The canonical Wnt/β-catenin signaling pathway upregulates carbonic anhydrase 2 via transcription factor 7-like 2 to promote cardiomyopathy in type 2 diabetic mice

Excessive activation of the canonical Wnt/β-catenin pathway contributes to the development of diabetic cardiomyopathy (DCM). Transcription factor 7-like 2 (TCF7L2) is the main β-catenin partner of the TCF family in adult human hearts. Carbonic anhydrase 2 (CA2) is implicated in various hypertrophic cardiomyopathy. In this study, we aimed to investigate the role of the Wnt/β-catenin/TCF7L2 signaling and CA2 in the development of DCM. Streptozotocin (STZ)/high-fat diet (HFD)-induced diabetic mice and high glucose-stimulated neonatal rat cardiomyocytes (NRCMs) were used as in-vivo and in-vitro models of Type 2 diabetes (T2DM), respectively. Histopathological changes in the mouse myocardium were assessed with hematoxylin-eosin (HE) or Masson's trichrome staining. Cardiac function was evaluated with echocardiography. TCF7L2, β-catenin, and CA2 expression was determined with RT-qPCR, western blotting, and immunohistochemistry. Immunoprecipitation (IP) was used to evaluate the formation of the β-catenin/TCF7L2 bipartite. The regulatory relationship between the β-catenin/TCF7L2 bipartite and CA2 was investigated with chromatin immunoprecipitation (ChIP) and a luciferase reporter assay. Compared with the control mice, the T2DM mice exhibited increased myocardial β-catenin and TCF7L2 expression that was concentrated in the nucleus. Treatment of diabetic mice with the β-catenin/TCF7L2 bipartite inhibitor iCRT14 prevented myocardial remodeling and improved cardiac dysfunction. iCRT14 also prevented high glucose-induced hypertrophy in NRCMs, while the β-catenin stabilizer SKL2001 worsened hypertrophy. IP experiments confirmed the formation of the β-catenin/TCF7L2 bipartite in the control and T2DM mouse cardiomyocytes. Moreover, based on the results of RNA-sequencing analysis, CA2 was upregulated in T2DM cardiomyocytes in vitro and in vivo. TCF7L2 overexpression upregulated CA2, while iCRT14 treatment or TCF7L2 knockdown downregulated CA2. CA2 knockdown ameliorated NRCM hypertrophy induced by high glucose and SKL2001. The ChIP experiments revealed an increased interaction between β-catenin/TCF7L2 and the transcription initiation region of CA2 in the heart tissue of T2DM mice. The luciferase reporter assay confirmed that CA2 is directly regulated by the β-catenin/TCF7L2 bipartite. The results indicate that the canonical Wnt/β-catenin pathway upregulates CA2 via TCF7L2 to promote DCM. This research sheds new light on the pathogenesis of DCM and presents new potential therapeutic targets for this disease.