title: Serum sclerostin increases in healthy adult men during bed rest.
abstract: BACKGROUND
  Animal models and human studies suggest that osteocytes regulate the skeleton's response to mechanical unloading in part by an increase in sclerostin. However, few studies have reported changes in serum sclerostin in humans exposed to reduced mechanical loading.
  
  
  OBJECTIVE
  We determined changes in serum sclerostin and bone turnover markers in healthy adult men undergoing controlled bed rest.
  
  
  METHODS
  Seven healthy adult men (31 ± 3 yr old) underwent 90 d of 6° head down tilt bed rest at the University of Texas Medical Branch Institute for Translational Sciences-Clinical Research Center.
  
  
  RESULTS
  Serum sclerostin, PTH, vitamin D, bone resorption and formation markers, urinary calcium and phosphorus excretion, and 24-h pooled urinary markers of bone resorption were evaluated before bed rest [baseline (BL)] and at bed rest d 28 (BR-28), d 60 (BR-60), and d 90 (BR-90). Bone mineral density was measured at BL, BR-60, and 5 d after the end of the study (BR+5). Data are reported as mean ± SD.
  
  
  RESULTS
  Consistent with prior reports, bone mineral density declined significantly (1-2% per month) at weight-bearing skeletal sites. Serum sclerostin was elevated above BL at BR-28 (+29 ± 20%; P = 0.003) and BR-60 (+42 ± 31%; P < 0.001), with a lesser increase at BR-90 (+22 ± 21%; P = 0.07). Serum PTH levels were reduced at BR-28 (-17 ± 16%; P = 0.02) and BR-60 (-24 ± 14%; P = 0.03) and remained lower than BL at BR-90 (-21 ± 21%; P = 0.14), but did not reach statistical significance. Serum bone turnover markers were unchanged; however, urinary bone resorption markers and calcium were significantly elevated at all time points after bed rest (P < 0.01).
  
  
  CONCLUSIONS
  In healthy men subjected to controlled bed rest for 90 d, serum sclerostin increased, with a peak at 60, whereas serum PTH declined, and urinary calcium and bone resorption markers increased.
authors: Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. jspatz@bidmc.harvard.edu
authors: J M
authors: JM
authors: Spatz
authors: E E
authors: EE
authors: Fields
authors: E W
authors: EW
authors: Yu
authors: P
authors: P
authors: Divieti Pajevic
authors: M L
authors: ML
authors: Bouxsein
authors: J D
authors: JD
authors: Sibonga
authors: S R
authors: SR
authors: Zwart
authors: S M
authors: SM
authors: Smith
mesh_terms: D015502:Absorptiometry, Photon; D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D001510:Bed Rest; D015415:Biomarkers / Q000652:urine; D015519:Bone Density; D019485:Bone Morphogenetic Proteins / Q000097:blood*; D001862:Bone Resorption / Q000378:metabolism / Q000652:urine; D001842:Bone and Bones / Q000378:metabolism; D002118:Calcium / Q000652:urine; D005819:Genetic Markers; D018475:Head-Down Tilt; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood; D010758:Phosphorus / Q000652:urine; D010809:Physical Fitness; D014807:Vitamin D / Q000097:blood
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015415:Biomarkers; D019485:Bone Morphogenetic Proteins; D005819:Genetic Markers; D010281:Parathyroid Hormone; C422903:SOST protein, human; D014807:Vitamin D; D010758:Phosphorus; D002118:Calcium