Influence of physical activity on plasma insulin-like growth factor-1 and insulin-like growth factor binding proteins in healthy older women.
It was examined whether physical activity could alter the bioavailability of insulin-like growth factor-1 (IGF-1) which is dependent upon plasma IGF-1 and insulin-like growth factor binding protein (IGFBPs) levels. The potential role that growth hormone (GH) and insulin play in this process was also examined. Seven healthy 62-69-year-old women performed four bouts of physical activity on separate occasions at either a low (L; heart rate = 100 bpm) or moderate intensity (M; heart rate = 120 bpm) for either 25 (S) or 50 (L) min (LS, low intensity/short duration; LL, low intensity/long duration; MS, moderate intensity/short duration; ML, moderate intensity/long duration). GH levels were elevated immediately following the physical activity from 1.3 to 2.6-fold (P < 0.05) whereas IGF-1 levels were not affected by any activity condition. Plasma insulin levels decreased about 35% under all activity conditions (P < 0.05). Plasma levels of IGFBP-1 (BP-1) were decreased immediately following the ML (-47%; P < 0.05) and the LL (-21%) activity bouts and remained lower than initial values 1 h after these activity bouts (-25 and 34%, respectively, P < 0.05). The ML exercise bout resulted in significant (P < 0.05) increases in IGFBP-2 (BP-2) and IGFBP-3 (BP-3) immediately following activity (+31, and +30%, respectively) and these binding proteins remained elevated following the activity (+28, and +48%, respectively). No relationship was found between any changes in plasma GH or insulin, and changes in plasma IGFBPs. Thus, moderate intensity physical activity of long duration may modulate the bioavailability of IGF-1 in the elderly via alterations in BP-1, -2 and -3. However, changes in circulating levels of GH, insulin or IGF-1 do not appear to be regulating IGF-1 bioavailability in response to physical activity.
Metabolic Biochemistry Lab, School of Kinesiology, Simon Fraser University, Burnaby, BC, Canada.
S G
SG
Chadan
R P
RP
Dill
K
K
Vanderhoek
W S
WS
Parkhouse
D000368:Aged; D000375:Aging / Q000097:blood*; D001837:Body Weights and Measures; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008875:Middle Aged; D013997:Time Factors
D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D006854:Hydrocortisone