Updated project metadata. Diabetic cardiomyopathy (DCM) is characterized by myocardial remodeling that may al-ready 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 (NDPK-B)-deficient prediabetes and streptozoto-cin-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 bi-osynthesis pathway. Profiling of O-GlcNAc-associated proteins uncovered extensive re-modeling 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 reprogram-ming and remodeling of mitochondrial proteins. These findings identify early remodeling of the mitochondrial O-GlcNAc-associated proteome as a molecular signature of predia-betic cardiomyopathy and highlight respiratory complex I proteins as candidate targets for future mechanistic investigations.