A new insight into cystatin C contained in milk basic protein to bone metabolism: Effects on osteoclasts and osteoblastic MC3T3-E1 cells invitro.

Abstract

A milk protein fraction possessing alkaline isoelectric points (milk basic protein [MBP]) improves bone metabolism invivo, and it inhibits bone resorption by osteoclasts and promotes mouse osteoblastic MC3T3-E1 cells proliferation invitro. Cystatin C (CysC) is a component of MBP and shows bone resorption inhibitory activity. Therefore, it is likely that MBP with higher CysC content improves bone metabolism more effectively. In this study, we prepared MBP with low and high contents of CysC and compared its effects on bone metabolism with standard MBP invitro. Our results showed that the CysC content in MBP was positively related to not only bone resorption inhibitory activity but also MC3T3-E1 cells proliferative activity. Furthermore, purified CysC stimulated MC3T3-E1 cells proliferation. These results indicate that CysC contributes to promotion of MC3T3-E1 cells proliferation, and MBP with higher CysC content shows enhanced bone resorption inhibitory activity and MC3T3-E1 cells proliferative activity. CysC is considered an important factor in the effect on bone metabolism of MBP.