Foof Sci. Technol. Res.,11(1),1-8,2005
Biological Significance of Milk Basic Protein (MBP) for Bone Health
Hiroshi Kawakami

8. Active components of MBP

MBP was further fractionated by various types of
chromatography to probe for active components using
osteoblast-proliferation activity as an indicator. The following substances were identified: Fragments +
, with MW +1 kDa of high molecular weight kininogen, a blood coagulating factor (Yamamura et al., ,***), and high mobility group (HMG)-like protein with MW +* kDa
(Yamamura et al., +333). Furthermore, functional compo-nents were investigated using the bone rptionsuppressing
activity in an isolated osteoclast culture system as an indicator, and a cystatin with MW +, kDa was identified (Matsuoka et al., ,**,). Cystatin is produced by osteoblasts and inhibits cysteine protease,which is produced by osteoclasts and destroys bones, so
that bone resorption is regulated (Johansson et al., ,***;Lerner et al., +331). In addition, several growth factors in milk are well known to possess basic isoelectric points (Francis et al., +33/). On the other hand, it has been reported in an in vitro cell culture study that lactoferrin, one of basic proteins in milk, stimulated the growth and di#erentiation of osteoblasts (Cornish et al., ,**.) and suppressed the di#erentiation and resorbing-activity of
osteoclasts (Lorget et al., ,**,). Cornish et al. (,**.) also reported that local injection of lactoferrin into mouse calvarium resulted in increased bone growth. However, in our in vivo study using a rat model of osteoporosis, it was confirmed that oral administration of MBP suppressed reduction in bone strength of the femur, whereas lactoferrin was not e#ective (Morita et al., ,**.). These results suggest that composite reactions of the various basic protein components contained in MBP comprehensively
produce an improvement in bone metabolism
and increase in bone mineral density.