中等强度运动对去卵巢大鼠骨组织自噬水平的影响

Effect of moderate-intensity exercise on the level of autophagy in bone tissue of ovariectomized rats

背景:运动是防治骨质疏松症的有效方式,但仍不清楚其影响绝经后骨质疏松的机制是否与骨自噬水平改变有关。目的:观察运动经细胞自噬对去卵巢大鼠骨组织形态和力学性能的影响,从自噬的角度来探讨运动对去卵巢大鼠骨量的作用机制。方法:建立去卵巢大鼠模型,进行为期24周的中等强度有氧运动干预。实验后使用ELISA法测定血清雌二醇水平,micro-CT检测胫骨皮质骨、松质骨骨密度以及骨微结构,三点弯曲实验检测胫骨生物力学指标,透射电镜观察自噬体,Western blot分析LC3、ATG7蛋白表达。结果与结论:①去卵巢安静组大鼠血清雌二醇水平显著低于假手术安静组和去卵巢运动组(P<0.01);②各组大鼠体质量均增加,且去卵巢安静组>去卵巢运动组>假手术安静组>假手术运动组;③各组大鼠骨密度、骨量均显著增加(P<0.01),但去卵巢安静组增加程度明显低于其他组,去卵巢运动组增加程度明显高于去卵巢安静组;④与假手术安静组相比,假手术运动组大鼠的胫骨松质骨骨密度显著增加(P<0.01),去卵巢安静组和去卵巢运动组显著降低(P<0.01);⑤去卵巢安静组大鼠骨体积分数、骨小梁数量、松质骨骨密度显著低于去卵巢运动组(P<0.05),骨小梁厚度极显著低于去卵巢运动组(P<0.01),骨小梁模式因子、骨小梁分离度、结构模型指数显著高于去卵巢运动组(P<0.01);⑥与去卵巢安静组相比,去卵巢运动组LC3-Ⅱ/LC3-Ⅰ和ATG7蛋白的相对表达量显著增加(P<0.05);与假手术安静组相比,假手术运动组大鼠骨组织中自噬体数量增加(P<0.05);与去卵巢安静组相比,去卵巢运动组大鼠骨组织中自噬体数量增加(P<0.05)。由此可见,中等强度跑台运动可通过提高去卵巢大鼠血清雌二醇水平和骨组织自噬水平,改善其胫骨松质骨的骨微结构和骨生物力学性能,增加骨量。

BACKGROUND:Exercise is an effective method for preventing and treating osteoporosis,but it is unclear whether its effect on postmenopausal osteoporosis is related to changes in bone autophagy levels.OBJECTIVE:To observe the effects of exercise via cellular autophagy on the morphology and mechanical properties of bone tissue in ovariectomized rats,and to explore the mechanism of exercise on bone mass in ovariectomized rats from the perspective of autophagy.METHODS:A rat model of postmenopausal osteoporosis was established,and a 24-week moderate-intensity exercise was used for intervention.After the experiment,serum estradiol levels were measured by ELISA,and bone mineral density and bone microstructure of the cortical and trabecular bone were detected by micro-CT.The biomechanical indicators of the tibia were tested by a three-point bending test.Autophagosomes were observed by transmission electron microscopy.The expression of LC3 and ATG7 proteins was analyzed by western blot.RESULTS AND CONCLUSION:The serum estradiol level in the ovariectomized group was significantly lower than that of the sham-operation group and ovariectomized+exercise group(P<0.01).The body mass of rats in each group increased,and the order was the ovariectomized group>the ovariectomized+exercise group>the sham-operation group>the sham-operation+exercise group.The bone mineral density and bone mass of rats in all groups significantly increased(P<0.01),but the increase in the ovariectomized group was significantly lower than that of the other groups,and the increase in the ovariectomized+exercise group was significantly higher than that of the ovariectomized group.Compared with the sham-operation group,the bone mineral density of the tibial cancellous bone in the sham-operation+exercise group was significantly increased(P<0.01),while the bone mineral density in the ovariectomized and ovariectomized+exercise groups was significantly decreased(P<0.01).Compared with the ovariectomized+exercise group,the ovariectomized group showed significantly lower bone volume fraction,number of trabeculae,and bone mineral density of cancellous bone(P<0.05),extremely significantly lower trabecular thickness(P<0.01),and significantly higher mean trabecular pattern factor,trabecular separation,and structural model index(P<0.01).Compared with the ovariectomized group,the LC3-II/LC3-I ratio and the relative expression of ATG7 protein significantly increased in the ovariectomized+exercise group(P<0.05).Compared with the sham-operation and ovariectomized groups,the number of autophagosomes increased in the sham-operation+exercise and ovariectomized+exercise groups,respectively.To conclude,moderate-intensity treadmill exercise can improve the bone microstructure and biomechanical properties of the tibial cancellous bone and increase bone mass in ovariectomized rats by increasing serum estradiol levels and bone autophagy levels.