Figure 5.

Metabolism of vitamin D and K. The active form of vitamin D can act as a transcription activator for the synthesis of OC and MGP. These are then carboxylated through the co-factors γ-glutamyl carboxylase and vitamin K. These proteins need to be further phosphorylated to enable normal physiological functions shown above, including phosphorylated carboxylated OC resulting in increased bone mineral density and phosphorylated carboxylated MGP decreasing vascular calcification. Multiple studies have demonstrated that vitamin D and K have a synergistic effect, and the diagram above outlines how they can be used in combination to prevent fractures in both healthy and osteoporotic subjects, as well as reducing vascular calcification. [47].