Arg64 variant of the beta3-adrenergic receptor is associated with gallstone formation

Physiology and pathophysiology of the β3-adrenergic receptor

The β₃-adrenergic receptor (β₃-AR) is an important regulator of various physiological functions, such as thermogenesis in brown adipose tissue, lipolysis in white adipose tissue, negative inotropic effect in cardiomyocyte, and relaxation in blood vessel. The activation of β₃-AR by its agonists is shown to have metabolic (antiobesity and antidiabetic) and cardiovascular effects in animal models, highlighting β₃-AR as a potential therapeutic target in the treatment of several human diseases. Moreover, a substantial number of studies performed on different populations have identified some β₃-AR polymorphic variants associated with obesity, diabetes, cardiovascular diseases, and other disorders. The clinical phenotypes and functional characteristics of these variants provide insights into potential pathophysiological roles of β₃-AR in the development of these diseases.

A Multiple Interaction Analysis Reveals ADRB3 as a Potential Candidate for Gallbladder Cancer Predisposition via a Complex Interaction with Other Candidate Gene Variations

Gallbladder cancer is the most common and a highly aggressive biliary tract malignancy with a dismal outcome. The pathogenesis of the disease is multifactorial, comprising the combined effect of multiple genetic variations of mild consequence along with numerous dietary and environmental risk factors. Previously, we demonstrated the association of several candidate gene variations with GBC risk. In this study, we aimed to identify the combination of gene variants and their possible interactions contributing towards genetic susceptibility of GBC. Here, we performed Multifactor-Dimensionality Reduction (MDR) and Classification and Regression Tree Analysis (CRT) to investigate the gene–gene interactions and the combined effect of 14 SNPs in nine genes (DR4 (rs20576, rs6557634); FAS (rs2234767); FASL (rs763110); DCC (rs2229080, rs4078288, rs7504990, rs714); PSCA (rs2294008, rs2978974); ADRA2A (rs1801253); ADRB1 (rs1800544); ADRB3 (rs4994); CYP17 (rs2486758)) involved in various signaling pathways. Genotyping was accomplished by PCR-RFLP or Taqman allelic discrimination assays. SPSS software version 16.0 and MDR software version 2.0 were used for all the statistical analysis. Single locus investigation demonstrated significant association of DR4 (rs20576, rs6557634), DCC (rs714, rs2229080, rs4078288) and ADRB3 (rs4994) polymorphisms with GBC risk. MDR analysis revealed ADRB3 (rs4994) to be crucial candidate in GBC susceptibility that may act either alone (p < 0.0001, CVC = 10/10) or in combination with DCC (rs714 and rs2229080, p < 0.0001, CVC = 9/10). Our CRT results are in agreement with the above findings. Further, in-silico results of studied SNPs advocated their role in splicing, transcriptional and/or protein coding regulation. Overall, our result suggested complex interactions amongst the studied SNPs and ADRB3 rs4994 as candidate influencing GBC susceptibility.

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.

Association of adrenergic receptor gene polymorphisms in gallbladder cancer susceptibility in a North Indian population

PURPOSE

Gallbladder cancer (GBC), the most common gastrointestinal and biliary tract malignancy, often coincides with gallstone disease (GSD). The genetic variants of adrenergic receptor (ADR) have been previously reported to be associated with hypomotility disorder of cardiovascular system and GSD. Since GSD may function as GBC precursor, the present study aimed to investigate the association of common functional genetic variants of ADRA2A C-1291G, ADRβ3 T190C or Trp64Arg, and ADRβ1 C1165G or Arg389Gly with GBC and GSD susceptibility.

METHODS

The present study included a total of 400 histologically confirmed GBC, 230 GSD, and 268 healthy controls. The ADRA2A C-1291G, ADRβ3 T190C, and ADRβ1 C1165G polymorphisms were determined by PCR-RFLP. Statistical analysis was performed by using SPSS version 16.

RESULTS

ADRβ3 T190C polymorphism was significantly associated with increased risk of GBC (CT: Pcorr = 0.015, OR 2.87; CC: Pcorr = 0.038, OR 10.33; C allele: Pcorr = 0.014, OR 2.7; CT + CC: Pcorr = 0.017, OR 3.05). These associations existed even after gallstone and gender stratification. Similarly, ADRβ3 T190C polymorphism was also associated with GSD risk, though limited only to female GSD patients. In contrary, ADRA2A C-1291G conferred a marginally increased risk only in GSD patients. ADRβ1 C1165G polymorphism was not associated with GBC and GSD susceptibility when compared to controls.

CONCLUSION

ADRβ3 T190C polymorphism is significantly associated with GBC and GSD susceptibility. The ADRβ3 T190C may be involved in the pathophysiology of GBC by both gallstone-dependent pathway and by some other independent mechanisms.

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.

Mucin genes in gallstone disease

Gallstone disease is a complex disorder that can be caused by environmental influences, common genetic factors and their interactions. Three major pathogenic abnormalities are considered to involve in gallstone formation: cholesterol supersaturation in bile, precipitation and nucleation of excess cholesterol, and gallbladder hypomotility, while, mucin takes part in the cholesterol nucleation process. Up to date, more than 20 mucin genes have been reported, 9 of them are identified at the mRNA and/or protein level in native gallbladder and its associated diseases. In the gallbladder, mucin is essential for best protection against detergent effect of high concentration of bile acids. Over the past decade, the properties, expressions and functions of the gallbladder mucins are delineated in animal and human studies. Alteration expressions of mucins are thought to response during the pathogenesis of gallstone formation. Moreover, recent genetic association study demonstrated mucin gene polymorphisms may also influence susceptibility to gallstone disease. This review is not to provide a complete coverage of all the aspects of mucin glycoproteins, but focus on the role and expression of mucins involve in the regulation of cholelithogenesis.

Relationship between gallbladder surgery and ethnic admixture in African American and Hispanic American women

OBJECTIVES

The objective of this study was to investigate whether differences in admixture in African American and Hispanic American adult women are associated with differences in gallbladder surgery.

METHODS

Gallbladder surgery history on entry to the Women's Health Initiative's (WHI) study was used as a dichotomous outcome measure for this study. The proportion of European, sub-Saharan African, and Amerindian (AMI) admixture was estimated for 10,841 African American and 4,620 Hispanic American women in WHI using 92 ancestry informative markers. Logistic regression analyses assessed the relationship between admixture and gallbladder surgery in WHI women (enrollment at ages >50, mean age 61 years) with or without adjusting for multiple covariates, including measures of adiposity, parity, alcohol use, and education.

RESULTS

There was a significant positive association between AMI admixture and the frequency of gallbladder surgery in Hispanic Americans. The odds ratio (OR) and 95% confidence intervals (CIs) for AMI admixture group was OR=2.97, CI=2.01-4.38, P<10(-4). Although there were strong positive associations with parity and adiposity, and negative associations with alcohol consumption and education, accounting for these covariates did not remove the admixture association (OR=2.46, CI=1.62-3.73). In contrast, the effect of African admixture was nearly indistinguishable from that of the European admixture, both of which were protective in the Hispanic American group, and African admixture had a marginal association with decreased gallbladder surgery in the African American group. Measures of adiposity were associated with increased risk for gallbladder surgery and remained significant after accounting for admixture and each of the other covariates. Education level and alcohol use were associated with decreased risk for gallbladder disease. However, after accounting for the other covariates these variably remained significant.

CONCLUSIONS

AMI admixture is strongly associated with gallbladder surgery in women, even after adjustment for selected risk factors for cholelithiasis. Additional studies to ascertain the specific genetic risk factors underlying these associations are warranted.

Concept of the pathogenesis and treatment of cholelithiasis

Gallstone disease (GD) is a chronic recurrent hepatobiliary disease, the basis for which is the impaired metabolism of cholesterol, bilirubin and bile acids, which is characterized by the formation of gallstones in the hepatic bile duct, common bile duct, or gallbladder. GD is one of the most prevalent gastrointestinal diseases with a substantial burden to health care systems. GD can result in serious outcomes, such as acute gallstone pancreatitis and gallbladder cancer. The epidemiology, pathogenesis and treatment of GD are discussed in this review. The prevalence of GD varies widely by region. The prevalence of gallstone disease has increased in recent years. This is connected with a change in lifestyle: reduction of motor activity, reduction of the physical load and changes to diets. One of the important benefits of early screening for gallstone disease is that ultrasonography can detect asymptomatic cases, which results in early treatment and the prevention of serious outcomes. The pathogenesis of GD is suggested to be multifactorial and probably develops from complex interactions between many genetic and environmental factors. It suggests that corticosteroids and oral contraceptives, which contain hormones related to steroid hormones, may be regarded as a model system of cholelithiasis development in man. The achievement in the study of the physiology of bile formation and the pathogenesis of GD has allowed expanding indications for therapeutic treatment of GD.

Polymorphism at the mucin-like protocadherin gene influences susceptibility to gallstone disease

BACKGROUND

Gallstone disease (GSD) is a common disease that can be caused by environmental influences, common genetic factors and their interactions. Mucin glycoproteins may be one important factor for GSD. We conducted a case-control study to investigate the relationship between the mucin-like protocadherin (MUPCDH) gene polymorphisms and GSD.

METHODS

The study included 452 GSD cases and 491 healthy controls who had no evidence of gallstones by ultrasound examination. Two common tagging single nucleotide polymorphism (SNP) rs3758650 and rs7932167, and four non-synonymous SNPs rs34362213, rs2740375, rs7108757 and rs2740379 were genotyped. The genetic effects were evaluated using the multivariate regression model.

RESULTS

The genotypes of these SNPs were all in Hardy-Weinberg equilibrium. Three non-synonymous SNPs (rs34362213, rs7108757 and rs2740379) were monomorphic. The single SNP analysis showed two SNPs (rs7932167 and rs2740375) were not associated with GSD and only SNP rs3758650 had the association of the presence of GSD with an odds ratio (OR) of 1.59 (adjusted P=0.013) for the AG genotype and 5.82 (adjusted P=0.007) for the AA genotype when compared with the reference GG genotype. The haplotype analysis of the three polymorphic SNPs showed GCA was significant for GSD (adjusted p=0.001) with an odds ratio (OR) of 1.41 when compared to other haplotypes.

CONCLUSIONS

The MUPCDH genetic polymorphism rs3758650 was considered a genetic marker to predict symptomatic GSD subjects. It may be of importance for GSD patients with the risk SNPs to be frequently checked because they may develop symptomatic GSD.

Multiple mucin genes polymorphisms are associated with gallstone disease in Chinese men

BACKGROUND

Gallstone is a complex disease caused by multiple environmental and genetic factors. One of these is mucin glycoproteins. This case-control study aimed to investigate the association between single nucleotide polymorphisms (SNPs) at the MUC1-4 genes and gallstone.

METHODS

The study included 475 cases and 941 controls. Eight tagging SNPs were selected: one at MUC1, two at MUC2, and five at MUC4. There was no available tagging SNP at MUC3. Genetic effects were initially evaluated by multivariate logistic regression. The combined effects from multiple genes were further evaluated, as well as the sex-specific effect. Permutation was used to correct for multiple testing.

RESULTS

The genotypes were all in Hardy-Weinberg equilibrium. SNP rs7396030 at MUC2 yielded a p value of 0.03. Further sex-specific analysis showed significance solely with male subjects (p=0.005). Similarly, SNP rs4072037 at MUC1 was only significant (p=0.035) in males. The permutation empirical p values were 0.005 for rs7396030 and 0.02 for rs4072037. For males, the combined genetic effect yielded an OR of 4.68 (p=0.0008).

CONCLUSIONS

The SNPs at MUC1 and MUC2 are significantly associated with gallstone in men but not in women. These genes can work jointly to further increase susceptibility to gallstone in a Chinese population.

The genetic background of gallstone formation: an update

Gallstone disease is one of the most prevalent gastrointestinal diseases with a substantial burden to health care systems that is expected to increase in ageing populations at risk. This review summarizes recent data on the genetic background of cholesterol gallstones and the role of biliary lipid composition. Three previously unknown non-synonymous mutations in the ABCB4 gene encoding the hepatobiliary phospholipid-flippase MDR3 are presented.

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

Background

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

Methodology/Principal Findings

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

Conclusions/Significance

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

Vitamin C supplement use may protect against gallstones: an observational study on a randomly selected population

BACKGROUND

Animal experiments have shown a protective effect of vitamin C on the formation of gallstones. Few data in humans suggest an association between reduced vitamin C intake and increased prevalence of gallstone disease. The aim of this study was to assess the possible association of regular vitamin C supplementation with gallstone prevalence.

METHODS

An observational, population-based study of 2129 subjects aged 18-65 years randomly selected from the general population in southern Germany was conducted. Abdominal ultrasound examination, completion of a standardized questionnaire, compilation of anthropometric data and blood tests were used. Data were collected in November and December 2002. Data analysis was conducted between December 2005 and January 2006.

RESULTS

Prevalence of gallstones in the study population was 7.8% (167/2129). Subjects reporting vitamin C supplementation showed a prevalence of 4.7% (11/232), whereas in subjects not reporting regular vitamin C supplementation, the prevalence was 8.2% (156/1897). Female gender, hereditary predisposition, increasing age and body-mass index (BMI) were associated with increased prevalence of gallstones. Logistic regression with backward elimination adjusted for these factors showed reduced gallstone prevalence for vitamin C supplementation (odds ratio, OR 0.34; 95% confidence interval, CI 0.14 to 0.81; P = 0.01), increased physical activity (OR 0.62; 95% CI, 0.42 to 0.94; P = 0.02), and higher total cholesterol (OR 0.65; 95% CI, 0.52 to 0.79; P < 0.001).

CONCLUSION

Regular vitamin C supplementation and, to a lesser extent, increased physical activity and total cholesterol levels are associated with a reduced prevalence of gallstones. Regular vitamin C supplementation might exert a protective effect on the development of gallstones.

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

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

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.

Genetics of biliary tract diseases: new insights into gallstone disease and biliary tract cancers

PURPOSE OF REVIEW

Chronic biliary diseases are due to complex interactions between environmental and genetic factors. Here we summarize the current knowledge of genetic factors that contribute to common biliary diseases, focusing on gallstones and carcinogenesis, and review the recent association studies.

RECENT FINDINGS

Since most studies were based on small sample sizes, replication of the findings is mandatory. Recently a large twin study confirmed a genetic predisposition to gallstones and a genome-wide association scan identified the hepatocanalicular cholesterol transporter ABCG8 as the common susceptibility factor for gallstone disease. Genetic studies in patients with cholangiocarcinoma indicate that genes controlling the metabolism and transport of xenobiotics or modulating chronic inflammation may determine individual susceptibility.

SUMMARY

Genetic studies have identified the first susceptibility factors for gallstones and biliary tract cancers, but most results have yet to be replicated. In the future, genome-wide studies in different populations are likely to identify the entire set of genes contributing to chronic biliary diseases. Since the disease phenotypes result from the manifestation of susceptibility factors under the influence of environmental triggers, the discovery of these genes will open avenues to control environmental challenges and lead to novel strategies for risk assessment ('gene signatures') and prevention.