Exercise training (EX) increases coronary blood flow capacity and alters coronary vasomotor responsiveness in normal animals. Endothelium-dependent dilation (EDO) is blunted in the left anterior descending coronary artery (LAD) of sedentary pigs (SED) with early stage coronary artery disease (CAD) produced by feeding a high fat/cholesterol diet for 5 months (HFC). EX of this HFC model of CAD restores EDO in the LAD. These interactive effects of EX and HFC diet form the foundation for the central hypothesis of Project 3: The beneficial effects of EX in prevention and treatment of CAD are mediated by restoration/maintenance of a normal coronary endothelialphenotype.
Aim 1 will determine mechanisms responsible for EX-induced improvements in EDO of LADs of HFC pigs. Preliminary results indicate that EX preserves/restores EDO in HFC pigs by increasing availability of endothelium-derived NO and decreasing production of a cyclooxygenase constrictor substance. We will use pharmacological, biochemical and molecular approaches to determine whether these modifications result from altered expression of genes for enzymes/receptors responsible for EDO and/or altered activity of these enzymes.
Aim 2 will determine whether mechanical signals (shear stress and stretch) produce EX like changes in expression of endothelial nitric oxide synthase (eNOS) and other protective genes in normal and diseased coronary arteries.
In Aim 3 we will determine whether EX produces a more atheroprotective phenotype of endothelial and/or foam cells during early development of CAD. We will use biochemical, molecular and morphologic approaches to characterize the phenotypes of vascular cells in SED and EX arteries.
Aim 4 experiments are designed to use genetically modified pigs (that over express eNOS and eNOS knock-out) to determine the role of eNOS in the interactive effects of EX and HFC on endothelial function and CAD. Available results indicate that much of the beneficial effects of EX on CAD are mediated by changes in NO release from eNOS.
Aim 5 will use the protocols and techniques applied to our model of early CAD to test the hypothesis that EX also has beneficial effects on more advanced disease (2 yrs on the HFC diet). Completion of the research proposed in Project 3 will improve understanding of mechanisms for anti-atherogenic effects of EX on endothelial function and phenotype in coronary arteries and the roles of inflamation, shear stress, and distention in producing or sustaining an anti-atherogenic phenotype of endothelial and foam cells in the arterial wall. This research will provide a solid fundamental basis for understanding the effects of EX in preventing/reversing CAD and for an improved ability to use exercise in treating and prevention of CAD.
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