Abstract 1728: The Defect in HDL Function and Reverse Cholesterol Transport Found in Diabetic Mice with the Haptoglobin 2–2 Genotype Can Be Corrected with High Dose Antioxidant Therapy

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Rabea O Asleh ◽  
Rachel Miller-Lotan ◽  
Zaid Abassi ◽  
Andrew P Levy
Keyword(s):  
Half Life ◽  
Reverse Cholesterol Transport ◽  
Fold Increase ◽  
Oxidative Modification ◽  
Antioxidant Therapy ◽  
Cholesterol Transport ◽  
High Dose ◽  
List Type ◽  
Free Hemoglobin ◽  
Hdl Function

Background. The primary function of the haptoglobin (Hp) protein is to clear free hemoglobin (Hb). Two common alleles exist at the Hp locus (1 and 2). We recently demonstrated that reverse cholesterol transport is impaired in individuals with Diabetes Mellitus (DM) and the Hp 2–2 genotype which may explain the increased incidence of cardiovascular disease in this population. We sought to test the hypothesis that clearance of the Hp 2-Hb complex is slower in DM allowing more complex to bind to HDL thereby resulting in increased oxidative modification of HDL and inhibition of reverse cholesterol transport and determine if antioxidant therapy could restore normal HDL function in Hp 2–2 DM mice. Methods and Results. Injection of 125 I-labeled Hp 1 or Hp 2-Hb complexes into non-DM mice demonstrated that the half-life of the Hp 2-Hb complex was 2–3 fold longer than the Hp 1-Hb complex (57.8 ± 2.8 vs. 20.4 ± 1.7 min). Moreover, in DM the half-life of the Hp 2-Hb complex was doubled while the half-life of the Hp 1-Hb complex was unchanged (103 ± 3.9 vs. 18.6 ± 1.8 min). Coimmunoprecipitation studies demonstrated that over 25% of the injected Hp 2-Hb complex was associated with HDL in DM mice representing a greater than 10 fold increase compared to Hp 1-Hb complex in non-DM mice. Coimmunoprecipitation studies in Hp 0 (knockout) mice demonstrated that the Hp protein was absolutely necessary for the interaction of Hb with HDL. Reverse cholesterol transport was impaired by DM in Hp 2 mice but this impairment was prevented by high dose antioxidant supplementation to these mice. Conclusions. These data may explain why the Hp 2 genotype promotes less efficient reverse cholesterol transport in DM and suggests that strategies targeted to decrease oxidation of HDL by the Hp 2-Hb complex may improve HDL function.

scholarly journals Human ApoA-I Overexpression Enhances Macrophage-Specific Reverse Cholesterol Transport but Fails to Prevent Inherited Diabesity in Mice

2019 ◽  
Vol 20 (3) ◽  
pp. 655 ◽  
Author(s):  
Karen Méndez-Lara ◽  
Núria Farré ◽  
David Santos ◽  
Andrea Rivas-Urbina ◽  
Jari Metso ◽  
...  
Keyword(s):  
Weight Gain ◽  
Fatty Liver ◽  
Reverse Cholesterol Transport ◽  
Caloric Intake ◽  
Density Lipoprotein ◽  
Ldl Oxidation ◽  
Cholesterol Transport ◽  
Metabolic Complications ◽  
Hdl Function

Human apolipoprotein A-I (hApoA-I) overexpression improves high-density lipoprotein (HDL) function and the metabolic complications of obesity. We used a mouse model of diabesity, the db/db mouse, to examine the effects of hApoA-I on the two main functional properties of HDL, i.e., macrophage-specific reverse cholesterol transport (m-RCT) in vivo and the antioxidant potential, as well as the phenotypic features of obesity. HApoA-I transgenic (hA-I) mice were bred with nonobese control (db/+) mice to generate hApoA-I-overexpressing db/+ offspring, which were subsequently bred to obtain hA-I-db/db mice. Overexpression of hApoA-I significantly increased weight gain and the incidence of fatty liver in db/db mice. Weight gain was mainly explained by the increased caloric intake of hA-I-db/db mice (>1.2-fold). Overexpression of hApoA-I also produced a mixed type of dyslipidemia in db/db mice. Despite these deleterious effects, the overexpression of hApoA-I partially restored m-RCT in db/db mice to levels similar to nonobese control mice. Moreover, HDL from hA-I-db/db mice also enhanced the protection against low-density lipoprotein (LDL) oxidation compared with HDL from db/db mice. In conclusion, overexpression of hApoA-I in db/db mice enhanced two main anti-atherogenic HDL properties while exacerbating weight gain and the fatty liver phenotype. These adverse metabolic side-effects were also observed in obese mice subjected to long-term HDL-based therapies in independent studies and might raise concerns regarding the use of hApoA-I-mediated therapy in obese humans.

Dysfunctional HDL as a Therapeutic Target for Atherosclerosis Prevention

2019 ◽  
Vol 26 (9) ◽  
pp. 1610-1630 ◽  
Author(s):  
Alice Ossoli ◽  
Chiara Pavanello ◽  
Eleonora Giorgio ◽  
Laura Calabresi ◽  
Monica Gomaraschi
Keyword(s):  
Reverse Cholesterol Transport ◽  
High Density Lipoproteins ◽  
Cholesterol Transport ◽  
Hdl Function ◽  
Investigational Drugs ◽  
Hdl Dysfunction ◽  
Atherosclerosis Prevention ◽  
Endothelial Homeostasis ◽  
Dysfunctional Hdl

Hypercholesterolemia is one of the main risk factors for the development of atherosclerosis. Among the various lipoprotein classes, however, high density lipoproteins (HDL) are inversely associated with the incidence of atherosclerosis, since they are able to exert a series of atheroprotective functions. The central role of HDL within the reverse cholesterol transport, their antioxidant and anti-inflammatory properties and their ability to preserve endothelial homeostasis are likely responsible for HDL-mediated atheroprotection. However, drugs that effectively raise HDL-C failed to result in a decreased incidence of cardiovascular event, suggesting that plasma levels of HDL-C and HDL function are not always related. Several evidences are showing that different pathologic conditions, especially those associated with an inflammatory response, can cause dramatic alterations of HDL protein and lipid cargo resulting in HDL dysfunction. Established and investigational drugs designed to affect lipid metabolism and to increase HDL-C are only partly effective in correcting HDL dysfunction.

Abstract 1182: Inflammation Impairs Reverse Cholesterol Transport in vivo

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Fiona C McGillicuddy ◽  
Christine C Hinkle ◽  
Michelle R Joshi ◽  
Elise H Chiquoine ◽  
Jeffrey T Billheimer ◽  
...  
Keyword(s):  
Reverse Cholesterol Transport ◽  
Ex Vivo ◽  
Hdl Cholesterol ◽  
Fold Increase ◽  
Cholesterol Transport ◽  
Transport Pathway ◽  
Hepatic Expression ◽  
Cholesterol Levels ◽  
Reverse Cholesterol Transport Pathway

Introduction : Activation of innate immune responses have been postulated to impair reverse cholesterol transport (RCT). In this proof of concept study we provide the first in vivo functional evidence to support this hypothesis by tracking macrophage 3 H-cholesterol into plasma, liver, bile and feces in C57BL/6 mice during endotoxemia. Methods: C57BL/6 mice were injected subcutaneously with lipopolysaccharide (LPS) (10mg/kg daily for 2 days) or saline prior to intraperitoneal (IP) administration of 3 H-cholesterol-loaded macrophages. 3 H-cholesterol levels in plasma, liver, spleen, bile and feces were measured over 48 h. Lipid profiles were analyzed, enzymatically, using a Cobas FARA analyzer. Plasma (5 %), isolated from control or LPS treated mice (without macrophage injection), was used as an acceptor in ex vivo cholesterol efflux studies from 3 H-cholesterol-loaded J774 macrophages. Results: In a pilot non-RCT study (n = 4), as previously reported, LPS significantly increased total and HDL cholesterol, phospholipid and triglyceride levels (2.05 ± 0.09, 2.41 ± 0.28, 1.98 ± 0.08 and 2.57 ± 0.33 fold increase respectively, p < 0.01). In RCT studies, despite increased HDL cholesterol, LPS significantly decreased 3 H-cholesterol plasma counts at 4 h (−20.4 ± 2.0 %, p < 0.001) and 24 h (−27.1 ± 3.4 %, p < 0.001), as well as 3 H-cholesterol in liver, bile and feces (22.9 ± 3.2, 41.9 ± 10.7, and 75.3 ± 4.1 % decrease, p < 0.05, p = 0.05 and p < 0.01 respectively) (n = 8 –12 per group). LPS decreased hepatic SRB1, ABCG1, ABCG5 and HL mRNA expression. Ex vivo efflux to plasma isolated from LPS treated mice was significantly impaired relative to control (77.5 ± 7.4 % of control, p < 0.05, n = 5). Conclusions: Sub-acute endotoxemia impaired RCT in mice, despite increased plasma HDL cholesterol levels. This coincided with reduced hepatic expression of the HDL receptor, SRB1, and the transporters responsible for cholesterol transport to bile, ABCG5/8. In addition, ex vivo studies suggest impaired HDL particle efflux function during endotoxemia. In summary, we demonstrate for the first time in vivo that inflammation impairs several components of the reverse cholesterol transport pathway.

Abstract P220: The Effect of Diet-Induced Weight Loss on HDL Functionality in Individuals with Metabolic Syndrome: Investigating Alteration of the Initial Step in Reverse Cholesterol Transport as a Function of Plasma Lipoprotein Composition

Circulation ◽  
2012 ◽  
Vol 125 (suppl_10) ◽  
Author(s):  
Madhuri M Vasudevan ◽  
Urban Tchoua ◽  
Baiba Gillard ◽  
Hu Yu Lin ◽  
Peter Jones ◽  
...  
Keyword(s):  
Metabolic Syndrome ◽  
Weight Loss ◽  
Reverse Cholesterol Transport ◽  
Cholesterol Efflux ◽  
Density Lipoprotein ◽  
Lipoprotein Cholesterol ◽  
Atherogenic Dyslipidemia ◽  
Cholesterol Transport ◽  
Hdl Function ◽  
Macrophage Cholesterol Efflux

The prevalence of metabolic syndrome (MetS) with obesity-linked diabetes continues to increase globally and is associated with atherogenic dyslipidemia characterized by high triglycerides (TG), small, dense low-density lipoprotein cholesterol (LDL-C), and low high-density lipoprotein cholesterol (HDL-C) levels. HDL orchestrates the reverse cholesterol transport (RCT) process, initiated by macrophage cholesterol efflux (MCE). The traditional hypothesis is that individuals with dyslipidemia have impaired RCT that leads to atherogenesis. However, a recent study showed that one metric of HDL function, macrophage cholesterol efflux (MCE) to diluted patient plasma, inversely correlated with atherosclerotic burden, independent of plasma HDL-C levels. Moreover, cholesterol efflux from ABCA1-upregulated macrophage cell lines to sera of diabetic hypertriglyceridemic subjects is enhanced compared to normolipidemic (NL) controls. The effect of weight loss on MCE in obese individuals with MetS is unknown. The purpose of this study is to evaluate MCE in obese individuals with MetS as a function of plasma dyslipidemia, and to determine the effect of weight loss on the RCT process. We measured the rate of MCE from human monocytic leukemia THP1 cells to plasma of NL controls (n=24) and obese MetS (n=24) patients before and after 4 to 6 weeks of very low calorie, diet-induced weight loss. Weight loss in the MetS patients was significant, averaged 21.3 lbs, with concurrent significant decreases in TG, apoB, TC, LDL-C and non-HDL-C. Measures of insulin resistance, systolic blood pressure and kidney function improved with weight loss. HDL-C was not significantly altered, but apoA-I decreased with weight loss. MCE to plasma of obese MetS patients was higher than MCE to control plasma ((7.44 + 1.36) % vs (6.39 + 1.23) %, p=0.0069). MCE to plasma of obese MetS patients significantly decreased after weight loss (6.23 + 1.69) %, comparable to control values. MCE was strongly correlated to apoB levels (r 2 = 0.13 - 0.38), consistent with apoB lipoprotein function as a cholesterol sink. This was confirmed by size exclusion chromatography analysis of the distribution of effluxed cholesterol among plasma lipoproteins in 1 control and 2 Mets patients. In conclusion, obese patients with MetS demonstrate increased MCE, a measure of HDL function, compared to NL controls, which significantly decreases in response to diet-induced weight loss, concurrent with a reduction in triglyceride and apoB levels. These results suggest that the high apoB lipoprotein levels in MetS pateints facilitate MCE, and may at least partially compensate for the low HDL-C to promote RCT in these patients.

Abstract 320: Procollagen C-Endopeptidase Enhancer Protein 2 Enhances SR-BI Mediated HDL Cholesterol Uptake and Reduces Atherosclerosis in Mice

2015 ◽  
Vol 35 (suppl_1) ◽  
Author(s):  
Ricquita D Pollard ◽  
Christopher N Blesso ◽  
Manal Zabalawi ◽  
Brian Fulp ◽  
Mark Gerelus ◽  
...  
Keyword(s):  
Reverse Cholesterol Transport ◽  
Disease Risk ◽  
Cardiovascular Disease Risk ◽  
Hdl Cholesterol ◽  
Cholesterol Transport ◽  
Elevated Concentration ◽  
Type I ◽  
Cholesterol Uptake ◽  
Hdl Function ◽  
Deficient Mice

Epidemiological studies have shown an inverse correlation between plasma high density lipoprotein (HDL) concentrations and cardiovascular disease risk. At variance with these observations, clinical trials that significantly raised plasma HDL-C levels did not have improved clinical outcomes, emphasizing the importance of understanding HDL function. Recently, a significant correlation has been reported between human procollagen c-endopeptidase enhancer protein 2 (PCPE2) single nucleotide polymorphisms and HDL. PCPE2, a 52 kDa glycoprotein found in the extracellular matrix enhances cleavage of C-terminal procollagen by bone morphogenetic protein 1. Mice lacking PCPE2 have elevated concentrations of enlarged plasma HDL, a phenomenon associated with defective cholesterol efflux. HDL synthesis depends on ABCA1-mediated lipid efflux to lipid-poor apoA-I balanced by cholesterol uptake through hepatic scavenger receptor class B type I (SR-BI). Our studies focused on investigating if the elevated concentration of enlarged plasma HDL in PCPE2 deficient mice was atheroprotective. PCPE2 deficient mice were crossed with LDLr -/- mice (SKO) giving LDLr -/- , PCPE2 -/- (DKO) mice that had elevated HDL levels compared to SKO mice. Despite elevated HDL levels, we found that DKO mice had significantly more lipid and CD68+ infiltration into the aortic root, similar to that reported for LDLr -/- , apoA-I -/- mice that lack plasma apoA-I/HDL. Furthermore, DKO mice showed reduced HDL apoA-I fractional clearance and reverse cholesterol transport rates compared to SKO mice suggesting PCPE2 plays a significant role in HDL remodeling and/or cholesterol uptake by the liver. To test the effect of PCPE2 on SR-BI function we incubated 3 H-cholesteryl ether ( 3 H-CE) enriched HDL from SKO and DKO mice with CHO cells overexpressing PCPE2. Compared to CHO control cells, overexpression of PCPE2 increased 3 H-CE HDL uptake that was independent of HDL particle origin. Western Blot analysis showed no difference in SR-BI expression between control and PCPE2 transfected cells, suggesting that PCPE2 enhanced SR-BI function and promoted HDL cholesterol ester uptake. We conclude that PCPE2 is atheroprotective and an essential component of the reverse cholesterol transport system.

Abstract 439: Niacin Does Not Accelerate Reverse Cholesterol Transport in Man

2013 ◽  
Vol 33 (suppl_1) ◽  
Author(s):  
Richard L Dunbar ◽  
Marina Cuchel ◽  
John S Millar ◽  
Amanda Baer ◽  
Rahul Poria ◽  
...  
Keyword(s):  
Reverse Cholesterol Transport ◽  
Ex Vivo ◽  
Hdl Cholesterol ◽  
Fecal Excretion ◽  
Cholesterol Transport ◽  
High Dose ◽  
Novel Method ◽  
Coronary Events ◽  
Post Therapy

Background HDL may be atheroprotective by accelerating reverse cholesterol transport (RCT). Niacin raises HDL cholesterol (HDL-c) and niacin monotherapy up to 3g/d prevented coronary events, possibly by accelerating RCT. However, up to 2g/d niacin did not prevent outcomes beyond aggressive LDL lowering including statins, arguing against RCT-mediated atheroprotection. We developed a novel method to assess macrophage-to-lipoprotein RCT in vivo. Preliminary studies in mice demonstrate that albumin-bound tritiated cholesterol (3H-Chol) is rapidly removed ( 95% in 30min) by resident macrophages. We monitored subsequent reappearance over 8d by macrophage-to-lipoprotein RCT as 3H-Chol rate of appearance (RA pre-post therapy, %3H-Chol injected/mol cholesterol/h) and tracer fecal excretion (%3H-Chol injected/g feces), and further analyzed RCT by multi-compartmental modeling. Results Niacin raised HDL-c 44% vs 17% on placebo (p=0.02) and dropped non HDL-c 40% (p<0.0001). Niacin and placebo did not differ by HDL 3H-Chol RA (placebo: 4.16-3.72, niacin: 3.24-2.61, p=0.8), total plasma 3H-Chol RA (placebo: 2.70-2.42, niacin: 2.35-2.14, p=0.9), macrophage-to-HDL transfer rate (placebo: 4.8-4.2, niacin: 5.1-4.7 fractional transfer/h, p=0.7), ex vivo cholesterol efflux capacity ratio (placebo: 0.73-0.82, niacin: 0.91-0.95, p=0.2), or tracer fecal excretion (placebo: 34.1-37.4, niacin: 21.2-28.0, p=0.6). Conclusion Despite potently raising HDL-c, high-dose niacin had no benefit on in vivo or ex vivo macrophage-to-lipoprotein RCT or fecal excretion in man, suggesting niacin’s atheroprotective potential lies elsewhere.

Abstract 29: Alpha-1-antitrypsin Protects High Density Lipoprotein From Functional Inactivation by Elastase

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Scott M Gordon ◽  
Denis Sviridov ◽  
Toshihiro Sakurai ◽  
Lita Freeman ◽  
Alan T Remaley
Keyword(s):  
Reverse Cholesterol Transport ◽  
Density Lipoprotein ◽  
High Density ◽  
Beta Particle ◽  
High Density Lipoproteins ◽  
Cholesterol Transport ◽  
Important Species ◽  
Hdl Function ◽  
Functional Inactivation ◽  
Alpha 1 Antitrypsin

High density lipoproteins (HDL) are complexes of lipid and protein with several known atheroprotective functions. These functions are driven by specific lipids and proteins contained on the HDL particle and include reverse cholesterol transport, suppression of inflammation, and modulation of endothelial function. These activities are most important within atherosclerotic plaque, a harsh environment where HDL interact with macrophage foam cells, activated neutrophils, and dysfunctional endothelial cells. Neutrophils and macrophages secrete proteases, such as elastase, which damage structural components and soluble proteins and propagate inflammatory signaling. It has been suggested that, in plaque, HDL become damaged and dysfunctional. We recently characterized a subspecies of HDL that carries the protein alpha-1-antitrypsin (A1AT), an abundant plasma serine protease inhibitor. In the current study, we tested the hypothesis that A1AT enriched HDL are protected from proteolytic damage and functional inactivation by elastase, the main protease inhibited by A1AT. Human HDL was isolated by ultracentrifugation and was enriched with A1AT by co-incubation and unbound A1AT was removed. Treatment of native HDL with elastase resulted in significant proteolytic degradation of both apoA-I and apoA-II, visualized by coomassie stained SDS-PAGE. Analysis of lipoprotein size by one dimensional native gel electrophoresis revealed that pre-beta HDL were completely degraded by elastase. Compared to native HDL, A1AT enriched HDL samples were protected from protein and pre-beta particle degradation by elastase. We next tested the effect of elastase treatment on HDL function. In native HDL, elastase had damaging effects on ABCA1 mediated cholesterol efflux (-32%; p<0.0001) and the ability to esterify free cholesterol (-14%; p<0.02). A1AT enriched HDL displayed no loss of functionality upon treatment with elastase. Both of these activities are required for HDL to perform what is thought to be its most important function, reverse cholesterol transport. In conclusion, the data presented indicate that HDL particles which contain A1AT may represent a functionally important species of HDL, which have an advantage in the protease-rich plaque environment.

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