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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent studies have shown that estrogen (E) likely plays a dominant role in inhibiting bone resorption in normal elderly men. Because both E and T inhibit osteoclast development and activity, stimulate osteoclast apoptosis, and inhibit osteoblast production of IL-6, it is unclear why T is less potent than E in inhibiting bone resorption in vivo. Osteoprotegerin (OPG) binds to and inactivates RANKL, the final mediator of osteoclastogenesis. In vitro, OPG production is stimulated by E, and preliminary data suggest that T has the opposite effect. Thus, we analyzed serum for OPG levels from a study in which 59 elderly men (mean age, 68 yr) were made acutely hypogonadal using a GnRH agonist and were also placed on an aromatase inhibitor to block conversion of androgens to estrogens. They were studied first under conditions of physiologic E and T replacement, and then randomized to no replacement, replacement with E alone, T alone, or both E and T. E alone resulted in an 18.6 +/- 7.9% (mean +/- SEM) increase in serum OPG levels (P < 0.05), whereas T alone tended to decrease OPG levels (by 10.0 +/- 8.5%; P < 0.05 compared with E alone). Using a two-factor ANOVA model, there was a highly significant T effect (P = 0.006) on decreasing serum OPG levels. Serum TNF-alpha, IL-6, and IL-6 soluble receptor levels increased significantly in the men who had both E and T withdrawn, and the increases in TNF-alpha and IL-6sR were absent in the men treated with either E or T. However, due to the variability in these cytokine measurements, the ANOVA models were not significant for E or T effects. Taken together, these data suggest that in vivo, T decreases OPG levels, whereas E tends to have the opposite effect. These differential effects of E vs. T on OPG production may explain, at least in part, why T has weaker effects than E on inhibiting bone resorption in vivo in humans.
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PMID:Effect of estrogen versus testosterone on circulating osteoprotegerin and other cytokine levels in normal elderly men. 1216 54

Granulocyte colony-stimulating factor (G-CSF) has been shown to affect the biochemical markers of bone metabolism, including serum bone alkaline phosphatase (BALP), serum osteocalcin, and urine deoxypyridinoline. To determine the association between bone resorption and formation and the G-CSF-induced mobilization of peripheral blood stem cells (PBSC), we examined these markers during mobilization in 19 healthy donors. The average (+/- SEM) serum BALP level before treatment was 81.6 +/- 17.0 IU/dL, and the level increased significantly to 117.7 +/- 15.8 IU/dL on day 5 of G-CSF administration (P < .0001). The urine deoxypyridinoline level before treatment was 12.3 +/- 2.4 nmol/mmol creatinine, and this level also increased significantly to 19.4 +/- 3.0 nmol/mmol creatinine on day 5 of G-CSF administration (P < .0001). In contrast, the average level of serum osteocalcin significantly decreased from 8.07 +/- 2.88 ng/mL to 1.53 +/- 0.18 ng/mL on day 5 (P = .0353). During G-CSF administration, we also studied the serum levels of various cytokines (IL-1beta, osteoclastogenesis inhibitory factor [OCIF], IL-6, tumor necrosis factor alpha, transforming growth factor beta, interferon-gamma, macrophage colony-stimulating factor) related to bone metabolism. Only the kinetics of OCIF were significantly affected. The serum level of OCIF increased immediately after the start of G-CSF administration and remained high during G-CSF administration. These results demonstrate that high-dose G-CSF affects bone metabolism and that OCIF may play a role in bone metabolism. Consistent with the notion that G-CSF affects bone metabolism, a significant correlation was observed between CD34+ cell yield and the increase in urine deoxypyridinoline but not for the changes in serum BALP and osteocalcin levels. This result suggests that bone resorption is either directly or indirectly related to the mobilization of PBSC by G-CSF.
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PMID:Effect of granulocyte colony-stimulating factor on bone metabolism during peripheral blood stem cell mobilization. 1256 3

Osteoprotegerin (OPG) is a soluble decoy receptor that inhibits bone resorption by binding to receptor activator of nuclear factor kappa B ligand. Murine studies suggest that OPG is elevated in pregnancy, but its role in human pregnancy is unknown. We evaluated the relationship among OPG, bone turnover, and bone density in a longitudinal study of planned human pregnancy and lactation (n = 17; age, 20-36 yr). Samples were collected before conception; at 16, 26, and 36 wk gestation; and at 2 and 12 wk postpartum. Indexes of bone resorption included serum beta C-terminal and urinary N-terminal (uNTX) telopeptides of type I collagen. OPG increased by 110 +/- 16% (mean +/- SEM) at 36 wk (P < 0.001), followed by a rapid postpartum decline in both lactating and nonlactating women. Bone resorption was elevated at 36 wk (serum beta C-terminal telopeptides by 76 +/- 17%; urinary N-terminal telopeptides by 219 +/- 41%; P < 0.001). The tissue source of OPG in pregnancy is unknown. Human breast milk contains large amounts of OPG (162 +/- 58 ng/ml in milk vs. 0.42 +/- 0.03 ng/ml in nonpregnant serum). However, the rapid postpartum decline in serum OPG and the low serum OPG in neonates suggest a placental source. There was no correlation between change in OPG and bone turnover or bone mineral density (P > 0.05), and the physiological importance of elevated OPG in human pregnancy remains uncertain.
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PMID:Serum osteoprotegerin as a determinant of bone metabolism in a longitudinal study of human pregnancy and lactation. 1460 74

Osteoporosis represents an important cause of morbidity in patients with beta-thalassemia major, and its etiology is multifactorial. Thus, the aim of this study was to characterize the possible role of the osteoprotegerin (OPG) and receptor activator of the NF-kappaB ligand (RANKL) system in thalassemia-related bone loss. Serum concentrations of OPG, soluble RANKL (s-RANKL), markers of bone turnover, and lumbar spine bone mineral density (BMD) were measured in random samples of males (n = 29; mean age +/- SEM, 24.26 +/- 1.29 years; range, 13-41 years) and females (n = 31; age, 24.59 +/- 0.95 years; range, 12-34 years) with beta-thalassemia major and in 30 healthy age-, height-, and weight-matched subjects. Thalassemic patients had significantly lower levels of OPG compared with controls (2.54 +/- 0.12 vs. 3.25 +/- 0.122, respectively; P < 0.05) and higher, albeit not statistically significantly, serum levels of s-RANKL (0.350 +/- 0.03 vs. 0.295 +/- 0.046, respectively; P < 0.05). s-RANKL correlated negatively with age (r = -0.3, P < 0.05), and OPG correlated positively with the duration of the interval between the onset of transfusions and chelation therapy (r = 0.52, P < 0.001). Regarding markers of bone metabolism, plasma values of osteocalcin correlated positively with s-RANKL (r = 0.40, P < 0.05) and negatively with OPG/s-RANKL ratio (r = -0.55, P < 0.01). In multiple regression analysis only cross-linked N-teleopeptide of type I collagen (NTX) significantly accounted for BMD. Although the OPG/RANKL system may have some clinical usefulness as a marker of bone turnover in beta-thalassemia, conventional markers of bone turnover more accurately represent changes in the BMD of these patients.
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PMID:Circulating osteoprotegerin and receptor activator of NF-kappaB ligand system in patients with beta-thalassemia major. 1718 95

Strontium is known to reduce bone resorption and stimulate bone formation. We have investigated the effect of strontium on the setting properties and in vitro bioactivity of a biomimetic gelatin-calcium phosphate bone cement. Gelatin-alpha-TCP powders, with a gelatin content of 15 wt %, were prepared by grinding and sieving the solid compounds obtained by casting gelatin aqueous solutions containing alpha-TCP. 5 wt % of CaHPO(4).2H(2)O were added to the cement powders before mixing with the liquid phase, with a L/P ratio of 0.3 mL/g. Strontium was added as SrCl(2).6H(2)O in different amounts up to 5 atom %. X-ray diffraction analysis, mechanical tests, and SEM investigations were carried out on the cements after different times of soaking in physiological solution. The presence of strontium affects both the initial and the final setting times of the cements, which increase with the ion content. The microstructural modifications observed in the SEM micrographs of the fractured surfaces are in agreement with the increase of the total porosity, and with the slight reduction of the compressive strength of the aged cements, on increasing strontium content. The rate of transformation of alpha-TCP into calcium deficient hydroxyapatite increases on increasing strontium content. SEM reveals that MG63 osteoblasts grown on the cements show a normal morphology and biological tests demonstrate very good rate of proliferation and viability in every experimental time. In particular, strontium stimulates Alkaline Phosphatase activity, Collagen type I, osteocalcin, and osteoprotegerin expression.
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PMID:Setting properties and in vitro bioactivity of strontium-enriched gelatin-calcium phosphate bone cements. 1764 40

The aim of the present work was to investigate the morphology and activity of the murine osteoblastic cell line MC3T3 on control smooth (Machined), commercially available rough (ZT) titanium discs, and on titanium samples obtained by modifying the ZT treatment protocol, and herein labelled as ZTF, ZTM and ZTFM. Cells were evaluated at SEM and immunofluorescence for morphology and cell-to-cell interactions and by MTT assay and real time PCR for cell growth and function. Microscopy showed that ZT modified protocols could differently affect cell shape and distribution. All the tested surfaces showed good biocompatibility by viability assay. However, cells on smoother surfaces appeared to express higher levels of transcript for Collagen 1a1, the main component of extracellular matrix, by real time PCR. Expression of the early differentiation marker Alkaline Phosphatase was higher on ZTF surfaces and ZTM enhanced the expression of later osteoblastic markers Osteoprotegerin and Osteocalcin. Noteworthy, the expression of Connexin 43, a component of cell-to-cell contacts and hemichannels, followed a similar pattern to differentiation marker genes and was higher in cells on ZTM surfaces, consistently with the microscopic observation of cell clusters. Taken together, this data showed that ZTF and ZTM treatment protocols appeared to improve the basal sand-blasting/acid-etching ZT procedure with ZTM surfaces promoting the most mature stage of differentiation.
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PMID:The response of osteoblastic MC3T3-E1 cells to micro- and nano-textured, hydrophilic and bioactive titanium surfaces. 2688 16