Mechanisms of sex steroid effects on bone

β-Caryophyllene and Statins in Bone Fracture Healing - A Narrative Review

Bone fractures are a leading cause of morbidity and healthcare expenditure globally. The complex healing process involves inflammation, cartilage formation, mineralization, and bone remodeling. Current treatments like immobilization, surgery, and bone grafting, though effective, pose significant challenges, such as prolonged recovery and high costs. Emerging therapies such as biological agents, pharmacological treatments, and physical stimulation techniques are also associated with high costs, side effects, and practical applicability limitations. There is a critical need for alternative therapies that are cost-effective, safe, and easy to use. Recent studies suggest the potential of β-caryophyllene (BCP) and statins in promoting bone healing. BCP, a naturally occurring anti-inflammatory and antioxidant compound found in essential oils, enhances osteoblast activity and inhibits osteoclastogenesis. Statins, known for their cholesterol-lowering effects, also promote bone formation and reduce bone resorption through multiple biochemical pathways. Both BCP and statins have shown promising results in preclinical studies, enhancing bone density and promoting fracture healing. This review explores the individual and potential synergistic effects of BCP and statins on bone fracture healing. It highlights the complementary mechanisms of these agents: BCP's anti-inflammatory and osteogenic properties and statins' ability to inhibit osteoclast activity and promote angiogenesis. Combining BCP and statins could offer a multifaceted approach to enhance fracture healing, reduce complications, and improve patient outcomes. While individual effects are supported preclinically, further studies investigating synergies, formulations, and clinical translation are needed to develop this promising novel therapeutic approach for improving fracture repair outcomes.

Personalized statin therapy: Targeting metabolic processes to modulate the therapeutic and adverse effects of statins

Statins are widely used for treating lipid disorders and cardiovascular diseases. However, the therapeutic efficiency and adverse effects of statins vary among different patients, which numerous clinical and epidemiological studies have attributed to genetic polymorphisms in statin-metabolizing enzymes and transport proteins. The metabolic processes of statins are relatively complex, involving spontaneous or enzyme-catalyzed interconversion between more toxic lactone metabolites and active acid forms in the liver and bloodstream, influenced by multiple factors, including the expression levels of many metabolic enzymes and transporters. Addressing the variable statin therapeutic outcomes is a pressing clinical challenge. Transcription factors and epigenetic modifications regulate the metabolic enzymes and transporters involved in statin metabolism and disposition and, therefore, hold promise as 'personalized' targets for achieving optimized statin therapy. In this review, we explore the potential for customizing therapy by targeting the metabolism of statin medications. The biochemical bases of adverse reactions to statin drugs and their correlation with polymorphisms in metabolic enzymes and transporters are summarized. Next, we mainly focus on the regulatory roles of transcription factors and epigenetic modifications in regulating the gene expression of statin biochemical machinery. The recommendations for future therapies are finally proposed by targeting the central regulatory factors of statin metabolism.

Environmental contaminants, sex hormones and SHBG in an elderly population

INTRODUCTION

Effects of environmental contaminants (ECs) on endocrine systems have been reported, but few studies assessed associations between ECs and sex hormones (SH) in elderly. Aim of this study was to investigate whether blood concentrations of four classes of ECs were associated with SH concentrations in elderly.

METHODS

Samples from participants of the cross-sectional population-based Prospective Investigation of the Vasculature in Uppsala Seniors study (PIVUS, 70-year-old men and women, n = 1016) were analyzed using validated mass spectrometry-based methods for SH (testosterone (T), dihydrotestosterone (DHT), estrone and estradiol (E2)); 23 persistent organic pollutants (POPs); 8 perfluoroalkyl substances (PFAS); 4 phthalates and 11 metals. SH binding globulin (SHBG) was analyzed using immunoassay. The measured concentrations were normalized, and the values converted to a z-scale. Linear regression analyses were conducted to assess association between concentration of the SH, SHBG and E2/T (aromatase enzyme index, AEI) with the ECs. Multiple linear regression analyses were performed to model the relationships.

RESULTS

The strongest associations were observed with the polychlorinated biphenyls (PCBs). In men, the strongest associations with concentrations of SH and SHBG were seen for PCBs containing >5 chlorine, monoethyl phthalate (MEP), Ni and Cd; and in women, with PCBs, MEP, several of the PFAS, Cd, Co, and Ni. Difference in the effect of ECs on AEI between men and women were observed. Area under the ROC curve for the models predicting abnormal values of SH and SHBG >0.75 due to the effects of ECs was observed for T, DHT, and E2 in men, and for E2 and SHBG in women.

CONCLUSIONS

Results of this study suggest that in elderly subjects, concentrations of many ECs associated with concentrations of SH and SHBG, and AEI. Further studies are needed to confirm the findings and to assess effect of the pollutants on endocrine system function in elderly.

Optimal Management of Osteoporosis in the Spinal Cord (Injury) Population

Spinal cord injury (SCI) leads to significant bone loss resulting in osteoporosis and an increased risk of fractures below the level of injury. It is imperative to screen for osteoporosis in all individuals with SCI starting immediately after the acute injury. Although data are limited, clinicians are encouraged to discuss preventative treatment in the acute SCI period and to treat osteoporosis when diagnosed.

Body composition and perceived stress levels in transgender individuals after one year of gender affirming hormone therapy

Introduction

Higher stress levels are linked to increased body fat and decreased bone density, effects that can be exacerbated by lifestyle choices. This is particularly relevant for transgender and gender diverse (TGD) individuals, who often face additional stress from transphobia and social stigma. However, there is limited research on how stress affects body composition and bone health in TGD individuals, particularly in relation to gender-affirming hormone therapy (GAHT). This study examines the impact of perceived stress on these factors in TGD individuals before and after one year of GAHT, compared to a cisgender control group.

Methods

The study assessed 181 individuals, including 74 TGD participants (44 assigned female at birth [AFAB] and 30 assigned male at birth [AMAB]) and 107 controls (56 AFAB and 51 AMAB). Fifty-seven TGD participants completed follow-up one year after starting GAHT. Data collected included clinical history, blood tests, body composition, bone density, and quality of life assessments (Patient Health Questionnaire-9 [PHQ-9] and Perceived Stress Scale [PSS]).

Results

After one year of GAHT, TGD AFAB individuals showed a bone mineral density (BMD) similar to cisgender AMAB individuals, while TGD AMAB individuals' BMD remained significantly lower than cisgender controls. TGD AFAB individuals experienced increases in muscle strength (+8% from baseline), while TGD AMAB individuals showed a 24% increase in fat mass from baseline and an approximate 8% reduction in lean mass. PSS and PHQ scores, initially higher in TGD individuals, did not change significantly after one year of GAHT. A significant correlation was found between body fat percentage and PHQ and PSS scores at baseline and one year after GAHT, respectively.

Discussion

These findings reveal a complex relationship between GAHT, body composition, and perceived stress in TGD individuals, highlighting the need for further research on stress and health outcomes in this population.

The path less traveled: Using structural equation modeling to investigate factors influencing bone functional morphology

OBJECTIVES

The relationship between an organism's mechanical environment and its bone strength has been long established by experimental research. Multiple intrinsic and extrinsic factors, including body mass, muscle strength, genetic background, and nutritional and/or hormonal status, are likely to influence bone deposition and resorption throughout the lifespan, complicating this relationship. Structural equation modeling (SEM) is uniquely positioned to parse this complex set of influences.

MATERIALS AND METHODS

Data from the Third National Health and Nutrition Examination Survey, including sex, total body mass, lean body mass, exercise frequency, peak body mass, and age, were analyzed using SEM to determine how they affect bone strength both individually and combined.

RESULTS

Body mass is typically the driver of cross-sectional area, but body mass and lean mass have similar effects on the polar moment of area (J). Peak body mass had a strong direct effect on J, despite decreasing strongly with increases in lean mass. Exercise also did not confer a large direct effect on cross-sectional area or J but did modify body mass and lean mass. In females, intentional weight loss was associated with decreased exercise levels.

DISCUSSION

SEM is a useful tool for parsing complex systems in bone functional morphology and has the potential to uncover causal links in the study of skeletal remodeling, including factors like weight loss or exercise that may have secondary effects.

Catalpol attenuates osteoporosis in ovariectomized rats through promoting osteoclast apoptosis via the Sirt6-ERα-FasL axis

BACKGROUND

Catalpol, a major active component of the Chinese herb Rehmannia glutinosa, possesses various pharmacological benefits, including anti-inflammatory, antidiabetic, and antitumor properties. Recent studies have reported that catalpol can attenuate bone loss and enhance bone formation. Nevertheless, the molecular mechanisms underlying its effects on osteoporosis pathogenesis remain unclear.

PURPOSE

We investigated whether catalpol had a protective effect against postmenopausal osteoporosis (PMOP) and explored its exact mechanism of action.

METHODS

Seventy-two rats were randomly divided into six groups: sham, model, low-dose catalpol (5 mg/kg/day), medium-dose catalpol (10 mg/kg/day), high-dose catalpol (20 mg/kg/day), and positive control (alendronate, 2.5 mg/kg). In this experiment, a ovariectomy was performed to establish a female rat model of PMOP. After 12 weeks of gavage, micro-computed tomography (micro-CT) and histochemical staining were performed to evaluate bone mass, bone microstructure and histological parameters. Furthermore, RAW 264.7 cells were induced by RANKL to form mature osteoclasts to investigate the effect of catalpol on osteoclast differentiation and apoptosis in vitro. Additionally, the osteoclast apoptosis-related proteins of Sirt6, ERα, FasL, NFATc1, cleaved-caspase 8, cleaved-caspase 3, and Bax were assessed using western blotting. The expressions of NFATc1, Ctsk, Oscar, and Trap were quantified using RT-qPCR. The apoptotic rate of the osteoclasts was determined using flow cytometry. Sirt6 knockdown was performed using siRNA gene silencing in experiments to investigate its role in catalpol-mediated osteoclast apoptosis. The deacetylation of ERα in osteoclasts was tested via co-immunoprecipitation.

RESULTS

Catalpol (10 and 20 mg/kg) and alendronate (2.5 mg/kg) could significantly improve bone mineral density (BMD) and microstructure and decrease osteoclast density in ovariectomized (OVX) rats. In addition, catalpol (10 and 20 mg/kg) upregulated the expression of Sirt6, ERα, FasL, cleaved-caspase 8, cleaved-caspase 3, Bax, and downregulated the expression of NFATc1, Ctsk, Oscar, Trap both in vivo and in vitro. Catalpol also promoted ERα deacetylation and stabilized ERα protein to enhance the expression of FasL. In addition, Sirt6 knockdown by siRNA prevented ERα deacetylation and eliminated catalpol-mediated osteoclast apoptosis.

CONCLUSIONS

The present study demonstrated that catalpol prevents estrogen deficiency-induced osteoporosis by promoting osteoclast apoptosis via the Sirt6-ERα-FasL axis. These findings revealed a novel molecular mechanism underpinning the impact of catalpol in the progression of osteoporosis and provided novel insights into the treatment of osteoporosis.

The Uses of Anabolic Androgenic Steroids Among Athletes; Its Positive and Negative Aspects- A Literature Review

The use of anabolic androgenic steroids (AAS) for strength training and muscle building is a widespread practice among athletes and young individuals. Athletes and bodybuilders are using these substances for various purposes, such as enhancing muscle mass, strengthening their bodies, and enhancing their performances. AAS exert a wide range of physiological effects that result in the activation of central signaling, resulting in adverse effects. Moreover, excessive use of AAS which can be categorized as AAS abuse; is linked to biological and psychological pathologies, which can lead to mortality. Complications arising from steroid abuse involve both cellular and physiological complications. Cellular complications arise when activation of signaling proteins like mTOR, Akt, etc. leads to alteration in protein synthesis pathways, cell cycle, oxidative stress, and apoptosis, contributing to damage at the cellular level. Physiological complications are evident with cardiovascular pathologies, including an altered lipid profile, cardiac hypertrophy, hypogonadism after discontinuation of AAS, and modulation of GABA receptors in the brain, all contributed by the androgen receptor signaling. Clinical complications budding from these altered physiological processes lead to clinical effects like testicular dysfunction, acne, gynecomastia, and neuropsychiatric disorders. Despite potential therapeutic benefits, AAS use is prohibited by the World Anti-Doping Agency (WADA) due to concerns over adverse health effects. This review highlights the molecular mechanisms, physiological processes, and clinical complications arising from the excessive use of AAS among athletes.

Estrogen receptor-mediated health benefits of phytochemicals: a review

Estrogen receptors (ERs) are transcription factors with two subtypes: estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), which are essential for the maintenance of human health and play a regulatory role in common diseases such as breast cancer, osteoporosis, neurodegenerative disorders, liver injuries and lung cancers. A number of phytochemicals extracted from various fruits and vegetables have been demonstrated to exhibit estrogenic effects and are termed phytoestrogens. As modulators of ERs, phytoestrogens can be involved in the prevention and treatment of multiple diseases as complementary or alternative therapeutic agents and have a variety of health benefits for humans. This article reviews the health benefits of phytoestrogens in clinical and epidemiologic studies for several diseases and also provides a detailed description of the molecular mechanisms of their action. A brief comparison of the advantages and disadvantages of natural phytochemicals compared to synthetic drugs is also presented. The role of phytoestrogens in the treatment of diseases and human health requires further research to fully realize their therapeutic potential.

Anti-Menopausal Effect of Soybean Germ Extract and Lactobacillus gasseri in the Ovariectomized Rat Model

Menopause is a significant phase in a woman's life. Menopausal symptoms can affect overall well-being and quality of life. Conventionally, hormone replacement therapy (HRT) is used to alleviate menopausal symptoms; however, depending on the conditions, HRT may lead to side effects, necessitating the exploration of alternative therapies with fewer side effects. In this study, we investigated the effects of a combination of soybean germ extract (S30) containing 30% (w/w) isoflavone and a probiotic, Lactobacillus gasseri (LGA1), on menopausal conditions in an ovariectomized (OVX) rat model. We evaluated the impact of S30+LGA on body weight, estrogen markers, uterine and bone health, vascular markers, and neurotransmitter levels. The results revealed that treatment with S30+LGA1 significantly improved body weight and uterine and bone health. Moreover, S30+LGA1 demonstrated promising effects on lipid profile, liver function, and vascular markers and positively impacted serotonin and norepinephrine levels, indicating potential mood-enhancing effects. In conclusion, S30+LGA1, possessing anti-menopausal effects in vitro and in vivo, can be recommended as a soy-based diet, which offers various health benefits, especially for menopausal women.

Using sequential pharmacotherapy for the treatment of osteoporosis: an update of the literature

INTRODUCTION

Osteoporosis, which is characterized by compromised bone density and heightened susceptibility to fractures, is a substantial public health concern, especially among the aging population. Underdiagnosis, undertreatment, and therapy non-adherence contribute to its impact. Anabolic and dual-action agents like teriparatide, abaloparatide, and romosozumab have emerged as effective treatments, allowing rapid gains in bone mineral density (BMD) and reducing fracture risk. However, administering treatments in the correct order is paramount, with an 'anabolic first' approach gaining traction for patients at high risk of fractures. This strategy involves starting anabolic therapies, followed by antiresorptive agents as maintenance therapy. It is important to note that the effectiveness of anabolic agents differs between treatment-naive and previously treated patients: tailored treatment approaches are therefore necessary. This comprehensive strategy adheres to clinical guidelines, emphasizing individualized care, early intervention, and patient-centered management to mitigate the burden of osteoporosis and enhance patients' quality of life.

AREA COVERED

The aim of this review is to summarize recent evidence on the sequential treatment of osteoporosis and to provide recommendations on the best treatment strategies.

EXPERT OPINION

Effective treatments, such as anabolic agents, are key in high-risk patients, who require an 'anabolic first' approach. Sequential therapy, specifically tailored to a patient's history, can help to optimize prevention and management of fractures.

Hypoxia-Inducible Factor-2α Signaling in the Skeletal System

Hypoxia-inducible factors (HIFs) are oxygen-dependent heterodimeric transcription factors that mediate molecular responses to reductions in cellular oxygen (hypoxia). HIF signaling involves stable HIF-β subunits and labile, oxygen-sensitive HIF-α subunits. Under hypoxic conditions, the HIF-α subunit is stabilized, complexes with nucleus-confined HIF-β subunit, and transcriptionally regulates hypoxia-adaptive genes. Transcriptional responses to hypoxia include altered energy metabolism, angiogenesis, erythropoiesis, and cell fate. Three isoforms of HIF-α-HIF-1α, HIF-2α, and HIF-3α-are found in diverse cell types. HIF-1α and HIF-2α serve as transcriptional activators, whereas HIF-3α restricts HIF-1α and HIF-2α. The structure and isoform-specific functions of HIF-1α in mediating molecular responses to hypoxia are well established across a wide range of cell and tissue types. The contributions of HIF-2α to hypoxic adaptation are often unconsidered if not outrightly attributed to HIF-1α. This review establishes what is currently known about the diverse roles of HIF-2α in mediating the hypoxic response in skeletal tissues, with specific focus on development and maintenance of skeletal fitness. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Association of total body fat and fat distribution with bone mineral density among children and adolescents aged 6-17 years from Guangzhou, China

This study aimed to assess the associations of total body fat and fat distribution with bone mineral density (BMD) among children and adolescents in this cross-sectional study. A total of 1032 boys and 897 girls aged 6-17 years were enrolled between May 2019 and June 2019 in Guangzhou, China. BMD, total body fat (fat mass index [FMI] and body fat percentage [BF%]), and fat distribution (trunk-to-limb and android-to-gynoid ratios) were measured by dual-energy X-ray absorptiometry. Inverse probability of treatment weighting regression was used to explore the association between fat and BMD. Traditional regression of covariate adjustment was applied as sensitivity analysis. Regression with inverse probability weighting suggested BF% and android-to-gynoid ratio were negatively associated with BMD in boys (β =  - 0.12 and - 0.16, respectively; P < 0.05). Android-to-gynoid ratio was also inversely associated with BMD in girls (β =  - 0.08, P < 0.05). When stratified by age, the negative associations were retained in boys aged 12-17 years (β =  - 0.23 and - 0.25, respectively; P < 0.001). But for girls, it showed a positive association of FMI with BMD in the 6-9 years group (β = 0.33, P < 0.001) and a negative association between the android-to-gynoid ratio and BMD in the 10-17 years group (β =  - 0.10, P < 0.05). Traditional regression supported the robustness of the results.  Conclusion: Total body fat is positively associated with BMD in younger girls but inversely associated in older boys. As for abdominal adipose, it is associated with lower BMD in both older boys and girls. What is Known: • The lean mass has been consistently positively associated with bone mineral density (BMD) among children and adolescents. However, the impact of fat mass on BMD remained controversial. • Beyond total body fat, site-specific fat mass, especially abdominal adiposity, might impede bone formation. What is New: • The associations of total body fat and fat distribution with BMD in children and adolescents were gender- and age-specific. • More attention should be paid to the abdominal fat accumulation to promote bone health in older children.

Dance-Related Foot and Ankle Injuries and Pathologies

Dancers are highly vulnerable to injuries due to high dynamic overload, extreme positions and motions, and excessive use. Increased load at the forefoot with jumping and high-impact lands can cause sesamoiditis and stress fractures of the metatarsals. Significant plantarflexion can lead to posterior joint impingement and flexor hallucis longus tendonitis, whereas forced dorsiflexion can cause anterior joint impingement. Most pathologies can be diagnosed on physical examination and various imaging modalities. Treatment should be tailored to the dancers' needs and should begin with a course of conservative therapy with immobilization, physical therapy, and activity cessation.

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

Delayed Recovery after Nonoperative Treatment of an Avulsion Fracture of the Ischial Tuberosity in an Adolescent Gymnast with a History of Growth Hormone Deficiency: A Case Report

Introduction

Avulsion fracture of the ischial tuberosity is uncommon. Patients typically present with symptoms consistent with hamstring strain. The purpose of this case report is to describe an avulsion fracture of the ischial tuberosity and subsequent recovery in an athlete with an endocrine disorder.

Case Description

A 15-year-old United States of America Gymnastics level 9 gymnast presented with right hamstring pain after regular practice. She had been diagnosed with isolated growth hormone deficiency at age 4 and was treated with growth hormone replacement therapy until age 14. Six months before presentation, she experienced the insidious onset of dull, aching pain in her right hamstring, near the junction of the thigh and buttocks, that was believed to be the result of a chronic hamstring strain. The pain increased gradually over a year and was relieved with rest, massage, and dry needling. Two days before presentation, she felt a "snap" and pain while performing a switch leap during regular practice. She had sharp localized pain in the proximal hamstring with walking and sitting. She was diagnosed with a minimally displaced avulsion fracture of the ischial tuberosity.

Outcome

With nonoperative treatment, the fracture healed at three months, which is longer than the expected six weeks. Although return to sports is expected three months after this injury, it did not occur until six months in this patient. She was unable to participate in competitive level 9 gymnastics until 12 months after injury.

Discussion

This case highlights that delayed recovery can occur after avulsion fracture of the ischial tuberosity in adolescent athletes with a history of growth hormone deficiency and treatment using growth hormone.

Level of Evidence

5.

The impact of sex steroids on osteonecrosis of the jaw

Sex steroid hormones play a major role in bone homeostasis. Therefore, the use of sex hormones or drugs may increase the risk of osteonecrosis of the jaw (ONJ), a complication caused by damaged bone homeostasis. However, few are known the impact of medications changing sex hormone levels on ONJ. The pathophysiology of ONJ is not clearly understood and many hypotheses exist: cessation of bone remodeling caused by its anti-resorptive effect on osteoclasts; compromised microcirculation due to medication affecting angiogenesis, including bisphosphonate; and impairment of defense mechanism toward local infection. The use of high-dose intravenous bisphosphonate in cancer patients is associated with a high prevalence of ONJ. Exogenous estrogen or androgen replacement was reported to be associated with ONJ. Polycystic ovarian syndrome (PCOS) patients demonstrate an androgen excess status, and androgen overproduction serves as a protective factor in the bone mineral density of young women. To date, there are no reports of ONJ occurrence due to androgen overproduction. In contrast, few reports on the occurrence of ONJ due to estrogen deficiency induced by drugs, such as selective estrogen receptor modulator (SERM), aromatase inhibitors, and gonadotropin-releasing hormone (GnRH) agonists, are available. Thus, the role of sex steroids in the development of ONJ is not known. Further studies are required to demonstrate the exact role of sex steroids in bone homeostasis and ONJ progression. In this review, we will discuss the relationship between medication associated with sex steroids and ONJ.

Micro-computed tomography assessment of bone structure in aging mice

High-resolution computed tomography (CT) is widely used to assess bone structure under physiological and pathological conditions. Although the analytic protocols and parameters for micro-CT (μCT) analyses in mice are standardized for long bones, vertebrae, and the palms in aging mice, they have not yet been established for craniofacial bones. In this study, we conducted a morphometric assessment of craniofacial bones, in comparison with long bones, in aging mice. Although age-related changes were observed in the microarchitecture of the femur, tibia, vertebra, and basisphenoid bone, and were more pronounced in females than in males, the microarchitecture of both the interparietal bone and body of the mandible, which develop by intramembranous ossification, was less affected by age and sex. By contrast, the condyle of the mandible was more affected by aging in males compared to females. Taken together, our results indicate that mouse craniofacial bones are uniquely affected by age and sex.

An Overlooked Bone Metabolic Disorder: Cigarette Smoking-Induced Osteoporosis

Cigarette smoking (CS) leads to significant bone loss, which is recognized as an independent risk factor for osteoporosis. The number of smokers is continuously increasing due to the addictive nature of smoking. Therefore it is of great value to effectively prevent CS-induced osteoporosis. However, there are currently no effective interventions to specifically counteract CS-induced osteoporosis, owing to the fact that the specific mechanisms by which CS affects bone metabolism are still elusive. This review summarizes the latest research findings of important pathways between CS exposure and bone metabolism, with the aim of providing new targets and ideas for the prevention of CS-induced osteoporosis, as well as providing theoretical directions for further research in the future.

Osteogenic differentiation of human induced pluripotent stem cell in the presence of testosterone and 17 β-estradiol in vitro

Recently, numerous scientific approaches have been explored to treat various diseases using stem cells. In 2006, induced pluripotent stem cell (iPSC) were introduced by Takahashi and Yamanaka and showed the potential of self-renewing and differentiation into all types of targeted cells in vitro. In this investigation, we studied the effect of testosterone (T) individually or in the presence of 17 β-estradiol (E2) on osteogenic differentiation of human iPSC (hiPSC) during 2 wk. The optimal concentrations of sex steroid hormones were examined by MTT assay and acridine orange (AO) staining. The impact of E2 and T either individually or together as a combination was examined by ALP activity; the content of total mineral calcium, by von Kossa and alizarin red staining. Additionally, the expression rate of osteogenic specific markers was studied via real-time RT-PCR and immunocytochemistry analyses at day 14 of differentiation. The obtained results illustrated that the differentiation medium supplemented with T-E2 increased not only the ALP enzyme activity and the content of calcium but also the osteogenic-related gene and protein expressions on the 14^th day. Furthermore, the results were confirmed by mineralized matrix staining. In conclusion, these data suggest that T could be used as an effective factor for osteogenic induction of hiPSCs combined with the E2 in bone regeneration.

Bone health in functional hypothalamic amenorrhea: What the endocrinologist needs to know

In the original definition by Klinefelter, Albright and Griswold, the expression "hypothalamic hypoestrogenism" was used to describe functional hypothalamic amenorrhoea (FHA). Given the well-known effects of estrogens on bone, the physiopathology of skeletal fragility in this condition may appear self-explanatory. Actually, a growing body of evidence has clarified that estrogens are only part of the story. FHA occurs in eating disorders, overtraining, and during psychological or physical stress. Despite some specific characteristics which differentiate these conditions, relative energy deficiency is a common trigger that initiates the metabolic and endocrine derangements contributing to bone loss. Conversely, data on the impact of amenorrhoea on bone density or microarchitecture are controversial, and reduced bone mass is observed even in patients with preserved menstrual cycle. Consistently, oral estrogen-progestin combinations have not proven beneficial on bone density of amenorrheic women. Low bone density is a highly prevalent finding in these patients and entails an increased risk of stress or fragility fractures, and failure to achieve peak bone mass and target height in young girls. Pharmacological treatments have been studied, including androgens, insulin-like growth factor-1, bisphosphonates, denosumab, teriparatide, leptin, but none of them is currently approved for use in FHA. A timely screening for bone complications and a multidisciplinary, customized approach aiming to restore energy balance, ensure adequate protein, calcium and vitamin D intake, and reverse the detrimental metabolic-endocrine changes typical of this condition, should be the preferred approach until further studies are available.

Gut-Bone Axis: A Non-Negligible Contributor to Periodontitis

Periodontitis is a polymicrobial infectious disease characterized by alveolar bone loss. Systemic diseases or local infections, such as diabetes, postmenopausal osteoporosis, obesity, and inflammatory bowel disease, promote the development and progression of periodontitis. Accumulating evidences have revealed the pivotal effects of gut microbiota on bone health via gut-alveolar-bone axis. Gut pathogens or metabolites may translocate to distant alveolar bone via circulation and regulate bone homeostasis. In addition, gut pathogens can induce aberrant gut immune responses and subsequent homing of immunocytes to distant organs, contributing to pathological bone loss. Gut microbial translocation also enhances systemic inflammation and induces trained myelopoiesis in the bone marrow, which potentially aggravates periodontitis. Furthermore, gut microbiota possibly affects bone health via regulating the production of hormone or hormone-like substances. In this review, we discussed the links between gut microbiota and periodontitis, with a particular focus on the underlying mechanisms of gut-bone axis by which systemic diseases or local infections contribute to the pathogenesis of periodontitis.

Gestational and lactational exposure to BPA, but not BPS, negatively impacts trabecular microarchitecture and cortical geometry in adult male offspring

Bisphenol-A (BPA) and bisphenol-S (BPS) are endocrine disrupting chemicals (EDCs) found primarily in plastics. Estrogen is a primary hormonal regulator of skeletal growth and development; however, the impact of gestational BPA or BPS exposure on skeletal health of offspring remains relatively unknown. Here, adult female mice were randomized into three treatment groups: 200 μg BPA/kg BW (BPA), 200 μg BPS/kg BW (BPS) or control (CON). Animals were then further randomized to exercising (EX) or sedentary (SED) groups. Treatment continued through mating, gestation, and lactation. One male offspring from each dam (n = 6-8/group) was assessed at 16 weeks of age to evaluate effects of EDC exposure on the adult skeleton. Cortical geometry of the mid-diaphysis and trabecular microarchitecture of the distal femur were assessed via micro-CT. Biomechanical strength and mineral apposition rate of the femoral diaphysis were assessed via three-point bending and dynamic histomorphometry, respectively. Two-factor ANOVA or ANCOVA were used to determine the effects of maternal EX and BPA or BPS on trabecular and cortical bone outcomes. Maternal EX led to a significant decrease in body fat percentage and bone stiffness, independent of EDC exposure. Offspring exposed to BPA had significantly lower trabecular bone volume, trabecular number, connectivity density, cortical thickness, and greater trabecular spacing compared to BPS or CON animals. In conclusion, gestational BPA, but not BPS, exposure negatively impacted trabecular microarchitecture and cortical geometry in adult male offspring. If these findings translate to humans, this could have significant public health impacts on expecting women or those seeking to become pregnant.

Gestational and lactational exposure to BPA or BPS has minimal effects on skeletal outcomes in adult female mice

Bisphenol-A (BPA) and bisphenol-S (BPS) are estrogen disrupting chemicals (EDCs) found in the environment and common household items. Estrogen is a primary hormonal regulator of bone growth and development; however, the impact of gestational BPA or BPS exposure on skeletal health of offspring remains relatively unknown. In this longitudinal study, adult female mice were randomized into three groups: 200 μg BPA/kg BW (BPA), 200 μg BPS/kg BW (BPS) or control (CON). Animals in each group were further randomized to exercise treatment (EX) or sedentary (SED) control, resulting in six overall groups. BPA/BPS/CON and EX/SED treatment were initiated prior to mating and continued through mating, gestation, and lactation. One female offspring from each dam (n = 6/group) was assessed at 17 weeks of age to evaluate effects of EDC exposure on the adult skeleton. Cortical geometry of the mid-diaphysis and trabecular microarchitecture of the distal femur were assessed via micro-computed tomography. Biomechanical strength and mineral apposition rate of the femoral diaphysis were assessed via three-point bending and dynamic histomorphometry, respectively. Sclerostin expression was measured using immunohistochemistry. Two-factor ANOVA or ANCOVA were used to determine the effects of maternal exercise and BPA or BPS exposure on trabecular and cortical bone outcomes, respectively. Consistent with prior studies, there were no significant differences in body weight, femoral length, cortical geometry, trabecular microarchitecture, or biomechanical strength between groups in female offspring. In conclusion, gestational BPA exposure and maternal exercise have minimal impact on skeletal outcomes in female adult offspring.

The role of estrogen and progesterone receptors in the rotator cuff disease: a retrospective cohort study

Background

Rotator cuff (RC) tears represent a common cause of shoulder pain and dysfunction in adults. The disease affects primarily women and occurs mainly in the postmenopausal period.

This study aimed to investigate immunohistochemically the presence of estrogen receptor-alpha (ER-⍺), estrogen receptor-beta (ER-β) and progesterone receptor (PR) in the supraspinatus tendon of patients with RC tendinopathy, searching for gender differences of expression. A secondary aim was to evaluate potential links between their expression and the typical histopathological findings of the ailment.

Methods

Biopsies of the supraspinatus tendon were collected intraoperatively from 15 postmenopausal women and 9 men undergoing RC surgery. Specimens were stained with Haematoxylin/Eosin, Masson-Goldner Trichrome, Alcian Blu and immunohistochemical stainings for ER-⍺, ER-β and PR were performed. Tendon alterations were evaluated with the Bonar histopathological scale. Statistical tests used in this study were the Spearman correlation coefficient and the Mann-Whitney U test.

Results

In the supraspinatus tendon, cells expressed ER-⍺ (p = 0.043), ER-β (p = 0.048) and PR (p = 0.004) with statistically significant differences related to age and sex of patients. Immunoreactivity was seen in the nuclei of tenocytes and vascular cells. Postmenopausal women’s samples showed a markedly higher expression of these receptors compared to their male counterpart. There was a positive correlation between the expression of ER-⍺ and ER-β (r = 0.59; p = 0.02) and between ER-β and PR (r = 0.72; p = 0.002) in women’s samples. Furthermore, in postmenopausal women the PR expression decreased with age (r = − 0.56; p = 0.027). Only in women, the ER-β expression positively correlated with the total Bonar histopathological score (p = 0.019) and the ER-β vascular expression positively correlated with ground substance alterations (p = 0.029).

Conclusions

These results reveal that ERs and PR are present in the supraspinatus tendon of patients with RC tears, suggesting a role of sex hormones in the pathogenesis of the disease.

Does the rate of orthodontic tooth movement change during the estrus cycle? A systematic review based on animal studies

BACKGROUND

As the fluctuation of sex hormone levels in menstruating women results in periodical effects in bone metabolism, understanding the implications for tooth movement could be of benefit to the orthodontist. This type of research presents practical and ethical problems in humans, but animal models could provide useful information. Our objective was to systematically investigate the available evidence on the question whether the rate of orthodontic tooth movement varies between the different stages of the estrus cycle in animals.

METHODS

Unrestricted searches in 7 databases and manual searching of the reference lists in relevant studies were performed up to February 2021 (Medline [PubMed], CENTRAL [Cochrane Library; includes records from Embase, CINAHL, ClinicalTrials.gov, WHO's ICTRP, KoreaMed, Cochrane Review Groups' Specialized Registers, and records identified by handsearching], Cochrane Database of Systematic Reviews [Cochrane Library], Scopus, Web of Knowledge [including Web of Science Core Collection, KCI Korean Journal Database, Russian Science Citation Index, SciELO Citation Index and Zoological Record], Arab World Research Source [EBSCO] and ProQuest Dissertation and Theses [ProQuest]). Our search focused on prospective controlled animal studies, whose samples included female subjects of any species that were quantitatively comparing the amount of tooth movement in the different stages of the estrus cycle. Following study retrieval and selection, relevant data was extracted, and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool.

RESULTS

From the finally assessed records, 3 studies met the inclusion criteria. Two of the studies experimented on Wistar rats, whereas the other on cats. Tooth movement was induced by expansion or coil springs. The rate of orthodontic tooth movement was increased during the stages of the estrus cycle when oestrogen and/or progesterone levels were lower. The risk of bias in the retrieved studies was assessed to be unclear.

CONCLUSION

Hormonal changes during the estrus cycle may affect the rate of orthodontic tooth movement. Although these animal experiment results should be approached cautiously regarding their translational potential, it could be useful to consider the possible impact of these physiological changes in the clinical setting until more information becomes available. Registration: PROSPERO (CRD42021158069).

Does exogenous female sex hormone administration affect the rate of tooth movement and root resorption? A systematic review of animal studies

BACKGROUND

The long-term use of contraceptive methods that contain estrogens, progestogens or combinations of the above among women aged 15 to 49 years is extensive. Both estrogens and progestogens affect bone metabolism.

OBJECTIVE

To systematically investigate and appraise the quality of the available evidence from animal studies regarding the impact of exogenous administration of female sex hormones on the rate of orthodontic tooth movement and root resorption.

SEARCH METHODS

Search without restriction in seven databases (including grey literature) and hand searching were performed until May 2021.

SELECTION CRITERIA

We looked for controlled animal studies investigating the effect from exogenous administration of formulations containing female sex hormones on the rate of orthodontic tooth movement and root resorption.

DATA COLLECTION AND ANALYSIS

After study retrieval and selection, relevant data was extracted, and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. The quality of available evidence was assessed with the Grades of Recommendation, Assessment, Development, and Evaluation.

RESULTS

Three studies were identified, all being at unclear risk of bias. Overall, administration of progesterone and the combinations of estradiol with norgestrel and desogestrel were shown to significantly decrease the rate of orthodontic tooth movement when given for longer periods (>3 weeks). Inconsistent information was detected for shorter periods of consumption. Estradiol, with desogestrel use, resulted in less root resorption. The quality of the available evidence was considered to be low.

CONCLUSIONS

Exogenous administration of female sex hormones may decelerate in the long term the rate of tooth movement and decrease orthodontically induced root resorption in animals. Until more information becomes available, an orthodontist should be able to identify a patient consuming such substances and understand the potential clinical implications and adverse effects that may arise.

REGISTRATION

PROSPERO: CRD42017078208; https://clinicaltrials.gov/.

STATINSWITH POTENTIAL TO CONTROL PERIODONTITIS: FROM BIOLOGICAL MECHANISMS TO CLINICAL STUDIES

BACKGROUND

Statins are widely used for the treatment of hyperlipidemia. However, these drugs have pleiotropic effects that can be promising for the prevention and treatment of oral diseases, such as periodontitis.

HIGHLIGHT

This review aimed to identify preclinical, observational, and clinical studies that evaluate the effects and biological mechanisms of statins on oral cells and tissues and those using these drugs to treat periodontitis. A LITERATURE SURVEY HAS BEEN CONDUCTED IN PUBMED USING COMBINATIONS OF THE UNITERMS: "statins," "dentistry," "periodontal disease," and "periodontal treatment." In vitro findings showed positive statin results in cell lines related to alveolar bone metabolism by altering the signaling pathway Osteoprotegerin/Receptor Activator of Nuclear Factor Kappa B/Receptor Activator of Nuclear Factor Kappa B Ligand (OPG/RANK/RANKL), stimulating the production of alkaline phosphatase and osteocalcin, and reducing the production of matrix metalloproteinases (MMPs). Animal studies have shown a reduction in alveolar bone loss and osteoclastic activity, in addition to a reduction in inflammatory markers, such as IL-1, IL-6, and TNF-α, when statins were used prophylactically. Clinical trials showed a positive impact on clinical parameters, leading to a higher reduction in probing depth and gain in clinical attachment when a local statin was adjunctively associated with mechanical therapy.

CONCLUSION

Statins were shown to be promising for regenerating and stimulating bone activity, with great potential for treating chronic periodontitis. However, further studies are required to confirm its effectiveness.

Alcoholism and Osteoimmunology

BACKGROUND

Chronic consumption of alcohol has an adverse effect on the skeletal system, which may lead to osteoporosis, delayed fracture healing and osteonecrosis of the femoral head. Currently, the treatment is limited, therefore, there is an urgent need to determine the underline mechanism and develop a new treatment. It is well-known that normal bone remodeling relies on the balance between osteoclast-mediated bone resorption and - mediated bone formation. Various factors can destroy the balance, including the dysfunction of the immune system. In this review, we summarized the relevant research in the alcoholic osteopenia with a focus on the abnormal osteoimmunology signals. We provided a new theoretical basis for the prevention and treatment of the alcoholic bone.

METHODS

We searched PubMed for publications from 1 January 1980 to 1 February 2020 to identify relevant and recent literature, summarizing evaluation and the prospect of alcoholic osteopenia. Detailed search terms were 'alcohol', 'alcoholic osteoporosis', 'alcoholic osteopenia' 'immune', 'osteoimmunology', 'bone remodeling', 'osteoporosis treatment' and 'osteoporosis therapy'.

RESULTS

A total of 135 papers are included in the review. About 60 papers described the mechanisms of alcohol involved in bone remodeling. Some papers were focused on the pathogenesis of alcohol on bone through osteoimmune mechanisms.

CONCLUSION

There is a complex network of signals between alcohol and bone remodeling and intercellular communication of osteoimmune may be a potential mechanism for alcoholic bone. Studying the osteoimmune mechanism is critical for drug development specific to the alcoholic bone disorder.

The Relationship Between Menopause and Metabolic Syndrome: Experimental and Bioinformatics Analysis

Menopausal hormonal changes have been associated with the emergence of the metabolic syndrome (MetS) and its consequences such as type 2 diabetes (T2D) and cardiovascular diseases (CVD). The common gene signature and the associated signaling pathways of MetS, T2D, CVD and menopause status have not been widely studied. We analyzed a total of 314 women aged between 35 and 75 years. The sample was divided into two groups: Group I, including women in the premenopausal period and Group II, comprising women in the post-menopausal period. The presence of MetS and its components were evaluated, as well as occurrence of T2D and CVD in both groups. We also exploited the translational bioinformatics approach to choose the common gene signatures for MetS, T2D, CVD and the menopause status. The frequency of the MetS was significantly higher in postmenopausal women than in premenopausal ones (67.1 vs. 27.2%, p < 0.001). Gene mining analysis revealed that a total of 47 genes were commonly associated with MetS, T2D, CVD and the menopausal changes. The gene enrichment analysis showed that these genes were markedly enriched in biological processes, including positive regulation of binding, positive regulation of leukocyte cell-cell adhesion, regulation of lipid localization. Furthermore, P53 signaling pathway, prolactin signaling pathway, parathyroid hormone synthesis, secretion and action were the top enriched pathways. Additionally, network analysis revealed TGFB1, SPP1, MMP2, MMP9, CCL2, IGF1, EGFR, ICAM1, TNF and IL6 as important hub genes with significant interacting partners. These hub genes identified in our study may play key role in menopausal changes and influence the risks of MetS, T2D and CVD.

Voluntary Wheel Running Partially Compensates for the Effects of Global Estrogen Receptor-α Knockout on Cortical Bone in Young Male Mice

Estrogen receptor-α knockout (ERKO) in female, but not male, mice results in an impaired osteogenic response to exercise, but the mechanisms behind this ability in males are unknown. We explored the main and interactive effects of ERKO and exercise on cortical geometry, trabecular microarchitecture, biomechanical strength, and sclerostin expression in male mice. At 12 weeks of age, male C57BL/6J ERKO and WT animals were randomized into two groups: exercise treatment (EX) and sedentary (SED) controls, until 22 weeks of age. Cortical geometry and trabecular microarchitecture were measured via μCT; biomechanical strength was assessed via three-point bending; sclerostin expression was measured via immunohistochemistry. Two-way ANOVA was used to assess sclerostin expression and trabecular microarchitecture; two-way ANCOVA with body weight was used to assess cortical geometry and biomechanical strength. ERKO positively impacted trabecular microarchitecture, and exercise had little effect on these outcomes. ERKO significantly impaired cortical geometry, but exercise was able to partially reverse these negative alterations. EX increased cortical thickness regardless of genotype. There were no effects of genotype or exercise on sclerostin expression. In conclusion, male ERKO mice retain the ability to build bone in response to exercise, but altering sclerostin expression is not one of the mechanisms involved.

Investigation into Possible Association of Oxandrolone and Heterotopic Ossification Following Burn Injury

Oxandrolone, a testosterone analog, is used to counteract the catabolic effects of burn injury. Recent animal studies suggest a possible hormonal association with heterotopic ossification (HO) development postburn. This work examines oxandrolone administration and HO development by exploring historical clinical data bridging the introduction of oxandrolone into clinical practice. Additionally, we examine associations between oxandrolone administration and HO in a standardized mouse model of burn/trauma-related HO. Acutely burned adults admitted between 2000 and 2014, survived through discharge, and had a HO risk factor of 7 or higher were selected for analysis from a single burn center. Oxandrolone administration, clinical and demographic data, and elbow HO were recorded and were analyzed with logistic regression. Associations of oxandrolone with HO were examined in a mouse model. Mice were administered oxandrolone or vehicle control following burn/tenotomy to examine any potential effect of oxandrolone on HO and were analyzed by Student's t test. Subjects who received oxandrolone had a higher incidence of elbow HO than those that did not receive oxandrolone. However, when controlling for oxandrolone administration, oxandrolone duration, postburn day oxandrolone initiation, HO risk score category, age, sex, race, burn size, and year of injury, there was no significant difference between rates of elbow HO between the two populations. In agreement with the review, in the mouse model, while there was a trend toward the oxandrolone group developing a greater volume of HO, this did not reach statistical significance.

Does the rate of orthodontic tooth movement change during pregnancy and lactation? A systematic review of the evidence from animal studies

BACKGROUND

The changes in bone homeostasis observed during pregnancy and lactation could result in alterations in the rate of orthodontic tooth movement, but research in human subjects presents significant ethical and practical limitations. Our aim was to compare the amount of orthodontic tooth movement between pregnant/lactating or not animals.

METHODS

We searched without restrictions 8 databases and performed hand searching until July 2019 (PubMed, Central, Cochrane Database of Systematic Reviews, SCOPUS, Web of Science, Arab World Research Source, ClinicalTrials.gov , ProQuest Dissertations and Theses Global). We searched for studies comparing quantitatively the amount of orthodontic tooth movement between pregnant/lactating or not animals. Following retrieval and selection of studies, the collection of related data was performed and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. Exploratory synthesis was carried out using the random effects model.

RESULTS

Four studies were finally identified raising no specific concerns regarding bias. One study showed that lactation increased the rate of tooth movement by 50 % [p < 0.05]. Although an overall increase was noted in the pregnancy group as well, it did not reach statistical significance [3 studies, Weighted Mean Difference: 0.10; 95% Confidence Interval: - 0.04 - 0.24; p = 0.165].

CONCLUSIONS

The metabolic changes occurring during pregnancy and lactation may have an impact on the rate of tooth movement in animals. Although these animal experimental results should be approached cautiously, it could be safe practice to consider the impact of these physiological changes in the clinical setting.

REGISTRATION

PROSPERO (CRD42018118003).

Estrogen effects on orthodontic tooth movement and orthodontically-induced root resorption

Estrogen is an essential regulator of the bone tissue. The remodeling of the alveolar bone and periodontal ligament is the basis of orthodontic tooth movement (OTM). There is a negative coregulation between physiological estrogen levels and the rate of OTM. As a possible inhibitory factor of OTM, estrogen suppresses bone resorption by inhibiting osteoclastic differentiation and restraining osteoclast lifespan though multiple pathways and cytokines, leading to the suppression of the initiation step of bone remodeling. On the other hand, estrogen stimulates osteoblastic differentiation and function. Estrogen receptor-α (ERα) involves in the osteogenic responses to mechanical stimulation, and the ERα expression is regulated positively by the levels of circulatory estrogen. Orthodontically induced root resorption (OIRR) is a common side-effect of orthodontic treatment. Estrogen may have some inhibitory effects on OIRR, but more studies are needed to get an effective conclusion.

Global estrogen receptor-α knockout has differential effects on cortical and cancellous bone in aged male mice

Estrogen receptor-α knockout (ERKO) in female rodents results in bone loss associated with increased osteocyte sclerostin expression; whether this also occurs in males is unknown. Here, we examined the effects of ERKO on femoral cortical geometry, trabecular microarchitecture, and osteocyte sclerostin expression of the femur and lumbar vertebrae. At 14 months of age, male ERKO and wild-type (WT) littermates ( n = 6 per group) were sacrificed, and femora and vertebra were collected. Cortical geometry and trabecular microarchitecture were assessed via micro-computed tomography; osteocyte sclerostin expression was assessed via immunohistochemistry. ANCOVA with body weight was used to compare ERKO and WT for cortical geometry; t-tests were used for all other outcomes. Regardless of skeletal site, ERKO mice had greater trabecular bone volume and trabecular number and decreased trabecular separation compared with WT. In the femoral diaphysis, ERKO had lower total area, cortical area, and cortical thickness compared with WT. The percentage of sclerostin+ osteocytes was increased in ERKO animals in cortical bone but not in cancellous bone of the femur or the lumbar vertebrae. In conclusion, ERKO improved trabecular microarchitecture in aged male mice, but negatively altered femoral cortical geometry associated with a trend towards increased cortical sclerostin expression.

Construction of benzofuranone library via a metal-free, one-pot intermolecular condensation, and their application as efficient estrogen receptor β modulators

Facile synthesis of benzofuranone was achieved through a metal-free, one-pot intermolecular condensation between α-hydroxy aryl ketones and resorcinol derivatives. A library of 20 compounds with moderate to good overall yields was prepared. These compounds showed strong binding toward estrogen receptors along with good selectivity for ERβ (>190-fold over ERα). Anti-proliferative activity on DU-145, U-87, and MCF-7 cells gave inhibition IC₅₀ values in the low μM range, which suggested the promising potential therapeutic applications of these new classes of benzofuranones.

Hormone-Independent Sexual Dimorphism in the Regulation of Bone Resorption by Krox20

Krox20/EGR2 is a zinc finger transcription factor, implicated in the development of the hindbrain, nerve myelination, and tumor suppression. In skeletal biology, we have demonstrated that Krox20 also regulates adult bone metabolism. We and others have characterized several functions of Krox20 in the osteoclast lineage, namely, preosteoclast proliferation and differentiation, and mature osteoclast apoptosis. We have previously reported that systemically Krox20-haploinsufficient mice have a low bone mass with increased bone resorption. However, new data have now revealed that this phenotype is restricted to females. In addition, we discovered that conditional knockout of Krox20 (cKO) restricted to osteoclast progenitors is sufficient to induce the same female-specific bone loss observed in systemic mutants. To test whether this sexual dimorphism results from an interaction between Krox20 and sex hormones, we examined the sex- and hormone-dependent role of Krox20 deficiency on proliferation and apoptosis in osteoclastic cells. Our results indicate that male and female sex hormones (dihydrotestosterone [DHT] and estradiol [E2], respectively) as well as Krox20 inhibit preosteoclast proliferation and augment osteoclast apoptosis. The observation that Krox20 expression is inhibited by DHT and E2 negates the hypothesis that the effect of sex hormones is mediated by an increase in Krox20 expression. Interestingly, the effect of Krox20 deficiency was observed only with cells derived from female animals, regardless of any sex hormones added in vitro. In addition, we have identified sexual dimorphism in the expression of several Krox20-related genes, including NAB2. This sex-specific epigenetic profile was established at puberty, maintained in the absence of sex hormones, and explains the female-specific skeletal importance of Krox20. The findings described in this study emphasize the medical importance of sex differences, which may be determined at the epigenetic level. © 2019 American Society for Bone and Mineral Research.

Effects of testosterone and 17β-estradiol on osteogenic and adipogenic differentiation capacity of human bone-derived mesenchymal stromal cells of postmenopausal women

Progressive bone loss is a predominant symptom of aging and osteoporosis. Therefore, the effects of sex steroids (i.e. testosterone and 17β-estradiol) on the differentiation capacity of human bone-derived mesenchymal stromal cells (hMSCs), as progenitors of osteoblasts and adipocytes, are of particular interest. The objectives of the present study were, thus, to elucidate whether bone-derived hMSCs of postmenopausal women produce aromatase (CYP19A1) and, whether they modulate their differentiation behaviour in response to testosterone and 17β-estradiol (E2), in relation to their steroid receptor expression. Supplementation of testosterone resulted in a considerable formation of E2 under osteogenic and adipogenic culture conditions, whereas E2 synthesis remained minimal in the cells cultured in basal medium. Concomitant with high aromatase expression and 17β-estradiol formation of the cells cultured in osteogenic medium supplemented with testosterone, a distinct promotion of late-stage osteogenesis was found, as shown by significant matrix mineralization and a notable increase in osteogenic markers. These effects were abrogated by the aromatase inhibitor anastrozole. Under adipogenic conditions, testosterone reduced the occurrence of lipid droplets and led to a decrease in PPARγ and AR expression, independent of anastrozole. Regardless of the culture conditions, ERα was detectable whilst ERβ was not. In conclusion, aromatase activity is limited to differentiated hMSCs and the resulting 17β-estradiol enhances late osteogenic differentiation stages via ERα. Adipogenic differentiation, on the other hand, is reduced by both sex steroids: testosterone via AR and 17β-estradiol.

A critical role for estrogen signaling in penis development

Hypospadias, a developmental defect of the penis, is one of the most common congenital malformations in humans. Its incidence has rapidly increased over recent decades, and this has been largely attributed to our increased exposure to endocrine-disrupting chemicals. Penis development is primarily an androgen-driven process; however, estrogen and xenoestrogens are known to affect penis development in both humans and mice. Here, we investigated the role of estrogen in the developing penis. Using a novel penis culture system, we showed that exogenous estrogen directly targets the developing penis in utero to cause hypospadias. In addition, we also uncovered an unexpected endogenous role for estrogen in normal postnatal penis development and showed that a loss of estrogen signaling results in a mild hypospadias phenotype, the most common manifestation of this disease in humans. Our findings demonstrated that both androgen and estrogen signaling are intrinsically required for normal urethral closure. These findings confirmed that penis development is not an entirely androgen-driven process but one in which endogenous estrogen signaling also plays a critical role.-Govers, L. C., Phillips, T. R., Mattiske, D. M., Rashoo, N., Black, J. R., Sinclair, A., Baskin, L. S., Risbridger, G. P., Pask, A. J. A critical role for estrogen signaling in penis development.

Chemokine-like receptor 1 deficiency leads to lower bone mass in male mice

The adipokine Chemerin and its receptor, chemokine-like receptor 1 (CMKLR1), are associated with osteoblastogenic differentiation of mesenchymal stem cells (MSCs) and osteoclastogenic differentiation of osteoclast precursors in vitro, suggesting that CMKLR1 would affect the bone mineral density (BMD). However, the role of CMKLR1 on BMD in vivo remains unknown. Here, using CMKLR1 knockout mouse model, we unveiled that CMKLR1 effected the amount of Leydig cells in testis and regulated androgen-dependent bone maintenance in male mice, which exhibited lower serum testosterone levels, thereby reducing the trabecular bone mass. Correspondingly, the mRNA expression of testosterone synthesis enzymes in testis decreased. The bone tissue also showed decreased mRNAs expression of osteogenic markers and increased mRNA levels for osteoclast markers. Furthermore, by in vitro differentiation models, we found CMKLR1-deficiency could break the balance between osteoblastogenesis and osteoclastogenesis that caused a shift from osteogenic to adipogenic differentiation in MSCs and enhanced osteoclast formation. In addition, bone mass increase in CMKLR1 KO male mice can be promoted by treatment with 5α-dihydrotestosterone (DHT), and the inactivation of CMKLR1 in male wild-type (WT) mice with antagonist treatment can lead to low bone mass. Taken together, these data indicate that CMKLR1 positively regulates bone metabolism through mediating testosterone production and the balance between osteoblast and osteoclast formation.

The Effect of Tobacco Smoking on Bone Mass: An Overview of Pathophysiologic Mechanisms

Recent evidence demonstrates that tobacco smoking causes an imbalance in bone turnover, leading to lower bone mass and making bone vulnerable to osteoporosis and fracture. Tobacco smoke influences bone mass indirectly through alteration of body weight, parathyroid hormone-vitamin D axis, adrenal hormones, sex hormones, and increased oxidative stress on bony tissues. Also, tobacco smoke influences bone mass through a direct effect on osteogenesis and angiogenesis of bone. A RANKL-RANK-OPG pathway is an essential regulatory pathway for bone metabolism and its importance lies in its interaction with most of the pathophysiologic mechanisms by which smoking influences bone mass. Both first- and secondhand smoke adversely affect bone mass; smoking cessation seems to reverse the effect of smoking and improve bone health. Recent advances in research on bone turnover markers could advance scientific knowledge regarding the mechanisms by which smoking may influence bone mass.

Intracrine Regulation of Estrogen and Other Sex Steroid Levels in Endometrium and Non-gynecological Tissues; Pathology, Physiology, and Drug Discovery

Our understanding of the intracrine (or local) regulation of estrogen and other steroid synthesis and degradation expanded in the last decades, also thanks to recent technological advances in chromatography mass-spectrometry. Estrogen responsive tissues and organs are not passive receivers of the pool of steroids present in the blood but they can actively modify the intra-tissue steroid concentrations. This allows fine-tuning the exposure of responsive tissues and organs to estrogens and other steroids in order to best respond to the physiological needs of each specific organ. Deviations in such intracrine control can lead to unbalanced steroid hormone exposure and disturbances. Through a systematic bibliographic search on the expression of the intracrine enzymes in various tissues, this review gives an up-to-date view of the intracrine estrogen metabolisms, and to a lesser extent that of progestogens and androgens, in the lower female genital tract, including the physiological control of endometrial functions, receptivity, menopausal status and related pathological conditions. An overview of the intracrine regulation in extra gynecological tissues such as the lungs, gastrointestinal tract, brain, colon and bone is given. Current therapeutic approaches aimed at interfering with these metabolisms and future perspectives are discussed.

Reproduction triggers adaptive increases in body size in female mole-rats

In social mole-rats, breeding females are larger and more elongated than non-breeding female helpers. This status-related morphological divergence is thought to arise from modifications of skeletal growth following the death or removal of the previous breeder and the transition of their successors from a non-breeding to a breeding role. However, it is not clear what changes in growth are involved, whether they are stimulated by the relaxation of reproductive suppression or by changes in breeding status, or whether they are associated with fecundity increases. Here, we show that, in captive Damaraland mole-rats (Fukomys damarensis), where breeding was experimentally controlled in age-matched siblings, individuals changed in size and shape through a lengthening of the lumbar vertebrae when they began breeding. This skeletal remodelling results from changes in breeding status because (i) females removed from a group setting and placed solitarily showed no increases in growth and (ii) females dispersing from natural groups that have not yet bred do not differ in size and shape from helpers in established groups. Growth patterns consequently resemble other social vertebrates where contrasts in size and shape follow the acquisition of the breeding role. Our results also suggest that the increases in female body size provide fecundity benefits. Similar forms of socially responsive growth might be more prevalent in vertebrates than is currently recognized, but the extent to which this is the case, and the implications for the structuring of mammalian dominance hierarchies, are as yet poorly understood.

Effects of strontium ranelate on wear particle‑induced aseptic loosening in female ovariectomized mice

Aseptic loosening and menopause‑induced osteoporosis are caused by an imbalance between bone formation and osteolysis. With an aging population, the probability of simultaneous occurrence of such conditions in an elderly individual is increasing. Strontium ranelate (SR) is an anti‑osteoporosis drug that promotes bone formation and inhibits osteolysis. The present study compared the effects of SR with those of the traditional anti‑osteoporosis drug alendronate (ALN) using an ovariectomized mouse model of osteolysis. The degree of firmness of the prosthesis and the surrounding tissue was examined, a micro‑CT scan of the prosthesis and the surrounding tissue was performed, and the levels of inflammatory and osteogenic and osteoclast factors were examined. It was observed that treatment with SR and ALN improved the bond between the prosthesis and the surrounding bone tissue by reducing the degree of osteolysis, thus improving the quality of bone around the prosthesis. SR increased the secretion of osteocalcin, runt‑related transcription factor 2 and osteoprotegerin (OPG). It additionally decreased the expression of the receptor activator of nuclear factor‑κB ligand (RANKL) and consequently increased the protein ratio OPG/RANKL, whereas ALN exhibited the opposite effect. Furthermore, SR and ALN suppressed tumor necrosis factor‑α and interleukin‑1β production, with SR exerting a more marked effect. The present results demonstrate that SR and ALN may stimulate bone formation and inhibit bone resorption in the ovariectomized mouse model of wear particle‑mediated osteolysis, with SR demonstrating better effects compared with ALN.

Risk factors for low bone mineral density in pediatric inflammatory bowel disease: the positive role of physical activity

OBJECTIVE

In pediatric inflammatory bowel disease (IBD), the prevalence of low bone mineral density (BMD) and bone fractures and the relationship between these are still debated. Our aim was to report data from a cohort of pediatric patients with IBD.

PATIENTS AND METHODS

Cross-sectional assessment of growth and BMD [(dual-energy x-ray absorptiometry (DXA)] and retrospective chart review were performed to report the lifetime prevalence of bone fractures and clinical associations with patients' data.

RESULTS

We examined 216 patients with IBD, 8-25 years old (median: 14 years). Low BMD was found in 12.5% (spine) and 27% (total body). Multiple regression analysis showed that BMD was predicted by Z-scores for height and weight at DXA. History of menstrual irregularities and nasogastric tube feedings was associated with lower BMD, whereas physical activity and higher Z-score for height at DXA were associated with higher BMD.The prevalence of lifetime fractures was 11.8%. Patients with a history of fractures had lower Z-scores for spine BMD (-1.20 vs. -0.69, P=0.020) and total-body BMD (-1.30 vs. -0.75, P=0.014) compared with those without a history of fractures. Patients with spine BMD Z-score of up to -2 SD score had significantly increased prevalence of fractures compared with those with Z-score more than -2 SD score (28 vs. 10%, P=0.015).

CONCLUSION

This study provides further insight into risk factors for low BMD in pediatric IBD. Novel findings were the association between low BMD and fractures, and the positive relationship between BMD and physical activity.

Bone metabolism in anorexia nervosa and hypothalamic amenorrhea

Anorexia nervosa (AN) and hypothalamic amenorrhea (HA) are states of chronic energy deprivation associated with severely compromised bone health. Poor bone accrual during adolescence followed by increased bone loss results in lifelong low bone density, degraded bone architecture, and higher risk of fractures, despite recovery from AN/HA. Amenorrhea is only one of several compensatory responses to the negative energy balance. Other hypothalamic-pituitary hormones are affected and contribute to bone deficits, including activation of hypothalamic-pituitary-adrenal axis and growth hormone resistance. Adipokines, particularly leptin, provide information on fat/energy stores, and gut hormones play a role in the regulation of appetite and food intake. Alterations in all these hormones influence bone metabolism. Restricted in scope, current pharmacologic approaches to improve bone health have had overall limited success.