bluuebunny/crossref_metadata_2025 huggingface dataset:
Bone Mineral Density in Girls with Forearm Fractures
Authors: Dr. Goulding A. , Cannan R. , Williams S. M. , Gold E. J. , Taylor R. W. , Lewis-Barned N. J.
Published: April 2006

In childhood, the most common site of fracture is the distal forearm. To determine whether young girls with these fractures have low bone density more commonly than fracture-free controls, we measured bone density at the radius, spine, hip, and whole body and total body bone mineral content, lean tissue mass, and fat mass by dual-energy X-ray absorptiometry in 100 Caucasian girls aged 3–15 years with recent distal forearm fractures and 100 age- and gender-matched controls. Bone density (age-adjusted ratios of all cases:controls with 95% confidence intervals) was lower in cases at the ultradistal radius 0.963 (0.930–0.996), 33% radius 0.972 (0.945–0.999), lumbar spine 0.945 (0.911–0.980), hip trochanter 0.952 (0.918–0.988), and total body 0.978 (0.961–0.995). Moreover, osteopenia (defined as Z score below −1), was more common in cases than controls (p < 0.05) in the forearm, spine, and hip, with one third of fracture cases having low spinal density. Odds ratios (95% confidence intervals) for low bone density were: ultradistal radius, 2.2 (1.1–4.6); lumbar spine, L2-L4, 2.6 (1.3–4.9); and femur trochanter, 2.0 (1.0–3.9). Fracture patients aged 8-10 years weighed more (mean ± SD) than age-matched controls (37.2 ± 8.0 kg vs. 32.5 ± 6.6 kg, p < 0.01) while older patients reported lower current and past calcium intakes than matched controls (p < 0.05). We conclude that low bone density is more common throughout the skeleton in girls with forearm fractures than in those who have never broken a bone, supporting the view that low bone density may contribute to fracture risk in childhood.
Inhibition of Avian Osteoclast Bone Resorption by Monoclonal Antibody 121F: A Mechanism Involving the Osteoclast Free Radical System
Authors: Collin-Osdoby Patricia , Li Li , Rothe Linda , Anderson Fred , Kirsch David , Oursler Merry Jo , Osdoby Philip
Published: April 2006

Osteoclasts generate high levels of superoxide anions during bone resorption that contribute to the degradative process, although excessive levels of this free radical may be damaging. One mechanism for their removal is via superoxide dismutase (SOD), a protective superoxide scavenging enzyme. We have previously described a novel developmentally regulated 150 kDa plasma membrane glycoprotein of avian osteoclasts which is reactive with the osteoclast-specific monoclonal antibody (Mab) 121F and is related immunologically, biochemically, and in protein sequence to mitochondrial Mn2+/Fe2+ SOD. We hypothesized that this unusual osteoclast surface component may be involved in protection against superoxides generated during active bone resorption. Increasing concentrations of monovalent Fab fragments prepared from Mab 121F, but not those from another antiosteoclast Mab designated 29C, markedly inhibited both bone particle and bone pit resorption by avian osteoclasts, while reducing tartrate-resistant acid phosphatase activity and causing the morphological contraction of osteoclasts on bone. Thus, the SOD-related membrane antigen may be essential for osteoclast bone resorption. Osteoclast superoxide production, monitored kinetically by cytochrome c reduction and histochemically by nitroblue tetrazolium reduction staining, was significantly greater in the presence of 121F, but not 29C, Fab treatment. Furthermore, the release of another free radical known as nitric oxide, which is produced by osteoclasts, can scavenge superoxides, and acts to potently inhibit osteoclast bone resorption, was dose-dependently increased by 121F Fab in resorbing osteoclast cultures. Therefore, Mab 121F binding may block the potential protective function of the osteoclast plasma membrane SOD-related glycoprotein, leading to a rapid elevation of superoxide levels and a subsequent rise in osteoclast nitric oxide release, feedback messages which may be sensed by the osteoclast as signals to cease active bone resorption.
Association of a Polymorphism of the Transforming Growth Factor-β1 Gene with Genetic Susceptibility to Osteoporosis in Postmenopausal Japanese Women
Authors: Yamada Yoshiji , Miyauchi Akimitsu , Goto Junki , Takagi Yasuyuki , Okuizumi Hiroyasu , Kanematsu Masahiro , Hase Makoto , Takai Hiroyuki , Harada Atsushi , Ikeda Kyoji
Published: April 2006

Transforming growth factor-β (TGF-β) is both abundant in bone and an important regulator of bone metabolism. A T→C transition at nucleotide 29 in the signal sequence region of the TGF-β1 gene results in a Leu→Pro substitution at amino acid position 10. The possible association of this polymorphism with bone mass and the prevalence of osteoporosis has now been investigated in a total of 287 postmenopausal women from two regions (Obu City, Aichi Prefecture, and Sanda City, Hyogo Prefecture) of Japan. A significant association of TGF-β1 genotype with bone mass was detected in both populations; bone mineral density (BMD) at the lumbar spine was greater in individuals with the CC genotype than in those with the TT or TC genotype. The frequency of vertebral fractures was significantly lower in individuals with the CC genotype than in those with the TC or TT genotypes. For each region, multivariable logistic regression analysis revealed that the frequency of the T allele was significantly higher in subjects with osteoporosis than in controls. Also, the serum concentration of TGF-β1 in individuals with the CC genotype was significantly higher than that in age-matched subjects with the TC or TT genotype in osteoporotic or osteopenic as well as healthy control groups. These results suggest that the T/C polymorphism of the TGF-β1 gene is one of the genetic determinants of bone mass and that the T allele is an independent risk factor for the genetic susceptibility to osteoporosis in postmenopausal Japanese women. Thus, analysis of the TGF-β1 genotype may be useful in the prevention and management of osteoporosis.
The Effects of Twelve Weeks of Bed Rest on Bone Histology, Biochemical Markers of Bone Turnover, and Calcium Homeostasis in Eleven Normal Subjects
Authors: Zerwekh Joseph E. , Ruml Lisa A. , Gottschalk Frank , Pak Charles Y. C.
Published: April 2006

This study was undertaken to examine the effects of 12 weeks of skeletal unloading on parameters of calcium homeostasis, calcitropic hormones, bone histology, and biochemical markers of bone turnover in 11 normal subjects (9 men, 2 women; 34 ± 11 years of age). Following an ambulatory control evaluation, all subjects underwent 12 weeks of bed rest. An additional metabolic evaluation was performed after 12 days of reambulation. Bone mineral density declined at the spine (−2.9%, p = 0.092) and at the hip (−3.8%, p = 0.002 for the trochanter). Bed rest prompted a rapid, sustained, significant increase in urinary calcium and phosphorus as well as a significant increase in serum calcium. Urinary calcium increased from a pre-bed rest value of 5.3 mmol/day to values as high as 7.3 mmol/day during bed rest. Immunoreactive parathyroid hormone and serum 1,25-dihydroxyvitamin D declined significantly during bed rest, although the mean values remained within normal limits. Significant changes in bone histology included a suppression of osteoblastic surface for cancellous bone (3.1 ± 1.3% to 1.9 ± 1.5%, p = 0.0142) and increased bone resorption for both cancellous and cortical bone. Cortical eroded surface increased from 3.5 ± 1.1% to 7.3 ± 4.0% (p = 0.018) as did active osteoclastic surface (0.2 ± 0.3% to 0.7 ± 0.7%, p = 0.021). Cancellous eroded surface increased from 2.1 ± 1.1% to 4.7 ± 2.2% (p = 0.002), while mean active osteoclastic surface doubled (0.2 ± 0.2% to 0.4 ± 0.3%, p = 0.020). Serum biochemical markers of bone formation (osteocalcin, bone-specific alkaline phosphatase, and type I procollagen extension peptide) did not change significantly during bed rest. Urinary biochemical markers of bone resorption (hydroxyproline, deoxypyridinoline, and N-telopeptide of type I collagen) as well as a serum marker of bone resorption (type I collagen carboxytelopeptide) all demonstrated significant increases during bed rest which declined toward normal during reambulation. Thus, under the conditions of this study, the human skeleton appears to respond to unloading by a rapid and sustained increase in bone resorption and a more subtle decrease in bone formation.
Parathyroid Hormone-Related Protein mRNA and Protein Expression in Multiple Myeloma: A Case Report
Authors: Schneider Hans-Gerhard , Kartsogiannis Vicky , Zhou Hong , Chou S. T. , Martin T. John , Grill Vivian
Published: April 2006

Multiple myeloma frequently leads to complications, such as osteolytic lesions, hypercalcemia, and pathological fractures. Increased bone resorption in myeloma is due to osteoclast activation. The nature of the osteoclast activator(s) remains unclear. We describe a case of multiple myeloma with marked hypercalcemia and skeletal complications that progressed rapidly despite chemotherapy. The patient had marked hypercalcemia at diagnosis (4.5 mmol/l), and elevated parathyroid hormone-related protein (PTHrP) levels were found in plasma. Analysis of the bone marrow trephine biopsy showed PTHrP gene transcription and protein in myeloma cells. These results provide strong evidence for the production of significant amounts of PTHrP by human myeloma cells. PTHrP has been measured as elevated in the plasma of patients with myeloma and might be an important contributor to the skeletal complications in this disease.
Evaluation of Low Density Spine Software for the Assessment of Bone Mineral Density in Children
Authors: Leonard Mary B. , Feldman Harold I. , Zemel Babette S. , Berlin Jesse A. , Barden Elizabeth M. , Stallings Virginia A.
Published: April 2006

Pediatric dual-energy X-ray absorptiometry spine scans often cannot be analyzed with standard software due to a failure to identify the bone edges of low density vertebrae. Low density spine (LDS) software improves bone detection compared with standard software. The objective of this study was to compare bone mineral density (BMD) measurements obtained with the standard and LDS software in 27 healthy nonobese, 32 obese, and 41 chronically ill children, ages 2–18 years. Lumbar spine (L1–L4) BMD, measured by standard analysis, ranged from 0.531–1.244 gm/cm2. Reanalysis with the LDS software resulted in a systematic increase (mean ± SD) in estimated bone area of 17.0 ± 5.0%, an increase in bone mineral content of 6.1 ± 6.3%, and a mean decrease in BMD of 8.7 ± 1.7% (all p < 0.001). This resulted in a mean decrease in BMD Z score of 0.7 ± 0.2. Linear regression models, predicting standard BMD from LDS BMD, were fit for the three subject groups (R2 = 0.993–0.995). Small differences in slopes were detected across groups (p = 0.07); LDS BMD predicted higher standard BMD in obese subjects. In conclusion, LDS analysis resulted in a clinically significant decrease in measured BMD. The association between analysis methods was exceptionally high (R2 > 0.99), indicating that LDS BMD accurately predicts standard BMD. Although LDS BMD in obese subjects predicts higher standard BMD results than in nonobese subjects, the small difference is of questionable clinical significance. LDS software is a useful tool for the assessment of BMD in children.
Human Osteoclast Formation and Activity In Vitro: Effects of Alendronate
Authors: Breuil V. , Cosman F. , Stein L. , Horbert W. , Nieves J. , Shen V. , Lindsay R. , Dempster D. W.
Published: April 2006

Recent advances in technique have made it possible to study human osteoclast (OC) formation and activity in vitro. The object of the present study was to determine the effects of alendronate (ALN) on human OCs generated from precursors obtained from standard peripheral blood samples. Peripheral blood mononuclear cells from 14 postmenopausal women were cocultured with ST2 stromal cells on bone slices in the presence of 10−7 M 1,25-dihydroxyvitamin D3, 10−8 M dexamethasone, and 25 ng/ml human macrophage colony-stimulating factor. After 21 days, the cultures contained numerous OCs, which were characterized by multinuclearity, the presence of tartrate-resistant acid phosphatase, calcitonin and vitronectin receptors, and the ability to resorb substantial amounts of bone, which was inhibited by calcitonin. The percentage area of bone resorbed per slice was highly correlated (r = 0.89, p < 0.001) with the concentration of Type I collagen cross-linked C-telopeptides (CTx) released into the culture medium. When added to the medium, ALN inhibited bone resorption at concentrations ≤10−7 M. At 10−7 M, inhibition was achieved primarily by a reduction in OC activity without a marked effect on OC number. At the highest concentration studied (10−5 M), both OC number and resorption were profoundly decreased. Overnight preincubation of bone slices in ALN, without further exposure to ALN, resulted in an inhibition of resorption that was similar to that seen when ALN was present in the medium throughout the entire culture period. We conclude that, except at very high concentrations, the predominant mechanism of action of ALN is to inhibit the activity of differentiated human OCs with little or no effect on recruitment. Interaction between the OC and ALN on the bone surface is an important component of the inhibitory mechanism. Measurement of CTx in tissue culture medium is a convenient method for assessment of bone resorption in human OC cultures and offers a number of advantages over morphometric analysis of the bone slice.
Treatment of Established Postmenopausal Osteoporosis with Raloxifene: A Randomized Trial
Authors: Lufkin Edward G. , Whitaker Michael D. , Nickelsen Thomas , Argueta Rodolfo , Caplan Robert H. , Knickerbocker Ronald K. , Riggs B. Lawrence
Published: April 2006

Raloxifene is a selective estrogen receptor modulator that in experimental animals acts as an estrogen receptor antagonist in breast and endometrium but as an estrogen receptor agonist in the skeletal and cardiovascular systems. We conducted a 1-year prospective, randomized, double-blind trial in 143 postmenopausal osteoporotic women (mean ± SD age, 68.4 ± 5.0 years) with at least one prevalent vertebral fractures and low bone mineral density (BMD), comparing groups receiving raloxifene at 60 mg/day (RLX60) or 120 mg/day (RLX120) and a control group receiving supplements of 750 mg/day of calcium and 400 IU/day of vitamin D. There were no differences among groups in the occurrence of uterine bleeding, thrombophlebitis, breast abnormalities, or increased endometrial thickness (assessed by ultrasonography). As compared with controls, the changes in values over 1 year for RLX60 and RLX120, respectively, were significant for serum bone alkaline phosphatase (−14.9%, −8.87%), serum osteocalcin (−20.7%, −17.0%), and urinary C-telopeptide fragment of type I collagen/creatinine (−24.9%, −30.8%), markers of bone turnover; for serum total cholesterol (−7.0% for RLX60) and low density lipoprotein cholesterol (LDL) (−11.4% for RLX60) and for the LDL/HDL cholesterol ratio (−13.2%, −8.3%). BMD increased significantly in the total hip (1.66% for RLX60) and ultradistal radius (2.92%, 2.50%). There were nonsignificant trends toward increases over controls in BMD for lumbar spine, total body, and total hip (for RLX120). Using a >15% cutoff definition, raloxifene had no effect on incident fractures, but using a >30% cutoff, there was a dose-related reduction (p = 0.047). We conclude that raloxifene therapy is well tolerated, reduces serum lipids, and does not stimulate the uterus or breasts. It has beneficial effects on bone, although, under the conditions of this study, these appear to be of a smaller magnitude than have been reported with estrogen therapy.
Intermittent Use of Nitrates Increases Bone Mineral Density: The Study of Osteoporotic Fractures
Authors: Jamal Sophie A. , Browner Warren S. , Bauer Douglas C. , Cummings Steven R.
Published: April 2006

Nitric oxide slows bone remodeling and bone loss in animals. Because nitroglycerin and other nitrates increase nitric oxide levels, we hypothesized that nitrate use may be associated with greater bone mineral density (BMD) and decreased risk of fracture in humans. Further, intermittent nitrate use may be associated with greater benefits than daily nitrate use, which results in tachyphylaxis. We tested this hypothesis using data from the Study of Osteoporotic Fractures. We prospectively studied 6201 elderly women of whom 317 took nitrates on a daily basis and 74 used them intermittently. We measured BMD at the hip and the heel and adjusted all comparisons for multiple potential confounders. We found that women taking daily nitrates had slightly greater hip BMD (difference, 1.3%; 95% confidence interval [CI], 0.14–4.1%) but the same heel BMD (difference, 0%; 95% CI −2.6–2.6%) as nonusers. By contrast, women using nitrates intermittently had substantially greater hip (difference, 2.6%; 95% CI, 0.4–6.8%) and heel BMD (difference, 5.3%; 95% CI, 2.6–11%) than nonusers. This study suggests that the intermittent administration of nitrates may enhance BMD.
Mechanical Loading Stimulates Bone Formation by Reactivation of Bone Lining Cells in 13-Week-Old Rats
Authors: Chow J. W. M. , Wilson A. J. , Chambers T. J. , Fox S. W.
Published: April 2006

The bone formation that occurs in response to mechanical stimulation is generally considered to be a means by which bone adapts to changes in its mechanical environment. We have previously shown that the expression of genes for bone matrix proteins is maximal 72 h after a single 5-minute episode of loading of tail vertebrae of 13-week-old female rats, that the predominant increase in mineralization occurs after 3 days, and that the osteogenic response to mechanical stimulation is not dependent on prior bone resorption. We have now investigated the cellular correlates of this osteogenic response. No proliferation was detected, by pulse or flash labeling, in the trabecular bone surface cells of animals killed 1 h to 10 days after the loading episode. Ultrastructural examination revealed that most of the cells covering the trabecular bone surface of control vertebrae were flat bone lining cells. After mechanical stimulation, the trabecular bone surface cells developed ultrastructural features of osteoblastic differentiation and activity, with acquisition of an increasingly cuboidal shape, rounded nuclei, and abundant rough endoplasmic reticulum. Morphometric analysis of the mean cell area, mean nuclear area, and cell and nuclear height showed that they were all maximal 48 h after loading. By 120 h after loading, the appearances of bone surface cells had reverted to those of control vertebrae. Thus, mechanical loading appears to activate lining cells, with a temporal sequence that correlates with bone matrix production.
Zoledronate Prevents the Development of Absolute Osteopenia Following Ovariectomy in Adult Rhesus Monkeys
Authors: Binkley Neil , Kimmel Donald , Bruner Julia , Haffa Arlene , Davidowitz Bradley , Meng Cliff , Schaffer Victoria , Green Jonathan
Published: April 2006

This study assessed effects of the bisphosphonate zoledronate (ZLN) on bone density and biochemical markers of bone turnover in ovariectomized (OVX) adult female rhesus monkeys. Forty monkeys were randomly assigned to one control or four OVX groups. The control and one OVX group received saline, and the other three OVX groups received ZLN (0.5, 2.5, or 12.5 μg/kg) by a single weekly subcutaneous injection for 69 weeks. Bone mass of the total body (TB), lumbar spine (LS), distal and central radius (dual-energy X-ray absorptiometry), and skeletal turnover markers were measured at baseline and at 13, 26, 39, 52, and 69 weeks of treatment. Increased skeletal turnover and decreased bone mass (LS and TB) were demonstrable by 13 weeks post-OVX. Maximal bone loss (7–8%) at these sites occurred by 39 weeks after OVX and persisted for the study duration. Long-term ZLN treatment was well tolerated and prevented increased skeletal turnover and bone loss in a dose-dependent fashion. Progressive turnover suppression was not observed with any ZLN dose. In conclusion, after OVX, adult rhesus monkeys develop persistent increased bone turnover and absolute osteopenia of the LS and TB, making them an outstanding model of skeletal behavior in perimenopausal women. These OVX-related skeletal changes are dose-dependently blocked by ZLN.
Changes in Bone Turnover Induced by Aerobic and Anaerobic Exercise in Young Males
Authors: Woitge Henning W. , Friedmann Birgit , Suttner Stefan , Farahmand Iris , Müller Martin , Schmidt-Gayk Heinrich , Baertsch Peter , Ziegler Reinhard , Seibel Markus J.
Published: April 2006

Physical activity is considered an important factor in attaining bone mass. However, the mechanisms by which exercise affects bone metabolism are not completely understood. The present study was performed to investigate the effects of aerobic and anaerobic exercise on bone turnover. Twenty healthy young males (aged 20–29 years) were followed through an 8-week program of aerobic (n = 10) and anaerobic training (n = 10). Ten age-matched individuals served as controls. Serum bone-specific alkaline phosphatase (BAP), serum osteocalcin (OC), and urinary pyridinoline (Pyd) and deoxypyridinoline (Dpd) were determined as indices of bone metabolism. After 4 weeks of aerobic training, serum BAP and OC (p < 0.01), and urinary Pyd (p < 0.001) and Dpd (p < 0.01) were significantly reduced. After 8 weeks, BAP and OC levels had returned to baseline values, whereas the urinary cross-link excretion remained low. In the anaerobic training group, elevated levels of BAP (p < 0.05 vs. week 4), OC (p < 0.05 vs. week 4), and Pyd (p < 0.01 vs. week 0) were observed after 8 weeks of exercise. Changes in urinary Pyd and Dpd (week 0 vs. week 8) were positively correlated with changes in the mean power level in the Wingate test, a parameter of the anaerobic performance capacity (r = 0.50 and r = 0.55, p < 0.01, respectively). In the controls, no significant changes in biochemical markers were observed. We conclude that aerobic and anaerobic training excert different effects on bone metabolism. While aerobic training led to changes compatible with reduced bone resorption activity, anaerobic training seems to result in an overall accelerated bone turnover. Therefore, the impact of physical activity on bone turnover may depend on the kind of exercise performed.
Homologous Up-Regulation of Vitamin D Receptors Is Tissue Specific in the Rat
Authors: Gensure Robert C. , Antrobus Steve D. , Fox John , Okwueze Martina , Talton Stephanie Y. , Walters Marian R.
Published: April 2006

1,25-dihydroxyvitamin D3 (1,25(OH)2D3) receptors (VDR) are expressed in multiple tissues within the body. VDR levels are increased by 1,25(OH)2D3 in intestine and kidney and in numerous cell models. The ability of 1,25(OH)2D3 to affect VDR levels in other target tissues in vivo was studied by assessing VDR levels by the3H-1,25(OH)2D3 binding assay under varied physiological conditions in the rat. When compared with vitamin D–deficient (−D) controls, rats raised on a normal vitamin D–sufficient (+D) diet showed elevated VDR levels in kidney (391 ± 53 vs. 913 ± 76 fmol/g of tissue; p < 0.05), but not in testis, heart, or lung. Up-regulation of the VDR also occurred in kidney of +D rats 1 day after a single 100-ng dose of 1,25(OH)2D3 (454 ± 43 vs. 746 ± 113 fmol/mg of DNA; p < 0.05), but no changes were seen in intestine, testis, or lung. Because 1,25(OH)2D3-induced hypercalcemia may independently affect VDR regulation, 1,25(OH)2D3 was infused into −D rats, and normocalcemia was maintained by reduced dietary calcium intake. In this model, the renal VDR was again up-regulated (446 ± 115 vs. 778 ± 58 fmol/mg of DNA; p < 0.05), but VDR levels in testis and lung were unaffected. Scatchard analysis and tests of 1,25(OH)2D3 dose (1–100 ng/day for 7 days) and temporal (100 ng/day for 1–7 days) responsiveness further supported the tissue-specific nature of the homologous VDR regulation. Assay of VDR levels by l-1-tosylamido-2-phenylethyl chloromethyl ketone–3H-1,25(OH)2D3 exchange assay ruled out differences in endogenous 1,25(OH)2D3 occupancy as the basis for the observed differences in VDR regulation. Finally, coidentity of the VDR-like sites in kidney versus testis was confirmed by competitive binding analysis comparing their relative affinities for 25(OH)D3 versus 1,25(OH)2D3 (30.5 ± 6.4 vs. 35.6 ± 3.6 in kidney and testis, respectively) and by immunoblot analysis using a highly specific monoclonal anti-rat VDR antibody. Thus, under a wide variety of experimental conditions, homologous up-regulation of the VDR occurs in the rat kidney in vivo, but not in several other target tissues which do not regulate plasma calcium homeostasis. Moreover, this differential VDR regulation did not result from secondary changes in plasma calcium, from differential 1,25(OH)2D3 responsiveness in the various tissues, nor from differences in endogenous 1,25(OH)2D3 occupancy of the VDR. These studies thus establish that, in contrast to observations in vitro, the widely described phenomenon of homologous VDR up-regulation in kidney and intestine is not a universal property of 1,25(OH)2D3 target tissues in vivo in the rat.
Morphometric X-Ray Absorptiometry: Reference Data for Vertebral Dimensions
Authors: Mrs. Rea J. A. , Steiger P. , Blake G. M. , Potts E. , Smith I. G. , Fogelman I.
Published: April 2006

Vertebral fractures are a common and important consequence of osteoporosis and are often identified via morphometric analysis of conventional lateral spine radiographs (morphometric radiography or MRX). A new method of performing vertebral morphometry using images acquired on dual-energy X-ray absorptiometry (DXA) scanners (morphometric X-ray absorptiometry or MXA) has recently been developed. In this study, we derive reference data for vertebral heights and height ratios using MXA scans as the data source and compare the results with previously published MRX studies. One thousand and nineteen Caucasian women (mean age 63 years, range 33–86) were recruited. An MXA scan, covering 13 vertebrae from L4 to T4, was acquired for each subject on one of four DXA systems located at three centers in the U.K. Analysis of variance found statistically significant but relatively small differences among centers, machines, and scan modes, and therefore data were pooled for reference range calculations. Three vertebral heights (anterior, mid, and posterior) were measured and four ratios (wedge, mid-wedge, and two crush) calculated. These data sets were trimmed using an iterative algorithm to remove extreme values assumed to represent deformed vertebrae, then mean and SD values were calculated using the remaining data. When the data were split by age, a small but statistically significant decrease in vertebral height between the sixth and eighth decades was found, but this was not replicated for the vertebral height ratios. Marked differences were observed between MXA data and MRX, but were comparable to those between different MRX studies. These may result from differences in image quality and point placement protocols, population differences, differences in radiographic technique, and differences in the derivation of a group of “normal” vertebrae. This study suggests that reference data of vertebral dimensions should be specific to the technique which uses those data as a reference, i.e., MXA.
Calcium Supplementation Suppresses Bone Turnover During Weight Reduction in Postmenopausal Women
Authors: Ricci Trina A. , Chowdhury Hasina A. , Heymsfield Steven B. , Stahl Theodore , Pierson Richard N. , Shapses Sue A.
Published: April 2006

Bone mobilization, lowering of bone mineral density (BMD), and osteoporotic fractures are recognized in postmenopausal women with weight loss. Because a high-calcium intake suppresses bone loss in peri- and postmenopausal women, the present randomized, double-blind, placebo-controlled study was designed to test the hypothesis that calcium supplementation prevents net bone mobilization and consequent bone mineral loss during voluntary weight reduction in obese postmenopausal women. Subjects were placed on a moderate energy-restricted diet and either calcium supplementation (1 g/day) or placebo for 6 months. Body weight, bone turnover markers (pyridinium cross-links), osteocalcin, and parathyroid hormone (PTH) were measured at treatment weeks 1–5, 7, 10, 13, 16, 20, and 25. Total body BMD, insulin-like growth factor, 25-hydroxyvitamin D, and sex hormone binding globulin (SHBG) were measured at baseline and week 25. The calcium supplemented (n = 15; age 60.9 ± 9.4 years, body mass index [BMI] 33.2 ± 4.6 kg/m2) and placebo (n = 16; age 55.8 ± 8.3 years, BMI 32.9 ± 4.5 kg/m2) groups lost similar amounts of weight over the study interval (10.2 ± 5.3% vs. 10.0 ± 5.2%) and both groups increased SHBG (p < 0.001). There was a statistical effect of calcium supplementation during weight loss to suppress pyridinium cross-links, osteocalcin, and PTH (p < 0.05, < 0.01, and < 0.05, respectively). Loss of BMD tended to be greater in the placebo group by 1.4% (p < 0.08) after weight loss. One gram per day calcium supplementation normalizes the increased calcium–PTH axis activity and the elevated bone turnover rate observed during moderate voluntary energy restriction in postmenopausal women.
Risk Factors for Hip Fracture in White Men: The NHANES I Epidemiologic Follow-up Study
Authors: Mussolino Michael E. , Looker Anne C. , Madans Jennifer H. , Langlois Jean A. , Orwoll Eric S.
Published: April 2006

This prospective population-based study assessed predictors of hip fracture risk in white men. Participants were members of the Epidemiologic Follow-up Study cohort of the First National Health and Nutrition Examination Survey, a nationally representative sample of noninstitutionalized civilians who were followed for a maximum of 22 years. A cohort of 2879 white men (2249 in the nutrition and weight-loss subsample, 1437 in the bone density subsample) aged 45–74 years at baseline (1971–1975) were observed through 1992. Ninety-four percent of the original cohort were successfully traced. Hospital records and death certificates were used to identify a total of 71 hip fracture cases (61 in the nutrition and weight-loss subsample, 26 in the bone-density subsample). Among the factors evaluated were age at baseline, previous fractures other than hip, body mass index, smoking status, alcohol consumption, nonrecreational physical activity, weight loss from maximum, calcium intake, number of calories, protein consumption, chronic disease prevalence, and phalangeal bone density. The risk adjusted relative risk (RR) of hip fracture was significantly associated with presence of one or more chronic conditions (RR = 1.91, 95% confidence interval [CI] = 1.19–3.06), weight loss from maximum ≥ 10% (RR = 2.27, 95% CI 1.13–4.59), and 1 SD change in phalangeal bone density (RR = 1.73, 95% CI 1.11–2.68). No other variables were significantly related to hip fracture risk. Although based on a small number of cases, this is one of the first prospective studies to relate weight loss and bone density to hip fracture risk in men.
Bone Morphogenetic Proteins and bFGF Exert Opposing Regulatory Effects on PTHrP Expression and Inorganic Pyrophosphate Elaboration in Immortalized Murine Endochondral Hypertrophic Chondrocytes (MCT Cells)
Authors: Terkeltaub Robert A. , Johnson Kristen , Rohnow David , Goomer Randy , Burton Doug , Deftos Leonard J.
Published: April 2006

A fundamental question in endochondral development is why the expression of parathyroid hormone–related protein (PTHrP), which inhibits chondrocyte maturation and mineralization, becomes attenuated at the stage of chondrocyte hypertrophy. To address this question, we used clonal, phenotypically stable SV40-immortalized murine endochondral chondrocytes that express a growth-arrested hypertrophic phenotype in culture (MCT cells). Addition of individual cytokines to the medium of MCT cells revealed that bone morphogenetic protein (BMP)-6, which commits chondrocytes to hypertrophy, markedly inhibited PTHrP production. This activity was shared by three other osteogenic bone morphogenetic proteins (BMP-2, BMP-4, and BMP-7) and by transforming growth factor β (TGF-β), which all inhibited the level of PTHrP mRNA. In contrast, basic fibroblast growth factor (bFGF), an inhibitor of chondrocyte maturation to hypertrophy, induced PTHrP in MCT cells and antagonized the effects of BMP-2, BMP-4, BMP-6, and BMP-7 and TGF-β on PTHrP expression. Opposing effects of bFGF and BMPs also were exerted on the elaboration of inorganic pyrophosphatase (PPi), which regulates the ability of hypertrophic chondrocytes to mineralize the matrix. Specifically, BMP-2 and BMP-4, but not BMP-6 and BMP-7, shared the ability of TGF-β to induce PPi release, and this activity was inhibited by bFGF in MCT cells. Our results suggest that effects on PTHrP expression could contribute to the ability of BMP-6 to promote chondrocyte maturation. BMPs and bFGF exert opposing effects on more than one function in immortalized hypertrophic chondrocytes. Thus, the normal decrease in bFGF responsiveness that accompanies chondrocyte hypertrophy may function in part by removing the potential for bFGF to induce PTHrP expression and to oppose the effects of BMPs. MCT cells may be useful in further understanding the mechanisms regulating the differentiation and function of hypertrophic chondrocytes.
A Third-Generation Bisphosphonate, YM175, Inhibits Osteoclast Formation in Murine Cocultures by Inhibiting Proliferation of Precursor Cells via Supporting Cell-Dependent Mechanisms
Authors: Nishikawa Miyuki , Yamamoto Michiko , Murakami Takehiko , Akatsu Takuhiko , Kugai Nobuo , Nagata Naokazu
Published: April 2006

The theory that bisphosphonates inhibit osteoclast formation through their effects on osteoblastic cells remains controversial. To confirm the inhibitory effect of bisphosphonates on osteoclast formation and gain some insights into the underlying mechanisms, we examined the effect of disodium dihydrogen (cycloheptylamino)-methylenebisphosphonate monohydrate (YM175) on osteoclast-like multinucleated cell (OCL) formation in various mouse coculture systems. When different origins of osteoclast precursors (bone marrow, spleen, or nonspecific esterase-positive cells) were cocultured with the same supporting cells (calvarial osteoblasts), YM175 inhibited OCL formation similarly in all cultures. When the same osteoclast precursors (spleen cells) were cocultured with supporting cells of different origin, the results were variable. YM175 inhibited OCL formation almost completely in cocultures with calvarial osteoblasts or osteoblastic cell line KS4, while it did not, or only slightly, inhibit OCL formation in cocultures with stromal cell lines, ST2 or MC3T3-G2/PA6. Temporal addition of YM175 in cocultures of spleen cells with osteoblastic cells revealed that YM175 was effective when it was present at an early phase of the culture period. Consistent with this observation, YM175 in the presence of osteoblastic cells inhibited proliferation of preosteoclastic cells, but did not inhibit the fusion of mononuclear prefusion osteoclasts. In conclusion, the inhibitory effect of YM175 on OCL formation was confirmed in various murine coculture systems, but the effect was dependent on the types of bone-derived cells supporting osteoclastogenesis. The findings suggest that YM175 inhibits osteoclastogenesis by inhibiting the proliferation of osteoclast precursors through its action on supporting cells of osteoblast lineage rather than acting directly on osteoclast precursors.
Expression of Bone Matrix Proteins mRNA During Distraction Osteogenesis
Authors: Sato Motohiko , Yasui Natsuo , Nakase Takanobu , Kawahata Hirohisa , Sugimoto Mizuo , Hirota Seiichi , Kitamura Yukihiko , Nomura Shintaro , Ochi Takahiro
Published: April 2006

Distraction osteogenesis is a recently advanced principle of bone lengthening in which a bone separated by osteotomy is subjected to slow progressive distraction using an external fixation device. Appropriate mechanical tension-stress is believed not to break the callus but rather to stimulate osteogenesis. To study the molecular features of this process, the expression and localization of the mRNAs encoding osteopontin (OPN), osteocalcin (OC), matrix Gla protein (MGP), osteonectin (ON), and collagen type I and II during distraction osteogenesis were examined by in situ hybridization and Northern blot analysis. The process can be divided into three distinct phases: the lag phase for 7 days between osteotomy and the beginning of distraction, the distraction phase for 21 days, and the consolidation phase for several weeks. The histologic and molecular events taking place during the lag phase were similar to those observed in fracture healing. The osteotomy site was surrounded by external callus consisting of hyaline cartilage. As distraction started at the rate of 0.25 mm/12 h, the cartilaginous callus was elongated, deformed, and eventually separated into proximal and distal segments. The chondrocytes were stretched along the tension vector and became fibroblast-like in shape. Although morphologically these cells were distinguishable from osteogenic cells, they expressed OPN, OC, and alkaline phosphatase mRNAs. As distraction advanced, the cartilaginous callus was progressively replaced by bony callus by endochondral ossification and thereafter new bone was formed directly by intramembranous ossification. OPN mRNA was detected in preosteoblasts and osteoblasts at the boundary between fibrous tissue and new bone. ON, MGP, and OC mRNAs appeared early in the differentiation stage. The variety of cell types expressing mRNA encoding bone matrix proteins in distraction osteogenesis was much greater than that detected in the embryonic bone formation and fracture healing process. Moreover, the levels of OPN, ON, MGP, and OC mRNA expression markedly increased during the distraction phase. These results suggested that mechanical tension-stress modulates cell shape and phenotype, and stimulates the expression of the mRNA for bone matrix proteins.
TNF-α Increases Expression of IL-6 and ICAM-1 Genes Through Activation of NF-κB in Osteoblast-like ROS17/2.8 Cells
Authors: Kurokouchi Kazutoshi , Kambe Fukushi , Yasukawa Kou , Izumi Ryutaro , Ishiguro Naoki , Iwata Hisashi , Seo Hisao
Published: April 2006

Tumor necrosis factor-α (TNF-α) plays a key role in inflammatory diseases such as rheumatoid arthritis and in postmenopausal osteoporosis. In various tissues, TNF-α action is mediated by a transcription factor, nuclear factor-kappa B (NF-κB). However, little is known about how TNF-α exerts its action in osteoblasts. We thus examined the effect of TNF-α on the activation of NF-κB in rat osteoblast-like osteosarcoma cells (ROS17/2.8). Electrophoretic mobility shift assay revealed that the activation of the p50-p65 heterodimer NF-κB was induced by TNF-α as early as 15 minutes followed by a persistent activation for 48 h. When the binding activity of NF-κB in cytosol was examined using detergents that dissociate NF-κB from an inhibitory protein IκB, it decreased during the initial 30 minutes and then increased to the unstimulated level. Northern blot analysis revealed a marked increase in the mRNA levels of p105, a precursor of p50, 6 h after TNF-α and a gradual increase in p65 mRNA levels during the initial 1 h. Significant increase in both mRNA levels continued until 24 h after TNF-α. These results suggest that the rapid activation of NF-κB by TNF-α is mainly due to the nuclear translocation of NF-κB pre-existing in cytosol, and that the subsequent increase in the expression of p50 and p65 may result in the persistent activation of NF-κB during TNF-α stimulation. TNF-α also increased the mRNA levels of interleukin-6 (IL-6) and intercellular adhesion molecule-1 (ICAM-1). An antioxidant, N-acetyl-L-cysteine, significantly attenuated the TNF-α–dependent increase in these mRNAs, and simultaneously reduced the activation of NF-κB by TNF-α, indicating that NF-κB mediates the TNF-α–dependent expression of IL-6 and ICAM-1 in ROS17/2.8 cells. These results suggest that the activation of NF-κB by TNF-α may play an important role in the production of cytokines and cell adhesion molecules from osteoblasts, leading to the promotion of bone resorption and inflammation.
Effects of Exercise on Bone Mineral Density in Mature Osteopenic Rats
Authors: Iwamoto Jun , Takeda Tsuyoshi , Ichimura Shoichi
Published: April 2006

Dual-energy X-ray absorptiometry (DXA) was used to examine the effects of quantitative application of treadmill running exercise on bone mineral density (BMD) of the tibia and the fourth and fifth lumbar (L4 + L5) vertebrae in mature osteopenic rats. Twenty 37-week-old rats with bone loss, resulting from feeding a relatively low calcium diet for 14 weeks after ovariectomy at the age of 23 weeks, were divided into four groups of five rats each according to the intensity and duration of the exercise: 12 m/minute, 1 h/day in group EX1; 18 m/minute, 1 h/day in group EX2; 12 m/minute, 2 h/day in group EX3; and sedentary control in group CON. With a standard calcium diet, the exercise was performed 5 days a week for 12 weeks, and the BMD of both the right tibia and the L4 + L5 vertebrae was measured using DXA at weeks 0, 4, 8, and 12. At the end of 12 weeks of exercise, the right femur and the L5 vertebra were dissected and the mechanical strength was measured using a three-point bending test and a compression test, respectively. After 12 weeks of exercise, a significant increase in the tibial BMD was observed in only group EX1 compared with that in group CON (p = 0.0039, by two-way analysis of variance). However, any significant increase in the L4 + L5 vertebral BMD was not observed in any exercise groups compared with that in the control group. While a maximum breaking force of the femoral shaft in group EX1 was significantly greater than that in group CON (p < 0.05, by Mann-Whitney's U-test), that in groups EX2 and EX3 did not significantly differ from that in group CON. However, there was no significant difference in a maximum breaking force of the L5 vertebral body among all the exercise and control groups. These results indicated that the beneficial effects of treadmill running exercise under a standard calcium diet were recognized only in the weight-bearing bones of the mature osteopenic rats resulting from estrogen deficiency and inadequate calcium intake only when an optimal level of exercise was applied.
The Exclusion of High Trauma Fractures May Underestimate the Prevalence of Bone Fragility Fractures in the Community: The Geelong Osteoporosis Study
Authors: Sanders K. M. , Pasco J. A. , Ugoni A. M. , Nicholson G. C. , Seeman E. , Martin T. J. , Skoric B. , Panahi S. , Kotowicz M. A.
Published: April 2006

Fractures associated with severe trauma are generally excluded from estimates of the prevalence of osteoporotic fractures in the community. Because the degree of trauma is difficult to quantitate, low bone mass may contribute to fractures following severe trauma. We ascertained all fractures in a defined population and compared the bone mineral density (BMD) of women who sustained fractures in either “low” or “high” trauma events with the BMD of a random sample of women from the same population. BMD was measured by dual-energy X-ray absorptiometry and expressed as a standardized deviation (Z score) adjusted for age. The BMD Z scores (mean ± SEM) were reduced in both the low and high trauma groups, respectively: spine-posterior-anterior (−0.50 ± 0.05 and −0.21 ± 0.08), spine-lateral (−0.28 ± 0.06 and −0.19 ± 0.10), femoral neck (−0.42 ± 0.04 and −0.26 ± 0.09), Ward's triangle (−0.44 ± 0.04 and −0.28 ± 0.08), trochanter (−0.44 ± 0.05 and −0.32 ± 0.08), total body (−0.46 ± 0.06 and −0.32 ± 0.08), ultradistal radius (−0.47 ± 0.05 and −0.42 ± 0.07), and midradius (−0.52 ± 0.06 and −0.33 ± 0.09). Except at the PA spine, the deficits were no smaller in the high trauma group. Compared with the population, the age-adjusted odds ratio for osteoporosis (t-score < −2.5) at one or more scanning sites was 3.1 (95% confidence interval 1.9, 5.0) in the high trauma group and 2.7 (1.9, 3.8) in the low trauma group. The data suggest that the exclusion of high trauma fractures in women over 50 years of age may result in underestimation of the contribution of osteoporosis to fractures in the community. Bone density measurement of women over 50 years of age who sustain fractures may be warranted irrespective of the classification of trauma.
Mutations of CTSK Result in Pycnodysostosis via a Reduction in Cathepsin K Protein
Authors: Ho Nicola , Punturieri Antonello , Wilkin Douglas , Szabo Jinny , Johnson Maureen , Whaley Justine , Davis Joie , Clark Alison , Weiss Stephen , Francomano Clair
Published: April 2006

Pycnodyostosis, an autosomal recessive osteosclerosing skeletal disorder, has recently been shown to result from mutations in the cathepsin K gene. Cathepsin K, a lysosomal cysteine protease with an abundant expression in osteoclasts, has been implicated in osteoclast-mediated bone resorption and remodeling. DNA sequence analysis of the cathepsin K gene in a nonconsanguineous family demonstrated compound heterozygozity for mutations in two affected siblings. We have identified a missense mutation with a single base G→A transition at cDNA nucleotide 236, resulting in conversion of a conserved glycine to a glutamine residue (G79E). The other mutation is an A→T transition at nucleotide 154, leading to the substitution of a lysine residue by a STOP codon (K52X) predicting premature termination of the precursor cathepsin K polypeptide. Sequencing of genomic and cDNAs from the parents demonstrated that the missense mutation was inherited from the father and the nonsense mutation from the mother. Protein expression in both affected children was virtually absent, while in the parents was reduced by 50–80% compared with controls. The protein studies demonstrate that even significantly reduced cathepsin K levels do not have any phenotypic effect, whereas absent cathepsin K results in pycnodysostosis.
Growth Retardation in Children with Chronic Renal Failure
Authors: Kuizon Beatriz D. , Salusky Isidro B.
Published: April 2006

Growth retardation is a major obstacle to full rehabilitation of children with chronic renal failure (CRF). Several factors have been identified as contributors to impaired linear growth and they include protein and calorie malnutrition, metabolic acidosis, growth hormone resistance, anemia, and renal osteodystrophy. Although therapeutic interventions such as the use of recombinant human growth hormone, recombinant human erythropoietin, and calcitriol have made substantial contributions, the optimal therapeutic strategy remains to be defined. Indeed, growth failure persists in a substantial proportion of children with renal failure and those treated with maintenance dialysis. In addition, the increasing prevalence of adynamic lesions of renal osteodystrophy and its effect on growth have raised concern about the continued generalized use of calcitriol in children with CRF. Recent studies have shown the critical roles of parathyroid hormone–related protein (PTHrP) and the PTH/PTHrP receptor in the regulation of endochondral bone formation. The PTH/PTHrP receptor mRNA expression has been shown to be down-regulated in kidney and growth plate cartilage of animals with renal failure. Differences in the severity of secondary hyperparathyroidism influence not only growth plate morphology but also the expression of selected markers of chondrocyte proliferation and differentiation in these animals. Such findings suggest potential molecular mechanisms by which cartilage and bone development may be disrupted in children with CRF, thereby contributing to diminished linear growth.