Effects of parathyroid hormone on bone mass, bone strength, and bone regeneration in male rats with type 2 diabetes mellitus.

Type 2 diabetes mellitus (T2DM) is associated with increased skeletal fragility and impaired fracture healing. Intermittent PTH therapy increases bone strength; however, its skeletal and metabolic effects in diabetes are unclear. We assessed whether PTH improves skeletal and metabolic function in rats with T2DM. Subcritical femoral defects were created in diabetic fa/fa and nondiabetic +/+ Zucker Diabetic Fatty (ZDF) rats and internally stabilized. Vehicle or 75 µg/kg/d PTH(1-84) was sc administered over 12 weeks. Skeletal effects were evaluated by µCT, biomechanical testing, histomorphometry, and biochemical markers, and defect regeneration was analyzed by µCT. Glucose homeostasis was assessed using glucose tolerance testing and pancreas histology. In diabetic rats, bone mass was significantly lower in the distal femur and vertebrae, respectively, and increased after PTH treatment by up to 23% in nondiabetic and up to 18% in diabetic rats (P < .0001). Diabetic rats showed 23% lower ultimate strength at the spine (P < .0005), which was increased by PTH by 36% in normal and by 16% in diabetic rats (P < .05). PTH increased the bone formation rate by 3-fold in normal and by 2-fold in diabetic rats and improved defect regeneration in normal and diabetic rats (P < .01). PTH did not affect serum levels of undercarboxylated osteocalcin, glucose tolerance, and islet morphology. PTH partially reversed the adverse skeletal effects of T2DM on bone mass, bone strength, and bone defect repair in rats but did not affect energy metabolism. The positive skeletal effects were generally more pronounced in normal compared with diabetic rats.

Clinical and endocrine correlates of circulating sclerostin levels in patients with type 1 diabetes mellitus.

AIM: Type 1 diabetes mellitus (T1DM) increases fragility fractures due to low bone mass, micro-architectural alterations and decreased bone formation. Sclerostin is expressed by osteocytes and inhibits osteoblastic bone formation. We evaluated serum sclerostin levels in T1DM and their association with bone mineral density (BMD), bone turnover, glycaemic control and physical activity. PATIENTS AND METHODS: In a cross-sectional study, 128 men and premenopausal women with long-standing T1DM (mean age 43·4 ± 8·8 years, diabetes duration 22·4 ± 9·5 years) and 77 age-, BMI (Body Mass Index) and gender-matched healthy individuals were evaluated. RESULTS: Serum sclerostin levels were higher in T1DM compared with controls, irrespective of gender (male 0·55 ± 0·17 vs 0·49 ± 0·12 ng/ml, P = 0·046; female 0·52 ± 0·19 ng/ml vs 0·43 ± 0·12 ng/ml, P = 0·012). Partial correlation analysis adjusted for age and gender revealed a positive correlation between serum sclerostin levels and BMD at lumbar spine and femoral neck in T1DM and between BMD at lumbar spine, femoral neck and total hip in controls. Bone turnover markers, parathyroid hormone, calcium and vitamin D did not correlate with serum sclerostin levels in T1DM or controls. Physical activity was not associated with serum sclerostin levels. A multivariate analysis revealed that only the interaction of T1DM and age affects serum sclerostin levels but not T1DM alone. The influence of age on serum sclerostin levels was more pronounced in T1DM compared with controls. CONCLUSIONS: Sclerostin serum levels were increased in patients with T1DM, and the positive correlation of age with serum sclerostin levels was stronger in T1DM. There was no effect of serum sclerostin levels on markers of bone metabolism and they do not explain the detrimental effects of T1DM on BMD.

Deconstructing vitamin D deficiency.

Vitamin D deficiency causes advanced aging of bone tissue with accumulation of microcracks (Busse et al., this issue).

Metal hypersensitivity and metal ion levels in patients with coated or uncoated total knee arthroplasty: a randomised controlled study.

PURPOSE: Metal ion release by orthopaedic implants may cause local and systemic effects and induce hypersensitivity reactions. Coated implants have been developed to prevent or reduce these effects. This study was initiated to investigate the safety of a novel coating for total knee arthroplasty (TKA) implants. METHODS: A total of 120 patients undergoing primary TKA with no history of hypersensitivity and no other metal implant were randomised to receive either a coated or uncoated implant. Chromium (Cr), cobalt (Co), molybdenum (Mb) and nickel (Ni) hypersensitivity patch testing and plasma ion concentrations were evaluated pre-operatively and one year post-operatively. RESULTS: At the one year follow-up both groups demonstrated significant improvement in knee function and quality of life. One new weakly positive reaction to Co in the TKA group with coated implant and two doubtful skin reactions to Ni (one in each group) were noted. Even with sensitisation to implant materials no skin reactions were observed. Plasma metal ion concentrations did not increase and were not elevated at the one year follow-up in either group. CONCLUSIONS: Sensitisation after TKA was rare and had no influence on clinical results. TKA with coated implant and standard TKA demonstrated no plasma metal ion elevation.

Trabectedin in the neoadjuvant treatment of high-grade pleomorphic sarcoma: report of a rare case and literature review.

Background. Pleomorphic sarcoma is an aggressive soft tissue sarcoma. In patients with high-risk extremity sarcomas, the significant survival benefits conferred by an intense regimen of neoadjuvant chemoradiotherapy and surgery were reported. To our knowledge, this is the first report in the literature of the neoadjuvant use of trabectedin in a patient with high-grade pleomorphic sarcoma, ineligible for standard neoadjuvant combination therapy with an anthracycline-based regimen. Case Presentation. Here we present a 58-year-old White male with a large tumor in the left thigh, but with no signs of metastases. Owing to the history of severe heart attack, three cycles of neoadjuvant trabectedin were administrated to achieve surgically wide margins. After two cycles, an 18F-FDG-PET showed a large proportion of the central tumor area was without metabolic activity. According to RECIST and Choi criteria, the tumor was stable. After the third cycle of trabectedin, the patient underwent a complete resection, which revealed completely necrotic high-grade pleomorphic sarcoma (stage pT2b), with only a small vital area. Conclusion. The present paper on a promising treatment with neoadjuvant trabectedin of patients with high-grade pleomorphic sarcoma might suggest that such treatment approach may provide a greater chance of cure and survival of such patients.

Correlates of bone microarchitectural parameters and serum sclerostin levels in men: the STRAMBO study.

Sclerostin is predominantly expressed by osteocytes. Serum sclerostin levels are positively correlated with areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) and bone microarchitecture assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT) in small studies. We assessed the relation of serum sclerostin levels with aBMD and microarchitectural parameters based on HR-pQCT in 1134 men aged 20 to 87 years using multivariable models adjusted for confounders (age, body size, lifestyle, comorbidities, hormones regulating bone metabolism, muscle mass and strength). The apparent age-related increase in serum sclerostin levels was faster before the age of 63 years than afterward (0.43 SD versus 0.20 SD per decade). In 446 men aged ≤63 years, aBMD (spine, hip, whole body), trabecular volumetric BMD (Tb.vBMD), and trabecular number (Tb.N) at the distal radius and tibia were higher in the highest sclerostin quartile versus the three lower quartiles combined. After adjustment for aBMD, men in the highest sclerostin quartile had higher Tb.vBMD (mainly in the central compartment) and Tb.N at both skeletal sites (p < 0.05 to 0.001). In 688 men aged >63 years, aBMD was positively associated with serum sclerostin levels at all skeletal sites. Cortical vBMD (Ct.vBMD) and cortical thickness (Ct.Th) were lower in the first sclerostin quartile versus the three higher quartiles combined. Tb.vBMD increased across the sclerostin quartiles, and was associated with lower Tb.N and more heterogeneous trabecular distribution (higher Tb.Sp.SD) in men in the lowest sclerostin quartile. After adjustment for aBMD, men in the lowest sclerostin quartile had lower Tb.vBMD and Tb.N, but higher Tb.Sp.SD (p < 0.05 to 0.001) at both the skeletal sites. In conclusion, serum sclerostin levels in men are strongly positively associated with better bone microarchitectural parameters, mainly trabecular architecture, regardless of the potential confounders.

Sclerostin antibody treatment improves bone mass, bone strength, and bone defect regeneration in rats with type 2 diabetes mellitus.

Type 2 diabetes mellitus results in increased risk of fracture and delayed fracture healing. ZDF fa/fa rats are an established model of type 2 diabetes mellitus with low bone mass and delayed bone healing. We tested whether a sclerostin-neutralizing antibody (Scl-AbVI) would reverse the skeletal deficits of diabetic ZDF rats. Femoral defects of 3 mm were created in 11-week-old diabetic ZDF fa/fa and nondiabetic ZDF +/+ rats and stabilized by an internal plate. Saline or 25 mg/kg Scl-AbVI was administered subcutaneously (s.c.) twice weekly for 12 weeks (n = 9-10/group). Bone mass and strength were assessed using pQCT, micro-computed tomography (µCT), and biomechanical testing. Bone histomorphometry was used to assess bone formation, and the filling of the bone defect was analyzed by µCT. Diabetic rats displayed lower spinal and femoral bone mass compared to nondiabetic rats, and Scl-AbVI treatment significantly enhanced bone mass of the femur and the spine of diabetic rats (p < 0.0001). Scl-AbVI also reversed the deficit in bone strength in the diabetic rats, with 65% and 89% increases in maximum load at the femoral shaft and neck, respectively (p < 0.0001). The lower bone mass in diabetic rats was associated with a 65% decrease in vertebral bone formation rate, which Scl-AbVI increased by sixfold, consistent with a pronounced anabolic effect. Nondiabetic rats filled 57% of the femoral defect, whereas diabetic rats filled only 21% (p < 0.05). Scl-AbVI treatment increased defect regeneration by 47% and 74%, respectively (p < 0.05). Sclerostin antibody treatment reverses the adverse effects of type 2 diabetes mellitus on bone mass and strength, and improves bone defect regeneration in rats.

Skeletal and extraskeletal actions of denosumab.

Osteoclasts and osteoblasts define skeletal mass, structure and strength through their respective actions in resorbing and forming bone. This remodeling process is orchestrated by the actions of hormones and growth factors, which regulate a cytokine system comprising the receptor activator of nuclear factor κB ligand (RANKL), its receptor RANK and the soluble decoy receptor osteoprotegerin (OPG). Bone resorption depends on RANKL, which determines osteoclast formation, activity and survival. Importantly, cells of the osteoblastic lineage mainly provide RANKL and therefore, are central in the regulation of osteoclast functions. Catabolic effects of RANKL are inhibited by OPG, a TNF receptor family member that binds RANKL, thereby preventing the activation of its receptor RANK, which is expressed by osteoclast precursors. Because this cytokine network is pivotal for the regulation of bone mass in health and diseases, including osteoporosis, rheumatoid arthritis and malignant bone conditions, it has been successfully used for the generation of a targeted therapy to block osteoclast actions. The clinical approval of denosumab, a fully monoclonal antibody against RANKL, provides a novel option to treat bone diseases with a potent, targeted and reversible inhibitor of bone resorption. Although RANKL is also expressed by endothelial cells, T lymphocytes, synovial fibroblasts and various tumor cells, no meaningful clinical extraskeletal effects have been reported after administration of denosumab. This article summarizes the molecular and cellular basis of the RANKL/RANK/OPG system and presents preclinical and clinical studies on the skeletal actions of denosumab.

Bone, sweet bone--osteoporotic fractures in diabetes mellitus.

Diabetes mellitus adversely affects the skeleton and is associated with an increased risk of osteoporosis and fragility fractures. The mechanisms underlying low bone strength are not fully understood but could include impaired accrual of peak bone mass and diabetic complications, such as nephropathy. Type 1 diabetes mellitus (T1DM) affects the skeleton more severely than type 2 diabetes mellitus (T2DM), probably because of the lack of the bone anabolic actions of insulin and other pancreatic hormones. Bone mass can remain high in patients with T2DM, but it does not protect against fractures, as bone quality is impaired. The class of oral antidiabetic drugs known as glitazones can promote bone loss and osteoporotic fractures in postmenopausal women and, therefore, should be avoided if osteoporosis is diagnosed. A physically active, healthy lifestyle and prevention of diabetic complications, along with calcium and vitamin D repletion, represent the mainstay of therapy for osteoporosis in patients with T1DM or T2DM. Assessment of BMD and other risk factors as part of the diagnostic procedure can help design tailored treatment plans. All osteoporosis drugs seem to be effective in patients with diabetes mellitus. Increased awareness of osteoporosis is needed in view of the growing and aging population of patients with diabetes mellitus.

The osteoclast-associated receptor (OSCAR) is a novel receptor regulated by oxidized low-density lipoprotein in human endothelial cells.

Cross talks between the vascular and immune system play a critical role in vascular diseases, in particular in atherosclerosis. The osteoclast-associated receptor (OSCAR) is a regulator of osteoclast differentiation and dendritic cell maturation. Whether OSCAR plays a role in vascular biology and has an impact on atherogenic processes provoked by proinflammatory stimuli is yet unknown. We identified OSCAR on the surface of human primary endothelial cells. Stimulation of endothelial cells with oxidized low-density lipoprotein (oxLDL) caused a time- and dose-dependent induction of OSCAR, which was lectin-like oxidized LDL receptor 1 and Ca(2+) dependent. OSCAR was transcriptionally regulated by oxLDL as shown by OSCAR promoter analysis. Specific inhibition of the nuclear factor of activated T cells (NFAT) pathway prevented the oxLDL-mediated increase of endothelial OSCAR expression. As assessed by EMSA, oxLDL induced binding of NFATc1 to the OSCAR promoter. Notably, in vivo-modified LDL from patients with diabetes mellitus stimulated OSCAR mRNA expression in human endothelial cells. Furthermore, apolipoprotein E knockout mice fed a high-fat diet showed an enhanced aortic OSCAR expression associated with increased expression of NFATc1. In summary, OSCAR is expressed in vascular endothelial cells and is regulated by oxLDL involving NFATc1. Our data suggest that OSCAR, originally described in bone as immunological mediator and regulator of osteoclast differentiation, may be involved in cell activation and inflammation during atherosclerosis.

Delayed bone regeneration and low bone mass in a rat model of insulin-resistant type 2 diabetes mellitus is due to impaired osteoblast function.

Patients with diabetes mellitus have an impaired bone metabolism; however, the underlying mechanisms are poorly understood. Here, we analyzed the impact of type 2 diabetes mellitus on bone physiology and regeneration using Zucker diabetic fatty (ZDF) rats, an established rat model of insulin-resistant type 2 diabetes mellitus. ZDF rats develop diabetes with vascular complications when fed a Western diet. In 21-wk-old diabetic rats, bone mineral density (BMD) was 22.5% (total) and 54.6% (trabecular) lower at the distal femur and 17.2% (total) and 20.4% (trabecular) lower at the lumbar spine, respectively, compared with nondiabetic animals. BMD distribution measured by backscattered electron imaging postmortem was not different between diabetic and nondiabetic rats, but evaluation of histomorphometric indexes revealed lower mineralized bone volume/tissue volume, trabecular thickness, and trabecular number. Osteoblast differentiation of diabetic rats was impaired based on lower alkaline phosphatase activity (-20%) and mineralized matrix formation (-55%). In addition, the expression of the osteoblast-specific genes bone morphogenetic protein-2, RUNX2, osteocalcin, and osteopontin was reduced by 40-80%. Osteoclast biology was not affected based on tartrate-resistant acidic phosphatase staining, pit formation assay, and gene profiling. To validate the implications of these molecular and cellular findings in a clinically relevant model, a subcritical bone defect of 3 mm was created at the left femur after stabilization with a four-hole plate, and bone regeneration was monitored by X-ray and microcomputed tomography analyses over 12 wk. While nondiabetic rats filled the defects by 57%, diabetic rats showed delayed bone regeneration with only 21% defect filling. In conclusion, we identified suppressed osteoblastogenesis as a cause and mechanism for low bone mass and impaired bone regeneration in a rat model of type 2 diabetes mellitus.

Denosumab for bone diseases: translating bone biology into targeted therapy.

Signalling of receptor activator of nuclear factor-κB (RANK) ligand (RANKL) through RANK is a critical pathway to regulate the differentiation and activity of osteoclasts and, hence, a master regulator of bone resorption. Increased RANKL activity has been demonstrated in diseases characterised by excessive bone loss such as osteoporosis, rheumatoid arthritis and osteolytic bone metastases. The development and approval of denosumab, a fully MAB against RANKL, has heralded a new era in the treatment of bone diseases by providing a potent, targeted and reversible inhibitor of bone resorption. This article summarises the molecular and cellular biology of the RANKL/RANK system and critically reviews preclinical and clinical studies that have established denosumab as a promising novel therapy for metabolic and malignant bone diseases. We will discuss the potential indications for denosumab along with a critical review of safety and analyse its potential within the concert of established therapies.

From bone to breast and back - the bone cytokine RANKL and breast cancer.

Receptor activator of nuclear factor-κB ligand (RANKL) plays a pivotal role in regulating bone homeostasis. Osteoporosis and malignant bone disease secondary to breast cancer are characterized by enhanced RANKL production and increased bone turnover. Thus, denosumab, a monoclonal antibody to RANKL, has been developed and is now approved for various bone loss conditions. Recent results indicate that RANKL may also promote the development and osseous migration of breast cancer.

Seizures associated with zoledronic acid for osteoporosis.

CONTEXT: Bisphosphonates represent potent antiresorptive drugs that are established for therapy of patients with benign and malignant bone diseases. Zoledronic acid is an iv aminobisphosphonate that is administered annually against osteoporosis. Because of its potency and the parenteral route of administration, zoledronic acid is an alternative to oral bisphosphonates, in particular in elderly patients with multiple comorbidities. The most common side effects include an acute-phase reaction and mild and transient hypocalcemia. OBJECTIVE: Here, we report three cases of seizures that developed after the administration of zoledronic acid. METHODS: We review case histories and laboratory results of three patients with seizures associated with the administration of zoledronic acid. We discuss their course and comorbidities in the context of the published literature. RESULTS: All three patients were elderly persons with multiple comorbidities, including neurological diseases, that required parenteral bisphosphonates for severe osteoporosis with concurrent contraindications for oral bisphosphonates. CONCLUSION: We analyze potential mechanisms underlying these seizures in association with zoledronic acid exposure and discuss potential strategies to minimize this risk.

Expression profile of WNT molecules in prostate cancer and its regulation by aminobisphosphonates.

Skeletal metastases represent a frequent complication in patients with advanced prostate cancer (PCa) and often require bisphosphonate treatment to limit skeletal-related events. Metastasized PCa cells disturb bone remodeling. Since the WNT signaling pathway regulates bone remodeling and has been implicated in tumor progression and osteomimicry, we analyzed the WNT profile of primary PCa tissues and PCa cell lines and assessed its regulation by bisphosphonates. Prostate tissue (n = 18) was obtained from patients with benign prostate hyperplasia (BPH) and PCa patients with different disease stages. Serum samples were collected from 62 patients. Skeletal metastases were present in 17 patients of whom 6 had been treated with zoledronic acid. The WNT profile and its regulation by bisphoshonates were analyzed in tissue RNA extracts and serum samples as well as in osteotropic (PC3) and non-osteotropic (DU145, LNCaP) PCa cell lines. Several members of the WNT pathway, including WNT5A, FZD5, and DKK1 were highly up-regulated in PCa tissue from patients with advanced PCa. Interestingly, osteotropic cells showed a distinct WNT profile compared to non-osteotropic cells. While WNT5A, FZD5, and DKK1 were highly expressed in PC3 cells, WNT1 and SFRP1 mRNA levels were higher in DU145 cells. Moreover, zoledronic acid down-regulated mRNA levels of WNT5A (-34%), FZD5 (-60%), and DKK1 (-46%) in PC3 cells. Interestingly, patients with skeletal metastases who received zoledronic acid had twofold higher DKK1 serum levels compared to bisphosphonate-naive patients. The WNT signaling pathway is up-regulated in advanced PCa, differentially expressed in osteotropic versus non-osteotropic cells, and is regulated by zoledronic acid.

Approach to the patient with secondary osteoporosis.

Secondary osteoporosis is characterized by low bone mass with microarchitectural alterations in bone leading to fragility fractures in the presence of an underlying disease or medication. Scenarios that are highly suspicious for secondary osteoporosis include fragility fractures in younger men or premenopausal women, very low bone mineral density (BMD) values, and fractures despite anti-osteoporotic therapy. An open-minded approach with a detailed history and physical examination combined with first-line laboratory tests are aimed at identifying clinical risk factors for fractures, osteoporosis-inducing drugs, and underlying endocrine, gastrointestinal, hematologic, or rheumatic diseases, which then need to be confirmed by specific and/or more invasive tests. BMD should be assessed with bone densitometry at the hip and spine. Lateral X-rays of the thoracic and lumbar spine should be performed to identify or exclude prevalent vertebral fractures which may be clinically silent. Management of secondary osteoporosis includes treatment of the underlying disease, modification of medications known to affect the skeleton, and specific anti-osteoporotic therapy. Calcium and vitamin D supplementation should be initiated with doses that result in normocalcemia and serum 25-hydroxyvitamin D concentrations of at least 30 ng/ml. Oral and i.v. bisphosphonates are effective and safe drugs for most forms of secondary osteoporosis. Severe osteoporosis may require the use of teriparatide.

Multimodal therapy for vertebral involvement of systemic mastocytosis.

STUDY DESIGN: Case report and clinical discussion. OBJECTIVE: To describe a rare case of vertebral involvement of systemic mastocytosis and its multimodal therapy. SUMMARY OF BACKGROUND DATA: Vertebral fractures in young men are rare events. A thorough diagnostic work-up that unravels the underlying cause of osteoporosis and appropriate therapy are crucial to prevent further fractures. METHODS: A 36-year-old man was evaluated for severe back pain and was found to suffer from progressive osteoporosis and multiple vertebral fractures. Bone biopsy analysis revealed tryptase-positive mast cells that were positive for c-KIT, thus confirming the diagnosis of systemic mastocytosis. RESULTS: In addition to zoledronic acid (4 mg per month) and prednisolone (50 mg per day) treatment, the patient underwent kyphoplasty. The procedure was associated with arterial hypotension which was most likely because of pressure-induced mast cell degranulation. Follow-up visits demonstrated stable bone mineral density and tolerable back pain while on zoledronic acid. CONCLUSION: Systemic mastocytosis is a rare cause of vertebral fractures in young men. Because of the potential risk of pressure-induced release of the allergy mediator histamine, kyphoplasty for vertebral involvement of systemic mastocytosis should be conducted with appropriate precautions.