Reflections on telomere dynamics and ageing-related diseases in humans

Shortening of the telomere length during the transition period of dairy cows in relation to biological stress

Telomere length (TL) is a recognized biomarker for ageing in multiple species. In dairy cattle, the transition period is considered a very stressful period. We hypothesized that TL shortens during this period. Holstein cows (n = 61) were followed during the transition period. Blood and milk samples were collected at - 7, 3, 6, 9, 21d relative to calving to determine concentrations of oxidative, energetic metabolic, and inflammatory markers. Average relative leukocyte TL was measured by a modified qPCR protocol 7d before and 21d after parturition. We confirmed TL attrition during the transition period (P = 0.02), as TL was 1.05 ± 0.229 (mean ± SD) before, and 0.97 ± 0.191 (mean ± SD) after parturition. Univariable analyses assessed associations between blood markers and TL shortening. Greater plasma oxidative parameters, including oxidized glutathione and glutathione peroxidase, were positively and negatively (respectively) associated with TL attrition. Higher blood α- and β-globulin were all positively associated, while IGF-1, albumin-globulin ratio and albumin were negatively associated with TL attrition. Greater serum amyloid A and haptoglobin were linked with greater TL shortening. This study reveals significant TL shortening during the transition period in dairy cows and identifies significant associations with oxidative stress, metabolic stress, and inflammation. While these associations are observed, no causality can be established. Our findings suggest the need for further research to explore the effects of transition-related stress on TL dynamics.

Association of dietary inflammatory index and systemic inflammatory markers with mortality risk in depressed adults: a mediation analysis of NHANES data

Background

Previous research has linked systemic inflammatory markers and the Dietary Inflammatory Index (DII) with depression. However, the relationship between DII and these markers, and their impact on mortality risk among depressed adults, remains underexplored. This study aims to explore the association between DII and systemic inflammatory markers and their mediating effect on mortality risk in adults with depression.

Methods

This study analyzed data from 4,981 adults with depression in the National Health and Nutrition Examination Survey (NHANES). This study quantified dietary inflammatory potential with the DII and systemic inflammation with the Systemic Immune-Inflammation Index (SII) and Systemic Inflammation Response Index (SIRI). Cox proportional hazards regression and inverse probability weighting evaluated the impact of DII, SII, and SIRI on mortality risk in depressed adults, as well as their mediating effects. Multiple linear regression analyzed the associations between DII and SII/SIRI. Restricted cubic spline analysis explored the non-linear relationship between DII and mortality risk.

Results

In adjusted regression models, DII, SII, and SIRI were significantly associated with all-cause mortality risk in depressed adults, with hazard ratios (HRs) (95% CIs) from 1.333 to 1.497 (1.051-1.233, 1.689-1.832). DII was linearly related to SII, with βs (95% CIs) from 0.001 to 0.121 (0.001-0.017, 0.001-0.224). SII significantly mediated the DII-mortality risk link, especially in males (8.07%). The DII-mortality relationship was linear (P non-linear = 0.174), with a beneficial threshold at 1.62.

Conclusion

DII and SII are associated with increased all-cause mortality risk in depressed adults. The DII-related mortality risk in depression can be partially mediated by SII, with a more pronounced effect in males.

Exercise to combat cancer: focusing on the ends

Cancer remains a leading cause of death worldwide and although prognosis and survivorship after therapy have improved significantly, current cancer treatments have long-term health consequences. For decades telomerase-mediated telomere maintenance has been an attractive anti-cancer therapeutic target due to its abundance and role in telomere maintenance, pathogenesis, and growth in neoplasms. Telomere maintenance-specific cancer therapies, however, are marred by off-target side effects that must be addressed before they reach clinical practice. Regular exercise training is associated with telomerase-mediated telomere maintenance in normal cells, which is associated with healthy aging. A single bout of endurance exercise training dynamically, but temporarily, increases TERT mRNA and telomerase activity, as well as several molecules that control genomic stability and telomere length (i.e., shelterin and TERRA). Considering the epidemiological findings and accumulating research highlighting that exercise significantly reduces the risk of many types of cancers and the anti-carcinogenic effects of exercise on tumor growth in vitro, investigating the governing molecular mechanisms of telomerase control in context with exercise and cancer may provide important new insights to explain these findings. Specifically, the molecular mechanisms controlling telomerase in both healthy cells and tumors after exercise could reveal novel therapeutic targets for tumor-specific telomere maintenance and offer important evidence that may refine current physical activity and exercise guidelines for all stages of cancer care.

Mapping the evolving trend of research on leukocyte telomere length: a text-mining study

BACKGROUND

Substantial evidence indicates that measuring leukocyte telomere length (LTL) is a useful tool that may be considered as a valuable biomarker of individual biological age, correlating with numerous chronic disorders. However, to date, there has been a lack of in-depth understanding regarding the current landscape and forthcoming developments in the LTL field. Therefore, this study aimed to utilize bibliometric methods to summarize the knowledge structure, current focus, and emerging directions in this field.

METHOD

Scientific publications on LTL spanning the period from 2000 to 2022 were acquired from the Web of Science Core Collection database. Several bibliometric tools including CiteSpace, VOSviewer, and an online website were utilized for bibliometric analysis. The primary evaluations encompassed investigating the major contributors and their collaborative relationships among countries/regions, institutions, and authors, conducting co-citation analyses of authors, journals, as well as reference, examining reference bursts, as well as performing co-occurrence analyses of keywords.

RESULTS

There are 1818 papers with 66,668 citations identified. Both the annual publication and citation counts on LTL exhibited significant upward trends. The United States emerged as the most prominent contributor, as evidenced by the greatest volume of papers and the highest H-index value. University of California San Francisco and Aviv A were identified as the most productive institution and author in this domain, respectively. Reference analysis revealed that longitudinal study and mendelian randomization study are the most concerned research method in this field recently. Keywords analysis showed that the most concerned diseases in LTL fields were aging, inflammation, cardiovascular diseases, endocrine diseases, neurological and psychiatric diseases, and cancers. In addition, the following research directions such as "COPD", "mendelian randomization", "adiposity", "colorectal cancer", "National Health and Nutrition Examination Survey (NHNES)", "telomerase reverse transcriptase", "pregnancy" have garnered increasing attention in recent times and hold the potential to evolve into research foci in the foreseeable future.

CONCLUSION

This is the first bibliometric study that provides comprehensive overview of LTL research. The findings of this study could become valuable references for investigators to explore and address the current and emerging challenges in LTL research.

Developmental origins of psycho-cardiometabolic multimorbidity in adolescence and their underlying pathways through methylation markers: a two-cohort study

Understanding the biological mechanisms behind multimorbidity patterns in adolescence is important as they may act as intermediary risk factor for long-term health. We aimed to explore relationship between prenatal exposures and adolescent's psycho-cardiometabolic intermediary traits mediated through epigenetic biomarkers, using structural equation modeling (SEM). We used data from mother-child dyads from pregnancy and adolescents at 16-17 years from two prospective cohorts: Northern Finland Birth Cohort 1986 (NFBC1986) and Raine Study from Australia. Factor analysis was applied to generate two different latent factor structures: (a) prenatal exposures and (b) adolescence psycho-cardiometabolic intermediary traits. Furthermore, three types of epigenetic biomarkers were included: (1) DNA methylation score for maternal smoking during pregnancy (DNAmMSS), (2) DNAm age estimate PhenoAge and (3) DNAm estimate for telomere length (DNAmTL). Similar factor structure was observed between both cohorts yielding three prenatal factors, namely BMI (Body Mass Index), SOP (Socio-Obstetric-Profile), and Lifestyle, and four adolescent factors: Anthropometric, Insulin-Triglycerides, Blood Pressure, and Mental health. In the SEM pathways, stronger direct effects of F1prenatal-BMI (NFBC1986 = β: 0.27; Raine = β: 0.39) and F2prenatal-SOP (β: -0.11) factors were observed on adolescent psycho-cardiometabolic multimorbidity. We observed an indirect effect of prenatal latent factors through epigenetic markers on a psycho-cardiometabolic multimorbidity factor in Raine study (P < 0.05). The present study exemplifies an evidence-based approach in two different birth cohorts to demonstrate similar composite structure of prenatal exposures and psycho-cardiometabolic traits (despite cultural, social, and genetic differences) and a common plausible pathway between them through underlying epigenetic markers.

Common DNA sequence variation influences epigenetic aging in African populations

Aging is associated with genome-wide changes in DNA methylation in humans, facilitating the development of epigenetic age prediction models. However, most of these models have been trained primarily on European-ancestry individuals, and none account for the impact of methylation quantitative trait loci (meQTL). To address these gaps, we analyzed the relationships between age, genotype, and CpG methylation in 3 understudied populations: central African Baka (n = 35), southern African ‡Khomani San (n = 52), and southern African Himba (n = 51). We find that published prediction methods yield higher mean errors in these cohorts compared to European-ancestry individuals, and find that unaccounted-for DNA sequence variation may be a significant factor underlying this loss of accuracy. We leverage information about the associations between DNA genotype and CpG methylation to develop an age predictor that is minimally influenced by meQTL, and show that this model remains accurate across a broad range of genetic backgrounds. Intriguingly, we also find that the older individuals and those exhibiting relatively lower epigenetic age acceleration in our cohorts tend to carry more epigenetic age-reducing genetic variants, suggesting a novel mechanism by which heritable factors can influence longevity.

Multiple factors influence telomere length and DNA damage in individuals environmentally exposed to a coal-burning power plant

Coal is a mixture of several chemicals, many of which have mutagenic and carcinogenic effects and are a key contributor to the global burden of mortality and disease. Previous studies suggest that coal is related to telomeric shortening in individuals occupationally exposed, however little is known about the effects of mining and burning coal on the telomeres of individuals living nearby. Therefore, the primary objective of this investigation was to assess the impact of proximity to coal power plants and coal mines on the genomic instability of individuals environmentally exposed, while also exploring potential associations with individual characteristics, oxidative stress, inflammatory responses, and the presence of inorganic elements. This study involved 80 men participants from three cities around a thermoelectric power plant and one city unexposed to coal and byproducts. DNA was extracted from peripheral blood samples obtained from each participant, and the telomeres length (TL) was assessed using quantitative real-time polymerase chain reaction (qPCR) methodology. No significant difference was observed between exposed individuals (6227 ± 2884 bp) when compared to the unexposed group (5638 ± 2452 bp). Nevertheless, TL decrease was associated with age and risk for cardiovascular disease; and longer TL was found to be linked with increased concentrations of silicon and phosphorus in blood samples. No correlations were observed between TL with comet assay (visual score), micronucleus test, oxidative stress, and inflammatory results. Additional research is required to ascertain the potential correlation between these changes and the onset of diseases and premature mortality.

Use of peptide nucleic acid probe to determine telomere dynamics in improving chromosome analysis in genetic toxicology studies

Genetic toxicology, strategically located at the intersection of genetics and toxicology, aims to demystify the complex interplay between exogenous agents and our genetic blueprint. Telomeres, the protective termini of chromosomes, play instrumental roles in cellular longevity and genetic stability. Traditionally karyotyping and fluorescence in situ hybridisation (FISH), have been indispensable tools for chromosomal analysis following exposure to genotoxic agents. However, their scope in discerning nuanced molecular dynamics is limited. Peptide Nucleic Acids (PNAs) are synthetic entities that embody characteristics of both proteins and nucleic acids and have emerged as potential game-changers. This perspective report comprehensively examines the vast potential of PNAs in genetic toxicology, with a specific emphasis on telomere research. PNAs' superior resolution and precision make them a favourable choice for genetic toxicological assessments. The integration of PNAs in contemporary analytical workflows heralds a promising evolution in genetic toxicology, potentially revolutionizing diagnostics, prognostics, and therapeutic avenues. In this timely review, we attempted to assess the limitations of current PNA-FISH methodology and recommend refinements.

Association between telomere length and Plasmodium falciparum malaria endemicity in sub-Saharan Africans

Leukocyte telomere length (LTL) varies significantly across human populations, with individuals of African ancestry having longer LTL than non-Africans. However, the genetic and environmental drivers of LTL variation in Africans remain largely unknown. We report here on the relationship between LTL, genetics, and a variety of environmental and climatic factors in ethnically diverse African adults (n = 1,818) originating from Botswana, Tanzania, Ethiopia, and Cameroon. We observe significant variation in LTL among populations, finding that the San hunter-gatherers from Botswana have the longest leukocyte telomeres and that the Fulani pastoralists from Cameroon have the shortest telomeres. Genetic factors explain ∼50% of LTL variation among individuals. Moreover, we observe a significant negative association between Plasmodium falciparum malaria endemicity and LTL while adjusting for age, sex, and genetics. Within Africa, adults from populations indigenous to areas with high malaria exposure have shorter LTL than those in populations indigenous to areas with low malaria exposure. Finally, we explore to what degree the genetic architecture underlying LTL in Africa covaries with malaria exposure.

Telomere length and cancer risk: finding Goldilocks

Telomeres are the nucleoprotein complex at chromosome ends essential in genomic stability. Baseline telomere length (TL) is determined by rare and common germline genetic variants but shortens with age and is susceptible to certain environmental exposures. Cellular senescence or apoptosis are normally triggered when telomeres reach a critically short length, but cancer cells overcome these protective mechanisms and continue to divide despite chromosomal instability. Rare germline variants in telomere maintenance genes cause exceedingly short telomeres for age (< 1st percentile) and the telomere biology disorders, which are associated with elevated risks of bone marrow failure, myelodysplastic syndrome, acute myeloid leukemia, and squamous cell carcinoma of the head/neck and anogenital regions. Long telomeres due to rare germline variants in the same or different telomere maintenance genes are associated with elevated risks of other cancers, such as chronic lymphocytic leukemia or sarcoma. Early epidemiology studies of TL in the general population lacked reproducibility but new methods, including creation of a TL polygenic score using common variants, have found longer telomeres associated with excess risks of renal cell carcinoma, glioma, lung cancer, and others. It has become clear that when it comes to TL and cancer etiology, not too short, not too long, but "just right" telomeres are important in minimizing cancer risk.

Leukocyte telomere length and sarcopenia-related traits: A bidirectional Mendelian randomization study

Accumulating evidence indicated that leukocyte telomere length (LTL) was related to sarcopenia. However, it is still not clear whether the association of changes in LTL with sarcopenia is likely to be causal, or could be explained by reverse causality. Thus, we carried on bidirectional Mendelian randomization (MR) and multivariable MR analyses to identify the causal relationship between LTL and sarcopenia-related traits. Summary-level data and independent variants used as instruments came from large genome-wide association studies of LTL (472,174 participants), appendicular lean mass (450,243 participants), low grip strength (256,523 participants), and walking pace (450,967 participants). We identified suggestive association of longer LTL with larger appendicular lean mass [odds ratio (OR) = 1.053; 95% confidence interval (CI), 1.009-1.099; P = 0.018], and causal association of longer LTL with a lower risk of low grip strength (OR = 0.915; 95% CI, 0.860-0.974; P = 0.005). In the reverse MR analysis, we also observed a positive causal association between walking pace and LTL (OR = 1.252; 95% CI, 1.121-1.397; P < 0.001). Similar results can be repeated in sensitivity analyses. While in the multivariable MR analysis, the estimate of the impact of walking pace on LTL underwent a transformation after adjusting for T2DM (OR = 1.141; 95%CI: 0.989-1.317; P = 0.070). The current MR analysis supported a causal relationship between shorter telomere length and both low muscle mass and strength. Additionally, walking pace may affect LTL through T2DM.

Ectoparasite presence and brood size manipulation interact to accelerate telomere shortening in nestling jackdaws

Early-life conditions impact fitness, but whether the combined effect of extrinsic stressors is additive or synergistic is not well known. This is a major knowledge gap because exposure to multiple stressors is frequent. Telomere dynamics may be instrumental when testing how stressors interact because many factors affect telomere shortening, and telomere shortening predicts survival. We evaluated the effect of manipulated brood size and natural infestation by the carnid fly Carnus hemapterus on nestling growth and telomere shortening of wild jackdaws (Corvus monedula). Telomere length, measured in blood using TRF, shortened on average by 264 bp, and on average, Carnus infection induced more telomere shortening. Further analyses showed that in enlarged broods, nestlings' telomeres shortened more when parasitized, while in reduced broods there was no effect of infection on telomere shortening. We conclude that there is a synergistic effect of number of siblings and Carnus infection on telomere shortening rate: blood-sucking parasites may negatively impact telomeres by increasing cell proliferation and/or physiological stress, and coping with infection may be less successful in enlarged broods with increased sibling competition. Larger nestlings had shorter telomeres independent of age, brood manipulation or infection. Growth was independent of infestation but in enlarged broods, nestlings were lighter at fledging. Our findings indicate that (i) evaluating consequences of early-life environmental conditions in isolation may not yield a full picture due to synergistic effects, and (ii) effects of environmental conditions may be cryptic, for example, on telomeres, with fitness consequences expressed beyond the temporal framework of the study.

The "telomereless" erythrocytes and telomere-length dependent erythropoiesis

Approximately 25 trillion erythrocytes (red blood cells) circulate in the bloodstream of an adult human, surpassing the number of circulating leukocytes (white blood cells) by a factor of about 1000. Moreover, the erythrocyte turnover rate accounts for approximately 76% of the turnover rate of all circulating blood cells. This simple math shows that the hematopoietic system principally spends its telomere length-dependent replicative capacity on building and maintaining the erythrocyte blood pool. Erythropoiesis (red blood cell production) is thus the principal cause of telomere shortening with age in hematopoietic cells (HCs), a conclusion that holds significant implications for linking telomere length dynamics in HCs to health and lifespan of modern humans.

Recent omics advances in hair aging biology and hair biomarkers analysis

Aging is a complex natural process that leads to a decline in physiological functions, which is visible in signs such as hair graying, thinning, and loss. Although hair graying is characterized by a loss of pigment in the hair shaft, the underlying mechanism of age-associated hair graying is not fully understood. Hair graying and loss can have a significant impact on an individual's self-esteem and self-confidence, potentially leading to mental health problems such as depression and anxiety. Omics technologies, which have applications beyond clinical medicine, have led to the discovery of candidate hair biomarkers and may provide insight into the complex biology of hair aging and identify targets for effective therapies. This review provides an up-to-date overview of recent omics discoveries, including age-associated alterations of proteins and metabolites in the hair shaft and follicle, and highlights the significance of hair aging and graying biomarker discoveries. The decline in hair follicle stem cell activity with aging decreased the regeneration capacity of hair follicles. Cellular senescence, oxidative damage and altered extracellular matrix of hair follicle constituents characterized hair follicle and hair shaft aging and graying. The review attempts to correlate the impact of endogenous and exogenous factors on hair aging. We close by discussing the main challenges and limitations of the field, defining major open questions and offering an outlook for future research.

The Shortening of Leukocyte Telomere Length Contributes to Alzheimer's Disease: Further Evidence from Late-Onset Familial and Sporadic Cases

Telomeres are structures at the ends of eukaryotic chromosomes that help maintain genomic stability. During aging, telomere length gradually shortens, producing short telomeres, which are markers of premature cellular senescence. This may contribute to age-related diseases, including Alzheimer's disease (AD), and based on this, several studies have hypothesized that telomere shortening may characterize AD. Current research, however, has been inconclusive regarding the direction of the association between leukocyte telomere length (LTL) and disease risk. We assessed the association between LTL and AD in a retrospective case-control study of a sample of 255 unrelated patients with late-onset AD (LOAD), including 120 sporadic cases and 135 with positive family history for LOAD, and a group of 279 cognitively healthy unrelated controls, who were all from Calabria, a southern Italian region. Following regression analysis, telomeres were found significantly shorter in LOAD cases than in controls (48% and 41% decrease for sporadic and familial cases, respectively; p < 0.001 for both). Interestingly, LTL was associated with disease risk independently of the presence of conventional risk factors (e.g., age, sex, MMSE scores, and the presence of the APOE-ε4 allele). Altogether, our findings lend support to the notion that LTL shortening may be an indicator of the pathogenesis of LOAD.

A Multibreed Genome-Wide Association Study for Cattle Leukocyte Telomere Length

Telomeres are terminal DNA regions of chromosomes that prevent chromosomal fusion and degradation during cell division. In cattle, leukocyte telomere length (LTL) is associated with longevity, productive lifespan, and disease susceptibility. However, the genetic basis of LTL in this species is less studied than in humans. In this study, we utilized the whole-genome resequencing data of 239 animals from 17 cattle breeds for computational leukocyte telomere length estimation and subsequent genome-wide association study of LTL. As a result, we identified 42 significant SNPs, of which eight were found in seven genes (EXOC6B, PTPRD, RPS6KC1, NSL1, AGBL1, ENSBTAG00000052188, and GPC1) when using covariates for two major breed groups (Turano-Mongolian and European). Association analysis with covariates for breed effect detected 63 SNPs, including 13 in five genes (EXOC6B, PTPRD, RPS6KC1, ENSBTAG00000040318, and NELL1). The PTPRD gene, demonstrating the top signal in analysis with breed effect, was previously associated with leukocyte telomere length in cattle and likely is involved in the mechanism of alternative lengthening of telomeres. The single nucleotide variants found could be tested for marker-assisted selection to improve telomere-length-associated traits.

Telomere DNA length regulation is influenced by seasonal temperature differences in short-lived but not in long-lived reef-building corals

Telomeres are environment-sensitive regulators of health and aging. Here,we present telomere DNA length analysis of two reef-building coral genera revealing that the long- and short-term water thermal regime is a key driver of between-colony variation across the Pacific Ocean. Notably, there are differences between the two studied genera. The telomere DNA lengths of the short-lived, more stress-sensitive Pocillopora spp. colonies were largely determined by seasonal temperature variation, whereas those of the long-lived, more stress-resistant Porites spp. colonies were insensitive to seasonal patterns, but rather influenced by past thermal anomalies. These results reveal marked differences in telomere DNA length regulation between two evolutionary distant coral genera exhibiting specific life-history traits. We propose that environmentally regulated mechanisms of telomere maintenance are linked to organismal performances, a matter of paramount importance considering the effects of climate change on health.

Compilation and functional classification of telomere length-associated genes in humans and other animal species

Telomeres are the terminal regions of chromosomes that ensure their stability while cell division. Telomere shortening initiates cellular senescence, which can lead to degeneration and atrophy of tissues, so the process is associated with a reduction in life expectancy and predisposition to a number of diseases. An accelerated rate of telomere attrition can serve as a predictor of life expectancy and health status of an individual. Telomere length is a complex phenotypic trait that is determined by many factors, including the genetic ones. Numerous studies (including genome-wide association studies, GWAS) indicate the polygenic nature of telomere length control. The objective of the present study was to characterize the genetic basis of the telomere length regulation using the GWAS data obtained during the studies of various human and other animal populations. To do so, a compilation of the genes associated with telomere length in GWAS experiments was collected, which included information on 270 human genes, as well as 23, 22, and 9 genes identified in the cattle, sparrow, and nematode, respectively. Among them were two orthologous genes encoding a shelterin protein (POT1 in humans and pot-2 in C. elegans). Functional analysis has shown that telomere length can be influenced by genetic variants in the genes encoding: (1) structural components of telomerase; (2) the protein components of telomeric regions (shelterin and CST complexes); (3) the proteins involved in telomerase biogenesis and regulating its activity; (4) the proteins that regulate the functional activity of the shelterin components; (5) the proteins involved in telomere replication and/or capping; (6) the proteins involved in the alternative telomere lengthening; (7) the proteins that respond to DNA damage and are responsible for DNA repair; (8) RNA-exosome components. The human genes identified by several research groups in populations of different ethnic origins are the genes encoding telomerase components such as TERC and TERT as well as STN1 encoding the CST complex component. Apparently, the polymorphic loci affecting the functions of these genes may be the most reliable susceptibility markers for telomere-related diseases. The systematized data about the genes and their functions can serve as a basis for the development of prognostic criteria for telomere length-associated diseases in humans. Information about the genes and processes that control telomere length can be used for marker-assisted and genomic selection in the farm animals, aimed at increasing the duration of their productive lifetime.

Is COVID-19 severity associated with telomere length? A systematic review and meta-analysis

Telomere shortening, a marker of cellular aging, has been linked to hospitalization and the severity of COVID-19. In this systematic review and meta-analysis, the mean difference in telomere length between non-severe and severe COVID-19 individuals was pooled to determine the association between short telomeres and COVID-19 severity. Relevant studies were retrieved through searches conducted in PubMed-Medline, Scopus, EMBASE, Medrxiv, Biorxiv, EuroPMC, and SSRN databases up to November 2022. Selected studies were systematically reviewed and assessed for risk of bias using AXIS tool. The standardized mean difference in telomere length between non-severe and severe COVID-19 was pooled using random-effects model. A total of thirteen studies were included in the review, out of which seven (1332 patients with the severe COVID-19 disease and 6321 patients with non-severe COVID-19) were eligible for meta-analysis. The estimated pooled mean difference in Leukocyte telomere length between severe COVID-19 and non-severe COVID-19 was 0.39 (95% CI - 0.02 to 0.81, I² = 93.5%) with substantial heterogeneity. Our findings do not provide clear evidence for association of shorter telomere length and severe COVID-19 disease. More extensive studies measuring absolute telomere length with age and gender adjustments are needed to draw definitive conclusions on the potential causal association between telomere shortening and COVID-19 severity.

Telomeres are shorter in wild Saccharomyces cerevisiae isolates than in domesticated ones

Telomeres are ribonucleoproteins that cap chromosome-ends and their DNA length is controlled by counteracting elongation and shortening processes. The budding yeast Saccharomyces cerevisiae has been a leading model to study telomere DNA length control and dynamics. Its telomeric DNA is maintained at a length that slightly varies between laboratory strains, but little is known about its variation at the species level. The recent publication of the genomes of over 1,000 S. cerevisiae strains enabled us to explore telomere DNA length variation at an unprecedented scale. Here, we developed a bioinformatic pipeline (YeaISTY) to estimate telomere DNA length from whole-genome sequences and applied it to the sequenced S. cerevisiae collection. Our results revealed broad natural telomere DNA length variation among the isolates. Notably, telomere DNA length is shorter in those derived from wild rather than domesticated environments. Moreover, telomere DNA length variation is associated with mitochondrial metabolism, and this association is driven by wild strains. Overall, these findings reveal broad variation in budding yeast's telomere DNA length regulation, which might be shaped by its different ecological life-styles.

Subchronic Low-Dose Methylmercury Exposure Accelerated Cerebral Telomere Shortening in Relevant with Declined Urinary aMT6s Level in Rats

Methylmercury (MeHg) is a global pollutant with established toxic effects on the central nervous system (CNS). However, early events and early-warning biomarkers of CNS damage following exposure to low-dose MeHg are still lacking. This study aimed to investigate whether subchronic low-dose MeHg exposure had adverse effects on the cerebral telomere length, as well as serum melatonin and its urinary metabolite 6-sulfatoxymelatonin (aMT6s) in rats. Sixteen male Sprague Dawley rats were divided into two groups. Group I was the control group. In group II, rats were exposed to MeHg by gavage at a dose of 0.1 mg/kg/day for 3 months. This study revealed that MeHg exposure resulted in impairment of learning and memory ability, a slightly reduced number of neurons and an irregular arrangement of neurons in the hippocampus. It also significantly accelerated telomere shortening in the cerebral cortex, hippocampus and hypothalamus. Moreover, MeHg exposure decreased the levels of melatonin in serum and aMT6s in urine, partly by suppressing the synthesis of 5-hydroxytryptamine (5-HT) in the brain but promoted the expression of melatonin-catalyzing AANAT and ASMT. Importantly, cerebral telomere length was positively correlated with MT and aMT6s after MeHg exposure. These results suggested that the shortened telomere length in the brain may be an early event in MeHg-induced CNS toxicity, and the level of aMT6s in urine may serve as an early-warning biomarker for MeHg-induced CNS damage.

Associations between prenatal multiple plasma metal exposure and newborn telomere length: Effect modification by maternal age and infant sex

Exposure to metals during pregnancy may affect maternal and infant health. However, studies on the combined effects of metals on the telomere length (TL) of newborns are limited. A prospective cohort study was conducted among 1313 mother-newborn pairs in the Guangxi Zhuang Birth Cohort. The concentrations of metals in maternal plasma during the first trimester were measured using inductively coupled plasma-mass spectrometry. We explored the associations between nine plasma metals and newborn TL using generalized linear models (GLMs), principal component analysis (PCA), quantile g-computation (qgcomp), and Bayesian kernel machine regression (BKMR). The GLMs revealed the inverse association between plasma arsenic (percent change, -5.56%; 95% CI: -7.69%, -3.38%) and barium concentrations (-9.84%; 95% CI: -13.81%, -5.68%) and newborn TL. Lead levels were related to significant decreases in newborn TL only in females. The PCA revealed a negative association between the PC3 and newborn TL (-4.52%; 95% CI: -6.34%, -2.68%). In the BKMR, the joint effect of metals was negatively associated with newborn TL. Qgcomp indicated that each one-tertile increase in metal mixture levels was associated with shorter newborn TL (-9.39%; 95% CI: -14.32%, -4.18%). The single and joint effects of multiple metals were more pronounced among pregnant women carrying female fetuses and among pregnant women <28 years of age. The finding suggests that prenatal exposure to arsenic, barium, antimony, and lead and mixed metals may shorten newborn TLs. The relationship between metal exposures and newborn TL may exhibit heterogeneities according to infant sex and maternal age.

Dyskeratosis congenita and telomere biology disorders

Numerous genetic discoveries and the advent of clinical telomere length testing have led to the recognition of a spectrum of telomere biology disorders (TBDs) beyond the classic dyskeratosis congenita (DC) triad of nail dysplasia, abnormal skin pigmentation, and oral leukoplakia occurring with pediatric bone marrow failure. Patients with DC/TBDs have very short telomeres for their age and are at high risk of bone marrow failure, cancer, pulmonary fibrosis (PF), pulmonary arteriovenous malformations, liver disease, stenosis of the urethra, esophagus, and/or lacrimal ducts, avascular necrosis of the hips and/or shoulders, and other medical problems. However, many patients with TBDs do not develop classic DC features; they may present in middle age and/or with just 1 feature, such as PF or aplastic anemia. TBD-associated clinical manifestations are progressive and attributed to aberrant telomere biology caused by the X-linked recessive, autosomal dominant, autosomal recessive, or de novo occurrence of pathogenic germline variants in at least 18 different genes. This review describes the genetics and clinical manifestations of TBDs and highlights areas in need of additional clinical and basic science research.

Within-individual repeatability in telomere length: A meta-analysis in nonmammalian vertebrates

Telomere length is increasingly used as a biomarker of long-term somatic state and future survival prospects. While most studies have overlooked this aspect, biological interpretations based on a given telomere length will benefit from considering the level of within-individual repeatability of telomere length through time. Therefore, we conducted a meta-analysis on 74 longitudinal studies in nonmammalian vertebrates, with the aim to establish the current pattern of within-individual repeatability in telomere length and to identify the methodological (e.g., qPCR/TRF) and biological factors (e.g., age class, phylogeny) that may affect it. While the median within-individual repeatability of telomere length was moderate to high (R = 0.55; 95% CI: 0.05-0.95; N = 82), marked heterogeneity between studies was evident. Measurement method affected the repeatability estimate strongly, with TRF-based studies exhibiting high repeatability (R = 0.80; 95% CI: 0.34-0.96; N = 25), while repeatability of qPCR-based studies was markedly lower and more variable (R = 0.46; 95% CI: 0.04-0.82; N = 57). While phylogeny explained some variance in repeatability, phylogenetic signal was not significant (λ = 0.32; 95% CI: 0.00-0.83). None of the biological factors investigated here significantly explained variation in the repeatability of telomere length, being potentially obscured by methodological differences. Our meta-analysis highlights the high variability in within-individual repeatability estimates between studies and the need to put more effort into separating technical and biological explanations. This is important to better understand to what extent biological factors can affect the repeatability of telomere length and thus the interpretation of telomere length data.

A meta-analysis on the heritability of vertebrate telomere length

Telomere dynamics are linked with both cellular and organismal senescence, and life history, individual quality and health. Telomere dynamics, particularly telomere length, have therefore garnered much research interest in evolutionary biology. To examine the evolution of telomere length, it is important to quantify its heritability, the proportion of total variation explained by additive genetic effects. Many studies have quantified telomere length heritability, but estimates are varied, and no general conclusion has been drawn. Additionally, it is unclear whether biological and methodological factors influence telomere length heritability estimates. We present the first meta-analysis of telomere length heritability, using 104 estimates from 43 studies over 18 vertebrate species. We calculated an overall mean heritability and examined how estimates varied by study, phylogeny, species-specific ecology, environmental setting, age at sampling, laboratory methods, statistical methods, sex and repeated measurements. Overall heritability was moderate (44.9%, 95% CI: 25.2-64.7%), and there was considerable heterogeneity in heritability estimates, in particular among studies and estimates. Laboratory method influenced heritability estimates, with in-gel hybridization TRF yielding higher heritabilities than qPCR and Southern blot TRF. There was also an effect from statistical method, with twin-based and SNP-based estimates lower than correlation-based or pedigree-based estimates. Our results highlight an overall heritable basis of telomere length, and we recommend future research on a wider range of taxa, and the use of variance-partitioning methods with relatedness or SNP data over correlation methods to minimize heritability estimation bias.

The bullwhip effect, T-cell telomeres, and SARS-CoV-2

Both myeloid cells, which contribute to innate immunity, and lymphoid cells, which dominate adaptive immunity, partake in defending against SARS-CoV-2. In response to the virus, the otherwise slow haematopoietic production supply chain quickly unleashes its preconfigured myeloid element, which largely resists a bullwhip-like effect. By contrast, the lymphoid element risks a bullwhip-like effect when it produces T cells and B cells that are specifically designed to clear the virus. As T-cell production is telomere-length dependent and telomeres shorten with age, older adults are at higher risk of a T-cell shortfall when contracting SARS-CoV-2 than are younger adults. A poorly calibrated adaptive immune response, stemming from a bullwhip-like effect, compounded by a T-cell deficit, might thus contribute to the propensity of people with inherently short T-cell telomeres to develop severe COVID-19. The immune systems of these individuals might also generate an inadequate T-cell response to anti-SARS-CoV-2 vaccination.

The Impact of Foods, Nutrients, or Dietary Patterns on Telomere Length in Childhood and Adolescence: A Systematic Review

Environmental factors such as diet can affect telomere length (TL) dynamics. However, the role that children’s and adolescents’ diets play in maintaining TL is not well understood. Thus, we conducted a systematic review to examine the association between the intake of nutrients, foods, food groups, and/or dietary patterns and TL in childhood and adolescence. Following the PRISMA guidelines, we searched MEDLINE via PubMed, Embase, and Cochrane databases and additional registers and methods. The five selected studies were cross-sectional and conducted in children and adolescents aged 2 to 18 years. The main results suggest that a higher consumption of fish, nuts and seeds, fruits and vegetables, green leafy and cruciferous vegetables, olives, legumes, polyunsaturated fatty acids, and an antioxidant-rich diet might positively affect TL. On the contrary, a higher intake of dairy products, simple sugar, sugar-sweetened beverages, cereals, especially white bread, and a diet high in glycaemic load were factors associated with TL shortening. To our knowledge, this is the first systematic review examining the impact of dietary intake factors on TL in childhood and adolescence. Although limited, these results are consistent with previous studies in different adult populations. Further research is needed to ascertain potential nutritional determinants of TL in childhood and adolescence.

Higher mercury contamination is associated with shorter telomeres in a long-lived seabird - A direct effect or a consequence of among-individual variation in phenotypic quality?

Mercury is a heavy metal, which is pervasive and persistent in the marine environment. It bioaccumulates within organisms and biomagnifies in the marine food chain. Due to its high toxicity, mercury contamination is a major concern for wildlife and human health. Telomere length is a biomarker of aging and health, because it predicts survival, making it a potential tool to investigate sublethal effects of mercury contamination. However, the relationship between telomeres and mercury contamination is unclear. We measured feather mercury concentration in Cory's Shearwaters Calonectris borealis, long-lived seabirds and top predators, between 9 and 35 years of age and related it to telomere length in erythrocytes. Cory's Shearwaters with higher mercury concentrations had shorter telomeres and the effect was sex-dependent, reaching significance in males only. This may be explained by the fact that males have longer telomeres and higher and more variable mercury concentrations than females in this population. The mercury effect on telomere length was stronger on longer telomeres in the genome within individuals. We discuss the hypotheses that the negative correlation could either be a direct effect of mercury on telomere shortening and/or a consequence of variation in phenotypic quality among individuals that results in a covariation between mercury contamination and telomere length.

Airway Aging and Methylation Disruptions in HIV-associated Chronic Obstructive Pulmonary Disease

Rationale: Age-related diseases like chronic obstructive pulmonary disease (COPD) occur at higher rates in people living with human immunodeficiency virus (PLWH) than in uninfected populations. Objectives: To identify whether accelerated aging can be observed in the airways of PLWH with COPD, manifest by a unique DNA methylation signature. Methods: Bronchial epithelial brushings from PLWH with and without COPD and HIV-uninfected adults with and without COPD (N = 76) were profiled for DNA methylation and gene expression. We evaluated global Alu and LINE-1 methylation and calculated the epigenetic age using the Horvath clock and the methylation telomere length estimator. To identify genome-wide differential DNA methylation and gene expression associated with HIV and COPD, robust linear models were used followed by an expression quantitative trait methylation (eQTM) analysis. Measurements and Main Results: Epigenetic age acceleration and shorter methylation estimates of telomere length were found in PLWH with COPD compared with PLWH without COPD and uninfected patients with and without COPD. Global hypomethylation was identified in PLWH. We identified 7,970 cytosine bases located next to a guanine base (CpG sites), 293 genes, and 9 expression quantitative trait methylation-gene pairs associated with the interaction between HIV and COPD. Actin binding LIM protein family member 3 (ABLIM3) was one of the novel candidate genes for HIV-associated COPD highlighted by our analysis. Conclusions: Methylation age acceleration is observed in the airway epithelium of PLWH with COPD, a process that may be responsible for the heightened risk of COPD in this population. Their distinct methylation profile, differing from that observed in patients with COPD alone, suggests a unique pathogenesis to HIV-associated COPD. The associations warrant further investigation to establish causality.

Telomere shortening and the transition to family caregiving in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study

Telomere length (TL) is widely studied as a possible biomarker for stress-related cellular aging and decreased longevity. There have been conflicting findings about the relationship between family caregiving stress and TL. Several initial cross-sectional studies have found associations between longer duration of caregiving or perceived stressfulness of caregiving and shortened TL, suggesting that caregiving poses grave risks to health. Previous reviews have suggested the need for longitudinal methods to investigate this topic. This study examined the association between the transition to family caregiving and change in TL across ~9 years. Data was utilized from the Caregiving Transitions Study, an ancillary study to the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. TL was assayed using qPCR and analyzed as the telomere-to-single copy gene ratio for each participant at baseline and follow-up. General linear models examined the association between caregiving status and the change in TL for 208 incident caregivers and 205 controls, as well as associations between perceived stress and TL among caregivers. No association was found between TL change and caregiving (p = 0.494), and fully adjusted models controlling for health and socioeconomic factors did not change the null relationship (p = 0.305). Among caregivers, no association was found between perceived caregiving stress and change in TL (p = 0.336). In contrast to earlier cross-sectional studies, this longitudinal, population-based study did not detect a significant relationship between the transition into a family caregiving role and changes in TL over time. Given the widespread citation of previous findings suggesting that caregiving shortens telomeres and places caregivers at risk of early mortality, these results demonstrate the potential need of a more balanced narrative about caregiving.

Association of shorter leucocyte telomere length with risk of frailty

BACKGROUND

Frailty is a multidimensional syndrome of decline that affects multiple systems and predisposes to adverse health outcomes. Although chronological age is the major risk factor, inter-individual variation in risk is not fully understood. Leucocyte telomere length (LTL), a proposed marker of biological age, has been associated with risk of many diseases. We sought to determine whether LTL is associated with risk of frailty.

METHODS

We utilized cross-sectional data from 441 781 UK Biobank participants (aged 40-69 years), with complete data on frailty indicators and LTL. Frailty was defined as the presence of at least three of five indicators: weaker grip strength, slower walking pace, weight loss in the past year, lower physical activity, and exhaustion in the past 2 weeks. LTL was measured using a validated qPCR method and reported as a ratio of the telomere repeat number (T) to a single-copy gene (S) (T/S ratio). Association of LTL with frailty was evaluated using adjusted (chronological age, sex, deprivation, smoking, alcohol intake, body mass index, and multimorbidity) multinomial and ordinal regression models, and results are presented as relative risk (RRR) or odds ratios (OR), respectively, alongside the 95% confidence interval (CI). Mendelian randomization (MR), using 131 genetic variants associated with LTL, was used to assess if the association of LTL with frailty was causal.

RESULTS

Frail participants (4.6%) were older (median age difference (95% CI): 3 (2.5; 3.5) years, P = 2.73 × 10-33 ), more likely to be female (61%, P = 1.97 × 10-129 ), and had shorter LTL (-0.13SD vs. 0.03SD, P = 5.43 × 10-111 ) than non-frail. In adjusted analyses, both age and LTL were associated with frailty (RRR = 1.03 (95% CI: 1.02; 1.04) per year of older chronological age, P = 3.99 × 10-12 ; 1.10 (1.08; 1.11) per SD shorter LTL, P = 1.46 × 10-30 ). Within each age group (40-49, 50-59, 60-69 years), the prevalence of frailty was about 33% higher in participants with shorter (-2SD) versus longer telomeres (+2SD). MR analysis showed an association of LTL with frailty that was directionally consistent with the observational association, but not statistically significant (MR-Median: OR (95% CI): 1.08 (0.98; 1.19) per SD shorter LTL, P = 0.13).

CONCLUSIONS

Inter-individual variation in LTL is associated with the risk of frailty independently of chronological age and other risk factors. Our findings provide evidence for an additional biological determinant of frailty.

Prenatal exposure to PM10 and changes in DNA methylation and telomere length in cord blood

BACKGROUND

Air pollution exposure in pregnancy can cause molecular level alterations that might influence later disease susceptibility.

OBJECTIVES

We investigated DNA methylation (DNAm) and telomere length (TL) in the cord blood in relation to gestational PM₁₀ exposure and explored potential gestational windows of susceptibility.

METHODS

Cord blood epigenome-wide DNAm (N = 384) and TL (N = 500) were measured in children of the Italian birth cohort Piccolipiù, using the Infinium Methylation EPIC BeadChip and qPCR, respectively. PM₁₀ daily exposure levels, based on maternal residential address, were estimated for different gestational periods using models based on satellite data. Epigenome-wide analysis to identify differentially methylated probes (DMPs) and regions (DMRs) was conducted, followed by a pathway analysis and replication analysis in an second Piccolipiù dataset. Distributed lag models (DLMs) using weekly exposures were used to study the association of PM₁₀ exposure across pregnancy with telomere length, as well as with the DMPs that showed robust associations.

RESULTS

Gestational PM₁₀ exposure was associated with the DNA methylation of more than 250 unique DMPs, most of them identified in early gestation, and 1 DMR. Out of 151 DMPs available in the replication dataset, ten DMPs showed robust associations: eight were associated with exposure during early gestation and 2 with exposure during the whole pregnancy. These exposure windows were supported by the DLM analysis. The PM₁₀ exposure between 15th and 20th gestational week seem to be associated with shorter telomeres at birth, while exposure between 24th and 29th was associated with longer telomeres.

DISCUSSION

The early pregnancy period is a potential critical window during which PM₁₀ exposure can influence cord blood DNA methylation. The results from the TL analysis were consistent with previous findings and merit further exploration in future studies. The study underlines the importance of considering gestational windows outside of the predefined trimesters that may not always overlap with biologically relevant windows of exposure.

Antipsychotics preserve telomere length in peripheral blood mononuclear cells after acute oxidative stress injury

Antipsychotics may prolong or retain telomere length, affect mitochondrial function, and then affect the metabolism of nerve cells. To validate the hypothesis that antipsychotics can prolong telomere length after oxidative stress injury, leukocytes from healthy volunteers were extracted using Ficoll-Histopaque density gradient. The mononuclear cells layer was resuspended in cell culture medium. Oxidative stress was induced with hydrogen peroxide in cultured leukocytes. Four days later, leukocytes were treated with aripiprazole, haloperidol or clozapine for 7 days. Real-time PCR revealed that treatments with aripiprazole and haloperidol increased the telomere length by 23% and 20% in peripheral blood mononuclear cells after acute oxidative stress injury. These results suggest that haloperidol and aripiprazole can reduce the damage to telomeres induced by oxidative stress. The experiment procedure was approved by the Ethics Committee of Faculty of Medicine of the University of São Paulo (FMUSP/CAAE approval No. 52622616.8.0000.0065).

Telomere-length dependent T-cell clonal expansion: A model linking ageing to COVID-19 T-cell lymphopenia and mortality

BACKGROUND

Severe COVID-19 T-cell lymphopenia is more common among older adults and entails poor prognosis. Offsetting the decline in T-cell count during COVID-19 demands fast and massive T-cell clonal expansion, which is telomere length (TL)-dependent.

METHODS

We developed a model of TL-dependent T-cell clonal expansion capacity with age and virtually examined the relation of T-cell clonal expansion with COVID-19 mortality in the general population.

FINDINGS

The model shows that an individual with average hematopoietic cell TL (HCTL) at age twenty years maintains maximal T-cell clonal expansion capacity until the 6th decade of life when this capacity rapidly declines by more than 90% over the next ten years. The collapse in the T-cell clonal expansion capacity coincides with the steep increase in COVID-19 mortality with age.

INTERPRETATION

Short HCTL might increase vulnerability of many older adults, and some younger individuals with inherently short HCTL, to COVID-19 T-cell lymphopenia and severe disease.

FUNDING

A full list of funding bodies that contributed to this study can be found in the Acknowledgements section.

Genetically predicted telomere length and multiple sclerosis

BACKGROUND

Previous epidemiological studies have indicated a role for telomere length in multiple sclerosis (MS) severity and phenotype. However, these studies failed to establish the causality between telomere length and MS susceptibility. Hence, we performed two-sample Mendelian randomization (MR) analysis to explore the causal relationship between telomere length and MS susceptibility.

METHODS

We used data of genetic variants associated with leukocyte telomere length as instrumental variables (IVs), which was identified from the largest and latest genome-wide association study (GWAS) from UK Biobank (UKB) with 472,174 participants. Summary data of MS was obtained from the International Multiple Sclerosis Genetics Consortium. We performed two-sample MR analyses using the inverse-variance weighted method as the primary approach. Other MR approaches, including the MR-Egger, the inverse variance weighted (multiplicative random effects), weighted median, simple median, weighted mode-based methods, and Causal Analysis Using Summary Effect estimates (CAUSE), were also conducted to detect the result robustness.

RESULTS

The genetic liability to longer telomere length was associated with a higher risk of MS susceptibility (odds ratio [OR] per one-SD telomere length, 1.91; 95% confidence interval [CI], 1.48-2.47; P = 8.04 × 10^-7). The results remained consistent across multiple sensitivity analyses.

CONCLUSIONS

Our study supports the causal relationship between longer telomere length and increased risk of MS susceptibility.

Association between maternal per- and polyfluoroalkyl substance exposure and newborn telomere length: Effect modification by birth seasons

BACKGROUND

Telomere length (TL) is an important biomarker of biological aging and disease that may be affected by prenatal exposure to environmental pollutants. Birth seasons have been linked to reproductive and immune-related diseases. Prenatal exposure to per- and polyfluoroalkyl substance (PFAS) has been associated with adverse birth outcomes, but the effects of PFAS and birth seasons on newborn TL are poorly understood.

OBJECTIVES

To explore the individual and combined effects of maternal PFAS exposure on newborn TL, with exploration of the interaction between PFAS and birth seasons on newborn TL.

METHODS

Between June 2015 and May 2018, a total of 499 mother-newborn pairs were recruited for a birth cohort study in Guangxi, China. Maternal blood samples were collected during pregnancy. Nine PFASs were measured by ultraperformance liquid chromatography-mass spectrometry. Newborn TL was assessed using quantitative real-time polymerase chain reaction. Modeling newborn TL as the outcome, multivariable linear regressions were performed for individual PFAS exposures, and Bayesian Kernel Machine Regressions were performed for PFAS mixtures. Furthermore, interaction analyses were conducted to evaluate the effect modification by birth seasons in these relationships.

RESULTS

For both single and multipollutant models, PFASs exposure were inversely associated with newborn TL, although none of the relationships were significant. The mixture of PFASs showed a potential positive trend of combined effect on newborn TL but non-statistically significant. Each ln-transformed unit concentration increase in PFOA was related to a 20.41% (95% CI: -30.44%, -8.93%) shorter TL in spring-born infants but not in those born in other birth seasons. Mothers in the middle and highest tertiles of PFOA exposure had 11.69% and 10.71% shorter TLs in spring-born infants, respectively.

CONCLUSION

Maternal PFAS exposure showed little association with newborn TL. The results suggested potential effect modification by birth season on the association between PFOA exposure and newborn TL.

Targeting G-Quadruplex Dna For Cancer Chemotherapy

The self-association of DNA formed by Hoogsteen hydrogen bonding comprises several layers of four guanine or G-tetrads or G4s. The distinct feature of G4s, such as the G-tetrads and loops, qualify structure-selective recognition by small molecules and various ligands and can act as potential anticancer therapeutic molecules. The G4 selective-ligands, can influence gene expression by targeting a nucleic acid structure rather than sequence. Telomere G4 can be targeted for cancer treatment by small molecules inhibiting the telomerase activity whereas c-MYC is capable of controlling transcription, can be targeted to influence transcription. The k-RAS is one of the most frequently encountered oncogenic driver mutations in pancreatic, colorectal, and lung cancers. The k-RAS oncogene plays important role in acquiring and increasing the drug resistance and can also be directly targeted by small molecules to combat k-RAS mutant tumors. Modular G4 ligands with different functional groups, side chains and rotatable bonds as well as conformation affect the binding affinity/selectivity in cancer chemotherapeutic interventions. These modular G4 ligands act by targeting the diversity of G4 loops and groves and assists to develop more drug-like compounds with selectivity. In this review, we present the recent research on synthetic G4 DNA-interacting ligands as an approach toward the discovery of target specific anticancer chemotherapeutic agents.

Association of telomere length with diabetes mellitus and idiopathic dilated cardiomyopathy in a South Indian population: A pilot study

Telomere shortening has been associated with ageing and with many age-related diseases including cancer, coronary artery disease, heart failure and diabetes. We sought to investigate the link between telomere shortening and age-related diseases like type 2 diabetes mellitus (DM) (without any complications: DM; with neuropathic complication: DN) and idiopathic dilated cardiomyopathy (IDCM) in south Indian population. We compared telomere lengths of blood lymphocytes taken from patients with associated age-related diseases, namely DM (n = 47), DN (n = 52) and IDCM (n = 34) and controls (n = 46). In addition, we evaluated the relationship between echocardiographic left ventricular ejection fraction (LVEF), left ventricular end diastolic and systolic diameters (LVEDd and LVESd) and telomere length in IDCM patients. Telomere length negatively correlated with age in the cohorts with diabetes and IDCM, and in controls. Average telomere length in diabetes and IDCM patients was significantly shorter than that of controls either before or after adjustments for age and sex. Duration of diabetes in patients with type 2 diabetes did not correlate with telomere length. No correlation was found between the length of telomeres and echocardiography parameters like LVEF, LVEDd and LVESd in IDCM patients. Though echocardiographic characteristics of IDCM did not correlate with telomere length, telomere shortening was found to be accelerated in diabetes (both DM and DN) and IDCM in a south Indian population. Neuropathic complication in diabetes had no effect on telomere shortening. While telomere shortening is a cause or a consequence of diabetic and cardiac pathology remains further investigation, the current study substantiates the usefulness of telomere length measurements as a marker in conjunction with other biochemical markers of age-related diseases.

Genetic determinants of telomere length from 109,122 ancestrally diverse whole-genome sequences in TOPMed

Genetic studies on telomere length are important for understanding age-related diseases. Prior GWAS for leukocyte TL have been limited to European and Asian populations. Here, we report the first sequencing-based association study for TL across ancestrally-diverse individuals (European, African, Asian and Hispanic/Latino) from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program. We used whole genome sequencing (WGS) of whole blood for variant genotype calling and the bioinformatic estimation of telomere length in n=109,122 individuals. We identified 59 sentinel variants (p-value <5×10-9) in 36 loci associated with telomere length, including 20 newly associated loci (13 were replicated in external datasets). There was little evidence of effect size heterogeneity across populations. Fine-mapping at OBFC1 indicated the independent signals colocalized with cell-type specific eQTLs for OBFC1 (STN1). Using a multi-variant gene-based approach, we identified two genes newly implicated in telomere length, DCLRE1B (SNM1B) and PARN. In PheWAS, we demonstrated our TL polygenic trait scores (PTS) were associated with increased risk of cancer-related phenotypes.

Telomere length as a biomarker of aging and diseases

As research related to healthspan and lifespan has become a hot topic, the necessity for a reliable and practical biomarker of aging (BoA), which can provide information about mortality and morbidity risk, along with remaining life expectancy, has increased. The chromosome terminus non-coding protective structure that prevents genomic instability is called a telomere. The continual shortening of telomeres, which affects their structure as well as function, is a hallmark of agedness. The aforementioned process is a potential cause of age-related diseases (ARDs), leading to a bad prognosis and a low survival rate, which compromise health and longevity. Hence, studies scrutinizing the BoAs often include telomere length (TL) as a prospective candidate. The results of these studies suggest that TL measurement can only provide an approximate appraisal of the aging rate, and its implementation into clinical practice and routine use as a BoA has many limitations and challenges. Nevertheless, measuring TL while determining other biomarkers can be used to assess biological age. This review focuses on the importance of telomeres in health, senescence, and diseases, as well as on summarizing the results and conclusions of previous studies evaluating TL as a potential BoA.

Leukocyte telomere length and amyotrophic lateral sclerosis: a Mendelian randomization study

Background

Observational studies have suggested that telomere length is associated with amyotrophic lateral sclerosis (ALS). However, whether this association is causal remains unclear. In this study, we aimed to explore the causal relationship between leukocyte telomere length (LTL) and ALS by a two-sample Mendelian randomization (MR) approach. Single-nucleotide polymorphisms (SNPs) for LTL were identified through high-quality genome-wide association studies (GWASs). The ALS GWAS summary data (20,806 cases; 59,804 controls) with largest sample size to date was obtained. We adopted the inverse variance weighted (IVW) method to examine the effect of LTL on ALS and used the weighted median method, simple median method, MR Egger method and MR-PRESSO method to perform sensitivity analyses.

Results

We found that genetically determined increased LTL was inversely associated with the risk of ALS (odds ratio (OR) = 0.846, 95% confidence interval (CI): 0.744–0.962, P = 0.011), which was mainly driven by rs940209 in the OBFC1 gene, suggesting a potential effect of OBFC1 on ALS. The results were further confirmed by sensitivity analysis with the MR Egger method (OR = 0.647, 95% CI = 0.447–0.936, P = 0.050). Analyses by the weighted median method (OR = 0.893, P = 0.201) and simple median method (OR = 0.935, P = 0.535) also showed a similar trend. The MR Egger analysis did not suggest directional pleiotropy, with an intercept of 0.025 (P = 0.168). Neither the influence of instrumental outliers nor heterogeneity was found.

Conclusions

Our results suggest that genetically predicted increased LTL has a causal relationship with a lower risk of ALS. Protecting against telomere loss may be of great importance in the prevention and treatment of ALS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02135-2.

A genetic determinant of VEGF-A levels is associated with telomere attrition

Telomere length (TL) is a hallmark of cellular aging and is associated with chronic diseases development. The vascular endothelial growth factor A (VEGF-A), a potent angiogenesis factor, is implicated in the pathophysiology of many chronic diseases. The aim of the present study was to investigate the associations between VEGF-A and TL.

TL in leukocytes (LTL) and skeletal muscle (MTL) were measured, 10 VEGF-related polymorphisms genotyped, and VEGF-A plasma concentrations determined in 402 individuals from the TELARTA cohort. LTL/MTL ratio was calculated as an estimate of lifelong TL attrition. Associations between VEGF-A variants and levels, and TL parameters were investigated.

We identified one significant association between the minor allele (T) of rs6993770 variant and LTL/MTL ratio (P=0.001143, β=0.0148, SE=0.004516). The rs6993770 is an intronic variant of the ZFPM2 gene, which is involved in haematopoiesis and the identified association with increased telomere attrition could be due to increased haematopoiesis. No significant epistatic interaction was identified, and no association was found between levels of VEGF-A and any of assessed phenotypes.

We identified a potential common genetic regulation between VEGF-A and telomere length attrition that could be explained by mechanisms of increased hematopoiesis and production of platelets. VEGF-A and TL could play an important role in personalized medicine of chronic diseases and identification of molecular links between them can promote the understanding of their complex implications.

Prenatal exposure to triclosan induced brain telomere shortening in a wild bird species

Exposure to the antimicrobial agent Triclosan (TCS) induces oxidative stress in diverse organisms, including birds. However, whether TCS-induced oxidative stress effectively translates into detrimental effects is still unclear. The present study examined whether prenatal TCS exposure induces oxidative stress and telomere shortening in the brain and the liver of near-term embryos of the yellow-legged gull (Larus michahellis). Prenatal TCS exposure caused a significant overproduction of reactive oxygen species (ROS) in the brain, but no oxidative damage occurred. Telomeres of TCS-exposed embryos had brain telomeres 30 % shorter compared to controls, probably because the relatively modest antioxidant defenses of this organ during prenatal development cannot counteract the impact of the TCS-induced ROS. No telomere shortening was observed in the liver. Our results demonstrated that prenatal exposure to TCS in wild bird species can modulate the oxidative status and induce telomere shortening in the brain of the yellow-legged gull embryos.

Longer Leukocytes Telomere Length Predicts a Significant Survival Advantage in the Elderly TRELONG Cohort, with Short Physical Performance Battery Score and Years of Education as Main Determinants for Telomere Elongation

Leukocyte telomere length (LTL) represents a key integrating component of the cumulative effects of environmental, lifestyle, and genetic factors. A question, however, remains on whether LTL can be considered predictive for a longer and healthier life. Within the elderly prospective TRELONG cohort (n = 612), we aimed to investigate LTL as a predictor of longevity and identify the main determinants of LTL among many different factors (physiological and lifestyle characteristics, physical performance and frailty measures, chronic diseases, biochemical measurements and apolipoprotein E genotyping). We found an ever-increasing relationship between LTL quartiles and survival. Hazard ratio analysis showed that for each unit increase in LTL and Short Physical Performance Battery (SPPB) scores, the mortality risk was reduced by 22.41% and 8.78%, respectively. Conversely, male gender, Charlson Comorbidity Index, and age threatened survival, with mortality risk growing by 74.99%, 16.57% and 8.5%, respectively. Determinants of LTL elongation were SPPB scores (OR = 1.1542; p = 0.0066) and years of education (OR = 1.0958; p = 0.0065), while male gender (OR = 0.4388; p =  0.0143) and increased Disease Count Index (OR = 0.6912; p  =  0.0066) were determinants of LTL attrition. Longer LTL predicts a significant survival advantage in elderly people. By identifying determinants of LTL elongation, we provided additional knowledge that could offer a potential translation into prevention strategies.

Age-related changes of human serum Sirtuin6 in adults

Background

Aging is a natural life process and with an aging population, age-related diseases (e.g. type 2 diabetes mellitus (T2DM), atherosclerosis-based cardiovascular diseases) are the primary mortality cause in older adults. Telomerase is often used as an aging biomarker. Detection and characterization of novel biomarkers can help in a more specific and sensitive identification of a person’s aging status. Also, this could help in age-related diseases early prevent, ultimately prolonging the population’s life span. Sirtuin 6 (Sirt6) - a member of the Sirtuins NAD⁺-dependent histone deacetylases family - is mainly intracellularly expressed, and is reported to be involved in the regulation of aging and aging-related diseases. Whether serum Sirt6 is correlated with aging and could be used as an aging biomarker is unknown. In the present study, we aimed to investigate the age-related Sirt6 changes in the serum of human adults.

Methods

Participants were divided into three groups according to age: 20–30 years (Young); 45–55 years (Middle-aged); and ≥ 70 years (Old). The Sirt6 and telomerase serum concentrations were determined by ELISA. The Sirt6 and human telomerase reverse transcriptase (hTERT) expression in vessels from amputated human lower limbs were analyzed using real-time quantitative PCR (RT-qPCR) and immunohistochemical staining. The relationships between variables were evaluated by Pearson correlation analysis.

Results

The Sirt6 and telomerase serum levels reduced with an increase in age. A similar tendency was observed for Sirt6 and hTERT in the vessel. Serum levels of Sirt6 were higher in females compared with males. Pearson’s regression analysis revealed that the Sirt6 serum level positively correlated with telomerase (r = 0.5743) and both were significantly negatively correlated with age (r = − 0.5830 and r = − 0.5993, respectively).

Conclusions

We reported a negative correlation between serum Sirt6 concentration and aging in human beings. Therefore, the Sirt6 serum level is a potential sex-specific aging marker.

Shorter leukocyte telomere length is associated with adverse COVID-19 outcomes: A cohort study in UK Biobank

Background Older age is the most powerful risk factor for adverse coronavirus disease-19 (COVID-19) outcomes. It is uncertain whether leucocyte telomere length (LTL), previously proposed as a marker of biological age, is also associated with COVID-19 outcomes. Methods We associated LTL values obtained from participants recruited into UK Biobank (UKB) during 2006-2010 with adverse COVID-19 outcomes recorded by 30 November 2020, defined as a composite of any of the following: hospital admission, need for critical care, respiratory support, or mortality. Using information on 130 LTL-associated genetic variants, we conducted exploratory Mendelian randomisation (MR) analyses in UKB to evaluate whether observational associations might reflect cause-and-effect relationships. Findings Of 6775 participants in UKB who tested positive for infection with SARS-CoV-2 in the community, there were 914 (13.5%) with adverse COVID-19 outcomes. The odds ratio (OR) for adverse COVID-19 outcomes was 1·17 (95% CI 1·05-1·30; P = 0·004) per 1-SD shorter usual LTL, after adjustment for age, sex and ethnicity. Similar ORs were observed in analyses that: adjusted for additional risk factors; disaggregated the composite outcome and reduced the scope for selection or collider bias. In MR analyses, the OR for adverse COVID-19 outcomes was directionally concordant but non-significant. Interpretation Shorter LTL is associated with higher risk of adverse COVID-19 outcomes, independent of several major risk factors for COVID-19 including age. Further data are needed to determine whether this association reflects causality. Funding UK Medical Research Council, Biotechnology and Biological Sciences Research Council and British Heart Foundation.

Repeated exposure to challenging environmental conditions influences telomere dynamics across adult life as predicted by changes in mortality risk

The effects of stress exposure are likely to vary depending on life-stage and stressor. While it has been postulated that mild stress exposure may have beneficial effects, the duration of such effects and the underlying mechanisms are unclear. While the long-term effects of early-life stress are relatively well studied, we know much less about the effects of exposure in adulthood since the early- and adult-life environments are often similar. We previously reported that repeated experimental exposure to a relatively mild stressor in female zebra finches, first experienced in young adulthood, initially had no effect on mortality risk, reduced mortality in middle age, but the apparently beneficial effects disappeared in old age. We show here that this is underpinned by differences between the control and stress-exposed group in the pattern of telomere change, with stress-exposed birds showing reduced telomere loss in middle adulthood. We thereby provide novel experimental evidence that telomere dynamics play a key role linking stress resilience and aging.

Short leukocyte telomeres predict 25-year Alzheimer's disease incidence in non-APOE ε4-carriers

BACKGROUND

Leukocyte telomere length (LTL) has been shown to predict Alzheimer's disease (AD), albeit inconsistently. Failing to account for the competing risks between AD, other dementia types, and mortality, can be an explanation for the inconsistent findings in previous time-to-event analyses. Furthermore, previous studies indicate that the association between LTL and AD is non-linear and may differ depending on apolipoprotein E (APOE) ε4 allele carriage, the strongest genetic AD predictor.

METHODS

We analyzed whether baseline LTL in interaction with APOE ε4 predicts AD, by following 1306 initially non-demented subjects for 25 years. Gender- and age-residualized LTL (rLTL) was categorized into tertiles of short, medium, and long rLTLs. Two complementary time-to-event models that account for competing risks were used; the Fine-Gray model to estimate the association between the rLTL tertiles and the cumulative incidence of AD, and the cause-specific hazard model to assess whether the cause-specific risk of AD differed between the rLTL groups. Vascular dementia and death were considered competing risk events. Models were adjusted for baseline lifestyle-related risk factors, gender, age, and non-proportional hazards.

RESULTS

After follow-up, 149 were diagnosed with AD, 96 were diagnosed with vascular dementia, 465 died without dementia, and 596 remained healthy. Baseline rLTL and other covariates were assessed on average 8 years before AD onset (range 1-24). APOE ε4-carriers had significantly increased incidence of AD, as well as increased cause-specific AD risk. A significant rLTL-APOE interaction indicated that short rLTL at baseline was significantly associated with an increased incidence of AD among non-APOE ε4-carriers (subdistribution hazard ratio = 3.24, CI 1.404-7.462, P = 0.005), as well as borderline associated with increased cause-specific risk of AD (cause-specific hazard ratio = 1.67, CI 0.947-2.964, P = 0.07). Among APOE ε4-carriers, short or long rLTLs were not significantly associated with AD incidence, nor with the cause-specific risk of AD.

CONCLUSIONS

Our findings from two complementary competing risk time-to-event models indicate that short rLTL may be a valuable predictor of the AD incidence in non-APOE ε4-carriers, on average 8 years before AD onset. More generally, the findings highlight the importance of accounting for competing risks, as well as the APOE status of participants in AD biomarker research.

The Nexus Between Telomere Length and Lymphocyte Count in Seniors Hospitalized With COVID-19

Profound T-cell lymphopenia is the hallmark of severe coronavirus disease 2019 (COVID-19). T-cell proliferation is telomere length (TL) dependent and telomeres shorten with age. Older COVID-19 patients, we hypothesize, are, therefore, at a higher risk of having TL-dependent lymphopenia. We measured TL by the novel Telomere Shortest Length Assay (TeSLA), and by Southern blotting (SB) of the terminal restriction fragments in peripheral blood mononuclear cells of 17 COVID-19 and 21 non-COVID-19 patients, aged 87 ± 8 (mean ± SD) and 87 ± 9 years, respectively. TeSLA tallies and measures single telomeres, including short telomeres undetected by SB. Such telomeres are relevant to TL-mediated biological processes, including cell viability and senescence. TeSLA yields 2 key metrics: the proportions of telomeres with different lengths (expressed in %) and their mean (TeSLA mTL), (expressed in kb). Lymphocyte count (109/L) was 0.91 ± 0.42 in COVID-19 patients and 1.50 ± 0.50 in non-COVID-19 patients (p < .001). In COVID-19 patients, but not in non-COVID-19 patients, lymphocyte count was inversely correlated with the proportion of telomeres shorter than 2 kb (p = .005) and positively correlated with TeSLA mTL (p = .03). Lymphocyte count was not significantly correlated with SB mTL in either COVID-19 or non-COVID-19 patients. We propose that compromised TL-dependent T-cell proliferative response, driven by short telomere in the TL distribution, contributes to COVID-19 lymphopenia among old adults. We infer that infection with SARS-CoV-2 uncovers the limits of the TL reserves of older persons. Clinical Trials Registration Number: NCT04325646.