OTUD5 protects against diabetic cardiomyopathy by preventing cardiomyocyte apoptosis through deubiquitination and stabilization of FOXO3a

Diabetic cardiomyopathy (DCM) represents one of the serious complications associated with diabetes. The role of deubiquitinating enzymes in the development of DCM has garnered increasing attention. In this study, we systematically examined the functional role and regulatory pathway involving the deubiquitinating enzyme OTUD5 in DCM. We evaluated the role of cardiomyocyte-specific knockout or overexpression of OTUD5 in ventricular remodeling of type 2 diabetic mice. Liquid chromotography with mass spectrometry/mass spectrometry analysis combined with Co-IP was used to identify FOXO3a protein, a transcriptional factor, as an interacting protein of OTUD5. We verified alterations in the level of mitophagy downstream of FOXO3a, thereby refining the mechanism underlying the regulation of diabetic cardiomyopathy by the OTUD5-FOXO3a interaction. Furthermore, pharmacological inhibition of FOXO3a was employed to further clarify the biological function of this interaction. Our findings demonstrate that OTUD5 is upregulated in cardiomyocytes from mouse models with DCM. In high-fat diet/streptozotocin-induced type II diabetic mice, selective deletion of OTUD5 in cardiomyocytes significantly exacerbates cardiac dysfunction and ventricular remodeling. Conversely, targeted overexpression of OTUD5 specifically in cardiomyocytes ameliorated cardiac dysfunction and mitigated ventricular remodeling in diabetic mice. Mechanistically, protein interaction analysis revealed FOXO3a as a direct substrate for OTUD5. The OTUD5-mediated deubiquitination removes K48-linked polyubiquitin chains from FOXO3a, thereby stabilizing the protein to activate the autophagy pathway in damaged cardiomyocytes. This process restores mitochondrial homeostasis and reduces apoptosis in cardiomyocytes. Our research identifies OTUD5 as a critical regulator of cardiac mitochondrial homeostasis through the OTUD5-FOXO3a-autophagy axis, indicating OTUD5 as a promising therapeutic target for treating DCM.