Exploring the causal effect between lipid-modifying drugs and idiopathic pulmonary fibrosis: a drug-target Mendelian randomization study.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a respiratory disorder of obscure etiology and limited treatment options, possibly linked to dysregulation in lipid metabolism. While several observational studies suggest that lipid-lowering agents may decrease the risk of IPF, the evidence is inconsistent. The present Mendelian randomization (MR) study aims to determine the association between circulating lipid traits and IPF and to assess the potential influence of lipid-modifying medications for IPF. METHODS: Summary statistics of 5 lipid traits (high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride, apolipoprotein A, and apolipoprotein B) and IPF were sourced from the UK Biobank and FinnGen Project Round 10. The study's focus on lipid-regulatory genes encompassed PCSK9, NPC1L1, ABCG5, ABCG8, HMGCR, APOB, LDLR, CETP, ANGPTL3, APOC3, LPL, and PPARA. The primary effect estimates were determined using the inverse-variance-weighted method, with additional analyses employing the contamination mixture method, robust adjusted profile score, the weighted median, weighted mode methods, and MR-Egger. Summary-data-based Mendelian randomization (SMR) was used to confirm significant lipid-modifying drug targets, leveraging data on expressed quantitative trait loci in relevant tissues. Sensitivity analyses included assessments of heterogeneity, horizontal pleiotropy, and leave-one-out methods. RESULTS: There was no significant effect of blood lipid traits on IPF risk (all P＞0.05). Drug-target MR analysis indicated that genetic mimicry for inhibitor of NPC1L1, PCSK9, ABCG5, ABCG8, and APOC3 were associated with increased IPF risks, with odds ratios (ORs) and 95% confidence intervals (CIs) as follows: 2.74 (1.05-7.12, P = 0.039), 1.36 (1.02-1.82, P = 0.037), 1.66 (1.12-2.45, P = 0.011), 1.68 (1.14-2.48, P = 0.009), and 1.42 (1.20-1.67, P = 3.17×10-5), respectively. The SMR method identified a significant association between PCSK9 gene expression in whole blood and reduced IPF risk (OR = 0.71, 95% CI: 0.50-0.99, P = 0.043). Sensitivity analyses showed no evidence of bias. CONCLUSIONS: Serum lipid traits did not significantly affect the risk of idiopathic pulmonary fibrosis. Drug targets MR studies examining 12 lipid-modifying drugs indicated that PCSK9 inhibitors could dramatically increase IPF risk, a mechanism that may differ from their lipid-lowering actions and thus warrants further investigation.

Genome-wide association study and meta-analysis of phytosterols identifies a novel locus for serum levels of campesterol.

Sitosterolemia is a rare inherited disorder caused by mutations in the ABCG5/ABCG8 genes. These genes encode proteins involved in the transport of plant sterols. Mutations in these genes lead to decreased excretion of phytosterols, which can accumulate in the body and lead to a variety of health problems, including premature coronary artery disease. We conducted the first genome-wide association study (GWAS) in the Middle East/North Africa population to identify genetic determinants of plant sterol levels in Qatari people. GWAS was performed on serum levels of ß-sitosterol and campesterol using the Metabolon platform from Qatar Biobank (QBB) and genome sequence data provided by Qatar Genome Program. A trans-ancestry meta-analysis of data from our Qatari cohort with summary statistics from a previously published large cohort (9758 subjects) of European ancestry was conducted. Using conditional analysis, we identified two independent single nucleotide polymorphisms associated with ß-sitosterol (rs145164937 and rs4299376), and two others with campesterol (rs7598542 and rs75901165) in the Qatari population in addition to previously reported variants. All of them map to the ABCG5/8 locus except rs75901165 which is located within the Intraflagellar Transport 43 (IFT43) gene. The meta-analysis replicated most of the reported variants, and our study provided significant support for the association of variants in SCARB1 and ABO with sitosterolemia. Evaluation of a polygenic risk score devised from European GWAS data showed moderate performance when applied to QBB (adjusted-R2 = 0.082). These findings provide new insights into the genetic architecture of phytosterol metabolism while showing the importance including under-represented populations in future GWAS studies.

Dried blood spot-based free sterol signatures in sitosterolemia diagnostics.

BACKGROUND: Sitosterolemia is a rare inherited lipid metabolic disorder characterized by increased levels of plant sterols and accelerated atherosclerosis. Although early detection is beneficial for the prevention of disease progression, it is largely underdiagnosed by routine screening based on conventional lipid profiles. MATERIALS AND METHODS: A gas chromatography-mass spectrometry (GC-MS)-based profiling has been developed and validated to measure the levels of biologically active free sterols, including five endogenous sterols and three plant sterols (sitosterol, campesterol, and stigmasterol) in dried blood spot (DBS). RESULTS: Within- and between-run precisions were 1.4-11.1 % and 2.2-14.1 %, respectively, while the accuracies were all 86.3 âˆ¼ 121.9 % with the correlation coefficients (r2) > 0.988 for all the sterols. In the patients (four girls and two boys, 6.5 ± 2.8 years), sitosterol levels were significantly increased, with an optimal cut-off value of 2.5 µg/mL distinguishing them from ninety-three age-matched healthy children. A cut-off value of 31.9 µg/mL differentiated the patients from six ABCG5/ABCG8 heterozygous carriers. In addition, the molecular ratios of sitosterol to cholesterol, desmosterol, and 7-dehydrocholesterol provided excellent cut-off values of 26.3, 67.6, and 21.6, respectively, to distinguish patients from both healthy controls and heterozygous carriers. CONCLUSIONS: The novel DBS-based GC-MS profiling of free sterols accurately identified patients with sitosterolemia, with a performance comparable to that of a serum assay. The DBS profiling could be more feasible method in clinical practice as well as population screening programs, and it can provide diagnostic cut-off values for individual plant sterols.

Lipid traits and lipid-lowering drug target genes and risk of melanoma: a mendelian randomization study.

Our study aimed to investigate the role of lipids in melanoma risk and the effect of lipid-lowering drug targets on melanoma. Using Mendelian Randomization analysis, we examined the genetic agents of nine lipid-lowering drugs and their association with melanoma risk. We found that genetically proxied inhibition of HMGCR, ABCG5/ABCG8, and ANGPTL3 was associated with a reduced risk of melanoma. On the other hand, inhibition of LPL and Apo-B100 was significantly associated with an increased risk of melanoma. Sensitivity analyses did not reveal any statistical evidence of bias from pleiotropy or genetic confounding. We did not find a robust association between lipid traits NPC1L1, PCSK9, APOC3 inhibition, and melanoma risk. These findings were validated using two independent lipid datasets. Our analysis also revealed that HMGCR, ANGPTL3, and ABCG5/ABCG8 inhibitors reduced melanoma risk independent of their effects on lipids. This suggests that these targets may have potential for melanoma prevention or treatment. In conclusion, our study provides evidence for a causal role of lipids in melanoma risk and highlights specific lipid-lowering drug targets that may be effective in reducing the risk of melanoma. These findings contribute to the understanding of the underlying mechanisms of melanoma development and provide potential avenues for further research and therapeutic interventions.

Heat-killed Lactiplantibacillus plantarum Shinshu N-07 exerts antiobesity effects in western diet-induced obese mice.

AIMS: The aim of this study was to evaluate the antiobesity effects of heat-killed Lactiplantibacillus plantarum Shinshu N-07 (N-07) isolated from fermented Brassica rapa L. METHODS AND RESULTS: Male mice were divided into three groups (n = 10/group); normal diet, western diet (WD), or WD + N-07 (N-07) group and administered each diet for 56 days. The N-07 group showed significant suppression of body weight gain and epididymal fat, perirenal fat, and liver weights compared with the WD group. Higher levels of fecal total cholesterol, triglyceride (TG), and free fatty acid (FFA) were observed in the N-07 group than in the WD group. The mRNA expression of the cholesterol transporter ATP-binding cassette transporter G5 (ABCG5) was significantly increased in the small intestine of N-07-fed mice compared with WD-fed mice. Moreover, N-07 supplementation significantly increased the mRNA expression of ABCG5 and ABCG8 in Caco-2 cells. Furthermore, the TG- and FFA-removal ability of N-07 was confirmed to evaluate its soybean oil- and oleic acid-binding capacities in in vitro experiments. CONCLUSIONS: The antiobesity effects of N-07 might be due to its ability to promote lipid excretion by regulating cholesterol transporter expression and lipid-binding ability.

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.

Associations of Dietary Cholesterol Consumption With Incident Diabetes and Cardiovascular Disease: The Role of Genetic Variability in Cholesterol Absorption and Disease Predisposition.

OBJECTIVE: Whether genetic susceptibility to disease and dietary cholesterol (DC) absorption contribute to inconsistent associations of DC consumption with diabetes and cardiovascular disease (CVD) remains unclear. RESEARCH DESIGN AND METHODS: DC consumption was assessed by repeated 24-h dietary recalls in the UK Biobank. A polygenetic risk score (PRS) for DC absorption was constructed using genetic variants in the Niemann-Pick C1-Like 1 and ATP Binding Cassettes G5 and G8 genes. PRSs for diabetes, coronary artery disease, and stroke were also created. The associations of DC consumption with incident diabetes (n = 96,826) and CVD (n = 94,536) in the overall sample and by PRS subgroups were evaluated using adjusted Cox models. RESULTS: Each additional 300 mg/day of DC consumption was associated with incident diabetes (hazard ratio [HR], 1.17 [95% CI, 1.07-1.27]) and CVD (HR, 1.09 [95% CI, 1.03-1.17]), but further adjusting for BMI nullified these associations (HR for diabetes, 0.99 [95% CI, 0.90-1.09]; HR for CVD, 1.04 [95% CI, 0.98-1.12]). Genetic susceptibility to the diseases did not modify these associations (P for interaction ≥0.06). The DC-CVD association appeared to be stronger in people with greater genetic susceptibility to cholesterol absorption assessed by the non-high-density lipoprotein cholesterol-related PRS (P for interaction = 0.04), but the stratum-level association estimates were not statistically significant. CONCLUSIONS: DC consumption was not associated with incident diabetes and CVD, after adjusting for BMI, in the overall sample and in subgroups stratified by genetic predisposition to cholesterol absorption and the diseases. Nevertheless, whether genetic predisposition to cholesterol absorption modifies the DC-CVD association requires further investigation.

Family sitosterolemia: report of two cases in Colombia. / Sitosterolemia familiar: reporte de dos casos en Colombia.

Sitosterolemia is an autosomal recessive and very rare disease. Its main characteristic is that there is a greater absorption and a decrease in the excretion of sterols, which leads to them being deposited in tissues. It is given by mutations in the ABCG5 or ABCG8 genes found on chromosome 2p21. In this clinical note, we describe the first two patients with familial sitosterolemia described in Colombia, brothers, one of them with xanthomas in extremities as the only symptom, and the other, completely asymptomatic. Genetic studies were performed as a diagnostic test in both patients, where a pathogenic homozygous variant could be identified in the ABCG8 gene in the first case (symptomatic), and a heterozygous variant in the ABCG8 gene in the second case (asymptomatic); the first patient has responded to treatment with ezetimibe. In conclusion, xanthomas should be studied in depth in pediatric age as they may be the only visible sign of such complex and hereditary diseases as familial sitosterolemia, which can be controlled and prevent cardiovascular complications of the disease.

Platelet proteomic profiling in sitosterolemia suggests thrombocytopenia is driven by lipid disorder and not platelet aberrations.

ABSTRACT: Sitosterolemia is a rare autosomal recessive genetic disorder in which patients develop hypercholesterolemia and may exhibit abnormal hematologic and/or liver test results. In this disease, dysfunction of either ABCG5 or ABCG8 results in the intestinal hyperabsorption of all sterols, including cholesterol and, more specifically, plant sterols or xenosterols, as well as in the impaired ability to excrete xenosterols into the bile. It remains unknown how and why some patients develop hematologic abnormalities. Only a few unrelated patients with hematologic abnormalities at the time of diagnosis have been reported. Here, we report on 2 unrelated pedigrees who were believed to have chronic immune thrombocytopenia as their most prominent feature. Both consanguineous families showed recessive gene variants in ABCG5, which were associated with the disease by in silico protein structure analysis and clinical segregation. Hepatosplenomegaly was absent. Thrombopoietin levels and megakaryocyte numbers in the bone marrow were normal. Metabolic analysis confirmed the presence of strongly elevated plasma levels of xenosterols. Potential platelet proteomic aberrations were longitudinally assessed following dietary restrictions combined with administration of the sterol absorption inhibitor ezetimibe. No significant effects on platelet protein content before and after the onset of treatment were demonstrated. Although we cannot exclude that lipotoxicity has a direct and platelet-specific impact in patients with sitosterolemia, our data suggest that thrombocytopenia is neither caused by a lack of megakaryocytes nor driven by proteomic aberrations in the platelets themselves.

Plasma campesterol and ABCG5/ABCG8 gene loci on the risk of cholelithiasis and cholecystitis: evidence from Mendelian randomization and colocalization analyses.

The causal relationships between plasma metabolites and cholelithiasis/cholecystitis risks remain elusive. Using two-sample Mendelian randomization, we found that genetic proxied plasma campesterol level showed negative correlation with the risk of both cholelithiasis and cholecystitis. Furthermore, the increased risk of cholelithiasis is correlating with the increased level of plasma campesterol. Lastly, genetic colocalization study showed that the leading SNP, rs4299376, which residing at the ABCG5/ABCG8 gene loci, was shared by plasma campesterol level and cholelithiasis, indicating that the aberrant transportation of plant sterol/cholesterol from the blood stream to the bile duct/gut lumen might be the key in preventing cholesterol gallstone formation.

Macrophage inhibitory cytokine-1 aggravates diet-induced gallstone formation via increased ABCG5/ABCG8 expression.

Macrophage inhibitory cytokine 1 (MIC-1), which is overproduced in various human cancers and associated with cachexia, acts on the hypothalamus to suppress appetite and reduce body weight. We investigated the mechanisms through which MIC-1 affects bile acid metabolism and gallstone formation, which are poorly understood. Over 6 weeks, male C57BL/6 mice fed either standard chow or a lithogenic diet were intraperitoneally injected with phosphate-buffered saline (PBS) or MIC-1 (200 µg/kg/week). Among lithogenic diet-fed mice, MIC-1 treatment resulted in increased gallstone formation compared with PBS treatment. Compared with PBS treatment, MIC-1 treatment decreased hepatic cholesterol and bile acid levels and reduced expression of HMG-CoA reductase (HMGCR), the master cholesterol metabolism regulator sterol regulatory element-binding protein 2, cholesterol 7α-hydroxylase (CYP7A1), mitochondrial sterol 27-hydroxylase, and oxysterol 7α-hydroxylase. Compared with PBS treatment, MIC-1 treatment had no effect on small heterodimer partner, farnesoid X receptor, or pregnane X receptor expression, and extracellular signal-related kinase and c-Jun N-terminal kinase phosphorylation decreased, suggesting that these factors do not contribute to the MIC-1-induced reduction in CYP7A1 expression. Compared with PBS treatment, MIC-1 treatment increased AMP-activated protein kinase (AMPK) phosphorylation. Treatment with the AMPK activator 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) reduced CYP7A1 and HMGCR expression, whereas the AMPK inhibitor Compound C reversed MIC-1-induced reductions in CYP7A1 and HMGCR expression. Furthermore, in MIC-1-treated mice, total biliary cholesterol levels increased together with increased ATP-binding cassette subfamily G (ABCG)5 and ABCG8 expression. Compared with PBS treatment, MIC-1 treatment did not affect expression of liver X receptors α and ß, liver receptor homolog 1, hepatocyte nuclear factor 4α, or NR1I3 (also known as constitutive androstane receptor), which are upstream of ABCG5/8; however, MIC-1 treatment increased ABCG5/8 expression and promoter activities. Our study indicates that MIC-1 influences gallstone formation by increasing AMPK phosphorylation, reducing CYP7A1 and HMGCR expression, and increasing ABCG5 and ABCG8 expression.

Correlation of serum biochemical characteristics and ABCG8 genetic variant (rs 11887534) with gall stone compositions and risk of gallstone disease in Egyptian patients.

BACKGROUND: The overexpression of the cholesterol transporter: ATP-binding cassette transporter (ABCG8) due to the effect of ABCG8 genetic variant (rs11887534) leads to the precipitation of cholesterol crystals and gallstone disease (GSD). OBJECTIVE: To evaluate the chemical composition of gallstones and the role of ABCG8 (rs11887534) in the susceptibility to GSD. METHODS: We enrolled 77 patients with GSD treated with standard laparoscopic or open cholecystectomy and 75 age and sex-matched healthy controls. Chemical analysis of the extracted gallstones was performed. Analysis of the rs11887534 was performed by real-time PCR TaqMan technique for both cases and controls. RESULTS: Pure cholesterol stones were the main type of stones in GSD patients. The CC genotype carriers of rs11887534 were more prone to gallstone formation than other genotypes. The CC genotype carriers were 100 folds at increased risk to develop pure cholesterol stones. CONCLUSION: The most prevalent type of gallbladder stones is pure cholesterol stone. ABCG8 (rs11887534) could be associated with increased risk for cholesterol gallstones formation, this risk was more pronounced in female patients.

Differential Effects of ABCG5/G8 Gene Region Variants on Lipid Profile, Blood Pressure Status, and Gallstone Disease History in Taiwan.

ABCG5 and ABCG8 are two key adenosine triphosphate-binding cassette (ABC) proteins that regulate whole-body sterol trafficking. This study aimed to elucidate the association between ABCG5/G8 gene region variants and lipid profile, cardiometabolic traits, and gallstone disease history in Taiwan. A total of 1494 Taiwan Biobank participants with whole-genome sequencing data and 117,679 participants with Axiom Genome-Wide CHB Array data were enrolled for analysis. Using genotype-phenotype and stepwise linear regression analyses, we found independent associations of four Asian-specific ABCG5 variants, rs119480069, rs199984328, rs560839317, and rs748096191, with total, low-density lipoprotein (LDL), and non-high-density lipoprotein (HDL) cholesterol levels (all p ≤ 0.0002). Four other variants, which were in nearly complete linkage disequilibrium, exhibited genome-wide significant associations with gallstone disease history, and the ABCG8 rs11887534 variant showed a trend of superiority for gallstone disease history in a nested logistic regression model (p = 0.074). Through regional association analysis of various other cardiometabolic traits, two variants of the PLEKHH2, approximately 50 kb from the ABCG5/G8 region, exhibited significant associations with blood pressure status (p < 10-6). In conclusion, differential effects of ABCG5/G8 region variants were noted for lipid profile, blood pressure status, and gallstone disease history in Taiwan. These results indicate the crucial role of individualized assessment of ABCG5/G8 variants for different cardiometabolic phenotypes.

Sitosterolemia.

Sitosterolemia is an inherited metabolic disorder characterized by increased levels of plant sterols, such as sitosterol. This disease is caused by loss-of-function genetic mutations in the ATP-binding cassette (ABC) subfamily G member 5 or member 8 (ABCG5 or ABCG8, respectively), both of which play important roles in the selective excretion of plant sterols from the liver and intestine, leading to a failure to excrete plant sterols. Sitosterolemia, which is currently considered a rare genetic disorder, has been described as a phenocopy of homozygous familial hypercholesterolemia (FH). Typical phenotypes of sitosterolemia, including elevated low-density lipoprotein (LDL) cholesterol, tendon xanthomas, and premature coronary artery disease, overlap those of homozygous FH; however, there are substantial differences between these two diseases in terms of treatments and prognoses. Moreover, it is of note that sitosterolemia appears to be quite underdiagnosed, although accurate diagnosis and appropriate interventions will likely to lead to better prognoses compared with homozygous FH. Unlike cases of homozygous FH, dietary counseling is quite effective in reducing the LDL cholesterol as well as sitosterol of patients with sitosterolemia. In this chapter, we summarize the current understandings of this disease and provide useful tips for the diagnosis as well as better treatment of patients with sitosterolemia.

Structural Analysis of Cholesterol Binding and Sterol Selectivity by ABCG5/G8.

The ATP-binding cassette (ABC) sterol transporters are responsible for maintaining cholesterol homeostasis in mammals by participating in reverse cholesterol transport (RCT) or transintestinal cholesterol efflux (TICE). The heterodimeric ABCG5/G8 carries out selective sterol excretion, preventing the abnormal accumulation of plant sterols in human bodies, while homodimeric ABCG1 contributes to the biogenesis and metabolism of high-density lipoproteins. A sterol-binding site on ABCG5/G8 was proposed at the interface of the transmembrane domain and the core of lipid bilayers. In this study, we have determined the crystal structure of ABCG5/G8 in a cholesterol-bound state. The structure combined with amino acid sequence analysis shows that in the proximity of the sterol-binding site, a highly conserved phenylalanine array supports functional implications for ABCG cholesterol/sterol transporters. Lastly, in silico docking analysis of cholesterol and stigmasterol (a plant sterol) suggests sterol-binding selectivity on ABCG5/G8, but not ABCG1. Together, our results provide a structural basis for cholesterol binding on ABCG5/G8 and the sterol selectivity by ABCG transporters.

Screening of ABCG5 and ABCG8 Genes for Sitosterolemia in a Familial Hypercholesterolemia Cascade Screening Program.

BACKGROUND: Sitosterolemia is a rare autosomal recessive disorder caused by homozygous or compound heterozygous variants in ABCG5/ABCG8. The disease is characterized by increased plasma plant sterols. Small case series suggest that patients with sitosterolemia have wide phenotypic heterogeneity with great variability on either plasma cholesterol levels or development of atherosclerotic cardiovascular disease. The present study aims to characterize the prevalence and clinical features of sitosterolemia participating in a familial hypercholesterolemia genetic cascade screening program. METHODS: From 443 familial hypercholesterolemia index cases, 260 were negative for familial hypercholesterolemia genes and were sequenced for the ABCG5/8 genes. Clinical and laboratory characteristics of affected individuals were determined. RESULTS: Eight (3.1%) index cases were found to be homozygous or compound heterozygous variant for ABCG5/ABCG8 genes, confirming the genetic diagnosis of sitosterolemia. Screening their relatives led to the identification of 6 additional confirmed sitosterolemia cases (3 homozygous and 3 compound heterozygous variant) and 18 carriers (heterozygous). The mean age of identified sitosterolemia cases (n=14) was 37.2±19.8 years, 50% were females, and 78.6% (all adults) presented either clinical or subclinical atherosclerotic cardiovascular disease. As expected, affected individuals presented elevated plasma plant sterol levels (mean ß-Sitosterol and campesterol, respectively, 160.3±107.1 and 32.0±19.6 µg/mL) and the highest plasma LDL (low-density lipoprotein)-cholesterol was 269.0±120.0 mg/dL (range: 122-521 mg/dL). LDL-cholesterol mean reduction with therapy among cases was 65%. Eighty-three percent (83%) of identified sitosterolemia patients presented hematologic abnormalities. CONCLUSIONS: Testing genes associated with sitosterolemia in the molecular routine workflow of a familial hypercholesterolemia cascade screening program allowed the precise diagnosis of sitosterolemia in a substantial number of patients with varying LDL-C levels and high incidence of early atherosclerotic cardiovascular disease and hematologic abnormalities.

Evolutionary origin and sequence signatures of the heterodimeric ABCG5/ABCG8 transporter.

ATP-binding cassette (ABC) systems, characterized by ABC-type nucleotide-binding domains (NBDs), play crucial roles in various aspects of human physiology. Human ABCG5 and ABCG8 form a heterodimeric transporter that functions in the efflux of sterols. We used sequence similarity search, multiple sequence alignment, phylogenetic analysis, and structure comparison to study the evolutionary origin and sequence signatures of ABCG5 and ABCG8. Orthologs of ABCG5 and ABCG8, supported by phylogenetic analysis and signature residues, were identified in bilaterian animals, Filasterea, Fungi, and Amoebozoa. Such a phylogenetic distribution suggests that ABCG5 and ABCG8 could have originated in the last common ancestor of Amorphea (the unikonts), the eukaryotic group including Amoebozoa and Opisthokonta. ABCG5 and ABCG8 were missing in genomes of various lineages such as snakes, jawless vertebrates, non-vertebrate chordates, echinoderms, and basal metazoan groups. Amino-acid changes in key positions in ABCG8 Walker A motif and/or ABCG5 C-loop were observed in most tetrapod organisms, likely resulted in the loss of ATPase activity at one nucleotide-binding site. ABCG5 and ABCG8 in Ecdysozoa (such as insects) exhibit elevated evolutionary rates and accumulate various changes in their NBD functional motifs. Alignment inspection revealed several residue positions that show different amino-acid usages in ABCG5/ABCG8 compared to other ABCG subfamily proteins. These residues were mapped to the structural cores of transmembrane domains (TMDs), the NBD-TMD interface, and the interface between TMDs. They serve as sequence signatures to differentiate ABCG5/ABCG8 from other ABCG subfamily proteins, and some of them may contribute to substrate specificity of the ABCG5/ABCG8 transporter.

Clinical and genetic features of sitosterolemia in Japan.

BACKGROUND AND AIM: Clinical manifestations and genetic backgrounds of Japanese patients with sitosterolemia have been unclear. MATERIALS AND METHODS: We searched PubMed for studies using the keywords "sitosterolemia" or "phytosterolemia" and "Japan". Moreover, we added information from the members of the Committee on Primary Dyslipidemia under the Research Program on Rare and Intractable Disease of the Ministry of Health, Labour and Welfare (MHLW) of Japan. RESULTS: We identified 36 patients with sitosterolemia caused by biallelic pathogenic mutations in the ATP-binding cassette subfamily G member 5 (ABCG5) or ATP-binding cassette subfamily G member 8 (ABCG8) from 31 families in Japan. The diagnosed age ranged from 0 to 64 years (median 13 years). The median sitosterol and LDL cholesterol levels were 100 µg/ml (IQR: 50-183), and 193 mg/dl (IQR: 108-295), respectively. All the patients exhibited cutaneous and/or tendon xanthomas, up to 9 (25%) patients exhibited premature coronary artery disease, 5 (16%) patients exhibited arthritis, and 8 (22%) patients exhibited blood abnormalities. Ezetimibe was administered to all the patients, including infantile cases, while statins, colestimide, evolocumab, probucol, and LDL apheresis were also used. CONCLUSION: We are providing a demographic overview of the clinical and genetic backgrounds of Japanese patients with sitosterolemia.

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.

Genome-wide meta-analysis of phytosterols reveals five novel loci and a detrimental effect on coronary atherosclerosis.

Phytosterol serum concentrations are under tight genetic control. The relationship between phytosterols and coronary artery disease (CAD) is controversially discussed. We perform a genome-wide meta-analysis of 32 phytosterol traits reflecting resorption, cholesterol synthesis and esterification in six studies with up to 9758 subjects and detect ten independent genome-wide significant SNPs at seven genomic loci. We confirm previously established associations at ABCG5/8 and ABO and demonstrate an extended locus heterogeneity at ABCG5/8 with different functional mechanisms. New loci comprise HMGCR, NPC1L1, PNLIPRP2, SCARB1 and APOE. Based on these results, we perform Mendelian Randomization analyses (MR) revealing a risk-increasing causal relationship of sitosterol serum concentrations and CAD, which is partly mediated by cholesterol. Here we report that phytosterols are polygenic traits. MR add evidence of both, direct and indirect causal effects of sitosterol on CAD.