Cardiac Phosphodiesterases Are Differentially Increased in Diabetic Cardiomyopathy

Aim: Diabetic cardiomyopathy (DCM) accomodates a spectrum of cardiac abnormalities. This study aims to investigate whether DCM is associated with changes in cyclic adenosine 3'-5' monophosphate (cAMP) signaling, particularly cyclic nucleotide phosphodiesterases (PDEs). Main methods: Type 1 diabetes (T1D) was induced in rats by streptozotocin (STZ, 65 mg/kg) injection. Myocardial remodeling, structure and function were evaluated by histology and echocardiography, respectively. We delineated the sequential changes affecting cAMP signaling and characterized the expression pattern of the predominant cardiac PDE isoforms (PDE 1-5) and beta-adrenergic (beta-AR) receptors at 4, 8 and 12 weeks following diabetes induction, by real-time quantitative PCR and Western blot. cAMP levels were measured by immunoassays. Key findings: T1D-induced DCM was associated with cardiac remodeling, steatosis and fibrosis. Upregulation of beta(1)-AR receptor transcripts was noted in diabetic hearts at 4 weeks along with an increase in cAMP levels and an upregulation in the ejection fraction and fraction shortening. However, beta(2)-AR receptors expression remained unchanged regardless of the disease stage. Moreover, we noted an early and specific upregulation of cardiac PDE1A, PDE2A, PDE4B, PDE4D and PDE5A expression at week 4, followed by increases in PDE3A levels in diabetic hearts at week 8. However, DCM was not associated with changes in PDE4A gene expression irrespective of the disease stage. Significance: We show for the first time differential and time-specific regulations in cardiac PDEs, data that may prove useful in proposing new therapeutic approaches in T1D-induced DCM.

Automated summary

This study found that T1D-induced DCM is associated with cardiac remodeling, steatosis, and fibrosis. Diabetes hearts showed an upregulation of β(1)-AR receptor transcripts at 4 weeks, along with an increase in cAMP levels and improvements in ejection fraction and fraction shortening. However, the expression of β(2)-AR receptors remained unchanged throughout the disease progression.