Telomere Length in Human Adults and High Level Natural Background Radiation

Abstract

BackgroundTelomere 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.Methodology/Principal FindingsThe present investigation is an attempt to determine the telomere length among human adults residing in high level natural radiation areas (HLNRA) and the adjacent normal level radiation areas (NLNRA) of Kerala coast in Southwest India. Genomic DNA was isolated from the peripheral blood mononuclear cells of 310 individuals (HLNRA: N = 233 and NLNRA: N = 77). Telomere length was determined using real time q-PCR. Both telomere (T) and single copy gene (S) specific primers were used to calculate the relative T/S and expressed as the relative telomere length. The telomere length was determined to be 1.22±0.15, 1.12±0.15, 1.08±0.08, 1.12±0.11, respectively, among the four dose groups (≤1.50, 1.51–3.00, 3.01–5.00 and >5.00 mGy per year), which did not show any dose response. The results suggested that the high level natural chronic radiation did not have significant effect on telomere length among young adult population living in HLNRA, which is indicative of better repair of telomeric ends. No significant difference in telomere length was observed between male and female individuals. In the present investigation, although the determination of telomere length was studied among the adults with an age group between 18 to 40 years (mean maternal age: 26.10±4.49), a negative correlation was observed with respect to age. However, inter-individual variation was (0.81–1.68) was clearly observed.Conclusions/SignificanceIn this preliminary investigation, we conclude that elevated level of natural background radiation has no significant effect on telomere length among the adult population residing in HLNRAs of Kerala coast. To our knowledge, this is the first report from HLNRAs of the world where telomere length was determined on human adults. However, more samples from each background dose group and samples from older population need to be studied to derive firm conclusions.

Global transcriptome profile reveals abundance of DNA damage response and repair genes in individuals from high level natural radiation areas of Kerala coast

“…Most importantly, the unique feature of HLNRA of Kerala coast is the non-uniform distribution of monazite in the beach sand which leads to varying level of background radiation (<1.0 to 45mGy/year) along the 55 km long stretch allowing us to investigate in-vivo dose response, if any at various biological end points. Several epidemiological (congenital malformation, cancer incidence etc) and biological studies carried out in this population have not revealed any significant difference between NLNRA and HLNRA population [ 9 , 11 , 16 , 17 , 18 , 20 , 22 ]. However, recent studies have shown a lower induction and efficient repair of DNA damage in HLNRA individuals [ 21 , 23 ].…”

“…So far, no significant changes are observed at phenotype level. This population has also been investigated for several biological end points such as chromosome aberrations, micronuclei, telomere length measurement and quantitation of DNA damage [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].None of the above DNA damage end points have shown significant difference between the population from HLNRA and the adjacent normal level natural radiation areas (NLNRA). The spontaneous level of DNA double strand breaks (DSBs) has not shown any increase in DSBs, rather showed marginal reduction in HLNRA individuals belonging to background dose group >5mGy/year [ 18 ].…”

Detection of alternative lengthening of telomeres by telomere quantitative PCR

“…The 36B4 (RPLP0) gene, located on chromosome 12q24, encodes acidic ribosomal phosphoprotein P0 and VAV2, located on chromosome 9q34, encodes guanine nucleotide exchange factor. 36B4, which has been applied as a SCG for both cancer (13) and non-cancer cells (9,11), was used for melanoma tumors and cell lines, as well as glioblastoma multiforme (GBM) tumors and soft tissue sarcomas (STS). Comparative Genomic Hybridization studies indicate that 36B4 is an appropriate SCG for melanoma (14) and GBM (15).…”

Immunosenescence is associated with human cytomegalovirus and shortened telomeres in type I bipolar disorder

“…Quantification of DNA samples was performed using Qubit (Invitrogen). TL was measured as previously described by Cawthon with some modifications . Measurement of TL using the quantitative PCR assay consists of determining the relative ratio of telomere (T) repeat copy number to single‐copy gene (S) copy number (T/S ratio) in experimental samples using a standard curve.…”