Figure 11.

Schematic diagram of the relationship between the arginine–proline metabolism pathway and DR. In the retina, arginine is metabolized through two distinct pathways. The diabetic status could cause increased proline to damage the retinal pigment epithelium (RPE) and induce cellular proliferation and fibrosis. Meanwhile, hyperglycemia may lead to a deficiency of NO and result in consequential endothelial cell dysfunction, impaired vasodilation, and an increased level of oxygen and nitrogen reactive species.