Palmitoylation-driven upregulation of NKAα2 improves diabetic cardiomyopathy: a role for the fumarate hydratase/fumarate metabolic pathway

The sodium pump Na⁺/K⁺-ATPase (NKA) plays an essential role in maintaining cellular ion homeostasis. Dysregulation of its α2 subunit (NKAα2) has been implicated in cardiovascular and metabolic diseases, yet its contribution to diabetes-induced cardiac dysfunction remains poorly defined. Therefore, this study aimed to elucidate the role of NKAα2 in diabetic cardiomyopathy (DCM). We performed gain-of-function experiments to investigate the effects of NKAα2 on DCM-associated pathological processes. Both in vivo mouse models and in vitro cardiomyocyte systems were employed to ensure mechanistic consistency. We found that both NKA activity and NKAα2 protein, rather than its transcriptional level, were significantly downregulated in the hearts of diabetic mice and high glucose/palmitic acid (HG/PA)-incubated NRCMs. Cardiac-specific overexpression of NKAα2 markedly alleviated myocardial injury and improved cardiac function in diabetic mice. Consistently, NKAα2 overexpression attenuated HG/PA–induced hypertrophy and apoptosis in primary neonatal rat cardiomyocytes (NRCMs). Mechanistically, ATP-1 mediated de-palmitoylation increased NKAα2 in the mitochondrial-enriched fraction, where it interacted with E3 ubiquitin protein ligase 1 (MUL1), which was responsible for NKAα2 ubiquitination and degradation. Metabolomic analyses revealed that NKAα2 downregulation dissociated Mul1 from fumarate hydratase (FH), leading to increased FH expression and decreased intracellular fumarate levels. Exogenous fumarate administration mimicked the cardioprotective effects of NKAα2 overexpression and mitigated the damage caused by NKAα2 deficiency in HG/PA-treated cardiomyocytes. Overexpression of FH blocked the effects of NKAα2 on diabetic cardiac dysfunction. Collectively, these findings identify NKAα2 as a critical regulator in DCM. These results also underscore the requirement of tightly controlled FH activity and fumarate metabolism for NKAα2-dependent cardioprotection.