A group of mice that flew to space onboard a space shuttle went back to Earth with nascent liver damage.

These mice boarded NASA's Atlantis space shuttle in 2011 for a 13.5-day space mission. Upon their return, several research teams procured the mice's internal organs for research.

The research team from the University of Colorado Anschutz Medical Campus analyzed the space mice's livers. In their study published in the PLOS ONE journal on April 20, they found that the liver health of the mice has been compromised.

"We saw the beginning of nascent liver damage in just 13.5 days. The mice also lost lean muscle mass," said Karen Jonscher, the study's lead researcher.

"We have seen this same phenomenon in humans on bed rest - muscles atrophy and proteins break down into amino acids."

When the team compared the livers of the space mice to the livers of the ones who remained Earth bound, the research team discovered that spaceflight led to a higher fat storage in the liver.

The space mice's livers also showed retinol (animal form of Vitamin A) loss as well as variations in the level of genes that play roles in fat breakdown.

All these changes led to signs of nonalcoholic fatty liver disease (NAFLD). Moreover, it could potentially lead to early signs of fibrosis development, which is an advanced after-effect of NAFLD.

Jonscher added that normally, it takes months, even years, to prompt fibrosis in mice specimen. This condition cannot be easily induced even with an unhealthy diet.

The space mice developed signs of the condition after just 13.5 days. And this took place without introducing an unhealthy diet. Further study is needed to analyze if the findings can become a potential problem for deep space missions.

Analyzing mice that spent longer time in space could help scientists determine if other mechanisms will develop that can potentially protect the animals from critical organ damage.

Findings from this research can help scientists who are focused on spaceflight's effects on the human physiology. Past studies showed that returning astronauts often develop prediabetes symptoms but these go away quickly on their own.

Photo: Reinhard Link | Flickr