Differential effects of HDL subpopulations on cellular ABCA1- and SR-BI-mediated cholesterol efflux

Relationships between HDL subpopulation proteome and HDL function in overweight/obese people with and without coronary heart disease

BACKGROUND AND AIMS

The structure-function relationships of high-density lipoprotein (HDL) subpopulations are not well understood. Our aim was to examine the interrelationships between HDL particle proteome and HDL functionality in subjects with and without coronary heart disease (CHD).

METHODS

We isolated 5 different HDL subpopulations based on charge, size, and apolipoprotein A1 (APOA1) content from the plasma of 33 overweight/obese CHD patients and 33 age-and body mass index (BMI)-matched CHD-free subjects. We measured the relative molar concentration of HDL-associated proteins by liquid chromatography tandem mass spectrometry (LC-MS/MS) and assessed particle functionality.

RESULTS

We quantified 110 proteins associated with the 5 APOA1-containing HDL subpopulations. The relative molar concentration of these proteins spanned five orders of magnitude. Only 10 proteins were present in >1% while 73 were present in <0.1% concentration. Only 6 of the 10 most abundant proteins were apolipoproteins. Interestingly, the largest (α-1) and the smallest (preβ-1) HDL particles contained the most diverse proteomes. The protein composition of each HDL subpopulation was altered in CHD cases as compared to controls with the most prominent differences in preβ-1 and α-1 particles. APOA2 concentration was positively correlated with preβ-1 particle functionality (ABCA1-CEC/mg APOA1 in preβ-1) (R2 = 0.42, p = 0.005), while APOE concentration was inversely correlated with large-HDL particle functionality (SRBI-CEC/mg APOA1 in α-1+α-2) (R2 = 0.18, p = 0.01).

CONCLUSIONS

The protein composition of the different HDL subpopulations was altered differentially in CHD patients. The functionality of the small and large HDL particles correlated with the protein content of APOA2 and APOE, respectively. Our data indicate that distinct particle subspecies and specific particle associated proteins provide new information about the role of HDL in CHD.

The Association of the Cholesterol Efflux Capacity with the Paraoxonase 1 Q192R Genotype and the Paraoxonase Activity

AIMS

Paraoxonase 1 (PON1) binds to high-density lipoprotein (HDL) and protects against atherosclerosis. However, the relationship between functional PON1 Q192R polymorphism, which is associated with the hydrolysis of paraoxon (POXase activity) and atherosclerotic cardiovascular disease (ASCVD), remains controversial. As the effect of PON1 Q192R polymorphism on the HDL function is unclear, we investigated the relationship between this polymorphism and the cholesterol efflux capacity (CEC), one of the biological functions of HDL, in association with the PON1 activity.

METHODS

The relationship between PON1 Q192R polymorphisms and CEC was investigated retrospectively in 150 subjects without ASCVD (50 with the PON1 Q/Q genotype, 50 with the Q/R genotype, and 50 with the R/R genotype) who participated in a health screening program. The POXase and arylesterase (AREase: hydrolysis of aromatic esters) activities were used as measures of the PON1 activity.

RESULTS

The AREase activity was positively correlated with CEC independent of the HDL cholesterol levels. When stratified by the PON1 Q192R genotype, the POXase activity was also positively correlated with CEC independent of HDL cholesterol. PON1 Q192R R/R genotype carriers had a lower CEC than Q/Q or Q/R genotype carriers, despite having a higher POXase activity. Moreover, in a multiple regression analysis, the PON1 Q192R genotype was associated with the degree of CEC, independent of the HDL cholesterol and POXase activity.

CONCLUSIONS

The PON1 Q192R R allele is associated with reduced CEC in Japanese people without ASCVD. Further studies on the impact of this association on the severity of atherosclerosis and ASCVD development are thus called for.

High-Density Lipoprotein Subclasses and Their Role in the Prevention and Treatment of Cardiovascular Disease: A Narrative Review

The association between high-density lipoprotein cholesterol (HDL-C) and cardiovascular disease (CVD) is controversial. HDL-C is one content type of high-density lipoprotein (HDL). HDL consists of diverse proteins and lipids and can be classified into different subclasses based on size, shape, charge, and density, and can change dynamically in disease states. Therefore, HDL-C levels alone cannot represent HDLs' cardioprotective role. In this review, we summarized the methods for separating HDL subclasses, the studies on the association between HDL subclasses and cardiovascular risk (CVR), and the impact of lipid-modifying medications and nonpharmacological approaches (exercise training, dietary omega fatty acids, and low-density lipoprotein apheresis) on HDL subclasses. As HDL is a natural nanoplatform, recombinant HDLs (rHDLs) have been used as a delivery system in vivo by loading small interfering RNA, drugs, contrast agents, etc. Therefore, we further reviewed the HDL subclasses used in rHDLs and their advantages and disadvantages. This review would provide recommendations and guidance for future studies on HDL subclasses' cardioprotective roles.

High-density lipoprotein infusion therapy: A review

Increased cholesterol-rich, low-density, non-calcified atheromas as assessed by computer coronary tomography angiography analyses have been shown to predict myocardial infarction significantly better than coronary artery calcium score or the presence of obstructive coronary artery disease (CAD) as evaluated with standard coronary angiography. Low serum high-density lipoprotein (HDL) cholesterol values are an independent risk factor for CAD. Very small, lipid-poor preβ-1 HDL particles have been shown to be most effective in promoting cellular cholesterol efflux. HDL infusions have been documented to reduce aortic atherosclerosis in cholesterol-fed animal models. However, human studies using infusions of either the HDL mimetic containing recombinant apolipoprotein (apo) A-I Milano or Cerenis Compound-001 with native recombinant apoA-I have been mainly negative in promoting coronary atherosclerosis progression as assessed by intravascular ultrasound. In contrast, a study using 7 weekly infusions of autologous delipidated HDL in six homozygous familial hypercholesterolemic patients was effective in promoting significant regression of low-density non-calcified coronary atheroma regression as assessed by computed coronary angiography. This therapy has received Food and Drug Administration approval. Commonwealth Serum Laboratories has carried out a large clinical endpoint trial using an HDL complex (native apoA-I with phospholipid), and the results were negative. Our purpose is to review animal and human studies using various forms of HDL infusion therapy to promote regression of atherosclerosis. In our view, differences in results may be due to: 1) the HDL preparations used, 2) the subjects studied, and 3) the methods used to assess coronary atherosclerosis.

Elder (Sambucus nigra), identified by high-content screening, counteracts foam cell formation without promoting hepatic lipogenesis

Cholesterol deposition in intimal macrophages leads to foam cell formation and atherosclerosis. Reverse cholesterol transport (RCT), initiated by efflux of excess cholesterol from foam cells, counteracts atherosclerosis. However, targeting RCT by enhancing cholesterol efflux was so far accompanied by adverse hepatic lipogenesis. Here, we aimed to identify novel natural enhancers of macrophage cholesterol efflux suitable for the prevention of atherosclerosis. Plant extracts of an open-access library were screened for their capacity to increase cholesterol efflux in RAW264.7 macrophages trace-labeled with fluorescent BODIPY-cholesterol. Incremental functional validation of hits yielded two final extracts, elder (Sambucus nigra) and bitter orange (Citrus aurantium L.) that induced ATP binding cassette transporter A1 (ABCA1) expression and reduced cholesteryl ester accumulation in aggregated LDL-induced foam cells. Aqueous elder extracts were subsequently prepared in-house and both, flower and leaf extracts increased ABCA1 mRNA and protein expression in human THP-1 macrophages, while lipogenic gene expression in hepatocyte-derived cells was not induced. Chlorogenic acid isomers and the quercetin glycoside rutin were identified as the main polyphenols in elder extracts with putative biological action. In summary, elder flower and leaf extracts increase macrophage ABCA1 expression and reduce foam cell formation without adversely affecting hepatic lipogenesis.

HDL Function across the Lifespan: From Childhood, to Pregnancy, to Old Age

The function of high-density lipoprotein (HDL) particles has emerged as a promising therapeutic target and the measurement of HDL function is a promising diagnostic across several disease states. The vast majority of research on HDL functional biology has focused on adult participants with underlying chronic diseases, whereas limited research has investigated the role of HDL in childhood, pregnancy, and old age. Yet, it is apparent that functional HDL is essential at all life stages for maintaining health. In this review, we discuss current data regarding the role of HDL during childhood, pregnancy and in the elderly, how disturbances in HDL may lead to adverse health outcomes, and knowledge gaps in the role of HDL across these life stages.

Differential Expression of Subsets of Genes Related to HDL Metabolism and Atherogenesis in the Peripheral Blood in Coronary Artery Disease

Differential expression of genes (DEGs) in coronary artery disease (CAD) and the association between transcript level and high-density lipoprotein cholesterol (HDL-C) were studied with 76 male patients with CAD and 63 control patients. The transcript level of genes related to HDL metabolism (24 genes) and atherosclerosis-prone (41 genes) in RNA isolated from peripheral blood mononuclear cells was measured by real-time RT-PCR. Twenty-eight DEGs were identified. The expression of cholesterol transporters, ALB, APOA1, and LCAT was down-regulated, while the expression of AMN, APOE, LDLR, LPL, PLTP, PRKACA, and CETP was up-regulated. The systemic inflammation in CAD is evidenced by the up-regulation of IL1B, TLR8, CXCL5, and TNFRSF1A. For the controls, TLR8 and SOAT1 were negative predictors of the HDL-C level. For CAD patients, PRKACG, PRKCQ, and SREBF1 were positive predictors, while PRKACB, LCAT, and S100A8 were negative predictors. For CAD patients, the efficiency of reverse cholesterol transport is 73-79%, and intracellular free cholesterol seems to accumulate at hyperalphalipoproteinemia. Both atheroprotective (via S100A8) and proatherogenic (via SREBF1, LCAT, PRKACG, PRKACB, and PRKCQ) associations of gene expression with HDL-C determine HDL functionality in CAD patients. The selected key genes and involved pathways may represent HDL-specific targets for the diagnosis and treatment of CAD and atherosclerosis.

Plasma and cerebrospinal fluid cholesterol esterification is hampered in Alzheimer's disease

OBJECTIVE

The purpose of this study was to evaluate cholesterol esterification and HDL subclasses in plasma and cerebrospinal fluid (CSF) of Alzheimer's disease (AD) patients.

METHODS

The study enrolled 70 AD patients and 74 cognitively normal controls comparable for age and sex. Lipoprotein profile, cholesterol esterification, and cholesterol efflux capacity (CEC) were evaluated in plasma and CSF.

RESULTS

AD patients have normal plasma lipids but significantly reduced unesterified cholesterol and unesterified/total cholesterol ratio. Lecithin:cholesterol acyltransferase (LCAT) activity and cholesterol esterification rate (CER), two measures of the efficiency of the esterification process, were reduced by 29% and 16%, respectively, in the plasma of AD patients. Plasma HDL subclass distribution in AD patients was comparable to that of controls but the content of small discoidal preβ-HDL particles was significantly reduced. In agreement with the reduced preβ-HDL particles, cholesterol efflux capacity mediated by the transporters ABCA1 and ABCG1 was reduced in AD patients' plasma. The CSF unesterified to total cholesterol ratio was increased in AD patients, and CSF CER and CEC from astrocytes were significantly reduced in AD patients. In the AD group, a significant positive correlation was observed between plasma unesterified cholesterol and unesterified/total cholesterol ratio with Aβ1-42 CSF content.

CONCLUSION

Taken together our data indicate that cholesterol esterification is hampered in plasma and CSF of AD patients and that plasma cholesterol esterification biomarkers (unesterified cholesterol and unesterified/total cholesterol ratio) are significantly associated to disease biomarkers (i.e., CSF Aβ1-42).

The small HDL particle hypothesis of Alzheimer's disease

We propose the hypothesis that small high-density lipoprotein (HDL) particles reduce the risk of Alzheimer's disease (AD) by virtue of their capacity to exchange lipids, affecting neuronal membrane composition and vascular and synaptic functions. Concentrations of small HDLs in cerebrospinal fluid (CSF) and plasma were measured in 180 individuals ≥60 years of age using ion mobility methodology. Small HDL concentrations in CSF were positively associated with performance in three domains of cognitive function independent of apolipoprotein E (APOE) ε4 status, age, sex, and years of education. Moreover, there was a significant correlation between levels of small HDLs in CSF and plasma. Further studies will be aimed at determining whether specific components of small HDL exchange across the blood, brain, and CSF barriers, and developing approaches to exploit small HDLs for therapeutic purposes.

Uncovering mechanisms of brain inflammation in Alzheimer's disease with APOE4: Application of single cell-type lipidomics

A chronic state of unresolved inflammation in Alzheimer's disease (AD) is intrinsically involved with the remodeling of brain lipids. This review highlights the effect of carrying the apolipoprotein E ε4 allele (APOE4) on various brain cell types in promoting an unresolved inflammatory state. Among its pleotropic effects on brain lipids, we focus on APOE4's activation of Ca²⁺ -dependent phospholipase A2 (cPLA2) and its effects on arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid signaling cascades in the brain. During the process of neurodegeneration, various brain cell types, such as astrocytes, microglia, and neurons, together with the neurovascular unit, develop distinct inflammatory phenotypes that impact their functions and have characteristic lipidomic fingerprints. We propose that lipidomic phenotyping of single cell-types harvested from brains differing by age, sex, disease severity stage, and dietary and genetic backgrounds can be employed to probe mechanisms of neurodegeneration. A better understanding of the brain cellular inflammatory/lipidomic response promises to guide the development of nutritional and drug interventions for AD dementia.

Identifying cell receptors for the nanoparticle protein corona using genome screens

Nanotechnology provides platforms to deliver medical agents to specific cells. However, the nanoparticle's surface becomes covered with serum proteins in the blood after administration despite engineering efforts to protect it with targeting or blocking molecules. Here, we developed a strategy to identify the main interactions between nanoparticle-adsorbed proteins and a cell by integrating mass spectrometry with pooled genome screens and Search Tool for the Retrieval of Interacting Genes analysis. We found that the low-density lipoprotein (LDL) receptor was responsible for approximately 75% of serum-coated gold nanoparticle uptake in U-87 MG cells. Apolipoprotein B and complement C8 proteins on the nanoparticle mediated uptake through the LDL receptor. In vivo, nanoparticle accumulation correlated with LDL receptor expression in the organs of mice. A detailed understanding of how adsorbed serum proteins bind to cell receptors will lay the groundwork for controlling the delivery of nanoparticles at the molecular level to diseased tissues for therapeutic and diagnostic applications.

HDL Cholesterol Efflux and Serum Cholesterol Loading Capacity Alterations Associate to Macrophage Cholesterol Accumulation in FH Patients with Achilles Tendon Xanthoma

Achilles tendon xanthoma (ATX) formation involves macrophage cholesterol accumulation within the tendon, similar to that occurring in atheroma. Macrophage cholesterol homeostasis depends on serum lipoprotein functions, namely the high-density lipoprotein (HDL) capacity to promote cell cholesterol efflux (cholesterol efflux capacity, CEC) and the serum cholesterol loading capacity (CLC). We explored the HDL-CEC and serum CLC, comparing 16 FH patients with ATX to 29 FH patients without ATX. HDL-CEC through the main efflux mechanisms mediated by the transporters ATP binding cassette G1 (ABCG1) and A1 (ABCA1) and the aqueous diffusion (AD) process was determined by a cell-based radioisotopic technique and serum CLC fluorimetrically. Between the two groups, no significant differences were found in terms of plasma lipid profile. A trend toward reduction of cholesterol efflux via AD and a significant increase in ABCA1-mediated HDL-CEC (+18.6%) was observed in ATX compared to no ATX patients. In ATX-presenting patients, ABCG1-mediated HDL-CEC was lower (−11%) and serum CLC was higher (+14%) compared to patients without ATX. Considering all the patients together, ABCG1 HDL-CEC and serum CLC correlated with ATX thickness inversely (p = 0.013) and directly (p < 0.0001), respectively. In conclusion, lipoprotein dysfunctions seem to be involved in ATX physiopathology and progression in FH patients.

Effects of PCSK9 inhibitors on HDL cholesterol efflux and serum cholesterol loading capacity in familial hypercholesterolemia subjects: a multi-lipid-center real-world evaluation

Proprotein convertase subtilisin/kexin type 9 (PCSK9), beyond regulating LDL cholesterol (LDL-c) plasma levels, exerts several pleiotropic effects by modulating lipid metabolism in extrahepatic cells such as macrophages. Macrophage cholesterol homeostasis depends on serum lipoprotein functions, including the HDL capacity to promote cell cholesterol efflux (CEC) and the serum capacity to promote cell cholesterol loading (CLC). The aim of this observational study was to investigate the effect of PCSK9 inhibitors (PCSK9-i) treatment on HDL-CEC and serum CLC in patients with familial hypercholesterolemia (FH). 31 genetically confirmed FH patients were recruited. Blood was collected and serum isolated at baseline and after 6 months of PCSK9-i treatment. HDL-CEC was evaluated through the main pathways with a radioisotopic cell-based assay. Serum CLC was assessed fluorimetrically in human THP-1 monocyte-derived macrophages. After treatment with PCSK9-i, total cholesterol and LDL-c significantly decreased (−41.6%, p < 0.0001 and −56.7%, p < 0.0001, respectively). Total HDL-CEC was not different between patients before and after treatment. Conversely, despite no changes in HDL-c levels between the groups, ABCG1 HDL-CEC significantly increased after treatment (+22.2%, p < 0.0001) as well as HDL-CEC by aqueous diffusion (+7.8%, p = 0.0008). Only a trend towards reduction of ABCA1 HDL-CEC was observed after treatment. PCSK9-i significantly decreased serum CLC (−6.6%, p = 0.0272). This effect was only partly related to the reduction of LDL-c levels. In conclusion, PCSK9-i treatment significantly increased HDL-CEC through ABCG1 and aqueous diffusion pathways and reduced the serum CLC in FH patients. The favorable effect of PCSK9-i on functional lipid profile could contribute to the cardiovascular benefit of these drugs in FH patients.

Bariatric Surgery-induced High-density Lipoprotein Functionality Enhancement Is Associated With Reduced Inflammation

BACKGROUND

Emerging evidence suggests an association between impaired high-density lipoprotein (HDL) functionality and cardiovascular disease (CVD). HDL is essential for reverse cholesterol transport (RCT) and reduces inflammation and oxidative stress principally via paraoxonase-1 (PON1). RCT depends on HDL's capacity to accept cholesterol (cholesterol efflux capacity [CEC]) and active transport through ATP-binding cassette (ABC) A1, G1, and scavenger receptor-B1 (SR-B1). We have studied the impact of Roux-en-Y gastric bypass (RYGB) in morbidly obese subjects on RCT and HDL functionality.

METHODS

Biomarkers associated with increased CVD risk including tumour necrosis factor-α (TNF-α), high-sensitivity C-reactive protein (hsCRP), myeloperoxidase mass (MPO), PON1 activity, and CEC in vitro were measured in 44 patients before and 6 and 12 months after RYGB. Overweight but otherwise healthy (mean body mass index [BMI] 28 kg/m2) subjects acted as controls. Twelve participants also underwent gluteal subcutaneous adipose tissue biopsies before and 6 months after RYGB for targeted gene expression (ABCA1, ABCG1, SR-B1, TNF-α) and histological analysis (adipocyte size, macrophage density, TNF-α immunostaining).

RESULTS

Significant (P < 0.05) improvements in BMI, HDL-cholesterol, hsCRP, TNF-α, MPO mass, PON1 activity, and CEC in vitro were observed after RYGB. ABCG1 (fold-change, 2.24; P = 0.005) and ABCA1 gene expression increased significantly (fold-change, 1.34; P = 0.05). Gluteal fat adipocyte size (P < 0.0001), macrophage density (P = 0.0067), and TNF-α immunostaining (P = 0.0425) were reduced after RYBG and ABCG1 expression correlated inversely with TNF-α immunostaining (r = -0.71; P = 0.03).

CONCLUSION

RYGB enhances HDL functionality in association with a reduction in adipose tissue and systemic inflammation.

Different Pathways of Cellular Cholesterol Efflux

Cholesterol efflux is the first and rate-limiting step of reverse cholesterol transport (RCT) from peripheric cells to the liver. The involvement of high-density lipoprotein (HDL) in RCT determines the atheroprotective properties of HDL. Cholesterol efflux from different membrane pools includes both passive and energy-dependent processes. The first type of route consists of cholesterol desorption from the cell membrane into the unstirred layer adjacent to the cell surface and diffusion in the water phase. Moreover, the selective uptake and facilitated diffusion of cholesterol and cholesteryl ester molecules through the hydrophobic tunnel in the scavenger receptor BI molecule does not require energy consumption. The second type of route includes active cholesterol export by the ATP-binding cassette transporters A1 (ABCA1) and G1 (ABCG1). Several cholesterol acceptors specifically bind cholesterol and phospholipid molecules, and cholesterol binding to the albumin molecule, which acts as a shuttle, significantly increases cholesterol movement between acceptors and red blood cells, thus functioning as a sink for cholesterol. Cholesterol and phospholipid molecules effluxed from macrophages by ABCA1 are accepted exclusively by the lipid-free apolipoprotein apoA-I, which is the major protein moiety of HDL, whereas those effluxed by ABCG1 are accepted by HDL. ABCA1- and ABCG1-mediated cholesterol transport, together with cholesterol diffusion, largely determine cholesterol turnover at the physiological level of intracellular cholesterol. However, at cholesterol overload, ABCA1-mediated efflux prevails over other routes. The exchange of apoA-I between lipid-free and lipid-associated states and the synergism of nascent and mature HDL contribute to cholesterol efflux efficiency. Moreover, extracellular cholesterol deposits and microvesicles may be involved in RCT.

Moderate- and High-Intensity Exercise Improves Lipoprotein Profile and Cholesterol Efflux Capacity in Healthy Young Men

Background

Exercise is associated with a reduced risk of cardiovascular disease. Increased high‐density lipoprotein cholesterol (HDL‐C) levels are thought to contribute to these benefits, but much of the research in this area has been limited by lack of well‐controlled subject selection and exercise interventions. We sought to study the effect of moderate and high‐intensity exercise on HDL function, lipid/lipoprotein profile, and other cardiometabolic parameters in a homogeneous population where exercise, daily routine, sleep patterns, and living conditions were carefully controlled.

Methods and Results

Male Army recruits (n=115, age 22±0.3 years) completed a 12‐week moderate‐intensity exercise program. A subset of 51 subsequently completed a 15‐week high‐intensity exercise program. Fitness increased and body fat decreased after moderate‐ and high‐intensity exercise (P<0.001). Moderate‐intensity exercise increased HDL‐C and apolipoprotein A‐I levels (6.6%, 11.6% respectively), and decreased low‐density lipoprotein cholesterol and apolipoprotein B levels (7.2%, 4.9% respectively) (all P<0.01). HDL‐C and apolipoprotein A‐I levels further increased by 8.2% (P<0.001) and 6.3% (P<0.05) after high‐intensity exercise. Moderate‐intensity exercise increased ABCA‐1 (ATP‐binding cassette transporter A1) mediated cholesterol efflux by 13.5% (P<0.001), which was sustained after high‐intensity exercise. In a selected subset the ability of HDLs to inhibit ICAM‐1 (intercellular adhesion molecule‐1) expression decreased after the high (P<0.001) but not the moderate‐intensity exercise program.

Conclusions

When controlling for exercise patterns, diet, and sleep, moderate‐intensity exercise improved HDL function, lipid/lipoprotein profile, fitness, and body composition. A sequential moderate followed by high‐intensity exercise program showed sustained or incremental benefits in these parameters. Improved HDL function may be part of the mechanism by which exercise reduces cardiovascular disease risk.

ABCA1, ABCG1, and Cholesterol Homeostasis

Cholesterol is a major component of mammalian cell membranes and plays important structural and functional roles. However, excessive cholesterol accumulation is toxic to cells and constitutes the molecular basis for many diseases, especially atherosclerotic cardiovascular disease. Thus, cellular cholesterol is tightly regulated to maintain a homeostasis. Reverse cholesterol transport (RCT) is thought to be one primary pathway to eliminate excessive cholesterol from the body. The first and rate-limiting step of RCT is ATP-binding cassette (ABC) transports A1 (ABCA1)- and ABCG1-dependent cholesterol efflux. In the process, ABCA1 mediates initial transport of cellular cholesterol to apolipoprotein A-I (apoA-I) for forming nascent high-density lipoprotein (HDL) particles, and ABCG1 facilitates subsequent continued cholesterol efflux to HDL for further maturation. In this chapter, we summarize the roles of ABCA1 and ABCG1 in maintaining cellular cholesterol homoeostasis and discuss the underlying mechanisms by which they mediate cholesterol export.

HDL particle subclasses in statin treated patients with peripheral artery disease predict long-term survival

Low-density lipoprotein-cholesterol (LDL-C) reduction showed a strong reduction of cardiovascular (CV) event rates in CV disease. However, the residual risk of future CV events remains high, which especially extends to peripheral arterial disease (PAD). Nuclear magnetic resonance (NMR)-spectroscopy offers a novel method for analyses of the lipoprotein spectrum. This study investigates lipoprotein subclasses using NMR-spectroscopy and assesses implications for long-term survival in PAD. NMR-spectroscopy was performed by Nightingale Inc. in 319 patients with stable PAD and well-controlled CV risk factors. Patients were followed-up for ten years. During that period 123 patients (38.5%) died, of those 68 (21.3%) were defined as CV-deaths. Outcome data were analyzed by the Kaplan-Meier method and multivariable Cox regression for lipoprotein particles. Small and medium high-density lipoprotein-particles (S-HDL-P and M-HDL-P) showed a significant inverse association with all-cause mortality in Cox-regression analyses after multivariable adjustment (S-HDL-P hazard ratio 0.71, 95% confidence interval 0.57-0.88; M-HDL-P 0.72, 0.58-0.90) for each increase of 1 standard deviation. In contrast, cholesterol-rich x-large HDL-particles (XL-HDL-P) showed a positive association with all-cause mortality (1.51, 1.20-1.89). Only the association between XL-HDL-P and CV-death sustained multivariable adjustment (1.49, 1.10-2.02), whereas associations for S-HDL-P and M-HDL-P were attenuated (0.76, 0.57-1.01; 0.80, 0.60-1.06). This study shows a novel association for a beneficial role of S-HDL-P and M-HDL-P but a negative association with higher cholesterol-rich XL-HDL-P for long-term outcome in well-treated patients with PAD. Thus, these results provide evidence that NMR-measured HDL particles identify patients at high CV residual risk beyond adequate lipid-lowering therapy.

HDL Is Not Dead Yet

High-density lipoprotein cholesterol (HDL-C) levels are inversely correlated with coronary heart disease (CHD) in multiple epidemiological studies, but whether HDL is causal or merely associated with CHD is unclear. Recent trials for HDL-raising drugs were either not effective in reducing CHD events or, if beneficial in reducing CHD events, were not conclusive as the findings could be attributed to the drugs’ LDL-reducing activity. Furthermore, the first large Mendelian randomization study did not causally relate HDL-C levels to decreased CHD. Thus, the hypothesis that HDL is protective against CHD has been rightfully challenged. However, subsequent Mendelian randomization studies found HDL characteristics that are causally related to decreased CHD. Many aspects of HDL structure and function, especially in reverse cholesterol transport, may be better indicators of HDL’s protective activity than simply measuring HDL-C. Cholesterol efflux capacity is associated with lower levels of prevalent and incident CHD, even after adjustment for HDL-C and apolipoprotein A-1 levels. Also, subjects with very high levels of HDL-C, including those with rare mutations that disrupt hepatic HDL uptake and reverse cholesterol transport, may be at higher risk for CHD than those with moderate levels. We describe here several cell-based and cell-free in vitro assays of HDL structure and function that may be used in clinical studies to determine which of HDL’s functions are best associated with protection against CHD. We conclude that the HDL hypothesis may need revision based on studies of HDL structure and function, but that the HDL hypothesis is not dead yet.

Impact of Sepsis on High-Density Lipoprotein Metabolism

Background: High-density lipoproteins (HDL) are thought to play a protective role in sepsis through several mechanisms, such as promotion of steroid synthesis, clearing bacterial toxins, protection of the endothelial barrier, and antioxidant/inflammatory activities. However, HDL levels decline rapidly during sepsis, but the contributing mechanisms are poorly understood. Methods/Aim: In the present study, we investigated enzymes involved in lipoprotein metabolism in sepsis and non-sepsis patients admitted to the intensive care unit (ICU). Results: In 53 ICU sepsis and 25 ICU non-sepsis patients, we observed significant differences in several enzymes involved in lipoprotein metabolism. Lecithin-cholesterol acyl transferase (LCAT) activity, LCAT concentration, and cholesteryl transfer protein (CETP) activity were significantly lower, whereas phospholipid transfer activity protein (PLTP) and endothelial lipase (EL) were significantly higher in sepsis patients compared to non-sepsis patients. In addition, serum amyloid A (SAA) levels were increased 10-fold in sepsis patients compared with non-sepsis patients. Furthermore, we found that LCAT activity was significantly associated with ICU and 28-day mortality whereas SAA levels, representing a strong inflammatory marker, did not associate with mortality outcomes. Conclusion: We provide novel data on the rapid and robust changes in HDL metabolism during sepsis. Our results clearly highlight the critical role of specific metabolic pathways and enzymes in sepsis pathophysiology that may lead to novel therapeutics.

HDL in COVID-19 Patients: Evidence from an Italian Cross-Sectional Study

A number of studies have highlighted important alterations of the lipid profile in COVID-19 patients. Besides the well-known atheroprotective function, HDL displays anti-inflammatory, anti-oxidative, and anti-infectious properties. The aim of this retrospective study was to assess the HDL anti-inflammatory and antioxidant features, by evaluation of HDL-associated Serum amyloid A (SAA) enrichment and HDL-paraoxonase 1 (PON-1) activity, in a cohort of COVID-19 patients hospitalized at the Cardiorespiratory COVID-19 Unit of Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico of Milan. COVID-19 patients reached very low levels of HDL-c (mean ± SD: 27.1 ± 9.7 mg/dL) with a marked rise in TG (mean ± SD: 165.9 ± 62.5 mg/dL). Compared to matched-controls, SAA levels were significantly raised in COVID-19 patients at admission. There were no significant differences in the SAA amount between 83 alive and 22 dead patients for all-cause in-hospital mortality. Similar findings were reached in the case of PON-1 activity, with no differences between alive and dead patients for all-cause in-hospital mortality. In conclusion, although not related to the prediction of in-hospital mortality, reduction in HDL-c and the enrichment of SAA in HDL are a mirror of SARS-CoV-2 positivity even at the very early stages of the infection.

Antioxidant Effect of Moroccan Pomegranate (Punica granatum L. Sefri Variety) Extracts Rich in Punicalagin against the Oxidative Stress Process

Natural antioxidants products are widely distributed in food and medicinal plants. These natural antioxidants, especially polyphenols, exhibit a wide range of biological activities including anti-cancer, anti-inflammatory, and anti-atherosclerosis activities. Pomegranate (Punica granatum L.) is a rich source of polyphenolic components. The purpose of this study was to characterize the phenolic composition and flavonoids and anthocyanin content of different parts (peel and aril) of the Sefri variety of pomegranate. Our results showed that Peel extract was richer in these compounds than that of the Arils, especially in Punicalagin (A and B). DPPH free radical scavenging, reducing power (FRAP), β-carotene bleaching, and hydrogen peroxide scavenging assays revealed a greater dose-dependent activity of pomegranate peel phenolic extract (PPPE) compared to pomegranate aril phenolic extract (PAPE). PPPE was also more potent than PAPE concerning its ability to inhibit conjugated diene formation and to reduce α-tocopherol disappearance induced by CuSO4-mediated LDL peroxidation. Interestingly, both extracts (PPPE and PAPE) significantly inhibited lipid peroxidation and the formation of reactive oxygen species (ROS) in stressed J82 human bladder cancer cells. These results reflect the protective effects that this Moroccan variety of pomegranate can provide against the development of metabolic disorder, cancer, atherosclerosis, and cardiovascular disease. Given these properties, further studies should be undertaken to investigate possible applications of Sefri pomegranate extracts in the fields of food preservation and health supplements.

Breakfast partly restores the anti-inflammatory function of high-density lipoproteins from patients with type 2 diabetes mellitus

Background and aims

High-density lipoproteins (HDL) of patients with type 2 diabetes mellitus (T2DM) have impaired anti-inflammatory activities. The anti-inflammatory activity of HDL has been determined ex vivo after isolation by different methods from blood mostly obtained after overnight fasting. We first determined the effect of the HDL isolation method, and subsequently the effect of food intake on the anti-inflammatory function of HDL from T2DM patients.

Methods

Blood was collected from healthy controls and T2DM patients after an overnight fast, and from T2DM patients 3 h after breakfast (n = 17 each). HDL was isolated by a two-step density gradient ultracentrifugation in iodixanol (HDL_DGUC2), by sequential salt density flotation (HDL_SEQ) or by PEG precipitation (HDL_PEG). The anti-inflammatory function of HDL was determined by the reduction of the TNFα-induced expression of VCAM-1 in human coronary artery endothelial cells (HCAEC) and retinal endothelial cells (REC).

Results

HDL isolated by the three different methods from healthy controls inhibited TNFα-induced VCAM-1 expression in HCAEC. With apoA-I at 0.7 μM, HDL_DGUC2 and HDL_SEQ were similarly effective (16% versus 14% reduction; n = 3; p > 0.05) but less effective than HDL_PEG (28%, p < 0.05). Since ultracentrifugation removes most of the unbound plasma proteins, we used HDL_DGUC2 for further experiments. With apoA-I at 3.2 μM, HDL from fasting healthy controls and T2DM patients reduced TNFα-induced VCAM-1 expression in HCAEC by 58 ± 13% and 51 ± 20%, respectively (p = 0.35), and in REC by 42 ± 13% and 25 ± 18%, respectively (p < 0.05). Compared to preprandial HDL, postprandial HDL from T2DM patients reduced VCAM-1 expression by 56 ± 16% (paired test: p < 0.001) in HCAEC and by 34 ± 13% (paired test: p < 0.05) in REC.

Conclusions

The ex vivo anti-inflammatory activity of HDL is affected by the HDL isolation method. Two-step ultracentrifugation in an iodixanol gradient is a suitable method for HDL isolation when testing HDL anti-inflammatory function. The anti-inflammatory activity of HDL from overnight fasted T2DM patients is significantly impaired in REC but not in HCAEC. The anti-inflammatory function of HDL is partly restored by food intake.

Biological anti-psoriatic therapy profoundly affects high-density lipoprotein function

Psoriasis is a common chronic inflammatory skin disease linked to increased cardiovascular risk. Functional impairment of high-density lipoprotein (HDL) may contribute to excessive cardiovascular mortality in psoriasis patients. Anti-cytokine therapies with biologics have been efficiently used for the management of psoriasis, however little data is available on the effects of biologic anti-psoriatic therapies on the composition and functionality of HDL. Blood samples were taken from 17 healthy volunteers and from 27 real-world psoriasis patients at baseline (no therapy with biologics) and after short-term (3 to 6 months) and intermediate-term (1 to 2 years) therapy. The biologics used included anti-interleukin (IL)-12/23p40 (ustekinumab), anti-IL17A (secukinumab) or anti-tumor necrosis factor-α (etanercept or adalimumab) antibodies. We observed that in psoriasis patients at baseline, metrics of HDL function including cholesterol efflux capacity of apolipoprotein B-depleted serum (p = 0.021), paraoxonase (p < 0.001) and lecithin-cholesterol acyltransferase (p < 0.001) activities were impaired, when compared to controls. Unexpectedly, we observed that short- and especially intermediate-term therapy with biologics markedly reduced HDL cholesterol efflux capacity (p < 0.001) and rendered HDL pro-inflammatory (p < 0.001), but increased paraoxonase (p = 0.009) and lecithin-cholesterol acyltransferase (p = 0.019) activities. All biologics caused similar changes in HDL composition, subclass distribution and cholesterol efflux capacity. Our results provide evidence that anti-psoriatic therapy with biologic agents is associated with changes in HDL functionality, particle composition and subclass distribution.

The role of abnormalities of lipoproteins and HDL functionality in small fibre dysfunction in people with severe obesity

Obesity and associated dyslipidemia may contribute to increased cardiovascular disease. Obesity has also been associated with neuropathy. We have investigated presence of peripheral nerve damage in patients with severe obesity without type 2 diabetes and the status of metabolic syndrome and lipoprotein abnormalities. 47participants with severe obesity and 30 age-matched healthy controls underwent detailed phenotyping of neuropathy and an assessment of lipoproteins and HDL-functionality. Participants with severe obesity had a higher neuropathy symptom profile, lower sural and peroneal nerve amplitudes, abnormal thermal thresholds, heart rate variability with deep breathing and corneal nerve parameters compared to healthy controls. Circulating apolipoprotein A1 (P = 0.009), HDL cholesterol (HDL-C) (P < 0.0001), cholesterol efflux (P = 0.002) and paroxonase-1 (PON-1) activity (P < 0.0001) were lower, and serum amyloid A (SAA) (P < 0.0001) was higher in participants with obesity compared to controls. Obese participants with small nerve fibre damage had higher serum triglycerides (P = 0.02), lower PON-1 activity (P = 0.002) and higher prevalence of metabolic syndrome (58% vs. 23%, P = 0.02) compared to those without. However, HDL-C (P = 0.8), cholesterol efflux (P = 0.08), apoA1 (P = 0.8) and SAA (P = 0.8) did not differ significantly between obese participants with and without small nerve fibre damage. Small nerve fibre damage occurs in people with severe obesity. Patients with obesity have deranged lipoproteins and compromised HDL functionality compared to controls. Obese patients with evidence of small nerve fibre damage, compared to those without, had significantly higher serum triglycerides, lower PON-1 activity and a higher prevalence of metabolic syndrome.

Effect of metformin on the high-density lipoprotein proteome in youth with type 1 diabetes

Background

Youth with type 1 diabetes (T1D) have normal or elevated High‐Density Lipoprotein Cholesterol (HDL‐C), however, the function of HDL, partly mediated by the HDL proteome, may be impaired. Metformin can be used as an adjunct therapy in youth with T1D, but its effects on the HDL proteome are unknown.

Objective

To determine the effect of metformin on the HDL proteome.

Subjects

Youth (12–20 years old) with T1D who had a BMI > 90th percentile, HbA1c > 8.0% and Tanner stage 5.

Methods

Double‐blinded, placebo‐controlled randomized sub‐study. We examined the effects of metformin (n = 25) or placebo (n = 10) after 6 months on HDL proteome. Changes in HDL proteins were measured by data‐independent acquisition (DIA) mass spectrometry and compared between treatment groups. As a secondary outcome, associations between proteins of interest and the most studied function of HDL, the cholesterol efflux capacity (CEC), was examined.

Results

The relative abundance of 84 HDL‐associated proteins were measured. Two proteins were significantly affected by metformin treatment, peptidoglycan recognition protein 2 (PGRP2; +23.4%, p = .0058) and alpha‐2‐macroglobulin (A2MG; +29.8%, p = .049). Metformin did not significantly affect CEC. Changes in affected HDL proteins did not correlate with CEC.

Conclusions

Despite having little effect on HDL‐C, metformin increased PGRP2 and A2MG protein on HDL in youth with T1D, but had no significant effect on CEC. Further studies are needed to understand the impact of PGRP2 and A2MG on other HDL functions.

The effect of transgender hormonal treatment on high density lipoprotein cholesterol efflux capacity

BACKGROUND AND AIMS

A decrease in high-density lipoprotein (HDL)-cholesterol concentrations during transgender hormone therapy has been shown. However, the ability of HDL to remove cholesterol from arterial wall macrophages, termed cholesterol efflux capacity (CEC), has proven to be a better predictor of cardiovascular disease (CVD) largely independently of HDL-concentrations. In addition, the serum capacity to load macrophages with cholesterol (cholesterol loading capacity, CLC) represents an index of pro-atherogenic potential. As transgender individuals are exposed to lifelong exogenous hormone therapy (HT), it becomes of interest to study whether HDL-CEC and serum CLC are affected by HT. HDL-CEC and serum CLC have been evaluated in 15 trans men treated with testosterone and in 15 trans women treated with estradiol and cyproterone acetate at baseline and after 12 months of HT.

METHODS

Total HDL-CEC from macrophages and its major contributors, the ATP-binding cassette transporters (ABC) A1 and ABCG1 HDL-CEC and HDL-CEC by aqueous diffusion were determined by a radioisotopic assay. CLC was evaluated in human THP-1 macrophages.

RESULTS

In trans women, total HDL-CEC decreased by 10.8% (95%CI: -14.3;-7.3; p < 0.001), ABCA1 HDL-CEC by 23.8% (-34.7; -12.9; p < 0.001) and aqueous diffusion HDL-CEC by 4.8% (-8.4;-1.1; p < 0.01). In trans men, only aqueous diffusion HDL-CEC decreased significantly, -9.8% (-15.7;-3.9; p < 0.01). ABCG1 HDL-CEC did not change in either group. Serum CLC and HDL subclass distribution were not modified by HT in both groups.

CONCLUSIONS

Total HDL-CEC decreased during HT in trans women, with a specific reduction in ABCA1 CEC. This finding might contribute to a higher CVD risk.

The role of high-density lipoprotein cholesterol, apolipoprotein A and paraoxonase-1 in the pathophysiology of neuroprogressive disorders

Lowered high-density lipoprotein (HDL) cholesterol has been reported in major depressive disorder, bipolar disorder, first episode of psychosis, and schizophrenia. HDL, its major apolipoprotein component, ApoA1, and the antioxidant enzyme paraoxonase (PON)1 (which is normally bound to ApoA1) all have anti-atherogenic, antioxidant, anti-inflammatory, and immunomodulatory roles, which are discussed in this paper. The paper details the pathways mediating the anti-inflammatory effects of HDL, ApoA1 and PON1 and describes the mechanisms leading to compromised HDL and PON1 levels and function in an environment of chronic inflammation. The molecular mechanisms by which changes in HDL, ApoA1 and PON1 might contribute to the pathophysiology of the neuroprogressive disorders are explained. Moreover, the anti-inflammatory actions of ApoM-mediated sphingosine 1-phosphate (S1P) signalling are reviewed as well as the deleterious effects of chronic inflammation and oxidative stress on ApoM/S1P signalling. Finally, therapeutic interventions specifically aimed at improving the levels and function of HDL and PON1 while reducing levels of inflammation and oxidative stress are considered. These include the so-called Mediterranean diet, extra virgin olive oil, polyphenols, flavonoids, isoflavones, pomegranate juice, melatonin and the Mediterranean diet combined with the ketogenic diet.

The lipid substrate preference of CETP controls the biochemical properties of HDL in fat/cholesterol-fed hamsters

Cholesteryl ester transfer protein (CETP) modulates lipoprotein metabolism by transferring cholesteryl ester (CE) and triglyceride (TG) between lipoproteins. However, differences in the way CETP functions exist across species. Unlike human CETP, hamster CETP prefers TG over CE as a substrate, raising questions regarding how substrate preference may impact lipoprotein metabolism. To understand how altering the CE versus TG substrate specificity of CETP might impact lipoprotein metabolism in humans, we modified CETP expression in fat/cholesterol-fed hamsters, which have a human-like lipoprotein profile. Hamsters received adenoviruses expressing no CETP, hamster CETP, or human CETP. Total plasma CETP mass increased up to 70% in the hamster and human CETP groups. Hamsters expressing human CETP exhibited decreased endogenous hamster CETP, resulting in an overall CE:TG preference of plasma CETP that was similar to that in humans. Hamster CETP overexpression had little impact on lipoproteins, whereas human CETP expression reduced HDL by 60% without affecting LDL. HDLs were TG enriched and CE depleted and much smaller, causing the HDL3:HDL2 ratio to increase threefold. HDL from hamsters expressing human CETP supported higher LCAT activity and greater cholesterol efflux. The fecal excretion of HDL-associated CE in human CETP animals was unchanged. However, much of this cholesterol accumulated in the liver and was associated with a 1.8-fold increase in hepatic cholesterol mass. Overall, these data show in a human-like lipoprotein model that modification of CETP's lipid substrate preference selectively alters HDL concentration and function. This provides a powerful tool for modulating HDL metabolism and impacting sterol balance in vivo.

Increased ABCA1 (ATP-Binding Cassette Transporter A1)-Specific Cholesterol Efflux Capacity in Schizophrenia

Objective:

Patients with schizophrenia have increased long-term mortality attributable to cardiovascular disease and commonly demonstrate features of mixed dyslipidemia with low HDL-C (high-density lipoprotein cholesterol). The removal of cholesterol from cells by HDL via specific ATP-binding cholesterol transporters is a major functional property of HDL, and its measurement as cholesterol efflux capacity (CEC) can predict cardiovascular risk. Whether HDL function is impaired in patients with schizophrenia is unknown.

Approach and Results:

We measured basal and ABCA1 (ATP-binding cassette transporter A1)- and ABCG1 (ATP-binding cassette transporter G1)-dependent CEC, comparing patients with schizophrenia with age- and sex-matched healthy controls, and related our findings to nuclear magnetic resonance analysis of lipoprotein subclasses. Total plasma cholesterol and LDL-C (low-density lipoprotein cholesterol) were comparable between healthy controls (n=51) and patients (n=120), but patients with schizophrenia had increased total plasma triglyceride, low HDL-C and apo (apolipoprotein) A-I concentrations. Nuclear magnetic resonance analysis indicated a marked (15-fold) increase in large triglyceride-rich lipoprotein particle concentration, increased small dense LDL particles, and fewer large HDL particles. Despite lower HDL-C concentration, basal CEC was 13.7±1.6% higher, ABCA1-specific efflux was 35.9±1.6% higher, and ABCG1 efflux not different, in patients versus controls. In patients with schizophrenia, ABCA1-specific efflux correlated with the abundance of small 7.8 nm HDL particles but not with serum plasminogen or triglyceride levels.

Conclusions:

Patients with schizophrenia have increased concentrations of atherogenic apoB-containing lipoproteins, decreased concentrations of large HDL particles, but enhanced ABCA1-mediated CEC. In this population, preventative strategies should focus on reducing atherogenic lipoproteins rather than increasing CEC.

Treatment with PCSK9 inhibitors induces a more anti-atherogenic HDL lipid profile in patients at high cardiovascular risk

BACKGROUND

Proprotein Convertase Subtilisin/Kexin type 9 inhibitors (PCSK9-I) have been reported to cause a moderate increase in high-density lipoprotein (HDL) cholesterol in human studies. We thus evaluated the effect of two approved PCSK9-I on the concentration and lipid composition of HDL particle subclasses.

SUBJECTS AND METHODS

95 patients (62.8 ± 10.3 years old, 58% men), with or without statin and/or ezetimibe treatment and eligible for PCSK9-I therapy, received either evolocumab (140 mg) or alirocumab (75 or 150 mg). Their HDL particle profiles were measured by NMR spectroscopy at baseline and after 4 weeks of PCSK9-I treatment.

RESULTS

PCSK9-I treatment increased the level of HDL-C by 7%. The level of medium-sized HDL particles (M-HDL-P) increased (+8%) while the level of XL-HDL-P decreased (-19%). The lipid core composition was altered in the smaller S- and M-HDL-P, with a reduction in triglycerides (TG) and an enrichment in cholesterol esters (CE), whereas the for the larger XL- and L-HDL-P the relative CE content decreased and the TG content increased. Ezetimibe therapy differentially impacted the HDL particle distribution, independently of statin use, with an increase in S-HDL-P in patients not receiving ezetimibe.

CONCLUSIONS

As S- and M-HDL-P levels are inversely related to cardiovascular risk, PCSK9-I treatment may result in a more atheroprotective HDL particle profile, particularly in patients not concomitantly treated with ezetimibe.

The lipid transfer properties of CETP define the concentration and composition of plasma lipoproteins

Cholesteryl ester transfer protein (CETP) facilitates the net transfer of cholesteryl esters (CEs) and TGs between lipoproteins, impacting the metabolic fate of these lipoproteins. Previous studies have shown that a CETP antibody can alter CETP's preference for CE versus TG as transfer substrate, suggesting that CETP substrate preference can be manipulated in vivo. Hamster and human CETPs have very different preferences for CE and TG. To assess the effect of altering CETP's substrate preference on lipoproteins in vivo, here, we expressed human CETP in hamsters. Chow-fed hamsters received adenoviruses expressing no CETP, hamster CETP, or human CETP. Plasma CETP mass increased 2-fold in both the hamster and human CETP groups. Although the animals expressing human CETP still had low levels of hamster CETP, the CE versus TG preference of their plasma CETP was similar to that of the human ortholog. Hamster CETP overexpression had little impact on lipoproteins. However, expression of human CETP reduced HDL up to 50% and increased VLDL cholesterol 2.5-fold. LDL contained 20% more CE, whereas HDL CE was reduced 40%, and TG increased 6-fold. The HDL3:HDL2 ratio increased from 0.32 to 0.60. Hepatic expression of three cholesterol-related genes (LDLR, SCARB1, and CYP7A1) was reduced up to 40%. However, HDL-associated CE excretion into feces was unchanged. We conclude that expression of human CETP in hamsters humanizes their lipoprotein profile with respect to the relative concentrations of VLDL, LDL, HDL, and the HDL3:HDL2 ratio. Altering the lipid substrate preference of CETP provides a novel approach for modifying plasma lipoproteins.

Rate and Extent of Recovery from Reproductive and Cardiac Dysfunction Due to Androgen Abuse in Men

CONTEXT

Androgen abuse impairs male reproductive and cardiac function, but the rate, extent, and determinants of recovery are not understood.

OBJECTIVE

To investigate recovery of male reproductive and cardiac function after ceasing androgen intake in current and past androgen abusers compared with healthy non-users.

METHODS

Cross-sectional, observational study recruited via social media 41 current and 31 past users (≥3 months since last use, median 300 days since last use) with 21 healthy, eugonadal non-users. Each provided a history, examination, and serum and semen sample and underwent testicular ultrasound, body composition analysis, and cardiac function evaluation.

RESULTS

Current abusers had suppressed reproductive function and impaired cardiac systolic function and lipoprotein parameters compared with non- or past users. Past users did not differ from non-users, suggesting full recovery of suppressed reproductive and cardiac functions after ceasing androgen abuse, other than residual reduced testicular volume. Mean time to recovery was faster for reproductive hormones (anti-Mullerian hormone [AMH], 7.3 months; luteinizing hormone [LH], 10.7 months) than for sperm variables (output, 14.1 months) whereas spermatogenesis (serum follicle-stimulating hormone [FSH], inhibin B, inhibin) took longer. The duration of androgen abuse was the only other variable associated with slower recovery of sperm output (but not hormones).

CONCLUSION

Suppressed testicular and cardiac function due to androgen abuse is effectively fully reversible (apart from testis volume and serum sex hormone binding globulin) with recovery taking between 6 to 18 months after ceasing androgen intake with possible cumulative effects on spermatogenesis. Suppressed serum AMH, LH, and FSH represent convenient, useful, and underutilized markers of recovery from androgen abuse.

Serum level of HDL particles are independently associated with long-term prognosis in patients with coronary artery disease: The GENES study

HDL-Cholesterol (HDL-C) is not an accurate surrogate marker to measure the cardioprotective functions of HDL in coronary artery diseases (CAD) patients. Hence, measurement of other HDL-related parameters may have prognostic superiority over HDL-C. In this work, we examined the predictive value of HDL particles profile for long-term mortality in CAD patients and to compare its informative value to that of HDL-C and apoA-I. HDL particles profiles were measured by nuclear magnetic resonance (NMR) spectroscopy in 214 male participants with stable CAD (45-74 years). Median follow up was 12.5 years with a 36.4% mortality rate. Cardiovascular mortality accounted for 64.5%. Mean concentrations of total HDL particles (HDL-P), small-sized HDL (SHDL-P) and apoA-I were lower in deceased than in surviving patients whereas no difference was observed according to HDL-C and large HDL particles. All NMR-HDL measures were correlated between themselves and with other HDL markers (HDL-C, apoA-I and LpA-I). In a multivariate model adjusted for cardiovascular risk factors and bioclinical variables, HDL-P and SHDL-P displayed the strongest inverse association with all-cause and cardiovascular mortality. Weaker associations were recorded for apoA-I. Based on our results, we conclude that HDL particle profile measured by NMR spectroscopy should be considered to better stratify risk in population at high risk or in the setting of pharmacotherapy.

Bariatric Surgery Improves HDL Function Examined by ApoA1 Exchange Rate and Cholesterol Efflux Capacity in Patients with Obesity and Type 2 Diabetes

Bariatric surgery improves glycemic control better than medical therapy; however, the effect of bariatric surgery on HDL function is not well characterized. Serum samples were available at baseline, 1-, and 5-years post procedures, for 90 patients with obesity and type 2 diabetes who were randomized to intensive medical therapy (n = 20), Roux-en-Y gastric bypass (RYGB, n = 37), or sleeve gastrectomy (SG, n = 33) as part of the STAMPEDE clinical trial. We examined serum HDL function by two independent assays, apolipoprotein A-1 exchange rate (AER) and cholesterol efflux capacity (CEC). Compared with baseline, AER was significantly higher at 5 years for participants in all treatment groups, but only increased significantly at 1 year in the RYGB and SG groups. CEC was divided into ABCA1-dependent and independent fractions, and the later was correlated with AER. ABCA1-independent CEC increased significantly only at 5 years in both surgical groups, but did not significantly change in the medical therapy group. There was no significant change in ABCA1-dependent CEC in any group. The increase in AER, but not ABCA1-independent CEC, was correlated with the reduction in body mass index and glycated hemoglobin levels among all subjects at 5 years, indicating that AER as a measure of HDL function would be a better reflection of therapy versus CEC.

Composition-function analysis of HDL subpopulations: influence of lipid composition on particle functionality

The composition-function relationship of HDL particles and its effects on the mechanisms driving coronary heart disease (CHD) is poorly understood. We tested the hypothesis that the functionality of HDL particles is significantly influenced by their lipid composition. Using a novel 3D-separation method, we isolated five different-sized HDL subpopulations from CHD patients who had low preβ-1 functionality (low-F) (ABCA1-dependent cholesterol-efflux normalized for preβ-1 concentration) and controls who had either low-F or high preβ-1 functionality (high-F). Molecular numbers of apoA-I, apoA-II, and eight major lipid classes were determined in each subpopulation by LC-MS. The average number of lipid molecules decreased from 422 in the large spherical α-1 particles to 57 in the small discoid preβ-1 particles. With decreasing particle size, the relative concentration of free cholesterol (FC) decreased in α-mobility but not in preβ-1 particles. Preβ-1 particles contained more lipids than predicted; 30% of which were neutral lipids (cholesteryl ester and triglyceride), indicating that these particles were mainly remodeled from larger particles not newly synthesized. There were significant correlations between HDL-particle functionality and the concentrations of several lipids. Unexpectedly, the phospholipid:FC ratio was significantly correlated with large-HDL-particle functionality but not with preβ-1 functionality. There was significant positive correlation between particle functionality and total lipids in high-F controls, indicating that the lipid-binding capacity of apoA-I plays a major role in the cholesterol efflux capacity of HDL particles. Functionality and lipid composition of HDL particles are significantly correlated and probably both are influenced by the lipid-binding capacity of apoA-I.

Nonlinear optical responses of oxidized low-density lipoprotein: Cutoff point for z-scan peak-valley distance

The development of new methods to assess biomarkers of cardiovascular disease is currently a subject of scientific research. This article broadens our view of nonlinear optical responses of oxidized low density lipoprotein (LDL) evaluated using the Z-scan peak-valley distance and proposes a cutoff point. We investigated the association of peak-valley distance and some cardiovascular risk factors related with sociodemographic, clinical and anthropometric profiles and plasma biomarkers such as lipid and glucose profile, apolipoprotein, lipoprotein subfractions and omega 3 fatty acids. Z-scan analysis was performed using isolated LDL after ultracentrifugation in human blood samples collected after fasting. Peak-valley distance is a parameter that decreases directly depending on the oxidizability of LDL. As peak-valley distance was associated with relevant biomarkers of cardiovascular risk, we tested cutoff points for categorization and the best results were obtained using percentile < 75 (Low_z-scan) and percentile ≥ 75 (High_z-scan). The regression logistic models tested after establishing the cutoff point for peak-valley distance showed that increased levels of plasma high-density lipoprotein cholesterol, apolipoprotein A-I, large high-density lipoprotein subfractions and docosahexaenoic acid are directly associated with High_Z-scan. Conversely, high levels of small LDL were associated with decreased odds of presenting High_Z-scan. In conclusion, the cutoff point for peak-valley distance was able to identify atherogenic characteristics of LDL and its relationship with some parameters of high-density lipoprotein functionality.

Targeting Foam Cell Formation in Atherosclerosis: Therapeutic Potential of Natural Products

Foam cell formation and further accumulation in the subendothelial space of the vascular wall is a hallmark of atherosclerotic lesions. Targeting foam cell formation in the atherosclerotic lesions can be a promising approach to treat and prevent atherosclerosis. The formation of foam cells is determined by the balanced effects of three major interrelated biologic processes, including lipid uptake, cholesterol esterification, and cholesterol efflux. Natural products are a promising source for new lead structures. Multiple natural products and pharmaceutical agents can inhibit foam cell formation and thus exhibit antiatherosclerotic capacity by suppressing lipid uptake, cholesterol esterification, and/or promoting cholesterol ester hydrolysis and cholesterol efflux. This review summarizes recent findings on these three biologic processes and natural products with demonstrated potential to target such processes. Discussed also are potential future directions for studying the mechanisms of foam cell formation and the development of foam cell-targeted therapeutic strategies.

The detrimental effect of asymmetric dimethylarginine on cholesterol efflux of macrophage foam cells: Role of the NOX/ROS signaling

BACKGROUND

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide synthase inhibitor and has been proposed to be an independent risk factor for cardiovascular diseases. However, little is known about its role in the regulation of lipid metabolism. In this study, we investigated the effect of ADMA on cholesterol metabolism and its underlying molecular mechanism.

METHODS

Oxidized low-density lipoprotein (oxLDL)-induced macrophage foam cells were used as an in vitro model. Apolipoprotein E-deficient (apoE^-/-) hyperlipidemic mice were used as an in vivo model. Western blot analysis was used to evaluate protein expression. Luciferase reporter assays were used to assess the activity of promoters and transcription factors. Conventional assay kits were used to measure the levels of ADMA, cholesterol, triglycerides, and cytokines.

RESULTS

Treatment with oxLDL decreased the protein expression of dimethylarginine dimethylaminohydrolase-2 (DDAH-2) but not DDAH-1. Incubation with ADMA markedly increased oxLDL-induced lipid accumulation in macrophages. ADMA impaired cholesterol efflux following oxLDL challenge and downregulated the expression of ATP-binding cassette transporter A1 (ABCA1) and ABCG1 by interfering with liver X receptor α (LXRα) expression and activity. Additionally, this inhibitory effect of ADMA on cholesterol metabolism was mediated through the activation of the NADPH oxidase/reactive oxygen species pathway. In vivo experiments revealed that chronic administration of ADMA for 4 weeks exacerbated systemic inflammation, decreased the aortic protein levels of ABCA1 and ABCG1, and impaired the capacity of reverse cholesterol transport, ultimately, leading to the progression of atherosclerosis in apoE^-/- mice.

CONCLUSION

Our findings suggest that the ADMA/DDAH-2 axis plays a crucial role in regulating cholesterol metabolism in macrophage foam cells and atherosclerotic progression.

High-density lipoprotein: our elusive friend

PURPOSE OF REVIEW

Despite advances in the research on HDL composition (lipidomics and proteomics) and functions (cholesterol efflux and antioxidative capacities), the relationship between HDL compositional and functional properties is not fully understood. We have reviewed the recent literature on this topic and pointed out the difficulties which limit our understanding of HDL's role in cardiovascular disease (CVD).

RECENT FINDINGS

Though current findings strongly support that HDL has a significant role in CVD, the underlying mechanisms by which HDL mitigates CVD risk are not clear. This review focuses on studies that investigate the cell-cholesterol efflux capacity and the proteomic and lipidomic characterization of HDL and its subfractions especially those that analyzed the relationship between HDL composition and functions.

SUMMARY

Recent studies on HDL composition and HDL functions have greatly contributed to our understanding of HDL's role in CVD. A major problem in HDL research is the lack of standardization of both the HDL isolation and HDL functionality methods. Data generated by different methods often produce discordant results on the particle number, size, lipid and protein composition, and the various functions of HDL.

High-Density Lipoprotein Particles, Cell-Cholesterol Efflux, and Coronary Heart Disease Risk

Objective- The cell-cholesterol efflux capacity of HDL (high-density lipoprotein) is inversely associated with coronary heart disease risk. ABCA1 (ATP-binding cassette transporter A1) plays a crucial role in cholesterol efflux from macrophages to preβ-1-HDL. We tested the hypothesis that coronary heart disease patients have functionally abnormal preβ-1-HDL. Approach and Results- HDL cell-cholesterol efflux capacity via the ABCA1 and the SR-BI (scavenger receptor class B type I) pathways, HDL antioxidative capacity, apo (apolipoprotein) A-I-containing HDL particles, and inflammatory- and oxidative-stress markers were measured in a case-control study of 100 coronary heart disease cases and 100 sex-matched controls. There were significant positive correlations between ABCA1-dependent cholesterol efflux and the levels of small lipid-poor preβ-1 particles ( R²=0.535) and between SR-BI-dependent cholesterol efflux and the levels of large lipid-rich (α-1+α-2) HDL particles ( R²=0.712). Cases had significantly higher (87%) preβ-1 concentrations than controls, but the functionality of their preβ-1 particles (preβ-1 concentration normalized ABCA1-dependent efflux capacity) was significantly lower (-31%). Cases had significantly lower (-12%) mean concentration of large HDL particles, but the functionality of their particles (α-1+α-2 concentration normalized SR-BI-dependent efflux capacity) was significantly higher (22%) compared with that of controls. HDL antioxidative capacity was significantly lower (-16%) in cases than in controls. There were no significant correlations between either preβ-1 functionality or large HDL particle functionality with HDL antioxidative capacity or the concentrations of inflammatory- and oxidative-stress markers. Conclusions- HDL cell-cholesterol efflux capacity is significantly influenced by both the concentration and the functionality of specific HDL particles participating in cell-cholesterol efflux. Coronary heart disease patients have higher than normal preβ-1 concentrations with decreased functionality and lower than normal large HDL particle concentrations with enhanced functionality.

Association Between ApoA-I (Apolipoprotein A-I) Immune Complexes and Adverse Cardiovascular Events-Brief Report

OBJECTIVE

The immune response is linked to the progression of atherosclerotic cardiovascular disease (CVD). Free autoantibodies targeting ApoA-I (apolipoprotein A-I) have been identified as a component of the inflammatory milieu in patients and have a moderate association with CVD progression. Based on the presence of these antibodies and the high concentration of circulating ApoA-I, we hypothesized that antibodies bound to ApoA-I as an immune complex would be predictive of incident adverse CVD outcomes. Approach and Results: The presence of ApoA-I/IgG immune complexes (ICs) in plasma was confirmed by ELISA in 3 subject cohorts. Characterization of the protein components of ApoAI/IgG ICs indicate that ICs are not correlated with total ApoA-I concentration and are enriched in the anti-inflammatory subclass, IgG4, relative to total plasma IgG (>30% versus 6%). In 359 patients with coronary artery disease (CAD), there were 71 incident adverse CVD events (death, myocardial infarction, and stroke) during a median 4.1-year follow-up. In Cox proportional hazard regression analysis, low levels of ApoA-I/IgG ICs were independent predictors of adverse cardiovascular outcomes after adjustment for age, sex, diabetes mellitus, estimated glomerular filtration rate, presence of obstructive CAD, heart failure, total cholesterol, and HDL (high-density lipoprotein) cholesterol (adjusted hazard ratio of 1.90 [95% CI, 1.03-3.49; P=0.038] between the lowest and the highest tertiles).

CONCLUSIONS

Low levels of ApoA-I/IgG ICs are associated with an increased risk of adverse events in patients with CAD, raising their potential to be used as a biomarker to predict CVD progression.

HSP70 induces liver X receptor pathway activation and cholesterol reduction in vitro and in vivo

Objective

Heat Shock Proteins (HSPs) maintain cellular homeostasis under stress. HSP70 represents a major stress-inducible family member and has been identified as a druggable target in inherited cholesterol-sphingolipid storage diseases. We investigated if HSP70 modulates cholesterol accumulation in more common conditions related to atherogenesis.

Methods

We studied the effects of recombinant HSP70 in cholesterol-laden primary macrophages from human blood donors and pharmacological HSP70 upregulation in high-cholesterol diet fed zebrafish.

Results

Recombinant HSP70 facilitated cholesterol removal from primary human macrophage foam cells. RNA sequencing revealed that HSP70 induced a robust transcriptional re-programming, including upregulation of key targets of liver X receptors (LXR), master regulators of whole-body cholesterol removal. Mechanistically, HSP70 interacted with the macrophage LXRalpha promoter, increased LXRalpha and its target mRNAs, and led to elevated levels of key proteins facilitating cholesterol efflux, including ATP-binding cassette transporters A1 and G1. Pharmacological augmentation of endogenous HSP70 in high-cholesterol diet fed zebrafish activated LXR and its target mRNAs and reduced cholesterol storage at the whole organism level.

Conclusion

These data demonstrate that HSP70 exerts a cholesterol lowering effect in primary human cells and animals and uncover a nuclear action of HSP70 in mediating cross-talk between HSP and LXR transcriptional regulation.

Biological Consequences of Dysfunctional HDL

Epidemiological studies have suggested an inverse correlation between high-density lipoprotein (HDL) cholesterol levels and the risk of cardiovascular disease. HDLs promote reverse cholesterol transport (RCT) and possess several putative atheroprotective functions, associated to the anti-inflammatory, anti-thrombotic and anti-oxidant properties as well as to the ability to support endothelial physiology. The assumption that increasing HDL-C levels would be beneficial on cardiovascular disease (CVD), however, has been questioned as, in most clinical trials, HDL-C-raising therapies did not result in improved cardiovascular outcomes. These findings, together with the observations from Mendelian randomization studies showing that polymorphisms mainly or solely associated with increased HDL-C levels did not decrease the risk of myocardial infarction, shift the focus from HDL-C levels toward HDL functional properties. Indeed, HDL from atherosclerotic patients not only exhibit impaired atheroprotective functions but also acquire pro-atherogenic properties and are referred to as "dysfunctional" HDL; this occurs even in the presence of normal or elevated HDL-C levels. Pharmacological approaches aimed at restoring HDL functions may therefore impact more significantly on CVD outcome than drugs used so far to increase HDL-C levels. The aim of this review is to discuss the pathological conditions leading to the formation of dysfunctional HDL and their role in atherosclerosis and beyond.

High-Density Lipoprotein Subspecies in Health and Human Disease: Focus on Type 2 Diabetes

Plasma cholesterol levels of high-density lipoproteins (HDL) have been associated with cardioprotection for decades. However, there is an evolving appreciation that this lipoprotein class is highly heterogeneous with regard to composition and functionality. With the advent of advanced lipid-testing techniques and methods that allow both the quantitation and recovery of individual particle populations, we are beginning to connect the functionality of HDL subspecies with chronic metabolic diseases. In this review, we examine type 2 diabetes (T2D) and explore our current understanding of how obesity, insulin resistance, and hyperglycemia affect, and may be affected by, HDL subspeciation. We discuss mechanistic aspects of how insulin resistance may alter lipoprotein profiles and how this may impact the ability of HDL to mitigate both atherosclerotic disease and diabetes itself. Finally, we call for more detailed studies examining the impact of T2D on specific HDL subspecies and their functions. If these particles can be isolated and their compositions and functions fully elucidated, it may become possible to manipulate the levels of these specific particles or target the protective functions to reduce the incidence of coronary heart disease.

Lipid trafficking in cardiovascular disease

The reduction of plasma apolipoprotein B (apoB) containing lipoproteins has long been pursued as the main modifiable risk factor for the development of cardiovascular disease (CVD). This has led to an intense search for strategies aiming at reducing plasma apoB-lipoproteins, culminating in reduction of overall CV risk. Despite 3 decades of progress, CVD remains the leading cause of morbidity and mortality worldwide and, as such, new therapeutic targets are still warranted. Clinical and preclinical research has moved forward from the original concept, under which some lipids must be accumulated and other removed to achieve the ideal condition in disease prevention, into the concept that mechanisms that orchestrate lipid movement between lipoproteins, cells and organelles is equally involved in CVD. As such, this review scrutinizes potentially atherogenic changes in lipid trafficking and assesses the molecular mechanisms behind it. New developments in risk assessment and new targets for the mitigation of residual CVD risk are also addressed.

Tailoring Porphyrin Conjugation for Nanoassembly-Driven Phototheranostic Properties

Lipoprotein mimetic nanostructures, which consist of an amphiphilic lipid shell, a hydrophobic core, and an apolipoprotein mimetic peptide, serve as a versatile platform for the design of drug delivery vehicles as well as the investigation of supramolecular assemblies. Porphyrin incorporation into biomimetic lipoproteins allows one to take advantage of the inherent multimodal photophysical properties of porphyrins, yielding various fluorescence, photoacoustic, and photodynamic agents. To facilitate their incorporation into a lipoprotein structure, porphyrins have been conjugated through a variety of strategies. However, the effects of the conjugate structure on the associated nanoparticle's phototherapeutic properties warrants further investigation. Herein, we systematically investigated the effects of two widely utilized porphyrin conjugates, oleylamide and lipid, on biophotonic properties of their resultant porphyrin-lipoprotein nanoparticles in vitro and in vivo. Specifically, we demonstrated that incorporation of the porphyrin moiety as an oleylamide conjugate leads to a highly stable J-aggregate with strong photoacoustic contrast, while incorporation as an ampiphilic lipid moiety into the lipid shell yields an effective fluorescent and photodynamic agent. The current study proposes a rational design strategy for next-generation lipoprotein-based phototheranostic agents, for which nanoassembly-driven biophotonic and therapeutic properties can be tailored through the specific selection of porphyrin conjugate structures.

Inflammatory status and severity of disease in dengue patients are associated with lipoprotein alterations

INTRODUCTION

The triggering of severe dengue has been associated with an exacerbated inflammatory process characterized by the production of pro-inflammatory cytokines such as IL-1β/IL-18, which are the product of inflammasome activation. Furthermore, alteration in the levels of high-density (HDL) and low-density lipoproteins (LDL) has been observed; and HDL are known to have immunomodulatory properties, including the regulation of inflammasomes. While HDL would be expected to counteract hyperactivation of the inflammasome, the relationship between HDL and dengue severity, has not previously been explored.

METHODOLOGY

We conducted a cross-sectional study of 30 patients with dengue and 39 healthy controls matched by sex and age. Lipid profile and levels of C-reactive protein were quantified. Serum levels of IL-1β, IL-6, IL-10, IL-18, and TNF-α, were assessed by ELISA. Expression of inflammasome-related genes in PBMC was quantified by qPCR.

RESULTS

Dengue patients presented an alteration in the parameters of the lipid profile, with a significant decrease in HDL levels, which was more pronounced in dengue patients with warning signs. Moreover, a decrease in the expression of the inflammasome-related genes NLRP1, NLRC4, caspase-1, IL-1β and IL-18 was observed, as well as an increase in serum levels of C-reactive protein and IL-10 in dengue patients versus healthy donors. Significant positive correlations between LDL levels and the relative expression of NLRP3, NLRC4, IL-1β and IL-18, were found.

CONCLUSION

The results suggest that there is a relationship between the alteration of LDL and HDL with the imbalance in the inflammatory response, which could be associated with the severity of dengue.