Effects of Exercise Training on Vasorelaxation Mediated by Insulin and Insulin‐like Growth Factor‐1 in Rat Aortas

Abstract

Exercise training has numerous benefits on vascular functions, but the underlying mechanism has not been totally understood. The aim of this study was to investigate effects of exercise training on insulin- and insulin-like growth factor-1 (IGF-1)-induced vasorelaxation. Male Wistar rats were randomly divided into sedentary control and exercise groups. The animals in the exercise group ran on a treadmill 60 min/day, 5 days/week for 12 weeks. Insulin- and IGF-1-induced vasorelaxant responses were evaluated, and the roles of phosphatidylinositol 3-kinase and nitric oxide synthase in vasorelaxant responses were examined by treating selective inhibitors, such as wortmannin and Nω-nitro-L-arginine methyl ester (L-NAME). Also, the vascular responses to sodium nitroprusside (SNP), a NO donor, were examined. We found that exercise training significantly enhanced insulin- and IGF-1-induced vasorelaxation in rat aortas; the enhanced insulin- or IGF-1-induced vasorelaxation was abolished by wortmannin or L-NAME; there was no significant difference of SNP-induced vasorelaxation between control and exercise groups. Our findings indicate that exercise training enhances insulin- and IGF-1-induced vasorelaxant responses which are mediated through the PI3K-NOS-dependent pathway. This study was supported by the National Science Council (Grant No. NSC93-2320-B-006-040) in Taiwan.