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Everything seems to become worse for our bodies the older we get. But what does aging mean in a biological context? And are there any ways to delay aging?

Today we talk about cellular aging. Cellular aging is defined by the so called hallmarks of aging which include telomere attrition, stem cell arrest, cellular senescence and genomic instability among other factors. There is a lot of research being conducted in the fields of each of these hallmarks.

Our chromosomes are linear meaning they comprise two ends, respectively. In each of these ends we find telomeres (repetitive sequences; in humans they comprise TTAGGG). These repetitive sequences have a lot of crucial functions for the stability of our chromosomes. For instance, they form loops together with proteins in order to protect our chromosomes from being fused by our own DNA repair mechanisms. Furthermore, telomeres are the solution to the so called end-replication problem. The end-replication problem arises while we copy our DNA upon cell division. Every time we replicate our DNA, the very end of the chromosome cannot be fully copied resulting in a slow, gradual shortening of the chromosome. The enzyme telomerase can increase the lengths of telomeres by adding its repetitive sequence. However, telomerase is normally only highly active during early development and the older we get the shorter our telomeres become. There is a certain point at which our cells only comprise a fraction of its original telomere repetitions and they stop dividing.

There are many implications to replicative senescence such as stem cell exhaustion, which is another aspect of aging. Many age-related diseases are associated with the inability of these stem cells to divide. If, for instance, hematopoietic stem cells in our bone marrow become senescent, anemia and an impaired immune system can develop. If mesenchymal stem cells are affected osteoporosis and decreased fracture repair can occur.

Nobel laureate Elizabeth and her colleagues and found out that chronic stress can have a negative impact on telomerase activity and the lengths of chromosomes (in this study, it was found that mothers of chronically ill children have 48% less telomerase activity). Another studies investigated the relationship between telomere lengths and lifestyle changes in men with prostate cancer. These men had to under change their habits over a period of five years: They had to have a special diet high in whole foods and low in fat. They walked 6x a week for 30 minutes each. They started yoga and relaxation exercises and they formed a social support group which met 1 x a week. Not only were the telomere lengths of these men longer than those measured in a control group but they also slightly increased over time.

This gives us some hope that we can actually slow down telomere attrition through lifestyle changes leading to potential longer lives.


For your further research:

Epel, Elissa S., et al. "Accelerated telomere shortening in response to life stress." Proceedings of the National Academy of Sciences 101.49 (2004): 17312-17315.
López-Otín, Carlos, et al. "The hallmarks of aging." Cell 153.6 (2013): 1194-1217.
Ornish, Dean, et al. "Effect of comprehensive lifestyle changes on telomerase activity and telomere length in men with biopsy-proven low-risk prostate cancer: 5-year follow-up of a descriptive pilot study." The lancet oncology 14.11 (2013): 1112-1120.


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About Clemens Steinek:
CLEMENS STEINEK is a postgraduate student/youtuber (LifeLabLearner) who is currently conducting stem cell research in Germany.

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