Oxidative stress plays a pivotal role in the development of
diabetes complications, both microvascular and cardiovascular. The metabolic abnormalities of diabetes cause mitochondrial
superoxide overproduction in endothelial cells of both large and small vessels, as well as in the myocardium. This increased
superoxide production causes the activation of 5 major pathways involved in the pathogenesis of complications:
polyol pathway flux, increased formation of AGEs (
advanced glycation end products), increased expression of the receptor for AGEs and its activating
ligands, activation of
protein kinase C isoforms, and overactivity of the
hexosamine pathway. It also directly inactivates 2 critical antiatherosclerotic
enzymes,
endothelial nitric oxide synthase and
prostacyclin synthase. Through these pathways, increased intracellular
reactive oxygen species (ROS) cause defective angiogenesis in response to
ischemia, activate a number of proinflammatory pathways, and cause long-lasting epigenetic changes that drive persistent expression of proinflammatory genes after glycemia is normalized ("hyperglycemic memory").
Atherosclerosis and
cardiomyopathy in
type 2 diabetes are caused in part by pathway-selective
insulin resistance, which increases mitochondrial ROS production from
free fatty acids and by inactivation of antiatherosclerosis
enzymes by ROS. Overexpression of
superoxide dismutase in transgenic diabetic mice prevents
diabetic retinopathy, nephropathy, and
cardiomyopathy. The aim of this review is to highlight advances in understanding the role of metabolite-generated ROS in the development of
diabetic complications.