Telomere length in different tissues of elderly patients

Posttraumatic Stress Disorder, Adverse Childhood Events, and Buccal Cell Telomere Length in Elderly Swiss Former Indentured Child Laborers

Posttraumatic stress disorder (PTSD) is associated with increased risk for age-related diseases and early mortality. Accelerated biological aging could contribute to this elevated risk. The aim of the present study was to assess buccal cell telomere length (BTL) - a proposed marker of biological age - in men and women with and without PTSD. The role of childhood trauma was assessed as a potential additional risk factor for shorter telomere length. The sample included 62 former indentured Swiss child laborers (age: M = 76.19, SD = 6.18) and 58 healthy controls (age: M = 71.85, SD = 5.97). Structured clinical interviews were conducted to screen for PTSD and other psychiatric disorders. The Childhood Trauma Questionnaire (CTQ) was used to assess childhood trauma exposure. Quantitative polymerase chain reaction was used to measure BTL. Covariates include age, sex, years of education, self-evaluated financial situation, depression, and mental and physical functioning. Forty-eight (77.42%) of the former indentured child laborers screened positive for childhood trauma, and 21 (33.87%) had partial or full-blown PTSD. Results did not support our hypotheses that PTSD and childhood trauma would be associated with shorter BTL. In fact, results revealed a trend toward longer BTL in participants with partial or full PTSD [F(2,109) = 3.27, p = 0.04, η(2) = 0.06], and longer BTL was marginally associated with higher CTQ scores (age adjusted: β = 0.17 [95% CI: -0.01 to 0.35], t = 1.90, p = 0.06). Furthermore, within-group analyses indicated no significant association between BTL and CTQ scores. To the best of our knowledge, this is the first study exploring the association between childhood trauma and BTL in older individuals with and without PTSD. Contrary to predictions, there were no significant differences in BTL between participants with and without PTSD in our adjusted analyses, and childhood adversity was not associated with BTL. Possible explanations and future research possibilities are discussed.

Early-Life Telomere Dynamics Differ between the Sexes and Predict Growth in the Barn Swallow (Hirundo rustica)

Telomeres are conserved DNA-protein structures at the termini of eukaryotic chromosomes which contribute to maintenance of genome integrity, and their shortening leads to cell senescence, with negative consequences for organismal functions. Because telomere erosion is influenced by extrinsic and endogenous factors, telomere dynamics may provide a mechanistic basis for evolutionary and physiological trade-offs. Yet, knowledge of fundamental aspects of telomere biology under natural selection regimes, including sex- and context-dependent variation in early-life, and the covariation between telomere dynamics and growth, is scant. In this study of barn swallows (Hirundo rustica) we investigated the sex-dependent telomere erosion during nestling period, and the covariation between relative telomere length and body and plumage growth. Finally, we tested whether any covariation between growth traits and relative telomere length depends on the social environment, as influenced by sibling sex ratio. Relative telomere length declined on average over the period of nestling maximal growth rate (between 7 and 16 days of age) and differently covaried with initial relative telomere length in either sex. The frequency distribution of changes in relative telomere length was bimodal, with most nestlings decreasing and some increasing relative telomere length, but none of the offspring traits predicted the a posteriori identified group to which individual nestlings belonged. Tail and wing length increased with relative telomere length, but more steeply in males than females, and this relationship held both at the within- and among-broods levels. Moreover, the increase in plumage phenotypic values was steeper when the sex ratio of an individual’s siblings was female-biased. Our study provides evidence for telomere shortening during early life according to subtly different dynamics in either sex. Furthermore, it shows that the positive covariation between growth and relative telomere length depends on sex as well as social environment, in terms of sibling sex ratio.

Human endometrial epithelial telomerase is important for epithelial proliferation and glandular formation with potential implications in endometriosis

STUDY QUESTION

How does regulation of telomerase activity (TA) in human endometrial epithelial cells (EEC) by ovarian hormones impact on telomere lengths (TL) and cell proliferation?

SUMMARY ANSWER

Healthy endometrial epithelial cell proliferation is characterized by high TA and endometrial TL changes according to the ovarian hormone cycle, with shortest TL observed in the progesterone dominant mid-secretory phase, when TA is lowest, implicating progesterone in the negative regulation of TA and TL.

WHAT IS KNOWN ALREADY

Critical shortening of telomeres may result in permanent cell cycle arrest while the enzyme telomerase maintains telomere length (TL) and replicative capacity of cells. Telomerase expression and activity change in the human endometrium with the ovarian hormone cycle, however the effect of this on endometrial TL and cell growth is not known.

STUDY DESIGN, SIZE, DURATION

A prospective observational study, which included endometrial and blood samples collected from 196 women.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We studied endometrial samples from five different groups of women. Endometrial and matched blood TL and circulating steroid hormones were studied in samples collected from 85 women (Group 1). Fresh epithelial and stromal cell isolation and culture in vitro for TL and TA was done on endometrial biopsies collected from a further 74 healthy women not on hormonal therapy (Group 2) and from 5 women on medroxyprogesterone acetate (MPA) for contraception (Group 3). The epithelial TL and telomerase protein expression was examined in active, peritoneal, ectopic endometriotic and matched uterine (eutopic) endometrial samples collected from 10 women with endometriosis (Group 4); the in vivo effect of mifepristone on telomerase protein expression by immunohistochemistry (IHC) was examined in endometrium from 22 healthy women in mid-secretory phase before (n = 8), and after administering 200 mg mifepristone (n = 14) (Group 5). TA was measured by telomere repeat amplification protocol (TRAP) assay; TL by qPCR, and Q-FISH; cell proliferation was assessed by immunoblotting of histone H3 and 3D-culture to assess the ability of EECs to form spheroids; telomerase reverse transcriptase protein levels and Ki-67 (proliferative index) were assessed with IHC.

MAIN RESULTS AND THE ROLE OF CHANCE

Endometrial TLs correlated negatively with serum progesterone levels (n = 58, r = -0.54) and were significantly longer than corresponding blood TLs (4893 ± 929 bp versus 3955 ± 557 bp, P = 0.002) suggesting a tissue-specific regulation. High TA and short TLs were observed in proliferating EECs in vivo and in vitro. During the progesterone dominant mid-secretory phase endometrial TL were significantly shorter compared with the proliferative phase (P = 0.0002). Progestagen treatment suppressed EEC TA in vivo and reduced endometrial TA in explant (P = 0.01) and in vitro cultures (P = 0.02) compared with untreated cells. Mifepristone (progesterone receptor antagonist) increased telomerase protein levels in vivo (P < 0.05). In 2D culture, Imetelstat inhibited EEC TA (P = 0.03), proliferation (P = 0.009) and in 3D culture disrupted endometrial glandular architecture (P = 0.03).

LIMITATIONS, REASONS FOR CAUTION

The in vitro telomerase inhibition data were tested in a mono-cellular system for a short-term. Further confirmation of the results in an in vivo model is necessary. The women in group 2 included a high proportion of women although with a regular menstrual cycle, with an increased BMI (>25) therefore this may affect extrapolation of data to other groups.

WIDER IMPLICATIONS OF THE FINDINGS

The observed effects of telomerase inhibition in vitro on epithelial cell proliferation, suggest that telomerase might be an attractive target in developing new therapies for proliferative disorders of the endometrium, such as endometriosis.

Telomere Length as an Indicator of the Robustness of B- and T-Cell Response to Influenza in Older Adults

BACKGROUND

Telomeres provide a key mechanism for protecting the integrity of chromosomes and their attrition after cell division and during aging are evident in lymphocytes. However, the significance of telomere shortening in age-associated decline of immune function is unknown.

METHODS

We selected 22 HLA-A2-positive healthy older adults who have relatively short or long telomere lengths to compare their antibody response against the influenza vaccine, and their CD8(+) T-cell response against an influenza antigen.

RESULTS

B cells from individuals with a robust antibody response to the influenza vaccine had significantly longer telomeres than those with a poor antibody response. Monocyte-derived antigen-presenting cells of both short and long telomere groups induced similar expansions of influenza M1-specific CD8(+) T cells. Vaccination did not increase M1-specific CD8(+) T cells in blood, but M1-specific CD8(+) T cells from the long telomere group exhibited significantly greater expansion in vitro than those from the short telomere group. Finally, M1-specific CD8(+) T cells that underwent more expansions had significantly longer telomeres than cells with fewer divisions.

CONCLUSIONS

Telomere length is positively associated with a robust lymphocyte response, and telomere attrition may contribute to the age-associated decline of adaptive immunity.

Telomere dysfunction in peripheral blood lymphocytes from patients with primary sclerosing cholangitis and inflammatory bowel disease

BACKGROUND AND AIMS

Primary sclerosing cholangitis and inflammatory bowel disease are two associated, chronic inflammatory, pre-malignant conditions. We hypothesized that patients with these disorders may harbour telomere dysfunction as a marker of chromosomal instability. The aim of our study was to compare parameters of the telomere-telomerase system in these cohorts.

METHODS

In this prospective study, peripheral blood was withdrawn from patients with primary sclerosing cholangitis (N=20), inflammatory bowel disease (N=20) and healthy controls (N=20), and lymphocytes were isolated. Telomere length was quantified as a function of the signal intensity and telomere number. Random aneuploidy and telomere capture were determined by fluorescence in situ hybridization technique with specific probes.

RESULTS

Patients with inflammatory bowel disease had higher measures of intestinal disease activity than patients with primary sclerosing cholangitis. Despite this, shorter telomere length and telomere aggregates, especially the fusion of 2-5 telomeres, were observed at significantly higher rate in patients with primary sclerosing cholangitis relative to inflammatory bowel disease or healthy controls. Rates of aneuploidy and telomere capture were higher in the two probes in both diseases compared to controls (p<0.001).

CONCLUSION

Dysfunction of telomeres was demonstrated in primary sclerosing cholangitis patients more than inflammatory bowel disease and healthy controls patients, which attests to genetic instability and immunosenescence.

TRIAL REGISTRATION NUMBER

NCT02247622.

Psychiatric disorders and leukocyte telomere length: Underlying mechanisms linking mental illness with cellular aging

Many psychiatric illnesses are associated with early mortality and with an increased risk of developing physical diseases that are more typically seen in the elderly. Moreover, certain psychiatric illnesses may be associated with accelerated cellular aging, evidenced by shortened leukocyte telomere length (LTL), which could underlie this association. Shortened LTL reflects a cell's mitotic history and cumulative exposure to inflammation and oxidation as well as the availability of telomerase, a telomere-lengthening enzyme. Critically short telomeres can cause cells to undergo senescence, apoptosis or genomic instability, and shorter LTL correlates with poorer health and predicts mortality. Emerging data suggest that LTL may be reduced in certain psychiatric illnesses, perhaps in proportion to exposure to the psychiatric illnesses, although conflicting data exist. Telomerase has been less well characterized in psychiatric illnesses, but a role in depression and in antidepressant and neurotrophic effects has been suggested by preclinical and clinical studies. In this article, studies on LTL and telomerase activity in psychiatric illnesses are critically reviewed, potential mediators are discussed, and future directions are suggested. A deeper understanding of cellular aging in psychiatric illnesses could lead to re-conceptualizing them as systemic illnesses with manifestations inside and outside the brain and could identify new treatment targets.

Physical Exercise Alleviates Health Defects, Symptoms, and Biomarkers in Schizophrenia Spectrum Disorder

Schizophrenia spectrum disorders are characterized by symptom profiles consisting of positive and negative symptoms, cognitive impairment, and a plethora of genetic, epigenetic, and phenotypic biomarkers. Assorted animal models of these disorders and clinical neurodevelopmental indicators have implicated neurodegeneration as an element in the underlying pathophysiology. Physical exercise or activity regimes--whether aerobic, resistance, or endurance--ameliorate regional brain and functional deficits not only in affected individuals but also in animal models of the disorder. Cognitive deficits, often linked to regional deficits, were alleviated by exercise, as were quality-of-life, independent of disorder staging and risk level. Apoptotic processes intricate to the etiopathogenesis of schizophrenia were likewise attenuated by physical exercise. There is also evidence of manifest benefits endowed by physical exercise in preserving telomere length and integrity. Not least, exercise improves overall health and quality-of-life. The notion of scaffolding as the outcome of physical exercise implies the "buttressing" of regional network circuits, neurocognitive domains, anti-inflammatory defenses, maintenance of telomeric integrity, and neuro-reparative and regenerative processes.

Telomeres and essential hypertension

OBJECTIVES

This review aims to clarify the relationship between telomeres and essential hypertension.

DESIGN AND METHODS

A PubMed search and a critical review were performed relating to studies about the clinical and biological relevance of telomeres in essential hypertension.

RESULTS

Telomeres and telomerase activity play an important role in the occurrence and development of hypertension in both animal and human studies.

CONCLUSIONS

A more complete understanding of the molecular mechanisms underlying the development of hypertension could reduce the incidence of hypertension-related diseases.

The relationship between telomere length and clinicopathologic characteristics in colorectal cancers among Tunisian patients

Alterations in telomere dynamics have emerged as having a causative role in carcinogenesis. Both the telomere attrition contribute to tumor initiation via increasing chromosomal instability and that the telomere elongation induces cell immortalization and leads to tumor progression. The objectives of this study are to investigate the dynamics of telomere length in colorectal cancer (CRC) and the clinicopathological parameters implicated. We measured the relative telomere length (RTL) in cancerous tissues and in corresponding peripheral blood leukocytes (PBL) using quantitative PCR (Q-PCR) from 94 patients with CRC. Telomere length correlated significantly in cancer tissues and corresponding PBL (r = 0.705). Overall, cancer tissue had shorter telomeres than PBL (p = 0.033). In both cancer tissue and PBL, the RTL was significantly correlated with age groups (p = 0.008 and p = 0.012, respectively). The RTL in cancer tissue was significantly longer in rectal tumors (p = 0.04) and in the late stage of tumors (p = 0.01). In PBL, the RTL was significantly correlated with the macroscopic aspect of tumors (p = 0.02). In addition, the telomere-length ratio of cancer to corresponding PBL increased significantly with late-stage groups. Shortening of the telomere was detected in 44.7%, elongation in 36.2%, and telomeres were unchanged in 19.1% of 94 tumors. Telomere shortening occurred more frequently in the early stage of tumors (p = 0.01). This study suggests that the telomere length in PBL is affected by the macroscopic aspect of tumors and that telomere length in cancer tissues is a marker for progression of CRC and depends on tumor-origin site.

Race-Ethnicity, Poverty, Urban Stressors, and Telomere Length in a Detroit Community-based Sample

Residents of distressed urban areas suffer early aging-related disease and excess mortality. Using a community-based participatory research approach in a collaboration between social researchers and cellular biologists, we collected a unique data set of 239 black, white, or Mexican adults from a stratified, multistage probability sample of three Detroit neighborhoods. We drew venous blood and measured telomere length (TL), an indicator of stress-mediated biological aging, linking respondents' TL to their community survey responses. We regressed TL on socioeconomic, psychosocial, neighborhood, and behavioral stressors, hypothesizing and finding an interaction between poverty and racial-ethnic group. Poor whites had shorter TL than nonpoor whites; poor and nonpoor blacks had equivalent TL; and poor Mexicans had longer TL than nonpoor Mexicans. Findings suggest unobserved heterogeneity bias is an important threat to the validity of estimates of TL differences by race-ethnicity. They point to health impacts of social identity as contingent, the products of structurally rooted biopsychosocial processes.

Setting the trajectory: racial disparities in newborn telomere length

OBJECTIVE

To explore racial differences in newborn telomere length (TL) and the effect moderation of the sex of the infant while establishing the methodology for the use of newborn blood spots for TL analyses.

STUDY DESIGN

Pregnant mothers were recruited from the Greater New Orleans area. TL was determined via monochrome multiplex quantitative real-time polymerase chain reaction on DNA extracted from infant blood spots. Demographic data and other covariates were obtained via maternal report before the infant's birth. Birth outcome data were obtained from medical records and maternal report.

RESULTS

Black infants weighed significantly less than white infants at birth and had significantly longer TL than white infants (P=.0134), with the strongest effect observed in black female infants. No significant differences in gestational age were present.

CONCLUSIONS

Significant racial differences in TL were present at birth in this sample, even after we controlled for a range of birth outcomes and demographic factors. Because longer initial TL is predictive of more rapid TL attrition across the life course, these findings provide evidence that, even at birth, biological vulnerability to early life stress may differ by race and sex.

In colon cancer, normal colon tissue and blood cells have altered telomere lengths

BACKGROUND

Telomere length (TL) shortened occurs in colorectal carcinogenetic process. Our objective is to determine if it is only a local fact or there are alterations in normal colon cells and in other body cells.

METHODS

TL of tumoral and normal mucosa and leukocytes of 40 patients operated of colorectal cancer (CRC) and 40 control patients with normal colonoscopy were measured by Southern-blot. Groups were matched by the same localization as tumors, sex, and age.

RESULTS

In CRC patients, TRFL (Telomere Repeat Factor Length) leukocytes mean was 8.84 kpb, normal colonic mucosa 7.97 kpb, and tumoral mucosa 7.33 kpb (P < 0.001). In the 40 normal control patients, mean TRFL of colonic mucosa was 7.76 kpb, while in blood cells was 7.01 kpb (P < 0.001). We observed an inverse correlation between leukocytes TRFL and age (r(2)  = 0.17, P = 0.008). Mucosa TRFL correlates significantly with patient's age (r(2)  = 0.138, P = 0.018). TRFL of controls colonic mucosa correlates with TRFL of their blood cells (r(2)  = 0.354, P < 0.001).

CONCLUSIONS

Normal colonic mucosa and leukocytes in CCR patients presents telomere altered in respect to normal patients. Telomere length in normal leukocytes could be an initial marker for colorectal cancer.

Peripheral blood leukocyte telomere length and mortality among 64,637 individuals from the general population

BACKGROUND

Short telomeres in peripheral blood leukocytes are associated with older age and age-related diseases. We tested the hypotheses that short telomeres are associated with both increased cancer mortality and all-cause mortality.

METHODS

Individuals (n = 64637) were recruited from 1991 onwards from two Danish prospective cohort studies: the Copenhagen City Heart Study and the Copenhagen General Population Study. All had telomere length measured by quantitative polymerase chain reaction and the genotypes rs1317082 (TERC), rs7726159 (TERT), and rs2487999 (OBFC1) determined. The sum of telomere-shortening alleles from these three genotypes was calculated. We conducted Cox regression analyses and instrumental variable analyses using the allele sum as an instrument. All statistical tests were two-sided.

RESULTS

Among 7607 individuals who died during follow-up (0-22 years, median = 7 years), 2420 had cancer and 2633 had cardiovascular disease as causes of death. Decreasing telomere length deciles were associated with increasing all-cause mortality (P(trend) = 2*10(-15)). The multivariable-adjusted hazard ratio of all-cause mortality was 1.40 (95% confidence interval [CI] = 1.25 to 1.57) for individuals in the shortest vs the longest decile. Results were similar for cancer mortality and cardiovascular mortality. Telomere length decreased 69 base pairs (95% CI = 61 to 76) per allele for the allele sum, and the per-allele hazard ratio for cancer mortality was 0.95 (95% CI = 0.91 to 0.99). Allele sum was not associated with cardiovascular, other, or all-cause mortality.

CONCLUSION

Short telomeres in peripheral blood leukocytes were associated with high mortality in association analyses. In contrast, genetically determined short telomeres were associated with low cancer mortality but not with all-cause mortality.

Depression, anxiety and telomere length in young adults: evidence from the National Health and Nutrition Examination Survey

Telomere length has been hypothesized to be a marker of cumulative exposure to stress, and stress is an established cause of depression and anxiety disorders. The aim of this study was to examine the relationship between depression, anxiety and telomere length, and to assess whether this relationship is moderated by race/ethnicity, gender and/or antidepressant use. Data were from the 1999-2002 National Health and Nutrition Examination Survey. Telomere length was assessed using the quantitative PCR method of telomere length relative to standard reference DNA. Past-year major depression (MD), generalized anxiety disorder (GAD) and panic disorder (PD), as well as depressed affect and anxious affect, were assessed using the Composite International Diagnostic Inventory (N=1290). Multiple linear regression was used to assess the relationship between depression and anxiety disorders and telomere length. Among women, those with GAD or PD had shorter telomeres than those with no anxious affect (β: -0.07, P<0.01), but there was no relationship among men (β: 0.08, P>0.05). Among respondents currently taking an antidepressant, those with MD had shorter telomeres than those without (β: -0.26, P<0.05), but there was no association between MD and telomere length among those not using antidepressants (β: -0.00, P>0.05). Neither depressive nor anxiety disorders were directly associated with telomere length in young adults. There was suggestive evidence that pharmacologically treated MD is associated with shorter telomere length, likely reflecting the more severe nature of MD that has come to clinical attention.

Dyslipidemia and chronic inflammation markers are correlated with telomere length shortening in Cushing's syndrome

Introduction

Cushing’s syndrome (CS) increases cardiovascular risk (CVR) and adipocytokine imbalance, associated with an increased inflammatory state. Telomere length (TL) shortening is a novel CVR marker, associated with inflammation biomarkers. We hypothesized that inflammatory state and higher CVR in CS might be related to TL shortening, as observed in premature aging.

Aim

To evaluate relationships between TL, CVR and inflammation markers in CS.

Methods

In a cross-sectional study, 77 patients with CS (14 males, 59 pituitary-, 17 adrenal- and 1 ectopic-origin; 21 active disease) and 77 age-, gender-, smoking-matched controls were included. Total white blood cell TL was measured by TRF-Southern technique. Clinical data and blood samples were collected (lipids, adrenal function, glucose). Adiponectin, interleukin-6 (IL6) and C-reactive protein (CRP) were available in a subgroup of patients (n=32). Correlations between TL and clinical features were examined and multiple linear regression analysis was performed to investigate potential predictors of TL.

Results

Dyslipidemic CS had shorter TL than non-dyslipidemic subjects (7328±1274 vs 7957±1137 bp, p<0.05). After adjustment for age and body mass index, cured and active CS dyslipidemic patients had shorter TL than non-dyslipidemic CS (cured: 7187±1309 vs 7868±1104; active: 7203±1262 vs 8615±1056, respectively, p<0.05). Total cholesterol and triglycerides negatively correlated with TL (r-0.279 and -0.259, respectively, p<0.05), as well as CRP and IL6 (r-0.412 and -0.441, respectively, p<0.05). No difference in TL according the presence of other individual CVR factors (hypertension, diabetes mellitus, obesity) were observed in CS or in the control group. Additional TL shortening was observed in dyslipidemic obese patients who were also hypertensive, compared to those with two or less CVR factors (6956±1280 vs 7860±1180, respectively, p<0.001). Age and dyslipidemia were independent negative predictors of TL.

Conclusion

TL is shortened in dyslipidemic CS patients, further worse if hypertension and/or obesity coexist and is negatively correlated with increased inflammation markers. Increased lipids and a “low” grade inflammation may contribute to TL shortening and consequently to premature ageing and increased morbidity in CS.

Telomerase dysregulation in the hippocampus of a rat model of depression: normalization by lithium

BACKGROUND

Telomeres are protective DNA-protein complexes at the ends of each chromosome, maintained primarily by the enzyme telomerase. Shortening of the blood leukocyte telomeres is associated with aging, several chronic diseases, and stress, eg, major depression. Hippocampus is pivotal in the regulation of cognition and mood and the main brain region of telomerase activity. Whether there is telomere dysfunction in the hippocampus of depressed subjects is unknown. Lithium, used in the treatment and relapse prevention of mood disorders, was found to protect against leukocyte telomere shortening in humans, but the mechanism has not been elucidated. To answer the questions whether telomeres are shortened and the telomerase activity changed in the hippocampus and whether lithium could reverse the process, we used a genetic model of depression, the Flinders Sensitive Line rat, and treated the animals with lithium.

METHODS

Telomere length, telomerase reverse transcriptase (Tert) expression, telomerase activity, and putative mediators of telomerase activity were investigated in the hippocampus of these animals.

RESULTS

The naïve Flinders Sensitive Line had shorter telomere length, downregulated Tert expression, reduced brain-derived neurotrophic factor levels, and reduced telomerase activity compared with the Flinders Resistant Line controls. Lithium treatment normalized the Tert expression and telomerase activity in the Flinders Sensitive Line and upregulated β-catenin.

CONCLUSION

This is the first report showing telomere dysregulation in hippocampus of a well-defined depression model and restorative effects of lithium treatment. If replicated in other models of mood disorder, the findings will contribute to understanding both the telomere function and the mechanism of lithium action in hippocampus of depressed patients.

Comparison of telomere length in black and white teachers from South Africa: the sympathetic activity and ambulatory blood pressure in Africans study

OBJECTIVE

Telomere length is a marker of biological aging that has been linked to cardiovascular disease risk. The black South African population is witnessing a tremendous increase in the prevalence of cardiovascular disease, part of which might be explained through urbanization. We compared telomere length between black South Africans and white South Africans and examined which biological and psychosocial variables played a role in ethnic difference in telomere length.

METHODS

We measured leukocyte telomere length in 161 black South African teachers and 180 white South African teachers aged 23 to 66 years without a history of atherothrombotic vascular disease. Age, sex, years having lived in the area, human immunodeficiency virus (HIV) infection, hypertension, body mass index, dyslipidemia, hemoglobin A1c, C-reactive protein, smoking, physical activity, alcohol abuse, depressive symptoms, psychological distress, and work stress were considered as covariates.

RESULTS

Black participants had shorter (median, interquartile range) relative telomere length (0.79, 0.70-0.95) than did white participants (1.06, 0.87-1.21; p < .001), and this difference changed very little after adjusting for covariates. In fully adjusted models, age (p < .001), male sex (p = .011), and HIV positive status (p = .023) were associated with shorter telomere length. Ethnicity did not significantly interact with any covariates in determining telomere length, including psychosocial characteristics.

CONCLUSIONS

Black South Africans showed markedly shorter telomeres than did white South African counterparts. Age, male sex, and HIV status were associated with shorter telomere length. No interactions between ethnicity and biomedical or psychosocial factors were found. Ethnic difference in telomere length might primarily be explained by genetic factors.

Stem cells and aberrant signaling of molecular systems in skin aging

The skin is the body's largest organ and it is able to self-repair throughout an individual's life. With advanced age, skin is prone to degenerate in response to damage. Although cosmetic surgery has been widely adopted to rejuvinate skin, we are far from a clear understanding of the mechanisms responsible for skin aging. Recently, adult skin-resident stem/progenitor cells, growth arrest, senescence or apoptotic death and dysfunction caused by alterations in key signaling genes, such as Ras/Raf/MEK/ERK, PI3K/Akt-kinases, Wnt, p21 and p53, have been shown to play a vital role in skin regeneration. Simultaneously, enhanced telomere attrition, hormone exhaustion, oxidative stress, genetic events and ultraviolet radiation exposure that result in severe DNA damage, genomic instability and epigenetic mutations also contribute to skin aging. Therefore, cell replacement and targeting of the molecular systems found in skin hold great promise for controlling or even curing skin aging.

Leukocyte telomere length variation due to DNA extraction method

BACKGROUND

Telomere length is indicative of biological age. Shorter telomeres have been associated with several disease and health states. There are inconsistencies throughout the literature amongst relative telomere length measured by quantitative PCR (qPCR) and different extraction methods or kits used. We quantified whole-blood leukocyte telomere length using the telomere to single copy gene (T/S) ratio by qPCR in 20 young (18-25 yrs) men after extracting DNA using three common extraction methods: Lahiri and Nurnberger (high salt) method, PureLink Genomic DNA Mini kit (Life Technologies) and QiaAmp DNA Mini kit (Qiagen). Telomere length differences of DNA extracted from the three extraction methods was assessed by one-way analysis of variance (ANOVA).

RESULTS

DNA purity differed between extraction methods used (P=0.01). Telomere length was impacted by the DNA extraction method used (P=0.01). Telomeres extracted using the Lahiri and Nurnberger method (mean T/S ratio: 2.43, range: 1.57-3.02) and PureLink Genomic DNA Mini Kit (mean T/S ratio: 2.57, range: 2.24-2.80) did not differ (P=0.13). Likewise, QiaAmp and Purelink-extracted telomeres were not statistically different (P=0.14). The Lahiri-extracted telomeres, however, were significantly shorter than those extracted using the QiaAmp DNA Mini Kit (mean T/S ratio: 2.71, range: 2.32-3.02; P=0.003). DNA purity was associated with telomere length.

CONCLUSION

There are discrepancies between the length of leukocyte telomeres extracted from the same individuals according to the DNA extraction method used. DNA purity could be responsible for the discrepancy in telomere length but this will require validation studies. We recommend using the same DNA extraction kit when quantifying leukocyte telomere length by qPCR or when comparing different cohorts to avoid erroneous associations between telomere length and traits of interest.

Long telomere length and a TERT-CLPTM1 locus polymorphism association with melanoma risk

Telomere length has been associated with the development of cancer. Studies have shown that shorter telomere length may be related to a decreased risk of cutaneous melanoma. Furthermore, deregulation of the telomere-maintaining gene complexes, has been related to this oncogenic process. Some variants in these genes seem to be correlated with a change in telomerase expression. We examined the effect of 10 single nucleotide polymorphisms (SNPs) in the TERT gene (encoding telomerase), one SNP in the related TERT-CLPTM1L locus and one SNP in the TRF1 gene with telomere length, and its influence on melanoma risk in 970 Spanish cases and 733 Spanish controls. Genotypes were determined using KASP technology, and telomere length was measured by quantitative polymerase chain reaction (PCR) on DNA extracted from peripheral blood leucocytes. Our results demonstrate that shorter telomere length is associated with a decreased risk of melanoma in our population (global p-value, 2.69×10(-11)), which may be caused by a diminution of proliferative potential of nevi (melanoma precursor cells). We also obtained significant results when we tested the association between rs401681 variant (TERT-CLPTM1L locus) with melanoma risk (Odds ratio, OR; 95% confidence interval, CI=1.24 (1.08-1.43); p-value, 3×10(-3)). This is the largest telomere-related study undertaken in a Spanish population to date. Furthermore, this study represents a comprehensive analysis of some of the most relevant telomere pathway genes in relation to cutaneous melanoma susceptibility.

Leukocyte telomere length and hemostatic factors in a South African cohort: the SABPA Study

BACKGROUND

Incident atherothrombotic disease is predicted by leukocyte telomere length, a marker of biological age, and hemostatic factor levels, indicating a hypercoagulable state. We hypothesized that shorter telomeres are associated with elevated circulating levels of hemostatic factors.

METHODS

We examined 171 South African (black) and 182 Caucasian (white) schoolteachers (mean age ± standard deviation, 48.5 ± 9.0 years; 50.4% women). Levels of fibrinogen, von Willebrand factor antigen (VWF:Ag), D-dimer and plasminogen activator inhibitor-1 antigen (PAI-1:Ag) were measured in plasma, and values were log-transformed before analysis. Relative average telomere length (content of telomere PCR product/content of human β-globin PCR product ratio, i.e. telomere/single-copy gene ratio) was assessed with multiplex quantitative real-time PCRs. Multivariate analyses included demographics, metabolic factors, health behavior, and medication.

RESULTS

Africans had shorter mean telomere length (0.82, 95% confidence interval [CI] 0.79-0.86 vs. 1.07, 95% CI 1.04-1.10) and higher fibrinogen (B = 0.085, 95% CI 0.061-0.109) and PAI-1:Ag (B = 0.255, 95% CI 0.206-0.303) levels, but lower VWF:Ag levels (B = - 0.059, 95% CI - 0.089 to - 0.028), than Caucasians. Shorter telomeres were associated with higher fibrinogen (B = - 0.045, 95% CI - 0.088 to - 0.001), VWF:Ag (B = - 0.137, 95% CI - 0.193 to - 0.081) and D-dimer (B = - 0.201, 95% CI - 0.377 to - 0.025) levels, conditional on ethnicity. An interaction emerged between ethnicity and telomere length for VWF:Ag level; that is, shorter telomeres were associated with higher VWF:Ag levels in Caucasians (B = - 0.170, 95% CI - 0.232 to - 0.108) but not in Africans.

CONCLUSIONS

Shorter telomeres were associated with increased levels of several hemostatic factors after adjustment for confounding variables, whereby ethnicity partially moderated this effect. A relationship between accelerated biological aging and hypercoagulability might contribute to the risk of premature atherothrombotic events.

Patients with multiple sclerosis show increased oxidative stress markers and somatic telomere length shortening

Lipid peroxidation due to oxidative stress (OS) may play an important role in the pathogenesis of chronic systemic inflammatory diseases such as multiple sclerosis (MS). Telomeres, repeated sequences that cap chromosome ends, undergo shortening with each cycle of cell division, resulting in cellular senescence. Research regarding telomere shortening has provided novel insight into the pathogenesis of various diseases. We hypothesized that OS damage leads to inflammatory reactions, which subsequently shortens the telomere length in MS. We enrolled 59 patients with MS, and age- and gender-matched 60 healthy controls. We divided MS subjects into three groups matched for age and gender according to the severity of disability: relatively benign course (BMS), secondary progressive MS, and primary progressive MS (PPMS). We analyzed the telomere length in peripheral blood mononuclear cells and the 8-iso-PGF2α concentration in urine, a reliable and stable marker of lipid peroxidation in vivo. The data showed significant higher levels of urinary 8-iso-PGF2α in MS subjects than in the controls. The lag-time, which represents the direct measurement of the resistance of low-density lipoprotein to oxidation, was shorter in the PPMS subjects than in the groups. Compared to that observed in the controls, the mean telomere length was significantly shorter in the PPMS group, whereas no significant telomere shortening was found between the controls and other subjects. Our data suggest that a decreased telomere length and enhanced lipid peroxidation reflects the severest stage of MS.

Shorter telomere length in peripheral blood leukocytes is associated with childhood autism

Telomeres are protective chromosomal structures that play a key role in preserving genomic stability. Epidemiologic studies have shown that the abnormal telomere length in leukocytes is associated with some mental disorders and age-related diseases. However, the association between leukocyte telomere length and autism has not been investigated. Here we investigated the possible association between relative telomere length (RTL) in peripheral blood leukocytes and childhood autism by using an established real-time polymerase chain reaction method. We observed significantly shorter RTL in patients with childhood autism than in controls (p = 0.006). Individuals with shorter RTL had a significantly increased presence of childhood autism compared with those who had long RTL. In patients, we found that family training interventions have a significant effect on telomere length (P = 0.012), but no correlations between RTL and clinical features (paternal age, maternal age, age of onset, illness of duration, CARS score and ABC score) were observed in this study. These results provided the first evidence that shorter leukocytes telomere length is significantly associated with childhood autism. The molecular mechanism underlying telomere length may be implicated in the development of autism.

Leukocyte telomere length in relation to pancreatic cancer risk: a prospective study

BACKGROUND

Several studies have examined leukocyte telomere length (LTL) as a possible predictor for cancer at various organ sites. The hypothesis originally motivating many of these studies was that shorter telomeres would be associated with an increase in cancer risk; the results of epidemiologic studies have been inconsistent, however, and suggested positive, negative, or null associations. Two studies have addressed the association of LTL in relation to pancreatic cancer risk and the results are contrasting.

METHODS

We measured LTL in a prospective study of 331 pancreatic cancer cases and 331 controls in the context of the European Prospective Investigation into Cancer and Nutrition (EPIC).

RESULTS

We observed that the mean LTL was higher in cases (0.59 ± 0.20) than in controls (0.57 ± 0.17), although this difference was not statistically significant (P = 0.07), and a basic logistic regression model showed no association of LTL with pancreas cancer risk. When adjusting for levels of HbA1c and C-peptide, however, there was a weakly positive association between longer LTL and pancreatic cancer risk [OR, 1.13; 95% confidence interval (CI), 1.01-1.27]. Additional analyses by cubic spline regression suggested a possible nonlinear relationship between LTL and pancreatic cancer risk (P = 0.022), with a statistically nonsignificant increase in risk at very low LTL, as well as a significant increase at high LTL.

CONCLUSION

Taken together, the results from our study do not support LTL as a uniform and strong predictor of pancreatic cancer.

IMPACT

The results of this article can provide insights into telomere dynamics and highlight the complex relationship between LTL and pancreatic cancer risk.

Short and long telomeres increase risk of amnestic mild cognitive impairment

Peripheral blood telomere length has been associated with age-related conditions including Alzheimer's disease (AD). This suggests that telomere length may identify subjects at increased risk of AD. Thus, we investigated the associations of peripheral blood telomere length with amnestic mild cognitive impairment (aMCI), a putative precursor of AD, among Mayo Clinic Study of Aging participants who were prospectively followed for incident aMCI. We matched 137 incident aMCI cases (mean age 81.1 years, [range 70.9-90.8]; 49.6% men) by age and sex to 137 cognitively normal controls. We measured telomere length (T/S ratio) at baseline using quantitative PCR. Compared to the middle T/S quintile (Q3), the risk of aMCI was elevated for subjects with the shortest (Q1: HR, 2.85, 95% Confidence interval [CI] 0.98, 8.25; p=0.05) and the longest telomere lengths (Q5: HR, 5.58, 95%CI, 2.21, 14.11; p=0.0003). In this elderly cohort, short and long telomeres were associated with increased risk of aMCI. Our findings suggest that both long and short telomere lengths may play a role in the pathogenesis of aMCI, and may be markers of increased risk of aMCI.

The assessment of CD146-based cell sorting and telomere length analysis for establishing the identity of mesenchymal stem cells in human umbilical cord

Adult stem cells are characterised by longer telomeres compared to mature cells from the same tissue. In this study, candidate CD146 (+) umbilical cord (UC) mesenchymal stem cells (MSCs) were purified by cell sorting from UC tissue digests and their telomere lengths were measured in comparison to donor-matched CD146-negative fraction. UC tissue fragments were enzymatically treated with collagenase and the cells were used for cell sorting, colony-forming fibroblast (CFU-F) assay or for long-term MSC cultivation. Telomere lengths were measured by qPCR in both culture-expanded MSCs and candidate native UC MSCs. Immunohistochemistry was undertaken to study the topography of CD146 (+) cells. Culture-expanded UC MSCs had a stable expression of CD73, CD90 and CD105, whereas CD146 declined in later passages which correlated with the shortening of telomeres in the same cultures. In five out of seven donors, telomeres in candidate native UC MSCs (CD45 (-)CD235α (-)CD31 (-)CD146 (+)) were longer compared to donor-matched CD146 (-) population (CD45 (-)CD235α (-)CD31 (-)CD146 (-)). The frequency of CD45 (-)CD235α (-)CD31 (-)CD146 (+) cells measured by flow cytometry was ~1000-fold above that of CFU-Fs (means 10.4% and 0.01%, respectively). CD146 (+) cells were also abundant in situ having a broad topography including high levels of positivity in muscle areas in addition to vessels. Although qPCR-based telomere length analysis in sorted populations could be limited in its sensitivity, very high frequency of CD146 (+) cells in UC tissue suggests that CD146 expression alone is unlikely to be sufficient to identify and purify native MSCs from the UC tissue.

The assessment of CD146-based cell sorting and telomere length analysis for establishing the identity of mesenchymal stem cells in human umbilical cord

Adult stem cells are characterised by longer telomeres compared to mature cells from the same tissue. In this study, candidate CD146 ⁺ umbilical cord (UC) mesenchymal stem cells (MSCs) were purified by cell sorting from UC tissue digests and their telomere lengths were measured in comparison to donor-matched CD146-negative fraction.

UC tissue fragments were enzymatically treated with collagenase and the cells were used for cell sorting, colony-forming fibroblast (CFU-F) assay or for long-term MSC cultivation. Telomere lengths were measured by qPCR in both culture-expanded MSCs and candidate native UC MSCs. Immunohistochemistry was undertaken to study the topography of CD146 ⁺ cells.

Culture-expanded UC MSCs had a stable expression of CD73, CD90 and CD105, whereas CD146 declined in later passages which correlated with the shortening of telomeres in the same cultures. In five out of seven donors, telomeres in candidate native UC MSCs (CD45 ^-CD235α ^-CD31 ^-CD146 ⁺) were longer compared to donor-matched CD146 ^- population (CD45 ^-CD235α ^-CD31 ^-CD146 ^-). The frequency of CD45 ^-CD235α ^-CD31 ^-CD146 ⁺ cells measured by flow cytometry was ~1000-fold above that of CFU-Fs (means 10.4% and 0.01%, respectively). CD146 ⁺ cells were also abundant in situ having a broad topography including high levels of positivity in muscle areas in addition to vessels.

Although qPCR-based telomere length analysis in sorted populations could be limited in its sensitivity, very high frequency of CD146 ⁺ cells in UC tissue suggests that CD146 expression alone is unlikely to be sufficient to identify and purify native MSCs from the UC tissue.

Telomere length in peripheral blood leukocytes and lung cancer risk: a large case-control study in Caucasians

Telomere dysfunction is a crucial event in malignant transformation and tumorigenesis. Telomere length in peripheral blood leukocytes has been associated with lung cancer risk, but the relationship has remained controversial. In this study, we investigated whether the association might be confounded by study of different histological subtypes of lung cancer. We measured relative telomere lengths in patients in a large case-control study of lung cancer and performed stratified analyses according to the two major histologic subtypes [adenocarcinoma and squamous cell carcinoma (SCC)]. Notably, patients with adenocarcinoma had longer telomeres than controls, whereas patients with SCC had shorter telomeres compared with controls. Long telomeres were associated with increased risk of adenocarcinoma, with the highest risk associated with female sex, younger age (<60 years), and lighter smoking (<30 pack-years). In contrast, long telomeres were protective against SCC, particularly in male patients. Our results extend the concept that telomere length affects risk of lung cancer in a manner that differs with histologic subtype.

Telomere shortening in neurological disorders: an abundance of unanswered questions

Telomeres, ribonucleoprotein complexes that cap eukaryotic chromosomes, typically shorten in leukocytes with aging. Aging is a primary risk factor for neurodegenerative disease (ND), and a common assumption has arisen that leukocyte telomere length (LTL) can serve as a predictor of neurological disease. However, the evidence for shorter LTL in Alzheimer's and Parkinson's patients is inconsistent. The diverse causes of telomere shortening may explain variability in LTL between studies and individuals. Additional research is needed to determine whether neuronal and glial telomeres shorten during aging and in neurodegenerative disorders, if and how LTL is related to brain cell telomere shortening, and whether telomere shortening plays a causal role in or exacerbates neurological disorders.

Acute exercise leads to regulation of telomere-associated genes and microRNA expression in immune cells

Telomeres are specialized nucleoprotein structures that protect chromosomal ends from degradation. These structures progressively shorten during cellular division and can signal replicative senescence below a critical length. Telomere length is predominantly maintained by the enzyme telomerase. Significant decreases in telomere length and telomerase activity are associated with a host of chronic diseases; conversely their maintenance underpins the optimal function of the adaptive immune system. Habitual physical activity is associated with longer leukocyte telomere length; however, the precise mechanisms are unclear. Potential hypotheses include regulation of telomeric gene transcription and/or microRNAs (miRNAs). We investigated the acute exercise-induced response of telomeric genes and miRNAs in twenty-two healthy males (mean age = 24.1±1.55 years). Participants undertook 30 minutes of treadmill running at 80% of peak oxygen uptake. Blood samples were taken before exercise, immediately post-exercise and 60 minutes post-exercise. Total RNA from white blood cells was submitted to miRNA arrays and telomere extension mRNA array. Results were individually validated in white blood cells and sorted T cell lymphocyte subsets using quantitative real-time PCR (qPCR). Telomerase reverse transcriptase (TERT) mRNA (P = 0.001) and sirtuin-6 (SIRT6) (P<0.05) mRNA expression were upregulated in white blood cells after exercise. Fifty-six miRNAs were also differentially regulated post-exercise (FDR <0.05). In silico analysis identified four miRNAs (miR-186, miR-181, miR-15a and miR-96) that potentially targeted telomeric gene mRNA. The four miRNAs exhibited significant upregulation 60 minutes post-exercise (P<0.001). Telomeric repeat binding factor 2, interacting protein (TERF2IP) was identified as a potential binding target for miR-186 and miR-96 and demonstrated concomitant downregulation (P<0.01) at the corresponding time point. Intense cardiorespiratory exercise was sufficient to differentially regulate key telomeric genes and miRNAs in white blood cells. These results may provide a mechanistic insight into telomere homeostasis and improved immune function and physical health.

Telomere shortening unrelated to smoking, body weight, physical activity, and alcohol intake: 4,576 general population individuals with repeat measurements 10 years apart

Cross-sectional studies have associated short telomere length with smoking, body weight, physical activity, and possibly alcohol intake; however, whether these associations are due to confounding is unknown. We tested these hypotheses in 4,576 individuals from the general population cross-sectionally, and with repeat measurement of relative telomere length 10 years apart. We also tested whether change in telomere length is associated with mortality and morbidity in the general population. Relative telomere length was measured with quantitative polymerase chain reaction. Cross-sectionally at the first examination, short telomere length was associated with increased age (P for trend across quartiles = 3 × 10(-77)), current smoking (P = 8 × 10(-3)), increased body mass index (P = 7 × 10(-14)), physical inactivity (P = 4 × 10(-17)), but not with increased alcohol intake (P = 0.10). At the second examination 10 years later, 56% of participants had lost and 44% gained telomere length with a mean loss of 193 basepairs. Change in leukocyte telomere length during 10 years was associated inversely with baseline telomere length (P<1 × 10(-300)) and age at baseline (P = 1 × 10(-27)), but not with baseline or 10-year inter-observational tobacco consumption, body weight, physical activity, or alcohol intake. Prospectively during a further 10 years follow-up after the second examination, quartiles of telomere length change did not associate with risk of all-cause mortality, cancer, chronic obstructive pulmonary disease, diabetes mellitus, ischemic cerebrovascular disease, or ischemic heart disease. In conclusion, smoking, increased body weight, and physical inactivity were associated with short telomere length cross-sectionally, but not with telomere length change during 10 years observation, and alcohol intake was associated with neither. Also, change in telomere length did not associate prospectively with mortality or morbidity in the general population.

The association of telomere length with colorectal cancer differs by the age of cancer onset

OBJECTIVES:

Telomeres are nucleoprotein structures that cap the end of chromosomes and shorten with sequential cell divisions in normal aging. Short telomeres are also implicated in the incidence of many cancers, but the evidence is not conclusive for colorectal cancer (CRC). Therefore, the aim of this study was to assess the association of CRC and telomere length.

METHODS:

In this case–control study, we measured relative telomere length from peripheral blood leukocytes (PBLs) DNA with quantitative PCR in 598 CRC patients and 2,212 healthy controls.

RESULTS:

Multivariate analysis indicated that telomere length was associated with risk for CRC, and this association varied in an age-related manner; younger individuals (≤50 years of age) with longer telomeres (80–99 percentiles) had a 2–6 times higher risk of CRC, while older individuals (>50 years of age) with shortened telomeres (1–10 percentiles) had 2–12 times the risk for CRC. The risk for CRC varies with extremes in telomere length in an age-associated manner.

CONCLUSIONS:

Younger individuals with longer telomeres or older individuals with shorter telomeres are at higher risk for CRC. These findings indicate that the association of PBL telomere length varies according to the age of cancer onset and that CRC is likely associated with at minimum two different mechanisms of telomere dynamics.

Telomere length reprogramming in embryos and stem cells

Telomeres protect and cap linear chromosome ends, yet these genomic buffers erode over an organism's lifespan. Short telomeres have been associated with many age-related conditions in humans, and genetic mutations resulting in short telomeres in humans manifest as syndromes of precocious aging. In women, telomere length limits a fertilized egg's capacity to develop into a healthy embryo. Thus, telomere length must be reset with each subsequent generation. Although telomerase is purportedly responsible for restoring telomere DNA, recent studies have elucidated the role of alternative telomeres lengthening mechanisms in the reprogramming of early embryos and stem cells, which we review here.

Telomere length in peripheral blood leukocytes is associated with risk of colorectal cancer in Chinese population

Background

Human telomeres, tandem repeats of TTAGGG nucleotides at the ends of chromosomes, are essential for maintaining genomic integrity and stability. Results of previous epidemiologic studies about the association of telomere length with risk of colorectal cancer (CRC) have been conflicting.

Methods

A case-control study was conducted in a Han population in Wuhan, central China. The relative telomere length (RTL) was measured in peripheral blood leukocytes (PBLs) using quantitative real-time polymerase chain reaction (PCR) in 628 CRC cases and 1,256 age and sex frequency matched cancer-free controls. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using unconditional logistic regression models to evaluate the association between RTL and CRC risk.

Results

Using median RTL in the controls as the cutoff, individuals with shorter RTL were associated with a significantly increased risk of CRC (adjusted OR = 1.27, 95%CI: 1.05–1.55). When participants were further categorized into 3 and 4 groups according to the tertile and quartile RTL values of controls, significant relationships were still observed between shorter RTL and increased CRC risk (OR per tertile = 1.13, 95%CI: 1.00–1.28, P_trend = 0.045; OR per quartile = 1.12, 95%CI: 1.03–1.23, P_trend = 0.012). In stratified analyses, significant association between shorter RTL and increased CRC risk was found in females, individuals younger than 60 years old, never smokers and never drinkers.

Conclusions

This study suggested that short telomere length in PBLs was significantly associated with an increased risk of CRC in Chinese Han population. Further validation in large prospective studies and investigation of the biologic mechanisms are warranted.

Age estimation via quantification of signal-joint T cell receptor excision circles in Koreans

The estimation of age from biological samples (i.e., remains) at crime scenes could provide useful information about both victims and other persons related to criminal activities. Signal-joint T cell receptor excision circle (sjTREC) levels in peripheral blood decline with age, and negative correlations between sjTREC levels and age have been demonstrated in several ethnic groups. To validate the utility of sjTREC for age estimation in Koreans, Taqman qPCR was used to quantify the sjTREC level in samples obtained from 172 individuals ranging from 16 to 65 years old. We modified the previously reported method by using a shorter amplicon and confirmed the efficiency and utility of this method in this report. Our results showed that the linear negative regression curve between sjTREC levels and age was characterized by r=-0.807 and a standard error of 8.49 years. These results indicate that sjTREC level is an effective age estimation method in Koreans. The value of the standard error of quantification was not different from previous reports for other population groups.

Leukocyte telomere length and age at menopause

BACKGROUND

Telomere length is a marker of cellular aging that varies with the individual, is inherited, and is highly correlated across somatic cell types within persons. Interindividual variability of telomere length may partly explain differences in reproductive aging rates. We examined whether leukocyte telomere length was associated with menopausal age.

METHODS

We evaluated the relationship between leukocyte telomere length and age at natural menopause in 486 white women ≥65 years of age. We fit linear regression models adjusted for age, income, education, body mass index, physical activity, smoking, and alcohol intake. We repeated the analysis in women with surgical menopause. We also performed sensitivity analyses excluding women (1) with unilateral oophorectomy, (2) who were nulliparous, or (3) reporting menopausal age <40 years, among other exclusions.

RESULTS

For every 1-kb increase in leukocyte telomere length, average age at natural menopause increased by 10.2 months (95% confidence interval = 1.3 to 19.0). There was no association among 179 women reporting surgical menopause. In all but one sensitivity analysis, the association between leukocyte telomere length and age at menopause became stronger. However, when excluding women with menopausal age <40 years, the association decreased to 7.5 months (-0.4 to 15.5).

CONCLUSIONS

Women with the longest leukocyte telomere length underwent menopause 3 years later than those with the shortest leukocyte telomere length. If an artifact, an association would likely also have been observed in women with surgical menopause. If these results are replicated, leukocyte telomere length may prove to be a useful predictor of age at menopause.

Telomeres in molecular epidemiology studies

Telomeres are long nucleotide repeats and protein complexes at the ends of chromosomes that are essential for maintaining chromosomal stability. They shorten with each cell division, and therefore, telomere length is a marker for cellular aging and senescence. Epidemiological research of telomeres investigates the role that these genetic structures have in disease risk and mortality in human populations. This chapter provides an overview of the current telomere epidemiology research and discusses approaches taken in these investigations. We also highlight important methodological considerations that may affect data interpretation.

Cumulative PM(2.5) exposure and telomere length in workers exposed to welding fumes

Telomeres are genomic structures that reflect both mitotic history and biochemical trauma to the genome. Metals inherent in fine particulate matter (PM(2.5)) were shown to be genotoxic via oxidative damage. However, few studies investigated the induction time of cumulative PM(2.5) exposure on telomere length in a longitudinal setting. Therefore, the purpose of this study was to assess the association between occupational PM(2.5) exposure in various time windows and telomere length. The study population consisted of 48 boilermakers and the follow-up period was 8 yr. The main exposures were cumulative occupational PM(2.5) in the month, year, and career prior to each blood draw, assessed via work history questionnaires and area air measures. Repeated telomere length measurements from leukocytes were assessed via real-time qualitative polymerase chain reaction (qPCR). Analysis was performed using linear mixed models controlling for confounders and white blood cell differentials. Cumulative PM(2.5) exposure was treated continuously and categorized into quartiles, in separate analyses. At any follow-up time, for each milligram per cubic meter per hour increase in cumulative PM(2.5) exposure in the prior month, there was a statistically significant decrease in relative telomere length of -0.04 units. When categorizing the exposure into quartiles, there was a significant negative association between telomere length and highest quartile of cumulative PM(2.5) exposure in the prior month (-0.16). These findings suggest that genomic trauma to leukocyte telomeres was more consistent with recent occupational PM(2.5) exposure, as opposed to cumulative exposure extending into the distant past.

Telomere length correlations among somatic tissues in adult zebra finches

Telomeres are repetitive non coding DNA sequences located at the end of eukaryotic chromosomes, which maintain the integrity of the genome by hiding the chromosome ends from being recognised as double stranded breaks. Telomeres are emerging as biomarkers for ageing and survival, and are susceptible to reflect different individual life history trajectories. In particular, the telomere length with which one starts in life has been shown to be linked with individual life-long survival, suggesting that telomere dynamics can be a proxy for individual fitness and thereby be implicated in evolutionary trade-offs. As a consequence, an increasing number of studies were conducted on telomeres in the fields of ecology and evolutionary biology, in which telomere length was almost exclusively measured from blood samples. However, not only do the number of repeats of the telomeric sequences vary among species, but also within species with great inter-individual telomere lengths variability with age, tissues, and chromosomes. This raises the issue of the exact biological meaning of telomere measurement in blood cells and stimulated the study of the correlation of telomere lengths among tissues over age. By measuring telomere length in adult zebra finches (Taeniopygia guttata) in different somatic tissues displaying variable cell turnovers (bone marrow, brain, spleen, pectoral muscle, heart, liver and in red blood cells), we checked that the measure of telomere length in red blood cells is related to telomere lengths in the other tissues. Here we show significant relationships between the telomere lengths of red blood cells and several somatic tissues at adulthood. As red blood cells are easily accessible and suitable for the longitudinal monitoring of the individual rate of telomere loss, our study confirms that telomere length measured in red blood cells could serve as a surrogate for telomere length in the whole avian organism.

Telomere length and risk of glioma

BACKGROUND

Telomere length in blood or buccal cell DNA has been associated with risk of various cancers. Glioma can be a highly malignant brain tumor and has few known risk factors. Genetic variants in or near RTEL1 and TERT, key components of telomere biology, are associated with glioma risk. Therefore, we evaluated the association between relative telomere length (RTL) and glioma in a prospective study.

MATERIALS AND METHODS

We performed a nested case-control study within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. RTL was determined by quantitative PCR on blood or buccal cell DNA obtained at least 2 years prior to diagnosis from 101 individuals with glioma cases. Healthy controls (n=198) were matched to cases (2:1) on age, gender, smoking status, calendar year, and DNA source. Conditional logistic regression was used to investigate the association between RTL and glioma.

RESULTS

As expected, RTL declined with increasing age in both cases and controls. There was no statistically significant association between RTL and glioma overall. An analysis stratified by gender suggested that short RTL (1st tertile) in males was associated with glioma (odds ratio, [OR]=2.29, 95% confidence interval [CI] 1.02-5.11); this association was not observed for females (OR=0.41, 95% CI 0.14-1.17).

CONCLUSIONS

This prospective study did not identify significant associations between RTL and glioma risk, but there may be gender-specific differences. Larger, prospective studies are needed to evaluate these findings.

Telomeres and human health

Telomeres are the tips of chromosomes and consist of proteins and hexanucleotide tandem repeats of DNA. The DNA repeats are shortened at each mitotic division of normal cells, and the telomere length chronicles how many divisions the cell has undergone. Thus, telomere length is a marker of fundamental biological pathways. It has been possible to measure telomere length for more than 20 years, and it has been established that telomere length is associated with age, sex and lifestyle factors. Here, the current knowledge of telomere length as a biomarker of disease susceptibility and mortality will be reviewed. In addition, technical difficulties and the reasons why measurement of telomeres has still not been introduced into routine clinical practice will be discussed. Findings from recent studies conducted in many thousands of individuals indicate that telomere length is not-or at best only marginally-independently associated with risk of common disorders such as cardiovascular, pulmonary and neoplastic diseases. However, in sufficiently powered studies, short telomeres are repeatedly and independently found to be associated with increased risk of early death in the general population or in subsets of individuals. This indicates that measurement of telomeres could be a valuable prognostic biomarker in many clinical settings. However, whether short telomeres are a causal factor for or simply a marker of increased risk of early death must be determined. Finally, how Mendelian randomization studies could clarify this issue, and which clinical studies might be carried out to refine this very promising biomarker for routine clinical use will be considered.

Telomeres shorten at equivalent rates in somatic tissues of adults

Telomere shortening in somatic tissues largely reflects stem cell replication. Previous human studies of telomere attrition were predominantly conducted on leukocytes. However, findings in leukocytes cannot be generalized to other tissues. Here we measure telomere length in leukocytes, skeletal muscle, skin and subcutaneous fat of 87 adults (aged 19–77 years). Telomeres are longest in muscle and shortest in leukocytes, yet are strongly correlated between tissues. Notably, the rates of telomere shortening are similar in the four tissues. We infer from these findings that differences in telomere length between proliferative (blood and skin) and minimally proliferative tissues (muscle and fat) are established during early life, and that in adulthood, stem cells of the four tissues replicate at a similar rate.

Telomere shortening as a result of cell proliferation has been implicated in human ageing. Here, Daniali and colleagues show that telomere length and the rate of age-dependent shortening vary between adults but are similar within tissues of the same individual.

Quantitative fluorescence in situ hybridization measurement of telomere length in skin with/without sun exposure or actinic keratosis

Chromosomal and genomic instability due to telomere dysfunction is known to play an important role in carcinogenesis. To study telomere shortening in the epidermis surrounding actinic keratosis, we measured telomere lengths of basal, parabasal, and suprabasal cells in epidermis with actinic keratosis (actinic keratosis group, n = 18) and without actinic keratosis (sun-protected, n = 15, and sun-exposed, n = 13 groups) and in actinic keratosis itself as well as in dermal fibroblasts in the 3 groups, using quantitative fluorescence in situ hybridization. Among the 3 cell types, telomeres of basal cells were not always the longest, suggesting that tissue stem cells are not necessarily located among basal cells. Telomeres of basal cells in the sun-exposed group were shorter than those in the sun-protected group. Telomeres in the background of actinic keratosis and in actinic keratosis itself and those of fibroblasts in actinic keratosis were significantly shorter than those in the controls. Our findings demonstrate that sun exposure induces telomere shortening and that actinic keratosis arises from epidermis with shorter telomeres despite the absence of any histologic atypia.

Telomere length and physical performance at older ages: an individual participant meta-analysis

BACKGROUND

Telomeres are involved in cellular ageing and shorten with increasing age. If telomere length is a valuable biomarker of ageing, then telomere shortening should be associated with worse physical performance, an ageing trait, but evidence for such an association is lacking. The purpose of this study was to examine whether change in telomere length is associated with physical performance.

METHODS

Using data from four UK adult cohorts (ages 53-80 years at baseline), we undertook cross-sectional and longitudinal analyses. We analysed each study separately and then used meta-analytic methods to pool the results. Physical performance was measured using walking and chair rise speed, standing balance time and grip strength. Telomere length was measured by quantitative real-time polymerase chain reaction (PCR) in whole blood at baseline and follow-up (time 1, time 2).

RESULTS

Total sample sizes in meta-analyses ranged from 1,217 to 3,707. There was little evidence that telomere length was associated with walking speed, balance or grip strength, though weak associations were seen with chair rise speed and grip strength at baseline (p = 0.02 and 0.01 respectively). Faster chair rise speed at follow-up, was associated with a smaller decline in telomere length between time 1 and time 2 (standardised coefficient per SD increase 0.061, 95% CI 0.006, 0.115, p = 0.03) but this was consistent with chance (p =0.08) after further adjustment.

CONCLUSIONS

Whereas shortening of leukocyte telomeres might be an important measure of cellular ageing, there is little evidence that it is a strong biomarker for physical performance.

Telomere length, telomere-related genes, and breast cancer risk: the breast cancer health disparities study

Telomeres are involved in maintaining genomic stability. Previous studies have linked both telomere length (TL) and telomere-related genes with cancer. We evaluated associations between telomere-related genes, TL, and breast cancer risk in an admixed population of US non-Hispanic white (1,481 cases, 1,586 controls) and U.S. Hispanic and Mexican women (2,111 cases, 2,597 controls) from the Breast Cancer Health Disparities Study. TL was assessed in 1,500 women based on their genetic ancestry. TL-related genes assessed were MEN1, MRE11A, RECQL5, TEP1, TERC, TERF2, TERT, TNKS, and TNKS2. Longer TL was associated with increased breast cancer risk [odds ratio (OR) 1.87, 95% confidence interval (CI) 1.38, 2.55], with the highest risk (OR 3.11, 95% CI 1.74, 5.67 p interaction 0.02) among women with high Indigenous American ancestry. Several TL-related single nucleotide polymorphisms had modest association with breast cancer risk overall, including TEP1 rs93886 (OR 0.82, 95% CI 0.70,0.95); TERF2 rs3785074 (OR 1.13, 95% CI 1.03,1.24); TERT rs4246742 (OR 0.85, 95% CI 0.77,0.93); TERT rs10069690 (OR 1.13, 95% CI 1.03,1.24); TERT rs2242652 (OR 1.51, 95% CI 1.11,2.04); and TNKS rs6990300 (OR 0.89, 95% CI 0.81,0.97). Several differences in association were detected by hormone receptor status of tumors. Most notable were associations with TERT rs2736118 (ORadj 6.18, 95% CI 2.90, 13.19) with estrogen receptor negative/progesterone receptor positive (ER-/PR+) tumors and TERT rs2735940 (ORadj 0.73, 95% CI 0.59, 0.91) with ER-/PR- tumors. These data provide support for an association between TL and TL-related genes and risk of breast cancer. The association may be modified by hormone receptor status and genetic ancestry.