High Density Lipoprotein Distribution Research Articles

High density lipoprotein heterogeneity & function among Indians with coronary artery disease.

Impaired high density lipoprotein (HDL) functionality has been shown to be associated with cardiovascular disease risk. The study was aimed to identify the alterations in HDL function [antioxidative activity (AOA)] and subfraction distribution between acute coronary syndrome (ACS) and stable coronary artery disease (SCAD) individuals and analysing the accuracy of HDL parameters to discriminate between the groups. HDL subfraction distribution analysis was performed in 200 coronary artery disease patients (ACS and SCAD) and 60 control individuals using dextran sulphate, heparin and manganese chloride precipitation method. In terms of HDL function, AOA was evaluated by dihydrorhodamine-based fluorescent cell-free assay and paraoxonase (PON1) enzyme paraoxonase and arylesterase activity. We found that higher AOA [odds ratio (95% confidence interval {CI})]: 0.09 (0.02-0.44), P<0.01 for SCAD; 0.008 (0.001-0.07), P<0.001 for ACS and higher PON1 activity [0.22 (0.8-0.59), P<0.01 for SCAD; 0.16 (0.06-0.4), P<0.001 for ACS] were associated with a lower odds of developing coronary artery disease (CAD). AOA of apoB-depleted serum was significantly correlated with HDL2-C/HDL3-C (HDL-cholesterol) ratio in controls (r=-0.31, P=0.01) and ACS (r=-0.18, P=0.04). It was observed that AOA and HDL subfraction distribution together could discriminate between the two groups of CAD with an accuracy of 72.8 per cent (P=0.004). Impaired AOA and altered subfraction distribution of HDL may be responsible for its diminished anti-athero protective activity and can discriminate between the two groups of CAD individuals.

Effects of Peroxyl Radicals on the Structural Characteristics and Fatty Acid Composition of High-Density Lipoprotein from Duck Egg Yolk

In this study, high-density lipoprotein (HDL) from duck egg yolk was subjected to oxidation with a system based on 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH)-derived peroxyl radicals. The effects of peroxyl radicals on the protein carbonyl, free sulfhydryl, secondary/tertiary structure, surface hydrophobicity, solubility, particle size distribution, zeta potential and fatty acid composition of HDL were investigated by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Fourier-transform infrared spectroscopy (FTIR), circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The results indicated that the content of protein carbonyl was significantly increased, that of free sulfhydryl was obviously reduced, and the ordered secondary structure was also decreased with increasing AAPH concentration. In addition, the surface hydrophobicity and solubility of HDL showed apparent increases due to the exposure of hydrophobic groups and aggregation of protein caused by oxidation. The fatty acid composition of HDL exhibited pronounced changes due to the disrupted protein–lipid interaction and lipid oxidation by AAPH-derived peroxyl radicals. These results may help to elucidate the molecular mechanism for the effect of lipid oxidation products on the oxidation of duck yolk proteins.

Thioredoxin Domain Containing 5 Suppression Elicits Serum Amyloid A-Containing High-Density Lipoproteins.

Thioredoxin domain containing 5 (TXNDC5) is a protein disulfide isomerase involved in several diseases related to oxidative stress, energy metabolism and cellular inflammation. In a previous manuscript, a negative association between fatty liver development and hepatic Txndc5 expression was observed. To study the role of TXNDC5 in the liver, we generated Txndc5-deficient mice. The absence of the protein caused an increased metabolic need to gain weight along with a bigger and fatter liver. RNAseq was performed to elucidate the putative mechanisms, showing a substantial liver overexpression of serum amyloid genes (Saa1, Saa2) with no changes in hepatic protein, but discrete plasma augmentation by the gene inactivation. Higher levels of malonyldialdehyde, apolipoprotein A1 and platelet activating factor-aryl esterase activity were also found in serum from Txndc5-deficient mice. However, no difference in the distribution of high-density lipoproteins (HDL)-mayor components and SAA was found between groups, and even the reactive oxygen species decreased in HDL coming from Txndc5-deficient mice. These results confirm the relation of this gene with hepatic steatosis and with a fasting metabolic derive remedying an acute phase response. Likewise, they pose a new role in modulating the nature of HDL particles, and SAA-containing HDL particles are not particularly oxidized.

Quantile-specific heritability of high-density lipoproteins with implications for precision medicine

We have previously shown that the effect of a high-density lipoprotein (HDL) genetic risk score depends on whether the phenotype (HDL cholesterol) is high or low relative to its distribution (quantile-dependent expressivity). Evidence for quantile-dependent expressivity was sought using a more inclusive genetic measure (quantile-specific heritability, h2) in a larger population (Framingham cohort). Quantile regression was used to test whether the offspring-parent (βOP) and full-sib (βFS) regression slopes increased with the percentiles of the offspring's HDL distribution in 10,650 parent-offspring pairs and 2130 sibships. Quantile-specific heritability was estimated by 2βOP/(1+ rspouse) and [(8βFSrspouse+ 1)0.5-1]/(2rspouse), where rspouse is the spouse correlation. HDL cholesterol heritability estimated from βOP increased significantly (P=4.2×10-5) from the 10th (h2 ± SE: 0.44±0.03), 25th (0.45±0.03), 50th (0.47±0.03), and 75th (0.56±0.04) to the 90th percentiles (0.65±0.06) of the offspring's age- and sex-adjusted HDL cholesterol distribution. Heritability estimated from βFS also increased significantly with the percentiles of the offspring's HDL cholesterol (P=.002), apo A1 (P=.006), HDL2 cholesterol (P=.003), and HDL3 cholesterol distribution (P=.02). Consistent with quantile-dependent expressivity, published pharmacologic and nutritional interventions that raised (eg, statin, fibrates, estrogen replacement therapy, efavirenz, and dietary fat) or lowered HDL cholesterol concentrations (tamoxifen, dietary carbohydrate) correspondingly increased and decreased genetic effects. HDL cholesterol heritability increased with increasing percentile of the offspring's HDL distribution. Whereas precision medicine is based on the premise that genetic markers identify patients most likely to benefit from drugs and diet, quantile-dependent expressivity postulates that the strong signals from these genetic markers simply trace the heritability increase with increasing plasma HDL concentrations. Thus, quantile-dependent expressivity provides an alternative interpretation to these genotype-specific effects.

ApoE and apoC-III-defined HDL subtypes: a descriptive study of their lecithin cholesterol acyl transferase and cholesteryl ester transfer protein content and activity

BackgroundThe functionality of high-density lipoproteins (HDL) is a better cardiovascular risk predictor than HDL concentrations. One of the key elements of HDL functionality is its apolipoprotein composition. Lecithin-cholesterol acyl transferase (LCAT) and cholesterol-ester transfer protein (CETP) are enzymes involved in HDL-mediated reverse cholesterol transport. This study assessed the concentration and activity of LCAT and CETP in HDL subspecies defined by their content of apolipoproteins E (apoE) and C-III (apoC-III) in humans.MethodsEighteen adults (ten women and eight men, mean age 55.6, BMI 26.9 Kg/m2, HbA1c 5.4%) were studied. HDL from each participant were isolated and divided into four subspecies containing respectively: No apoE and no apoC-III (E-C-), apoE but not apoC-III (E + C-), apoC-III but no apoE (E-C+) and both apoE and apoC-III (E + C+). The concentration and enzymatic activity of LCAT and CETP were measured within each HDL subspecies using immunoenzymatic and fluorometric methods. Additionally, the size distribution of HDL in each apolipoprotein-defined fraction was determined using non-denaturing electrophoresis and anti-apoA-I western blotting.ResultsHDL without apoE or apoC-III was the predominant HDL subtype. The size distribution of HDL was very similar in all the four apolipoprotein-defined subtypes. LCAT was most abundant in E-C- HDL (3.58 mg/mL, 59.6% of plasma LCAT mass), while HDL with apoE or apoC-III had much less LCAT (19.8, 12.2 and 8.37% of plasma LCAT respectively for E + C-, E-C+ and E + C+). LCAT mass was lower in E + C- HDL relative to E-C- HDL, but LCAT activity was similar in both fractions, signaling a greater activity-to-mass ratio associated with the presence of apoE. Both CETP mass and CETP activity showed only slight variations across HDL subspecies. There was an inverse correlation between plasma LCAT activity and concentrations of both E-C+ pre-beta HDL (r = − 0.55, P = 0.017) and E-C- alpha 1 HDL (r = − 0.49, P = 0.041). Conversely, there was a direct correlation between plasma CETP activity and concentrations of E-C+ alpha 1 HDL (r = 0.52, P = 0.025).ConclusionsThe presence of apoE in small HDL is correlated with increased LCAT activity and esterification of plasma cholesterol. These results favor an interpretation that LCAT and apoE interact to enhance anti-atherogenic pathways of HDL.

A Study of Serum Lipid Profile Changes in Children with Dengue Haemorrhagic Fever and its Correlation with Severity in a Tertiary Care Hospital

Introduction: Dengue Virus (DENV) infection now remains as the most rapidly spreading viral disease worldwide. Lower lipid level occurs in critically ill patients with DENV infection and is postulated as an independent predictor of the clinical outcome. Aim: To find the correlation between serum lipid levels and severity in children admitted with various grades of Dengue Haemorrhagic Fever (DHF) and secondarily to correlate serum lipid levels with factors like platelet count and duration of hospital stay. Materials and Methods: This was a prospective descriptive study done in the Paediatric ward from October 2019 to December 2019. Febrile Children with a platelet count of less than 1 lakh/cu.mm and positive for DENV IgM antibodies by Enzyme Linked Immuno Sorbent Assay (ELISA) formed the study group. Demographic details, number of days of fever on admission, duration of stay in hospital and severity grading of DENV infection as per the National guidelines were collected. These children were evaluated with Complete Blood Counts (CBC), fasting lipid profile, X-ray chest and ultrasound abdomen. Mean and standard deviation was used for categorical variables. Chi-square test was used to assess the strength of association between lipids and severity of DENV infections. Pearson correlation coefficient was used to assess R value between length of stay and serum lipid levels. Results: The Total Cholesterol, Low Density Lipoprotein (LDL), Triglyceride and Very Low Density Lipoprotein (VLDL) showed a simple linear decline as the severity grade advanced from grade I to grade IV. However, statistical significance was found only for total cholesterol and LDL with p-values of 0.046 and 0.041 respectively. The distribution of High Density Lipoprotein (HDL) across the grades of severity did not follow any pattern and was randomly distributed. On analysis of Pearson correlation between number of days of hospital stay and lipid profile, statistical significance was observed for LDL alone (p=0.023). Conclusion: The serum levels of total cholesterol and LDL were significantly reduced in severe grades of DHF. Serum levels of total cholesterol and LDL can be used as an economical surrogate marker to predict the severity of DHF at the time of admission.

Microencapsulated Pomegranate Reverts High-Density Lipoprotein (HDL)-Induced Endothelial Dysfunction and Reduces Postprandial Triglyceridemia in Women with Acute Coronary Syndrome.

(1) Background: the composition of high-density lipoproteins (HDL) becomes altered during the postprandial state, probably affecting their functionality vis-à-vis the endothelium. Since acute coronary syndrome (ACS) in women is frequently associated with endothelial dysfunction, it is likely that HDL are unable to improve artery vasodilation in these patients. Therefore, we characterized HDL from women with ACS in fasting and postprandial conditions. We also determined whether microencapsulated pomegranate (MiPo) reverts the HDL abnormalities, since previous studies have suggested that this fruit improves HDL functionality. (2) Methods: Eleven women with a history of ACS were supplemented daily with 20 g of MiPo, for 30 days. Plasma samples were obtained during fasting and at different times, after a lipid load test to determine the lipid profile and paraoxonase–1 (PON1) activity. HDL were isolated by sequential ultracentrifugation to determine their size distribution and to assess their effect on endothelial function, by using an in vitro model of rat aorta rings. (3) Results: MiPo improved the lipid profile and increased PON1 activity, as previously reported, with fresh pomegranate juice. After supplementation with MiPo, the incremental area under the curve of triglycerides decreased to half of the initial values. The HDL distribution shifted from large HDL to intermediate and small-size particles during the postprandial period in the basal conditions, whereas such a shift was no longer observed after MiPo supplementation. Consistently, HDL isolated from postprandial plasma samples hindered the vasodilation of aorta rings, and this endothelial dysfunction was reverted after MiPo consumption. (4) Conclusions: MiPo exhibited the same beneficial effects on the lipid profile and PON1 activity as the previously reported fresh pomegranate. In addition, MiPo supplementation reverted the negative effects of HDL on endothelial function generated during the postprandial period in women with ACS.

Protein markers of dysfunctional HDL in scavenger receptor class B type I deficient mice

BackgroundScavenger receptor class B type I (SR-BI) plays a key role in high density lipoproteins (HDL) metabolism. SR-BI deficiency in mice results in enhanced susceptibility to atherosclerosis with abnormal large, cholesterol enriched, and functional impaired HDL. This study was to characterize the protein markers of dysfunctional HDL in SR-BI deficient (SR-BI−/−) mice and to test if the defective of HDL might be affected by probucol treatment.MethodsShotgun proteomics and 2-D gel electrophoresis were performed to examine the profile of HDL protein and distribution of HDL particles isolated from SR-BI−/− mice. HDL’s cell-function, paraoxonase 1 (PON1) and myeloperoxidase activity were assessed. The mice were treated with 1.2 mg/g/day probucol for 6 weeks and the impact on HDL protein markers was analyzed. The differential proteins were quantified by Western blotting.ResultsThe relative amount of protein in SR-BI−/− HDL was decreased by about 25% compared to that in HDL from wild type (WT) mice. Compared to WT HDL, relative protein abundance of representative apoAI and PON1 in SR-BI−/− HDL were significantly reduced, whereas acute-phase protein serum amyloid A (SAA) and apoAIV, proteinase inhibitor proteins α-1-antitrypsin (A1AT) were increased. The distribution of plasma apoAI-containing HDL particles in SR-BI−/− mice was also dramatically altered, although plasma apoAI level was no difference. The protein alterations were accompanied with dysfunction of SR-BI−/− HDL, evidenced by impaired cholesterol homeostasis in macrophages, and reduced anti-oxidative and anti-inflammatory effects. Probucol treatment of SR-BI−/− mice could restored the relative contents of critical proteins including apoAI, PON1, SAA, apoAIV and A1AT on HDL, and improve HDL dysfunction despite decreased HDL-C level.ConclusionSR-BI deficiency leading to dysfunctional HDL is closely related to alteration of HDL protein, suggesting that identification of apoAI, PON1, SAA, apoAIV, and A1AT may serve as the valuable protein markers for diagnosis and therapeutics of dysfunctional HDL-related metabolic diseases.

Alterations of HDL Particles in Children with End-stage Renal Disease.

SummaryBackgroundUnfavorable lipid profile presents one of most important risk factor for cardiovascular disease in renal pathology. Myeloperoxidase (MPO) as enzyme which oxidizes lipoproteins and paraoxonase1 (PON1) as anti-oxidative enzyme have been involved in pathogenesis of cardiovascular disease. In the present study we sought to assess oxidative stress status, lipoprotein subclasses distribution as well as functionality of high density lipoprotein (HDL) trough MPO/PON1 ratio in children with chronic kidney disease (CKD) and children after renal transplantation.MethodsPON1 activity and oxidative stress parameters were measured spectrophotometrically, while MPO concentration was determined using immunoassay. Separation of lipoprotein subclasses was performed by vertical gradient gel electrophoresis in 19 children with different stage of CKD and 19 post-transplantation patients (PT).ResultsCKD patients had increased MPO/PON1 ratio and higher prevalence of smaller HDL subclasses when compared to PT subjects. Also, there was a significant positive correlation between MPO level and MPO/PON1 ratio with relative proportion of smaller HDL subclasses.ConclusionChildren with CKD have impaired HDL distribution that is improved after kidney transplantation. Since that measurement of HDL distribution and functionality are not routinely available, MPO/PON1 ratio may be useful marker that could provide necessary information.

Itinerary of high density lipoproteins in endothelial cells

High density lipoprotein (HDL) and its main protein component apolipoprotein A-I (ApoA-I) have multiple anti-atherogenic functions. Some of them are exerted within the vessel wall, so that HDL needs to pass the endothelial barrier. To elucidate their itinerary through endothelial cells (ECs), we labelled ApoA-I and HDL either fluorescently or with 1.4nm nanogold and investigated their cellular localization by using immunofluorescent microscopy (IFM) and electron microscopy (EM). HDL as well as ApoA-I is taken up by ECs into the same route of intracellular trafficking. Time kinetics and pulse chase experiments revealed that HDL is trafficked through different vesicles. HDL partially co-localized with LDL, albumin, and transferrin. HDL did not co-localize with clathrin and caveolin-1. Fluorescent HDL was recovered at small proportions in early endosomes and endosome to trans-golgi network vesicles but not at all in recycling endosomes, in late endosomes or lysosomes. EM identified HDL mainly in large filled vesicles which however upon IFM did not colocalize with markers of multivesicular bodies or autophagosomes. The uptake or cellular distribution of HDL was altered upon pharmacological interference with cytochalasine D, colchicine and dynasore. Blockage of fluid phase uptake with Amiloride or EIPA did not reduce the uptake of HDL. Neither did we observe any co-localization of HDL with dextran as the marker of fluid phase uptake. In conclusion, HDL and ApoA-I are internalized and trafficked by endothelial cells through a non-classical endocytic route.

Skew of Plasma Low- and High-Density Lipoprotein Distributions to Less Dense Subfractions in Normotriglyceridemic Chronic Kidney Disease Patients on Maintenance Hemodialysis Treatment

Background: Plasma levels of small, dense low-density lipoprotein (LDL) were reported to increase in chronic kidney disease (CKD) patients on hemodialysis (HD), but most of these patients were hypertriglyceridemic. Plasma levels of small, dense LDL are known to increase in hypertriglyceridemic subjects. Therefore, to investigate the direct effect of CKD on the distribution of LDL subfractions, we investigated the distribution of LDL subfractions in normotriglyceridemic CKD patients on HD. Methods: The levels of plasma lipoprotein subfractions and lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP), which markedly influence the distributions of plasma LDL and high-density lipoprotein (HDL) subfractions, were compared between 40 HD patients and 40 normolipidemic controls. Plasma lipoproteins were subfractionated into seven subfractions by ultracentrifugation. Results: Plasma levels of cholesterol (C) in remnant-like particle, which is equivalent to the triglyceride (TG)-rich lipoprotein remnant, were twice as high in HD patients as those in controls with matched TG levels. Plasma levels of C and TG in VLDL and IDL (intermediate density lipoprotein) were slightly higher in HD patients than in controls. The C/TG ratio of VLDL was significantly higher in HD patients than in controls. In comparison with the corresponding values in controls, the C and TG levels in low-density LDL and HDL₂ in HD patients were high, whereas those in medium-density LDL, high-density LDL, and HDL₃ were low. Plasma LCAT activity and CETP mass were lower in HD patients than in controls. Conclusion: Distribution of LDL and HDL skewed toward less dense fractions in normotriglyceridemic CKD patients on HD. A decrease in reverse C transport likely played an important role in these changes in the patients.

Exploring Avenues for Raising HDL Cholesterol

Exploring Avenues for Raising HDL Cholesterol

Abstract 106: Corticosteroid Treatment Induces Structural and Functional Changes in High-Density Lipoproteins

Rationale: We have previously shown that high-density lipoproteins (HDL) have potent anti-inflammatory properties. HDL levels are decreased in most inflammatory diseases. Corticosteroid therapy modifies lipoproteins profiles in subjects with chronic obstructive pulmonary disease (COPD) but results from these studies are inconsistent. Here, we hypothesize that in COPD subjects, prednisone treatment induces beneficial structural and functional changes in HDL thus improving HDL anti-inflammatory properties. Objectives: To elucidate the effect of prednisone on (i) HDL size, composition and subpopulation distribution (ii) the lipid and lipoprotein profiles of subjects with COPD and (iii) HDL anti-inflammatory properties. Methods: We recruited COPD subjects (n=11) treated with prednisone and people treated with antibiotics (n=6) for lower respiratory tract infections (control). Blood samples were collected on days 1, 5 of prednisone treatment and 6 weeks post-treatment. The treatment started with a high-dose (&gt;50 mg) and was reduced over a 5-7 day treatment period. We used gel-filtration chromatography to analyse plasma lipoprotein profiles. ApoA-I, apoA-II, apoB levels were determined immunoturbidometrically; total cholesterol, HDL-C, triglyceride and phospholipid concentrations were determined colorimetrically; and size distribution and surface charge of HDL were determined by 2-D gel electrophoresis. HDL was isolated from plasma and incubated for 16h on human endothelial cells (final protein concentration 1 mg/ml). Cells were further stimulated for 5h with TNF-α (0.2 ng/ml). Adhesion molecule expression (ICAM-1 and VCAM-1) was assessed by flow cytometry. Results: Plasma from prednisone treated subjects showed increased apoA-I (36%), apo-B (51%), total cholesterol (13%) and phospholipid (37%) levels and decreased plasma triglycerides (41%) relative to 6 weeks post-treatment. HDL-C levels were higher in subjects that received high-dose prednisone (0.94±0.21 mmol/L) compared to 6 weeks post-treatment (0.65±0.06 mmol/L) and antibiotic-treated subjects (0.43±0.17 mmol/L). HDL diameter in prednisone treated subjects increased from 7.9 nm to 10 nm. HDL from prednisone-treated subjects suppressed ICAM-1 (70%) and VCAM-1 (65%) protein expression more effectively than the HDL from 6-weeks post-treatment (25% and 12% respectively) or the HDL from the antibiotics-treated subjects (36% and 24% respectively) (p&lt;0.05 for all). Conclusions: In this study, we have shown the evidence that high-dose, short-term prednisone treatment increases HDL levels and improves their anti-inflammatory properties.

Waist circumference is a strong and independent determinant of the distribution of HDL subfractions in overweight patients with cardiovascular risk factors

Our aim was to determine the influence of waist circumference on the repartition of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) subfractions in patients with increased waist perimeter and one or more cardiovascular risk factor. All 117 patients without lipid-lowering therapy underwent routine clinical, biological evaluation and isolation of the following lipid subfractions: HDL2b, HDL2a, HDL3a, HDL3b, HDL3c and LDL1, LDL2, LDL3, LDL4. Mean waist circumference was 102.9 cm for women and 109.4 cm for men, and 92 patients presented with metabolic syndrome. In the highest waist circumference tertile, when compared with the lowest one, an increased HDL3c (7.7% vs. 5.7% p=0.02) and a non-significant decrease of HDL2b percentages were observed with no difference in other subfractions. In multivariate analysis, only plasma triglycerides and waist circumference remained independent predictors of HDL3c percentage. In our population, waist circumference was a strong and independent determinant of a shift in the distribution of HDL toward denser particles.

TheSrb1+1050TAllele Is Associated with Metabolic Syndrome in Children but Not with Cholesteryl Ester Plasma Concentrations of High-Density Lipoprotein Subclasses

Low cholesterol and phospholipid plasma levels of some high-density lipoprotein (HDL) subclasses have been described in children with metabolic syndrome. Scavenger receptor class B type I (SR-BI) has been proposed to be at the origin of such HDL alterations because of its key role on cholesteryl esters-HDL metabolism. However, the possible contribution of SR-BI has not been specifically explored in this kind of patients. Plasma lipid concentrations of HDL subclasses, i.e., triglycerides (TG), phosphatidylcholine (Ph), free cholesterol (FC), and total cholesterol (TC), were determined by enzymatic staining on polyacrylamide gradient gels (PAGE) in 39 pediatric patients with metabolic syndrome and 65 children as controls. Cholesteryl esters were estimated by the difference between TC and FC. Proteins of HDL subclasses were also stained for the assessment of the relative size distribution of HDL. For statistical analysis, the study population was grouped by Srb1 +1050C-->T polymorphism (rs5888) as carriers or noncarriers of the T allele, and data were corrected by metabolic syndrome status. The Srb1 +1050T allele was associated with metabolic syndrome [odds ratio (OR)=2.18 (1.12-4.22), P=0.02]. Plasma TG corresponding to HDL3a, as well as the relative proportion of this HDL subclass, were slightly higher in carriers of the T allele as compared to CC homozygous subjects. Cholesteryl esters plasma concentrations of all HDL subclasses were comparable between T allele carriers and noncarriers after correction by metabolic syndrome status. Srb1 +1050T was associated with metabolic syndrome, but T carrier subjects did not show important differences concerning HDL subclasses as compared to noncarriers.

Characteristics of low-density and high-density lipoprotein subclasses in pediatric renal transplant recipients

Renal transplant recipients often suffer from dyslipidemia which is one of the principal risk factors for cardiovascular disease. This study sought to determine characteristics of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles and their associations with carotid intima-media thickness (cIMT) in a group of pediatric renal transplant recipients. We also examined the influence of immunosuppressive therapy on measured LDL and HDL particle characteristics. HDL size and subclass distribution were determined using gradient gel electrophoresis, while concentrations of small, dense LDL (sdLDL)-cholesterol (sdLDL-C) and sdLDL-apolipoprotein B (sdLDL-apoB) using heparin-magnesium precipitation method in 21 renal transplant recipients and 32 controls. Renal transplant recipients had less HDL 2b (P < 0.001), but more HDL 3a (P < 0.01) and 3b (P < 0.001) subclasses. They also had increased sdLDL-C (P < 0.01) and sdLDL-apoB (P < 0.05) levels. The proportion of the HDL 3b subclasses was a significant predictor of increased cIMT (P < 0.05). Patients treated with cyclosporine had significantly higher sdLDL-C and sdLDL-apoB concentrations (P < 0.05) when compared with those on tacrolimus therapy. Pediatric renal transplant recipients have impaired distribution of HDL and LDL particles. Changes in the proportion of small-sized HDL particles are significantly associated with cIMT. Advanced lipid testing might be useful in evaluating the effects of immunosuppressive therapy.

Atherogenic Lipid Profile in Behçet’s Disease: Evidence of Alteration of HDL Subclasses

Behçet's disease (BD) is an inflammatory vasculitis, most common in the Mediterranean area and Asia. Evidence for accelerated atherosclerosis in BD has been observed. The relationship between cardiovascular risk factors and accelerated atherosclerosis in patients with BD is still controversial. The aim of this study was to evaluate the lipid profile and to investigate the low-density lipoprotein (LDL) size and the distribution of high-density lipoprotein (HDL) subpopulations in BD patients. Thirty six BD patients were compared to 36 healthy controls. Total cholesterol (TC), triglycerides (TG) and HDL-cholesterol (HDL-C) levels were measured using standard techniques. HDL subclasses and LDL-C size were estimated using polyacrylamide linear gradient gel electrophoresis. The LDL-C/HDL-C ratio was also calculated. High-sensitive C-reactive protein (hsCRP) level was measured by a turbidimetric method. Homocysteine (Hcy) level was determined using a liquid chromatography tandem mass spectrometry (LC/MS/MS). In BD patients, HDL-C levels as well as its subfraction levels were decreased (respectively, p <10(-6) and p <10(-3)). Percentage of HDL2 subpopulation was also decreased (p=0.02). HDL3 subfraction was significantly higher (p=0.02). The LDL-C/HDL-C ratio and CRP level were increased (respectively, p=10(-4) and p=0.003). TC was correlated with CRP. HDL-C and its subfractions were correlated with CRP and TG levels. HDL subparticle percentages were also correlated with age. Our findings of a reduction of HDL-C and HDL2 subpopulation and an increase HDL3 subclass and a higher LDL-C/HDL-C ratio may be considered as important predictors of cardiovascular events in BD patients.

Application of Fluorescence Correlation Spectroscopy to Measure High-Density Lipoprotein (HDL) Metabolism

High-density lipoprotein (HDL) protects vascular system from atherosclerosis by several mechanisms, including reverse cholesterol and therefore understanding its metabolism has important implications for public health. A major factor in HDL metabolism is endothelial lipase (EL). The goal of this study was to elucidate the kinetics of EL-HDL metabolism using fluorescence correlation spectroscopy (FCS). FCS is an advanced microscopy technique in which fluctuations in the fluorescence of a dye or dye-labeled molecule is recorded as the particles freely diffuse through a small focal volume. In this case, we measured the fluorescence of dye-labeled (Nile Red) HDL in the presence of wild type and mutant EL. The data can be analyzed mathematically using the cross-correlation function, from which the diffusion coefficient of the molecule is obtained. The lipase activity of EL changes HDL size, in turn affecting the diffusion coefficient, and can be calculated using the Stokes-Einstein relation. Our preliminary results suggest the hydrolysis of HDL occurs rapidly and proportionately to the concentration of EL. Several mutations in EL have been identified in human population studies. Our future goal is to compare the rate of hydrolysis between wild type and mutant EL and with normal and oxidized HDL. In addition, fluorescence measurements were used to investigate the composition of HDL. The fluorescence spectrum of Nile Red is dependent upon the local lipid environment. By monitoring the change in fluorescence emission as a function of EL metabolism, we investigate the content of HDL while being remodeled by EL. These fluorescence techniques allow us to answer some of the key questions regarding the HDL lipid collection and distribution function.

Scavenger Receptor BI-mediated Selective Uptake Is Required for the Remodeling of High Density Lipoprotein by Endothelial Lipase

Endothelial lipase (EL) is a negative regulator of high density lipoprotein (HDL) cholesterol plasma levels, and scavenger receptor BI (SR-BI) is involved in remodeling of HDL. The present study investigates the requirement of SR-BI for the effects of EL-mediated phospholipid hydrolysis on HDL metabolism in vivo. In vitro, selective uptake from EL-modified HDL was 129% higher than selective uptake from control HDL in SR-BI-overexpressing cells (p=0.01). In vivo overexpression of human EL by means of recombinant adenovirus decreased HDL plasma levels significantly (p<0.01). Fast protein liquid chromatography analysis and agarose gel electrophoresis revealed that EL expression resulted in the generation of small pre-beta HDL particles in wild-type mice, whereas in SR-BI-/- mice small HDL were preferentially removed. In kinetic experiments the fractional catabolic rate (FCR) of HDL cholesteryl ester increased by 110% (p<0.001), and the FCR of HDL apolipoproteins increased by 64% (p<0.001) in response to EL overexpression in wild-type mice. In SR-BI-/- mice a similar increase in the HDL apolipoprotein FCR occurred (p<0.001); however, there was no further increase in HDL cholesteryl ester catabolism. The apparent whole body selective uptake was increased 3-fold by EL in wild-type mice (p<0.001), whereas there was no selective uptake in SR-BI knock-out mice. EL overexpression increased hepatic selective uptake as well as holoparticle uptake (each p<0.01) in wild-type mice, whereas in SR-BI knock-out mice only holoparticle uptake increased (p<0.01). Our results indicate that SR-BI-mediated selective uptake of HDL cholesteryl ester is essential for the remodeling of large alpha-migrating HDL particles by EL.

Altered Flow-Mediated Vasodilatation, Low Paraoxonase-1 Activity, and Abnormal High-Density Lipoprotein Subclass Distribution in Takayasu's Arteritis

Takayasu's arteritis (TA) is an idiopathic chronic inflammatory disease that causes occlusion of large arteries, but little is known about whether affected patients are characterized by endothelial dysfunction, different high-density lipoproteins (HDL) subclasses and paraoxonase-1 (PON1) activity. In the present study, 30 patients with TA, 30 age- and gender-matched volunteers (controls) and 15 patients with essential hypertension were studied. Flow-mediated vasodilation (FMD) and maximal blood flow velocity, assessed in the brachial artery by high-resolution ultrasound, were significantly lower in patients. HDL subclass distribution was determined by polyacrylamide gradient gel electrophoresis. HDL-cholesterol, HDL3b subclass and PON1 activity, assessed spectrophotometrically using phenylacetate as the substrate, were also lower in patients compared with controls. In a multiple regression analysis, the use of prednisone and systolic blood pressure were independent variables that predicted the FMD. A low FMD, abnormal size distribution of HDLs, and low PON1 activity are observed in TA patients. These abnormalities appear independently and constitute a cluster that may contribute to the vascular dysfunction of TA arteritis.