Diabetes induces modifications in costameric proteins and increases cardiomyocyte stiffness.

Several studies have demonstrated that diabetes mellitus can increase the risk of cardiovascular disease and remains the principal cause of death in these patients. Costameres connect the sarcolemma with the cytoskeleton and extracellular matrix, facilitating the transmission of mechanical forces and cell signaling. They are related to cardiac physiology because individual cardiac cells are connected by intercalated discs that synchronize muscle contraction. Diabetes impacts the nanomechanical properties of cardiomyocytes, resulting in increased cellular and left ventricular stiffness, as evidenced in clinical studies of these patients. The question of whether costameric proteins are affected by diabetes in the heart has not been studied. This work analyzes whether type 1 diabetes mellitus (T1DM) modifies the costameric proteins and coincidentally changes the cellular mechanics in the same cardiomyocytes. The samples were analyzed by immunotechniques using laser confocal microscopy. Significant statistical differences were found in the spatial arrangement of the costameric proteins. However, these differences are not due to their expression. Atomic force microscopy was used to compare intrinsic cellular stiffness between diabetic and normal cardiomyocytes and obtain the first elasticity map sections of diabetic living cardiomyocytes. Data obtained demonstrated that diabetic cardiomyocytes had higher stiffness than control. The present work shows experimental evidence that intracellular changes related to cell-cell and cell-extracellular matrix communication occur, which could be related to cardiac pathogenic mechanisms. These changes could contribute to alterations in the mechanical and electrical properties of cardiomyocytes and, consequently, to diabetic cardiomyopathy. The structural organization of cardiomyocyte proteins is critical for their efficient functioning as a contractile unit in the heart. This work shows that diabetes mellitus induces significant changes in the spatial organization of costamere proteins, tubules, and intercalated discs. We obtained the first elasticity map sections of living diabetic cardiomyocytes. The results show statistical differences in the map sections of diabetic and control cardiomyocytes, with diabetic cardiomyocytes being stiffer than normal ones.