Long-term space flight appears to trigger a number of genetic and biological changes in astronauts, according to preliminary results from a NASA study.
Researchers compared astronaut Scott Kelly, who returned home last March after nearly a year aboard the International Space Station, and his identical twin Mark, a retired astronaut. Mark remained on Earth during that time.
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"Ten researchers are sharing biological samples taken from each twin before, during and after Scott's mission," according to a NASA news release. The goal of the NASA Twins Study is to learn more about how extended time in space affects the body.
1. Different levels of lipids
According to the report, Scott had altered levels of lipids (an indication of inflammation), and the telomeres on the ends of chromosomes in his white blood cells increased in length while he was in space. However, the telomeres started to shorten again after his return to Earth.
2. Lengthened telomeres
Telomeres decrease in length as a person ages. The lengthening of Scott's telomeres while in space could have been due to increased exercise and reduced caloric intake, researchers suggest.
Scientists found that telomerase activity (the enzyme that repairs telomeres and lengthens them) increased in both twins in November. This might be due to a major stressful family event that occurred around that time, the researchers said.
3. Decreased thinking speed
The study also found a slight decrease in Scott's thinking speed and accuracy after his one-year space mission. But his overall thinking wasn't all that different than what is seen after a six-month space mission, the researchers noted.
4. Decline in bone formation
Scott also appeared to have a decline in bone formation during the second half of his mission, and an increase in inflammation soon after his return to Earth. One theory attributed this to the stress of re-entry and landing.
5. Changes in digestive system
Differences in the viral, bacterial and fungal populations in the twins' digestive systems were noted while Scott was in space. These were likely due to their different environments and diets, the scientists determined. The ratio of two dominant bacterial groups shifted while Scott was in space but returned to pre-flight levels when he returned to Earth, they said.
Also of note, more than 200,000 RNA molecules in white blood cells were expressed differently in the twins while Scott was in space. Researchers plan to investigate if a "space gene" could have been activated while Scott was on the space station.
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The scientists also looked at the level of chemical modifications (methylation) in the DNA of Scott's white blood cells. These decreased while in space, but returned to normal when he was back on earth, the findings showed.
While variability in methylation patterns was seen in both twins, it was slightly higher in Scott during his spaceflight but went back to baseline levels after his return. This could indicate genes that are more sensitive to a changing environment whether on Earth or in space.
The findings were presented at a recent NASA meeting and will be published later this year. Until that time, they should be considered preliminary.
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