Bone metabolism during strict head-down tilt bed rest and exposure to elevated levels of ambient CO2
Abstract Astronauts on the International Space Station are exposed to levels of atmospheric carbon dioxide (CO2) above typical terrestrial levels. We explored the possibility that increased levels of ambient CO2 further stimulate bone resorption during bed rest. We report here data from 2 ground-bas...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2022-12-01
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| Series: | npj Microgravity |
| Online Access: | https://doi.org/10.1038/s41526-022-00245-0 |
| _version_ | 1797429263966666752 |
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| author | Emily R. McGrath Petra Frings-Meuthen Jean Sibonga Martina Heer Gilles R. Clement Edwin Mulder Scott M. Smith Sara R. Zwart |
| author_facet | Emily R. McGrath Petra Frings-Meuthen Jean Sibonga Martina Heer Gilles R. Clement Edwin Mulder Scott M. Smith Sara R. Zwart |
| author_sort | Emily R. McGrath |
| collection | DOAJ |
| description | Abstract Astronauts on the International Space Station are exposed to levels of atmospheric carbon dioxide (CO2) above typical terrestrial levels. We explored the possibility that increased levels of ambient CO2 further stimulate bone resorption during bed rest. We report here data from 2 ground-based spaceflight analog studies in which 12 male and 7 female subjects were placed in a strict 6° head-down tilt (HDT) position for either 30 days at 0.5% ambient CO2 or 60 days with nominal environmental exposure to CO2. Bone mineral density (BMD) and bone mineral content (BMC) were determined using dual-energy X-ray absorptiometry (DXA). Blood and urine were collected before and after HDT for biochemical analysis. No change was detected in either BMD or BMC, as expected given the study duration. Bone resorption markers increased after bed rest as expected; however, elevated CO2 had no additive effect. Elevated CO2 did not affect concentrations of minerals in serum and urine. Serum parathyroid hormone and 1,25-dihydroxyvitamin D were both reduced after bed rest, likely secondary to calcium efflux from bone. In summary, exposure to 0.5% CO2 for 30 days did not exacerbate the typical bone resorption response observed after HDT bed rest. Furthermore, results from these strict HDT studies were similar to data from previous bed rest studies, confirming that strict 30–60 days of HDT can be used to evaluate changes in bone metabolism. This is valuable in the continuing effort to develop and refine efficacious countermeasure protocols to mitigate bone loss during spaceflight in low-Earth orbit and beyond. |
| first_indexed | 2024-03-09T09:10:39Z |
| format | Article |
| id | doaj.art-14768428c79c43c8be592e55609834f7 |
| institution | Directory Open Access Journal |
| issn | 2373-8065 |
| language | English |
| last_indexed | 2024-03-09T09:10:39Z |
| publishDate | 2022-12-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | npj Microgravity |
| spelling | doaj.art-14768428c79c43c8be592e55609834f72023-12-02T08:38:05ZengNature Portfolionpj Microgravity2373-80652022-12-01811910.1038/s41526-022-00245-0Bone metabolism during strict head-down tilt bed rest and exposure to elevated levels of ambient CO2Emily R. McGrath0Petra Frings-Meuthen1Jean Sibonga2Martina Heer3Gilles R. Clement4Edwin Mulder5Scott M. Smith6Sara R. Zwart7Cornell UniversityGerman Aerospace CenterNASA Johnson Space CenterIU International University of Applied Sciences and University of BonnKBRGerman Aerospace CenterNASA Johnson Space CenterUniversity of Texas Medical BranchAbstract Astronauts on the International Space Station are exposed to levels of atmospheric carbon dioxide (CO2) above typical terrestrial levels. We explored the possibility that increased levels of ambient CO2 further stimulate bone resorption during bed rest. We report here data from 2 ground-based spaceflight analog studies in which 12 male and 7 female subjects were placed in a strict 6° head-down tilt (HDT) position for either 30 days at 0.5% ambient CO2 or 60 days with nominal environmental exposure to CO2. Bone mineral density (BMD) and bone mineral content (BMC) were determined using dual-energy X-ray absorptiometry (DXA). Blood and urine were collected before and after HDT for biochemical analysis. No change was detected in either BMD or BMC, as expected given the study duration. Bone resorption markers increased after bed rest as expected; however, elevated CO2 had no additive effect. Elevated CO2 did not affect concentrations of minerals in serum and urine. Serum parathyroid hormone and 1,25-dihydroxyvitamin D were both reduced after bed rest, likely secondary to calcium efflux from bone. In summary, exposure to 0.5% CO2 for 30 days did not exacerbate the typical bone resorption response observed after HDT bed rest. Furthermore, results from these strict HDT studies were similar to data from previous bed rest studies, confirming that strict 30–60 days of HDT can be used to evaluate changes in bone metabolism. This is valuable in the continuing effort to develop and refine efficacious countermeasure protocols to mitigate bone loss during spaceflight in low-Earth orbit and beyond.https://doi.org/10.1038/s41526-022-00245-0 |
| spellingShingle | Emily R. McGrath Petra Frings-Meuthen Jean Sibonga Martina Heer Gilles R. Clement Edwin Mulder Scott M. Smith Sara R. Zwart Bone metabolism during strict head-down tilt bed rest and exposure to elevated levels of ambient CO2 npj Microgravity |
| title | Bone metabolism during strict head-down tilt bed rest and exposure to elevated levels of ambient CO2 |
| title_full | Bone metabolism during strict head-down tilt bed rest and exposure to elevated levels of ambient CO2 |
| title_fullStr | Bone metabolism during strict head-down tilt bed rest and exposure to elevated levels of ambient CO2 |
| title_full_unstemmed | Bone metabolism during strict head-down tilt bed rest and exposure to elevated levels of ambient CO2 |
| title_short | Bone metabolism during strict head-down tilt bed rest and exposure to elevated levels of ambient CO2 |
| title_sort | bone metabolism during strict head down tilt bed rest and exposure to elevated levels of ambient co2 |
| url | https://doi.org/10.1038/s41526-022-00245-0 |
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