YY1 nitration participates in DbCM cardiomyocyte lipotoxicity by inhibiting ANXA3-induced microlipophagy

Diabetic cardiomyopathy (DbCM), a severe complication of type 2 diabetes mellitus (T2DM), is pathologically characterized by myocardial lipid deposition leading to cardiomyocyte lipotoxic injury. Annexin A3 (ANXA3), a lipid storage inhibitory protein highly expressed in cardiomyocytes, shows altered expression in T2DM tissues, yet its regulatory role in myocardial lipid deposition remains unclear. Enhanced nitrosative stress in T2DM cardiomyocytes induces abnormal protein nitration, and while anti-nitration therapy demonstrates cardioprotective effects, the nitration-mediated regulation of ANXA3 expression requires elucidation. This study investigates ANXA3's regulatory function in T2DM-induced lipid deposition and explores nitration-mediated mechanisms underlying ANXA3 dysregulated expression.

The T2DM mouse model was established using db/db mice to investigate the pathological mechanisms of DbCM. ANXA3 was overexpressed via cardiac-specific adeno-associated virus delivery to assess its role in lipid deposition. Peroxynitrite scavengers were administered to evaluate lipid droplet accumulation reversal. Site-directed mutagenesis plasmids identified tyrosine residues undergoing nitration.

1) Lipid deposition in the myocardial tissue of DbCM mice is related to downregulation of ANXA3 expression. ANXA3 regulates lipid droplet degradation in DbCM myocardial tissue though regulation of the microlipophagy-Rab7a pathway; 2) The transcription of ANXA3 gene was regulated positively by YY1; 3) In the pathological environment of T2DM, the ability of YY1 to transcribe the ANXA3 gene was decreased, which was related to its nitration at the Y¹⁸⁵ site of YY1 protein.

T2DM promoted cardiomyocyte YY1 nitration at Y¹⁸⁵ and Y³⁸³ residues. Y¹⁸⁵ site nitration inhibited YY1 nuclear translocation, thereby attenuating ANXA3 transcription. Microlipophagy emerged as the principal lipid droplet degradation mechanism in diabetic cardiomyocytes. ANXA3 downregulation suppresses Rab7a expression, impairing microlipophagy and causing lipid deposition that exacerbates DbCM progression. Therapeutic strategies targeting YY1 nitration inhibition or enhancing ANXA3-mediated microlipophagy demonstrate therapeutic potential for mitigating.