New developments in the pathogenesis and treatment of steroid-induced osteoporosis

No impact of tumor necrosis-factor antagonists on the joint manifestations of sarcoidosis

Objective

The use of anti-tumor necrosis factor (TNF) agents to treat joint manifestations of sarcoidosis has not been described. We evaluated the efficacy and safety of three such biologics in patients with these symptoms refractory to conventional therapy (nonsteroidal anti-inflammatory drugs, corticosteroids, and/or disease-modifying antirheumatic drugs).

Methods

This retrospective study, covering January 2001 to September 2011, examined clinical–biological parameters collected before anti-TNF treatment (age, sex, duration of disease evolution, drugs taken), and at introduction and under anti-TNF therapy (number of painful and swollen joints, visual analog scale score of global disease activity, disease-activity score of 28 joints with erythrocyte sedimentation rate or C-reactive protein, TNF-antagonist duration). At 3, 6, and 12 months, anti-TNF impact on joints and the therapeutic response according to European League Against Rheumatism criteria used for rheumatoid arthritis were assessed.

Results

Ten patients’ data were evaluated; some of them had received several anti-TNF agents (median [range] duration on each biotherapy was 10 [4–30] months), which enabled analysis of 19 prescriptions. The total duration of anti-TNF exposure was 17.6 patient-years, which was started a median of 3 (0.33–17) years after sarcoidosis diagnosis. The median numbers of painful and swollen joints were 1 (0–28) and 0 (0–9), respectively. Despite rapid efficacy, after 1 year of treatment, clinical (especially joint) and biological parameters were comparable to pretreatment, and only the corticosteroid dose was significantly lower (P=0.03). One case of mild skin toxicity was noted.

Conclusion

TNF antagonists allowed significant steroid sparing and were well tolerated, but do not seem to be effective against sarcoidosis joint involvement.

Immunosuppressant-related hip pain after orthotopic liver transplant

OBJECTIVES

Immunosuppressant-related hip pain can greatly affect a patient's mobility and increase the number of total hip arthroplasties. We investigated risk factors and causes of hip pain after orthotopic liver transplant.

MATERIALS AND METHODS

The medical records of 175 adult orthotopic liver transplant patients, who were followed-up for more than 2 years, were retrospectively reviewed. Data collected from the records included primary disease, medications, biochemical results, Child-Turcotte-Pugh score, death, rejection, and complications related to liver transplant.

RESULTS

A total of 11 patients (6.3%) complained of hip pain, which was diagnosed as calcineurin-inhibitor-induced pain syndrome in 4 patients (2.3%), osteonecrosis of the femoral head in 3 patients (1.7%), and osteoporosis in 2 patients (1.1%). The incidence of calcineurin-inhibitor-induced pain syndrome was related to the dosage of tacrolimus (P > .05) but independent of methylprednisolone use. The occurrence of osteonecrosis of the femoral head was independent of the dosage and early withdrawal of methylprednisolone (P > .05). Patients with methylprednisolone withdrawal within 6 months had significantly longer survival than those using methylprednisolone for more than 6 months (50 ± 15 vs 41 ± 18 mo; P = .007).

CONCLUSIONS

Calcineurin-inhibitor-induced pain syndrome and osteonecrosis of the femoral head are main causes of hip pain in adult orthotopic liver transplant patients. Osteonecrosis of the femoral head was not common, but the incidence of hip pain owing to calcineurin-inhibitor-induced pain syndrome was relatively high in orthotopic liver transplant patients. Early withdrawal of methylprednisolone could benefit the patients' survival.

Effects of thalidomide on the development of bone damage caused by prednisolone in rats

BACKGROUND

The methods used in treatment of osteoporosis induced by glucocorticosteroids are not effective enough. There is a need for new drugs which could be useful in counteracting the influence of glucocorticosteroids on osseous tissue. The aim of the present study was to investigate the effects of thalidomide on the development of osteoporosis induced by glucocorticoid (prednisolone) in rats.

METHODS

The experiments were carried out on 3-month-old male Wistar rats. The animals were divided into 4 groups: I--control rats; II--prednisolone (10 mg/kg po); III--prednisolone (10 mg/kg po) + thalidomide (15 mg/kg po); IV--prednisolone (10 mg/kg po) + thalidomide (60 mg/kg po). The drugs were administered for 3 weeks. The body mass gain, bone mass in the tibia, femur and L-4 vertebra, histomorphometric parameters of the tibia (width of osteoid, diaphysis transverse growth, area of the transverse cross-sectional of the bone marrow cavity and the cortical bone) and the femur (width of trabeculae, width of epiphyseal cartilage, diaphysis transverse growth, area of the transverse cross-sectional of the bone marrow cavity and the cortical bone) were studied.

RESULTS

Prednisolone induced osteoporotic skeletal changes in mature male rats (decreases in the bone mass, the width of the periosteal and endosteal osteoid, the transverse cross-sectional area of the cortical bone, the width of trabeculae, and the diaphysis transverse growth were observed). Thalidomide administered at a dose of 15 mg/kg po inhibited the development of changes in macrometric and histomorphometric parameters induced by prednisolone in the skeletal system of rats.

CONCLUSION

The results may constitute indirect evidence for possible clinical trials conducted in order to define the possibility to apply thalidomide in treatment of bone diseases in humans.

Bone disease in organ transplant patients: pathogenesis and management

Bone disease is common in recipients of kidney, heart, lung, liver, and bone marrow transplants, and causes debilitating complications, such as osteoporosis, osteonecrosis, bone pain, and fractures. The frequency of fractures ranges from 6% to 45% for kidney transplant recipients to 22% to 42% for heart, lung, and liver transplant recipients. Bone disease in transplant patients is the sum of complex mechanisms that involve both preexisting bone disease before transplant and post-transplant bone loss due to the effects of immunosuppressive medications. Evaluation of bone disease should preferably start before the transplant or in the early post-transplant period and include assessment of bone mineral density and other metabolic factors that influence bone health. This requires close coordination between the primary care physician and transplant team. Patients should be stratified based on their fracture risk. Prevention and treatment include risk factor reduction, antiresorptive medications, such as bisphosphonates and calcitonin, calcitriol, and/or gonadal hormone replacement. A steroid-avoidance protocol may be considered.

Bone health and associated metabolic complications in neuromuscular diseases

This article reviews the recent literature regarding bone health as it relates to the patient living with neuromuscular disease (NMD). Studies defining the scope of bone-related disease in NMD are scant. The available evidence is discussed, focusing on abnormal calcium metabolism, increased fracture risk, and the prevalence of both scoliosis and hypovitaminosis D in Duchenne muscular dystrophy, amyotrophic lateral sclerosis, and spinal muscular atrophy. Future directions are discussed, including the urgent need for studies both to determine the nature and extent of poor bone health, and to evaluate the therapeutic effect of available osteoporosis treatments in patients with NMD.

Circulating sclerostin levels are decreased in patients with endogenous hypercortisolism and increase after treatment

CONTEXT

Increased bone fragility is a frequent complication of hypercortisolism due predominantly to suppression of bone formation. Sclerostin is an osteocyte-produced negative regulator of bone formation, which is up-regulated by glucocorticoids in mice.

OBJECTIVE

Our objective was to assess the effect of endogenous hypercortisolism on circulating sclerostin and bone turnover in humans.

DESIGN

We measured sclerostin, β-C-terminal telopeptide, amino-terminal propeptide of type 1 procollagen, and fibroblast growth factor 23 in blood samples of 21 patients with endogenous hypercortisolism and 21 age- and gender-matched controls. In 12 patients, measurements were repeated at various time intervals after successful surgical treatment (transsphenoidal surgery or adrenalectomy).

RESULTS

Plasma sclerostin levels were significantly decreased in patients compared with controls (112±49 vs. 207±48 pg/ml, P<0.001). In the 12 patients who were evaluated after surgical treatment, sclerostin levels increased from 121.4±46.5 to 175.8±78.5 pg/ml (P=0.003). These changes in plasma sclerostin levels were accompanied by significant increases in levels of fibroblast growth factor 23 (from 44.2±12.2 to 84.0±58.8 pg/ml, P=0.017) and of the bone turnover markers amino-terminal propeptide of type 1 procollagen (from 31.7±18.2 to 94.2±92.2 ng/ml, P=0.037) and β-C-terminal telopeptide (from 134.2±44 to 409.2±285 pg/ml, P=0.005).

CONCLUSIONS

Contrary to the findings in mice, circulating sclerostin is decreased in patients with chronic endogenous hypercortisolism and increases after treatment. These findings suggest that in humans, chronic exposure to glucocorticoids affects the number or function of osteocytes rather than the production of sclerostin.

Fat Embolism Syndrome following minor trauma in Duchenne muscular dystrophy

We describe five patients with Duchenne muscular dystrophy who presented with acute neurologic and respiratory symptoms following minor trauma. Four of the five deteriorated rapidly and died within 36 h after falling. X-rays for fractures were negative. Four of the five patients were taking corticosteroids daily. All five patients fulfilled the clinical criteria for Fat Embolism Syndrome. Autopsy findings were consistent with fat embolism in two cases. Fat Embolism Syndrome needs to be considered in patients with Duchenne muscular dystrophy following minor trauma even without fractures. Early recognition of Fat Embolism Syndrome and aggressive resuscitation are important to improve survival. This report serves as an important reminder that seatbelts need to be used at all times.

Fullerol antagonizes dexamethasone-induced oxidative stress and adipogenesis while enhancing osteogenesis in a cloned bone marrow mesenchymal stem cell

Increased oxidative stress is currently considered as a crucial cause of corticosteroid-induced osteonecrosis. The aim of this study was to evaluate the effect of fullerol, a powerful antioxidant, on adipogenic and osteogenic differentiation of a mouse bone marrow derived multipotent cell line, D1. Upon treatment with dexamethasone, D1 cells containing lipid vesicles were distinguishable from the surrounding cells by Oil Red O staining at day 21. Simultaneous treatment of dexamethasone with antioxidant glutathione or fullerol decreased the number of cells containing lipid vesicles. Treatment with dexamethasone for 7 days resulted in a significant increase in adipogenic markers peroxisome proliferator-activated receptor gamma and adipocyte protein 2 gene expression and decrease in expression of osteogenic markers runt-related transcription factor 2 and osteocalcin and antioxidative enzymes superoxide dismutase and catalase as revealed by quantitative real-time PCR. While glutathione and fullerol both were able to antagonize the effects of dexamethasone, fullerol had a greater effect than glutathione. Staining with a fluorescent dye CM-H(2) DCFDA as indicator of cellular reactive oxygen species revealed that the percentage of positively stained cells increased after dexamethasone treatment, and addition of fullerol attenuated this activity. These results indicated that fullerol inhibited adipogenesis and simultaneously enhanced osteogenesis by marrow mesenchymal stem cells possibly through elimination of cellular reactive oxygen species. The results indicated that fullerol can potentially be used for prevention and treatment of corticosteroid-induced osteonecrosis.

The prevalence of low bone mineral density in Brazilian patients with systemic lupus erythematosus and its relationship with the disease damage index and other associated factors

The aim of this study was to examine the prevalence of osteoporosis, osteopenia, and bone mineral density (BMD) less than the expected range based on age in patients with systemic lupus erythematosus (SLE) in a tropical region of Brazil and the relationship between reduced BMD and several associated factors, especially the SLE disease damage index (SDI). We scored 159 patients with creatinine clearance of 60 mL/min or more for SDI, which was modified by excluding the osteoporosis item. For postmenopausal women and men older than 50 yr, T-scores identified osteopenia (<-1.0 and >-2.5) and osteoporosis (≤-2.5). For all patients, a Z-score of -2.0 or less identified BMD less than the expected range for age. Other variables that influence BMD were studied. The prevalence of osteoporosis, osteopenia, and BMD less than the expected range for age was 28%, 54%, and 29.6%, respectively. The Z-scores were significantly lower in patients with a modified SDI ≥ 1 (mean ± standard deviation [SD]=-1.45 ± 1.18) compared with patients with a modified SDI=0 (mean ± SD=-0.94 ± 1.01; p=0.01). The lowest Z-score had a significant association with postmenopausal status (p=0.038) and significant correlations with the duration of glucocorticoid (GC) usage (p=0.033, r=-0.17), the cumulative amount of GC (p=0.000, r=-0.28), and parathyroid hormone levels (p=0.003, r=-0.24). A multiple linear regression revealed that the modified SDI (p=0.003) and the cumulative amount of GC (p=0.006) had significant independent associations with the lowest Z-score. In conclusion, a BMD less than the expected range for age occurs frequently in Brazilian patients with SLE independent of the renal failure. The patients with greater SDIs had lower Z-scores, which suggests a direct association between chronic inflammation from disease and a reduced BMD.

Comparison of β-adrenergic and glucocorticoid signaling on clock gene and osteoblast-related gene expressions in human osteoblast

Most living organisms exhibit circadian rhythms that are generated by endogenous circadian clocks, the master one being present in the suprachiasmatic nuclei (SCN). Output signals from the SCN are believed to transmit standard circadian time to peripheral tissue through sympathetic nervous system and humoral routes. Therefore, the authors examined the expression of clock genes following treatment with the β-adrenergic receptor agonist, isoprenaline, or the synthetic glucocorticoid, dexamethasone, in cultured human osteoblast SaM-1 cells. Cells were treated with 10(-6) M isoprenaline or 10(-7) M dexamethasone for 2 h and gene expressions were determined using real-time polymerase chain reaction (PCR) analysis. Treatment with isoprenaline or dexamethasone induced the circadian expression of clock genes human period 1 (hPer1), hPer2, hPer3, and human brain and muscle Arnt-like protein 1 (hBMAL1). Isoprenaline or dexamethasone treatment immediately increased hPer1 and hPer2 and caused circadian oscillation of hPer1 and hPer2 with three peaks within 48 h. hPer3 expression had one peak after isoprenaline or dexamethasone treatment. hBMAL expression had two peaks after isoprenaline or dexamethasone treatment, the temporal pattern being in antiphase to that of the other clock genes. Dexamethasone treatment delayed the oscillation of all clock genes for 2-6 h compared with isoprenaline treatment. The authors also examined the expression of osteoblast-related genes hα-1 type I collagen (hCol1a1), halkaline phosphatase (hALP), and hosteocalcin (hOC). Isoprenaline induced oscillation of hCol1a1, but not hALP and hOC. On the other hand, dexamethasone induced oscillation of hCol1a1 and hALP, but not hOC. Isoprenaline up-regulated hCol1a1 expression, but dexamethasone down-regulated hCol1a1 and hALP expression in the first phase.

Timing of androgen deprivation therapy use and fracture risk among elderly men with prostate cancer in the United States

PURPOSE

Fractures are a recognized consequence of androgen deprivation therapy (ADT); however, less is known about the incidence of fracture in relation to the timing of ADT use or the impact of fracture on mortality in men with prostate cancer.

METHODS

Using data from the Surveillance, Epidemiology, and End Results-Medicare linked database, we estimated adjusted hazard ratios (aHRs) using time-dependent Cox regression for fracture incidence related to the recency of exposure and dose among prostate cancer patients on gonadotropin-releasing hormone (GnRH) agonists, as well as mortality associated with fractures.

RESULTS

In our cohort of 80 844 patients, ADT was associated with an increased rate of fracture in both non-metastatic patients (aHR = 1.34; 95% confidence interval [CI] = 1.29-1.39) and metastatic patients (aHR = 1.51; 95%CI = 1.36-1.67). Fracture rates increased with increasing cumulative GnRH dose but decreased with increasing number of months since last use in each dose category. The mortality rate doubled for men experiencing a fracture after their diagnosis compared with that for men who did not experience a fracture (aHR = 2.05; 95%CI = 1.98-2.12).

CONCLUSIONS

ADT in elderly men with prostate cancer increased the incidence of fractures, and the effect appears to diminish with increasing time since the last dose of a GnRH agonist. Experiencing a fracture after the diagnosis of prostate cancer was associated with decreased survival.

Assessment of skeletal status by quantitative ultrasound at the hand phalanges in children with bronchial asthma--a pilot study

The aim of the study was to assess the skeletal status by quantitative ultrasound measurement at hand phalanges in asthmatic children treated with inhaled corticosteroids. Sixty-nine (69) children with a mean age of 10.9 ± 2.6 y and 251 controls matched for age and body size were enrolled into the study. The mean value of amplitude-dependent speed of sound in asthmatic children was 1953.8 ± 60.2 m/s and the mean Z-score was -0.05 ± 1.02; the corresponding values in the controls were 1951.0 ± 53.9 m/s and -0.26 ± 1.05, respectively. The results did not differ between the asthmatic and the healthy (control) children. A cumulative dose of inhaled steroids was identified in a stepwise regression analysis as a factor with potentially negative influence on bone status. In conclusion, the skeletal status in asthmatic children, assessed by quantitative ultrasound, shows no difference in comparison with healthy children. Nonetheless, special caution is necessary in case of long-term corticosteroid therapy, in which a slightly negative influence of treatment on the skeleton cannot be excluded.

Recommendations for Diagnosis and Management of Osteoporosis in COPD Men

Patients with chronic obstructive pulmonary disease (COPD) are at increased risk for osteoporosis and fractures because of lifestyle factors, systemic effects of the disease, side effects of treatment, and comorbidities. The initial evaluation of COPD men for osteoporosis must include a detailed medical history and physical examination, assessment of COPD severity, and additional tests, as suggested by results of clinical evaluation. Osteoporosis is diagnosed on the basis of bone mineral density (BMD) measurement with DEXA of the lumbar spine and hip, but fracture risk assessments tools, as FRAX, could be used as useful supplements to BMD assessments for therapeutics interventions. The prevention and treatment of osteoporosis in COPD involves nonpharmacologic and pharmacologic measures, as lifestyle measures and nutritional recommendations, management of COPD treatment (based on the use of limited corticosteroids doses), and drug therapy (bisphosphonates, teriparatide). In this paper, the current recommendations for diagnosis and management of osteoporosis in COPD men, based on recent medical bibliography, are presented and discussed.

Raman spectroscopy detects deterioration in biomechanical properties of bone in a glucocorticoid-treated mouse model of rheumatoid arthritis

Although glucocorticoids are frequently prescribed for the symptomatic management of inflammatory disorders such as rheumatoid arthritis, extended glucocorticoid exposure is the leading cause of physician-induced osteoporosis and leaves patients at a high risk of fracture. To study the biochemical effects of glucocorticoid exposure and how they might affect biomechanical properties of the bone, Raman spectra were acquired from ex vivo tibiae of glucocorticoid- and placebo-treated wild-type mice and a transgenic mouse model of rheumatoid arthritis. Statistically significant spectral differences were observed due to both treatment regimen and mouse genotype. These differences are attributed to changes in the overall bone mineral composition, as well as the degree of phosphate mineralization in tibial cortical bone. In addition, partial least squares regression was used to generate a Raman-based prediction of each tibia's biomechanical strength as quantified by a torsion test. The Raman-based predictions were as accurate as those produced by microcomputed tomography derived parameters, and more accurate than the clinically-used parameter of bone mineral density. These results suggest that Raman spectroscopy could be a valuable tool for monitoring bone biochemistry in studies of bone diseases such as osteoporosis, including tests of drugs being developed to combat these diseases.

Effects of glucocorticoid on BMD, micro-architecture and biomechanics of cancellous and cortical bone mass in OVX rabbits

The incidence of osteoporosis continues to increase with progressively aging populations. The purpose of this study was to detect the effects of glucocorticoid (GC) treatment on bone mineral density (BMD), biomechanical strength and micro-architecture in cancellous and cortical bone in ovariectomized (OVX) rabbits. Twenty adult female New Zealand white rabbits were randomly divided into three groups. The OVX-GC group (n=8) received a bilateral ovariectomy first and then daily GC treatment (methylprednisolone sodium succinate, 1mg/kg/day) for 4 weeks beginning 2 weeks after ovariectomy treatment. The OVX group (n=4) received a bilateral ovariectomy without GC treatment. The sham group (n=8) only received the sham operation. BMD was determined prior to and 6 weeks after the operation in the spine. Six weeks after the operation, the animals were sacrificed, and cancellous bone specimens were harvested from the femoral condyle and lumbar vertebrae. Cortical bone specimens were obtained from the femoral midshaft. The femoral specimens were scanned for apparent BMD. All specimens were tested mechanically and analyzed by microcompute tomography (micro-CT). In cancellous bone, GC treatment resulted in significant decreases in BMD, bone biomechanical strength and micro-architecture parameters in lumbar vertebrae. Similar trends in BMD and micro-architectural changes were also observed in the femoral condyle in the OVX-GC group compared with the sham group. However, there was no significant decline in any parameter in either lumbar vertebrae or femoral condyle in the OVX group. Similarly, no significant difference was found in any parameter in cortical bone among the three groups. Thus, the 4-week GC treatment in OVX rabbits could result in a significant bone loss in cancellous bone but not in cortical bone. This model is comparable to the osteoporosis-related changes in humans. OVX alone was not sufficient to induce osteoporosis.

[Mechanisms and therapeutics of glucocorticoid-induced osteoporosis]

Mechanisms of glucocorticoid-induced osteoporosis (GIOP) are categorized into local and systemic effects. In the local mechanisms, direct inhibitory effect of glucocorticoid on bone formation is thought to be one of the important mechanisms of GIOP. In contrast, secondary hyperparathyroidism induced by negative balance of calcium due to inhibition of absorption and increase of excretion is an important systemic mechanism of GIOP. Other mechanisms of GIOP are also shown in this review. From clinical points of view, serum markers for evaluation of GIOP have been discussed. Osteocalcin, procollagen type I N-terminal peptide, and bone-specific alkaline phosphatase as markers of bone formation are decreased in GIOP. Collagen I N-terminal telopeptide and tartrate resistent acid phosphatase isoform 5b as markers of bone resorption are increased in GIOP. Clinical guidelines have recommended that bisphosphonate is the first choice for the treatment of GIOP. Teriparatide is recombinant human parathyroid hormone 1-34, which should be considered as a therapeutic option for those at high risk of bone fracture. Denosumab, an anti receptor activator of nuclear factor-β ligand approved as a drug for postmenopausal osteoporosis was also effective for GIOP in clinical trials.

The protective role of bone morphogenetic protein-8 in the glucocorticoid-induced apoptosis on bone cells

One of the side effects associated with glucocorticoid therapy is glucocorticoid-induced bone loss. Glucocorticoids partly detain bone formation via the inhibition of osteoblastic function, however, the exact mechanism of this inhibition remains elusive. In this study, we examined the effect of dexamethasone, an active glucocorticoid analogue, on cell viability and expression of bone remodelling-related genes in primary mouse calvarial and cloned MC3T3-E1 osteoblasts. Using sensitive biochemical assays, we demonstrated the apoptotic effect of dexamethasone on osteoblastic cells. Then, utilizing Taqman probe-based quantitative RT-PCR technology, gene expression profiles of 111 bone metabolism-related genes were determined. As a result of dexamethasone treatment we have detected significant apoptotic cell death, and six genes, including Smad3, type-2 collagen α-1, type-9 collagen α-1, matrix metalloproteinase-2, bone morphogenetic protein-4 and bone morphogenetic protein-8 showed (BMP-8) significant changes in their expression on a time- and concentration-dependent manner. BMP-8, (a novel player in bone-metabolism) exhibited a two orders of magnitude elevation in its mRNA level and highly elevated protein concentration by Western blot in response to dexamethasone treatment. The knockdown of BMP-8 by RNA interference significantly increased dexamethasone-induced cell death, confirming a protective role for BMP-8 in the glucocorticoid-induced apoptosis of osteoblasts. Our results suggest that BMP-8 might be an essential player in bone metabolism, especially in response to glucocorticoids.

A roadmap to the brittle bones of cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disorder which despite advances in medical care continues to be a life-limiting and often fatal disease. With increase in life expectancy of the CF population, bone disease has emerged as a common complication. Unlike the osteoporosis seen in postmenopausal population, bone disease in CF begins at a young age and is associated with significant morbidity due to fractures, kyphosis, increased pain, and decreased lung function. The maintenance of bone health is essential for the CF population during their lives to prevent pain and fractures but also as they approach lung transplantation since severe bone disease can lead to exclusion from lung transplantation. Early recognition, prevention, and treatment are key to maintaining optimal bone health in CF patients and often require a multidisciplinary approach. This article will review the pathophysiology, current clinical practice guidelines, and potential future therapies for treating CF-related bone disease.

New understanding of glucocorticoid action in bone cells

Glucocorticoids (GCs) are useful drugs for the treatment of various diseases, but their use for prolonged periods can cause severe side effects such as osteoporosis. GCs have a direct effect on bone cells, where they can arrest bone formation, in part through the inhibition of osteoblast. On the other hand, GCs potently suppress osteoclast resorptive activity by disrupting its cytoskeleton based on the inhibition of RhoA, Rac and Vav3 in response to macrophage colony-stimulating factor. GCs also interfere with microtubule distribution and stability, which are critical for cytoskeletal organization in osteoclasts. Thus, GCs inhibit microtubule-dependent cytoskeletal organization in osteoclasts, which, in the context of bone remodeling, further dampens bone formation.

Mechanical induction of PGE2 in osteocytes blocks glucocorticoid-induced apoptosis through both the β-catenin and PKA pathways

Glucocorticoids are known to induce osteocyte apoptosis, whereas mechanical loading has been shown to sustain osteocyte viability. Here we show that mechanical loading in the form of fluid-flow shear stress blocks dexamethasone-induced apoptosis of osteocyte-like cells (MLO-Y4). Prostaglandin E(2) (PGE(2) ), a rapidly induced signaling molecule produced by osteocytes, was shown to be protective against dexamethasone-induced apoptosis, whereas indomethacin reversed the antiapoptotic effects of shear stress. This protective effect of shear stress was mediated through EP2 and EP4 receptors, leading to activation of the cAMP/protein kinase A signaling pathway. Activation of phosphatidylinositol 3-kinase, an inhibitor of glycogen synthesis kinase 3, also occurred, leading to the nuclear translocation of β-catenin, an important signal transducer of the Wnt signaling pathway. Both shear stress and prostaglandin increased the phosphorylation of glycogen synthesis kinase 3 α/β. Lithium chloride, an activator of the Wnt pathway, also was protective against glucocorticoid-induced apoptosis. Whereas it is known that mechanical loading increases cyclooxygenase-2 and EP2 receptor expression and prostaglandin production, dexamethasone was shown to inhibit expression of these components of the prostaglandin pathway and to reduce β-catenin protein expression. β-catenin siRNA knockdown experiments abrogated the protective effects of PGE(2), confirming the central role of β-catenin in mediating the protection against dexamethasone-induced cell death. Our data support a central role for PGE(2) acting through the cAMP/PKA and β-catenin signaling pathways in the protection of osteocyte apoptosis by fluid-flow shear stress.

Age-related changes in biological characteristics of human alveolar osteoblasts

OBJECTIVES

Age-related changes are common in many tissues and organs. However, cell-related causes in human alveolar bone remain unclear. This study has been carried out to explore the possibility that advancing age might change the biological characteristics of alveolar osteoblasts (AOBs) in women.

MATERIALS AND METHODS

Alveolar osteoblasts from women donors (five women aged 33-38 years and five women aged 62-68 years) were cultured in vitro. The cells were serially passaged and maximal lifespan evaluated. Cell viability, ultramicrostructure and osteogenic differentiation ability were determined respectively, using MTT assay, transmission electron microscopy, alkaline phosphatase (ALP) activity assay and von Kossa staining assay. These parameters of the two groups of AOBs were evaluated.

RESULTS

When compared with cells from young adult donors, AOBs from elderly women exhibited lower maximal lifespan (P < 0.05). Mean rate of population doubling was lower in elderly donor cells compared to those from young adult cells (P < 0.05). Organelles from AOBs of elderly donors were much fewer than those from young donors. MTT value of elderly donor cells was significantly lower than those of young adult donors from day 2 (P < 0.05). Relative ratio of ALP activity in elderly donor cells was significantly lower than those of the young womens' cells at 8, 12, 16 and 20 days (P < 0.05). Calcium nodules of young adult donors' specimens were significantly more numerous and larger than those from elderly donors.

CONCLUSIONS

Comparison of biological characteristics of AOBs from young adult women with those from elderly women in vitro revealed differences in proliferative capacity and bone formation functions, which decreased with aging. These data indicate that aging may play an important role in pathogenesis of human AOBs loss.

From estrogen-centric to aging and oxidative stress: a revised perspective of the pathogenesis of osteoporosis

Estrogen deficiency has been considered the seminal mechanism of osteoporosis in both women and men, but epidemiological evidence in humans and recent mechanistic studies in rodents indicate that aging and the associated increase in reactive oxygen species (ROS) are the proximal culprits. ROS greatly influence the generation and survival of osteoclasts, osteoblasts, and osteocytes. Moreover, oxidative defense by the FoxO transcription factors is indispensable for skeletal homeostasis at any age. Loss of estrogens or androgens decreases defense against oxidative stress in bone, and this accounts for the increased bone resorption associated with the acute loss of these hormones. ROS-activated FoxOs in early mesenchymal progenitors also divert ss-catenin away from Wnt signaling, leading to decreased osteoblastogenesis. This latter mechanism may be implicated in the pathogenesis of type 1 and 2 diabetes and ROS-mediated adverse effects of diabetes on bone formation. Attenuation of Wnt signaling by the activation of peroxisome proliferator-activated receptor gamma by ligands generated from lipid oxidation also contributes to the age-dependent decrease in bone formation, suggesting a mechanistic explanation for the link between atherosclerosis and osteoporosis. Additionally, increased glucocorticoid production and sensitivity with advancing age decrease skeletal hydration and thereby increase skeletal fragility by attenuating the volume of the bone vasculature and interstitial fluid. This emerging evidence provides a paradigm shift from the "estrogen-centric" account of the pathogenesis of involutional osteoporosis to one in which age-related mechanisms intrinsic to bone and oxidative stress are protagonists and age-related changes in other organs and tissues, such as ovaries, accentuate them.

Mechanical vibration preserves bone structure in rats treated with glucocorticoids

Glucocorticoids are an important cause of secondary osteoporosis in humans, which decreases bone quality and leads to fractures. Mechanical stimulation in the form of low-intensity and high-frequency vibration seems to be able to prevent bone loss and to stimulate bone formation. The objective of this study was to evaluate the effects of mechanical vibration on bone structure in rats treated with glucocorticoids. Thirty 3-month-old adult male Wistar rats were randomized to three groups: control (C), glucocorticoid (G), and glucocorticoid with vibration (GV). The G and GV groups received 3.5mg/kg/day of methylprednisolone 5 days/week for a duration of 9 weeks, and the C group received vehicle (saline solution) during the same period. The GV group was vibrated on a special platform for 30 min per day, 5 days per week during the experiment. The platform was set to provide a vertical acceleration of 1 G and a frequency of 60 Hz. Skeletal bone mass was evaluated by total body densitometry (DXA). Fracture load threshold, undecalcified bone histomorphometry, and bone volume were measured in tibias. Glucocorticoids induced a significantly lower weight gain (-9.7%) and reduced the bone mineral content (-9.2%) and trabecular number (-41.8%) and increased the trabecular spacing (+98.0%) in the G group, when compared to the control (C). Vibration (GV) was able to significantly preserve (29.2%) of the trabecular number and decrease the trabecular spacing (+26.6%) compared to the G group, although these parameters did not reach C group values. The fracture load threshold was not different between groups, but vibration significantly augmented the bone volume of the tibia by 21.4% in the GV group compared to the C group. Our study demonstrated that low-intensity and high-frequency mechanical vibration was able to partially inhibit the deleterious consequences of glucocorticoids on bone structure in rats.

IL-6 may modulate the skeletal response to glucocorticoids during exacerbations of inflammatory bowel disease

Whether inflammatory cytokines affect the skeletal response to glucocorticoid (GC) treatment is unclear. Our objectives were to (1) identify the cytokine(s) elevated during exacerbations of inflammatory bowel disease (IBD); (2) determine whether the cytokine(s) identified in this way is related to systemic GC sensitivity; and (3) examine whether cytokines and/or measures of GC sensitivity are related to changes in bone formation or resorption following GC therapy. We designed a combined cross-sectional and prospective study, including patients with active (n = 31) and inactive (n = 34) IBD as well as controls (n = 29). We assessed circulating concentrations of cytokines, PINP and betaCTX, as well as GC sensitivity in peripheral blood mononuclear cells. IL-6 was the only cytokine increased in active IBD, 2.35 (2.63) versus 1.64 (1.21) versus 1.31 (2.79) pg/microl active IBD, inactive IBD, and controls, respectively (median [interquartile range]) (P = 0.03, ANOVA). IL-6 was positively related to magnitude of GC sensitivity (beta = 0.02, 95% CI 0.008-0.04, P = 0.005). Following treatment with GC in active IBD, PINP decreased (P < 0.001), whereas betaCTX showed no significant change (P = 0.2). Subsequently, multiple regression analyses revealed that plasma IL-6 concentrations were inversely related to the extent of PINP suppression following GC (beta = 3.3, 95% CI 0.2-6.4, P = 0.04, adjusted for baseline PINP and duration of GC treatment), while no association was observed with GC sensitivity. In conclusion, IL-6 is elevated in active IBD and may protect against GC-induced suppression of bone formation via a mechanism which appears to be independent of systemic GC sensitivity.

Vitamin K2 promotes bone healing in a rat femoral osteotomy model with or without glucocorticoid treatment

The purpose of the present preclinical study was to determine whether vitamin K(2) would promote bone healing in a rat femoral osteotomy model with or without glucocorticoid (GC) treatment. Thirty-eight 6 week-old female Sprague-Dawley rats underwent a unilateral osteotomy of the femoral diaphysis followed by intramedullary wire fixation and then were randomized into four groups that received the following treatment schedules: vehicle, vitamin K(2), GC + vehicle, and GC + vitamin K(2). GC (prednisolone, 2.5 mg/kg) was administered subcutaneously twice a week. Vitamin K(2) (menatetrenone, 30 mg/kg) was administered orally five times a week. After 8 weeks of treatment, the wires were removed and a bone histomorphometric analysis was performed on the bone tissue inside the callus. Vitamin K(2) administration to GC-untreated rats decreased the osteoclast surface/bone surface (OcS/BS), osteoblast surface (ObS)/BS, eroded surface (ES)/BS, and bone formation rate (BFR)/BS and increased the lamellar area/bone area. Although GC treatment increased the ES/BS and decreased the ObS/BS, BFR/BS, and lamellar area/bone area, vitamin K(2) administration to GC-treated rats decreased the OcS/BS and prevented an increase in the ES/BS and a decrease in the lamellar area/bone area. These results suggested that vitamin K(2) downregulated bone turnover and stimulated lamellar bone formation in GC-untreated rats and prevented an increase in bone resorption while maintaining bone formation and prevented a decrease in lamellar bone formation in GC-treated rats. Thus, vitamin K(2) appears to be effective for promoting bone healing in a rat femoral osteotomy model with or without GC treatment.

Use of risedronate to prevent bone loss following a single course of glucocorticoids: findings from a proof-of-concept study in inflammatory bowel disease

SUMMARY

We performed a randomised controlled trial (RCT) to determine whether risedronate 35 mg once weekly prevents bone loss following an 8-week reducing course of prednisolone given for an exacerbation of inflammatory bowel disease (IBD). The greatest change in bone mineral density (BMD) was at Ward's triangle (WT), which fell by 2.2% in the placebo group, compared with a reduction of 0.8% in the risedronate group.

INTRODUCTION

Whether bisphosphonates can prevent bone loss associated with intermittent glucocorticoid (GC) therapy is unknown, reflecting the difficulty in performing RCTs in this context.

METHOD

To explore the feasibility of RCTs to examine this question, lumbar spine (LS; L2-4) and hip dual X-ray absorptiometry (DXA) scans were performed in 78 patients commencing a GC therapy course for a relapse of IBD. They were then randomised to receive placebo or risedronate 35 mg weekly for 8 weeks, after which the DXA scan was repeated.

RESULTS

For LS BMD, there was no change in the placebo group (0.1 +/- 0.4, p = 0.9), but there was an increase after risedronate (0.8 +/- 0.4, p = 0.04; mean% +/- SEM by paired Student's t test). There were small decreases in both groups at the total hip (-0.5 +/- 0.3, p = 0.04; -0.5 +/- 0.3, p < 0.05, placebo and risedronate, respectively). At WT, BMD fell after placebo (-2.2 +/- 0.5, p = 0.001) but not risedronate (-0.8 +/- 0.5, p = 0.09; p = 0.05 for between-group comparison).

CONCLUSION

RCTs can be used to examine whether bisphosphonates prevent bone loss associated with intermittent GC therapy, providing metabolically active sites such as WT are employed as the primary outcome.

Prevention and treatment of systemic glucocorticoid side effects

BACKGROUND

Systemic glucocorticoids are used in dermatologic practice for various diseases including connective tissue disorders, bullous diseases, and many other dermatologic conditions. Patients with these diseases are at times treated with long-term courses of glucocorticoids, which place them at increased risk for glucocorticoid-induced side effects. Therefore, dermatologists must be knowledgeable of risks related to glucocorticoid use and be familiar with guidelines to manage them.

OBJECTIVE

To provide an update of recent advances in the prevention and treatment of major glucocorticoid-induced side effects.

METHODS

Review of the literature.

RESULTS

Data regarding the prevention and treatment of glucocorticoid-induced side effects are presented.

CONCLUSION

This review should help dermatologists optimally manage and prevent glucocorticoid-induced side effects.

Separating therapeutic efficacy from glucocorticoid side-effects in rodent arthritis using novel, liposomal delivery of dexamethasone phosphate: long-term suppression of arthritis facilitates interval treatment

INTRODUCTION

Glucocorticoids have extensively been used in the treatment of rheumatoid arthritis and other inflammatory diseases. However, their side-effects remain the major limitation in clinical use and an improved therapeutic index is needed.

METHODS

Therapeutic efficacy and persistence of free and liposomal dexamethasone phosphate (DXM-P) were determined in mouse collagen-induced arthritis. For regimens with equal therapeutic benefit, the side-effect profiles were analysed over time with respect to collagen breakdown, suppression of the hypothalamus-pituitary-adrenal (HPA) axis, changes in blood glucose levels and the haematological profile. In addition, the presence of drug was monitored in plasma.

RESULTS

Liposomal DXM-P, but not free drug, resulted in a persistent anti-inflammatory effect. Comparable clinical benefit was achieved with a single administration of 4 mg/kg liposomal DXM-P or daily administrations of 1.6 mg/kg free drug for at least 7 days. For the liposomal form, but not for the free form, we observed a limitation of the suppression of the HPA axis in time and an absence of the drug-induced gluconeogenesis.

CONCLUSIONS

Liposomal DXM-P, but not free DXM-P, achieves therapeutic persistence in mouse collagen-induced arthritis, which results in drug-free periods of therapeutic benefit. The physical absence of drug after day 2 is associated with a reduction of the typical glucocorticoid side-effects profile. Liposomal DXM-P thereby has an improved therapeutic window.

OP-1 augments glucocorticoid-inhibited fracture healing in a rat fracture model

Glucocorticoids inhibit bone remodeling and fracture healing. We sought to determine whether osteogenic protein 1 (OP-1) can overcome this inhibition in a closed fracture model in the rat. Time-released prednisolone or placebo pellets were implanted subcutaneously; closed femoral fractures were created 2 weeks later in rats. Fractures received sham, OP-1 and collagen, or collagen-only implants. Femurs were harvested at 3, 10, 21, 28, and 42 days postfracture. Fractures were examined radiographically for amount of hard callus; mechanically for torque and stiffness (also expressed as a percentage of the contralateral intact femur); and histomorphometrically for amount of cartilaginous and noncartilaginous soft callus, hard callus, and total callus. Glucocorticoid administration inhibited fracture healing. The application of a devitalized Type I collagen matrix mitigated the inhibitory effects of prednisolone on fracture healing However, further increases in indices of fracture healing were observed when OP-1 was added to the collagen matrix compared with collagen alone. OP-1 and collagen was more effective than collagen alone.

Prevention of glucocorticoid-induced osteoporosis

Glucocorticoid-induced osteoporosis is the most common cause of secondary osteoporosis. The role of the Wnt signaling pathway in bone formation and the ratio of receptor activator for NF-kappaB ligand versus osteoprotegerin in bone resorption are exciting new insights. The absolute fracture risk helps both clinicians and patients to interpret the results of bone density measurement, which may have a positive influence on adherence to therapy. The bisphosphonates alendronate and risedronate are the first-line treatment in the prevention of glucocorticoid-induced osteoporosis, because both increase the bone mineral density of the spine and hips and reduce the vertebral fracture rate. Treatment with the anabolic agent parathyroid hormone (1 - 34) strongly stimulates bone turnover, and seems to be superior to treatment with alendronate. It might be attractive for glucocorticoid-treated patients with new vertebral fractures during treatment with bisphosphonates, and/or with severe fracture risk.

Dielectric screening of early differentiation patterns in mesenchymal stem cells induced by steroid hormones

In the framework of this study, target identification and localization of differentiation patterns by means of dielectric spectroscopy is presented. Here, a primary pre-osteoblastic bone marrow-derived MBA-15 cellular system was used to study the variations in the dielectric properties of mesenchymal stem cells while exposed to differentiation regulators. Using the fundamentals of mixed dielectric theories combined with finite numerical tools, the permittivity spectra of MBA-15 cell suspensions have been uniquely analyzed after being activated by steroid hormones to express osteogenic phenotypes. Following the spectral analysis, significant variations were revealed in the dielectric properties of the activated cells in comparison to the untreated populations. Based on the differentiation patterns of MBA-15, the electrical modifications were found to be highly correlated with the activation of specific cellular mechanisms which directly react to the hormonal inductions. In addition, by describing the dielectric dispersion in terms of transfer functions, it is shown that the spectral perturbations are well adapted to variations in the electrical characteristics of the cells. The reported findings vastly emphasize the tight correlation between the cellular and electrical state of the differentiated cells. It therefore emphasizes the vast abilities of impedance-based techniques as potential screening tools for stem cell analysis.

Androgen deprivation therapy and estrogen deficiency induced adverse effects in the treatment of prostate cancer

Androgen deprivation therapy (ADT) is the standard of care for metastatic prostate cancer and is increasingly used to treat asymptomatic patients with prostate-specific antigen recurrence after failed primary therapy. Although effective, ADT is associated with multiple adverse effects, many of which are related to the estrogen deficiency that occurs as a result of treatment. These include increased fracture risk, hot flashes, gynecomastia, serum lipid changes and memory loss. By providing clinicians with a greater awareness of the estrogen deficiency induced adverse effects from ADT, they can proactively intervene on the physical and psychological impact these effects have on patients.

Risk of fractures after renal transplantation in the United States

BACKGROUND

Although it is known that the incidence of fracture events is increased in renal transplantation recipients, the timing and the factors associated with risk of fractures are less well understood. The objective of this study was to estimate the time to fracture in renal transplantation recipients and to determine whether risk was associated with patient and transplantation characteristics.

METHODS

Using the U. S. Renal Data System, we retrospectively studied 68,814 patients, who underwent renal transplantation between 1988 and 1998. Fractures were identified from International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes in billing data. Time to first fracture was modeled during the first 5 years posttransplant using the Kaplan-Meier method and Cox proportional hazards models.

RESULTS

Of the patients who underwent transplantation, 22.5% developed a fracture within 5 years. Woman (hazard ratio [HR] 1.36, P<0.0001), patients older than 45 years of age (HR 1.14, P<0.0001) especially older than 65 years (HR 1.69, P<0.0001), and whites (HR 1.28, P<0.0001) were at increased risk of a fracture. Additionally, receipt of a deceased donor kidney (HR 1.30, P<0.0001), increased human leukocyte antigen mismatches (HR 1.09, P<0.014), diabetes (HR 1.88, P<0.0001), pretransplant dialysis (HR 1.08, P<0.0001), and an aggressive induction immunosuppression regimen (HR 1.14, P<0.0001) all significantly increased risk of fracture events during the first 5 years.

CONCLUSIONS

In addition to patient demographic features, donor factors, including suboptimal organ quality and the need for more intense immunosuppression, were associated with an increased risk of fractures during the first 5 years after a renal transplant.

The negative effect of dexamethasone on calcium-processing gene expressions is associated with a glucocorticoid-induced calcium-absorbing disorder

AIMS

Although dexamethasone (Dex) is used widely as an anti-inflammatory and immunosuppressive drug, Dex appears to have severe side-effects, including osteoporosis. This study determined the effects of Dex on duodenal and renal expressions of the calcium-processing genes transient receptor potential cation channel, subfamily V, member 5/6 (TRPV5/6), calbindin-D9k/-D28k (CaBP-9k/28k), Na+/Ca2+ exchanger 1 (NCX1), and plasma membrane Ca(2+)-ATPase (PMCA) 1b.

MAIN METHODS

Mice were injected subcutaneously with Dex for 1 or 5 days. The mRNA and protein expression levels of these calcium-processing genes were measured by real-time PCR and immunohistochemistry/immunoblot analysis, respectively. In addition, serum parathyroid hormone (PTH) levels were measured following Dex treatments.

KEY FINDINGS

Treatment with Dex for 24 h resulted in the inductions of duodenal TRPV6, CaBP-9k and PMCA1b transcripts and renal TRPV5, CaBP-9k, and NCX1 transcripts, while it reduced the transcription of renal TRPV6. Although the expressional changes were weak, duodenal expressions of glucocorticoid receptor (GR), the vitamin D receptor (VDR), and renal expressions of the parathyroid hormone receptor (PTHR) and VDR were increased following 24 h treatment with Dex. A five-day treatment with Dex reduced the transcriptional levels of duodenal TRPV6 and CaBP-9k by 60%. Transcripts for VDR and GR in the duodenum increased marginally.

SIGNIFICANCE

These results suggest that the expressions of TRPV6 and CaBP-9k in the duodenum appear to be a major regulatory target for glucocorticoids (GCs), and may be involved in the negative regulation of calcium absorption in GC-induced osteoporosis (GIO). The transcriptional regulation of TRPV6 and CaBP-9k in the duodenum seems complex given that there is an increase at 1-day treatment followed by a decrease at 5-day treatment.

Minireview: live and let die: molecular effects of glucocorticoids on bone cells

Glucocorticoids (GCs) are efficient drugs that are used to treat various immune-mediated diseases, but their long-term administration is associated with multiple metabolic side effects, including osteoporosis. Molecular analyses of the mechanisms exerted by the GC receptor have resulted in the development of GC receptor agonists that selectively repress or activate GC target genes. This review summarizes the cellular and molecular effects of GCs on bone cells and highlights the critical signaling pathways that may evolve into future therapeutic strategies.

Comparison of the effect of vitamin K(2) and risedronate on trabecular bone in glucocorticoid-treated rats: a bone histomorphometry study

PURPOSE

To compare the effect of vitamin K(2) and risedronate on trabecular bone in glucocorticoid (GC)-treated rats.

MATERIALS AND METHODS

Forty-eight Sprague-Dawley female rats, 3 months of age, were randomized by the stratified weight method into 5 groups according to the following treatment schedule: age-matched control, GC administration, and GC administration with concomitant administration of vitamin K(2), risedronate, or vitamin K(2) + risedronate. GC (methylprednisolone sodium succinate, 5.0 mg/kg) and risedronate (10 microg/kg) were administered subcutaneously three and five times a week, respectively. Vitamin K(2) (menatetrenone, 30 mg/kg) was administered orally three times a week. At the end of the 8-week experiment, bone histomorphometric analysis was performed on trabecular bone of the tibial proximal metaphysis.

RESULTS

GC administration decreased trabecular bone mass compared with age-matched controls because of decreased bone formation (mineralizing surface, mineral apposition rate, and bone formation rate) and increased bone erosion. Vitamin K(2) attenuated GC-induced trabecular bone loss by preventing GC-induced decrease in bone formation (mineralizing surface) and subsequently reducing GC-induced increase in bone erosion. Risedronate prevented GC-induced trabecular bone loss by preventing GC-induced increase in bone erosion although it also suppressed bone formation (mineralizing surface, mineral apposition rate, and bone formation rate). Vitamin K(2) mildly attenuated suppression of bone formation (mineralizing surface) and bone erosion caused by risedronate without affecting trabecular bone mass when administered in combination.

CONCLUSION

The present study showed differential effect of vitamin K(2) and risedronate on trabecular bone in GC-treated rats.

Effect of eicosapentaenoic acid on bone changes due to methylprednisolone in rats

The present study was conducted to investigate the effects of eicosapentaenoic acid on glucocorticoid-induced bone changes in rats, and to compare them with those of alendronate. Thirty six male Wistar rats, 2.5 months of age, were divided into six groups (n = 6 each) and treated with 0.9% NaCl (control), methylprednisolone 7 mg/kg, once a week subcutaneously, methylprednisolone + alendronate 20 microg/kg, twice a week subcutaneously and methylprednisolone + 80 or 160 or 320 mg/kg eicosapentaenoic acid, per day orally, for 6 weeks. At the end of the experiment, serum and urinary parameters of bone metabolism determined and bone histomorphometric analyses performed on cancellous bone of femoral epiphysis and metaphysis and cortical bone of tibial diaphysis. There were no significant differences in serum and urinary parameters among groups. Decrease of epiphyseal and metaphyseal trabecular width, epiphyseal bone area/tissue area and increase of epiphyseal trabecular separation observed in the methylprednisolone group compared to control. Alendronate restored all of these parameters except metaphyseal trabecular width, which increased significantly by eicosapentaenoic acid at the doses of 80 and 160 mg/kg. Effects of alendronate and 160 mg/kg eicosapentaenoic acid on bone area/tissue area, alendronate and eicosapentaenoic acid at the doses of 80 and 160 mg/kg on trabecular separation and alendronate and eicosapentaenoic acid at doses of 160 and 320 mg/kg on epiphyseal trabecular width were statistically similar. Methylprednisolone did not significantly change cortical bone parameters including cortical width and marrow area/cortical area. Eicosapentaenoic acid, especially, at the dose of 160 mg/kg exerts beneficial effects on methylprednisolone-induced bone changes in rats; these effects are similar or sometimes even better than alendronate.

Validation of the sheep as a large animal model for the study of vertebral osteoporosis

Rats have long been the animal of choice for research in the field of osteoporosis. In the search for a complementary large animal model the sheep appears useful but hitherto the extent of bone loss from the spine has failed to reach a level that is generally accepted as osteoporotic in humans. Osteoporosis was induced in ten sheep using ovariectomy, low calcium diet and steroid injection for 6 months. Bone samples of iliac crest (IC), lumbar spine (LS), and proximal femur (PF) from the osteoporotic sheep were compared with those from four normal sheep using densitometry, histomorphometry, biochemistry and basic mechanical testing. The differences were examined using an analysis of variance with Tukey-Kramer test. Overall, the bone mineral density at LS and PF decreased more than 25% after treatment. Trabecular bone volume decreased by 29.2, 33.4 and 42.6% in IC, LS and PF, respectively. The failure load of the LS in axial compression was reduced to 2,003 from 6,140 N. The extent of bone loss was sufficient to categorise these sheep as osteoporotic although the pattern of bone loss varied between sites. Reduced mechanical competence in LS confirmed the suitability of this model for evaluation of potential treatments for osteoporosis.

AMPK activator, AICAR, inhibits palmitate-induced apoptosis in osteoblast

Osteoblast apoptosis reduces bone mineral density. Apoptosis can be induced in a variety of cells by palmitate, which is one of the most common saturated fatty acids in dietary fat. The AMPK activator, AICAR, has been shown to inhibit palmitate-induced apoptosis. However, the role of palmitate in osteoblast apoptosis is currently unknown. This study examined whether palmitate could induce apoptosis in osteoblasts, and if so, whether AICAR could alleviate palmitate-induced apoptosis. Palmitate reduced cell survival and induced apoptosis in a dose- and time-dependent manner in human fetal osteoblasts (hFOB) 1.19. While the long-chain acyl-CoA synthetase inhibitor, triacsin C, inhibited palmitate-induced apoptosis, anti-oxidants and ceramide synthesis inhibitors did not attenuate the apoptosis. AICAR prevented palmitate-induced apoptosis and the inhibition of AICAR-mediated increase in fatty acid oxidation by etomoxir did not affect the prevention of apoptosis by AICAR. Constitutively-active AMPK also inhibited palmitate-induced apoptosis. Treatment with an AMPK inhibitor (compound C) and a dominant-negative AMPK adenovirus suppressed the inhibitory effect of AICAR on apoptosis. Palmitate impaired the activation of ERK by fetal bovine serum, which was blocked by AICAR. Moreover, AICAR increased ERK activation, and ERK inhibitors, PD98059 and U0126, as well as a dominant-negative MEK1, abolished the inhibitory effect of AICAR on palmitate-induced apoptosis. AICAR also inhibited palmitate-induced apoptosis in osteoblastic differentiated cells from human bone marrow, which was accompanied by recovered ERK activity. These results suggest that palmitate induces apoptosis in osteoblasts through the impaired activation of ERK, and the activation of AMPK inhibits palmitate-induced apoptosis by activating ERK.

Risk factors, prevention, and treatment of corticosteroid-induced osteoporosis in adults

An orthopedist can play a critical role in corticosteroid induced osteoporosis management by identifying at-risk patients and selecting appropriate prophylactic measures. This article is part two in a two-part series on osteoporosis. Part one appeared in the July 2008 issue of ORTHOPEDICS.