Effects of treadmill exercise on osteoporosis and wnt/beta-catenin signal pathway in aged rats / 中国组织工程研究

ABSTRACT

BACKGROUND:Exercise training can improve osteoporosis,but its effects and mechanisms on senile osteoporosis are not fully understood. OBJECTIVE:To observe the effect of treadmill exercise on osteoporosis and wnt/β-catenin signal pathway in aged rats. METHODS:Sixteen 24-month-old male Sprague-Dawley rats were randomly divided into osteoporosis group(n=8)and treadmill group(n=8)and eight 6-month-old male Sprague-Dawley rats were used as young control group.The model of senile osteoporosis was replicated by natural aging and the rats in the treadmill group were treated with treadmill exercise once a day,5 days a week,for 8 weeks.Levels of bone metabolic markers such as type I collagen cross-linked C-terminal peptide,tartrate resistant acid phosphatase,osteocalcin and bone specific alkaline phosphatase were detected by ELISA;bone mineral density of the left femur and L5 was measured by dual energy X-ray;bone scanning and bone microstructure quantitative analysis were performed by bone micro-CT;and the mRNA and protein expression levels of wnt3a,β-catenin,LRP5,DKK1 and GSK3β were detected by RT-PCR and western blot,respectively. RESULTS AND CONCLUSION:Compared with the young control group,the osteoporosis group showed a reduction in serum bone specific alkaline phosphatase and osteocalcin levels(P<0.05),bone mineral density of the femur and L5,the number of tibia and L4 bone trabeculae,bone volume,bone volume fraction(P<0.05),and mRNA and protein expression of wnt3a,β-catenin,and LRP5 in bone marrow tissue(P<0.05)as well as an increase in serum levels of tartrate resistant acid phosphatase and type I collagen cross-linked C-terminal peptide(P<0.05),the intertrabecular space between the tibia and L4,structural model index(P<0.05),and mRNA and protein expression of DKK1 and GSK3 β in bone marrow tissue(P<0.05).In addition to the reduced number of trabeculae in the tibia and L4 vertebrae,the trabeculae were structurally disturbed and sparsely aligned and fractured.Compared with the osteoporosis group,the treadmill group showed an increase in serum bone specific alkaline phosphatase and osteocalcin levels(P<0.05),bone mineral density of the femur and L5(P<0.05),the number of tibial trabeculae,bone volume,bone volume fraction(P<0.05),mRNA and protein expression of wnt3a,β-catenin,and LRP5 in bone marrow tissue(P<0.05)but a reduction in the serum levels of tartrate resistant acid phosphatase and type I collagen cross-linked C-terminal peptide,L4 trabecular space,tibial trabecular space,structural model index,and mRNA and protein expression of DKK1 and GSK3 β in bone marrow tissue(P<0.05).In addition to the increased number of tibial and L4 trabeculae,the trabeculae were arranged in a regular and dense pattern and were connected to a network.To conclude,treadmill exercise may improve osteoporosis in aged rats by activating the wnt/β-catenin signal pathway.