Genetic and environmental influences on symptomatic gallstone disease: a Swedish study of 43,141 twin pairs

Copy number variants in lipid metabolism genes are associated with gallstones disease in men

Gallstones Disease (GSD) is one of the most common digestive diseases requiring hospitalization and surgical procedures in the world. GSD has a high prevalence in populations with European or Amerindian ancestry (10–20%) and the influence of genetic factors is broadly acknowledged. However, known genetic variants do not entirely explain the disease heritability suggesting that additional genetic variants remain to be identified. Here, we examined the association of copy number variants (CNVs) with GSD in a sample of 4778 individuals (1929 GSD cases and 2849 controls) including two European cohorts from Germany (n = 3702) and one admixed Latin American cohort from Chile (n = 1076). We detected 2936 large and rare CNVs events (size > 100 kb, frequency < 1%). Case-control burden analysis and generalized linear regression models revealed significant association of CNVs with GSD in men, with the strongest effect observed with CNVs overlapping lipid metabolism genes (p-value = 6.54 × 10^–4; OR = 2.76; CI 95% = 1.53–4.89). Our results indicate a clear link between CNVs and GSD in men and provides additional evidence that the genetic components of risk for GSD are complex, can be sex specific and include CNVs affecting genes involved in lipid metabolism.

Identification and Replication of Six Loci Associated With Gallstone Disease

Gallstone disease is a common complex disease that confers a substantial economic burden on society. The genetic underpinnings of gallstone disease remain incompletely understood. We aimed to identify genetic associations with gallstone disease using publicly available data from the UK Biobank and two large Danish cohorts. We extracted genetic associations with gallstone disease from the Global Biobank Engine (GBE), an online browser of genome-wide associations in UK Biobank participants (14,940 cases and 322,268 controls). Significant associations (P < 5 × 10^-8 ) were retested in two Copenhagen cohorts (comprising 1,522 cases and 18,266 controls). In the Copenhagen cohorts, we also tested whether a genetic risk score was associated with gallstone disease and whether individual gallstone loci were associated with plasma levels of lipids, lipoproteins, and liver enzymes. We identified 19 loci to be associated with gallstone disease in the GBE. Of these, 12 were replicated in the Copenhagen cohorts, including six previously unknown loci (in hepatocyte nuclear factor 4 alpha [HNF4A], fucosyltransferase 2, serpin family A member 1 [SERPINA1], jumonji domain containing 1C, AC074212.3, and solute carrier family 10A member 2 [SLC10A2]) and six known loci (in adenosine triphosphate binding cassette subfamily G member 8 [ABCG8], sulfotransferase family 2A member 1, cytochrome P450 7A1, transmembrane 4 L six family member 4, ABCB4, and tetratricopeptide repeat domain 39B). Five of the gallstone associations are protein-altering variants, and three (HNF4A p.Thr139Ile, SERPINA1 p.Glu366Lys, and SLC10A2 p.Pro290Ser) conferred per-allele odds ratios for gallstone disease of 1.30-1.36. Individuals with a genetic risk score >2.5 (prevalence 1%) had a 5-fold increased risk of gallstones compared to those with a score <1.0 (11%). Of the 19 lithogenic loci, 11 and ten exhibited distinct patterns of association with plasma levels of lipids and liver enzymes, respectively. Conclusion: We identified six susceptibility loci for gallstone disease.

The association between apolipoprotein E and gallstone disease: an updated meta-analysis

BACKGROUND

Gallstone disease (GSD) is a common biliary tract disease worldwide. Previous studies have investigated the association of apolipoprotein E (APOE) E4 with GSD and reported inconsistent results.

METHODS

In this paper, we conducted meta-analyses to examine whether APOE E4 is associated with the risk of GSD. A systematic literature search was performed in PubMed, Cochrane Library, EMBASE, and Google Scholar using the following inclusion criteria: 1) Studies on human subjects; 2) subjects in the control group must undergo ultrasound GSD screening, and presence of GSD in the experiment group can be clearly determined, e.g., diagnosis of GSD through ultrasound screening or a previous history of cholecystectomy or cholelithiasis; 3) the studies reported APOE genotype data (APOE E4+ vs. E4-) for subjects with and without GSD. In all the meta-analyses, we used random-effects models to calculate the odds ratios (ORs) as a measure of association as well as the corresponding confidence intervals (CIs).

RESULTS

Our literature search found 13 publications with 14 studies, including a total of 1632 GSD patients and 5001 controls, that met the eligibility criteria and were included in the meta-analyses. We did not find a significant association between APOE E4 and risk of GSD (OR = 1.23, 95% CI: 0.89-1.68; p = 0.205). No significant associations were observed in subgroup analyses by gender and mean age. We obtained similar insignificant findings if an additive model was used, if subjects who had E2E4 genotype were excluded, or if low-quality studies were excluded.

CONCLUSION

Our meta-analysis found insufficient evidence for the effect of APOE E4 on GSD risk. Future studies with large sample sizes that control for important confounding/risk factors are needed to validate our findings and to explore other genetic loci that might affect GSD risk.

Genetics of gallstone disease revisited: updated inventory of human lithogenic genes

PURPOSE OF REVIEW

Gallstone disease is one of the most frequent diseases in gastroenterology and treatment by endoscopy and surgery causes high costs in our health-care systems. Family and twin studies have demonstrated that gallstones are, in part, genetically determined. Here we review all recent genome-wide and phenome-wide studies of gallstones in humans and provide an updated 'inventory of human lithogenic genes.'

RECENT FINDINGS

The largest population attributable risk is conferred by the common variant (p.D19H) of the hepatic and intestinal cholesterol transporter ABCG5/G8. A second ABC transporter, the hepatic phosphatidylcholine translocase ABCB4, increases the risk for gallstone disease, gallbladder cancer and chronic liver diseases in general, whereas the common PNPLA3 risk variant p.I148M decreases gallstone risk.

SUMMARY

Better understanding of the pathomechanisms of gallstone disease might help to overcome the current invasive treatment of this exceptionally prevalent and economically significant digestive disease by personalized prevention in at-risk patients.

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.

The Role of Diet in the Pathogenesis of Cholesterol Gallstones

Cholesterol gallstone disease is a major health problem in Westernized countries and depends on a complex interplay between genetic factors, lifestyle and diet, acting on specific pathogenic mechanisms. Overweigh, obesity, dyslipidemia, insulin resistance and altered cholesterol homeostasis have been linked to increased gallstone occurrence, and several studies point to a number of specific nutrients as risk- or protective factors with respect to gallstone formation in humans. There is a rising interest in the identification of common and modifiable dietetic factors that put the patients at risk of gallstones or that are able to prevent gallstone formation and growth. In particular, dietary models characterized by increased energy intake with highly refined sugars and sweet foods, high fructose intake, low fiber contents, high fat, consumption of fast food and low vitamin C intake increase the risk of gallstone formation. On the other hand, high intake of monounsaturated fats and fiber, olive oil and fish (ω-3 fatty acids) consumption, vegetable protein intake, fruit, coffee, moderate alcohol consumption and vitamin C supplementation exert a protective role. The effect of some confounding factors (e.g., physical activity) cannot be ruled out, but general recommendations about the multiple beneficial effects of diet on cholesterol gallstones must be kept in mind, in particular in groups at high risk of gallstone formation.

Genome-wide association meta-analysis yields 20 loci associated with gallstone disease

Gallstones are responsible for one of the most common diseases in the Western world and are commonly treated with cholecystectomy. We perform a meta-analysis of two genome-wide association studies of gallstone disease in Iceland and the UK, totaling 27,174 cases and 736,838 controls, uncovering 21 novel gallstone-associated variants at 20 loci. Two distinct low frequency missense variants in SLC10A2, encoding the apical sodium-dependent bile acid transporter (ASBT), associate with an increased risk of gallstone disease (Pro290Ser: OR = 1.36 [1.25-1.49], P = 2.1 × 10-12, MAF = 1%; Val98Ile: OR = 1.15 [1.10-1.20], P = 1.8 × 10-10, MAF = 4%). We demonstrate that lower bile acid transport by ASBT is accompanied by greater risk of gallstone disease and highlight the role of the intestinal compartment of the enterohepatic circulation of bile acids in gallstone disease susceptibility. Additionally, two low frequency missense variants in SERPINA1 and HNF4A and 17 common variants represent novel associations with gallstone disease.

Recent advances in understanding and managing cholesterol gallstones

The high prevalence of cholesterol gallstones, the availability of new information about pathogenesis, and the relevant health costs due to the management of cholelithiasis in both children and adults contribute to a growing interest in this disease. From an epidemiologic point of view, the risk of gallstones has been associated with higher risk of incident ischemic heart disease, total mortality, and disease-specific mortality (including cancer) independently from the presence of traditional risk factors such as body weight, lifestyle, diabetes, and dyslipidemia. This evidence points to the existence of complex pathogenic pathways linking the occurrence of gallstones to altered systemic homeostasis involving multiple organs and dynamics. In fact, the formation of gallstones is secondary to local factors strictly dependent on the gallbladder (that is, impaired smooth muscle function, wall inflammation, and intraluminal mucin accumulation) and bile (that is, supersaturation in cholesterol and precipitation of solid crystals) but also to "extra-gallbladder" features such as gene polymorphism, epigenetic factors, expression and activity of nuclear receptors, hormonal factors (in particular, insulin resistance), multi-level alterations in cholesterol metabolism, altered intestinal motility, and variations in gut microbiota. Of note, the majority of these factors are potentially manageable. Thus, cholelithiasis appears as the expression of systemic unbalances that, besides the classic therapeutic approaches to patients with clinical evidence of symptomatic disease or complications (surgery and, in a small subgroup of subjects, oral litholysis with bile acids), could be managed with tools oriented to primary prevention (changes in diet and lifestyle and pharmacologic prevention in subgroups at high risk), and there could be relevant implications in reducing both prevalence and health costs.

Protective Effects of Yinchenhao Decoction on Cholesterol Gallstone in Mice Fed a Lithogenic Diet by Regulating LXR, CYP7A1, CYP7B1, and HMGCR Pathways

The study attempted to elucidate whether lipid genes are closely associated with lipid metabolic abnormalities during the lithogenic time and how Yinchenhao Decoction (YCHD) works on the transcriptions of lipid genes against cholesterol gallstone model. C57BL/6J mice fed on lithogenic diet (LD) were used for model establishment and randomized into 5 groups. All groups received LD for different weeks with isometrically intragastric administration of YCHD or NS. Biochemical tests were measured and liver tissues were harvested for histological and genetic detection. It was found that all groups with increasing LD showed a following tendency of gallstone incidence, bile cholesterol, phospholipids, total bile acid, and cholesterol saturation index (CSI). Conversely, YCHD could significantly normalize the levels of gallstone incidence, bile lipids, and CSI (CSI<1). As lithogenic time progressed, ABCG5, ABCG8, PPAR-α, and ABCB4 were upregulated, and SREBP2, CYP7A1, and CYP7B1 were downregulated, while CYP7A1, CYP7B1, LXR, and HMGCR mRNA were increased 3-fold under the administration of YCHD. It was concluded that abnormal expressions of the mentioned genes may eventually progress to cholesterol gallstone. CYP7A1, CYP7B1, LXR, and HMGCR mRNA may be efficient targets of YCHD, which may be a preventive drug to reverse liver injury, normalize bile lipids, facilitate gallstone dissolution, and attenuate gallstone formation.

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.

Sex and ethnic/racial-specific risk factors for gallbladder disease

BACKGROUND

Gallbladder disease (GBD) is a highly prevalent condition; however, little is known about potential differences in risk factors by sex and ethnicity/race. Our aim was to evaluate dietary, reproductive and obesity-related factors and GBD in multiethnic populations.

METHODS

We performed a prospective analysis from the Multiethnic Cohort study who self-identified as non-Hispanic White (n = 32,103), African American (n = 30,209), Japanese (n = 35,987), Native Hawaiian (n = 6942) and Latino (n = 39,168). GBD cases were identified using Medicare and California hospital discharge files (1993-2012) and self-completed questionnaires. We used exposure information on the baseline questionnaire to identify exposures of interest. Associations were estimated by hazard ratios and 95% confidence intervals using Cox models adjusted for confounders.

RESULT

After a median 10.7 years of follow-up, there were 13,437 GBD cases. BMI over 25 kg/m2, diabetes, past and current smoking, red meat consumption, saturated fat and cholesterol were significant risk factors across ethnic/racial populations (p-trends < 0.01). Protective factors included vigorous physical activity, alcohol use, fruits, vegetables and foods rich in dietary fiber (p-trends < 0.01). Carbohydrates were inversely associated with GBD risk only among women and Latinos born in South America/Mexico (p-trend < 0.003). Parity was a significant risk factor among women; post-menopausal hormones use was only associated with an increased risk among White women (estrogen-only: HR = 1.24; 95% CI = 1.07-1.43 and estrogen + progesterone: HR = 1.23; 95% CI = 1.06-1.42).

CONCLUSION

Overall, dietary, reproductive and obesity-related factors are strong risk factors for GBD affecting men and women of different ethnicities/races; however some risk factors appear stronger in women and certain ethnic groups.

What Twin Studies Have Taught Us About Myopia

Myopia has become epidemic, particularly in East Asia, and is a major cause of visual impairment worldwide. Twin studies are an important resource to investigate the genetics and the gene-environment interaction in myopia. This article aims to provide an overview of major findings regarding myopia from different types of twin studies, from the heritability of myopia-related traits to novel findings of genome-wide association studies. In the postgenomic era, twin studies will continue to serve as a unique method in the investigation of gene-environment interaction.

Combined microstructural and mineralogical phase characterization of gallstones in a patient-based study in SW Spain - Implications for environmental contamination in their formation

This study explores the environmental impact of metal exposure on humans through detailed phase and structural characterization of gallstones from two environmentally contrasting populations in Huelva Province (SW Spain). A total of 42 gallstone samples, obtained after surgical intervention at the Riotinto Hospital, were studied by powder X-ray diffraction (XRD), Fourier Transformed Infra-Red spectroscopy (FTIR), FTIR-μ-ATR (Attenuated Total Reflection) coupled with an optical microscope, and by Environmental Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (ESEM-EDS), and subsequently classified according to their phase composition and structure. Additionally, the patients were enquired for their living habits in order to analyze the source of possible exposure to metal contamination. The gallstones were classified into pure, mixed and composite cholesterol stones, black and brown pigment stones, and carbonate stones. The patients from the study group residing in a region with acknowledged metal contamination of both natural and anthropogenic origin have a higher risk of metal exposure through contaminated soil, particle matter in the air, and consumption of local water and food products. According to our findings, the metal exposure is related to a higher tendency of forming black pigment stones in the study group in comparison to the control group residing in a natural park with nearly pristine environmental conditions. Moreover, the gallstones from the study group showed to contain more abundant metal components, such as Cu, Fe, Ni, and Zn, than those from the control group. To our knowledge this is the first study to examine the regional environmental impact of metal exposure on human gallstones.

Gallbladder cancer incidence in Gwalior district of India: Five-year trend based on the registry of a regional cancer center

BACKGROUND

We have reported here the 5-year incidence (2004-2008) of gallbladder cancer (GBC) in North Central India along with its descriptive epidemiology. This provides potential clues for better prevention. The present study has also evaluated the association of ABO blood groups with GBC.

PATIENTS AND METHODS

The study comprised 742 GBC cases referred to the regional cancer hospital, Gwalior, during 2004-2008. The demographic statistics of Gwalior district was considered to calculate the relative risk and incidence rates. ABO blood group distribution amongst 90,000 healthy subjects registered in the local blood bank during 2002-2007 was taken as controls to study the association of blood groups with GBC.

RESULTS

The age-standardized total incidence rate of GBC was calculated to be 7.16/1,00,000. The relative risk of females getting GBC was 2.693 at 95% confidence interval of 2.304-3.151 (P < 0.0001). The females formed 69.5% of total cancer cases, with age-standardized incidence rate of 10/1,00,000. The mean age of male and female GBC cases was found to be 55.4 years (SD = 13, SE = 0.77) and 51.5 years (SD = 12.3, SE = 0.50), respectively. The blood groups A (P = 0.0022) and AB (P < 0.0001) had a positive association with GBC with significant level of differences in comparison to controls.

CONCLUSION

Our study provided an estimate of a 5-year incidence of GBC in North Central India for the first time. With regard to the association of risk factors like obesity, age, and urban living with GBC, the findings of the present study are contradictory to the general opinion. Blood groups A and AB were found to be associated with GBC, which would be provisional for further investigations.

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.

Twin Studies: A Unique Epidemiological Tool

Twin studies are a special type of epidemiological studies designed to measure the contribution of genetics as opposed to the environment, to a given trait. Despite the facts that the classical twin studies are still being guided by assumptions made back in the 1920s and that the inherent limitation lies in the study design itself, the results suggested by earlier twin studies have often been confirmed by molecular genetic studies later. Use of twin registries and various innovative yet complex software packages such as the (SAS) and their extensions (e.g., SAS PROC GENMOD and SAS PROC PHREG) has increased the potential of this epidemiological tool toward contributing significantly to the field of genetics and other life sciences.

Preventing a Mass Disease: The Case of Gallstones Disease: Role and Competence for Family Physicians

Gallstone formation is the result of a complex interaction between genetic and nongenetic factors. We searched and reviewed the available literature to define how the primary prevention of gallstones (cholesterol gallstones in particular) could be applied in general practice. Electronic bibliographical databases were searched. Prospective and retrospective cohort studies and case-controlled studies were analyzed and graded for evidence quality. The epidemiological data confirmed that genetic factors are estimated to account for only approximately 25% of the overall risk of gallstones, while metabolic/environmental factors are at least partially modifiable in stone-free risk groups, and are thus modifiable by primary prevention measures related to diet, lifestyle, and environmental factors (i.e., rapid weight loss, bariatric surgery, somatostatin or analogues therapy, transient gallbladder stasis, and hormone therapy). There is no specific recommendation for the secondary prevention of recurrent gallstones. Family physicians can contribute to preventing gallstones due to their capability to identify and effectively manage several risk factors discussed in this study. Although further studies are needed to better elucidate the involvement of epigenetic factors that may regulate the effect of environment and lifestyle on gene expression in the primary prevention of gallstone formation, preventive interventions are feasible and advisable in the general practice setting.

Prevention of gallbladder hypomotility via FATP2 inhibition protects from lithogenic diet-induced cholelithiasis

Gallstone disease is a widespread disorder costing billions for annual treatment in the United States. The primary mechanisms underlying gallstone formation are biliary cholesterol supersaturation and gallbladder hypomotility. The relative contribution of these two processes has been difficult to dissect, as experimental lithogenic diets cause both bile supersaturation and alterations in gallbladder motility. Importantly, there is no mechanistic explanation for obesity as a major risk factor for cholelithiasis. We discovered that lithogenic diets induce ectopic triacylglycerol (TAG) accumulation, a major feature of obesity and a known muscle contraction impairing condition. We hypothesized that prevention of TAG accumulation in gallbladder walls may prevent gallbladder contractile dysfunction without impacting biliary cholesterol saturation. We utilized adeno-associated virus-mediated knock down of the long-chain fatty acid transporter 2 (FATP2; Slc27A2), which is highly expressed by gallbladder epithelial cells, to downregulate lithogenic diet-associated TAG accumulation. FATP2-knockdown significantly reduced gallbladder TAG, but did not affect key bile composition parameters. Importantly, measurements with force displacement transducers showed that contractile strength in FATP2-knockdown gallbladders was significantly greater than in control gallbladders following lithogenic diet administration, and the magnitude of this effect was sufficient to prevent the formation of gallstones. FATP2-driven fatty acid uptake and the subsequent TAG accumulation in gallbladder tissue plays a pivotal role in cholelithiasis, and prevention of this process can protect from gallstone formation, even in the context of supersaturated bile cholesterol levels, thus pointing to new treatment approaches and targets.

Gallstones

Gallstones grow inside the gallbladder or biliary tract. These stones can be asymptomatic or symptomatic; only gallstones with symptoms or complications are defined as gallstone disease. Based on their composition, gallstones are classified into cholesterol gallstones, which represent the predominant entity, and bilirubin ('pigment') stones. Black pigment stones can be caused by chronic haemolysis; brown pigment stones typically develop in obstructed and infected bile ducts. For treatment, localization of the gallstones in the biliary tract is more relevant than composition. Overall, up to 20% of adults develop gallstones and >20% of those develop symptoms or complications. Risk factors for gallstones are female sex, age, pregnancy, physical inactivity, obesity and overnutrition. Factors involved in metabolic syndrome increase the risk of developing gallstones and form the basis of primary prevention by lifestyle changes. Common mutations in the hepatic cholesterol transporter ABCG8 confer most of the genetic risk of developing gallstones, which accounts for ∼25% of the total risk. Diagnosis is mainly based on clinical symptoms, abdominal ultrasonography and liver biochemistry tests. Symptoms often precede the onset of the three common and potentially life-threatening complications of gallstones (acute cholecystitis, acute cholangitis and biliary pancreatitis). Although our knowledge on the genetics and pathophysiology of gallstones has expanded recently, current treatment algorithms remain predominantly invasive and are based on surgery. Hence, our future efforts should focus on novel preventive strategies to overcome the onset of gallstones in at-risk patients in particular, but also in the population in general.

Genetic Factors Are Not the Major Causes of Chronic Diseases

The risk of acquiring a chronic disease is influenced by a person’s genetics (G) and exposures received during life (the ‘exposome’, E) plus their interactions (G×E). Yet, investigators use genome-wide association studies (GWAS) to characterize G while relying on self-reported information to classify E. If E and G×E dominate disease risks, this imbalance obscures important causal factors. To estimate proportions of disease risk attributable to G (plus shared exposures), published data from Western European monozygotic (MZ) twins were used to estimate population attributable fractions (PAFs) for 28 chronic diseases. Genetic PAFs ranged from 3.4% for leukemia to 48.6% for asthma with a median value of 18.5%. Cancers had the lowest PAFs (median = 8.26%) while neurological (median = 26.1%) and lung (median = 33.6%) diseases had the highest PAFs. These PAFs were then linked with Western European mortality statistics to estimate deaths attributable to G for heart disease and nine cancer types. Of 1.53 million Western European deaths in 2000, 0.25 million (16.4%) could be attributed to genetics plus shared exposures. Given the modest influences of G-related factors on the risks of chronic diseases in MZ twins, the disparity in coverage of G and E in etiological research is problematic. To discover causes of disease, GWAS should be complemented with exposome-wide association studies (EWAS) that profile chemicals in biospecimens from incident disease cases and matched controls.

Cholestasis beyond the Neonatal and Infancy Periods

Cholestasis results from impairment in the excretion of bile, which may be due to mechanical obstruction of bile flow or impairment of excretion of bile components into the bile canaliculus. When present, cholestasis warrants prompt diagnosis and treatment. The differential diagnosis of cholestasis beyond the neonatal period is broad and includes congenital and acquired etiologies. It is imperative that the clinician differentiates between intrahepatic and extrahepatic origin of cholestasis. Treatment may be supportive or curative and depends on the etiology. Recent literature shows that optimal nutritional and medical support also plays an integral role in the management of pediatric patients with chronic cholestasis. This review will provide a broad overview of the pathophysiology, diagnostic approach, and management of cholestasis beyond the neonatal and infancy periods.

Association of Statin Therapy and Risks of Cholelithiasis, Biliary Tract Diseases, and Gallbladder Procedures: Retrospective Cohort Analysis of a US Population

BACKGROUND

Gallstone disease is a leading cause of morbidity in Western countries and carries a high economic burden. Statin medications decrease hepatic cholesterol biosynthesis and may, therefore, lower the risk of cholesterol cholelithiasis by reducing the cholesterol concentration in the bile. Population-based evidence, however, is sparse.

OBJECTIVE

To assess the risk of gallbladder diseases among statin users compared with nonusers in an American patient cohort.

METHODS

We performed a retrospective cohort study of patients enrolled in the San Antonio Tricare health system using data between October 2003 and March 2012. We defined 2 groups: statin users (use for 90 days or greater) and nonusers (no prior statin). A propensity score based on 82 variables was generated to match statin users and nonusers 1:1. Outcomes included incidence of cholelithiasis, biliary tract diseases, and gallbladder procedures.

RESULTS

A total of 43 438 patients were identified; 13 626 (31.4%) were statin users, and 29 812 (68.6%) were nonusers. We matched 6342 pairs of statin users and nonusers based on propensity score. The odds ratios (ORs) in statin users in comparison to nonusers were similar for cholelithiasis (OR = 0.86; 95% CI = 0.73, 1.02), biliary tract disease (OR = 0.85; 95% CI = 0.67-1.08), and gall bladder procedures (OR = 0.85; 95% CI = 0.69, 1.04).

CONCLUSIONS

Statin use was not significantly associated with either an increased or decreased risk of cholelithiasis or gallbladder disease.

Phase composition and morphological analysis of human gallstones using IR spectroscopy, scanning electron microscopy and X-ray Rietveld analysis

Quantitative phase composition and morphological characterization of 12 human gallbladder stones (GS1–GS12) retrieved from patients of eastern India have been carried out using IR-spectroscopy, powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The FTIR spectra indicated that the primary composition of gallstones studied was cholesterol. X-ray powder diffraction study revealed cholesterol monohydrate (CHM) as the major crystalline phase in GS1–GS12. The Rietveld analysis showed that nine of the gallstones were composed exclusively of CHM, while the remaining three stones contained in addition to CHM, small amounts (4.2–10.6 wt%) of calcium carbonate as aragonite and vaterite. The crystallite size of CHM in GS1–GS12 varied between 82(6) and 249(3) nm. The SEM images of gallstones showed different crystal habits of CHM such as plates, thin rods, rectangular and hexagonal blocks, which resulted into different levels of agglomeration at the mesoscopic scale. Presence of numerous parasitic eggs with a typical muskmelon surface in three gallstones (GS2, GS7 and GS9) suggests possible association between the liver fluke infection and biliary stone formation in these patients. To the best of our knowledge, the study constitutes the first report of X-ray quantitative phase analysis of gallstones using the Rietveld methodology.

Management of gallstones and its related complications

The majority of gallstone patients remain asymptomatic; however, interest toward the gallstone disease is continuing because of the high worldwide prevalence and management costs and the development of gallstone symptoms and complications. For cholesterol gallstone disease, moreover, a strong link exists between this disease and highly prevalent metabolic disorders such as obesity, dyslipidemia, type 2 diabetes, hyperinsulinemia, hypertriglyceridemia and the metabolic syndrome. Information on the natural history as well as the diagnostic, surgical (mainly laparoscopic cholecystectomy) and medical tools available to facilitate adequate management of cholelithiasis and its complications are, therefore, crucial to prevent the negative outcomes of gallstone disease. Moreover, some risk factors for gallstone disease are modifiable and some preventive strategies have become necessary to reduce the onset and the severity of complications.

Influence of ApoE and FABP2 polymorphisms and environmental factors in the susceptibility to gallstone disease

BACKGROUND

Gallstone disease (GSD) is a common chronic disease in the Western hemisphere, yet environmental and genetic factors may be responsible for the variations in the prevalence of GSD among populations.

AIM

To analyze the relationship of the ApoE and FABP2 polymorphisms with diet, physical activity and emotional health in patients with GSD from West Mexico.

MATERIAL AND METHODS

A total of 120 patients with GSD and 370 healthy subjects were enrolled. Anthropometric, biochemical, nutritional, clinical and physical activity parameters were measured. ApoE and FABP2 genotypes were assesed by PCR-RFLPs assays.

RESULTS

ApoE E3/E4 genotype and the ApoE E4 allele was highly prevalent among the GSD patients compared to the controls (32% vs. 12.0% and 22% vs. 8.4% respectively p < 0.01). Patients with the Apo E4 allele showed an upward trend of cholesterol levels compared to non-Apo E4 allele carriers (E4 186 ± 30 mg/dL; E3 143 ± 37 mg/dL; E2 129 ± 34 mg/dL). High triglyceride levels were associated with patients that were FABP2 Thr54 allele carriers (p < 0.05) but lacked association with GSD. This may be due to changes in dietary fats after GSD diagnosis, masking the clinical course of the disease. Sedentary lifestyle and negative emotions were detected in 83% and 63% of patients, respectively.

CONCLUSION

These data suggest that the Apo E4 allele could confer genetic susceptibility for the development of GSD among the Mexican population. The Ala54Thr polymorphism of FABP2 was associated with high triglycerides levels, but not to GSD; suggesting that environmental factors modulate such susceptibility.

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

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

Lipids, obesity and gallbladder disease in women: insights from genetic studies using the cardiovascular gene-centric 50K SNP array

Gallbladder disease (GBD) has an overall prevalence of 10–40% depending on factors such as age, gender, population, obesity and diabetes, and represents a major economic burden. Although gallstones are composed of cholesterol by-products and are associated with obesity, presumed causal pathways remain unproven, although BMI reduction is typically recommended. We performed genetic studies to discover candidate genes and define pathways involved in GBD. We genotyped 15 241 women of European ancestry from three cohorts, including 3216 with GBD, using the Human cardiovascular disease (HumanCVD) BeadChip containing up to ~53 000 single-nucleotide polymorphisms (SNPs). Effect sizes with P-values for development of GBD were generated. We identify two new loci associated with GBD, GCKR rs1260326:T>C (P=5.88 × 10⁻⁷, ß=−0.146) and TTC39B rs686030:C>A (P=6.95x10⁻⁷, ß=0.271) and detect four independent SNP effects in ABCG8 rs4953023:G>A (P=7.41 × 10⁻⁴⁷, ß=0.734), ABCG8 rs4299376:G^>T (P=2.40 × 10⁻¹⁸, ß=0.278), ABCG5 rs6544718:T>C (P=2.08 × 10⁻¹⁴, ß=0.044) and ABCG5 rs6720173:G>C (P=3.81 × 10⁻¹², ß⁼0.262) in conditional analyses taking genotypes of rs4953023:G>A as a covariate. We also delineate the risk effects among many genotypes known to influence lipids. These data, from the largest GBD genetic study to date, show that specific, mainly hepatocyte-centred, components of lipid metabolism are important to GBD risk in women. We discuss the potential pharmaceutical implications of our findings.

The APOB gene polymorphism in the pathogenesis of gallstone disease in pre- and postmenopausal women

Aim of the study

The decrease in estrogen levels in the postmenopausal period changes the lipid profile by the expression of hepatic genes related to metabolism of cholesterol and bile acid synthesis that could be important in the pathogenesis of cholelithiasis. The aim of the study was to determine the APOB gene 7673C>T and 12669G>A polymorphisms in the pathogenesis of gallstones and analysis of the composition of gallstones in pre- and postmenopausal women.

Material and methods

The study group consisted of 94 women qualified to the laparoscopic cholecystectomy while the control group consisted of 81 women in whom gallstones and other changes in the bile ducts were excluded. Gallstones composition analysis was performed using commercially available assays. The prevalence of the APOB gene polymorphisms was determined using the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).

Results

When assessing the composition of gallstones in pre- and postmenopausal women, we observed differences in the studied parameters. Analysis of genetic variants of APOB gene 7673C>T and 12669G>A polymorphisms showed no significant statistical differences between studied groups and controls.

Conclusions

Analysis of 7673C>T and 12669G>A polymorphisms showed no relationship between specific genetic variants and the risk of gallstones in pre- and postmenopausal women, pointing to the fact that the investigated polymorphisms are not relevant as prognostic factors in gallstone disease in the Caucasian population. Because of the possible contribution of a variety of factors in gallstones pathogenesis the studies are required to take account of additional environmental factors, what may indicate different occurrence between investigated polymorphisms, gallstone disease development and gallstones composition in Caucasians.

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

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

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.

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.

Relationship between CYP7A1 -204A>C polymorphism with gallbladder stone disease and serum lipid levels: a meta-analysis

Background

The CYP7A1 gene polymorphism has been reported to be associated with gallbladder stone disease (GSD) and serum lipid levels, but the results were inconsistent. This meta-analysis aimed to evaluate the influence of the -204A > C polymorphism in the promoter of CYP7A1 gene on the GSD and serum lipid levels.

Methods

According to inclusion/exclusion criteria, eligible studies on CYP7A1 gene -204A > C polymorphism of serum lipid levels and the risk of GSD were retrieved. Depending on the between-study heterogeneity, the fixed- or random-effects model was applied, and the data were analyzed using the RevMan software (V5.2).

Results

Five studies totaling 830 GSD patients and 882 healthy controls were used to evaluate the relation of CYP7A1 -204A > C polymorphism with GSD. Overall comparison of alleles A with C in all study population yielded 5% but non-significant increased risk of GSD (OR = 1.05, 95% CI: 0.91 − 1.22, P = 0.48). Subgroup analysis by ethnic differences did not show any association between CYP7A1 -204A > C polymorphism and GSD either. Four studies totaling 802 cases and 691 controls were used to assess the relation of CYP7A1 -204A > C polymorphism with serum lipid levels. All the subjects were from the Asian population. The pooled effects indicated that AC genotype had higher levels of TG than AA (MD = -0.42, 95% CI: -0.76 − -0.08, P = 0.01). CC genotype in cases had higher levels of TC (MD = 0.65, 95% CI: 0.25 − 1.05, P = 0.001) and LDL-C (MD = 0.40, 95% CI: 0.06 − 0.73, P = 0.02) than AA, AA (MD = -0.35, 95% CI: -0.60 − -0.10, P = 0.007) and AC (MD = −0.35, 95% CI: -0.61 − -0.08, P = 0.01) genotypes in controls had higher levels of TC than CC, and AA genotype in controls had higher levels of HDL-C than CC (MD = -0.15, 95% CI: -0.21 − -0.09, P < 0.00001).

Conclusions

The CYP7A1 -204A > C polymorphism is significantly associated with serum lipid levels in Asian population, but not gallbladder stone disease.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-511X-13-126) contains supplementary material, which is available to authorized users.

Can the type of gallstones be predicted with known possible risk factors?: A comparison between mixed cholesterol and black pigment stones

BACKGROUND

Pathogenesis of gallstones (GS) is multifactorial and multiple genetic and environmental factors have been identified in different populations for different types of GS with varying prevalence. However the role of the each aetiological factor on the formation of mixed cholesterol and black pigment GS has not being addressed adequately. Hence in this study we attempted to compare known possible risk factors for mixed cholesterol and black pigment GS among two groups of patients with two types of GS.

METHODS

The study was done on a cohort of patients with symptomatic GS admitted to the Teaching Hospital Peradeniya, Sri Lanka over a period of 18 months. Clinical and epidemiological data and physical parameters of the patients were recorded and surgically removed GS were analyzed chemically and physically to identify the type of GS. In addition lipid profile was done in all the patients with normal serum bilirubin levels.

RESULTS

A total of 86 patients were included in the study. Mixed cholesterol GS was significantly common among females than males (χ2 test, p = 0.029). Mixed cholesterol GS was commonly seen among patients belonging to Moor ethnicity (χ2 test, p = 0.009). Majority of patients with mixed cholesterol GS had body mass index above 25 kg/m2 (χ2 test, p = 0.018). Black pigment GS were significantly common among patients with type II diabetes mellitus (Fisher's exact test, p = 0.035). Further all the patients with chronic haemolytic anaemia and alcoholic cirrhosis had black pigment GS. Age, family history, Fasting Blood Glucose, dyslipidaemia, lipid profile, parity and use of oral contraceptive pills in females, smoking and alcohol intake in males did not differ significantly among patients in the two groups.

CONCLUSION

Gender, ethnicity and body mass index can be used to predict the formation of mixed cholesterol GS and black pigment GS.

Helicobacter pylori infection is positively associated with gallstones: a large-scale cross-sectional study in Japan

BACKGROUND

Our aim is to elucidate causative factors for gallstones, especially focusing on Helicobacter pylori (HP) infection.

METHODS

We analyzed 15,551 Japanese adults who had no history of gastrectomy, cholecystectomy, HP eradication, and didn't use proton pump inhibitors, anti-diabetic drugs, or anti-cholesterol drugs. 1,057 subjects who previously had HP eradication were analyzed separately.

RESULTS

Gallstones were detected in 409 of 8,625 men (4.74%) and 285 of 6,926 women (4.11%) by ultrasonography. Among the 25 factors univariately analyzed, age, HP infection, alcohol intake, weight, body mass index (BMI), and 14 blood test values (AST, ALT, ALP, γ-GTP, T-Chol, HDL-Chol, LDL-Chol, TG, TP, Hb, HbA1c, pepsinogen I, pepsinogen II, and pepsinogen I/II ratio) displayed significant association with gallstones (p < 0.05), whereas gender, smoking, height, and three blood test values (Alb, T-Bil, MCV) did not. Multivariate analysis showed that age, gender, alcohol intake, BMI, γ-GTP, LDL-Chol, TP, and HP infection had significant association (p < 0.05). Successive multiple logistic regression analysis calculating odds ratio (OR) and standardized coefficients (β) showed that age (OR/β = 1.57/0.450), BMI (OR/β = 1.30/0.264), HP infection (OR/β = 1.51/0.206), lower alcohol intake (OR/β = 1.33/0.144), γ-GTP (OR/β = 1.15/0.139), and pepsinogen I/II ratio (OR/β = 1.08/0.038) have significant positive association with gallstones, whereas gender does not. The gallstone prevalence among HP-negative, HP-eradicated, and HP-positive subjects was 3.81, 4.73 and 6.08%, respectively. The matched analysis controlling age, BMI, γ-GTP, alcohol intake, pepsinogen I/II ratio and gender also demonstrated that gallstone prevalence among HP-eradicated subjects was significantly lower compared with HP-positive subjects (p < 0.05).

CONCLUSIONS

HP infection is positively associated with gallstones. HP eradication may lead to prevention of gallstones.

Association of three common single nucleotide polymorphisms of ATP binding cassette G8 gene with gallstone disease: a meta-analysis

BACKGROUND

In this study, we evaluated the association between these polymorphisms and gallstone disease using meta-analysis and compared the hepatic ABCG5/G8 mRNA expression and biliary lipids composition in patients with different genotypes of T400K and Y54C.

METHODS

Data were analyzed using the Stata/SE 11.0 software and a random- effects model was applied irrespective of between-study heterogeneity. Hepatic mRNA expression of ABCG5/G8 genes in 182 patients with gallstone disease and 35 gallstone-free patients who underwent cholecystectomy were determined using real-time PCR. Genotypes of Y54C and T400K in the ABCG8 gene were determined by allelic discrimination using either genomic DNA or hepatic cDNA as template by Taqman assays. Biliary compostion in gallbladder bile was assayed in these patients as well.

RESULTS

Ten papers including 13 cohorts were included for the final analysis. In the genotype model, the overall association between genotype with gallstone was significant for D19H (OR = 2.43, 95%CI: 2.23-2.64, P<0.001), and for Y54C (OR = 1.36, 95%CI: 1.01-1.83, P = 0.044), or T400K (OR = 1.17, 95%CI: 0.96-1.43. P = 0.110). In allele model, minor alleles of D19H polymorphism (allele D: OR = 2.25, 95%CI: 2.10-2.42, P<0.001) and of T400K polymorphism (allele K: OR = 1.18, 95%CI: 1.06-1.31, P<0.001) were related with an increased risk of gallstone disease. However, minor allele of Y54C polymorphism (allele Y, OR = 1.08, 95%CI: 0.96-1.21, P = 0.146) was not related with gallstone disease. I(2) statistics indicated no significant between-study heterogeneity for all genetic models for any of the three polymorphisms. Funnel plot and Egger's test suggested the absence of publication bias as well. However, no association of T400K and Y54C polymorphism with hepatic ABCG8/G5 mRNA expression or biliary lipids composition was found.

CONCLUSIONS

Our study showed strong association of D19H polymorphism with gallstone disease. T400K and Y54C polymorphism, though to a less extent, may also relate with gallstone disease.

Trends in cholecystectomy rates in a defined population during and after the period of transition from open to laparoscopic surgery

OBJECTIVE

To evaluate cholecystectomy rates in a Norwegian county during the transition time from open to laparoscopic surgery, with focus on the incident rate of laparoscopic operations, sex differences, age at operation, and indications for cholecystectomy.

MATERIAL AND METHODS

All 2615 patients living in North Trondelag County and operated with cholecystectomy for benign biliary disease between 1990 and 2011 were identified. Poisson regression was used to analyze factors associated with cholecystectomy incidence rate ratios (IRRs).

RESULTS

The proportion of completed laparoscopic cholecystectomies was 8% in 1992, 50% in 1994, 94% in 2003 and 99% in 2011. The incidence of cholecystectomy increased from 6.2 per 10 000 person-years in 1990-1992, 8.0 in 1993-1997, to 10.0 in 1998-2003 and remained at this level with a rate of 10.7 during 2004-2011. Adjusting for age at each year of surgery the IRR for females compared with males was 2.3(2.1-2.5) p < 0.001. The median age at operation was 60.2 years (13-90) in males, 50.1 years (12-93) in females p < 0.001. The median age diminished by 5 years in both males and females. A conversion from laparoscopic to open surgery decreased significantly by calendar year of surgery, increased with age of the patient, and was less often in surgery for gallstone colic than for other indications.

CONCLUSIONS

During the introduction of laparoscopic surgery, the rates of cholecystectomy increased and remained stable at a higher level during the later years of the study. The rate of completed laparoscopic operations increased from 8% in 1992 to 99% in 2011.

Elevated body mass index as a causal risk factor for symptomatic gallstone disease: a Mendelian randomization study

Elevated body mass index (BMI) is associated with an increased risk of gallstone disease. Whether this reflects a causal association is unknown. Using a Mendelian randomization approach, we studied 77,679 individuals from the general population. Of these, 4,106 developed symptomatic gallstone disease during up to 34 years of follow-up. Subjects were genotyped for three common variants known to associate with BMI: FTO(rs9939609); MC4R(rs17782313); and TMEM18(rs6548238). The number of BMI-increasing alleles was calculated for each participant. In observational analyses, mean baseline BMI was 55% (11.6 kg/m(2) ) increased in individuals in the fifth quintile versus the first quintile, similar in women and men. The corresponding multifactorially adjusted hazard ratio (HR) for symptomatic gallstone disease was 2.84 (95% confidence interval [CI]: 2.32-3.46) overall, 3.36 (95% CI: 2.62-4.31) in women, and 1.51 (95% CI: 1.09-2.11) in men (P trend: 0.001 to <0.001; P interaction: BMI*sex on risk = 0.01). In genetic analyses, carrying 6 versus 0-1 BMI-increasing alleles was associated with a 5.2% (1.3 kg/m(2) ) increase in BMI overall and with increases of 4.3% in women and 6.1% in men (all P trend: <0.001). Corresponding HRs for symptomatic gallstone disease were 1.43 (95% CI: 0.99-2.05) overall, 1.54 (95% CI: 1.00-2.35) in women, and 1.19 (95% CI: 0.60-2.38) in men (P trend = 0.007, 0.02, and 0.26, respectively; P interaction allele score*sex on risk = 0.49). The estimated causal odds ratio (OR) for symptomatic gallstone disease, by instrumental variable analysis for a 1 kg/m(2) increase in genetically determined BMI, was 1.17 (95% CI: 0.99-1.37) overall and 1.20 (95% CI: 1.00-1.44) and 1.02 (95% CI: 0.90-1.16) in women and men, respectively. Corresponding observational HRs were 1.07 (95% CI: 1.06-1.08), 1.08 (95% CI: 1.07-1.10), and 1.04 (95% CI: 1.02-1.07), respectively.

CONCLUSION

These results are compatible with a causal association between elevated BMI and increased risk of symptomatic gallstone disease, which is most pronounced in women.

Lipid trait-associated genetic variation is associated with gallstone disease in the diverse Third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND

Gallstone disease is one of the most common digestive disorders, affecting more than 30 million Americans. Previous twin studies suggest a heritability of 25% for gallstone formation. To date, one genome-wide association study (GWAS) has been performed in a population of European-descent. Several candidate gene studies have been performed in various populations, but most have been inconclusive. Given that gallstones consist of up to 80% cholesterol, we hypothesized that common genetic variants associated with high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG) would also be associated with gallstone risk.

METHODS

To test this hypothesis, the Epidemiologic Architecture for Genes Linked to Environment (EAGLE) study as part of the Population Architecture using Genomics and Epidemiology (PAGE) study performed tests of association between 49 GWAS-identified lipid trait SNPs and gallstone disease in non-Hispanic whites (446 cases and 1,962 controls), non-Hispanic blacks (179 cases and 1,540 controls), and Mexican Americans (227 cases and 1,478 controls) ascertained for the population-based Third National Health and Nutrition Examination Survey (NHANES III).

RESULTS

At a liberal significance threshold of 0.05, five, four, and four SNP(s) were associated with disease risk in non-Hispanic whites, non-Hispanic blacks, and Mexican Americans, respectively. No one SNP was associated with gallstone disease risk in all three racial/ethnic groups. The most significant association was observed for ABCG5 rs6756629 in non-Hispanic whites [odds ratio (OR) = 1.89; 95% confidence interval (CI) = 1.44-2.49; p = 0.0001). ABCG5 rs6756629 is in strong linkage disequilibrium with rs11887534 (D19H), a variant previously associated with gallstone disease risk in populations of European-descent.

CONCLUSIONS

We replicated a previously associated variant for gallstone disease risk in non-Hispanic whites. Further discovery and fine-mapping efforts in diverse populations are needed to fully describe the genetic architecture of gallstone disease risk in humans.

The systematic classification of gallbladder stones

Background

To develop a method for systematic classification of gallbladder stones, analyze the clinical characteristics of each type of stone and provide a theoretical basis for the study of the formation mechanism of different types of gallbladder stones.

Methodology

A total of 807 consecutive patients with gallbladder stones were enrolled and their gallstones were studied. The material composition of gallbladder stones was analyzed using Fourier Transform Infrared spectroscopy and the distribution and microstructure of material components was observed with Scanning Electron Microscopy. The composition and distribution of elements were analyzed by an X-ray energy spectrometer. Gallbladder stones were classified accordingly, and then, gender, age, medical history and BMI of patients with each type of stone were analyzed.

Principal Findings

Gallbladder stones were classified into 8 types and more than ten subtypes, including cholesterol stones (297), pigment stones (217), calcium carbonate stones (139), phosphate stones (12), calcium stearate stones (9), protein stones (3), cystine stones (1) and mixed stones (129). Mixed stones were those stones with two or more than two kinds of material components and the content of each component was similar. A total of 11 subtypes of mixed stones were found in this study. Patients with cholesterol stones were mainly female between the ages of 30 and 50, with higher BMI and shorter medical history than patients with pigment stones (P<0.05), however, patients with pigment, calcium carbonate, phosphate stones were mainly male between the ages of 40 and 60.

Conclusion

The systematic classification of gallbladder stones indicates that different types of stones have different characteristics in terms of the microstructure, elemental composition and distribution, providing an important basis for the mechanistic study of gallbladder stones.

Intrahepatic cholestasis of pregnancy and associated hepatobiliary disease: a population-based cohort study

Intrahepatic cholestasis of pregnancy (ICP) is the most common liver disease in pregnancy. We aimed to estimate the risk of developing hepatobiliary disease in women with ICP and the odds of developing ICP in women with prevalent hepatobiliary disease. We analyzed data of women with births between 1973 and 2009 and registered in the Swedish Medical Birth Register. By linkage with the Swedish Patient Register, we identified 11,388 women with ICP who were matched to 113,893 women without this diagnosis. Diagnoses of preexisting or later hepatobiliary disease were obtained from the Patient Register. Main outcome measures were hazard ratios (HRs) for later hepatobiliary disease in women with ICP and odds ratios (ORs) for developing ICP in preexisting hepatobiliary disease. Risk estimates were calculated through Cox and logistic regression analyses. Women with ICP were more often diagnosed with later hepatobiliary disease (HR 2.62; 95% confidence interval [CI] 2.47-2.77; increment at 1% per year), hepatitis C or chronic hepatitis (HR 4.16; 3.14-5.51 and 5.96; 3.43-10.33, respectively), fibrosis/cirrhosis (HR 5.11; 3.29-7.96), gallstone disease or cholangitis (HR 2.72; 2.55-2.91, and 4.22; 3.13-5.69, respectively) as compared to women without ICP (P < 0.001 for all HRs). Later ICP was more common in women with prepregnancy hepatitis C (OR 5.76; 1.30-25.44; P = 0.021), chronic hepatitis (OR 8.66; 1.05-71.48; P = 0.045), and gallstone disease (OR 3.29; 2.02-5.36; P < 0.0001).

CONCLUSION

Women with ICP have substantially increased risk for later hepatobiliary disease. Beyond gallstone-related morbidity we found a strong positive association between ICP and hepatitis C both before and after ICP diagnosis. Thus, we advocate testing for hepatitis C in women with ICP, in particular, since this potentially life-threatening infection can be treated successfully in the majority of patients.

Presence of coronary artery disease increases the risk of biliary events in patients with asymptomatic gallstones

BACKGROUND AND AIM

Propensity score indicates a probability of having a confounding factor. It is used to match each patient with the closest propensity score between two groups, which is known as propensity score matching. This study aimed to evaluate the gallstone-related biliary events, defined as biliary colic and acute cholecystitis between coronary artery disease (CAD) and non-CAD patients using propensity score matching.

METHODS

This retrospective cohort study evaluated 267 asymptomatic gallstone patients with CAD and 459 asymptomatic gallstone patients without CAD from March 2003 to December 2009 at two tertiary teaching hospitals in the Republic of Korea. After propensity score matching, total 378 patients, including 126 in study group (with CAD) and 252 in control group (without CAD), were evaluated.

RESULTS

During a median follow-up of 47 months, overall gallstone-related biliary event rate was 33.5% in the study group and 27.5% in the control group. The 5-year cumulative rates were 25.3% versus 17.7% in gallstone-related biliary event and 10.9% versus 1.6% in acute cholecystitis (study versus control group). After propensity score adjustment, the risk of gallstone-related biliary events in the CAD patients significantly increased (hazard ratio 2.11, 95% confidence interval 1.14-3.90, P = 0.017 in matched patients).

CONCLUSION

In patients with asymptomatic gallstones, the coexistence of CAD can increase the risk of gallstone-related biliary events, particularly acute cholecystitis. Therefore, gallstone patients with CAD should be carefully monitored, even if they are asymptomatic.

Validating the 5Fs mnemonic for cholelithiasis: time to include family history

BACKGROUND

The time-honoured mnemonic of '5Fs' is a reminder to students that patients with upper abdominal pain and who conform to a profile of 'fair, fat, female, fertile and forty' are likely to have cholelithiasis. We feel, however, that a most important 'F'-that for 'family history'-is overlooked and should be introduced to enhance the value of a useful aide memoire.

METHODS

To assess the usefulness of each of the existing factors of a popular mnemonic, 398 patients admitted with upper abdominal pain between March 2009 and April 2010 were studied. The clinical features expressed in the cholelithiasis mnemonic in patients with sonographic evidence of cholelithiasis were compared with those of patients without.

FINDINGS

In the cholelithiasis group, significantly more patients were women (150/198 (75.8%) vs 111/200 (55.5%), p<0.001), fair (144/198 (62.9%) vs 54/200 (32.1%), (p<0.001)), fertile (135/198 (68.2%) vs 50/200 (25%) (p<0.001)) and had a body mass index >30 (56/198 (28.3%) vs 19/200 (9.5%) (p<0.001)) compared with controls; but age over 40 years did not predict cholelithiasis (82/198 (41.4%) vs 79/200 (39.5%) (p=0.697)). In the cholelithiasis group, 78/198 (39.4%) had a family history in at least one first-degree relative, compared with 27/200 (13.5%) of controls, (p<0.001). Where the phenotypic elements of the history existed in combination, that patient was found to be at an increased risk of cholelithiasis.

INTERPRETATION

Our study found that the validated 'students' 5Fs' mnemonic retains a role in clinical diagnosis of patients suspected of cholelithiasis but the factor 'familial' should be substituted for 'forty' in recognition of the role of inheritance and the changing demographics of gallstone incidence.

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

BACKGROUND AND AIMS

Cholesterol gallstone disease is a complex process involving both genetic and environmental variables. No information exists regarding what role if any the indigenous gastrointestinal microbiota may play in cholesterol gallstone pathogenesis and whether variations in the microbiota can alter cholesterol gallstone prevalence rates.

METHODS

Genetically related substrains (BALB/cJ and BALB/cJBomTac) and (BALB/AnNTac and BALB/cByJ) of mice obtained from different vendors were compared for cholesterol gallstone prevalence after being fed a lithogenic diet for 8 weeks. The indigenous microbiome was altered in these substrains by oral gavage of fecal slurries as adults, by cross-fostering to mice with divergent flora at <1 day of age or by rederiving into a germ-free state.

RESULTS

Alterations in the indigenous microbiome altered significantly the accumulation of mucin gel and normalized gallbladder weight but did not alter cholesterol gallstone susceptibility in conventionally housed SPF mice. Germ-free rederivation rendered mice more susceptible to cholesterol gallstone formation. This susceptibility appeared to be largely due to alterations in gallbladder size and gallbladder wall inflammation. Colonization of germ-free mice with members of altered Schaedler flora normalized the gallstone phenotype to a level similar to conventionally housed mice.

CONCLUSIONS

These data demonstrate that alterations in the gastrointestinal microbiome may alter aspects of cholesterol gallstone pathogenesis and that in the appropriate circumstances these changes may impact cholesterol cholelithogenesis.

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.

The genetics of complex cholestatic disorders

Cholestatic liver diseases are caused by a range of hepatobiliary insults and involve complex interactions among environmental and genetic factors. Little is known about the pathogenic mechanisms of specific cholestatic diseases, which has limited our ability to manage patients with these disorders. However, recent genome-wide studies have provided insight into the pathogenesis of gallstones, primary biliary cirrhosis, and primary sclerosing cholangitis. A lithogenic variant in the gene that encodes the hepatobiliary transporter ABCG8 has been identified as a risk factor for gallstone disease; this variant has been associated with altered cholesterol excretion and metabolism. Other variants of genes encoding transporters that affect the composition of bile have been associated with cholestasis, namely ABCB11, which encodes the bile salt export pump, and ABCB4, which encodes hepatocanalicular phosphatidylcholine floppase. In contrast, studies have associated primary biliary cirrhosis and primary sclerosing cholangitis with genes encoding major histocompatibility complex proteins and identified loci associated with microbial sensing and immune regulatory pathways outside this region, such as genes encoding IL12, STAT4, IRF5, IL2 and its receptor (IL2R), CD28, and CD80. These discoveries have raised interest in the development of reagents that target these gene products. We review recent findings from genetic studies of patients with cholestatic liver disease. Future characterization of genetic variants in animal models, stratification of risk alleles by clinical course, and identification of interacting environmental factors will increase our understanding of these complex cholestatic diseases.

Genetic and functional identification of the likely causative variant for cholesterol gallstone disease at the ABCG5/8 lithogenic locus

The sterolin locus (ABCG5/ABCG8) confers susceptibility for cholesterol gallstone disease in humans. Both the responsible variant and the molecular mechanism causing an increased incidence of gallstones in these patients have as yet not been identified. Genetic mapping utilized patient samples from Germany (2,808 cases, 2,089 controls), Chile (680 cases, 442 controls), Denmark (366 cases, 766 controls), India (247 cases, 224 controls), and China (280 cases, 244 controls). Analysis of allelic imbalance in complementary DNA (cDNA) samples from human liver (n = 22) was performed using pyrosequencing. Transiently transfected HEK293 cells were used for [(3) H]-cholesterol export assays, analysis of protein expression, and localization of allelic constructs. Through fine mapping in German and Chilean samples, an ∼250 kB disease-associated interval could be defined for this locus. Lack of allelic imbalance or allelic splicing of the ABCG5 and ABCG8 transcripts in human liver limited the search to coding single nucleotide polymorphisms. Subsequent mutation detection and genotyping yielded two disease-associated variants: ABCG5-R50C (P = 4.94 × 10(-9) ) and ABCG8-D19H (P = 1.74 × 10(-10) ) in high pairwise linkage disequilibrium (r(2) = 0.95). [(3) H]-cholesterol export assays of allelic constructs harboring these genetic candidate variants demonstrated increased transport activity (3.2-fold, P = 0.003) only for the ABCG8-19H variant, which was also superior in nested logistic regression models in German (P = 0.018), Chilean (P = 0.030), and Chinese (P = 0.040) patient samples.

CONCLUSION

This variant thus provides a molecular basis for biliary cholesterol hypersecretion as the mechanism for cholesterol gallstone formation, thereby drawing a link between "postgenomic" and "pregenomic" pathophysiological knowledge about this common complex disorder. (HEPATOLOGY 2012).