EFFECTS OF SIMULATED MICROGRAVITY ON THE GUT MICROBIOME OF THE PARTICIPANTS OF THE AGBRESA STUDY

Abstract

The Artificial Gravity Bed Rest – European Space Agency (AGBRESA) study proposed to examine the impact of weightlessness on the human body in a space analog initiative, consequence of the first joint bed rest study by ESA, the DLR, and NASA. Herein, we report on the effects of simulated microgravity on the gut microbiome of 12 participants of the AGBRESA study, subjected to a strict isolation protocol at the :envihab facilities for a 6° Head Down Treatment (HDT) for 60 days. We profiled by metaproteomics the fecal content at three time points during HDT in comparison to a baseline timepoint and to a recovery sample, both without microgravity simulation, as well as measured the short-chain fatty acid (SCFA) moieties during these times. The analysis of the fecal proteome revealed that even though 60 days of HDT produces only a mild effect on the microbiome composition and diversity scores, the microgravity simulation produces diverse microbial patterns and pathway expression distinct from centrifugal countermeasure application. The quantitation of SCFA suggested that even though HDT produces a rise in abundance of all molecules screened, these would diminished during the recovery period. Conversely, the countermeasure protocols selectively potentiated the abundance of those SCFA reported to have beneficial effects on the intestine health, i.e. acetate, butyrate and propionate, during the recovery period post-HDT. Overall, microbiome profiling has become a relevant and informative readout to assess health, rising in importance to assess onset of severe GI (gastrointestinal) and non-GI disorders. As microgravity is one of the stimuli experienced during spaceflight impacting human physiology, this approach is relevant for astronauts exposed to hazardous settings, since it accurately measures gut health regardless of intestinal complaints. In conformity, profiling the gut microbiome also informs the success and outcome of countermeasure protocols that attempt to mitigate the damage caused by spaceflight.