Skeletal and extraskeletal actions of denosumab

Role of denosumab in bone erosions in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by systemic inflammation and synovitis which evolve into joint destruction and deformity. Bone abnormalities are represented by marginal bone erosions and iuxta-articular and generalized osteoporosis. Overactivation of osteoclasts along with dysregulation of osteoblasts are the key events. Bone resorption is mediated by the receptor activator of nuclear factor (NF)-κB (RANK) ligand (RANK-L), responsible for the differentiation, proliferation, and activation of osteoclasts. RANK-L binds its receptor RANK, localized on the surface of preosteoclasts and mature osteoclasts promoting osteoclastogenesis. High levels of RANK-L were demonstrated in active RA patients. Denosumab, a fully human monoclonal antibody, binds RANK-L and suppresses the RANK-RANK-L signaling pathway leading to the inhibition of osteoclastogenesis. A retrospective analysis of published studies such as clinical trials evidenced the efficacy of denosumab in preventing bone erosion progression in RA patients. Key messages Key questions to answer in future include the following: Could denosumab be associated with other biologic therapies in RA patients? Could denosumab block the progression of bone damage in RA? Could denosumab be used for the prevention of bone erosion in RA?

Remote management of osteoporosis in the first wave of the COVID-19 pandemic

We conducted a survey during the first pandemic wave of coronavirus disease 2019 (COVID-19) on a large group of osteoporotic patients to evaluate the general conditions of osteoporotic patients and the impact of the pandemic on the management of osteoporosis, finding high compliance to treatments and low COVID-19 lethality.

INTRODUCTION

During the first pandemic wave of coronavirus disease 2019 (COVID-19), 209,254 cases were diagnosed in Italy; fatalities were 26,892 and were overwhelmingly older patients. The high prevalence of osteoporosis in this age group suggests a potential relationship between SARS-CoV-2 infection and bone metabolism.

METHODS

In a telephone survey conducted from April to May 2020, patients from the Osteoporosis Center, Clinic of Endocrinology and Metabolic Diseases of Umberto I Hospital (Ancona, Italy), were interviewed to evaluate the general clinical conditions of osteoporotic patients, compliance with osteoporosis medications, COVID-19 prevalence, hospitalization rate, COVID-19 mortality, and lethality.

RESULTS

Among the 892 patients interviewed, 77.9% were taking osteoporosis treatment and 94.6% vitamin D supplementation as prescribed at the last visit. COVID-19-like symptoms were reported by 5.1%, whereas confirmed cases were 1.2%. A total number of 33 patients had been in hospital and the hospitalization rate of those who had not discontinued vitamin D supplementation was less than 4%. There were eight deaths, two with a concomitant COVID-19 diagnosis. The prevalence of severe osteoporosis was 50% in total COVID-19 patients and 87.5% in deceased COVID-19 patients. The overall COVID-19 mortality was 0.2%; lethality was 20%, lower than the national rate of the same age group.

CONCLUSIONS

This large group of osteoporotic patients showed high compliance and lower COVID-19 lethality compared to patients of the same age. Novel approaches such as telemedicine can provide critical support for the remote follow-up of patients with chronic diseases also in the setting of routine care.

The effect of osteoporosis treatment on bone mass

Over the last two decades there have been significant developments in the pharmacotherapy of osteoporosis. The therapeutic arsenal has expanded with monoclonal antibodies which have been developed based on discoveries of the molecular mechanisms underlying bone resorption and bone formation. Denosumab, the antibody binding RANKL, inhibits bone resorption, and romosozumab, the antibody binding sclerostin, inhibits bone resorption and stimulates bone formation as well. Both antibodies have shown potent anti-fracture efficacy in randomized clinical trials and this review will discuss the preclinical and clinical studies focusing on the effects on bone mass. After discontinuation of these antibodies, bone mineral density quickly returns to baseline and in the case of denosumab, discontinuation can not only induce rebound bone loss, but also the occurrence of vertebral fractures. Therefore, sequential antiresorptive therapy to maintain bone mass gains and anti-fracture efficacy is of utmost importance and will also be discussed in this review.

Inhibition of the RANKL with denosumab has no effect on circulating markers of atherosclerosis in women with postmenopausal osteoporosis: a pilot study

PURPOSE

We evaluated the early effect of denosumab on circulating markers of atherosclerosis in women with postmenopausal osteoporosis.

METHODS

Denosumab (60 mg) was administered subcutaneously every 6 months (m) in 27 women (mean age 75 ± 5 years) with postmenopausal osteoporosis and high cardiovascular risk for a total of 24 m. Zoledronic acid was administered in 6 age-matched women as a single intravenous dose. Serum levels of vascular cell adhesion protein 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), E and P selectin, CD-40 ligand (CD40L), interleukin-6 (IL-6), matrix metalloproteinase (MMP) 1 and 9, monocyte chemoattractant protein-1 (MCP-1), fibrinogen (FBG), and high sensitivity C-reactive protein (hs-CRP) were measured at baseline, 15 days (d), 2, 6 and 12 m after dosing. In the denosumab group, observation was extended to 24 m as secondary endpoint.

RESULTS

Serum ICAM-1 levels showed significant increase in the zoledronic acid group (+18 ± 0.1%; p < 0.01) at 12 m. In the denosumab group, we observed a significant increase in serum CD40L (+2 ± 0.8%; p < 0.001), MMP-1 (+11 ± 0.4%, p < 0.02), and MMP-9 (+39.4 ± 0.8%, p < 0.01) at 24 m. There was a significant increase in serum FBG and hs-CRP in both groups at 12 m (denosumab:+2.2 ± 0.2% and +50.3 ± 1.6%; zoledronic acid: +9.4 ± 0.1 and +81.8 ± 0.8%; p < 0.01). No significant between-group differences were found.

CONCLUSIONS

24-m treatment with denosumab has no effect on the circulating markers of atherosclerosis in women with postmenopausal osteoporosis. Fluctuation of serum ICAM-1, CD40L, MMPs, FBG and hs-CRP can be ascribed to perturbation of immunological mechanisms stimulated by denosumab and zoledronic acid.

Bone Metabolism in SARS-CoV-2 Disease: Possible Osteoimmunology and Gender Implications

Even though inflammatory conditions are known to exert adverse effects on bone metabolism, there are no published data regarding SARS-CoV-2 infection and subsequent fracture risk. We present a brief review of the molecular mechanisms linking inflammatory diseases to increased fracture risk/osteoporosis and of the therapeutic strategies that can prevent bone resorption in patients with inflammatory disease, focusing on the RANK-RANKL system. We also make some considerations on gender differences in infection response and on their implications for survival and for the consequences of COVID-19. Several inflammatory cytokines, especially IL-1, IL-6, and TNF-α, stimulate osteoclast activity, favoring bone resorption through the RANK-RANKL system. Data from the previous SARS-CoV outbreak suggest that the present disease also has the potential to act directly on bone resorption units, although confirmation is clearly needed. Even though the available data are limited, the RANK-RANKL system may provide the best therapeutic target to prevent bone resorption after COVID-19 disease. Vitamin D supplementation in case of deficiency could definitely be beneficial for bone metabolism, as well as for the immune system. Supplementation of vitamin D in case of deficiency could be further advantageous. In COVID-19 patients, it would be useful to measure the bone metabolism markers and vitamin D. Targeting the RANK-RANKL system should be a priority, and denosumab could represent a safe and effective choice. In the near future, every effort should be made to investigate the fracture risk after SARS-CoV-2 infection.

Adherence to anti-osteoporosis medication associated with lower mortality following hip fracture in older adults: a nationwide propensity score-matched cohort study

Background

We investigated the association of anti-osteoporosis medication with mortality risk in older adults with hip fractures and evaluated the influence of medication adherence on mortality.

Methods

We conducted a population-based cohort study and identified a total of 13,123 patients aged 65 years or older with hip fracture from the Taiwan National Health Insurance Database during the period 2001–2010. Individuals with (n = 2092) and without (n = 2092) receiving anti-osteoporosis medication were matched using propensity score matching (1:1 ratio). The 1-, 3- and 5-year survival rates after the index fracture were compared between patients with and without treatment. In the treated group, survival rate was compared between those with good and non-adherence. Good adherence was defined as the medication possession ratio of ≥80% and non-adherence as a ratio < 80%.

Results

The 1-, 3- and 5-year mortality rates were significantly lower in the treated vs. the non-treated group (all p < 0.0001). In the treated group, the estimated 1-, 3- and 5-year survival rates were higher in those with good adherence than in those with non-adherence (all p < 0.0001). Regarding all-cause mortality, the adjusted hazard ratio in the treated vs. the non-treated group was 0.63 (95% confidence interval 0.58–0.68, p < 0.0001). The good adherence subgroup showed a significantly lower mortality risk than that in the non-adherence subgroup (hazard ratio 0.41, 95% confidence interval 0.32–0.51, p < 0.0001).

Conclusions

The 1-, 3- and 5-year survival rates were significantly higher in patients receiving anti-osteoporosis medication than in the untreated group. All-cause mortality rates were lower in patients with good adherence to anti-osteoporosis medication.

Current Understanding of the Pathophysiology of Osteonecrosis of the Jaw

PURPOSE OF REVIEW

Osteonecrosis of the jaw (ONJ) is a rare and severe necrotic bone disease reflecting a compromise in the body's osseous healing mechanisms and unique to the craniofacial region. Antiresorptive and antiangiogenic medications have been suggested to be associated with the occurrence of ONJ; yet, the pathophysiology of this disease has not been fully elucidated. This article raises the current theories underlying the pathophysiology of ONJ.

RECENT FINDINGS

The proposed mechanisms highlight the unique localization of ONJ. The evidence-based mechanisms of ONJ pathogenesis include disturbed bone remodeling, inflammation or infection, altered immunity, soft tissue toxicity, and angiogenesis inhibition. The role of dental infections and the oral microbiome is central to ONJ, and systemic conditions such as rheumatoid arthritis and diabetes mellitus contribute through their impact on immune resiliency. Current experimental studies on mechanisms of ONJ are summarized. The definitive pathophysiology is as yet unclear. Recent studies are beginning to clarify the relative importance of the proposed mechanisms. A better understanding of osteoimmunology and the relationship of angiogenesis to the development of ONJ is needed along with detailed studies of the impact of drug holidays on the clinical condition of ONJ.

Transcriptional network systems in cartilage development and disease

Transcription factors play important roles in the regulation of cartilage development by controlling the expression of chondrogenic genes. Genetic studies have revealed that Sox9/Sox5/Sox6, Runx2/Runx3 and Osterix in particular are essential for the sequential steps of cartilage development. Importantly, these transcription factors form network systems that are also required for appropriate cartilage development. Molecular cloning approaches have largely contributed to the identification of several transcriptional partners for Sox9 and Runx2 during cartilage development. Although the importance of a negative-feedback loop between Indian hedgehog (Ihh) and parathyroid hormone-related protein (PTHrP) in chondrocyte hypertrophy has been well established, recent studies indicate that several transcription factors interact with the Ihh-PTHrP loop and demonstrated that Ihh has multiple functions in the regulation of cartilage development. The most common cartilage disorder, osteoarthritis, has been reported to result from the pathological action of several transcription factors, including Runx2, C/EBPβ and HIF-2α. On the other hand, NFAT family members appear to play roles in the protection of cartilage from osteoarthritis. It is also becoming important to understand the homeostasis and regulation of articular chondrocytes, because they have different cellular and molecular features from chondrocytes of the growth plate. This review summarizes the regulation and roles of transcriptional network systems in cartilage development and their pathological roles in osteoarthritis.

Pathophysiology of Osteonecrosis of the Jaws

Osteonecrosis of the jaw (ONJ) is a multifactorial disease in patients with primary or metastatic bone malignancy or osteoporosis undergoing systemic antiresorptive therapy, where pathophysiology has not yet been fully determined. The staging of ONJ is based on severity of symptoms and extent of clinical and radiographic findings. Treatment strategies range from conservative local wound care to aggressive resective surgery of all necrotic bone. The first ONJ cases were reported in 2003 and 2004, and although significant progress has been made in our understanding of the disease, much more work needs to be done to completely explain its pathophysiology.

A High-grade Sarcoma Arising in a Patient With Recurrent Benign Giant Cell Tumor of the Proximal Tibia While Receiving Treatment With Denosumab

BACKGROUND

A giant cell tumor of bone is a primary benign but locally aggressive neoplasm. Malignant transformation in a histologically typical giant cell tumor of bone, without radiotherapy exposure, is an uncommon event, occurring in less than 1% of giant cell tumors of bone. Although surgery is the standard initial treatment, denosumab, a monoclonal antibody drug that inhibits receptor activator of nuclear factor-κB ligand (RANKL), has shown considerable activity regarding disease and control of symptoms in patients with recurrence, unresectable, and metastatic giant cell tumors of bone.

CASE DESCRIPTION

We report the case of a 20-year-old woman with a recurrent benign, giant cell tumor of bone, who had a bone sarcoma develop while receiving denosumab treatment.

LITERATURE REVIEW

To our knowledge, there have been no reports of infection or malignancy with low-dose denosumab administration for osteoporosis. However, while there are relatively few reported side effects, the safety of denosumab and adverse events seen with higher doses, as used in treatment of giant cell tumors of bone are not well defined.

CLINICAL RELEVANCE

Denosumab has become a valuable adjunct for treatment of recurrent or unresectable giant cell tumor of bone. It is not clear if our patient's malignant transformation of a giant cell tumor of bone while receiving denosumab treatment was caused by denosumab, but it is important to be aware of the possibility if more cases occur. Future studies should focus on the safety of high-dose denosumab administration in patients with a benign unresectable giant cell tumor of bone.

Assessment of the Effect of Methotrexate Therapy on Bone Metabolism in Patients with Rheumatoid Arthritis

Proinflammatory cytokines and growth factors, which regulate mutual interactions between immune system cells and bone tissue cells, play a major role in the formation of bone changes in rheumatoid arthritis (RA). The aim of the work was to assess serum concentration of osteoprotegerin (OPG), RANKL, Dkk-1 and sclerostin in RA patients compared to a control group and to analyze changes of these concentrations during methotrexate (MTX) therapy. Patients enrolled in the study were 30 women of Caucasian origin aged 30-74 years with RA. Patients with active form of the disease were administered recommended doses of MTX for at least 6 months. The study group was divided into subgroup I-patients with improvement; and subgroup II-patients with no improvement. The control group consisted of 12 healthy women in the age of 41-73. Before MTX therapy, RA patients had higher levels of RANKL (644.97 ± 477.13 vs. 255.19 ± 130.26 pmol/l), lower values of OPG/RANKL (0.01 ± 0.0101 vs. 0.02 ± 0.0078) and higher levels of Dkk-1 protein (1821.32 ± 1060.28 vs. 548.52 ± 36.35 pg/ml) compared to the control group. In the analyzed group of patients (all patients receiving MTX regardless of responder non responder status) after 6 months of therapy, a statistically significant increase in the ratio of OPG/RANKL was found (0.0118 ± 0.0102 vs. 0.0141 ± 0.0118; p = 0.02). The index value of OPG/RANKL differed significantly depending on the resultant effect of treatment (0.01702 ± 0.01274 in the subgroup of improvement vs. 0.00675 ± 0.00289 in the subgroup without improvement). The difference in the mean concentrations of Dkk-1 before and after treatment with MTX between subgroups I and II was statistically significant (p = 0.002). In subgroup I, mean concentration of Dkk-1 decreased after 6 months of treatment with MTX (2054.72 ± 1004.74 vs. 1831.70 ± 851.70 pg/ml); while in subgroup II, the mean concentration of Dkk-1 increased (1214.48 ± 738.32 vs. 2275.01 ± 1385.23 pg/ml). There were no statistically significant changes in the mean concentrations of sclerostin before and after treatment with MTX (in whole group treatment with MTX, in subgroup I, and in subgroup II). The results confirm the presence of disorders of bone metabolism in patients with RA. Treatment with MTX affects the value of the ratio of OPG/RANKL and concentration of Dkk-1.

Osteoclast formation elicited by interleukin-33 stimulation is dependent upon the type of osteoclast progenitor

Osteoclasts are bone resorbing multinucleated cells (MNCs) derived from macrophage progenitors. IL-33 has been reported to drive osteoclastogenesis independently of receptor activator of NFκB ligand (RANKL) but this remains controversial as later studies did not confirm this. We found IL-33 clearly elicited functional dentine-resorbing osteoclast formation from human adult monocytes. However, monocytes from only 3 of 12 donors responded this way, while all responded to RANKL. Human cord blood-derived progenitors and murine bone marrow macrophages lacked an osteoclastogenic response to IL-33. In RAW264.7 cells, IL-33 elicited NFκB and p38 responses but not NFATc1 signals (suggesting poor osteoclastogenic responses) and formed only mononuclear tartrate-resistant acid phosphatase positive (TRAP(+)) cells. Since TGFβ boosts osteoclastogenesis in RAW264.7 cells we employed an IL-33/TGFβ co-treatment, which resulted in small numbers of MNCs expressing key osteoclast markers TRAP and calcitonin receptors. Thus, IL-33 possesses weak osteoclastogenic activity suggesting pathological significance and, perhaps, explaining previous conflicting reports.

Effects of antibody to receptor activator of nuclear factor κ-B ligand on inflammation and cartilage degradation in collagen antibody-induced arthritis in mice

Background

Rheumatoid arthritis (RA) is an inflammatory disease that leads to destruction of both articular cartilage and bone tissues. In rheumatic joints, synoviocytes and T-lymphocytes as well as bone cells produce the receptor activator of nuclear factor κ-B (RANK) ligand (RANKL), which binds to RANK on the surface of osteoclasts and their precursor cells to induce differentiation and activation of osteoclasts. Hence, inhibition of RANKL may be a promising approach to suppress osteolysis in RA. On the other hand, RANKL production by lymphocytes indicates the possibility that its inhibition would be effective to suppress inflammation in RA. In addition, it has been reported that cathepsin K, a predominant cysteine protease in osteoclasts, is involved in cartilage destruction in RA model mice. Here, we evaluated the effects of an anti-RANKL antibody on inflammation in footpads and degradation of articular cartilage in RA model mice.

Results

We induced arthritis in mice by injection of anti-type II collagen antibodies and lipopolysaccharide (LPS). Inhibition of RANKL by an anti-RANKL antibody (OYC1, Oriental Yeast, Tokyo, Japan) was confirmed by increased bone volume in the metaphysis of tibias. Swelling in either limb until day 14 was seen in 5 of 6 mice injected with anti-collagen antibodies and LPS without treatment with OYC1, while that was seen in 4 of 5 mice treated with OYC1. The average arthritis scores on day 14 in those groups were 2.17 and 3.00, respectively, indicating that OYC1 did not ameliorate inflammation in the limbs. Histological analyses indicated that OYC1 does not protect articular cartilage from destruction in mice with arthritis.

Conclusions

Our present study failed to show the effectiveness of an anti-RANKL antibody to ameliorate inflammation in the limbs or protect articular cartilage from degradation in a collagen antibody-induced arthritis mouse model.

Electronic supplementary material

The online version of this article (doi:10.1186/s12952-014-0018-0) contains supplementary material, which is available to authorized users.

Alternative pathways of osteoclastogenesis in inflammatory arthritis

Osteoclasts are cells of haematopoietic origin that are uniquely specialized to degrade bone. Under physiological conditions, the osteoclastogenesis pathway depends on macrophage colony-stimulating factor 1 (CSF-1, also known as M-CSF) and receptor activator of nuclear factor κB ligand (RANKL). However, an emerging hypothesis is that alternative pathways of osteoclast generation might be active during inflammatory arthritis. In this Perspectives article, we summarize the physiological pathway of osteoclastogenesis and then focus on experimental findings that support the hypothesis that infiltrating inflammatory cells and the cytokine milieu provide multiple routes to bone destruction. The precise identity of osteoclast precursor(s) is not yet known. We propose that myeloid cell differentiation during inflammation could be an important contributor to the differentiation of osteoclast populations and their associated pathologies. Understanding the dynamics of osteoclast differentiation in inflammatory arthritis is crucial for the development of therapeutic strategies for inflammatory joint disease in children and adults.

The inhibition of RANK-ligand in the management of postmenopausal osteoporosis and related fractures: the role of denosumab

There is great interest in new treatments of osteoporosis owing to general ageing of population and increased risk for fragility fractures in the elderly. Current therapies show a good efficacy in improving bone quality and bone density, but, in spite of a certain reduction in fracture rate, according to each treatment, the problem of osteoporotic fractures is yet far from to be solved. Moreover, some treatments may produce different side effects. Denosumab (Dmab), a receptor activator of nuclear factor kappa-B ligand (RANKL)-inhibitor, is an agent recently introduced in clinical practice for treatment of osteoporosis of postmenopausal women. Dmab has improved bone mineral density and prevented new vertebral and non-vertebral fractures with a similar efficacy in comparison with alendronate. Many clinical studies showed Dmab produces also significant improvement versus placebo in bone quality as indicated by decreasing markers of bone turnover. Patients using Dmab reported less risk of AFF (Atypical Femoral Fractures) and ONJ (Osteonecrosis of the Jaw) with an increased number of cellulitis. Here, we review articles using Dmab for female post-menopausal osteoporosis.

Prevalence of osteoporosis in prostate cancer survivors: a meta-analysis

Androgen deprivation therapy (ADT), which is used in the treatment of prostate cancer (PCa), is associated with increased morbidity. Severe bone loss is a major consequence of androgen ablation and with an increasing number of patients undergoing this treatment, the incidence of osteoporosis and fractures can be expected to increase with a significant impact on healthcare. To evaluate the prevalence of osteoporosis, we conducted a review of the literature on bone health in men with PCa undergoing ADT. A meta-analysis was conducted using the quality effects model, and sources of heterogeneity were further explored by consideration of discordant effect sizes of included studies in the meta-analysis and examining reasons thereof. Our analyses indicate that the prevalence of osteoporosis varies between 9 and 53 % with this variation partially explained by treatment duration, disease stage, ethnicity and site of osteoporosis measurement. While it is well known that a rapid decline in bone health amongst men with PCa on ADT occurs, this meta-analysis documents the high prevalence of osteoporosis in this population and reinforces the need of preventative approaches as part of usual care of PCa patients.

Sinomenine suppresses osteoclast formation and Mycobacterium tuberculosis H37Ra-induced bone loss by modulating RANKL signaling pathways

Receptor activator of NF-κB ligand (RANKL) is essential for osteoclastogenesis. Targeting RANKL signaling pathways has been an encouraging strategy for treating lytic bone diseases such as osteoporosis and rheumatoid arthritis (RA). Sinomenine (SIN), derived from Chinese medicinal plant Sinomenioumacutum, is an active compound to treat RA, but its effect on osteoclasts has been hitherto unknown. In the present study, SIN was found to ameliorate M. tuberculosis H37Ra (Mt)-induced bone loss in rats with a decreased serum level of TRACP5b and RANKL, and an increased level of osteoprotegerin (OPG). In vitro study also showed that SIN could inhibit RANKL-induced osteoclast formation and bone resorption. The osteoclastic specific marker genes induced by RANKL including c-Src, MMP-9, TRACP were inhibited by SIN in a dose dependent manner. Signal transduction studies showed that SIN could obviously reduce the expression of RANK adaptor molecule TRAF6 and down-regulate RANKL-induced NF-κB activation. It decreased the RANKL-induced p38, JNK posphorylation but not ERK1/2 posphorylation. SIN could also reduce RANKL-mediated calcium influx which is associated with TRAF6/c-Src complex. Finally, SIN suppressed RANKL induced AP-1 and NFAT transcription, as well as the gene expression of NFATc1 and AP-1 components (Fra-1, Fra-2, c-Fos). The protein expression of c-Fos and TRAF6 were also inhibited by SIN after RANKL stimulation. Taken together, SIN could attenuate osteoclast formation and Mt-induced bone loss by mediating RANKL signaling pathways.

Osteoporosis in men: recent progress

As osteoporosis in men has been recognized as an important clinical problem, new information is being accumulated on its scope, pathophysiology, evaluation, and treatment. Fracture risk calculators, such as FRAX, identify a large proportion of the older male population to be at heightened risk for fracture. The classification of osteoporosis into primary and secondary forms, while still useful, is affected by the fact that many men have multiple contributing factors to their fracture risk. The role of sex steroids is being better defined as other risk factors for fracture are delineated. As longevity continues to increase in men and until osteoporotic fracture is truly recognized as a potentially fatal disorder, many men will be undiagnosed and untreated. Two recent studies provide more evidence that treatments which decrease fracture risk in women do the same in men. With the publication of guidelines and increasing strength of evidence for treatment efficacy, it is hoped that more men will be evaluated and treated for this often neglected disorder.

Serum extracellular secreted antagonists of the canonical Wnt/β-catenin signaling pathway in patients with Cushing's syndrome

Patients with endogenous hypercortisolism have higher sclerostin, but do not differ in Dickkopf 1 (Dkk1) or secreted frizzled-related protein 1 (SFRP1) levels as compared to healthy control.

INTRODUCTION

Endogenous Cushing's syndrome (CS), usually affecting young and otherwise healthy patients, is a good model to validate the effects of supraphysiological levels of glucocorticoids in humans. This study evaluates circulating levels of extracellular antagonists of the Wnt/β-catenin signaling pathway (sclerostin, Dkk1, SFRP1) in patients with CS versus healthy individuals.

METHODS

Forty patients with clinically and biochemically evident CS and 40 sex-, age-, and body mass index-matched healthy subjects provided fasting serum samples for sclerostin, SFRP1 and Dkk1, along with bone turnover markers.

RESULTS

Patients with CS had higher sclerostin levels (34.5 (30.3-37.1) pmol/L) versus healthy individuals (29.9 (24.3-36.8) pmol/L) (p = 0.032). Differences in sclerostin were due to the lack of lower sclerostin values rather than an increase in protein levels above the upper limits of the healthy control. The odds of sclerostin levels being higher than 30 pmol/L were greater in patients with CS as compared with the odds in healthy subjects (odds ratio = 3.81 95 % confidence interval 1.45-10.02) (p = 0.01). It coexisted with suppressed bone formation and unchanged bone resorption markers. Dkk1, SFRP1 did not differ from the control group.

CONCLUSIONS

Of all the tested proteins (sclerostin, Dkk1, SFRP1), only sclerostin showed a significant difference when contrasting CS with healthy subjects. Hypercortisolism might prevent the down-regulation of sclerostin. Targeting sclerostin seems to be a promising therapeutic approach to treating osteoporosis in patients with CS.

Periapical disease and bisphosphonates induce osteonecrosis of the jaws in mice

Osteonecrosis of the jaw (ONJ) is a well-recognized complication of antiresorptive medications, such as bisphosphonates (BPs). Although ONJ is most common after tooth extractions in patients receiving high-dose BPs, many patients do not experience oral trauma. Animal models using tooth extractions and high BP doses recapitulate several clinical, radiographic, and histologic findings of ONJ. We and others have reported on rat models of ONJ using experimental dental disease in the absence of tooth extraction. These models emphasize the importance of dental infection/inflammation for ONJ development. Here, we extend our original report in the rat, and present a mouse model of ONJ in the presence of dental disease. Mice were injected with high dose zoledronic acid and pulpal exposure of mandibular molars was performed to induce periapical disease. After 8 weeks, quantitative and qualitative radiographic and histologic analyses of mouse mandibles were done. Periapical lesions were larger in vehicle-treated versus BP-treated mice. Importantly, radiographic features resembling clinical ONJ, including thickening of the lamina dura, periosteal bone deposition, and increased trabecular density, were seen in the drilled site of BP-treated animals. Histologically, osteonecrosis, periosteal thickening, periosteal bone apposition, epithelial migration, and bone exposure were present in the BP-treated animals in the presence of periapical disease. No difference in tartrate-resistant acid phosphatase (TRAP)+ cell numbers was observed, but round, detached, and removed from the bone surface cells were present in BP-treated animals. Although 88% of the BP-treated animals showed areas of osteonecrosis in the dental disease site, only 33% developed bone exposure, suggesting that osteonecrosis precedes bone exposure. Our data further emphasize the importance of dental disease in ONJ development, provide qualitative and quantitative measures of ONJ, and present a novel mouse ONJ model in the absence of tooth extraction that should be useful in further exploring ONJ pathophysiological mechanisms.

Monocytic expression of osteoclast-associated receptor (OSCAR) is induced in atherosclerotic mice and regulated by oxidized low-density lipoprotein in vitro

The osteoclast-associated receptor (OSCAR), primarily described as a co-stimulatory regulator of osteoclast differentiation, represents a potential link between bone metabolism and vascular biology. Previously, we identified OSCAR as an endothelial cell-derived target of the proatherogenic factor oxidized low density lipoprotein (oxLDL). Since monocytes play an important role in the progression of atherosclerosis, we assessed whether atherogenic stimuli also regulate the expression of OSCAR on monocytes. Four-week-old male wild-type (WT), apolipoprotein e knockout (apoe KO), and LDL receptor knockout (ldlr KO) mice were fed a high-fat diet or normal chow for 6weeks. Peripheral blood mononuclear cells (PBMCs) isolated from the spleen were stained with antibodies against CD14 and OSCAR for subsequent flow cytometric analysis. OSCAR surface expression on CD14-positive monocytes increased 2-fold in PBMCs from apoe KO mice compared to WT mice. Feeding a high-fat diet further increased OSCAR surface expression 1.5-fold in apoe KO mice compared to normal diet. Moreover, OSCAR-positive macrophages were detected in atherosclerotic plaques of apoe KO mice. Interestingly, monocytic OSCAR expression was not altered in ldlr KO mice. In the murine macrophage cell line RAW 264.7, TNFα and oxLDL induced OSCAR mRNA expression by 2-fold and 5-fold (p<0.01), respectively. Blocking the oxLDL receptor LOX-1 and inhibiting the NF-κB pathway prevented OSCAR induction. In conclusion, OSCAR expression in monocytic cells is regulated by proatherogenic stimuli further pointing towards a role in vascular inflammation or plaque vulnerability during atherosclerosis.

The role of osteoprotegerin in cardiovascular disease

Osteoprotegerin (OPG) is a 401 amino acid N-glycosylated protein, which is highly expressed in a large number of tissues. OPG mainly binds to two ligands, i.e. RANKL (receptor activator of nuclear factor κB ligand) and TRAIL (tumor necrosis factor- related apoptosis-inducing ligand). Upon binding to the former ligand, OPG inhibits the activation of osteoclasts and promotes apoptosis of osteoclasts, whereas the binding of OPG with TRAIL prevents apoptosis of tumor cells. There is now emerging evidence that OPG participates in the pathogenesis of atherosclerosis and cardiovascular diseases by amplifying the adverse effects of inflammation and several traditional risk factors such as hyperlipidemia, endothelial dysfunction, diabetes mellitus, and hypertension. Some epidemiological studies also showed a positive association between OPG levels and cardiovascular morbidity and mortality. The aim of this article is to provide an overview of the main biochemical, physiological, and pathological aspects of OPG biology in cardiovascular disease.

Osteoporosis in chronic inflammatory disease: the role of malnutrition

Osteoporosis is a metabolic bone disorder affecting million of people worldwide. Increased understanding of bone disease has led to a greater recognition of factors affecting bones, and consequently many secondary causes of osteoporosis were demonstrated. In this study, we aim to explore possible causes of bone loss and fractures in subjects affected by chronic inflammatory disease and to suggest new targets for intervention. In fact several studies, evaluated to perform this study, suggest that the patients with chronic inflammatory disease could be at high risk for fractures due to bone loss as consequence of malnutrition, caused by inflammation and hormonal change. Consequently, some actions could derive from the considerations of these mechanisms: a change in actual approach of chronic patients, that may include the investigation on the possible presence of osteoporosis, as well as further research on this topic to find a better therapy to prevent osteoporosis considering all the mechanisms described.