Myocardial cell death in human diabetes

Area of Science:

• Cardiovascular Medicine
• Endocrinology
• Cell Biology

Background:

• The renin-angiotensin system (RAS) is implicated in diabetic complications.
• Diabetes can lead to dilated myopathy, characterized by cardiac hypertrophy, dilation, and impaired function.
• Coexisting hypertension exacerbates myocardial damage in diabetic patients.

Purpose of the Study:

• To investigate the roles of Angiotensin II (Ang II) and oxidative stress in diabetic cardiomyopathy.
• To quantify apoptosis and necrosis in cardiac cells of diabetic and diabetic-hypertensive patients.

Main Methods:

• Analysis of ventricular myocardial biopsies from diabetic and diabetic-hypertensive patients.
• Quantitative evaluation of Ang II labeling and nitrotyrosine (oxidative stress marker).
• Measurement of myocyte, endothelial cell, and fibroblast apoptosis and necrosis.

Main Results:

• Diabetic hearts exhibited hypertrophy, dilation, and reduced ventricular performance, worsened by hypertension.
• Diabetes significantly increased apoptosis and necrosis in myocytes, endothelial cells, and fibroblasts.
• Combined diabetes and hypertension led to greater increases in necrosis and Ang II/nitrotyrosine levels compared to diabetes alone.

Conclusions:

• Local Angiotensin II (Ang II) upregulation in diabetes contributes to cardiac oxidative damage.
• Oxidative stress, indicated by nitrotyrosine, is present in apoptotic and necrotic cardiac cells.
• The renin-angiotensin system plays a critical role in the pathogenesis of diabetic cardiomyopathy, particularly when hypertension is present.