Long-term calcitonin therapy in postmenopausal osteoporosis

Ex vivo exposure to calcitonin or raloxifene improves mechanical properties of diseased bone through non-cell mediated mechanisms

Raloxifene (RAL) reduces clinical fracture risk despite modest effects on bone mass and density. This reduction in fracture risk may be due to improved material level-mechanical properties through a non-cell mediated increase in bone hydration. Synthetic salmon calcitonin (CAL) has also demonstrated efficacy in reducing fracture risk with only modest bone mass and density improvements. This study aimed to determine if CAL could modify healthy and diseased bone through cell-independent mechanisms that alter hydration similar to RAL. 26-week-old male C57BL/6 mice induced with chronic kidney disease (CKD) beginning at 16 weeks of age via 0.2 % adenine-laced casein-based (0.9 % P, 0.6 % C) chow, and their non-CKD control littermates (Con), were utilized. Upon sacrifice, right femora were randomly assigned to the following ex vivo experimental groups: RAL (2 μM, n = 10 CKD, n = 10 Con), CAL (100 nM, n = 10 CKD, n = 10 Con), or Vehicle (VEH; n = 9 CKD, n = 9 Con). Bones were incubated in PBS + drug solution at 37 °C for 14 days using an established ex vivo soaking methodology. Cortical geometry (μCT) was used to confirm a CKD bone phenotype, including porosity and cortical thinning, at sacrifice. Femora were assessed for mechanical properties (3-point bending) and bone hydration (via solid state nuclear magnetic resonance spectroscopy with magic angle spinning (ssNMR)). Data were analyzed by two-tailed t-tests (μCT) or 2-way ANOVA for main effects of disease, treatment, and their interaction. Tukey's post hoc analyses followed a significant main effect of treatment to determine the source of the effect. Imaging confirmed a cortical phenotype reflective of CKD, including lower cortical thickness (p < 0.0001) and increased cortical porosity (p = 0.02) compared to Con. In addition, CKD resulted in weaker, less deformable bones. In CKD bones, ex vivo exposure to RAL or CAL improved total work (+120 % and +107 %, respectively; p < 0.05), post-yield work (+143 % and +133 %), total displacement (+197 % and +229 %), total strain (+225 % and +243 %), and toughness (+158 % and +119 %) vs. CKD VEH soaked bones. Ex vivo exposure to RAL or CAL did not impact any mechanical properties in Con bone. Matrix-bound water by ssNMR showed CAL treated bones had significantly higher bound water compared to VEH treated bones in both CKD and Con cohorts (p = 0.001 and p = 0.01, respectively). RAL positively modulated bound water in CKD bone compared to VEH (p = 0.002) but not in Con bone. There were no significant differences between bones soaked with CAL vs. RAL for any outcomes measured. RAL and CAL improve important post-yield properties and toughness in a non-cell mediated manner in CKD bone but not in Con bones. While RAL treated CKD bones had higher matrix-bound water content in line with previous reports, both Con and CKD bones exposed to CAL had higher matrix-bound water. Therapeutic modulation of water, specifically the bound water fraction, represents a novel approach to improving mechanical properties and potentially reducing fracture risk.

Yeast Hydrolysate and Postmenopausal Osteoporosis

We used an ovariectomy (OVX) rat model to test whether yeast hydrolysate (YH) has therapeutic effects on postmenopausal osteoporosis-induced bone loss. The rats were separated into five treatment groups: the sham group (sham operation); the control group (no treatment after OVX); the estrogen group (estrogen treatment after OVX); YH 0.5% group (drinking water supplementation with 0.5% YH after OVX); and the YH 1% group (drinking water supplementation with 1% YH after OVX). In addition, the YH treatment restored serum testosterone concentration in the OVX rats up to the normal level. Further, YH treatment affected bone markers; a significant increase in serum calcium concentration was observed after adding YH to the diet. The levels of serum alkaline phosphatase, osteocalcin, and cross-linked telopeptides of type I collagen were reduced by YH supplementation, unlike those in the no-treatment control. Although not statistically significant, YH treatment in OVX rats improved trabecular bone microarchitecture parameters. These results show that YH may ameliorate the bone loss caused by postmenopausal osteoporosis because of the normalization of serum testosterone concentration.

Edible Bird's Nest: The Functional Values of the Prized Animal-Based Bioproduct From Southeast Asia-A Review

Edible Bird's Nest (EBN) is the most prized health delicacy among the Chinese population in the world. Although some scientific characterization and its bioactivities have been studied and researched, no lights have been shed on its actual composition or mechanism. The aim of this review paper is to address the advances of EBN as a therapeutic animal bioproduct, challenges and future perspectives of research involving EBN. The methodology of this review primarily involved a thorough search from the literature undertaken on Web of Science (WoS) using the keyword "edible bird nest". Other information were obtained from the field/market in Malaysia, one of the largest EBN-producing countries. This article collects and describes the publications related to EBN and its therapeutic with diverse functional values. EBN extracts display anti-aging effects, inhibition of influenza virus infection, alternative traditional medicine in athletes and cancer patients, corneal wound healing effects, stimulation of proliferation of human adipose-derived stem cells, potentiate of mitogenic response, epidermal growth factor-like activities, enhancement of bone strength and dermal thickness, eye care, neuroprotective and antioxidant effects. In-depth literature study based on scientific findings were carried out on EBN and its properties. More importantly, the future direction of EBN in research and development as health-promoting ingredients in food and the potential treatment of certain diseases have been outlined.

The effects of calcitonin on post-orthodontic relapse in rats

Objectives

To determine the effects of systematic calcitonin administration on post‐orthodontic relapse in rat model.

Material and methods

This experimental animal model involved 36 male Wister rats. The maxillary right first molars were moved mesially, using a modified orthodontic appliance delivered 50 gm, for 14 days, retained for 4 days and left to relapse for 10 days. The study group was divided into three subgroups in which a single injection of calcitonin (20 IU/Kg), three injections of calcitonin (20 IU/Kg), each every other day, and normal saline were administered subcutaneously after orthodontic tooth movement has finished. The relapse ratio, histomorphometric analysis including osteoblasts, osteoclasts numbers and bone area and immunohistochemical analysis including the expression of receptor activator of nuclear factor kappa Β (RANK), receptor activator of nuclear factor kappa Β ligand (RANKL) and osteoprotegerin (OPG) were measured and assessed.

Results

The relapse ratio was significantly reduced in the three‐dose calcitonin group (28%) compared to the single dose calcitonin group (34%) and the control group (46%). This was accompanied by a nonsignificant increase in osteoblasts number and bone area in three‐dose calcitonin group and a nonsignificant reduction in osteoclast number. However, the immune histochemical expression of RANK, RANKL and OPG did not show statistically significant difference at the end of relapse period.

Conclusions

Systemic administration of three doses of calcitonin may minimize the relapse ratio in experimentally moved rat molars.

Isoliquiritigenin Derivatives Inhibit RANKL-Induced Osteoclastogenesis by Regulating p38 and NF-κB Activation in RAW 264.7 Cells

Bone diseases may not be imminently life-threatening or a leading cause of death such as heart diseases or cancers. However, as aging population grows in almost every part of the world, they surely impose significant socioeconomic burden on the society, not to mention the patients and their families. Osteoporosis is the most common type of bone disease, which frequently develops in seniors, especially in postmenopausal women. Although currently several anti-osteoclastic drugs designed to suppress excessive osteoclast activation, a major cause of osteoporosis, are commercially available, accompanying adverse effects ranging from mild to severe have been reported as well. Natural products have become increasingly popular because of their effectiveness with fewer side effects. Isoliquiritigenin (ILG), a natural flavonoid from licorice, has been reported to suppress osteoclast differentiation and activation. In the present study, newly synthesized ILG derivatives were screened for their anti-osteoporotic activity as more potent substitute candidates to ILG. Out of the 12 ILG derivatives tested, two compounds demonstrated significantly improved bone loss in vitro by inhibiting both osteoclastogenesis and osteoclast activity. The results of the present study indicate that these compounds may serve as a potential drug for osteoporosis and warrant further studies to evaluate their in vivo efficacy.

Design and Characterizations of Inhalable Poly(lactic-co-glycolic acid) Microspheres Prepared by the Fine Droplet Drying Process for a Sustained Effect of Salmon Calcitonin

The present study aimed to develop inhalable poly (lactic-co-glycolic acid) (PLGA)-based microparticles of salmon calcitonin (sCT) for sustained pharmacological action by the fine droplet drying (FDD) process, a novel powderization technique employing printing technologies. PLGA was selected as a biodegradable carrier polymer for sustained-release particles of sCT (sCT/SR), and physicochemical characterizations of sCT/SR were conducted. To estimate the in vivo efficacy of the sCT/SR respirable powder (sCT/SR-RP), plasma calcium levels were measured after intratracheal administration in rats. The particle size of sCT/SR was 3.6 µm, and the SPAN factor, one of the parameters to present the uniformity of particle size distribution, was calculated to be 0.65. In the evaluation of the conformational structure of sCT, no significant changes were observed in sCT/SR even after the FDD process. The drug release from sCT/SR showed a biphasic pattern with an initial burst and slow diffusion in simulated lung fluid. sCT/SR-RP showed fine inhalation performance, as evidenced by a fine particle fraction value of 28% in the cascade impactor analysis. After the insufflation of sCT samples (40 µg-sCT/kg) in rats, sCT/SR-RP could enhance and prolong the hypocalcemic action of sCT possibly due to the sustained release and pulmonary absorption of sCT. From these observations, the strategic application of the FDD process could be efficacious to provide PLGA-based inhalable formulations of sCT, as well as other therapeutic peptides, to enhance their biopharmaceutical potentials.

Oleanolic acid exerts bone protective effects in ovariectomized mice by inhibiting osteoclastogenesis

Postmenopausal osteoporosis (POP) is quite prevalent and many new drugs are under development to obtain better therapeutic outcomes. Oleanolic acid (OA) has been reported to prevent bone loss in ovariectomized (OVX) rats by stimulating osteoblastogenesis. One previous study has demonstrated that acetate of OA suppressed lipopolysaccharides (LPS)-induced bone loss in mice. However, the role of OA in the receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated osteoclastogenesis is still not elucidated. Here we show that OA dose-dependently inhibits RANKL-mediated osteoclastogenesis and the formation of functional osteoclasts without impairing the viability and osteoclastic potential in bone marrow macrophages (BMMs). Moreover, OA administration attenuates bone loss in OVX mice by inhibiting osteoclast's densities. Mechanistically, OA does not affect RANKL-induced activation of the NF-кB, JNK, p38, ERK and Akt pathways, but inhibits the expression of the nuclear factor of activated T-cells c1(NFATc1) and c-Fos. Moreover, OA significantly suppresses the expression of RANKL-activated osteoclast genes encoding matrix metalloproteinase 9 (MMP9), Cathepsin K(Ctsk), tartrate-resistant acid phosphatase (TRAP) and carbonic anhydrase II (Car2). This work has elucidated the molecular mechanism of OA in RANKL-mediated osteoclastogenesis and revealed the promising potential of OA to be further developed as a new drug to prevent and treat POP.

Recent advances in the identification and authentication methods of edible bird's nest

Edible bird's nest (EBN) is an expensive animal bioproduct due to its reputation as a food and delicacy with diverse medicinal properties. One kilogram of EBN costs ~$6000 in China. EBN and its products are consumed in mostly Asian countries such as China, Hong Kong, Taiwan, Singapore, Malaysia, Indonesia, Vietnam and Thailand, making up almost 1/3 of world population. The rapid growth in EBN consumption has led to a big rise in the trade scale of its global market. Presently, various fake materials such as tremella fungus, pork skin, karaya gum, fish swimming bladder, jelly, agar, monosodium glutamate and egg white are used to adulterate EBNs for earning extra profits. Adulterated or fake EBN may be hazardous to the consumers. Thus, it is necessary to identify of the adulterants. Several sophisticated techniques based on genetics, immunochemistry, spectroscopy, chromatography and gel electrophoresis have been used for the detection of various types of adulterants in EBN. This article describes the recent advances in the authentication methods for EBN. Different genetic, immunochemical, spectroscopic and analytical methods such as genetics (DNA) based techniques, enzyme-linked immunosorbent assays, Fourier transform infrared and Raman spectroscopic techniques, and chromatographic and gel electrophoretic methods have been discussed. Besides, significance of the reported methods that might pertain them to applications in EBN industry has been described. Finally, efforts have been made to discuss the challenges and future perspectives of the authentication methods for EBN.

Response of trabecular bone, thyroid C and follicular cells to synthetic salmon calcitonin in middle-aged orchidectomized male rats

In contrast to studies in women, male osteoporosis is poorly understood and strictly related to advancing age. Among the first antiresorptive substances used in the prevention and treatment of osteoporosis is calcitonin (CT), a hypocalcemic hormone that potently inhibits osteoclastic bone resorption. Natural CT is produced and secreted by thyroid C-cells. The other endocrine population of thyroid cells produces thyroid hormones (TH), which also affect bone turnover. The aim of this study was to evaluate the influence of salmon CT on trabecular bone microarchitecture with special reference to effects on the structure and function of both CT- and TH-producing thyroid cells in orchidectomized (Orx) middle-aged rats. Twenty-four male Wistar rats aged 15 months were randomly divided into Orx and sham-operated (SO) groups. One group of Orx animals received (s.c.) synthetic salmon CT (Orx + CT; 100 IU kg-1 b.w.) subcutaneously every second day for 6 weeks. The second Orx group and SO rats were given the same volume of vehicle alone by the same schedule. Trabecular bone histomorphometrical parameters were: cancellous bone area (B.Ar), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular separation (Tb.Sp) were obtained with an ImageJ public-domain image-processing program. The peroxidase-antiperoxidase method was applied for localization of CT in C-cells. Anti-human CT antisera served as the primary antibodies. For immunohistochemical characterization of vascular endothelial growth factor (VEGF) in thyroid tissue, rabbit antisera against human VEGF, served as primary antibodies. CT-immunopositive thyroid C-cells, thyroid follicular epithelium, interstitium and colloid were evaluated morphometrically. Blood serum samples were analyzed for CT, osteocalcin (OC), and thyroxine (T4 ), and calcium (Ca2+ ) concentration was determined in urine samples. Salmon CT application significantly increased B.Ar, TbTh and TbN, but markedly decreased Tb.Sp. Administration of exogenous CT significantly decreased mean volume (Vc) and relative volume density (Vv) of thyroid C-cells in relation to both SO and Orx groups. The Vv of the colloid was higher, whereas the VV of the follicular epithelium was lower after CT treatment compared with Orx alone. CT treatment markedly elevated serum CT, whereas serum OC, T4 and urinary Ca2+ concentrations were lower than in the Orx group. These results indicate that salmon CT stimulates trabecular bone microarchitecture, strongly inhibits thyroid C-cells and changes the structure of the thyroid gland, indicating hypoactivity.

Sialoglycoproteins prepared from the eggs of Carassius auratus prevent bone loss by inhibiting the NF-κB pathway in ovariectomized rats

In this study, we investigated the improvement of osteoporosis by sialoglycoproteins isolated from the eggs of Carassius auratus (Ca-SGP) in ovariectomized rats. Ca-SGP was supplemented to ovariectomized Sprague-Dawley rats for 90 days. The results showed that Ca-SGP treatment remarkably prevented the reduction of bone mass, improved cancellous bone structure and biochemical properties. Ca-SGP also significantly decreased the serum contents of TRAP, Cath-K, MMP-9, DPD, CTX-1, Ca, and P. Mechanism investigation revealed that Ca-SGP significantly increased the OPG/RANKL ratio in mRNA expression, protein expression and serum content. Further research suggested that NF-κB signaling pathways were inhibited by suppressing the mRNA and protein expressions of NFATc1 and TRAF6, diminishing the mRNA expression and phosphorylation of NF-κB p65, three key transcription factors in NF-κB pathways. These results suggest that Ca-SGP can improve osteoporosis by inhibiting bone resorption via suppressing the activation of osteoclastogenesis related NF-κB pathways.

Estrogen-like osteoprotective effects of glycine in in vitro and in vivo models of menopause

Recently, the placenta mesotherapy has been widely used to treat menopause. Placenta contains amino acids, peptides, minerals, and estrogen. Here, we investigated the estrogen-like osteoprotective effects of glycine (a main ingredient of placenta) in in vitro and in vivo models of menopause. We assessed the effect of glycine on MG-63 osteoblast cell line, MCF-7 estrogen-dependent cell line, and ovariectomized (OVX) mice. Glycine significantly increased the MG-63 cell proliferation in a dose-dependent manner. Activity of alkaline phosphatase (ALP) and phosphorylation of extracellular-signal-regulated kinase were increased by glycine in MG-63 cells. Glycine also increased the BrdU-incorporation and Ki-67 mRNA expression in MCF-7 cells. Glycine induced the up-regulation of estrogen receptor-β mRNA expression and estrogen-response element-luciferase activity in MG-63 and MCF-7 cells. In OVX mice, glycine was administered orally at a daily dose of 10 mg/kg per day for 8 weeks. Glycine resulted in the greatest decrease in weight gain caused by ovariectomy. Meanwhile, vaginal weight reduced by ovariectomy was increased by glycine. Glycine significantly increased the ALP activity in OVX mice. MicroCT-analysis showed that glycine significantly enhanced bone mineral density, trabecular number, and connectivity density in OVX mice. Moreover, glycine significantly increased the serum 17β-estradiol levels reduced by ovariectomy. Glycine has an estrogen-like osteoprotective effect in menopause models. Therefore, we suggest that glycine may be useful for the treatment of menopause.

Rosmarinic acid exerts an antiosteoporotic effect in the RANKL-induced mouse model of bone loss by promotion of osteoblastic differentiation and inhibition of osteoclastic differentiation

SCOPE

Bone homeostasis is ensured by the balance between bone formation and resorption. Thus, control of the recruitment, proliferation, and differentiation of bone cells is essential to maintain bone mass. The aim of this study was to elucidate the effects of rosmarinic acid as a potential therapeutic agent on bone metabolism using bone cells and a mouse model.

METHODS AND RESULTS

Rosmarinic acid increased alkaline phosphatase activity and induced mineralization in osteoblasts. Addition of rosmarinic acid to cultures of calvarial osteoblastic cells prepared from T-cell factor/β-catenin TOP-GAL mutant mice strongly induced the expression of LacZ and promoted stabilization of β-catenin in the cytoplasm of ST2 cells, suggesting that rosmarinic acid affects the canonical Wnt signaling pathway. Moreover, rosmarinic acid inhibited not only osteoclast formation in cocultures of mouse bone marrow cells and osteoblasts, but also receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclastic differentiation in bone marrow-derived macrophages. RANKL-induced p38 mitogen-activated protein kinase and the expression of nuclear factor of activated T cell, c-Jun, and c-Fos were inhibited by rosmarinic acid in bone marrow macrophages. Finally, we confirmed that rosmarinic acid improved bone mass in a soluble RANKL-induced bone loss mouse model.

CONCLUSION

Rosmarinic acid has dual regulatory effects on bone metabolism and may control the bone functions by controlling osteoblastic and osteoclastic differentiation.

Isolation of antiosteoporotic compounds from seeds of Sophora japonica

Chemical investigation of Sophora japonica seeds resulted in the isolation of seven metabolites identified as: genistin (1), sophoricoside (2), sophorabioside (3), sophoraflavonoloside (4), genistein 7,4'-di-O-β-D-glucopyransoide (5), kaempferol 3-O-α-L-rhamnopyranosyl(1 → 6)β-D-glucopyranosyl(1 → 2)β-D-glucopyranoside (6) and rutin (7). Compounds 1, 2 and 5 showed significant estrogenic proliferative effect in MCF-7 cell in sub-cytotoxic concentration range. Compounds 1 and 2 showed minimal cell membrane damaging effect using LDH leakage assay. Accordingly, compound 2 (sophoricoside, (SPH)) was selected for further in-vivo studies as a potential anti-osteoporosis agent. The anti-osteoporotic effect of SPH was assessed in ovarectomized (OVX) rats after oral administration (15 mg/kg and 30 mg/kg) for 45 days compared to estradiol (10 µg/kg) as a positive control. Only in a dose of 30 mg/kg, SPH regained the original mechanical bone hardness compared to normal non-osteoporotic group. However, SPH (15 mg/kg) significantly increased the level of alkaline phosphatase (ALP) to normal level. Treatment with SPH (30 mg/kg) increased the level of ALP to be higher than normal group. SPH (15 mg/kg) did not significantly increase the serum level of osteocalcin (OC) compared to OVX group. On the other hand, treatment with SPH (30 mg/kg) significantly increased the level of OC to 78% higher than normal non-ovarectomized animals group. In addition, SPH (15 mg/kg) decreased the bone resorption marker, acid phosphatase (ACP) to normal level and SPH (30 mg/kg) further diminished the level of serum ACP. Histopathologically, sophoricoside ameliorated the ovarectomy induced osteoporosis in a dose dependent manner. The drug showed thicker bony trabeculae, more osteoid, and more osteoblastic rimming compared to OVX group.

Management of age-related osteoporosis and prevention of associated fractures

Osteoporosis and related fractures are a significant concern for the global community. As the population continues to age, morbidity and mortality from fractures due to low bone mineral density (BMD) will likely continue to increase. Efforts should be made to screen those at risk for osteoporosis, identify and address various risk factors for falls and associated fractures, ensure adequate calcium and vitamin D intake, and institute pharmacological therapy to increase BMD when indicated. Agents which increase BMD and have been shown to decrease fractures, particularly at the hip, should be considered preferentially over those for which only BMD data are available. Drugs which have been shown to decrease the risk of age-related osteoporotic fractures include oral bisphosphonates (alendronate, ibandronate, and risedronate), intranasal calcitonin, estrogen receptor stimulators (eg, estrogen, selective estrogen receptor modulators [raloxifene]), parathyroid hormone (teriparatide), sodium fluoride, and strontium ranelate. Data are beginning to emerge supporting various combination therapies (eg, bisphosphonate plus an estrogen receptor stimulator), though more data are needed to identify combinations which are most effective and confer added fracture protection. In addition, further research is needed to identify ideal regimens in special populations such as nursing home patients and men.

Anti-osteoporotic activity of aqueous-methanol extract of Berberis aristata in ovariectomized rats

ETHNOPHARMACOLOGICAL RELEVANCE

Traditionally Berberis aristata is employed for its supposed properties in treatment of joint pain and also used in alleviating symptoms of menopause.

AIM OF THE STUDY

The aim of the present study is to evaluate the antiosteoporotic effect of Berberis aristata in ovariectomized (OVX) rats.

MATERIALS AND METHODS

Sprague-Dawley rats were divided into sham and OVX groups. The OVX rats were further divided into four groups, which received standard estrogen (0.0563 mg/kg) and 100, 300, and 500 mg/kg aqueous-methanol extract of Berberis aristata, daily for 42 days. The uterine weight, bone loss, ash content, biomechanical, biochemical and histopathological observation were carried out for antiosteoporotic activity.

RESULTS

The experimental animals treated with Berberis aristata aqueous-methanol extract showed dose dependent activity. The significant increase in uterine weight, femur BMD, ash content and lumbar hardness were observed. In addition, increased levels of calcium and phosphorus in serum and significant decreased in urine were observed as compared to control OVX group. The histopathological results also confirm the protective effect of extract.

CONCLUSION

The present findings strongly suggest that Berberis aristata possess the potent antiosteoporosis activity in ovariectomized rats and substantiates the ethnic use in treatment of postmenopausal osteoporosis.

Improvement of bone strength and dermal thickness due to dietary edible bird's nest extract in ovariectomized rats

Oral administration of edible bird's nest extract (EBNE) improved bone strength and calcium concentration in the femur of ovariectomized rats. Dermal thickness was also increased by EBNE supplementation, whereas EBNE administration did not affect the serum estradiol concentration. These results suggest that EBNE is effective for the improvement of bone loss and skin aging in postmenopause all women.

Disorders of bone remodeling

The skeleton provides mechanical support for stature and locomotion, protects vital organs, and controls mineral homeostasis. A healthy skeleton must be maintained by constant bone modeling to carry out these crucial functions throughout life. Bone remodeling involves the removal of old or damaged bone by osteoclasts (bone resorption) and the subsequent replacement of new bone formed by osteoblasts (bone formation). Normal bone remodeling requires a tight coupling of bone resorption to bone formation to guarantee no alteration in bone mass or quality after each remodeling cycle. However, this important physiological process can be derailed by a variety of factors, including menopause-associated hormonal changes, age-related factors, changes in physical activity, drugs, and secondary diseases, which lead to the development of various bone disorders in both women and men. We review the major diseases of bone remodeling, emphasizing our current understanding of the underlying pathophysiological mechanisms.

Development of cell-based high-throughput assays for the identification of inhibitors of receptor activator of nuclear factor-kappa B signaling

Bone loss due to metabolic or hormonal disorders and osteolytic tumor metastasis continues to be a costly health problem, but current therapeutics offer only modest efficacy. Unraveling of the critical role for the receptor activator of nuclear factor-kappa B (RANK) and its ligand, RANK ligand (RANKL), in osteoclast biology provides an opportunity to develop more effective antiresorptive drugs. The in vivo effectiveness of RANKL inhibitors demonstrates the potency of the RANKL/RANK system as a drug target. Here, we report the development of cell-based assays for high-throughput screening to identify compounds that inhibit signaling from two RANK cytoplasmic motifs (PVQEET(559-564) and PVQEQG(604-609)), which play potent roles in osteoclast formation and function. Inhibitors of these motifs' signaling have the potential to be developed into new antiresorptive drugs that can complement current therapies. The cell-based assays consist of cell lines generated from RAW264.7 macrophages stably expressing a nuclear factor-kappa B-responsive luciferase reporter and a chimeric receptor containing the human Fas external domain linked to a murine RANK transmembrane and intracellular domain in which only one of the RANK motifs is functional. With these cells, specific RANK motif activation after chimeric receptor stimulation can be measured as an increase in luciferase activity. These assays demonstrated >300% increases in luciferase activity after RANK motif activation and Z '-factor values over 0.55. Our assays will be used to screen compound libraries for molecules that exhibit inhibitory activity. Follow-up assays will refine hits to a smaller group of more specific inhibitors of RANK signaling.

Selective targeting of RANK signaling pathways as new therapeutic strategies for osteoporosis

IMPORTANCE OF THE FIELD

Osteoporosis has become a worldwide health and social issue due to an aging population. Four major antiresorptive drugs (agents capable of inhibiting osteoclast formation and/or function) are currently available on the market: estrogen, selective estrogen receptor modulators (SERMs), bisphosphonates and calcitonin. These drugs either lack satisfactory efficacy or have potential to cause serious side effects. Thus, development of more efficacious and safer drugs is warranted.

AREAS COVERED IN THIS REVIEW

The discovery of the receptor activator of NF-kappaB ligand (RANKL) and its two receptors, RANK and osteoprotegerin (OPG), has not only established a crucial role for the RANKL/RANK/OPG axis in osteoclast biology but also created a great opportunity to develop new drugs targeting this system for osteoporosis therapy. This review focuses on discussion of therapeutic targeting of RANK signaling.

WHAT THE READER WILL GAIN

An update on the functions of RANKL and an overview of the known RANK signaling pathways in osteoclasts. A discussion of rationales for exploring RANK signaling pathways as potent and specific therapeutic targets to promote future development of better drugs for osteoporosis.

TAKE HOME MESSAGE

Several RANK signaling components have the potential to serve as potent and specific therapeutic targets for osteoporosis.

Quality analysis of salmon calcitonin in a polymeric bioadhesive pharmaceutical formulation: sample preparation optimization by DOE

A sensitive and selective HPLC method for the assay and degradation of salmon calcitonin, a 32-amino acid peptide drug, formulated at low concentrations (400 ppm m/m) in a bioadhesive nasal powder containing polymers, was developed and validated. The sample preparation step was optimized using Plackett-Burman and Onion experimental designs. The response functions evaluated were calcitonin recovery and analytical stability. The best results were obtained by treating the sample with 0.45% (v/v) trifluoroacetic acid at 60 degrees C for 40 min. These extraction conditions did not yield any observable degradation, while a maximum recovery for salmon calcitonin of 99.6% was obtained. The HPLC-UV/MS methods used a reversed-phase C(18) Vydac Everest column, with a gradient system based on aqueous acid and acetonitrile. UV detection, using trifluoroacetic acid in the mobile phase, was used for the assay of calcitonin and related degradants. Electrospray ionization (ESI) ion trap mass spectrometry, using formic acid in the mobile phase, was implemented for the confirmatory identification of degradation products. Validation results showed that the methodology was fit for the intended use, with accuracy of 97.4+/-4.3% for the assay and detection limits for degradants ranging between 0.5 and 2.4%. Pilot stability tests of the bioadhesive powder under different storage conditions showed a temperature-dependent decrease in salmon calcitonin assay value, with no equivalent increase in degradation products, explained by the chemical interaction between salmon calcitonin and the carbomer polymer.

Effect of safflower seeds supplementation on stimulation of the proliferation, differentiation and mineralization of osteoblastic MC3T3-E1 cells

Anti-bone resorption properties of the Korean herbal formulation, Gami-Honghwain (HJ), which comprises Carthamus tinctorius L. seed and hominis placenta, were investigated. We demonstrate that the production of PGE2 is inhibited by 20-100 microg/ml HJ in nontransformed osteoblastic cells (MC3T3-E1 cells), indicating that HJ inhibits PGE2 production. The effect of HJ on the proliferation and osteoblastic differentiation in MC3T3-E1 was also studied. HJ dose-dependently increased DNA synthesis (significant at 20-100 microg/ml), and increased alkaline phosphatase (ALP) and prolyl hydroxylase activities of MC3T3-E1 cells (20-100 microg/ml), while anti-estrogen tamoxifen eliminated the stimulation of proliferation and ALP activity of MC3T3-E1 which was induced by HJ. These results indicate that HJ directly stimulates cell proliferation and differentiation of osteoblasts. Also, when we assessed the effects of HJ on osteoblastic differentiation in MC3T3-E1, HJ enhanced ALP activity and mineralization in a dose- and time-dependent fashion. This stimulatory effect of the HJ was observed at relatively low doses (significant at 20-100 microg/ml and maximal at 100 microg/ml). Northern blot analysis showed that the HJ (60 microg/ml) increased in bone morphogenetic protein-2 as well as ALP mRNA concentrations in MC3T3-E1 cells. HJ (100 microg/ml) slightly increased in type I collagen mRNA abundance throughout the culture period, whereas it markedly inhibited the gene expression of collagenase-1 between days 15 and 20 of culture. These results indicate that HJ has anabolic effect on bone through the promotion of osteoblastic differentiation, suggesting that it could be used for the treatment of common metabolic bone diseases.

Cathepsin K inhibitors prevent matrix-derived growth factor degradation by human osteoclasts

The coupling between bone formation and resorption creates a therapeutic impasse in osteoporosis: antiresorptive therapy halts bone loss, but also inhibits bone formation, and therefore does not cure the condition. Surprisingly, recent preliminary reports suggest that inhibition of resorption by cathepsin K (CathK) inhibitors augments bone formation. Uniquely amongst resorption-inhibitors, CathK-inhibitors suppress degradation of the organic matrix of bone while allowing demineralization. We hypothesized that these unique characteristics might explain a capacity of CathK inhibitors to enhance bone formation: the inhibitors might prevent degradation not only of collagen, but also other proteins, including growth factors embedded in matrix. We tested this hypothesis using osteocalcin and insulin-like growth factor I (IGF-I) as examples of matrix-embedded proteins, and found that CathK-inhibitors, unlike other resorption-inhibitors, dramatically increased the concentrations of these matrix-derived proteins in supernatants of osteoclasts on bone, most likely through protection against intracellular degradation. We found that protons are both necessary and sufficient for the release of IGF-I from bone matrix, and that recombinant CathK can degrade both marker proteins. In the presence of a CathK-inhibitor, the amount of IGF-I released from matrix substantially exceeded the amount secreted by osteoclasts. CathK-inhibition similarly augmented bone morphogenetic protein (BMP)-2 release. Lastly, MC3T3-E1 numbers were greater after co-culture with osteoclasts on bone with versus without CathK-inhibitor, showing that, in the presence of CathK-inhibitor, osteoclasts release biologically-significant quantities of biologically-active matrix-derived growth factors. These results support a model in which osteoclastic secretion of protons demineralizes bone, causing release of growth factors from bone matrix. Normally these are largely degraded, with collagen, in the resorptive hemivacuole and during transcytosis to the basal surface of the osteoclast, but in the presence of CathK inhibitor they are released intact, and so might augment bone formation.

Estrogen and alendronate therapies may prevent the influence of estrogen deficiency on the tooth-supporting alveolar bone: a histometric study in rats

BACKGROUND AND OBJECTIVE

The aim of this study was to evaluate histometrically the influence of estrogen deficiency, and its therapies, on the quality of the tooth-supporting alveolar bone.

MATERIAL AND METHODS

Seventy-three female rats were randomly assigned to one of the following groups: group 1 (n = 15), sham surgery; group 2 (n = 15), bilateral ovariectomy (OVX); group 3 (n = 14), OVX plus calcitonin (16 IU/kg); group 4 (n = 14), OVX plus estrogen (20 microg/kg); and group 5 (n = 15), OVX plus alendronate (5 mg/kg). Eighty days after surgery, the animals were killed and their mandibles were removed and processed for histology. Bone density (BD) in the furcation area of the first mandibular molar (i.e. the percentage of demineralized bone tissue in a 1,000 microm zone under the furcation) was histometrically obtained.

RESULTS

Data analysis demonstrated that estrogen deficiency negatively affected the tooth-supporting bone density (79.45% +/- 4.22 and 55.23% +/- 6.45, for groups 1 and 2, respectively), and that estradiol and alendronate therapies prevented this effect (61.67% +/- 6.87, 78.09% +/- 3.12 and 81.47% +/- 4.58, for groups 3, 4 and 5, respectively).

CONCLUSION

Within the limits of this study, it can be concluded that the density of tooth-supporting bone is affected by estrogen deficiency, and that estradiol and alendronate therapies, but not calcitonin, provide protection against this effect.

Osteoporosis prevention and therapy: preserving and building strength through bone quality

While bone mineral density measurements play a central role in osteoporosis management, the degree to which increases in this parameter contribute to bone fragility, fracture risk, and the therapeutic efficacy of osteoporosis agents is controversial. Indeed, bone strength is also significantly dependent upon bone turnover and bone quality, including microarchitecture, mineralization, and geometry. Given the critical role of these factors, it is essential to understand how they are affected by therapeutic agents. Even though a number of technological advances, such as microcomputed tomography, magnetic resonance imaging, and computerized analysis of radiographic patterns, help to provide critical information toward a more comprehensive assessment of bone turnover and bone quality, clinical trials addressing these factors are scarce. This article provides a review of studies relating to how osteoporosis therapies impact parameters of bone strength and quality.

EFFECTS OF ULMUS DAVIDIANA PLANCH ON MINERALIZATION, BONE MORPHOGENETIC PROTEIN-2, ALKALINE PHOSPHATASE, TYPE I COLLAGEN, AND COLLAGENASE-1 IN BONE CELLS

Ulmus davidiana Planch (Ulmaceae) (UD) long has been known to have anti-inflammatory and protective effects on damaged tissue, inflammation, and bone among other functions. The herbal medicine also is being used in Oriental medicine to treat osteoporosis. In a preliminary study, treatment of osteoclasts containing long bone cells with the water extract of UD bark prevented the intracellular maturation of cathepsin K (cat K), and thus, it was considered that UD is a pro-drug of a potent bone-resorption inhibitor. To further clarify the role of UD in ossification, we investigated the effects of UD on the proliferation and differentiation of osteoblastic cell lines in vitro. In this study, we assessed the effects of UD on osteoblastic differentiation in nontransformed osteoblastic cells (MC3T3-E1) and rat bone marrow cells. UD enhanced alkaline phosphatase (ALP) activity and mineralization in a dose- and time-dependent fashion. This stimulatory effect of the UD was observed at relatively low doses (significant at 5-50 microg/ml and maximal at 50 microg/ml). Northern blot analysis showed that UD (100 microg/ml) increases in bone morphogenic protein-2 as well as ALP mRNA concentrations in MC3T3-E1 cells. UD slightly increased in type I collagen mRNA abundance throughout the culture period, whereas it markedly inhibited the gene expression of collagenase-1 between days 15 and 20 of culture. These results indicate that UD has anabolic effects on bone through the promotion of osteoblastic differentiation, suggesting that it could be used for the treatment of common metabolic bone diseases such as osteoporosis.

Activity of Wedelia calendulacea Less. in post-menopausal osteoporosis

Wedelia calendulacea Less., a perennial herb containing isoflavanoids, is used in liver disorders, uterine hemorrhage and menorrhagia. Osteoporosis in women occurs mainly due to estrogen deficiency following menopause. Studies indicate that isoflavones are estrogenic enough to promote bone formation. Our study was aimed to investigate the antiosteoporotic effect of the ethanol extract of W. calendulacea in the ovariectomized rat model of osteoporosis, at two different dose levels of 500 and 750 mg/kg/body wt. day. The findings, assessed on the basis of biomechanical and biochemical parameters, showed that the ethanol extract of the plant had a definite protective effect. This was further supported by the histopathological studies. Phytochemical investigation revealed the presence of isoflavones and wedelolactone, which are known to act as phytoestrogens and may be responsible for the antiosteoporotic activity.

Teriparatide vs. calcitonin in the treatment of Asian postmenopausal women with established osteoporosis

This study compared the clinical efficacy, safety, and tolerability of daily subcutaneous injections of teriparatide and salmon calcitonin in the treatment of postmenopausal women with established osteoporosis in Taiwan. This 6-month, multicenter, randomized, controlled study enrolled 63 women with established osteoporosis. They were randomized to receive either teriparatide 20 microg or calcitonin 100 IU daily in an open-label fashion. Lumber spine, femoral neck, total hip bone mineral density (BMD), and biochemical markers of bone turnover were measured, and adverse events and tolerability were recorded. The results at 6 months showed that patients using teriparatide had larger mean increases in spinal BMD than those who used calcitonin (4.5% vs. 0.1%), but the BMD changes in these two groups at the femoral neck and the total hip were not significant. There were also larger mean increases in bone markers in the teriparatide group than in the calcitonin group (bone specific alkaline phosphatase 142% vs. 37%; osteocalcin 154% vs. 23%). We conclude that teriparatide has more positive effects on bone formation than salmon calcitonin, as shown by the larger increments of lumbar spine BMD and bone formation markers, and caused only mild adverse events and no significant change in liver, kidney or hematological parameters. Compared with the published global results, teriparatide seems to be equally effective and safe to use in this Asian population.

Bone loss preventing effect of Sophorae Fructus on ovariectomized rats

The preventive effects of Sophorae Fructus extracts (I: hot water extract and II: combination product using I) on bone loss in ovariectomized (OVX) rats were investigated. Sophorae Fructus extracts were orally administrated to OVX rats for 9 weeks. Ovariectomy caused the increase of body weight and deoxypyridinoline (Dpd: bone resorption marker) and decrease of calcium (Ca: bone formation marker) level in serum. Dpd level were significantly decreased and Ca levels were elevated at 9 weeks in Sophorae Fructus extracts administered groups after ovariectomy at a dose of 0.556 g/kg/day compared with control group. In administered groups, trabecular bone area (TBA) in the tibia and lumbar were also increased compared with control group in histomorphological analysis. The preventive or treatment effects of Sophorae Fructus extracts on bone loss in OVX rats appears to be due to suppression of bone turnover.

Stimulative effects of Drynariae Rhizoma extracts on the proliferation and differentiation of osteoblastic MC3T3-E1 cells

Pharmacological factors are needed to prevent bone loss that occurs with increasing age. The chemical compounds that act on bone metabolism in herbal medicines, however, are poorly understood. Effects of traditional Korean medicine, Drynariae Rhizoma [Drynaria fortunei (kunze) J. Sm] extract (DR), on the osteoblastic proliferation and differentiation were investigated. The effect of DR, a natural phyto herb, on the proliferation and osteoblastic differentiation in non-transformed osteoblastic cells (MC3T3-E1) was studied. DR dose-dependently increased DNA synthesis (significant at 50-150 microg/ml). DR increased alkaline phosphatase (ALP) activity and prolyl hydroxylase activity of MC3T3-E1 cells (50-150 microg/ml). Antiestrogen tamoxifen eleminated the stimulation of proliferation and ALP activity of MC3T3-E1, which were induced by DR. DR at concentrations ranged from 30-100 microg/ml inhibited prostaglandin E2 production in MC3T3-E1. These results indicate that DR directly stimulates cell proliferation and differentiation of osteoblasts. These results also suggest and DR is effective for bone anti-resorptive action in bone cells.

Effect of intermittent administration of 200 IU intranasal salmon calcitonin and low doses of 1α(OH) vitamin D3 on bone mineral density of the lumbar spine and hip region and biochemical bone markers in women with postmenopausal osteoporosis: a pilot study

A 1-year prospective, open, randomized, controlled trial was conducted as a pilot study to examine the effect of intermittent administration of 200 IU intranasal salmon calcitonin and 1alpha(OH) vitamin D3 [1alpha(OH)D3] on bone mineral density (BMD) of the lumbar spine and hip as well as on the markers of bone metabolism in women with postmenopausal osteoporosis. A total of 102 randomly recruited women received either 200 IU intranasal salmon calcitonin (Miacalcic nasal 200, Novartis, Basel, Switzerland) daily, 1 month on-1 month off, 0.25 mug 1alpha(OH)D3, and 500 mg elemental calcium continuously (n=57 women) or only 0.25 mug 1alpha(OH)D3 and 500 mg calcium (n=45 women) for a period of 1 year. BMD of the lumbar spine and hip plus biochemical markers reflecting calcium (Ca) metabolism and bone turnover [serum Ca, serum phosphorus, intact parathormone (iPTH), total and bone-specific alkaline phosphatase, osteocalcin levels, 24-h urinary Ca, morning fasting urinary Ca/creatinine, and Pyrilinks-D/creatinine ratio] were measured at the beginning of the study before treatment and after 6 and 12 months of treatment. Baseline characteristics of participants, including age, body mass index, lumbar and hip BMD, and biochemical markers were similar between the two groups. A total of 91 patients completed the study (50 in the salmon calcitonin nasal spray group and 41 in the other group). Lumbar BMD increased significantly in the salmon calcitonin group from baseline (3.0%, p=0.005) and in comparison to the non-calcitonin-treated group (p=0.009). The salmon calcitonin group also had a significant increase in femoral neck BMD compared with baseline values (3.1%, p=0.0005) and in comparison to the non-calcitonin-treated group (p=0.0005) in Ward's triangle BMD (2.9% from baseline values, p=0.009) and in comparison to the non-calcitonin-treated group (p=0.005) in trochanteric BMD (3.4% from baseline values, p=0.007) and in comparison to the non-calcitonin-treated group (P=0.01). Urinary Ca/creatinine and Pyrilinks-D/creatinine levels were significantly decreased from baseline in the salmon calcitonin-treated group (-6.1 and -6.3%, respectively, p=0.001). Bone-specific alkaline phosphatase levels were also significantly decreased from baseline in the salmon calcitonin-treated group (-3.6%, p=0.003). In the same group, a significant decrease in iPTH serum levels compared to baseline values (-2.5%, p=0.005) and in comparison to the non-calcitonin-treated group (p=0.005) was noted. In conclusion, in this pilot study, 1-year intermittent treatment with 200 IU intranasal salmon calcitonin and low doses of 1alpha(OH)D3 produced a significant effect on bone turnover and BMD in postmenopausal women with osteoporosis.

Femoral neck trabecular microstructure in ovariectomized ewes treated with calcitonin: MRI microscopic evaluation

Ovariectomy induces deterioration of the trabecular structure in the femoral neck of ewes, as depicted by MR microscopic imaging. This structural deterioration is prevented by salmon calcitonin treatment.

INTRODUCTION

This study evaluated the trabecular (Tb) microarchitecture of an ovariectomy (OVX)-induced osteoporotic model in ewes and determined the effects of salmon calcitonin (sCT), an osteoclast inhibitor, on the Tb structure. This is the first report of OVX-induced changes in the Tb structure in the femoral neck in the ewes and effect of sCT on the microarchitecture.

MATERIALS AND METHODS

Ewes (5-8 years old, n = 28) were equally allocated into sham (Sham), OVX injected with vehicle, or OVX injected with sCT at 50 or 100 IU, three injections per week. They were killed 6 months after OVX. The femoral neck was examined with an MR imager at 9.4 T in axial, coronal, and sagittal planes. An internal calibration procedure as a means of standardizing image analysis was used to adjust the segmentation threshold. Data from all three planes were averaged.

RESULTS AND CONCLUSIONS

Compared with Sham, OVX induced significant changes (p < 0.0125) in the MRI-derived femoral neck Tb structure: Tb bone volume fraction (BV/TV), -18%; Tb number, -20%; Tb separation, +23%; number of free ends, +28%; number of nodes, -39%; number of Tb branches, -23%; mean length of Tb branches, -19%. Compared with OVX, treatment of sCT at 100 IU significantly improved all the Tb structural parameters to the Sham level (p < 0.0001 approximately p = 0.0281), whereas 50 IU significantly increased the Tb number and the mean length of the Tb branches. BV/TV explained 74% of the variation of compressive stress of the trabecular cylinder cores of the femoral neck. Combining all structural parameters in a multivariate regression analysis significantly improved the explanation to 84%, and adding BMD further improved the predictive ability of the model to 92%. We conclude that OVX induces deterioration of the MRI-derived Tb microstructure in the femoral neck of ewes. sCT treatment prevents OVX-induced changes. The femoral neck microarchitecture significantly correlates with its biomechanical properties. Combining microstructural parameters with BMD further improves the prediction of bone biomechanical properties. The effects of sCT on OVX ewes may help explain reduced fracture risk in postmenopausal osteoporotic women treated with sCT.

Effectiveness of salmon calcitonin nasal spray in the treatment of lumbar canal stenosis: a double-blind, randomized, placebo-controlled, parallel group trial

STUDY DESIGN

Double-blind, randomized, placebo-controlled study to assess the effectiveness of calcitonin nasal spray on symptoms and function in patients with lumbar canal stenosis.

OBJECTIVE

To compare effectiveness of calcitonin administered by nasal spray with placebo in patients with clinically symptomatic lumbar canal stenosis.

SUMMARY OF BACKGROUND DATA

Lumbar canal stenosis is the most common reason for spine surgery in individuals over 65 years of age. Nonoperative approaches have been not well studied and limited primarily to physical therapy exercises. Several small trials in the past have suggested that subcutaneous and intramuscular calcitonin is an effective nonsurgical option in treating the symptoms of spinal stenosis patients. Only three trials were randomized and placebo-controlled.

METHODS

Fifty-five patients with clinical lumbar canal stenosis (pseudoclaudication), confirmatory MR imaging, and pain intensity index (VAS) of > or =6 were randomized to either placebo or intranasal calcitonin daily for 6 weeks, followed by an open label 6-week extension, during which all patients received active drug. Outcome parameters performed at baseline, 6 weeks, and 12 weeks, included pain intensity index, walking time and distance to pain, SF-36, and Oswestry disability index.

RESULTS

Thirty-six patients received calcitonin, and 19 placebo. Eight (14.54%) calcitonin and 4 (7.27%) placebo patients withdrew from the study. The mean baseline pain score for calcitonin group was 7.8 and 7.5 for placebo. Comparisons at week 6 showed no statistically significant difference in the change in pain intensity (VAS) between calcitonin group (-2.9) and placebo (-2.4) (P = 0.4382) from baseline. There was no significant difference in walking time to pain (calcitonin -10.0 seconds; placebo +32.2 seconds; P = 0.5136). Walking distance to pain showed a mean improvement of +91.4 ft in the calcitonin group and +254.7 ft in the placebo group (P = 0.4948). No significant difference was observed in the SF-36 score between the treatment groups. Using a threshold of at least 50% reduction in pain from baseline to 6 weeks, 12 of 29 (41.37%) of calcitonin patients were considered responders versus 7 of 18 (38.88%) of placebo patients (P = 0.4238)

CONCLUSIONS

In this first ever largest randomized placebo-controlled parallel group trial of nasal calcitonin in spinal stenosis, nasal calcitonin was not superior to placebo in treating the symptoms of spinal stenosis at 6 weeks. Based on this study, nasal calcitonin does not appear to have a role in nonoperative treatment of lumbar canal stenosis.

Calcitonin: physiological actions and clinical applications

Calcitonin (CT) was first reported as a hypocalcemic principle, initially thought to originate from the parathyroid gland, a view subsequently corrected to an origin from parafollicular C-cells. Human CT is a 32 amino acid peptide with an N-terminal disulphide bridge and a C-terminal prolineamide residue, shown to potently inhibit bone resorption. More recent studies have demonstrated that this may take place through a direct osteoclastic action. A number of osteoclast CT receptors have subsequently been characterized and particular receptor regions necessary for ligand binding and intracellular signaling identified. Its potent anti-resorptive effect has led to its use in treating Paget's bone disease, osteoporosis, hypercalcaemia and osteogenesis imperfecta. This review summarises some key aspects of its synthesis, structure and its actions at the cellular and molecular levels, and leads on to its therapeutic uses that have emerged since its discovery as well as possibilities for future clinical applications.

Effect of estrogen and calcitonin therapies on bone density in a lateral area adjacent to implants placed in the tibiae of ovariectomized rats

BACKGROUND

This study evaluated the influence of estrogen and calcitonin administration on tibial bone density in a lateral area adjacent to implants placed in ovariectomized rats (OVX).

METHODS

One screw-type titanium implant was placed bilaterally in the ovariectomized rats, and the animals assigned to one of the following groups: group 1 (n = 15): sham surgeries; group 2 (n = 15): OVX; group 3 (n = 14): OVX subcutaneously administered with calcitonin (CT) 4 days/week (16 IU/kg); group 4 (n = 14): OVX administered daily with 17beta estradiol (20 microg/kg). After 60 days, the animals were sacrificed and undecalcified sections obtained. Blood samples were collected to measure serum levels of alkaline phosphatase and calcium at the time of sacrifice. Bone density was measured in a 500 microm wide mineralized zone lateral to the implant.

RESULTS

Alkaline phosphatase levels in groups 2 and 3 (P > 0.05) were statistically higher than groups 1 and 4 (P < 0.05), and calcium serum levels were higher in group 2 than the other groups (P < 0.05). Regarding bone density, the data were grouped separately for cortical (zone A) and cancellous (zone B) bone. In zone A, intergroup analysis revealed no significant difference among groups (P > 0.05). However, in zone B, the animals that received estrogen administration (group 4) presented a higher bone density than groups 2 and 3 (P < 0.05).

CONCLUSION

It appears that estrogen therapy may prevent the negative influence of endogenous estrogen deficiency on bone density around titanium implants placed in ovariectomized rats.

Effects of nasal calcitonin on bone mineral density following parathyroidectomy in patients with primary hyperparathyroidism

AIM

To investigate whether nasal salmon calcitonin (CT; 200 U/day) given in addition to calcium helps to restore the bone mass after parathyroidectomy (PTX) in patients with primary hyperparathyroidism (PHPT).

METHODS

Twenty patients with PHPT were enrolled after successful PTX and received 1 g calcium per os daily for 1 year. They were randomly assigned either to nasal CT (CT group) or to no treatment. The bone mass was measured using dual-energy X-ray absorptiometry at multiple sites.

RESULTS

Eight patients in each group completed the study. After 12 months, the bone mass increased significantly at whole-body level and at lumbar spine in both groups, increased at hip and epiphyses of tibia or radius in the CT group only, and did not change at diaphyses of tibia and radius in either group.

CONCLUSIONS

Bone mass increases after PTX for PHPT in patients receiving oral calcium. CT may help to restore the bone mass at sites of the appendicular skeleton, where trabecular bone predominates.

Calcitonin

Calcitonin is FDA approved for the treatment of postmenopausal osteoporosis but not for prevention. The preferred delivery system is nasal. Nasal calcitonin is safe and well tolerated. The vertebral fracture efficacy of calcitonin is less robust than the two approved bisphosphonates (alendronate and risedronate) but is similar to raloxifene in the treatment of established osteoporosis. Calcitonin has not been demonstrated to reduce hip fracture risk, although a post-hoc pooled analysis suggests potential effectiveness of nasal calcitonin. Calcitonin produces small increments in bone mass of the spine and modestly reduces bone turnover in women with osteoporosis. Calcitonin may have analgesic benefit in patients with acute painful vertebral fractures. Treatment with calcitonin should be considered for older women with osteoporosis with painful vertebral fractures and for women who fail to respond to or cannot tolerate bisphosphonates. Calcitonin may also be indicated for women who are unable to take bisphosphonates because of impaired renal function.

Calcitonin: the other thyroid hormone

Calcitonin was originally discovered as a hypocalcemic factor synthesized by thyroid parafollicular C cells. Early experiments demonstrated that calcitonin inhibited bone resorption and decreased calcium efflux from isolated cat tibiae and subsequent histologic and culture studies confirmed the osteoclast as its major site of action. Its potent antiresorptive effect and analgesic action have led to its clinical use in treatment of Paget's bone disease, osteoporosis, and hypercalcemia of malignancy. This review surveys the cellular and molecular basis of these physiologic and clinical actions.

Meta-analyses of therapies for postmenopausal osteoporosis. VI. Meta-analysis of calcitonin for the treatment of postmenopausal osteoporosis

OBJECTIVE

To review the effect of calcitonin on bone density and fractures in postmenopausal women.

DATA SOURCE

We searched MEDLINE and EMBASE from 1966 to 2000 and examined citations of relevant articles and the proceedings of international osteoporosis meetings. We contacted osteoporosis investigators to identify additional studies and primary authors for unpublished data.

STUDY SELECTION

We included 30 studies that randomized women to calcitonin or an alternative (placebo or calcium and/or vitamin D) and measured bone density or fracture incidence for at least 1 yr.

DATA EXTRACTION

For each trial, three independent reviewers assessed the methodological quality and abstracted data.

DATA SYNTHESIS

Calcitonin reduced the incidence of vertebral fractures, with a pooled relative risk (RR) of 0.46 [95% confidence interval (CI) 0.25-0.87, P = 0.02, n = 1404, 4 trials]. However, the RR from the one relatively large randomized controlled trial (RCT) was 0.79 (95% CI 0.62-1.00, P = 0.05, n = 1108). For nonvertebral fractures, the pooled RR was 0.52 (95% CI 0.22-1.23, P = 0.14, n = 1481, 3 trials). Once again, the single large trial showed a less impressive effect than the smaller trials (RR 0.80, 95% CI 0.59-1.09, P = 0.16, n = 1245). For bone density of the lumbar spine, the pooled weekly dose of 250 to 2800 IU per week resulted in significant increase in the weighted mean difference (WMD) of 3.74 (2.04-5.43, P < 0.01, n = 2260, 24 trials). The combined forearm showed a similar effect, with a WMD of 3.02 (95% CI 0.98-5.07, P < 0.01, n = 468, 9 trials). At the femoral neck, the pooled weighted mean difference showed a nonsignificant trend toward benefit, WMD 3.80 (95% CI -0.32-7.91, P = 0.07, 9 trials, n = 513). Methodologically weaker studies tended to show greater effects on bone density, and the lumbar spine results suggested the possibility of publication bias.

CONCLUSIONS

Calcitonin likely increases bone density in postmenopausal women predominantly at the lumbar spine and forearm for weekly doses of greater than 250 IU, although the true effect may be smaller than the pooled estimate would suggest. Calcitonin likely reduces the risk of vertebral fracture; its effect on nonvertebral fracture remains uncertain.

Calcitonin for the long-term prevention and treatment of postmenopausal osteoporosis

Calcitonin is a powerful inhibitor of osteoclast activity that exerts a rapid, transient, and reversible inhibition of bone resorption. Prolonged administration of parenteral calcitonin, by injections of 100 IU every 1 or 2 days, can prevent postmenopausal or postovariectomy bone loss, and is also able to increase trabecular bone mass among patients presenting an established osteoporosis. Prolonged treatment with calcitonin injections is, however, difficult to maintain over the long run. In addition to the ease of administration compared with the injectable forms, nasal calcitonin is much better tolerated, the side effects being rare and generally negligible. A prolonged administration of 200 IU intranasal calcitonin acutely inhibits parameters of bone resorption and can increase lumbar spine bone mineral density (BMD) by 1.7%-3.3% after 1 year. Lower doses also appear to be efficient to prevent early postmenopausal bone loss, but the data are conflictual. The results are more consistent in patients who already suffer from established osteoporosis. The increase in lumbar spine BMD is in the order of 1%-2% after 1 year with 200 IU daily. A therapeutic benefit of calcitonin at the level of the cortical bone has been less well demonstrated than for the trabecular bone. As for other antiosteoporotic therapies, the effect of calcitonin on the reduction of fracture risk has been examined less than the beneficial effect on trabecular bone mass. Currently, there is still no prospective, placebo-controlled study with a sufficient number of patients that demonstrates that long-term parenteral calcitonin administration reduces the risk of osteoporotic fractures. The efficacy of nasal calcitonin treatment to reduce vertebral fracture rate has been best examined in the PROOF (Prevent Recurrence of Osteoporotic Fractures) study. This was a prospective 5-year, placebo-controlled, dose-response study of nasal calcitonin (100, 200, or 400 IU daily). The increase in lumbar spine BMD was modest but significant and not clearly dose dependent, as was the reduction in bone turnover. The relative risk of developing new vertebral fractures was reduced by 33% at the end of the study in the 200-IU dose group (relative risk = 0.67, 95% CI 0.47-0.97, p = 0.03). There was also a nonsignificant reduction in the risk of hip fracture in this dose group. The doses of 100 and 400 IU of calcitonin also reduced the vertebral fracture risk, but the difference did not reach the classical level of statistical significance. A possible effect of calcitonin to enhance bone quality, which cannot be assessed by routinely available methods, is currently being investigated in a prospective placebo-controlled trial that could provide a rational explanation for these effects of calcitonin on the reduction in the vertebral fracture rate without much increase in bone mass or a marked reduction in bone turnover.

Forty years of calcitonin--where are we now? A tribute to the work of Iain Macintyre, FRS

Calcitonin was discovered as a hypocalcemic principal that was initially thought to originate from the parathyroid gland. This view was corrected subsequently, and an origin from the thyroid C cells was documented. The purification and sequencing of various calcitonins soon followed. Calcitonin is a 32-amino-acid-long peptide with an N-terminal disulfide bridge and a C-terminal prolineamide residue. The peptide was shown to potently inhibit bone resorption; however, a direct osteoclastic action of the peptide was confirmed only in the early 1980s. Several osteoclast calcitonin receptors have subsequently been cloned and sequenced. Specific regions of the receptor necessary for ligand binding and intracellular signaling through cyclic AMP and calcium have been identified through systematic deletion mutagenesis and chimeric receptor studies. Calcitonin's potent antiresorptive effect has led to its use in treating Paget's disease of bone, osteoporosis, and hypercalcemia. This review retraces key aspects of the synthesis and structure of calcitonin, its cellular and molecular actions, and its therapeutic uses as they have emerged over the 40 years since its discovery. The review also examines the implications of these findings for future clinical applications as a tribute to early workers to whom credit must be given for creation of an important and expanding field. Notable are the new approaches currently being used to enhance calcitonin action, including novel allosteric activators of the calcitonin receptor, modulation of the release of endogenous calcitonin by calcimimetic agents, as well as the development of oral calcitonins.