There is increasing evidence from our laboratory and others that autophagy is an adaptive response to ischemia and plays an important role in limiting inflammation. Given that autophagy is deficient in the setting of nutritional excess it is likely that autophagy is suppressed in the setting of metabolic syndrome (MetS), a clinical condition characterized by a constellation of factors which include obesity, insulin resistance, and dyslipidemia. We predict that impaired autophagy underlies cardiac pathology in the setting of MetS. We propose to determine the impact of MetS on autophagy in the heart and the adaptive role autophagy plays in the setting of acute ischemia/reperfusion (l/R) injury and post-infarction remodeling.
Aim 1 will use mCherry- LCS mice to test the hypothesis that autophagic activity varies with time and anatomic location in the heart. Utilizing transgenic mouse models and protein transduction technology we will test the hypothesis that autophagy plays an important role in the protection conferred by ischemic or pharmacologic preconditioning (IPC, PPC) and postconditioning (IPoC). We further hypothesize that autophagy ameliorates post-infarction remodeling. A panel of mass spectrometry-based multiple reaction monitoring assays for autophagy and nutrient-sensing proteins, their splice variants, and posttranslational modifications will be used to thoroughly characterize the state of autophagy in heart tissue.
Aim 2 will evaluate the effects of MetS on autophagy and the heart's response to ischemic stress in the setting of IPC, PPC, IPoC, acute l/R injury, and remodeling using Zucker obese (ZO) rats and Yucatan mini-swine models of MetS. The use of ZO rats will allow us to assess the impact of obesity, dyslipidemia, insulin resistance and elevated fasting glucose on autophagy in the setting of ischemia-reperfusion and permanent coronary artery occlusion (cardiac remodeling). Pharmacologic agents that can override the MetS block to autophagy in ZO rats will be validated in obese Yucatan mini-swine when the agent is given before ischemia, at reperfusion, or throughout. Benefit in the obese swine will be established by demonstrating that treatment results in a reduction in infarct size (scar size), less adverse remodeling and improved recovery of cardiac function 4wk post-reperfusion. Finally human heart tissue will be studied to determine whether autophagy is induced in patients undergoing cardiac surgery and whether this is altered in individuals with advanced age or features of MetS.
This proposal will investigate the beneficial role of autophagy in cardioprotection and the response to ischemic stress in animals and humans with features of metabolic syndrome (MetS). Obesity, which has reached epidemic proportions, gives rise to MetS which is associated with adverse cardiac outcomes. These studies will enable us to overcome barriers to cardioprotection and improve survival in patients with MetS.
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