Multibiomarker analysis in patients with acute myocardial infarction

Growing evidence demonstrates widespread deficiencies in the reporting of health research studies. The EQUATOR Network is an international initiative that aims to enhance the reliability and value of the published health research literature. EQUATOR provides resources, education and training to facilitate good research reporting and assists in the development, dissemination and implementation of robust reporting guidelines. This paper presents a collection of tools and guidelines available on the EQUATOR website (http://www.equator-network.org) that have been developed to increase the accuracy and transparency of health research reporting.

Data from the Women's Health Study show that serum levels of growth-differentiation factor-15 (GDF-15), a distant member of the transforming growth factor-beta superfamily, are an independent risk indicator for adverse cardiovascular events. However, the cellular sources, upstream regulators, and functional effects of GDF-15 in the cardiovascular system have not been elucidated. We have identified GDF-15 by cDNA expression array analysis as a gene that is strongly upregulated by nitrosative stress in cultured cardiomyocytes isolated from 1- to 3-day-old rats. GDF-15 mRNA and pro-peptide expression levels were also induced in cardiomyocytes subjected to simulated ischemia/reperfusion (I/R) via NO-peroxynitrite-dependent signaling pathways. GDF-15 was actively secreted into the culture supernatant, suggesting that it might exert autocrine/paracrine effects during I/R. To explore the in vivo relevance of these findings, mice were subjected to transient or permanent coronary artery ligation. Myocardial GDF-15 mRNA and pro-peptide abundance rapidly increased in the area-at-risk after ischemic injury. Similarly, patients with an acute myocardial infarction had enhanced myocardial GDF-15 pro-peptide expression levels. As shown by immunohistochemistry, cardiomyocytes in the ischemic area contributed significantly to the induction of GDF-15 in the infarcted human heart. To delineate the function of GDF-15 during I/R, Gdf-15 gene-targeted mice were subjected to transient coronary artery ligation for 1 hour followed by reperfusion for 24 hours. Gdf-15-deficient mice developed greater infarct sizes and displayed more cardiomyocyte apoptosis in the infarct border zone after I/R compared with wild-type littermates, indicating that endogenous GDF-15 limits myocardial tissue damage in vivo. Moreover, treatment with recombinant GDF-15 protected cultured cardiomyocytes from apoptosis during simulated I/R as shown by histone ELISA, TUNEL/Hoechst staining, and annexin V/propidium iodide fluorescence-activated cell sorting (FACS) analysis. Mechanistically, the prosurvival effects of GDF-15 in cultured cardiomyocytes were abolished by phosphoinositide 3-OH kinase inhibitors and adenoviral expression of dominant-negative Akt1 (K179M mutation). In conclusion, our study identifies induction of GDF-15 in the heart as a novel defense mechanism that protects from I/R injury.

Mechanically overloaded cardiomyocytes secrete a soluble interleukin-1 receptor family member called ST2. Serum levels of ST2 are associated with prognosis in nonischemic heart failure, but the predictive value of ST2 in patients with acute myocardial infarction is unknown. ST2 levels were measured in serum from 810 patients with acute myocardial infarction in the Thrombolysis In Myocardial Infarction (TIMI) 14 (362 patients) and Enoxaparin and TNK-tPA With or Without GPIIb/IIIa Inhibitor as Reperfusion Strategy in STEMI (ENTIRE)-TIMI 23 (448 patients) clinical trials. Baseline levels of ST2 were significantly higher in those patients who died (0.379 versus 0.233 ng/mL, P=0.0001) or developed new congestive heart failure (0.287 versus 0.233 ng/mL, P=0.009) by 30 days. In an analysis of outcomes at 30 days by ST2 quartiles, both death (P=0.001) and the combined death/heart failure end point (P=0.001) showed a significant graded association with levels of ST2; furthermore, in-hospital death (P=0.003) and death/heart failure (P=0.004) were also significantly associated with higher ST2 levels. In a logistic regression analysis that controlled for important clinical factors, increasing levels of ST2 remained associated with death at 30 days (P=0.047). ST2 levels rose during the first day after infarction and were maximal at 12 hours; ST2 levels at 12 hours were also independently associated with death at 30 days (P<0.001). Serum levels of the interleukin-1 receptor family member ST2 predict mortality and heart failure in patients with acute myocardial infarction. These data suggest that ST2 may be a useful biomarker and that this novel inflammatory receptor may play a role in cardiac pathophysiology.