Paper Information

Journal:   HARAKAT   Fall 2003 , Volume - , Number 17; Page(s) 63 To 80.
 
Paper: 

WILL IGFBP-1 RESPONSE TO ENDURANCE EXERCISE BE ABOLISHED IN EFFECT OF HYPERGLYCEMIA AND HYPERINSULINEMIA ?

 
 
Author(s):  MOHEBI HAMID*
 
* GILAN UNIVERSITY
 
Abstract: 

Prolonged exercise increases plasma insulin growth factor binding protein-1 (IGFBP-1) in response to a decline in plasma insulin and glucose. In a previous study, it was speculated that factors of exercise per se might also regulate IGFBP-1 secretion, as values increased despite euglycaemia under carbohydrate feeding. Therefore, to determine the effect of exercise per se on circulation of IGFBP-1, the present study undertook prolonged exercise during hyperglycemic and hyperinsulinemic clamps. Eight trained male cyclists cycled at 70% VO2max for 120 min on two separate occasions under either an intravenous glucose clamp (G) at 10 mmol/l, or a glucose (10 mmol/l) and insulin clamp (GI) at 40 mU/sqm/min. Fasting venous blood samples taken at rest both before and after clamp and also during exercise were analyzed for IGFI, IGFBP-1 and IGFBP-3 using specific radio immunoassay. Plasma glucose was maintained at 10 mmol/l in both trials. Plasma insulin averaged 32±7.3 and 102±16.6 mU/ml during exercise in G and GI trials respectively. Plasma IGFBP-1 was not changed 30 min after either clamps, but significantly decreased after 60 min and 120 min exercise in both trials (P<0.001). It would appear from these findings that the high levels of exogenous glucose and insulin completely suppress IGFBP-1 secretion during the exercise and/or enhance IGFBP-1 clearance from the circulation. We conclude that insulin is the primary regulator of IGFBP-1 and that there is no effect of exercise on IGFBP-1 regulation.

 
Keyword(s): SPORT, GLUCOSE, INSULIN, IGFBP-1, IGFS
 
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