The clinical utility of TRACP-5b to monitor anti-resorptive treatments of osteoporosis

TRACP-5b can be used to monitor the response of treatments in osteoporosis. We investigated the effect of feeding on levels of TRACP-5b and how these markers perform in a clinical setting. After feeding, there was no effect on levels TRACP-5b. It has similar diagnostic accuracy to CTX and PINP.

INTRODUCTION

Bone turnover markers (BTMs) can be used to monitor response to osteoporosis treatment. However, some are affected by food intake and are not suitable to measure in a clinical setting. An assay is available which is capable of detecting the active isoform 5b of tartrate resistance acid phosphatase (TRACP-5b) and it may have minimal biological variation. Our aims were to investigate the effect of feeding on levels of TRACP-5b and compare this to CTX and PINP and then to compare the diagnostic accuracy of TRACP-5b to CTX and PINP in patients with osteoporosis given commonly used treatments.

METHODS

Eighteen patients were recruited to investigate the effect of feeding on BTMs. Ninety-seven patients (74 females and 23 males) receiving 5 mg annual intra-venous zoledronate (mean age 70) and 97 patients receiving no treatment were recruited as group-matched controls. Sixteen patients receiving 60 mg subcutaneous denosumab every 6 months, (mean age 76) and 16 matched controls were recruited. Seventy-six patients were receiving oral bisphosphonates: 70 mg alendronate weekly, 35 mg risedronate and 150 mg monthly ibandronate (4%). Thirty of these patients had BMD measured at the total hip and lumbar spine. An estimate of compliance was not determined. Eighty patients receiving no treatment were recruited as group-matched controls. TRACP-5b (ELISA, Nittobo) and CTX and PINP were measured in serum in the non-fasting state between 0800 and 1700.

RESULTS

After feeding, there was no effect on levels TRACP-5b and significant reductions in CTX and PINP, 29% and 10%, respectively (p < 0.001). In the zoledronate and denosumab groups, there were no differences in the areas under the curves (AUCs) between TRACP-5b, PINP and CTX. In the oral bisphosphonates group, the AUCs between TRACP-5b and PINP and TRACP-5b and CTX were significantly different, p < 0.01 and p = 0.001, respectively. TRACP-5b was negatively correlated with BMD.

CONCLUSION

TRACP-5b is not affected by food intake, unlike CTX and PINP. All three BTMs correlate with change in BMD at the lumbar spine and total hip. TRACP-5b has similar diagnostic accuracy to CTX and PINP with commonly used treatments for osteoporosis with the exception of oral bisphosphonate therapy.

Overexpression of PIK3R1 Promotes Bone Formation by Regulating Osteoblast Differentiation and Osteoclast Formation

In an effort to bolster our understanding of regulation of bone formation in the context of osteoporosis, we screened out differentially expressed genes in osteoporosis patients with high and low bone mineral density by bioinformatics analysis. PIK3R1 is increasingly being nominated as a pivotal mediator in the differentiation of osteoblasts and osteoclasts that is closely related to bone formation. However, the specific mechanisms underlying the way that PIK3R1 affects bone metabolism are not fully elucidated. We intended to examine the potential mechanism by which PIK3R1 regulates osteoblast differentiation. Enrichment analysis was therefore carried out for differentially expressed genes. We noted that the estrogen signaling pathway, TNF signaling pathway, and osteoclast differentiation were markedly associated with ossification, and they displayed enrichment in PIK3R1. Based on western blot, qRT-PCR, and differentiation analysis in vitro, we found that upregulation of PIK3R1 enhanced osteoblastic differentiation, as evidenced by increased levels of investigated osteoblast-related genes as well as activities of ALP and ARS, while it notably decreased levels of investigated osteoclast-related genes. On the contrary, downregulation of PIK3R1 decreased levels of osteoblast-related genes and increased levels of osteoclast-related genes. Besides, in vitro experiments revealed that PIK3R1 facilitated proliferation and repressed apoptosis of osteoblasts but had an opposite impact on osteoclasts. In summary, PIK3R1 exhibits an osteoprotective effect via regulating osteoblast differentiation, which can be represented as a promising therapeutic target for osteoporosis.

DUSP6 expression is associated with osteoporosis through the regulation of osteoclast differentiation via ERK2/Smad2 signaling

Osteoporosis-related fractures, such as femoral neck and vertebral fractures, are common in aged people, resulting in increased disability rate and health-care costs. Thus, it is of great importance to clarify the mechanism of osteoclast-related osteoporosis and find effective ways to avoid its complication. In this study, gene expression profile analysis and real-time polymerase chain reaction revealed that DUSP6 expression was suppressed in human and mice osteoporosis cases. In vitro experiments confirmed that DUSP6 overexpression prevented osteoclastogenesis, whereas inhibition of DUSP6 by small interference RNA or with a chemical inhibitor, (E/Z)-BCI, had the opposite effect. (E/Z)-BCl significantly accelerated the bone loss process in vivo by enhancing osteoclastogenesis. Bioinformatics analyses and in vitro experiments indicated that miR-181a was an upstream regulator of DUSP6. Moreover, miR-181a positively induced the differentiation and negatively regulated the apoptosis of osteoclasts via DUSP6. Furthermore, downstream signals by ERK2 and SMAD2 were also found to be involved in this process. Evaluation of ERK2-deficiency bone marrow-derived macrophages confirmed the role of ERK2 signaling in the DUSP6-mediated osteoclastogenesis. Additionally, immunoprecipitation assays confirmed that DUSP6 directly modified the phosphorylation status of SMAD2 and the subsequent nuclear transportation of NFATC1 to regulate osteoclast differentiation. Altogether, this study demonstrated for the first time the role of miRNA-181a/DUSP6 in the progression of osteoporosis via the ERK2 and SMAD2 signaling pathway. Hence, DUSP6 may represent a novel target for the treatment of osteoclast-related diseases in the future.

Inhibition of Lipoxygenases Showed No Benefit for the Musculoskeletal System in Estrogen Deficient Rats

BACKGROUND

In previous studies, we reported the beneficial impact of two lipoxygenase-inhibitors, Baicalein and Zileuton, on osteoporotic bone in a postmenopausal rat model. Whereas subcutaneous Baicalein predominantly improved cortical bone, Zileuton enhanced vertebral and femoral trabecular bone. In this study, we aimed to reveal whether the oral administration of Baicalein caused similar effects on bone and whether a combined administration of Baicalein and Zileuton could act synergistically to ameliorate the formerly reported effects in the musculoskeletal system.

METHODS

We treated ovariectomized (OVX) female Sprague-Dawley rats either with Baicalein (10mg/kg BW), Zileuton (10mg/kg BW) or a combination of both (each 10mg/kg BW) for 13 weeks and compared with untreated OVX and NON-OVX groups (n=12-16 rats per group). Lumbar vertebral bodies and femora were analyzed. Tibiae were osteotomized, plate-stabilized (at week 8 after OVX) and likewise analyzed by biomechanical, histological, micro-computed tomographical and ashing tests. The skeletal muscle structure was analyzed.

RESULTS

Oral administration of Baicalein did not confirm the reported favorable cortical effects in neither vertebra nor femur. Zileuton showed a beneficial effect on trabecular vertebra, while the femur was negatively affected. Callus formation was enhanced by all treatments; however, its density and biomechanical properties were unaltered. Lipoxygenase inhibition did not show a beneficial effect on skeletal muscle. The combination therapy did not ameliorate OVX-induced osteoporosis but induced even more bone loss.

CONCLUSIONS

The preventive anti-osteoporotic treatments with two lipoxygenase inhibitors applied either alone or in combination showed no benefit for the musculoskeletal system in estrogen deficient rats.

Long Term Ovariectomy-Induced Osteoporosis is Associated with High Stearoyl-CoA Desaturase Indexes in Rat Femur

Osteoporosis is characterized by a bone loss associated to an increased bone marrow adiposity; however, it is still unclear what kind of lipids are involved. Therefore, the main purpose of this study was to see if there is any local bone lipid changes related to osteoporosis, by using the ovariectomy-induced osteoporosis (OVX) rat model. Female SD rats (operated at 6 months of age for skeletal maturity) were divided in control SHAM and OVX groups (n = 6/group) and maintained for 9 month post-surgery. Lipids were analyzed in two compartments of femoral diaphyses: bone marrow (BM) and mineralized tissue (MT), by chromatographic methods. As expected, osteoporotic femurs had a larger BM mass associated with a two-fold increase of lipid content. The MT had a similar lipid enrichment, indicating that adiposity affected the mineral part as well. The main lipids concerned were triglycerides, sphingomyelin, phosphatidylcholine and phosphatidylserine in BM, and triglycerides and cholesterol esters in MT. The increase of both energy-storage and membrane-associated lipids in BM suggested that cell number and/or size was enhanced to allow more triglyceride storage. Interestingly, in MT of osteoporotic femurs, sphingomyelin was decreased, suggesting that its catabolism could be linked to osteoporosis. In both femoral compartments, fatty acid profiles were enriched in 14:0 and 16:1, lowered in 18:0 and 20:4 n-6, and two-fold higher stearoyl-CoA desaturase indexes (16:1/16:0 and 18:1/18:0 ratios), suggesting an increased de novo lipogenesis in osteoporotic femurs. Thus, the present study is first to report local changes of individual lipids in rat osteoporotic femurs and suggests that osteoporosis is a pathologic condition associated with an enhanced de novo lipogenesis. Further studies will be needed to better understand the consequences of these lipid changes in osteoporotic bones.

Ferulic acid, a natural polyphenol, protects against osteoporosis by activating SIRT1 and NF-κB in neonatal rats with glucocorticoid-induced osteoporosis

Osteoporosis is a chronic disease whose symptoms include a reduction in bone strength, osteopenia, and damage to the bone microstructure. Ferulic acids are natural polyphenols present in various fruits that suppress the fusion and apoptosis of mature osteoclasts. Rats were divided into sham, control (osteoporosis), 10 mg/kg body weight ferulic acid, 20 mg/kg body weight ferulic acid, and 30 mg/kg body weight ferulic acid treatment groups. Osteoporosis was induced in neonatal by administration of dexamethasone (glucocorticoids). Bone mineral density (BMD), osteocalcin and alkaline phosphatase (ALP) levels, bone mechanical parameters, and mRNA and protein levels of sirtuin1 (SIRT1) and nuclear factor kappa-B (NF-κB) in the osteoporotic neonatal rats were assessed. Histopathological analysis was also conducted. Treatment with 20 and 30 mg/kg body weight ferulic acid increased BMD by 25% and 141.7%, respectively, but reduced ALP and osteocalcin levels. Furthermore, treatment with 20 or 30 mg/kg body weight ferulic acid significantly reduced the pixel intensity and significantly increased the peak load and ultimate stiffness. Ferulic acid significantly increased the mRNA and protein levels of SIRT1 and reduced those of NF-κB. Finally, the histopathological analysis showed that ferulic acid increased BMD. In summary, ferulic acid exhibited protective effects against osteoporosis in neonatal rats.

Effects of 17β-HSD2 inhibition in bones on osteoporosis based on an animal rat model

Hormone replacement therapy is a viable option to protect bone from postmenopausal osteoporosis. Systemically elevated estrogen levels, however, are disadvantageous because of the risk of harmful side effects in other organs. The rationale of the study presented here is to target a key enzyme in estradiol (E2) and testosterone (T) metabolism to increase E2 levels in an organ-specific manner, thereby avoiding the disadvantages of systemically increased E2 levels. The 17ß-hydroxysteroid dehydrogenase (17β-HSD2), which is e.g. expressed in bone, catalyzes the oxidation of E2 and T into estrone (E1) and androstenedione. We postulate that inhibiting 17β-HSD2 should lead to elevated E2 and T levels in organs expressing the enzyme. Therefore, we can use the benefits of E2 directly, or those of T following aromatization into E2, in the bone without affecting systemic levels. We tested for the first time, the novel and potent 17β-HSD2 inhibitor, compound 24 (C24), to explore the therapeutic potential of a 17β-HSD2 inhibition in an ovariectomy (ovx)-induced rat model of bone loss. We tested the inhibitor alone and, together with low dose estrogen supplementation to model estrogen levels in the postmenopausal situation. Female mature Wistar-Hannover rats were treated for 8 weeks with doses of 2, 10, 50 mg C24 per kg body weight per day alone or in the presence of estradiol benzoate (E2B) supplementation to alleviate ovx-induced bone loss. Ovx placebo and sham operated animals served as negative and positive controls. The experiment was evaluated regarding aspects of efficacy and safety: Bone was analyzed to evaluate bone protective effects, and uterus for potential, unwanted E2-mediated side effects. We observed a good bioavailability of C24 as very high plasma concentrations were measured, up to a group mean of 15,412 nM for the ovx C24-high group. Histomorphometrical analyses and in vivo &ex vivo μCT revealed significant bone protective effects for the lowest inhibitor concentration used. Irrespective of the plasma concentration, no proliferative effects in the uterus could be observed. These results support our approach of intracellular targeting key enzymes of E2 and T metabolism to increase E2 and T levels in an organ specific manner.

Clinical and translational pharmacology of the cathepsin K inhibitor odanacatib studied for osteoporosis

Cathepsin K (CatK) is a cysteine protease abundantly expressed by osteoclasts and localized in the lysosomes and resorption lacunae of these cells. CatK is the principal enzyme responsible for the degradation of bone collagen. Odanacatib is a selective, reversible inhibitor of CatK at subnanomolar potency. The pharmacokinetics of odanacatib have been extensively studied and are similar in young healthy men, postmenopausal women and elderly men, and were qualitatively similar throughout Phase 1 development and in-patient studies. Following 3 weeks of 50 mg once weekly dosing the geometric mean area under the curve from 0 to 168 hours was 41.1 μM h, the concentration at 168 hours was 126 nM and the harmonic mean apparent terminal half-life was 84.8 hr. Odanacatib exposure increased in a less than dose proportional manner due to solubility limited absorption. It is estimated that approximately 70% of the absorbed dose of odanacatib is eliminated via metabolism, 20% is excreted as unchanged drug in the bile or faeces, and 10% is excreted as unchanged drug in the urine. The systemic clearance was low (approximately 13 mL/min). Odanacatib decreases the degradation of bone matrix proteins and reduces the efficiency of bone resorption with target engagement confirmed by a robust decrease in serum C-telopeptides of type 1 collagen (approximately 60%), urinary aminoterminal crosslinked telopeptides of type 1 collagen to creatinine ratio (approximately 50%) and total urine deoxypyridinoline/Cr (approximately 30%), with an increase in serum cross-linked carboxy-terminal telopeptide of type 1 collagen (approximately 55%). The 50-mg weekly dosing regimen evaluated in Phase 3 achieved near maximal reduction in bone resorption throughout the treatment period. The extensive clinical programme for odanacatib, together with more limited clinical experience with other CatK inhibitors (balicatib and ONO-5334), provides important insights into the clinical pharmacology of CatK inhibition and the potential role of CatK in bone turnover and mineral homeostasis. Key findings include the ability of this mechanism to: (i) provide sustained reductions in resorption markers, increases in bone mineral density, and demonstrated fracture risk reduction; (ii) be associated with relative formation-sparing effects such that sustained resorption reduction is achieved without accompanying meaningful reductions in bone formation; and (iii) lead to increases in osteoclast number as well as other osteoclast activity (including build-up of CatK enzyme), which may yield transient increases in resorption following treatment discontinuation and the potential for nonmonotonic responses at subtherapeutic doses.

Unified mechanisms for self-RNA recognition by RIG-I Singleton-Merten syndrome variants

The innate immune sensor retinoic acid-inducible gene I (RIG-I) detects cytosolic viral RNA and requires a conformational change caused by both ATP and RNA binding to induce an active signaling state and to trigger an immune response. Previously, we showed that ATP hydrolysis removes RIG-I from lower-affinity self-RNAs (Lässig et al., 2015), revealing how ATP turnover helps RIG-I distinguish viral from self-RNA and explaining why a mutation in a motif that slows down ATP hydrolysis causes the autoimmune disease Singleton-Merten syndrome (SMS). Here we show that a different, mechanistically unexplained SMS variant, C268F, which is localized in the ATP-binding P-loop, can signal independently of ATP but is still dependent on RNA. The structure of RIG-I C268F in complex with double-stranded RNA reveals that C268F helps induce a structural conformation in RIG-I that is similar to that induced by ATP. Our results uncover an unexpected mechanism to explain how a mutation in a P-loop ATPase can induce a gain-of-function ATP state in the absence of ATP.

[Estradiol significantly increases the expression of antioxidant enzymes in osteoporotic rats and osteoblasts in vitro]

OBJECTIVE

To investigate the effect of estradiol on the expression of antioxidant enzymes in osteoblasts and its role in postmenopausal osteoporosis.

METHODS

Rat models of osteoporosis established by ovariectomy were treated with estradiol for 3 months, and the changes in serum levels of reactive oxygen species (H₂O₂) and antioxidant enzymes (γ -GCS, GSH-ST and GSH-px) were detected. The effects of estradiol on the expression of γ -GCS mRNA and protein in osteoblast-like cells MC3T3-E1, MG63 and OB were examined with PCR and Western blotting. Using a mRNA microarray, we analyzed the changes in the expressions of 84 antioxidant enzymes in the osteoblast cell line MC3T3-E1 following estradiol treatment, and the enzymes with significant changes were verified by PCR. CCK-8 kit was used to evaluate the effect of estradiol and antioxidant NAC on the proliferation of MC3T3-E1 cells.

RESULTS

Rat models of osteoporosis were successfully established with ovariectomy. The osteoporotic rats showed significantly increased serum level of reactive oxygen species (H2O2) and decreased levels of antioxidant enzymes. Estrogen treatment of the osteoporotic rats obviously reversed the phenotype of osteoporosis, lowered serum level of reactive oxygen species, and increased the level of γ -GCS. In MC3T3-E1, MG63 and OB cells, estradiol treatment significantly upregulated the expression levels of γ -GCS mRNA and protein. In MC3T3-E1 cells treated with estrogen, the mRNA chip identified 6 upregulated antioxidant enzymes (Gpx6, Gstk1, Nos2, Prdx2, Ngb and Ccs), and the results of PCR verified that estradiol upregulated Ccs and Ngb mRNAs in MC3T3-E1, MG63 and OB cells. Estradiol and antioxidant NAC obviously promoted the proliferation of MC3T3-E1 cells.

CONCLUSION

Estradiol significantly increases the expression of antioxidase γ -Gcs, Ccs and Ngb in osteoblasts in vitro. Postmenopausal osteoporosis is closely related with the increase of reactive oxygen species and the decrease of antioxidant levels. In osteoblasts, estrogen deficiency may increase the level of reactive oxygen species, decrease the level of antioxidant enzymes, activate the oxidative stress cascade, and consequently inhibit the proliferation of osteoblasts to aggravate the condition of osteoporosis.

Prolidase

Prolidase (EC.3.4.13.9) or proline dipeptidase, is one of the unique enzyme capable of degrading dipeptides, in which a proline or hydroxyproline residue is located at the C-terminal position. Prolidase has a unique function in all cell types; therefore, the mechanisms and parameters involved in prolidase activity regulation are of special interest. Could prolidase be a good biomarker in different physiologic and pathologic conditions? This is an important question. There is no consensus on the answer to this question. It is of great importance during collagen turnover, inflammation, tissue fibrosis and skeletal abnormalities.Prolidase itself without other biochemical markers may not provide information to clinicians about disease activity. So, I think it should be evaluated together with other serum biochemical markers.This review will serve to discuss many in vivo functions of prolidase, as well as level prolidase activity in diagnosis and monitoring of treatment in the various diseases (Ref. 50).

[Klotho not only antiageing protein]

Klotho, the gene encoding the antiaging protein, was discovered in 1997 and named after a Greek Goddes who spun the thread of life. Numerous experiments on mice confirmed that destruction of the klotho gene or loss of klotho function leads to an accelerated aging and premature death. In addition to shortened life span, klotho-deficient mice demonstrated changes in functioning of multiple organs, ectopic calcification, enhanced development of arteriosclerosis, osteoporosis and atrophy of skin. In contrast, overexpression of a gene in mice inhibited aging and prolonged survival. The multisystemic phenotype induced by Klotho deficiency indicates that Klotho works on a variety of organs. Klotho is highly expressed in the kidney, brain, and to a lesser extent in other organs. Protein Klotho exists in two forms: membrane and secreted which play different functions. Membrane Klotho function as an obligate co-receptor required for signaling for the phosphaturic factor FGF23, regulates calcium-phosphate homeostasis through renal ion transport in addition to modulation of PTH and 1,25(OH)2D3. Soluble klotho functions as a humoral factor and regulates the activity of several ion channels and transporters. The secreted Klotho can also inhibit oxydative stres and the insulin and insulin-like growth factor 1 (IGF-1) pathways. The discovery of the protein klotho led to the identification of new axes connecting endocrine disturbances in the homeostasis of the calcium-phosphate to the aging of the organism. Klotho deficiency may not only be a trigger for accelerated aging but also in development of age- -associated diseases, including hypertension, osteoporosis, cardiovascular disease, and CKD. Conceivably, better understanding of Klotho protein might provide a novel treatment strategy for aging and age-associated diseases.

Curcumin improves bone microarchitecture in glucocorticoid-induced secondary osteoporosis mice through the activation of microRNA-365 via regulating MMP-9

The present study aimed to investigate bone microarchitecture of the proximal tibia in glucocorticoid-induced osteoporosis (GIOP) mice, and the underlying molecular mechanisms of curcumin in DXM-induced osteoporosis were performed. DXM-treated facilitated to induce hypercalciuria in mice, and curcumin-treated showed a decrease in urine calcium. Curcumin reversed DXM-induced bone resorption, including an increase in serum OCN and a decrease in bone resorption markers CTX and TRAP-5b. H&E staining showed the increased disconnections and separation in trabecular bone network as well as the reduction of trabecular thickness throughout the proximal metaphysis of tibia in GIOP group. Importantly, curcumin reversed DXM-induced trabecular deleterious effects and stimulated bone remodeling. The further evidence showed that curcumin supplement significantly decreased the TRAP-positive stained area and inhibited the activity of OPG/RANKL/RANK signaling in the GIOP mice. Moreover, bioinformatics analysis suggested that miR-365 was a regulator of MMP9. The levels of miR-365 were markedly suppressed; however, curcumin treatment could reverse the downregulation of miR-365 in the tibia of GIOP mice. Simultaneously, the results demonstrated that the mRNA and protein expression of MMP-9 were significantly increased in GIOP mice compared with that of the control group. Curcumin treatment could suppress the expression of MMP-9 in the tibia of GIOP mice. The present study demonstrated the protective effects of curcumin against bone deteriorations in the experimentally DIOP mice, and the underlying mechanism was mediated, at least partially, through the activation of microRNA-365 via suppressing MMP9.

The interaction of MMP-2/B7-H3 in human osteoporosis

The immune costimulatory molecule B7-H3 has been shown to be involved in the regulation of murine bone formation. However, the role of B7-H3 in bone metabolic diseases remains unknown. In our study, matrix metalloproteinase 2 (MMP-2) and soluble B7-H3 (sB7-H3) were found to be correlatively up-regulated in the sera of osteoporosis patients. Furthermore, our results showed that MG63 cells treated with MMP-2 inhibitors produced lower amounts of sB7-H3 while cells with recombinant MMP-2 had an increased membrane B7-H3 (mB7-H3) shedding. Therefore, elevated MMP-2 levels resulted in an elevation of serum sB7-H3 and reduction of osteoblastic mB7-H3. B7-H3 knockdown in MG63 cells significantly decreased osteoblastic markers and substantially decreased the number of mineralized nodules after 21days. Thus, B7-H3-deficient MG63 cells exhibited impaired bone formation. These results suggest that mB7-H3 is required for the later phases of osteoblast differentiation and that MMP-2/B7-H3 plays a negative regulatory role in osteoporosis.

Promoter polymorphism T-786C, 894G→T at exon 7 of endothelial nitric oxide synthase gene are associated with risk of osteoporosis in Sichuan region male residents

OBJECTIVE

To investigate the association between genetic polymorphism of T-786C in promoter region, 894G→T at exon 7 of endothelial nitric oxide synthase (eNOS) gene and osteoporosis (OP) disease.

METHOD

The genotypes of 350 patients with osteoporosis and 350 healthy controls were detected by polymerase chain reaction (PCR) and DNA sequencing. The allele ratios and genotype distributions in the patients and controls were assessed using the Pearson χ(2)-test. Odds ratios (OR) with two tailed P-values and 95% confidence intervals (CI) were calculated as a measure of the association of the eNOS genotypes with OP.

RESULT

the C allele distribution frequency of T-786C eNOS gene in OP group (8.5%) was significantly higher than that in control group (3.9%), relative risk (OR) of OP associated with the CC genotype was 2.68 (95% CI, 0.92 to 1.37). The T allele frequency of 894G→T at exon 7 in eNOS gene in OP group (11.5%) was also significantly higher than that in control group (5.2%), OR of OP associated with the TT genotype was 2.60 (all P<0.05).

CONCLUSION

The analysis results indicated that both T-786C in promoter region and 894G→T at exon 7 of eNOS gene might be genetic predisposal factors of OP, these polymorphisms may be independently or synergic with other loci to have an impact on the incidence of OP.

Age-related NADPH Oxidase (arNOX) Activity Correlated with Cartilage Degradation and Bony Changes in Age-related Osteoarthritis

The purpose of this study was to investigate the age-related NADPH oxidase (arNOX) activity in patients with age-related knee osteoarthritis (OA). Serum and cartilage arNOX activities were determined using an oxidized ferricytochrome C reduction assay. Full-thickness knee joint cartilages obtained through total knee replacement surgery were graded according to the Outerbridge (OB) classification. Radiographic severity of OA was determined on Knee X-rays according to the Kellgren-Lawrence (K/L) grading system. Cartilage β-galactosidase, HIF-1α, and GLUT-1 expression levels were evaluated as markers for tissue senescence, hypoxia, and glycolysis. Higher arNOX activities occurred with higher levels of cartilage β-galactosidase, HIF-1α, and GLUT-1 (P = 0.002). arNOX activity in cartilages with surface defects (OB grade II, III) was higher than in those without the defects (OB grade 0, I) (P = 0.012). Cartilage arNOX activity showed a positive correlation with serum arNOX activity (r = -0.577, P = 0.023). Serum arNOX activity was significantly higher in the OA subgroup with bilateral ROA than in the OA with no or unilateral ROA (2.449 ± 0.81, 2.022 ± 0.251 nM/mL, respectively, P = 0.019). The results of this study demonstrate that OA itself is not a cause to increase arNOX activities, however, arNOX hyperactivity is related to a high degree of cartilage degradation, and a high grade and extent of ROA in age-related OA.

Inhibition of CaMKK2 reverses age-associated decline in bone mass

Decline in bone formation is a major contributing factor to the loss of bone mass associated with aging. We previously showed that the genetic ablation of the tissue-restricted and multifunctional Ca(2+)/calmodulin (CaM)-dependent protein kinase kinase 2 (CaMKK2) stimulates trabecular bone mass accrual, mainly by promoting anabolic pathways and inhibiting catabolic pathways of bone remodeling. In this study, we investigated whether inhibition of this kinase using its selective cell-permeable inhibitor STO-609 will stimulate bone formation in 32 week old male WT mice and reverse age-associated of decline in bone volume and strength. Tri-weekly intraperitoneal injections of saline or STO-609 (10 μM) were performed for six weeks followed by metabolic labeling with calcein and alizarin red. New bone formation was assessed by dynamic histomorphometry whereas micro-computed tomography was employed to measure trabecular bone volume, microarchitecture and femoral mid-shaft geometry. Cortical and trabecular bone biomechanical properties were assessed using three-point bending and punch compression methods respectively. Our results reveal that as they progress from 12 to 32 weeks of age, WT mice sustain a significant decline in trabecular bone volume, microarchitecture and strength as well as cortical bone strength. However, treatment of the 32 week old WT mice with STO-609 stimulated apposition of new bone and completely reversed the age-associated decrease in bone volume, quality, as well as trabecular and cortical bone strength. We also observed that regardless of age, male Camkk2(-/-) mice possessed significantly elevated trabecular bone volume, microarchitecture and compressive strength as well as cortical bone strength compared to age-matched WT mice, implying that the chronic loss of this kinase attenuates age-associated decline in bone mass. Further, whereas STO-609 treatment and/or the absence of CaMKK2 significantly enhanced the femoral mid-shaft geometry, the mid-shaft cortical wall thickness and material bending stress remained similar among the cohorts, implying that regardless of treatment, the material properties of the bone remain similar. Thus, our cumulative results provide evidence for the pharmacological inhibition of CaMKK2 as a bone anabolic strategy in combating age-associated osteoporosis.

Probing the activity modification space of the cysteine peptidase cathepsin K with novel allosteric modifiers

Targeting allosteric sites is gaining increasing recognition as a strategy for modulating the activity of enzymes, especially in drug design. Here we investigate the mechanisms of allosteric regulation of cathepsin K as a representative of cysteine cathepsins and a promising drug target for the treatment of osteoporosis. Eight novel modifiers are identified by computational targeting of predicted allosteric sites on the surface of the enzyme. All act via hyperbolic kinetic mechanisms in presence of low molecular mass substrates, as expected for allosteric effectors. Two compounds have sizable effects on enzyme activity using interstitial collagen as a natural substrate of cathepsin K and four compounds show a significantly stabilizing effect on cathepsin K. The concept of activity modification space is introduced to obtain a global perspective of the effects elicited by the modifiers. Analysis of the activity modification space reveals that the activity of cathepsin K is regulated via multiple, different allosteric mechanisms.

NADPH oxidases in bone homeostasis and osteoporosis

Bone formation and degradation are perfectly coordinated. In case of an imbalance of these processes diseases occur associated with exaggerated formation of new bone or bone loss as in osteoporosis. Most studies investigating osteoporosis either focus on osteoblast or osteoclast function and differentiation. Both processes have been suggested to be affected by reactive oxygen species (ROS). Besides a potentially harmful role of ROS, these small molecules are important second messengers. The family of NADPH oxidases produces ROS in a controlled and targeted manner, to specifically regulate signal transduction. This review will highlight the role of reactive oxygen species in bone cell differentiation and bone-loss associated disease with a special focus on osteoporosis and NADPH oxidases as specialized sources of ROS.

Anti-osteoporotic and antioxidant activities of chemical constituents of the aerial parts of Ducrosia ismaelis

A new pterocarpan glycoside, glycinol-3-O-β-D-glucopyranoside (1), and a new dihydrochalcone glycoside, ismaeloside A (2), were isolated together with 13 known compounds, including several flavonoids (3-8), lignans (9-11), and phenolic compounds (12-15), from the methanol extract of the aerial parts of Ducrosia ismaelis. The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of these data with previously published results. The anti-osteoporotic and antioxidant activities of the isolated compounds were assessed using tartrate-resistant acid phosphatase (TRAP), oxygen radical absorbance capacity (ORAC), and reducing capacity assays. Compound 15 exhibited a dose-dependent inhibition of osteoclastic TRAP activity with a TRAP value of 86.05±6.55% of the control at a concentration of 10 μM. Compounds 1, 3-5, and 8 showed potent peroxyl radical-scavenging capacities with ORAC values of 22.79±0.90, 25.57±0.49, 20.41±0.63, 26.55±0.42, and 24.83±0.12 μM Trolox equivalents (TE) at 10 μM, respectively. Only compound 9 was able to significantly reduce Cu(I) with 23.44 μM TE at a concentration of 10 μM. All of the aforementioned compounds were isolated for the first time from a Ducrosia species.

Cytosolic phospholipase A2 and eicosanoids modulate life, death and function of human osteoclasts in vitro

INTRODUCTION

Eicosanoids are important in bone physiology but the specific function of phopholipase enzymes has not been determined in osteoclasts. The objective of this is study was to determine the presence of cPLA2 in human in vitro-differentiated osteoclasts as well as osteoclasts in situ from bone biopsies.

MATERIALS AND METHODS

Osteoclastogenesis, apoptosis, bone resorption and the modulation of actin cytoskeleton assays were performed on osteoclasts differentiated in vitro. Immunohistochemistry was done in differentiated osteoclasts as well as on bone biopsies.

RESULTS

Human osteoclasts from normal, fetal, osteoarthritic, osteoporotic and Pagetic bone biopsies express cPLA2 and stimulation with RANKL increases cPLA2 phosphorylation in vitro. Inhibition of cPLA2 increased osteoclastogenesis and decreased apoptosis but decreased the capacity of osteoclasts to generate actin rings and to resorb bone.

DISCUSSION AND CONCLUSIONS

These results suggest that cPLA2 modulates osteoclast functions and could be a useful target in bone diseases with hyperactivated osteoclasts.

Seven sirtuins for seven deadly diseases of aging

Sirtuins are a class of NAD(+)-dependent deacetylases having beneficial health effects. This extensive review describes the numerous intracellular actions of the seven mammalian sirtuins, their protein targets, intracellular localization, the pathways they modulate, and their role in common diseases of aging. Selective pharmacological targeting of sirtuins is of current interest in helping to alleviate global disease burden. Since all sirtuins are activated by NAD(+), strategies that boost NAD(+) in cells are of interest. While most is known about SIRT1, the functions of the six other sirtuins are now emerging. Best known is the involvement of sirtuins in helping cells adapt energy output to match energy requirements. SIRT1 and some of the other sirtuins enhance fat metabolism and modulate mitochondrial respiration to optimize energy harvesting. The AMP kinase/SIRT1-PGC-1α-PPAR axis and mitochondrial sirtuins appear pivotal to maintaining mitochondrial function. Downregulation with aging explains much of the pathophysiology that accumulates with aging. Posttranslational modifications of sirtuins and their substrates affect specificity. Although SIRT1 activation seems not to affect life span, activation of some of the other sirtuins might. Since sirtuins are crucial to pathways that counter the decline in health that accompanies aging, pharmacological agents that boost sirtuin activity have clinical potential in treatment of diabetes, cardiovascular disease, dementia, osteoporosis, arthritis, and other conditions. In cancer, however, SIRT1 inhibitors could have therapeutic value. Nutraceuticals such as resveratrol have a multiplicity of actions besides sirtuin activation. Their net health benefit and relative safety may have originated from the ability of animals to survive environmental changes by utilizing these stress resistance chemicals in the diet during evolution. Each sirtuin forms a key hub to the intracellular pathways affected.

Impairment of osteoblast differentiation due to proliferation-independent telomere dysfunction in mouse models of accelerated aging

We undertook genetic and nongenetic approaches to investigate the relationship between telomere maintenance and osteoblast differentiation, as well as to uncover a possible link between a known mediator of cellular aging and senile bone loss. Using mouse models of disrupted telomere maintenance molecules, including mutants in the Werner helicase (Wrn(-/-) ), telomerase (Terc(-/-) ), and Wrn(-/-) Terc(-/-) double mutants predisposed to accelerated bone loss, we measured telomere dysfunction-induced foci (TIFs) and markers of osteoblast differentiation in mesenchymal progenitor cells (MPCs). We found that telomere maintenance is directly and significantly related to osteoblast differentiation, with dysfunctional telomeres associated with impaired differentiation independent of proliferation state. Telomere-mediated defects in osteoblast differentiation are associated with increased p53/p21 expression and concomitant reduction in RUNX2. Conversely, MPCs from p53(-/-) mice do not have substantial telomere dysfunction and spontaneously differentiate into osteoblasts. These results suggest that critical telomere dysfunction may be a prominent mechanism for age-related osteoporosis and limits MPC differentiation into bone-forming cells via the p53/p21 pathway.

Applications of 'TissueQuant'- a color intensity quantification tool for medical research

This paper demonstrates the use of TissueQuant - an image analysis tool for quantification of color intensities which was developed for use in medical research where the stained biological specimen such as tissue or antigen needs to be quantified. TissueQuant provides facilities for user interaction to choose and quantify the color of interest and its shades. Gaussian weighting functions are used to provide a color score which quantifies how close the shade is to the user specified reference color. We describe two studies in medical research which use TissueQuant for quantification. The first study evaluated the effect of petroleum-ether extract of Cissus quadrangularis (CQ) on osteoporotic rats. It was found that the analysis results correlated well with the manual evaluation, p < 0.001. The second study evaluated the nerve morphometry and it was found that the adipose and non adipose tissue content was maximum in radial nerve among the five nerves studied.

Malic enzyme gene polymorphism is associated with responsiveness in circulating parathyroid hormone after long-term calcium supplementation

OBJECTIVE

To identify genetic variations associated with parathyroid hormone (PTH) suppression after long-term calcium supplementation.

DESIGN AND PARTICIPANTS

For high throughput SNP screening, subjects consisted of 171 postmenopausal women without osteoporosis at the lumbar spine. A separate group of 19 premenpausal women were recruited for calcium absorption study. Postmenopausal women in the screening group were given 500 mg/day calcium supplementation.

SETTING

Bangkok, Thailand.

MEASUREMENTS

Parathyroid hormone (PTH) and bone mineral density (BMD) were measured at baseline and 2 years after calcium supplementation. High throughput single-nucleotide polymorphism (SNP) screening was performed by comparing estimated allele frequencies derived from hybridization signal intensities of pooled DNA samples on Affymetrix's 10K SNP genotyping microarrays based responsiveness in PTH after calcium supplementation. Genotyping of SNP rs1112482 in malic enzyme gene (ME1) gene, a SNP among those with highest odds ratio of being related to PTH suppression after calcium, was performed in all postmenopausal subjects in the screening group and premenopausal women in the calcium absorption study group in which fractional calcium absorption was assessed by stable isotope dilution. Data were expressed as mean +/- SEM.

RESULTS

PTH significantly decreased after 2 years of calcium supplementation (4.7 ± 1.9 vs. 4.4 ± 1.6 pmol/L, P < 0.01). There was a significant increase in lumbar spine BMD (1.03 ± 0.01 vs. 1.01 ± 0.01 g/cm2, P < 0.001) but not femoral neck BMD. In 108 subjects whose PTH levels decreased after calcium, the suppression of PTH was higher in those with at least one C allele in rs1112482 of ME1 gene (-26.3 ± 2.1 vs. -16.9 ± 1.4%, P < 0.001). Fractional calcium absorption also tends to the higher in subjects in the calcium absorption study group with at least one C allele (n = 6) compared to those without the C allele (n = 13) (58.0 ± 4.9 vs. 49.3 ± 2.8%, P = 0.054).

CONCLUSION

Cytosolic malic enzyme 1 gene polymorphism is associated with the degree of suppression of parathyroid hormone after long-term calcium supplementation. The effect is probably mediated through an increase in intestinal calcium absorption.

[Role of matrix metalloproteinase-9 in the pathogenesis of osteoporosis in patients with chronic obstructive pulmonary disease]

AIM

To determine a relationship between matrix metalloproteinase-9 (MMP-9) activity and its tissue inhibitors TIMP-1 and 2, tumor necrosis factor-alpha (TNF-alpha), bone mineral density (BMD), and bone exchange in chronic obstructive pulmonary disease (COPD).

SUBJECTS AND METHODS

Seventy-six patients with COPD and 20 healthy volunteers were examined using dual-energy X-ray absorptiometry n the lumbar spine (L(II)-L(IV)) and femoral neck (FN). The serum levels of MMP-9, TIMP-1 and TIMP-2, TNF-alpha, and beta-Crosslaps (betaCL) were measured.

RESULTS

There was a higher MMP-9 level in COPD than that in the controls ((383.8 +/- 54.2 and 137.6 +/- 31.4 pg/ml, respectively; p < 0.01). The levels of TIMP-1 and TIMP-2 were not different from those in the control group. An inverse correlation was found between forced expiratory volume in one second (FEV1) and MMP-9 concentration (r = -0.59; p = 0.002) and a positive correlation with smoking index (r = 0.47; p = 0.04). There was an inverse correlation between MMP-9 concentration and BMD in both L(II)-L(IV) and FN (r = -0.67; p < 0.001 and r = -0.61; p < 0.01, respectively) and a direct correlation with betaCL (r = 0.53; p = 0.04). An inverse correlation was established between TNF-alpha and T index in both L(II)-L(IV) (r = -0.54; p < 0.01) and FN (r = -0.48; p < 0.01). At the same time, the level of TNF-alpha directly correlated with the bone resorption marker betaCL (r = 0.53; p = 0.002) and MMP-9 (r = 0.57; p = 0.003).

CONCLUSION

Elevated MMP-9 levels may play an important role in type I collagen degradation, giving rise to enhanced bone resorption in COPD.

Piper sarmentosum prevents glucocorticoid-induced osteoporotic bone resorption by increasing 11β-hydroxysteroid dehydrogenase type 1 activity

AIMS

Osteoporosis is a proven complication of long-term glucocorticoid therapy. Concern on glucocorticoid induced osteoporosis has increased dramatically in recent years with the widespread use of synthetic glucocorticoids. Glucocorticoid action in bone depends upon the activity of 11βhydroxysteroid dehydrogenase type 1 enzyme (11βHSD1). This enzyme plays an important role in regulating corticosteroids by locally interconverting cortisone into active cortisol. This has been demonstrated in primary cultures of human, mouse or rat osteoblasts. Therefore, inhibition of this enzyme may reduce bone resorption markers. Piper sarmentosum (Ps) is a potent inhibitor of 11βHSD1 in liver and adipose tissue. In this study we determined the effect of Ps on 11βHSD1 activity in bones of glucocorticoid-induced osteoporotic rats.

MATERIALS AND METHODS

Three-month old male Sprague-Dawley rats were adrenalectomised to remove the main source of circulating glucocorticoids. The animals were administered with dexamethasone 120 µg/kg body weight/day. Treatment with Ps 125 mg/kg body weight and glycirrhizic acid (GCA) 120 mg/kg body weight were given simultaneously.

RESULTS

The results showed that Ps extract reduced plasma corticosterone concentration (1.05+0.02 µg/ml) and induced 11βHSD1 dehydrogenase activity in bone (87.69+1.41%). Consequently, it also reduced the bone resorption marker, pyridinoline, in dexamethasone-treated adrenalectomised rats (2.07+0.62/L). Despite that, our data showed an inverse relationship between the plasma corticosterone level and the dehydrogenase activity of 11βHSD1 in the bone.

CONCLUSIONS

This suggests that 11βHSD1 acts as the local regulator of glucocorticoid and its activity in bone was not correlated to systemic corticosterone level.

Further genetic evidence suggesting a role for the RhoGTPase-RhoGEF pathway in osteoporosis

Osteoporosis is a highly heritable trait that appears to be influenced by multiple genes. Genome-wide linkage studies have highlighted the chromosomal region 3p14-p21 as a quantitative trait locus for BMD. We have previously published evidence suggesting that the ARHGEF3 gene from this region is associated with BMD in women. The product of this gene activates the RHOA GTPase, the gene for which is also located within this region. The aim of this study was to evaluate the influence of genetic polymorphism in RHOA on bone density in women. Sequence variation within the RHOA gene region was determined using 9 single nucleotide polymorphisms (SNPs) in a discovery cohort of 769 female sibs. Of the 9 SNPs, one was found to be monomorphic with the others representing 3 distinct linkage disequilibrium (LD) blocks. Using FBAT software, significant associations were found between two of these LD blocks and BMD Z-score of the spine and hip (P=0.001-0.036). The LD block tagged by the SNP rs17595772 showed maximal association, with the more common G allele at rs17595772 associated with decreased BMD Z-score. Genotyping for rs17595772 in a replication cohort of 780 postmenopausal women confirmed an association with BMD Z-score (P=0.002-0.036). Again, the G allele was found to be associated with a reduced hip and spine BMD Z-score. These results support the implication of the RhoGTPase-RhoGEF pathway in osteoporosis, and suggest that one or more genes in this pathway may be responsible for the linkage observed between 3p14-p21 and BMD.

Cathepsin K inhibitors for osteoporosis and potential off-target effects

Cathepsin K is a highly potent collagenase and the predominant papain-like cysteine protease expressed in osteoclasts. Cathepsin K deficiencies in humans and mice have underlined the central role of this protease in bone resorption and, thus, have rendered the enzyme as an attractive target for anti-resorptive osteoporosis therapy. In the past decade, a lot of efforts have been made in developing highly potent, selective and orally applicable cathepsin K inhibitors. Some of these inhibitors have passed preclinical studies and are presently in clinical trials at different stages of advancement. The development of the inhibitors and preliminary results of the clinical trials revealed problems and lessons concerning the in situ specificity of the compounds and their tissue targeting. In this review, we briefly summarize the history of cathepsin K research and discuss the current development of cathepsin K inhibitors as novel anti-resorptives for the treatment of osteoporosis. We also discuss potential off-target effects of cathepsin K inhibition and alternative applications of cathepsin K inhibitors in arthritis, atherosclerosis, blood pressure regulation, obesity and cancer.

Alkaline phosphatase in women with osteoporosis

Altogether 15 partially independent measurements of bone mass in 100 women with clinical and roentgenological signs of osteoporosis were correlated to the alkaline phosphatase activities of the same individuals. There was a slight but significant negative correlation indicating an increasing alkaline phosphatase activity with decreasing bone mass. This correlation was not caused by interaction of age. There was no correlation or morphological signs of osteomalacia. The changes could not be explained by fractures. It is suggested that a slight increase in the alkaline phosphatase activity in women with a more severe osteoporosis is related to bone resorption.

Nucleotide variations in genes encoding carbonic anhydrase 8 and 10 associated with femoral bone mineral density in Japanese female with osteoporosis

Osteoporosis is a multi-factorial common disease, which is caused by combination of genetic as well as environmental factors. Among several factors, osteoclast acidification pathways during bone resorption might play an important role. Carbonic anhydrases, consisting of a gene family, are essential for pH regulation by the osteoclast. Clinically, use of carbonic anhydrase inhibitors has been known to be associated with a bone-sparing effect as judged by spine bone mineral density (BMD). Here, we investigated single nucleotide polymorphisms (SNPs) in carbonic anhydrase genes that are expressed in bone tissues, i.e., CA8 and CA10, for possible association with femoral and lumbar BMD among 337 Japanese women with osteoporosis participated in BioBank Japan project. Significant correlation was observed between CA8 SNP, rs6984526, and femoral BMD (P = 0.00029); homozygous carriers of the major (C) allele (n = 166) had the highest BMD (0.754 +/- 0.006 g/cm(2), mean +/- SD), while heterozygous carriers (n = 135) were intermediate (0.741 +/- 0.07 g/cm(2)) and homozygous T-allele carriers (n = 31) had the lowest BMD (0.691 +/- 0.012 g/cm(2)). CA8 SNP as well displayed significant association with lumbar BMD in recessive model (P = 0.00017). In addition, CA10 SNP, rs2106329, also displayed strong association with femoral BMD (P = 0.00002). The results suggest that the variations of CA8 and CA10 loci may be important determinants of osteoporosis in Japanese women.

Polymorphisms in the CYP19 gene that influence bone mineral density

Osteoporosis is a prevalent disease with a strong genetic component. Estrogens play a critical role in bone homeostasis. The aromatization of androgenic precursors is the main source of estrogens in men and postmenopausal women. Thus, aromatase is an attractive osteoporosis candidate gene. In this paper the influence of aromatase activity and aromatase gene variants on skeletal homeostasis is reviewed. The results of studies regarding the association between some common polymorphisms of the aromatase gene and bone mineral density and the risk of osteoporotic fractures are described. The mechanisms involved and the potential usefulness of those genetic data in the prevention and management of osteoporosis are discussed.

Association between physical activity and BMD in young men is modulated by catechol-O-methyltransferase (COMT) genotype: the GOOD study

In this large population-based study in young men, we show that the COMT val158met polymorphism modulates the association between physical activity, aBMD (DXA), and trabecular vBMD (pQCT).

INTRODUCTION

Peak BMD is an important predictor of future risk of osteoporosis and is largely determined by genetic factors but also by environmental factors, among which physical activity (PA) is a strong contributor. Estrogens are believed to influence the mechanical strain signal generated by bones subjected to mechanical loading. Catechol-O-methyltransferase (COMT) is involved in the degradation of estrogens. A functional polymorphism in the COMT gene (val158met), results in a 60-75% difference in enzyme activity between the val (high activity = H) and met (low activity = L) variants. The aim of this study was to determine if the COMT val158met polymorphism modulates the association between PA and BMD in young men.

MATERIALS AND METHODS

The Gothenburg Osteoporosis and Obesity Determinants (GOOD) study consists of 1068 men (age, 18.9 +/- 0.6 yr). Areal BMD (aBMD) was measured by DXA, whereas cortical and trabecular volumetric BMD (vBMD) were measured by pQCT. Study subjects were genotyped and classified as COMT(LL), COMT(HL), or COMT(HH). The amount (h/wk) of PA was determined through questionnaires.

RESULTS

Using a linear regression model (including age, height, weight, smoking, and calcium intake as covariates), significant interactions between the COMT genotype and PA were seen for aBMD at all sites and for trabecular vBMD in both the radius and the tibia. The difference in adjusted aBMD and trabecular vBMD between high (>or=4 h/wk) and low PA (<4 h/wk) was greater in COMT(LL) subjects than in subjects homozygous for the COMT(HH) (total body aBMD: COMT(LL) 4.2% versus COMT(HH) 1.5%, p = 0.02; lumbar spine aBMD: COMT(LL) 7.8% versus COMT(HH) 3.9%, p = 0.04; tibia trabecular vBMD: COMT(LL) 7.1% versus COMT(HH) 1.0%, p < 0.01). The COMT polymorphism was associated with aBMD, at all sites and with trabecular vBMD in the low-PA subjects, but not in their high-PA counterparts.

CONCLUSIONS

We show that the COMT val158met polymorphism modulates the association between PA, aBMD, and trabecular vBMD, suggesting that this polymorphism is of importance for BMD in subjects with a low level of PA.

Plasma homocysteine, folate, and vitamin B 12 and the risk of hip fracture: the hordaland homocysteine study

Homocysteine and related factors were evaluated as risk factors for subsequent hip fractures among 4766 elderly men and women. High levels of homocysteine and low levels of folate predicted fracture, whereas vitamin B12 and genotypes were not related to fracture risk. High homocysteine may be a modifiable risk factor for hip fracture.

INTRODUCTION

Elevated plasma total homocysteine (tHcy) and deficiencies of folate and vitamin B12 are associated with risk of osteoporosis and fracture. We examined whether plasma levels of tHcy, folate, and vitamin B12 and the methylenetetrahydrofolate reductase (MTHFR) 677C-->T and 1298C-->T polymorphisms predicted hip fracture.

MATERIALS AND METHODS

This was a population-based prospective study of 2639 women and 2127 men who were 65-67 yr at enrollment in 1992-1993. Information on hip fracture was obtained from computerized records of discharge diagnoses from all hospitalizations in the region in the period between enrollment and November 30, 2005. Cox proportional hazard regression was used to estimate fracture risk according to levels of plasma tHcy, folate, and vitamin B12 and for different genotypes.

RESULTS

Over a median follow-up period of 12.6 yr, hip fracture was recorded in 184 (7.0%) women and 90 (4.2%) men. The adjusted hazard ratio (95% CI) for fracture in subjects with high (>or=15 microM) compared with low levels (<9.0 microM) of tHcy was 2.42 (1.43-4.09) among women and 1.37 (0.63-2.98) among men. Dose-response analyses indicated a positive association between plasma tHcy and risk of fracture in both sexes and a negative association between plasma folate and risk of fracture among women only. Plasma vitamin B12 level or MTHFR genotype was not significantly related to risk of fracture after adjustments for confounding factors. The association between tHcy and risk of hip fracture was only slightly weakened by adjustments for plasma levels of vitamin B12 and folate.

CONCLUSIONS

tHcy seems to be a predictor for hip fracture among elderly men and women. Folate was a predictor among women only, whereas vitamin B12 and MTHFR genotype did not predict hip fracture. Our data corroborate the hypothesis that homocysteine may play a role in the pathogenesis of osteoporotic fractures.

Emerging roles of cysteine cathepsins in disease and their potential as drug targets

The general view on cysteine cathepsins, which were long believed to be primarily involved in intracellular protein turnover, has dramatically changed in last 10 to 15 years. The discovery of new cathepsins, such as cathepsins K, V, X, F and O, and their tissue distribution suggested that at least some of them are involved in very specific cellular processes. Moreover, gene ablation experiments revealed that cathepsins play a vital role in numerous physiological processes, such as antigen processing and presentation, bone remodelling, prohormone processing and wound healing. Their involvement in several pathologies, including osteoporosis, rheumatoid arthritis, osteoarthritis, bronchial asthma and cancer have also been confirmed and today several of them have been validated as relevant targets for therapies. Compounds targeting cathepsins S and K are already in clinical evaluation, whereas others are in experimental phases. The cathepsin K inhibitor AAE-581 (balicatib) as the most advanced of them passed Phase II clinical trials in 2005. In this review, we discuss the current view on cathepsins as an emerging group of targets for several diseases and the development of cathepsin K and S inhibitors for treatment of osteoporosis and various immune disorders.

Expression of bone resorption genes in osteoarthritis and in osteoporosis

Cathepsin K and MMP-9 are considered to be the most abundant proteases in osteoclasts. TRAP is a marker for osteoclasts, and there is increasing evidence of its proteolytic role in bone resorption. RANKL is a recently discovered regulator of osteoclast maturation and activity and induces expression of many genes. This study compared cathepsin K, MMP-9, TRAP, RANKL, OPG, and osteocalcin gene expression in the proximal femur of patients with osteoarthritis with that of patients with femoral neck fracture. Fifty-six patients undergoing arthroplasty because of osteoarthritis or femoral neck fracture were included in the study. Total mRNA was extracted from the bone samples obtained from the intertrochanteric region of the proximal femur. Real-time RT-PCR was used to quantify CTSK (cathepsin K), MMP-9 (matrix metalloproteinase 9), ACP5 (TRAP), TNFSF11 (RANKL), TNFRSF11B (OPG), and BGLAP (osteocalcin) mRNAs. The levels of mRNAs coding for MMP-9 and osteocalcin indicated higher expression in the osteoarthritic group (P = 0.011, P = 0.001, respectively), whereas RANKL expression and the ratio RANKL/OPG were both significantly lower in the osteoarthritic group than in the fracture group. Expression of cathepsin K, MMP-9, and TRAP relative to RANKL was significantly higher in the osteoarthritic group. Ratios of all three proteolytic enzymes relative to formation marker osteocalcin were higher in the fracture group. Gene expression of cathepsin K, MMP-9, TRAP, RANKL, OPG, and osteocalcin and the association between their mRNA levels pointed to higher bone resorption and bone formation in osteoarthritis, differences in balance between them, and differences in regulation of bone resorption in osteoarthritic and osteoporotic bone.

Intravenous zoledronic acid treatment in thalassemia-induced osteoporosis: results of a phase II clinical trial

Osteoporosis is an important cause of morbidity in beta-thalassemia patients. Bisphosphonates have been recently used for the treatment of osteoporosis in beta-thalassemia. This study is a prospective quasi-experimental study to assess the efficacy and safety of zoledronic acid in thalassemics with osteoporosis. Eighteen thalassemia patients with osteoporosis were given zoledronic acid 4 mg intravenously every 3 months over a period of 12 months. The efficacy of treatment was assessed by measuring (BMD) at the lumbar spine, femoral neck, and hip at baseline, 6, and 12 months. Z-score was used to measure the BMD. Other medical assessments included markers of bone formation and resorption (bone alkaline phosphatase (BAP), osteocalcin (OC), and urinary deoxypyridinoline), and the assessment of pain score, analgesic score, and performance score. Ten thalassemic osteoporotic patients were followed up only with serial BMDs as controls. Both groups had no significant difference with respect to age, gender, and baseline BMD. Patients taking zoledronic acid had a significant increase in their lumbar spine, femoral neck, trochanter, and total hip BMD measurements over the 12-month period. Patients in the control group did not have any significant change in BMD measurements. There was a significant change in the levels of OC and BAP over the 12-month follow-up period. There was also a significant decrease in the number of painful sites experienced by the patients. Treatment of thalassemic osteoporotic patients with zoledronic acid is very effective in increasing BMD at the lumbar spine and hip and in reducing pain; it is also well-tolerated.

Pathophysiology of interleukin-1 receptor-associated kinase-M: implications in refractory state

PURPOSE OF REVIEW

The pseudo-kinase interleukin-1 receptor-associated kinase-M has emerged as a critical molecule in the down-regulation of inflammatory responses. Dysregulation of the toll-like receptor-interleukin-1 receptor-associated kinase system, and in particular interleukin-1 receptor-associated kinase-M up-regulation, are associated with a number of pathologies. This review highlights recent findings on interleukin-1 receptor-associated kinase-M reported in biomedical literature.

RECENT FINDINGS

Interleukin-1 receptor-associated kinase-M plays a critical role in generating a refractory state of the immune system following monocytes/macrophages encounter with bacteria or tumor cells. This state has been demonstrated so far in patients who suffer from sepsis, leukemia, and acute coronary syndrome, and seems to be associated with interleukin-1 receptor-associated kinase-M overexpression in their circulating monocytes. In addition, the pseudo-kinase represents a central regulator of osteoclast differentiation and activation, and might thus be related to the onset of osteoporosis.

SUMMARY

Interleukin-1 receptor-associated kinase-M is involved in the control of endotoxin tolerance in monocytes, in osteoporosis, as well as in the deactivation of tumor-infiltrating macrophages. Additionally, patients who suffer from several pathologies related to inflammatory responses express high levels of this molecule in their circulating monocytes. Human monocytes treated with a nitric oxide donor also express large amounts of interleukin-1 receptor-associated kinase-M, apparently under the control of tumor necrosis factor-alpha. This mechanism could explain the induction of interleukin-1 receptor-associated kinase-M in monocytes from patients who suffer from an inflammatory pathology.

Effect of antiepileptic medication on bone mineral measures

OBJECTIVE

Long-term antiepileptic drug (AED) use has been associated with bone disease, but many previous studies have been limited by inadequate control subjects. We used a cotwin affected sib-pair model to investigate this issue.

METHODS

The authors studied 31 female twin (15 monozygous and 16 dizygous) and four sibling pairs (< 3 years age difference) aged 21 to 75 years, in which one member had > 12 months of AED treatment. Areal bone mineral density (ABMD, g/cm2) was measured at the lumbar spine (LS), total hip (TH), femoral neck (FN), and total forearm (FA). Three primary a priori defined subgroups were analyzed: a) use for > 2 years, b) use of enzyme-inducing AEDs, or c) age older than 40 years.

RESULTS

For all pairs (n = 35), there were no significant within-pair differences in any ABMD measure. However, in Subgroup a (n = 27), there was a within-pair difference at the FA (0.513 vs 0.534, -3.9%, p = 0.016). In Subgroup b (n = 29), there was also a within-pair difference at the FA for AED user vs nonuser (0.508 vs 0.529, -3.8%, p = 0.010). In Subgroup c (n = 15), there were within-pair differences at the FA (0.492 vs 0.524, -6.1%, p = 0.017) and the LS (0.884 vs 0.980, -9.8%, p = 0.036).

CONCLUSIONS

Patients using AEDs for > 2 years, in particular those taking enzyme-inducing AEDs and those older than 40 years, have significantly lower bone mineral density at clinically relevant fracture risk sites.

Calcineurin regulates bone formation by the osteoblast

Two of the most commonly used immunosuppressants, cyclosporine A and tacrolimus (FK506), inhibit the activity of a ubiquitously expressed Ca(2+)/calmodulin-sensitive phosphatase, calcineurin. Because both drugs also cause profound bone loss in humans and in animal models, we explored whether calcineurin played a role in regulating skeletal remodeling. We found that osteoblasts contained mRNA and protein for all isoforms of calcineurin A and B. TAT-assisted transduction of fusion protein TAT-calcineurin Aalpha into osteoblasts resulted in the enhanced expression of the osteoblast differentiation markers Runx-2, alkaline phosphatase, bone sialoprotein, and osteocalcin. This expression was associated with a dramatic enhancement of bone formation in intact calvarial cultures. Calcineurin Aalpha(-/-) mice displayed severe osteoporosis, markedly reduced mineral apposition rates, and attenuated colony formation in 10-day ex vivo stromal cell cultures. The latter was associated with significant reductions in Runx2, bone sialoprotein, and osteocalcin expression, paralleled by similar decreases in response to FK506. Together, the gain- and loss-of-function experiments indicate that calcineurin regulates bone formation through an effect on osteoblast differentiation.

Long-term culture in dexamethasone unmasks an abnormal phenotype in osteoblasts isolated from osteoporotic subjects

We have shown that osteoblastic cells derived from trabecular bone explants of osteoporotic subjects (OP cells) exhibited an altered alkaline phosphatase (ALP) response to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] compared to control (CON) cells. Our hypothesis that OP cells have other intrinsic abnormalities was investigated using our cell models representing two different stages of differentiation. OP and CON cells were cultured in the absence (-DEX) or presence (+DEX) of 10 nM dexamethasone (DEX) in 10% fetal calf serum (FCS) prior to exposure to serum-free medium containing 1 nM of PTH and/or 17-beta estradiol (E2). Both OP and CON cells responded to DEX with a two-fold increase in basal ALP activity. While E2 or PTH+E2 had no effect on OP cells, both treatments inhibited ALP activity in CON cells (p<0.05). OP and CON cells grown in DEX also expressed PTH-stimulated adenylate cyclase (AC) activities higher than those of (-DEX) cells. OP+DEX cells, however, exhibited activities which were 8-fold higher than those of CON+DEX cells (p<0.001). In OP+DEX cells, E2 stimulated basal AC activity (p<0.05) but did not affect PTH-stimulated activity. In contrast, in CON+DEX cells, E2 had no effect on basal activity but inhibited PTH-stimulated AC activity (p<0.001). Osteocalcin production was 4-fold lower in OP+DEX cells compared to OP-DEX and CON cells (p<0.05) while osteocalcin mRNA levels were significantly lower in OP+DEX and CON+/-DEX cells compared to OP-DEX cells (p<0.05). E2 did not affect osteocalcin protein or mRNA levels in either OP or CON cells. No differences in mRNA levels were found for estrogen receptor-alpha (ER-a) in OP+/-DEX cells whereas these levels were significantly higher in CON+DEX compared to CON-DEX cells (p<0.05). These results indicate that DEX amplified the differences between OP and CON cells and confirm the presence of intrinsic osteoblastic abnormalities in patients with osteoporosis that persist in culture.

Recent developments in cathepsin K inhibitor design

Cathepsin K is abundantly and selectively expressed in osteoclasts where it plays a critical role in bone degradation. Cathepsin K inhibitors are the first antiresorptive agents that prevent bone loss while allowing bone formation to continue, thereby enhancing the quality and ultimately the strength of bone. The development of cathepsin K inhibitors requires appropriate cell-based assays and animal models. Advances in reversible cathepsin K inhibitor design from January 2004 are reviewed herein.

11beta-hydroxysteroid dehydrogenase and the pre-receptor regulation of corticosteroid hormone action

Two isozymes of 11beta-hydroxysteroid dehydrogenase (11beta-HSD1 and 11beta-HSD2) catalyse the interconversion of hormonally active cortisol and inactive cortisone. The enzyme evolved from a metabolic pathway to a novel mechanism underpinning human disease with the elucidation of the role of the type 2 or 'kidney' isozyme and an inherited form of hypertension, 'apparent mineralocorticoid excess'. 'Cushing's disease of the kidney' arises because of a failure of 11beta-HSD2 to inactivate cortisol to cortisone resulting in cortisol-induced mineralocorticoid excess.Conversely, 11beta-HSD1 has been linked to human obesity and insulin resistance, but also to other diseases in which glucocorticoids have historically been implicated (osteoporosis, glaucoma). Here, the activation of cortisol from cortisone facilitates glucocorticoid hormone action at an autocrine level. The molecular basis for the putative human 11beta-HSD1 'knockout'--'cortisone reductase deficiency'--has recently been described, an observation that also answers a long standing conundrum relating to the set-point of 11beta-HSD1 activity. In each case, these clinical studies have been underpinned by studies in vitro and the manipulation of enzyme expression in vivo using recombinant mouse models.

Soluble cathepsin K: A novel marker for the prediction of nontraumatic fractures?

We sought to evaluate serum concentrations of cathepsin K in peripheral blood and to determine whether they correlated with bone-mineral density (BMD) and the incidence of nontraumatic fractures. We took blood samples from 162 patients (101 with osteoporosis, 48 with osteopenia) and 13 healthy controls, then conducted quantitative measurements of cathepsin K using a commercially available enzyme-linked immunosorbent assay. Cathepsin K concentrations were correlated with the incidence of nontraumatic fracture, BMD, markers of bone turnover (alkaline phosphatase, bone-specific alkaline phosphatase, osteocalcin, parathyroid hormone, and C-telopeptide). The correlations between cathepsin K concentrations in subjects without fractures and in those with multiple nontraumatic fractures were statistically significant ( t = -2.1, degrees of freedom = 107, P = .036). The cathepsin K levels of controls and patients with osteoporosis were significantly different ( t = -3.7, degrees of freedom = 58.9, p>0.0001) These results suggest that the serum level of cathepsin K could serve as a marker for fracture prediction and BMD.

Aromatase gene and osteoporosis: relationship of ten polymorphic loci with bone mineral density

Aromatase activity appears to be important for bone homeostasis in postmenopausal women. In fact, therapy with aromatase inhibitors is associated with bone loss and fractures. A common biallelic A/G polymorphism in the 3'-untranslated region (UTR) of CYP19-aromatase gene has been associated with differences in gene transcription and the risk of estrogen-responsive tumors. We explored the relationship of such a polymorphism and other 9 polymorphisms situated within or near CYP19 gene with bone mass. The study group comprised 286 postmenopausal women. DNA was isolated from peripheral blood. Biallelic and insertion/deletion polymorphisms were analyzed with exonuclease assays using TaqMan probes. A microsatellite polymorphism in intron 4 was studied by capillary electrophoresis. Bone mineral density (BMD) was determined by DXA. In this cross-sectional study, the postmenopausal decrease in bone mass appeared to be slower in women with AA genotype in the 3'UTR, than in those with AG or GG genotypes. Consequently, there were significant genotype-related differences in BMD. In women after age of 60, hip T-scores were: AA -1.3 +/- 0.1, AG -1.3 +/- 0.2, GG -1.9 +/- 0.1 (P = 0.002). Lumbar spine T-scores were: AA -1.9 +/- 10.2, AG -2.2 +/- 0.1, GG -3.0 +/- 0.2 (P = 0.001). Moreover, GG genotype showed a trend for lower free estrogen levels. This polymorphism was strongly linked to a tetranucleotide repeat in intron 4, as well as to other biallelic polymorphisms situated between 3'UTR and I.2 promoter regions. They all were associated with BMD. However, biallelic polymorphisms in the extreme 5' region of CYP19 and two polymorphisms in neighbor genes were not associated with BMD. In conclusion, common variations of CYP19-aromatase are associated with differences in BMD that seem to be important from an individual as well as from a population perspective.

Functional proteome of bones in rats with osteoporosis following ovariectomy

Osteoporosis is a chronic condition chiefly affecting postmenopausal women, in whom the skeleton loses a significant percentage of its mineralized mass and mechanical resiliency, thereby becoming prone to fracture. Although the effect of the loss of estrogen on bone metabolism has been documented, its mechanism is still poorly understood. In the present proteomic study, we characterized the effect of estrogen deficiency on protein expression in rat bones. Using two-dimensional gel electrophoresis, mass spectrometry and rat protein database, we successfully identified three distinctly changed proteins named thioredoxin peroxidase 1, myosin light polypeptide 2 and ubiquitin-conjugating enzyme E2-17 kD, among which ubiquitin-conjugating enzyme E2-17 kD has been documented to be an estrogen-related protein, but the other two are first reported to be osteoporosis-related proteins in the current study. These results provide valuable experimental evidences for the elucidation of the molecular mechanism of osteoporosis related to the loss of estrogen.

Changes in receptor activator of nuclear factor-kappaB, and its ligand, osteoprotegerin, bone-type alkaline phosphatase, and tartrate-resistant acid phosphatase in ovariectomized rats

We investigated time-course changes in the expression of receptor activator of nuclear factor-kappaB (RANK), its ligand (RANKL), osteoprotegerin (OPG), bone-type alkaline phosphatase (BAP), and tartrate-resistant acid phosphatase (TRAP) in ovariectomized (OVX) rats. Samples of sera and coccyges were used for analysis of the enzyme activities and expression levels of proteins and mRNAs, and an immunohistochemical analysis was also performed. Serum BAP activity increased to 158.6% of the pre-operation value at 1 week after OVX, and then decreased to 38.7% at 8 weeks after OVX. On the other hand, the serum TRAP activity increased to 130.9% of the pre-operation level at 1 week after OVX, and was maintained at a high level, compared with the pre-operation level. The patterns of BAP and TRAP activity in the coccyges specimens were similar to those seen in the sera. The expression profiles of TRAP, RANK, and RANKL proteins in the coccyx specimens were similar to the pattern of serum TRAP activity, while the profiles of the BAP and OPG proteins were similar to the pattern of serum BAP activity in OVX rats. The changes in the mRNA expression levels of the osteogenic proteins were similar to those for protein expression. These biochemical changes in OVX rats were confirmed by immunohistochemical studies. Our results suggest that not only osteoclastogenesis accelerated but also osteoblastogenesis transiently increased during the early phase of osteoporosis.

Clues for new therapeutics in osteoporosis and periodontal disease: new roles for lipoxygenases?

Lipoxygenase (LOX) pathways are well appreciated for their ability to regulate key events contributing to the cardinal signs of inflammation. Recent evidence indicates that LOX genes are associated with osteoporosis. Also, overexpression of the 15-LOX Type 1 in transgenic rabbits leads to a reduced inflammatory phenotype and protection from periodontal disease, as well as atherosclerosis. Osteoporosis and inflammation-associated bone degradation, such as periodontitis, affect many individuals worldwide and are known to have pathogenesis that involves local mediators via communication between osteoclasts and osteoblasts during osteogenesis. Evidence has emerged indicating that LOX gene expression is associated with reduced bone strength in murine models of osteoporosis. Overexpression of the 15-LOX gene and its products, such as lipoxins, confers endogenous anti-inflammation. This article discusses the recent findings that may link aberrant LOX pathway expression in these diseases, suggesting new avenues for therapeutic approaches via activation of endogenous pathways for resolution of local inflammation.

Soluble cathepsin-L: a marker of bone resorption and bone density?

We sought to evaluate cathepsin L serum levels in the peripheral blood of patients with low bone density. Blood samples from 60 patients (32 osteoporotic, 28 osteopenic) and 16 healthy controls were taken and quantitative measurements of cathepsin L were performed with the use of a commercially available enzyme-linked immunosorbent assay. Dual x-ray absorptionometry measurements and serum levels of alkaline phosphatase, bone-specific alkaline phosphatase, osteocalcin, parathyroid hormone, sexual hormones, and N -terminal crosslinks of type I collagen were examined. Group comparisons between patients with osteoporosis and controls showed significant differences with respect to cathepsin L ( t = -2.839; df = 29; P =.008). Osteoporosis treatment decreased the serum level of cathespsin L in a statistically significant fashion ( P =.002). These results suggest that the serum level of cathepsin L can serve as a marker of bone resorption and bone density.