Formononetin attenuates early diabetic retinal and renal microvascular injury associated with EGR1/VEGF-related endothelial responses

Formononetin (FMN) is a natural isoflavone found in several medicinal plants. Its effects on diabetic retinal and renal microvascular injury and EGR1/VEGF-related endothelial responses remain incompletely defined.

To assess whether FMN attenuates early diabetes-associated retinal and renal injury and whether EGR1 is involved.

Alloxan-induced diabetic rabbits received FMN orally at 25 mg/kg/day from Week 4 to Week 16 after pretreatment renal and OCT/OCTA assessment. Renal function, histopathology, retinal flat mounts, longitudinal OCTA, and tissue EGR1/VEGF expression were examined. High-glucose-treated retinal, renal microvascular, and umbilical vein endothelial cells were used for functional assays. EGR1 overexpression, VEGFA promoter reporter assays, SPR, docking, and molecular dynamics simulations were also performed.

FMN lowered serum creatinine, blood urea nitrogen, and urinary albumin-to-creatinine ratio, and reduced renal histopathological injury. It also attenuated retinal capillary loss, retinal thinning, and OCTA abnormalities despite persistent hyperglycemia. Retinal and renal tissues from FMN-treated rabbits showed lower EGR1 and VEGF expression. In endothelial cells, FMN reduced EGR1 and VEGF expression, abnormal tube formation, permeability, invasion, ROS, and inflammatory mediator release, while increasing NO-related signals. EGR1 overexpression weakened several effects and increased VEGFA promoter activity through the predicted EGR1-binding sequence. SPR detected FMN–EGR1 binding with a K_D of 3.245 μM. Computational analyses provided structural context.

FMN attenuated early diabetes-associated retinal and renal injury and was linked to EGR1/VEGF-related endothelial responses. The data support EGR1 involvement but do not establish it as the sole target or mediator of FMN.