A novel BRD4 inhibitor suppresses osteoclastogenesis and ovariectomized osteoporosis by blocking RANKL-mediated MAPK and NF-κB pathways.

Bromodomain-containing protein 4 (BRD4) has emerged as a promising treatment target for bone-related disorders. (+)-JQ1, a thienotriazolodiazepine compound, has been shown to inhibit pro-osteoclastic activity in a BRD4-dependent approach and impede bone loss caused by ovariectomy (OVX) in vivo. However, clinical trials of (+)-JQ1 are limited because of its poor druggability. In this study, we synthesized a new (+)-JQ1 derivative differing in structure and chirality. One such derivative, (+)-ND, exhibited higher solubility and excellent inhibitory activity against BRD4 compared with its analogue (+)-JQ1. Interestingly, (-)-JQ1 and (-)-ND exhibited low anti-proliferative activity and had no significant inhibitory effect on RANKL-induced osteoclastogenesis as compared with (+)-JQ1 and (+)-ND, suggesting the importance of chirality in the biological activity of compounds. Among these compounds, (+)-ND displayed the most prominent inhibitory effect on RANKL-induced osteoclastogenesis. Moreover, (+)-ND could inhibit osteoclast-specific gene expression, F-actin ring generation, and bone resorption in vitro and prevent bone loss in OVX mice. Collectively, these findings indicated that (+)-ND represses RANKL-stimulated osteoclastogenesis and averts OVX-triggered osteoporosis by suppressing MAPK and NF-κB signalling cascades, suggesting that it may be a prospective candidate for osteoporosis treatment.

Protective effect of resveratrol on estrogen deficiency-induced osteoporosis though attenuating NADPH oxidase 4/nuclear factor kappa B pathway by increasing miR-92b-3p expression.

INTRODUCTION: Resveratrol (RES) exhibits estrogen-like effects and has potential applications to treatment of osteoporosis caused by estrogen deficiency; however, the specific mechanism of action of RES remains unclear. Here, we examined the therapeutic effects of RES on ovariectomized (OVX) rats with osteoporosis and determined the underlying mechanism. METHODS: We established an OVX rat model to study osteoporosis caused by estrogen deficiency. The treatment groups were given orally with RES (50, 100, and 200 mg/day), the estrogen group received 0.8 mg/kg E2 daily via oral route, and the sham-operated and control groups received an equivalent dose of sodium carboxymethylcellulose orally. After 12 weeks of treatment, we used real-time quantitative polymerase chain reaction (PCR) and Western blot analysis to measure the gene and protein expression of miR-92b-3p, Nox4, NF-κBp65, IκB, BMP2, Smad7, and RUNX-2 in bone tissues. Right femur structural parameters were evaluated by micro-CT. Dual-energy X-ray 4500 W was used to determine systemic bone mineral density (BMD). Enzyme-linked immunosorbent assay (ELISA) kits were used to determine the serum levels of bone alkaline phosphatase (BALP), osteoprotegerin (OPG), anti-tartrate acid phosphatase-5b (PTRA5b), and carboxylated terminal peptide (CTX-I). The rat femoral bone specimens were stained using hematoxylin and eosin for pathological examination. RESULTS: We observed increased levels of serum estrogen in both ovaries, elevated miR-92b-3p levels in bone tissues, reduced levels of Nox4, NF-κBp65, p-IκB-a, and cathepsin K, and elevated gene and protein expression of BMP2, Smad7, and RUNX-2 in the OVX rat model of osteoporosis after treatment with RES. Elevated levels of BALP, OPG, ALP, and BMD along with reduced levels of TRAP-5b and CTX-I were also observed. The structural model index (SMI) and the trabecular space (Tb. Sp) decreased, while the trabecular thickness (Tb. Th), bone volume fraction (BV/TV), trabecular number (Tb.N), and tissue bone density (Conn.D) increased, thereby improving osteoporosis induced by estrogen deficiency in both ovaries. CONCLUSION: Cathepsin K expression and Nox4/NF-κB signaling pathway were suppressed by the elevated expression of miR-92b-3p. This inhibition was pivotal in the protective effect of RES against osteoporosis induced by estrogen deficiency in both ovaries. Thus, RES efficiently alleviated osteoporosis induced by estrogen deficiency in rats.

LncRNA AK077216 promotes RANKL-induced osteoclastogenesis and bone resorption via NFATc1 by inhibition of NIP45.

Osteoclasts derived from the monocyte/macrophage hematopoietic lineage regulate bone resorption, a process balanced by bone formation in the continual renewal of the skeletal system. As dysfunctions of these cells result in bone metabolic diseases such as osteoporosis and osteopetrosis, the exploration of the mechanisms regulating their differentiation is a priority. A potential mechanism may involve long noncoding RNAs (lncRNAs), which are known to regulate various cell biology activities, including proliferation, differentiation, and apoptosis. The expression of the lncRNA AK077216 (Lnc-AK077216) is significantly upregulated during osteoclastogenesis identified by microarray and verified by qPCR. Up- and downregulation of Lnc-AK077216, respectively promotes and inhibits osteoclast differentiation, bone resorption, and the expression of related genes on the basis of tartrate-resistant acid phosphatase staining, qPCR, and western blot results. In addition, Lnc-AK077216 suppresses NIP45 expression and promotes the expression of NFATc1, an essential transcription factor during osteoclastogenesis. Besides, it was found that the expression of Lnc-AK077216 and Nfatc1 is upregulated, whereas Nip45 expression is downregulated in bone marrow and spleen tissues of ovariectomized mice. The results suggest that Lnc-AK077216 regulates NFATc1 expression and promotes osteoclast formation and function, providing a novel mechanism of osteoclastogenesis and a potential biomarker or a new drug target for osteoporosis.

Association of CYP1A1 and CYP1B1 polymorphisms with bone mineral density variations in postmenopausal Mexican-Mestizo women.

Herein, we investigated potential associations between polymorphisms of genes related to estrogen metabolism and bone mineral density (BMD) in postmenopausal women. This was a cross-sectional study, in which two hundred and ninety postmenopausal Mexican-Mestizo women were studied. The BMD of the lumbar spine (LS), total hip (TH), and femoral neck (FN) was measured. The distribution of the genetic polymorphisms, including rs1799814 and rs1048943 at CYP1A1 as well as rs1056836 at CYP1B1, were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), single-stranded conformational polymorphism (SSCP), and DNA sequencing. Deviations from Hardy-Weinberg equilibrium (HWE) were tested, and linkage disequilibrium (LD) was calculated by direct correlation (r2). Moreover, haplotype analysis was performed. All polymorphisms were in HWE. The genotype and allele distributions of the three single nucleotide polymorphisms (SNPs) studied showed no significant differences. However, statistical significance was reached when constructing haplotypes. The CG haplotype in CYP1A1 was associated with variations in LS and FN BMD after adjustment for covariates (p = 0.021 and 0.045, respectively), but the association with TH BMD was not significant. These results suggested that the CG haplotype in CYP1A1 may play an important role in the mechanism of osteoporosis and may be useful as a genetic marker.

Association of circulating dipeptidyl-peptidase 4 levels with osteoporotic fracture in postmenopausal women.

Postmenopausal women with osteoporotic fracture (OF) had higher plasma dipeptidyl-peptidase 4 (DPP4) levels than those without. Furthermore, higher plasma DPP4 levels were significantly associated with higher bone turnover and a higher prevalence of OF. These results indicated that DPP4 may be associated with OF by mediating bone turnover rate. INTRODUCTION: Evidence indicates that dipeptidyl-peptidase 4 (DPP4) plays a distinct role in bone metabolism. However, there has been no report on the association, if any, between circulating DPP4 levels and osteoporosis-related phenotypes, including osteoporotic fracture (OF). Therefore, we performed a case-control study to investigate these associations in postmenopausal women. METHODS: This study was conducted in multiple centers in Korea. We enrolled 178 cases with OF and 178 age- and body mass index-matched controls. OF was assessed by an interviewer-assisted questionnaire and lateral thoracolumbar radiographs. Bone turnover markers (BTMs), bone mineral density (BMD), and plasma DPP4 levels were obtained in all subjects. RESULTS: After adjustment for potential confounders, subjects with OF had significantly higher DPP4 levels than those without (P = 0.021). Higher DPP4 levels were significantly positively associated with higher levels of all BTMs, but not with BMD at all measured sites. The differences in DPP4 levels according to OF status disappeared after an additional adjustment for each BTM, but not after adjustment for any BMD values. BTMs explained approximately half of the relationship between DPP4 and OF. The risk of OF was 3.80-fold (95% confidence interval = 1.53-9.42) higher in subjects in the highest DPP4 quartile than in those in the lowest quartile after adjustment for potential confounders, including femoral neck BMD. CONCLUSIONS: DPP4 may be associated with OF by at least partly mediating the bone turnover rate. Circulating DPP4 levels may be a potential biomarker that could increase the predictive power of current fracture risk assessment models.

Pharmacological inhibition of cathepsin K: A promising novel approach for postmenopausal osteoporosis therapy.

Osteoporosis is a metabolic bone disease that is characterized by heightened state of bone resorption accompanied by diminished bone formation, leading to a reduction of bone mineral density (BMD) and deterioration of bone quality, thus increasing the risk of developing fractures. Molecular insight into bone biology identified cathepsin K (CatK) as a novel therapeutic target. CatK is a lysosomal cysteine protease secreted by activated osteoclasts during bone resorption, whose primary substrate is type I collagen, the major component of organic bone matrix. Available anti-resorptive drugs affect osteoclast survival and influence both resorption and formation of bone. CatK inhibitors are distinct from the existing anti-resorptives as they only target the resorption process itself without impairing osteoclast differentiation and do not interfere with bone formation. An inhibitor of CatK, odanacatib, robustly increased both trabecular and cortical BMD in postmenopausal osteoporosis patients. The phase III fracture prevention trial with odanacatib ended early due to good efficacy and a favorable benefit/risk profile, thus, enhancing the opportunity for CatK as a pharmacological target for osteoporosis. So far, all the inhibitors that reached to the stage of clinical trial targeted active site of CatK to abrogate the entire proteolytic activity of the enzyme in addition to the desired blockage of excessive elastin and collagen degradation, and could thus pose safety concerns with long term use. Identification of selective exosite inhibitors that inhibit CatK's elastase and/or collagenase activity but do not affect the hydrolysis of other physiologically relevant substrates of CatK would be an improved strategy to inhibit this enzyme.

Serum chitotriosidase in postmenopausal women with severe osteoporosis.

UNLABELLED: Human chitotriosidase (Chit) increases during the osteoclast differentiation and their activity. We demonstrated that serum Chit was significantly higher in osteoporotic subjects than in healthy control ones and revealed a negative correlation between Chit and bone mineral density (BMD). This is the first study showing a correlation between Chit and severe postmenopausal osteoporosis. INTRODUCTION: Mammalian chitinases exert important biological roles in the monocyte lineage and chronic inflammatory diseases. In particular, Chit seems to promote bone resorption in vitro. No in vivo studies have been performed to confirm this finding. We aim to evaluate Chit activity in postmenopausal women affected by severe osteoporosis. METHODS: In this cross-sectional study, 91 postmenopausal women affected by osteoporosis and 61 with either osteopenia or normal BMD were screened. All subjects were assessed by dual-energy X-ray absorptiometry (DXA) and X-ray vertebral morphometry. Osteoporotic subjects were considered eligible if they were affected by at least one vertebral osteoporotic fracture (group A = 57 subjects). Osteopenic or healthy subjects were free from osteoporotic fractures (group B = 51 subjects). Enzymatic Chit and serum ß-CrossLaps (CTX) were measured in the whole population. RESULTS: Group A showed higher serum levels of beta-CTX compared to group B (0.40 ± 0.26 ng/mL vs 0.29 ± 0.2 ng/mL, p = 0.022). Chit was significantly higher in group A than in group B (1042 ± 613 nmol/mL/h vs 472 ± 313 nmol/mL/h, p < 0.001, respectively) even after adjustment for age (p < 0.001). Spearman correlation test revealed a negative correlation between Chit and BMD at each site (lumbar spine: r = -0.38, p = 0.001, femoral neck: r = -0.35, p = 0.001, total femur: r = -0.39, p < 0.001). Furthermore, a positive correlation between Chit and PTH was observed (r = 0.26, p = 0.013). No significant correlation was found between Chit and beta-CTX (r = 0.12, p = 0.229). After a multivariate analysis, a positive correlation between severe osteoporosis and Chit (p < 0.001), beta-CTX (p = 0.013), and age (p < 0.001) was observed. CONCLUSION: This is the first clinical study showing a correlation between Chit and severe postmenopausal osteoporosis. Larger and prospective studies are needed to evaluate if Chit may be a promising clinical biomarker and/or therapeutic monitor in subjects with osteoporosis.

Ursolic acid derivatives as bone anabolic agents targeted to tryptophan hydroxylase 1 (Tph-1).

Tryptophan hydroxylase 1 (Tph-1) initiates the biosynthesis of peripheral serotonin. As peripheral serotonin suppresses bone formation, inhibitor of Tph-1 provides a useful tool to discover anabolic agents for osteoporosis. In the present study, series of ursolic acid (UA) derivatives were synthesized, and their inhibitory activity on serotonin biosynthesis and cytotoxicity were evaluated. Among the derivatives, 8d with potent inhibitory activity on serotonin was applied for further research. The data revealed that 8d significantly inhibited protein and mRNA expressions of Tph-1, and an SPR study indicated that 8d directly interacted to Tph-1 with a binding affinity of KD=15.09µM. Oral administration of 8d significantly prevented bone loss via suppressing serotonin biosynthesis without estrogenic side-effects in ovariectomized (OVX) rats.

Soluble guanylate cyclase as a novel treatment target for osteoporosis.

Osteoporosis is a major health problem leading to fractures that cause substantial morbidity and mortality. Current osteoporosis therapies have significant drawbacks, creating a need for novel bone-anabolic agents. We previously showed that the nitric oxide/cyclic GMP (cGMP)/protein kinase G pathway mediates some of the anabolic effects of estrogens and mechanical stimulation in osteoblasts and osteocytes, leading us to hypothesize that cGMP-elevating agents may have bone-protective effects. We tested cinaciguat, a prototype of a novel class of soluble guanylate cyclase activators, in a mouse model of estrogen deficiency-induced osteoporosis. Compared with sham-operated mice, ovariectomized mice had lower serum cGMP concentrations, which were largely restored to normal by treatment with cinaciguat or low-dose 17ß-estradiol. Microcomputed tomography of tibiae showed that cinaciguat significantly improved trabecular bone microarchitecture in ovariectomized animals, with effect sizes similar to those obtained with estrogen replacement therapy. Cinaciguat reversed ovariectomy-induced osteocyte apoptosis as efficiently as estradiol and enhanced bone formation parameters in vivo, consistent with in vitro effects on osteoblast proliferation, differentiation, and survival. Compared with 17ß-estradiol, which completely reversed the ovariectomy-induced increase in osteoclast number, cinaciguat had little effect on osteoclasts. Direct guanylate cyclase stimulators have been extremely well tolerated in clinical trials of cardiovascular diseases, and our findings provide proof-of-concept for this new class of drugs as a novel, anabolic treatment strategy for postmenopausal osteoporosis, confirming an important role of nitric oxide/cGMP/protein kinase G signaling in bone.

The Sirtuin1 activator SRT3025 down-regulates sclerostin and rescues ovariectomy-induced bone loss and biomechanical deterioration in female mice.

Estrogen deficiency leads to rapid bone loss and skeletal fragility. Sclerostin, encoded by the sost gene, and a product of the osteocyte, is a negative regulator of bone formation. Blocking sclerostin increases bone mass and strength in animals and humans. Sirtuin1 (Sirt1), a player in aging and metabolism, regulates bone mass and inhibits sost expression by deacetylating histone 3 at its promoter. We asked whether a Sirt1-activating compound could rescue ovariectomy (OVX)-induced bone loss and biomechanical deterioration in 9-week-old C57BL/6 mice. OVX resulted in a substantial decrease in skeletal Sirt1 expression accompanied by an increase in sclerostin. Oral administration of SRT3025, a Sirt1 activator, at 50 and 100 mg/kg·d for 6 weeks starting 6 weeks after OVX fully reversed the deleterious effects of OVX on vertebral bone mass, microarchitecture, and femoral biomechanical properties. Treatment with SRT3025 decreased bone sclerostin expression and increased cortical periosteal mineralizing surface and serum propeptide of type I procollagen, a bone formation marker. In vitro, in the murine long bone osteocyte-Y4 osteocyte-like cell line SRT3025 down-regulated sclerostin and inactive ß-catenin, whereas a reciprocal effect was observed with EX-527, a Sirt1 inhibitor. Sirt1 activation by Sirt1-activating compounds is a potential novel pathway to down-regulate sclerostin and design anabolic therapies for osteoporosis concurrently ameliorating other metabolic and age-associated conditions.

Increased tartrate-resistant Acid phosphatase expression in osteoblasts and osteocytes in experimental osteoporosis in rats.

Tartrate-resistant acid phosphatase (TRAP) is known as an osteoclast marker, but osteoblasts and osteocytes in the vicinity of bone remodeling sites also express TRAP. Cell culture studies suggest that osteoblasts endocytose osteoclastic TRAP for inactivation. To evaluate whether changes in osteoclast activity could alter TRAP expression in osteoblasts and/or osteocytes in vivo, we studied the ovariectomized and vitamin D-deficient rat (Ovx-D) and rats healing from rickets. Bone sections were analyzed for TRAP gene expression by in situ hybridization, TRAP protein by immunogold labeling, and TRAP enzyme activity using the fluorescent substrate ELF97. Osteoblasts and osteocytes close to intracortical remodeling sites and bone surfaces demonstrated TRAP, most prominently in cancellous bone and osteocytes. Intracellular TRAP was located to electron-dense vesicles with similar morphology in both cell types. Ovx-D increased osteoclast activity (p < 0.001) and ELF97⁺ osteocytes (p < 0.05) in cancellous bone, but no corresponding increase was observed in the osteocyte lacunar area. The level of TRAP⁺ vesicles in cortical osteoblasts (p < 0.01) in Ovx-D rats was also increased. Enhanced osteoclast activity was noted in healing rickets after 72 h (p < 0.05), but no differences in TRAP expression were detected in osteoblasts or osteocytes. Thus, increased osteoclast activity does not affect TRAP expression in osteoblasts and osteocytes, favoring the notion that increased TRAP in these cells is rather due to increased synthesis. Although the role of TRAP in osteoblasts and osteocytes remains elusive, we speculate that the function is related to the capability of the enzyme to regulate the phosphorylation of proteins known to be expressed by these cells.

A susceptibility haplotype within the endothelial nitric oxide synthase gene influences bone mineral density in hypertensive women.

The influence of the coordinated effect of various single-nucleotide polymorphisms (SNPs) within the endothelial nitric oxide synthase (eNOS) gene on the risk of osteoporosis in hypertension has remained undetermined. Four pertinent SNPs of the eNOS gene, rs2070774, rs1799983, rs1800780 and rs3918181, were examined for the risk of osteoporosis in 313 hypertensive postmenopausal women in Northwest India. All the hypertensive women were verified with dual energy X-ray absorptiometry and categorized as 150 with osteoporosis and 163 without osteoporosis. The minor allele (T) of rs1799983 exerts a statistically significant risk for osteoporosis both in dominant [odds ratio (OR) 3.71, 95 % confidence interval (CI) 2.12-6.49, P < 0.001] and recessive mode (OR 5.75, 95 % CI 1.24-26.69, P = 0.036) after Bonferroni correction. Bone mineral density (BMD) values (corrected for the effects of risk variables) according to eNOS SNP genotypes revealed a significant association with rs1799983 at both the lumbar spine (P = 0.001) and femoral neck (P = 0.023). Risk association analyses revealed a susceptibility haplotype TTAG which influences the risk of osteoporosis (OR 2.02, 95 % CI 1.05-3.39, P = 0.042) in hypertension after adjusting for the effects of risk factors. Furthermore, this haplotype was significantly associated with BMD at the lumbar spine (P = 0.029) and femoral neck (P = 0.021) in a dose-dependent manner. The results suggest that possession of the TTAG haplotype of the eNOS gene may increase the risk of osteoporosis two-fold in hypertensive postmenopausal women in Northwest India.

The effect of the cathepsin K inhibitor ONO-5334 on trabecular and cortical bone in postmenopausal osteoporosis: the OCEAN study.

ONO-5334 (Ono Pharmaceutical Co., Ltd., Osaka, Japan) inhibits cathepsin K and has been shown to increase areal bone mineral density (BMD) at the hip and spine in postmenopausal osteoporosis. Quantitative computed tomography (QCT) allows the study of the cortical and trabecular bone separately and provides structural information such as cortical thickness. We investigated the impact of 2 years of cathepsin K inhibition on these different bone compartments with ONO-5334. The clinical study was a randomized, double-blind, placebo, and active controlled parallel group study conducted in 13 centers in six European countries. The original study period of 12 months was extended by another 12 months. A total of 147 subjects (age 55-75 years) of the QCT substudy who participated in the extension period were included. Subjects had been randomized into one of five treatment arms: placebo; ONO-5334 50 mg twice per day (BID); ONO-5334 100 mg once daily (QD); ONO-5334 300 mg QD; or alendronate 70 mg once weekly (QW). QCT was obtained to evaluate bone structure at the lumbar spine and proximal femur. After 24 months ONO-5334 showed statistically significant increases versus placebo for integral, trabecular, and cortical BMD at the spine and the hip (for ONO-5334 300 mg QD, BMD increases were 10.5%, 7.1%, and 13.4% for integral, cortical, and trabecular BMD at the spine, respectively, and 6.2%, 3.4%, and 14.6% for integral, cortical, and trabecular total femur BMD, respectively). Changes in cortical and trabecular BMD in the spine and hip were similar for alendronate as for ONO-5334. Integral volume did not demonstrate statistically significant changes under ONO-5334 treatment, thus there was no evidence of periosteal apposition, neither at the spine nor at the femur. Cortical thickness changes were not statistically significant for ONO-5334 in the spine and hip, with exception of a 2.1% increase after month 24 in the intertrochanter for ONO-5334 300 mg QD. Over 2 years ONO-5334 showed a statistically significant and persistent increase of trabecular and integral BMD at the spine and the hip. Cortical BMD also progressively increased but at a lower rate. Changes in bone size and of periosteal apposition were not observed.

A negative feedback model for a mechanism based description of longitudinal observations. Application for bone turnover biomarkers.

UNLABELLED: In modern medicine the diagnosis and prognosis of an abnormal metabolic condition is based on blood borne measurements involving one or more biomarker. OBJECTIVE: This paper reports the development of a minimal negative feedback model for the description of longitudinal biomarkers concentrations for treatment of osteoporosis in postmenopausal women. METHODS: Literature data were obtained from double-blind, placebo-controlled clinical trial over three years. There were four treatment groups: 1) Placebo, 2) Alendronate, 3) Conjugated Estrogen, and/or 4) Combination therapy. The negative feedback model consists of a biomarker and a companion controller. By considering the above basal biomarker values it is shown that the dynamics can be described by a second order differential equation without the involvement of biomarker production rate. The second order differential equation is also analogous to classical negative feedback servomechanism model with two parameters ω(n) and ξ. It was assumed that the rate constants defining the negative feedback model were equal which would set ξ to 0.707 with only ω(n) to be estimated. RESULTS: ω(n) was estimated for both lumbar spine bone mineral density (BMD) and bone-specific alkaline phosphatase (BAP) in four treatments groups. The t(½) of BMD and BAP were estimated at 26.8 (0.30) and 9.4 (0.30) days respectively. CONCLUSIONS: The negative feedback model of BMD supports the mechanism whereby Conjugated Estrogen and Alendronate decrease the clearance rate constant of BMD analogous to increased apoptosis of osteoclasts. The linked negative feedback models facilitate a mechanism based prediction of BMD using the concentrations of the bone turnover marker BAP.

Strontium ranelate treatment improves oxidative damage in osteoporotic rat model.

BACKGROUND: Osteoporosis is the most common skeletal disorder and is considered a risk of fracture. Most medication used for the treatment of osteoporosis is antiresorptive; however, strontium ranelate (Sr) therapy in postmenopausal women has shown a double effect on resorption and bone formation. In this study, the effect of Sr on status of the oxidative stress and antioxidant defence system was investigated. METHODS: Twenty-one adult albino female Wistar rats were used. The animals were randomly assigned into three groups, control (sham operated rats, received saline), OVX (ovariectomized rats), OVX + Sr (4 months later ovariectomy, strontium ranelate treatment was begun and continued for 120 days) each containing 7 animals. Strontium ranelate (500 mg/kg/day) and placebo (saline) were administered via oral gavage. At the end of the treatment, liver and kidney of rats were removed and malondialdehyde (MDA) level, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities were determined by biochemical analysis methods. RESULTS: In liver, MDA levels were significantly higher in the OVX and OVX + Sr groups than the control group. GSH-Px activity decreased in OVX group and increased in OVX + Sr group compared with values of control group. CAT activity was increased in the OVX + Sr group when compared to control group. In kidney, MDA level was increased in OVX group. SOD activity was decreased in the OVX + Sr group. GSH-Px activity decreased in OVX group and increased in OVX + Sr group compared with control group. CAT activity increased in the OVX + Sr group when compared to control. CONCLUSION: According to our results, Sr has preventive effect on oxidative damage in ovariectomized rats.

Phospholipase Cγ2 is required for basal but not oestrogen deficiency-induced bone resorption.

BACKGROUND: Osteoclasts play a critical role in bone resorption under basal conditions, but they also contribute to pathological bone loss during diseases including postmenopausal osteoporosis. Phospholipase Cγ2 (PLCγ2) is an important signalling molecule in diverse haematopoietic lineages. Here, we tested the role of PLCγ2 in basal and ovariectomy-induced bone resorption, as well as in in vitro osteoclast cultures using PLCγ2-deficient (PLCγ2(-/-) ) mice. MATERIALS AND METHODS: The trabecular architecture of long bone metaphyses was tested by micro-CT and histomorphometric analyses. Postmenopausal osteoporosis was modelled by surgical ovariectomy. Osteoclast development and function, gene expression and PLCγ2 phosphorylation were tested on in vitro osteoclast and macrophage cultures. RESULTS: PLCγ2(-/-) mice had significantly higher trabecular bone mass under basal conditions than wild-type mice. PLCγ2 was required for in vitro development and resorptive function of osteoclasts, but not for upregulation of osteoclast-specific gene expression. PLCγ2 was phosphorylated in a Src-family-dependent manner upon macrophage adhesion but not upon stimulation by M-CSF or RANKL. Surprisingly, ovariectomy-induced bone resorption in PLCγ2(-/-) mice was similar to, or even more robust than, that in wild-type animals. CONCLUSIONS: Our results indicate that PLCγ2 participates in bone resorption under basal conditions, likely because of its role in adhesion receptor signalling during osteoclast development. In contrast, PLCγ2 does not appear to play a major role in ovariectomy-induced bone loss. These results suggest that basal and oestrogen deficiency-induced bone resorption utilizes different signalling pathways and that PLCγ2 may not be a suitable therapeutic target in postmenopausal osteoporosis.

Effects of denosumab on bone turnover markers in postmenopausal osteoporosis.

Denosumab, a fully human monoclonal antibody to RANKL, decreases bone remodeling, increases bone density, and reduces fracture risk. This study evaluates the time course and determinants of bone turnover marker (BTM) response during denosumab treatment, the percentage of denosumab-treated women with BTMs below the premenopausal reference interval, and the correlations between changes in BTMs and bone mineral density (BMD). The BTM substudy of the Fracture REduction Evaulation of Denosumab in Osteoporosis every 6 Months (FREEDOM) Trial included 160 women randomized to subcutaneous denosumab (60 mg) or placebo injections every 6 months for 3 years. Biochemical markers of bone resorption (serum C-telopeptide of type I collagen [CTX] and tartrate-resistant acid phosphatise [TRACP-5b]) and bone formation (serum procollagen type I N-terminal propeptide [PINP] and bone alkaline phosphatase [BALP]) were measured at baseline and at 1, 6, 12, 24, and 36 months. Decreases in CTX were more rapid and greater than decreases in PINP and BALP. One month after injection, CTX levels in all denosumab-treated subjects decreased to levels below the premenopausal reference interval. CTX values at the end of the dosing period were influenced by baseline CTX values and the dosing interval. The percentage of subjects with CTX below the premenopausal reference interval before each subsequent injection decreased from 79% to 51% during the study. CTX and PINP remained below the premenopausal reference interval at all time points in 46% and 31% denosumab-treated subjects, respectively. With denosumab, but not placebo, there were significant correlations between CTX reduction and BMD increase (r = -0.24 to -0.44). The BTM response pattern with denosumab is unique and should be appreciated by physicians to monitor this treatment effectively.

Effects of bone disease and calcium supplementation on antioxidant enzymes in postmenopausal women.

OBJECTIVES: The study was aimed at investigating the effects of osteopenia and calcium supplementation on antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT; and glutathione peroxidase, GPx) in postmenopausal women. DESIGN AND METHODS: Postmenopausal women (n=75) were divided into two groups, control (no bone disease) and osteopenia, according to their bone mineral density. Each group was still divided into calcium-supplemented and nonsupplemented sub-groups. Antioxidant enzyme activities were determined in whole blood using spectrophotometric methods. RESULTS: CAT and SOD activities were not different among the studied groups. However, GPx activity was significantly higher in osteopenia groups as compared to control groups. Calcium supplementation had no effect on the parameters evaluated. Bone mineral density was negatively correlated with GPx activity (p<0.05). CONCLUSIONS: Increased GPx activity could be interpreted as a defense response to counteract the overproduction of reactive oxygen species in women with osteopenia, and this effect was not prevented by calcium supplementation.

[Impact of CYP3A7*1C polymorphism on bone mineral content in postmenopausal women]. / A CYP3A7*1C-polimorfizmus hatása a csont ásványanyag-tartalmára posztmenopauzás nokben.

INTRODUCTION: CYP3A7*1C polymorphism has been shown to be associated with lower levels of serum dehydroepiandrosterone sulphate in men. The age-related decline of dehydroepiandrosterone sulphate levels is believed to contribute to the development of osteoporosis. We hypothesized that CYP3A7*1C may lead to bone loss through decreased levels of dehydroepiandrosterone sulphate in postmenopausal women. PATIENTS AND METHODS: 319 postmenopausal women were studied and divided into two subgroups: 217 women with osteoporosis and 102 aged-matched women without osteoporosis. The CYP3A7*1C polymorphism was genotyped. Serum dehydroepiandrosterone sulphate levels and bone mineral density were measured. RESULTS: Homozygous CYP3A7*1C carriers had significantly lower bone mineral density at lumbar spine than that of wild type (T-score with CYP3A7*1C mutant type: -3.27 +/- 1.02, T-score with wild type: -1.35 +/- 1.53, p = 0.041) after adjusting for age and DHEAS levels. No association was found between genotypes and dehydroepiandrosterone sulphate levels. CONCLUSION: Our data suggest that CYP3A7 polymorphism might have an influence on bone mass at the lumbar spine independently of serum dehydroepiandrosterone sulphate concentrations.

Role of antioxidant systems, lipid peroxidation, and nitric oxide in postmenopausal osteoporosis.

In this study we assessed activities of antioxidant enzymes, lipid peroxidation end-products, and nitric oxide (NO) levels in women with postmenopausal osteoporosis (PMO). Relationship between oxidative stress parameters and NO levels with bone mineral density (BMD) and clinical variables influencing bone mass and health related quality of life measures was also investigated in women with PMO. Postmenopausal women (n=87), aged 40-65, without previous diagnosis or treatment for osteoporosis and independent in daily living activities were included. BMD was measured at the lumbar spine and proximal femur using dual-X-ray absorptiometry (DXA). Erythrocyte catalase (CATe) enzyme activity, erythrocyte and plasma enzyme activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and lipid peroxidation end-product malondialdehyde (MDA) and nitrite/nitrate levels, by product of NO were studied. A total of 23 healthy non-porotic women were included as controls. Women with PMO had significantly lower erythrocyte CATe enzyme activity and higher erythrocyte malondialdehyde (MDAe) and erythrocyte nitric oxide (NOe) levels in comparison to controls whereas erythrocyte SODe and GSH-Px enzyme activity was similar. In plasma, osteoporotic women had significantly higher SOD enzyme activity and higher MDA levels whereas similar GSH-Px enzyme activity and NO levels compared to non-porotic controls. Significant correlation was found between erythrocyte SODe, CATe enzyme activity and NOe levels with proximal femur BMD. Some of the quality of life scores as pain, mental, and social functions correlated with antioxidant enzyme activities and NO levels.Consequently, oxidative stress markers may be an important indicator for bone loss in postmenopausal women. Further researches assessing the oxidative stress markers and NO in bone tissue and changes with anti-osteoporotic drugs would be valuable to better understand the role of free radicals, antioxidants, and NO in the regulation of bone mass.