Department of Cell and Molecular Medicine, Rush University Medical Center, Chicago, IL, USA.
Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA.
J Bone Miner Metab. 2019 Jul;37(4):648-657. doi: 10.1007/s00774-018-0969-1. Epub 2018 Oct 25.
Dietary calcium (Ca) restriction during lactation in the rat, which induces intra-cortical and endocortical remodeling, has been proposed as a model to study bone matrix maturation in the adult skeleton. The purpose of this study was to assess the effects of dietary Ca restriction during lactation on post-weaning mineral metabolism and bone formation. Mated female Sprague-Dawley rats were randomized into groups receiving either 0.6% Ca (lactation/normal Ca) or 0.01% Ca (lactation/low Ca) diets during lactation. Virgin animals fed normal Ca were used as controls (virgin/normal Ca). At the time of weaning, animals on the low Ca diet were returned to normal Ca and cohorts of all three groups were sacrificed at days 0, 1, 2, 7, and 14 post-weaning. Lactation caused bone loss, particularly at the endocortical surface, but the amount was not affected by dietary Ca. Rats in the lactation/low Ca group had increased cortical porosity compared to the other groups, particularly within the size range of secondary osteons. Dietary Ca restriction during lactation did not affect post-weaning bone formation kinetics or serum Ca and phosphate levels. In both lactation groups, there was a transient increase in phosphate and fibroblast growth factor 23 (FGF23) post-weaning, which trended toward virgin/normal Ca levels over time. Thus, the additional challenge of low dietary Ca during lactation to induce intra-cortical remodeling in the rat has minimal effects on bone formation kinetics and mineral metabolism during the post-weaning period, providing further justification for this model to study matrix maturation in the adult skeleton.
哺乳期大鼠的膳食钙（Ca）限制可诱导皮质内和皮质内重塑，被提议作为研究成年骨骼中骨基质成熟的模型。本研究的目的是评估哺乳期膳食 Ca 限制对断奶后矿物质代谢和骨形成的影响。交配的雌性 Sprague-Dawley 大鼠在哺乳期随机分为接受 0.6%Ca（哺乳期/正常 Ca）或 0.01%Ca（哺乳期/低 Ca）饮食的组。正常 Ca 喂养的处女动物用作对照（处女/正常 Ca）。在断奶时，低 Ca 饮食的动物恢复为正常 Ca，所有三组动物在断奶后 0、1、2、7 和 14 天处死。哺乳期导致骨丢失，特别是在内皮质表面，但数量不受膳食 Ca 的影响。哺乳期/低 Ca 组的大鼠与其他组相比，皮质孔隙率增加，尤其是在次级骨单位的大小范围内。哺乳期膳食 Ca 限制并不影响断奶后骨形成动力学或血清 Ca 和磷酸盐水平。在哺乳期组中，断奶后磷酸盐和成纤维细胞生长因子 23（FGF23）短暂增加，随着时间的推移，其水平趋于接近处女/正常 Ca 水平。因此，哺乳期低钙饮食的额外挑战对内皮质重塑的诱导对断奶后时期的骨形成动力学和矿物质代谢的影响最小，为该模型提供了进一步的理由，以研究成年骨骼中的基质成熟。
