Transcription factor EB as a novel target for dimethyl fumarate to restore endothelial function in diabetes

Diabetes mellitus-associated endothelial dysfunction represents a pivotal early event in diabetic vasculopathy, linking metabolic derangements to vascular injury. Dimethyl fumarate (DMF), an FDA-approved drug for multiple sclerosis and psoriasis, exhibits potent anti-inflammatory and antioxidant properties, yet whether it protects against diabetic endothelial dysfunction and the underlying molecular mechanisms remain unclear. Here, diabetic db/db mice and the non-diabetic db/m⁺ littermates were treated with DMF (100 mg·kg^-1·d^-1) or vehicle for 4 weeks, and vascular function in aortic and mesenteric artery rings was assessed by wire myography. Human umbilical vein endothelial cells (HUVECs) and endothelial cell (EC)-specific Tfeb knockout (Tfeb^ECKO) mice were employed to investigate the target of DMF in vitro and in vivo. DMF restored the impaired endothelium-dependent relaxations (EDRs) in db/db mouse aortas and insulin-induced relaxations in mesenteric arteries, improved glucose tolerance, reduced aortic endothelial mitochondrial ROS (mito-ROS) accumulation, and lowered the expression of inflammatory markers. IL-1β induced phosphorylation and cytoplasmic retention of TFEB (indicative of TFEB inhibition), mito-ROS production, and inflammatory responses in HUVECs and mouse aortas, all of which were reversed by DMF pretreatment. These protective effects of DMF were largely reversed by TFEB knockdown in HUVECs or in aortas of Tfeb^ECKO mice. RNA sequencing data analysis revealed a substantial overlap between DMF-regulated and TFEB-overexpression transcriptional profiles, implicating a role of TFEB in DMF-induced suppression of inflammatory and oxidative pathways. Together, DMF ameliorates endothelial dysfunction in diabetes by inhibiting TFEB phosphorylation and restoring TFEB nuclear activity. Endothelial TFEB represents a critical mediator responsible for the vaso-protective effects of DMF and a promising therapeutic target for the treatment of diabetic vascular complications.