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的主要饮食来源来自牛奶。牛奶中添加的维生素D的数量有助于防止身体储存非常低的维生素D。最近，从婴儿和成年人的血液样本中发现了一种新的维生素D形式，称为C-3异构体。唯一的区别是，一个化学键有不同的取向，然而，这可能会改变它的工作方式。例如，维生素D的工作原理是与人体细胞中的受体结合，就像用锁上的钥匙打开门一样。一个小小的改变可能会改变密钥的工作方式。因此，目前还不清楚C-3异构体在帮助骨骼生长和保持强壮方面是否与正常形式的维生素D一样好。这项研究旨在测试更高的维生素D摄入量是否会导致C-3同分异构体比例增加，并测试这是否会对生长或成人骨骼产生任何影响。这项研究将在喂食不同剂量维生素D形式的幼鼠和成年鼠超过8周后进行。通过拍摄一系列专门设计的X光照片来检查骨骼，以显示骨骼中填充了多少钙，并估计骨骼强度。这一结果将有助于乳制品行业了解C-3异构体来自哪里，以及它是否对骨骼有好处。

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.