Biological importance of C-3 alpha epimer of 25-hydroxy vitamin D regarding bone mineral density in young and adult rats

维生素D是一种帮助骨骼生长和保持强壮的营养物质。在加拿大，维生素D的主要膳食来源是牛奶。牛奶中添加了大量的维生素D，有助于防止人体缺乏维生素D。最近，在婴儿和成人的血液样本中发现了一种名为C-3外显体的新形式的维生素D。唯一的区别是一个化学键有不同的方向，然而，这可能会改变它的工作方式。例如，维生素D通过与人体细胞中的受体结合而起作用，其作用方式类似于使用锁中的钥匙打开门。一个小小的改变就可能改变钥匙的工作方式。因此，在帮助骨骼生长和保持强壮方面，C-3表聚体是否和正常形式的维生素D一样好还不清楚。这项研究旨在测试维生素D的高摄入量是否会导致C-3外显体的比例增加，并测试这是否对生长或成人骨骼有任何影响。这项工作将在年轻和成熟的大鼠中进行，喂养不同数量的维生素D形式超过8周。骨骼检查将通过一系列专门设计的x光片来显示骨骼中含有多少钙，并估计骨骼强度。这一结果将有助于乳品行业了解C-3外显体的来源，以及它是否对骨骼有益。

Vitamin D is a nutrient that helps bones grow and stay strong. In Canada, the main dietary source of vitamin D comes from milk. Milk has vitamin D added in amounts that help to prevent the body from having very low stores of this vitamin D. Recently, a new form of vitamin D, called C-3 epimer, has been discovered in blood samples taken from infants and adults. The only difference is that one chemical bond has a different orientation, however, this might alter how well it works. For example, vitamin D works by binding to receptors in the body's cells in a similar way as using a key in a lock to open a door. A small change could alter how the key works. Therefore, it is unclear if the C-3 epimer is as good as the normal form of vitamin D in helping bones grow and stay strong. This research is designed to test if higher intakes of vitamin D result in proportional increases in C-3 epimer and to test if this has any consequences to growing or adult bone. The work will be conducted in young and mature rats over 8 weeks of feeding various amounts of the vitamin D forms. Bone will be examined by taking a series of x-rays specially designed to show how much calcium is packed into bone and also to estimate bone strength. The results will help the dairy industry to know where the C-3 epimer comes from and if it is good for bone.