DGK Herztage 2025. Clin Res Cardiol (2025). https://doi.org/10.1007/s00392-025-02737-x
1Universitätsklinikum Heidelberg Klinik für Innere Med. III, Kardiologie, Angiologie u. Pneumologie Heidelberg, Deutschland; 2Heidelberg Univerisity Hospital, Heidelberg Internal Medicine III Heidelberg, Deutschland; 3Universität Greifswald Interfaculty Institute of Genetics and Functional Genome Research Greifswald, Deutschland; 4MSH Medical School Hamburg Hamburg, Deutschland
Background:
Cardiometabolic diseases, including heart failure with preserved ejection fraction (HFpEF), insulin resistance, and metabolic dysfunction-associated steatotic liver disease (MASLD), represent growing global health challenges, driven by shared molecular mechanisms. E3 ubiquitin ligases, key regulators of protein turnover, are increasingly recognized for their roles in metabolic adaptation under stress. Among them, TRIM32 (T32) is highly expressed in the heart, yet its function in cardiometabolic regulation remains largely unexplored. While previous studies have linked T32 to skeletal muscle physiology and hepatic insulin signaling, its role in cardiac glucose metabolism and systemic energy balance is not well understood. This study investigates the role of T32 in cardiomyocyte metabolism and cardiometabolic health.
Methods:
We employed neonatal rat ventricular cardiomyocytes (NRVCMs) to overexpress T32 and disease-associated T32 mutants. Molecular and functional analyses, including immunoblotting, qPCR, glucose uptake assays, and multi-omics profiling, were performed to identify T32-dependent pathways. In silico modeling predicted protein interactions, which were validated through pulldown assays. A global T32 knockout (KO) mouse model was aged and assessed via echocardiography, glucose and insulin tolerance tests, histological analysis, and molecular profiling of cardiac, hepatic and adipose tissue. The KO mice were also subjected to Chow or High-Fat Diet (HFD) to evaluate the metabolic impact of T32 deficiency under dietary stress, using the same analytical approaches.
Results:
T32 expression was markedly upregulated in NRVCMs under high-glucose conditions. Overexpression of T32 induced cardiomyocyte apoptosis and disrupted glucose metabolism, with proteomic analysis revealing downregulation of key glycolytic enzymes, including GLUT4, an insulin-regulated glucose transporter. Surprisingly, glucose uptake increased despite reduced GLUT4 levels, indicating dysfunctional glucose handling. Computational modeling revealed a putative binding interface between T32 and GLUT4, which was validated via pulldown experiments identifying GLUT4 as a novel bona fide T32 substrate. Interestingly, aged KO mice exhibited classical features of metabolic syndrome and HFpEF, including increased body weight, adiposity, and impaired insulin tolerance. Echocardiographic analysis revealed diastolic dysfunction (elevated E/E′ ratio) with preserved ejection fraction. T32 deficiency also led to increased metabolic remodeling, with preserved cardiac GLUT4 levels consistent with in vitro findings. Under HFD conditions, KO mice exhibited an exacerbated metabolic phenotype, characterized by enhanced adiposity, combined glucose and insulin intolerance resembling type 2 diabetes, and severe adipocyte hypertrophy. Moreover, liver histology revealed the development of steatosis consistent with MASLD, highlighting aggravated metabolic dysfunction under HFD.
Conclusion:
Our data show that T32 acts as a critical regulator of cardiac glucose metabolism and systemic energy balance. It mediates cardiomyocyte apoptosis and metabolic remodeling, in part through interaction with GLUT4. Loss of T32 results in profound cardiometabolic dysfunction, including HFpEF, insulin resistance, and MASLD. These findings identify T32 as a key molecular nexus linking cardiac and systemic metabolism, offering new avenues for therapeutic intervention in cardiometabolic diseases.