Telomere Length: Implications for Atherogenesis

PURPOSE OF REVIEW

The purpose of the study is to explore the evidence linking telomere length with atherosclerotic ischemic disease.

RECENT FINDINGS

There has been a recent expansion in strategies for measuring telomere length, including analyzing genome sequence data and capitalizing on genomic loci that associate with telomere length. These, together with more established approaches, have been used to generate a more complete picture of telomere length relationships with ischemic disease. Whereas earlier meta-analyses suggested an association between short leukocyte telomeres and ischemic disease, several recent large population studies now provide particularly compelling data, including an association with cardiovascular mortality. In addition, whether short leukocyte telomeres might be causally related to ischemic disease has been interrogated using Mendelian randomization strategies, which point to shorter leukocyte telomeres as a determining risk factor. Importantly however, the wide, interindividual variability in telomere length still means that a single assessment of leukocyte telomere length in an individual does not reliably report on a biological aging process. In this regard, recent multi-tissue analyses of telomere length dynamics are providing both new mechanistic insights into how telomere length and shortening rates may participate in atherogenesis and risk prediction opportunities. The balance of evidence indicates that short leukocyte telomeres confer a risk for atherosclerotic cardiovascular disease. Moreover, an integrated analysis of telomere lengths in leukocytes and other tissues may provide a window into individualized telomere dynamics, raising new prospects for risk management.

Telomere Length: A Cardiovascular Biomarker and a Novel Therapeutic Target

Coronary artery disease (CAD) is a multifactorial disease with a high prevalence, particularly in developing countries. Currently, the investigation of telomeres as a potential tool for the early detection of the atherosclerotic disease seems to be a promising method. Telomeres are repetitive DNA sequences located at the extremities of chromosomes that maintain genetic stability. Telomere length (TL) has been associated with several human disorders and diseases while its attrition rate varies significantly in the population. The rate of TL shortening ranges between 20 and 50 bp and is affected by factors such as the end-replication phenomenon, oxidative stress, and other DNA-damaging agents. In this review, we delve not only into the pathophysiology of TL shortening but also into its association with cardiovascular disease and the progression of atherosclerosis. We also provide current and future treatment options based on TL and telomerase function, trying to highlight the importance of these cutting-edge developments and their clinical relevance.

Telomere length is associated with intima-media thickness in pediatric liver transplant patients: A prospective cohort study

Leukocyte telomere length (LTL) is a marker for biological age. Pediatric liver transplant recipients show a high rate of subclinical atherosclerosis, indicated by elevated intima-media thickness (IMT). We hypothesized that atherosclerosis is associated with biological age in these patients and investigated the course of LTL over time. We measured LTL from peripheral blood leukocytes by quantitative polymerase chain reaction and IMT from 97 pediatric patients after liver transplantation in a prospective cohort study. Of the patients, 71% (n = 69) had two or more assessments (total, 228 observations; median follow-up, 1.1 years). Lower LTL was associated with higher IMT (β = -0.701, p = 0.01) and higher aspartate aminotransferase (β = -0.001, p = 0.02), adjusted for age, sex, and age at transplantation. Of the patients, 45% showed decreasing LTL over time, whereas 55% exhibited stable LTL. Patients with stable LTL showed a decrease in IMT (median, -0.02 mm/year) and a decrease of tacrolimus trough levels (median, -0.08 μg/L/year). LTL is associated with IMT independent of age in pediatric liver transplant patients, suggesting that early aging contributes to the high burden of subclinical cardiovascular damage and may furthermore negatively affect the graft.

Association Between Telomere Length and Cardiovascular Risk: Pharmacological Treatments Affecting Telomeres and Telomerase Activity

Telomeres represent the ends of chromosomes, and they are composed of an extensive number of - TTAGGG nucleotide sequence repeats in humans. Telomeres prevent chromosome degradation, participate in stabilization, and regulate the DNA repair system. Inflammation and oxidative stress have been identified as important processes causing cardiovascular disease and accelerating telomere shortening rate. This review investigates the link between telomere length and pathological vascular conditions from experimental and human studies. Also, we discuss pharmacological treatments affecting telomeres and telomerase activity.

Telomere Length as a marker of biological aging: A critical review of recent literature

INTRODUCTION

Aging is characterized as a syndrome of deleterious, progressive, universal, and irreversible function changes affecting every structural and functional aspect of the organism and accompanied by a generalized increase in mortality. Although a substantial number of candidates for biomarkers of aging have been proposed, none has been validated or universally accepted. Human telomeres constitute hexameric repetitive DNA sequence nucleoprotein complexes that cap chromosome ends, regulating gene expression and modulating stress-related pathways. Telomere length (TL) shortening is observed both in cellular senescence and advanced age, leading to the investigation of TL as a biomarker for aging and a risk factor indicator for the development and progression of the most common age-related diseases.

OBJECTIVE

The present review underlines the connection between TL and the pathophysiology of the diseases associated with telomere attrition.

METHODS

We performed a structured search of the PubMed database for peer-reviewed research of the literature regarding leukocyte TL and cardiovascular diseases (CVD), more specifically stroke and heart disease, and focused on the relevant articles published during the last 5 years. We also applied Hill's criteria of causation to strengthen this association.

RESULTS

We analyzed the recent literature regarding TL length, stroke, and CVD. Although approximately one-third of the available studies support the connection, the results of different studies seem to be rather conflicting as a result of different study designs, divergent methods of TL determination, small study samples, and patient population heterogeneity. After applying Hill's criteria, we can observe that the literature conforms to them weakly, with chronology being the only Hill criterion of causality that probably cannot be contested.

CONCLUSION

The present review attempted to examine the purported relation between leukocyte TL and age-related diseases such as CVD and more specific stroke and heart disease in view of the best established, comprehensive, medical and epidemiological criteria that have characterized the focused recent relevant research. Although several recommendations have been made that may contribute significantly to the field, a call for novel technical approaches and studies is mandatory to further elucidate the possible association.

The Length of Leukocyte and Femoral Artery Telomeres in Patients with Peripheral Atherosclerosis

The length of telomeres (TLs) that protect chromosome ends may reflect the age of cells as well as the degree of genetic material damage caused by external factors. Since leukocyte telomere length is associated with cardiovascular diseases, the aim of this study was to evaluate whether leukocyte TL reflects femoral artery wall telomeres of patients with atherosclerosis and lower limb ischemia. Samples of femoral artery wall and blood were collected from 32 patients qualified to surgical revascularization. The analysis included blood and artery wall telomere length measurement and biochemical parameters. The study indicated that there was a moderate correlation between artery wall TL and leukocyte TL. Leukocyte TL was, on average, two times shorter than artery wall TL and correlated with the number of white blood cells. In turn, artery TL was impacted by total cholesterol level. The results suggest that the length of leukocyte telomeres may reflect artery wall TL and indirectly reflect the processes taking place in the artery wall in patients with atherosclerosis.

Prenatal stress enhances atherosclerosis and telomere shortening in ApoE knockout mouse offspring

Children born to women who experience stress during pregnancy have an increased risk of atherosclerosis in later life, but few animal models have explored mechanisms. To study this phenomena, timed-bred ApoE knockout mice were determined pregnant with ultrasound and randomly assigned on gestation day 8.5 to either a control (no stress) or prenatal stress (PS) group using two hours of restraint for five consecutive days. PS significantly increased plasma corticosterone levels in pregnant mice. The litters from PS mice showed increased neonatal mortality within the first week of life. Body weights (at euthanasia) of adult offspring at 25 weeks from the PS group were significantly increased compared to weights of controls. Adult offspring from these pregnancies were serially imaged with ultrasound to measure plaque thickness and were compared with plaque macro- and microscopic pathology. PS groups had increased plaques thickness by ultrasound, gross, histological evaluation and increased aortic root and valve macrophage infiltration at 25 weeks. Five-week old mice from PS group had significant decrease in mean arterial pressure, yet blood pressure normalized by 10 weeks. Since prenatal stress induced increased atherosclerosis, and telomeres are susceptible to stress, aortas from 10 week old mice were compared for telomere lengths and were found to be significantly shorter in PS mice compared to control mice. These studies support future investigation of how stress impacts telomere shortening in animal models and human aortas. This model could be further utilized to investigate the role of prenatal stress, telomere biology and atherosclerosis pathogenesis in adults.

Pathophysiology of Circulating Biomarkers and Relationship With Vascular Aging: A Review of the Literature From VascAgeNet Group on Circulating Biomarkers, European Cooperation in Science and Technology Action 18216

Impairment of the arteries is a product of sustained exposure to various deleterious factors and progresses with time; a phenomenon inherent to vascular aging. Oxidative stress, inflammation, the accumulation of harmful agents in high cardiovascular risk conditions, changes to the extracellular matrix, and/or alterations of the epigenetic modification of molecules, are all vital pathophysiological processes proven to contribute to vascular aging, and also lead to changes in levels of associated circulating molecules. Many of these molecules are consequently recognized as markers of vascular impairment and accelerated vascular aging in clinical and research settings, however, for these molecules to be classified as biomarkers of vascular aging, further criteria must be met. In this paper, we conducted a scoping literature review identifying thirty of the most important, and eight less important, biomarkers of vascular aging. Herein, we overview a selection of the most important molecules connected with the above-mentioned pathological conditions and study their usefulness as circulating biomarkers of vascular aging.

The relationship between telomere length and putative markers of vascular ageing: A systematic review and meta-analysis

Accelerated biological aging contributes to the evolution of cardiovascular disease. However, its influence on subclinical organ damage remains unclear. Leukocyte telomere length (LTL) is emerging as a marker of biological cardiovascular aging. We performed a systematic review and meta-analysis to assess the association between LTL and measures of end-organ damage. PubMed, Medline, Embase, Cinahl Plus, ClinicalTrials.gov, and grey literature databases were searched for studies that assessed the association of LTL with arterial pulse wave velocity (aPWV), carotid intima-media thickness (cIMT), left ventricular mass (LVM or LVMI), renal outcomes, coronary artery calcium (CAC) and presence of carotid plaques. In a sample of 7256 patients, we found that cIMT (pooled correlation coefficient (r) = -0.249; 95 %CI -0.37, -0.128) and aPWV (pooled r = -0.194; 95 % CI -0.290, -0.100) inversely correlate with LTL. Compared to aPWV, cIMT had a stronger correlation with LTL. Patients without carotid plaques had longer telomeres than patients with carotid plaques. Quantitative analyses documented LTL association with renal outcomes and CAC, but not with LVM/LVMI. Among measures of end-organ damage, cIMT and aPWV provide the most accurate information on the contribution of biological aging to the process of vascular remodeling/damage.

Progression of Early Subclinical Atherosclerosis (PESA) Study: JACC Focus Seminar 7/8

Atherosclerosis starts early in life and progresses silently for decades. Considering atherosclerosis as a "systemic disease" invites the use of noninvasive methodologies to detect disease in various regions before symptoms appear. The PESA-(Progression of Early Subclinical Atherosclerosis) CNIC-SANTANDER study is an ongoing prospective cohort study examining imaging, biological, and behavioral parameters associated with the presence and progression of early subclinical atherosclerosis. Between 2010 and 2014, PESA enrolled 4,184 asymptomatic middle-aged participants who undergo serial 3-yearly follow-up examinations including clinical interviews, lifestyle questionnaires, sampling, and noninvasive imaging assessment of multiterritorial subclinical atherosclerosis (carotids, iliofemorals, aorta, and coronaries). PESA tracks the trajectories of atherosclerosis and associated disorders from early stages to the transition to symptomatic phases. A joint venture between the CNIC and the Santander Bank, PESA is expected to run until at least 2029, and its significant contributions to date are presented in this review paper.

Telomere Length and Oxidative Stress in Patients with ST-Segment Elevation and Non-ST-Segment Elevation Myocardial Infarction

PURPOSE

The telomere length is shown to act as a biomarker, especially for biological aging and cardiovascular diseases, and it is also suggested that with this correlation, increased exposure to the oxidative stress accelerates the vascular aging process. Therefore, this study aims to understand the correlation between the plasma oxidative stress index (OSI) status and leukocyte telomere length (LTL) and cardiologic parameters between the ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) groups.

METHOD

One hundred one newly diagnosed patients with STEMI (n = 55) and NSTEMI (n = 46) were included in the study, along with 100 healthy controls who matched the patients in terms of age and gender. Plasma total antioxidant status (TAS), total oxidant status (TOS), and LTL were measured.

RESULTS

When LTL, TAS, TOS, and OSI values were evaluated between the patient and control group, OSI (p = 0.000) and LTL (p = 0.05) values were statistically significant in the patient group compared to the control group. Evaluation was conducted to understand whether there is a difference between the STEMI and NSTEMI groups. The plasma OSI (p = 0.007) and LTL (p = 0.05) were found to be significantly lower in STEMI patients. However, LTL and OSI results were not statistically significant in NSTEMI patients.

CONCLUSION

This is the first study evaluating telomere length and oxidative stress in STEMI and NSTEMI patients in Turkey. Our results support the existence of short telomere length in STEMI patients. Future studies on telomere length and oxidative stress will support the importance of our findings.

Telomeres and telomerase in risk assessment of cardiovascular diseases

Telomeres are repetitive nucleoprotein structures located at the ends of chromosomes. Reduction in the number of repetitions causes cell senescence. Cells with high proliferative potential age with each replication cycle. Post-mitotic cells (e.g. cardiovascular cells) have a different aging mechanism. During the aging of cardiovascular system cells, permanent DNA damage occurs in the telomeric regions caused by mitochondrial dysfunction, which is a phenomenon independent of cell proliferation and telomere length. Mitochondrial dysfunction is accompanied by increased production of reactive oxygen species and development of inflammation. This phenomenon in the cells of blood vessels can lead to atherosclerosis development. Telomere damage in cardiomyocytes leads to the activation of the DNA damage response system, histone H2A.X phosphorylation, p53 activation and p21 and p16 protein synthesis, resulting in the SASP phenotype (senescence-associated secretory phenotype), increased inflammation and cardiac dysfunction. Cardiovascular cells show the activity of the TERT subunit of telomerase, an enzyme that prevents telomere shortening. It turns out that disrupting the activity of this enzyme can also contribute to the formation of cardiovascular diseases. Measurements of telomere length according to the "blood-muscle" model may help in the future to assess the risk of cardiovascular complications in people undergoing cardiological procedures, as well as to assess the effectiveness of some drugs.

Leukocyte telomere length is associated with iron overload in male adults with hereditary hemochromatosis

Background: Hereditary hemochromatosis (HH) is a primary iron overload (IO) condition. Absolute telomere length (ATL) is a marker of cellular aging and DNA damage associated with chronic diseases and mortality.

Aim: To evaluate the relationship between ATL and IO in patients with HH.

Methods: Cross-sectional study including 25 patients with HH: 8 with IO and 17 without IO (ferritin < 300 ng/ml) and 25 healthy controls. Inclusion criteria were: age > 18 years, male sex and HH diagnosis. Patients with diabetes or other endocrine and autoimmune diseases were excluded. ATL was measured by real-time PCR.

Results: HH patients with IO were older (P<0.001) and showed higher ferritin concentration (P<0.001). Patients with HH, disregarding the iron status, showed higher glucose and body mass index (BMI) than controls (both P<0.01). ATL was shorter in patients with IO than controls [with IO: 8 (6–14), without IO: 13 (9–20), and controls: 19 (15–25) kilobase pairs, P<0.01]; with a linear trend within groups (P for trend <0.01). Differences in ATL remained statistically significant after adjusting by age, BMI and glucose (P<0.05).

Discussion: Patients with IO featured shorter ATL while patients without IO showed only mild alterations vs. controls. Screening for IO is encouraged to prevent iron-associated cellular damage and early telomere attrition.

The Importance of Telomere Shortening for Atherosclerosis and Mortality

Telomeres are the protective end caps of chromosomes and shorten with every cell division. Short telomeres are associated with older age and adverse lifestyle factors. Leucocyte telomere length (LTL) has been proposed as a biomarker of biological age. The shortening of LTL with age is the result of the end-replication problem, environmental, and lifestyle-related factors. Epidemiologic studies have shown that LTL predicts cardiovascular disease, all-cause mortality, and death from vascular causes. Age appears to be an important co-variate that explains a substantial fraction of this effect. Although it has been proposed that short telomeres promote atherosclerosis and impair the repair of vascular lesions, existing results are inconsistent. Oxidative stress and chronic inflammation can both accelerate telomere shortening. Multiple factors, including homocysteine (HCY), vitamin B6, and vitamin B12 modulate oxidative stress and inflammation through direct and indirect mechanisms. This review provides a compact overview of telomere physiology and the utility of LTL measurements in atherosclerosis and cardiovascular disease. In addition, it summarizes existing knowledge regarding the impact of oxidative stress, inflammation, HCY, and B-vitamins on telomere function.

The molecular biomarkers of vascular aging and atherosclerosis: telomere length and mitochondrial DNA4977 common deletion

Age is the dominant risk factor for the most prevalent atherosclerotic vascular diseases, including coronary artery disease, myocardial infarction, cerebrovascular disease and stroke. In human, telomere erosion and mitochondrial DNA (mtDNA) damage play a central role in the mechanisms leading to cellular aging decline. This review summarizes the most relevant findings on the role of telomere shortening and the common mtDNA⁴⁹⁷⁷ deletion in the progression and evolution of atherosclerosis by combining insight from experimental models and human clinical studies. The current evidence shows a link between telomere erosion and compromised mitochondrial function and provides a new perspective regarding their potential role as clinical biomarkers and therapeutic targets.

Leukocyte telomere length and serum polyunsaturated fatty acids, dietary habits, cardiovascular risk factors and features of myocardial infarction in elderly patients

BACKGROUND

Telomeres are non-coding sequences at the end of eukaryote chromosomes, which in complex with associated proteins serve to protect subtelomeric DNA. Telomeres shorten with each cell division, are regarded as a biomarker for aging and have also been suggested to play a role in atherosclerosis and cardiovascular disease (CVD). The aim of the present study was to explore the associations between leukocyte telomere length and serum polyunsaturated fatty acids, diet, cardiovascular risk factors and features of myocardial infarction (MI) in elderly patients.

METHODS

The material is based upon the first 299 included patients in the OMEMI trial, where patients aged 70-82 years of age are randomized to receive omega-3 supplements or corn oil (placebo) after MI. Patients were included 2-8 weeks after the index MI. DNA was extracted from whole blood, and leukocyte telomere length (LTL) was analyzed by qPCR and reported as a number relative to a reference gene. Serum long chain polyunsaturated fatty acid (LCPUFA) content was analyzed by gas chromatography. Diet was evaluated with the validated SmartDiet food frequency questionnaire. Medical records, patient interviews and clinical examination provided previous medical history and anthropometric data. Non-parametric statistical tests were used.

RESULTS

Median (25, 75 percentile) LTL was 0.55 (0.42, 0.72). Patients had a median age of 75 years, 70.2% were male and 45.2% used omega-3 supplements. There was a weak, but significant correlation between LTL and linoleic acid (r = 0.139, p = 0.017), but not with other LCPUFAs. There was a trend towards longer telomeres with a healthier diet, but this did not reach statistical significance (p = 0.073). No associations were found between LTL and CVD risk factors or features of MI.

CONCLUSIONS

In our population of elderly with a recent myocardial infarction LTL was associated with linoleic acid concentrations, but not with other LCPUFAs. Patients with a healthy diet tended to have longer telomeres. The limited associations may be due to age and the narrow age-span in our population. Further studies, designed to detect longitudinal changes should be performed to explore the role of telomeres in cardiovascular aging.

TRIAL REGISTRATION

Clinical trials no. NCT01841944, registration date April 29, 2013.

Diet-induced leukocyte telomere shortening in a baboon model for early stage atherosclerosis

Reported associations between leukocyte telomere length (LTL) attrition, diet and cardiovascular disease (CVD) are inconsistent. This study explores effects of prolonged exposure to a high cholesterol high fat (HCHF) diet on LTL in a baboon model of atherosclerosis. We measured LTL by qPCR in pedigreed baboons fed a chow (n = 105) or HCHF (n = 106) diet for 2 years, tested for effects of diet on LTL, and association between CVD risk factors and atherosclerotic lesions with LTL. Though not different at baseline, after 2 years median LTL is shorter in HCHF fed baboons (P < 0.0001). Diet predicts sex- and age-adjusted LTL and LTL attrition (P = 0.0009 and 0.0156, respectively). Serum concentrations of CVD biomarkers are associated with LTL at the 2-year endpoint and LTL accounts approximately 6% of the variance in aortic lesions (P = 0.04). Although heritable at baseline (h² = 0.27, P = 0.027) and after 2 years (h² = 0.46, P = 0.0038), baseline LTL does not predict lesion extent after 2 years. Atherogenic diet influences LTL, and LTL is a potential biomarker for early atherosclerosis. Prolonged exposure to an atherogenic diet decreases LTL and increases LTL attrition, and shortened LTL is associated with early-stage atherosclerosis in pedigreed baboons.

Telomere Length as Cardiovascular Aging Biomarker: JACC Review Topic of the Week

Telomeres shorten with age, the major risk factor for atherosclerotic cardiovascular disease (aCVD). The observation of shorter telomeres in aCVD patients thus suggested that critical telomere shortening may contribute to premature biological aging and aCVD. Therefore, telomere length often is suggested as a causal aCVD risk factor, a proposal supported by recent Mendelian randomization studies; however, epidemiological research has shown disappointingly low effect sizes. It therefore remains uncertain whether telomere shortening is a cause of aCVD or merely a consequence. The authors argue that elucidating the mechanistic foundation of these findings is essential for any possible translation of telomere biology to the clinic. Here, they critically evaluate evidence for causality in animal models and human studies, and review popular hypotheses and discuss their clinical implications. The authors identify 4 key questions that any successful mechanistic theory should address, and they discuss how atherosclerosis-associated local telomere attrition may provide the answers.

Telomere Length: A Potential Biomarker for the Risk and Prognosis of Stroke

Stroke is one of the leading causes of death and disability worldwide. Age is associated with increased risk of stroke, while telomere length shortening plays a pivotal role in the process of aging. Moreover, telomere length shortening is associated with many risk factors of stroke in addition to age. Accumulated evidence shows that short leukocyte telomere length is not only associated with stroke occurrence but also associated with post-stroke recovery in the elderly population. In this review, we aimed to summarize the association between leukocyte telomere length and stroke, and discuss that telomere length might serve as a potential biomarker to predict the risk and prognosis of stroke.

Telomere Length and Vascular Phenotypes in a Population-Based Cohort of Children and Midlife Adults

Background Telomere length has been inversely associated with cardiovascular disease in adulthood, but its relationship to preclinical cardiovascular phenotypes across the life course remains unclear. We investigated associations of telomere length with vascular structure and function in children and midlife adults. Methods and Results Population-based cross-sectional CheckPoint (Child Health CheckPoint) study of 11- to 12-year-old children and their parents, nested within the LSAC (Longitudinal Study of Australian Children). Telomere length (telomeric genomic DNA [T]/β-globin single-copy gene [S] [T/S ratio]) was measured by quantitative polymerase chain reaction from blood-derived genomic DNA. Vascular structure was assessed by carotid intima-media thickness, and vascular function was assessed by carotid-femoral pulse-wave velocity and carotid elasticity. Mean (SD) T/S ratio was 1.09 (0.55) in children (n=1206; 51% girls) and 0.81 (0.38) in adults (n=1343; 87% women). Linear regression models, adjusted for potential confounders, revealed no evidence of an association between T/S ratio and carotid intima-media thickness, carotid-femoral pulse-wave velocity, or carotid elasticity in children. In adults, longer telomeres were associated with greater carotid elasticity (0.14% per 10-mm Hg higher per unit of T/S ratio; 95% CI, 0.04%-0.2%; P=0.007), but not carotid intima-media thickness (-0.9 μm; 95% CI, -14 to 13 μm; P=0.9) or carotid-femoral pulse-wave velocity (-0.10 m/s; 95% CI, -0.3 to 0.07 m/s; P=0.2). In logistic regression analysis, telomere length did not predict poorer vascular measures at either age. Conclusions In midlife adults, but not children, there was some evidence that telomere length was associated with vascular elasticity but not thickness. Associations between telomere length and cardiovascular phenotypes may become more evident in later life, with advancing pathological changes.

Early and late childhood telomere length predict subclinical atherosclerosis at age 14 yrs. - The CardioCAPS study

INTRODUCTION

Carotid Intima Media Thickness (CIMT) is a marker of subclinical atherosclerosis, associated with cardiovascular risk in adults. Telomere length (TL) is a marker of cellular ageing. We sought to determine whether telomere length in early childhood and/or at 14-years is associated with CIMT in adolescence, in a community-based cohort study.

METHODS

118 children had TL measured at mean age 3.6-years and 165 children had TL and CIMT, measured at 14-years, from the community-based Childhood Asthma Prevention Study.

RESULTS

TL in early childhood was significantly inversely associated with CIMT at 14 years, p = 0.04. TL in teenage life was also significantly inversely associated with CIMT at 14 years, p = 0.03. This latter association was no longer significant, however, after adjusting for early life TL.

CONCLUSION

TL measured in early childhood and adolescence is significantly associated with CIMT at 14-years, suggesting that telomere length is a biological marker or even early determinant of late cardiovascular risk.

Body mass index is negatively associated with telomere length: a collaborative cross-sectional meta-analysis of 87 observational studies

Background

Even before the onset of age-related diseases, obesity might be a contributing factor to the cumulative burden of oxidative stress and chronic inflammation throughout the life course. Obesity may therefore contribute to accelerated shortening of telomeres. Consequently, obese persons are more likely to have shorter telomeres, but the association between body mass index (BMI) and leukocyte telomere length (TL) might differ across the life span and between ethnicities and sexes.

Objective

A collaborative cross-sectional meta-analysis of observational studies was conducted to investigate the associations between BMI and TL across the life span.

Design

Eighty-seven distinct study samples were included in the meta-analysis capturing data from 146,114 individuals. Study-specific age- and sex-adjusted regression coefficients were combined by using a random-effects model in which absolute [base pairs (bp)] and relative telomere to single-copy gene ratio (T/S ratio) TLs were regressed against BMI. Stratified analysis was performed by 3 age categories ("young": 18-60 y; "middle": 61-75 y; and "old": >75 y), sex, and ethnicity.

Results

Each unit increase in BMI corresponded to a -3.99 bp (95% CI: -5.17, -2.81 bp) difference in TL in the total pooled sample; among young adults, each unit increase in BMI corresponded to a -7.67 bp (95% CI: -10.03, -5.31 bp) difference. Each unit increase in BMI corresponded to a -1.58 × 10(-3) unit T/S ratio (0.16% decrease; 95% CI: -2.14 × 10(-3), -1.01 × 10(-3)) difference in age- and sex-adjusted relative TL in the total pooled sample; among young adults, each unit increase in BMI corresponded to a -2.58 × 10(-3) unit T/S ratio (0.26% decrease; 95% CI: -3.92 × 10(-3), -1.25 × 10(-3)). The associations were predominantly for the white pooled population. No sex differences were observed.

Conclusions

A higher BMI is associated with shorter telomeres, especially in younger individuals. The presently observed difference is not negligible. Meta-analyses of longitudinal studies evaluating change in body weight alongside change in TL are warranted.

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.

Leukocyte telomere length and cardiovascular disease in African Americans: The Jackson Heart Study

BACKGROUND AND AIMS

In European descent populations, shorter leukocyte telomere length (LTL) has been associated with subclinical atherosclerosis, cardiovascular disease (CVD), and mortality, while longer LTL has been associated with greater left ventricular hypertrophy. We evaluated the relationship of LTL with subclinical cardiovascular disease indices and incident clinical events and mortality in African Americans (AAs).

METHODS

Analyses were restricted to 2518 participants of the Jackson Heart Study (JHS) with LTL measured by Southern blot in baseline blood samples.

RESULTS

Adjusting for established CVD risk factors, longer LTL was significantly associated with lower prevalence of coronary artery calcification (CAC) (odds ratio (OR) = 0.810) per 1 kb increase in LTL; (95% confidence interval [CI] 0.656, 0.9998), p=0.0498). Longer LTL was also associated with higher ankle brachial index (ABI) (β = 0.023; (95% CI 0.004, 0.042), p=0.017) when comparing the highest to the lowest LTL quartile. There were no significant associations between LTL and abdominal aortic calcification, carotid intima-media thickness, or left ventricular mass. After a median follow-up of 9 years, longer LTL was associated with lower risk of incident ischemic stroke (hazard ratio (HR) 0.69 (95% CI 0.48, 0.99), p=0.044) and total mortality (HR 0.81 (95% CI 0.67, 0.97), p=0.026) in age and sex adjusted models, but these associations were no longer significant in fully adjusted models.

CONCLUSIONS

Among a community-based cohort of AAs, longer LTL was nominally associated with lower odds of CAC and increased ABI, indicative of decreased prevalence of subclinical atherosclerosis and peripheral arterial disease. These findings do not offer strong support for LTL as an independent biomarker of CVD risk in AAs.

Short Telomeres, but Not Telomere Attrition Rates, Are Associated With Carotid Atherosclerosis

Short telomeres are associated with atherosclerosis. However, the temporal relationship between atherosclerosis and telomere length is unclear. The objective of this work was to examine the temporal formation and progression of carotid atherosclerotic plaques in relation to telomere dynamics. In a longitudinal study, comprising 154 French men and women (aged 31-76 years at baseline), carotid plaques were quantified by echography, and telomere length on leucocytes was measured by Southern blots at baseline and follow-up examinations. Telomere attrition rates during the 9.5-year follow-up period were not different in individuals with plaques at both baseline and follow-up examinations (23.3±2.0 base pairs/y) than in individuals who developed plaques during the follow-up period (26.5±2.0 base pairs/y) and those without plaques at either baseline or follow-up examination (22.5±2.3 base pairs/y; P=0.79). At baseline, telomere length was associated with presence of carotid plaques (P=0.02) and with the number of regions with plaques (P=0.005). An interaction (P=0.03) between age and the presence of plaques was observed, such that the association between plaques and telomere length was more pronounced at a younger age. In conclusion, carotid atherosclerosis is not associated with increased telomere attrition during a 9.5-year follow-up period. Short telomere length is more strongly associated with early-onset than late-onset carotid atherosclerosis. Our results support the thesis that heightened telomere attrition during adult life might not explain the short telomeres observed in subjects with atherosclerotic disease. Rather, short telomeres antecedes the clinical manifestation of the disease.

Telomere Shortening, Regenerative Capacity, and Cardiovascular Outcomes

RATIONALE

Leukocyte telomere length (LTL) is a biological marker of aging, and shorter LTL is associated with adverse cardiovascular outcomes. Reduced regenerative capacity has been proposed as a mechanism. Bone marrow-derived circulating progenitor cells are involved in tissue repair and regeneration.

OBJECTIVE

Main objective of this study was to examine the relationship between LTL and progenitor cells and their impact on adverse cardiovascular outcomes.

METHODS AND RESULTS

We measured LTL by quantitative polymerase chain reaction in 566 outpatients (age: 63±9 years; 76% men) with coronary artery disease. Circulating progenitor cells were enumerated by flow cytometry. After adjustment for age, sex, race, body mass index, smoking status, and previous myocardial infarction, a shorter LTL was associated with a lower CD34⁺ cell count: for each 10% shorter LTL, CD34⁺ levels were 5.2% lower (P<0.001). After adjustment for the aforementioned factors, both short LTL (<Q1) and low CD34+ levels (<Q1) predicted adverse cardiovascular outcomes (death, myocardial infarction, coronary revascularization, or cerebrovascular events) independently of each other, with a hazard ratio of 1.8 and 95% confidence interval of 1.1 to 2.0, and a hazard ratio of 2.1 and 95% confidence interval of 1.3 to 3.0, respectively, comparing Q1 to Q2-4. Patients who had both short LTL (<Q1) and low CD34+ cell count (<Q1) had the greatest risk of adverse outcomes (hazard ratio =3.5; 95% confidence interval, 1.7-7.1).

CONCLUSIONS

Although shorter LTL is associated with decreased regenerative capacity, both LTL and circulating progenitor cell levels are independent and additive predictors of adverse cardiovascular outcomes in coronary artery disease patients. Our results suggest that both biological aging and reduced regenerative capacity contribute to cardiovascular events, independent of conventional risk factors.

The Ten-Year History of the Asklepios Study: An Interview with Professor Ernst R. Rietzschel, Primary Investigator and Leader of the Asklepios Study

The Asklepios study started 10 years ago when 2,500 subjects were screened between 2002 and 2004. And all of the 90+ publications we have for the moment are from those cross-sectional data. This is called round 1. Since 2011, in round 2, all of those patients have started to come back for a 10-year follow-up. At this moment, approximately 1,750 of those patients have been seen. The patients were followed by general practitioners (GP), and the GP again provided the information about what has happened with the medical status in the past 10 years including drug therapy: not only the drugs that they are taking at the moment were evaluated, but, because patients often use many drugs, the chronicles of drugs for major risk factors, for hypertension, lipids, contraceptives and more. Then, patients come to the study center where the same cluster of examinations are undertaken by one single doctor, Prof. Ernst R. Rietzschel and one study nurse, just like 10 years ago. Again, using a single observer at the two time frames has kept the methodology very strict.

Short leukocyte telomere length predicts incidence and progression of carotid atherosclerosis in American Indians: the Strong Heart Family Study

Short leukocyte telomere length (LTL) has been associated with atherosclerosis in cross-sectional studies, but the prospective relationship between telomere shortening and risk of developing carotid atherosclerosis has not been well-established. This study examines whether LTL at baseline predicts incidence and progression of carotid atherosclerosis in American Indians in the Strong Heart Study. The analysis included 2,819 participants who were free of overt cardiovascular disease at baseline (2001-2003) and were followed through the end of 2006-2009 (average 5.5-yr follow-up). Discrete atherosclerotic plaque was defined as focal protrusion with an arterial wall thickness ≥50% the surrounding wall. Carotid progression was defined as having a higher plaque score at the end of study follow-up compared to baseline. Associations of LTL with incidence and progression of carotid plaque were examined using Cox proportional hazard regression, adjusting for standard coronary risk factors. Compared to participants in the highest LTL tertile, those in the lowest tertile had significantly elevated risk for both incident plaque (HR, 1.49; 95% CI, 1.09–2.03) and plaque progression (HR, 1.61; 95% CI, 1.26–2.07). Our results provide initial evidence for a potential prognostic utility of LTL in risk prediction for atherosclerosis.

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.

On cross-sectional associations of leukocyte telomere length with cardiac systolic, diastolic and vascular function: the Asklepios study

BACKGROUND

Systemic telomere length has been associated with measures of diastolic function, vascular stiffness and left ventricular mass mainly in smaller, patient-specific settings and not in a general population. In this study we describe the applicability of these findings in a large, representative population.

METHODS AND RESULTS

Peripheral blood leukocyte telomere length (PBL TL) was measured using telomere restriction fragment analysis in the young to middle-aged (>2500 volunteers, ∼35 to 55 years old) Asklepios study population, free from overt cardiovascular disease. Subjects underwent extensive echocardiographic, hemodynamic and biochemical phenotyping. After adjusting for relevant confounders (age, sex, systolic blood pressure, heart rate, body mass index and use of antihypertensive drugs) we found no associations between PBL TL and left ventricular mass index (P = 0.943), ejection fraction (P = 0.933), peak systolic septal annular motion (P = 0.238), pulse wave velocity (P = 0.971) or pulse pressure (P = 0.999). In contrast, our data showed positive associations between PBL TL and parameters of LV filling: the transmitral flow early (E) to late (A) velocity ratio (E/A-ratio; P<0.001), the ratio of early (e') to late (a') mitral annular velocities (e'/a'-ratio; P = 0.012) and isovolumic relaxation time (P = 0.015). Interestingly, these associations were stronger in women than in men and were driven by associations between PBL TL and the late diastolic components (A and a').

CONCLUSIONS

In a generally healthy, young to middle-aged population, PBL TL is not related to LV mass or systolic function, but might be associated with an altered LV filling pattern, especially in women.

WITHDRAWN: Telomeres and atherosclerosis

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INTERRELATION BETWEEN CARDIOVASCULAR RISK FACTORS AND TELOMERE BIOLOGY WITH THE SIGNS OF VASCULAR AGING

Aim.To study interrelationship between cardiovascular risk factors and cellular and vascular aging processes. Material and methods. Totally 136 patients were included having no signs of cardiovascular diseases, diabetes 2nd type and receiving no drug therapy, but with one or several risk factors for cardiovascular diseases (smoking, arterial hypertension, obesity, dyslipidemia, fasting hyperglycemia). The telomere length and telomerase activity was measured by polymerase chain reaction. The thickness of intima-media complex (TIMC) and presence of atherosclerotic plaques (ASP) were measured by duplex scanning of right and left carotid arteries. Pulse wave velocity (PWV) was measured by applanation tonometry. Biochemical tests done by standard.

Results.PWV significantly correlated with age, body mass index, glycosilated hemoglobin level, fasting glycemia and telomere length. Presence of ASP and increased TIMC significantly correlated with age, body mass index, arterial hypertension, dyslipidemia.Conclusion.Increase of arterial wall stiffness and subclinical atherosclerotic disease have different causes. The level of PWV more linked with carbohydrate metabolism disorder, and TIMC and ASP are linked with lipid disorders.

Select aging biomarkers based on telomere length and chronological age to build a biological age equation

The purpose of this study is to build a biological age (BA) equation combining telomere length with chronological age (CA) and associated aging biomarkers. In total, 139 healthy volunteers were recruited from a Chinese Han cohort in Beijing. A genetic index, renal function indices, cardiovascular function indices, brain function indices, and oxidative stress and inflammation indices (C-reactive protein [CRP]) were measured and analyzed. A BA equation was proposed based on selected parameters, with terminal telomere restriction fragment (TRF) and CA as the two principal components. The selected aging markers included mitral annulus peak E anterior wall (MVEA), intima-media thickness (IMT), cystatin C (CYSC), D-dimer (DD), and digital symbol test (DST). The BA equation was: BA = −2.281TRF + 26.321CYSC + 0.025DD − 104.419MVEA + 34.863IMT − 0.265DST + 0.305CA + 26.346. To conclude, telomere length and CA as double benchmarks may be a new method to build a BA.

Lack of causal relationship between leukocyte telomere length and coronary heart disease

OBJECTIVE

To investigate the association between genetic variation in telomerase RNA component (TERC) and leukocyte telomere length (LTL) with risk of coronary heart disease (CHD).

METHODS AND RESULTS

An analysis of LTL was conducted, focusing on two SNPs in 2 community-based cohort populations comprising 3500 Chinese Han individuals. In addition, LTL ratio was determined in a case-control setting involving 4351 participants: 2211 healthy individuals and 2140 CHD patients. The association between LTL and the presence and extent of cardiovascular and cerebrovascular lesions were tested. Results confirmed the association of rs12696304 and rs16847897 with LTL in the Chinese Han population (P=1.63×10(-6) and P=1.44×10(-7), respectively). However, these SNPs confer a moderate risk for CHD but did not achieve significant threshold after multiple corrections. Decreased LTL ratio was associated with CHD (odds ratio [OR], 1.13; 95% confidence interval [CI], 1.02-1.34; P<0.01). In addition, the LTL ratio in CHD patients was related to numbers of vascular disease lesions.

CONCLUSIONS

Our results do not support a causal role of LTL for the development of CHD. However, LTL may be related to complex conditions associated with cardiovascular and cerebrovascular disease manifestations.

Homocysteine-related hTERT DNA demethylation contributes to shortened leukocyte telomere length in atherosclerosis

AIMS

Leukocyte telomere length (LTL) is shortened in patients with clinical atherosclerosis (AS). Here we aimed to explore the contribution of elevated homocysteine (Hcy) level to LTL shortening in AS patients and the underlying mechanism.

METHODS

Circulating leukocytes were collected from 197 patients with AS and 165 sex- and age-matched healthy subjects for LTL determination. mRNA expression or DNA methylation of human telomerase reverse transcriptase (hTERT) was determined by real-time PCR and methylation-specific PCR assay, respectively. We established a hyperhomocysteinemia (HHcy) mice model to confirm human results.

RESULTS

Hcy was negatively correlated with LTL shortening in AS patients (r = -0.179, p = 0.015) and controls (r = -0.146, p = 0.031). Serum folate and high-sensitivity C-reactive protein levels significantly interacted with Hcy in LTL shortening. Hcy was related to hTERT mRNA downregulation and promoter demethylation, which combined was associated with LTL shortening in AS patients. Hcy-induced LTL shortening did not differ by sites of AS lesions or infarction. Similar to clinical observations, our HHcy mice model suggested that Hcy induced DNA demethylation and downregulation of mouse TERT and further contributed to LTL shortening.

CONCLUSIONS

Elevated Hcy level induced DNA demethylation of hTERT and was closely related with hTERT downregulation, which led to LTL shortening in AS. These findings provide novel insights into an epigenetic mechanism for Hcy-related AS.

Leukocyte telomere length and coronary artery calcification in Palestinians

OBJECTIVE

Shorter leukocyte telomere length (LTL) is associated with higher incidence of coronary heart disease (CHD) and increased mortality. We examined the association of LTL with coronary artery calcification (CAC), which reflects the cumulative burden of coronary atherosclerosis, in an urban Arab sample of Palestinians, a population at high risk of CHD.

METHODS

Using a cross-sectional design, a random sample of East Jerusalem residents, comprising 250 men aged 45-77 and women aged 55-76 and free of CHD or past stroke, was drawn from the Israel national population register. LTL was measured by Southern blots. CAC was determined by 16-slice multidetector helical CT scanning using Agatston scoring. We applied multivariable logistic modeling to examine the association between sex-specific tertiles of LTL and CAC (comparing scores >100 vs. <100, and the upper third vs. the lower 2 thirds), controlling for age, sex, education and coronary risk factors.

RESULTS

CAC, evident in 65% of men and 52% of women, was strongly associated with age (sex-adjusted Spearman's rho 0.495). The multivariable-adjusted odds ratios for CAC >100 (found in 30% of men and 29% of women) were 2.92 (95% CI 1.28-6.68) and 2.29 (0.99-5.30) for the lower and mid-tertiles of LTL vs. the upper tertile, respectively (Ptrend = 0.008). Findings were similar for CAC scores in the upper tertile (Ptrend = 0.006), and persisted after the exclusion of patients with diabetes or receiving statins.

CONCLUSIONS

Shorter LTL was associated with a greater prevalence of asymptomatic coronary atherosclerosis in an urban Arab population-based sample. Mechanisms underlying this association should be sought.

Telomeres and atherosclerosis

Abstract

In humans and other multicellular organisms that have an extended lifespan, the leading causes of death are atherosclerotic cardiovascular disease and cancer. Experimental and clinical evidence indicates that these age-related disorders are linked through dysregulation of telomere homeostasis. Telomeres are DNA protein structures located at the terminal end of chromosomes and shorten with each cycle of cell replication, thereby reflecting the biological age of an organism. Critically shortened telomeres provoke cellular senescence and apoptosis, impairing the function and viability of a cell. The endothelial cells within atherosclerotic plaques have been shown to display features of cellular senescence. Studies have consistently demonstrated an association between shortened telomere length and coronary artery disease (CAD).

Several of the CAD risk factors and particularly type 2 diabetes are linked to telomere shortening and cellular senescence. Our interest in telomere biology was prompted by the high incidence of premature CAD and diabetes in a subset of our population, and the hypothesis that these conditions are premature-ageing syndromes. The assessment of telomere length may serve as a better predictor of cardiovascular risk and mortality than currently available risk markers, and anti-senescence therapy targeting the telomere complex is emerging as a new strategy in the treatment of atherosclerosis. We review the evidence linking telomere biology to atherosclerosis and discuss methods to preserve telomere length.

Telomere length in patients with systemic lupus erythematosus and its associations with carotid plaque

OBJECTIVE

To evaluate telomere length (TL) between patients with SLE and healthy controls and to test if TL is associated with carotid plaque.

METHODS

A pilot study of 154 patients with SLE and 152 controls was performed from the SOLVABLE (Study of Lupus Vascular and Bone Long-Term Endpoints) cohort. Demographic and cardiovascular disease (CVD) factors were collected at baseline. The presence or absence of plaque was evaluated by B-mode US. Genomic DNA was isolated from whole peripheral blood. TL was quantified using real-time quantitative PCR.

RESULTS

SLE women had a short TL compared with healthy controls (4.57 vs 5.44 kb, P = 0.03). SLE women showed shorter TL than controls across all age groups: <35 years (4.38 vs 6.37 kb), 35-44 years (4.52 vs 5.30 kb), 45-54 years (4.77 vs 5.68 kb) and ≥55 years (4.60 vs 4.71 kb). Among patients with SLE and carotid plaque there was a trend towards shorter TL at a younger age and it was significantly lower in the 35- to 44-year age group when compared with controls (P = 0.025). Multiple logistic regression analysis indicated a risk of carotid plaque with older age [odds ratio (OR) 1.09; 95% CI 1.06, 1.12] but not with TL (OR 1.05; 95% CI 0.97, 1.13).

CONCLUSION

SLE women had significantly shorter TL than controls. SLE women trended towards shorter TL at a younger age. When carotid plaque was identified, the younger SLE women had shorter TL. Only older age but not shorter TL was independently associated with carotid plaque. Additional studies are needed to confirm if TL is a novel biomarker for cardiovascular disease in SLE.

Telomere length in epidemiology: a biomarker of aging, age-related disease, both, or neither?

Telomeres are nucleoprotein caps flanking DNA. They are shortened by cell division and oxidative stress and are lengthened by the enzyme telomerase and DNA exchange during mitosis. Short telomeres induce cellular senescence. As an indicator of oxidative stress and senescence (2 processes thought to be fundamental to aging), telomere length is hypothesized to be a biomarker of aging. This hypothesis has been tested for more than a decade with epidemiologic study methods. In cross-sectional studies, researchers have investigated whether leukocyte telomere length (LTL) is associated with demographic, behavioral, and health variables. In prospective studies, baseline LTL has been used to predict mortality and occasionally other adverse health outcomes. Conflicting data have generated heated debate about the value of LTL as a biomarker of overall aging. In this review, we address the epidemiologic data on LTL and demonstrate that shorter LTL is associated with older age, male gender, Caucasian race, and possibly atherosclerosis; associations with other markers of health are equivocal. We discuss the reasons for discrepancy across studies, including a detailed review of methods for measuring telomere length as they apply to epidemiology. Finally, we conclude with questions about LTL as a biomarker of aging and how epidemiology can be used to answer these questions.

Telomere length variation in juvenile acute myocardial infarction

Leukocyte telomere length (LTL) provides a potential marker of biological age, closely related to the endothelial dysfunction and consequently to the atherosclerotic process. To investigate the relationship between the LTL and the risk of premature acute myocardial infarction and to evaluate the predictive value of LTL on the onset of major cardiovascular events, 199 patients from 18 to 48 years old with first diagnosis of acute myocardial infarction were enrolled and were matched with 190 controls for sex and age (± 1 year). Clinical data and coronary artery disease were evaluated at enrollment and at follow up. LTL was measured at enrollment using a quantitative PCR-based method. No significant differences were observed in LTL between cases and controls (p = 0.20) and with the presence of coronary artery disease in patients (p = 0.47). Hypercholesterolemic cases presented LTL significantly longer than cases without hypercholesterolemia (t/s: 0.82 ± 0.16 p = 0.79 and t/s norm: 0.79 ± 0.19 p = 0.01), as confirmed in multivariate regression analysis (p = 0.005, β = 0.09). Furthermore, multivariate regression analysis showed LTL significantly shorter in hypertensive cases than in normotensive cases (p = 0.04, β = -0.07). One hundred seventy-one cases (86%) ended the average follow up of 9 ± 5 years, 92 (54%) presented a major cardiovascular event. At multivariate regression analysis the LTL detected at enrollment did not represent a predictive factor of major cardiovascular events nor it significantly impacted with cumulative events. Based on present cohort of young Italian patients, the LTL did not represent a marker of acute myocardial infarction nor had a predictive role at medium term follow up.

No shorter telomeres in subjects with a family history of cardiovascular disease in the Asklepios study

OBJECTIVE

Shorter telomere length is associated with the occurrence of cardiovascular events, but the question of causality is complicated by the intertwined effects of inheritance, aging, and lifestyle factors on both telomere length and cardiovascular disease (CVD). Some studies indicated that healthy offspring of coronary artery disease patients exhibited shorter telomeres than subjects without a family history. Importantly, this result would imply that inheritance of shorter telomeres is a primary abnormality associated with an increased risk of CVD, the so-called Telomere Hypothesis of CVD. Therefore, we aimed at further validating the latter results in the large, population-representative Asklepios Study.

METHODS AND RESULTS

Peripheral blood leukocyte telomere length was measured using telomere restriction fragment analysis in the young to middle-aged (≈ 35-55 years old) Asklepios study population, free from overt CVD, and could be successfully combined with data from the Asklepios Family History Database for 2136 subjects. No shorter telomere length could be found in healthy subjects with a family history of CVD compared with those without.

CONCLUSIONS

These findings cast serious doubt on the hypothesis that telomere length is shorter in families with an increased risk of CVD and do not support the Telomere Hypothesis of CVD.

Functionality, growth and accelerated aging of tissue engineered living autologous vascular grafts

Living autologous tissue engineered vascular-grafts (TEVGs) with growth-capacity may overcome the limitations of contemporary artificial-prostheses. However, the multi-step in vitro production of TEVGs requires extensive ex vivo cell-manipulations with unknown effects on functionality and quality of TEVGs due to an accelerated biological age of the cells. Here, the impact of biological cell-age and tissue-remodeling capacity of TEVGs in relation to their clinical long-term functionality are investigated. TEVGs were implanted as pulmonary-artery (PA) replacements in juvenile sheep and followed for up to 240 weeks (∼4.5years). Telomere length and telomerase activity were compared amongst TEVGs and adjacent native tissue. Telomerase-activity of in vitro expanded autologous vascular-cells prior to seeding was <5% as compared to a leukemic cell line, indicating biological-aging associated with decreasing telomere-length with each cellular-doubling. Up to 100 weeks, the cells in the TEVGs had consistently shorter telomeres compared to the native counterpart, whereas no significant differences were detectable at 240 weeks. Computed tomography (CT) analysis demonstrated physiological wall-pressures, shear-stresses, and flow-pattern comparable to the native PA. There were no signs of degeneration detectable and continuous native-analogous growth was confirmed by vessel-volumetry. TEVGs exhibit a higher biological age compared to their native counterparts. However, despite of this tissue engineering technology related accelerated biological-aging, growth-capacity and long-term functionality was not compromised. To the contrary, extensive in-vivo remodeling processes with substantial endogenous cellular turnover appears to result in "TEVG rejuvenation" and excellent clinical performance. As these large-animal results can be extrapolated to approximately 20 human years, this study suggests long-term clinical-safety of cardiovascular in vitro tissue engineering and may contribute to safety-criteria as to first-in-man clinical-trials.

Oxidative stress-induced telomeric erosion as a mechanism underlying airborne particulate matter-related cardiovascular disease

Particulate matter (PM) pollution is responsible for hundreds of thousands of deaths worldwide, the majority due to cardiovascular disease (CVD). While many potential pathophysiological mechanisms have been proposed, there is not yet a consensus as to which are most important in causing pollution-related morbidity/mortality. Nor is there consensus regarding which specific types of PM are most likely to affect public health in this regard. One toxicological mechanism linking exposure to airborne PM with CVD outcomes is oxidative stress, a contributor to the development of CVD risk factors including atherosclerosis. Recent work suggests that accelerated shortening of telomeres and, thus, early senescence of cells may be an important pathway by which oxidative stress may accelerate biological aging and the resultant development of age-related morbidity. This pathway may explain a significant proportion of PM-related adverse health outcomes, since shortened telomeres accelerate the progression of many diseases. There is limited but consistent evidence that vehicular emissions produce oxidative stress in humans. Given that oxidative stress is associated with accelerated erosion of telomeres, and that shortened telomeres are linked with acceleration of biological ageing and greater incidence of various age-related pathology, including CVD, it is hypothesized that associations noted between certain pollution types and sources and oxidative stress may reflect a mechanism by which these pollutants result in CVD-related morbidity and mortality, namely accelerated aging via enhanced erosion of telomeres. This paper reviews the literature providing links among oxidative stress, accelerated erosion of telomeres, CVD, and specific sources and types of air pollutants. If certain PM species/sources might be responsible for adverse health outcomes via the proposed mechanism, perhaps the pathway to reducing mortality/morbidity from PM would become clearer. Not only would pollution reduction imperatives be more focused, but interventions which could reduce oxidative stress would become all the more important.

Telomere length in cardiovascular disease: new challenges in measuring this marker of cardiovascular aging

Atherosclerosis is an age-related systemic disease characterized by systemic oxidative stress and low grade chronic inflammation. Various types of leukocytes play an important role within this process. Telomeres, the ends of chromosomes, shorten during each and every cell division and have therefore been regarded as a cellular clock. Telomere dysfunction has been implicated in aging and senescence, and shorter leukocyte telomere length (LTL) has been demonstrated to predict cardiovascular disease and mortality. However, although LTL can predict cardiovascular events in population studies, a number of factors have prevented its broad use as a surrogate end point, such as serum levels of LDL cholesterol. In this article we will provide an overview of telomere biology and telomere dynamics of different leukocyte populations, and we will also discuss pitfalls in the methodology of LTL quantification, in context with landmark studies, which measured LTL in cardiovascular disease. Finally, we will attempt to critically assess and explain the shortcomings of LTL as a biomarker and identify further research avenues that require further investigation before telomere length can be implemented as an individual biomarker for cardiovascular aging. From this it becomes evident that LTL can be susceptible to methodological errors affecting longitudinal reproducibility. LTL is generally confounded at least by genetic factors, population variation and leukocyte composition.