High-density Apolipoprotein Research Articles

Effects of simvastatin and carnitine versus simvastatin on lipoprotein(a) and apoprotein(a) in type 2 diabetes mellitus

Aim: The aim of the present study was to compare the effects of simvastatin and L-carnitine coadministration versus simvastatin monotherapy on lipid profile, lipoprotein(a) (Lp(a)) and apoprotein(a) (Apo(a)) levels in type II diabetic patients. Patients/methods: In this double-blind, randomized clinical trial, 75 patients were assigned to one of two treatment groups for 4 months. Group A received simvastatin monotherapy; group B received L-carnitine and simvastatin. The following variables were assessed at baseline, after washout and at 1, 2, 3 and 4 months of treatment: body mass index, fasting plasma glucose, glycated hemoglobin, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, Apolipoprotein A1, Apo B, lipoprotein(a) and apoprotein(a). Results: At the end of treatment in the carnitine and simvastatin combined group compared with the simvastatin alone group, we observed a significant decrease in glycemia (p < 0.001), tryglicerides (p < 0.001), Apo B (p < 0.05), Lp(a) (p < 0.05), apo(a) (p < 0.05), while HDL significantly increased (p < 0.05). Conclusions: The coadministration of carnitine and simvastatin resulted in a significant reduction in Lp(a) and apo(a) and may represent a new therapeutic option in reducing plasma Lp(a) levels, LDL cholesterol and Apo B100.

Pharmacokinetic, Pharmacodynamic, and Safety Profile of a New Cholesteryl Ester Transfer Protein Inhibitor in Healthy Human Subjects

A new cholesteryl ester (CE) transfer protein (CETP) inhibitor (CP-800,569) was evaluated. Doses of 30-1,800 mg were administered once daily to healthy subjects for 14 days. Serum CP-800,569 levels increased, and CETP activity decreased, in a dose-related manner. Serum levels of high-density lipoprotein (HDL) increased (by a maximum of 156%), and those of low-density lipoprotein (LDL) decreased (by a maximum of 47%). CP-800,569 also had the effect of lowering postprandial triglyceride levels. Trough concentrations of apolipoprotein E (apoE) increased: the maximum increases were 89% for total plasma apoE and 280% for HDL apoE. By contrast, the postprandial increases in total plasma levels of apoE and non HDL apoE were either diminished by CP-800,569 or reversed to decreases. CP-800,569 was very well tolerated, with some nonserious gastrointestinal adverse events seen only with the 1,800-mg dose. No changes in blood pressure (BP) were observed. The possible effects of higher CP-800,569 doses on aldosterone and cortisol levels could not be excluded. The results of this study may be useful in CP-800,569 dose selection.

Effects of cholesteryl ester transfer protein inhibition on apolipoprotein A-II-containing HDL subspecies and apolipoprotein A-II metabolism

This study was designed to establish the mechanism responsible for the increased apolipoprotein (apo) A-II levels caused by the cholesteryl ester transfer protein inhibitor torcetrapib. Nineteen subjects with low HDL cholesterol (<40 mg/dl), nine of whom were also treated with 20 mg of atorvastatin daily, received placebo for 4 weeks, followed by 120 mg of torcetrapib daily for the next 4 weeks. Six subjects in the nonatorvastatin cohort participated in a third phase, in which they received 120 mg of torcetrapib twice daily for 4 weeks. At the end of each phase, subjects underwent a primed-constant infusion of [5,5,5-(2)H(3)]L-leucine to determine the kinetics of HDL apoA-II. Relative to placebo, torcetrapib significantly increased apoA-II concentrations by reducing HDL apoA-II catabolism in the atorvastatin (-9.4%, P < 0.003) and nonatorvastatin once- (-9.9%, P = 0.02) and twice- (-13.2%, P = 0.02) daily cohorts. Torcetrapib significantly increased the amount of apoA-II in the alpha-2-migrating subpopulation of HDL when given as monotherapy (27%, P < 0.02; 57%, P < 0.003) or on a background of atorvastatin (28%, P < 0.01). In contrast, torcetrapib reduced concentrations of apoA-II in alpha-3-migrating HDL, with mean reductions of -14% (P = 0.23), -18% (P < 0.02), and -18% (P < 0.01) noted during the atorvastatin and nonatorvastatin 120 mg once- and twice-daily phases, respectively. Our findings indicate that CETP inhibition increases plasma concentrations of apoA-II by delaying HDL apoA-II catabolism and significantly alters the remodeling of apoA-II-containing HDL subpopulations.

AAV gene therapy as a means to increase apolipoprotein (Apo) A‐I and high‐density lipoprotein‐cholesterol levels: correction of murine ApoA‐I deficiency

Inherited apolipoprotein (Apo) A-I deficiency is an orphan disorder characterized by high-density lipoprotein (HDL)-cholesterol deficiency and premature atherosclerosis. Constitutive over-expression of ApoA-I might provide a means to treat this disease. The present study provides a comprehensive evaluation of adeno-associated virus (AAV)-mediated ApoA-I gene delivery to express human (h)ApoA-I and correct the low HDL-cholesterol phenotype associated with ApoA-I deficiency. In an effort to maximize AAV-mediated gene expression, we performed head-to-head comparisons of recombinant AAVs with pseudotype capsids 1, 2, 6 and 8 administered by different routes with the use of five different liver-specific promoters in addition to cytomegalovirus as single-stranded or as self-complementary (sc) AAV vectors. Intravenous administration of 1 x 10(13) gc/kg scAAV8, in combination with the liver-specific promoter LP1, in female ApoA-I(-/-) mice resulted in hApoA-I expression levels of 634 +/- 69 mg/l, which persisted for the duration of the study (15 weeks). This treatment resulted in full recovery of HDL-cholesterol levels with correction of HDL particle size and apolipoprotein composition. In addition, we observed increased adrenal cholesterol content and a significant increase in bodyweight in treated mice. The present study demonstrates that systemic delivery of a scAAV8 vector provides a means for efficient liver expression of hApoA-I, thereby correcting the lipid abnormalities associated with murine ApoA-I deficiency. Importantly, the study demonstrates that AAV-based gene therapy can be used to express therapeutic proteins at a high level for a prolonged period of time and, as such, provides a basis for further development of this strategy to treat hApoA-I deficiency.

Marked high density lipoprotein deficiency due to apolipoprotein A-I Tomioka (codon 138 deletion)

We report a novel apolipoprotein A-I (apoA-I) mutation identified in a 64-year-old patient with marked plasma high density lipoprotein (HDL) cholesterol (4 mg/dl) and apoA-I (5 mg/dl) deficiency, prior myocardial infarction, and moderate corneal opacities. Coronary angiography revealed extensive atherosclerosis in all three major vessels. Genomic DNA sequencing of the proband revealed a homozygous novel deletion of two successive adenine residues in codon 138 in the apoA-I gene, resulting in a frameshift mutation at amino acid residues 138–178, which we have designated as apoA-I Tomioka. His elder brother was also homozygous for apoA-I Tomioka with marked HDL cholesterol and apoA-I deficiency, but had no clinical evidence of coronary heart disease. Other family members including three siblings and two sons were heterozygous for the mutation, and had approximately 50% of normal plasma HDL cholesterol, and apoA-I. Analysis of apoA-I-containing HDL particles by two-dimensional gel electrophoresis revealed undetectable apoA-I HDL particles in the homozygotes, while in heterozygotes, the mean concentrations of apoA-I in large α-1 and very small preβ-1 HDL subpopulations were significantly decreased at about 35% of normal. Thus, apoA-I Tomioka, a novel deletion mutation in codon 138 of the apoA-I gene, is the causative defect in this case of HDL deficiency.

Formation of Two Intramolecular Disulfide Bonds Is Necessary for ApoA-I-dependent Cholesterol Efflux Mediated by ABCA1

ABCA1 plays a major role in cholesterol homeostasis and high density lipoprotein (HDL) metabolism. ABCA1 contains disulfide bond(s) between its N- and C-terminal halves, but it remains unclear whether disulfide bond formation is important for the functions of ABCA1 and which cysteines are involved in disulfide bond formation. To answer these questions, we constructed >30 ABCA1 mutants in which 16 extracellular domain (ECD) cysteines were replaced with serines and examined disulfide bond formation, apoA-I binding, and HDL formation in these mutants. From the single cysteine replacements, two cysteines (Cys(75) and Cys(309)) in ECD1 were found to be essential for apoA-I binding. In contrast, in ECD2, only Cys(1477) was found to be essential for HDL formation, and no single cysteine replacement impaired apoA-I binding. The concurrent replacement of two cysteines, Cys(1463) and Cys(1465), impaired apoA-I binding and HDL formation, suggesting that four of five extracellular cysteines (Cys(75), Cys(309), Cys(1463), Cys(1465), and Cys(1477)) are involved in these functions of ABCA1. Trypsin digestion experiments suggested that one disulfide bond is not sufficient and that two intramolecular disulfide bonds (between Cys(75) and Cys(309) in ECD1 and either Cys(1463) or Cys(1465) and Cys(1477) in ECD2) are required for ABCA1 to be fully functional.

A Freshwater Clam (Corbicula fluminea) Extract Reduces Cholesterol Level and Hepatic Lipids in Normal Rats and Xenobiotics-Induced Hypercholesterolemic Rats

We investigated whether a freshwater clam (Corbicula fluminea) extract (FCE) could improve cholesterol metabolism and hepatic lipids accumulation in rats fed xenobiotics such as chloretone. Feeding chloretone resulted in hypercholesterolemia and fatty liver. An increase in serum cholesterol, high density lipoproteins (HDL) in particular, after intake of chloretone was observed. Serum cholesterol was decreased by supplementation with FCE. Accumulation of the hepatic lipids including triacylglycerol, cholesterol, and phospholipid was significantly suppressed by supplementation with FCE. The excretion of neutral and acidic sterols into the feces was enhanced by FCE. The hepatic gene expression of cholesterol 7alpha-hydroxylase was enhanced in rats fed a FCE-containing diet. Apolipoprotein A-I gene expression in the liver, which is a major apolipoprotein of HDL, was suppressed by FCE. These results demonstrated that FCE reduced cholesterol level and hepatic lipids in normal rats and hypercholesterolemic rats fed chloretone.

From Menace to Marvel

Diabetes mellitus is a major risk factor for cardiovascular disease, and its prevalence is suspected to further increase in the coming years in the Western hemisphere and also in countries with emerging economies, like India, China, and Brazil. Together with the increasing prevalence of obesity and metabolic syndrome and the subsequent development of arterial hypertension, the epidemic of adiposity and diabetes mellitus may eat up most of the improvement of cardiovascular outcomes that we have seen within the last decades.1 The risk of atherosclerosis is inversely related to circulating levels of high-density lipoprotein (HDL) cholesterol. Results from the Framingham Study demonstrated that this association is independent of low-density lipoprotein. Clinical trials using agents (eg, fibrates) that increase HDL have been shown to decrease cardiovascular event rates. On the other hand, therapy with the HDL-raising substance torcetrapib is associated with increased cardiovascular events, although the mechanism for this remains unclear and is probably independent of the effects on HDL cholesterol.2 The classical function of HDL is the so called “reverse cholesterol transport” removing cholesterol from peripheral tissue and delivering it to the liver by binding of the major HDL apolipoprotein (apo), apoA-I, to the HDL receptor scavenger receptor B type I. Intra-arterial infusion of apoA-I/phosphatidylcholine in hypercholesterolemic patients with normal HDL improves endothelial dysfunction, suggesting that HDL is a positive modulator of vascular NO bioavailability. Infusion of reconstituted HDL even leads to acute changes in human atherosclerotic plaque composition characterized by a reduction in lipid content within the atherosclerotic plaque.3 With respect to …

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.

Serum paraoxonase‐I activity is unaffected by short‐term administration of simvastatin, bezafibrate, and their combination in type 2 diabetes mellitus

The high-density lipoprotein (HDL)-associated anti-oxidative and anti-inflammatory enzyme, paraoxonase-I, has been found previously to be lower in type 2 diabetes mellitus. We studied whether statin and fibrate treatment, alone and in combination, affect serum paraoxonase-I activity in conjunction with changes in HDL cholesterol in diabetic patients. A placebo-controlled crossover study was carried out in 14 type 2 diabetic patients to test the effect of 8 weeks of active treatment with simvastatin (40 mg daily), bezafibrate (400 mg daily), and their combination on serum paraoxonase-I activity, measured as its activity towards arylesterase and paraoxon. Serum paraoxonase-I activity was also compared between these diabetic patients and 49 non-diabetic control subjects. Serum arylesterase activity was lower in type 2 diabetic patients compared to control subjects (P < 0.001), but the difference in paraoxonase activity was not significant (P = 0.22). Neither arylesterase (P = 0.24) nor paraoxonase activity (P = 0.37) was increased in response to treatment, despite higher HDL cholesterol and apolipoprotein A-I during combination therapy (P < 0.05 for both). Short-term administration of simvastatin and bezafibrate, even when combined, is ineffective in raising serum paraoxonase-I activity in type 2 diabetes.

Thermal Stability of Apolipoprotein A-I in High-Density Lipoproteins by Molecular Dynamics

Apolipoprotein (apo) A-I is an unusually flexible protein whose lipid-associated structure is poorly understood. Thermal denaturation, which is used to measure the global helix stability of high-density lipoprotein (HDL)-associated apoA-I, provides no information about local helix stability. Here we report the use of temperature jump molecular dynamics (MD) simulations to scan the per-residue helix stability of apoA-I in phospholipid-rich HDL. When three 20 ns MD simulations were performed at 500 K on each of two particles created by MD simulations at 310 K, bilayers remained intact but expanded by 40%, and total apoA-I helicity decreased from 95% to 72%. Of significance, the conformations of the overlapping N- and C-terminal domains of apoA-I in the particles were unusually mobile, exposing hydrocarbon regions of the phospholipid to solvent; a lack of buried interhelical salt bridges in the terminal domains correlated with increased mobility. Nondenaturing gradient gels show that 40% expansion of the phospholipid surface of 100:2 particles by addition of palmitoyloleoylphosphatidylcholine exceeds the threshold of particle stability. As a unifying hypothesis, we propose that the terminal domains of apoA-I are phospholipid concentration-sensitive molecular triggers for fusion/remodeling of HDL particles. Since HDL remodeling is necessary for cholesterol transport, our model for remodeling has substantial biomedical implications.

Impaired anti-inflammatory function of apolipoprotein A-II concentrations predicts metabolic syndrome and diabetes at 4 years follow-up in elderly Turks

We evaluated prospectively the predictive value of serum apolipoprotein (apo) A-II, the second major apolipoprotein of high-density lipoprotein (HDL), for cardiometabolic risk in Turkish adults showing abnormalities in other proteins that normally confer protection. Determinants of apoA-II and its associations with coronary heart disease (CHD), metabolic syndrome (MetS) and diabetes were investigated at 4 years follow-up in 193 elderly men and women. ApoA-II concentrations at baseline, in addition to being significantly related to HDL-cholesterol, were directly associated with complement C3 in multivariate linear regression analyses comprising nine variables. Following adjustment for gender, age and HDL-cholesterol (>30/>33 g/L, in men and women, respectively), low serum apoA-II concentrations predicted incident MetS [relative risk (RR) 3.5 (95% CI 1.4; 8.6)] and type 2 diabetes [RR 4.5 (95% CI 1.3; 15.6)] in both genders at an increment of 1 SD. Increased apoA-II values were not associated with prevalent or incident CHD, and tended to be marginally atheroprotective only in males. Serum apoA-II concentrations confer risk for MetS and diabetes and exhibit evidence of anti-inflammatory properties among Turks. These findings support the effects seen for several other HDL protein constituents. This finding may explain the increased cardiometabolic risk among Turks.

Very Low Density Lipoprotein Metabolism and Plasma Adiponectin as Predictors of High-Density Lipoprotein Apolipoprotein A-I Kinetics in Obese and Nonobese Men

Hypercatabolism of high-density lipoprotein (HDL) apolipoprotein (apo) A-I results in low plasma apoA-I concentration. The mechanisms regulating apoA-I catabolism may relate to alterations in very low density lipoprotein (VLDL) metabolism and plasma adiponectin and serum amyloid A protein (SAA) concentrations. We examined the associations between the fractional catabolic rate (FCR) of HDL-apoA-I and VLDL kinetics, plasma adiponectin, and SAA concentrations. The kinetics of HDL-apoA-I and VLDL-apoB were measured in 50 obese and 37 nonobese men using stable isotopic techniques. In the obese group, HDL-apoA-I FCR was positively correlated with insulin, homeostasis model of assessment for insulin resistance (HOMA-IR) score, triglycerides, VLDL-apoB, and VLDL-apoB production rate (PR). In the nonobese group, HDL-apoA-I FCR was positively correlated with triglycerides, apoC-III, VLDL-apoB, and VLDL-apoB PR and negatively correlated with plasma adiponectin. Plasma SAA was not associated with HDL-apoA-I FCR in either group. In multiple regression analyses, VLDL-apoB PR and HOMA-IR score, and VLDL-apoB PR and adiponectin were independently predictive of HDL-apoA-I FCR in the obese and nonobese groups, respectively. HDL-apoA-I FCR was positively and strongly associated with HDL-apoA-I PR in both groups. Variation in VLDL-apoB production, and hence plasma triglyceride concentrations, exerts a major effect on the catabolism of HDL-apoA-I. Insulin resistance and adiponectin may also contribute to the variation in HDL-apoA-I catabolism in obese and nonobese subjects, respectively. We also hypothesize that apoA-I PR determines a steady-state, lowered plasma of apoA-I, which may reflect a compensatory response to a primary defect in the catabolism of HDL-apoA-I due to altered VLDL metabolism.

Serum Amyloid A, but Not C-Reactive Protein, Stimulates Vascular Proteoglycan Synthesis in a Pro-Atherogenic Manner

Inflammatory markers serum amyloid A (SAA) and C-reactive protein (CRP) are predictive of cardiac disease and are proposed to play causal roles in the development of atherosclerosis, in which the retention of lipoproteins by vascular wall proteoglycans is critical. The purpose of this study was to determine whether SAA and/or CRP alters vascular proteoglycan synthesis and lipoprotein retention in a pro-atherogenic manner. Vascular smooth muscle cells were stimulated with either SAA or CRP (1 to 100 mg/L) and proteoglycans were then isolated and characterized. SAA, but not CRP, increased proteoglycan sulfate incorporation by 50 to 100% in a dose-dependent manner (P < 0.0001), increased glycosaminoglycan chain length, and increased low-density lipoprotein (LDL) binding affinity (K(d), 29 microg/ml LDL versus 90 microg/ml LDL for SAA versus control proteoglycans; P < 0.005). Furthermore, SAA up-regulated biglycan via the induction of endogenous transforming growth factor (TGF)-beta. To determine whether SAA stimulated proteoglycan synthesis in vivo, ApoE(-/-) mice were injected with an adenovirus expressing human SAA-1, a null virus, or saline. Mice that received adenovirus expressing SAA had increased TGF-beta concentrations in plasma and increased aortic biglycan content compared with mice that received either null virus or saline. Thus, SAA alters vascular proteoglycans in a pro-atherogenic manner via the stimulation of TGF-beta and may play a causal role in the development of atherosclerosis.

The effects of ezetimibe and orlistat, alone or in combination, on high-density lipoprotein (HDL) subclasses and HDL-associated enzyme activities in overweight and obese patients with hyperlipidaemia

Background: High-density lipoprotein (HDL) includes discrete subfractions. HDL exhibits anti-atherogenic properties, which have been partly linked to the activity of HDL-associated enzymes, such as the lipoprotein associated phospholipase A2 (HDL-LpPLA2) and paraoxonase-1 (PON1). Objective: We assessed in an open-label randomised study the effect of orlistat and ezetimibe, alone or in combination, on plasma HDL subclasses and HDL-associated enzyme activities in overweight and obese subjects (body mass index > 28 kg/m2) with hypercholesterolemia [total cholesterol > 200 mg/100 ml (5.2 mmol/l)]. Methods: Eighty-six people were prescribed a low-fat low-calorie diet and were randomly allocated to receive orlistat 120 mg, three times daily (O group), ezetimibe 10 mg/day (E group) or both (OE group) for 6 months. HDL subfractions were determined using a polyacrylamide gel-tube electrophoresis method. Results: Levels of HDL cholesterol (HDL-C) and apolipoprotein AI did not change significantly in any group. In group O the cholesterol concentration of HDL-2 subclass increased significantly, while the cholesterol of HDL-3 subclass decreased significantly. In groups E and OE HDL-2 subclass did not significantly change, while the cholesterol concentration of HDL-3 subclass decreased significantly. We observed a non-significant decrease in the HDL-LpPLA2 and PON1 activity in all groups. However, the ratios of both enzyme activities to low-density lipoprotein cholesterol (LDL-C) levels (an index of atherogenicity) significantly increased in all groups. Conclusion: Although HDL-C levels did not change after treatment with orlistat and ezetimibe, alone or in combination, there were alterations of the HDL-2 and HDL-3 subclasses. The activity of HDL-LpPLA2 and PON1 per mg LDL-C increased significantly in all groups.

HDL concentration, lipid transfer to HDL, and HDL size in normolipidemic nonobese menopausal women

Objective To determine the impact of menopause on lipid transfer from donor lipoproteins to high-density lipoproteins (HDLs)—a process that is related to the protective function of HDL—and the size of HDL particles. Method Plasma from 22 premenopausal and 18 postmenopausal nonobese, normolipidemic women paired for age (40–50 years) was incubated in an artificial nanoemulsion labeled with radioactive lipids. Then the HDL fraction was assessed for radioactivity; the percentage of radioactive lipids transferred from the nanoemulsion to HDL was determined; and the size of HDL particles was measured by laser light scattering. Results There were no differences between the 2 groups in serum concentration of HDL cholesterol (61 ± 12 mg/dL vs 61 ± 14 mg/dL) or apolipoprotein A 1 (1.5 ± 0.3 g/L vs 1.5 ± 0.2 g/L); lipid transfer to HDL; or size of HDL particles (8.8 ± 0.8 vs 9.0 ± 0.5 nm). Conclusion Menopause was not found to affect HDL cholesterol plasma concentration, lipid transfer to HDL, or size of HDL particles in normolipidemic nonobese women.

High-density lipoproteins are abnormal in young women with uncomplicated systemic lupus erythematosus

Little is known about qualitative abnormalities of high-density lipoproteins (HDL) in systemic lupus erythematosus (SLE). We studied distribution and composition of HDL subclasses in 30 premenopausal women with uncomplicated SLE, and 18 controls matched for age and sex. Plasma and HDL lipids were determined by colorimetric enzymatic assays, HDL size distribution by native gradient polyacrylamide gel electrophoresis (PAGE) and apolipoproteins in HDL by sodium dodecyl sulphate denaturing PAGE. Compared with controls, SLE patients had significantly lower proportions of HDL(2b) (-14.7%) and higher proportions of HDL(3b) (+8.8%) and HDL(3c) (+23.3%). Cholesteryl ester (-18%) and apolipoprotein AI (-9%) were lower, whereas triglycerides (+32%) and apolipoprotein E (+27%) were higher in SLE HDL (P < 0.05; for all). In the whole population, stepwise regression analysis showed that only insulin concentrations (R(2) = 0.327) and plasma total apo AI (R(2) = 0.114) accounted independently to the variance in HDL size. This study shows that HDL distribution and composition are abnormal in non-complicated SLE patients. These HDL abnormalities have been reported to be associated to impaired atheroprotective properties of HDL and prevalence of coronary heart disease. Therefore, they may contribute to the premature atherosclerosis observed in young women with SLE.

Abstract 5478: P2Y 13 ADP-Receptor Regulates Plasma HDL Clearance, Biliary Cholesterol and Bile Acids Secretions In Vivo

Plasma high density lipoprotein (HDL) protects against atherosclerosis, in part through the removal of cholesterol from peripheral tissues and its delivery to the liver for metabolism and bile excretion. Thus understanding of the molecular event implicated in HDL-cholesterol uptake by the liver is critical to the development of therapeutic strategies to enhance HDL catabolism. The scavenger receptor (SR)-BI modulates plasma HDL level and contributes to cholesteryl ester uptake from HDL in mice but a distinct pathway for holo-HDL particle uptake (protein + lipid) has been recently identified in human hepatocytes. This pathway which strictly depends on extracellular ADP level involves different cell surface partners: ADP generated from the activation by apo AI (the main HDL apolipoprotein) of a cell surface F 1 -ATPase, activates the P2Y 13 ADP-receptor and subsequent HDL endocytosis through an unknown low-affinity HDL receptor. To evaluate the physiological relevance of this P2Y 13 -mediated HDL endocytosis pathway in vivo in mice, P2Y 13 receptor was activated by treating C57BL/6 and liver specific SR-BI-KO mice (SR-BI-KO liver ) with the specific agonist (AR-C69931MX, 8nmol/kg, intra-orbital injection). Expression of P2Y 13 protein in liver was also disrupted by siRNA adenovirus (10 9 vp/mice, intra-orbital injection) and in P2Y 13 KO mice. Plasma clearance of 125 I-labeled HDL was rapidly enhanced under AR-C69931MX treatment in SR-BI-KO liver mouse. Conversely, HDL clearance was decreased in P2Y 13 KO mice but no modification was observed in plasma lipids profile versus control mice, suggesting a mechanism of modulation of plasma HDL turnover rather than a simply disruption of HDL uptake. Furthermore, biliary lipids content was decreased under P2Y 13 extinction in mice (bile acids: −60%, cholesterol: −30%), whereas it was dramatically increased under stimulation of P2Y 13 by AR-C69931MX treatment in C57BL/6 mice (bile acids: +85%, cholesterol: +50%,). These results indicate that P2Y 13 has an important role in hepatic HDL metabolism in controlling circulating HDL turnover and biliary lipids elimination, and thus may have an impact on the development of atherosclerosis.

Fasting and Nonfasting Lipid Levels

Lipid profiles are usually measured after fasting. We tested the hypotheses that these levels change only minimally in response to normal food intake and that nonfasting levels predict cardiovascular events. We cross-sectionally studied 33 391 individuals 20 to 95 years of age from the Copenhagen General Population Study. We also studied 9319 individuals 20 to 93 years of age from the Copenhagen City Heart Study, 1166 of whom developed cardiovascular events during 14 years of follow-up. Compared with fasting levels, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein (HDL) cholesterol, and albumin levels were reduced up to 3 to 5 hours after the last meal; triglycerides levels were increased up to 6 hours after the last meal; and non-HDL cholesterol level, apolipoprotein A1 level, apolipoprotein B level, ratio of total cholesterol to HDL cholesterol, and ratio of apolipoprotein B to apolipoprotein A1 did not change in response to normal food intake. The maximum changes after normal food and fluid intake from fasting levels were -0.2 mmol/L for total cholesterol, -0.2 mmol/L for low-density lipoprotein cholesterol, -0.1 mmol/L for HDL cholesterol, and 0.3 mmol/L for triglycerides. Highest versus lowest tertile of nonfasting total cholesterol, non-HDL cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, triglycerides, ratio of total cholesterol to HDL cholesterol, and ratio of apolipoprotein B/apolipoprotein A1 and lowest versus highest tertile of nonfasting HDL cholesterol and apolipoprotein A1 predicted 1.7- to 2.4-fold increased risk of cardiovascular events. Lipid profiles at most change minimally in response to normal food intake in individuals in the general population. Furthermore, nonfasting lipid profiles predicted increased risk of cardiovascular events.

Relevance of the amino acid conversions L144R (Zaragoza) and L159P (Zavalla) in the apolipoprotein A-I binding site for haptoglobin

The high-density lipoprotein apolipoprotein A-I (ApoA-I) stimulates the enzyme lecithin-cholesterol acyltransferase (LCAT) in the reverse cholesterol transport pathway. Two ApoA-I variants, Zaragoza (L144R) and Zavalla (L159P), are associated with low levels of HDL-cholesterol but normal LCAT activity. Haptoglobin interacts with ApoA-I, impairing LCAT stimulation. Synthetic peptides matching the haptoglobin-binding site of native or variant ApoA-I (native, P2a; variants, Zav-pep and Zar-pep) bound haptoglobin with different activity: Zar-pep>P2a>Zav-pep. They also differently rescued LCAT in vitro activity in the presence of haptoglobin (P2a=Zar-pep>Zav-pep). Therefore, both amino acid conversions affect haptoglobin binding and LCAT regulation. We highlight the role of haptoglobin in LCAT regulation in subjects with ApoA-I variants.