Daidzein administration positively affects thyroid C cells and bone structure in orchidectomized middle-aged rats.
CONCLUSIONS
Thyroid C cells hormone, calcitonine, inhibits bone resorption. We have demonstrated that daidzein treatment of orchidectomized rats (model for osteoporosis) stimulated C cells and increased trabecular bone mass. These results suggest that, besides direct action, daidzein may also affect bone structure indirectly through enhancement of thyroid C cell activity.


BACKGROUND
Thyroid C cells produce calcitonin (CT) which acts as an inhibitor of bone resorption. In this study, the influence of daidzein treatment on thyroid C cells, bone structure, and bone function in orchidectomized (Orx) middle-aged rats was investigated.


METHODS
Sixteen-month-old Wistar rats were divided into Orx and sham-operated (SO) groups. Half the Orx rats were given subcutaneous injections of daidzein (30 mg/kg b.w./day) for 3 weeks. CT-immunopositive thyroid C cells were morphometrically analyzed. The metaphyseal region of the proximal tibia was measured histomorphometrically, and cancellous bone area (B.Ar), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were calculated. Serum samples were analyzed for CT and osteocalcin (OC), calcium (Ca) and phosphorus concentrations, and urine samples for Ca levels.


RESULTS
Treatment of Orx animals with daidzein significantly increased volume of C cells compared to the Orx rats. Daidzein also enhanced B.Ar, Tb.Th, and Tb.N and reduced Tb.Sp. The serum OC and urinary Ca concentrations decreased significantly in comparison with the Orx group.


CONCLUSIONS
These findings indicate that daidzein treatment stimulates thyroid C cells, increase trabecular bone mass, and decrease bone turnover in Orx middle-aged rats, which is the model of male osteoporosis.
Institute for Biological Research, Belgrade, Serbia. brankof@ibiss.bg.ac.rs
B
B
Filipović
B
B
Sosić-Jurjević
V
V
Ajdzanović
D
D
Brkić
M
M
Manojlović-Stojanoski
V
V
Milosević
M
M
Sekulić
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D050071:Bone Density Conservation Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002116:Calcitonin / Q000096:biosynthesis; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical / Q000379:methods; D007529:Isoflavones / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D009919:Orchiectomy; D010024:Osteoporosis / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D013977:Tibia / Q000187:drug effects / Q000473:pathology
D015415:Biomarkers; D050071:Bone Density Conservation Agents; D007529:Isoflavones; C004742:daidzein; D002116:Calcitonin