Pajamäki Ilari, Sievänen Harri, Kannus Pekka, Jokihaara Jarkko, Vuohelainen Tuomo, Järvinen Teppo L N
Department of Surgery and the Institute of Medical Technology, University of Tampere, Tampere, Finland.
Bone. 2008 Oct;43(4):748-57. doi: 10.1016/j.bone.2008.06.005. Epub 2008 Jun 20.
Estrogen has been suggested to influence skeletal homeostasis by both increasing the sensitivity of the feedback control system for skeletal rigidity and acting directly on bone surfaces. The objective of the present study was to explore the proposed interaction between the skeletal effects of estrogen and locomotion. Thirty 3-week-old littermates of female Sprague-Dawley rats were first randomly assigned into bilateral sham (E(+)) or ovariectomy (E(-)) surgery after which, the left hindlimb each study animal was cast immobilized (L(-)) while the right limb served as locomotively loaded control (L(+)), a classic 2x2 factorial study design. After 8-week study period, femoral neck, femur midshaft and distal metaphysis were analyzed by peripheral quantitative computed tomography (pQCT), microcomputed tomography (microCT), and mechanical testing. The loading-induced effects were virtually identical in the estrogen-replete (E(+)) and estrogen-deplete (E(-)) groups (Femoral neck: +78% vs. +69% in the tCSA, +74% vs. +55% in the tBMC, -6.0% vs. -7.2% in the tBMD, and +33% vs. +58% in the F(max); Femoral midshaft: +6.9% vs. +3.9% in the cCSA, +13% vs. +13% in the tCSA, +23% vs. +16% in the cBMC, +5.2% vs. +5.1% in the cBMD, and +8.0% vs. +8.0% in the F(max), respectively. All comparisons, NS), challenging the alleged modulatory effect of estrogen on skeletal mechanosensitivity. Estrogen did not have an independent effect on the periosteal apposition at any of the evaluated bone regions. Instead, according to its primary reproductive function, the effects of estrogen were restricted to accrual of bone mass only, the stimulus being apparent at the endosteal surface of cortex and trabecular structure of the distal metaphysis. In conclusion, the present results indicate that that the actions of estrogen and loading on bone structure are independent and additive in nature.
雌激素被认为可通过提高骨骼硬度反馈控制系统的敏感性以及直接作用于骨表面来影响骨骼稳态。本研究的目的是探讨雌激素的骨骼效应与运动之间的相互作用。将30只3周龄的雌性斯普拉格-道利大鼠同窝仔首先随机分为双侧假手术（E(+)）或卵巢切除术（E(-)）两组，之后，将每只实验动物的左后肢进行石膏固定（L(-)），而右肢作为运动负荷对照（L(+)），这是一种经典的2×2析因研究设计。经过8周的研究期后，通过外周定量计算机断层扫描（pQCT）、显微计算机断层扫描（microCT）和力学测试对股骨颈、股骨干中段和远端干骺端进行分析。在雌激素充足（E(+)）组和雌激素缺乏（E(-)）组中，负荷诱导效应几乎相同（股骨颈：横截面积（tCSA）增加78%对69%，骨矿含量（tBMC）增加74%对55%，骨密度（tBMD）降低6.0%对7.2%，最大负荷（F(max)）增加33%对58%；股骨干中段：皮质横截面积（cCSA）增加6.9%对3.9%，tCSA增加13%对13%，皮质骨矿含量（cBMC）增加23%对16%，皮质骨密度（cBMD）增加5.2%对5.1%，F(max)增加8.0%对8.0%，所有比较，无显著性差异），这对雌激素对骨骼机械敏感性的所谓调节作用提出了质疑。在任何评估的骨区域，雌激素对骨膜附着均无独立作用。相反，根据其主要生殖功能，雌激素的作用仅限于骨量的积累，这种刺激在皮质的骨内膜表面和远端干骺端的小梁结构处明显。总之，目前的结果表明，雌激素和负荷对骨骼结构的作用在本质上是独立且相加的。
