The Effects of Isoflavones Intake Level on Bone Markers and Bone Related Hormones in Growing Female Rats

The overall purpose of this study was to investigate the effects of level of isoflavones supplementation on bone metabolism in growing female rats. Forty-five rats divided into three groups; Control, 1/2IF, and 1IF. Serum osteocalcin and alkaline phosphatase (ALP) activity, urinary deoxypyridinoline (DPD) crosslinks value were measured to monitor bone formation and resorption at the ninth week after feeding. Hormones related to bone metabolism were determined, included parathyroid hormone (PTH), calcitonin, estradiol, growth hormone and insulin-like growth factor I (IGF-I). The results of this study were as follows: the isoflavones intake level did not affect weight gain, mean food intake and food efficiency ratio. The serum concentration of osteocalcin and the activity of ALP were not significantly different by different levels of isoflavones supplementation. The urinary DPD crosslinks value was not significantly different by different levels of isoflavones supplementation. There were no significant differences in serum PTH, estradiol and IGFI among all groups. However, calcitonin was shown significantly higher in the groups of 1IF and 1/2IF than control group. And growth hormone was shown significantly higher in the groups of 1IF than control group.

The Effects of Level of Isoflavones Supplementation on Bone Mineral Density in Growing Female Rats

The overall purpose of this study was to investigate the effects of level of isoflavones supplementation on bone metabolism in growing female rats. The effects of level of isoflavones supplementation on bone mineral density (BMD) and bone mineral content (BMC) were inspected in this study. Forty-five rats divided into three groups: Casein, 1/2IF, IF. The serum and urine concentrations of calcium and phosphorus were determined. BMD and BMC were estimated by using PIXImus (GE Lunar Co, Wisconsin.) in spine and femur on 3, 6, 9 weeks after feeding. This study of results were as follows: The isoflavones supplementation level did not affect weight gain, mean food intake and food efficiency ratio. The serum concentration of calcium, phosphorus were not significantly different by different level of isoflavones supplementation. The urinary calcium and phosphorus excretion were not significantly different, too. Spine and femur BMD, BMC were not significantly increased by different level of isoflavones supplementation on 3 and 6 weeks after feeding. Spine BMD and spine BMC per weight, femur BMC per weight were significantly increased in the groups 1/2IF and IF at the ninth week after feeding, but there was no significant difference by different level of isoflavones supplementation. Spine BMD per weight and femur BMD per weight were significantly higher in the group of IF than in the group of Casein and 1/2IF at the ninth week after feeding. These results suggest that the group of IF with rich isoflavones supplementation was effective to the increase of BMD spine and femur in growing female rats, respectively.

Effects of Soy and Isoflavones on Bone Metabolism in Growing Female Rats

The purpose of this study was to determine which differences in the source of protein (soy vs casein) and isoflavones in soy protein are responsible for the differential effects of bone marks and hormones in growing female rats. Forty-two 21-day-old Sprague-Dawley female rats were randomly assigned to one of three groups, consuming casein (control group), soy protein isolate (57 mg isoflavones/100 g diet), or soy protein concentrate (about 1.2 mg isoflavones/100 g diet). All rats were fed on experimental diet and deionized water ad libitum for 9 weeks. Bone formation was measured by serum osteocalcin and alkaline phosphatase (ALP) concentrations. And bone resorption rate was measured by deoxypyridinoline (DPD) crosslinks immunoassay and corrected for creatinine. Serum osteocalcin, growth hormone, estrogen and calcitonin were analyzed using radioimmunoassay kits. Diet did not affect weight gain and mean food intake. Food efficiency ratio was lower in the soy protein groups. The soy isolate group had a higher ALP and osteocalcin concentration and lower crosslinks value than the casein group. Therefore, the soy isolate groups had a higher bone formation/resorption ratio than the casein group. And, the soy group had significantly higher growth hormone than the casein group. The findings of this study suggest that soy protein and isoflavones are beneficial for bone formation in growing female rats. Therefore, exposure to these soy protein and isoflavones early in life may have benefits for osteoporosis prevention.