E2F6 Impairs Glycolysis and Activates BDH1 Expression Prior to Dilated Cardiomyopathy

The data reveal a novel role for the E2F pathway in regulating glycolysis in the developing myocardium through a mechanism involving cyclin B1. We reveal BDH1 expression as an early biomarker of heart failure and its potential impact, through ketone signaling, on CX-43 levels in E2F6-induced DCM.

To define the role of the E2F pathway in cardiac metabolism and dilated cardiomyopathy (DCM) with a focus on BDH1.

We previously developed transgenic (Tg) mice expressing the transcriptional repressor, E2F6, to interfere with the E2F/Rb pathway in post-natal myocardium. These Tg mice present with an E2F6 dose dependent DCM and deregulated connexin-43 (CX-43) levels in myocardium. Using the Seahorse platform, a 22% decrease in glycolysis was noted in neonatal cardiomyocytes isolated from E2F6-Tg hearts. This was associated with a 39% reduction in the glucose transporter GLUT4 and 50% less activation of the regulator of glucose metabolism AKT2. The specific reduction of cyclin B1 (70%) in Tg myocardium implicates its importance in supporting glycolysis in the postnatal heart. No changes in cyclin D expression (known to regulate mitochondrial activity) were noted and lipid metabolism remained unchanged in neonatal cardiomyocytes from Tg hearts. However, E2F6 induced a 40-fold increase of the Bdh1 transcript and 890% increase in its protein levels in hearts from Tg pups implying a potential impact on ketolysis. By contrast, BDH1 expression is not activated until adulthood in normal myocardium. Neonatal cardiomyocytes from Wt hearts incubated with the ketone β-hydroxybutyrate (β-OHB) showed a 100% increase in CX-43 protein levels, implying a role for ketone signaling in gap junction biology. Neonatal cardiomyocyte cultures from Tg hearts exhibited enhanced levels of BDH1 and CX-43 and were not responsive to β-OHB. Conclusions: The data reveal a novel role for the E2F pathway in regulating glycolysis in the developing myocardium through a mechanism involving cyclin B1. We reveal BDH1 expression as an early biomarker of heart failure and its potential impact, through ketone signaling, on CX-43 levels in E2F6-induced DCM.