Effect of zoledronic acid on vertebral marrow adiposity in postmenopausal osteoporosis assessed by MR spectroscopy

Efficacy and safety of zoledronic acid in the treatment of osteoporosis: A meta-analysis of randomized controlled trials

Purpose

Zoledronic acid can inhibit the activity of osteoclasts, and thus, may slow or inhibit bone loss. The purpose of this study was to systematically evaluate the efficacy and safety of zoledronic acid in the treatment of osteoporosis.

Methods

Four databases, PubMed, Embase, Cochrane Library, and Web of Science, were systematically searched up to December 26, 2022. The primary outcomes included bone mineral density (BMD), carboxy-terminal cross-linked telopeptide of type 1 collagen (CTX), bone-specific alkaline phosphatase (BSAP), procollagen type 1 N-terminal prope-ptide (P1NP), adverse events, and fracture. Secondary outcomes included serum sclerostin level, Visual Analogue Scale (VAS) score, and Oswestry Disability Index (ODI).

Results

A total of 22 randomized controlled trials were included in this meta-analysis. Meta-analysis results showed that zoledronic acid was effective in increasing BMD of the lumbar spine, femoral neck, trochanter and serum sclerostin level; and reduced CTX, BSAP, P1NP, VAS score, and ODI in patients with osteoporosis. Regarding safety, zoledronic acid could reduce the incidence of fractures but had relatively more adverse events.

Conclusion

Zoledronic acid can significantly improve BMD of the lumbar spine, femoral neck and trochanter, and effectively reduce incidence of fracture in patients with osteoporosis, thereby significantly improving patients' quality of life. However, the incidence of adverse events was higher than that of patients treated with placebo.

Bone Marrow Adipose Tissue as a Critical Regulator of Postmenopausal Osteoporosis - A Concise Review

Postmenopausal osteoporosis (PMOP) is a major health problem affecting millions of women worldwide. PMOP patients are often accompanied by abnormal accumulation of bone marrow adipose tissue (BMAT). BMAT is a critical regulator of bone homeostasis, and an increasing BMAT volume is negatively associated with bone mass reduction or fracture. BMAT regulates bone metabolism via adipokines, cytokines and the immune system, but the specific mechanisms are largely unknown. This review emphasizes the impact of estrogen deficiency on bone homeostasis and BMAT expansion, and the mechanism by which BMAT regulates PMOP, providing a promising strategy for targeting BMAT in preventing and treating PMOP.

The unique role of bone marrow adipose tissue in ovariectomy-induced bone loss in mice

BACKGROUND

Accumulation of bone marrow adipose tissue (BMAT) is always seen in osteoporosis induced by estrogen deficiency. Herein, we aimed to investigate the mechanisms and consequences of this phenomenon by establishing a mouse model of osteoporosis caused by ovariectomy (OVX)-mimicked estrogen deficiency.

METHODS

Micro-CT, osmium tetroxide staining, and histological analyses were performed to examine the changes in bone microstructure, BMAT and white adipose tissue (WAT) in OVX mice compared to sham mice. The osteogenesis and adipogenesis of primary bone marrow stromal cells (BMSCs) isolated from sham and OVX mice were compared in vitro. The molecular phenotypes of BMAT and WAT were determined and compared by quantitative PCR (qPCR). Bone marrow adipocyte-conditioned medium (BMA CM) was prepared from sham or OVX mice for coculture assays, and BMSCs or bone marrow monocytes/macrophages (BMMs) were isolated and subjected to osteoblast and osteoclast differentiation, respectively. Cell staining and qPCR were used to assess the effects of BMAT on bone metabolism.

RESULTS

OVX-induced estrogen deficiency induced reductions in both cortical and trabecular bone mass along with an expansion of BMAT volume. At the cellular level, loss of estrogen inhibited BMSC osteogenesis and promoted BMSC adipogenesis, whereas addition of estradiol exerted the opposite effects. In response to estrogen deficiency, despite the common proinflammatory molecular phenotype observed in both fat depots, BMAT, unlike WAT, unexpectedly exhibited an increase in adipocyte differentiation and lipolytic activity as well as the maintenance of insulin sensitivity. Importantly, BMAT, but not WAT, presented increased mRNA levels of both BMP receptor inhibitors (Grem1, Chrdl1) and Rankl following OVX. In addition, treatment with BMA CM, especially from OVX mice, suppressed the osteoblast differentiation of BMSCs while favoring the osteoclast differentiation of BMMs.

CONCLUSION

Our study illustrates that OVX-induced estrogen deficiency results in bone loss and BMAT expansion by triggering imbalance between the osteogenesis and adipogenesis of BMSCs. Furthermore, expanded BMAT, unlike typical WAT, may negatively regulate bone homeostasis through paracrine inhibition of osteoblast-mediated bone formation and promotion of osteoclast-mediated bone resorption.

Intravenous zoledronate for postmenopausal women with osteopenia and osteoporosis: a systematic review and metanalysis

BACKGROUND

Osteoporosis compromises bone strength and increases the risk of fractures. Zoledronate prevents loss of bone mass and reduces the risk of fractures.

OBJECTIVES

To determine the efficacy and safety of zoledronate in postmenopausal women with osteopenia and osteoporosis.

DESIGN AND SETTINGS

A systematic review and meta-analysis was conducted within the evidence-based health program at the Universidade Federal de São Paulo.

METHODS

An electronic search of the CENTRAL, MEDLINE, Embase, and LILACS databases was performed until February 2022. Randomized controlled trials comparing zoledronate with placebo or other bisphosphonates were included. Standard methodological procedures were performed according to the Cochrane Handbook and the certainty of evidence for the Grading of Recommendations Assessment, Development, and Evaluation Working Group. Two authors assessed the risk of bias and extracted data on fractures, adverse events, bone turnover markers (BTM), and bone mineral density (BMD).

RESULTS

Twelve trials from 6,652 records were included: nine compared zoledronate with placebo, two trials compared zoledronate with alendronate, and one trial compared zoledronate with ibandronate. Zoledronate reduced the incidence of fractures in osteoporotic [three years: morphometric vertebral fractures (relative risk, RR = 0.30 (95% confidence interval, CI: 0.24-0.38))] and osteopenic women [six years: morphometric vertebral fractures (RR = 0.39 (95%CI: 0.25-0.61))], increased incidence of post-dose symptoms [RR = 2.56 (95%CI: 1.80-3.65)], but not serious adverse events [RR = 0.97 (95%CI: 0.91-1.04)]. Zoledronate reduced BTM and increased BMD in osteoporotic and osteopenic women.

CONCLUSION

This review supports the efficacy and safety of zoledronate in postmenopausal women with osteopenia for six years and osteoporosis for three years.

PROSPERO REGISTRATION NUMBER

CRD42022309708, https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=309708.

Chidamide suppresses adipogenic differentiation of bone marrow derived mesenchymal stem cells via increasing REEP2 expression

Increased propensity of bone marrow-derived mesenchymal stem cells (BM-MSCs) toward adipogenic differentiation at the expense of osteogenesis has been implicated in obesity, diabetes, and age-related osteoporosis as well as various hematopoietic disorders. Defining small molecules with role in rectifying the adipo-osteogenic differentiation imbalance is of great significance. Here, we unexpectedly found that Chidamide, a selective histone deacetylases inhibitor, exhibited remarkably suppressive effect on the in vitro induced adipogenic differentiation of BM-MSCs. Multifaceted alterations in the spectrum of gene expression were observed in Chidamide-managed BM-MSCs during adipogenic induction. Finally, we focused on REEP2, which presented decreased expression in BM-MSCs-mediated adipogenesis and was restored by Chidamide treatment. REEP2 was subsequently demonstrated as a negative regulator of adipogenic differentiation of BM-MSCs and mediated the suppressive effect of Chidamide on adipocyte development. Our findings provide the theoretical and experimental foundation for the clinical application of Chidamide for disorders associated with excessive marrow adipocytes.

Osteoporosis and Bone Marrow Adipose Tissue

PURPOSE OF REVIEW

This review focuses on the recent findings regarding bone marrow adipose tissue (BMAT) concerning bone health. We summarize the variations in BMAT in relation to age, sex, and skeletal sites, and provide an update on noninvasive imaging techniques to quantify human BMAT. Next, we discuss the role of BMAT in patients with osteoporosis and interventions that affect BMAT.

RECENT FINDINGS

There are wide individual variations with region-specific fluctuation and age- and gender-specific differences in BMAT content and composition. The Bone Marrow Adiposity Society (BMAS) recommendations aim to standardize imaging protocols to increase comparability across studies and sites. Water-fat imaging (WFI) seems an accurate and efficient alternative for spectroscopy (¹H-MRS). Most studies indicate that greater BMAT is associated with lower bone mineral density (BMD) and a higher prevalence of vertebral fractures. The proton density fat fraction (PDFF) and changes in lipid composition have been associated with an increased risk of fractures independently of BMD. Therefore, PDFF and lipid composition could potentially be future imaging biomarkers for assessing fracture risk. Evidence of the inhibitory effect of osteoporosis treatments on BMAT is still limited to a few randomized controlled trials. Moreover, results from the FRAME biopsy sub-study highlight contradictory findings on the effect of the sclerostin antibody romosozumab on BMAT. Further understanding of the role(s) of BMAT will provide insight into the pathogenesis of osteoporosis and may lead to targeted preventive and therapeutic strategies.

Changes in adipose bone marrow and bone morphology in X-linked hypophosphatemic rickets

INTRODUCTION

X-linked hypophosphatemic (XLH) rickets causes significant bone deformities in the lower limbs resulting from a bone mineralization defect. According to Frost's Mechanostat theory, compensatory modeling of the bones takes place during increased mechanical loads. In addition, mechanical stimuli modulate the differentiation of mesenchymal stem cells; common precursors to bone marrow adipocytes and osteoblasts.

HYPOTHESIS

Bone deformities of the lower limbs lead to increased femoral bone mass and decreased fatty infiltration of the bone marrow (FIBM) in children with XLH rickets compared to a control group.

PATIENTS AND METHODS

Eleven children (10.3years [6-17]) with XLH rickets and 22 healthy children (10.2years [5-15.5]) underwent lower limb Magnetic Resonance Imaging. A calculation of FIBM was performed at the mid-femur, as well as a calculation of the total bone cross-sectional area (CSA), the cortical CSA, the anteroposterior and mediolateral axes of the femur, bone marrow and the thickness of the femoral cortices.

RESULTS

Total bone CSA, total cortical CSA and bone marrow CSA were higher in the XLH group than in the control group (p<0.05). The mid-lateral diameters of the femur and bone marrow were more elongated than those of the control group (p<0.001). Only the anterior cortex was thinned in the XLH group (p=0.001), while there was no difference with the control group for the posterior, medial and lateral cortices. The total percentage of FIBM was 72.81% [±3.95] and 77.4% [±5.52] for the XLH and control groups respectively (p<0.001).

DISCUSSION

The increase in bone mass in the XLH population reflects an adaptation of bone tissue to the bone deformities present in this pathology. The decrease in FIBM indicates a lower risk of osteoporosis in the XLH population and may constitute a new monitoring parameter in this pathology.

LEVEL OF STUDY

III; Case-control study.

People living with HIV have low trabecular bone mineral density, high bone marrow adiposity, and poor trabecular bone microarchitecture at the proximal femur

People living with HIV (PLWH) have increased risk of osteoporosis and fractures. We assessed the proximal femur of PLWH and age-matched seronegative controls using quantitative computed tomography and magnetic resonance imaging. Results suggest that the trabecular compartment is compromised at fracture-prone regions in the proximal femur of PLWH.

INTRODUCTION

People living with HIV (PLWH) have increased risk of osteoporosis and fractures. However, studies assessing the main determinants of bone strength in the proximal femur exclude this vulnerable population. We assessed the proximal femur of 40 PLWH and 26 age-matched seronegative controls using quantitative computed tomography and magnetic resonance imaging.

METHODS

We examined cortical volumetric bone mineral density (Ct.vBMD), trabecular vBMD (Tb.vBMD), cortical thickness (Ct.Th), bone marrow adiposity (BMA), and trabecular number, separation, and bone volume fraction. Parametric comparisons between the two groups were made for the femoral head, femoral neck, trochanter, and total hip using linear regression adjusting for several covariates, including metrics of body composition. In addition, we investigated the associations of BMA with Tb.vBMD and trabecular microarchitecture with Spearman's rank partial correlations.

RESULTS

PLWH had lower Tb.vBMD and deteriorated trabecular microarchitecture in the femoral neck, trochanter and total hip, and elevated BMA in the femoral head, femoral neck, and total hip. Ct.vBMD and Ct.Th were not significantly different between the two groups. BMA was significantly associated with lower Tb.vBMD and deteriorated trabecular microarchitecture in both groups albeit at different femoral regions.

CONCLUSIONS

Our findings suggest that the trabecular, and not the cortical, compartment is compromised in the proximal femur of PLWH. The observed impairments in fracture-prone regions in PLWH indicate lower femoral strength and suggest higher fracture risk. The inverse associations of BMA with trabecular bone density and microarchitecture quality agree with findings at other anatomic sites and in other populations, suggesting that excess BMA possibly due to a switch from the osteoblast to the adipocyte lineage may be implicated in the pathogenesis of bone fragility at the femur in PLWH.

Osteal macrophages support osteoclast-mediated resorption and contribute to bone pathology in a postmenopausal osteoporosis mouse model

Osteal macrophages (osteomacs) support osteoblast function and promote bone anabolism, but their contribution to osteoporosis has not been explored. Although mouse ovariectomy (OVX) models have been repeatedly used, variation in strain, experimental design and assessment modalities have contributed to no single model being confirmed as comprehensively replicating the full gamut of osteoporosis pathological manifestations. We validated an OVX model in adult C3H/HeJ mice and demonstrated that it presents with human postmenopausal osteoporosis features with reduced bone volume in axial and appendicular bone and bone loss in both trabecular and cortical bone including increased cortical porosity. Bone loss was associated with increased osteoclasts on trabecular and endocortical bone and decreased osteoblasts on trabecular bone. Importantly, this OVX model was characterized by delayed fracture healing. Using this validated model, we demonstrated that osteomacs are increased post-OVX on both trabecular and endocortical bone. Dual F4/80 (pan-macrophage marker) and tartrate-resistant acid phosphatase (TRAP) staining revealed osteomacs frequently located near TRAP⁺ osteoclasts and contained TRAP⁺ intracellular vesicles. Using an in vivo inducible macrophage depletion model that does not simultaneously deplete osteoclasts, we observed that osteomac loss was associated with elevated extracellular TRAP in bone marrow interstitium and increased serum TRAP. Using in vitro high-resolution confocal imaging of mixed osteoclast-macrophage cultures on bone substrate, we observed macrophages juxtaposed to osteoclast basolateral functional secretory domains scavenging degraded bone byproducts. These data demonstrate a role for osteomacs in supporting osteoclastic bone resorption through phagocytosis and sequestration of resorption byproducts. Overall, our data expose a novel role for osteomacs in supporting osteoclast function and provide the first evidence of their involvement in osteoporosis pathogenesis. © 2021 American Society for Bone and Mineral Research (ASBMR).

The Effect of Roux-en-Y Gastric Bypass on Bone Marrow Adipose Tissue and Bone Mineral Density in Postmenopausal, Nondiabetic Women

OBJECTIVES

This study aimed to determine the effect of bariatric surgery-induced weight loss on bone marrow adipose tissue (BMAT) and bone mineral density (BMD) in postmenopausal, nondiabetic women.

METHODS

A total of 14 postmenopausal, nondiabetic women with obesity who were scheduled for laparoscopic Roux-en-Y gastric bypass surgery (RYGB) were included in this study. Vertebral bone marrow fat signal fraction was determined by quantitative chemical shift magnetic resonance imaging, and vertebral volumetric BMD (vBMD) was determined by quantitative computed tomography before surgery and 3 and 12 months after surgery. Data were analyzed by linear mixed model.

RESULTS

Body weight [mean (SD)] decreased after surgery from 108 (13) kg at baseline to 89 (12) kg at 3 months and 74 (11) kg at 12 months (P < 0.001). BMAT decreased after surgery from 51% (8%) at baseline to 50% (8%) at 3 months and 46% (7%) at 12 months (P = 0.004). vBMD decreased after surgery from 101 (26) mg/cm³ at baseline to 94 (28) mg/cm³ at 3 months (P = 0.003) and 94 (28) mg/cm³ at 12 months (P = 0.035). Changes in BMAT and vBMD were not correlated (ρ = -0.10 and P = 0.75). Calcium and vitamin D concentrations did not change after surgery.

CONCLUSIONS

RYGB decreases both BMAT (after 12 months) and vBMD (both after 3 months and 12 months) in postmenopausal, nondiabetic women. Changes in BMAT and vBMD were not correlated. These findings suggest that BMAT does not contribute to bone loss following RYGB.

Fat and bone: the multiperspective analysis of a close relationship

The study of bone has for many years been focused on the study of its mineralized component, and one of the main objects of study as radiology developed as a medical specialty. The assessment has until recently been almost limited to its role as principal component of the scaffolding of the human body. Bone is a very active tissue, in continuous cross-talk with other organs and systems, with functions that are endocrine and paracrine and that have an important involvement in metabolism, ageing and health in general. Bone is also the continent for the bone marrow, in the form of "yellow marrow" (mainly adipocytes) or "red marrow" (hematopoietic cells and adipocytes). Recently, numerous studies have focused on these adipocytes contained in the bone marrow, often referred to as marrow adipose tissue (MAT). Bone marrow adipocytes do not only work as storage tissue, but are also endocrine and paracrine cells, with the potential to contribute to local bone homeostasis and systemic metabolism. Many metabolic disorders (osteoporosis, obesity, diabetes) have a complex and still not well-established relationship with MAT. The development of imaging methods, in particular the development of cross-sectional imaging has helped us to understand how much more laid beyond our classical way to look at bone. The impact on the mineralized component of bone in some cases (e.g., osteoporosis) is well-established, and has been extensively analyzed and quantified through different radiological methods. The application of advanced magnetic resonance techniques has unlocked the possibility to access the detailed study, characterization and quantification of the bone marrow components in a non-invasive way. In this review, we will address what is the evidence on the physiological role of MAT in normal skeletal health (interaction with the other bone components), during the process of normal aging and in the context of some metabolic disorders, highlighting the role that imaging methods play in helping with quantification and diagnosis.

The relationship between bone marrow adipose tissue and bone metabolism in postmenopausal osteoporosis

Postmenopausal osteoporosis (PMOP) is a prevalent skeletal disorder associated with menopause-related estrogen withdrawal. PMOP is characterized by low bone mass, deterioration of the skeletal microarchitecture, and subsequent increased susceptibility to fragility fractures, thus contributing to disability and mortality. Accumulating evidence indicates that abnormal expansion of marrow adipose tissue (MAT) plays a crucial role in the onset and progression of PMOP, in part because both bone marrow adipocytes and osteoblasts share a common ancestor lineage. The cohabitation of MAT adipocytes, mesenchymal stromal cells, hematopoietic cells, osteoblasts and osteoclasts in the bone marrow creates a microenvironment that permits adipocytes to act directly on other cell types in the marrow. Furthermore, MAT, which is recognized as an endocrine organ, regulates bone remodeling through the secretion of adipokines and cytokines. Although an enhanced MAT volume is linked to low bone mass and fractures in PMOP, the detailed interactions between MAT and bone metabolism remain largely unknown. In this review, we examine the possible mechanisms of MAT expansion under estrogen withdrawal and further summarize emerging findings regarding the pathological roles of MAT in bone remodeling. We also discuss the current therapies targeting MAT in osteoporosis. A comprehensive understanding of the relationship between MAT expansion and bone metabolism in estrogen deficiency conditions will provide new insights into potential therapeutic targets for PMOP.

Vertebral bone marrow fat fraction changes in postmenopausal women with breast cancer receiving combined aromatase inhibitor and bisphosphonate therapy

Background

Quantification of vertebral bone marrow (VBM) water–fat composition has been proposed as advanced imaging biomarker for osteoporosis. Estrogen deficiency is the primary reason for trabecular bone loss in postmenopausal women. By reducing estrogen levels aromatase inhibitors (AI) as part of breast cancer therapy promote bone loss. Bisphosphonates (BP) are recommended to counteract this adverse drug effect. The purpose of our study was to quantify VBM proton density fat fraction (PDFF) changes at the lumbar spine using chemical shift encoding-based water-fat MRI (CSE-MRI) and bone mineral density (BMD) changes using dual energy X-ray absorptiometry (DXA) related to AI and BP treatment over a 12-month period.

Methods

Twenty seven postmenopausal breast cancer patients receiving AI therapy were recruited for this study. 22 subjects completed the 12-month study. 14 subjects received AI and BP (AI+BP), 8 subjects received AI without BP (AI-BP).

All subjects underwent 3 T MRI. An eight-echo 3D spoiled gradient-echo sequence was used for CSE-based water-fat separation at the lumbar spine to generate PDFF maps. After manual segmentation of the vertebral bodies L1-L5 PDFF values were extracted for each vertebra and averaged for each subject.

All subjects underwent DXA of the lumbar spine measuring the average BMD of L1-L4.

Results

Baseline age, PDFF and BMD showed no significant difference between the two groups (p > 0.05). There was a relative longitudinal increase in mean PDFF (∆rel_PDFF) in both groups (AI+BP: 5.93%; AI-BP: 3.11%) which was only significant (p = 0.006) in the AI+BP group. ∆rel_PDFF showed no significant difference between the two groups (p > 0.05). There was no significant longitudinal change in BMD (p > 0.05).

Conclusions

Over a 12-month period, VBM PDFF assessed with CSE-MRI significantly increased in subjects receiving AI and BP. The present results contradict previous results regarding the effect of only BP therapy on bone marrow fat content quantified by magnetic resonance spectroscopy and bone biopsies. Future longer-term follow-up studies are needed to further characterize the effects of combined AI and BP therapy.

Du-Zhong (Eucommia ulmoides Oliv.) Cortex Extract Alleviates Lead Acetate-Induced Bone Loss in Rats

The purpose of this study was to evaluate the protective effect of Du-Zhong cortex extract (DZCE) on lead acetate-induced bone loss in rats. Forty female Sprague-Dawley rats were randomly divided into four groups: group I (control) was provided with distilled water. Group II (PbAc) received 500 ppm lead acetate in drinking water for 60 days. Group III (PbAc+DZCE) received 500 ppm lead acetate in drinking water, and given intragastric DZCE (100 mg/kg body weight) for 60 days. Group IV (DZCE) was given intragastric DZCE (100 mg/kg body weight) for 60 days. The bone mineral density, serum biochemical markers, bone histomorphology, and bone marrow adipocyte parameters were analyzed using dual-energy X-ray absorptiometry, biochemistry, histomorphometry, and histopathology, respectively. The results showed that the lumbar spine and femur bone mineral density was significantly decreased in PbAc group compared with the control (P < 0.05); however, this decrease was inhibited by the intake of Du-Zhong cortex extract (P < 0.05, vs. PbAc group; P > 0.05, vs. control and DZCE group). Serum calcium and serum phosphorus in the PbAc+DZCE group were greater than that in the PbAc group (P < 0.05). The PbAc group had higher ALP, osteocalcin, and RANKL than the control group (P < 0.01), and they were significantly lower in the PbAc+DZCE group compared with the PbAc group. There were no significant differences of ALP, osteocalcin, and RANKL among the PbAc+DZCE, control, and DZCE groups (P > 0.05). Serum OPG and OPG/RANKL ration were significantly higher in the PbAc+DZCE group than that in the PbAc group (P < 0.05). The bone histomorphometric analyses showed that bone volume and trabecular thickness in the femoral trabecular bone were significantly lower in the PbAc group than that in the control group, but those were restored in the PbAc+DZCE groups. The bone marrow adipocyte number, percent adipocyte volume per tissue volume (AV/TV), and mean adipocyte diameter were significantly increased in the PbAc group compared to the control (P < 0.01), and those were restored in the PbAc+DZCE group. The differences of those parameters between PbAc+DZCE, DZCE, and the control group were not significant. The results above indicate that the Du-Zhong cortex extract has protective effects on both stimulation of bone formation and suppression of bone resorption in lead-exposed rats, therefore, Du-Zhong cortex extract has the potential to prevent or treat osteoporosis resulting from lead expose.

Minimally effective concentration of zoledronic acid to suppress osteoclasts in vitro

Zoledronic acid is regarded as the most potent bisphosphonate and is widely used in patients with osteoporosis; however, its side effects, including acute-phase reactions, gastrointestinal complaints, renal dysfunction and bisphosphonate-associated osteonecrosis impair the safety and quality of life of patients. The present study was designed to determine the minimal effective concentration of zoledronic acid through testing the dose-dependent effects of zoledronic acid on osteoclast suppression. A primary culture of bone marrow mononuclear cells obtained from C57 mice (age, 6 weeks) was established and induced to form osteoclasts. The number of multinuclear cells was determined by tartrate-resistant acid phosphatase staining and compared among cultured marrow cells treated with different concentrations of zoledronic acid. Furthermore, the cellular properties, including adhesion, migration and bone resorption, were compared at the minimal effective concentration. At a concentration of 1×10⁻⁶ mol/l, zoledronic acid significantly inhibited the formation of osteoclasts. This inhibitory effect was further enhanced at the concentration of 1×10⁻⁵ mol/l. However, the inhibitory effect of zoledronic acid tapered at the concentration of 1×10⁻⁴ mol/l and there was no further dose-dependent increase. In addition, the concentration of 1×10⁻⁶ mol/l was sufficient to alter cellular functions, including cell adhesion, migration and bone resorption. In conclusion, zoledronic acid was effective in reducing osteoclast formation and suppressing cellular functions. The minimal effective concentration of zoledronic acid in vitro was 1 µmol/l. Based on these results, a comparable dosage should be explored in clinical applications.

A network meta-analysis on the short-term efficacy and adverse events of different anti-osteoporosis drugs for the treatment of postmenopausal osteoporosis

A network meta-analysis was conducted to compare the short-term efficacy and adverse events of different drugs for the treatment of postmenopausal osteoporosis (PMO), providing a more effective treatment for PMO. We initially searched through various databases like PubMed, Cochrane Library, and EMBASE from inception till October 2016. All randomized controlled trials (RCTs) of drugs for the treatment of PMO were included for direct and indirect comparison. A combination of direct and indirect evidence of different inhibitors of anti-diabetic drugs for treatment of PMO were considered for calculating the weighted mean difference (WMD) value or odd ratio (OR) value and to draw surface under the cumulative ranking (SUCRA) curves. Twenty-seven RCTs were ultimately incorporated into this network meta-analysis comprising of 48 200 patients suffering from PMO. The network meta-analysis revealed that compared with placebo, alendronate had better efficacy on improving bone mineral density (BMD) at lumbar spine, femoral neck, and total hip. Risedronate and raloxifene had relatively lower incidence of new vertebral fractures. The SUCRA analysis showed that alendronate had better efficacy on improving BMD, risedronate could significantly decrease the incidence of fresh fracture and bazedoxifene was relatively safe. The available evidence suggested that alendronate and risedronate might be the superior choices for the treatment of PMO, while bazedoxifene was a comparatively safer option for patients.

Clinical implications of bone marrow adiposity

Marrow adipocytes, collectively termed marrow adipose tissue (MAT), reside in the bone marrow in close contact to bone cells and haematopoietic cells. Marrow adipocytes arise from the mesenchymal stem cell and share their origin with the osteoblast. Shifts in the lineage allocation of the mesenchymal stromal cell could potentially explain the association between increased MAT and increased fracture risk in diseases such as postmenopausal osteoporosis, anorexia nervosa and diabetes. Functionally, marrow adipocytes secrete adipokines, such as adiponectin, and cytokines, such as RANK ligand and stem cell factor. These mediators can influence both bone remodelling and haematopoiesis by promoting bone resorption and haematopoietic recovery following chemotherapy. In addition, marrow adipocytes can secrete free fatty acids, acting as a energy supply for bone and haematopoietic cells. However, this induced lipolysis is also used by neoplastic cells to promote survival and proliferation. Therefore, MAT could represent a new therapeutic target for multiple diseases from osteoporosis to leukaemia, although the exact characteristics and role of the marrow adipocyte in health and diseases remain to be determined.

Zoledronic acid, an FPPS inhibitor, ameliorates liver steatosis through inhibiting hepatic de novo lipogenesis

Currently, there is no standard therapy for non-alcoholic fatty liver disease (NAFLD), and statins have been developed as a first-line pharmaceutical therapeutic option for NAFLD-associated dyslipidemia. However, prolonged statins therapy has side effects, as statins inhibit HMG-CoA reductase, an enzyme at the very beginning of the mevalonate pathway. Here, we found that zoledronic acid (ZA), an inhibitor of farnesyl diphosphate synthase in the downstream mevalonate pathway, could attenuate hepatic lipid accumulation and improve liver injury in both high-fat diet-induced C57BL/6J mice and ob/ob mice. Moreover, the hepatic lipid metabolism was largely inhibited after ZA administration in high-fat diet-induced obese mice. Mechanically, ZA inhibited SREBP-1c-mediated de novo lipogenesis through suppressing RhoA activation via decreasing farnesyl diphosphate and geranylgeranyl diphosphate levels. In conclusion, our data provide a novel application of ZA in improving hepatic steatosis.

Bone-Fat Interaction

Marrow adipose tissue (MAT) is a recently identified endocrine organ capable of modulating a host of responses. Given its intimate proximity to the bone microenvironment, the impact marrow adipocytes exert on bone has attracted much interest and scientific inquiry. Although many questions and controversies remain about marrow adipocytes, multiple conditions/disease states in which alterations occur have provided clues about their function. The consensus is that MAT is associated inversely with bone density and quality. While further investigation is warranted, MAT has clearly been demonstrated as an active dynamic depot that contributes to bone turnover and overall metabolic homeostasis.