Low Density Lipoprotein Receptor Gene Research Articles

LDLR expression in the cochlea suggests a role in endolymph homeostasis and cochlear amplification

There is now growing evidence that hypercholesterolemia and high serum levels of low-density lipoproteins (LDL) predispose to sensorineural hearing loss. Circulating LDL-cholesterol is delivered to peripheral tissues via LDL receptor (LDLR) -mediated endocytosis. Recently, it has been shown that LDLR gene polymorphisms are associated with higher susceptibility to sudden deafness. These findings suggested that we should investigate the expression of LDLR from the postnatal maturation of the mouse cochlea until adulthood. In the cochlea of newborn mice, we observed that LDLR is mostly expressed in the lateral wall of the cochlea, especially in a band of cells directly facing the cochlear duct. Moreover, LDLR is expressed in the inner and outer hair cells, as well as in the adjacent greater epithelial ridge. In early postnatal stages, LDLR is expressed in the marginal cells of the immature stria vascularis, in the root cells of the spiral ligament, and in the adjacent outer sulcus cells. At the same time, LDLR begins to be expressed in the pillar cells of the immature organ of Corti. From the onset of hearing, LDLR is expressed in the marginal cells of the stria vascularis, in the outer sulcus cells, and in the capillaries of the adjacent spiral ligament. In the organ of Corti, LDLR is expressed in outer pillar cells and Deiters’ cells, i.e. in the non-sensory supporting cells that directly surround the outer hair cells. These cells are believed to provide a mechanical coupling with the outer hair cells to modulate electromotility and cochlear amplification. In the stria vascularis of three-month-old mice, LDLR is further expressed in both marginal and intermediate cells. Overall, our results suggest that LDLR is mostly present in cochlear cells that are involved in endolymph homeostasis and cochlear amplification. Further functional studies will be needed to unravel how LDLR regulates extracellular and intracellular levels of cholesterol and lipoproteins in the cochlea, and how it could influence cochlear homeostasis.

Variable and Severe Phenotypic Expression of the “Lebanese Allele” in Two Sisters with Familial Hypercholesterolemia

The “Lebanese allele” {LDLR c.2043 C>A (p.cys681X)} is a nonsense mutation in the low-density lipoprotein receptor (LDLR) gene that results in a truncated non-functioning LDLR protein. We report two sisters of Lebanese descent who presented with familial hypercholesterolemia (FH) and were both heterozygous for the Lebanese allele, but had very distinct LDL-C levels and clinical phenotypes. Whereas one of the sisters had LDL-C in the expected range of Heterozygous FH (HeFH) with the Lebanese allele (LDL-C of 292 mg/dl), the other sister had a more severe LDL-C phenotype in the Homozygous FH (HoFH) range (LDL-C of 520 mg/dl) along with manifest atherosclerosis. Surprisingly, she did not demonstrate a compound heterozygote or double heterozygote status. We discuss different mechanisms that are purported to play a role in modifying the phenotype of FH, including different variants and polygenic modifiers. HeFH patients with the Lebanese allele can have a wide spectrum of LDL-C levels that range from the typical heterozygous to homozygous phenotypes.

Evinacumab Approval Adds a New Option for Homozygous Familial Hypercholesterolemia With a Hefty Price Tag

Evinacumab Approval Adds a New Option for Homozygous Familial Hypercholesterolemia With a Hefty Price Tag

The Dual Role of Low-Density Lipoprotein Receptor-Related Protein 1 in Atherosclerosis.

Low-density lipoprotein receptor–related protein-1 (LRP1) is a large endocytic and signaling receptor belonging to the LDL receptor (LDLR) gene family and that is widely expressed in several tissues. LRP1 comprises a large extracellular domain (ECD; 515 kDa, α chain) and a small intracellular domain (ICD; 85 kDa, β chain). The deletion of LRP1 leads to embryonic lethality in mice, revealing a crucial but yet undefined role in embryogenesis and development. LRP1 has been postulated to participate in numerous diverse physiological and pathological processes ranging from plasma lipoprotein homeostasis, atherosclerosis, tumor evolution, and fibrinolysis to neuronal regeneration and survival. Many studies using cultured cells and in vivo animal models have revealed the important roles of LRP1 in vascular remodeling, foam cell biology, inflammation and atherosclerosis. However, its role in atherosclerosis remains controversial. LRP1 not only participates in the removal of atherogenic lipoproteins and proatherogenic ligands in the liver but also mediates the uptake of aggregated LDL to promote the formation of macrophage- and vascular smooth muscle cell (VSMC)-derived foam cells, which causes a prothrombotic transformation of the vascular wall. The dual and opposing roles of LRP1 may also represent an interesting target for atherosclerosis therapeutics. This review highlights the influence of LRP1 during atherosclerosis development, focusing on its dual role in vascular cells and immune cells.

Diet-Responsive Hypercholesterolemia With Cardiofaciocutaneous Syndrome Type 3

Background: Molecular basis of diet responsive hypercholesterolemia remains unclear. We report diet-responsive severe hypercholesterolemia in a young female with cardiofaciocutaneous syndrome type 3 (CFC3) due to a heterozygous pathogenic MAP2K1 variant, suggesting a role of common MAPK variants in LDL-cholesterol (LDL-C) response to diet. Clinical case: A 3-year-old Caucasian female with CFC3 (macrocephaly, frontal bossing, wide nasal root with depressed bridge, anteverted nares, low set fleshy ears, congenital pulmonic valve stenosis, postnatal growth deficiency, hypotonia, and neurocognitive impairment) due to a de novo heterozygous c.389A>G, p.Tyr130Cys pathogenic variant in MAP2K1, presented with extremely elevated serum total cholesterol of 446 mg/dL, triglycerides of 239 mg/dL, HDL-cholesterol of 53 mg/dL, LDL-C of 335 mg/dL (normal range < 110 mg/dL) and serum apolipoprotein B level 219 mg/dL (normal range < 90 mg/dL). Her LDL-C was 252 mg/dL a year ago and 215 mg/dL one month prior to presentation. Reducing total dietary fat to 20–25% of total energy and saturated fat to <6% of total energy over the next 4 months lowered LDL-C to 104 mg/dL. However, her weight decreased by 0.5 kg and liberalization of fat intake again increased LDL-C to 222 mg/dL. Her father has mildly elevated LDL-C of 160 mg/dL and her mother had normal LDL-C of 80 mg/dL. Her plasma phytosterol levels were normal and she had ApoE3/E3 genotype. Targeted genetic testing of the patient and parents showed a benign heterozygous LDL receptor (LDLR) variant c.2242G>A; p.Asp748Asn, (Minor allele frequency 0.00008) in the patient and her father. Whole exome sequencing of the patient and both parents showed no known disease-causing variants in LDLR, APOB, PCSK9, LDLRAP1, APOE, STAP1, LIPA, ABCG5, ABCG8 and other known hyperlipidemia-related genes. There are no previous reports of hypercholesterolemia in patients with CFC3. MAP2K1 stimulates various MAP kinases upon wide variety of extra- and intracellular signal and is involved in cell proliferation, differentiation, transcription regulation and development. Previous studies of the relationship between p42/44MAPK activation and LDLR expression in human hepatoma HepG2-derived cell line showed that that activation of the Raf-1/MEK/p42/44MAPK cascade induces LDLR expression and modulation of the Raf-1 kinase signal strength can determine LDLR expression levels. Thus, extent of MAPK activation can alter signaling of LDLR, resulting in hypercholesterolemia. Conclusion: Our case report suggests that MAP2K1 may play a significant role in LDLR signaling, and some MAP2K1 variants may be associated with diet-responsive hypercholesterolemia. Larger studies are required to assess dietary response to LDL-C in subjects with MAP2K1 variants.

Screening of PCSK9 and LDLR genetic variants in Familial Hypercholesterolemia (FH) patients in India.

Familial Hypercholesterolemia (FH) is an autosomal, dominant, inherited disorder characterized by severely elevated LDL-cholesterol (LDL-C) levels with high risk for Coronary Artery Disease (CAD). There are limited genetic studies especially on genes other than Low Density Lipoprotein receptor (LDLR) conducted in Indian population. Thus, our aim was to screen the entire Proprotein Convertase Subtilisin/Kexin type 9 gene (PCSK9) gene & hotspot exons 3, 4 and 9 of LDLR gene in FH cases and controls. 50 FH cases were categorized into definite, probable and possible cases according to Dutch Lipid Network Criteria (DLNC) who were gender matched with 50 healthy controls. All 12 exons of PCSK9, and hotspot exons 3, 4 & 9 of LDLR gene were screened through High Resolution Melt (HRM) curve analysis. Enzyme linked immunosorbent assay was performed to measure circulating PCSK9 levels. Total cholesterol and LDL-C were significantly high in all three groups of cases. Total 8 nonpathogenic variants in exon 1, 5, 7 and 9 of the PCSK9 gene were detected. In LDLR gene, 3 known pathogenic and 1 benign variant were found in exon 3 & 4. In FH cases, PCSK9 levels were significantly high compared to controls (P = 0.0001), and were directly correlated to LDL-C (P = 0.0001) and Total Cholesterol (P = 0.0001). Our study is first to screen the entire PCSK9 gene in western part of India. Since no pathogenic variants were identified, it is possible that PCSK9 variants are clinically less relevant. However, 3 known pathogenic variants were found in the LDLR gene. These findings support our understanding of the genetic spectrum of FH in India.

Hipercolesterolemia familiar en Gran Canaria: mutación con efecto fundador y alta frecuencia de diabetes

IntroductionGran Canaria is a region of genetic isolation of familial hypercholesterolemia due to a founder mutation, p. [Tyr400_Phe402del], in the LDL receptor (LDLR) gene. Initial data suggest that its carriers could have a high prevalence of diabetes. Material and methodsPatients over 30 years of age with familial hypercholesterolemia and a confirmed mutation in LDLR were recruited from a tertiary hospital in Gran Canaria. The prevalence of diabetes and other clinical data were compared among carriers of p. [Tyr400_Phe402del] and those with other LDLR mutations. Results76.4% of the 89 participants were carriers of p.[Tyr400_Phe402del]. The prevalence of diabetes in this group was significantly higher (25 vs. 4%, P=.045). These cases also had a higher prevalence of cardiovascular disease and higher levels of LDL cholesterol and triglycerides. There were no differences in age, weight, body mass index, waist, age of onset, and time of statin treatment. However, they required PCSK9 inhibitors more often (51.5 vs 24%, P=.027). ConclusionsThe mutation p.[Tyr400_Phe402del] is associated with a high prevalence of diabetes, not explained by classic risk factors, such as age, obesity, or long-term use of statins.

In-silico analysis of non-synonymous SNPs of human LDLR gene and their impact on familial hypercholesterolemia

Single nucleotide polymorphisms (SNPs) are the most regular type of genetic variation among human genome. The low-density lipoprotein receptors (LDLR) gene encoded receptor protein that specifically binds to low density lipoprotein (LDL), to act as prime cholesterol carriers in the blood. Unregulated removal of LDL from the circulation results from inherited mutations in the LDLR gene or, more rarely, in the apo B gene, the ligand for the LDLR causes familial hypercholesterolemia (FH). Several studies have shown that non-synonymous single nucleotide polymorphisms (nsSNPs) induce more than 50% genetic diseases. However, the growing number of SNPs in databases makes it difficult to evaluate the SNPs that come up with disease development. Therefore, we tried to identify the nsSNP within LDLR gene used mainly computational tools like: PROVEAN, Predict-SNP, SIFT, MAAP, SNAP, PhD-SNP, Polyphen v1, Polyphen v2, PANTHER and nsSNPAnalyzer. After analysing a total of 1114 missense SNPs, we found only 39 nsSNPs are most deleterious, whose conservation score ranges from grade ranges 7 to 9 that is assessed through ConSurf web server. Among 39 most significant nsSNPs, 11were predicted for involving in post translational modifications. Additionally, I-Mutant 2.0 and MUpro tool showed a decreased instability for these nsSNPs upon mutation. Protein structural analysis of these amino acid variants was performed by using I-Mutant 2.0. Stability analysis predicted 11 nsSNPs (C313W, F408K, A431P, A431S, A431T, D433H, D433Y, G546D, G546V, G546E and C697W), these are decreased protein stability. The in-silico analysis in current study may be a significant model for future research design studies.

SCREENING FOR GENETIC MUTATIONS IN LDLR GENE WITH FAMILIAL HYPERCHOLESTEROLEMIA IN THE MONGOLIAN POPULATION

Abstract Objective: The objective of this study was to characterize LDLR (low density lipoprotein receptor) gene mutation in patients with familial hypercholesterolemia. Design and method: Methods: This cross-sectional study was included subjects aged from 20 to 64 years, with a clinical diagnosis of familial hypercholesterolemia. Clinical diagnosis of familial hypercholesterolemia was based on Dutch Lipid Clinic Network diagnostic criteria. Possible and probable familial hypercholesterolemia were defined as a total score was 3–5 and 6–8 points. Ten ml of venous blood samples were collected from all the subjects and used for biochemical and genetic analysis. Deoxyribonucleic acid was isolated from peripheral blood samples and precise primers were designed for LDLR gene which includes 18 exons. Polymerize chain reaction test was followed by deoxyribonucleic acid sequence analysis. Results: Results: A total of 89 subjects included in the study of which, 32 (36%) were men and 57 (64%) were women. The mean age of the participants was 46.5 ± 7.8 years. In our study, we found the following 3 LDLR mutations: S265R mutation in Exon-6, C308Y mutation Exon-8 and V502 M mutation in Exon-10. Conclusions: Conclusion: This was the first study to identify genetic mutations in LDLR gene in Mongolia. We conclude that screening of family hypercholesterolemia among the Mongolian population is very important to identify individuals who are prone to develop the atherosclerotic cardiovascular disease.

Molecular Genetic Approach and Evaluation of Cardiovascular Events in Patients with Clinical Familial Hypercholesterolemia Phenotype from Romania.

This study identifies the genetic background of familial hypercholesterolemia (FH) patients in Romania and evaluates the association between mutations and cardiovascular events. We performed a prospective observational study of 61 patients with a clinical diagnosis of FH selected based on Dutch Lipid Clinic Network (DLCN) and Simon Broome score between 2017 and 2020. Two techniques were used to identify mutations: multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing. The mutation rate was 37.7%, i.e., 23 patients with mutations were identified, of which 7 subjects had pathogenic mutations and 16 had polymorphisms. Moreover, 10 variants of the low-density lipoprotein receptor (LDLR) gene were identified in 22 patients, i.e., one variant of the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene in six patients, and one variant of the apolipoprotein B (APOB) gene in three patients. Of the LDLR gene variants, four were LDLR pathogenic mutations (c.81C > G, c.502G > A, c.1618G > A mutations in exon 2, exon 4, exon 11, and exon 13–15 duplication). The PCSK9 and APOB gene variants were benign mutations. The pathogenic LDLR mutations were significant predictors of the new cardiovascular events, and the time interval for new cardiovascular events occurrence was significantly decreased, compared to FH patients without mutations. In total, 12 variants were identified, with four pathogenic variants identified in the LDLR gene, whereas 62.3% of the study population displayed no pathological mutations.

Initial characterization of the vitellogenin receptor from a Psocoptera insect: Function analysis and RNA interference in Liposcelis entomophila (Enderlein)

The psocid Liposcelis entomophila (Enderlein) is a nuisance pest of stored products, owing to its high reproduction capability. While vitellogenin receptor (VgR) is an important carrier for the uptake of vitellogenin (Vg) into developing oocytes, the identification and function of VgR in psocids remain unexplored currently. This study identified and characterised the full-length cDNA of L. entomophila vitellogenin receptor (LeVgR). The results revealed that LeVgR is 5916 bp long; encodes 1811 amino acid residues, and belongs to the low-density lipoprotein receptor (LDLR) gene superfamily. LeVgR was expressed exclusively in the ovary, first transcribed in 4th-instar nymphs, and then the transcript level increased gradually from adult emergence, reached the highest level in 13-day-old female adults, and gradually declined in 15- to 23-day-old female adults with slight fluctuations. Feeding with dsLeVgR disturbed the normal expression pattern of LeVgR, leading to a decrease in egg count and hatchability and inhibited ovary maturation. These results suggest that VgR is critical for the uptake of Vg into oocytes and plays a vital role in female reproduction. Furthermore, VgR may be an important potential target to disrupt insect reproduction for pest management by oral delivery of dsRNA.

Amplification of the Hazelnut-Induced Epigenetic Modulation of LDLR Gene Expression in THLE-2 Human Primary Hepatocytes Compared to HepG2 Hepatocarcinoma Cells

Dietary supplementation with tree nuts, including hazelnuts, has been associated with reduced cardiovascular disease risk factors, due to improved blood lipid profile. In the attempt to identify the molecular mechanism(s) underlying such beneficial effect, we here characterized the response of the human primary hepatocytes (THLE-2 cells) to the administration of an ethanolic extract of hazelnut (Corylus avellana L., cultivar Tonda Gentile Romana) in terms of regulation of the Low-Density Lipoprotein Receptor (LDLR), a major blood cholesterol carrier that positively correlates with improved blood lipids level. We demonstrated that hazelnut (0.004-0.4 mg/ml) does not alter viability and growth of primary liver cells, but significantly stimulates (P&lt;0.05) the LDLR mRNA and membrane protein expression. We also proved that LDLR increase is driven by an epigenetic-based mechanism, as hazelnut treatments trigger a strong DNA hypo-methylation of two CpG-rich regions in the LDLR gene promoter, mapping at -739/-548 and -221/+174 position. The hazelnutmediated hypo-methylation is much stronger and extensive in THLE-2 than in HepG2 human hepatocarcinoma cells, supporting the significance of the liver context for performing studies on dietary supplementation. As overall, our findings demonstrate that hazelnut triggers an epigenetic-dependent regulation of LDLR expression in human primary liver cells in vitro, thus identifying in the LDLR stimulation a molecular mechanism contributing to the health promoting functions of hazelnuts.

Selaginellin Derivatives from Selaginella tamariscina and Their Upregulating Effects on Low-Density Lipoprotein Receptor Expression.

Two new dimeric selaginellins, diselaginellins C and D (1 and 2), a new unusual derivative, selapiginellin A (4), a new selaginpulvilin U (5), and a known derivative, diselaginellin A (3), were isolated from Selaginella tamariscina (P. Beauv.) Spring. Among these compounds, selapiginellin A (4) is the first naturally occurring compound comprising an ether-linked dimer of a selaginellin and a selaginpulvilin. The absolute configurations of 1, 2, and 4 were elucidated by spectroscopic data analyses. Compound 5 was found to regulate mRNA expression of the low-density lipoprotein receptor (LDLR) gene and LDLR-related genes.

Transcription Factor MAFF (MAF Basic Leucine Zipper Transcription Factor F) Regulates an Atherosclerosis Relevant Network Connecting Inflammation and Cholesterol Metabolism.

Coronary artery disease (CAD) is a multifactorial condition with both genetic and exogenous causes. The contribution of tissue-specific functional networks to the development of atherosclerosis remains largely unclear. The aim of this study was to identify and characterize central regulators and networks leading to atherosclerosis. Based on several hundred genes known to affect atherosclerosis risk in mouse (as demonstrated in knockout models) and human (as shown by genome-wide association studies), liver gene regulatory networks were modeled. The hierarchical order and regulatory directions of genes within the network were based on Bayesian prediction models, as well as experimental studies including chromatin immunoprecipitation DNA-sequencing, chromatin immunoprecipitation mass spectrometry, overexpression, small interfering RNA knockdown in mouse and human liver cells, and knockout mouse experiments. Bioinformatics and correlation analyses were used to clarify associations between central genes and CAD phenotypes in both human and mouse. The transcription factor MAFF (MAF basic leucine zipper transcription factor F) interacted as a key driver of a liver network with 3 human genes at CAD genome-wide association studies loci and 11 atherosclerotic murine genes. Most importantly, expression levels of the low-density lipoprotein receptor (LDLR) gene correlated with MAFF in 600 CAD patients undergoing bypass surgery (STARNET [Stockholm-Tartu Atherosclerosis Reverse Network Engineering Task]) and a hybrid mouse diversity panel involving 105 different inbred mouse strains. Molecular mechanisms of MAFF were tested in noninflammatory conditions and showed positive correlation between MAFF and LDLR in vitro and in vivo. Interestingly, after lipopolysaccharide stimulation (inflammatory conditions), an inverse correlation between MAFF and LDLR in vitro and in vivo was observed. Chromatin immunoprecipitation mass spectrometry revealed that the human CAD genome-wide association studies candidate BACH1 (BTB domain and CNC homolog 1) assists MAFF in the presence of lipopolysaccharide stimulation with respective heterodimers binding at the MAF recognition element of the LDLR promoter to transcriptionally downregulate LDLR expression. The transcription factor MAFF was identified as a novel central regulator of an atherosclerosis/CAD-relevant liver network. MAFF triggered context-specific expression of LDLR and other genes known to affect CAD risk. Our results suggest that MAFF is a missing link between inflammation, lipid and lipoprotein metabolism, and a possible treatment target.

Molecular genetic testing for autosomal dominant hypercholesterolemia in 29,449 Norwegian index patients and 14,230 relatives during the years 1993–2020

Background and aimsIn this study, we present the status regarding molecular genetic testing for mutations in the genes encoding the low density lipoprotein receptor (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) as causes of autosomal dominant hypercholesterolemia (ADH) in Norway. MethodsWe have extracted data from the laboratory information management system at Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital for the period 1993–2020. This laboratory is the sole laboratory performing molecular genetic testing for ADH in Norway. ResultsA total of 29,449 unrelated hypercholesterolemic patients have been screened for mutations in the LDLR gene, in the APOB gene and in the PCSK9 gene. Of these, 2818 (9.6%) were heterozygotes and 11 were homozygotes or compound heterozygotes. Most of the 264 different mutations identified were found in the LDLR gene. Only two and three mutations were found in the APOB gene or in the PCSK9 gene, respectively. Several founder mutations were identified. After testing of 14,230 family members, a total of 8811 heterozygous patients have been identified. Of these, 94.0% had a mutation in the LDLR gene, 5.4% had a mutation in the APOB gene and 0.6% had a mutation in the PCSK9 gene. ConclusionsA large proportion of Norwegian ADH patients have been provided with a molecular genetic diagnosis. Norway is probably only second to the Netherlands in this respect. A molecular genetic diagnosis may form the basis for starting proper preventive measures and for identifying affected family members by cascade genetic screening.

Role of Genetic & Epigenetic Modifications of Low-Density Lipoprotein Receptor (LDLR) Gene in South Indian Acute Myocardial Infraction Patients

Background: Acute Myocardial Infarction (AMI) has conventional risk factors as well as genetic and epigenetic modifications of various genes. Among them gene coding for Low density lipoprotein receptor (LDLR) plays a strategic role in cholesterol homeostasis by eliminating excess LDL-C in blood. LDLR gene promoter polymorphism & DNA methylation status might regulate the expression of genes & its activity. Objective: The present study is designed to evaluate the association of LDLR gene promoter c.-139delCTCCCCCTGC polymorphism & DNA methylation status with Acute Myocardial Infarction (AMI). Methods: 300 angiographically documented MI patients and 300 healthy individuals were recruited for the study. Genomic DNA & RNA was extracted from the whole blood using commercially available assay kits further RNA was converted to cDNA. Biochemical parameters like Total cholesterol, LDL-C, HDL-C, and Triglycerides were estimated using kit methods. Results: The risk factors like systolic, diastolic blood pressures, hypertension, diabetes mellitus, smoking, lipids were found to be significantly higher in AMI patients compared to controls. The genotype and allele distributions of the LDLR c.-139del polymorphism revealed that DD genotype & D-allele were found to be higher among the AMI patients than that of controls. Furthermore, we have observed LDLR gene differential promoter DNA methylation status & mRNA expression. In addition, Insilco analysis have shown that there is a change in TF binding at the Insertion & Deletion sites. Conclusion: The findings of the study suggest that the LDLR c.-139del DD genotype might be used as prognostic marker in risk prediction of Acute Myocardial Infarction.

Apolipoprotein E, low-density lipoprotein receptor, and immune cells control blood-brain barrier penetration by AAV-PHP.eB in mice.

Rationale: The blood-brain barrier (BBB) prevents the effective delivery of therapeutic molecules to the central nervous system (CNS). A recently generated adeno-associated virus (AAV)-based vector, AAV-PHP.eB, has been found to penetrate the BBB more efficiently than other vectors including AAV-PHP.B. However, little is known about the mechanisms. In this study, we investigated how AAV-PHP.eB penetrates the BBB in mice.Methods: We injected AAV-PHP.eB into the bloodstream of wild-type C57BL/6 and BALB/c mice as well as mouse strains carrying genetic mutation in apolipoprotein E gene (Apoe) or low-density lipoprotein receptor gene (Ldlr), or lacking various components of the immune system. Then, we evaluated AAV-PHP.eB transduction to the brain and spinal cord in these mice.Results: We found that the transduction to the CNS of intravenous AAV-PHP.eB was more efficient in C57BL/6 than BALB/c mice, and significantly reduced in Apoe or Ldlr knockout C57BL/6 mice compared to wild-type C57BL/6 mice. Moreover, poor CNS transduction in BALB/c mice was dramatically increased by B-cell or natural killer-cell depletion.Conclusions: Our findings demonstrate that the ApoE-LDLR pathway underlies the CNS tropism of AAV-PHP.eB and that the immune system contributes to the strain specificity of AAV-PHP.eB.

A case of autosomal recessive hypercholesterolemia with a novel mutation in the LDLRAP1 gene.

Familial hypercholesterolemia (FH, OMIM number #143890), a life-threatening monogenic disorder characterized by high levels of low-density lipoprotein cholesterol (LDL-C), is classified into dominant and recessive types (1). The dominant form of FH may result from mutations in the LDLR, APOB, and PCSK9 genes (2). However, mutations in the low-density lipoprotein receptor (LDLR) adaptor protein-1 (LDLRAP1) gene cause an autosomal recessive inheritance pattern of FH called autosomal recessive hypercholesterolemia (ARH, OMIM number #603813). The LDLRAP1 protein, encoded by the LDLRAP1 gene, is required for receptor-mediated endocytosis of LDL-C (2). ARH is a rare disorder with an estimated prevalence of less than 1 in a population of one million. This disease is considered a phenocopy of the most severe form of FH, homozygous familial hypercholesterolemia (HoFH; OMIM number 143890). Hence, most ARH patients are clinically indiscernible from HoFH, which is caused by two defective LDLR genes with an approximate prevalence of one individual per million (8). Considering that ARH patients may develop aggressive and premature atherosclerotic cardiovascular disease (ASCVD) due to hypercholesterolemia during early adulthood, lipid-lowering therapy must be initiated during childhood (3). Early identification of ARH patients through genetic analysis of the proband and their relatives can provide prognosis and subsequently appropriate, timely treatment. In this report, we describe a novel variant, c.649G>T, p.Glu217Ter, in the homozygous state in exon 7 of the LDLRAP1 gene, causing severe ARH.

Ameliorative Effect of Trigonella Foenum Graecum L. on Lipid Profile, Liver Histology and LDL-Receptor Gene Expression in High Cholesterol-Fed Hamsters.

Trigonella foenum graecum L. (Fenugreek, FG) is used in many countries as a medicinal plant. Evidence has suggested the hypolipidemic effect of Fenugreek; however, its actual mechanism has not been determined yet. The purpose of our research was to investigate the effect of Fenugreek on lipid profile, liver histology and LDL receptor gene expression in male hamsters fed with high cholesterol diet. These animals were given normal diet (ND), high cholesterol diet (HCD: 2% cholesterol and 0.5% cholic acid added to ND), HCD supplemented with 2g and 8g fenugreek per 100g ND (HCD+FG2 and HCD+FG8) respectively for four weeks. At the end of treatment, serum lipids, lipoproteins and liver enzymes were measured. Finally, LDL receptor (LDLR) gene expression was determined in the liver of the studied animals using Real Time-PCR method and liver histological changes were evaluated by H&E staining method. A significant reduction was observed in serum triglyceride (p<0.01), total cholesterol, low and very low density cholesterol, aspartate and alanine transaminases in HCD+FG8 group (p<0.05) compared with HCD group, while serum level of HDL-c (p<0.01) increased. In addition, LDLR gene expression in HCD+FG8 group increased 7.8 folds. The results confirm the protection effect of liver tissue in HCD+FG8 group against pathological changes. There was no significant change in LDLR gene expression in HCD+FG2 group. In conclusion, fenugreek ameliorated dyslipidemia by up-regulation of LDLR gene expression and can be used as a protective agent against hypercholesterolemia.

Characterisation of LDL receptor gene mutations in a North Indian cohort of children with homozygous familial hypercholesterolaemia.

Homozygous familial hypercholesterolaemia (HoFH) carries agrave prognosis but is often underdiagnosed and undertreated. Confirmation of molecular diagnosis helps in planning effective management and determining prognosis accurately. Aim of the study: To determine the spectrum of mutations in the LDLR gene in acohort of children with aclinical diagnosis of HoFH. Genomic DNA was extracted from peripheral blood samples of 8 patients, who were children of either sex, aged under 16 years, and diagnosed clinically with HoFH using the Simon Broome criteria. The potential variants in the LDLR gene were analysed by Sanger sequencing. Fifty variations were found in the 8 patients; 39 (78%) were single nucleotide variations while 8 (16%) and 3 (6%) were deletions and insertions, respectively. The pathogenic variants in the LDLR gene were detected in four patients; three showed duplication in exon 17 (c.2416dupG) creating an amino acid change at position 806 (p.Val806GlyfsTer11) while one had amissense variant in the exon 9 at position c.1285G>A resulting in achange in amino acid at position 429 (p.Val429Met). The variants were found in heterozygous state in the parents or siblings of probands who showed pathogenic variants. The frequency of disease-causing variants in the LDLR gene in our patients with HoFH was 50%. Further studies to characterise mutations in genes for apolipoprotein B, proprotein convertase subtilisin/kexin type 9, or LDL adaptor protein are suggested in all children with aclinical diagnosis of HoFH.