2023, Vol. 27 ›› Issue (5): 676-682

Effects of exercise training on bone mass and bone microstructure in aged osteoporotic rats

Wang Jinling1, 2, 3, Huang Xiarong1, 2, 3, Qu Mengjian1, 2, 3, Huang Fujin1, 2, 3, Yin Lingwei1, 2, 3, Zhong Peirui1, 2, 3, Liu Jin1, 2, 3, Sun Guanghua1, 2, 3, Liao Yang1, 2, 3, Zhou Jun1, 2, 3   

Abstract: BACKGROUND: Exercise training can maintain bone mass and improve bone mineral density. However, its effect on senile osteoporosis and its possible mechanism are not clear.
OBJECTIVE: To study the effects of exercise training on senile osteoporosis and to explore its possible molecular mechanism.
METHODS: Sixteen Sprague-Dawley rats aged 24 months old were regarded as the model of senile osteoporosis and randomly divided into elderly model group (n=8) and exercise training group (n=8), while eight young Sprague-Dawley rats of 3 months old were randomly selected as young control group. All rats moved freely in their cages and those in the exercise training group underwent exercise training every day for 8 weeks. After 8 weeks of intervention, serum bone-specific alkaline phosphatase, type I procollagen amino-terminal peptide, tartrate-resistant acid phosphatase 5b and type I collagen amino-terminal peptide were detected using ELISA assay. Bone mineral density of the femur and the fourth lumbar vertebra were measured by dual energy X-ray absorptiometry, while bone microstructural parameters of the tibia and the fifth lumbar vertebra were determined by Micro-CT in each group. mRNA and protein expressions of bone morphogenetic protein 2, Runt-related transcription factor 2, Osterix, and peroxisome proliferator-activated receptor γ in bone marrow of the femur were detected by reverse transcriptase polymerase chain reaction and western blot.
RESULTS AND CONCLUSION: Compared with the elderly model group, the serum levels of bone-specific alkaline phosphatase and type I procollagen amino-terminal peptide (P < 0.05), bone mineral density of the femur (P < 0.05) but not that of the fourth lumbar vertebra (P > 0.05), bone volume fraction and trabecular number of the tibia (P < 0.05), and the mRNA and protein expression of bone morphogenetic protein 2, Runt-related transcription factor 2, and Osterix in the femur (P < 0.05) were significantly increased in the elderly model group, while the serum levels of tartrate-resistant acid phosphatase 5b and type I collagen amino-terminal peptide (P < 0.05), trabecular separation of the tibia and the fifth lumbar vertebra (P < 0.05), and the mRNA and protein expression of peroxisome proliferator-activated receptor γ were significantly decreased (P < 0.05). In addition, exercise training could improve the bone volume fraction, trabecular number and trabecular thickness of the fifth lumbar vertebra in rats with senile osteoporosis, although the differences in changes were not always statistically significant
(P > 0.05). The trabecular thickness of the tibia had no significant changes after exercise training (P > 0.05). To conclude, exercise training can significantly improve bone mineral density and bone microstructure, promote osteogenic differentiation, and inhibit adipogenic differentiation in aged osteoporotic rats. The mechanism may be related to the bone morphogenetic protein 2/Runt-related transcription factor 2/Osterix signaling pathway.
Key words: senile osteoporosis, exercise training, bone morphogenetic protein 2, Runt-related transcription factor 2, Osterix, signaling pathway, bone formation, bone resorption, rat