Our long-term goal is to determine if exercise training attenuates the excess coronary artery disease (CAD) in diabetes and the vascular smooth muscle (VSM) Ca (Cam) signaling mechanisms involved. In our porcine model of diabetic dyslipidemia coronary arteries show increases in contraction to prostaglandin F2alpha (PGF) and Cam responses to endothelin-1 (ET). Exercise of normal swine decreases Ca release from the sarcoplasmic reticulum (SR) and increases Ca influx, while decreasing ET-induced contraction and DNA synthesis. However, ET-induced contraction does not require Ca release that is dependent on tyrosine kinase, a signal for cell growth. Overall hypothesis: after exercise training increased ET-induced Ca influx attenuates contraction, while decreased SR Ca release attenuates growth of smooth muscle. Design: low fat control pigs (C), high fat fed (HF), and alloxan diabetic and high fat fed (D) pigs are maintained for 20 and 30 wk to study the progression of CAD and compared to D pigs exercise trained (D plus EX).
Specific Aims are to test the hypotheses that in diabetes: 1) Exercise improves glycemic and lipidemic status. Diabetes will be defined by measures of blood glucose, glycated protein, insulin, etc. HDL, LDL, VLDL, triglycerides, apoproteins, glycated LDL, and ET will define features of diabetic dyslipidemia. 2) Exercise attenuates the increase in CAD. Intravascular ultrasound will assess atheroma and vasoconstrictor responses to PGF and ET in vivo. Histology and contractile tension responses of coronary rings to PGF and ET will provide in vitro measures of CAD. 3) Exercise attenuates the conversion of VSM from the contractile (cVSM) to synthetic (sVSM) phenotype. sVSM cell phenotype will be identified using digital imaging microscopy by the Cam response to UTP, perinuclear SR, DNA, smooth muscle actin, desmin, and vimentin. 4) Exercise attenuates the increased contraction of cVSM by increasing ET receptor-dependent Ca influx. Mn and Ba influx used as Ca surrogates will assess Ca influx. Subsarcolemmal Ca localization relative to ryanodine receptors will be digitally imaged. 5) Exercise attenuates the increased ET-induced Cam amplitude and nuclear Ca localization by decreasing tyrosine kinase-dependent Ca release from the SR. Imaging will assay in single cells the relative content and spatial distribution of ET, ryanodine, and IP3 receptors, tyrosine phosphorylation, DNA and Cam. Significance: the first study of Ca localization mechanisms involved in the excess CAD in diabetic dyslipidemia and the therapeutic effects of exercise on CAD.
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