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Mechanical signaling in the development of postmenopausal osteoporosisEstrogen deficiency results in increased bone turnover and net bone loss in rats as well as humans. The respective roles of bone turnover and mechanical strain in mediating estrogen deficiency-induced cancellous bone loss were investigated in ovariectomized rats. Ovariectomy resulted in increased bone turnover in long bones. However, cancellous bone was preferentially lost in the metaphysis, a site that experiences low strain energy during normal physical activity. No bone loss was observed in the epiphysis, a site experiencing higher strain energy, despite a similar increase in bone turnover. The role of mechanical strain in maintaining bone balance was investigated by altering the strain history. Mechanical strain was increased or decreased in long bones of ovariectomized rats by treadmill exercise or functional unloading, respectively. Increasing mechanical loading reduced bone loss in the metaphysis. In contrast, decreasing weight bearing accentuated bone loss in the metaphysis and resulted in bone loss in the epiphysis. Finally, administration of estrogen to ovariectomized rats reduced bone loss in unloaded limbs and prevented bone loss in the loaded limbs. These results suggest that estrogen alters the mechanosensory (mechanostat) set point for skeletal adaptation, effectively reducing the minimum strain energy levels at which bone is added. Additionally, these studies suggest that physical activity as well as endocrine status play an important role in maintenance of the female skeleton during aging.
Document ID
20040141855
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Turner, R. T.
(Mayo Clinic Rochester, MN 55905, United States)
Date Acquired
August 22, 2013
Publication Date
January 1, 1999
Publication Information
Publication: Lupus
Volume: 8
Issue: 5
ISSN: 0961-2033
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: AR41418
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
Review
Review, Tutorial
NASA Discipline Regulatory Physiology

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