Data from: The effect of locomotion on the mobilization of minerals from the maternal skeleton

Bone is a dynamic tissue from which minerals are deposited or withdrawn according to the body’s demand. During late pregnancy and lactation, female mammals mobilize mineral from bone to support the ossification of offspring skeleton(s). Conversely, in response to mechanical loading, minerals are deposited in bone enabling it to develop a stronger architecture. Despite their central importance to reproductive performance and skeletal integrity, the interactions between these potentially opposing forces remains poorly understood. It is possible that inter-individual differences in the loading imposed by different forms of locomotion may alter the amount of mineral mobilized during reproduction. Here, the impact of vertical versus horizontal locomotion on bone mobilization was examined during reproduction in the laboratory mouse. The vertical, or climbing, group had access to a 60-cm tower, increasing strain on their appendicular skeleton. The horizontal, or tunnel, group had access to a 100-cm tunnel, which encouraged movements within the horizontal plane. Form of locomotion did not impact the amount of bone females mobilized during reproduction or the amount of mineral females deposited in the litter, but maternal bone architecture differed between groups. The climbing group displayed more trabeculae than the tunnel group, whereas the tunnel group displayed greater cortical bone mineral density mid-shaft. Interestingly, pups born to mothers in the climbing group had a higher concentration of total body calcium at 16 days than pups of mothers in the tunnel group. As maternal total body calcium composition and the amount of calcium invested in the full litter were not different between groups, the difference in the relative calcium content of pups between groups is not suspected to reflect difference in mineral allocation. Future research should consider the impact of maternal activity on the efficiency of offspring skeletal ossification via hormones and other bioactive factors transferred in utero and in milk.骨骼是一种动态组织，可根据机体需求进行矿物质沉积或析出。在妊娠晚期与哺乳阶段，雌性哺乳动物会动员骨骼中的矿物质，以支持子代骨骼的骨化（ossification）过程。反之，当受到机械载荷刺激时，骨骼会沉积矿物质，从而形成更坚固的结构。尽管这两种过程对繁殖性能与骨骼完整性均至关重要，但二者之间潜在的拮抗相互作用机制仍未得到充分阐释。不同运动形式所施加的载荷存在个体间差异，这可能会改变繁殖期间骨骼动员的矿物质总量。本研究以实验小鼠为模型，探究了垂直运动与水平运动对繁殖期间骨骼矿物质动员的影响。垂直运动（攀爬）组可接触60厘米高的攀爬塔，这会增加其附肢骨骼（appendicular skeleton）所承受的应变。水平运动（隧道）组可接触100厘米长的隧道，该装置可促使小鼠在水平面内进行运动。运动形式并未对雌性小鼠繁殖期间骨骼动员的矿物质总量，以及向整窝子代投入的矿物质总量产生显著影响，但两组小鼠的母体骨骼结构存在差异。攀爬组的骨小梁（trabeculae）数量多于隧道组，而隧道组的骨干中部皮质骨矿物质密度（cortical bone mineral density）更高。有趣的是，攀爬组母鼠所产的幼崽在出生16天时的全身总钙浓度，显著高于隧道组母鼠的幼崽。由于两组母鼠的全身总钙组成以及投入整窝幼崽的总钙量均无显著差异，因此两组幼崽相对钙含量的差异，并非源于矿物质分配量的不同。未来的研究应探讨母体运动通过子宫内与乳汁中传递的激素及其他生物活性因子，对子代骨骼骨化效率的影响。