The effect of exercise on systemic and bone concentrations of growth factors in rats

Abstract

Exercise can prevent bone loss and increase bone density. Growth factors such as insulin-like growth factor-I (IGF-I) and transforming growth factor P (TGFB) are thought to be involved in the local response to mechanical loading, resulting in bone remodelling. We tested the effect of additional weight bearing during exercise on the systemic response of IGF-I and local bone response of IGF-I and TGFP.Thirty-four female Wistar rats (aged 3 months, weight 226.9 4~ 20.2 g) were randomly divided in four groups: group 1 baseline controls; group 2 sedentary controls; group 3 ran 15 min a day on a motor-driven exercise belt: group 4 ran 15 min a day with a backpack containing 40 g. The animals ran 5 days a week, for 6 weeks, with an average velocity of 16.6 i 4.4 mlmin, and a slope of 5" uphill.The serum growth hormone (GH) concentration was significantly higher in the running rats (group 3, P = 0.009) than in the sedentary controls (group 2). The IGF-I and I G F binding protein 3 (IGFBP3) levels in serum and the IGF-I levels in liver were similar in all groups. In the tibia no significant differences were observed in IGF-I, IGFBP3 and TGFP concentration. In the humerus, the IGF-I concentration was lower in the running rats (group 3 ) than in the sedentary controls ( P = 0.04), but it was higher in the rats that ran with additional weight than in those without ( P = 0.009). The TGFP concentration in the humerus was lower in both group 3 ( P = 0,001) and 4 (P = 0.03) than in the sedentary controls.The effects in bone caused by mechanical stimulation cannot be explained by changes in serum IGF-I and IGF-I produced in the liver. The concentrations of IGF-I and TGFP in bone appeared to be modulated by running exercise. 0

IGF-1 Mediates Exercise-Induced Phospholipid Alteration in the Murine Skin Tissues

“…It was found that the plasma IGF-1 levels did not decrease either by short bout exercise or physical training in adults [32]. In rodent models, both our studies and others found that exercise with ad libitum feeding was not sufficient to decrease plasma IGF-1 levels [7,33]. When the exercised mice were fed an iso-caloric diet as their sedentary counterpart, the plasma levels of IGF-1 were significantly reduced [7].…”

Conditional disruption of IGF-I gene in type 1α collagen-expressing cells shows an essential role of IGF-I in skeletal anabolic response to loading

“…Similarly, ML has been shown to stimulate IGF-I expression in bone cells in vivo (7,18,25). Although there is a considerable body of data in the literature to implicate a role for IGF-I in mediating the mechanical strain response in bone, direct evidence to demonstrate a cause-and-effect relationship between an increase in IGF-I expression and skeletal changes is lacking.…”

The effects of G-CSF and naproxen sodium on the serum TGF-β1 level and fracture healing in rat tibias

“…Blood samples (1 ml each) were taken by intracardiac puncture on day 1 and in weeks 1, 2 and 4, and stored at −20°C until analysis (Bravenboer et al, 2001). Serum TGF-β1 concentration was measured with a commercially available enzyme-linked immunosorbent assay (ELISA) (BMS608/2 m TGF-β1, Bender Med Systems, CA, USA).…”