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Review
. 2011 Jan;14(1):28-34.
doi: 10.1097/MCO.0b013e32834121b1.

Telomeres, lifestyle, cancer, and aging

Masood A Shammas  1
Affiliations
Review

Telomeres, lifestyle, cancer, and aging

Masood A Shammas. Curr Opin Clin Nutr Metab Care. 2011 Jan.

Abstract

Purpose of review: There has been growing evidence that lifestyle factors may affect the health and lifespan of an individual by affecting telomere length. The purpose of this review was to highlight the importance of telomeres in human health and aging and to summarize possible lifestyle factors that may affect health and longevity by altering the rate of telomere shortening.

Recent findings: Recent studies indicate that telomere length, which can be affected by various lifestyle factors, can affect the pace of aging and onset of age-associated diseases.

Summary: Telomere length shortens with age. Progressive shortening of telomeres leads to senescence, apoptosis, or oncogenic transformation of somatic cells, affecting the health and lifespan of an individual. Shorter telomeres have been associated with increased incidence of diseases and poor survival. The rate of telomere shortening can be either increased or decreased by specific lifestyle factors. Better choice of diet and activities has great potential to reduce the rate of telomere shortening or at least prevent excessive telomere attrition, leading to delayed onset of age-associated diseases and increased lifespan. This review highlights the role of telomeres in aging and describes the lifestyle factors which may affect telomeres, human health, and aging.

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Figures

Figure 1
Figure 1. Telomeres, the DNA–protein structures which protect chromosomes
Our chromosomes end with repeats of conserved ‘TTAGGG’ sequence. These sequences interact with specific proteins and attain a looped conformation which protects chromosomal DNA from degradation. The length of telomeric DNA shortens with each cell division and when it reaches below a critical limit, the cell undergoes replicative senescence or apoptotic cell death. The length of telomeric DNA determines the lifespan of a cell in culture.
Figure 2
Figure 2. Length of telomeric DNA is important for lifespan of a cell
(a) Telomere length can be prevented from shortening by an enzyme Telomerase. Telomerase has a protein subunit (hTERT) and an RNA subunit (hTR). This enzyme is active in germline and stem cells and maintains their telomere length by adding ‘TTAGGG’ repeats to the ends of chromosomes. Therefore, telomeres do not shorten in these types of cells. (b) Telomerase is inactive in normal somatic cells. These cells, therefore, lose telomeres over time and when telomere length reaches below a critical limit, cells either senesce or die. (c) In the absence of appropriate signals for senescence or apoptotic death, continued cell division leads to severe telomere shortening and genomic instability. Although rare, but cells which survive this crisis, activate a telomere maintenance mechanism (either telomerase or homologous recombination-based ALT) and may become oncogenic. Therefore, most cancer cells have very short but stable telomeres. TA, telomere attrition; TL, telomere length.
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