Space flight is associated with rapid decreases of undercarboxylated osteocalcin and increases of markers of bone resorption without changes in theircircadian variation: Observations in two cosmonauts
A. Caillot-augusseau et al., Space flight is associated with rapid decreases of undercarboxylated osteocalcin and increases of markers of bone resorption without changes in theircircadian variation: Observations in two cosmonauts, CLIN CHEM, 46(8), 2000, pp. 1136-1143
Background: Microgravity induces bone loss by mechanism(s) that remain larg
ely unknown.
Methods: We measured biochemical markers related to bone remodeling in two
cosmonauts before, during, and after 21- and 180-day space flights, respect
ively.
Results: During both flights, type I procollagen propeptide and bone alkali
ne phosphatase decreased as early as 8 days after launch. Undercarboxylated
osteocalcin percentage increased early and remained high during both fligh
ts. Vitamin It supplementation restored carboxylation of osteocalcin during
the long-term flight. Urinary and serum C-telopeptide of type I collagen (
CTX) increased as early as day 8 of the flights; the increase was greater i
n serum than in urine. Pyridinoline, free deoxypyridinoline, and N-telopept
ide increased less than CTX during the short-term space flight. The circadi
an rhythm of bone resorption assessed by urine CTX and free deoxypyridinoli
ne was not altered by microgravity.
Conclusion: Vitamin K metabolism or action and bone remodeling may be alter
ed in cosmonauts. (C) 2000 American Association for Clinical Chemistry.