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
