Lipoprotein-associated phospholipase A2 and risk of incident peripheral arterial disease in a multi-ethnic cohort: The Multi-Ethnic Study of Atherosclerosis

Novel Plasma Biomarkers Associated with Future Peripheral Atherosclerotic Disease and Abdominal Aortic Aneurysm-Insights from Contemporary Prospective Studies from the Malmö Diet and Cancer Study

INTRODUCTION

The potential utility of inflammatory and hemodynamic plasma biomarkers for the prediction of incident lower extremity arterial disease (LEAD), carotid artery stenosis (CAS), isolated atherosclerotic disease without concomitant abdominal aortic aneurysm (AAA), and isolated AAA without concomitant atherosclerotic disease has not yet been integrated in clinical practice. The main objective of this prospective study was to find predictive plasma biomarkers for cardiovascular disease and to evaluate differences in plasma biomarker profiles between asymptomatic and symptomatic CAS, as well as between isolated atherosclerotic disease and isolated AAA.

METHODS

Blood samples collected at baseline from participants in the prospective Malmö Diet and Cancer study (MDCS) cardiovascular cohort (n = 5550 middle-aged individuals; baseline 1991-1994) were used for plasma biomarker analysis. Validation of each incident cardiovascular diagnosis was performed by random sampling. Cox regression analysis was used to calculate hazard ratios (HRs) per one standard deviation increment of each respective log-transformed plasma biomarker with 95% confidence intervals (CI).

RESULTS

Adjusted lipoprotein-associated phospholipase A2 (Lp-PLA2) activity (HR 1.33; CI 1.17-1.52) and mass (HR 1.20; CI 1.05-1.37), C-reactive protein (CRP) (HR 1.55; CI 1.36-1.76), copeptin (HR 1.46; CI 1.19-1.80), N-terminal pro-B-type natriuretic peptide (N-BNP) (HR 1.28; 1.11-1.48), and cystatin C (HR 1.19; 95% 1.10-1.29) were associated with incident symptomatic LEAD. Adjusted N-BNP (HR 1.59; CI 1.20-2.11), mid-regional proadrenomedullin (HR 1.40; CI 1.13-1.73), cystatin C (HR 1.21; CI 1.02-1.43), and CRP (HR 1.53; CI 1.13-1.73) were associated with incident symptomatic but not asymptomatic CAS. Adjusted HR was higher for Lp-PLA2 (mass) for incident isolated AAA compared to for isolated atherosclerotic disease.

CONCLUSIONS

Plasma biomarker profile data support that subclinical vascular inflammation and cardiovascular stress seem to be relevant for the development of atherosclerotic disease and AAA.

Association of chronic neutrophil activation with risk of mortality

BACKGROUND

Levels of free myeloperoxidase (MPO), a cardiovascular risk marker, have been reported to decline with standard care. Whether such declines signify decreased risk of mortality remains unknown.

DESIGN

Cox proportional hazard models were generated using data from a retrospective cohort study of prospectively collected measures.

PARTICIPANTS

Patients (3,658) who had MPO measurements and LDL-C ≥ 90 mg/dL during 2011-2015 were selected based on a stratified random sampling on MPO risk level. Baseline MPO was either low (<470 pmol/L), moderate (470-539 pmol/L), or high (≥540 pmol/L).

MAIN OUTCOMES AND MEASURES

First occurrence of MACE (myocardial infarction, stroke, coronary revascularization, or all-cause death).

RESULTS

Mean age was 66.5 years, and 64.7% were women. During a mean 6.5-year follow-up, crude incidence per 1000 patient years was driven by death. The incidence and all-cause death was highest for patients with high MPO (21.2; 95% CI, 19.0-23.7), then moderate (14.6; 95% CI, 11.5-18.5) and low (2.3; 95% CI, 1.2-4.6) MPO. After adjusting for age, sex, and cardiovascular risk factors, risk of cardiovascular death did not differ significantly between patients with high and low MPO (HR, 1.57; 95% CI, 0.56-4.39), but patients with high MPO had greater risk of non-cardiovascular (HR, 6.15; 95% CI, 2.27-16.64) and all-cause (HR, 3.83; 95% CI, 1.88-7.78) death. During follow-up, a 100 pmol/L decrease in MPO correlated with a 5% reduction in mortality (HR, 0.95; 95% CI, 0.93-0.97) over 5 years.

CONCLUSIONS

Free circulating MPO is a strong marker of risk of mortality. Monitoring changes in MPO levels over time may provide insight into changes in physiology that mark a patient for increased risk of mortality.

Circulating Biomarkers in Lower Extremity Artery Disease

Lower extremity artery disease (LEAD), a chronic condition with disturbed lower extremity circulation due to narrowing of the arteries, is predominantly caused by atherosclerosis and is associated with the presence of cardiovascular risk factors and an increased risk of cardiovascular events. LEAD is prevalent among older individuals and predicted to rise with the ageing population. In progressive disease, the patient experiences symptoms of ischaemia when walking and, in advanced critical limb-threatening ischaemia, even at rest. However, LEAD is asymptomatic in most patients, delaying diagnosis and treatment. In this setting, circulating biomarkers may facilitate earlier diagnosis in selected individuals. This review provides a broad overview of the circulating biomarkers investigated to date in relation to LEAD and discusses their usefulness in clinical practice.

Inflammatory Markers in Cardiovascular Disease; Lessons Learned and Future Perspectives

BACKGROUND

Cardiovascular disease (CVD) still remains the leading cause of morbidity and mortality worldwide. It is now established that inflammation plays a crucial role in atherosclerosis and atherothrombosis, and thus, it is closely linked to cardiovascular disease.

OBJECTIVE

The aim of the present review is to summarize and critically appraise the most relevant evidence regarding the potential use of inflammatory markers in the field of CVD.

METHODS

We conducted a comprehensive research of the relevant literature, searching MEDLINE from its inception until November 2018, primarily for meta-analyses, randomized controlled trials and observational studies.

RESULTS

Established markers of inflammation, mainly C-reactive protein, have yielded significant results both for primary and secondary prevention of CVD. Newer markers, such as lipoprotein-associated phospholipase A2, lectin-like oxidized low-density lipoprotein receptor-1, cytokines, myeloperoxidase, cell adhesion molecules, matrix metalloproteinases, and the CD40/CD40 ligand system, have been largely evaluated in human studies, enrolling both individuals from the general population and patients with established CVD. Some markers have yielded conflicting results; however, others are now recognized not only as promising biomarkers of CVD, but also as potential therapeutic targets, establishing the role of anti-inflammatory and pleiotropic drugs in CVD.

CONCLUSION

There is significant evidence regarding the role of consolidated and novel inflammatory markers in the field of diagnosis and prognosis of CVD. However, multimarker model assessment, validation of cut-off values and cost-effectiveness analyses are required in order for those markers to be integrated into daily clinical practice.

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.

Lipoprotein-associated phospholipase A2 predicts lower limb ischemia in hemodialysis subjects

Hemodialyzed patients (HD) have high prevalence of peripheral arterial disease. In the general population, lipoprotein-associated phospholipase A2 (Lp-PLA² ) is associated with peripheral arterial disease but no data are available for renal subjects. The aim of this study was to evaluate the relationship between Lp-PLA₂ and lower limb ischemia among dialyzed patients. One hundred and two dialyzed subjects, with median (IQR) age of 71 (59-78) years, enrolled in June 2013 and followed until June 2018, were investigated for Lp-PLA₂ activity and the occurrence of peripheral arterial disease and lower limb ischemia. The median (IQR) levels of Lp-PLA₂ were 184 nmol/min/mL (156.5-214.5). The 43 HD patients with abnormal Lp-PLA₂ activity (>194 nmol/min/mL) had higher levels of total and LDL-cholesterol, ApoB/A1 ratio, and higher occurrence of lower limb ischemia during the follow up (44% vs 17%, P = .003). In multivariate analysis, Lp-PLA₂ activity (P = .018) and diabetes (P < .001) were independently associated with time to lower limb ischemia, and when the presence of previous PAD was added to the multivariate model, only presence of previous PAD (P < .001) and Lp-PLA₂ (P = .003) remained associated. Lp-PLA₂ is an independent predictor of lower limb ischemia in dialyzed patients.

Lp-PLA2 activity and mass and CRP are associated with incident symptomatic peripheral arterial disease

Long follow up is needed in prospective cohort study evaluation of plasma biomarkers for incident peripheral arterial disease (PAD) Middle-aged PAD-free individuals from the cardiovascular cohort of the Malmö Diet and Cancer study (n = 5550; 1991-94) were followed prospectively for a median time of 23.4 years. The plasma biomarkers lipoprotein-associated phospholipase A2 (Lp-PLA₂) activity and mass, proneurotensin, and CRP, were studied in relation to incidence of PAD until December 31^st, 2016. The diagnosis of PAD could be validated and confirmed in 98%. Cox regression was used to calculate hazard ratios (HR) per 1 standard deviation increment of each respective log transformed plasma biomarker. Cumulative incidence of PAD was 4.4% (men 5.9%, women 3.3%). Adjusting for age, gender, smoking, body mass index, hypertension, diabetes mellitus, Lp-PLA₂ activity (HR 1.33; 95% CI 1.17-1.52), Lp-PLA₂ mass (HR 1.20; 95% CI 1.05-1.37) and CRP (HR 1.55; 95% CI 1.36-1.76) remained independently associated with incident PAD. The plasma biomarkers Lp-PLA₂ activity and mass, and CRP were markers of PAD risk, implying that they might be useful biomarkers for subclinical atherosclerosis and atherosclerotic disease.

Markers of Atherosclerosis: Part 1 - Serological Markers

Atherosclerosis is a major contributor to morbidity and mortality worldwide. With therapeutic consequences in mind, several risk scores are being used to differentiate individuals with low, intermediate or high cardiovascular (CV) event risk. The most appropriate management of intermediate risk individuals is still not known, therefore, novel biomarkers are being sought to help re-stratify them as low or high risk. This narrative review is presented in two parts. Here, in Part 1, we summarise current knowledge on serum (serological) biomarkers of atherosclerosis. Among novel biomarkers, high sensitivity C-reactive protein (hsCRP) has emerged as the most promising in chronic situations, others need further clinical studies. However, it seems that a combination of serum biomarkers offers more to risk stratification than either biomarker alone. In Part 2, we address genetic and imaging markers of atherosclerosis, as well as other developments relevant to risk prediction.

Association of Lipoprotein-Associated Phospholipase A2 with the Prevalence of Nonalcoholic Fatty Liver Disease: A Result from the APAC Study

Nonalcoholic fatty liver disease (NAFLD) is a worldwide chronic liver disease. Few studies have investigated the association between NAFLD and Lipoprotein-associated phospholipase A₂ (Lp-PLA₂), a unique enzyme correlated with oxidative stress. The aim of this study was to assess the relationship between Lp-PLA₂ and NAFLD in a Chinese community-based cohort. A total of 1587 adults aged ≥40 years were enrolled in the current study. Participants underwent a standardized evaluation. The serum Lp-PLA2 concentration was measured by ELISA and NAFLD was diagnosed by ultrasonography. Multivariable logistic regression was used to assess the association between Lp-PLA2 and NAFLD. Increased Lp-PLA2 levels were significantly associated with decreased NAFLD prevalence after adjusting for other potential confounders. The adjusted ORs of NAFLD in Q2, Q3 and Q4 compared with Q1 were 0.88 (0.64–1.21), 0.71 (0.51–0.98) and 0.67 (0.48–0.95), respectively (P < 0.05). Furthermore, the adjusted ORs of moderate and heavy NAFLD in Q2, Q3 and Q4 compared to Q1 were 0.64 (0.41–1.01), 0.48 (0.29–0.80) and 0.47 (0.28–0.79), respectively (P < 0.01). In conclusions, increased Lp-PLA2 levels were independently associated with decreased NAFLD prevalence.

Knowledge of an inflammatory biomarker of cardiovascular risk leads to biomarker-based decreased risk in pre-diabetic and diabetic patients

Objective

Diabetes is a risk equivalent for cardiovascular events. The increase in vascular inflammation with diabetes is believed to be responsible for increased risk of ischemic events in diabetic patients. Our goal was to assess whether knowledge of vascular inflammation alters cardiovascular risk over time, and how knowledge of vascular inflammation changes risk in non-diabetic, pre-diabetic and diabetic patients.

Methods

We retrospectively studied >100,000 primary-care patients per annum for 5 years (baseline in 2011 through 2015) with tests including lipoprotein profile, hemoglobin A1C and the vascular-specific inflammation risk marker myeloperoxidase. Results were obtained during the patient’s MD Value In Prevention (MDVIP) annual wellness program physical.

Results

We show that rates of patients with elevated myeloperoxidase levels were reduced from 14.4%, 15.2% and 21.3% to 4.0%, 4.0% and 6.7% in non-diabetic, pre-diabetic and diabetic patients, respectively, over the 5-year period. Decreases in vascular inflammation were achieved without decreases in the prevalence of pre-diabetes (hemoglobin A1C 5.7%–6.4%) or diabetes (hemoglobin A1C >6.4%) and were observed in patients below or above guideline low-density lipoprotein targets.

Conclusions

These data demonstrate that physicians informed of elevated markers of vascular inflammation can lower vascular inflammation correlating with biomarker-based decreased risk of cardiovascular events.

Lipoprotein-associated phospholipase A2 and risk of incident peripheral arterial disease: Findings from The Atherosclerosis Risk in Communities study (ARIC)

BACKGROUND AND AIMS

Results from prospective studies evaluating the relationship between elevated lipoprotein-associated phospholipase A₂ (Lp-PLA₂) activity and incident peripheral arterial disease (PAD) have been mixed. We investigated whether higher Lp-PLA₂ levels are associated with increased risk of incident PAD and whether PLA2G7 gene variants, which result in lower Lp-PLA₂ levels, are associated with reduced risk of incident PAD.

METHODS

Our analysis included 9922 participants (56% female; 21% African-American; mean age 63 years) without baseline PAD at ARIC Visit 4 (1996-1998), who had Lp-PLA₂ activity measured and were subsequently followed for the development of PAD, defined by occurrence of a PAD-related hospitalization, through 2012. Cox proportional hazard models were performed to determine the association of Lp-PLA₂ levels and PLA2G7 gene variants with incident PAD.

RESULTS

During a median follow-up of 14.9 years, we identified 756 incident cases of PAD. In analyses adjusting for age, race, and sex, each standard deviation increment in Lp-PLA₂ activity (62 nmol/ml/min) was associated with a higher risk of developing PAD (hazard ratio (HR) 1.17; 95% confidence interval (CI) 1.09, 1.26). This association remained significant after additional adjustment for risk factors, other cardiovascular disease, and medication use, but was strongly attenuated (HR: 1.09; 95% CI 1.00, 1.20). PLA2G7 variants were not associated with a lower risk of PAD in both white carriers (HR: 1.21; 95% CI: 0.17-8.56) and African-American carriers (HR: 0.83; 95% CI: 0.41-1.67), although statistical power was quite limited for this analysis, particularly in whites.

CONCLUSIONS

While higher Lp-PLA₂ activity was associated with an increased risk for incident PAD, it is likely a risk marker largely represented by traditional risk factors.