Circulating pregnancy-associated plasma protein a predicts outcome in patients with acute coronary syndrome but no troponin I elevation

Biomarkers to monitor the prognosis, disease severity, and treatment efficacy in coronary artery disease

INTRODUCTION

Coronary Artery Disease (CAD) is a prevalent condition characterized by the presence of atherosclerotic plaques in the coronary arteries of the heart. The global burden of CAD has increased significantly over the years, resulting in millions of deaths annually and making it the leading health-care expenditure and cause of mortality in developed countries. The lack of cost-effective strategies for monitoring the prognosis of CAD warrants a pressing need for accurate and efficient markers to assess disease severity and progression for both reducing health-care costs and improving patient outcomes.

AREA COVERED

To effectively monitor CAD, prognostic biomarkers and imaging techniques play a vital role in risk-stratified patients during acute treatment and over time. However, with over 1,000 potential markers of interest, it is crucial to identify the key markers with substantial utility in monitoring CAD progression and evaluating therapeutic interventions. This review focuses on identifying and highlighting the most relevant markers for monitoring CAD prognosis and disease severity. We searched for relevant literature using PubMed and Google Scholar.

EXPERT OPINION

By utilizing the markers discussed, health-care providers can improve patient care, optimize treatment plans, and ultimately reduce health-care costs associated with CAD management.

Synopsis of Biomarkers of Atheromatous Plaque Formation, Rupture and Thrombosis in the Diagnosis of Acute Coronary Syndromes

Acute coronary syndrome is the main cause of mortality and morbidity worldwide and early diagnosis is a challenge for clinicians. Though cardiac Troponin, the most commonly used biomarker, is the gold standard for myocardial necrosis, it is blind for ischemia without necrosis. Therefore, ideal biomarkers are essential in the care of patients presenting with symptoms suggestive of cardiac ischemia. The ideal biomarker or group of biomarkers of atheromatous plaque formation, rupture and thrombosis for timely and accurate diagnosis of acute coronary syndrome is a current need. Therefore, we discuss the existing understanding and future of biomarkers of atheromatous plaque formation, rupture and thrombosis of acute coronary syndrome in this review. Keywords were searched from Medline, ISI, IBSS and Google Scholar databases. Further, the authors conducted a manual search of other relevant journals and reference lists of primary articles. The development of high-sensitivity troponin assays facilitates earlier exclusion of acute coronary syndrome, contributing to a reduced length of stay at the emergency department, and earlier treatment resulting in better outcomes. Although researchers have investigated biomarkers of atheromatous plaque formation, rupture and thrombosis to help early diagnosis of cardiac ischemia, most of them necessitate validation from further analysis. Among these biomarkers, pregnancy-associated plasma protein-A, intercellular adhesion molecule-1, and endothelial cell-specific molecule- 1(endocan) have shown promising results in the early diagnosis of acute coronary syndrome but need further evaluation. However, the use of a combination of biomarkers representing varying pathophysiological mechanisms of cardiac ischemia will support risk assessment, diagnosis and prognosis in these patients and this is the way forward.

Status of biomarkers for the identification of stable or vulnerable plaques in atherosclerosis

Atherosclerosis is a systemic inflammation of the arteries characterized by atherosclerotic plaque due to the accumulation of lipids, inflammatory cells, apoptotic cells, calcium and extracellular matrix (ECM) proteins. Stable plaques present a chronic inflammatory infiltration, whereas vulnerable plaques present an 'active' inflammation involved in the thinning of the fibrous cap that predisposes to plaque rupture. Several complex biological cellular processes lead plaques to evolve from stable to vulnerable predisposing them to rupture and thrombosis. In this review, we analyze some emerging circulating biomarkers related to inflammation, ECM and lipid infiltration, angiogenesis, metalloproteinases and microRNA (miRNA), as possible diagnostic and prognostic indicators of plaque vulnerability.

Pregnancy Associated Plasma Protein-A as a Cardiovascular Risk Marker in Patients with Stable Coronary Heart Disease During 10 Years Follow-Up-A CLARICOR Trial Sub-Study

Elevated pregnancy-associated plasma protein A (PAPP-A) is associated with mortality in acute coronary syndromes. Few studies have assessed PAPP-A in stable coronary artery disease (CAD) and results are conflicting. We assessed the 10-year prognostic relevance of PAPP-A levels in stable CAD. The CLARICOR trial was a randomized controlled clinical trial including outpatients with stable CAD, randomized to clarithromycin versus placebo. The placebo group constituted our discovery cohort (n = 1.996) and the clarithromycin group the replication cohort (n = 1.975). The composite primary outcome was first occurrence of cardiovascular event or death. In the discovery cohort, incidence rates (IR) for the composite outcome were higher in those with elevated PAPP-A (IR 12.72, 95% Confidence Interval (CI) 11.0-14.7 events/100 years) compared to lower PAPP-A (IR 8.78, 8.25-9.34), with comparable results in the replication cohort. Elevated PAPP-A was associated with increased risk of the composite outcome in both cohorts (discovery Hazard Ratio (HR) 1.45, 95% CI 1.24-1.70; replication HR 1.29, 95% CI 1.10-1.52). In models adjusted for established risk factors, these trends were attenuated. Elevated PAPP-A was associated with higher all-cause mortality in both cohorts. We conclude that elevated PAPP-A levels are associated with increased long-term mortality in stable CAD, but do not improve long-term prediction of death or cardiovascular events when added to established predictors.

The Biomarkers for Acute Myocardial Infarction and Heart Failure

The use of a large number of cardiovascular biomarkers, meant to complement the use of the electrocardiogram, echocardiography cardiac imaging, and clinical symptom assessment, has become a routine in clinical diagnosis, differential diagnosis, risk stratification, and prognosis and guides the management of patients with suspected cardiovascular diseases. There is a broad consensus that cardiac troponin and natriuretic peptides are the preferred biomarkers in clinical practice for the diagnosis of the acute coronary syndrome and heart failure, respectively, while the roles and possible clinical applications of several other potential biomarkers are still under study. This review mainly focuses on the recent studies of the roles and clinical applications of troponin and natriuretic peptides, which seem to be the best-validated markers in distinguishing and predicting the future cardiac events of patients with suspected cardiovascular diseases. Additionally, the review briefly discusses some of the large number of potential markers that may play a more prominent role in the future.

Pregnancy-associated plasma protein A as a predictor of all-cause mortality and cardiovascular events in patients with chronic kidney disease: a meta-analysis of prospective studies

INTRODUCTION

The aim of the study was to assess the association of elevated serum pregnancy associated plasma protein A (PAPP-A) and the risk of all-cause mortality, cardiovascular events and mortality due to infection in patients with chronic kidney disease (CKD).

MATERIAL AND METHODS

We systematically searched the Medline database up to March 2017. A random effects model was used to pool the relative risks (RRs) and their 95% confidence intervals (CIs). Sensitivity analysis and subgroup analysis were performed to explore the potential sources of heterogeneity.

RESULTS

Six studies involving 2034 subjects were included. The pooled RRs for the risk of all-cause mortality and cardiovascular events were 1.50 (95% CI: 1.17-1.92), 1.26 (95% CI: 0.95-1.69), respectively. Sensitivity analysis by excluding each individual study showed no influence on the main results. Subgroup analysis showed that age, male proportion, follow-up term, and assay methods were not modifiable factors.

CONCLUSIONS

Our study suggests that elevated serum PAPP-A is associated with the risk of all-cause mortality in patients with CKD.

Pregnancy-Associated Plasma Protein A Induces Inflammatory Cytokine Expression by Activating IGF-I/PI3K/Akt Pathways

Pregnancy-associated plasma protein A (PAPP-A) was previously reported to be an inflammatory biomarker and a prognostic marker of acute coronary syndrome (ACS) and involved in the process of atherosclerosis and plaque rupture. However, the role of PAPP-A in inflammation is poorly understood. In this study, we aimed to investigate the role of PAPP-A in macrophage activation and inflammatory cytokine production. RAW264.7 macrophages were treated with or without PAPP-A. Reverse-transcriptase quantitative real-time PCR (RT-qPCR) and Western blot were performed to detect gene and protein expressions. The concentration of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in culture supernatants was determined by ELISA. Results showed that PAPP-A significantly stimulated the expression of MCP-1, TNF-α, and IL-6 at both transcriptional and translational levels in a dose-dependent and time-dependent manner. The secretion of these inflammatory cytokines by macrophages was also increased after PAPP-A treatment. Moreover, PAPP-A activated the IGF-I/PI3K/Akt signaling pathway in macrophages. The PAPP-A-mediated upregulation of MCP-1, TNF-α, and IL-6 mRNA and protein levels were strongly inhibited by PI3K inhibitors or IGF-IR siRNA, indicating that the upregulation of MCP-1, TNF-α, and IL-6 could involve the IGF-I/PI3K/Akt pathway. Together, this study demonstrates that PAPP-A activates the macrophage signaling pathway (IGF-I/PI3K/Akt), which drives the expression and production of inflammatory cytokines known to contribute to the initiation and progression of ACS. These findings indicate that PAPP-A may play a proinflammatory role in the pathophysiology of ACS and serve as a potential therapeutic target.

IGF-1 and cardiovascular disease

Atherosclerosis is an inflammatory arterial pathogenic condition, which leads to ischemic cardiovascular diseases, such as coronary artery disease and myocardial infarction, stroke, and peripheral arterial disease. Atherosclerosis is a multifactorial disorder and its pathophysiology is highly complex. Changes in expression of multiple genes coupled with environmental and lifestyle factors initiate cascades of adverse events involving multiple types of cells (e.g. vascular endothelial cells, smooth muscle cells, and macrophages). IGF-1 is a pleiotropic factor, which is found in the circulation (endocrine IGF-1) and is also produced locally in arteries (endothelial cells and smooth muscle cells). IGF-1 exerts a variety of effects on these cell types in the context of the pathogenesis of atherosclerosis. In fact, there is an increasing body of evidence suggesting that IGF-1 has beneficial effects on the biology of atherosclerosis. This review will discuss recent findings relating to clinical investigations on the relation between IGF-1 and cardiovascular disease and basic research using animal models of atherosclerosis that have elucidated some of the mechanisms underlying atheroprotective effects of IGF-1.

Pregnancy-associated plasma protein-a is associated with subclinical atherosclerosis in men with HIV infection

The pathophysiology of an early and accelerated atherosclerotic process is complex and multifactorial in HIV-infected men compared with HIV-non-infected men. Several biomarkers have been well studied in the detection of the early stage of atherosclerosis, but studies are limited in HIV-infected men. The objective of this study was to investigate the association between serum pregnancy-associated plasma protein-A (PAPP-A) and carotid intima-media wall thickness (CIMT) in asymptomatic HIV-infected men. This a case-control study group comprising 118 HIV-infected men and 60 age-matched and gender-matched HIV-non-infected men. Serum PAPP-A was measured using an ELISA kit and carotid IMT was evaluated by Doppler ultrasonography in all subjects. Statistical analysis included receiver-operating characteristic (ROC) analysis, Pearson correlation and logistic regression analysis. Serum PAPP-A level was significantly higher in HIV +CIMT+ group compared with HIV +CIMT group and HIV-CIMT- group. We found a positive correlation between PAPP-A and increased CIMT (r=0.737, p<0.0001), and a negative correlation between nadir CD4 T cell counts and increased CIMT (r=-0.526, p<0.001). In multivariate logistic regression analyses, PAPP-A, nadir CD4 T cell count and age were significantly associated with subclinical atherosclerosis (p<0.001, p=0.006 and p=0.032, respectively). In ROC analysis, PAPP-A levels of >3.70 µg/mL were associated with subclinical atherosclerosis in HIV+ men with a specificity of 100% and a sensitivity of 71% (area under the curve: 0.949, 95% CI 0.875 to 1.000, p<0.001). Serum PAPP-A level was strongly correlated with increased CIMT in HIV-infected men. PAPP-A might be used as an early biomarker to identify atherosclerosis in asymptomatic HIV-infected men.

Pregnancy-Associated Plasma Protein A (PAPP-A) Concentration in Population of Healthy Young People: Interactions with Tobacco Smoke and Anti-oxidative Status

Pregnancy-associated plasma protein A (PAPP-A) is a high-molecular zinc-binding metalloproteinase that was first detected in the serum of pregnant women. It can also be detected in men and non-pregnant women. Recently, a growing interest in determining the concentration of PAPP-A as a marker of oxidative stress and atherosclerotic processes has been observed. Among the factors that could potentially influence the PAPP-A formation is the exposure to tobacco smoke. Some components of tobacco smoke have an immediate effect on the body and also direct influence on the cardiovascular system. The aim of this study was to evaluate the relation between PAPP-A concentration and either passive or active exposure to tobacco smoke in the population of medicine students (n = 152). The relation between PAPP-A concentration and chosen markers of inflammatory response and anti-oxidative processes was analyzed. The samples of serum, urine, and saliva were collected and main nicotine metabolites in urine samples were determined using ELISA technique. Comparison of the PAPP-A concentrations in the study group revealed that in the group of active smokers, the concentration of the protein was significantly higher than in the group of passive smokers (p = .04) and the group of not-exposed students (p = .006). PAPP-A concentration showed significant positive correlation with the values of FRAP and main nicotine metabolites. The evident influence of both active and passive tobacco smoke exposure on PAPP-A levels in the studied population of young people who in general are not included in the group of high-risk cardiovascular incidents, shows how important early prevention of anti-health behaviors is.

Pregnancy-Associated Plasma Protein a during Hemodialysis with Polyamide and Diacetate Cellulosic Membranes

Pregnancy-associated plasma protein A (PAPP-A) is a new prognostic factor of acute coronary syndrome in the general population. It is elevated in hemodialysis (HD) patients and at baseline, it was shown to be related to inflammation and oxidative stress. The aim of the study was to examine the relationship of PAPP-A and oxidative stress and inflammatory markers to HD treatment. Studied parameters were determined in 10 chronic HD patients treated with low flux polyamide (1st session) and diacetate cellulosic membranes (2nd session) at the beginning, after 15 minutes and at the end of the dialysis session. TRACE method (Time Resolved Amplified Cryptate Emission) was used for PAPP-A assessment. Results were evaluated with ANOVA.

PAPP-A levels did not depend on the type of HD membrane but changed significantly with the time of the HD session. They increased significantly from the beginning of HD to 15 min and then decreased to the end of the HD session – p<0.05 15 min of HD vs start, p<0.01 end vs start, p<0.0001 end vs 15 min of HD for polyamide membrane and p=0.05 15 min of HD vs start, p<0.01 end vs start, p<0.0001 end vs 15 min of HD for diacetate cellulosic membrane. Changes in other parameters and differences between membranes were only minimal.

We can conclude that PAPP-A as a marker of cardiovascular damage shows significant changes during the HD session. Its initial increase might be ascribed to its release from complexes or storage. During dialysis, it might be destroyed or cleaved and removed as free fragments. Its levels both before and after the HD session are higher than in healthy subjects.

Pregnancy associated plasma protein-A as a prognostic biomarker of all-cause mortality and cardiovascular events in patients presenting with chest pain: a systematic review

AIM

Novel biomarkers have been proposed for identification of patients at greater risk of future adverse events among those presenting with chest pain. In this review, we aim to elucidate the ability of pregnancy associated plasma protein-A (PAPP-A) to predict mortality and other cardiovascular events in this patient population.

METHODS

A literature search of the electronic databases Medline, Scopus, Cochrane Library and ClinicalTrials.gov was performed in order to identify studies investigating the utility of PAPP-A to predict mortality and adverse cardiovascular events in patients with chest pain.

RESULTS

Eight studies met our inclusion criteria. Five of these studies pertained to patients with confirmed ischemic chest pain, while the rest included patients presenting with chest pain possibly due to acute coronary syndrome, irrespectively of the underlying cause. Although the results for long-term events were inconclusive in both groups of patients, higher PAPP-A concentrations were found to be a significant predictor of short-term adverse events in patients with confirmed ischemic chest pain.

CONCLUSIONS

PAPP-A appears to be a potentially useful biomarker for short-term risk stratification of patients presenting with chest pain of ischemic origin. However, there is an eminent need for more standardized clinical studies investigating the prognostic value of this biomarker.

Increased Levels of Oxidative Stress Markers, Soluble CD40 Ligand, and Carotid Intima-Media Thickness Reflect Acceleration of Atherosclerosis in Male Patients with Ankylosing Spondylitis in Active Phase and without the Classical Cardiovascular Risk Factors

Objective

The primary aim of the study was to assess levels of oxidative stress markers, soluble CD40 ligand (sCD40L), serum pregnancy-associated plasma protein-A (PAPP-A), and placental growth factor (PlGF) as well as carotid intima-media thickness (IMT) in patients with ankylosing spondylitis (AS) with active phase without concomitant classical cardiovascular risk factors.

Material and methods

The observational study involved 96 male subjects: 48 AS patients and 48 healthy ones, who did not differ significantly regarding age, BMI, comorbid disorders, and distribution of classical cardiovascular risk factors. In both groups, we estimated levels of oxidative stress markers, lipid profile, and inflammation parameters as well as sCD40L, serum PAPP-A, and PlGF. In addition, we estimated carotid IMT in each subject.

Results

The study showed that markers of oxidative stress, lipid profile, and inflammation, as well as sCD40L, PlGF, and IMT, were significantly higher in the AS group compared to the healthy group.

Conclusion

Our results demonstrate that ankylosing spondylitis may be associated with increased risk for atherosclerosis.

Interplay between PAPP-A, inflammation and adiposity in patients with angiographically proven acute coronary syndrome (ACS)

Introduction Studies conducted in the recent past have demonstrated the role of inflammation, obesity and dysfunctional insulin signaling as contributing factors in the pathogenesis of acute coronary syndrome (ACS). However, pharmacological interventions targeting a single pathway have not proven useful in the long run. This indicates that a synergism occurs between the various risk factors and hence calls for a combinatorial approach. This study was planned to study the interplay, if any, between pregnancy associated plasma protein-A (PAPP-A), inflammation and adiposity in patients with ACS. Materials and methods The study was conducted in a tertiary care hospital in Delhi. The study population consisted of 128 subjects, divided into two groups. The control group consisted of 64 healthy subjects without ACS. Cases consisted of 64 subjects with angiographically proven ACS cases. PAPP-A and high sensitivity C-reactive protein (hs-CRP) were estimated by enzyme-linked immunosorbent assay (ELIZA) kits. Results The mean level of PAPP-A and hs-CRP were significantly higher in cases as compared to the controls. A positive correlation of PAPP-A was observed with hs-CRP, insulin, ApoB and Lp(a). The relative risk for ACS was 14.2 with a p value of <0.001 when all the three parameters - hs-CRP, PAPP-A and body mass index (BMI) were considered together. This was significantly higher when each risk factor was assessed standalone. Conclusions Our study results suggest a possible interplay between chronic inflammation, obesity and plaque instability among patients with ACS. This interaction can accelerate the process of plaque rupture in patients with increased BMI as compare to those patients with low/normal BMI.

Pregnancy-associated plasma protein-A promotes TF procoagulant activity in human endothelial cells by Akt-NF-κB axis

Pregnancy-associated plasma protein-A (PAPP-A) is a metalloproteinase with a controversial role in pathophysiology of cardiovascular disease. It seems involved in progression of atherosclerosis and is widely represented in atherosclerotic plaque. PAPP-A plasma levels are elevated in patients with acute coronary syndromes (ACS), thus it has been suggested that it might be a prognostic marker for developing major cardiovascular events. However, the pathophysiological link(s) between PAPP-A and ACS are still unknown. Several studies have indicated that tissue factor (TF) plays a pivotal role in the pathophysiology of ACS by triggering the formation of intracoronary thrombi following endothelial injury. This study investigates whether PAPP-A, at concentrations measurable in ACS patients, might induce TF expression in human endothelial cells in culture (HUVEC). In HUVEC, PAPP-A induced TF-mRNA transcription as demonstrated by real time PCR and expression of functionally active TF as demonstrated by FACS analysis and pro-coagulant activity assay. PAPP-A induced TF expression through the activation of Akt/NF-κB axis, as demonstrated by luciferase assay and by suppression of TF-mRNA transcription as well as of TF expression/activity by Akt and NF-κB inhibitors. These data indicate that PAPP-A promotes TF expression in human endothelial cells and support the hypothesis that this proteinase, besides being involved in progression of atherosclerosis, does not represent an independent risk factor for adverse cardiovascular events, but it rather might play an "active" role in the pathophysiology of ACS as an effector molecule able to induce a pro-thrombotic phenotype in endothelial cells.

Combination of change in hematological parameters with exercise stress test to predict coronary artery disease

OBJECTIVE

Treadmill exercise stress testing for identifying patients with a higher likelihood of coronary artery disease (CAD) before elective coronary angiography is recommended in the current guidelines. In this study, we aimed to evaluate the changes in the hematological parameters before and after exercise stress test in relation with the presence of CAD.

METHODS

A total of 113 patients with chest pain who underwent treadmill exercise testing and coronary angiography were included in this study.

RESULTS

Neutrophil count (4.38±0.99 vs 5.19±0.93, P<.001), and neutrophil to lymphocyte ratio (NLR) (2.04±0.63 vs 2.41±0.78, P<.001) were significantly elevated after treadmill exercise test in all the patients. Increase in the NLR after exercise test was significantly higher in patients with positive exercise test (n=68) than negative exercise test (n=45) (0.49±0.58 vs 0.19±0.44, P=.016). The sensitivity and specificity of treadmill exercise testing according to coronary angiography was 79% and 64%, respectively. A cut-off point of 0.2 for the change in the NLR in addition to positive treadmill exercise testing had 91% sensitivity and 92% specificity in predicting significant coronary artery stenosis (AUC:0.913, 95% CI: 0.805-1.000, P<.001).

CONCLUSIONS

Neutrophil to lymphocyte ratio is an important inflammatory marker that can contribute to treadmill ECG testing in predicting CAD.

Evaluation of Pregnancy-Associated Plasma Protein-A Levels in Patients with Chronic Obstructive Pulmonary Disease and Associations with Disease Severity

Chronic obstructive pulmonary disease (COPD) represents a systemic disorder characterized by chronic airflow limitation and an increased inflammatory response of the airways. Comorbidities are frequent in COPD and it is crucial to predict these in early stage for adequate management of COPD. Recent studies have reported that elevated levels of pregnancy-associated plasma protein-A (PAPP-A), a zinc-binding metalloproteinase, detected in patients with asthma, lung cancer, and pulmonary embolism and independently associated with cardiovascular events. We aimed to assess serum PAPP-A levels in COPD and the associations between disease severity. The study population consisted of 75 COPD patients and 35 healthy subjects as a control group. PAPP-A levels were measured by using ultrasensitive enzyme-linked immunosorbent assay. Elevated levels of PAPP-A were observed in patients with COPD on comparison with the controls (p = 0.000). The levels in stage 1 (34.73 ± 22.97) and stage 2 (48.29 ± 53.35) were significantly higher than stage 3 (20.58 ± 22.98) and stage 4 (27.36 ± 21.46) (p = 0.049). Increased PAPP-A levels may be a useful marker in management of COPD that seeks to prevent the development of comorbidities such as adverse cardiovascular diseases.

Can pregnancy-associated plasma protein-A be a marker for the assessment of atherosclerosis risk in patients with chronic plaque psoriasis?

Introduction

Psoriasis is an immune-mediated chronic inflammatory dermatosis. Several studies have shown that patients with psoriasis have a much greater risk of cardiovascular diseases than the normal population. The chronic inflammation observed in psoriasis is thought to have a role in the development of atherosclerosis and vascular endothelial injury.

Aim

To examine serum pregnancy-associated plasma protein-A (PAPP-A) levels, which has been regarded as a marker of early stage atherosclerosis in patients with psoriasis that do not have concurrent conventional cardiovascular risk markers.

Material and methods

Forty-one patients diagnosed with a chronic plaque type of psoriasis and 42 equally matched healthy volunteers were included in this study. The PAPP-A levels were compared between patient and control groups and the association between PAPP-A levels and disease duration and severity were evaluated in the patient group.

Results

Statistically, serum PAPP-A levels were significantly higher in the psoriasis group than in the control group (p = 0.015). Serum PAPP-A levels were found to be positively correlated with severity (p = 0.036, r = 0.329) and duration (p = 0.014, r = 0.269) of the disease.

Conclusions

As a marker of early stage atherosclerosis, PAPP-A levels were elevated in the psoriasis group and were correlated with disease duration and severity. This elevation reveals the presence of atherosclerosis in patients with psoriasis. Further studies are needed to confirm the use of PAPP-A as an available and inexpensive screening test and cardiovascular risk assessment for all centers.

Potentially pathogenic circulating autoantibodies to cardiac troponin are present in hemodialysis patients

INTRODUCTION

Repetitive dialysis-induced cardiac injury is associated with elevated troponin levels, inflammation, and longitudinal reduction in cardiac function. Pathogenic autoantibodies to cardiac troponins (cTnAAb) produce inflammatory cardiomyopathy in murine models. This study aimed to explore the possibility that analogous autoimmune processes might occur in hemodialysis (HD) patients, by initially investigating cTnAAb prevalence, and exploring potential links with HD-induced myocardial stunning.

METHODS

In 130 prevalent HD patients from two centers (Derby, UK; Turku, Finland), cTnAAb (immunoassay) and cardiac troponins were quantified. Sixty-four patients underwent serial echocardiography to assess myocardial stunning.

FINDINGS

cTnAAb were present in 7% of patients. Dual positivity to cTnAAb and elevated cTn occurred in 3% and 6% for cTnI and cTnT, respectively. Patients with cTnAAb had significantly longer dialysis vintage (82 vs. 30 months, P = 0.024), higher cTnT (0.1 vs. 0.05 pg/mL, P = 0.04), cTnI (0.02 vs. 0.01 pg/mL, P = 0.029), and free PAPP-A (6.4 vs. 3.3 mIU/L, P = 0.038).

DISCUSSION

This is the first description of cTnAAb in HD patients, which raises the possibility that longitudinal exposure to repetitive HD-induced cardiac injury may lead to further autoimmune-based myocardial insult.

Pregnancy-associated plasma protein-A (PAPP-A) as a possible biomarker in patients with coronary artery disease

BACKGROUND

Cardiovascular disease is the leading cause of death in the Western world, and a major cause of this disease is atherosclerosis. Research has demonstrated that pregnancy-associated plasma protein A (PAPP-A) plays a role in cardiovascular disease, as evidenced by the association between PAPP-A and severity of heart damage.

AIM

The aim of this work was to investigate the correlation between PAPP-A concentrations in coronary and peripheral blood and certain clinicopathological factors and antioxidant enzyme activities in patients diagnosed with coronary artery disease.

METHODS

For 65 patients, arterial blood was obtained by puncturing the femoral or radial artery, and coronary blood was obtained via percutaneous coronary intervention. PAPP-A, catalase (CAT), superoxide dismutase-1 (SOD-1), and superoxide dismutase-2 (SOD-2) levels were measured using spectrometric methods.

RESULTS

Coronary PAPP-A levels were slightly higher than peripheral PAPP-A levels (81.25 ± 2.34 and 62 ± 3 ng/mL, respectively, P < 0.0001); these levels were correlated with each other (r = 0.6629, P < 0.001) but not with clinicopathological factors (P > 0.05). Coronary PAPP-A levels were significantly elevated among patients at risk for cardiovascular disease (P < 0.05). Antioxidant enzyme activities were significantly higher in coronary samples than in peripheral samples from subjects with ischemic cardiopathy secondary to atherosclerosis (P < 0.001). Neither coronary nor peripheral PAPP-A levels were correlated with antioxidant enzyme activities in patients with cardiopathy secondary to atherosclerosis (P > 0.05).

CONCLUSIONS

PAPP-A levels could be used as biomarkers to identify patients at risk of coronary artery disease.

Level of Pregnancy-associated Plasma Protein-A Correlates With Coronary Thin-cap Fibroatheroma Burden in Patients With Coronary Artery Disease: Novel Findings From 3-Vessel Virtual Histology Intravascular Ultrasound Assessment

Pregnancy-associated plasma protein-A (PAPP-A) level is an independent predictor of acute cardiovascular event occurrence. To test the hypothesis that increased PAPP-A levels would be associated with a higher burden of coronary thin-cap fibroatheroma (TCFA) thereby underlying the heightened risk for cardiovascular events in patients with coronary artery disease; 154 patients (462 vessels and 975 plaques) with stable angina or non-ST-segment elevation acute coronary syndrome (NSTE-ACS) referred for percutaneous coronary intervention were assessed using 3-vessel virtual histology (VH)-intravascular ultrasound (IVUS). Thin-cap fibroatheroma virtual histology was defined as focal, necrotic core (NC)-rich (≥10% of cross-sectional area) plaques in contact with the lumen, and plaque burden ≥40%. Pregnancy-associated plasma protein-A levels were determined by sandwich enzyme-linked immunosorbent assay, and patients were divided into 3 groups based on PAPP-A level tertiles. Although the highest PAPP-A level tertile was not associated with 3-vessel plaque number, it was associated with 3-vessel VH-TCFA number and necrotic core volume. Patients with ≥3 VH-TCFAs had a higher PAPP-A level than patients with 1 to 3 VH-TCFAs or without any VH-TCFA (13.3 ± 11.8 versus 7.8 ± 4.7 versus 7.4 ± 4.7 mIU/L, P < 0.001, respectively). Moreover, PAPP-A level was an independent predictor of higher total number of VH-TCFAs (OR 1.18; 95% CI 1.07-1.29, P = 0.001). This VH-IVUS study demonstrated, for the first time to our knowledge, that higher PAPP-A levels are associated with higher 3-vessel TCFA burden in patients with coronary artery disease. Pregnancy-associated plasma protein-A, therefore, might be a useful serum biomarker to predict increased coronary TCFA burden and plaque instability.

The utility of pregnancy-associated plasma protein A for determination of prognosis in a cohort of patients with coronary artery disease

Background: Pregnancy-associated plasma protein-A (PAPP-A) is discussed as a biomarker representing unstable plaques in coronary artery disease (CAD). Methods: In this study 927 patients with CAD (534 with stable angina and 393 with acute coronary syndrome [ACS]) and 217 patients without CAD and measured PAPP-A levels were included. Follow-up for a median of 5 years was documented. Results: Rising quartiles of PAPP-A concentration had a higher cardiovascular mortality in the overall cohort of patients with CAD (p = 0.002) and the cohort with ACS (p = 0.01). Patients with suspected ACS below the LOD for troponin I but elevated PAPP-A levels had an increased cardiovascular mortality. A cut-off of 11.4 IU/l identified patients with a higher mortality during follow-up. Conclusion: Rising PAPP-A levels are prognostic in patients with CAD. PAPP-A levels were especially predictive in ACS patients with troponin below 10% CV of the 99th percentile for cardiovascular mortality.

Pregnancy-associated plasma protein-A and the vulnerable plaque

For more than a decade, pregnancy-associated plasma protein-A (PAPP-A) has been examined for its relation to acute coronary syndrome (ACS) and the vulnerable plaque. This review summarizes the current knowledge of plasma PAPP-A in relation to nonpregnant individuals focusing on patients with ACS, discusses its use as a possible biomarker for diagnosis and prognosis in ACS, briefly describes the challenges in different assay technologies and describes the effect of heparin administration on PAPP-A concentrations in plasma.

Characterization of endogenously circulating IGFBP-4 fragments-Novel biomarkers for cardiac risk assessment

BACKGROUND

Recent findings show that circulating N- and C-terminal fragments of IGF-binding protein-4 (NT-IGFBP-4 and CT-IGFBP-4) can be utilized as biomarkers for cardiac risk assessment in acute coronary syndrome (ACS) patients. The fragments are thought to be the products of pregnancy-associated plasma protein A (PAPP-A)-dependent proteolysis. Two immunoassays for the measurement of IGFBP-4 fragments have been proposed. However, properties of the endogenous IGFBP-4 fragments that could influence the performance of the immunoassays were still not investigated.

METHODS

NT- and CT-IGFBP-4 were extracted from pooled ACS plasma using affinity purification, and their concentrations were measured using sandwich immunoassays utilizing antibodies specific to their proteolytic neo-epitopes or internal epitopes. The extracted fragments were characterized by Western blots (WB) and mass-spectrometry. ACS plasma samples were analyzed by size exclusion chromatography (SEC).

RESULTS

Immunoassays utilizing the neo-epitope-specific and the internal epitope-specific antibodies measured equal concentrations of the analyte in the endogenous IGFBP-4 fragments preparations. Only the 18 kDa NT-IGFBP-4 and 14 kDa CT-IGFBP-4 were detected in the WB analysis. Using mass-spectrometry, peaks corresponding to intact non-truncated and non-modified NT-IGFBP-4 (14626 Da) and CT-IGFBP-4 (11346 Da) were observed. The absence of complexed forms of IGFBP-4 in patients' plasma was demonstrated using SEC.

CONCLUSIONS

Endogenous NT- and CT-IGFBP-4 from ACS patients' plasma correspond to the PAPP-A-derived IGFBP-4 fragments and do not undergo any truncation, modification, or complex formation in the patients' blood. Because of the demonstrated intact state of the circulating IGFBP-4 fragments, the neo-epitope-specific immunoassays perform reliably, allowing further clinical validation of these novel biomarkers.

Pregnancy Associated Plasma Protein-A (PAPP-A) Levels in Acute Coronary Syndrome: A Case Control Study in a Tertiary Care Centre

In recent years, an important objective of cardiovascular research has been to find new markers that would improve the risk stratification and diagnosis of patients presenting with symptoms of acute coronary syndrome (ACS). Established biomarkers for diagnosis of ACS includes troponins and creatine kinase MB (CK-MB). Pregnancy associated plasma protein A (PAPP-A) is an emerging marker which has been described as a marker of plaque instability. PAPP-A is a large metalloproteinase involved in insulin-like growth factor signaling and has been shown to be involved in pathological processes like atherosclerosis. Many studies have been published regarding release of PAPP-A in circulation during ACS. The objective of this study was to evaluate the role of PAPP-A as an early marker of ACS by comparing levels of PAPP-A in patients with acute myocardial infarction (AMI) and unstable angina (UA) with asymptomatic controls. The association of PAPP-A with markers of myocardial necrosis and the association of PAPP-A levels to the presence of risk factors for coronary artery disease was also studied. We measured PAPP-A levels in patients with AMI (30), UA (23) and asymptomatic controls (45). PAPP-A was estimated using PAPP-A US (ultra sensitive) ELISA manufactured by DRG (Germany). PAPP-A levels were significantly elevated in patients with AMI and in patients with UA (mean levels 64.26 ± 1.05 and 36.23 ± 1.05 ng/ml respectively; p < 0.001). Mean PAPP-A levels in controls were 10.68 ± 1.04 ng/ml. In UA cases PAPP-A levels were elevated when the troponin I and CK-MB levels were within the normal range. No correlation was observed between PAPP-A with markers of myocardial necrosis. PAPP-A can serve as a useful biomarker in the diagnosis of ACS, especially UA, where cardiac troponin levels and CK-MB levels are not elevated and ECG changes are inconclusive.

Elevated serum free pregnancy-associated plasma protein-A independently predicts mortality in haemodialysis patients but is not associated with recurrent haemodialysis-induced ischaemic myocardial injury

BACKGROUND/AIMS

Pregnancy-associated plasma protein-A (PAPP-A) is a putative marker of atheroma instability and ischaemic myocardial stress prior to necrosis. Total PAPP-A (tPAPP-A) levels in acute coronary syndromes predict adverse outcomes. However, free PAPP-A (fPAPP-A) predominates in the circulation. Ischaemic haemodialysis (HD)-induced cardiac injury (myocardial stunning) is common and is associated with markers of myocardial necrosis, inflammation, cardiovascular events and mortality. Coronary plaque instability in pathophysiology of HD-induced myocardial stunning has not been studied. We aimed to investigate the relationship of fPAPP-A with stunning and mortality.

METHODS

130 prevalent patients from two HD centres (Finland and UK) were studied. Pre-HD free, complexed and total PAPP-A were measured by immunoassay. A subset of 62 patients underwent echocardiography to assess HD-induced myocardial stunning. The mean duration of follow-up was 407 ± 98 days.

RESULTS

fPAPP-A was elevated (median: 3.45 mIU/l) and correlated with dialysis vintage (r = 0.391, p < 0.001), cardiac troponin T (cTnT; r = 0.29, p = 0.001) and cardiac troponin I (cTnI; r = 0.22, p = 0.01). PAPP-A was not related to stunning. Dialysis vintage and cTnT independently predicted Ln fPAPP-A (model R = 0.463). fPAPP-A, cTnT and age independently predicted death (Nagelkerke R(2) = 0.362).

CONCLUSIONS

fPAPP-A, a novel predictor of HD-related mortality, demonstrates better prognostic power than tPAPP-A. Coronary plaque instability may contribute to sub-lethal myocardial injury, but may not be critical in pathogenesis of HD-induced ischaemic cardiac injury.

Cys327Cys polymorphism of the PAPP-A gene (pregnancy associated plasma protein A) is related to mortality of long term hemodialysis patients

OBJECTIVES

PAPP-A is an independent mortality predictor of long term hemodialysis patients and a prognostic marker of acute coronary syndrome in general population. Cys327Cys PAPP-A polymorphism (SNP) (rs12375498) was found to be of significance in preeclampsia and the C allele of the PAPP-A C/G SNP (rs13290387) was defined as an independent risk factor for acute myocardial infarction. The aim of the study was to test the role of these PAPP-A SNPs in long term hemodialysis patients.

DESIGN AND METHODS

The studied group consisted of 464 subjects - 319 long term hemodialysis patients (183 men, 136 women, 62±14years) and 145 controls (65 men, 80 women, 49±14years). A subgroup of 211 hemodialysis patients (118 men, 93 women, 63±13years) was prospectively followed up for 4.5years. During the follow up, 111 patients died, 51 of them due to cardiovascular events. PAPP-A SNPs were analyzed by DNA sequencing and serum PAPP-A was measured by TRACE.

RESULTS

Both SNPs were in Hardy-Weinberg equilibrium. Allelic and genotype frequencies did not differ between patients and controls and were not related to serum PAPP-A concentrations. Cys327Cys SNP was significant for patients' survival (HR (95% CI): 1.616 (1.110-2.353), nominal p=0.012, corrected p=0.036) while C/G SNP was not.

CONCLUSIONS

Our study shows for the first time the significance of Cys327Cys PAPP-A SNP (rs12375498) for overall mortality of long term hemodialysis patients. Although it does not influence the concentration of PAPP-A it still could affect the correct function of this enzyme which has to be clarified in further studies.

Interleukin-6 as a predictor of cardiovascular events in troponin-negative non-ST elevation acute coronary syndrome patients

AIM

Risk stratification in acute coronary syndrome without ST-segment elevation (NSTE-ACS) and troponin-negative remains a challenge. We evaluated the value of interleukin-6 (IL-6) and amino-terminal pro-B-type natriuretic peptide (NT-proBNP) in the prognosis assessment of low-moderate risk NSTE-ACS and troponin-negative, and whether these biomarkers could improve the predictive performance of the established thrombolysis in myocardial infarction (TIMI) risk score.

METHODS

A total of 212 low-moderate risk patients with NSTE-ACS and troponin-negative were prospectively studied. Clinical follow up at 6 months was performed for adverse endpoints.

RESULTS

A total of 28 patients (13.5%) presented adverse clinical events. Those with adverse clinical events were associated with higher levels of IL-6 [8.58 (5.13-20.95) ng/l vs. 6.12 (4.16-9.14) ng/l, p = 0.043] and NT-proBNP [275.3 (108.6-548.2) ng/l vs. 126.8 (55.97-430.20) ng/l, p = 0.046]. In moderate risk group, we observed a higher event rate in patients with troponin-negative but elevated levels of IL-6 (p = 0.024). Only elevated IL-6 (> 12.40 ng/l) was an independent predictor of adverse outcomes [hazard ratios: 3.62, 95% confidence interval (CI) 1.69-7.75, p = 0.001]. The addition of IL-6 and history of ischaemic heart disease (IHD) to TIMI risk score significantly improved both the discrimination (integrated discrimination improvement, p = 0.003) and reclassification (Clinical Net reclassification improvement, p = 0.010) of the model for adverse events.

CONCLUSIONS

Interleukin-6 is an independent predictor of adverse events in low-moderate risk patients with NSTE-ACS and troponin-negative. Its use identifies a higher risk population in moderate-risk patients. This provides together with history of IHD a better discrimination and reclassification beyond that achieved with clinical risk variables from TIMI risk score in these patients.

Utility of Neutrophil–Lymphocyte Ratio in Predicting Troponin Elevation in the Emergency Department Setting

There is little data regarding the diagnostic ability of neutrophil–lymphocyte ratio (NLR) in acute coronary syndrome. Therefore, we aimed to assess the predictive value of NLR in the discrimination of troponin-positive patients. We enrolled 244 patients (mean age 61.3 ± 11.7 years, 70.5% male) who presented to the emergency service with acute chest pain. Patients were divided into 2 groups based upon the troponin positivity in the 12- to 24-hour follow-up. The admission NLR was significantly higher in the troponin-positive group (5.49 ± 4.01 vs 2.40 ± 1.36, P < .001). A cutoff point of 2.80 for NLR measured on admission had 79% sensitivity and 73% specificity in predicting follow-up troponin positivity. After multivariate analysis, admission NLR and glucose levels remained significant predictors of follow-up troponin positivity. In conclusion, NLR may be an early diagnostic marker in emergency service for discriminating patients who will have a positive troponin test in the follow-up.

Clinical differences between total PAPP-A and measurements specific for the products of free PAPP-A activity in patients with stable cardiovascular disease

OBJECTIVES

We have previously reported that increases in total pregnancy-associated plasma protein-A (PAPP-A) which are thought to be indicative of vulnerable plaques and thus poor outcomes predict outcomes in patients with stable coronary artery disease. We hypothesized that the determination of CT- and NT-fragments of insulin-like growth factor binding protein 4 (CT- and NT-IGFBP4) which should be indicative of free PAPP-A would result in better performance.

METHODS

In 229 stable cardiovascular patients with indication for heart catheterization after performance of a stress test and an echocardiogram, CT- and NT-IGFBP4 were measured. Their values were investigated in relation to clinical characteristics, findings of noninvasive investigations, laboratory data and coronary angiography as well as to outcomes after a follow-up of 1094±307days.

RESULTS

CT-IGFBP4 values were independently predicted by patients with B-type (p=0.0069) or complex coronary lesions (p=0.0445). B-type and vulnerable coronary lesions were independently predicted by levels of CT-IGFBP4≥a cutoff of 31.55ng/mL derived from ROC analysis (p=0.0090 and 0.0480). NT-IGFBP4 was not predictive of coronary characteristics. Both IGFBP4 fragments were strongly dependent on age and renal function and were not predictive of outcomes.

CONCLUSION

Despite the relation of CT-IGFBP4 to a more severe coronary artery disease, CT- and NT-IGFBP4, in contrast to our report based on total PAPP-A, failed to predict any long-term outcomes in patients with stable cardiovascular disease. Further knowledge about the interaction of the PAPP-A-insulin-like growth factor system is needed to explain values of IGFBP4 fragments in these patients.

Association of pregnancy-associated plasma protein-A gene polymorphism with ischemic stroke in northern Chinese Han population

OBJECTIVES

The pregnancy-associated plasma protein-A (PAPP-A), belonging to the metalloproteinase superfamily, plays an important role in destabilization of atherosclerotic plaques. The aim of this study is to evaluate whether PAPP-A gene polymorphism is associated with the risk of ischemic stroke (IS) in northern Chinese Han populations.

METHODS

A total of 368 patients with IS and 374 aged-matched healthy controls in a Chinese Han population were included in the case-control study. The single-nucleotide polymorphism (SNP) IVS6+95 (rs13290387) in the PAPP-A gene was analyzed by the polymerase chain reaction-ligation detection reaction (PCR-LDR) method.

RESULTS

Compared with the GG+CG genotype, the frequencies of the CC genotype of IVS6+95 (rs13290387) in the patients with IS were significantly higher than those in the controls (P  =  0·026). After adjusting the confounding risk factors of IS (age, gender, smoking, alcohol drinking, hypertension, diabetes mellitus, and hyperlipidemia) by the multivariate logistic analysis, this significant correlation still remained (P  =  0·010).

DISCUSSION

The CC genotype of IVS6+95 (rs13290387) was associated with increased incidence of IS in northern Chinese Han populations. This is an initial study to indicate that PAPP-A (rs13290387) might contribute to IS susceptibility in northern Chinese Han populations.

Assessment of serum leptin, pregnancy-associated plasma protein A and CRP levels as indicators of plaque vulnerability in patients with acute coronary syndrome

INTRODUCTION

A multifactorial aetiology of coronary artery disease (CAD) has been established in the recent past. Extensive research is now underway to understand the mechanisms responsible for plaque vulnerability. The identification of a novel biomarker that will help in the assessment of plaque status is urgently needed for the purpose of patient stratification and prognostication. The aim of the present study was to evaluate leptin, pregnancy-associated plasma protein A (PAPP-A) and C-reactive protein (CRP) levels in patients with acute coronary syndrome and to assess their diagnostic efficacy in the identification of vulnerable plaques.

METHODS

The study group comprised 105 patients who had chest pain along with ECG changes (ST elevation, ST depression, T inversion) and raised cardiac enzyme levels. Sixty-two patients with chest pain and ECG changes but with normal cardiac enzyme profiles were included in the control group. Lipid profiles, and leptin, PAPP-A and CRP levels were assessed in these two groups. Receiver operating characteristics (ROC) curves were plotted to determine the utility of the parameters under study as markers of plaque vulnerability.

RESULTS

Significantly higher levels of serum lipoprotein (a), leptin, PAPP-A and high-sensitivity CRP (hs-CRP) were observed in the cases than in the controls. A positive correlation was observed between CRP and PAPP-A levels as well as CRP and leptin concentrations. ROC curve analysis revealed similar efficacies of CRP and PAPP-A levels in their ability to detect unstable plaques with areas under the curve of 0.762 and 0.732, respectively. Multivariate analysis established the superiority of hs-CRP as a predictor of plaque instability.

CONCLUSIONS

Our study highlights the utility of both CRP and PAPP-A levels as determinants of plaque instability. Our findings necessitate population-based follow-up studies to establish the superiority of either of the two biomarkers in the field of preventive cardiology.

Pregnancy-associated plasma protein A predicts adverse vascular events in patients with coronary heart disease: a systematic review and meta-analysis

INTRODUCTION

Prospective studies about the association between elevated circulating pregnancy-associated plasma protein A (PAPP-A) and adverse vascular events in patients with coronary heart diseases (CHD) are inconsistent. We performed a meta-analysis to clarify this issue.

MATERIAL AND METHODS

We identified prospective studies by searching MEDLINE. The vascular outcomes included all-cause mortality, combination of all-cause mortality and non-fatal myocardial infarction (MI), and combined cardiovascular events. Prospective studies providing multivariable adjusted relative risks (RRs) and their 95% confidence intervals (CIs) of pre-mentioned outcomes were included. A random-effects model was used to calculate the pooled RRs. Subgroup and sensitivity analyses were used to explore the potential sources of heterogeneity or modifiable factors.

RESULTS

Fourteen studies with a total of 12 830 participants were included. Elevated PAPP-A level was associated with all-cause mortality (pooled RR 1.74, 95% CI: 1.45 to 2.09, p < 0.001), combined all-cause mortality and non-fatal MI (RR 1.59, 95% CI: 1.37 to 1.85, p < 0.001) and combined cardiovascular events (RR 1.50, 95% CI: 1.22 to 1.85, p < 0.001). There was no significant heterogeneity. Subgroup and sensitivity analyses showed that the positive association was not affected by follow-up term, CHD type, different assay methods of PAPP-A, or studies with less than 5 adjusted variables.

CONCLUSIONS

Elevated serum PAPP-A level is associated with adverse vascular outcomes in patients with CHD.

Novel biomarkers for risk stratification and identification of life-threatening cardiovascular disease: troponin and beyond

Chest pain and other symptoms that may represent acute coronary syndromes (ACS) are common reasons for emergency department (ED) presentations, accounting for over six million visits annually in the United States [1]. Chest pain is the second most common ED presentation in the United States. Delays in diagnosis and inaccurate risk stratification of chest pain can result in serious morbidity and mortality from ACS, pulmonary embolism (PE), aortic dissection and other serious pathology.

Because of the high morbidity, mortality, and liability issues associated with both recognized and unrecognized cardiovascular pathology, an aggressive approach to the evaluation of this patient group has become the standard of care. Clinical history, physical examination and electrocardiography have a limited diagnostic and prognostic role in the evaluation of possible ACS, PE, and aortic dissection, so clinicians continue to seek more accurate means of risk stratification. Recent advances in diagnostic imaging techniques particularly computed-tomography of the coronary arteries and aorta, have significantly improved our ability to diagnose life-threatening cardiovascular disease.

In an era where health care utilization and cost are major considerations in how disease is managed, it is crucial to risk-stratify patients quickly and efficiently. Historically, biomarkers have played a significant role in the diagnosis and risk stratification of several cardiovascular disease states including myocardial infarction, congestive heart failure, and pulmonary embolus. Multiple biomarkers have shown early promise in answering questions of risk stratification and early diagnosis of cardiovascular pathology however many do not yet have wide clinical availability. The goal of this review will be to discuss these novel biomarkers and describe their potential role in direct patient care.

Pathophysiological roles and clinical importance of biomarkers in acute coronary syndrome

Early diagnosis of acute coronary syndrome (ACS) is important to guide appropriate therapy at a time when it is most likely to be of value. Accurate prognostic and risk stratification will facilitate high-risk patients to have early advanced diagnostic investigations and early appropriate interventions in a cost-effective and efficient manner, while those patients at low risk of ACS complications do not need such costly diagnostic tests and unnecessary hospital admission. Recent investigations have demonstrated that elevation of biomarkers upstream from acute-phase biomarkers, biomarkers of plaque destabilization and rupture, biomarkers of myocardial ischemia, necrosis, and dysfunction may provide an earlier assessment of patient risk and identify patients with higher risk of having an adverse event. This review provides an overview of the pathophysiology and clinical characteristics of several well-established biomarkers as well as emerging biomarkers that may have potential clinical utility in patients with ACS. Such emerging biomarkers hold promise and need to be more thoroughly evaluated before utilization in routine clinical practice.

Examination of serum pregnancy-associated plasma protein A clinical value in acute coronary syndrome prediction and monitoring

INTRODUCTION

Chronic vascular inflammatory process promotes and intensifies all atherogenic events. The aim of this research was to estimate the clinical value of pregnancy-associated plasma protein A (PAPP-A) measurement associated with plaque destabilization and rupture in prediction and monitoring of acute coronary syndromes (ACS) as well as to assess the predictive value of this biomarker in comparison to traditional myocardial infarction (MI) risk markers.

MATERIAL AND METHODS

The study included 119 patients in 2 investigated groups and one control group. PAPP-A assay was performed using manual ELISA kit, DRG. All other parameters were determined using automatic analyzers: Olympus and Dade Behring.

RESULTS

A statistically significant difference between PAPP-A concentration median value was found in the investigated group MI individuals' serum and control group individuals' serum (11.42 ng/ml and 7.22 ng/ml respectively, p = 0.003). PAPP-A assay had the highest specificity (83.3%) and sensitivity (53.8%), and therefore the highest clinical value. In patients with clinically and laboratory confirmed MI we proved that PAPP-A serum level is a clinically useful biomarker in ACS prediction, better than C-reactive protein (hsCRP) and fibrinogen (FBG) level.

CONCLUSIONS

The highest diagnostic efficiency for ACS prediction was proved for simultaneous panel assays consisting of 2-3 parameters (PAPP-A - hsCRP, PAPP-A - FBG, PAPP-A - hsCRP - FBG), while PAPP-A itself does not show characteristics necessary for it to be used as a biomarker for MI dynamic monitoring. It is possible that prothrombotic component is mainly responsible for repeated major adverse cardiac events, more than inflammatory process.

PAPP-A in cardiac and non-cardiac conditions

Pregnancy-associated plasma protein-A (PAPP-A), a newly discovered member of insulin like growth factors (IGFs) axis, has been reported to be a biomarker in both cardiac and non-cardiac conditions. PAPP-A mainly acts as a protease cleaving IGF inhibitors - IGF binding proteins (IGFBPs), thereby setting free IGFs. In cardiac conditions, PAPP-A plays an important role in progressive atherosclerosis. As a biomarker, PAPP-A is not only sensitive, specific and early for diagnosis of acute coronary syndrome, but also an independent risk factor for all-cause mortality or combined cardiovascular events. In non-cardiac conditions, PAPP-A is a new anti-aging target. PAPP-A knock out (KO) mice have a prolonged lifespan than the wild type. In addition, PAPP-A is also a biomarker associated with malignant cancer and end stage renal disease.

Reference interval of pregnancy-associated plasma protein-a in healthy men and non-pregnant women

OBJECTIVE

The serum pregnancy-associated plasma protein-A (PAPP-A) concentration is a predictor of ischemic cardiac events and renal impairment. However, the reference interval of PAPP-A has not been determined. This study determined the reference interval of PAPP-A in men and non-pregnant women.

METHODS

The study enrolled 126 apparently healthy individuals (52 males and 74 females). The mean age of the men and women was 34.7 (range 20-66) years and 34.6 (range 18-65) years, respectively. Serum PAPP-A concentrations were determined using an ultrasensitive enzyme-linked immunoassay kit. Reference intervals were calculated using the bootstrap method.

RESULTS

The results for three subjects were outliers, so the reference interval of PAPP-A was calculated using the data for 123 subjects. PAPP-A was undetectable in 26 subjects. The reference interval of PAPP-A for men and women (with the 90% confidence interval) was <22.9 ng/mL (19.7-23.3) and <33.6 ng/mL (25.2-36.7), respectively. In male subjects, serum PAPP-A levels of smokers [3.10 (UD, 7.30)ng/mL] were significantly lower than that of non-smokers [11.00 (UD, 24.4)ng/mL] (p<0.001) and there was a positive correlation between serum PAPP-A levels and subjects' age (r=0.439; p<0.001).

CONCLUSIONS

The reference interval of PAPP-A differed for men and non-pregnant women. In clinical practice, <22.9 ng/mL for men and <33.6 ng/mL for non-pregnant women may be used as reference intervals for PAPP-A.

Prospective evaluation of pregnancy-associated plasma protein-a and outcomes in patients with acute coronary syndromes

OBJECTIVES

This study sought to investigate whether pregnancy-associated plasma protein-A (PAPP-A) is useful for risk assessment in non-ST-segment elevation acute coronary syndrome (NSTE-ACS).

BACKGROUND

PAPP-A is a high molecular weight, zinc-binding metalloproteinase that is associated with vulnerable plaque and may be a predictor of cardiovascular disease and mortality.

METHODS

We measured PAPP-A at baseline in 3,782 patients with non NSTE-ACS randomized to ranolazine or placebo in the MERLIN-TIMI 36 (Metabolic Efficiency With Ranolazine for Less Ischemia in Non-ST Elevation Acute Coronary Syndromes) trial and followed for an average of 1 year. A cut point of 6.0 μIU/ml was chosen from pilot work in this cohort.

RESULTS

PAPP-A >6.0 μIU/ml at presentation was associated with higher rates of cardiovascular death (CVD) or myocardial infarction (MI) at 30 days (7.4% vs. 3.7%, hazard ratio [HR]: 2.01; 95% confidence interval [CI]: 1.43 to 2.82; p < 0.001) and at 1 year (14.9% vs. 9.7%, HR: 1.63; 95% CI: 1.29 to 2.05; p < 0.001). PAPP-A was also associated with higher rates of CVD (HR: 1.94; 95% CI: 1.07 to 3.52, p = 0.027) and myocardial infarction (HR: 1.82; 95% CI: 1.22 to 2.71, p = 0.003) individually at 30 days. There was no difference in the risk associated with PAPP-A stratified by baseline cardiac troponin I [Accu-TnI >0.04 μg/l], p interaction = 0.87). After adjustment for cardiac troponin I, ST-segment deviation, age, sex, diabetes, smoking, hypertension, and coronary artery disease, PAPP-A was independently associated with CVD/myocardial infarction at 30 days (adjusted HR: 1.62, 95% CI: 1.15 to 2.29; p = 0.006) and 1 year (adjusted HR: 1.35, 95% CI: 1.07 to 1.71; p = 0.012). PAPP-A also improved the net reclassification for CVD/MI (p = 0.003). There was no significant interaction with ranolazine.

CONCLUSIONS

PAPP-A was independently associated with recurrent cardiovascular events in patients with NSTE-ACS. This finding supports PAPP-A as a candidate prognostic marker in patients with ACS and supports investigation of its therapeutic implications.

CRP and TNF-α induce PAPP-A expression in human peripheral blood mononuclear cells

Objective. The effects of C-reactive protein (CRP) and tumor necrosis factor-α (TNF-α) on pregnancy-associated plasma protein-A (PAPP-A) expression in human peripheral blood mononuclear cells (PBMCs) require further investigation. Methods. The PAPP-A levels in culture supernatants, PAPP-A mRNA expression, and cellular PAPP-A expression were measured in human PBMCs isolated from fresh blood donations provided by 6 healthy volunteers (4 donations per volunteer). Analyses were conducted by ultrasensitive ELISA, western blotting, and RT-PCR following stimulation with CRP or TNF-α cytokines. Results. PAPP-A mRNA and protein levels after CRP stimulation peaked at 24 hours, whereas peak PAPP-A mRNA and protein levels were achieved after TNF-α stimulation at only 2 and 8 hours, respectively. These findings indicate the dose-dependent effect of CRP and TNF-α stimulation. Actinomycin D treatment completely prevented CRP and TNF-α induction of PAPP-A mRNA and protein expression. Additionally, nuclear factor- (NF-) κB inhibitor (BAY11-7082) potently inhibited both CRP and TNF-α stimulated PAPP-A mRNA and protein expression. Conclusions. Human PBMCs are capable of expressing PAPP-A in vitro, expression that may be regulated by CRP and TNF-α through the NF-κB pathway. This mechanism may play a significant role in the observed increase of serum PAPP-A levels in acute coronary syndrome (ACS).