Objective: To investigate the effects of 4-week moderate aerobic exercise plus diet control on serum levels of total insulin-like growth factor 1(IGF-1) and IGF-1 binding protein-3 (IGFBP-3) as well as IGF-1 activity (reflected by molar ratio of IGF-1/IGFBP-3) in female obese adolescents and youths, and their possible role on fat loss, and improvement of glucose and lipid metabolism.
Methods: Nine female obese youths (age:18~19 y) and 30 female obese adolescents (age:14~16 y) were recruited and undertook 4-week aerobic exercise such as swimming and jogging (6 days/week, twice a day, 2 h/time with 5 min rest per 30 min exercise) with gradual increase of intensity from low (heart rate immediately post-exercise of 1st week:100~120 beats/min) to moderate (heart rate immediately post-exercise of 2nd-4th weeks:120~140 beats/min) level, combined with a diet intervention (total daily energy intake of 1 400 or 1 600 kcal according to basal metabolism rate) in Shanghai Dianfeng weight loss enclosed camp. Nine normal weight young women and 9 female children matched at age and nationality were recruited as the normal control. Before and after the experimental period, anthropometric index (body weight, body mass index(BMI) and waist circumference), glucose and lipid metabolism parameters including fasting blood glucose (FBG), fasting insulin (FINS), homeostasis model assessment of insulin resistance (HOMA-IR), triglyceride (TG); total cholesterol (TC), low density lipoprotein (LDL) and high density lipoprotein (HDL), and serum levels of total IGF-1 and IGFBP-3 were measured, and IGF-1 activity was calculated in the obese and normal control female adolescents.
Results: ①Compared with normal control, the serum levels of total IGF-1 and IGFBP-3 were decreased in the female obese youths and adolescents, and IGF-1 activity was reduced only in the obese female adolescents. ②The serum level of IGFBP-3 was down-regulated and IGF-1 activity was up-regulated while no change of serum total IGF-1 was induced by 4-week moderate aerobic exercise plus diet control, accompanied with significant decreases of body weight, BMI and waist circumference as well as improvement of glucose and lipid metabolism in the female obese youths and adolescents. Except for a positive association between the increased IGF-1 activity and the decreased waist circumference was found in the female obese youths by Pearson's correlation analysis, there was no relation of the decreased IGFBP-3, the increased IGF-1 activity with the improvements of anthropometric index and glucose and lipid metabolism in female obese youths and adolescents.
Conclusions: The serum level of IGFBP-3 was down-regulated and the IGF-1 activity was up-regulated by 4-week moderate aerobic exercise plus diet control in female obese youths and adolescents. The increase of IGF-1 activity might be associated with the exercise-plus-diet-induced decrease of waist circumstance in female obese youths.
Keywords: IGF-1; IGFBP-3; aerobic exercise plus diet; obesity.