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PubMed1996

Coated-tube radioimmunoassay for C-telopeptides of type I collagen to assess bone resorption.

We present a coated-tube RIA that is useful for assessment of bone resorption. The assay uses a monoclonal antibody raised against a linear 8-amino-acid sequence (EKAHDGGR) derived from the C-telopeptides of type I collagen. Within-run and total CVs were 4.4% and 5.3-6.2%, respectively, at concentrations of 1-7 mg/L (n = 4-20). Analytical recovery was 98% +/- 8% and dilution 97% +/- 7%. Values obtained in a group of 36 premenopausal women were 227 +/- 89.6 mg/mol creatinine. In a group of 141 postmenopausal women, the values obtained were 429 +/- 225 mg/mol creatinine, a highly significant increase of 89% (P <0.001) over the premenopausal value. In a double-blind placebo-controlled clinical study of these postmenopausal women receiving five different doses of a bisphosphonate, a significant decrease of RIA-measured C-telopeptide values was seen in all bisphosphonate-treated groups, after just 3 months. Values in urine samples from postmenopausal women assayed with the RIA (gamma) and the CrossLaps(TM) ELISA (x) agreed well: slope = 0.98 (95% confidence interval, 0.94-1.01), intercept = 0.34 (0.25-0.43) mg/L, and Sylx = 0.93 mg/L (n = 678). We conclude that this RIA represents a valuable tool for assessing bone resorption.

Adult↗
PubMedDate not supplied

Bone resorption levels by age and menopausal status in 5,157 women.

OBJECTIVE: The purpose of this study was to describe bone resorption activity using a biochemical marker according to the categories of age, menopausal status, and selected drug/supplement use in middle-aged and elderly community-based women. DESIGN: This was a cross-sectional study that assessed urinary cross-linked N-telopeptide of type I collagen (NTx) and used self-report data to group women as premenopausal (Pre), perimenopausal (Peri), postmenopausal without hormone replacement therapy (Post), and postmenopausal with hormone replacement therapy (HRT). RESULTS: Mean NTx values were found to be significantly different by group and controlling for age (p = 0.001), with post hoc tests showing all pairwise group comparisons as significantly different (p = 0.001), except that the Pre and HRT groups were not significantly different. Both the Peri and the Post NTx levels were significantly higher than the Pre and the HRT groups'. NTx values in the Peri group varied with age-the youngest Peri women were similar to Pre women, and the oldest Peri women were similar to Post women. Significantly lower NTx levels were found only in the Post (p = 0.009) and HRT (p < 0.001) groups using diuretics compared with nonuse and only in the HRT group using calcium supplements compared with nonuse (p = 0.006). No differences by thyroid use were found. With a biochemical marker, the results showed that bone resorption activity differences could be demarcated in women according to age, estimated menopausal stage, and selected drug/supplement use. CONCLUSIONS: These results support the usefulness of NTx assessment for indicating bone resorption activity and therefore the potential for osteoporosis or for monitoring the efficacy of antiresorptive therapies.

Adult↗
PubMed1983

The role of cyclic AMP, calcium, and prostaglandins in the induction of osteoclastic bone resorption associated with experimental tooth movement.

Administration of imidazole and verapamil inhibited the appearance of osteoclasts and bone resorption induced by experimental tooth movement in rats. On the other hand, administration of theophylline and ouabain enhanced the appearance of osteoclasts. A mixed solution of DB cyclic AMP and A-23187 injected in gingiva near the orthodontically-treated teeth caused enhancement of the appearance of osteoclasts and bone resorption.

Animals↗
PubMed2002

Urinary excretion of cross-linked N-telopeptides of type 1 collagen to assess bone resorption in infants from birth to 1 year of age.

OBJECTIVES: To evaluate noninvasively bone resorption in infants and more specifically, to assess the accuracy of urinary collagen type 1 cross-linked N-telopeptide (NTX) excretion normalized to creatinine (NTX/Cr) in a spot urine sample as a reflection of daily NTX production in infants and to compute normative values for NTX excretion from birth to 1 year of age. METHODS: NTX/Cr values obtained from a single spot urine sample were compared with daily urinary NTX excretion and NTX/Cr obtained in 24-hour urine collected from 8 hospitalized infants. Normative values for NTX excretion were collated with a cross-sectional study in 70 healthy French infants (42 boys, 28 girls) aged 0 to 374 days (weight: 2700-11 340 g; length: 46-76.5 cm) and free of diseases or treatments that could influence growth, bone mineralization, or renal function. RESULTS: NTX/Cr values from single spot urine sample were significantly and linearly correlated with both daily NTX excretion (r = 0.783) and daily NTX/Cr (r = 0.952). In healthy infants, NTX excretion is low at birth, increases dramatically and significantly during the first 10 days of life, remains significantly elevated for approximately 3 months, and then decreases progressively to return to values similar to that observed at birth by 1 year of age. CONCLUSIONS: These data provide new insights regarding the use of spot urine analysis for assessing NTX excretion during the first year of life. The normative data demonstrate significant age-related variations in this marker, which probably reflect adaptation to extrauterine life and accelerated bone turnover in infancy and which should be considered for the interpretation of this noninvasive bone resorption marker in the clinical setting.

Biomarkers, Tumor↗
PubMed1995

Uniformity of resorptive bone loss induced by disuse.

Strains induced in the skeleton by functional activity are critical to the homeostasis of bone tissue. An in vivo model of disuse osteopenia was used to examine whether the removal of these regulatory stimuli induces a uniform loss of cortical bone through the whole organ or whether the loss of bone is focused at specific sites of the cortex. The right radii of five adult male turkeys were isolated from their normal functional loading for 8 weeks. The corresponding left radius from each animal served as an intact contralateral control. An additional group of five turkeys was used as time-zero controls to assess the initial areal symmetry of the left and right radii. Areal properties were assessed at three sites at equal intervals spanning the middle 3 cm of the diaphysis. Adaptation was determined for each cross section as a whole, as well as specifically by site by division of each cross section into 12 equal angle sectors. The average across all experimental sections after 8 weeks of disuse was 12.1 +/- 1.9% (+/- SE) loss of bone mass. The change in mean cross-sectional area varied little between the three diaphyseal sites (-10.2 +/- 3.3%, -13.5 +/- 3.8%, and -12.6 +/- 4.0%) and occurred primarily (84%) by uniform expansion of the endosteal envelope. However, elevated intracortical porosity following 8 weeks of disuse was highly nonuniform, with 58% of the increased porosity preferentially located in the ventral/caudal cortex (representing only 25% of the cortical area).(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed2005

Changes in bone volume and bone resorption by olpadronate treatment in an experimental model of uremic bone disease.

Thirty male adult Wistar rats (300-/+10 g body weight) underwent either 5/6 nephrectomy (Nx, n=20) or sham operation (SHAM, n=10) to determine olpadronate effects in an experimental model of uremic bone disease. For a 38-day period, 10 rats received olpadronate (16microg/100g bw) once a week (Nx+OPD) and the other vehicle (Nx). SHAM received vehicle. At baseline, treatment onset (t=7 days) and end of study (t=45 days) calcium, phosphorus, creatinine, bone alkaline phosphatase (b-ALP) and deoxypyridinoline crosslinks (DPyr) were determined. At t=0 and t=45 bone mineral density (BMD) was measured by DXA. At t=45 the right tibia was removed for bone histology. There were no differences in serum calcium. Phosphorus increased in Nx and Nx+OPD compared to SHAM (p<lt 0.05). The b-ALP increased from t=0 to t=7 in Nx and Nx+OPD (p<0.05) and decreased thereafter to SHAM levels. DPyr/creat increased in Nx compared to SHAM (p<0.05) and Nx+OPD (p<0.001). Nx+OPD presented lower DPyr excretion than SHAM rats (p<0.01). At t=45, tibia BMD of Nx was 20% and 26% lower than in SHAM (p<0.005) and Nx+OPD, respectively, (p<0.001). BMD was higher Nx+OPD than in SHAM (p<0.05). OPD prevented the loss of bone volume, the increment in osteoid volume and erosion surface observed in Nx group (p<0.05). OPD also prevent the increment in the number of osteoclasts (OC) and the active OC surface and decreases the number of TRAP(+)-OC (p<0.05). In summary, OLP may be beneficial in osteopenia associated to high turnover bone disease of CRF. However, the use of bisphosphonate therapy for renal insufficiency must be further investigated in order to clarify essential aspects of treatment as the patient selection and several aspects of treatment, such as optimum dose, frequency, and safe period of administration.

Alkaline Phosphatase↗
PubMed1989

Osteoclastic bone resorption by a polarized vacuolar proton pump.

Bone resorption depends on the formation, by osteoclasts, of an acidic extracellular compartment wherein matrix is degraded. The mechanism by which osteoclasts transport protons into that resorptive microenvironment was identified by means of adenosine triphosphate-dependent weak base accumulation in isolated osteoclast membrane vesicles, which exhibited substrate and inhibition properties characteristic of the vacuolar, electrogenic H+-transporting adenosine triphosphatase (H+-ATPase). Identify of the proton pump was confirmed by immunoblot of osteoclast membrane proteins probed with antibody to vacuolar H+-ATPase isolated from bovine kidney. The osteoclast's H+-ATPase was immunocytochemically localized to the cell-bone attachment site. Immunoelectron microscopy showed that the H+-ATPase was present in the ruffled membrane, the resorptive organ of the cell.

Animals↗
PubMed1987

Effects of forskolin on bone resorption in the absence and presence of parathyroid hormone and calcitonin.

Release of previously incorporated 45Ca from fetal rat long bones was determined with the diterpene forskolin, both in the absence and presence of parathyroid hormone (PTH) and calcitonin (CT). In the absence of hormone, increased bone resorption was observed with 10(-7)M forskolin, but biphasic responses, consisting of initial decreases in 45Ca release that were followed by increased calcium mobilization, were produced with 10(-6)M and 10(-5)M forskolin. Inhibition of 45Ca release was pronounced and delayed more with 10(-5)M forskolin while the greatest stimulation of bone resorption was elicited by 10(-6)M forskolin, a response that was inhibited by 100 mU/ml CT. In the presence of 250 ng/ml PTH, a synergistic enhancement of 45Ca release occurred with 10(-7)M forskolin treatment while, in contrast, calcium mobilization was inhibited by 10(-6)M and 10(-5)M forskolin. Inhibition by 10(-6)M forskolin was characterized by "escape" while that of 10(-5)M forskolin was continuous over a 5 day interval. Inhibition throughout the experimental period also was noted when 10(-5)M forskolin was combined with 2.5 ng/ml PTH, but no effect on calcium mobilization was observed upon addition of 10(-7)M forskolin and, rather than inhibition, an enhancement of 45Ca release occurred when 10(-6)M forskolin was combined with 2.5 ng/ml PTH. Inhibition of 250 ng/ml PTH, but lack of inhibition of 2.5 ng/ml PTH by 10(-6)M forskolin suggests a 10(-6)M forskolin-sensitive portion of PTH-mediated calcium efflux. Absence of "escape" when 10(-5) M forskolin is combined with 250 ng/ml PTH suggests that heterologous desensitization may not play a major role in the "escape" which occurs with 10(-6) M forskolin.

Animals↗
PubMed1989

Cyclosporin A in the oophorectomized rat: unexpected severe bone resorption.

Local factors, such as interleukin-1, may mediate the accelerated bone remodeling in the acute estrogen-deficient rat. Cyclosporin A (CsA), which in vitro inhibits some of these local factors, was administered to oophorectomized (OX) rats in an attempt to modify this high turnover state. Three groups of 15 rats were studied. Group A was sham operated, group B was OX, and group C was OX and received CsA (15 mg/kg per day) by gavage commencing 4 days postoophorectomy for 28 days. Estradiol levels were determined to confirm oophorectomy. Blood was sampled on days -7, 0, 7, 14, 21, and 28 for ionized calcium (Ca2+), 1,25-(OH)2-vitamin D, PTH, and bone gla protein (BGP). Rats received tetracycline hydrochloride for bone histomorphometric labeling. All results were compared to group A. Body weight was increased in group B (p less than 0.003) but not in group C. There was no difference in Ca2+ or PTH between the groups. BGP levels were higher in group B by day 28 (p less than 0.005); BGP levels were increased in group C from days 7-28 (p less than 0.002). 1,25-(OH)2-vitamin D was significantly increased in group C (p less than 0.0001) but not in group B. Tibial bone histomorphometry revealed increased measurements of bone formation and osteoclast number without a loss of bone volume (BV/TV) in group B. Group C showed a dramatic increase in bone turnover with significant loss of BV/TV (p less than 0.001). In conclusion, CsA in the OX rat resulted in unexpected enhanced bone remodeling with high BGP levels and severe bone resorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

The diuretic indapamide increases bone mass and decreases bone resorption in spontaneously hypertensive rats supplemented with sodium.

Clinical and epidemiological studies suggest that thiazide diuretics can prevent bone loss and decrease the incidence of hip fractures. However, the mechanism of the effect of diuretics on bone is not clearly established. Indapamide (IDP), a sulfonamide diuretic related to thiazides, is used to treat hypertension. Sixty spontaneously hypertensive rats (SHRs) were divided into four groups and treated with or without IDP (1.5 mg/kg/day) during 8 weeks in the presence or absence of a high sodium load (8% NaCl supplementation in the diet). Sodium and calcium excretions were increased in the rats receiving the high sodium load (SHR + 8% NaCl) comparatively with control rats (SHR). IDP decreased and increased, respectively, calcium and sodium excretions. Serum parathyroid hormone (PTH) was unchanged in any group. Bone density was measured at the femur, tibia, and vertebrae, and bone morphometry was performed at the metaphysis of the femur to evaluate bone architecture. Rats fed a high sodium diet had an average 5.5% decreased bone density at every site except the femoral diaphysis. The trabecular bone volume was also decreased (SHR + 8% NaCl vs. SHR, 11.99+/-0.78 vs. 17.51+/-1.5%, p < 0.05). An increase in trabecular separation suggested that these changes were due to increased bone resorption. In the SHR + 8% NaCl + IDP group, IDP increased bone density and trabecular bone volume (SHR + 8% NaCl + IDP vs. SHR + 8% NaCl, 16.52+/-1.04 vs. 11.99+/-0.78%, p < 0.05). Trabecular separation and pyridinoline/creatinine excretion (SHR + 8% NaCl + IDP vs. SHR + 8% NaCl, 136.39+/-9.62 vs. 195.18+/-22.34 nmol/mmol, p < 0.05) were also decreased by IDP. These results show that in rats receiving a high sodium diet, IDP can reverse sodium-induced bone loss and increased bone resorption independently of changes in serum PTH.

Absorptiometry, Photon↗
PubMed2005

Current insights into the role of transforming growth factor-beta in bone resorption.

Transforming growth factor-beta (TGF-beta) elicits a variety of effects on cellular proliferation and differentiation. The major repository for TGF-beta is bone, where it possesses separate facilitative and suppressive actions on osteoclast differentiation and bone resorption. Without a direct enabling stimulus from TGF-beta monocytes cannot form osteoclasts but instead follow macrophage differentiation pathways. This facilitative action depends on an ability to promote a state in which precursors are resistant to anti-osteoclastic inflammatory signals. Following the initiation of resorption TGF-beta is released from bone matrix. This acts on osteoblasts to reduce the availability of the osteoclast differentiation factor, RANKL (receptor activator of NFkappaB ligand) and thereby indirectly limits further osteoclast formation. Thus TGF-beta has a fundamental role in the control of bone resorption having actions that first allow monocytes to develop into osteoclasts then subsequently limiting the extent and duration of resorption after its release from the bone matrix.

Animals↗
PubMed1991

Regulation of the production of plasminogen activators by bone resorption enhancing and inhibiting factors in three types of osteoblast-like cells.

Production of proteolytic enzymes by osteoblasts is considered to be important for the initiation of osteoclastic bone resorption. We examined the production of tissue-type (tPA) and urokinase-type plasminogen activator (uPA) activity by three types of osteoblast-like cells (normal rat osteoblasts, rat and human osteosarcoma cells) using a quantitative spectrophotometric assay and a qualitative gel overlay technique. All 3 types of cells released both types of PA-activity into the medium, but normal rat osteoblasts released uPA probably in an inactive form. Treatment with different concentrations of the bone resorbing factors bovine Parathyroid Hormone [1-84], synthetic human Parathyroid Hormone-Like Protein [1-34]. Prostaglandin E2, Interleukin-1 beta, Tumor Necrosis Factor alpha and 1,25-dihydroxyvitamin D3 increased in general the production of both PA's by all three cell types. However, there were differences in the relative potencies of these factors. In contrast, Transforming Growth Factor beta, which inhibits bone resorption, decreased PA-activity in osteoblast-like cells. In all three types of cells, under control as well as under stimulated conditions, a high molecular weight form of PA was demonstrated by the gel overlay technique, most likely a complex of tPA with the PA-inhibitor PAI-1. The uniform increase in production of PA's by osteoblast-like cells in response to bone resorbing factors and its decrease by TGF beta supports the notion that PA's are involved in bone resorption. The exact mechanism however, remains to be elucidated.

Animals↗
PubMed1984

Tetracyclines inhibit parathyroid hormone-induced bone resorption in organ culture.

Several tetracyclines (minocycline, doxycycline, tetracycline), in levels approximating physiologic concentrations, were found to inhibit parathyroid hormone-induced bone resorption in organ culture; the specificity of this effect was demonstrated by comparison with other (non-tetracycline) types of antibiotics. The ability of tetracyclines to inhibit bone resorption is consistent with the recent proposal by Golub et al. that these antibiotics can inhibit mammalian collagenolytic enzymes by a mechanism unrelated to the drug's antibacterial efficacy, a property which could be therapeutically useful in diseases characterized by excessive collagen breakdown.

Animals↗
PubMed1983

Ultrastructural localization of concanavalin-A binding sites on bone cells: effects of con A on osteoclastic bone resorption.

When osteoclasts on the endocranial surface of 10-day old rat calvaria are treated with concanavalin-A and hemocyanin, con A binding sites can be visualized by scanning electron microscopy (SEM). The hemocyanin label was uniformly distributed on the dorsal (unapposed) surface of all osteoclasts observed by SEM; it could be visualized on smooth surfaces, microvillous projections and filopodia. Osteoblasts were also labeled with the hemocyanin marker, demonstrating con A binding sites. 45Ca bone release assays of prelabeled calvaria incubated in varying concentrations of con A were conducted to determine whether or not con A has any functional effects on osteoclasts. At low concentrations of con A (0.1 micrograms/ml), there was an increase in bone resorption at 24, 48 and 72 hours of incubation. In contrast, calvaria incubated in high concentrations of con A (50 micrograms/ml and 100 micrograms/ml) showed a marked decrease in bone resorption significantly different from that of controls (incubated without the addition of con A) at each of the three 24 hour time periods. These differences in the release of 45Ca may indicate direct, dose-dependent effects of con A on osteoclastic bone resorption.

Animals↗
PubMed1996

Phenothiazines are potent inhibitors of osteoclastic bone resorption.

1. We have previously shown that promethazine inhibits osteoclastic bone resorption in the in vitro bone slice assay (IC50 = 0.8 microM), but the mechanism(s) involved are unclear. 2. We have now tested the effects on osteoclast activity of five other structurally related compounds. Phenothiazine, chlorpromazine, amitriptyline, phenazine, and phenoxazine had IC50 values of 0.8, 0.9, 6, 7, and > 10 microM, respectively, in the bone slice assay, indicating that the basic phenothiazine structural element itself is important for osteoclast inhibitory activity. 3. The results are discussed in terms of the known effects of phenothiazines on plasma membrane fluidity, blocking of ion channels, and inhibition of calmodulin.

Animals↗
PubMed1994

Response of three murine macrophage populations to particulate debris: bone resorption in organ cultures.

Particulate wear debris from bone cement or prosthetic components can stimulate macrophages to cause bone resorption. We compared the effect of particle composition (titanium and polymethylmethacrylate as inherent components of prosthetic materials or bone cement and polystyrene as a reference material) on the secretion of interleukin-1 and prostaglandin E2 by peritoneal macrophages and monocyte/macrophage cell lines (P388D1 and IC-21) and on the bone-resorbing activity of conditioned medium harvested from these particle-challenged macrophages. Titanium particles (1-3 microns) in peritoneal macrophage cultures exhibited significantly enhanced bone-resorbing activity measured as 45Ca release, whereas polymethylmethacrylate and polystyrene exhibited this effect to a greater extent in the P388D1 and IC-21 monocyte/macrophage cultures. Although exogenous prostaglandin E2 and recombinant human interleukin-1 could significantly increase the 45Ca release and indomethacin significantly reduced both the spontaneous calcium efflux and active 45Ca release from calvarial bones labeled in vivo, the levels of interleukin-1 and prostaglandin E2, alone or together, did not always correlate with the bone-resorbing activity of conditioned media. Thus, the actual levels of potent bone-resorbing agents (prostaglandin E2 and interleukin-1) measured in conditioned tissue culture media did not necessarily reflect the bone-resorbing capability. An important result of this study is that different macrophage populations may respond differently to the same microenvironmental signal, which in our investigation was particulate wear debris of differing composition and size.

Animals↗
PubMed2003

Correlation between histomorphometric parameters of bone resorption and serum type 5b tartrate-resistant acid phosphatase in uremic patients on maintenance hemodialysis.

BACKGROUND: Serum tartrate-resistant acid phosphatase 5b (TRACP) is a new marker of potential clinical use to monitor osteoclastic activity and bone resorption rate. The relationship between histomorphometric parameters of bone resorption and serum TRACP was evaluated in 14 chronically dialyzed patients and 6 healthy control subjects. METHODS: All patients underwent bone biopsies and serum biochemical testing for TRACP, intact parathyroid hormone (iPTH), pyridinoline cross-linked telopeptide domain of type I collagen (ICTP), total calcium, phosphorus, and albumin, which were measured at the time of biopsy. RESULTS: Bone histological examination showed predominant hyperparathyroid bone disease (HPT) in 6 patients, mixed uremic osteodystrophy in 3 patients, low-turnover osteomalacia in 1 patient, and adynamic bone disease in 4 patients. Mean TRACP activity was 3.25 +/- 0.59 U/L in control subjects. Median TRACP activity was significantly greater in patients with HPT (11.97 +/- 8.92 U/L) than those with other types of renal osteodystrophy (ROD; 2.17 +/- 0.61 U/L). Serum iPTH levels were greatest in all patients with HPT, but also were significantly elevated in 7 of 8 patients with other types of ROD. Serum ICTP levels also were significantly elevated in all patients with HPT and 6 of 8 patients with other types of ROD. Serum TRACP levels correlated more strongly with histological parameters of osteoclasts than those of erosion. Also, correlations between TRACP and histological parameters of osteoclasts were stronger than those of iPTH and ICTP levels. CONCLUSION: These early results suggest that serum TRACP levels correlate well with histological indices of osteoclasts and may serve as a specific marker for osteoclastic activity in patients with renal bone disease.

Acid Phosphatase↗