Enhanced expression of neuronal nitric oxide synthase in islets of exercise-trained rats.
It is well known that glucose-stimulated insulin secretion (GSIS) decreases after exercise training. In the present study, we investigated the effects of exercise training (9 weeks of running) on the activity of glucokinase (GK), the production of nitric oxide (NO), and the protein expressions of both glucose transporter-2 (GLUT-2) and NO synthase (NOS) in rat pancreatic islets. Exercise training significantly reduced GSIS, with decreases in GK activity and GLUT-2 protein expression. The NO releases and cGMP contents were higher in the islets of trained rats than in those of control rats. Exercise training enhanced cNOS activity, the protein expression of both neuronal nitric oxide synthase (nNOS) and calmodulin, and NADPH-cytochrome c reductase activity in the homogenates of islets. Thus, exercise training-induced reduction of GSIS would result from, at least in part, decreases in both glucose entry and the first step in glycolytic utilization of glucose. Moreover, exercise training could enhance the protein expression of nNOS, which in turn enhances two catalytic activities of nNOS, an NO production and a cytochrome c reductase activity.
Ueda
Hiroshi
H
Department of Kinesiology, Graduate School of Science, Tokyo Metropolitan University, 1-1, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan.
Urano
Yuriko
Y
Sakurai
Tomonobu
T
Kizaki
Takako
T
Hitomi
Yoshiaki
Y
Ohno
Hideki
H
Izawa
Tetsuya
T
D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation; D005941:Glucokinase / Q000378:metabolism*; D051273:Glucose Transporter Type 2; D007515:Islets of Langerhans / Q000201:enzymology*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009474:Neurons; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D052248:Nitric Oxide Synthase Type I; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D012420:Running / Q000502:physiology*
D051273:Glucose Transporter Type 2; D009004:Monosaccharide Transport Proteins; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D005941:Glucokinase