Serum protein of 135-kDa molecular weight--a molecular signal for cardiac hypertrophy

Molecular form and concentration of serum α2-macroglobulin in diabetes

α₂-Macroglobulin is a highly abundant serum protein involved in the development of atherosclerosis and cardiac hypertrophy. However, its circulating molecular form and exact concentrations in human health/diseases are not known. Blue native-polyacrylamide gel electrophoresis of human serum was used to confirm the native conformation of α₂-macroglobulin. We created an enzyme-linked immunosorbent assay suitable for quantifying its circulating molecular form and undertook a cross-sectional study to measure its serum levels in 248 patients with diabetes mellitus and 59 healthy volunteers. The predominant circulating molecular form of α₂-macroglobulin was the tetramer, whereas its dimer was detectable in patients with high serum levels of α₂-macroglobulin. The serum α₂-macroglobulin concentration was not associated with glycated hemoglobin or any other glycemic variable as evaluated from 48-h continuous glucose monitoring, but showed close correlation with left ventricular posterior wall thickness, carotid artery intima-media thickness, urinary albumin:creatinine ratio (ACR) and brachial–ankle pulse wave velocity (baPWV). Multivariate analysis revealed only the ACR and baPWV to be independent variables influencing serum levels of α₂-macroglobulin. Thus, an increased ACR and baPWV are associated with higher serum concentrations of α₂-macroglobulin, and the latter may contribute to the mechanism by which albuminuria increases the risk of developing cardiovascular diseases.

Role of cardiac isoform of alpha-2 macroglobulin in diabetic myocardium

Earlier studies from one of the investigator's laboratory have demonstrated the presence of a high molecular weight protein (182 kDa) in the blood serum of laboratory animals subjected to pressure-induced cardiac hypertrophy and suggested that this protein may be involved in the development of cardiac hypertrophy. Studies have shown that this protein is also involved in earlier stages of cardiac complications associated with diabetes, but the role of this protein in diabetic heart is less understood. So we aimed to check whether this protein is having any protective role in diabetic heart. The protein was purified from serum of rats induced with cardiac hypertrophy and the purified protein was injected through tail vein of diabetic rats for further studies. The results of various antioxidant enzymes and the TBARS levels have indicated the antioxidant activity of this protein. Real-time PCR analysis of gene expression revealed the upregulation of certain muscle-specific genes like β-MHC, MLC-2, and skeletal α actin in diabetic group and also in presence of 182-kDa protein. The results further showed a down regulation of genes such as cardiac α-actin and α- MHC implicating the role of this protein in the development of cardiac hypertrophy in diabetes. Increased cardiac hypertrophy as revealed by the expression of various genes and improved antioxidant potential in presence of 182 kDa protein in diabetes at the earlier stages is beneficial for counteracting the myocardial damage associated with diabetes.

Cardiac isoform of alpha 2 macroglobulin, an early diagnostic marker for cardiac manifestations in AIDS patients

This study investigated the possible role of the cardiac isoform of alpha 2-macroglobulin (CA2M) as an early diagnostic marker for HIV-associated cardiovascular manifestations. A total of 349 samples were analysed by Western blot and quantified by sandwich enzyme-linked immunosorbent assay. The levels of CA2M present in sera of HIV-associated cardiac diseases were significantly higher than those of HIV without cardiac involvement and healthy sera. CA2M may act as a novel diagnostic marker to identify cardiac manifestations in HIV/AIDS patients.

Cardiac isoform of alpha-2 macroglobulin—A new biomarker for myocardial infarcted diabetic patients

Cardiac isoform of alpha-2 macroglobulin [cardiac alpha2M] has been shown to be an early marker in cardiac hypertrophy and left ventricular mass in humans. We, here, for the first time report its presence in myocardial infarcted humans and tried to explore the possibility of using this protein as a novel diagnostic marker for myocardial infarcted diabetic patients. A total of 260 samples were analyzed in this study for the presence of cardiac alpha2M. These include 55 patients of diabetic with post myocardial infarction [PMI], 45 diabetic patients without PMI, 60 patients of PMI alone and 100 controls without any ailments. Levels of cardiac alpha2M present in the sera of diabetic patients with PMI are significantly higher than that of normal human sera and diabetic patients without PMI but not with PMI alone group, suggesting this protein as a marker for PMI itself. However, our results reveal that cardiac alpha2M could be a valuable marker for the diagnosis of myocardial infarcted diabetic patients and differentiating them from diabetic patients without myocardial infarction by sandwich ELISA.