[Soy isoflavones with supplemental calcium provide protection against the loss of bone mass and influence insulin-like growth factor (IGF)-I after ovariectomy in rat].
OBJECTIVE
To compare the effects of soy isoflavone with supplemental calcium to soy isoflavone or Ca alone on preservation of bone mineral density (BMD) and the expression of insulin-like growth factor (IGF)-I.


METHODS
Sprague-Dawley (SD) female Rats, 6 months old, were ovariectomized and randomized into five groups: sham-operated group (n = 10) or ovx (n = 40) group. Shams were fed a 3.272 g/kg Ca diet. Ovx rats were randomized to a 3.272 g/kg Ca diet alone (OVX) or with soy isoflavone (SI) extract (37.95 mg/kg.bw) or to a supplemental Ca diet (Ca, 4.676 g/kg) alone or a supplemental Ca diet with the isoflavone extract (SI + Ca) for 12 weeks. BMD of femur was measured by scanner of bone mineral density. The level of IGF-1 mRNA expression was measured by reverse transcriptase-polymerase chain reaction (RT-PCR), respectively.


RESULTS
There was no significant difference between group Sham (0.267 +/- 0.008) and group SI + Ca (0.263 +/- 0.007) g/cm(2) (P > 0.05) on femur BMD of distal end. Femur BMD of distal end in group Sham and group SI + Ca was greater (P < 0.05) as compared to group OVX (0.245 +/- 0.005) g/cm(2), SI (0.258 +/- 0.011) g/cm(2) or Ca (0.255 +/- 0.004) g/cm(2), P < 0.05. The liver tissue IGF-1 mRNA contents (IGF-1 cDNA/B-actin cDNA) were significantly decreased in group Sham (0.200 +/- 0.023) g/cm(2), SI (0.278 +/- 0.019) g/cm(2), Ca (0.302 +/- 0.026) g/cm(2) or SI + Ca (0.231 +/- 0.025) g/cm(2) as compared to group OVX (0.362 +/- 0.031) g/cm(2), P < 0.05; The liver tissue IGF-1 mRNA contents (IGF-1 cDNA/B-actin cDNA) were significantly decreased in group SI + Ca (0.231 +/- 0.025) g/cm(2) compared to group SI (0.278 +/- 0.019) g/cm(2) and Ca (0.302 +/- 0.026) g/cm(2), P < 0.05.


CONCLUSIONS
Soy isoflavones combined with supplemental Ca are more protective against the loss of femur BMD than soy isoflavones or supplemental Ca diet alone. The dose of SI (37.95 mg/kg.bw) might significantly restrain the rising of the liver tissue IGF-1 mRNA contents caused by ovariectomy.
Cheng
Mao-wei
MW
Inspcetion Part of Hygiece Inspcetion and Guard Institute of Control and Prevention of Hubei Provincial Center for Disease Control and Prevention, Wuhan 430079, China.
Liu
Jia-fa
JF
Yi
Guo-qin
GQ
Zhang
Xi-ping
XP
Zhu
Qing-hua
QH
Liu
Lie-gang
LG
D000818:Animals; D015519:Bone Density / Q000187:drug effects*; D002136:Calcium, Dietary / Q000494:pharmacology*; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000235:genetics; D007529:Isoflavones / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D010052:Ovariectomy; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013025:Glycine max
D002136:Calcium, Dietary; D007529:Isoflavones; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I