Posttranscriptional Regulation of the Human LDL Receptor by the U2-Spliceosome

2021 ◽  
Author(s):  
Paolo Zanoni ◽  
Grigorios Panteloglou ◽  
Alaa Othman ◽  
Joel T Haas ◽  
Roger Meier ◽  
...  
Keyword(s):  
Human Plasma ◽  
Ldl Cholesterol ◽  
Human Populations ◽  
Atherosclerotic Cardiovascular Disease ◽  
Alcoholic Fatty Liver ◽  
Hepatic Expression ◽  
Cholesterol Levels ◽  
A Genome ◽  
Ldl Uptake

Background: The low-density lipoprotein receptor (LDLR) in the liver is the major determinant of LDL-cholesterol levels in human plasma. The discovery of genes that regulate the activity of LDLR helps to identify pathomechanisms of hypercholesterolemia and novel therapeutic targets against atherosclerotic cardiovascular disease. Methods: We performed a genome-wide RNA interference screen for genes limiting the uptake of fluorescent LDL into Huh-7 hepatocarcinoma cells. Top hit genes were validated by in vitro experiments as well as analyses of datasets on gene expression and variants in human populations. Results: The knockdown of 54 genes significantly inhibited LDL uptake. Fifteen of them encode for components or interactors of the U2-spliceosome. Knocking down any one of 11 out of 15 genes resulted in the selective retention of intron 3 of LDLR. The translated LDLR fragment lacks 88% of the full length LDLR and is detectable neither in non-transfected cells nor in human plasma. The hepatic expression of the intron 3 retention transcript is increased in non-alcoholic fatty liver disease as well as after bariatric surgery. Its expression in blood cells correlates with LDL-cholesterol and age. Single nucleotide polymorphisms and three rare variants of one spliceosome gene, RBM25, are associated with LDL-cholesterol in the population and familial hypercholesterolemia, respectively. Compared to overexpression of wild type RBM25, overexpression of the three rare RBM25 mutants in Huh-7 cells led to lower LDL uptake. Conclusions: We identified a novel mechanism of post-transcriptional regulation of LDLR activity in humans and associations of genetic variants of RBM25 with LDL-cholesterol levels.

Abstract 321: LRP6 Regulates LDL Receptor Internalization and LDL Uptake

2012 ◽  
Vol 32 (suppl_1) ◽  
Author(s):  
Arya Mani ◽  
Gwang-Woong Go ◽  
Zhi-jia Ye ◽  
Rajvir Singh
Keyword(s):  
Cho Cells ◽  
Ldl Cholesterol ◽  
Ldl Receptor ◽  
High Serum ◽  
Skin Fibroblasts ◽  
Receptor Internalization ◽  
Cholesterol Levels ◽  
Endocytic Machinery ◽  
Ldl Uptake

Genetic variations in LRP6 gene are associated with high serum LDL cholesterol levels and atherosclerosis. We examined the role of LRP6 in LDL receptor (LDLR) mediated LDL uptake. LDL uptake was increased when LRP6 was overexpressed and reduced when it was knocked down in LDLR deficient CHO cells. Interestingly, LRP6 knockdown in wildtype CHO cells resulted in a much greater decline in LDL uptake compared to ldlA7 cells. This finding suggested interaction between LRP6 and other proteins involved in LDL uptake. Strikingly, LDL receptor internalization was severely diminished when LRP6 was knocked down and was restored after LRP6 was reintroduced. Further investigations showed that LRP6 forms a complex with the LDL endocytic machinery including LDLR, clathrin and ARH and undergoes endocytosis after stimulation with LDL. LDLR internalization was defective in skin fibroblasts of the LRP6 R611C mutation carriers. LDLR and LRP6 internalizations as well as LDL uptake were significantly impaired in wildtype CHO cells expressing LRP6 R611C mutation(figa,b). These studies introduce LRP6 as a critical modulator of receptor-mediated LDL endocytosis and identify a mechanism by which variation in LRP6 may contribute to high serum LDL levels and atherosclerosis.

Dyslipidaemia

2019 ◽  
pp. 33-48
Author(s):  
Heinz Drexel
Keyword(s):  
Cardiovascular Disease ◽  
Randomized Clinical Trials ◽  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
Epidemiological Studies ◽  
Residual Risk ◽  
Atherosclerotic Cardiovascular Disease ◽  
Cholesterol Levels

Lipid metabolism has gained cardiological interest only after statins were demonstrated to reduce cardiovascular disease in secondary and primary prevention. Therefore, this chapter first introduces the physiological and atherogenic properties of lipoproteins, before focusing on interventions. Both the efficacy and safety of statins have been proven in numerous randomized clinical trials. Because there is a considerable residual risk in statin-treated patients, additional approaches have been investigated. The focus is now on further reductions in low-density lipoprotein (LDL) cholesterol levels. First, high-intensity statin regimens were shown to reduce residual risk. Subsequently, ezetimibe was demonstrated, for the first time, to have a beneficial effect as a non-statin lipid intervention. More recently, inhibitors of the enzyme PCSK9 have demonstrated a very high efficacy in reducing LDL cholesterol levels. Although the causality of LDL for atherosclerotic cardiovascular disease has been proven in epidemiological studies, including Mendelian randomization studies, as well as interventional trials, adherence to statins and other therapies is far from optimal. In contrast, interventions to increase high-density lipoprotein (HDL) cholesterol levels could not proven to have further benefits when combined with statins.

scholarly journals Whole grains protect against atherosclerotic cardiovascular disease

2003 ◽  
Vol 62 (1) ◽  
pp. 135-142 ◽  
Author(s):  
James W. Anderson
Keyword(s):  
Cardiovascular Disease ◽  
Vascular Reactivity ◽  
Ldl Cholesterol ◽  
Hdl Cholesterol ◽  
Whole Grains ◽  
Atherosclerotic Cardiovascular Disease ◽  
Protective Effects ◽  
Whole Grain ◽  
Cholesterol Levels ◽  
Diabetes And Obesity

Atherosclerotic cardiovascular disease (ASCVD) is the most common cause of death in most Western countries. Nutrition factors contribute importantly to this high risk for ASCVD. Favourable alterations in diet can reduce six of the nine major risk factors for ASCVD, i.e. high serum LDL-cholesterol levels, high fasting serum triacylglycerol levels, low HDL-cholesterol levels, hypertension, diabetes and obesity. Wholegrain foods may be one the healthiest choices individuals can make to lower the risk for ASCVD. Epidemiological studies indicate that individuals with higher levels (in the highest quintile) of whole-grain intake have a 29% lower risk for ASCVD than individuals with lower levels (lowest quintile) of whole-grain intake. It is of interest that neither the highest levels of cereal fibre nor the highest levels of refined cereals provide appreciable protection against ASCVD. Generous intake of whole grains also provides protection from development of diabetes and obesity. Diets rich in whole-grain foods tend to decrease serum LDL-cholesterol and triacylglycerol levels as well as blood pressure while increasing serum HDL-cholesterol levels. Whole-grain intake may also favourably alter antioxidant status, serum homocysteine levels, vascular reactivity and the inflammatory state. Whole-grain components that appear to make major contributions to these protective effects are: dietary fibre; vitamins; minerals; antioxidants; phytosterols; other phytochemicals. Three servings of whole grains daily are recommended to provide these health benefits.

scholarly journals Management of Familial Hypercholesterolemia: Current Status and Future Perspectives

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
David T W Lui ◽  
Alan C H Lee ◽  
Kathryn C B Tan
Keyword(s):  
Familial Hypercholesterolemia ◽  
Ldl Cholesterol ◽  
Genetic Disorder ◽  
Lipid Lowering ◽  
Current Status ◽  
Atherosclerotic Cardiovascular Disease ◽  
Inadequate Response ◽  
Cholesterol Lowering ◽  
Cholesterol Levels ◽  
Pubmed Database

Abstract Familial hypercholesterolemia (FH) is the most common monogenic disorder associated with premature atherosclerotic cardiovascular disease. Early diagnosis and effective treatment can significantly improve prognosis. Recent advances in the field of lipid metabolism have shed light on the molecular defects in FH and new therapeutic options have emerged. A search of PubMed database up to March 2020 was performed for this review using the following keywords: “familial hypercholesterolemia,” “diagnosis,” “management,” “guideline,” “consensus,” “genetics,” “screening,” “lipid lowering agents.” The prevalence rate of heterozygous FH is approximately 1 in 200 to 250 and FH is underdiagnosed and undertreated in many parts of the world. Diagnostic criteria have been developed to aid the clinical diagnosis of FH. Genetic testing is now available but not widely used. Cascade screening is recommended to identify affected family members, and the benefits of early interventions are clear. Treatment strategy and target is currently based on low-density lipoprotein (LDL) cholesterol levels as the prognosis of FH largely depends on the magnitude of LDL cholesterol-lowering that can be achieved by lipid-lowering therapies. Statins with or without ezetimibe are the mainstay of treatment and are cost-effective. Addition of newer medications like PCSK9 inhibitors is able to further lower LDL cholesterol levels substantially, but the cost is high. Lipoprotein apheresis is indicated in homozygous FH or severe heterozygous FH patients with inadequate response to cholesterol-lowering therapies. In conclusion, FH is a common, treatable genetic disorder, and although our understanding of this disease has improved, many challenges still remain for its optimal management.

scholarly journals Modulation of Bile Acid Metabolism to Improve Plasma Lipid and Lipoprotein Profiles

2021 ◽  
Vol 11 (1) ◽  
pp. 4
Author(s):  
Boyan Zhang ◽  
Folkert Kuipers ◽  
Jan Freark de de Boer ◽  
Jan Albert Kuivenhoven
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Acid Metabolism ◽  
Ldl Cholesterol ◽  
Farnesoid X Receptor ◽  
New Drugs ◽  
Bile Acid Metabolism ◽  
Atherosclerotic Cardiovascular Disease ◽  
Faecal Excretion ◽  
Alcoholic Fatty Liver

New drugs targeting bile acid metabolism are currently being evaluated in clinical studies for their potential to treat cholestatic liver diseases, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Changes in bile acid metabolism, however, translate into an alteration of plasma cholesterol and triglyceride concentrations, which may also affect cardiovascular outcomes in such patients. This review attempts to gain insight into this matter and improve our understanding of the interactions between bile acid and lipid metabolism. Bile acid sequestrants (BAS), which bind bile acids in the intestine and promote their faecal excretion, have long been used in the clinic to reduce LDL cholesterol and, thereby, atherosclerotic cardiovascular disease (ASCVD) risk. However, BAS modestly but consistently increase plasma triglycerides, which is considered a causal risk factor for ASCVD. Like BAS, inhibitors of the apical sodium-dependent bile acid transporter (ASBTi’s) reduce intestinal bile acid absorption. ASBTi’s show effects that are quite similar to those obtained with BAS, which is anticipated when considering that accelerated faecal loss of bile acids is compensated by an increased hepatic synthesis of bile acids from cholesterol. Oppositely, treatment with farnesoid X receptor agonists, resulting in inhibition of bile acid synthesis, appears to be associated with increased LDL cholesterol. In conclusion, the increasing efforts to employ drugs that intervene in bile acid metabolism and signalling pathways for the treatment of metabolic diseases such as NAFLD warrants reinforcing interactions between the bile acid and lipid and lipoprotein research fields. This review may be considered as the first step in this process.

scholarly journals SUN-574 A1AT: Novel Inhibitor of Active PCSK9

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Quantil Melendez ◽  
Catherine Wooten ◽  
Sumaira Ahmed ◽  
Ariel Renee’ Williams ◽  
Kevin Sean Kimbro ◽  
...  
Keyword(s):  
Heart Disease ◽  
Ldl Cholesterol ◽  
Metabolic Diseases ◽  
Cholesterol Metabolism ◽  
Ldl Receptor ◽  
Response Analysis ◽  
Statin Intolerance ◽  
Receptor Complexes ◽  
Cholesterol Levels

Abstract Heart disease is the principal cause of death and disability for both men and women in the US, accounting for 40% of all annual deaths. African American populations are disproportionately burdened with metabolic diseases, due in part to cholesterol metabolism deficiencies. Elevated low density lipoprotein (LDL) cholesterol levels and inflammation promote atherogenic conditions which lead to heart disease. Proprotein convertase subtilisin/kexin-9 (PCSK9) is a biomarker which enhances athrogenic progression by controlling the number of LDL receptor molecules expressed at the plasma membrane. PCSK9 indirectly regulates LDL-cholesterol levels. Previous reports show some patients do not respond well to general anti-cholesterolemic treatments. We believe this is due to altered PCSK9 activity, which is currently not being evaluated. We have developed a novel assay to detect active PCSK9. A1AT is a SERPIN family member whose primary objective is inhibition of proteases. Specific levels of A1AT are required to maintain metabolic homeostasis. Based on this, we hypothesized that a specific ratio between A1AT serum levels and PCSK9 activity levels would eliminate statin intolerance/resistance, regulating LDL-cholesterol metabolism congruently. Using this novel active PCSK9 detection assay, we provide evidence that A1AT interacts with PCSK9 in the medium of C3A hepatic-like cells, preventing the formation of PCSK9/LDL receptor complexes in vitro. There was an approximate 20% inhibition in PCSK9-LDL receptor complex formation when liver cells were treated with recombinant A1AT (rA1AT). A dose dependent response analysis proved 200ng/ml of rA1AT had an 46% reduction in PCSK9 activity. We determined PCSK9 activty and A1AT levels correlate with key diabetic factors in humans, suggesting that A1AT could effect diabetes progression.

scholarly journals Whole genome screen reveals a novel relationship between Wolbachia levels and Drosophila host translation

2018 ◽  
Author(s):  
Yolande Grobler ◽  
Chi Y. Yun ◽  
David J. Kahler ◽  
Casey M. Bergman ◽  
Hangnoh Lee ◽  
...  
Keyword(s):  
Gene Networks ◽  
Virus Transmission ◽  
Antiviral Effect ◽  
Human Populations ◽  
West Nile ◽  
Genome Wide ◽  
A Genome ◽  
Vector Borne

AbstractWolbachia is an intracellular bacterium that infects a remarkable range of insect hosts. Insects such as mosquitos act as vectors for many devastating human viruses such as Dengue, West Nile, and Zika. Remarkably, Wolbachia infection provides insect hosts with resistance to many arboviruses thereby rendering the insects ineffective as vectors. To utilize Wolbachia effectively as a tool against vector-borne viruses a better understanding of the host-Wolbachia relationship is needed. To investigate Wolbachia-insect interactions we used the Wolbachia/Drosophila model that provides a genetically tractable system for studying host-pathogen interactions. We coupled genome-wide RNAi screening with a novel high-throughput fluorescence in situ hybridization (FISH) assay to detect changes in Wolbachia levels in a Wolbachia-infected Drosophila cell line JW18. 1117 genes altered Wolbachia levels when knocked down by RNAi of which 329 genes increased and 788 genes decreased the level of Wolbachia. Validation of hits included in depth secondary screening using in vitro RNAi, Drosophila mutants, and Wolbachia-detection by DNA qPCR. A diverse set of host gene networks was identified to regulate Wolbachia levels and unexpectedly revealed that perturbations of host translation components such as the ribosome and translation initiation factors results in increased Wolbachia levels both in vitro using RNAi and in vivo using mutants and a chemical-based translation inhibition assay. This work provides evidence for Wolbachia-host translation interaction and strengthens our general understanding of the Wolbachia-host intracellular relationship.Author summaryInsects such as mosquitos act as vectors to spread devastating human diseases such as Dengue, West Nile, and Zika. It is critical to develop control strategies to prevent the transmission of these diseases to human populations. A novel strategy takes advantage of an endosymbiotic bacterium Wolbachia pipientis. The presence of this bacterium in insect vectors prevents successful transmission of RNA viruses. The degree to which viruses are blocked by Wolbachia is dependent on the levels of the bacteria present in the host such that higher Wolbachia levels induce a stronger antiviral effect. In order to use Wolbachia as a tool against vector-borne virus transmission a better understanding of host influences on Wolbachia levels is needed. Here we performed a genome-wide RNAi screen in a model host system Drosophila melanogaster infected with Wolbachia to identify host systems that affect Wolbachia levels. We found that host translation can influence Wolbachia levels in the host.

Dyslipidaemia

2019 ◽  
pp. 33-48
Author(s):  
Heinz Drexel
Keyword(s):  
Cardiovascular Disease ◽  
Randomized Clinical Trials ◽  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
Epidemiological Studies ◽  
Residual Risk ◽  
Atherosclerotic Cardiovascular Disease ◽  
Cholesterol Levels

Lipid metabolism has gained cardiological interest only after statins were demonstrated to reduce cardiovascular disease in secondary and primary prevention. Therefore, this chapter first introduces the physiological and atherogenic properties of lipoproteins, before focusing on interventions. Both the efficacy and safety of statins have been proven in numerous randomized clinical trials. Because there is a considerable residual risk in statin-treated patients, additional approaches have been investigated. The focus is now on further reductions in low-density lipoprotein (LDL) cholesterol levels. First, high-intensity statin regimens were shown to reduce residual risk. Subsequently, ezetimibe was demonstrated, for the first time, to have a beneficial effect as a non-statin lipid intervention. More recently, inhibitors of the enzyme PCSK9 have demonstrated a very high efficacy in reducing LDL cholesterol levels. Although the causality of LDL for atherosclerotic cardiovascular disease has been proven in epidemiological studies, including Mendelian randomization studies, as well as interventional trials, adherence to statins and other therapies is far from optimal. In contrast, interventions to increase high-density lipoprotein (HDL) cholesterol levels could not proven to have further benefits when combined with statins.

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