IGF-I/IGFBP system: metabolism outline and physical exercise

Area of Science:

• Endocrinology
• Exercise Physiology
• Molecular Biology

Background:

• The growth hormone/insulin-like growth factor-I (GH/IGF-I) system mediates anabolic and insulin-sensitizing effects through endocrine and local mechanisms.
• This system includes binding proteins like IGF-I binding proteins (IGFBP), crucial for GH/IGF-I activity.
• The GH/IGF-I axis is integral to physiological adaptations to physical exercise, particularly in muscle tissue.

Purpose of the Study:

• To review the GH/IGF-I/IGFBP system's general aspects.
• To elucidate the role of the GH/IGF-I/IGFBP system in physical exercise, considering type, duration, and training.
• To explore the mechanisms by which exercise influences muscle adaptation via this system.

Main Methods:

• Literature review of studies investigating the GH/IGF-I/IGFBP system and exercise.
• Analysis of correlations between exercise parameters (tolerance, strength, speed) and IGF-I/IGFBP-3 levels.
• Examination of evidence for both endocrine and local (paracrine/autocrine) mediation of exercise effects.

Main Results:

• Correlations between exercise capacity and circulating IGF-I/IGFBP-3 are inconsistently reported, with some studies showing positive, inverse, or absent associations.
• Physical exercise stimulates skeletal muscles, potentially through increased local IGF-I synthesis involving IGFBPs.
• An absent link between exercise performance and circulating IGF-I suggests a predominant role for local mediators.

Conclusions:

• The GH/IGF-I/IGFBP system is critical for exercise adaptation, with both systemic and local effects.
• Local IGF-I production appears to be a key mechanism for exercise-induced muscle strength gains.
• Understanding the interplay between GH/IGF-I/IGFBP and exercise is vital for optimizing training and performance.