SIRT1, Polyphenols, and Endothelial Oxidants

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Increased oxidants are associated with insulin resistance, the metabolic syndrome, and a predisposition to atherosclerosis. This laboratory has demonstrated that the increase in oxidants causes oxidative post- translational modifications (OPTM) in key vascular cell proteins, including endothelial nitric oxide synthase (eNOS), the sarcoplasmic reticulum calcium ATPase, p21ras, and manganese superoxide dismutase. These OPTM including tyrosine nitration and cysteine sulfoxidation of specific amino acid residues have been implicated in cellular dysfunction. In an example key to endothelial function, high glucose oxidizes the redox- sensitive zinc thiolate that normally binds eNOS dimers, resulting in eNOS dysfunction. Our preliminary studies have identified another potential oxidant target, sirtuin-1 (SIRT-1), a class III histone deacetylase that is thought to be responsible for the increased life span caused by caloric restriction. Polyphenols, including the red wine component, resveratrol, directly activate SIRT-1 and mimic the effects of caloric restriction, and they have also recently been shown by others and us to reduce weight, hyperlipidemia, adhesion molecule expression, oxidants, and atherosclerosis in fat-fed mice. We discovered that polyphenols stimulate AMP- activated protein kinase (AMPK), and implicated AMPK in mediating improvements in hyperlipidemia and atherosclerosis in diabetic mice. Together with other projects within this program, we now propose that chronic oxidant stress associatedwith the metabolic syndrome can directly target and inactivate SIRT1, contributing to the down-regulation of AMPK activity and endothelial dysfunction observed in the metabolic syndrome. In addition, we propose that polyphenols stimulate SIRT1/LKB1/AMPK/ eNOS signaling to maintain endothelial function, decrease oxidants, and suppressadhesion molecule expression, apoptosis, and atherogenesis. Our aims are to determine, 1) the role of down- and up-regulation of SIRT1/LKB1/ AMPK/eNOS signaling in mediating the effect of oxidants and the response to polyphenols, 2) what OPTM occur in SIRT-1 during exposure to oxidants, and 3) the role of SIRT1,LKB1 and eNOS in the therapeutic effect of polyphenols on inflammation, oxidants, and atherogenesis in fat-fed mice.