Effects Of High-density Lipoprotein Research Articles

The effects of n-3 fatty acids intake on PON1 activity and fatty acid status in type 2 diabetic patients – A pilot study

Background: Paraoxonase–1 (PON1) enzymatic activity appears to play a role in maintaining the endothelial-atheroprotective effects of high density lipoprotein (HDL)-cholesterol and has been linked to vascular disease and diabetes. The objective of this study was to determine the effect of fish oil consumption on antioxidative capacity of HDL-cholesterol by measuring erythrocyte activity of antioxidant enzymes [catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and PON1], malonil dialdehide (MDA) parameter of oxidative stress, metabolic parameters and phospholipids fatty acid status in type 2 diabetic patients. Methods: Twenty patients (12 females, 8 males, mean age 53±6) received daily 4 g natural fish oil (1.2g n-3 fatty acids; 20:5n-3 [EPA] and 22:6 n-3 [DHA]) during 12 weeks. Results: PON-1 activity increased by 105.2 % (p<0.05) and SOD increased by 23.5% (p<0.05). Improvement of PON-1 activity was associated with serum n-3 fatty acid increment by 52% (p=0.01). Increased PON-1/HDL-C ratio (by 95%) was independently associated with changing of MDA and 20:4n-6 (AA)/EPA ratio (p=0.01). HbA 1 c was improved significantly by 21% (p<0.01), and HDL-C by 19% (p=0.05). Conclusion: Results of this study confirm that n-3 fatty acid status presented biomarker of intake and indicated that low dose of fish oil (1.2 g EPA+DHA) added to a habitual diet improved antioxidant property of HDL-C, by increasing PON1 activity, as well as SOD and MDA in type 2 diabetic patients.

Paraoxonase-1 gene Q192R and L55M polymorphisms and risk of cardiovascular disease in Egyptian patients with type 2 diabetes mellitus.

BackgroundIncreased oxidative stress or an impaired antioxidant defense mechanism may play a crucial role in the onset and progression of atherosclerosis. Recently, Paraoxonase −1 (PON1) which accounts for most of the antioxidant effect of high density lipoprotein (HDL) cholesterol has been presented as a potential therapeutic agent against atherosclerosis development. Allele frequencies for PON1 gene that influence enzyme concentration as well as activity differ greatly among ethnic groups and data from several studies showed ethnic variations in the interpretation of cardiovascular disease (CVD) associated with PON1 polymorphisms. In this work, we investigated PON1 Q192R and L55M polymorphisms in Egyptian patients with type 2 diabetes mellitus (T2DM) and its association with CVD.MethodsThe study included 184 subjects classified into 3 groups; T2DM, T2DM + CVD, and healthy controls. PON1 polymorphisms were genotyped by real-time PCR and PON1 concentration was assayed in serum by ELISA (enzyme linked immunesorbent assay).ResultsGenotype and allele frequencies of Q192R were significantly different between controls and diabetic patients. Frequency of QQ genotype was significantly higher in healthy controls, while QR and RR genotypes were significantly higher in diabetic patients (p = 0.02). Frequency of 55LL and LM genotypes were significantly higher in patients than in controls (p = 0.009). Q192R polymorphism associated with CVD in our diabetic patients (p = 0.01) and with low serum PON1 concentration (p = 0.04). Multiple logistic regression analysis revealed significant correlations between 192R and other independent CVD risk factors.ConclusionPON1 192R and 55 L alleles are associated with T2DM. Q192R polymorphism is associated with CVD and lower serum enzyme concentration and might represents a novel risk factor for CVD in Egyptian patients with T2DM.

High density lipoprotein level is negatively associated with the increase of oxidized low density lipoprotein lipids after a fatty meal.

Recent reports show that a fatty meal can substantially increase the concentration of oxidized lipids in low density lipoprotein (LDL). Knowing the LDL-specific antioxidant effects of high density lipoprotein (HDL), we aimed to investigate whether HDL can modify the postprandial oxidative stress after a fatty meal. Subjects of the study (n = 71) consumed a test meal (a standard hamburger meal) rich in lipid peroxides, and blood samples were taken before, 120, 240, and 360 min after the meal. The study subjects were divided into four subgroups according to the pre-meal HDL cholesterol value (HDL subgroup 1, 0.66-0.91; subgroup 2, 0.93-1.13; subgroup 3, 1.16-1.35; subgroup 4, 1.40-2.65 mmol/L). The test meal induced a marked postprandial increase in the concentration of oxidized LDL lipids in all four subgroups. The pre-meal HDL level was associated with the extent of the postprandial rise in oxidized LDL lipids. From baseline to 6 h after the meal, the concentration of ox-LDL increased by 48, 31, 24, and 16% in the HDL subgroup 1, 2, 3, and 4, respectively, and the increase was higher in subgroup 1 compared to subgroup 3 (p = 0.028) and subgroup 4 (p = 0.0081), respectively. The pre-meal HDL correlated with both the amount and the rate of increase of oxidized LDL lipids. Results of the present study show that HDL is associated with the postprandial appearance of lipid peroxides in LDL. It is therefore likely that the sequestration and transport of atherogenic lipid peroxides is another significant mechanism contributing to cardioprotection by HDL.

Abstract 549: High-Density Lipoprotein from Valvular Heart Disease and Cardiac Surgery Uncouples Endothelial Nitric Oxide Synthase Activity to Impair Vasodilation

Background: The vascular effects of high density lipoprotein (HDL) may be highly heterogeneous. Normal HDL protects vascular function. Vascular function plays an important role in maintaining the circulation stable post-cardiac surgery. The vascular effects of HDL in valvular heart disease (VHD) and cardiac surgery remain unknown. The present study is to determine the vascular effects of HDL from VHD and cardiac surgery. Methods: HDL was isolated from healthy subjects and patients with VHD and during cardiac surgery. HDL inflammation index was measured by cell free assay. Effects of HDL on vasodilation, protein interaction, generation of nitric oxide (NO) and superoxide anion (O 2 ·– ) were determined. Results: HDL inflammation index significantly increased in VHD patients and post-cardiac surgery. HDL from VHD patients and post-cardiac surgery significantly impaired endothelium-dependent vasodilation, inhibited both Akt and endothelial nitric oxide synthase (eNOS) phosphorylation, eNOS associated with heat shock protein 90, NO production and increased O 2 ·– generation. Conclusions: The vasoprotective effects of HDL from VHD patients and cardiac surgery is impaired by uncoupled eNOS activity. HDL may be a therapeutic target for maintaining the stable circulation in post-cardiac surgery.

Abstract 268: Atherosclerosis in Silico: A Computational Model for Early Inflammatory Events, Including the Effects of High-Density Lipoproteins

Objective: To develop a computational model to visualize in continuous time how the early plaque develops under different physiological conditions and to use it to explore the effects of changing concentrations of HDL. Methods: Atherosclerosis is the result of a sequence of specific responses to a failure of the endothelium. We devised a model for the interactions between modified LDL, monocytes and macrophages, HDL, chemoattractants and other cytokines immediately after endothelial injury. We included the dynamics of these interactions both at the endothelium and inside the intima. We computed the results for the model on a cross-section of an artery for different levels of blood cholesterol and immune system activity and produced a series of simulations to display the model results. Results: Using the model, we can visualize the changing movement and distribution of modified LDL, cytokines, macrophages and foam cells in the early plaque as a function of time, rather than as static post-mortem images. The model shows qualitatively how a fatty streak is initiated and develops after the initial inflammation, including distortion of the blood vessel wall by the developing plaque. The simulations show an initial phase with high macrophage densities in the plaque which settles to a low level of chronic inflammation and sustained foam cell accumulation. When we increase the level of HDL early in plaque development, the simulated plaque ceases to grow and may regress; when we increase HDL by the same amount but at a later time in plaque development, then the plaque continues to grow. Conclusion: This model provides a new tool for visualizing and for thinking about early atherosclerosis. It allows us to explore the effects of blood cholesterol levels and the level of the inflammatory response on the size and lipid density of the plaque. The results of model simulations suggest that the timing of increases in HDL may be important in determining whether or not a plaque regresses and, hence, that the inherent dynamics of the process of plaque formation may have an influence on the efficacy of HDL action.

Athero-protective effects of High Density Lipoproteins (HDL): An ODE model of the early stages of atherosclerosis.

We present an ODE model which we use to investigate how High Density Lipoproteins (HDL) reduce the inflammatory response in atherosclerosis. HDL causes atherosclerotic plaque stabilisation and regression, and is an important potential marker and prevention target for cardiovascular disease. HDL enables cholesterol efflux from the arterial wall, macrophage and foam cell emigration, and has other athero-protective effects. Our basic inflammatory model is augmented to include several different ways that HDL can act in early atherosclerosis. In each case, the action of HDL is represented via a parameter in the model. The long-term model behaviour is investigated through phase plane analysis and simulations. Our results indicate that only HDL-enabled cholesterol efflux can stabilise the internalised lipid content in the lesion so that it does not continue to grow, but this does not reduce macrophage numbers which is required to stabilise the lesion or prevent rupture. HDL-enabled macrophage emigration guarantees lesion stabilisation by maintaining stable macrophage content.

The Impact of Lipoproteins on Wound Healing: Topical HDL Therapy Corrects Delayed Wound Healing in Apolipoprotein E Deficient Mice

Chronic non-healing wounds lead to considerable morbidity and mortality. Pleiotropic effects of high density lipoproteins (HDL) may beneficially affect wound healing. The objectives of this murine study were: (1) to investigate the hypothesis that hypercholesterolemia induces impaired wound healing and (2) to study the effect of topical HDL administration in a model of delayed wound healing. A circular full thickness wound was created on the back of each mouse. A silicone splint was used to counteract wound contraction. Coverage of the wound by granulation tissue and by epithelium was quantified every 2 days. Re-epithelialization from day 0 till day 10 was unexpectedly increased by 21.3% (p < 0.05) in C57BL/6 low density lipoprotein (LDLr) deficient mice with severe hypercholesterolemia (489 ± 14 mg/dL) compared to C57BL/6 mice and this effect was entirely abrogated following cholesterol lowering adenoviral LDLr gene transfer. In contrast, re-epithelialization in hypercholesterolemic (434 ± 16 mg/dL) C57BL/6 apolipoprotein (apo) E−/− mice was 22.6% (p < 0.0001) lower than in C57BL/6 mice. Topical HDL gel administered every 2 days increased re-epithelialization by 25.7% (p < 0.01) in apo E−/− mice. In conclusion, topical HDL application is an innovative therapeutic strategy that corrects impaired wound healing in apo E−/− mice.

Role of the ubiquitin–proteasome system in the regulation of P2Y13 receptor expression: impact on hepatic HDL uptake

The protective effect of high density lipoproteins (HDL) against atherosclerosis is mainly attributed to their capacity to transport excess cholesterol from peripheral tissues back to the liver for further elimination into the bile, a process called reverse cholesterol transport (RCT). Recently, the importance of the P2Y13 receptor (P2Y13-R) was highlighted in HDL metabolism since HDL uptake by the liver was decreased in P2Y13-R deficient mice, which translated into impaired RCT. Here, we investigated for the first time the molecular mechanisms regulating cell surface expression of P2Y13-R. When transiently expressed, P2Y13-R was mainly detected in the endoplasmic reticulum (ER) and strongly subjected to proteasome degradation while its homologous P2Y12 receptor (P2Y12-R) was efficiently targeted to the plasma membrane. We observed an inverse correlation between cell surface expression and ubiquitination level of P2Y13-R in the ER, suggesting a close link between ubiquitination of P2Y13-R and its efficient targeting to the plasma membrane. The C-terminus tail exchange between P2Y13-R and P2Y12-R strongly restored plasma membrane expression of P2Y13-R, suggesting the involvement of the intra-cytoplasmic tail of P2Y13-R in expression defect. Accordingly, proteasomal inhibition increased plasma membrane expression of functionally active P2Y13-R in hepatocytes, and consequently stimulated P2Y13-R-mediated HDL endocytosis. Importantly, proteasomal inhibition strongly potentiated HDL hepatic uptake (>200%) in wild-type but not in P2Y13-R-deficient mice, thus reinforcing the role of P2Y13-R expression in regulating HDL metabolism. Therefore, specific inhibition of the ubiquitin-proteasome system might be a novel powerful HDL therapy to enhance P2Y13-R expression and consequently promote the overall RCT.

Torcetrapib therapy in patients with coronary artery disease does not lead to further impairment of endothelial effects of High-Density Lipoprotein (HDL)

Introduction: CETP inhibition leading to increased HDL cholesterol and reduced LDL cholesterol is currently examined as a potential strategy for prevention of cardiovascular events in patients with coronary disease. However, vascular effects of HDL are recently found to be highly heterogeneous in patients with coronary artery disease (CAD). We therefore studied in patients with CAD the effect of the CETP inhibitor by torcetrapib, that resulted in increased cardiovascular events due to side effects, to understand whether intense CETP inhibition impairs endothelial effects of HDL. Methods: HDL was isolated by sequential ultracentrifugation from patients randomized to receive either a combination of atorvastatin plus torcetrapib (60 mg/day; n=31) or atorvastation alone (n=36) at baseline and 6 months, and from healthy subjects. The effect of HDL on endothelial nitric oxide (NO) production was measured by ESR spectroscopy and on endothelial pro-inflammatory and pro-apoptotic activation determined by VCAM-1 and active caspase-3 expression assays, respectively. Results: There was no significant improvement in the capacity of HDL to stimulate endothelial NO production, reduce VCAM-1 activation or inhibit active caspase-3 expression following torcetrapib/atorvastatin treatment or atorvastatin alone in patients with CAD. These vascular effects of HDL remained largely impaired as compared to HDL from healthy subjects. Importantly, however, there was no further impairment in the capacity of HDL to stimulate endothelial NO production (10.6±52.1% vs 20.0±72.8% at baseline, p=0.33), reduce VCAM-1 activation (11.0±7.3% vs 9.0±8.1% at baseline, p=0.12) or inhibit caspase-3 activation (5.5±14.9% vs 10.0±7.3% at baseline, p=0.061) following 6-month treatment with torcetrapib. Conclusions: Despite a significant increase in HDL-C levels, torcetrapib treatment did not restore the potential anti-atherosclerotic properties of HDL on the endothelium as found in the healthy controls. Importantly, torcetrapib treatment did not further impair the endothelial effects of HDL. These data suggest that the adverse effects of torcetrapib on cardiovascular events were not caused by worsening of vascular effects of HDL.

Serum Paraoxonase 1 Activity Is Associated with Fatty Acid Composition of High Density Lipoprotein

Introduction. Cardioprotective effect of high density lipoprotein (HDL) is, in part, dependent on its related enzyme, paraoxonase 1 (PON1). Fatty acid composition of HDL could affect its size and structure. On the other hand, PON1 activity is directly related to the structure of HDL. This study was designed to investigate the association between serum PON1 activity and fatty acid composition of HDL in healthy men. Methods. One hundred and forty healthy men participated in this research. HDL was separated by sequential ultracentrifugation, and its fatty acid composition was analyzed by gas chromatography. PON1 activity was measured spectrophotometrically using paraxon as substrate. Results. Serum PON1 activity was directly correlated with the amount of stearic acid and dihomo-gamma-linolenic acid (DGLA). PON1/HDL-C was directly correlated with the amount of miristic acid, stearic acid, and DGLA and was inversely correlated with total amount of ω6 fatty acids of HDL. Conclusion. The fatty acid composition of HDL could affect the activity of its associated enzyme, PON1. As dietary fats are the major determinants of serum lipids and lipoprotein composition, consuming some special dietary fatty acids may improve the activity of PON1 and thereby have beneficial effects on health.

Striking Differences Between the Atheroprotective Effects of High Density Lipoproteins in Early-stage and Late-stage Atherosclerosis: Insights into the Lack of Efficacy of HDL-raising Therapy

Conclusions: A sustainable program of PE improved IR in community-based children, thereby offering a primordialpreventative strategy that couldbecoordinatedwidely though a school-based approach. http://dx.doi.org/10.1016/j.hlc.2013.05.156

TRANSFORMING GROWTH FACTOR-β2 RELEASED BY MESENCHYMAL STEM CELLS PRECONDITIONED WITH HIGH DENSITY LIPOPROTEIN PROTECTS CARDIOMYOCYTES FROM HYPOXIA

ObjectivesThe effect of high density lipoprotein (HDL) on the secretome of mesenchymal stem cells (MSCs) has not been well elucidated yet. The aim of the study is to examine the...

HIGH DENSITY LIPOPROTEIN CHOLESTEROL PROMOTES THE PROLIFERATION OF BONE-DERIVED MESENCHYMAL STEM CELLS VIA BINDING SCAVENGER RECEPTOR-B TYPE I AND ACTIVATION OF PI3K/AKT, MAPK/ERK PATHWAYS

ObjectivesTo investigate the effect of high density lipoprotein (HDL) on the proliferation of mesenchymal stem cells (MSCs), and to elucidate the molecular mechanisms involved.MethodsMSCs derived from rats was treated with...

Altered expression of apoA-I, apoA-IV and PON-1 activity in CBS deficient homocystinuria in the presence and absence of treatment: Possible implications for cardiovascular outcomes

Classical homocystinuria (HCU) is caused by mutations in cystathionine beta-synthase (CBS) which, if untreated, typically results in cognitive impairment, thromboembolic complications and connective tissue disturbances. Paraoxonase-1 (PON1) and apolipoprotein apoA-I are both synthesized in the liver and contribute to much of the cardioprotective effects of high density lipoprotein. Additionally, apoA-I exerts significant neuro-protective effects that act to preserve cognition. Previous work in a Cbs null mouse model that incurs significant liver injury, reported that HCU dramatically decreases PON1 expression. Conflicting reports exist in the literature concerning the relative influence of homocysteine and cysteine upon apoA-I expression. We investigated expression of PON1 and apoA-I in the presence and absence of homocysteine lowering therapy, in both the HO mouse model of HCU and human subjects with this disorder. We observed no significant change in plasma PON1 paraoxonase activity in either mice or humans with HCU indicating that this enzyme is unlikely to contribute to the cardiovascular sequelae of HCU. Plasma levels of apoA-I were unchanged in mice with mildly elevated homocysteine due to CBS deficiency but were significantly diminished in both mice and humans with HCU. Subsequent experiments revealed that HCU acts to dramatically decrease apoA-I levels in the brain. Cysteine supplementation in HO mice had no discernible effect on plasma levels of apoA-I while treatment to lower homocysteine normalized plasma levels of this lipoprotein in both HO mice and humans with HCU. Our results indicate that plasma apoA-I levels in HCU are inversely related to homocysteine and are consistent with a plausible role for decreased expression of apoA-I as a contributory factor for both cardiovascular disease and cognitive impairment in HCU.

Mesenchymal stem cells preconditioned with high density lipoprotein resist oxidative stress-induced apoptosis and improve cardiac function in a rat model of myocardial infarction

ObjectiveTo explore the effect of high density lipoprotein (HDL) on mesenchymal stem cells (MSCs) implanted in infarcted myocardium, and to unveil the role of MAPK/ERK1/2 pathways in the potential mechanism...

High density lipoprotein induces rats mesenchymal stem cells proliferation through activating PI3K-Akt pathway

ObjectiveTo explore the effect of high density lipoprotein (HDL) on the proliferation of mesenchymal stem cells (MSCs), and to elucidate the role of PI3K-Akt pathway in the potential regulation of...

Expression and purification of recombinant apolipoprotein A-I Zaragoza (L144R) and formation of reconstituted HDL particles

Apolipoprotein A-I Zaragoza (L144R) (apo A-I Z), has been associated with severe hypoalphalipoproteinemia and an enhanced effect of high density lipoprotein (HDL) reverse cholesterol transport. In order to perform further studies with this protein we have optimized an expression and purification method of recombinant wild-type apo A-I and apo A-I Z and produced mimetic HDL particles with each protein. An pET-45 expression system was used to produce N-terminal His-tagged apo A-I, wild-type or mutant, in Escherichia coli BL21 (DE3) which was subsequently purified by affinity chromatography in non-denaturing conditions. HDL particles were generated via a modified sodium cholate method. Expression and purification of both proteins was verified by SDS–PAGE, MALDI-TOF MS and immunochemical procedures. Yield was 30 mg of purified protein (94% purity) per liter of culture. The reconstituted HDL particles checked via non-denaturing PAGE showed high homogeneity in their size when reconstituted both with wild-type apo A-I and apo A-I Z. An optimized system for the expression and purification of wild-type apo A-I and apo A-I Z with high yield and purity grade has been achieved, in addition to their use in reconstituted HDL particles, as a basis for further studies.

Protective effect of HDL on endothelial NO production: the role of DDAH/ADMA pathway

Accumulating studies have demonstrated that the dimethylarginine dimethylaminohydrolase/asymmetric dimethylarginine (DDAH/ADMA) system is a novel pathway for modulating nitric oxide (NO) production. The aim of this study was to investigate whether the protective effect of high density lipoprotein (HDL) on endothelial NO production was related to its effect on DDAH/ADMA pathway. Human umbilical vein endothelial cells (HUVECs) were prior exposed to HDL (10, 50, or 100 μg/ml) for 1 h, and then incubated with oxidized low density lipoprotein (ox-LDL) (100 μg/ml) for 24 h. The cultured medium was collected for measuring the concentration of NO and ADMA. The cells were collected for measuring the mRNA and protein expression of DDAH-II as well as DDAH activity. HUVECs treated with ox-LDL (100 μg/ml) for 24 h significantly decreased the concentration of NO, the mRNA and protein expression of DDAH-II as well as DDAH activity and increased the level of ADMA. Pretreatment with HDL (10, 50, or 100 μg/ml) could counteract these changes induced by ox-LDL (100 μg/ml). HDL significantly increased the attenuated endothelial cell NO production induced by ox-LDL, which was attributed to its effect on DDAH/ADMA pathway.

Effect of high-density lipoprotein on interleukin-8 secretion in 3T3-L1 adipocytes

3T3-L1 adipocytes were cultured with various concentrations of high-density lipoprotein ( HDL, 0, 10, 50, and 100 μg/ml ) for 16 h and with lipopolysaccharide ( LPS, 100 ng/ml ) for another 6 h. Interleukin-8 in the medium was determined by ELISA, and PPAR-γ mRNA expression by reverse transacription polymerase chain reaction (RT-PCR). Interleukin-8 levels were increased in LPS-treated cells ( P＜0.05 ), but decreased in HDL-treated cells in the dose-dependent manner. PPARγ mRNA expressions were increased in HDL-treated groups than those treated only with LPS. These results suggested HDL may decrease interleukin-8 secretion via up-regulating PPARγ expression in adipocytes. Key words: High-density lipoprotein; Adipocytes; Interleukin-8; PPARγ

Acute global effects of high-density lipoprotein on activated endothelial cells—Inhibition of CXCL10

Acute global effects of high-density lipoprotein on activated endothelial cells—Inhibition of CXCL10