SIRT1 and diabetic retinopathy: Activation of SIRT1 by Resveratrol maintains the epithelial barrier by increasing the expression of TJ proteins ZO1, Occludin and Claudin1 (Ma et al., 2014), while it negatively regulates MMP9 in diabetic retinopathy, and reduction of SIRT1 levels through oxidative stress confers an increase in MMP9 (Kowluru et al., 2014).