ビタミンK研究 : 医学・生物学における新たな展開

概要

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Vitamin K was originally identified as an essential cofactor for activation of blood coagulants, and thereafter, it was found to activate anti-coagulants as well. Thus, vitamin K has now been recognized to play pivotal roles in the regulation of blood coagulation system by through participating into γ-glutamyl carboxylation of several vitamin K-dependent proteins. As a momentum with the finding of its bone-fracture healing potency, it became evident that vitamin K is deeply involved in the calcification of skeletal tissues and vasculatures, resulting in the discoveries of osteocalcin, matrix gla protein (MGP) or protein S in these tissues. Intriguingly, osteocalcin in bone promotes calcification while MGP in cardiovascular endothelial cells inhibits calcification. This phenomenon resembles the vitamin K actions on coagulants and anticoagulants in the blood coagulation system, and makes us feel that complicated regulatory systems via interacting with vitamin K may exist in the body. Beyond carboxylation, vitamin K has been found to modulate the transcription factor (Msx2)-related gene expression via binding to nuclear receptor (SXR/PXR) in target cells. These findings should contribute to the elucidation of novel molecular mechanism of vitamin K action on the inhibition of cancer cell proliferation, the suppression of cancer cell metastasis and invasion, and the induction of apoptosis not only in cancer cells but also in normal cells.
2007-09-25