Studies on action of menaquinone-7 in regulation of bone metabolism and its preventive role of osteoporosis

The effect of menaquinone‐7 (MK‐7) on bone components and bone resorbing factors induced‐bone resorption using the femoral‐diaphyseal and ‐ metaphyseal tissues obtained from elderly female rats in vitro were examined. Calcium content, alkaline phosphatase activity and deoxyribonucleic acid (DNA) in the diaphyseal and metaphyseal tissues in elderly females rats were significantly decreased as compared with that of young rats, indicating that aging causes a deterioration of bone formation. The presence of MK‐7 (10−6−10−5 M) caused a significant prevention of reduction of biochemical components. On the other hand, the bone‐resorbing factor, parathyroid hormone (1–34) (PTH; 10−7 M) and prostaglandin E2 (PGE2; 10−5 M) caused a significant decrease in calcium content in the diaphyseal and metaphyseal tissues. This decreases was completely inhibited in the presence of MK‐7 (10−7−10−5 M). In addition, MK‐7 (10−7−10−5 M) completely prevented the PTH (10−7 M) or PGE2 (10−5 M) induced increases in medium glucose consumption and lactic acid production by bone tissues, Furthermore, the effect of the prolonged intake of dietary MK‐7 on bone loss in ovariectomized rats was investigated. As a result, it was found that the intake of experimental diets containing the fermented soybean (natto) with supplemental MK‐7 caused significant elevations of MK‐7 and γ‐carboxylated osteocalcin concentration, a bio marker of bone formation, in the serum of both ovariectomized rats and normal subjects, suggesting that MK‐7 may play an important role in the prevention of age‐related bone loss.