Prolonged exercise increases serum insulin-like growth factor-binding protein concentrations.
We studied the response of serum 34K insulin-like growth factor-binding protein (IGF-BP) to two types of prolonged exercise. In the first study, 11 normal men performed cycle ergometer exercise, after an overnight fast, for 3 h at the intensity corresponding to 45-50% of their maximal aerobic power. After the exercise, the mean serum IGF-BP concentration was 4.9-fold higher than the baseline level (P less than 0.01), while the IGF-I concentration did not change. Resting for the same time period resulted in a 38% fall in the serum IGF-BP level (P less than 0.01). In the second study, 10 normal men and 8 type 1 diabetic men exercised, on the average, for 7.5 h in a 75-km cross-country ski race. The mean serum IGF-BP concentration increased 5.4-fold (P less than 0.01) in the normal men and 4.2-fold (P less than 0.01) in the diabetic men. The serum IGF-I concentration decreased by 19% and 21% in the normal and diabetic men, respectively (P less than 0.01). After completion of the ski race, the serum insulin and IGF-BP levels (r = -0.70; P less than 0.05), and serum IGF-I and IGF-BP levels (r = -0.72; P less than 0.05) were inversely correlated in the normal men. No such correlations were found in the diabetic men. We conclude that 1) long term exercise increases serum IGF-BP concentrations in both normal and type 1 diabetic men; and 2) the increases are inversely related to alterations in serum IGF-I and insulin concentrations in normal men. These data suggest that IGF-BP may be involved in regulation of the biological action of IGF-I during prolonged exercise.
Suikkari
A M
AM
First Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Finland.
Sane
T
T
Seppälä
M
M
Yki-Järvinen
H
H
Karonen
S L
SL
Koivisto
V A
VA
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002352:Carrier Proteins / Q000097:blood* / Q000502:physiology; D003920:Diabetes Mellitus / Q000097:blood; D015444:Exercise; D006801:Humans; D007328:Insulin / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins; D008297:Male
D001786:Blood Glucose; D002352:Carrier Proteins; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins