Relationship between bone mineral density and fragility fracture risk: a case-control study in Changsha, China.

BACKGROUND: Fragility fracture is associated with bone mineral density (BMD), and most databases used in related researches are instrument-matched. Little is known about the relationship between BMD and fragility fracture risk of native Chinese, especially using local databases as reference databases. OBJECTIVE: To investigate relationship between BMD and risk of fragility fracture in native China. METHODS: 3,324 cases, including 2,423 women (67.7 ± 8.9 years) and 901 men (68.4 ± 11.6 years) having radiological fragility fractures and 3,324 age- and gender-matched controls participated in the study. We measured BMD at posteroanterior spine and hip using dual-energy X-ray absorptiometry (DXA), calculated BMD measurement parameters based on our own BMD reference database. RESULTS: BMDs and mean T-scores were lower in case group (with clinical fragility) than in control group (without clinical fragility). In patients with fragility fractures, prevalence of lumbar osteoporosis, low bone mass, and normal BMD were 78.9 %, 19.3 %, and 1.8 %, respectively, in women, and 49.5, 44.8 %, and 5.7 %, respectively, in men. In hip, these prevalence rates were 67.2 %, 28.4 %, and 4.4 % in females, and 43.2 %, 45.9 %, and 10.9 % in males, respectively, showing differences between females and males. Multivariate Cox regression analysis showed that after adjusting age, height, weight, and body mass index, fracture hazard ratio (HR) increased by 2.7-2.8 times (95 % CI 2.5-3.1) and 3.6-4.1 times (95 %CI 3.0-5.1) for women and men respectively with decreasing BMD parameters. In both sexes, risk of fragility fracture increased approximately 1.6-1.7 times (95 % CI 1.5-1.8) for every 1 T-score reduction in BMD. CONCLUSIONS: Risk of clinical fragility fracture increases with decreasing BMD measurement parameters and anthropometric indicators in native China, and fracture HR varies from gender and site.

Calcifediol (25-hydroxyvitamin D) improvement and calcium-phosphate metabolism of alendronate sodium/vitamin D3 combination in Chinese women with postmenopausal osteoporosis: a post hoc efficacy analysis and safety reappraisal.

BACKGROUND: Vitamin D (VD) insufficiency or deficiency is a frequent comorbidity in Chinese women with postmenopausal osteoporosis (PMO). The present study aimed to investigate 25-hydroxyvitamin D [25(OH) D] improvement and calcium-phosphate metabolism in Chinese PMO patients treated with 70 mg of alendronate sodium and 5600 IU of vitamin D3 (ALN/D5600). METHODS: Chinese PMO women (n = 219) were treated with 12-month ALN/D5600 (n = 111) or calcitriol (n = 108). Changes in 25(OH) D at month 12 were post hoc analyzed by the baseline 25 (OH) D status using the longitudinal analysis. The main safety outcome measures included serum calcium and phosphate and 24-h urine calcium, and the repeated measures mixed model was used to assess the frequencies of the calcium-phosphate metabolic disorders. RESULTS: Absolute change in mean serum 25(OH) D level was the greatest in VD-deficient patients and least in VD-sufficient patients at months six and 12 (both, P < 0.01). Serum calcium level remained significantly lower in the ALN/D5600 treatment group than in the calcitriol treatment group throughout the 12 months. Mean 24-h urine calcium slightly increased in the ALN/D5600 treatment group and significantly increased in the calcitriol treatment group (+ 1.1 and + 0.9 mmol/L at months six and 12; both, P < 0.05). Calcitriol treatment was associated with more frequent hypercalciuria at month six (9.4% vs. 18.5%, P = 0.05), but not at month 12 (12.3% vs. 13.0%). CONCLUSION: Baseline VD status predicted 25(OH) D improvement in PMO patients on 12-month ALN/D5600 treatment. The daily use of 0.25 µg of calcitriol was associated with more frequent hypercalciuria at month six, compared to ALN/5600 treatment, necessitating the safety re-evaluation of calcitriol at a higher dosage.

Dose-dependent effects of neuropeptide Y on the regulation of preadipocyte proliferation and adipocyte lipid synthesis via the PPARγ pathways.

The objective of this study was to investigate the impact of neuropeptide Y (NPY) on preadipocyte proliferation and differentiation. Preadipocytes were incubated with a range of concentrations of NPY (10(-15)M - 10(-7)M). After NPY-induced differentiation, the extent of preadipocyte adipogenesis was evaluated. The expressions levels of related adipocyte markers such as PPARγ, C/EBPα and DLK-1 were examined by real-time PCR (RT-PCR) or western blot analysis. Furthermore, the mitogen-activated protein kinase (MAPK) signaling pathway proteins were also analyzed by western blot. Our results showed that low doses of NPY stimulated preadipocyte viability and proliferation, while high NPY doses inhibited cell viability. At high concentrations of NPY significantly promoted lipid accumulation and increased the size of lipid droplets. DLK-1 mRNA expression was inhibited, but the expression levels of PPARγ and C/EBPα were increased during differentiation with the presence of high concentration of NPY. High-dose NPY also suppressed the phosphorylation of the extracellular signal-regulated kinase (ERK) 1/2 protein. We conclude that NPY has a biphasic effect on preadipocyte proliferation. A high dose inhibits the proliferation of 3T3-L1 cell while promotes adipocyte differentiation, increasing lipid accumulation especially enlarged lipid droplets' size. NPY may lead to a better understanding for drug development to prevent hyperplastic obesity and hypertrophic obesity.

Age-related bone turnover markers and osteoporotic risk in native Chinese women.

BACKGROUND: The rate of bone turnover is closely related to osteoporosis risk. We investigated the correlation between bone turnover markers and BMD at various skeletal sites in healthy native Chinese women, and to study the effect of changes in the levels of bone turnover markers on the risk of osteoporosis. METHODS: A cross-section study of 891 healthy Chinese women aged 20-80 years was conducted. The levels of serum osteocalcin (OC), bone-specific alkaline phosphatase (BAP), serum cross-linked N-terminal telopeptides of type I collagen (sNTX), cross-linked C-terminal telopeptides of type I collagen (sCTX), urinary NTX (uNTX), urinary CTX (uCTX) and total urinary deoxypyridinoline (uDPD) were determined. BMD at the posteroanterior spine and the hip was measured using DXA. RESULTS: Pearson's correlation coefficient found significant negative correlation between bone turnover marker and BMD T-score at different skeletal sites (r = -0.08 to -0.52, all P = 0.038-0.000). After adjustments for age and body mass index, the partial correlation coefficients between the OC, BAP, sNTX, sCTX and uCTX, and the T-scores at various skeletal sites were still significant. After adjustment of height and weight, the correlation coefficients between most BTMs and PA lumbar spine BMD were also significant. Multiple linear regression analysis showed that bone turnover markers were negative determinants of T-scores. BAP and OC accounted for 33.1% and 7.8% of the variations in the T-scores of the PA spine, respectively. Serum OC, BAP, uDPD, and sNTX accounted for 0.4-21.9% of the variations in the femoral neck and total hip T-scores. The bone turnover marker levels were grouped as per quartile intervals, and the T-scores, osteoporosis prevalence and risk were found to markedly and increase with increase in bone turnover marker levels. CONCLUSIONS: This study clarified the relationship between bone turnover markers and osteoporosis risk in native Chinese women. Bone turnover marker levels were found to be important determinants of BMD T-scores. Furthermore, osteoporotic risk significantly increased with increase in the levels of bone turnover markers.

Relationships between age-related biochemical markers of bone turnover and OPG, TGF-ß1 and TGF-ß2 in native Chinese women.

Osteoprotegerin (OPG), transforming growth factor-ß1 (TGF-ß1) and TGF-ß2 are cytokines closely associated with bone metabolism. However, their association with bone turnover markers in native Chinese women remains unknown. The study aims to investigate the relationship between bone metabolism related cytokines including OPG, TGF-ß1, TGF-ß2 and bone turnover markers in native Chinese women. The cross-sectional study was conducted on 691 healthy Chinese women (20-80 years old). Levels of OPG, TGF-ß1, TGF-ß2, serum bone-specific alkaline phosphatase (BAP), osteocalcin (OC), cross-linked N-terminal telopeptides of type I collagen (sNTX), cross-linked C-terminal telopeptides of type I collagen (sCTX), urinary NTX (uNTX), urinary CTX (uCTX) and total urinary deoxypyridinoline (uDPD) were determined. The present study showed that OPG and TGF-ß2 had positive correlation with BAP, OC, uNTX, uCTX and uDPD, while TGF-ß1 showed negative correlation with BAP, OC, sCTX, uNTX and uCTX, and most of the coefficients of partial correlation remained significant after adjustments for age and body mass index (BMI). Multiple linear regression stepwise analysis showed that OPG and TGF-ß2 were positive determinative factors for BAP, sCTX, uNTX and uCTX, which could explain 0.6-16.6% of the variation in these markers. TGF-ß1 was a negative determinative factor for BAP, OC, sCTX and uCTX, which could explain 0.7-7.3% of the variation in these markers. This study suggested that measuring bone turnover indicators and serum cytokines simultaneously might help evaluating changes in bone turnover rate caused by aging or menopause in women.

Ghrelin inhibits the apoptosis of MC3T3-E1 cells through ERK and AKT signaling pathway.

Ghrelin is a 28-amino-acid peptide that acts as a natural endogenous ligand of the growth hormone secretagogue receptor (GHSR) and strongly stimulates the release of growth hormone from the hypothalamus-pituitary axis. Previous studies have identified the important physiological effects of ghrelin on bone metabolism, such as regulating proliferation and differentiation of osteoblasts, independent of GH/IGF-1 axis. However, research on effects and mechanisms of ghrelin on osteoblast apoptosis is still rare. In this study, we identified expression of GHSR in MC3T3-E1 cells and determined the effects of ghrelin on the apoptosis of osteoblastic MC3T3-E1 cells and the mechanism involved. Our data demonstrated that ghrelin inhibited the apoptosis of osteoblastic MC3T3-E1 cells induced by serum deprivation, as determined by terminal deoxynucleotidyl transferase-mediated deoxyribonucleotide triphosphate nick end-labeling (TUNEL) and ELISA assays. Moreover, ghrelin upregulated Bcl-2 expression and downregulated Bax expression in a dose-dependent manner. Our study also showed decreased activated caspase-3 activity under the treatment of ghrelin. Further study suggested that ghrelin stimulated the phosphorylation of ERK and AKT. Pretreatment of cells with the ERK inhibitor PD98059, PI3K inhibitor LY294002, and GHSR-siRNA blocked the ghrelin-induced activation of ERK and AKT, respectively; however, ghrelin did not stimulate the phosphorylation of p38 or JNK. PD90859, LY294002 and GHSR-siRNA attenuated the anti-apoptosis effect of ghrelin in MC3T3-E1 cells. In conclusion, ghrelin inhibits the apoptosis of osteoblastic MC3T3-E1 cells induced by serum deprivation, which may be mediated by activating the GHSR/ERK and GHSR/PI3K/AKT signaling pathways.

Vaspin attenuates the apoptosis of human osteoblasts through ERK signaling pathway.

It has been hypothesized that adipocytokines originating from adipose tissue may have an important role in bone metabolism. Vaspin is a novel adipocytokine isolated from visceral white adipose tissue, which has been reported to have anti-apoptotic effects in vascular endothelial cells. However, to the best of our knowledge there is no information regarding the effects of vaspin on osteoblast apoptosis. This study therefore examined the possible effects of vaspin on apoptosis in human osteoblasts (hOBs). Our study established that vaspin inhibits hOBs apoptosis induced by serum deprivation, as determined by ELISA and TUNEL assays. Western blot analysis revealed that vaspin upregulates the expression of Bcl-2 and downregulates that of Bax in a dose-dependent manner. Vaspin stimulated the phosphorylation of ERK, and pretreatment of hOBs with the ERK inhibitor PD98059 blocked the vaspin-induced activation of ERK, however, vaspin did not stimulate the phosphorylation of p38, JNK or Akt. Vaspin protects hOBs from serum deprivation-induced apoptosis, which may be mediated by activating the MAPK/ERK signaling pathway.

[Relationship of age-related levels of serum sex hormones with bone mineral density decreasing rate in women].

OBJECTIVE: To explore the relationship between the changes of estrogen, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels and bone mineral density (BMD) decreasing rate (BDR) at different skeletal regions and examine the effects of hormones levels on BDR. METHODS: An age cross-sectional study was conducted in 694 healthy adult women excluded from diseases and drugs affecting bone metabolism. Their age range was 20-80 years. The serum concentrations of FSH, LH and estradiol (E2) were measured with radioimmunoassay. And BDR was measured with a DXA fan-beam bone densitometer at various skeletal regions including lumbar spine, left hip and left forearm. RESULTS: The serum levels of FSH (r = -0.597 to -0.479, all P < 0.01) and LH r = -0.452 to -0.283, all P < 0.01) were significantly negatively correlated with BDR at various skeletal regions. Meanwhile, the serum level of E2 only had slightly positive correlation with hip and distal forearm (r = 0.077 to 0.122, all P < 0.05). After adjusting age and body mass index (BMI), serum FSH still had markedly negative correlation with BDR at various skeletal regions. However, the correlation coefficients became weak. Multiple line regression stepwise analysis revealed that serum FSH was a negative determinant factor of BDR at various skeletal regions: 20%-32% changes in BDR of various skeletal regions were determined by FSH, while LH only produced very small negative effects (0.6%-0.8%) on BDR of lumbar spine. Serum E2 seemed to be a positive determinant factor of skeletal regions and 2.5%-5.4% changes in BDR were determined by E2. The effects of serum FSH on BDR were approximately 3.8-12.8 folds than those of serum E2. CONCLUSIONS: BDR is correlated with increased FSH in women. The most critical factor for aging-related BDR is FSH in women while a decreased level of estrogen may be secondary.

Apelin-APJ induces ICAM-1, VCAM-1 and MCP-1 expression via NF-κB/JNK signal pathway in human umbilical vein endothelial cells.

Apelin receptor (APJ) deficiency has been reported to be preventive against atherosclerosis. However, the mechanism of this effect remains unknown. In this study, quantitative real-time RT-PCR, Western blotting and ELISA analyses revealed a significant increase in the expression of intercellular adhesion molecule-1(ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) in human umbilical vein endothelial cells (HUVECs) treated with apelin. Inhibitors of cellular signal transduction molecules were used to demonstrate involvement of nuclear factor kappa-B (NF-κB) and c-Jun N-terminal kinase (JNK) pathways in apelin-APJ-induced activation of adhesion molecules and chemokines. Inhibition of APJ expression by RNA interference abrogated apelin-induced expression of adhesion molecules and chemokines and apelin-stimulated cellular signal transduction in HUVECs. The apelin-APJ system in endothelial cells is involved in the expression of adhesion molecules and chemokines, which are important for the initiation of endothelial inflammation-related atherosclerosis. Therefore, apelin-APJ and the cell signaling pathways activated by this system in endothelial cells may represent targets for therapy of atherosclerosis.

Stretch-inducible expression of connective tissue growth factor (CTGF) in human osteoblasts-like cells is mediated by PI3K-JNK pathway.

To explore the possible role for connective tissue growth factor (CTGF) during tooth movement, we evaluated CTGF gene and protein expression in MG-63 cells subjected to cyclic stretch. Cyclic stretch caused a time-dependent increase in CTGF mRNA and protein levels.Inhibition of p38 MAP kinase or ERK activation did not affect cyclic stretch-induced CTGF expression. Specific inhibitors of PI3K suppressed stretch -induced CTGF expression in a time-dependent manner. cyclic stretch activated JNK and ERK, but not p38 MAP kinase in osteoblast-like cells. PI3K inhibitors suppressed cyclic stretch-induced JNK, but not p38 MAP kinase activation. Finally, SP600125, a Specific Inhibitor of JNK, suppressed stretch -induced CTGF Expression. These results suggest that stretch-induced CTGF expression is mediated through the PI3K-JNK -dependent pathway, not by p38 MAP kinase and ERK pathways.

Phospholipase C-gamma1 is required for the epidermal growth factor receptor-induced squamous cell carcinoma cell mitogenesis.

The epidermal growth factor receptor (EGFR) is a key driver in the process of squamous cell carcinoma (SCC) cell mitogenesis. Phospholipase C-gamma1 (PLC-gamma1) is a downstream target of EGFR signaling, but the role and necessity of PLC-gamma1 in EGFR-induced cell mitogenesis remain unclear. In the present study, we report an elevated expression of PLC-gamma1 in human SCC biopsies relative to adjacent normal epidermis, and in human SCC cell lines compared to normal human keratinocytes. EGFR-induced SCC cell mitogenesis was blocked by small interfering RNA knockdown of PLC-gamma1. However, inhibition of the catalytic activity of phospholipase C had no effect on EGFR-induced SCC cell mitogenesis. In response to the EGFR ligand epidermal growth factor (EGF), PLC-gamma1 was translocated not only to the plasma membrane but also to the nucleus. These data suggest that PLC-gamma1 is required for EGFR-induced SCC cell mitogenesis and the mitogenic function of PLC-gamma1 is independent of its lipase activity.

Connective tissue growth factor is a downstream mediator for preptin-induced proliferation and differentiation in human osteoblasts.

Preptin, a newly isolated 34-amino-acid peptide hormone that is cosecreted with insulin and amylin from pancreatic beta-cells, has emerged as a regulatory element in bone metabolism, but its mechanism remains unclear. We assessed the effects of preptin on proliferation and differentiation of human osteoblasts and investigated the mechanism involved. Our results demonstrated that preptin promoted human osteoblasts proliferation and alkaline phosphatase activity. Suppression of connective tissue growth factor (CTGF), which was upregulated by preptin in a dose- and time-dependent manner, with small interfering RNA (siRNA) abolished the preptin-induced human osteoblasts proliferation and differentiation. Preptin induced activation of ERK mitogen-activated protein kinase (MAPK), but not p38 or JNK in human osteoblasts. Furthermore, pretreatment of human osteoblasts with the ERK inhibitor PD98059 abolished the preptin-induced CTGF secretion and blocked the promoting effect of preptin on osteoblasts proliferation and differentiation. These data demonstrated that preptin is involved in bone anabolism mediated by ERK/CTGF in human osteoblasts and may contribute to the preservation of bone mass observed in hyperinsulinemic states, such as obesity.

Taurine inhibits osteoclastogenesis through the taurine transporter.

Several studies have suggested a direct link between taurine and bone homeostasis. However, the mechanisms of taurine on the regulation of bone metabolism have not been elucidated. Using a coculture of osteoblasts and bone marrow cells as a model for the study of osteoclastogenesis, RANKL-stimulated RAW264.7 cells and M-CSF- and RANKL-induced bone marrow macrophages were investigated to elucidate the possible roles of taurine in osteoclastogenesis. Taurine inhibited osteoclastogenesis in the coculture of osteoblasts and bone marrow cells, but did not influence the expression of OPG and RANKL in osteoblasts. The taurine transporter (TAUT) expressed by RAW264.7 and bone marrow macrophages exhibited typical taurine uptake activity. Taurine directly reduced osteoclastogenesis in RANKL-stimulated RAW264.7 cells and M-CSF- and RANKL-induced bone marrow macrophages, while TAUT siRNA relieved this effect. Our study demonstrated that taurine directly inhibited osteoclastogenesis through the taurine transporter. Taken together, these data suggest that taurine plays a direct role in bone homeostasis by inhibiting osteoclastogenesis.

Apelin suppresses apoptosis of human vascular smooth muscle cells via APJ/PI3-K/Akt signaling pathways.

Apoptosis of vascular smooth muscle cells (VSMCs) plays an important role in regulating vascular remodeling during cardiovascular diseases. Apelin is the endogenous ligand for the G-protein-coupled receptor APJ and plays an important role in the cardiovascular system. However, the mechanisms of apelin on apoptosis of VSMCs have not been elucidated. Using a culture of human VSMCs as a model for the study of apoptosis, the relationship between apelin and apoptosis of human VSMCs and the signal pathway involved were investigated. Using western blotting, we confirmed that VSMCs could express APJ. To evaluate the possible role of apelin in VSMC apoptosis, we assessed its effect on apoptosis of human VSMCs. The results showed that apelin inhibited human VSMCs apoptosis induced by serum deprivation. Suppression of APJ with small-interfering RNA (siRNA) abolished the anti-apoptotic activity of apelin. Apelin increased Bcl-2 protein expression, but decreased Bax protein expression. An increase in activation of extracellular signal-regulated protein kinase (ERK) and Akt (a downstream effector of phosphatidylinositol 3-kinase) was shown after apelin stimulation. Suppression of APJ with siRNA abolished the apelin-induced activation of ERK and Akt. LY294002 (a PI3-K inhibitor) blocked apelin-induced activation of Akt and abolished the apelin-induced antiapoptotic activity. Our study suggests that apelin suppresses serum deprivation-induced apoptosis of human VSMCs, and that the anti-apoptotic action is mediated through the APJ/PI3-K/Akt signaling pathways.

Suppressive effect of dexamethasone on TIMP-1 production involves murine osteoblastic MC3T3-E1 cell apoptosis.

High dose glucocorticoid (GC) treatment induces osteoporosis partly via increasing osteoblast apoptosis. However, the mechanism of GC-induced apoptosis has not been fully elucidated. Osteoblast-derived tissue inhibitor of metalloproteinase-1 (TIMP-1) was recently reported to be involved in bone metabolism. Our previous study demonstrated that TIMP-1 suppressed apoptosis of the mouse bone marrow stromal cell line MBA-1 (pre-osteoblast) induced by serum deprivation. Therefore, we tested the effect of the GC dexamethasone (Dex) on TIMP-1 production in murine osteoblastic MC3T3-E1 cells and further determined whether this action is associated with Dex-induced osteoblast apoptosis. Dex decreased TIMP-1 production in MC3T3-E1 cells, and this effect was blocked by the glucocorticoid receptor (GR) antagonists, RU486 and RU40555. Recombinant TIMP-1 protein reduced caspase-3 activation and apoptosis induced by Dex in MC3T3-E1 cells. In addition, the pro-apoptotic effect of the Dex was augmented by suppression of TIMP-1 with siRNA. Furthermore, mutant TIMP-1, which has no inhibitory effects on MMPs, yet protects MC3T3-E1 cells against Dex-induced apoptosis. Our study demonstrates that Dex suppresses TIMP-1 production in osteoblasts through GR, and this effect is associated with its induction of osteoblast apoptosis. The anti-apoptotic action of TIMP-1 is independent of its inhibitory effects on MMPs activities. The decrease in TIMP-1 production caused by Dex may contribute to the mechanisms of Dex-induced bone loss.

Effect of progesterone on apoptosis of murine MC3T3-E1 osteoblastic cells.

Progesterone (P) has been suggested as a bone-trophic hormone. Previous studies have shown that P promoted bone formation by stimulating the proliferation and differentiation of osteoblasts. But, the effect of P on apoptosis of osteoblast in vitro has not been reported. We propose that P may promote bone formation by suppressing the apoptosis of osteoblast. The present study was performed to investigate the effect of P on apoptosis of murine MC3T3-E1 osteoblastic cells. Cell apoptosis was measured by acidine orange/ethidium bromide (AO/EB) staining and sandwich-enzyme-immunoassay. Progesterone receptor (PR), cytochrome c, caspase-9 and caspase-3 protein levels were determined by Western blot analysis. The enzyme substrate was also used to assess the activation of caspase-3 and caspase-9. Progesterone suppressed MC3T3-E1 cells apoptosis induced by serum deprivation, and this effect was blocked by a PR antagonist RU486. Furthermore, the suppressive effects of P on cytochrome c release and caspase-9 and caspase-3 activation in serum-deprived MC3T3-E1 cells were also reversed by RU486. Our study demonstrated that P protects osteoblast against apoptosis through PR and the downstream mitochondrial pathway. Thus, the data suggest that the effects of P on osteoblast apoptosis may contribute to the mechanisms by which P exerts its action on bone formation.

[The effects of glucocorticoid on expression of cannabinoid-1 receptors in osteoclasts from tibial proximal metaphysis of rats].

OBJECTIVE: To explore the molecular mechanism of glucocorticoid (GC)-induced osteoporosis (GIOP). METHODS: Thirty-two female SD rats after matching body weight were divided randomly into three groups: baseline group (n = 10), control group (n = 11) and GC-treated group (n = 11). The administration time was 9 weeks. Bone mineral density (BMD) was measured with dual energy X-ray absorptiometry. A high resolution micro-CT was used to quantify the densitometric and microarchitectural properties of trabeculae in the proximal metaphysis of right tibia. In situ hybridization histochemistry and immunohistochemistry were used to detect the expression of cannabinoid type 1 receptor (CB1R) in the proximal metaphysis of left tibia. RESULTS: At the end of the experiment, whole-body BMD in vivo in the control group [(0.156 +/- 0.008) g/cm(2)] was higher than that in the baseline group [(0.147 +/- 0.006) g/cm(2)], while the whole-body BMD in vivo [(0.147 +/- 0.006) g/cm(2)] and total BMD in vitro at femurs in the GC-treated group [(0.220 +/- 0.011) g/cm(2)] was lower than those in the control group [(0.240 +/- 0.024) g/cm(2)]. Compared with the baseline group and control group, there was a remarkable decrease in the volumetric BMD, tissue BMD, trabecular number and trabecular connectivity (P < 0.05) in the GC-treated group, while there was a significant increase in trabecular separation (P < 0.05) and trabecular thickness also increased in the proximal metaphysis of tibiae in the GC-treated group. The expression level of CB1R mRNA and protein in osteoclasts in the GC-treated group was markedly higher than that in the baseline group and control group (P < 0.05). There was a close correlation between the expression level of CB1R mRNA, protein in osteoclasts and some microarchitectural parameters in the proximal metaphysis in the GC-treated group (P < 0.05). CONCLUSIONS: The administration of GC is associated with a decrease in BMD and deterioration in microarchitecture of trabecular bone in rats tibiae. Glucocorticoid may up-regulate the CB1R expression level in osteoclasts and this may be a kind of molecular mechanism of GIOP.

[Bone mass change and its possible mechanisms in murine knockout apolipoprotein E(ApoE-/-)].

OBJECTIVE: To study bone mass changes and its mechanisms in murine knockout apolipoprotein E (ApoE-/-). METHODS: Both 28-week-old male ApoE-/- mice (n = 6) and wild-type (WT) mice (n = 10) were euthanized. The trabecular and cortical bone microarchitecture were assessed by micro-CT (microCT) in right distal femur. The total body BMD (bone mineral density) of left femur was determined by dual-energy X-ray absorptiometry (DXA). The serum concentrations of osteoprotegerin (OPG) and receptor activator of nuclear factor kappaB ligand (RANKL) were analyzed using enzyme-linked immunosorbent assay (ELISA). The left tibias were dissected and fixed in 4% paraformaldehyde after decalcified in 0.15M EDTA buffer for 30 days. And the expressions of OPG and RANKL were detected by immunohistochemical staining. RESULTS: Compared with WT mice, the ApoE-/- mice showed an increased volumetric BMD (294 +/- 38) mg/mm(3), tissue BMD (627 +/- 23) mg/mm(3), BMC (bone mineral content) (0.57 +/- 0.08) mg, bone volume fraction (20.38 +/- 4.74)%, trabecular number (6.67 +/- 0.78) mm(-1), trabecular thickness (0.03 +/- 0.01) mm with an decreased bone surface fraction (69 +/- 18) mm(-1), trabecular separation (0.12 +/- 0.01) and structure mode index (1.73 +/- 0.24). The total body BMD was higher in ApoE-/- mice than WT mice [(0.063 +/- 0.004) g/cm(2) vs (0.056 +/- 0.004) g/cm(2)]. The serum level of OPG was significantly higher in ApoE-/- mice than WT mice [(4.98 +/- 0.97) ng/ml vs (3.54 +/- 0.65) ng/ml]. The results of immunohistochemical staining showed that the OPG expression was at a higher level in bone cell of ApoE-/- mice and RANKL showed no obvious change in either sera or bone cells. CONCLUSION: A decreased bone resorption causes an increased bone mass in ApoE-/- mice and leads to an imbalanced ratio of OPG/ RANKL.

Association between serum soluble membrane type matrix metalloproteinase-1 (MT1-MMP) levels and bone mineral density, and biochemical markers in postmenopausal women.

BACKGROUND: Recently, membrane type matrix metalloproteinase-1 (MT1-MMP) was found to participate in bone metabolism. We investigated the relationship between serum MT1-MMP and bone mineral density (BMD) as well as bone metabolic markers in 206 Chinese postmenopausal women aged 43-80 years. METHODS: Western analysis and ELISA were performed to detect serum soluble MT1-MMP levels. BMD was measured by dual energy X-ray absorptiometry (DXA). Serum alkaline phosphatase (BAP) and N-telopeptides of type I collagen (NTX) were assayed using ELISA. RESULTS: We found that soluble MT1-MMP abundantly existed in human serum as protein lack of transmembrane domain. Serum MT1-MMP levels were detectable in all participants and the range of value was 221.2-863.0 ng/ml (435.6+/-98.2 ng/ml). We found a significant negative weaker correlation between MT1-MMP and BMD at lumbar spine, total hip (Thip), and femoral neck (FN) (all P<0.05). After adjustment for age and BMI, the correlation with BMD at FN and Thip disappeared (all P>0.05). Multiple linear stepwise regression analysis showed that MT1-MMP was not a determinant factor for BMD. The significant positive correlations between MT1-MMP and BAP, NTX were found, and remained significant after adjustment for age and BMI (all P<0.05). Moreover, serum MT1-MMP, BAP, and NTX decreased in response to alendronate therapy. CONCLUSION: Circulating MT1-MMP and bone turnover markers are correlated, and serum MT1-MMP levels may rise with increase in bone turnover.

Relationships between serum adiponectin, leptin, resistin, visfatin levels and bone mineral density, and bone biochemical markers in Chinese men.

BACKGROUND: Adiponectin, leptin, resistin, and visfatin, as the main circulating peptides secreted by adipose tissue, are potential contributors to bone metabolism. We investigated whether these serum adipocytokines levels are associated with BMD and bone turnover biochemical markers in 232 Chinese men (20-80 y). METHODS: Serum adiponectin, leptin, resistin, and visfatin levels were determined by ELISA. RESULTS: Leptin had a positively correlation with fat mass, and remained significant after adjustment for age and BMI. There was a significant negative weak correlation between adiponectin and fat mass, and disappear after adjustment for age and BMI. Resistin and visfatin were not significantly correlated with fat mass. In the multiple linear stepwise regression analysis, lean mass and adiponectin, but not leptin, resistin and visfatin, were independent predictors of BMD. The significant positive correlations between adiponectin and bone-specific alkaline phosphatase (BAP), bone cross-linked N-telopeptides of type collagen (NTX) were found, and remained significant after adjustment for age and fat mass. CONCLUSIONS: Adiponectin was an independent predictor of BMD in Chinese men, and positively correlated with bone turnover biochemical markers. It suggested that adiponectin exert a negative effect on bone mass in men.