Diabetic retinopathy involves early retinal vascular barrier breakdown and pericyte loss, yet the initiating molecular events remain poorly defined. Vascular endothelial cadherin (VE-cadherin), a key regulator of endothelial integrity, is notably reduced in diabetic and prediabetic nucleoside diphosphate kinase B–deficient (NDPKB-deficient) mouse retinas, particularly in the retinal deep capillary layer, and this decline precedes pericyte loss. In vitro, high glucose (HG) and NDPKB deficiency induced VE-cadherin Y685 phosphorylation, promoting its junctional internalization, activating the hexosamine biosynthesis pathway, and increasing angiopoietin 2 (Ang2), resulting in impaired endothelial barrier function and disrupting pericyte attachment. Preventing Y685 phosphorylation through VE-cadherin Y685F mutation blocked these HG- and NDPKB-driven pathological effects. Pharmacological intervention experiments identified protein O-linked β-N-acetyl glucosamine (O-GlcNAc) modification as a mediator of Y685-dependent Ang2 upregulation. In vivo, VE-cadherin Y685F-knockin mice were protected from diabetes- and prediabetes-induced vascular hyperpermeability, exhibited reduced protein O-GlcNAcylation and Ang2 induction, and maintained neuronal function. O-GlcNAc–enriched retinal proteomics further showed that the Y685F mutation restored balanced neurovascular and mitochondrial pathways. These findings highlight the potential of targeting VE-cadherin Y685 phosphorylation as a promising therapeutic approach to maintain retinal vascular integrity and attenuate the pathological progression of diabetic and prediabetic retinopathy. Disrupting a harmful protein change protects retinal blood vessels in diabetes, reducing leakage and preventing loss of supportive cells that keep vessels stable and healthy.

Diabetic cardiomyopathy (DCM) is characterized by myocardial remodeling that may already be evident during prediabetes, yet the molecular alterations accompanying these early changes remain poorly understood. The present study examined mouse models of Nucleoside diphosphate kinase B (NDPK-B)-deficient prediabetes and streptozotocin-induced diabetes using O-GlcNAc-associated proteomic profiling to define stage-specific molecular alterations during the progression from prediabetic to diabetic cardiomyopathy. Both models exhibited increased left ventricular extracellular matrix deposition and impaired diastolic function, together with activation of the hexosamine biosynthesis pathway. Profiling of O-GlcNAc-associated proteins uncovered extensive remodeling of the mitochondrial proteome already at the prediabetic stage, with respiratory complex I among the most prominently altered targets, alongside changes in substrate metabolism and inflammatory signaling. In overt DCM, the putative O-GlcNAc proteomic profile was associated with a shift toward wider lipid-dependent metabolic reprogramming and remodeling of mitochondrial proteins. These findings identify early remodeling of the mitochondrial O-GlcNAc-associated proteome as a molecular signature of prediabetic cardiomyopathy and highlight respiratory complex I proteins as candidate targets for future mechanistic investigations.