Abstract 650: Dose-response Effect of Hyperglycemia in Maternal Diabetes Mediated Congenital Heart Defects

Abstract

Congenital heart defects (CHDs) are the leading cause of infant morbidity and mortality. The etiology is multifactorial and maternal pre-existing diabetes is a non-genetic risk factor, which perturbs embryonic development and increases the risk of CHDs by 3-to 5-fold. We have previously demonstrated that maternal hyperglycemia (matHG) leads to an increase in reactive oxygen species and reduced nitric oxide bioavailability and found an epigenetic mechanism for altered expression of Notch1 , a gene critical for endocardial cushion formation, cardiomyocyte (CM) differentiation, outflow tract development, and ventricular trabeculation. We also noted spectrum of cardiac defects in developing embryos when exposed to increased severity of matHG, the underlying molecular basis of which remains unclear. To this end, we hypothesized that matHG alters gene-expression of cardiac progenitor cells in a spatiotemporal manner to predispose embryos to diabetes-induced CHDs. To test cell-specific responses to HG, murine embryonic cell-lines [AVM, atrioventricular cushion mesenchymal and ECC1, endothelial] were cultured in normal (NG, 5.5mM) and different doses of HG (10, 25 and 40mM). RNA-seq was performed after 48hrs of treatment and gene-set enrichment analysis of AVM NG and HG (25mM) identified genes associated with metabolic processes, response to oxidative-stress (OS), chromatin regulation and altered Wnt/Notch signaling pathways with HG. Similarly, RNA-seq analysis of protein-coding genes in ECC1-HG revealed increasing numbers (8, 311, 1072) of differentially expressed genes compared to NG, and associated with OS, ATP-synthesis, cardiac development, suggesting a dose-response relationship. Additionally, a streptozotocin-induced murine model of diabetes was used to characterize the influence of matHG dose on CHD susceptibility. Examination of E9.5, E11.5, E13.5 embryos displayed defects in CM proliferation, ventricular trabeculation, thin ventricular myocardium and septal defects with matHG. Together, our in vitro transcriptomic analysis and in vivo histologic characterization support a variable molecular and phenotypic response to hyperglycemic stress during cardiac development that contribute to matHG associated CHDs.