High Density Lipoprotein Structure Research Articles

Cholesterol transport and beyond: Illuminating the versatile functions of HDL apolipoproteins through structural insights and functional implications.

High-density lipoproteins (HDLs) play a vital role in lipid metabolism and cardiovascular health, as they are intricately involved in cholesterol transport and inflammation modulation. The proteome of HDL particles is indeed complex and distinct from other components in the bloodstream. Proteomics studies have identified nearly 285 different proteins associated with HDL; however, this review focuses more on the 15 or so traditionally named "apo" lipoproteins. Important lipid metabolizing enzymes closely working with the apolipoproteins are also discussed. Apolipoproteins stand out for their integral role in HDL stability, structure, function, and metabolism. The unique structure and functions of each apolipoprotein influence important processes such as inflammation regulation and lipid metabolism. These interactions also shape the stability and performance of HDL particles. HDLs apolipoproteins have multifaceted roles beyond cardiovascular diseases (CVDs) and are involved in various physiological processes and disease states. Therefore, a detailed exploration of these apolipoproteins can offer valuable insights into potential diagnostic markers and therapeutic targets. This comprehensive review article aims to provide an in-depth understanding of HDL apolipoproteins, highlighting their distinct structures, functions, and contributions to various physiological processes. Exploiting this knowledge holds great potential for improving HDL function, enhancing cholesterol efflux, and modulating inflammatory processes, ultimately benefiting individuals by limiting the risks associated with CVDs and other inflammation-based pathologies. Understanding the nature of all 15 apolipoproteins expands our knowledge of HDL metabolism, sheds light on their pathological implications, and paves the way for advancements in the diagnosis, prevention, and treatment of lipid and inflammatory-related disorders.

Lipid exchange of apolipoprotein A-I amyloidogenic variants in reconstituted high-density lipoprotein with artificial membranes.

High-density lipoproteins (HDLs) are responsible for removing cholesterol from arterial walls, through a process known as reverse cholesterol transport. The main protein in HDL, apolipoprotein A-I (ApoA-I), is essential to this process, and changes in its sequence significantly alter HDL structure and functions. ApoA-I amyloidogenic variants, associated with a particular hereditary degenerative disease, are particularly effective at facilitating cholesterol removal, thus protecting carriers from cardiovascular disease. Thus, it is conceivable that reconstituted HDL (rHDL) formulations containing ApoA-I proteins with functional/structural features similar to those of amyloidogenic variants hold potential as a promising therapeutic approach. Here we explored the effect of protein cargo and lipid composition on the function of rHDL containing one of the ApoA-I amyloidogenic variants G26R or L174S by Fourier transformed infrared spectroscopy and neutron reflectometry. Moreover, small-angle x-ray scattering uncovered the structural and functional differences between rHDL particles, which could help to comprehend higher cholesterol efflux activity and apparent lower phospholipid (PL) affinity. Our findings indicate distinct trends in lipid exchange (removal vs. deposition) capacities of various rHDL particles, with the rHDL containing the ApoA-I amyloidogenic variants showing a markedly lower ability to remove lipids from artificial membranes compared to the rHDL containing the native protein. This effect strongly depends on the level of PL unsaturation and on the particles' ultrastructure. The study highlights the importance of the protein cargo, along with lipid composition, in shaping rHDL structure, contributing to our understanding of lipid-protein interactions and their behavior.

Lipoprotein dysfunction in patients with chronic kidney disease (CKD). Pathogenesis and treatment of CKD dyslipidemia (literature review)

Dyslipidemia develops in the initial stages of chronic kidney disease (CKD) and worsens as nephropathy progresses. The main manifestation of dyslipidemia is hypercholesterolemia, especially in nephrotic syndrome. However, with CKD of stages 4-5, it is replaced by hypertriglyceridemia in combination with an increase in blood levels of lipoproteins low and very low density. Such changes are closely related to the development of cardiovascular pathology with high mortality. The content of high-density lipoproteins (HDL) in the blood is gradually decreasing, as well as the reversible transport of cholesterol. Thus, their anti-atherogenic, antioxidant and anti-inflammatory functions are lost. The main components of HDL – apolipoproteins ApoA-I and ApoA-II, which provide functionality, are replaced by acute-phase proteins, and HDL lose their cardioprotective potential and acquire a proinflammatory and proatherogenic phenotype. According to modern concepts, HDL dysfunction, along with metabolic shifts, is largely due to epigenetic disorders affecting gene expression and partially eliminated by prescribing drugs containing microRNAs (mRNAs) or antisense nucleotides. Drugs with interfering RNAs created in recent years have been successfully used not only for the treatment of dyslipidemia in nephrological patients, but also in patients with neoplastic processes, inflammatory arthritis, degenerative diseases of the central nervous system, porphyria, hemophilia and many other diseases. The proposed review is devoted to the mechanisms of disorders of the structure and functions of HDL in patients with CKD and the correction of these disorders.

Assessment of amino-terminal C-type natriuretic peptide serum level and its correlation with high-density lipoprotein structure and function in patients with end stage renal disease before and after kidney transplantation

We aimed to investigate serum amino-terminal C-type natriuretic peptide (NT-proCNP) and its relationship with quantitative and qualitative HDL-parameters in patients with end-stage renal disease (ESRD) before, then 1 and 6 months after kidney transplantation (TX). Seventy patients (47 males, 23 females, mean age 51.7 ± 12.4 years) were enrolled in a prospective follow-up study. We examined serum creatinine, C-reactive protein, procalcitonin, fasting glucose and lipid parameters before, then 1 and 6 months after TX. High-density lipoprotein- (HDL)-associated paraoxonase-1 (PON1) paraoxonase and arylesterase activities were measured spectrophotometrically. Lipoprotein subfractions were determined by Lipoprint. NT-proCNP and oxidized low-density lipoprotein (oxLDL) levels were measured by ELISA. Mean NT-proCNP was 45.8 ± 21.9 pmol/L before renal transplantation and decreased markedly 1 month and 6 months after transplantation (5.3 ± 2.5 and 7.7 ± 4.9 pmol/L, respectively, P = 1 × 10−4). During the 6 months’ follow-up, PON1 arylesterase, paraoxonase and salt-stimulated paraoxonase activities improved. NT-proCNP positively correlated with procalcitonin and creatinine and negatively with GFR, LDL-cholesterol (LDL-C) and HDL-cholesterol (HDL-C). There was a negative correlation between serum NT-proCNP and PON1 arylesterase activity. According to the multiple regression analysis, the best predicting variables of NT-proCNP were serum procalcitonin, creatinine and PON1 arylesterase activity. NT-proCNP might be a novel link between HDL dysfunction and impaired vascular function in ESRD, but not after kidney transplantation. Further studies in larger populations are needed to clarify the exact role of NT-proCNP in the risk prediction for cardiovascular comorbidities and complications in ESRD.

Effects of CaCl2 on the structure of high-density lipoprotein and low-density lipoprotein isolated from rapidly salted separated egg yolk

According to previous research, adding CaCl2 to the salting solution improves the quality of salted separated egg yolk. To further understand the improvement mechanism of CaCl2, this paper investigated the effect of CaCl2 on the structure of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) during the salting process. The results indicated that the addition of CaCl2 can affect the composition of HDL and LDL apolipoproteins, improving the orderliness of the HDL structure and the looseness of the LDL structure. It was discovered by atomic force microscopy (AFM) that adding CaCl2 to the salting solution can weaken the aggregation behavior of HDL. Simultaneously, the addition of CaCl2 decreased the relative content of intermolecular β-sheets in the secondary structure of HDL and LDL, influenced their tertiary conformation, and prevented HDL and LDL from participating in the formation of a three-dimensional gel structure by influencing their hydrogen bonds and hydrophobic interactions.

Unravelling the influence of surface lipids on the structure, dynamics and interactome of high-density lipoproteins

Surface lipids influence the biological activities of high-density lipoproteins (HDLs) but their species-specific effects on HDL structure, dynamics, and surface interactome has remained unclear. Building upon the five-lipid species HDL models developed and characterised in previous work, representative models of the major HDL subpopulations found in human plasma containing apolipoprotein A-I (apoA-I) have been studied using molecular dynamics simulation to describe their varying degrees of surface lipidome complexity. Specifically, two additional sets of representative HDL subpopulation particles were developed, one with sphingomyelin (SM) and the other with SM, phosphatidylethanolamine, phosphatidylinositol, and ceramide in quantities reflecting average levels characterised for HDL subpopulations derived from normolipidemic patients. These lipid species were assessed in terms of HDL size, morphology, dynamics, and overall interactome. The findings reveal that the presence of a representative SM fraction marginally enhanced HDL interfacial curvature and surface monolayer rigidity, manifesting in tighter phospholipid packing and slower surface lipid dynamics relative to SM-deficient HDL models. Furthermore, the presence of SM resulted in a reduction in the solvent exposure of core lipids and cholesterol molecules, whilst also enhancing apolipoprotein conformational flexibility and its overall twisting across the HDL surface. The hydrophobicity of apoA-I-bound lipid patches and the proportion of apoA-I hydrophobic surface area is enhanced by the overall lipidation of apoA-I irrespective of lipid composition. These findings offer new insights into how the surface lipid composition of different HDL subpopulations can significantly impact the overall interactome of HDL particles, potentially influencing subpopulation-specific biological functions like lipid scavenging and receptor interactions.

High Density Lipoproteins: Metabolism, Biological Functions and Risk of cardiovascular pathology

High levels of high-density lipoproteins (HDL) in blood plasma have traditionally been considered an anti-atherogenic factor, but this opinion is not always supported by epidemiological and genetic studies. The functions of lipoproteins are of much greater importance, the main of which is the implementation of the reverse cholesterol transport (RCT) from cells to the liver. The part 1 of the review presents the sequence of passage of cholesterol in HDL, shows the importance of each link in this chain for the development of atherosclerosis; the main methods for determining RCT are given. Changes in the structure and function of HDL, which play the important role in the pathogenesis of a number of chronic diseases that in one way or another stimulate the development of atherosclerosis, are considered in part 2 of the review.

High-Density Lipoprotein in Metabolic Disorders and Beyond: An Exciting New World Full of Challenges and Opportunities.

High-density lipoprotein (HDL) is an enigmatic member of the plasma lipid and lipoprotein transport system, best known for its ability to promote the reverse cholesterol efflux and the unloading of excess cholesterol from peripheral tissues. More recently, data in experimental mice and humans suggest that HDL may play important novel roles in other physiological processes associated with various metabolic disorders. Important parameters in the HDL functions are its apolipoprotein and lipid content, further reinforcing the principle that HDL structure defines its functionality. Thus, based on current evidence, low levels of HDL-cholesterol (HDL-C) or dysfunctional HDL particles contribute to the development of metabolic diseases such as morbid obesity, type 2 diabetes mellitus, and nonalcoholic fatty liver disease. Interestingly, low levels of HDL-C and dysfunctional HDL particles are observed in patients with multiple myeloma and other types of cancer. Therefore, adjusting HDL-C levels within the optimal range and improving HDL particle functionality is expected to benefit such pathological conditions. The failure of previous clinical trials testing various HDL-C-raising pharmaceuticals does not preclude a significant role for HDL in the treatment of atherosclerosis and related metabolic disorders. Those trials were designed on the principle of "the more the better", ignoring the U-shape relationship between HDL-C levels and morbidity and mortality. Thus, many of these pharmaceuticals should be retested in appropriately designed clinical trials. Novel gene-editing-based pharmaceuticals aiming at altering the apolipoprotein composition of HDL are expected to revolutionize the treatment strategies, improving the functionality of dysfunctional HDL.

Power doppler ultrasound signal predicts abnormal HDL function in patients with rheumatoid arthritis

Active rheumatoid arthritis (RA) is associated with increased cardiovascular risk and impaired function of high-density lipoprotein (HDL). Previous work suggests that HDL may become dysfunctional through oxidative modifications within the RA joint. The current work evaluates an association of synovial power doppler ultrasound signal (PDUS) with HDL function and structure. Two open-label clinical therapeutic studies using PDUS as a disease outcome measure were included in this analysis, including a 12-month trial of subcutaneous abatacept in 24 RA patients and a 6-month trial of IV tocilizumab in 46 RA patients. Laboratory assays included assessments of HDL function and structure, HDL and total cholesterol levels, and a cytokine/chemokine panel. Patients with the highest baseline PDUS scores in both clinical studies, had worse HDL function, including suppression of paraoxonase 1 (PON1) activity as well as lower HDL-C levels. Associations between other disease assessments (DAS28 and CDAI) and HDL function/structure were noted but were generally of lesser magnitude and consistency than PDUS across the HDL profile. Treatment with tocilizumab for 6 months was associated with increases in cholesterol levels and improvements in the HDL function profile, which correlated with greater decreases in PDUS scores. Similar trends were noted following treatment with abatacept for 3 months. Higher baseline PDUS scores identified patients with worse HDL function. This data supports previous work suggesting a direct association of joint inflammation with abnormal HDL function.

Anti-Inflammatory Activity of CIGB-258 against Acute Toxicity of Carboxymethyllysine in Paralyzed Zebrafish via Enhancement of High-Density Lipoproteins Stability and Functionality.

Background: Hyperinflammation is frequently associated with the chronic pain of autoimmune disease and the acute death of coronavirus disease (COVID-19) via a severe cytokine cascade. CIGB-258 (Jusvinza®), an altered peptide ligand with 3 kDa from heat shock protein 60 (HSP60), inhibits the systemic inflammation and cytokine storm, but the precise mechanism is still unknown. Objective: The protective effect of CIGB-258 against inflammatory stress of N-ε-carboxymethyllysine (CML) was tested to provide mechanistic insight. Methods: CIGB-258 was treated to high-density lipoproteins (HDL) and injected into zebrafish and its embryo to test a putative anti-inflammatory activity under presence of CML. Results: Treatment of CML (final 200 μM) caused remarkable glycation of HDL with severe aggregation of HDL particles to produce dysfunctional HDL, which is associated with a decrease in apolipoprotein A-I stability and lowered paraoxonase activity. Degradation of HDL3 by ferrous ions was attenuated by a co-treatment with CIGB-258 with a red-shift of the Trp fluorescence in HDL. A microinjection of CML (500 ng) into zebrafish embryos resulted in the highest embryo death rate, only 18% of survivability with developmental defects. However, co-injection of CIGB-258 (final 1 ng) caused the remarkable elevation of survivability around 58%, as well as normal developmental speed. An intraperitoneal injection of CML (final 250 μg) into adult zebrafish resulted acute paralysis, sudden death, and laying down on the bottom of the cage with no swimming ability via neurotoxicity and inflammation. However, a co-injection of CIGB-258 (1 μg) resulted in faster recovery of the swimming ability and higher survivability than CML alone injection. The CML alone group showed 49% survivability, while the CIGB-258 group showed 97% survivability (p < 0.001) with a remarkable decrease in hepatic inflammation up to 50%. A comparison of efficacy with CIGB-258, Infliximab (Remsima®), and Tocilizumab (Actemra®) showed that the CIGB-258 group exhibited faster recovery and swimming ability with higher survivability than those of the Infliximab group. The CIGB-258 group and Tocilizumab group showed the highest survivability, the lowest plasma total cholesterol and triglyceride level, and the infiltration of inflammatory cells, such as neutrophils in hepatic tissue. Conclusion: CIGB-258 ameliorated the acute neurotoxicity, paralysis, hyperinflammation, and death induced by CML, resulting in higher survivability in zebrafish and its embryos by enhancing the HDL structure and functionality.

Using adenovirus-mediated gene transfer to study the effect of myeloperoxidase on plasma lipid levels, HDL structure and functionality in mice expressing human apoA-I forms

Apolipoprotein A-I (apoA-I), the main protein component of High-Density Lipoprotein (HDL), is modified in plasma and the arterial wall by various enzymes. Myeloperoxidase (MPO), a leukocyte-derived peroxidase, is highly expressed during inflammation and associates with HDL reducing its functionality and contributing to atherosclerosis. In the present study we sought to explore further the effect of MPO on HDL structure and functionality in vivo using adenovirus-mediated gene transfer of human MPO combined with human apoA-I forms containing substitutions at MPO-sensitive sites or wild type apoA-I. We found that overexpression of MPO in mice significantly increased plasma apoA-I and HDL levels without affecting the expression of genes involved in HDL biogenesis or catabolism in the liver. Overexpression of MPO in the liver reduced the expression of pro-inflammatory genes and increased or did not affect the expression of anti-inflammatory genes suggesting that MPO had no toxic effects in this organ. In the plasma of mice overexpressing MPO, no significant alterations in HDL size or electrophoretic mobility was observed with the exception of mice expressing apoA-I (M148A) which showed enriched pre-β relative to α HDL particles, suggesting that the apoA-I (M148A) mutation may interfere with HDL remodelling. Overexpression of MPO was associated with reduced anti-oxidant capacity of HDL particles in all mice. Interestingly, HDL particles bearing apoA-I (Y192A) showed enhanced ABCA1-dependent cholesterol efflux from macrophages which was not affected by MPO and these mice had reduced levels of LDL-c. These findings provide new insights on the role of specific amino acid residues of apoA-I in HDL structure and function following modification by MPO. This knowledge may facilitate the development of novel therapies based on improved HDL forms for patients with chronic diseases that are characterized by dysfunctional HDL.

Glycosylation of HDL-Associated Proteins and Its Implications in Cardiovascular Disease Diagnosis, Metabolism and Function.

High-density lipoprotein (HDL) particles, long known for their critical role in the prevention of cardiovascular disease (CVD), were recently identified to carry a wide array of glycosylated proteins, and the importance of this glycosylation in the structure, function and metabolism of HDL are starting to emerge. Early studies have demonstrated differential glycosylation of HDL-associated proteins in various pathological states, which may be key to understanding their etiological role in these diseases and may be important for diagnostic development. Given the vast array and specificity of glycosylation pathways, the study of HDL-associated glycosylation has the potential to uncover novel mechanisms and biomarkers of CVD. To date, no large studies examining the relationships between HDL glycosylation profiles and cardiovascular outcomes have been performed. However, small pilot studies provide promising preliminary evidence that such a relationship may exist. In this review article we discuss the current state of the evidence on the glycosylation of HDL-associated proteins, the potential for HDL glycosylation profiling in CVD diagnostics, how glycosylation affects HDL function, and the potential for modifying the glycosylation of HDL-associated proteins to confer therapeutic value.

Adaptation of Native GELFrEE for HDL Particle Size Subtype Separation and Differential Apolipoprotein Proteoform Quantification

High‐density lipoproteins (HDL) are central to cholesterol transport, and higher concentration of HDL‐bound cholesterol (HDL‐C) is associated with lower coronary artery disease (CAD) risk. Recent reports refute a causal link between these variables, suggesting better understanding of HDL variation is necessary. HDL particles differ in size and size subtypes differ in proteome, lipidome, and functional characteristics. Apolipoprotein A‐I (ApoA‐I), a major determinant of HDL structure and biochemistry, is made up of 15 distinct proteoforms. ApoA‐I proteoforms correlate with HDL efflux, a measure of cholesterol transport efficiency, but it is unknown if ApoA‐I proteoforms vary with HDL particle size. Herein, we adapt a native separation methodology to inquire on the relationship between HDL size subtypes, their function, and apolipoprotein proteoform profiles.Pooled serum (20μl) from 30 individuals with high, medium and low HDL‐C levels, were loaded to CN‐GELFrEE, a native electrophoretic technique, to separate HDL particles by size. Mid‐resolution and high‐resolution modes were employed. Immunoassays were done to characterize ApoA‐I content and average particle size of the electrophoretic fractions. Proteoform quantification was performed on ApoA‐I‐containing fractions by top‐down LC‐MS. SIM scans were devised for higher sensitivity in ApoA‐I proteoform detection. Custom software matched, scored and quantified proteoform‐specific spectra, and calculated association to particle size.In both resolution modes, average fraction sizes were roughly linearly correlated to fraction collection time, and size‐range overlap between fractions was small. In mid‐resolution mode 3‐4 fractions contained ApoA‐I, while high‐resolution mode yielded 36 distinct HDL size fractions. Fractions roughly spanned the range between 5 to 11nm, similar to previously reported ranges for HDL particles.Proteoform quantification revealed significant variation of proteoform profiles in different size‐ranges of HDL. Fatty‐acylated ApoA‐I, a species previously correlated to higher cholesterol efflux, had higher relative abundance (~1.5x to 2x) in the pre‐beta‐1 (5‐7.1nm) and alpha‐3 (9‐11nm) size ranges of HDL, while glycated and oxidized proteoforms were significantly more abundant (~3x to 4x) in the medium size ranges (alpha‐4, alpha‐3 and alpha‐2). Interestingly, the truncated proteoform of ApoA‐I had no significant differences in abundance between different particle sizes.Our experimental data suggest that the profile of ApoA‐I proteoforms in HDL particles is size‐dependent and thus ApoA‐I proteoforms may be important markers or mediators of HDL size regulation. Notably, the differences in PTM prevalence from medium sizes to large and pre‐beta subtypes may be markers of the pathway of HDL maturation and/or different functions of each subtype.

High-density lipoprotein: Quality is more important than quantity!

High density lipoproteins (HDLs) are complex lipid carriers which replace their own structures and functions according to different conditions including healthy or pathological status. HDL has substantial roles in reverse cholesterol transport system for regulation of lipid metabolism. Also HDL has many functions such as antiinflammation, antioxidation, antithrombotic and vasodilator actions. However, these functions may be compromised under pathological conditions. Nowadays, it’s known that the function of HDL is more important than it’s dose for preventing against cardiovascular diseases. This review mostly summarizes available information of HDL structure, metabolism and the real information related to the physicochemical changes of HDLs causing their different functions. Also HDLs, that lost their protective functions have been associated with oxidative stress and systemic inflammation diseases.

Understanding Myeloperoxidase-Induced Damage to HDL Structure and Function in the Vessel Wall: Implications for HDL-Based Therapies.

Atherosclerosis is a disease of increased oxidative stress characterized by protein and lipid modifications in the vessel wall. One important oxidative pathway involves reactive intermediates generated by myeloperoxidase (MPO), an enzyme present mainly in neutrophils and monocytes. Tandem MS analysis identified MPO as a component of lesion derived high-density lipoprotein (HDL), showing that the two interact in the arterial wall. MPO modifies apolipoprotein A1 (apoA-I), paraoxonase 1 and certain HDL-associated phospholipids in human atheroma. HDL isolated from atherosclerotic plaques depicts extensive MPO mediated posttranslational modifications, including oxidation of tryptophan, tyrosine and methionine residues, and carbamylation of lysine residues. In addition, HDL associated plasmalogens are targeted by MPO, generating 2-chlorohexadecanal, a pro-inflammatory and endothelial barrier disrupting lipid that suppresses endothelial nitric oxide formation. Lesion derived HDL is predominantly lipid-depleted and cross-linked and exhibits a nearly 90% reduction in lecithin-cholesterol acyltransferase activity and cholesterol efflux capacity. Here we provide a current update of the pathophysiological consequences of MPO-induced changes in the structure and function of HDL and discuss possible therapeutic implications and options. Preclinical studies with a fully functional apoA-I variant with pronounced resistance to oxidative inactivation by MPO-generated oxidants are currently ongoing. Understanding the relationships between pathophysiological processes that affect the molecular composition and function of HDL and associated diseases is central to the future use of HDL in diagnostics, therapy, and ultimately disease management.

High-density lipoprotein cholesterol — friend or enemy?

The article provides a review of the literature on the effect of excess and deficiency of high-density lipoprotein cholesterol on the prevention and treatment of cardiovascular pathology. Information about high-density lipoproteins structure, function, antiatherogenic role and the prospect of using various high-density lipoproteins subclasses in the pharmacotherapy of dyslipidemic conditions are also described. It is proven that a lowered level of such cholesterol is a predictor of cardiovascular disease. At the same time, many observations confirm the correlation between elevated high-density lipoprotein levels and mortality from myocardial infarction and other acute cardiovascular conditions. In large studies, the use of cholesterol ester transfer protein inhibitors and other drugs increased the level of high-density lipoprotein, but the unreduced risk of cardiovascular disease confirms the lack of positive results from the use as a therapeutic target. In addition, it was found that the composition of high-density lipoprotein cholesterol protein differs in healthy and diseased people: it becomes dysfunctional, losing its antioxidant and anti-inflammatory properties in diseased individuals. The atheroprotective activity of properly functioning high-density lipoprotein cholesterol is often impaired in clinical situations associated with oxidative stress. In these cases, high-density lipoproteins can have some changes, and even if the quantity is within the normal range, the quality is no longer the same. Thus, it is necessary to identify a better therapeutic target than high-density lipoprotein cholesterol levels, as there is currently insufficient clinical trial data to recommend targeted high-density lipoprotein therapy.

Dietary Strategies to Improve Cardiovascular Health: Focus on Increasing High-Density Lipoprotein Functionality.

Cardiovascular disease is one of the leading causes of morbidity and mortality worldwide, with increasing incidence. A cornerstone of cardiovascular disease prevention is lifestyle modification through dietary changes to influence various risk factors such as obesity, hypertension and diabetes. The effects of diet on cardiovascular health are complex. Some dietary components and metabolites directly affect the composition and structure of high-density lipoproteins (HDL) and increase anti-inflammatory and vasoprotective properties. HDLs are composed of distinct subpopulations of particles of varying size and composition that have several dynamic and context-dependent functions. The identification of potential dietary components that improve HDL functionality is currently an important research goal. One of the best-studied diets for cardiovascular health is the Mediterranean diet, consisting of fish, olive oil, fruits, vegetables, whole grains, legumes/nuts, and moderate consumption of alcohol, most commonly red wine. The Mediterranean diet, especially when supplemented with extra virgin olive oil rich in phenolic compounds, has been shown to markedly improve metrics of HDL functionality and reduce the burden, or even prevent the development of cardiovascular disease. Particularly, the phenolic compounds of extra virgin olive oil seem to exert the significant positive effects on HDL function. Moreover, supplementation of anthocyanins as well as antioxidants such as lycopene or the omega−3 fatty acid eicosapentaenoic acid improve parameters of HDL function. In this review, we aim to highlight recent discoveries on beneficial dietary patterns as well as nutritional components and their effects on cardiovascular health, focusing on HDL function.

High-density lipoprotein: a double-edged sword in cardiovascular physiology and pathophysiology

: High-density lipoprotein (HDL) plays a central role in vascular biology. HDL participates in multiple pathways that may be involved in the development of atherosclerosis and coronary artery disease (CAD), including cholesterol removal from the tissues (including vascular arterial wall), endothelial function protection through anti-inflammatory, antioxidant and anti-apoptotic effects, endothelial repair, angiogenesis and improved endothelial cell survival. Initial epidemiological evidence supported an inverse relationship between HDL level and the risk for atherosclerosis and CAD. Although HDL showed an inverse relationship with cardiovascular risk, pharmacologically-based HDL-raising therapies and Mendelian randomization studies refuted a causal relationship between HDL and the risk for atherosclerosis and CAD. So far, no HDL-raising therapy that increased HDL level without a concomitant decrease in the low-density lipoprotein (LDL) level reduced the cardiovascular risk. HDL structure and function alterations in various morbid conditions including inflammatory states, metabolic diseases, chronic kidney disease, cardiovascular risk factors and CAD transform HDL from a vasoprotective and anti-atherosclerotic particle into a pro-inflammatory and pro-atherosclerotic dysfunctional equivalent. Genetic studies, failure of HDL-raising therapies to improve clinical outcome despite markedly raising HDL levels and a better understanding of HDL functions led to a paradigm shift in HDL studies from investigation of HDL concentration to investigation of HDL functions (such as, cholesterol efflux capacity and anti-inflammatory indices) as a response to various therapeutic interventions. Several therapies aiming to improve HDL functions are in clinical use or under development. Future studies are needed to assess the role of HDL in vascular biology and cardiovascular epidemiology, pathophysiology and pharmacology.

Good Cholesterol Gone Bad? HDL and COVID-19

The transmissible respiratory disease COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected millions of people worldwide since its first reported outbreak in December of 2019 in Wuhan, China. Since then, multiple studies have shown an inverse correlation between the levels of high-density lipoprotein (HDL) particles and the severity of COVID-19, with low HDL levels being associated with an increased risk of severe outcomes. Some studies revealed that HDL binds to SARS-CoV-2 particles via the virus’s spike protein and, under certain conditions, such as low HDL particle concentrations, it facilitates SARS-CoV-2 binding to angiotensin-converting enzyme 2 (ACE2) and infection of host cells. Other studies, however, reported that HDL suppressed SARS-CoV-2 infection. In both cases, the ability of HDL to enhance or suppress virus infection appears to be dependent on the expression of the HDL receptor, namely, the Scavenger Receptor Class B type 1 (SR-B1), in the target cells. SR-B1 and HDL represent crucial mediators of cholesterol metabolism. Herein, we review the complex role of HDL and SR-B1 in SARS-CoV-2-induced disease. We also review recent advances in our understanding of HDL structure, properties, and function during SARS-CoV-2 infection and the resulting COVID-19 disease.

New insights into the emerging effects of inflammatory response on HDL particles structure and function.

According to the increasing results, it has been well-demonstrated that the chronic inflammatory response, including systemic lupus erythematosus, rheumatoid arthritis, and inflammatory bowel disease are associated with an increased risk of atherosclerotic cardiovascular disease. The mechanism whereby inflammatory response up-regulates the risk of cardio-metabolic disorder disease is multifactorial; furthermore, the alterations in high density lipoprotein (HDL) structure and function which occur under the inflammatory response could play an important modulatory function. On the other hand, the serum concentrations of HDL cholesterol (HDL-C) have been shown to be reduced significantly under inflammatory status with remarked alterations in HDL particles. Nevertheless, the potential mechanism whereby the inflammatory response reduces serum HDL-C levels is not simply defined but reduces apolipoprotein A1 production. The alterations in HDL structure mediated by the inflammatory response has been also confirmed to decrease the ability of HDL particle to play an important role in reverse cholesterol transport and protect the LDL particles from oxidation. Recently, it has been shown that under the inflammatory condition, diverse alterations in HDL structure could be observed which lead to changes in HDL function. In the current review, the emerging effects of inflammatory response on HDL particles structure and function are well-summarized to elucidate the potential mechanism whereby different inflammatory status modulates the pathogenic development of dyslipidemia.