Estrogens and Androgens in Skeletal Physiology and Pathophysiology

SIRT1 haplo-insufficiency results in reduced cortical bone thickness, increased porosity and decreased estrogen receptor alpha in bone in adult 129/Sv female mice

INTRODUCTION

Sirtuin 1 (SIRT1) is a key player in aging and metabolism and regulates bone mass and architecture. Sexual dimorphism in skeletal effects of SIRT1 has been reported, with an unfavorable phenotype primarily in female mice.

METHODS

To investigate the mechanisms of gender differences in SIRT1 skeletal effect, we investigated femoral and vertebral cortical and cancellous bone in global Sirt1 haplo-insufficient 129/Sv mice aged 2,7,12 months lacking Sirt1 exons 5,6,7 (Sirt1^+/Δ ) and their wild type (WT) counterparts.

RESULTS

In females, femoral bone mineral content, peak cortical thickness, and trabecular bone volume (BV/TV%), number and thickness were significantly lower in Sirt1^+/Δ compared to WT mice. Increased femoral cortical porosity was observed in 7-month-old Sirt1^+/Δ compared to WT female mice, accompanied by reduced biomechanical strength. No difference in vertebral indices was detected between Sirt1^+/Δ and WT female mice. SIRT1 decreased with aging in WT female mice and was lower in vertebrae and femur in 18- and 30- versus 3-month-old 129/Sv and C57BL/6J female mice, respectively. Decreased bone estrogen receptor alpha (ERα) was observed in Sirt1^+/Δ compared to WT female mice and was significantly higher in Sirt1 over-expressing C3HT101/2 murine mesenchymal stem cells. In males no difference in femoral indices was detected in Sirt1^+/Δ versus WT mice, however vertebral BV/TV%, trabecular number and thickness were higher in Sirt1^+/Δ vs. WT mice. No difference in androgen receptor (AR) was detected in bone in Sirt1^+/Δ vs. WT male mice. Bone SIRT1 was significantly lower in male compared to female WT mice, suggesting that SIRT1 maybe more significant in female than male skeleton.

DISCUSSION

These findings demonstrate that 50% reduction in SIRT1 is sufficient to induce the hallmarks of skeletal aging namely, decreased cortical thickness and increased porosity in female mice, highlighting the role of SIRT1 as a regulator of cortical bone quantity and quality. The effects of SIRT1 in cortical bone are likely mediated in part by its regulation of ERα. The age-associated decline in bone SIRT1 positions SIRT1 as a potential therapeutic target to ameliorate age-related cortical bone deterioration in females. The crosstalk between ERα, AR and SIRT1 in the bone microenvironment remains to be further investigated.

Association between perfluoroalkyl substances concentration and bone mineral density in the US adolescents aged 12-19 years in NHANES 2005-2010

BACKGROUND

Reports on the association of perfluoroalkyl substances (PFASs) exposure with adolescent bone health are scarce, and studies have primarily targeted maternal serum.

OBJECTIVE

We evaluated the relationship between autologous serum perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS) and perfluorononanoic acid (PFNA) levels and bone mineral density (BMD) in adolescents.

METHODS

We analyzed data from 1228 adolescents aged 12-19 years in the National Health and Nutrition Examination Survey (NHANES) 2005-2010 and used multiple regression analysis to identify the relationship between serum PFOA, PFOS, PFHxS, and PFNA concentrations and total femur, femoral neck, and lumbar spine BMD, in addition to multiple stratified subgroup analyses.

RESULTS

The mean age of participants was 15 years, males had higher serum PFAS concentrations than females. The results of multiple regression analysis showed that the natural log(ln)-transformed serum PFOA, PFOS, and PFNA concentrations were negatively correlated with total femur, femoral neck, and lumbar spine BMD (all p < 0.05), and ln-PFHxS was positively correlated with total femur and femoral neck BMD (all p< 0.05). In males, ln-PFOA was negatively associated with total femur and lumbar spine BMD (all p< 0.05), ln-PFOS was associated with the reduced total femur, femoral neck, and lumbar spine BMD (all p< 0.05), while ln-PFHxS and ln-PFNA were not observed to correlate with BMD at these three sites. In females, both ln-PFOA and ln-PFOS were negatively correlated with total femur and lumbar spine BMD (all p< 0.05), ln-PFHxS is associated with the increased total femur and femoral neck BMD (all p< 0.05), and ln-PFNA was negatively correlated with total femur and femoral neck BMD (all p< 0.05), most of the associations were confined to females. The associations of ln-PFOS with femoral neck BMD and ln-PFNA with total femur BMD were more significant in those who were overweight/obese and had anemia, respectively (all p for interaction < 0.05).

CONCLUSIONS

In this representative sample of US adolescents aged 12-19 years, certain PFAS were associated with lower bone mineral density, and most of the associations were confined to females. The negative effect of PFAS on BMD is more pronounced in those who are overweight/obese and have anemia. However, further studies are needed to confirm this finding.

The Role of NRF2 in Bone Metabolism - Friend or Foe?

Bone metabolism is closely related to oxidative stress. As one of the core regulatory factors of oxidative stress, NRF2 itself and its regulation of oxidative stress are both involved in bone metabolism. NRF2 plays an important and controversial role in the regulation of bone homeostasis in osteoblasts, osteoclasts and other bone cells. The role of NRF2 in bone is complex and affected by several factors, such as its expression levels, age, sex, the presence of various physiological and pathological conditions, as well as its interaction with certains transcription factors that maintain the normal physiological function of the bone tissue. The properties of NRF2 agonists have protective effects on the survival of osteogenic cells, including osteoblasts, osteocytes and stem cells. Activation of NRF2 directly inhibits osteoclast differentiation by resisting oxidative stress. The effects of NRF2 inhibition and hyperactivation on animal skeleton are still controversial, the majority of the studies suggest that the presence of NRF2 is indispensable for the acquisition and maintenance of bone mass, as well as the protection of bone mass under various stress conditions. More studies show that hyperactivation of NRF2 may cause damage to bone formation, while moderate activation of NRF2 promotes increased bone mass. In addition, the effects of NRF2 on the bone phenotype are characterized by sexual dimorphism. The efficacy of NRF2-activated drugs for bone protection and maintenance has been verified in a large number of in vivo and in vitro studies. Additional research on the role of NRF2 in bone metabolism will provide novel targets for the etiology and treatment of osteoporosis.

Anabolic Androgenic Steroids in Orthopaedic Surgery: Current Concepts and Clinical Applications

Despite the well-documented effects of testosterone and its synthetic derivatives—collectively termed anabolic androgenic steroids (AASs)—on the musculoskeletal system, the therapeutic use of these agents has received limited investigation within the field of orthopaedic surgery. In the last 2 decades, preclinical and clinical research has started to identify promising applications of the short-term use of AASs in the perioperative period. There is evidence to suggest that AASs may improve postoperative recovery after anterior cruciate ligament reconstruction and total joint arthroplasty. In addition, AASs may augment the biological healing environment in specific clinical scenarios including muscle injury, fracture repair, and rotator cuff repair. Current literature fails to present strong evidence for or against the use of AASs in orthopaedics, but there is continuous research on this topic. The purpose of this study was to provide a comprehensive overview of the current status of AAS applications in orthopaedic surgery, with an emphasis on preclinical data, clinical studies, and future directions.

Association between Serum Total Testosterone Level and Bone Mineral Density in Middle-Aged Postmenopausal Women

BACKGROUND

Hormone status strongly affects women's health and quality of life. To date, studies investigating the association between total testosterone (T) level and bone mineral density (BMD) in women are limited and have yielded contradictory conclusions. The aim of our study was to examine the association between serum total T level and lumbar BMD in postmenopausal women aged 40-59 years.

METHODS

The study group included 1,058 women from the 2011-2016 National Health and Nutrition Examination Survey. Multiple regression analyses were used to evaluate the association between serum total T level and lumbar BMD.

RESULTS

After adjusting for covariates, there was a positive association between the serum total T level and lumbar BMD (β, 1.07; 95% confidence interval, 0.17-1.97). A non-linearity in this association was identified, with a point of inflection at 30 ng/dL.

CONCLUSIONS

Serum total T level was positively associated with lumbar BMD in middle-aged postmenopausal women up to a T level >30 ng/dL. Therefore, increasing T level in women with a low serum total T level may have beneficial outcomes on bone health.

Effects of bisphosphonates on bone of osteoporotic men with different androgen levels: a case-control study

OBJECTIVE

Osteoporosis in men has been neglected despite its association with disability and mortality. We evaluated effects of bisphosphonates (BPs) on bone mineral density (BMD) and bone turnover biomarkers of osteoporotic men with different androgen levels.

METHODS

This case-control study included 136 men with osteopenia or osteoporosis who were divided into normal androgen group (n=75) and hypogonadism group (n=61) (patients treated with testosterone were excluded) according to serum testosterone levels (cutoff value: 3.5 ng/ml). BMD, serum testosterone, total alkaline phosphatase (ALP) and cross-linked C-telopeptide of type I collagen (β-CTX) were detected. Relationship between testosterone levels and BMD at baseline was evaluated. All patients received BPs, calcium and vitamin D treatment for two years. We evaluated and compared effects of BPs on BMD and bone turnover biomarkers between two groups.

RESULTS

At baseline, there were no significant differences in BMD and bone turnover biomarkers between two groups. Testosterone levels were positively correlated with BMD in hypogonadism group. After treatment, lumbar BMD increased by 7.65±1.54% and 7.47±1.88% in normal and hypogonadism groups (both P<0.01 vs. baseline), and hip BMD increased, without significant differences between two groups. Serum β-CTX and ALP levels decreased by 56.5±6.3% and 16.8±3.5% in normal group and similarly decreased by 51.8±6.4% and 13.8±6.8% in hypogonadism group (all P<0.01 vs. baseline).

CONCLUSION

Testosterone level is positively correlated with BMD in men with hypogonadism. In men with osteoporosis, BPs significantly increase spine and hip BMD and decrease bone resorption, and efficacy of BPs is similar in men with or without hypogonadism.

Estrogen Receptor α Signaling in Osteoblasts is Required for Mechanotransduction in Bone Fracture Healing

Biomechanical stimulation by whole-body low-magnitude high-frequency vibration (LMHFV) has demonstrated to provoke anabolic effects on bone metabolism in both non-osteoporotic and osteoporotic animals and humans. However, preclinical studies reported that vibration improved fracture healing and bone formation in osteoporotic, ovariectomized (OVX) mice representing an estrogen-deficient hormonal status, but impaired bone regeneration in skeletally healthy non-OVX mice. These effects were abolished in general estrogen receptor α (ERα)-knockout (KO) mice. However, it remains to be elucidated which cell types in the fracture callus are targeted by LMHFV during bone healing. To answer this question, we generated osteoblast lineage-specific ERα-KO mice that were subjected to ovariectomy, femur osteotomy and subsequent vibration. We found that the ERα specifically on osteoblastic lineage cells facilitated the vibration-induced effects on fracture healing, because in osteoblast lineage-specific ERα-KO (ERα^{fl/fl; Runx2Cre}) mice the negative effects in non-OVX mice were abolished, whereas the positive effects of vibration in OVX mice were reversed. To gain greater mechanistic insights, the influence of vibration on murine and human osteogenic cells was investigated in vitro by whole genome array analysis and qPCR. The results suggested that particularly canonical WNT and Cox2/PGE₂ signaling is involved in the mechanotransduction of LMHFV under estrogen-deficient conditions. In conclusion, our study demonstrates a critical role of the osteoblast lineage-specific ERα in LMHFV-induced effects on fracture healing and provides further insights into the molecular mechanism behind these effects.

Postmenopausal osteoporosis: risk evaluation and treatment options

Postmenopausal osteoporosis is a chronic progressive condition characterized by reduced bone mass and impaired bone quality, leading to an increased risk of fragility fractures. Osteoporotic fractures reduce quality of life and are associated with high morbidity, mortality and economic burden. Primary and secondary prevention interventions are always recommended starting from the premenopausal age, in women after menopause, however, it is essential to develop a long-term intervention strategy that allows to identify patients at high risk of fracture and the choice of therapy based on the estimated risk. This narrative review described the tools for layering the management approach in relation to low, high and very high fracture risk. Several medications are now available for the treatment of osteoporosis and the prevention of fractures; the knowledge of the efficacy, safety and additional benefits profile of the individual preparations allows an appropriate choice between the different drugs available and the possibility of adapting the prescription to the lifetime fracture risk spectrum. From the literature it emerges that menopausal hormone therapy (MHT), TSEC combination and SERMs can be drugs of choice to counteract postmenopausal bone loss in younger women or at low risk of fracture, while bisphosphonates and denosumab are appropriate for women with high risk or at an older age. Therapy with denosumab and anabolic agents such as teriparatide and romosozumab is particularly indicated for subjects with very high risk of fracture.

Temporal and Quantitative Transcriptomic Differences Define Sexual Dimorphism in Murine Postnatal Bone Aging

Time is a central element of the sexual dimorphic patterns of development, pathology, and aging of the skeleton. Because the transcriptome is a representation of the phenome, we hypothesized that both sex and sex‐specific temporal, transcriptomic differences in bone tissues over an 18‐month period would be informative to the underlying molecular processes that lead to postnatal sexual dimorphism. Regardless of age, sex‐associated changes of the whole bone transcriptomes were primarily associated not only with bone but also vascular and connective tissue ontologies. A pattern‐based approach used to screen the entire Gene Expression Omnibus (GEO) database against those that were sex‐specific in bone identified two coordinately regulated gene sets: one related to high phosphate–induced aortic calcification and one induced by mechanical stimulation in bone. Temporal clustering of the transcriptome identified two skeletal tissue‐associated, sex‐specific patterns of gene expression. One set of genes, associated with skeletal patterning and morphology, showed peak expression earlier in females. The second set of genes, associated with coupled remodeling, had quantitatively higher expression in females and exhibited a broad peak between 3 to 12 months, concurrent with the animals' reproductive period. Results of phenome‐level structural assessments of the tibia and vertebrae, and in vivo and in vitro analysis of cells having osteogenic potential, were consistent with the existence of functionally unique, skeletogenic cell populations that are separately responsible for appositional growth and intramedullary functions. These data suggest that skeletal sexual dimorphism arises through sex‐specific, temporally different processes controlling morphometric growth and later coupled remodeling of the skeleton during the reproductive period of the animal. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Estrogens and phytoestrogens in body functions

Estrogens are the hormones of reproduction in women as well as of many other important functions in the male and female body. They undergo significant changes in the different phases of life, e.g. during puberty, pregnancy or at menopause/andropause. Phytoestrogens are natural non-steroidal phenolic plant compounds that can mimic the activity of estrogens and their beneficial effects in women and in men. This narrative review summarizes the literature on the physiological role of estrogens and the several potential health benefits of phytoestrogens, with particular attention given to the possible role of phytoestrogens in aging.

Clinical application of aromatase inhibitors to treat male infertility

BACKGROUND

Infertility affects 15% of men and contributes to nearly half of all cases of infertility. Infertile men usually have impaired spermatogenesis, presenting as azoospermia or various degrees of asthenospermia and oligozoospermia. Spermatogenesis is a complex and coordinated process, which is under precise modulation by the hypothalamic-pituitary-gonadal (HPG) axis. An aberrant hormone profile, especially an imbalance between testosterone (T) and estradiol (E2), plays an essential role in male infertility. In the male, E2 is produced mainly from the conversion of T by the aromatase enzyme. Theoretically, reducing an abnormally elevated T:E2 ratio using aromatase inhibitors (AIs) could restore the balance between T and E2 and optimize the HPG axis to support spermatogenesis. For decades, AIs have been used to treat male infertility empirically. However, owing to the lack of large-scale randomized controlled studies and basic research, the treatment efficacy and safety of AIs in male infertility remain controversial. Therefore, there is a need to summarize the clinical trials and relevant basic research on the application of AIs in the treatment of male infertility.

OBJECTIVE AND RATIONALE

In this narrative review, we summarized the application of AIs in the treatment of male infertility, including the pharmacological mechanisms involved, clinical trials focused on patients with different types of infertility, factors affecting treatment efficacy and the side-effects.

SEARCH METHODS

A literature search was performed using MEDLINE/PubMed and EMBASE, focusing on publications in the past four decades concerning the use of AIs for treating male infertility. The search terms included AI, male infertility, letrozole, anastrozole, testolactone, azoospermia, oligozoospermia, aromatase polymorphisms, obesity and antiestrogens, in various combinations.

OUTCOMES

Clinical studies demonstrate that AIs, especially nonsteroidal letrozole and anastrozole, could significantly inhibit the production of E2 and its negative feedback on the HPG axis, resulting in increased T and FSH production as well as improved semen parameters in infertile men. Large-scale surveys suggest that obesity may result in symptoms of hypogonadism in both fertile and infertile males, such as decreased semen quality and attenuated sexual function, which can be improved by AIs treatment. Polymorphisms of the aromatase gene CYP19A1, including single nucleotide polymorphisms and tetranucleotide TTTA repeats polymorphism (TTTAn), also influence hormone profiles, semen quality and treatment efficacy of AIs in male hypogonadotropic hypogonadism and infertility. The side-effects of AIs in treating male infertility are various, but most are mild and well tolerated.

WIDER IMPLICATIONS

The application of AIs in treating male infertility has been off-label and empirical for decades. This narrative review has summarized the target patients, dose, treatment duration and side-effects of AIs. Polymorphisms of CYP19A1 that may affect AIs treatment efficacy were also summarized, but a full understanding of the mechanisms involved in AIs action requires further study.

DNA methylation in genes associated with the evolution of ageing and disease: A critical review

Ageing is characterised by a physical decline in biological functioning which results in a progressive risk of mortality with time. As a biological phenomenon, it is underpinned by the dysregulation of a myriad of complex processes. Recently, however, ever-increasing evidence has associated epigenetic mechanisms, such as DNA methylation (DNAm) with age-onset pathologies, including cancer, cardiovascular disease, and Alzheimer's disease. These diseases compromise healthspan. Consequently, there is a medical imperative to understand the link between epigenetic ageing, and healthspan. Evolutionary theory provides a unique way to gain new insights into epigenetic ageing and health. This review will: (1) provide a brief overview of the main evolutionary theories of ageing; (2) discuss recent genetic evidence which has revealed alleles that have pleiotropic effects on fitness at different ages in humans; (3) consider the effects of DNAm on pleiotropic alleles, which are associated with age related disease; (4) discuss how age related DNAm changes resonate with the mutation accumulation, disposable soma and programmed theories of ageing; (5) discuss how DNAm changes associated with caloric restriction intersect with the evolution of ageing; and (6) conclude by discussing how evolutionary theory can be used to inform investigations which quantify age-related DNAm changes which are linked to age onset pathology.

Epidemiology and secular trends of pelvic fractures in Belgium: A retrospective, population-based, nationwide observational study

INTRODUCTION

Fractures of the pelvis and acetabulum are associated with osteoporosis, and their incidence is rising in older adults. In the last decade an increasing number of these fractures are being operated in older patients in certain regions. The goal of this study was to describe the incidence of pelvic and acetabular fractures in Belgium between 1988 and 2018.

MATERIALS & METHODS

This retrospective, nationwide, population-based study was conducted with the help of the national health insurance database from the Belgian National Institute for Health and Disability Insurance (NIHDI-RIZIV-INAMI). Multiple codes for the reimbursement of the diagnosis and treatment of pelvic and acetabular fractures were collated and (since 2006) linked to the patients' age group, sex and region.

RESULTS

Between 1988 and 2018, 91.317 pelvic and acetabular fractures were diagnosed. The overall incidence increased from 15,8/100.000 persons per year in 1988 to 29,7/100.000 persons per year in 2006 and to 37,6/100.000 persons per year in 2018. These fractures showed a bimodal incidence, with a small peak in children (particularly boys), and an increasing incidence in older adults, particularly in women. Between 2006 and 2018, 5.957 (12,4%) patients underwent surgical treatment for their pelvic fracture. 2.088 patients underwent an osteosynthesis of the acetabulum and 3869 patients underwent an osteosynthesis of the pelvic ring. There were 3622 osteosynthesises (60.8%) in patients younger than 60 years old and 2335 (39,1%) in patients over 60 years old.

CONCLUSION

There is an increasing incidence of pelvic and acetabular fractures in Belgium with the majority of these fractures occurring in older people. Younger adults have the highest proportion of surgical treatment, but given the much higher incidence in older adults, there is a considerable amount of operations in older adults too.

Aucubin slows the development of osteoporosis by inhibiting osteoclast differentiation via the nuclear factor erythroid 2-related factor 2-mediated antioxidation pathway

CONTEXT

Osteoporosis (OP) is a metabolic disease. We have previously demonstrated that aucubin (AU) has anti-OP effects that are due to its promotion of the formation of osteoblasts.

OBJECTIVES

To investigate the mechanisms of anti-OP effects of AU.

MATERIALS AND METHODS

C57BL/6 mice were randomly divided into control group, 30 mg/kg Dex-induced OP group (OP model group, 15 μg/kg oestradiol-treated positive control group, 5 or 45 mg/kg AU-treated group), and 45 mg/kg AU-alone-treated group. The administration lasted for 7 weeks. Subsequently, 1, 2.5 and 5 µM AU were incubated with 50 ng/mL RANKL-induced RAW264.7 cells for 7 days to observe osteoclast differentiation. The effect of AU was evaluated by analysing tissue lesions, biochemical factor and protein expression.

RESULTS

The LD₅₀ of AU was greater than 45 mg/kg. AU increased the number of trabeculae and reduced the loss of chondrocytes in OP mice. Compared to OP mice, AU-treated mice exhibited decreased serum concentrations of TRAP5b (19.6% to 28.4%), IL-1 (12.2% to 12.6%), IL-6 (12.1%) and ROS (5.9% to 10.7%) and increased serum concentrations of SOD (14.6% to 19.4%) and CAT (17.2% to 27.4%). AU treatment of RANKL-exposed RAW264.7 cells decreased the numbers of multi-nuclear TRAP-positive cells, reversed the over-expression of TRAP5, NFATc1 and CTSK. Furthermore, AU increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream proteins in RANKL-exposed RAW264.7 cells.

CONCLUSIONS

AU slows the development of OP via Nrf2-mediated antioxidant pathways, indicating the potential use of AU in OP therapy and other types of OP research.

Bone Phenotyping Approaches in Human, Mice and Zebrafish - Expert Overview of the EU Cost Action GEMSTONE ("GEnomics of MusculoSkeletal traits TranslatiOnal NEtwork")

A synoptic overview of scientific methods applied in bone and associated research fields across species has yet to be published. Experts from the EU Cost Action GEMSTONE ("GEnomics of MusculoSkeletal Traits translational Network") Working Group 2 present an overview of the routine techniques as well as clinical and research approaches employed to characterize bone phenotypes in humans and selected animal models (mice and zebrafish) of health and disease. The goal is consolidation of knowledge and a map for future research. This expert paper provides a comprehensive overview of state-of-the-art technologies to investigate bone properties in humans and animals - including their strengths and weaknesses. New research methodologies are outlined and future strategies are discussed to combine phenotypic with rapidly developing -omics data in order to advance musculoskeletal research and move towards "personalised medicine".

Novel Elongator Protein 2 Inhibitors Mitigating Tumor Necrosis Factor-α Induced Osteogenic Differentiation Inhibition

Tumor necrosis factor-α is a common cytokine that increases in inflammatory processes, slows the differentiation of bone formation, and induces osteodystrophy in the long-term inflammatory microenvironment. Our previous study confirmed that the Elongation protein 2 (ELP2) plays a significant role in osteogenesis and osteogenic differentiation, which is considered a drug discovery target in diseases related to bone formation and differentiation. In this study, we applied an in silico virtual screening method to select molecules that bind to the ELP2 protein from a chemical drug molecule library and obtained 95 candidates. Then, we included 11 candidates by observing the docking patterns and the noncovalent bonds. The binding affinity of the ELP2 protein with the candidate compounds was examined by SPR analysis, and 5 out of 11 compounds performed good binding affinity to the mouse ELP2 protein. After in vitro cell differentiation assay, candidates 2# and 5# were shown to reduce differentiation inhibition after tumor necrosis factor-α stimulation, allowing further optimization and development for potential clinical treatment of inflammation-mediated orthopedic diseases.

Sex Steroid Regulation of Oxidative Stress in Bone Cells: An In Vitro Study

Environmental stimuli, including sex hormones and oxidative stress (OS), affect bone balance, modifying the epigenetic profiles of key osteogenic genes. Nonetheless, the interplay between sex steroids, epigenome and OS has yet be fully elucidated. This paper aims to study in vitro the role of sex steroids in OS-induced alteration in bone cells’ homeostasis, and to assess the possible contribution of epigenetic modifications. Toward this purpose, osteoblast (MC3T3-E1) and osteocyte (MLOY-4) cell lines were exposed to two different sources of free oxygen radicals, i.e., tert-butyl hydroperoxide and dexamethasone, and the protective effect of pre-treatment with androgens and estrogens was evaluated. In particular, we analyzed parameters that reflect bone cell homeostasis such as cell viability, cell migration, transcriptomic profile, transcriptional activity, and epigenetic signature. Our findings indicate that estrogens and androgens counteract OS effects. Using partially overlapping strategies, they reduce OS outcomes regarding cell viability, cell migration, the transcriptomic profile of gene families involved in bone remodeling, and epigenetic profile, i.e., H3K4me3 level. Additionally, we demonstrated that the protective effect of steroids against OS on bone homeostasis is partially mediated by the Akt pathway. Overall, these results suggest that the hormonal milieu may influence the mechanisms of age-related bone disease.

The Relationship Between Bone and Reproductive Hormones Beyond Estrogens and Androgens

Reproductive hormones play a crucial role in the growth and maintenance of the mammalian skeleton. Indeed, the biological significance for this hormonal regulation of skeletal homeostasis is best illustrated by common clinical reproductive disorders, such as primary ovarian insufficiency, hypothalamic amenorrhea, congenital hypogonadotropic hypogonadism, and early menopause, which contribute to the clinical burden of low bone mineral density and increased risk for fragility fracture. Emerging evidence relating to traditional reproductive hormones and the recent discovery of newer reproductive neuropeptides and hormones has deepened our understanding of the interaction between bone and the reproductive system. In this review, we provide a contemporary summary of the literature examining the relationship between bone biology and reproductive signals that extend beyond estrogens and androgens, and include kisspeptin, gonadotropin-releasing hormone, follicle-stimulating hormone, luteinizing hormone, prolactin, progesterone, inhibin, activin, and relaxin. A comprehensive and up-to-date review of the recent basic and clinical research advances is essential given the prevalence of clinical reproductive disorders, the emerging roles of upstream reproductive hormones in bone physiology, as well as the urgent need to develop novel safe and effective therapies for bone fragility in a rapidly aging population.

Centenarian longevity had inverse relationships with nutritional status and abdominal obesity and positive relationships with sex hormones and bone turnover in the oldest females

Objective

The number of older people is estimated to increase from 524 million in 2010 to 1.5 billion in 2050. The factors and models of human longevity and successful aging are questions that have intrigued individuals for thousands of years. For the first time, the current study was designed to investigate the relationships between sex hormones, bone turnover, abdominal obesity, nutritional status and centenarian longevity in the oldest females.

Methods

The China Hainan Centenarian Cohort Study was performed in 18 cities and counties of Hainan Province using standard methodology in 500 centenarian females and 237 oldest females aged between 80 and 99 years.

Results

Centenarians were inversely associated with the geriatric nutritional risk index [Exp(B) (95% CI): 0.901 (0.883–0.919)] and abdominal obesity [Exp(B) (95% CI): 0.719 (0.520–0.996)] and positively associated with prolactin [Exp(B) (95% CI): 1.073 (1.044–1.103)], progesterone [Exp(B) (95% CI): 44.182 (22.036–88.584)], estradiol [Exp(B) (95% CI): 1.094 (1.071–1.119)], osteocalcin [Exp(B) (95% CI): 1.041 (1.028–1.054)], β-crossLaps [Exp(B) (95% CI): 63.141 (24.482–162.848)] and parathyroid [Exp(B) (95% CI): 1.022 (1.013–1.031)] hormone levels (P < 0.05 for all). The geriatric nutritional risk index and abdominal obesity were inversely associated with luteinizing hormone [β coefficient (95% CI): − 0.001 (− 0.002 to 0.001)]; Exp(B) (95% CI): 0.985 (0.974–0.996)], follicle-stimulating hormone [β coefficient (95% CI): 0.000 (− 0.001 to 0.000)]; Exp(B) (95% CI): 0.990 (0.985–0.996)], osteocalcin [β coefficient (95% CI): − 0.001 (− 0.001 to 0.000)]; Exp(B) (95% CI): 0.987(0.977–0.997)] and β-crossLaps [β coefficient (95% CI): − 0.100 (− 0.130 to 0.071)]; Exp(B) (95% CI): 0.338 (0.166–0.689)] levels (P < 0.05 for all).

Conclusions

Centenarian longevity had inverse relationships with nutritional status and abdominal obesity and positive relationships with sex hormones and bone turnover. Nutritional status and abdominal obesity had inverse relationships with sex hormones and bone turnover. Increased sex hormones and bone turnover may be representative of centenarian longevity. Optimizing nutritional status and avoiding abdominal obesity may increase sex hormones and bone turnover and promote centenarian longevity and successful aging.

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).

High bone mineral density in lifelong trained female team handball players and young elite football players

PURPOSE

Low bone mineral density (BMD) and fractures are a major concern in the female population and preventative strategies are needed. Whether team sports participation may reduce age-related bone loss in elderly women is still uncertain.

METHODS

One hundred and thirty healthy, non-smoking women participated in this cross-sectional study, i.e., elderly (60-80 years) team handball players (EH, n = 35), elderly untrained controls (EC, n = 35), young (18-30 years) elite football players (YF, n = 30) and young untrained controls (YC, n = 30). A whole-body and two regional dual-energy X-ray absorptiometry (DXA) scans were performed to evaluate BMD and a blood sample was collected for measurement of bone turnover markers (BTMs).

RESULTS

EH had higher BMD in all regions of the lumbar spine, except for L1, compared to EC (8-10%), and higher BMD in the femoral Ward's triangle (9%) and trochanter (7%) of the left leg. Furthermore, EH had higher mean leg BMD (8%) and whole-body BMD (5%) than EC. EH and YC had similar BMD in femoral trochanter, L1-L4 and mean leg despite an age difference of ~ 40 years. YF had higher BMD in all regions of the proximal femur (18-29%) and lumbar spine (12-16%) compared to YC, as well as higher mean leg BMD (20%) and whole-body BMD (13%). Sclerostin was 14% lower in EH compared to EC. YF showed higher PINP (98%), osteocalcin (57%), and CTX (83%) compared to YC.

CONCLUSION

Lifelong team handball training and elite football training are associated with superior bone mineralization and changed bone turnover in elderly and young women.

FSH Level and Changes in Bone Mass and Body Composition in Older Women and Men

CONTEXT

FSH may have independent actions on bone remodeling and body fat regulation. Cross-sectionally, we have shown that serum FSH is associated with bone mineral density (BMD) and body fat in older postmenopausal women, but it remains unknown whether FSH predicts bone and fat changes.

OBJECTIVE

We examined whether baseline FSH level is associated with subsequent bone loss or body composition changes in older adults.

SETTING, DESIGN, PARTICIPANTS

We studied 162 women and 158 men (mean age 82 ± 4 years) from the Age, Gene/Environment Susceptibility (AGES)-Bone Marrow Adiposity cohort, a substudy of the AGES-Reykjavik Study of community-dwelling older adults. Skeletal health and body composition were characterized at baseline and 3 years later.

MAIN OUTCOMES

Annualized change in BMD and body composition by dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). Models were adjusted for serum estradiol and testosterone levels.

RESULTS

There was no evidence for an association between baseline FSH level and change in BMD or body composition by DXA or QCT. For femoral neck areal BMD, adjusted mean difference (95% CI) per SD increase in FSH was 1.3 (-0.7 to 3.3) mg/cm2/y in women, and -0.2 (-2.6 to 2.2) mg/cm2/y in men. For visceral fat, adjusted mean difference (95% CI) per SD increase in FSH was 1.80 (-0.03 to 3.62) cm2/y in women, and -0.33 (-3.73 to 3.06) cm2/y in men.

CONCLUSIONS

Although cross-sectional studies and studies in perimenopausal women have demonstrated associations between FSH and BMD and body composition, in older adults, FSH level is not associated with bone mass or body composition changes.

G-Protein-Coupled Estrogen Receptor-1 Positively Regulates the Growth Plate Chondrocyte Proliferation in Female Pubertal Mice

Estrogen enhances long bone longitudinal growth during early puberty. Growth plate chondrocytes are the main cells that contribute to long bone elongation. The role of G-protein-coupled estrogen receptor-1 (GPER-1) in regulating growth plate chondrocyte function remains unclear. In the present study, we generated chondrocyte-specific GPER-1 knockout (CKO) mice to investigate the effect of GPER-1 in growth plate chondrocytes. In control mice, GPER-1 was highly expressed in the growth plates of 4- and 8-week-old mice, with a gradual decline through 12 to 16 weeks. In CKO mice, the GPER-1 expression in growth plate chondrocytes was significantly lower than that in the control mice (80% decrease). The CKO mice also showed a decrease in body length (crown-rump length), body weight, and the length of tibias and femurs at 8 weeks. More importantly, the cell number and thickness of the proliferative zone of the growth plate, as well as the thickness of primary spongiosa and length of metaphysis plus diaphysis in tibias of CKO mice, were significantly decreased compared with those of the control mice. Furthermore, there was also a considerable reduction in the number of proliferating cell nuclear antigens and Ki67-stained proliferating chondrocytes in the tibia growth plate in the CKO mice. The chondrocyte proliferation mediated by GPER-1 was further demonstrated via treatment with a GPER-1 antagonist in cultured epiphyseal cartilage. This study demonstrates that GPER-1 positively regulates chondrocyte proliferation at the growth plate during early puberty and contributes to the longitudinal growth of long bones.

Antioxidant, Mineralogenic and Osteogenic Activities of Spartina alterniflora and Salicornia fragilis Extracts Rich in Polyphenols

Osteoporosis is an aging-related disease and a worldwide health issue. Current therapeutics have failed to reduce the prevalence of osteoporosis in the human population, thus the discovery of compounds with bone anabolic properties that could be the basis of next generation drugs is a priority. Marine plants contain a wide range of bioactive compounds and the presence of osteoactive phytochemicals was investigated in two halophytes collected in Brittany (France): the invasive Spartina alterniflora and the native Salicornia fragilis. Two semi-purified fractions, prepared through liquid-liquid extraction, were assessed for phenolic and flavonoid contents, and for the presence of antioxidant, mineralogenic and osteogenic bioactivities. Ethyl acetate fraction (EAF) was rich in phenolic compounds and exhibited the highest antioxidant activity. While S. fragilis EAF only triggered a weak proliferative effect in vitro, S. alterniflora EAF potently induced extracellular matrix mineralization (7-fold at 250 μg/mL). A strong osteogenic effect was also observed in vivo using zebrafish operculum assay (2.5-fold at 10 μg/mL in 9-dpf larvae). Results indicate that polyphenol rich EAF of S. alterniflora has both antioxidant and bone anabolic activities. As an invasive species, this marine plant may represent a sustainable source of molecules for therapeutic applications in bone disorders.

Serum 25-hydroxyvitamin D concentrations are inversely associated with body adiposity measurements but the association with bone mass is non-linear in postmenopausal women

Vitamin D deficiency has been linked to increased adiposity and decreased bone density. It is not known if vitamin D is linked to adiposity measures and bone mass in postmenopausal Qatar women. We investigated an association between serum vitamin D [25-hydroxyvitmain D (25(OH)D)] and adiposity measurements in postmenopausal women using Qatar Biobank data (n = 935). The post-menopausal status was self-reported by participants. Multivariate adjusted regression was applied to determine the association between serum 25(OH)D and body adiposity markers and bone mass. Serum 25(OH)D was significantly, inversely associated with body mass index (p < 0.0005), waist circumference (0.044), fat mass (p < 0.003), gynoid fat (p < 0.001), and android fat (p < 0.009). Serum 25(OH)D appeared to have an inverse 'U' association with several adiposity measures. Overall, body adiposity markers were the lowest in the 4^th quartile serum 25(OH)D and significantly lower compared to the 1^st quartile serum 25(OH)D. In multivariable adjusted analysis, no association was found between serum 25(OH)D concentration and bone mass when serum 25(OH)D was categorized. In a continuous variable analysis, the association between 25(OH)D and bone mass was significant, non-linear, inverse 'U'. In conclusion, serum 25-hydroxyvitamin D was inversely associated with adiposity measures and non-linearly associated to bone mass in postmenopausal Qatari women.

Endocrine disrupting chemicals and bone

Endocrine-disrupting chemicals (EDCs) are defined as chemicals that interfere with the function of the endocrine system. EDCs exert their hormonal effects through several mechanisms; modulating hormone receptors or changing metabolism of different hormones. EDCs also influence multiple signalling pathways while effecting the hormonal systems and possess complex dose-response curves. EDCs can exert deleterious effects on bone tissue through changing bone modelling and remodelling via altering bone paracrine hormone synthesis, the release of systemic hormones, cytokines, chemokines and growth factors, and effecting stem cell fate, as well as bone marrow mesenchymal stem cell differentiation. Evidence is accumulating of the bone disrupting effect of different groups of EDCs, such as; the perfluoroalkyl substances, the phthalate esters, the bisphenol A, the organotin compounds, the alkylphenols and the dioxin and dioxin-like compounds. This review highlights the recent discoveries of the effects of commonly found environmental chemicals on bone from basic molecular findings to clinical implications.

The role of endocrine hormones in the pathogenesis of adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a common spinal deformity characterized by changes in the three-dimensional structure of the spine. It usually initiates during puberty, the peak period of human growth when the secretion of numerous hormones is changing, and it is more common in females than in males. Accumulating evidence shows that the abnormal levels of many hormones including estrogen, melatonin, growth hormone, leptin, adiponectin and ghrelin, may be related to the occurrence and development of AIS. The purpose of this review is to provide a summary and critique of the research published on each hormone over the past 20 years, and to highlight areas for future study. It is hoped that the presentation will help provide a better understanding of the role of endocrine hormones in the pathogenesis of AIS.

Probiotics as a New Regulator for Bone Health: A Systematic Review and Meta-Analysis

Despite the proposed role of the gut microbiota-bone axis, findings on the association between probiotic consumption and bone health are conflicting. This systematic review aimed to assess the effect of probiotic consumption on bone health parameters. A systematic literature search of relevant reports published in PubMed/Medline, Web of Science, SCOPUS, EMBASE, and Google scholar before December 2020 was conducted. All clinical trials or experimental studies, which examined the relationship between probiotic consumption and bone health parameters, were included. No limitation was applied during the search. After screening articles based on inclusion criteria, 44 studies remained. In clinical trials, probiotic consumption affects bone health parameters such as serum calcium levels (3.82; 95% CI: 1.05, 6.59 mmol/l), urinary calcium levels (4.85; 95% CI: 1.16, 8.53 mmol/l), and parathyroid hormone (PTH) levels (−5.53; 95% CI: −9.83, −0.86 ng/l). In most studies, Lactobacillus species such as L. helveticus, L. reuteri, and L. casei were consumed and women aged 50 years or older were assessed. Spinal and total hip bone mineral density (BMD) was not affected significantly by probiotic consumption. In 37 animal experiments, probiotic or symbiotic feeding mostly had effects on bone health parameters. Some strains of Bifidobacterium and Lactobacillus including L. reuteri, L. casei, L. paracasei, L. bulgaricus, and L. acidophilus have indicated beneficial effects on bone health parameters. In conclusion, this systematic review and meta-analysis indicate that probiotic supplementation might improve bone health. Further studies are needed to decide on the best probiotic species and appropriate dosages.

Cortical bone development, maintenance and porosity: genetic alterations in humans and mice influencing chondrocytes, osteoclasts, osteoblasts and osteocytes

Cortical bone structure is a crucial determinant of bone strength, yet for many years studies of novel genes and cell signalling pathways regulating bone strength have focused on the control of trabecular bone mass. Here we focus on mechanisms responsible for cortical bone development, growth, and degeneration, and describe some recently described genetic-driven modifications in humans and mice that reveal how these processes may be controlled. We start with embryonic osteogenesis of preliminary bone structures preceding the cortex and describe how this structure consolidates then matures to a dense, vascularised cortex containing an increasing proportion of lamellar bone. These processes include modelling-induced, and load-dependent, asymmetric cortical expansion, which enables the cortex's transition from a highly porous woven structure to a consolidated and thickened highly mineralised lamellar bone structure, infiltrated by vascular channels. Sex-specific differences emerge during this process. With aging, the process of consolidation reverses: cortical pores enlarge, leading to greater cortical porosity, trabecularisation and loss of bone strength. Each process requires co-ordination between bone formation, bone mineralisation, vascularisation, and bone resorption, with a need for locational-, spatial- and cell-specific signalling pathways to mediate this co-ordination. We will discuss these processes, and a number of cell-signalling pathways identified in both murine and human genetic studies to regulate cortical bone mass, including signalling through gp130, STAT3, PTHR1, WNT16, NOTCH, NOTUM and sFRP4.

Neutralization of oxidized phospholipids attenuates age-associated bone loss in mice

Oxidized phospholipids (OxPLs) are pro‐inflammatory molecules that affect bone remodeling under physiological conditions. Transgenic expression of a single‐chain variable fragment (scFv) of the antigen‐binding domain of E06, an IgM natural antibody that recognizes the phosphocholine (PC) moiety of OxPLs, increases trabecular and cortical bone in adult male and female mice by increasing bone formation. OxPLs increase with age, while natural antibodies decrease. Age‐related bone loss is associated with increased oxidative stress and lipid peroxidation and is characterized by a decline in osteoblast number and bone formation, raising the possibility that increased OxPLs, together with the decline of natural antibodies, contribute to age‐related bone loss. We show here that transgenic expression of E06‐scFv attenuated the age‐associated loss of spinal, femoral, and total bone mineral density in both female and male mice aged up to 22 and 24 months, respectively. E06‐scFv attenuated the age‐associated decline in trabecular bone, but not cortical bone, and this effect was associated with an increase in osteoblasts and a decrease in osteoclasts. Furthermore, RNA‐seq analysis showed that E06‐scFv increased Wnt10b expression in vertebral bone in aged mice, indicating that blocking OxPLs increases Wnt signaling. Unlike age‐related bone loss, E06‐scFv did not attenuate the bone loss caused by estrogen deficiency or unloading in adult mice. These results demonstrate that OxPLs contribute to age‐associated bone loss. Neutralization of OxPLs, therefore, is a promising therapeutic target for senile osteoporosis, as well as atherosclerosis and non‐alcoholic steatohepatitis (NASH), two other conditions shown to be attenuated by E06‐scFv in mice.

Osteoblasts Generate Testosterone From DHEA and Activate Androgen Signaling in Prostate Cancer Cells

Bone metastasis is a complication of prostate cancer in up to 90% of men afflicted with advanced disease. Therapies that reduce androgen exposure remain at the forefront of treatment. However, most prostate cancers transition to a state whereby reducing testicular androgen action becomes ineffective. A common mechanism of this transition is intratumoral production of testosterone (T) using the adrenal androgen precursor dehydroepiandrosterone (DHEA) through enzymatic conversion by 3β- and 17β-hydroxysteroid dehydrogenases (3βHSD and 17βHSD). Given the ability of prostate cancer to form blastic metastases in bone, we hypothesized that osteoblasts might be a source of androgen synthesis. RNA expression analyses of murine osteoblasts and human bone confirmed that at least one 3βHSD and 17βHSD enzyme isoform was expressed, suggesting that osteoblasts are capable of generating androgens from adrenal DHEA. Murine osteoblasts were treated with 100 nM and 1 μM DHEA or vehicle control. Conditioned media from these osteoblasts were assayed for intermediate and active androgens by liquid chromatography-tandem mass spectrometry. As DHEA was consumed, the androgen intermediates androstenediol and androstenedione were generated and subsequently converted to T. Conditioned media of DHEA-treated osteoblasts increased androgen receptor (AR) signaling, prostate-specific antigen (PSA) production, and cell numbers of the androgen-sensitive prostate cancer cell lines C4-2B and LNCaP. DHEA did not induce AR signaling in osteoblasts despite AR expression in this cell type. We describe an unreported function of osteoblasts as a source of T that is especially relevant during androgen-responsive metastatic prostate cancer invasion into bone. © 2021 American Society for Bone and Mineral Research (ASBMR). This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Rethinking of osteoporosis through a sex- and gender-informed approach in the COVID-19 era

Standards and models of reference for osteoporosis (OP) have been developed for female individuals as they are more likely to be affected by the disease. Nonetheless, OP is also responsible for one-third of hip fractures in male individuals suggesting that a sexblinded approach to OP may lead to miss opportunities for equity in bone health. OPrelated fractures, especially hip fractures, are a matter of immediate concern as they are associated with limited mobility, chronic disability, loss of independence, and reduced quality of life in both sexes. When it comes to sociocultural gender, the effect of gender domains (i.e., identity, roles, relations, and institutionalized gender) on development and management of OP is largely overlooked despite risk factors or protective conditions are gendered. Clinical trials testing the efficacy and safety of anti-OP drugs as well as non-pharmacological interventions have been conducted mainly in female participants, limiting the generalizability of the findings. The present narrative review deals with the sex and gender-based challenges and drawbacks in OP knowledge and translation to clinical practice, also considering the impact of coronavirus disease 2019 pandemic.

The Development of Molecular Biology of Osteoporosis

Osteoporosis is one of the major bone disorders that affects both women and men, and causes bone deterioration and bone strength. Bone remodeling maintains bone mass and mineral homeostasis through the balanced action of osteoblasts and osteoclasts, which are responsible for bone formation and bone resorption, respectively. The imbalance in bone remodeling is known to be the main cause of osteoporosis. The imbalance can be the result of the action of various molecules produced by one bone cell that acts on other bone cells and influence cell activity. The understanding of the effect of these molecules on bone can help identify new targets and therapeutics to prevent and treat bone disorders. In this article, we have focused on molecules that are produced by osteoblasts, osteocytes, and osteoclasts and their mechanism of action on these cells. We have also summarized the different pharmacological osteoporosis treatments that target different molecular aspects of these bone cells to minimize osteoporosis.

Biased and allosteric modulation of bone cell-expressing G protein-coupled receptors as a novel approach to osteoporosis therapy

On the cellular level, osteoporosis (OP) is a result of imbalanced bone remodeling, in which osteoclastic bone resorption outcompetes osteoblastic bone formation. Currently available OP medications include both antiresorptive and bone-forming drugs. However, their long-term use in OP patients, mainly in postmenopausal women, is accompanied by severe side effects. Notably, the fundamental coupling between bone resorption and formation processes underlies the existence of an undesirable secondary outcome that bone anabolic or anti-resorptive drugs also reduce bone formation. This drawback requires the development of anti-OP drugs capable of selectively stimulating osteoblastogenesis and concomitantly reducing osteoclastogenesis. We propose that the application of small synthetic biased and allosteric modulators of bone cell receptors, which belong to the G-protein coupled receptors (GPCR) family, could be the key to resolving the undesired anti-OP drug selectivity. This approach is based on the capacity of these GPCR modulators, unlike the natural ligands, to trigger signaling pathways that promote beneficial effects on bone remodeling while blocking potentially deleterious effects. Under the settings of OP, an optimal anti-OP drug should provide fine-tuned regulation of downstream effects, for example, intermittent cyclic AMP (cAMP) elevation, preservation of Ca²⁺ balance, stimulation of osteoprotegerin (OPG) and estrogen production, suppression of sclerostin secretion, and/or preserved/enhanced canonical β-catenin/Wnt signaling pathway. As such, selective modulation of GPCRs involved in bone remodeling presents a promising approach in OP treatment. This review focuses on the evidence for the validity of our hypothesis.

Recent Progresses in the Treatment of Osteoporosis

Osteoporosis (OP) is a chronic bone disease characterized by aberrant microstructure and macrostructure of bone, leading to reduced bone mass and increased risk of fragile fractures. Anti-resorptive drugs, especially, bisphosphonates, are currently the treatment of choice in most developing countries. However, they do have limitations and adverse effects, which, to some extent, helped the development of anabolic drugs such as teriparatide and romosozumab. In patients with high or very high risk for fracture, sequential or combined therapies may be considered with the initial drugs being anabolic agents. Great endeavors have been made to find next generation drugs with maximal efficacy and minimal toxicity, and improved understanding of the role of different signaling pathways and their crosstalk in the pathogenesis of OP may help achieve this goal. Our review focused on recent progress with regards to the drug development by modification of Wnt pathway, while other pathways/molecules were also discussed briefly. In addition, new observations made in recent years in bone biology were summarized and discussed for the treatment of OP.

Chrysin alleviates alteration of bone-remodeling markers in ovariectomized rats and exhibits estrogen-like activity in silico

BACKGROUND

Evidences are beginning to accrue that flavonoids, particularly phytoestrogens, could have beneficial effects against several age-related diseases linked to estrogen deficiency including postmenopausal osteoporosis.

METHODS

In this study, the effect of chrysin on selected bone-remodeling markers in ovariectomized rats and its estrogen-like activity in silico were investigated.

RESULTS

The data indicated that administration of chrysin at 50 mg/kg and 100 mg/kg for 6 weeks to OVX rats significantly (p < 0.05) prevented body weight gain and partially reverse uterine weight loss. In addition, treatment of OVX rats significantly (p < 0.01) increased femur dry weight, femur ash weight, bone ash calcium, and phosphorous levels in a dose-dependent manner. However, there was significant (p < 0.001) decline in serum estradiol level in all OVX rats compared to the sham-operated group. Interestingly, administration of chrysin significantly (p < 0.05) reversed the reduction of estradiol induced by ovariectomy compared to untreated OVX rats. Moreover, administration of chrysin to OVX rats significantly (p < 0.05) suppressed excessive elevation of bone-remodeling markers expression compared to untreated OVX rats. Similarly, molecular docking analysis revealed that chrysin interacts with both α and β estrogen receptors with exothermic binding energies of -229.83 kcal/Mol and -252.72 kcal/Mol, respectively, and also fits perfectly into the active site of both α and β estrogen receptors.

CONCLUSION

This study demonstrated that chrysin exhibits potential antiosteoporotic effects against bone loss in OVX rats through enhanced bone mineral contents and preventing excessive elevation of bone-remodeling markers and bone-resorbing cytokine.

Development of Hormonal Intravaginal Rings: Technology and Challenges

Intravaginal rings (IVRs) are minimally invasive polymeric devices specifically designed to be used for the sustained and prolonged release of various type of drugs such as hormones. One of the benefits of using topical drug delivery systems (e.g., IVRs) is the fact that systemic drug delivery may cause drug resistance due to elevated drug levels. Topical drug delivery also provides higher concentrations of the drug to the target site and has fewer side effects. In addition, when a drug is administered vaginally, the hepatic first-pass effect is avoided, resulting in higher absorption. Contraception and treatments for specific diseases such as endometriosis and hormone deficiencies can be improved by the administration of hormones via an IVR. This article aims to classify and compare various designs of commercially available and non-commercial hormonal IVRs and to analyze their performance. Current challenges affecting the development of IVRs are investigated, and proposed solutions are discussed. A comprehensive search of publications in MEDLINE/PubMed and of commercial product data of IVRs was performed, and the materials, designs, performance, and applications (e.g., contraception, endometriosis, estrogen deficiency and urogenital atrophy) of hormonal IVRs were thoroughly evaluated. Most hormonal IVRs administer female sex hormones, i.e., estrogen and progestogens. In terms of material, IVRs are divided into 3 main groups: silicone, polyurethane, and polyethylene-co-vinyl acetate IVRs. As regards their design, there are 4 major designs for IVRs which strongly affect their performance and the timing and rate of hormone release. Important challenges include reducing the burst release and maintaining the bioavailability of hormones at their site of action over a prolonged period of administration as well as lowering production costs. Hormonal IVRs are a promising method which could be used to facilitate combination therapies by administering multiple drugs in a single IVR while eliminating the side effects of conventional drug administration methods. IVRs could considerably improve womenʼs quality of life all over the world within a short period of time.

Melatonin as a Trigger of Therapeutic Bone Regenerating Capacity in Biomaterials

Bone defects are usually treated with bone grafting. Several synthetic biomaterials have emerged to replace autologous and allogeneic bone grafts, but there are still shortcomings in bone regeneration. Melatonin has demonstrated a beneficial effect on bone metabolism with the potential to treat fractures, bone defects, and osteoporosis. The hormone promoted osteogenesis, inhibited osteoclastogenesis, stimulated angiogenesis, and reduced peri-implantitis around the graft. Recently, a growing number of studies showed beneficial effects of melatonin to treat bone defects. However, cellular and molecular mechanisms involved in bone healing are still poorly understood. In this review, we recapitulate the potential mechanisms of melatonin, providing a new horizon to the clinical treatment of bone defects.

Reproductive History and Age of Onset for Women Diagnosed with Amyotrophic Lateral Sclerosis: Data from the National ALS Registry: 2010-2018

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurological disease of largely unknown etiology with no cure. The National ALS Registry is a voluntary online system that collects demographic and reproductive history (females only) data from patients with ALS. We will examine the association between demographic and reproductive history among female patients aged >18 years and various ages of onset for ALS.

METHODS

Data from a cross-sectional study were collected and examined for 1,018 female ALS patients. Patient characteristics examined were demographics including race, BMI, and familial history of ALS. Among patients, information on reproductive history, including age at menopause, ever pregnant, and age at first pregnancy was collected. Unadjusted and adjusted logistic regression models were used to estimate OR and 95% CI in this study.

RESULTS

Women were more likely to be diagnosed with ALS before age 60 if they were nonwhite (p = 0.015), had attended college (p = 0.0012), had a normal BMI at age 40 (p < 0.0001), completed menopause before age 50 (p < 0.0001), and had never been pregnant (p = 0.046) in the univariate analysis. Women diagnosed with ALS before age 60 were also more likely to have limb site of onset (p < 0.0001). In the multivariate analysis, those who completed menopause before age 50 were more likely to be diagnosed with ALS before age 60 (OR = 1.8, 95% CI: 1.4-2.3) compared with women who completed menopause at or after age 50, after controlling for race, ever pregnant, age at first pregnancy, family history of ALS, education status, smoking history, and BMI at age 40. For women who were diagnosed with ALS before age 50, the odds of them entering menopause before age 50 climb to 48.7 (95% CI: 11.8, 200.9). The mean age of ALS diagnosis for women who completed menopause before age 50 was 58 years and 64 years for women who entered menopause after age 50 (p < 0.0001).

CONCLUSION

Women who reported completing menopause before age 50 were significantly more likely to be diagnosed with ALS before age 60 compared with those who reported entering menopause after age 50. More research is needed to determine the relationship between female reproductive history, especially regarding endogenous estrogen exposure and early-onset ALS.

Morphology and serum and bone tissue calcium and magnesium concentrations in the bones of male rats chronically treated with letrozole, a nonsteroidal cytochrome P450 aromatase inhibitor

Purpose/Aim of the study: The role of estrogen (E) in the regulation of bone turnover in women is well established, though the contributions of E versus testosterone (T) in the control of bone turnover in men are poorly understood. The aim of this study was to examine the association between chronic treatment with letrozole, a nonsteroidal inhibitor blocking the aromatase activity and thus the conversion of androgens into estrogens, and cortical bone morphology in the femur and humerus of male adult rats.Materials and Methods: Adult male rats were treated with letrozole for 6 months and the body and femur weight, morphology, collagen structure, blood serum, and bone tissue concentrations of calcium and magnesium were examined.Results: Long-term aromatase inhibition resulted in a decrease in femur mass, a wavelike arrangement of bone and lamellae with an altered organization of collagen in compact bone, a increased concentration of calcium in blood serum, and no change in calcium bone tissue concentration, magnesium serum, or bone tissue concentration. MicroCT study of the humerus revealed significant decreases of whole bone tissue volume, cortical bone thickness, cortical bone volume, and external cortical bone thickness with letrozole treatment.Conclusion: Chronic treatment with letrozole affected cortical bone structure and produced histomorphological changes in male rat bone similar to that observed in the aging processes.

Bone structure assessed with pQCT in prepubertal males with delayed puberty or congenital hypogonadotropic hypogonadism

OBJECTIVE

Congenital hypogonadotropic hypogonadism (CHH) is associated with impaired bone mineral density in adulthood, whereas the estimates on bone structure in adolescents with CHH has not been previously evaluated. This study describes bone structure in CHH patients and compares it to that in boys with constitutional delay of growth and puberty (CDGP).

DESIGN

A cross-sectional study.

METHODS

Peripheral quantitative computed tomography (pQCT) of non-dominant arm and left leg were performed. Volumetric bone mineral density (BMD), bone mineral content, and area in trabecular and cortical bone compartments were evaluated, and bone age-adjusted Z-scores for the bone parameters were determined.

RESULTS

The participants with CHH had more advanced bone age and were older, taller and heavier than the CDGP boys, yet they had lower trabecular BMD in distal radius (147.7 mg/mm³ [95% CI, 128-168 mg/mm³ ] vs. 181.2 mg/mm³ [172-192 mg/mm³ ], p = .002) and distal tibia (167.6 mg/mm³ [145-190 mg/mm³ ] vs. 207.2 mg/mm³ [187-227 mg/mm³ ], p = .012), respectively. CHH males had lower cortical thickness at diaphyseal tibia than the participants with CDGP (p = .001). These between-group differences remained significant in corresponding Z-scores adjusted for bone age and height (p = .001). In CDGP group, serum testosterone correlated positively with trabecular BMD (r = 0.51, p = .013) at distal radius, and estradiol levels correlated positively with trabecular BMD at the distal site of tibia (r = 0.58, p = .004).

CONCLUSIONS

Five treatment-naïve male patients with CHH exhibited poorer trabecular BMD than untreated males with CDGP. We speculate that timely low-dose sex steroid replacement in CHH males may benefit skeletal health in adulthood.

Osteocyte exosomes accelerate benign prostatic hyperplasia development

Benign prostatic hyperplasia (BPH) is one of the most common diseases in elderly men. BPH patients exhibit an increased risk of vertebral and hip fractures, which are most attributable to pre-existing osteoporosis. However, the relationship between BPH and osteoporosis is still unknown. Here we found that osteocytes, the most abundant bone cells, promoted BPH development by secreting exosomes. In vitro, osteocyte exosomes (OCY-Exo) directly promoted cell proliferation of a prostate epithelial cell line BPH-1 and a macrophage cell line RAW264.7, OCY-Exo also stimulated macrophage-induced proliferation of BPH-1 cells. In vivo, intramedullary injection of OCY-Exo accumulated in prostate. Intravenous administration of OCY-Exo exacerbated testosterone-induced BPH in C57BL/6J mice. Our study uncovers the role of OCY-Exo as a stimulator of BPH, suggesting a novel mechanism in bone-prostate communication.

The way toward adulthood for females with nonclassic congenital adrenal hyperplasia

Females with NC21OHD may present as asymptomatic or develop a wide range of androgen excess expression. Clinical manifestations may become evident in childhood and adolescence and include premature pubarche, precocious puberty, acne, hirsutism, and menstrual disorders or present later in life as oligo-ovulation and infertility. Glucocorticoids have been the mainstay of treatment as they regulate excess androgen expression by dampening ACTH activation. Their use requires a careful dose monitoring to avoid overtreatment and subsequently the risk of obesity, type 2 diabetes, dyslipidemia, hypertension, and osteoporosis. Women with NC21OHD need regular follow up throughout their life in order to overcome the physical and psychological burden of hyperandrogenism.

T-Cell Mediated Inflammation in Postmenopausal Osteoporosis

Osteoporosis is the most prevalent metabolic bone disease that affects half the women in the sixth and seventh decade of life. Osteoporosis is characterized by uncoupled bone resorption that leads to low bone mass, compromised microarchitecture and structural deterioration that increases the likelihood of fracture with minimal trauma, known as fragility fractures. Several factors contribute to osteoporosis in men and women. In women, menopause - the cessation of ovarian function, is one of the leading causes of primary osteoporosis. Over the past three decades there has been growing appreciation that the adaptive immune system plays a fundamental role in the development of postmenopausal osteoporosis, both in humans and in mouse models. In this review, we highlight recent data on the interactions between T cells and the skeletal system in the context of postmenopausal osteoporosis. Finally, we review recent studies on the interventions to ameliorate osteoporosis.

Risk Factors for New Vertebral Fracture After Percutaneous Vertebroplasty for Osteoporotic Vertebral Compression Fractures

Purpose

To analyze the risk factors for new vertebral fractures after percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fractures (OVCFs).

Patients and Methods

We retrospectively reviewed the records of patients with symptomatic OVCFs who underwent PVP in our hospital, from January 2014 to January 2019. Demographic and lifestyle data on the presence of underlying chronic disease, preoperative bone mineral density, details of vertebral fractures, postoperative osteoporosis treatment, and new fracture development were collected. Patients were divided into postoperative fracture and non-fracture groups. To identify the independent risk factors for new vertebral fracture development, variables significant on univariate analysis were included in a multivariate regression model.

Results

Of the 2202 patients treated with PVP, 362 (16.43%) had a new postoperative vertebral fracture. All patients were followed up for >12 months (mean 14.7 months). Univariate analysis revealed no significant difference in height; body weight; preoperative bone mineral density; number of fractured vertebrae; injection volume of bone cement in a single vertebra; leakage rate of bone cement; or presence of hypertension, coronary heart disease, and chronic obstructive pulmonary disease between the fracture and non-fracture groups (P>0.05). Age, sex, smoking, alcohol consumption, diabetes mellitus, postoperative exercise, and postoperative osteoporosis treatment were associated with new vertebral fractures (all P<0.05). A multivariate analysis showed that age (odds ratio [OR]=1.212, P<0.0001), female sex (OR=1.917, P<0.0001), smoking (OR=1.538, P=0.026), and diabetes (OR=1.915, P<0.0001) were positively correlated with new vertebral fracture development, whereas postoperative exercise (OR=0.220, P<0.0001) and osteoporosis treatment (OR=0.413, P<0.0001) were negatively correlated.

Conclusion

Elderly patients, females, and those with a history of smoking and diabetes are at high risk of new vertebral fracture after PVP. Patients should be encouraged to stop smoking and consuming alcohol, control blood glucose level, participate in sufficient physical activity, and adhere to osteoporosis treatment to prevent new vertebral fractures.

A functional motif of long noncoding RNA Nron against osteoporosis

Long noncoding RNAs are widely implicated in diverse disease processes. Nonetheless, their regulatory roles in bone resorption are undefined. Here, we identify lncRNA Nron as a critical suppressor of bone resorption. We demonstrate that osteoclastic Nron knockout mice exhibit an osteopenia phenotype with elevated bone resorption activity. Conversely, osteoclastic Nron transgenic mice exhibit lower bone resorption and higher bone mass. Furthermore, the pharmacological overexpression of Nron inhibits bone resorption, while caused apparent side effects in mice. To minimize the side effects, we further identify a functional motif of Nron. The delivery of Nron functional motif to osteoclasts effectively reverses bone loss without obvious side effects. Mechanistically, the functional motif of Nron interacts with E3 ubiquitin ligase CUL4B to regulate ERα stability. These results indicate that Nron is a key bone resorption suppressor, and the lncRNA functional motif could potentially be utilized to treat diseases with less risk of side effects.

LncRNAs are implicated in the pathogenesis of a number of diseases. Here, the authors show that the lncRNA Nron suppresses bone resorption, and show that delivery of a functional motif of Nron increases bone mass in mouse models of osteoporosis.

Sarcopenia and Appendicular Muscle Mass as Predictors of Impaired Fasting Glucose/Type 2 Diabetes in Elderly Women

Elderly women exhibit a high risk of type 2 diabetes (T2D), but no definitive data exist about the possible role of postmenopausal increases in visceral adiposity, the loss of lean body mass, or decreases in the sum of the lean mass of arms and legs (appendicular skeletal muscle mass (ASMM)). This retrospective, longitudinal study investigated whether body composition (bioelectrical impedance analysis) predicted the development of impaired fasting glucose (IFG) or T2D in a cohort of 159 elderly women (age: 71 ± 5 years, follow-up: 94 months) from southern Italy (Clinical Nutrition and Geriatric Units of the “Mater Domini” University Hospital in Catanzaro, Calabria region, and the “P. Giaccone ”University Hospital in Palermo, Sicily region). Sarcopenia was defined in a subgroup of 128 women according to the EWGSOP criteria as the presence of low muscle strength (handgrip strength <16 kg) plus low muscle mass (reported as appendicular skeletal muscle mass <15 kg). Participants with a low ASMM had a higher IFG/T2D incidence than those with a normal ASMM (17% vs. 6%, p-adjusted = 0.044); this finding was independent of BMI, fat mass, waist circumference, and habitual fat intake (OR = 3.81, p = 0.034). A higher incidence of IFG/T2D was observed in the subgroup with sarcopenia than those without sarcopenia (33% vs. 7%, p-adjusted = 0.005) independent of BMI and fat mass (OR = 6.75, p = 0.007). In conclusion, this study demonstrates that elderly women with low ASMM had a higher probability of developing IFG/T2D. Further studies are needed to confirm these results in men and in other age groups.

Testosterone Reduces Body Fat in Male Mice by Stimulation of Physical Activity Via Extrahypothalamic ERα Signaling

Testosterone (T) reduces male fat mass, but the underlying mechanisms remain elusive, limiting its clinical relevance in hypogonadism-associated obesity. Here, we subjected chemically castrated high-fat diet-induced adult obese male mice to supplementation with T or the nonaromatizable androgen dihydrotestosterone (DHT) for 20 weeks. Both hormones increased lean mass, thereby indirectly increasing oxygen consumption and energy expenditure. In addition, T but not DHT decreased fat mass and increased ambulatory activity, indicating a role for aromatization into estrogens. Investigation of the pattern of aromatase expression in various murine tissues revealed the absence of Cyp19a1 expression in adipose tissue while high levels were observed in brain and gonads. In obese hypogonadal male mice with extrahypothalamic neuronal estrogen receptor alpha deletion (N-ERαKO), T still increased lean mass but was unable to decrease fat mass. The stimulatory effect of T on ambulatory activity was also abolished in N-ERαKO males. In conclusion, our work demonstrates that the fat-burning action of T is dependent on aromatization into estrogens and is at least partially mediated by the stimulation of physical activity via extrahypothalamic ERα signaling. In contrast, the increase in lean mass upon T supplementation is mediated through the androgen receptor and indirectly leads to an increase in energy expenditure, which might also contribute to the fat-burning effects of T.