Exercise and Lifespan

A class of molecules released during intense physical activity promotes
the growth of telomeres, which play a critical role in replenishing cell
tissue.

It may be passé to suggest that physical exercise is good for you but
there is evidence from an unusual source that explains just how — at the
level of individual cells — exercise keeps the body from ageing.

Telomeres are specialised caps on the end of chromosomes and have been
known to play a critical role in ensuring that cells, which are damaged
by daily wear and tear and metabolism, are able to replenish themselves
properly. Short telomeres indicate that a cell has aged — not
necessarily chronologically but in its ability to replenish tissues —
and studies over decades have shown that those who live long frequently
have long telomeres.

Since 2011, scientists have found that those who exercised — even
moderate walking — had longer telomeres. This was evidenced from studies
in athletes as well as in a study of elderly women, who turned out to
have longer telomeres and better bone density than that of their
sedentary counterparts.

Jacob Koshy

TERRA and telomeres

This week, however, a group of scientists report in Science Advances
about a set of chemical factors that are released during exercise and
may be closely linked to producing a class of molecules called TERRA
(Telomeric RNA) that promote the growth of telomeres. TERRA, the authors
claim, have a key role in maintaining the health of telomeres.

Aurelie Diman and her colleagues identified Nuclear Respiratory Factor 1
(NRF1), found on the tips of chromosomes, and another molecule, PGC-1
álpha, involved in energy metabolism and one that's known to interact
with NRF1. When they tested 10 healthy, young volunteers who performed
endurance exercise (cycling) for 45 minutes, they found that precursors
to TERRA molecules, called TERRA transcripts, increased in skeletal
muscle biopsies of volunteers post-workout. This increase was also
positively correlated with the activation of AMPK, the enzyme involved
in PGC-1 álpha activation in response to exercise. Being able to fully
describe the chemical pathway — from exercise to telomere — could also
help identify new therapeutic drugs that could slow down ageing,
according to Dr. Diman in an accompanying statement.

Still a work in progress

Mere physical exercise, however, isn't enough. Anabelle Decottignies,
one of the authors involved with the study and based at Université
Catholique de Louvain, Belgium told The Scientist that exercise led to
an increase in reactive oxidative species (ROS) that may damage
telomeres. So it was possible that TERRA molecules produced in the way
her team had shown actually consumed the ROS and protected the telomere.
That, however, is a hypothesis and still remains to be tested.

Independent commentators said that while the study did show good
evidence that exercise was connected to the formation of TERRA, it
didn't yet make a convincing case that TERRA played a role in
maintaining telomeres. "That NRF1 and PGC-1 álpha are linked to exercise
is well-known, and the paper suggests the role of these factors in
increase of TERRA. But, since how TERRA impacts telomere maintenance is
still not quite clear, more TERRA doesn't necessarily mean healthier
telomeres," says Shantanu Chowdhury, a researcher at the CSIR-Institute
of Genomics and Integrative Biology, Delhi, and who investigates the
role of telomeres in the genome. "The TERRA molecules have an
interesting structure for therapeutic purposes but the link (with
telomere maintenance) is still correlative."

Dietary recommendations

Focussing on exercise alone for telomere isn't a viable strategy — as
the authors themselves admit in their Science Advances study — and
several other lifestyle factors may be more important. As telomeres
shorten with age and progressive telomere shortening leads to
senescence, they lead to genomic instability and cancer. Older people
with shorter telomeres have three and eight times increased risk of
death from heart and infectious diseases, respectively.

Smoking, exposure to pollution, a lack of physical activity, obesity,
stress, and an unhealthy diet increase oxidative burden and the rate of
telomere shortening. In a review of existing research on telomeres and
health, researcher Masood Shammas, in Current Opinion in Clinical
Nutrition and Metabolic Care suggests that "to preserve telomeres and
reduce cancer risk and pace of aging, we may consider to eat less;
include antioxidants, fiber, soy protein and healthy fats (derived from
avocados, fish, and nuts) in our diet".

This, he says, is in addition to staying lean, active, healthy, and
stress-free through regular exercise and meditation. Specific dietary
recommendations for healthy telomeres include tuna, salmon, herring,
mackerel, halibut, anchovies, catfish, grouper, flounder, flax seeds,
chia seeds, sesame seeds, kiwi, black raspberries, lingonberry, green
tea, broccoli, sprouts, red grapes, tomatoes, olive fruit, and other
vitamin C-rich and E-rich foods. "It's also premature to say to what
extent exercise is more important than these other factors," Dr.
Chowdhury adds.

jacob.koshy@thehindu.co.in

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