Electrical conduction system apoptosis in type II diabetes mellitus.

Even though apoptosis is known to be associated with various cardiovascular pathologies, its presence in cardiac nodal tissue in adults was only scarcely researched. Cardiomyocyte apoptosis was associated with diabetic cardiovascular pathology. Our main objective was to test whether programmed cell death is present in nodal tissue in type II diabetes mellitus and, if present to characterize it. The study was designed as a qualitative one. We used autopsy samples of hearts from 10 patients (56 to 73-year-old, 6:4 male to female ratio), positive for type II diabetes mellitus. Samples from sinoatrial and atrioventricular nodes were stained with Hematoxylin-Eosin. For immunohistochemistry, we used primary antibodies for caspases 3 and 9, cathepsin B, and TRADD. Nodal tissue in all samples was characterized by diffuse interstitial fibrosis and chronic ischemic lesions; nuclear damage and foci of irreversible ischemic necrosis intermingled with isles of relatively morphologically normal myocytes. Sinoatrial and atrioventricular nodes were caspase-3 and -9 positive, and also cathepsin-B-positive, suggesting an overlap between apoptotic and necrotic mechanisms. Central area of the sinus node seemed to have the most severe lesions. As a conclusion, nodal apoptosis is present in nodal tissue in type II diabetes mellitus; it involves the intrinsic pathway and associated concomitant and/or post-apoptotic necrosis.