High density lipoproteins (HDLs) and atherosclerosis; the unanswered questions

Overexpression of CuZn superoxide dismutase improves high-density lipoprotein function in swine

Cardiovascular disease (CVD) has been the leading cause of death worldwide. As a chronic inflammatory disease, atherosclerosis (AS) acts as the initiating factor for CVD and reactive oxygen species (ROS) play a vital role in its development. Superoxide dismutases (SOD) can alleviate the detrimental effects of ROS and serve as the first line of defense through detoxifying the products derived from oxidative stress in vivo. Considering the potential preventive effects of high-density lipoprotein (HDL) on AS and the close relationship between CuZn superoxide dismutase (CuZnSOD) and HDL, the present work investigated whether CuZnSOD overexpression in swine could improve the function of HDL. Seven CuZnSOD transgenic swine, constructed by sperm and magnetic nanoparticles, demonstrated overexpressed CuZnSOD in the liver (P < 0.01) but comparable level to control in plasma (P > 0.05). CuZnSOD overexpression significantly down-regulated the levels of triglyceride (TG), apolipoprotein A-I (apoA-I) (P < 0.05), and high-density lipoprotein cholesterol (HDL-C) (P < 0.01) in plasma. In the presence of CuZnSOD overexpression, HDL3 significantly inhibited levels of IL-6 and TNF-α induced by oxidized low-density lipoprotein (oxLDL) (P < 0.05), indicating enhanced anti-inflammatory activity of HDL. At the same time, HDL-mediated cholesterol efflux did not decrease (P > 0.05). CuZnSOD overexpression improves the anti-inflammatory function of HDL despite decreased levels of HDL-C. In Conclusion, CuZnSOD overexpression improves HDL function in swine.

Relationship between the cholesterol and triglyceride content of lipoprotein subclasses and carotid intima-media thickness: A cross-sectional population-based study

BACKGROUND

The association between lipoprotein subclasses and carotid intima-media thickness (cIMT) progression has yet to be fully evaluated. We assessed which lipoprotein subclasses were associated with maximum cIMT levels in the general population.

METHODS

In this study, cholesterol and triglyceride content of 20 lipoprotein subclasses were analyzed using gel permeation high-performance liquid chromatography (GP-HPLC) in 864 Japanese women and men (mean age 57 y, free of chronic liver or kidney diseases and off lipid-lowering, hormone replacement, or adrenocorticosteroid medications). Univariate and multivariate regression analyses and univariate and partial correlation analyses were performed to examine the relationships between lipoprotein subclasses and maximum cIMT levels.

RESULTS

After adjusting for age, sex, systolic blood pressure, smoking, diabetes, and anti-hypertensive agents, elevated low-density lipoprotein (LDL)-2 and -3 cholesterol (particle diameter 25.5 nm and 23.0 nm, respectively; medium and small LDL) were associated with higher maximum cIMT levels in both women and men (all p for trend < 0.05). These associations were significant even after participants taking anti-diabetic or anti-hypertensive agents were excluded. No significant associations were found between any triglyceride subclasses and maximum cIMT levels.

CONCLUSIONS

Smaller LDL particle cholesterol values are the most atherogenic lipoprotein parameter.

Interaction between SIDT2 and ABCA1 Variants with Nutrients on HDL-c Levels in Mexican Adults

Previous studies have reported that the SIDT2 and ABCA1 genes are involved in lipid metabolism. We aimed to analyze the association-the gene x gene interaction between rs17120425 and rs1784042 on SIDT2 and rs9282541 on ABCA1 and their diet interaction on the HDL-c serum levels-in a cohort of 1982 Mexican adults from the Health Workers Cohort Study. Demographic and clinical data were collected through a structured questionnaire and standardized procedures. Genotyping was performed using a predesigned TaqMan assay. The associations and interactions of interest were estimated using linear and logistic regression. Carriers of the rs17120425-A and rs1784042-A alleles had slightly higher blood HDL-c levels compared to the non-carriers. In contrast, rs9282541-A was associated with low blood HDL-c levels (OR = 1.34, p = 0.013). The rs1784042 x rs9282541 interaction was associated with high blood HDL-c levels (p = 3.4 × 10^-4). Premenopausal women who carried at least one rs17120425-A allele and consumed high dietary fat, protein, monounsaturated, or polyunsaturated fatty acids levels had higher HDL-c levels than the non-carriers. These results support the association between the genetic variants on SIDT2 and ABCA1 with HDL-c levels and suggest gene-gene and gene-diet interactions over HDL-c concentrations in Mexican adults. Our findings could be a platform for developing clinical and dietary strategies for improving the health of the Mexican population.

Molecular Genetic Mechanisms in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is among the leading causes of irreversible blindness worldwide. In addition to environmental risk factors, such as tobacco use and diet, genetic background has long been established as a major risk factor for the development of AMD. However, our ability to predict disease risk and personalize treatment remains limited by our nascent understanding of the molecular mechanisms underlying AMD pathogenesis. Research into the molecular genetics of AMD over the past two decades has uncovered 52 independent gene variants and 34 independent loci that are implicated in the development of AMD, accounting for over half of the genetic risk. This research has helped delineate at least five major pathways that may be disrupted in the pathogenesis of AMD: the complement system, extracellular matrix remodeling, lipid metabolism, angiogenesis, and oxidative stress response. This review surveys our current understanding of each of these disease mechanisms, in turn, along with their associated pathogenic gene variants. Continued research into the molecular genetics of AMD holds great promise for the development of precision-targeted, personalized therapies that bring us closer to a cure for this debilitating disease.

Serum Cholesterol Efflux Capacity in Age-Related Macular Degeneration and Polypoidal Choroidal Vasculopathy

Purpose

To investigate serum cholesterol efflux capacity (the ability of the serum to accept cholesterol) and factors that regulate it using nuclear magnetic resonance-quantified measures of lipoprotein particle composition and size and apolipoproteins metrics in patients with age-related macular degeneration (AMD).

Design

Case-control study.

Participants

Four hundred two serum samples from 80 patients with early AMD (eAMD), and 212 patients with neovascular AMD (nAMD), including 80 with typical nAMD (tAMD) and 132 with polypoidal choroidal vasculopathy (PCV), and 110 age- and gender matched control participants.

Methods

Serum from participants showed cholesterol efflux capacity measured using in vitro cell assays and lipoprotein subfractions measured using nuclear magnetic resonance (Nightingale, Ltd). Associations between cholesterol efflux capacity (measured in percentage) and lipid subfractions were investigated in the patients and control participants.

Main Outcome Measures

Cholesterol efflux capacity and lipid subfractions in control, eAMD, and nAMD. Associations between HDL subfractions and cholesterol efflux capacity.

Results

Cholesterol efflux capacity was higher in patients with eAMD (68.0 ± 11.3% [mean ± standard deviation]) and nAMD (75.9 ± 27.7%) than in the control participants (56.9 ± 16.7%) after adjusting for age, gender, and use of lipid-lowering drug (P < 0.0001). Nuclear magnetic resonance lipidomics demonstrated that the mean diameter of HDL was larger both in eAMD (9.96 ± 0.27 mm [mean ± standard deviation]) and PCV (9.97 ± 0.23 mm) compared with that of the control participants (9.84 ± 0.24 mm; P = 0.0001 for both). Among the 28 HDL subfractions, most of the small, medium, and large HDLs, but none of the 7 extra large HDLs fractions, were associated moderately with cholesterol efflux capacity in eAMD and PCV (R = 0.149-0.277).

Conclusions

Serum cholesterol efflux capacity was increased in eAMD and PCV, but not tAMD, possibly reflecting differential underlying pathophysiologic features of lipid dysregulation in tAMD and PCV. Further studies should be directed toward investigating the diverse biological activities of HDL in AMD, including macular pigment transport, regulation of inflammation, and local cholesterol transport system.

Changes in lipoprotein particle subclasses, standard lipids, and apolipoproteins after supplementation with n-3 or n-6 PUFAs in abdominal obesity: A randomized double-blind crossover study

BACKGROUND & AIMS

Marine-derived omega-3 (n-3) polyunsaturated fatty acids (PUFAs), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), lower circulating levels of triacylglycerols (TAGs), and the plant-derived omega-6 (n-6) PUFA linoleic acid (LA) may reduce cholesterol levels. Clinical studies on effects of these dietary or supplemental PUFAs on other blood fat fractions are few and have shown conflicting results. This study aimed to determine effects of high-dose supplemental n-3 (EPA + DHA) and n-6 (LA) PUFAs from high-quality oils on circulating lipoprotein subfractions and standard lipids (primary outcomes), as well as apolipoproteins, fatty acids, and glycemic control (secondary outcomes), in females and males with abdominal obesity.

METHODS

This was a randomized double-blind crossover study with two 7-wk intervention periods separated by a 9-wk washout phase. Females (n = 16) were supplemented with 3 g/d of EPA + DHA (TAG fish oil) or 15 g/d of LA (safflower oil), while males (n = 23) received a dose of 4 g/d of EPA + DHA or 20 g/d of LA. In fasting blood samples, we investigated lipoprotein particle subclasses by nuclear magnetic resonance spectroscopy, as well as standard lipids, apolipoproteins, fatty acid profiles, and glucose and insulin. Data were analyzed by linear mixed-effects modeling with 'subjects' as the random factor.

RESULTS

The difference between interventions in relative change scores was among the lipoprotein subfractions significant for total very-low-density lipoproteins (VLDLs) (n-3 vs. n-6: -38%∗ vs. +16%, p < 0.001; ∗: significant within-treatment change score), large VLDLs (-58%∗ vs. -0.91%, p < 0.001), small VLDLs (-57%∗ vs. +41%∗, p < 0.001), total low-density lipoproteins (LDLs) (+5.8%∗ vs. -4.3%∗, p = 0.002), large LDLs (+23%∗ vs. -2.1%, p = 0.004), total high-density lipoproteins (HDLs) (-6.0%∗ vs. +3.7%, p < 0.001), large HDLs (+11%∗ vs. -5.3%, p = 0.001), medium HDLs (-24%∗ vs. +6.2%, p = 0.030), and small HDLs (-9.9%∗ vs. +9.6%∗, p = 0.002), and among standard lipids for TAGs (-16%∗ vs. -2.6%, p = 0.014), non-esterified fatty acids (-19%∗ vs. +5.5%, p = 0.033), and total cholesterol (-0.28% vs. -4.4%∗, p = 0.042). A differential response in relative change scores was also found for apolipoprotein (apo)B (+0.40% vs. -6.0%∗, p = 0.008), apoA-II (-6.0%∗ vs. +1.5%, p = 0.001), apoC-II (-11%∗ vs. -1.7%, p = 0.025), and apoE (+3.3% vs. -3.8%, p = 0.028).

CONCLUSIONS

High-dose supplementation of high-quality oils with n-3 (EPA + DHA) or n-6 (LA) PUFAs was followed by reductions in primarily TAG- or cholesterol-related markers, respectively. The responses after both interventions point to changes in the lipoprotein-lipid-apolipoprotein profile that have been associated with reduced cardiometabolic risk, also among people with TAG or LDL-C levels within the normal range.

REGISTRATION

Registered under ClinicalTrials.gov Identifier: NCT02647333.

CLINICAL TRIAL REGISTRATION

Registered at https://clinicaltrials.gov/ct2/show/NCT02647333.

Cardiovascular Risk Reduction With Icosapent Ethyl: A Systematic Literature Review

Cardiovascular disease is the leading cause of death in the United States of America due to elevated triglyceride levels. High triglyceride levels lead to higher risks of ischemic events. There are multiple pieces of research and analyses on statin therapy and its ability to reduce the prevalence of heart complications. Heart ailments can reduce through the use of icosapent ethyl in the form of statin therapy. This literature review will explain the reduction of cardiovascular risks with icosapent ethyl. Though some genetic conditions can cause some of these ailments, the rest of the predisposing conditions revolve around cholesterol, lipoproteins, and triglycerides.

Lipoproteins in Atherosclerosis Process

BACKGROUND

Dyslipidaemias is a recognized risk factor for atherosclerosis, however, new evidence brought to light by trials investigating therapies to enhance HDLcholesterol have suggested an increased atherosclerotic risk when HDL-C is high.

RESULTS

Several studies highlight the central role in atherosclerotic disease of dysfunctional lipoproteins; oxidised LDL-cholesterol is an important feature, according to "oxidation hypothesis", of atherosclerotic lesion, however, there is today a growing interest for dysfunctional HDL-cholesterol. The target of our paper is to review the functions of modified and dysfunctional lipoproteins in atherogenesis.

CONCLUSION

Taking into account the central role recognized to dysfunctional lipoproteins, measurements of functional features of lipoproteins, instead of conventional routine serum evaluation of lipoproteins, could offer a valid contribution in experimental studies as in clinical practice to stratify atherosclerotic risk.

Specific Cholesterol Binding Drives Drastic Structural Alterations in Apolipoprotein A1

Proteins typically adopt a multitude of flexible and rapidly interconverting conformers, many of which are governed by specific protein interaction domains. Whereas disc-shaped oligomeric HDL and its major protein component ApoA1 have been the focus of several investigations, the structural properties of monomeric ApoA1 remain poorly understood. Using tens of independent molecular simulations (>50 μs), we reveal that ApoA1 adopts a compact conformation. Upon the addition of a physiological concentration of cholesterol to ApoA1, the monomeric protein spontaneously formed a circular conformation. Remarkably, these drastic structural perturbations are driven by a specific cholesterol binding site at the C-terminal and a novel cholesterol binding site at the N-terminal. We propose a mechanism whereby ApoA1 opens in a stagewise manner and mutating the N-terminal binding site destroys the open "belt-shaped" topology. Complementary experiments confirm that the structural changes are induced by specific association of cholesterol with ApoA1, not by the nonspecific hydrophobic effect.

HDL cholesterol efflux capacity and cholesteryl ester transfer are associated with body mass, but are not changed by diet-induced weight loss: A randomized trial in abdominally obese men

BACKGROUND AND AIMS

Obesity is associated with a lower HDL-mediated cholesterol efflux from macrophages and a higher CETP (cholesteryl ester transfer protein) activity, but effects of weight loss are not clear. In addition, associations with visceral and subcutaneous adipose tissue are not known. We therefore investigated effects of diet-induced weight loss on HDL-mediated cholesterol efflux and cholesterol ester (CE) transfer in abdominally obese men. Differences between normal-weight and abdominally obese men were also examined.

METHODS

Twenty-five apparently healthy, normal-weight men (waist circumference: <94 cm) and 52 abdominally obese men (waist circumference: 102-110 cm) were included. Abdominally obese subjects were randomly allocated to a dietary weight-loss intervention group or a no-weight loss control group. Individuals from the intervention group followed a very-low-calorie diet for 6 weeks to obtain a waist circumference below 102 cm, followed by a 2-week weight-stable period. Cholesterol efflux was measured in BODIPY-labeled murine J774 macrophages. CE transfer was measured by quantifying the transfer of CE from radiolabeled exogenous HDL to apoB-containing lipoproteins.

RESULTS

Cholesterol efflux capacity was 9 percentage point (pp) lower in abdominally obese than in normal-weight men (p≤0.001), while CE transfer was 5 pp higher (p≤0.01). Diet-induced weight-loss of 10.3 kg did not change cholesterol efflux and CE transfer. In addition, stepwise regression analysis did not suggest that the different fat depots are differently related to efflux capacity and CE transfer.

CONCLUSIONS

After a 2-week weight-stable period, dietary weight loss of 10 kg did not improve ABCA1-mediated cholesterol efflux and CE transfer in abdominally obese men.

Lipid transfers to HDL are diminished in long-term bedridden patients: association with low HDL-cholesterol and increased inflammatory markers

Plasma lipids have been extensively studied in sedentary and in subjects practicing exercise training, but not in extreme inactivity as occurs in bedridden patients. This is important for the care of bedridden patients and understanding the overall plasma lipid regulation. Here, we investigated plasma lipids, lipid transfers to HDL and inflammatory markers in bedridden patients. Fasting blood samples were collected from 23 clinically stable bedridden patients under long-term care (>90 days) and 26 normolipidemic sedentary subjects, paired for age and gender. In vitro transfer of four lipids to HDL was performed by incubating plasma with donor nanoparticles containing radioactive lipids. Total (193 ± 36 vs 160 ± 43, p = 0.005), LDL (124 ± 3 vs 96 ± 33 p = 0.003) and HDL-cholesterol (45 ± 10 vs 36 ± 13, p = 0.008), apolipoprotein A-I (134 ± 20 vs 111 ± 24, p = 0.001) and oxidized LDL (53 ± 13 vs 43 ± 12, p = 0.011) were lower in bedridden patients, whereas triglycerides, apolipoprotein B, CETP and LCAT were equal in both groups. Transfers of all lipids, namely unesterified cholesterol, cholesterol esters, triglycerides and phospholipids, to HDL were lower in bedridden patients, probably due to their lower HDL-cholesterol levels. Concentrations of IL-1β, IL-6, IL-8, HGF and NGF were higher in bedridden patients compared to sedentary subjects. In conclusion, inactivity had great impact on HDL, by lowering HDL-cholesterol, apolipoprotein A-I and thereby cholesterol transfers to the lipoprotein, which suggests that inactivity may deteriorate HDL protection beyond the ordinary sedentary condition.

Association of High-Density Lipoprotein Subclasses with Carotid Intima-Media Thickness: Shimane CoHRE Study

AIMS

Recent studies suggested that subclasses of high-density lipoprotein (HDL) may be a better biomarker to predict the risk of atherosclerotic disorders. We aimed to examine the association of HDL2- and HDL3-cholesterol (HDL2-C and HDL3-C) with carotid intima-media thickness (IMT) using a new method to quantify the HDL-C subclasses.

METHODS

Participants were 657 Japanese subjects (434 women) who received a health examination (mean age: 73 years). Serum samples were analyzed by the homogenous assay for HDL-C and HDL3-C. HDL2-C was calculated indirectly by subtracting HDL3-C from HDL-C. HDL3-C measured by this assay was well correlated with that measured by ultracentrifugation (r=0.898, p＜0.001). The maximum IMT (max-IMT) and plaque score (PS) were evaluated by ultrasonography following the standard protocol.

RESULTS

HDL3-C was associated with age both in men (r=－0.322, p＜0.0001) and women (r=－0.315, p＜0.0001). In a simple regression analysis, max-IMT showed an inverse association with HDL3-C, whereas no significant association was observed with HDL2-C. A multiple linear regression analysis indicated, however, that the association between HDL3-C and max-IMT was not significant in both aged and younger populations when age was included in the analysis. Further, not only HDL2-C but also HDL3-C was not a significant predictor of 'atherosclerotic arteries' defined as the max-IMT ≥1.5 mm. Similar results were observed in the analysis on PS.

CONCLUSIONS

Neither HDL3-C nor HDL2-C was significantly associated with carotid atherosclerosis in the Japanese population in this study.

Associations between follicular fluid high density lipoprotein particle components and embryo quality among in vitro fertilization patients

PURPOSE

Follicular redox balance is likely to be important for embryo quality during in vitro fertilization (IVF), and the anti-oxidative high desity lipoprotein (HDL) particle is the sole lipoprotein measured in follicular fluid (FF). Therefore, we investigated FF HDL particle components as predictors of embryo quality during IVF.

METHODS

Two research follicles collected from each participant were individually tracked, and 103 women having at least one developed embryo were included in the analysis. Concentrations of 15 non-cholesterol HDL particle components and 26 HDL-cholesterol (HDL-C) particle size subfractions were determined. Embryo quality was assessed for embryo cell number, embryo fragmentation, and embryo symmetry. Multivariable Poisson regression with a sandwich variance estimator was used to evaluate associations between HDL particle components and embryo quality, adjusted for covariates.

RESULTS

Higher γ-tocopherol concentration was associated with less embryo fragmentation (relative risk [RR] = 4.43; 95 % confidence interval [CI] 1.78, 11.06), and higher apolipoprotein A-1 concentration was associated with full embryo symmetry (RR = 3.92; 95 % CI 1.56, 9.90). Higher concentrations of HDL-C subfractions in the large and medium particle size ranges were associated with poorer embryo quality.

CONCLUSIONS

FF HDL lipophilic micronutrients and protein components, as well as HDL-C particle size, may be important predictors of embryo quality during IVF.

Pharmacokinetics, pharmacodynamics and safety of CKD-519, a CETP inhibitor, in healthy subjects

CKD-519 is a selective and potent cholesteryl ester transfer protein (CETP) inhibitor being developed for the treatment of dyslipidemia to raise high-density lipoprotein cholesterol. We investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of single doses of CKD-519 in healthy adult subjects. A randomized, double-blinded, placebo-controlled, single ascending dose study was performed. Eight healthy subjects were enrolled in each CKD-519 dose group (25, 50, 100, 200, or 400 mg) and randomized to CKD-519 (n=6) or matching placebo (n=2). CKD-519 reached the maximum plasma concentration (C_max) at 5–6 h post-dose, and had a long terminal half-life ranging between 40–70 h. The area under the plasma concentration–time curve (AUC) and C_max increased with the dose, however, C_max and AUC normalized by dose decreased with each incremental dose. CETP activity decreased with dose, and the maximum decrease (63%–83%) was observed at 6–8 h post-dose. A sigmoid E_max model best described the relationship between CKD-519 plasma concentrations and CETP activity with an EC₅₀ of 17.3 ng/mL. Overall, 11 adverse events (AEs) were observed. All AEs were mild or moderate in intensity, and resolved without any complications. There were no clinically significant effects on blood pressure. In conclusion, single doses of CKD-519 up to 400 mg were well tolerated and showed potent inhibition of CETP activity.

Apolipoprotein C-III Nanodiscs Studied by Site-Specific Tryptophan Fluorescence

Apolipoprotein C-III (ApoC-III) is found on high-density lipoproteins (HDLs) and remodels 1,2-dimyristoyl-sn-glycero-3-phosphocholine vesicles into HDL-like particles known as nanodiscs. Using single-Trp-containing ApoC-III mutants, we have studied local side chain environments and interactions in nanodiscs at positions W42, W54, and W65. Using transmission electron microscopy and circular dichroism spectroscopy, nanodiscs were characterized at the ultrastructural and secondary conformational levels, respectively. Nearly identical particles (15 ± 2 nm) were produced from all proteins containing approximately 25 ± 4 proteins per particle with an average helicity of 45-51% per protein. Distinct residue-specific fluorescence properties were observed with W54 residing in the most hydrophobic environment followed by W42 and W65. Interestingly, time-resolved anisotropy measurements revealed that Trp side chain mobility is uncorrelated to the polarity of its surroundings. W54 is the most mobile compared to W65 and W42, which are more immobile in a nanodisc-bound state. On the basis of Trp spectral comparisons of ApoC-III in micellar and vesicle environments, ApoC-III binding within nanodiscs more closely resembles a bilayer-bound state. Despite the nanodiscs being structurally similar, we found marked differences during nanodisc formation by the Trp variants as a function of temperature, with W42 behaving the most like the wild-type protein. Our data suggest that despite the modest mutations of Trp to Phe at two of the three native sites, the interfacial location of W42 is important for lipid binding and nanodisc assembly, which may be biologically meaningful as of the three Trp residues, only W42 is invariant among mammals.

Monocyte to HDL ratio in prediction of BMS restenosis in subjects with stable and unstable angina pectoris

AIM

This study aims to assess the predictive role of the preprocedural circulating monocyte to high-density lipoprotein (HDL) cholesterol ratio (MHR) on the occurrence of stent restenosis (SR) in patients with stable and unstable angina pectoris undergoing successful bare-metal stenting (BMS).

PATIENTS & METHODS

Between February 2008 and June 2014, a total of 831 patients with stable and unstable angina pectoris who underwent successful BMS were retrospectively analyzed. Demographic and clinical characteristics of the patients were recorded. Left ventricular ejection fraction and laboratory data were also noted.

RESULTS

In the receiver operating characteristics curve analysis, MHR >14 had 71% sensitivity and 69% specificity in predicting SR.

CONCLUSION

Our study results show that preprocedural MHR is an independent predictor of SR in this patient population.

Systematic review and meta-analysis deciphering the impact of fibrates on paraoxonase-1 status

OBJECTIVE

A significant residual cardiovascular risk is consistently observed in patients treated with statins. A combined treatment with fibrates reduces cardiovascular events in very high-risk patients. Because this is apparently unconnected to an improvement in lipid-related outcomes we hypothesized that the cardioprotective effects of fibrates might be associated with an improvement in paraoxonase-1 (PON1) status.

METHOD

The search for existing evidence, using the Medline, Scopus and Cochrane databases, was systematic and followed the PRISMA statement without restrictions on publication date. We excluded non-clinical and observational studies and we extracted data on baseline and post-treatment values of serum PON1 activity and other measurements of PON1 status.

RESULTS

Nine studies (including 12 treatment arms) in patients with hyperlipidemia, diabetes or metabolic syndrome treated with fibrates, alone or in combination with statins, were included to synthesize results. A meta-analysis of the data using a random-effects model revealed a significant increase in serum PON1 activity following fibrate therapy (WMD: 15.64U/L, 95% CI: 6.94, 24.34, p<0.001), an effect that was robust and not sensitive to any particular study. Subgroup analysis indicated differences in the effect size among types of fibrates and that PON1 alterations were associated with high-density lipoprotein cholesterol changes following fibrate therapy.

CONCLUSIONS

Results indicate a significant PON1-enhancing effect of fibrates. Whether this effect is associated with a clinical benefit, although likely, remains to be further investigated.

Advances in the Study of the Antiatherogenic Function and Novel Therapies for HDL

The hypothesis that raising high-density lipoprotein cholesterol (HDL-C) levels could improve the risk for cardiovascular disease (CVD) is facing challenges. There is multitudinous clear clinical evidence that the latest failures of HDL-C-raising drugs show no clear association with risks for CVD. At the genetic level, recent research indicates that steady-state HDL-C concentrations may provide limited information regarding the potential antiatherogenic functions of HDL. It is evident that the newer strategies may replace therapeutic approaches to simply raise plasma HDL-C levels. There is an urgent need to identify an efficient biomarker that accurately predicts the increased risk of atherosclerosis (AS) in patients and that may be used for exploring newer therapeutic targets. Studies from recent decades show that the composition, structure and function of circulating HDL are closely associated with high cardiovascular risk. A vast amount of data demonstrates that the most important mechanism through which HDL antagonizes AS involves the reverse cholesterol transport (RCT) process. Clinical trials of drugs that specifically target HDL have so far proven disappointing, so it is necessary to carry out review on the HDL therapeutics.

Mass Spectrometry-Based Proteomic Study Makes High-Density Lipoprotein a Biomarker for Atherosclerotic Vascular Disease

High-density lipoprotein (HDL) is a lipid and protein complex that consists of apolipoproteins and lower level HDL-associated enzymes. HDL dysfunction is a factor in atherosclerosis and decreases patient survival. Mass spectrometry- (MS-) based proteomics provides a high throughput approach for analyzing the composition and modifications of complex HDL proteins in diseases. HDL can be separated according to size, surface charge, electronegativity, or apoprotein composition. MS-based proteomics on subfractionated HDL then allows investigation of lipoprotein roles in diseases. Herein, we review recent developments in MS-based quantitative proteomic techniques, HDL proteomics and lipoprotein modifications in diseases, and HDL subfractionation studies. We also discuss future directions and perspectives in MS-based proteomics on HDL.

Learning from biology: synthetic lipoproteins for drug delivery

Synthetic lipoproteins represent a relevant tool for targeted delivery of biological/chemical agents (chemotherapeutics, siRNAs, photosensitizers, and imaging contrast agents) into various cell types. These nanoparticles offer a number of advantages for drugs delivery over their native counterparts while retaining their natural characteristics and biological functions. Their ultra-small size (<30 nm), high biocompatibility, favorable circulation half-life, and natural ability to bind specific lipoprotein receptors, i.e., low-density lipoprotein receptor (LDLR) and Scavenger receptor class B member 1 (SRB1) that are found in a number of pathological conditions (e.g., cancer, atherosclerosis), make them superior delivery strategies when compared with other nanoparticle systems. We review the various approaches that have been developed for the generation of synthetic lipoproteins and their respective applications in vitro and in vivo. More specifically, we summarize the approaches employed to address the limitation on use of reconstituted lipoproteins by means of natural or recombinant apolipoproteins, as well as apolipoprotein mimetic molecules. Finally, we provide an overview of the advantages and disadvantages of these approaches and discuss future perspectives for clinical translation of these nanoparticles.

Understanding high-density lipoprotein function in disease: recent advances in proteomics unravel the complexity of its composition and biology

Although the epidemiology of high-density lipoprotein (HDL) cholesterol and cardiovascular risk has been consistent, pharmacologic interventions to increase HDL-cholesterol by delaying HDL catabolism did not translate into reduction in cardiovascular risk. HDL particles are small, protein-rich when compared to other plasma lipoprotein classes. Latest progresses in proteomics technology have dramatically increased our understanding of proteins carried by HDL. In addition to proteins with well-established functions in lipid transport, iron transport proteins, members of the complement pathway, and proteins involved in immune function and acute phase response were repeatedly identified on HDL particles. With the unraveling of the complexity of the HDL proteome, different laboratories have started to monitor its changes in various disease states. In addition, dynamic aspects of HDL subgroups are being discovered. These recent studies clearly illustrate the promise of HDL proteomics for deriving new biomarkers for disease diagnosis and to measure the effectiveness of current and future treatment regimens. This review summarizes recent advances in proteomics and lipidomics helping to understand HDL function in health and disease.

High-density lipoprotein subfractions and carotid plaque: the Northern Manhattan Study

OBJECTIVE

The objective of this cross-sectional analysis was to investigate the relation between two major high-density lipoprotein cholesterol (HDL-C) subfractions (HDL2-C and HDL3-C) and carotid plaque in a population based cohort.

METHODS

We evaluated 988 stroke-free participants (mean age 66 ± 8 years; 40% men; 66% Hispanic and 34% Non-Hispanic) with available data on HDL subfractions using precipitation method and carotid plaque area and thickness assessed by a high-resolution 2D ultrasound. The associations between HDL-C subfractions and plaque measurements were analyzed by quantile regression.

RESULTS

Plaque was present in 56% of the study population. Among those with plaque, the mean ± SD plaque area was 19.40 ± 20.46 mm² and thickness 2.30 ± 4.45 mm. The mean ± SD total HDL-C was 46 ± 14 mg/dl, HDL2-C 14 ± 8 mg/dl, and HDL3-C 32 ± 8 mg/dl. After adjusting for demographics and vascular risk factors, there was an inverse association between HDL3-C and plaque area (per mg/dl: beta = -0.26 at the 75th percentile, p = 0.001 and beta = -0.32 at the 90th percentile, p = 0.02). A positive association was observed between HDL2-C and plaque thickness (per mg/dl; beta = 0.02 at the 90% percentile, p = 0.003). HDL-C was associated with plaque area (per mg/dl: beta = -0.18 at the 90th percentile, p = 0.01), but only among Hispanics.

CONCLUSION

In our cohort we observed an inverse association between HDL3-C and plaque area and a positive association between HDL2-C and plaque thickness. HDL-C subfractions may have different contributions to the risk of vascular disease. More studies are needed to fully elucidate HDL-C anti-atherosclerotic functions in order to improve HDL-based treatments in prevention of vascular disease and stroke.

Short communication: effects of omega-3 fatty acids on triglycerides and high-density lipoprotein subprofiles in HIV-infected persons with hypertriglyceridemia

Hypertriglyceridemia and low high-density lipoprotein (HDL)-cholesterol (HDL-C) may contribute to a presumed accelerated risk for cardiovascular disease in HIV-infected individuals. We evaluated the effect of omega-3 fatty acid treatment on triglycerides, low-density lipoprotein (LDL)-C, HDL-C, and HDL subpopulations. Forty-one HIV-seropositive subjects with hypertriglyceridemia (≥150 mg/dl) on active antiretroviral therapy were enrolled in this placebo-controlled, double-blind, randomized, crossover trial comparing the effects of omega-3 fatty acid treatment (1.9 g EPA and 1.5 g DHA) on triglycerides, LDL-C, HDL-C, and HDL subpopulations. An independent sample t-test was used to assess the study start to posttreatment change for all components. After omega-3 fatty acid treatment, triglyceride levels decreased 63.2±86.9 mg/dl (p<0.001). No significant changes in total cholesterol, LDL-C, or HDL-C were found. Within HDL subpopulations, significant changes were seen in the most atheroprotective HDL particles, α-1, which increased by 2.5±5.6 mg/dl (p<0.05), and preα-1, which increased by 0.6±1.0 mg/dl (p<0.001). Preα-3, a presumably atherogenic HDL particle, decreased by 0.5±0.9 mg/dl (p<0.01). Omega-3 fatty acid treatment significantly lowered triglyceride levels in HIV-positive patients with moderate hypertriglyceridemia. While no study-wide improvements in LDL-C or HDL-C were detected, the HDL subpopulation profile changed in a beneficial way suggesting more cardioprotection after treatment.

HIV/hepatitis C virus coinfection ameliorates the atherogenic lipoprotein abnormalities of HIV infection

BACKGROUND

Higher levels of small low-density lipoprotein (LDL) and lower levels of high-density lipoprotein (HDL) subclasses have been associated with increased risk of cardiovascular disease. The extent to which HIV infection and HIV/hepatitis C virus (HCV) coinfection are associated with abnormalities of lipoprotein subclasses is unknown.

METHODS

Lipoprotein subclasses were measured by nuclear magnetic resonance (NMR) spectroscopy in plasma samples from 569 HIV-infected and 5948 control participants in the Fat Redistribution and Metabolic Change in HIV Infection (FRAM), Coronary Artery Risk Development in Young Adults (CARDIA), and Multi-Ethnic Study of Atherosclerosis (MESA) studies. Multivariable regression was used to estimate the association of HIV and HIV/HCV coinfection with lipoprotein measures with adjustment for demographics, lifestyle factors, and waist-to-hip ratio.

RESULTS

Relative to controls, small LDL levels were higher in HIV-monoinfected persons (+381 nmol/l, P <0.0001), with no increase seen in HIV/HCV coinfection (-16.6 nmol/l). Levels of large LDL levels were lower (-196 nmol/l, P <0.0001) and small HDL were higher (+8.2 μmol/l, P < 0.0001) in HIV monoinfection with intermediate values seen in HIV/HCV coinfection. Large HDL levels were higher in HIV/HCV-coinfected persons relative to controls (+1.70 μmol/l, P <0.0001), whereas little difference was seen in HIV-monoinfected persons (+0.33, P = 0.075). Within HIV-infected participants, HCV was associated independently with lower levels of small LDL (-329 nmol/l, P <0.0001) and small HDL (-4.6 μmol/l, P <0.0001), even after adjusting for demographic and traditional cardiovascular risk factors.

CONCLUSION

HIV-monoinfected participants had worse levels of atherogenic LDL lipoprotein subclasses compared with controls. HIV/HCV coinfection attenuates these changes, perhaps by altering hepatic factors affecting lipoprotein production and/or metabolism. The effect of HIV/HCV coinfection on atherosclerosis and the clinical consequences of low small subclasses remain to be determined.

Does plasma HDL-C concentration interact with whole-body cholesterol metabolism?

This review examines the interactions between plasma high density lipoprotein (HDL) metabolism and whole-body cholesterol economy. More specifically, this review addresses three questions: 1) does plasma HDL-C concentration correlate with the parameters of whole-body cholesterol metabolism? 2) Do variations in cholesterol metabolism interfere with plasma HDL-C concentrations? 3) Are the markers of cholesterol synthesis and intestinal absorption specifically under the control of plasma HDL? The following answers were provided to each question, respectively: 1) plasma HDL influences whole-body cholesterol synthesis rate but the evidence that HDL modifies the total amount of cholesterol absorbed by the intestine is not clearly supported by present investigations; 2) there are suggestions that changes in whole body cholesterol metabolism rates do not interfere with plasma HDL-C concentrations; 3) markers of cholesterol synthesis and absorption may specifically be controlled by plasma HDL-C concentrations regarding the genetic causes of extremely low HDL-C concentrations, although within the general population plasma HDL-C concentration is likely ascribed to insulin resistance or diabetes mellitus.

High-density lipoprotein subclasses and risk of stroke and its subtypes in Japanese population: the Circulatory Risk in Communities Study

BACKGROUND AND PURPOSE

High-density lipoprotein (HDL) cholesterol is an established protective factor for ischemic stroke. However, the contribution of HDL subclasses to stroke risk and its subtypes is uncertain.

METHODS

A prospective nested case-control study of 40- to 85-year-old Japanese was undertaken using frozen serum samples collected from 5280 men and 7524 women. They participated in cardiovascular risk surveys from 1985 to 1999 (1 community) and 1989 to 1998 (2 communities) under Circulatory Risk in Communities Study. HDL cholesterol subclasses were classified by high-performance liquid chromatography into 3 subgroups: S-HDL (very small or small HDL), M-HDL (medium HDL), and L-HDL (large or very large HDL) cholesterol. One control subject per case was matched by sex, age, community, serum storage year, and fasting status.

RESULTS

In 2005, we identified 241 strokes (155 ischemic and 86 hemorrhagic). S-HDL and M-HDL cholesterol levels were inversely associated with total stroke risk, ischemic stroke, specifically lacunar infarction, and hemorrhagic stroke. After adjustment for cardiovascular risk factors, these associations remained statistically significant. Multivariable conditional odds ratios (95% confidence interval) for 1 SD (0.12 mmol/L) increment of S-HDL cholesterol levels were 0.34 (0.23-0.52) for total stroke, 0.38 (0.23-0.63) for ischemic stroke, 0.33 (0.18-0.61) for lacunar infarction, 0.30 (0.14-0.65) for hemorrhagic stroke, and 0.30 (0.12-0.77) for intraparenchymal hemorrhage. The respective multivariable odds ratios for 1SD (0.10 mmol/L) increment of M-HDL cholesterol levels were 0.56 (0.41-0.75), 0.63 (0.45-0.88), 0.59 (0.40-0.87), 0.41 (0.21-0.80), and 0.38 (0.16-0.90). No associations were found between L-HDL cholesterol levels and risk of total stroke and its subtypes.

CONCLUSIONS

Small- to medium-sized HDL, not large HDL, cholesterol levels were inversely associated with total stroke risk.

Reverse cholesterol transport in familial hypercholesterolemia

PURPOSE OF REVIEW

Familial hypercholesterolemia is characterized by a major elevation in circulating LDL-cholesterol levels, cholesterol deposition within the arterial wall and an increased risk of premature coronary artery disease. The reverse cholesterol transport (RCT) is now considered as a key process that protects against development of atherosclerosis. The major antiatherogenic action of HDL particles is intimately linked to their determinant role in RCT pathway. However, the steady-sate of HDL-cholesterol levels does not represent the optimal marker to evaluate the efficiency of the RCT in all circumstances.

RECENT FINDINGS

By using ex-vivo systems for the evaluation of the efficacy of RCT a strong inverse relationship between HDL efflux capacity from macrophages and atherosclerosis progression has been demonstrated. Low HDL-C phenotype observed in familial hypercholesterolemia patients is associated with defective capacities of HDL particles to mediate major steps of the centripetal movement of cholesterol from peripheral cells to feces. However, current available treatment used to reduce LDL-C to therapeutic goals does not correct altered functions of HDL particles in humans.

SUMMARY

In the context of familial hypercholesterolemia, a growing body of evidence suggests that impaired efficacy of the RCT pathway contributes significantly to the progression of atherosclerosis.

Genetic control of high density lipoprotein-cholesterol in AcB/BcA recombinant congenic strains of mice

Epidemiological studies show that high HDL-cholesterol (HDLc) decreases the risk of cardiovascular disease. To map genes controlling lipid metabolism, particularly HDLc levels, we screened the plasma lipids of 36 AcB/BcA RC mouse strains subjected to either a normal or a high-fat/cholesterol diet. Strains BcA68 and AcB65 showed deviant HDLc plasma levels compared with the parental A/J and C57BL/6J strains; they were thus selected to generate informative F2 crosses. Linkage analyses in the AcB65 strain identified a locus on chromosome 4 (Hdlq78) responsible for high post-high fat diet HDLc levels. This locus has been previously associated at genome-wide significance to two regions in the human genome. A second linkage analysis in strain BcA68 identified linkage in the vicinity of a gene cluster known to control HDLc levels. Sequence analysis of these candidates identified a de novo, loss-of-function mutation in the ApoA1 gene of BcA68 that prematurely truncates the ApoA1 protein. The possibility of dissecting the specific effects of this new ApoA1 deficiency in the context of isogenic controls makes the BcA68 mouse a valuable new tool.

Antiatherosclerotic Effect of Canarium odontophyllum Miq. Fruit Parts in Rabbits Fed High Cholesterol Diet

The effect of C. odontophyllum (CO) fruit parts was investigated in hypercholesterolemic rabbits. Forty-nine rabbits, which were randomly divided into seven groups of seven animals (n = 7), received a diet containing different parts of CO fruit parts for 8 weeks. The groups were as follows: (1) normal diet: NC group and (2) hypercholesterolemic diet: PC, HS (10 mg/kg/day simvastatin), HPO (20 g kg(-1) oil extracted from the pulp of CO), HKO (20 g kg(-1) oil extracted from the kernel of CO), HF (50 g kg(-1) fullfat pulp of CO), and HD (50 g kg(-1) defatted pulp of CO). Among these groups, rabbits receiving defatted pulp of CO showed the greatest cholesterol lowering effect as it had reduced plasma LDL-C, TC, and thiobarbiturate reactive substance (TBARS) levels as well as atherosclerotic plaques. The presence of high dietary fiber and antioxidants activity are potential factors contributing to the cholesterol lowering effect. Consequently, these results indicate the potential use of CO defatted pulp as a cholesterol lowering and antioxidant agent.

Lipids and lipoproteins and risk of different vascular events in the MRC/BHF Heart Protection Study

BACKGROUND

Low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol are established risk factors for vascular disease, but lipoprotein particle concentrations may be stronger determinants of risk.

METHODS AND RESULTS

Associations between vascular events and baseline concentrations of cholesterol fractions, apolipoproteins B and A(1), and lipoprotein particles assessed by nuclear magnetic resonance were considered in the Heart Protection Study randomized trial of simvastatin versus placebo (>5000 vascular events during 5.3 years of follow-up among 20 000 participants). Major occlusive coronary events were equally strongly associated with the cholesterol- and particle-based total LDL measures; adjusted hazard ratios per 1-SD-higher level were 1.25 (95% confidence interval [CI], 1.16-1.34) for LDL cholesterol, 1.22 (95% CI, 1.14-1.32) for non-HDL cholesterol, 1.23 (95% CI, 1.15-1.33) for apolipoprotein B, and 1.25 (95% CI, 1.16-1.35) for LDL particle number. Given the total LDL particle number, the distribution between small and large particles did not add predictive value. Associations of these different LDL-related measures were similar with arterial revascularization procedures but much weaker or nonexistent with ischemic stroke and other cardiac events (mainly heart failure). After adjustment for LDL particle number, the hazard ratios for major occlusive coronary event per 1-SD-higher level were 0.91 (95% CI, 0.86-0.96) for HDL cholesterol and 0.89 (95% CI, 0.85-0.93) for HDL particle number. Other cardiac events were inversely associated with total (hazard ratio, 0.84; 95% CI, 0.79-0.90) and small (0.82; 95% CI, 0.76-0.89) HDL particle number but only very weakly associated with HDL cholesterol (0.94; 95% CI, 0.88-1.00).

CONCLUSIONS

In a population at 2% average coronary event risk per year, cholesterol, apolipoprotein, and particle measures of LDL were strongly correlated and had similar predictive values for incident major occlusive vascular events. It is unclear whether the associations between HDL particle numbers and other cardiac events represent a causal or reverse-causal effect.

Effect of dalcetrapib plus pravastatin on lipoprotein metabolism and high-density lipoprotein composition and function in dyslipidemic patients: results of a phase IIb dose-ranging study

BACKGROUND

Cholesteryl ester transfer protein (CETP) is involved in high-density lipoprotein (HDL) remodeling and transfer of lipids between HDL particles and other lipoproteins. Epidemiologic studies show that both elevated HDL-cholesterol (HDL-C) and reduced CETP activity attenuate cardiovascular risk, making inhibition or modulation of CETP a potential therapeutic target. This study analyzed the effect of dalcetrapib on lipoprotein profile, CETP activity, and cellular cholesterol efflux when co-administered with pravastatin in patients with low or average HDL-C.

METHODS

Patients were randomized in a double-blind fashion to receive placebo or dalcetrapib 300, 600, or 900 mg once daily for 12 weeks. All patients were concomitantly treated to their low-density lipoprotein cholesterol target with pravastatin. Lipoprotein profile was analyzed by nuclear magnetic resonance spectroscopy and polyacrylamide gradient gel electrophoresis. Composition of the HDL fraction was assessed after polyethylene glycol precipitation. Contribution of this fraction to cholesterol efflux was assessed using radiolabeled donor cells.

RESULTS

Co-administration of dalcetrapib with pravastatin increased HDL-C, apolipoproteins (apo) A-I and A-II, and CETP mass, and decreased CETP activity. A relative increase in large HDL and low-density lipoprotein subparticle fractions was observed. High-density lipoprotein composition showed increased association of esterified cholesterol, free cholesterol, phospholipids, apo A-I, and apo E. Adenosine 5'-triphosphate-binding cassette A1- and scavenger receptor type BI-mediated cholesterol efflux increased.

CONCLUSIONS

Dalcetrapib up to 600 mg, combined with pravastatin, increased HDL-C and altered lipoprotein profile, HDL composition, and HDL function, with little further change at a 900-mg dose. The impact on cardiovascular events in dyslipidemic patients is being evaluated.

Niacin extended-release/simvastatin combination therapy produces larger favorable changes in high-density lipoprotein particles than atorvastatin monotherapy

Background

The purpose of this research was to compare the effects of niacin extended-release in combination with simvastatin (NER/S) versus atorvastatin monotherapy on high-density lipoprotein (HDL) particle number and size in patients with hyperlipidemia or dyslipidemia from the SUPREME study.

Methods

This was a post hoc analysis of patients (n = 137) who completed the SUPREME study and who had lipid particle number and size measurements at both baseline and at week 12 by nuclear magnetic resonance spectroscopy. Following ≥4 weeks without lipid-modifying therapy (washout period), the patients received NER/S 1000/40 mg/day for 4 weeks followed by NER/S 2000/40 mg/day for 8 weeks, or atorvastatin 40 mg/day for 12 weeks. Median percent changes in HDL particle number and size from baseline to week 12 were compared between the NER/S and atorvastatin treatment groups using the Wilcoxon rank-sum test. Distribution of HDL particle subclasses at week 12 was compared between the treatment groups using the Cochran–Mantel–Haenszel test.

Results

Treatment with NER/S resulted in a significantly greater percent reduction in small HDL particle number at week 12 compared with atorvastatin monotherapy (−1.8% versus 4.2%, P = 0.014), and a numerically greater percent increase in large HDL particle number (102.4% versus 39.2%, P = 0.078) compared with atorvastatin monotherapy. A significantly greater percent increase in HDL particle size from baseline at week 12 was observed with NER/S compared with atorvastatin (6.0% versus 1.3%, P < 0.001). NER/S treatment also resulted in a significant shift in HDL particle size from small and medium at baseline to large at week 12 (P < 0.0001).

Conclusion

Treatment with NER/S resulted in larger favorable changes in number and size of HDL particle subclasses compared with atorvastatin monotherapy, including a numerically greater increase in number of large HDL particles, and a significantly greater decrease in number of small HDL particles compared with atorvastatin monotherapy. In addition, NER/S treatment resulted in a significant change in HDL particle size distribution from small and medium to large.

Apolipoprotein A-II-mediated conformational changes of apolipoprotein A-I in discoidal high density lipoproteins

It is well accepted that HDL has the ability to reduce risks for several chronic diseases. To gain insights into the functional properties of HDL, it is critical to understand the HDL structure in detail. To understand interactions between the two major apolipoproteins (apos), apoA-I and apoA-II in HDL, we generated highly defined benchmark discoidal HDL particles. These particles were reconstituted using a physiologically relevant phospholipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) incorporating two molecules of apoA-I and one homodimer of apoA-II per particle. We utilized two independent mass spectrometry techniques to study these particles. The techniques are both sensitive to protein conformation and interactions and are namely: 1) hydrogen deuterium exchange combined with mass spectrometry and 2) partial acetylation of lysine residues combined with MS. Comparison of mixed particles with apoA-I only particles of similar diameter revealed that the changes in apoA-I conformation in the presence of apoA-II are confined to apoA-I helices 3-4 and 7-9. We discuss these findings with respect to the relative reactivity of these two particle types toward a major plasma enzyme, lecithin:cholesterol acyltransferase responsible for the HDL maturation process.

High-density lipoprotein subspecies between patients with type 1 diabetes and type 2 diabetes without / with intensive insulin therapy

The reduced levels of high-density lipoprotein (HDL) 2-cholesterol (C) in diabetes and other metabolic disorders associated with a high risk of cardiovascular disease are well established. Few studies, however, have compared the HDL subspecies in type 1 diabetes (T1D) with those in type 2 diabetes (T2D) with or without insulin. We examined HDL subspecies in 27 T1D with insulin, 33 T2D with insulin or insulin plus oral-anti-diabetic drugs (OADs), 36 T2D with OADs or diet/exercise, and 25 non-diabetic controls. Insulin was injected four times daily in a basal-bolus manner for both T1D and T2D. Plasma levels of C, apolipoprotein (apo) AI, and AII were determined in HDL2 and HDL3 by the single precipitation method. HDL-C levels were significantly higher in T1D and lower in T2D, compared with the controls. Insulin-treated T2D had higher HDL-C than non-insulin-treated T2D. T1D had higher HDL2-C and HDL2-apo AI levels than T2D. Insulin-treated T2D had higher HDL2-C and HDL2-apo AI levels than non-insulin-treated T2D. All of these differences were more pronounced for men than for women. HDL3 levels were comparable among controls,T1D and T2D. HDL2-C levels were inversely associated with BMI, HbA1c, triglyceride, small dense LDL-C, and LDL-C. Multiple regression analysis revealed that HDL2-C was independently associated with triglyceride, LDL-C, and intensive insulin therapy but not with HbA1c. In conclusion, these results suggest that intensive insulin therapy is associated with alterations of HDL subspecies, irrespective of the type of diabetes.

Preparation and characterization of a lovastatin-loaded protein-free nanostructured lipid carrier resembling high-density lipoprotein and evaluation of its targeting to foam cells

This study was designed to investigate whether a non-protein nanostructured lipid carrier (NLC) resembling high-density lipoprotein (HDL) could deliver a hydrophobic anti-atherogenic drug, lovastatin, to foam cells. Lovastatin-loaded NLC (LT-NLC) was prepared by a nanoprecipitation/solvent diffusion method. The LT-NLC-apoprotein (LT-NLC-apo) was prepared by incubating LT-NLC with native HDL. The physicochemical parameters of LT-NLC were characterized in terms of particle size, zeta potential, morphology, entrapment efficiency, and crystallization behavior. Targeting behavior and mechanism were demonstrated by the incubation of LT-NLC-apo with a RAW 264.7 macrophage-derived foam cell model in the presence or absence of very-low-density lipoprotein (VLDL) and lipase. The results showed that LT-NLC was solid spherical or oval in shape with an average diameter of 13.8 ± 2.2 nm, zeta potential of −29.3 ± 0.2 mV and entrapment efficiency of 96.2 ± 1.3%. Phagocytosis studies showed that uptake of LT-NLC-apo by macrophages was significantly lower than LT-NLC (p < 0.01), suggesting that LT-NLC-apo could possibly escape recognition from macrophages in vivo. The uptake was increased twofold when LT-NLC-apo was incubated with transfected foam cells containing VLDL and lipase. These results indicated that non-protein NLC resembling HDL could be a useful tool to deliver lipophilic anti-atherogenic drugs to foam cells, and that uptake could be enhanced by the VLDL receptor pathway.

Dietary omega-3 polyunsaturated fatty acid intake is related to a protective high-density lipoprotein subspecies profile independent of genetic effects: a monozygotic twin pair study

BACKGROUND

Studies on diet and high-density lipoprotein (HDL) subspecies distribution are limited.

OBJECTIVE

We examined the relationship between macronutrient composition and lipoprotein particle size and HDL subspecies independent of genetic effects by studying monozygotic (MZ) twins.

METHODS

24 healthy MZ twin pairs aged 23-33 years were identified from two longitudinal population-based studies, FinnTwin16 and FinnTwin12. Total energy and nutrient intake were assessed with 3-day food records and physical activity was measured by the Baecke index. HDL subspecies distribution was determined by non-denaturing gradient gel electrophoresis. Associations between diet composition and HDL mean particle size were determined by multivariate nutrient density models adjusted for confounding variables.

RESULTS

Substituting one energy percentage from omega-3 polyunsaturated fatty acids (n-3 PUFAs) for a corresponding amount of energy from other type of fats was related to changes in the relative proportions of the HDL subspecies 2b, 3a and 3b toward a larger mean particle size in men (β ± SE: 1.00 ± 0.26 nm, p = 0.004) and women (β ± SE: 0.90 ± 0.21 nm, p = 0.001). This association remained significant in analyses controlling for genetic and shared environmental influences using within-pair differences of the measures in MZ twin pairs (β ± SE: 0.37 ± 0.14 nm, p = 0.019). Twins with the higher n-3 PUFA intake had significantly higher proportions of large HDL(2b) particles and lower proportions of smaller-sized HDL(3a) and HDL(3b) particles as compared to their co-twins with lower intakes (p < 0.05).

CONCLUSIONS

Our data suggest that n-3 PUFA intake is associated with a favorable change in the distribution of HDL subspecies towards larger particles independent of genetic and shared environmental factors.

Imaging apolipoprotein AI in vivo

Coronary disease risk increases inversely with high-density lipoprotein (HDL) level. The measurement of the biodistribution and clearance of HDL in vivo, however, has posed a technical challenge. This study presents an approach to the development of a lipoprotein MRI agent by linking gadolinium methanethiosulfonate (Gd[MTS-ADO3A]) to a selective cysteine mutation in position 55 of apo AI, the major protein of HDL. The contrast agent targets both liver and kidney, the sites of HDL catabolism, whereas the standard MRI contrast agent, gadolinium-diethylenetriaminepentaacetic acid-bismethylamide (GdDTPA-BMA, gadodiamide), enhances only the kidney image. Using a modified apolipoprotein AI to create an HDL contrast agent provides a new approach to investigate HDL biodistribution, metabolism and regulation in vivo.

A novel fluorogenic substrate for the measurement of endothelial lipase activity

Endothelial lipase (EL) is a phospholipase A1 (PLA1) enzyme that hydrolyzes phospholipids at the sn-1 position to produce lysophospholipids and free fatty acids. Measurement of the PLA1 activity of EL is usually accomplished by the use of substrates that are also hydrolyzed by lipases in other subfamilies such as PLA2 enzymes. In order to distinguish PLA1 activity of EL from PLA2 enzymatic activity in cell-based assays, cell supernatants, and other nonhomogeneous systems, a novel fluorogenic substrate with selectivity toward PLA1 hydrolysis was conceived and characterized. This substrate was preferred by PLA1 enzymes, such as EL and hepatic lipase, and was cleaved with much lower efficiency by lipases that exhibit primarily triglyceride lipase activity, such as LPL or a lipase with PLA2 activity. The phospholipase activity detected by the PLA1 substrate could be inhibited with the small molecule esterase inhibitor ebelactone B. Furthermore, the PLA1 substrate was able to detect EL activity in human umbilical vein endothelial cells in a cell-based assay. This substrate is a useful reagent for identifying modulators of PLA1 enzymes, such as EL, and aiding in characterizing their mechanisms of action.

Adeno-associated virus serotype 2 mediated transduction and coexpression of the human apoAI and SR-BI gene in HepG2 cells

Cholesterol efflux is the first step in the reverse cholesterol transport (RCT) pathway, removing excess cholesterol from tissues, including the arterial wall, thus preventing the development of atherosclerosis. Adeno-associated virus (rAAV) has demonstrated significant promise as a DNA-delivery vector to treat serious human diseases. In this study, we constructed recombinant adeno-associated viruses coexpressing apoAI and SR-BI successfully, the double gene mRNA and protein were both strongly expressed in transduced HepG2 cells. A novel safe and efficient method of promoting the reverse cholesterol transport (RCT) may be established. These results may provide a new method for gene therapy of Arteriosclerosis.

The biological properties of iron oxide core high-density lipoprotein in experimental atherosclerosis

Lipoproteins are a family of plasma nanoparticles responsible for the transportation of lipids throughout the body. High-density lipoprotein (HDL), the smallest of the lipoprotein family, measures 7-13 nm in diameter and consists of a cholesteryl ester and triglyceride core that is covered with a monolayer of phospholipids and apolipoproteins. We have developed an iron oxide core HDL nanoparticle (FeO-HDL), which has a lipid based fluorophore incorporated in the phospholipid layer. This nanoparticle provides contrast for optical imaging, magnetic resonance imaging (MRI) and transmission electron microscopy (TEM). Consequently, FeO-HDL can be visualized on the anatomical, cellular and sub-cellular level. In the current study we show that the biophysical features of FeO-HDL closely resemble those of native HDL and that FeO-HDL possess the ability to mimic HDL characteristics both in vitro as well as in vivo. We demonstrate that FeO-HDL can be applied to image HDL interactions and to investigate disease settings where HDL plays a key function. More generally, we have demonstrated a multimodal approach to study the behavior of biomaterials in vitro as well as in vivo. The approach allowed us to study nanoparticle dynamics in circulation, as well as nanoparticle targeting and uptake by tissues and cells of interest. Moreover, we were able to qualitatively assess nanoparticle excretion, critical for translating nanotechnologies to the clinic.