Re-Adaption on Earth after Spaceflights Affects the Mouse Liver Proteome

Harsh environmental conditions including microgravity and radiation during prolonged spaceflights are known to alter hepatic metabolism. Our studies have focused on the analysis of possible changes in metabolic pathways in livers of mice which experienced 30 days of spaceflight with and without an additional re-adaption period of 7 days compared to control mice on Earth. Utilizing shotgun mass spectrometry and label-free quantification we performed proteomic profiling to investigate mice livers from the spaceflight project xe2 x80 x9cBion-M 1 xe2 x80 x9d. No significant alterations in protein levels were observed between control mice liver and spaceflight mice which is possibly caused by insufficient fold change detection combined with high variances within the groups. In contrast our results show that more than a third of the quantified protein levels are altered comparing the liver proteome of mice with and without re-adaption time after their spaceflight. Proteins related to amino acid metabolism showed higher levels after re-adaption which may indicate higher rates of gluconeogenesis. Members of the peroxisome proliferator-activated receptor pathway reconstitute their level after 7 days due to a decrease in fold change which indicates decreased signs of non-alcoholic fatty liver disease. Moreover bile acid secretion regenerates on Earth due to reconstitution of related transmembrane proteins and elevated levels of the drug-metabolising enzymes belonging to the CYP superfamily decrease 7 days after the spaceflight. Thus our study demonstrates reconstitution of pharmacological response and early signs of non-alcoholic fatty liver disease recover within 7 days whereas glucose uptake should be monitored due to alterations in gluconeogenesis.