The effect of 17 beta-estradiol treatment on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin

Protective effects of Tualang honey on bone structure in experimental postmenopausal rats

OBJECTIVE

The objective of this study was to evaluate the effects of Tualang honey on trabecular structure and compare these effects with those of calcium supplementation in ovariectomized rats.

METHODS

Forty female, Sprague-Dawley rats were randomly divided into five groups (n =8): four controls and one test arm. The control arm comprised a baseline control, sham-operated control, ovariectomized control, and ovariectomized calcium-treated rats (receiving 1% calcium in drinking water ad libitum). The test arm was composed of ovariectomized, Tualang honey-treated rats (received 0.2 g/kg body weight of Tualang honey). Both the sham-operated control and ovariectomized control groups received vehicle treatment (deionized water), and the baseline control group was sacrificed without treatment.

RESULTS

All rats were orally gavaged daily for six weeks after day one post-surgery. The bone structural analysis of rats in the test arm group showed a significant increase in the bone volume per tissue volume (BV/TV), trabecular thickness (Tb.Th) and trabecular number (Tb.N) and a significant decrease in inter-trabecular space (Tb.Sp) compared with the ovariectomized control group. The trabecular thickness (Tb.Th) in the test arm group was significantly higher compared with the ovariectomized-calcium treated group, and the inter-trabecular space (Tb.Sp) in the test arm group was significantly narrower compared with the ovariectomized-calcium treated group.

CONCLUSION

In conclusion, ovariectomized rats that received Tualang honey showed more improvements in trabecular bone structure than the rats that received calcium.

A novel synthetic triazolotriazepine derivative JTT-606 inhibits bone resorption by down-regulation of action and production of bone resorptive factors

In the search for a new class of bone-sparing agents, we have conducted random screening of the domestic chemical library using 45Ca release assay from prelabeled cultured neonatal mouse calvariae and identified a novel synthetic triazolotriazepine JTT-606 as a candidate for a potent inhibitor of bone resorption. JTT-606 inhibited 45Ca release dose dependently not only in the control calvarial culture but also in the stimulated cultures by interleukin-1alpha (IL-1alpha), fibroblast growth factor 2 (FGF-2), and parathyroid hormone (PTH). JTT-606 also inhibited both basal and stimulated osteoclast-like (OCL) cell formation in the coculture of mouse osteoblastic cells and bone marrow cells dose dependently, indicating its inhibitory effect on osteoclast differentiation. Ex vivo OCL cell formation by cultured bone marrow cells collected from ovariectomized (OVX) mice also was decreased dose dependently by in vivo application of JTT-606 to a level similar to that from sham-operated mice. Furthermore, JTT-606 inhibited resorbed pit formation by isolated mature osteoclasts as well as by unfractionated bone cells derived from rabbit long bones in the control and FGF-2-stimulated cultures dose dependently, indicating both the direct and the indirect actions of JTT-606 on mature osteoclast function. In addition, JTT-606 reduced production of IL-1alpha, tumor necrosis factor alpha (TNF-alpha), IL-6, and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the human peripheral blood mononuclear cell culture. In vivo analyses of mature OVX rats revealed that the application of JTT-606 for 12 weeks increased the BMD of the lumbar spine and decreased the levels of serum osteocalcin and urine deoxypyridinoline to levels similar to those of 17beta-estradiol-treated OVX rats. We propose that JTT-606 may inhibit both osteoclast differentiation and function by down-regulating both the action and the production of bone resorptive factors. It is speculated that JTT-606 could be a potent agent for the treatment of osteopenic disorders with elevated osteoclastic bone resorption.

The effect of olpadronate in ovariectomized thyroxine-treated rats

Hyperthyroidism increases bone turnover and induces bone loss. This study examines the effect of thyroid hormone excess on two biochemical markers of bone turnover (hydroxyproline and bone alkaline phosphatase) as well as on bone mineral content (BMC) and bone mineral density (BMD). The possible protective role of dimethyl-APD (olpadronate, OLP), on both suppression of bone turnover and bone mineral loss in ovariectomized (ovx) rats, was also studied. Female Sprague-Dawley rats, were assigned to five groups of eight rats each: sham, ovx, ovx OLP treated (0.3 mg/kg per week), ovx T4 treated (250 micrograms/kg per day), and ovx T4-OLP rats. Rats were killed after 5 weeks of treatment. At the end of the study, blood samples were analyzed for serum calcium, phosphorus, T4, total and bone alkaline phosphatase (ALP and b-ALP), and urinary samples for hydroxyproline/creatinine ratio (HOProl/creat). Moreover, total BMC, BMD, and scanned area were determined by DXA. Ovx T4-OLP-treated rats presented higher values of b-ALP than ovx T4-treated, ovx, and sham rats (p < 0.05). Ovx increased HOProl/creat excretion compared with sham (p < 0.05), but it was similar compared with ovx T4-treated rats. OLP treatment reduced HOProl/creat excretion in both ovx T4-treated (p < 0.05) and ovx rats (p < 0.05). The final BMC in ovx was lower than in the sham group, but the difference was not statistically significant (p < 0.08). The lowest BMC was observed in ovx T4 rats (p < 0.05). When final BMC was expressed per body weight (BMC/W), ovx rats presented a significantly lower BMC/W than sham rats (p < 0.05). Ovx OLP rats had BMC/W levels higher than ovx (p < 0.005), ovx T4 (p < 0.01), and ovx T4-OLP rats (p < 0.01). The ovx group had a final BMD lower than sham animals (p < 0.05), but not significantly different than the ovx T4 rats. BMC and BMD of OLP ovx rats, whether they received T4 or not, was similar to the sham group. The highest final BMD was observed in the ovx T4-OLP group. In summary, the prevention of an increase in HOProl excretion accompanied by the fact that final BMD and BMC in OLP-treated animals were comparable to sham control rats may reflect that OLP administration could inhibit bone resorption in both T4-treated or -untreated rats. Although further studies are necessary, these findings may have clinical relevance in estrogen-depleted patients to whom medical management other than the reduction of T4 administration would be desirable.

Local bone turnover in the metaphysis of the proximal tibia and the lumbar vertebra during the early periods after ovariectomy in rats

To clarify the local changes in bone formation and resorption during the early period after ovariectomy (OVX), 200 SD rats, 4 months of age, underwent OVX or sham surgeries and seven to nine rats from each group were terminated at 1, 3, 7, 11, 15, 19, 23, 28, 35, 63, and 91 days postsurgery after tetracycline labeling. Serum intact osteocalcin levels were measured. Undecalcified sections of the 5th lumbar body (L5) and the right proximal tibia were measured for trabecular bone area, the labeled perimeters and the interlabeling distances after Villanueva's staining. On the 4th lumbar body (L4) and the left proximal tibia, undecalcified sections were measured for the trabecular osteoclast by tartrate-resistant acid phosphatase staining. The uterine horns were atrophied on the 3rd postovariectomy day (day 3). Serum osteocalcin levels increased on day 7 and reached the highest value on day 23. In either L5 or the metaphysis of the proximal tibia, trabecular bone volume (BV/TV) significantly decreased on day 15. The trabecular bone loss on day 28 was approximately 50% in the tibia and 15% in the L5. In either the lumbar or the tibia, osteoclast numbers significantly increased at day 3, and peaked between days 15 and 23. In the tibia, however, the bone formation rates (BFR/BS) were significantly reduced on the 3rd and 7th post-surgical days compared with the start value for both the OVX and sham groups. The BFR/BS values in L5 did not decrease during the first 7 days in either group. The BFR/BS values were then increased for both L5 and the tibia after day 7. These data clearly demonstrated that the local bone turnover 7 days post-OVX was identical in the proximal tibia and the lumbar vertebra. In the proximal tibia, however, it may be suggested that the increased bone resorption and reduced formation within 7 days after OVX due to the combined effects of both an estrogen deficiency and the surgical intervention would possibly play a critical role in the greater magnitude of the trabecular bone loss.