Lipoprotein Research Articles

Dissecting the shared genetic architecture between Alzheimer's disease and frailty: a cross-trait meta-analyses of genome-wide association studies.

Introduction: Frailty is the most common medical condition affecting the aging population, and its prevalence increases in the population aged 65 or more. Frailty is commonly diagnosed using the frailty index (FI) or frailty phenotype (FP) assessments. Observational studies have indicated the association of frailty with Alzheimer's disease (AD). However, the shared genetic and biological mechanism of these comorbidity has not been studied. Methods: To assess the genetic relationship between AD and frailty, we examined it at single nucleotide polymorphism (SNP), gene, and pathway levels. Results: Overall, 16 genome-wide significant loci (15 unique loci) (p meta-analysis < 5 × 10-8) and 22 genes (21 unique genes) were identified between AD and frailty using cross-trait meta-analysis. The 8 shared loci implicated 11 genes: CLRN1-AS1, CRHR1, FERMT2, GRK4, LINC01929, LRFN2, MADD, RP11-368P15.1, RP11-166N6.2, RNA5SP459, and ZNF652 between AD and FI, and 8 shared loci between AD and FFS implicated 11 genes: AFF3, C1QTNF4, CLEC16A, FAM180B, FBXL19, GRK4, LINC01104, MAD1L1, RGS12, ZDHHC5, and ZNF521. The loci 4p16.3 (GRK4) was identified in both meta-analyses. The colocalization analysis supported the results of our meta-analysis in these loci. The gene-based analysis revealed 80 genes between AD and frailty, and 4 genes were initially identified in our meta-analyses: C1QTNF4, CRHR1, MAD1L1, and RGS12. The pathway analysis showed enrichment for lipoprotein particle plasma, amyloid fibril formation, protein kinase regulator, and tau protein binding. Conclusion: Overall, our results provide new insights into the genetics of AD and frailty, suggesting the existence of non-causal shared genetic mechanisms between these conditions.

Lipoproteins are key immunostimulatory components of Bacillus species for dendritic cell maturation and activation

Dendritic cells (DCs) play an important role in immunity by sensing and responding to invasive microbes. Bacillus species are rod-shaped sporulating bacteria that include the pathogenic Bacillus cereus and commensal Bacillus subtilis. Although the interaction between DC and these two Bacillus species has been studied, their key structural component that prompts DC activation is poorly understood. Here, we investigated the two Bacillus species in DC activation by whole cells and their representative microbe-associated molecular patterns (MAMPs). MAMPs including lipoteichoic acid (LTA), lipoprotein (LPP), and peptidoglycan (PGN) were purified from the two Bacillus species. Among the MAMPs, LPP from both species most potently induced the maturation and activation of DCs while PGN, but not LTA, moderately stimulated DCs. LPPs from both Bacillus species enhanced the expression of DC maturation markers including CCR7, CD40, CD80, CD83, CD86, CD205, MHC-I, and MHC-II. Among the MAMPs from B. cereus, PGN most considerably lowered the endocytic capacity of DCs implying DC maturation whereas PGN from B. subtilis lowered it to a similar degree to its LPP. Furthermore, DCs sensitized with LPPs from both Bacillus species and PGN from B. subtilis moderately induced TNF-α and IL-6 production. Notably, a combination of MAMPs did not show any synergistic effect on DC activation. Taken together, our results demonstrate that LPP is the key structural component in B. cereus and B. subtilis that leads to DC activation.

Unique Metabolomic and Lipidomic Profile in Serum From Patients With Crohn's Disease and Ulcerative Colitis Compared With Healthy Control Individuals.

Accurate biomarkers for disease activity and progression in patients with inflammatory bowel disease (IBD) are a prerequisite for individual disease characterization and personalized therapy. We show that metabolic profiling of serum from IBD patients is a promising approach to establish biomarkers. The aim of this work was to characterize metabolomic and lipidomic serum profiles of IBD patients in order to identify metabolic fingerprints unique to the disease. Serum samples were obtained from 55 patients with Crohn's disease (CD), 34 patients with ulcerative colitis (UC), and 40 healthy control (HC) individuals and analyzed using proton nuclear magnetic resonance spectroscopy. Classification of patients and HC individuals was achieved by orthogonal partial least squares discriminant analysis and univariate analysis approaches. Disease activity was assessed using the Gastrointestinal Symptom Rating Scale. Serum metabolome significantly differed between CD patients, UC patients, and HC individuals. The metabolomic differences of UC and CD patients compared with HC individuals were more pronounced than the differences between UC and CD patients. Differences in serum levels of pyruvic acid, histidine, and the branched-chain amino acids leucine and valine were detected. The size of low-density lipoprotein particles shifted from large to small dense particles in patients with CD. Of note, apolipoprotein A1 and A2 serum levels were decreased in CD and UC patients with higher fecal calprotectin levels. The Gastrointestinal Symptom Rating Scale is negatively associated with the concentration of apolipoprotein A2. Metabolomic assessment of serum samples facilitated the differentiation of IBD patients and HC individuals. These differences were constituted by changes in amino acid and lipoprotein levels. Furthermore, disease activity in IBD patients was associated with decreased levels of the atheroprotective apolipoproteins A1 and A2.

Prediction and verification of the prognostic biomarker SLC2A2 and its association with immune infiltration in gastric cancer.

Gastric cancer (GC) is the fifth most common cause of cancer-associated deaths; however, its treatment options are limited. Despite clinical improvements, chemotherapy resistance and metastasis are major challenges in improving the prognosis and quality of life of patients with GC. Therefore, effective prognostic biomarkers and targets associated with immunological interventions need to be identified. Solute carrier family 2 member 2 (SLC2A2) may serve a role in tumor development and invasion. The present study aimed to evaluate SLC2A2 as a prospective prognostic marker and chemotherapeutic target for GC. SLC2A2 expression in several types of cancer and GC was analyzed using online databases, and the effects of SLC2A2 expression on survival prognosis in GC were investigated. Clinicopathological parameters were examined to explore the association between SLC2A2 expression and overall survival (OS). Associations between SLC2A2 expression and immune infiltration, immune checkpoints and IC50 were estimated using quantification of the tumor immune contexture from human RNA-seq data, the Tumor Immune Estimation Resource 2.0 database and the Genomics of Drug Sensitivity in Cancer database. Differential SLC2A2 expression and the predictive value were validated using the Human Protein Atlas, Gene Expression Omnibus, immunohistochemistry and reverse transcription-quantitative PCR. SLC2A2 expression was downregulated in most types of tumor but upregulated in GC. Functional enrichment analysis revealed an association between SLC2A2 expression and lipid metabolism and the tumor immune microenvironment. According to Gene Ontology term functional enrichment analysis, SLC2A2-related differentially expressed genes were enriched predominantly in 'chylomicron assembly', 'plasma lipoprotein particle assembly', 'high-density lipoprotein particle', 'chylomicron', 'triglyceride-rich plasma lipoprotein particle', 'very-low-density lipoprotein particle'. 'intermembrane lipid transfer activity', 'lipoprotein particle receptor binding', 'cholesterol transporter activity' and 'intermembrane cholesterol transfer activity'. In addition, 'cholesterol metabolism', and 'fat digestion and absorption' were significantly enriched in the Kyoto Encyclopedia of Genes and Genomes pathway analysis. Patients with GC with high SLC2A2 expression had higher levels of neutrophil and M2 macrophage infiltration and a significant inverse correlation was observed between SLC2A2 expression and MYC targets, tumor mutation burden, microsatellite instability and immune checkpoints. Furthermore, patients with high SLC2A2 expression had worse prognosis, including OS, disease-specific survival and progression-free interval. Multivariate regression analysis demonstrated that SLC2A2 could independently prognosticate GC and the nomogram model showed favorable performance for survival prediction. SLC2A2 may be a prospective prognostic marker for GC. The prediction model may improve the prognosis of patients with GC in clinical practice, and SLC2A2 may serve as a novel therapeutic target to provide immunotherapy plans for GC.

Associations of diet quality and food consumption with serum biomarkers for lipid and amino acid metabolism in Finnish children: the PANIC study.

To investigate the associations of overall diet quality and dietary factors with serum biomarkers for lipid and amino acid metabolism in a general population of children. We studied 194 girls and 209 boys aged 6-8years participating in the Physical Activity and Nutrition in Children study. Food consumption was assessed by 4-day food records and diet quality was quantified by the Finnish Children Healthy Eating Index (FCHEI). Fasting serum fatty acids, amino acids, apolipoproteins, as well as lipoprotein particle sizes were analyzed with high-throughput nuclear magnetic resonance spectroscopy. Data were analyzed using linear regression adjusted for age, sex, and body fat percentage. FCHEI was directly associated with the ratio of polyunsaturated (PUFA) to saturated fatty acids (SFA) (PUFA/SFA), the ratio of PUFA to monounsaturated fatty acids (MUFA) (PUFA/MUFA), the ratio of PUFA to total fatty acids (FA) (PUFA%), the ratio of omega-3-fatty acids to total FA (omega-3 FA%), and inversely associated with the ratio of MUFA to total FA (MUFA%), alanine, glycine, histidine and very-low density lipoprotein (VLDL) particle size. Consumption of vegetable oils and vegetable-oil-based margarine (≥ 60% fat) was directly associated with PUFA/SFA, PUFA/MUFA, PUFA%, the ratio of omega-6 FA to total FA (omega-6 FA%), and inversely associated with SFA, MUFA, SFA to total FA (SFA%), MUFA%, alanine and VLDL particle size. Consumption of high-fiber grain products directly associated with PUFA/SFA, PUFA/MUFA, omega-3 FA%, omega-6 FA%, PUFA% and inversely associated with SFA and SFA%. Fish consumption directly related to omega-3 FA and omega-3 FA%. Consumption of sugary products was directly associated with histidine and VLDL particle size. Vegetable, fruit, and berry consumption had direct associations with VLDL particle size and the ratio of apolipoprotein B to apolipoprotein A1. Consumption of low fat (< 1%) milk was directly associated with phenylalanine. A higher consumption of high-fat (≥ 1%) milk was associated with lower serum MUFA/SFA and higher SFA%. Sausage consumption was directly related to SFA% and histidine. Red meat consumption was inversely associated with glycine. Better diet quality, higher in intake of dietary sources of unsaturated fat and fiber, and lower in sugary product intake were associated with more favorable levels of serum biomarkers for lipid and amino acid metabolism independent of adiposity. ClinicalTrials.gov: NCT01803776, registered March 3, 2013.

Consuming Mushrooms When Adopting a Healthy Mediterranean-Style Dietary Pattern Does Not Influence Short-Term Changes of Most Cardiometabolic Disease Risk Factors in Healthy Middle-Aged and Older Adults

BackgroundMushrooms are a nutritious food, though knowledge of the effects of mushroom consumption on cardiometabolic risk factors is limited and inconsistent. ObjectiveWe assessed the effects of consuming mushrooms as part of a healthy United States Mediterranean-style dietary pattern (MED) on traditional and emerging cardiometabolic disease (CMD) risk factors. We hypothesized that adopting a MED diet with mushrooms would lead to greater improvements in multiple CMD risk factors. MethodsUsing a randomized, parallel study design, 60 adults (36 females, 24 males; aged 46 ± 12 y; body mass index 28.3 ± 2.84 kg/m2, mean ± standard deviation) without diagnosed CMD morbidities consumed a MED diet (all foods provided) without (control with breadcrumbs) or with 84 g/d of Agaricus bisporus (White Button, 4 d/wk) and Pleurotus ostreatus (Oyster, 3 d/wk) mushrooms for 8 wk. Fasting baseline and postintervention outcome measurements were traditional CMD risk factors, including blood pressure and fasting serum lipids, lipoproteins, glucose, and insulin. Exploratory CMD-related outcomes included lipoprotein particle sizes and indexes of inflammation. ResultsAdopting the MED-mushroom diet compared with the MED-control diet without mushrooms improved fasting serum glucose (change from baseline −2.9 ± 1.18 compared with 0.6 ± 1.10 mg/dL; time × group P = 0.034). Adopting the MED diet, independent of mushroom consumption, reduced serum total cholesterol (−10.2 ± 3.77 mg/dL; time P = 0.0001). Concomitantly, there was a reduction in high-density lipoprotein (HDL) cholesterol, buoyant HDL2b, and apolipoprotein A1, and an increase in lipoprotein(a) concentrations (main effect of time P < 0.05 for all). There were no changes in other measured CMD risk factors. ConclusionsConsuming a Mediterranean-style healthy dietary pattern with 1 serving/d of whole Agaricus bisporus and Pleurotus ostreatus mushrooms improved fasting serum glucose but did not influence other established or emerging CMD risk factors among middle-aged and older adults classified as overweight or obese but with clinically normal cardiometabolic health. Trial registration numberhttps://www.clinicaltrials.gov/study/NCT04259229?term=NCT04259229&rank=1

Novel Insights into the Link Between Myeloperoxidase Modified LDL, LOX-1, and Neuroserpin in Stroke.

Cardiovascular disease that is caused by atherosclerosis is the leading cause of death worldwide. Atherosclerosis is primarily triggered by endothelial dysfunction and the accumulation of modified low-density lipoprotein (LDL) particles in the subendothelial space of blood vessels. Early reports have associated oxidized LDL with altered fibrinolysis and atherogenesis. It has been suggested that myeloperoxidase oxidized LDL (Mox-LDL) is involved in atherosclerosis because of its significant pathophysiological role in the modification of LDL in vivo. It has been equally demonstrated that Mox-LDL binds to the lectin-like oxidized low-density lipoprotein receptor-1 (lox-1) scavenger receptor which leads to the upregulation of inflammatory mediators in endothelial cells and the progression of cardiovascular disease. It has been also shown that neuroserpin, a member of the serine proteinase inhibitor (serpin) superfamily, has an important role at the level of fibrinolysis in the nervous tissue. Since little is known about the effects of Mox-LDL on endothelial cell fibrinolytic activity and the involvement of lox-1 in this process, our study aimed at evaluating the in vitro effects of Mox-LDL on neuroserpin release from human aortic endothelial cells (HAECs) and the role of lox-1 scavenger receptor in this context by relying on lox-1 gene silencing in HAECs, culturing the cells in the presence of Mox-LDL, measuring their neuroserpin expression and release by quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA), respectively, and assessing their fibrinolytic activity using the Euglobulin Clot Lysis Time (ECLT) method. Our data show that Mox-LDL decreases endothelial cell fibrinolytic capacity by upregulating neuroserpin in lox-1 knockdown cells. Lox-1 protects the endothelial cells from a Mox-LDL-induced decrease in pro-fibrinolytic capacity, which has important consequences in the context of stroke.

Acute myocardial infarction preferentially alters low-abundant, long-chain unsaturated phospholipid and sphingolipid species in plasma high-density lipoprotein subpopulations

AimHigh-density lipoprotein (HDL) particles in ST-segment elevation myocardial infarction (STEMI) are deficient in their anti-atherogenic function. Molecular determinants of such deficiency remain obscure. MethodsFive major HDL subpopulations were isolated using density-gradient ultracentrifugation from STEMI patients (n = 12) and healthy age- and sex-matched controls (n = 12), and 160 species of phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylglycerol, phosphatidylserine, phosphatidic acid, sphingomyelin and ceramide were quantified by LC-MS/MS. ResultsMultiple minor species of proinflammatory phosphatidic acid and lysophosphatidylcholine were enriched by 1.7–27.2-fold throughout the majority of HDL subpopulations in STEMI. In contrast, minor phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, sphingomyelin and ceramide species were typically depleted up to 3-fold in STEMI vs. control HDLs, while abundances of their major species did not differ between the groups. Intermediate-to-long-chain phosphatidylcholine, phosphatidylinositol and phosphatidylglycerol species were more affected by STEMI than their short-chain counterparts, resulting in positive correlations between their fold decrease and the carbon chain length. Additionally, fold decreases in the abundances of multiple lipid species were positively correlated with the double bond number in their carbon chains. Finally, abundances of several phospholipid and ceramide species were positively correlated with cholesterol efflux capacity and antioxidative activity of HDL subpopulations, both reduced in STEMI vs controls. KEGG pathway analysis tied these species to altered glycerophospholipid and linoleic acid metabolism. ConclusionsMinor unsaturated intermediate-to-long-chain phospholipid and sphingolipid species in HDL subpopulations are most affected by STEMI, reflecting alterations in glycerophospholipid and linoleic acid metabolism with the accumulation of proinflammatory lysolipids and maintenance of homeostasis of major phospholipid species.

Defining the Cell Surface Cysteinome Using Two-Step Enrichment Proteomics.

The plasma membrane proteome is a rich resource of functionally important and therapeutically relevant protein targets. Distinguished by high hydrophobicity, heavy glycosylation, disulfide-rich sequences, and low overall abundance, the cell surface proteome remains undersampled in established proteomic pipelines, including our own cysteine chemoproteomics platforms. Here, we paired cell surface glycoprotein capture with cysteine chemoproteomics to establish a two-stage enrichment method that enables chemoproteomic profiling of cell Surface Cysteinome. Our "Cys-Surf" platform captures >2,800 total membrane protein cysteines in 1,046 proteins, including 1,907 residues not previously captured by bulk proteomic analysis. By pairing Cys-Surf with an isotopic chemoproteomic readout, we uncovered 821 total ligandable cysteines, including known and novel sites. Cys-Surf also robustly delineates redox-sensitive cysteines, including cysteines prone to activation-dependent changes to cysteine oxidation state and residues sensitive to addition of exogenous reductants. Exemplifying the capacity of Cys-Surf to delineate functionally important cysteines, we identified a redox sensitive cysteine in the low-density lipoprotein receptor (LDLR) that impacts both the protein localization and uptake of low-density lipoprotein (LDL) particles. Taken together, the Cys-Surf platform, distinguished by its two-stage enrichment paradigm, represents a tailored approach to delineate the functional and therapeutic potential of the plasma membrane cysteinome.

Genetic study of the causal effect of lipid profiles on insomnia risk: a Mendelian randomization trial

ObjectivesIn response to the controversy surrounding observational studies of the association between lipid profiles and the risk of insomnia, the aim of this study was to analyze lipid profiles, including triglycerides (TG), apolipoprotein A-1 (ApoA-1), apolipoprotein B (ApoB) and lipoprotein A (LPA), in a European population to further assess the causal relationship between these lipid types and insomnia.Materials and methodsThis study explores the causal effect of lipid profiles on insomnia based on a genome-wide association study (GWAS)-derived public dataset using two-sample and multivariate Mendelian randomization (MVMR) analysis. The main MR analyses used inverse variance weighting (IVW) odds ratio (OR), and the sensitivity analyses included weighted median (WM) and MR‒Egger.ResultsBoth MR and MVMR showed that lowering ApoA-1 and LPA levels had causal effects on the risk of insomnia [MR: per 10 units, ApoA-1: OR: 0.7546, 95% CI: 0.6075–0.9372, P = 0.011; LPA: OR: 0.8392, 95% CI: 0.7202–0.9778, P = 0.025; MVMR: per 10 units, ApoA-1: OR: 0.7600, 95% CI: 0.6362–0.9079, P = 0.002; LPA, OR: 0.903, 95% CI: 0.8283–0.9845, P = 0.021]. There were no causal effects of TG or ApoB on insomnia (all P > 0.05). The MR‒Egger intercept test, funnel plot, and IVW methods all suggested an absence of strong directional pleiotropy, and leave-one-out permutation analysis did not detect any single single-nucleotide polymorphism that had a strong influence on the results.ConclusionElevated levels of ApoA-1 and LPA were independently and causally associated with the risk of insomnia, suggesting that elevated ApoA-1 and LPA levels may contribute to a reduced risk of insomnia.

A pH-Mediated Highly Selective System Enabling Simultaneous Analysis of Circulating RNAs Carried by Extracellular Vesicles and Lipoproteins.

Extracellular vesicles (EVs) and lipoproteins (LPPs) serve as important carriers of circulating miRNAs in peripheral blood, offering immense potential for disease diagnosis and therapeutic interventions. Due to their shared physicochemical attributes, EVs and LPPs are frequently coisolated, potentially leading to misunderstandings regarding their distinct functional roles in physiological and pathological processes. Here, we report a highly selective magnetic system based on the pH-mediated affinity displayed by cibacron blue (CB) toward EVs and LPPs, enabling successful separation and collection of these two nanoparticles without cross-contamination for subsequent circulating RNA analysis. First, we found that CB-modified magnetic beads (CBMBs) exhibit a strong affinity toward LPP particles while displaying little interaction with EVs in standard samples under physiological pH conditions. We further demonstrate that the affinity between CB molecules and bionanoparticles in plasma samples is highly pH-dependent. Specifically, CBMBs show affinities for both LPP and EV particles under neutral and acidic conditions. However, at basic pH levels, CB molecules selectively bind only to LPP particles. Consequently, the remaining EV particles present in plasma are subsequently isolated by using titanium dioxide-modified beads (TiMBs) through phospholipid affinity. The simultaneous analysis of the transcriptomic contents of EV and LPP reveals clear differences in their small RNA profiles, with the differentially expressed RNAs reflecting distinct biological processes. Significantly, in a proof-of-concept study, we successfully demonstrated a strong correlation between miRNAs carried by both EV and LPP particles with the occurrence of ocular neovascularization during the progression of diabetic retinopathy. The involved miRNAs may serve as potential biomarkers for DR diagnostics and severity classification. To sum up, this pH-mediated separation system is not only user-friendly but also highly compatible, rendering it a potent tool for probing the molecular compositions, biomarkers, and underlying biological mechanisms of EVs and LPPs.

AQP1 as a novel biomarker to predict prognosis and tumor immunity in glioma patients

Abstract Background Glioma is a kind of nervous system cancer with a low overall survival rate. Aquaporin 1 (AQP1) is linked to a number of cancers. Its prognostic relevance and immunological consequences in gliomas, however, are unclear. Objectives Our objective was to thoroughly examine the modified expression of AQP1, its prognostic significance, and its correlation with immune cells and markers to discover innovative molecular immunotherapy strategies for glioma patients. Methods RNA sequencing data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were used. In addition, we used real-time reverse transcription polymerase chain reaction (RT-PCR) and Western Blot methods to monitor AQP1 expression in glioma tissues. Results AQP1 expression was greater in gliomas than in traumatized brain tissues. The increased AQP1 expression in gliomas was additionally confirmed through immunohistochemical analysis in the Human Protein Atlas (HPA) repository. An elevated level of AQP1 expression was identified as a separate determinant of the overall survival (OS) and prognosis of individuals with glioma. AQP1 expression was shown to be tightly linked to the tumor immune milieu, immune checkpoint blockade (ICB) and temozolomide drug reaction. In conclusion, the 50 genes that show coexpression with AQP1 indicate that the predominant functions and pathways are related to anterior pattern specification, pattern specification, regionalization, high-density lipoprotein particles, protein–lipid complexes, glycosaminoglycan binding, DNA-binding transcription repressor specific activation to RNA polymerase II, DNA-binding transcription repressor activity, nitrogen metabolism, alpha-linolenic acid metabolism, and fat digestion and absorption. Conclusions The results indicate that AQP1 could serve as both a predictive marker and a potential treatment target in glioma.

Importance of Dyslipidaemia Treatment in Individuals with Type 2 Diabetes Mellitus—A Narrative Review

Type 2 diabetes mellitus (T2DM) is a common metabolic disease characterised by insulin resistance and elevated blood glucose levels, affecting millions of people worldwide. T2DM individuals with dyslipidaemia have an increased risk of cardiovascular disease (CVD). A complex interplay of risk factors such as hyperglycaemia, dyslipidaemia, hypertension, obesity, inflammation, and oxidative stress favour the development of atherosclerosis, a central mechanism in the pathogenesis of cardiovascular disease. Dyslipidaemia, a hallmark of T2DM, is characterised by elevated triglycerides, decreased high-density lipoprotein (HDL) cholesterol and the presence of small, dense low-density lipoprotein (LDL) particles, all of which promote atherosclerosis. In this article, we have attempted to present various treatment strategies that include pharmacological interventions such as statins, ezetimibe, PCSK9 inhibitors, fibrates, and omega-3 fatty acids. We have also tried to highlight the pivotal role of lifestyle modifications, including physical activity and dietary changes, in improving lipid profiles and overall cardiovascular health in T2DM individuals. We have also tried to present the latest clinical guidelines for the management of dyslipidaemia in T2DM individuals. In conclusion, the treatment of dyslipidaemia in T2DM individuals is of great importance as it lowers lipid particle levels, slows the progression of atherosclerosis, and ultimately reduces susceptibility to cardiovascular disease.

Functional characterization of missense variants affecting the extracellular domains of ABCA1 using a fluorescence-based assay

Excess cholesterol originating from nonhepatic tissues is transported within HDL particles to the liver for metabolism and excretion. Cholesterol efflux is initiated by lipid-free or lipid-poor apolipoprotein A1 interacting with the transmembrane protein ABCA1, a key player in cholesterol homeostasis. Defective ABCA1 results in reduced serum levels of HDL cholesterol, deposition of cholesterol in arteries, and an increased risk of early onset CVD. Over 300 genetic variants in ABCA1 have been reported, many of which are associated with reduced HDL cholesterol levels. Only a few of these have been functionally characterized. In this study, we have analyzed 51 previously unclassified missense variants affecting the extracellular domains of ABCA1 using a sensitive, easy, and low-cost fluorescence-based assay. Among these, only 12 variants showed a distinct loss-of-function phenotype, asserting their direct association with severe HDL disorders. These findings emphasize the crucial role of functional characterization of genetic variants in pathogenicity assessment and precision medicine. The functional rescue of ABCA1 loss-of-function variants through proteasomal inhibition or by the use of the chemical chaperone 4-phenylbutyric acid was genotype specific. Genotype-specific responses were also observed for the ability of apolipoprotein A1 to stabilize the different ABCA1 variants. In view of personalized medicine, this could potentially form the basis for novel therapeutic strategies.

Isoform‐ and cellular metabolism‐specific apolipoprotein E (ApoE) lipidation in astrocytes

AbstractBackgroundApolipoprotein E (ApoE) is the major lipoprotein in the brain and connects the metabolic interactions between astrocytes and neurons. The E4 variant (APOE4) affects this function and represents a genetic predisposition for Alzheimer’s disease (AD), but the molecular mechanisms remain unclear.MethodWe have integrated cell‐free in vitro assays, a new cell system based on isogenic iPSC‐derived astrocytes and lipidomics to study ApoE lipidation, and how this is affected by genetic polymorphism.ResultWe show that ApoE produces different types of lipoprotein particles via distinct lipidation pathways. ApoE forms high‐density lipoprotein (HDL)‐like, cholesterol‐rich particles via the ATP‐binding cassette transporter 1 (ABCA1), a mechanism largely unaffected by ApoE polymorphism. Alternatively, ectopic accumulation of fat in astrocytes, a stress‐associated condition, redirects ApoE toward the assembly and secretion of triacylglycerol‐rich lipoprotein particles, a process boosted by the APOE4 variant. We demonstrate in vitro that ApoE can detect triacylglycerol in membranes and spontaneously assemble lipoprotein particles (10‐20 nm) rich in unsaturated triacylglycerol, and that APOE4 has remarkable properties behaving as a strong triacylglycerol binder. Fatty APOE4 astrocytes have reduced ability to clear toxic fatty acids from the extracellular milieu, because APOE4 reroutes them back to secretion.ConclusionThe molecular mechanisms discussed here provide a new model explaining the interaction between genetic polymorphism and environmental factors, such as dyslipidaemia or aging, in the aetiology of late‐onset AD, as well as inspire possible new strategies for therapeutic intervention.Graphical abstract from https://doi.org/10.1016/j.celrep.2022.110435.

Apolipoprotein E polymorphism‐dependent effects on cellular function

AbstractBackgroundWe have used a combination of cell‐based and biophysical approaches to investigate mechanisms by which apolipoprotein E (APOE) isoforms induce either protective or Alzheimer’s Disease (AD)‐associated pathological features.MethodAPOE polymorphism‐driven phenotypic and functional changes were investigated in both primary human astrocytes and central nervous system (CNS) cell types generated from a set of APOE isogenic hiPSC lines (APOE KO, E2, E3, E4). Using fluorescently‐labeled APOE, the transport of E2, E3 and E4 isoforms were tracked in live cells and changes in organelle co‐localization was assessed. Lipoprotein particles were isolated from conditioned media to investigate APOE polymorphism‐specific alternations in the assembly and secretion of high‐density lipoprotein (HDL) particles.ResultWe have identified APOE polymorphism‐specific changes in subcellular localization of APOE that are correlated with changes in cellular function, as well as the function of APOE as a major transporter of lipids and cholesterol in the brain.ConclusionOur results provide mechanistic insight into structure:function relationship of APOE in the context of pathological and protective isoforms.

Effects of Biodegradable Biomaterials Combined with Bone Marrow Mesenchymal Stem Cells Transplantation on Neurological Function in Rats with Ischemic Cerebral Infarction

The aim of this research was to explore the effects of degradable biomaterial self-polypeptide nanofiber scaffolds plus bone marrow mesenchymal stem cells (BMSCs) on the behavior and neurological function of rats with focal ischemic cerebral infarction (ICI). BMSCs were isolated and cultured. The self-assembling peptides and BMSCs were mixed to prepare self-assembling peptides/BMSCs (SAP/BMSCs) material. BMSCs and SAP/BMSCs were injected into the carotid artery of rats in Model group. The rats without ligation were used as Sham group. Longa 5 and modified neurological severity scores (mNSS) of each group were evaluated. The adhesive removal test and forelimb asymmetry test were used to examine the behavior of the rats. The brain tissues were collected, and the infarct size, neuronal apoptosis, and the protein expression of Nogo-A and lipoprotein a (LPA) in the hippocampus were detected by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining, TdT-mediated dUTP nick end labeling (TUNEL) staining, enzyme-linked immunosorbent assay (ELISA), and Western blot. The results indicated that the fiber diameter of the self-polymerizing peptide material was about 12 nm, and the length was about 100-250 nm. The cells grew well after composite BMSCs. Compared with Sham group, Longa 5, mNSS score, adhesive removal time, forelimb asymmetry test score, cerebral infarction volume, and neuronal apoptosis rate were increased, interleukin 6 (IL-6) and Tumor Necrosis Factor alpha (TNF-α) were raised, IL-10 was decreased, and Nogo-A and LPA protein was increased in Model group (P &lt; 0.05). As against Model group, Longa 5, mNSS score, adhesive removal time, forelimb asymmetry test score, cerebral infarction volume, neuronal apoptosis rate, IL-6 and TNF-α were clearly decreased, and IL-10 was raised, and Nogo-A and LPA protein was clearly decreased in BMSCs and SAP/BMSCs groups (P &lt; 0.05). As against BMSCs group, Longa 5, mNSS score, adhesive removal time, forelimb asymmetry test score, cerebral infarction volume, and neuronal apoptosis rate were clearly decreased, and IL-6 and TNF-α were decreased, and IL-10 was raised, and Nogo-A and LPA protein was decreased in SAP/BMSCs group (P &lt; 0.05). Early transplantation of BMSCs can improve the neurobehavioral symptoms of ICI rats and inhibit neuronal apoptosis and inflammatory response. The effect of self-polymerizing peptide nanofiber scaffold plus BMSCs transplantation in ICI is superior to the transplantation of BMSCs alone.

Mechanisms of reduced Apolipoprotein E4 lipidation in iPSC‐derived astrocytes

AbstractBackgroundCarrying the apolipoprotein E ε4 (APOE4) allele is the highest known genetic risk factor for late‐onset Alzheimer’s disease (LOAD). Although how APOE4 leads to LOAD is not known, dysregulated endo‐lysosomal trafficking and lipid metabolism are key defects associated with APOE4. Cholesterol accumulation in glia instigates intracellular trafficking defects, increases cellular stress, and disrupts secretion. Additionally, enlarged endosomes were observed in the frontal lobes of APOE4‐carrying individuals, decades before the appearance of Aβ fibrilization. Therefore, we asked if cholesterol and endo‐lysosomal trafficking dysregulation in APOE4 carriers were due to differential lipidation of APOE3 and APOE4.MethodLocalization of ATP Binding Cassette Subfamily A Member 1 (ABCA1) in early, late, and recycling endosomal compartments were analyzed in human isogenic induced pluripotent stem cell (iPSC)‐derived neural cells and in cell lines treated with recombinant APOE in microscopic images. Membrane and cytoplasmic ABCA1 were compared using Western blots. Secreted high‐density lipoprotein (HDL) particles containing fluorescently tagged APOE3 or APOE4 were analyzed using ion‐mobility spectrometry. CS‐6253, an ABCA1 agonist peptide, was used to increase APOE lipidation.ResultThe protein levels of ABCA1, which mediates cholesterol and phospholipid efflux to the nascent apolipoprotein particles, were lower in APOE4/4 iPSC‐derived astrocytes compared to astrocytes derived from isogenic APOE3/3 iPSCs. Advanced image analysis revealed lower ABCA1 protein levels in Rab11+ recycling endosomes and less colocalization between ABCA1 and Rab7, a late endosome marker, in APOE4/4 astrocytes than APOE3/3 astrocytes. Consequently, less ABCA1 was detected at the cell membrane. Combined with previous data, these findings suggest APOE4 lipidation was reduced due to reduced ABCA1 activity. Additionally, BHK cells treated with recombinant APOE3 or APOE4 showed differences in ABCA1 localization that were altered by increasing APOE lipidation by activating ABCA1 via CS‐6253. Finally, fluorescently tagged APOE3 and APOE4 were incorporated in HDL particles and were secreted whose sizes were altered after CS‐6253 treatment, suggesting differences in lipidation levels.ConclusionWe demonstrated that diminished APOE4 lipidation is, at least in part, due to dysregulation of endo‐lysosomal trafficking of ABCA1 and that increasing APOE4 lipidation could alleviate cellular defects.

The Soret coefficient of human low-density lipoprotein in solution: a thermophilic behavior.

Thermodiffusion, or Soret effect, is the physical phenomenon of matter gradients originated by the migration of chemical species induced by thermal gradients. Thermodiffusion has been widely applied in the study of colloidal suspensions. In this study, we investigate the termodiffusion behavior of low-density lipoprotein (LDL) particles, by the Soret coefficient measurement. It is a new approach to studies of plasma lipoproteins. The experimental work was based on thermal- and Soret-lens effects. These effects were induced by laser irradiation of the samples, at two different time scales, in a Z-scan setup. LDL samples were analyzed under physiological conditions, notedly, ionic strength and pH, and at different temperatures. Temperature dependence of Soret coefficient showed a slight decrease in the absolute value of this coefficient, as a function of temperature increasing. However, its sign does not change at the temperatures investigated (15, 22.5 and 37.5°C). The results show that LDL particles exhibit thermophilic behavior. The origin of this thermophilic behavior is not yet completely understood. We discuss some aspects that can be related with the Soret effect in LDL samples.

Apolipoprotein E Status Mediates Pericyte Recruitment Mechanisms in the Presence of Excess Cholesterol

AbstractBackgroundApolipoprotein E (APOE) is a multifunctional lipid transporter, involved in lipoprotein metabolism and mediation of cholesterol homeostasis. The E4 variant of APOE is a primary genetic risk factor for Alzheimer’s disease and has been associated with vascular conditions such as hyperlipidemia, hypercholesterolemia, atherosclerosis and coronary artery disease (CAD). The mechanisms underlying APOE involvement in blood‐brain barrier breakdown (BBB‐B) are not well understood. In vivo, in vitro and clinical models of E4 have all demonstrated distinct profiling of molecular factors involved in ECM remodelling ‐ such as upregulation of PDGF‐BB in plasma and downregulation of VEGF in CSF. Associations between PDGF‐BB and white matter disease burden have also been reported. Investigating how APOE contributes to BBB‐B, through its function as a lipid transporter, could be imperative to understanding the pathophysiology behind vascular contributions to dementia.MethodUsing data from the Alzheimer’s Disease Neuroimaging Institute (ADNI), we analyzed plasma concentrations PDGF‐BB, VEGF and serum‐derived lipoprotein cholesterol (measured as LDL.C/HDL.C) for 521 patients with differing APOE status (E3/E3: n = 216, E3/E4: n = 195, E4/E4: n = 60). The LDL.C/HDL.C ratio has been used to assess the prevalence lipoprotein particles in cardiovascular diseases, such as CAD and is a studied marker of lipoprotein expression.ResultOur findings revealed that APOE‐dependent upregulation of PDGF‐BB was predicted by blood derived measures of VEGF, LDL.C/HDL.C and an interaction effect of both. Interestingly, results of this model for the E3/E4 subgroup were non‐significant, instead we found that PDGF‐BB and VLDL.C/HDL.C predicted white matter hyperintensity burden on MRI. To further explore this relationship, biofluidic protein quantification and immunohistochemical staining of humanized APOE knock‐in mice (APOEε3/ε3, APOEε3/ε4 and APOEε4/ε4 ) are being conducted to characterize differences of peripheral vascular protein expression and brain‐specific PDGFRβ upregulation. In vitro modelling of pericyte‐endothelial cells is also being conducted to further investigate interactions of APOE‐dependent glio‐vascular signaling.ConclusionThis study provides additional support to previous reports that APOE4 contributes to impaired cerebrovascular function through mechanisms related to pericyte recruitment, vascular destabilization, and cognitive impairment. It may also provide additional insights for concepts which focus on APOE‐dependent cholesterol trafficking and lipid metabolism contribution to BBB destabilization.