Ryan Jackson W, Reinke Daniel, Kogawa Masakazu, Turner Andrew G, Atkins Gerald J, Anderson Paul H, Morris Howard A
School of Pharmacy and Medical Sciences, University of South Australia, GPO Box 2471, Adelaide SA 5001, Australia.
Curr Drug Targets. 2013 Dec;14(14):1683-8. doi: 10.2174/138945011131400212.
The active form of vitamin D, 1,25-dihydroxyvitamin D3, carries out its diverse range of biological activities by binding to the nuclear vitamin D receptor, present in almost every cell of the body. It is well established that adequate serum 25-hydroxyvitamin D levels correlate with a reduction in the incidence of osteoporosis; however, the physiological basis for this relationship remains elusive. Although, the endocrine actions of vitamin D are thoroughly appreciated, the effect of vitamin D on bone tissue and bone cells is yet to be completely understood. There exists a wealth of literature that suggests the VDR within the three major bone cell types, osteoblasts, osteocytes and osteoclasts, is responsible for the regulation of bone homeostasis. The circumstances, under which the action of 1,25-dihydroxyvitamin D3 elicits an anabolic or catabolic role have not been elucidated. However, it would seem that vitamin D can evoke both of these effects and that this is partly mediated by calcium homeostasis. This raises the possibility that dietary calcium intake and vitamin D metabolism act concomitantly at the kidney, intestine and the bone in a coordinated response. Thus, to maintain adequate bone homeostasis and reduce the risk of metabolic bone disease via the diet, it is important to consider this duality of vitamin D action in relation to the overall calcium economy.
维生素D的活性形式，1,25-二羟基维生素D3，通过与核维生素D受体结合来发挥其广泛的生物活性，该受体存在于人体几乎每个细胞中。充分的血清25-羟基维生素D水平与骨质疏松症发病率的降低相关，这一点已得到充分证实；然而，这种关系的生理基础仍然难以捉摸。尽管维生素D的内分泌作用已得到充分认识，但维生素D对骨组织和骨细胞的影响尚未完全了解。有大量文献表明，三种主要骨细胞类型（成骨细胞、骨细胞和破骨细胞）中的维生素D受体负责骨稳态的调节。1,25-二羟基维生素D3的作用引发合成代谢或分解代谢作用的情况尚未阐明。然而，维生素D似乎可以引发这两种作用，并且这部分是由钙稳态介导的。这就增加了膳食钙摄入量和维生素D代谢在肾脏、肠道和骨骼中协同作用以产生协调反应的可能性。因此，为了通过饮食维持充分的骨稳态并降低代谢性骨病的风险，考虑维生素D作用与整体钙代谢的这种双重性很重要。
