Gender and telomere length: systematic review and meta-analysis

Validation of quantitative polymerase chain reaction with Southern blot method for telomere length analysis

Aim:

Telomere length (TL) measurement by quantitative polymerase chain reaction (PCR) has been widely accepted, but limited information regarding its validation with a gold-standard technique is available.

Materials & methods:

We measured TL by Southern blot and monochrome multiplex quantitative PCR (MMqPCR) and validated the results of TL in leukocytes of 94 participants with mean age 43.2 years, BMI 19–41 (mean 27.8 ± 4.3) kg/m².

Results:

A significant positive correlation was observed between TL measured by MMqPCR and Southern blot assay (correlation coefficient r = +0.896, p < 0.0001). The inter- and intra-assay CVs of the MMqPCR assay were 5.3 and 4.07%, respectively.

Conclusion:

We observed that experimental discrepancies have an impact on TL analysis and there is a need to improve the optimum conditions.

The aim of this study was to validate the relative telomere length measurements by different methods. We measured leukocyte telomere lengths by Southern blot and monochrome multiplex quantitative polymerase chain reaction in 94 participants and a strong correlation was shown between both techniques. The results of our study suggest that the monochrome multiplex quantitative polymerase chain reaction method can be employed reliably for measurement of telomere length in epidemiological studies involving a large number of samples.

Organ reserve, excess metabolic capacity, and aging

"Organ reserve" refers to the ability of an organ to successfully return to its original physiological state following repeated episodes of stress. Clinical evidence shows that organ reserve correlates with the ability of older adults to cope with an added workload or stress, suggesting a role in the process of aging. Although organ reserve is well documented clinically, it is not clearly defined at the molecular level. Interestingly, several metabolic pathways exhibit excess metabolic capacities (e.g., bioenergetics pathway, antioxidants system, plasticity). These pathways comprise molecular components that have an excess of quantity and/or activity than that required for basic physiological demand in vivo (e.g., mitochondrial complex IV or glycolytic enzymes). We propose that the excess in mtDNA copy number and tandem DNA repeats of telomeres are additional examples of intrinsically embedded structural components that could comprise excess capacity. These excess capacities may grant intermediary metabolism the ability to instantly cope with, or manage, added workload or stress. Therefore, excess metabolic capacities could be viewed as an innate mechanism of adaptability that substantiates organ reserve and contributes to the cellular defense systems. If metabolic excess capacities or organ reserves are impaired or exhausted, the ability of the cell to cope with stress is reduced. Under these circumstances cell senescence, transformation, or death occurs. In this review, we discuss excess metabolic and structural capacities as integrated metabolic pathways in relation to organ reserve and cellular aging.

Dietary Copper Intake and Its Association With Telomere Length: A Population Based Study

Background: Telomere is regarded as the fundamental aspect of cellular aging and copper is recognized as one of the most essential trace elements. The role of dietary copper intake in telomere length maintenance is seldom examined. This study aims to investigate if telomere length is to be associated with daily dietary copper intake. Methods: We used epidemiological data from a large national population-based health and nutrition survey. Dietary intake was assessed during the 24-h period before the interview date when blood sample was collected. Telomere length was measured from blood leukocyte using PCR method. The relationship between telomere length and dietary copper intake was assessed using multivariable linear regression models. We also examined if obesity, measured by body mass index, could modify the observed association. Results: There are 7,324 participants had both leukocyte telomere length measured and dietary copper intake assessed, around 48.0% of them were men. Telomere length was longer in women than that in men (1.05 ± 0.26 vs. 1.00 ± 0.26 T/S ratio), while dietary copper intake was less in women than that in men (1.12 ± 0.80 vs. 1.51 ± 1.61 mg). After controlling for age, sex, ethnicity, physical activity, current smoking status, hypertension, cardiovascular diseases, and body mass index in the multivariable linear regression models, one unit increase of log-transformed dietary copper intake was significantly associated with longer telomere length (β = 0.02, 95% confidence interval: 0.01, 0.04). We did not find a significant sex difference for this association. Conclusions: Dietary copper intake was significantly associated telomere length.The role of copper in human health might be involved in biological aging process.

Peripheral Blood Leukocyte Telomere Length Is Associated with Age but Not Renal Function: A Cross-Sectional Follow-Up Study

OBJECTIVES

We aimed to evaluate the relationship between baseline renal function and changes in telomere length in Han Chinese.

METHODS

The telomere restriction fragment (TRF) length of leukocytes in the peripheral blood was measured in healthy volunteers recruited in 2014. The estimated glomerular filtration rate (eGFR) was calculated based on serum creatinine (Scr) and serum cystatin C (CysC)-eGFRcys and eGFRScr-cys through the Cockcroft-Gault formula (eGFRC-G) or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI / eGFRCKD-EPI) equation. The correlation between telomere length changes over time and renal function was analyzed.

RESULTS

Leukocyte TRF lengths were negatively correlated to age (r = -0.393, p < 0.001) and serum CysC (r = -0.180, p < 0.01), while positively associated with eGFRCKD-EPI, eGFRC-G, eGFRcys, and eGFRScr-cys (r = 0.182, 0.122, 0.290, and 0.254 respectively, p < 0.01). The 3-year change of telomere length was 46 bp/years. When adjusted for age, the associations between telomere length changes and baseline, subsequent TRF lengths, and serum CysC were no longer present. No association was observed between TRF length changes and renal function.

CONCLUSION

The rate of telomere length changes was affected by age and baseline telomere length. The telomere length changes might be important markers for aging.

Sterol 27-Hydroxylase Polymorphism Significantly Associates With Shorter Telomere, Higher Cardiovascular and Type-2 Diabetes Risk in Obese Subjects

BACKGROUND/OBJECTIVES

The pathologic relationship linking obesity and lipid dismetabolism with earlier onset of aging-related disorders, including cardiovascular disease (CVD) and type-2 diabetes (T2D), is not fully elucidate. Chronic inflammatory state, in obese individuals, may accelerate cellular aging. However, leukocyte telomere length (LTL), the cellular biological aging indicator, is elusively linked with obesity. Recent studies indicate that sterol 27-hydroxylase (CYP27A1) is an emerging antiatherogenic enzyme, that, by converting extrahepatic cholesterol to 27-hydroxycholesterol, facilitates cholesterol removal via high-density lipoprotein-cholesterol (HDL-C). We tested the hypothesis that obese subjects who carry at least three copies of CYP27A1 low-hydroxylation (LH) activity genome-wide-validated alleles (rs4674345A, rs1554622A, and rs4674338G) present premature aging, as reflected in shorter LTL and higher levels of CVD/T2D risk factors, including reduced HDL-C.

SUBJECTS/METHODS

Obese subjects from SPHERE project {n = 1,457; overweight [body mass index (BMI) 25-30 kg/m²] 65.8% and severe-obese (BMI > 30 kg/m²) 34.2%} were characterized for the presence from 0 to 6 LH-CYP27A1 allele copy number. Univariate and multivariable sex-age-smoking-adjusted linear-regression models were performed to compare CVD/T2D risk factors and biological aging (LTL) in relation to the combined BMI-LH groups: overweight-LH: 0-2, overweight-LH: 3-6, severe-obese-LH: 0-2, and severe-obese-LH: 3-6.

RESULTS

Higher LTL attrition was found in severe-obese than overweight individuals (p < 0.001). Multivariable model reveals that among severe-obese patients those with LH: 3-6 present higher LTL attrition than LH: 0-2 (p < 0.05). Univariate and multivariable models remarkably show that insulin resistance is higher both in overweight-LH: 3-6 vs overweight-LH: 0-2 (p < 0.001) and in severe-obese-LH: 3-6 vs severe-obese-LH: 0-2 (p < 0.0001), and HDL-C is lower in overweight-LH: 3-6 than overweight-LH: 0-2 (p < 0.05 and p < 001). Finally, most of the well-known (i.e., blood pressure, heart rate, waist to hip, triglycerides, and HDL-C) and novel CVD risk factors [i.e., inflammation markers (C-reactive protein, leukocytes, and chemoattractant protein-1), fibrinogen, and glucose homeostasis (i.e., insulin resistance, and glycated hemoglobin)] are substantially (p < 0.0001) altered in severe-obese-LH: 0-2 vs overweight-LH: 0-2, pointing to the fact that obesity leads to worsen the CVD/T2D risk factor profile.

CONCLUSION

Our study supports evidence that CYP27A1 genetic characterization identifies persons at higher risk to develop CVD and T2D, on which better converge preventive measures, and opens new perspectives on mechanisms that link obesity with aging-related disorders.

Validation of Minimally-Invasive Sample Collection Methods for Measurement of Telomere Length

Objective: The discovery of telomere length (TL) as a biomarker of cellular aging and correlate of age-related disease has generated a new field of research in the biology of healthy aging. Although the most common method of sample collection for TL is venous blood draw, less-invasive DNA collection methods are becoming more widely used. However, how TL relates across tissues derived from these sample collection methods is poorly understood. The current study is the first to characterize the associations in TL across three sample collection methods: venous whole blood, finger prick dried blood spot and saliva.

Methods: TL was measured in 24 healthy young adults using three modes of sample collection for each participant: venous whole blood, finger prick dried blood spot and saliva. Relative TL was measured using quantitative polymerase chain reaction.

Results: TL in finger prick dried blood spots (DBS) washighly correlated with TL in whole blood (r = 0.84, p < 0.001). Salivary TL was also correlated with whole blood TL (r = 0.56, p = 0.005), but this association was not as strong as that of dried blood spot TL (Steiger’s Z = 2.12, p = 0.034). TL was longer in saliva than in whole blood or DBS (p’s < 0.001).

Conclusions: These findings have important implications for future study design by supporting the validity of less-invasive methods that can be implemented with vulnerable populations or in the field. Further, these findings aid in interpreting the burgeoning area of biological aging research and may shed light on our understanding of inconsistencies in the empirical literature.

Shaping long-term primate development: Telomere length trajectory as an indicator of early maternal maltreatment and predictor of future physiologic regulation

The molecular, neurobiological, and physical health impacts of child maltreatment are well established, yet mechanistic pathways remain inadequately defined. Telomere length (TL) decline is an emerging molecular indicator of stress exposure with definitive links to negative health outcomes in maltreated individuals. The multiple confounders endemic to human maltreatment research impede the identification of causal pathways. This study leverages a unique randomized, cross-foster, study design in a naturalistic translational nonhuman primate model of infant maltreatment. At birth, newborn macaques were randomly assigned to either a maltreating or a competent control mother, balancing for sex, biological mother parenting history, and social rank. Offspring TL was measured longitudinally across the first 6 months of life (infancy) from peripheral blood. Hair cortisol accumulation was also determined at 6, 12, and 18 months of age. TL decline was greater in animals randomized to maltreatment, but also interacted with biological mother group. Shorter TL at 6 months was associated with higher mean cortisol levels through 18 months (juvenile period) when controlling for relevant covariates. These results suggest that even under the equivalent social, nutritional, and environmental conditions feasible in naturalistic translational nonhuman primate models, early adverse caregiving results in lasting molecular scars that foreshadow elevated health risk and physiologic dysregulation.

Telomeres, Aging and Exercise: Guilty by Association?

Telomeres are repetitive tandem DNA sequences that cap chromosomal ends protecting genomic DNA from enzymatic degradation. Telomeres progressively shorten with cellular replication and are therefore assumed to correlate with biological and chronological age. An expanding body of evidence suggests (i) a predictable inverse association between telomere length, aging and age-related diseases and (ii) a positive association between physical activity and telomere length. Both hypotheses have garnered tremendous research attention and broad consensus; however, the evidence for each proposition is inconsistent and equivocal at best. Telomere length does not meet the basic criteria for an aging biomarker and at least 50% of key studies fail to find associations with physical activity. In this review, we address the evidence in support and refutation of the putative associations between telomere length, aging and physical activity. We finish with a brief review of plausible mechanisms and potential future research directions.

Telomere length heterogeneity in placenta revealed with high-resolution telomere length analysis

INTRODUCTION

Telomeres, are composed of tandem repeat sequences located at the ends of chromosomes and are required to maintain genomic stability. Telomeres can become shorter due to cell division and specific lifestyle factors. Critically shortened telomeres are linked to cellular dysfunction, senescence and aging. A number of studies have used low resolution techniques to assess telomere length in the placenta. In this study, we applied Single Telomere Length Analysis (STELA) which provides high-resolution chromosome specific telomere length profiles to ask whether we could obtain more detailed information on the length of individual telomeres in the placenta.

METHODS

Term placentas (37-42 weeks) were collected from women delivering at University Hospital of Wales or Royal Gwent Hospital within 2 h of delivery. Multiple telomere-length distributions were determined using STELA. Intraplacental variation of telomere length was analysed (N = 5). Telomere length distributions were compared between labouring (N = 10) and non-labouring (N = 11) participants. Finally, telomere length was compared between female (N = 17) and male (N = 20) placenta.

RESULTS

There were no significant influences of sampling site, mode of delivery or foetal sex on the telomere-length distributions obtained. The mean telomere length was 7.7 kb ranging from 5.0 kb to 11.7 kb across all samples (N = 42) and longer compared with other human tissues at birth. STELA also revealed considerable telomere length heterogeneity within samples.

CONCLUSIONS

We have shown that STELA can be used to study telomere length homeostasis in the placenta regardless of sampling site, mode of delivery and foetal sex. Moreover, as each amplicon is derived from a single telomeric molecule, from a single cell, STELA can reveal the full detail of telomere-length distributions, including telomeres within the length ranges observed in senescent cells. STELA thus provides a new tool to interrogate the relationship between telomere length and pregnancy complications linked to placental dysfunction.

Telomere length, ATM mutation status and cancer risk in Ataxia-Telangiectasia families

Recent studies have linked constitutive telomere length (TL) to aging-related diseases including cancer at different sites. ATM participates in the signaling of telomere erosion, and inherited mutations in ATM have been associated with increased risk of cancer, particularly breast cancer. The goal of this study was to investigate whether carriage of an ATM mutation and TL interplay to modify cancer risk in ataxia-telangiectasia (A-T) families.The study population consisted of 284 heterozygous ATM mutation carriers (HetAT) and 174 non-carriers (non-HetAT) from 103 A-T families. Forty-eight HetAT and 14 non-HetAT individuals had cancer, among them 25 HetAT and 6 non-HetAT were diagnosed after blood sample collection. We measured mean TL using a quantitative PCR assay and genotyped seven single-nucleotide polymorphisms (SNPs) recurrently associated with TL in large population-based studies.HetAT individuals were at increased risk of cancer (OR = 2.3, 95%CI = 1.2-4.4, P = 0.01), and particularly of breast cancer for women (OR = 2.9, 95%CI = 1.2-7.1, P = 0.02), in comparison to their non-HetAT relatives. HetAT individuals had longer telomeres than non-HetAT individuals (P = 0.0008) but TL was not associated with cancer risk, and no significant interaction was observed between ATM mutation status and TL. Furthermore, rs9257445 (ZNF311) was associated with TL in HetAT subjects and rs6060627 (BCL2L1) modified cancer risk in HetAT and non-HetAT women.Our findings suggest that carriage of an ATM mutation impacts on the age-related TL shortening and that TL per se is not related to cancer risk in ATM carriers. TL measurement alone is not a good marker for predicting cancer risk in A-T families.

Effects of water, sanitation, handwashing, and nutritional interventions on telomere length among children in a cluster-randomized controlled trial in rural Bangladesh

Background:

Shorter childhood telomere length (TL) and more rapid TL attrition are widely regarded as manifestations of stress. However, the potential effects of health interventions on child TL are unknown. We hypothesized that a water, sanitation, handwashing (WSH), and nutritional intervention would slow TL attrition during the first two years of life.

Methods:

In a trial in rural Bangladesh, we randomized geographical clusters of pregnant women into individual water treatment, sanitation, handwashing, nutrition, combined WSH, combined nutrition plus WSH (N + WSH), or control arms. We conducted a substudy enrolling children from the control arm and the N + WSH intervention arm. Participants and outcome assessors were not masked; analyses were masked. Relative TL was measured at 1 and 2 years after intervention, and the change in relative TL was reported. Analysis was intention-to-treat.

Results:

Between May 2012 and July 2013, in the overall trial, we randomized 720 geographical clusters of 5551 pregnant women to a control or an intervention arm. In this substudy, after 1 year of intervention, we assessed a total of 662 children (341 intervention and 321 control) and 713 children after 2 years of intervention (383 intervention and 330 control). Children in the intervention arm had significantly shorter relative TL compared with controls after 1 year of intervention (difference −163 base pairs (bp), p=0.001). Between years 1 and 2, TL increased in the intervention arm (+76 bp) and decreased in the controls (−23 bp) (p=0.050). After 2 years, there was no difference between the arms (p=0.305).

Conclusions:

Our unexpected finding of increased telomere attrition during the first year of life in the intervention group suggests that rapid telomere attrition during this critical period could reflect the improved growth in the intervention group, rather than accumulated stress.

Funding:

Funded by The Bill and Melinda Gates Foundation.

Clinical trial number:

NCT01590095.

Stress negatively affects health by causing changes in cells. As a result, excess stress may predispose people to fall ill more often or age faster. It is difficult to measure stress. Some studies suggest that measuring the ends of chromosomes, known as telomeres, may be one way to measure stress. Like the plastic tips on shoelaces, telomeres protect chromosomes from fraying. All peoples’ telomeres shorten over their lifetime with each cell division. Many studies show that telomeres shorten faster in people who experience more stress. When telomeres become too short, cells die faster without being replaced, and the body ages.

Most studies on telomere length have looked at adults. Few studies have looked at children early in life or asked whether there are ways to intervene to stop or reverse stress-related telomere shortening. The first two years of life are a crucial period for the developing brain and immune system, which could set children on a lifelong course toward health or disease. Young children living in low-resource settings often encounter many sources of stress, like poor nutrition, infectious diseases or violence. Studies are needed to determine if interventions in early childhood aimed at reducing some sources of stress improve telomere length or long-term health.

Now, Lin et al. show that interventions to provide safe water, sanitation, handwashing facilities, and better nutrition to children in rural Bangladesh unexpectedly shortened telomeres. As part of a larger study, pregnant women in rural Bangladesh were divided, at random, into groups. One group received a suite of interventions, which included more sanitary toilets, handwashing facilities, and nutritional supplements for their infants. Another group served as a control and did not receive this extra help. Lin et al. looked at telomere length, growth, and infections in a subset of 713 children whose mothers participated in the study.

Children who got the extra help grew faster and were less likely to get diarrhea or parasitic infections than the children in the control group. Unexpectedly, children in the intervention group had shorter telomeres at 14 months of age than the children in the control group. Lin et al. suggest that the telomere shortening in the intervention group might be a consequence of rapid growth and immune system development in the first year of life rather than resulting from biological stress. More studies are needed to ask whether telomere shortening is indeed linked to faster growth and development early in life. The strong and unexpected findings highlight how little is known about how the length of telomeres can be used to predict future health or disease. Interpreting the length of telomeres over a person’s lifetime could prove more nuanced than originally thought.

Cigarette smoking and telomere length: A systematic review of 84 studies and meta-analysis

BACKGROUND

Cigarette smoking is a risk factor for ageing-related disease, but its association with biological ageing, indicated by telomere length, is unclear.

METHODS

We systematically reviewed evidence evaluating association between smoking status and telomere length. Searches were performed in MEDLINE (Ovid) and EMBASE (Ovid) databases, combining variation of keywords "smoking" and "telomere". Data was extracted for study characteristics and estimates for association between smoking and telomere length. Quality of studies was assessed with a risk of bias score, and publication bias was assessed with a funnel plot. I2 test was used to observe heterogeneity. Meta-analysis was carried out to compare mean difference in telomere length by smoking status, and a dose-response approach was carried out for pack-years of smoking and telomere length. A sensitivity analysis was carried out to examine sources of heterogeneity.

RESULTS

A total of 84 studies were included in the review, and 30 among them were included in our meta-analysis. Potential bias was addressed in half of included studies, and there was little evidence of small study bias. Telomere length was shorter among ever smokers compared to never smokers (summary standard mean difference [SMD]: -0.11 (95% CI -0.16 to -0.07)). Similarly, shorter telomere length was found among smokers compared to non-smokers, and among current smokers compared to never or former smokers. Dose-response meta-analysis suggested an inverse trend between pack-years of smoking and telomere length. However, heterogeneity among some analyses was observed.

CONCLUSION

Shorter telomeres among ever smokers compared to those who never smoked may imply mechanisms linking tobacco smoke exposure to ageing-related disease.

Telomere length dynamics in early life: the blood-and-muscle model

Telomere length (TL) trajectories in somatic tissues during human growth and development are poorly understood. We examined a blood-and-muscle model during early life, focusing on TL trajectories in leukocytes, representing the highly proliferative hematopoietic system, and skeletal muscle, a minimally proliferative tissue. Leukocyte TL (LTL) and skeletal muscle TL (MTL) were measured in 28 fetuses and 73 children. LTL and MTL were highly variable across individuals (sd: fetal LTL = 0.72 kb, MTL = 0.72 kb; children LTL = 0.81 kb, MTL = 0.82 kb) but were highly correlated within individuals (fetuses, r = 0.76, P < 0.0001; children, r = 0.87, P < 0.0001). LTL was shorter than MTL in fetuses (10.63 vs. 11.01 kb; P = 0.0004) and children (8.46 vs. 9.40 kb; <0.0001). The LTL-MTL gap was smaller in fetuses than children. TL in children was inversely correlated with body mass index (BMI) (LTL: -0.047 ± 0.016 kb/BMI, P < 0.005; MTL: -0.037 ± 0.017 kb/BMI, P = 0.03). We conclude that variations in TL across adults and differences in TL between somatic tissues are largely established in early life. Because TL plays a significant role in aging-related diseases, insight into the factors that fashion TL in somatic tissues during early development should contribute to an understanding of the relationship of TL with these disease and longevity in humans.-Sabharwal, S., Verhulst, S., Guirguis, G., Kark, J. D., Labat, C., Roche, N. E., Martimucci, K., Patel, K., Heller, D. S., Kimura, M., Chuang, D., Chuang, A., Benetos, A., Aviv, A. Telomere length dynamics in early life: the blood-and-muscle model.

Telomere Shortening, Inflammatory Cytokines, and Anti-Cytomegalovirus Antibody Follow Distinct Age-Associated Trajectories in Humans

A number of biological parameters have been cited as hallmarks of immune aging. However, it is not clear whether these multiple biological changes are the result of common underlying aging processes and follow correlated trajectories, or whether the patterns of change for multiple parameters vary across individuals and reflect heterogeneity in the aging process. Here, we have studied parameters of immune system aging through longitudinal analysis of telomere length, inflammatory cytokines, and antibody titer to cytomegalovirus (CMV) in 465 subjects ranging in age from 21 to 88 years at the first visit, with an average of 13 years (7-19 years) follow-up. We observed a highly variable rate of change in telomere length of PBMCs with a relatively slow average rate of telomere shortening (-16 bp/year). Similarly, there were significant increases with age in vivo in three inflammation-related cytokines (interferon gamma, IL-6, and IL-10) and in anti-CMV IgG titer, which varied widely across individuals as well. We further observed positive correlative changes among different inflammatory cytokines. However, we did not find significant correlations among the rate of changes in telomere length, inflammatory cytokines, and anti-CMV IgG titers. Our findings thus reveal that age-related trajectories of telomere attrition, elevated circulating inflammatory cytokines, and anti-CMV IgG are independent and that aging individuals do not show a uniform pattern of change in these variables. Immune aging processes are complex and vary across individuals, and the use of multiple biomarkers is essential to evaluation of biological aging of the immune system.

Evaluation of telomere length in human cardiac tissues using cardiac quantitative FISH

Telomere length has been correlated with various diseases, including cardiovascular disease and cancer. The use of currently available telomere-length measurement techniques is often restricted by the requirement of a large amount of cells (Southern-based techniques) or the lack of information on individual cells or telomeres (PCR-based methods). Although several methods have been used to measure telomere length in tissues as a whole, the assessment of cell-type-specific telomere length provides valuable information on individual cell types. The development of fluorescence in situ hybridization (FISH) technologies enables the quantification of telomeres in individual chromosomes, but the use of these methods is dependent on the availability of isolated cells, which prevents their use with fixed archival samples. Here we describe an optimized quantitative FISH (Q-FISH) protocol for measuring telomere length that bypasses the previous limitations by avoiding contributions from undesired cell types. We have used this protocol on small paraffin-embedded cardiac-tissue samples. This protocol describes step-by-step procedures for tissue preparation, permeabilization, cardiac-tissue pretreatment and hybridization with a Cy3-labeled telomeric repeat complementing (CCCTAA)₃ peptide nucleic acid (PNA) probe coupled with cardiac-specific antibody staining. We also describe how to quantify telomere length by means of the fluorescence intensity and area of each telomere within individual nuclei. This protocol provides comparative cell-type-specific telomere-length measurements in relatively small human cardiac samples and offers an attractive technique to test hypotheses implicating telomere length in various cardiac pathologies. The current protocol (from tissue collection to image procurement) takes ∼28 h along with three overnight incubations. We anticipate that the protocol could be easily adapted for use on different tissue types.

Telomere length and hTERT in mania and subsequent remission

OBJECTIVE

The findings of telomere length (TL) studies in bipolar disorder (BD) are controversial. The aim of the present study was to detect TL, human telomerase reverse transcriptase (hTERT), and brain derived neurotrophic factor (BDNF) in severe mania and subsequent remission.

METHODS

Twenty-one medication-free male patients and 20 age and gender matched controls were recruited. The patients were followed in the inpatient clinic, and comparisons were made between the same patients in their remission state and controls. Patients received lithium plus antipsychotics during the follow-up period. Quantitative real-time polymerase chain reaction was performed to verify leukocyte TL and whole blood hTERT gene expression levels. Serum BDNF levels were verified by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared to controls, manic patients presented shorter telomeres (p < 0.001) whose length increased with treatment (p = 0.001). Patients in the late stages showed shorter TL than those in the early stages and controls (p < 0.001). hTERT gene expression levels were up-regulated in mania and remission compared to controls (p = 0.03 and p = 0.01, respectively). BDNF changes did not reach statistically significant levels.

CONCLUSIONS

TL and hTERT gene expression might reflect a novel aspect of BD pathophysiology and TL might represent a novel biomarker for BD staging.

Cardiac telomere length in heart development, function, and disease

Telomeres are repetitive nucleoprotein structures at chromosome ends, and a decrease in the number of these repeats, known as a reduction in telomere length (TL), triggers cellular senescence and apoptosis. Heart disease, the worldwide leading cause of death, often results from the loss of cardiac cells, which could be explained by decreases in TL. Due to the cell-specific regulation of TL, this review focuses on studies that have measured telomeres in heart cells and critically assesses the relationship between cardiac TL and heart function. There are several lines of evidence that have identified rapid changes in cardiac TL during the onset and progression of heart disease as well as at critical stages of development. There are also many factors, such as the loss of telomeric proteins, oxidative stress, and hypoxia, that decrease cardiac TL and heart function. In contrast, antioxidants, calorie restriction, and exercise can prevent both cardiac telomere attrition and the progression of heart disease. TL in the heart is also indicative of proliferative potential and could facilitate the identification of cells suitable for cardiac rejuvenation. Although these findings highlight the involvement of TL in heart function, there are important questions regarding the validity of animal models, as well as several confounding factors, that need to be considered when interpreting results and planning future research. With these in mind, elucidating the telomeric mechanisms involved in heart development and the transition to disease holds promise to prevent cardiac dysfunction and potentiate regeneration after injury.

The role of epigenetics in renal ageing

An ability to separate natural ageing processes from processes specific to morbidities is required to understand the heterogeneity of age-related organ dysfunction. Mechanistic insight into how epigenetic factors regulate ageing throughout the life course, linked to a decline in renal function with ageing, is already proving to be of value in the analyses of clinical and epidemiological cohorts. Noncoding RNAs provide epigenetic regulatory circuits within the kidney, which reciprocally interact with DNA methylation processes, histone modification and chromatin. These interactions have been demonstrated to reflect the biological age and function of renal allografts. Epigenetic factors control gene expression and activity in response to environmental perturbations. They also have roles in highly conserved signalling pathways that modulate ageing, including the mTOR and insulin/insulin-like growth factor signalling pathways, and regulation of sirtuin activity. Nutrition, the gut microbiota, inflammation and environmental factors, including psychosocial and lifestyle stresses, provide potential mechanistic links between the epigenetic landscape of ageing and renal dysfunction. Approaches to modify the renal epigenome via nutritional intervention, targeting the methylome or targeting chromatin seem eminently feasible, although caution is merited owing to the potential for intergenerational and transgenerational effects.

The Association of Telomere Length in Peripheral Blood Cells with Cancer Risk: A Systematic Review and Meta-analysis of Prospective Studies

The association between telomere length (TL) in peripheral blood cells and cancer risk remains inconclusive. We carried out a meta-analysis on prospective studies. The study-specific RR estimates were first transformed to a common comparable scale and then were pooled by a random-effects model. The dataset was composed of 13,894 cases and 71,672 controls from 28 studies in 25 articles. In the comparison of the longest versus shortest third of TL, we observed a marginally positive association between longer TL and higher risk of total cancers [OR = 1.086; 95% confidence interval (CI), 0.952-1.238]. Subgroup analyses showed that the association was stronger in lung cancer (n = 3; OR = 1.690; 95% CI, 1.253-2.280), in men (n = 6; OR = 1.302; 95% CI, 1.120-1.514) and in studies with more precise methods for DNA extraction (phenol-chloroform, salting-out or magnetic bead, n = 6, OR = 1.618; 95% CI, 1.320-1.985) and TL measurement (multiplex Q-PCR, n = 8; OR = 1.439; 95% CI, 1.118-1.852). Our meta-analysis suggested longer TL in peripheral blood cells is a likely risk factor for lung cancer or cancers in men. Accurate DNA extraction and TL measurement methods make it more liable to find significant associations between TL and cancer risk and thus should be taken into consideration in future epidemiologic studies. Cancer Epidemiol Biomarkers Prev; 26(9); 1381-90. ©2017 AACR.

Telomere Length Is Associated With Cardiometabolic Factors in US Adults

Telomere length (TL) has been associated with age-related health outcomes. We investigated the relationship of TL with cardiometabolic risk profile in adult Americans. We used the National Health and Nutrition Examination Surveys for 1999 to 2002, accounting for complex sampling and survey design. Of the 8892 eligible participants, 47.8% (n = 4123) were men. Mean serum high-density lipoprotein cholesterol concentrations significantly increased across increasing TL quarters ( P = .013), and mean fat mass, fat-free mass, hemoglobin A_1c (HbA_1c), and C-reactive protein significantly decreased across increasing TL quarters (all P < .001) in men. Only HbA_1c levels significantly decreased across increasing TL quarters ( P = .041) in women. Males in the upper quarter of TL had lower (38%) odds of prevalent metabolic syndrome compared with those in the lower quarter ( P < .001). These results support the hypotheses that cardiometabolic factors are related to TL, especially in men.

Preliminary evidence that age and sex affect exercise-induced hTERT expression

The ability to repair cellular damage is reduced with aging, resulting in cellular senescence. Telomeres shorten as cells divide but the rate of telomere attrition is modulated by telomerase, an enzyme that adds nucleotides to the chromosome. Shelterin is a protein complex that acts as a negative regulator of telomerase. The aim of the present study was to investigate age-related differences in telomerase and shelterin responses to acute exercise. We hypothesized that acute exercise would stimulate an increased activity of telomerase (measured by telomerase reverse transcriptase, hTERT) without an increase in activity of shelterin (measured by telomeric repeat binding factor 2, TRF2) in both young and older individuals and that hTERT response would be attenuated in older individuals. Young (22±2y, n=11) and older (60±2y, n=8) men and women performed 30min of cycling. Blood was collected pre-exercise and 30, 60, and 90-min post-exercise. The trial induced a significant hTERT response in the cohort as a whole (p<0.05) with greater increases in the young as compared to the older group (time-by-group interaction p<0.05). As expected, TRF2 did not change in response to the trial, however older individuals had a higher TRF2 response at 60min (p<0.05). There was an unexpected sex difference, regardless of age, where men had significantly greater hTERT and TRF2 responses to the acute exercise as compared to women (p<0.05). These data support the hypothesis that aging is associated with attenuated telomerase activation in response to high-intensity exercise; however, this was only evident in men.

The Relationship Between Childhood Psychosocial Stressor Level and Telomere Length: A Meta-Analysis

This meta-analysis examined the association between the level of childhood psychosocial stressors and telomere length, an important health biomarker. The meta-analysis, including 27 samples and 16,238 participants, found a significant association of -0.08 between a higher level of childhood stressors and shorter telomere length at a mean age of 42 across studies. Moderator analyses showed a trend in the direction of effect sizes being significantly larger with shorter times between the stressors and telomere measurement. Moderator analyses showed significantly higher effect sizes for studies that used a categorical method for assessing child stressor level and for assays completed with qPCR rather than with the Southern blot method. There was no significant moderation of effect size by whether study assayed leukocytes or buccal cells, whether the study assessed child stressor level by memory-based recall versus archival records, and whether the study controlled for age, sex, or additional variables. The results, focused on childhood events, add to prior findings that perceived stress and negative emotions are associated with telomere length.

Traffic-Related Air Pollution and Telomere Length in Children and Adolescents Living in Fresno, CA: A Pilot Study

OBJECTIVE

The main objective of this pilot study was to gather preliminary information about how telomere length (TL) varies in relation to exposure to polycyclic aromatic hydrocarbons (PAHs) in children living in a highly polluted city.

METHODS

We conducted a cross-sectional study of children living in Fresno, California (n = 14). Subjects with and without asthma were selected based on their annual average PAH level in the 12-months prior to their blood draw. We measured relative telomere length from peripheral blood mononuclear cells (PBMC).

RESULTS

We found an inverse linear relationship between average PAH level and TL (R = 0.69), as well as between age and TL (R = 0.21). Asthmatics had shorter mean telomere length than non-asthmatics (TLasthmatic = 1.13, TLnon-asthmatic = 1.29).

CONCLUSIONS

These preliminary findings suggest that exposure to ambient PAH may play a role in telomere shortening.Become familiar with previous evidence suggesting that telomere length may be a biomarker of air pollution-induced cytotoxicity.Summarize the new findings on the association between polycyclic aromatic hydrocarbon (PAH) exposure and telomere length in adolescents, including those with asthma.Discuss the implications for recommendations and policies to mitigate the health and respiratory effects of traffic-related air pollution.

Biological Age Predictors

The search for reliable indicators of biological age, rather than chronological age, has been ongoing for over three decades, and until recently, largely without success. Advances in the fields of molecular biology have increased the variety of potential candidate biomarkers that may be considered as biological age predictors. In this review, we summarize current state-of-the-art findings considering six potential types of biological age predictors: epigenetic clocks, telomere length, transcriptomic predictors, proteomic predictors, metabolomics-based predictors, and composite biomarker predictors. Promising developments consider multiple combinations of these various types of predictors, which may shed light on the aging process and provide further understanding of what contributes to healthy aging. Thus far, the most promising, new biological age predictor is the epigenetic clock; however its true value as a biomarker of aging requires longitudinal confirmation.

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Telomere length is the most well studied biological age predictor, but many new predictors are emerging.

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The epigenetic clock is currently the best biological age predictor, as it correlates well with age and predicts mortality.

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The various biological age predictors tend to reflect different aspects of the aging process.

Telomeres and the natural lifespan limit in humans

An ongoing debate in demography has focused on whether the human lifespan has a maximal natural limit. Taking a mechanistic perspective, and knowing that short telomeres are associated with diminished longevity, we examined whether telomere length dynamics during adult life could set a maximal natural lifespan limit. We define leukocyte telomere length of 5 kb as the 'telomeric brink', which denotes a high risk of imminent death. We show that a subset of adults may reach the telomeric brink within the current life expectancy and more so for a 100-year life expectancy. Thus, secular trends in life expectancy should confront a biological limit due to crossing the telomeric brink.

Effects of size at birth, childhood growth patterns and growth hormone treatment on leukocyte telomere length

BACKGROUND

Small size at birth and rapid growth in early life are associated with increased risk of cardiovascular disease in later life. Short children born small for gestational age (SGA) are treated with growth hormone (GH), inducing catch-up in length. Leukocyte telomere length (LTL) is a marker of biological age and shorter LTL is associated with increased risk of cardiovascular disease.

OBJECTIVES

To investigate whether LTL is influenced by birth size, childhood growth and long-term GH treatment.

METHODS

We analyzed LTL in 545 young adults with differences in birth size and childhood growth patterns. Previously GH-treated young adults born SGA (SGA-GH) were compared to untreated short SGA (SGA-S), SGA with spontaneous catch-up to a normal body size (SGA-CU), and appropriate for gestational age with a normal body size (AGA-NS). LTL was measured using a quantitative PCR assay.

RESULTS

We found a positive association between birth length and LTL (p = 0.04), and a trend towards a positive association between birth weight and LTL (p = 0.08), after adjustments for gender, age, gestational age and adult body size. Weight gain during infancy and childhood and fat mass percentage were not associated with LTL. Female gender and gestational age were positively associated with LTL, and smoking negatively. After adjustments for gender, age and gestational age, SGA-GH had a similar LTL as SGA-S (p = 0.11), SGA-CU (p = 0.80), and AGA-NS (p = 0.30).

CONCLUSIONS

Larger size at birth is positively associated with LTL in young adulthood. Growth patterns during infancy and childhood are not associated with LTL. Previously GH-treated young adults born SGA have similar LTL as untreated short SGA, SGA with spontaneous catch-up and AGA born controls, indicating no adverse effects of GH-induced catch-up in height on LTL.

Telomere length and incident atrial fibrillation - data of the PREVEND cohort

BACKGROUND

The incidence of atrial fibrillation (AF) increases with age. Telomere length is considered a marker of biological ageing. We investigated the association between leukocyte telomere length and incident AF in the Dutch Prevention of Renal and Vascular End-stage Disease (PREVEND) study.

METHODS

We included 7775 individuals without prevalent AF, and with leukocyte telomere length measured. Mean telomere length was determined by a monochrome multiplex quantitative polymerase chain reaction-based assay.

RESULTS

Mean age of our cohort was 49±13 years, and 50% were men. During a mean follow-up of 11.4±2.9 years incident AF was detected in 367 (4.7%) individuals. Telomere length was shorter in individuals developing incident AF compared to those without AF (p = 0.013). Incident AF was inversely related to the telomere length. In the quartile with the longest telomere length 68 (3.5%) individuals developed AF, in the shortest telomere length quartile 100 (5.1%) individuals (p = 0.032). Telomere length was associated with incident AF in the second shortest telomere length quartile using the longest telomere length quartile as reference (hazard ratio 1.64; 95% CI 1.02-2.66; p = 0.043). After including age or AF risk factors, the relation between telomere length and incident AF was no longer significant. We found a significant interaction of age, male sex, systolic blood pressure, BMI, heart failure, and myocardial infarction with telomere length for the association with incident AF.

CONCLUSIONS

We found that shorter leukocyte telomere length is not independently associated with incident AF in a community-based cohort.

Leukocyte telomere length: Effects of schizophrenia, age, and gender

BACKGROUND

Schizophrenia is linked with early medical comorbidity and mortality. These observations indicate possible "accelerated biological aging" in schizophrenia, although prior findings are mixed, and few such studies have examined the role of gender. One putative marker of biological aging is leukocyte telomere length (LTL), which typically shortens with age.

METHODS

We assessed LTL in phenotypically well characterized 134 individuals with schizophrenia (60 women and 74 men) and 123 healthy comparison subjects (HCs) (66 women and 57 men), aged 26 to 65 years.

RESULTS

Overall, LTL was inversely associated with age (t(249) = -6.2, p < 0.001), and a gender effect on the rate of LTL decrease with age was found (t(249) = 2.20, p = 0.029), with men declining more rapidly than women. No significant overall effect of diagnosis on the rate of decline was detected. However, at the average sample age (48 years), there was a significant gender effect in both schizophrenia and HC groups (t(249) = 2.48, p = 0.014), with women having longer LTL than men, and a significant gender X diagnosis effect (t(249) = 2.43, p = 0.016) - at the average sample age, women with schizophrenia had shorter LTL than HC women.

DISCUSSION

Gender, not the diagnosis of schizophrenia, was the major factor involved with LTL shortening across the age range studied. We discuss the constraints of a cross-sectional design and other methodological issues, and indicate future directions. Understanding the impact of schizophrenia on biological aging will require separate evaluations in men and women.

Sex differences in leucocyte telomere length in a free-living mammal

Mounting evidence suggests that average telomere length reflects previous stress and predicts subsequent survival across vertebrate species. In humans, leucocyte telomere length (LTL) is consistently shorter during adulthood in males than in females, although the causes of this sex difference and its generality to other mammals remain unknown. Here, we measured LTL in a cross‐sectional sample of free‐living Soay sheep and found shorter telomeres in males than in females in later adulthood (>3 years of age), but not in early life. This observation was not related to sex differences in growth or parasite burden, but we did find evidence for reduced LTL associated with increased horn growth in early life in males. Variation in LTL was independent of variation in the proportions of different leucocyte cell types, which are known to differ in telomere length. Our results provide the first evidence of sex differences in LTL from a wild mammal, but longitudinal studies are now required to determine whether telomere attrition rates or selective disappearance are responsible for these observed differences.

see also the Perspective by Dantzer and Garratt

Liposome-Adenoviral hTERT-siRNA Knockdown in Fibroblasts from Keloids Reduce Telomere Length and Fibroblast Growth

Keloids, which possess invasive tumor-like behavior, have been clinically challenging to clinicians especially surgeons. Excessive extracellular matrix secreted from fibroblasts is the main histo-pathological feature of keloids. In this study, we transfected hTERT-siRNA into scar fibroblasts by liposome-adenoviral transduction in order to disrupt telomere length homeostasis and influence the cell cycle of fibroblasts. Our results showed that liposome hTERT-siRNA was able to knock down hTERT gene expression in scar fibroblasts. Moreover, the telomerase activity in hTERT-siRNA group was significantly reduced compared with the control groups. And the telomeric length of hTERT-siRNA group was significantly shortened as well. Further, flow cytometry studies and MTT assay demonstrated that apoptosis rate of fibroblasts in liposome hTERT-siRNA group significantly increased. These results indicated that the liposome-mediated hTERT gene transduction could inhibit the growth of fibroblasts in scar tissues suggesting a promising strategy of keloids treatment in the future.

Telomere Length Assessment for Prediction of Organ Transplantation Outcome. Future or Failure: A Review of the Literature

Telomeres are located at each end of eukaryotic chromosomes. Their functional role is genomic stability maintenance. The protective role of telomeres depends on various factors, including number of nucleotides repeats, telomere-binding proteins, and telomerase activity. Organ transplantation is the preferred replacement therapy in the case of chronic kidney disease and the only possibility of sustaining recipients’ life in the case of advanced liver failure. While the prevalence of acute rejection is constantly decreasing, prevention of transplanted organ long-term function loss is still challenging. It has been demonstrated that post-transplant stressors accelerate aging of the allografts manifested through telomere shortening.

The aim of this paper was to evaluate the importance of telomere length assessment for prediction of organ transplantation outcome. Literature review included the 10 most important studies regarding linkage between allograft function and telomere erosion, including 2 of our own reports.

Telomere length assessment is useful to predict organ transplantation outcome. The importance of telomere length as a prediction marker depends on the analyzed material. To obtain reliable results, both graft cells (donor material) and lymphocytes (recipient material) should be examined. In the case of kidney transplantation, assessment of telomere length in the early post-transplant period allows prediction of the long-term function of the transplanted organ. To increase the accuracy of transplantation outcome prediction, telomere length assessment should be combined with evaluation of other aging biomarkers, like CDKN2A (p16). Large-scale clinical studies regarding telomere length measurement, including genome wide association analysis introducing relevant genetic factors, are needed for the future.

Depressive Symptoms and Salivary Telomere Length in a Probability Sample of Middle-Aged and Older Adults

OBJECTIVE

To examine the association between depressive symptoms and salivary telomere length in a probability sample of middle-aged and older adults, and to evaluate age and sex as potential moderators of this association and test whether this association was incremental to potential confounds.

METHODS

Participants were 3,609 individuals from the 2008 wave of the Health and Retirement Study. Telomere length assays were performed using quantitative real-time polymerase chain reaction on DNA extracted from saliva samples. Depressive symptoms were assessed via interview, and health and lifestyle factors, traumatic life events, and neuroticism were assessed via self-report. Regression analyses were conducted to examine the associations between predictor variables and salivary telomere length.

RESULTS

After adjusting for demographics, depressive symptoms were negatively associated with salivary telomere length (b = -.003; p = .014). Furthermore, this association was moderated by sex (b = .005; p = .011), such that depressive symptoms were significantly and negatively associated with salivary telomere length for men (b = - .006; p < .001) but not for women (b = - .001; p = .644). The negative association between depressive symptoms and salivary telomere length in men remained statistically significant after additionally adjusting for cigarette smoking, body mass index, chronic health conditions, childhood and lifetime exposure to traumatic life events, and neuroticism.

CONCLUSIONS

Higher levels of depressive symptoms were associated with shorter salivary telomeres in men, and this association was incremental to several potential confounds. Shortened telomeres may help account for the association between depression and poor physical health and mortality.

Psychological Profiles in the Prediction of Leukocyte Telomere Length in Healthy Individuals

BACKGROUND

Shorter telomere length (TL) may signal premature cellular aging and increased risk for disease. While depression and psychosocial stress have been associated with shorter telomeres, other psychological risk factors for cardiovascular disease have received less attention.

PURPOSE

To evaluate the association between TL and psychological risk factors (symptoms of anxiety and depression, hostility and defensiveness traits) for heart disease, and to examine whether chronological age and sex moderate the associations observed.

METHODS

132 healthy men and women (Mage = 45.34 years) completed the Marlowe-Crowne Social Desirability Scale, the Beck Depression Inventory II, The Beck Anxiety Inventory and the Cook-Medley Hostility Scale. Relative TL was measured by quantitative polymerase chain reaction (PCR) of total genomic DNA samples. A series of hierarchical linear regressions were performed controlling for pertinent covariates.

RESULTS

Shorter TL was observed among individuals high in defensiveness (β = -.221) and depressive symptoms (β = -.213), as well as in those with less hostility (β =.256) and anxiety (β =.220)(all Ps<.05). Psychological variables explained 19% of the variance over and above that explained by covariates (age, sex, exercise, alcohol consumption, systemic inflammation, and 24-hr mean arterial pressure). Age moderated the relation between TL and defensiveness (β =.179, p =.03). Sex did not influence any of the relations.

CONCLUSIONS

Telomere length is associated with psychological burden though the direction of effect differs depending on the psychological variables under study. Further research is needed to determine the reasons for and implications of these seemingly contradictory findings.

Age-Dependent Gender Disparities in Post Lung Transplant Survival Among Patients With Idiopathic Pulmonary Fibrosis

BACKGROUND

The influence of age and gender on survival after lung transplant in patients with idiopathic pulmonary fibrosis (IPF) is not well defined.

METHODS

The United Network for Organ Sharing database was queried to identify IPF patients receiving lung transplant between 2005 and 2015.

RESULTS

There were 6,677 patients receiving lung transplant between May 2015 and June 2015 who met the inclusion criteria, predominantly males (n = 4,769, 71%). Within 1 year posttransplant, the survival curves of male and female recipients diverged, with male recipients having significantly worse survival (log-rank test p = 0.008). Univariate Cox proportional hazards regressions demonstrated no gender difference in survival below age 65 years (HR = 1.051; 95% CI = 0.945, 1.168; p = 0.362) but a significant increase in mortality hazard associated with male gender among patients age 65 years and older (HR = 1.161; 95% CI = 1.000, 1.347; p = 0.049). Multivariable Cox regression accounting for age modulation of the gender effect further demonstrated the emergence of a male disadvantage in post-transplant survival above age 65 years at transplantation.

CONCLUSIONS

In patients with IPF receiving lung transplant at greater than 65 years of age, male gender is associated with significantly increased risk for death, so referral for lung transplant in IPF should be considered early in the disease course.

Shortened telomere length in bipolar disorder: a comparison of the early and late stages of disease

Objective:

Bipolar disorder (BD) has been associated with increased rates of age-related diseases, such as type II diabetes, metabolic syndrome, osteoporosis, and cardiovascular disorders. Several biological findings have been associated with age-related disorders, including increased oxidative stress, inflammation, and telomere shortening. The objective of this study was to compare telomere length among participants with BD at early and late stages and age- and gender-matched healthy controls.

Methods:

Twenty-six euthymic subjects with BD and 34 healthy controls were recruited. Genomic DNA was extracted from peripheral blood and mean telomere length was measured using real-time quantitative polymerase chain reaction.

Results:

Telomere length was significantly shorter in both the early and late subgroups of BD subjects when compared to the respective controls (p = 0.002 and p = 0.005, respectively). The sample size prevented additional subgroup analyses, including potential effects of medication, smoking status, and lifestyle.

Conclusion:

This study is concordant with previous evidence of telomere shortening in BD, in both early and late stages of the disorder, and supports the notion of accelerated aging in BD.

Childhood Personality, Betrayal Trauma, and Leukocyte Telomere Length in Adulthood: A Lifespan Perspective on Conscientiousness and Betrayal Traumas as Predictors of a Biomarker of Cellular Aging

Conscientiousness is associated with longevity. As such, identifying the biological pathways linking personality to mortality is important. This study employs longitudinal data spanning >40 years to test prospective associations with Leukocyte Telomere Length (LTL), a potential marker of cellular aging. Because telomeres shorten over time, and are sensitive to oxidative stress, shorter LTL may reflect cumulative damage associated with negative health behaviors and past stressful events. We investigated childhood conscientiousness as a protective factor, expecting an association with longer LTL in adulthood, possibly reflecting slower LTL shortening. Potential lifespan pathways involving childhood trauma, smoking behaviors, and Body Mass Index (BMI) were explored. Childhood conscientiousness showed a small raw association with LTL (r = .08, p = .04), although this effect did not persist when controlling for age and sex. Despite this lack of a direct effect on LTL, we detected an indirect effect operating jointly through BMI and smoking. Higher rates of childhood betrayal trauma were associated with shorter LTL. Contrary to our hypothesis that conscientiousness would buffer this effect, we found evidence for an interaction with childhood betrayal traumas where the association between childhood betrayal traumas and LTL was larger for those higher on conscientiousness in childhood.

The Association Between Psychiatric Disorders and Telomere Length: A Meta-Analysis Involving 14,827 Persons

OBJECTIVE

This study examined the relationship between leukocyte telomere length (LTL), a marker of cell aging, and psychiatric disorders in adults compared with controls using meta-analytic methods.

METHODS

Data were abstracted from studies examining the relationship between LTL and adult psychiatric disorders. In addition to an overall estimate of effect size, subgroup analyses and meta-regression were performed to examine whether covariates (including psychiatric diagnoses) moderated the estimate.

RESULTS

A significant overall effect size showing LTL shortening was found across all psychiatric disorders (Hedge g = -0.50, p < .001). Subgroup analyses did not demonstrate significant differences in effect size based on individual covariates (psychiatric disorder, sex, age, or assay method). The meta-regression indicated that although type of disorder and, likely, age moderate the overall effect size, the heterogeneity between studies could not be explained by a model that included these variables as well as sex and assay method. Although not significantly different, posttraumatic stress disorder, anxiety disorders, and depressive disorders had comparatively larger effect sizes (-1.27, -0.53, and -0.55), and psychotic and bipolar disorders had comparatively smaller ones (-0.23 and -0.26).

CONCLUSIONS

We observed a robust effect size of LTL shortening for psychiatric disorders as a whole compared with controls. The results were less straightforward regarding relative differences in the strength of this association by specific disorder. Future studies should focus on mechanisms explaining accelerated cell aging with psychiatric illness, defining directions (if any) of causality and elucidating possible differences in this association between disorders.

Racial and Socioeconomic Variation in Genetic Markers of Telomere Length: A Cross-Sectional Study of U.S. Older Adults

Background

Shorter telomere length (TL) has been associated with stress and adverse socioeconomic conditions, yet U.S. blacks have longer TL than whites. The role of genetic versus environmental factors in explaining TL by race and socioeconomic position (SEP) remains unclear.

Methods

We used data from the U.S. Health and Retirement Study (N = 11,934) to test the hypothesis that there are differences in TL-associated SNPs by race and SEP. We constructed a TL polygenic risk score (PRS) and examined its association with race/ethnicity, educational attainment, assets, gender, and age.

Results

U.S. blacks were more likely to have a lower PRS for TL, as were older individuals and men. Racial differences in TL were statistically accounted for when controlling for population structure using genetic principal components. The GWAS-derived SNPs for TL, however, may not have consistent associations with TL across different racial/ethnic groups.

Conclusions

This study showed that associations of race/ethnicity with TL differed when accounting for population stratification. The role of race/ethnicity for TL remains uncertain, however, as the genetic determinants of TL may differ by race/ethnicity. Future GWAS samples should include racially diverse participants to allow for better characterization of the determinants of TL in human populations.

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Blacks, older individuals, and men are more likely to have a polygenic risk score predisposing them to longer telomeres.

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There is no association between telomere length and race/ethnicity after controlling for population structure.

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GWAS studies have not included diverse samples, and genetic associations with telomere length may differ by race/ethnicity.

Telomeres are structures that protect the ends of chromosomes from damage. Shorter telomeres may be a marker of human aging. Shorter telomeres have been associated with higher stress and lower levels of education, but U.S. blacks have longer telomeres than whites. We show that blacks, older individuals, and men have genetic markers that may predispose them to longer telomeres. After accounting for genetic population structure, there is no longer an association between telomere length and self-reported race/ethnicity. Because genetic determinants of telomere length may differ by race/ethnicity, it is critical that future genetic studies include racially/ethnically diverse populations.

Telomere length is independently associated with subclinical atherosclerosis in subjects with type 2 diabetes: a cross-sectional study

AIMS

Individuals with type 2 diabetes show shorter leukocyte telomere length (LTL) compared to people without diabetes. Reduced LTL is associated with increased carotid intima-media thickness (IMT) in healthy subjects. The aim of the study is to assess whether LTL also correlates with IMT in patients with diabetes.

METHODS

In a cohort of 104 subjects with type 2 diabetes and atherogenic dyslipidemia, we assessed anthropometric, hemodynamic and metabolic parameters. Common carotid IMT was expressed as the maximum IMT. LTL was assessed by a specific real-time PCR reaction.

RESULTS

At univariate analysis, IMT values were positively correlated with age (p < 0.001), previous history of cardiovascular events (p < 0.005), fasting plasma glucose (p < 0.01), HbA1c (p < 0.05) and negatively correlated with LTL (p < 0.05). In a multivariate model, age (p < 0.001) and LTL (p < 0.05) were the only independent predictors of maximum IMT, with an adjusted R (2) of 0.22.

CONCLUSIONS

LTL is an independent predictor of subclinical atherosclerosis pointing to a role of LTL as an early marker of vascular burden and cardiovascular disease also in type 2 diabetes.

Short telomere length and its correlation with gene mutations in myelodysplastic syndrome

Background

Telomere erosion can lead to genomic instability and cancer progression. It has been suggested that the shortest telomere, not the average telomere length (TL), is critical for cell viability. Some studies have shown shorter TL in myelodysplastic syndrome (MDS) patients but the critically short telomeres, the variability of TL within individual patient has not been evaluated. Thus, we aimed to investigate the TL of MDS patients and assessed the association of TL with recurrent genetic mutations in MDS.

Methods

We measured the TL of bone marrow nucleated cells for diagnostic samples at a single-cell level by quantitative fluorescence in situ hybridization (Q-FISH) for 58 MDS patients and analyzed the minimum, median, average, standard deviation, average of the 0th to 10th percentile TL within a patient, and the proportion of cells with TL that is shorter than the lowest 10th percentile of the normal control (NC). The correlations of TL to clinical parameters, cytogenetic results, and genetic mutations were assessed.

Results

MDS patients showed eroded telomeres and narrow distribution compared to the NC (P < 0.001, P = 0.018, respectively). Patients with mutation showed significantly lesser cells with short TL, below the lowest 10th percentile of the NC (P = 0.017), but no differences in TL were found according to mutations/cytogenetic abnormalities except for CSF3R mutation. However, those patients with a high percentage (≥80 %) of cells with short TL showed poorer overall survival (P = 0.021), and this was an independent prognostic factor, along with TP53, U2AF1 mutation, and high BM blast count (P = 0.044, 0.001, 0.004, 0.012, respectively).

Conclusions

The shortest TL, which determines the fate of the cell, was significantly shorter, and higher burden of cells with short TL were found in MDS, which correlated with poor survival, suggesting the need to measure TL in single cells by Q-FISH.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0287-9) contains supplementary material, which is available to authorized users.

Telomere Length Among Older U.S. Adults: Differences by Race/Ethnicity, Gender, and Age

OBJECTIVE

We examine race/ethnic, gender, and age differences in telomere length (TL) within a diverse, nationally representative sample of older adults.

METHOD

Data come from 5,228 White, Black, and Hispanic respondents aged 54+ in the 2008 Health and Retirement Study. TL was assayed from saliva using quantitative polymerase chain reaction (qPCR) by comparing telomere sequence copy number with a single gene copy number (T/S ratio). Linear regression was used to examine TL by race/ethnicity, gender, and age adjusting for social, economic, and health characteristics.

RESULTS

Women had longer TL than men (p < .05). Blacks ( p < .05) and Hispanics ( p < .10) had longer TL than Whites. Black women and men had the longest TL relative to other groups ( p < .05), while White men had the shortest TL ( p < .05). Black women and Hispanic men showed greater differences in TL with age.

DISCUSSION

Findings indicate social patterns in TL by race/ethnicity, gender, and age among older adults do not reflect differences observed in most population health outcomes.

Shorter telomeres in adults with Type 1 diabetes correlate with diabetes duration, but only weakly with vascular function and risk factors

OBJECTIVE

To determine if white blood cell (WBC) telomeres are shorter in Type 1 diabetes (T1D) than in subjects without diabetes (non-DB), and shorter in T1D subjects with vs. without vascular complications; and to determine associations with vascular biomarkers.

RESEARCH DESIGN AND METHODS

WBC relative telomere length (RTL) was determined by quantitative PCR in a cross-sectional study of 140 non-DB and 199 T1D adults, including 128 subjects without vascular complications (T1DNoCx) and 71 subjects with vascular complications (T1DCx). Relationships of RTL with age, T1D duration, arterial elasticity, pulse pressure and vascular risk factors were determined.

RESULTS

RTL did not differ by gender within T1D and non-DB groups. Age-adjusted RTL was shorter in T1D vs. non-DB subjects (1.48±0.03 AU vs. 1.64±0.04 AU, p=0.002), but did not differ by T1D complication status (T1DNoCX 1.50±0.04 vs. T1DCX 1.46±0.05, p=0.50), nor correlate with arterial elasticity. Univariate analysis in T1D showed RTL correlated (inversely) with age r=-0.27, p=0.0001, T1D duration r=-0.16, p=0.03, and pulse pressure (r=-0.15, p=0.04), but not with HbA1c, BP, renal function (serum creatinine, ACR, eGFR), lipids, insulin sensitivity, inflammation (CRP, CAMs) or oxidative stress (OxLDL, OxLDL/LDL-C, MPO, PON-1). Multiple regression analysis showed independent determinants of RTL were age and T1D presence (r=0.29, p<0.0001).

CONCLUSIONS

In this cross-sectional study telomeres were shorter in T1D. RTL correlated inversely with T1D duration, but did not differ by complication status and weakly correlated with pulse pressure and vascular risk factors. Only age and T1D were independent determinants of RTL. Longitudinal studies are merited.