Effect of short-term exercise training on insulin-stimulated PI 3-kinase activity in middle-aged men.
The purpose of this study was to determine whether the improved insulin action with short-term exercise training in middle-aged individuals is associated with enhanced phosphatidylinositol (PI) 3-kinase activity in skeletal muscle. Nine men of ages 50-70 yr were studied before and after 7 consecutive days of supervised exercise (60 min/day, 70% peak O2 consumption). Insulin sensitivity was measured with a euglycemic hyperinsulinemic glucose clamp in the sedentary condition and 15-17 h after the final exercise session. Anti-phosphotyrosine-associated PI 3-kinase activity was determined from muscle samples obtained in the fasted condition and after 60 min of insulin infusion during the clamp. With exercise, the glucose infusion rate increased (P < 0.001) by 33%, indicating enhanced insulin action (mean +/- SE, 6.6 +/- 0.6 vs. 8.7 +/- 0.8 mg x kg(-1) x min(-1)). Short-term exercise training did not, however, increase insulin-stimulated (insulin stimulated/fasting) PI 3-kinase activity (1.8 +/- 0.8 vs. 1.8 +/- 0.7-fold stimulation with insulin pre- vs. posttraining, respectively). There was also no change in insulin-stimulated protein kinase B activity (1.3 +/- 0.1 vs. 1.4 +/- 0.2-fold stimulation with insulin) with training. These data suggest that insulin action is enhanced with short-term exercise training via an adaptation distal to PI 3-kinase in middle-aged, insulin-resistant individuals.
Tanner
Charles J
CJ
Human Performance Laboratory, Diabetes/Obesity Center, East Carolina University, Greenville, North Carolina 27858, USA. TANNERC@MAIL.ECU.EDU
Koves
Timothy R
TR
Cortright
Ronald L
RL
Pories
Walter J
WJ
Kim
Young-Bum
YB
Kahn
Barbara B
BB
Dohm
G Lynis
GL
Houmard
Joseph A
JA
D000368:Aged; D001786:Blood Glucose / Q000032:analysis; D005215:Fasting / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010806:Physical Education and Training; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt