Lipoprotein Transport Research Articles

Mass transport of low density lipoprotein in reconstructed hemodynamic environments of human carotid arteries: the role of volume and solute flux through the endothelium.

The accumulation of low density lipoprotein (LDL) in the arterial intima is a critical step in the initiation and progression of atheromatous lesions. In this study we examine subject-specific LDL transport into the intima of carotid bifurcations in three human subjects using a three-pore model for LDL mass transfer. Subject-specific carotid artery computational models were derived using magnetic resonance imaging (MRI) to obtain the geometry and phase-contract MRI (PC-MRI) to acquire pulsatile inflow and outflow boundary conditions for each subject. The subjects were selected to represent a wide range of anatomical configurations and different stages of atherosclerotic development from mild to moderate intimal thickening. A fluid-solid interaction (FSI) model was implemented in the computational fluid dynamics (CFD) approach in order to consider the effects of a compliant vessel on wall shear stress (WSS). The WSS-dependent response of the endothelium to LDL mass transfer was modeled by multiple pathways to include the contributions of leaky junctions, normal junctions, and transcytosis to LDL solute and plasma volume flux from the lumen into the intima. Time averaged WSS (TAWSS) over the cardiac cycle was computed to represent the spatial WSS distribution, and wall thickness (WTH) was determined from black blood MRI (BBMRI) so as to visualize intimal thickening patterns in the bifurcations. The regions which are exposed to low TAWSS correspond to elevated WTH and higher mass and volume flux via the leaky junctions. In all subjects, the maximum LDL solute flux was observed to be immediately downstream of the stenosis, supporting observations that existing atherosclerotic lesions tend to progress in the downstream direction of the stenosis.

Lipids around the Clock: Focus on Circadian Rhythms and Lipid Metabolism.

Disorders of lipid and lipoprotein metabolism and transport are responsible for the development of a large spectrum of pathologies, ranging from cardiovascular diseases, to metabolic syndrome, even to tumour development. Recently, a deeper knowledge of the molecular mechanisms that control our biological clock and circadian rhythms has been achieved. From these studies it has clearly emerged how the molecular clock tightly regulates every aspect of our lives, including our metabolism. This review analyses the organisation and functioning of the circadian clock and its relevance in the regulation of physiological processes. We also describe metabolism and transport of lipids and lipoproteins as an essential aspect for our health, and we will focus on how the circadian clock and lipid metabolism are greatly interconnected. Finally, we discuss how a deeper knowledge of this relationship might be useful to improve the recent spread of metabolic diseases.

MiR-28-5p Involved in LXR-ABCA1 Pathway is Increased in the Plasma of Unstable Angina Patients

Previous studies confirmed that the intronic miRNAs participated in regulating host gene-primed biological processes. The coordinated roles of miR-28 with its host gene, LIM domain lipoma-preferred partner (LPP), remain unknown in atherosclerosis. In this study, we determined to assess circulating levels of miR-28-5p in unstable angina patients, compared with age- and sex- matched control subjects by quantitative PCR. Furthermore, we attempted to explore whether miR-28-5p could influence the expression of ATP-binding cassette transporter A1 (ABCA1) and liver X receptor (LXR), major mediators of high density lipoprotein (HDL) synthesis and transportation in hepatic cells and macrophages. It was found that plasma levels of miR-28-5p were significantly increased in unstable angina patients with or without type 2 diabetes mellitus. Notably, miR-28-5p upregulated ABCA1 expression at transcription and translation levels, strongly correlated with translational activation of LXRα in HepG2 and THP-1-derived macrophages. Our findings suggest that circulating miR-28-5p, involved in LXRα-ABCA1 pathway, may be a potential biomarker for diagnosis and prognosis of unstable angina.

Small-molecule inhibitors of gram-negative lipoprotein trafficking discovered by phenotypic screening.

In Gram-negative bacteria, lipoproteins are transported to the outer membrane by the Lol system. In this process, lipoproteins are released from the inner membrane by the ABC transporter LolCDE and passed to LolA, a diffusible periplasmic molecular chaperone. Lipoproteins are then transferred to the outer membrane receptor protein, LolB, for insertion in the outer membrane. Here we describe the discovery and characterization of novel pyridineimidazole compounds that inhibit this process. Escherichia coli mutants resistant to the pyridineimidazoles show no cross-resistance to other classes of antibiotics and map to either the LolC or LolE protein of the LolCDE transporter complex. The pyridineimidazoles were shown to inhibit the LolA-dependent release of the lipoprotein Lpp from E. coli spheroplasts. These results combined with bacterial cytological profiling are consistent with LolCDE-mediated disruption of lipoprotein targeting to the outer membrane as the mode of action of these pyridineimidazoles. The pyridineimidazoles are the first reported inhibitors of the LolCDE complex, a target which has never been exploited for therapeutic intervention. These compounds open the door to further interrogation of the outer membrane lipoprotein transport pathway as a target for antimicrobial therapy.

Numerical simulation of blood flow and plaque progression in carotid–carotid bypass patient specific case

This study describes computer simulation of blood flow and plaque progression pattern in a patient who underwent surgical treatment for infected carotid prosthetic tube graft using carotid–carotid cross-over bypass. The 3D blood flow is governed by the Navier–Stokes equations, together with the continuity equation. Mass transfer within the blood lumen and through the arterial wall is coupled with the blood flow and is modelled by the convection–diffusion equation. Low-density lipoprotein (LDL) transport in lumen of the vessel is described by Kedem–Katchalsky equations. The inflammatory process is solved using three additional reaction–diffusion partial differential equations. Calculation based on a computer simulation showed that flow distribution in the left carotid artery (CA) was around 40–50% of the total flow in the right common CA. Also, the left CA had higher pressure gradient after surgical intervention. Plaque progression simulation predicted development of the atherosclerotic plaque in the position of the right common CA and the left internal CA. A novel way of atherosclerotic plaque progression modelling using computer simulation shows a potential clinical benefit with significant impact on the treatment strategy optimization.

Transport of Low-Density Lipoprotein Into the Blood Vessel Wall During Atherogenic Diet in the Isolated Rabbit Carotid Artery.

Atherosclerosis is a chronic fibroproliferative disease that includes accumulation of cholesterol-rich lipids in the arterial wall. Though numerous studies have investigated atherosclerosis, not enough is known about the exact mechanisms of low-density lipoprotein (LDL) transport into the blood vessel wall. Therefore, we explored the (125)I-LDL transport into the arterial wall under constant perfusion flow and pressure as well as the influence of duration of atherogenic diet on (125)I-LDL transport and biomechanical properties of carotid artery. The isolated segment of rabbit carotid artery was used under constant perfusion flow and pressure-induced (0 mmHg and 140 mmHg) blood vessel distension, with the possibility to change and precisely calculate shear stress during the experiment. Obtained results indicate the influence of atherogenic diet duration and consequent variation of shear stress on (125)I-LDL transport into the blood vessel wall. (125)I-LDL transport into the blood vessel wall at low pressure-induced blood vessel distension decreases by the increase of the shear stress and in relation to the atherogenic diet duration. At high pressure-induced blood vessel distension, (125)I-LDL transport increases in relation to the atherogenic diet duration and the increase of shear stress. The influence of shear stress is a more dominant parameter on LDL uptake at low pressure-induced blood vessel distension; however, the atherogenic diet duration has more of a dominant influence on LDL uptake at high pressure-induced vessel distension.

Deeper insight into chronic kidney disease-related atherosclerosis: comparative proteomic studies of blood plasma using 2DE and mass spectrometry

BackgroundAtherosclerosis is a major cause of cardiac events and mortality in patients suffering from chronic kidney disease (CKD). Moreover, the risk of cardiovascular disease (CVD) development in patients with CKD increases as kidney function declines. Although the close connection between atherosclerosis and kidney dysfunction is undeniable, particular risk factors and specific mechanisms that promote CVD in patients with CKD remain unclear. To gain insight into better recognition of the mechanisms of accelerated atherosclerosis in patients with CKD, we performed a comparative proteomic analysis of blood plasma from patients in various stages of CKD and thus distinct progression of atherosclerosis (n = 90), patients with advanced CVD and normal renal function (n = 30) and healthy volunteers (n = 30).MethodsPlasma samples were depleted using affinity chromatography and divided into three fractions: high-abundant, low-abundant and low-molecular weight proteins. The first two fractions were analyzed by two-dimensional gel electrophoresis and mass spectrometry, the last one has been subjected to direct MS/MS analysis. A proteomic profiles for high-abundant, low-abundant and low-molecular weight proteins fractions were obtained. Differential accumulated proteins were confirmed by selected reaction monitoring analysis (SRM). The Gene Ontology (GO) function and the interaction networks of differentially expressed proteins were then analyzed.ResultsForty-nine proteins (13 high- and 36 low-molecular mass) showed differences in accumulation levels. For eleven of them differential expression were confirmed by selected reaction monitoring analysis. Bioinformatic analysis showed that identified differential proteins were related to three different processes: the blood coagulation cascade, the transport, binding and metabolism of lipoproteins and inflammatory processes.ConclusionsObtained data provide an additional line of evidence that different molecular mechanisms are involved in the development of CKD- and CVD-related atherosclerosis. The abundance of some anti-atherogenic factors revealed in patients with CKD suggests that these factors are not associated with the reduction of atherosclerosis progression in CKD that is typically observed in “classical” CVD. Moreover, obtained data also suggest that mechanism of CVD acceleration may be different in initial and advanced stages of CKD. Undoubtedly, in advanced stages of CKD inflammation is highly pronounced.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-014-0378-8) contains supplementary material, which is available to authorized users.

Analysis of Low Density Lipoprotein (LDL) Transport Within a Curved Artery.

To elucidate the mechanism of the effect of LDL concentration on the thickening of intima in a curved artery, LDL transport in each layer of the curved arterial wall is studied analytically. A comprehensive concentration distribution expression of LDL in each layer of the curved artery wall is presented along with the characterization and estimation of the effect of curvature on the growth of atherosclerosis within the arterial wall. The effect of curvature on species concentration distribution is analyzed and the results are thoroughly benchmarked against prior pertinent works. The concentration at the interface of lumen and endothelium will directly affect the concentration profile inside the arterial wall layers. The results show that the average concentration in the circumferential direction is actually decreasing in the axial direction for a curved artery compared with a straight artery. Small radius ratio and Reynolds number will augment the LDL accumulation at the lumen endothelium interface. The increase in concentration at the lumen/endothelium interface in the axial direction has a minor effect on the concentration profile at the other wall interface layers.

Effects of External and Internal Hyperthermia on LDL Transport and Accumulation Within an Arterial Wall in the Presence of a Stenosis.

Effects of hyperthermia on transport of low-density lipoprotein (LDL) through a stenosed arterial wall are analyzed comprehensively in the present work. The realistic and pertinent aspects of an arterial wall is represented by a multi-layer model, with a proper representation of the thickened intima region due to the atherosclerotic plaque formation. Effects of external and internal hyperthermia on LDL concentration levels are established along with the range of influence of these effects. Various modules of the current work are comprehensively compared with pertinent literature and are found to be in excellent agreement. The effects of external and internal hyperthermia as well as the load level and the axial location of the plaque formation on LDL transport and accumulation for a stenosed artery are established in this work.

Body condition score at calving affects systemic and hepatic transcriptome indicators of inflammation and nutrient metabolism in grazing dairy cows

Calving body condition score (BCS) is an important determinant of early-lactation dry matter intake, milk yield, and disease incidence. The current study investigated the metabolic and molecular changes induced by the change in BCS. A group of cows of mixed age and breed were managed from the second half of the previous lactation to achieve mean group BCS (10-point scale) that were high (HBCS, 5.5; n=20), medium (MBCS, 4.5; n=18), or low (LBCS, 3.5; n=19). Blood was sampled at wk −4, −3, −2, 1, 3, 5, and 6 relative to parturition to measure biomarkers of energy balance, inflammation, and liver function. Liver was biopsied on wk 1, 3, and 5 relative to parturition, and 10 cows per BCS group were used for transcript profiling via quantitative PCR. Cows in HBCS and MBCS produced more milk and had greater concentrations of nonesterified fatty acids and β-hydroxybutyrate postpartum than LBCS. Peak concentrations of nonesterified fatty acids and β-hydroxybutyrate and greater hepatic triacylglycerol concentrations were recorded in HBCS at wk 3. Consistent with blood biomarkers, HBCS and MBCS had greater expression of genes associated with fatty acid oxidation (CPT1A, ACOX1), ketogenesis (HMGCS2), and hepatokines (FGF21, ANGPTL4), whereas HBCS had the lowest expression of APOB (lipoprotein transport). Greater expression during early lactation of BBOX1 in MBCS and LBCS suggested greater de novo carnitine synthesis. The greater BCS was associated with lower expression of growth hormone/insulin-like growth factor-1 signaling axis genes (GHR1A, IGF1, and IGFALS) and greater expression of gluconeogenic genes. These likely contributed to the higher milk production and greater gluconeogenesis. Despite greater serum haptoglobin around calving, cows in HBCS and MBCS had greater blood albumin. Cows in MBCS, however, had a higher albumin:globulin ratio, probably indicating a less pronounced inflammatory status and better liver function. The marked decrease in expression of NFKB1, STAT3, HP, and SAA3 coupled with the increase in ALB on wk 3 in MBCS cows were consistent with blood measures. Overall, results suggest that the greater milk production of cows with higher calving BCS is associated with a proinflammatory response without negatively affecting expression of genes related to metabolism and the growth hormone/insulin-like growth factor-1 axis. Results highlight the sensitivity of indicators of metabolic health and inflammatory state to subtle changes in calving BCS and, collectively, indicate a suboptimal health status in cows calving at either BCS 3.5 or 5.5 relative to BCS 4.5.

Abstract B29: In vivo alteration of nucleoside pools does not lead to carcinogenesis but rather protects from fatty liver caused by anti-neoplastic agents.

Abstract Imbalance in the concentrations of nucleotides and deoxynucleotides essential for the replication, recombination and repair of DNA has been shown extensively in vitro to induce mutations through misinsertion of incorrect dNTP, insertion-deletion errors and DNA strand misalignment, therefore reducing the fidelity of DNA synthesis. However the consequences of nucleosides-nucleotides imbalances have not been fully explored in vivo in a mammalian system. We have recently generated murine models with altered expression of uridine phosphorylase 1 (UPP1) leading to disruption of uridine homeostasis and causing severe nucleotide pools imbalances. We generated a UPP1 knockout model where we nullified the nucleoside phosphorolytic activity in all tissues except liver that showed a residual activity below 10% due to the expression of hepatic uridine phosphorylase 2. We also developed a UPP1 transgenic model with ubiquitous overexpression of UPP1. Both models have shown altered plasma and tissue levels of uridine and changes in nucleotide deoxy-nucleotide pools, however, we did not detect abnormalities in their growth, development, sexual maturation and reproductive ability and we did not observe any neoplastic growth, possibly associated to induced mutations, even after 22 months of age. We were able to observe changes in sensitivity to fluoropyrimidines: the UPP1 knockout mice resulted to be more resistant to 5-fluorouracil (5-FU) toxicity, therefore able to tolerate a dosage 75% higher than the control C57/Bl6 mice; on the contrary the UPP1 transgenic mice were only able to stand a dose of 5-FU that was 40% less than the control mice. These effects are likely to be attributed to changes in the activation of 5-FU to 5-fluorouridine, particularly in the gastrointestinal tract. Surprisingly, our UPP1 murine models unveiled a linkage between uridine homeostasis and liver lipid metabolism. We discovered that uridine is an effective suppressor of fatty liver induced by multiple drugs with unrelated acting mechanisms. Among others, tamoxifen, an antagonist of the estrogen receptor in breast tissue, the therapy of choice for hormone receptor-positive breast cancer in pre-menopausal women; and methotrexate, an antifolate antimetabolite used alone or in combination for the treatment of a number of cancers including: breast, head and neck, leukemia, lymphoma and osteosarcoma. We have so far identified a number of target proteins whose expression or post-translational modifications are affected by uridine. These proteins participate in liver energy metabolism including mitochondrial respiration, peroxisomal and mitochondrial fatty acid β-oxidation, and transport of fatty acids, triacylglycerides, and lipoproteins. We are currently in the process of establishing if these changes are the result of a direct uridine effect or a defect in the rate of translation initiation and/or other steps in the translation process due to alterations in the size of nucleotide pools. Citation Format: Thuc Tim Le, Yasuyo Urasaki, Robert Kirsh, Giuseppe Pizzorno. In vivo alteration of nucleoside pools does not lead to carcinogenesis but rather protects from fatty liver caused by anti-neoplastic agents.. [abstract]. In: Proceedings of the AACR Special Conference: The Translational Impact of Model Organisms in Cancer; Nov 5-8, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(11 Suppl):Abstract nr B29.

Effects of shear stress on low-density lipoproteins (LDL) transport in the multi-layered arteries

Abstract The mathematical, four-layer model of the LDL transport across the arterial wall including the sensitivity of the transport coefficients to the wall shear stress (WSS) is studied. In that model the advection–diffusion equations in porous media are used to determine the LDL concentration profiles in each layer of the arterial wall. We demonstrate the effect of the giant accumulation of the LDL in the intima layer. This property turns out to be an interplay between the layered structure of the arterial wall and WSS sensitivity of the endothelium. Interestingly, we also show that the single-layer models with the same WSS sensitivity mechanism and corresponding parameters, obscure the accumulation phenomenon, which predicts the one order of magnitude larger LDL concentration. The paper is supplemented by the repository with source code of the model (Git repository).

Effect of compounds affecting ABCA1 expression and CETP activity on the HDL pathway involved in intestinal absorption of lutein and zeaxanthin.

The antioxidant xanthophylls lutein and zeaxanthin are absorbed from the diet in a process involving lipoprotein formation. Selective mechanisms exist for their intestinal uptake and tissue-selective distribution, but these are poorly understood. We investigated the role of high-density lipoprotein (HDL), apolipoprotein (apo) A1 and ATP-binding cassette transporter (ABC) A1 in intestinal uptake of lutein in a human polarized intestinal cell culture and a hamster model. Animals received dietary lutein and zeaxanthin and either a liver X receptor (LXR) agonist or statin, which up- or down-regulate intestinal ABCA1 expression, respectively. The role of HDL was studied following treatment with the cholesteryl ester transfer protein (CETP) modulator dalcetrapib or the CETP inhibitor anacetrapib. In vitro, intestinal ABCA1 at the basolateral surface of enterocytes transferred lutein and zeaxanthin to apoA1, not to mature HDL. In hamsters, plasma lutein and zeaxanthin levels were markedly increased with the LXR agonist and decreased with simvastatin. Dalcetrapib, but not anacetrapib, increased plasma and liver lutein and zeaxanthin levels. ABCA1 expression and apoA1 acceptor activity are important initial steps in intestinal uptake and maintenance of lutein and zeaxanthin levels by an HDL-dependent pathway. Their absorption may be improved by physiological and pharmacological interventions affecting HDL metabolism.

Mendelian randomization provides no evidence for a causal role of serum urate in increasing serum triglyceride levels.

Triglycerides and their lipoprotein transport molecules are risk factors for heart disease. Observational studies have associated elevated levels of serum urate (SU) with triglycerides and risk of heart disease. However, owing to unmeasured confounding, observational studies do not provide insight into the causal relationship between SU and triglyceride. The aim of this study was to test for a causal role of SU in increasing triglyceride using Mendelian randomization that accounts for unmeasured confounding. Subjects were of European ancestry from the atherosclerosis risk in communities (n=5237) and Framingham heart (n=2971) studies. Mendelian randomization by the 2-stage least squares regression method was done with SU as the exposure, a uric acid transporter genetic risk score as instrumental variable, and triglyceride as the outcome. In ordinary linear regression, SU was significantly associated with triglyceride levels (β=2.69 mmol/L change in triglyceride per mmol/L increase in SU). However, Mendelian randomization-based estimation showed no evidence for a direct causal association of SU with triglyceride concentration-there was a nonsignificant 1.01 mmol/L decrease in triglyceride per mmol/L increase in SU attributable to the genetic risk score (P=0.21). The reverse analysis using a triglyceride genetic risk score provided evidence of a causal role for triglyceride in raising urate in men (P(Corrected)=0.018). These data provide no evidence for a causal role for SU in raising triglyceride levels, consistent with a previous Mendelian randomization report of no association between SU and ischemic heart disease.

New insights into statin action on the dyslipidemia of type 2 diabetes: normalisation of the plasma lipid profile

Objectives: Statin therapy favours normalisation of elevated atherogenic lipoprotein levels and of low HDL-C concentrations in the dyslipidemia of metabolic syndrome (MetS) and type 2 diabetes. Lipoproteins transport >300 lipid species. This study aimed to determine whether lipidomic analysis can identify global changes in the plasma lipidome resulting from statin action which impact on type 2 diabetes risk.

Effect of bariatric surgery on HDL-associated microRNAs

Objectives: We have recently demonstrated that high-density lipoproteins (HDL) transport microRNAs (miRNAs) in the plasma. Here we aim to investigate how HDL-associated miRNAs are regulated in morbidly obese subjects and more importantly, how weight loss after bariatric surgery affected HDL-miRNAs in these subjects.

Molecular cloning, expression profile and transcriptional modulation of two splice variants of very low density lipoprotein receptor during ovarian follicle development in geese (Anser cygnoide)

Very low density lipoprotein receptor (VLDLR)-mediated endocytosis of plasma lipoproteins into the ovary is essential for ovarian follicle development. Two splice variants of VLDLR have been identified in several species, yet little is known about their distinctive roles in ovarian developing follicles. In the present study, the full-length cDNAs of two splice isoforms of VLDLR were obtained from geese (Anser cygnoide) ovaries using the RACE method. The longer isoform (TypeI VLDLR) is 3141bp and contains five conserved structural domains, while the other (TypeII VLDLR) lacks 90bp encoding for the O-linked sugar domain. TypeII VLDLR was predominantly expressed in the ovary, with greater amounts of mRNA in theca and granulosa cells from early stages of follicle development but decreased during vitellogenesis. However, there was minimal expression of the TypeI VLDLR gene in theca cells and expression was almost undetectable in granulosa cells throughout follicle development. Yolk VLDL concentrations decreased as stage of development advanced while yolk triglyceride and cholesterol concentrations increased in a follicular size-dependent manner. The significant correlations between transcripts of TypeII VLDLR and yolk lipids supported its important role on yolk lipid deposition. In addition, in vitro experiments suggested that exogenous cholesterol, 25-hydroxycholesterol and mevinolin (a highly potent competitive inhibitor of HMG-CoA) treatment could significantly alter TypeII VLDLR gene expression in granulosa cells from both pre-hierarchical and pre-ovulatory follicles. Collectively, data from the present study indicate that TypeII VLDLR is more important for the transport of plasma lipoproteins into developing follicles than TypeI VLDLR, and provide new evidence about the influence of steroids in modulating VLDLR gene expression in ovarian cells.

Abstract 612: Effect of Bariatric Surgery on HDL-Associated MicroRNAs

Background and aims: We have recently demonstrated that high-density lipoproteins (HDL) transport microRNAs (miRNAs) in the plasma. Here we aim to investigate how HDL-associated miRNAs are regulated in morbidly obese subjects and more importantly, how weight loss after bariatric surgery affected HDL-miRNAs in these subjects. Methods: Plasma HDL were isolated from morbidly obese subjects (n=23) before, 6 months and 12 months after bariatric surgery by immunoprecipitation using goat anti-human apoA-I microbeads. We also isolated HDL from 12 normal subjects using the same methods. miRNAs were extracted from the isolated HDL and miR-223, miR-24 and miR-126 levels were determined by TaqMan miRNA assays. Results: miR-223, miR-24 and miR-126 were present on HDL from obese subjects before and after bariatric surgery. Before surgery, levels of miR-223, miR-24 and miR-126 on HDL from morbidly obese subjects were significantly higher than the levels on HDL from normal subjects. At 12 months after bariatric surgery, miR-223, miR-24 and miR-126 levels on HDL from obese subjects were increased by 2.9-fold, 2.3-fold and 2.7-fold (p<0.05 all), respectively, compared to before surgery. Conclusion: HDL-associated miRNAs are differentially regulated in healthy versus morbidly obese subjects. miR-223, miR-24 and miR-126 are sensitive to weight loss induced by bariatric surgery.

Select Articles Published on the Topic of Coronary Heart Disease in 2013

Select Articles Published on the Topic of Coronary Heart Disease in 2013

Transport of high density lipoproteins though endothelial cells (855.7)

Atherosclerosis is a progressive accumulation of lipids in the arterial intima leading to plaque formation. Epidemiological studies show an inverse association of high density lipoprotein (HDL) cholesterol with cardiovascular events. HDL has multiple anti‐atherogenic functions, some of which take place in the vessel wall. To get access to the intima and the lipid‐laden macrophages, HDL has to pass the endothelial barrier.To elucidate the itinerary of HDL through endothelial cells (ECs), we investigated localisation and distribution of fluorescently and 1.4 nm Nanogold labelled HDL in fluorescent (FL) as well as electron microscopy (EM). For EM, we used high pressure freezing (HPF) and to avoid lipid extraction we developed a fast method for silver enhancement of the nanogold‐HDL after fixation in OsO4.HDL is detectable in ECs in a concentration and time dependent manner. Colocalisations of HDL with dextran were negative excluding fluid phase uptake and transferrin and albumin show only slight colocalisation indicating an atypical uptake mechanism.Further experiments showed that HDL is neither targeted to lysosomes nor to the Golgi or the endoplasmatic reticulum. Only small amounts can be detected in early endosomes (Rab5) and endosome to trans‐golgi network (Rab9), but not at all with late endosomes (Rab7), the recycling endosomes (Rab11a) or vesicles involved in trans‐Golgi network sorting (Stx6). EM ultrastructure shows HDL to be located mainly in multivesicular bodies.We corroborated our findings in aortic artery endothelium. Live microscopy experiments as well as biochemical data help us to understand the itinerary of HDL through aortic ECs.