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NASA Technical Reports Server (NTRS) 20110023185: Retrospective Stu... |
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by NASA Technical Reports Server (NTRS) |
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Animal models and human studies suggest that osteocytes |
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regulate the skeleton s response to mechanical unloading |
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at the cellular level in part by an increase in |
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sclerostin, an inhibitor of the anabolic Wnt pathway. |
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However, few studies have reported changes in serum |
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sclerostin in humans exposed to reduced mechanical |
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loading. Thus, we determined changes in serum sclerostin |
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and bone turnover markers in healthy adult men who |
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participated in a controlled bed rest study. Seven |
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healthy adult men (31 +/- 3 yrs old) underwent 90-day six- |
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degree head down tilt bed rest at the University of Texas |
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Medical Branch in Galveston's Institute for Translational |
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Sciences - Clinical Research Center (ITS-CRC). Serum |
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sclerostin, PTH, serum markers of bone turnover (bone |
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specific alkaline phosphatase, RANKL/OPG, and |
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osteocalcin), urinary calcium and phosphorus excretion, |
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and 24 hour pooled urinary markers of bone resorption |
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(NTX, DPD, PYD) were evaluated pre-bed rest (BL), bed |
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rest day 28 (BR-28), bed rest day 60 (BR-60), and bed |
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rest day 90 (BR-90). In addition, bone mineral density |
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(BMD) was assessed by dual-energy X-ray absorptiometry |
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(DXA) at BL, BR-60, and post bed rest day 5 (BR+5). Data |
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are reported as mean +/- standard deviation. We used |
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repeated measures ANOVA to compare baseline values to BR- |
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28, BR-60, and BR-90. RESULTS Consistent with prior |
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reports, BMD declined significantly (1-2% per month) at |
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weight-bearing skeletal sites (spine, hip, femur neck, |
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and calcaneus). Serum sclerostin levels were elevated |
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above BL at BR-28 (+29% +/- 20%, p = 0.003), BR-60 (+42% |
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+/- 31%, p < 0.001), and BR-90 (22% +/- 21%, p = 0.07). |
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Serum PTH levels were reduced at BR-28 (-17% +/- 16%, p = |
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0.02), BR-60 (-24% +/- 14%, p = 0.03), and returned to |
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baseline at BR-90 (-21% +/- 21%, p = 0.14). Serum bone |
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turnover markers did not change, however urinary bone |
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resorption markers and calcium were significantly |
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elevated following bed rest (p < 0.01). CONCLUSION We |
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observed an increase of serum sclerostin associated with |
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decreased serum PTH and elevated bone resorption markers |
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in otherwise healthy men subjected to long-term |
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immobilization. |
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Date Published: 2016-11-07 18:36:45 |
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Identifier: NASA_NTRS_Archive_20110023185 |
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Item Size: 960647 |
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Language: english |
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Media Type: texts |
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