Quercetin has also been reported to protect human retinal pigment epithelial (ARPE-19) cells against H2O2-induced injury [29], inhibit the expression of vascular cell adhesion molecule-1, ICAM-1, matrix metalloproteinase-2 (MMP-2) and MMP-9 in vascular endothelial growth factor-stimulated 661W cells [30], decrease TNF-α and IL-1β expression in rats with streptozotocin-induced diabetes [31], and reduce the production of IL-6, IL-8 and MCP-1 in 4-hydroxynonenal-stimulated ARPE-19 cells [15]. This evidence concerns the gene MMP2 and diabetes mellitus.