Objectives The purpose of this study was to assess the prognostic utility of lipoprotein(a) Lp(a) in individuals with coronary artery disease (CAD). Background Data regarding an association between ...Lp(a) and cardiovascular (CV) risk in secondary prevention populations are sparse. Methods Plasma Lp(a) was measured in 6,708 subjects with CAD from 3 studies; data were then combined with 8 previously published studies for a total of 18,978 subjects. Results Across the 3 studies, increasing levels of Lp(a) were not associated with the risk of CV events when modeled as a continuous variable (odds ratio OR: 1.03 per log-transformed SD, 95% confidence interval CI: 0.96 to 1.11) or by quintile (Q5:Q1 OR: 1.05, 95% CI: 0.83 to 1.34). When data were combined with previously published studies of Lp(a) in secondary prevention, subjects with Lp(a) levels in the highest quantile were at increased risk of CV events (OR: 1.40, 95% CI: 1.15 to 1.71), but with significant between-study heterogeneity (p = 0.001). When stratified on the basis of low-density lipoprotein (LDL) cholesterol, the association between Lp(a) and CV events was significant in studies in which average LDL cholesterol was ≥130 mg/dl (OR: 1.46, 95% CI: 1.23 to 1.73, p < 0.001), whereas this relationship did not achieve statistical significance for studies with an average LDL cholesterol <130 mg/dl (OR: 1.20, 95% CI: 0.90 to 1.60, p = 0.21). Conclusions Lp(a) is significantly associated with the risk of CV events in patients with established CAD; however, there exists marked heterogeneity across trials. In particular, the prognostic value of Lp(a) in patients with low cholesterol levels remains unclear.
Abstract
Aims
Myocardial ischaemia followed by reperfusion (IR) causes an oxidative burst resulting in cellular dysfunction. Little is known about the impact of oxidative stress on cardiomyocyte ...lipids and their role in cardiac cell death. Our goal was to identify oxidized phosphatidylcholine-containing phospholipids (OxPL) generated during IR, and to determine their impact on cell viability and myocardial infarct size.
Methods and results
OxPL were quantitated in isolated rat cardiomyocytes using mass spectrophotometry following 24 h of IR. Cardiomyocyte cell death was quantitated following exogenously added OxPL and in the absence or presence of E06, a ‘natural’ murine monoclonal antibody that binds to the PC headgroup of OxPL. The impact of OxPL on mitochondria in cardiomyocytes was also determined using cell fractionation and Bnip expression. Transgenic Ldlr−/− mice, overexpressing a single-chain variable fragment of E06 (Ldlr−/−-E06-scFv-Tg) were used to assess the effect of inactivating endogenously generated OxPL in vivo on myocardial infarct size. Following IR in vitro, isolated rat cardiomyocytes showed a significant increase in the specific OxPLs PONPC, POVPC, PAzPC, and PGPC (P < 0.05 to P < 0.001 for all). Exogenously added OxPLs resulted in significant death of rat cardiomyocytes, an effect inhibited by E06 (percent cell death with added POVPC was 22.6 ± 4.14% and with PONPC was 25.3 ± 3.4% compared to 8.0 ± 1.6% and 6.4 ± 1.0%, respectively, with the addition of E06, P < 0.05 for both). IR increased mitochondrial content of OxPL in rat cardiomyocytes and also increased expression of Bcl-2 death protein 3 (Bnip3), which was inhibited in presence of E06. Notably cardiomyocytes with Bnip3 knock-down were protected against cytotoxic effects of OxPL. In mice exposed to myocardial IR in vivo, compared to Ldlr−/− mice, Ldlr−/−-E06-scFv-Tg mice had significantly smaller myocardial infarct size normalized to area at risk (72.4 ± 21.9% vs. 47.7 ± 17.6%, P = 0.023).
Conclusions
OxPL are generated within cardiomyocytes during IR and have detrimental effects on cardiomyocyte viability. Inactivation of OxPL in vivo results in a reduction of infarct size.
Background Familial hypercholesterolemia (FH) is characterized by severely elevated LDL-cholesterol and up to a 20-fold increase in premature cardiovascular disease (CVD). Objective Mipomersen has ...been shown to lower the levels of these atherogenic lipoproteins, but whether it lowers major adverse cardiac events (MACEs) has not been addressed. Methods This post hoc analysis of prospectively collected data of three randomized trials and an open-label extension phase included patients that were exposed to ≥12 months of mipomersen. MACE rates that occurred during 24 months before randomization in the mipomersen group were compared to MACE rates after initiation of mipomersen. Data from the trials included in this report are registered in Clinicaltrials.gov ( NCT00607373 , NCT00706849 , NCT00794664 , NCT00694109 ). The occurrence of MACE events, defined as cardiovascular death, nonfatal acute myocardial infarction, hospitalization for unstable angina, coronary revascularization and nonfatal ischemic stroke, was obtained from medical history data pre-treatment and adjudicated by an independent adjudication committee for events occurring post-treatment with mipomersen. Results MACEs were identified in 61.5% of patients (64 patients with 146 events 39 myocardial infarctions, 99 coronary revascularizations, 5 unstable angina episodes, 3 ischemic strokes) during 24 months before mipomersen treatment, and in 9.6% of patients (10 patients with 13 events 1 cardiovascular death, 2 myocardial infarctions, 6 coronary interventions, 4 unstable angina episodes) during a mean of 24.4 months after initiation of mipomersen (MACE rate 25.7 of 1000 patient-months vs 3.9 of 1000 patient-months, OR = 0.053 95% CI, 0.016–0.168, P < .0001 by the exact McNemar test). The reduction in MACE coincided with a mean absolute reduction in LDL-C of 70 mg/dL (−28%) and of non-HDL cholesterol of 74 mg/dL (−26%) as well as reduction in Lp(a) of 11 mg/dL (−17%). Conclusion Long-term mipomersen treatment not only lowers levels of atherogenic lipoproteins but may also lead to a reduction in cardiovascular events in FH patients.
Objectives This study sought to assess whether oxidation-specific biomarkers are associated with an increased risk of coronary artery disease (CAD) events. Background The relationship of a panel of ...oxidative biomarkers and lipoprotein(a) Lp(a) to CAD risk is not fully determined. Methods A prospective case-control study nested in the EPIC (European Prospective Investigation of Cancer)-Norfolk cohort of 45- to 79-year-old apparently healthy men and women followed for ∼6 years was designed. Cases consisted of participants in whom fatal or nonfatal CAD developed, matched by sex, age, and enrollment time with controls without CAD. Baseline levels of oxidized phospholipids on apolipoprotein B-100 particles and Lp(a) were measured in 763 cases and 1,397 controls. Their relationship to secretory phospholipase A2 type IIA mass and activity, myeloperoxidase mass, and lipoprotein-associated phospholipase A2 activity and association with CAD events were determined. Results After adjusting for age, smoking, diabetes, low- and high-density lipoprotein cholesterol, and systolic blood pressure, the highest tertiles of oxidized phospholipids on apolipoprotein B-100 particles and Lp(a) were associated with a significantly higher risk of CAD events (odds ratios: 1.67 and 1.64, respectively; p < 0.001) compared with the lowest tertiles. The odds ratio of CAD events associated with the highest tertiles of oxidized phospholipids on apolipoprotein B-100 particles or Lp(a) was significantly potentiated (approximately doubled) by the highest tertiles of secretory phospholipase A2 activity and mass but less so for myeloperoxidase and lipoprotein-associated phospholipase A2 activity. The odds ratios for fatal CAD were higher than for the combined end point. After taking into account the Framingham Risk Score, c -index values progressively increased when oxidative biomarkers were added to the model. Conclusions This EPIC-Norfolk study links pathophysiologically related oxidation-specific biomarkers and Lp(a) with CAD events. Oxidation-specific biomarkers provide cumulative predictive value when added to traditional cardiovascular risk factors.
Lipoprotein (a) Lp(a) is a risk factor for CVD and a target of therapy, but Lp(a) measurements are not globally standardized. Commercially available assays generally use polyclonal antibodies that ...detect multiple sites within the kringle (K)IV2 repeat region of Lp(a) and may lead to inaccurate assessments of plasma levels. With increasing awareness of Lp(a) as a cardiovascular risk factor and the active clinical development of new potential therapeutic approaches, the broad availability of reagents capable of providing isoform independence of Lp(a) measurements is paramount. To address this issue, we generated a murine monoclonal antibody that binds to only one site on apo(a). A BALB/C mouse was immunized with a truncated version of apo(a) that contained eight total KIV repeats, including only one copy of KIV2. We generated hybridomas, screened them, and successfully produced a KIV2-independent monoclonal antibody, named LPA-KIV9. Using a variety of truncated apo(a) constructs to map its binding site, we found that LPA-KIV9 binds to KIV9 without binding to plasminogen. Fine peptide mapping revealed that LPA-KIV9 bound to the sequence 4076LETPTVV4082 on KIV9. In conclusion, the generation of monoclonal antibody LPA-KIV9 may be a useful reagent in basic research studies and in the clinical application of Lp(a) measurements.
OBJECTIVE—Little is known about the role(s) B cells play in obesity-induced metabolic dysfunction. This study used a mouse with B-cell–specific deletion of Id3 (Id3) to identify B-cell functions ...involved in the metabolic consequences of obesity.
APPROACH AND RESULTS—Diet-induced obese Id3 mice demonstrated attenuated inflammation and insulin resistance in visceral adipose tissue (VAT), and improved systemic glucose tolerance. VAT in Id3 mice had increased B-1b B cells and elevated IgM natural antibodies to oxidation-specific epitopes. B-1b B cells reduced cytokine production in VAT M1 macrophages, and adoptively transferred B-1b B cells trafficked to VAT and produced natural antibodies for the duration of 13-week studies. B-1b B cells null for Id3 demonstrated increased proliferation, established larger populations in Rag1 VAT, and attenuated diet-induced glucose intolerance and VAT insulin resistance in Rag1 hosts. However, transfer of B-1b B cells unable to secrete IgM had no effect on glucose tolerance. In an obese human population, results provided the first evidence that B-1 cells are enriched in human VAT and IgM antibodies to oxidation-specific epitopes inversely correlated with inflammation and insulin resistance.
CONCLUSIONS—NAb-producing B-1b B cells are increased in Id3 mice and attenuate adipose tissue inflammation and glucose intolerance in diet-induced obese mice. Additional findings are the first to identify VAT as a reservoir for human B-1 cells and to link anti-inflammatory IgM antibodies with reduced inflammation and improved metabolic phenotype in obese humans.
The aim of this article is to review, analyze and interpret the growing body of evidence on circulating oxidized low-density lipoprotein and its relationship to diagnosis and prognosis of ...cardiovascular disease.
Previous studies focused on indirect measures of oxidative stress such as susceptibility of low-density lipoprotein to oxidation and measurement of autoantibodies to oxidized low-density lipoprotein. The generation of monoclonal antibodies recognizing distinct oxidation-specific epitopes has allowed the development of sensitive and specific assays to measure circulating oxidized low-density lipoprotein. Recent work in human populations has demonstrated that circulating oxidized low-density lipoprotein is associated with preclinical atherosclerosis, coronary and peripheral arterial atherosclerosis, acute coronary syndromes and vulnerable plaques. Several studies have also suggested that elevated levels of oxidized low-density lipoprotein are a prognostic indicator of cardiovascular outcomes. In addition, it has been shown that lipoprotein(a) is the primary carrier of oxidized phospholipids in the circulation of humans, suggesting additional mechanisms through which lipoprotein(a) may be pro-atherogenic.
Research on circulating oxidized low-density lipoprotein biomarkers is rapidly accelerating and providing novel insights into the pathophysiology of cardiovascular disease. Future studies will further assess the clinical utility of oxidized low-density lipoprotein biomarkers by determining their prognostic value in the diagnosis and prognosis of cardiovascular disease and will also evaluate the relative merit of specific assays by performing comparative studies.
Abstract Background Biomarkers to predict recurrent stroke and targets of therapy to prevent stroke are lacking. Objectives This study evaluated whether patients with prior cerebrovascular events and ...elevated levels of oxidized phospholipids on apolipoprotein B-100 (OxPL-apoB), but without prior coronary artery disease (CAD), are at risk for recurrent stroke and CAD events following high-dose statin therapy. Methods In the SPARCL (Stroke Prevention by Aggressive Reduction in Cholesterol Levels) trial, OxPL-apoB levels were measured in 4,385 patients with stroke or transient ischemic attack at baseline and in 3,106 patients at 5 years following randomization to placebo or 80 mg atorvastatin. The primary endpoint was the time from randomization to a second nonfatal or fatal stroke. Secondary endpoints included first major coronary events and any cardiovascular event. Results Patients with recurrent stroke had higher baseline median OxPL-apoB levels than patients without (15.5 nmol/l vs. 11.6 nmol/l; p < 0.0001). After multivariable adjustment, elevated baseline OxPL-apoB predicted recurrent stroke (hazard ratio HR: 4.3; p < 0.0001), first major coronary events (HR: 4.0; p < 0.0001), and any cardiovascular event (HR: 4.4; p < 0.0001). These comparisons for any endpoint did not differ by treatment, shown as a nonsignificant interaction test. The net reclassification improvement, integrated discrimination improvement, and area under the receiver-operating characteristic curve (AUC) were all significantly improved by adding OxPL-apoB to the models, with ΔAUC +0.0505 (p < 0.0001) for recurrent stroke, ΔAUC +0.0409 (p < 0.0001) for first major coronary event, and ΔAUC +0.0791 (p < 0.0001) for any cardiovascular event. Conclusions Elevated OxPL-apoB levels predicted recurrent stroke and first major coronary events in patients with prior stroke or transient ischemic attack. The lack of statin–OxPL-apoB treatment interaction suggested that OxPLs might be statin-independent therapeutic targets to reduce risk of cardiovascular events. (Lipitor in the Prevention of Stroke, for Patients Who Have Had a Previous Stroke SPARCL; NCT00147602 )
Oxidized phospholipids (OxPLs) on apolipoprotein B-100 (apoB-100) particles are strongly associated with lipoprotein a (Lpa). In this study, we evaluated whether Lpa is preferentially the carrier of ...OxPL in human plasma. The content of OxPL on apoB-100 particles was measured with monoclonal antibody E06, which recognizes the phosphocholine (PC) headgroup of oxidized but not native phospholipids. To assess whether OxPLs were preferentially bound by Lpa as opposed to other lipoproteins, immunoprecipitation and ultracentrifugation experiments, in vitro transfer studies, and chemiluminescent ELISAs were performed. Immunoprecipitation of Lpa from human plasma with an apolipoprotein a (apoa)-specific antibody demonstrated that more than 85% of E06 reactivity (i.e., OxPL) coimmunoprecipitated with Lpa. Ultracentrifugation experiments showed that nearly all OxPLs were found in fractions containing apoa, as opposed to other apolipoproteins. In vitro transfer studies showed that oxidized LDL preferentially donates OxPLs to Lpa, as opposed to LDL, in a time- and temperature-dependent manner, even in aqueous buffer. Approximately 50% of E06 immunoreactivity could be extracted from isolated Lpa following exposure of plasma to various lipid solvents. These data demonstrate that Lpa is the preferential carrier of PC-containing OxPL in human plasma. This unique property of Lpa suggests novel insights into its physiological function and mechanisms of atherogenicity.
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