Biomedical subjects

Kuniko Hara

Publications and source records attributed to Kuniko Hara.

5 recordsLinked to original sources

PubMed2007

Infrared analysis of bones in magnesium-deficient rats treated with vitamin K2.

In this study, we compared the effects of vitamin K(2) menatetrenone on bone mechanical properties in rats fed a low-magnesium (Mg) diet. In addition, the mechanism of bone quality was examined using Fourier transform infrared imaging (FTIRI). Thirty 4-week-old male Wistar rats were divided into three groups: intact, low-Mg-control, and low-Mg-MK-4 groups. Rats in the low-Mg groups were given a diet containing 6 mg/100 g Mg (intact, 90 mg/100 g). After an 8-week-treatment, the cortical bone mineral content (CtBMC), outer perimeter, and endo perimeter of the femoral diaphysis in the low-Mg-control group were significantly higher, while the maximum load (ML) and elastic modulus (EM) were 81% and 50% of those in the intact group, respectively (respectively, P < 0.05). In the low-Mg-MK-4 group, ML and EM were significantly higher than in the low-Mg-control group (P < 0.05), with no differences in CtBMC. The mineral/matrix ratios for the periosteal and central regions in the low-Mg-control group were 162% and 120% of those in the intact group (both, P < 0.05), respectively. MK-4 significantly inhibited these increases (P < 0.05). We found that the mineral/matrix ratios for the periosteal region of the femoral diaphysis were negatively correlated with EM, suggesting that an increase in the mineral/matrix ratio may be involved in the reduction of EM and that MK-4 may improve EM by improving the mineral/matrix ratio.

Animals↗

PubMed2005

Comparison of inhibitory effects of warfarin on gamma-carboxylation between bone and liver in rats.

The purposes of this study were to clarify that warfarin (WF, vitamin K antagonist) levels that inhibit gamma-carboxylation are different in liver and bone (experiment 1), and to investigate whether the plasma osteocalcin (OC) level reflects bone OC levels (experiments 2 and 3). Four-week-old male rats were treated with 0.2, 0.4, 0.6, 0.8, 1.0, or 1.2 mg/l of WF solution as drinking water for 4 weeks. Blood coagulation activity, an index of gamma-carboxylation of prothrombin in the liver, was significantly decreased in rats receiving 0.8 mg/l or larger doses of WF. A significant decrease of plasma gamma-carboxylated OC (GlaOC), an index of gamma-carboxylation of OC in bone, was shown in rats receiving 0.2 mg/l or larger doses. Significantly lower OC levels in the femoral diaphysis and metaphysis were shown in the 0.2 mg/l and 0.4 mg/l groups. However, femoral bone mineral density (BMD) values in the WF-treated groups were almost the same as those in the intact group. In experiment 2, we evaluated changes in bone OC levels 4 weeks after discontinuing an 8-week WF treatment. Four-week-old male rats received 0.8 mg/l WF as drinking water for 8 or 12 weeks. Recovery of the OC level after discontinuing the WF treatment was shown in the femoral metaphysis, but not in the diaphysis. In experiment 3, 0.3 mg/kg WF was administrated to 25-week-old male rats three times a week for 8, 12, or 16 weeks. In aged rats, decreased bone OC was shown in the femoral metaphysis, but not in the diaphysis. From these findings, it is suggested that the effects of WF on gamma-carboxylation are likely to appear in bone at lower doses than in the liver, that the bone OC level does not always correspond directly to plasma GlaOC, and that the bone OC level is not directly linked with BMD.

Animals↗

PubMed2005

[Vitamin K2 and bone quality].

Effects of vitamin K(2) (menatetrenone) and alendronate on bone mineral content and bone mechanical property in rats fed a low-magnesium diet. Recent clinical studies have shown that the occurrence of new fractures does not always depend on bone mineral density. Therefore bone quality has become an important issue in osteoporosis research. No animal model for evaluating bone quality has been established. In this study, we found that the treatment of rats with a low-magnesium (Mg) diet reduced their bone strength without decreasing bone mineral content (BMC), so the low Mg diet model is considered to be a good model for examining bone quality. Using this model, we investigated the effects of vitamin K(2) (V.K(2)) and alendronate (ALN). V.K(2) increased maximum load and elastic modulus without influencing BMC. ALN increased maximum load with increasing BMC. By using Fourier transform infrared microscopic analysis, the low-Mg diet treatment increased the mineral/matrix ratio of bones, and V.K(2) suppressed the increase in this ratio. These findings suggest that the mineral/matrix ratio may be a factor involved in bone quality, and that V.K(2) may improve bone quality.

Animals↗

PubMed2002

[Effect of menatetrenone (V.K2) on bone mineral density and bone strength in Ca/Mg deficient rats].

Two experiments were carried out using 7-week-old male Wistar rats. Exp. 1: Rats in the intact group were fed with normal diet (0.5% Ca, 0.09% Mg). Ca/Mg deficient rats were fed low Ca (0.01%) diets containing 0.003, 0.015 or 0.09% Mg for 4 weeks. After 4 weeks, the bone mineral density (BMD) and maximum load in the femur were decreased in Ca/Mg deficient rats, but this was not dependent on dietary Mg concentration. The elasticity, stiffness, and Mg concentration in the femur of these rats were also decreased and Ca deposition in the kidney were increased, compared to those of normal rats, which were related to Mg concentration in the diet. From these results, Mg may play an important role in qualitative changes in bone (i.e., reduced stiffness). Exp. 2: We investigated the effects of V.K2 on the changes in BMD and bone strength in femur induced by low Ca/Mg (0.01%/0.003%) diet for 8 weeks. Compared to the intact group, Ca and Mg levels in serum and femur and cortical thickness, cortical area, and maximum load of the femoral midshaft were decreased in the Ca/Mg-deficient group. In these rats, PTH in the serum and renal Ca concentration were increased. In V.K2-treated rats, these changes in the serum Ca, Mg and PTH levels and the renal Ca concentration were improved. V.K2 also improved the decrease in maximum load in spite of no influence on the cortical thickness, cortical area and Mg concentration in the femur. These findings suggest that V.K2 may affect the qualitative change in bone.

Animals↗

PubMed2002

Effects of vitamin K2 (menatetrenone) on calcium balance in ovariectomized rats.

Vitamin K2 (menatetrenone) has been used for the treatment of osteoporosis in Japan. We investigated the effects of ovariectomy (OVX) and vitamin K2 on the calcium (Ca) balance in 20-week-old female Fischer rats. Vitamin K2 (31 mg/kg per day) was given to animals as a dietary supplement. At weeks 4 and 8 after OVX, a Ca balance study was performed for 5 days. The intestinal Ca transport was determined using the everted gut-sac technique at week 9. The Ca balance was poorer in the OVX-control group than in the sham-control group at weeks 4 and 8 after OVX. The Ca balance improved significantly in the vitamin K2 groups as compared with the sham- and OVX-control groups. The intestinal Ca transport decreased due to OVX and was higher in the vitamin K2 administration groups than in the sham- and OVX-control groups, but not to a significant extent. The bone mineral density in the femoral metaphysis as well as the cortical area and cortical thickness in the femoral diaphysis in the OVX-control group were lower than in the sham-control group. The administration of vitamin K2 significantly inhibited an OVX-induced decrease in cortical area and cortical thickness in the femur. These findings suggest that the poor Ca balance observed in ovariectomized rats may be improved by vitamin K2; vitamin K2 may be involved in preventing bone loss in vivo.

Animals↗