Transfer of low density lipoprotein into the arterial wall and risk of atherosclerosis

Blood Lipoproteins Shape the Phenotype and Lipid Content of Early Atherosclerotic Lesion Macrophages: A Dual-Structured Mathematical Model

Macrophages in atherosclerotic lesions exhibit a spectrum of behaviours or phenotypes. The phenotypic distribution of monocyte-derived macrophages (MDMs), its correlation with MDM lipid content, and relation to blood lipoprotein densities are not well understood. Of particular interest is the balance between low density lipoproteins (LDL) and high density lipoproteins (HDL), which carry bad and good cholesterol respectively. To address these issues, we have developed a mathematical model for early atherosclerosis in which the MDM population is structured by phenotype and lipid content. The model admits a simpler, closed subsystem whose analysis shows how lesion composition becomes more pathological as the blood density of LDL increases relative to the HDL capacity. We use asymptotic analysis to derive a power-law relationship between MDM phenotype and lipid content at steady-state. This relationship enables us to understand why, for example, lipid-laden MDMs have a more inflammatory phenotype than lipid-poor MDMs when blood LDL lipid density greatly exceeds HDL capacity. We show further that the MDM phenotype distribution always attains a local maximum, while the lipid content distribution may be unimodal, adopt a quasi-uniform profile or decrease monotonically. Pathological lesions exhibit a local maximum in both the phenotype and lipid content MDM distributions, with the maximum at an inflammatory phenotype and near the lipid content capacity respectively. These results illustrate how macrophage heterogeneity arises in early atherosclerosis and provide a framework for future model validation through comparison with single-cell RNA sequencing data.

Tiaogan daozhuo formula attenuates atherosclerosis via activating AMPK -PPARγ-LXRα pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Tiaogan Daozhuo Formula (TGDZF) is a common formulation against atherosclerosis, however, there is limited understanding of its therapeutic mechanism.

AIM OF THIS STUDY

To examine the effectiveness of TGDZF in the treatment of atherosclerosis and to explore its mechanisms.

MATERIALS AND METHODS

In ApoE-/- mice, atherosclerosis was induced by a high-fat diet for 12 weeks and treated with TGDZF at different doses. The efficacy of TGDZF in alleviating atherosclerosis was evaluated by small animal ultrasound and histological methods. Lipid levels were measured by biochemical methods. The capacity of cholesterol efflux was tested with a cholesterol efflux assay in peritoneal macrophage, and the expression of AMPKα1, PPARγ, LXRα, and ABCA1 was examined at mRNA and protein levels. Meanwhile, RAW264.7-derived macrophages were induced into foam cells by ox-LDL, and different doses of TGDZF-conducting serum were administered. Similarly, we examined differences in intracellular lipid accumulation, cholesterol efflux rate, and AMPKα1, PPARγ, LXRα, and ABCA1 levels following drug intervention. Finally, changes in the downstream molecules were evaluated following the inhibition of AMPK by compound C or PPARγ silencing by small interfering RNA.

RESULTS

TGDZF administration reduced aortic plaque area and lipid accumulation in aortic plaque and hepatocytes, and improved the serum lipid profiles of ApoE-/- mice. Further study revealed that its efficacy was accompanied by an increase in cholesterol efflux rate and the expression of PPARγ, LXRα, and ABCA1 mRNA and protein, as well as the promotion of AMPKα1 phosphorylation. Moreover, similar results were caused by the intervention of TGDZF-containing serum in vitro experiments. Inhibition of AMPK and PPARγ partially blocked the regulatory effect of TGDZF, respectively.

CONCLUSIONS

TGDZF alleviated atherosclerosis and promoted cholesterol efflux from macrophages by activating the AMPK-PPARγ-LXRα-ABCA1 pathway.

Plant-Based Nutrition: Exploring Health Benefits for Atherosclerosis, Chronic Diseases, and Metabolic Syndrome-A Comprehensive Review

Atherosclerosis, chronic non-communicable diseases, and metabolic syndrome are highly interconnected and collectively contribute to global health concerns that reduce life expectancy and quality of life. These conditions arise from multiple risk factors, including inflammation, insulin resistance, impaired blood lipid profile, endothelial dysfunction, and increased cardiovascular risk. Adopting a plant-based diet has gained popularity as a viable alternative to promote health and mitigate the incidence of, and risk factors associated with, these three health conditions. Understanding the potential benefits of a plant-based diet for human health is crucial, particularly in the face of the rising prevalence of chronic diseases like diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer. Thus, this review focused on the plausible advantages of consuming a type of food pattern for the prevention and/or treatment of chronic diseases, emphasizing the dietary aspects that contribute to these conditions and the evidence supporting the benefits of a plant-based diet for human health. To facilitate a more in-depth analysis, we present separate evidence for each of these three concepts, acknowledging their intrinsic connection while providing a specific focus on each one. This review underscores the potential of a plant-based diet to target the underlying causes of these chronic diseases and enhance health outcomes for individuals and populations.

Divergence of the normalized wall shear stress as an effective computational template of low-density lipoprotein polarization at the arterial blood-vessel wall interface

BACKGROUND AND OBJECTIVE

Near-wall transport of low-density lipoproteins (LDL) in arteries plays a relevant role in the initiation of atherosclerosis. Although it can be modelled in silico by coupling the Navier-Stokes equations with the 3D advection-diffusion (AD) equation, the associated computational cost is high. As wall shear stress (WSS) represents a first-order approximation of the near-wall velocity in arteries, we aimed at identifying computationally convenient WSS-based quantities to infer LDL near-wall transport based on the underlying near-wall hemodynamics in five models of three human arterial districts (aorta, carotid bifurcations, coronary arteries). The simulated LDL transport and its WSS-based surrogates were qualitatively compared with in vivo longitudinal measurements of wall thickness growth on the coronary artery models.

METHODS

Numerical simulations of blood flow coupled with AD equations for LDL transport and blood-wall transfer were performed. The co-localization of the simulated LDL concentration polarization patterns with luminal surface areas characterized by low cycle-average WSS, near-wall flow stagnation and WSS attracting patterns was quantitatively assessed by the similarity index (SI). In detail, the latter two represent features of the WSS topological skeleton, obtained respectively through the Lagrangian tracking of surface-born particles, and the Eulerian analysis of the divergence of the normalized cycle-average WSS vector field.

RESULTS

Convergence of the solution of the AD problem required the simulation of 3 (coronary artery) to 10 (aorta) additional cardiac cycles with respect to the Navier-Stokes problem. Co-localization results underlined that WSS topological skeleton features indicating near-wall flow stagnation and WSS attracting patterns identified LDL concentration polarization profiles more effectively than low WSS, as indicated by higher SI values (SI range: 0.17-0.50 for low WSS; 0.24-0.57 for WSS topological skeleton features). Moreover, the correspondence between the simulated LDL uptake and WSS-based quantities profiles with the in vivo measured wall thickness growth in coronary arteries appears promising.

CONCLUSIONS

The recently introduced Eulerian approach for identifying WSS attracting patterns from the divergence of normalized WSS provides a computationally affordable template of the LDL polarization at the arterial blood-wall interface without simulating the AD problem. It thus candidates as an effective biomechanical tool for elucidating the mechanistic link amongst LDL transfer at the arterial blood-wall interface, WSS and atherogenesis.

A Non-Canonical Link between Non-Coding RNAs and Cardiovascular Diseases

Cardiovascular diseases (CVDs) are among the top leading causes of mortality worldwide. Besides canonical environmental and genetic changes reported so far for CVDs, non-coding RNAs (ncRNAs) have emerged as key regulators of genetic and epigenetic mechanisms involved in CVD progression. High-throughput and sequencing data revealed that almost 80% of the total genome not only encodes for canonical ncRNAs, such as micro and long ncRNAs (miRNAs and lncRNAs), but also generates novel non-canonical sub-classes of ncRNAs, such as isomiRs and miRNA- and lncRNA-like RNAs. Moreover, recent studies reveal that canonical ncRNA sequences can influence the onset and evolution of CVD through novel “non-canonical” mechanisms. However, a debate exists over the real existence of these non-canonical ncRNAs and their concrete biochemical functions, with most of the dark genome being considered as “junk RNA”. In this review, we report on the ncRNAs with a scientifically validated canonical and non-canonical biogenesis. Moreover, we report on canonical ncRNAs that play a role in CVD through non-canonical mechanisms of action.

The Reciprocal Relationship between LDL Metabolism and Type 2 Diabetes Mellitus

Type 2 diabetes mellitus and insulin resistance feature substantial modifications of the lipoprotein profile, including a higher proportion of smaller and denser low-density lipoprotein (LDL) particles. In addition, qualitative changes occur in the composition and structure of LDL, including changes in electrophoretic mobility, enrichment of LDL with triglycerides and ceramides, prolonged retention of modified LDL in plasma, increased uptake by macrophages, and the formation of foam cells. These modifications affect LDL functions and favor an increased risk of cardiovascular disease in diabetic individuals. In this review, we discuss the main findings regarding the structural and functional changes in LDL particles in diabetes pathophysiology and therapeutic strategies targeting LDL in patients with diabetes.

S1P in the development of atherosclerosis: roles of hemodynamic wall shear stress and endothelial permeability

Atherosclerosis is characterized by focal accumulations of lipid within the arterial wall, thought to arise from effects of hemodynamic wall shear stress (WSS) on endothelial permeability. Identifying pathways that mediate the effects of shear on permeability could therefore provide new therapeutic opportunities. Here, we consider whether the sphingosine-1-phosphate (S1P) pathway could constitute such a route. We review effects of S1P in endothelial barrier function, the influence of WSS on S1P production and signaling, the results of trials investigating S1P in experimental atherosclerosis in mice, and associations between S1P levels and cardiovascular disease in humans. Although it seems clear that S1P reduces endothelial permeability and responds to WSS, the evidence that it influences atherosclerosis is equivocal. The effects of specifically pro- and anti-atherosclerotic WSS profiles on the S1P pathway require investigation, as do influences of S1P on the vesicular pathways likely to dominate low-density lipoprotein transport across endothelium.

Macrophages in Atherosclerosis, First or Second Row Players?

Macrophages represent a cell type that has been widely described in the context of atherosclerosis since the earliest studies in the 17th century. Their role has long been considered to be preponderant in the onset and aggravation of atherosclerosis, in particular by participating in the establishment of a chronic inflammatory state by the release of pro-inflammatory cytokines and by uncontrolled engorgement of lipids resulting in the formation of foam cells and later of the necrotic core. However, recent evidence from mouse models using an elegant technique of tracing vascular smooth muscle cells (VSMCs) during plaque development revealed that resident VSMCs display impressive plastic properties in response to an arterial injury, allowing them to switch into different cell types within the plaque, including mesenchymal-like cells, macrophage-like cells and osteochondrogenic-like cells. In this review, we oppose the arguments in favor or against the influence of macrophages versus VSMCs in all stages of atherosclerosis including pre-atherosclerosis, formation of lipid-rich foam cells, development of the necrotic core and the fibrous cap as well as calcification and rupture of the plaque. We also analyze the relevance of animal models for the investigation of the pathophysiological mechanisms of atherosclerosis in humans, and discuss potential therapeutic strategies targeting either VSMCs or macrophage to prevent the development of cardiovascular events. Overall, although major findings have been made from animal models, efforts are still needed to better understand and therefore prevent the development of atherosclerotic plaques in humans.

ClC-3: A Novel Promising Therapeutic Target for Atherosclerosis

Chloride channel 3 (ClC-3), a Cl^-/H⁺ antiporter, has been well established as a member of volume-regulated chloride channels (VRCCs). ClC-3 may be a crucial mediator for activating inflammation-associated signaling pathways by regulating protein phosphorylation. A growing number of studies have indicated that ClC-3 overexpression plays a crucial role in mediating increased plasma low-density lipoprotein levels, vascular endothelium dysfunction, pro-inflammatory activation of macrophages, hyper-proliferation and hyper-migration of vascular smooth muscle cells (VSMCs), as well as oxidative stress and foam cell formation, which are the main factors responsible for atherosclerotic plaque formation in the arterial wall. In the present review, we summarize the molecular structures and classical functions of ClC-3. We further discuss its emerging role in the atherosclerotic process. In conclusion, we explore the potential role of ClC-3 as a therapeutic target for atherosclerosis.

Obesity and Diabetes: A Sword of Damocles for Future Generations

Childhood obesity is one of the most challenging problem of the 21st century. The prevalence has increased, reaching an alarming rate. Furthermore, the problem is global and is also affecting low- and middle-income countries. This global obesity epidemic explains how the roots of cardiovascular disease, the most common cause of mortality among adults, begin in childhood. Overweight and obese children are likely to stay obese into adulthood and to develop noncommunicable diseases such as diabetes and cardiovascular diseases at a younger age. Thus, prevention should be the major goal and should start early in life. The aim of this review is to present an updated framework of the current understanding of the cardiovascular and metabolic risks in obese children and adolescents and to discuss the available therapeutic options.

Pre-atherosclerotic flow and oncotically active solute transport across the arterial endothelium

Atherosclerosis starts with transmural (transwall) pressure-driven advective transport of blood-borne low-density lipoprotein (LDL) cholesterol across rare endothelial cell (EC) monolayer leaks into the arterial subendothelial intima (SI) wall layer where they can spread, bind to extracellular matrix and seed lesions. The local SI LDL concentration, which governs LDL's binding kinetics, depends on the overall diluting transmural liquid flow. Transmural pressures typically compress the SI at physiological pressures, which keeps this flow low. Nguyen et al. (2015) showed that aortic ECs express the water channel protein aquaporin-1 (AQP1) and the transEC (δP) portion of the transmural (ΔP) pressure difference drives, in parallel, water across AQP1s and plasma across interEC junctions. Since the lumen is isotonic, selective AQP1-mediated water flow should quickly render the ECs' lumen side hypertonic and the SI hypotonic; resulting transEC oncotic pressure differences, δπ, should oppose δP and quickly halt transEC flow. Yet Nguyen et al.'s (2015) transAQP1 flows persist for hours. To resolve this paradox, we extend our fluid filtration theory Joshi et al. (2015) to include mass transfer for oncotically active solutes like albumin. This addition nonlinearly couples mass transfer, fluid flow and wall mechanics. We simultaneously solve these problems at steady state. Surprisingly it finds that media layer filtration causes steady SI to exceed EC glycocalyx albumin concentration. Thus δπ reinforces rather than opposes δP, i.e., it sucks water from, rather than pushing water into the lumen from the SI. Endothelial AQP1s raise the overall driving force for flow across the EC above δP, most significantly at pressures too low to compress the SI, and they increase the ΔP needed for SI compression. This suggests the intriguing possibility that increasing EC AQP1 expression can raise this requisite compression pressure to physiological values. That is, increasing EC AQP1 may decompress the SI at physiological pressures, which would significantly increase SI thickness, flow and subsequently SI LDL dilution. This could retard LDL binding and delay preatherosclerotic lesion onset. The model also predicts that glycocalyx-degrading enzymes decrease overall transEC driving forces and thus lower, not raise, transmural water flux.

LDL Receptor Regulates the Reverse Transport of Macrophage-Derived Unesterified Cholesterol via Concerted Action of the HDL-LDL Axis: Insight From Mouse Models

RATIONALE

The HDL (high-density lipoprotein)-mediated stimulation of cellular cholesterol efflux initiates macrophage-specific reverse cholesterol transport (m-RCT), which ends in the fecal excretion of macrophage-derived unesterified cholesterol (UC). Early studies established that LDL (low-density lipoprotein) particles could act as efficient intermediate acceptors of cellular-derived UC, thereby preventing the saturation of HDL particles and facilitating their cholesterol efflux capacity. However, the capacity of LDL to act as a plasma cholesterol reservoir and its potential impact in supporting the m-RCT pathway in vivo both remain unknown.

OBJECTIVE

We investigated LDL contributions to the m-RCT pathway in hypercholesterolemic mice.

METHODS AND RESULTS

Macrophage cholesterol efflux induced in vitro by LDL added to the culture media either alone or together with HDL or ex vivo by plasma derived from subjects with familial hypercholesterolemia was assessed. In vivo, m-RCT was evaluated in mouse models of hypercholesterolemia that were naturally deficient in CETP (cholesteryl ester transfer protein) and fed a Western-type diet. LDL induced the efflux of radiolabeled UC from cultured macrophages, and, in the simultaneous presence of HDL, a rapid transfer of the radiolabeled UC from HDL to LDL occurred. However, LDL did not exert a synergistic effect on HDL cholesterol efflux capacity in the familial hypercholesterolemia plasma. The m-RCT rates of the LDLr (LDL receptor)-KO (knockout), LDLr-KO/APOB100, and PCSK9 (proprotein convertase subtilisin/kexin type 9)-overexpressing mice were all significantly reduced relative to the wild-type mice. In contrast, m-RCT remained unchanged in HAPOB100 Tg (human APOB100 transgenic) mice with fully functional LDLr, despite increased levels of plasma APO (apolipoprotein)-B-containing lipoproteins.

CONCLUSIONS

Hepatic LDLr plays a critical role in the flow of macrophage-derived UC to feces, while the plasma increase of APOB-containing lipoproteins is unable to stimulate m-RCT. The results indicate that, besides the major HDL-dependent m-RCT pathway via SR-BI (scavenger receptor class B type 1) to the liver, a CETP-independent m-RCT path exists, in which LDL mediates the transfer of cholesterol from macrophages to feces. Graphical Abstract: A graphical abstract is available for this article.

Lipid profiling in maternal and fetal circulations in preeclampsia and fetal growth restriction-a prospective case control observational study

Background

While many risk factors for preeclampsia, such as increased body mass index, advanced maternal age, chronic hypertension, diabetes, are now established in clinical practice, maternal lipid profile has not been included in the risk assessment for preeclampsia. We aim to characterize the serum levels of Total Cholesterol (TC), High density lipoprotein (HDL), Low density lipoprotein (LDL), Triglycerides (TG), Apolipoprotein A1, Apolipoprotein B and their ratios TC/HDL and ApoB/ApoA1 in the maternal and fetal circulations of normal pregnancy, preeclampsia (PE), fetal growth restriction (FGR) and PE + FGR.

Methods

A prospective cross-sectional case control study was conducted measuring maternal and fetal lipid levels by enzymatic analysis and immune-turbidimetric enzymatic assays. FGR was defined by elevated umbilical artery Doppler resistance in association with estimated fetal weight < 10%. Kruskal Wallis non-parametric analysis of variance was used to test for homogeneity across the clinical groups for each of the variables, Mann-Whitney tests for pairwise comparisons and Spearman rank correlation were used to quantify gestational age-related changes.

Results

(1) TG levels were elevated in maternal PE and cord blood PE + FGR groups compared to normal pregnancies. (2) A statistically significant elevation of fetal ApoB levels was observed in PE, FGR and PE + FGR compared to normal pregnancies. Apolipoprotein levels A1 and B were not different between maternal groups. (3) TC, HDL, LDL and TC/HDL levels did not show any significant gestational variation or between clinical groups in the maternal or fetal circulation.

Conclusions

Elevation in maternal TG levels may have a role in the pathogenesis of PE. The implications of elevated maternal and fetal TG levels and elevated fetal Apolipoprotein B levels deserves further exploration of their role in long term cardiovascular risk in the mother as well as the offspring.

Effect of arterial curvature on hemodynamics and mass transport

BACKGROUND

Atherosclerotic lesions develop preferentially at certain sites in the human arterial system, such as the inner wall of curved segments and the outer wall of bifurcations. Local wall shear stress (WSS) and concentration of low density lipoprotein (LDL) have been identified as two important factors contributing to these lesions.

OBJECTIVE

To determine if a connection exists between arterial curvature and the formation of atherosclerosis.

METHODS

A set of 3-D vessel models with different bend angles was constructed. By comparing blood flow, WSS, and LDL aggregation, the influence of bend curvature on atherosclerotic lesions was assessed.

RESULTS

Upon increasing arterial bending, low WSS regions were formed at the outer wall of the junction between straight and curved segments, as well as the inner wall of curved segments. However, high LDL concentrations only appeared at the inner wall of the bend region. A connection between secondary flow and LDL concentration was observed; high LDL concentration regions had stronger secondary flow. Higher water infiltration velocity could enhance LDL aggregation, while blood non-Newtonian properties, by easing secondary flow, diminished its aggregation.

CONCLUSIONS

Under the same flow rate, a larger bend angle increased flow resistance, lowered WSS, and increased LDL surface concentrations, thus indicating an increased risk of atherosclerosis.

Endothelial permeability, LDL deposition, and cardiovascular risk factors-a review

Early atherosclerosis features functional and structural changes in the endothelial barrier function that affect the traffic of molecules and solutes between the vessel lumen and the vascular wall. Such changes are mechanistically related to the development of atherosclerosis. Proatherogenic stimuli and cardiovascular risk factors, such as dyslipidaemias, diabetes, obesity, and smoking, all increase endothelial permeability sharing a common signalling denominator: an imbalance in the production/disposal of reactive oxygen species (ROS), broadly termed oxidative stress. Mostly as a consequence of the activation of enzymatic systems leading to ROS overproduction, proatherogenic factors lead to a pro-inflammatory status that translates in changes in gene expression and functional rearrangements, including changes in the transendothelial transport of molecules, leading to the deposition of low-density lipoproteins (LDL) and the subsequent infiltration of circulating leucocytes in the intima. In this review, we focus on such early changes in atherogenesis and on the concept that proatherogenic stimuli and risk factors for cardiovascular disease, by altering the endothelial barrier properties, co-ordinately trigger the accumulation of LDL in the intima and ultimately plaque formation.

Efficiently Generating Mixing by Combining Differing Small Amplitude Helical Geometries

Helical geometries have been used in recent years to form cardiovascular prostheses such as stents and shunts. The helical geometry has been found to induce swirling flow, promoting in-plane mixing. This is hypothesised to reduce the formation of thrombosis and neo-intimal hyperplasia, in turn improving device patency and reducing re-implantation rates. In this paper we investigate whether joining together two helical geometries, of differing helical radii, in a repeating sequence, can produce significant gains in mixing effectiveness, by embodying a ‘streamline crossing’ flow environment. Since the computational cost of calculating particle trajectories over extended domains is high, in this work we devised a procedure for efficiently exploring the large parameter space of possible geometry combinations. Velocity fields for the single geometries were first obtained using the spectral/hp element method. These were then discontinuously concatenated, in series, for the particle tracking based mixing analysis of the combined geometry. Full computations of the most promising combined geometries were then performed. Mixing efficiency was evaluated quantitatively using Poincaré sections, particle residence time data, and information entropy. Excellent agreement was found between the idealised (concatenated flow field) and the full simulations of mixing performance, revealing that a strict discontinuity between velocity fields is not required for mixing enhancement, via streamline crossing, to occur. Optimal mixing was found to occur for the combination R = 0.2 D and R = 0.5 D , producing a 70 % increase in mixing, compared with standard single helical designs. The findings of this work point to the benefits of swirl disruption and suggest concatenation as an efficient means to determine optimal configurations of repeating geometries for future designs of vascular prostheses.

Nutritional Relevance of Flavonoids in Disease Prevention

Flavonoids are not essential nutrients in that their absence from the diet does not produce deficiency conditions in animals and man. However, many have important similarities to pharmacological agents used in the treatment of disease. Their role as dietary components in disease prevention is less clear. Many potentially anti-carcinogenic and anti-atherogenic effects observed in cell cultures will not be of nutritional relevance unless flavonoids gain access to appropriate cellular sites. The bioavailability of flavonoids will depend on numerous factors including molecular structure, the amount consumed, the food matrix, degree of bioconversion in the gut and tissues, the nutrient status of the host and genetic factors. Moreover, extensive and rapid intestinal and hepatic metabolism of flavonoids suggests that the body may treat them as xenobiotic and potentially toxic compounds requiring rapid elimination. Consequently, in addition to potential health benefits, possible adverse effects of flavonoids in the diet also need to be considered when assessing their roles in the prevention of degenerative diseases.

In vitro measurements of hemodynamic forces and their effects on endothelial cell mechanics at the sub-cellular level

This paper presents micro-particle tracking velocimetry measurements over cultured bovine aortic endothelial cell monolayers in microchannels. The objective was to quantify fluid forces and cell morphology at the sub-cellular scale for monolayers subjected to steady shear rates of 5, 10, and 20 dyn/cm2. The ultimate goal of this study was to develop an experimental methodology for in vitro detailed study of physiologically realistic healthy and diseased conditions. Cell topography, shear stress, and pressure distributions were calculated from sets of velocity fields made in planes parallel to the microchannel wall. For each experiment, measurements were made in 3 h intervals for 18 h. It was found that there is a three-dimensional change in cell morphology as a result of applied shear stress. That is, cells flatten and become more wedge shaped in the stream direction while conserving volume by spreading laterally, i.e., in the cross-stream direction. These changes in cell morphology are directly related to local variations in fluid loading, i.e., shear stress and pressure. This paper describes the first flow measurements over a confluent layer of endothelial cells that are spatially resolved at the sub-cellular scale with a simultaneous temporal resolution to quantify the response of cells to fluid loading.

Endocytosis of lipoproteins

During their metabolism, all lipoproteins undergo endocytosis, either to be degraded intracellularly, for example in hepatocytes or macrophages, or to be re-secreted, for example in the course of transcytosis by endothelial cells. Moreover, there are several examples of internalized lipoproteins sequestered intracellularly, possibly to exert intracellular functions, for example the cytolysis of trypanosoma. Endocytosis and the subsequent intracellular itinerary of lipoproteins hence are key areas for understanding the regulation of plasma lipid levels as well as the biological functions of lipoproteins. Indeed, the identification of the low-density lipoprotein (LDL)-receptor and the unraveling of its transcriptional regulation led to the elucidation of familial hypercholesterolemia as well as to the development of statins, the most successful therapeutics for lowering of cholesterol levels and risk of atherosclerotic cardiovascular diseases. Novel limiting factors of intracellular trafficking of LDL and the LDL receptor continue to be discovered and to provide drug targets such as PCSK9. Surprisingly, the receptors mediating endocytosis of high-density lipoproteins or lipoprotein(a) are still a matter of controversy or even new discovery. Finally, the receptors and mechanisms, which mediate the uptake of lipoproteins into non-degrading intracellular itineraries for re-secretion (transcytosis, retroendocytosis), storage, or execution of intracellular functions, are largely unknown.

Extracellular Lipids Accumulate in Human Carotid Arteries as Distinct Three-Dimensional Structures and Have Proinflammatory Properties

Lipid accumulation is a key characteristic of advancing atherosclerotic lesions. Herein, we analyzed the ultrastructure of the accumulated lipids in endarterectomized human carotid atherosclerotic plaques using three-dimensional (3D) electron microscopy, a method never used in this context before. 3D electron microscopy revealed intracellular lipid droplets and extracellular lipoprotein particles. Most of the particles were aggregated, and some connected to needle-shaped or sheet-like cholesterol crystals. Proteomic analysis of isolated extracellular lipoprotein particles revealed that apolipoprotein B is their main protein component, indicating their origin from low-density lipoprotein, intermediate-density lipoprotein, very-low-density lipoprotein, lipoprotein (a), or chylomicron remnants. The particles also contained small exchangeable apolipoproteins, complement components, and immunoglobulins. Lipidomic analysis revealed differences between plasma lipoproteins and the particles, thereby indicating involvement of lipolytic enzymes in their generation. Incubation of human monocyte-derived macrophages with the isolated extracellular lipoprotein particles or with plasma lipoproteins that had been lipolytically modified in vitro induced intracellular lipid accumulation and triggered inflammasome activation in them. Taken together, extracellular lipids accumulate in human carotid plaques as distinct 3D structures that include aggregated and fused lipoprotein particles and cholesterol crystals. The particles originate from plasma lipoproteins, show signs of lipolytic modifications, and associate with cholesterol crystals. By inducing intracellular cholesterol accumulation (ie, foam cell formation) and inflammasome activation, the extracellular lipoprotein particles may actively enhance atherogenesis.

A mechanistic model for atherosclerosis and its application to the cohort of Mayak workers

We propose a stochastic model for use in epidemiological analysis, describing the age-dependent development of atherosclerosis with adequate simplification. The model features the uptake of monocytes into the arterial wall, their proliferation and transition into foam cells. The number of foam cells is assumed to determine the health risk for clinically relevant events such as stroke. In a simulation study, the model was checked against the age-dependent prevalence of atherosclerotic lesions. Next, the model was applied to incidence of atherosclerotic stroke in the cohort of male workers from the Mayak nuclear facility in the Southern Urals. It describes the data as well as standard epidemiological models. Based on goodness-of-fit criteria the risk factors smoking, hypertension and radiation exposure were tested for their effect on disease development. Hypertension was identified to affect disease progression mainly in the late stage of atherosclerosis. Fitting mechanistic models to incidence data allows to integrate biological evidence on disease progression into epidemiological studies. The mechanistic approach adds to an understanding of pathogenic processes, whereas standard epidemiological methods mainly explore the statistical association between risk factors and disease outcome. Due to a more comprehensive scientific foundation, risk estimates from mechanistic models can be deemed more reliable. To the best of our knowledge, such models are applied to epidemiological data on cardiovascular diseases for the first time.

Endometriosis and Risk of Coronary Heart Disease

BACKGROUND

Endometriosis is a prevalent gynecologic disease associated with systemic chronic inflammation, heightened oxidative stress, and atherogenic lipid profile that may increase women's risk for coronary heart disease (CHD).

METHODS AND RESULTS

We examined the prospective association between laparoscopically confirmed endometriosis and subsequent CHD among 116 430 women in the Nurses' Health Study II (1989-2009). Participants with a history of heart disease and stroke were excluded. When compared with women without endometriosis, women with laparoscopically confirmed endometriosis had a higher risk of myocardial infarction (relative risk, 1.52; 95% confidence interval, 1.17-1.98), angiographically confirmed angina (1.91; 1.59-2.29), coronary artery bypass graft surgery/coronary angioplasty procedure/stent (1.35; 1.08-1.69), or any of these CHD end points combined (1.62; 1.39-1.89), independent of potential demographic, anthropometric, family history, reproductive, and lifestyle confounders. Relative risk for the combined CHD end point was highest among women aged ≤40 years (3.08; 2.02-4.70) and decreased as age increased (40< age ≤50 years, 1.65; 1.35-2.02; 50< age ≤55 years, 1.44; 1.07-1.94; and age >55 years, 0.98; 0.56-1.72; P value, test for heterogeneity=0.001). Having had a hysterectomy/oophorectomy was associated with higher risk of combined CHD compared with not having had a hysterectomy/oophorectomy (1.51; 1.34-1.71). A percentage of 42 of the association between endometriosis and CHD could be explained by greater frequency of hysterectomy/oophorectomy and earlier age at surgery after endometriosis diagnosis.

CONCLUSIONS

In this large, prospective cohort, laparoscopically confirmed endometriosis was associated with increased risk of CHD. The association was strongest among young women. Hysterectomy/oophorectomy was associated with higher risk of CHD and could partially explain the association between endometriosis and CHD.

Visible aging signs as risk markers for ischemic heart disease: Epidemiology, pathogenesis and clinical implications

Association of common aging signs (i.e., male pattern baldness, hair graying, and facial wrinkles) as well as other age-related appearance factors (i.e., arcus corneae, xanthelasmata, and earlobe crease) with increased risk of ischemic heart disease was initially described in anecdotal reports from clinicians observing trends in the physical appearance of patients with ischemic heart disease. Following these early observations numerous epidemiological studies have reported these associations. Since the prevalences of both visible aging signs and ischemic heart disease have a strong correlation with increasing age, it has been extensively debated whether the observed associations could be entirely explained by a common association with age. Furthermore, the etiologies of the visible aging signs are rarely fully understood, and pathophysiological explanations for these associations remain controversial, and are mostly speculative. As a consequence of inconsistent findings and lack of mechanistic explanations for the observed associations with ischemic heart disease, consensus on the clinical importance of these visible aging signs has been lacking. The aim of this review is for each of the visible aging signs to (i) review the etiology, (ii) to discuss the current epidemiological evidence for an association with risk of ischemic heart disease, and (iii) to present possible pathophysiological explanations for these associations. Finally this review discusses the potential clinical implications of these findings.

Altered metabolism of LDL in the arterial wall precedes atherosclerosis regression

RATIONALE

Plasma cholesterol lowering is beneficial in patients with atherosclerosis. However, it is unknown how it affects entry and degradation of low-density lipoprotein (LDL) particles in the lesioned arterial wall.

OBJECTIVE

We studied the effect of lipid-lowering therapy on LDL permeability and degradation of LDL particles in atherosclerotic aortas of mice by measuring the accumulation of iodinated LDL particles in the arterial wall.

METHODS AND RESULTS

Cholesterol-fed, LDL receptor-deficient mice were treated with either an anti-Apob antisense oligonucleotide or a mismatch control antisense oligonucleotide once a week for 1 or 4 weeks before injection with preparations of iodinated LDL particles. The anti-Apob antisense oligonucleotide reduced plasma cholesterol by ≈90%. The aortic LDL permeability and degradation rates of newly entered LDL particles were reduced by ≈50% and ≈85% already after 1 week of treatment despite an unchanged pool size of aortic iodinated LDL particles. In contrast, the size, foam cell content, and aortic pool size of iodinated LDL particles of aortic atherosclerotic plaques were not reduced until after 4 weeks of treatment with the anti-Apob antisense oligonucleotide.

CONCLUSIONS

Improved endothelial barrier function toward the entry of plasma LDL particles and diminished aortic degradation of the newly entered LDL particles precede plaque regression.

Low-density lipoprotein accumulation within a carotid artery with multilayer elastic porous wall: fluid-structure interaction and non-Newtonian considerations

Low-density lipoprotein (LDL), which is recognized as bad cholesterol, typically has been regarded as a main cause of atherosclerosis. LDL infiltration across arterial wall and subsequent formation of Ox-LDL could lead to atherogenesis. In the present study, combined effects of non-Newtonian fluid behavior and fluid-structure interaction (FSI) on LDL mass transfer inside an artery and through its multilayer arterial wall are examined numerically. Navier-Stokes equations for the blood flow inside the lumen and modified Darcy's model for the power-law fluid through the porous arterial wall are coupled with the equations of mass transfer to describe LDL distributions in various segments of the artery. In addition, the arterial wall is considered as a heterogeneous permeable elastic medium. Thus, elastodynamics equation is invoked to examine effects of different wall elasticity on LDL distribution in the artery. Findings suggest that non-Newtonian behavior of filtrated plasma within the wall enhances LDL accumulation meaningfully. Moreover, results demonstrate that at high blood pressure and due to the wall elasticity, endothelium pores expand, which cause significant variations on endothelium physiological properties in a way that lead to higher LDL accumulation. Additionally, results describe that under hypertension, by increasing angular strain, endothelial junctions especially at leaky sites expand more dramatic for the high elastic model, which in turn causes higher LDL accumulation across the intima layer and elevates atherogenesis risk.

Apolipoprotein B Is Related to Metabolic Syndrome Independently of Low Density Lipoprotein Cholesterol in Patients with Type 2 Diabetes

BACKGROUND

Increased low density lipoprotein cholesterol (LDL-C) level and the presence of metabolic syndrome (MetS) are important risk factors for cardiovascular disease (CVD) in type 2 diabetes mellitus (T2DM). Recent studies demonstrated apolipoprotein B (apoB), a protein mainly located in LDL-C, was an independent predictor of the development of CVD especially in patients with T2DM. The aim of this study was to investigate the relationship between apoB and MetS in T2DM patients.

METHODS

We analyzed 912 patients with T2DM. Fasting blood samples were taken for glycated hemoglobin, high-sensitivity C-reactive protein, total cholesterol, triglyceride (TG), high density lipoprotein cholesterol, LDL-C, and apoB. MetS was defined by the modified National Cholesterol Education Program Adult Treatment Panel III criteria. We performed a hierarchical regression analysis with apoB as the dependent variable. Age, sex, the number of components of MetS and LDL-C were entered at model 1, the use of lipid-lowering medications at model 2, and the individual components of MetS were added at model 3.

RESULTS

Seventy percent of total subjects had MetS. ApoB level was higher in subjects with than those without MetS (104.5±53.3 mg/dL vs. 87.7±33.7 mg/dL, P<0.01) even after adjusting for LDL-C. ApoB and LDL-C were positively correlated to the number of MetS components. The hierarchical regression analysis showed that the increasing number of MetS components was associated with higher level of apoB at step 1 and step 2 (β=0.120, P<0.001 and β=0.110, P<0.001, respectively). At step 3, TG (β=0.116, P<0.001) and systolic blood pressure (β=0.099, P<0.05) were found to significantly contribute to apoB.

CONCLUSION

In patients with T2DM, apoB is significantly related to MetS independently of LDL-C level. Of the components of MetS, TG, and systolic blood pressure appeared to be determinants of apoB.

Enhanced vascular permeability facilitates entry of plasma HDL and promotes macrophage-reverse cholesterol transport from skin in mice

Reverse cholesterol transport (RCT) pathway from macrophage foam cells initiates when HDL particles cross the endothelium, enter the interstitial fluid, and induce cholesterol efflux from these cells. We injected [(3)H]cholesterol-loaded J774 macrophages into the dorsal skin of mice and measured the transfer of macrophage-derived [(3)H]cholesterol to feces [macrophage-RCT (m-RCT)]. Injection of histamine to the macrophage injection site increased locally vascular permeability, enhanced influx of intravenously administered HDL, and stimulated m-RCT from the histamine-treated site. The stimulatory effect of histamine on m-RCT was abolished by prior administration of histamine H1 receptor (H1R) antagonist pyrilamine, indicating that the histamine effect was H1R-dependent. Subcutaneous administration of two other vasoactive mediators, serotonin or bradykinin, and activation of skin mast cells to secrete histamine and other vasoactive compounds also stimulated m-RCT. None of the studied vasoactive mediators affected serum HDL levels or the cholesterol-releasing ability of J774 macrophages in culture, indicating that acceleration of m-RCT was solely due to increased availability of cholesterol acceptors in skin. We conclude that disruption of the endothelial barrier by vasoactive compounds enhances the passage of HDL into interstitial fluid and increases the rate of RCT from peripheral macrophage foam cells, which reveals a novel tissue cholesterol-regulating function of these compounds.

Atherogenic dyslipidemia and cardiovascular risk factors in obese children

Childhood obesity when associated with serum lipoprotein changes triggers atherosclerosis. Evidences suggest that the atherosclerotic process begins in childhood and that the extent of early atherosclerosis of the aorta and coronary arteries can be associated with lipoprotein levels and obesity. Furthermore, many studies in childhood demonstrate an important relationship between parameters of insulin sensitivity, body fat distribution, and the development of lipid abnormalities. This review focuses on the most recent findings on the relationship between obesity, dyslipidemia, and cardiovascular risk in children.

Elevated uptake of plasma macromolecules by regions of arterial wall predisposed to plaque instability in a mouse model

Atherosclerosis may be triggered by an elevated net transport of lipid-carrying macromolecules from plasma into the arterial wall. We hypothesised that whether lesions are of the thin-cap fibroatheroma (TCFA) type or are less fatty and more fibrous depends on the degree of elevation of transport, with greater uptake leading to the former. We further hypothesised that the degree of elevation can depend on haemodynamic wall shear stress characteristics and nitric oxide synthesis. Placing a tapered cuff around the carotid artery of apolipoprotein E -/- mice modifies patterns of shear stress and eNOS expression, and triggers lesion development at the upstream and downstream cuff margins; upstream but not downstream lesions resemble the TCFA. We measured wall uptake of a macromolecular tracer in the carotid artery of C57bl/6 mice after cuff placement. Uptake was elevated in the regions that develop lesions in hyperlipidaemic mice and was significantly more elevated where plaques of the TCFA type develop. Computational simulations and effects of reversing the cuff orientation indicated a role for solid as well as fluid mechanical stresses. Inhibiting NO synthesis abolished the difference in uptake between the upstream and downstream sites. The data support the hypothesis that excessively elevated wall uptake of plasma macromolecules initiates the development of the TCFA, suggest that such uptake can result from solid and fluid mechanical stresses, and are consistent with a role for NO synthesis. Modification of wall transport properties might form the basis of novel methods for reducing plaque rupture.

The effects of treatment on lipoprotein subfractions evaluated by polyacrylamide gel electrophoresis in patients with autoimmune hypothyroidism and hyperthyroidism

BACKGROUND

Atherogenic dyslipoproteinemia is one of the most important risk factor for atherosclerotic changes development. Hypothyroidism is one of the most common causes of secondary dyslipidemias which results from reduced LDL clearance and therefore raised levels of LDL and apoB. Association between small dense LDL (sdLDL) presentation and thyroid status has been examinated using polyacrylamide gel electrophoresis for lipoprotein subfractions evaluation.

METHODS

40 patients with diagnosed autoimmune hypothyroidism and 30 patients with autoimmune hyperthyroidism were treated with thyroxine replacement or thyreo-suppressive treatment. In both groups lipid profiles, LDL subractions, apolipoproteins (apoA1, apoB), apoA1/apoB ratio and atherogenic index of plazma (AIP) were examined before treatment and in state of euthyreosis.

RESULTS

Thyroxine replacement therapy significantly reduced levels of total cholesterol (TC), LDL, triglycerides (TG) and also decreased levels of sdLDL (8,55±11,671 vs 0,83±1,693mg/dl; p<0,001), apoB and AIP. For estimation of atherogenic lipoprotein profile existence an AIP evaluation seems to be better than apoB measurement because of the more evident relationship with sdLDL (r=0,538; p<0,01). Thyreo-suppressive therapy significantly increased levels of TC, LDL, TG and apoB. The sdLDL was not found in hyperthyroid patients.

CONCLUSIONS

Atherogenic lipoprotein profile was present in 52.5% of hypothyroid subjects, which is higher prevalence than in normal, age-related population. Substitution treatment leads to an improvement of the lipid levels, TG, apoB, AIP and LDL subclasses. It significantly changed the presentation of sdLDL - we noticed shift to large, less atherogenic LDL particles. Significantly positive correlation between sdLDL and TAG; sdLDL and VLDL alerts to hypertriglyceridemia as a major cardiovascular risk factor.

Carnitine therapy for the treatment of metabolic syndrome and cardiovascular disease: evidence and controversies

As the incidence of metabolic syndrome increases, there is also a growing interest in finding safe and inexpensive treatments to help lower associated risk factors. L-carntine, a natural dietary supplement with the potential to ameliorate atherosclerosis, has been the subject of recent investigation and controversy. A majority of studies have shown benefit of L-C supplementation in the metabolic syndrome or cardiovascular risk factors. However, recent work has suggested that dietary L-C may accelerate atherosclerosis via gut microbiota metabolites, complicating the role of L-C supplementation in health.

A combined numerical and experimental framework for determining permeability properties of the arterial media

The medial layer of the arterial wall may play an important role in the regulation of water and solute transport across the wall. In particular, a high medial resistance to transport could cause accumulation of lipid-carrying molecules in the inner wall. In this study, the water transport properties of medial tissue were characterised in a numerical model, utilising experimentally obtained data for the medial microstructure and the relative permeability of different constituents. For the model, a new solver for flow in porous materials, based on a high-order splitting scheme, was implemented in the spectral/hp element library nektar++ and validated. The data were obtained by immersing excised aortic bifurcations in a solution of fluorescent protein tracer and subsequently imaging them with a confocal microscope. Cuboidal regions of interest were selected in which the microstructure and relative permeability of different structures were transformed to a computational mesh. Impermeable objects were treated fictitiously in the numerical scheme. On this cube, a pressure drop was applied in the three coordinate directions and the principal components of the permeability tensor were determined. The reconstructed images demonstrated the arrangement of elastic lamellae and interspersed smooth muscle cells in rat aortic media; the distribution and alignment of the smooth muscle cells varied spatially within the extracellular matrix. The numerical simulations highlighted that the heterogeneity of the medial structure is important in determining local water transport properties of the tissue, resulting in regional and directional variation of the permeability tensor. A major factor in this variation is the alignment and density of smooth muscle cells in the media, particularly adjacent to the adventitial layer.

MicroRNA-126-5p promotes endothelial proliferation and limits atherosclerosis by suppressing Dlk1

Atherosclerosis, a hyperlipidemia-induced chronic inflammatory process of the arterial wall, develops preferentially at sites where disturbed laminar flow compromises endothelial cell (EC) function. Here we show that endothelial miR-126-5p maintains a proliferative reserve in ECs through suppression of the Notch1 inhibitor delta-like 1 homolog (Dlk1) and thereby prevents atherosclerotic lesion formation. Endothelial recovery after denudation was impaired in Mir126(-/-) mice because lack of miR-126-5p, but not miR-126-3p, reduced EC proliferation by derepressing Dlk1. At nonpredilection sites, high miR-126-5p levels in endothelial cells confer a proliferative reserve that compensates for the antiproliferative effects of hyperlipidemia, such that atherosclerosis was exacerbated in Mir126(-/-) mice. In contrast, downregulation of miR-126-5p by disturbed flow abrogated EC proliferation at predilection sites in response to hyperlipidemic stress through upregulation of Dlk1 expression. Administration of miR-126-5p rescued EC proliferation at predilection sites and limited atherosclerosis, introducing a potential therapeutic approach.

Relationship between oxidized LDL, IgM, and IgG autoantibodies to ox-LDL levels with recurrent cardiovascular events in Swedish patients with previous myocardial infarction

We determined whether plasma levels of circulating oxidized low-density lipoprotein (LDL; E06), immunoglobulin (Ig) G, and IgM autoantibodies binding to malonyldialdehyde-modified LDL (MDA-LDL) may predict cardiovascular events (CVEs). Patients (n=123) with a previous myocardial infarction (MI) were included. The primary end point was defined as any of the following: cardiovascular death from any cause, nonfatal reinfarction or stroke, percutaneous coronary intervention, coronary artery bypass grafting, and hospitalization due to angina pectoris. There were 43 CVEs during the follow-up period of 8.4±3.5 years. There was no significant difference in the levels of E06 and MDA-LDL IgG between the CVE and the event-free group. However, MDA-LDL IgM levels were significantly lower in patients in the CVE group (9524±6326 relative light unit [RLU]) compared with the event-free (10,975±5398 RLU) group (P=.04). In conclusion, levels of MDA-LDL IgM were associated with an increased risk of CVE in patients with a previous MI.

Advanced lipoprotein measures and recurrent preterm birth

OBJECTIVE

Lipoproteins are associated with atherogenic and inflammatory processes, and these processes may be related to adverse pregnancy outcomes. We therefore examined whether variations in lipoprotein particle size and concentration are associated with preterm birth (PTB) <35 weeks' gestation.

STUDY DESIGN

This is a case-control ancillary study to a randomized trial of omega-3 fatty acid supplementation to prevent recurrent PTB. We measured standard lipids and used nuclear magnetic resonance (NMR) spectroscopy to characterize 17 lipoprotein particles from plasma collected at the baseline randomization visit (16-21 weeks' gestation) in 128 cases (PTB <35 weeks' gestation) and 132 term controls. Logistic regression models controlled for study center, race/ethnicity, number of prior PTB, smoking, and treatment group, as well as total low-density lipoprotein (LDL), high-density lipoprotein, and triglyceride concentrations when examining LDLNMR, high-density lipoproteinNMR, and very LDL (VLDL)NMR, respectively.

RESULTS

Only 1 of the 17 NMR lipoproteins was associated with recurrent PTB. We observed an increased odds of recurrent PTB of 1.04 (95% confidence interval, 1.01-1.08; P = .02) per nanometer increase in VLDLNMR particle size and an odds ratio of 3.00 (confidence interval, 1.40-6.43; P = .005) for the third tertile of VLDLNMR particle size compared with the first tertile.

CONCLUSION

In women with prior PTB, variations in midpregnancy lipoproteins were not associated with recurrent PTB overall, however the association observed with VLDLNMR particle size is suggestive that PTB may be amenable to lifestyle, nutritional, or pharmacologic interventions.

Atrial natriuretic peptide genetic variant rs5065 and risk for cardiovascular disease in the general community: a 9-year follow-up study

We analyzed the phenotype associated with the atrial natriuretic peptide (ANP) genetic variant rs5065 in a random community-based sample. We also assessed and compared the biological action of 2 concentrations (10(-10) mol/L, 10(-8) mol/L) of ANP and ANP-RR, the protein variant encoded by the minor allele of rs5065, on activation of the guanylyl cyclase (GC)-A and GC-B receptors, production of the second messenger 3',5'-cGMP in endothelial cells, and endothelial permeability. rs5065 genotypes were determined in a cross-sectional adult cohort from Olmsted County, MN (n=1623). Genotype frequencies for rs5065 were 75%, 24%, and 1% for TT, TC, and CC, respectively. Multivariate analysis showed that the C allele was associated with increased risk of cerebrovascular accident (hazard ratio, 1.43; 95% confidence interval, 1.09-1.86; P=0.009) and higher prevalence of myocardial infarction (odds ratio, 1.82; 95% confidence interval, 1.07-3.09; P=0.026). ANP-RR 10(-8) mol/L activated the GC-A receptor (83.07±8.31 versus no treatment 0.18±0.04 per 6 wells; P=0.006), whereas ANP-RR 10(-10) mol/L did not. Neither 10(-8) mol/L nor 10(-10) mol/L ANP-RR activated GC-B receptor (P=0.10, P=0.35). ANP 10(-8) mol/L and ANP-RR 10(-8) mol/L stimulated 3',5'-cGMP production in endothelial cells similarly (P=0.58). Both concentrations of ANP-RR significantly enhanced human aortic endothelial cell permeability (69 versus 29 relative fluorescence units [RFUs], P=0.012; 58 versus 39 RFUs, P=0.015) compared with ANP. The minor allele of rs5065 was associated with increased cardiovascular risk. ANP-RR activated the GC-A receptor, increased 3',5'-cGMP in endothelial cells, and when compared with ANP, augmented endothelial cell permeability.

Mipomersen, an apolipoprotein B synthesis inhibitor, reduces atherogenic lipoproteins in patients with severe hypercholesterolemia at high cardiovascular risk: a randomized, double-blind, placebo-controlled trial

OBJECTIVES

This study sought to examine the efficacy and safety of mipomersen for reducing atherogenic lipids and lipoproteins in patients with hypercholesterolemia.

BACKGROUND

Many patients on lipid-lowering therapies remain unable to achieve target low-density lipoprotein (LDL) cholesterol levels. Mipomersen, an antisense oligonucleotide inhibitor of apolipoprotein B, reduces LDL cholesterol and atherogenic lipoproteins.

METHODS

This randomized, double-blind, multicenter study enrolled 158 patients with baseline LDL cholesterol levels ≥100 mg/dl with, or at high risk for, coronary heart disease who were receiving maximally tolerated lipid-lowering therapy. Patients received weekly subcutaneous mipomersen 200 mg (n = 105) or placebo (n = 52) for 26 weeks, with a 24-week follow-up period. Randomization was stratified by type 2 diabetes status.

RESULTS

Sixty mipomersen and 44 placebo patients completed treatment. Mean baseline LDL cholesterol levels were 122.7 and 122.6 mg/dl in the placebo and mipomersen patients, respectively. Mipomersen reduced LDL cholesterol by -36.9% compared with placebo at -4.5% (p < 0.001). Target LDL cholesterol <100 mg/dl was attained in 76% of mipomersen and 38% of placebo patients. Mipomersen also significantly reduced apolipoprotein B (-38%) and lipoprotein(a) (-24%) (p < 0.001). Common adverse events included injection site reactions (78% with mipomersen, 31% with placebo) and flu-like symptoms (34% with mipomersen, 21% with placebo). Elevations in transaminases and liver fat also occurred in some patients, and these levels returned toward baseline after treatment cessation.

CONCLUSIONS

Mipomersen significantly reduced LDL cholesterol, apolipoprotein B, and lipoprotein(a) in patients with hypercholesterolemia with, or at risk for, coronary heart disease not controlled by existing therapies. (Safety and Efficacy of Mipomersen [ISIS 301012] as Add-On Therapy in High Risk Hypercholesterolemic Patients; NCT00770146).

LDL decreases the membrane compliance and cell adhesion of endothelial cells under fluid shear stress

Atherosclerosis is an inflammatory disease of large and medium sized arteriole walls that is precipitated by elevated levels of low-density lipoprotein (LDL) cholesterol in the blood. However, the mechanisms that lead to the initiation of atherosclerosis are not fully understood. In this study, endothelial cells (ECs) were incubated with LDL for 24 h, and then the lipid was detected with Oil Red O staining and cholesterol ester was assayed with high-performance liquid chromatography (HPLC). F-actin was examined by fluorescence microscopy and the viscoelasticity of ECs was investigated using the micropipette aspiration technique. Then, a parallel-plate flow chamber device was used to observe the adhesion and retention of ECs under shear stress. The results demonstrated that elevated LDL significantly increased the cellular lipid content and induced the rearrangement of cytoskeletal F-actin. The initial rapid deformability (l/K 1 + l/K 2) was reduced by elevated cellular LDL levels, while membrane viscosity (μ) was increased by LDL accumulation. After treatment with 150 mg L(-1) LDL for 24 h, the adhesion of ECs under fluid shear stress was significantly decreased (p < 0.05). These results suggested that LDL induced cellular lipid accumulation and cytoskeleton reorganization which increased the cellular stiffness and decreased the adhesion of ECs.

High throughput en face mapping of arterial permeability using tile scanning confocal microscopy

Elevated uptake of plasma macromolecules by the arterial wall has been implicated in the initiation of atherosclerosis. Here we describe a new method for mapping such uptake in laboratory animals. Albumin was labelled with a fluorescent dye and administered intravenously. After 10 min, the aorta was fixed in situ, excised and opened. En face confocal microscopy employing a computer-controlled stage was used to obtain contiguous tiles, each consisting of a stack of images of fluorescence emission at different depths in the wall. To obtain two-dimensional maps, intensities were summed in each column of voxels starting at the endothelial surface and extending 10 μm into the wall. Variation in the sensitivity of the system with time and in all three spatial directions was assessed and corrected using calibration standards and model specimens. In immature rabbits, uptake around aorto-intercostal branches was greatest in an arrowhead-shaped region around the downstream half of each ostium, and at its lateral margins. Uptake around branches in mature rabbits was more uniform; it was highest upstream of the ostium. Patches and streaks of high uptake were also seen at non-branch locations in the descending thoracic aorta. Transport was more uniform around branches in mice, except for small regions of high uptake at the ostial rim and at the leading edge of an intimal cushion upstream of the ostium, where lesions develop. The technique provides accurate quantification in three dimensions over large areas; it has high throughput, sensitivity and resolution and is suitable for widespread use.