Polymorphisms at the apoB, apoA-I, and cholesteryl ester transfer protein gene loci in patients with gallbladder disease

Mendelian randomization rules out the causal relationship between serum lipids and cholecystitis

BACKGROUND

The relationship between serum lipids and cholecystitis is still under investigation. To examine the causal effect of serum lipids on cholecystitis using the Mendelian randomization method.

METHODS

We conducted univariable Mendelian randomization (MR) analyses using summary statistics from two independent genome-wide association studies (GWAS) on serum lipids (n = 132,908) and cholecystitis (n = 361,194). Mainly, the inverse-variance weighted (IVW) method was utilized to combine each SNP's causal estimation, and the MR-Egger was adopted as a complementary method, together with the weighted median. Cochrane's Q value was employed to appraise heterogeneity. The MR-Egger intercept and MR-PRESSO were used to detect the horizontal pleiotropy.

RESULTS

Our univariable results displayed a minor protective effect of serum low-density lipoprotein (LDL) cholesterol (OR [95% CI] = 0.9984483 [0.9984499, 0.9984468]; p = 0.008) on cholecystitis. No significant causal effect of total cholesterol (TC) (OR [95% CI] = 0.9994228 [0.9994222, 0.9994233]; p = 0.296), triglycerides (OR [95% CI] = 0.9990893 [0.9990882, 0.9990903]; p = 0.238) and high-density lipoprotein (HDL) cholesterol (OR [95% CI] = 0.9997020 [0.9997017, 0.9997023]; p = 0.565) was found on cholecystitis.

CONCLUSION

These findings suggest that LDL cholesterolhas a slight protective effect on cholecystitis, which can be easily affected by confounding factors. TC, triglycerides and HDL cholesterol don't have causal effect on cholecystitis. The protective effect of serum lipids on cholecystitis, though possible, remain less certain.

Association of apolipoprotein B XbaI (rs693) polymorphism and gallstone disease risk based on a comprehensive analysis

BACKGROUND

Our aim was to investigate the association between XbaI gene polymorphisms in the apolipoprotein B (APOB) gene and gallstone disease (GD) risk through a comparison of the allele and genotype distribution frequencies at this site using meta-analysis.

METHODS

A literature search was performed using PubMed and Wanfang through Jun 1, 2020. Odds ratios (ORs) and 95 % confidence intervals (CIs) were used to assess the strength of associations.

RESULTS

After a comprehensive search, 14 different articles that met the inclusion criteria were selected, with 1583 cases and 1794 controls. Individuals carrying the A-allele or AA genotype of the rs693 polymorphism were determined to possibly have an increased risk of GD. For example, there was a significant relationship between the rs693 polymorphism and increased GD risk in the whole group (OR: 1.40, 95 % CI: 1.05-1.87 in the allelic contrast model), the Asian population (OR: 1.58, 95 % CI: 1.48-2.84 in the heterozygote model), and the hospital-based source of the control (OR: 1.79, 95 % CI: 1.13-2.84 in the dominant model).

CONCLUSIONS

This study suggests that the APOB rs693 polymorphism is potentially associated with GD susceptibility, which might offer a detection marker for use in future large scale clinic research.

Hepatic expression of cholesterol regulating genes favour increased circulating low-density lipoprotein in HIV infected patients with gallstone disease: a preliminary study

BACKGROUND

HIV endemic populations are displaying higher incidence of metabolic disorders. HIV and the standard treatment are both associated with altered lipid and cholesterol metabolism, however gallstone disease (a cholesterol related disorder) in Sub-Saharan African populations is rarely investigated.

METHODS

This study sought to evaluate hepatic expression of key genes in cholesterol metabolism (LDLr, HMGCR, ABCA1) and transcriptional regulators of these genes (microRNA-148a, SREBP2) in HIV positive patients on antiretroviral therapy presenting with gallstones. Liver biopsies from HIV positive patients (cases: n = 5) and HIV negative patients (controls: n = 5) were analysed for miR-148a and mRNA expression using quantitative PCR.

RESULTS

Circulating total cholesterol was elevated in the HIV positive group with significantly elevated LDL-c levels(3.16 ± 0.64 mmol/L) relative to uninfected controls (2.10 ± 0.74 mmol/L; p = 0.04). A scavenging receptor for LDL-c, LDLr was significantly decreased (0.18-fold) in this group, possibly contributing to higher LDL-c levels. Transcriptional regulator of LDLr, SREBP2 was also significantly lower (0.13-fold) in HIV positive patients. Regulatory microRNA, miR-148a-3p, was reduced in HIV positive patients (0.39-fold) with a concomitant increase in target ABCA1 (1.5-fold), which regulates cholesterol efflux.

CONCLUSIONS

Collectively these results show that HIV patients on antiretroviral therapy display altered hepatic regulation of cholesterol metabolizing genes, reducing cholesterol scavenging, and increasing cholesterol efflux.

Association of Common Single Nucleotide Polymorphisms of Candidate Genes with Gallstone Disease: A Meta-Analysis

Numerous studies have investigated the relationship between various candidate gene polymorphisms and gallbladder stone disease (GSD) across ethnic populations; however, the results are often inconsistent. This meta-analysis aims to comprehensively evaluate the influence of common ABCG8 T400K, ABCG8 D19H, ABCG8 C54Y, ApoB100 EcoRI, ApoB100 XbaI, ApoE HhaI, CETP TaqI, CYP7A1 Bsa, LRPAP1 I/D and TNF-α A308G polymorphisms on the risk of gallbladder stone disease. 33 Full-text articles with 9250 cases and 12,029 healthy controls (total 21,279 subjects) were analyzed using the RevMan software (V5.1) and the Comprehensive Meta-analysis software (Version 2.0, BIOSTAT, Englewood, NJ) a Random-effects model was applied. Begg's funnel plots, Fail-safe number, Egger's regression intercept and Begg and Mazumdar rank correlation tests were performed for the potential publication bias and sensitivity analysis. The studies were also sub-grouped into European and non-European groups to find out role of ethnicity, if any, on GSD risk. Studies included in quantitative synthesis were ABCG8 T400K rs4148217 (cases/controls, n = 671/1416) (4 studies), ABCG8 D19H rs11887534 (n = 1633/2306) (8 studies), ABCG8 C54Y rs4148211 (n = 445/1194) (3 studies), ApoB100 EcoRI rs1042031 (n = 503/390) (4 studies), ApoB100 XbaI rs693 (n = 1214/1389) (9 studies), ApoE HhaI rs429358 (n = 1335/1482) (12 studies), CETP TaqI rs708272 (n = 1038/1025) (5 studies), CYP7A1 Bsa rs3808607 (n = 565/514) (3 studies), LRPAP1 I/D rs11267919 (n = 849/900) (3 studies), TNF-α A308G rs1800629 (n = 997/1413) (3 studies). The combined results displayed significant association of ABCG8 D19H (GC + CC) [OR with 95%CI = 2.2(1.7-2.8); p < 0.00001], ABCG8 Y54C (GA + GG) [OR with 95%CI = 0.65(0.5-0.9); p = 0.01]. APOB100 EcoRI (GG vs. AA) [OR with 95%CI = 0.51(0.3-0.9); p = 0.05], (GG vs. GA) [OR with 95%CI = 0.6(0.4-0.9); p = 0.04], (GA + AA) [OR with 95%CI = 0.6(0.4-0.9); p = 0.006]. APOB Xba I (X- vs. X+) [OR with 95%CI = 0.53(0.3-0.8); p = 0.006. APOE Hha I (E4/E4 vs. E3/E3) [OR with 95%CI = 3.5(1.1-14.9); p = 0.04] and LRPAP1 I/D (ID + II) [OR with 95%CI = 1.27(1.0-1.6); p = 0.03] with the GSD risk. It was found that ABCG D19H was significantly associated with GSD in both European and Non-European populations. While APOB XbaI and LRPAP1 I/D markers were associated with gallstone disease only in Non- European population. Additionally, APOE HhaI and APOB 100 ECoRI were found to be associated with GSD only in European population. The results of quantitative synthesis suggest that the ABCG8 D19H polymorphism was associated with the increased risk of GSD in both European and Non-European populations, APOE Hha I and LRPAP1 I/D polymorphisms were associated with the increased risk of GSD in European and Non-European population respectively. However, no association was found in ABCG8 T400K, CETP Taq1, CYP7A1 Bsa and TNF-A308G polymorphisms with Gallstone Disease.

Associations of cholesteryl ester transfer protein (CETP) gene variants with pituitary adenoma

AIM

The aim was to evaluate the association of CETP (rs5882 and rs708272) single nucleotide polymorphisms with the presence, invasiveness, hormonal activity and recurrence of pituitary adenoma (PA).

METHODS

The study group included 142 patients with PA and the control group, 753 healthy subjects. The genotyping of CETP (rs5882 and rs708272) was performed using a real-time PCR method.

RESULTS

After statistical analysis we found that CETP rs708272 genotype G/A under the over-dominant model was associated with the decreased odds of PA (OR=0.637; 95%CI: 0.443-0.917; P=0.015), active PA (OR=0.538; 95%CI: 0.335-0.865; P =0.01) and non-recurrent PA (OR=0.602; 95% CI: 0.402 - 0.902; P =0.014). When compared to controls, the rs708272 genotype G/A was less frequent in the active PA subgroup (37.5% vs 52.7%, P =0.009) and the non-recurrent PA subgroup (40.2% vs 52.7%, P=0.013), while the rs5882 genotype A/A was less frequent in the non-recurrent PA subgroup (37.5% vs 46.2%, P=0.015).

CONCLUSION

Our study showed that CETP rs708272 genotype G/A may be associated with a decreased risk of PA.

Association of Gallbladder Polyp and Stroke: A Nationwide, Population-Based Study

Gallbladder polyp (GP) and stroke share several metabolic disorders as risk factors. We assessed the association between GP and subsequent stroke risk. From 2000 to 2011, patients with GP aged >20 years were identified from the Longitudinal Health Insurance Database 2000. Of the 15,975 examined patients, 12,780 and 3195 were categorized into the non-GP and GP cohorts, respectively. The relative risks of stroke were estimated using the Cox proportional hazard model after adjusting for age, sex, and comorbidities. The overall incidence of stroke was higher in the GP cohort than in the non-GP cohort (6.66 vs 5.20/1000 person-yr), with an incidence rate ratio (IRR) of 1.28 (95% confidence interval [CI] = 1.15-1.42). The risk of stroke was 1.32-fold (95% CI = 1.06-1.63) in patients with GP compared with patients without GP after adjusting for age, sex, income level, urbanization level, occupation and comorbidities of gallstone, alcohol-related illness, diabetes, hyperlipidemia, hypertension, obesity, COPD, coronary heart disease, and asthma. Furthermore, the stroke risk was higher among elderly patients (with 1-yr intervals; adjusted HR [aHR] = 1.06, 95% CI = 1.05-1.07), the male sex (aHR = 1.62, 95% CI = 1.35-1.96), lower income level (aHR = 1.37, 95% CI = 1.02-1.85 for level I; aHR = 1.62, 95% CI = 1.25-2.10 for level II), living in second urbanized areas (aHR = 1.28, 95% CI = 1.00-1.63), alcohol-related illness (aHR = 1.56, 95% CI = 1.07-2.28), diabetes (aHR = 1.78, 95% CI = 1.41-2.24), and hypertension (aHR = 2.74, 95% CI = 2.19-3.42). GP is associated with stroke; however, GP may be less influential than other risk factors are, such as male sex, lower income level, alcohol-related illness, diabetes, and hypertension, on stroke development. Additional studies are required to clarify whether GP is a risk factor for or an epiphenomenon of stroke development.

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.

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.

Roles of ApoB-100 gene polymorphisms and the risks of gallstones and gallbladder cancer: a meta-analysis

Background

Gallstones (GS) is the major manifestation of gallbladder disease, and is the most common risk factor for gallbladder cancer (GBC). Previous studies investigating the association between ApoB-100 gene polymorphisms and the risks of GS and GBC have yielded conflicting results. Therefore, we performed a meta-analysis to clarify the effects of ApoB-100 gene polymorphisms on the risks of GS and GBC.

Methods

A computerized literature search was conducted to identify the relevant studies from PubMed and Embase. Fixed or random effects model was selected based on heterogeneity test. Publication bias was estimated using Begg’s funnel plots and Egger’s regression test.

Results

A total of 10, 3, and 3 studies were included in the analyses of the association between ApoB-100 XbaI, EcoRI, or insertion/deletion (ID) polymorphisms and the GS risks, respectively, while 3 studies were included in the analysis for the association between XbaI polymorphism and GBC risk. The combined results showed a significant association in Chinese (X+ vs. X−, OR = 2.37, 95%CI 1.52–3.70; X+X+/X+X- vs. X+X+, OR = 2.47, 95%CI 1.55–3.92), but not in Indians or Caucasians. Null association was observed between EcoRI or ID polymorphisms and GS risks. With regard to the association between XbaI polymorphism and GBC risk, a significant association was detected when GBC patients were compared with healthy persons and when GBC patients were compared with GS patients. A significant association was still detected when GBC patients (with GS) were compared with the GS patients (X+X+ vs. X-X−, OR = 0.33, 95%CI 0.12–0.90).

Conclusion

The results of this meta-analysis suggest that the ApoB-100 X+ allele might be associated with increased risk of GS in Chinese but not in other populations, while the ApoB-100 X+X+ genotype might be associated with reduced risk of GBC. Further studies with larger sample sizes are needed to confirm these results.

Epidemiology of gallbladder disease: cholelithiasis and cancer

Diseases of the gallbladder are common and costly. The best epidemiological screening method to accurately determine point prevalence of gallstone disease is ultrasonography. Many risk factors for cholesterol gallstone formation are not modifiable such as ethnic background, increasing age, female gender and family history or genetics. Conversely, the modifiable risks for cholesterol gallstones are obesity, rapid weight loss and a sedentary lifestyle. The rising epidemic of obesity and the metabolic syndrome predicts an escalation of cholesterol gallstone frequency. Risk factors for biliary sludge include pregnancy, drugs like ceftiaxone, octreotide and thiazide diuretics, and total parenteral nutrition or fasting. Diseases like cirrhosis, chronic hemolysis and ileal Crohn's disease are risk factors for black pigment stones. Gallstone disease in childhood, once considered rare, has become increasingly recognized with similar risk factors as those in adults, particularly obesity. Gallbladder cancer is uncommon in developed countries. In the U.S., it accounts for only ~ 5,000 cases per year. Elsewhere, high incidence rates occur in North and South American Indians. Other than ethnicity and female gender, additional risk factors for gallbladder cancer include cholelithiasis, advancing age, chronic inflammatory conditions affecting the gallbladder, congenital biliary abnormalities, and diagnostic confusion over gallbladder polyps.

Organic anion transporter 1B1 (SLCO1B1) polymorphism and gallstone formation: High incidence of Exon4 CA genotype in female patients in North India

AIM

  Gallstone disease is an important cause of abdominal morbidity Organic anion transport protein 1B1 (OATP1B1) (encoded by SLCO1B1) is a major transporter protein for bile salt uptake in enterohepatic circulation of bile salts. Disturbance in this pathway can decrease relative concentration of bile salts in gallbladder and may lead to formation of gallstones. We investigated role of SLCO1B1 polymorphisms [(Exon4 C > A (Pro155Thr; rs11045819) and Ex6 + 40T > C (Val174Ala; rs4149056)] in conferring interindividual susceptibility to gallstone disease.

METHODS

  A total of 173 healthy controls and 226 gallstone patients (USG positive) were recruited. Genotyping was done by using standard polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

  The observed control frequencies of both polymorphisms of SLCO1B1 gene [(Exon4 C > A (Pro155Thr; rs11045819) and Ex6 + 40T > C (Val174Ala; rs4149056)] were in agreement with Hardy-Weinberg equilibrium. The frequency CA genotype and A allele of Exon4 C > A polymorphism was higher in gallstones patients (12.4% and 6.2%) as compared to controls (5.2% and 2.6%) which was statistically significant [(P = 0.029; OR = 2.31; 95% CI = 1.1-5.0); (P = 0.034; OR = 2.22; 95% CI = 1.1-4.8)], respectively). However, distribution of genotypes and alleles of Ex6 + 40T > C polymorphism was almost similar between gallstone patients and controls. Haplotype analysis showed frequency of A,T haplotype consisting of was significantly higher in gallstone patients as compared to controls and was imposing risk for the disease (P = 0.036; OR = 2.34; 95% CI = 1.0-5.1).

CONCLUSION

  These results suggest that SLCO1B1 Exon4 C > A polymorphism confers increased risk for gallstone disease in North Indian population.

Cholesterol metabolism gene polymorphisms and the risk of biliary tract cancers and stones: a population-based case-control study in Shanghai, China

Biliary tract cancers are rare but fatal malignancies, with increasing incidence in Shanghai, China. Gallstones, the primary risk factor for biliary tract cancer, typically result from oversaturation of cholesterol in bile. We examined the association of five variants in three lipid metabolism-related genes (CETP, ABCG8 and LRPAP1) and biliary tract cancers and stones in a population-based case-control study in Shanghai, China. We included 439 biliary tract cancer cases (253 gallbladder, 133 extrahepatic bile duct and 53 ampulla of Vater cancer cases), 429 biliary stone cases and 447 population controls. Carriers of the CG genotype of ABCG8 rs11887534 had higher risk of biliary stones [odds ratio (OR) = 2.3, 95% confidence interval (CI) 0.82-6.5), gallbladder cancer (OR = 4.3, 95% CI 1.7-10.4) and bile duct cancer (OR = 1.94, 95% CI 0.64-5.91), compared with carriers of the GG genotype. Analysis stratified by gender showed both male and female carriers of CG rs11887534 had higher risks of biliary stones and gallbladder cancer, although the association was statistically significant only for women and gallbladder cancer (OR = 6.3, 95% CI 1.86-22.3). Carriers of the ABCG8 haplotype C-C (rs4148217-rs11887534) had a 4.16-fold (95% CI 1.71-10.1) risk of gallbladder cancer compared with those carrying the C-G haplotype. Our findings suggest that ABCG8 rs11887534, identified as a gallstone risk single-nucleotide polymorphism by whole genome scan, is also associated with an increased risk of biliary tract cancer.

Lith genes and genetic analysis of cholesterol gallstone formation

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

APOA1/A5 variants and haplotypes as a risk factor for obesity and better lipid profiles in a Brazilian Elderly Cohort

Genetic variations in the APOA1/C3/A4/A5 gene cluster have been studied and proposed to be the leading key for susceptibility to cardiovascular diseases and age-associated disorders. We aimed to investigate the associations of rs12721026 (APOA1) and rs1729408 (APOA5) polymorphisms and their haplotypes with some age-related diseases, as well as with lipids and proteins serum levels in a cohort from a Brazilian Elderly Longitudinal Study (EPIDOSO). Genotyping was performed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Statistical analyses were carried out using logistic regression analysis, Student's t-test, and linkage disequilibrium (LD) analysis. Polymorphic allele frequencies were 0.095 and 0.449 for rs12721026 and rs1729408, respectively. The C-allele of rs1729408 was associated with higher high-density lipoprotein (HDL) (P = 0.022) and glycated hemoglobin levels (P = 0.020). We also showed that rs12721026 and rs1729408 were in LD. The GC haplotype, which is composed of the G-allele of rs12721026 and the C-allele of rs1729408, was significantly associated with obesity (P = 0.028), with higher glycated hemoglobin (P = 0.006), and fasting glucose (P = 0.0003) compared to the TT haplotype, which includes the wild-type alleles of both polymorphisms. Moreover, we found an association between the TC haplotype and higher HDL levels (P = 0.0039). This is the first time that haplotypes involving these polymorphisms were evaluated. Our results showed that these polymorphisms were involved in the development of obesity and in alterations of lipids and proteins serum levels in a Brazilian population. The present findings might also clarify the role of these polymorphisms and their haplotypes in lipids and proteins metabolism.

Determinants of transhepatic cholesterol flux and their relevance for gallstone formation

Cholesterol available for bile secretion is controlled by a wide variety of proteins that mediate lipoprotein cholesterol uptake and cholesterol transport and metabolism in the liver. From a disease perspective, abnormalities in the transhepatic traffic of cholesterol from plasma into the bile may influence the risk of cholesterol gallstone formation. This review summarizes some recent progress in understanding the hepatic determinants of biliary cholesterol secretion and its potential pathogenic implications in cholesterol gallstone disease. This information together with new discoveries in this field may lead to improved risk evaluation, novel surrogate markers and earlier diagnosis, better preventive approaches and more effective pharmacological therapies for this prevalent human disease.

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.

Higher alleles of apolipoprotein B gene 3' VNTR: Risk for gallstone disease

Imbalance in cholesterol homeostasis may lead to gallstone disease. Apolipoprotein B is sole component of low-density lipoprotein and plays an important role in cholesterol metabolism. The present study was carried out to explore the association of APOB 3' VNTR, exon 26 XbaI and signal peptide insertion/ deletion polymorphisms with gallstone disease. 214 ultrasonographically proven gallstone patients and 322 healthy, age and sex matched controls were taken for the study. Genotyping was done using PCR followed by polyacrylamide gel electrophoresis for VNTR and insertion/ deletion analysis. For APOB XbaI polymorphism PCR product was digested with XbaI restriction enzyme, followed by agarose gel electrophoresis. All statistical analyses were done using SPSS v11.5. Higher repeat alleles of APOB 3' VNTR polymorphism were more frequent in gallstone patients than in controls. Alleles with more than 57 repeats were present only in patient group. Long (L) alleles with repeat higher than 49, were significantly higher (P=0.000; OR=3.705, 95% CI 2.577-5.326) and medium (M) alleles were lower (P=0.000; OR=0.406, 95% CI 0.304-0.542) in patients than in controls. To nullify the effect of gender, data was further stratified into male and female population. APOB 3' VNTR, L alleles were imposing risk and M alleles were protective in both male and female population. APOBXbaI and insertion/deletion polymorphisms were not found to be associated with the gallstone disease. Longer alleles of APOB 3' VNTR occur more frequently in gallstone patients, and may be an important risk factor for the development of gallstone disease. APOB XbaI and signal peptide insertion/deletion polymorphisms may not be contributing to the risk for gallstone disease.

Polymorphisms of genes in the lipid metabolism pathway and risk of biliary tract cancers and stones: a population-based case-control study in Shanghai, China

Biliary tract cancers, encompassing the gallbladder, extrahepatic bile duct, and ampulla of Vater, are uncommon yet highly fatal malignancies. Gallstones, the primary risk factor for biliary cancers, are linked with hyperlipidemia. We examined the associations of 12 single nucleotide polymorphisms of five genes in the lipid metabolism pathway with the risks of biliary cancers and stones in a population-based case-control study in Shanghai, China. We included 235 gallbladder, 125 extrahepatic bile duct, and 46 ampulla of Vater cancer cases, 880 biliary stone cases, and 779 population controls. Subjects completed an in-person interview and gave blood. Genotyping was conducted by TaqMan assay using DNA from buffy coats. The effects of APOE IVS1+69 (rs440446) and APOB IVS6+360C>T (rs520354) markers were limited to men. Men carrying the G allele of APOE IVS1+69 had a 1.7-fold risk of stones [95% confidence interval (95% CI), 1.2-2.4], a 1.8-fold risk of gallbladder cancer (95% CI, 1.0-3.3), a 3.7-fold risk of bile duct cancer (95% CI, 2.0-7.0), and a 4-fold risk of ampullary cancer (95% CI, 1.4-12.4). Male carriers of the T allele of APOB IVS6+360C>T had a 2-fold risk of bile duct cancer (95% CI, 1.2-3.4). The APOB T-T haplotype (APOB IVS6+360C>T, EX4+56C>T) was associated with a 1.6-fold risk of bile duct cancer (95% CI, 1.1-2.3). Male and female carriers of the T allele of LDLR IVS9-30C>T (rs1003723) had a 1.5-fold risk of bile duct cancer. Our findings suggest that gene variants in the lipid metabolism pathway contribute to the risk of biliary tract stones and cancers, particularly of the bile duct.

Haplotype analysis of signal peptide (insertion/deletion) and XbaI polymorphisms of the APOB gene in gallbladder cancer

PURPOSE

The incidence of gallbladder cancer (GBC) is usually paralleled by the prevalence of gallstone disease, and genes of cholesterol metabolism have been implicated in gallstone disease. The XbaI and insertion/deletion (ins/del) polymorphism of Apolipoprotein B (APOB) appears to influence cholesterol homoeostasis and possibly risk for gallstone disease. We examined the effect of these polymorphisms individually as well as their haplotypes on GBC and gallstone patients in North Indian population.

METHODS

The study comprises 123 consecutive cases of proven GBC, 172 cases of gallstone and 232 healthy subjects of similar age and sex. The genomic DNA was extracted from peripheral blood leucocytes and genotyping was performed using polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism.

RESULTS

In a case-control study, APOB XbaI and ins/del polymorphisms were not significantly associated with risk of GBC. Using the expectation maximization algorithm, four haplotypes were obtained, and haplotype X(+),D was found to be significantly higher in GBC patients without stone in comparison with healthy subjects [odds ratio (OR) 2.9, 95% confidence interval 1.2-6.6 P=0.012].

CONCLUSIONS

The X(+),D haplotype of APOB is associated with increased risk for development of GBC and the risk is not modified in the presence of gallstones.

Apolipoprotein B (APOB) Gene Polymorphism in Patients with Gallbladder Disease

Cholelithiasis is one of the most prevalent gastroenterological diseases, precipitated mainly by environmental factors. However, twin studies provided strong evidence for a role of genetic factors in the disease pathogenesis. An association between plasma lipoprotein levels and gallstone disease (GSD) was presented. Apolipoprotein B is an essential structural component of triglyceride-rich lipoprotein particles and plays an important role in the maintenance of cholesterol homeostasis in mammals. Various studies have shown a relationship between APOB gene polymorphisms and lipoprotein levels, but only few investigated a potential association between APOB polymorphism and GSD, giving contrary results. In the current study, an association between common polymorphisms in APOB gene (T2488T and E4154K) and cholesterol gallstone disease was examined. Two hundred and forty patients of Caucasian origin suffering from cholelithiasis, as well as 217 healthy individuals, were included in the study. Patients were genotyped for two single nucleotide polymorphisms (SNPs) in APOB gene: 2488C>T (XbaI), and 4154G>A (EcoRI) using PCR-RLFP method. The resulting analysis has shown that polymorphic loci in positions 2488 and 4154 in APOB gene are in full linkage in a Polish population and form only three haplotypes: 2488C-4154G, 2488T-4154G and 2488C-4154A. Frequency and distribution of 2488C>T alleles did not differ significantly between patients and controls. The 4154G allele has been found to be associated with GSD (p=0.001). A risk of gallstone formation was reduced in 4154AA homozygotes (OR=0.25, p=0.009) and heterozygous individuals (OR=0.63, p=0.03) as compared to 4154GG homozygotes. Additionally, 2488C-4154A haplotype was identified as a protective factor against GSD (p=0.04). Our results suggest that SNPs in APOB, potentially considered as one of lith genes as well as certain haplotypes, may be risk factors for GSD.

Gallstone Disease and Cholesterolosis in Monozygotic Twin Sisters

Gallstone disease and Cholesterolosis may be independent diseases or forms of the same disease, caused by impairment of cholesterol metabolism. Gallstone disease is characterized by formation of cholesterol concrements in the gallbladder cavity. Cholesterolosis is a hyperplastic cholecistosis, caused by cholesterol accumulation in the gallbladder wall with subsequent proliferation of gallbladder normal tissue elements. We describe monozygotic twin sisters, one of whom developed gallstone disease and the other developed cholesterolosis. Monozygosity was verified by a DNA fingerprinting method. Both had identical heterogeneity of plasma low density lipoprotein (LDL) subfractions, but associated with different functional conditions within the gallbladder. The different manifestations may be due to epigenetic, metabolic or environmental factors, since both had a common genetic basis.

Apolipoprotein AI-CIII-AIV gene cluster polymorphisms in relation to cholesterol gallstone

OBJECTIVE

To investigate the frequency of variants at Xmn I, Msp I sites of apolipoprotein (Apo), A I-CIII-AIV gene cluster, and its relation to cholesterol gallstones in Chinese patients.

METHODS

Restriction fragment length polymorphisms (RFLP) at Xmn I, Msp I sites of ApoAI-CIII-AIV gene cluster were studied using a polymerase chain reaction (PCR) in 161 patients with cholesterol gallstones and 94 healthy subjects from a Chinese population in Sichuan Province.

RESULTS

In both the cholesterol gallstone group and the healthy control group, X1 and M1 alleles were the major alleles and homozygous X1X1 and M1M1 genotypes were the most frequent. However, the frequency of X2 allele mutation in female patients of the cholesterol gallstones group was significantly higher than that in women in the healthy control group (P<0.05), but no difference was found in the frequency of M2 alleles mutation (P>0.05).

CONCLUSION

The data showed that Xmn I RFLP of ApoAI-CIII-AIV gene cluster is associated to some extent with cholesterol gallstones in female Chinese patients.

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

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

Genetic predisposition of cholesterol gallstone disease

Gallstone disease (GSD) is the result of the interaction between genetic and environmental factors and it is a major disease cause of surgery with high costs to health systems. Worldwide prevalence varies according to the ethnic population suggesting that high prevalence of GSD in certain ethnic groups is due to the presence of genetic factors implicated in different metabolic pathways. However, environmental factors play a determinant role in gene expression. This review summarizes the genes involved in biliary salt and cholesterol synthesis, lipids transport and the Lith genes. Future studies should be focused on the study of interactions between genetic and environmental factors which could be specific for each population.

Association of APOE-C1 gene cluster polymorphisms with gallstone disease

BACKGROUND

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

AIM

To find out the association of APOE HhaI and APOC1 HpaI polymorphisms with gallstone disease.

SUBJECTS

HhaI polymorphism of APOE and HpaI polymorphism of APOC1 were analysed in DNA samples of 214 gallstone patients and 322 age- and sex-matched healthy controls.

METHODS

For genotyping DNA samples of all study subjects were amplified using polymerase chain reaction, followed by restriction digestion. All statistical analyses were done using SPSS v11.5 and ARLEQUIN v2.0 softwares.

RESULT

APOC1 HpaI polymorphism was found to be significantly associated with gallstone disease. Frequency of H2H2 was significantly higher (P = 0.017) in patients than in controls and it was imposing very high risk (OR 9.416, 95% CI 1.125-78.786) for gallstone disease. When data were stratified in male and female, H2H2 was associated (P = 0.011) with disease in females only. Analysis at allele level revealed no association. APOE HhaI polymorphism and APOE-C1 haplotypes showed no association with gallstone disease.

CONCLUSION

APOC1 HpaI polymorphism is associated with gallstone disease and shows gender-specific differences. APOE HhaI polymorphism may not be associated with gallstone disease.

Genetics of hepatobiliary diseases

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

Gallstone disease. Pathogenesis of gallstones: A genetic perspective

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

Mechanisms of disease: the genetic epidemiology of gallbladder stones

Cholelithiasis is one of the most prevalent and most expensive gastroenterologic diseases. It belongs to the group of complex metabolic disorders that affect humans, and its critical pathogenic mechanisms are not well defined. As a result, primary or secondary prevention strategies are sparse, and the only effective treatment is cholecystectomy. Here we provide an update on the molecular pathogenesis of gallbladder stones, evidence supporting the hypothesis that genetic factors are key elements predisposing to gallstones, and progress in human genetic studies of cholesterol stones. Data from recent identical twin, family and linkage studies provide conclusive evidence for a strong genetic component to gallstone disease. Furthermore, epidemiologic studies in at-risk populations indicate that gallstone formation is caused by multiple environmental influences and common genetic factors and their interactions. By contrast, monogenic subtypes of cholelithiasis, such as ATP-binding-cassette transporter deficiencies, appear to be rare. The summary of human association studies illustrates that distinct common gene variants might contribute to gallstone formation in different ethnic groups. The characterization of lithogenic genes in knockout and transgenic mice and the identification of many gallstone-susceptibility loci in inbred mice provide the basis for studies of the corresponding genes in patients with gallstones. The transfer of findings from mouse genetics to the bedside might lead to new strategies for individual risk assessment and reveal novel molecular targets for prevention and medical therapies.

Role of candidate genes in the lipid responses to intensified treatment in Type 2 diabetes

OBJECTIVE

To identify genetic factors related to individual differences in lipid responses to intensified treatment in Type 2 diabetes.

DESIGN AND METHODS

After evaluation and intensification of their treatment, 107 Type 2 diabetes patients with poor metabolic control were re-evaluated after mean follow-up time of 15.6 (0, 4) (SE) months. The genes coding major lipid regulatory proteins and their relations to plasma lipid and lipoprotein changes were studied.

RESULTS

During the follow-up, levels of glycohemoglobin A1 (GHBA1) decreased (-1.7%), plasma HDL cholesterol (+0.05 mmol/l) and lipoprotein (a) [Lp(a)] (+4.2 mg/dl) increased, while triglyceride (TG) levels decreased (-1.2mmol/l) despite mean weight gain of 2.1 kg (p from <0.01 to <0.001). Of the gene markers studied, the lipoprotein lipase (LPL) Pvull (p=0.005) independently affected changes in HDL-cholesterol and was associated with the frequency of coronary heart disease (CHD). Lp(a) changes were associated with apolipoprotein B (ApoB) Glu4154Lys polymorphism (p=0.004).

CONCLUSIONS

These results suggest that genetic variations at LPL and ApoB loci are among the factors contributing to the variability in response to lipid parameters to therapy in Type 2 diabetes. LPL Pvull rare allele homozygote status seems to be beneficial with more favorable lipid changes and protection against CHD.

Reduced susceptibility to cholesterol gallstone formation in mice that do not produce apolipoprotein B48 in the intestine

It has been found that polymorphisms in the apolipoprotein (APO)-B gene are associated with cholesterol gallstones in humans. We hypothesized that APO-B plays a major regulatory role in the response of biliary cholesterol secretion to high dietary cholesterol and contributes to cholesterol gallstone formation. In the present study, we investigated whether lack of expression of intestinal Apob48 or Apob100 reduces susceptibility to cholesterol gallstones by decreasing intestinal absorption and biliary secretion of cholesterol in male mice homozygous for an "APO-B48 only" allele (Apob(48/48)), an "APO-B100 only" allele (Apob(100/100)), or a wild-type APO-B allele (Apob+/+) before and during an 8-week lithogenic diet. We found that cholesterol absorption was significantly decreased as a result of the APO-B48 deficiency in Apob(100/100) mice compared with wild-type and Apob(48/48) mice, regardless of whether chow or the lithogenic diet was administered. Consequently, hepatic cholesterol synthesis was significantly increased in Apob(100/100) mice compared with wild-type and Apob(48/48) mice. On chow, the APO-B100 deficiency in Apob(48/48) mice with reduced plasma levels of LDL/VLDL--but not HDL cholesterol--induced relative hyposecretion of biliary bile salts and phospholipids accompanying normal biliary cholesterol secretion. Compared with Apob(48/48) and wild-type mice, lithogenic diet-fed Apob(100/100) mice displayed significantly lower secretion rates of biliary cholesterol, but not phospholipid or bile salts, which results in significant decreases in prevalence rates, numbers, and sizes of gallstones. In conclusion, absence of expression of intestinal Apob48, but not Apob100, reduces biliary cholesterol secretion and cholelithogenesis, possibly by decreasing intestinal absorption and hepatic bioavailability.

Hepatic cholesterol transport from plasma into bile: implications for gallstone disease

PURPOSE OF REVIEW

The transhepatic traffic of cholesterol from plasma lipoproteins into the bile is critical for overall cholesterol homeostasis and its alterations may lead to cholesterol gallstone formation. This review summarizes recent progress in understanding the key hepatic cholesterol metabolism-related proteins and pathways that influence biliary secretion of cholesterol.

RECENT FINDINGS

In cholesterol-fed apolipoprotein E knockout mice, the availability of dietary cholesterol for biliary disposal is decreased and diet-induced gallstone formation is impaired. Scavenger receptor class B type I is relevant for cholesterol transport from plasma HDL into the bile in chow-fed mice, however its expression is not critical for biliary cholesterol secretion and gallstone formation in lithogenic diet-fed mice. Intrahepatic cholesterol transport proteins (e.g. sterol carrier protein-2, Niemann Pick type C-1 protein) also determine liver cholesterol available for biliary secretion in mice. Genetic manipulation of canalicular ATP-binding cassette transporter G5 and G8 expression in mice has established their essential role for biliary cholesterol secretion.

SUMMARY

Recent studies have underscored that different proteins involved in hepatic cholesterol transport regulate the availability of cholesterol for biliary secretion. These advances may provide new avenues for prevention and treatment of various disease conditions linked to abnormal cholesterol metabolism.

Genetic analysis of cholesterol gallstone formation: searching for Lith (gallstone) genes

The genetics of cholesterol cholelithiasis is complex because a number of interacting genes regulate biliary cholesterol homeostasis. Quantitative trait locus (QTL) analysis is a powerful method for identifying primary rate-limiting genetic defects and discriminating them from secondary downstream lithogenic effects caused by mutations of the primary genes. The subsequent positional cloning of such genes responsible for QTLs may lead to the discovery of pathophysiologic functions of Lith (gallstone) genes. In this review, we present a map of candidate genes for Lith genes that may determine gallstone susceptibility in mice. The physical-chemical, pathophysiologic, and genetic studies of Lith genes in bile, liver, gallbladder, and intestine will be crucial for elucidating the genetic mechanisms of cholesterol gallstone disease in mice and in humans. Because exceptionally close homology exists between mouse and human genomes, the orthologous human LITH genes can often be recognized after mouse genes are identified.

Relevance of hereditary defects in lipid transport proteins for the pathogenesis of cholesterol gallstone disease

In the formation of cholesterol gallstones, cholesterol hypersecretion into bile causing cholesterol supersaturation and crystallization appears to be the primary factor, with disturbed gallbladder and intestinal motility as secondary factors. Although intestinal uptake mechanisms have not yet been fully elucidated, the HDL receptor scavenger receptor B1 (SRB1) may be involved. Since HDL-cholesterol, both from the intestine and peripheral sources, is the preferred type of cholesterol for biliary secretion, increased HDL transport to the liver can also cause cholesterol hypersecretion in bile. In the hepatocyte, bile formation is regulated by several transmembrane proteins, all belonging to the ABC family. A change in the activity in one of these proteins can have a profound impact on biliary lipid secretion. The bile salt export pump (BSEP or ABCB11) regulates the excretion of bile salts into bile and mutations cause severe cholestasis. The second ABC transporter, ABCB4 (MDR3) regulates the secretion in bile of phosphatidylcholine (PC), while ABCG5/G8 is active in the excretion of cholesterol and sterols into bile. These transporters also facilitate transport of sterols back into the intestinal lumen. Mutations in either of these genes cause sitosterolaemia with increased absorption of plant sterols and cholesterol. Until now, evidence for a genetic background of human gallstone disease is mostly indirect and based on ethnic differences. Only two single gene defects are associated with gallstones. One is an ABCB4 mutation which causes a deficiency in biliary PC secretion and the other is a CYP7A1 mutation, the rate-limiting enzyme in the synthesis of bile salts from cholesterol in the liver. Recently, several common DNA polymorphisms in the ABCG8 gene were discovered that are associated with variations in plasma sterols, which could also influence biliary cholesterol secretion, but there is still a paucity of human studies.

Natural genetic variation as a tool in understanding the role of CETP in lipid levels and disease

Since the identification of cholesteryl ester transfer protein (CETP), its role in the modulation of HDL levels and cardiovascular disease has been debated. With the early detection of genetic variants followed by the finding of families deficient in CETP, genetic studies have played a large role in the attempts to understand the association of CETP with lipids and disease; however, results of these studies have often led to disparate conclusions. With the availability of a greater variety of genetic polymorphisms and larger studies in which disease has been examined, it is now possible to compare the breadth of CETP genetic studies and draw better conclusions. The most broadly studied polymorphism is TaqIB for which over 10,000 individuals have been genotyped and had HDL levels determined. When these studies are subjected to a meta-analysis, the B2B2 homozygotes are found to have higher HDL levels than B1B1 homozygotes (0.12 mmol/l, 95% CI = 0.11-0.13, P < 0.0001). A similar analysis of the I405V polymorphism yields 0.05 mmol/l higher HDL levels in 405VV homozygotes than in 405II homozygotes (95% CI = 0.03-0.07, P < 0.0001). The implications of these studies for cardiovascular disease will be addressed.

Association Between Serum Concentration of Apolipoproteins A-I and B with Gallbladder Disease

BACKGROUND

A total of 1,255 subjects attending a private health care facility in Mexico City were studied to evaluate the association of serum concentration of Apo A-I and Apo B with presence of gallbladder disease (gallstones or cholecystectomy).

METHODS

A cross-sectional study was carried out. All participants provided data on sociodemographic status and previous diagnoses of type 2 diabetes, hypertension, cardiovascular events, alcohol consumption, and smoking habits. Women additionally reported their obstetric-gynecologic history. Weight and height were measured; liver and biliary tract ultrasound assessed gallbladder disease. Plasma levels of total cholesterol, triglycerides, high-density lipoproteins (HDL) cholesterol, and apolipoproteins A-I (Apo A-I) and B (Apo B) were determined after a 12-h fasting period.

RESULTS

In multivariate models, Apo A-I > or = 120 mg/dL was positively associated with gallbladder disease with odds ratio (OR) = 1.64, 95% confidence interval (95% CI) = 1.03-2.62, whereas Apo B > or = 120 mg/dL showed an inverse association (OR = 0.71, 95% CI = 0.48-1.05). Ratio of Apo B/Apo A-I > or = 1 was inversely associated with risk of gallbladder disease (OR = 0.54, 95% CI = 0.37-0.80). All models were adjusted for age, gender, body mass index (BMI), previous diagnosis of type 2 diabetes, triglycerides, alcohol consumption, tobacco, and contraceptive use, as well as for total cholesterol in HDL-cholesterol and Apo A-I models.

CONCLUSIONS

Our results suggested the relationship between serum concentration of apolipoproteins and gallbladder disease. These findings support the hypothesis of increased biliary catabolism of cholesterol in subjects with gallbladder disease characterized by lower Apo B and higher Apo A-I serum concentrations.

Genetic background of cholesterol gallstone disease

Cholesterol gallstone formation is a multifactorial process involving a multitude of metabolic pathways. The primary pathogenic factor is hypersecretion of free cholesterol into bile. For people living in the Western Hemisphere, this is almost a normal condition, certainly in the elderly, which explains the very high incidence of gallstone disease. It is probably because the multifactorial background genes responsible for the high incidence have not yet been identified, despite the fact that genetic factors clearly play a role. Analysis of the many pathways involved in biliary cholesterol secretion reveals many potential candidates and considering the progress in unraveling the regulatory mechanisms of the responsible genes, identification of the primary gallstone genes will be successful in the near future.

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

Epidemiologic and family studies indicate that cholesterol gallstone formation is in part genetically determined. The major contribution to our current understanding of gallstone genes derives from animal studies, particularly cross-breeding experiments in inbred mouse strains that differ in genetic susceptibility to cholesterol gallstone formation (quantitative trait loci mapping). In this review we summarize how the combined use of genomic strategies and phenotypic studies in inbred mice has proven to be a powerful means of dissecting the complex pathophysiology of this common disease. We present a "gallstone map" for the mouse, consisting of all genetic loci that have been identified to confer gallstone susceptibility as well as putative candidate genes. Translation of the genetic loci and genes between mouse and human predicts chromosomal regions in the human genome that are likely to harbor gallstone genes. Both the number and the precise understanding of gallstone genes are expected to further increase with rapid progress of the genome projects, and multiple new targets for early diagnosis and prevention of gallstone disease should become possible.

Genetic determinants of variation in gallbladder disease in the Mexican-American population

Since there have not been any studies that quantify the influence of genetic factors on gallbladder disease (GBD) in humans using information from families, we utilized pedigree data to explore the genetic control of variation in liability to GBD. Using an extension of a variance components approach, we performed genetic analyses of GBD using information from 32 low-income Mexican-American families with two slightly different general models incorporating several sex-specific GBD risk factors. After evaluating the relative magnitudes of the covariate effects from these two models, we identified a parsimonious model including only significant predictors of GBD. According to this model, heritability for GBD was high (h2 = 0.44+/-0.18), after accounting for the significant effects of age, leptin in both sexes, total cholesterol, and HDL cholesterol in males only. We have shown quantitatively that variation in GBD is under strong genetic control. However, there are two major limitations to our findings: (1) since GBD was defined by a self-reported clinical history rather than an ultrasound examination, the prevalence of GBD could have been underestimated; and (2) since our design did not allow for shared environmental effects, our estimate of heritability may have been inflated.

Apolipoprotein B-100 gene Xba I polymorphism and cholesterol gallstone disease

The apolipoprotein (apo) B gene Xba I polymorphism is associated with alterations in serum lipids. Disturbances in serum lipids may be a risk factor for cholesterol gallstone disease. However, the relation between the Xba I polymorphism and cholesterol gallstones is unknown. This study was aimed at characterizing the polymorphism of the apo B gene Xba I in patients with gallbladder stones and the association of Xba I polymorphism with serum lipids. Xba I genotypes were measured by PCR-RFLP, and serum lipids assayed in 190 patients with gallbladder stones and 441 control subjects. The frequency of the X+/- genotype (20.63 vs. 7.94%) and X+ allele (10.79 vs. 3.97%) was significantly higher in the patient group than in the control group. Patients with the X+/- genotype had a significantly higher concentration of total cholesterol, low-density lipoprotein (LDL)-cholesterol, and apo B in serum than patients with the X-/- genotype. The X+ allele of the apo B gene is characterized by a higher cholesterol concentration and a higher LDL-cholesterol concentration in serum, and it may be a marker for increased risk of cholesterol gallstone disease.

Apolipoprotein E genotype and the risk of gallbladder disease in pregnancy

The E4 allele of apolipoprotein E (apoE4) has previously been associated with symptomatic gallstone disease. The aim of this study was to determine if apoE4 is associated with the development of gallbladder sludge and/or stones during pregnancy. We conducted a nested case-control study based on an ongoing cohort study of gallbladder disease in pregnancy. Women in this study receive gallbladder ultrasounds in each trimester of pregnancy. Cases (n = 52) were defined as women with incident gallbladder sludge or stones diagnosed at the third trimester ultrasound. Controls (n = 104) were defined as women without gallbladder sludge or stones on any of 3 study ultrasounds. ApoE genotyping was performed from stored white blood cell pellets. Data were analyzed by stratified analysis and multivariate logistic regression. Cases and controls were similar in baseline characteristics. Forty-two women had sludge, 6 had gallstones, and 4 had both sludge and stones. After adjusting for risk factors such as age, parity, and body mass index, the odds ratio (OR) for the association between heterozygosity or homozygosity for the apoE4 allele and incident gallbladder sludge or stones was 0.91 (95% confidence interval [CI], 0.41-2.02). Further adjustment for family medical history and serum lipid levels did not substantially change these results (OR, 0.73; 95% CI, 0.29-1.82). In conclusion, apoE4 appears to have little or no overall association with the development of new gallbladder sludge or stones in pregnancy. However, an effect could not be ruled out in certain subgroups, such as blacks or women who are homozygous for apoE4.

Effect of apolipoprotein E gene Hha I restricting fragment length polymorphism on serum lipids in cholecystolithiasis

AIM: To investigate the role of apolipoprotein E (apoE) polymorphism in the lithogenesis of gallstone and the hereditary pathogenesis of the disease.

METHODS: Polymerase chain reaction (PCR) was used to study apoE phenotypes and allele frequencies in patients with gallstones and control, and the fasting serum lipids of subjects were also measured by enzymatic methods.

RESULTS: The levels of triglyceride (TG) and very low density lipoprotein cholesterol (VLDL-C) were much higher in E_2/3 patients than that in E_2/3 control. E_3/3 patients were accompanied with remarkably low levels of high density lipoprotein cholesterol(HDL-C) and its subforms. But in E_3/4 patients there were only slight changes in levels of VLDL-C and low density lipoprotein cholesterol (LDL-C).

CONCLUSION: Different apoE phenotype patients with gallstones have different cheracteristics of dyslipidemia and the average level of serum lipids in patients with gallstones are higher than subjects without gallstones in the same apoE gene phenotype. ε2 allele is possibly one of the dangerous factors in the lithogenesis of chole-cystolithiasis.

Charge heterogeneity of LDL in asymptomatic hypercholesterolemic men is related to lipid parameters and variations in the ApoB and CIII genes

This study was carried out to examine the relationship between the charge on low density lipoproteins (LDLs) and lipid and clinical parameters in 104 asymptomatic dyslipidemic men and to identify biochemical and genetic factors that could contribute to the charge variability of LDL. LDL charge heterogeneity was evaluated by relative electrophoretic mobility (REM) on preformed 0.5% agarose gels and by chromatographic quantification of a minor electronegative LDL subfraction designated LDL(-). The mean REM value for LDL was 0.147+/-0.016 and the mean LDL(-) subfraction percentage was 5.6+/-2.8%. Both were positively correlated with common atherosclerotic risk factors, especially total cholesterol [for REM, r=0.27, P<0.005; for LDL(-), r=0.28, P=0.008] and LDL cholesterol [for REM, r=0.27, P=0.007; for LDL(-), r=0.26, P=0.01)] levels, and REM was positively correlated with triglycerides (r=0.27, P<0.005) and negatively with apoAI levels (r=-0.30, P<0.002). The variations in LDL charge were not due to oxidation, as measured by the lag phase and binding to the LDL receptor. The results of the 2 methods used to measure LDL charge were significantly correlated and had some identical characteristics (eg, association with LDL apoCIII content and plasma triglyceride levels in borderline and IIb dyslipidemic subjects); these methods reflect different specific features of LDL charge. The percentage of LDL(-) was correlated positively with the LDL sialic acid content (P<0.0001), whereas the REM was related to at least 2 distinct chromosomal loci. Multiple logistic analysis showed that individuals carrying minor alleles of BsrDI (P<0.05), apoCIII/SacI (P<0.01), as well as the frequent allele of XbaI (P<0.05) at the apoB and CIII gene loci had high REMs. This result suggests that LDL charge heterogeneity, which is positively correlated with the atherogenic lipid profile, is influenced by both genetic and biochemical factors.

Genetic epidemiology of cholesterol cholelithiasis among Chilean Hispanics, Amerindians, and Maoris

BACKGROUND & AIMS

The etiology of cholesterol gallstones is multifactorial, with interactions of genes and the environment. The hypothesis that aborigine cholesterol lithogenic genes are widely spread among Chileans, a population with a high prevalence of gallstones, was tested.

METHODS

Medical history and anthropometric measurements were obtained and abdominal ultrasonography was performed in 182 Mapuche Indians, 225 Maoris of Easter Island, and 1584 Hispanics. Blood groups, DNA, lipids, and glucose were analyzed. The Amerindian Admixture Index and mitochondrial DNA (mtDNA) assessed the ethnicity and degree of racial admixture.

RESULTS

Amerindian Admixture Index was 0.8 in Mapuches and 0.4 in Hispanics. All Mapuches, 88% of Hispanics, but none of Maoris had Amerindian mtDNA haplotypes. Age- and sex-adjusted global prevalence of gallstone disease was higher in Mapuches (35%) than in Hispanics (27%) and Maoris (21%). Compared with Hispanics, the youngest group of Mapuches had the greatest corrected risk of gallstones: odds ratios of 6.0 in women and 2.3 in men. In contrast, the gallstone risk in Maoris was lower compared with Hispanics: odds ratios of 0.6 for women and 0.5 for men.

CONCLUSIONS

Cholesterol lithogenic genes appear widely spread among Chilean Indians and Hispanics. They could determine the early formation of gallstones and explain the high prevalence of gallbladder diseases among some South American populations.

Changes of lipid metabolism in plasma, liver and bile during cholesterol gallstone formation in rabbit model

AIM: To find out the relationship between the disturbances of lipid metabolism and the formation of cholesterol gallstones by studying the changes of lipid metabolism in plasma, liver tissue and the bile.

METHODS: Male and female white Japanese rabbits were divided randomly into a control group (Con) and four experimental groups of 10 rabbits each fed with a diet containing 1.2% cholesterol for one, two, three and four weeks (1 wk, 2 wk, 3 wk and 4 wk group). The measurement of plasma triglyceride (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C) and its subfractions (HDL2-C, HDL3-C), very low and low density lipoprotein cholesterol (VLDL-C, LDL-C) was taken with standard enzymatic techniques. Apolipoprotein (apo) concentrations in plasma were measured by radial immunodiffusion assay for apoA1, apoB100, aopC¢ò and apoC II. Total cholesterol of liver was measured by the enzymatic procedure for each animal. Bile acids, mainly glycocholate (GCA) and glycodeoxycholate (GDCA) were detected by dual wavelength thin layer scanner.

RESULTS: In all the experimental groups fed with dietary cholesterol, cholesterol crystal was found in the gallbladder in 2/10 cases of the 1 wk group, 4/10 of the 2 wk group,6/10 of the 3 wk group and 7/10 of the 4 wk group respectively. The concentration of plasma total cholesterol (TC), triglyceride (TG), phospholipid (pl), VLDL-C, LDL-C, apoB100, apoC II, apoC III gradually increased (P < 0.05)with the prolonged feeding time of dietary cholesterol. High density lipoprotein cholesterol and its subfractions (HDL-C, HDL2-C, HDL3-C) showed a tendency to decrease, but without statistical significance (P > 0.05). ApoA1 was reduced with increased feeding time of dietary cholesterol (P < 0.05). The hepatic and biliary cholesterol increased 1-1.5 times as compared with the control group (t = 5.221 and 3.445, P < 0.05). The GCA gradually decreased beginning from the control group to the 4 wk group (P < 0.05).

CONCLUSION: Owing to the high cholesterol diet, the increased concentrations of plasma TC, TG, VLDL-C, LDL-C, hepatic TC and TG, apoB100, apoC II and apoC III possibly enhanced the secretion of biliary cholesterol into bile; the decreased plasma apoA1 level might reduce the secretion of antinucleating factor into bile. All those factors mentioned above probably contribute to the formation of cholesterol gallstones.