Disorders of bile acid metabolism in cholesterol gallstone disease

The impact of long-term (≥5 years) cholecystectomy on gut microbiota changes and its influence on colorectal cancer risk: based on 16S rDNA sequencing analysis

BACKGROUND

Colorectal cancer (CRC) continues to be a major global health concern. Recent advances in molecular biology have highlighted the gut microbiota's role in CRC. This study investigates long-term (≥5 years) gut microbiota changes in patients postcholecystectomy, comparing them with CRC patients and healthy controls to assess their impact on CRC development.

METHODS

Sixty participants were divided into three groups: 20 healthy controls, 20 postcholecystectomy (PCE) patients, and 20 CRC patients. Demographic data and stool samples were collected. Gut microbiota composition, abundance, and diversity were analyzed using high-throughput 16S rDNA sequencing.

RESULTS

Significant differences in microbial community, α-diversity ( P  < 0.05) and β-diversity ( P  = 0.006), were observed among the three groups. At the phylum level, Firmicutes abundance was significantly reduced in PCE and CRC groups compared with the control group ( P  = 0.002), while changes in other phyla were not significant ( P >0.05). At the genus level, Bacteroides , Dialister , and Parabacteroides increased progressively from control to PCE to CRC groups ( P  = 0.004, 0.001, and 0.002). Prevotella decreased across these groups ( P  = 0.041). Faecalibacterium and Roseburia abundances were reduced in PCE and CRC groups compared with controls ( P  = 0.001 and 0.003). The Random Forest algorithm identified Parabacteroides , Bacteroides , Roseburia , and Dialister as key distinguishing genera.

CONCLUSION

The gut microbiota of long-term (≥5 years) PCE patients significantly differs from that of controls and resembles that of CRC patients, suggesting a potential link between cholecystectomy and CRC development through key microbial changes.

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.

Gallbladder microbial species and host bile acids biosynthesis linked to cholesterol gallstone comparing to pigment individuals

Gallstones are crystalline deposits in the gallbladder that are traditionally classified as cholesterol, pigment, or mixed stones based on their composition. Microbiota and host metabolism variances among the different types of gallstones remain largely unclear. Here, the bile and gallstone microbial species spectra of 29 subjects with gallstone disease (GSD, 24 cholesterol and 5 pigment) were revealed by type IIB restriction site-associated DNA microbiome sequencing (2bRAD-M). Among them (21 subjects: 18 cholesterol and 3 pigment), plasma samples were subjected to liquid chromatography-mass spectrometry (LC-MS) untargeted metabolomics. The microbiome yielded 896 species comprising 882 bacteria, 13 fungi, and 1 archaeon. Microbial profiling revealed significant enrichment of Cutibacterium acnes and Microbacterium sp005774735 in gallstone and Agrobacterium pusense and Enterovirga sp013044135 in the bile of cholesterol GSD subjects. The metabolome revealed 2296 metabolites, in which malvidin 3-(6''-malonylglucoside), 2-Methylpropyl glucosinolate, and ergothioneine were markedly enriched in cholesterol GSD subjects. Metabolite set enrichment analysis (MSEA) demonstrated enriched bile acids biosynthesis in individuals with cholesterol GSD. Overall, the multi-omics analysis revealed that microbiota and host metabolism interaction perturbations differ depending on the disease type. Perturbed gallstone type-related microbiota may contribute to unbalanced bile acids metabolism in the gallbladder and host, representing a potential early diagnostic marker and therapeutic target for GSD.

Impact of cholecystectomy on acute coronary syndrome according to metabolic condition: a nationwide population-based cohort study

Gallbladder stones (GS) is associated with an increased risk of cardiovascular disease. However, the relationship between cholecystectomy for GS and acute coronary syndrome (ACS) is unknown. We investigated the ACS risk in patients with GS and its association with cholecystectomy. Data from the Korean National Health Insurance Service-National Sample Cohort from 2002 to 2013 was extracted. Overall, 64,370 individuals were selected through a 1:3 propensity score matching. Patients were stratified into two groups for comparison: the gallstone group, GS patients with or without cholecystectomy; and the control group, patients without GS or cholecystectomy. The gallstone group exhibited a higher risk of ACS than the control group (hazard ratio [HR], 1.30; 95% confidence interval [CI] 1.15-1.47; P < 0.0001). In the gallstone group, individuals without cholecystectomy had a higher risk of ACS development (HR: 1.35, 95% CI 1.17-1.55, P < 0.0001). Patients with GS with diabetes, hypertension, or dyslipidemia, had a higher risk of developing ACS than GS patients without the metabolic diseases (HR: 1.29, P < 0.001). The risk did not significantly differ after cholecystectomy compared to those without GS (HR: 1.15, P = 0.1924), but without cholecystectomy, the risk of ACS development was significantly higher than control group (1.30, 95% CI 1.13-1.50, P = 0.0004). Among patients without above metabolic disorders, cholecystectomy was still associated with increased ACS risk in the gallstone group (HR: 2.93, 95% CI 1.27-6.76, P = 0.0116). GS increased the risk of ACS. The effect of cholecystectomy on ACS risk differs according to the presence or absence of metabolic disorders. Thus, the decision to perform cholecystectomy for GS should consider both the ACS risk and the underlying disorders.

Bile acid metabolism and signaling, the microbiota, and metabolic disease

The diversity, composition, and function of the bacterial community inhabiting the human gastrointestinal tract contributes to host health through its role in producing energy or signaling molecules that regulate metabolic and immunologic functions. Bile acids are potent metabolic and immune signaling molecules synthesized from cholesterol in the liver and then transported to the intestine where they can undergo metabolism by gut bacteria. The combination of host- and microbiota-derived enzymatic activities contribute to the composition of the bile acid pool and thus there can be great diversity in bile acid composition that depends in part on the differences in the gut bacteria species. Bile acids can profoundly impact host metabolic and immunological functions by activating different bile acid receptors to regulate signaling pathways that control a broad range of complex symbiotic metabolic networks, including glucose, lipid, steroid and xenobiotic metabolism, and modulation of energy homeostasis. Disruption of bile acid signaling due to perturbation of the gut microbiota or dysregulation of the gut microbiota-host interaction is associated with the pathogenesis and progression of metabolic disorders. The metabolic and immunological roles of bile acids in human health have led to novel therapeutic approaches to manipulate the bile acid pool size, composition, and function by targeting one or multiple components of the microbiota-bile acid-bile acid receptor axis.

Hepatotoxicity of the Major Anthraquinones Derived From Polygoni Multiflori Radix Based on Bile Acid Homeostasis

Polygoni Multiflori Radix (PMR), the dried root of Polygonum Multiflorum Thunb., has been widely used as traditional Chinese medicines in clinical practice for centuries. However, the frequently reported hepatotoxic adverse effects hindered its safe use in clinical practice. This study aims to explore the hepatotoxic effect of PMR extract and the major PMR derived anthraquinones including emodin, chrysophanol, and physcion in mice and the underlying mechanisms based on bile acid homeostasis. After consecutively treating the ICR mice with PMR extract or individual anthraquinones for 14 or 28 days, the liver function was evaluated by measuring serum enzymes levels and liver histological examination. The compositions of bile acids (BAs) in the bile, liver, and plasma were measured by LC-MS/MS, followed by Principal Component Analysis (PCA) and Partial Least Squares Discriminate Analysis (PLS-DA). Additionally, gene and protein expressions of BA efflux transporters, bile salt export pump (Bsep) and multidrug resistance-associated protein 2 (Mrp2), were examined to investigate the underlying mechanisms. After 14-day administration, mild inflammatory cell infiltration in the liver was observed in the physcion- and PMR-treated groups, while it was found in all the treated groups after 28-day treatment. Physcion and PMR extract induced hepatic BA accumulation after 14-day treatment, but such accumulation was attenuated after 28-day treatment. Based on the PLS-DA results, physcion- and PMR-treated groups were partially overlapping and both groups showed a clear separation with the control group in the mouse liver. The expression of Bsep and Mrp2 in the physcion- and PMR-treated mouse liver was decreased after 14-day treatment, while the downregulation was abrogated after 28-day treatment. Our study, for the first time, demonstrated that both PMR extract and tested anthraquinones could alter the disposition of either the total or individual BAs in the mouse bile, liver, and plasma via regulating the BA efflux transporters and induce liver injury, which provide a theoretical basis for the quality control and safe use of PMR in practice.

Chronic cholecystitis: Diagnostic and therapeutic insights from formerly bile-farmed Asiatic black bears (Ursus thibetanus)

Across Southeast Asia and China, more than 17000 Asian bears are kept under suboptimal conditions and farmed for their bile to meet the consumer demand for traditional medicine products. Years of unsterile and repetitive bile extraction contribute to the development of chronic sterile or bacterial cholecystitis, a pathology commonly diagnosed in formerly bile-farmed bears. In both human and veterinary medicine, the diagnostic value of the macroscopic bile examination for assessing gallbladder disease is unclear. The objective of this study is to identify the role of gallbladder bile color, viscosity, and turbidity, while comparing them with established markers of cholecystitis. Moreover, it aims to define the optimal duration of oral antibiotic treatment for chronic bacterial cholecystitis in bears associated with bile farming. Thirty-nine adult, formerly bile-farmed Asiatic black bears (Ursus thibetanus) were examined under anesthesia and underwent percutaneous ultrasound guided cholecystocentesis. A total of 59 bile samples were collected with 20 animals sampled twice to evaluate the therapeutic success. All bile aspirates were assessed macroscopically and microscopically followed by submission for bacterial culture and antimicrobial sensitivity. In the majority of bears, samples with cytological evidence of bactibilia lacked inflammatory cells and did not always correlate with positive bacterial cultures. The most common bacterial isolates were Enterococcus spp, Streptococcus spp and Escherichia coli. Based on our findings, the optimal duration of antibiotic treatment for chronic bacterial cholecystitis is 30 days. Moreover, unlike Gamma-glutamyl Transferase (GGT) and gallbladder wall thickness, the organoleptic properties of bile were found to be reliable markers of chronic gallbladder inflammation with color and turbidity indicating cholestasis. The current study highlights the importance of cholecystocentesis for the management of gallbladder disease and provides initial results on the possible diagnostic value of macroscopic bile examination.

Polygonum multiflorum Thunb suppress bile acid synthesis by activating Fxr-Fgf15 signaling in the intestine

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonum multiflorum Thunb (Heshouwu, HSW) is commonly used in clinical medicine, while the hepatotoxicities of HSW are reported increasingly in recent years. Currently, researchers have demonstrated an essential role of Bile Acids (BAs) in liver diseases. The occurrence of hepatotoxicity cases linked to HSW are characterized by jaundice and cholestasis, suggesting an interaction that between BAs and HSW AIM OF THE STUDY: This study was designed to investigate the HSW-induced liver functional and histological changes in mice and the role of HSW on bile acid synthesis, metabolism, clearance and intestinal absorption.

MATERIALS AND METHODS

The mice were intragastrically (i.g.) given HSW at doses of 1.275 and 3.825 g/kg (Crude extracts /body weight) once a day for seven days. Liver function was evaluated by measuring the serum levels of enzymes and analyzing the liver histology. The LC/MS analysis was performed to quantify BAs from liver, ileum and serum. Moreover, the expression of bile metabolic-related transporters and metabolic enzymes at both protein and mRNA levels were observed to elucidate the underlying mechanisms.

RESULTS

Oral administration of HSW for 7 days could not cause liver damage. A significant change was observed for the concentrations of liver and serum BAs in treatment groups compared with normal control. The mRNA expression levels of bile acid excretory transporter (Bsep) and basolateral uptake transporter (Ntcp) were increased with the development of HSW. The concentrations of unconjugated BAs increased in mice intestines after the administration of HSW. Western blot and qRT-PCR analyses showed that HSW upregulated the protein and mRNA expression of Shp and Fgf15 in the ileum of the mice.

CONCLUSION

HSW treatment for 7days did not cause liver damage. HSW accelerated bile acid enterohepatic circulation and changed the composition of intestinal BAs, leding to the activation of Fxr-Fgf15 signal in intestines, and further inhibited the expression of Cyp7a1 in the liver.

Gallstone disease and increased risk of mortality: Two large prospective studies in US men and women

BACKGROUND AND AIM

Gallstone disease has been related to a higher prevalence and incidence of chronic conditions, such as dyslipidemia, obesity, and cardiovascular disease (CVD). However, limited data are available regarding whether gallstone disease is related to mortality.

METHODS

We examined the relationship of a history of gallstone disease and risk of death, using Cox proportional hazards regression analysis, among 86 030 women from the Nurses' Health Study and 43 949 men from the Health Professionals Follow-up Study.

RESULTS

During the up-to 32 years of follow-up, 34 011 all-cause deaths were confirmed, of which 8138 were CVD deaths and 12 173 were cancer deaths. For the participants with a history of gallstone disease compared with those without, the hazard ratio of total mortality was 1.16 (95% confidence interval 1.13, 1.20), of CVD mortality 1.11 (1.05, 1.17), of cancer mortality 1.15 (1.09, 1.20), and of other mortality 1.19 (1.14, 1.25) from a pooled-analysis of women and men (all P < 0.001). The multi-adjusted associations between gallstone disease and total mortality persisted among women and men, and among participants with various risk profiles including the different status of body mass index, hormone therapy use, diabetes, hypertension, and hypercholesterolemia (all P for interaction ≥ 0.09).

CONCLUSION

These data suggest that gallstone disease is associated with a higher risk of total mortality and disease-specific mortality, including CVD and cancer mortality, independent of various traditional risk factors.

MUC Expression in Gallbladder Epithelial Tissues in Cholesterol-Associated Gallbladder Disease

Background/Aims

Gallstone pathogenesis is linked to mucin hypersecretion and bacterial infection. Several mucin genes have been identified in gallbladder epithelial cells (GBECs). We investigated MUC expression in cholesterol-associated gallbladder disease and evaluated the relationship between mucin and bacterial infection.

Methods

The present study involved 20 patients with cholesterol stones with cholecystitis, five with cholesterol stones with cholesterolosis, six with cholesterol polyps, two with gallbladder cancer, and six controls. Canine GBECs treated with lipopolysaccharide were also studied. MUC3, MUC5AC, MUC5B, and MUC6 antibodies were used for dot/slot immunoblotting and immunohistochemical studies of the gallbladder epithelial tissues, canine GBECs, and bile. Reverse-transcription polymerase chain reaction was performed to evaluate MUC3 and MUC5B expression.

Results

MUC3, MUC5AC, MUC5B, and MUC6 were expressed in the normal gallbladder epithelium, and of those, MUC3 and MUC5B exhibited the highest expression levels. Greatly increased levels of MUC3 and MUC5B expression were observed in the cholesterol stone group, and slightly increased levels were observed in the cholesterol polyp group; MUC3 and MUC5B mRNA was also upregulated in those groups. Canine GBECs treated with lipopolysaccharide also showed upregulation of MUC3 and MUC5B.

Conclusions

The mucin genes with the highest expression levels in gallbladder tissue in cholesterol-associated diseases were MUC3 and MUC5B. Cholesterol stones and gallbladder infections were associated with increased MUC3 and MUC5B expression.

Gallstones and Risk of Coronary Heart Disease: Prospective Analysis of 270 000 Men and Women From 3 US Cohorts and Meta-Analysis

OBJECTIVE

Gallstone disease has been related to cardiovascular risk factors; however, whether presence of gallstones predicts coronary heart disease (CHD) is not well established.

APPROACH AND RESULTS

We followed up 269 142 participants who were free of cancer and cardiovascular disease at baseline from 3 US cohorts: the Nurses' Health Study (112 520 women; 1980-2010), Nurses' Health Study II (112 919 women; 1989-2011), and the Health Professionals Follow-up Study (43 703 men; 1986-2010) and documented 21 265 incident CHD cases. After adjustment for potential confounders, the hazard ratio for the participants with a history of gallstone disease compared with those without was 1.15 (95% confidence interval, 1.10-1.21) in Nurses' Health Study, 1.33 (95% confidence interval, 1.17-1.51) in Nurses' Health Study II, and 1.11 (95% confidence interval, 1.04-1.20) in Health Professionals Follow-up Study. The associations seemed to be stronger in individuals who were not obese, not diabetic, or were normotensive, compared with their counterparts. We identified 4 published prospective studies by searching PUBMED and EMBASE up to October 2015, coupled with our 3 cohorts, involving 842 553 participants and 51 123 incident CHD cases. The results from meta-analysis revealed that a history of gallstone disease was associated with a 23% (15%-33%) increased CHD risk.

CONCLUSION

Our findings support that a history of gallstone disease is associated with increased CHD risk, independently of traditional risk factors.

Oxidative stress markers, secondary bile acids and sulfated bile acids classify the clinical liver injury type: Promising diagnostic biomarkers for cholestasis

Clinicians sometimes encounter difficulty in choosing a therapeutic strategy due to the uncertainty regarding the type of liver injury. In particular, cholestasis is difficult to diagnose by conventional markers at an early stage of disease. The aim of this study was to identify promising biomarkers for distinguishing the symptom-based types of liver injury (e.g. hepatocellular injury, cholestasis), which was derived from a rigorously statistical perspective. The associations between diagnostic biomarkers (e.g. bile acid components, oxidative stress markers and liver fibrosis markers) and the liver injury types were assessed by a multiple logistic regression analysis using 304 blood samples from patients with liver disease. As a result, reductions in the lithocholic acid (LCA) and deoxycholic acid (DCA) levels, and elevation of the serum sulfated bile acid (SSBA), liver fibrosis marker IV collagen (type IV collagen), hyaluronic acid (HA) and reactive oxygen species (ROS) levels were all significantly associated with cholestasis. On the other hand, elevations in the LCA and type IV collagen levels, and a reduction in the ursodeoxy cholic acid (UDCA) level, were significantly associated with hepatocellular injury. The receiver operating characteristic (ROC) analyses showed that the largest area under the ROC curve (AUC) was found for ROS, followed by DCA, HA, LCA, SSBA and type IV collagen in the cholestatic-type cases. These results indicated that ROS, the secondary bile acid levels such as DCA and LCA, and SSBA are promising biomarkers for cholestasis and for classifying the type of liver injuries. This comprehensive approach will allow for an accurate diagnosis, which will facilitate the selection of an appropriate therapy at the onset of disease.

Kinetics of primary bile acids in patients after proctocolectomy and ileal pouch-anal anastomosis

BACKGROUND

The high incidence of cholesterol gallstones in patients after proctocolectomy with ileal pouch-anal anastomosis (IPAA) may be due to an increased loss of bile acids. We aimed to evaluate the kinetics of the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) in these patients.

METHODS

Pool sizes, synthesis rates, and fractional turnover rates of CA and CDCA were determined by combined capillary gas chromatography/isotope ratio mass spectrometry in serum samples after administration of [¹³C]CA and [¹³C]CDCA in 6 patients and 9 healthy volunteers.

RESULTS

In patients with IPAA, pool sizes of CA and CDCA were 11.5 (8.2-23.8) and 12.1 (6.7-20.1) µmol/kg, respectively, and were significantly lower than in healthy controls [36.0 (24-47) and 29.0 (21-42) µmol/kg, respectively; p < 0.05, each]. Fractional turnover rates of CA [1.19 (1.06-1.82) vs. 0.31 (0.13-0.54) per day] and CDCA [1.01 (0.50-1.63) vs. 0.23 (0.09-0.36) per day] were increased fourfold in patients with IPAA (p < 0.05, each). Synthesis rates of CDCA [10.2 (5.2-32.9) vs. 6.6 (2.7-10.5) µmol/kg per day, p = 0.05] and CA [15.1 (9.3-39.4) vs. 11.5 (3.1-20.5) µmol/kg per day, n.s.] tended to be higher in patients with IPAA than in controls.

CONCLUSION

The reduced pool size of primary bile acids may contribute to the high incidence of cholesterol gallstones in patients after proctocolectomy and IPAA.

Association of FXR gene variants with cholelithiasis

BACKGROUND AND AIM

Impairment of bile acid homeostasis is the most important risk factor of gallstone disease. Thereby the bile acid sensor farnesoid X receptor (FXR) plays a pivotal role in hepatic and intestinal bile acid metabolism. In this explorative study, the FXR gene was investigated to identify gene variants, associated with gallstone formation in a Caucasian population.

METHODS

Sequencing of the FXR gene was conducted in a randomly selected cohort of gallstone carriers (n=30) and control subjects (n=16) from Stuttgart, Germany. Genomic DNA was obtained from blood leukocytes. Genotype frequencies were established in the total cohort (controls: n=133, gallstone carriers: n=74). For expression analysis, total RNA and protein were isolated from ileal biopsies.

RESULTS

The sequencing showed the sole appearance of 10 SNPs in gallstone carriers. Further genotype analysis revealed significant gender- and weight-dependent frequency differences of 3 SNPs between gallstone carriers and controls in males (rs35724: OR=4.73, P=0.022) and normal weight subjects (rs11110385: OR=3.67, P=0.027; rs11110386: OR=3.67, P=0.027) applying the 11+12<>22 allele model. Furthermore, rs11110385 carriers showed a significantly decreased FXR protein expression (11+12<>22: P=0.003). Significant mRNA expression differences between lean rs11110385 carriers and non-carriers were observed in FXR target genes (decrease: ILBP: P=0.042, OSTalpha: P=0.071, FGF19: P=0.011. Increase: LRH1: P=0.044).

CONCLUSIONS

Three FXR gene variants (rs35724, rs11110385, rs11110386) were identified as potential susceptibility factors for cholelithiasis in a German cohort in gender- and weight-dependent manners. Thereby the tag SNP rs11110385 seemed to influence the activation of the FXR gene.

Role of farnesoid X receptor in inflammation and resolution

OBJECTIVE

The aim of this paper is to review the developments of farnesoid X receptor (FXR) biology, its ligands, and various functions, in particular we discuss the anti-inflammatory and anti-fibrotic role in chronic inflammatory diseases.

INTRODUCTION

FXR is a ligand-dependent transcription factor belonging to the nuclear hormone receptor superfamily. The accrued data have shown that the FXR plays important roles not only in bile acid, lipid metabolism, and carbohydrate homeostasis, but also in inflammatory responses. The anti-inflammatory and anti-fibrotic effects of FXR on chronic inflammatory diseases are not well documented.

METHODS

A literature survey was performed using PubMed database search to gather complete information regarding FXR and its role in inflammation.

RESULTS AND DISCUSSION

FXR is highly expressed in liver, intestine, kidney and adrenals, but with lower expression in fat tissue, heart and recently it has been found to express in lungs too. Primary bile acids, cholic acid and chenodeoxycholic acid are the natural endogenous ligands for FXR. GW4064 and 6α-ethyl-chenodeoxycholic acid are the synthetic high-affinity agonists. An exhaustive literature survey revealed that FXR acts as a key metabolic regulator and potential drug target for many metabolic syndromes that include chronic inflammatory diseases.

Upregulation of hepatic bile acid synthesis via fibroblast growth factor 19 is defective in gallstone disease but functional in overweight individuals

BACKGROUND

Fibroblast growth factor 19 (FGF19) is an enteric hormone regulating bile acid de novo synthesis by sensing ileal bile acid flux. However, the role of FGF19 in cholelithiasis has not yet been elucidated and therefore is investigated in the present study.

METHODS

Total mRNA and protein were isolated from ileal biopsies and used for tissue expression analysis. FGF19, 7α-hydroxycholesterol (7α-OH-Chol), 27-hydroxycholesterol (27-OH-Chol), and different bile acids were determined in the blood samples.

RESULTS

FGF19 serum levels did not differ between gallstone carriers and controls but were significantly decreased in the overweight individuals (-32%, p = 0.0002), irrespective of gallstone status (normalweight to overweight controls -29%, p = 0.0017; normalweight to overweight gallstone carriers -44%, p = 0.0338), and correlated inversely with bodyweight (p < 0.0001, ρ = -0.3317). Compared to non-overweight controls, apical sodium-dependent bile acid transporter expression was significantly diminished in the non-overweight gallstone carriers (-42%, P mRNA = 0.0393; -52%, p protein = 0.0169) as well as in the overweight controls (-24%, P mRNA = 0.0148; -43%, p protein = 0.0017). FGF19 expression varied widely and was similar in all groups. A significant negative correlation was noted between 7α-OH-Chol, 27-OH-Chol, and FGF19 serum levels (p < 0.01; ρ7α-OH-Chol = -0.2155; ρ27-OH-Chol = -0.2144) in obesity.

CONCLUSION

Upregulation of hepatic bile acid synthesis via FGF 19 is defective in gallstone disease but functional in overweight individuals.

Risk of primary liver cancer associated with gallstones and cholecystectomy: a meta-analysis

Background

Recent epidemiological evidence points to an association between gallstones or cholecystectomy and the incidence risk of liver cancer, but the results are inconsistent. We present a meta-analysis of observational studies to explore this association.

Methods

We identified studies by a literature search of PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and relevant conference proceedings up to March 2014. A random-effects model was used to generate pooled multivariable adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Between-study heterogeneity was assessed using Cochran’s Q statistic and the I².

Results

Fifteen studies (five case-control and 10 cohort studies) were included in this analysis. There were 4,487,662 subjects in total, 17,945 diagnoses of liver cancer, 328,420 exposed to gallstones, and 884,507 exposed to cholecystectomy. Pooled results indicated a significant increased risk of liver cancer in patients with a history of gallstones (OR = 2.54; 95% CI, 1.71–3.79; n = 11 studies), as well as cholecystectomy (OR = 1.62; 95% CI, 1.29–2.02; n = 12 studies), but there was considerable heterogeneity among these studies. The effects estimates did not vary markedly when stratified by gender, study design, study region, and study quality. The multivariate meta-regression analysis suggested that study region and study quality appeared to explain the heterogeneity observed in the cholecystectomy analysis.

Conclusions

Our results suggest that individuals with a history of gallstones and cholecystectomy may have an increased risk of liver cancer.

Anticancer steroids: linking natural and semi-synthetic compounds

Steroids, a widespread class of natural organic compounds occurring in animals, plants and fungi, have shown great therapeutic value for a broad array of pathologies. The present overview is focused on the anticancer activity of steroids, which is very representative of a rich structural molecular diversity and ability to interact with various biological targets and pathways. This review encompasses the most relevant discoveries on steroid anticancer drugs and leads through the last decade and comprises 668 references.

Role of the ABCG8 19H risk allele in cholesterol absorption and gallstone disease

BACKGROUND

Gallstone disease is associated with p.D19H of ABCG8 as well as alterations of cholesterol and bile acid metabolism. However, molecular mechanisms have not been fully elucidated. It is important to understand the link between the sterol transporters ABCG5/8 and NPC1L1 and intestinal cholesterol absorption as well as de novo synthesis in gallstone patients stratified according to 19H risk allele. Moreover, the functional importance of the 19H variant on intestinal ABCG8 feature remains to be clarified.

METHODS

Measurements of serum surrogate markers of cholesterol absorption (plant sterols: sitosterol, campesterol) and synthesis (cholesterol precursor: lathosterol) were carried out by gas chromatography/mass spectrometry (GC/MS). For expression studies, total RNA was isolated from 168 ileal biopsies of study participants with (34) and without gallstone disease (134). Messenger RNA was measured by LightCycler real-time PCR. Genomic DNA was obtained from blood leukocytes. Genotype frequencies of p.D19H were established using MALDI-TOF mass spectrometry.

RESULTS

Compared to controls, cholesterol absorption but not synthesis in gallstone carriers was diminished by about 21% based on low serum sitosterol (P = 0.0269) and campesterol (P = 0.0231) to cholesterol ratios. D19H was found to be significantly associated with gallstones (odds ratio [OR] = 2.9, P = 0.0220, 95% confidence interval [CI]:1.22-6.89), particularly in the overweight cohort (OR = 3.2, P = 0.0430, 95% CI:1.07-9.26). Cholesterol absorption was about 24% lower in individuals carrying p.D19H compared to wild type (Psitosterol = 0.0080, Pcampesterol = 0.0206). Moreover, irrespective of phenotype, carriers of p.D19H displayed a significant lower absorption than carriers of the major allele. The most pronounced effect on cholesterol absorption ratio was observed for serum campesterol levels (wild type controls to mutated controls 28%, P = 0.0347 and wild type controls to gallstone carriers with 19H allele 37%, P = 0.0030). Notably, ABCG5/8 and NPC1L1 expression was similar in gallstone carriers and controls regardless of p.D19H presence.

CONCLUSIONS

Both gallstone disease and p.D19H of ABCG8 are associated with diminished cholesterol absorption. However, p.D19H is not responsible for the differences in small intestinal sterol transporter expression.

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.

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.

A population-based cohort study of symptomatic gallstone disease in diabetic patients

AIM: To investigate the prevalence of gallstone disease (GSD) and to evaluate the risk of symptomatic GSD among diabetic patients.

METHODS: The study was conducted by analyzing the National Health Research Institutes (NHRI) dataset of ambulatory care patients, inpatient claims, and the updated registry of beneficiaries from 2000 to 2008. A total of 615 532 diabetic patients without a prior history of hospital treatment or ambulatory care visits for symptomatic GSD were identified in the year 2000. Age- and gender-matched control individuals free from both GSD and diabetes from 1997 to 1999 were randomly selected from the NHIR database (n = 614 871). The incidence densities of symptomatic GSD were estimated according to the subjects’ diabetic status. The distributions of age, gender, occupation, income, and residential area urbanization were compared between diabetic patients and control subjects using Cox proportion hazards models. Differences between the rates of selected comorbidities were also assessed in the two groups.

RESULTS: Overall, 60 734 diabetic patients and 48 116 control patients developed symptomatic GSD and underwent operations, resulting in cumulative operation rates of 9.87% and 7.83%, respectively. The age and gender distributions of both groups were similar, with a mean age of 60 years and a predominance of females. The diabetic group had a significantly higher prevalence of all comorbidities of interest. A higher incidence of symptomatic GSD was observed in females than in males in both groups. In the control group, females under the age of 64 had a significantly higher incidence of GSD than the corresponding males, but this difference was reduced with increasing age. The cumulative incidences of operations for symptomatic GSD in the diabetic and control groups were 13.06 and 9.52 cases per 1000 person-years, respectively. Diabetic men exhibited a higher incidence of operations for symptomatic GSD than did their counterparts in the control group (12.35 vs 8.75 cases per 1000 person-years).

CONCLUSION: The association of diabetes with increased symptomatic GSD may provide insight to the treatment or management of diabetes in clinical settings.

Bile acids down-regulate caveolin-1 in esophageal epithelial cells through sterol responsive element-binding protein

Bile acids are synthesized from cholesterol and are major risk factors for Barrett adenocarcinoma (BAC) of the esophagus. Caveolin-1 (Cav1), a scaffold protein of membrane caveolae, is transcriptionally regulated by cholesterol via sterol-responsive element-binding protein-1 (SREBP1). Cav1 protects squamous epithelia by controlling cell growth and stabilizing cell junctions and matrix adhesion. Cav1 is frequently down-regulated in human cancers; however, the molecular mechanisms that lead to this event are unknown. We show that the basal layer of the nonneoplastic human esophageal squamous epithelium expressed Cav1 mainly at intercellular junctions. In contrast, Cav1 was lost in 95% of tissue specimens from BAC patients (n = 100). A strong cytoplasmic expression of Cav1 correlated with poor survival in a small subgroup (n = 5) of BAC patients, and stable expression of an oncogenic Cav1 variant (Cav1-P132L) in the human BAC cell line OE19 promoted proliferation. Cav1 was also detectable in immortalized human squamous epithelial, Barrett esophagus (CPC), and squamous cell carcinoma cells (OE21), but was low in BAC cell lines (OE19, OE33). Mechanistically, bile acids down-regulated Cav1 expression by inhibition of the proteolytic cleavage of 125-kDa pre-SREBP1 from the endoplasmic reticulum/Golgi apparatus and nuclear translocation of active 68-kDa SREBP1. This block in SREBP1's posttranslational processing impaired transcriptional activation of SREBP1 response elements in the proximal human Cav1 promoter. Cav1 was also down-regulated in esophagi from C57BL/6 mice on a diet enriched with 1% (wt/wt) chenodeoxycholic acid. Mice deficient for Cav1 or the nuclear bile acid receptor farnesoid X receptor showed hyperplasia and hyperkeratosis of the basal cell layer of esophageal epithelia, respectively. These data indicate that bile acid-mediated down-regulation of Cav1 marks early changes in the squamous epithelium, which may contribute to onset of Barrett esophagus metaplasia and progression to BAC.

The use of stable and radioactive sterol tracers as a tool to investigate cholesterol degradation to bile acids in humans in vivo

Alterations of cholesterol homeostasis represent important risk factors for atherosclerosis and cardiovascular disease. Different clinical-experimental approaches have been devised to study the metabolism of cholesterol and particularly the synthesis of bile acids, its main catabolic products. Most evidence in humans has derived from studies utilizing the administration of labeled sterols; these have several advantages over in vitro assay of enzyme activity and expression, requiring an invasive procedure such as a liver biopsy, or the determination of fecal sterols, which is cumbersome and not commonly available. Pioneering evidence with administration of radioactive sterol derivatives has allowed to characterize the alterations of cholesterol metabolism and degradation in different situations, including spontaneous disease conditions, aging, and drug treatment. Along with the classical isotope dilution methodology, other approaches were proposed, among which isotope release following radioactive substrate administration. More recently, stable isotope studies have allowed to overcome radioactivity exposure. Isotope enrichment studies during tracer infusion has allowed to characterize changes in the degradation of cholesterol via the "classical" and the "alternative" pathways of bile acid synthesis. Evidence brought by tracer studies in vivo, summarized here, provides an exceptional tool for the investigation of sterol metabolism, and integrate the studies in vitro on human tissue.

Biliary physiology and disease: reflections of a physician-scientist

A review is presented of Gustav Paumgartner's five decades of research and practice in hepatology focusing on biliary physiology and disease. It begins with studies of the excretory function of the liver including hepatic uptake of indocyanine green, bilirubin, and bile acids. The implications of these studies for diagnosis and understanding of liver diseases are pointed out. From there, the path of scientific research leads to investigations of hepatobiliary bile acid transport and the major mechanisms of bile formation. The therapeutic effects of the hydrophilic bile acid, ursodeoxycholic acid, have greatly stimulated these studies. Although ursodeoxycholic acid therapy for dissolution of cholesterol gallstones and some other nonsurgical treatments of gallstones were largely superseded by surgical techniques, ursodeoxycholic acid is currently considered the mainstay of therapy of some chronic cholestatic liver diseases, such as primary biliary cirrhosis. The major mechanisms of action of ursodeoxycholic acid therapy in cholestatic liver diseases are discussed. An attempt is made to illustrate how scientific research can lead to advances in medical practice that help patients.

Fecal bile acid excretion and messenger RNA expression levels of ileal transporters in high risk gallstone patients

BACKGROUND

Cholesterol gallstone disease (GS) is highly prevalent among Hispanics and American Indians. In GS, the pool of bile acids (BA) is decreased, suggesting that BA absorption is impaired. In Caucasian GS patients, mRNA levels for ileal BA transporters are decreased. We aimed to determine fecal BA excretion rates, mRNA levels for ileal BA transporter genes and of regulatory genes of BA synthesis in Hispanic GS patients.

RESULTS

Excretion of fecal BA was measured in seven GS females and in ten GS-free individuals, all with a body mass index < 29. Participants ingested the stool marker Cr2O3 (300 mg/day) for 10 days, and fecal specimens were collected on the last 3 days. Chromium was measured by a colorimetric method, and BA was quantitated by gas chromatography/mass spectroscopy. Intake of calories, nutrients, fiber and cholesterol were similar in the GS and GS-free subjects. Mean BA excretion levels were 520 +/- 80 mg/day for the GS-free group, and 461 +/- 105 mg/day for the GS group. Messenger RNA expression levels were determined by RT-PCR on biopsy samples obtained from ileum during diagnostic colonoscopy (14 GS-free controls and 16 GS patients) and from liver during surgery performed at 8 and 10 AM (12 GS and 10 GS-free patients operated on for gastrointestinal malignancies), all with a body mass index < 29. Messenger RNA level of the BA transporter genes for ileal lipid binding protein, multidrug resistance-associated protein 3, organic solute transporter alpha, and organic solute transporter beta were similar in GS and GS-free subjects. Messenger RNA level of Cyp27A1, encoding the enzyme 27alpha-hydroxylase, the short heterodimer partner and farnesoid X receptor remained unchanged, whereas the mRNA level of Cyp7A1, the rate limiting step of BA synthesis, was increased more than 400% (p < 0.01) in the liver of GS compared to GS-free subjects.

CONCLUSION

Hispanics with GS have fecal BA excretion rates and mRNA levels of genes for ileal BA transporters that are similar to GS-free subjects. However, mRNA expression levels of Cyp7A1 are increased in GS, indicating that regulation of BA synthesis is abnormal in Hispanics with GS.

Developments in bile acid kinetic measurements using (13)C and (2)H: 10(5) times improved sensitivity during the last 40 years

Bile acid kinetics involve the measurement of pool sizes and turnover rates of individual bile acids. The technique is based on isotope dilution and was first described in the 1950s using radioactive (14)C-labelled cholic acid (CA). It took until the 1970s before stable isotopes were introduced for this purpose ((13)C, (2)H) and isotope analysis methods were developed for CA and chenodeoxycholic acid (CDCA) applying gas chromatography/electron impact mass spectrometry. Until the 1980s, the isotope enrichment measurements were performed in bile samples aspirated from the duodenum. Thereafter, methodology became available allowing measurements to be performed in blood requiring at least 2 ml serum samples. Simultaneous measurement of kinetics of metabolically dependent CA and deoxycholic acid using (13)C and (2)H labels was introduced. Until the 1990s, this technique was only possible in adult humans due to the large sample sizes. Introduction of pentafluorobenzyl bromide derivatisation and electron capture negative ion mass spectrometry (GC/ECN-MS) reduced the sample volume to 50 microl serum. This allowed isotope abundance measurement of CA in rats and in mice. However, repetitive collection of 100 microl blood samples in mice is too invasive (collection via the orbita) and exhaustive. Therefore, the method development is now focussing on enhanced sensitivity and reduction of blank effects originating from the sample preparation. The final goal is to determine CA isotope enrichments in 20 microl mouse blood obtained from the tail vein. This paper shows the feasibility of reaching this goal.

A variant of the SLC10A2 gene encoding the apical sodium-dependent bile acid transporter is a risk factor for gallstone disease

Background

Cholelithiasis is a multifactorial process and several mechanisms of gallstone formation have been postulated. As one of these mechanisms, a decreased expression of the ileal apical sodium-dependent bile acid transporter gene SLC10A2 in gallstone carriers was described previously. In this study the SLC10A2 gene was investigated to identify novel genetic variants and their association with gallstone formation.

Methodology/Principal Findings

Study subjects were selected with the presence or absence of gallstones confirmed by ultrasound and medical history. Genomic DNA was obtained from blood leukocytes. Sequence analysis was performed of all six exonic and flanking regions as well as of 2,400 base pairs of the SLC10A2 promoter in a cohort of gallstone carriers and control subjects from Stuttgart, Germany. Genotype frequencies of newly identified genetic variants (n = 6) and known single nucleotide polymorphisms (n = 24) were established using MALDI-TOF mass spectrometry. Six new genetic variants were found within the SLC10A2 gene. Although none of the variants was linked to gallstone disease in the Stuttgart cohort overall, the minor allele of SNP rs9514089 was more prevalent in male non-obese gallstone carriers (p = 0.06680, OR = 11.00). In a separate population from Aachen, Germany, the occurrence of rs9514089 was two-fold higher in gallstone patients (22%) than in corresponding controls (11%) (p = 0.00995, OR = 2.19). In the pooled Aachen/Stuttgart cohort rs9514089 was highly significantly linked to cholelithiasis (p = 0.00767, OR = 2.04). A more frequent occurrence was observed for male gallstone carriers (22%) compared to controls (9%) (p = 0.01017, OR = 2.99), for the total normal weight group (p = 0.00754, OR = 2.90), and for male non-obese gallstone patients (p = 0.01410, OR = 6.85). Moreover, for the minor allele of rs9514089 an association with low plasma cholesterol levels was found especially in gallstone carriers (p = 0.05).

Conclusions/Significance

We have identified SLC10A2 as a novel susceptibility gene for cholelithiasis in humans. Comprehensive statistical analysis provides strong evidence that rs9514089 is a genetic determinant especially in male non-obese gallstone carriers. The minor allele of rs9514089 is related to differences in plasma cholesterol levels among the subjects.

Mutation screening of apical sodium-dependent bile acid transporter (SLC10A2): novel haplotype block including six newly identified variants linked to reduced expression

The apical sodium-dependent bile acid transporter (SLC10A2) plays a key role in the reabsorption of luminal bile acids into the enterohepatic circulation. Rare variations in SLC10A2 have been reported to be associated with Crohn's disease, primary bile acid malabsorption and familial hypertriglyceridemia; however, variants associated with reduced SLC10A2 expression have not been reported to date. In this study, we have performed a sequence analysis of SLC10A2 using genomic DNA of 93 individuals. A new haplotype structure was identified including ten variants with complete linkage disequilibrium (LD' = 1.0, r (2) = 1.0) of which six polymorphisms were novel. The sequence variants were confirmed in three independent cohorts (n = 1,290) by a recently established MALDI-TOF MS iPLEX assay. Remarkably, haplotype carriers with the minor allele exhibited significant reduced ileal SLC10A2 expression on mRNA levels (2.6-fold, P = 0.0009) and protein levels (2.4-fold, P = 0.0157). In future studies a single tag SNP selected of this haplotype block will provide reliable genetic testing to investigate systemically the influence of the SLC10A2 haplotype for disease susceptibility and/or drug response.

Reduced ileal expression of OSTalpha-OSTbeta in non-obese gallstone disease

Cholelithiasis is a multifactorial process, and several mechanisms have been postulated. A decreased expression of the ileal apical sodium-dependent bile acid transporter (ASBT) and of the cytosolic ileal lipid binding protein (ILBP) was recently described in female non-obese patients. The role of the recently identified organic solute transporters alpha and beta (OSTalpha, OSTbeta) in gallstone pathogenesis remains unclear. Therefore, we performed analysis of OSTalpha-OSTbeta in gallstone patients according to body weight. Ileal mucosal biopsies were collected during routine colonoscopy from female gallstone carriers (n = 19) and controls (n = 34). OSTalpha-OSTbeta mRNA expression was measured using the LightCycler sequence detection system; protein was analyzed by immunohistochemistry and Western blot. The mRNA expression of OSTalpha-OSTbeta was significantly reduced (OSTalpha: 3.3-fold, P = 0.006; OSTbeta: 2.6-fold, P = 0.03) in normal-weight but not overweight gallstone carriers compared with controls. OSTalpha-OSTbeta protein levels also showed a reduction by 40-67%. The expression of OSTalpha-OSTbeta correlated positively with ASBT (r = 0.65, 0.58, respectively), ILBP (r = 0.77, 0.67), and the farnesoid X receptor (r = 0.58, 0.50). Fibroblast growth factor-19 showed a 2.8-fold reduction (P = 0.06), and liver receptor homolog-1 showed a 2-fold reduction (P = 0.04) in non-obese patients. In conclusion, an impaired function of all three ileal bile acid transporters may lead to low ileal bile acid reabsorption and an altered bile acid pool composition and therefore may contribute to the formation of gallstones in non-obese patients.

Apical sodium bile acid transporter and ileal lipid binding protein in gallstone carriers

Although a cholesterol supersaturation of gallbladder bile has been identified as the underlying pathophysiologic defect, the molecular pathomechanism of gallstone formation in humans remains poorly understood. A deficiency of the apical sodium bile acid transporter (ASBT) and ileal lipid binding protein (ILBP) in the small intestine may result in bile acid loss into the colon and might promote gallstone formation by reducing the bile acid pool and increasing the amount of hydrophobic bile salts. To test this hypothesis, protein levels and mRNA expression of ASBT and ILBP were assessed in ileal mucosa biopsies of female gallstone carriers and controls. Neither ASBT nor ILBP levels differed significantly between gallstone carriers and controls. However, when study participants were subgrouped by body weight, ASBT and ILBP protein were 48% and 67% lower in normal weight gallstone carriers than in controls (P < 0.05); similar differences were found for mRNA expression levels. The loss of bile transporters in female normal weight gallstone carriers was coupled with a reduction of protein levels of hepatic nuclear factor 1alpha and farnesoid X receptor. In conclusion, in normal weight female gallstone carriers, the decreased expression of ileal bile acid transporters may form a molecular basis for gallstone formation.

The Farnesoid X receptor: a molecular link between bile acid and lipid and glucose metabolism

Bile acids are the end products of cholesterol metabolism. They are synthesized in the liver and secreted via bile into the intestine, where they aid in the absorption of fat-soluble vitamins and dietary fat. Subsequently, bile acids return to the liver to complete their enterohepatic circulation. The Farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily and has emerged as a key player in the control of multiple metabolic pathways. On its activation by bile acids, FXR regulates bile acid synthesis, conjugation, and transport, as well as various aspects of lipid and glucose metabolism. This review summarizes recent advances in deciphering the role of FXR in the context of hepatic lipid and glucose homeostasis and discusses the potential of FXR as a pharmacological target for therapeutic applications.

Pathways of cholesterol crystallization in model bile and native bile

Hypersecretion of hepatic cholesterol, chronic supersaturation of bile with cholesterol and rapid precipitation of cholesterol crystals in the gallbladder from cholesterol-enriched vesicles represent the primum movens in cholesterol gallstone formation. Physical-chemical factors and pathways leading to cholesterol crystallization can be investigated in artificial model biles and ex vivo in fresh human bile. Depending on modulatory factors (i.e., lipid concentration, bile salt or phospholipid species, humidity, mucins, etc.), cholesterol can precipitate in several forms (i.e., monohydrate, anhydrous) and habits (i.e., plate-like, needle-like, intermediate arcs, filaments, tubules, spirals). Careful analysis of biliary cholesterol crystals includes biochemical analysis of precipitated crystals, polarizing quantitative light microscopy, and turbidimetric methods. In this paper, recent concepts on cholesterol crystallization in artificial model biles as well as in human bile will be reviewed.

Alternative treatment of gallbladder disease

Major risk factors for gallbladder disease include a sedentary lifestyle and a diet rich in refined sugars. In genetically prone individuals, these two factors lead to an abnormal bile composition, altered gut microflora, and hyperinsulinemia, with resulting gallstone formation. As a large percentage of gallbladder patients have continued digestive complaints following cholecystectomy, the author examines complementary and alternative medicine (CAM) treatments to counteract gallstone formation. Herbal medicine such as turmeric, oregon grape, bupleurum, and coin grass may reduce gallbladder inflammation and relieve liver congestion. Elimination of offending foods, not necessarily 'fatty' foods, is often successful and recommended by many holistic physicians. Regular aerobic exercise has a beneficial effect on hyperinsulinemia, which is often associated with gallbladder disease. Dietary changes that lower plasma insulin levels, such as a change in dietary fats and substitution of unrefined carbohydrates for refined carbohydrates, may also be helpful.

Bile acid regulation of gene expression: roles of nuclear hormone receptors

Bile acids derived from cholesterol and oxysterols derived from cholesterol and bile acid synthesis pathways are signaling molecules that regulate cholesterol homeostasis in mammals. Many nuclear receptors play pivotal roles in the regulation of bile acid and cholesterol metabolism. Bile acids activate the farnesoid X receptor (FXR) to inhibit transcription of the gene for cholesterol 7alpha-hydroxylase, and stimulate excretion and transport of bile acids. Therefore, FXR is a bile acid sensor that protects liver from accumulation of toxic bile acids and xenobiotics. Oxysterols activate the liver orphan receptors (LXR) to induce cholesterol 7alpha-hydroxylase and ATP-binding cassette family of transporters and thus promote reverse cholesterol transport from the peripheral tissues to the liver for degradation to bile acids. LXR also induces the sterol response element binding protein-1c that regulates lipogenesis. Therefore, FXR and LXR play critical roles in coordinate control of bile acid, cholesterol, and triglyceride metabolism to maintain lipid homeostasis. Nuclear receptors and bile acid/oxysterol-regulated genes are potential targets for developing drug therapies for lowering serum cholesterol and triglycerides and treating cardiovascular and liver diseases.

Ebselen protects against the reduction in levels of drug-metabolizing enzymes in livers of rats with deoxycholic acid-induced liver injury

Ebselen is a seleno-organic compound that inhibits oxidative stress by lipid peroxidation through a glutathione peroxidase-like activity. We studied the effect of ebselen on the expression of hepatic drug-metabolizing enzymes in rats with deoxycholic acid-induced liver injury. Hydrophobic bile acids, such as deoxycholic acid, are known to cause cholestatic liver injury, and it was reported that expression of hepatic cytochrome P-450 (CYP) was reduced by deoxycholic acid administration in rats. Hydrophobic bile acids induce lipid peroxidation in the liver, and this may be one mechanism of the development of liver injury. In the present study, we investigated the effect of ebselen (30 mg/kg/day for 10 days) on rats ingesting deoxycholic acid (1% of diet for 10 days). Deoxycholic acid decreased levels of CYP1A1, 2B1, 2E1 and 3A2 to 34, 58, 62 and 37% of control values, respectively, and increased serum alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities to 1.8 and 8.6 times the levels of controls, respectively. Administration of ebselen with deoxycholic acid prevented the decreases in levels of CYP1A1 and 3A2 (86 and 65% of control, respectively) and the increases in serum ALP and ALT activities (1.4 and 1.9 times of control, respectively) caused by deoxycholic acid. These results indicate that ebselen may have a protective effect against hydrophobic bile acid-induced liver injury.

Colonic transit influences deoxycholic acid kinetics

BACKGROUND & AIMS

Prolonged large bowel transit, and an increase in the proportion of deoxycholic acid (DCA), have been implicated in the pathogenesis of cholesterol gallstones-including those developing in acromegalics treated with octreotide. However, there are few data on the effects of intestinal transit on bile acid kinetics.

METHODS

We therefore measured the kinetics of DCA and cholic acid (CA) using stable isotopes, serum sampling, and mass spectrometry. The results were related to mouth-to-caecum (MCTT) and large bowel transit times (LBTTs) in 4 groups of 8 individuals: (1) non-acromegalic controls, (2) acromegalics untreated with octreotide, (3) acromegalics on long-term octreotide, and (4) patients with constipation. Paired, before and during octreotide, studies were performed in 5 acromegalics.

RESULTS

In the unpaired and paired studies, octreotide significantly prolonged MCTT and LBTT. In the paired studies, the octreotide-induced prolongation of LBTT caused an increase in the DCA input rate (6.4 +/- 2.8 to 12 +/- 2.6 micromol. kg. d, P < 0.05) and pool size (18 +/- 12 to 40 +/- 13 micromol/kg, P < 0.05), and a decrease in CA pool size (45 +/- 15 to 25 +/- 11 micromol/kg, P < 0.05). Furthermore, during octreotide treatment, the mean conversion of 13C-CA to 13C-DCA (micromoles) was greater (P < 0.05) on study days 3, 4, and 5. There were also positive linear relationships between LBTT and DCA input rate (r = 0.78), pool size (r = 0.82, P < 0.001), and a weak (r = -0.49) negative linear relationship between LBTT and CA pool size (P < 0.01).

CONCLUSIONS

These data support the hypothesis that, by increasing DCA formation and absorption, prolongation of large bowel transit is a pathogenic factor in the formation of octreotide-induced gallstones.

Severe impairment of postprandial cholecystokinin release and gall-bladder emptying and high risk of gallstone formation in acromegalic patients during Sandostatin LAR

BACKGROUND

Acromegalic patients treated three times daily with subcutaneous injections of the somatostatin analogue octreotide frequently develop gallstones, due to suppressed cholecystokinin release and impaired gall-bladder emptying.

AIM

To elucidate the effects of a new long-acting octreotide formulation (Sandostatin LAR) on gall-bladder emptying, cholecystokinin release and gallstone formation.

METHODS

Postprandial gall-bladder and gastric emptying were determined by ultrasonography and cholecystokinin release was measured in seven patients on days 0, 14, 28, and 75 (Sandostatin LAR, 20 mg intramuscularly on days 1, 30, and 60).

RESULTS

During treatment, fasting gall-bladder volumes increased from 26.5 +/- 3.2 mL to 61.4 +/- 7.5 mL, but postprandial cholecystokinin release and gall-bladder emptying (from 63.9 +/- 3.8% to 12.3 +/- 3.5%) were severely suppressed. Gallstones formed in six out of seven patients within 8 months of treatment. Gastric emptying did not change during the therapy.

CONCLUSIONS

The risk of gallstone formation is greatly increased during Sandostatin LAR. This is probably related to profound suppression of cholecystokinin release and gall-bladder emptying.

An ultrasonographic evaluation of gallbladder emptying in patients with cholelithiasis

Impaired gallbladder emptying producing biliary stasis may provide potent carcinogen, which comes in contact with gallbladder mucosa for a prolonged period, inducing carcinogenesis. The aim was to study gallbladder emptying pattern in cholelithiasis. Postprandial gallbladder emptying was measured ultrasonographically in terms of fasting volume (FV), postprandial residual volume at 30 minutes (PP30), 60 minutes (PP60), and 90 minutes (PP90), residual fraction, and ejection volume (EV) in 58 patients with gallstones. Patients were divided into two groups of poor and good contractors on the basis of 50% maximal postprandial gallbladder emptying. Malonaldehyde level was estimated in 15 patients with cholelithiasis. Twenty-nine patients (50%) were poor contractors. The FV in patients with cholelithiasis (mean, 30.08 mL) was larger than the controls (mean, 17.55 mL) and the difference was statistically significant (p < 0.02). The FV in the cholelithiasis group correlated significantly with the PP30 (r = 0.85, p < 0.001), PP60 (r = 0.85, p < 0.001), PP90 (r = 0.78, p < 0.001), and EV (r = 0.65, p < 0.001). Ejection volume was significantly less in poor contractors (p <0.001). Residual fraction was significantly higher in poor contractors (p < 0.001). The biliary malonaldehyde in poor contractors (2.27 micromol/mL) was higher than in good contractors (1.78 micromol/mL), but the difference was statistically not significant. Significantly larger volumes of PP30, PP60, PP90, and residual fraction and a low EV indicate poor contraction leading to biliary stasis.

In vivo gallbladder bile diffusion coefficient measurement by diffusion-weighted echo planar imaging in hamster fed normal and lithogenic diets

It is shown that in vivo measurement of bile water apparent diffusion coefficient (ADC) by diffusion-weighted echo-planar imaging (EPI) in hamster gallbladder is possible providing motion artifact-free ADC values. These ADC values are used to estimate bile viscosity variation induced by normal diets, cholesterol gallstone-inducing diets, and an antilithiasic drug, and to determine if a link exists between bile viscosity and cholesterol gallstone formation. Measurements were performed at 4.7 T with respiratory triggering in five groups of hamsters fed a commercial (RC) or a semisynthetic (SSD) diet, a SSD containing 0.2% hyodeoxycholic acid (SSD+HDC) and two lithogenic diets (LD5, LD10). ADC decreased significantly in LD10 (2.15+/-0.07x 10(-3) mm(2)s(-1)) and SSD+HDC (2.03+/-0.04) compared to RC (2.40+/-0.05) but not in the most lithogenic LD5 diet (2.33+/-0.06). No direct relationship was found between bile viscosity and gallstone incidence; however, viscosity seems to be related to lipid contents of diets. Magn Reson Med 43:854-859, 2000.

Gallbladder motility and cholesterol crystallization in bile from patients with pigment and cholesterol gallstones

BACKGROUND

Little is known about gallbladder motility in patients with black pigment stones when compared to cholesterol gallstone patients, or about their relationship to biliary composition, crystallization and stone characteristics.

DESIGN

Fasting and postprandial gallbladder volumes were studied by ultrasonography in 49 gallstone patients with pigment (n = 14) or cholesterol (n = 35) stones and 30 healthy controls. After cholecystectomy stone composition, gallbladder wall inflammation, cholesterol saturation index and appearance of platelike cholesterol crystals in bile were evaluated in gallstone patients.

RESULTS

Fasting gallbladder volume was significantly (P < 0.05) increased in cholesterol stone patients (31.7 +/- 1.9 mL) but not in pigment stone patients (21.9 +/- 3.1 mL), compared to controls (21.0 +/- 1.5 mL). Postprandial emptying was delayed in patients (half-emptying time: 31 +/- 2 min, 35 +/- 3 min, 24 +/- 2 min in cholesterol stone patients, pigment stone patients and controls, respectively, P < 0.05) and incomplete (residual volume: 43.2 +/- 2.7%, 40.0 +/- 4.3%, 15.8 +/- 1.6% min in cholesterol stone patients, pigment stone patients and controls, respectively, P < 0.05). The inflammation of the gallbladder wall was mild or absent in all cases. Biliary cholesterol saturation index was 152.3 +/- 8.5% and 92.9 +/- 4.8% in patients with cholesterol and pigment stones, respectively (P < 0.01). Whereas cholesterol crystals never appeared during 21 days in biles from patients with pigment stones, crystal observation time in patients with cholesterol gallstone was 5 days (median) and was significantly shorter in patients with multiple (4 days) than in patients with solitary (12 days) cholesterol stones (P = 0.0019).

CONCLUSIONS

Patients with black pigment stones who do not have excess cholesterol and do not grow cholesterol crystals in bile have decreased gallbladder emptying, although to a lesser extent than patients with cholesterol stones. Thus, gallbladder stasis is likely to put a subset of subjects at risk for the formation of pigment gallstones, and pathogenic mechanisms need to be further investigated.

Methylprednisolone administration in primary biliary cirrhosis increases cholic acid turnover, synthesis, and deoxycholate concentration in bile

As immunosuppressive agents, corticosteroids may be considered an appropriate treatment for primary biliary cirrhosis, even if bone loss and other side effects may occur. We studied biliary lipid metabolism in 10 nonicteric patients, with histologically proven primary biliary cirrhosis (stage I-IV). We administered methylprednisolone (24 mg daily) for 30 days to ascertain its effects on biliary lipid metabolism, which are largely still unknown. All patients underwent a 30-day drug-washout period before entering the trial. The following parameters were studied before and after methylprednisolone treatment: serum biochemistry; cholic acid pool size, kinetics and synthesis; biliary lipid secretion; biliary bile acid pattern; biliary lipid molar percentage; and cholesterol saturation index. Methylprednisolone induced a statistically significant (Wilcoxon rank test) increase in cholic acid turnover (from 0.26+/-0.04 to 0.50+/-0.05 K/day, P = 0.005) and synthesis (from 0.42+/-0.12 to 0.78+/-0.11 mmol/day, P = 0.04), and in bile deoxycholic acid molar percentage (from 19.4+/-2.7 to 30.6+/-4.4% molar, P = 0.01). On the other hand, a significant decrease in biliary cholesterol molar percentage (from 7.9+/-0.7 to 6.4+/-0.5% molar, P = 0.005), cholesterol saturation index (from 1.11+/-0.11 to 0.95+/-0.07, P = 0.05), and biliary cholesterol secretion (from 64.7+/-5.4 to 53.0+/-4.5 micromol/hr, P = 0.005) was observed. These findings show that short-term administration of methylprednisolone in patients with primary biliary cirrhosis does not induce expansion of the cholic acid pool but increases cholic acid synthesis and turnover, as well as intestinal production of deoxycholic acid. If long-term treatment is considered, the beneficial immunosuppressive effects of corticosteroids have to be weighed against the hepatotoxic properties of deoxycholic acid.

Deoxycholic acid is not related to lithogenic factors in gallbladder bile

The influence of deoxycholic acid (DCA) on the factors in gallbladder bile responsible for cholesterol gallstone disease has been a controversial subject of discussion. This might be partially due to patient selection or inappropriate methods. Therefore, we investigated the relationship between the percentage of DCA and lithogenic factors in the gallbladder bile of patients with cholesterol gallstones and with normal or moderately impaired gallbladder contractility. Patients with pigment stones served as a control group. The percentage of DCA in the gallbladder bile of 20 patients with cholesterol stones (23.2%+/-6.5%; mean+/-SD) was comparable to the DCA percentage in the gallbladder bile of 11 patients with pigment stones (26.5%+/-8.5%). No correlation was seen between the DCA percentage of total bile acids and the crystal observation time, cholesterol saturation index (CSI), total protein value, mucin level, and amount of cholesterol in vesicles or crystals in the total group of patients or in the subgroups with cholesterol or pigment stones, respectively. The lack of correlation between DCA percentage and CSI was determined in native bile (r = 0.048) as well as in crystal-free bile after ultracentrifugation (r = 0.107). Our findings demonstrate that in patients with gallstones, the percentage of DCA in gallbladder bile is not related to any of the known biliary factors associated with cholesterol gallstone disease. We conclude that in patients with normal or moderately impaired gallbladder function, an elevated DCA level in the gallbladder bile is of minor pathophysiologic significance for the formation of cholesterol gallstones.

Physical and metabolic factors in gallstone pathogenesis

Gallstones form when the tenuous balance of solubility of biliary lipids tips in favor of precipitation of cholesterol, unconjugated bilirubin, or bacterial degradation products of biliary lipids. For cholesterol gallstones, metabolic alterations in hepatic cholesterol secretion combine with changes in gallbladder motility and intestinal bacterial degradation of bile salts to destabilize cholesterol carriers in bile and produce cholesterol crystals. For black pigment gallstones, changes in heme metabolism or bilirubin absorption lead to increased bilirubin concentrations and precipitation of calcium bilirubinate. In contrast, mechanical obstruction of the biliary tract is the major factor leading to bacterial degradation and precipitation of biliary lipids in brown pigment stones. Further understanding of the physical and metabolic factors of cholesterol and black pigment formation is likely to provide interventions to interrupt the earliest stages of gallstone formation.

Bile acids in serum and bile of patients with cholesterol gallstone

AIM: To analyze serum bile acids and biliary lipids of patients with cholesterol gallstone(CS) and explore the relationship between deoxycholic acid (DCA) and CS disease.

METHODS: Analysis of bile acids in serum was done with gas-chromatography in two groups: CS group (n = 151) and control group (n = 256). Serum bile acids and biliary lipids were also studied in 90 matched samples.

RESULTS: The serum DCA was 0.955 μmol/L ± 0.078 μmol/L in CS group, which was more than that of control group (0.696 μmol/L ± 0.047 μmol/L), P < 0.01. The ratio of DCA/chenodeoxycholic acids (CDCA) was 1.76 ± 0.30 in CS group, about two times that in control group (0.92 ± 0.14). The mole percent of DCA in bile was positively related to cholesterol saturation index (CSI) (P < 0.01) and the mole percent of CDCA in bile negatively to CSI (P = 0.01). There was correlation between the mole percent of DCA, CDCA and cholic acid in bile and in serum.

CONCLUSION: It is suggested that DCA is lithogenic and the increased amount of DCA or the ratio of DCA/CDCA in serum may be one of the features of cholesterol gallstone patients.

Biochemical and morphological correlations in human gallbladder with reference to membrane permeability

There is good evidence that gallbladder epithelium is permeable to a diverse range of molecules which move into the epithelial cell from the lumen or the basement membrane. Morphological investigations have shown both secretory mucous droplets, components of the endocytosis pathway together with evidence of a system allowing passage of molecules across the basement membrane. This indicates that the gallbladder epithelium may be influenced by molecules presented via the apical and basal membranes, complicating our understanding of gallbladder function, particularly in disease. Gallbladder disease increases the proteoglycan content of the basement membrane, but the implication of this in terms of permeability remains to be defined. Indeed, it remains unknown whether this precedes disease or is a manifestation of the disease process. The removal of water from hepatic bile by gallbladder involves two counter ion transport systems. Autoradiography shows that ion transport occurs into the lateral intracellular spaces but it remains unclear whether this leads to a hypertonic solution in these spaces causing an osmotically driven water absorption or if the process involves an osmotically linked isotonic secretion. These ion pumps are reversible, for water is absorbed during the interdigestive phase but fluid is secreted into the lumen during digestion or in the presence of disease. Appropriate neural stimulation can increase or decrease fluid absorption from the lumen while vasoactive intestinal peptide or secretin promote fluid secretion, probably mediated by prostaglandins leading to raised cyclic AMP acting at the cellular level. Immediate control may depend on intracellular Ca2+ which activates a calmodulin-protein kinase, phosphorylating the counter ion transporters to downregulate their activity. Failure of this regulatory process may explain the initial increase in bile concentrating potential seen in the development of gallstones although the mechanism of such failure remains unknown. More concentrated bile increases movement of biliary compounds into gallbladder epithelial cells which alter gallbladder function in a complex manner. Secondary bile acids are raised in gallstone disease and increase permeability of the gallbladder epithelium to molecules including cholesterol. This cholesterol absorbed from the lumen may have paramount importance to gallbladder function. Raised biliary cholesterol reduces gallbladder motility, possibly by increasing the amount of cholesterol in gallbladder muscle membranes and reducing contraction in response to cholecystokinin. However, increased secondary bile acids are also associated with an alteration in phospholipid acyl groups which may alter ion transport activity and/or cholesterol solubility within the micelle/vesicle. As the acyl groups show increased arachidonate levels the production of prostaglandins could be raised, although currently it is not known if this phospholipid arachidonate enters the epithelial cells. In addition, gallbladder inflammation is associated with raised phospholipase A2 activity, leading to formation of fatty acids and lysophospholipid which causes membrane damage. The fatty acids are likely to displace cholesterol from the micelle but may also act directly on the epithelium, possibly increasing prostaglandin production and thus stimulating mucin secretion. Increased mucin secretion is seen early in gallstone disease but the evidence presently available cannot determine if this is a causative factor.