Macrophage Cholesterol Efflux Capacity Research Articles

Flipped C-Terminal Ends of APOA1 Promote ABCA1-Dependent Cholesterol Efflux by Small HDLs.

Cholesterol efflux capacity (CEC) predicts cardiovascular disease independently of high-density lipoprotein (HDL) cholesterol levels. Isolated small HDL particles are potent promoters of macrophage CEC by the ABCA1 (ATP-binding cassette transporter A1) pathway, but the underlying mechanisms are unclear. We used model system studies of reconstituted HDL and plasma from control and lecithin-cholesterol acyltransferase (LCAT)-deficient subjects to investigate the relationships among the sizes of HDL particles, the structure of APOA1 (apolipoprotein A1) in the different particles, and the CECs of plasma and isolated HDLs. We quantified macrophage and ABCA1 CEC of 4 distinct sizes of reconstituted HDL. CEC increased as particle size decreased. Tandem mass spectrometric analysis of chemically cross-linked peptides and molecular dynamics simulations of APOA1, the major protein of HDL, indicated that the mobility of C-terminus of that protein was markedly higher and flipped off the surface in the smallest particles. To explore the physiological relevance of the model system studies, we isolated HDL from LCAT-deficient subjects, whose small HDLs (like reconstituted HDLs) are discoidal and composed of APOA1, cholesterol, and phospholipid. Despite their very low plasma levels of HDL particles, these subjects had normal CEC. In both the LCAT-deficient subjects and control subjects, the CEC of isolated extra-small HDL (a mixture of extra-small and small HDL by calibrated ion mobility analysis) was 3- to 5-fold greater than that of the larger sizes of isolated HDL. Incubating LCAT-deficient plasma and control plasma with human LCAT converted extra-small and small HDL particles into larger particles, and it markedly inhibited CEC. We present a mechanism for the enhanced CEC of small HDLs. In smaller particles, the C-termini of the 2 antiparallel molecules of APOA1 are "flipped" off the lipid surface of HDL. This extended conformation allows them to engage with ABCA1. In contrast, the C-termini of larger HDLs are unable to interact productively with ABCA1 because they form a helical bundle that strongly adheres to the lipid on the particle. Enhanced CEC, as seen with the smaller particles, predicts decreased cardiovascular disease risk. Thus, extra-small and small HDLs may be key mediators and indicators of the cardioprotective effects of HDL.

Cholesterol accumulation induced by acetylated LDL exposure modifies the enzymatic activities of the TCA cycle without impairing the respiratory chain functionality in macrophages

The unregulated uptake of modified low-density lipoproteins (LDL) by macrophages leads to foam cell formation, promoting atherosclerotic plaque progression. The cholesterol efflux capacity of macrophages by the ATP-Binding Cassette transporters depends on the ATP mitochondrial production. Therefore, the mitochondrial function maintenance is crucial in limiting foam cell formation. Thus, we aimed to investigate the mechanisms involved in the mitochondrial dysfunction that may occur in cholesterol-laden macrophages.We incubated THP-1 macrophages with acetylated LDL (acLDL) to obtain cholesterol-laden cells or with mildly oxidized LDL (oxLDL) to generate cholesterol- and oxidized lipids-laden cells. Cellular cholesterol content was measured in each condition. Mitochondrial function was evaluated by measurement of several markers of energetic metabolism, oxidative phosphorylation, oxidative stress, mitochondrial biogenesis and dynamics.OxLDL-exposed macrophages exhibited a significantly reduced mitochondrial respiration and complexes I and III activities, associated to an oxidative stress state and a reduced mitochondrial DNA copy number. Meanwhile, acLDL-exposed macrophages featured an efficient oxidative phosphorylation despite the decreased activities of aconitase, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.Our study revealed that mitochondrial function was differently impacted according to the nature of modified LDL. Exposure to cholesterol and oxidized lipids carried by oxLDL leads to a mitochondrial dysfunction in macrophages, affecting the mitochondrial respiratory chain functional capacity, whereas the cellular cholesterol enrichment induced by acLDL exposure results in a tricarboxylic acid cycle shunt while maintaining mitochondrial energetic production, reflecting a metabolic adaptation to cholesterol intake. These new mechanistic insights are of direct relevance to the understanding of the mitochondrial dysfunction in foam cells.

Phosphatidylserine-containing liposomes: Therapeutic potentials against hypercholesterolemia and atherosclerosis

Liposomes have been suggested as potential tools for cholesterol deposit mobilization from atherosclerotic lesions. Here, we explored the anti-atherosclerotic effects of phosphatidylserine (PS)-containing liposomes in vivo. High-fat diet-fed New Zealand white rabbits which were divided into groups receiving weekly intravenous injections of PS liposomes, atorvastatin-loaded PS (PSA) liposomes (100 μg phospholipid/kg), or control buffer for four weeks. The size and severity grade of atherosclerotic plaques as well as lipid profile were evaluated at the completion of study. In vitro, the expression and levels of anti/pro-inflammatory genes and proteins, respectively, and macrophage cholesterol efflux capacity (CEC) of nanoliposomes were evaluated. Both PS and PSA lowered serum LDL-C (P = 0.0034, P = 0.0041) and TC (P = 0.029, P = 0.0054) levels but did not alter TG and HDL-C levels. Plaque size and grade were reduced by PS (P = 0.0025, P = 0.0031) and PSA (P = 0.016, P = 0.027) versus control. Moreover, intima-media thickness was significantly reduced in the PS vs. control group (P = 0.01). In cultured cells, ICAM-1 expression in the PS (P = 0.022) and VCAM-1 expression in the PS and PSA groups (P = 0.037, P = 0.004) were suppressed while TGF-β expression was induced by both PS and PSA (P = 0.048, P = 0.046). Moreover, CEC from macrophages to nanoliposomes was enhanced by PSA (P = 0.003). Administration of anionic PS-containing liposomes could improve lipid profile and promote plaque regression through mechanisms that may involve cholesterol efflux and modulation of adhesion molecules.

Effects of phytochemicals on macrophage cholesterol efflux capacity: Impact on atherosclerosis

High-density lipoprotein cholesterol (HDL) is the major promoter of reverse cholesterol transport and efflux of excess cellular cholesterol. The functions of HDL, such as cholesterol efflux, are associated with cardiovascular disease rather than HDL levels. We have reviewed the evidence base on the major classes of phytochemicals, including polyphenols, alkaloids, carotenoids, phytosterols, and fatty acids, and their effects on macrophage cholesterol efflux and its major pathways. Phytochemicals show the potential to improve the efficiency of each of these pathways. The findings are mainly in preclinical studies, and more clinical research is warranted in this area to develop novel clinical applications.

Defects in High Density Lipoprotein metabolism and hepatic steatosis in mice with liver-specific ablation of Hepatocyte Nuclear Factor 4A

BackgroundAberrant concentration, structure and functionality of High Density Lipoprotein (HDL) are associated with many prevalent diseases, including cardiovascular disease and non-alcoholic fatty liver disease (NAFLD). Mice with liver-specific ablation of Hnf4α (H4LivKO) present steatosis and dyslipidemia by mechanisms that are not completely understood. The aim of this study was to explore the role of liver HNF4A in HDL metabolism and the development of steatosis. Methods and resultsSerum and tissue samples were obtained from 6-weeks old H4LivKO mice and their littermate controls. Liver and serum lipids were measured and HDL structure and functionality were assessed. Global gene expression changes in the liver were analyzed by expression arrays, validations were performed by RT-qPCR and DNA-protein interactions were studied by chromatin immunoprecipitation (ChIP). H4LivKO mice presented liver steatosis, increased liver triglyceride content and decreased concentration of serum total cholesterol, HDL cholesterol, triglycerides, phospholipids and cholesteryl esters. Most classes of phospholipids showed significant changes in species ratio and sphingosine-1-phosphate (S1P) levels were reduced. H4LivKO serum was enriched in the smaller, denser HDL particles, devoid of APOA2 and APOM apolipoproteins, exhibiting decreased activity of paraoxonase-1 but retaining macrophage cholesterol efflux capacity and phospho-AKT activation in endothelial cells. Global gene expression analysis revealed the association of liver HNF4A with known and novel regulators of HDL metabolism as well as NAFLD-susceptibility genes. ConclusionsHNF4A ablation in mouse liver causes hepatic steatosis, perturbations in HDL structure and function and significant global changes in gene expression. This study reveals new targets of HNF4A involved in HDL metabolism and the development of steatosis and enriches our knowledge on HDL functionality in NAFLD.

Dietary sucrose induces metabolic inflammation and atherosclerotic cardiovascular diseases more than dietary fat in LDLr−/−ApoB100/100 mice

Background and aimsPoor dietary habits contribute to the obesity pandemic and related cardiovascular diseases but the respective impact of high saturated fat versus added sugar consumption remains debated. Herein, we aimed to disentangle the individual role of dietary fat versus sugar in cardiometabolic disease progression. MethodsWe fed pro-atherogenic LDLr−/−ApoB100/100 mice either a low-fat/high-sucrose (LFHS) or a high-fat/low-sucrose (HFLS) diet for 24 weeks. Weekly body weight gain was registered. 16S rRNA gene-based gut microbial analysis was performed to investigate gut microbial modulations. Intraperitoneal insulin (ipITT) and oral glucose tolerance test (oGTT) were conducted to assess glucose homeostasis and insulin sensitivity. Cytokines were assessed in fasted plasma, epididymal white adipose tissue and liver lysates. Heart function was evaluated by echocardiography. Aortic atheroma lesions were quantified according to the en face technique. ResultsHFLS feeding increased obesity, insulin resistance and dyslipidemia compared to LFHS feeding. Conversely, high sucrose consumption decreased gut microbial diversity while augmenting inflammation and the adaptative immune defense against metabolic endotoxemia and reduced macrophage cholesterol efflux capacity. This led to more severe cardiovascular complications as revealed by remarkably high level of atherosclerotic lesions and the early development of cardiac dysfunction in LFHS vs HFLS fed mice. ConclusionsWe uncoupled obesity-associated insulin resistance from cardiovascular diseases and provided novel evidence that dietary sucrose, not fat, is the main driver of metabolic inflammation accelerating severe atherosclerosis in hyperlipidemic mice.

Effects of Virgin Olive Oil and Phenol-Enriched Virgin Olive Oils on Lipoprotein Atherogenicity.

The atherogenicity of low-density lipoprotein (LDL) and triglyceride-rich lipoproteins (TRLs) may be more significant than LDL cholesterol levels. Clinical trials which have led to increased high-density lipoprotein (HDL) cholesterol have not always seen reductions in cardiovascular disease (CVD). Furthermore, genetic variants predisposing individuals to high HDL cholesterol are not associated with a lower risk of suffering a coronary event, and therefore HDL functionality is considered to be the most relevant aspect. Virgin olive oil (VOO) is thought to play a protective role against CVD. This review describes the effects of VOO and phenol-enriched VOOs on lipoprotein atherogenicity and HDL atheroprotective properties. The studies have demonstrated a decrease in LDL atherogenicity and an increase in the HDL-mediated macrophage cholesterol efflux capacity, HDL antioxidant activity, and HDL anti-inflammatory characteristics after various VOO interventions. Moreover, the expression of cholesterol efflux-related genes was enhanced after exposure to phenol-enriched VOOs in both post-prandial and sustained trials. Improvements in HDL antioxidant properties were also observed after VOO and phenol-enriched VOO interventions. Furthermore, some studies have demonstrated improved characteristics of TRL atherogenicity under postprandial conditions after VOO intake. Large-scale, long-term randomized clinical trials, and Mendelian analyses which assess the lipoprotein state and properties, are required to confirm these results.

Modified sites and functional consequences of 4-oxo-2-nonenal adducts in HDL that are elevated in familial hypercholesterolemia

The lipid aldehyde 4-oxo-2-nonenal (ONE) is a highly reactive protein crosslinker derived from peroxidation of n-6 polyunsaturated fatty acids and generated together with 4-hydroxynonenal (HNE). Lipid peroxidation product-mediated crosslinking of proteins in high-density lipoprotein (HDL) causes HDL dysfunction and contributes to atherogenesis. Although HNE is relatively well-studied, the role of ONE in atherosclerosis and in modifying HDL is unknown. Here, we found that individuals with familial hypercholesterolemia (FH) had significantly higher ONE-ketoamide (lysine) adducts in HDL (54.6 ± 33.8 pmol/mg) than healthy controls (15.3 ± 5.6 pmol/mg). ONE crosslinked apolipoprotein A-I (apoA-I) on HDL at a concentration of > 3 mol ONE per 10 mol apoA-I (0.3 eq), which was 100-fold lower than HNE, but comparable to the potent protein crosslinker isolevuglandin. ONE-modified HDL partially inhibited HDL's ability to protect against lipopolysaccharide (LPS)-induced tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) gene expression in murine macrophages. At 3 eq, ONE dramatically decreased apoA-I exchange from HDL, from ∼46.5 to ∼18.4% (p < 0.001). Surprisingly, ONE modification of HDL or apoA-I did not alter macrophage cholesterol efflux capacity. LC-MS/MS analysis revealed that Lys-12, Lys-23, Lys-96, and Lys-226 in apoA-I are modified by ONE ketoamide adducts. Compared with other dicarbonyl scavengers, pentylpyridoxamine (PPM) most efficaciously blocked ONE-induced protein crosslinking in HDL and also prevented HDL dysfunction in an in vitro model of inflammation. Our findings show that ONE-HDL adducts cause HDL dysfunction and are elevated in individuals with FH who have severe hypercholesterolemia.

Anti-ApoA-1 IgGs in Familial Hypercholesterolemia Display Paradoxical Associations with Lipid Profile and Promote Foam Cell Formation.

Aims: Anti-Apolipoprotein A-1 autoantibodies (anti-ApoA-1 IgG) promote atherogenesis via innate immune receptors, and may impair cellular cholesterol homeostasis (CH). We explored the presence of anti-ApoA-1 IgG in children (5–15 years old) with or without familial hypercholesterolemia (FH), analyzing their association with lipid profiles, and studied their in vitro effects on foam cell formation, gene regulation, and their functional impact on cholesterol passive diffusion (PD). Methods: Anti-ApoA-1 IgG and lipid profiles were measured on 29 FH and 25 healthy children. The impact of anti-ApoA-1 IgG on key CH regulators (SREBP2, HMGCR, LDL-R, ABCA1, and miR-33a) and foam cell formation detected by Oil Red O staining were assessed using human monocyte-derived macrophages. PD experiments were performed using a validated THP-1 macrophage model. Results: Prevalence of high anti-ApoA-1 IgG levels (seropositivity) was about 38% in both study groups. FH children seropositive for anti-ApoA-1 IgG had significant lower total cholesterol LDL and miR-33a levels than those who were seronegative. On macrophages, anti-ApoA-1 IgG induced foam cell formation in a toll-like receptor (TLR) 2/4-dependent manner, accompanied by NF-kB- and AP1-dependent increases of SREBP-2, LDL-R, and HMGCR. Despite increased ABCA1 and decreased mature miR-33a expression, the increased ACAT activity decreased membrane free cholesterol, functionally culminating to PD inhibition. Conclusions: Anti-ApoA-1 IgG seropositivity is frequent in children, unrelated to FH, and paradoxically associated with a favorable lipid profile. In vitro, anti-ApoA-1 IgG induced foam cell formation through a complex interplay between innate immune receptors and key cholesterol homeostasis regulators, functionally impairing the PD cholesterol efflux capacity of macrophages.

The future of apolipoprotein E mimetic peptides in the prevention of cardiovascular disease.

This review aims to discuss the recent developments in the area of apolipoprotein E (apoE) mimetics and their therapeutic potential for treating cardiovascular disease, the leading cause of mortality worldwide. Ongoing research efforts target the development of novel therapies that would not only reduce circulating levels of atherogenic lipoproteins, but could also increase high density lipoprotein cholesterol (HDL-C) levels and/or improve HDL function. Among them, synthetic peptides that mimic the structure of natural human apoE, a component of triglyceride-rich lipoproteins and HDL, have been designed and proven to be functionally similar to apoE. In specific, apoE mimetic peptides mediate hepatic clearance of circulating atherogenic lipoproteins, dramatically reduce plasma cholesterol, and lead to attenuation of atherosclerosis development in vivo. These peptides also exhibit pleiotropic antiatherogenic properties, such as macrophage cholesterol efflux capacity, as well as anti-inflammatory and antioxidative functions. ApoE mimetics are undergoing preclinical and clinical evaluation with promising results to date that render them attractive candidates in cardiovascular disease prevention and treatment.

Activation profiles of monocyte-macrophages and HDL function in healthy women in relation to menstrual cycle and in polycystic ovary syndrome patients.

Hormonal status and menopause affect human macrophage function and cardiometabolic risk. In polycystic ovary syndrome (PCOS) patients the cardiometabolic risk increases through mechanisms that are largely unknown. We tested the hypotheses that macrophage activation is influenced by menstrual cycle and that ovarian dysfunction in PCOS patients is associated with altered macrophage inflammatory responses and cholesterol efflux capacity of serum HDL. Blood samples were obtained in the follicular and luteal phases from cycling women (n = 10) and on a single visit from PCOS patients with ovarian dysfunction (n = 11). Monocyte-derived macrophage activation and monocyte subsets were characterized ex vivo using flow cytometry. The capacity of HDL to promote cell cholesterol efflux through the main efflux pathways, namely aqueous diffusion, ATP-binding cassette A1 and G1, was also evaluated. Hormone and metabolic profiles differed as expected in relation to menstrual cycle and ovulatory dysfunction. Overall, macrophage responses to activating stimuli in PCOS patients were blunted compared with cycling women. Macrophages in the follicular phase were endowed with enhanced responsiveness to LPS/interferon-γ compared with the luteal phase and PCOS. These changes were not related to baseline differences in monocytes. HDL cholesterol efflux capacity through multiple pathways was significantly impaired in PCOS patients compared to healthy women, at least in part independent from lower HDL-cholesterol levels. Regular menstrual cycles entailed fluctuations in macrophage activation. Such dynamic pattern was attenuated in PCOS. Along with impaired HDL function, this may contribute to the increased cardiometabolic risk associated with PCOS.

Genetic control of the mouse HDL proteome defines HDL traits, function, and heterogeneity

HDLs are nanoparticles with more than 80 associated proteins, phospholipids, cholesterol, and cholesteryl esters. The potential inverse relation of HDL to coronary artery disease (CAD) and the effects of HDL on myriad other inflammatory conditions warrant a better understanding of the genetic basis of the HDL proteome. We conducted a comprehensive genetic analysis of the regulation of the proteome of HDL isolated from a panel of 100 diverse inbred strains of mice (the hybrid mouse diversity panel) and examined protein composition and efflux capacity to identify novel factors that affect the HDL proteome. Genetic analysis revealed widely varied HDL protein levels across the strains. Some of this variation was explained by local cis-acting regulation, termed cis-protein quantitative trait loci (QTLs). Variations in apoA-II and apoC-3 affected the abundance of multiple HDL proteins, indicating a coordinated regulation. We identified modules of covarying proteins and defined a protein-protein interaction network that describes the protein composition of the naturally occurring subspecies of HDL in mice. Sterol efflux capacity varied up to 3-fold across the strains, and HDL proteins displayed distinct correlation patterns with macrophage and ABCA1-specific cholesterol efflux capacity and cholesterol exchange, suggesting that subspecies of HDL participate in discrete functions. The baseline and stimulated sterol efflux capacity phenotypes were associated with distinct QTLs with smaller effect size, suggesting a multigenetic regulation. Our results highlight the complexity of HDL particles by revealing the high degree of heterogeneity and intercorrelation, some of which is associated with functional variation, and support the concept that HDL-cholesterol alone is not an accurate measure of HDL’s properties, such as protection against CAD.

Nutritionally Derived Metabolic Cues Typical of the Obese Microenvironment Increase Cholesterol Efflux Capacity of Adipose Tissue Macrophages.

BackgroundCholesterol retention within plasma membranes of macrophages is associated with increased inflammatory signaling. Cholesterol efflux via the transporters ABCA1, ABCG1, and SR‐BI to high‐density lipoprotein (HDL) particles is a critical mechanism to maintain cellular cholesterol homeostasis. Little is known about the impact of the obese microenvironment on cholesterol efflux capacity (CEC) of macrophages. In this study, the CEC of obese‐derived primary adipose‐tissue macrophages (ATM) is evaluated and the in vivo microenvironment is modeled in vitro to determine mechanisms underlying modulated CEC.Materials and MethodsF4/80+ ATM are labeled with 3H‐cholesterol ex vivo, and CEC and ABCA1/ABCG1 protein levels are determined. Total, ABCA1‐dependent, and ABCA1‐independent CECs are determined in J774 macrophages polarized to M1 (LPS&IFNγ), M2 (IL‐4&IL‐13), or metabolic phenotypes (glucose, insulin, and palmitic acid).ResultsObese ATM exhibit enhanced CEC and ABCA1 and ABCG1 expression compared to lean ATM. In contrast, ABCA1‐CEC is suppressed from M1 polarized macrophages compared to untreated in vitro, by activation of the JAK/STAT pathway. Incubation of macrophages in vitro in high glucose augments cAMP‐induced ABCA1 protein expression and ABCA1‐CEC.ConclusionsThese novel findings demonstrate remarkable plasticity of macrophages to respond to their environment with specific modulation of ABCA1 depending on whether classical pro‐inflammatory or metabolic cues predominate.

Impaired HDL cholesterol efflux capacity in patients with non-alcoholic fatty liver disease is associated with subclinical atherosclerosis

Non-alcoholic fatty liver disease (NAFLD) is associated with a substantial increased risk of atherosclerotic cardiovascular disease (ASCVD), which is partly related to dyslipidemia and low HDL-C level. The cardioprotective activity of HDL in the body is closely connected to its role in promoting cholesterol efflux, which is determined by cholesterol efflux capacity (CEC). Hitherto, the role of HDL, as defined by CEC has not been assessed in NAFLD patients. In this research study, we present the results of a study of cAMP-treated J774 CEC and THP-1 macrophage CEC in ApoB-depleted plasma of 55 newly diagnosed NAFLD patients and 30 controls. Circulating levels of ApoA-I, ApoB, preβ-HDL, plasma activity of CETP, PLTP, LCAT and carotid intima-media thickness (cIMT) were estimated. cAMP-treated J774 and THP-1 macrophage CEC were found to be significantly lower in NAFLD patients compared to controls (P < 0.001 and P = 0.003, respectively). In addition, it was discovered that both ApoA-I and preβ1-HDL were significantly lower in NAFLD patients (P < 0.001). Furthermore, cAMP-treated J774 CEC showed independent negative correlation with cIMT, as well as the presence of atherosclerotic plaque in NAFLD patients. In conclusion, our findings showed that HDL CEC was suppressed in NAFLD patients, and impaired cAMP-treated J774 CEC was an independent risk factor for subclinical atherosclerosis in NAFLD patients, suggesting that impaired HDL functions as an independent risk factor for atherosclerosis in NAFLD.

Glycation and Deamidation Result in HDL Dysfunction in Patients with Type 2 Diabetes

Diabetes is associated with HDL dysfunction and perturbed iron metabolism. ApoAI, transferrin (Trf) and ceruloplasmin (Cp) are the key HDL proteins involved in cholesterol efflux and iron metabolism. We tested the hypothesis that hyperglycemia-induced glycation contributes to HDL dysfunction and altered iron metabolism in diet-controlled patients with T2D. HDL from patients with T2D and matched healthy controls (n=9/group) was isolated and it’s anti-oxidant and cholesterol efflux properties were quantified. HDL proteome composition and post-translational modification of proteins were quantified by proteomics aproach. Metabolic 2H2O-labeling was applied to quantify HDL proteome dynamics. Patients with T2D and controls had similar lipid (triglycerides, total cholesterol, and HDL cholesterol) profile. HDL from T2D patients had reduced anti-oxidant (PON1 activity) and macrophage-cholesterol efflux capacity (P&amp;lt;0.05) and was enriched with glycated apoAI and transferrin (Tf), and deamidated ceruloplasmin (Cp), the key HDL proteins involved in cholesterol and iron transport. Both ApoAI and Trf glycation were directly correlated with HbA1c and the extent of glycations were associated with their increased degradation. ApoAI glycation was inversely correlated with cholesterol efflux activity of HDL. Trf glycations at Lys-2and Lys-534 sites involved in iron coordination, were 2-3 fold higher in T2D than in the controls. The PTM search on Cp revealed five asparagine deamidation sites in T2D patients with N-943 being located on one of the oxidation-prone motifs and may result in the loss of Cp’s ferroxidase activity. In vivo HDL flux study demonstrated that glycated apoAI and Tf, and deamidated Cp species were degraded 3, 10, and 2 fold faster than the respective non-modified native proteins. HDL dysfunction and oxidative stress in T2D is related to glycation- and deamidation-induced instability of HDL proteins, including ApoAI, Tf and Cp. Disclosure T. Kasumov: None. M. Golizeh: None. S. Kashyap: None.

Abstract 384: Differential Effects of Niacin and Omega-3 Fatty Acids on HDL-apolipoprotein A-I Exhange and Cholesterol Efflux Capacity in Subjects with Metabolic Syndrome

Objective: Niacin and omega-3 fatty acids are two therapeutic agents that have been extensively studied for their ability to reduce cardiovascular disease risk, but their effectiveness has more recently been called into question. In this study, we investigate whether these agents alone and in combination alter HDL function, in particular, HDL-apolipoprotein A-I exchange (HAE), a measure of HDL dynamics, and serum cholesterol efflux capacity (CEC). Approach: Fifty-six subjects with metabolic syndrome (MetSyn) were recruited to a double-blind trial and randomized to 16 weeks of treatment with dual placebo, extended release niacin (ERN, 2g/day), prescription omega-3 ethyl esters (P-OM3, 4g/day), or combination. HDL function was assessed at baseline and following 16 weeks of treatment by measuring HAE, macrophage CEC, and ABCA1-specific CEC. Results: Compared to placebo, ERN and P-OM3 alone significantly increased HAE by 15.1 [8.2, 22.0] (p&lt;0.0001) and 12.4% [5.9, 18.9] ( P &lt;0.0001) respectively while the combination therapy increased HAE by 10.0% [3.2, 16.8] ( P =0.002). When evaluated by HAE:apoA-I ratio (a measure of apoA-I specific activity), ERN increased apoA-I specific activity by 20.1% [4.8, 36.9] ( P =0.008), P-OM3 by 30.1% [14.4, 45.9] ( P&lt; 0.0001), however with combination there was no increase, 9% [-6.6, 26.6] ( P =0.34). Triglyceride-adjusted macrophage CEC showed marginally significant increases with P-OM3 therapy ( P =0.05). No therapy significantly improved ABCA1-specific CEC. Conclusions: Much of the effect of ERN on HDL function can be attributed to this therapy raising apoA-I levels, but P-OM3 raises HDL function by independent means, increasing apoA-I specific activity. Future investigation is needed to determine whether interaction between ERN and P-OM3 therapies in combination reduces their overall effectiveness.

Sex steroids mediate discrete effects on HDL cholesterol efflux capacity and particle concentration in healthy men

Exogenous testosterone decreases serum concentrations of high-density lipoprotein cholesterol (HDL-C) in men, but whether this alters cardiovascular risk is uncertain. To investigate the effects of testosterone and estradiol on HDL particle concentration (HDL-Pima) and metrics of HDL function. We enrolled 53 healthy men, 19 to 55years of age, in a double-blinded, placebo-controlled, randomized trial. Subjects were rendered medically castrate using the GnRH receptor antagonist acyline and administered either (1) placebo gel, (2) low-dose transdermal testosterone gel (1.62%, 1.25g), (3) full replacement dose testosterone gel (1.62%, 5g) or (4) full replacement dose testosterone gel together with an aromatase inhibitor for 4weeks. At baseline and end of treatment, serum HDL total macrophage and ABCA1-specific cholesterol efflux capacity (CEC), HDL-Pima and size, and HDL protein composition were determined. Significant differences in serum HDL-C were observed with treatment across groups (P=.01 in overall repeated measures ANOVA), with increases in HDL-C seen after both complete and partial testosterone deprivation. Medical castration increased total HDL-Pima (median [interquartile range] 19.1 [1.8] nmol/L at baseline vs 21.3 [3.1] nmol/L at week 4, P=.006). However, corresponding changes in total macrophage CEC and ABCA1-specific CEC were not observed. Change in serum 17β-estradiol concentration correlated with change in total macrophage CEC (β=0.33 per 10 pg/mL change in serum 17β-estradiol, P=.03). Testosterone deprivation in healthy men leads to a dissociation between changes in serum HDL-C and HDL CEC. Changes in serum HDL-C specifically due to testosterone exposure may not reflect changes in HDL function.

Cholesterol efflux in the transplant patient.

Cholesterol metabolism is increasingly recognized in inflammatory diseases including transplantation. This review discusses the mechanistic underpinnings that tie macrophage cholesterol efflux capacity (CEC) of high-density lipoprotein (HDL) to chronic rejection in transplanted patients. Animal studies suggest that administration of apolipoprotein A-I, the main protein constituent of HDL, can prevent transplant arteriosclerosis. apoA-I administration increases CEC of HDL. In patients with cardiac allograft vasculopathy (CAV), decreased CEC has been associated with poorer survival. In addition, reduced CEC in recipients, pretransplant, has been associated with the development of CAV and renal allograft survival. These recent findings raise the hypothesis that increasing cholesterol efflux may prevent chronic rejection and improve allograft survival after transplant. Reconstituted HDL significantly increases CEC and is currently in clinical development for traditional atherosclerosis. Clinical trials of reconstituted HDL administration in transplantation should be performed.

Pre-transplant Macrophage Cholesterol Efflux Capacity is Associated With Angiographic Cardiac Allograft Vasculopathy in a Multi-center Observational Study

Pre-transplant Macrophage Cholesterol Efflux Capacity is Associated With Angiographic Cardiac Allograft Vasculopathy in a Multi-center Observational Study

Bariatric surgery improves lipoprotein profile in morbidly obese patients by reducing LDL cholesterol, apoB, and SAA/PON1 ratio, increasing HDL cholesterol, but has no effect on cholesterol efflux capacity

Bariatric surgery has been shown to reduce cardiovascular events and cause-specific mortality for coronary artery disease in obese patients. Lipoprotein biomarkers relating to low-density lipoprotein (LDL), high-density lipoprotein (HDL), their subfractions, and macrophage cholesterol efflux have all been hypothesized to be of value in cardiovascular risk assessment. The objective of this study was to examine the effect of a lifestyle intervention followed by bariatric surgery on the lipid profile of morbidly obese patients. Thirty-four morbidly obese patients were evaluated before and after lifestyle changes and then 1 year after bariatric surgery. They were compared with 17 lean subjects. Several lipoprotein metrics, serum amyloid A (SAA), serum paraoxonase-1 (PON1), and macrophage cholesterol efflux capacity (CEC) were assessed. Average weight loss after the lifestyle intervention was 10.5% and 1 year after bariatric surgery was 33.9%. The lifestyle intervention significantly decreased triglycerides (TGs; -28.7mg/dL, P<.05), LDL cholesterol (LDL-C; -32.3mg/dL, P<.0001), and apolipoprotein B (apoB; -62.9μg/mL, P<.001). Bariatric surgery further reduced TGs (-36.7mg/dL, P<.05), increased HDL cholesterol (+12mg/dL, P<.0001), and reductions in LDL-C and apoB were sustained. Bariatric surgery reduced large, buoyant LDL (P<.0001), but had no effect on the small, dense LDL. The large HDL subfractions increased (P<.0001), but there was no effect on the smaller HDL subfractions. The ratio for SAA/PON1 was reduced after the lifestyle intervention (P<.01) and further reduced after bariatric surgery (P<.0001). Neither the lifestyle intervention nor bariatric surgery had any effect on CEC. Lifestyle intervention followed by bariatric surgery in 34 morbidly obese patients showed favorable effects on TGs, LDL-C, and apoB. HDL cholesterol and apoA1 was increased, apoB/apoA1 ratio as well as SAA/PON1 ratio reduced, but bariatric surgery did not influence CEC.