Elevated serum glyceraldehyde phosphate dehydrogenase activity following acute myocardial infarction

A Quantitative Serum Proteomic Analysis Helps to Explore the Comprehensive Mechanism and Identify Serum Biomarkers of Shengmai Injection's Effect on Isoproterenol-Induced Myocardial Ischemia in Rats

Shengmai injection (SMI), a traditional Chinese medicine formula with the nature of multicomponent and multi-target, has been widely used in clinic for treating cardiovascular diseases in China; however, its comprehensive mechanism of action remains unclear. In this study, a TMT-based quantitative serum proteomics was performed to explore SMI’s global mechanism and help identify serum biomarkers of its effect on isoproterenol (ISO)-induced myocardial ischemia rats. The results of TMT-based proteomic analysis identified 227, 100, and 228 differentially expressed proteins (DEPs) for the model compared to the control group, SMI pretreatment + model compared to the model group, and SMI pretreatment + model compared to the control group, respectively. Based on bioinformatics analyses of gene ontology (GO), KEGG pathways, and the protein-protein interaction (PPI) networks for the DEPs, it is concluded that the comprehensive mechanism of SMI’s effect on ISO-induced myocardial ischemia injury includes regulation of energy metabolism, reducing endothelial cell permeability, regulation of vessel and cardiac contractility, anti-inflammation, and prevention of cell apoptosis. Furthermore, 10 common DEPs were found, and six of them were regulated in model vs. control group, while back-regulated in SMI pretreatment + model vs. model group. Among them, three functional proteins of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Fas apoptotic inhibitory molecule 3 (FAIM3), and uncharacterized protein (M0R5J4), which were verified by the PRM analysis, might be the potential serum biomarkers on SMI’s effects. Overall, this serum proteomics of SMI not only provides insights into the comprehensive mechanism underlying SMI’s effects on ischemic heart disease but also helps identify serum biomarkers for directing SMI’s cardioprotective effects.

Occurrence of a multimeric high-molecular-weight glyceraldehyde-3-phosphate dehydrogenase in human serum

Cellular glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a phylogenetically conserved, ubiquitous enzyme that plays an indispensable role in energy metabolism. Although a wealth of information is available on cellular GAPDH, there is a clear paucity of data on its extracellular counterpart (i.e., the secreted or extracellular GAPDH). Here, we show that the extracellular GAPDH in human serum is a multimeric, high-molecular-weight, yet glycolytically active enzyme. The high-molecular-weight multimers of serum GAPDH were identified by immunodetection on one- and two-dimensional gel electrophoresis using multiple antibodies specific for various epitopes of GAPDH. Partial purification of serum GAPDH by DEAE Affigel affinity/ion exchange chromatography further established the multimeric composition of serum GAPDH. In vitro data demonstrated that human cell lines secrete a multimeric, high-molecular-weight enzyme similar to that of serum GAPDH. Furthermore, LC-MS/MS analysis of extracellular GAPDH from human cell lines confirmed the presence of unique peptides of GAPDH in the high-molecular-weight subunits. Furthermore, data from pulse-chase experiments established the presence of high-molecular-weight subunits in the secreted, extracellular GAPDH. Taken together, our findings demonstrate the presence of a high-molecular-weight, enzymatically active secretory GAPDH in human serum that may have a hitherto unknown function in humans.

Inhibitor of apoptosis protein-like protein-2 as a novel serological biomarker for breast cancer

Inhibitor of apoptosis protein-like protein-2 (ILP-2) has only been detected in the testis and in lymphoblastoid cells. Although previous studies have not reported the presence of ILP-2 in breast cancer tissues, this study indicates the presence of ILP-2 in breast cancer serum samples. To validate whether ILP-2 is a novel serological biomarker for breast cancer, we conducted two-dimensional gel electrophoresis (2DE) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry analysis on 400 breast cancer serum samples and 40 non-cancer serum samples (i.e., healthy controls). We then performed a Western blot analysis of 10 breast cancer serum samples and 10 non-cancer serum samples. Finally, we analyzed 35 serum samples from healthy controls or subjects with breast cancer, other types of cancer, galactophore hyperplasia or breast cancer post-surgery by using 2DE and enzyme-linked immunosorbent assay. Our results indicate that ILP-2 is a novel breast cancer biomarker in the peripheral blood.

Evaluation of myocardial infarction with enzymatic indices

The severity of myocardial damage appears to be a common denominator contributing to electrophysiologic derangements, impaired ventricular function, and prognosis after myocardial infarction. Physiologically based models of processes affecting appearance and disappearance of CPK from the circulation may improve predictions and estimates of infarct size. Elevation of serum MB CPK isoenzyme activity appears to be a highly sensitive and specific indicator of myocardial injury. Despite the limitations discussed, recently developed enzymatic methods for detection, projection, and quantification of infarct dize have demonstrated that the extent of myocardial injury may be limited in selected patients by appropriate therapeutic measures. Further investigation may help to define the intervals between the onset of infarction and implementation of therapeutic maneuvers during which myocardial protection is possible, and may help to identify and differentiate inter ventions which salvage myocardium, those which improve cardiac performance without altering infarct size, and those which augment cardiac injury despite improving hemodynamics. Thus, in conjunction with electrophysiologic, radioisotopic, and hemodynamic techniques, enzymatic estimates and projection of infarct size should facilitate increased understanding of factors influencing the evolution of infarction and hasten development of effective therapeutic interventions designed to reduce myocardial damage.

The assay of glycogen phosphorylase in human blood serum and its application to the diagnosis of myocardial infarction

Methods are described (a) for the estimation of glycogen phosphorylase activity (EC 2.4.1.1) in human blood serum based on the chemical determination of liberated orthophosphate or on the enzymic determination of glucose 1-phosphate in a coupled assay system and (b) for the electrophoretic separation of isophosphorylases I, II, and III in human. Glycogen phosphorylase activities ranging from 1.5 to 18 mU/ml were found in the serum of patients with acute myocardial infarction. In contrast, no glycogen phosphorylase activity was detected in the serum of healthy persons. The enzyme appears in the serum 4 hours after the onset of the infarction and reaches a maximum after 20 to 30 hours. Acrylamide gel electrophoresis of serum after a myocardial infarction revealed only muscle isophosphorylase I, the isoenzyme characteristic of the heart. No phosphorylase activity was detected in serum of patients with angina pectoris, endocarditis, and uncomplicative congestive heart failure. From these findings it appears that the new serum enzyme test may prove to be a valuable addition to presently existing methods for the early differential diagnosis of acute myocardial infarction.

The importance of identification of the myocardial-specific isoenzyme of creatine phosphokinase (MB form) in the diagnosis of acute myocardial infarction

Serial plasma determinations of the isoenzymes of CPK were performed in all patients (376) admitted to a coronary care unit during a 12-month period with diagnosis of possible acute myocardial infarction. Results were compared with data from other enzyme studies and from the electrocardiogram. An attempt was made to determine the incidence of falsely positive CPK-MB (myocardial-specific form). "No acute infarction" was diagnosed in all patients in whom neither total CPK nor the isoenzymes of LDH indicated myocardial necrosis, and in whom there were no QRS changes on ECG. Incidence of falsely negative CPK isoenzyme data was also determined. All patients, in whom total CPK was transiently elevated, and LDH 1 exceeded LDH 2 , and new QRS changes occurred, were termed "definite" acute infarction. CPK-MB form was present in all 55 of these (0% false negative). Therefore, determination of the isoenzymes of CPK by this method provides both a sensitive and specific indication of acute myocardial infarction.

Estimation of infarct size in man and its relation to prognosis

Infarct size was assessed quantitatively in 33 patients with acute myocardial infarction with a new technic based on analysis of serial serum creatine phosphokinase (CPK) changes to determine its relationship to prognosis. We have recently measured infarct size in the conscious dog with this method which takes into account CPK distribution space, fractional disappearance rate, proportion degraded in myocardium, and proportion released into the circulation, and we have validated the method by measurement of myocardial CPK depletion in the same animals. In the present study, CPK activity (determined spectrophotometrically) and isoenzyme profiles (assayed electrophoretically) were measured in patient serum samples obtained every 2 hours. Infarct size was estimated by mathematical analysis of serial CPK changes utilizing the method previously developed in the conscious dog model. CPK isoenzyme profiles demonstrated prominent anodal bands, absent from normal serum, indicating that enzyme elevations reflected CPK released from heart rather than skeletal muscle. In 19 class I-II survivors (New York Heart Association) estimated infarct size was 31 ± 4 CPK-gram-equivalents (CPK-g-Eq). It was significantly larger ( P < 0.01), 103 ± 14, in nine patients who died and in four class III or IV survivors (91 ± 8). Estimation of cumulative infarct size differentiated patients with electrocardiographic changes and clinical sequelae from complications such as pericarditis from those patients with extension of infarction. Thus, infarct size can be assessed quantitatively in patients with acute myocardial infarction and provide a useful diagnostic and prognostic index based on the extent of myocardial damage.