| 1. |
- Bergström, I., et al.
(författare)
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Prednisolone treatment reduces the osteogenic effects of loading in mice
- 2018
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Ingår i: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 112, s. 10-18
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Tidskriftsartikel (refereegranskat)abstract
- Glucocorticoid treatment, a major cause of drug-induced osteoporosis and fractures, is widely used to treat inflammatory conditions and diseases. By contrast, mechanical loading increases bone mass and decreases fracture risk. With these relationships in mind, we investigated whether mechanical loading interacts with GC treatment in bone. Three-month-old female C57BL/6 mice were treated with high-dose prednisolone (15 mg/60 day pellets/mouse) or vehicle for two weeks. During the treatment, right tibiae were subjected to short periods of cyclic compressive loading three times weekly, while left tibiae were used as physiologically loaded controls. The bones were analyzed using peripheral quantitative computed tomography, histomorphometry, real-time PCR, three-point bending and Fourier transform infrared micro-spectroscopy. Loading alone increased trabecular volumetric bone mineral density (vBMD), cortical thickness, cortical area, osteoblast-associated gene expression, osteocyte- and osteoclast number, and bone strength. Prednisolone alone decreased cortical area and thickness and osteoblast-associated gene expression. Importantly, prednisolone treatment decreased the load-induced increase in trabecular vBMD by 57% (p < 0.001) and expression of osteoblast-associated genes, while completely abolishing the load-induced increase in cortical area, cortical thickness, number of osteocytes and osteoclasts, and bone strength. When combined, loading and prednisolone decreased the collagen content. In conclusion, high-dose prednisolone treatment strongly inhibits the loading-induced increase in trabecular BMD, and abolishes the loading-induced increase in cortical bone mass. This phenomenon could be due to prednisolone inhibition of osteoblast differentiation and function.
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| 2. |
- Börjesson, Anna E, et al.
(författare)
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SERMs have substance-specific effects on bone, and these effects are mediated via ER alpha AF-1 in female mice
- 2016
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Ingår i: American Journal of Physiology-Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 310:11, s. E912-E918
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Tidskriftsartikel (refereegranskat)abstract
- The bone-sparing effect of estrogens is mediated primarily via estrogen receptor (ER)alpha, which stimulates gene transcription through activation function (AF)-1 and AF-2. The role of ER alpha AF-1 for the estradiol (E-2) effects is tissue specific. The selective ER modulators (SERMs) raloxifene (Ral), lasofoxifene (Las), and bazedoxifene (Bza) can be used to treat postmenopausal osteoporosis. They all reduce the risk for vertebral fractures, whereas Las and partly Bza, but not Ral, reduce the risk for nonvertebral fractures. Here, we have compared the tissue specificity of Ral, Las, and Bza and evaluated the role of ER alpha AF-1 for the effects of these SERMs, with an emphasis on bone parameters. We treated ovariectomized (OVX) wild-type (WT) mice and OVX mice lacking ER alpha AF-1 (ER alpha AF-1(0)) with E-2, Ral, Las, or Bza. All three SERMs increased trabecular bone mass in the axial skeleton. In the appendicular skeleton, only Las increased the trabecular bone volume/tissue volume and trabecular number, whereas both Ral and Las increased the cortical bone thickness and strength. However, Ral also increased cortical porosity. The three SERMs had only a minor effect on uterine weight. Notably, all evaluated effects of these SERMs were absent in ovx ER alpha AF-1(0) mice. In conclusion, all SERMs had similar effects on axial bone mass. However, the SERMs had slightly different effects on the appendicular skeleton since only Las increased the trabecular bone mass and only Ral increased the cortical porosity. Importantly, all SERM effects require a functional ER alpha AF-1 in female mice. These results could lead to development of more specific treatments for osteoporosis.
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| 3. |
- Börjesson, Anna E, et al.
(författare)
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The role of activation functions 1 and 2 of estrogen receptor-alpha for the effects of estradiol and selective estrogen receptor modulators in male mice
- 2013
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Ingår i: Journal of Bone and Mineral Research. - : Wiley. - 0884-0431 .- 1523-4681. ; 28:5
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Tidskriftsartikel (refereegranskat)abstract
- Estradiol (E2) is important for male skeletal health and the effect of E2 is mediated via estrogen receptor (ER)-. This was demonstrated by the findings that men with an inactivating mutation in aromatase or a nonfunctional ER had osteopenia and continued longitudinal growth after sexual maturation. The aim of the present study was to evaluate the role of different domains of ER for the effects of E2 and selective estrogen receptor modulators (SERMs) on bone mass in males. Three mouse models lacking either ERAF-1 (ERAF-10), ERAF-2 (ERAF-20), or the total ER (ER/) were orchidectomized (orx) and treated with E2 or placebo. E2 treatment increased the trabecular and cortical bone mass and bone strength, whereas it reduced the thymus weight and bone marrow cellularity in orx wild type (WT) mice. These parameters did not respond to E2 treatment in orx ER/ or ERAF-20 mirx ERAF-10 mice were tissue-dependent, with a clear response in cortical bone parameters and bone marrow cellularity, but no response in trabecular bone. To determine the role of ERAF-1 for the effects of SERMs, we treated orx WT and ERAF-10 mice with raloxifene (Ral), lasofoxifene (Las), bazedoxifene (Bza), or vehicle. These SERMs increased total body areal bone mineral density (BMD) and trabecular volumetric BMD to a similar extent in orx WT mice. Furthermore, only Las increased cortical thickness significantly and only Bza increased bone strength significantly. However, all SERMs showed a tendency toward increased cortical bone parameters. Importantly, all SERM effects were absent in the orx ERAF-10 mice. In conclusion, ERAF-2 is required for the estrogenic effects on all evaluated parameters, whereas the role of ERAF-1 is tissue-specific. All evaluated effects of Ral, Las and Bza are dependent on a functional ERAF-1. Our findings might contribute to the development of bone-specific SERMs in males. (c) 2013 American Society for Bone and Mineral Research.
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| 4. |
- Farman, Helen H., 1983, et al.
(författare)
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Female Mice Lacking Estrogen Receptor-alpha in Hypothalamic Proopiomelanocortin (POMC) Neurons Display Enhanced Estrogenic Response on Cortical Bone Mass
- 2016
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 157:8, s. 3242-3252
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Tidskriftsartikel (refereegranskat)abstract
- Estrogens are important regulators of bone mass and their effects are mainly mediated via estrogen receptor(ER)alpha. Central ER alpha exerts an inhibitory role on bone mass. ER alpha is highly expressed in the arcuate (ARC) and the ventromedial (VMN) nuclei in the hypothalamus. To test whether ER alpha in proopiomelanocortin (POMC) neurons, located in ARC, is involved in the regulation of bone mass, we used mice lacking ER alpha expression specifically in POMC neurons (POMC-ER alpha(-/-)). Female POMC-ER alpha(-/-) and control mice were ovariectomized (OVX) and treated with vehicle or estradiol (0.5 mu g/d) for 6 weeks. As expected, estradiol treatment increased the cortical bone thickness in femur, the cortical bone mechanical strength in tibia and the trabecular bone volume fraction in both femur and vertebrae in OVX control mice. Importantly, the estrogenic responses were substantially increased in OVX POMC-ER alpha(-/-) mice compared with the estrogenic responses in OVX control mice for cortical bone thickness (+ 126 +/- 34%, P < .01) and mechanical strength (+ 193 +/- 38%, P <.01). To test whether ER alpha in VMN is involved in the regulation of bone mass, ER alpha was silenced using an adeno-associated viral vector. Silencing of ER alpha in hypothalamic VMN resulted in unchanged bone mass. In conclusion, mice lacking ER alpha in POMC neurons display enhanced estrogenic response on cortical bone mass and mechanical strength. We propose that the balance between inhibitory effects of central ER alpha activity in hypothalamic POMC neuronsin ARC and stimulatory peripheral ER alpha-mediated effects in bone determines cortical bone mass in female mice.
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| 5. |
- Farman, Helen H., 1983, et al.
(författare)
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Membrane estrogen receptor alpha is essential for estrogen signaling in the male skeleton
- 2018
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Ingår i: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 239:3, s. 303-312
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Tidskriftsartikel (refereegranskat)abstract
- The importance of estrogen receptor alpha (ER alpha) for the regulation of bone mass in males is well established. ERa mediates estrogenic effects both via nuclear and membraneinitiated ER alpha (mER alpha) signaling. The role of mERa signaling for the effects of estrogen on bone in male mice is unknown. To investigate the role of mERa signaling, we have used mice (Nuclear-Only-ER; NOER) with a point mutation (C451A), which results in inhibited trafficking of ER alpha to the plasma membrane. Gonadal-intact male NOER mice had a significantly decreased total body areal bone mineral density (aBMD) compared to WT littermates at 3, 6 and 9 months of age as measured by dual-energy X-ray absorptiometry (DEXA). High-resolution microcomputed tomography (mu CT) analysis of tibia in 3-month-old males demonstrated a decrease in cortical and trabecular thickness in NOER mice compared to WT littermates. As expected, estradiol (E2) treatment of orchidectomized (ORX) WT mice increased total body aBMD, trabecular BV/TV and cortical thickness in tibia compared to placebo treatment. E2 treatment increased these skeletal parameters also in ORX NOER mice. However, the estrogenic responses were significantly decreased in ORX NOER mice compared with ORX WT mice. In conclusion, mER alpha is essential for normal estrogen signaling in both trabecular and cortical bone in male mice. Increased knowledge of estrogen signaling mechanisms in the regulation of the male skeleton may aid in the development of new treatment options for male osteoporosis.
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| 6. |
- Funck-Brentano, Thomas, et al.
(författare)
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Porcupine inhibitors impair trabecular and cortical bone mass and strength in mice
- 2018
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Ingår i: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 238:1, s. 13-23
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Tidskriftsartikel (refereegranskat)abstract
- WNT signaling is involved in the tumorigenesis of various cancers and regulates bone homeostasis. Palmitoleoylation of WNTs by Porcupine is required for WNT activity. Porcupine inhibitors are under development for cancer therapy. As the possible side effects of Porcupine inhibitors on bone health are unknown, we determined their effects on bone mass and strength. Twelve-week-old C57BL/6N female mice were treated by the Porcupine inhibitors LGK974 (low dose = 3 mg/kg/day; high dose = 6 mg/kg/day) or Wnt-C59 (10 mg/kg/day) or vehicle for 3 weeks. Bone parameters were assessed by serum biomarkers, dual-energy X-ray absorptiometry, mu CT and histomorphometry. Bone strength was measured by the 3-point bending test. The Porcupine inhibitors were well tolerated demonstrated by normal body weight. Both doses of LGK974 and Wnt-C59 reduced total body bone mineral density compared with vehicle treatment (P < 0.001). Cortical thickness of the femur shaft (P < 0.001) and trabecular bone volume fraction in the vertebral body (P < 0.001) were reduced by treatment with LGK974 or Wnt-C59. Porcupine inhibition reduced bone strength in the tibia (P < 0.05). The cortical bone loss was the result of impaired periosteal bone formation and increased endocortical bone resorption and the trabecular bone loss was caused by reduced trabecular bone formation and increased bone resorption. Porcupine inhibitors exert deleterious effects on bone mass and strength caused by a combination of reduced bone formation and increased bone resorption. We suggest that cancer targeted therapies using Porcupine inhibitors may increase the risk of fractures.
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| 7. |
- Gustafsson, Karin L., 1987, et al.
(författare)
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The role of membrane ER alpha signaling in bone and other major estrogen responsive tissues
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Estrogen receptor a (ER alpha) signaling leads to cellular responses in several tissues and in addition to nuclear ER alpha-mediated effects, membrane ER alpha (mER alpha) signaling may be of importance. To elucidate the significance, in vivo, of mER alpha signaling in multiple estrogen-responsive tissues, we have used female mice lacking the ability to localize ER alpha to the membrane due to a point mutation in the palmitoylation site (C451A), so called Nuclear-Only-ER (NOER) mice. Interestingly, the role of mER alpha signaling for the estrogen response was highly tissue-dependent, with trabecular bone in the axial skeleton being strongly dependent (>80% reduction in estrogen response in NOER mice), cortical and trabecular bone in long bones, as well as uterus and thymus being partly dependent (40-70% reduction in estrogen response in NOER mice) and effects on liver weight and total body fat mass being essentially independent of mER alpha (<35% reduction in estrogen response in NOER mice). In conclusion, mER alpha signaling is important for the estrogenic response in female mice in a tissue-dependent manner. Increased knowledge regarding membrane initiated ER alpha actions may provide means to develop new selective estrogen receptor modulators with improved profiles.
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| 8. |
- Lagerquist, Marie K, et al.
(författare)
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Acute fat loss does not affect bone mass
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Obesity has previously been thought to protect bone since high body weight and body mass index are associated with high bone mass. However, some more recent studies suggest that increased adiposity negatively impacts bone mass. Here, we aimed to test whether acute loss of adipose tissue, via adipocyte apoptosis, alters bone mass in age-related obese mice. Adipocyte apoptosis was induced in obese male FAT-ATTAC mice through AP20187 dimerizer-mediated activation of caspase 8 selectively in adipocytes. In a short-term experiment, dimerizer was administered to 5.5 month-old mice that were terminated 2 weeks later. At termination, the total fat mass weighed 58% less in dimerizer-treated mice compared with vehicle-treated controls, but bone mass did not differ. To allow for the detection of long-term effects, we used 9-month-old mice that were terminated six weeks after dimerizer administration. In this experiment, the total fat mass weighed less (- 68%) in the dimerizer-treated mice than in the controls, yet neither bone mass nor biomechanical properties differed between groups. Our findings show that adipose tissue loss, despite the reduced mechanical loading, does not affect bone in age-related obese mice. Future studies are needed to test whether adipose tissue loss is beneficial during more severe obesity.
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| 9. |
- Lawenius, Lina, et al.
(författare)
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Transplantation of gut microbiota from old mice into young healthy mice reduces lean mass but not bone mass
- 2023
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Ingår i: Gut Microbes. - 1949-0976. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Aging is associated with low bone and lean mass as well as alterations in the gut microbiota (GM). In this study, we determined whether the reduced bone mass and relative lean mass observed in old mice could be transferred to healthy young mice by GM transplantation (GMT). GM from old (21-month-old) and young adult (5-month-old) donors was used to colonize germ-free (GF) mice in three separate studies involving still growing 5- or 11-week-old recipients and 17-week-old recipients with minimal bone growth. The GM of the recipient mice was similar to that of the donors, demonstrating successful GMT. GM from old mice did not have statistically significant effects on bone mass or bone strength, but significantly reduced the lean mass percentage of still growing recipient mice when compared with recipients of GM from young adult mice. The levels of propionate in the cecum of mice receiving old donor GM were significantly lower than those in mice receiving young adult donor GM. Bacteroides ovatus was enriched in the microbiota of recipient mice harboring GM from young adult donors. The presence of B. ovatus was not only significantly associated with high lean mass percentage in mice, but also with lean mass adjusted for fat mass in the large human HUNT cohort. In conclusion, GM from old mice reduces lean mass percentage but not bone mass in young, healthy, still growing recipient mice. Future studies are warranted to determine whether GM from young mice improves the musculoskeletal phenotype of frail elderly recipient mice.
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| 10. |
- Lionikaite, Vikte, et al.
(författare)
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Clinically relevant doses of Vitamin A decrease cortical bone mass in mice
- 2018
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Ingår i: Journal of Endocrinology. - 0022-0795 .- 1479-6805. ; 239:3, s. 389-402
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Tidskriftsartikel (refereegranskat)abstract
- Excess vitamin A has been associated with decreased cortical bone thickness and increased fracture risk. While most studies in rodents have employed high dosages of vitamin A for short periods of time, we investigated the bone phenotype in mice after longer exposure to more clinically relevant doses. For 1, 4 and 10 weeks, mice were fed a control diet (4.5µg retinyl acetate/g chow), a diet modeled from the human upper tolerable limit (UTL; 20µg retinyl acetate/g chow) and a diet three times UTL (supplemented; 60µg retinyl acetate/g chow). Time-dependent decreases in periosteal circumference and bone mineral content were noted with the supplemented dose. These reductions in cortical bone resulted in a significant time-dependent decrease of predicted strength and a non-significant trend toward reduced bone strength as analyzed by three-point bending. Trabecular bone in tibiae and vertebrae remained unaffected when vitamin A was increased in the diet. Dynamic histomorphometry demonstrated that bone formation was substantially decreased after 1 week of treatment at the periosteal site with the supplemental dose. Increasing amount of vitamin A decreased endocortical circumference, resulting in decreased marrow area, a response associated with enhanced endocortical bone formation. In the presence of bisphosphonate, vitamin A had no effect on cortical bone, suggesting that osteoclasts are important, even if effects on bone resorption were not detected by osteoclast counting, genes in cortical bone or analysis of serum TRAP5b and CTX. In conclusion, our results indicate that even clinically relevant doses of vitamin A have a negative impact on the amount of cortical bone. © 2018 The authors Published by Bioscientifica Ltd.
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