Astronaut twins Mark and Scott Kelly participated in a study conducted by ten researchers on the effects of long duration space flight. Scott was aboard the International Space Station for 340 days while Mark remained on Earth. Scott returned to Earth 1 March 2016. For details about his return, read this previous post.
Ten researchers reported preliminary results on 23 Jan 2017 in Galveston TX of their comparative studies of the twins. The NASA issued statement is here. I’ll attempt to summarize eight of their findings below.
There is a long history to the argument of Nature vs Nurture. Does our DNA guide development or is environment more influential? The Twins Study was an opportunity to shed some light on that question. Mark served as the control subject on the ground. Scott was the experimental subject in a very different environment for 340 days.
Biological samples of each were collected before, during, and after the mission. Cognitive and motor skill tests were also performed. How the body is affected by extended time in space gives insight into our nature. It will help plan future long-term missions including those to Mars. A more complete report of the studies is due near the end of 2017.
Summary of Findings
Mike Snyder, the Integrated Omics investigator, reported changes to a set of lipids in Scott. Inflammation is a likely cause. Mark showed an increase of a metabolite 3-indolepropionic (IPA). It is produced only by gut bacteria. IPA helps maintain normal insulin and blood sugar after meals.
Susan Bailey studied Telomeres and Telomerase. Telomeres are a protective end cap on our DNA molecules. They decrease in length as a person ages. During his 340 days in space, Bailey found Scott’s telomeres increased in length. It might be related to increased exercise and reduced caloric intake while in space. They started to shorten again once he returned to Earth.
Telomerase is an enzyme that repairs telomeres and lengthens them. Both twins showed an increase in telomerase during the same month of November 2015. A stressful family event took place about then.
Mathias Basner compared cognitive ability before, during, and after the mission. He found a slight decrease in speed and accuracy of Scott after the mission. Most long duration missions place astronauts in space up to six months. Scott stayed nearly twelve. Basner did not find a change in cognitive performance from the first six months when compared to final six months.
Scott Smith studied biochemical markers. The C-Reactive Protein levels, a marker for inflammation, showed a spike in inflammation soon after landing. That might be related to the stress of reentry and landing. Scott’s stress hormone Cortisol was low to normal during the mission.
Smith found a decline in Scott’s bone formation during the second half of the mission. A hormone associated with bone and muscle health increased during the mission. It might be due to rigorous exercise during flight. Astronauts use exercise to counteract bone loss.
Fred Turek studied the micro-organisms in the GI tract which aid in digestion. There were differences in the viral, bacterial, and fungal microbiome between the Mark and Scott all the time. Because of their very different diets and environments, this was expected. The ratio between two bacterial groups in Scott changed during his time in space compared to on the ground. The ratio returned to pre-flight levels upon his return.
Emmanuel Mignot studied the immune response before and after a flu vaccine was given to each twin. Flu vaccines cause “personalized” T-cell receptors to be created in each person and help us not catch the flu. Both twins showed an increase in T-cell receptors as expected.
Chris Mason is studying genome sequences of the DNA and RNA contained in their white blood cells. The studies show each twin has hundreds of unique mutations in their genome. This is normal. The sequencing showed more than 200,000 RNA molecules were expressed differently between the twins. Mason will look to see if a “space gene” was activated for Scott and can be identified due to his exposure to the unique environment of space.
Andy Feinberg studies how environment regulates gene expression, sometimes called Epigenomics. He found chemical modifications to Scott’s DNA decreased while inflight. They returned to normal upon return. He found the same modifications increased for Mark at the midpoint of the study. They returned to normal in the end. Variability was observed for both twins but in opposite directions. These results for Scott could indicate some genes are more sensitive to his changed environment. Results are not conclusive.
More research will integrate these preliminary findings. Other physiological, psychological, and technological investigations will help NASA ensure that astronauts undertake missions safely, efficiently, and effectively.