Clinical studies report a higher incidence of ischemic heart disease and mortality after myocardial infarction, coronary angioplasty, or cardiac surgery in patients older than 60 years of age, which appear to be related to a decline in intrinsic myocardial resistance to injury. The mechanisms responsible for age-related ischemic intolerance are incompletely understood and the signaling pathways involved in regulating cellular responses to ischemia/reperfusion remain largely unknown. We recently reported that an aging-associated reduction in AMP-activated protein kinase (AMPK) signaling is an important contributing factor leading to increased sensitivity to ischemic stress via modulation of the glucose transporter (GLUT4) translocation. Intriguingly, Sirtuin 1 (SIRT1), a longevity protein, is emerging as a potential AMPK downstream target involved in heart disease. Therefore, it is hypothesized that the impaired AMPK-SIRT1 signaling cascade in the aged heart contributes to intolerance to ischemic insults in the elderly. We will test this hypothesis to investigate the importance of SIRT1 signaling in the susceptibility of the aged heart to ischemic insults.
Aim 1 : To characterize the SIRT1 activation in the aged heart during ischemia/reperfusion;
Aim 2 : To determine the role of SIRT1 in regulating cardiac function during ischemia-reperfusion stress;
Aim 3 : To evaluate the capability of a small-molecule AMPK or SIRT1 agonist to improve ischemia/reperfusion-induced adaptive response in the aged heart. In this manner, we will advance our understanding of the mechanisms behind aging-associated alterations in cardiac SIRT1 signaling pathways in response to ischemic stress. Furthermore, we propose a novel therapeutic strategy that might up-regulate cardiac SIRT1 signaling and thus protect against ischemia- induced cardiac injury in this segment of population.
We seek to understand the basis for increased susceptibility of the aged myocardium to ischemic injury via investigating signaling mechanisms underlying altered adaptive responses to cardiac ischemic stress with aging. The study also explores whether a pharmacological approach targeting a novel signaling pathway in addition to dietary changes could improve the adaptive signaling mechanisms in the aged heart. Findings from the study could lead to novel therapeutic strategies aimed at limiting ischemic cardiac damage in aging populations.
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