Abstract P2054: Epigenetic Regulation Of TLR2 By Gut Microbial Antigens Aggravates Myocardial Fibrosis Through Activating Myd88/IRAK4/NF-kB Signaling In Type 2 Diabetes

Abstract

Background: Type 2 diabetic (T2D) patients are 40% more likely to develop cardiovascular diseases compared to healthy individuals. Previously, we have shown that circulating gut peptides such as peptidoglycan (PGN) aggravate myocardial fibrosis through DNA hypomethylation-induced activation of TLR2; however, the underlying molecular mechanisms responsible remain elusive. Hypothesis: Gut microbial antigens activate MyD88/IRAK4/NF-κB signaling through TLR2 in cardiac tissue, resulting in myocardial fibrosis and cardiac dysfunction in T2D. Methods: Gut barrier integrity, cardiac inflammation, and DNA hypomethylation (5hmC) were measured in cardiac tissue via IHC, qPCR, ELISA, and western blot analysis in db/db mice, a murine model of T2D with 4 months of diabetes and age-matched controls. PGN-treated cardiac fibroblasts were analyzed via in-vitro studies with and without IRAK4 and NF-κB inhibitors. Results: db/db mice exhibited cardiac dysfunction and myocardial fibrosis as measured by reduced LVEF and LVFS with increased LV mass and collagen synthesis. These mice also exhibited higher gut permeability as observed by reduced tight junctional proteins (ZO-1, p120-catenin, and VE-cadherin, YAP, PV1) and increased levels of plasma FABP-2. The levels of PGN were higher in plasma (p<0.003) and cardiac tissue (p<0.001) of db/db mice. The expression of TLR2 (p<0.003) and pro-inflammatory cytokines IL-1β (p<0.008) and TNF-α (p<0.0004) were significantly up-regulated in diabetic hearts compared to WT. Expression of 5hmC was significantly higher (p<0.001) in the hearts of diabetic mice. Increased expression of 5hmC, ten-eleven translocation 1-3 (TET-1, 2, 3), IL-1β, IL-6, and TNF-α were also observed in PGN-treated cardiac fibroblasts. IRAK4 (PF-06650883; 10μM) and NF-κB (CAPE; 50 μM) inhibition reduced the PGN-mediated fibroblast activation, resulting in reduced inflammation. Conclusions: Increased circulating gut microbial antigens by induction of systemic and cardiac inflammatory pathways result in damage to the myocardium of db/db mice. Therapies designed to restore the gut barrier and reduce TLR2 activation may potentially minimize the risk of diabetes-induced cardiovascular complications.