Lipoprotein-associated phospholipase A(2) and risk of coronary disease, stroke, and mortality: collaborative analysis of 32 prospective studies

Lipoprotein-associated phospholipase A2 and outcome in patients with type 2 diabetes on haemodialysis

BACKGROUND

  Lipoprotein-associated phospholipase A2 (LpPLA2) is a lipoprotein-bound enzyme involved in inflammation and atherosclerosis. In a post hoc analysis of a controlled trial with atorvastatin in patients with type 2 diabetes (T2D) on haemodialysis, we examined the association between baseline and change by measuring baseline LpPLA2 activity on cardiovascular events (CVE) and mortality.

METHODS AND RESULTS

  LpPLA2 activity was available of 1202 patients at baseline and 6 months after randomisation from 1255 patients in the German Diabetes Dialysis Study. During the 4-year follow-up, 445 patients (37%) suffered from CVE and 583 patients (49%) died. The highest quartile of LpPLA2 activity (≥615 U/L) was associated with elevated risk for CVE [HR 1·35 (1·02-1·87); P = 0·035]. This association was mainly driven by the placebo group [HR 1·51 (1·01-2·25); P = 0·046]. Receiver-operating characteristics analysis revealed that including LpPLA2 activity in an already adjusted model increased the area under the curve (AUC) for CVE from 0·586 (0·553-0·620) to 0·632 (0·599-0·664; P = 0·020) and for death from 0·704 (0·674-0·733) to 0·708 (0·679-0·737; P = 0·026). In atorvastatin-treated patients, the decrease in LpPLA2 was associated with reduced fatal risk [HR per standard deviation 0·74 (0·62-0·90); P = 0·002], an effect not seen in the placebo group. In contrast, those patients in the placebo group presenting a > 25% decrease in LpPLA2 activity (n = 33) had a more than doubled risk of dying [HR 2·48 (1·56-3·95); P < 0·001].

CONCLUSION

  LpPLA2 activity is predictive for cardiovascular outcome and total mortality. Reducing LpPLA2 by atorvastatin was associated with reduced mortality in patients with T2D on haemodialysis.

New directions in cardiovascular risk assessment: the role of secondary risk stratification markers

Cardiovascular disease (CVD) risk screening is performed by multivariate methods relying on calculators derived from the Framingham study, other epidemiological studies or primary care records. However, it only identifies 70% of individuals at risk for CVD events and there has been interest in adding other risk factors to improve its predictive capacity. The addition of a family history of premature CVD is well established and there is evidence for adding lipoprotein (a) in some populations and possibly C-reactive protein may be suitable for general use in CVD risk assessment. Most new biochemical and imaging markers have been assessed in the context of improving risk classification in intermediate-risk groups rather than in the general population. There is evidence that N-terminal pro-B-type natriuretic peptide and coronary artery calcium score add significantly to risk prediction. The data for carotid intima-media thickness, ankle-brachial index are less strong and high sensitivity troponins look promising, but have had only limited data to date. Large scale meta-analyses ideally of pooled primary patient data will be required to determine the best additional markers to add to conventional risk prediction and in what groups to apply them.

Inhibition of secretory phospholipase A(2) in patients with acute coronary syndromes: rationale and design of the vascular inflammation suppression to treat acute coronary syndrome for 16 weeks (VISTA-16) trial

BACKGROUND

The action of secretory phospholipase A(2) (sPLA(2)) on lipoproteins may render them more susceptible to oxidation, thereby promoting vascular inflammation and increasing cardiovascular risk. Patients with acute coronary syndrome face a high risk of early, recurrent cardiovascular events that is associated with biomarkers of inflammation, including sPLA(2). The Vascular Inflammation Suppression to Treat Acute Coronary Syndrome for 16 Weeks (VISTA-16, NCT01130246) tests the hypothesis that varespladib methyl, an inhibitor of several sPLA(2) isoforms with a causal role in atherosclerosis, reduces cardiovascular risk among patients with acute coronary syndromes.

METHODS

Up to 6,500 patients with acute coronary syndrome will be randomized to receive treatment with varespladib methyl 500 mg daily or placebo for 16 weeks, in addition to background treatment with atorvastatin and other evidence-based therapies. The primary efficacy parameter is the combination of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke or hospitalization for unstable angina with objective evidence of myocardial ischemia. Effects of varespladib methyl on lipid and inflammatory markers, in addition to safety and tolerability, will also be evaluated.

CONCLUSION

sPLA(2) inhibition has the potential to exert a favorable effect on the artery wall. The VISTA-16 study will determine whether varespladib methyl has a beneficial impact on cardiovascular events in patients with an acute coronary syndrome.

Variation of lipoprotein associated phospholipase A2 across demographic characteristics and cardiovascular risk factors: a systematic review of the literature

BACKGROUND

Lipoprotein association phospholipase A2 (Lp-PLA(2)), an enzyme which has been found in atherosclerotic plaque is currently under investigation in large Phase III clinical trials of vascular disease prevention. We assessed in a variety of different population settings variation of Lp-PLA(2) mass and activity across gender, ethnicity, diabetes, kidney disease and metabolic syndrome. We also assessed correlations with measures of circulating lipids, systemic inflammation and adiposity.

METHODS

Systematic review of studies measuring Lp-PLA(2) and at least one of the relevant characteristics in >50 participants.

RESULTS

We identified a total of 77 studies involving 102,499 participants meeting the inclusion criteria. Lp-PLA(2) mass and activity were consistently approximately 10% higher in males than females and 15% higher in Caucasians than African Americans or Hispanics. There were no clear associations of Lp-PLA(2) mass or activity with type II diabetes, markers of systemic inflammation (C-reactive protein, fibrinogen) or with body mass index. Correlations of Lp-PLA(2) mass or activity with low density lipoprotein cholesterol and apolipoprotein B were moderate and positive, whilst correlations with high density lipoprotein cholesterol were negative and moderate to weak. There was no clear differences in associations with any of the above characteristics in groups defined based upon prevalent cardiovascular disease or its risk factors.

CONCLUSIONS

Despite considerable variability in absolute levels of Lp-PLA(2) across studies, the variability of Lp-PLA(2) across gender, ethnicity, and levels of circulating lipids and markers of systemic inflammation are more consistent and appear not to vary importantly across categories defined by CVD or its risk factors.

Lipid-related markers and cardiovascular disease prediction

CONTEXT

The value of assessing various emerging lipid-related markers for prediction of first cardiovascular events is debated.

OBJECTIVE

To determine whether adding information on apolipoprotein B and apolipoprotein A-I, lipoprotein(a), or lipoprotein-associated phospholipase A2 to total cholesterol and high-density lipoprotein cholesterol (HDL-C) improves cardiovascular disease (CVD) risk prediction.

DESIGN, SETTING, AND PARTICIPANTS

Individual records were available for 165,544 participants without baseline CVD in 37 prospective cohorts (calendar years of recruitment: 1968-2007) with up to 15,126 incident fatal or nonfatal CVD outcomes (10,132 CHD and 4994 stroke outcomes) during a median follow-up of 10.4 years (interquartile range, 7.6-14 years).

MAIN OUTCOME MEASURES

Discrimination of CVD outcomes and reclassification of participants across predicted 10-year risk categories of low (<10%), intermediate (10%-<20%), and high (≥20%) risk.

RESULTS

The addition of information on various lipid-related markers to total cholesterol, HDL-C, and other conventional risk factors yielded improvement in the model's discrimination: C-index change, 0.0006 (95% CI, 0.0002-0.0009) for the combination of apolipoprotein B and A-I; 0.0016 (95% CI, 0.0009-0.0023) for lipoprotein(a); and 0.0018 (95% CI, 0.0010-0.0026) for lipoprotein-associated phospholipase A2 mass. Net reclassification improvements were less than 1% with the addition of each of these markers to risk scores containing conventional risk factors. We estimated that for 100,000 adults aged 40 years or older, 15,436 would be initially classified at intermediate risk using conventional risk factors alone. Additional testing with a combination of apolipoprotein B and A-I would reclassify 1.1%; lipoprotein(a), 4.1%; and lipoprotein-associated phospholipase A2 mass, 2.7% of people to a 20% or higher predicted CVD risk category and, therefore, in need of statin treatment under Adult Treatment Panel III guidelines.

CONCLUSION

In a study of individuals without known CVD, the addition of information on the combination of apolipoprotein B and A-I, lipoprotein(a), or lipoprotein-associated phospholipase A2 mass to risk scores containing total cholesterol and HDL-C led to slight improvement in CVD prediction.

Circulating levels of secretory- and lipoprotein-associated phospholipase A2 activities: relation to atherosclerotic plaques and future all-cause mortality

AIMS

Secretory- and lipoprotein-associated phospholipases A2 (sPLA2 and Lp-PLA2) are enzymes both suggested to be of importance for atherosclerosis. We investigated relationships between the activities of these enzymes in the circulation and atherosclerosis as well as future clinical events.

METHODS AND RESULTS

The population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study included 1016 randomly selected subjects, all aged 70. The prevalence of carotid artery plaques was recorded by ultrasound (n= 954), and arterial stenosis was assessed by whole-body magnetic resonance angiography (WBMRA, n= 302). Secretory-associated phospholipase A2 [odds ratio 1.23 for 1 SD increase, 95% confidence interval (CI): 1.05-1.44, P= 0.007], but not Lp-PLA2 (P= 0.26), activity was significantly related to carotid atherosclerosis and to the amount of stenosis at WBMRA (P= 0.006) following adjustment for multiple risk factors (waist circumference, serum triglycerides, body mass index, C-reactive protein, high density lipoprotein-C, low density lipoprotein-C, triglycerides, GFR, fasting glucose, blood pressure, statin use, and exercise habits). Secretory-associated phospholipase A2 [hazard ratio (HR) 1.45 for 1 SD increase, 95% CI: 1.15-1.84, P= 0.001], but not Lp-PLA2 (HR 0.95, P= 0.55), activity was a significant risk factor for all-cause mortality (114 had died) during 7.0 years follow-up after adjustment for the risk factors described above. In a sample of 1029 post-myocardial infarction (MI) patients (French registry of Acute ST-elevation and non-ST-elevation Myocardial Infarction), sPLA2 (adjusted HR 1.32 for 1 unit increase, 95% CI: 1.02-1.71, P= 0.036), but not Lp-PLA2 (HR 1.03, P= 0.90), activity predicted death or recurrent MI during 1-year follow-up (n= 136 cases).

CONCLUSION

sPLA2 activity was related to atherosclerosis and predicted all-cause mortality in a sample of elderly subjects, as well as death or MI in post-MI patients.

Modulation of oxidative stress, inflammation, and atherosclerosis by lipoprotein-associated phospholipase A2

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), also known as platelet-activating factor acetylhydrolase (PAF-AH), is a unique member of the phospholipase A(2) superfamily. This enzyme is characterized by its ability to specifically hydrolyze PAF as well as glycerophospholipids containing short, truncated, and/or oxidized fatty acyl groups at the sn-2 position of the glycerol backbone. In humans, Lp-PLA(2) circulates in active form as a complex with low- and high-density lipoproteins. Clinical studies have reported that plasma Lp-PLA(2) activity and mass are strongly associated with atherogenic lipids and vascular risk. These observations led to the hypothesis that Lp-PLA(2) activity and/or mass levels could be used as biomarkers of cardiovascular disease and that inhibition of the activity could offer an attractive therapeutic strategy. Darapladib, a compound that inhibits Lp-PLA(2) activity, is anti-atherogenic in mice and other animals, and it decreases atherosclerotic plaque expansion in humans. However, disagreement continues to exist regarding the validity of Lp-PLA(2) as an independent marker of atherosclerosis and a scientifically justified target for intervention. Circulating Lp-PLA(2) mass and activity are associated with vascular risk, but the strength of the association is reduced after adjustment for basal concentrations of the lipoprotein carriers with which the enzyme associates. Genetic studies in humans harboring an inactivating mutation at this locus indicate that loss of Lp-PLA(2) function is a risk factor for inflammatory and vascular conditions in Japanese cohorts. Consistently, overexpression of Lp-PLA(2) has anti-inflammatory and anti-atherogenic properties in animal models. This thematic review critically discusses results from laboratory and animal studies, analyzes genetic evidence, reviews clinical work demonstrating associations between Lp-PLA(2) and vascular disease, and summarizes results from animal and human clinical trials in which administration of darapladib was tested as a strategy for the management of atherosclerosis.

Psoriasis alters HDL composition and cholesterol efflux capacity

Psoriasis, a chronic inflammatory skin disease, has been linked to increased myocardial infarction and stroke. Functional impairment of HDL may contribute to the excess cardiovascular mortality of psoriatic patients. However, data available regarding the impact of psoriasis on HDL composition and function are limited. HDL from psoriasis patients and healthy controls was isolated by ultracentrifugation and shotgun proteomics, and biochemical methods were used to monitor changed HDL composition. We observed a significant reduction in apoA-I levels of HDL from psoriatic patients, whereas levels of apoA-II and proteins involved in acute-phase response, immune response, and endopeptidase/protease inhibition were increased. Psoriatic HDL contained reduced phospholipid and cholesterol. With regard to function, these compositional alterations impaired the ability of psoriatic HDL to promote cholesterol efflux from macrophages. Importantly, HDL-cholesterol efflux capability negatively correlated with psoriasis area and severity index. We observed that control HDL, as well as psoriatic HDL, inhibited dihydrorhodamine (DHR) oxidation to a similar extent, suggesting that the anti-oxidative activity of psoriatic HDL is not significantly altered. Our observations suggest that the compositional alterations observed in psoriatic HDL reflect a shift to a pro-inflammatory profile that impairs cholesterol efflux capacity of HDL and may provide a link between psoriasis and cardiovascular disease.

Acute impact of apheresis on oxidized phospholipids in patients with familial hypercholesterolemia

We measured oxidized phospholipids (OxPL), lipoprotein (a) [Lp(a)], and lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) pre- and postapheresis in 18 patients with familial hypercholesterolemia (FH) and with low(∼10 mg/dl; range 10-11 mg/dl), intermediate (∼50 mg/dl; range 30-61 mg/dl), or high (>100 mg/dl; range 78-128 mg/dl) Lp(a) levels. By using enzymatic and immunoassays, the content of OxPL and Lp-PLA(2) mass and activity were quantitated in lipoprotein density fractions plated in microtiter wells, as well as directly on apoB-100, Lp(a), and apoA-I immunocaptured within each fraction (i.e., OxPL/apoB and Lp-PLA(2)/apoB). In whole fractions, OxPL was primarily detected in the Lp(a)-containing fractions, whereas Lp-PLA(2) was primarily detected in the small, dense LDL and light Lp(a) range. In lipoprotein capture assays, OxPL/apoB and OxPL/apo(a) increased proportionally with increasing Lp(a) levels. Lp-PLA(2)/apoB and Lp-PLA(2)/apoA-I levels were highest in the low Lp(a) group but decreased proportionally with increasing Lp(a) levels. Lp-PLA(2)/apo(a) was lowest in patients with low Lp(a) levels and increased proportionally with increasing Lp(a) levels. Apheresis significantly reduced levels of OxPL and Lp-PLA(2) on apoB and Lp(a) (50-75%), particularly in patients with intermediate and high Lp(a) levels. In contrast, apheresis increased Lp-PLA(2)-specific activity (activity/mass ratio) in buoyant LDL fractions. The impact of apheresis on Lp(a), OxPL, and Lp-PLA(2) provides insights into its therapeutic benefits beyond lowering apoB-containing lipoproteins.

Translational studies of lipoprotein-associated phospholipase A₂ in inflammation and atherosclerosis

OBJECTIVES

This study sought to examine the role of lipoprotein-associated phospholipase A₂ (Lp-PLA₂/PLA2G7) in human inflammation and coronary atherosclerosis.

BACKGROUND

Lp-PLA₂ has emerged as a potential therapeutic target in coronary heart disease. Data supporting Lp-PLA₂ are indirect and confounded by species differences; whether Lp-PLA₂ is causal in coronary heart disease remains in question.

METHODS

We examined inflammatory regulation of Lp-PLA₂ during experimental endotoxemia in humans, probed the source of Lp-PLA₂ in human leukocytes under inflammatory conditions, and assessed the relationship of variation in PLA2G7, the gene encoding Lp-PLA₂, with coronary artery calcification.

RESULTS

In contrast to circulating tumor necrosis factor-alpha and C-reactive protein, blood and monocyte Lp-PLA₂ messenger ribonucleic acid decreased transiently, and plasma Lp-PLA₂ mass declined modestly during endotoxemia. In vitro, Lp-PLA₂ expression increased dramatically during human monocyte to macrophage differentiation and further in inflammatory macrophages and foamlike cells. Despite only a marginal association of single nucleotide polymorphisms in PLA2G7 with Lp-PLA₂ activity or mass, numerous PLA2G7 single nucleotide polymorphisms were associated with coronary artery calcification. In contrast, several single nucleotide polymorphisms in CRP were significantly associated with plasma C-reactive protein levels but had no relation with coronary artery calcification.

CONCLUSIONS

Circulating Lp-PLA₂ did not increase during acute phase response in humans, whereas inflammatory macrophages and foam cells, but not circulating monocytes, are major leukocyte sources of Lp-PLA₂. Common genetic variation in PLA2G7 is associated with subclinical coronary atherosclerosis. These data link Lp-PLA₂ to atherosclerosis in humans while highlighting the challenge in using circulating Lp-PLA₂ as a biomarker of Lp-PLA₂ actions in the vasculature.

Lipoprotein-associated phospholipase A(2) mass and activity and risk of cardiovascular disease in a population with high prevalences of obesity and diabetes: the Strong Heart Study

OBJECTIVE

To investigate the association of lipoprotein-associated phospholipase A(2) (LpPLA(2)) mass and activity with incident cardiovascular disease (CVD) in a population with high prevalences of insulin resistance and diabetes, conditions for which epidemiological data remain sparse.

RESEARCH DESIGN AND METHODS

We conducted a nested, case-control study (n = 1,008) within a population-based cohort of American Indians. Case subjects were defined by incidence of first-ever CVD up to 10 years later. Control subjects comprised participants free of CVD events during the follow-up period who were frequency matched to case subjects by age, sex, and diabetes status. LpPLA(2) mass and activity were measured using commercially available assays.

RESULTS

LpPLA(2) mass and activity were moderately correlated with each other (r = 0.30), but only LpPLA(2) activity exhibited moderate correlations with lipid fractions. After extensive adjustment for covariates, both LpPLA(2) measures were significantly associated with incident CVD, but the relationship was inverse for LpPLA(2) mass (highest versus lowest tertile, relative risk [RR] 0.55 [95% CI 0.39-0.79]) and positive for LpPLA(2) activity (highest versus lowest tertile, 1.65 [1.12-2.42]). These associations were similar when participants with and without diabetes were examined separately.

CONCLUSIONS

In this population-based cohort enriched with dysmetabolic phenotypes, LpPLA(2) mass and activity showed divergent associations with CVD. The inverse relationship for LpPLA(2) mass is contrary to observations from predominantly nondiabetic populations and will require independent replication. Whether this finding relates to redistribution of LpPLA(2) to lipoprotein classes where it is less atherogenic or reflects incomplete measurement of LpPLA(2) mass associated with altered lipoprotein composition in insulin resistance warrants further investigation.

Association of serum lipoprotein-associated phospholipase A2 level with nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and is one of the most common causes of chronic liver disease, worldwide. Lipoprotein-associated phospholipase A2 (Lp-PLA2) was recently characterized as a novel inflammatory biomarker that is correlated with several components constituting the metabolic syndrome.

METHODS

In this study, we determined the serum levels of Lp-PLA2 in patients with definite nonalcoholic steatohepatitis (NASH, n=25), borderline NASH (n=22), simple fatty liver (n=10), and healthy controls without evidence of liver disease (n=38). The levels of Lp-PLA2 were measured by enzyme-linked immunosorbent assay and compared in the four study groups. Moreover, concentrations of Lp-PLA2 were assessed in relation to the general characteristics of the study participants and the results of liver biopsy.

RESULTS

Concentrations of Lp-PLA2 were significantly higher in patients with definite NASH (161.8±0.9 μg/L, P<0.001), borderline NASH (135.4±47.7 μg/L, P=0.001), and simple fatty liver (132.4±46.2 μg/L, P=0.042) compared with healthy controls (86.2±40.7 μg/L). Furthermore, the serum Lp-PLA2 level was strongly associated to histological steatosis scores in patients with NAFLD (β=0.32, t=2.50, P=0.016).

CONCLUSION

Although subject to future confirmation, our data suggest that Lp-PLA2 levels are elevated in NAFLD.

Interleukin-6 receptor pathways in coronary heart disease: a collaborative meta-analysis of 82 studies

BACKGROUND

Persistent inflammation has been proposed to contribute to various stages in the pathogenesis of cardiovascular disease. Interleukin-6 receptor (IL6R) signalling propagates downstream inflammation cascades. To assess whether this pathway is causally relevant to coronary heart disease, we studied a functional genetic variant known to affect IL6R signalling.

METHODS

In a collaborative meta-analysis, we studied Asp358Ala (rs2228145) in IL6R in relation to a panel of conventional risk factors and inflammation biomarkers in 125,222 participants. We also compared the frequency of Asp358Ala in 51,441 patients with coronary heart disease and in 136,226 controls. To gain insight into possible mechanisms, we assessed Asp358Ala in relation to localised gene expression and to postlipopolysaccharide stimulation of interleukin 6.

FINDINGS

The minor allele frequency of Asp358Ala was 39%. Asp358Ala was not associated with lipid concentrations, blood pressure, adiposity, dysglycaemia, or smoking (p value for association per minor allele ≥0·04 for each). By contrast, for every copy of 358Ala inherited, mean concentration of IL6R increased by 34·3% (95% CI 30·4-38·2) and of interleukin 6 by 14·6% (10·7-18·4), and mean concentration of C-reactive protein was reduced by 7·5% (5·9-9·1) and of fibrinogen by 1·0% (0·7-1·3). For every copy of 358Ala inherited, risk of coronary heart disease was reduced by 3·4% (1·8-5·0). Asp358Ala was not related to IL6R mRNA levels or interleukin-6 production in monocytes.

INTERPRETATION

Large-scale human genetic and biomarker data are consistent with a causal association between IL6R-related pathways and coronary heart disease.

FUNDING

British Heart Foundation; UK Medical Research Council; UK National Institute of Health Research, Cambridge Biomedical Research Centre; BUPA Foundation.

Relationship of lipoprotein-associated phospholipase A₂ mass and activity with incident vascular events among primary prevention patients allocated to placebo or to statin therapy: an analysis from the JUPITER trial

BACKGROUND

Although lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) levels are associated with cardiovascular events, Lp-PLA(2) is physically linked to LDL cholesterol (LDL-C). Whether measures of Lp-PLA(2) mass or activity continue to predict risk after LDL-C reduction by statin therapy is uncertain.

METHODS

Lp-PLA(2) mass concentration and activity were evaluated at baseline and after treatment in the Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) trial comparing rosuvastatin 20 mg to placebo among 17 802 men and women without cardiovascular disease or diabetes at study entry. The relationships of Lp-PLA(2) mass and activity with risk of future vascular events were evaluated in the placebo and rosuvastatin groups.

RESULTS

Before randomization, levels of Lp-PLA(2) mass and activity correlated moderately with each other and with LDL-C. The magnitude of these correlations increased after statin therapy. Rosuvastatin reduced Lp-PLA(2) mass by 33.8%, Lp-PLA(2) activity by 33.2%, and LDL-C by 48.7% (all P < 0.0001). Among those study participants allocated to placebo, increasing quartiles of Lp-PLA(2) activity (P(trend) = 0.04) but not Lp-PLA(2) mass (P(trend) = 0.92) were associated with incident cardiovascular events after adjustment for LDL-C and conventional risk factors. Comparable analyses conducted among those allocated to rosuvastatin revealed no significant relationship between Lp-PLA(2) levels and subsequent vascular events. The ability of rosuvastatin to reduce vascular events was not significantly modified by baseline Lp-PLA(2) level.

CONCLUSIONS

Among JUPITER trial participants allocated to placebo, levels of Lp-PLA(2) activity, but not mass, were associated with cardiovascular risk. However, Lp-PLA(2) no longer predicted risk or modified clinical outcomes when participants were treated with rosuvastatin.

Lipoprotein-associated phospholipase A2 (Lp-PLA2): a review of its role and significance as a cardiovascular biomarker

OBJECTIVE

To conduct a comprehensive, systematic review of studies assessing the significance of lipoprotein-associated phospholipase A2 in cardiovascular diseases (CVDs).

MATERIAL AND METHODS

A review of the literature was performed using the search term "Lipoprotein-associated phospholipase A2 (Lp-PLA2)" and each of the following terms: "cardiovascular risk," "cardiovascular death," "atherosclerotic disease," "coronary events," "transient ischemic attack (TIA)," "stroke," and "heart failure." The searches were performed on Medline, Google Scholar and ClinicalTrials.gov.

RESULTS

The majority of published studies showed a significant association between Lp-PLA2 levels and cardiovascular events after multivariate adjustment. The association was consistent across a wide variety of subjects of both sexes and different ethnic backgrounds.

CONCLUSIONS

The role of Lp-PLA2 as a significant biomarker of vascular inflammation was confirmed, and Lp-PLA2 seems to be closely correlated to cardiovascular events. It may be an important therapeutic target and may have an important role in prevention, risk stratification and personalised medicine.

Clinical utility of inflammatory markers and advanced lipoprotein testing: advice from an expert panel of lipid specialists

The National Cholesterol Education Program Adult Treatment Panel guidelines have established low-density lipoprotein cholesterol (LDL-C) treatment goals, and secondary non-high-density lipoprotein (HDL)-C treatment goals for persons with hypertriglyceridemia. The use of lipid-lowering therapies, particularly statins, to achieve these goals has reduced cardiovascular disease (CVD) morbidity and mortality; however, significant residual risk for events remains. This, combined with the rising prevalence of obesity, which has shifted the risk profile of the population toward patients in whom LDL-C is less predictive of CVD events (metabolic syndrome, low HDL-C, elevated triglycerides), has increased interest in the clinical use of inflammatory and lipid biomarker assessments. Furthermore, the cost effectiveness of pharmacological intervention for both the initiation of therapy and the intensification of therapy has been enhanced by the availability of a variety of generic statins. This report describes the consensus view of an expert panel convened by the National Lipid Association to evaluate the use of selected biomarkers [C-reactive protein, lipoprotein-associated phospholipase A(2), apolipoprotein B, LDL particle concentration, lipoprotein(a), and LDL and HDL subfractions] to improve risk assessment, or to adjust therapy. These panel recommendations are intended to provide practical advice to clinicians who wrestle with the challenges of identifying the patients who are most likely to benefit from therapy, or intensification of therapy, to provide the optimum protection from CV risk.

Cardiovascular metabolic syndrome: mediators involved in the pathophysiology from obesity to coronary heart disease

Patients with obesity and diabetes mellitus are at increased risk for cardiovascular events and have a higher cardiovascular morbidity and mortality. This worse prognosis is partly explained by the late recognition of coronary heart disease in these patients, due to the absence of symptoms. Early identification of coronary heart disease is vital, to initiate preventive medical therapy and improve prognosis. At present, with the use of cardiovascular risk models, the identification of coronary heart disease in these patients remains inadequate. To this end, biomarkers should improve the early identification of patients at increased cardiovascular risk. The first part of this review describes the pathophysiologic pathway from obesity to coronary heart disease. The second part evaluates several mediators from this pathophysiologic pathway for their applicability as biomarkers for the identification of coronary heart disease.

Phospholipase A2 enzymes, high-dose atorvastatin, and prediction of ischemic events after acute coronary syndromes

BACKGROUND

Secretory phospholipase A2 (sPLA(2)) and lipoprotein-associated phospholipase A2 (Lp-PLA(2)) are enzyme biomarkers of increased cardiovascular risk and targets of emerging therapeutic agents. Their relationship to cardiovascular events in the setting of high-dose statin therapy compared with placebo in patients with acute coronary syndrome is not known.

METHODS AND RESULTS

sPLA(2) and Lp-PLA(2) mass and activity were measured in 2587 patients in the Myocardial Ischemia Reduction With Acute Cholesterol Lowering (MIRACL) trial at baseline and after 16 weeks of treatment with atorvastatin 80 mg/d or placebo. Baseline levels of sPLA(2) and Lp-PLA(2) mass and activity were not associated with the primary efficacy measure of the trial of death, myocardial infarction, or unstable angina. However, in the overall cohort, baseline sPLA(2) mass predicted risk of death after multivariable adjustment (hazard ratio for 2-fold increase, 1.30; 95% confidence interval, 1.09-1.56; P=0.004). This association remained significant when examined separately in the placebo group but not in the atorvastatin group. Compared with placebo, atorvastatin reduced median sPLA(2) mass (-32.1% versus -23.1%), sPLA(2) activity (-29.5% versus -19.2%), Lp-PLA(2) mass (-35.8% versus -6.2%), and Lp-PLA(2) activity (-24.3% versus 5.4%; P<0.001 for all). Atorvastatin reduced the hazard of death associated with elevated sPLA(2) mass and activity by ≈50%.

CONCLUSIONS

sPLA(2) mass independently predicts death during a 16-week period after acute coronary syndrome. High-dose atorvastatin significantly reduces sPLA(2) and Lp-PLA(2) mass and activity after acute coronary syndrome and mitigates the risk of death associated with sPLA(2) mass. Atorvastatin may exert antiinflammatory effects on phospholipases that contribute to its therapeutic benefit after acute coronary syndrome.

Eight genetic loci associated with variation in lipoprotein-associated phospholipase A2 mass and activity and coronary heart disease: meta-analysis of genome-wide association studies from five community-based studies

AIMS

Lipoprotein-associated phospholipase A2 (Lp-PLA2) generates proinflammatory and proatherogenic compounds in the arterial vascular wall and is a potential therapeutic target in coronary heart disease (CHD). We searched for genetic loci related to Lp-PLA2 mass or activity by a genome-wide association study as part of the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium.

METHODS AND RESULTS

In meta-analyses of findings from five population-based studies, comprising 13 664 subjects, variants at two loci (PLA2G7, CETP) were associated with Lp-PLA2 mass. The strongest signal was at rs1805017 in PLA2G7 [P = 2.4 × 10(-23), log Lp-PLA2 difference per allele (beta): 0.043]. Variants at six loci were associated with Lp-PLA2 activity (PLA2G7, APOC1, CELSR2, LDL, ZNF259, SCARB1), among which the strongest signals were at rs4420638, near the APOE-APOC1-APOC4-APOC2 cluster [P = 4.9 × 10(-30); log Lp-PLA2 difference per allele (beta): -0.054]. There were no significant gene-environment interactions between these eight polymorphisms associated with Lp-PLA2 mass or activity and age, sex, body mass index, or smoking status. Four of the polymorphisms (in APOC1, CELSR2, SCARB1, ZNF259), but not PLA2G7, were significantly associated with CHD in a second study.

CONCLUSION

Levels of Lp-PLA2 mass and activity were associated with PLA2G7, the gene coding for this protein. Lipoprotein-associated phospholipase A2 activity was also strongly associated with genetic variants related to low-density lipoprotein cholesterol levels.

Circulating lipoprotein-associated phospholipase A2 in high-grade carotid stenosis: a new biomarker for predicting unstable plaque

OBJECTIVE

To test plasma levels of lipoprotein-associated phospholipase A2 (Lp-PLA2) in patients with high-grade carotid stenosis according to plaque histology.

METHODS

This cross-sectional single-centre study included patients with ≥70% North American Symptomatic Carotid Endarterectomy Trial (NASCET) carotid stenosis, who were treated surgically. Serum Lp-PLA2 and high-sensitivity C-reactive protein (hs-CRP) were determined on the day of surgery. Histopathological analysis classified carotid plaque as stable or unstable, according to AHA classification.

RESULTS

Of the 42 patients (mean age 70.4 ± 10.5 years; 67% men), neurological symptoms were present in 16 (38%). Unstable plaques were found in 23 (55%). Median plasma level of Lp-PLA2 was significantly higher in patients with unstable plaque compared to those with stable plaque (222.4 (174.9-437.5) interquartile range (IQR) 63.5 vs. 211.1 (174.9-270.6) IQR 37.2 ng ml(-1); p = 0.02). Moreover, median Lp-PLA2 level were higher in asymptomatic patients with unstable plaque (226.8 ng ml(-1) (174.9-437.5) IQR 76.8) vs. stable plaque (206.9 ng ml(-1) (174.9-270.6) IQR 33.7; p = 0.16). Logistic regression showed that only the neurological symptoms (OR = 30.9 (3.7-244.6); p < 0.001) and the plasma Lp-PLA2 level (OR = 1.7 (1.1-12.3); p = 0.03) were independently associated with unstable carotid plaque as defined by histology.

CONCLUSIONS

This study showed that circulating Lp-PLA2 was increased in patients with high-grade carotid stenosis and unstable plaque. Lp-PLA2 may be a relevant biomarker to guide for invasive therapy in asymptomatic patients with carotid artery disease.

Prognostic effect size of cardiovascular biomarkers in datasets from observational studies versus randomised trials: meta-epidemiology study

OBJECTIVE

To compare the reported effect sizes of cardiovascular biomarkers in datasets from observational studies with those in datasets from randomised controlled trials.

DESIGN

Review of meta-analyses.

STUDY SELECTION

Meta-analyses of emerging cardiovascular biomarkers (not part of the Framingham risk score) that included datasets from at least one observational study and at least one randomised controlled trial were identified through Medline (last update, January 2011).

DATA EXTRACTION

Study-specific risk ratios were extracted from all identified meta-analyses and synthesised with random effects for (a) all studies, and (b) separately for observational and for randomised controlled trial populations for comparison.

RESULTS

31 eligible meta-analyses were identified. For seven major biomarkers (C reactive protein, non-HDL cholesterol, lipoprotein(a), post-load glucose, fibrinogen, B-type natriuretic peptide, and troponins), the prognostic effect was significantly stronger in datasets from observational studies than in datasets from randomised controlled trials. For five of the biomarkers the effect was less than half as strong in the randomised controlled trial datasets. Across all 31 meta-analyses, on average datasets from observational studies suggested larger prognostic effects than those from randomised controlled trials; from a random effects meta-analysis, the estimated average difference in the effect size was 24% (95% CI 7% to 40%) of the overall biomarker effect.

CONCLUSIONS

Cardiovascular biomarkers often have less promising results in the evidence derived from randomised controlled trials than from observational studies.

PAF and its metabolic enzymes in healthy volunteers: interrelations and correlations with basic characteristics

PAF (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine), a potent inflammatory mediator, is synthesized via the remodeling and the de novo route, key enzymes of which are acetyl-CoA:lyso-PAF acetyltransferase (lyso-PAF-AT) and DTT-insensitive CDP-choline:1-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase (PAF-CPT), respectively. PAF-acetylhydrolase (PAF-AH) and its extracellular isoform lipoprotein-associated phospholipase-A(2) (Lp-PLA(2)) catabolize PAF. This study evaluated PAF levels together with leukocyte PAF-CPT, lyso-PAF-AT, PAF-AH and Lp-PLA(2) activities in 106 healthy volunteers. Men had lower PAF levels and higher activity of both catabolic enzymes and lyso-PAF-AT than women (P-values <0.05). Age was inversely correlated with PAF levels in men (r=-0.279, P=0.06) and lyso-PAF-AT in women (r=-0.280, P=0.05). In contrast, Lp-PLA(2) was positively correlated with age (r=0.201, P=0.04). Moreover, PAF-CPT was positively correlated with glucose (r=0.430, P=0.002) in women. In addition, Principal Component Analysis revealed three PAF metabolic patterns: (i) increased activities of PAF-CPT and PAF-AH, (ii) increased activities of PAF-CPT and lyso-PAF-AT and (iii) increased activity of Lp-PLA(2). The present study underlines the complexity of PAF's metabolism determinants.

Kidney function decline in the elderly: impact of lipoprotein-associated phospholipase A(2)

BACKGROUND

Whether lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) levels are associated with kidney function decline has not been well studied.

METHODS

We investigated associations of Lp-PLA(2) antigen and activity with kidney function decline and rapid decline over 5.7 years in the Cardiovascular Health Study (n = 4,359). We estimated kidney function by cystatin C (eGFRcys) in repeated measures, and defined rapid decline as ≥3 ml/min/1.73 m(2) per year. We stratified by baseline preserved GFR (≥60 ml/min/1.73 m(2)).

RESULTS

Mean age was 72 ± 5 years. Average eGFRcys decline was -1.79 ml/min/1.73 m(2) (SD = 2.60) per year. Among persons with preserved GFR, compared to the lowest quartile of Lp-PLA(2) antigen, eGFRcys decline was faster among persons in the second, β -0.31 (95% CI -0.52, -0.10), third -0.19 (-0.41, 0.02) and fourth quartiles -0.26 (-0.48, -0.04) after full adjustment. Persons in the highest quartile of Lp-PLA(2) antigen had increased odds of rapid decline 1.34 (1.03, 1.75), compared to the lowest. There was no significant association between levels of Lp-PLA(2) activity and eGFRcys decline or rapid decline. Associations were not statistically significant among persons with low eGFR (<60 ml/min/1.73 m(2)) at baseline.

CONCLUSION

Higher levels of Lp-PLA(2) antigen but not activity were significantly associated with faster rates of kidney function decline. These findings may suggest a novel vascular pathway for kidney disease progression.

Association of lipoprotein-associated phospholipase A₂ with characteristics of vulnerable coronary atherosclerotic plaques

PURPOSE

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is an inflammatory enzyme expressed in atherosclerotic plaques. We investigated the association of circulating Lp-PLA₂ with characteristics of vulnerable coronary atherosclerotic plaques.

MATERIALS AND METHODS

We recruited 113 patients with either unstable angina (UA, n=59) and stable angina (SA, n=54) by coronary angiography. Thirty-six healthy subjects served as controls. Intravascular ultrasound (IVUS) was used to evaluate the characteristics of coronary atherosclerotic plaque, and serum Lp-PLA₂ concentration was measured as well.

RESULTS

Lp-PLA₂ concentration was significantly higher in both UA and SA patients [(396±36) μg/L and (321±39) μg/L, respectively] compared with the controls [(127 ± 49) μg/L, p<0.01], and higher in UA than SA group. IVUS findings showed that remodeling index (RI) (0.91 ± 0.15 vs. 0.85 ± 0.11, p=0.005) and eccentricity index (EI) (0.73 ± 0.16 vs. 0.65 ± 0.22, p=0.039) were larger in UA than in SA group, and fibrous caps were thicker in SA than UA group [(0.91 ± 0.23) mm vs. (0.63 ± 0.21) mm, p=0.032]. Moreover, Lp-PLA₂ correlated positively with EI (r=0.439, p<0.01) and RI (r=0.592, p<0.05) in UA group. There was an inverse relationship between Lp-PLA₂ and fibrous cap thickness in both UA (r=-0.587, p<0.001) and SA (r=-0.318, p<0.05) groups. The independent risk factors in UA group were Lp-PLA₂ (OR=1.055, 95% CI: 1.03-1.08, p=0.013), LDL-cholesterol (OR=0.032, 95% CI: 0.00-0.05, p=0.041) and fibrous cap thickness (OR=0.008, 95% CI: 0.00-0.45, p=0.019). Lp-PLA₂ was strongly associated with both EI and fibrous cap thickness in both groups.

CONCLUSION

Serum level of Lp-PLA₂ is associated with both eccentricity index and fibrous cap thickness in both UA and SA groups. Elevated levels of circulating Lp-PLA₂ might to be a strong risk factor and more serious for unstable angina than stable angina.

Association between lipoprotein-associated phospholipase A2 gene polymorphism and coronary artery disease in the Chinese Han population

The role of the lipoprotein-associated phospholipase A(2) gene (PLA2G7) in atherosclerosis remains controversial. We investigated the frequency of single-nucleotide polymorphisms (SNPs) of PLA2G7 (rs16874954 and rs1051931) and their association with coronary artery disease (CAD) in a cohort of CAD patients (n= 806) and age-matched healthy controls (n= 482) in the Chinese Han population. The VF and FF genotype of rs16874954 was significantly more frequent in the CAD patients (13.5%) than in the controls (9.3%, P= 0.024). The association remained after adjustment for age, gender, body mass index, smoking status, history of diabetes, positive family history of CAD, high-density lipoprotein cholesterol, and triglyceride (OR = 1.922; 95% CI [1.146-3.224]; P= 0.013). There was no significant difference in the frequency of any genotype of rs1051931 between the two groups. However, the frequency of the allele V379 was significantly greater in CAD patients with a history of myocardial infarction (MI) than in those without a history of MI (18.7% and 14.8%, P= 0.038). We conclude that there is significant association between the rs16874954 mutation and CAD in the Chinese Han population. The expression of rs1051931 variant in CAD patients may entail increased risk of MI.

The Role of IL-33 in the Inflammation Process of Asthma and Atherosclerosis

Interleukin-33 (IL-33) is a newly found cytokine of the interleukin-1 (IL-1) family. It's mainly expressed by epithelial and endothelial cells. This expression is upregulated by pro-inflammatory stimulation, thus has an important role in inflammatory responses, such as hypersensitive diseases (asthma), autoimmune diseases (rheumatoid arthritis), cardiovascular diseases (heart failure) and neurodegenerative diseases (Alzheimer). Several studies explored the complicated mechanism of IL-33 action in asthma and atherosclerosis, as this IL is significantly increased in these pathologies, and suggested its potential use in the therapeutic procedures.

Study design and rationale for the Stabilization of pLaques usIng Darapladib-Thrombolysis in Myocardial Infarction (SOLID-TIMI 52) trial in patients after an acute coronary syndrome

BACKGROUND

Higher levels of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) are associated with a higher risk of cardiovascular events and may play a causal role in atherogenesis. Darapladib inhibits Lp-PLA(2) activity in plasma and in arterial plaques and may confer clinical benefit in preventing cardiovascular events.

STUDY DESIGN

The SOLID-TIMI 52 trial is a randomized, double-blind, placebo-controlled, multicenter, event-driven trial. Approximately 13,000 subjects are being randomized to darapladib (160 mg enteric-coated tablet daily) or matching placebo within 30 days of hospitalization with an acute coronary syndrome. The primary end point is the composite of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. Secondary end points include major and total coronary events, individual components of the primary end point, and all-cause mortality. The study will continue until approximately 1,500 primary end point events have occurred to achieve 90% power to detect a 15.5% reduction in the primary end point. The median treatment duration is anticipated to be approximately 3 years, with a total study duration of approximately 4.1 years.

CONCLUSIONS

The SOLID-TIMI 52 trial will determine the clinical benefit of direct inhibition of Lp-PLA(2) activity with darapladib in patients after an acute coronary syndrome.

Systematic Review of the Association between Lipoprotein-Associated Phospholipase A2 and Atherosclerosis

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a novel inflammatory biomarker. Basic research has shown that Lp-PLA2 is involved in the pathogenesis of atherosclerosis. In the past decade, an increasing number of epidemiological studies have investigated the association of Lp-PLA2 with atherosclerosis, but its roles in the different stages of atherosclerosis are not established. By undertaking a systematic review of the epidemiological studies on the relationship between Lp-PLA2 and atherosclerotic cardiovascular disease (CVD)/subclinical atherosclerosis, we tried to evaluate the relationship between Lp-PLA2 and the different stages of atherosclerosis. MEDLINE, Cochrane Library, and National Knowledge Infrastructure (CNKI) were searched up to September 1st, 2011. The references in all the located articles were manually searched. Epidemiological studies on the association of Lp-PLA2 with CVD and subclinical atherosclerosis, with total CVD, coronary heart disease (CHD), stroke, and subclinical atherosclerosis as their observation endpoints or outcome variables, were included in this study. Studies which did not assess the hazard ratio (HR), relative risk (RR), or odds ratio (OR) of Lp-PLA2 or which did not adjust for other known risk factors were excluded. The general information, study design, sample size, outcome variables and their definitions, follow-up duration, Lp-PLA2 measurements, variables adjusted in the multivariate analysis and main results in the literatures were retrieved. Thirty-nine studies were enrolled in this systematic review. Thirty-three studies (49, 260 subjects) investigated the relationship between Lp-PLA2 and CVD, among which 31 showed that increased Lp-PLA2 is associated to high risk for incidence or mortality of CVD: HR/RR per 1 standard deviation (SD) increase = 1.17-1.40; RR for the highest as compared with the lowest quartile was 1.41-3.75 (1.8-2.5 in most studies). Six studies (four cross-sectional studies and two case-control studies, with an overall sample size of 5,537) explored the relationship between Lp-PLA2 and subclinical atherosclerosis; among them, two studies demonstrated that Lp-PLA2 was associated with coronary artery calcification in young adults and men. In conclusion, many epidemiological studies have demonstrated that Lp-PLA2 increases the risk of clinical CVD events. However, whether there is a similar association between Lp-PLA2 and subclinical atherosclerosis remains unclear. Whether Lp-PLA2 exerts its effect during the occurrence of clinical events promoted by unstable plaques or at the early stage of atherosclerosis needs to be clarified in further prospective studies.

Antioxidant and inflammatory aspects of lipoprotein-associated phospholipase A₂ (Lp-PLA₂): a review

The association of cardiovascular events with Lp-PLA₂ has been studied continuously today. The enzyme has been strongly associated with several cardiovascular risk markers and events. Its discovery was directly related to the hydrolysis of the platelet-activating factor and oxidized phospholipids, which are considered protective functions. However, the hydrolysis of bioactive lipids generates lysophospholipids, compounds that have a pro-inflammatory function. Therefore, the evaluation of the distribution of Lp-PLA₂ in the lipid fractions emphasized the dual role of the enzyme in the inflammatory process, since the HDL-Lp-PLA₂ enzyme contributes to the reduction of atherosclerosis, while LDL-Lp-PLA₂ stimulates this process. Recently, it has been verified that diet components and drugs can influence the enzyme activity and concentration. Thus, the effects of these treatments on Lp-PLA₂ may represent a new kind of prevention of cardiovascular disease. Therefore, the association of the enzyme with the traditional assessment of cardiovascular risk may help to predict more accurately these diseases.

What is the role of alternative biomarkers for coronary heart disease?

Predictive models for future risk of coronary heart disease (CHD) based on traditional risk factors, such as age, male gender, LDL cholesterol, HDL cholesterol, diabetes mellitus, hypertension, smoking and family history of premature CHD, are quite robust but leave room for further improvement. Thus, efforts are being made to assess additional biomarkers for CHD, such as, lipoprotein (a), C-reactive protein, fibrinogen, lipoprotein-associated phospholipase A2, homocysteine and others. However, none of the novel biomarkers has demonstrated improved prediction beyond traditional risk factor models in a consistent fashion across multiple cohorts. Many criteria have to be fulfilled before a biomarker can be considered clinically relevant. Another way is to develop new models predicting long-term or life-time risk of CHD. Further research using novel biomarkers and long-term predictive models has the potential to improve CHD risk prediction.

Inflammatory and neuroendocrine biomarkers of prognosis after ischemic stroke

Stroke is the third leading cause of mortality in the USA and one of the leading causes of severe morbidity. It is important to provide stroke patients and physicians with the most accurate prognostic information to optimize care and allocation of healthcare resources. Reliable prognostic markers available during the initial phase after acute stroke may aid clinical decision-making. Several interesting candidate biomarkers have been studied to address prognostic questions; this article will focus on selected inflammatory and neuroendocrine markers. The utility of a biomarker is defined by its ability to improve clinical decision-making and add timely information beyond that readily available from clinical examination and routine imaging. This aim has not been completely achieved yet for any biomarkers, but promising data are available and further studies are ongoing.

Short-term fenofibrate treatment reduces elevated plasma Lp-PLA2 mass and sVCAM-1 levels in a subcohort of hypertriglyceridemic GOLDN participants

High levels of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) are associated with inflammation, atherosclerosis, and coronary heart disease events. In addition, Lp-PLA(2) has been linked to classical markers of endothelial activation, including soluble vascular cell adhesion molecule-1 (sVCAM-1). Although treatment with fenofibrate reduces Lp-PLA(2) mass, it is unclear whether fenofibrate reduces sVCAM-1 levels or whether an association exists between any changes observed in Lp-PLA(2) and sVCAM-1. Concentrations of Lp-PLA(2) mass and sVCAM-1 levels were measured in plasma at baseline and after 3 weeks of fenofibrate treatment (160 mg/d) in 96 hypertriglyceridemic participants of the Genetics of Lipid-lowering Drugs and Diet Network study. Lp-PLA(2) and sVCAM-1 were stratified by tertiles as determined by baseline levels of the respective target. Fenofibrate treatment resulted in a 30.1% mean increase in Lp-PLA(2) mass (P = 0.0003) and a 14.7% mean increase in sVCAM-1 levels (P = 0.0096) but only in tertile1 of either target. In contrast, Lp-PLA(2) mass was reduced by 35.3% (P < 0.0001) in tertile 3. Soluble VCAM-1 levels were significantly reduced by 7.74% (P = 0.0109) and 17.2% (P < 0.0001) in tertiles 2 and 3, respectively. No associations were observed between Lp-PLA(2) and sVCAM-1 at baseline or post-treatment. In conclusion, fenofibrate treatment in hypertriglyceridemic subjects reduced the levels of Lp-PLA(2) mass and sVCAM-1, but only in those with elevated baseline levels of these biomarkers. The greatest reductions in Lp-PLA(2) levels were observed in individuals with Lp-PLA(2) concentrations indicative of increased cardiovascular disease risk (>200 ng/mL).

Carotid intima media thickness is associated with plasma lipoprotein-associated phospholipase A2 mass in nondiabetic subjects but not in patients with type 2 diabetes

BACKGROUND

A recent meta-analysis showed that both plasma lipoprotein-associated phospholipase A(2) (Lp-PLA(2) ) mass and activity independently predict cardiovascular events. Notably, Lp-PLA(2) activity but not mass was found to be a determinant of cardiovascular outcome in type 2 diabetes mellitus. We questioned whether relationships of carotid intima media thickness (IMT), a measure of subclinical atherosclerosis, with Lp-PLA(2) mass differ between diabetic and nondiabetic subjects.

MATERIALS AND METHODS

Relationships of IMT with plasma Lp-PLA(2) mass (turbidimetric immunoassay) were compared in 74 patients with type 2 diabetes and in 64 nondiabetic subjects.

RESULTS

IMT was increased (P=0·016), but plasma Lp-PLA(2) mass was decreased in patients with diabetes compared to nondiabetic subjects (277±66 vs. 327±62μgL(-1) , P<0·001). In nondiabetic subjects, IMT was correlated positively with Lp-PLA(2) (r=0·325, P<0·009); multiple linear regression analysis confirmed an independent association of IMT with Lp-PLA(2) (ß=0·192, P=0·048). In contrast, IMT was unrelated to Lp-PLA(2) in patients with diabetes (r=0·021, P=0·86), and the relationship of IMT with Lp-PLA(2) was different in diabetic and control subjects (P<0·001). The relationship of Lp-PLA(2) with the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio also differed between diabetic and nondiabetic subjects (P<0·001).

CONCLUSIONS

Plasma Lp-PLA(2) may relate to early stages of atherosclerosis development. In diabetes mellitus, in contrast, the association of IMT with plasma Lp-PLA(2) mass is abolished, which could be partly ascribed to redistribution of Lp-PLA(2) mass from apolipoprotein B-containing lipoproteins towards HDL. These findings raise questions about the usefulness of plasma Lp-PLA(2) mass measurement as a marker of subclinical atherosclerosis in type 2 diabetes mellitus.

Uremia alters HDL composition and function

Functional impairment of HDL may contribute to the excess cardiovascular mortality experienced by patients with renal disease, but the effect of advanced renal disease on the composition and function of HDL is not well understood. Here, we used mass spectrometry and biochemical analyses to study alterations in the proteome and lipid composition of HDL isolated from patients on maintenance hemodialysis. We identified a significant increase in the amount of acute phase protein serum amyloid A1, albumin, lipoprotein-associated phospholipase A2, and apoC-III composing uremic HDL. Furthermore, uremic HDL contained reduced phospholipid and increased triglyceride and lysophospholipid. With regard to function, these changes impaired the ability of uremic HDL to promote cholesterol efflux from macrophages. In summary, the altered composition of HDL in renal disease seems to inhibit its cardioprotective properties. Assessing HDL composition and function in renal disease may help identify patients at increased risk for cardiovascular disease.

Prognostic utility of secretory phospholipase A(2) in patients with stable coronary artery disease

BACKGROUND

Secretory phospholipase A(2) (sPLA(2)) may contribute to atherogenesis. To date, few prospective studies have examined the utility of sPLA(2) for risk stratification in coronary artery disease (CAD).

METHODS

We measured plasma sPLA(2) activity at baseline in 3708 subjects in the PEACE randomized trial of trandolapril vs placebo in stable CAD. Median follow-up was 4.8 years. We used Cox regression to adjust for demographics, clinical risk factors, apolipoprotein B, apolipoprotein A1, and medications.

RESULTS

After multivariable adjustment, sPLA(2) was associated with an increased risk of cardiovascular death, myocardial infarction, or stroke (adjusted hazard ratio Q4:Q1 1.55, 95% CI 1.13-2.14) and cardiovascular death or heart failure (1.91, 1.20-3.03). In further multivariable assessment, increased activity levels of sPLA(2) were associated with the risk of cardiovascular death, myocardial infarction, or stroke (adjusted hazard ratio 1.47, 95% CI 1.06-2.04), independent of lipoprotein-associated phospholipase A(2) mass and C-reactive protein, and modestly improved the area under the curve (AUC) beyond established clinical risk factors (AUC 0.668-0.675, P = 0.01). sPLA(2), N-terminal pro-B-type natriuretic peptide, and high-sensitivity cardiac troponin T all were independently associated with cardiovascular death or heart failure, and each improved risk discrimination (P = 0.02, P < 0.001, P < 0.001, respectively).

CONCLUSIONS

sPLA(2) activity provides independent prognostic information beyond established risk markers in patients with stable CAD. These data are encouraging for studies designed to evaluate the role of sPLA(2) as a therapeutic target.

Anti-inflammatory therapeutics for the treatment of atherosclerosis

Atherosclerosis is the primary cause of heart disease and stroke and is thus the underlying pathology of the leading causes of death in the western world. Although risk can be reduced by lowering lipid levels, the equally important contribution of inflammation to the development of cardiovascular disease is not adequately addressed by existing therapies. Here, we summarize the evidence supporting a role for inflammation in the pathogenesis of atherosclerosis, discuss agents that are currently in the clinic and provide a perspective on the challenges faced in the development of drugs that target vascular inflammation.

Blood biomarkers of ischemic stroke

This review provides a summary of the protein and RNA biomarkers that have been studied for the diagnosis and assessment of ischemic stroke. Many of the biomarkers identified relate to the pathophysiology of ischemic stroke, including ischemia of CNS tissue, acute thrombosis and inflammatory response. These biomarkers are summarized by their intended clinical application in ischemic stroke including diagnosis, prediction of stroke severity and outcome, and stratification of patients for stroke therapy. Among the biomarkers discussed are recent whole genome studies using RNA expression profiles to diagnose ischemic stroke and stroke etiology. Though many candidate blood based biomarkers for ischemic stroke have been identified, none are currently used in clinical practice. With further well designed study and careful validation, the development of blood biomarkers to improve the care of patients with ischemic stroke may be achieved.

Ambient air pollution and lipoprotein-associated phospholipase A₂ in survivors of myocardial infarction

BACKGROUND

Increasing evidence suggests a proatherogenic role for lipoprotein-associated phospholipase A₂ (Lp-PLA2). A meta-analysis of published cohorts has shown that Lp-PLA2 is an independent predictor of coronary heart disease events and stroke.

OBJECTIVE

In this study, we investigated whether the association between air pollution and cardiovascular disease might be partly explained by increased Lp-PLA2 mass in response to exposure.

METHODS

A prospective longitudinal study of 200 patients who had had a myocardial infarction was performed in Augsburg, Germany. Up to six repeated clinical examinations were scheduled every 4-6 weeks between May 2003 and March 2004. Supplementary to the multicenter AIRGENE protocol, we assessed repeated plasma Lp-PLA2 concentrations. Air pollution data from a fixed monitoring site representing urban background concentrations were collected. We measured hourly means of particle mass [particulate matter (PM) < 10 µm (PM₁₀) and PM < 2.5 µm (PM(2.5)) in aerodynamic diameter] and particle number concentrations (PNCs), as well as the gaseous air pollutants carbon monoxide (CO), sulfur dioxide (SO₂), ozone (O₃), nitric oxide (NO), and nitrogen dioxide (NO₂). Data were analyzed using mixed models with random patient effects.

RESULTS

Lp-PLA2 showed a positive association with PM₁₀, PM(2.5), and PNCs, as well as with CO, NO₂, NO, and SO₂ 4-5 days before blood withdrawal (lag 4-5). A positive association with O₃ was much more immediate (lag 0). However, inverse associations with some pollutants were evident at shorter time lags.

CONCLUSION

These preliminary findings should be replicated in other study populations because they suggest that the accumulation of acute and subacute effects or the chronic exposure to ambient particulate and gaseous air pollution may result in the promotion of atherosclerosis, mediated, at least in part, by increased levels of Lp-PLA2.

The effects of rosuvastatin alone or in combination with fenofibrate or omega 3 fatty acids on inflammation and oxidative stress in patients with mixed dyslipidemia

OBJECTIVE

Mixed dyslipidemia, oxidative stress and inflammation are related to a high risk for cardiovascular events. The aim of this open-label randomized study was to compare the effects of high-dose rosuvastatin, low-dose rosuvastatin plus fenofibrate and low-dose rosuvastatin plus omega 3 fatty acids on inflammation and oxidative stress indices in patients with mixed dyslipidemia.

METHODS

Ninety patients with mixed dyslipidemia participated in the study. Patients were randomly allocated to receive rosuvastatin 40 mg (n = 30, group R), rosuvastatin 10 mg plus fenofibrate 200 mg (n = 30, group RF) or rosuvastatin 10 mg plus omega 3 fatty acids 2 g daily (n = 30, group RΩ). Plasma and high-density lipoprotein (HDL)-associated lipoprotein-associated phospholipase A2 (LpPLA2) activities, high-sensitivity C reactive protein (hsCRP), plasma isoprostane and paraoxonase (PON1) activities were measured at baseline and after 3 months of treatment.

RESULTS

Serum concentrations of non-HDL cholesterol and low-density lipoprotein cholesterol (LDL-C) were significantly reduced in all study groups. However, these changes were more pronounced in the rosuvastatin monotherapy group. In all treatment groups a significant reduction in total plasma LpPLA2 activity was observed (by 41, 38 and 30% for groups R, RF and RΩ, respectively). This decrease was greater in the R and RF groups compared with the RΩ combination (p < 0.05). HDL-LpPLA2 activity was increased more in the RF group (+43%) compared with the R and RΩ groups (+ 18% and + 35%, respectively; p < 0.05 for both comparisons). In all treatment groups there was a nonsignificant reduction in plasma 8-iso-PGF2α levels. A 53% reduction of hsCRP levels was observed in the R group, while in the RF and RΩ groups the reduction was 28 and 23%, respectively (p < 0.05 and p < 0.01 for the comparisons of group R with groups RF and RΩ, respectively). No significant changes were observed in PON activities in all treatment groups.

CONCLUSION

The greater non-HDL-C- and LDL-C-lowering efficiency of rosuvastatin monotherapy along with its more potent effect on LpPLA2 activity and hsCRP levels indicate that this regimen is a better treatment option for patients with mixed dyslipidemia.

Racial variation in lipoprotein-associated phospholipase A₂ in older adults

Background

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is a predictor of cardiovascular events that has been shown to vary with race. The objective of this study was to examine factors associated with this racial variation.

Methods

We measured Lp-PLA₂ mass and activity in 714 healthy older adults with no clinical coronary heart disease and not taking dyslipidemia medication. We evaluated the association between race and Lp-PLA₂ mass and activity levels after adjustment for various covariates using multivariable linear regression. These covariates included age, sex, diabetes, hypertension, body mass index, lipid measurements, C-reactive protein, smoking status, physical activity, diet, income, and education level. We further examined genetic covariates that included three single nucleotide polymorphisms shown to be associated with Lp-PLA₂ activity levels.

Results

The mean age was 66 years. Whites had the highest Lp-PLA₂ mass and activity levels, followed by Hispanics and Asians, and then African-Americans; in age and sex adjusted analyses, these differences were significant for each non-White race as compared to Whites (p < 0.0001). For example, African-Americans were predicted to have a 55.0 ng/ml lower Lp-PLA₂ mass and 24.7 nmol/ml-min lower activity, compared with Whites, independent of age and sex (p < 0.0001). After adjustment for all covariates, race remained significantly correlated with Lp-PLA₂ mass and activity levels (p < 0.001) with African-Americans having 44.8 ng/ml lower Lp-PLA₂ mass and 17.3 nmol/ml-min lower activity compared with Whites (p < 0.0001).

Conclusion

Biological, lifestyle, demographic, and select genetic factors do not appear to explain variations in Lp-PLA₂ mass and activity levels between Whites and non-Whites, suggesting that Lp-PLA₂ mass and activity levels may need to be interpreted differently for various races.