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This study was designed to identify molecules in the plasma and urine that are altered in response to a simulated space environment, the head down tilt bed rest (HDTBR). The goal was to identify biomarkers that may be used to predict risk for the physiological manifestations of simulated spaceflight beyond current clinical measures and predictors.
To accomplish this goal, we conducted untargeted and targeted metabolomic assays on archived 24 hour-pooled urine and plasma samples collected longitudinally for the 70 day HDTBR study at the University of Texas Medical Branch between June 2011 and May 2014. The samples were obtained from 11 bed rest CONTROL subjects, 10 subjects in the EXERCISE arm of the study, and 8 subjects from the COMBINED EXERCISE AND TESTOSTERONE arm.
We applied untargeted metabolomics assays on plasma samples at 10- and 3-days pre-bed rest, day 28 of bed rest, return of normal position day 0, and post bed rest day 5 to measure metabolites related to primary metabolism, biogenic amines, and complex lipids. Due to our recent findings of spaceflight related changes in urine proteins, we extended our aims to also apply MS based proteomics on the urine samples at 9 days pre-bed rest, days 29 and 70 of bed rest, and 70 days post-bed rest to identify proteins that are altered in response to HDTBR.
We identified metabolic pathways related to mitochondrial function that are altered during bed rest. We also identified metabolic pathways that differentiate by study arm. By comparing the results of the present study with metabolomics data from the VaPER study which was done in parallel, we were able to identify metabolic responses that are related to specific factors of simulated spaceflight such as elevated CO2 and physical activity.
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