A genome-wide association scan identifies the hepatic cholesterol transporter ABCG8 as a susceptibility factor for human gallstone disease

Association of Age-Related Macular Degeneration with Cholelithiasis

Purpose

Dysregulated lipid metabolism likely contributes to the pathogenesis of age-related macular degeneration (AMD). There is an overlap in risk factors between AMD and diseases of lipid metabolism, such as cholelithiasis, suggesting that an association between these diseases could provide insight into AMD pathogenesis. This study sought to determine if there is an association between cholelithiasis and AMD.

Design

A cohort study was conducted using patients in the Optum deidentified Clinformatics Data Mart database from January 1, 2000, to June 30, 2022.

Participants

Patients over the age of 55 with ≥2 years of data and no prior history of AMD were included. The exposed cohort included patients who had a history of cholelithiasis, cholecystitis, or cholecystectomy. The control cohort included patients with gastroesophageal reflux disease (GERD), matched for age ±3 years, sex, race, and year of index date.

Methods

Propensity scores were created using multivariable logistic regression and applied to inverse probability of treatment weighting (IPTW). Cox proportional hazard regression modeling with IPTW was used to compare progression to AMD in each cohort.

Main Outcome Measures

Progression to AMD for patients with cholelithiasis, cholecystitis, or a history of cholecystectomy.

Results

A total of 332 536 patients with cholelithiasis and 776 591 matched GERD controls were analyzed. After IPTW, the mean age (±standard deviation) was 66.6 ± 9.4 years in the cholelithiasis cohort and 67.5 (±10.3) years in the GERD cohort. Women comprised 58% of the cholelithiasis cohort and 57% of the GERD cohort. In the cholelithiasis cohort, 3511.7 (1.14%) were diagnosed with AMD, compared with 23 367.1 (2.92%) in the GERD cohort and corresponding to a significantly decreased hazard of AMD (adjusted hazard ratio [aHR] = 0.72, 95% confidence interval [CI]: 0.69-0.75, P < 0.0001). In the subanalysis, before IPTW weighting, AMD developed in 3809 of 275 897 (1.4%) patients with only cholelithiasis (aHR = 0.76, 95% CI: 0.73-0.80, P < 0.0001), 335 of 47 166 (0.71%) patients with cholecystitis (aHR = 0.54, 95% CI: 0.47-0.61, P < 0.0001), and 114 of 9473 (1.20%) patients who underwent cholecystectomy (aHR = 0.50, 95% CI: 0.41-0.63, P < 0.0001).

Conclusions

Cholelithiasis was associated with a 28% hazard reduction in AMD. More severe gallbladder disease conferred greater protection.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Long-term weight change patterns in American adulthood in relation to gallstones: evidence from NHANES

BACKGROUND

The aim of this study is to investigate the association between weight change patterns across adulthood and gallstones in the United States.

METHODS

The analysis is based on data from participants aged 40-70 years taken from the National Health and Nutrition Examination Survey 2017-2020. Weight status and weight change patterns were categorized based on body mass index at three time points. Weighted logistic regression was used to estimate the association of weight status at the three time points and weight change patterns over the three periods with gallstones.

RESULT

Compared with normal weight, obese status at age 25 was associated with an 86% increased risk of gallstones (OR 1.86, 95%CI 1.07-3.24). No significant associations were observed for underweight or overweight status. Weight status at baseline or 10 years before baseline showed no relation to gallstones. Notably, the stable obese pattern from age 25 to baseline was positively associated with gallstones (OR 1.94, 95%CI 1.03-3.65). A similar association was observed from age 25 to 10 years before baseline (OR 1.92, 95%CI 1.05-3.49). However, weight change patterns from 10 years before baseline to baseline were not significantly associated with gallstone risk. Subgroup analyses revealed stronger associations among females, diabetic individuals, and those with low physical activity.

CONCLUSION

The stable obese pattern starting from early adulthood is associated with an increased risk of gallstones in Americans. Preventing or controlling obesity in early adulthood may be helpful in the primary prevention of gallstones.

Examining the link between 179 lipid species and 7 diseases using genetic predictors

BACKGROUND

Genome-wide association studies of lipid species have identified several loci shared with various diseases, however, the relationship between lipid species and disease risk remains poorly understood. Here we investigated whether the plasma levels of lipid species are causally linked to disease risk.

METHODS

We built genetic predictors of 179 lipid species, measured in 7174 Finnish individuals, by utilising either 11 high-impact genomic loci or genome-wide polygenic scores (PGS). We assessed the impact of the lipid species on seven diseases by performing disease association across FinnGen (n = 500,348), UK Biobank (n = 420,531), and Generation Scotland (n = 20,032). We performed univariable Mendelian randomisation (MR) and multivariable MR (MVMR) analyses to examine whether lipid species impact disease risk independently of standard lipids.

FINDINGS

PGS explained >4% of the variance for 34 lipid species but variants outside the high-impact loci had only a marginal contribution. Variants within the high-impact loci showed association with all seven diseases. MVMR supported a causal role of ApoB in ischaemic heart disease after accounting for lipid species. Phosphatidylethanolamine-increasing LIPC variants seemed to lower age-related macular degeneration risk independently of HDL-cholesterol. MVMR suggested a protective effect of four lipid species containing arachidonic acid on cholelithiasis risk independently of Total Cholesterol.

INTERPRETATION

Our study demonstrates how genetic predictors of lipid species can be utilised to gain insights into disease risk. We report potential links between lipid species and age-related macular degeneration and cholelithiasis risk, which can be explored for their utility in disease risk prediction and therapy.

FUNDING

The funders had no role in the study design, data analyses, interpretation, or writing of this article.

Trans-ancestry genome-wide association meta-analysis of gallstone disease

Gallstone disease is a highly prevalent and costly gastrointestinal disease. Yet, genetic variation in susceptibility to gallstone disease and its implication in metabolic regulatory pathways remain to be explored. We report a trans-ancestry genome-wide association meta-analysis of gallstone disease including 88,063 cases and 1,490,087 controls in the UK Biobank, FinnGen, Biobank Japan, and Million Veteran Program. We identified 91 (37 novel) risk loci across the meta-analysis and found replication in statistically compelling signals in the All of Us Research Program. A polygenic risk score constructed from trans-ancestry lead variants was positively associated with liver chemistry and alpha-1-antitrypsin deficiency and negatively associated with total cholesterol and low-density lipoprotein levels among trans-ancestry and European ancestry groups in the Penn Medicine BioBank. Cross-trait colocalization analysis between risk loci and 44 liver, metabolic, renal, and inflammatory traits yielded 350 significant colocalizations as well as 97 significant colocalizations and 65 prioritized genes from expression quantitative trait loci from eight tissues. These findings broaden our understanding of the genetic architecture of gallstone disease.

Higher relative fat mass was associated with a higher prevalence of gallstones in US adults

AIMS

Our study aimed to investigate the association between the relative fat mass (RFM) and gallstones in adults.

METHODS

Information obtained from the National Health and Nutrition Examination Survey (NHANES) 2017-2023 was utilized to examine the correlation between RFM and gallstones based on weighted multivariable regression analysis, smoothing curve fitting, and threshold effect analyses. Using subgroup analysis and interaction tests, we investigated whether this association remained consistent across different populations. We evaluated the effectiveness of RFM and Body Mass Index (BMI) in detecting gallstones through receiver operating characteristic (ROC) analysis and by calculating the area under the curve (AUC).

RESULTS

The study involved 7618 participants in total. RFM mean was 30.74 ± 5.68. Based on the fully adjusted model, gallstone prevalence was positively associated with RFM (OR = 1.09; 95% CI: 1.07-1.11; p < 0.001), with a 9% increase for each unit increase in RFM. This correlation was particularly evident among individuals under the age of 40 and among females. Smoothing curve fitting revealed a nonlinear association between RFM and the occurrence of gallstones, with an inflection point identified at 19.8. Additionally, ROC analysis showed that RFM (AUC = 0.674) outperformed BMI (AUC = 0.634) as a predictor of gallstone formation.

CONCLUSIONS

Higher RFM was associated with higher gallstone prevalence. RFM may be a more useful tool for gallstone prediction than BMI in the general population. Gallstones may be alleviated or improved by RFM management at an early age.

CLINICAL TRIAL NUMBER

Not applicable.

A family with gallstone disease: defining inherited risk in the era of clinical genetic testing

Gallstones are among the most frequent hepatobiliary conditions. Although in most cases, they remain asymptomatic, they can cause complications and, in such cases, invasive treatments like endoscopic retrograde cholangiography (ERC) or cholecystectomy are required. Here, we present the results of genetic testing of a single family with a high incidence of symptomatic gallstones and cholestatic liver phenotypes. Gallstone disease was detected among seven family members spanning three generations, and DNA samples were available from five of them. Genotyping was performed using TaqMan assays for known, selected genetic risk factors for gallstones and cholestasis, as well as next generation sequencing (NGS) of three genes involved in hepatobiliary transport. In all genotyped patients, we detected at least one copy of the gallstone-predisposing p.D19H variant in the hepatobiliary sterol transporter ABCG5/8, and in three cases, this variant was found in the rare homozygous state. In addition, the patients were all homozygous carriers of two intronic variants (c.2211+16C >T and c.3508-16T>C) and two common polymorphisms (c.504C>T and c.711A>T) in the ABCB4 gene, as well as the ATP8B1 gene variant c.696T>C. All genotyped patients also carried the predisposing variants c.1331C>T and c.3084A>G of the hepatobiliary bile salt export pump ABCB11 in either heterozygous or homozygous form. Hence, we propose that these variants taken together may have contributed to the high frequency of gallstone disease in this family, although functional studies for some variants are still lacking. In this report, we present these findings and discuss the challenges associated with interpreting sequencing data.

Genetics of Gallstones

Gallstone disease (GSD) is a common gastrointestinal disorder affecting approximately 10-20% of the global adult population, characterized by the presence of gallstones, predominantly cholesterol-based, in the gallbladder and/or biliary ducts. While many patients remain asymptomatic, more than 20% develop clinical symptoms such as abdominal pain, nausea, vomiting, jaundice, and anorexia, potentially leading to severe complications like acute cholecystitis and biliary pancreatitis. GSD has a significant genetic predisposition, with the variable prevalence of the disease according to ethnicity being highest in American and European countries and lowest in Asian and African populations. Numerous genes encoding membrane transporters involved in bile metabolism are associated with GSD, including in particular members of ATP-binding cassette transporters and others, which affect bile lithogenicity and contribute to the development of gallstones. Specific mutations in these genes are linked to an increased risk of gallstone formation, especially in individuals with certain hereditary conditions such as hemolytic diseases, thyroid disorders, and hyperparathyroidism. Advances in genetic studies have identified new variants that influence the risk of cholelithiasis, although the exact mechanisms remain partially understood in many cases. This review briefly summarizes the genetic causes of cholelithiasis, highlighting various pathogenetic mechanisms. It presents the currently used treatments and the potential implications of widely applied genetic diagnostics.

The association of ABC proteins with multidrug resistance in cancer

Multidrug resistance (MDR) poses one of the primary challenges for cancer treatment, especially in cases of metastatic disease. Various mechanisms contribute to MDR, including the overexpression of ATP-binding cassette (ABC) proteins. In this context, we reviewed the literature to establish a correlation between the overexpression of ABC proteins and MDR in cancer, considering both in vitro and clinical studies. Initially, we presented an overview of the seven subfamilies of ABC proteins, along with the subcellular localization of each protein. Subsequently, we identified a panel of 20 ABC proteins (ABCA1-3, ABCA7, ABCB1-2, ABCB4-6, ABCC1-5, ABCC10-11, ABCE1, ABCF2, ABCG1, and ABCG2) associated with MDR. We also emphasize the significance of drug sequestration by certain ABC proteins into intracellular compartments. Among the anticancer drugs linked to MDR, 29 were definitively identified as substrates for at least one of the three most crucial ABC transporters: ABCB1, ABCC1, and ABCG2. We further discussed that the most commonly used drugs in standard regimens for mainly breast cancer, lung cancer, and acute lymphoblastic leukemia could be subject to MDR mediated by ABC transporters. Collectively, these insights will aid in conducting new studies aimed at a deeper understanding of the clinical MDR mediated by ABC proteins and in designing more effective pharmacological treatments to enhance the objective response rate in cancer patients.

Relationship between mucin gene polymorphisms and different types of gallbladder stones

BACKGROUND

Gallstones, a common surgical condition globally, affect around 20% of patients. The development of gallstones is linked to abnormal cholesterol and bilirubin metabolism, reduced gallbladder function, insulin resistance, biliary infections, and genetic factors. In addition to these factors, research has shown that mucins play a role in gallstone formation. This study aims to explore the connection between different types of gallstones and mucin gene polymorphisms.

METHODS

For this purpose, a total of 121 patients with gallbladder stones PNS and 107 patients with healthy controls PNS were enrolled in this case-control study. One SNPs (rs4072037) of MUC1 gene、 three SNPs (rs2856111、rs41532344、rs41349846) of MUC2 gene、four SNPs (rs712005、rs2246980、rs2258447、rs2259292) of MUC4 gene、seven SNPs (rs28415193、rs56047977、rs2037089、rs2075854、rs3829224、rs2672785、rs2735709) of MUC5 gene、eight SNPs (rs10902268、rs61869016、rs573849895、rs59257210、rs7396383、rs74644072、rs7481521、rs9704308) of MUC6 gene、five SNPs (rs10229731、rs73168398、rs4729655、rs55903219、rs74974199) of MUC17 gene. We amplified SNP sites by polymerase chain reaction (PCR) using specific primer sets followed by DNA sequencing.

RESULTS

The frequencies of MUC2 rs2856111 C/T genotype (OR = 3.81, 95%CI: 1.06-13.68) was higher than the control group. MUC17 rs10229731 A/C genotype (OR = 0.33, 95%CI: 0.12-0.95), rs73168398 G/A genotype (OR = 0.26, 95%CI: 0.07-0.98), MUC6 rs10902268 G/A genotype (OR = 0.40, 95%CI: 0.17-0.95) at lower frequencies than controls. The frequencies of MUC2 rs41532344 T allele (OR = 2.55, 95%CI: 1.06-6.13), MUC4 rs712005 G allele (OR = 2.51, 95%CI: 1.20-5.22), MUC5B rs2037089 C allele (OR = 3.54, 95%CI: 1.14-11.01) and MUC5AC rs28415193 G allele (OR = 1.77, 95%CI: 1.02-3.07) were higher than the control group. MUC6 rs10902268 A allele (OR = 0.004, 95%CI: 0.00-0.27), rs61869016 C allele (OR = 0.07, 95%CI: 0.01-0.63) at lower frequencies than controls.

CONCLUSIONS

Polymorphisms in the mucin gene were linked to the formation of gallbladder stones. The MUC4 rs712005 G allele, MUC5B rs2037089 C allele, MUC2 rs41532344 T allele and MUC5AC rs28415193 G allele were found to predispose individuals to the development of the disease. MUC6 rs10902268 A allele and rs61869016 C allele were identified as protective factors. Meanwhile, MUC2 rs2856111 CT genotype was found to predispose individuals to the development of the disease. MUC17 rs10229731 AC genotype, rs73168398 GA genotype and MUC6 rs10902268 GA genotype were identified as protective factors.

Hepatic Insulin Resistance Increases Risk of Gallstone Disease in Indigenous Americans in the Southwestern United States

INTRODUCTION

Animal models indicate that hepatic insulin resistance (IR) promotes cholesterol gallstone disease (GSD). We sought to determine whether hepatic and whole-body IR is associated with incident GSD.

METHODS

At baseline, 450 Southwestern Indigenous American adults without GSD were included. Participants had a 2-step hyperinsulinemic-euglycemic clamp with glucose tracer at submaximal and maximal insulin stimulation (240 and 2,400 pmol/m 2 /min) for whole-body IR (M-low and M-high) and hepatic glucose production (HGP) before and during submaximal insulin infusion (HGP-basal and HGP-insulin). Incident GSD was identified during follow-up visits conducted at ∼2-year intervals. The associations of HGP (basal, insulin, and % suppression), M-low, and M-high with risk of GSD were assessed by Cox regression models adjusted for age, sex, body fat (%), glucose, and insulin.

RESULTS

Sixty participants (13%) developed GSD (median follow-up: 11.6 years). Participants who developed GSD were of similar age and whole-body IR as those who did not ( P 's > 0.07) but were more likely to be female; have higher body fat, higher HGP-basal, and HGP-insulin; and lower % suppression of HGP ( P 's < 0.02). In separate adjusted models, higher HGP-insulin and lower % suppression of HGP were associated with increased risk for GSD (hazard ratio [HR] per SD: HR 1.38, 95% CI 1.12-1.69, P = 0.002; HR 1.41, 95% CI 1.16-1.72, P = 0.0007). HGP-basal, M-low, and M-high were not associated with GSD in adjusted models ( P 's > 0.22).

DISCUSSION

Resistance to insulin suppression of HGP increases risk for GSD. Hepatic IR is a link between GSD and other conditions of the metabolic syndrome.

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

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

The ABCG8 polymorphism increases the risk of gallbladder cancer in the general population and gallstones in obese patients from Poland

BACKGROUND

Gallstone disease (GD) is common but remains asymptomatic in most cases. However, gallstones can lead to complications like choledocholithiasis or gallbladder cancer. In this study, we analyse the common genetic risk factor for GD, the p.D19H variant in the sterol transporter ABCG8, in Polish patients with gallstones and gallbladder cancer.

METHODS

Three adult cohorts were prospectively recruited: 65 patients with gallbladder cancer, 170 obese individuals scheduled for bariatric surgery and 72 patients who underwent endoscopic retrograde cholangiopancreatography due to recurrent choledocholithiasis. The control cohort consisted of 172 gallstone-free adults. The ABCG8 p.D19H (rs11887534) polymorphism was genotyped using TaqMan assays.

RESULTS

The minor allele frequency (MAF) of the ABCG8 p.D19H polymorphism was significantly (p = .02) higher among cases with either gallstones or gallbladder cancer (MAF = 8.4%) as compared to controls (MAF = 4.0%). The highest frequency of the risk allele was detected in patients with gallbladder cancer (18.5%) and obese patients with GD (17.5%), followed by individuals with choledocholithiasis (13.9%). Notably, the p.19H variant was associated with an increased risk of developing gallbladder cancer (OR 2.76, 95% CI 1.16-6.54, p = .01) and an increased risk of GD in obese individuals scheduled for bariatric surgery (OR = 2.70, 95% CI 1.05-6.49, p = .03), but did not significantly affect the risk of choledocholithiasis.

CONCLUSIONS

The ABCG8 p.D19H common risk variant increases the risk of developing gallbladder cancer in Central Europeans and enhances the risk of gallstones in the obese. Carriers of the p.D19H variant might benefit from personalized preventive strategies, particularly regarding gallbladder cancer.

Significance of family history of cholelithiasis in a Pakistani population: A single center, descriptive cross-sectional study

Linkage studies have indicated a potential genetic predisposition to cholelithiasis. This study aims to determine the frequency of positive family history of gallstone disease in patients presenting with gallstones in a Pakistani population. A descriptive, cross-sectional study was conducted at the surgical department of the University of Lahore Teaching Hospital from June 30, 2023 to August 30, 2023. A total of 102 radiologically confirmed cholelithiasis patients were enrolled. Out of 102 participants, 75.5% (n = 77) were females, with a mean age at presentation of 42.1 ± 12.1 years. The study found that 32.4% (n = 33) of participants had a single family member with gallstones, 3.9% (n = 4) had 2 family members affected, and 1% (n = 1) had 3 family members affected. The attributable risk of genetics from our study was 37.2%. Additionally, there was no significant association between positive family history and earlier onset of disease. A significant percentage of Pakistani population may have gallstone disease due to genetic factors.

Genetics of Gallstone Disease and Their Clinical Significance: A Narrative Review

Gallstone (GS) disease is common and arises from a combination of genetic and environmental factors. Although genetic abnormalities specifically leading to cholesterol GSs are rare, there are clinically significant gene variants associated with cholesterol GSs. In contrast, most bilirubin GSs can be attributed to genetic defects. The pathogenesis of cholesterol and bilirubin GSs differs greatly. Cholesterol GSs are notably influenced by genetic variants within the ABC protein superfamily, including ABCG8, ABCG5, ABCB4, and ABCB11, as well as genes from the apolipoprotein family such as ApoB100 and ApoE (especially the E3/E3 and E3/E4 variants), and members of the MUC family. Conversely, bilirubin GSs are associated with genetic variants in highly expressed hepatic genes, notably UGT1A1, ABCC2 (MRP2), ABCC3 (MRP3), CFTR, and MUC, alongside genetic defects linked to hemolytic anemias and conditions impacting erythropoiesis. While genetic cases constitute a small portion of GS disease, recognizing genetic predisposition is essential for proper diagnosis, treatment, and genetic counseling.

Association between HNF4A rs1800961 polymorphisms and gallstones in a Taiwanese population

BACKGROUND AND AIM

A large genetic effect of a novel gallstone-associated genetic variant, the hepatocyte nuclear factor 4α (HNF4A) rs1800961 polymorphism, has been identified through recent genome-wide association studies. However, this effect has not been validated in Asian populations. We investigated the association between the rs1800961 variant and gallstones among a Taiwanese population.

METHODS

A total of 20 405 participants aged between 30 and 70 years voluntarily enrolled in the Taiwan Biobank. Self-report questionnaires, physical examinations, biochemical tests, and genotyping were used for analysis. The association of the HNF4A rs1800961 variant and other metabolic risks with gallstone disease was analyzed using multiple logistic regression models.

RESULTS

The minor T allele of HNF4A rs1800961 was associated with an increased risk of gallstone, and the association remained significant even after adjustment for other risk factors including age, body mass index (BMI), diabetes, hyperlipidemia, hypertension, and cigarette smoking (adjusted odds ratio [OR] = 1.90, 95% confidence interval [CI] = 1.31 to 2.75) in male participants. When further stratified by BMI and age, the lithogenic effect was the most significant in male participants with obesity (adjusted OR = 3.55, 95% CI = 1.92 to 6.56) and who were younger (adjusted OR = 2.45, 95% CI = 1.49 to 4.04).

CONCLUSION

The novel gallstone-associated HNF4A rs1800961 variant was associated with the risk of gallstone in the Taiwanese men. Screening for the rs1800961 polymorphism may be particularly useful in assessing the risk of gallstone formation in younger or obese men.

Association of ABCG5 and ABCG8 Transporters with Sitosterolemia

Sitosterolemia is a rare genetic lipid disorder, mainly characterized by the accumulation of dietary xenosterols in plasma and tissues. It is caused by inactivating mutations in either ABCG5 or ABCG8 subunits, a subfamily-G ATP-binding cassette (ABCG) transporters. ABCG5/G8 encodes a pair of ABC half transporters that form a heterodimer (G5G8). This heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the hepatobiliary and transintestinal secretion of cholesterol and dietary plant sterols to the surface of hepatocytes and enterocytes, promoting the secretion of cholesterol and xenosterols into the bile and the intestinal lumen. In this way, ABCG5/G8 function in the reverse cholesterol transport pathway and mediate the efflux of cholesterol and xenosterols to high-density lipoprotein and bile salt micelles, respectively. Here, we review the biological characteristics and function of ABCG5/G8, and how the mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumulation and premature atherosclerosis, among other features.

Causal effect of gallstone disease on the risk of coronary heart disease or acute myocardial infarction: a Mendelian randomization study

Gallstone disease (GSD) is thought to be associated with the risk of coronary heart disease (CHD) or acute myocardial infarction (AMI), which may be due to abnormal cholesterol metabolism. We used multiple Mendelian randomization (MR) methods based on publicly available genome-wide association study data to assess whether this association is genetically causal and to search for loci driving causality. Pooled data for GSD were obtained from FinnGen Biobank and Biobank Japan, while CHD and AMI were obtained as pooled data from the CARDIoGRAMplusC4D consortium. In this MR study, we found a significant negative causal effect of genetic susceptibility to GSD on AMI in the Finnish population, but no causal effect was found on CHD. This causal effect was not confounded by reverse causality and the same findings were obtained in the Japanese population. Furthermore, the negative causal effect of GSD on AMI risk may be driven by the rs4245791-regulated ABCG5/8 protein. In conclusion, the results of this MR study support a negative causal effect of GSD on AMI and suggest that rs4245791 is the causal driver locus of this effect, which provides new ideas and evidence for the prevention and etiologic study of AMI in patients with GSD.

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

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

Association of milk consumption with the incidence of cholelithiasis disease in the US adult population

BACKGROUND

Cholelithiasis is a common digestive system disease that imposes major burden on patients and society. Investigating the relationship between dietary factors and cholelithiasis risk can provide a basis for disease prevention. Previous studies on milk intake and cholelithiasis incidence have been limited.Therefore, the aim of our study was to assess the association between milk consumption and the incidence of cholelithiasis in males and females.

METHODS

We selected 14,722 adults (≥ 18 years old) from National Center for Health Statistics (NHANSE) 2017-2020, and collected general characteristics of patients in the database, such as age, gender, race and body mass index (BMI), as well as dietary information (milk consumption). The occurrence of cholelithiasis was used as the outcome event, and the group was divided into cholelithiasis and non-cholelithiasis groups according to the outcome event. We used logistic regression models in generalized linear model (GLM) functions, controlling for demographic, lifestyle, and dietary factors, to estimate the association between milk intake and the incidence of cholelithiasis in males and females.

RESULTS

A total of 14,722 adults were included. In the present study, the overall weighted prevalence of cholelithiasis was 10.96%, with 15.18% and 6.48% prevalence in females and males, respectively. Compared to infrequent milk intake, frequent milk intake (once a week or more) in females was associated with reduced cholelithiasis risk (OR 0.74, 95% CI 0.61-0.90). Daily milk intake in males was also related to lower cholelithiasis risk (OR 0.69-0.82). As adjusted variables increased in the models, predictive performance was improved (AUC 0.711 in females, 0.730 in males).

CONCLUSIONS

Appropriate milk intake may correlate with decreased cholelithiasis risk. Our study provides a basis for dietary interventions against gallstones, but prospective studies are needed to verify the results.

Gallstones, Cholecystectomy, and Kidney Cancer: Observational and Mendelian Randomization Results Based on Large Cohorts

BACKGROUND & AIMS

Gallstones (cholelithiasis) constitute a major health burden with high costs related to surgical removal of the gallbladder (cholecystectomy), generally indicated for symptomatic gallstones. The association between gallstones and cholecystectomy and kidney cancer is controversial. We comprehensively investigated this association, considering age at cholecystectomy and time from cholecystectomy to kidney cancer diagnosis, and assessed the causal effect of gallstones on kidney cancer risk by Mendelian randomization (MR).

METHODS

We compared the risk of kidney cancer in cholecystectomized and noncholecystectomized patients (16.6 million in total) from the Swedish nationwide cancer, census, patient, and death registries using hazard ratios (HRs). For 2-sample and multivariable MR, we used summary statistics based on 408,567 UK Biobank participants.

RESULTS

During a median follow-up of 13 years, 2627 of 627,870 cholecystectomized Swedish patients developed kidney cancer (HR, 1.17; 95% CI, 1.12-1.22). Kidney cancer risk was particularly increased in the first 6 months after cholecystectomy (HR, 3.79; 95% CI, 3.18-4.52) and in patients cholecystectomized before age 40 years (HR, 1.55; 95% CI, 1.39-1.72). MR results based on 18,417 patients with gallstones and 1788 patients with kidney cancer from the United Kingdom revealed a causal effect of gallstones on kidney cancer risk (9.6% risk increase per doubling in gallstone prevalence; 95% CI, 1.2%-18.8%).

CONCLUSIONS

Both observational and causal MR estimates based on large prospective cohorts support an increased risk of kidney cancer in patients with gallstones. Our findings provide solid evidence for the compelling need to diagnostically rule out kidney cancer before and during gallbladder removal, to prioritize kidney cancer screening in patients undergoing cholecystectomy in their 30s, and to investigate the underlying mechanisms linking gallstones and kidney cancer in future studies.

Gallstone Disease and Its Association With Nonalcoholic Fatty Liver Disease, All-Cause and Cause-Specific Mortality

BACKGROUND & AIMS

Presence of gallstone disease may influence outcomes in patients with nonalcoholic fatty liver disease (NAFLD). We studied the impact of gallstone disease on mortality in individuals with and without NAFLD.

METHODS

Prospective cohort study used the Third National Health and Nutrition Examination Survey (1988-1994) with mortality data through 2015. Gallstone disease was defined as ultrasonographic evidence of gallstones or absence of the gallbladder (prior cholecystectomy). NAFLD was defined using standardized ultrasonographic criteria.

RESULTS

Gallstone disease and cholecystectomy were independently associated with NAFLD (odds ratio [OR], 1.75; 95% confidence interval [CI], 1.43-2.15 for gallstone disease and OR, 2.77; 95% CI, 2.01-3.83 for cholecystectomy compared with no gallstone disease). During the median follow-up of 23 years, gallstone disease was associated with a higher risk of all-cause mortality (hazard ratio [HR], 1.19; 95% CI, 1.05-1.37) and cause-specific mortality. Gallstone disease was associated with a higher risk of all-cause mortality in non-NAFLD sub-cohort (HR, 1.42; 95% CI, 1.23-1.64) but not in NAFLD (HR, 1.03; 95% CI, 0.87-1.22). Gallstone disease was associated with a higher risk of cardiovascular-related (HR, 1.40; 95% CI, 1.10-1.78) and cancer-related (HR, 1.71; 95% CI, 1.18-2.48) mortality in non-NAFLD sub-cohort. Gallstone disease was associated with increased cardiovascular mortality (HR, 1.36; 95% CI, 1.05-1.77) in NAFLD.

CONCLUSIONS

Gallstone disease is an independent risk factor for NAFLD, but gallstone disease is not associated with all-cause mortality in individuals with NAFLD. Screening for gallstone disease in individuals at risk for developing NAFLD may help with risk stratification for all-cause mortality related to gallstone disease.

Proteome-Wide Mendelian Randomization Identifies Causal Links Between Blood Proteins and Acute Pancreatitis

BACKGROUND & AIMS

Acute pancreatitis (AP) is a complex disease and the leading cause of gastrointestinal disease-related hospital admissions. Few therapeutic options exist for AP prevention. Blood proteins with causal evidence may represent promising drug targets, but few have been causally linked with AP. Our objective was to identify blood proteins linked with AP by combining genome-wide association meta-analysis and proteome-wide Mendelian randomization (MR) studies.

METHODS

We performed a genome-wide association meta-analysis totalling 10,630 patients with AP and 844,679 controls and a series of inverse-variance weighted MR analyses using cis-acting variants on 4719 blood proteins from the deCODE study (n = 35,559) and 4979 blood proteins from the Fenland study (n = 10,708).

RESULTS

The meta-analysis identified genome-wide significant variants (P <5 × 10^-8) at 5 loci (ABCG5/8, TWIST2, SPINK1, PRSS2 and MORC4). The proteome-wide MR analyses identified 68 unique blood proteins that may causally be associated with AP, including 29 proteins validated in both data sets. Functional annotation of these proteins confirmed expression of many proteins in metabolic tissues responsible for digestion and energy metabolism, such as the esophagus, adipose tissue, and liver as well as acinar cells of the pancreas. Genetic colocalization and investigations into the druggable genome also identified potential drug targets for AP.

CONCLUSIONS

This large genome-wide association study meta-analysis for AP identified new variants linked with AP as well as several blood proteins that may be causally associated with AP. This study provides new information on the genetic architecture of this disease and identified pathways related to AP, which may be further explored as possible therapeutic targets for AP.

Research progress on the immune microenvironment of the gallbladder in patients with cholesterol gallstones

Cholesterol gallstones are very common in hepatobiliary surgery and have been studied to a certain extent by doctors worldwide for decades. However, the mechanism of cholesterol gallstone formation is not fully understood, so there is currently no completely effective drug for the treatment and prevention of cholesterol gallstones. The formation and development of cholesterol gallstones are caused by a variety of genetic and environmental factors, among which genetic susceptibility, intestinal microflora disorders, impaired gallbladder motility, and immune disorders are important in the pathogenesis of cholesterol gallstones. This review focuses on recent advances in these mechanisms. We also discuss some new targets that may be effective in the treatment and prevention of cholesterol gallstones, which may be hot areas in the future.

The human ATP-binding cassette (ABC) transporter superfamily

The ATP-binding cassette (ABC) transporter superfamily comprises membrane proteins that efflux various substrates across extra- and intracellular membranes. Mutations in ABC genes cause 21 human disorders or phenotypes with Mendelian inheritance, including cystic fibrosis, adrenoleukodystrophy, retinal degeneration, cholesterol, and bile transport defects. To provide tools to study the function of human ABC transporters we compiled data from multiple genomics databases. We analyzed ABC gene conservation within human populations and across vertebrates and surveyed phenotypes of ABC gene mutations in mice. Most mouse ABC gene disruption mutations have a phenotype that mimics human disease, indicating they are applicable models. Interestingly, several ABCA family genes, whose human function is unknown, have cholesterol level phenotypes in the mouse. Genome-wide association studies confirm and extend ABC traits and suggest several new functions to investigate. Whole-exome sequencing of tumors from diverse cancer types demonstrates that mutations in ABC genes are not common in cancer, but specific genes are overexpressed in select tumor types. Finally, an analysis of the frequency of loss-of-function mutations demonstrates that many human ABC genes are essential with a low level of variants, while others have a higher level of genetic diversity.

GWAS meta-analysis of intrahepatic cholestasis of pregnancy implicates multiple hepatic genes and regulatory elements

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder affecting 0.5-2% of pregnancies. The majority of cases present in the third trimester with pruritus, elevated serum bile acids and abnormal serum liver tests. ICP is associated with an increased risk of adverse outcomes, including spontaneous preterm birth and stillbirth. Whilst rare mutations affecting hepatobiliary transporters contribute to the aetiology of ICP, the role of common genetic variation in ICP has not been systematically characterised to date. Here, we perform genome-wide association studies (GWAS) and meta-analyses for ICP across three studies including 1138 cases and 153,642 controls. Eleven loci achieve genome-wide significance and have been further investigated and fine-mapped using functional genomics approaches. Our results pinpoint common sequence variation in liver-enriched genes and liver-specific cis-regulatory elements as contributing mechanisms to ICP susceptibility.

Common variant p.D19H of the hepatobiliary sterol transporter ABCG8 increases the risk of gallstones in children

INTRODUCTION

Gallstones are increasingly common in children. Genetic analyses of adult cohorts demonstrated that the sterol transporter ABCG8 p.D19H and Gilbert UGT1A1*28 variants enhance the odds of developing gallstones. The genetic background of common lithiasis in children remains unknown.

METHODS

Overall, 214 children with gallstone disease (1 month-17 years, 107 boys) were inclueded. The control cohorts comprised 214 children (age 6-17 years, 115 boys) and 172 adults (age 40-92 years, 70 men) without gallstones. The ABCG8 p.D19H and UGT1A1*28 polymorphisms as well as ABCB4 (c.504C>T rs1202283, c.711A>T rs2109505) and NPC1L1 variants (p.V1296V rs217434, c.-18C>A rs41279633) were genotyped using TaqMan assays. Serum concentrations of plant sterols and cholesterol precursors were measured by gas chromatography/mass spectrometry.

RESULTS

The ABCG8 risk allele was associated with an increased risk of stones (OR = 1.82, p = .03). Children carrying the p.19H allele presented with lower serum concentrations of surrogate markers of intestinal cholesterol absorption and decreased ratios of phytosterols to the cholesterol precursor desmosterol. Carriers of the common NPC1L1 rs217434 allele had an increased gallstone risk compared with stone-free adults (OR 1.90, p < .01). This variant also affected the ratio of phytosterols to cholesterol precursors (p = .03). Other tested variants were not associated with gallstone risk.

CONCLUSIONS

The p.D19H ABCG8 and, to a lesser extent, NPC1L1 rs217434 variants increase the risk of early-onset gallstone formation. These results point to the presence of a common lithogenic pathway in children and adults.

Genetic Analysis of ABCB4 Mutations and Variants Related to the Pathogenesis and Pathophysiology of Low Phospholipid-Associated Cholelithiasis

Clinical studies have revealed that the ABCB4 gene encodes the phospholipid transporter on the canalicular membrane of hepatocytes, and its mutations and variants are the genetic basis of low phospholipid-associated cholelithiasis (LPAC), a rare type of gallstone disease caused by a single-gene mutation or variation. The main features of LPAC include a reduction or deficiency of phospholipids in bile, symptomatic cholelithiasis at <40 years of age, intrahepatic sludge and microlithiasis, mild chronic cholestasis, a high cholesterol/phospholipid ratio in bile, and recurrence of biliary symptoms after cholecystectomy. Needle-like cholesterol crystals, putatively “anhydrous” cholesterol crystallization at low phospholipid concentrations in model and native bile, are characterized in ABCB4 knockout mice, a unique animal model for LPAC. Gallbladder bile with only trace amounts of phospholipids in these mice is supersaturated with cholesterol, with lipid composition plotting in the left two-phase zone of the ternary phase diagram, consistent with “anhydrous” cholesterol crystallization. In this review, we summarize the molecular biology and physiological functions of ABCB4 and comprehensively discuss the latest advances in the genetic analysis of ABCB4 mutations and variations and their roles in the pathogenesis and pathophysiology of LPAC in humans, based on the results from clinical studies and mouse experiments. To date, approximately 158 distinct LPAC-causing ABCB4 mutations and variants in humans have been reported in the literature, indicating that it is a monogenic risk factor for LPAC. The elucidation of the ABCB4 function in the liver, the identification of ABCB4 mutations and variants in LPAC patients, and the exploration of gene therapy for ABCB4 deficiency in animal models can help us to better understand the cellular, molecular, and genetic mechanisms underlying the onset of the disease, and will pave the way for early diagnosis and prevention of susceptible subjects and effective intervention for LPAC in patients.

Genome-wide analysis identifies gallstone-susceptibility loci including genes regulating gastrointestinal motility

BACKGROUND AND AIMS

Genome-wide association studies (GWAS) have identified several risk loci for gallstone disease. As with most polygenic traits, it is likely that many genetic determinants are undiscovered. The aim of this study was to identify genetic variants that represent new targets for gallstone research and treatment.

APPROACH AND RESULTS

We performed a GWAS of 28,627 gallstone cases and 348,373 controls in the UK Biobank, replicated findings in a Scottish cohort (1089 cases, 5228 controls), and conducted a GWA meta-analysis (43,639 cases, 506,798 controls) with the FinnGen cohort. We assessed pathway enrichment using gene-based then gene-set analysis and tissue expression of identified genes in Genotype-Tissue Expression project data. We constructed a polygenic risk score (PRS) and evaluated phenotypic traits associated with the score. Seventy-five risk loci were identified (p < 5 × 10-8 ), of which 46 were new. Pathway enrichment revealed associations with lipid homeostasis, glucuronidation, phospholipid metabolism, and gastrointestinal motility. Anoctamin 1 (ANO1) and transmembrane Protein 147 (TMEM147), both in novel, replicated loci, are expressed in the gallbladder and gastrointestinal tract. Both regulate gastrointestinal motility. The gallstone risk allele rs7599-A leads to suppression of hepatic TMEM147 expression, suggesting that the protein protects against gallstone formation. The highest decile of the PRS demonstrated a 6-fold increased odds of gallstones compared with the lowest decile. The PRS was strongly associated with increased body mass index, serum liver enzymes, and C-reactive protein concentrations, and decreased lipoprotein cholesterol concentrations.

CONCLUSIONS

This GWAS demonstrates the polygenic nature of gallstone risk and identifies 46 novel susceptibility loci. We implicate genes influencing gastrointestinal motility in the pathogenesis of gallstones.

Obesity, Adiposity, and Risk of Symptomatic Gallstone Disease According to Genetic Susceptibility

BACKGROUND & AIMS

Adiposity has been consistently associated with gallstone disease risk. We aimed to characterize associations of anthropometric measures (body mass index [BMI], recent weight change, long-term weight change, waist circumference, and waist-to-hip ratio) with symptomatic gallstone disease according to strata of gallstone disease polygenic risk score (PRS).

METHODS

We conducted analysis among 34,626 participants with available genome-wide genetic data within 3 large, prospective, U.S. cohorts-the Nurses' Health Study (NHS), Health Professionals Follow-Up Study, and NHS II. We characterized joint associations of PRS and anthropometric measures and tested for interactions on the relative and absolute risk scales.

RESULTS

Women in the highest BMI and PRS categories (BMI ≥30 kg/m² and PRS ≥1 SD above mean) had odds ratio for gallstone disease of 5.55 (95% confidence interval, 5.29 to 5.81) compared with those in the lowest BMI and PRS categories (BMI <25 kg/m² and PRS <1 SD below the mean). The corresponding odds ratio among men was 1.65 (95% confidence interval, 1.02 to 2.29). Associations for BMI did not vary within strata of PRS on the relative risk scale. On the absolute risk scale, the incidence rate difference between obese and normal-weight individuals was 1086 per 100,000 person-years within the highest PRS category, compared with 666 per 100,000 person-years in the lowest PRS category, with strong evidence for interaction with the ABCG8 locus.

CONCLUSIONS

While maintenance of a healthy body weight reduces gallstone disease risk among all individuals, risk reduction is higher among the subset with greater genetic susceptibility to gallstone disease.

Genome-wide association studies of metabolites in Finnish men identify disease-relevant loci

Few studies have explored the impact of rare variants (minor allele frequency < 1%) on highly heritable plasma metabolites identified in metabolomic screens. The Finnish population provides an ideal opportunity for such explorations, given the multiple bottlenecks and expansions that have shaped its history, and the enrichment for many otherwise rare alleles that has resulted. Here, we report genetic associations for 1391 plasma metabolites in 6136 men from the late-settlement region of Finland. We identify 303 novel association signals, more than one third at variants rare or enriched in Finns. Many of these signals identify genes not previously implicated in metabolite genome-wide association studies and suggest mechanisms for diseases and disease-related traits.

Association Study of SLCO1B3 and ABCC3 Genetic Variants in Gallstone Disease

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

Risk of gallstones based on ABCG8 rs11887534 single nucleotide polymorphism among Taiwanese men and women

BACKGROUND

Gallstones are abnormal masses caused by impaired metabolism of cholesterol, bilirubin, or bile salts in the gallbladder or biliary tract. ATP-binding cassette subfamily G member 8 (ABCG8) is a protein that regulates cholesterol efflux from the liver. Genome-wide association studies (GWAS) and meta-analyses of GWAS revealed the ABCG8 rs11887534 variant as the most common genetic determinant of gallstones in humans. These findings have not been extensively replicated in Taiwanese. Therefore, we appraised the relationship between gallstones and rs11887534 in a relatively large Taiwanese sample.

METHODS

We retrieved data collected through questionnaires, physical and biochemical tests from the Taiwan Biobank Bank (TWB). The study participants comprised 7388 men and 13,880 women who voluntarily enrolled in the Taiwan Biobank project between 2008 and 2019. Gallstones were self-reported.

RESULTS

The overall sample size was 21,268 comprising 938 gallstone patients and 20,330 non-gallstone individuals. Among the participants, 20,640 had the GG and 628 had the GC + CC genotype. At p-value < 0.05, the baseline genotypes and gallstone status between men and women were not significantly different. The risk of gallstones was higher in participants having the GC + CC compared to the GG genotype: odds ratio (OR); 95% confidence interval (CI) = 1.698; 1.240-2.325), but was lower in men compared to women (OR = 0.763; 95% CI = 0.638-0.913). Compared to men with the rs11887534 GG genotype, women with the GG and GC + CC genotypes had a higher risk of gallstone (OR; 95% CI = 1.304; 1.087-1.565 for GG and 2.291; 1.514-3.467 for GC + CC). The positive association between GC + CC and gallstones was retained after we restricted the analysis to the female participants (OR; 95% CI = 1.789 = 1.208-2.648). Hormone use was associated with an elevated risk of gallstones (OR; 95% CI = 1.359; 1.107-1.668). Relative to GG and no hormone use, we found a significantly high risk among hormone users with the GC + CC genotype (OR; 95% CI = 3.596; 1.495-8.650).

CONCLUSIONS

The rs11887534 GC + CC genotype was independently associated with a higher risk of gallstones. This risk was much higher among women, especially those who used hormones for various gynecological purposes.

Genetic factors associated with alterations in liver function test results in adult hospitalized patients treated with parenteral nutrition: A substudy of a clinical trial

OBJECTIVES

The presence of phytosterols in vegetable-based lipid emulsions has been associated with alterations in the results of liver function tests (LFTs). Serum levels of phytosterols are under strict genetic control. T-allele carriers in rs41360247 and C-allele carriers in rs4245791 of ABCG8genes are associated with higher phytosterolemia. The objective of this study was to determine the association between these single-nucleotide polymorphisms (SNPs) and LFT result alterations in an adult hospitalized population treated with parenteral nutrition.

METHODS

This is a substudy of a previous clinical trial (EudraCT 2014-003597-17). It included adult hospitalized patients who had received at least 7 d of parenteral nutrition with 0.8 g/kg/d of an olive/soybean lipid emulsion, randomized 1:1 to receive the same olive/soybean emulsion or 100% fish oil at a dose of 0.4 g/kg/d for 7 d. Plasma phytosterols and their fractions, rs41360247 and rs4245791 of ABCG8 genes, and LFT were determined. Analyses of variance were performed to determine the association between the SNPs and LFT values, as well as total phytosterol values and their fractions. Simple linear regressions were performed to analyze LFT variations and the different interactions of the SNPs studied with phytosterols and their fractions. Interactions of the synergic variable plasma phytosterol and its fractions with SNPs allow us to study the interaction of the SNPs with phytosterols with a regression.

RESULTS

We included 19 participants. In the multivariate model, total phytosterols, sitosterol, and lanosterol were positively associated with increases in γ-glutamyltransferase. Significant increases with stigmasterol were associated with the T allele of rs41360247, whereas campesterol showed only a tendency to increase that was not significant. Increases in alkaline phosphatase were associated with T-rs41360247 independent of the presence of phytosterols. With stigmasterol, C-allele carriers of rs4245791 showed a tendency to increase, and also for sitosterol and lanosterol, although independent of the SNP analyzed. Increases in alanine aminotransferase were positively associated with total phytosterol and sitostanol, whereas lanosterol and stigmasterol were associated with the presence of the T allele of rs41360247.

CONCLUSIONS

With both SNPs rs41360247 and rs4245791, the alteration in parameters of liver function in adult patients with short-term parenteral nutrition is conditional.

Obesity and Gallstones

BACKGROUND

The prevalence of obesity has been increasing globally and represents the main risk factor for the development of gallstone disease (GD).

SUMMARY

Excess body weight represents the main cause for the development of GD; nevertheless, there have been described multiple risk factors for its development, among them modifiable risk factors as diet, lifestyle, physical inactivity, and non-modifiable risk factors as ethnicity, female sex, advanced age, parity, and genetic mutations. Body mass index, abdominal perimeter, and waist-hip index have been used to determine the degree of adiposity of a person. Hence, central abdominal fat has been mostly associated with insulin resistance with the consequent increase in the hepatic cholesterol secretion; contributing as one of the multiple mechanisms associated with the development of gallstones. This disease has a low mortality; however, it has been associated with multiple diseases such as cardiovascular diseases, carotid atherosclerosis, metabolic associated fatty liver disease, and gallbladder cancer, probably because they share many of the risk factors.

KEY MESSAGES

GD continues to be considered a disease with a high medical burden, in which it is sought to intervene in modifiable risk factors to reduce its development.

GWAS of serum ALT and AST reveals an association of SLC30A10 Thr95Ile with hypermanganesemia symptoms

Understanding mechanisms of hepatocellular damage may lead to new treatments for liver disease, and genome-wide association studies (GWAS) of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) serum activities have proven useful for investigating liver biology. Here we report 100 loci associating with both enzymes, using GWAS across 411,048 subjects in the UK Biobank. The rare missense variant SLC30A10 Thr95Ile (rs188273166) associates with the largest elevation of both enzymes, and this association replicates in the DiscovEHR study. SLC30A10 excretes manganese from the liver to the bile duct, and rare homozygous loss of function causes the syndrome hypermanganesemia with dystonia-1 (HMNDYT1) which involves cirrhosis. Consistent with hematological symptoms of hypermanganesemia, SLC30A10 Thr95Ile carriers have increased hematocrit and risk of iron deficiency anemia. Carriers also have increased risk of extrahepatic bile duct cancer. These results suggest that genetic variation in SLC30A10 adversely affects more individuals than patients with diagnosed HMNDYT1.

Genetic variability in the absorption of dietary sterols affects the risk of coronary artery disease

AIMS

To explore whether variability in dietary cholesterol and phytosterol absorption impacts the risk of coronary artery disease (CAD) using as instruments sequence variants in the ABCG5/8 genes, key regulators of intestinal absorption of dietary sterols.

METHODS AND RESULTS

We examined the effects of ABCG5/8 variants on non-high-density lipoprotein (non-HDL) cholesterol (N up to 610 532) and phytosterol levels (N = 3039) and the risk of CAD in Iceland, Denmark, and the UK Biobank (105 490 cases and 844 025 controls). We used genetic scores for non-HDL cholesterol to determine whether ABCG5/8 variants confer greater risk of CAD than predicted by their effect on non-HDL cholesterol. We identified nine rare ABCG5/8 coding variants with substantial impact on non-HDL cholesterol. Carriers have elevated phytosterol levels and are at increased risk of CAD. Consistent with impact on ABCG5/8 transporter function in hepatocytes, eight rare ABCG5/8 variants associate with gallstones. A genetic score of ABCG5/8 variants predicting 1 mmol/L increase in non-HDL cholesterol associates with two-fold increase in CAD risk [odds ratio (OR) = 2.01, 95% confidence interval (CI) 1.75-2.31, P = 9.8 × 10-23] compared with a 54% increase in CAD risk (OR = 1.54, 95% CI 1.49-1.59, P = 1.1 × 10-154) associated with a score of other non-HDL cholesterol variants predicting the same increase in non-HDL cholesterol (P for difference in effects = 2.4 × 10-4).

CONCLUSIONS

Genetic variation in cholesterol absorption affects levels of circulating non-HDL cholesterol and risk of CAD. Our results indicate that both dietary cholesterol and phytosterols contribute directly to atherogenesis.

Cryo-EM structure of ABCG5/G8 in complex with modulating antibodies

The heterodimer of ATP-binding cassette transporter ABCG5 and ABCG8 mediates the excretion of sterols from liver and intestine, playing a critical role in cholesterol homeostasis. Here, we present the cryo-EM structure of ABCG5/G8 in complex with the Fab fragments from two monoclonal antibodies at 3.3Å resolution. The high-resolution structure reveals a unique dimer interface between the nucleotide-binding domains (NBD) of opposing transporters, consisting of an ordered network of salt bridges between the conserved NPXDFXXD motif and serving as a pivot point that may be important for the transport cycle. While mAb 11F4 increases the ATPase activity potentially by stabilization of the NBD dimer formation, mAb 2E10 inhibits ATP hydrolysis, likely by restricting the relative movement between the RecA and helical domain of ABCG8 NBD. Our study not only provides insights into the structural elements important for the transport cycle but also reveals novel epitopes for potential therapeutic interventions.

Analysis of Sequence Divergence in Mammalian ABCGs Predicts a Structural Network of Residues That Underlies Functional Divergence

The five members of the mammalian G subfamily of ATP-binding cassette transporters differ greatly in their substrate specificity. Four members of the subfamily are important in lipid transport and the wide substrate specificity of one of the members, ABCG2, is of significance due to its role in multidrug resistance. To explore the origin of substrate selectivity in members 1, 2, 4, 5 and 8 of this subfamily, we have analysed the differences in conservation between members in a multiple sequence alignment of ABCG sequences from mammals. Mapping sets of residues with similar patterns of conservation onto the resolved 3D structure of ABCG2 reveals possible explanations for differences in function, via a connected network of residues from the cytoplasmic to transmembrane domains. In ABCG2, this network of residues may confer extra conformational flexibility, enabling it to transport a wider array of substrates.

Biomarkers of cholestasis

Cholestasis is a major pathological manifestation, often resulting in detrimental liver conditions, which occurs in a variety of indications collectively termed cholestatic liver diseases. The frequent asymptomatic character and complexity of cholestasis, together with the lack of a straightforward biomarker, hampers early detection and treatment of the condition. The 'omics' era, however, has resulted in a plethora of cholestatic indicators, yet a single clinically applicable biomarker for a given cholestatic disease remains missing. The criteria to fulfil as an ideal biomarker as well as the challenging molecular pathways in cholestatic liver diseases advocate for a scenario in which multiple biomarkers, originating from different domains, will be assessed concomitantly. This review gives an overview of classical clinical and novel molecular biomarkers in cholestasis, focusing on their benefits and drawbacks.

Sitosterolemia: Twenty Years of Discovery of the Function of ABCG5ABCG8

Sitosterolemia is a lipid disorder characterized by the accumulation of dietary xenosterols in plasma and tissues caused by mutations in either ABCG5 or ABCG8. ABCG5 ABCG8 encodes a pair of ABC half transporters that form a heterodimer (G5G8), which then traffics to the surface of hepatocytes and enterocytes and promotes the secretion of cholesterol and xenosterols into the bile and the intestinal lumen. We review the literature from the initial description of the disease, the discovery of its genetic basis, current therapy, and what has been learned from animal, cellular, and molecular investigations of the transporter in the twenty years since its discovery. The genomic era has revealed that there are far more carriers of loss of function mutations and likely pathogenic variants of ABCG5 ABCG8 than previously thought. The impact of these variants on G5G8 structure and activity are largely unknown. We propose a classification system for ABCG5 ABCG8 mutants based on previously published systems for diseases caused by defects in ABC transporters. This system establishes a framework for the comprehensive analysis of disease-associated variants and their impact on G5G8 structure-function.

Advances in Risk Factors for Recurrence of Common Bile Duct Stones

Choledocholithiasis is a chronic common disease. The incidence of cholelithiasis is 5%-15%, of which 5%-30% are combined with Choledocholithiasis. Although endoscopic cholangiopancreatography (ERCP) + endoscopic sphincterotomy (EST) is the most common treatment procedure, which clearance rate is up to 95%, the incidence of recurrent choledocholithiasis was 4%-25%. The risk factors of recurrence after choledocholithiasis clearance are the focuses of current researches, which are caused by multiple factors. We first systematically summarize the risk factors of common bile duct stones (CBDS) recurrence into five aspects: first-episode stone related factors, congenital factors, biological factors, behavioral intervention factors, and the numbers of stone recurrence.

Evaluation of the chemopreventive potentials of ezetimibe and aspirin in a novel mouse model of gallbladder preneoplasia

Gallbladder stones (cholecystolithiasis) are the main risk factor for gallbladder cancer (GBC), a lethal biliary malignancy with poor survival rates worldwide. Gallbladder stones are thought to damage the gallbladder epithelium and trigger chronic inflammation. Preneoplastic lesions that arise in such an inflammatory microenvironment can eventually develop into invasive carcinoma, through mechanisms that are not fully understood. Here, we developed a novel gallbladder preneoplasia mouse model through the administration of two lithogenic diets (a low‐ or a high‐cholesterol diet) in wild‐type C57BL/6 mice over a period of 9 months. Additionally, we evaluated the chemopreventive potentials of the anti‐inflammatory drug aspirin and the cholesterol absorption inhibitor ezetimibe. Both lithogenic diets induced early formation of gallbladder stones, together with extensive inflammatory changes and widespread induction of metaplasia, an epithelial adaptation to tissue injury. Dysplastic lesions were presented only in mice fed with high‐cholesterol diet (62.5%) in late stages (9th month), and no invasive carcinoma was observed at any stage. The cholesterol absorption inhibitor ezetimibe inhibited gallbladder stone formation and completely prevented the onset of metaplasia and dysplasia in both lithogenic diets, whereas aspirin partially reduced metaplasia development only in the low‐cholesterol diet setting. This model recapitulates several of the structural and inflammatory findings observed in human cholecystolithiasic gallbladders, making it relevant for the study of gallbladder carcinogenesis. In addition, our results suggest that the use of cholesterol absorption inhibitors and anti‐inflammatory drugs can be evaluated as chemopreventive strategies to reduce the burden of GBC among high‐risk populations.

A Mitochondrial DNA Variant Elevates the Risk of Gallstone Disease by Altering Mitochondrial Function

BACKGROUND AND AIMS

Gallstone disease (cholelithiasis) is a cholesterol-related metabolic disorders with strong familial predisposition. Mitochondrial DNA (mtDNA) variants accumulated during human evolution are associated with some metabolic disorders related to modified mitochondrial function. The mechanistic links between mtDNA variants and gallstone formation need further exploration.

METHODS

In this study, we explored the possible associations of mtDNA variants with gallstone disease by comparing 104 probands and 300 controls in a Chinese population. We constructed corresponding cybrids using trans-mitochondrial technology to investigate the underlying mechanisms of these associations. Mitochondrial respiratory chain complex activity and function and cholesterol metabolism were assessed in the trans-mitochondrial cell models.

RESULTS

Here, we found a significant association of mtDNA 827A>G with an increased risk of familial gallstone disease in a Chinese population (odds ratio [OR]: 4.5, 95% confidence interval [CI]: 2.1-9.4, P=1.2×10-4). Compared with 827A cybrids (haplogroups B4a and B4c), 827G cybrids (haplogroups B4b and B4d) had impaired mitochondrial respiratory chain complex activity and function and activated JNK and AMPK signaling pathways. Additionally, the 827G cybrids showed disturbances in cholesterol transport and accelerated development of gallstones. Specifically, cholesterol transport through the transporter ABCG5/8 was increased via activation of the AMPK signaling pathway in 827G cybrids.

CONCLUSIONS

Our findings reveal that mtDNA 827A>G induces aberrant mitochondrial function and abnormal cholesterol transport, resulting in increased occurrence of gallstones. The results provide an important biological basis for the clinical diagnosis and prevention of gallstone disease in the future.

Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter

The heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the biliary and transintestinal secretion of cholesterol and dietary plant sterols. Missense mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumulation and premature atherosclerosis. A new molecular framework was recently established by a crystal structure of human ABCG5/G8 and reveals a network of polar and charged amino acids in the core of the transmembrane domains, namely, a polar relay. In this study, we utilize genetic variants to dissect the mechanistic role of this transmembrane polar relay in controlling ABCG5/G8 function. We demonstrated a sterol-coupled ATPase activity of ABCG5/G8 by cholesteryl hemisuccinate (CHS), a relatively water-soluble cholesterol memetic, and characterized CHS-coupled ATPase activity of three loss-of-function missense variants, R543S, E146Q, and A540F, which are respectively within, in contact with, and distant from the polar relay. The results established an in vitro phenotype of the loss-of-function and missense mutations of ABCG5/G8, showing significantly impaired ATPase activity and loss of energy sufficient to weaken the signal transmission from the transmembrane domains. Our data provide a biochemical evidence underlying the importance of the polar relay and its network in regulating the catalytic activity of ABCG5/G8 sterol transporter.

Structure and Function of Hepatobiliary ATP Binding Cassette Transporters

The liver is beyond any doubt the most important metabolic organ of the human body. This function requires an intensive crosstalk within liver cellular structures, but also with other organs. Membrane transport proteins are therefore of upmost importance as they represent the sensors and mediators that shuttle signals from outside to the inside of liver cells and/or vice versa. In this review, we summarize the known literature of liver transport proteins with a clear emphasis on functional and structural information on ATP binding cassette (ABC) transporters, which are expressed in the human liver. These primary active membrane transporters form one of the largest families of membrane proteins. In the liver, they play an essential role in for example bile formation or xenobiotic export. Our review provides a state of the art and comprehensive summary of the current knowledge of hepatobiliary ABC transporters. Clearly, our knowledge has improved with a breath-taking speed over the last few years and will expand further. Thus, this review will provide the status quo and will lay the foundation for new and exciting avenues in liver membrane transporter research.

Picky ABCG5/G8 and promiscuous ABCG2 - a tale of fatty diets and drug toxicity

Structural data on ABCG5/G8 and ABCG2 reveal a unique molecular architecture for subfamily G ATP‐binding cassette (ABCG) transporters and disclose putative substrate‐binding sites. ABCG5/G8 and ABCG2 appear to use several unique structural motifs to execute transport, including the triple helical bundles, the membrane‐embedded polar relay, the re‐entry helices, and a hydrophobic valve. Interestingly, ABCG2 shows extreme substrate promiscuity, whereas ABCG5/G8 transports only sterol molecules. ABCG2 structures suggest a large internal cavity, serving as a binding region for substrates and inhibitors, while mutational and pharmacological analyses support the notion of multiple binding sites. By contrast, ABCG5/G8 shows a collapsed cavity of insufficient size to hold substrates. Indeed, mutational analyses indicate a sterol‐binding site at the hydrophobic interface between the transporter and the lipid bilayer. In this review, we highlight key differences and similarities between ABCG2 and ABCG5/G8 structures. We further discuss the relevance of distinct and shared structural features in the context of their physiological functions. Finally, we elaborate on how ABCG2 and ABCG5/G8 could pave the way for studies on other ABCG transporters.

Clinical characteristics and genetic profiles of young and adult patients with cholestatic liver disease

BACKGROUND AND AIMS

heterozygous ABCB4, ABCB11 and ATP8B1 sequence variants were previously reported to be associated with low phospholipid-associated cholelithiasis, intrahepatic cholestasis of pregnancy, benign recurrent intrahepatic cholestasis and biliary lithiasis. The present study aimed to identify the presence of sequence variations in genes responsible for Mendelian liver disorders in patients with cholestatic liver disease.

METHODS

targeted massive parallel sequencing of a panel of genes involved in bile acid homeostasis was performed in 105 young and adult patients with cholestatic liver disease in our laboratory for molecular diagnosis. The effects of novel variants were evaluated using bioinformatics prediction tools and the Protter and Phyre2 software programs were used to create 2D, 3D topology protein modeling. Genotype-phenotype correlation was established according to molecular analysis and clinical records.

RESULTS

twenty novel heterozygous ABCB4 sequence variations, one heterozygous ABCB4 large intragenic deletion and only one novel missense variant in ABCB11 and ATP8B1 were identified. Interestingly, heterozygous and homozygous SLC4A2 missense variants were detected in patients with low phospholipid-associated cholelithiasis. Two patients harbored heterozygous GPBAR1 variants. Common variants such as homozygous ABCB11 p.Val444Ala and heterozygous ABCG8 p.Asp19His were also identified in 12 cases.

CONCLUSIONS

forty-eight variants were identified in five genes including ABCB4, ABCB11, ATP8B1, SLC4A2 and GPBAR1, twenty-five of which were novel. This study expands the phenotypic and mutational spectrum in genes involved in bile acid homeostasis and highlights the genetic and phenotypic heterogeneity in patients with inherited liver disorders.

Molecular Physiology of Bile Acid Signaling in Health, Disease, and Aging

Over the past two decades, bile acids (BAs) have become established as important signaling molecules that enable fine-tuned inter-tissue communication from the liver, their site of production, over the intestine, where they are modified by the gut microbiota, to virtually any organ, where they exert their pleiotropic physiological effects. The chemical variety of BAs, to a large extent determined by the gut microbiome, also allows for a complex fine-tuning of adaptive responses in our body. This review provides an overview of the mechanisms by which BA receptors coordinate several aspects of physiology and highlights new therapeutic strategies for diseases underlying pathological BA signaling.

Genetic architecture of complex traits and disease risk predictors

Genomic prediction of complex human traits (e.g., height, cognitive ability, bone density) and disease risks (e.g., breast cancer, diabetes, heart disease, atrial fibrillation) has advanced considerably in recent years. Using data from the UK Biobank, predictors have been constructed using penalized algorithms that favor sparsity: i.e., which use as few genetic variants as possible. We analyze the specific genetic variants (SNPs) utilized in these predictors, which can vary from dozens to as many as thirty thousand. We find that the fraction of SNPs in or near genic regions varies widely by phenotype. For the majority of disease conditions studied, a large amount of the variance is accounted for by SNPs outside of coding regions. The state of these SNPs cannot be determined from exome-sequencing data. This suggests that exome data alone will miss much of the heritability for these traits-i.e., existing PRS cannot be computed from exome data alone. We also study the fraction of SNPs and of variance that is in common between pairs of predictors. The DNA regions used in disease risk predictors so far constructed seem to be largely disjoint (with a few interesting exceptions), suggesting that individual genetic disease risks are largely uncorrelated. It seems possible in theory for an individual to be a low-risk outlier in all conditions simultaneously.