bluuebunny/crossref_metadata_2025 huggingface dataset:
Bone Loss and Fracture Risk After Reduced Physical Activity
Authors: Nordström Anna , Karlsson Caroline , Nyquist Fredrik , Olsson Tommy , Nordström Peter , Karlsson Magnus
Published: April 2006

Former male young athletes partially lost benefits in BMD (g/cm2) with cessation of exercise, but, despite this, had a higher BMD 4 years after cessation of career than a control group. A higher BMD might contribute to the lower incidence of fragility fractures found in former older athletes ⩾60 years of age compared with a control group.

Introduction: Physical activity increases peak bone mass and may prevent osteoporosis if a residual high BMD is retained into old age.

Materials and Methods: BMD was measured by DXA in 97 male young athletes 21.0 ± 4.5 years of age (SD) and 48 controls 22.4 ± 6.3 years of age, with measurements repeated 5 years later, when 55 of the athletes had retired from sports. In a second, older cohort, fracture incidence was recorded in 400 former older athletes and 800 controls ⩾60 years of age.

Results: At baseline, the young athletes had higher BMD than controls in total body (mean difference, 0.08 g/cm2), spine (mean difference, 0.10 g/cm2), femoral neck (mean difference, 0.13 g/cm2), and arms (mean difference, 0.05 g/cm2; all p < 0.001). During the follow-up period, the young athletes who retired lost more BMD than the still active athletes at the femoral neck (mean difference, 0.07 g/cm2; p = 0.001) and gained less BMD at the total body (mean difference, 0.03 g/cm2; p = 0.004). Nevertheless, BMD was still higher in the retired young athletes (mean difference, 0.06-0.08 g/cm2) than in the controls in the total body, femoral neck, and arms (all p < 0.05). In the older cohort, there were fewer former athletes ⩾60 of age than controls with fragility fractures (2.0% versus 4.2%; p < 0.05) and distal radius fractures (0.75% versus 2.5%; p < 0.05).

Conclusions: Although exercise-induced BMD benefits are reduced after retirement from sports, former male older athletes have fewer fractures than matched controls.
αvβ Integrins Play an Essential Role in BMP-2 Induction of Osteoblast Differentiation
Authors: Lai Chung-Fang , Cheng Su-Li
Published: April 2006

Both integrins and BMP-2 exert similar effects on osteoblasts. We examined the relationship between the αv-containing integrins (αvβ) and BMP-2 in osteoblast function. BMP-2 stimulates αvβ expression. BMP-2 receptors co-localize/overlap with αvβ integrins, and the intact function of αvβ is essential in BMP-2 activity.

Introduction: Bone morphogenetic protein (BMP)-2 not only induces osteoblast differentiation and bone matrix mineralization, but also stimulates osteoblast migration on and adhesion to bone matrix proteins. The αvβ- and β1- (αβ1) containing integrins mediate osteoblast interaction with many bone matrix proteins and play important roles in osteoblast adhesion, migration, and differentiation. Because αvβ integrins and BMP-2 share common effects on osteoblasts, we analyzed their relationship in osteoblast function.

Materials and Methods: The effects of BMP-2 on integrin expression were determined by surface labeling/immunoprecipitation and cell adhesion to matrix proteins. Confocal analysis of the immunostained cells and co-immunoprecipitation of cell extracts were used to study the spatial relationship between integrins and BMP-2 receptors. A function-blocking anti-αvβ integrin antibody (L230) was employed to investigate the roles of αvβ integrins in BMP-2 function.

Results: Human osteoblasts (HOBs) express αβ1, αvβ3, αvβ5, αvβ6, and αvβ8 integrins at focal adhesion sites. BMP-2 increases the levels of these integrins on osteoblast surface and enhances HOB adhesion to osteopontin and vitronectin. Immunoprecipitation and immunostaining analyses show that BMP-2 receptors co-localize or overlap with αvβ and αβ1 integrins. Incubation of HOBs with L230 abolishes the antiproliferative effect of BMP-2 and reduces the capacity of BMP-2 to stimulate alkaline phosphatase activity and the expression of osteocalcin, osteopontin, and bone sialoprotein. Furthermore, L230 prevents BMP-2 induction of matrix mineralization. Although BMP-2 retains its receptor-binding capability in the presence of L230, BMP-2 stimulation of Smad signaling is abolished by L230.

Conclusion: BMP-2 upregulates the expression of αvβ integrins, and these integrins, in turn, play a critical role in BMP-2 function in osteoblasts.
Multidomain Synthetic Peptide B2A2 Synergistically Enhances BMP-2 In Vitro
Authors: Lin Xinhua , Zamora Paul O , Albright Sarah , Glass John D , Peña Louis A
Published: April 2006

A multidomain, synthetic peptide designated B2A2 synergizes the activity of BMP-2. B2A2 interacts with BMP receptor isoforms, potentiating the action of BMP-2 in activating alkaline phosphatase and triggering Smad and MAPK signaling. B2A2's design permits its delivery as a local surface coating as well as a soluble co-factor, thus broadening potential bioengineering applications.

Introduction: BMP-2 induces osteogenic differentiation and accelerates bone repair. Although BMP-2 inhibitors have been discovered, no BMP-2 mimetics or enhancers that function in the physiological range have yet been found. Here we report that a synthetic peptide designated B2A2, consisting of (1) a BMP receptor-targeting sequence, (2) a hydrophobic spacer, and (3) a heparin-binding sequence, is a positive modulator of recombinant BMP-2.

Materials and Methods: Cultures of mesenchymal cell lines C2C12 and C3H10T1/2 were given B2A2, recombinant BMP-2, or both. Alkaline phosphatase (ALP) activity was assayed by conversion of paranitrophenol phosphate (PNPP). Signaling through Smad and MAP kinase pathways was monitored by Western blot. Receptor binding was assessed by incubating immobilized B2A2 with soluble recombinant receptor-Fc chimeras and detecting bound receptor by anti-Fc antibody ELISA. Surface coating of medical device materials was done by first dip-coating with silyl-heparin, followed by B2A2.

Results and Conclusions: Treatment of cells with B2A2 alone marginally increased ALP activity. However, B2A2 plus BMP-2 resulted in 5- to 40-fold augmentation of ALP compared with BMP-2 alone in C3H10T1/2 or C2C12 cells, respectively. This synergistic enhancement was observed over a broad concentration range (4-1000 ng/ml BMP-2). B2A2 interacted directly with BMP receptor isoforms (preferentially to BMPR-Ib and ActivinR-II). In cells, B2A2 + BMP-2 led to a repression of MAP kinase and an increase of Smad activation, consistent with known activation pathways of BMP-2. B2A2 was ineffective when paired with other cytokine/growth factors (basic fibroblast growth factor [FGF-2], TGF-β1, vascular endothelial growth factor [VEGF]). Simultaneous co-administration was not strictly required. Pulse-chase experiments revealed that temporal separations up to 1 h were still effective. B2A2 was also effective when delivered in a polystyrene- or stainless steel-coated surface through a heparin platform (silyl-heparin) while BMP-2 was added exogenously in solution. These results suggest that B2A2 might promote aggregation of receptor subunits, enabling BMP-2 to activate signaling pathways at effectively lower concentrations. Synthetic multidomain constructs like B2A2 may be useful to accelerate bone repair/deposition through augmentation of endogenous levels of BMP-2 or through local BMP-2 contained in artificial or engineered matrices.
Two Related Low Molecular Mass Polypeptide Isoforms of Amelogenin Have Distinct Activities in Mouse Tooth Germ Differentiation In Vitro
Authors: Tompkins Kevin , Alvares Keith , George Anne , Veis Arthur
Published: April 2006

Embryonic mouse tooth germs were cultured in vitro in the presence of two related amelogenin isoforms to determine their effects on tooth development. Our results show that these individual proteins have specific but quite different effects on epithelial-derived ameloblasts versus mesenchymal-derived odontoblasts.

Introduction: Amelogenins, the main protein components of enamel matrix, have been shown to have signaling activity. Amelogenin isoforms differing only by the presence or exclusion of exon 4, designated ‘A+4’ (composed of exons 2, 3, 4, 5, 6d, and 7) and ‘A-4’ (composed of exons 2, 3, 4, 5, 6d, and 7) and ‘A-4’ (composed of exons 2, 3, 5, 6d, and 7), showed similar, but different, effects both in vitro and in vivo on postnatal teeth.

Materials and Methods: Lower first molar tooth germs of E15/16 CD1 mice were microdissected and cultured in vitro in a semisolid media containing either 20% FBS, 2% FBS, or 2% FBS with either 1.5 nM ‘A+4’, ‘A-4’, or both for 6 days. Tooth germs were analyzed by H&E staining and immunohistochemistry for collagen I, dentin matrix protein 2, and DAPI nuclear staining.

Results: Teeth cultured in media containing 20% FBS showed normal development with polarized ameloblasts, and odontoblasts producing dentin matrix, and DMP2 expression in odontoblasts and pre-ameloblasts. Culture in 2% FBS media resulted in no ameloblast polarization and modest odontoblast differentiation with scant dentin matrix. Tooth germs cultured with ‘A+4’ in 2% FBS media had well-polarized odontoblasts with robust dentin production and concomitant ameloblast polarization. DMP2 expression was equal to or greater than seen in the 20% FBS culture condition. In cultures with ‘A-4’ in 2% FBS media, odontoblast polarization and dentin production was reduced compared with ‘A+4’. However, the pre-ameloblast layer was disorganized, with no ameloblast polarization occurring along the dentin surface. DMP2 expression was reduced in the odontoblasts compared with the 20% FBS and ‘A+4’ conditions and was almost completely abrogated in the pre-ameloblasts.

Conclusion: These data show different signaling activities of these closely related amelogenin isoforms on tooth development. Here we make the novel observation that ‘A−4’ has an inhibitory effect on ameloblast development, whereas ‘A+4’ strongly stimulates odontoblast development. We show for the first time that specific amelogenin isoforms have effects on embryonic tooth development in vitro and also hypothesize that DMP2 may play a role in the terminal differentiation of both ameloblasts and odontoblasts.
Gorham-Stout Disease—Stabilization During Bisphosphonate Treatment
Authors: Hammer Fabian , Kenn Werner , Wesselmann Ulrich , Hofbauer Lorenz C , Delling Günter , Allolio Bruno , Arlt Wiebke
Published: April 2006

A 45-year-old woman presented with recent onset of left-sided chest pain. On clinical examination, these symptoms seemed to be strictly localized to a region that was marked by a long-standing cutaneous erythematous lesion. Laboratory results showed no gross abnormalities. Radiological imaging including conventional X-ray, MRI scans, and 3D CT reconstruction of the rib cage revealed circumscript destruction of the left lateral ribs 9–11. Histological analysis of a rib biopsy showed angiomatous hypervascularization and intracortical fibrosis. In keeping with these findings, the patient's condition was diagnosed as Gorham-Stout disease, a rare condition with localized, often unilateral, bone destruction. Monotherapy with bisphosphonates (pamidronate 30 mg IV every 3 months) was initiated, leading to rapid disappearance of local pain. Follow-up over 24 months documented a stable clinical and radiological picture without evidence of progressive bone destruction.
Drugs Used to Treat Osteoporosis: The Critical Need for a Uniform Nomenclature Based on Their Action on Bone Remodeling
Authors: Riggs B Lawrence , Parfitt A Michael
Published: April 2006

There continues to be uncertainty about the classification of available drugs for treating osteoporosis. We find that grouping them into anti-catabolic and anabolic classes based on the mechanisms of their action on bone remodeling and fracture reduction removes ambiguities and provides a relatively straightforward classification.

The recent introduction of teriparatide into clinical practice initiated the era of anabolic therapy for osteoporosis, but it is still unclear how to define an anabolic drug. All drugs that increase bone mass do so by affecting bone remodeling. When their mechanisms of action on bone remodeling and on fracture reduction are considered, we find that anti-osteoporotic drugs fall naturally into either anti-catabolic or anabolic classes. Anti-catabolic drugs increase bone strength and reduce fractures mainly by decreasing the number of bone multicellular units (BMUs). This reduces perforative resorption and preserves skeletal microarchitecture (by preventing further structural damage to trabecular bone and increased porosity in cortical bone induced by high bone remodeling). Reduction in bone remodeling by anti-catabolic drugs may increase bone mass moderately during the interval in which previously initiated BMUs are completing mineralization. Some anti-catabolic drugs may also enhance the formation phase of the remodeling cycle, but their major action is to reduce overall bone turnover (i.e., the number of BMUs in bone). In contrast, anabolic drugs increase bone strength and reduce fractures by substantially increasing bone mass as a result of an overall increase in the number of BMUs combined with a positive BMU balance (the magnitude of the formation phase is greater than that of the resorption phase). Some anabolic drugs also induce renewed modeling, increase periosteal apposition and repair of trabecular microstructure. We hope that this classification will serve as a starting point for continued discussion on the important issue of nomenclature.
L-Arginine, the Natural Precursor of NO, Is Not Effective for Preventing Bone Loss in Postmenopausal Women
Authors: Baecker Natalie , Boese Andrea , Schoenau Eckhard , Gerzer Rupert , Heer Martina
Published: April 2006

NO is an important regulator of bone turnover. L-Arginine, the natural precursor of NO, can enhance NO production. However, no effect of L-arginine hydrochloride supplementation was found on bone metabolism or on BMD, bone mass, or bone structure of healthy postmenopausal women.

Introduction: Recent studies indicate that NO exerts an anabolic effect on bone cell activity. The NO level of the human body can be elevated by administering pharmacological NO donors. Animal studies and the first human trial showed that NO donor administration had a positive effect on bone formation and a negative effect on bone resorption. L-arginine, the natural precursor of NO, can enhance NO production. This study was conducted to examine the effect of an oral L-arginine supplement on bone metabolism of healthy postmenopausal women.

Materials and Methods: The participants in this study were 30 healthy, age-matched postmenopausal women, divided into two groups. For 6 months, one group (54.5 ± 4.1 years; 66.3 ± 10.5 kg) received a daily oral supplement with 18 g L-arginine hydrochloride (14.8 g free L-arginine). The other 15 volunteers (55.3 ± 4.4 years; 64.2 ± 9.1 kg) received 18 g dextrose as a placebo. To verify compliance, 24-h urinary excretion of nitrogen was analyzed for 2 consecutive days at baseline and after 2, 4, and 6 months. At baseline and after 2, 4, and 6 months of supplementation, blood was drawn for analysis of insulin-like growth factor-I (IGF-I) and biomarkers of bone metabolism. At baseline, after 6 months, and after 1 year, pQCT measurements were performed at trabecular and cortical sites of the radius and tibia. The two groups of subjects were compared by repeated measures ANOVA.

Results: As expected, in the group with L-arginine hydrochloride supplementation, nitrogen excretion rose, and in the placebo group, it remained constant. Only bone formation marker, procollagen type I propeptides (PICP), increased significantly (p < 0.05) after 6 months of L-arginine supplementation. The results from pQCT showed no significant changes at any site in either group. No significant change in IGF-I concentration, which might have been caused by the L-arginine hydrochloride supplementation, was evident.

Conclusions: We conclude from these results that supplementation with L-arginine hydrochloride is not effective for improving bone mass in humans.
PGE2 Signal Through EP2 Promotes the Growth of Articular Chondrocytes
Authors: Aoyama Tomoki , Liang Bojian , Okamoto Takeshi , Matsusaki Takashi , Nishijo Koichi , Ishibe Tatsuya , Yasura Ko , Nagayama Satoshi , Nakayama Tomitaka , Nakamura Takashi , Toguchida Junya
Published: April 2006

EP2 was identified as the major PGE2 receptor expressed in articular cartilage. An EP2 agonist increased intracellular cAMP in articular chondrocytes, stimulating DNA synthesis in both monolayer and 3D cultures. Hence, the EP2 agonist may be a potent therapeutic agent for degenerative cartilage diseases.

Introduction: Prostaglandin E2 (PGE2) exhibits pleiotropic effects in various types of tissue through four types of receptors, EP1-4. We examined the expression of EPs and effects of agonists for each EP on articular chondrocytes.

Materials and Methods: The expression of each EP in articular chondrocytes was examined by immunohistochemistry and RT-PCR. A chondrocyte cell line, MMA2, was established from articular cartilage of p53−/− mice and used to analyze the effects of agonists for each EP. A search for molecules downstream of the PGE2 signal through the EP2 agonist was made by cDNA microarray analysis. The growth-promoting effect of the EP2 agonist on chondrocytes surrounded by cartilage matrix was examined in an organ culture of rat femora.

Results and Conclusion: EP2 was identified as the major EP expressed in articular cartilage. Treatment of MMA2 cells with specific agonists for each EP showed that only the EP2 agonist significantly increased intracellular cAMP levels in a dose-dependent manner. Gene expression profiling of MMA2 revealed a set of genes upregulated by the EP2 agonist, including several growth-promoting and apoptosis-protecting genes such as the cyclin D1, fibronectin, integrin α5, AP2α, and 14-3-3γ genes. The upregulation of these genes by the EP2 agonist was confirmed in human articular chondrocytes by quantitative mRNA analysis. On treatment with the EP2 agonist, human articular chondrocytes showed an increase in the incorporation of 5-bromo-2-deoxyuracil (BrdU), and the organ culture of rat femora showed an increase of proliferating cell nuclear antigen (PCNA) staining in articular chondrocytes surrounded by cartilage matrix, suggesting growth-promoting effects of the PGE2 signal through EP2 in articular cartilage. These results suggested that the PGE2 signal through EP2 enhances the growth of articular chondrocytes, and the EP2 agonist is a candidate for a new therapeutic compound for the treatment of degenerative cartilage diseases.
Azidothymidine Induces Apoptosis and Inhibits Cell Growth and Telomerase Activity of Human Parathyroid Cancer Cells in Culture
Authors: Falchetti Alberto , Franchi Alessandro , Bordi Cesare , Mavilia Carmelo , Masi Laura , Cioppi Federica , Recenti Raffaella , Picariello Lucia , Marini Francesca , Del Monte Francesca , Ghinoi Valentina , Martineti Valentina , Tanini Annalisa , Brandi Maria Luisa
Published: April 2006

Telomerase activity has been correlated to parathyroid carcinoma. Because its role in acquisition of a malignant phenotype by parathyroid cells is unclear, we treated telomerase-positive cultured human parathyroid cancer cells with the telomerase inhibitor AZT, evaluating cell telomerase activity, cytotoxic effects, growth, and morphological changes. In vitro exposure of these cells to AZT correlated with inhibition of cell proliferation.

Introduction: Parathyroid carcinoma represents an uncommon cause of primary hyperparathyroidism, whose spectrum of clinical presentation, degree of malignancy, and prognosis are difficult to be properly identified. Neck surgery, specifically an en bloc resection of primary tumor, is the only curative treatment. Alternatively, affected patients could undergo repetitive palliative surgical exeresis of metastatic nodules. It has been previously shown that telomerase activity is specifically present in parathyroid carcinoma cells, being absent in hyperplastic and adenomatous tissues. Thus, determination of telomerase activity could represent either a useful diagnostic molecular marker for human parathyroid carcinoma or a potential target for pharmacological intervention in a malignant neoplasia usually resistant to chemo- and radiotherapeutic interventions.

Materials and Methods: To further investigate the role of telomerase activity in acquisition of a malignant phenotype by parathyroid cells, we treated telomeric repeat amplification protocol-positive cultured human parathyroid cells with the telomerase inhibitor zidovudine, 3′-azido-3′deoxythymidine (AZT), evaluating cell telomerase activity, growth characteristics, potential cytotoxic effects, and morphological changes.

Results: Our findings indicate that in vitro exposure of human parathyroid cancer cells to AZT resulted in intracellular accumulation of AZT-monophosphate (AZT-MP) and inhibition of telomerase, which correlate with inhibition of human parathyroid cancer cell proliferation. Moreover, we also found that AZT induced an apoptotic rather than a necrotic type of cellular death. None of these effects were observed in human adenomatous parathyroid cells in culture.

Conclusions: Altogether these results indicate that AZT may be a highly effective agent against cancer parathyroid cells proliferation, which is an extremely important observation for a neoplasia which shows lack of response to classical pharmacological and physical antiblastic treatments.
Mechanotransduction in Bone Does Not Require a Functional Cyclooxygenase-2 (COX-2) Gene
Authors: Alam Imranul , Warden Stuart J , Robling Alexander G , Turner Charles H
Published: April 2006

COX-2 is a key enzyme involved in the response of bone to loading. However, using mice with a null mutation of the COX-2 gene, we found that a functional COX-2 gene is not required for mechanotransduction. This paradoxical finding may have resulted, in part, from mechanically induced COX-1 activity.

Introduction: Cyclooxygenase-2 (COX-2) is an important mediator in the response of bone to mechanical loading, with pharmacological inhibition of COX-2 effectively eliminating or reducing mechanically induced bone formation. In this study, we further investigated the role of COX-2 in skeletal mechanotransduction using a genetic approach. The aim was to compare the skeletal responsiveness of COX-2 homozygous mutant (COX-2−/−) and wildtype control (COX-2+/+) mice to investigate whether a functional COX-2 gene is necessary for mechanotransduction.

Materials and Methods: Adult female COX-2+/+ and COX-2−/− mice on a C57BL/6×129/ola background were studied using the ulna axial loading model. The response to 2 days of loading for 120 cycles/day at 2 Hz was measured histomorphometrically. Phenotypic characterization of the femurs in these mice was also performed. In a separate group of animals, the expression of the remaining COX isozyme, COX-1, was assessed using real-time RT-PCR 4 h after one bout of 120 loading cycles.

Results: Null mutation of the COX-2 gene resulted in a consistent femoral phenotype of reduced bone mass, altered architecture, and inferior mechanical properties. Many of these differences were nullified after adjustment for body weight. Nevertheless, body weight-corrected values showed a consistent trend of reduced mechanical properties in COX-2−/− mice. Genotype did not influence the response to mechanical loading, with no histomorphometric differences being found between COX-2+/+ and COX-2−/− mice. Real-time RT-PCR showed COX-2−/− mice to express significantly greater COX-1 expression in loaded ulnas than in loaded ulnas in COX-2+/+ mice. There were no differences in COX-1 expression in nonloaded ulnas.

Conclusions: A functional COX-2 gene was not found to be required for skeletal mechanotransduction. This is in contrast to previous pharmacological studies showing that COX-2 is critical to the response of bone to loading. Investigating a potential reason for the absence of a genotype difference in this study, we found that mice with a null mutation in the COX-2 gene possess inductive skeletal COX-1 expression.
Impaired Marrow Osteogenesis Is Associated With Reduced Endocortical Bone Formation but Does Not Impair Periosteal Bone Formation in Long Bones of SAMP6 Mice
Authors: Silva Matthew J , Brodt Michael D , Ko Mike , Abu-Amer Yousef
Published: April 2006

We used the SAMP6 osteoporotic mouse to examine the link between marrow osteogenic potential and in vivo cortical bone formation. SAMP6 marrow supported less in vitro osteogenesis than marrow from SAMR1 controls; SAMP6 mice had a corresponding deficit in endocortical mineralizing surface. This marrow/endocortical defect did not affect the periosteum, where SAMP6 mice had normal to enhanced bone formation.

Introduction: With aging, there may be a reduction in the number or proliferative capacity of bone marrow osteoprogenitors that may contribute to age-related decreases in bone formation. To examine the link between the ability of the marrow to support osteogenesis and age-related changes in bone formation, we measured in vitro and in vivo indices of osteogenesis in a model of osteoporosis, the senescence-accelerated mouse SAMP6.

Materials and Methods: Femora and tibias from SAMP6 and SAMR1 (control) mice were harvested at 2, 4, 6, and 12 months of age (168 bones total). Bone marrow cells were cultured under osteogenic conditions and stained for alkaline phosphatase (ALP) and alizarin red. Dynamic indices of bone formation were assessed histologically from calcein labels.

Results: ALP+ and alizarin red-positive areas were significantly less in cultures from SAMP6 bones versus SAMR1 (p < 0.05), indicating less osteogenic potential. For example, SAMP6 tibial cultures had 21% less ALP+ area and 36% less alizarin red-positive area than SAMR1. Marrow from tibias had 2-fold greater osteogenesis than femoral marrow (p < 0.001). SAMP6 mice had a deficit in endocortical mineralizing surface across all age groups (p < 0.05), but no deficit in mineral apposition rate. Last, despite the marrow and endocortical deficits, SAMP6 mice had normal or slightly increased periosteal bone formation, consistent with their larger bone size.

Conclusion: SAMP6 bone marrow supports less in vitro osteogenesis than SAMR1, consistent with a lower concentration of marrow osteoprogenitors in SAMP6. SAMP6 mice have less endocortical mineralizing surface than SAMR1 at all ages but no detectable deficit in mineral apposition rate, which suggests a reduction in osteoblast number but normal function. Periosteal bone formation is unimpaired in SAMP6 mice, indicating that the marrow/endocortical defect does not affect the periosteal surface.
Overweight Postmenopausal Women Lose Bone With Moderate Weight Reduction and 1 g/day Calcium Intake
Authors: Riedt Claudia S , Cifuentes Mariana , Stahl Theodore , Chowdhury Hasina A , Schlussel Yvette , Shapses Sue A
Published: April 2006

Overweight postmenopausal women may be more susceptible to bone loss with weight reduction than previously studied obese women. The influence of energy restriction and Ca intake on BMD was assessed in 66 individuals. Weight reduction resulted in bone loss at several sites in women consuming 1 g Ca/day and was mitigated with higher calcium intake at 1.7 g/day.

Introduction: Bone loss is associated with weight loss in obese postmenopausal women and can be prevented with calcium (Ca) supplementation. However, because bone loss caused by weight loss may be greater in overweight than obese women, it is not clear whether Ca supplementation is also beneficial in overweight women.

Materials and Methods: We assessed the influence of caloric restriction at two levels of Ca intake on BMD and BMC in 66 overweight postmenopausal women (age, 61 ± 6 years; body mass index, 27.0 ± 1.8 kg/m2). Subjects completed either a 6-month energy-restricted diet (WL, n = 47) and lost 9.3 ± 3.9 % weight or maintained weight (WM; 1 g Ca/day, n = 19). Participants in the WL group were randomly assigned to either normal (1 g/day; WL NL-Ca) or high (1.7 g/day; WL Hi-Ca) Ca intake. Regional BMD and BMC were measured at baseline and after 6 months.

Results: During normal Ca intake, trochanter BMD and BMC and total spine BMD were decreased more in WL than WM women (p < 0.05). The WL NL-Ca group lost more trochanter BMD (−4.2 ± 4.1%) and BMC (−4.8 ± 7.1%) than the WL Hi-Ca group (−1.4 ± 5.6% and −1.1 ± 8.1%, respectively; p < 0.05). There were no significant changes in BMD or BMC at the femoral neck in any group. Weight loss correlated with trochanter BMD loss (r = 0.687, p < 0.001) in the WL NL-Ca group.

Conclusion: Despite an intake of 1 g Ca/day, bone loss occurred at some sites because of weight loss. Calcium intake of 1.7 g/day will minimize bone loss during weight loss in postmenopausal overweight women.
Development and Initial Validation of a Risk Score for Predicting In‐Hospital and 1‐Year Mortality in Patients With Hip Fractures
Authors: Jiang Hong X , Majumdar Sumit R , Dick Donald A , Moreau Marc , Raso James , Otto David D , Johnston D William C
Published: April 2006

Our objectives were to better define the rates and determinants of in‐hospital and 1‐year mortality after hip fracture. We studied a population‐based cohort of 3981 hip fracture patients. Using multivariable regression methods, we identified risk factors for mortality (older age, male sex, long‐term care residence, 10 prefracture co‐morbidities) and calculated a hip fracture‐specific score that could accurately predict or risk‐adjust in‐hospital and 1‐year mortality. Our methods, after further validation, may be useful for comparing outcomes across hospitals or regions.

Introduction: Hip fractures in the elderly are common and associated with significant mortality and variations in outcome. The rates and determinants of mortality after hip fracture are not well defined. Our objectives were (1) to define the rate of in‐hospital and 1‐year mortality in hip fracture patients, (2) to describe co‐morbidities at the time of fracture, and (3) to develop and validate a multivariable risk‐adjustment model for mortality.

Materials and Methods: We studied a population‐based cohort of 3981 hip fracture patients ≥60 years of age admitted to hospitals in a large Canadian health region from 1994 to 2000. We collected sociodemographic and prefracture co‐morbidity data. Main outcomes were in‐hospital and 1‐year mortality. We used multivariable regression methods to first derive a risk‐adjustment model for mortality in 2187 patients treated at one hospital and then validated it in 1794 patients treated at another hospital. These models were used to calculate a score that could predict or risk‐adjust in‐hospital and 1‐year mortality after hip fracture.

Results and Conclusions: The median age of the cohort was 82 years, 71% were female, and 26% had more than four prefracture co‐morbidities. In‐hospital mortality was 6.3%; 10.2% for men and 4.7% for women (adjusted odds ratio, 1.8; 95% CI, 1.3‐2.4). Mortality at 1 year was 30.8%; 37.5% for men and 28.2% for women (adjusted p < 0.001). Older age, male sex, long‐term care residence, and 10 different co‐morbidities were independently associated with mortality. Risk‐adjustment models based on these variables had excellent accuracy for predicting mortality in‐hospital (c‐statistic = 0.82) and at 1 year (c‐statistic = 0.74). We conclude that 1 in 15 elderly patients with hip fracture will die during hospitalization, and almost one‐third of those who survive to discharge will die within the year. The determinants of mortality were primarily older age, male sex, and prefracture co‐morbidities. Our hip fracture‐specific risk‐adjustment tool is pragmatic and reliable, and after further validation, may be useful for comparing outcomes across different hospitals or regions.
Interobserver Reproducibility of Criteria for Vertebral Body Exclusion
Authors: Hansen Karen E , Binkley Neil , Christian Rose , Vallarta-Ast Nellie , Krueger Diane , Drezner Marc K , Blank Robert D
Published: April 2006

We studied reproducibility of the ISCD vertebral exclusion criteria among four interpreters. Surprisingly, agreement among interpreters was only moderate, because of differences in threshold for diagnosing focal structural defects and choice of which vertebra among a pair discordant for T-score, area, or BMC to exclude. Our results suggest that reproducibility may be improved by specifically addressing the sources of interobserver disagreement.

Introduction: Although DXA is widely used to measure vertebral BMD, its interpretation is subject to multiple confounders including osteoarthritis, aortic calcification, and scoliosis. In an attempt to standardize interpretation and minimize the impact of artifacts, the International Society for Clinical Densitometry (ISCD) established criteria for vertebral exclusion, including the presence of a focal structural defect (FSD), discrepancy of >1 SD in T-score between adjacent vertebrae, and a lack of increase in BMC or area from L1 to L4. Whereas the efforts of the ISCD represent an important advance in BMD interpretation, the interobserver reproducibility with application of these criteria is unknown. We hypothesized that there would be substantial agreement among four interpreters regarding application of the exclusion criteria and the final lumbar spine T-score.

Materials and Methods: Each interpreter read a set of 200 lumbar DXA scans obtained on male veterans, applying the ISCD vertebral body exclusion criteria.

Results: Surprisingly, agreement among interpreters was only moderate. Differences in interpretation resulted from differing thresholds for recognition of FSD and the choice of excluding the upper or lower vertebral body for the criteria requiring comparison between adjacent vertebrae.

Conclusions: Despite their apparent simplicity, the ISCD vertebral exclusion criteria are difficult to apply consistently. In principle, appropriate refinement of the exclusion criteria may significantly improve interobserver agreement.
Loss of Ubiquitin-Binding Associated With Paget's Disease of Bone p62 (SQSTM1) Mutations
Authors: Cavey James R , Ralston Stuart H , Hocking Lynne J , Sheppard Paul W , Ciani Barbara , Searle Mark S , Layfield Robert
Published: April 2006

We have studied the effects of various PDB-causing mutations of SQSTM1 on the in vitro ubiquitin-binding properties of the p62 protein. All mutations caused loss of monoubiquitin-binding and impaired K48-linked polyubiquitin-binding, which was only evident at physiological temperature. This suggests that SQSTM1 mutations predispose to PDB through a common mechanism that depends on loss of ubiquitin-binding by p62.

Introduction: Mutations in the SQSTM1 gene, which affect the ubiquitin-associated (UBA) domain of the p62 protein, are a common cause of Paget's disease of bone (PDB). We previously showed that the isolated UBA domain of p62 binds K48-linked polyubiquitin chains in vitro and that PDB-causing mutations in the UBA domain can be resolved in to those which retain (P392L and G411S) or lose (M404V and G425R) the ability to bind K48-linked polyubiquitin. To further clarify the mechanisms by which these mutations predispose to PDB, we have extended these analyses to study the ubiquitin-binding properties of the PDB-causing mutations in the context of the full-length p62 protein.

Materials and Methods: We studied the effects of various PDB-causing mutations on the interaction between glutathione S-transferase (GST)-tagged p62 proteins and monoubiquitin, as well as K48-linked polyubiquitin chains, using in vitro ubiquitin-binding assays.

Results: All of the PDB-causing mutations assessed (P392L, E396X, M404V, G411S, and G425R) caused loss of monoubiquitin binding and impaired K48-linked polyubiquitin-binding when introduced into the full-length p62 protein. However, these effects were only observed when the binding experiments were conducted at physiological temperature (37°C); they were not seen at room temperature or at 4°C.

Conclusions: Our in vitro findings suggest that PDB-causing mutations of SQSTM1 could predispose to disease through a common mechanism that is dependent on impaired binding of p62 to a ubiquitylated target and show that 5q35-linked PDB is the first example of a human disorder caused by loss of function mutations in a UBA domain.
Evaluation of a Prediction Model for Long-Term Fracture Risk
Authors: Melton L Joseph , Atkinson Elizabeth J , Khosla Sundeep , Oberg Ann L , Riggs B Lawrence
Published: April 2006

The NOF cost-effectiveness model, based on clinical risk factors and femoral neck aBMD, predicted overall fracture risk in a cohort of postmenopausal women followed for up to 22 years.

Introduction: To assess the ability of a statistical model to predict long-term fracture risk for a population of postmenopausal women, we compared observed fractures to those predicted by the National Osteoporosis Foundation's (NOF) cost-effectiveness model.

Materials and Methods: In this population-based study, 393 postmenopausal Rochester, MN, women had baseline measurements of femoral neck areal BMD (aBMD) and assessment of the clinical risk factors (personal fracture history, family history of osteoporotic fracture, low body weight, and smoking status) that were included in the NOF model. They were then followed prospectively for up to 22 years. Fractures were ascertained by periodic interview and review of community medical records. Standardized incidence ratios (SIRs) compared observed fractures to predicted numbers.

Results: During 4782 person-years of follow-up, 212 women experienced 503 fractures, two-thirds of which were caused by moderate trauma. When undiagnosed (incidentally noted) vertebral and rib fractures were excluded, there was general concordance between observed and predicted fractures of the hip (SIR, 0.78; 95% CI, 0.56-1.01), distal forearm (SIR, 1.22; 95% CI, 0.86-1.68), spine (SIR, 0.76; 95% CI, 0.50-1.11), and all other sites combined (SIR, 1.18; 95% CI, 0.97-1.42). Fracture prediction by the NOF model was about as good after 10 years as it was earlier during follow-up.

Conclusions: This study validates the ability of a statistical model based on femoral neck aBMD and common clinical risk factors to predict the actual occurrence of fractures in a cohort of postmenopausal white women.
Bone Resorption and Osteoporotic Fractures in Elderly Men: The Dubbo Osteoporosis Epidemiology Study
Authors: Meier Christian , Nguyen Tuan V , Center Jacqueline R , Seibel Markus J , Eisman John A
Published: April 2006

Among the potential risk factors for fragility fractures, bone turnover is considered an important determinant. In a case-cohort control study of 151 elderly men followed prospectively over 6.3 years, high bone resorption as assessed by S-ICTP was associated with increased risk of osteoporotic fracture, independent of BMD. Combining measurements of BMD and bone turnover may improve fracture prediction in elderly men.

Introduction: Approximately one-third of osteoporotic fractures occur in men. Among the potential risk factors for fragility fractures, bone turnover is considered an important determinant. The association between fracture risk and rates of bone turnover has not been well established in men. We examined this relationship in elderly community-dwelling men.

Materials and Methods: This case-cohort control study included 50 men with incident low-trauma fractures (cases; age, 72.3 ± 6.7 years) and 101 men without fracture (controls; age, 70.4 ± 4.1 years), who have been prospectively followed in the Dubbo Osteoporosis Epidemiology Study for a median of 6.3 years (range, 2-13 years). BMD at the lumbar spine (LSBMD) and at the femoral neck (FNBMD) and markers of bone turnover were measured at baseline. Bone resorption was assessed by measuring nonfasting serum concentrations of the carboxyterminal cross-linked telopeptide of type I collagen (S-ICTP) and of a linear octapeptide derived from the carboxyterminal type I collagen telopeptide (S-CTX). Bone formation was assessed by measuring the serum levels of the aminoterminal propeptide of type I procollagen (S-PINP).

Results: Men with subsequent fractures had lower BMD at baseline, both at the femoral neck and the spine, lower dietary calcium intake, and higher S-ICTP levels than age-and weight-matched controls. Smoking habits, S-CTX, and S-PINP did not differ between groups. Based on univariate regression analyses, S-ICTP (relative risk [RR] for 1 SD change: 1.8; 95% CI, 1.4-2.3) and serum creatinine levels (RR, 1.4; 95% CI, 1.1-1.7) were associated with increased risk of fracture. In multivariate regression analyses, S-ICTP (RR, 1.4; 95% CI, 1.0-1.9) and FNBMD (RR, 1.8; 95% CI, 1.4-2.3) remained independent predictors of fracture risk. Men within the highest quartile of S-ICTP had a 2.8-fold (95% CI 1.4-5.4) increased risk of fracture compared with those in the lowest quartile. The incidence of osteoporotic fractures was 10 times higher in men with high S-ICTP and low FNBMD compared with men with low S-ICTP and high FNBMD. Of the fracture risk in the population, 20% was attributable to high S-ICTP and low FNBMD, and S-ICTP contributed 17% to this increased risk.

Conclusion: High bone resorption is associated with an increased risk of osteoporotic fracture in elderly men, independent of BMD. Combining measurements of BMD and bone turnover, which correlated with fracture in this cohort, could improve fracture risk prediction in elderly men.
Chondrocyte-Specific Knockout of the G Protein Gsα Leads to Epiphyseal and Growth Plate Abnormalities and Ectopic Chondrocyte Formation
Authors: Sakamoto Akio , Chen Min , Kobayashi Tatsuya , Kronenberg Henry M , Weinstein Lee S
Published: April 2006

Gsα is a ubiquitously expressed G protein α-subunit that couples receptors to adenylyl cyclase. Mice with chondrocyte-specific ablation of the Gsα gene had severe epiphyseal and growth plate abnormalities and ectopic cartilage formation within the metaphyseal region of the tibia. These results show that Gsα negatively regulates chondrocyte differentiation and is the critical signaling mediator of the PTH/PTH-rP receptor in growth plate chondrocytes.

Introduction: Gsα is a ubiquitously expressed G protein α-subunit that mediates signaling through G protein-coupled receptors to activate the cAMP/protein kinase A signaling pathway. Although studies suggest an important role for Gsα in regulating growth plate development, direct in vivo results examining this role are lacking.

Materials and Methods: The Gsα gene was ablated in murine cartilage by mating mice with loxP sites surrounding the Gsα promoter and first exon with collagen 2a1 promoter-Cre recombinase transgenic mice. Skeletal tissues were studied by gross and microscopic pathology, and gene expression was determined by in situ hybridization.

Results and Conclusions: Mice with complete chondrocyte-specific Gsα deficiency (homozygotes) died within minutes after birth and had severe epiphyseal and growth plate defects with shortening of the proliferative zone and accelerated hypertrophic differentiation of growth plate chondrocytes, a phenotype similar to that of PTH/PTH-related peptide (PTHrP) receptor knockout mice. Indian hedgehog and PTH/PTHrP receptor expression in prehypertrophic chondrocytes was unaffected in mutant mice. PTHrP expression in periarticular cartilage was increased in the mutant mice, probably because of the closer proximity of Ihh-secreting chondrocytes to the periarticular zone. In addition, these mice developed ectopic cartilage at the anterior side of the metaphyseal region in the tibia. Mice with partial Gsα deficiency (heterozygotes) exhibited no phenotype. These results show that Gsα negatively regulates chondrocyte differentiation and is the critical signaling mediator of the PTH/PTHrP receptor in epiphyseal and growth plate chondrocytes.
Inhibition of RANKL-Induced Osteoclastogenesis by (−)-DHMEQ, a Novel NF-κB Inhibitor, Through Downregulation of NFATc1
Authors: Takatsuna Hiroshi , Asagiri Masataka , Kubota Takeshi , Oka Kotaro , Osada Toshihiro , Sugiyama Chie , Saito Hiroaki , Aoki Kazuhiro , Ohya Keiichi , Takayanagi Hiroshi , Umezawa Kazuo
Published: April 2006

(−)-DHMEQ, a newly designed NF-κB inhibitor, inhibited RANKL-induced osteoclast differentiation in mouse BMMs through downregulation of the induction of NFATc1, an essential transcription factor of osteoclastogenesis.

Introduction: Bone destruction is often observed in advanced case of rheumatoid arthritis and neoplastic diseases, including multiple myeloma. Effective and nontoxic chemotherapeutic agents are expected for the suppression of these bone destructions. RANKL induces activation of NF-κB and osteoclastogenesis in bone marrow-derived monocyte/macrophage precursor cells (BMMs). Targeted disruption or pharmacological suppression of NF-κB result in impaired osteoclastogenesis, but how NF-κB is involved in the regulation of osteoclastogenesis is not known.

Materials and Methods: The effect of (−)-dehydroxymethylepoxyquinomicin [(−)-DHMEQ] on osteoclast differentiation was studied using a culture system of mouse BMMs stimulated with RANKL and macrophage colony-stimulating factor. The mechanism of the inhibition was studied by biochemical analysis such as immunoblotting and retroviral transfer experiments.

Results: (−)-DHMEQ strongly inhibited RANKL-induced NF-κB activation in BMMs and inhibited RANKL-induced formation of TRACP+ multinucleated cells. Interestingly, (−)-DHMEQ specifically inhibited the RANKL-induced expression of NFATc1 but not the expressions of TRAF6 or c-fos. Inhibition of osteoclast differentiation by (−)-DHMEQ was rescued by overexpression of NFATc1, suggesting that the inhibition is not caused by a toxic effect. Moreover, pit formation assays showed that (−)-DHMEQ also inhibited the bone-resorbing activity of mature osteoclasts.

Conclusion: The inhibition of NF-κB suppresses osteoclastogenesis by downregulation of NFATc1, suggesting that NFATc1 expression is regulated by NF-κB in RANKL-induced osteoclastogenesis. Our results also indicate the possibility of (−)-DHMEQ becoming a new therapeutic strategy against bone erosion.
Diabetes and Bone Loss at the Hip in Older Black and White Adults
Authors: Schwartz Ann V , Sellmeyer Deborah E , Strotmeyer Elsa S , Tylavsky Frances A , Feingold Kenneth R , Resnick Helaine E , Shorr Ronald I , Nevitt Michael C , Black Dennis M , Cauley Jane A , Cummings Steven R , Harris Tamara B
Published: April 2006

Type 2 diabetes may be associated with elevated fracture risk, but the impact on bone loss is unknown. Analysis of 4-year change in hip BMD data from a cohort of white and black well-functioning men and women 70-79 years of age found that white women with diabetes had more rapid bone loss at the femoral neck than those with normal glucose metabolism.

Introduction: Type 2 diabetes may be associated with elevated fracture risk in older adults. Although type 2 diabetes is not associated with lower BMD, older diabetic adults have a higher prevalence of other risk factors for fracture, including more frequent falls, functional limitations, and diabetic complications. With this burden of risk factors, loss of BMD could place older adults with diabetes at higher risk of sustaining a fracture.

Materials and Methods: To determine if bone loss is increased with type 2 diabetes, we analyzed data from the Health, Aging, and Body Composition Study of white and black well-functioning men and women 70-79 years of age. Hip BMD was measured at baseline and 4 years later in 480 (23%) participants with diabetes, 439 with impaired glucose metabolism, and 1172 with normal glucose homeostasis (NG).

Results: Those with diabetes had higher baseline hip BMD and weight, but among white women, had more weight loss over 4 years. White women with diabetes lost more femoral neck and total hip BMD than those with NG in age-adjusted models. After multivariable adjustment, diabetes was associated with greater loss of femoral neck BMD (−0.32%/year; 95% CI: −0.61, −0.02) but not total hip BMD. In men and black women, change in hip BMD was similar for participants with diabetes and NG.

Conclusions: Despite having higher baseline BMD, diabetic white women, but not men or black women, had more rapid bone loss at the femoral neck than those with NG. This increased bone loss may contribute to the higher fracture risk observed in older diabetic women.