Abstract 16558: Epigenetic Regulation of p66Shc by SIRT1 Causes Persistent Myocardial Oxidative Stress and Inflammation Despite Optimal Glycemic Control in Diabetes
Introduction: Intensive glycemic control (IGC) does not reduce the risk of heart failure in the diabetic population. Long-lasting effects of hyperglycemia are indeed emerging as a major determinant of cardiovascular morbidity. The mitochondrial adaptor p66Shc, critically involved in reactive oxygen species (ROS) production, mediates hyperglycemia-induced cardiomyopathy.
Hypothesis: To investigate whether p66Shc drives persistent oxidative stress in the diabetic heart despite IGC.
Methods: Diabetes was induced in wild-type male 129sv mice (4-6 months old) by streptozotocin. Mice were divided into 5 experimental groups: 1) controls; 2) diabetics; 3) diabetics treated with insulin, 4) diabetics receiving insulin together with p66Shc siRNA or 5) scrambled siRNA (n=6-7/group). Insulin implants were placed subcutaneously 3 weeks after the induction of diabetes for the following 3 weeks. Silencing of p66Shc was obtained by i.v. administration every 5 days. Isolated mitochondria from hearts were used for measurement of superoxide anion (O2-) by ESR spectroscopy and mitochondrial swelling. NF-kB activity was assessed by p65 nuclear translocation and binding activity. Chromatin immunoprecipitation (ChIP) was performed to investigate epigenetic modifications of p66Shc promoter.
Results: O2- production, and mitochondrial swelling were significantly increased in the heart of diabetic mice and IGC did not revert this phenomenon. These findings were associated with persistent upregulation of p66Shc protein. Moreover, expression of pro-hypertrophic and pro-inflammatory genes IL-6, MCP-1 and VCAM-1 was elevated in the diabetic heart and did not change despite IGC. Interestingly, in vivo siRNA of p66Shc in mice with IGC blunted ROS production, restored mitochondrial integrity and suppressed ongoing myocardial inflammation by inhibiting NF-kB. Persistent p66Shc overexpression was explained by reduced histone 3 deacetylation by SIRT1, leading to an open chromatin and continued gene transcription.
Conclusions: Our findings suggest that a SIRT1- p66Shc-NF-kB signalling perpetuates ROS-mediated myocardial damage despite IGC. Reprogramming SIRT1-dependent epigenetic changes may rescue features of diabetic cardiomyopathy.
- © 2013 by American Heart Association, Inc.