Complementary roles for biomarkers of biomechanical strain ST2 and N-terminal prohormone B-type natriuretic peptide in patients with ST-elevation myocardial infarction

Soluble ST2 and interleukin-33 levels in coronary artery disease: relation to disease activity and adverse outcome

Objectives

ST2 is a receptor for interleukin (IL)-33. We investigated an association of soluble ST2 (sST2) and IL-33 serum levels with different clinical stages of coronary artery disease. We assessed the predictive value of sST2 and IL-33 in patients with stable angina, non-ST elevation myocardial infarction (NSTEMI) and ST elevation myocardial infarction (STEMI).

Methods

We included 373 patients of whom 178 had stable angina, 97 had NSTEMI, and 98 had STEMI. Patients were followed for a mean of 43 months. The control group consisted of 65 individuals without significant stenosis on coronary angiography. Serum levels of sST2 and IL-33 were measured by ELISAs.

Results

sST2 levels were significantly increased in patients with STEMI as compared to patients with NSTEMI and stable angina as well as with controls. IL-33 levels did not differ between the four groups. During follow-up, 37 (10%) patients died and the combined endpoint (all cause death, MI and rehospitalisation for cardiac causes) occurred in 66 (17.6%) patients. sST2 serum levels significantly predicted mortality in the total cohort. When patients were stratified according to their clinical presentation, the highest quintile of sST2 significantly predicted mortality in patients with STEMI, but not with NSTEMI or stable coronary artery disease. sST2 was a significant predictor for the combined endpoint in STEMI patients and in patients with stable angina. Serum levels of IL-33 were not associated with clinical outcome in the total cohort, but the highest quintile of IL-33 predicted mortality in patients with STEMI.

Conclusions

Serum levels of sST2 are increased in patients with acute coronary syndromes as compared to levels in patients with stable coronary artery disease and in individuals without coronary artery disease. sST2 and IL-33 were associated with mortality in patients with STEMI but not in patients with NSTEMI or stable angina.

Increased Soluble ST2 Predicts Long-term Mortality in Patients with Stable Coronary Artery Disease: Results from the Ludwigshafen Risk and Cardiovascular Health Study

BACKGROUND

Soluble suppression of tumorigenicity 2 (sST2) has emerged as a strong prognostic biomarker in patients with heart failure and myocardial infarction. The aim of this study was to evaluate the long-term prognostic value of sST2 in patients with stable coronary artery disease (CAD).

METHODS

sST2 plasma concentrations were measured in 1345 patients with stable CAD referred for coronary angiography at a single tertiary care center. The primary endpoint was all-cause mortality.

RESULTS

During a median follow-up time of 9.8 years, 477 (36%) patients died. The median sST2 plasma concentration at baseline was significantly higher among decedents than survivors (21.4 vs 18.5 ng/mL; P < 0.001). In multivariate Cox proportional hazards regression analysis, sST2 was an independent predictor of all-cause mortality (risk ratio 1.16 per 1-SD increase in log-transformed values; 95% CI 1.05–1.29; P = 0.004). In the same multivariate analysis, amino-terminal pro–B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hs-cTnT) were also independent predictors, whereas galectin-3 was not. Patients with sST2 in the highest quartile (>24.6 ng/mL) displayed a 2-fold increased risk of death in univariate analysis, which was attenuated but remained significant in a fully adjusted model (risk ratio 1.39; 95% CI 1.10–1.76; P = 0.006). Further analysis showed that the prognostic impact of sST2 was additive to NT-proBNP and hs-cTnT. Using a multibiomarker approach combining these 3 complementary makers, we demonstrated that patients with all 3 biomarkers in the highest quartiles had the poorest outcome.

CONCLUSIONS

In this cohort of patients with stable CAD, increased sST2 was an independent predictor of long-term all-cause mortality and provided complementary prognostic information to hs-cTnT and NT-proBNP.

Cardiac biomarkers in heart failure

BACKGROUND

Heart failure is a syndrome characterized by the inability of the heart to meet the body's circulatory demands. Heart failure is a growing health issue worldwide and the prevalence of heart failure is expected to rise as populations age. Therapies and interventions for a variety of cardiac conditions continue to advance and biomarkers will play an increasing role in patient management.

METHODS

This is a review of the clinical research in blood based biomarkers for diagnosis, prognosis and therapeutic guidance of heart failure. The focus of this review is biomarkers that are currently available for clinical measurement, and their current and potential for applications for managing heart failure patients.

RESULTS

The various biologic pathways and physiologic processes of heart failure biomarkers represent a host of different including inflammation, remodeling, strain, neurohormonal activation, metabolism and cardiac myocyte injury. The clinical characteristics and applications of each heart failure biomarker are discussed.

CONCLUSION

As populations age and effective treatments and interventions for coronary artery disease improve, heart failure will increase in incidence and prevalence. Blood biomarkers will play an increasing role in the early diagnosis, therapeutic monitoring and management of heart failure patients in the future.

Soluble ST2 predicts elevated SBP in the community

BACKGROUND

Soluble ST2 (sST2) is an emerging prognostic biomarker in patients with existing cardiovascular disease. ST2 and its ligand, interleukin-33 (IL-33), are expressed in endothelial cells, and may play an important role in the development of early atherosclerosis and vascular biology. We sought to investigate the association of sST2 and progression of blood pressure (BP), as well as the development of hypertension.

METHODS

Circulating sST2 concentrations were measured in 1834 participants (mean age 56 years, 57% women) of the community-based Framingham Offspring study. Participants were free of hypertension at baseline. Multivariable linear and logistic regression models were used to evaluate the association of sST2 concentrations and subsequent BP outcomes.

RESULTS

Higher sST2 concentrations were associated with incident hypertension over 3 years of follow-up [multivariable-adjusted odds ratio per 1 standard deviation increase in sST2 1.22, 95% confidence interval 1.05-1.42, P=0.01]. Individuals in the upper sST2 quartile had a 2.6 mmHg greater increase in SBP compared with those in the lowest quartile (P for trend across quartiles 0.002) and a 1.8 mmHg greater increase in pulse pressure (P for trend 0.005). In contrast, sST2 concentrations were not associated with changes in DBP (P=0.27).

CONCLUSION

These findings suggest that sST2 concentrations predict changes in BP physiology typically seen with aging and progressive arterial stiffness. Further studies are needed to elucidate underlying mechanisms by which the ST2/IL-33 pathway may contribute to BP physiology.

Soluble ST2 and galectin-3 in heart failure

Circulating biomarkers that directly reflect disease progression, hemodynamics, and ventricular remodeling at a molecular level are critical to risk stratification in heart failure (HF), affording unique insights into pathophysiology not fully captured by traditional risk markers. Despite the wealth of data confirming the importance of natriuretic peptides in HF diagnosis and prognosis, residual clinical risk in HF suggests that additional biomarkers complementary to natriuretic peptides may be useful. In this article, the current literature addressing the role of these biomarkers in the clinical diagnosis and risk stratification in HF is summarized.

Risk assessment of post-infarction heart failure. Systematic review on the role of emerging biomarkers

The prognostic significance of cardiospecific troponins and natriuretic peptides in patients with myocardial ischemia is well established, and their measurement is now endorsed by the most important guidelines and recommendations for diagnosis and management of heart failure (HF). Additional biomarkers have also been investigated to support clinical judgment and diagnostic imaging in the stratification of risk of cardiac dysfunction in patients with myocardial infarction (MI). We have performed a systematic analysis of the current scientific literature regarding the most important biomarkers of HF, selecting all prospective studies with adequate sample size (i.e. >100 patients) that have assessed, during the early phase of myocardial ischemia, the prognostic value of emergent biomarkers for new-onset HF or deterioration of cardiac function in patients with MI. This analysis has provided some good evidence suggesting that, in most cases, the use of diagnostic biomarkers of cardiac dysfunction does not translate into efficient risk prediction of HF. However, some notable exceptions were found, including biomarkers of cardiac fibrosis (especially galectin-3), growth differentiation factor-15 (GDF-15), osteoprotegerin, C-reactive protein (CRP), and red blood cell distribution width (RDW). Nevertheless, future studies with well-defined characteristics including the use of larger sample sizes, standardized end points, and replication populations, along with benchmark analyses against other consolidated biomarkers (i.e. cardiospecific troponins and natriuretic peptides), should be planned. Such evaluations will help to establish whether an integrated approach including biomarkers of different pathogenetic pathways - for example, apoptosis, stress of cardiomyocytes, cardiac fibrosis, inflammation, and extra-cardiac involvement - may be cost effective for identifying patients at increased risk of developing HF, and who, therefore, may benefit from a tailored therapeutic strategy.

Relation between soluble ST2, growth differentiation factor-15, and high-sensitivity troponin I and incident atrial fibrillation

BACKGROUND

We investigated whether circulating concentrations of soluble ST2, growth differentiation factor-15 (GDF-15), and high-sensitivity troponin I (hsTnI) are associated with incident atrial fibrillation (AF) and whether these biomarkers improve current risk prediction models including AF risk factors, B-type natriuretic peptide (BNP), and C-reactive protein (CRP).

METHODS

We studied the relation between soluble ST2, GDF-15, and hsTnI and development of AF in Framingham Heart Study participants without prevalent AF. We used Cox proportional hazard regression analysis to examine the relation of incident AF during a 10-year follow-up period with each biomarker. We adjusted for standard AF clinical risk factors, BNP, and CRP.

RESULTS

The mean age of the 3,217 participants was 59 ± 10 years, and 54% were women. During a 10-year follow-up, 242 participants developed AF. In age- and sex-adjusted models, GDF-15 and hsTnI were associated with risk of incident AF; however, after including the AF risk factors and BNP and CRP, only hsTnI was significantly associated with AF (hazard ratio per 1 SD of loge hsTnI, 1.12, 95% CI 1.00-1.26, P = .045). The c statistic of the base model including AF risk factors, BNP, and CRP was 0.803 (95% CI 0.777-0.830) and did not improve by adding individual or all 3 biomarkers. None of the discrimination and reclassification statistics were significant compared with the base model.

CONCLUSION

In a community-based cohort, circulating hsTnI concentrations were associated with incident AF. None of the novel biomarkers evaluated improved AF risk discrimination or reclassification beyond standard clinical AF risk factors and biomarkers.

Prognostic and diagnostic value of plasma soluble suppression of tumorigenicity-2 concentrations in acute respiratory distress syndrome

OBJECTIVES

Soluble suppression of tumorigenicity-2 is a biomarker of myocardial strain and inflammation. The characteristics of acute respiratory distress syndrome include inflammation and cardiovascular dysfunction. We sought to determine whether plasma soluble suppression of tumorigenicity-2 concentration is associated with outcome and response to conservative fluid management and whether soluble suppression of tumorigenicity-2 concentration discriminates acute respiratory distress syndrome from decompensated heart failure.

DESIGN

A retrospective analysis of the Fluid and Catheter Treatment Trial, a multi-center randomized controlled trial of conservative fluid management in the acute respiratory distress syndrome, as well as of a cohort of patients with decompensated heart failure.

SETTING

Twenty acute care hospitals.

PATIENTS

Eight hundred twenty-six patients with acute respiratory distress syndrome and 209 patients with acutely decompensated heart failure.

MEASUREMENTS AND MAIN RESULTS

Nonsurvivors had higher day 0 (p < 0.0001) and day 3 (p < 0.0001) soluble suppression of tumorigenicity-2 concentrations. After adjustment for severity of illness, higher soluble suppression of tumorigenicity-2 concentration was associated with mortality, with odds ratioadj 1.47 (95% CI, 0.99-2.20; p = 0.06) at day 0, 2.94 (95% CI, 2.00-4.33; p < 0.0001) at day 3, and 3.63 (95% CI, 2.38-5.53; p < 0.0001) if soluble suppression of tumorigenicity-2 increased between days. Cumulative fluid balance was more positive among patients with higher day 0 (median, 5,212 mL [interquartile range, 200-12,284 mL] vs median, 2,020 mL [interquartile range, -2,034 to 7,091 mL]; p < 0.0001) and day 3 soluble suppression of tumorigenicity-2 (median, 7,678 mL [interquartile range, 2,217-14,278 mL] vs median, 1,492 mL [interquartile range, -2,384 to 6,239 mL]; p < 0.0001). Soluble suppression of tumorigenicity-2 showed excellent discriminative ability between the Fluid and Catheter Treatment Trial and heart failure populations (area under receiver-operating characteristic curve = 0.98; p < 0.0001).

CONCLUSIONS

Higher soluble suppression of tumorigenicity-2 concentrations are associated with worse outcome in acute respiratory distress syndrome and may have value for discriminating acute respiratory distress syndrome from heart failure.

Soluble ST2 as a biomarker for detecting stable heart failure with a normal ejection fraction in hypertensive patients

BACKGROUND

We investigated the measurement of soluble ST2 (sST2) in stable heart failure (HF) with a normal ejection fraction (HFNEF) in hypertensive patients.

METHODS AND RESULTS

Echocardiography and serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) and sST2 concentrations were evaluated in 107 hypertensive patients (65 ± 12 years, 57 male) with ejection fraction (EF) >50%. Among them, 68 patients with stable HF in functional class II and III were the HFNEF group. We found that the area under the receiver operating characteristic curve (AUC) for sST2 was 0.80 (95% CI 0.70-0.89; P < .001), relatively better than that for NT-proBNP (AUC 0.70, 95% CI 0.58-0.79; P = .003) to detect HFNEF. However, the NT-proBNP concentration, rather than sST2, was higher in HFNEF patients with functional class III (562 ± 891 vs 185 ± 242 pg/mL in functional class II; P = .009), and correlated better with mitral E/e' (annular early diastolic velocity) (r = 0.327; P = .008) than sST2 concentrations in HFNEF patients. Multivariate analysis showed that sST2 >13.5 ng/mL was independently associated with HFNEF in hypertensive patients (odds ratio 11.7, 95% CI = 2.9-47.4; P = .001).

CONCLUSIONS

sST2 measurement provides diagnostic aid of stable HFNEF for hypertensive patients. Addition of NT-proBNP to sST2 could give further information regarding HF functional class and diastolic abnormality.

A novel cardiac bio-marker: ST2: a review

Cardiovascular diseases (CVD) are the major cause of death worldwide. The identification of markers able to detect the early stages of such diseases and/or their progression is fundamental in order to adopt the best actions in order to reduce the worsening of clinical condition. Brain natriuretic peptide (BNP) and NT-proBNP are the best known markers of heart failure (HF), while troponins ameliorated the diagnosis of acute and chronic coronary artery diseases. Nevertheless, many limitations reduce their accuracy. Physicians have tried to develop further detectable molecules in order to improve the detection of the early moments of CVD and prevent their development. Soluble ST2 (suppression of tumorigenicity 2) is a blood protein confirmed to act as a decoy receptor for interleukin-33. It seems to be markedly induced in mechanically overloaded cardiac myocytes. Thus, HF onset or worsening of a previous chronic HF status, myocardial infarct able to induce scars that make the myocardium unable to stretch well, etc, are all conditions that could be detected by measuring blood levels of soluble ST2. The aim of this review is to explore the possible role of ST2 derived-protein as an early marker of cardiovascular diseases, above all in heart failure and ischemic heart diseases.

Soluble ST2 and N-terminal pro-brain natriuretic peptide combination. Useful biomarker for predicting outcome of childhoodpulmonary arterial hypertension

BACKGROUND

Some potential biomarkers have been reported recently in patients with pulmonary arterial hypertension (PAH), but the most clinically useful among these potential biomarkers, especially in childhood PAH, has not been identified. Therefore, this study investigated which biomarker is useful in assessing severity of and patient prognosis in childhood idiopathic PAH (IPAH)/heritable PAH (HPAH).

METHODS AND RESULTS

Fifty-nine patients who were younger than 16 years at onset of IPAH/HPAH were selected. The following 10 biomarker candidates were quantified: high-sensitivity troponin T, human heart fatty acid-binding protein, N-terminal pro-brain natriuretic peptide (NT-proBNP), pentraxin-3, soluble ST2 (sST2), angiopoietin-2 (Ang-2), matrix metalloproteinase 2, tenascin C, endostatin (ES), and thymidine kinase. Functional characteristics and clinical outcomes were analyzed retrospectively. NT-proBNP, sST2, Ang-2, and ES correlated well with New York Heart Association class. On area under the receiver operating characteristic curve analysis, sST2 had a significantly good relationship with prognosis. On Kaplan-Meier curve and univariate Cox regression analyses, elevated sST2 and NT-proBNP level predicted poor outcome of the present patients with childhood IPAH/HPAH. Furthermore, patients with elevated sST2 had significantly worse prognosis among those with high NT-proBNP.

CONCLUSIONS

The sST2 and NT-proBNP combination is a useful biomarker to predict clinical condition and outcome in patients with childhood IPAH/HPAH.  

Soluble ST2, a modulator of the inflammatory response, in preterm and term labor

OBJECTIVE

Intra-amniotic infection/inflammation (IAI) is causally linked with spontaneous preterm labor and delivery. The ST2L receptor and its soluble form (sST2) are capable of binding to interleukin (IL)-33, a member of the IL-1 superfamily. Members of this cytokine family have been implicated in the onset of spontaneous preterm labor in the context of infection. Soluble ST2 has anti-inflammatory properties, and plasma concentrations are elevated in systemic inflammation, such as sepsis, acute pyelonephritis in pregnancy and the fetal inflammatory response syndrome. The aims of this study were to examine: (1) whether amniotic fluid concentrations of sST2 change with IAI, preterm, and term parturition; and (2) if mRNA expression of ST2 in the chorioamniotic membranes changes with acute histologic chorioamnionitis in women who deliver preterm.

METHOD

A cross-sectional study was conducted to determine amniotic fluid concentrations of sST2 in: (1) women with preterm labor (PTL) who delivered at term (n=49); (2) women with PTL who delivered preterm without IAI (n=21); (3) women with PTL who delivered preterm with IAI (n=31); (4) term pregnancies not in labor (n=13); and (5) term pregnancies in labor (n=43). The amniotic fluid concentration of sST2 was determined by ELISA. The mRNA expression of ST2 in the chorioamniotic membranes of women who delivered preterm with (n=24), and without acute histologic chorioamnionitis (n=19) was determined by qRT-PCR.

RESULTS

(1) Patients with PTL who delivered preterm with IAI had a lower median amniotic fluid concentration of sST2 compared to those with PTL who delivered preterm without IAI [median 410 ng/mL, inter-quartile range (IQR) 152-699 ng/mL versus median 825 ng/mL, IQR 493-1216 ng/mL; p=0.0003] and those with PTL who delivered at term [median 410 ng/mL, IQR 152-699 ng/mL versus median 673 ng/mL, IQR 468-1045 ng/mL; p=0.0003]; (2) no significant differences in the median amniotic fluid concentration of sST2 were observed between patients with PTL who delivered at term and those who delivered preterm without IAI (p=0.4), and between women at term in labor and those at term not in labor (p=0.9); (3) the mean mRNA expression of ST2 was 4-fold lower in women who delivered preterm with acute histologic chorioamnionitis than in those without this lesion (p=0.008).

CONCLUSIONS

The median sST2 amniotic fluid concentration and mRNA expression of ST2 by chorioamniotic membranes is lower in PTL associated with IAI and acute histologic chorioamnionitis than in PTL without these conditions. Changes in the median amniotic fluid sST2 concentration are not observed in preterm and term parturition without IAI. Thus, amniotic fluid sST2 in the presence of IAI behaves differently when compared to sST2 in the plasma of individuals affected by fetal inflammatory response syndrome, acute pyelonephritis in pregnancy, and adult sepsis. Decreased concentrations of sST2 in IAI are likely to promote a pro-inflammatory response, which is important for parturition in the context of infection.

The use of biomarkers in the patient with heart failure

Heart failure is a major burden to the health care system in terms of not only cost, but also morbidity and mortality. Appropriate use of biomarkers is critically important to allow rapid identification and optimal risk stratification and management of patients with both acute and chronic heart failure. This review will discuss the biomarkers that have the most diagnostic, prognostic, and therapeutic value in patients with heart failure. We will discuss established biomarkers such as natriuretic peptides as well as emerging biomarkers reflective of myocyte stress, myocyte injury, extracellular matrix injury, and both neurohormonal and cardio-renal physiology.

ST2 in emergency department patients with noncardiac dyspnea

OBJECTIVES

Serum levels of soluble ST2, a member of the interleukin-1 receptor family, predict mortality in emergency department (ED) patients with dyspnea secondary to acute heart failure and acute coronary syndrome. Elevated levels of ST2 have also been described in pulmonary disease, but it is unclear if these are associated with adverse outcomes. The hypothesis for this study was that elevated ST2 levels would be associated with 180-day mortality and 180-day return ED visits or hospital readmission in patients presenting to the ED with noncardiac causes of dyspnea.

METHODS

This prospective observational cohort study enrolled a convenience sample of patients presenting to a single academic tertiary care ED with a chief complaint of dyspnea. Exclusion criteria included dyspnea due to chest wall trauma, airway obstruction, and known cardiac etiology (new onset heart failure, prior heart failure with current brain natriuretic peptide > 500 pg/mL, presumed ischemic chest pain, elevated troponin, electrocardiogram changes indicating myocardial infarction or ischemia, heart transplant). ST2 levels were measured at ED presentation and compared between those with and without adverse outcomes. Staff were blinded to ST2 levels. Differences between groups were assessed using the Mann-Whitney U test.

RESULTS

Of the 82 patients enrolled, 45 (55%) were female, 48 (59%) were African American, and 34 (42%) were hospitalized. The most frequent ED or hospital diagnosis was chronic obstructive pulmonary disease (COPD) or asthma, in 29 (35%) patients. At 180 days, 36 of 81 patients (44%) had return ED visits, 21 of 81 patients (26%) were readmitted, and five of 82 patients (6%) were deceased. Median ST2 level was 227 ng/mL in patients who died versus 32 ng/mL in those who survived (difference = 195 ng/mL, 95% confidence interval [CI] = 48 to 342 ng/mL, p = 0.006). Median ST2 level was 59 ng/mL in readmitted patients versus 31 ng/mL in nonreadmitted patients (difference = 28 ng/mL, 95% CI = -3 to 60 ng/mL, p = 0.036). Median ST2 levels were 41 ng/mL in patients with return ED visits versus 31 ng/mL in those without return visits (difference = 10 ng/mL, 95% CI = -10 to 20 ng/mL, p = 0.23).

CONCLUSIONS

Patients with noncardiac dyspnea who died or required readmission to the hospital within 180 days had higher levels of ST2 compared with nonadmitted survivors. Further research into ST2 as a prognostic tool in pathologic processes not involving the heart, such as pulmonary disease, is warranted.

Soluble ST2 in ambulatory patients with heart failure: Association with functional capacity and long-term outcomes

BACKGROUND

ST2 is involved in cardioprotective signaling in the myocardium and has been identified as a potentially promising biomarker in heart failure (HF). We evaluated ST2 levels and their association with functional capacity and long-term clinical outcomes in a cohort of ambulatory patients with HF enrolled in the Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) study-a multicenter, randomized study of exercise training in HF.

METHODS AND RESULTS

HF-ACTION randomized 2331 patients with left ventricular ejection fraction <0.35 and New York Heart Association class II to IV HF to either exercise training or usual care. ST2 was analyzed in a subset of 910 patients with evaluable plasma samples. Correlations and Cox models were used to assess the relationship among ST2, functional capacity, and long-term outcomes. The median baseline ST2 level was 23.7 ng/mL (interquartile range, 18.6-31.8). ST2 was modestly associated with measures of functional capacity. In univariable analysis, ST2 was significantly associated with death or hospitalization (hazard ratio, 1.48; P<0.0001), cardiovascular death or HF hospitalization (hazard ratio, 2.14; P<0.0001), and all-cause mortality (hazard ratio, 2.33; P<0.0001; all hazard ratios for log2 ng/mL). In multivariable models, ST2 remained independently associated with outcomes after adjustment for clinical variables and amino-terminal pro-B-type natriuretic peptide. However, ST2 did not add significantly to reclassification of risk as assessed by changes in the C statistic, net reclassification improvement, and integrated discrimination improvement.

CONCLUSIONS

ST2 was modestly associated with functional capacity and was significantly associated with outcomes in a well-treated cohort of ambulatory patients with HF although it did not significantly affect reclassification of risk.

CLINICAL TRIAL INFORMATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00047437.

Common genetic variation at the IL1RL1 locus regulates IL-33/ST2 signaling

The suppression of tumorigenicity 2/IL-33 (ST2/IL-33) pathway has been implicated in several immune and inflammatory diseases. ST2 is produced as 2 isoforms. The membrane-bound isoform (ST2L) induces an immune response when bound to its ligand, IL-33. The other isoform is a soluble protein (sST2) that is thought to be a decoy receptor for IL-33 signaling. Elevated sST2 levels in serum are associated with an increased risk for cardiovascular disease. We investigated the determinants of sST2 plasma concentrations in 2,991 Framingham Offspring Cohort participants. While clinical and environmental factors explained some variation in sST2 levels, much of the variation in sST2 production was driven by genetic factors. In a genome-wide association study (GWAS), multiple SNPs within IL1RL1 (the gene encoding ST2) demonstrated associations with sST2 concentrations. Five missense variants of IL1RL1 correlated with higher sST2 levels in the GWAS and mapped to the intracellular domain of ST2, which is absent in sST2. In a cell culture model, IL1RL1 missense variants increased sST2 expression by inducing IL-33 expression and enhancing IL-33 responsiveness (via ST2L). Our data suggest that genetic variation in IL1RL1 can result in increased levels of sST2 and alter immune and inflammatory signaling through the ST2/IL-33 pathway.

The Presage(®) ST2 Assay: analytical considerations and clinical applications for a high-sensitivity assay for measurement of soluble ST2

The Presage(®) ST2 Assay (Critical Diagnostics, CA, USA) is an in vitro diagnostic device that quantitatively measures soluble suppression of tumorigenicity 2 (sST2) in serum and plasma by ELISA. This assay is US FDA approved and is indicated to be used in conjunction with clinical evaluation as an aid in assessing the prognosis of patients diagnosed with chronic heart failure. sST2 binds to IL-33 and functions as a 'decoy' receptor for IL-33, thereby attenuating the systemic effects of IL-33. Due to the role of IL-33/transmembrane isoform of suppression of tumorigenicity 2 signaling in cardiac remodeling, sST2 has emerged as a novel cardiovascular biomarker. In recent studies, it was shown that sST2 is a valuable predictor of several end points in heart failure, in acute coronary syndromes and in critically ill patients. In this review, analytical considerations and clinical applications of the Presage ST2 Assay will be discussed, as well as probable future concepts for adoption of sST2 measurements into clinical practice.

Maternal plasma concentrations of sST2 and angiogenic/anti-angiogenic factors in preeclampsia

OBJECTIVES

Angiogenic/anti-angiogenic factors have emerged as one of the promising biomarkers for the prediction of preeclampsia. Since not all patients with preeclampsia can be identified by these analytes, the search for additional biomarkers continues. The soluble form of ST2 (sST2), a protein capable of binding to interleukin (IL)-33 and thus contributing to a Th1-biased immune response, has been reported to be elevated in maternal plasma of women with preeclampsia. The aims of this study were to examine: (1) differences in maternal plasma concentrations of sST2 and IL-33 between women diagnosed with preeclampsia and those having uncomplicated pregnancies; (2) the relationship between sST2, umbilical and uterine artery Doppler velocimetry, and the severity of preeclampsia; and (3) the performance of sST2 and angiogenic/anti-angiogenic factors in identifying patients with preeclampsia at the time of diagnosis.

METHODS

This cross-sectional study included women with preeclampsia (n = 106) and women with an uncomplicated pregnancy (n = 131). Plasma concentrations of sST2, IL-33, soluble vascular endothelial growth factor receptor (sVEGFR)-1, soluble endoglin (sEng) and placental growth factor (PlGF) were determined by enzyme linked immune sorbent assay. Area under the receiver operating characteristic curve (AUC) for the identification of preeclampsia was examined for each analyte.

RESULTS

(1) Patients with preeclampsia had a higher mean plasma concentrations of sST2 than those with an uncomplicated pregnancy (p < 0.0001), while no significant difference in the mean plasma concentration of IL-33 between the two groups was observed; (2) the magnitude of this difference was greater in early-onset, compared to late-onset disease, and in severe compared to mild preeclampsia; (3) sST2 plasma concentrations did not correlate with the results of uterine or umbilical artery Doppler velocimetry (p = 0.7 and p = 1, respectively) among women with preeclampsia; (4) sST2 correlated positively with plasma concentrations of sVEGFR1-1 and sEng (Spearman's Rho = 0.72 and 0.63; each p < 0.0001), and negatively with PlGF (Spearman's Rho = -0.56, p < 0.0001); and (5) while the AUC achieved by sST2 and angiogenic/anti-angiogenic factors in identifying women with preeclampsia at the time of diagnosis were non-significantly different prior to term (<37 weeks of gestation), thereafter the AUC achieved by sST2 was significantly less than that achieved by angiogenic/anti-angiogenic factors.

CONCLUSIONS

Preeclampsia is associated with increased maternal plasma concentrations of sST2. The findings that sST2 concentrations do not correlate with uterine or umbilical artery Doppler velocimetry in women with preeclampsia suggest that elevated maternal plasma sST2 concentrations in preeclampsia are not related to the increased impedance to flow in the utero-placental circulation. The performance of sST2 in identifying preeclampsia at the time of diagnosis prior to 37 weeks of gestation was comparable to that of angiogenic/anti-angiogenic factors. It remains to be elucidated if an elevation of maternal plasma sST2 concentrations in pregnancy is specific to preeclampsia.

Soluble ST2 protein in chronic heart failure is independent of traditional factors

INTRODUCTION

ST2 protein is the interleukin 33 (IL-33) receptor, whose serum level depends on the biomechanical strain of cardiac myocytes. The aim of this study was to analyse the relationship between soluble ST2 (sST2) level and traditional factors in patients with chronic heart failure.

MATERIAL AND METHODS

Sixty-six patients (mean age 62 years, 75% males) in stable NYHA class I-III with left ventricular ejection fraction < 45% were included in the study. Clinical, biochemical, electrocardiographic, echocardiographic and angiographic data were analysed. Patients were divided into groups depending on sST2 median: > 0.28 ng/ml (n = 31) vs. ≤ 0.28 ng/ml (n = 35). sST2 was measured using a quantitative ELISA kit. In order to define factors associated with sST2 levels uni- and multivariate regression analysis was performed.

RESULTS

There was no relationship between sST2 levels and age (p = 0.67), body mass index (p = 0.19), hsTnT (p = 0.7) or other analysed parameters (all p > 0.05), except for N-terminal prohormone B-type natriuretic peptide (NT-proBNP). A significant positive correlation between sST2 and NT-proBNP was found (p = 0.013, R = 0.395). Multivariate analysis revealed that the stage of coronary artery disease and NT-proBNP were independent factors associated with sST2 concentration (p = 0.04). Intriguing is the fact that the fewer the sclerotic changes present in arteries, the higher was the sST2 level (β = -0.381, p = 0.04).

CONCLUSIONS

sST2 protein is independent of traditional factors which usually affect levels of NT-proBNP. In chronic heart failure, sST2 protein may be of greater importance in idiopathic dilated cardiomyopathy than in ischaemic aetiology, which seems to be associated with the molecular mechanism (biomechanical strain) related to sST2.

Heart failure

Despite major improvements in the treatment of virtually all cardiac disorders, heart failure (HF) is an exception, in that its prevalence is rising, and only small prolongations in survival are occurring. An increasing fraction, especially older women with diabetes, obesity, and atrial fibrillation exhibit HF with preserved systolic function. Several pathogenetic mechanisms appear to be operative in HF. These include increased hemodynamic overload, ischemia-related dysfunction, ventricular remodeling, excessive neurohumoral stimulation, abnormal myocyte calcium cycling, excessive or inadequate proliferation of the extracellular matrix, accelerated apoptosis, and genetic mutations. Biomarkers released as a consequence of myocardial stretch, imbalance between formation and breakdown of extracellular matrix, inflammation, and renal failure are useful in the identification of the pathogenetic mechanism and, when used in combination, may become helpful in estimating prognosis and selecting appropriate therapy. Promising new therapies that are now undergoing intensive investigation include an angiotensin receptor neprilysin inhibitor, a naturally-occurring vasodilator peptide, a myofilament sensitizer and several drugs that enhance Ca++ uptake by the sarcoplasmic reticulum. Cell therapy, using autologous bone marrow and cardiac progenitor cells, appears to be promising, as does gene therapy. Chronic left ventricular assistance with continuous flow pumps is being applied more frequently and successfully as destination therapy, as a bridge to transplantation, and even as a bridge to recovery and explantation. While many of these therapies will improve the care of patients with HF, significant reductions in prevalence will require vigorous, multifaceted, preventive approaches.

Soluble ST2 associates with diabetes but not established cardiovascular risk factors: a new inflammatory pathway of relevance to diabetes?

Preliminary data mostly from animal models suggest the sST2/IL-33 pathway may have causal relevance for vascular disease and diabetes and thus point to a potential novel inflammatory link to cardiometabolic disease. However, the characterisation of sST2 levels in terms of metabolic or vascular risk in man is completely lacking. We sought to address this gap via a comprehensive analysis of risk factor and vascular correlates of sST2 in a cross-sectional study (pSoBid). We measured sST2 in plasma in 639 subjects and comprehensively related it to cardiovascular and diabetes risk factors and imaged atherosclerosis measures. Circulating sST2 levels increased with age, were lower in women and in highest earners. After adjusting for age and gender, sST2 levels associated strongly with markers of diabetes, including triglycerides [effect estimate (EE) per 1 standard deviation increase in sST2:1.05 [95%CI 1.01,1.10]), liver function (alanine aminotransaminase [ALT] and γ-glutamyl transferase [GGT]: EE 1.05 [1.01,1.09] and 1.13 [1.07,1.19] respectively), glucose (1.02 [1.00,1.03]) and sICAM-1 (1.05 [1.02,1.07]). However, sST2 levels were not related to smoking, cholesterol, blood pressure, or atheroma (carotid intima media thickness, plaque presence). These results suggest that sST2 levels, in individuals largely without vascular disease, are related principally to markers associated with diabetes and ectopic fat and add support for a role of sST2 in diabetes. Further mechanistic studies determining how sST2 is linked to diabetes pathways may offer new insights into the inflammatory paradigm for type 2 diabetes.

Prognostic utility of novel biomarkers of cardiovascular stress: the Framingham Heart Study

BACKGROUND

Biomarkers for predicting cardiovascular events in community-based populations have not consistently added information to standard risk factors. A limitation of many previously studied biomarkers is their lack of cardiovascular specificity.

METHODS AND RESULTS

To determine the prognostic value of 3 novel biomarkers induced by cardiovascular stress, we measured soluble ST2, growth differentiation factor-15, and high-sensitivity troponin I in 3428 participants (mean age, 59 years; 53% women) in the Framingham Heart Study. We performed multivariable-adjusted proportional hazards models to assess the individual and combined ability of the biomarkers to predict adverse outcomes. We also constructed a "multimarker" score composed of the 3 biomarkers in addition to B-type natriuretic peptide and high-sensitivity C-reactive protein. During a mean follow-up of 11.3 years, there were 488 deaths, 336 major cardiovascular events, 162 heart failure events, and 142 coronary events. In multivariable-adjusted models, the 3 new biomarkers were associated with each end point (P<0.001) except coronary events. Individuals with multimarker scores in the highest quartile had a 3-fold risk of death (adjusted hazard ratio, 3.2; 95% confidence interval, 2.2-4.7; P<0.001), 6-fold risk of heart failure (6.2; 95% confidence interval, 2.6-14.8; P<0.001), and 2-fold risk of cardiovascular events (1.9; 95% confidence interval, 1.3-2.7; P=0.001). Addition of the multimarker score to clinical variables led to significant increases in the c statistic (P=0.005 or lower) and net reclassification improvement (P=0.001 or lower).

CONCLUSION

Multiple biomarkers of cardiovascular stress are detectable in ambulatory individuals and add prognostic value to standard risk factors for predicting death, overall cardiovascular events, and heart failure.

Potential Markers in Cardiac Hypertrophy?

Cardiomyopathies are diagnosed based on medical history of patient (symptoms and family history), physical examination, results of echocardiogram and in some situations additionally ECG or chest-X-ray results. Currently used non-invasive diagnostic methods, could be complemented by biochemical tests. In this review some emerging potential biomarkers such as: osteopontin, ST-2 receptor, osteoprotegerin, neopterin, urocortins, growth differentiation factor 15 and urotensin II are described. In current article human and non human investigations have been reviewed, since rat is most commonly used model in experimental cardiology and gives important foundations to clinical knowledge.

Identification of follistatin-like 1 by expression cloning as an activator of the growth differentiation factor 15 gene and a prognostic biomarker in acute coronary syndrome

BACKGROUND

Growth differentiation factor 15 (GDF15) is a stress-responsive cytokine and biomarker that is produced after myocardial infarction and that is related to prognosis in acute coronary syndrome (ACS). We hypothesized that secreted proteins that activate GDF15 production may represent new ACS biomarkers.

METHODS

We expressed clones from an infarcted mouse heart cDNA library in COS1 cells and assayed for activation of a luciferase reporter gene controlled by a 642-bp fragment of the mouse growth differentiation factor 15 (GDF15) gene promoter. We measured the circulating concentrations of follistatin-like 1 (FSTL1) and GDF15 in 1369 patients with ACS.

RESULTS

One cDNA clone that activated the GDF15 promoter-luciferase reporter encoded the secreted protein FSTL1. Treatment with FSTL1 activated GDF15 production in cultured cardiomyocytes. Transgenic production of FSTL1 stimulated GDF15 production in the murine heart, whereas cardiomyocyte-selective deletion of FSTL1 decreased production of GDF15 in cardiomyocytes, indicating that FSTL1 is sufficient and required for GDF15 production. In ACS, FSTL1 emerged as the strongest independent correlate of GDF15 (partial R(2) = 0.26). A total of 106 patients died of a cardiovascular cause during a median follow-up of 252 days. Patients with an FSTL1 concentration in the top quartile had a 3.7-fold higher risk of cardiovascular death compared with patients in the first 3 quartiles (P < 0.001). FSTL1 remained associated with cardiovascular death after adjustment for clinical, angiographic, and biochemical variables.

CONCLUSIONS

Our study is the first to use expression cloning for biomarker discovery upstream of a gene of interest and to identify FSTL1 as an independent prognostic biomarker in ACS.

First Identification of Circulating Prepro–A-Type Natriuretic Peptide (PreproANP) Signal Peptide Fragments in Humans: Initial Assessment as Cardiovascular Biomarkers

BACKGROUND

New biomarkers are needed to assist clinical decision making in cardiovascular disease. We have recently shown that signal peptides may represent a novel biomarker target in cardiovascular diseases.

METHODS

We developed a novel immunoassay for the signal peptide of preproANP (ANPsp) and used it to document cardiac tissue levels of ANPsp in explant human hearts (n = 9), circulating venous concentrations of ANPsp in healthy volunteers (n = 65), temporal ANPsp concentrations in patients with ST-elevation myocardial infarction (STEMI) &lt;4 h after chest pain onset (n = 23), and regional plasma ANPsp concentrations in patients undergoing clinically indicated catheterization (n = 10). We analyzed the structure and sequence of circulating ANPsp by tandem mass spectrometry (MS/MS).

RESULTS

ANPsp levels in human heart tissue were 50–1000 times lower than those of ANP/NT-proANP. ANPsp was detectable in control human plasma at concentrations comparable with ANP itself (approximately 20 ng/L). In STEMI patients, plasma concentrations of ANPsp rose to peak values at 5 h after symptom onset, significantly earlier than myoglobin, creatine kinase-MB, and troponin (P &lt; 0.001). There were significant arteriovenous increases in ANPsp concentrations (P &lt; 0.05) across the heart and kidney; arterial and coronary sinus concentrations of ANPsp both negatively correlated with systolic and mean arterial blood pressures (both P &lt; 0.01). MS/MS verified circulating ANPsp to be preproANP(16–25) and preproANP(18–25).

CONCLUSIONS

ANPsp is a novel circulating natriuretic peptide with potential to act as a cardiovascular biomarker. The rapid increase of plasma ANPsp in STEMI and its significant relationship with blood pressure encourage further study of its potential clinical utility.

Cardiac biomarkers in acute myocardial infarction

Each year, a large number of patients are seen in the Emergency Department with presentations necessitating investigation for possible acute myocardial infarction. Patients can be stratified by symptoms, risk factors and electrocardiogram results but cardiac biomarkers also have a prime role both diagnostically and prognostically. This review summarizes both the history of cardiac biomarkers as well as currently available (established and novel) assays. Cardiac troponin, our current "gold standard" biomarker criterion for the diagnosis of myocardial infarction has high sensitivity and specificity for this diagnosis and therapies instituted in patients with elevated troponin have been shown to influence outcomes. Other markers of myocardial necrosis, inflammation and neurohormonal activity have also been shown to have either diagnostic or prognostic utility, but none have been shown to be superior to troponin. The measurement of multiple biomarkers and the use of point of care markers may accelerate current diagnostic protocols for the assessment of such patients.

Daily exposure to dust alters innate immunity

Pig farmers are exposed to organic material in pig barns on a daily basis and have signs of an ongoing chronic airway inflammation and increased prevalence of chronic inflammatory airway diseases, predominantly chronic bronchitis. Interestingly, the inflammatory response to acute exposure to organic dust is attenuated in farmers. The aim of the study was to closer characterize innate immunity features in blood and airways in farmers and in naïve, non-exposed, controls. The expression of pattern recognition receptors (TLR2, TLR4 and CD14) whose ligands are abundant in pig barn dust and adhesion proteins (CD11b, CD62L and CD162L) on blood and sputum neutrophils in pig farmers and soluble TLR2 and CD14 (sTLR2 and sCD14) in blood and sputum were assessed in pig farmers and previously unexposed controls. The release of pro-inflammatory cytokines from blood cells stimulated with LPS ex vivo was measured in the absence and presence of anti-ST2. We also examined, in a separate study population, serum levels of soluble ST2 (sST2), before and after exposure in a pig barn and a bronchial LPS challenge. Farmers had signs of ongoing chronic inflammation with increased number of blood monocytes, and decreased expression of CD62L and CD162 on blood neutrophils. Farmers also had lower levels of sTLR2 and sCD14 in sputum and reduced expression of CD14 on sputum neutrophils than controls. Exposure to organic dust and LPS induced increase of serum sST2 in controls but not in farmers. In conclusion, farmers have signs of local and systemic inflammation associated with altered innate immunity characteristics.

Soluble ST2 is associated with adverse outcome in patients with heart failure of ischaemic aetiology

AIMS

In patients with ischaemic heart failure (HF), myocardial dysfunction often progresses. Elevated levels of soluble ST2 (sST2) are associated with a poor prognosis, but an association between sST2 and worsening heart failure per se has not been established. We assessed the association between sST2 and cause-specific outcome in 1449 patients enrolled in the Controlled Rosuvastatin Multinational Trial in Heart Failure (CORONA study).

METHODS AND RESULTS

Soluble ST2 was measured with a highly sensitive immunoassay in 1449 patients ≥60 years of age with left ventricular ejection fraction (LVEF) ≤40% due to ischaemic heart disease. By Cox regression analyses, we found sST2 to be associated with the primary endpoint, i.e. a composite of cadiovascular (CV) death, non-fatal myocardial infarction, or stroke, as well as all pre-defined secondary endpoints in the CORONA study, even after adjustment for baseline clinical variables. After adjustment for N-terminal pro brain natriuretic peptide and C-reactive protein, the association between sST2 and the primary endpoint was attenuated and no longer statistically significant. However, sST2 remained associated with death due to worsening HF, hospitalization due to worsening HF, and hospitalization due to any CV cause, even after full adjustment.

CONCLUSIONS

Soluble ST2 is associated with adverse outcomes in older patients with systolic, ischaemic HF. In particular, sST2 is independently associated with worsening HF.

Soluble ST2 levels in patients with cardiogenic and septic shock are not predictors of mortality

BACKGROUND

Soluble ST2 (sST2) is an interleukin-33 receptor. sST2 was found to be an independent prognostic factor in patients with myocardial infarction, sepsis and heart failure.

OBJECTIVES

To assess sST2 levels in patients with cardiogenic shock (CS) and septic shock (SS), and to evaluate the prognostic value of sST2 for short-term mortality.

METHODS

The present prospective observational study evaluated 32 patients with CS, 17 patients with SS and 61 patients with ST segment elevation myocardial infarction (STEMI )(control group). Samples of serum were collected eight times and the follow-up time was three months.

RESULTS

sST2 levels were elevated from admission in SS patients relative to patients with CS and STEMI, who exhibited peak sST2 levels 24 h after admission. On admission, CS patients had a median (5th percentile; 95th percentile) sST2 level of 62.5 pg/mL (8.3 pg/mL; 315.8 pg/mL) and SS patients had a median sST2 level of 216.4 pg/mL (46.8 pg/mL; 364.4 pg/mL). ROC analysis found sST2 to be a biomarker that could distinguish between CS and SS at admission (area under the curve [AUC] 0.813; P<0.01) with a cut-off value of 210.4 pg/mL. Patients with STEMI had significantly lower sST2 levels at admission (20.3 pg/mL (4.2 pg/mL; 339.8 pg/mL) compared with CS patients. The AUC of the ROC analysis was 0.671 (P=0.007) for the detection of CS in patients with STEMI. Only a weak correlation was observed between sST2 and B-type natriuretic peptide (r=0.376, P=0.05) and sST2 and N-terminal pro-B-type natriuretic peptide (r=0.496, P=0.019). No statistically significant differences were observed in sST2 levels in patients with CS and SS relative to three-month mortality.

CONCLUSION

Levels of sST2 at admission are significantly higher in patients with SS compared with CS. sST2 could be a diagnostic marker to distinguish SS and CS as well as CS and STEMI at the time of admission. Levels of sST2 are related to levels of natriuretic peptides in CS but not in SS. sST2 levels are not a suitable prognostic marker for patients with CS and SS.

Toll/interleukin-1 receptor member ST2 exhibits higher soluble levels in type 2 diabetes, especially when accompanied with left ventricular diastolic dysfunction

BACKGROUND

Soluble ST2, a member of the of the Toll/IL-1 superfamily, is a novel biomarker with exceptional predictive value in heart failure and myocardial infarction- related mortality as well as in acute dyspneic states. Soluble ST2 is considered a decoy receptor of IL 33 that blocks the protective effects of the cytokine in atherosclerosis and cardiac remodeling. In the present study we investigated the differences in the levels of soluble ST2, BNP and hs-CRP between healthy controls and patients with type 2 diabetes with and without left ventricular diastolic dysfunction. A secondary aim was to investigate correlations between sST2 and other biomarkers of type 2 diabetes, such as HbA1c.

METHODS

158 volunteers were recruited and underwent a complete Doppler-echocardiographic evaluation of both systolic & diastolic cardiac function. All subjects with ejection fraction<50% were excluded. The study population was divided in 4 groups as follows: A: 42 healthy controls, B: 18 subjects without diabetes with LVDD, C: 48 patients with type 2 diabetes without LVDD & D: 50 patients with type 2 diabetes & LVDD. ELISA technique was performed to measure sST2 levels. Statistical analysis was performed with Kruskal-Wallis & Mann-Whitney test (continuous variables), chi squared & Fischer exact test (discrete variables), Spearman coefficient (univariate analysis) and step-wise backward method (multivariate analysis).

RESULTS

Patients with type 2 diabetes with (p<0.001) or without LVDD (p=0.007) had higher serum ST2 levels compared to healthy controls, state found also for hs-CRP levels but not for the corresponding BNP levels (p=0.213 & p=0.207 respectively). Patients with type 2 diabetes & LVDD had higher serum ST2 in relation to diabetic patients without LVDD (p=0.001). In multivariate analysis HbA1c positively and independently correlated with sST2 levels in both groups of patients with type 2 diabetes.

CONCLUSIONS

Patients with type 2 diabetes exhibit higher sST2 levels compared to healthy controls. The presence of LVDD in patients with type 2 diabetes is associated with even higher sST2 levels. A significant correlation between glycemic control and sST2 levels was also revealed.

Role of ST2 in non-ST-elevation acute coronary syndrome in the MERLIN-TIMI 36 trial

OBJECTIVE

We investigated the prognostic performance of ST2 with respect to cardiovascular death (CVD) and heart failure (HF) in patients with non-ST-elevation acute coronary syndrome (NSTE-ACS) in a large multinational trial.

BACKGROUND

Myocytes that are subjected to mechanical stress secrete ST2, a soluble interleukin-1 receptor family member that is associated with HF after STE-ACS.

METHODS

We measured ST2 with a high-sensitivity assay in all available baseline samples (N=4426) in patients enrolled in the Metabolic Efficiency With Ranolazine for Less Ischemia in the Non-ST-Elevation Acute Coronary Syndrome Thrombolysis in Myocardial Infarction 36 (MERLIN-TIMI 36), a placebo-controlled trial of ranolazine in NSTE-ACS. All events, including cardiovascular death and new or worsening HF, were adjudicated by an independent events committee.

RESULTS

Patients with ST2 concentrations in the top quartile (>35 μg/L) were more likely to be older and male and have diabetes and renal dysfunction. ST2 was only weakly correlated with troponin and B-type natriuretic peptide. High ST2 was associated with increased risk for CVD/HF at 30 days (6.6% vs 1.6%, P<0.0001) and 1 year (12.2% vs 5.2%, P<0.0001). The risk associated with ST2 was significant after adjustment for clinical covariates and biomarkers (adjusted hazard ratio CVD/HF 1.90, 95% CI 1.15-3.13 at 30 days, P=0.012; 1.51, 95% CI 1.15-1.98 at 1 year, P=0.003), with a significant integrated discrimination improvement (P<0.0001). No significant interaction was found between ST2 and ranolazine (Pinteraction=0.15).

CONCLUSIONS

ST2 correlates weakly with biomarkers of acute injury and hemodynamic stress but is strongly associated with the risk of HF after NSTE-ACS. This biomarker and related pathway merit further investigation as potential therapeutic targets for patients with ACS at risk for cardiac remodeling.

Systems biology of heart failure, challenges and hopes

PURPOSE OF REVIEW

Heart failure remains a leading cause of morbidity and mortality in developed nations. Our current understanding of molecular pathways involved in heart failure reveals little of the multiscale biological systems at work. Here we consider recent advances in understanding the integrative multiscale biology, or systems biology, of heart failure and present a framework for future work in the area.

RECENT FINDINGS

Multiplexed assays of gene expression and the complex dynamics of protein-protein interactions in heart failure have illuminated key pathways important to myocardial adaptation. Modeling of complex systems has advanced to incorporate these dynamic data sources into networks that capture fundamental interactions on different biological scales. The complex syndrome of heart failure, like other complex disease syndromes, can be viewed as an emergent property of these multiscale systems.

SUMMARY

A comprehensive understanding of adaptive mechanisms in heart failure requires integration of multiple data sources on several biological scales. A combination of holistic systems biology approaches and traditional reductionist experimentation will be required for a nuanced understanding of this multifaceted disease process.

Role of IL-33 in inflammation and disease

Interleukin (IL)-33 is a new member of the IL-1 superfamily of cytokines that is expressed by mainly stromal cells, such as epithelial and endothelial cells, and its expression is upregulated following pro-inflammatory stimulation. IL-33 can function both as a traditional cytokine and as a nuclear factor regulating gene transcription. It is thought to function as an 'alarmin' released following cell necrosis to alerting the immune system to tissue damage or stress. It mediates its biological effects via interaction with the receptors ST2 (IL-1RL1) and IL-1 receptor accessory protein (IL-1RAcP), both of which are widely expressed, particularly by innate immune cells and T helper 2 (Th2) cells. IL-33 strongly induces Th2 cytokine production from these cells and can promote the pathogenesis of Th2-related disease such as asthma, atopic dermatitis and anaphylaxis. However, IL-33 has shown various protective effects in cardiovascular diseases such as atherosclerosis, obesity, type 2 diabetes and cardiac remodeling. Thus, the effects of IL-33 are either pro- or anti-inflammatory depending on the disease and the model. In this review the role of IL-33 in the inflammation of several disease pathologies will be discussed, with particular emphasis on recent advances.

The IL-33/ST2 pathway--A new therapeutic target in cardiovascular disease

Numerous pro-inflammatory cytokines have been implicated in the pathogenesis of several cardiovascular diseases. Interleukin (IL)-33 is a new member of the IL-1 family of cytokines that promotes Th2 type immune responses by signaling through the ST2L and IL-1RAcP dimeric receptor complex. Furthermore, the biological effects of IL-33 are limited by a soluble decoy form of ST2 (sST2). Recent studies indicate a protective role for IL-33 and ST2L in atherosclerosis, obesity and cardiac remodeling. The present review summarizes currently available data showing the role for IL-33 and its receptor ST2L within cardiovascular disease, and the potential use of sST2 as a predictive cardiovascular biomarker.

Established and novel biomarkers in ST-elevation myocardial infarction

Cardiac biomarkers assist in the diagnosis of and risk stratification in acute coronary syndromes. In ST-elevation myocardial infarction (STEMI), rapid diagnosis and initiation of reperfusion via primary percutaneous coronary intervention or fibrinolysis is often based on the clinical history and presenting ECG, but measurement of biomarkers in the early and/or late phases of STEMI may allow the selection of patients who are at increased or decreased risk of subsequent complications. Although the measurement of only three biomarkers (troponin, natriuretic peptides and C-reactive protein) are currently included in practice guidelines, more than 20 other novel cardiac biomarkers have been proposed to provide improved risk stratification after a STEMI.

Cardiovascular biomarkers in acute Kawasaki disease

BACKGROUND

Endomycocardial biopsies have demonstrated that subclinical myocarditis is a universal feature of acute Kawasaki disease (KD).

METHODS

We investigated biochemical evidence of myocardial strain, oxidative stress, and cardiomyocyte injury in 55 acute KD subjects (30 with paired convalescent samples), 54 febrile control (FC), and 50 healthy control (HC) children by measuring concentrations of cardiovascular biomarkers.

RESULTS

Levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and soluble ST2 (sST2) were elevated in acute vs. convalescent KD, FC, and HC (p≤0.002), while γ-glutamyl transferase and alanine amino transferase as measures of oxidative stress were increased in acute vs. FC (p≤0.0002). Cardiac troponin I (cTnI) levels, using a highly sensitive assay, were elevated in 30% and 40% of paired acute and convalescent KD subjects, respectively, and normalized within two years of disease onset. NT-proBNP and sST2 negatively correlated with deceleration time, but only NT-proBNP correlated with MV E:A ratio and internal diameter of the coronary arteries (RCA/LAD Zworst).

CONCLUSIONS

NT-proBNP and sST2 were elevated in acute KD subjects and correlated with impaired myocardial relaxation. These findings, combined with elevated levels of cTnI, suggest that both cardiomyocyte stress and cell death are associated with myocardial inflammation in acute KD.

Novel biomarkers in human terminal heart failure and under mechanical circulatory support

This review summarizes recent findings on novel biochemical plasma biomarkers in terminal heart failure patients, which might predict an advanced mortality risk or even recovery. Moreover, we discussed the regulation of these heart failure-related biomarkers under mechanical circulatory support.

Interleukin 33 and ST2 in non-ST-elevation myocardial infarction: comparison with Global Registry of Acute Coronary Events Risk Scoring and NT-proBNP

BACKGROUND

Soluble ST2 is a marker of biomechanical strain for which the natural ligand is interleukin 33 (IL-33). They have not been studied together in non-ST-elevation myocardial infarction (NSTEMI). We investigated their relationship with death, heart failure (HF) readmission, and reinfarction combined (termed major adverse cardiac events [MACE]) and, separately, in unselected patients using Global Registry of Acute Coronary Events Risk Scoring (GRACE-RS) and n terminal pro B type natriuretic peptide (NT-proBNP) as benchmark comparators.

METHODS

ST2 and IL-33 were measured in 577 patients 3 to 5 days after admission. Mean follow-up was 532 (150-1059) days, during which 156 patients (27%) reached the primary end point.

RESULTS

ST2 was higher in those who experienced MACE when compared with event-free survivors (median 782 pg/mL vs 596, P < .001), but there was no difference in IL-33 levels across any end point. Multivariate Cox regression analysis reveals that elevated ST2 is independently associated with increased risk of MACE during the long term (hazard ratio [HR] 2.01, P = .005). This relationship continues on further adjustment for either GRACE risk score or NT-proBNP individually but not on adjustment for both. ST2 also independently predicts reinfarction (HR 2.48, P = .03) and 30-day mortality (HR 4.43, P = .02, c-statistic 0.73, P < .001). Adding ST2 to GRACE or to NT-proBNP did not lead to significant improvements in the c-statistic for MACE for long-term follow-up (P = .27 and P = .57, respectively) or the net reclassification index. Neither IL-33 nor its ratio with ST2 was associated with study end points.

CONCLUSIONS

Elevated ST2 predicts adverse outcome in non-ST-elevation myocardial infarction but does not significantly improve risk stratification for established markers. Interleukin 33 was not related to adverse events.

Recent advances on the role of cytokines in atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall driven by innate and adaptive immune responses. Inflammation controls the development and the destabilization of arterial plaque. Cells involved in the atherosclerotic process secrete and are activated by soluble factors, known as cytokines. Important recent advances in the comprehension of the mechanisms of atherosclerosis have provided evidence for a dual role of cytokines: proinflammatory and T helper-1-related cytokines promote the development and progression of the disease, whereas antiinflammatory and regulatory T cell-related cytokines exert clear antiatherogenic activities. This review focuses on recent advances regarding the role of cytokines, with the exception of chemokines, in the development, progression, and complications of atherosclerosis.