| 1. |
- Slootweg, M C, et al.
(författare)
-
Growth hormone binds to a single high affinity receptor site on mouse osteoblasts: modulation by retinoic acid and cell differentiation.
- 1996
-
Ingår i: The Journal of endocrinology. - 0022-0795. ; 150:3, s. 465-72
-
Tidskriftsartikel (refereegranskat)abstract
- Growth hormone (GH) exerts direct differentiative and proliferative effects on osteoblasts. We studied 125I-labeled human (h) GH binding to primary mouse osteoblasts derived from collagenase-treated 18-day fetal mouse calvaria. Scatchard analysis of the data revealed a single class of high affinity GH receptors (apparent Ka = 5.74 x 10(9) M-1) with 2200 sites per cell. Affinity crosslinking and SDS-PAGE electrophoresis showed two bands with apparent molecular masses of 120 and 70 kDa. Mouse osteoblasts express GH receptor mRNA with gene transcripts of 4.2 and 1.2 kb, at levels which reach approximately 1/6 of those in mouse liver and 1/3 of those in mouse muscle. Two populations of undifferentiated and diffentiated osteoblasts, obtained by sequential collagenase digestion of mouse calvaria, were used to study the relationship between osteoblastic phenotype and GH receptor expression. Although the affinity of the receptors in undifferentiated and differentiated cells was the same, the capacity was significantly higher (1.45 +/- 1.0% vs 2.39 +/- 0.9%, P = 0.03) in differentiated cells. This stresses the specific importance of the osteoblast as a target cell for GH. The differentiating potential of the vitamin A derivative retinoic acid was subsequently used experimentally to induce differentiation in the cells. Retinoic acid increased 125I-hGH binding to preosteoblasts (153%, P = 0.02). Together, these data demonstrate the presence of a high affinity GH receptor in mouse osteoblasts which is related to differentiation.
|
|
| 2. |
- Slootweg, M C, et al.
(författare)
-
Growth hormone receptor activity is stimulated by insulin-like growth factor binding protein 5 in rat osteosarcoma cells.
- 1996
-
Ingår i: Growth regulation. - 0956-523X. ; 6:4, s. 238-46
-
Tidskriftsartikel (refereegranskat)abstract
- Osteoblast-like UMR-106.01 rat osteosarcoma cells express high affinity growth hormone (GH) receptors (GHRs). Because osteoblasts secrete insulin-like growth factor binding protein-5 (IGFBP-5), we evaluated whether it also modulates GH binding and GHR expression in UMR cells. Human recombinant intact IGFBP-5 stimulated 125I-hGH binding in a dose-dependent manner (dose range 300-3000 ng/ml), inducing an increase to 193.6 +/- 2.1% of control binding at 3000 ng/ml (P < 0.001). Carboxy-truncated IGFBP-5 also stimulated GH binding but with less potency (125 +/- 2.7% of control at 3000 ng/ml, P < 0.01). GHRs identified by chemical crosslinking of 125I-hGH to cell monolayers increased after treatment with IGFBP-5 and decreased in response to insulin-like growth factor-I (IGF-I). GHR mRNA levels, as quantitated by a solution hybridization RNAse protection assay, increased up to 3 to 7-fold in a time-dependent manner by intact IGFBP-5 but not by carboxy-truncated IGFBP-5. An antiserum to IGFBP-5 reduced basal GH binding to 56.7 +/- 4.3% of control value at a concentration of 0.5% (P < 0.001), showing that IGFBP-5 produced by the cells is a strong regulator of GH binding. IGFBP-5 antiserum also decreased GH binding to 85.9 +/- 0.9% of IGFBP-5 stimulated value (P < 0.001), showing the specificity of IGFBP-5 stimulation. To determine whether the GHR upregulation was physiologically significant, cell proliferation was evaluated after coincubation of IGFBP-5 with low, non-stimulatory concentrations of GH. IGFBP-5 (1000 ng/ml) induced cell proliferation to 116.2 +/- 3.2% of control levels, and coincubation with hGH at 10 ng/ml induced an increase to 133.3 +/- 0.1% of control levels. We conclude that exogenous and endogenous IGFBP-5 upregulate GHR mRNA levels and GH binding and this interaction potentiates GH-stimulated mitogenesis in osteoblastic cells.
|
|
| 3. |
- Slootweg, M C, et al.
(författare)
-
Insulin-like growth factor binding proteins-2 and -3 stimulate growth hormone receptor binding and mitogenesis in rat osteosarcoma cells.
- 1995
-
Ingår i: Endocrinology. - 0013-7227. ; 136:10, s. 4210-7
-
Tidskriftsartikel (refereegranskat)abstract
- GH exerts its biological actions on osteoblasts through a specific high affinity receptor expressed on these cells. GH receptor binding is positively modulated by a number of factors, including retinoic acid and dexamethasone, whereas fetal calf serum strongly decreases the binding. To identify responsible factors in serum, components of serum, the insulin-like growth factors (IGFs)-I and -II, and IGF binding proteins (IGFBPs)-2 and -3 were tested for a possible negative modulatory role. IGF-I and -II decreased [125I]hGH binding at an optimal concentration of 30 ng/ml for IGF-I and 100 ng/ml IGF-II, reducing the binding to 51% and 55%, respectively, of control values. A stimulation of [125I]hGH binding was observed with IGFBP-2 as well as IGFBP-3, inducing an increase to 148% and 151% of control binding at an optimal concentration of 3000 ng/ml for both peptides. The effects of all peptides were dependent on the incubation time, being significantly increased after 8 h of incubation and reaching the full effect thereafter. The effects were declined at 24 h compared with 16 h for IGFBP-2 and -3 but not for IGF-I and -II. Coincubation of the cells with IGF-I and -II and IGFBP-2 and -3 neutralized the effects of the factors alone. In conclusion, these results show that IGF-I and -II on the one hand and IGFBP-2 and -3 on the other hand exert opposite actions on [125I]hGH binding, IGFBP-2 and -3 exerting probably an IGF-independent effect. Further, IGF-I and -II decreased GH receptor messenger RNA (mRNA) levels, as quantified by a solution hybridization ribonuclease protection assay, from 8.65 +/- 1.78 attomoles (amol)/microgram DNA (control) to 2.4 +/- 0.68 and 2.16 +/- 0.92 amol/microgram DNA, respectively. IGFBP-2 increased GH receptor mRNA levels from 5.26 +/- 1.17 (control) to 13.19 +/- 3.48. Incubation with IGFBP-3 did not result in stimulation of GH receptor mRNA levels (8.59 +/- 2.91 amol/microgram DNA). This shows that the mechanism of regulation of the GH receptor is, except for IGFBP-3, at least in part on the mRNA level. Lastly, IGFBP-2 and IGFBP-3 are mitogenic for UMR-106.01 rat osteosarcoma cells, inducing an increase in cell number to 125% and 142% of control cell counts after 48 h of incubation with 1000 ng/ml IGFBP-2 and -3, whereas IGF-I, IGF-II and Long R3 IGF-I did not stimulate proliferation. IGFBP-2 and -3 potentiate hGH induced mitogenesis at low hGH concentrations of both factors, whereas at higher concentrations no such effect is observed.(ABSTRACT TRUNCATED AT 400 WORDS)
|
|
| 4. |
- Nilsson, L O, et al.
(författare)
-
Demonstration of estrogen receptor-beta immunoreactivity in human growth plate cartilage.
- 1999
-
Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 0021-972X. ; 84:1, s. 370-3
-
Tidskriftsartikel (refereegranskat)abstract
- Estrogens affect longitudinal bone growth through their action on endochondral bone formation. Two estrogen receptors are known, the classical estrogen receptor-alpha (ER alpha), newly demonstrated in human growth plate cartilage, and a recently cloned estrogen receptor-beta (ER beta). The present study aimed to localize a possible expression of ER beta protein in human growth plates. Tissue samples were obtained from tibial and femoral growth plates in four female pubertal patients undergoing epiphyseal surgery. Immunohistochemistry, using two different ER beta-specific antibodies, demonstrated positive staining for ER beta in hypertrophic epiphyseal chondrocytes from all patients. No staining was noted in resting or proliferative chondrocytes. These data suggest that in addition to ER alpha, human epiphyseal chondrocytes also express ER beta. The physiological role of ER beta in the regulation of longitudinal bone growth in humans remains to be elucidated.
|
|
| 5. |
- Pauwels, R A, et al.
(författare)
-
Long-term treatment with inhaled budesonide in persons with mild chronic obstructive pulmonary disease who continue smoking. European Respiratory Society Study on Chronic Obstructive Pulmonary Disease
- 1999
-
Ingår i: New England Journal of Medicine. - 0028-4793. ; 340:25, s. 1948-1953
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Although patients with chronic obstructive pulmonary disease (COPD) should stop smoking, some do not. In a double-blind, placebo-controlled study, we evaluated the effect of the inhaled glucocorticoid budesonide in patients with mild COPD who continued smoking. After a six-month run-in period, we randomly assigned 1277 subjects (mean age, 52 years; mean forced expiratory volume in one second [FEV1], 77 percent of the predicted value; 73 percent men) to twice-daily treatment with 400 microg of budesonide or placebo, inhaled from a dry-powder inhaler, for three years. RESULTS: Of the 1277 subjects, 912 (71 percent) completed the study. Among these subjects, the median decline in the FEV1 after the use of a bronchodilator over the three-year period was 140 ml in the budesonide group and 180 ml in the placebo group (P=0.05), or 4.3 percent and 5.3 percent of the predicted value, respectively. During the first six months of the study, the FEV1 improved at the rate of 17 ml per year in the budesonide group, as compared with a decline of 81 ml per year in the placebo group (P<0.001). From nine months to the end of treatment, the FEV1 declined at similar rates in the two groups (P=0.39). Ten percent of the subjects in the budesonide group and 4 percent of those in the placebo group had skin bruising (P<0.001). Newly diagnosed hypertension, bone fractures, postcapsular cataracts, myopathy, and diabetes occurred in less than 5 percent of the subjects, and the diagnoses were equally distributed between the groups. CONCLUSIONS: In patients with mild COPD who continue smoking, the use of inhaled budesonide is associated with a small one-time improvement in lung function but does not appreciably affect the long-term progressive decline.
|
|
| 6. |
- Sandstedt, J, et al.
(författare)
-
Elevated levels of growth hormone increase bone mineral content in normal young mice, but not in ovariectomized mice.
- 1996
-
Ingår i: Endocrinology. - 0013-7227. ; 137:8, s. 3368-74
-
Tidskriftsartikel (refereegranskat)abstract
- Both estrogens and GH are necessary for normal bone remodeling. This study investigates the effect of elevated GH levels on the amount and density of bone in young female mice and its dependence on intact ovarian function. Metallothionein promoter-GH-transgenic mice were either sham operated or ovariectomized at 25-29 days of age, and the bone measurements were made at about 90 days of age. A 6-mm high cylinder containing only cortical bone was cut from the right tibia, and lumbar vertebrae 6 was measured as a bone with predominantly cancellous bone. The amounts of tibial and vertebral bone, measured by dry weight, mineral weight, organic weight, bone mineral content (measured by dual energy x-ray analysis), and volume, were increased in GH-transgenic animals compared to those in normal littermates. This stimulatory effect of elevated GH levels was not seen in ovariectomized mice. The real density of the tibial bone were slightly decreased in GH-transgenic animals compared to normal littermates. In conclusion, elevated levels of GH increase the amounts of vertebral (predominantly cancellous) bone and tibial (cortical) bone in young mice. Intact ovaries are a prerequisite for the stimulatory effect of elevated levels of GH. The fact that ovariectomy decreases the stimulatory effect of elevated GH levels suggests that the effect of elevated GH levels in bone is dependent upon the presence of basic sex steroid secretion.
|
|
| 7. |
- Sjögren, Klara, 1970, et al.
(författare)
-
Liver-derived insulin-like growth factor I (IGF-I) is the principal source of IGF-I in blood but is not required for postnatal body growth in mice.
- 1999
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 96:12, s. 7088-92
-
Tidskriftsartikel (refereegranskat)abstract
- The body growth of animals is regulated by growth hormone and IGF-I. The classical theory of this regulation is that most IGF-I in the blood originates in the liver and that body growth is controlled by the concentration of IGF-I in the blood. We have abolished IGF-I production in the livers of mice by using the Cre/loxP recombination system. These mice demonstrated complete inactivation of the IGF-I gene in the hepatocytes. Although the liver accounts for less than 5% of body mass, the concentration of IGF-I in the serum was reduced by 75%. This finding confirms that the liver is the principal source of IGF-I in the blood. However, the reduction in serum IGF-I concentration had no discernible effect on postnatal body growth. We conclude that postnatal body growth is preserved despite complete absence of IGF-I production by the hepatocytes.
|
|
| 8. |
- Slootweg, M C, et al.
(författare)
-
Estrogen enhances growth hormone receptor expression and growth hormone action in rat osteosarcoma cells and human osteoblast-like cells.
- 1997
-
Ingår i: The Journal of endocrinology. - 0022-0795. ; 155:1, s. 159-64
-
Tidskriftsartikel (refereegranskat)abstract
- Postmenopausal bone loss is primarily due to estrogen deficiency. Recent clinical observation demonstrate that GH increases bone mass in GH deficient patients. The present study investigates whether estrogen regulates GH action and GH receptor expression in osteoblasts. 17 beta-estradiol or GH added to the culture medium as single substances did not influence rat osteosarcoma cell proliferation nor human osteoblast-like (hOB) cell proliferation. However, together they synergistically induced osteoblast proliferation (rat osteosarcoma cells 160.1 +/- 15.5% of control cells; human osteoblast-like cells 159.6 +/- 5.1% of control cells). 17 beta-estradiol stimulated 125I-GH binding and GH receptor (GHR) mRNA levels in rat osteosarcoma cells. The stimulatory effect of estradiol was time dependent, reaching a peak after 8 h of incubation with 17 beta-estradiol (binding 216.9 +/- 27.8% and mRNA 374.6 +/- 30.8% of control). The finding that estradiol stimulated 125I-GH binding was confirmed in human osteoblast-like cells. In these cells, 17 beta-estradiol (10(-12) M) increased 125I-GH binding to 203.8 +/- 3.6% of control levels. We conclude that estrogen stimulates GH activity as well as GH binding and GHR mRNA levels in osteoblasts. These findings indicate that estrogen potentiates the effect of GH at the receptor level.
|
|
| 9. |
- Svensson, Johan, 1964, et al.
(författare)
-
Treatment with the oral growth hormone secretagogue MK-677 increases markers of bone formation and bone resorption in obese young males.
- 1998
-
Ingår i: Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research. - 0884-0431. ; 13:7, s. 1158-66
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of 2 months of treatment with the oral growth hormone (GH) secretagogue MK-677 on markers of bone metabolism was determined in healthy obese male subjects. This was a randomized, double-blind, parallel, placebo-controlled study. Twenty-four healthy obese males, 19-49 years of age, with body mass index > 30 kg/m2 were treated with MK-677 (25 mg/day; n = 12) or placebo (n = 12) for 8 weeks. MK-677 increased markers of bone formation; a 23% increase in the carboxy-terminal propeptide of type I procollagen levels and a 28% increase in procollagen III peptide levels were seen with as little as 2 weeks of MK-677 treatment (p < 0.01 and p = 0.001 vs. placebo, respectively) while a 15% increase in serum levels of osteocalcin was not detected until 8 weeks of treatment (p < 0.01 vs. placebo). Markers of bone resorption were induced within 2 weeks of treatment with MK-677; serum levels of the carboxy-terminal cross-linked telopeptide of type I collagen were increased 26% at 8 weeks (p = 0.001 vs. placebo), and urine hydroxyproline/creatinine and calcium/creatinine ratios at 8 weeks were increased by 23% (p < 0.05 vs. placebo) and 46% (p < 0.05 vs placebo), respectively, MK-677 increased serum insulin-like growth factor binding protein-5 (IGFBP-5) by 43-44% after 2-8 weeks of treatment (p < 0.01 vs. placebo). Serum IGFBP-4 was increased by 25% after 2 weeks of treatment (p < 0.001 vs. placebo) but no significant change from baseline was observed after 8 weeks of treatment. Plasma interleukin-6 was not significantly changed by active treatment. In conclusion, short-term treatment of healthy obese male volunteers with the GH secretagogue MK-677 increases markers of both bone resorption and formation. Large increases in serum levels of IGF-1 and IGFBP-5 and a transient increase in serum IGFBP-4 were found. Future long-term studies are needed to investigate if prolonged treatment with MK-677 increases bone mass.
|
|
| 10. |
- Vidal, Olle, et al.
(författare)
-
Disproportional body growth in female estrogen receptor-alpha-inactivated mice.
- 1999
-
Ingår i: Biochemical and biophysical research communications. - : Elsevier BV. - 0006-291X. ; 265:2, s. 569-71
-
Tidskriftsartikel (refereegranskat)abstract
- Estrogens play an important role in the regulation of longitudinal bone growth in man, as demonstrated by recent descriptions of individuals with estrogen insensitivity or aromatase deficiency. Two estrogen receptors, ERalpha and ERbeta, have been cloned. The aim of the present study was to investigate the function of ERalpha in the regulation of body growth and skeletal growth. Adult female mice with inactivated ERalpha (ERalpha-/-) demonstrated an increased body weight compared with wild-type mice (114% of control). However, the length of the appendicular skeleton was decreased in adult ERalpha-/- mice (femur 93% of control). In contrast, the axial skeleton was normal (crown-rump length 98% of control). The decreased growth of the appendicular skeleton was associated with decreased serum levels of IGF-I (77% of control), indicating that the GH/IGF-I axis may be involved in the decreased longitudinal bone growth seen in female ERalpha-/- mice.
|
|
