Circulating levels of the signaling molecule adenosine increase under simulated microgravity and reduced oxygen supply, finds the EU-funded Planetary Habitat Simulation Study (PlanHab). Adenosine plays a central role in physiological processes, often as part of the energy storage molecule ATP, and its levels are sensitive to low-oxygen environments. The team behind this paper, led by LMU Munich’s Alexander Chouker, assessed adenosine level changes in response to these conditions, using bedrest to emulate reduced muscle usage in microgravity. Subjects underwent three 21-day periods of either low-oxygen (hypoxic) bed rest, hypoxic conditions with permitted physical activity, or bed rest under normal oxygen conditions. 

The team confirmed their hypothesis that hypoxia increased adenosine levels; however, they also found that bedrest alone also had the same, albeit smaller, effect. Further investigations will be needed to fully discern the cause of this, as well as what impact increased adenosine might have on astronauts on long-distance spaceflights or future colonization missions.

Read the original research paper on Scientific Reports.

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Poster image: A crater near the Sirenum Fossae region of Mars. With space agencies and corporations contemplating ambitious long-term missions, such an expedition to Mars, predicting human resilience to off-planet conditions is now a key step in future space exploration. Image courtesy of NASA/JPL/University of Arizona.