Statins and Bisphosphonates Inhibit Menaquinone-4 Biosynthesis in Bone
Bone, Cartilage and Connective Tissue Matrix & Development
Poster Sessions, Presentation Number: MO0219
Session: Poster Session III and Poster Tours
Monday, October 15, 2012 11:30 AM - 1:30 PM, Minneapolis Convention Center, Discovery Hall-Hall B
* Toshio Okano, , AF, YOSHIHISA HIROTA, , JP, , JAPAN
Introduction: We have recently identified a novel human enzyme, UBIAD1, responsible for the conversion of phylloquinone(PK) to menaquinone-4(MK-4) that is a cofactor for g-glutamyl carboxylase(GGCX) involved in the activation of vitamin K-dependent proteins such as blood clotting factors in the liver and osteocalcin in bone (Nature, 2010;468:117). MK-4 is also known to be an active ligand for steroid and xenobiotic receptor(SXR) and modulates the expression of various genes related to osteoblastic functions via binding to SXR. The aims of the present study were to characterize the enzymatic properties of UBIAD1 and to examine the effects of statin, bisphosphonates and warfarin on the MK-4 biosynthesis by UBIAD1 in bone of animals and human osteoblast-like MG-63 cells.
Methods: Lovastatin(LOV) and Simvastatin(SIM) as lipophilic statins and Pravastatin(PRA) as a hydrophilic statin were used in this study. Etidronate(ETI) as a FPP synthase inhibitory activity negative bisphosphonate, and Alendronate(ALN) and Zoledronate(ZOL) as FPP synthase inhibitory positive bisphosphonates were used in this study. MG-63 cells were treated with either statins at the concentrations of 0.5 to 10 mM or with bisphosphonates at the concentrations of 5 to 100 mM in the medium for 24hrs, and thereafter incubated with 1mM deuterium-labeled phylloquinone(PK-d7) for further 24hrs. After incubation, the amounts of MK-4-d7 generated from PK-d7were measured by LC-MS/MS. Mice were singly orally given warfarin at the dose of 5 mg/kg body weight, and the concentrations of MK-4 in bone were periodically measured by LC-MS/MS after administration.
Results: LOV and SIM significantly inhibited the MK-4 biosynthesis by UBIAD1, but PRV did not influenced MK-4 biosynthesis. ALN and ZOL significantly inhibited MK-4 biosynthesis, but ETI did not influenced MK-4 biosynthesis. The concentrations of MK-4 in bone of mice were remarkably reduced at 1 day after warfarin administration, and thereafter the MK-4 concentrations gradually increased to the normal level at 10 days after administration. The MK-4 biosynthesis in MG-63 remarkably reduced by warfarin treatment, but warfarin did not directly inhibit MK-4 biosynthesis by UBIAD1 in a cell-free system.
Conclusion: Statins with lipophilic property and bisphosphonates with FPP synthase inhibitory activity appear to inhibit MK-4 biosynthesis in bone probably due to inhibition of geranylgeranyl pyrophosphate in a mevalonate pathway, and lead to lack of vitamin K action on bone. Therefore, it is suggested the combination use of statins and bisphosphonates with vitamin K during the treatment of osteoporosis.
* Presenting Authors(s):