Treadmill running increases phosphatidylinostol 3-kinase activity in rat skeletal muscle.
Exercise has been shown to increase insulin-stimulated skeletal muscle glucose transport. Activation of phosphatidylinostol 3-kinase (PI 3-kinase) is required for insulin to stimulate glucose transport. The present study was designed to investigate whether treadmill running (60 min, 8% grade, 30 m/min) augments insulin-stimulated activation of PI 3-kinase. Insulin dramatically increased insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation (p < 0.05). Treadmill running did not induce IRS-1 tyrosine phosphorylation, not did it alter insulin-stimulated IRS-1 tyrosine phosphorylation. Insulin increased PI 3-kinase activity by 3.0-fold (over basal activity) in white muscle and 5.2-fold in red muscle (p < 0.05). Exercise did not alter basal PI 3-kinase activity in either white or red muscle. However, in response to exercise, insulin-stimulated PI 3-kinase activity was significantly increased in both muscle fibers (p < 0.05). These results suggest that increased insulin responsiveness induced by exercise may be due, in part, to enhanced insulin-stimulated PI 3-kinase activity.
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Department of Biochemistry, East Carolina University School of Medicine, Greenville, North Carolina 27858, USA.
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D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D019000:Phosphotyrosine / Q000378:metabolism; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D010750:Phosphoproteins; D019000:Phosphotyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D005947:Glucose