科研之友
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摘要
As they age, mice deficient for the beta 2-adrenergic receptor (Adrb2-/-) maintain greater trabecular bone microarchitecture, as a result of lower bone resorption and increased bone formation. The role of beta 1-adrenergic receptor signaling and its interaction with beta 2-adrenergic receptor on bone mass regulation, however, remains poorly understood. We first investigated the skeletal response to mechanical stimulation in mice deficient for beta 1-adrenergic receptors and/or beta 2-adrenergic receptors. Upon axial compression loading of the tibia, bone density, cancellous and cortical microarchitecture, as well as histomorphometric bone forming indices, were increased in both Adrb2-/- and wild-type (WT) mice, but not in Adrb1-/- nor in Adrb1b2-/- mice. Moreover, in the unstimulated femur and vertebra, bone mass and microarchitecture were increased in Adrb2-/- mice, whereas in Adrb1-/- and Adrb1b2-/- double knockout mice, femur bone mineral density (BMD), cancellous bone volume/total volume (BV/TV), cortical size, and cortical thickness were lower compared to WT. Bone histomorphometry and biochemical markers showed markedly decreased bone formation in Adrb1b2-/- mice during growth, which paralleled a significant decline in circulating insulin-like growth factor 1 (IGF-1) and IGFbinding protein 3 (IGF-BP3). Finally, administration of the beta-adrenergic agonist isoproterenol increased bone resorption and receptor activator of NF-?B ligand (RANKL) and decreased bone mass and microarchitecture in WT but not in Adrb1b2-/- mice. Altogether, these results demonstrate that beta 1- and beta 2-adrenergic signaling exert opposite effects on bone, with beta 1 exerting a predominant anabolic stimulus in response to mechanical stimulation and during growth, whereas beta 2-adrenergic receptor signaling mainly regulates bone resorption during aging.
- 出版日期2012-6
- 单位河北医科大学
