Naomi Omi

The effect of voluntary exercise on bone mineral density and skeletal muscles in the rat model at ovariectomized and sham stages.

The changes of bone mineral density (BMD) and skeletal muscles were evaluated in the rat model at either sham or ovariectomized stages to attempt to make clear the effect of voluntary running exercise on bone metabolism. In comparison with the control groups within the ovariectomized (OVX) and the sham groups, in the running groups, (1) the urinary phosphorus (P) and creatinine (Cr) excretions showed an increase concurrently with the increase in the running distance; (2) the weight of the quadriceps femoris was significantly higher; and (3) the BMD of appendicular and axial bones was significantly greater. These results suggest that voluntary running exercise could effect the BMD, the weight of the skeletal muscles, and the acceleration of energy metabolism.

Effect of 1α-hydroxyvitamin D3 and egg-shell calcium on bone metabolism in ovariectomized osteoporotic model rats

Abstract Egg-shell calcium (Ca) is one of the effective Ca sources for bone metabolism. In the present study, we investigated whether egg-shell Ca had similar effects compared with calcium carbonate (CaCO3) when vitamin D3 (1α(OH)D3) treatment was given to an osteopo-rotic rat model. In both 1α(OH)D3-supplemented and -unsupplemented rats, the bone mineral density (BMD) of the lumber spine in the vitamin-supplemented group increased significantly compared with the unsupplemented group. In a Ca balance study, there were also significant differences in intestinal Ca absorption, urinary Ca and fecal Ca between the vitamin-supplemented and -unsupplemented groups. These results show that egg-shell Ca could have similar effects to CaCO3 on bone metabolism. In contrast with CaCO3, vitamin D3 supplementation did not significantly increase serum Ca levels in the egg-shell Ca group; however, the mechanism of Ca absorption is still unclear. Our results suggest that egg-shell Ca may be an effective nutrient in Ca metabolism for people treated with vitamin D3.

Bone loss in a rat model of non-insulin-dependent diabetes mellitus, the OLETF (Otsuka Long-Evans Tokushima fatty strain) rat

Abstract: A long-term investigation of bone metabolism was conducted in a newly developed strain, the OLETF (Otsuka Long-Evans Tokushima fatty strain) rat, which spontaneously develops non-insulin-dependent diabetes (NIDDM). The OLETF rats used in this study developed hyperglycemia before the age of 24 weeks and overt diabetes before 40 weeks. The bone mineral density (BMD) of the lumbar spine peaked at the age of 24 weeks in the OLETF rats, and declined rapidly after 40 weeks. In addition, the BMD of the tibial proximal metaphysis and diaphysis and the bone strength of the femoral diaphysis peaked at 40 weeks, then declined rapidly. In contrast, the BMD and the bone strength of the LETO (Long-Evans Tokushima Otsuka) rats, used as a control, peaked at 24 weeks, and did not change thereafter. The serum vitamin D metabolites [25-hydroxy vitamin D (25-OHD), 24,25-dihydroxyvitamin D (24,25(OH)2D), and 1,25-dihydroxy vitamin D (1,25(OH)2D)] levels for the OLETF rats declined with age, and were significantly lower than those of the control LETO rats. The level of serum bone-specific alkaline phosphatase (Alp) activity and serum tartrate-resistant acid phosphatase (Tr-Acp) activity in the OLETF rats increased remarkably with age from 24 weeks, and there were significant differences in the 56- and the 69-week values between the OLETF rats and the age-matched control LETO rats. These results suggested that this strain can serve as a useful model for NIDDM with osteopenia.

The effect of “AA Ca (active absorbable calcium)” on bone metabolism of ovariectomized rats

It is necessary to take enough calcium (Ca) for prevention of osteoporosis. In most cases nutrient intake has been sufficient in Japan. However, it was found that Ca intake, in particular, was insufficient according to the national nutrition survey conducted by the Ministry of Health and Welfare. This suggests that adequate intake of Ca from normal daily diet is difficult. Recently there have been a great deal of studies about the development of Ca sources.In this study, three experiments were carried out to examine the effect of “AA Ca (Active Absorbable Calcium)” on bone metabolism in ovariectomized young and old rats. Five-week-old SD-strain female rats, seven-month-old Wistar-strain femalle rats, and eleven-month-old Wistar-strain female rats were ovariectomized and were fed a low Ca diet for approximately the one month. Thereafter within each experiment, all the rats were divided into two groups; a control group was fed a CaCO3 diet (0.3% Ca, 0.3% P) and an experimental AA Ca group was fed an AA Ca dietad libitum during the experimental period.The results were as follows: in comparison with the CaCO3 group, the AA Ca group within each experiment,1 the bone mineral density (BMD) of tibias measured using DXA (Hologics QDR-1000) had significantly increased;2 the breaking force of femurs had shown an increase; and3 the intestinal Ca absorption was high.These results suggest the “AA Ca” is effective in increasing the BMD, the breaking force, and the intestinal Ca absorption at every stage of development. The AA Ca could be regarded as a valuable, effective source of Ca in the prevention of osteoporosis.