Structure of low density lipoprotein (LDL) particles: Basis for understanding molecular changes in modified LDL

Low density lipoproteins (LDL) are the major cholesterol carrying particles in the blood. Using cultured cells, it has been shown that LDL particles interact with specific surface receptors and are internalized via a coated pit-coated vesicle pathway for lysosomal catabolism. This (Pathway has been visualized using LDL labeled to ferritin or colloidal gold. It is now recognized that certain lysomotropic agents, such as chloroquine, inhibit lysosomal enzymes that degrade protein and cholesterol esters. By interrupting cholesterol ester hydrolysis, chloroquine treatment results in lysosomal accumulation of cholesterol esters from internalized LDL. Using LDL conjugated to colloidal gold, we have examined the ultrastructural effects of chloroquine on lipoprotein uptake by normal cultured fibroblasts.

Download Full-text

Aggregation Susceptibility of Low-Density Lipoproteins—A Novel Modifiable Biomarker of Cardiovascular Risk

Journal of Clinical Medicine ◽

10.3390/jcm10081769 ◽

2021 ◽

Vol 10 (8) ◽

pp. 1769

Author(s):

Katariina Öörni ◽

Petri T. Kovanen

Keyword(s):

Ex Vivo ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Atherosclerotic Cardiovascular Disease ◽

Low Density ◽

Cholesterol Crystals ◽

Ldl Particles ◽

Arterial Intima ◽

Matrix Bound ◽

Atherosclerotic Cardiovascular Diseases

Circulating low-density lipoprotein (LDL) particles enter the arterial intima where they bind to the extracellular matrix and become modified by lipases, proteases, and oxidizing enzymes and agents. The modified LDL particles aggregate and fuse into larger matrix-bound lipid droplets and, upon generation of unesterified cholesterol, cholesterol crystals are also formed. Uptake of the aggregated/fused particles and cholesterol crystals by macrophages and smooth muscle cells induces their inflammatory activation and conversion into foam cells. In this review, we summarize the causes and consequences of LDL aggregation and describe the development and applications of an assay capable of determining the susceptibility of isolated LDL particles to aggregate when exposed to human recombinant sphingomyelinase enzyme ex vivo. Significant person-to-person differences in the aggregation susceptibility of LDL particles were observed, and such individual differences largely depended on particle lipid composition. The presence of aggregation-prone LDL in the circulation predicted future cardiovascular events in patients with atherosclerotic cardiovascular disease. We also discuss means capable of reducing LDL particles’ aggregation susceptibility that could potentially inhibit LDL aggregation in the arterial wall. Whether reductions in LDL aggregation susceptibility are associated with attenuated atherogenesis and a reduced risk of atherosclerotic cardiovascular diseases remains to be studied.

Download Full-text

Long-term fasting improves lipoprotein-associated atherogenic risk in humans

European Journal of Nutrition ◽

10.1007/s00394-021-02578-0 ◽

2021 ◽

Author(s):

Franziska Grundler ◽

Dietmar Plonné ◽

Robin Mesnage ◽

Diethard Müller ◽

Cesare R. Sirtori ◽

...

Keyword(s):

Low Density Lipoprotein ◽

Plasma Lipid ◽

Density Lipoprotein ◽

Apolipoprotein A1 ◽

Health Concern ◽

Low Density ◽

Lipoprotein Subclasses ◽

Ldl Particles ◽

Increased Risk

Abstract Purpose Dyslipidemia is a major health concern associated with an increased risk of cardiovascular mortality. Long-term fasting (LF) has been shown to improve plasma lipid profile. We performed an in-depth investigation of lipoprotein composition. Methods This observational study included 40 volunteers (50% men, aged 32–65 years), who underwent a medically supervised fast of 14 days (250 kcal/day). Changes in lipid and lipoprotein levels, as well as in lipoprotein subclasses and particles, were measured by ultracentrifugation and nuclear magnetic resonance (NMR) at baseline, and after 7 and 14 fasting days. Results The largest changes were found after 14 fasting days. There were significant reductions in triglycerides (TG, − 0.35 ± 0.1 mmol/L), very low-density lipoprotein (VLDL)-TG (− 0.46 ± 0.08 mmol/L), VLDL-cholesterol (VLDL-C, − 0.16 ± 0.03 mmol/L) and low-density lipoprotein (LDL)-C (− 0.72 ± 0.14 mmol/L). Analysis of LDL subclasses showed a significant decrease in LDL1-C (− 0.16 ± 0.05 mmol/L), LDL2-C (− 0.30 ± 0.06 mmol/L) and LDL3-C (− 0.27 ± 0.05 mmol/L). NMR spectroscopy showed a significant reduction in large VLDL particles (− 5.18 ± 1.26 nmol/L), as well as large (− 244.13 ± 39.45 nmol/L) and small LDL particles (− 38.45 ± 44.04 nmol/L). A significant decrease in high-density lipoprotein (HDL)-C (− 0.16 ± 0.04 mmol/L) was observed. By contrast, the concentration in large HDL particles was significantly raised. Apolipoprotein A1 decreased significantly whereas apolipoprotein B, lipoprotein(a), fibrinogen and high-sensitivity C-reactive protein were unchanged. Conclusion Our results suggest that LF improves lipoprotein levels and lipoprotein subclasses and ameliorates the lipoprotein-associated atherogenic risk profile, suggesting a reduction in the cardiovascular risk linked to dyslipidemia. Trial Registration Study registration number: DRKS-ID: DRKS00010111 Date of registration: 03/06/2016 “retrospectively registered”.

Download Full-text

Development of Capture Assays for Different Modifications of Human Low-Density Lipoprotein

Clinical and Diagnostic Laboratory Immunology ◽

10.1128/cdli.12.1.68-75.2005 ◽

2005 ◽

Vol 12 (1) ◽

pp. 68-75 ◽

Cited By ~ 27

Author(s):

Gabriel Virella ◽

M. Brooks Derrick ◽

Virginia Pate ◽

Charlyne Chassereau ◽

Suzanne R. Thorpe ◽

...

Keyword(s):

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Gas Chromatography Mass Spectrometry ◽

Low Density ◽

Modified Ldl ◽

Capture Assay ◽

Carboxymethyl Lysine

ABSTRACT Antibodies to malondialdehyde (MDA)-modified low-density lipoprotein (LDL), copper-oxidized LDL (oxLDL), N ε(carboxymethyl) lysine (CML)-modified LDL, and advanced glycosylation end product (AGE)-modified LDL were obtained by immunization of rabbits with in vitro-modified human LDL preparations. After absorption of apolipoprotein B (ApoB) antibodies, we obtained antibodies specific for each modified lipoprotein with unique patterns of reactivity. MDA-LDL antibodies reacted strongly with MDA-LDL and also with oxLDL. CML-LDL antibodies reacted strongly with CML-LDL and also AGE-LDL. oxLDL antibodies reacted with oxLDL but not with MDA-LDL, and AGE-LDL antibodies reacted with AGE-LDL but not with CML-LDL. Capture assays were set with each antiserum, and we tested their ability to capture ApoB-containing lipoproteins isolated from precipitated immune complexes (IC) and from the supernatants remaining after IC precipitation (free lipoproteins). All antibodies captured lipoproteins contained in IC more effectively than free lipoproteins. Analysis of lipoproteins in IC by gas chromatography-mass spectrometry showed that they contained MDA-LDL and CML-LDL in significantly higher concentrations than free lipoproteins. A significant correlation (r = 0.706, P < 0.019) was obtained between the MDA concentrations determined by chemical analysis and by the capture assay of lipoproteins present in IC. In conclusion, we have developed capture assays for different LDL modifications in human ApoB/E lipoprotein-rich fractions isolated from precipitated IC. This approach obviates the interference of IC in previously reported modified LDL assays and allows determination of the degree of modification of LDL with greater accuracy.

Download Full-text

Markedly Increased Small Dense Low-Density Lipoprotein During Acute Phase in Childhood and Adolescent Nephrotic Syndrome

10.21203/rs.3.rs-55523/v1 ◽

2020 ◽

Author(s):

Keisuke Sugimoto ◽

Kohei Miyazaki ◽

Takuji Enya ◽

Tomoki Miyazawa ◽

Yuichi Morimoto ◽

...

Keyword(s):

Nephrotic Syndrome ◽

Acute Phase ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Lipid Profiles ◽

Atherogenic Index ◽

Childhood And Adolescence ◽

Low Density ◽

Ldl Particles ◽

Initial Onset

Abstract Background: Hyperlipidemia is an important characteristic feature of idiopathic nephrotic syndrome (NS) in children. This study was conducted to examine the lipid profiles, including small dense low-density lipoprotein (sdLDL-C), in childhood-onset NS.Methods: This retrospective study enrolled patients diagnosed with initial-onset NS in childhood and adolescence. Study parameters included lipid profiles. The “alternative LDL window” comprises the number and sizes of LDL particles estimated according to non-HDL-C and TG levels.Results: A total of 39 patients were enrolled who exhibited markedly increased lipid abnormalities, including TC, TG, LDL-C, and non-HDL-C levels (TC, 409.7 TC, TG, and sizes of LDL particles estimated as non-HDL-C, 332.3). Of the 39 patients, 32 (82%) were categorized in the area of hyper-TG/-non-HDL levels, which is considered as sdLDL. A positive correlation was found between non-HDL-C and TC (r = 0.96, P < 0.001), TG (r = 0.38, P = 0.018), LDL-C (r = 0.84, P < 0.001), TC/HDL (r = 0.53, P < 0.001), and atherogenic index of plasma (r = 0.42, P = 0.008).Conclusions: Our study demonstrated markedly increased lipid profiles during the acute phase of NS. Evaluation of lipid profiles using the “alternative LDL window” may help understand the state of hyperlipidemia in NS.

Download Full-text

Abstract 566: MicroRNA-146a Deficiency Prevents PCSK9 Gain-of-Function Mutation-induced Hypercholesterolemia in Mice

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.37.suppl_1.566 ◽

2017 ◽

Vol 37 (suppl_1) ◽

Author(s):

Shayan Mohammadmoradi ◽

Aida Javidan ◽

Weihua Jiang ◽

Jessica Moorleghen ◽

Venkateswaran Subramanian

Keyword(s):

Plasma Cholesterol ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Western Diet ◽

Size Exclusion ◽

Gel Chromatography ◽

Low Density ◽

Distribution Analysis ◽

Gain Of Function ◽

Ldl Particles

Background and Objective: Mimetic mediated activation of microRNA 146a (miR-146a) reduces atherosclerosis via suppression of nuclear factor-κB-driven inflammation in mice. The purpose of this study was to determine whether miR-146a influences plasma cholesterol in hypercholesterolemic mice. Methods and Results: To induce hypercholesterolemia, female C57BL/6 miR-146a WT (n=8) and miR-146a KO (n=8) mice were injected intraperitoneally with an adeno-associated viral vector (AAV) expressing the proprotein convertase subtilisin/kexin type 9 (PSCK9 D377Y) gain-of-function mutant at a dose of 3 x 10 10 genomic copies/mouse. After infection, mice were fed a Western diet (21% wt/wt milk fat; 0.15% wt/wt cholesterol) for sixteen weeks, and plasma PCSK9 and total cholesterol concentrations were monitored monthly using an enzymatic assay. Plasma PCSK9 concentrations were profoundly increased 4 weeks post injection (Baseline: WT - 179 ± 12 vs KO - 207 ± 12; Week 4: WT - 1700 ± 148 vs KO - 2689 ± 305 ng/ml) and remained significantly high during 16 weeks (WT - 882 ± 142 vs KO - 718 ± 109 ng/ml; p<0.05 vs baseline) of Western diet feeding. Consistent with increased plasma PCSK9 concentrations, plasma cholesterol concentrations were increased in both groups of mice. Interestingly, miR-146a KO group mice showed less significant increase in plasma cholesterol compared to WT group (Baseline: WT - 88 ± 3 vs KO - 83 ± 3; Week 4: WT - 328 ± 25 vs KO - 195 ± 18 mg/dl) irrespective of the comparable plasma PCSK9 concentrations. Also, lipoprotein distribution analysis with size exclusion gel chromatography revealed that miR-146a KO mice showed a strong reduction in high density lipoprotein (HDL) particles while very low density lipoprotein (VLDL) and low density lipoprotein (LDL) particles were not affected. Conclusion: Our findings suggests that miR146a plays a critical role in the regulation of HDL particles in PCSK9 gain-of-function mutant-induced hypercholesterolemia in mice. Future studies will identify gene targets influenced by miR-146a in regulating HDL-cholesterol in hypercholesterolemic mice.

Download Full-text

Could ornithine supplementation be beneficial to prevent the formation of pro-atherogenic carbamylated low-density lipoprotein (c-LDL) particles?

Medical Hypotheses ◽

10.1016/j.mehy.2019.03.004 ◽

2019 ◽

Vol 126 ◽

pp. 20-22 ◽

Cited By ~ 3

Author(s):

Bahadir Simsek ◽

Ufuk Çakatay

Keyword(s):

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Low Density ◽

Ldl Particles

Download Full-text

Immunohistochemical Localization of Apolipoprotein B-100 (ApoB-100) and Expression of Glutathione Peroxidase (GSH-PO) in Canine Atherosclerotic Lesions

Veterinary Pathology ◽

10.1177/030098589803500310 ◽

1998 ◽

Vol 35 (3) ◽

pp. 227-229 ◽

Cited By ~ 4

Author(s):

Y. Kagawa ◽

E. Uchida ◽

H. Yokota ◽

M. Yamaguchi ◽

H. Taniyama

Keyword(s):

Glutathione Peroxidase ◽

Apolipoprotein B ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Immunohistochemical Localization ◽

Low Density ◽

Modified Ldl ◽

Atherosclerotic Lesions ◽

Foamy Cytoplasm ◽

Tunica Intima

We used immunohistochemistry to localize canine Apolipoprotein B-100 (CApoB-100) and glutathione peroxidase (GSH-PO) in canine atherosclerotic lesions. CApoB-100 was deposited in the tunica intima and cytoplasms of infiltrating macrophages in early atherosclerotic lesions. In advanced atherosclerotic lesions, the cystic space of the lesions contained a large amount of CApoB-100 immunoreaetive material. Expression of GSH-PO was recognized in the foamy cytoplasm of macrophages and smooth muscle cells in the early and advanced atherosclerotic lesions. These results indicate that expression of GSH-PO is closely associated with the deposition of CApoB-100. In addition, they suggest that, as in human atheromas, low-density lipoprotein (LDL) is peroxidized and changed into modified LDL. Deposition of modified LDL (oxidized or acetylated) may be a critical step in the formation of canine atherosclerotic lesions.

Download Full-text

Modified LDL Particles Activate Inflammatory Pathways in Monocyte-derived Macrophages: Transcriptome Analysis

Current Pharmaceutical Design ◽

10.2174/1381612824666180911120039 ◽

2018 ◽

Vol 24 (26) ◽

pp. 3143-3151 ◽

Cited By ~ 14

Author(s):

Alexander N. Orekhov ◽

Yumiko Oishi ◽

Nikita G. Nikiforov ◽

Andrey V. Zhelankin ◽

Larisa Dubrovsky ◽

...

Keyword(s):

Cholesterol Metabolism ◽

Low Density Lipoprotein ◽

Atherosclerotic Lesion ◽

Density Lipoprotein ◽

Primary Response ◽

Secondary Response ◽

Modified Ldl ◽

Ldl Particles ◽

Regulator Genes ◽

Lipid Metabolism Genes

Background: A hallmark of atherosclerosis is its complex pathogenesis, which is dependent on altered cholesterol metabolism and inflammation. Both arms of pathogenesis involve myeloid cells. Monocytes migrating into the arterial walls interact with modified low-density lipoprotein (LDL) particles, accumulate cholesterol and convert into foam cells, which promote plaque formation and also contribute to inflammation by producing proinflammatory cytokines. A number of studies characterized transcriptomics of macrophages following interaction with modified LDL, and revealed alteration of the expression of genes responsible for inflammatory response and cholesterol metabolism. However, it is still unclear how these two processes are related to each other to contribute to atherosclerotic lesion formation. Methods: We attempted to identify the main mater regulator genes in macrophages treated with atherogenic modified LDL using a bioinformatics approach. Results: We found that most of the identified genes were involved in inflammation, and none of them was implicated in cholesterol metabolism. Among the key identified genes were interleukin (IL)-7, IL-7 receptor, IL- 15 and CXCL8. Conclusion: Our results indicate that activation of the inflammatory pathway is the primary response of the immune cells to modified LDL, while the lipid metabolism genes may be a secondary response triggered by inflammatory signalling.

Download Full-text