Roles of Olfactomedin 1 in Muscle and Bone Alterations Induced by Gravity Change in Mice.

Microgravity causes both muscle and bone loss. Although we previously revealed that gravity change influences muscle and bone through the vestibular system in mice, its detailed mechanism has not been elucidated. In this study, we investigated the roles of olfactomedin 1 (OLFM1), whose expression was upregulated during hypergravity in the soleus muscle, in mouse bone cells. Vestibular lesion significantly blunted OLFM1 expression in the soleus muscle and serum OLFM1 levels enhanced by hypergravity in mice. Moreover, a phosphatidylinositol 3-kinase inhibitor antagonized shear stress-enhanced OLFM1 expression in C2C12 myotubes. As for the effects of OLFM1 on bone cells, OLFM1 inhibited osteoclast formation from mouse bone marrow cells and mouse preosteoclastic RAW264.7 cells. Moreover, OLFM1 suppressed RANKL expression and nuclear factor-κB signaling in mouse osteoblasts. Serum OLFM1 levels were positively related to OLFM1 mRNA levels in the soleus muscle and trabecular bone mineral density of mice. In conclusion, we first showed that OLFM1 suppresses osteoclast formation and RANKL expression in mouse cells.

microRNA-143-3p regulates odontogenic differentiation of human dental pulp stem cells through regulation of the osteoprotegerin-RANK ligand pathway by targeting RANK.

NEW FINDINGS: What is the central question of this study? What is the role of miR-143-3p during human dental pulp stem cell (hDPSC) differentiation. What is the main finding and its importance? miR-143-3p negatively regulates receptor activator of nuclear factor-κB (RANK). RANK ligand (RANKL) binds to RANK and stimulates the development of osteoclasts. Osteoprotegerin (OPG) inhibits the interaction between RANK and RANKL. The OPG-RANKL signalling pathway regulates odontogenic differentiation of hDPSCs. ABSTRACT: Human dental pulp stem cells (hDPSCs) are capable of differentiating into odontoblast-like cells, which secrete reparative dentin after injury, in which the role of microRNA-143-3p (miR-143-3p) has been identified. Therefore, we investigated the mechanism by which miR-143-3p influences odontoblastic differentiation of hDPSCs. The relationship between miR-143-3p and receptor activator of nuclear factor-κB (RANK) was initially identified by bioinformatics prediction and further verified by dual luciferase reporter gene assay. Gain- and loss-of-function analysis with miR-143-3p mimic and miR-143-3p inhibitor was subsequently conducted. Dentin sialophosphoprotein (DSPP), bone sialoprotein (BSP), alkaline phosphatase (ALP), osteocalcin (OCN) and osteopontin (OPN) mRNA levels were then evaluated by RT-qPCR. Osteoprotegerin (OPG), RANK ligand (RANKL), nuclear factor-κB (NF-κB) p65 protein levels and the extent of NF-κB p65 phosphorylation were examined by western blot analysis. Alizarin red staining was performed to assess the mineralization of hDPSCs. Cell apoptosis and cell cycle distribution were determined using flow cytometry. During odontoblastic differentiation of hDPSC, miR-143-3p had high expression, but RANK expression was low. miR-143-3p was found to target RANK, and its inhibition enhanced mineralization and hDPSC apoptosis, while blocking cell cycle entry. At the same time, miR-143-3p inhibition elevated the extent of NF-κB p65 phosphorylation, as well as the expression of RANK, RANKL, DSPP, BSP, ALP, OCN and OPN, while decreasing the OPG level. Silencing RANK had opposite effects on these markers. miR-143-3p regulates odontoblastic differentiation of hDPSCs via the OPG-RANKL pathway that targets RANK. The elucidation of the mechanisms of odontogenic differentiation of hDPSCs may contribute to the development of effective dental pulp repair therapies for the clinical setting.

Acute ketamine administration corrects abnormal inflammatory bone markers in major depressive disorder.

Patients with major depressive disorder (MDD) have clinically relevant, significant decreases in bone mineral density (BMD). We sought to determine if predictive markers of bone inflammation-the osteoprotegerin (OPG)-RANK-RANKL system or osteopontin (OPN)-play a role in the bone abnormalities associated with MDD and, if so, whether ketamine treatment corrected the abnormalities. The OPG-RANK-RANKL system plays the principal role in determining the balance between bone resorption and bone formation. RANKL is the osteoclast differentiating factor and diminishes BMD. OPG is a decoy receptor for RANKL, thereby increasing BMD. OPN is the bone glue that acts as a scaffold between bone tissues matrix composition to bind them together and is an important component of bone strength and fracture resistance. Twenty-eight medication-free inpatients with treatment-resistant MDD and 16 healthy controls (HCs) participated in the study. Peripheral bone marker levels and their responses to IV ketamine infusion in MDD patients and HCs were measured at four time points: at baseline, and post-infusion at 230 min, Day 1, and Day 3. Patients with MDD had significant decreases in baseline OPG/RANKL ratio and in plasma OPN levels. Ketamine significantly increased both the OPG/RANKL ratio and plasma OPN levels, and significantly decreased RANKL levels. Bone marker levels in HCs remained unaltered. We conclude that the OPG-RANK-RANKL system and the OPN system play important roles in the serious bone abnormalities associated with MDD. These data suggest that, in addition to its antidepressant effects, ketamine also has a salutary effect on a major medical complication of depressive illness.

Dynamics of Bone Cell Interactions and Differential Responses to PTH and Antibody-Based Therapies.

We propose a mathematical model describing the dynamics of osteoblasts and osteoclasts in bone remodeling. The goal of this work is to develop an integrated modeling framework for bone remodeling and bone cell signaling dynamics that could be used to explore qualitatively combination treatments for osteoporosis in humans. The model has been calibrated using 57 checks from the literature. Specific global optimization methods based on qualitative objectives have been developed to perform the model calibration. We also added pharmacokinetics representations of three drugs to the model, which are teriparatide (PTH(1-34)), denosumab (a RANKL antibody) and romosozumab (a sclerostin antibody), achieving excellent goodness-of-fit of human clinical data. The model reproduces the paradoxical effects of PTH on the bone mass, where continuous administration of PTH results in bone loss but intermittent administration of PTH leads to bone gain, thus proposing an explanation of this phenomenon. We used the model to simulate different categories of osteoporosis. The main attributes of each disease are qualitatively well captured by the model, for example changes in bone turnover in the disease states. We explored dosing regimens for each disease based on the combination of denosumab and romosozumab, identifying adequate ratios and doses of both drugs for subpopulations of patients in function of categories of osteoporosis and the degree of severity of the disease.

Taurine Chloramine Inhibits Osteoclastic Differentiation and Osteoclast Marker Expression in RAW 264.7 Cells.

Taurine is an abundant sulfur-containing amino acid in myeloid cells. It undergoes halogenation in activated phagocytes and is converted to taurine chloramine (TauCl) and taurine bromamine. Bone homeostasis is mediated by the balance between bone-forming osteoblasts and bone-resorbing osteoclasts. Osteoclasts are bone-resorbing multinucleated cells differentiated from monocyte/macrophage precursor cells in response to receptor activator of NF-κB ligand (RANKL). In this study, we investigated the effect of TauCl on RANKL-induced osteoclastogenesis from RAW 264.7 macrophages. TauCl inhibited the formation of multi-nucleated osteoclast and the activity of tartrate-resistant acid phosphatase (TRAP). TauCl decreased the mRNA expression of osteoclast markers, such as TRAP, cathepsin K, and calcitonin receptor. TauCl also inhibited expression of the transcription factors, c-Fos and nuclear factor of activated T cells, which are important for osteoclast differentiation. These results suggest that TauCl might be used as a therapeutic agent to treat bone diseases associated with excessive bone resorption.

Oleanolic acid exerts bone protective effects in ovariectomized mice by inhibiting osteoclastogenesis.

Postmenopausal osteoporosis (POP) is quite prevalent and many new drugs are under development to obtain better therapeutic outcomes. Oleanolic acid (OA) has been reported to prevent bone loss in ovariectomized (OVX) rats by stimulating osteoblastogenesis. One previous study has demonstrated that acetate of OA suppressed lipopolysaccharides (LPS)-induced bone loss in mice. However, the role of OA in the receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated osteoclastogenesis is still not elucidated. Here we show that OA dose-dependently inhibits RANKL-mediated osteoclastogenesis and the formation of functional osteoclasts without impairing the viability and osteoclastic potential in bone marrow macrophages (BMMs). Moreover, OA administration attenuates bone loss in OVX mice by inhibiting osteoclast's densities. Mechanistically, OA does not affect RANKL-induced activation of the NF-кB, JNK, p38, ERK and Akt pathways, but inhibits the expression of the nuclear factor of activated T-cells c1(NFATc1) and c-Fos. Moreover, OA significantly suppresses the expression of RANKL-activated osteoclast genes encoding matrix metalloproteinase 9 (MMP9), Cathepsin K(Ctsk), tartrate-resistant acid phosphatase (TRAP) and carbonic anhydrase II (Car2). This work has elucidated the molecular mechanism of OA in RANKL-mediated osteoclastogenesis and revealed the promising potential of OA to be further developed as a new drug to prevent and treat POP.

RANKL Reduces Body Weight and Food Intake via the Modulation of Hypothalamic NPY/CART Expression.

The receptor activator of nuclear factor-κB ligand (RANKL) modulates energy metabolism. However, how RANKL regulates energy homeostasis is still not clear. This study aims to investigate the central mechanisms by which central administration of RANKL inhibits food intake and causes weight loss in mice. We carried out a systematic and in-depth analysis of the neuronal pathways by which RANKL mediates catabolic effects. After intracerebroventricle (i.c.v.) injection of RANKL, the expression of neuropeptide Y (NPY) mRNA in the Arc was significantly decreased, while the CART mRNA expression dramatically increased in the Arc and DMH. However, the agouti-related protein (AgRP) and pro-opiomelanocortin (POMC) mRNA had no significant changes compared with control groups. Together, the results suggest that central administration of RANKL reduces food intake and causes weight loss via modulating the hypothalamic NPY/CART pathways.

RANKL, Ephrin-Eph and Wnt10b are key intercellular communication molecules regulating bone remodeling in autologous transplanted goldfish scales.

This study aimed to investigate the precise data of gene expression, functions, and chronological relationships amongst communication molecules involved in the bone remodeling process with an in vivo model using autologous transplanted scales of goldfish. Autotransplantation of methanol-fixed cell-free scales triggers scale resorption and regeneration, as well as helps elucidate the process of bone remodeling. We investigated osteoclastic markers, osteoblastic markers, and gene expressions of communicating molecules (RANKL, ephrinB2, EphB4, EphA4, Wnt10b) by qPCR, in situ hybridization for Wnt10b, and immunohistochemistry for EphrinB2 and EphA4 proteins to elucidate the bone remodeling process. Furthermore, functional inhibition experiments for the signaling of ephrinB2/Eph, ephrin/EphA4, and Wnt10b using specific antibodies, revealed that these proteins are involved in key signaling pathways promoting normal bone remodeling. Our data suggests that the remodeling process comprises of two successive phases. In the first absorption phase, differentiation of osteoclast progenitors by RANKL is followed by the bone absorption by mature, active osteoclasts, with the simultaneous induction of osteoblast progenitors by multinucleated osteoclast-derived Wnt10b, and proliferation of osteoblast precursors by ehprinB2/EphB4 signaling. Subsequently, during the second formation phase, termination of bone resorption by synergistic cooperation occurs, with downregulation of RANKL expression in activated osteoblasts and Ephrin/EphA4-mediated mutual inhibition between neighboring multinucleated osteoclasts, along with simultaneous activation of osteoblasts via forward and reverse EphrinB2/EphB4 signaling between neighboring osteoblasts. In addition, the present study shows that autologous transplantation of methanol-fixed cell-free scale is an ideal in vivo model to study bone remodeling.

IL-15 and RANKL Play a Synergistically Important Role in Osteoclastogenesis.

Interleukin-15 (IL-15), a cytokine secreted by several cell types, has important physiological roles in the activity, proliferation, and viability of immune cells. It has both chemoattractant and proinflammatory properties, and may promote bone destruction. A previous study has shown that IL-15 alone exerts no effect on osteoclastogenesis. Therefore, the current study addressed the synergistic effect of IL-15 on osteoclast formation using RAW264.7 (RAW) cells by co-stimulation with receptor activator of nuclear factor (NF)-κB ligand (RANKL) that has a major role in osteoclastogenesis involving the pathogenesis of rheumatoid arthritis and periodontal disease. Co-stimulation of RAW cells by IL-15 and RANKL significantly increased the gene expression of osteoclast differentiation and osteoclastogenesis markers compared with stimulation by RANKL or IL-15 independently as evaluated by tartrate-resistant acid phosphate-positive cell numbers, the fusion index, a pit formation assay with Alizarin red staining (calcification estimation), and quantitative polymerase chain reaction. Phosphorylation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase, p38 mitogen-activated protein kinase, and NF-κB was significantly increased by RANKL and IL-15 (P < 0.05) compared with RANKL alone. In addition, these differentiation activities induced by RANKL and IL-15 were comparatively suppressed by inhibition of ERK, suggesting that this synergistic effect on osteoclastogenesis is mainly mediated by ERK. Taken together, our results demonstrate that IL-15 and RANKL induce osteoclastogenesis synergistically, and IL-15 might play a novel and major role in destructive inflammatory bone diseases. J. Cell. Biochem. 118: 739-747, 2017. © 2016 Wiley Periodicals, Inc.

Porphyromonas gingivalis Stimulates Bone Resorption by Enhancing RANKL (Receptor Activator of NF-κB Ligand) through Activation of Toll-like Receptor 2 in Osteoblasts.

Periodontitis has been associated with rheumatoid arthritis. In experimental arthritis, concomitant periodontitis caused by oral infection with Porphyromonas gingivalis enhances articular bone loss. The aim of this study was to investigate how lipopolysaccharide (LPS) from P. gingivalis stimulates bone resorption. The effects by LPS P. gingivalis and four other TLR2 ligands on bone resorption, osteoclast formation, and gene expression in wild type and Tlr2-deficient mice were assessed in ex vivo cultures of mouse parietal bones and in an in vivo model in which TLR2 agonists were injected subcutaneously over the skull bones. LPS P. gingivalis stimulated mineral release and matrix degradation in the parietal bone organ cultures by increasing differentiation and formation of mature osteoclasts, a response dependent on increased RANKL (receptor activator of NF-κB ligand). LPS P. gingivalis stimulated RANKL in parietal osteoblasts dependent on the presence of TLR2 and through a MyD88 and NF-κB-mediated mechanism. Similarly, the TLR2 agonists HKLM, FSL1, Pam2, and Pam3 stimulated RANKL in osteoblasts and parietal bone resorption. LPS P. gingivalis and Pam2 robustly enhanced osteoclast formation in periosteal/endosteal cell cultures by increasing RANKL. LPS P. gingivalis and Pam2 also up-regulated RANKL and osteoclastic genes in vivo, resulting in an increased number of periosteal osteoclasts and immense bone loss in wild type mice but not in Tlr2-deficient mice. These data demonstrate that LPS P. gingivalis stimulates periosteal osteoclast formation and bone resorption by stimulating RANKL in osteoblasts via TLR2. This effect might be important for periodontal bone loss and for the enhanced bone loss seen in rheumatoid arthritis patients with concomitant periodontal disease.

IL-1R/TLR2 through MyD88 Divergently Modulates Osteoclastogenesis through Regulation of Nuclear Factor of Activated T Cells c1 (NFATc1) and B Lymphocyte-induced Maturation Protein-1 (Blimp1).

Toll-like receptors (TLR) and the receptor for interleukin-1 (IL-1R) signaling play an important role in bacteria-mediated bone loss diseases including periodontitis, rheumatoid arthritis, and osteomyelitis. Recent studies have shown that TLR ligands inhibit the receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation from un-committed osteoclast precursors, whereas IL-1 potentiates RANKL-induced osteoclast formation. However, IL-1R and TLR belong to the same IL-1R/TLR superfamily, and activate similar intracellular signaling pathways. Here, we investigate the molecular mechanisms underlying the distinct effects of IL-1 and Porphyromonas gingivalis lipopolysaccharide (LPS-PG) on RANKL-induced osteoclast formation. Our results show that LPS-PG and IL-1 differentially regulate RANKL-induced activation of osteoclast genes encoding Car2, Ctsk, MMP9, and TRAP, as well as expression of NFATc1, a master transcription factor of osteoclastogenesis. Regulation of osteoclast genes and NFATc1 by LPS-PG and IL-1 is dependent on MyD88, an important signaling adaptor for both TLR and IL-1R family members. Furthermore, LPS-PG and IL-1 differentially regulate RANKL-costimulatory receptor OSCAR (osteoclast-associated receptor) expression and Ca(2+) oscillations induced by RANKL. Moreover, LPS-PG completely abrogates RANKL-induced gene expression of B lymphocyte-induced maturation protein-1 (Blimp1), a global transcriptional repressor of anti-osteoclastogenic genes encoding Bcl6, IRF8, and MafB. However, IL-1 enhances RANKL-induced blimp1 gene expression but suppresses the gene expression of bcl6, irf8, and mafb. Our study reveals the involvement of multiple signaling molecules in the differential regulation of RANKL-induced osteoclastogenesis by TLR2 and IL-1 signaling. Understanding the signaling cross-talk among TLR, IL-1R, and RANK is critical for identifying therapeutic strategies to control bacteria-mediated bone loss.

Mutation in Osteoactivin Promotes Receptor Activator of NFκB Ligand (RANKL)-mediated Osteoclast Differentiation and Survival but Inhibits Osteoclast Function.

We previously reported on the importance of osteoactivin (OA/Gpnmb) in osteogenesis. In this study, we examined the role of OA in osteoclastogenesis, using mice with a nonsense mutation in the Gpnmb gene (D2J) and wild-type controls (D2J/Gpnmb(+)). In these D2J mice, micro-computed tomography and histomorphometric analyses revealed increased cortical thickness, whereas total porosity and eroded surface were significantly reduced in D2J mice compared with wild-type controls, and these results were corroborated by lower serum levels of CTX-1. Contrary to these observations and counterintuitively, temporal gene expression analyses supported up-regulated osteoclastogenesis in D2J mice and increased osteoclast differentiation rates ex vivo, marked by increased number and size. The finding that MAPK was activated in early differentiating and mature D2J osteoclasts and that survival of D2J osteoclasts was enhanced and mediated by activation of the AKT-GSK3ß pathway supports this observation. Furthermore, this was abrogated by the addition of recombinant OA to cultures, which restored osteoclastogenesis to wild-type levels. Moreover, mix and match co-cultures demonstrated an induction of osteoclastogenesis in D2J osteoblasts co-cultured with osteoclasts of D2J or wild-type. Last, in functional osteo-assays, we show that bone resorption activity of D2J osteoclasts is dramatically reduced, and these osteoclasts present an abnormal ruffled border over the bone surface. Collectively, these data support a model whereby OA/Gpnmb acts as a negative regulator of osteoclast differentiation and survival but not function by inhibiting the ERK/AKT signaling pathways.

Proinflammatory M1 Macrophages Inhibit RANKL-Induced Osteoclastogenesis.

In response to a defined panel of stimuli, immature macrophages can be classified into two major phenotypes: proinflammatory (M1) and anti-inflammatory (M2). Although both phenotypes have been implicated in several chronic inflammatory diseases, their direct role in bone resorption remains unclear. The present study investigated the possible effects of M1 and M2 macrophages on RANKL-induced osteoclastogenesis. In osteoclastogenesis assays using RAW264.7 cells or bone marrow cells as osteoclast precursors, addition of M1 macrophages significantly suppressed RANKL-induced osteoclastogenesis compared to nonstimulated conditions (M0), addition of M2 macrophages, or no macrophage addition (P < 0.05), suggesting that M1 macrophages can downregulate osteoclastogenesis. This effect was maintained when direct contact between M1 and osteoclast precursors was interrupted by cell culture insertion, indicating engagement of soluble factors released from M1. M1 macrophages developed from interferon gamma (IFN-γ) knockout (IFN-γ-KO) mice lost the ability to downregulate osteoclastogenesis. Antibody-based neutralization of interleukin-12 (IL-12), but not IL-10, produced by M1 macrophages also abrogated M1-mediated downregulation of osteoclastogenesis. Real-time PCR analyses showed that IFN-γ suppressed gene expression of NFATc1, a master regulator of osteoclastogenesis, whereas IL-12 increased the apoptosis of osteoclasts, suggesting molecular mechanisms underlying the possible roles of IFN-γ or IL-12 in M1-mediated inhibition of osteoclastogenesis. These findings were confirmed in an in vivo ligature-induced mouse periodontitis model in which adoptive transfer of M1 macrophages showed a significantly lower level of bone loss and less tartrate-resistant acid phosphatase (TRAP)-positive cell induction than M0 or M2 macrophage transfer. In conclusion, by its secretion of IFN-γ and IL-12, M1, but not M0 or M2, was demonstrated to inhibit osteoclastogenesis.

Progesterone drives mammary secretory differentiation via RankL-mediated induction of Elf5 in luminal progenitor cells.

Progesterone-RankL paracrine signaling has been proposed as a driver of stem cell expansion in the mammary gland, and Elf5 is essential for the differentiation of mammary epithelial progenitor cells. We demonstrate that Elf5 expression is induced by progesterone and that Elf5 and progesterone cooperate to promote alveolar development. The progesterone receptor and Elf5 are expressed in a mutually exclusive pattern, and we identify RankL as the paracrine mediator of the effects of progesterone on Elf5 expression in CD61+ progenitor cells and their consequent differentiation. Blockade of RankL action prevented progesterone-induced side branching and the expansion of Elf5(+) mature luminal cells. These findings describe a mechanism by which steroid hormones can produce the expansion of steroid hormone receptor-negative mammary epithelial cells.

Osteoclasts are recruited to the subchondral bone in naturally occurring post-traumatic equine carpal osteoarthritis and may contribute to cartilage degradation.

UNLABELLED: The role of osteoclasts in osteochondral degeneration in osteoarthritis (OA) has rarely been investigated in spontaneous disease or animal models of OA. OBJECTIVE: The objectives of the current study were to investigate osteoclast density and location in post-traumatic OA (PTOA) and control specimens from racehorses. METHOD: Cores were harvested from a site in the equine third carpal bone, that undergoes repetitive, high intensity loading. Histological and immunohistochemical (Cathepsin K and Receptor-activator of Nuclear Factor kappa-ß ligand (RANKL)) stained sections were scored (global and subregional) and the osteoclast density calculated. The cartilage histological scores were compared with osteoclast density and RANKL scores. RESULTS: There was a greater density of osteoclasts in PTOA samples and they were preferentially located in the subchondral bone plate. RANKL scores positively correlated to the scores of cartilage degeneration and the osteoclast density. The relationship between hyaline articular cartilage RANKL score and osteoclast density was stronger than that of the subchondral bone RANKL score suggesting that cartilage RANKL may have a role in recruiting osteoclasts. The RANKL score in the articular calcified cartilage correlated with the number of microcracks also suggesting that osteoclasts recruited by RANKL may contribute to calcified cartilage degeneration in PTOA. CONCLUSION: Our results support the hypothesis that osteoclasts are recruited during the progression of spontaneous equine carpal PTOA by cartilage RANKL, contributing to calcified cartilage microcracks and focal subchondral bone loss.

Bone marrow stromal cells induced activation of nuclear factor κB signaling protects non-Hodgkin's B lymphoma cells from apoptosis.

The microenvironment encompassing a variety of non-malignant cells in close proximity with malignant tumor cells has been well known to significantly affect the behavior of tumor cells. In this study, we therefore studied the mechanism of bone marrow stromal cells in protection of lymphoma cells from spontaneous apoptosis. We demonstrated that adhesion of the freshly isolated lymphoma B cells to bone marrow stromal cells or freshly isolated lymphoma stromal cells inhibited B cell spontaneous apoptosis in culture. This inhibition of apoptosis correlated with decreased cleavage of caspase-3/8 and increased activation of canonical and non-canonical NF-κB signaling pathway. In addition to BAFF signaling which has been reported as a functional determinant for B lymphoma cell survival in the bone marrow environment, we demonstrated RANKL from BMSCs works synergistically with BAFF to activate NF-κB signaling pathway and thus protects lymphoma B cells from spontaneous apoptosis.

Glucagon-like peptide-1(GLP-1) receptor agonists: potential to reduce fracture risk in diabetic patients?

This review summarizes current knowledge about glucagon-like peptide 1 receptor agonists (GLP-1 RA) and their effects on bone metabolism and fracture risk. Recent in vivo and in vitro experiments indicated that GLP-1 RA could improve bone metabolism. GLP-1 could affect the fat-bone axis by promoting osteogenic differentiation and inhibiting adipogenic differentiation of bone mesenchymal precursor cells (BMSCs), which express the GLP-1 receptor. GLP-1 RA may also influence the balance between osteoclasts and osteoblasts, thus leading to more bone formation and less bone resorption. Wnt/ß-catenin signalling is involved in this process. Mature osteocytes, which also express the GLP-1 receptor, produce sclerostin which inhibits Wnt/ß-catenin signalling by binding to low density lipoprotein receptor-related protein (LRP) 5 and preventing the binding of Wnt. GLP-1 RA also decreases the expression of sclerostin (SOST) and circulating levels of SOST. In addition, GLP-1 receptors are expressed in thyroid C cells, where GLP-1 induces calcitonin release and thus indirectly inhibits bone resorption. Furthermore, GLP-1 RA influences the osteoprotegerin(OPG)/receptor activator of nuclear factor-κB ligand (RANKL)/receptor activator of nuclear factor-κB (RANK) system by increasing OPG gene expression, and thus reverses the decreased bone mass in rats models. However, a recent meta-analysis and a cohort study did not show a significant relationship between GLP-RA use and fracture risk. Future clinical trials will be necessary to investigate thoroughly the relationship between GLP-1 RA use and fracture risk in diabetic patients.

miR-218 is involved in the negative regulation of osteoclastogenesis and bone resorption by partial suppression of p38MAPK-c-Fos-NFATc1 signaling: Potential role for osteopenic diseases.

The increased osteoclastic activity accounts for pathological bone loss in diseases including osteoporosis. MicroRNAs are widely accepted to be involved in the regulation of osteopenic diseases. Recently, the low expression of miR-218 was demonstrated in CD14(+) peripheral blood mononuclear cells (PBMCs) from patients with postmenopausal osteoporosis. However, its role and the underlying mechanism in osteoporosis are still undefined. Here, an obvious decrease in miR-218 expression was observed during osteoclastogenesis under receptor activator of nuclear factor κB ligand (RANKL) stimulation, in both osteoclast precursors of bone marrow macrophages (BMMs) and RAW 264.7. Further analysis confirmed that overexpression of miR-218 obviously attenuated the formation of multinuclear mature osteoclasts, concomitant with the decrease in Trap and Cathepsin K levels, both the master regulators of osteoclastogenesis. Moreover, miR-218 up-regulation dramatically inhibited osteoclast precursor migration, actin ring formation and bone resorption. Mechanism assay demonstrated that miR-218 overexpression attenuated the expression of p38MAPK, c-Fos and NFATc1 signaling molecules. Following preconditioning with P79350, an agonist of p38MAPK, the inhibitor effect of miR-218 on osteoclastogenesis and bone-resorbing activity was strikingly ameliorated. Together, this study revealed a crucial role of miR-218 as a negative regulator for osteoclastogenesis and bone resorption by suppressing the p38MAPK-c-Fos-NFATc1 pathway. Accordingly, this research will provide a promising therapeutic agent against osteopenic diseases including osteoporosis.

Ginger hexane extract suppresses RANKL-induced osteoclast differentiation.

Osteoporosis is a debilitating disease caused by decreased bone density. Compounds with anti-osteoclastic activity, such as bisphosphonates, may help in the prevention and treatment of osteoporosis. Herein, we determined the inhibitory effects of ginger hexane extract (GHE) on receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclastogenesis in RAW264.7 cells. The results showed that GHE (1) suppressed osteoclast differentiation and the formation of actin rings; (2) inhibited the expression of Nfatc1, a master transcriptional factor for osteoclast differentiation, in a dose-dependent manner (10-20 µg/mL); and (3) inhibited other osteoclastogenesis-related genes, such as Oscar, Dc-stamp, Trap, and Mmp9. These findings suggest that GHE may be used to prevent and treat osteoporosis by inhibiting osteoclast differentiation.

[Diagnostic criteria for vitamin D-deficient rickets and hypocalcemia-].

Vitamin D deficiency causes rickets or osteomalacia, which is associated with hypomineralization of bone and chondrocytes, and/or hypocalcemia. Accumulating evidence indicates increase in frequency of vitamin D deficiency due to insufficient intake of vitamin D and calcium and decrease in sunshine. It is necessary for clinician to diagnose vitamin D deficiency accurately and treat patients with vitamin D deficiency adequately. For the purpose, clinical guideline or expert opinion on vitamin D deficiency has been reported.