Abstract 12315: Circulating Gut Microbial Peptides Aggravate Cardiac Inflammation and Promote DNA Hypomethylation at the TLR-2 Promoter Region in Type 2 Diabetic Mice

Abstract

Introduction: Epigenetic modifications, especially DNA methylation, influence key biological processes, including inflammation, and are considered as a “switch” between gene silencing and gene activation. Promoter DNA hypomethylation activates TLR-2, a modulator of inflammation, and may impact cardiac function in T2D. Hypothesis: The gut microbial peptide peptidoglycan (PGN) enters the circulation via a leaky gut and activates TLR-2 in cardiac tissue by DNA hypomethylation contributing to cardiac dysfunction in T2D. Methods: T2D ( db/db ) and wild-type mice were euthanized after four months of diabetes. Assessment of gut permeability, gut and systemic inflammation, and hypomethylation (5hmC) of cardiac tissue was performed using IHC, qPCR, ELISA, and western blot analysis. In-vitro studies were conducted in PGN-treated cardiomyocytes with and without 2-hydroxyglutarate (2HG). Results: db/db mice showed cardiac dysfunction as measured by reduced percent of LVEF (46.2±2.7 vs. 65.8±1.8; p<0.001), LVFS(22.7±1.6 vs. 35.4±1.3; p<0.001), and increased LV mass (192.4±17.0 vs. 105.8±12.4; p<0.006) compared with WT controls. db/db mice also exhibited higher gut permeability as observed by reduction of tight junction proteins (ZO-1, p120-catenin, and β-catenin) and increased levels of plasma FABP-2. The levels of PGN were higher in plasma (84.19 ± 13.56 vs. 27.21 ± 8.4; p<0.003) and cardiac tissue (1361 ± 236.1 vs. 113 ± 25.58; p<0.001) of db/db mice. The expression of TLR-2 (2.26 folds; p<0.003), pro-inflammatory cytokines IL-1β (p<0.008), and TNF-α (p<0.0004) were significantly up-regulated compared to WT mice. Expression of 5hmC was significantly higher (18.48±1.32 vs. 5.91±0.28; 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 cardiomyocytes. 2HG treatment blocked PGN- mediated DNA hypomethylation and inflammation in cardiomyocytes. Conclusions: Circulating gut peptides have deleterious effects on cardiac health in diabetic mice by promoting DNA hypomethylation of TLR2 and increased inflammation. Strategies aiming to restore gut barrier integrity may beneficially impact diabetic cardiovascular complications.