Glucocorticoids and bone: local effects and systemic implications

Workup and Management of Premenopausal Osteoporosis

The diagnosis and management of premenopausal low bone mass or osteoporosis is challenging as its relationship to low bone mass and risk of fracture is less defined. Premenopausal or perimenopausal women with low bone density or a history of fragility fractures should undergo a thorough evaluation of causes that predispose them to bone loss. Identification of these underlying risk factors such as estrogen deficiency or malabsorptive disorders offers a treatment strategy to reverse bone loss. This is a review of the diagnostic approach and subsequent management strategies of premenopausal low bone mass or osteoporosis.

Trabecular bone score (TBS) in Cushing's disease: TBS gain after hypercortisolism normalization

CONTEXT

Hypercortisolism frequently induces trabecular bone loss, more pronounced at the lumbar spine, resulting in osteoporosis, and thus an increase in fracture risk. Several studies have shown bone mass recovery in patients with Cushing's disease (CD) after treatment.

OBJECTIVE

To examine treatment effects on TBS (trabecular bone score) in addition to aBMD (areal bone mineral density) in a cohort of patients with CD.

DESIGN AND SETTING

Single-center retrospective longitudinal study in patients diagnosed with CD and successfully treated following surgery and/or medical treatment.

PATIENTS

We included 31 patients with median age and BMI (body mass index) of 37.7 [28.4;43.3] years old and 27.7 [25.8;30.4] kg/m2, respectively. Median 24 h urinary cortisol before treatment was 213.4 [168.5;478.5] μg/24 h. All subjects were completely biochemically controlled or cured after treatment.

MAIN OUTCOME MEASURES

aBMD and TBS were evaluated at AP Spine (L1-L4) with DXA prodigy (GE-Lunar), QDR 4500 (Hologic), and TBS iNsight® (Med-Imaps) before and after treatment.

RESULTS

Absolute TBS and aBMD gains following cure of CD were significant (p < 0.0001, and p < 0.001, respectively). aBMD and TBS increased by +3.9 and 8.2 % respectively after cure of CD. aBMD and TBS were not correlated before (p = 0.43) and after treatment (p = 0.53). Linear regression analyses showed that TBS gain was independent of baseline BMI and that low TBS at baseline was predictive of TBS gain after treatment.

CONCLUSION

The more significant improvement of microarchitecture assessed by TBS than aBMD and the absence of correlation between TBS and aBMD suggest that TBS may be an adequate marker of bone restoration after cure of CD. To support this conclusion, future studies with larger sample sizes and longer follow-up periods should be carried out.

Drug-induced osteoporosis and mechanisms of bone tissue regeneration through trace elements

Osteoporosis is associated with an imbalance in bone formation, with certain drugs used in disease treatment being implicated in its development. Supplementation with trace elements may contribute to bone regeneration, offering an alternative approach by enhancing bone mineral density (BMD) and thereby thwarting the onset of osteoporosis. This review aims to assess the mechanisms through which trace elements such as copper (Cu), iron (Fe), selenium (Se), manganese (Mn), and zinc (Zn) are linked to increased bone mass, thus mitigating the effects of pharmaceuticals. Our findings underscore that the use of drugs such as aromatase inhibitors (AIs), proton pump inhibitors (PPIs), antiretrovirals, glucocorticoids, opioids, or anticonvulsants can result in decreased BMD, a primary contributor to osteoporosis. Research indicates that essential elements like Cu, Fe, Se, Mn, and Zn, through various mechanisms, can bolster BMD and forestall the onset of the disease, owing to their protective effects. Consequently, our study recommends a minimum daily intake of these essential minerals for patients undergoing treatment with the aforementioned drugs, as the diverse mechanisms governing the effects of trace elements Cu, Fe, Mn, Se, and Zn facilitate bone remodeling.

Plasminogen activator inhibitor-1 is involved in glucocorticoid-induced decreases in angiogenesis during bone repair in mice

INTRODUCTION

Glucocorticoids delay fracture healing and induce osteoporosis. Angiogenesis plays an important role in bone repair after bone injury. Plasminogen activator inhibitor-1 (PAI-1) is the principal inhibitor of plasminogen activators and an adipocytokine that regulates metabolism. However, the mechanisms by which glucocorticoids delay bone repair remain unclear.

MATERIALS AND METHODS

Therefore, we herein investigated the roles of PAI-1 and angiogenesis in glucocorticoid-induced delays in bone repair after femoral bone injury using PAI-1-deficient female mice intraperitoneally administered dexamethasone (Dex).

RESULTS

PAI-1 deficiency significantly attenuated Dex-induced decreases in the number of CD31-positive vessels at damaged sites 4 days after femoral bone injury in mice. PAI-1 deficiency also significantly ameliorated Dex-induced decreases in the number of CD31- and endomucin-positive type H vessels and CD31-positive- and endomucin-negative vessels at damaged sites 4 days after femoral bone injury. Moreover, PAI-1 deficiency significantly mitigated Dex-induced decreases in the expression of vascular endothelial growth factor as well as hypoxia inducible factor-1α, transforming growth factor-β1, and bone morphogenetic protein-2 at damaged sites 4 days after femoral bone injury.

CONCLUSION

The present results demonstrate that Dex-reduced angiogenesis at damaged sites during the early bone-repair phase after femoral bone injury partly through PAI-1 in mice.

Excess glucocorticoids inhibit murine bone turnover via modulating the immunometabolism of the skeletal microenvironment

Elevated bone resorption and diminished bone formation have been recognized as the primary features of glucocorticoid-associated skeletal disorders. However, the direct effects of excess glucocorticoids on bone turnover remain unclear. Here, we explored the outcomes of exogenous glucocorticoid treatment on bone loss and delayed fracture healing in mice and found that reduced bone turnover was a dominant feature, resulting in a net loss of bone mass. The primary effect of glucocorticoids on osteogenic differentiation was not inhibitory; instead, they cooperated with macrophages to facilitate osteogenesis. Impaired local nutrient status - notably, obstructed fatty acid transportation - was a key factor contributing to glucocorticoid-induced impairment of bone turnover in vivo. Furthermore, fatty acid oxidation in macrophages fueled the ability of glucocorticoid-liganded receptors to enter the nucleus and then promoted the expression of BMP2, a key cytokine that facilitates osteogenesis. Metabolic reprogramming by localized fatty acid delivery partly rescued glucocorticoid-induced pathology by restoring a healthier immune-metabolic milieu. These data provide insights into the multifactorial metabolic mechanisms by which glucocorticoids generate skeletal disorders, thus suggesting possible therapeutic avenues.

Comorbidities in childhood atopic dermatitis: A population-based study

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is associated with allergic comorbidities. However, studies examining comorbidities in childhood AD are incomplete, which may contribute to suboptimal care.

OBJECTIVE

The objective was to compare the risk of developing different allergic and non-allergic comorbidities among children with AD to that of a matched non-AD reference cohort in Sweden.

METHODS

This was a nationwide population-based cohort study using longitudinal data from primary and specialist care registers. Patients with AD were identified by confirmed diagnosis in primary or specialist care. The non-AD reference cohort was randomly drawn from the general population and matched 1:1 with the AD patients. The risk of developing the following conditions was evaluated: hypersensitivity and allergic disorders, neurological disorders, psychiatric disorders, infections, immunological and inflammatory disorders, Type 1 diabetes (T1D), endocrine and metabolic disorders, skeletal disorders, ocular disorders and malignancies.

RESULTS

This study included 165,145 patients with AD (mild-to-moderate [n = 126,681] and severe [n = 38,464]) and an equally sized reference cohort. Patients with AD displayed a higher risk of developing comorbid conditions for all investigated categories, except for T1D and skeletal disorders, compared with the reference cohort. The highest risk compared with the reference cohort was observed for hypersensitivity and allergic disorders (hazard ratio [HR]: 3.87), followed by malignancies (HR: 2.53) and immunological and inflammatory disorders (HR: 2.36). Patients with AD also had higher risk of developing multiple comorbidities (≥2). The risk of comorbidity onset increased alongside AD severity and patients with active AD were associated with increased risk of comorbidity onset compared with patients in remission.

CONCLUSIONS

The clinical burden of AD is substantial for children with AD and patients are at an increased risk of developing several comorbid conditions extending beyond the atopic march. Our results also showed a positive association between worsening severity of AD and an increased risk of comorbidity onset.

Microscopic colitis is a risk factor for low bone density: a systematic review and meta-analysis

Background

Microscopic colitis (MC) is a chronic inflammatory disease of the large bowel characterized by watery diarrhea, substantially decreasing the patient's quality of life. Scarce data suggest that MC is associated with low bone density (LBD).

Objectives

We aimed to assess whether MC is a risk factor for LBD and the proportion of patients with MC having LBD.

Design

A systematic review and meta-analysis of studies reporting bone density measurements in MC patients.

Data Sources and Methods

We systematically searched five databases from inception to October 16, 2021 (Pubmed, Embase, Cochrane, Scopus, and Web of Science). We used the random-effect model to calculate pooled odds ratios (ORs) and pooled event rates with 95% confidence intervals (CIs). To ascertain the quality of evidence of our outcomes, we followed the recommendations of the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) Working Group.

Results

The systematic search yielded a total of 3046 articles. Four articles were eligible for quantitative synthesis. All of them used age- and sex-matched controls to evaluate LBD occurrence among patients with MC. The odds of having LBD were twofold increased (OR = 2.13, CI: 1.42-3.20) in the presence of MC, the odds of osteopenia occurrence were 2.4 (OR = 2.45, CI: 1.11-5.41), and of osteoporosis 1.4 (OR = 1.42, CI: 0.65-3.12). The proportion of LBD was 0.68 (CI: 0.56-0.78), osteopenia was 0.51 (CI: 0.43-0.58), and osteoporosis was 0.11 (CI: 0.07-0.16) among the MC population. Our findings' certainty of the evidence was very low following the GRADEPro guideline.

Conclusion

Our data demonstrate that MC is associated with a twofold risk for LBD. Based on our findings, we suggest screening patients for bone mineral density upon diagnosis of MC. Further prospective studies with higher patient numbers and longer follow-up periods on this topic are needed.

Registration

Our protocol was prospectively registered with PROSPERO (CRD42021283392).

Oxylipin-PPARγ-initiated adipocyte senescence propagates secondary senescence in the bone marrow

The chronic use of glucocorticoids decreases bone mass and quality and increases bone-marrow adiposity, but the underlying mechanisms remain unclear. Here, we show that bone-marrow adipocyte (BMAd) lineage cells in adult mice undergo rapid cellular senescence upon glucocorticoid treatment. The senescent BMAds acquire a senescence-associated secretory phenotype, which spreads senescence in bone and bone marrow. Mechanistically, glucocorticoids increase the synthesis of oxylipins, such as 15d-PGJ2, for peroxisome proliferator-activated receptor gamma (PPARγ) activation. PPARγ stimulates the expression of key senescence genes and also promotes oxylipin synthesis in BMAds, forming a positive feedback loop. Transplanting senescent BMAds into the bone marrow of healthy mice is sufficient to induce the secondary spread of senescent cells and bone-loss phenotypes, whereas transplanting BMAds harboring a p16INK4a deletion did not show such effects. Thus, glucocorticoid treatment induces a lipid metabolic circuit that robustly triggers the senescence of BMAd lineage cells that, in turn, act as the mediators of glucocorticoid-induced bone deterioration.

Effects of topical corticosteroid versus tacrolimus on insulin sensitivity and bone homeostasis in adults with atopic dermatitis-A randomized controlled study

INTRODUCTION

Topical corticosteroids (TCS), used to treat atopic dermatitis (AD), have been associated with type 2 diabetes and osteoporosis in epidemiological studies, possibly explained by systemic absorption.

OBJECTIVES

We examined whether intensive daily whole-body TCS treatment over 2 weeks followed by twice weekly application for 4 weeks could elicit insulin resistance and increase bone resorption in adults with AD.

METHODS

A randomized parallel-group double-blind double-dummy non-corticosteroid-based active comparator study design was completed in Copenhagen, Denmark. Thirty-six non-obese, non-diabetic adults with moderate-to-severe AD were randomized to whole-body treatment with betamethasone 17-valerate 0.1% plus a vehicle once daily or tacrolimus 0.1% twice daily after washout. Insulin sensitivity assessed by the hyperinsulinemic-euglycemic clamp combined with tracer infusions and biomarkers of bone formation (P1NP) and resorption (CTX) were evaluated at baseline, after 2 weeks of daily treatment and after further 4 weeks of twice-weekly maintenance treatment.

RESULTS

AD severity improved with both treatments and systemic inflammation was reduced. After 2 weeks, we observed similar increase in peripheral insulin sensitivity with use of betamethasone (n = 18) and tacrolimus (n = 18). Bone resorption biomarker, CTX, was unchanged, while bone formation marker, P1NP, decreased after betamethasone treatment after both 2 and 6 weeks but remained unchanged in the tacrolimus arm.

CONCLUSIONS

Whole-body treatment with TCS leads to systemic exposure but appears not to compromise glucose metabolism during short-term use, which may be a result of reduced systemic inflammatory activity. The negative impact on bone formation could be regarded an adverse effect of TCS.

The emerging roles of GPR158 in the regulation of the endocrine system

G protein-coupled receptor 158 (GPR158) is a member of class C G protein-coupled receptors (GPCRs) and is highly expressed in the central nervous system (CNS) while lowly expressed in peripheral tissues. Previous studies have mainly focused on its functions in the CNS, such as regulating emotions, memory, and cognitive functions, whereas studies on its role in the non-nervous system are limited. It has been recently reported that GPR158 is directly involved in adrenal regulation, suggesting its role in peripheral tissues. Moreover, GPR158 is a stable dimer coupled to the regulator of G protein signaling protein 7 (RGS7) that forms the GPR158-RGS7-Gβ5 complex. Given that the RGS7-Gβ5 complex is implicated in endocrine functions, we speculate that GPR158 might be an active component of the endocrine system. Herein, we reviewed the relevant literature on GPR158, including its molecular structure, regulatory molecules, expression, and functions, and highlighted its roles in endocrine regulation. These findings not only enhance our understanding of GPR158 from an endocrine perspective but also provide valuable insights into drug exploration targeting GPR158 and their applicability in endocrine disorders.

Glucocorticoid-induced expansion of classical monocytes contributes to bone loss

Classical monocytes are commonly involved in the innate inflammatory response and are the progenitors of osteoclasts. Excess endogenous glucocorticoids (GCs) can increase the levels of classical monocytes in blood and bone marrow. The role of this cell population in high-dose exogenous GC-induced osteoporosis (GIOP) remains to be elucidated. In this study, GIOP was established in rats and mice by daily methylprednisolone injection, and monocyte subsets were analyzed by flow cytometry. We demonstrated that classical monocytes accumulate in bone marrow during GIOP. Similarly, the monocyte proportion among bone marrow nucleated cells was also increased in patients with steroid treatment history. We sorted classical monocytes and analyzed their transcriptional profile in response to GCs by RNA sequencing. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that classical monocytes isolated from GC-treated rats exhibited osteoclast differentiation potential. Deletion of classical monocytes by clodronate liposome treatment prevented GIOP via inhibition of osteoclastogenesis and restoration of CD31^Hiendomucin^Hi vessels. Regarding the molecular mechanism, classical monocytes express high levels of glucocorticoid receptors. In vitro treatment with GCs increased both the percentage and absolute number of monocytes and promoted their proliferation. In summary, classical monocytes mediated GC-induced bone loss and are a potential target for therapeutic intervention in GIOP treatment.

Fisetin: An Integrated Approach to Identify a Strategy Promoting Osteogenesis

Flavonoids may modulate the bone formation process. Among flavonoids, fisetin is known to counteract tumor growth, osteoarthritis, and rheumatoid arthritis. In addition, fisetin prevents inflammation-induced bone loss. In order to evaluate its favorable use in osteogenesis, we assayed fisetin supplementation in both in vitro and in vivo models and gathered information on nanoparticle-mediated delivery of fisetin in vitro and in a microfluidic system. Real-time RT-PCR, Western blotting, and nanoparticle synthesis were performed to evaluate the effects of fisetin in vitro, in the zebrafish model, and in ex vivo samples. Our results demonstrated that fisetin at 2.5 µM concentration promotes bone formation in vitro and mineralization in the zebrafish model. In addition, we found that fisetin stimulates osteoblast maturation in cell cultures obtained from cleidocranial dysplasia patients. Remarkably, PLGA nanoparticles increased fisetin stability and, consequently, its stimulating effects on RUNX2 and its downstream gene SP7 expression. Therefore, our findings demonstrated the positive effects of fisetin on osteogenesis and suggest that patients affected by skeletal diseases, both of genetic and metabolic origins, may actually benefit from fisetin supplementation.

Antenatal dexamethasone retarded fetal long bones growth and development by down-regulating of insulin-like growth factor 1 signaling in fetal rats

OBJECTIVE

Dexamethasone (DEX), a synthetic glucocorticoid, has been widely used as a medication for premature delivery. However, the side effects of antenatal DEX treatment on fetal bone development, as well as the underlying mechanisms still remain to be elucidated. Here, we aimed to explore the effects and the related mechanisms of antenatal DEX exposure during late pregnancy on fetal bone growth and development.

METHODS

Pregnant Sprague-Dawley rats were randomly divided into DEX group and vehicle group from gestational day 14 (GD14). Pregnant rats in DEX group were intraperitoneally injected once with DEX (200 µg/kg body weight) on GD14, 16, 18, and 20. The vehicle group rats were administered the same amount of normal saline at the same time. Pregnant rats were anesthetized at GD21 to harvest fetal femurs for analysis.

RESULTS

Antenatal DEX treatment delayed fetal skeletal growth via inhibiting extracellular matrix (ECM) synthesis and downregulating insulin-like growth factor 1 (IGF1) signaling. Several components of IGF1 signaling pathway, including IGF1 receptor, insulin receptor substrate, as well as serine-threonine protein kinase, were down-regulated in fetal growth plate chondrocytes following DEX treatment.

CONCLUSION

This study indicated that antenatal DEX treatment-retarded fetal skeletal growth was associated with the down-regulation of IGF1 signaling in growth plate chondrocytes, providing important information about the impact of antenatal DEX application four courses on premature infant.

Effects of Alendronate and Dexamethasone on Osteoclast Gene Expression and Bone Resorption in Mouse Marrow Cultures

Osteoclasts are cells whose main function is the resorption of bone matrix. However, several factors, including medications, can interfere with the resorption process. Alendronate (ALN), a nitrogen-containing type of bisphosphonate, and dexamethasone (DEX), a glucocorticoid, are drugs that may affect the resorption activity. The aim of this study is to investigate the effects of ALN, and/or DEX on osteoclast gene expression and resorption activity in primary mouse marrow cultures stimulated with 1,25-dihydroxyvitamin D3, a model for the bone microenvironment. Cultures were treated only with ALN (10^-5 M), DEX (10^-6 M), and with a combination of both agents. Viability assays performed at days 5, 7, and 9 showed the highest number of viable cells at day 7. All the following assays were then performed at day 7 of cell culture: tartrate resistant acid phosphatase (TRAP) histochemistry, receptor activator of nuclear factor kappa B ligand (RANKL) immunofluorescence, osteoprotegerin (OPG), and RANKL gene expression by qPCR and resorption analysis by scanning electron microscopy. Treatment with ALN, DEX, and the combination of both did not promote significant changes in the number of TRAP+ cells, although larger giant cells were detected in groups treated with DEX. DEX treatment increased the gene expression of RANKL and reduced OPG. The treatment with ALN reduced the depth of the resorption pits, but their inhibitory effect was less effective when administered with DEX.

Dilemmas in the Management of Osteoporosis in Younger Adults

Osteoporosis in premenopausal women and men younger than 50 years is challenging to diagnose and treat. There are many barriers to optimal management of osteoporosis in younger adults, further enhanced by a limited research focus on this cohort. Herein we describe dilemmas commonly encountered in diagnosis, investigation, and management of osteoporosis in younger adults. We also provide a suggested framework, based on the limited available evidence and supported by clinical experience, for the diagnosis, assessment, and management of osteoporosis in this cohort. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

[Glucocorticoid-induced osteoporosis-Focus treatment (part 1)]

With a fracture prevalence of 30-50%, glucocorticoid (GC)-induced osteoporosis is one of the most important comorbidities in inflammatory rheumatic diseases. Because of a reduction of bone quality with a lack of correlation with bone mineral density, the fracture risk during long-term GC treatment is not sufficiently represented by the currently available methods of osteodensitometry and therefore underestimated. According to the Confederation for Osteology (DVO) guidelines, a baseline osteological diagnosis including osteodensitometry is indicated in all postmenopausal women and in men aged 60 years and older who receive or are scheduled to receive GC at a dose of ≥ 2.5 mg prednisolone equivalent/day for > 3 months. Basic measures in GC-treated patients include vitamin D and calcium supplementation as well as measures to promote muscle strength and coordination and to prevent falls. The indications for a specific osteological treatment depend on the calculated GC dose, age, sex, and other fracture risk factors in addition to bone mineral density and prevalent fractures.

Systemic effects of abnormal bone resorption on muscle, metabolism, and cognition

Skeletal tissue is dynamic, undergoing constant remodeling to maintain musculoskeletal integrity and balance in the human body. Recent evidence shows that apart from maintaining homeostasis in the local microenvironment, the skeleton systemically affects other tissues. Several cancer-associated and noncancer-associated bone disorders can disrupt the physiological homeostasis locally in the bone microenvironment and indirectly contribute to dysregulation of systemic body function. The systemic effects of bone on the regulation of distant organ function have not been widely explored. Recent evidence suggests that bone can interact with skeletal muscle, pancreas, and brain by releasing factors from mineralized bone matrix. Currently available bone-targeting therapies such as bisphosphonates and denosumab inhibit bone resorption, decrease morbidity associated with bone destruction, and improve survival. Bisphosphonates have been a standard treatment for bone metastases, osteoporosis, and cancer treatment-induced bone diseases. The extraskeletal effects of bisphosphonates on inhibition of tumor growth are known. However, our knowledge of the effects of bisphosphonates on muscle weakness, hyperglycemia, and cognitive defects is currently evolving. To be able to identify the molecular link between bone and distant organs during abnormal bone resorption and then treat these abnormalities and prevent their systemic effects could improve survival benefits. The current review highlights the link between bone resorption and its systemic effects on muscle, pancreas, and brain.

Bad to the Bone: The Effects of Therapeutic Glucocorticoids on Osteoblasts and Osteocytes

Despite the continued development of specialized immunosuppressive therapies in the form of monoclonal antibodies, glucocorticoids remain a mainstay in the treatment of rheumatological and auto-inflammatory disorders. Therapeutic glucocorticoids are unmatched in the breadth of their immunosuppressive properties and deliver their anti-inflammatory effects at unparalleled speed. However, long-term exposure to therapeutic doses of glucocorticoids decreases bone mass and increases the risk of fractures - particularly in the spine - thus limiting their clinical use. Due to the abundant expression of glucocorticoid receptors across all skeletal cell populations and their respective progenitors, therapeutic glucocorticoids affect skeletal quality through a plethora of cellular targets and molecular mechanisms. However, recent evidence from rodent studies, supported by clinical data, highlights the considerable role of cells of the osteoblast lineage in the pathogenesis of glucocorticoid-induced osteoporosis: it is now appreciated that cells of the osteoblast lineage are key targets of therapeutic glucocorticoids and have an outsized role in mediating their undesirable skeletal effects. As part of this article, we review the molecular mechanisms underpinning the detrimental effects of supraphysiological levels of glucocorticoids on cells of the osteoblast lineage including osteocytes and highlight the clinical implications of recent discoveries in the field.

Role of Macrophages and Plasminogen Activator Inhibitor-1 in Delayed Bone Repair Induced by Glucocorticoids in Mice

Glucocorticoids delay fracture healing and induce osteoporosis. However, the mechanisms by which glucocorticoids delay bone repair have yet to be clarified. Plasminogen activator inhibitor-1 (PAI-1) is the principal inhibitor of plasminogen activators and an adipocytokine that regulates metabolism. We herein investigated the roles of macrophages in glucocorticoid-induced delays in bone repair after femoral bone injury using PAI-1-deficient female mice intraperitoneally administered with dexamethasone (Dex). Dex significantly decreased the number of F4/80-positive macrophages at the damaged site two days after femoral bone injury. It also attenuated bone injury-induced decreases in the number of hematopoietic stem cells in bone marrow in wild-type and PAI-1-deficient mice. PAI-1 deficiency significantly weakened Dex-induced decreases in macrophage number and macrophage colony-stimulating factor (M-CSF) mRNA levels at the damaged site two days after bone injury. It also significantly ameliorated the Dex-induced inhibition of macrophage phagocytosis at the damaged site. In conclusion, we herein demonstrated that Dex decreased the number of macrophages at the damaged site during early bone repair after femoral bone injury partly through PAI-1 and M-CSF in mice.

Effect of adrenocorticotropic hormone infusion on circulating sclerostin levels

Glucocorticoid use is the most common cause of secondary osteoporosis. Poor skeletal health related to glucocorticoid use is thought to involve inhibition of the Wnt/β-catenin signaling pathway, a key pathway in osteoblastogenesis. Sclerostin, a peptide produced primarily by osteocytes, is an antagonist of the Wnt/β-catenin signaling pathway, raising the possibility that sclerostin is involved in glucocorticoids' adverse effects on bone. The aim of this study was to determine whether an acute infusion of cosyntropin (i.e. ACTH(1-24)), which increases endogenous cortisol, increases serum sclerostin levels as compared to a placebo infusion. This study was performed using blood samples obtained from a previously published, double-blind, placebo-controlled, randomized, cross-over study among healthy men and women who received infusions of placebo or cosyntropin after being supine and fasted overnight (ClinicalTrials.gov NCT02339506). A total of 17 participants were analyzed. There was a strong correlation (R2 = 0.65, P < 0.0001) between the two baseline sclerostin measurements measured at the start of each visit, and men had a significantly higher average baseline sclerostin compared to women. As anticipated, cosyntropin significantly increased serum cortisol levels, whereas cortisol levels fell during placebo infusion, consistent with the diurnal variation in cortisol. There was no significant effect of cosyntropin as compared to placebo infusions on serum sclerostin over 6-24 h (P = 0.10). In conclusion, this randomized, placebo-controlled study was unable to detect a significant effect of a cosyntropin infusion on serum sclerostin levels in healthy men and women.

The skeletal consequences of epidural steroid injections: a literature review

This literature review summarized studies that evaluated the effects of epidural steroid injections (ESIs) on skeletal health. While evidence is limited, studies suggest that ESIs may cause bone loss. Better understanding of these skeletal consequences will help foster strategies to prevent bone loss in the growing population of patients receiving ESIs.

PURPOSE

Approximately nine million epidural steroid injections (ESIs) are administered annually in the United States to treat radicular back pain. ESIs often provide pain relief and functional improvement. While the overall incidence of adverse events resulting from ESIs is low, their effects on the skeleton are poorly understood. This is an important consideration given the profound skeletal impact of other forms of glucocorticoids.

METHODS

Ovid MEDLINE and PubMed search results since 2010, including older, frequently referenced publications were reviewed.

RESULTS

Systemic absorption of glucocorticoids occurs after ESI, which can cause hyperglycemia and endogenous cortisol suppression. The majority of studies investigating the skeletal effects of ESIs are retrospective. Several have found a relationship between low areal bone mineral density (BMD) by dual-energy x-ray absorptiometry and ESI exposure, but this finding is not uniform. Recently a dose-response relationship between ESI exposure and low spine volumetric BMD by computed tomography has been reported. Few studies have investigated the relationship between ESI exposure and fracture risk. Results of these studies are conflicting, and most have not been adequately powered to detect fracture outcomes.

CONCLUSIONS

While evidence is limited, studies suggest that ESIs may cause bone loss, particularly those investigating volumetric BMD. Larger doses appear to confer greater risk. Further prospective studies are needed to investigate the relationship between ESI and fracture risk. Better understanding of the skeletal consequences of ESIs will help foster strategies to prevent bone loss in the growing population of patients receiving this treatment.

25-hydroxycholecalciferol reverses heat induced alterations in bone quality in finisher broilers associated with effects on intestinal integrity and inflammation

BACKGROUND

Alterations in ambient temperature have been associated with multiple detrimental effects on broilers such as intestinal barrier disruption and dysbiosis resulting in systemic inflammation. Inflammation and 25-hydroxycholecalciferol (25-OH-D₃) have shown to play a negative and positive role, respectively, in the regulation of bone mass. Hence the potential of 25-OH-D₃ in alleviating heat induced bone alterations and its mechanisms was studied.

RESULTS

Heat stress (HS) directly induced a decrease in tibia material properties and bone mass, as demonstrated by lower mineral content, and HS caused a notable increase in intestinal permeability. Treatment with dietary 25-OH-D₃ reversed the HS-induced bone loss and barrier leak. Broilers suffering from HS exhibited dysbiosis and increased expression of inflammatory cytokines in the ileum and bone marrow, as well as increased osteoclast number and activity. The changes were prevented by dietary 25-OH-D₃ administration. Specifically, dietary 25-OH-D₃ addition decreased abundance of B- and T-cells in blood, and the expression of inflammatory cytokines, especially TNF-α, in both the ileum and bone marrow, but did not alter the diversity and population or composition of major bacterial phyla. With regard to bone remodeling, dietary 25-OH-D₃ supplementation was linked to a decrease in serum C-terminal cross-linked telopeptide of type I collagen reflecting bone resorption and a concomitant decrement in osteoclast-specific marker genes expression (e.g. cathepsin K), whereas it did not apparently change serum bone formation markers during HS.

CONCLUSIONS

These data underscore the damage of HS to intestinal integrity and bone health, as well as that dietary 25-OH-D₃ supplementation was identified as a potential therapy for preventing these adverse effects.

Loss of glucocorticoid rhythm induces an osteoporotic phenotype in female mice

Glucocorticoid (GC)-induced osteoporosis is a widespread health problem that is accompanied with increased fracture risk. Detrimental effects of anti-inflammatory GC therapy on bone have been ascribed to the excess in GC exposure, but it is unknown whether there is also a role for disruption of the endogenous GC rhythm that is inherent to GC therapy. To investigate this, we implanted female C57Bl/6J mice with slow-release corticosterone (CORT) pellets to blunt the rhythm in CORT levels without inducing hypercortisolism. Flattening of CORT rhythm reduced cortical and trabecular bone volume and thickness, whilst bone structure was maintained in mice injected with supraphysiologic CORT at the time of their endogenous GC peak. Mechanistically, mice with a flattened CORT rhythm showed disrupted circadian gene expression patterns in bone, along with changes in circulating bone turnover markers indicative of a negative balance in bone remodelling. Indeed, double calcein labelling of bone in vivo revealed a reduced bone formation in mice with a flattened CORT rhythm. Collectively, these perturbations in bone turnover and structure decreased bone strength and stiffness, as determined by mechanical testing. In conclusion, we demonstrate for the first time that flattening of the GC rhythm disrupts the circadian clock in bone and results in an osteoporotic phenotype in mice. Our findings indicate that at least part of the fracture risk associated with GC therapy may be the consequence of a disturbed GC rhythm, rather than excess GC exposure alone, and that a dampened GC rhythm may contribute to the age-related risk of osteoporosis.

Glucocorticoid-induced osteonecrosis in systemic lupus erythematosus patients

Osteonecrosis (ON) is a complex and multifactorial complication of systemic lupus erythematosus (SLE). ON is a devastating condition that causes severe pain and compromises the quality of life. The prevalence of ON in SLE patients is variable, ranging from 1.7% to 52%. However, the pathophysiology and risk factors for ON in patients with SLE have not yet been fully determined. Several mechanisms for SLE patients' propensity to develop ON have been proposed. Glucocorticoid is a widely used therapeutic option for SLE patients and high-dose glucocorticoid therapy in SLE patients is strongly associated with the development of ON. Although the hips and knees are the most commonly affected areas, it may be present at multiple anatomical locations. Clinically, ON often remains undetected until patients feel discomfort and pain at specific sites at which point the process of bone death is already advanced. However, strategies for prevention and options for treatment are limited. Here, we review the epidemiology, risk factors, diagnosis, and treatment options for glucocorticoid-induced ON, with a specific focus on patients with SLE.

A Neuroprotective Bovine Colostrum Attenuates Apoptosis in Dexamethasone-Treated MC3T3-E1 Osteoblastic Cells

Glucocorticoid-induced osteoporosis (GIO) is one of the most common secondary forms of osteoporosis. GIO is partially due to the apoptosis of osteoblasts and osteocytes. In addition, high doses of dexamethasone (DEX), a synthetic glucocorticoid receptor agonist, induces neurodegeneration by initiating inflammatory processes leading to neural apoptosis. Here, a neuroprotective bovine colostrum against glucocorticoid-induced neuronal damage was investigated for its anti-apoptotic activity in glucocorticoid-treated MC3T3-E1 osteoblastic cells. A model of apoptotic osteoblastic cells was developed by exposing MC3T3-E1 cells to DEX (0-700 μM). Colostrum co-treated with DEX was executed at 0.1-5.0 mg/mL. Cell viability was measured for all treatment schedules. Caspase-3 activation was assessed to determine both osteoblast apoptosis under DEX exposure and its potential prevention by colostrum co-treatment. Glutathione reduced (GSH) was measured to determine whether DEX-mediated oxidative stress-driven apoptosis is alleviated by colostrum co-treatment. Western blot was performed to determine the levels of p-ERK1/2, Bcl-XL, Bax, and Hsp70 proteins upon DEX or DEX plus colostrum exposure. Colostrum prevented the decrease in cell viability and the increase in caspase-3 activation and oxidative stress caused by DEX exposure. Cells, upon colostrum co-treated with DEX, exhibited higher levels of p-ERK1/2 and lower levels of Bcl-XL, Bax, and Hsp70. Our data support the notion that colostrum may be able to reduce DEX-induced apoptosis possibly via the activation of the ERK pathway and modulation of the Hsp70 system. We provided preliminary evidence on how bovine colostrum, as a complex and multi-component dairy product, in addition to its neuroprotective action, may affect osteoblastic cell survival undergoing apoptosis.

Ferulic acid attenuates osteoporosis induced by glucocorticoid through regulating the GSK-3β/Lrp-5/ERK signalling pathways

Objective

To evaluate in-vivo and in-vitro effects of ferulic acid (FA) on glucocorticoid-induced osteoarthritis (GIO) to establish its possible underlying mechanisms.

Methods

The effects of FA on cell proliferation, cell viability (MTT assay), ALP activity, and mineralization assay, and oxidative stress markers (ROS, SOD, GSH LDH and MDA levels) were investigated by MC3T3-E1 cell line. Wistar rats received standard saline (control group) or dexamethasone (GC, 2 mg-1 kg) or DEX+FA (50 and 100 mg-1 kg) orally for 8 weeks. Bone density, micro-architecture, bio-mechanics, bone turnover markers and histo-morphology were determined. The expression of OPG, RANKL, osteogenic markers, and other signalling proteins was assessed employing quantitative RT-PCR and Western blotting.

Results

The findings indicated the elevation of ALP mRNA expressions, osteogenic markers (Runx-2, OSX, Col-I, and OSN), and the β-Catenin, Lrp-5 and GSK-3β protein expressions. FA showed the potential to increase MC3T3-E1 cell differentiation, proliferation, and mineralization. FA increased oxidative stress markers (SOD, MDA, and GSH) while decreasing ROS levels and lactate dehydrogenase release in GIO rats. The OPG/RANKL mRNA expression ratio was increased by FA, followed by improved GSK-3β and ERK phosphorylation with enhanced mRNA expressions of Lrp-5 and β-catenin.

Conclusion

These findings showed that FA improved osteoblasts proliferation with oxidative stress suppression by controlling the Lrp-5/GSK-3β/ERK pathway in GIO, demonstrating the potential pathways involved in the mechanism of actions of FA in GIO therapy.

Risk of Fractures and Other Injuries in Children Treated with Antiseizure Medications for Epilepsy

This study aimed to investigate the prevalence of fractures and non-fracture injuries, including associated risk factors, in children with epilepsy prescribed antiseizure medications (ASM). A controlled, cross-sectional study was conducted in a hospital outpatient setting, comparing children with epilepsy prescribed ASMs with their non-epileptic siblings. Information was collected by questionnaire included history of fractures, non-fracture injuries and epilepsy, comorbidities and ASM use. 261 participants completed the questionnaire, 133 children with epilepsy (aged 10.7 ± 3.5 years, mean ± SD) and 128 siblings (10.1 ± 3.7 years). There were 49 non-seizure-related fractures in 34 ASM patients while prescribed ASMs, compared with 21 lifetime fractures in 15 controls, giving a 2.7 (95% CI 1.3-5.3, p = 0.007) times greater fracture prevalence in children treated with ASMs compared to healthy siblings. The rates of non-fracture injuries were similar across groups, except that concussion was more common in children taking ASMs (9.0% vs 1.6%, p = 0.026). Duration of ASM use and generalized tonic-clonic seizures (GTCS) were independent predictors of fractures (OR 1.55; 95% CI 1.03-2.31, p = 0.03; OR 2.50; 95% CI 1.05-5.94, p = 0.04, respectively). Fewer than 20% of participants and/or their families were aware that ASM use was related to bone health. Children with epilepsy treated with ASMs had a higher fracture prevalence than their sibling controls. Duration of ASM treatment and GTCS were associated with fracture risk. Longitudinal prospective studies are required to further explore risk and the direct impact of epilepsy on bone health.

Lycii radicis cortex inhibits glucocorticoid‑induced bone loss by downregulating Runx2 and BMP‑2 expression

Lycii radicis cortex (LRC) has been used to regulate high blood pressure, body temperature, pain and bone disorders in East Asia. Glucocorticoids (GCs), also known as steroids, are potent immunity regulators widely used in the treatment of inflammatory diseases. However, despite their effectiveness, GC usage is strictly controlled due to severe side‑effects, such as osteoporosis. However, further research is required as to date, at least to the best of our knowledge, there is no appropriate model to overcome secondary osteoporosis as a side‑effect of GC use. Thus, the aim of the present study was to establish an experimental model of osteoporosis induced by GC. Furthermore, the present study aimed to establish the research methodology for medical evaluations of the effectiveness and side‑effects of GCs. A secondary osteoporosis animal model was established, and the animals were divided into two groups as follows: The allergic contact dermatitis (ACD)‑induced group and the non‑ACD‑induced group. In the ACD‑induced group, a GC topical application group was compared with a GC subcutaneous injection group. The results revealed that the presence of ACD affected the induction of GC‑mediated osteoporosis. Therefore, the group exhibiting induced ACD that was treated with a topical application of GC was selected for examining the side‑effects of GCs. The effects of LRC on secondary osteoporosis were confirmed in vivo and in vitro. The results indicated that LRC regulated dexamethasone‑induced osteoblast apoptotic markers, including caspase‑6, caspase‑9, X‑linked inhibitor of apoptosis, apoptosis inhibitor 1 and apoptosis inhibitor 2, and increased the expression of osteoblast differentiation‑related genes, such as Runt‑related transcription factor 2 and bone morphogenetic protein 2 in the MC3T3E‑1 cell line. LRC also significantly reduced GC‑induced osteoporosis and exerted anti‑inflammatory effects in vivo. In addition, LRC inhibited the reduction of calbindin‑D28k in the kidney. Overall, the results of the present study suggest that the use of LRC alleviates GC‑induced secondary osteoporosis.

Evaluation of Dexamethasone-Induced Osteoporosis In Vivo Using Zebrafish Scales

Glucocorticoid-induced osteoporosis (GIOP) is a major cause of secondary osteoporosis, and the pathogenic mechanisms of GIOP remain to be elucidated. Here, we show a rapid dexamethasone-induced osteoporosis animal model using zebrafish scales. Intraperitoneal injection of dexamethasone over a 5-day period suppressed the regeneration of scales. Furthermore, the circularity of the newly formed regenerated scales was also slightly reduced compared to that of the control group on day 5. The changes in bone-related enzymes, such as cathepsin K, tartrate-resistant acid phosphatase (TRAP) for bone resorption, and alkaline phosphatase (ALP) for bone formation, provide insight into the progression of bone diseases; therefore, we further developed a method to measure the activities of cathepsin K, TRAP, and ALP using zebrafish scales. We found that a lysis buffer with detergent at neutral pH under sonication efficiently helped extract these three enzymes with high activity levels. Interestingly, treatment with a dexamethasone injection produced considerably higher levels of cathepsin K activity and a lower Ca/P ratio than those in the control group, suggesting that dexamethasone increased osteoclast activity, with no significant changes in the activities of TRAP and ALP. Our GIOP model and enzyme assay method could help to design better treatments for GIOP.

Dexamethasone Induces Changes in Osteogenic Differentiation of Human Mesenchymal Stromal Cells via SOX9 and PPARG, but Not RUNX2

Despite the huge body of research on osteogenic differentiation and bone tissue engineering, the translation potential of in vitro results still does not match the effort employed. One reason might be that the protocols used for in vitro research have inherent pitfalls. The synthetic glucocorticoid dexamethasone is commonly used in protocols for trilineage differentiation of human bone marrow mesenchymal stromal cells (hBMSCs). However, in the case of osteogenic commitment, dexamethasone has the main pitfall of inhibiting terminal osteoblast differentiation, and its pro-adipogenic effect is well known. In this work, we aimed to clarify the role of dexamethasone in the osteogenesis of hBMSCs, with a particular focus on off-target differentiation. The results showed that dexamethasone does induce osteogenic differentiation by inhibiting SOX9 expression, but not directly through RUNX2 upregulation as it is commonly thought. Rather, PPARG is concomitantly and strongly upregulated, leading to the formation of adipocyte-like cells within osteogenic cultures. Limiting the exposure to dexamethasone to the first week of differentiation did not affect the mineralization potential. Gene expression levels of RUNX2, SOX9, and PPARG were simulated using approximate Bayesian computation based on a simplified theoretical model, which was able to reproduce the observed experimental trends but with a different range of responses, indicating that other factors should be integrated to fully understand how dexamethasone influences cell fate. In summary, this work provides evidence that current in vitro differentiation protocols based on dexamethasone do not represent a good model, and further research is warranted in this field.

The bone bridge significantly affects the decrease in bone mineral density measured with quantitative computed tomography in ankylosing spondylitis

INTRODUCTION AND OBJECTIVE

Ankylosing spondylitis (AS) has characteristics of spinal bone bridge and fusion. Although BMD reduction in AS may be presumed to be due to spinal inflammation, this study was designed to confirm whether immobilization of the spine due to syndesmophytes is related to BMD reduction, as immobilization itself is a risk factor for BMD reduction.

METHODS

Among male patients diagnosed with AS according to the modified New York criteria, those who underwent bone density tests with quantitative computed tomography (QCT) were retrospectively analyzed through a chart review. The correlation between the presence or absence of bone bridges for each vertebral body level of the L spine confirmed with radiography and BMD confirmed with QCT was analyzed.

RESULTS

A total of 47 male patients with AS were enrolled. The mean patient age was 46.8 ± 8.2 years, and the mean disease duration was 7.9 ± 6.4 years. The trabecular BMD of the lumbar spine (L1-L4) ranged from 23.1 to 158.45 mg/cm3 (mean 102.2 ± 37 mg/cm3), as measured with QCT. The lumbar BMD measurements showed that 30 patients (63.8%) had osteopenia or osteoporosis. Bone bridge formation showed a negative correlation with BMD. Low BMD was significantly correlated with bone bridge in the vertebral body (p < 0.05). Positive correlations were observed between bone bridge score and BASMI flexion score, whereas significant negative correlations were found between BMD and BASMI flexion score (p < 0.05).

CONCLUSION

Decreased mobility of the vertebrae due to bone bridge formation affects the decrease in BMD in patients with AS.

Paeoniflorin Attenuates Dexamethasone-Induced Apoptosis of Osteoblast Cells and Promotes Bone Formation via Regulating AKT/mTOR/Autophagy Signaling Pathway

Paeoniflorin, a natural product derived from Paeonia lactiflora, possesses diverse pharmacological activities such as anti-inflammatory, antitumor, and antidiabetic effects. It has been reported for promoting osteoblastogenesis and inhibiting osteoclastogenesis. This study investigates the therapeutic effects of paeoniflorin in glucocorticoid-induced osteoporosis (GIOP) in vitro and in vivo. MC3T3-E1 cells were incubated with dexamethasone (DEX; 200 μM) and/or paeoniflorin (10 μM), followed by the investigation of cell proliferation, differentiation, mineralization, apoptosis, and autophagy. The AKT activator SC79 was used for evaluating the involvement of the AKT/mTOR signaling pathway. After DEX pretreatments, paeoniflorin promoted osteoblast differentiation and mineralization characterized by increase in Runx2, ALP, beclin-1, and LC3-II/LC3-I ratio levels and a decrease in apoptosis. The autophagy-promoting effects of paeoniflorin were reversed by SC79. C57BL/6 mice were given DEX (1 mg/kg) once daily and paeoniflorin (15 mg/kg) 48 hours for a total of 8 weeks followed by the investigation of histological changes, the trabecular bone microarchitecture, and the levels of bone turnover markers. The results showed that paeoniflorin increased alkaline phosphatase (ALP) activity and upregulated the expression of osteocalcin and beclin-1 but reduced the levels of Bax and C-terminal telopeptide of type I collagen (CTX-1). Thus, paeoniflorin may alleviate DEX-induced osteoporosis by promoting osteogenic differentiation and autophagy via inhibition of the AKT/mTOR signaling pathway.

The PPAR-γ/SFRP5/Wnt/β-catenin signal axis regulates the dexamethasone-induced osteoporosis

BACKGROUND

The inhibition of glucocorticoid (GC) on osteoblastic differentiation of bone marrow stromal stem cells (BMSC) is an important pathway for GC to reduce bone formation. Recent studies implicated an important role of peroxisome proliferator-activated receptor-gamma (PPAR-γ) in GC-mediated cell proliferation and differentiation. Thus, our purpose is to investigate the role of PPAR-γ in regulating rat BMSC (rBMSC) osteoblastic differentiation.

METHODS

The rBMSC treated with dexamethasone (Dex) was used to construct an in vitro cell model of GC-induced osteoporosis. The expressions of PPAR-γ, RUNX2, ALP, OPN and SFRP5 in cells were detected by RT-qPCR and western blot assays. Osteogenic differentiation of rBMSC was measured by Alizarin Red S (ARS) staining analysis. Lentivirus-delivered shRNA was used to knock down PPAR-γ or SFRP5, and lentivirus-delivered constructs were used to overexpress SFRP5 in rBMSC to verify the effect of PPAR-γ or SFRP5 on cell osteogenic differentiation.

RESULTS

Dex significantly reduced rBMSC osteoblastic differentiation. The expression of PPAR-γ was enhanced in Dex treated rBMSC. PPAR-γ down-regulation improved Dex inhibition of rBMSC osteogenic differentiation. Moreover, PPAR-γ knockdown promoted protein levels of RUNX2, ALP, OPN and Dex-decreased rBMSC osteogenic differentiation. The expression of SFRP5 was reduced while Wnt and β-catenin were increased in PPAR-γ knockdown and Dex treated rBMSC. Moreover, the up-regulation of SFRP5 reversed the osteogenic differentiation of rBMSC induced by PPAR-γ knockdown.

CONCLUSION

These data indicated that in GC-induced osteoporosis, PPAR-γ/SFRP5 affects osteogenic differentiation by regulating the Wnt/β-catenin signaling pathway.

Osteoclasts protect bone blood vessels against senescence through the angiogenin/plexin-B2 axis

Synthetic glucocorticoids (GCs), one of the most effective treatments for chronic inflammatory and autoimmune conditions in children, have adverse effects on the growing skeleton. GCs inhibit angiogenesis in growing bone, but the underlying mechanisms remain unclear. Here, we show that GC treatment in young mice induces vascular endothelial cell senescence in metaphysis of long bone, and that inhibition of endothelial cell senescence improves GC-impaired bone angiogenesis with coupled osteogenesis. We identify angiogenin (ANG), a ribonuclease with pro-angiogenic activity, secreted by osteoclasts as a key factor for protecting the neighboring vascular cells against senescence. ANG maintains the proliferative activity of endothelial cells through plexin-B2 (PLXNB2)-mediated transcription of ribosomal RNA (rRNA). GC treatment inhibits ANG production by suppressing osteoclast formation in metaphysis, resulting in impaired endothelial cell rRNA transcription and subsequent cellular senescence. These findings reveal the role of metaphyseal blood vessel senescence in mediating the action of GCs on growing skeleton and establish the ANG/PLXNB2 axis as a molecular basis for the osteoclast-vascular interplay in skeletal angiogenesis.

Glucocorticoid-induced autophagy and apoptosis in bone

Glucocorticoids are widely prescribed to treat various allergic and autoimmune diseases; however, long-term use results in glucocorticoid-induced osteoporosis, characterized by consistent changes in bone remodeling with decreased bone formation as well as increased bone resorption. Not only bone mass but also bone quality decrease, resulting in an increased incidence of fractures. The primary role of autophagy is to clear up damaged cellular components such as long-lived proteins and organelles, thus participating in the conservation of different cells. Apoptosis is the physiological death of cells, and plays a crucial role in the stability of the environment inside a tissue. Available basic and clinical studies indicate that autophagy and apoptosis induced by glucocorticoids can regulate bone metabolism through complex mechanisms. In this review, we summarize the relationship between apoptosis, autophagy and bone metabolism related to glucocorticoids, providing a theoretical basis for therapeutic targets to rescue bone mass and bone quality in glucocorticoid-induced osteoporosis.

Effects of dietary supplementation of a probiotic (Bacillus subtilis) on bone mass and meat quality of broiler chickens

The aim of this study was to investigate the effect of a dietary probiotic supplement on bone mass and meat quality of broiler chickens. Two hundred ten 1-day-old male Ross 708 broiler chicks were divided among 21 floor pens (10 chicks per pen). The pens were randomly distributed to 1 of 3 dietary treatments containing a probiotic, Bacillus subtilis, at 0 (control), 0.25 (0.25X), and 0.5 (0.5X) g/kg (n = 7). Gait score, footpad dermatitis (FPD), leg straightness, and hock burn (HB) were examined at day 33, and a latency-to-lie test was performed at day 34. At the end of the experiment (day 35), plasma, right leg, and litter samples were collected for mineral contents, meat quality, bone morphometric parameters, and litter quality assessments. The results indicated that probiotic-fed birds stood much longer during the latency-to-lie test with a greater tibial length, weight, and strength as well as higher plasma levels of calcium and phosphorus compared with the controls. In addition, probiotic-fed birds' leg muscle had higher color lightness at both 30 min and 5 h postmortem and greater water-holding capacity with a trend for less cooking loss (P = 0.056) and lower pH values (P < 0.05) at 5 h postmortem. Probiotic-fed birds' leg meat was tastier (P < 0.05) at 24 h after slaughter. These probiotic effects were greater in the 0.5X group than in the 0.25X group. There were no treatment effects on other measured parameters including gait score, HB, FPD, tibial lateral and medial wall thickness, diaphysis and medullary canal diameters, robusticity and tibiotarsal indexes, plasma magnesium concentrations, and litter moisture and pH values (P > 0.05). These findings indicate that the probiotic supplement could be a useful management tool for improving broiler production and welfare by enhanced bone mass and meat quality.

Cycloastragenol protects against glucocorticoid-induced osteogenic differentiation inhibition by activating telomerase

Glucocorticoid-induced osteoporosis (GIOP) that is mainly featured as low bone density and increased risk of fracture is prone to occur with the administration of excessive glucocorticoids. Cycloastragenol (CAG) has been verified to be a small molecule that activates telomerase. Studied showed that up-regulated telomerase was associated with promoting osteogeneic differentiation, so we explored whether CAG could promote osteogenic differentiation to protect against GIOP and telomerase would be the target that CAG exerted its function. Our results demonstrated that CAG prominently increased the ALP activity, mineralization, mRNA of runt-related transcription factor 2, osteocalcin, osteopontin, collagen type I in both MC3T3-E1 cells and dexamethasone (DEX)-treated MC3T3-E1 cells. CAG up-regulated telomerase reverse transcriptase and the protective effect of CAG was blocked by telomerase inhibitor TMPyP4. Moreover, CAG improved bone mineralization in DEX-induced bone damage in a zebrafish larvea model. Therefore, the study showed that CAG could alleviate the osteogenic differentiation inhibition induced by DEX in vitro and in vivo, and CAG might be considered as a candidate drug for the treatment of GIOP.

Arthritis and the role of endogenous glucocorticoids

Rheumatoid arthritis and osteoarthritis, the most common forms of arthritis, are chronic, painful, and disabling conditions. Although both diseases differ in etiology, they manifest in progressive joint destruction characterized by pathological changes in the articular cartilage, bone, and synovium. While the potent anti-inflammatory properties of therapeutic (i.e., exogenous) glucocorticoids have been heavily researched and are widely used in clinical practice, the role of endogenous glucocorticoids in arthritis susceptibility and disease progression remains poorly understood. Current evidence from mouse models suggests that local endogenous glucocorticoid signaling is upregulated by the pro-inflammatory microenvironment in rheumatoid arthritis and by aging-related mechanisms in osteoarthritis. Furthermore, these models indicate that endogenous glucocorticoid signaling in macrophages, mast cells, and chondrocytes has anti-inflammatory effects, while signaling in fibroblast-like synoviocytes, myocytes, osteoblasts, and osteocytes has pro-inflammatory actions in rheumatoid arthritis. Conversely, in osteoarthritis, endogenous glucocorticoid signaling in both osteoblasts and chondrocytes has destructive actions. Together these studies provide insights into the role of endogenous glucocorticoids in the pathogenesis of both inflammatory and degenerative joint disease.

Short-Term Glucocorticoid Treatment Reduces Circulating Sclerostin Concentrations in Healthy Young Men: A Randomized, Placebo-Controlled, Double-Blind Study

Glucocorticoid use is the most common cause of osteoporosis in young individuals. In the current study, we investigated the effects of glucocorticoid treatment on circulating sclerostin concentrations and serum bone turnover markers in healthy young men. We performed additional measurements in two combined randomized, placebo‐controlled, double‐blind, dose–response intervention studies: 64 healthy men (age: 22 ± 2 years; BMI: 22.1 ± 1.7 kg/m²) were allocated to receive placebo (n = 16), prednisolone 7.5 mg once daily (n = 24), or prednisolone 30 mg once daily (n = 24) for 2 weeks using block randomization. Primary outcome variables were serum sclerostin and serum bone turnover markers (CTx and P1NP), before and after the intervention. Baseline characteristics and variables did not differ between intervention groups. Compared with placebo, prednisolone high‐dose decreased serum sclerostin concentrations (−8.5 [−28.0 to 7.3] versus 1.5 [−6.5 to 20.0] pg/mL, p = 0.048), decreased P1NP concentrations (−28.0 [−39.3 to −18.3] versus –1.5 [−15.3 to 11.3] μg/L, p < 0.001) and increased CTx concentrations (108.0 [55.0 to 177.0] versus 64.0 [−24.3 to 120.0] ng/L, p = 0.038). Compared with placebo, prednisolone low‐dose did not alter sclerostin concentrations (p = 0.5) or CTx concentrations (p = 0.7), but tended to decrease P1NP concentrations (−9.0 [−24.0 to −1.3] versus –1.5 [−15.3 to 11.3] μg/L, p = 0.095). At baseline concentrations of sclerostin were positively correlated with concentrations of CTx (Spearman's rank correlation coefficient ρ = +0.409, p = 0.001), but not with P1NP. No significant correlations were observed between changes in outcome variables during the interventions. Short‐term high‐dose, but not low‐dose, prednisolone treatment reduces serum sclerostin concentrations in healthy young men. Whether this reflects a counter regulatory mechanism to compensate glucocorticoid‐induced negative effects through other mechanisms remains to be elucidated. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Nuclear receptors in osteoclasts

Osteoclasts are bone-resorbing cells that play an essential role in the remodeling of bone under physiological conditions and numerous pathological conditions, such as osteoporosis, bone metastasis, and inflammatory bone erosion. Nuclear receptors are crucial to various physiological processes, including metabolism, development and inflammation, and function as transcription factors to activate target genes. Synthetic ligands of nuclear receptors are also available for the treatment of metabolic and inflammatory diseases. However, dysregulated bone phenotypes have been documented in patients who take synthetic nuclear receptor ligands as a therapy. Therefore, the effect of nuclear receptors on bone cells has become an important area of exploration; additionally, the molecular mechanisms underlying the action of nuclear receptors in osteoclasts have not been completely understood. Here, we cover the recent progress in our understanding of the roles of nuclear receptors in osteoclasts.

Dexras1 plays a pivotal role in maintaining the equilibrium between adipogenesis and osteogenesis

BACKGROUND

Chronic steroid treatment causes an increase in visceral adiposity and osteoporosis. It is believed that steroids may alter a balance between differentiation of mesenchymal stem cells (MSCs) into either adipocytes or osteoblasts; however, the detailed molecular mechanisms are unclear. We previously identified Dexras1 as a critical factor that potentiates adipogenesis in response to glucocorticoids. Thus, in this study, we investigated the role of Dexras1 in maintaining the balance between chronic steroid treatment-associated adipogenesis and osteoporosis.

MATERIAL AND METHODS

We treated wild type (WT) and Dexras1 knockout (KO) mice with dexamethasone for five weeks followed by 60% HFD for additional two weeks with dexamethasone. The changes of glucocorticoid-induced body weight gain and osteoporosis were analyzed. Bone marrow derived stromal cells (BMSCs) and mouse embryonic fibroblasts (MEFs) extracted from WT and Dexras1 KO mice, as well as MC3T3-E1 pre-osteoblasts and osteoclasts differentiated from RAW264.7 were analyzed to further define the role of Dexras1 in osteoblasts and osteoclasts.

RESULTS

Dual-energy X-ray absorptiometry and micro-computed tomography analyses in murine femurs revealed that Dexras1 deficiency was associated with increased osteogenesis, concurrent with reduced adipogenesis. Furthermore, Dexras1 deficiency promoted osteogenesis of BMSCs and MEFs in vitro, suggesting that Dexras1 deficiency prevents steroid-induced osteoporosis. We also observed that Dexras1 downregulated SMAD signaling pathways, which reduced the osteogenic differentiation capacity of pre-osteoblast MC3T3-E1 cells into mature osteoblasts.

CONCLUSION

We propose that Dexras1 is critical for maintaining the equilibrium between adipogenesis and osteogenesis upon steroid treatment.

Nicotinamide mononucleotide attenuates glucocorticoid‑induced osteogenic inhibition by regulating the SIRT1/PGC‑1α signaling pathway

Long-term and high-dose glucocorticoid treatment is recognized as an important influencing factor for osteoporosis and osteonecrosis. Nicotinamide mononucleotide (NMN) is an intermediate of NAD⁺ biosynthesis, and is widely used to replenish the levels of NAD⁺. However, the potential role of NMN in glucocorticoid-induced osteogenic inhibition remains to be demonstrated. In the present study, the protective effects of NMN on dexamethasone (Dex)-induced osteogenic inhibition, and its underlying mechanisms, were investigated. Bone mesenchymal stem cells were treated with Dex, which decreased the levels of the osteogenic markers alkaline phosphatase, Runt-related transcription factor 2 and osteocalcin. NMN treatment attenuated Dex-induced osteogenic inhibition and promoted the expression of sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α. SIRT1 knockdown reversed the protective effects of NMN and reduced the expression levels of PGC-1α. Collectively, the results of the present study reveal that NMN may be a potential therapeutic target for glucocorticoid-induced osteoporosis.

PAI-1 is involved in delayed bone repair induced by glucocorticoids in mice

Glucocorticoid (GC) treatments induce osteoporosis and chronic GC treatments have been suggested to induce delayed bone repair; however, the mechanisms by which GC induces delayed bone repair remain unclear. We herein investigated the roles of plasminogen activator inhibitor-1 (PAI-1) in GC-induced effects on bone repair after femoral bone injury using female mice with a PAI-1 deficiency and their wild-type counterparts. Dexamethasone (Dex) increased plasma PAI-1 levels as well as PAI-1 mRNA levels in the adipose tissues and muscles of wild-type mice. PAI-1 deficiency significantly blunted Dex-induced delayed bone repair in mice. Moreover, PAI-1 deficiency significantly blunted Runx2 mRNA levels suppressed by Dex as well as Dex-induced osteoblast apoptosis at the damaged site 7 days after bone injury in mice. On the other hand, PAI-1 deficiency did not affect adipogenic gene expression enhanced by Dex at the damaged site 7 days after bone injury in mice. In conclusion, we herein showed for the first time that PAI-1 is involved in delayed bone repair after bone injury induced by GC in mice. PAI-1 may influence early stage osteoblast differentiation and apoptosis during the osteoblastic restoration phase of the bone repair process.

Bone Control of Muscle Function

Bone and muscle represent a single functional system and are tightly connected to each other. Indeed, diseases characterized by alterations of muscle physiology have effects on bone remodeling and structure and vice versa. Muscle influence on bone has been deeply studied, and recent studies identified irisin as new molecule involved in this crosstalk. Muscle regulation by bone needs to be extensively investigated since in the last few years osteocalcin was recognized as a key molecule in the bone–muscle interaction. Osteocalcin can exist in two forms with different degrees of carboxylation. The undercarboxylated form of osteocalcin is a hormone released by the bone matrix during the osteoclast bone resorption and can bind its G-protein coupled receptor GPRC6A expressed in the muscle, thus regulating its function. Recently, this hormone was described as an antiaging molecule for its ability to regulate bone, muscle and cognitive functions. Indeed, the features of this bone-related hormone were used to test a new therapeutic approach for sarcopenia, since injection of osteocalcin in older mice induces the acquirement of physical abilities of younger animals. Even if this approach should be tested in humans, osteocalcin represents the most surprising molecule in endocrine regulation by the skeleton.

Osteoporosis Therapeutics 2020

Numerous safe and efficient drug therapies are currently available to decrease risk of low trauma fractures in patients with osteoporosis including postmenopausal, male, and secondary osteoporosis. In this chapter, we give first an overview of the most important outcomes regarding fracture risk reduction, change in bone mineral density (BMD by DXA) and/or bone markers of the phase III clinical studies of well-established therapies (such as Bisphosphonates, Denosumab or Teriparatide) and also novel therapies (such as Romosozumab or Abaloparatide) and highlight their mechanisms of action at bone tissue/material level. The latter understanding is not only essential for the choice of drug, duration and discontinuation of treatment but also for the interpretation of the clinical outcomes (in particular of eventual changes in BMD) after drug administration. In the second part of this chapter, we focus on the management of different forms of osteoporosis and give a review of the respective current guidelines for treatment. Adverse effects of treatment such as atypical femoral fractures, osteonecrosis of the jaw or influence of fracture healing are considered also in this context.

Role of the FKBP5 polymorphism rs1360780, age, sex, and type of surgery in weight loss after bariatric surgery: a follow-up study

BACKGROUND

Emerging evidence suggests that the FK506 binding protein 51 (FKBP5/FKBP51), encoded by the FKBP5 gene, influences weight and metabolic regulation. The T allele of a functional polymorphism in FKBP5 (rs1360780), has been associated with the expression of FKBP51 and weight loss after bariatric surgery.

OBJECTIVE

To examine the role of the FKBP5 rs1360780 polymorphism in relation to age, sex, and type of surgery in weight loss after bariatric surgery in patients with severe obesity.

SETTING

University Hospital in Spain METHODS: A cohort of 151 obese patients submitted to Roux-en-Y gastric bypass (62.3%) and sleeve gastrectomy (37.7%) were followed-up during 24-months (t_24m; loss to follow-up: 0%). During the postoperative period body mass index (BMI) and percentage of excess and total weight loss were evaluated.

RESULTS

The BMI analysis showed an effect of the interaction FKBP5 genotype by sex (P = .0004) and a tendency to the interaction genotype by surgery (P = .048), so that men carrying the T allele had higher BMI at t_24m than those without the T allele, and T-allele carriers that underwent sleeve gastrectomy had higher BMI at t_24m than the noncarriers. Additionally, we found an interaction between FKBP5 and age for the percentage of excess weight loss and BMI (P = .0005 and P = 1.5e-7, respectively), whereby individuals >48 years with the T allele displayed significant differences for the analyzed variables at t_24m compared with the homozygotes for the alternate C allele showing lower weight loss.

CONCLUSION

FKBP5 rs1360780 genotype has specific effects on weight loss outcomes after bariatric surgery depending on sex, age, and type of surgery, suggesting worse results in older males carrying the T allele who have undergone sleeve gastrectomy.

Endogenous Glucocorticoid Signaling in the Regulation of Bone and Marrow Adiposity: Lessons from Metabolism and Cross Talk in Other Tissues

PURPOSE OF REVIEW

The development of adiposity in the bone marrow, known as marrow adipose tissue (MAT), is often associated with musculoskeletal frailty. Glucocorticoids, which are a key component of the biological response to stress, affect both bone and MAT. These molecules signal through receptors such as the glucocorticoid receptor (GR), but the role of the GR in regulation of MAT is not yet clear from previous studies. The purpose of this review is to establish and determine the role of GR-mediated signaling in marrow adiposity by comparing and contrasting what is known against other energy-storing tissues like adipose tissue, liver, and muscle, to provide better insight into the regulation of MAT during times of metabolic stress (e.g., dietary challenges, aging).

RECENT FINDINGS

GR-mediated glucocorticoid signaling is critical for proper storage and utilization of lipids in cells such as adipocytes and hepatocytes and proteolysis in muscle, impacting whole-body composition, energy utilization, and homeostasis through a complex network of tissue cross talk between these systems. Loss of GR signaling in bone promotes increased MAT and decreased bone mass. GR-mediated signaling in the liver, adipose tissue, and muscle is critical for whole-body energy and metabolic homeostasis, and both similarities and differences in GR-mediated GC signaling in MAT as compared with these tissues are readily apparent. It is clear that GC-induced pathways work together through these tissues to affect systemic biology, and understanding the role of bone in these patterns of tissue cross talk may lead to a better understanding of MAT-bone biology that improves treatment strategies for frailty-associated diseases.

Update on the safety and efficacy of teriparatide in the treatment of osteoporosis

Following the completion of the Fracture Prevention Trial, teriparatide was approved by the United States Food and Drug Administration and the European Medicine Agency as the first therapeutic anabolic agent for the treatment of postmenopausal women with severe osteoporosis. It subsequently received additional approval for the treatment of osteoporosis in men, and for the treatment of osteoporosis associated with glucocorticoid therapy in men and women at risk of fracture. In this review, we summarize the most important data concerning PTH 1-34 therapy before 2016 in the treatment of osteoporosis, and report some outstanding results published in the last 2 years. New data on safety will also discussed, together with the state of art of nonclassical utilization. Finally, in view of the recent approval of biosimilars, possible future landscapes are discussed.

Undercarboxylated Osteocalcin Improves Insulin-Stimulated Glucose Uptake in Muscles of Corticosterone-Treated Mice

Short-term administration of glucocorticoids (GCs) impairs muscle insulin sensitivity at least in part via the reduction of undercarboxylated osteocalcin (ucOC). However, whether ucOC treatment reverses the GC-induced muscle insulin resistance remains unclear. To test the hypothesis that ucOC directly ameliorates impaired insulin-stimulated glucose uptake (ISGU) induced by short-term GC administration in mice muscle and to identify the molecular mechanisms, mice were implanted with placebo or corticosterone (CS) slow-release pellets. Two days post-surgery, insulin-tolerance tests (ITTs) were performed. On day 3, serum was collected and extensor digitorum longus (EDL) and soleus muscles were isolated and treated ex vivo with vehicle, ucOC (30 ng/mL), insulin (60 µU/mL), or both. Circulating hormone levels, muscle glucose uptake, and muscle signaling proteins were assessed. CS administration reduced both serum osteocalcin and ucOC levels, whole-body insulin sensitivity, and muscle ISGU in EDL. Ex vivo ucOC treatment restored ISGU in CS-affected muscle, without increasing non-insulin-stimulated glucose uptake. In CS-affected EDL muscle, ucOC enhanced insulin action on phosphorylated (p-)protein kinase B (Akt)^Ser473 and the p-extracellular signal-regulated kinase isoform 2 (ERK2)^{Thr202/Tyr204} /total (t)ERK2 ratio, which correlated with ISGU. In CS-affected soleus muscle, ucOC enhanced insulin action on p-mammalian target of rapamycin (mTOR)^Ser2481 , the p-mTOR^Ser2481 /tmTOR ratio, p-Akt substrate of 160kD (AS160)^Thr642 , and p-protein kinase C (PKC) (pan)^Thr410 , which correlated with ISGU. Furthermore, p-PKC (pan)^Thr410 correlated with p-Akt^Ser473 and p-AS160^Thr642 . ucOC exerts direct insulin-sensitizing effects on CS-affected mouse muscle, likely through an enhancement in activity of key proteins involved in both insulin and ucOC signaling pathways. Furthermore, these effects are muscle type-dependent. © 2019 American Society for Bone and Mineral Research.