FLT1 and diabetes mellitus: VEGFR1 blockade significantly inhibited diabetes-related vascular leakage, leukocytes-endothelial cell (EC) adhesion (or retinal leukostasis), expression of intercellular adhesion molecule- (ICAM-) 1 protein, abnormal localization and degeneration of the tight junction protein zonula occludens- (ZO-) 1, and the cell adhesion protein vascular endothelial (VE) cadherin.