About 50% of diabetics with diabetic cardiomyopathy show pathologic evidence for microangiopathy such as sub-endothelial and endothelial fibrosis, compared to only 21% of non-diabetic heart failure patients. Over the years, several hypotheses were postulated to explain the endothelial dysfunction observed in diabetes. It was hypothesized that the extracellular hyperglycemia leads to an intracellular hyperglycemia in cells unable to regulate their glucose uptake, most predominantly, endothelial cells. Indeed, while hepatocytes and myocytes have mechanisms allowing them to internalize their glucose transporter, endothelial cells do not possess this ability. The consequences of increased intracellular glucose concentration are fourfold, all resulting from increasing concentration of glycolytic intermediates upstream of the rate-limiting glyceraldehyde-3-phosphate reaction which is inhibited by mechanisms activated by increased free radical formation, common in diabetes. Four pathways, enumerated below all explain part of the diabetic complications. First, it has been widely reported since the 1960s that hyperglycemia causes an increase in the flux through aldose reductase and the polyol pathway. Increased activity of the detoxifying aldose reductase enzyme leads to a depletion of the essential cofactor NADH, thereby disrupting crucial cell processes. Second, increasing fructose 6-phosphate, a glycolysis intermediate, will lead to increased flux through the hexosamine pathway. This produces N-acetyl glucosamine that can add on serine and threonine residues and alter signaling pathways as well as cause pathological induction of certain transcription factors. Third, hyperglycemia causes an increase in diacylglycerol, which is also an activator of the Protein Kinase C (PKC) signaling pathway.
An analysis of major clinical trials shows that diabetic patients with heart failure benefit from such a therapy to a similar degree as non-diabetics. Similarly, beta blockers are also common in the treatment of heart failure concurrently with ACE inhibitors. == References ==