Glucocorticoid suppression of IGF I transcription in osteoblasts

Novel evidence in vivo: Berberine ameliorated glucocorticoid-induced post-natal growth retardation by regulating the GH/IGF-1 axis through KMT1A downregulation

BACKGROUND

Glucocorticoids (GCs) are widely used anti-inflammatory agents that inhibit growth in children. However, their mechanisms and effect on the growth hormone (GH)/insulin-like growth factor (IGF)-1 axis remain unclear.

PURPOSE

This study, we aimed to establish a mouse model of GC-induced growth retardation during the critical growth period and explore the underlying mechanisms. Additionally, we aimed to identify novel biomarkers and potential therapeutic agents for GC-induced growth impairment.

METHODS

Four-week-old mice were treated with GCs for two weeks and subsequently assessed for body length, weight, and body composition. Immunohistochemical analysis of the growth plate in the proximal tibia and biochemical assays of blood were performed to evaluate changes in growth plate length and GH/IGF-1 axis. KMT1A expression and its effects on Ghr expression were examined, and the impact of berberine on GC-induced growth retardation was assessed.

RESULTS

GCs significantly reduced growth by impairing growth plate expansion, disrupting the GH/IGF-1 axis, and downregulation of the GH receptor (Ghr) and Igf-1 levels in the liver. These changes were attributed to the upregulation of the H3K9 trimethyltransferase KMT1A, which decreased Ghr transcription in the liver. In vitro screening of natural compounds revealed that berberine chloride hydrate decreased the KMT1A levels and increased GHR levels. Berberine chloride hydrate also effectively ameliorated GC-induced growth retardation by restoring Ghr expression via KMT1A inhibition, thereby enhancing the circulating IGF-1 levels.

CONCLUSION

Overall, our findings highlight the potential of targeting KMT1A using berberine chloride hydrate as an epigenetic modifier to treat GC-induced growth impairment.

Height development and multiple bone health indicators in children aged 2-12 years with Duchenne muscular dystrophy (DMD)

INTRODUCTION

Short stature is a frequent complication of DMD, and its pathomechanisms and influencing factors are specific to this disease and the idiosyncratic treatment for DMD.

PURPOSE

To establish the height growth curve of early DMD, and evaluate the potential influencing markers on height growth, provide further evidence for pathological mechanism, height growth management and bone health in DMD.

METHODS

A retrospective, cross-sectional study of 348 participants with DMD aged 2-12 years was conducted at West China Second Hospital of Sichuan University from January 2023 to October 2023.

RESULTS

The growth curve for 2-12 years old boys with DMD indicates a slower growth rate compared to the average population. At age two, children with DMD have a similar height to their peers, but gradually falls behind afterwards. Short stature was observed in children with DMD before and after GC exposure, and prolonged GC use exacerbated the retardation. BMI (β = -0.47, p = 0.007), BMD (β = -0.005, p = 0.014), β-CTX (β = 0.001, p = 0.002), delayed BA (β = 0.417, p < .001), GC duration (β = -0.006, p = 0.047) were independent influencing factors of height. Relevant bone health markers showed different sequential changing patterns.

CONCLUSION

The high proportion and progression of short stature are associated with the broad bone health status. Different bone indicators have different sensitivities and specificities and need to be considered together for clinical monitoring of bone health. This study provides evidence for the early monitoring of height development and relevant factors as part of bone health management in DMD, to minimize the occurrence of bone-related complications later in life.

Effect of Gabapentin on Tendon-to-Bone Healing in a Rat Model of Rotator Cuff Repair

BACKGROUND

Gabapentin is often used as an analgesic after rotator cuff repair surgery and is recommended as an additional analgesic for arthroscopic rotator cuff repairs. However, evidence of its effects on biological healing mechanisms is lacking. The objective of this study was to investigate the potential of gabapentin in improving tendon-to-bone healing after rotator cuff repair using a rat model.

MATERIALS AND METHODS

A total of 20 male rats were randomly allocated to one of two groups: group 1 (repair only, n=10) or group 2 (gabapentin injection, n=10). The rats in the experimental group (group 2) were administered 80 mg/kg of gabapentin subcutaneously 30 minutes before surgery, followed by 80 mg/kg subcutaneously every 24 hours for 48 hours. We used the left shoulder of every rat, while for biomechanical analysis, we used the right shoulder.

RESULTS

There was no significant difference in the load to failure, ultimate stress, or elongation between the groups. Collagen continuity, orientation, and density were better in group 2 than group 1.

CONCLUSION

In a rat model of rotator cuff repair, gabapentin had a positive impact on the quality of collagen organization at the junction between the tendon and bone, while preserving the biomechanical properties. We propose the use of gabapentin as a supplementary analgesic agent for postoperative pain relief after arthroscopic rotator cuff repair; however, further studies of the effect of gabapentin on biological healing mechanisms are required. [Orthopedics. 2024;47(5):e241-e246.].

Diagnosis and therapeutic approach to bone health in patients with hypopituitarism

The results of many studies in recent years indicate a significant impact of pituitary function on bone health. The proper function of the pituitary gland has a significant impact on the growth of the skeleton and the appearance of sexual dimorphism. It is also responsible for achieving peak bone mass, which protects against the development of osteoporosis and fractures later in life. It is also liable for the proper remodeling of the skeleton, which is a physiological mechanism managing the proper mechanical resistance of bones and the possibility of its regeneration after injuries. Pituitary diseases causing hypofunction and deficiency of tropic hormones, and thus deficiency of key hormones of effector organs, have a negative impact on the skeleton, resulting in reduced bone mass and susceptibility to pathological fractures. The early appearance of pituitary dysfunction, i.e. in the pre-pubertal period, is responsible for failure to achieve peak bone mass, and thus the risk of developing osteoporosis in later years. This argues for the need for a thorough assessment of patients with hypopituitarism, not only in terms of metabolic disorders, but also in terms of bone disorders. Early and properly performed treatment may prevent patients from developing the bone complications that are so common in this pathology. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary disease.

The interplay of rheumatoid arthritis and osteoporosis: exploring the pathogenesis and pharmacological approaches

Rheumatoid arthritis (RA) and osteoporosis are two chronic disorders that are often seen together. RA is an autoimmune disorder that causes pain and inflammation in the joints, while osteoporosis is a disorder in which the bones become weak and fragile. Risk factors for bone loss in RA include disease activity, longer disease duration, erosive disease, autoantibody positivity, and joint damage leading to impaired physical activity. Recent research has shown that there is a complex interplay between immune cells, cytokines, and bone remodeling processes in both RA and osteoporosis. The bone remodeling process is regulated by cytokines and immune system signaling pathways, with osteoclasts activated through the RANK/RANKL/OPG pathway and the Wnt/DKK1/sclerostin pathway. Understanding these mechanisms can aid in developing targeted therapies for treatment of osteoporosis in RA patients. Current pharmacological approaches include anti-osteoporotic drugs such as bisphosphonates, denosumab, teriparatide, abaloparatide, raloxifene, and romosozumab. Conventional disease-modifying antirheumatic drugs such as methotrexate and biologicals including TNF inhibitors, IL-6 inhibitors, rituximab, and abatacept lower disease activity in RA and can improve bone metabolism by reducing inflammation but have limited impact on bone mineral density. This review will shed light on the relationship between osteoporosis and rheumatoid arthritis as well as the various factors that influence the onset of osteoporosis in RA patients. We also explore several treatment approaches to effectively managing osteoporosis in RA patients.

Metabolic bone disorders and the promise of marine osteoactive compounds

Metabolic bone disorders and associated fragility fractures are major causes of disability and mortality worldwide and place an important financial burden on the global health systems. These disorders result from an unbalance between bone anabolic and resorptive processes and are characterized by different pathophysiological mechanisms. Drugs are available to treat bone metabolic pathologies, but they are either poorly effective or associated with undesired side effects that limit their use. The molecular mechanism underlying the most common metabolic bone disorders, and the availability, efficacy, and limitations of therapeutic options currently available are discussed here. A source for the unmet need of novel drugs to treat metabolic bone disorders is marine organisms, which produce natural osteoactive compounds of high pharmaceutical potential. In this review, we have inventoried the marine osteoactive compounds (MOCs) currently identified and spotted the groups of marine organisms with potential for MOC production. Finally, we briefly examine the availability of in vivo screening and validation tools for the study of MOCs.

Local Effects of Steroid Hormones within the Bone Microenvironment

Steroid hormone production via the adrenal cortex, gonads, and placenta (so-called glandular steroidogenesis) is responsible for the endocrine control of the body's homeostasis and is organized by a feedback regulatory mechanism based on the hypothalamus-pituitary-steroidogenic gland axis. On the other hand, recently discovered extraglandular steroidogenesis occurring locally in different tissues is instead linked to paracrine or autocrine signaling, and it is independent of the control by the hypothalamus and pituitary glands. Bone cells, such as bone-forming osteoblasts, osteoblast-derived osteocytes, and bone-resorbing osteoclasts, respond to steroid hormones produced by both glandular and extraglandular steroidogenesis. Recently, new techniques to identify steroid hormones, as well as synthetic steroids and steroidogenesis inhibitors, have been introduced, which greatly empowered steroid hormone research. Based on recent literature and new advances in the field, here we review the local role of steroid hormones in regulating bone homeostasis and skeletal lesion formation. The novel idea of extraglandular steroidogenesis occurring within the skeletal system raises the possibility of the development of new therapies for the treatment of bone diseases.

The influence of growth hormone deficiency on bone health and metabolisms

Growth hormone (GH) is a key peptide hormone in the regulation of bone metabolism, through its systemic and paracrine action mediated directly as well as by insulin-like growth factor-1 (IGF-1). Growth hormone exerts pleiotropic effects leading to an increase in linear bone growth, accumulation of bone mineral content and preservation of peak bone mass. Furthermore, it influences protein, lipid, and carbohydrate metabolism.Growth hormone deficiency (GHD) causes a low bone turnover rate leading to reduced bone mineral density (BMD) and increased bone fragility. The results of GH insufficiency are the most pronounced among children as it negatively affects longitudinal bone growth, causing short stature and in adolescents, in whom it hinders the acquisition of peak bone mass. Most studies show that treatment with recombinant human growth hormone (rhGH) in GHD patients could improve BMD and decrease fracture risk. This review aims to summarize the pathophysiology, clinical picture and management of bone complications observed in GHD.

Effect of AZD4017, a Selective 11β-HSD1 Inhibitor, on Bone Turnover Markers in Postmenopausal Osteopenia

CONTEXT

The causative link between circulating glucocorticoid excess and osteoporosis is well-established. The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which increases local cortisol production, is expressed in human osteoblasts and its activity increases with age.

OBJECTIVE

We hypothesized that local 11β-HSD1 might mediate an age-related decrease in bone formation and that selective 11β-HSD1 inhibition may enhance bone formation.

METHODS

A dual-center, phase II, randomized, double-blind, placebo-controlled trial of 90 days' treatment with AZD4017 (a selective 11β-HSD1 inhibitor) was conducted in 55 postmenopausal women with osteopenia. Participants received 400 mg oral AZD4017 twice daily vs matched placebo over 90 days. The primary outcome measure was the impact on the bone formation marker osteocalcin. Secondary objectives included correlation with 11β-HSD1 activity.

RESULTS

At 90 days, osteocalcin levels did not differ between treatment groups: active (mean 22.3 [SD 8.6] ng/mL, n = 22) and placebo (21.7 [SD 9.2] ng/mL, n = 24), with a baseline-adjusted treatment effect of 0.95 (95% CI: -2.69, 4.60). The results from the urinary [THF + alloTHF]/THE ratio (index of 11β-HSD1 activity) and the urinary cortisol/cortisone ratio (index of 11β-HSD2 activity) confirmed a > 90% inhibition of 11β-HSD1 but no change in activity of 11β-HSD2.

CONCLUSION

This trial demonstrates that AZD4017 selectively inhibits 11β-HSD1 activity in vivo in a safe and reversible manner. Following 90 days of treatment, there is no effect on bone formation, indicating that the relative impairment of bone mineral density in postmenopausal women is not mediated by local intracellular production of cortisol under normal physiological concentrations.

Neuroendocrine-Immune Regulatory Network of Eucommia ulmoides Oliver

Eucommia ulmoides Oliver (E. ulmoides) is a popular medicinal herb and health supplement in China, Japan, and Korea, and has a variety of pharmaceutical properties. The neuroendocrine-immune (NEI) network is crucial in maintaining homeostasis and physical or psychological functions at a holistic level, consistent with the regulatory theory of natural medicine. This review aims to systematically summarize the chemical compositions, biological roles, and pharmacological properties of E. ulmoides to build a bridge between it and NEI-associated diseases and to provide a perspective for the development of its new clinical applications. After a review of the literature, we found that E. ulmoides has effects on NEI-related diseases including cancer, neurodegenerative disease, hyperlipidemia, osteoporosis, insomnia, hypertension, diabetes mellitus, and obesity. However, clinical studies on E. ulmoides were scarce. In addition, E. ulmoides derivatives are diverse in China, and they are mainly used to enhance immunity, improve hepatic damage, strengthen bones, and lower blood pressure. Through network pharmacological analysis, we uncovered the possibility that E. ulmoides is involved in functional interactions with cancer development, insulin resistance, NAFLD, and various inflammatory pathways associated with NEI diseases. Overall, this review suggests that E. ulmoides has a wide range of applications for NEI-related diseases and provides a direction for its future research and development.

Selective Serotonin Reuptake Inhibitor Promotes Bone-Tendon Interface Healing in a Rotator Cuff Tear Rat Model

BACKGROUND

Selective serotonin reuptake inhibitor (SSRI) is believed to accelerate wound healing, and thus expected to have a positive effect on rotator cuff repair. We hypothesized that SSRI has a positive effect on the healing of the bone-tendon interface (BTI), and improved rotator cuff tear healing would be confirmed by mechanical strength measurements and histological assessment of the restored tendon.

METHODS

The study used 40 adult male Sprague-Dawley wild-type rats. The animals were divided into two groups: group-SSRI, the supraspinatus repair with SSRI injection group, and group-C, conventional supraspinatus repair only without SSRI. Biomechanical and histological analyses were performed 8 weeks after index rotator cuff surgery.

RESULTS

The ultimate load (N) was significantly higher in group-SSRI than in group-C (54.8 ± 56.9 Vs 25.1 ± 11.1, p = .031). In the histological evaluation, the Bonar score confirmed significant differences in collagen fiber density (group-C: 0.6 ± 0.5, group-SSRI: 1.1 ± 0.6, p = .024), vascularity (group-C: 0.1 ± 0.2, group-SSRI: 0.3 ± 0.4, p = .024) and cellularity (group-C: 1.7 ± 0.4, group-SSRI: 2.0 ± 0.0, p = .023) between the groups. Based on the total score, group-SSRI was significantly better compared with group-C (6.3 ± 2.7 Vs 4.3 ± 1.9, p = .019).

CONCLUSION

Our study demonstrated that SSRI could facilitate improved biomechanical and histological outcomes 8 weeks after rotator cuff repair in a rat model. Consequently, SSRI may improve healing after rotator cuff repair.

Combined growth hormone and insulin-like growth factor-1 rescues growth retardation in glucocorticoid-treated mdxmice but does not prevent osteopenia

Short stature and osteoporosis are common in Duchenne muscular dystrophy (DMD) and its pathophysiology may include an abnormality of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis, which is further exacerbated by long-term glucocorticoid (GC) treatment. Hence, an agent that has anabolic properties and may improve linear growth would be beneficial in this setting and therefore requires further exploration. A 5-week-old x-linked muscular dystrophy (mdx) mice were used as a model of DMD. They were treated with prednisolone ± GH + IGF-1 for 4 weeks and then compared to control mdx mice to allow the study of both growth and skeletal structure. GC reduced cortical bone area, bone fraction, tissue area and volume and cortical bone volume, as assessed by micro computed tomography (CT) In addition, GC caused somatic and skeletal growth retardation but improved grip strength. The addition of GH + IGF-1 therapy rescued the somatic growth retardation and induced additional improvements in grip strength (16.9% increase, P < 0.05 compared to control). There was no improvement in bone microarchitecture (assessed by micro-CT and static histomorphometry) or biomechanical properties (assessed by three-point bending). Serum bone turnover markers (Serum procollagen 1 intact N-terminal propeptide (P1NP), alpha C-terminal telopeptide (αCTX)) also remained unaffected. Further work is needed to maximise these gains before proceeding to clinical trials in boys with DMD.

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.

Understanding and Managing Corticosteroid-Induced Osteoporosis

Glucocorticoids are effective immunosuppressants used in a wide variety of diseases. Their use results in secondary osteoporosis in about 30–50% of chronic glucocorticoid users. Glucocorticoids cause a rapid decline in bone strength within the first 3–6 months mostly due to increased bone resorption by osteoclasts. This is followed by a more gradual loss of bone partly due to decreased osteoblastogenesis and osteoblast and osteocyte apoptosis. The loss of bone strength induced by glucocorticoids is not fully captured by bone mineral density measurements. Other tools such as the trabecular bone score and advanced imaging techniques give insight into bone quality; however, these are not used widely in clinical practice. Glucocorticoid-induced osteoporosis should be seen as a widely preventable disease. Currently, only about 15% of chronic glucocorticoid users are receiving optimal care. Glucocorticoids should be prescribed at the lowest dose and shortest duration. All patients should be counselled on lifestyle measures to maintain bone strength including nutrition and weight-bearing exercise. Pharmacological therapy should be considered for all patients at moderate to high risk of fracture as there is evidence for the prevention of bone loss and fractures with a favourable safety profile. Oral bisphosphonates are the current mainstay of therapy, whereas osteoanabolic agents may be considered for those at highest risk of fracture.

Factors Related to Bone Metabolism in Kidney Transplant Recipients

This study is aimed at establishing the prevalence of osteoporosis and osteopenia in kidney transplant recipients (KTRs) and determining the risk factors for bone mass loss. We invited KTRs who were under regular follow-up at Jiangxi Provincial People's Hospital Affiliated with Nanchang University to attend an assessment of osteoporotic risk assessed by questionnaire, biochemical profile, and dual-energy X-ray absorptiometry (DXA) scanning of the lumbar spine, total hip, and femoral neck. Binary logistic regression models were used to investigate the relationship between the different variables and bone mass density (BMD). A total of 216 patients satisfied the inclusion criteria. The group consisted of 156 men (72.22%) and 60 women (27.78%), and the mean age was 41.50 ± 9.98 years. There were 81 patients with normal bone mass (37.50%) and 135 patients with bone mass loss (62.50%). Logistic regression analysis showed that a higher phosphorus value and higher alkaline phosphatase concentration and a longer use of glucocorticoids were risk factors for bone mass loss in KTRs, and maintaining an appropriate weight and exercising an appropriate number of times per week helped to maintain bone mass.

Pathogenesis of glucocorticoid-induced osteoporosis and options for treatment

Glucocorticoids are widely used to suppress inflammation or the immune system. High doses and long-term use of glucocorticoids lead to an important and common iatrogenic complication, glucocorticoid-induced osteoporosis, in a substantial proportion of patients. Glucocorticoids mainly increase bone resorption during the initial phase (the first year of treatment) by enhancing the differentiation and maturation of osteoclasts. Glucocorticoids also inhibit osteoblastogenesis and promote apoptosis of osteoblasts and osteocytes, resulting in decreased bone formation during long-term use. Several indirect effects of glucocorticoids on bone metabolism, such as suppression of production of insulin-like growth factor 1 or growth hormone, are involved in the pathogenesis of glucocorticoid-induced osteoporosis. Fracture risk assessment for all patients with long-term use of oral glucocorticoids is required. Non-pharmacological interventions to manage the risk of fracture should be prescribed to all patients, while pharmacological management is reserved for patients who have increased fracture risk. Various treatment options can be used, ranging from bisphosphonates to denosumab, as well as teriparatide. Finally, appropriate monitoring during treatment is also important.

Amelioration of muscle wasting by glucagon-like peptide-1 receptor agonist in muscle atrophy

BACKGROUND

Skeletal muscle atrophy is defined as a reduction of muscle mass caused by excessive protein degradation. However, the development of therapeutic interventions is still in an early stage. Although glucagon-like peptide-1 receptor (GLP-1R) agonists, such as exendin-4 (Ex-4) and dulaglutide, are widely used for the treatment of diabetes, their effects on muscle pathology are unknown. In this study, we investigated the therapeutic potential of GLP-1R agonist for muscle wasting and the mechanisms involved.

METHODS

Mouse C2C12 myotubes were used to evaluate the in vitro effects of Ex-4 in the presence or absence of dexamethasone (Dex) on the regulation of the expression of muscle atrophic factors and the underlying mechanisms using various pharmacological inhibitors. In addition, we investigated the in vivo therapeutic effect of Ex-4 in a Dex-induced mouse muscle atrophy model (20 mg/kg/day i.p.) followed by injection of Ex-4 (100 ng/day i.p.) for 12 days and chronic kidney disease (CKD)-induced muscle atrophy model. Furthermore, we evaluated the effect of a long-acting GLP-1R agonist by treatment of dulaglutide (1 mg/kg/week s.c.) for 3 weeks, in DBA/2J-mdx mice, a Duchenne muscular dystrophy model.

RESULTS

Ex-4 suppressed the expression of myostatin (MSTN) and muscle atrophic factors such as F-box only protein 32 (atrogin-1) and muscle RING-finger protein-1 (MuRF-1) in Dex-treated C2C12 myotubes. The suppression effect was via protein kinase A and protein kinase B signalling pathways through GLP-1R. In addition, Ex-4 treatment inhibited glucocorticoid receptor (GR) translocation by up-regulating the proteins of GR inhibitory complexes. In a Dex-induced muscle atrophy model, Ex-4 ameliorated muscle atrophy by suppressing muscle atrophic factors and enhancing myogenic factors (MyoG and MyoD), leading to increased muscle mass and function. In the CKD muscle atrophy model, Ex-4 also increased muscle mass, myofiber size, and muscle function. In addition, treatment with a long-acting GLP-1R agonist, dulaglutide, recovered muscle mass and function in DBA/2J-mdx mice.

CONCLUSIONS

GLP-1R agonists ameliorate muscle wasting by suppressing MSTN and muscle atrophic factors and enhancing myogenic factors through GLP-1R-mediated signalling pathways. These novel findings suggest that activating GLP-1R signalling may be useful for the treatment of atrophy-related muscular diseases.

Growth, pubertal development, and skeletal health in boys with Duchenne Muscular Dystrophy

PURPOSE OF REVIEW

Glucocorticoid therapy is currently the most widely used treatment for Duchenne muscular dystrophy (DMD), having consistently shown to prolong ambulation by 2 years, reduce the frequency of scoliosis, and improve cardiorespiratory function. Among the most frequent side effects of glucocorticoids are fractures due to osteoporosis, linear growth retardation or arrest, and pubertal delay, the subjects of this review.

RECENT FINDINGS

The diagnosis of osteoporosis has shifted in recent years away from a bone mineral density-centric to a fracture-focused approach, with particular emphasis on early vertebral fracture identification (one of the key triggers for osteoporosis intervention). Delayed puberty should be addressed in an age-appropriate manner, with numerous options available for sex steroid replacement. Growth impairment, however, is a more challenging complication of glucocorticoid-treated DMD, one that is most likely best addressed through growth-sparing therapies that target the dystrophinopathy.

SUMMARY

With glucocorticoid prescription an increasingly prevalent component of DMD care, early attention to management of osteoporosis and delayed puberty are important components of multidisciplinary and anticipatory care. The treatment of short stature remains controversial, with no accepted therapy currently available to over-ride the toxic effects of glucocorticoids on the growth axis.

A characteristic signature of insulin-like growth factor (IGF) axis expression during osteogenic differentiation of human dental pulp cells (hDPCs): Potential co-ordinated regulation of IGF action

The IGF axis is represented by two growth factors (IGF1 and IGF2), two cognate cell surface receptors (IGF1R and IGF2R), six soluble high affinity IGF binding proteins (IGFBP1-6) and several IGFBP proteases. IGF1 and IGF2 are present at high concentrations in bone and play a crucial role in the maintenance and differentiation of both foetal and adult skeleton. In order to understand the role of the IGF axis in bone and other tissues it is necessary to profile the expression and activity of all genes in the axis together with the activity of relevant ancillary proteins (including IGFBP proteases). In the current report we used differentiating human dental pulp cells (hDPC) to examine the expression and activity of the IGF axis during osteogenic differentiation of these cells. We found that, with the exception of IGF1 and IGFBP1, all components of the IGF axis are expressed in hDPCs. IGFBP-4 is the most abundantly expressed IGFBP species at both mRNA and protein levels under both basal and osteogenic conditions. Although we found no difference in IGFBP-4 expression under osteogenic conditions, we report increased expression and activity of pregnancy associated plasma protein-A (PAPP-A - an IGFBP-4 proteinase) leading to increased IGFBP-4 proteolysis in differentiating cell cultures. Further to this we report increased expression of IGF-2 (an activator of PAPP-A), and decreased expression of stanniocalcin-2 (STC2- a recently discovered inhibitor of PAPP-A) under osteogenic conditions. We also demonstrate that STC2 and PAPP-A are able to form complexes in hDPC conditioned medium indicating the potential for regulation of IGFBP-4 proteolysis through this mechanism. We suggest that these changes in the expression and activity of the IGF axis may represent part of an osteogenic signature characteristic of differentiating hDPCs.

Pituitary Diseases and Bone

Neuroendocrinology of bone is a new area of research based on the evidence that pituitary hormones may directly modulate bone remodeling and metabolism. Skeletal fragility associated with high risk of fractures is a common complication of several pituitary diseases such as hypopituitarism, Cushing disease, acromegaly, and hyperprolactinemia. As in other forms of secondary osteoporosis, pituitary diseases generally affect bone quality more than bone quantity, and fractures may occur even in the presence of normal or low-normal bone mineral density as measured by dual-energy X-ray absorptiometry, making difficult the prediction of fractures in these clinical settings. Treatment of pituitary hormone excess and deficiency generally improves skeletal health, although some patients remain at high risk of fractures, and treatment with bone-active drugs may become mandatory. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary diseases.

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.

Glucocorticoid therapy causes contradictory changes of serum Wnt signaling-related molecules in systemic autoimmune diseases

The objective of this study was to investigate the clinical significance of the Wnt/β-catenin signaling pathway in glucocorticoid-induced osteoporosis. A total of 91 patients with systemic autoimmune diseases who received initial glucocorticoid therapy with prednisolone (30-60 mg daily) were prospectively enrolled. We measured serum levels of N-terminal peptide of type I procollagen (P1NP), bone alkaline phosphatase (BAP), tartrate-resistant acid phosphatase isoform 5b (TRACP-5b), N-telopeptide cross-linked type I collagen (NTX), sclerostin, Dickkopf-1 (Dkk-1), and Wnt3a before starting glucocorticoid therapy and every week for 4 weeks after its initiation. The effects of dexamethasone on expression of mRNA and protein of sclerostin and Dkk-1 by cultured normal human osteoblasts (NHOst) were evaluated by RT-PCR and ELISA, respectively. Serum levels of sclerostin and Dkk-1 increased significantly by 1 week of glucocorticoid therapy and then decreased from the second week onward. Serum Wnt3a tended to decrease and serum P1NP showed a significant decrease. However, TRACP-5b was significantly elevated from the first week of treatment onwards. In vitro study, dexamethasone increased Dkk-1 mRNA expression in cultured NHOst, but sclerostin mRNA was not detected. Dexamethasone also increased Dkk-1 protein production by osteoblasts, whereas sclerostin protein was not detected. Bone formation might be impaired at least in the first week of the initiation of glucocorticoid therapy by increase of the serum Wnt signaling inhibitors; however, their reductions in the subsequent weeks were contradictory to the maintained suppression of the bone formation markers after glucocorticoid therapy for patients with systemic autoimmune diseases.

Focus on growth hormone deficiency and bone in adults

Growth hormone (GH) exerts several effects on the skeleton, mediated either directly or indirectly, leading to increased bone formation and resorption rates. Patients with growth hormone deficiency (GHD) of adult onset have decreased bone mineral density (BMD) and increased fracture risk. Some, but not all, studies have found that adults with childhood onset GHD also have lower BMD than healthy controls. Adults with GHD of childhood onset have smaller bone dimensions, leading to possible underestimation of areal BMD (measured by dual energy X-ray absorptiometry), thus potentially confounding the interpretation of densitometric data. Available data suggest that patients with childhood onset GHD are at increased fracture risk. Prospective studies and some clinical trials found that GH replacement for at least 18-24 months leads to increased BMD. Retrospective and prospective data suggest that GH replacement is associated with decreased fracture risk in adults. However, data from randomized clinical trials are lacking.

Levodopa attenuates cellular apoptosis in steroid-associated necrosis of the femoral head

The present study aimed to investigate the effects of levodopa (LEV) on cellular apoptosis in a rabbit model of steroid-associated necrosis of the femoral head (SANFH). A total of 44 healthy adult Chinese rabbits were randomly divided into three groups: Group A (n=15), administered a combination of lipopolysaccharide and hormone to establish the SANFH animal model; group B (n=15), SANFH animal model as in group A orally administered LEV (0.4 g/kg/day) on the day of injection; and group C (n=14), the control group. On the 6th and 8th week of modeling, seven rabbits from each group were sacrificed to harvest bilateral femoral head specimens for hematoxylin and eosin staining and apoptosis detection by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay analysis, as well as for observing pathological changes and analyzing cellular apoptosis. Eight weeks after modeling, the serum insulin-like growth factor (IGF)-1 levels of the three groups were measured. The empty lacunae rate and apoptosis index of bone cells in the treatment group were significantly lower than that of the model group (P<0.01). Eight weeks after treatment, the serum levels of IGF-1 were significantly higher than that of the model group (P<0.01). These findings suggested that LEV was able to reduce steroid-induced bone cellular apoptosis, reduce the occurrence of necrosis of the femoral head and, through in vivo metabolism, it may promote the synthesis and release of IGF-1, which could be one of its biological pathways to prevent and treat SANFH.

IGFBP-2 and -3 co-ordinately regulate IGF1 induced matrix mineralisation of differentiating human dental pulp cells

Human dental pulp cells (DPCs), which are known to contain a subset of stem cells capable of reforming a dentin and pulp-like complex upon in vivo transplantation, were isolated from third molars of three healthy donors and differentiated to a matrix mineralisation phenotype using by culture in dexamethasone and l-ascorbic acid. qRT-PCR analysis of insulin-like growth factor ( IGF) axis gene expression indicated that all genes, except insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein-1 ( IGFBP-1), were expressed in DPCs. During differentiation upregulation of insulin-like growth factor binding protein-2 (IGFBP-2) and downregulation of insulin-like growth factor binding protein-3 (IGFBP-3) expression was observed. Changes in IGFBP-2 and IGFBP-3 mRNA expression were confirmed at the protein level by ELISA of DPC conditioned medium functional analysis indicated that IGF1 stimulated the differentiation of DPCs and that the activity of the growth factor was enhanced by pre-complexation with IGFBP-2 but inhibited by pre-complexation with IGFBP-3. Therefore changes in IGFBP-2 and -3 expression during differentiation form part of a co-ordinated functional response to enhance the pro-differentiative action of IGF1 and represent a novel mechanism for the regulation of DPC differentiation.

Implications of exercise-induced adipo-myokines in bone metabolism

Physical inactivity has been recognized, by the World Health Organization as the fourth cause of death (5.5 % worldwide). On the contrary, physical activity (PA) has been associated with improved quality of life and decreased risk of several diseases (i.e., stroke, hypertension, myocardial infarction, obesity, malignancies). Bone turnover is profoundly affected from PA both directly (load degree is the key determinant for BMD) and indirectly through the activation of several endocrine axes. Several molecules, secreted by muscle (myokines) and adipose tissues (adipokines) in response to exercise, are involved in the fine regulation of bone metabolism in response to the energy availability. Furthermore, bone regulates energy metabolism by communicating its energetic needs thanks to osteocalcin which acts on pancreatic β-cells and adipocytes. The beneficial effects of exercise on bone metabolism depends on the intermittent exposure to myokines (i.e., irisin, IL-6, LIF, IGF-I) which, instead, act as inflammatory/pro-resorptive mediators when chronically elevated; on the other hand, the reduction in the circulating levels of adipokines (i.e., leptin, visfatin, adiponectin, resistin) sustains these effects as well as improves the whole-body metabolic status. The aim of this review is to highlight the newest findings about the exercise-dependent regulation of these molecules and their role in the fine regulation of bone metabolism.

Prenatal food restriction induces poor-quality articular cartilage in female rat offspring fed a post-weaning high-fat diet and its intra-uterine programming mechanisms

Epidemiological data show that osteoarthritis (OA) is significantly associated with lower birth weight, and that OA may be a type of fetal-originated adult disease. The present study aimed to investigate the prenatal food-restriction (PFR) effect on the quality of articular cartilage in female offspring to explore the underlying mechanisms of fetal-originated OA. Maternal rats were fed a restricted diet from gestational day (GD) 11 to 20 to induce intra-uterine growth retardation. Female fetuses and female adult offspring fed a post-weaning high-fat diet were killed at GD20 and postnatal week 24, respectively. Serum and knee cartilage samples from fetuses and adult female offspring were collected and examined for cholesterol metabolism and histology. Fetal serum corticosterone and insulin-like growth factor-1 (IGF-1) in the PFR group were lower than those of the control, but the serum cholesterol level was not changed. The lower expression of IGF-1 in the PFR group lasted into adulthood. The expression of extracellular matrix (ECM) genes, including type II collagen, aggrecan and cholesterol efflux genes including liver X receptor, were significantly induced, but the ATP-binding-cassette transporter A1 was unchanged. PFR could induce a reduction in ECM synthesis and impaired cholesterol efflux in female offspring, and eventually led to poor quality of articular cartilage and OA.

Defining human insulin-like growth factor I gene regulation

Growth hormone (GH) plays an essential role in controlling somatic growth and in regulating multiple physiological processes in humans and other species. Insulin-like growth factor I (IGF-I), a conserved, secreted 70-amino acid peptide, is a critical mediator of many of the biological effects of GH. Previous studies have demonstrated that GH rapidly and potently promotes IGF-I gene expression in rodents and in some other mammals through the transcription factor STAT5b, leading to accumulation of IGF-I mRNAs and production of IGF-I. Despite this progress, very little is known about how GH or other trophic factors control human IGF1 gene expression, in large part because of the absence of any cellular model systems that robustly express IGF-I. Here, we have addressed mechanisms of regulation of human IGF-I by GH after generating cells in which the IGF1 chromosomal locus has been incorporated into a mouse cell line. Using this model, we found that physiological levels of GH rapidly stimulate human IGF1 gene transcription and identify several potential transcriptional enhancers in chromatin that bind STAT5b in a GH-regulated way. Each of the putative enhancers also activates a human IGF1 gene promoter in reconstitution experiments in the presence of the GH receptor, STAT5b, and GH. Thus we have developed a novel experimental platform that now may be used to determine how human IGF1 gene expression is controlled under different physiological and pathological conditions.

Rapid Eye Movement Sleep Deprivation Produces Long-Term Detrimental Effects in Spatial Memory and Modifies the Cellular Composition of the Subgranular Zone

Sleep deprivation (SD) affects spatial memory and proliferation in the dentate gyrus. It is unknown whether these deleterious effects persist in the long run. The aim of this study was to evaluate the proliferation, differentiation and maturation of neural progenitors as well as spatial memory 21 days after suffering SD. Sixty-day old male Balb/C mice were exposed to 72-h REM-SD. Spatial memory, cell fate, apoptosis and expression levels of insulin-like growth factor 1 receptor (IGF-1R) were evaluated in the hippocampus at 0, 14, and 21 days after SD or control conditions. After 21-days recovery period, memory performance was assessed with the Barnes maze, we found a significant memory impairment in SD mice vs. control (94.0 ± 10.2 s vs. 25.2 ± 4.5 s; p < 0.001). The number of BrdU+ cells was significantly decreased in the SD groups at day 14 (controls = 1.6 ± 0.1 vs. SD mice = 1.2 ± 0.1 cells/field; p = 0.001) and at day 21 (controls = 0.2 ± 0.03 vs. SD mice = 0.1 ± 0.02 cells/field; p < 0.001). A statistically significant decrease was observed in neuronal differentiation (1.4 ± 0.1 cells/field vs. 0.9 ± 0.1 cells/field, p = 0.003). Apoptosis was significantly increased at day 14 after SD (0.53 ± 0.06 TUNEL+ cells/field) compared to controls (0.19 ± 0.03 TUNEL+ cells/field p < 0.001) and at 21-days after SD (SD mice 0.53 ± 0.15 TUNEL+ cells/field; p = 0.035). At day 0, IGF-1R expression showed a statistically significant reduction in SD animals (64.6 ± 12.2 units) when compared to the control group (102.0 ± 9.8 units; p = 0.043). However, no statistically significant differences were found at days 14 and 21 after SD. In conclusion, a single exposition to SD for 72-h can induce deleterious effects that persist for at least 3 weeks. These changes are characterized by spatial memory impairment, reduction in the number of hippocampal BrdU+ cells and persistent apoptosis rate. In contrast, changes IGF-1R expression appears to be a transient event. Highlight Sleep deprivation affects spatial memory and proliferation in the dentate gyrus. To date it is unknown whether these deleterious effects are persistent over a long period of time. We analyzed the effects of sleep deprivation in the hippocampus after 21 days of recovery sleep. Our findings indicate that after sleep recovery, the detrimental effects of SD can be observed for at least 2 weeks, as shown by a reduction in memory performance, changes in the hippocampal cellular composition and higher apoptotic rate over a long period of time.

Vitamin D Signaling Modulators in Cancer Therapy

The antiproliferative and pro-apoptotic effects of 1α,25-dihydroxycholecalciferol (1,25(OH)2D3, 1,25D3, calcitriol) have been demonstrated in various tumor model systems in vitro and in vivo. However, limited antitumor effects of 1,25D3 have been observed in clinical trials. This may be attributed to a variety of factors including overexpression of the primary 1,25D3 degrading enzyme, CYP24A1, in tumors, which would lead to rapid local inactivation of 1,25D3. An alternative strategy for improving the antitumor activity of 1,25D3 involves the combination with a selective CYP24A1 inhibitor. The validity of this approach is supported by numerous preclinical investigations, which demonstrate that CYP24A1 inhibitors suppress 1,25D3 catabolism in tumor cells and increase the effects of 1,25D3 on gene expression and cell growth. Studies are now required to determine whether selective CYP24A1 inhibitors+1,25D3 can be used safely and effectively in patients. CYP24A1 inhibitors plus 1,25D3 can cause dose-limiting toxicity of vitamin D (hypercalcemia) in some patients. Dexamethasone significantly reduces 1,25D3-mediated hypercalcemia and enhances the antitumor activity of 1,25D3, increases VDR-ligand binding, and increases VDR protein expression. Efforts to dissect the mechanisms responsible for CYP24A1 overexpression and combinational effect of 1,25D3/dexamethasone in tumors are underway. Understanding the cross talk between vitamin D receptor (VDR) and glucocorticoid receptor (GR) signaling axes is of crucial importance to the design of new therapies that include 1,25D3 and dexamethasone. Insights gained from these studies are expected to yield novel strategies to improve the efficacy of 1,25D3 treatment.

Effects of Growth Hormone on Bone

PURPOSE

Describe the effects of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) on the skeleton.

FINDINGS

The GH and IGF-1 axis has pleiotropic effects on the skeleton throughout the lifespan by influencing bone formation and resorption. GH deficiency leads to decreased bone turnover, delayed statural growth in children, low bone mass, and increased fracture risk in adults. GH replacement improves adult stature in GH deficient children, increases bone mineral density (BMD) in adults, and helps to optimize peak bone acquisition in patients, during the transition from adolescence to adulthood, who have persistent GH deficiency. Observational studies suggest that GH replacement may mitigate the excessive fracture risk associated with GH deficiency. Acromegaly, a state of GH and IGF-1 excess, is associated with increased bone turnover and decreased BMD in the lumbar spine observed in some studies, particularly in patients with hypogonadism. In addition, patients with acromegaly appear to be at an increased risk of morphometric-vertebral fractures, especially in the presence of active disease or concurrent hypogonadism. GH therapy also has beneficial effects on statural growth in several conditions characterized by GH insensitivity, including chronic renal failure, Turner syndrome, Prader-Willi syndrome, postnatal growth delay in patients with intrauterine growth retardation who do not demonstrate catchup growth, idiopathic short stature, short stature homeobox-containing (SHOX) gene mutations, and Noonan syndrome.

SUMMARY

GH and IGF-1 have important roles in skeletal physiology, and GH has an important therapeutic role in both GH deficiency and insensitivity states.

Glucocorticoid-Induced Osteoporosis

Osteoporosis is among the most devastating side effects of glucocorticoid (GC) therapy for the management of inflammatory and auto-immune diseases. Evidence from both humans and mice indicate deleterious skeletal effects within weeks of pharmacological GC administration, both related and unrelated to a decrease in bone mineral density (BMD). Osteoclast numbers and bone resorption are also rapidly increased, and together with osteoblast inactivation and decreased bone formation, these changes lead the fastest loss in BMD during the initial disease phase. Bone resorption then decreases to sub-physiological levels, but persistent and severe inhibition of bone formation leads to further bone loss and progressively increased fracture risk, up to an order of magnitude higher than that observed in untreated individuals. Bone forming osteoblasts are thus considered the main culprits in GC-induced osteoporosis (GIO). Accordingly, we focus this review primarily on deleterious effects on osteoblasts: inhibition of cell replication and function and acceleration of apoptosis. Mediating these adverse effects, GCs target pivotal regulatory mechanisms that govern osteoblast growth, differentiation and survival. Specifically, GCs inhibit growth factor pathways, including Insulin Growth Factors, Growth Hormone, Hepatocyte Growth/Scatter Factor and IL6-type cytokines. They also inhibit downstream kinases, including PI3-kinase and the MAP kinase ERK, the latter attributable in part to direct transcriptional stimulation of MAP kinase phosphatase 1. Most importantly, however, GCs inhibit the Wnt signaling pathway, which plays a pivotal role in osteoblast replication, function and survival. They transcriptionally stimulate expression of Wnt inhibitors of both the Dkk and Sfrp families, and they induce reactive oxygen species (ROS), which result in loss of ß-catenin to ROS-activated FoxO transcription factors. Identification of dissociated GCs, which would suppress the immune system without causing osteoporosis, is proving more challenging than initially thought, and GIO is currently managed by co-treatment with bisphosphonates or PTH. These drugs, however, are not ideally suited for GIO. Future therapeutic approaches may aim at GC targets such as those mentioned above, or newly identified targets including the Notch pathway, the AP-1/Il11 axis and the osteoblast master regulator RUNX2.

Management of endocrine disease: Secondary osteoporosis: pathophysiology and management

Osteoporosis is a skeletal disorder characterized by decreased mass and compromised bone strength predisposing to an increased risk of fractures. Although idiopathic osteoporosis is the most common form of osteoporosis, secondary factors may contribute to the bone loss and increased fracture risk in patients presenting with fragility fractures or osteoporosis. Several medical conditions and medications significantly increase the risk for bone loss and skeletal fragility. This review focuses on some of the common causes of osteoporosis, addressing the underlying mechanisms, diagnostic approach and treatment of low bone mass in the presence of these conditions.

Effects of Collagen Crosslinking on Bone Material Properties in Health and Disease

Data have accumulated to show that various types of collagen crosslinking are implicated in the health of individuals, as well as in a number of disease states, such as osteoporosis, diabetes mellitus, chronic kidney disease, inflammatory bowel disease, or in conditions of mild hyperhomocysteinemia, or when glucocorticoid use is indicated. Collagen crosslinking is a posttranslational modification of collagen molecules and plays important roles in tissue differentiation and in the mechanical properties of collagenous tissue. The crosslinking of collagen in the body can form via two mechanisms: one is enzymatic crosslinking and the other is nonenzymatic crosslinking. Lysyl hydroxylases and lysyl oxidases regulate tissue-specific crosslinking patterns and quantities. Enzymatic crosslinks initially form via immature divalent crosslinking, and a portion of them convert into mature trivalent forms such as pyridinoline and pyrrole crosslinks. Nonenzymatic crosslinks form as a result of reactions which create advanced glycation end products (AGEs), such as pentosidine and glucosepane. These types of crosslinks differ in terms of their mechanisms of formation and function. Impaired enzymatic crosslinking and/or an increase of AGEs have been proposed as a major cause of bone fragility associated with aging and numerous disease states. This review focuses on the effects of collagen crosslinking on bone material properties in health and disease.

The role of the insulin‑like growth factor (IGF) axis in osteogenic and odontogenic differentiation

The insulin-like growth factor (IGF) axis is a multicomponent molecular network which has important biological functions in the development and maintenance of differentiated tissue function(s). One of the most important functions of the IGF axis is the control of skeletal tissue metabolism by the finely tuned regulation of the process of osteogenesis. To achieve this, the IGF axis controls the activity of several cell types—osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts to achieve the co-ordinated development of appropriate hard tissue structure and associated matrix deposition. In addition, there is an increasing awareness that the IGF axis also plays a role in the process of odontogenesis (tooth formation). In this review, we highlight some of the key findings in both of these areas. A further understanding of the role of the IGF axis in hard tissue biology may contribute to tissue regeneration strategies in cases of skeletal tissue trauma.

Phenotypic differences in white-tailed deer antlerogenic progenitor cells and marrow-derived mesenchymal stromal cells

Deer antlers are bony appendages that are annually cast and rapidly regrown in a seasonal process coupled to the reproductive cycle. Due to the uniqueness of this process among mammals, we reasoned that a fundamental characterization of antler progenitor cell behavior may provide insights that could lead to improved strategies for promoting bone repair. In this study, we investigated whether white-tailed deer antlerogenic progenitor cells (APC) conform to basic criteria defining mesenchymal stromal cells (MSC). In addition, we tested the effects of the artificial glucocorticoid dexamethasone (DEX) on osteogenic and chondrogenic differentiation as well as the degree of apoptosis during the latter. Comparisons were made to animal-matched marrow-derived MSC. APC and MSC generated similar numbers of colonies. APC cultures expanded less rapidly overall but experienced population recovery at later time points. In contrast to MSC, APC did not display adipogenic in vitro differentiation capacity. Under osteogenic culture conditions, APC and MSC exhibited different patterns of alkaline phosphatase activity over time. DEX increased APC alkaline phosphatase activity only initially but consistently led to decreased activity in MSC. APC and MSC in osteogenic culture underwent different time and DEX-dependent patterns of mineralization, yet APC and MSC achieved similar levels of mineral accrual in an ectopic ossicle model. During chondrogenic differentiation, APC exhibited high levels of apoptosis without a reduction in cell density. DEX decreased proteoglycan production and increased apoptosis in chondrogenic APC cultures but had the opposite effects in MSC. Our results suggest that APC and MSC proliferation and differentiation differ in their dependence on time, factors, and milieu. Antler tip APC may be more lineage-restricted osteo/chondroprogenitors with distinctly different responses to apoptotic and glucocorticoid stimuli.

The many faces of C/EBPδ and their relevance for inflammation and cancer

The CCAAT/enhancer binding protein delta (CEBPD, C/EBPδ) is a transcription factor that modulates many biological processes including cell differentiation, motility, growth arrest, proliferation, and cell death. The diversity of C/EBPδ's functions depends in part on the cell type and cellular context and can have opposing outcomes. For example, C/EBPδ promotes inflammatory signaling, but it can also inhibit pro-inflammatory pathways, and in a mouse model of mammary tumorigenesis, C/EBPδ reduces tumor incidence but promotes tumor metastasis. This review highlights the multifaceted nature of C/EBPδ's functions, with an emphasis on pathways that are relevant for cancer and inflammation, and illustrates how C/EBPδ emerged from the shadow of its family members as a fascinating “jack of all trades.” Our current knowledge on C/EBPδ indicates that, rather than being essential for a specific cellular process, C/EBPδ helps to interpret a variety of cues in a cell-type and context-dependent manner, to adjust cellular functions to specific situations. Therefore, insights into the roles and mechanisms of C/EBPδ signaling can lead to a better understanding of how the integration of different signaling pathways dictates normal and pathological cell functions and physiology.

The interrelationship between bone and fat: from cellular see-saw to endocrine reciprocity

The number of mature osteoblasts and marrow adipocytes in bone is influenced by the differentiation of the common mesenchymal progenitor cell towards one phenotype and away from the other. Consequently, factors which promote adipogenesis not only lead to fatty marrow but also inhibit osteoblastogenesis, resulting in decreased osteoblast numbers, diminished bone formation and, potentially, inadequate bone mass and osteoporosis. In addition to osteoblast and bone adipocyte numbers being influenced by this skewing of progenitor cell differentiation towards one phenotype, mature osteoblasts and adipocytes secrete factors which may evoke changes in the cell fate and function of each other. This review examines the endogenous factors, such as PPAR-γ2, Wnt, IGF-1, GH, FGF-2, oestrogen, the GP130 signalling cytokines, vitamin D and glucocorticoids, which regulate the selection between osteoblastogenesis and adipogenesis and the interrelationship between fat and bone. The role of adipokines on bone, such as adiponectin and leptin, as well as adipose-derived oestrogen, is reviewed and the role of bone as an energy regulating endocrine organ is discussed.

Mechanical-tactile stimulation (MTS) intervention in a neonatal stress model alters adult adipose tissue deposition and prevents hyperinsulinemia in male rats

Preterm infants are exposed to numerous stressors during hospitalization and by term corrected gestational age they have lower body weight but a greater proportion of total body as well as abdominal visceral adipose tissue (VAT) accumulation. Greater abdominal VAT stores have a known association with metabolic syndrome. Mechanical-tactile stimulation (MTS) improves modulation of stress response in both humans and rodents. We hypothesize that MTS, administered during an established model of neonatal stress, would decrease stress-driven adiposity and prevent associated metabolic imbalances in adult rats. Neonatal stress, administered to rat pups from postnatal days 5 to P9, consisted of needle puncture and hypoxic/hyperoxic challenge during 60 min of maternal separation (STRESS; n=20). Mechanical-tactile stimulation (MTS; n=20) was administered to rat pups for 10 min during maternal separation in the stress protocol. Control animals received standard care (CTL; n=20). MRI measured adult (P120) abdominal total fat mass, subcutaneous (SAT) and visceral adipose tissue (VAT). Body weight and fasting serum adiponectin, leptin, glucose, insulin, and corticosterone were also measured. STRESS results in elevated VAT/SAT ratio compared to CTL but lower abdominal total fat mass and abdominal SAT. STRESS males experience hyperinsulinemia. Both STRESS and MTS had elevated leptin with lower adiponectin and corticosterone compared to CTL. In summary, neonatal stress promotes greater abdominal VAT accumulation and, in males, caused hyperinsulinemia and hypoadiponectinemia. Importantly, MTS normalized the VAT/SAT ratio and prevented hyperinsulinemia. We speculate that MTS ameliorates some of the negative metabolic consequences of early life perturbations due to neonatal stress exposure.

Glycyrrhizic acid (GCA) as 11β-hydroxysteroid dehydrogenase inhibitor exerts protective effect against glucocorticoid-induced osteoporosis

Rapid onset of bone loss is a frequent complication of systemic glucocorticoid therapy which may lead to fragility fractures. Glucocorticoid action in bone depends upon the activity of 11β-hydroxysteroid dehydrogenase type 1 enzyme (11β-HSD1). Regulations of 11β-HSD1 activity may protect the bone against bone loss due to excess glucocorticoids. Glycyrrhizic acid (GCA) is a potent inhibitor of 11β-HSD. Treatment with GCA led to significant reduction in bone resorption markers. In this study we determined the effect of GCA on 11β-HSD1 activity in bones of glucocorticoid-induced osteoporotic rats. Thirty-six male Sprague-Dawley rats (aged 3 months and weighing 250-300 g) were divided randomly into groups of ten. (1) G1, sham operated group; (2) G2, adrenalectomized rats administered with intramuscular dexamethasone 120 μg/kg/day and oral vehicle normal saline vehicle; and (3) G3, adrenalectomized rats administered with intramuscular dexamethasone 120 μg/kg/day and oral GCA 120 mg/kg/day The results showed that GCA reduced plasma corticosterone concentration. GCA also reduced serum concentration of the bone resorption marker, pyridinoline and induced 11β-HSD1 dehydrogenase activity in the bone. GCA improved bone structure, which contributed to stronger bone. Therefore, GCA has the potential to be used as an agent to protect the bone against glucocorticoid induced osteoporosis.

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.

Fetal programming of brain development: intrauterine stress and susceptibility to psychopathology

The fetal brain is highly plastic and is not only receptive to but requires cues from its environment to develop properly. Based on an understanding of evolutionary biology, developmental plasticity, and life history theory, one can predict that stressors are an important environmental condition that may influence brain development. In fact, the available empirical evidence appears to support the notion that exposure to excess stress in intrauterine life has the potential to adversely affect short- and long-term neurodevelopmental outcomes with implications for altered susceptibility for mental health disorders in childhood and adult life. In this presentation, we provide a rationale for proposing that endocrine and inflammatory stress mediators are key candidate pathways for programming brain development. These mediators are responsive to a diverse set of intrauterine perturbations and alter key signaling pathways critical for brain development, including but not limited to mammalian target of rapamycin, Wnt (wingless), Sonic hedgehog, and reelin signaling. We suggest that recent advances in neuroimaging and other methods now afford us an unprecedented opportunity to advance our understanding of this important topic. Additionally, we provide empirical evidence from two recently published papers for fetal programming of human brain development. We conclude by suggesting some future directions for expanding this field of research.

Effect of DHEA supplementation on serum IGF-1, osteocalcin, and bone mineral density in postmenopausal, glucocorticoid-treated women

PURPOSE

DHEA therapy increases bone formation in postmenopausal women. We have found only a few reports of dehydroepiandrosterone replacement therapy in women receiving long-term glucocorticoid medication. The purpose of this study was to establish whether DHEA replacement therapy may be useful in the treatment of steroid-induced osteoporosis in postmenopausal women.

MATERIALS AND METHODS

Nineteen women, aged 50-78 years, treated at least for three years with average daily doses of more than 7.5 mg prednisone, with T-score L2/L4<-1.5 and bisphosphonates intolerance, were enrolled to the study. For the first year of the study the patients were given calcium, vitamin D3 and thiazide diuretics. For another year the patients received orally micronized DHEA 25-50 mg daily. Before the study, after twelve months of Calcium/D3 therapy, then after six weeks and six months of DHEA therapy, serum concentrations of DHEAS, androstenedione, testosterone, estradiol, FSH, IGF-1 and osteocalcin were assessed. Bone mineral density (BMD) in lumbar spine and femoral neck was measured before the treatment, after a year on Calcium/D3 and after six and twelve months of DHEA replacement therapy.

RESULTS

In all treated women, DHEA significantly increased serum DHEAS, androstenedione and testosterone concentrations. A significant elevation of serum IGF-1 and osteocalcin concentrations was found as early as after six weeks of DHEA treatment. A significant increase of bone mineral density in the lumbar spine and femoral neck was observed after six and twelve months of DHEA treatment.

CONCLUSION

Our results suggest a beneficial role of DHEA replacement therapy in the treatment of steroid-induced osteoporosis.

Spontaneous recovery of bone mass after cure of endogenous hypercortisolism

Patients with Cushing's syndrome (CS) develop osteopenia-osteoporosis. The present study evaluates the recovery of bone mass within 2 years after remission of hypercortisolism and in long term follow up, an issue rarely addressed. Twenty patients (6M, 14F, 3 post-menopausal, 15-64 years old), 15 with Cushing's disease, 2 with ectopic ACTH syndrome, 3 with ACTH-independent CS were studied. BMD, T and Z scores at lumbar spine and proximal femur were assessed by dual-energy X-ray absorptiometry before and 7-33 months after treatment of hypercortisolism. Five patients were treated with bisphosphonates. Four patients had hypogonadism and 4 GH-deficiency. At baseline all patients showed osteopenia/osteoporosis and the spine appeared more damaged than the femur; femur BMD was positively related with body mass index (BMI). No correlations were observed between spine and femur bone parameters and duration of disease or severity of hypercortisolism. Bone parameters did not differ in patients with or without GH or other pituitary deficiencies. After cure of hypercortisolism a significant improvement in spine BMD, Z and T scores and in femur Z and T scores was observed with normalization in 3 patients; there was no significant difference in percent improvement between femur and spine. The increase in bone parameters at spine and femur was independent from values at baseline. The percent increase in spine T and Z scores was positively related with time elapsed since cure. Bisphosphonates did not influence the recovery of bone mineralization. In long term follow up, after a median period of 7 years a further improvement in bone density was observed in 100% of patients at spine and in 9/11 at femur, although 8/11 patients still had femoral and/or vertebral T score in the range of osteopenia/osteoporosis. Spontaneous improvement of osteoporosis after cure of hypercortisolism occurs both at spine and femur, is independent from basal conditions and not affected by bisphosphonates. The improvement at spine depends on time since cure.

Adverse effects of corticosteroids on bone metabolism: a review

Glucocorticoid (GC) exposure is the most common etiology of drug-induced (secondary) osteoporosis. Twenty percent of all cases of osteoporosis have been attributed to GC exposure. Significant risk factors for the development of fractures after GC exposure include age older than 65 years, prolonged GC exposure (>3 months), positive family history of osteoporosis, and low calcium intake. GCs are known to inhibit bone remodeling and to increase fracture risk. GC exposure alters the fragile balance between osteoclast and osteoblast activity in bone metabolism. GC stimulates osteoclast-mediated bone resorption and reduces osteoblast-mediated bone formation, which results in increased overall net bone resorption. Specifically, the 2 main effects of GCs on bone metabolism are (1) inducing apoptosis in osteoblasts and osteocytes, thereby decreasing bone formation, and (2) prolonging the lifespan of osteoclasts and increasing bone resorption. The risk of fracture decreases 3 months after cessation of GC therapy; thus, a 3-month period may be ideal between GC exposures in patients at high risk for the development of osteoporosis. Patients managed with GCs who are at high risk for the development of secondary osteoporosis should have appropriate diagnostic testing; pre-GC exposure medication management (ie, use of bisphosphonates, human parathyroid hormone); and a limitation of GC therapy, with a wait period of 3 months between GC exposures if possible.

Extrinsic mechanisms involved in age-related defective bone formation

CONTEXT

Age-related bone loss is associated with progressive changes in bone remodeling characterized by decreased bone formation relative to bone resorption. Both trabecular and periosteal bone formation decline with age in both sexes, which contributes to bone fragility and increased risk of fractures. Studies in rodents and humans revealed that, independent of sex hormone deficiency, the age-related decline in bone formation is characterized by decreased osteoblast number and lifespan and reduced bone-forming capacity of individual osteoblasts. An important clinical question is to identify the mechanisms involved in the age-related defective bone formation.

EVIDENCE ACQUISITION

The mechanisms discussed in this review are based on a PubMed search and knowledge of the authors in the field.

EVIDENCE SYNTHESIS

Available basic and clinical studies indicate that multiple mechanisms are involved in the alterations of osteoblastogenesis and the resulting decline in bone formation with aging. Notably, the age-related osteoblast dysfunctions and defective bone formation are caused by a number of extrinsic clinical factors that inhibit anabolic signaling pathways in bone. Thus, targeting these pathways can abolish age-related bone loss.

CONCLUSIONS

The identification of extrinsic mechanisms involved in osteoblast dysfunctions associated with aging improves our knowledge of age-related bone loss and provides a basis for therapeutic intervention to improve bone formation and bone mass in the aging population.

Novel regulation of 25-hydroxyvitamin D3 24-hydroxylase (24(OH)ase) transcription by glucocorticoids: cooperative effects of the glucocorticoid receptor, C/EBP beta, and the Vitamin D receptor in 24(OH)ase transcription

Glucocorticoid-induced bone loss has been proposed to involve direct effects on bone cells as well as alterations in calcium absorption and excretion. Since vitamin D is important for the maintenance of calcium homeostasis, in the present study the effects of glucocorticoids on vitamin D metabolism through the expression of 24(OH)ase, an enzyme involved in the catabolism of 1,25(OH)(2)D(3), were examined. Injection of vitamin D replete mice with dexamethasone (dex) resulted in a significant induction in 24(OH)ase mRNA in kidney, indicating a regulatory effect of glucocorticoids on vitamin D metabolism. Whether glucocorticoids can affect 24(OH)ase transcription is not known. Here we demonstrate for the first time a glucocorticoid receptor (GR) dependent enhancement of 1,25(OH)(2)D(3)-induced 24(OH)ase transcription. Dex treatment of GR and vitamin D receptor (VDR) transfected COS-7 cells and dex treatment of osteoblastic cells (in which VDR and GR are present endogenously) potentiated 1,25(OH)(2)D(3)-induced 24(OH)ase transcription. In addition, GR was found to cooperate with C/EBP beta to enhance VDR-mediated 24(OH)ase transcription. Using the rat 24(OH)ase promoter with the C/EBP site mutated, GR-mediated potentiation of 1,25(OH)(2)D(3)-induced 24(OH)ase transcription was inhibited. Immunoprecipitation indicated that that GR can interact with C/EBP beta and ChIP/re-ChIP analysis showed that C/EBP beta and GR bind simultaneously to the 24(OH)ase promoter. These findings indicate a novel mechanism whereby glucocorticoids can alter VDR-mediated 24(OH)ase transcription through functional cooperation between C/EBP beta and GR that results in an enhanced ability of C/EBP beta to cooperate with VDR in the regulation of 24(OH)ase.

Effects of stocking density and feed ration on growth and gene expression in the Senegalese sole (Solea senegalensis): potential effects on the immune response

Stocking density and ration size are two major factors influencing aquaculture production. To evaluate their effects on growth and immune system in Senegalese sole (Solea senegalensis) juveniles, a 2 x 2 experimental design using two rations (1.0% and 0.25% of the total fish biomass) and two different initial stocking densities (7 and 30 kg m(-2)) was performed throughout a 60 days culture period. Soles fed 1.0% showed a higher specific growth rate (SGR) than those fed 0.25% (3.3-fold). No differences in SGR at 60 days were found between densities in spite of reduced values were detected at high density after 20 days (soles fed 0.25%) and 40 days (soles fed 1%) suggesting a compensatory growth. Physiologically, plasma cortisol levels were elevated in soles at high density (45-fold higher than at 7 kg m(-2)) whereas no differences associated to the feeding ration were observed. To assess the effects at a molecular level, the mRNA levels of genes involved in cellular stress (heat shock proteins HSP70 and HSP90), growth (insulin-like growth factors IGF-I, the spliced variants IGF-Ia and IGFI-b, and IGF-II) and innate immune system (g-type lysozyme and hepcidin (HAMP1)) were quantified. No differences in HSP90 expression were detected between densities or rations. In contrast, IGF-I, IGF-Ia and IGF-II showed reduced transcript levels in liver and HSP70 in liver and kidney at high density. Finally, g-type lysozyme and HAMP1 expression was greatly affected by both factors exhibiting an important reduction in the transcript levels at high density and low ration. Overall, our results show that S. senegalensis juveniles might exhibit satisfactory SGR at high density although the high plasma cortisol levels indicate a crowding stress that could negatively affect the expression levels of some of the genes studied.