Abstract 5: Sortilin Regulates Hepatic VLDL Secretion and LDL Uptake in a Lysosome-Dependent Manner

2012 ◽  
Vol 32 (suppl_1) ◽  
Author(s):  
Alanna Strong ◽  
Qiurong Ding ◽  
Andrew Edmondson ◽  
Sumeet Khetarpal ◽  
Carlos Morales ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Plasma Cholesterol ◽  
Association Studies ◽  
Ldl Receptor ◽  
Genome Wide Association Studies ◽  
Dependent Manner ◽  
Ldl Particles ◽  
Vldl Secretion ◽  
Ldl Uptake

Sortilin, the protein product of the SORT1 gene, is a multi-ligand sorting receptor involved in Golgi to lysosome and plasma membrane to lysosome protein trafficking. Genome wide association studies for lipid traits have identified the 1p13 locus harboring the SORT1 gene as strongly associated both with plasma low-density lipoprotein cholesterol (LDL-C) and myocardial infarction (MI) risk in humans. Adeno-associated virus (AAV)-mediated hepatic sortilin overexpression in LDL receptor deficient mice reduced plasma cholesterol by 30% at two weeks ( n = 6 mice per group, P = 0.02), with a concomitant reduction in LDL-C. In vivo VLDL production studies demonstrated a 50% reduction in the VLDL triglyceride secretion rate ( P = 0.007) and a 50% reduction in apoB secretion ( P = 0.02) with sortilin overexpression. In vivo LDL turnover studies demonstrated a 3-fold increase in the LDL fractional catabolic rate (FCR) with sortilin overexpression ( n = 6 mice per group, P = 0.00002). Sortilin deficiency both alone and on an LDL receptor deficient background led to a 40% and 50% reduction in FCR ( n = 6 mice per group, P = 0.002 and P = 0.01). The effect of sortilin on both VLDL secretion and LDL turnover is dependent on the ability of sortilin to traffic to the lysosome, as sortilin mutants that cannot traffic to the lysosome do not affect VLDL secretion or LDL uptake in vivo or in vitro . Surface plasmon reasonance demonstrated a high affinity interaction between sortilin and the apoB in LDL particles at physiological pH with a K d of ∼2 nM, and this affinity virtually disappears at the acidic lysosomal pH. In sum, these data are consistent with a model in which sortilin binds apoB-containing lipoprotein particles in the Golgi apparatus and at the plasma membrane and traffics them to the endolysosomal compartment for degradation, thereby reducing VLDL secretion and facilitating LDL uptake, explaining the strong association of hepatic sortilin overexpression in humans with reduced plasma cholesterol.

scholarly journals Statins Stimulate Hepatic Glucose Production via the miR-183/96/182 Cluster

2019 ◽  
Author(s):  
Tyler J. Marquart ◽  
Ryan M. Allen ◽  
Mary R. Chen ◽  
Gerald W. Dorn ◽  
Scot J. Matkovich ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Association Studies ◽  
Hepatic Glucose Production ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Hepatic Clearance ◽  
Glucose Production ◽  
Genome Wide Association Studies ◽  
Medical Advance

Statins are the most common pharmacologic intervention in hypercholesterolemic patients, and their use is recognized as a key medical advance leading to a 50% decrease in deaths from heart attack or stroke over the past 30 years. The atheroprotective outcomes of statins are largely attributable to the accelerated hepatic clearance of low-density lipoprotein (LDL)-cholesterol from circulation, following the induction of the LDL receptor. However, multiple studies suggest that these drugs exert additional LDL–independent effects. The molecular mechanisms behind these so-called pleiotropic effects of statins, either beneficial or undesired, remain largely unknown. Here we determined the coding transcriptome, miRNome, and RISCome of livers from mice dosed with saline or atorvastatin to define a novel in vivo epitranscriptional regulatory pathway that links statins to hepatic gluconeogenesis, via the SREBP2–miR-183/96/182–TCF7L2 axis. Notably, multiple genome-wide association studies identified TCF7L2 (transcription factor 7 like 2) as a candidate gene for type 2 diabetes, independent of ethnicity. Conclusion: our data reveal an unexpected link between cholesterol and glucose metabolism, provides a mechanistic explanation to the elevated risk of diabetes recently observed in patients taking statins, and identifies the miR-183/96/182 cluster as an attractive pharmacological candidate to modulate non-canonical effects of statins.

scholarly journals 25-Hydroxycholesterol amplifies microglial IL-1β production in an apoE isoform-dependent manner

2020 ◽  
Author(s):  
Man Ying Wong ◽  
Michael Lewis ◽  
James J. Doherty ◽  
Yang Shi ◽  
Patrick M. Sullivan ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Brain Tissue ◽  
Mouse Brain ◽  
Association Studies ◽  
Amyloid Β ◽  
Genome Wide Association Studies ◽  
Dependent Manner ◽  
Potassium Efflux ◽  
Caspase 1

AbstractGenome-wide association studies associated with Alzheimer’s disease (AD) have implicated pathways related to both lipid homeostasis and innate immunity in the pathophysiology of AD. However, the exact cellular and chemical mediators of neuroinflammation in AD remain poorly understood. The oxysterol 25-hydroxycholesterol (25-HC) is an important immunomodulator produced by peripheral macrophages with wide-ranging effects on cell signaling and innate immunity. Genetic variants of the enzyme responsible for 25-HC production, cholesterol 25-hydroxylase (CH25H), have been found to be associated with AD. In the present study, we found that the CH25H expression is upregulated in human AD brain tissue and in transgenic mouse brain tissue bearing amyloid-β (Aβ) plaques or tau pathology. Treatment with the toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS) markedly upregulates CH25H expression in the mouse brain in vivo. LPS also stimulates CH25H expression and 25-HC secretion in cultured mouse primary microglia. We also found that LPS-induced microglial production of the pro-inflammatory cytokine IL1β is markedly potentiated by 25-HC and attenuated by genetic deletion of CH25H. Microglia expressing apolipoprotein E4 (apoE4), a genetic risk factor for AD, produce greater amounts of 25-HC than apoE3-expressing microglia following treatment with LPS. Remarkably, treatment of microglia with 25-HC results in a much greater level of IL1β secretion in LPS-activated apoE4-expressing microglia than in apoE2- or apoE3-expressing microglia. Blocking potassium efflux or inhibiting caspase-1 prevents 25-HC-potentiated IL1β release in apoE4-expressing microglia, indicating the involvement of caspase-1/NLRP3 inflammasome activity. 25-HC may function as a microglial secreted inflammatory mediator in brain, promoting IL1β-mediated neuroinflammation in an apoE isoform-dependent manner (E4≫E2/E3) and thus may be an important mediator of neuroinflammation in AD.

A Variant Noncoding Region Regulates Prrx1 and Predisposes to Atrial Arrhythmias

2021 ◽  
Author(s):  
Fernanda M Bosada ◽  
Mathilde R Rivaud ◽  
Jae-Sun Uhm ◽  
Sander Verheule ◽  
Karel van Duijvenboden ◽  
...  
Keyword(s):  
Sodium Current ◽  
Association Studies ◽  
Noncoding Region ◽  
Specific Gene ◽  
Genome Wide Association Studies ◽  
Enhancer Activity ◽  
Atrial Cardiomyocytes ◽  
The Impact ◽  
Lineage Specific Gene

Rationale: Atrial Fibrillation (AF) is the most common cardiac arrhythmia diagnosed in clinical practice. Genome-wide association studies have identified AF-associated common variants across 100+ genomic loci, but the mechanism underlying the impact of these variant loci on AF susceptibility in vivo has remained largely undefined. One such variant region, highly associated with AF, is found at 1q24, close to PRRX1, encoding the Paired Related Homeobox 1 transcription factor. Objective: To identify the mechanistic link between the variant region at 1q24 and AF predisposition. Methods and Results: The mouse orthologue of the noncoding variant genomic region (R1A) at 1q24 was deleted using CRISPR genome editing. Among the genes sharing the topologically associated domain with the deleted R1A region (Kifap3, Prrx1, Fmo2, Prrc2c), only the broadly expressed gene Prrx1 was downregulated in mutants, and only in cardiomyocytes. Expression and epigenetic profiling revealed that a cardiomyocyte lineage-specific gene program (Mhrt, Myh6, Rbm20, Tnnt2, Ttn, Ckm) was upregulated in R1A-/- atrial cardiomyocytes, and that Mef2 binding motifs were significantly enriched at differentially accessible chromatin sites. Consistently, Prrx1 suppressed Mef2-activated enhancer activity in HL-1 cells. Mice heterozygous or homozygous for the R1A deletion were susceptible to atrial arrhythmia induction, had atrial conduction slowing and more irregular RR intervals. Isolated R1A-/- mouse left atrial cardiomyocytes showed lower action potential upstroke velocities and sodium current, as well as increased systolic and diastolic calcium concentrations compared to controls. Conclusions: The noncoding AF variant region at 1q24 modulates Prrx1 expression in cardiomyocytes. Cardiomyocyte-specific reduction of Prrx1 expression upon deletion of the noncoding region leads to a profound induction of a cardiac lineage-specific gene program and to propensity for AF. These data indicate that AF-associated variants in humans may exert AF predisposition through reduced PRRX1 expression in cardiomyocytes.

scholarly journals Combined knockout of Lrrk2 and Rab29 does not result in behavioral abnormalities in vivo

2020 ◽  
Author(s):  
Melissa Conti Mazza ◽  
Victoria Nguyen ◽  
Alexandra Beilina ◽  
Jinhui Ding ◽  
Mark R. Cookson
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Kinase Activity ◽  
Association Studies ◽  
Dopamine Neurons ◽  
Substantia Nigra Pars Compacta ◽  
Genome Wide Association Studies ◽  
Double Knockout ◽  
Knockout Mouse Model

AbstractCoding mutations in the LRRK2 gene, encoding for a large protein kinase, have been shown to cause familial Parkinson’s disease (PD). The immediate biological consequence of LRRK2 mutations is to increase kinase activity, leading to the suggestion that inhibition of this enzyme might be useful therapeutically to slow disease progression. Genome-wide association studies have identified the chromosomal loci around LRRK2 and one of its proposed substrates, RAB29, as contributors towards the lifetime risk of sporadic PD. Considering the evidence for interactions between LRRK2 and RAB29 on the genetic and protein levels, here we generated a double knockout mouse model and determined whether there are any consequences on brain function with aging. From a battery of motor and non-motor behavioral tests, we noted only that 18-24 month Rab29-/- and double (Lrrk2-/-/Rab29-/-) knockout mice had diminished locomotor behavior in open field compared to wildtype mice. However, no genotype differences were seen in number of substantia nigra pars compacta (SNc) dopamine neurons or in tyrosine hydroxylase levels in the SNc and striatum, which might reflect a PD-like pathology. These results suggest that depletion of both Lrrk2 and Rab29 is tolerated, at least in mice, and support that this pathway might be able to be safely targeted for therapeutics in humans.Significance statementGenetic variation in LRRK2 that result in elevated kinase activity can cause Parkinson’s disease (PD), suggesting LRRK2 inhibition as a therapeutic strategy. RAB29, a substrate of LRRK2, has also been associated with increased PD risk. Evidence exists for an interactive relationship between LRRK2 and RAB29. Mouse models lacking either LRRK2 or RAB29 do not show brain pathologies. We hypothesized that the loss of both targets would result in additive effects across in vivo and post-mortem assessments in aging mice. We found that loss of both LRRK2 and RAB29 did not result in significant behavioral deficits or dopamine neuron loss. This evidence suggests that chronic inhibition of this pathway should be tolerated clinically.

scholarly journals Perspective of the GEMSTONE Consortium on Current and Future Approaches to Functional Validation for Skeletal Genetic Disease Using Cellular, Molecular and Animal-Modeling Techniques

2021 ◽  
Vol 12 ◽  
Author(s):  
Martina Rauner ◽  
Ines Foessl ◽  
Melissa M. Formosa ◽  
Erika Kague ◽  
Vid Prijatelj ◽  
...  
Keyword(s):  
Resource Sharing ◽  
Complex Traits ◽  
Cellular Localization ◽  
Target Genes ◽  
Mission Statement ◽  
Association Studies ◽  
Repetitive Sequences ◽  
Genome Wide Association Studies ◽  
Causal Genes

The availability of large human datasets for genome-wide association studies (GWAS) and the advancement of sequencing technologies have boosted the identification of genetic variants in complex and rare diseases in the skeletal field. Yet, interpreting results from human association studies remains a challenge. To bridge the gap between genetic association and causality, a systematic functional investigation is necessary. Multiple unknowns exist for putative causal genes, including cellular localization of the molecular function. Intermediate traits (“endophenotypes”), e.g. molecular quantitative trait loci (molQTLs), are needed to identify mechanisms of underlying associations. Furthermore, index variants often reside in non-coding regions of the genome, therefore challenging for interpretation. Knowledge of non-coding variance (e.g. ncRNAs), repetitive sequences, and regulatory interactions between enhancers and their target genes is central for understanding causal genes in skeletal conditions. Animal models with deep skeletal phenotyping and cell culture models have already facilitated fine mapping of some association signals, elucidated gene mechanisms, and revealed disease-relevant biology. However, to accelerate research towards bridging the current gap between association and causality in skeletal diseases, alternative in vivo platforms need to be used and developed in parallel with the current -omics and traditional in vivo resources. Therefore, we argue that as a field we need to establish resource-sharing standards to collectively address complex research questions. These standards will promote data integration from various -omics technologies and functional dissection of human complex traits. In this mission statement, we review the current available resources and as a group propose a consensus to facilitate resource sharing using existing and future resources. Such coordination efforts will maximize the acquisition of knowledge from different approaches and thus reduce redundancy and duplication of resources. These measures will help to understand the pathogenesis of osteoporosis and other skeletal diseases towards defining new and more efficient therapeutic targets.

scholarly journals Asthma-associated genetic variants induce IL33 differential expression through an enhancer-blocking regulatory region

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ivy Aneas ◽  
Donna C. Decker ◽  
Chanie L. Howard ◽  
Débora R. Sobreira ◽  
Noboru J. Sakabe ◽  
...  
Keyword(s):  
Association Studies ◽  
Regulatory Region ◽  
Airway Epithelial Cells ◽  
Genome Wide Association Studies ◽  
Airway Epithelial ◽  
Allele Specific ◽  
Enhancer Blocking ◽  
Underlying Mechanisms

AbstractGenome-wide association studies (GWAS) have implicated the IL33 locus in asthma, but the underlying mechanisms remain unclear. Here, we identify a 5 kb region within the GWAS-defined segment that acts as an enhancer-blocking element in vivo and in vitro. Chromatin conformation capture showed that this 5 kb region loops to the IL33 promoter, potentially regulating its expression. We show that the asthma-associated single nucleotide polymorphism (SNP) rs1888909, located within the 5 kb region, is associated with IL33 gene expression in human airway epithelial cells and IL-33 protein expression in human plasma, potentially through differential binding of OCT-1 (POU2F1) to the asthma-risk allele. Our data demonstrate that asthma-associated variants at the IL33 locus mediate allele-specific regulatory activity and IL33 expression, providing a mechanism through which a regulatory SNP contributes to genetic risk of asthma.

Abstract 49: Adipose-Specific Knockout of Trib1 Reduces Plasma Lipids and Diet-Induced Insulin Resistance, and Increases Circulating Adiponectin

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Mikhaila A Smith ◽  
Jian Cui ◽  
Sumeet A Kheterpal ◽  
Daniel J Rader ◽  
Robert C Bauer
Keyword(s):  
Body Mass ◽  
Plasma Lipids ◽  
Association Studies ◽  
Genome Wide Association Studies ◽  
Genetic Associations ◽  
Tissue Mass ◽  
Fed State ◽  
Plasma Adiponectin ◽  
Metabolic Role

Tribbles-1 (TRIB1) was recently identified through genome-wide association studies as a novel mediator of plasma lipids and coronary artery disease in humans. While subsequent in vivo mouse work confirmed a role for hepatic TRIB1 in these associations, little is known about metabolic roles for extra-hepatic Trib1. Interestingly, SNPs near the TRIB1 gene are significantly associated with circulating adiponectin levels in humans, suggesting a metabolic role for adipose TRIB1 . To further investigate this, we generated adipose-specific Trib1 KO mice (Trib1_ASKO) by crossing Trib1 cKO mice to transgenic Adiponectin-Cre mice. Chow-fed Trib1_ASKO mice exhibited no differences in adipose tissue mass and overall body mass as compared to control littermates (N=8/group). However, Trib1_ASKO mice had reduced total (-16.9%, p <0.01), HDL (-16.7%, p <0.01), and non-HDL cholesterol (-17.3%, p =0.068), as well as plasma triglycerides (-28.6%, p <0.001) as compared to WT mice. Trib1_ASKO mice also had increased plasma adiponectin levels, a finding more pronounced in female mice (+33.3%, p <0.001) than in males (+16.4%, p =0.072). Despite this increase, transcript levels of adipoQ were moderately decreased in Trib1_ASKO mice, suggesting a post-transcriptional mode of regulation. Transcript and protein levels of C/EBPα, the best described target of Trib1 and a key regulator of adipogenesis, remained unchanged. To further investigate the metabolic consequences of adipose-specific KO of Trib1 , WT and Trib1_ASKO mice were fed high-fat diet (HFD, 45% kCal fat) for 12 weeks to induce obesity. HFD-fed Trib1_ASKO mice had reduced fasting plasma glucose (-22.3%, p <0.05), insulin (-38.2%, p <0.05), and glucose tolerance (-19.8% AUC, p <0.05) compared to control mice. Body mass and fat mass of HFD-fed Trib1_ASKO mice remained unchanged from WT, and the reductions in plasma lipids and increase in plasma adiponectin persisted in the HFD-fed state. In summary, we present here the first in vivo validation of the human genetic association between TRIB1 and plasma adiponectin, and provide evidence suggesting that adipose TRIB1 contributes to the genetic associations observed in humans between TRIB1 and multiple metabolic parameters.

scholarly journals The VNTR of the AS3MT gene is associated with brain activations during a memory span task and their training-induced plasticity

2020 ◽  
pp. 1-6 ◽  
Author(s):  
Wan Zhao ◽  
Qiumei Zhang ◽  
Xiongying Chen ◽  
Yang Li ◽  
Xiaohong Li ◽  
...  
Keyword(s):  
Neural Plasticity ◽  
Large Scale ◽  
Memory Span ◽  
Association Studies ◽  
Variable Number Tandem Repeat ◽  
Brain Activation ◽  
Head Movements ◽  
Span Task ◽  
Genome Wide Association Studies

Abstract Background The Arsenic (+3 oxidation state) methyltransferase (AS3MT) gene has been identified as a top risk gene for schizophrenia in several large-scale genome-wide association studies. A variable number tandem repeat (VNTR) of this gene is the most significant expression quantitative trait locus, but its role in brain activity in vivo is still unknown. Methods We first performed a functional magnetic resonance imaging (fMRI) scan of 101 healthy subjects during a memory span task, trained all subjects on an adaptive memory span task for 1 month, and finally performed another fMRI scan after the training. After excluding subjects with excessive head movements for one or more scanning sessions, data from 93 subjects were included in the final analyses. Results The VNTR was significantly associated with both baseline brain activation and training-induced changes in multiple regions including the prefrontal cortex and the anterior and posterior cingulate cortex. Additionally, it was associated with baseline brain activation in the striatum and the parietal cortex. All these results were corrected based on the family-wise error rate method across the whole brain at the peak level. Conclusions This study sheds light on the role of AS3MT gene variants in neural plasticity related to memory span training.

scholarly journals Hypertriglyceridemia and Lower LDL Cholesterol Concentration in Relation to Apolipoprotein E Phenotypes in Myotonic Dystrophy

1989 ◽  
Vol 16 (1) ◽  
pp. 129-133 ◽  
Author(s):  
Sital Moorjani ◽  
Daniel Gaudet ◽  
Claude Laberge ◽  
Marie Christine Thibault ◽  
Jean Mathieu ◽  
...  
Keyword(s):  
Myotonic Dystrophy ◽  
Ldl Cholesterol ◽  
Plasma Cholesterol ◽  
Plasma Lipid ◽  
Cholesterol Concentration ◽  
Plasma Triglycerides ◽  
Ldl Particles ◽  
Vldl Cholesterol ◽  
Apo E

ABSTRACT:Plasma lipid, lipoprotein levels and apolipoprotein apo E phenotypes were determined in 70 patients with myotonic dystrophy (MyD) and 81 controls. Marked differences were noticed in the apo E phenotype frequencies between the two groups. Plasma triglycerides and VLDL cholesterol were higher in MyD than controls, but only the latter was related to differences in the apo E phenotypes between two groups. Accordingly, the ratio of VLDL cholesterol/plasma triglycerides was increased significantly in MyD, suggesting accumulation of intermediary density particles due to lower affinity of E2 containing lipoproteins for lipoprotein cell receptors. The LDL cholesterol concentration was lower in MyD than controls and was related to differences in the apo E phenotype frequencies between the two groups. These results indicate increased removal of LDL particles in the apo E2 phenotypes, perhaps due to upregulation of LDL (B, E) receptor activity. Plasma cholesterol and HDL cholesterol concentrations were similar in both groups. Another feature of the study was lower levels of plasma cholesterol, triglycerides, VLDL and LDL cholesterol in the homozygous E4:E4 phenotype. These results suggest increased clearance rate of both VLDL and LDL particles and support the concept that apo E4-containing lipoproteins have higher in vivo affinity for ape E and/or B, E receptors.

scholarly journals Atherosclerosis in Different Vascular Locations Unbiasedly Approached with Mouse Genetics

Genes ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1427
Author(s):  
Yukako Kayashima ◽  
Nobuyo Maeda-Smithies
Keyword(s):  
Progenitor Cells ◽  
Plasma Cholesterol ◽  
Association Studies ◽  
Strain Differences ◽  
Mouse Genetics ◽  
Genome Wide Association Studies ◽  
Vascular Integrity ◽  
Plaque Development ◽  
Inflammatory Stimuli ◽  
Clinical Consequences

Atherosclerosis in different vascular locations leads to distinct clinical consequences, such as ischemic stroke and myocardial infarction. Genome-wide association studies in humans revealed that genetic loci responsible for carotid plaque and coronary artery disease were not overlapping, suggesting that distinct genetic pathways might be involved for each location. While elevated plasma cholesterol is a common risk factor, plaque development in different vascular beds is influenced by hemodynamics and intrinsic vascular integrity. Despite the limitation of species differences, mouse models provide platforms for unbiased genetic approaches. Mouse strain differences also indicate that susceptibility to atherosclerosis varies, depending on vascular locations, and that the location specificity is genetically controlled. Quantitative trait loci analyses in mice suggested candidate genes, including Mertk and Stab2, although how each gene affects the location-specific atherosclerosis needs further elucidation. Another unbiased approach of single-cell transcriptome analyses revealed the presence of a small subpopulation of vascular smooth muscle cells (VSMCs), which are “hyper-responsive” to inflammatory stimuli. These cells are likely the previously-reported Sca1+ progenitor cells, which can differentiate into multiple lineages in plaques. Further spatiotemporal analyses of the progenitor cells are necessary, since their distribution pattern might be associated with the location-dependent plaque development.

Sign in / Sign up

Export Citation Format

Share Document