Telomerase and telomeres in aging theory and chronographic aging theory (Review) Author: Mayya P Razgonova1, Alexander M Zakharenko1, Kirill S Golokhvast1, Maria Thanasoula2, Evangelia Sarandi2, Konstantinos Nikolouzakis3, Persefoni Fragkiadaki3, Dimitris Tsoukalas2, Demetrios A Spandidos4, Aristidis Tsatsakis3 Affiliation: <sup>1</sup> N.I. Vavilov All‑Russian Institute of Plant Genetic Resources, 190000 Saint‑Petersburg, Russia. <sup>2</sup> Metabolomic Μedicine, Health Clinics for Autoimmune and Chronic Diseases, 10674 Athens, Greece. <sup>3</sup> Laboratory of Toxicology, Medical School, University of Crete, 71003 Heraklion, Greece. <sup>4</sup> Laboratory of Clinical Virology, School of Medicine, University of Crete, Heraklion 71003, Greece. Conference/Journal: Mol Med Rep Date published: 2020 Sep Other: Volume ID: 22 , Issue ID: 3 , Pages: 1679-1694 , Special Notes: doi: 10.3892/mmr.2020.11274. , Word Count: 155 The current review focuses on the connection of telomerase and telomeres with aging. In this review, we describe the changes in telomerase and telomere length (TEL) during development, their role in carcinogenesis processes, and the consequences of reduced telomerase activity. More specifically, the connection of TEL in peripheral blood cells with the development of aging‑associated diseases is discussed. The review provides systematic data on the role of telomerase in mitochondria, the biology of telomeres in stem cells, as well as the consequences of the forced expression of telomerase (telomerization) in human cells. Additionally, it presents the effects of chronic stress exposure on telomerase activity, the effect of TEL on fertility, and the effect of nutraceutical supplements on TEL. Finally, a comparative review of the chronographic theory of aging, presented by Olovnikov is provided based on currently available scientific research on telomere, telomerase activity, and the nature of aging by multicellular organisms. PMID: 32705188 DOI: 10.3892/mmr.2020.11274