Hormone replacement therapy prevents osteoclastic hyperactivity: A histomorphometric study in early postmenopausal women

Changes in Collagen Type I C-Telopeptide and Procollagen Type I N-Terminal Propeptide During the Menopause Transition

CONTEXT

Collagen type I C-telopeptide (CTX) and procollagen type I N-terminal propeptide (PINP) are reference bone resorption and formation markers, respectively.

OBJECTIVE

To characterize CTX and PINP trajectories across the menopause transition (MT).

METHODS

This 18-year longitudinal analysis of a community-based cohort from the Study of Women's Health Across the Nation included 541 women (126 Black, 90 Chinese, 87 Japanese, 238 White) who transitioned from pre- to postmenopause. Multivariable mixed effects regression fit piecewise linear models of CTX or PINP relative to years from final menstrual period (FMP); covariates were race/ethnicity, body mass index (BMI), and age at FMP. In the referent participant (White, 52.46 years at FMP, BMI 27.12 kg/m2), CTX and PINP were stable until 3 years pre-FMP (premenopause). During the MT (3 years before to 3 years after the FMP), CTX and PINP increased 10.3% (P < .0001) and 7.5% (P < .0001) per year, respectively; MT-related gains totaled 61.9% for CTX and 45.2% for PINP. Starting 3 years post-FMP (postmenopause), CTX and PINP decreased 3.1% (P < .0001) and 2.9% (P < .0001) per year, respectively. Compared with the White participants, during the MT, Chinese participants had larger gains in CTX (P = .01), and Japanese women experienced greater increases in CTX (P < .0001) and PINP (P = .02). In postmenopause, CTX (P = .01) and PINP (P = .01) rose more in Japanese relative to White women.

CONCLUSION

CTX and PINP are stable in premenopause, increase during the MT, and decrease in postmenopause. During the MT and postmenopause, bone turnover change rates vary by race/ethnicity.

Longitudinal changes in bone mineral density during perimenopausal transition: the Vietnam Osteoporosis Study

Based on the prospective cohort of the Vietnam Osteoporosis Study, we show that bone loss occurred before menopause, and that the loss accelerated in the first 5 years post-menopause.

PURPOSE

To define the change in bone mineral density (BMD) among women during the menopausal transition.

METHODS

The study involved 1062 women aged 40-59 who were participants of the population-based prospective Vietnam Osteoporosis Study. BMD at the femoral neck (FN), lumbar spine (LS), and whole body scan was measured by DXA. Each woman has had two BMD measurements separated by approximately 2 years, and the rate of BMD change was calculated for each woman. Multivariable linear regression models were used to quantify the association between body composition parameters and the rate of BMD change.

RESULTS

At FN, there were 3 phases of BMD change: a slight decline before the age of 45-49 (average loss of 0.51%/year); a substantial decline between the ages of 49 and 54 (average loss of 1.39%/year); and then slowed down between the ages of 54 and 59 (average loss of 0.31%/year). The same trend was also observed at LS: a slight decline (- 0.56%/year) among women aged 45-49; then a significant decline between the ages of 50 and 54 (- 1.33%/year); but then slowed down at - 0.31%/year after the age of 55. Changes in BMD were not significantly associated with changes in lean mass or fat mass.

CONCLUSIONS

Although bone loss occurred before menopause, the loss accelerated in the early perimenopausal transition (45-50 years of age). This finding suggests that screening for osteoporosis in women should be considered at the age of 45.

Interindividual differences contribute to variation in microbiota composition more than hormonal status: A prospective study

Aims

Ovarian hormone deficiency is one of the main risk factors for osteoporosis and bone fractures in women, and these risks can be mitigated by menopausal hormone therapy. Recent evidence suggests that gut microbiota may link changes in estrogen levels and bone metabolism. This study was conducted to investigate the potential relationship between hormonal and bone changes induced by oophorectomy and subsequent hormonal therapy and shifts in gut microbiota composition.

Methods

We collected 159 stool and blood samples in several intervals from 58 women, who underwent bilateral oophorectomy. Changes in fecal microbiota were assessed in paired samples collected from each woman before and after oophorectomy or the start of hormone therapy. Bacterial composition was determined by sequencing the 16S rRNA gene on Illumina MiSeq. Blood levels of estradiol, FSH, biomarkers of bone metabolism, and indices of low-grade inflammation were measured using laboratory analytical systems and commercial ELISA. Areal bone mineral density (BMD) of the lumbar spine, proximal femur, and femur neck was measured using dual-energy X-ray absorptiometry.

Results

We found no significant changes in gut microbiota composition 6 months after oophorectomy, despite major changes in hormone levels, BMD, and bone metabolism. A small decrease in bacterial diversity was apparent 18 months after surgery in taxonomy-aware metrics. Hormonal therapy after oophorectomy prevented bone loss but only marginally affected gut microbiota. There were no significant differences in β-diversity related to hormonal status, although several microbes (e.g., Lactococcus lactis) followed estrogen levels. Body mass index (BMI) was the most significantly associated with microbiota variance. Microbiota was not a suitable predictive factor for the state of bone metabolism.

Conclusions

We conclude that neither the loss of estrogens due to oophorectomy nor their gain due to subsequent hormonal therapy is associated with a specific gut microbiota signature. Sources of variability in microbiota composition are more related to interindividual differences than hormonal status.

Neuro-immune-endocrine mechanisms with poor adherence to aromatase inhibitor therapy in breast cancer

As the most commonly used endocrine therapy regimen for patients with hormone receptor-positive (HR+) breast cancer (BC) at present, aromatase inhibitors (AIs) reduce the risk of localized and distant recurrence, contralateral BC and secondary cancer, and prolong disease-free survival. Clinical data show that poor adherence during AI treatment is mainly attributed to muscle and joint pain, fatigue, anxiety, depression and sleep disturbances during treatment. The rapid decline of estrogen caused by AIs in a short period of time enhances sympathetic activity, activates T cells in the body, produces inflammatory factors such as tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and interleukin (IL)-17A, and promotes the occurrence of inflammation and bone loss. This article reviewed the mechanism of poor dependence on AIs in BC patients from the neuro-immuno-endocrine (NIE) perspective and provided clues for clinical intervention against poor adherence.

Effect of hormone replacement therapy on bone formation quality and mineralization regulation mechanisms in early postmenopausal women

Post-menopausal osteoporosis is characterized by a negative imbalance between bone formation and bone resorption resulting in a net bone loss, increasing the risk of fracture. One of the earliest interventions to protect against this was hormonal replacement therapy (HRT). Bone strength depends on both the amount and quality of bone, the latter including compositional / material and structural properties. Bone compositional / material properties are greatly dependent on both patient-, and tissue-age. Raman spectroscopy is an analytical tool ideally suited for the determination of bone compositional / material properties as a function of tissue age as it is capable of analyzing areas ~1 × 1 μm² in tetracycline labeled bone forming areas. Using such analysis of humeri from an ovariectomized primate animal model, we reported that loss of estrogen results in alteration in the mineralization regulation mechanisms by osteoid organic matrix attributes at actively forming bone surfaces. In the present work, we used Raman microspectroscopic techniques to compare osteoid and youngest mineralized tissue composition, as well as relationships between osteoid organic matrix quality and quality attributes of the earliest mineralized tissue in paired iliac crest biopsies obtained from early postmenopausal women before and after two years of HRT therapy. Significant correlations between osteoid proteoglycans, sulfated proteoglycans, pyridinoline, and earliest mineralized tissue mineral content were observed, suggesting that in addition to changes in bone turnover rates, HRT affects the osteoid composition, mineralization regulation mechanisms, and potentially fibrillogenesis.

Ethanol Extract of Amomum tsao-ko Ameliorates Ovariectomy-Induced Trabecular Loss and Fat Accumulation

In Asia, Amomum tsao-ko has long been used as a spice or seasoning in food to stimulate digestion. In the present study, we evaluated the effects of ethanol extract of Amomum tsao-ko (EEAT) on menopausal osteoporosis and obesity. After the administration of EEAT in ovariectomy (OVX) mice models for five weeks, microcomputed tomography and a histological analysis were performed to assess, respectively, the trabecular structure and the fat accumulation in adipose, liver, and bone tissues. We also examined the effects of EEAT on a bone marrow macrophage model of osteoclastogenesis by in vitro stimulation from the receptor activator of nuclear factor-kappa Β ligand (RANKL) through real-time PCR and Western blot analysis. In addition, ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with authentic standards was applied to characterize the phytochemical profiling of EEAT. We found that EEAT significantly decreased OVX-induced body weight gain and fat accumulation, significantly prevented OVX-induced deterioration of bone mineral density and microstructure of trabecular tissues, and significantly inhibited osteoclast differentiation by downregulating NF-κB/Fos/NFATc1 signaling in osteoclasts. Furthermore, UHPLC-MS/MS identified eight beneficial phytochemicals in EEAT. Collectively, these results suggest that EEAT might be an effective nutraceutical candidate to attenuate menopausal osteoporosis by inhibiting osteoclastogenesis and to prevent obesity by suppressing fat accumulation.

Bone Health and Osteoporosis Prevention and Treatment

Postmenopausal osteoporosis is a common condition and is associated with increased risk of fracture, including hip and vertebral fractures that in turn can have devastating consequences on morbidity and mortality. In this article, we review the pathogenesis and diagnostic approach to postmenopausal osteoporosis. We review available nonpharmacologic and pharmacologic therapies and we discuss their clinical efficacy and complications, with a detailed discussion of atypical femur fractures and osteonecrosis of the jaw.

Denosumab for cancer-related bone loss

INTRODUCTION

Prolonged use of anti-cancer treatments in breast and prostate tumors alters physiological bone turnover leading to adverse skeletal related events, such as osteoporosis, loss of bone mass, and increased risk of fractures. These complications known as cancer treatment-induced bone loss (CTIBL) should be managed with bone targeting agents such as the bisphosphonates and denosumab. The latter is a monoclonal antibody against the receptor activator of nuclear factor-kB ligand (RANKL) that suppresses osteoclasts function and survival increasing bone mass.

AREAS COVERED

This review will focus on the mechanisms associated with bone loss induced by cancer treatments and the most recent evidence about the use of denosumab as preventive and therapeutic strategy to protect bone health. Moreover, we will discuss several key aspects regarding the clinical practical use of denosumab to optimize the management of CTLIB in breast and prostate cancer.

EXPERT OPINION

Denosumab treatment strongly prevents cancer therapies-related skeletal issues in breast and prostate cancer with a good safety profile. Adjuvant six-monthly denosumab delays the time to first fracture onset in early stage breast cancer patients with normal or altered bone mineral density (BMD). Similarly, denosumab treatment is able to prevent fractures and BMD loss in nonmetastatic prostate cancer patients.

Long-Term Outcomes from a 10-Year Follow-Up of Women Living with a Restrictive Eating Disorder: A Brief Report

BACKGROUND

This study aimed to evaluate several socio-demographic and long-term clinical outcomes in a cohort of women living with a restrictive eating disorder.

METHODS

Patients were asked to fill in a general data collection form aiming to investigate their current conditions and to attend the outpatient unit for a 10-year follow-up clinical and laboratory evaluation.

RESULTS

Forty-four patients completed the follow-up general data collection form and 20 agreed to attend the outpatient unit for the 10 year-follow-up evaluation. In total, 52% of patients were single, 55% had achieved a university degree, and 55% had steady employment. After 10 years, there was a clear improvement in biochemical markers, but cholesterol levels were still slightly high. The prevalence of osteopenia in the whole sample was 70% when measured on the lumbar column and 20% on the total body, while osteoporosis was found in 10% of patients and only on the lumbar column.

CONCLUSION

According to the collected data, women with a history of restrictive eating disorders appear to re-adapt well to social life by obtaining the level of their unaffected peers in terms of education and employment.

Zoledronate

Zoledronate is the most potent and most long-acting bisphosphonate in clinical use, and is administered as an intravenous infusion. Its major uses are in osteoporosis, Paget's disease, and in myeloma and cancers to reduce adverse skeletal related events (SREs). In benign disease, it is a first- or second-line treatment for osteoporosis, achieving anti-fracture efficacy comparable to that of the RANKL blocker, denosumab, over 3 years, and it reduces fracture risk in osteopenic older women. It is the preferred treatment for Paget's disease, achieving higher rates of remissions which are much more prolonged than with any other agent. Some trials have suggested that it reduces mortality, cardiovascular disease and cancer, but these findings are not consistent across all studies. It is nephrotoxic, so should not be given to those with significant renal impairment, and, like other potent anti-resorptive agents, can cause hypocalcemia in patients with severe vitamin D deficiency, which should be corrected before administration. Its most common adverse effect is the acute phase response, seen in 30-40% of patients after their first dose, and much less commonly subsequently. Clinical trials in osteoporosis have not demonstrated increases in osteonecrosis of the jaw or in atypical femoral fractures. Observational databases are currently inadequate to determine whether these problems are increased in zoledronate users. Now available as a generic, zoledronate is a cost-effective agent for fracture prevention and for management of Paget's disease, but wider provision of infusion facilities is important to increase patient access. There is a need to further explore its potential for reducing cancer, cardiovascular disease and mortality, since these effects could be substantially more important than its skeletal actions.

Cellular Communication in Bone Homeostasis and the Related Anti-osteoporotic Drug Development

Background：Intercellular crosstalk among osteoblast, osteoclast, osteocyte and chondrocyte is involved in the precise control of bone homeostasis. Disruption of this cellular and molecular signaling would lead to metabolic bone diseases such as osteoporosis. Currently a number of anti-osteoporosis interventions are restricted by side effects, complications and long-term intolerance. This review aims to summarize the bone cellular communication involved in bone remodeling and its usage to develop new drugs for osteoporosis. Methods：We searched PubMed for publications from 1 January 1980 to 1 January 2018 to identify relevant and latest literatures, evaluation and prospect of osteoporosis medication were summarized. Detailed search terms were 'osteoporosis', 'osteocyte', 'osteoblast', 'osteoclast', 'bone remodeling', 'chondrocyte', 'osteoporosis treatment', 'osteoporosis therapy', 'bisphosphonates', 'denosumab', 'Selective Estrogen Receptor Modulator (SERM)', 'PTH', 'romosozumab', 'dkk-1 antagonist', 'strontium ranelate'. Results：A total of 170 papers were included in the review. About 80 papers described bone cell interactions involved in bone remodeling. The remaining papers were focused on the novel advanced and new horizons in osteoporosis therapies. Conclusion：There exists a complex signal network among bone cells involved in bone remodeling. The disorder of cell-cell communications may be the underlying mechanism of osteoporosis. Current anti-osteoporosis therapies are effective but accompanied by certain drawbacks simultaneously. Restoring the abnormal signal network and individualized therapy are critical for ideal drug development.

An In Silico Model for the Prediction of Changes in Mineral Density in Cortical Bone Remodeling

An in silico model for the estimation of volumetric bone mineral density (vBMD) changes at a cortical bone site subjected to mechanobiological bone remodeling is proposed in this manuscript. Mechanisms of cell differentiation, receptor-ligand binding, mechanical signaling, and resorption or deposition of bone matrix were considered, therefore providing a comprehensive description of mechanobiological bone remodeling in the bone microenvironment and enabling the analysis of temporal evolution of disease or therapy scenarios. The proposed model is composed by five modules, namely, bone cells populations, mechanobiology, volume fractions and porosity, mineral density, and structural stiffness. The model is an extension of other models found in the literature because equations for the obtaining of cortical vBMD and the binding of parathyroid hormone (PTH) to parathyroid hormone 1 receptor are included. The proposed model showed a satisfactory agreement with the solutions of other in silico models found in the literature. Simulations of walking and running exercise routines were performed for the evaluation of model capability regarding the control of the numerical error and prediction of vBMD. The computational method used to solve the case study controlled the relative numerical error by less than 1 × 10-7 for approximately 1.7 × 106 time steps. The predicted values correlate with the concept of increasing BMD by vigorous physical activity; however, they contrast with the specific effect of physical activities on cortical vBMD.

Pyroptosis in Osteoblasts: A Novel Hypothesis Underlying the Pathogenesis of Osteoporosis

Osteoporosis has become a worldwide disease characterized by a reduction in bone mineral density and the alteration of bone architecture leading to an increased risk of fragility fractures. And an increasing number of studies have indicated that osteoblasts undergo a large number of programmed death events by many different causes in osteoporosis and release NLRP3 and interleukin (e.g., inflammatory factors), which play pivotal roles in contributing to excessive differentiation of osteoclasts and result in exaggerated bone resorption. NLRP3 is activated during pyroptosis and processes the precursors of IL-1β and IL-18 into mature forms, which are released into the extracellular milieu accompanied by cell rupture. All of these compounds are the classical factors of pyroptosis. The cellular effects of pyroptosis are commonly observed in osteoporosis. Although many previous studies have focused on the pathogenesis of these inflammatory factors in osteoporosis, pyroptosis has not been previously evaluated. In this review, pyroptosis is proposed as a novel hypothesis of osteoporosis pathogenesis for the first time, thus providing a new direction for the treatment of osteoporosis in the future.

In vivo efficacy of calcium phosphate-based synthetic-bone-mineral on bone loss resulting from estrogen and mineral deficiencies

Osteopenia and osteoporosis affect over 40 million US adults 50 years and older. Both diseases are strongly influenced by estrogen and nutritional-mineral deficiencies. This study investigates the efficacy of orally delivered synthetic-bone-mineral (SBM), a newly developed calcium phosphate based biomaterial, on reversing bone loss induced by these two critical deficiencies. Thirty 3-month-old female rats were randomly allocated to either control-sham surgery on normal diet; or one of the four experimental groups: Sham surgery on a low mineral diet (LMD), ovariectomized (OVX) on LMD, OVX on LMD with SBM with/without fluoride (F). The rats were sacrificed after 6 months, at 9-month-old. After 6 months, although all groups lost bone mineral density relative to controls, the supplemented OVX rats showed higher bone mineral density than their unsupplemented counterparts. The 2 SBM supplemented groups improved bone loading capacity by 28.1 and 35.4% compared to the OVX LMD group. Bones from supplemented rats exhibited higher inorganic/organic ratios. The addition of F did not have a significant influence on bone loss. Our findings suggest that SBM supplement is effective in maintaining bone health and offsetting the deleterious effects of estrogen and/or mineral deficiencies on bone density, microarchitecture, and strength.

Update on Menopausal Hormone Therapy for Fracture Prevention

PURPOSE OF REVIEW

The goal of the review is to assess the appropriateness of menopausal hormone therapy (MHT) for the primary prevention of bone loss in women at elevated risk in the early years after menopause.

RECENT FINDINGS

Estrogen alone or combined with progestin to protect the uterus from cancer significantly reduces the risk of osteoporosis-related fractures. MHT increases type 1 collagen production and osteoblast survival and maintains the equilibrium between bone resorption and bone formation by modulating osteoblast/osteocyte and T cell regulation of osteoclasts. Estrogens have positive effects on muscle and cartilage. Estrogen, but not antiresorptive therapies, can attenuate the inflammatory bone-microenvironment associated with estrogen deficiency. However, already on second year of administration, MHT is associated with excess breast cancer risk, increasing steadily with duration of use. MHT should be considered in women with premature estrogen deficiency and increased risk of bone loss and osteoporotic fractures. However, MHT use for the prevention of bone loss is hindered by increase in breast cancer risk even in women younger than 60 years old or who are within 10 years of menopause onset.

Inhibition of osteoclastogenesis by mechanically stimulated osteoblasts is attenuated during estrogen deficiency

Osteoporotic bone loss and fracture have long been regarded to arise upon depletion of circulating estrogen, which increases osteoclastogenesis and bone resorption. Osteoblasts from human osteoporotic patients also display deficient osteogenic responses to mechanical loading. However, while osteoblasts play an important role in regulating osteoclast differentiation, how this relationship is affected by estrogen deficiency is unknown. This study seeks to determine how mechanically stimulated osteoblasts regulate osteoclast differentiation and matrix degradation under estrogen deficiency. Here, we report that osteoblast-induced osteoclast differentiation (indicated by tartrate-resistant acid phosphatase, cathepsin K, and nuclear factor of activated T cells, cytoplasmic 1) and matrix degradation were inhibited by estrogen treatment and mechanical loading. However, estrogen-deficient osteoblasts exacerbated osteoclast formation and matrix degradation in conditioned medium and coculture experiments. This was accompanied by higher expression of cyclooxygenase-2 and macrophage colony-stimulating factor, but not osteoprotegerin, by osteoblasts under estrogen deficiency. Interestingly, this response was exacerbated under conditions that block the Rho-Rho-associated protein kinase signaling pathway. This study provides an important, but previously unrecognized, insight into bone loss in postmenopausal osteoporosis, whereby estrogen-deficient osteoblasts fail to produce inhibitory osteoprotegerin after mechanical stimulation but upregulate macrophage colony-stimulating factor and cyclooxygenase-2 expression and, thus, leave osteoclast activity unconstrained.

Microbial osteoporosis: The interplay between the gut microbiota and bones via host metabolism and immunity

The complex relationship between intestinal microbiota and host is a novel field in recent years. A large number of studies are being conducted on the relationship between intestinal microbiota and bone metabolism. Bone metabolism consisted of bone absorption and formation exists in the whole process of human growth and development. The nutrient components, inflammatory factors, and hormone environment play important roles in bone metabolism. Recently, intestinal microbiota has been found to influence bone metabolism via influencing the host metabolism, immune function, and hormone secretion. Here, we searched relevant literature on Pubmed and reviewed the effect of intestinal microbiota on bone metabolism through the three aspects, which may provide new ideas and targets for the clinical treatment of osteoporosis.

Advances and Unmet Needs in the Therapeutics of Bone Fragility

The prevalence of fragility fractures increases as longevity increases the proportion of the elderly in the community. Until recently, the majority of studies have targeted women with osteoporosis defined as a bone mineral density (BMD) T score of < -2.5 SD, despite evidence that the population burden of fractures arises from women with osteopenia. Antiresorptive agents reduce vertebral and hip fracture risk by ~50 percent during 3 years but efficacy against non-vertebral fractures, 80% of all fractures in the community, is reported in few studies, and of those, the risk reduction is only 20-30%. Recent advances in the use of antiresorptives and anabolic agents has addressed some of these unmet needs. Zoledronic acid is now reported to reduce vertebral and non-vertebral fractures rates in women with osteopenia. Studies using teriparatide demonstrate better vertebral and clinical (symptomatic vertebral and non-vertebral) antifracture efficacy than risedronate. Abaloparatide, a peptide sharing amino acid sequences with teriparatide, reduces vertebral and non-vertebral fractures. Romosozumab, a monoclonal antibody suppressing sclerostin, reduces vertebral and non-vertebral fractures within a year of starting treatment, and does so more greatly than alendronate. Some recent studies signal undesirable effects of therapy but provide essential cautionary insights into long term management. Cessation of denosumab is associated with a rapid increase in bone remodeling and the uncommon but clinically important observation of increased multiple vertebral fractures suggesting the need to start alternative anti-resorptive therapy around the time of stopping denosumab. Antiresorptives like bisphosphonates and denosumab suppress remodeling but not completely. Antifracture efficacy may be limited, in part, as a consequence of continued unsuppressed remodeling, particularly in cortical bone. Bisphosphonates may not distribute in deeper cortical bone, so unbalanced intracortical remodeling continues to cause microstructural deterioration. In addition, suppressed remodeling may compromise the material composition by increasing matrix mineral density and glycosylation of collagen. As antiresorptive agents do not restore microstructural deterioration existing at the time of starting treatment, under some circumstances, anabolic therapy may be more appropriate first line treatment. Combining antiresorptive and anabolic therapy is an alternative but whether anti-fracture efficacy is greater than that achieved by either treatment alone is not known.

A novel miR17/protein tyrosine phosphatase-oc/EphA4 regulatory axis of osteoclast activity

Information about the molecular mechanisms leading to the activation of the osteoclast is relatively limited. While there is compelling evidence that the signaling mechanisms of Src and integrin β₃ are essential for osteoclast activation, the regulation of these two signaling mechanisms is not fully understood. In this review, evidence supporting a novel regulatory axis of osteoclast activation that plays an upstream regulatory role in both the Src and integrin β₃ signaling during osteoclast activation is discussed. This regulatory axis contains three unique components: a structurally unique transmembrane protein-tyrosine phosphatase, PTP-oc, EphA4, and miR17. In the first component, PTP-oc activates the Src signaling through dephosphorylation of the inhibitory tyr-527 of Src. This in turn activates the integrin β₃ signaling, enhances the JNK2/NFκB signaling, promotes the ITAM/Syk signaling, and suppresses the ITIM/Shp1 signaling; the consequence of which is activation of the osteoclast. In the second component, EphA4 inhibits osteoclast activity by suppressing the integrin β₃ signaling. PTP-oc relieves the suppressive actions of EphA4 by directly dephosphorylating EphA4. In the third component, PTP-oc expression is negatively regulated by miR17. Accordingly, suppression of miR17 during osteoclast activation upregulates the PTP-oc signaling and suppresses the EphA4 signaling, resulting in the activation of the osteoclast. This regulatory axis is unique, in that each of the three components acts to exert suppressive action on their respective immediate downstream inhibitory step. Because the final downstream event is the EphA4-mediated inhibition of osteoclast activation, the overall effect of this mechanism is the stimulation of osteoclast activity.

Menopause-Related Appendicular Bone Loss is Mainly Cortical and Results in Increased Cortical Porosity

After menopause, remodeling becomes unbalanced and rapid. Each of the many remodeling transactions deposits less bone than it resorbed, producing microstructural deterioration. Trabecular bone is said to be lost more rapidly than cortical bone. However, because 80% of the skeleton is cortical, we hypothesized that most menopause-related bone loss and changes in bone microstructure are cortical, not trabecular in origin, and are the result of intracortical remodeling. Distal tibial and distal radial microstructure were quantified during 3.1 years (range, 1.5 to 4.5 years) of follow-up using high-resolution peripheral quantitative computed tomography and StrAx software in 199 monozygotic and 125 dizygotic twin pairs aged 25 to 75 years in Melbourne, Australia. The annual increases in tibial cortical porosity accelerated, being 0.44%, 0.80%, and 1.40% in women remaining premenopausal, transitioning to perimenopause, and from perimenopausal to postmenopause, respectively. Porosity increased in the compact-appearing, outer, and inner transitional zones of the cortex (all p < 0.001). The annual decrease in trabecular bone volume/tissue volume (BV/TV) also accelerated, being 0.17%, 0.26%, and 0.31%, respectively. Little bone loss was observed before menopause. The reduction in BV/TV was due to a decrease in trabecular number (p < 0.001). The greatest bone loss, 7.7 mg hydroxyapatite (HA) annually, occurred in women transitioning from perimenopausal to postmenopause and of this, 6.1 mg HA (80%) was cortical. Results were similar for the distal radius. Despite microarchitectural changes, no significant bone loss was observed before menopause. Over 90% of appendicular bone loss occurs during and after menopause, over 80% is cortical, and this may explain why 80% of fractures are appendicular. © 2017 American Society for Bone and Mineral Research.

Lack of NOD2 attenuates ovariectomy-induced bone loss via inhibition of osteoclasts

Nucleotide-binding oligomerization domain-2 (NOD2) is a pattern recognition receptor of the innate immune system. It interacts with serine-threonine kinases to induce activation of nuclear factor κB (NF-κB), which is important for receptor activator of nuclear factor kappa-B ligand (RANKL) signaling. We tested the idea that NOD2 modulates bone metabolism via an action on osteoclasts (OCs). The absence of NOD2 reduced ovariectomy-induced bone loss in mice, and lowered the area and the activity of OCs, by impairing RANKL signaling. It also reduced the level of reactive oxygen species (ROS), as well as of NF-κB-DNA binding upon RANKL exposure. NOD2 was found to physically interact with nicotinamide adenine dinucleotide phosphate oxidase 1, and this led to increased production of ROS in OCs. Our data suggest that NOD2 contributes to bone loss in estrogen deficiency by elevating ROS levels in OCs.

Irreversible Deterioration of Cortical and Trabecular Microstructure Associated With Breastfeeding

Estrogen deficiency associated with menopause is accompanied by an increase in the rate of bone remodeling and the appearance of a remodeling imbalance; each of the greater number of remodeling transactions deposits less bone than was resorbed, resulting in microstructural deterioration. The newly deposited bone is also less completely mineralized than the older bone resorbed. We examined whether breastfeeding, an estrogen-deficient state, compromises bone microstructure and matrix mineral density. Distal tibial and distal radial microarchitecture were quantified using high-resolution peripheral quantitative computed tomography in 58 women before, during, and after breastfeeding and in 48 controls during follow-up of 1 to 5 years. Five months of exclusive breastfeeding increased cortical porosity by 0.6% (95% confidence interval [CI] 0.3-0.9), reduced matrix mineralization density by 0.26% (95% CI 0.12-0.41) (both p < 0.01), reduced trabecular number by 0.22 per mm (95% CI 0.15-0.28), and increased trabecular separation by 0.07 mm (95% CI 0.05-0.08) (all p < 0.001). Relative to prebreastfeeding, at a median of 2.6 years (range 1 to 4.8) after cessation of breastfeeding, cortical porosity remained 0.58 SD (95% CI 0.48-0.68) higher, matrix mineralization density remained 1.28 SD (95% CI 1.07-1.49) lower, and trabeculae were 1.33 SD (95% CI 1.15-1.50) fewer and 1.06 SD (95% CI 0.91-1.22) more greatly separated (all p < 0.001). All deficits were greater than in controls. The results were similar at distal radius. Bone microstructure may be irreversibly deteriorated after cessation of breastfeeding at appendicular sites. Studies are needed to establish whether this deterioration compromises bone strength and increases fracture risk later in life. © 2016 American Society for Bone and Mineral Research.

The Periosteal Bone Surface is Less Mechano-Responsive than the Endocortical

Dynamic processes modify bone micro-structure to adapt to external loading and avoid mechanical failure. Age-related cortical bone loss is thought to occur because of increased endocortical resorption and reduced periosteal formation. Differences in the (re)modeling response to loading on both surfaces, however, are poorly understood. Combining in-vivo tibial loading, in-vivo micro-tomography and finite element analysis, remodeling in C57Bl/6J mice of three ages (10, 26, 78 week old) was analyzed to identify differences in mechano-responsiveness and its age-related change on the two cortical surfaces. Mechanical stimulation enhanced endocortical and periosteal formation and reduced endocortical resorption; a reduction in periosteal resorption was hardly possible since it was low, even without additional loading. Endocortically a greater mechano-responsiveness was identified, evident by a larger bone-forming surface and enhanced thickness of formed bone packets, which was not detected periosteally. Endocortical mechano-responsiveness was better conserved with age, since here adaptive response declined continuously with aging, whereas periosteally the main decay in formation response occurred already before adulthood. Higher endocortical mechano-responsiveness is not due to higher endocortical strains. Although it is clear structural adaptation varies between different bones in the skeleton, this study demonstrates that adaptation varies even at different sites within the same bone.

Altered distributions of bone tissue mineral and collagen properties in women with fragility fractures

Heterogeneity of bone tissue properties is emerging as a potential indicator of altered bone quality in pathologic tissue. The objective of this study was to compare the distributions of tissue properties in women with and without histories of fragility fractures using Fourier transform infrared (FTIR) imaging. We extended a prior study that examined the relationship of the mean FTIR properties to fracture risk by analyzing in detail the widths and the tails of the distributions of FTIR properties in biopsies from fracture and non-fracture cohorts. The mineral and matrix properties of cortical and trabecular iliac crest tissue were compared in biopsies from women with a history of fragility fracture (+Fx; n=21, age: mean 54±SD 15y) and with no history of fragility fracture (-Fx; n=12, age: 57±5y). A subset of the patients included in the -Fx group were taking estrogen-plus-progestin hormone replacement therapy (HRT) (-Fx+HRT n=8, age: 58±5y) and were analyzed separately from patients with no history of HRT (-Fx-HRT n=4, age: 56±7y). When the FTIR parameter mean values were examined by treatment group, the trabecular tissue of -Fx-HRT patients had a lower mineral:matrix ratio (M:M) and collagen maturity (XLR) than that of -Fx+HRT patients (-22% M:M, -18% XLR) and +Fx patients (-17% M:M, -18% XLR). Across multiple FTIR parameters, tissue from the -Fx-HRT group had smaller low-tail (5th percentile) values than that from the -Fx+HRT or +Fx groups. In trabecular collagen maturity and crystallinity (XST), the -Fx-HRT group had smaller low-tail values than those in the -Fx+HRT group (-16% XLR, -5% XST) and the +Fx group (-17% XLR, -7% XST). The relatively low values of trabecular mineral:matrix ratio and collagen maturity and smaller low-tail values of collagen maturity and crystallinity observed in the -Fx-HRT group are characteristic of younger tissue. Taken together, our data suggest that the presence of newly formed tissue that includes small/imperfect crystals and immature crosslinks, as well as moderately mature tissue, is an important characteristic of healthy, fracture-resistant bone. Finally, the larger mean and low-tail values of mineral:matrix ratio and collagen maturity noted in our -Fx+HRT vs. -Fx-HRT biopsies are consistent with greater tissue age and greater BMD arising from decreased osteoclastic resorption in HRT-treated patients.

Bone turnover markers are associated with higher cortical porosity, thinner cortices, and larger size of the proximal femur and non-vertebral fractures

Bone turnover markers (BTM) predict bone loss and fragility fracture. Although cortical porosity and cortical thinning are important determinants of bone strength, the relationship between BTM and cortical porosity has, however, remained elusive. We therefore wanted to examine the relationship of BTM with cortical porosity and risk of non-vertebral fracture. In 211 postmenopausal women aged 54-94 years with non-vertebral fractures and 232 age-matched fracture-free controls from the Tromsø Study, Norway, we quantified femoral neck areal bone mineral density (FN aBMD), femoral subtrochanteric bone architecture, and assessed serum levels of procollagen type I N-terminal propeptide (PINP) and C-terminal cross-linking telopeptide of type I collagen (CTX). Fracture cases exhibited higher PINP and CTX levels, lower FN aBMD, larger total and medullary cross-sectional area (CSA), thinner cortices, and higher cortical porosity of the femoral subtrochanter than controls (p≤0.01). Each SD increment in PINP and CTX was associated with 0.21-0.26 SD lower total volumetric BMD, 0.10-0.14 SD larger total CSA, 0.14-0.18 SD larger medullary CSA, 0.13-0.18 SD thinner cortices, and 0.27-0.33 SD higher porosity of the total cortex, compact cortex, and transitional zone (all p≤0.01). Moreover, each SD of higher PINP and CTX was associated with increased odds for fracture after adjustment for age, height, and weight (ORs 1.49; 95% CI, 1.20-1.85 and OR 1.22; 95% CI, 1.00-1.49, both p<0.05). PINP, but not CTX, remained associated with fracture after accounting for FN aBMD, cortical porosity or cortical thickness (OR ranging from 1.31 to 1.39, p ranging from 0.005 to 0.028). In summary, increased BTM levels are associated with higher cortical porosity, thinner cortices, larger bone size and higher odds for fracture. We infer that this is produced by increased periosteal apposition, intracortical and endocortical remodeling; and that these changes in bone architecture are predisposing to fracture.

A comparison of the periodontal status in patients with type 2 diabetes based on glycated haemoglobin levels and other risk factors

PURPOSE

The aim of this study was to compare the periodontal status in patients with type 2 diabetes based on glycated haemoglobin levels and other risk factors.

MATERIAL/METHODS

75 patients with DM2 were grouped according to glycemic control: 40 subjects with HbA1c<7.0% and 35 subjects with HbA1c≥7.0%. We performed measurements of HbA1c, C-reactive protein (CRP), Approximal Plaque Index (API), Gingival Severity Index (GSI), tooth mobility (TM) as well as periodontal parameters such as probing depth (PD) and clinical attachment level (CAL). Age, gender and duration of the disease were analyzed too.

RESULTS

No significant differences in PD, CAL, API, GSI and TM were found between the analyzed groups. HbA1c positively correlated with CRP (p=0.046) and the duration of DM2 (p=0.012) but not with the periodontal parameters. Patients' age was positively correlated with both the duration of DM2 (p=0.002) and CAL (p=0.034). Regardless of HbA1c, men had significantly worse periodontal parameters compared to women (respectively: PD 2.73mm vs. 2.18mm, p=0.01; CAL 3.84mm vs. 2.54mm, p=0.005; proportion of deep pockets 9.06% vs. 2.97%, p=0.01; proportion of teeth with grade 2 mobility 9.14% vs. 2.8%, p=0.02).

CONCLUSIONS

The selected group of patients attending the Diabetes Outpatient Clinic showed a similar periodontal status with regard to glycated haemoglobin levels and other risk factors except gender. Male gender turned out to be a significant risk factor for periodontal disease in patients with type 2 diabetes mellitus.

Role of oestrogens on oxidative stress and inflammation in ageing

Abstract Females live longer than males. We have shown that this could be in part due to the higher levels of oestrogens in females, which protect them against ageing, by up-regulating the expression of antioxidant, longevity-related genes. However, the low concentration of oestrogens makes it unlikely that they exhibit significant antioxidant capacity in the organism. Our results show that physiological concentrations of oestrogens activate the expression of manganese superoxide dismutase and glutathione peroxidase by oestrogen receptors and the mitogen-activated protein kinase and nuclear factor kappa B pathway. Moreover, when considering oestrogen replacement therapy, it is of utmost importance to take into account when to start the therapy after menopause. We have shown that only early-onset administration of oestrogen replacement therapy is effective on oestrogen deprivation associated with oxidative and metabolic stress. This is due to a change in oestrogen receptor distribution after oestrogen deprivation. Oestrogens are also involved in inflammatory processes. Their role on inflammation is very complex, because their effects are different depending on the doses and also on the oestrogen receptor distribution.

Safety of drugs used in the treatment of osteoporosis

A number of drug classes are licensed for the treatment of osteoporosis including bisphosphonates, recombinant human parathyroid hormone (PTH), strontium, hormone replacement therapy (HRT), selective oestrogen receptor modulators (SERMS) and denosumab. This review discusses the safety of osteoporosis treatments and their efficacies. Recent concerns about the safety of calcium and high-dose vitamin D are discussed. Bisphosphonates have substantial postmarketing experience and a clearer picture of safety issues is emerging. Along with the well recognized effects on the gastrointestinal tract and kidney function, recently described adverse effects such as osteonecrosis of the jaw, oesophageal cancer, atrial fibrillation, subtrochanteric femur fractures and ocular complications of bisphosphonate therapy are discussed. Therapy with PTH is limited to two years' duration because of the development of osteogenic sarcomas in animal studies, which appeared related to dose, duration and timing of therapy. Strontium should be used with caution in patients with renal impairment and its use has been associated with venous thromboembolism. The role of HRT and SERMs in the treatment of postmenopausal osteoporosis is restricted as a result of an increased risk of stroke, venous thromboembolism and breast cancer. Postmarketing experience with denusomab is limited but a number of potential safety concerns including osteonecrosis of the jaw are emerging. All of these drugs have been proven to reduce fractures. The decision to use a drug to reduce fracture risk should be based on risk-benefit analysis of the drug and its suitability for individual patients.

Quantification of the relative contribution of estrogen to bone mineral density in men and women

Background

The study quantified the relative contributions of estrogen (E2) and total testosterone (TT) to variation in bone mineral density in men and women.

Methods

This was a cross-sectional study which involved 200 men and 415 women aged 18 to 89 years. BMD at the lumbar spine (LS) and femoral neck (FN) was measured by DXA. Serum levels of E2 and TT were measured by electrochemiluminescence immunoassays. The association between E2, TT, and BMD was analyzed by the multiple linear regression model, adjusting for age and BMI. The contribution of each hormone to the variation in BMD was quantified by the bootstrap method.

Results

In women, higher serum levels of E2, but not TT, were significantly associated with greater BMD at the FN (P = 0.001) and LS (P < 0.0001). In men, higher serum levels of E2 were independently associated with greater FNBMD (P = 0.008) and LSBMD (P = 0.086). In the multiple linear regression model, age, body weight and E2 accounted for 50-55% variance in FNBMD, and 25% (in men) and 48% (in women) variance in LSBMD. Variation in E2 accounted for 2.5% (95% CI 0.4 - 7.8%) and 11.3% (95% CI 8.1 - 15.3%) variation in FNBMD in men and women, respectively. Moreover, E2 contributed 1.2% (95% CI 0.1 - 5.8%) and 11.7% (95% CI 8.5 - 15.9%) variation in LSBMD in men and women, respectively.

Conclusions

Estrogen is more important than testosterone in the determination of age-related bone mineral density men and women of Vietnamese background. However, the relative contributions of estrogen to bone mineral density in men are likely modest.

Diminished response to in vivo mechanical loading in trabecular and not cortical bone in adulthood of female C57Bl/6 mice coincides with a reduction in deformation to load

Bone loss occurs during adulthood in both women and men and affects trabecular bone more than cortical bone. The mechanism responsible for trabecular bone loss during adulthood remains unexplained, but may be due at least in part to a reduced mechanoresponsiveness. We hypothesized that trabecular and cortical bone would respond anabolically to loading and that the bone response to mechanical loading would be reduced and the onset delayed in adult compared to postpubescent mice. We evaluated the longitudinal adaptive response of trabecular and cortical bone in postpubescent, young (10 week old) and adult (26 week old) female C57Bl/6J mice to axial tibial compression using in vivo microCT (days 0, 5, 10, and 15) and dynamic histomorphometry (day 15). Loading elicited an anabolic response in both trabecular and cortical bone in young and adult mice. As hypothesized, trabecular bone in adult mice exhibited a reduced and delayed response to loading compared to the young mice, apparent in trabecular bone volume fraction and architecture after 10 days. No difference in mechanoresponsiveness of the cortical bone was observed between young and adult mice. Finite element analysis showed that load-induced strain was reduced with age. Our results suggest that trabecular bone loss that occurs in adulthood may in part be due to a reduced mechanoresponsiveness in this tissue and/or a reduction in the induced tissue deformation which occurs during habitual loading. Therapeutic approaches that address the mechanoresponsiveness of the bone tissue may be a promising and alternate strategy to maintain trabecular bone mass during aging.

Treatment of osteopenia

The majority of osteoporotic fractures happen in individuals with BMD t-scores in the osteopenic range (-2,5< t-score <-1). However, widespread use of anti-osteoporotic medication in this group based on t-score alone is not advisable because: 1) the number needed to treat is much higher (NNT>100) than in patients with fractured and t-score below -2,5 (NNT 10-20); 2)while specific osteoporosis treatments have demonstrated significant reductions of the fracture risk in patients with t-score <-2, 5, the efficacy in patients in the osteopenic range is less well established. Therefore, an osteopenic t-score does not in itself constitute a treatment imperative. Generally, osteopenia has to be associated with either low energy fracture(s) or very high risk for future fracture as assessed with risk calculators like FRAX to warrant specific osteoporosis therapy. Vertebral fractures are now conveniently assessed using lateral x-rays from DXA machines. In the vast majority of cases antiresorptive treatments (mainly hormone replacement therapy and SERMS in younger and bisphosphonates or Denosumab in older women) are the treatments of choice in this group of patients,-only rarely is anabolic therapy indicated.

(-)-Epigallocathechin-3-gallate, an AMPK activator, decreases ovariectomy-induced bone loss by suppression of bone resorption

Previously, we showed that AMP-activated protein kinase (AMPK) negatively regulates receptor activator of nuclear factor-κB ligand-induced osteoclast formation in vitro. The present study investigated the effect of (-)-epigallocathechin-3-gallate (EGCG), an AMPK activator, on ovariectomy (OVX)-induced bone loss in mice. Female mice subjected to OVX were administered EGCG for 8 weeks. We measured total-body bone mineral density (BMD) before and after the operation at an interval of 4 weeks. We performed micro-computed tomography (micro-CT) of the tibia and bone histomorphometric examination of the femur. Western blot analysis was additionally performed, to detect levels of the phosphorylated and total forms of AMPK-α in calvarial extracts. EGCG prevented OVX-induced body weight gain. The OVX control did not show a significant increase in BMD values at baseline and after treatment, unlike the sham control. EGCG attenuated OVX-induced bone loss. Micro-CT experiments revealed that EGCG induced a significant increase in trabecular bone volume and trabecular number and a decrease in trabecular spacing compared to the OVX control. Histomorphometric analyses further showed that EGCG suppressed osteoclast surface and number. Phosphorylated AMPK expression was significantly elevated in bone following EGCG treatment. Our findings collectively indicate that EGCG decreases OVX-induced bone loss via inhibition of osteoclasts.

Histomorphometric interpretation of bone biopsies for the evaluation of osteoporosis treatment

Bone histomorphometry is a valuable tool in the evaluation of bone safety and the mechanism of action of drugs used in the treatment of osteoporosis. Recent studies in patients treated with anti-resorptive agents have highlighted technical issues, in particular, related to the calculation of dynamic indices of bone turnover using fluorochrome labelling. This review addresses the need for standardised approaches for overcoming these problems in order to enable valid comparison of the effects of different interventions on bone remodelling.

Remodeling markers are associated with larger intracortical surface area but smaller trabecular surface area: a twin study

All postmenopausal women become estrogen deficient but not all remodel their skeleton rapidly or lose bone rapidly. As remodeling requires a surface to be initiated upon, we hypothesized that a volume of mineralized bone assembled with a larger internal surface area is more accessible to being remodeled, and so decayed, after menopause. We measured intracortical, endocortical and trabecular bone surface area and microarchitecture of the distal tibia and distal radius in 185 healthy female twin pairs aged 40 to 61 years using high-resolution peripheral quantitative computed tomography (HR-pQCT). We used generalized estimation equations to analyze (i) the trait differences across menopause, (ii) the relationship between remodeling markers and bone surface areas, and (iii) robust regression to estimate associations between within-pair differences. Relative to premenopausal women, postmenopausal women had higher remodeling markers, larger intracortical and endocortical bone surface area, higher intracortical porosity, smaller trabecular bone surface area and fewer trabeculae at both sites (all p<0.01). Postmenopausal women had greater deficits in cortical than trabecular bone mass at the distal tibia (-0.98 vs. -0.12 SD, p<0.001), but similar deficits at the distal radius (-0.45 vs. -0.39 SD, p=0.79). A 1 SD higher tibia intracortical bone surface area was associated with 0.22-0.29 SD higher remodeling markers, about half the 0.53-0.67 SD increment in remodeling markers across menopause (all p<0.001). A 1 SD higher porosity was associated with 0.20-0.30 SD higher remodeling markers. A 1 SD lower trabecular bone surface area was associated with 0.15-0.18 SD higher remodeling markers (all p<0.01). Within-pair differences in intracortical and endocortical bone surface areas at both sites and porosity at the distal tibia were associated with within-pair differences in some remodeling markers (p=0.05 to 0.09). We infer intracortical remodeling may be self perpetuating by creating intracortical porosity and so more bone surface for remodeling to occur upon, while remodeling upon the trabecular bone surface is self limiting because it removes trabeculae with their surface.

Strategies of spinal fusion on osteoporotic spine

The prevalence of osteoporosis has been increasing globally. Recently surgical indications for elderly patients with osteoporosis have been increasing. However, only few strategies are available for osteoporotic patients who need spinal fusion. Osteoporosis is a result of negative bone remodeling from enhanced function of the osteoclasts. Because bone formation is the result of coupling between osteoblasts and osteoclasts, anti-resorptive agents that induce osteoclast apoptosis may not be effective in spinal fusion surgery, necessitating new bone formation. Therefore, anabolic agents may be more suitable for osteoporotic patients who undergo spinal fusion surgery. The instrumentations and techniques with increased pullout strength may increase fusion rate through rigid fixation. Studies on new osteoinductive materials, methods to increase osteogenic cells, strengthened and biocompatible osteoconductive scaffolds are necessary to enable osteoporotic patients to undergo spinal fusion. When osteoporotic patients undergo spinal fusion, surgeons should consider appropriate osteoporosis medication, instrumentation and technique.

Estrogens in rheumatoid arthritis; the immune system and bone

Rheumatoid arthritis (RA) is an autoimmune disease that is more common in women than in men. The peak incidence in females coincides with menopause when the ovarian production of sex hormones drops markedly. RA is characterized by skeletal manifestations where production of pro-inflammatory mediators, connected to the inflammation in the joint, leads to bone loss. Animal studies have revealed distinct beneficial effects of estrogens on arthritis, and a positive effect of hormone replacement therapy has been reported in women with postmenopausal RA. This review will focus on the influence of female sex hormones in the pathogenesis and progression of RA.

Abnormal bone remodeling in patients with spontaneous painful vertebral fracture

The application of tetracycline-based iliac bone histomorphometry to the study of the pathogenesis of osteoporosis has given conflicting results. Accordingly, we performed this procedure in 78 postmenopausal white women with one or more vertebral fractures identified according to rigorous criteria that excluded other causes of vertebral deformity and 66 healthy postmenopausal white women recruited from the same geographic region; the groups did not differ in age or weight. In each subject, measurements were made separately on the cancellous (Cn), endocortical (Ec), and intracortical (Ct) subdivisions of the endosteal envelope. In the fracture patients, osteoblast surface was reduced substantially on each subdivision, most markedly on the Cn surface, where about 25% of the deficit was in cuboidal (type II) osteoblasts, suggesting impaired recruitment; the remaining 75% of the deficit was in intermediate (type III) cells, suggesting earlier transition from type III to type IV (flat) cells. On the Ec and Ct surfaces, the deficit was exclusively in type III cells. Mean bone formation rate was reduced by about 18% on the Cn but not on the Ec or Ct surfaces. The deficit was more significant in subjects matched for Cn BV/TV when adjusted for the inverse regression on osteocyte density and after logarithmic transformation. The difference in bone formation rate resulted from a corresponding reduction in wall thickness without a change in activation frequency. The frequency distribution of bone formation rate was more skewed to the left in the fracture patients than in the controls. Osteoclast surface was significantly lower on each subdivision. The variation in osteoblast surface, bone formation rate, and osteoclast surface was significantly greater in the fracture patients than in the controls, with more abnormally low and abnormally high values. The data suggest the following conclusions: (1) The histologic heterogeneity of postmenopausal osteoporosis is reaffirmed; (2) the different subdivisions of the endosteal envelope, although in continuity, behave differently in health and disease; (3) a combination of defective osteoblast recruitment and premature osteoblast apoptosis would account for the deficit in type II and III cells and the reductions in wall thickness and bone formation rate on the Cn surface and the previously reported osteocyte deficiency in Cn bone; (4) premature disaggregation of multinuclear to mononuclear resorbing cells could account for the osteoclast deficit; and (5) some patients with vertebral fracture have one or another disorder of bone remodeling that at present cannot be identified by noninvasive means.

Osteoclast activity and subtypes as a function of physiology and pathology--implications for future treatments of osteoporosis

Osteoclasts have traditionally been associated exclusively with catabolic functions that are a prerequisite for bone resorption. However, emerging data suggest that osteoclasts also carry out functions that are important for optimal bone formation and bone quality. Moreover, recent findings indicate that osteoclasts have different subtypes depending on their location, genotype, and possibly in response to drug intervention. The aim of the current review is to describe the subtypes of osteoclasts in four different settings: 1) physiological, in relation to turnover of different bone types; 2) pathological, as exemplified by monogenomic disorders; 3) pathological, as identified by different disorders; and 4) in drug-induced situations. The profiles of these subtypes strongly suggest that these osteoclasts belong to a heterogeneous cell population, namely, a diverse macrophage-associated cell type with bone catabolic and anabolic functions that are dependent on both local and systemic parameters. Further insight into these osteoclast subtypes may be important for understanding cell-cell communication in the bone microenvironment, treatment effects, and ultimately bone quality.

Sex differences in destructive periodontal disease: exploring the biologic basis

BACKGROUND

Epidemiologic studies provide broad-based evidence that men are at greater risk for developing destructive periodontal disease than women, even after adjusting for behavioral and environmental factors, such as oral hygiene practice and smoking. What requires clarification, however, is whether sex-specific differences in immune function provide a plausible biologic basis for a sexual dimorphism in susceptibility to destructive periodontal disease. This review examines evidence that might provide an underlying biologic basis for a sexual dimorphism in the prevalence and severity of destructive periodontal disease.

METHODS

A narrative review of the literature related to sexual dimorphism in pathogen-mediated inflammatory diseases and immune response was retrieved from searches of computerized databases (MEDLINE, PubMed, and SCOPUS).

RESULTS

Sex steroids exert profound effects on multiple immunologic parameters regulating both the amplification and resolution of inflammation. Strong evidence exists for sexual dimorphisms in immune function, involving both innate and acquired immunity. Injury and infection have been associated with higher levels of inflammatory cytokines, including interleukin-1β and tumor necrosis factor-α, in men than women, paralleling observed sex-specific differences in periodontitis.

CONCLUSION

Differential gene regulation, particularly in sex steroid-responsive genes, may contribute to a sexual dimorphism in susceptibility to destructive periodontal disease.

The differences of femoral neck geometric parameters: effects of age, gender and race

This study aims at investigating the effects of age, sex, and ethnicity on five femoral neck geometric parameters (FNGPs): femoral neck periosteal diameter, cross-sectional area, cortical thickness, sectional modulus, and buckling ratio and found that the three factors would influence the FNGPs.

INTRODUCTION

Bone geometry is one of the most important predictors of bone strength and osteoporotic fractures. This study aims at investigating the effects of age, sex, and ethnicity on five femoral neck geometric parameters (FNGPs): femoral neck periosteal diameter (W), cross-sectional area (CSA), cortical thickness (CT), sectional modulus (Z), and buckling ratio (BR).

METHODS

In the studied 861 Caucasian subjects and 3,021 Chinese individuals, CSA, CT, and Z displayed trends of decrease with age, but W and BR showed increasing trends with age in both Chinese and Caucasian females and males (p < 0.05). W, CSA, CT, and Z were significantly higher (p <or= 0.001) in Caucasians than in Chinese and higher in males than in females except for BR between Chinese males and Chinese females.

CONCLUSION

In conclusion, the differences of FNGPs according to gender and ethnicity provide important implications in the different prevalence of osteoporotic fracture among different gender and ethnic groups.

Bone histomorphometry: a concise review for endocrinologists and clinicians

Bone histomorphometry is a quantitative histological examination of an undecalcified bone biopsy performed to obtain quantitative information on bone remodeling and structure. Labeling agents taken before the procedure deposit at sites of bone formation allowing a dynamic analysis. Biopsy is indicated to make the diagnosis of subclinical osteomalacia, to characterize the different forms of renal osteodystrophy and to elucidate cases of unexplained skeletal fragility. Bone histomorphometric parameters are divided into structural and remodeling subgroups, with the latter being subdivided into static and dynamic categories. Metabolic bone disorders such as osteomalacia, hyperparathyroidism, hypothyroidism, osteoporosis and renal osteodystrophy display different histomorphometric profiles. Antiresorptive and anabolic drugs used for the treatment of osteoporosis also induce characteristic changes in the bone biopsy. Bone histomorphometry is an important research tool in the field of bone metabolism and provides information that is not available by any other investigative approach.

Thinking inside and outside the envelopes of bone: dedicated to PDD

INTRODUCTION

Bone modeling and remodeling is the final common pathway expressing all genetic and environmental factors that influence the attainment and maintenance of bone's material and structural strength. Modeling and remodeling require a surface, and during growth this cellular machinery fashions bone's external size, shape, and internal architecture by depositing bone on, and removing bone from, both its periosteal (external) and endosteal (internal) envelopes. Bone is distributed and redistributed to achieve strength commensurate with its loading requirements.

METHODS

Advancing age is associated with: (1) a reduction in the volume of bone resorbed by each basic multicellular unit (BMU); (2) an even greater reduction in the volume of bone formed by each BMU so that each remodeling event, whether adaptive or reparative, removes bone from the bone; (3) increased remodeling (number of BMUs) on the three (endocortical, intracortical, and trabecular) components of its endosteal envelope in midlife in women and late in life in both sexes; and (4) reduced bone formation on the periosteal envelope. The net effect is cortical thinning, increased intracortical porosity, trabecular thinning, and loss of connectivity.

RESULTS

While remodeling intensity on an envelope determines structure (e.g., trabecular perforations), the surface area of the envelope determines remodeling intensity, and, so, structure. High remodeling on trabecular surfaces decreases as trabeculae (with their surface) are lost. Conversely, remodeling on the endocortical and intracortical envelopes increases their surface area, so remodeling intensity increases and bone loss becomes predominantly cortical.

CONCLUSIONS

Understanding bone structural strength and its decay and the effects of genetic factors, exercise, nutrition, and drug therapy on bone requires thinking outside and inside these envelopes; their absolute and relative movements during growth and aging determine bone structure and its strength.

To stop or not to stop, that is the question

Treatment aimed at preventing fractures should be stopped if evidence of continued antifracture efficacy is lacking, if continued treatment increases bone fragility by adversely affecting matrix properties, and if stopping does not increased bone fragility. Credible evidence of antifracture efficacy beyond 5 years is lacking because of attrition of the cohort originally allocated to treatment or placebo and lack of controls. Prolonged suppression of remodeling is associated with accumulation of microdamage, advanced glycation products and increased tissue mineral density in animal studies but the structural benefits appear to out weight these adverse effects. Atypical minimal trauma subtrochanteric fractures are associated with prolonged treatment in human subjects but these are exceedingly rare. Stopping treatment does result in the reemergence of remodeling, rapidly with some drugs, more slowly with others while fracture rates are increased in poor compliers to treatment. Thus, within the constraints of limited evidence, I infer that stopping therapy is more likely to do net harm than continuing therapy - treatment should be continued in the majority of individuals.

Prevalence of Secondary Causes of Bone Loss Among Breast Cancer Patients With Osteopenia and Osteoporosis

Purpose

To determine the prevalence of secondary causes of bone loss among patients with breast cancer with osteopenia and osteoporosis.

Patients and Methods

All women referred to a bone health clinic over a 6-year period for bone evaluation were included in this retrospective study and stratified based on presence or absence of a breast cancer history. The prevalence of secondary causes of bone loss in the two groups was compared.

Results

Of the 238 women identified, 64 women had breast cancer. The non–breast cancer group (n = 174) was significantly older (P = .015), had a lower mean weight (P = .019), lower 25 hydroxy-vitamin D level (P = .019), and greater degree of bone loss in both the spine and hip (P < .001 and 0.004, respectively). The presence of at least one secondary cause of bone loss, excluding cancer-related therapies, was seen in 78% of the breast cancer patient group and in 77% of the non–breast cancer group (P = not significant). Newly diagnosed metabolic bone disorders were seen in 58% of the breast cancer population. The most common was vitamin D deficiency, seen in 38% of patients in the breast cancer group and 51% of patients in the non–breast cancer group. Idiopathic hypercalciuria was diagnosed in 15.6%, primary hyperparathyroidism in 1.6%, and normocalcemic hyperparathyroidism in 3.1% of the breast cancer population.

Conclusion

A high prevalence of secondary causes of bone loss among patients with breast cancer supports a comprehensive evaluation in these patients, particularly those considering therapy with an aromatase inhibitor.

Bone remodelling: its local regulation and the emergence of bone fragility

Bone modelling prevents the occurrence of damage by adapting bone structure - and hence bone strength - to its loading circumstances. Bone remodelling removes damage, when it inevitably occurs, in order to maintain bone strength. This cellular machinery is successful during growth, but fails during advancing age because of the development of a negative balance between the volumes of bone resorbed and formed during remodelling by the basic multicellular unit (BMU), high rates of remodelling during midlife in women and late in life in both sexes, and a decline in periosteal bone formation. together resulting in bone loss and structural decay each time a remodelling event occurs. The two steps in remodelling - resorption of a volume of bone by osteoclasts and formation of a comparable volume by osteoblasts - are sequential, but the regulatory events leading to these two fully differentiated functions are not. Reparative remodelling is initiated by damage producing osteocyte apoptosis, which signals the location of damage via the osteocyte canalicular system to endosteal lining cells which forms the canopy of a bone-remodelling compartment (BRC). Within the BRC, local recruitment of osteoblast precursors from the lining cells, the marrow and circulation, direct contact with osteoclast precursors, osteoclastogenesis and molecular cross-talk between precursors, mature cells, cells of the immune system, and products of the resorbed matrix, titrate the birth, work and lifespan of the cells of this multicellular remodelling machinery to either remove or form a net volume of bone appropriate to the mechanical requirements.