bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
(−)-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

Abstract
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.
Oropharyngeal Skeletal Disease Accompanying High Bone Mass and Novel LRP5 Mutation
Authors: Rickels Michael R , Zhang Xiafang , Mumm Steven , Whyte Michael P 
Published: April 2006

Abstract
Gain-of-function mutation in the gene encoding LRP5 causes high bone mass. A 59-year-old woman carrying a novel LRP5 missense mutation, Arg154Met, manifested skeletal disease affecting her oropharynx as well as dense bones, showing that exuberant LRP5 effects are not always benign.
Introduction: Gain-of-function mutation (Gly171Val) of LDL receptor-related protein 5 (LRP5) was discovered in 2002 in two American kindreds with high bone mass and benign phenotypes. In 2003, however, skeletal disease was reported for individuals from the Americas and Europe carrying any of six novel LRP5 missense mutations affecting the same LRP5 protein domain. Furthermore, in 2004, we described a patient with neurologic complications from dense bones and extensive oropharyngeal exostoses caused by the Gly171Val defect.
Materials and Methods: A 59-year-old woman was referred for dense bones. Three years before, mandibular buccal and lingual exostoses (osseous “tori”) were removed because of infections from food trapping between the teeth and exostoses. Maxillary buccal and palatal exostoses were asymptomatic. Radiographic skeletal survey showed marked thickening of the skull base and diaphyses of long bones (endosteal hyperostosis). BMD Z scores assessed by DXA were +8.5 and +8.7 in the total hip and L1-L4 spine (both ∼195% average control), respectively. LRP5 mutation analysis was carried out for the LRP5 domain known to cause high bone mass.
Results: Biochemical evaluation excluded most secondary causes of dense bones, and male-to-male transmission in her family indicated autosomal dominant inheritance. PCR amplification and sequencing of LRP5 exons 2-4 and adjacent splice sites revealed heterozygosity for a new LRP5 missense mutation, Arg154Met.
Conclusions: LRP5 Arg154Met is a novel defect that changes the same first “β-propeller” module as the eight previously reported LRP5 gain-of-function missense mutations. Arg154Met alters a region important for LRP5 antagonism by dickkopf (Dkk). Therefore, our patient's extensive oropharyngeal exostoses and endosteal hyperostosis likely reflect increased Wnt signaling and show that exuberant LRP5 effects are not always benign.
Influence of Glucocorticoids on Human Osteoclast Generation and Activity
Authors: Sivagurunathan Sutharshani , Muir Meloni M , Brennan Tara C , Seale J Paul , Mason Rebecca S 
Published: April 2006

Abstract
Using human peripheral blood mononuclear cells as osteoclast precursors, we showed that dexamethasone stimulated osteoclast generation at a pharmacological concentration but did not affect the life span of human osteoclasts. Dexamethasone also dose-dependently increased signals for osteoclastogenesis.
Introduction: Glucocorticoid-induced osteoporosis is a common and serious disease. Glucocorticoids predominantly affect osteoblast proliferation and life span. Much of the bone loss is caused by reduced bone formation, but there is also an element of increased bone resorption.
Materials and Methods: Human peripheral blood mononuclear cells were cultured on whale dentine and induced to differentiate to osteoclasts by RANKL and human macrophage-colony stimulating factor (M-CSF). Osteoclast activity was quantified by pit area. RANKL and osteoprotegerin (OPG) expression in osteoblasts were measured by real-time RT-PCR.
Results: In the early phase of osteoclast generation (0-16 days), cultures from two different donors showed that dexamethasone at 10−8 M increased pit area by 2.5-fold, whereas lower concentrations had no effect. At the highest dexamethasone concentration (10−7 M), pit area was reduced. In 21-day cultures from three other donors, a similar increase was seen with dexamethasone at 10−8 M. There was, however, no evidence of increased life span of osteoclasts with dexamethasone. In human primary osteoblasts, dexamethasone dose-dependently reduced OPG and increased RANKL expression as measured by quantitative real time RT-PCR.
Conclusion: These data provide some explanation at a cellular and molecular level for the observed increase in bone resorption seen in patients treated with glucocorticoids and indicate that there are clear direct effects of glucocorticoids on bone resorption in human cell systems that may differ from other species.
Retinoid Signaling Regulates CTGF Expression in Hypertrophic Chondrocytes With Differential Involvement of MAP Kinases
Authors: Shimo Tsuyoshi , Koyama Eiki , Sugito Hiroki , Wu Changshan , Shimo Satoko , Pacifici Maurizio 
Published: April 2006

Abstract
Retinoids are important for growth plate chondrocyte maturation, but their downstream effectors remain unclear. Recently, CTGF (CCN2) was found to regulate chondrocyte function, particularly in the hypertrophic zone. The goal of the study was to determine whether CTGF is a retinoid signaling effector molecule, how it is regulated, and how it acts.
Introduction: Using a combination of in vivo and in vitro approaches, we carried out a series of studies at the cellular, biochemical, and molecular level to determine whether and how retinoid signaling is related to expression and function of connective tissue growth factor (CTGF) in chondrocyte maturation and endochondral ossification.
Materials and Methods: Limbs of chick embryos in ovo were implanted with retinoic pan-antagonist RO 41-5253-filled beads, and phenotypic changes were assessed by in situ hybridization. CTGF gene expression and roles were tested in primary cultures of immature and hypertrophic chondrocytes. Cross-talk between retinoid signaling and other pathways was tested by determining endogenous levels of active ERK1/2 and p38 MAP kinases and phenotypic modulations exerted by specific antagonists of mitogen-activated protein (MAP) kinases and BMP signaling (Noggin).
Results: Interference with retinoid signaling blocked expression of CTGF and other posthypertrophic markers in long bone anlagen in vivo and hypertrophic chondrocyte cultures, whereas all-trans-retinoic acid (RA) boosted CTGF expression and even induced it in immature proliferating cultures. Exogenous recombinant CTGF stimulated chondrocyte maturation, but failed to do so in presence of retinoid antagonists. Immunoblots showed that hypertrophic chondrocytes contained sizable levels of phosphorylated ERK1/2 and p38 MAP kinases that were dose- and time-dependently increased by RA treatment. Experimental ERK1/2 inhibition led to a severe drop in baseline and RA-stimulated CTGF expression, whereas p38 inhibition increased it markedly. These responses were gene-specific, because the opposite was seen with other hypertrophic chondrocyte genes such as collagen X and RA receptor γ (RARγ). Tests with Noggin showed that RA induction of CTGF expression was negatively influenced by BMP signaling, whereas induction of collagen X expression was BMP-dependent.
Conclusions: Retinoids appear to have a preeminent role in controlling expression and function of CTGF in hypertrophic and posthypertrophic chondrocytes and do so with differential cooperation and intervention of MAP kinases and BMP signaling.
Ghrelin Directly Regulates Bone Formation
Authors: Fukushima Nobuhiro , Hanada Reiko , Teranishi Hitoshi , Fukue Yoshihiko , Tachibana Toshiaki , Ishikawa Hiroshi , Takeda Shu , Takeuchi Yasuhiro , Fukumoto Seiji , Kangawa Kenji , Nagata Kensei , Kojima Masayasu 
Published: April 2006

Abstract
To clarify the role of ghrelin in bone metabolism, we examined the effect of ghrelin in vitro and in vivo. Ghrelin and its receptor, GHS-R1a, were identified in osteoblasts, and ghrelin promoted both proliferation and differentiation. Furthermore, ghrelin increased BMD in rats. Our results show that ghrelin directly affects bone formation.
Introduction: Ghrelin is a gut peptide involved in growth hormone (GH) secretion and energy homeostasis. Recently, it has been reported that the adipocyte-derived hormone leptin, which also regulates energy homeostasis and opposes ghrelin's actions in energy homeostasis, plays a significant role in bone metabolism. This evidence implies that ghrelin may modulate bone metabolism; however, it has not been clarified. To study the role of ghrelin in skeletal integrity, we examined its effects on bone metabolism both in vitro and in vivo.
Materials and Methods: We measured the expression of ghrelin and growth hormone secretagogue receptor 1a (GHS-R1a) in rat osteoblasts using RT-PCR and immunohistochemistry (IHC). The effect of ghrelin on primary osteoblast-like cell proliferation was examined by recording changes in cell number and the level of DNA synthesis. Osteoblast differentiation markers (Runx2, collagen α1 type I [COLI], alkaline phosphatase [ALP], osteocalcin [OCN]) were analyzed using quantitative RT-PCR. We also examined calcium accumulation and ALP activity in osteoblast-like cells induced by ghrelin. Finally, to address the in vivo effects of ghrelin on bone metabolism, we examined the BMD of Sprague-Dawley (SD) rats and genetically GH-deficient, spontaneous dwarf rats (SDR).
Results: Ghrelin and GHS-R1a were identified in osteoblast-like cells. Ghrelin significantly increased osteoblast-like cell numbers and DNA synthesis in a dose-dependent manner. The proliferative effects of ghrelin were suppressed by [D-Lys3]-GHRP-6, an antagonist of GHS-R1a, in a dose-dependent manner. Furthermore, ghrelin increased the expression of osteoblast differentiation markers, ALP activity, and calcium accumulation in the matrix. Finally, ghrelin definitely increased BMD of both SD rats and SDRs.
Conclusions: These observations show that ghrelin directly stimulates bone formation.