changes of synthesis, transformation, absorption, and transportation of cholesterol.

Dynamic distribution of gallbladder microbiota in rabbit at different ages and health states

The internal environment of the gallbladder has been considered extremely unfavorable for bacterial growth, and the microbial profile of the gallbladder still unknown. By high-throughput sequencing of the bacterial 16S rRNA gene, we studied the microbial profile of the gallbladder from healthy rabbits before and after weaning. Moreover, we investigated the difference of microbiota between the gallbladder and gut. Our results showed that the gallbladder was dominantly populated by Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria in the phylum throughout the developmental stages of rabbits. The adult rabbits showed higher species richness and exhibited higher bacterial diversity than rabbits before weaning based on the results of alpha diversity. Beta diversity analyses indicated differences in the bacterial community composition between different developmental stages. In the comparison of the gallbladder and feces, Firmicutes and Bacteroidetes were dominant in the phylum, as they were present in about 61% and 21% of the feces, respectively. Conversely, in the gallbladder, Firmicutes was the most dominant (about 41%), and Bacteroidetes and Proteobacteria were present in about 16% and 22% of the gallbladder, respectively. The Unweighted UniFrac Principal Coordinate Analysis results illustrated samples clustered into 2 categories: the gallbladder and feces. Our study might provide a foundation for knowledge on gallbladder microbiota for the first time and a basis for further studies on gallbladder and intestinal health.

Association of circulating inflammation proteins and gallstone disease

BACKGROUND AND AIM

Inflammation plays a role in the development of both gallstones and gallbladder cancer; however, few studies have investigated the association of circulating inflammation proteins with risk of gallstones.

METHODS

This study measured 13 cytokines (including 10 interleukins [ILs]) that have been associated with cancer in serum samples collected from 150 gallstone patients and 149 population-based controls from Shanghai, China, in 1997-2001. This study estimated the associations of each cytokine, categorized into quartiles and coded as a trend, with risk of gallstones using logistic regression models adjusted for potential confounders.

RESULTS

Higher levels of IL-6, IL-10, IL-12 (p70), and IL-13 were associated with increased risk of gallstones (i.e. P_trend  < 0.003, Bonferroni corrected), with odds ratios (ORs) that ranged from OR_{highest quartile [Q4] versus lowest quartile [Q1]}  = 3.2 (95% confidence interval: 1.4, 7.5) for IL-13 to OR_{Q4 versus Q1}  = 5.7 (95% confidence interval: 2.5, 13.5) for IL-12 (p70). In a regression model including all four ILs, only IL-12 retained statistical significance (P < 0.05).

CONCLUSION

This study found four circulating ILs that were associated with gallstones. Future studies are needed to validate the findings and evaluate the common pathway or mechanism in the development of gallbladder diseases associated with these cytokine signatures.

Alteration of gut microbiota in association with cholesterol gallstone formation in mice

Background

The gut microbiome exerts extensive roles in metabolism of nutrients, pharmaceuticals, organic chemicals. Little has been known for the role of gut microbiota in regulating cholesterol and bile acids in association with gallstone formation. This study investigated the changes in the composition of gut microbiota in mice fed with lithogenic diet (LD).

Methods

Adult male C57BL/6 J mice were fed with either lithogenic diet (1.25% cholesterol and 0.5% cholic acid) or chow diet as control for 56 days. The fecal microbiota were determined by 16S rRNA gene sequencing.

Results

LD led to formation of cholesterol gallstone in mice. The richness and alpha diversity of gut microbial reduced in mice fed with LD. Firmicutes was significantly decreased from 59.71% under chow diet to 31.45% under LD, P < 0.01, as well as the ratio of Firmicutes to Bacteroidetes. Differences in gut microbiota composition were also observed at phylum, family and genus levels between the two groups.

Conclusion

Our results suggested that gut microbiota dysbiosis might play an important role in the pathogenesis of cholesterol gallstone formation in mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-017-0629-2) contains supplementary material, which is available to authorized users.

Smog induces oxidative stress and microbiota disruption

Smog is created through the interactions between pollutants in the air, fog, and sunlight. Air pollutants, such as carbon monoxide, heavy metals, nitrogen oxides, ozone, sulfur dioxide, volatile organic vapors, and particulate matters, can induce oxidative stress in human directly or indirectly through the formation of reactive oxygen species. The outermost boundary of human skin and mucous layers are covered by a complex network of human-associated microbes. The relation between these microbial communities and their human host are mostly mutualistic. These microbes not only provide nutrients, vitamins, and protection against other pathogens, they also influence human’s physical, immunological, nutritional, and mental developments. Elements in smog can induce oxidative stress to these microbes, leading to community collapse. Disruption of these mutualistic microbiota may introduce unexpected health risks, especially among the newborns and young children. Besides reducing the burning of fossil fuels as the ultimate solution of smog formation, advanced methods by using various physical, chemical, and biological means to reduce sulfur and nitrogen contains in fossil fuels could lower smog formation. Additionally, information on microbiota disruption, based on functional genomics, culturomics, and general ecological principles, should be included in the risk assessment of prolonged smog exposure to the health of human populations.

Cholesterol gallstones and bile host diverse bacterial communities with potential to promote the formation of gallstones

The prevalence of cholesterol gallstones has increased in recent years. Bacterial infection correlates with the formation of gallstones. We studied the composition and function of bacterial communities in cholesterol gallstones and bile from 22 cholesterol gallstone patients using culture-dependent and culture-independent methods. Altogether fourteen and eight bacterial genera were detected in cholesterol gallstones and bile, respectively. Pseudomonas spp. were the dominant bacteria in both cholesterol gallstones and bile. As judged by diversity indices, hierarchical clustering and principal component analysis, the bacterial communities in gallstones were different from those in bile. The gallstone microbiome was considered more stable than that of bile. The different microbial communities may be partially explained by differences in their habitats. We found that 30% of the culturable strains from cholesterol gallstones secreted β-glucuronidase and phospholipase A2. Pseudomonas aeruginosa strains showed the highest β-glucuronidase activity and produced the highest concentration of phospholipase A2, indicating that Ps. aeruginosa may be a major agent in the formation of cholesterol gallstones.

Towards a more comprehensive concept for prebiotics

The essential role of the gut microbiota for health has generated tremendous interest in modulating its composition and metabolic function. One of these strategies is prebiotics, which typically refer to selectively fermented nondigestible food ingredients or substances that specifically support the growth and/or activity of health-promoting bacteria that colonize the gastrointestinal tract. In this Perspective, we argue that advances in our understanding of diet-microbiome-host interactions challenge important aspects of the current concept of prebiotics, and especially the requirement for effects to be 'selective' or 'specific'. We propose to revise this concept in an effort to shift the focus towards ecological and functional features of the microbiota more likely to be relevant for host physiology. This revision would provide a more rational basis for the identification of prebiotic compounds, and a framework by which the therapeutic potential of modulating the gut microbiota could be more fully materialized.

Impaired cholecystokinin-induced gallbladder emptying incriminated in spontaneous "black" pigment gallstone formation in germfree Swiss Webster mice

"Black" pigment gallstones form in sterile gallbladder bile in the presence of excess bilirubin conjugates ("hyperbilirubinbilia") from ineffective erythropoiesis, hemolysis, or induced enterohepatic cycling (EHC) of unconjugated bilirubin. Impaired gallbladder motility is a less well-studied risk factor. We evaluated the spontaneous occurrence of gallstones in adult germfree (GF) and conventionally housed specific pathogen-free (SPF) Swiss Webster (SW) mice. GF SW mice were more likely to have gallstones than SPF SW mice, with 75% and 23% prevalence, respectively. In GF SW mice, gallstones were observed predominately in heavier, older females. Gallbladders of GF SW mice were markedly enlarged, contained sterile black gallstones composed of calcium bilirubinate and <1% cholesterol, and had low-grade inflammation, edema, and epithelial hyperplasia. Hemograms were normal, but serum cholesterol was elevated in GF compared with SPF SW mice, and serum glucose levels were positively related to increasing age. Aged GF and SPF SW mice had deficits in gallbladder smooth muscle activity. In response to cholecystokinin (CCK), gallbladders of fasted GF SW mice showed impaired emptying (females: 29%; males: 1% emptying), whereas SPF SW females and males emptied 89% and 53% of volume, respectively. Bilirubin secretion rates of GF SW mice were not greater than SPF SW mice, repudiating an induced EHC. Gallstones likely developed in GF SW mice because of gallbladder hypomotility, enabled by features of GF physiology, including decreased intestinal CCK concentration and delayed intestinal transit, as well as an apparent genetic predisposition of the SW stock. GF SW mice may provide a valuable model to study gallbladder stasis as a cause of black pigment gallstones.

The mechanism of enterohepatic circulation in the formation of gallstone disease

Bile acids entering into enterohepatic circulating are primary acids synthesized from cholesterol in hepatocyte. They are secreted actively across canalicular membrane and carried in bile to gallbladder, where they are concentrated during digestion. About 95 % BAs are actively taken up from the lumen of terminal ileum efficiently, leaving only approximately 5 % (or approximately 0.5 g/d) in colon, and a fraction of bile acids are passively reabsorbed after a series of modifications in the human large intestine including deconjugation and oxidation of hydroxy groups. Bile salts hydrolysis and hydroxy group dehydrogenation reactions are performed by a broad spectrum of intestinal anaerobic bacteria. Next, hepatocyte reabsorbs bile acids from sinusoidal blood, which are carried to liver through portal vein via a series of transporters. Bile acids (BAs) transporters are critical for maintenance of the enterohepatic BAs circulation, where BAs exert their multiple physiological functions including stimulation of bile flow, intestinal absorption of lipophilic nutrients, solubilization, and excretion of cholesterol. Tight regulation of BA transporters via nuclear receptors (NRs) is necessary to maintain proper BA homeostasis. In conclusion, disturbances of enterohepatic circulation may account for pathogenesis of gallstones diseases, including BAs transporters and their regulatory NRs and the metabolism of intestinal bacterias, etc.

Draft genome sequences of the altered schaedler flora, a defined bacterial community from gnotobiotic mice

The altered Schaedler flora (ASF) is a bacterial community that supports normal growth and development of gnotobiotic mice. We report here the draft genome sequences of the 8 bacteria that comprise the ASF.