NASA’s research on the Scott Twins can help us understand the effects of long stays in a microgravity environment.
What are the human body’s reactions to a long space flight? This is the question that all those working in space programs ask themselves, in view of the flights to Mars and the Moon that are scheduled between 2020 and 2030.
This question is difficult to answer because, if you want to give a scientifically accurate answer, you should have what’s called “positive control” in the laboratory; this means that something that is identical to what you’re studying, but is in known and easily measurable conditions. NASA has found the solution in the monozygotic (i.e. identical) Kelly twins, Scott and Mark. The former spent 340 days within the International Space Station (ISS) and the other; also an astronaut, waited back here on Earth.
In the news, it was emphasized last month, that Scott’s space flight took place between 2015 and 2016. The news was shared about three years later because Scott’s physiological, genetic, and general medical parameters were monitored for another six months after the astronaut’s return, and then the data were processed and finally published in a long article in “Science” last April.
Which parameters were analyzed?
- Body mass and nutrition
- Length of telomeres
- Maintaining genome stability
- Cardiovascular health
- Structural adaptations of the eye
- Transcriptional and metabolic changes
- Epigenetic modifications
- Alteration in lipid level
- Changes in the microbiome
- Cognitive functions
Without going into too many details for each of the parameters listed, in this article I will go into detail on only the data related to the microbiome that constitutes the second genome of humans.
In order to study the variations of the intestinal microbiome, it was necessary to take and analyze the fecal samples of Scott (the twin in space) and Mark; to be exact, 317 samples collected before departure, during the mission and upon return. Some of Scott’s samples were stored at -80°c on the ISS until the astronaut returned to Earth; these samples were stored at room temperature.
What did the scientists expect from the microbiome analysis?
First of all, it was important to study the possible alteration of the microbiome, as its interaction with our immune system and metabolic diseases has now been proven.
Furthermore, since it’s known that the intestinal microbiome is influenced by diet and the environment, it was reasonable to conclude that a space trip could lead to significant changes in its composition.
Although Scott’s and Mark’s microbiome retained their individual characteristics, a greater number of changes in the composition and function of the microbial community was observed during Scott’s flight period than during Mark’s flight.
In particular, Scott’s microbiome showed an increase in the ratio of phyla Firmicutes to Bacteroidetes. Firmicutes are bacteria known to be associated with a high-fat diet and obesity. However, this ratio returned to pre-space flight levels within a few weeks of returning to Earth. This evidence may be useful in developing better diets for astronauts, not only for weight control but also to keep the immune system in good running order.
Finally, the good news is that microbiome diversity, often associated with a health indication of the microbiome itself, had not decreased during space flight.
So what are the conclusions to be made?
Essentially, that there are no serious contraindications for humans to make long-term space travel — and not only for the microbiome, but also for physiological and genetic parameters. Of course, further analysis must be performed, in order to exclude any risk, but it’s known that new frontiers are conquered step-by-step, and even at the cost of some sacrifice.
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