50-OR: Metabolic Dysfunction Attenuates D-dopachrome Tautomerase (DDT) Expression in the Heart—A Key Mechanism Exacerbates Myocardial Post-ischemic Injury

Metabolic abnormalities affect clinical recovery and long-term survival in patients with acute myocardial infarction, but the underlying mechanisms remain unclear. D-dopachrome tautomerase (DDT) in cardiomyocytes protects the heart from injury during hypoxia-ischemia in mice. Our present study found that metabolic dysfunction induced by high fat diet (HFD) was associated with reduced cardiac DDT expression and aggravated cardiac injury following ischemia-reperfusion. Supplementation of DDT prior to ischemia decreased post-ischemic injury in these hearts, suggesting that DDT reduction is an important mechanism regulating post-ischemic cardiac injury associated with metabolic dysfunction. Among all the major fatty acid species in HFD, high palmitic acid (PA) triggered the expression and activation of protease activated receptor 2 (PAR2), which upregulated the transcriptional factors, CREB1 and FOXO1 leading to downregulation of DDT expression in the heart. PAR2 stimulated ERK phosphorylation, thereby upregulating CREB1 phosphorylation. Attenuation of CREB by siRNA significantly decreased FOXO1 expression and accumulation in the nucleus, thereby reducing cardiac DDT expression. Accordingly, PAR2 deficient mice exhibited normal ERK and CREB phosphorylation and DDT levels in the heart following HFD and reversed cardiac function recovery following reperfusion. Overall, our data reveal for the first time a novel role for DDT in mediating myocardial ischemia-reperfusion injury associated with metabolic dysfunction.