Abstract
Hyperglycemia plays an important role in the pathogenesis of diabetic complications including accumulation of methylglyoxal (MG), a highly reactive α-dicarbonyl metabolite of glucose degradation pathways. MG reacts in a non-enzymatic reaction with arginine residues of proteins which results in the formation of argpyrimidine. In several cell lines Hsp27 was found to be the most argpyrimidine containing protein. Whether Hsp27, which is high expressed in cardiac tissue, is also modified in heart, remains unclear. The aim of this investigation was to study the extent of Hsp27-modifications in heart failure and diabetes mellitus. Transmural myocardial samples from the left ventricle of explanted terminal failing hearts (diabetic: n=8; non-diabetic: n=8) and non-failing myocardium (NF) (n=6) without apparent signs of cardiac failure were collected. Cardiac tissue samples and rat cardiomyoblast cells H9c2, which were grown under normal and hyperglycaemic conditions, were investigated for the Hsp27-expression and modification by real-time PCR, western blotting and immunohistology. Hsp27 was significantly decreased (p<0.05) in CM/DM (cardiomyopathy and diabetes mellitus) compared to NF. Relating to Hsp27-expression the MG-modification in diabetic hearts was significantly increased 3-fold (p<0.05) compared to CM (cardiomyopathy) and 9-fold (p<0.05) compared to NF. Consistent with the results in human heart samples, high glucose levels induced a down-regulation of Hsp27 in H9c2-cells in a dose-dependent manner. We also found an increased MG-modification of Hsp27 with higher concentrations of glucose. Noteworthy, we detected Hsp27 in the myocardial intercalated disc and in the M-line of the sarcomer in human cardiac tissue by immunohistology. In summary, we observed an increased argpyrimidine-modification of Hsp27 in the myocardium of patients with terminal heart failure and diabetes in comparison to non-failing donor hearts and explanted hearts from patients with cardiomyopathy. The argpyrimidine-modification of Hsp27 probably results from the diabetic myocardial metabolism and might be of impact for the progress of a cardiomyopathy in patients with diabetes mellitus.
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