| 31. |
- Windahl, Sara H, 1971, et al.
(författare)
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Reduced bone mass and muscle strength in male 5α-reductase type 1 inactivated mice.
- 2011
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 6:6
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Tidskriftsartikel (refereegranskat)abstract
- Androgens are important regulators of bone mass but the relative importance of testosterone (T) versus dihydrotestosterone (DHT) for the activation of the androgen receptor (AR) in bone is unknown. 5α-reductase is responsible for the irreversible conversion of T to the more potent AR activator DHT. There are two well established isoenzymes of 5α-reductase (type 1 and type 2), encoded by separate genes (Srd5a1 and Srd5a2). 5α-reductase type 2 is predominantly expressed in male reproductive tissues whereas 5α-reductase type 1 is highly expressed in liver and moderately expressed in several other tissues including bone. The aim of the present study was to investigate the role of 5α-reductase type 1 for bone mass using Srd5a1⁻/⁻ mice. Four-month-old male Srd5a1⁻/⁻ mice had reduced trabecular bone mineral density (-36%, p<0.05) and cortical bone mineral content (-15%, p<0.05) but unchanged serum androgen levels compared with wild type (WT) mice. The cortical bone dimensions were reduced in the male Srd5a1⁻/⁻ mice as a result of a reduced cortical periosteal circumference compared with WT mice. T treatment increased the cortical periosteal circumference (p<0.05) in orchidectomized WT mice but not in orchidectomized Srd5a1⁻/⁻ mice. Male Srd5a1⁻/⁻ mice demonstrated a reduced forelimb muscle grip strength compared with WT mice (p<0.05). Female Srd5a1⁻/⁻ mice had slightly increased cortical bone mass associated with elevated circulating levels of androgens. In conclusion, 5α-reductase type 1 inactivated male mice have reduced bone mass and forelimb muscle grip strength and we propose that these effects are due to lack of 5α-reductase type 1 expression in bone and muscle. In contrast, the increased cortical bone mass in female Srd5a1⁻/⁻ mice, is an indirect effect mediated by elevated circulating androgen levels.
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| 32. |
- 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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