Low Density Lipoprotein apoB Research Articles

Lipoprotein(a) cardiovascular disease risk not captured by low density lipoprotein cholesterol and apolipoprotein B

Abstract Background Elevated lipoprotein(a) affects 1 in 5 individuals and is considered a causal risk factor for atherosclerotic cardiovascular disease (ASCVD) and aortic valve stenosis (AVS). However, lipoprotein(a) measurements are not widely implemented in clinical practice. Low-density lipoprotein (LDL) cholesterol and apolipoprotein B (ApoB) measurements include contributions from lipoprotein(a), yet whether these measurements can replace measurements of lipoprotein(a) in assessing cardiovascular disease risk from this causal risk factor is unknown. Purpose We tested the hypotheses that lipoprotein(a) risk of ASCVD and AVS is captured by LDL cholesterol or ApoB. Methods We included 70,189 individuals from a prospective contemporary cohort study of the general population. Mediated risk by LDL cholesterol and ApoB in the association between lipoprotein(a) and risk of ASCVD and AVS was examined using four-way decomposition analyses stratified by statin treatment at baseline. Results During a median follow-up of 10.8 years, 7,127 developed ASCVD and 1,516 AVS. Per 50 mg/dL higher lipoprotein(a), multivariable adjusted hazard ratios were 1.22 (95% CI: 1.18-1.26) for ASCVD and 1.36 (1.28-1.46) for AVS. In individuals without statin use, LDL cholesterol mediated 19% (15%-24%) of the risk of ASCVD from lipoprotein(a) and 7.7% (1.5%-14%) of the risk of AVS from lipoprotein(a) (Figure 1). Corresponding values for ApoB were 14.0% (11%-18%) and 6.6% (2.8%-10%). In statin users (n=9,570), LDL cholesterol did not mediate risk of ASCVD from lipoprotein(a) but mediated 8.0% (0.8%-15%) of the risk of AVS from lipoprotein(a). Correspondingly, ApoB mediated 9.8% (2.2%-17%) of the risk of ASCVD and 4.2% (0.4%-8.0%) of the risk of AVS from lipoprotein(a). Conclusion Lipoprotein(a) risk of ASCVD and AVS is not adequately captured by LDL cholesterol and ApoB. Therefore, lipoprotein(a) measurement is needed in all individuals to capture the cardiovascular disease risk from this causal risk factor.

ANGPTL3 Inhibition With Evinacumab Results in Faster Clearance of IDL and LDL apoB in Patients With Homozygous Familial Hypercholesterolemia—Brief Report

The mechanism by which evinacumab, a fully human monoclonal antibody directed against ANGPTL3 (angiopoietin-like 3 protein) lowers plasma LDL (low-density lipoprotein) cholesterol levels in patients with homozygous familial hypercholesterolemia is unknown. We investigated apoB (apolipoprotein B) containing lipoprotein kinetic parameters in patients with homozygous familial hypercholesterolemia, before and after treatment with evinacumab. Approach and Results: Four patients with homozygous familial hypercholesterolemia underwent apoB kinetic analyses in 2 centers as part of a substudy of a trial evaluating the efficacy and safety of evinacumab in patients with homozygous familial hypercholesterolemia. The enrichment of apoB with the stable isotope (5,5,5-2H3)-Leucine was measured in VLDL (very LDL), IDL (intermediate-density lipoprotein), and LDL at different time points before and after intravenous administration of 15 mg/kg evinacumab. Evinacumab lowered LDL-cholesterol by 59±2% and increased IDL apoB and LDL apoB fractional catabolic rate in all 4 homozygous familial hypercholesterolemia subjects, by 616±504% and 113±14%, respectively. VLDL-apoB production rate decreased in 2 of the 4 subjects. In this small study, ANGPTL3 inhibition with evinacumab is associated with an increase in the fractional catabolic rate of IDL apoB and LDL apoB, suggesting that evinacumab lowers LDL-cholesterol predominantly by increasing apoB-containing lipoprotein clearance from the circulation. Additional studies are needed to unravel which factors are determinants in this biological pathway. URL: https://www.clinicaltrials.gov; Unique identifier: NCT04722068.

Cholesterol Efflux Capacity and Cardiovascular Disease: The Ludwigshafen Risk and Cardiovascular Health (LURIC) Study.

(1) Background and Aims: Efforts to reduce coronary artery disease (CAD) by raising high-density lipoprotein (HDL) cholesterol (HDL-C) have not been uniformly successful. A more important factor than HDL-C may be cellular cholesterol efflux mediated by HDL, which has been shown to be associated with CAD. In this report, we analyzed the influence of cardiovascular biomarkers and risk factors on cholesterol efflux in a prospective observational study of patients referred to coronary angiography. (2) Methods: HDL-mediated efflux capacity was determined for 2468 participants of the Ludwigshafen Risk and Cardiovascular Health (LURIC) study who were referred to coronary angiography at baseline between 1997 and 2000. Median follow-up time was 9.9 years. Primary and secondary endpoints were cardiovascular and all-cause mortality, respectively. (3) Results: Cholesterol efflux strongly correlated with HDL-related markers including HDL cholesterol, HDL phospholipids, and apolipoproteins AI and AII, as well as HDL particle concentration, which was not seen for low density lipoprotein (LDL) markers including LDL cholesterol and apoB. Cholesterol efflux was associated negatively with C-reactive protein (CRP), fibrinogen, interleukin-6 (IL-6), and serum amyloid A. Cardiovascular mortality was higher in patients in the lowest cholesterol efflux quartile. This association was weakened, but not fully abolished, after adjustment for HDL cholesterol. (4) Conclusions: We demonstrate that cholesterol efflux was associated with HDL-composition as well as inflammatory burden in patients referred for coronary angiography, and that this inversely predicts cardiovascular mortality independently of HDL cholesterol.

Binding to heparin triggers deleterious structural and biochemical changes in human low-density lipoprotein, which are amplified in hyperglycemia

Low-density lipoprotein (LDL) binding to arterial proteoglycans initiates LDL retention and modification in the arterial wall, triggering atherosclerosis. The details of this binding, its effectors, and its ramifications are incompletely understood. We combined heparin affinity chromatography with biochemical, spectroscopic and electron microscopic techniques to show that brief binding to heparin initiates irreversible pro-atherogenic remodeling of human LDL. This involved decreased structural stability of LDL and increased susceptibility to hydrolysis, oxidation and fusion. Furthermore, phospholipid hydrolysis, mild oxidation and/or glycation of LDL in vitro increase the proteolytic susceptibility of apoB and its heparin binding affinity, perhaps by unmasking additional heparin-binding sites. For LDL from hyperglycemic type-2 diabetic patients, heparin binding was particularly destabilizing and caused apoB fragmentation and LDL fusion. However, for similar patients whose glycemic control was restored upon therapy, LDL-heparin binding affinity was rectified and LDL structural stability was partially restored. These results complement previous studies of LDL binding to arterial proteoglycans and suggest that such interactions may produce a particularly pro-atherogenic subclass of electronegative LDL. In summary, binding to heparin alters apoB conformation, perhaps by partially peeling it off the lipid, and triggers pro-atherogenic LDL modifications including hydrolysis, oxidation, and destabilization. Furthermore, phospholipid lipolysis, mild oxidation and glycation of LDL in vitro strengthen its binding to heparin, which helps explain stronger binding observed in hyperglycemic LDL. Combined effects of hyperglycemia and heparin binding are especially deleterious but are largely rectified upon diabetes therapy. These findings help establish a mechanistic link between diabetes and atherosclerosis.

Effects of red meat, white meat, and nonmeat protein sources on atherogenic lipoprotein measures in the context of low compared with high saturated fat intake: a randomized controlled trial

Dietary recommendations to limit red meat are based on observational studies linking intake to cardiovascular disease (CVD) risk together with the potential of its saturated fatty acid (SFA) content to raise low-density lipoprotein (LDL) cholesterol. However, the relation of white meat to CVD risk, and the effects of dietary protein source on lipoprotein particle subfractions, have not been extensively evaluated. We tested whether levels of atherogenic lipids and lipoproteins differed significantly following consumption of diets with high red meat content compared with diets with similar amounts of protein derived from white meat or nonmeat sources, and whether these effects were modified by concomitant intake of high compared with low SFAs. Generally healthy men and women, 21-65 y, body mass index 20-35 kg/m2, were randomly assigned to 1 of 2 parallel arms (high or low SFA) and within each, allocated to red meat, white meat, and nonmeat protein diets consumed for 4 wk each in random order. The primary outcomes were LDL cholesterol, apolipoprotein B (apoB), small+medium LDL particles, and total/high-density lipoprotein cholesterol. Analysis included participants who completed all 3 dietary protein assignments (61 for high SFA; 52 for low SFA). LDL cholesterol and apoB were higher with red and white meat than with nonmeat, independent of SFA content (P<0.0001 for all, except apoB: red meat compared with nonmeat [P=0.0004]). This was due primarily to increases in large LDL particles, whereas small+medium LDL and total/high-density lipoprotein cholesterol were unaffected by protein source (P=0.10 and P=0.51, respectively). Primary outcomes did not differ significantly between red and white meat. Independent of protein source, high compared with low SFA increased LDL cholesterol (P=0.0003), apoB (P=0.0002), and large LDL (P=0.0002). The findings are in keeping with recommendations promoting diets with a high proportion of plant-based food but, based on lipid and lipoprotein effects, do not provide evidence for choosing white over red meat for reducing CVD risk. This trial was registered at Clinicaltrials.gov as NCT01427855.

High-Dose DHA Has More Profound Effects on LDL-Related Features Than High-Dose EPA: The ComparED Study.

Supplementation with high-dose docosahexaenoic acid (DHA) increases serum low-density lipoprotein (LDL) cholesterol (LDL-C) concentrations more than high-dose eicosapentaenoic acid (EPA). The mechanisms underlying this difference are unknown. To examine the phenotypic change in LDL and mechanisms responsible for the differential LDL-C response to EPA and DHA supplementation in men and women at risk of cardiovascular disease. In a double-blind, controlled, crossover study, 48 men and 106 women with abdominal obesity and subclinical inflammation were randomized to a sequence of three treatment phases: phase 1, 2.7 g/d of EPA; phase 2, 2.7 g/d of DHA; and phase 3, 3 g/d of corn oil. All supplements were provided as three 1-g capsules for a total of 3 g/d. The 10-week treatment phases were separated by a 9-week washout period. In vivo kinetics of apolipoprotein (apo)B100-containing lipoproteins were assessed using primed-constant infusion of deuterated leucine at the end of each treatment in a subset of participants (n = 19). Compared with EPA, DHA increased LDL-C concentrations (+3.3%; P = 0.038) and mean LDL particle size (+0.7 Å; P < 0.001) and reduced the proportion of small LDL (-3.2%; P < 0.01). Both EPA and DHA decreased proprotein convertase subtilisin/kexin type 9 concentrations similarly (-18.2% vs -25.0%; P < 0.0001 vs control). Compared with EPA, DHA supplementation increased both the LDL apoB100 fractional catabolic rate (+11.4%; P = 0.008) and the production rate (+9.4%; P = 0.03). The results of the present study have shown that supplementation with high-dose DHA increases LDL turnover and contributes to larger LDL particles compared with EPA.

Differential Effects of Estrogen and Progestin on Apolipoprotein B100 and B48 Kinetics in Postmenopausal Women.

The distinct effects of the estrogen and progestin components of hormonal therapy on the metabolism of apolipoprotein (apo) B-containing lipoproteins have not been studied. We enrolled eight healthy postmenopausal women in a placebo-controlled, randomized, double-blind crossover study. Each subject received placebo, conjugated equine estrogen (CEE, 0.625 mg/day) and CEE plus medroxyprogesterone acetate (MPA, 2.5 mg/day) for 8 weeks in a randomized order, with a 4-week washout between phases. Main outcomes were the fractional catabolic rate (FCR) and production rate (PR) of apo B100 in triglyceride-rich lipoproteins (TRL), intermediate-density lipoproteins (IDL) and low -density lipoprotein (LDL) and of apo B48 in TRL. Compared to placebo, CEE increased TRL apo B100 PR (p = 0.04). CEE also increased LDL apo B100 FCR (p = 0.02), but this effect was offset by a significant increase in LDL apo B100 PR (p = 0.04). Adding MPA to CEE negated the CEE effects resulting in no significant changes in TRL apo B100 PR and LDL apo B100 FCR and PR relative to placebo. Relative to placebo, during CEE there was a trend toward a reduction in plasma apo B48 concentrations and PR (p = 0.07 and p = 0.12, respectively). Compared with CEE, CEE + MPA significantly increased TRL apo B48 FCR (p = 0.02) as well as apo B48 PR (p = 0.01), resulting in no significant changes in apo B48 concentration. Estrogen and progestin have independent and opposing effects on the metabolism of the atherogenic apo B100- and apo B48-containing lipoproteins.

Effects of oolonghomobisflavan A on oxidation of low-density lipoprotein.

Oxidation of low-density lipoprotein (LDL) by reactive oxygen species (ROS) and reactive nitrogen species (RNS) has been suggested to be involved in the onset of atherosclerosis. Oolong tea contains unique polyphenols including oolonghomobisflavan A (OFA). In this study, the effects of OFA on LDL oxidation by ROS and RNS were investigated in vitro. OFA suppressed formation of cholesterol ester hydroperoxides in LDL oxidized by peroxyl radical and peroxynitrite, and formation of thiobarbituric acid reactive substances in LDL oxidized by Cu2+. In addition, OFA inhibited fragmentation, carbonylation, and nitration of apolipoprotein B-100 (apo B-100) in the oxidized LDL, in which heparin-binding activity of apo B-100 was protected by OFA. Our results suggest that OFA exhibits antioxidant activity against both lipid peroxidation and oxidative modification of apo B-100 in LDL oxidized by ROS and RNS. Polyphenols in oolong tea may prevent atherosclerosis by reducing oxidative stress.

Solution State Structure of P1, the Mimetic Peptide Derived from IgM Antigen Apo B-100 by NMR

Apolipoprotein B-100 (Apo-B100) is a major component of low density lipoprotein (LDL). Apo B-100 protein has 4,536 amino acid sequence and these amino acids are classified into peptide groups A to G with subsequent 20 amino acids (P1-P302). The peptide groups were act as immunoglobulin (Ig) antigens which oxidized via malondialdehyde (MDA). The mimetic peptide P1 (EEEMLENVSLVCPKDAT RFK) out of D-group peptides carrying the highest value of IgG antigens were selected for structural studies that may provide antigen specificity. Circular Dichroism (CD) spectra were measured for peptide secondary structure in the range of 190-250 nm. Experimental results show that P1 exhibit partial of <TEX>${\beta}-sheet$</TEX> and random coil structure. Homonuclear (COSY, TOCSY, NOESY) 2D-NMR experiments were carried out for NMR signal assignments and structure determination for P1. On the basis of these completely assigned NMR spectra and distance data, distance geometry (DG) and Molecular dynamics (MD) were carried out to determine the structures of P1. The proposed structure was selected by comparisons between experimental NOE spectra and back calculated 2D NOE results from determined structure showing acceptable agreement. The total Root-Mean-Square-Deviation (RMSD) value of P1 obtained upon superposition of all atoms was in the range <TEX>$0.33{\AA}$</TEX>. The solution state P1 has mixed structure of <TEX>${\beta}-sheet$</TEX> (Glu[1] to Cys[12]) and random coil (Pro[13] to Lys[20]). These NMR results are well consistent with secondary structure from experimental results of circular dichroism. Structural studies based on NMR may contribute to the studies of atherosclerosis and observed conformational characteristics of apo B-100 in LDL using monoclonal antibodies.

Enhanced Sphingomyelinase Activity Contributes to the Apoptotic Capacity of Electronegative Low-Density Lipoprotein

Sphingomyelinase (SMase) catalyzes the degradation of sphingomyelin to ceramide. In patients with metabolic syndrome or diabetes, circulating plasma ceramide levels are significantly higher than in normal individuals. Our data indicate that electronegative low-density lipoprotein (LDL) shows SMase activity, which leads to increased ceramide levels that can produce pro-inflammatory effects and susceptibility to aggregation. According to sequence alignment and protein structure predictions, the putative catalytic site of SMase activity is in the α2 region of apoB-100. To identify specific post-translational modifications of apoB100 near the catalytic region, we performed data-independent, parallel-fragmentation liquid chromatography/mass spectrometry (LC/MS(E)), followed by data analysis with ProteinLynx GlobalServer v2.4. Results showed that the serine of apoB100 in electronegative LDL was highly O-glycosylated, including S(1732), S(1959), S(2378), S(2408), and S(2429). These findings may support the changing of the α-helix/β-pleated sheets ratio in protein structure analysis. Further study is necessary to confirm the activation of SMase activity by electronegative LDL.

Effects of the Particulate Matter₂.₅ (PM₂.₅) on Lipoprotein Metabolism, Uptake and Degradation, and Embryo Toxicity.

Particulate matter2.5 (PM2.5) is notorious for its strong toxic effects on the cardiovascular, skin, nervous, and reproduction systems. However, the molecular mechanism by which PM2.5 aggravates disease progression is poorly understood, especially in a water-soluble state. In the current study, we investigated the putative physiological effects of aqueous PM2.5 solution on lipoprotein metabolism. Collected PM2.5 from Seoul, Korea was dissolved in water, and the water extract (final 3 and 30 ppm) was treated to human serum lipoproteins, macrophages, and dermal cells. PM2.5 extract resulted in degradation and aggregation of high-density lipoprotein (HDL) as well as low-density lipoprotein (LDL); apoA-I in HDL aggregated and apo-B in LDL disappeared. PM2.5 treatment (final 30 ppm) also induced cellular uptake of oxidized LDL (oxLDL) into macrophages, especially in the presence of fructose (final 50 mM). Uptake of oxLDL along with production of reactive oxygen species was accelerated by PM2.5 solution in a dose-dependent manner. Further, PM2.5 solution caused cellular senescence in human dermal fibroblast cells. Microinjection of PM2.5 solution into zebrafish embryos induced severe mortality accompanied by impairment of skeletal development. In conclusion, water extract of PM2.5 induced oxidative stress as a precursor to cardiovascular toxicity, skin cell senescence, and embryonic toxicity via aggregation and proteolytic degradation of serum lipoproteins.

Effects of extended-release niacin on the postprandial metabolism of Lp(a) and ApoB-100-containing lipoproteins in statin-treated men with type 2 diabetes mellitus.

The effects of extended-release niacin (ERN; 1-2 g/d) on the metabolism of lipoprotein(a) (Lp(a)) and apolipoprotein (apo) B-100-containing lipoproteins were investigated in 11 statin-treated white men with type 2 diabetes mellitus in a randomized, crossover trial of 12-weeks duration. The kinetics of Lp(a) and very low-density lipoprotein (VLDL), intermediate-density lipoprotein, and low-density lipoprotein (LDL) apoB-100 were determined following a standardized oral fat load (87% fat) using intravenous administration of D3-leucine, gas chromatography-mass spectrometry, and compartmental modeling. ERN significantly decreased fasting plasma total cholesterol, LDL cholesterol, and triglyceride concentrations. These effects were achieved without significant changes in body weight or insulin resistance. ERN significantly decreased plasma Lp(a) concentration (-26.5%) and the production rates of apo(a) (-41.5%) and Lp(a)-apoB-100 (-32.1%); the effect was greater in individuals with elevated Lp(a) concentration. ERN significantly decreased VLDL (-58.7%), intermediate-density lipoprotein (-33.6%), and LDL (-18.3%) apoB-100 concentrations and the corresponding production rates (VLDL, -49.8%; intermediate-density lipoprotein, -44.7%; LDL, -46.1%). The number of VLDL apoB-100 particles secreted increased in response to the oral fat load. Despite this, total VLDL apoB-100 production over the 10-hour postprandial period was significantly decreased with ERN (-21.9%). In statin-treated men with type 2 diabetes mellitus, ERN decreased plasma Lp(a) concentrations by decreasing the production of apo(a) and Lp(a)-apoB-100. ERN also decreased the concentrations of apoB-100-containing lipoproteins by decreasing VLDL production and the transport of these particles down the VLDL to LDL cascade. Our study provides further mechanistic insights into the lipid-regulating effects of ERN.

Abstract 129: Effects of a Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitor, Alirocumab, on Lipid and Lipoprotein Metabolism in Normal Subjects

Background: Proprotein convertase subtilisin/kexin type (PCSK9) inhibitors are promising new drugs for the treatment of hypercholesterolemia. They inhibit the binding of PCSK9 to the low density lipoprotein (LDL) receptor that, in turn, decreases lysosomal degradation of LDL receptors and increases their numbers on the cell surface. In Phase 2/3 studies, alirocumab significantly lowered plasma levels of LDL-cholesterol (C) and apolipoprotein B (apoB). The mechanism underlying the LDL-C lowering effects of PCSK9 inhibition has not been reported. Method: We enrolled 10 healthy volunteers (4 male, 6 female), into a Phase 1, placebo-controlled, single-blind, single-sequence study to examine the effects of alirocumab, 150 mg administered subcutaneously every two weeks, on lipid and lipoproteins levels and the metabolism of apoB in very low density (VLDL), intermediate density (IDL) and LDL. Subjects received 2 doses of placebo followed by 5 doses of alirocumab. At the end of each treatment period, fasting lipids and lipoprotein levels were measured, and stable isotope studies of the apoB turnover in VLDL, IDL and LDL were performed. Results: Alirocumab significantly reduced plasma levels of total-C by 37% (178.4±34 to 112.7±29 mg/dL), LDL-C by 59% (110.2±25 to 45.5±26 mg/dL), and apoB by 51% (93.6±25 to 45.5±13 mg/dL) compared to placebo. Plasma triglycerides (TG) and HDL-C did not change. Levels of LDL-C, LDL-TG, and LDL-apoB fell by 55.8±10%, 33.9±13%, and 56.0±11%, respectively (all p&lt;0.0001), on alirocumab. The reductions in LDL apoB were explained by a dramatic increase in the fractional clearance rate (FCR) of LDL apoB from 0.50±0.18 on placebo to 1.02±0.35 pools/day on alirocumab (p&lt;0.001) and a trend toward lower LDL apoB production rates on alirocumab (15.1±4.6 vs 12.9±3.3 mg/kg/day; p=0.10). Levels of IDL-C, IDL-TG and IDL-apoB were also reduced significantly and there was a trend toward an increase in IDL apoB FCR on alirocumab (placebo: 9.2±4 vs alirocumab: 10.8±3 pools/day; p=0.06). Additional kinetic parameters will be presented at the meeting. Summary: Alirocumab treatment significantly reduced the levels of IDL and LDL, and these changes were due to increases in the FCRs of these lipoproteins, particularly LDL.

Abstract 310: Oxidized LDL-binding Cationic Peptides and Proteins in Inflammation and Atherosclerosis: Novel Insights

Background: Apolipoprotein A1 and apolipoprotein E mimetic peptides have attracted attention due to their ability to reduce atherosclerosis and exhibit antioxidant, anti-inflammatory, and hypolipidemic properties. We previously reported that the non-lipoprotein-related Lys-Arg-rich cationic peptides have anti-inflammatory properties both in vitro and in vivo. In this study, we have determined whether ApoB100 of low density lipoprotein (N-LDL), which is Lys-Arg rich, has similar properties. Methods: 5F-mimetic peptide of ApoA1, LL27 derived from the anti-microbial peptide CAMP, and a human glycodelin derived peptide, were commercially synthesized. N-LDL was prepared and used. The ability of these peptides and protein to neutralize charges of modified lipoproteins, as well as attenuate macrophage uptake and inflammation, were analyzed. Oxidized LDL (Ox-LDL) was pretreated with increasing concentrations of peptides and N-LDL to evaluate charge neutralizing properties of the peptides as well as that of the protein (ApoB100). RAW cells were incubated with LPS or Ox-LDL pretreated with and without peptides and N-LDL. RNA was isolated from treated cells and real time PCR was performed using mouse IL-1α and IL-6 primers. Results: Cationic peptides as well as ApoB100 protein of N-LDL decomposed the peroxide content of 13-HPODE. Incubation of Ox-LDL and Ac-LDL with the peptides as well as ApoB100 resulted in charge neutralization as noted by agarose gel electrophoresis. Pre-incubation of the peptides and N-LDL with modified lipoproteins reduced the uptake of the latter by macrophages and foam cell formation as detected by Oil-Red O staining. Reduced inflammation was observed in the presence of N-LDL as compared to LPS/Ox-LDL. Conclusions: Based on these studies, we postulate that cationic peptides and protein might have properties that would a) affect events that are unrelated to lipid lowering, b) might play an additional role in immune competent cells, including macrophages, and c) might interact with other biologically important anionic molecules, including lipids and proteins. We also predict that lysine-rich cationic peptides and proteins could have therapeutic potential in reducing CVD/atherosclerosis-associated inflammation.

Association of Plasma Ceramides and Sphingomyelin With VLDL apoB-100 Fractional Catabolic Rate Before and After Rosuvastatin Treatment.

The objective of the study was to examine post hoc associations between plasma sphingolipids and lipoprotein kinetics in men with the metabolic syndrome after rosuvastatin treatment. Plasma sphingolipid profiling, determined by tandem mass spectrometry, was performed in a randomized, double-blind, triple-crossover trial (n = 12) of 5-week treatment periods with placebo or rosuvastatin (10 or 40 mg/d) with 2-week washouts between treatments. Baseline plasma ceramides were associated with very low-density lipoprotein (VLDL) apolipoprotein (apo)-B-100 concentration (r = 0.58, P < .05) and inversely with VLDL apoB-100 fractional catabolic rate (FCR; r = -0.67, P = .02). Posttreatment changes with rosuvastatin (40 mg/d) in plasma ceramides were inversely associated with VLDL apoB-100 FCR (r = -0.62, P = .03) independent of changes in plasma triglycerides, cholesterol, and low-density lipoprotein-cholesterol. By contrast, baseline and postrosuvastatin treatment plasma sphingomyelin levels were not associated with apoB-100 kinetics. Plasma ceramides and sphingomyelin were not associated with the kinetics or concentrations of high-density lipoprotein apoA-I, and low-density lipoprotein apoB. In the metabolic syndrome, the ability of rosuvastatin to increase VLDL apoB-100 FCR may reflect ceramide-specific mechanistic actions and/or sphingolipid exchange.

LDL cholesterol and apolipoprotein B are associated with ascending aorta dilatation in bicuspid aortic valve patients.

The factors related to ascending aorta dilation (AAD) in patients with bicuspid aortic valve (BAV) are not completely understood. In addition, the role of cholesterol metabolism in AAD has not been studied. We analyzed the relationship between different lipid parameters and the ascending aorta diameter/presence of aortic dilatation in 91 consecutive patients with BAV. We observed a positive linear correlation between the total cholesterol, low-density lipoprotein (LDL) cholesterol and apolipoprotein B (ApoB) levels and the ascending aorta diameter. The patients with AAD had higher LDL cholesterol and ApoB levels. Whereas LDL cholesterol and ApoB were identified as independent factors predictors of the aortic root diameter, only ApoB predicted the diameter of the ascending aorta. On the other hand, the levels of ApoB were an independent factor related to the dilatation of the aortic root. We have observed that cholesterol is associated with ascending aorta diameter and dilation in BAV patients. Further experimental and clinical studies are needed to explain the pathobiology of this association.

Selection for behavior and correlation with the macroglobuline and lypoproteine systems in the American mink (Neovison vison)

A population-genetic comparison between mink populations with tame and aggressive behavior was performed. Six allotypes of the Lpm system, the AIM alpha macroglobulin, and two allotypes of the Ld system, a homologue of APOB low-density lipoprotein, were analyzed. The pairwise compared groups differed in markers Lpml, Lpm3, Lpm5, and Lpm10. Alleles with allotypes Lpml and Lpm3 were significantly associated with aggressive behavior, whereas allele Lpm non-10 was associated tame behavior. No statistically significant differences in the frequencies of Ldl and Ld2 allotypes of the Ld low-density lipoprotein system have been found.

In vitro oxidative footprinting provides insight into apolipoprotein B-100 structure in low-density lipoprotein.

Low-density lipoprotein (LDL) is a major cholesterol carrier in human blood. Oxidations of apolipoprotein B-100 (apo B-100, LDL protein) could be proatherogenic and play critical roles in early stages of plaque formation in the arterial wall. The structure of apo B-100 is still poorly understood, partially due to its size (550 KDa, 4563 amino acids). To gain an insight into LDL structure, we mapped the regions of apo B-100 in human LDL that were prone to oxidation using peroxynitrite and hypochlorite as probes. In this study, LDL was incubated with various concentrations of peroxynitrite and sodium hypochlorite in bicarbonate buffer. The LDL protein apo B-100 was delipidated, denatured, alkylated, and subjected to tryptic digestion. Tryptic peptides were analyzed employing LC-MS/MS. Database search was performed against the apo B-100 database (SwissProt accession #P04114) using "SEQUEST" algorithm to identify peroxynitrite and hypochlorite-mediated oxidations markers nitrotyrosine, nitrotryptophan, hydroxy-tryptophan, and 3-chlorotyrosine. Several site-specific oxidations were identified in apo B-100 after treatment of intact LDL particles with the oxidants. We hypothesize that these regions could be accessible to oxidant and critical for early events in atherosclerotic plaque deposition.

Laboratory validation of a low density lipoprotein apolipoprotein-B assay

ObjectivesNumerous publications have shown strong association between CHD risk and either apolipoprotein B (Apo-B) or low density lipoprotein (LDL) particle number (LDL-P). It is however unknown if Apo-B or LDL-P has a stronger predictive ability for future CHD. This uncertainty may be due to the inability of current Apo-B assays to separate the contribution of very low-density lipoprotein particles from the total Apo-B concentration. As such we have performed a laboratory validation of the Maine Standards® LDL Apo-B assay on the Roche Cobas 6000 analyzer. Design and methodsImprecision, linear range, and limit of quantitation studies were performed using quality control materials. Plasma samples collected for lipid profile analysis were analyzed via the LDL Apo-B assay and compared to the LDL cholesterol (LDL-C) concentration determined via direct LDL assay and Friedewald equation. ResultsThe LDL Apo-B within-run imprecision was 2.3% at 62mg/dL and 2.2% at 109mg/dL. The within-laboratory imprecision was 9.7% at 57mg/dl and 6.1% at 104mg/dL. Linear regression analysis of LDL Apo-B versus calculated and measured LDL-c resulted in equations of LDL Apo-B=0.620∗(LDL)+45.4, R=0.9063 and LDL-Apo-B=0.607∗(LDL)+38.8, R=0.9393, respectively. Bias plot analyses revealed that at low LDL-C concentration, there was a tendency for a higher than anticipated LDL Apo-B concentration. ConclusionsThe Maine Standards LDL Apo-B assay is a precise automated assay and comparison of LDL Apo-B to LDL-c concentration demonstrates that low LDL-C concentrations may still carry residual risk of CHD due to increased concentration of small dense LDL particles.

The relationship between the postprandial lipemic response and lipid composition in persons with spinal cord injury

ObjectiveTo determine the influence of lipid concentration, lipid particle size, and total abdominal fat (TAF) on postprandial lipemic response (PPLr) in persons with spinal cord injury (SCI).MethodsThirty-five persons with SCI (17 paraplegia, 18 tetraplegia) and 18 able-bodied (AB) individuals participated. Following a 10-hour fast, blood was drawn for lipids, apolipoprotein (apo) A1 and B concentrations, and low-density (LSP) and high-density (HSP) lipoprotein particle sizes. A high-fat milkshake was consumed (∼1.3 g fat/kg). Blood was drawn at 2, 4, and 6 hours to determine PPLr, (triglyceride (TG) area under the curve). TAF and visceral (VF) fat were measured by ultrasonography; total body fat (TBF) by dual-energy X-ray absorptiometry. Differences between the groups were determined by independent sample t-tests. Pearson correlation coefficients determined the relationship among PPLr and lipids, and TAF.ResultsThere were no significant differences in fasting TG, low-density lipoprotein (LDL), apoB, TAF, or PPLr values between the groups. In SCI, PPLr significantly correlated with: apoB (r = 0.63, P < 0.01, LSP (r = 0.57, P < 0.01), and TAF (r = 0.36, P < 0.01). After controlling for age and duration of injury, PPLr significantly correlated with apoB (r = 0.66, P = 0.001), TBF (r = 0.45, P = 0.03), VF (r = 0.66, P = 0.02), and TAF (r = 0.56, P = 0.007).ConclusionsAlthough concentrations of LDL cholesterol and apoB were not different between SCI and AB groups, LSP, apoB, and TAF correlated with PPLr in persons with SCI. ApoB was associated with a greater PPLr in those with motor complete SCI, after controlling for age and duration of injury.