Spaceflight is hard on the human body, and our mitochondria are not immune to its pressures.
Space travel presents unique challenges to biology, primarily extended exposure to microgravity and high levels of cosmic radiation. Mitochondria are the organelles responsible for the cell's energy demands, converting sugar into energy, facilitating life. How they react to these challenges is poorly understood. New research from a multidisciplinary team including researchers from the National Aeronautics and Space Administration (NASA), California, and the Georgetown Lombardi Comprehensive Cancer Centre, Washington DC, led by Dr Afshin Beheshti, unites the impact of two threats on this organelle.
'What we found over and over was that something is happening with the mitochondria regulation that throws everything out of whack' Dr Beheshti explained.
Dr Beheshti's team analysed a breadth of 'multi-omics' data, made possible by NASA's GeneLab, an online 'omics' database consisting of transcriptome, proteome and epigenome data from a variety of experiments involving spaceflight. The group employed this database to take a systems biology approach, looking at multiple species, including humans and mice, isolated human cells, and a variety of tissues, such as muscle and liver.
Their curated dataset was then queried for trends which correlated and overlapped between these diverse samples. The common thread which emerged from the data on gene expression, protein content and epigenetic status of the genome was the signature of changes to mitochondrial activity, across nearly all the samples.
Dr Beheshti 'was completely surprised to see that mitochondria are so important, because they weren't on our radar'. Despite this, the impact of spaceflight on mitochondria was not completely unknown, having previously been observed in soybean seedlings.
Analysis of blood and urine samples from some 59 astronauts and from the NASA Twin Study provided physiological evidence of altered mitochondrial function to support the omics data.
Their work, published in the journal Cell, shows a universally negative impact of spaceflight on mitochondria and the team believe that impacts on mitochondria, given their critical role in energy generation, could underpin other effects of spaceflight on biology, such as disruption to circadian rhythms and cardiovascular health. Previously identified problems with liver function in astronauts, for example, can now be linked to impaired mitochondria. The team propose a combination of exercise, drugs and diet as a means of minimising the impact of spaceflight on mitochondria in future.
The precise mechanism underlying this impact on mitochondria remains to be uncovered. Nonetheless, the groundwork laid by this study will facilitate future space exploration, which inevitably dictates prolonged periods of spaceflight for humans.