Chromosomal organization of candidate genes involved in cholesterol gallstone formation: a murine gallstone map

Sphincter of Oddi Dysfunction Induces Gallstone by Inhibiting the Expression of ABCB11 via PKC-α

The abnormal increase of Oddi sphincter pressure and total bile duct pressure may play an important role in the formation of cholesterol stones, but the specific molecular mechanism is still unclear. This study aims to investigate it through in vitro and in vivo experiments. A mouse model of Oddi sphincter dysfunction was constructed by stone-inducing diet. We compared the two groups with PKC-α inhibitor GÖ6976 and PKC-α agonist thymeleatoxin. Oddi sphincter pressure and total bile duct pressure were measured. Biochemical analysis of total cholesterol, bile acid and bilirubin was then conducted. The histopathologic changes of bile duct were observed by HE staining and the ultrastructure of liver cells and surrounding tissues was observed by transmission electron microscopy. Through the above experiments, we found that the change of PKC-α expression may affect the formation process of gallstones. The relationship between PKC-α and ABCB11 was further verified by in vitro and in vivo experiments. Our results suggest that ABCB11 and PKC-α are co-expressed in the tubule membrane of hepatocytes and interact with each other in hepatocytes. The high cholesterol diet further enhances the activation of PKC-α and thus reduces the expression of ABCB11. The formation of cholesterol stones is associated with the down-regulation of ABCB11 expression in the tubule membrane of hepatocytes due to kinase signaling. This is the first study to demonstrate that sphincter of Oddi dysfunction induces gallstones through PKC-α inhibition of ABCB11 expression.

Acute cholangitis: a state-of-the-art review

Acute cholangitis is a potentially life-threatening bacterial infection of the intra and/or extrahepatic bile ducts. It remains the second and third cause of community-acquired and hospital-acquired bacteremia, respectively, and is associated with mortality rates of up to 15%, despite advances in broad-spectrum antimicrobial therapy and improved access to emergency biliary tract decompression procedures. Even though not much has changed in recent years in terms of diagnosis or treatment, new data have emerged regarding multidrug-resistant bacteria that serve as etiologic agents of cholangitis. Moreover, different approaches in antibiotic regimes depending on severity grading and bile sample cultures as well as novel minimally invasive endoscopic procedures that can help when consecrated treatments such as endoscopic retrograde cholangiopancreatography (ERCP) fail, cannot be performed, or are unavailable have been proposed. This state-of-the-art review aims to offer a complete and updated assessment of the epidemiology, novel diagnostic and therapeutic methods, complications, and prognostic variables of acute cholangitis. The authors will review the prognostic implications of unusual complications, the relevance of regular bile samples and antibiograms, and their new role in guiding antibiotic therapy and limiting antibiotic resistance to present an organized and comprehensive approach to the care of acute cholangitis.

Gallstone Disease and Its Correlation With Thyroid Disorders: A Narrative Review

Over the years, several studies have revealed an important link between thyroid disorders and gallstone disease. According to these studies, hypothyroidism and hyperthyroidism are associated with cholesterol gallstone disease. This association between thyroid hormone disorders and cholesterol gallstone disease is due to the importance of thyroid hormones on cholesterol synthesis, bile functioning and content, and gallbladder motility. Several genes and receptors have been found on the thyroid gland, liver, and gallbladder to verify this association. These genes affect thyroid hormone secretion, lipid metabolism, and bile secretion. Defects in these various gene expression and protein functions lead to bile duct diseases. Other causes that lead to cholesterol gallstone disease are supersaturation of the bile with cholesterol and impaired gallbladder motility, which leads to bile stasis. This article has discussed these factors in detail while highlighting the association between thyroid hormones and cholesterol gallstone disease.

Association Study of SLCO1B3 and ABCC3 Genetic Variants in Gallstone Disease

There is growing evidence that gallstone formation may be genetically determined. Recent studies have shown that polymorphism of genes encoding proteins involved in bile acid transport may be associated with the risk of gallstone disease. The aim of this study was to investigate the association between SLCO1B3 (rs4149117:G>T, rs7311358:A>G) and ABCC3 (rs4793665:T>C, rs11568591:G>A) genetic variants and susceptibility to cholesterol gallstone disease, as well as gallstone composition. The study included 317 patients suffering from cholelithiasis who underwent cholecystostomy and 249 controls with no evidence of stones, confirmed by ultrasound examination. There were no statistically significant differences in the distribution of studied gene polymorphisms between patients with gallstone disease and healthy controls. No significant associations were observed between studied genotypes and the content of analyzed gallstone components: total cholesterol, bilirubin, CaCO3, nor the total bile acids. There was also no association between bile acid content in gallstones and the polymorphisms studied. The results of this study suggest that polymorphisms of SLCO1B3 and ABCC3 genes are not a valuable marker of gallstone disease susceptibility and do not influence gallstone composition.

The Need for Standardizing Diagnosis, Treatment and Clinical Care of Cholecystitis and Biliary Colic in Gallbladder Disease

Gallstones affect 20% of the Western population and will grow in clinical significance as obesity and metabolic diseases become more prevalent. Gallbladder removal (cholecystectomy) is a common treatment for diseases caused by gallstones, with 1.2 million surgeries in the US each year, each costing USD 10,000. Gallbladder disease has a significant impact on the logistics and economics of healthcare. We discuss the two most common presentations of gallbladder disease (biliary colic and cholecystitis) and their pathophysiology, risk factors, signs and symptoms. We discuss the factors that affect clinical care, including diagnosis, treatment outcomes, surgical risk factors, quality of life and cost-efficacy. We highlight the importance of standardised guidelines and objective scoring systems in improving quality, consistency and compatibility across healthcare providers and in improving patient outcomes, collaborative opportunities and the cost-effectiveness of treatment. Guidelines and scoring only exist in select areas of the care pathway. Opportunities exist elsewhere in the care pathway.

Gut microbiota promotes cholesterol gallstone formation by modulating bile acid composition and biliary cholesterol secretion

Cholesterol gallstone disease is a worldwide common disease. Cholesterol supersaturation in gallbladder bile is the prerequisite for its pathogenesis, while the mechanism is not completely understood. In this study, we find enrichment of gut microbiota (especially Desulfovibrionales) in patients with gallstone disease. Fecal transplantation of gut microbiota from gallstone patients to gallstone-resistant strain of mice can induce gallstone formation. Carrying Desulfovibrionales is associated with enhanced cecal secondary bile acids production and increase of bile acid hydrophobicity facilitating intestinal cholesterol absorption. Meanwhile, the metabolic product of Desulfovibrionales, H₂S increase and is shown to induce hepatic FXR and inhibit CYP7A1 expression. Mice carrying Desulfovibrionales present induction of hepatic expression of cholesterol transporters Abcg5/g8 to promote biliary secretion of cholesterol as well. Our study demonstrates the role of gut microbiota, Desulfovibrionales, as an environmental regulator contributing to gallstone formation through its influence on bile acid and cholesterol metabolism.

Metabolic conditions associated with alterations of the gut microbiome, such as obesity and diabetes, predispose to gallstone disease. Here the authors demonstrate that the gut microbiome, in particular the genus Desulfovibrionale, contribute to gallstone formation in mice.

The effect of ursodeoxycholic acid on the relative expression of the lipid metabolism genes in mouse cholesterol gallstone models

BACKGROUND

Many studies indicate that gallstone formation has genetic components. The abnormal expression of lipid-related genes could be the basis for particular forms of cholesterol gallstone disease. The aim of this study was to obtain insight into lipid metabolism disorder during cholesterol gallstone formation and to evaluate the effect of ursodeoxycholic acid (UDCA) on the improvement of bile lithogenicity and its potential influence on the transcription of lipid-related genes.

METHODS

Gallstone-susceptible mouse models were induced by feeding with a lithogenic diet (LD) for 8 weeks. Bile and liver tissues were obtained from these mouse models after 0, 4 and 8 weeks. Bile lipids were measured enzymatically, and the cholesterol saturation index (CSI) was calculated to evaluate the bile lithogenicity by using Carey's critical tables. Real-time polymerase chain reaction (RT-PCR) was used to detect the mRNA expression levels of farnesoid X receptor (FXR), liver X receptor (LXR), adenosine triphosphate-binding cassette subfamily G member 5/8 (ABCG5/8), cholesterol 7-α hydroxylase (CYP7A1), oxysterol 7-α hydroxylase (CYP7B1), sterol 27-α hydroxylase (CYP27A1), peroxisome proliferator-activated receptor alpha (PPAR-α) and adenosine triphosphate-binding cassette subfamily B member 11 (ABCB11).

RESULTS

The rate of gallstone formation was 100% in the 4-week group but only 30% in the UDCA-treated group. The UDCA-treated group had a significantly lower CSI compared with other groups. Of special note, the data on the effects of UDCA showed higher expression levels of ABCG8, ABCB11 and CYP27A1, as well as lower expression levels of LXR and PPAR-α, compared to the model control group.

CONCLUSIONS

UDCA exhibits tremendously potent activity in restraining lipid accumulation, thus reversing the lithogenic effect and protecting hepatocytes from serious pathological damage. The abnormal expression of ABCG8, CYP7A1, CYP27A1, LXR and PPAR-α might lead to high lithogenicity of bile. These results are helpful in exploring new lipid metabolism pathways and potential targets for the treatment of cholesterol stones and for providing some basis for the study of the pathogenesis and genetic characteristics of cholelithiasis. Research on the mechanism of UDCA in improving lipid metabolism and bile lithogenicity may be helpful for clinical treatment and for reducing the incidence of gallstones.

FMO3 and its metabolite TMAO contribute to the formation of gallstones

Trimethylamine-N-oxide (TMAO) is a metabolite derived from trimethylamine (TMA), which is first produced by gut microbiota and then oxidized by flavin-containing monooxygenase 3 (FMO3) in the liver. TMAO may contribute to the development of diseases such as atherosclerosis because of its role in regulating lipid metabolism. In this study, we found that high plasma TMAO levels were positively associated with the presence of gallstone disease in humans. We further found increased hepatic FMO3 expression and elevated plasma TMAO level in a gallstone-susceptible strain of mice C57BL/6J fed a lithogenic diet (LD), but not in a gallstone-resistant strain of mice AKR/J. Dietary supplementation of TMAO or its precursor choline increased hepatic FMO3 expression and plasma TMAO levels and induced hepatic canalicular cholesterol transporters ATP binding cassette (Abc) g5 and g8 expression in mice. Up-regulation of ABCG5 and ABCG8 expression was observed in hepatocytes incubated with TMAO in vitro. Additionally, in AKR/J mice fed a LD supplemented with 0.3% TMAO, the incidence of gallstones rose up to 70% compared with 0% in AKR/J mice fed only a LD. This was associated with increased hepatic Abcg5 and g8 expression induced by TMAO. Our study demonstrated TMAO could be associated with increased hepatic Abcg5/g8 expression, biliary cholesterol hypersecretion and gallstone formation.

Cholesterol cholelithiasis: part of a systemic metabolic disease, prone to primary prevention

Cholesterol gallstone disease have relationships with various conditions linked with insulin resistance, but also with heart disease, atherosclerosis, and cancer. These associations derive from mechanisms active at a local (i.e. gallbladder, bile) and a systemic level and are involved in inflammation, hormones, nuclear receptors, signaling molecules, epigenetic modulation of gene expression, and gut microbiota. Despite advanced knowledge of these pathways, the available therapeutic options for symptomatic gallstone patients remain limited. Therapy includes oral litholysis by the bile acid ursodeoxycholic acid (UDCA) in a small subgroup of patients at high risk of postdissolution recurrence, or laparoscopic cholecystectomy, which is the therapeutic radical gold standard treatment. Cholecystectomy, however, may not be a neutral event, and potentially generates health problems, including the metabolic syndrome. Areas covered: Several studies on risk factors and pathogenesis of cholesterol gallstone disease, acting at a systemic level have been reviewed through a PubMed search. Authors have focused on primary prevention and novel potential therapeutic strategies. Expert commentary: The ultimate goal appears to target the manageable systemic mechanisms responsible for gallstone occurrence, pointing to primary prevention measures. Changes must target lifestyles, as well as experimenting innovative pharmacological tools in subgroups of patients at high risk of developing gallstones.

Mouse models of gallstone disease

PURPOSE OF REVIEW

The establishment of mouse models of gallstones, and the contribution of mouse models to genetic studies of gallstone disease, as well as the latest advances in the pathophysiology of gallstones from mouse experiments are summarized.

RECENT FINDINGS

The combined uses of genomic strategies and phenotypic studies in mice have successfully led to the identification of many Lith genes, which pave the way for the discovery of human LITH genes. The physical-chemical, genetic, and molecular biological studies of gallstone disease in mice with knockout or transgene of specific target genes have provided many novel insights into the complex pathophysiological mechanisms of this very common hepatobiliary disease worldwide, showing that interactions of five primary defects play a critical role in the pathogenesis of cholesterol gallstones. Based on mouse studies, a new concept has been proposed that hepatic hypersecretion of biliary cholesterol is induced by multiple Lith genes, with insulin resistance as part of the metabolic syndrome interacting with cholelithogenic environmental factors to cause the phenotype.

SUMMARY

The mouse model of gallstones is crucial for elucidating the physical-chemical and genetic mechanisms of cholesterol crystallization and gallstone formation, which greatly increase our understanding of the pathogenesis of this disease in humans.

An update on the pathogenesis of cholesterol gallstone disease

PURPOSE OF REVIEW

Gallstone disease is a major epidemiologic and economic burden worldwide, and the most frequent form is cholesterol gallstone disease.

RECENT FINDINGS

Major pathogenetic factors for cholesterol gallstones include a genetic background, hepatic hypersecretion of cholesterol, and supersaturated bile which give life to precipitating cholesterol crystals that accumulate and grow in a sluggish gallbladder. Additional factors include mucin and inflammatory changes in the gallbladder, slow intestinal motility, increased intestinal absorption of cholesterol, and altered gut microbiota. Mechanisms of disease are linked with insulin resistance, obesity, the metabolic syndrome, and type 2 diabetes. The role of nuclear receptors, signaling pathways, gut microbiota, and epigenome are being actively investigated.

SUMMARY

Ongoing research on cholesterol gallstone disease is intensively investigating several pathogenic mechanisms, associated metabolic disorders, new therapeutic approaches, and novel strategies for primary prevention, including lifestyles.

Prevalence of Cholelithiasis Among Igbo Adult Subjects in Nnewi, Southeast Nigeria

Aim: To determine the prevalence of cholelithiasis in a Nigerian population. Subjects and Methods: A cross-sectional study of Igbo adult subjects in Nnewi, Nigeria, was conducted from June 2011 to April 2014. A sample of 3501 adult subjects’ gallbladders and associated biliary systems was evaluated by sonography, and the presence or absence of cholelithiasis was documented. The age and anthropometric variables of the subjects were recorded. Results: The subjects (18-92 years) comprised 1731 men (49.4%) and 1770 women (50.6%). Only 4.4% (n = 154) had cholelithiasis. It is more common in women than men, at a ratio of 2.8:1. It is also more common in subjects with a high body mass index. Conclusion: The prevalence of cholelithiasis among the Igbo people in Nnewi is 4.40%, and it is about three times more common in women than men.

Four Susceptibility Loci for Gallstone Disease Identified in a Meta-analysis of Genome-Wide Association Studies

BACKGROUND & AIMS

A genome-wide association study (GWAS) of 280 cases identified the hepatic cholesterol transporter ABCG8 as a locus associated with risk for gallstone disease, but findings have not been reported from any other GWAS of this phenotype. We performed a large-scale, meta-analysis of GWASs of individuals of European ancestry with available prior genotype data, to identify additional genetic risk factors for gallstone disease.

METHODS

We obtained per-allele odds ratio (OR) and standard error estimates using age- and sex-adjusted logistic regression models within each of the 10 discovery studies (8720 cases and 55,152 controls). We performed an inverse variance weighted, fixed-effects meta-analysis of study-specific estimates to identify single-nucleotide polymorphisms that were associated independently with gallstone disease. Associations were replicated in 6489 cases and 62,797 controls.

RESULTS

We observed independent associations for 2 single-nucleotide polymorphisms at the ABCG8 locus: rs11887534 (OR, 1.69; 95% confidence interval [CI], 1.54-1.86; P = 2.44 × 10(-60)) and rs4245791 (OR, 1.27; P = 1.90 × 10(-34)). We also identified and/or replicated associations for rs9843304 in TM4SF4 (OR, 1.12; 95% CI, 1.08-1.16; P = 6.09 × 10(-11)), rs2547231 in SULT2A1 (encodes a sulfoconjugation enzyme that acts on hydroxysteroids and cholesterol-derived sterol bile acids) (OR, 1.17; 95% CI, 1.12-1.21; P = 2.24 × 10(-10)), rs1260326 in glucokinase regulatory protein (OR, 1.12; 95% CI, 1.07-1.17; P = 2.55 × 10(-10)), and rs6471717 near CYP7A1 (encodes an enzyme that catalyzes conversion of cholesterol to primary bile acids) (OR, 1.11; 95% CI, 1.08-1.15; P = 8.84 × 10(-9)). Among individuals of African American and Hispanic American ancestry, rs11887534 and rs4245791 were associated positively with gallstone disease risk, whereas the association for the rs1260326 variant was inverse.

CONCLUSIONS

In this large-scale GWAS of gallstone disease, we identified 4 loci in genes that have putative functions in cholesterol metabolism and transport, and sulfonylation of bile acids or hydroxysteroids.

The expression of hepatic carboxypeptidase E is decreased in patients with cholesterol gallstone

BACKGROUND/AIMS

Decreased carboxypeptidase E (CPE) expression is associated with numerous pathophysiological conditions. This study aimed to investigate the potential function of hepatic CPE in cholesterol gallstone formation.

PATIENTS AND METHODS

Patients with cholesterol gallstone (CGS group) and patients without cholesterol gallstones (non-CGS group) were enrolled. The serum total cholesterol, triglyceride, and biliary composition were analyzed. Eight liver samples from two patients without CGS and six patients with CGS were subjected to cDNA microarray analysis. Hepatic CPE expression was detected by quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and immunohistochemical analysis. Plasma CCK level was measured by ELISA.

RESULTS

cDNA microarray identified CPE as a gene downregulated in the CGS group. RT-PCR showed that CPE mRNA level was lower in CGS group than in control (P < 0.05, t-test). Moreover, Western blot and immunohistochemistry analysis showed that CPE protein level was significantly lower in CGS group than in the control group. In addition, plasma CCK level was lower in CGS group than in the control group. A positive correlation was found between serum CCK level and hepatic CPE mRNA level (r2 = 0.713, P = 0.003).

CONCLUSIONS

Down-expression of liver CPE may reduce the secretion of serum CCK and contribute to the formation of cholesterol gallstone.

Nutritional factors (nutritional aspects) in biliary disorders: bile acid and lipid metabolism in gallstone diseases and pancreaticobiliary maljunction

Nutritional factors play a key role in the pathogenesis of biliary diseases such as gallstones and pancreaticobiliary maljunction. Gallstones are primarily classified into cholesterol stone and pigment stone according to the major composition. Cholesterol gallstone formation is very likely based upon supersaturated bile formation, and pigment stones are formed in bile rich in bilirubin. Thus, defects of hepatic metabolism of lipids and organic anions lead to biliary stones. Here, the recent understanding of cholesterol gallstone pathogenesis is elaborated. On the other hand, there is another important link of biliary lipid degradation to serious biliary disease, namely pancreaticobiliary maljunction. Lysophosphatidylcholine (lysoPC), a derivative of phosphatidylcholine hydrolysis by phospholipase A2, is a highly abundant bioactive lipid mediator present in circulation as well as in bile. Increases in bile of lysoPC and phospholipase A2 have been reported in pancreaticobiliary maljunction and considered to be the major risk factor for biliary tract cancers. Further, oxidized fatty acids have been established as a potent ligand for G2A, a member of G protein-coupled receptor family that mediates a diverse array of biological processes including cell growth and apoptosis. Thus, both of lysoPC and free fatty acids are supposed to play an important role through G2A in biliary inflammation and carcinogenesis of pancreaticobiliary maljunction. Taken together, nutritional factors, especially lipid compounds, are seemingly crucial in the pathogenesis of biliary diseases, and such a causal relationship is reviewed by mainly authors' previous publications.

Genetics of gallstone disease

Gallstone disease (GSD) is one of the most common biliary tract disorders worldwide. The prevalence, however, varies from 5.9-21.9% in Western society to 3.1-10.7% in Asia. Most gallstones (75%) are silent. Approximately half of symptomatic gallstone carriers experience a second episode of biliary pain within 1 year. These individuals are at increased risk of developing acute cholecystitis, acute cholangitis, and biliary pancreatitis. As can be expected, these complications burden health care systems because of their invasive nature and surgical cost. Factors that contribute to gallstone formation include supersaturation of cholesterol in bile, gallbladder hypomotility, destabilization of bile by kinetic protein factors, and abnormal mucins. Epidemiologic studies have implicated multiple environmental factors and some common genetic elements in gallstone formation. Genetic factors that influence gallstone formation have been elaborated from linkage studies of twins, families, and ethnicities. Accumulating evidence suggests that genetic factors play a role in GSD.

Gallstone disease in Swedish twins is associated with the Gilbert variant of UGT1A1

BACKGROUND & AIMS

The Gilbert syndrome-associated functional TATA box variant UGT1A1*28 (A(TA)7TAA) was found to increase susceptibility to pigment gallstone formation in patients with haemolytic anaemia. Further studies in extensive cohorts demonstrated an increased risk of this variant for cholesterol gallstone disease (GD). We now investigated this polymorphism as a determinant of symptomatic GD in Swedish twins.

METHODS

The Swedish Twin Registry was merged with the Hospital Discharge and Causes of Death Registries and searched for GD-related diagnoses among monozygotic (MZ) twins living in the Stockholm area. In addition, we screened the TwinGene database for GD. In total, we found 44 MZ twin pairs with and eight MZ twins without GD to be evaluable. GD-free twins from TwinGene (109 concordantly MZ and 126 independent DZ) served as controls. UGT1A1*28 genotyping was performed using TaqMan assays.

RESULTS

Overall, 58 and 8 of 106 twins with GD were hetero- and homozygous UGT1A1 risk allele carriers respectively. The case-control association tests showed a significantly (P < 0.05) increased risk of developing GD (OR = 1.62, 95% CI 1.00-2.63) in heterozygotes carriers and in addition, a trend (P = 0.075) for an increased risk among carriers (OR = 1.52, 95% CI 0.97-2.44) of the risk allele.

CONCLUSION

These data from Swedish twins confirm the Gilbert variant as risk factor for GD. Our observation is in line with nucleation in bilirubin supersaturated bile representing an initial step in cholelithogenesis.

Recurrence of gallstones after cholecystectomy is associated with ABCG5/8 genotype

BACKGROUND

Gallstone disease is a frequent and economically highly relevant disorder, with cholecystectomy representing one of the most frequently performed operations world-wide. Gallstone recurrence after cholecystectomy is associated with complications such as biliary sepsis and pancreatitis. As yet, variant ABCG8-D19H is the most widely recognized genetic risk factor for gallstone disease. The aim of the study is to investigate whether ABCG8-D19H is associated with gallstone recurrence after cholecystectomy.

METHODS

Two thousand three hundred and eight patients from an earlier study of gallstone risk factors were re-contacted by mail, leading to 1,915 patients with available clinical and genetic information. Symptomatic gallstone recurrence was established if it occurred more than six months after surgery. Median follow-up time after cholecystectomy was eight years.

RESULTS

Gallstones recurred in 37 patients (1.9%). ABCG-D19H was found to be significantly associated with gallstone recurrence (p = 0.034). The allelic odds ratio was 1.97 (95% CI 1.12-∞). In a multivariate logistic regression analysis adjusted for age, sex, BMI and type of surgery, ABCG8-D19H remained a significant predictor, both in the total cohort (p = 0.024) and in the subgroup for whom information on type and scheduling of surgery was available (N = 1,650, p = 0.020).

CONCLUSIONS

ABCG8-D19H is a predictor of gallstone recurrence, a major long term postoperative biliary complication. Moreover, the observed association also reemphasizes the importance of the sterolin transporter for stone formation.

Augmented cholesterol absorption and sarcolemmal sterol enrichment slow small intestinal transit in mice, contributing to cholesterol cholelithogenesis

Cholesterol gallstones are associated with slow intestinal transit in humans as well as in animal models, but the molecular mechanism is unknown. We investigated in C57L/J mice whether the components of a lithogenic diet (LD; 1.0% cholesterol, 0.5% cholic acid and 17% triglycerides), as well as distal intestinal infection with Helicobacter hepaticus, influence small intestinal transit time. By quantifying the distribution of 3H-sitostanol along the length of the small intestine following intraduodenal instillation,we observed that, in both sexes, the geometric centre (dimensionless) was retarded significantly (P <0.05) by LD but not slowed further by helicobacter infection (males, 9.4±0.5 (uninfected), 9.6±0.5 (infected) on LD compared with 12.5±0.4 and 11.4±0.5 on chow). The effect of the LD was reproduced only by the binary combination of cholesterol and cholic acid. We inferred that the LD-induced cholesterol enrichment of the sarcolemmae of intestinal smooth muscle cells produced hypomotility from signal-transduction decoupling of cholecystokinin (CCK), a physiological agonist for small intestinal propulsion in mice. Treatment with ezetimibe in an amount sufficient to block intestinal cholesterol absorption caused small intestinal transit time to return to normal. In most cholesterol gallstone-prone humans, lithogenic bile carries large quantities of hepatic cholesterol into the upper small intestine continuously, thereby reproducing this dietary effect in mice. Intestinal hypomotility promotes cholelithogenesis by augmenting formation of deoxycholate, a pro-lithogenic secondary bile salt, and increasing the fraction of intestinal cholesterol absorbed.

Risk factors in patients with hereditary gallstones in Chinese pedigrees

OBJECTIVE

We aimed to define the risk factors and to evaluate the impact of family background on the prevalence of gallstones in China.

SUBJECTS AND METHODS

Thirty-eight gallstone pedigrees were collected and a case-control study was conducted. This study consisted of 272 first-degree relatives and 201 non-first-degree relatives of index patients. The participants completed a questionnaire and underwent physical and ultrasonographic examinations. The risk factors examined included age, sex, body mass index (BMI), smoking status, alcohol consumption, pregnancy, fat content in dietary meat, history of gastrointestinal surgery, hypertension, hyperlipidemia, fatty liver, coronary heart disease and diabetes.

RESULTS

The prevalence of gallstones in first-degree and non-first-degree relatives of index patients was 38.2 and 10.9%, respectively. Age, pregnancy and BMI significantly differed between cases and controls (p < 0.05). The relative risks were: consumption of meat with a high fat content 1.4 (95% CI 1.1-1.8); hyperlipidemia 2.4 (95% CI 1.3-4.6); diabetes 1.9 (95% CI 1.1-3.2); fatty liver 4.9 (95% CI 1.0-24); coronary heart disease 2.5 (95% CI 1.7-3.9).

CONCLUSION

Data showed that age, overweight, more consumption of high-fat food, high frequency of pregnancy, fatty liver, hyperlipidemia, coronary heart disease and diabetes could increase the risk of gallstones in the first-degree relatives of index patients.

Molecular Mechanisms Underlying the Link between Nuclear Receptor Function and Cholesterol Gallstone Formation

Cholesterol gallstone disease is highly prevalent in western countries, particularly in women and some specific ethnic groups. The formation of water-insoluble cholesterol crystals is due to a misbalance between the three major lipids present in the bile: cholesterol, bile salts, and phospholipids. Many proteins implicated in biliary lipid secretion in the liver are regulated by several transcription factors, including nuclear receptors LXR and FXR. Human and murine genetic, physiological, pathophysiological, and pharmacological evidence is consistent with the relevance of these nuclear receptors in gallstone formation. In addition, there is emerging data that also suggests a role for estrogen receptor ESR1 in abnormal cholesterol metabolism leading to gallstone disease. A better comprehension of the role of nuclear receptor function in gallstone formation may help to design new and more effective therapeutic strategies for this highly prevalent disease condition.

Disruption of the murine protein kinase Cbeta gene promotes gallstone formation and alters biliary lipid and hepatic cholesterol metabolism

The protein kinase C (PKC) family of Ca(2+) and/or lipid-activated serine-threonine protein kinases is implicated in the pathogenesis of obesity and insulin resistance. We recently reported that protein kinase Cβ (PKCβ), a calcium-, diacylglycerol-, and phospholipid-dependent kinase, is critical for maintaining whole body triglyceride homeostasis. We now report that PKCβ deficiency has profound effects on murine hepatic cholesterol metabolism, including hypersensitivity to diet-induced gallstone formation. The incidence of gallstones increased from 9% in control mice to 95% in PKCβ(-/-) mice. Gallstone formation in the mutant mice was accompanied by hyposecretion of bile acids with no alteration in fecal bile acid excretion, increased biliary cholesterol saturation and hydrophobicity indices, as well as hepatic p42/44(MAPK) activation, all of which enhance susceptibility to gallstone formation. Lithogenic diet-fed PKCβ(-/-) mice also displayed decreased expression of hepatic cholesterol-7α-hydroxylase (CYP7A1) and sterol 12α-hydroxylase (CYP8b1). Finally, feeding a modified lithogenic diet supplemented with milk fat, instead of cocoa butter, both increased the severity of and shortened the interval for gallstone formation in PKCβ(-/-) mice and was associated with dramatic increases in cholesterol saturation and hydrophobicity indices. Taken together, the findings reveal a hitherto unrecognized role of PKCβ in fine tuning diet-induced cholesterol and bile acid homeostasis, thus identifying PKCβ as a major physiological regulator of both triglyceride and cholesterol homeostasis.

Association between BSEP V444A polymorphism and risk of idiopathic neonatal hepatitis/cholestasis

AIM: To explore the association between the V444A polymorphism in the bile salt export pump (BSEP) gene and the risk of idiopathic neonatal hepatitis/cholestasis.

METHODS: Eighty-one infants with idiopathic hepatitis/cholestasis (case group) and 48 healthy infants without intrahepatic cholestasis (control group) were included in this study. The V444A polymorphism was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS: There are three V444A genotypes: AA homozygote, GA heterozygote, and GG homozygote. The frequencies of AA and AG and GG genotypes were 0.6%, 4.9% and 44.4% in the case group and 14.6%, 62.5% and 22.9% in the control group, respectively, with a significant difference between the two groups (P = 0.019). The distribution of GG genotype was significantly different between the two groups (P < 0.05, OR = 2.691, 95%CI: 1.205-6.008). The risk of suffering from idiopathic intrahepatic cholestasis in G allele carriers was 1.951 times higher than that in A allele carriers (OR = 1.951, 95%CI: 1.56-3.291).

CONCLUSION: The G allele of the BSEP V444A G polymorphism may be a risk factor for idiopathic intrahepatic cholestasis in infants.

Genome-wide association studies and genetic risk assessment of liver diseases

Genetic tests can help clinicians to diagnose rare monogenic liver diseases. For most common liver diseases, however, multiple gene variants that have small to moderate individual phenotypic effects contribute to the overall risk of disease. An individual's level of risk depends on interactions between environmental factors and a wide range of modifier genes, which are yet to be identified systematically. The latest genome-wide association studies in large cohorts of patients with gallstones, fatty liver disease, viral hepatitis, chronic cholestatic liver diseases or drug-induced liver injury have provided new insights into the pathophysiology of these illnesses and have suggested the contribution of previously unsuspected pathogenic pathways. Studies in mouse models have identified further susceptibility genes for several complex liver diseases. As a result, in the future polygenic risk scores might help to define subgroups of patients at risk of developing liver diseases who would benefit from preventative measures and/or personalized therapy. Now that whole-genome sequencing is possible, comprehensive strategies for integrating genomic data and counseling of patients need to be developed.

Loci from a genome-wide analysis of bilirubin levels are associated with gallstone risk and composition

BACKGROUND & AIMS

Genome-wide association studies have mapped loci that are associated with serum levels of bilirubin. Bilirubin is a major component of gallstones so we investigated whether these variants predict gallstone bilirubin content and overall risk for gallstones.

METHODS

Loci that were identified in a meta-analysis to attain a genome-wide significance level of a P value less than 1.0×10(-7) (UGT1A1, SLCO1B1, LST-3TM12, SLCO1A2) were analyzed in 1018 individuals with known gallstone composition. Gallstone risk was analyzed in 2606 German choleystecomized individuals and 1121 controls and was replicated in 210 cases and 496 controls from South America.

RESULTS

By using the presence of bilirubin as a phenotype, variants rs6742078 (UGT1A1; P = .003), rs4149056 (SLCO1B1; P = .003), and rs4149000 (SLCO1A2; P = .015) were associated with gallstone composition. In regression analyses, only UGT1A1 and SLCO1B1 were independently retained in the model. UGT1A1 (rs6742078; P = .018) was associated with overall gallstone risk. In a sex-stratified analysis, only male carriers of rs6742078 had an increased risk for gallstone disease (P = 2.1×10(-7); odds ratio(recessive), 2.34; P(women) = .47). The sex-specific association of rs6742078 was confirmed in samples from South America (P(men) = .046; odds ratio(recessive), 2.19; P(women) = .96).

CONCLUSIONS

The UGT1A1 Gilbert syndrome variant rs6742078 is associated with gallstone disease in men; further studies are required regarding the sex-specific physiology of bilirubin and bile acid metabolism. Variants of ABCG8 and UGT1A1 are the 2 major risk factors for overall gallstone disease, they contribute a population attributable risk of 21.2% among men.

Gallstone disease in Swedish twins: risk is associated with ABCG8 D19H genotype

OBJECTIVE

Recently, variants of the hepatocanalicular cholesterol hemitransporters ABCG5/8 were linked to gallstone disease; ABCG8 D19H in Caucasians and ABCG5 Q604E in Chinese. We investigated these polymorphisms in Swedish twins by merging the Swedish Twin Registry with the Hospital Discharge and Causes of Death Registries for gallstone disease-related diagnoses.

DESIGN

All monozygotic (MZ) twins with gallstone disease alive in the Stockholm area were invited to participate. Gallstone disease was defined by entry in all above mentioned registries, questionnaire or abdominal ultrasound.

SUBJECTS

ABCG5 Q604E and ABCG8 D19H genotyping was performed in 24 unique MZ and eight dizygotic (DZ) twins from concordant pairs. Screening of the TwinGene database for gallstone disease resulted in an additional 20 concordant MZ and 54 twins from concordant DZ pairs. We included 109 concordantly stone-free MZ and 126 stone-free independent DZ twins as controls.

RESULTS

Amongst the 341 twins, 20.8% carried at least one D19H allele as compared to 9.4% of stone-free controls. The association analysis showed that D19H positivity significantly increased the risk of gallstone disease [odds ratio (OR), 2.54; 95% confidence interval (CI), 1.33-4.82; P = 0.004]. We also found a trend for a positive association between gallstone disease and the Q604E variant (OR, 1.47; 95% CI, 1.00-2.16; P = 0.052).

CONCLUSION

Twins carrying a heterozygous or homozygous ABCG8 D19H genotype have a significantly increased risk of gallstone disease. Our study confirms the ABCG8 D19H genotype as a major risk factor for gallstone disease.

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.

Lith genes and genetic analysis of cholesterol gallstone formation

Epidemiologic investigations, clinical observations, and family and twin studies in humans, as well as gallstone prevalence investigations in inbred mouse models, support the concept that cholesterol cholelithiasis could result from a complex interaction of environmental factors and the effects of multiple undetermined genes. Quantitative trait locus (QTL) analysis is a powerful genetic method for identifying primary rate-limiting genetic defects and discriminating them from secondary downstream lithogenic effects caused by mutations of the primary genes, and the subsequent positional cloning of such genes responsible for QTLs, followed by the use of manufactured mouse strains with "knockout" or "knockin" of the genes, could lead to the discovery of lithogenic actions of gallstone (LITH) genes. The combined use of genomic strategies and phenotypic studies in inbred strains of mice has successfully resulted in the identification of many candidate LITH genes. Because there is exceptionally close homology between mouse and human genomes, the orthologous human LITH genes can be identified from the mouse study. The discovery of LITH genes and more fundamental knowledge concerning the genetic determinants and molecular mechanisms underlying the formation of cholesterol gallstones in humans will pave the way for critical diagnostic and prelithogenic preventive measures for this exceptionally prevalent digestive disease.

Hepatic cholesterol transporter ABCG8 polymorphisms in gallstone disease in an Indian population

BACKGROUND AND AIM

Gallstone formation is characterized by the abnormal regulation of cholesterol trafficking and solubilization. The prevalence of gallstone disease (GSD) differs between ethnic groups sharing the common environment. These differences can be explained by a genetic predisposition to gallstone formation. Studies have identified single nucleotide polymorphisms (SNP) D19H and T400K in the cholesterol transporter gene ATP-binding cassette, subfamily G, member 8 (ABCG8) in patients with cholesterol gallstones. The aim of this study was to analyze the relationship between D19H and T400K polymorphisms in the ABCG8 gene and GSD in an Indian population, and the effects of these polymorphisms on cholesterol levels in sera and bile.

METHODS

A total of 226 patients with GSD were analyzed for their lipid profile in plasma and bile. A total of 289 controls were recruited, and their plasma lipid profile was analyzed by standard protocols. The genotype of SNP D19H and T400K of ABCG8 was analyzed in 226 patients and 222 control samples. SNP D19H was analyzed by direct sequencing, and SNP T400K genotyping was assayed by the amplification refractory mutation system-polymerase chain reaction.

RESULTS

There was no significant difference in the allelic distribution of SNP T400K between the GSD and gallstone-free groups (P > 0.05), but the distribution of the SNP variant, D19H, was significantly higher (P = 0.017, odds ratio = 2.274) in patients compared to controls. The analysis of serum and bile cholesterol followed a strong association with genotypes.

CONCLUSION

SNP D19H, but not SNP T400K, in the ABCG8 gene is significantly associated with GSD in an Indian population.

Transgenic overexpression of Abcb11 enhances biliary bile salt outputs, but does not affect cholesterol cholelithogenesis in mice

BACKGROUND

Cholesterol gallstone disease is a complex genetic trait and induced by multiple but as yet unknown genes. A major Lith gene, Lith1 was first identified on chromosome 2 in gallstone-susceptible C57L mice compared with resistant AKR mice. Abcb11, encoding the canalicular bile salt export pump in the hepatocyte, co-localizes with the Lith1 QTL region and its hepatic expression is significantly higher in C57L mice than in AKR mice.

MATERIAL AND METHODS

To investigate whether Abcb11 influences cholesterol gallstone formation, we created an Abcb11 transgenic strain on the AKR genetic background and fed these mice with a lithogenic diet for 56 days.

RESULT

We excluded functionally relevant polymorphisms of the Abcb11 gene and its promoter region between C57L and AKR mice. Overexpression of Abcb11 significantly promoted biliary bile salt secretion and increased circulating bile salt pool size and bile salt-dependent bile flow rate. However, biliary cholesterol and phospholipid secretion, as well as gallbladder size and contractility were comparable in transgenic and wild-type mice. At 56 days on the lithogenic diet, cholesterol saturation indexes of gallbladder biles and gallstone prevalence rates were essentially similar in these two groups of mice.

CONCLUSION

Overexpression of Abcb11 augments biliary bile salt secretion, but does not affect cholelithogenesis in mice.

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.

Decreased expression of cholesterol 7alpha-hydroxylase and altered bile acid metabolism in Apobec-1-/- mice lead to increased gallstone susceptibility

Quantitative trait mapping in mice identified a susceptibility locus for gallstones (Lith6) spanning the Apobec-1 locus, the structural gene encoding the RNA-specific cytidine deaminase responsible for production of apolipoprotein B48 in mammalian small intestine and rodent liver. This observation prompted us to compare dietary gallstone susceptibility in Apobec-1(-/-) mice and congenic C57BL/6 wild type controls. When fed a lithogenic diet (LD) for 2 weeks, 90% Apobec-1(-/-) mice developed solid gallstones in comparison with 16% wild type controls. LD-fed Apobec-1(-/-) mice demonstrated increased biliary cholesterol secretion as well as increased cholesterol saturation and bile acid hydrophobicity indices. These changes occurred despite a relative decrease in cholesterol absorption in LD-fed Apobec-1(-/-) mice. Among the possible mechanisms to account for this phenotype, expression of Cyp7a1 mRNA and protein were significantly decreased in chow-fed Apobec-1(-/-) mice, decreasing further in LD-fed animals. Cyp7a1 transcription in hepatocyte nuclei, however, was unchanged in Apobec-1(-/-) mice, excluding transcriptional repression as a potential mechanism for decreased Cyp7a1 expression. We demonstrated that APOBEC-1 binds to AU-rich regions of the 3'-untranslated region of the Cyp7a1 transcript, containing the UUUN(A/U)U consensus motif, using both UV cross-linking to recombinant APOBEC-1 and in vivo RNA co-immunoprecipitation. In vivo Apobec-1-dependent modulation of Cyp7a1 expression was further confirmed following adenovirus-Apobec-1 administration to chow-fed Apobec-1(-/-) mice, which rescued Cyp7a1 gene expression. Taken together, the findings suggest that the AU-rich RNA binding-protein Apobec-1 mediates post-transcriptional regulation of murine Cyp7a1 expression and influences susceptibility to diet-induced gallstone formation.

Gallstone disease: from genes to evidence-based therapy

The number of gallstone patients is increasing in ageing populations with a high prevalence of metabolic syndrome and obesity. Recently variants of hepatic ATP binding cassette transporters have been identified as genetic susceptibility factors for gallstone disease, pointing to novel means for risk assessment and prevention. Although laparoscopic cholecystectomy is the mainstay of therapy for symptomatic gallbladder stones, the clinical management of gallstone disease is changing rapidly, with an increase in day case surgery and the advent of transluminal endoscopic surgery. Here, we summarize the molecular and genetic mechanisms of gallstone formation as well as the current evidence-based algorithms for diagnosis and therapy of gallbladder and bile duct stones.

Association of apolipoprotein A1-C3 gene cluster polymorphisms with gallstone disease

INTRODUCTION

Genetic polymorphisms in apolipoprotein genes may be associated with alteration in lipid profile and susceptibility to gallstone disease.

AIM

To determine the association between apolipoprotein A1 (APOA1) -75 guanine [G] to adenine [A] and +83/84 M2(+/-), MspI) and apolipoprotein C3 (APOC3) (SstI) polymorphisms with gallstone disease.

METHODS

MspI polymorphisms of the APOA1 gene and SstI polymorphisms of APOC3 were analyzed in DNA samples of 214 gallstone patients and 322 age- and sex-matched healthy controls. All statistical analyses were performed using SPSS version 11.5 (SPSS, USA) and Arlequin version 2.0 (Arlequin, Switzerland).

RESULTS

The APOA1 -75 G/A polymorphism was significantly associated with gallstone disease. Patients with the GG genotype (P=0.015) and G allele carriers (P=0.004) had a significantly higher risk of gallstone disease (1.087-fold and 1.561-fold, respectively), whereas patients with AA genotypes (P=0.011) and A allele carriers (P=0.004) were protected (OR 0.230 and 0.641, respectively) against gallstone disease. APOA1 +83 M2(+/-) and APOC3 SstI polymorphisms were not associated with gallstone disease. Case-control analysis of haplotypes showed a significant association in males only. G-M2(+)-S1 conferred risk for gallstone disease (P=0.036; OR 1.593, 95% CI 1.029 to 2.464), while A-M2(+)-S1 was protective (P=0.002; OR 0.370, 95% CI 0.197 to 0.695) against gallstone disease. In APOA1(-75)-APOA1(+83) bilocus haplotypes, G-M2(+) was associated (P=0.0001) with very high risk (OR 3.173, 95% CI 1.774 to 5.674) for gallstone disease in males only. APOA1(-75)-APOC3(SstI) haplotypes also showed significant association while APOA1(+83)-APOC3(SstI) haplotypes showed no association with gallstone disease.

CONCLUSIONS

The APOA1 -75 G/A polymorphism is associated with gallstone disease and shows sex-specific differences. On the other hand, APOA1 M2(+/-) and APOC3 SstI polymorphisms may not be associated with gallstone disease. Haplotype analysis is a better predictor of risk for gallstone disease.

Increased expression of LXR alpha, ABCG5, ABCG8, and SR-BI in the liver from normolipidemic, nonobese Chinese gallstone patients

Cholesterol supersaturation of bile is one prerequisite for gallstone formation. In the present study of Chinese patients with gallstones, we investigated whether this phenomenon was correlated with the hepatic expression of genes participating in the metabolism of cholesterol and bile acids. Twenty-two nonobese, normolipidemic patients (female-male, 11:11) with gallstones were investigated with 13 age- and body mass index-matched gallstone-free controls (female-male, 10:3). The bile from the gallstone patients had higher cholesterol saturation than that from the controls. The mRNA levels of ABCG5, ABCG8, and liver X receptor alpha (LXRalpha) in the gallstone patients were increased by 51, 59, and 102%, respectively, and significantly correlated with the molar percentage of biliary cholesterol and cholesterol saturation index (CSI). The mRNA and protein levels of the hepatic scavenger receptor class B type I (SR-BI) were increased, and a significant correlation was found between the protein levels and the CSI. No differences were recorded between the two groups concerning the hepatic synthesis of cholesterol, bile acids, and esterification of cholesterol. Our results suggest that the upregulation of ABCG5/ABCG8 in gallstone patients, possibly mediated by increased LXRalpha, may contribute to the cholesterol supersaturation of bile. Our data are consistent with the possibility that increased amounts of biliary cholesterol may originate from plasma HDL cholesterol by enhanced transfer via SR-BI.

Increased gallstone risk in humans conferred by common variant of hepatic ATP-binding cassette transporter for cholesterol

Genomewide scans of inbred strains of mice have linked the genes encoding the hepatocanalicular cholesterol transporter ABCG5/G8 to gallstone formation. Five nonsynonymous coding single-nucleotide polymorphisms (SNPs) in the orthologous human genes are associated with differences in serum cholesterol and plant sterol levels. We now tested these ABCG5/G8 SNPs for linkage and association with gallstone susceptibility in humans. Prospectively, we collected data from 178 white individuals with gallbladder stones or history of cholecystectomy in 84 families and from 70 stone-free controls, as confirmed by abdominal ultrasound. We performed nonparametric linkage (NPL) analysis of affected sib pairs (ASPs) and association tests of cases and controls. In ASPs, gallstones were strongly linked to the D19H variant of the ABCG8 gene (NPL score = 7.1; P = 4.6 x 10(-13)). The risk of gallstones in carriers of the 19H allele was significantly increased in randomly selected cases from the ASP cohort compared to the stone-free controls (OR = 3.018; P = 0.017). Consistent with the mouse model, heterozygosity for the lithogenic ABCG8 allele was associated with gallstones in humans; 21.4% of gallstone patients carried the heterozygous D19H genotype, compared with 8.6% of controls (OR = 2.954; P = 0.026).

CONCLUSION

The linkage and association studies identified the cholesterol transporter ABCG5/G8 as a genetic determinant of gallstone formation, or LITH gene, in humans. The function of this transporter and the results of the genetic study taken together indicate that in gallstone-susceptible carriers of the ABCG8 19H allele, cholesterol cholelithiasis is secondary to increased hepatobiliary cholesterol secretion.

Investigation of the Lith6 candidate genes APOBEC1 and PPARG in human gallstone disease

BACKGROUND

Genetic susceptibility contributes to the aetiology of gallbladder diseases as shown by multiple epidemiological studies. A major gallstone susceptibility locus (Lith6) was identified in 2003 by quantitative trait locus mapping in mice. Two attractive positional and functional candidate genes in apolipoprotein B mRNA-editing protein (APOBEC1) and peroxisome proliferator-activated receptor gamma (PPARG) are located in this interval.

AIMS

To investigate APOBEC1 and PPARG as candidate genes for common symptomatic gallstone disease in humans.

PATIENTS AND METHODS

Eight hundred and ten patients who underwent cholecystectomy for symptomatic gallstone disease (median age of onset 50) were compared with 718 sex-matched control individuals. An independent additional sample included 368 gallstone patients and 368 controls. Control individuals were sonographically free of gallstones. Haplotype tagging and all known coding single nucleotide polymorphisms were genotyped for PPARG (N=32) and APOBEC1 (N=11).

RESULTS

The investigated high-risk patient sample provides a power of greater than 80% for the detection of odds ratios down to 1.45. No evidence of association of the two genes in the single-point tagging markers, coding variants and in the sliding window haplotype analysis was detected (all nominal single point P-values >0.04). A logistic regression analysis including age, sex and BMI as covariates was also negative (nominal P-values > or =0.08).

CONCLUSIONS

In the investigated German samples, no evidence of association of APOBEC1 and PPARG with gallstone susceptibility was detected. Systematic fine mapping of the complete Lith6 region is required to identify the causative genetic variants for gallstone in mice and humans.

Low phospholipid associated cholelithiasis: association with mutation in the MDR3/ABCB4 gene

Low phospholipid-associated cholelithiasis (LPAC) is characterized by the association of ABCB4 mutations and low biliary phospholipid concentration with symptomatic and recurring cholelithiasis. This syndrome is infrequent and corresponds to a peculiar small subgroup of patients with symptomatic gallstone disease. The patients with the LPAC syndrome present typically with the following main features: age less than 40 years at onset of symptoms, recurrence of biliary symptoms after cholecystectomy, intrahepatic hyperechoic foci or sludge or microlithiasis along the biliary tree. Defect in ABCB4 function causes the production of bile with low phospholipid content, increased lithogenicity and high detergent properties leading to bile duct luminal membrane injuries and resulting in cholestasis with increased serum gamma-glutamyltransferase (GGT) activity. Intrahepatic gallstones may be evidenced by ultrasonography (US), computing tomography (CT) abdominal scan or magnetic resonance cholangiopancreatography, intrahepatic hyperechogenic foci along the biliary tree may be evidenced by US, and hepatic bile composition (phospholipids) may be determined by duodenoscopy. In all cases where the ABCB4 genotyping confirms the diagnosis of LPAC syndrome in young adults, long-term curative or prophylactic therapy with ursodeoxycholic acid (UDCA) should be initiated early to prevent the occurrence or recurrence of the syndrome and its complications. Cholecystectomy is indicated in the case of symptomatic gallstones. Biliary drainage or partial hepatectomy may be indicated in the case of symptomatic intrahepatic bile duct dilatations filled with gallstones. Patients with end-stage liver disease may be candidates for liver transplantation.

Gallstone disease

Gallstone disease is one of the most prevalent gastrointestinal diseases with a substantial burden to health care systems that is supposed to increase in ageing populations at risk. Aetiology and pathogenesis of cholesterol gallstones still are not well defined, and strategies for prevention and efficient nonsurgical therapies are missing. This review summarizes current concepts on the pathogenesis of cholesterol gallstones with focus on the uptake and secretion of biliary lipids and special emphasis on recent studies into the genetic background.

Age-associated gallstone formation in male and female CCK-1(A) receptor-deficient mice

BACKGROUND

Gallbladder dysmotility accelerates cholelithiasis. In turn, gallbladder dysmotility can occur secondary to inflammation and excess cholesterol accumulation in gallbladder smooth muscle.

METHODS

The present study was designed to determine how much gallbladder dysmotility contributes to gallstone formation as a primary cause and whether a sex difference exists in gallstone formation by comparing cholecystokinin-1 receptor gene-deficient [CCK-1R(-/-)] male and female mice.

RESULTS

No sludge or gallstone formation was observed in mice at 6 months of age. The frequency of sludge and gallstone formation in mice at 12 and 24 months of age was slightly higher in female CCK-1R(-/-) mice than in males, but the difference was not significant.

CONCLUSIONS

Gallbladder dysmotility may have accelerated sludge and gallstone formation, but its contribution was limited. A 12-month period was required to produce gallstones, and after the mice reached 12 months of age, further ageing did not increase the frequency of gallstones. The effect of sex did not reach a significant level.

Are plasma lipid levels related to ABCG5/ABCG8 polymorphisms? A preliminary study in siblings with gallstones

BACKGROUND

The role of ABCG5 and ABCG8 genes in the determination of plasma lipid levels is currently under intensive investigation. The aim of this study was to evaluate plasma lipid levels in sibling pairs with gallstones and to assess their correlation with common gene polymorphisms in the ABCG5/ABCG8 genes.

METHODS

Plasma levels of cholesterol, HDL-cholesterol, and triglycerides were measured in 68 patients belonging to 34 sibling pairs with gallstones (affected sibling pairs, mean age 56.3 years) and in 68 gallstone carriers with stone-free siblings (age/gender-matched controls in a ratio of 2:1 with the index patients of the study group). Four and one non-synonymous sequence variants in ABCG8 and ABCG5 genes, respectively, were determined in the affected sibling pairs, employing allelic discrimination with 5' nuclease assays.

RESULTS

Plasma triglyceride levels were higher and HDL-cholesterol levels lower in the index patients than in controls. Plasma lipid levels were correlated in the members of the affected sibling pairs. Triglyceride levels were higher in carriers of the common alleles for ABCG5 Q604E and ABCG8 D19H sequence variants, and HDL-cholesterol was lower in carriers of the common alleles for ABCG5 Q604E than in carriers of the rare alleles.

CONCLUSIONS

The significantly different plasma lipid levels in siblings with gallstones versus controls, as well as the correlation of plasma lipids in affected sibling pairs, confirm the genetic influence in gallstone disease. Polymorphisms in ABCG5/ABCG8 genes might contribute to the genetic variation in plasma lipid levels and in cholesterol saturation of the bile.

Investigation of the Lith1 candidate genes ABCB11 and LXRA in human gallstone disease

Genetic susceptibility in the causation of gallbladder diseases was recognized as early as 1937. A major gallstone susceptibility locus (Lith1) was identified in 1995 by quantitative trait locus mapping in mice. Two attractive positional and functional candidate genes in LXRA and ABCB11 are located in this interval. ABCB11 is associated with progressive familial cholestasis. This study was undertaken to investigate LXRA and ABCB11 as candidate genes for gallstone disease in humans. Eight hundred and ten patients who underwent cholecystectomy for symptomatic gallstone disease (median age of onset, 50 years) were compared with 718 sex-matched control individuals. Control individuals were sonographically free of gallstones. Haplotype tagging and all known coding single nucleotide polymorphisms (SNPs) were genotyped for ABCB11 (n=29) and LXRA (n=10). The investigated high-risk patient sample provides a power of greater than 80% for the detection of odds ratios down to 1.55. No evidence of association of the two genes in the single point tagging markers, coding variants or in the sliding window haplotype analysis was detected (all nominal single-point P values>or=.08). In conclusion, in the investigated German sample, no evidence of association of ABCB11 and LXRA to gallstone susceptibility was detected. The gallstone trait is not allelic to progressive familial cholestasis at the ABCB11 locus. Systematic fine mapping of the Lith1 region is required to identify the causative genetic variants for gallstone in mice and humans.

Association of low density lipoprotein receptor related protein-associated protein (LRPAP1) gene insertion/deletion polymorphism with gallstone disease

BACKGROUND AND AIM

Gallstones are byproducts of cholesterol supersaturated bile. Various studies have indicated that there might be a genetic predisposition to the disease. Receptor-associated protein (RAP) is a molecular chaperone for low density lipoprotein receptor-related protein (LRP), which plays a key role in cholesterol metabolism. Intron 5 insertion/deletion polymorphism of RAP gene (LRPAP1) has been implicated in other diseases sharing etiology with gallstone disease (GSD).

METHODS

To analyze the association of insertion/deletion polymorphism in GSD, 130 gallstone patients and 202 healthy subjects took part in the present study. For genotyping, polymerase chain reaction was followed by 2% agarose gel electrophoresis.

RESULTS

The results showed that frequencies of D and I allele were 65.77% and 34.23% in patients, 76.24% and 23.76% in controls, respectively. Frequency of I allele was significantly higher in the patient group than in the control group (P = 0.003).

CONCLUSION

In the present study I (insertion) allele was found to be associated with GSD.

Genetics of hepatobiliary diseases

With the recent publication of the first human map of genetic variation (ie, Human Haplotype Map), genomic-based discoveries will likely affect not only the research bench but also the bedside. These advances will improve the understanding of the genetics of hepatobiliary diseases, resulting in better prevention measures and diagnosis as well as more effective therapies. Currently, alcoholic liver disease, nonalcoholic fatty liver disease, and symptomatic gallbladder stones affect a sizable portion of the population. On the other hand, chronic cholestatic liver diseases, hepatocellular carcinoma, and polycystic liver disease, although rare, shorten life expectancy and diminish the quality of life of patients. In the genomic era, we have the opportunity to start dissecting the susceptibility genetic variants of liver diseases. We are now in a position to begin elucidating the complex genotype/phenotype relationships of liver diseases with the anticipation to understand disease pathogenesis better. These efforts will require the application of genomic-based approaches in large well-organized translational studies in the diseases of interest.

A genomewide search finds major susceptibility loci for gallbladder disease on chromosome 1 in Mexican Americans

Gallbladder disease (GBD) is one of the major digestive diseases. Its risk factors include age, sex, obesity, type 2 diabetes, and metabolic syndrome (MS). The prevalence of GBD is high in minority populations, such as Native and Mexican Americans. Ethnic differences, familial aggregation of GBD, and the identification of susceptibility loci for gallstone disease by use of animal models suggest genetic influences on GBD. However, the major susceptibility loci for GBD in human populations have not been identified. Using ultrasound-based information on GBD occurrence and a 10-cM gene map, we performed multipoint variance-components analysis to localize susceptibility loci for GBD. Phenotypic and genotypic data from 715 individuals in 39 low-income Mexican American families participating in the San Antonio Family Diabetes/Gallbladder Study were used. Two GBD phenotypes were defined for the analyses: (1) clinical or symptomatic GBD, the cases of cholecystectomies due to stones confirmed by ultrasound, and (2) total GBD, the clinical GBD cases plus the stone carriers newly diagnosed by ultrasound. With use of the National Cholesterol Education Program/Adult Treatment Panel III criteria, five MS risk factors were defined: increased waist circumference, hypertriglyceredemia, low high-density lipoprotein cholesterol, hypertension, and high fasting glucose. The MS risk-factor score (range 0-5) for a given individual was used as a single, composite covariate in the genetic analyses. After accounting for the effects of age, sex, and MS risk-factor score, we found stronger linkage signals for the symptomatic GBD phenotype. The highest LOD scores (3.7 and 3.5) occurred on chromosome 1p between markers D1S1597 and D1S407 (1p36.21) and near marker D1S255 (1p34.3), respectively. Other genetic locations (chromosomes 2p, 3q, 4p, 8p, 9p, 10p, and 16q) across the genome exhibited some evidence of linkage (LOD >or=1.2) to symptomatic GBD. Some of these chromosomal regions corresponded with the genetic locations of Lith loci, which influence gallstone formation in mouse models. In conclusion, we found significant evidence of major genetic determinants of symptomatic GBD on chromosome 1p in Mexican Americans.

Gallstone disease. Pathogenesis of gallstones: A genetic perspective

Cholelithiasis is one of the most prevalent gastroenterological diseases, imposing a huge economic burden on health-care systems. Gallbladder stones form when the concentration of cholesterol or bilirubin exceeds the solubility in the bile salt and phospholipid-rich bile. The physiology of biliary lipid secretion by a number of specialized transport proteins has recently been elucidated, and underlying genetic defects in these proteins have been identified as susceptibility factors for gallstone disease. Recent studies of identical twins and family strongly support the idea of a genetic component to gallstone disease. Epidemiological studies in high-risk populations indicate that gallstone formation is caused by multiple environmental influences and common genetic factors and their interactions. Monogenic subtypes of cholelithiasis, such as biliary lipid transporter deficiencies, appear to be rare. The characterization of lithogenic genes in knockout and transgenic mice, and the identification of many gallstone susceptibility loci in inbred mice, provide the basis for studies of the corresponding genes in patients with gallstones. The transfer of findings from mouse genetics to the bedside might lead to new strategies for individual risk assessment and reveal molecular targets for the development of new treatment strategies.