Betaine can inhibit the activation of protein kinase B (Akt) in the retina of STZ-induced diabetic rats, thereby attenuating the increase in vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1-alpha (HIF-1α) expression and inhibiting neovascularization to delay diabetic retinopathy-associated complications (59) (Figure 4C). Here, HIF1A is linked to diabetic retinopathy.