SNPS LOCATED IN ABCA1, CETP AND APOA5/A4/C3/A1 ARE ASSOCIATED WITH PLASMA CHOLESTEROL EFFLUX

Treatment of cholesterol-fed male hamsters kept on a diet of purina chow with beta beta'-methyl-substituted hexadecanedioic acid (MEDICA 16) resulted in a progressive hypocholesterolaemic effect, amounting to a 50% decrease in the cholesterol content of all plasma lipoproteins. The decrease in plasma cholesterol could be accounted for by activation of plasma-cholesterol efflux through the liver into the bile mediated by MEDICA 16-induced (a) increase of the number of liver LDL receptors, (b) activation of liver neutral cholesteryl ester hydrolase with a concomitant inhibition of liver acyl-CoA cholesterol acyltransferase, resulting in shifting of the liver cholesteryl ester/free-cholesterol cycle in the direction of free cholesterol, and (c) activation of cholesterol efflux from the liver into the bile. The increase in bile cholesterol output was accompanied by an increase in bile phospholipids but not in bile acids. In contrast with rats, MEDICA 16-treatment of male hamsters did not result in a hypotriacylglycerolaemic effect, inhibition of lipogenesis, nor in a substantial decrease in plasma apolipoprotein C-III content.

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EARLY TIME RESTRICTED FEEDING IMPROVES HIGH DENSITY LIPOPROTEIN FUNCTION IN GERIATRIC MONKEYS

Innovation in Aging ◽

10.1093/geroni/igz038.389 ◽

2019 ◽

Vol 3 (Supplement_1) ◽

pp. S104-S104

Author(s):

Kylie Kavanagh ◽

Alexander Bashore ◽

Matthew Davis ◽

Chrissy Sherrill ◽

John Parks

Keyword(s):

High Density Lipoprotein ◽

Cholesterol Efflux ◽

Plasma Cholesterol ◽

Biological Effects ◽

Density Lipoprotein ◽

Early Time ◽

High Density ◽

Vervet Monkeys ◽

Restricted Feeding ◽

Hdl Function

Abstract Ageing conveys the greatest risk for cardiovascular disease (CVD) development, which is the dominant cause of mortality in developed nations. High density lipoprotein (HDL) particles mediate reverse cholesterol transport, are anti-inflammatory and their function predicts CVD. We observed lower plasma cholesterol efflux capacity in geriatric vervet monkeys (p=0.03) when consuming either healthy or Western diets. Adult (n=16) and geriatric (n=19) monkeys were stratified into groups fed Western diet on ad libitum (Ad Lib) or early time restricted feeding (eTFR) schedules. eTRF supplied excess food only between 6am to 2pm. Housing, seasonality and fasting conditions for data and sample collections were equivalent. After 6 months, cholesterol efflux to HDL was greater in eTRF monkeys (p=0.01), with no age by group interaction. Efflux media and plasma was chromatographically separated to confirm labelled cholesterol, and enzymatically measured cholesterol, respectively, was affiliated with HDL particles. eTRF monkeys had higher total plasma cholesterol levels (p=0.03) which was due to greater cholesterol amounts associated with only HDL, and resulted in HDL particles that were larger. eTRF resulted in robustly better HDL function such that measures from geriatric individuals were comparable to younger adults. Additionally, no differences in adiposity was observed in eTRF monkeys. Few interventions are known to raise HDL levels, and more importantly, are confirmed to improve HDL function. Our study is to date the largest, longest, controlled eTRF evaluation in primates and we show that positive biological effects are observable in HDL isolated from both adult and geriatric individuals independently of weight change.

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Abstract 5482: Reduction of Established Atherosclerosis in Hypercholesterolemic Mouse Models by ATI-5261: a Novel α-helix Peptide that Stimulates ABCA1 Cholesterol Efflux with High Efficiency

Circulation ◽

10.1161/circ.118.suppl_18.s_558-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

John K Bielicki ◽

Haiyan Zhang ◽

Rakia Azhar ◽

Jan Johansson ◽

Salman Azhar

Keyword(s):

Mouse Models ◽

Lipid Content ◽

Cholesterol Efflux ◽

High Efficiency ◽

Foam Cell ◽

Plasma Cholesterol ◽

Cell Phenotype ◽

Lesion Area ◽

Α Helix ◽

The Impact

Apolipoprotein(apo)s of HDL stimulate cholesterol efflux via the ATP-binding cassette transporter A1 (ABCA1), generating HDL and reversing the macrophage foam-cell phenotype. Despite these anti-atherogenic roles, the impact of specifically promoting ABCA1 cholesterol efflux on atherosclerosis development is largely unknown. Progress in this area has been hindered by a lack of synthetic agonists and/or apo mimetics optimized to mediate ABCA1 cholesterol efflux. The latter can be attributed, in part, to the fact that long segments of α-helical structure constituting the C-terminal (CT) domains of apoA-I and E are required to mediate ABCA1 cholesterol efflux efficiently. To begin to address these issues, we compressed the activity determinants of these CT helices into a single α-helix, creating a peptide (ATI-5261) that stimulates ABCA1 efflux with apo molar efficiency. Treatment of LDLr−/− mice made atherosclerotic by a high-fat western-diet (13 weeks) with ATI-5261 (30 mg/kg) ip on alternate days for 6 weeks reduced atherosclerosis by ~30%, as judged by lesion-area (Sudan IV) covering the aorta (7.9±2 vs.11.3±2.5% control, p=0.011), and the lipid-content (oil-red O) of aortic-sinus plaque (25±5.8 vs. 33±4.9% control, p=0.034). In similarly designed studies, ATI-5261 reduced atherosclerosis in apoE−/− mice by ~45% (lesion-area = 14±8 vs. 25±9% control, p=0.011; plaque lipid-content = 22±6 vs. 41±7% control, p=0.001). The minimum effective dose of ATI-5261 was 3 mg/kg in apoE−/− mice, consistent with the potent cholesterol efflux activity of the peptide. In both mouse models, ATI-5261 reduced atherosclerosis to the same extent as ATI-5261:POPC complexes (~7 nm). Single ip injection of ATI-5261 increased reverse cholesterol transport from macrophage foam-cells to feces for up to 48 h. To our knowledge, ATI-5261 is the first synthetic α-helix able to reduce atherosclerosis in mice having substantial plaque-lipid accumulation. This did not require peptide formulation with phospholipids and was achieved in the presence of vastly different lipoprotein profiles and plasma cholesterol concentrations. The data suggest that accelerating ABCA1 lipid-efflux may represent a viable approach to reduce atherosclerosis and stabilize vulnerable plaque.

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Abstract 334: The LXRβ Selective Agonist, VTP-38443, Significantly Decreases Plaque Cholesterol Ester Content and Inflammation in a Murine Model of Accelerated Atherosclerosis

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.35.suppl_1.334 ◽

2015 ◽

Vol 35 (suppl_1) ◽

Author(s):

Gerard M McGeehan ◽

Deepak S Lala ◽

Yi Zhao ◽

Paul B Noto ◽

Linghang Zhuang ◽

...

Keyword(s):

Carotid Artery ◽

Cholesterol Ester ◽

Cholesterol Efflux ◽

Plasma Cholesterol ◽

Vascular Inflammation ◽

Western Diet ◽

Accelerated Atherosclerosis ◽

Ester Content ◽

Plaque Inflammation ◽

Dose Dependent

The ligand-activated transcription factors LXRα and LXRβ are important regulators of cholesterol metabolism and inflammation. Activation of LXR was previously shown to inhibit atherosclerosis in animal models through activation of reverse cholesterol transport (RCT) and suppression of vascular inflammation. VTP-38443 is a potent selective and orally bioavailable modulator of LXRβ that is being pursued for the prevention of subsequent vascular events following an acute coronary syndrome (ACS) episode. VTP-38443 is a potent binder (Ki=12 nM) and activator (EC50=17 nM) of LXRβ. It is ~20x selective for LXRβ versus LXRβ in both binding and activation. In primary human cells, it induces the expression of the cholesterol efflux pumps ABCA1 and ABCG1, markers of RCT, and promotes cholesterol efflux from human fibroblasts at low concentrations (EC50 = 14 nM). Orally dosed VTP-38443 demonstrates robust induction of ABCA1 and ABCG1 in mice (ED50 < 0.3 mg/kg) and primates (ED50 < 0.1 mg/kg). Based on this robust activity, VTP-38443 was tested in the apoE -/- carotid artery ligated mouse model, an accelerated atherosclerosis model. ApoE-/- mice (9 week) were fed a Western diet for 2 weeks at which point the left common carotid artery was ligated. Mice remained on the Western diet for 2 weeks post-surgery and were dosed BID with VTP-38443 (0.05, 0.2 and 1 mg/kg/dose) or a non-selective LXR agonist, TO90137 (20 mg/kg/day) during this time. Plasma cholesterol and TGs were measured as were cholesterol esters and FDG-6-phosphate, a biomarker of plaque inflammation, in the carotid plaques. VTP-38443 gave a dose-dependent reduction in plasma cholesterol (35% at 1 mg/kg) and a modest dose-dependent increase in plasma TGs ranging from 5% to 45% of the TG increase seen with TO90137. Plaque analysis showed a highly significant decrease in carotid cholesterol ester content at all doses, achieving >90% reduction at the highest dose. In addition, there was a significant reduction (~40-50%) in FDG-6 phosphate at all doses of VTP-38443, indicating a decrease in vascular inflammation. These data indicate that LXRβ activation may decrease plaque cholesterol content and reduce plaque inflammation in ACS.

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Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood

The Journal of Lipid Research ◽

10.1194/jlr.ra120000635 ◽

2020 ◽

Vol 61 (12) ◽

pp. 1577-1588

Author(s):

Ryunosuke Ohkawa ◽

Hann Low ◽

Nigora Mukhamedova ◽

Ying Fu ◽

Shao-Jui Lai ◽

...

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Cholesterol Efflux ◽

Cholesterol Metabolism ◽

Plasma Cholesterol ◽

Translocator Protein ◽

Plasma Lipoproteins ◽

Cholesterol Transport ◽

Autologous Plasma

Lipoproteins play a key role in transport of cholesterol to and from tissues. Recent studies have also demonstrated that red blood cells (RBCs), which carry large quantities of free cholesterol in their membrane, play an important role in reverse cholesterol transport. However, the exact role of RBCs in systemic cholesterol metabolism is poorly understood. RBCs were incubated with autologous plasma or isolated lipoproteins resulting in a significant net amount of cholesterol moved from RBCs to HDL, while cholesterol from LDL moved in the opposite direction. Furthermore, the bi-directional cholesterol transport between RBCs and plasma lipoproteins was saturable and temperature-, energy-, and time-dependent, consistent with an active process. We did not find LDLR, ABCG1, or scavenger receptor class B type 1 in RBCs but found a substantial amount of ABCA1 mRNA and protein. However, specific cholesterol efflux from RBCs to isolated apoA-I was negligible, and ABCA1 silencing with siRNA or inhibition with vanadate and Probucol did not inhibit the efflux to apoA-I, HDL, or plasma. Cholesterol efflux from and cholesterol uptake by RBCs from Abca1+/+ and Abca1−/− mice were similar, arguing against the role of ABCA1 in cholesterol flux between RBCs and lipoproteins. Bioinformatics analysis identified ABCA7, ABCG5, lipoprotein lipase, and mitochondrial translocator protein as possible candidates that may mediate the cholesterol flux. Together, these results suggest that RBCs actively participate in cholesterol transport in the blood, but the role of cholesterol transporters in RBCs remains uncertain.

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Abstract 319: Design of Novel Chimeras to Provide Insight Into Structure/Function Activity of Apolipoprotein E3 and Apolipoprotein AI

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.35.suppl_1.319 ◽

2015 ◽

Vol 35 (suppl_1) ◽

Author(s):

Mark Lek ◽

Nnejiuwa Ibe ◽

Wendy Beck ◽

John K Bielicki ◽

Paul M Weers ◽

...

Keyword(s):

Rate Constant ◽

Cholesterol Efflux ◽

Plasma Cholesterol ◽

Dominant Role ◽

Density Lipoprotein ◽

Lipid Binding ◽

Plasma Lipoproteins ◽

Peripheral Tissues ◽

Terminal Domain ◽

Cholesterol Levels

Apolipoprotein (apo) E3 and apoAI are exchangeable apolipoproteins that play a dominant role in regulating plasma cholesterol levels and are considered anti-atherogenic. ApoE3 (299 residues, ~34 kDa) serves as a ligand for the low density lipoprotein receptor (LDLr) family of proteins that mediate cellular uptake and clearance of plasma lipoproteins. The ability of apoE3 to function as a ligand for LDLr resides in the N-terminal domain (NT) of apoE3. ApoAI (243 residues, ~28 kDa) lowers cholesterol levels through its ability to promote cholesterol efflux from peripheral tissues such as macrophages, forming HDL, which transports cholesterol back to the liver. Residues located in the C-terminal domain (CT) of apoAI mediate this function of promoting cholesterol efflux. The objective of this study is to generate chimeric apolipoproteins composed of apoE3 and apoAI to better understand the role of the C-terminal tail of the parent proteins. Two chimeras were generated by “domain swapping”: apoE3-NT/apoAI-CT and apoAI-NT/apoE-CT. They were overexpressed in E. coli, isolated and purified. Western blot analysis revealed the presence of epitopes from both parent proteins. Circular dichroism spectroscopy revealed that the α-helical content of apoE3-NT/apoAI-CT and apoAI-NT/E-CT was 43 and 54 %, respectively, which is comparable to that of the parent proteins. Chemical denaturation was used to probe for changes in protein stability. Addition of CT of apoE3 to NT of apoAI conferred more stability to apoAI, while addition of CT of apoAI to NT of apoE3 had no significant effect on apoE3. The rate of apolipoprotein-induced conversion of DMPC vesicles to discoidal structures was followed to assess their lipid binding capability. ApoE3-NT/AI-CT displayed a rate constant that was ~10x higher compared to apoE3, while apoAI-NT/apoE-CT showed a rate constant similar to that of apoAI. Whereas apoE3-NT/apoAI-CT elicits the ability to bind to the LDLr, apoAI-NT/apoE-CT did not. Lastly, both chimeras promote ABCA1-mediated cholesterol efflux from J774 macrophages, with the efflux capability being 2-fold greater for apoAI-NT/apoE-CT. These results show that CT of apoAI can promote lipid binding of apoE3, while CT of apoE3 can improve cholesterol efflux ability of apoAI.

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