Research Article: Telomere Length in Human Adults and High Level Natural Background Radiation

Date Published: December 23, 2009

Publisher: Public Library of Science

Author(s): Birajalaxmi Das, Divyalakshmi Saini, M. Seshadri, Eric J. Bernhard. http://doi.org/10.1371/journal.pone.0008440

Abstract: Telomere length is considered as a biomarker of aging, stress, cancer. It has been associated with many chronic diseases such as hypertension and diabetes. Although, telomere shortening due to ionizing radiation has been reported in vitro, no in vivo data is available on natural background radiation and its effect on telomere length.

Partial Text: High Level Natural Radiation Areas (HLNRA) in the world provide ample opportunities to study the biological and health effects of natural chronic low level radiation directly on humans. The level of natural background radiation in these areas is sometimes ∼10–100 times higher than normal areas. The level of background radiation is high either due to hot springs with high radium contents like Ramsar in Iran or due to monazite bearing sand in Yangjiang in China, Guarapari in Brazil and and the coastal belt of Kerala in south India. The monazite bearing sand contains thorium and its daughter products. The non-uniform distribution of radiation exposure prevailing in monazite bearing HLNRA of Kerala coast in South west India (contains 8–10% of thorium, highest in the world) gives an unique opportunity to conduct in vivo dose response studies on humans. This costal belt is approximately 55 kms long and 0.5 km wide, extending from Neendakara (Kollam district) in south to Purakkadu (Alapuzha district) in north [1]. It is thickly populated and the total population in this area is about 4,00,000 with approximately one third residing in high level natural radiation area and the rest in adjacent control area (normal level natural radiation area). The human population residing there is more than 50 generations old. Thus, it is considered as an ideal place to study the long term detrimental effects if any due to chronic natural low dose radiation on human population.

Regulation of telomere length plays an important role in the maintenance of genome stability in human. Although, research has been progressed in understanding telomere biology at molecular and cellular level, very little is known about the causes of telomere attrition. In recent years, there are innumerable reports showing telomere attrition due to infections and inflammation [20], exposure to infectious agents and other types of oxidative stress [15], [21], cardiovascular diseases [22]–[24], hypertension [25], [26], [27], diabetes [28], [29], dementia [30]. All these may cause damage to telomeric ends and impair their repair mechanisms [31]. Telomere shortening has also been reported in many cancer patients due to rapid cell proliferation [32]. Telomere shortening may play a vital role in biological aging [13]. There are many reports showing that oxidative stress induces increased erosion at telomeric ends resulting telomere length shortening [12], [15], [16], [33].

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http://doi.org/10.1371/journal.pone.0008440

 

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