Association between Lp-PLA2 and coronary artery disease: focus on its relationship with lipoproteins and markers of inflammation and hemostasis

The role of inflammation in percutaneous coronary intervention, from balloon angioplasty to drug eluting stents

The role of inflammation in percutaneous coronary intervention (PCI) has been investigated in numerous studies. Both pre-PCI and post-PCI inflammatory status have been demonstrated to be linked with patient outcomes. C-reactive protein continues to be the most studied inflammatory biomarker, while a growing number of additional biomarkers, including cytokines and immune cells, are being assessed. As insights are gained into the complexities of the inflammatory response to PCI, it becomes evident that a targeted approach is necessary to ensure optimal patient outcomes. Here, we review the biomarkers that can predict patient outcomes following PCI and specifically how they differ for balloon angioplasty, bare metal stents and drug eluting stents. A specific focus is given to human studies and periprocedural inflammation rather than inflammation associated with myocardial infarction.

Differentiation of Alkyl- and Plasmenyl-phosphatidylcholine by Endogenous Sphingomyelin RT-XLOGP3 Regression for Coronary Artery Disease Plasma Lipidomics Analysis

Accurate identification between alkyl- and plasmenyl-phosphatidylcholine (PC(O-) and PC(P-)) isomers is a major analytical challenge in lipidomics studies due to a lack of structure-specific ions in conventional tandem mass spectrometry (MS/MS) methods and the absence of universal retention time (RT) references. Given the importance of PC(O-) and PC(P-), an easy-to-apply method for current research is urgently needed. In this study, we present a quadratic RT-XLOGP3SM regression model that uses endogenous sphingomyelin (SM) species in blood samples as retention time (RT) indicators to predict the RTs of PC(O-) and PC(P-) species by coupling their calculated partition coefficients based on XLOGP3. The prediction results were obtained with a root-mean-square error (RMSE) of 0.12 min (1.3%) for the RRHD (rapid resolution high definition) nonlinear LC condition. A lipidomic analysis with RT-XLOGP3SM regression was used to study lipid regulation in coronary artery disease (CAD) outpatient plasma samples, and we found that the types of exhibited regulation were highly dependent on the lipid subclasses in comparison to the healthy control group. In conclusion, given that the quadratic RT-XLOGP3SM regression model predicts the RTs of PC species based on the relative value of XLOGP3 and the RTs of endogenous SM species, it can be expected that most of the C18-based lipidomics analyses could apply this method to increase the identification ability of the PC(O-) and PC(P-) subclasses and to improve the understanding of their physiological functions.

Atherogenic Index of Plasma Predicts Obstructive Coronary Artery Disease in Patients with Stable Angina Pectoris

AIMS

Chronic coronary syndrome is associated with several risk factors, such as dyslipidemia and hypertension. The atherogenic index of plasma (AIP) has been demonstrated to be a biochemical risk factor for coronary artery disease (CAD). This study aimed to determine whether the AIP is an effective parameter for estimating obstructive CAD.

METHODS AND RESULTS

A total of 345 patients (with a mean age of 62.2 ± 10.3; 63% male) who underwent coronary angiography were included in this study. Obstructive CAD is defined as having one or more vessels with a stenosis level of ≥50%. Depending on the presence of obstructive CAD, all patients were divided into two groups. The mean AIP value was found to be 0.538 ± 0.26 in the study group. The AIP values were significantly higher in the obstructive coronary artery group (AIP; 0.49 ± 0.26 vs. 0.58 ± 0.27, p = 0.002). According to a univariable analysis, AIP values were significantly associated with obstructive coronary artery disease [OR: 3.74 (CI 95% 1.62-8.64), p = 0.020]. The AIP was further adjusted for confounding risk factors in three multivariable analysis models and, all three models showed a significant association. According to an ROC analysis, 0.49 is the cut-off value for AIP, and a value above 0.49 indicates 50% coronary artpery stenosis.

CONCLUSIONS

The AIP may be used in the assessment of cardiovascular risk for patients with stable angina pectoris, and it may also be used to estimate obstructive CAD.

Lp-PLA2 (Lipoprotein-Associated Phospholipase A2) Deficiency Lowers Cholesterol Levels and Protects Against Atherosclerosis in Rabbits

BACKGROUND

Elevated plasma Lp-PLA₂ (lipoprotein-associated phospholipase A₂) activity is closely associated with an increased risk of cardiovascular events. However, whether and how Lp-PLA₂ is directly involved in the pathogenesis of atherosclerosis is still unclear. To examine the hypothesis that Lp-PLA₂ could be a potential preventative target of atherosclerosis, we generated Lp-PLA₂ knockout rabbits and investigated the pathophysiological functions of Lp-PLA₂.

METHODS

Lp-PLA₂ knockout rabbits were generated using CRISPR/Cas9 system to assess the role of Lp-PLA₂ in plasma lipids regulation and identify its underlying molecular mechanisms. Homozygous knockout rabbits along with wild-type rabbits were fed a cholesterol-rich diet for up to 14 weeks and their atherosclerotic lesions were compared. Moreover, the effects of Lp-PLA₂ deficiency on the key cellular behaviors in atherosclerosis were assessed in vitro.

RESULTS

When rabbits were fed a standard diet, Lp-PLA₂ deficiency led to a significant reduction in plasma lipids. The decreased protein levels of SREBP2 (sterol regulatory element-binding protein 2) and HMGCR (3-hydroxy-3-methylglutaryl coenzyme A reductase) in livers of homozygous knockout rabbits indicated that the cholesterol biosynthetic pathway was impaired with Lp-PLA₂ deficiency. In vitro experiments further demonstrated that intracellular Lp-PLA₂ efficiently enhanced SREBP2-related cholesterol biosynthesis signaling independently of INSIGs (insulin-induced genes). When fed a cholesterol-rich diet, homozygous knockout rabbits exhibited consistently lower level of hypercholesterolemia, and their aortic atherosclerosis lesions were significantly reduced by 60.2% compared with those of wild-type rabbits. The lesions of homozygous knockout rabbits were characterized by reduced macrophages and the expression of inflammatory cytokines. Macrophages of homozygous knockout rabbits were insensitive to M1 polarization and showed reduced DiI-labeled lipoprotein uptake capacity compared with wild-type macrophages. Lp-PLA₂ deficiency also inhibited the adhesion between monocytes and endothelial cells.

CONCLUSIONS

These results demonstrate that Lp-PLA₂ plays a causal role in regulating blood lipid homeostasis and Lp-PLA₂ deficiency protects against dietary cholesterol-induced atherosclerosis in rabbits. Lp-PLA₂ could be a potential target for the prevention of atherosclerosis.

Atherogenic index of plasma and coronary artery disease: A systematic review

Various studies suggest that the atherogenic index of plasma (AIP) is associated with the risk of coronary artery disease (CAD) in different clinical scenarios. This review aimed to synthesize evidence of the association between AIP values and CAD. A literature search was carried out on four databases, namely, PubMed, Scopus, Web of Science, and Ovid-Medline. A handsearch was performed on preprint repositories (MedRxiv and Research Square). The effect measurements were expressed as odds ratios (OR) with their corresponding 95% confidence intervals (CI). For the quantitative synthesis, we employed a random-effects model. We analyzed 14 articles (with 40,902 participants) from seven different countries. The quantitative analysis revealed that an increase in one unit of AIP was associated with higher odds of developing CAD (OR 2.11; 95% CI 1.65-2.69; P < 0.001; I ² = 98%). We conducted subgroup analyses of Chinese (OR 1.89; 95% CI 1.40-2.56; P < 0.001) and non-Chinese studies (OR 2.51; 95% CI 1.42-4.42; P < 0.001). The sensitivity analysis by risk of bias continued to demonstrate an association, and the heterogeneity remained unchanged (OR 1.75; 95% CI 1.33-2.31; P < 0.001; I ² = 98%). Higher AIP values were associated with higher odds of developing CAD.

Lipoprotein-associated Phospholipase A2 in Coronary Artery Disease

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in western societies. Therefore the identification of novel biomarkers to be used as diagnostic or therapeutic targets is of significant scientific interest. Lipoprotein-associated phospholipase A2 (Lp-PLA2) is one such protein shown to be involved in endothelial dysfunction, vascular inflammation and atherogenesis. Several epidemiological studies have associated high Lp-PLA2 activity with an increased risk for CAD even when other CAD risk factors or inflammation markers were included in the multivariate analysis. These findings were strengthened by the results of relevant meta-analyses. However, randomized trials failed to establish Lp-PLA2 as a therapeutic target. Specifically, pharmaceutical inhibition of Lp-PLA2 when compared to the placebo failed to demonstrate a significant association with improved prognosis of patients with stable CAD or after an acute coronary syndrome (ACS). This review focuses on the available data that have investigated the potential role of Lp- PLA2 as a biomarker for CAD.

The Predictive Value of Carotid Ultrasonography With Cardiovascular Risk Factors-A "SPIDER" Promoting Atherosclerosis

Insufficient recommendations do not support the clinical use of carotid ultrasonography for further risk stratification in moderate-to-high risk patients with cardiovascular disease (CVD). A literature review was performed to assess six aspects of the research progress and limitations of carotid ultrasonography and carotid atherosclerosis-related risk factors: (1) structures of the carotid intima and media; (2) plaques; (3) inflammation; (4) dynamics of carotid blood flow; (5) early detection and intervention; and (6) risk factors for CVD. Although carotid intima-media thickness and carotid plaques are well-acknowledged independent predictors of CVD risk, normative and cut-off values are difficult to define due to the heterogeneous measurements reported in previous studies. Plaque properties, including location, number, density, and size, become more important risk predictors for cardiovascular disease, but a better approach for clinical use needs to be further established. Three-dimensional ultrasound and contrast-enhanced ultrasound are promising for promoting risk stratification with more details on plaque morphology. Moreover, inflammatory diseases and biomarkers should be evaluated for a full assessment of the inflammatory burden for atherosclerosis. Carotid flow velocity is not only an indicator for stenosis but also a potential risk predictor. Carotid atherosclerosis should be detected and treated early, and additional clinical trials are needed to determine the efficacy of these measures in reducing CVD risk. Cardiovascular risk factors tend to affect carotid plaques, and early treat-to-target therapy might yield clinical benefits. Based on the aforementioned six aspects, we consider that these six important factors act like a “SPIDER” spinning the web of atherosclerosis; a timely comprehensive assessment and intervention may halt the progression to CVD. Carotid ultrasound results should be combined with other atherosclerotic factors, and a comprehensive risk assessment may help to guide cardiovascular prevention decisions.

Circulating Biomarkers Reflecting Destabilization Mechanisms of Coronary Artery Plaques: Are We Looking for the Impossible?

Despite significant strides to mitigate the complications of acute coronary syndrome (ACS), this clinical entity still represents a major global health burden. It has so far been well-established that most of the plaques leading to ACS are not a result of gradual narrowing of the vessel lumen, but rather a result of sudden disruption of vulnerable atherosclerotic plaques. As most of the developed imaging modalities for vulnerable plaque detection are invasive, multiple biomarkers were proposed to identify their presence. Owing to the pivotal role of lipids and inflammation in the pathophysiology of atherosclerosis, most of the biomarkers originated from one of those processes, whereas recent advancements in molecular sciences shed light on the use of microRNAs. Yet, at present there are no clinically implemented biomarkers or any other method for that matter that could non-invasively, yet reliably, diagnose the vulnerable plaque. Hence, in this review we summarized the available knowledge regarding the pathophysiology of plaque instability, the current evidence on potential biomarkers associated with plaque destabilization and finally, we discussed if search for biomarkers could one day bring us to non-invasive, cost-effective, yet valid way of diagnosing the vulnerable, rupture-prone coronary artery plaques.

Inflammation during Percutaneous Coronary Intervention-Prognostic Value, Mechanisms and Therapeutic Targets

Periprocedural myocardial injury and myocardial infarction (MI) are not infrequent complications of percutaneous coronary intervention (PCI) and are associated with greater short- and long-term mortality. There is an abundance of preclinical and observational data demonstrating that high levels of pre-, intra- and post-procedural inflammation are associated with a higher incidence of periprocedural myonecrosis as well as future ischaemic events, heart failure hospitalisations and cardiac-related mortality. Beyond inflammation associated with the underlying coronary pathology, PCI itself elicits an acute inflammatory response. PCI-induced inflammation is driven by a combination of direct endothelial damage, liberation of intra-plaque proinflammatory debris and reperfusion injury. Therefore, anti-inflammatory medications, such as colchicine, may provide a novel means of improving PCI outcomes in both the short- and long-term. This review summarises periprocedural MI epidemiology and pathophysiology, evaluates the prognostic value of pre-, intra- and post-procedural inflammation, dissects the mechanisms involved in the acute inflammatory response to PCI and discusses the potential for periprocedural anti-inflammatory treatment.

Relationship between Plasma Lipoprotein-Associated Phospholipase A2 Concentrations and Apolipoprotein in Stable Coronary Artery Disease Patients

Background

Increasing evidence states that the plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) levels and apolipoprotein particles are regarded as the risk maker for cardiovascular heart disease. Nevertheless, the issue about whether Lp-PLA2 is associated with apolipoprotein particles in individuals who have been diagnosed as stable coronary artery disease (CAD) remains largely unexplored.

Method

All 569 participants engaged in this research, who never took lipid-lowering drugs, had been divided into groups by the coronary angiography (CAG), namely, stable CAD: n = 291; non-CAD: n = 278. The results concerning Lp-PLA2 levels were calculated by Elisa Kit, while apolipoprotein particles were measured by the department of laboratory.

Results

The plasma concentration of Lp-PLA2 was remarkably higher in stable CAD group than the non-CAD group (136.0 ± 60.5 ng/mL vs. 113.2 ± 65.6 ng/mL, P < 0.001). Pearson correlation analyses explained the plasma Lp-PLA2 concentration was correlated with apoB (r = 0.390, P < 0.001) and apoB/apoA1 (r = 0.450, P < 0.001), not associated with apoA1 (r = −0.099, P = 0.101). Conversely, the association remains unobserved among non-CAD patients except apoA1. Moreover, multiple linear regression revealed the relations between Lp-PLA2 concentrations and apoB (β = 0.390, P < 0.001), as well as apoB/apoA1 (β = 0.450, P < 0.001), but not apoA1 (β = −0.099, P = 0.121). After adjustment for several risk factors regarding CAD, like hypertension, gender, smoking, age, and diabetes mellitus, there had still been positive associations between the Lp-PLA2 concentration and apoB (β = 0.364, P < 0.001), as well as apoB/apoA1 (β = 0.390, P < 0.001).

Conclusion

The plasma levels of Lp-PLA2 provide positively a key link with apoB, apoB/apoA-1 among stable CAD, denoting the communication between Lp-PLA2 and apolipoprotein particles in the state of CAD.

The associations of stroke, transient ischemic attack, and/or stroke-related recurrent vascular events with Lipoprotein-associated phospholipase A2: A systematic review and meta-analysis

BACKGROUND

Studies on stroke and lipoprotein-associated phospholipase A2 (Lp-PLA2) have produced conflicting results.

OBJECTIVE

The aim of the study was to assess the associations of Lp-PLA2 levels (mass and activity) with recurrent vascular events in patients with transient ischemic attack (TIA) and/or first ischemic stroke and with stroke in the general population.

METHODS

The MEDLINE, Embase, the Cochrane Library, Web of Science, Science Direct, China National Knowledge Infrastructure, China Biology Medical Disc (CBMdisc), and WanFang were searched for prospective observational studies reported until January 2017. Eligible studies reported Lp-PLA2 levels and adjusted risk estimates of recurrent vascular events and/or stroke. Risk ratio (RR) with corresponding 95% confidence intervals (CIs) were used to express the pooled data in a random-effects model.

RESULTS

A total of 11 studies that comprised 20,284 participants (4,045 were TIA and/or first ischemic stroke patients and 16,239 were residents in general population) were identified, which reported either Lp-PLA2 mass levels (4 studies) or Lp-PLA2 activity levels (10 studies). The pooled RR of recurrent vascular events (467 cases) in TIA and/or first ischemic group was 2.24 (95% CI, 1.33-3.78), whereas the pooled RR of stroke (1604 cases) in the general population was 1.47 (95% CI, 1.10-1.97). The pooled RRs of Lp-PLA2 mass and activity levels with the risk of stroke in the general population were 1.69 (95% CI, 1.03-2.79) and 1.28 (95% CI, 0.88-1.85), respectively.

CONCLUSIONS

In patients with TIA and first ischemic stroke, elevated Lp-PLA2 activity levels were associated with recurrent vascular events. And in the general population elevated Lp-PLA2 levels were associated with the risk of stroke, although the association between Lp-PLA2 activity levels and the risk of stroke was less profound compared with the corresponding association of stroke risk with the Lp-PLA2 mass levels.

AMP-activated protein kinase mediates the effects of lipoprotein-associated phospholipase A2 on endothelial dysfunction in atherosclerosis

The present study aimed to investigate the effects of lipoprotein-associated phospholipase A2 (Lp-PLA2) on endothelial dysfunction in an in vitro cell model of atherosclerosis, and to determine whether AMP-activated protein kinase (AMPK) mediates the effects of Lp-PLA2 on endothelial dysfunction. A total of 392 patients with coronary artery disease (CAD), including various sub-conditions, were recruited, and the plasma concentrations of Lp-PLA2 were evaluated. In addition, an in vitro model of atherosclerosis was established by exposing human umbilical vein endothelial cells (HUVECs) to oxidized low-density lipoprotein (oxLDL). SB-435495 was used to inhibit Lp-PLA2, and compound C was used to suppress AMPK expression. Lp-PLA2, AMPKα and phosphorylated-AMPKα (T172) expression in HUVECs were evaluated using western blot analysis. The concentrations of nitric oxide (NO), endothelin 1 (ET-1), intercellular adhesion molecule 1 (ICAM-1) and platelet/endothelial cell adhesion molecule 1 (PECAM-1) in cell culture supernatant were determined using commercially available ELISA kits. MTT assays were employed to indicate changes in cell viability. The current study found the plasma Lp-PLA2 levels were elevated in the CAD patients with stable angina pectoris, unstable angina pectoris, acute coronary syndromes and acute myocardial infarction, compared with a healthy control population. In addition, the in vitro results showed that Lp-PLA2 expression levels were elevated in oxLDL-exposed HUVECs. Lp-PLA2 suppression could increase cell viability, induce the production of NO and decrease the secretion of ET-1, in addition to suppressing the expression of cell adhesion molecules, including ICAM-1 and PECAM-1 in oxLDL-exposed HUVECs. The expression of AMPKα and phosphorylated-AMPKα (T172) was regulated by Lp-PLA2, and AMPK suppression was able to reverse the effects of Lp-PLA2 with regard to cell viability, endothelial vasorelaxation capacity and the secretion of adhesion molecules in oxLDL-exposed HUVECs. In conclusion, the present study provides initial evidence that Lp-PLA2 is able to cause endothelial dysfunction in an in vitro model of atherosclerosis, and the effects of Lp-PLA2 on endothelial dysfunction was at least partially a result of the downregulation of AMPKα, thus contributing to the progression of atherosclerosis.

Relationship between plasma phospholipase A2 concentrations and lipoprotein subfractions in patients with stable coronary artery disease

BACKGROUND

Both increased lipoprotein-associated phospholipase A2 (Lp-PLA2) concentrations and atherogenic lipoprotein subfractions have been shown to reflect unfavourable cardiovascular risk. However, the correlation between Lp-PLA2 and lipoprotein subfractions in patients with coronary artery disease (CAD) has not been assessed yet.

METHODS

A total of 324 consecutive subjects who were not treated with lipid-lowering drugs were enrolled (angiographically proven CAD: n = 253; non-CAD: n = 71). Plasma Lp-PLA2 concentrations were measured using ELISA. The low-density lipoprotein (LDL) and high-density lipoprotein (HDL) subfractions were determined by Lipoprint System.

RESULTS

Plasma Lp-PLA2 concentrations were higher in patients with CAD compared with those without CAD (153.61 ± 78.73 vs. 131.41 ± 65.49 ng/ml, p = 0.028). The univariable correlation analysis revealed that Lp-PLA2 concentrations were positively correlated with the cholesterol concentrations of each LDL subfractions and the intermediate as well as small HDL subfractions, while negatively linked with the LDL particle size and large HDL-cholesterol (HDL-C) concentrations in CAD group. However, no similar results were observed in the non-CAD group. Furthermore, multivariable regression analysis was performed in patients with CAD and showed that plasma Lp-PLA2 concentrations were independently correlated with the cholesterol concentrations of each LDL subfractions [large LDL-cholesterol (LDL-C): β = 0.263, p < 0.001; intermediate LDL-C: β = 0.327, p < 0.001; small LDL-C: β = 0.135, p = 0.033] and small HDL-C (β = 0.133, p = 0.034).

CONCLUSION

Lp-PLA2 concentrations were positively associated with all LDL subfractions and small HDL subfraction, suggesting an interaction between Lp-PLA2 and lipoprotein subfraction phenotypes in the status of CAD.

Circulating Lp-PLA₂ activity correlates with oxidative stress and cytokines in overweight/obese postmenopausal women not using hormone replacement therapy

Controversy remains regarding whether there is an association between circulating lipoprotein-associated phospholipase A2 (Lp-PLA2), cytokines, and oxidative stress in healthy postmenopausal women. We investigated the influence of age on Lp-PLA2 activity in postmenopausal women not using hormone therapy and the relationship of Lp-PLA2 enzyme activity to serum cytokine levels and oxidative stress indices. Normal weight (n = 1284) and overweight/obese (n = 707) postmenopausal women not using hormone therapy were categorized into five age groups: 50-54, 55-59, 60-64, 65-69, and 70-89 years. Overweight-obese women showed higher plasma Lp-PLA2 activity, urinary 8-epi-prostaglandin F2α (8-epi-PGF2α), serum interleukin (IL)-6, and smaller LDL particles than normal-weight women after adjusting for age, years postmenopause, smoking, drinking, blood pressure, glucose, insulin, lipid profiles, BMI, and waist circumference. Overweight/obese women 70-89 years old showed higher Lp-PLA2 activity than those aged 50-54 years, whereas no significant difference in Lp-PLA2 activity existed across normal-weight female age groups. Overweight/obese women aged ≥ 65 years showed higher Lp-PLA2, oxidized LDL (ox-LDL), IL-6, and 8-epi-PGF2α than age-matched normal-weight controls. Overweight/obese women aged ≥ 70 years had higher ox-LDL levels than those aged 50-59, and overweight/obese women aged 65-89 showed higher IL-6 and 8-epi-PGF2α. There were strong positive correlations between Lp-PLA2 and ox-LDL (r = 0.385, P < 0.001), Lp-PLA2 and IL-6 (r = 0.293, P < 0.001), and ox-LDL and IL-6 (r = 0.303, P < 0.001) in overweight/obese women; however, these relationships were weak in normal-weight women. These results suggest that aging and obesity-related oxidative and inflammatory mediators are associated with Lp-PLA2 activity in overweight/obese postmenopausal women not using hormone therapy.

Risk of anaphylaxis in opioid dependent persons: effects of heroin versus substitution substance

Background

Across Europe, illicit drug-related mortality has not declined despite ever increasing prevention measures. The cause of these deaths has traditionally been associated with overdose. Previous findings have revealed the appearance of non-lethal opioid concentrations, leading us to investigate a further cause of death. The symptoms of heroin intoxication with asphyxia and/or cardiovascular involvement resemble anaphylaxis, and therefore it has been speculated that such deaths might be caused by an allergic reaction. The study´s aims were to investigate levels of allergic mediators in long-term injecting drug users (IDU) compared to healthy controls and to determine if oral opioid substitution therapy (OST) resulted in similar allergic symptoms to those reported by IDU after intravenous (IV) heroin use.

Methods

We quantified the concentrations of histamine, diamine oxidase (DAO), tryptase and lipoprotein-associated phospholipase A₂ (LpPLA₂) at baseline and 1 h after administration of Substitol®retard (482 ± 220 mg) in 56 patients at a withdrawal centre (Austria) and compared them with healthy controls (n = 103). Questionnaires and face-to-face interviews were used to assess allergic symptoms and side effects in IDU. Descriptive statistical analyses of quantitative data were performed by using SPSS.

Results

Baseline histamine, tryptase and LpPLA₂ were significantly elevated in IDU compared to the healthy control group, while DAO decreased. Blood levels showed no significant change after oral substitution uptake. Self-reported allergic symptoms and side effects after IV heroin use were reported in 55 cases (98.2%), minimal symptoms were documented after OST (12.5%, 7/56).

Conclusions

This study revealed that baseline histamine concentrations were elevated in chronic IDU, although only relatively small changes in tryptase plasma levels occurred. After IV heroin application the reported allergic symptoms were mostly mild and did not lead to clinically relevant side effects. The substitution substance was clearly better tolerated than IV administered heroin. Elevated levels of allergic mediators such as histamine in IDUs may place them at greater risk of severe or fatal anaphylaxis when exposed to heroin; however, this requires further investigation.

Elevated lipoprotein-associated phospholipase A2 is associated with progression of nonculprit lesions after percutaneous coronary intervention

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is an enzyme that hydrolyzes oxidized phospholipids to generate bioactive proatherogenic products. Nonculprit lesions have been assumed to contribute to the pathogenesis of recurrent acute coronary syndrome (ACS). The role of LP-PLA2 in the progression of nonculprit coronary lesions after successful percutaneous coronary intervention (PCI) remains unclear. Our study included 123 patients with ACS who underwent initial PCI and a long-term follow-up (mean interval, one year) with coronary angiography. Among them, 19 patients were diagnosed as the progression of nonculprit lesions, based on the presence of at least one of the following factors: (1) ≥ 10% reduction in the diameter of a preexisting ≥ 50% stenosis; (2) ≥ 30% reduction in the diameter of a < 50% stenosis; and (3) early-onset stenosis with ≥ 30% reduction in the diameter of a segment that was normal on the primary angiogram. Blood sampling was drawn from all patients at 12-14 hours after PCI. The ACS patients with progression had higher total cholesterol (4.47 ± 1.02 mmol/L vs. 3.59 ± 0.57 mmol/L, P < 0.05), higher levels of Lp-PLA2 activity (14.39 ± 6.13 nmol/min/ml vs. 8.86 ± 3.14 nmol/min/ml, P < 0.001) and a higher proportion of multi-vessel disease than those without progression. Multivariate logistic regression analysis showed that Lp-PLA2 activity (β = 0.024, P = 0.005) was an independent predictor for rapid progression of nonculprit coronary lesions. In conclusion, elevated Lp-PLA2 activity is associated with rapid progression of nonculprit coronary lesions in ACS patients who underwent PCI.

Cardiovascular disease risk prediction in women: is there a role for novel biomarkers?

BACKGROUND

Risk prediction is an integral part of the current US guidelines for cardiovascular disease in women. Although current risk prediction algorithms exist to identify women at increased 10-year risk of cardiovascular disease (CVD), clinicians and researchers have been interested in developing novel biomarkers that might improve predictive accuracy further. These biomarkers have led to important insights into the pathophysiology of CVD, but results for their ability to improve prediction or guide preventive therapy have been mixed. The incidence of CVD is lower in women than men, and the effects of a number of traditional biomarkers on CVD risk differ in women compared to men. Both of these factors influence the ability to accurately predict CVD risk.

CONTENT

We review the distinctive aspects of CVD risk prediction in women, discuss the statistical challenges to improved risk prediction, and discuss a number of biomarkers in varying stages of development with a range of performance in prediction.

SUMMARY

A variety of biomarkers from different pathophysiologic pathways have been evaluated for improving CVD risk. While many have been incompletely studied or have not been shown to improve risk prediction in women, others, such as high-sensitivity troponin T, have shown promise in improving risk prediction. Increasing inclusion of women in CVD studies will be crucial to providing opportunities to evaluate future biomarkers.

Predicting the Risk of Cardiovascular Disease

Although an atherogenic lipoprotein phenotype has been well recognized as an important predictor of cardiovascular disease, recent studies have demonstrated a number of additional lipid-related markers as emerging biomarkers to identify patients at risk for future coronary heart disease. Among them, lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), seems to be a promising candidate that might be added to the clinical armamentarium for improved prediction of cardiovascular disease in the future. Of particular note, Lp-PLA(2) is the only enzyme that cleaves oxidized low-density lipoprotein (oxLDL) in the subendothelial space, with further generation of proinflammatory mediators such as lysophosphatidylcholine (LysoPC) and oxidized fatty acid (oxFA), thereby probably linking two important features of atherogenesis, namely oxidation of LDL and local inflammatory processes within the atherosclerotic plaque. This overview aims to summarize our current knowledge based on observations from recent experimental and clinical studies. Emphasis has been put on potential pathophysiological mechanisms of action and on the clinical relevance of Lp-PLA(2) in a wide variety of clinical settings, including apparently healthy individuals, patients with stable angina or acute coronary syndromes, after myocardial infarction, and with subclinical disease. Although a growing body of evidence from epidemiological and clinical studies suggests that Lp-PLA(2) may represent an independent and clinically relevant long-term risk marker for coronary heart disease and, probably, also for stroke, the role of this enzyme in the setting of the acute coronary syndrome remains to be established.

Clinical utility of lipoprotein-associated phospholipase A₂ for cardiovascular disease prediction in a multiethnic cohort of women

BACKGROUND

Findings regarding the association of lipoprotein-associated phospholipase A₂ (Lp-PLA2) activity and mass with incident cardiovascular disease (CVD) have been inconsistent, and their role in risk prediction is uncertain.

METHODS

A case-cohort sample from the Women's Health Initiative Observational Study (WHI-OS) comprised 1821 CVD cases and a reference subcohort of 1992 women. We used Cox regression models with inverse sampling weights to assess the association of Lp-PLA2 mass and activity with CVD (myocardial infarction, stroke, and CVD mortality).

RESULTS

Subcohort means were 184.3 mmol/min/mL for Lp-PLA2 activity and 499.2 μg/L for Lp-PLA2 mass, with 99% having mass above 200 μg/L, the clinically recommended cut point. Both activity and mass were positively associated with incident CVD in age- and race/ethnicity-adjusted analyses. Following adjustment according to CVD risk factors, the association with activity became null (hazard ratio = 1.02 for top vs bottom quartile, 95% CI = 0.79-1.33, P for trend = 0.65), but the association with mass remained (hazard ratio = 1.84, 95% CI = 1.45-2.34, P for trend < 0.0001). In contrast to blood pressure, HDL, and hsCRP, reclassification statistics for Lp-PLA2 mass did not suggest improvement for overall CVD after full adjustment.

CONCLUSIONS

In the WHI-OS Lp-PLA2 mass, but not activity, was independently associated with CVD. However, model fit did not significantly improve with Lp-PLA2 mass, and assay calibration remains a clinical concern.

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.

Evidence supporting a key role of Lp-PLA2-generated lysophosphatidylcholine in human atherosclerotic plaque inflammation

OBJECTIVE

To determine whether the level of lysophosphatidylcholine (lysoPC) generated by lipoprotein-associated phospholipase A2 (Lp-PLA2) is associated with severity of inflammation in human atherosclerotic plaques. Elevated plasma Lp-PLA2 is associated with increased cardiovascular risk. Lp-PLA2 inhibition reduces atherosclerosis. Lp-PLA2 hydrolyzes low-density lipoprotein-oxidized phospholipids generating lysoPCs. According to in vitro studies, lysoPCs are proinflammatory but the association between their generation and plaque inflammation remains unknown.

METHODS AND RESULTS

Inflammatory activity in carotid plaques (162 patients) was determined immunohistochemically and by analyzing cytokines in homogenates (multiplex immunoassay). LysoPCs were quantified using mass spectrometry and Lp-PLA2 and the lysoPC metabolite lysophosphatidic acid (LPA) by ELISA. There was a strong correlation among lysoPC 16:0, 18:0, 18:1, LPA, and Lp-PLA2 in plaques. LysoPC 16:0, 18:0, 18:1, LPA, and Lp-PLA2 correlated with interleukin-1β, interleukin-6, monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, regulated on activation normal T-cell expressed and secreted, and tumor necrosis factor-α in plaques. High lysoPC and Lp-PLA2 correlated with increased plaque macrophages and lipids and with low content of smooth muscle cells, whereas LPA only correlated with plaque macrophages. Lp-PLA2, lysoPC 16:0, 18:0, and 18:1, but not LPA were higher in symptomatic than in asymptomatic plaques.

CONCLUSIONS

The associations among Lp-PLA2, lysoPCs, LPA, and proinflammatory cytokines in human plaques suggest that lysoPCs play a key role in plaque inflammation and vulnerability. Our findings support Lp-PLA2 inhibition as a possible strategy for the prevention of cardiovascular disease.

Circulating and PBMC Lp-PLA2 associate differently with oxidative stress and subclinical inflammation in nonobese women (menopausal status)

BACKGROUND

This study aimed to determine the association of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) activity in circulation and peripheral blood mononuclear cells (PBMCs) with inflammatory and oxidative stress markers in nonobese women and according to menopausal status. Lp-PLA(2) activity, a marker for cardiovascular risk is associated with inflammation and oxidative stress.

METHODOLOGY/PRINCIPAL FINDINGS

Eighty postmenopausal women (53.0±4.05 yr) and 96 premenopausal women (39.7±9.25 yr) participated in this study. Lp-PLA(2) activities, interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β in plasma as well as in PBMCs were measured. Plasma ox-LDL was also measured. Postmenopausal women demonstrated higher circulating levels of ox-LDL and IL-6, as well as IL-6, TNF-α, and IL-1β in PBMCs, than premenopausal women. In both groups, plasma Lp-PLA(2) activity positively correlated with Lp-PLA(2) activity in PBMCs and plasma ox-LDL. In premenopausal women, Lp-PLA(2) activities in plasma and PBMCs positively correlated with IL-6, TNF-α, and IL-1β in PBMCs. In postmenopausal women, plasma ox-LDL positively correlated with PBMC cytokine production. In subgroup analysis of postmenopausal women according to plasma ox-LDL level (median level: 48.715 U/L), a significant increase in Lp-PLA(2) activity in the plasma but not the PBMCs was found in the high ox-LDL subgroup. Plasma Lp-PLA(2) activity positively correlated with unstimulated PBMC Lp-PLA(2) activity in the low ox-LDL subgroup (r = 0.627, P<0.001), whereas in the high ox-LDL circulating Lp-PLA(2) activity positively correlated with plasma ox-LDL (r = 0.390, P = 0.014) but not with Lp-PLA(2) activity in PBMCs.

CONCLUSIONS/SIGNIFICANCE

The lack of relation between circulating Lp-PLA(2) activity and Lp-PLA(2) activity in PBMCs was found in postmenopausal women with high ox-LDL. This may indicate other sources of circulating Lp-PLA(2) activity except PBMC in postmenopausal women with high ox-LDL. We also demonstrated that circulating Lp-PLA(2) and PBMC secreted Lp-PLA(2) associate differently with markers of oxidative stress and sub clinical inflammation in nonobese women, particularly according to the menopausal states.

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.

Lipoprotein-associated phospholipase A2: a new therapeutic target

Lipoprotein-associated phospholipase A2 is an enzyme produced by inflammatory cells, which binds to apolipoprotein B-containing lipoproteins and degrades oxidatively modified phospholipids in low-density lipoprotein cholesterol particles, leading to formation of proinflammatory and cytotoxic products. Experimental studies suggest a role for lipoprotein-associated phospholipase A2 in the formation of advanced rupture-prone atherosclerotic lesions, and epidemiological investigations have linked it to increased cardiovascular risk. Ongoing trials are evaluating the role of novel pharmacological inhibitors of this enzyme, such as darapladib, in the management of high-risk coronary artery disease patients.

Lipoprotein-associated phospholipase A2 activity and incident coronary heart disease among men and women with type 2 diabetes

OBJECTIVE

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) has been shown to be associated with increased risk of coronary heart disease (CHD) in general adult populations. Because men and women with type 2 diabetes are at particularly high risk for CHD, the aim of this study was to assess the association of Lp-PLA(2) with future coronary events among diabetic men and women.

RESEARCH DESIGN AND METHODS

We measured Lp-PLA(2) activity among 740 men and 777 women with confirmed diabetes enrolled in the Health Professionals Follow-Up Study (HPFS) and Nurses' Health Study (NHS). Participants were free of all cardiovascular disease and cancer at baseline.

RESULTS

During 10 years of follow-up among men and 14 years among women, we documented 178 and 146 cases of CHD, respectively. We defined CHD as coronary artery bypass graft, angioplasty, nonfatal myocardial infarction, and fatal CHD. After adjustment for age, smoking, medical history, and biomarkers including C-reactive protein, HDL, and LDL, the relative risk of total CHD comparing extreme tertiles of Lp-PLA(2) was 1.39 (95% CI 1.01-1.90; P trend = 0.03). When we restricted analyses to only nonfatal myocardial infarction and fatal CHD, the relative risk was 1.75 (95% CI 1.05-2.92; P for trend = 0.001). LDL, HDL, C-reactive protein, hormone replacement therapy use, and diabetes duration did not modify these relationships.

CONCLUSIONS

Levels of Lp-PLA(2) activity were significantly associated with incident CHD among men and women with type 2 diabetes, independent of traditional and inflammatory risk factors. This positive association was strongest for more severe clinical end points.

Dietary, lifestyle, and clinical predictors of lipoprotein-associated phospholipase A2 activity in individuals without coronary artery disease

BACKGROUND

Elevated lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) may be positively associated with risk of coronary artery disease, yet little is known about potentially modifiable factors related to Lp-PLA(2).

OBJECTIVE

The aim of this study was to determine dietary, lifestyle, and clinical measures associated with Lp-PLA(2) activity.

DESIGN

We measured Lp-PLA(2) activity in 853 female participants of the Nurses' Health Study and 878 male participants of the Health Professionals Follow-Up Study who were free of cancer and cardiovascular disease. Multivariable linear regression models were used to assess the relation between potentially modifiable factors and Lp-PLA(2).

RESULTS

The replacement of 5% of energy from carbohydrates with energy from protein was associated with 2.2 nmol . min(-1) . mL(-1) lower levels of Lp-PLA(2) (95% CI: -3.1, -0.4) activity, and every 15-g/d increase in alcohol consumption was associated with 4.4 nmol . min(-1) . mL(-1) lower levels of Lp-PLA(2) activity (95% CI: -6.4, -2.4). Smoking (beta = 10.2; 95% CI: 4.8, 15.5), being overweight (beta = 7.5; 95% CI: 3.6, 11.3), aspirin use (beta = 6.0; 95% CI: 2.1, 10.0), hypercholesterolemia (beta = 15.0; 95% CI: 11.3, 18.8), and age (beta = 2.5; 95% CI: 1.34, 3.74) were associated with elevated Lp-PLA(2) activity, whereas postmenopausal hormone use (beta = -15.8; 95% CI: -19.4, -12.1) and cholesterol medication use (beta = -9.6; 95% CI: -18.2, -1.1) were inversely associated.

CONCLUSION

We found that not smoking, use of postmenopausal hormones, having a body mass index (in kg/m(2)) < or =25, increased alcohol consumption, and increased protein consumption all represent potential modifiable factors that may favorably influence Lp-PLA(2) activity.

Synthesis of oligo(ethylene glycol) substituted phosphatidylcholines: secretory PLA2-targeted precursors of NSAID prodrugs

A series of new phosphatidylcholine analogues with structurally modified sn-2-substituents have been prepared. The synthetic compounds include oligo(ethylene glycol) derivatives with chain-terminal pharmacophores that upon catalytic hydrolysis by phospholipase A(2) yielded a series of oligo(ethylene glycol)-conjugates of the respective drugs. The approach here outlined may open a new way to employ OEG derivatives of phospholipids for therapeutic applications as secretory PLA(2)-targeted precursors of prodrugs.

Lipoprotein-associated phospholipase A2: a cardiovascular risk predictor and a potential therapeutic target

Lipoprotein-associated phospholipase A2 (Lp-PLA2), present in the circulation and in atherosclerotic plaque, is an inflammatory marker with potential use as a predictor of cardiovascular risk and as a therapeutic target. Although Lp-PLA2 is associated with both LDL and HDL, it is important to determine whether Lp-PLA2 has a predominantly pro- or anti-atherogenic effect. Increasing evidence suggests a proatherogenic role for Lp-PLA2. ©iEpidemiologic and clinical evidence suggests Lp-PLA2 is an independent predictor of risk and may be superior to other inflammatory markers owing to its specificity and minimal biovariation. Lp-PLA2 inhibitors currently being investigated in clinical trials are promising novel anti-inflammatory agents with a specificity for the vascular bed and a potential for decreasing plaque vulnerability.

Association of Lipoprotein-Associated Phospholipase A2 Mass and Activity with Coronary and Aortic Atherosclerosis: Findings from the Dallas Heart Study

Background: Our aim was to characterize the association of lipoprotein-associated phospholipase A2 (Lp-PLA2) with coronary and aortic atherosclerosis in a large population-based study.

Methods: Lp-PLA2 mass and activity were measured in 2171 subjects 30–65 years old participating in the Dallas Heart Study. We examined the association of Lp-PLA2 levels with 3 atherosclerosis phenotypes: coronary artery calcium (CAC) measured by electron-beam computed tomography and abdominal aortic plaque (AAP) and aortic wall thickness (AWT) measured by magnetic resonance imaging.

Results: CAC and AAP were detected in 21% and 40% of subjects, respectively, and mean AWT (SD) was 1.70 (0.32) mm. In univariable analyses, Lp-PLA2 mass (but not activity) was higher in both men (P = 0.04) and women (P = 0.02) with detectable CAC. Lp-PLA2 mass and activity were higher (P = 0.004 and P = 0.01, respectively) and AWT was greater (P &lt; 0.001 and P = 0.02, respectively) in women with aortic atheroma, but not in men. After adjustment for traditional atherosclerosis risk factors and C-reactive protein concentrations, Lp-PLA2 mass and activity were not associated with AAP or AWT in either sex, but Lp-PLA2 mass remained modestly associated with detectable CAC only in men (odds ratio 1.20 per 1 standard deviation increase, 95% CI 1.01–1.42, P = 0.04).

Conclusions: Although Lp-PLA2 mass was independently associated with CAC in men, it was not associated with AAP or AWT in men or with any of the atherosclerosis phenotypes in women. These findings suggest that if Lp-PLA2 independently influences clinical events, it does so by promoting atherosclerotic plaque instability rather than by stimulating atherogenesis.

Effects of a low-calorie diet associated with weight loss on lipoprotein-associated phospholipase A2 (Lp-PLA2) activity in healthy obese women

INTRODUCTION

Platelet-activating factor acetylhydrolase (PAF-AH or Lp-PLA(2)) is a Ca(2+)-independent phospholipase A(2) primarily associated in plasma with low density lipoproteins (LDL), especially with small dense LDL (sdLDL) particles. Increased plasma Lp-PLA(2) levels have been associated with increased cardiovascular risk in large clinical trials.

AIM

To assess the effects of weight loss on Lp-PLA(2) activity and to examine the association of Lp-PLA(2) activity changes with the alterations of sdLDL, the primary carrier of Lp-PLA(2) in plasma.

METHODS

Twenty-eight obese, non-diabetic women participated in a weight reduction program. Anthropometric parameters were assessed and parameters of glucose metabolism, lipid profile, Lp-PLA(2) activity, and LDL phenotype (using a 3% polyacrylamide gel-tube electrophoresis method), were determined at baseline and after 4months of weight loss.

RESULTS

A 10% diet-induced weight loss resulted in significant improvement in most parameters of lipid and glucose metabolism. Moreover, Lp-PLA(2) activity was significantly reduced (-10.2%, p<0.01). Mean LDL particle diameter did not change after the weight loss program. The cholesterol levels of very low-density lipoprotein (VLDL) and large-buoyant LDL particles were significantly reduced, but neither the cholesterol levels of sdLDL particles nor the % proportion of the sdLDL-cholesterol over the total LDL-cholesterol were changed after the intervention program. Interestingly, the changes in Lp-PLA(2) activity were correlated with the changes of VLDL-cholesterol (r=0.39, p<0.05), but not with the changes of anthropometric or other lipid variables.

CONCLUSIONS

A low-calorie diet associated with weight loss in obese women resulted in the significant reduction of the plasma levels of Lp-PLA(2), the potentially new predictor for incident atherosclerotic disease.

Lipoprotein-associated phospholipase A2 activity is associated with coronary artery disease and markers of oxidative stress: a case-control study

BACKGROUND

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is a lipoprotein-bound enzyme that can release atherogenic isoprostanes from esterified phospholipids and that may be involved in inflammation and atherosclerosis.

OBJECTIVE

This study investigates the association between Lp-PLA(2) activity and coronary artery disease (CAD) in relation to oxidative stress markers, in particular urinary 8-epi-prostaglandin F(2alpha) (8-epi-PGF(2alpha)).

DESIGN

We conducted a case-control study in which the cross-sectional relation between Lp-PLA(2) activity, lipoproteins, and oxidative stress markers was determined in 799 patients with angiographically confirmed CAD and 925 healthy controls.

RESULTS

Lp-PLA(2) activity was significantly (P < 0.001) higher in CAD cases than in controls (32.9 +/- 0.46 and 29.7 +/- 0.42 nmol . mL(-1) . min(-1), respectively). Both elevated Lp-PLA(2) activity and urinary excretion concentrations of 8-epi-PGF(2alpha) were associated with greater CAD risk (P for trend < 0.001). Odds ratios for the upper quartiles of Lp-PLA(2) activity and 8-epi-PGF(2alpha).excretion were 2.47 (95% CI: 1.79, 3.40) and 2.19 (1.52, 3.15), respectively, after adjustment for sex, age, BMI, blood pressure, smoking and alcohol consumption status, and LDL and HDL cholesterol. When we examined the additive effect of both markers for CAD risk, the relation between 8-epi-PGF(2alpha) and CAD was weakened above the second quartile of Lp-PLA(2) activity. Moreover, Lp-PLA(2) activity was positively correlated with urinary excretion concentrations of 8-epi-PGF(2alpha) in controls (r = 0.277, P < 0.001) and cases (r = 0.202, P < 0.001) and with the tail moment of lymphocyte DNA (r = 0.213, P < 0.001) in controls.

CONCLUSION

This study shows an association of elevated Lp-PLA(2) activity with CAD risk in relation to oxidant stress and thus supports a proatherogenic role of Lp-PLA(2).

The role of phospholipid oxidation products in inflammatory and autoimmune diseases: evidence from animal models and in humans

Since the discovery of oxidized phospholipids (OxPL) and their implication as modulators of inflammation in cardiovascular disease, roles for these lipid oxidation products have been suggested in many other disease settings. Lipid oxidation products accumulate in inflamed and oxidatively damaged tissue, where they are derived from oxidative modification of lipoproteins, but also from membranes of cells undergoing apoptosis. Thus, increased oxidative stress as well as decreased clearance of apoptotic cells has been implied to contribute to accumulation of OxPL in chronically inflamed tissues.A central role for OxPL in disease states associated with dyslipedemia, including atherosclerosis, diabetes and its complications, metabolic syndrome, and renal insufficiency, as well as general prothrombotic states, has been proposed. In addition, in organs which are constantly exposed to oxidative stress, including lung, skin, and eyes, increased levels of OxPL are suggested to contribute to inflammatory conditions. Moreover, accumulation of OxPL causes general immunmodulation and may lead to autoimmune diseases. Evidence is accumulating that OxPL play a role in lupus erythematosus, antiphospholipid syndrome, and rheumatoid arthritis. Last but not least, a role for OxPL in neurological disorders including multiple sclerosis (MS), Alzheimer's and Parkinson's disease has been suggested.This chapter will summarize recent findings obtained in animal models and from studies in humans that indicate that formation of OxPL represents a general mechanism that may play a major role in chronic inflammatory and autoimmune diseases.

Lipoprotein-associated phospholipase A2 predicts progression of cardiac allograft vasculopathy and increased risk of cardiovascular events in heart transplant patients

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a risk factor for coronary artery disease (CAD) in nontransplant patients. We evaluated the association between Lp-PLA2, cardiac allograft vasculopathy (CAV) assessed by 3D intravascular ultrasound, and incidence of cardiac adverse events in heart transplant recipients.

MATERIALS AND METHODS

Fasting blood samples were obtained and stored from a cross-section of 112 cardiac transplant recipients attending the Mayo cardiac transplant clinic in 2000 to 2001, mean of 4.7 years after transplant. Lp-PLA2 was measured in plasma aliquots using an enzyme-linked immunoassay. Fifty-six of these patients subsequently underwent two 3D intravascular ultrasound studies in 2004 to 2006 12 months apart. Cardiovascular (CV) events included percutaneous coronary intervention, coronary artery bypass grafting (CABG), reduction in left ventricular ejection fraction (LVEF) < or =45% secondary to CAV and CV death.

RESULTS

High Lp-PLA2 level was associated with increase in plaque volume (r=0.43, P=0.0026) and percent plaque volume (r=0.45, P=0.0004). The association remained significant after adjusting for clinical and lipid variables. During follow-up of 5.1+/-1.6 years, 24 CV adverse events occurred in 15 of 112 (13%) heart transplant patients. Lp-PLA2 level>236 ng/mL (higher tertile) identified a subgroup of patients having a 2.4-fold increase of relative risk for combined endpoint of CV events (percutaneous coronary intervention, CABG, LVEF<45%, and CV death; 95% CI 1.16-5.19, P=0.012) compared with patients with Lp-PLA2< or =236 ng/mL.

CONCLUSIONS

Lp-PLA2 is independently associated with progression of CAV and predicts a higher incidence of CV events and CV death in transplant patients. This finding supports the concept that systemic inflammation is an important mediator of CAV. Lp-PLA2 may be a useful marker for risk of CAV and a therapeutic target in posttransplant patients.

Lipoprotein-associated phospholipase A2: an independent predictor of coronary artery disease events in primary and secondary prevention

In recent years, atherosclerosis has become recognized as an inflammatory disease whose activity can be assessed by circulating biomarkers. Along with C-reactive protein (CRP), lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) may now be considered as a biomarker with sufficient accumulated evidence to support its application in clinical practice. Lp-PLA(2) is especially appealing because of its vascular specificity, which directly derives from its role in plaque pathophysiology. This article reviews the highlights of the >25 prospective epidemiologic studies now published on Lp-PLA(2) as a risk marker in primary or secondary prevention. These trials demonstrate generally consistent correlations between elevated Lp-PLA(2) levels and the increased risk for cardiovascular events, even after multivariable adjustment for traditional risk factors, with roughly a doubling of risk associated with upper quantile levels. Furthermore, Lp-PLA(2) as a risk predictor has been shown to be independent of and complementary to high-sensitivity CRP. These study results combined with recommendations from the American Heart Association/Centers for Disease Control (AHA/CDC) and the National Cholesterol Education Program III (NCEP III) suggest that Lp-PLA(2) might best be used in current clinical practice to refine risk prediction in those at intermediate cardiovascular risk. An increasingly prevalent group at intermediate risk shown to benefit from Lp-PLA(2) risk modification is the population with the cardiovascular metabolic syndrome, clinically identified as overweight patients with features of mixed dyslipidemia, dysglycemia, and hypertension. An additional application supported by these studies is further risk stratification of high- (often secondary-) risk patients into a group at very high risk, for whom a more aggressive target for low-density lipoprotein of <70 mg/dL (1 mg/dL = 0.02586 mmol/L) is now recommended as a reasonable therapeutic goal.

Lipoprotein-associated phospholipase A2: a risk marker or a risk factor?

Multiple cardiovascular biomarkers are associated with increased cardiovascular disease (CVD) risk. Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) appears to be relatively unique in its high specificity for and the causal pathway of plaque inflammation. In both primary and secondary prevention study populations, Lp-PLA(2) was consistently associated with higher cardiovascular risk, and the risk estimate appears to be relatively unaffected by adjustment for conventional CVD risk factors. Risk ratios were similar, whether the mass concentration or activity of the enzyme was measured. The purpose of this article is to review the evidence for the clinical utility of Lp-PLA(2), both as a risk marker and as a risk factor involved in the causal pathway of plaque inflammation and the formation of rupture-prone plaque.

Review of the evidence for the clinical utility of lipoprotein-associated phospholipase A2 as a cardiovascular risk marker

A substantial body of peer-reviewed studies has been published validating the role of inflammation in atherogenesis and supporting lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) as a cardiovascular risk marker independent of and additive to traditional risk factors. As with elevated high-sensitivity C-reactive protein, an elevated Lp-PLA(2) level approximately doubles the risk for primary and secondary cardiovascular events. Interestingly, when both inflammatory markers are increased together, they provide an even greater predictive capability to help identify very-high-risk individuals who would benefit most from aggressive lipid-lowering therapy. High levels of Lp-PLA(2) are present in inflamed, rupture-prone plaques, and it appears that Lp-PLA(2) is released from these plaques into the circulation. Over 25 prospective epidemiologic studies have demonstrated the association of elevated Lp-PLA(2) levels with future coronary events and stroke-11 of 12 prospective studies have shown a statistically significant association between elevated Lp-PLA(2) and primary coronary or cardiovascular events, 12 of 13 have shown a statistically significant association with recurrent coronary or cardiovascular events, and 6 studies have shown a positive association with stroke. Lp-PLA(2) should be viewed today as an important cardiovascular risk marker whose utility is as an adjunct to the major risk factors to adjust absolute risk status and thereby modify low-density lipoprotein cholesterol goals. The low biologic fluctuation and high vascular specificity of Lp-PLA(2) makes it possible to use a single measurement in clinical decision making, and it also permits clinicians to follow the Lp-PLA(2) marker serially. Ultimately, Lp-PLA(2) may also be classified as a risk factor, but this should not detract from its utility today as a risk marker.

The effect of darapladib on plasma lipoprotein-associated phospholipase A2 activity and cardiovascular biomarkers in patients with stable coronary heart disease or coronary heart disease risk equivalent: the results of a multicenter, randomized, double-blind, placebo-controlled study

OBJECTIVES

This study examined the effects of darapladib, a selective lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) inhibitor, on biomarkers of cardiovascular (CV) risk.

BACKGROUND

Elevated Lp-PLA(2) levels are associated with an increased risk of CV events.

METHODS

Coronary heart disease (CHD) and CHD-risk equivalent patients (n = 959) receiving atorvastatin (20 or 80 mg) were randomized to oral darapladib 40 mg, 80 mg, 160 mg, or placebo once daily for 12 weeks. Blood samples were analyzed for Lp-PLA(2) activity and other biomarkers.

RESULTS

Baseline low-density lipoprotein cholesterol (LDL-C) was 67 +/- 22 mg/dl. Plasma Lp-PLA(2) was higher in older patients (>or=75 years), in men, in those taking atorvastatin 20 mg, at LDL-C >or=70 mg/dl or high-density lipoprotein cholesterol (HDL-C) <40 mg/dl, or in those with documented vascular disease (multivariate regression; p < 0.01). Darapladib 40, 80, and 160 mg inhibited Lp-PLA(2) activity by approximately 43%, 55%, and 66% compared with placebo (p < 0.001 weeks 4 and 12). Sustained dose-dependent inhibition was noted overall in both atorvastatin groups and at different baseline LDL-C (>or=70 vs. <70 mg/dl) and HDL-C (<40 vs. >or=40 mg/dl). At 12 weeks, darapladib 160 mg decreased interleukin (IL)-6 by 12.3% (95% confidence interval [CI] -22% to -1%; p = 0.028) and high-sensitivity C-reactive protein (hs-CRP) by 13.0% (95% CI -28% to +5%; p = 0.15) compared with placebo. The Lp-PLA(2) inhibition produced no detrimental effects on platelet biomarkers (P-selectin, CD40 ligand, urinary 11-dehydrothromboxane B(2)). No major safety concerns were noted.

CONCLUSIONS

Darapladib produced sustained inhibition of plasma Lp-PLA(2) activity in patients receiving intensive atorvastatin therapy. Changes in IL-6 and hs-CRP after 12 weeks of darapladib 160 mg suggest a possible reduction in inflammatory burden. Further studies will determine whether Lp-PLA(2) inhibition is associated with favorable effects on CV events.

Cardiovascular events with increased lipoprotein-associated phospholipase A(2) and low high-density lipoprotein-cholesterol: the Veterans Affairs HDL Intervention Trial

OBJECTIVE

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), a proinflammatory enzyme that predominantly circulates with low-density lipoprotein (LDL), has been shown in general populations to predict cardiovascular (CV) events. We sought to determine whether increased Lp-PLA(2) would also predict CV events in the absence of high LDL-cholesterol (LDL-C), in a population with low high-density lipoprotein-cholesterol (HDL-C).

METHODS AND RESULTS

Plasma Lp-PLA(2) activity was measured at baseline and after 6 months on-trial in 1451 men with low HDL-C (mean, 32 mg/dL) and low LDL-C (mean 110 mg/dL), randomized to either placebo or gemfibrozil therapy in the Veterans Affairs HDL Intervention Trial (VA-HIT). Over a quartile range of increasing Lp-PLA(2) there was a significant increase in LDL-C and decrease in HDL-C (P < 0.0001), and an increased percentage of myocardial infarction (MI), stroke, or CHD death (P=0.03 for trend). In Cox models, adjusted for major CV risk factors, a 1-SD increase in Lp-PLA(2) was associated with a significant increase in CV events (hazard ratio [HR] 1.17 95% CI 1.04 to 1.32). Although gemfibrozil reduced Lp-PLA(2) only modestly (6.6%), at higher levels of Lp-PLA(2) gemfibrozil produced a significant reduction in CV events.

CONCLUSIONS

In VA-HIT, a population with low HDL-C and LDL-C, high Lp-PLA(2) independently predicted CV events that were reduced by gemfibrozil.

Association of lipoprotein-associated phospholipase A2 with coronary calcification among American and Japanese men

BACKGROUND

We have previously reported that the prevalence of coronary artery calcification (CAC) was substantially lower among Japanese than American men despite a less favorable profile of many traditional risk factors in Japanese men. To determine whether lipoprotein-associated phospholipase A2 (Lp-PLA2) levels are related to the difference in the prevalence of CAC between the two populations.

METHODS

A total of 200 men aged 40-49 years were examined: 100 residents in Allegheny County, Pennsylvania, United States, and 100 residents in Kusatsu City, Shiga, Japan. Coronary calcium score (CCS) was evaluated by electron-beam tomography, Lp-PLA2 levels, nuclear magnetic resonance (NMR) lipoprotein subclasses, and other factors were assessed in 2001-2002.

RESULTS

Lp-PLA2 levels were higher among American than Japanese men (Mean ± standard deviation 301.7 ± 82.6 versus 275.9 ± 104.7 ng/mL, respectively, p=0.06). Among all Japanese men and those with low density lipoprotein (LDL) cholesterol >130 mg/dL, there was an inverse association of the prevalence of CCS>0 with the fertile groups of Lp-PLA2 levels (p=0.08 and p=0.03, respectively). American men did not have any association between CCS>0 with the fertile groups of Lp-PLA2 (p=0.62). Although Lp-PLA2 among both populations correlated positively with LDL and total cholesterol, American and Japanese men had different correlations with NMR lipoprotein subclasses. Reported high odds ratio for CCS>0 among American compared to Japanese men was not reduced after adjusting for Lp-PLA2 levels.

CONCLUSION

Lp-PLA2 may have different mechanisms of action among American and Japanese men. Lp-PLA2 levels can not explain the observed CAC differences between the two populations.

Variability of Serial Lipoprotein-Associated Phospholipase A2 Measurements in Post–Myocardial Infarction Patients: Results from the AIRGENE Study Center Augsburg

Background: Of the numerous emerging biomarkers for coronary heart disease (CHD), lipoprotein-associated phospholipase A2 (Lp-PLA2), an enzyme involved in lipid metabolism and inflammatory pathways, seems to be a promising candidate. Implementation of Lp-PLA2 measurement into clinical practice, however, requires data on the reliability of such measurements.

Methods: We measured Lp-PLA2 concentrations by ELISA in blood samples drawn from 200 post–myocardial infarction patients (39–76 years) at 6 monthly intervals between May 2003 and February 2004, for a total of 1143 samples. We estimated analytical, within-individual, and between-individual variation, the critical difference, and the intraclass correlation coefficient of reliability (ICC) to assess the reliability of serial Lp-PLA2 measurements.

Results: The mean (SD) plasma Lp-PLA2 concentration for the study participants was 188.7 (41.8) μg/L, with no significant difference between men and women. The analytical CV for Lp-PLA2 was 4.4%, the within-individual biological CV was 15%, and the between-individual CV was 22%. The ICC was 0.66. An important part of the total variation in plasma Lp-PLA2 concentration was explained by the between-individual variation (as a percentage of the total variance, 66.1%), whereas the within-individual variance was 31.3%. The analytical variance was as low as 2.6%.

Conclusions: Between-individual variation in Lp-PLA2 concentration was substantially greater than within-individual variation. In general, our data demonstrate considerable stability and good reproducibility of serial Lp-PLA2 measurements, results that compared favorably with those for the more commonly measured lipid markers.

Prognostic utility of lipoprotein-associated phospholipase A2 for cardiovascular outcomes in patients with stable coronary artery disease

OBJECTIVE

To determine the prognostic utility of lipoprotein-associated phospholipase A2 (Lp-PLA2) for specific adverse cardiovascular outcomes in patients with stable coronary artery disease (CAD), independent of traditional risk factors and high-sensitivity C-reactive protein (hs-CRP).

METHODS AND RESULTS

We measured Lp-PLA2 in 3766 patients with stable CAD from the PEACE trial. Patients were followed for a median of 4.8 years for adverse cardiovascular events including death, myocardial infarction (MI), coronary revascularization, hospitalization for unstable angina (UA), and stroke. Multivariable Cox regression was used to adjust for traditional cardiovascular risk factors and to conduct multimarker analyses that included hs-CRP. After adjustment for baseline characteristics, patients in higher quartiles of Lp-PLA2 remained at significantly greater risk for the composite of cardiovascular death, MI, coronary revascularization, UA, or stroke (P<0.001 for trend, adj HR 1.41, 95% CI 1.17 to 1.70, for patients in 4th versus 1st quartile). The association was consistent regardless of a patient's sex, cholesterol levels, or use of lipid-lowering therapy. When analyzed together, both hs-CRP and Lp-PLA2 were highly significant predictors of acute coronary syndromes (cardiovascular death, MI, or UA) (P for trend <0.001 for hs-CRP and 0.005 for Lp-PLA2), whereas only Lp-PLA2 was a significant predictor of coronary revascularization (P=0.01 for trend).

CONCLUSIONS

In stable CAD, an elevated level of Lp-PLA2 was a significant predictor of nonfatal adverse cardiovascular outcomes independent of traditional clinical risk factors and hs-CRP. Further investigation will be needed to establish whether therapies that lower Lp-PLA2 reduce cardiovascular risk.