Hengsberger Stefan, Ammann Patrick, Legros Brian, Rizzoli René, Zysset Philippe
Laboratory of Bone Biomechanics, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland.
Bone. 2005 Jan;36(1):134-41. doi: 10.1016/j.bone.2004.09.013. Epub 2004 Nov 24.
Bone strength depends on bone mass, geometry, microarchitecture, and intrinsic tissue quality. Whether intrinsic bone tissue properties could be influenced by changes in dietary protein is not known. To address this issue, nanoindentation tests were performed on the lateral, anterior, and posterior site of L5 vertebral bodies in adult female rats fed a normal protein containing diet and in ovariectomized (OVX) rats receiving an isocaloric low protein diet with or without isocaloric essential amino acids supplements. The tissue properties varied significantly between the different sites (anterior, posterior, lateral), suggesting possible effects of heterogeneous stress distribution on the vertebrae in vivo. Isocaloric low protein intake associated with ovariectomy led to significant decreases of indentation modulus, hardness, and dissipated energy on the posterior vertex. Axial compression tests of adjacent vertebral bodies were correlated with the indentation results. Correlations between macroscopic mechanical data obtained by axial compression of vertebral body, and intrinsic tissue properties measured by nanoindentation test suggest that postelastic behavior strongly varied with material fragility detected on the tissue level. Macroscopic stiffness however may be dominated by bone geometry changes and less by variations of intrinsic bone tissue properties. Combining parameters of tissue properties and bone mineral density was highly predictive of vertebral body ultimate strength. Besides geometry and microarchitecture, intrinsic bone tissue properties are important determinants of the mechanical competence of rat vertebrae. Changes in intrinsic tissue properties could thus contribute to the increased bone fragility found in protein undernutrition.
骨强度取决于骨量、几何形状、微结构和内在组织质量。膳食蛋白质的变化是否会影响骨组织的内在特性尚不清楚。为了解决这个问题，对喂食正常蛋白质饮食的成年雌性大鼠以及接受等热量低蛋白饮食（含或不含等热量必需氨基酸补充剂）的去卵巢（OVX）大鼠的L5椎体的外侧、前侧和后侧进行了纳米压痕测试。不同部位（前侧、后侧、外侧）的组织特性差异显著，表明体内异质应力分布可能对椎骨有影响。与去卵巢相关的等热量低蛋白摄入导致后顶点的压痕模量、硬度和耗散能量显著降低。相邻椎体的轴向压缩试验与压痕结果相关。通过椎体轴向压缩获得的宏观力学数据与通过纳米压痕测试测量的内在组织特性之间的相关性表明，弹性后行为随组织水平检测到的材料脆性而强烈变化。然而，宏观刚度可能主要由骨几何形状变化决定，而较少受骨组织内在特性变化的影响。结合组织特性参数和骨矿物质密度可高度预测椎体的极限强度。除了几何形状和微结构外，骨组织内在特性是大鼠椎骨力学性能的重要决定因素。因此，内在组织特性的变化可能导致蛋白质营养不良时骨脆性增加。
