Comparative safety of bone remodeling agents with a focus on osteoporosis therapies

Protective effects of gallium, germanium, and strontium against ovariectomized osteoporosis in rats

The effects of trace elements of gallium (Ga), germanium (Ge), and strontium (Sr) on ovariectomized (OVX) osteopenic rats were studied in this paper. The urine calcium content, serum calcium, and phosphorus contents, bone mineral content, mineral dissolution, and mechanical strength of the osteopenic rats were analyzed respectively. After the rats were fed with Ga, Ge, and Sr diet for 8 weeks, respectively, the urine calcium content decreased (P < 0.01). Plasma calcium and phosphate concentrations decreased in the order of OVX group > Ge group > Sr group > Ga group > Sham group. Mineral content increased in the order of OVX group < Ge group < Sr group < Ga group < Sham group. A dramatic decrease in calcium solubility was found both in the gallium and strontium treated animals (P < 0.05). However, the same result did not occur in germanium treated groups. The data provide an important proof of concept that gallium and strontium might be a new potential therapy for the management of postmenopausal osteoporosis in humans.

Characteristics of patients initiating raloxifene compared to those initiating bisphosphonates

Background

Both raloxifene and bisphosphonates are indicated for the prevention and treatment of postmenopausal osteoporosis, however these medications have different efficacy and safety profiles. It is plausible that physicians would prescribe these agents to optimize the benefit/risk profile for individual patients. The objective of this study was to compare demographic and clinical characteristics of patients initiating raloxifene with those of patients initiating bisphosphonates for the prevention and treatment of osteoporosis.

Methods

This study was conducted using a retrospective cohort design. Female beneficiaries (45 years and older) with at least one claim for raloxifene or a bisphosphonate in 2003 through 2005 and continuous enrollment in the previous 12 months and subsequent 6 months were identified using a collection of large national commercial, Medicare supplemental, and Medicaid administrative claims databases (MarketScan^®). Patients were divided into two cohorts, a combined commercial/Medicare cohort and a Medicaid cohort. Within each cohort, characteristics (demographic, clinical, and resource utilization) of patients initiating raloxifene were compared to those of patients initiating bisphosphonate therapy. Group comparisons were made using chi-square tests for proportions of categorical measures and Wilcoxon rank-sum tests for continuous variables. Logistic regression was used to simultaneously examine factors independently associated with initiation of raloxifene versus a bisphosphonate.

Results

Within both the commercial/Medicare and Medicaid cohorts, raloxifene patients were younger, had fewer comorbid conditions, and fewer pre-existing fractures than bisphosphonate patients. Raloxifene patients in both cohorts were less likely to have had a bone mineral density (BMD) screening in the previous year than were bisphosphonate patients, and were also more likely to have used estrogen or estrogen/progestin therapy in the previous 12 months. These differences remained statistically significant in the multivariate model.

Conclusion

In this sample of patients enrolled in commercial, Medicare, and Medicaid plans, patients who initiated raloxifene treatment differed from those initiating bisphosphonates. Raloxifene patients were younger, had better overall health status and appeared to be less likely to have risk factors for new osteoporotic fractures than bisphosphonate patients. Differences in the clinical profiles of these agents may impact prescribing decisions. Investigators using observational data to make comparisons of treatment outcomes associated with these medications should take these important differences in patient characteristics into consideration.

Combination of receptor-binding assays and designed mutant receptors for discerning agonists and antagonists

Competitive receptor-binding assays are convenient for analyzing interactions between receptors and their ligands and for screening pharmaceutical drugs and potential endocrine-disrupting chemicals. Although these assays can be used for high-throughput screening, they cannot discern antagonists and agonists. Based on three-dimensional structures of complexes between ligand-binding domain of human estrogen receptor-alpha and its ligands, we designed mutant receptors with modified mode of ligand-binding. In the current studies we examined the binding of endogenous ligands, artificial ligands, and potent endocrine-disrupting chemicals to wild-type and Asp351 mutants of the human estrogen receptor-alpha ligand-binding domain. The new combination assay showed the decrease of relative biding affinity (RBA) values for antagonists. For example, RBA for tamoxifen was changed from 4.8 (using the Asp351 receptor) to less than 1.5 (using the Glu351 receptor). On the other hand, the agonists showed increase of RBA values. For example, RBA for bisphenol A was changed from 0.011 (using the Asp351 receptor) to less than 0.030 (using the Glu351 receptor). The variation of RBA was dependant on the type of mutant receptors. The change of RBA from wild-type to mutant-type can be an index for discerning agonists and antagonists. Comparison of RBA values obtained by assays using wild-type and mutant receptors is a simple way of discerning agonists and antagonists, and this approach could be extended to other types of receptors, if information of the receptors was enough to construct a designed mutant receptor.

Elemental distributions in femoral bone of rat under osteoporosis preventive treatments

One of the abnormalities of bone architecture is osteoporosis as occurring in post-menopausal women. Especially long bones, such as femur, become more fragile and more prone to fracture. The efficiency of several osteoporosis preventative treatments based on oestrogen and progestin in bone structure and mineral recovery was studied using ovariectomized Wistar rats as an osteoporosis experimental model. Diagonal cross-sections of the proximal epiphysis of femoral bones were analysed using nuclear microscopy techniques in order to map and determine the concentration profiles of P, Ca, S, Fe and Zn from the epiphysis to diaphysis and across the cortical and trabecular bone structures. In control animals (not ovariectomized), the S and Zn contents significantly characterized differences between cortical and trabecular bone structures, whereas P and Ca showed increased gradients from the epiphyseal region to the diaphysis. After ovariectomy the differences observed were differential according to the type of hormonal supplementation. A significant decrease in P and Ca contents and depletion of minor and trace minerals, such as S, Fe and Zn, were found for both cortical and trabecular bone structures after ovariectomy relative to controls. Bone mineral contents were reversed to control levels by synthetic oestrogen supplementation, and combined oestrogen and progesterone treatment. Recovery was more evident in the femoral epiphysis and neck than in the diaphysis. The use of oestrogen alone did not lead to bone recovery after ovariectomy. Alterations in bone mineral composition observed for animals receiving synthetic oestrogen and combined oestrogen and progesterone supplement might reflect beneficial structural changes in critical regions of long bones, mostly affected in post-menopausal osteoporosis.

Fluoride levels in drinking water in the Central Province of Saudi Arabia

BACKGROUND

This study was designed to assess the fluoride levels in drinking water in the Central Province of Saudi Arabia.

MATERIALS AND METHODS

A total of 817 water samples were collected from 260 locations in Central Saudi Arabia. An atomic absorption spectrophotometer [HACH instrument, model DR 3000] was used in the analyses of water samples for fluoride levels.

RESULTS

The results showed that fluoride levels vary between 0.00 and 6.20 ppm. About 75% and 6% of the population in Riyadh and Qassim regions, respectively, were exposed to very low fluoride levels (0.00-0.03 ppm), while less than 3% of the population in both regions were exposed to fluoride levels ranging from 0.61 to 0.80 ppm. A higher percentage of the population in Qassim than Riyadh region were exposed to high fluoride levels (>0.81 ppm); 28.63% than in Riyadh with 9.24%.

CONCLUSION

The findings of this study can serve as a baseline data for water fluoridation and other dental preventive programs in the area.

Storage function of cartilage oligomeric matrix protein: the crystal structure of the coiled-coil domain in complex with vitamin D(3)

The five-stranded coiled-coil domain of cartilage oligomeric matrix protein (COMPcc) forms a continuous axial pore with binding capacities for hydrophobic compounds, including prominent cell signalling molecules. Here, we report the X-ray structure of the COMPcc domain in complex with vitamin D(3) at 1.7 A resolution. The COMPcc pentamer harbours two molecules of the steroid hormone precursor in a planar s-trans conformation of the conjugated triene, with the aliphatic tails lying along the molecule axis. A hydrophilic ring of five Gln54 side chains divides the channel into two hydrophobic compartments in which the bound vitamin D(3) pair is fixed in a head-to-head orientation. Vitamin D(3) binding induces a volumetric increase of the cavities of approximately 30% while the main chain distances of the pentamer are retained. This adaptation to the bulky ring systems of the ligands is accomplished by a rotamer re-orientation of beta-branched side chains that form the knobs into holes of the coiled-coil structure. Compared with binding of vitamin D and retinoic acid by their classical receptors, COMP exerts a distinct mechanism of interaction mainly defined by the pattern of hydrophobic core residues.

Tolerability of once-weekly alendronate in patients with osteoporosis: a randomized, double-blind, placebo-controlled study

OBJECTIVE

To compare the upper gastrointestinal (GI) tract tolerability of once-weekly oral alendronate, 70 mg, and placebo.

PATIENTS AND METHODS

This was a 12-week multicenter, randomized, double-blind, placebo-controlled study. The first patient initiated treatment on June 5, 2000, and the last patient completed treatment on March 1, 2001. The study enrolled 450 postmenopausal women and men with osteoporosis (224 took alendronate, 226 took placebo) who were ambulatory and community dwelling at 48 outpatient study centers in the United States. By design, approximately half of the patients were naive to bisphosphonates. The primary end point was upper GI tract tolerability based on the incidence of any upper GI tract adverse events. Secondary end points included the number of discontinuations due to drug-related upper GI tract adverse events and the change from baseline in bone resorption, assessed by the urinary N-telopeptide-creatinine ratio at 12 weeks. A subgroup analysis of the primary and secondary end points was performed on the patients stratified by prior bisphosphonate use. The safety and tolerability of the weekly alendronate and placebo regimens were captured as clinical and laboratory adverse events.

RESULTS

A total of 11% of the alendronate patients and 13% of the placebo patients reported an upper GI tract adverse event. Discontinuations due to drug-related upper GI tract adverse events occurred in 3% of alendronate patients and 1% of placebo patients. The differences between the treatment groups for the primary and secondary end points were not significant. For the primary end point, the upper limit of the 95% confidence interval of the difference was well within the prespecified 14% comparability bound (-2.2%; 95% confidence interval, -8.3% to 3.9%). The overall incidence of upper GI tract adverse events was lower in the subgroup of patients with prior bisphosphonate exposure (8%) than in those who were bisphosphonate naive (16%). However, regardless of prior bisphosphonate exposure, the incidence of upper GI tract adverse events was similar between the alendronate and placebo patients. The urinary N-telopeptide-creatinine ratio showed a significant decrease in the alendronate patients (72% of baseline, P<.001) compared with a slight increase in the placebo patients (106% of baseline) at week 12.

CONCLUSION

In this 3-month study, the incidence of upper GI tract adverse events in patients treated with once-weekly alendronate, 70 mg, was comparable to that with placebo.

Bioavailability and biological efficacy of a new oral formulation of salmon calcitonin in healthy volunteers

Salmon calcitonin (SCT) is a well-tolerated peptide drug with a wide therapeutic margin and is administered parenterally for long-term treatments of bone diseases. Its clinical usefulness would be enhanced by the development of an orally active formulation. In this randomized crossover double-blinded phase I trial, controlled by both a placebo and a parenteral verum, we have tested a new oral formulation of SCT associated with a caprylic acid derivative as carrier. Eight healthy volunteers received single doses of 400, 800, and 1200 microg of SCT orally, a placebo, and a 10-microg (50 IU) SCT intravenous infusion. SCT was reliably absorbed from the oral formulation, with an absolute bioavailability of 0.5-1.4%, depending on the dose. It induced a marked, dose-dependent drop in blood and urine C-terminal telopeptide of type I collagen (CTX), a sensitive and specific bone resorption marker, with the effects of 1200 microg exceeding those of 10 microg intravenously. It also decreased blood calcium and phosphate, and increased the circulating levels of parathyroid hormone (PTH) and, transiently, the urinary excretion of calcium. It was well-tolerated, with some subjects presenting mild and transient nausea, abdominal cramps, diarrheic stools, and headaches. This study shows that oral delivery of SCT is feasible with reproducible absorption and systemic biological efficacy. Such an oral formulation could facilitate the use of SCT in the treatment of osteoporosis and other bone diseases.