[Vitamin K function mediated by activation of steroid and xenobiotic receptor].

Insufficient vitamin K nutrition is one of the risks for bone fracture. Vitamin K is clinically applied to osteoporosis treatment in Japan and Asian countries, as the administration has preventive effects on bone fracture. Recent studies have revealed that vitamin K functions as a ligand for Steroid and Xenobiotic Receptor (SXR), as well as a cofactor for gamma-carboxylase. In osteoblastic cells, several SXR responsive genes have been identified, including tsukushi, matrilin-2, CD14, and Msx2. Working together with gamma-carboxylated bone proteins, these SXR targets will function in the vitamin K-mediated bone protection. It has been also suggested that vitamin K could prevent or treat the hepatocellular carcinoma (HCC) in some clinical studies. SXR may also contribute to the vitamin K-dependent reduction of HCC.