Telomeres are important because they are critical to how cells stop multiplying. Telomeres generally shorten as cells divide, or undergo DNA replication stress, and/or chemical damage including as oxidative damage. Telomerase, a specialized ribonucleoprotein reverse transcriptase, replenishes the DNA at telomeres and is important for long-term eukaryotic cell proliferation and genomic stability.
These discoveries relied on basic biology, mostly done on small short-lived model organisms. Yet, humans’ relatively long lifespan is a key factor in how telomere maintenance, in complex interplay with genetic and non-genetic factors, determines human healthspan and disease.
Accumulated data indicate that loss of telomere protection (measured as shortening of telomeres) is both linked to and, in some cases, causally contributes to, human aging and aging-related diseases. These include cardiovascular disease, stroke, osteoporosis, inflammatory diseases, dementia, diabetes and certain cancers.
While new cancer treatments are imperative, telomere biology is highly relevant to the emerging importance of cancer prevention and interception. Data from multiple studies demonstrate that exercising regularly, smoking reduction, nutritious foods (as well as ample sleep, managing stress, and engaging in positive social interactions) are associated with better telomere maintenance. Similarly, epidemiological data reveal that 50% of U.S. cancer cases would be prevented by reducing obesity, smoking, inflammation reduction (together with appropriate vaccinations, avoidance of environmental toxins and carcinogens, screening exams and overexposure to sunlight). However, it is too simplistic and even dangerous to suggest that grossly extending telomere length will invariably extend healthspan. Disease mechanisms are interconnected and manipulating one mechanism has the potential to positively or negatively impact other mechanisms. For example, telomerase is linked with certain cancers. Telomerase is highly active in many human malignancies, and a potential target for anti-cancer stratagems. But conversely, genetic deficiency of telomerase causes certain hemopoietic, skin, and gastrointestinal cancers. Hence human telomerase activity and telomere maintenance present delicate balancing acts throughout human life, requiring further understanding about the molecular and environmental switches that control them.