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The uncertainty of science: Mice flown for almost two weeks on the last space shuttle mission in 2011 have shown evidence of the early symptoms of liver disease.
The mice spent time orbiting the Earth on the final space shuttle flight in 2011. Once they returned home, teams of scientists were allowed to share and study their internal organs.
Jonscher’s team found that spaceflight resulted in increased fat storage in the liver, comparing pair-fed mice on Earth to those on the shuttle. This was accompanied by a loss of retinol, an animal form of Vitamin A, and changes to levels of genes responsible for breaking down fats. As a result, mice showed signs of nonalcoholic fatty liver disease (NAFLD) and potential early indicators for the beginnings of fibrosis, which can be one of the more progressive consequences of NAFLD. “It generally takes a long time, months to years, to induce fibrosis in mice, even when eating an unhealthy diet,” Jonscher said. “If a mouse is showing nascent signs of fibrosis without a change in diet after 13 ½ days, what is happening to the humans?”
This result doesn’t prove that weightlessness causes liver damage. It only suggests that more research is needed, though the data from six month to year long missions suggest that the liver harm to humans is either non-existent or temporary.