雄激素及其受体在运动改善高脂膳食小鼠骨骼中的作用

Effects of androgen and androgen receptor on exercise-induced bone strength in high-fat diet mice

目的研究雄激素及其受体(androgen receptor,AR)在运动改善高脂膳食小鼠骨骼(包括增强骨密度、骨量和骨生物力学性能)中的作用。方法用去势手术(castration,Cas)和颈部包埋AR阻断剂氟他胺(flutamide,F)缓释剂分别建立去势和AR阻断小鼠模型。8周高脂膳食(high fat diet,HFD)喂养的雄性C57BL/6小鼠随机分为HFD组、HFD+运动(exercise,E)组、HFD+Cas组、HFD+Cas+E组、HFD+F组、HFD+F+E组,每组6只。运动组进行6周中等强度有氧运动,1 h/d,6 d/周。末次运动后36 h内取材。称量股骨和胫骨湿重;ELISA检测血清睾酮水平;Micro-CT检测骨密度和骨量;三点弯曲法检测骨生物力学指标;Western blot检测AR、IGF-1及其IGF-1R蛋白水平。结果(1)HFD降低小鼠血清睾酮水平、股骨和胫骨湿重,以及骨密度和骨量。有氧运动改善HFD小鼠的上述多数指标及骨生物力学性能。(2)去势逆转了有氧运动对HFD小鼠血清睾酮、骨密度和骨量及骨生物力学性能的增强作用。AR阻断剂逆转了有氧运动对HFD小鼠骨小梁BMD、骨量和骨微结构以及骨生物力学性能的改善作用。(3)去势和AR阻断后,有氧运动对HFD小鼠骨AR、IGF-1、IGF-1R蛋白水平的增加作用消失。结论雄激素/AR在有氧运动改善高脂膳食小鼠松质骨BMD、骨量以及骨生物力学性能中发挥重要作用,且该作用可能与雄激素/AR增加骨IGF-1/IGF-1R蛋白水平有关。

Objective To explore the role of androgen and androgen receptor(AR)in exercise-induced bone strength including the increase of bone mineral density(BMD),bone mass,and bone biomechanical properties in high-fat diet mice.Methods Castration and AR-blockaded mouse models were established using castration surgery(Cas)and neck-embedded AR antagonist flutamide(F)releasing pellets,respectively.For exploring the effects of androgen and AR on exercise-induced bone strength,HFD mice were divided into 6 groups after 8-week high-fat diet,HFD,HFD+E,HFD+Cas,HFD+Cas+E,HFD+F,and HFD+F+E groups,with 6 mice in each group.Mice in exercise groups participated in 6-week moderate-intensity aerobic exercise,1 h/day,6 days/week.Samples were collected within 36 h after the last exercise.Femur and tibia wet weights were weighed using electronic balance.Serum testosterone level was detected with ELISA.BMD and bone mass of the left femur were assessed with micro-CT.Biomechanical properties of the right femur were determined with three-point bending test.The protein levels of AR,IGF-1,and IGF-1R were detected using Western blotting.Results(1)HFD significantly decreased the levels of serum testosterone,femur and tibia wet weight,BMD,and bone mass in mice.Six-week aerobic exercise significantly improved the above indicators(except for SMI)and bone biomechanical properties in HFD mice.(2)Castration reversed the improving effects of aerobic exercise on serum testosterone,BMD,bone mass,and bone biomechanical properties in HFD mice.The benefits of aerobic exercise on trabecular BMD,bone mass and bone microstructure,and bone biomechanical properties in HFD mice were reversed by AR antagonist.(3)The exercise-induced increases of AR,IGF-1,and IGF-1R proteins in the bone of HFD mice were completely blocked by castration or AR blocking.Conclusion Androgen/AR plays important roles in aerobic exercise-induced increases of BMD in cancellous bone,bone mass,and bone biomechanical properties in high-fat diet mice,which may be fulfilled by androgen/AR mediated increases of IGF-1/IGF-1R in the bone.