A novel heterozygous deletion in ABCB4 gene in a Chinese family with intrahepatic cholestasis of pregnancy, neonatal hyperbilirubinemia, and cholelithiasis: Case reports and literature review.

BACKGROUND: ABCB4 gene (OMIM *171060) variant is associated with a wide clinical spectrum of hepatobiliary diseases, including familial intrahepatic cholestasis of pregnancy (ICP), progressive familial intrahepatic cholestasis type 3 (PFIC3), and neonatal hyperbilirubinemia due to impaired protection of the bile duct. The majority of reported cases, however, were missense or nonsense variants, with few deletion variant findings in the Chinese population. METHOD: We performed whole genome sequencing and confirmed it with Sanger sequencing of the proband infant and his families. Clinical courses and laboratory results were documented and collected from the proband infant and his mother. We also reviewed other published cases related to genetic variants in ABCB4 in the Chinese population. RESULTS: A 26-year-old Chinese female (II.2) who had recurrent intrahepatic cholestasis of pregnancy and her 49-day-old son (III.4) who had hyperbilirubinemia, both presented with extremely elevated total bile acid, cholestatic dominant pattern liver function abnormalities. They were able to stay relatively stable with mild pruritus on ursodeoxycholic acid treatment. After ruling out other possibilities, genetic sequencing revealed a diagnosis of heterozygous deletion variant NM_018849.3:c.1452_1454del (NP_061337.1:p.Thr485del) in ABCB4, which was not reported before, in the symptomatic mother (II.2), index patient (III.4), and the symptomatic grandmother (I.2). This variant resulted in clinical spectrums of ICP, neonatal hyperbilirubinemia, and cholelithiasis in our pedigree. CONCLUSION: We reported a novel heterozygous deletion variant of the ABCB4 gene in a Chinese family, as well as a literature review of ABCB4-related disorders. We aim to facilitate healthcare professionals to better understand genetic factors as an uncommon cause of hepatobiliary diseases, as well as improve therapeutic strategies in challenging clinical situations such as pregnancy and neonatal care.

Obeticholic acid as a second-line treatment for low phospholipid-associated cholelithiasis syndrome.

BACKGROUND: Low phospholipid-associated cholelithiasis (LPAC) syndrome is a rare genetic cause of hepatolithiasis. A pathogenic variant of the ABCB4 gene is reported in half of all patients. Ursodeoxycholic acid (UDCA) is the only drug approved. However, in some patients, UDCA fails to prevent recurrence of symptoms and complications. Experimental evidence suggests that agonists of the farnesoid-X receptor (FXR), the main transcription factor regulating ABCB4, may be beneficial in this context. AIM: To study the efficacy of obeticholic acid (OCA) in patients with LPAC syndrome with an inadequate response or intolerance to UDCA. METHODS: This was a retrospective study of patients with LPAC syndrome treated with OCA, a selective FXR agonist. RESULTS: We reviewed the records of five OCA-treated patients (4 women; median age 29; ABCB4 variant in 4; no hepatic fibrosis). All patients received OCA at an initial dose of 5 mg daily and then 10 mg daily for a median period of 36 months in combination with UDCA (4 patients) or as a monotherapy (one patient). There were no adverse effects reported. Four patients had improvement in their symptoms - three completely and one partially. One patient had no clinical benefit. Abnormalities of blood liver tests persisted in one patient despite resolution of symptoms. Radiological signs of hepatolithiasis persisted in three of the four patients who responded clinically to OCA. CONCLUSIONS: These preliminary observations suggest that OCA may have the potential to effectively treat LPAC syndrome in patients with inadequate response or intolerance to UDCA. Larger studies are needed to confirm these data.

Causal association between serum total bilirubin and cholelithiasis: a bidirectional two-sample Mendelian randomization study.

Background: Observational studies about the association between serum total bilirubin and cholelithiasis are inconsistent. Hence, it is essential to reevaluate the association between serum total bilirubin and cholelithiasis and to verify whether such association is causal or not. Methods: We selected single-nucleotide polymorphisms (SNPs) that are strongly associated with exposure as instrumental variable and conducted a bidirectional two-sample Mendelian randomization (MR) study to explore the causal association between serum total bilirubin and cholelithiasis. We implemented the inverse-variance weighted approach as a primary analysis to combine the Wald ratio estimates. Four additional analyses, namely, MR-Egger regression, weighted median, weighted mode, and MR-pleiotropy residual sum and outlier (PRESSO), were utilized to investigate the causal association and the influence of potential pleiotropy. Results: A total of 116 SNPs were selected as valid instrumental variables to estimate the causal association of serum total bilirubin on cholelithiasis, and causal association between genetically determined serum total bilirubin and cholelithiasis was demonstrated [beta = 0.10; 95% confident interval (CI), 0.07 to 0.14; p < 0.001]. Likewise, the other methods, namely, the weighted median (beta = 0.12; 95% CI, 0.08 to 0.15; p < 0.001), MR-Egger (beta = 0.11; 95% CI, 0.08 to 0.15; p < 0.001), weighted mode (beta = 0.11; 95% CI, 0.08 to 0.15; p < 0.001), and MR-PRESSO approaches, further confirmed that this result (p = 0.054) indicates similar results. In addition, seven SNPs were selected as instrumental variable to estimate causal association of cholelithiasis on serum total bilirubin, and the result supported the causal effect of cholelithiasis to serum total bilirubin (beta = 0.12; 95% CI, 0.09 to 0.15; p < 0.001). At the same time, the other methods, namely, the weighted median (beta = 0.10; 95% CI, 0.06 to 0.13; p < 0.001), MR-Egger (beta = 0.12; 95% CI, 0.07 to 0.18; p = 0.007), weighted mode (beta = 0.09; 95% CI, 0.03 to 0.14, p = 0.019), and MR-PRESSO methods, further confirmed this result (p < 0.001). Conclusion: Our MR study revealed that the serum total bilirubin was causally associated with the risk of cholelithiasis, and the genetic predisposition to cholelithiasis was causally associated with the increased serum total bilirubin levels.

Causal associations between human gut microbiota and cholelithiasis: a mendelian randomization study.

Background: There was some evidence that gut microbiota was closely related to cholelithiasis, but the causal relationship between them remained unclear. In this study, we try to use Two-sample Mendelian randomization (MR) to clarify the potential causal relationship between gut microbiota and cholelithiasis. Methods: Summary Genome-Wide Association Studies (GWAS) statistical data for gut microbiota was obtained from MiBioGen, and the data of cholelithiasis was obtained from UK Biobank (UKB). Two-sample MR analyses were performed to assess causalities between gut microbiota and cholelithiasis mainly using the inverse-variance weighted (IVW) method. Sensitivity analyses were used to determine the robustness of the MR results. Reverse MR analyses were performed to examine the reverse causal association. Results: Our research results, based primarily on the IVW method, support the existence of a causal relationship between nine gut microbial taxa and cholelithiasis. We observed a positive association between Genus Butyrivibrio (p=0.032), Genus Lachnospiraceae_UCG_001 (p=0.015), Genus Ruminococcaceae_NK4A214_group (p=0.003), Genus Ruminococcaceae_UCG_011 (p=0.010) and cholelithiasis, while Order Rhodospirillales (p=0.031), Genus Actinomyces (p=0.010), Genus Phascolarctobacterium (p=0.036), Genus Rikenellaceae_RC9_gutgroup (p=0.023), Genus Ruminococcaceae_UCG_013 (p=0.022) may be associated with a reduced risk of cholelithiasis. We did not find a reverse causal relationship between cholelithiasis and 9 specific gut microbial taxa. Conclusions: This is the first mendelian randomization study to explore the causalities between specific gut microbiota taxa and cholelithiasis, which may provide new ideas and a theoretical basis for the prevention and treatment of cholelithiasis in the future.

Associations of cholecystectomy with the risk of colorectal cancer: a Mendelian randomization study.

BACKGROUND: Cholecystectomy is a standard surgery for patients suffering from gallbladder diseases, while the causal effects of cholecystectomy on colorectal cancer (CRC) and other complications are still unknown. METHODS: We obtained genetic variants associated with cholecystectomy at a genome-wide significant level ( P value <5 × 10 -8 ) as instrumental variables (IVs) and performed Mendelian randomization (MR) to identify the complications of cholecystectomy. Furthermore, the cholelithiasis was also treated as the exposure to compare its causal effects to those of cholecystectomy, and multivariable MR analysis was carried out to judge whether the effect of cholecystectomy was independent of cholelithiasis. The study was reported based on Strengthening the Reporting of Observational Studies in Epidemiology Using Mendelian Randomization guidelines. RESULTS: The selected IVs explained 1.76% variance of cholecystectomy. Our MR analysis suggested that cholecystectomy cannot elevate the risk of CRC (odds ratio [OR] =1.543, 95% confidence interval [CI]: 0.607-3.924). Also, it was not significant in either colon or rectum cancer. Intriguingly, cholecystectomy might decrease the risk of Crohn's disease (OR = 0.078, 95% CI: 0.016-0.368) and coronary heart disease (OR = 0.352, 95% CI: 0.164-0.756). However, it might increase the risk of irritable bowel syndrome (IBS) (OR = 7.573, 95% CI: 1.096-52.318). Cholelithiasis could increase the risk of CRC in the largest population (OR = 1.041, 95% CI: 1.010-1.073). The multivariable MR analysis suggested that genetic liability to cholelithiasis could increase the risk of CRC in the largest population (OR = 1.061, 95% CI: 1.002-1.125) after adjustment of cholecystectomy. CONCLUSIONS: The study indicated that cholecystectomy might not increase the risk of CRC, but such a conclusion needs further proving by clinical equivalence. Additionally, it might increase the risk of IBS, which should be paid attention to in clinical practice.

Causal effect of adiposity on the risk of 19 gastrointestinal diseases: a Mendelian randomization study.

OBJECTIVE: Although the association between adiposity and gastrointestinal (GI) diseases has been explored, the causal effects of adiposity on GI diseases are largely unknown. METHODS: Mendelian randomization was conducted using single-nucleotide polymorphisms associated with BMI and waist circumference (WC) as instrumental variables, and the causal associations of BMI or WC with GI conditions were estimated among >400,000 UK Biobank participants, >170,000 Finnish-descent participants, and numerous consortia participants of predominantly European ancestry. RESULTS: Genetically predicted BMI was robustly associated with increased risk of nonalcoholic fatty liver disease (NAFLD), cholecystitis, cholelithiasis, and primary biliary cholangitis. For the diseases, the odds ratio per 1-SD increase in genetically predicted BMI (4.77 kg/m2 ) ranged from 1.22 (95% CI: 1.12-1.34; p < 0.0001) for NAFLD to 1.65 (95% CI: 1.31-2.06; p < 0.0001) for cholecystitis. Genetically predicted WC was robustly associated with increased risk of NAFLD, alcoholic liver disease, cholecystitis, cholelithiasis, colon cancer, and gastric cancer. Alcoholic liver disease was consistently associated with WC even after adjusting for alcohol consumption in a multivariable Mendelian randomization analysis. The odds ratio per 1-SD increase in genetically predicted WC (12.52 cm) for such associations ranged from 1.41 (95% CI: 1.17-1.70; p = 0.0015) for gastric cancer to 1.74 (95% CI: 1.21-1.78; p < 0.0001) for cholelithiasis. CONCLUSIONS: High genetically predicted adiposity was causally associated with an increased risk of GI abnormalities, particularly of hepatobiliary organs (liver, biliary tract, and gallbladder) that are functionally related to fat metabolism.

Causal associations between modifiable risk factors and pancreatitis: A comprehensive Mendelian randomization study.

Background: The pathogenesis of pancreatitis involves diverse environmental risk factors, some of which have not yet been clearly elucidated. This study systematically investigated the causal effects of genetically predicted modifiable risk factors on pancreatitis using the Mendelian randomization (MR) approach. Methods: Genetic variants associated with 30 exposure factors were obtained from genome-wide association studies. Summary-level statistical data for acute pancreatitis (AP), chronic pancreatitis (CP), alcohol-induced AP (AAP) and alcohol-induced CP (ACP) were obtained from FinnGen consortia. Univariable and multivariable MR analyses were performed to identify causal risk factors for pancreatitis. Results: Genetic predisposition to smoking (OR = 1.314, P = 0.021), cholelithiasis (OR = 1.365, P = 1.307E-19) and inflammatory bowel disease (IBD) (OR = 1.063, P = 0.008) as well as higher triglycerides (OR = 1.189, P = 0.016), body mass index (BMI) (OR = 1.335, P = 3.077E-04), whole body fat mass (OR = 1.291, P = 0.004) and waist circumference (OR = 1.466, P = 0.011) were associated with increased risk of AP. The effect of obesity traits on AP was attenuated after correcting for cholelithiasis. Genetically-driven smoking (OR = 1.595, P = 0.005), alcohol consumption (OR = 3.142, P = 0.020), cholelithiasis (OR = 1.180, P = 0.001), autoimmune diseases (OR = 1.123, P = 0.008), IBD (OR = 1.066, P = 0.042), type 2 diabetes (OR = 1.121, P = 0.029), and higher serum calcium (OR = 1.933, P = 0.018), triglycerides (OR = 1.222, P = 0.021) and waist-to-hip ratio (OR = 1.632, P = 0.023) increased the risk of CP. Cholelithiasis, triglycerides and the waist-to-hip ratio remained significant predictors in the multivariable MR. Genetically predicted alcohol drinking was associated with increased risk of AAP (OR = 15.045, P = 0.001) and ACP (OR = 6.042, P = 0.014). After adjustment of alcohol drinking, genetic liability to IBD had a similar significant causal effect on AAP (OR = 1.137, P = 0.049), while testosterone (OR = 0.270, P = 0.002) a triglyceride (OR = 1.610, P = 0.001) and hip circumference (OR = 0.648, P = 0.040) were significantly associated with ACP. Genetically predicted higher education and household income levels could lower the risk of pancreatitis. Conclusions: This MR study provides evidence of complex causal associations between modifiable risk factors and pancreatitis. These findings provide new insights into potential therapeutic and prevention strategies.

Association of demographic and clinical factors with risk of acute pancreatitis: An exposure-wide Mendelian randomization study.

BACKGROUND: The incidence of acute pancreatitis (AP) is increasing over years, which brings enormous economy and health burden. However, the aetiologies of AP and underlying mechanisms are still unclear. Here, we performed a two-sample Mendelian randomization (MR) analysis to investigate the associations between all reported possible risk factors and AP using publicly available genome-wide association study summary statistics. METHODS: A series of quality control steps were taken in our analysis to select eligible instrumental single nucleotide polymorphisms which were strongly associated with exposures. To make the conclusions more robust and reliable, we utilized several analytical methods (inverse-variance weighting, MR-PRESSO method, weighted median, MR-Egger regression) that are based on different assumptions of two-sample MR analysis. The MR-Egger intercept test, radial regression and leave-one-out sensitivity analysis were performed to evaluate the horizontal pleiotropy, heterogeneities, and stability of these genetic variants on each exposure. A two-step MR method was applied to explore mediators in significant associations. RESULTS: Genetic predisposition to cholelithiasis (effect estimate: 17.30, 95% CI: 12.25-22.36, p = 1.95 E-11), body mass index (0.32, 95% CI: 0.13-0.51, p < 0.001), body fat percentage (0.57, 95% CI: 0.31-0.83, p = 1.31 E-05), trunk fat percentage (0.36, 95% CI: 0.14-0.59, p < 0.005), ever smoked (1.61, 95% CI: 0.45-2.77, p = 0.007), and limbs fat percentage (0.55, 95% CI: 0.41-0.69, p < 0.001) were associated with an increased risk of AP. In addition, whole-body fat-free mass (-0.32, 95% CI: -0.55 to -0.10, p = 0.004) was associated with a decrease risk of AP. CONCLUSION: Genetic predisposition to cholelithiasis, obesity and smoking could be causally associated with an increased risk of AP, and whole body fat-free mass could be associated with a decreased risk of AP.

Associations of genetically predicted fatty acid levels across the phenome: A mendelian randomisation study.

BACKGROUND: Fatty acids are important dietary factors that have been extensively studied for their implication in health and disease. Evidence from epidemiological studies and randomised controlled trials on their role in cardiovascular, inflammatory, and other diseases remains inconsistent. The objective of this study was to assess whether genetically predicted fatty acid concentrations affect the risk of disease across a wide variety of clinical health outcomes. METHODS AND FINDINGS: The UK Biobank (UKB) is a large study involving over 500,000 participants aged 40 to 69 years at recruitment from 2006 to 2010. We used summary-level data for 117,143 UKB samples (base dataset), to extract genetic associations of fatty acids, and individual-level data for 322,232 UKB participants (target dataset) to conduct our discovery analysis. We studied potentially causal relationships of circulating fatty acids with 845 clinical diagnoses, using mendelian randomisation (MR) approach, within a phenome-wide association study (PheWAS) framework. Regression models in PheWAS were adjusted for sex, age, and the first 10 genetic principal components. External summary statistics were used for replication. When several fatty acids were associated with a health outcome, multivariable MR and MR-Bayesian method averaging (MR-BMA) was applied to disentangle their causal role. Genetic predisposition to higher docosahexaenoic acid (DHA) was associated with cholelithiasis and cholecystitis (odds ratio per mmol/L: 0.76, 95% confidence interval: 0.66 to 0.87). This was supported in replication analysis (FinnGen study) and by the genetically predicted omega-3 fatty acids analyses. Genetically predicted linoleic acid (LA), omega-6, polyunsaturated fatty acids (PUFAs), and total fatty acids (total FAs) showed positive associations with cardiovascular outcomes with support from replication analysis. Finally, higher genetically predicted levels of DHA (0.83, 0.73 to 0.95) and omega-3 (0.83, 0.75 to 0.92) were found to have a protective effect on obesity, which was supported using body mass index (BMI) in the GIANT consortium as replication analysis. Multivariable MR analysis suggested a direct detrimental effect of LA (1.64, 1.07 to 2.50) and omega-6 fatty acids (1.81, 1.06 to 3.09) on coronary heart disease (CHD). MR-BMA prioritised LA and omega-6 fatty acids as the top risk factors for CHD. Although we present a range of sensitivity analyses to the address MR assumptions, horizontal pleiotropy may still bias the reported associations and further evaluation in clinical trials is needed. CONCLUSIONS: Our study suggests potentially protective effects of circulating DHA and omega-3 concentrations on cholelithiasis and cholecystitis and on obesity, highlighting the need to further assess them as prevention treatments in clinical trials. Moreover, our findings do not support the supplementation of unsaturated fatty acids for cardiovascular disease prevention.

Clinical, biological, radiological, and genetic study of LPAC syndrome in Tunisian patients.

BACKGROUND AND STUDY AIMS: Low phospholipid-associated cholelithiasis (LPAC) syndrome is a form of cholelithiasis associated with the ABCB4 gene mutation. The defects of the protein ABCB4 encoded by this gene promote the formation of biliary cholesterol microcalculations. ABCB4 screening is negative in a significant proportion of patients. PATIENTS AND METHODS: An analytical study of the epidemiological, clinical, biological, and radiological characteristics of 19 patients was conducted, followed by Sanger-type sequencing of the 27 exons encoding the ABCB4 gene. RESULTS: Our results showed a female predominance, symptomatic vesicular lithiasis predominance, and a high frequency of biliary complications in patients carrying an ABCB4 mutation. Normal ​​ liver enzyme values were found in 84.2% of the cases. Intrahepatic hyperechoic foci were present in 68.4%. Molecular analysis detected a pathogenic mutation of the ABCB4 gene in 31.57% of patients. The mutations found were a nonsense mutation and three missense mutations, including two new mutations. CONCLUSION: Our epidemiological, clinical, and genetic results concord with previous studies of LPAC syndrome. Two of the mutations we found have never been detected in patients with LPAC. The low percentage of ABCB4 gene mutations can be explained by the absence of studies of other genes involved in bile acid homeostasis besides the ABCB4 gene and by the inclusion criteria used in this study.

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.

Identification of blood metabolites linked to the risk of cholelithiasis: a comprehensive Mendelian randomization study.

BACKGROUND AND AIMS: Observational and Mendelian randomization (MR) studies have identified several modifiable risk factors of cholelithiasis. However, there is limited evidence about the causal effect of blood metabolites on the cholelithiasis risk. METHODS: To have a comprehensive understanding to causal relations between blood metabolites and cholelithiasis, for the primary discovery, we applied two MR methods to explore the associations between 249 circulating metabolites and cholelithiasis. For secondary validations, we replicated the examinations using another metabolic dataset with 123 metabolites. The summary statistics of cholelithiasis were retrieved from FinnGen Consortium Release 5 and UK Biobank. Inverse-variance weighted, weight median and MR-egger methods were used for calculating causal estimates. Furthermore, Bayesian model averaging MR (MR-BMA) method was employed to detect the dominant causal metabolic traits with adjustment for pleiotropy effects. RESULTS: In the primary analysis, sphingomyelin showed consistent protective causal associations with cholelithiasis; while plasma cholesterol-associated traits showed generally inverse correlation with cholelithiasis risk. Notably, large numbers of traits within the (un)saturated fatty acid category demonstrated significant causal effects. Secondary analyses demonstrated similar results, with traits related to the levels of bisallylic groups in fatty acids showing protective effects. Lastly, MR-BMA analyses discovered that the degree of unsaturation plays a predominant role in reducing the risk of cholelithiasis. CONCLUSION: Our MR study provides a complete atlas of associations between plasma metabolites on cholelithiasis risk. It highlighted that genetically predicted sphingomyelin and degree of unsaturation of fatty acid were causally associated with the reduced risk of cholelithiasis.

Insights into modifiable risk factors of cholelithiasis: A Mendelian randomization study.

BACKGROUND AND AIMS: The risk factors of cholelithiasis have not been clearly identified, especially for total cholesterol. Here, we try to identify these causal risk factors. APPROACH AND RESULTS: We obtained genetic variants associated with the exposures at the genome-wide significance (p < 5 × 10-8 ) level from corresponding genome-wide association studies. Summary-level statistical data for cholelithiasis were obtained from FinnGen and UK Biobank (UKB) consortia. Both univariable and multivariable Mendelian randomization (MR) analyses were conducted to identify causal risk factors of cholelithiasis. Results from FinnGen and UKB were combined using the fixed-effect model. In FinnGen, the odds of cholelithiasis increased per 1-SD increase of body mass index (BMI) (OR = 1.631, p = 2.16 × 10-7 ), together with body fat percentage (OR = 2.108, p = 4.56 × 10-3 ) and fasting insulin (OR = 2.340, p = 9.09 × 10-3 ). The odds of cholelithiasis would also increase with lowering of total cholesterol (OR = 0.789, p = 8.34 × 10-5 ) and low-density lipoprotein-cholesterol (LDL-C) (OR = 0.792, p = 2.45 × 10-4 ). However, LDL-C was not significant in multivariable MR. In UKB, the results of BMI, body fat percentage, total cholesterol, and LDL-C were replicated. In meta-analysis, the liability to type 2 diabetes mellitus and smoking could also increase the risk of cholelithiasis. Moreover, there were no associations with other predominant risk factors. CONCLUSIONS: Our MR study corroborated the risk factors of cholelithiasis from previous MR studies. Furthermore, lower total cholesterol level could be an independent risk factor.

The wide phenotypic and genetic spectrum of ABCB4 gene deficiency: A case series.

BACKGROUND: ABCB4-gene mutations are responsible for several cholestatic diseases with a heterogeneous clinical spectrum. AIMS: To analyse phenotype/genotype relationships in ABCB4-mutations. METHODS: Retrospective characterization of adult patients with ABCB4-variations diagnosed between 2015 and 2020. Genotype-phenotype correlations were analysed and compared with previously reported data. RESULTS: Twenty patients from 12 families were included. Thirteen patients presented recurrent elevated liver tests, eight fulfilled Low-Phospholipid-Associated-Cholelithiasis syndrome criteria, five had Intrahepatic Cholestasis of Pregnancy and three patients developed Drug-Induced-Liver-Injury. ABCB4 screening identified eight different mutations. Five patients were homozygotes to the variant c.504T > C. Ten patients had one mutation in heterozygote-state and five patients had two mutations in compound-heterozygosity. Portal fibrosis occurred in two patients. One of these patients presented progressive fibrosis and progression of cholestasis despite ursodeoxycholic-acid treatment, this patient also harbours a ABCB11 polymorphism. CONCLUSION: Although, phenotype-genotype relationships have not been clearly defined, an early diagnosis of ABCB4-variants may have an important role in management decisions and patient outcomes. To our knowledge, we describe a not previously reported deletion (c.1181delT) in ABCB4. The c.504T > C polymorphism, although a silent mutation at the protein level, seems to be associated to different cholestatic diseases. The role of other genes variants, namely ABCB11, as co-factor for progression, needs to be clarified.

Causal effects of gallstone disease on risk of gastrointestinal cancer in Chinese.

BACKGROUND: Gallstone disease (GSD) is associated with a higher risk of gastrointestinal (GI) cancer. However, it is unclear whether the associations are causal. METHODS: The prospective China Kadoorie Biobank (CKB) recorded 17,598 cases of GI cancer among 510,137 participants without cancer at baseline during 10 years of follow-up. Cox regression was used to estimate hazard ratios (HRs) for specific cancer by GSD status and duration. Mendelian randomisation was conducted to assess the genetic associations of GSD with specific cancer. RESULTS: Overall 6% of participants had symptomatic GSD at baseline. Compared with those without GSD, individuals with symptomatic GSD had adjusted HRs of 1.13 (1.01-1.29) for colorectal, 2.01 (1.78-2.26) for liver, 3.70 (2.88-4.87) for gallbladder, 2.31 (1.78-3.07) for biliary tract, and 1.38 (1.18-1.74) for pancreatic cancer. Compared with participants without GSD, the risks of colorectal, liver, gallbladder, biliary tract, and pancreatic cancer were highest during 0 to <5 years following disease diagnosis. There was evidence of genetic associations of GSD with these cancers, with odds ratios per 1-SD genetic score of 1.08 (1.05-1.11) for colorectal, 1.22 (1.19-1.25) for liver, 1.56 (1.49-1.64) for gallbladder, 1.39 (1.31-1.46) for biliary tract, and 1.16 (1.10-1.22) for pancreatic cancer. When meta-analysing the genetic estimates in CKB and UK Biobank, there was evidence of causal associations of GSD with colon cancer, gallbladder and biliary tract cancer (GBTC), and total GI cancer (RR per 1-SD: 1.05 [0.99-1.11], 2.00 [1.91-2.09], and 1.09 [1.05-1.13]). CONCLUSIONS: GSD was associated with higher risks of several GI cancers, warranting future studies on the underlying mechanisms.

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.

Influence of UGT1A1 promoter polymorphism, α-thalassemia and ßs haplotype in bilirubin levels and cholelithiasis in a large sickle cell anemia cohort.

Hyperbilirubinemia in patients with sickle cell anemia (SCA) as a result of enhanced erythrocyte destruction, lead to cholelithiasis development in a subset of patients. Evidence suggests that hyperbilirubinemia may be related to genetic variations, such as the UGT1A1 gene promoter polymorphism, which causes Gilbert syndrome (GS). Here, we aimed to determine the frequencies of UGT1A1 promoter alleles, alpha thalassemia, and ßS haplotypes and analyze their association with cholelithiasis and bilirubin levels. The UGT1A1 alleles, -3.7 kb alpha thalassemia deletion and ßS haplotypes were determined using DNA sequencing and PCR-based assays in 913 patients with SCA. The mean of total and unconjugated bilirubin and the frequency of cholelithiasis in GS patients were higher when compared to those without this condition, regardless of age (P < 0.05). Cumulative analysis demonstrated an early age-at-onset for cholelithiasis in GS genotypes (P < 0.05). Low fetal hemoglobin (HbF) levels and normal alpha thalassemia genotype were related to cholelithiasis development (P > 0.05). However, not cholelithiasis but total and unconjugated bilirubin levels were associated with ßS haplotype. These findings confirm in a large cohort that the UGT1A1 polymorphism influences cholelithiasis and hyperbilirubinemia in SCA. HbF and alpha thalassemia also appear as modulators for cholelithiasis risk.

Lack of an association between gallstone disease and bilirubin levels with risk of colorectal cancer: a Mendelian randomisation analysis.

BACKGROUND: Epidemiological studies of the relationship between gallstone disease and circulating levels of bilirubin with risk of developing colorectal cancer (CRC) have been inconsistent. To address possible confounding and reverse causation, we examine the relationship between these potential risk factors and CRC using Mendelian randomisation (MR). METHODS: We used two-sample MR to examine the relationship between genetic liability to gallstone disease and circulating levels of bilirubin with CRC in 26,397 patients and 41,481 controls. We calculated the odds ratio per genetically predicted SD unit increase in log bilirubin levels (ORSD) for CRC and tested for a non-zero causal effect of gallstones on CRC. Sensitivity analysis was applied to identify violations of estimator assumptions. RESULTS: No association between either gallstone disease (P value = 0.60) or circulating levels of bilirubin (ORSD = 1.00, 95% confidence interval (CI) = 0.96-1.03, P value = 0.90) with CRC was shown. CONCLUSIONS: Despite the large scale of this study, we found no evidence for a causal relationship between either circulating levels of bilirubin or gallstone disease with risk of developing CRC. While the magnitude of effect suggested by some observational studies can confidently be excluded, we cannot exclude the possibility of smaller effect sizes and non-linear relationships.

Relationship of Cholelithiasis and Urolithiasis with Methylenetetrahydrofolate Reductase Polymorphisms.

AIM: To investigate the relationship of cholelithiasis and urolithiasis with Methylenetetrehydrofolate Reductase (MTHFR) polymorphism(s) in patients with poor obstetric history to search whether they are risk factors for adverse pregnancy outcome. MATERIALS AND METHOD: This study is consisted of 94 patients with poor obstetric history. Patients were evaluated in terms of the presence of cholelithiasis and urolithiasis in association with MTHFR polymorphism(s). Additional laboratory tests including homocysteine measurements were also performed. ROC analysis for assessing the performance of blood homocysteine level in predicting the presence of cholelithiasis and urolithiasis were also performed. RESULTS: Patients were divided into three groups such as cholelithiasis group (n = 9, 9.6%), urolithiasis group (n = 18, 19.1%) and control group (n = 67, 71.3%). Groups did not differ in term of age and Beksac obstetrics index (BOI) which is "[living child+(π/10)]/gravidity." The rate of the presence of MTHFR polymorphisms were 88.9% (8/9), 88.9% (16/18) and 43.3% (29/67) in cholelithiasis, urolithiasis and control groups respectively. Median homocysteine levels were found to be 13.1, 11.6 and 7.2 micromol/lt for the groups respectively. Statistically significant differences were found for MTHFR polymorphism rates and homocysteine levels (<0.001 for both). According to ROC analysis, 10.9 mcmol/L (88.9% sensitivity, 89.6% specificity) and 9.25 mcmol/L (83.3% sensitivity, 73.1% specificity) were determined to be cutoff values of homocysteine for cholelithiasis and urolithiasis respectively. CONCLUSION: More frequent MTHFR polymorphisms are observed in women with a clinical history of gall or renal stones. Thus, screening of these patients may be benefical for the approprate management of their subsequent pregnancies.