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How cancellous and cortical bones adapt to loading and growth hormone
1Department of Physiology, The University of Texas Health Science Center, San Antonio, USA.
Journal of Musculoskeletal & Neuronal Interactions
|March 11, 2005
Summary
Growth hormone (GH) and exercise (EX) independently and together promote bone growth by increasing bone mass and strength. Reduced body weight from food restriction (FR) decreased bone mass, suggesting muscle loading influences bone health.
Area of Science:
- Bone Biology and Physiology
- Endocrinology
- Exercise Science
Background:
- Growth hormone (GH) influences muscle mass, a key regulator of bone modeling and remodeling.
- Understanding the interplay between GH, muscle loading (exercise), and bone health is crucial for skeletal integrity.
Purpose of the Study:
- To investigate the independent and combined effects of growth hormone (GH) and exercise (EX) on bone and skeletal muscle.
- To examine the impact of reduced muscle load, via food restriction (FR), on bone parameters.
Main Methods:
- Female F344 rats were assigned to baseline control, age-matched control, GH treatment, voluntary wheel running exercise (EX), GH+EX, and food restriction (FR) groups.
- Animals were treated for 4.5 months, followed by analysis of body weight, tibial muscle mass, and various bone parameters (cortical area, thickness, mineral content, periosteal and endocortical perimeters, bone strength-strain index [SSI], and maximum force [Fmax]).
Main Results:
- GH significantly increased body weight and tibial muscle mass. EX slightly decreased body weight and partially counteracted GH's effect on body weight in the GH+EX group.
- Both GH and EX independently enhanced tibial diaphyseal cortical bone area, thickness, mineral content, periosteal perimeter, and SSI. GH+EX showed additive effects on most parameters, including SSI.
- FR decreased body weight but did not significantly affect tibial muscle mass; however, it led to increased endocortical perimeter and bone formation rate, with cortical bone area and mineral content above baseline but below controls.
Conclusions:
- Bone anabolic effects of GH, with or without EX, may be partly mediated by increased bone loading from elevated muscle mass and body weight.
- Osteogenic effects of EX, with or without GH, may stem from increased muscle load frequency on bone, despite a decrease in body weight.
- Reduced bone loading due to lower body weight in FR rats may contribute to enhanced endocortical bone loss.
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