Telomere length determines the mitochondrial copy number in blastocyst-stage embryos.

Telomere length (TL) and mitochondrial DNA copy number (mt-cn) are associated with embryonic development. Here, we investigated the correlation between TL and mt-cn in bovine embryos to determine whether TL regulates mt-cn. TL and mt-cn were closely correlated in embryos derived from six bulls. Treatment of embryos with a telomerase inhibitor (TMPyP) and siTERT shortened the TL and reduced mt-cn in blastocysts. RNA-sequencing of blastocysts developed with TMPyP revealed differentially expressed genes associated with transforming growth factor-ß1 signaling and inflammation. In conclusion, TL regulates mt-cn in embryos.

New insights from bidirectional Mendelian randomization: causal relationships between telomere length and mitochondrial DNA copy number in aging biomarkers.

Mitochondrial DNA (mtDNA) copy number and telomere length (TL) are dynamic factors that have been linked to the aging process in organisms. However, the causal relationship between these variables remains uncertain. In this research, instrumental variables (IVs) related to mtDNA copy number and TL were obtained from publicly available genome-wide association studies (GWAS). Through bidirectional Mendelian randomization (MR) analysis, we examined the potential causal relationship between these factors. The forward analysis, with mtDNA copy number as the exposure and TL as the outcome, did not reveal a significant effect (B=-0.004, P>0.05). On the contrary, upon conducting a reverse analysis, it was found that there exists a positive causal relationship (B=0.054, P<0.05). Sensitivity analyses further confirmed the reliability of these results. The outcomes of this study indicate a one-way positive causal relationship, indicating that telomere shortening in the aging process may lead to a decrease in mtDNA copy number, providing new perspectives on their biological mechanisms.

Telomerase is essential for cardiac differentiation and sustained metabolism of human cardiomyocytes.

Telomeres as the protective ends of linear chromosomes, are synthesized by the enzyme telomerase (TERT). Critically short telomeres essentially contribute to aging-related diseases and are associated with a broad spectrum of disorders known as telomeropathies. In cardiomyocytes, telomere length is strongly correlated with cardiomyopathies but it remains ambiguous whether short telomeres are the cause or the result of the disease. In this study, we employed an inducible CRISPRi human induced pluripotent stem cell (hiPSC) line to silence TERT expression enabling the generation of hiPSCs and hiPSC-derived cardiomyocytes with long and short telomeres. Reduced telomerase activity and shorter telomere lengths of hiPSCs induced global transcriptomic changes associated with cardiac developmental pathways. Consequently, the differentiation potential towards cardiomyocytes was strongly impaired and single cell RNA sequencing revealed a shift towards a more smooth muscle cell like identity in the cells with the shortest telomeres. Poor cardiomyocyte function and increased sensitivity to stress directly correlated with the extent of telomere shortening. Collectively our data demonstrates a TERT dependent cardiomyogenic differentiation defect, highlighting the CRISPRi TERT hiPSCs model as a powerful platform to study the mechanisms and consequences of short telomeres in the heart and also in the context of telomeropathies.

DNA methylation-based telomere length is associated with HIV infection, physical frailty, cancer, and all-cause mortality.

Telomere length (TL) is an important indicator of cellular aging. Shorter TL is associated with several age-related diseases including coronary heart disease, heart failure, diabetes, osteoporosis, and cancer. Recently, a DNA methylation-based TL (DNAmTL) estimator has been developed as an alternative method for directly measuring TL. In this study, we examined the association of DNAmTL with cancer prevalence and mortality risk among people with and without HIV in the Veterans Aging Cohort Study Biomarker Cohort (VACS, N = 1917) and Women's Interagency HIV Study Cohort (WIHS, N = 481). We profiled DNAm in whole blood (VACS) or in peripheral blood mononuclear cells (WIHS) using an array-based method. Cancer prevalence was estimated from electronic medical records and cancer registry data. The VACS Index was used as a measure of physiologic frailty. Models were adjusted for self-reported race and ethnicity, batch, smoking status, alcohol consumption, and five cell types (CD4, CD8, NK, B cell, and monocyte). We found that people with HIV had shorter average DNAmTL than those without HIV infection [beta = -0.25, 95% confidence interval (-0.32, -0.18), p = 1.48E-12]. Greater value of VACS Index [beta = -0.002 (-0.003, -0.001), p = 2.82E-05] and higher cancer prevalence [beta = -0.07 (-0.10, -0.03), p = 1.37E-04 without adjusting age] were associated with shortened DNAmTL. In addition, one kilobase decrease in DNAmTL was associated with a 40% increase in mortality risk [hazard ratio: 0.60 (0.44, 0.82), p = 1.42E-03]. In summary, HIV infection, physiologic frailty, and cancer are associated with shortening DNAmTL, contributing to an increased risk of all-cause mortality.

The impact of telomere length on prostate cancer aggressiveness, genomic instability and health disparities.

The telomere repetitive TTAGGG motif at the ends of chromosomes, serves to preserve genomic integrity and chromosomal stability. In turn, genomic instability is a hallmark of cancer-implicating telomere disturbance. Prostate cancer (PCa) shows significant ancestral disparities, with men of African ancestry at the greatest risk for aggressive disease and associated genomic instability. Yet, no study has explored the role of telomere length (TL) with respect to ancestrally driven PCa health disparities. Patient- and technically-matched tumour-blood whole genome sequencing data for 179 ancestrally defined treatment naïve PCa patients (117 African, 62 European), we assessed for TL (blood and tumour) associations. We found shortened tumour TL to be associated with aggressive PCa presentation and elevated genomic instabilities, including percentage of genome alteration and copy number gains, in men of African ancestry. For European patients, tumour TL showed significant associations with PCa driver genes PTEN, TP53, MSH2, SETBP1 and DDX11L1, while shorter blood TL (< 3200 base pairs) and tumour TL (< 2861 base pairs) were correlated with higher risk for biochemical recurrence. Concurring with previous studies linking TL to PCa diagnosis and/or prognosis, for the first time we correlated TL differences with patient ancestry with important implications for future treatments targeting telomere dysfunction.

Study of association of leptin with leukocyte telomere length in a Chinese rural population.

BACKGROUND: Previous studies have demonstrated the relationship between adipocyte factors, insulin resistance, and other indicators with telomere length. However, these studies did not consider the influence of changes in different indicators on telomere length over time. Therefore, the aim of this study is to elucidate the impact of changes in adipocyte factors, HOMA-IR, and other indicators on the dynamic variation of telomere length. METHODS: The data were from a cohort study conducted in Ningxia, China. A total of 1624 subjects were analyzed. Adipokines and relative leukocyte telomere length (RLTL) were measured, and changes in Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), Homeostatic Model Assessment for ß-Cell Function (HOMA-ß), and Quantitative Insulin Sensitivity Check Index (QUICKI) were calculated. Generalized linear models evaluated associations between changes in adipokines and RLTL changes. Furthermore, univariate analyses examined the effects of changes in adipokines and insulin resistance indicators on ΔRLTL. RESULTS: The research findings indicate that females generally have shorter telomeres compared to males. In comparison to the low-level group of Δleptin (LEP), the high-level group of ΔLEP shows a negative correlation with ΔRLTL (B=-1.32, 95% CI (-2.38, -0.27)). Even after multivariable adjustments, this relationship persists (B=-1.31, 95% CI (-2.24, -0.23)). Further analysis reveals that after adjusting for ΔHOMA-IR, ΔHOMA-ß, and ΔQUICKI, the high-level group of ΔLEP still exhibits a significant negative correlation with ΔRLTL (B=-1.37, 95% CI (-2.43, -0.31)). However, the interaction effects between ΔHOMA-IR, ΔHOMA-ß, ΔQUICKI, and ΔLEP do not affect ΔRLTL. CONCLUSIONS: Elevated levels of leptin were significantly correlated with shortened telomere length. This suggests that increased leptin levels may impact overall individual health by affecting telomere length, underscoring the importance of measures to reduce leptin levels to mitigate the onset and progression of related diseases.

Shorter telomere length increases the risk of lymphocyte immunodeficiency: A Mendelian randomization study.

BACKGROUND: For a long time, the prevailing viewpoint suggests that shorter telomere contribute to chromosomal instability, which is a shared characteristic of both aging and cancer. The newest research presented that T cell immune deficiency rather than chromosome instability predisposes patients with short telomere syndromes to some cancers. However, the relationship between genetically determined telomere length (TL) and immune cells remains unclear. METHODS: The two-sample Mendelian randomization analysis was conducted to elucidate the potential causal relationship. The genetic data of TL and immune cells were obtained from the Genome-Wide Association Study. The inverse variance weighted (IVW) method was used to estimate the effects primarily and another four methods were as a supplement. Sensitivity analysis was used to test the results. RESULTS: The IVW method showed a significant correlation between TL and the percentage of T cells in lymphocytes (odds ratio [OR]: 1.222, 95% confidence interval [CI]: 1.014-1.472, p = .035), indicating that shorter TL significantly increases the risk of low T cell percentage. Further analysis of T cell subsets indicated that shorter TL may primarily lead to a lower percentage of Natural Killer T cells (OR: 1.574, 95% CI: 1.281-1.935, p < .001). Analysis of B cell subsets revealed that shorter TL may be associated with a higher percentage of Naive-mature B cells, and a lower percentage of Memory B cells. And the sensitivity analysis indicated the validity and robustness of our findings. CONCLUSION: In summary, our findings suggest that shorter TL may be associated with a decline in the percentage of T cell, as well as impediments in the differentiation of B cell, consequently leading to the onset of immunosenescence and immunodeficiency. The relevant mechanisms and potential therapeutic avenues still need further investigation.

Evaluation of miR-130b-3p and miR-375 levels and telomere length with telomerase activity in prostate cancer.

Prostate cancer (PC) is the most frequent cancer in males, as well as the second highest cause of cancer-related deaths in men. Differences in expression levels of miRNAs were linked with prostat cancer pathogenesis. qPCR was used to evaluate the expression of miR-130b-3p and miR-375 in Benign Prostate Hyperplasia (BPH (n = 20) and PC (n = 22, pre- and post-operative) patients plasma. Relative telomere lengths (RLTs) in genomic DNA isolated from plasma were measured with qPCR, and telomerase activity analyzed by the ELISA method. PSA levels of PC patients were greater than of BPH patients (p = 0.0473). miR-130b-3p and miR-375 levels were significantly lower in pre-operative specimens of PC patients according to BPH (p = 0,0362, p = 0.0168, respectively). Similarly, post-operative miR-375 levels were lower in PC patients than in BPH patients (p = 0.1866). BPH patients had shorter RTLs than PC patients in both pre- (p=0.0438) and post-operative (p=0.0297) specimens. Telomerase activity was higher in PC patients than BPH(p = 0.0129). Interestingly, telomerase activity was further increased after surgery (p = 0.0003). We aim to identify the levels of miR-130b-3p and miR-375 expression and their relationship with telomerase activity in PC patients. Our data suggest that miRNAs and telomere length (TL) with telomerase activity may play a role in regulating prostate tumorgenesis and may be used as biomarkers for PC diagnosis.

Association of Obesity with Telomere Length in Human Sperm.

Background: Telomere attrition and mitochondrial dysfunction are two fundamental aspects of aging. Calorie restriction (CR) is the best strategy to postpone aging since it can enhance telomere attrition, boost antioxidant capacity, and lower the generation of reactive oxygen species (ROS). Since ROS is produced by mitochondria and can readily travel to cell nuclei, it is thought to be a crucial molecule for information transfer between mitochondria and cell nuclei. Important variables that affect the quality and functionality of sperm and may affect male reproductive health and fertility include telomere length, mitochondrial content, and the ratio of mitochondrial DNA (mtDNA) to nuclear DNA (nDNA). Telomere damage results from mitochondrial failure, whereas nuclear DNA remains unaffected. This research aims to investigate potential associations between these three variables and how they might relate to body mass index. Methods: Data were collected from 82 men who underwent IVF/ICSI at the University Hospital of Ioannina's IVF Unit in the Obstetrics and Gynecology Department. Evaluations included sperm morphology, sperm count, sperm motility, and participant history. To address this, male participants who were categorized into three body mass index (ΒΜΙ) groups-normal, overweight, and obese-had their sperm samples tested. Results: For both the normal and overweight groups, our results show a negative connection between relative telomere length and ΒΜI. As an illustration of a potential connection between mitochondrial health and telomere maintenance, a positive correlation was found for the obese group. Only the obese group's results were statistically significant (p < 0.05). More evidence that longer telomeres are associated with lower mitochondrial content can be found in the negative connection between telomere length and mitochondrial content in both the normal and overweight groups. However, the obese group showed a positive association. The data did not reach statistical significance for any of the three groups. These associations may affect sperm quality since telomere length and mitochondrial concentration are indicators of cellular integrity and health. Moreover, the ratio of mtDNA to nDNA was positively correlated with the relative telomere lengths of the obese group, but negatively correlated with the normal and overweight groups. In every group that was studied, the results were not statistically significant. According to this, male fertility may be negatively impacted by an imbalance in the copy number of the mitochondrial genome compared to the nuclear DNA in sperm. Conclusions: Essentially, the goal of our work is to determine whether mitochondria and telomere length in human sperm interact. Understanding these connections may aid in the explanation of some male infertility causes and possibly contribute to the creation of new treatment modalities for problems pertaining to reproductive health. The functional implications of these connections and their applications in therapeutic settings require further investigation.

Evaluating Leukocyte Telomere Length and Myeloid-Derived Suppressor Cells as Biomarkers for Prostate Cancer.

BACKGROUND: Leukocyte telomere length (LTL) and myeloid-derived suppressor cells (MDSC) are associated with aging and the development and progression of cancer. However, the exact nature of this relationship remains unclear. Our study aimed to investigate the potential of LTL and MDSC as diagnostic biomarkers for prostate cancer while also seeking to deepen our understanding of the relationship of these potential biomarkers to each other. METHODS: Our study involved patients undergoing a prostate biopsy. We analyzed the relative LTL in genomic DNA obtained from peripheral blood leukocytes as well as the percentage of MDSC and their subtypes in peripheral blood mononuclear cells (PBMC). Our evaluation focused on examining the relationship between LTL and MDSC and pathological diagnoses as well as investigating the correlation between LTL and MDSC levels. RESULTS: In our study of 102 participants, 56 were pathologically diagnosed with localized prostate cancer (cancer group), while 46 tested negative (control group). The cancer group exhibited significantly shorter LTL in comparison to the control group (p = 0.024). Additionally, the cancer group showed a tendency towards a higher percentage of monocytic MDSC (M-MDSC), although this difference did not reach statistical significance (p = 0.056). Our multivariate logistic regression analysis revealed that patients with shorter LTL and higher percentages of M-MDSC had a 2.98-fold (95% CI = 1.001-8.869, p = 0.049) and 3.03-fold (95% CI = 1.152-7.977, p = 0.025) increased risk of prostate cancer diagnosis, respectively. There was also a significant negative correlation between LTL and M-MDSC. (r = -0.347, p < 0.001). CONCLUSIONS: Our research has established a correlation between LTL and MDSC in patients undergoing biopsy for prostate cancer. Notably, we observed that individuals with localized prostate cancer tend to have shorter LTL and a higher percentage of M-MDSC prior to their diagnosis. These findings suggest that LTL and M-MDSC could potentially serve as adjunctive biomarkers for the early diagnosis of prostate cancer.

Parental status and markers of brain and cellular age: A 3D convolutional network and classification study.

Recent research shows prominent effects of pregnancy and the parenthood transition on structural brain characteristics in humans. Here, we present a comprehensive study of how parental status and number of children born/fathered links to markers of brain and cellular ageing in 36,323 UK Biobank participants (age range 44.57-82.06 years; 52% female). To assess global effects of parenting on the brain, we trained a 3D convolutional neural network on T1-weighted magnetic resonance images, and estimated brain age in a held-out test set. To investigate regional specificity, we extracted cortical and subcortical volumes using FreeSurfer, and ran hierarchical clustering to group regional volumes based on covariance. Leukocyte telomere length (LTL) derived from DNA was used as a marker of cellular ageing. We employed linear regression models to assess relationships between number of children, brain age, regional brain volumes, and LTL, and included interaction terms to probe sex differences in associations. Lastly, we used the brain measures and LTL as features in binary classification models, to determine if markers of brain and cellular ageing could predict parental status. The results showed associations between a greater number of children born/fathered and younger brain age in both females and males, with stronger effects observed in females. Volume-based analyses showed maternal effects in striatal and limbic regions, which were not evident in fathers. We found no evidence for associations between number of children and LTL. Classification of parental status showed an Area under the ROC Curve (AUC) of 0.57 for the brain age model, while the models using regional brain volumes and LTL as predictors showed AUCs of 0.52. Our findings align with previous population-based studies of middle- and older-aged parents, revealing subtle but significant associations between parental experience and neuroimaging-based surrogate markers of brain health. The findings further corroborate results from longitudinal cohort studies following parents across pregnancy and postpartum, potentially indicating that the parenthood transition is associated with long-term influences on brain health.

Low-molecular-weight fucoidan increases telomere length and immunostimulatory effects on NK-92 cells following inhaled anesthetic injury.

Inhaled anesthetics, such as isoflurane, may cause side effects, including short-term immunosuppression and DNA damage. In contrast, low molecular weight fucoidan (LMF), derived from brown seaweed, exhibits promising immunomodulatory effects. In this study, we determined the effect of isoflurane on telomeres and examined the potential of LMF to ameliorate the harmful effects of isoflurane. Male Lewis rats, the mouse lymphoma cell line YAC-1, and the human nature killer cell line NK-92 MI were exposed to isoflurane. The relative telomere length (T/S) ratio and mRNA expression were determined by quantitative PCR. The viability assay was used to assess cell viability. In vivo, 2% isoflurane exposure, which is a clinically relevant concentration, reduced telomere length, and correlated with exposure frequency and duration. Isoflurane concentrations above 2% shortened YAC-1 telomeres, with minimal impact on cell viability. LMF pre-treatment enhanced NK-92 MI cell survival resulting from isoflurane exposure and exerted superior telomere protection compared with LMF post-treatment. Furthermore, adding LMF during isoflurane exposure resulted in a significant increase in IFN-γ, TNF-α, and IL-10 mRNA compared with the untreated group. LMF protected against isoflurane-induced telomere shortening, enhanced NK cell viability, and modulated cytokine expression, thus mitigating postoperative immune suppression and risk of tumor metastasis.

Early-life tobacco smoke elevating later-life osteoporosis risk: Mediated by telomere length and interplayed with genetic predisposition.

INTRODUCTION: The growing prevalence of osteoporosis (OP) in an aging global population presents a significant public health concern. Tobacco smoke negatively affects bone turnover, leading to reduced bone mass and heightened OP and fracture risk. However, the impact of early-life tobacco smoke exposure on later-life OP risk remains unclear. OBJECTIVES: This study was to explore the effects of early-life tobacco smoke exposure on incident OP risk in later life. The mediating role of telomere length (TL) and the interaction with genetic predisposition were also studied. METHODS: Data on in utero tobacco smoke exposure (IUTSE) status and age of tobacco use initiation from the UK Biobank were used to estimate early-life tobacco smoke exposure. Incident OP cases were identified according to health-related records. Linear, Cox, and Laplace regression models were mainly used for data analysis. RESULTS: Individuals with IUTSE showed a higher OP risk [hazard ratio (HR): 1.06, 95 % confidence interval (CI): 1.01, 1.11] and experienced earlier OP onset by 0.30 years [50th percentile difference = -0.30, 95 % CI: -0.51, -0.09] compared to those without. Participants initiating tobacco smoke in childhood, adolescence, and adulthood had 1.41 times (95 % CI: 1.23, 1.61), 1.17 times (95 % CI:1.10, 1.24), and 1.14 times (95 % CI: 1.07, 1.20) the risk of OP, respectively, compared to never smokers. They also experienced earlier OP onset by 2.16, 0.95, and 0.71 years, sequentially. The TL significantly mediated the early-life tobacco exposure and OP association. Significant joint and interactive effects were detected between early-life tobacco smoke exposure and genetic elements. CONCLUSIONS: Our findings implicate that early-life tobacco smoke exposure elevates the later-life OP risk, mediated by telomere length and interplayed with genetic predisposition. These findings highlight the importance of early-life intervention against tobacco smoke exposure and ageing status for precise OP prevention, especially in individuals with a high genetic risk.

Causal relationship between immune cells and telomere length: mendelian randomization analysis.

BACKGROUND: The causal relationship between immune cells and telomere length remains controversial. METHODS: Data on the immune cells were obtained from a previous study with 3,757 participants. Data on telomere length were obtained from the OpenGWAS database. Genome-Wide Association Study (GWAS) data were obtained and screened for eligible instrumental variables (IVs) using the TwoSampleMR package and the Phenoscanner database. To investigate the genetic causality between immune cells and telomere length, Mendelian randomization (MR) analysis and Bayesian weighted Mendelian randomization (BWMR) analysis were used. RESULTS: MR analysis showed that there is indeed a genetic causal relationship between immune cells and telomere length. A total of 16 immune cells were successfully validated. A positive correlation was found between telomere length and immune cells such as CD28 + CD45RA + CD8br %CD8br (OR = 1.002, 95%CI: 1.000-1.003). A negative correlation was found between telomere length and immune cells such as Transitional AC (OR = 0.991, 95%CI: 0.984-0.997) (P < 0.05). Reverse MR analysis similarly confirmed that telomere length can affect four types of immune cells, including CD25 on IgD + CD24- (OR = 1.291, 95%CI: 1.060-1.571), at the genetic level. CONCLUSION: There is indeed a mutual genetic causality between immune cells and telomere length, which will provide theoretical basis and support for more subsequent clinical studies.

Frailty mediating the causality between leucocyte telomere length and mortality: a cohort study of 440,551 UK Biobank participants.

Introduction: Previous studies reported leucocyte telomere length (LTL) and frailty were associated with mortality, but it remains unclear whether frailty serves as a mediator in the relationship between leucocyte telomere length and mortality risk. This study aimed to evaluate how measuring LTL and frailty can support early monitoring and prevention of risk of mortality from the prospective of predictive, preventive, and personalized medicine (PPPM/3PM). Methods: We included 440,551 participants from the UK Biobank between the baseline visit (2006-2010) and November 30, 2022. The time-dependent Cox proportional hazards model was conducted to assess the association between LTL and frailty index with the risk of mortality. Furthermore, we conducted causal mediation analyses to examine the extent to which frailty mediated the association between LTL and mortality. Results: During a median follow-up of 13.74 years, each SD increase in LTL significantly decreased the risk of all-cause [hazard ratio (HR): 0.94, 95% confidence interval (CI): 0.93-0.95] and CVD-specific mortality (HR: 0.92, 95% CI: 0.90-0.95). The SD increase in FI elevated the risk of all-cause (HR: 1.35, 95% CI: 1.34-1.36), CVD-specific (HR: 1.47, 95% CI: 1.44-1.50), and cancer-specific mortality (HR: 1.22, 95% CI: 1.20-1.24). Frailty mediated approximately 10% of the association between LTL and all-cause and CVD-specific mortality. Conclusions: Our results indicate that frailty mediates the effect of LTL on all-cause and CVD-specific mortality. There findings might be valuable to predict, prevent, and reduce mortality through primary prevention and healthcare in context of PPPM. Supplementary Information: The online version contains supplementary material available at 10.1007/s13167-024-00355-7.

Causal Association of Telomere Length and Loss of Bone: a Directional Mendelian Randomization Study of Multi-Outcomes.

This study employed a genome-wide association study (GWAS) to investigate the relationship between telomere length and marginal bone loss (MBL), a marker of bone health and aging. Telomere length, a biological indicator of aging, was analyzed alongside several serum markers of bone loss. Following a screen for appropriate instrumental variables, telomere length was designated as the exposure variable. We conducted the main analysis using random-effects inverse variance weighting (IVW) and supplemented it with MR Egger, weighted median, simple mode, and weighted mode analyses, employing a total of five methods. Positive outcomes underwent scrutiny through heterogeneity analysis, horizontal multiplicity analysis, and leave-one-out plot. Subsequently, the effective gene locus was chosen for a reverse MR analysis, with positive results serving as the exposure variable. We found a causal relationship between telomere length and the expression of osteocalcin (OC), matrix metalloproteinase-3 (MMP-3), and matrix metalloproteinase-12 (MMP-12), key markers of bone metabolism. Our findings suggest that telomere wear and shortening may contribute to increased activity of OC, MMP-3, and MMP-12, thus affecting bone metabolism. However, reverse Mendelian randomization analysis did not indicate a significant impact of OC, MMP-3, and MMP-12 on telomere length, implying a unidirectional relationship. Overall, this meta-analysis underscores the association between telomere length and bone loss, highlighting the importance of timing and duration of telomere wear and shortening in influencing bone metabolism.

Telomere length is an epigenetic trait - Implications for the use of telomerase-deficient organisms to model human disease.

Telomere length, unlike most genetic traits, is epigenetic, in the sense that it is not fully coded by the genome. Telomeres vary in length and randomly assort to the progeny leaving some individuals with longer and others with shorter telomeres. Telomerase activity counteracts this by extending telomeres in the germline and during embryogenesis but sizeable variances remain in telomere length. This effect is exacerbated by the absence of fully active telomerase. Telomerase heterozygous animals (tert+/-) have reduced telomerase activity and their telomeres fail to be elongated to wild-type average length, meaning that - with every generation - they decrease. After a given number of successive generations of telomerase-insufficient crosses, telomeres become critically short and cause organismal defects that, in humans, are known as telomere biology disorders. Importantly, these defects also occur in wild-type (tert+/+) animals derived from such tert+/- incrosses. Despite these tert+/+ animals being proficient for telomerase, they have shorter than average telomere length and, although milder, develop phenotypes that are similar to those of telomerase mutants. Here, we discuss the impact of this phenomenon on human pathologies associated with telomere length, provide a brief overview of telomere biology across species and propose specific measures for working with telomerase-deficient zebrafish.

Effect of long-term caloric restriction on telomere length in healthy adults: CALERIE™ 2 trial analysis.

Caloric restriction (CR) modifies lifespan and aging biology in animal models. The Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE™) 2 trial tested translation of these findings to humans. CALERIE™ randomized healthy, nonobese men and premenopausal women (age 21-50y; BMI 22.0-27.9 kg/m2 ), to 25% CR or ad-libitum (AL) control (2:1) for 2 years. Prior analyses of CALERIE™ participants' blood chemistries, immunology, and epigenetic data suggest the 2-year CR intervention slowed biological aging. Here, we extend these analyses to test effects of CR on telomere length (TL) attrition. TL was quantified in blood samples collected at baseline, 12-, and 24-months by quantitative PCR (absolute TL; aTL) and a published DNA-methylation algorithm (DNAmTL). Intent-to-treat analysis found no significant differences in TL attrition across the first year, although there were trends toward increased attrition in the CR group for both aTL and DNAmTL measurements. When accounting for adherence heterogeneity with an Effect-of-Treatment-on-the-Treated analysis, greater CR dose was associated with increased DNAmTL attrition during the baseline to 12-month weight-loss period. By contrast, both CR group status and increased CR were associated with reduced aTL attrition over the month 12 to month 24 weight maintenance period. No differences were observed when considering TL change across the study duration from baseline to 24-months, leaving it unclear whether CR-related effects reflect long-term detriments to telomere fidelity, a hormesis-like adaptation to decreased energy availability, or measurement error and insufficient statistical power. Unraveling these trends will be a focus of future CALERIE™ analyses and trials.

Associations between ZNF676, CTC1 Gene Polymorphisms and Relative Leukocyte Telomere Length with Myopia and Its Degree.

BACKGROUND: The interaction between environmental and genetic factors that influence eye growth, regulated by vision, contributes to the development and progression of myopia. This dynamic interaction significantly contributes to the multifaceted development and progression of myopia, a prevalent ocular condition. Our study delves into the associations between ZNF676 and CTC1 gene polymorphisms and their impact on the relative leukocyte telomere length (relative LTL) in myopia, as well as its degree. By unravelling these underpinnings in conjunction with environmental influences, we aim to enhance our understanding of the complex mechanisms that drive the onset and severity of myopia. METHODS: This study included patients with myopia and ophthalmologically healthy subjects. DNA was extracted from peripheral venous blood by the salting out method. Genotyping of ZNF676 rs412658 and CTC1 rs3027234, as well as the measurement of relative LTL, were conducted using a real-time polymerase chain reaction method (RT-PCR). The data obtained were statistically analyzed using the "IBM SPSS Statistics 29.0" software program. RESULTS: The results show that myopic patients who are homozygous for the rs3027234 rare allele genotype of the CTC1 gene have statistically significantly shorter relative LTL compared to patients with the CC and CT genotypes. Also, men with the CTC1 rs3027234 TT genotype have statistically significantly longer leukocyte telomeres than women with the same genotype. The respective median (IQR) of the relative LTL for women and men is 0.280 (0.463) vs. 0.696 (0.440), with a p-value of 0.027. The myopia group with the ZNF676 rs412658 CC genotype has statistically significantly shorter leukocyte telomeres than the control group with the same genotype (age ≤ 29), and the p-value is 0.011. Also, the myopia group with the ZNF676 rs412658 CT and CTC1 rs3027234 CT genotypes have statistically significantly longer leukocyte telomeres than the control group with the same genotypes (age > 29), with p-values that are, respectively, 0.016 and 0.012. The evaluation of the genotype distributions of the polymorphisms in the myopia patients showed that ZNF676 rs412658 CT genotype carriers have 4-fold decreased odds of high myopia occurrence (OR = 0.250; CI: 0.076-0.826; p = 0.023). Also, the evaluation of the allele distributions of the polymorphism under the additive genetic model in the myopia group showed that the ZNF676 rs412658 T allele was associated with similar odds of high myopia (OR = 0.269; 95% CI: 0.090-0.807; p = 0.019). The comprehensive p-value, assessing the relative LTL of subjects across the different levels of myopia, signifies a statistical difference in the relative LTL among individuals with varying degrees of myopia. There was a statistically significant difference in relative LTL between mild and moderate myopia degrees (0.819 (1.983) vs. 0.083 (0.930), p = 0.007). CONCLUSIONS: CTC1 rs3027234 TT may be considered a protective genotype for telomere shortening in men, while the overall telomere shortening might be linked to the worse myopia degree. The ZNF676 rs412658 T allele may protect against a high myopia occurrence.

The Causality between Human Immunoglobulin G (IgG) N-Glycosylation and Aging: A Mendelian Randomization Study.

BACKGROUND: Immunoglobulin G (IgG) N-glycosylation is considered a potential biomarker for aging and various pathological conditions. However, whether these changes in IgG N-glycosylation are a consequence or a contributor to the aging process remains unclear. This study aims to investigate the causality between IgG N-glycosylation and aging using Mendelian randomization (MR) analysis. METHODS: We utilized genetic variants associated with IgG N-glycosylation traits, the frailty index (FI), and leukocyte telomere length (LTL) from a previous genome-wide association study (GWAS) on individuals of European ancestry. Two-sample and multivariable MR analyses were conducted, employing the inverse-variance weighted (IVW) method. Sensitivity analyses were performed to assess potential confounding factors. RESULTS: Using the IVW method, we found suggestive evidence of a causal association between GP14 and FI (ß 0.026, 95% CI 0.003 to 0.050, p = 0.027) and LTL (ß -0.020, 95% CI -0.037 to -0.002, p = 0.029) in the two-sample MR analysis. In the multivariable MR analysis, suggestive evidence was found for GP23 and FI (ß -0.119, 95% CI -0.219 to -0.019, p = 0.019) and GP2 and LTL (ß 0.140, 95% CI 0.020 to 0.260, p = 0.023). CONCLUSIONS: In conclusion, our results supported a potentially causal effect of lower GP23 levels on an advanced aging state. Additional verification is required to further substantiate the causal relationship between glycosylation and aging.