Abstract
AbstractThe growth hormone–insulin-like growth factor I (IGF-I) axis is an important physiological regulator muscle for development. Although there is evidence that aging muscle retains the ability to synthesize IGF-I, there is also evidence that aging may be associated with attenuation of the ability of exercise to induce an isoform of IGF-I that promotes satellite cell proliferation. However, it is clear that overexpression of IGF-I in the muscle can protect against age-related sarcopenia. Strength training appears to be the intervention of choice for the prevention and treatment of sarcopenia. IGF-I has been implicated in the loss of the muscle with age, and IGF-I expression levels change as a consequence of strength training in older adults. However, it seems that advancing age, rather than declining serum levels of IGF-I, appears to be a major determinant of life-time changes in body composition in women and men. We concluded that resistive exercise is a significant determinant of muscle mass and function. Elevated levels of IGF-I have been found in physically active compared to sedentary individuals. Recent work suggests that IGF-I as a mediator plays an important role in muscle hypertrophy and angiogenesis, both of which characterize the anabolic adaptation of muscles to exercise.
Highlights
The growth hormone–insulin-like growth factor I (IGF-I) axis is an important physiological regulator muscle for development
There is evidence that the aging muscle retains the ability to synthesize IGF-I, there is evidence that aging may be associated with attenuation of the ability of exercise to induce an isoform of IGF-I that promotes satellite cell proliferation
The aging muscle may be resistant to IGF-I, an effect that is reversed by exercise
Summary
The growth hormone–insulin-like growth factor I (IGF-I) axis is an important physiological regulator muscle for development. From results of epidemiological studies and interventional trials using recombinant human GH, serum IGF-I levels have shown a positive association with muscle strength, lean body mass [95, 96], and physical activity [62], and they have shown a negative correlation with body mass index and the body fat index [81, 93]. Based on several studies done in healthy young adults, there is an increase in circulating IGF-I in response to different types of exercise, either aerobic, resistance, or heavy ergometer cycling [10, 54, 58, 91], while exercise training improves local IGF-I expression without significant changes of systemic parameters of the GH–IGF-I axis.
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