Lp-PLA2--a novel marker of atherosclerosis: to treat or not to treat?

Research Advance of Chinese Medicine in Treating Atherosclerosis: Focus on Lipoprotein-Associated Phospholipase A2

As a serious cardiovascular disease, atherosclerosis (AS) causes chronic inflammation and oxidative stress in the body and poses a threat to human health. Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a member of the phospholipase A2 (PLA2) family, and its elevated levels have been shown to contribute to AS. Lp-PLA2 is closely related to a variety of lipoproteins, and its role in promoting inflammatory responses and oxidative stress in AS is mainly achieved by hydrolyzing oxidized phosphatidylcholine (oxPC) to produce lysophosphatidylcholine (lysoPC). Moreover, macrophage apoptosis within plaque is promoted by localized Lp-PLA2 which also promotes plaque instability. This paper reviews those researches of Chinese medicine in treating AS via reducing Lp-PLA2 levels to guide future experimental studies and clinical applications related to AS.

Lipoprotein-associated phospholipase A2 levels, endothelial dysfunction and arterial stiffness in patients with stable coronary artery disease

BACKGROUND

Lipoprotein-associated Phospholipase A2 (Lp-PLA2), can exert proinflammatory as well as proatherogenic properties on the vascular wall. The current study sought to evaluate the influence of high Lp-PLA2 levels on indices of arterial wall properties in patients with stable coronary artery disease (CAD).

METHODS

Three hundred seventy-four consecutive patients with stable CAD (mean age 61 ± 11 years, 89% males) were enrolled in this single-center cross-sectional study. Flow-mediated dilation (FMD) was used to assess endothelial function and augmentation index (AIx) of the central aortic pressure was used to assess reflected waves. ELISA was used to determine Lp-PLA2 serum levels.

RESULTS

After dividing the participants in 3 equal groups based on the tertiles of circulating Lp-PLA2 values, no significant differences were demonstrated between those in the 3rd tertile with Lp-PLA2 values > 138 μg/L, in the 2nd tertile with Lp-PLA2 values between 101 and 138 μg/L and in the 1st tertile (Lp-PLA2 values < 101 μg/L) regarding age, male gender, smoking habits, family history of CAD or history of a previous myocardial infarction, diabetes mellitus, arterial hypertension, hyperlipidemia, duration of CAD and treatment with relevant medication. Importantly, subjects with Lp-PLA2 values in the highest tertile, had significantly reduced FMD values compared to the middle and lower tertile (4.43 ± 2.37% vs. 4.61 ± 1.97% vs. 5.20 ± 2.52% respectively, P = 0.03). Patients in the highest tertile of Lp-PLA2 values had significantly higher AIx values (24.65 ± 8.69% vs. 23.33 ± 9.65%, P = 0.03), in comparison to the lowest tertile, with Lp-PLA2 values < 101 μg/L. A linear regression analysis showed that Lp-PLA2 values > 138 μg/L negatively correlated to FMD [b = - 0.45 (95% CI: - 0.79 - -0.11), P = 0.01] and AIx values [b = 1.81 (95% CI: 0.57-3.05), P < 0.001] independently of cofounders like gender, age, diabetes mellitus, arterial hypertension, dyslipidemia, smoking habits, family history of CAD, history of previous myocardial infarction, serum glucose, circulating lipid levels, duration of CAD, antihypertensive medication, antidiabetic drugs, statin therapy and treatment with β-blockers.

CONCLUSIONS

Elevated Lp-PLA2 levels relate to endothelial dysfunction and arterial stiffness in patients with stable CAD independently from classical risk factors for CAD, statin use, antihypertensive treatment, and duration of the disease.

Vascular inflammation, atherosclerosis, and lipid metabolism and the occurrence of non-high albuminuria diabetic kidney disease: A cross-sectional study

AIM

Atherosclerosis involves vascular endothelial damage and lipid metabolism disorder, which is closely related to the occurrence and development of diabetic kidney disease (DKD). However, studies on non-high albuminuria DKD (NHADKD) with an albumin to creatinine ratio (ACR) <30 mg/g are rare. This study is to investigate the relationship between atherogenic factors and the occurrence of NHADKD.

METHODS

Serum lipid indicators, lipoprotein-associated phospholipase A2 (Lip-PLA2) and homocysteine levels were measured in 1116 subjects to analyze their relationship with NHADKD.

RESULTS

Among all subjects, Lip-PLA2 had the closest but relatively weak correlation with ACR (r = 0.297, p < 0.001) and only homocysteine was moderately correlated with eGFR (r = -0.465, p < 0.001). However, in patients with NHADKD, these atherosclerotic factors were weakly correlated or uncorrelated with eGFR (max. |r| = 0.247). Stratified risk analysis showed that when ACR was <10 mg/g, homocysteine [OR = 6.97(4.07-11.95)], total cholesterol (total-Chol) [OR = 6.04(3.03-12.04)], and high-density lipoprotein cholesterol (HDL-Chol) [OR = 5.09(2.99-8.64)] were risk factors for NHADKD. There was no significant difference of OR between these three factors (Z = 0.430-1.044, all p > 0.05). When ACR was ⩾10mg/g, homocysteine [OR = 17.26(9.67-30.82)] and total-Chol [OR = 5.63(2.95-10.76)] were risk factors for NHADKD, and ORhomocysteine was significantly higher than ORtotal-Chol (Z = 3.023, p < 0.05).

CONCLUSIONS

The occurrence of NHADKD may be related to the levels of homocysteine, total-Chol, HDL-Chol, and Lip-PLA2 in blood. Among them, homocysteine may be most closely related to NHADKD.

The relationship of lipoprotein-associated phospholipase A2 activity with the seriousness of coronary artery disease

BACKGROUND

The level of lipoprotein-associated phospholipase A2 (LP-PLA2) in serum is independently correlated to coronary artery diseases (CAD). The aim of the study was to determine whether LP-PLA2 activity is positively associated with the seriousness of CAD.

METHODS

Amount to 1056 patients suspected of having CAD underwent coronary angiography (CAG) to determine the seriousness of CAD. According to the amount of diseased coronary branches, the 1056 patients were split into three groups: single-vessel stenosis group, multiple-vessels stenosis group (> or = 2 diseased coronary branches),and control group (no diseased coronary branches). According to CAG results, electrocardiography, cardiac biomarker, and clinical presentation, all patients were split into four groups: acute myocardial infarction (AMI), unstable angina (UA), stable angina (SA), and control groups (excluding CAD). The activity of LP-PLA2 was compared statistically among the subgroups. Receiver operating characteristic analysis was applied to investigate the role of LP-PLA2 in evaluating the presence and seriousness of CAD.

RESULTS

The level of LP-PLA2 increased in line with the number of diseased coronary branches. The levels of LP-PLA2 in the AMI and UA groups were observably higher when compared with the control and SA groups. LP-PLA2 had 75.6% sensitivity and 67.3% specificity for recognizing CAD, and 53.0% sensitivity and 80.3% specificity for recognizing severe coronary artery lesions.

CONCLUSION

The activity of LP-PLA2 is positively correlated to the seriousness of CAD.

Phospholipase A2 is an Inflammatory Predictor in Cardiovascular Diseases: Is there any Spacious Room to Prove the Causation?

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is an enzyme family of phospholipase A2 produced by the inflammatory cell in atherosclerotic plaque. It is transported in the circulation, attached mainly to low-density lipoprotein-cholesterol (LDL-C). It hydrolyzes glycerophospholipids particularly fatty acids at the sn-2 position and produces numerous bioactive lipids; and leads to endothelial dysfunction, atherosclerotic plaque inflammation, and development of the necrotic core in plaques. There are two kinds of phospholipase A2, namely: secretory phospholipase A2 (sPLA2) and Lp- PLA2. They are deemed as evolving predictors of cardiovascular disease (CVD) risk in hospitaland population-based studies, including healthy subjects, acute coronary syndromes (ACS) and patients with CVD. Unfortunately, Lp-PLA2 inhibitor (darapladib) and s-PLA2 inhibitor (varespladib methyl) failed to prove to lower the risk of composite CVD mortality, myocardial infarction and stroke in those with stable CVD and ACS. Herein, we describe the explanation based on the existing data why there is still a discrepancy among them. So, it highlights the opinion that phospholipase A2 is merely the inflammatory biomarkers of CVD and playing an important role in atherosclerosis. Further, there is more spacious room to prove the causation.

The role of phospholipase A2 in multiple Sclerosis: A systematic review and meta-analysis

Phospholipases A2 (PLA₂) are a diverse group of enzymes that cleave the fatty acids of membrane phospholipids. They play critical roles in pathogenesis of neurodegenerative diseases such as multiple sclerosis by enhancing oxidative stress and initiating inflammation. The levels of PLA₂ activity in MS patients compared to controls and role of inhibiting PLA₂ activity on severity scores in different experimental models are not comprehensively assessed in the light of varying evidence from published studies. The objective of this systematic review is to determine the association between PLA₂ activity and multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). We performed a systematic review of six studies that assessed PLA₂ activity in MS patients compared to controls and nine studies that assessed PLA₂ activity in EAE. sPLA₂ nor Lp-PLA₂ activity were not increased in MS compared to controls in five of those six studies. A difference in sPLA₂ activity was only found in a study that measured the enzyme activity in urine. However, inhibiting cPLA₂ or sPLA₂ led to lower clinical severity or no signs of EAE in mice, and a lower incidence of EAE lesions compared to animals without cPLA₂ inhibition. These findings indicate that PLA₂ appears to play a role in the pathogenesis of EAE.

Exploration of Adhesion Molecule Expression in Cardiac Muscle of Early Atherosclerosis Dyslipidemic Sprague Dawley Rats

OBJECTIVE

This study is aimed to examine the expression of ICAM-1 and VCAM-1 in cardiac tissue of dyslipidemic Sprague Dawley rats.

METHODS

Eight Sprague Dawley strain rats, with 150-200 gram body weight, were divided into two groups. The control group was fed a standard diet, the positive control group was fed a high-fat diet as our previous study for 8 weeks. The pattern of distribution of ICAM-1 and VCAM-1 in cardiac muscle cell was examined by immunofluorescence and observed with a confocal laser scanning microscope. Lipid profile was also examined at the end of the study.

RESULT

Independent t-test showed no differences in ICAM-1 and VCAM-1 expression in cardiac muscle of hypercholesterol-diet-fed Sprague Dawley rat compared to control.

CONCLUSION

The expression of ICAM-1 and VCAM-1 in cardiac muscle did not change after the onset of atherosclerosis.

Lipoprotein-associated phospholipase A2 and risks of coronary heart disease and ischemic stroke in the general population: A systematic review and meta-analysis

BACKGROUND

This study investigated the associations between lipoprotein-associated phospholipase A2 (Lp-PLA2) and the risks of coronary heart disease (CHD) and ischemic stroke (IS) in the general population.

METHODS

PubMed, Embase, and the Cochrane Library databases were searched for prospective cohort studies published prior to June 2016. Multivariate-adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) for CHD and IS risks according to Lp-PLA2 activity or mass were extracted, pooled, and weighted using random-effects modeling.

RESULTS

Twelve studies examining Lp-PLA2 activity or mass and long-term risks of CHD and IS were included. Combined HRs for CHD and IS risks for the highest category referring to lowest category of Lp-PLA2 were 1.46 (95% CI: 1.20-1.78, P<0.001) and 1.58 (95% CI: 1.21-2.07, P=0.001), respectively. The same patterns were observed for both mass and activity, with the exception of those for CHD. For every 1-standard deviation (SD) increase in Lp-PLA2 activity, CHD risk increased by 12% (HR: 1.12, 95% CI: 1.05-1.22, P=0.002); no association between 1-SD increases in Lp-PLA2 activity and IS was observed. Lp-PLA2 mass was associated with CHD risk (HR: 1.02-1.24, 95% CI: 1.02-1.24, P=0.021). Lp-PLA2 mass per 1-SD increase was not associated with IS risk.

CONCLUSIONS

Greater Lp-PLA2 activity or mass was associated with an increased risk of CHD and IS; however, additional well-designed trials are warranted to confirm this association.

The Importance of Age and Statin Therapy in the Interpretation of Lp-PLA2 in ACS Patients, and Relation to CRP

C-reactive protein (CRP) is a marker of arterial inflammation while lipoprotein-associated phospholipase A2 (Lp-PLA2) is related to plaque instability. The aim of this study was to evaluate the correlation between the risk of unstable plaque presenting as acute coronary syndrome (ACS) and Lp-PLA2, and to assess the influence of statins on interpretation of Lp-PLA2. A total of 362 consecutive patients presenting to the emergency department (ED) with acute chest pain suggestive of ACS were evaluated by cardiologists as STEMI, NSTEMI, or unstable angina, and non-ACS. Serum biomarkers measured on admission: troponin I, C-reactive protein (Abbott), and Lp-PLA2 (DiaDexus). Four groups were defined according to the final diagnosis and history of statin medication: ACS/statin−; ACS/statin+; non-ACS/statin−; non-ACS/statin+. Lp-PLA2 was highest in ACS/statin− group; statins decreased Lp-PLA2 both in ACS and non-ACS of about 20 %. Lp-PLA2 was higher in ACS patients in comparison with non-ACS patients group without respect to statin therapy (p<0.001). Lp-PLA2 predicted worse outcome (in terms of acute coronary syndrome) effectively in patients up to 62 years; limited prediction was found in older patients. C-reactive protein (CRP) failed to discriminate four groups of patients. Statin therapy and age should be taken into consideration while interpreting Lp-PLA2 concentrations and lower cut-off values should be used for statin-treated persons.