Cancellous bone formation response to simulated resistance training during disuse is blunted by concurrent alendronate treatment

Authors

  • Joshua M Swift,

    1. Departments of Health and Kinesiology, Texas A&M University, College Station, TX, USA
    Current affiliation:
    1. Radiation Combined Injury Program, Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, MD 20889-5603, USA.
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  • Sibyl N Swift,

    1. Departments of Intercollegiate Faculty of Nutrition, Texas A&M University, College Station, TX, USA
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  • Mats I Nilsson,

    1. Departments of Health and Kinesiology, Texas A&M University, College Station, TX, USA
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  • Harry A Hogan,

    1. Departments of Mechanical Engineering, Texas A&M University, College Station, TX, USA
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  • Scott D Bouse,

    1. Departments of Mechanical Engineering, Texas A&M University, College Station, TX, USA
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  • Susan A Bloomfield

    Corresponding author
    1. Departments of Health and Kinesiology, Texas A&M University, College Station, TX, USA
    2. Departments of Intercollegiate Faculty of Nutrition, Texas A&M University, College Station, TX, USA
    • Department of Health and Kinesiology, MS 4243, Texas A&M University, College Station, TX 77843-4243, USA.
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Abstract

The purpose of this study was to assess the effectiveness of simulated resistance training (SRT) exercise combined with alendronate (ALEN) in mitigating or preventing disuse-associated losses in cancellous bone microarchitecture and formation. Sixty male Sprague-Dawley rats (6 months old) were randomly assigned to either cage control (CC), hind limb unloading (HU), HU plus either ALEN (HU + ALEN), SRT (HU + SRT), or a combination of ALEN and SRT (HU + SRT/ALEN) for 28 days. HU + SRT and HU + SRT/ALEN rats were anesthetized and subjected to muscle contractions once every 3 days during HU (four sets of five repetitions, 1000 ms isometric + 1000 ms eccentric). Additionally, HU + ALEN and HU + SRT/ALEN rats received 10 µg/kg of body weight of ALEN three times per week. HU reduced cancellous bone-formation rate (BFR) by 80%, with no effect of ALEN treatment (−85% versus CC). SRT during HU significantly increased cancellous BFR by 123% versus CC, whereas HU + SRT/ALEN inhibited the anabolic effect of SRT (−70% versus HU + SRT). SRT increased bone volume and trabecular thickness by 19% and 9%, respectively, compared with CC. Additionally, osteoid surface (OS/BS) was significantly greater in HU + SRT rats versus CC (+32%). Adding ALEN to SRT during HU reduced Oc.S/BS (−75%), Ob.S/BS (−72%), OS/BS (−61%), and serum TRACP5b (−36%) versus CC. SRT and ALEN each independently suppressed a nearly twofold increase in adipocyte number evidenced with HU and inhibited increases in osteocyte apoptosis. These results demonstrate the anabolic effect of a low volume of high-intensity muscle contractions during disuse and suggest that both bone resorption and bone formation are suppressed when SRT is combined with bisphosphonate treatment. © 2011 American Society for Bone and Mineral Research

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