Telomere shortening by transgenerational transmission of TNF-α-induced TERRA via ATF7

Joint Effects of Exercise and Ramadan Fasting on Telomere Length: Implications for Cellular Aging

Aging is a fundamental biological process that progressively impairs the functionality of the bodily systems, leading to an increased risk of diseases. Telomere length is one of the most often used biomarkers of aging. Recent research has focused on developing interventions to mitigate the effects of aging and improve the quality of life. The objective of this study was to investigate the combined effect of exercise and Ramadan fasting on telomere length. Twenty-nine young, non-obese, healthy females were randomized into two groups: the control group underwent a 4-week exercise training program, and the second group underwent a 4-week exercise training program while fasting during Ramadan. Blood samples were collected, and measurements of clinical traits, cytokines, oxidative stress, and telomere length were performed before and after intervention. Telomere length increased significantly from baseline in the exercise-while-fasting group, but showed no significant change in the exercise control group. This increase was accompanied by a reduction in TNF-α, among other cytokines. Additionally, a significant positive correlation was observed between the mean change in telomere length and HDL in the exercise-while-fasting group only. This study is the first to report an increase in telomere length after combining Ramadan fasting with training, suggesting that exercising while fasting may be an effective tool for slowing down the aging rate. Further studies using larger and more diverse cohorts are warranted.

Low-intensity exercise training improves systolic function of heart during metastatic melanoma-induced cachexia in mice

Cardiac dysfunction frequently emerges in the initial stages of cancer cachexia, posing a significant complication of the disease. Physical fitness is commonly recommended in these early stages of cancer cachexia due to its beneficial impacts on various aspects of the condition, including cardiac dysfunction. However, the direct functional impacts of exercise on the heart during cancer cachexia largely remain unexplored. In this study, we induced cancer cachexia in mice using a metastatic B16F10 melanoma model. Concurrently, these mice underwent a low-intensity exercise regimen to investigate its potential role in cardiac function during cachexia. Our findings indicate that exercise training can help prevent metastatic melanoma-induced muscle loss without significant alterations to body and fat weight. Moreover, exercise improved the melanoma-induced decline in left ventricular ejection fraction and fractional shortening, while also mitigating the increase in high-sensitive cardiac troponin T levels caused by metastatic melanoma in mice. Transcriptome analysis revealed that exercise significantly reversed the transcriptional alterations in the heart induced by melanoma, which were primarily enriched in pathways related to heart contraction. These results suggest that exercise can improve systolic heart function and directly influence the transcriptome of the heart during metastatic melanoma-induced cachexia.

Heat stress-induced activation of MAPK pathway attenuates Atf1-dependent epigenetic inheritance of heterochromatin in fission yeast

Eukaryotic cells are constantly exposed to various environmental stimuli. It remains largely unexplored how environmental cues bring about epigenetic fluctuations and affect heterochromatin stability. In the fission yeast Schizosaccharomyces pombe, heterochromatic silencing is quite stable at pericentromeres but unstable at the mating-type (mat) locus under chronic heat stress, although both loci are within the major constitutive heterochromatin regions. Here, we found that the compromised gene silencing at the mat locus at elevated temperature is linked to the phosphorylation status of Atf1, a member of the ATF/CREB superfamily. Constitutive activation of mitogen-activated protein kinase (MAPK) signaling disrupts epigenetic maintenance of heterochromatin at the mat locus even under normal temperature. Mechanistically, phosphorylation of Atf1 impairs its interaction with heterochromatin protein Swi6HP1, resulting in lower site-specific Swi6HP1 enrichment. Expression of non-phosphorylatable Atf1, tethering Swi6HP1 to the mat3M-flanking site or absence of the anti-silencing factor Epe1 can largely or partially rescue heat stress-induced defective heterochromatic maintenance at the mat locus.

CD163 protein inhibits lipopolysaccharide-induced macrophage transformation from M2 to M1 involved in disruption of the TWEAK-Fn14 interaction

Macrophages play a crucial role in regulating inflammation and innate immune responses, and their polarization into distinct phenotypes, such as M1 and M2, is involved in various diseases. However, the specific role of CD163, a scavenger receptor expressed by macrophages, in the transformation of M2 to M1 macrophages remains unclear. Here, dexamethasone-induced M2 macrophages were treated with lipopolysaccharide (LPS) to induce the transformation of M2 to M1 macrophages. We found that treatment with lipopolysaccharide (LPS) induced the transformation of M2-like macrophages to an M1-like phenotype, as evidenced by increased mRNA levels of Il1b and Tnf, decreased mRNA levels of Cd206 and Il10, and increased TNF-α secretion. Knockdown of CD163 enhanced the phenotypic features of M1 macrophages, while treatment with recombinant CD163 protein (rmCD163) inhibited the LPS-induced M2-to-M1 transformation. Furthermore, LPS stimulation resulted in the activation of P38, ERK, JNK, and NF-κB P65 signaling pathways, and this activation was increased after CD163 knockdown and suppressed after rmCD163 treatment during macrophage transformation. Additionally, we observed that LPS treatment reduced the expression of CD163 in dexamethasone-induced M2 macrophages, leading to a decrease in the CD163-TWEAK complex and an increase in the interaction between TWEAK and Fn14. Overall, our findings suggest that rmCD163 can inhibit the LPS-induced transformation of M2 macrophages to M1 by disrupting the TWEAK-Fn14 interaction and modulating the MAPK-NF-κB pathway.

Longevity-Associated Transcription Factor ATF7 Promotes Healthspan by Suppressing Cellular Senescence and Systematic Inflammation

Aging is characterized by persistent low-grade systematic inflammation, which is largely responsible for the occurrence of various age-associated diseases. We and others have previously reported that long-lived people (such as centenarians) can delay the onset of or even escape certain major age-related diseases. Here, by screening blood transcriptome and inflammatory profiles, we found that long-lived individuals had a relatively lower inflammation level (IL6, TNFα), accompanied by up-regulation of activating transcription factor 7 (ATF7). Interestingly, ATF7 expression was gradually reduced during cellular senescence. Loss of ATF7 induced cellular senescence, while overexpression delayed senescence progress and senescence-associated secretory phenotype (SASP) secretion. We showed that the anti-senescence effects of ATF7 were achieved by inhibiting nuclear factor kappa B (NF-κB) signaling and increasing histone H3K9 dimethylation (H3K9me2). In Caenorhabditis elegans, ATF7 overexpression significantly suppressed aging biomarkers and extended lifespan. Our findings suggest that ATF7 is a longevity-promoting factor that lowers cellular senescence and inflammation in long-lived individuals.

Mouse HP1γ regulates TRF1 expression and telomere stability

AIMS

Telomeric repeat-containing RNAs are long non-coding RNAs generated from the telomeres. TERRAs are essential for the establishment of heterochromatin marks at telomeres, which serve for the binding of members of the heterochromatin protein 1 (HP1) protein family of epigenetic modifiers involved with chromatin compaction and gene silencing. While HP1γ is enriched on gene bodies of actively transcribed human and mouse genes, it is unclear if its transcriptional role is important for HP1γ function in telomere cohesion and telomere maintenance. We aimed to study the effect of mouse HP1γ on the transcription of telomere factors and molecules that can affect telomere maintenance.

MAIN METHODS

We investigated the telomere function of HP1γ by using HP1γ deficient mouse embryonic fibroblasts (MEFs). We used gene expression analysis of HP1γ deficient MEFs and validated the molecular and mechanistic consequences of HP1γ loss by telomere FISH, immunofluorescence, RT-qPCR and DNA-RNA immunoprecipitation (DRIP).

KEY FINDINGS

Loss of HP1γ in primary MEFs led to a downregulation of various telomere and telomere-accessory transcripts, including the shelterin protein TRF1. Its downregulation is associated with increased telomere replication stress and DNA damage (γH2AX), effects more profound in females. We suggest that the source for the impaired telomere maintenance is a consequence of increased telomeric DNA-RNA hybrids and TERRAs arising at and from mouse chromosomes 18 and X.

SIGNIFICANCE

Our results suggest an important transcriptional control by mouse HP1γ of various telomere factors including TRF1 protein and TERRAs that has profound consequences on telomere stability, with a potential sexually dimorphic nature.

RBMX involves in telomere stability maintenance by regulating TERRA expression

Telomeric repeat-containing RNA (TERRA) is a class of long noncoding RNAs (lncRNAs) that are transcribed from subtelomeric to telomeric region of chromosome ends. TERRA is prone to form R-loop structures at telomeres by invading into telomeric DNA. Excessive telomere R-loops result in telomere instability, so the TERRA level needs to be delicately modulated. However, the molecular mechanisms and factors controlling TERRA level are still largely unknown. In this study, we report that the RNA binding protein RBMX is a novel regulator of TERRA level and telomere integrity. The expression level of TERRA is significantly elevated in RBMX depleted cells, leading to enhanced telomere R-loop formation, replication stress, and telomere instability. We also found that RBMX binds to TERRA and the nuclear exosome targeting protein ZCCHC8 simultaneously, and that TERRA degradation slows down upon RBMX depletion, implying that RBMX promotes TERRA degradation by regulating its transportation to the nuclear exosome, which decays nuclear RNAs. Altogether, these findings uncover a new role of RBMX in TERRA expression regulation and telomere integrity maintenance, and raising RBMX as a potential target of cancer therapy.

The regulatory feedback of inflammatory signaling and telomere/telomerase complex dysfunction in chronic inflammatory diseases

Inflammation is believed to play a role in the progression of numerous human diseases. Research has shown that inflammation and telomeres are involved in a feedback regulatory loop: inflammation increases the rate of telomere attrition, leading to telomere dysfunction, while telomere components also participate in regulating the inflammatory response. However, the specific mechanism behind this feedback loop between inflammatory signaling and telomere/telomerase complex dysfunction has yet to be fully understood. This review presents the latest findings on this topic, with a particular focus on the detailed regulation and molecular mechanisms involved in the progression of aging, various chronic inflammatory diseases, cancers, and different stressors. Several feedback loops between inflammatory signaling and telomere/telomerase complex dysfunction, including NF-κB-TERT feedback, NF-κB-RAP1 feedback, NF-κB-TERC feedback, STAT3-TERT feedback, and p38 MAPK-shelterin complex-related gene feedback, are summarized. Understanding the latest discoveries of this feedback regulatory loop can help identify novel potential drug targets for the suppression of various inflammation-associated diseases.

Acetylation of Atp5f1c Mediates Cardiomyocyte Senescence via Metabolic Dysfunction in Radiation-Induced Heart Damage

Objective

Ionizing radiation (IR) causes cardiac senescence, which eventually manifests as radiation-induced heart damage (RIHD). This study is aimed at exploring the mechanisms underlying IR-induced senescence using acetylation proteomics.

Methods

Irradiated mouse hearts and H9C2 cells were harvested for senescence detection. Acetylation proteomics was used to investigate alterations in lysine acetylation. Atp5f1c acetylation after IR was verified using coimmunoprecipitation (Co-IP). Atp5f1c lysine 55 site acetylation (Atp5f1c K55-Ac) point mutation plasmids were used to evaluate the influence of Atp5f1c K55-Ac on energy metabolism and cellular senescence. Deacetylation inhibitors, plasmids, and siRNA transfection were used to determine the mechanism of Atp5f1c K55-Ac regulation.

Results

The mice showed cardiomyocyte and cardiac aging phenotypes after IR. We identified 90 lysine acetylation sites from 70 protein alterations in the heart in response to IR. Hyperacetylated proteins are primarily involved in energy metabolism. Among them, Atp5f1c was hyperacetylated, as confirmed by Co-IP. Atp5f1c K55-Ac decreased ATP enzyme activity and synthesis. Atp5f1c K55 acetylation induced cardiomyocyte senescence, and Sirt4 and Sirt5 regulated Atp5f1c K55 deacetylation.

Conclusion

Our findings reveal a mechanism of RIHD through which Atp5f1c K55-Ac leads to cardiac aging and Sirt4 or Sirt5 modulates Atp5f1c acetylation. Therefore, the regulation of Atp5f1c K55-Ac might be a potential target for the treatment of RIHD.

The Leucocyte Telomere Length, GSTM1 and GSTT1 Null Genotypes and the Risk of Chronic Obstructive Pulmonary Disease

Simple Summary

Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation and oxidative stress, both in the airways and blood, and in other organs. Elevated oxidative stress and inflammation have been reported to affect leucocyte telomere length (LTL). We explored the link between GSTM1 and GSTT1 gene polymorphisms, LTL and COPD risk. For GSTM1 and GSTT1, we genotyped 152 COPD patients and 131 non-affected controls, while for TL, we assessed 91 patients and 88 controls. There was a significant difference in GSTM1 null genotype frequency between the patients and controls (0.59 vs. 0.38, p ≤ 0.000), but such was not found for GSTT1 (p = 0.192). COPD patients carrying the GSTM1 null genotype had shorter telomeres compared to those carrying the non-null genotype (15,720 bp vs. 22,442 bp, p = 0.008); and in controls, the opposite occurred (31,354 bp vs. 17,800 bp, p = 0.020). According to our results GSTM1, but not GSTT1, null genotypes might play role in leucocyte telomere shortening, and thus be involved in the pathogenesis of COPD.

Abstract

Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation and oxidative stress both in the airways and blood and other organs. Elevated oxidative stress and inflammation have been reported to affect leucocyte telomere length (LTL). Glutathione S-transferase (GST) enzymes are a large family of xenobiotic-metabolizing enzymes that utilize different ROS products. We aimed to explore the link between GSTM1 and GSTT1 gene polymorphisms, LTL and COPD risk. For GSTM1, we genotyped 152 COPD patients and 131 non-affected controls; for GSTT1, we genotyped 149 COPD patients and 130 controls. We were able to assess TL for 91 patients and 88 controls. There was a significant difference in the GSTM1 null genotype frequency between the patients and controls (0.59 vs. 0.38, p ≤ 0.000), but such was not found for GSTT1 (p = 0.192). When combining both polymorphisms, we obtained a significantly greater presence of at least one null genotype among patients (0.12 vs. 0.05, p = 0.027). An association between GSTT1 and LTL was not found. COPD patients carrying the GSTM1 null genotype had shorter telomeres compared to those carrying the non-null genotype (15,720 bp vs. 22,442 bp, p = 0.008); as for the controls, it was the opposite (31,354 bp vs. 17,800 bp, p = 0.020). The significance in both groups remained when combining GSTM1 and GSTT1 (COPD (at least one null) 16,409 bp vs. COPD (non-null) 22,092 bp, p = 0.029; control (at least one null) 29,666 bp vs. control (non-null) 16,370 bp, p = 0.027). The total glutathione level in GSTM1 non-null controls was higher compared to the null genotype (15.39 ng/mL vs. 5.53 ng/mL, p = 0.002). In COPD patients, we found no association (p = 0.301). In conclusion, according to our results, GSTM1, but not GSTT1, null genotypes might play a role in leucocyte telomere shortening, and thus be involved in the pathogenesis of COPD.

Genetic and Epigenetic Inheritance at Telomeres

Transgenerational inheritance can occur at telomeres in distinct contexts. Deficiency for telomerase or telomere-binding proteins in germ cells can result in shortened or lengthened chromosome termini that are transmitted to progeny. In human families, altered telomere lengths can result in stem cell dysfunction or tumor development. Genetic inheritance of altered telomeres as well as mutations that alter telomeres can result in progressive telomere length changes over multiple generations. Telomeres of yeast can modulate the epigenetic state of subtelomeric genes in a manner that is mitotically heritable, and the effects of telomeres on subtelomeric gene expression may be relevant to senescence or other human adult-onset disorders. Recently, two novel epigenetic states were shown to occur at C. elegans telomeres, where very low or high levels of telomeric protein foci can be inherited for multiple generations through a process that is regulated by histone methylation.Together, these observations illustrate that information relevant to telomere biology can be inherited via genetic and epigenetic mechanisms, although the broad impact of epigenetic inheritance to human biology remains unclear.

Single Cell Proteomics Profiling Reveals That Embryo-Secreted TNF-α Plays a Critical Role During Embryo Implantation to the Endometrium

It has been long-known that endometrium-secreted cytokines play a critical role during embryo implantation. However, whether cytokines secreted from the embryo are relevant to the process of embryo implantation remains unclear. The concentration of cytokines in embryo culture medium was tested using a newly developed, high-sensitivity single-cell proteomic platform and evaluated in comparison to embryo quality and clinical outcome. The effect of TNF-α on embryo and endometrium Ishikawa cells was investigated using immunofluorescence staining, CCK-8 assay, TUNEL staining, and RT-qPCR. Of the 10 cytokines measured, only TNF-α concentration was significantly higher in the group with embryo implantation failure. Immunofluorescence staining showed that the expression of TNF-α was unevenly distributed in blastocysts, and the expression level was significantly correlated with the blastocyst inner cell mass (ICM) quality score. Gene profiling showed that addition of TNF-α led to increased expression of tumor necrosis factor receptor 1 (TNFR1) and apoptosis-related genes and that this could be inhibited by the TNF-α receptor inhibitor etanercept (ETA). In addition, an increased expression of water and ion channels, including AQP3, CFTR, ENaCA, and CRISP2 was also observed which could also be inhibited by ETA. Our results show that higher embryo-secreted TNF-α levels are associated with implantation failure through activation of TNF-α receptor, and TNF-α may be an independent predictor for pre-transfer assessment of the embryo development potential in IVF patients.

The leukocyte telomere length, single nucleotide polymorphisms near TERC gene and risk of COPD

Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airflow obstruction and is associated with chronic local and systemic inflammation and oxidative stress. The enhanced oxidative stress and inflammation have been reported to affect telomere length (TL). Furthermore, a number of SNPs at loci encoding the main components of the telomerase genes, TERT and TERC have been shown to correlate with TL. We aimed to explore the leukocyte TL and genotypes for single nucleotide polymorphisms, rs12696304 (C > G) and rs10936599 (C > T) near TERC in COPD cases and matched healthy controls using q-PCR technologies. Successful assessment of TL was performed for 91 patients and 88 controls. The patients had shorter TL (17919.36 ± 1203.01 bp) compared to controls (21 271.48 ± 1891.36 bp) although not significant (p = 0.137). The TL did not associate with the gender, age, spirometric indexes, smoking habits but tended to correlate negatively with BMI (Rho = − 0.215, p = 0.076) in the controls, but not in COPD patients. The genotype frequencies of the SNPs rs12696304 and rs10936599 were compared between patients and controls and the odds ratios (OR) for developing COPD were calculated. The carriers of the common homozygous (CC) genotypes of the SNPs had higher risk for COPD, compared to carriers of the variants alleles (rs12696304 CG+GG vs. CC; OR: 0.615, 95% CI [0.424–0.894], p = 0.011 and for rs10936599 CT+TT vs. CC OR = 0.668, 95% CI [0.457–0.976], p = 0.044). Analysis on the combined effects of the TERCrs12696304 (C > G) and rs10936599 (C > T) genotypes, CC/CC genotype combination was associated with higher risk for COPD (p < 0.0001) and marginally lower FEV1% pr. in patients with GOLD II (p = 0.052). There was no association between the SNP genotypes and TL. In summary, our results suggest that COPD patients may have shorter TL, and rs12696304 and rs10936599 near TERC may affect the risk of COPD independently of TL.

Relationships of Telomere Homeostasis with Oxidative Stress and Cardiac Dysfunction in Human Ischaemic Hearts

Although the roles of telomeres and oxidative stress in ischaemic cardiomyopathy (ICM) are known, mechanisms of telomere homeostasis and their relationship with oxidative stress are incompletely understood. We performed two RNA-seq analyses (mRNA n = 23; ncRNA n = 30) and protein validation on left ventricles of explanted hearts from ICM and control subjects. We observed dysregulation of the shelterin and cohesin complexes, which was related to an increase in the response to cellular oxidative stress. Moreover, we found alterations at mRNA level in the mechanisms of telomeric DNA repair. Specifically, increased RAD51D mRNA levels were correlated with left ventricular diameters. RAD51D protein levels were unaltered, however, and were inversely corelated with the miR-103a-3p upregulation. We also observed the overexpression of lncRNAs (TERRA and GUARDIN) involved in telomere protection in response to stress and alterations in their regulatory molecules. Expression of the TERRA transcription factor ATF7 was correlated with superoxide dismutase 1 expression and left ventricular diameters. The levels of GUARDIN and its transcription factor FOSL2 were correlated with those of catalase. Therefore, we showed specific alterations in the mechanisms of telomeric DNA repair and protection, and these alterations are related to an increase in the response mechanisms to oxidative stress and cardiac dysfunction in ICM.

Long Noncoding RNA Cardiac Physiological Hypertrophy-Associated Regulator Induces Cardiac Physiological Hypertrophy and Promotes Functional Recovery After Myocardial Ischemia-Reperfusion Injury

BACKGROUND

The benefits of exercise training in the cardiovascular system have been well accepted; however, the underlying mechanism remains to be explored. Here, we report the initial functional characterization of an exercise-induced cardiac physiological hypertrophy-associated novel long noncoding RNA (lncRNA).

METHODS

Using lncRNA microarray profiling, we identified lncRNAs in contributing the modulation of exercise-induced cardiac growth that we termed cardiac physiological hypertrophy-associated regulator (CPhar). Mice with adeno-associated virus serotype 9 driving CPhar overexpression and knockdown were used in in vivo experiments. Swim training was used to induce physiological cardiac hypertrophy in mice, and ischemia reperfusion injury surgery was conducted to investigate the protective effects of CPhar in mice. To investigate the mechanisms of CPhar's function, we performed various analyses including quantitative reverse transcription polymerase chain reaction, Western blot, histology, cardiac function (by echocardiography), functional rescue experiments, mass spectrometry, in vitro RNA transcription, RNA pulldown, RNA immunoprecipitation, chromatin immunoprecipitation assay, luciferase reporter assay, and coimmunoprecipitation assays.

RESULTS

We screened the lncRNAs in contributing the modulation of exercise-induced cardiac growth through lncRNA microarray profiling and found that CPhar was increased with exercise and was necessary for exercise-induced physiological cardiac growth. The gain and loss of function of CPhar regulated the expression of proliferation markers, hypertrophy, and apoptosis in cultured neonatal mouse cardiomyocytes. Overexpression of CPhar prevented myocardial ischemia reperfusion injury and cardiac dysfunction in vivo. We identified DDX17 (DEAD-Box Helicase 17) as a binding partner of CPhar in regulating CPhar downstream factor ATF7 (activating transcription factor 7) by sequestering C/EBPβ (CCAAT/enhancer binding protein beta).

CONCLUSIONS

Our study of this lncRNA CPhar provides new insights into the regulation of exercise-induced cardiac physiological growth, demonstrating the cardioprotective role of CPhar in the heart, and expanding our mechanistic understanding of lncRNA function, as well.

Radiation-induced abscopal reproductive effect is driven by TNF-α/p38 MAPK/Rac1 axis in Sertoli cells

Rationale: Radiotherapy has become a mainstay for tumor management, and more than 50% of patients with thoracic tumor need to be treated with radiotherapy. However, the potential adverse effects of thoracic radiotherapy on the reproductive system remain elusive.

Methods: Western blot analysis, immunofluorescence assay and transmission electron microscopy (TEM) analysis were performed to investigate the integrity of blood-testis barrier (BTB) in male mice after hypofractionated irradiation (IR) on the right thorax. RNA sequencing, co-immunoprecipitation (IP), Duolink PLA and inhibitor experiments were carried out to demonstrate the molecular mechanisms of the BTB dynamics changes and the subsequent reproductive effect.

Results: It was found that the hypofractionated IR on right thorax evoked ultrastructural destruction in distant testes, and thus caused radiation-induced abscopal reproductive effect (RIARE) in male mice. Mechanistically, thoracic IR induced significant nuclear translocation of Rac Family Small GTPase 1 (Rac1) in abscopal Sertoli cells, which closely correlated with the activation of TNF-α/p38 mitogen activated protein kinase (MAPK) pathway. Of note, YWHAZ, a critical polarity protein, was found to be co-localized with Rac1 in Sertoli cells, and this interaction was indispensable for thoracic IR-induced Rac1 nuclear translocation and subsequent degradation of BTB-associated proteins.

Conclusions: Our findings imply for the first time that YWHAZ-mediated Rac1 nuclear translocation plays central roles in RIARE, and TNF-α/p38 MAPK/Rac1 axis can be employed as a therapeutic target against RIARE for young male patients receiving hypofractionated radiotherapy.

Regulation of telomeric function by DNA methylation differs between humans and mice

The most distal 2 kb region in the majority of human subtelomeres contains CpG-rich promoters for TERRA, a long non-coding RNA. When the function of the de novo DNA methyltransferase DNMT3B is disrupted, as in ICF1 syndrome, subtelomeres are abnormally hypomethylated, subtelomeric heterochromatin acquires open chromatin characteristics, TERRA is highly expressed, and telomeres shorten rapidly. In this study, we explored whether the regulation of subtelomeric epigenetic characteristics by DNMT3B is conserved between humans and mice. Studying the DNA sequence of the distal 30 kb of the majority of murine q-arm subtelomeres indicated that these regions are relatively CpG-poor and do not contain TERRA promoters similar to those present in humans. Despite the lack of human-like TERRA promoters, we clearly detected TERRA expression originating from at least seven q-arm subtelomeres, and at higher levels in mouse pluripotent stem cells in comparison with mouse embryonic fibroblasts (MEFs). However, these differences in TERRA expression could not be explained by differential methylation of CpG islands present in the TERRA-expressing murine subtelomeres. To determine whether Dnmt3b regulates the expression of TERRA in mice, we characterized subtelomeric methylation and associated telomeric functions in cells derived from ICF1 model mice. Littermate-derived WT and ICF1 MEFs demonstrated no significant differences in subtelomeric DNA methylation, chromatin modifications, TERRA expression levels, telomere sister chromatid exchange or telomere length. We conclude that the epigenetic characteristics of murine subtelomeres differ substantially from their human counterparts and that TERRA transcription in mice is regulated by factors others than Dnmt3b.

TRF2 recruits nucleolar protein TCOF1 to coordinate telomere transcription and replication

Telomeres are transcribed into telomeric RNA termed as TERRA. However, the transcription itself and excessive TERRA may interfere with telomere replication during S phase. The mechanism that coordinates telomere transcription and replication is unknown. Here, we report that TCOF1 leaves the nucleolus and is recruited to telomeres specifically during S phase by interacting with TRF2. Therein, TCOF1 acts to suppress telomere transcription by binding and inhibiting Pol II. Thus, TERRA is limited to low levels in S phase. Depletion of TCOF1 leads to abnormally elevated TERRA and formation of DNA/RNA hybrids (R-loops) at telomeres, which induces replication fork stalling and fragile telomeres. Importantly, telomere replication defect induced by TCOF1 deficiency can be rescued by either masking TERRA or expressing an R-loop eraser RNase H1, demonstrating a critical role of TCOF1 in coordinating telomere transcription and replication. These findings link nucleolus to telomeres and uncover a novel function of TCOF1 on ensuring telomere integrity.

Potential Protective Effect of Dietary Intake of Non-α-Tocopherols on Cellular Aging Markers Mediated by Tumor Necrosis Factor-α in Prediabetes: A Cross-Sectional Study of Chinese Adults

It remains unknown how different glucose tolerance status affects the relationships between dietary intake of different tocopherol isoforms (α-, β-, γ-, and δ-tocopherol) and cellular aging, oxidative stress, and inflammatory markers. The authors conducted a cross-sectional study among 582 Chinese adults with different glucose tolerance status to explore the association between dietary intake of different tocopherol isoforms and cellular aging, oxidative stress, and inflammatory markers. The inverse correlations between non-α-tocopherols and tumor necrosis factor-alpha (TNF-α) varied substantially across different glucose tolerance status, with the strongest observed in prediabetes (r = −0.33 for β-/γ-tocopherol, r = −0.37 for δ-tocopherol, p < 0.01), followed by normal glucose tolerance (NGT). While such correlations were abolished in established diabetes. Furthermore, within prediabetes, the strongest inverse correlations between non-α-tocopherols and TNF-α were observed in impaired fasting glucose (IFG) (r = −0.42 for β-/γ-tocopherol, r = −0.55 for δ-tocopherol, p < 0.01), while such correlations were significantly attenuated in individuals with impaired glucose tolerance (IGT) and IFG+IGT. And mediation model analysis displayed that TNF-α mediated the protective effect of non-α-tocopherols on leukocyte telomere length and mitochondrial DNA copy number, which was uniquely observed in prediabetes, while such mediation effect was statistically nonsignificant in NGT and established diabetes. In conclusion, our findings indicate that dietary intake of non-α-tocopherols might protect against cellular aging markers mediated by TNF-α in prediabetes. Individuals with prediabetes, especially for IFG, might benefit from increasing dietary intake of non-α-tocopherol in alleviating inflammation and cellular aging, which might provide a new dietary avenue for delaying diabetes onset.

Leukocyte Telomere Length Independently Predicts 3-Year Diabetes Risk in a Longitudinal Study of Chinese Population

Cellular aging markers, including telomere length and mitochondrial function, as well as oxidative stress and inflammation markers influence each other and form a complex network, which is affected in diabetes. However, it remains unknown whether these markers could independently predict future diabetes after adjustment for their mutual effects. We conducted a 3-year longitudinal study in a Chinese cohort that comprised 108 nondiabetic individuals at baseline. The 2-hour 75 g oral glucose tolerance tests were performed at baseline and at 3-year follow-up. At baseline, leukocyte telomere length (LTL) and mitochondrial DNA copy number (mtDNAcn) in leukocytes were determined using the polymerase chain reaction method. Tumor necrosis factor (TNF-α), interleukin-6, 8-hydroxy-2-deoxyguanosine levels, and superoxide dismutase (SOD) activity were measured by the enzyme-linked immunosorbent assay. Participants who developed diabetes at the 3-year follow-up (n = 28) had shorter LTL and higher levels of TNF-α and SOD activity at baseline. Baseline LTL was found to be independently associated with the development of diabetes at the 3-year follow-up after the adjustment for mtDNAcn, markers of oxidative stress and inflammation, and conventional diabetes risk factors. Our findings suggest that LTL is an independent predictor for 3-year diabetes risk, which might inform timely prevention and treatment of diabetes. Telomere shortening might be involved in the pathogenesis of diabetes independently of conventional diabetes risk factors, mtDNAcn, or oxidative stress and inflammation pathways.

Testing for paternal influences on offspring telomere length in a human cohort in the Philippines

OBJECTIVES

Telomeres, emerging biomarkers of aging, are comprised of DNA repeats located at chromosomal ends that shorten with cellular replication and age in most human tissues. In contrast, spermatocyte telomeres lengthen with age. These changes in telomere length (TL) appear to be heritable, as older paternal ages of conception (PAC) predict longer offspring TL. Mouse-model studies raise questions about the potential for effects of paternal experiences on human offspring TL, as they suggest that smoking, inflammation, DNA damage, and stressors all shorten sperm TL. Here, we examined whether factors from the paternal environment predict offspring TL as well as interact with PAC to predict offspring TL.

MATERIALS AND METHODS

Using data from the Philippines, we tested if smoking, psychosocial stressors, or shorter knee height (a measure of early life adversity) predict shorter offspring TL. We also tested if these interacted with PAC in predicting offspring TL.

RESULTS

While we did not find the predicted associations, we observed a trend toward fathers with shorter knee height having offspring with longer TL. In addition, we found that knee height interacted with PAC to predict offspring TL. Specifically, fathers with shorter knee heights showed a stronger positive effect of PAC on offspring TL.

DISCUSSION

While the reasons for these associations remain uncertain, shorter knee height is characteristic of earlier puberty. Since spermatocyte TL increases with the production of sperm, we speculate that individuals with earlier puberty, and its concomitant commencement of production of sperm, had more time to accumulate longer sperm telomeres.

Expression and differential regulation of human TERRA at several chromosome ends

The telomeric long noncoding RNA TERRA has been implicated in regulating telomere maintenance by telomerase and homologous recombination, and in influencing telomeric protein composition during the cell cycle and the telomeric DNA damage response. TERRA transcription starts at subtelomeric regions resembling the CpG islands of eukaryotic genes extending toward chromosome ends. TERRA contains chromosome-specific subtelomeric sequences at its 5' end and long tracts of UUAGGG-repeats toward the 3' end. Conflicting studies have been published as to whether TERRA is expressed from one or several chromosome ends. Here, we quantify TERRA species by RT-qPCR in normal and several cancerous human cell lines. By using chromosome-specific subtelomeric DNA primers, we demonstrate that TERRA is expressed from a large number of telomeres. Deficiency in DNA methyltransferases leads to TERRA up-regulation only at the subset of chromosome ends that contain CpG-island sequences, revealing differential regulation of TERRA promoters by DNA methylation. However, independently of the differences in TERRA expression, short telomeres were uniformly present in a DNA methyltransferase deficient cell line, indicating that telomere length was not dictated by TERRA expression in cis Bioinformatic analyses indicated the presence of a large number of putative transcription factors binding sites at TERRA promoters, and we identified a subset of them that repress TERRA expression. Altogether, our study confirms that TERRA corresponds to a large gene family transcribed from multiple chromosome ends where we identified two types of TERRA promoters, only one of which is regulated by DNA methylation.

Stress-induced and ATF7-dependent epigenetic change influences cellular senescence

Cellular senescence plays an important role in aging and is induced by cyclin-dependent kinase (Cdk) inhibitors that accumulate following stresses during aging. However, the underlying mechanism remains elusive. Herein, we demonstrate that activating transcription factor 7 (ATF7), the stress-responsive recruiter of histone H3K9 di- and trimethyltransferases, functions in the accumulation of Cdk inhibitors. Atf7-deficient (Atf7^-/- ) mice have a shorter lifespan than wild-type (WT) mice. Levels of p16^Ink4a Cdk inhibitor mRNA increased with age more rapidly in Atf7^-/- mice than in WT animals. ATF7 binds to the p16^Ink4a gene promoter and was released with age. Consistently, histone H3K9me2 levels on the p16^Ink4a gene promoter were lower in Atf7^-/- mice than in WT animals. Similar results were obtained when Atf7^-/- and WT mouse embryonic fibroblasts (MEFs) were cultured under 20% oxygen conditions, which induces cellular senescence via oxidative stress. Phosphorylation of ATF7 by p38 was also increased with the passage of MEFs, consistent with previous observations that ATF7 phosphorylation by p38 induces its release from chromatin. These results indicate that stress-induced and ATF7-dependent epigenetic changes on p16^Ink4a genes play an important role in cellular senescence.