Anouar Hafiane
McGill University, Medecine, Post-Doc
- McGill University, Biochemistry, Department Memberadd
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Background: Adiponectin (APN) is an adipokine most abundantly secreted by adipocytes and possesses vasculoprotective properties. We and others have previously showed that APN receptor 2 (adipoR2) pathway is impaired in foam cells when... more
Background: Adiponectin (APN) is an adipokine most abundantly secreted by adipocytes and possesses vasculoprotective properties. We and others have previously showed that APN receptor 2 (adipoR2) pathway is impaired in foam cells when compared to macrophages. Nevertheless, the functional role of adipoR2 pathway in foam cells has not been fully investigated. We hypothesize that APN kinetics involving AdipoR2 and its subsequent downstream signaling peroxisome proliferator-activated receptor-α (PPAR-α) expression are altered in foam cells when compared to macrophages. Methods: We used THP-1 human macrophage-derived foam cells loaded with oxidized LDL (60μg/ml) and 3H-cholesterol (2μCi/ml) versus control macrophages. APN isomers and PPAR-α protein expression were detected by gradient SDS-PAGE, and Western blotting, respectively. Media cell cultures mixtures were analysed under protease inhibitor by a size-exclusion centrifugal filter molecular weight cut-off 10 kDa. Results: PPAR-α activation significantly increased in APN-treated macrophages (24h) when compared with APN-treated foam cells (24h) with a maximum fold difference of 1.90±1.21, p=0.002 at 10μg APN/mL (PPAR-α: β actin ratio, spectral count; n=10 repeats for each). As a result, in foam cells, APN stimulated PPAR-α with a lower Km molar efficiency (0.06 ± 0.13 μM) and lower velocity Vmax 0.67±0.08 /h-as compared to macrophages (0.023±0.02 μM and 1.37±0.11 /h respectively, p=0.01 for both). In macrophages, APN had smaller dissociation constant Kd (0.037±0.56 μM) than in foam cells (0.10±1.30 μM). APN increased significantly PPAR-α activity rate over time reaching a maximum of 2h, with 1.19±0.02 PPAR-α protein expression in macrophages vs 0.85±0.057 in foam cells. Additionally, the APN dimer/monomer ratio increased over 24h when compared to foam cells, reaching a maximum at 2h in macrophages. Strong correlations were noted between PPARα and APN dimers: in macrophages (r=0.85; p=0.006) and in foam cells (r=0.68, p=0.05). Conclusion: APN stimulates PPARα activity in macrophages, but significantly less in foam cells (weaker kinetic affinity process), suggesting that APN interaction and binding with adipoR2 and subsequent downstream PPARα expression are affected in foam cells.
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Research Interests: Metabolism, Atherosclerosis, Medicine, Autoimmune Disease, Autoimmune diseases, and 7 moreCholesterol, Clinical Sciences, Public health systems and services research, High Density Lipoprotein, reverse cholesterol transport, Cardiovascular medicine and haematology, and Medical biochemistry and metabolomics
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Cholesterol efflux is the initial step in the reverse cholesterol transport pathway by which excess cholesterol in peripheral cells is exported and subsequently packaged into high-density lipoprotein (HDL) particles. Adiponectin is the... more
Cholesterol efflux is the initial step in the reverse cholesterol transport pathway by which excess cholesterol in peripheral cells is exported and subsequently packaged into high-density lipoprotein (HDL) particles. Adiponectin is the most abundantly secreted adipokine that possesses anti-inflammatory and vasculoprotective properties via interaction with transmembrane receptors, AdipoR1 and AdipoR2. Evidence suggests that low levels of adiponectin may be a useful marker for atherosclerotic disease. A proposed anti-atherogenic mechanism of adiponectin involves its ability to promote cholesterol efflux. We performed a systematic review of the role of adiponectin in cholesterol efflux and HDL biogenesis, and of the proteins and receptors believed to be implicated in this process. Nineteen eligible studies (7 clinical, 11 fundamental, 1 clinical + fundamental) were identified through Ovid Medline, Ovid Embase, and Pubmed, that support the notion that adiponectin plays a key role in promoting ABCA1-dependent cholesterol efflux and in modulating HDL biogenesis via activation of the PPAR-γ/LXR-α signalling pathways in macrophages. AdipoR1 and AdipoR2 are suggested to also be implicated in this process, however the data are conflicting/ insufficient to establish any firm conclusions. Once the exact mechanisms are unravelled, adiponectin may be critical in defining future treatment strategies directed towards increasing HDL functionality and ultimately reducing atherosclerotic disease.
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Adiponectin exerts its atheroprotection by stimulating adenosine triphosphate binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux to apolipoprotein A-I (apoA-I). However, involvement of the apoA-I residues in this process... more
Adiponectin exerts its atheroprotection by stimulating adenosine triphosphate binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux to apolipoprotein A-I (apoA-I). However, involvement of the apoA-I residues in this process have not been studied. In Tamm-Horsfall 1 (THP-1) macrophages and baby hamster kidney (BHK) cells we assessed adiponectin's potential to restore cholesterol efflux in the presence of apoA-I and ABCA1 mutants, respectively. Adiponectin was unable to restore efflux from THP-1 macrophages in the presence of apoA-I carboxy-terminal domain (CTD) successive mutants from residues 187-243 versus apoA-I mutants alone. Furthermore, adiponectin did not significantly influence cholesterol efflux to apoA-I from BHK-ABCA1 mutant cells. Adiponectin appears to require functional apoA-I CTD residues 187-243 and wild-type ABCA1 to mediate efficient cholesterol efflux from THP-1 macrophages and BHK cells, respectively. Therefore, adiponectin cannot rescue defective cholesterol efflux in apoA-I- or ABCA1-mutant conditions, but rather increases cholesterol efflux in wild-type apoA-I conditions compared to apoA-I exposure alone.
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Introduction and Hypothesis: Aortic valve calcification (AVC), is the intrinsic mechanism of valvular obstruction in severe aortic stenosis (AS), sharing similarities with atherosclerosis. There are differences in AVC by sex, with women... more
Introduction and Hypothesis: Aortic valve calcification (AVC), is the intrinsic mechanism of valvular obstruction in severe aortic stenosis (AS), sharing similarities with atherosclerosis. There are differences in AVC by sex, with women having a lower burden of calcification than men, but the mechanism for this is unclear. Improved HDL functionality has been associated with protection against coronary artery calcification, but its relationship to AVC is less studied. Methods: We evaluated measures of high-density lipoprotein (HDL) functionality in 46 patients with severe AS, n= 30 men, n=16 women. ATP-Binding Cassette A1 (ABCA1) mediated cholesterol efflux capacity (CEC) was measured from human cultured Tamm-Horsfall protein 1 (THP-1) macrophages to apoB-depleted patient plasma samples. Lipid profile, lecithin-cholesterol acyltransferase activity (LCAT), fast protein liquid chromatography (FPLC), HDL size, and small pre-β1 and α-HDL particles, were measured in apolipoprotein B-depleted patient plasma. Proteomic analysis was used to explore sex-based differences in the HDL proteome. Results: Women with severe AS had higher ABCA1-mediated CEC, as compared to men (n=46, p=0.04). We found differences in FPLC profiles between sexes in severe AS along with a reduction in preβ and α-particles in men vs women by spectral counts, (preβ-HDL, 15661.74±789.00 vs 20298.29±1076.15, p=0.002), and (α-HDL, 50447.00± 546.52 vs 63006.35±756.81, p=0.03). Conversion of free cholesterol into cholesteryl esters by LCAT was decreased in men vs. women (12.00±8.07 %/h vs 16.44±9.11 %/h, p=0.03). We identified 108 HDL-associated proteins in a representative man and woman, of which, 15 were found only in the female sample Conclusions: Sex-specific differences in measures of HDL functionality were found in patients with severe AS. Future studies should consider whether sex-based differences in HDL functionality might account for the decreased burden of calcification in women vs. men with severe AS.
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The objective of this study was to examine the function of high-density lipoproteins (HDL) in patients with severe carotid atherosclerosis undergoing carotid endarterectomy (CEA) and in patients with coronary artery disease (CAD). We... more
The objective of this study was to examine the function of high-density lipoproteins (HDL) in patients with severe carotid atherosclerosis undergoing carotid endarterectomy (CEA) and in patients with coronary artery disease (CAD). We examined clinical, biochemical and lipoprotein profiles and HDL cholesterol efflux capacity (CEC) in 155 patients undergoing CEA and compared the results with patients with an acute coronary syndrome (ACS time 0 n=26) measured within 48 hours of the event, and again at 12 weeks (ACS recovery, n=26), in patients with chronic, stable CAD (sCAD) n=27 and in healthy controls. There were 110 men (71%) and 45 women (29%) with a mean age 69±10 years in the CEA group. Mean HDL-C was 0.96±0.26 mmol/L (38±10 mg/dL). There were no significant differences in HDL-C between CEA, ACS and sCAD subjects. HDL was obtained after depletion of apo B-containing lipoproteins with PEG precipitation. Cellular efflux capacity was determined by incubating HDL in cAMP-stimulated J774 mouse peritoneal macrophages for 6 hours. Specific cholesterol efflux was obtained by subtracting total efflux from efflux in non-cAMP stimulated cells. The procedure was standardized to enable medium throughput. Coefficient of variability was approximately 5%. HDL from CEA patients differ in its ability to promote cholesterol efflux. The range of CEC observed was: min 14.7%, max 34.0% mean 22.4±0.6%; (IQR 18.9-27.3% median 22.0). We found a weak correlation between HDL-C and CEC in patients CEA (r= 0.20, P=0.012); a significant correlation was found between apo A-I and CEC (r=0.23, P=0.005). Subjects with similar HDL-C or apoA-I differed in their ability to promote cellular cholesterol efflux, suggesting that the HDL-C mass does not reflect functionality. We found similar CEC in patients with CAD and ACS recovery. Here, we report that patients with severe carotid atherosclerosis have low HDL-C and a CEC similar to that observed in CAD patients. The function of HDL to promote cellular cholesterol efflux, as determined by CEC, varied over a wide range and was only weakly correlated with HDL-C. The significant correlation between apo AI and CEC suggests that HDL particle size -and composition may also be an important determinant of the ability to promote cellular cholesterol efflux.
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Two novel (26-AA) apolipoprotein (apo) mimetic peptides ATI-5261 and CS-6253 were studied in vitro for their ability to interact with ABCA1 and ABCG1 and to generate functional HDL-like particles. ...
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Chronic subclinical inflammation is a key process in the pathogenesis of atherosclerotic cardiovascular disease (ASCVD). Along with lipids, inflammation is essential for the initiation and progression of atherosclerosis with macrophages... more
Chronic subclinical inflammation is a key process in the pathogenesis of atherosclerotic cardiovascular disease (ASCVD). Along with lipids, inflammation is essential for the initiation and progression of atherosclerosis with macrophages playing a pivotal role through the induction of oxidative stress and cytokine secretion. Several pro-inflammatory cytokines have been described in the primary and secondary prevention of ASCVD. Although extensive work over the past decades has established the role of lipid-lowering medications in the prevention and treatment of ASCVD, modulation of inflammation is a subject of active debate. It remains to be confirmed whether targeting the residual cardiovascular risk by adding anti-inflammatory agents to the conventional cardiovascular treatment becomes a shifting paradigm for ASCVD management. This review aims to discuss novel therapeutic agents targeting inflammatory pathways in ASCVD in light of the canakinumab anti-inflammatory thrombosis outcomes study (CANTOS) trial results. Further we discuss the effects of different anti-inflammatory agents administered in patients with ASCVD and their potential to change clinical practice in preventive cardiology.
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Background and Purpose— Statins are widely used for cardiovascular disease prevention through cholesterol-lowering and anti-inflammatory effects. Adiponectin, an anti-inflammatory adipokine, acts via two receptors, AdipoR1 and AdipoR2, to... more
Background and Purpose— Statins are widely used for cardiovascular disease prevention through cholesterol-lowering and anti-inflammatory effects. Adiponectin, an anti-inflammatory adipokine, acts via two receptors, AdipoR1 and AdipoR2, to exert atheroprotective effects on the vasculature. We investigated whether statins can modulate the adiponectin-AdipoR pathway in the human monocyte-macrophage lineage. Methods— Monocytes were isolated from the whole blood of patients with severe carotid atherosclerosis (cross-sectional study) or from patients with cardiovascular risk factors (longitudinal study) and assessed for AdipoR1 and AdipoR2 gene expression using quantitative real-time polymerase chain reaction. In vitro, THP-1 (Tamm-Horsfall protein 1) macrophages were treated with increasing atorvastatin or rosuvastatin doses for 24- or 72-hours to determine the effect of statins on AdipoR expression and activity. Macrophage cytokine secretion (IL [interleukin]-1β, IL-10, IL-6, and TNF [tumor necrosis factor]-α) was assessed by electrochemiluminescence. Results— AdipoR1 and AdipoR2 mRNA expression on circulating monocytes from patients with carotid atherosclerosis, was significantly lower by 1.36- and 1.17-fold, respectively, in statin users versus statin-naïve patients. Specifically, patients on high doses of atorvastatin (40–80 mg) or rosuvastatin (20–40 mg) had significantly lower AdipoR gene expression versus statin-naïve patients. Similarly, in the longitudinal in vivo study, longer atorvastatin/rosuvastatin treatment (≥5 months) in patients with cardiovascular risk factors resulted in lower AdipoR gene expression on circulating monocytes versus prestatin levels. In vitro, higher statin doses and longer exposure resulted in a greater decrease in AdipoR mRNA expression and greater macrophage secretion of pro-inflammatory cytokines, IL-1β, IL-6, and TNF-α. High statin doses also reduced adiponectin’s capacity to suppress intracellular cholesteryl ester levels in oxLDL (oxidized LDL)-loaded macrophages, with rosuvastatin exhibiting higher potency than atorvastatin. Conclusions— Our in vivo and in vitro studies identified a novel pleiotropic property of statins in modulating the adiponectin-AdipoR pathway in the human monocyte-macrophage lineage, where intensive statin therapy compromised the expression and function of adiponectin and its receptors.
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Objectives: High plasma levels of lipoprotein (a) (Lp(a)) are associated with increased risk of aortic valve stenosis. The purpose of this study was to determine ability of human aortic valve interstitial cells (HAVICs) to generate HDL... more
Objectives: High plasma levels of lipoprotein (a) (Lp(a)) are associated with increased risk of aortic valve stenosis. The purpose of this study was to determine ability of human aortic valve interstitial cells (HAVICs) to generate HDL particles from plasma of patients with high Lp(a), and understand the mechanism involved. Methods: HAVICs were isolated from consented participants and cultured in DMEM, 10% FBS, 5% glucose. ABCA1 proteins expression was tested in HAVICs lyses after detection by polyclonal anti-ABCA1 antibody. Cholesterol efflux was determined in HAVICs against HDL isolated by PEG from patients with aortic valve stenosis exhibiting mild or severe plasma Lp(a), compared to normolipidemic controls. FPLC and 2D-PAGGE were used to illustrate HDL profiles from these patients after incubation with HAVICs. Results: Our data showed abundant expression of ABCA1, and a significant decrease in HAVICs cholesterol efflux (5%, for 8h) in response to HDL from plasma of patients with high Lp(a) and aortic valve stenosis (mild 16±0.01%cpm, severe 23.4±0.21%cpm) compared to normolipidemic HDL (29.57cpm; P<0.01). This was consistent with FPLC profiles indicating a similar reduction in in cholesterol within nascent HDL (nHDL) when compared to nHDL generated from HDL isolated from plasma of normal controls. Importantly, we noticed a generation of smaller population of HDL particles formed following cholesterol efflux. Plasma from patient with aortic valve stenosis showed a distinct decrease in preβ- and α1-migrating HDL, but no in other α-migrating HDL particles, when compared to plasma from normolipidemic controls. We also observed a defect in α1-HDL in the nHDL generated from patient with high Lp(a) and aortic valve stenosis compared to nHDL from plasma of normal controls. Conclusion: These findings demonstrate a defect in HAVICs ABCA1 cholesterol removal associated a loss of α1 species of nHDL in patient with high Lp(a) and aortic valve stenosis. Therefore, the HAVICs cholesterol efflux defect associated with the elevated plasma Lp(a) may explain the pathological changes associated aortic valve calcification.
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Novel apolipoprotein (apo) mimetic peptides are potent mediators of ABCA1-mediated cholesterol efflux, mimicking native apoA-I. We investigated CS-6253 (CS) and ATI-5261 (ATI) in their ability to promote lipid transfer between nascent... more
Novel apolipoprotein (apo) mimetic peptides are potent mediators of ABCA1-mediated cholesterol efflux, mimicking native apoA-I. We investigated CS-6253 (CS) and ATI-5261 (ATI) in their ability to promote lipid transfer between nascent (n)HDL particles and plasma lipoproteins and examined cholesterol influx from remodelled HDL-like particles to hepatic cells through the SR-BI receptor. nHDL-like lipoproteins nHDL-CS and nHDL-ATI were generated by incubating CS or ATI in the presence of BHK cells expressing ABCA1 labelled with 3 [H]cholesterol and 3 [H] choline; native apoA-I was used as control. These nHDL particles were incubated with plasma at 37°C. Both CS and ATI increased LCAT activity significantly, although were approximately 50% less efficient than nHDL-apoA-I (fractional esterification rate (FER) =22.32±0.86%/h; vs nHDL-CS and nHDL-ATI; FER=11.40±0.045%/h; p<0.05). The majority of 3 [H]cholesterol from nHDL mimetics was esterified by LCAT, resulting in an increase in α1-migrating HDL-like particles in plasma (as shown by 2D-PAGGE). The ability of nHDL mimetics to transfer 3 [H]-phosphatidyl choline to plasma apoB-containing lipoproteins is (76±20%) in HDL-apoA-I, (38±0.5%) in nHDL-ATI and (54±13%) in nHDL-CS. These data show that nHDL mimetics are actively remodelled in the presence of plasma lipoproteins. We then investigated cholesterol delivery from HDL-CS and HDL-ATI mimetic to hepatic tissue via SR-BI using Fu5AH cells, having HDL-apoA-I as control. Kinetic parameters for SR-BI-mediated cholesterol influx are as follows: HDL-CS ( K m = 0.30±0.05 ug/ml; p<0.05) efficient as HDL apoA-I at promoting cholesterol uptake into Fu5AH cells ( K m = 0.37±0.13 ug/ml), while HDL-ATI was least efficient ( K m = 1.03±0.20 ug/ml). The inhibition of SR-BI selective uptake with BLT-1 affected the uptake of cholesterol from apoB precipitated plasma containing either HDL-CS, HDL-ATI or apoA-I. Here we present an in-vitro model of nHDL-CS and nHDL-ATI that actively undergo remodelling and maturation in plasma and replicate the function of apoA-I. These mature HDL mimetics generated from ABCA1 agonist peptides deliver cholesterol efficiently to hepatocytes specifically through the SR-BI receptor.
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HDL mimetic peptides hold promise for the treatment of cardio-metabolic diseases. Transient increases in plasma TG and/or safety concerns may limit their therapeutic applications however, particularly in high risk patients with... more
HDL mimetic peptides hold promise for the treatment of cardio-metabolic diseases. Transient increases in plasma TG and/or safety concerns may limit their therapeutic applications however, particularly in high risk patients with hypertriglyceridemia and diabetes. Presently, we sought to identify peptide structural features responsible for these adverse effects. The single helix peptide ATI-5261 was used as a model, since it forms a class A α-helix like many HDL mimetic peptides and has exceptional secondary structure and solubility. High dose ip injection (300 mg/kg) of ATI-5261 induced muscle toxicity in C57Bl/6 mice vs. vehicle (serum CPK@4 h = 32,314±2359 vs 143±44 IU/L), increased ALT and AST activities (233±10 & 4595±933 vs 26±6 & 84±21 IU/L) and elevated plasma TG (1951±77 vs 37±7 mg/dl). A majority (~90%) of the cytotoxicity and TG increase was eliminated by removing phenylalanine residues from the apolar face of ATI-5261. Similar results were obtained by removing cationic arginine residues from the lipid-water interface. Thus both features were necessary, but each not sufficient, to induce cytotoxicity and TG elevations. Based on this, a peptide (CS6253) was created that was non-toxic (no adverse effect level >500 mg/kg; t1/2 =7.0±0.6 h in rats), retained secondary structure (75±5% α-helicity), high solubility and ability to stimulate ABCA1-dependent cholesterol efflux efficiently (Km=0.80±0.40 vs. 0.86±0.25 μg/ml ATI-5261). In vivo CS6253 was TG neutral, promoted macrophage RCT, and reduced (32%) substantial atherosclerosis in apoE KO mice fed western diet 10 wks (lesion area = 22±4 vs. 15±2% with 30 mg CS6253/kg, ip injection every 48 h for 6 wks, p<0.01) and improved glucose - and insulin- tolerance tests with lowering of HbA1c levels in C57Bl/6 mice fed high-fat diet (DIO model). In summary, the cytotoxic and TG elevating effects of high-dose ATI-5261 were dependent on class A α-helix structure. CS6253 with its improved safety margin represents a novel ABCA1 ligand peptide with potential to treat diabetes and associated cardiovascular disease.
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Research Interests: Cardiology, Cell line, Humans, Internal Medicine, Cholesterol, and 15 morecyclic AMP, Female, Animals, Clinical Sciences, Aged, Adult, Efflux, Biological markers, Chi Square Distribution, Disease Progression, Cross Sectional Studies, Cerebrovascular Disorders, Carotid Stenosis, Case Control Studies, and Cardiovascular medicine and haematology
Novel approaches that target HDL biogenesis may increase nascent HDL-like particle formation that can be used for therapeutic purposes. Here, we evaluated two 26-amino acid apoA-I mimetic peptides designed from c-terminus of apoE,... more
Novel approaches that target HDL biogenesis may increase nascent HDL-like particle formation that can be used for therapeutic purposes. Here, we evaluated two 26-amino acid apoA-I mimetic peptides designed from c-terminus of apoE, ATI-5261 and CS-6253 in their ability to promote cellular cholesterol efflux via the ABCA1 transporter. Using mifepristone-inducible ABCA1 BHK cells and cAMP-stimulated J774 macrophages, we examined ABCA1 oligomerization with dithiobis[succinimidyl propionate] (DSP) as a cross linker. Like native apoA-I, ATI-5261 and CS-6253 induced ABCA1 oligomerization at equimolar concentrations, and appear to interact with native oligomers of ABCA1, similar to apoA-I, as judged by crosslinking revealed by SDS-PAGE. By sucrose density gradient fractionation, we show that ABCA1 oligomerization occurs in non-raft domains. ATI-5261 and CS-6253 promoted cellular cholesterol efflux in a dose-dependent saturable manner. In BHK cells, the efficiency of cholesterol efflux (Km) on an equimolar basis was: apoA-I (0.16±0.02), ATI-5261 (0.45±0.08) and CS-6253 (0.68±0.15) and the efflux capacity (Vmax) (% in 24h) was: apoA-I (14.54±0.61), ATI-5261 (11.98±0.51) and CS-6253 (10.87±0.66), indicating a higher efflux efficiency for the apoA-I mimetics but with less capacity than native apoA-I. A similar trend was observed in J774 cells. Desorption of cellular cholesterol at 45 min occurred in both non-raft and raft-like membrane domains. We then examined by HPLC and 2-dimentional PAGGE the size and types of HDL-like particles formed. In 3[H]-cholesterol loaded BHK-ABCA1 cells, incubation with ATI-5261 and CS-6253 for 45 min and 12 hours yielded α-migrating particles with an apparent size ranging between 9 and 17 nm, as revealed by specific antibodies directed against ATI-5261 and CS-6253. Taken together, these observations suggest that ATI-5261 and CS-6253 induce cellular cholesterol efflux via ABCA1 oligomerization at molar concentrations similar to apoA-I and with higher efficiency. The particles generated by ATI-5261 and CS-6253 have α-migrating mobility with a size ranging between 9 and 17 nm and contain cholesterol, similar to nascent HDL particles.
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Background: Type 2 Diabetes Mellitus (T2DM) is associated with high cardiovascular disease (CVD) risk. Addressing the underlying atherogenesis and diabetes causing CVD in T2DM is important. CS6253 is an ABCA1 agonist peptide derived from... more
Background: Type 2 Diabetes Mellitus (T2DM) is associated with high cardiovascular disease (CVD) risk. Addressing the underlying atherogenesis and diabetes causing CVD in T2DM is important. CS6253 is an ABCA1 agonist peptide derived from the C-terminal of apoE that has shown macrophage specific reverse cholesterol transport, anti-atherosclerosis and anti-diabetic properties. Further studies were carried out to characterize metabolic effects. Methods: CS6253 was incubated with a) INS-1 823/13 cells to assess effects on insulin secretion and b) with L6-Glut4myc rat myoblasts to assess glucose uptake properties. Diet Induced Obesity (DIO) mice, i.e. C57BL/6 mice that had been fed 60% high-fat diet for 6 weeks, were treated with CS6253 and Glucose Tolerance Tests (GTT) performed after overnights fasting administering glucose 1g/kg ip. Results: CS6253 1mg/mL incubated for 2 hours under standard conditions with 3mM glucose showed a 3-fold increase in insulin secretion compared to control, i.e. 232(32) vs. 79(7) ng/M cells, p<0.001. 3 H-glucose uptake by CS6253 peptide in L6-Glut4myc rat myoblasts increased insulin’s glucose uptake capacity from 3800 to 4619 DPM/well, p<0.001 . CS6253 alone had no effect on 3 H-glucose uptake compared to control. DIO mice were treated with CS6253 30mg/kg sc alternate days or PBS control for 16 weeks. GTTs were performed after 2, 6 and 15 weeks treatment showing 39%, 45% and 57% reductions in the glucose-AUC compared to control, respectively, p<0.01 for all time points. Insulin response to GTT after 5 weeks treatment showed a strong improvement of the insulin-curve by CS6253, p<0.05 vs. placebo. CS6253 treated DIO mice showed a non-significant body weight decrease and a 17% reduction in liver weight, 5.28g vs. 4.36g, p<0.01. Discussion: CS6253 shows potent, sustained and increased anti-diabetic actions over the 16 weeks treatment period in DIO mice. In vivo and in vitro studies show improved pancreas β-cell function with increased glucose-mediated insulin secretion and also insulin sensitizing properties. CS6253’s combined anti-diabetic and anti-atherosclerosis properties suggest utility in the treatment of CVD and T2DM.
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Background: Lipoprotein-associated phospholipase A2 (Lp-PLA2) might play a role in the formation of vulnerable atherosclerotic plaques. Its plasma distribution and mass in subjects with acute coronary syndrome (ACS) has yet to be... more
Background: Lipoprotein-associated phospholipase A2 (Lp-PLA2) might play a role in the formation of vulnerable atherosclerotic plaques. Its plasma distribution and mass in subjects with acute coronary syndrome (ACS) has yet to be characterized. Methods: We compared plasma levels of Lp-PLA2 in 24 patients within 48 hours of an ACS (acute) and 12 weeks after (recovery), in 26 patients with stable coronary artery disease and in 10 normal healthy control subjects. Lp-PLA2 mass was determined using enzyme-linked immunosorbent assay. Results: The ACS patients (mean age 57 � 8.7 years) had highsensitivity C-reactive protein (hsCRP) levels of 30.46 � 57.57 mg/L (ACSacute)vs1.69 � 1.32mg/L(ACSrecovery).Plasma Lp-PLA2levels were significantly higher in ACS acute subjects than in ACS recovery subjects (143.13 � 60.88 ng/mL vs 88.74 � 39.12 ng/mL; P < 0.0001). Interestingly, stable coronary artery disease patients had higher Lp-PLA2 levels than ACS recovery patients (121.72 � 31.11 ng/ mL vs...
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HDL is thought to exert its atheroprotective role by promoting cholesterol efflux from lipid-laden macrophages. Cholesterol efflux capacity (CEC) has been shown to be inversely associated with carotid intima-media thickness and presence... more
HDL is thought to exert its atheroprotective role by promoting cholesterol efflux from lipid-laden macrophages. Cholesterol efflux capacity (CEC) has been shown to be inversely associated with carotid intima-media thickness and presence of coronary artery disease. We assessed the hypothesis that CEC is associated with severity of carotid atherosclerosis and with cerebrovascular symptomatology. Symptomatic (n=114) and asymptomatic (n=41) patients with carotid stenosis were recruited from Vascular Surgery at the Royal Victoria and Jewish General hospitals, Montreal, Canada. Carotid Doppler ultrasound was performed and stenosis (50-79%, 80-99%) was graded according to velocities. Detailed information on symptomatology obtained. A blood sample was collected on the day of the ultrasound; HDL was obtained by polyethylene glycol precipitation after depletion of apoB-containing lipoproteins. CEC was determined by incubating HDL in cAMP-stimulated J774 mouse peritoneal macrophages for 6 hours. Specific cholesterol efflux was obtained by subtracting total efflux from efflux in non-cAMP stimulated cells. Differences in CEC were assessed using linear regression according to 1) stenosis, 2) symotomatology and, 3) timing of symptomatology. Compared to patients with 50-79% stenosis (n=31), patients with 80-99% stenosis (n=124) had significantly decreased CEC (beta=-2.23, P=0.04) after adjustment for age, sex, apoAI, and systolic BP. CEC was not significantly different between symptomatic or asymptomatic patients. However, in symptomatic patients CEC increased with increasing time since cerebrovascular event. Specifically, compared to 0-30 days (n=72), CEC was non-significantly increased 31-90 days since event (n=31, beta=1.64, P=NS), while increased significantly ≥ 90 days since event (n=11, beta=4.48, P=0.01), after adjustment as described above. These results suggest that CEC is inversely associated with severity of carotid stenosis and that CEC increases with increasing time since symptomatic event. This may be related to remodeling of HDL during the acute phase reaction after a recent ischemic event.
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Anti-diabetic activities of HDL apolipoprotein(apo)s have been described, complementing ability to reduce atherosclerosis. These effects have been attributed, in part, to apos stimulating cholesterol efflux from cells via ABCA1. This... more
Anti-diabetic activities of HDL apolipoprotein(apo)s have been described, complementing ability to reduce atherosclerosis. These effects have been attributed, in part, to apos stimulating cholesterol efflux from cells via ABCA1. This suggests apo mimetic peptides that promote ABCA1 cholesterol efflux may be useful to combat diabetes and its cardiovascular complications. Two such peptides (CS6253 and T6991-2) with optimized safety features (NOAEL = 500 mg/kg) and little TG elevating effects have been designed by us through structure-activity studies of a prototypic ABCA1 ligand peptide, ATI-5261, derived from the C-terminal (CT) domain of apoE. Glucose lowering and insulin sensitizing effects of these new peptides were presently evaluated in mouse models of obesity and diabetes. Peptides CS6253 and T6991-2 stimulated cholesterol efflux from macrophages via ABCA1 with high potency similar to the native apoE CT domain (Km= 0.33±0.14, 0.24±02, 0.21±0.02 μM). Administration of CS6253 at a dose of 30 mg/kg (SC) on alternate days for 6 weeks reduced atherosclerosis by 32% in apoE deficient mice fed high-fat, Western diet for 14 weeks (15±2 vs. 22±4% plaque lesions, CS6253 vs. control, p&amp;amp;lt;0.01). T6991-2 administered (SC) at a dose of 10 mg/kg for 6 weeks in chow-fed ob/ob mice showed little effect on steady-state plasma glucose levels vs. controls (126±22 vs. 135±11 mg/dl, respectively); however, the levels of glucose were greatly attenuated with peptide treatment vs. controls in response to GTT (1.8±0.5 vs. 2.8±0.4 fold increases in plasma glucose at 60 min, respectively, p&amp;amp;lt;0.01). Treatment of C57BL/6J mice fed high-fat diet (HFD) with T6991-2 (6 weeks, 30 mg/kg) also enhanced insulin sensitivity by 2.2±0.7 fold vs. controls (55±17 vs. 25±5% reduction in basal glucose levels, respectively, at 15 minutes post insulin, 0.75 Units/kg, p&amp;amp;lt;0.01). The favorable anti-diabetic effects of T6991-2 were not due to changes in total body weight or β-cell function (i.e. unchanged plasma C-peptide levels). Our data indicate that single amphipathic α-helix peptides derived from apoE CT domain are sufficient to confer potent cellular cholesterol efflux and anti-diabetic activities, with therapeutic potential for diabetes and cardiovascular disease.
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It has been suggested that initial apoA-I binding to ABCA1 is coupled to the activation of signal transduction pathways, allowing excess cholesterol removal from tissues. However, the role of the h...
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Introduction: Adiponectin (APN) is an anti-inflammatory and anti-atherogenic adipokine that is strongly correlated with circulating HDL levels. However, its role in macrophage lipid metabolism, a crucial process in atherogenesis, remains... more
Introduction: Adiponectin (APN) is an anti-inflammatory and anti-atherogenic adipokine that is strongly correlated with circulating HDL levels. However, its role in macrophage lipid metabolism, a crucial process in atherogenesis, remains poorly investigated. We examined the effect of APN on cholesterol efflux from human THP-1 macrophages, elucidated its kinetics, and investigated its role in HDL biogenesis. Methods: APN dose-dependent (0.1 to 60 μM) and time-dependent (0.5 to 24 hours) cholesterol efflux studies were performed in 3 [H]-cholesterol labeled human THP-1 macrophages in the presence of apoA-I. Following efflux studies, the HDL fractions within media were concentrated (10kDa cut-off filter) and subjected to analytical FPLC and 2D-PAGGE technique to reveal HDL species. Results: APN stimulated ABCA1-mediated cholesterol efflux in a dose-dependent and time-dependent manner. Kinetics analysis revealed that increased molar doses of APN and apoA-I had similar Km efficiency of cholesterol efflux but greater velocity ( Km =3.24±0.71 μM, Vmax =4.90±0.07 efflux/6h) when compared to apoA-I alone ( Km =3.33±0.57 μM, Vmax =3.83±0.24 efflux/6h). Importantly, once APN was tested against a fixed dose of apoA-I (10 μg/mL), it promoted cholesterol efflux with Km = 0.17±0.06 μM. This was associated with a 75.7% decrease in intracellular free cholesterol in THP-1 cells in the presence of APN and apoA-I when compared to apoA-I alone (P&lt;0.01). APN alone had no effect on the level of residual efflux (reached a level of 1%). The FPLC cholesterol profiles demonstrated that in the presence of APN and apoA-I there was increased lipidated nascent HDL (nHDL) during the process of cholesterol efflux, compared to apoA-I alone. This was associated with increased size of nHDL-apoA-1 pre-β and α species via 2D-PAGGE analyses. By immunoblotting for apoA-I and APN, APN oligomers exhibited a molecular weight range of 9 to 20 nm, appearing within the size range of nHDL-apoA-I. Conclusion: In addition to promoting macrophage cholesterol efflux in vitro , APN can modulate HDL-apoA-I biogenesis, by increasing the generation of nHDL particles. These findings suggest that APN may be of potential therapeutic value in the modulation of HDL’s protective role in atherosclerosis.
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Lipoprotein associated phospholipase A2 (Lp-PLA2) may play a role in the formation of vulnerable atherosclerotic plaques and plaque rupture. Its plasma distribution and mass in subjects with acute coronary syndromes (ACS) are not... more
Lipoprotein associated phospholipase A2 (Lp-PLA2) may play a role in the formation of vulnerable atherosclerotic plaques and plaque rupture. Its plasma distribution and mass in subjects with acute coronary syndromes (ACS) are not characterized. The objective of this study was to examine plasma levels and distribution of Lp-PLA2 in patient with ACS. We compared plasma levels of LP-PLA2 in 23 patients within 48 hours of presentation of an ACS (visit 1) and 12 weeks after (visit 2), in 24 patients with chronic, stable coronary artery disease (sCAD) and in normal healthy controls. The distribution of Lp-PLA2 was determined by ultracentrifugation (UTC), high-performance liquid chromatography (HPLC), and polyethylene glycol (PEG) precipitation of plasma lipoproteins and immunoblotting analysis. Lp-PLA2 mass was determined by ELISA The ACS patients (18 males/5 females, mean age 57±9.2) had hsCRP levels of 32.6±60.4 mg/L (ACS visit1) vs. 1.9±1.3 mg/L (ACS visit2), reflecting systemic inflammation. Stable CAD hsCRP 1.3±1.3 mg/L and controls 0.6±0.2 mg/L did not differ significantly. HDL cholesterol levels were 1.02±0.24 mmol/L for ACS visit 1, 1.00±0.3 mmol/L for ACS visit2, and 1.11±0.29 mmol/L for stable CAD. Plasma Lp-PLA2 levels were significantly higher in ACS visit1 subjects than in the ACS visit2 (144.3±60.6 vs. 89.5±40.0 ng/mL, p&amp;lt;0.0001). Interestingly, sCAD patients had slightly higher Lp-PLA2 levels that ACS visit 2 (p=0.003). The distribution of Lp-PLA2 differed according to the technique used. We found that only approximately 45% of Lp-PLA2 mass remained in the lipoprotein fraction (d&amp;lt;1.21 g/L) after UTC, with the majority (43%) in the LDL fraction and only &amp;lt;3% in the HDL fraction. The remainder (55% was found in the d&amp;gt;1.21 g/L, suggesting that Lp-PLA2 is only loosely bound to lipoproteins, and the majority resides in LDL. Here, we show that subjects with an ACS have markedly increased Lp-PLA2 levels acutely and that these levels fall within 12 weeks. Surprisingly, Lp-PLA2 is only loosely bound to lipoproteins and may be displaced in inflammatory conditions. The increase in Lp-PLA2 in ACS may contribute to the generation of oxidized fatty acyls and lysophopsphlipids and potentially compound the local inflammatory reaction.
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Purpose of review The primary cardioprotective function of high-density lipoprotein (HDL) is to remove excess cellular free cholesterol (FC) from peripheral tissues and deliver it to the liver. Here, we summarize recent research that... more
Purpose of review The primary cardioprotective function of high-density lipoprotein (HDL) is to remove excess cellular free cholesterol (FC) from peripheral tissues and deliver it to the liver. Here, we summarize recent research that examines apolipoprotein A-I (apoA-I) lipidation models by adenosine triphosphate binding cassette transporter A1 (ABCA1) and discuss its relevance in atherosclerotic cardiovascular disease (ASCVD). Recent findings The first step in HDL formation involves the interaction between apoA-I and ABCA1, where ABCA1 mediates the removal of FC and phospholipids from lipid-laden macrophages to form discoidal nascent HDL (nHDL). However, there are currently no clear-cut systematic models that characterize HDL formation. A number of recent studies have investigated the importance of apoA-I C- and N-terminal domains required for optimal cholesterol efflux and nHDL production. Furthermore, functional ABCA1 is required for direct or indirect binding to apoA-I where ABCA1 dimer-monomer interconversion facilitates apoA-I lipidation from plasma membrane microdomains. Microparticles are also another lipid source for apoA-I solubilization into nHDL. Summary ApoA-I and ABCA1 are key factors in macrophage-mediated cholesterol efflux and nHDL production. Understanding of the key steps in HDL formation may unlock the therapeutic potential of HDL and improve clinical management of ASCVD.
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Cholesterol efflux is the initial step in the reverse cholesterol transport pathway by which excess cholesterol in peripheral cells is exported and subsequently packaged into high-density lipoprotein (HDL) particles. Adiponectin is the... more
Cholesterol efflux is the initial step in the reverse cholesterol transport pathway by which excess cholesterol in peripheral cells is exported and subsequently packaged into high-density lipoprotein (HDL) particles. Adiponectin is the most abundantly secreted adipokine that possesses anti-inflammatory and vasculoprotective properties via interaction with transmembrane receptors, AdipoR1 and AdipoR2. Evidence suggests that low levels of adiponectin may be a useful marker for atherosclerotic disease. A proposed anti-atherogenic mechanism of adiponectin involves its ability to promote cholesterol efflux. We performed a systematic review of the role of adiponectin in cholesterol efflux and HDL biogenesis, and of the proteins and receptors believed to be implicated in this process. Nineteen eligible studies (7 clinical, 11 fundamental, 1 clinical + fundamental) were identified through Ovid Medline, Ovid Embase, and Pubmed, that support the notion that adiponectin plays a key role in pro...