MMP9 and retinal disorder: Recent studies have indicated that quercetin at 150 mg/kg improved retinopathy in STZ-induced rats by reducing the expression of monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase-9 (MMP-9), and vascular endothelial growth factor (VEGF), and decreased protein damage caused by oxidative stress [49,141].