NASA has a twins study to look at how space travel affects human health during long missions. The One Year Mission astronaut, Scott Kelly, has an identical twin brother (a scientist’s dream!). The thought was to look at a multitude of changes between the twin in space vs. the twin on Earth: physiology, cognition, biochemical profiles, microbiome, and immune response. This time also included genomics. They decided to look at DNA RNA, epigenome, proteins, and metabolites.
For our science of aging, they were focused on telomeres.
What is a telomere?
Telomeres are the natural ends of chromosome. They shorten with cell division and lifestyle factors and stressors. Telomeres are thought to be key molecular determinants of aging and aging trajectories.
Telomere lengths vary considerably between people, ranging from 5 – 15 kb in humans. They preserve genome stability by preventing the ends of the chromosomes from being recognized as broken DNA, which would trigger DNA damage responses. Telomere length naturally erodes over time with cell division, which causes telomeres to shorten until they reach a critical shortened length, at which point the cell cycle stops, and the cell stops dividing.
Telomerase can counteract telomere attrition by adding telomeric repeats onto the ends of newly replicated chromosomes. But telomerase activity is only prominent in stem cell, germline cells, and cancer cells. Telomerase is insufficient in normal cells, so it cannot prevent normal cells from age related decline.
What adds to telomere loss? It is thought oxidative stress, inflammation, sex, lifestyle factors (diet, smoking, obesity, physical activity, and psychological stress), chronic stress, and disease can affect telomere length. Environmental things like pollution, UV and ionizing radiation can also affect telomere length.
Why are telomeres important in aging? Telomere length maintenance over time is important to look at the cumulative effects of genetic, environmental, and lifestyle factors. Long telomeres are associated with longevity. The degeneration is linked to
- reduced immune function
- dementia
- cardiovascular disease
- cancer (LONG telomeres were associated with cancer)
- and for us plastic surgeons, aging of the skin and tissue (which leads to wrinkling, sagging, drooping, poor skin quality, etc)
Study:
- They proposed telomere length dynamics was particularly interesting for space travel, as telomere health is an integrative biomarker (looking at the combined experiences and environmental exposures)
- They looked at telomere length and telomerase activity. Chromosomal aberrations (a signature of radiation exposure) was also evaluated.
Findings?
- The telomere lengths prior to space flight were similar.
- The earth bound twins telomeres remained relatively stable
- The space twin’s telomeres were LONGER during space flight, but then shortened rapidly upon return to Earth, resulting in many more short telomeres after spaceflight than before.
- Chromosomal signatures of radiation exposure were elevated during spaceflight, and these persisted after return home, indicating ongoing genome instability.
They conclude that these telomere changes have important implications for aging science and improving healthspan for those on Earth as well.
My thoughts?
Telomeres and chromosomal aging clearly lead to bunch of things we don’t like. We are always searching for the fountain of youth, and after seeing what the stem cells from my fat injecting do to the skin quality, I believe we can reverse aging at a more cellular level. Lengthening telomeres may be part of that fountain.
But these are things we need to understand from all perspectives. As I noted above, long telomeres are good for longevity and a host of other things, but they may increase cancer risk. We need a metered response to these discoveries. “More” is not always better.