Mechanism for the transit-induced increase in colonic deoxycholic acid formation in cholesterol cholelithiasis

Gut Microbiome and Bile Acid Interactions: Mechanistic Implications for Cholangiocarcinoma Development, Immune Resistance, and Therapy

Cholangiocarcinoma (CCA) is a rare but highly malignant carcinoma of bile duct epithelial cells with a poor prognosis. The major risk factors of CCA carcinogenesis and progression are cholestatic liver diseases. The key feature of primary sclerosing cholangitis and primary biliary cholangitis is chronic cholestasis. It indicates a slowdown of hepatocyte secretion of biliary lipids and metabolites into bile as well as a slowdown of enterohepatic circulation (bile acid recirculation) of bile acids with dysbiosis of the gut microbiome. This leads to enterohepatic recirculation and an increase of toxic secondary bile acids. Alterations of serum and liver bile acid compositions via the disturbed enterohepatic circulation of bile acids and the disturbance of the gut microbiome then activate a series of hepatic and cancer cell signaling pathways that promote CCA carcinogenesis and progression. This review focuses on the mechanistic roles of bile acids and the gut microbiome in the pathogenesis and progression of CCA. It also evaluates the therapeutic potential of targeting the gut microbiome and bile acid-mediated signaling pathways for the therapy and prophylaxis of CCA.

Gallstones, cholecystectomy, and cancer risk: an observational and Mendelian randomization study

This study aimed to comprehensively examine the association of gallstones, cholecystectomy, and cancer risk. Multivariable logistic regressions were performed to estimate the observational associations of gallstones and cholecystectomy with cancer risk, using data from a nationwide cohort involving 239 799 participants. General and gender-specific two-sample Mendelian randomization (MR) analysis was further conducted to assess the causalities of the observed associations. Observationally, a history of gallstones without cholecystectomy was associated with a high risk of stomach cancer (adjusted odds ratio (aOR)=2.54, 95% confidence interval (CI) 1.50-4.28), liver and bile duct cancer (aOR=2.46, 95% CI 1.17-5.16), kidney cancer (aOR=2.04, 95% CI 1.05-3.94), and bladder cancer (aOR=2.23, 95% CI 1.01-5.13) in the general population, as well as cervical cancer (aOR=1.69, 95% CI 1.12-2.56) in women. Moreover, cholecystectomy was associated with high odds of stomach cancer (aOR=2.41, 95% CI 1.29-4.49), colorectal cancer (aOR=1.83, 95% CI 1.18-2.85), and cancer of liver and bile duct (aOR=2.58, 95% CI 1.11-6.02). MR analysis only supported the causal effect of gallstones on stomach, liver and bile duct, kidney, and bladder cancer. This study added evidence to the causal effect of gallstones on stomach, liver and bile duct, kidney, and bladder cancer, highlighting the importance of cancer screening in individuals with gallstones.

High leafy and root vegetables and high rice dietary patterns were associated with primary and secondary bile acid levels in the feces

Colorectal cancer has the second highest mortality among cancer sites worldwide, with increasing morbidity, high recurrence rates, and even poorer postoperative quality of life. Therefore, preventive strategies for colorectal cancer should be established. This study aimed to cross-sectionally explore dietary patterns affecting the intestinal metabolism of bile acids (BAs), a risk factor for colorectal cancer, in young Japanese women. We collected fecal samples for intestinal microbiota and BA analysis. We used the Bristol scale to determine 1-week defecation status. Moreover, the brief-type self-administered diet history questionnaire was used for habitual dietary intake status. Reduced-rank regression analysis revealed dietary patterns related to fecal BA levels. The relationship between dietary patterns and fecal BA levels was adjusted for defecation status and intestinal microbiota variables using analysis of covariance. Reduced-rank regression analysis generated two dietary pattern scores related to fecal BA levels. First, the score was associated with a greater intake of leafy and root vegetables, and higher values were associated with greater fecal cholic and chenodeoxycholic acid levels and lower deoxycholic and lithocholic acid levels. Second, the score was associated with greater rice intake and lower Western sweets, pork, beef, and egg intake, and higher values were associated with lower deoxycholic and lithocholic acid levels. These relationships remained after adjusting for intestinal microbiota and defecation status variables.

Association between bowel movement frequency, stool consistency and MAFLD and advanced fibrosis in US adults: a cross-sectional study of NHANES 2005-2010

BACKGROUND

Although previous studies have established associations between specific gut microbiota (GM) and metabolic dysfunction-associated fatty liver disease (MAFLD), research examining the relationship between functional gastrointestinal symptoms and MAFLD, including advanced fibrosis, remains limited. This study aims to investigate the association between stool consistency, bowel movement frequency (BMF), and the occurrence of MAFLD and advanced fibrosis in U.S. adults.

METHODS

This population-based study included 9,928 adults from the 2005-2010 National Health and Nutrition Examination Survey (NHANES), with a mean age of 47.19 ± 16.65 years, comprising 47.7% males and 52.3% females. Weighted logistic regression was used to assess the association between stool consistency, BMF, and MAFLD or advanced fibrosis. A linear trend was assessed by treating BMF categories as continuous variables with ordinal values. The dose-response relationship between BMF and MAFLD was analyzed using restricted cubic splines (RCS) regression. Sensitivity and subgroup analyses were performed to confirm the robustness of the findings.

RESULTS

In the RCS regression, no significant nonlinear relationship was observed between BMF and the risk of MAFLD (p-overall < 0.0001; p-nonlinear = 0.0663). The multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for MAFLD were 0.82 (95% CI 0.69-0.98), 1.31 (95% CI 1.16-1.46), and 1.50 (95% CI 1.14-1.99) for participants with 3-6 BMs/week, 1-2 BMs/day, and > 2 BMs/day, respectively, compared to those with once/day (p-trend < 0.001). For stool consistency, hard stools were associated with a decreased risk of MAFLD (OR 0.77; 95% CI 0.62-0.95), whereas loose stools increased the risk (OR 1.37; 95% CI 1.05-1.80), relative to normal stools. A significant interaction between BMF and age was observed. No significant associations were found between stool consistency or BMF and advanced liver fibrosis. Sensitivity analyses confirmed the robustness of these findings.

CONCLUSIONS

This cross-sectional study demonstrates that a BMF of 3-6 BMs/week and hard stools are associated with a reduced risk of MAFLD, whereas a BMF of more than once/day and loose stools are linked to an increased risk of MAFLD. Moreover, no significant associations were observed between stool consistency, BMF, and advanced fibrosis among individuals diagnosed with MAFLD.

CLINICAL TRIAL NUMBER

Not applicable.

Predictive value of bile acids as metabolite biomarkers for gallstone disease: A systematic review and meta-analysis

BACKGROUND

The profiles of bile acids (BAs) in patients with gallstone disease (GSD) have been found to be altered markedly though in an inconsistent pattern. This study aims to characterize the variation of the BA profiles in GSD patients, thereby to discover the potential metabolite biomarkers for earlier detection of GSD.

METHODS

Literature search of eight electronic database in both English and Chinese was completed on May 11, 2023. The qualitative and quantitative reviews were performed to summarize the changes of BA profiles in GSD patients compared with healthy subjects. The concentrations of BAs were adopted as the primary outcomes and the weighted mean differences (WMDs) and 95% confidence interval (CI) were generated by random-effects meta-analysis models.

RESULTS

A total of 30 studies were enrolled which included 2313 participants and reported the 39 BAs or their ratios. Qualitative review demonstrated serum Taurocholic Acid (TCA), Glycochenodeoxycholic acid (GCDCA), Glycocholic acid (GCA), Taurochenodeoxycholic acid (TCDCA), Glycodeoxycholic acid (GDCA) and Deoxycholic acid (DCA) were significantly increased in GSD patients compared with healthy subjects. Meta analysis was performed in 16 studies and showed that serum Total BAs (TBA) (WMD = 1.36μmol/L, 95%CI = 0.33; 2.4) was elevated however bile TBA (WMD = -36.96mmol/L, 95%CI = -52.32; -21.6) was declined in GSD patients. GCA (WMD = 0.83μmol/L, 95%CI = 0.06; 1.6) and TCA (WMD = 0.51μmol/L; 95%CI = 0.18; 0.85) were both increased in serum sample; TCDCA (WMD = 2.64mmol/L, 95%CI = 0.16; 5.12) was rising, however GCDCA (WMD = -13.82mmol/L, 95%CI = -21.86; -5.78) was falling in bile sample of GSD patients. The level of serum DCA in the GSD patients was found to be increased by using chromatography, yet decreased by chromatography mass spectrometry.

CONCLUSION

The profiles of BAs demonstrated distinctive changes in GSD patients compared with healthy control subjects. Serum GCA, TCA and GCDCA, as the typically variant BAs, presented as a potential marker for earlier diagnosis of GSD, which could facilitate early prophylactic intervention. Yet, further validation of these biomarkers by longitudinal studies is still warranted in the future. PROSPERO registration number CRD42022339649.

The effects of pks+ Escherichia coli and bile acid in colorectal tumorigenesis among people with cholelithiasis or cholecystectomy

BACKGROUND AND AIM

Patients with cholelithiasis (CL) or cholecystectomy (CE) would have more chances of getting colorectal adenoma (CRA) or cancer (CRC). We aimed to figure out the effects of gut microbiota and bile acid on colorectal neoplasm in CL and CE patients.

METHODS

This was a retrospective observational study that recruited 514 volunteers, including 199 people with normal gallbladders (normal), 152 CL, and 163 CE patients. Discovery cohort was established to explore the difference in gut microbiota through 16S rRNA and metagenomics sequencing. Validation cohort aimed to verify the results through quantitative polymerase chain reaction (qPCR).

RESULTS

Significant enrichment of Escherichia coli was found in patients with cholelithiasis or cholecystectomy both in the discovery cohort (16S rRNA sequencing, PNormal-CL = 0.013, PNormal-CE = 0.042; metagenomics sequencing, PNormal-CE = 0.026) and validation cohort (PNormal-CL < 0.0001, PNormal-CE < 0.0001). Pks+ E. coli was found enriched in CL and CE patients through qPCR (in discovery cohort: PNormal-CE = 0.018; in validation cohort: PNormal-CL < 0.0001, PNormal-CE < 0.0001). The differences in bile acid metabolism were found both through Tax4Fun analysis of 16S rRNA sequencing (Ko00120, primary bile acid biosynthesis, PNormal-CE = 0.014; Ko00121, secondary bile acid biosynthesis, PNormal-CE = 0.010) and through metagenomics sequencing (map 00121, PNormal-CE = 0.026). The elevation of serum total bile acid of CE patients was also found in validation cohort (PNormal-CE < 0.0001). The level of serum total bile acid was associated with the relative abundance of pks+ E. coli (r = 0.1895, P = 0.0012).

CONCLUSIONS

E. coli, especially pks+ species, was enriched in CL and CE patients. Pks+ E. coli and bile acid metabolism were found associated with CRA and CRC in people after cholecystectomy.

Evidence-based clinical practice guidelines for cholelithiasis 2021

The Japanese Society of Gastroenterology first published evidence-based clinical practice guidelines for cholelithiasis in 2010, followed by a revision in 2016. Currently, the revised third edition was published to reflect recent evidence on the diagnosis, treatment, and prognosis of cholelithiasis conforming to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. Following this revision, the present English version of the guidelines was updated and published herein. The clinical questions (CQ) in the previous version were reviewed and rearranged into three newly divided categories: background questions (BQ) dealing with basic background knowledge, CQ, and future research questions (FRQ), which refer to issues that require further accumulation of evidence. Finally, 52 questions (29 BQs, 19 CQs, and 4 FRQs) were adopted to cover the epidemiology, pathogenesis, diagnosis, treatment, complications, and prognosis. Based on a literature search using MEDLINE, Cochrane Library, and Igaku Chuo Zasshi databases for the period between 1983 and August 2019, along with a manual search of new information reported over the past 5 years, the level of evidence was evaluated for each CQ. The strengths of recommendations were determined using the Delphi method by the committee members considering the body of evidence, including benefits and harms, patient preference, and cost-benefit balance. A comprehensive flowchart was prepared for the diagnosis and treatment of gallbladder stones, common bile duct stones, and intrahepatic stones, respectively. The current revised guidelines are expected to be of great assistance to gastroenterologists and general physicians in making decisions on contemporary clinical management for cholelithiasis patients.

No association between cholecystectomy and risk of colorectal cancer: a meta-analysis of cohort studies

OBJECTIVE

Cohort studies have reported an association between colorectal cancer and cholecystectomy. However, the conclusions are inconsistent. Thus, this meta-analysis will quantify the risk of colorectal cancer following cholecystectomy.

METHODS

PubMed, EMBASE and Cochrane Library databases were searched for relevant cohort studies. The quality of individual observational studies was assessed using the Newcastle-Ottawa Quality Assessment Scale. The relative risk of colorectal cancer after cholecystectomy was calculated using STATA 14.0 software. Subgroup and sensitivity analyses were used to examine the source of heterogeneity. Funnel plots and Egger's test were finally performed to assess the publication bias.

RESULTS

This meta-analysis included 14 studies comprising 2,283,616 subjects. Pooled analysis indicated that cholecystectomy was not a risk factor for colorectal cancer (Colorectal: RR 1.06; 95% CI 0.75-1.51, p = 0.739 Colon: RR 1.30; 95% CI 0.88-1.93, p = 0.182 Rectal: RR 0.99; 95% CI 0.74-1.32, p = 0.932). Subgroup showed that patients are at an increased risk of sigmoid colon following cholecystectomy (RR 1.42; 95% CI 1.27-1.58, p = 0.000). Furthermore, it was shown that both females and males undergoing cholecystectomy may have higher risks of colon cancer (Female: RR = 1.47, 95% CI 1.01-2.14, P = 0.042 Male: RR = 1.32; 95% CI 1.07-1.63, P = 0.010), which is similarly observed in the right colon (Female: RR 1.99; 95% CI 1.31-3.03, p = 0.001, P = 0.017 Male: RR 1.68; 95% CI 0.81-3.49, p = 0.166).

CONCLUSIONS

No clear evidence to support the association between cholecystectomy and an increased risk of colorectal cancer. For patients with valid indications, timely cholecystectomy could be performed without the risk of colorectal cancer.

Defecation status, intestinal microbiota, and habitual diet are associated with the fecal bile acid composition: a cross-sectional study in community-dwelling young participants

PURPOSE

Bile acid (BA) metabolism by intestinal bacteria is associated with the risk of gastrointestinal diseases; additionally, its control has become a modern strategy for treating metabolic diseases. This cross-sectional study investigated the influence of defecation status, intestinal microbiota, and habitual diet on fecal BA composition in 67 community-dwelling young participants.

METHODS

Feces were collected for intestinal microbiota and BA analyses; data about defecation status and dietary habits were collected using the Bristol stool form scales and a brief-type self-administered diet history questionnaire, respectively. The participants were categorized into four clusters based on their fecal BA composition, according to cluster analysis, and tertiles based on deoxycholic acid (DCA) and lithocholic acid (LCA) levels.

RESULTS

The high primary BA (priBA) cluster with high fecal cholic acid (CA) and chenodeoxycholic acid (CDCA) levels had the highest frequency of normal feces, whereas the second BA (secBA) cluster with high levels of fecal DCA and LCA had the lowest. Alternately, the high-priBA cluster had a distinct intestinal microbiota, with higher Clostridium subcluster XIVa and lower Clostridium cluster IV and Bacteroides. The low-secBA cluster with low fecal DCA and LCA levels had the lowest animal fat intake. Nevertheless, the insoluble fiber intake of the high-priBA cluster was significantly higher than that of the high-secBA cluster.

CONCLUSION

High fecal CA and CDCA levels were associated with distinct intestinal microbiota. Conversely, high levels of cytotoxic DCA and LCA were associated with increased animal fat intake and decreased frequency of normal feces and insoluble fiber intake.

CLINICAL TRIAL REGISTRY

University Hospital Medical Information Network (UMIN) Center system (UMIN000045639); date of registration: 15/11/2019.

Advancing human gut microbiota research by considering gut transit time

Accumulating evidence indicates that gut transit time is a key factor in shaping the gut microbiota composition and activity, which are linked to human health. Both population-wide and small-scale studies have identified transit time as a top covariate contributing to the large interindividual variation in the faecal microbiota composition. Despite this, transit time is still rarely being considered in the field of the human gut microbiome. Here, we review the latest research describing how and why whole gut and segmental transit times vary substantially between and within individuals, and how variations in gut transit time impact the gut microbiota composition, diversity and metabolism. Furthermore, we discuss the mechanisms by which the gut microbiota may causally affect gut motility. We argue that by taking into account the interindividual and intraindividual differences in gut transit time, we can advance our understanding of diet-microbiota interactions and disease-related microbiome signatures, since these may often be confounded by transient or persistent alterations in transit time. Altogether, a better understanding of the complex, bidirectional interactions between the gut microbiota and transit time is required to better understand gut microbiome variations in health and disease.

Letter: association of circulating bile acid concentrations and non-alcoholic fatty liver disease

This article is linked to Rivera–Andrade et al papers. To view these articles, visit https://doi.org/10.1111/apt.16948 and https://doi.org/10.1111/apt.17059

Surgical Treatment for Colorectal Cancer Partially Restores Gut Microbiome and Metabolome Traits

The gut microbiome and metabolites are associated with CRC progression and carcinogenesis. Postoperative CRC patients are reported to be at an increased CRC risk; however, how gut microbiome and metabolites are related to CRC risk in postoperative patients remains only partially understood.

Gut Microbiota Dysbiosis and COVID-19: Possible Links

Microbiota in the gastrointestinal system is a major determinant in health and disease status with its influence on immunity. Bidirectional relationship between gut microbiota and host immune system is well balanced in healthy individuals and a disruption (dysbiosis) can lead to gastrointestinal inflammations and metabolic disorders. Growing evidence support the cross-talk between gastrointestinal microbiota and lung that maintains host homeostasis and reduces the risk of disease development. The Gut-lung axis is possibly involved in the severity of COVID-19 with the association of dysbiosis. Targeted alterations in the gut microbiota could be considered to alleviate the disease severity.

An Update on the Lithogenic Mechanisms of Cholecystokinin a Receptor (CCKAR), an Important Gallstone Gene for Lith13

The cholecystokinin A receptor (CCKAR) is expressed predominantly in the gallbladder and small intestine in the digestive system, where it is responsible for CCK's regulation of gallbladder and small intestinal motility. The effect of CCKAR on small intestinal transit is a physiological response for regulating intestinal cholesterol absorption. The Cckar gene has been identified to be an important gallstone gene, Lith13, in inbred mice by a powerful quantitative trait locus analysis. Knockout of the Cckar gene in mice enhances cholesterol cholelithogenesis by impairing gallbladder contraction and emptying, promoting cholesterol crystallization and crystal growth, and increasing intestinal cholesterol absorption. Clinical and epidemiological studies have demonstrated that several variants in the CCKAR gene are associated with increased prevalence of cholesterol cholelithiasis in humans. Dysfunctional gallbladder emptying in response to exogenously administered CCK-8 is often found in patients with cholesterol gallstones, and patients with pigment gallstones display an intermediate degree of gallbladder motility defect. Gallbladder hypomotility is also revealed in some subjects without gallstones under several conditions: pregnancy, total parenteral nutrition, celiac disease, oral contraceptives and conjugated estrogens, obesity, diabetes, the metabolic syndrome, and administration of CCKAR antagonists. The physical-chemical, genetic, and molecular studies of Lith13 show that dysfunctional CCKAR enhances susceptibility to cholesterol gallstones through two primary mechanisms: impaired gallbladder emptying is a key risk factor for the development of gallbladder hypomotility, biliary sludge (the precursor of gallstones), and microlithiasis, as well as delayed small intestinal transit augments cholesterol absorption as a major source for the hepatic hypersecretion of biliary cholesterol and for the accumulation of excess cholesterol in the gallbladder wall that further worsens impaired gallbladder motor function. If these two defects in the gallbladder and small intestine could be prevented by the potent CCKAR agonists, the risk of developing cholesterol gallstones could be dramatically reduced.

Somatostatin analogues in the therapy of neuroendocrine tumors: Indications, contraindications, side-effects

The presence of somatostatin receptors (SSTRs) is crucial in planning the therapy of patients with neuroendocrine tumors. This applies especially to patients in whom surgery has proven unsuccessful or there are contraindications for it. Increased SSTR expression has been observed in many cancers originating in the neuroendocrine system. Among them we distinguish anterior pituitary adenomas producing GH in excess and leading to the development of acromegaly, adenocorticotropic adenomas that autonomously synthesize ACTH, which leads to the development of ACTH-dependent Cushing’s syndrome (Cushing’s disease), as well as adenomas of the anterior pituitary from thyrotropic cells. Rich expression of these receptors has been confirmed in epithelial tumors of neuroendocrine origin in the gastrointestinal tract, pancreas and lungs. Somatostatin analogues, also called somatostatin receptor ligands, are effective in symptomatic therapy; they enable disease control, exhibit anti-proliferative effects and allow hormonal balance, which reduces mortality among patients and improves their quality of life. The antitumor effect of somatostatin analogues has been proven in in vitro and in vivo studies. In therapy they are usually well tolerated and safe. For many years, somatostatin analogues have maintained an important place in the treatment of neuroendocrine tumors and are still the subject of many studies. The aim of the study is to analyze, based on available literature, therapeutic indications for the use of somatostatin analogues, taking into account contraindications for therapy and its possible side effects.

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.

The Effect of Cholecystectomy on the Risk of Colorectal Cancer in Patients with Gallbladder Stones

To evaluate the risk of colorectal cancer (CRC) after cholecystectomy for gallbladder stones (GBS).

METHODS

This nationwide population-based cohort study analyzed the inpatient data from the Taiwan National Health Insurance Research Database. The study cohort comprised of 83,963 patients aged 20 years undergoing cholecystectomy for GBS between 2000 and 2010. The control cohort comprised the GBS patients without cholecystectomy, who were propensity matched with the study cohort at a 1:1 ratio based on age, sex, comorbidities, and the index date for cholecystectomy.

RESULTS

The cumulative incidence of CRC within 6 months of follow-up was higher in the cholecystectomy cohort than that in the non-cholecystectomy cohort (aHR (adjusted hazard ratio) = 7.90, 95% confidence interval (CI) = 6.27-9.94; log-rank test, p < 0.001). The cumulative incidence of CRC after 6 months of follow-up was lower in the cholecystectomy cohort than that in the non-cholecystectomy cohort (aHR = 0.66, 95% CI = 0.60-0.73; log-rank test, p < 0.001), but the reduced risk of CRC for the cholecystectomy cohort was statistically significant only in rectal cancer after separately considering females (aHR = 0.64, 95% CI = 0.46-0.88) and males (aHR = 0.59, 95% CI = 0.44-0.79).

CONCLUSIONS

The positive association between cholecystectomy and the CRC risk within the first 6 months after cholecystectomy might be due to a detection bias or pre-existing CRC. However, cholecystectomy is associated with a decreased risk of rectal cancer, rather than proximal or distal colon cancer, after more than 6 months of follow-up.

Probiotic Enterococcus faecalis AG5 effectively assimilates cholesterol and produces fatty acids including propionate

Probiotics are known for their health-promoting abilities through the production of various metabolites, and also benefits are membrane associated. Probiotic Enterococcus faecalis AG5 has been previously assessed for its probiotic properties and this study further strengthens that claim. Strain AG5 was inoculated with 0.3% sodium glychocholate (glycine conjugated) and bile salt mixture for different time periods. The percentage assimilation of cholesterol ranged from 14% to 33.1% in the bile salt mixture, but was slightly higher, ranging from 16.55% to 53.1%, in sodium thioglycocholate alone. Similarly, the bile salt hydrolysis activity was measured in terms of cholic acid release at different intervals. The overall range of cholic acid released ranged from 70.4 to 479 µg/mL. Fatty acid production is also an important criterion for a probiotic selection and it was found that the strain produced several long-chain fatty acids (LCFA) such as tetradecanoic acid, hexadecanoic acid, octadecanoic acid and bis(6-methylheptyl) phthalate. Besides LCFA, AG5 produced short-chain fatty acids (SCFA) such as propionic acid, which was estimated comparing liquid chromatography and mass spectrometry with standard SCFA. Thus the ability of deconjugation of bile salt and SCFA production is a value-added property of probiotic AG5, with the promise of being beneficial for human health.

Gallbladder Polyps Are Associated with Proximal Colon Polyps

Background

The association between gallbladder (GB) disease and colorectal precancerous lesions remains elusive. This study sought to explore the association between GB disease and colorectal neoplasms at different locations.

Methods

Patients who received general health checkup from January to December 2008 were included and subgrouped into three groups by polyp location: proximal, distal, and whole colon. GB disease and other known risk factors for colon cancer were compared and analyzed. Different types of polyps at different locations were further investigated.

Results

Of a total of 3136 patients (1776 men and 1360 women; mean age, 49.3 years) who had colon polyps, 212 (6.8%) had GB stone and 512 (16.3%) had GB polyps. Patients in the proximal colon polyp group had higher rates of GB polyps and stones. GB polyps were independently associated with proximal colon polyps, including both hyperplastic polyps (odds ratio, 1.523; P = 0.034) and adenomatous polyps (odds ratio, 1.351; P = 0.048). No relationship between GB polyps and distal or any colon polyps was observed. Irrespective of the polyp location (i.e., proximal, distal, or any part of the colon), GB stone did not show any association with colon polyp.

Conclusions

We suggested that GB polyps are associated with proximal colon polyps. Colonoscopy may be a more effective strategy for screening proximal precancerous lesions among patients with GB polyps. The association between GB disease and colon polyps demands further prospective investigation.

Gastrointestinal defects in gallstone and cholecystectomized patients

BACKGROUND AND AIM

Several gallstone patients complain of dyspeptic symptoms, irrespective of the presence of typical colicky pain. Symptoms often persist after a cholecystectomy. Systematic studies on dyspepsia and dynamic gastrointestinal motor function are missing in gallstone patients with preserved gallbladder or after a cholecystectomy.

MATERIALS AND METHODS

Forty-six gallstone patients (age 55 ± 2 years; 15M, 31F) and 24 cholecystectomized patients (age 57 ± 2 years; 6M, 18F) (no difference in type and volume of gallstones between the two groups) were compared against a group of 65 healthy controls (age 51 ± 2 years; 30M, 35F). Dyspepsia occurring in the prior months was assessed by a questionnaire, gastric and gallbladder emptying by functional ultrasonography and orocecal transit time by a hydrogen breath test using a lactulose-enriched standard liquid meal.

RESULTS

Gallstone patients had significantly greater dyspepsia, fasting and residual gallbladder volumes, and slower gallbladder emptying, gastric emptying and small intestinal transit time than controls. In cholecystectomized patients, gastric emptying further delayed, compared to gallstone patients and controls.

CONCLUSION

Gallstone patients with the gallbladder "in situ" or after a cholecystectomy display dyspeptic symptoms. Symptoms are associated with multiple gastrointestinal motility defects involving the gallbladder, stomach and small intestine. After cholecystectomy, gastric emptying worsens.

Update on the Molecular Mechanisms Underlying the Effect of Cholecystokinin and Cholecystokinin-1 Receptor on the Formation of Cholesterol Gallstones

Cholecystokinin (CCK) is an important neuro-intestinal peptide hormone produced by the enteroendocrine I-cells in the upper part of small intestine. Protein- and fat-enriched food plays an important role in triggering CCK secretion from the intestine. Carbohydrates stimulate only small amounts of CCK release. The CCK-1 receptor (CCK-1R) is largely localized in the gallbladder, sphincter of Oddi, pancreas, small intestine, gastric mucosa, and pyloric sphincter, where it is responsible for CCK to regulate multiple digestive processes including gallbladder contraction, pancreatic secretion, small intestinal transit, and gastric emptying. Accumulated evidence clearly demonstrates that CCK regulates gallbladder and small intestinal motility through CCK-1R signaling cascade and the effect of CCK-1R on small intestinal transit is a physiological response for regulating intestinal cholesterol absorption. Disruption of the Cck or the Cck-1r gene in mice significantly increases the formation of cholesterol gallstones by disrupting gallbladder emptying and biliary cholesterol metabolism, as well as promoting intestinal absorption of cholesterol. Abnormalities in gallbladder motility function in response to exogenously administered CCK are found primarily in patients with cholesterol gallstones. Patients with pigment gallstones display an intermediate degree of gallbladder motility defect without gallbladder inflammation and enlarged fasting gallbladder. Dysfunctional gallbladder contractility has been found under several conditions such as pregnancy, obesity, diabetes, celiac disease, and total parenteral nutrition although gallstones are not observed. The gallbladder-specific CCK-1R-selective agonist may lead to an efficacious novel way for preventing gallstone formation by promoting gallbladder emptying, particularly for pregnant women and subjects with dysfunctional gallbladder motility function such as celiac patients, as well as patients with total parenteral nutrition.

Gallbladder stones and gallbladder polyps associated with increased risk of colorectal adenoma in men

BACKGROUND AND AIMS

Most cases of colorectal cancer develop via an adenoma to carcinoma sequence. Gallbladder polyps share some risk factors with colorectal polyps. Little is known about the relationship between gallbladder diseases and different status of colorectal polyps by gender. This study was to investigate the association of gallbladder stones and polyps with colorectal adenomas by gender in a Taiwanese population.

METHODS

A total of 7066 eligible subjects who underwent a total colonoscopy as a part of health check-up between January 2001 and August 2009 were recruited. Colonoscopic findings were classified into polyp-free, non-neoplastic polyps and colorectal adenomas. Gallbladder stones and gallbladder polyps were diagnosed based on ultrasonographic findings.

RESULTS

There was a significant difference in the status of colon polyps between subjects with and without gallbladder polyps. However, the status of colon polyps was not significantly different between subjects with or without gallbladder stones. After adjusting obesity, fasting plasma glucose, and other variables, there was a positive relationship between gallbladder polyps and colorectal adenomas (odds ratio [OR]: 1.396, 95% confidence interval [CI]: 1.115-1.747) but not non-neoplastic polyps in all subjects. In men, gallbladder polyps (OR: 1.560, 95% CI: 1.204-2.019) and gallbladder stones (OR: 1.465, 95% CI 1.081-1.984) were positively associated with colorectal adenomas. In women, neither gallbladder polyps nor gallbladder stones were significantly related to colon polyps.

CONCLUSIONS

Both gallbladder polyps and gallbladder stones were associated with an increased risk of colorectal adenomas in men but not in women. Gender difference was significant for the association between gallbladder lesions and colorectal polyps.

Alcohol, smoking and benign hepato-biliary disease

Gallstone disease and pancreatitis are the most frequent benign hepato-biliary causes of hospital admissions. Gallstone disease is prevalent, but symptomatic disease develops only in about one out of five carriers. Alcohol intake seems to protect gallstone formation in cohort studies possibly through effects on bile cholesterol metabolism, the enterohepatic circulation, and gallbladder function. The impact of smoking on gallstone formation seems minor. Both alcohol intake and smoking do not alter the clinical course of gallstone disease carriers. Cholecystectomy is the preferred treatment for symptomatic gallstone disease. Studies about the impact of alcohol and smoking on the post-cholecystectomy state are few and future studies should be performed. Pancreatitis is associated with both excessive alcohol intake and smoking in observational studies. Interpretation of associations with pancreatitis is hampered by an incomplete understanding of underlying mechanisms and by the co-existence of excessive alcohol intake and smoking. Smoking cessation and alcohol abstinence is recommended in the treatment of pancreatitis, but higher-level evidence is needed.

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.

Probiotics and the BSH-related cholesterol lowering mechanism: a Jekyll and Hyde scenario

Probiotic microorganisms have been documented over the past two decades to play a role in cholesterol-lowering properties via various clinical trials. Several mechanisms have also been proposed and the ability of these microorganisms to deconjugate bile via production of bile salt hydrolase (BSH) has been widely associated with their cholesterol lowering potentials in prevention of hypercholesterolemia. Deconjugated bile salts are more hydrophobic than their conjugated counterparts, thus are less reabsorbed through the intestines resulting in higher excretion into the feces. Replacement of new bile salts from cholesterol as a precursor subsequently leads to decreased serum cholesterol levels. However, some controversies have risen attributed to the activities of deconjugated bile acids that repress the synthesis of bile acids from cholesterol. Deconjugated bile acids have higher binding affinity towards some orphan nuclear receptors namely the farsenoid X receptor (FXR), leading to a suppressed transcription of the enzyme cholesterol 7-alpha hydroxylase (7AH), which is responsible in bile acid synthesis from cholesterol. This notion was further corroborated by our current docking data, which indicated that deconjugated bile acids have higher propensities to bind with the FXR receptor as compared to conjugated bile acids. Bile acids-activated FXR also induces transcription of the IBABP gene, leading to enhanced recycling of bile acids from the intestine back to the liver, which subsequently reduces the need for new bile formation from cholesterol. Possible detrimental effects due to increased deconjugation of bile salts such as malabsorption of lipids, colon carcinogenesis, gallstones formation and altered gut microbial populations, which contribute to other varying gut diseases, were also included in this review. Our current findings and review substantiate the need to look beyond BSH deconjugation as a single factor/mechanism in strain selection for hypercholesterolemia, and/or as a sole mean to justify a cholesterol-lowering property of probiotic strains.

Helicobacter pylori infection is associated with gallstones: Epidemiological survey in China

AIM

To elucidate the prevalence and risk factors for gallstones, primarily focusing on Helicobacter pylori (H. pylori) infection.

METHODS

A total of 10016 Chinese subjects, who had undergone physical examination, fasting (13)C urea breath test and abdominal ultrasonography, had sufficient blood test data, and had finished a questionnaire, were included in this cross-sectional study. Participants (n = 1122) who had previous eradication of H. pylori were studied separately.

RESULTS

Gallstones were discovered in 9.10% of men and 8.58% of women, with no significant sex difference. Multivariate analyses displayed that age, aspartate aminotransferase, total cholesterol, H. pylori infection, hepatitis C virus (HCV) infection, and fatty liver had a significant association with gallstones (P < 0.05). Successive multiple logistic regression analysis including index of odds ratio (OR) and standardized coefficient (β) indicated that older age (OR/β = 1.056/0.055), H. pylori infection (OR/β = 1.454/0.109), HCV infection (OR/β = 1.871/0.123), and fatty liver (OR/β = 1.947/0.189) had a significant positive association with gallstones. After age stratification, H. pylori infection and fatty liver still had a significant positive association with gallstones in any age-specific groups, whereas HCV infection had a significant positive association in patients aged > 40 years. The prevalence of gallstones among H. pylori-positive, H. pylori-eradicated, and H. pylori-negative subjects was 9.47%, 9.02%, and 8.46%, respectively. The matched analysis showed that gallstones among H. pylori eradicated subjects was significantly lower compared with H. pylori-positive subjects (P < 0.05).

CONCLUSION

H. pylori infection and fatty liver have a significant positive association with gallstones. H. pylori eradication may lead to prevention of 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.

Bile acids are nutrient signaling hormones

Bile salts play crucial roles in allowing the gastrointestinal system to digest, transport and metabolize nutrients. They function as nutrient signaling hormones by activating specific nuclear receptors (FXR, PXR, Vitamin D) and G-protein coupled receptors [TGR5, sphingosine-1 phosphate receptor 2 (S1PR2), muscarinic receptors]. Bile acids and insulin appear to collaborate in regulating the metabolism of nutrients in the liver. They both activate the AKT and ERK1/2 signaling pathways. Bile acid induction of the FXR-α target gene, small heterodimer partner (SHP), is highly dependent on the activation PKCζ, a branch of the insulin signaling pathway. SHP is an important regulator of glucose and lipid metabolism in the liver. One might hypothesize that chronic low grade inflammation which is associated with insulin resistance, may inhibit bile acid signaling and disrupt lipid metabolism. The disruption of these signaling pathways may increase the risk of fatty liver and non-alcoholic fatty liver disease (NAFLD). Finally, conjugated bile acids appear to promote cholangiocarcinoma growth via the activation of S1PR2.

Preliminary evaluation of probiotic properties of Lactobacillus strains isolated from Sardinian dairy products

Twenty-three Lactobacillus strains of dairy origin were evaluated for some functional properties relevant to their use as probiotics. A preliminary subtractive screening based on the abilities to inhibit the growth of microbial pathogens and hydrolyze conjugated bile salts was applied, and six strains were selected for further characterization including survival under gastrointestinal environmental conditions, adhesion to gut epithelial tissue, enzymatic activity, and some safety properties. All selected strains maintained elevated cell numbers under conditions simulating passage through the human gastrointestinal tract, well comparable to the values obtained for the probiotic strain Lactobacillus rhamnosus GG, and were able to adhere to Caco-2 cells to various extents (from 3 to 20%). All strains exhibited high aminopeptidase, and absent or very low proteolytic and strong β-galactosidase activities; none was found to be haemolytic or to produce biogenic amines and all were susceptible to tetracycline, chloramphenicol, erythromycin, ampicillin, and amoxicillin/clavulanic acid. Our results indicate that the Lactobacillus strains analyzed could be considered appropriate probiotic candidates, due to resistance to GIT simulated conditions, antimicrobial activity, adhesion to Caco-2 cell-line, and absence of undesirable properties. They could be used as adjunct cultures for contributing to the quality and health related functional properties of dairy products.

Bile acid malabsorption in chronic diarrhea: pathophysiology and treatment

BACKGROUND

Bile acid malabsorption (BAM) is a common but frequently under-recognized cause of chronic diarrhea, with an estimated prevalence of 4% to 5%.

METHODS

The published literature for the period 1965 to 2012 was examined for articles regarding the pathophysiology and treatment of BAM to provide an overview of the management of BAM in gastroenterology practice.

RESULTS

BAM is classified as type 1 (secondary to ileal dysfunction), type 2 (idiopathic) or type 3 (secondary to gastrointestinal disorders not associated with ileal dysfunction). The estimated prevalence of BAM is >90% in patients with resected Crohn disease (CD) and 11% to 52% of unresected CD patients (type 1); 33% in diarrhea-predominant irritable bowel syndrome (type 2); and is a frequent finding postcholecystectomy or postvagotomy (type 3). Investigations include BAM fecal bile acid assay, 23-seleno-25-homo-tauro-cholic acid (SeHCAT) testing and high-performance liquid chromatography of serum 7-α-OH-4-cholesten-3-one (C4), to determine the level of bile acid synthesis. A less time-consuming and expensive alternative in practice is an empirical trial of the bile acid sequestering agent cholestyramine. An estimated 70% to 96% of chronic diarrhea patients with BAM respond to short-course cholestyramine. Adverse effects include constipation, nausea, borborygmi, flatulence, bloating and abdominal pain. Other bile acid sequestering agents, such as colestipol and colesevelam, are currently being investigated for the treatment of BAM-associated diarrhea.

CONCLUSIONS

BAM is a common cause of chronic diarrhea presenting in gastroenterology practice. In accordance with current guidelines, an empirical trial of a bile acid sequestering agent is warranted as part of the clinical workup to rule out BAM.

Gut microbes, diet, and cancer

An expanding body of evidence supports a role for gut microbes in the etiology of cancer. Previously, the focus was on identifying individual bacterial species that directly initiate or promote gastrointestinal malignancies; however, the capacity of gut microbes to influence systemic inflammation and other downstream pathways suggests that the gut microbial community may also affect risk of cancer in tissues outside of the gastrointestinal tract. Functional contributions of the gut microbiota that may influence cancer susceptibility in the broad sense include (1) harvesting otherwise inaccessible nutrients and/or sources of energy from the diet (i.e., fermentation of dietary fibers and resistant starch); (2) metabolism of xenobiotics, both potentially beneficial or detrimental (i.e., dietary constituents, drugs, carcinogens, etc.); (3) renewal of gut epithelial cells and maintenance of mucosal integrity; and (4) affecting immune system development and activity. Understanding the complex and dynamic interplay between the gut microbiome, host immune system, and dietary exposures may help elucidate mechanisms for carcinogenesis and guide future cancer prevention and treatment strategies.

Comparison among Fecal Secondary Bile Acid Levels, Fecal Microbiota andClostridium scindensCell Numbers in Japanese

Bile acid 7alpha-dehydroxylation by intestinal bacteria, which converts cholic acid and chenodeoxycholic acid to deoxycholic acid (DCA) and lithocholic acid (LCA), respectively, is an important function in the human intestine. Clostridium scindens is one of the most important bacterial species for bile acid 7alpha-dehydroxylation because C. scindens has high levels of bile acid 7alpha-dehydroxylating activity. We quantified C. scindens and secondary bile acids, DCA and LCA, in fecal samples from 40 healthy Japanese and investigated their correlation. Moreover, we used terminal restriction fragment length polymorphism (T-RFLP) analysis to investigate the effect of fecal microbiota on secondary bile acid levels. There was no correlation between C. scindens and secondary bile acid in fecal samples. On the other hand, T-RFLP analysis demonstrated that fecal microbiota associated with high levels of DCA were different from those associated with low levels of DCA, and furthermore that fecal microbiota in the elderly (over 72 years) were significantly different from those in younger adults (under 55 years). These results suggest that intestinal microbiota have a stronger effect on DCA level than does the number of C. scindens cells.

Laxative treatment with polyethylene glycol decreases microbial primary bile salt dehydroxylation and lipid metabolism in the intestine of rats

Polyethylene glycol (PEG) is a frequently used osmotic laxative that accelerates gastrointestinal transit. It has remained unclear, however, whether PEG affects intestinal functions. We aimed to determine the effect of PEG treatment on intestinal sterol metabolism. Rats were treated with PEG in drinking water (7%) for 2 wk or left untreated (controls). We studied the enterohepatic circulation of the major bile salt (BS) cholate with a plasma stable isotope dilution technique and determined BS profiles and concentrations in bile, intestinal lumen contents, and feces. We determined the fecal excretion of cholesterol plus its intestinally formed metabolites. Finally, we determined the cytolytic activity of fecal water (a surrogate marker of colorectal cancer risk) and the amount and composition of fecal microbiota. Compared with control rats, PEG treatment increased the pool size (+51%; P < 0.01) and decreased the fractional turnover of cholate (-32%; P < 0.01). PEG did not affect the cholate synthesis rate, corresponding with an unaffected fecal primary BS excretion. PEG reduced fecal excretion of secondary BS and of cholesterol metabolites (each P < 0.01). PEG decreased the cytolytic activity of fecal water [54 (46-62) vs. 87 (85-92)% erythrocyte potassium release in PEG-treated and control rats, respectively; P < 0.01]. PEG treatment increased the contribution of Verrucomicrobia (P < 0.01) and decreased that of Firmicutes (P < 0.01) in fecal flora. We concluded that PEG treatment changes the intestinal bacterial composition, decreases the bacterial dehydroxylation of primary BS and the metabolism of cholesterol, and increases the pool size of the primary BS cholate in rats.

Gallstones are associated with colonic adenoma: a meta-analysis

BACKGROUND

Increased levels of secondary bile acids after gallstone disease and cholecystectomy are believed to increase the risk of colorectal cancer. It remains unclear whether there is a similar risk of developing adenomas. The aim of this meta-analysis was to determine the risk of developing colonic adenomas following gallstone disease or cholecystectomy.

METHODS

The study was based on a systematic search of PubMed, MEDLINE, EMBASE, and Current Contents (1950-2012). Selection criteria were developed to sort for studies exploring the relationship between cholelithiasis, cholecystectomy, and colonic adenoma in an adult population. A random-effects model was used to generate pooled odds ratios (OR) and 95 % confidence intervals (CI). Publication bias and heterogeneity were assessed.

RESULTS

Of the 1,276 studies identified, 14 were suitable for final analysis. There were 253,059 subjects in total, 42,543 of whom were diagnosed with colonic adenoma, and 28,281 of whom had gallstones or underwent cholecystectomy. There was a significant risk of developing colonic adenoma if gallstones were present (OR = 2.26; 95 % CI = 1.83-2.81). A risk was also seen with cholecystectomy (OR = 1.15; 95 % CI = 1.04-1.26), but this risk was negated when only adjusted odds were selected (OR = 1.01; 95 % CI = 0.91-1.12). No publication bias and only low levels of heterogeneity existed.

CONCLUSIONS

Gallstones increase the risk of colonic adenoma. No association exists with cholecystectomy.

Incidence of gall stone formation in acromegalic patients on octreotide therapy

OBJECTIVE

Octreotide, a long-acting synthetic somatostatin analog, has been widely used for ac-romegalic patients. Gastrointestinal (GI) side effects and gall stones are predominant side effects. We report incidence of gall stones in our cohort of acromegalic patients treated with octreotide therapy.

DESIGN

Retrospective case observational study.

SETTING

Endocrinology Unit, Dr. Ram Manohar Lohia, Hospital, New Delhi.

MATERIALS AND METHODS

Patients of acromegaly on primary or secondary octreotide therapy.

INTERVENTION

Patients were enquired regarding complaints related to the GI system and their medical records were reviewed. Ultrasound films at various intervals while on octerotide therapy were evaluated by the radiologist for presence of sludge and development of gall stones.

RESULTS

Of seven patients, five developed gallstones and sludge was seen in three patients at intervals ranging from 11 to 36 months postoctreotide initiation.

CONCLUSION

A high incidence of gall stone formation in the present study as compared to the West was noted, the reasons for which are not clear.

Gallstone disease is associated with rectal cancer: a meta-analysis

BACKGROUND

Increased levels of secondary bile acids after cholecystectomy and cholelithiasis are believed to increase the risk of colorectal cancer, and several studies have suggested that the risk of colorectal cancer may be the greatest proximally. Numerous conflicting studies have been published and it remains unclear whether the risk is apparent in the rectum. This meta-analysis aims to determine the risk of developing rectal cancer following gallstone disease or cholecystectomy.

METHODS

The prospective protocol included a literature search of PubMed, MEDLINE, EMBASE, and Current Contents (1950-2011). Selection criteria were developed to sort for studies exploring the relationship between cholelithiasis, cholecystectomy, and rectal cancer in an adult population. A random-effects model was used to generate pooled odds ratios (OR) and 95% confidence intervals (CI). Publication bias and heterogeneity were assessed.

RESULTS

Of the 2358 studies identified, 42 were suitable for final analysis. There were 1,547,506 subjects in total, 14,226 diagnosed with rectal cancer, and 496,552 with gallstones or cholecystectomy. There was a statistically significant risk of rectal cancer following cholelithiasis (OR = 1.33; 95% CI = 1.02-1.73), though no risk was apparent following cholecystectomy (OR = 1.14; 95% CI = 0.92-1.41).

CONCLUSIONS

Cholelithiasis increases the risk of rectal cancer. No association exists between cholecystectomy and rectal cancer.

Voluntary wheel running exercise and dietary lactose concomitantly reduce proportion of secondary bile acids in rat feces

According to epidemiologic studies, a negative correlation exists between exercise amount and subsequent cancer development risk in the large intestine. The proportion of secondary bile acids (SBA) in the large intestine is related to subsequent risk for colorectal carcinogenesis. The aim of this study was to investigate the effects of voluntary wheel running exercise and dietary intervention on bile acid (BA) metabolism in the large intestine. Wistar/ST rats (6 wk old) were divided into two groups, exercise and sedentary, after acclimation. Four days after the animals were assigned to a group, rats in each group were fed diets supplemented with different carbohydrate sources including dextrin, sucrose, and lactose. The wheel running period was 4 wk in the exercise group, whereas rats in the sedentary group remained in individual cages during this period. BA composition in collected feces was analyzed with ultraperformance liquid chromatography-electrospray ionization mass spectrometry. We found that wheel running exercise decreased plasma concentrations of cholesterol, triglyceride, and free fatty acids. These decreases were accompanied by a reduction in the proportion of SBA to primary BA (PBA) in feces; however, daily excretion of BA was comparable regardless of wheel running exercise. In addition, ingestion of lactose decreased the SBA-to-PBA ratio and suppressed production of hyodeoxycholic acid in feces. In conclusion, voluntary wheel running exercise, in combination with dietary intervention, could independently reduce the SBA-to-PBA ratio within the large intestine without changing BA excretion. These changes may contribute to the prevention of colorectal carcinogenesis.

Bile acids: short and long term effects in the intestine

Bile acids have secretory, motility and antimicrobial effects in the intestine. In patients with bile acid malabsorption the amount of primary bile acids in the colon is increased compared to healthy controls. Deoxycholic acid is affecting the intestinal smooth muscle activity. Chenodeoxycholic acid has the highest potency to affect intestinal secretion. Litocholic acid has little effect in the lumen of intestine compared to both deoxycholic acid and chenodeoxycholic acid. There is no firm evidence that clinically relevant concentrations of bile acids induce colon cancer. Alterations in bile acid metabolism may be involved in the pathophysiology of constipation.

Pathogenesis of gallstones

Cholesterol gallstone formation is a complex process and involves phase separation of cholesterol crystals from supersaturated bile. In most cases, cholesterol hypersecretion is considered the primary event in gallstone formation. The sterol is transported through the hepatocytic canalicular membrane by ABCG5-G8. Expression of this transport protein is regulated by transcription factor Liver X Receptor-alpha, which may be responsible for biliary hypersecretion. Hydrophobic bile salt pool, bile concentration, excess pronucleating mucin, and impaired gallbladder and intestinal motility are secondary phenomena in most cases but nevertheless may contribute to gallstone formation.

The prevalence and risk factors for gallstone disease

Gallstone disease is one of the most prevalent gastrointestinal disorders. In addition, the costs associated with the diagnosis and treatment of gallstone disease have been rapidly increasing. The etiology and pathogenesis of gallstone disease remains incompletely understood. Gallstone formation may result from a complex interaction of genetic and environmental factors. This article reviews the prevalence and risk factors associated with gallstone disease. Understanding the pathogenesis of gallstone disease could lead to the development of better therapeutic and preventive strategies for dealing with this disease.

Cholelithiasis is a risk factor for colorectal adenoma

OBJECTIVES

Postcholecystectomy patients show moderate risk of colorectal cancer. However, few studies have investigated the relationship between cholelithiasis and colorectal adenoma. We examined this possibility through a combination of colonoscopy and ultrasonography in asymptomatic Japanese.

METHODS

We reviewed a subgroup of subjects drawn from a prospective annual colonoscopy screening survey. Subjects who underwent both ultrasonography and colonoscopy, and completed a questionnaire regarding lifestyle habits were entered. We investigated whether subjects with cholelithiasis or a previous cholecystectomy showed an increased risk of colorectal adenoma, as compared with subjects with normal gallbladders.

RESULTS

Data of 4,458 subjects (men 3,053, women 1,405, mean age +/- SD 46.1 +/- 8.62 yr) were analyzed. Cholelithiasis was detected in 206 subjects, 4,189 subjects had normal gallbladders, and 63 subjects had cholecystectomies. The prevalence of colorectal adenoma was 29.6% (61/206) in subjects with cholelithiasis, which was significantly higher when compared with normal subjects, with a prevalence of 17.7% (741/4,189, P < 0.001). In cholecystectomy patients, only 15.9% (10/63) developed colorectal adenomas, which was not significantly different from the control group. In a multivariate analysis controlling for sex, age, family history of colorectal cancer, alcohol, smoking, and body mass index, cholelithiasis was shown to be an independent risk factor for colorectal adenoma (adjusted OR 1.57, 95% CI 1.14-2.18). Cholelithiasis was strongly associated with multiple (> or = 3 lesions, adjusted OR 2.39, 95% CI 1.21-4.72) and left-sided colorectal adenomas (adjusted OR 1.82, 95% CI 1.28-2.59).

CONCLUSIONS

Cholelithiasis is a risk factor for colorectal adenoma.

Intestinal bile acid physiology and pathophysiology

Bile acids (BAs) have a long established role in fat digestion in the intestine by acting as tensioactives, due to their amphipathic characteristics. BAs are reabsorbed very efficiently by the intestinal epithelium and recycled back to the liver via transport mechanisms that have been largely elucidated. The transport and synthesis of BAs are tightly regulated in part by specific plasma membrane receptors and nuclear receptors. In addition to their primary effect, BAs have been claimed to play a role in gastrointestinal cancer, intestinal inflammation and intestinal ionic transport. BAs are not equivalent in any of these biological activities, and structural requirements have been generally identified. In particular, some BAs may be useful for cancer chemoprevention and perhaps in inflammatory bowel disease, although further research is necessary in this field. This review covers the most recent developments in these aspects of BA intestinal biology.