Telomere length: how the length makes a difference

Abstract

Telomerase is perceived as an immortality enzyme that might provide longevity to cells and whole organisms. Importantly, it is generally inactive in most somatic cells of healthy, adult men. Consequently, its substrates, i.e. telomeres, get shorter in most human cells with time. Noteworthy, cell life limitation due to telomere attrition during cell divisions, may not be as bad as it looks since longer cell life means longer exposition to harmful factors. Consequently, telomere length (attrition rate) becomes a factor that is responsible for inducing the signaling that leads to the elimination of cells that lived long enough to acquire severe damage. It seems that telomere length that depends on many different factors (including telomerase activity but also genetic factors, a hormonal profile that reflects sex, etc.) might become a useful marker of aging and exposition to stress. Thus in the current paper, we review the factors that affect telomere length in human cells focusing on sex that all together with different environmental and hormonal regulations as well as parental aspect affect telomere attrition rate. We also raise some limitations in the assessment of telomere length that hinders a trustworthy meta-analysis that might lead to acknowledgment of the real value of this parameter.

A Longitudinal Epigenetic Aging and Leukocyte Analysis of Simulated Space Travel: The Mars-500 Mission

“…With each round of DNA replication, telomeres shorten. Hence, many studies have utilized telomere length as a marker of cellular aging, where aging is usually associated with decreased telomere length ( Lulkiewicz et al, 2020 ). The National Aeronautics and Space Administration (NASA) Twin Study—where one identical twin astronaut was monitored before, during, and after a 1-year mission onboard the ISS, with his twin serving as a genetically matched ground control—showed associations of long periods in space with lengthened telomeres ( Garrett-Bakelman et al, 2019 ).…”

TERRA: A Novel Biomarker of Embryo Quality and Art Outcome

“…Due to end-replication problems of chromosome ends, the telomeres shorten at each cell division until they reach a critical length leading to cell senescence. Furthermore, telomere length can also be influenced by other causes such as altered telomerase activity, genetic defects and stress agents, all factors contributing to telomere erosion and, consequently, to genome instability [ 31 ].…”

IL-15 Upregulates Telomerase Expression and Potently Increases Proliferative Capacity of NK, NKT-Like, and CD8 T Cells

“…We considered carefully about including this data in our study and assessed different methods for obtaining the data for telomerase length. However, from our review of the methods and the results obtained from telomerase length analysis there is a large consensus that a) telomere length is a very variable parameter and is influenced by many environmental factors apart from the effects of cytokines, such as hormonal factors, age, sex of the individual donor ( 43 ) and b) the length of telomeres in individual leukocyte cells varies widely ( 44 ) so that the mean telomerase length may not change with our agents and the statistical power required to allow for the variance would mean testing many more donors than is practically possible. A previous study with lymphocytes examined telomere length with no changes recorded either for activation with IL-2 or for inhibition of activation with signaling inhibitors and this may be due to the above factors ( 40 ).…”