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Collagen cross-link excretion during space flight and bed rest
S M Smith1, J L Nillen, A Leblanc
1Life Sciences Research Laboratories, National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas 77058, USA. smsmith@ems.jsc.nasa.gov
The Journal of Clinical Endocrinology and Metabolism
|October 13, 1998
Summary
Extended space missions cause significant bone loss due to increased bone resorption. This study monitored collagen breakdown products, revealing rapid changes in bone metabolism during weightlessness and bed rest.
Area of Science:
- Space medicine
- Bone metabolism
- Biochemistry
Background:
- Extended weightlessness leads to bone loss, but the specifics remain unclear.
- Bone resorption releases collagen breakdown products like N-telopeptide and pyridinium (PYD) cross-links.
- Urinary PYD cross-links increase during bed rest, indicating bone resorption.
Purpose of the Study:
- To investigate the nature and time course of bone loss during prolonged space flight.
- To assess changes in bone metabolism markers during space missions and bed rest.
- To understand the impact of weightlessness on bone resorption.
Main Methods:
- Assessed urinary excretion of PYD cross-links and N-telopeptide.
- Collected data before, during, and after long Skylab missions (28-84 days).
- Analyzed samples from short (14-day) and long (119-day) bed-rest studies.
Main Results:
- Urinary cross-link excretion doubled during space flight compared to pre-flight levels.
- Collagen breakdown products increased by 40-50% during both short and long bed rest.
- These findings indicate increased bone resorption associated with space flight and bed rest.
Conclusions:
- Space flight significantly increases bone resorption, a key factor in weightlessness-induced bone loss.
- Alterations in bone metabolism occur rapidly, within days to weeks of exposure to weightlessness.
- Understanding these changes is crucial for managing bone health in astronauts and bedridden individuals.