| 1. |
- Farman, H. H., et al.
(författare)
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Female mice lacking estrogen receptor-α 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)α.CentralERα exertsaninhibitoryroleonbonemass.ERα ishighlyexpressedinthearcuate (ARC) and the ventromedial (VMN) nuclei in the hypothalamus. To test whether ERα in proopiomelanocortin (POMC) neurons, located in ARC, is involved in the regulation of bone mass, we used mice lacking ERα expression specifically in POMC neurons (POMC-ERα -/- ). Female POMC-ERα -/- and control mice were ovariectomized (OVX) and treated with vehicle or estradiol (0.5 μg/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-ERα -/- 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 ERα in VMN is involved in the regulation of bone mass, ERα was silenced using an adeno-associated viral vector. Silencing of ERα in hypothalamic VMN resulted in unchanged bone mass. In conclusion, mice lacking ERα in POMC neurons display enhanced estrogenic response on cortical bone mass and mechanical strength. We propose that the balance between inhibitory effects of central ERα activity in hypothalamic POMC neurons in ARC and stimulatory peripheral ERaα-mediated effects in bone determines cortical bone mass in female mice.
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| 2. |
- Nilsson, Maria E., et al.
(författare)
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Measurement of a comprehensive sex steroid profile in rodent serum by high-sensitive gas chromatography-tandem mass spectrometry.
- 2015
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Ingår i: Endocrinology. - : The Endocrine Society. - 1945-7170 .- 0013-7227. ; 156:7, s. 2492-502
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Tidskriftsartikel (refereegranskat)abstract
- Accurate measurement of sex steroid concentrations in rodent serum is essential to evaluate mouse and rat models for sex steroid-related disorders. The aim of the present study was to develop a sensitive and specific gas chromatography-tandem mass spectrometry (GC-MS/MS) method to assess a comprehensive sex steroid profile in rodent serum. A major effort was invested in reaching an exceptionally high sensitivity for measuring serum estradiol concentrations. We established a GC-MS/MS assay with a lower limit of detection for estradiol, estrone, testosterone, dihydrotestosterone, progesterone, androstenedione and dehydroepiandrosterone of 0.3, 0.5, 4, 1.6, 8, 4 and 50 pg/ml, respectively, while the corresponding values for the lower limit of quantification were 0.5, 0.5, 8, 2.5, 74, 12 and 400 pg/ml, respectively. Calibration curves were linear, intra- and inter-assay CVs were low and accuracy was excellent for all analytes. The established assay was used to accurately measure a comprehensive sex steroid profile in female rats and mice according to estrus cycle phase. In addition, we characterized the impact of age, sex, gonadectomy, and estradiol treatment on serum concentrations of these sex hormones in mice. In conclusion, we have established a highly sensitive and specific GC-MS/MS method to assess a comprehensive sex steroid profile in rodent serum in a single run. This GC-MS/MS assay has, to the best of our knowledge, the best detectability reported for estradiol. Our method therefore represents an ideal tool to characterize sex steroid metabolism in a variety of sex steroid-related rodent models and in human samples with low estradiol levels.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Iravani, M., et al.
(författare)
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Effects of the selective GPER1 agonist G1 on bone growth
- 2019
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Ingår i: Endocrine Connections. - 2049-3614. ; 8:9, s. 1302-1309
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Tidskriftsartikel (refereegranskat)abstract
- Estrogens may affect bone growth locally or systemically via the known estrogen receptors ESR1, ESR2 and G protein-coupled estrogen receptor 1 (GPER1). Mouse and human growth plate chondrocytes have been demonstrated to express GPER1 and ablation of this receptor increased bone length in mice. Therefore, GPER1 is an attractive target for therapeutic modulation of bone growth, which has never been explored. To investigate the effects of activated GPER1 on the growth plate, we locally exposed mouse metatarsal bones to different concentrations of the selective GPER1 agonist G1 for 14 days ex vivo. The results showed that none of the concentrations of G1 had any direct effect on metatarsal bone growth when compared to control. To evaluate if GPER1 stimulation may systemically modulate bone growth, ovariectomized C57BL/6 mice were treated with G1 or beta-estradiol (E2). Similarly, G1 did not influence tibia and femur growth in treated mice. As expected, E2 treatment suppressed bone growth in vivo. We conclude that ligand stimulation of GPER1 does not influence bone growth in mice.
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| 7. |
- Movérare-Skrtic, Sofia, et al.
(författare)
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The bone-sparing effects of estrogen and WNT16 are independent of each other
- 2015
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:48, s. 14972-14977
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Tidskriftsartikel (refereegranskat)abstract
- Wingless-type MMTV integration site family (WNT)16 is a key regulator of bone mass with high expression in cortical bone, and Wnt16-/- mice have reduced cortical bone mass. As Wnt16 expression is enhanced by estradiol treatment, we hypothesized that the bone-sparing effect of estrogen in females isWNT16-dependent. This hypothesis was tested in mechanistic studies using two genetically modified mouse models with either constantly high osteoblastic Wnt16 expression or no Wnt16 expression. We developed a mouse model with osteoblast-specific Wnt16 overexpression (Obl-Wnt16). These mice had several-fold elevated Wnt16 expression in both trabecular and cortical bone compared with wild type (WT) mice. Obl- Wnt16 mice displayed increased total body bone mineral density (BMD), surprisingly caused mainly by a substantial increase in trabecular bone mass, resulting in improved bone strength of vertebrae L3. Ovariectomy (ovx) reduced the total body BMD and the trabecular bone mass to the same degree in Obl-Wnt16 mice and WT mice, suggesting that the bone-sparing effect of estrogen is WNT16-independent. However, these bone parameters were similar in ovx Obl- Wnt16 mice and sham operated WT mice. The role of WNT16 for the bone-sparing effect of estrogen was also evaluated in Wnt16-/- mice. Treatment with estradiol increased the trabecular and cortical bone mass to a similar extent in both Wnt16-/- and WT mice. In conclusion, the bone-sparing effects of estrogen and WNT16 are independent of each other. Furthermore, loss of endogenous WNT16 results specifically in cortical bone loss, whereas overexpression of WNT16 surprisingly increases mainly trabecular bone mass. WNT16- targeted therapies might be useful for treatment of postmenopausal trabecular bone loss.
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| 8. |
- Ohlsson, Claes, 1965, et al.
(författare)
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Inducible Wnt16 inactivation: WNT16 regulates cortical bone thickness in adult mice.
- 2018
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Ingår i: The Journal of endocrinology. - 1479-6805. ; 237:2, s. 113-122
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Tidskriftsartikel (refereegranskat)abstract
- Substantial progress has been made in the therapeutic reduction of vertebral fracture risk in patients with osteoporosis, but non-vertebral fracture risk has been improved only marginally. Human genetic studies demonstrate that the WNT16 locus is a major determinant of cortical bone thickness and non-vertebral fracture risk and mouse models with life-long Wnt16 inactivation revealed that WNT16 is a key regulator of cortical thickness. These studies, however, could not exclude that the effect of Wnt16 inactivation on cortical thickness might be caused by early developmental and/or growth effects. To determine the effect of WNT16 specifically on adult cortical bone homeostasis, Wnt16 was conditionally ablated in young adult and old mice through tamoxifen-inducible Cre-mediated recombination using CAG-Cre-ER; Wnt16flox/flox (Cre-Wnt16flox/flox) mice. First, 10-week-old Cre-Wnt16flox/flox and Wnt16flox/flox littermate control mice were treated with tamoxifen. Four weeks later, Wnt16 mRNA levels in cortical bone were reduced and cortical thickness in femur was decreased in Cre-Wnt16flox/flox mice compared to Wnt16flox/flox mice. Then, inactivation of Wnt16 in 47-week-old mice (evaluated four weeks later) resulted in a reduction of Wnt16 mRNA levels, cortical thickness and cortical bone strength with no effect on trabecular bone volume fraction. Mechanistic studies demonstrated that the reduced cortical bone thickness was caused by a combination of increased bone resorption and reduced periosteal bone formation. In conclusion, WNT16 is a crucial regulator of cortical bone thickness in young adult and old mice. We propose that new treatment strategies targeting the adult regulation of WNT16 might be useful to reduce fracture risk at cortical bone sites.
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| 9. |
- Wu, Jianyao, et al.
(författare)
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Enzalutamide Reduces the Bone Mass in the Axial but not the Appendicular Skeleton in Male Mice.
- 2016
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Ingår i: Endocrinology. - : The Endocrine Society. - 1945-7170 .- 0013-7227. ; 157:2, s. 969-977
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Tidskriftsartikel (refereegranskat)abstract
- Testosterone is a crucial regulator of the skeleton but the role of the androgen receptor (AR) for the maintenance of the adult male skeleton is unclear. In the present study, the role of the AR for bone metabolism and skeletal growth after sexual maturation was evaluated by means of the drug enzalutamide, which is a new AR antagonist used in the treatment of prostate cancer patients. Nine-week-old male mice were treated with 10, 30, or 100 mg/kg/day of enzalutamide for 21 days or were surgically castrated, and compared with vehicle-treated gonadal intact mice. Although orchidectomy (orx) reduced the cortical bone thickness and trabecular bone volume fraction in the appendicular skeleton, these parameters were unaffected by enzalutamide. In contrast, both enzalutamide and orx reduced the bone mass in the axial skeleton as demonstrated by reduced lumbar spine areal bone mineral density (p<0.001) and trabecular bone volume fraction in L5 vertebrae (p<0.001) compared with vehicle-treated gonadal intact mice. A compression test of the L5 vertebrae revealed that the mechanical strength in the axial skeleton was significantly reduced by enzalutamide (maximal load at failure, -15.3±3.5%; p<0.01). The effects of enzalutamide in the axial skeleton were associated with a high bone turnover. In conclusion, enzalutamide reduces the bone mass in the axial but not the appendicular skeleton in male mice after sexual maturation. We propose that the effect of testosterone on the axial skeleton in male mice is mainly mediated via the AR.
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