bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deletion of Aspartate 182 in OPG Causes Juvenile Paget' Disease by Impairing Both Protein Secretion and Binding to RANKL
Authors: Middleton-Hardie Catherine , Zhu Qing , Cundy Harry , Lin Jian-ming , Callon Karen , Tong Pak Cheung , Xu Jiake , Grey Andrew , Cornish Jill , Naot Dorit 
Published: April 2006

Abstract
Mutations in the OPG gene cause idiopathic hyperphosphatasia. We characterized the effects of one such mutation and found that the mutant OPG is poorly secreted and has reduced biological activity compared with the wildtype protein. Therefore, correct structure and cellular processing of OPG is essential for normal bone remodeling.
Introduction: Inactivating mutations in osteoprotegerin (OPG) cause juvenile Paget' disease (JPD). We recently reported a family with JPD in which affected members were homozygous for an in-frame mutation resulting in the deletion of aspartate 182 in OPG. Here we report the structural and functional characterization of the OPGΔD182 mutant protein.
Materials and Methods: Inhibition of osteoclastogenesis by the recombinant OPG proteins was studied in a murine bone marrow culture. Binding of wildtype and mutant OPG to RANKL was measured in two experimental systems: glutathione-S-transferase (GST) pull-down assay and surface plasmon resonance. Site-directed mutagenesis was used to study the glycosylation of OPGΔD182 in two potential glycosylation sites adjacent to the deleted aspartate residue at position 182. ELISA and Western blots were used to determine OPG concentrations in cell lysates and conditioned media from transiently transfected cells.
Results: OPGΔD182 inhibited the generation of osteoclasts less effectively than the wildtype protein and had a reduced ability to bind to RANKL. The apparent higher molecular weight of OPGΔD182 compared with the wildtype is a result of hyperglycosylation of asparagine residues at positions 178 and 183. Glycosylation at N183 has the potential to disrupt OPG structure by interfering with disulphide bond formation and correct protein folding. Transient transfection experiments in SaOS2 cells suggest that OPGΔD182 is retained within the cell, a typical response to unstable or incorrect protein folding.
Conclusions: Taken together, these data suggest that the deletion of aspartate 182 impairs both the secretion and activity of OPG, which in turn provides an explanation for the increased osteoclastogenesis and high bone turnover observed in JPD patients with this mutation.
Genome-Wide Scan Identified QTLs Underlying Femoral Neck Cross-Sectional Geometry That Are Novel Studied Risk Factors of Osteoporosis
Authors: Xiong Dong-Hai , Shen Hui , Xiao Peng , Guo Yan-Fang , Long Ji-Rong , Zhao Lan-Juan , Liu Yao-Zhong , Deng Hong-Yi , Li Jin-Long , Recker Robert R , Deng Hong-Wen 
Published: April 2006

Abstract
A genome-wide screen was conducted using a large white sample to identify QTLs for FNCS geometry. We found significant linkage of FNCS parameters to 20q12 and Xq25, plus significant epistatic interactions and sex-specific QTLs influencing FNCS geometry variation.
Introduction: Bone geometry, a highly heritable trait, is a critical component of bone strength that significantly determines osteoporotic fracture risk. Specifically, femoral neck cross-sectional (FNCS) geometry is significantly associated with hip fracture risk as well as genetic factors. However, genetic research in this respect is still in its infancy.
Materials and Methods: To identify the underlying genomic regions influencing FNCS variables, we performed a remarkably large-scale whole genome linkage scan involving 3998 individuals from 434 pedigrees for four FNCS geometry parameters, namely buckling ratio (BR), cross-sectional area (CSA), cortical thickness (CT), and section modulus (Z). The major statistical approach adopted is the variance component method implemented in SOLAR.
Results: Significant linkage evidence (threshold LOD = 3.72 after correction for tests of multiple phenotypes) was found in the regions of 20q12 and Xq25 for CT (LOD = 4.28 and 3.90, respectively). We also identified eight suggestive linkage signals (threshold LOD = 2.31 after correction for multiple tests) for the respective geometry traits. The above findings were supported by principal component linkage analysis. Of them, 20q12 was of particular interest because it was linked to multiple FNCS geometry traits and significantly interacted with five other genomic loci to influence CSA variation. The effects of 20q12 on FNCS geometry were present in both male and female subgroups. Subgroup analysis also revealed the presence of sex-specific quantitative trait loci (QTLs) for FNCS traits in the regions such as 2p14, 3q26, 7q21 and 15q21.
Conclusions: Our findings laid a foundation for further replication and fine-mapping studies as well as for positional and functional candidate gene studies, aiming at eventually finding the causal genetic variants and hidden mechanisms concerning FNCS geometry variation and the associated hip fractures.
Calcium- and Vitamin D3-Fortified Milk Reduces Bone Loss at Clinically Relevant Skeletal Sites in Older Men: A 2-Year Randomized Controlled Trial
Authors: Daly Robin M , Brown Melanie , Bass Shona , Kukuljan Sonja , Nowson Caryl 
Published: April 2006

Abstract
In this 2-year randomized controlled study of 167 men &gt;50 years of age, supplementation with calcium-vitamin D3-fortified milk providing an additional 1000 mg of calcium and 800 IU of vitamin D3 per day was effective for suppressing PTH and stopping or slowing bone loss at several clinically important skeletal sites at risk for fracture.
Introduction: Low dietary calcium and inadequate vitamin D stores have long been implicated in age-related bone loss and osteoporosis. The aim of this study was to assess the effects of calcium and vitamin D3 fortified milk on BMD in community living men &gt;50 years of age.
Materials and Methods: This was a 2-year randomized controlled study in which 167 men (mean age ± SD, 61.9 ± 7.7 years) were assigned to receive either 400 ml/day of reduced fat (∼1%) ultra-high temperature (UHT) milk containing 1000 mg of calcium plus 800 IU of vitamin D3 or to a control group receiving no additional milk. Primary endpoints were changes in BMD, serum 25(OH)D, and PTH.
Results: One hundred forty-nine men completed the study. Baseline characteristics between the groups were not different; mean dietary calcium and serum 25(OH)D levels were 941 ± 387 mg/day and 77 ± 23 nM, respectively. After 2 years, the mean percent change in BMD was 0.9-1.6% less in the milk supplementation compared with control group at the femoral neck, total hip, and ultradistal radius (range, p &lt; 0.08 to p &lt; 0.001 after adjusting for covariates). There was a greater increase in lumbar spine BMD in the milk supplementation group after 12 and 18 months (0.8-1.0%, p ≤ 0.05), but the between-group difference was not significant after 2 years (0.7%; 95% CI, −0.3, 1.7). Serum 25(OH)D increased and PTH decreased in the milk supplementation relative to control group after the first year (31% and −18%, respectively; both p &lt; 0.001), and these differences remained after 2 years. Body weight remained unchanged in both groups at the completion of the study.
Conclusions: Supplementing the diet of men &gt;50 years of age with reduced-fat calcium- and vitamin D3-enriched milk may represent a simple, nutritionally sound and cost-effective strategy to reduce age-related bone loss at several skeletal sites at risk for fracture in the elderly.
Dissimilar PTH, Gastrin, and Calcitonin Responses to Oral Calcium and Peptones in Hypocalciuric Hypercalcemia, Primary Hyperparathyroidism, and Normal Subjects: A Useful Tool for Differential Diagnosis
Authors: Bevilacqua Maurizio , Dominguez Ligia J , Righini Velella , Valdes Valeria , Vago Tarcisio , Leopaldi Ennio , Baldi Gabriella , Barrella Massimo , Barbagallo Mario 
Published: April 2006

Abstract
We analyzed gastrin, PTH, and calcitonin responses to oral calcium and peptones in hypocalciuric hypercalcemia, mild primary hyperparathyroidism, and normal controls. We observed diverse hormonal responses that may help in the differential diagnosis of these conditions.
Introduction: Hypocalciuric hypercalcemia (HH) is consequent to calcium-sensing receptor (CaSR) genetic mutations or anti-CaSR antibodies. CaSR is expressed in parathyroid tissue, thyroid C cells, and gastrin-secreting cells, where it has been suggested that on calcium and/or amino acid allosteric activation, promotes gastrin secretion.
Materials and Methods: We evaluated gastrin, PTH, and calcitonin responses to oral calcium (1 g) and peptones (10 g) in 10 patients with HH (mean age, 58.5 ± 10.3 years; F/M = 9/1), 15 patients with primary hyperparathyroidism (PH; mean age, 60.4 ± 8.3 years; F/M = 11/4), and 30 healthy controls (mean age, 60.3 ± 8.1 years). Statistical analyses for differences during oral loading tests were calculated with ANOVA for repeated measurements and comparisons between two groups were performed with Student's t-test.
Results: PTH response to peptones was markedly increased in patients with PH compared with flat responses in controls and HH patients (p &lt; 0.05). Gastrin increase after oral calcium was absent in HH and PH subjects (p &lt; 0.05 versus controls), and gastrin responses to peptones were blunted in HH and PH subjects compared with controls (p &lt; 0.05). PTH drop and calcitonin increase after calcium load observed in controls were absent in HH and PH subjects (p &lt; 0.05).
Conclusions: The marked difference in PTH response elicited by peptones observed in PH compared with subjects with HH may help in the differential diagnosis of these conditions without genetic studies. Peptones may stimulate CaSR-controlled hormones as an allosteric regulatory pathway. CaSR abnormalities may help to explain the different calcium- and peptones-induced hormonal responses observed in PH and HH compared with normal subjects.
Platelet-Derived Growth Factor Stimlates Sodium-Dependent Pi Transport in Osteoblastic Cells via Phospholipase Cγ and Phosphatidylinositol 3′-Kinase
Authors: Zhen Xuechu , Bonjour Jean-Philippe , Caverzasio Joseph 
Published: April 2006

Abstract
Inorganic phosphate (Pi) is a major regulator of cell metabolism. The Pi transport activity in the plasma membrane is a main determinant of the intracellular level of this ion. In bone-forming cells, Pi transport is important for the calcification of the bone matrix. In this study, the effect of platelet-derived growth factor (PDGF) on Pi transport activity and the signaling mechanism involved in this cellular response were analyzed. The results indicate that PDGF is a potent and selective stimulator of sodium-dependent Pi transport in the mouse calvaria-derived MC3T3-E1 osteoblast-like cells. The change in Pi transport induced by PDGF-BB was dependent on translational processes and affected the Vmax of the Pi transport system. These observations suggested that enhanced Pi transport activity in response to PDGF resulted from insertion of newly synthesized Pi transporters in the plasma membrane. The role of activation of mitogen activated protein (MAP) kinase, phospholipase C (PLC)γ or phosphatidylinositol 3-kinase (PI-3–kinase), in mediating this effect of PDGF, was investigated. A selective inhibitor of the PDGF receptor tyrosine kinase activity (CGP 53716) completely blocked PDGF-induced protein tyrosine phosphorylation of several proteins including the PDGF receptor, PLCγ, MAP kinase, and association of the p85 subunit of PI-3′-kinase. Associated with this effect, the increase in Pi transport induced by PDGF was completely blunted by 5 μM CGP 53716. Inhibition of MAP kinase activity by cAMP agonists did not influence Pi transport stimulation induced by PDGF. However, inhibitors of protein kinase C completely blocked this response. A selective inhibitor of PI-3-kinase, LY294002, also significantly reduced this effect of PDGF. In summary, these results indicate that PDGF is a potent and selective stimulator of Pi transport in osteoblastic cells. The mechanism responsible for this effect is not mediated by MAP kinase but involves tyrosine phosphorylation-dependent activation of PLCγ and PI-3-kinase.
Expression of Tenascin-C in Bones Responding to Mechanical Load
Authors: Webb Chloë M. B. , Zaman Gul , Mosley John R. , Tucker Richard P. , Lanyon Lance E. , Dr. Mackie Eleanor J. 
Published: April 2006

Abstract
A number of early biochemical responses of bone cells to mechanical loading have been identified, but the full sequence of events from the sensing of strain to the formation of new bone is poorly characterized. Extracellular matrix proteins can modulate cell behavior and would be ideal molecules to amplify the early response to loading. The extracellular matrix protein, tenascin-C, supports differentiation of cultured osteoblast-like cells. The current study was carried out to investigate whether expression patterns of tenascin-C in loaded bones support a role for this protein as a mediator of the osteoregulatory response to loading. Tenascin-C expression was investigated by Northern blot analysis in rat ulnae subjected to an established noninvasive loading regimen engendering physiological strain levels. RNA extracted from loaded compared with contralateral control bones 6 h after loading showed a significant increase in tenascin-C transcript expression. The presence of tenascin-C was investigated by immunohistochemistry in bones of animals killed 3, 5, or 15 days after the initiation of daily loading. In animals killed at 3 or 5 days, periosteal surfaces undergoing load-induced reversal from resorption to formation showed enhanced tenascin-C staining. In animals killed at 15 days, the bone formed in response to loading was clearly demarcated from old bone by strong tenascin-C staining of reversal lines. Within this new bone, tenascin-C staining was seen in the lacunae of older but not more recently embedded osteocytes. The results presented here indicate that tenascin-C expression by bone cells is enhanced in the early osteogenic response to loading. This may indicate that tenascin-C acts as a mediator of the mechanically adaptiveresponse.
Pooling of Clodronate Urinary Excretion Data: A New Pharmacokinetic Method to Study Drugs with Highly Variable Gastrointestinal Absorption
Authors: Castrén-Kortekangas Päivi , Löyttyniemi Eliisa , Liukko-Sipi Sirpa , Juhakoski Auni , Smal Jaana , Dr. Laitinen Kalevi 
Published: April 2006

Abstract
Gastrointestinal absorption of bisphosphonates is highly variable from individual to individual (between-subject variation) and from day to day (within-subject variation), a fact that creates problems both in research and in clinical use of these drugs. We conducted a randomized, two-period cross-over pharmacokinetic (phase I) study to assess the relative bioavailability of two different clodronate preparations: an 800 mg tablet and a 400 mg capsule. Urinary excretion of clodronate correlates with gastrointestinal absorption. To minimize the confounding effect of the high variability of gastrointestinal absorption, we chose as the primary parameter the cumulative amount of clodronate excreted into urine (Ae0-t) during 9 days (7 days of treatment, 2 days of follow-up). The 90% confidence interval calculated for the population medians of Ae0-t was 0.83–1.09, well within the 90% confidence interval stipulated for bioequivalence for the area under the curve values (0.80–1.25). This new procedure for pooling urinary excretion data offered a clear advantage over previous methods, and thus could presumably be used to study other drugs as well that are not metabolized and may show highly variable gastrointestinal absorption.
Is Skeletal Responsiveness to Thyroid Hormone Altered in Primary Osteoporosis or Following Estrogen Replacement Therapy?
Authors: Langdahl Bente L. , Loft Anne Gitte , Møller Niels , Weeke Jørgen , Eriksen Erik F. , Mosekilde Leif , Charles Peder 
Published: April 2006

Abstract
Hyperthyroidism is characterized by increased bone turnover and resorptive activity. Similar changes in remodeling are seen in osteoporosis. To study the pathogenetic role of thyroid hormone in osteoporosis, we measured concentrations of free and total thyroid hormones and investigated the sensitivity of the skeleton toward thyroid hormones in 14 osteoporotic, 16 estrogen-treated, and 15 normal postmenopausal women with comparable thyroid status. Triiodothyronine (T3, 60 μg/day for 7 days) was administered to the three groups. The skeletal response was assessed by monitoring bone alkaline phosphatase (BAP), osteocalcin (BGP), and pyridinium cross-linked telopeptide domain of type I collagen (ICTP) in serum and urinary excretion of hydroxyproline (OHP), pyridinoline (PYR), and deoxypyridinoline (DPR) at days 0, 8, 15, and 57. Women on estrogen replacement therapy exhibited lower bone turnover than the normal postmenopausal women. Markers of bone formation were reduced by 19–43% and markers of resorption by 22–48%. The osteoporotic women displayed lower bone mass at the lumbar spine and the distal forearm (p &lt; 0.01–0.001), but the levels of biochemical markers of bone formation and resorption were comparable to values obtained in the normal postmenopausal women. T3 stimulation caused significant increases (p values ranging between 0.05–0.001) in all three groups of the resorptive markers: ICTP (47%, 47%, 45%), OHP (29%, 30%, 33%), PYR (43%, 27%, 51%), and DPR (42%, 24%, 59%). Of the formative markers, only BGP increased significantly (32%, 40%, 47%) (p &lt; 0.001). At day 57, however, all three formative markers increased compared with day 15 (p &lt; 0.05–0.001). No significant differences in bone markers were demonstrated between groups. In the osteoporotic group, as the only group, serum calcium increased (p &lt; 0.05) and serum PTH fell (p &lt; 0.05). In conclusion, osteoporosis and estrogen substitution are not characterized by altered concentrations of thyroid hormones or responsiveness to thyroid hormones at the level of individual bone cells; however, altered responses pertaining to PTH and calcium were detected.
Recombinant Transforming Growth Factor-β1 Induces Endochondral Bone in the Baboon and Synergizes with Recombinant Osteogenic Protein-1 (Bone Morphogenetic Protein-7) to Initiate Rapid Bone Formation
Authors: Ripamonti U. , Duneas N. , van Den Heever B. , Bosch C. , Crooks J. 
Published: April 2006

Abstract
Several members of the bone morphogenetic protein (BMP) and transforming growth factor-β (TGF-β) families are molecular regulators of cartilage and bone regeneration, although their actual roles and combined interactions in skeletal repair are poorly understood. The presence of several molecular forms suggests multiple functions in vivo as well as synergistic interactions during both embryonic bone development and regeneration of cartilage and bone in postfetal life. Here we show for the first time that recombinant human transforming growth factor-β1 (TGF-β1) induces endochondral bone formation in extraskeletal sites of adult baboons. We also show that TGF-β1 and recombinant human osteogenic protein-1 (OP-1, bone morphogenetic protein-7) synergize in inducing large ossicles in extraskeletal sites of the primate as early as 15 days after implantation. A single application of OP-1, in conjunction with an insoluble collagenous matrix as carrier (5, 25, and 125 μg/100 mg of carrier matrix) induced bone differentiation in the rectus abdominis of the baboon. This level of tissue induction was raised several-fold by the simultaneous addition of comparatively low doses of TGF-β1 (0.5, 1.5, and 5 μg), which by itself induces bone formation in the rectus abdominis at doses of 5 μg/100 mg of carrier matrix. Combinations of OP-1 and TGF-β1 yielded a 2- to 3-fold increase in cross-sectional area of the newly generated ossicles, with markedly elevated key parameters of bone formation, and corticalization of the newly formed bone by day 15, culminating in bone marrow generation by day 30. The tissue generated by the combined application of OP-1 and TGF-β1 showed distinct morphological differences when compared with OP-1–treated specimens, with large zones of endochondral development and extensive bone marrow formation. At the doses tested, synergy was optimal at a ratio of 1:20 by weight of TGF-β1 and OP-1, respectively. These results provide evidence for a novel function of TGF-β1 in the primate and the scientific basis for synergistic molecular therapeutics for the rapid regeneration of cartilage and bone.
Stimulatory Effects of Basic Fibroblast Growth Factor and Bone Morphogenetic Protein-2 on Osteogenic Differentiation of Rat Bone Marrow-Derived Mesenchymal Stem Cells
Authors: Hanada Keigo , Dennis James E. , Caplan Arnold I. 
Published: April 2006

Abstract
Bone marrow stroma contains multipotential mesenchymal progenitor cells which can differentiate into osteoblastic cells; we refer to these cells as mesenchymal stem cells (MSCs). Basic fibroblast growth factor (bFGF) and bone morphogenetic protein-2 (BMP-2) have been implicated in the osteogenic regulatory process by virtue of their mitogenic and differentiation activities, respectively. This study examines and compares the effects of bFGF and BMP-2 on dexamethasone (Dex)-dependent in vitro osteogenic differentiation of rat marrow–derived MSCs. A 6-day exposure to bFGF markedly stimulated cell growth and induced osteoblastic differentiation as shown by osteocalcin mRNA expression (day 14), bone nodule formation (day 18), and calcium deposition (day 18). These results indicate that bFGF enhances both mitogenic activity and osteogenic development of Dex-treated marrow MSCs. In contrast, BMP-2 did not induce osteogenesis as strongly as bFGF. Thus, exposure to BMP-2 slightly increased bone nodule number and calcium content compared with the control. Exposure of MSCs to both BMP-2 and bFGF induced expression of osteocalcin mRNA and mineralizing bone-like nodules as early as day 11 and resulted in enhancement of bone formation more markedly than either factor alone. Consistent with these results, porous calcium phosphate ceramic cubes implanted in vivo, which were loaded with MSCs pre-exposed to both bFGF and BMP-2, showed higher histologic score for bone formation than those with MSCs pre-exposed to either bFGF or BMP-2 alone. These data indicate that combined treatment with bFGF and BMP-2 synergistically enhances the osteogenic potency of bFGF in rat marrow MSC culture.