Telomeres are located on the end of chromosomes and, act like a “mitotic clock.” The biological job that telomeres perform is to protect the coding DNA of a cell's genome. However telomeres shorten with each cell division and, for that reason, they appear to control cell death by limiting somatic cells to a set number of divisions. The shortening occurs because DNA is synthesized in only one direction and some DNA loss occurs with each cell division.
Some cells, including stem cells and leukocytes, can replenish the telomeres with an enzyme called telomerase. That enzyme is also activated in many cancer cells and is important in immortalization, permitting uncontrolled growth that is characteristic of cancer. Cancers associated with a longer telomere length include melanoma and cancers of the lung, breast, pancreas and prostate. (1-5).
In vivo, shorter telomere lengths are associated with age-related disorders including diabetes (6), obesity (7) and atherosclerosis (8). Some researchers have suggested that chronic inflammation and oxidative stress increases the telomere loss during cell division. Both inflammation and oxidative stress are related to the development and progression of cardiovascular disease as a person ages.
Work from Kornilov et al. (10.1542/peds.2015-2469) may challenge that idea of the telomeric clock by showing variation in telomere length exists at birth. Telomere length is measured in kilobases (KB). Researchers measured leukocyte telomere length (LTL) in blood samples from 490 newborns and their parents in New York City and Delaware. Mean LTL was longer in newborns (9.50 KB) than their mothers (7.92 KB) or fathers (7.70 KB). Newborn LTL was longer in girls (by 0.144 KB) than boys. Maternal LTL was longer (by 0.175 kb) than the paternal LTL.
Repeated studies have documented that telomeres do shorten with repeated cell division, but this study shows variation in length at birth. Understanding the long and short of telomeres is going to require more scientific research.
- Antic GM, Sondak VK, Messina JL et al. Telomere length and the risk of melanoma, squamous cell carcinoma, and basal cell carcinoma. Cancer Epidemiol. 2013; 37(4):434-439.
- Show WJ, Cawthron RM, Purdue MP et al. Telomere length in white blood cell DNA and lung cancer: a pooled analysis of three prospective cohorts. Cancer Res. 2014; 74 (15);4090-4098.
- Qu S, Wen W, Sho Xo et al. Association of leukocyte telomere length with breast cancer risk: nested case-control findings from the Shanghi Women’s Health Study. Am J Epidemiol 2013; 177(7): 617-624.
- Lynch SM, Major JM, Cawthon R et al. A prospective analysis of telomere length and pancreatic cancer in the alpha-tocopherol beta-carotene cancer (ATBC) prevention study. Int J Cancer 2013; 133 (11):2672-2680.
- Julian B, Shui I, Heaphy CM et al. Circulating leukocyte telomere length and risk of overall and aggressive prostate cancer. Br J Cancer 2015; 112(4):769-776.
- Jeanclos E, Krolewski A, Skurnick J et al. Shortened telomere length in white blood cells of patients with IDDM. Diabetes 1998; 47:482-486.
Valdes AM, Andrew T, Gardner JP et al. Obesity, cigarette smoking and telomere length in women. Lancet 2005; 366-662