Axis of ageing: telomeres, p53 and mitochondria. Nat Rev Mol Cell Biol. 2012;13:397-404. [PMID: 22588366 DOI: 10.1038/nrm3352]

Autophagy, Aging, and Longevity

Autophagy is a conserved process that degrades intracellular components through lysosomes, thereby maintaining energy homeostasis and renewal of organelles. Mounting evidence indicates that autophagy plays a key role in aging and aging-related diseases. Enhanced autophagy can delay aging and prolong life span. The absence of autophagy leads to the accumulation of mutant and misfolded proteins in the cell, which is the basis for the emergence and development of neurodegenerative diseases and other aging-related diseases. It will be of importance to develop approaches to extend the lifespan and improve the health of elderly individuals through the modulation of autophagy.

Enzymatic antioxidants but not baseline glucocorticoids mediate the reproduction-survival trade-off in a wild bird

The trade-off between reproductive investment and survival is central to life-history theory, but the relative importance and the complex interactions among the physiological mechanisms mediating it are still debated. Here we experimentally tested whether baseline glucocorticoid hormones, the redox system or their interaction mediate reproductive investment-survival trade-offs in wild great tits (Parus major). We increased the workload of parental males by clipping three feathers on each wing, and 5 days later determined effects on baseline corticosterone concentrations (Cort), redox state (reactive oxygen metabolites, protein carbonyls, glutathione peroxidase [GPx], total non-enzymatic antioxidants), body mass, body condition, reproductive success and survival. Feather-clipping did not affect fledgling numbers, chick body condition, nest provisioning rates or survival compared with controls. However, feather-clipped males lost mass and increased both Cort and GPx concentrations. Within feather-clipped individuals, GPx increases were positively associated with reproductive investment (i.e. male nest provisioning). Furthermore, within all individuals, males that increased GPx suffered reduced survival rates. Baseline Cort increases were related to mass loss but not to redox state, nest provisioning or male survival. Our findings provide experimental evidence that changes in the redox system are associated with the trade-off between reproductive investment and survival, while baseline Cort may support this trade-off indirectly through a link with body condition. These results also emphasize that plastic changes in individuals, rather than static levels of physiological signals, may mediate life-history trade-offs.

The role of melatonin, a multitasking molecule, in retarding the processes of ageing

Biological ageing is generally accompanied by a gradual loss of cellular functions and physiological integrity of organ systems, the consequential enhancement of vulnerability, senescence and finally death. Mechanisms which underlie ageing are primarily attributed to an array of diverse but related factors including free radical-induced damage, dysfunction of mitochondria, disruption of circadian rhythms, inflammaging, genomic instability, telomere attrition, loss of proteostasis, deregulated sensing of nutrients, epigenetic alterations, altered intercellular communication, and decreased capacity for tissue repair. Melatonin, a prime regulator of human chronobiological and endocrine physiology, is highly reputed as an antioxidant, immunomodulatory, antiproliferative, oncostatic, and endocrine-modulatory molecule. Interestingly, several recent reports support melatonin as an anti-ageing agent whose multifaceted functions may lessen the consequences of ageing. This review depicts four categories of melatonin's protective effects on ageing-induced molecular and structural alterations. We also summarize recent findings related to the function of melatonin during ageing in various tissues and organs.

Mitochondrial DNA copy number is associated with psychosis severity and anti-psychotic treatment

Mitochondrial pathology has been implicated in the pathogenesis of psychotic disorders. A few studies have proposed reduced leukocyte mitochondrial DNA (mtDNA) copy number in schizophrenia and bipolar disorder type I, compared to healthy controls. However, it is unknown if mtDNA copy number alteration is driven by psychosis, comorbidity or treatment. Whole blood mtDNA copy number was determined in 594 psychosis patients and corrected for platelet to leukocyte count ratio (mtDNAcn_res). The dependence of mtDNAcn_res on clinical profile, metabolic comorbidity and antipsychotic drug exposure was assessed. mtDNAcn_res was reduced with age (β = −0.210, p < 0.001), use of clozapine (β = −0.110,p = 0.012) and risperidone (β = −0.109,p = 0.014), dependent on prescribed dosage (p = 0.006 and p = 0.026, respectively), and the proportion of life on treatment (p = 0.006). Clozapine (p = 0.0005) and risperidone (p = 0.0126) had a reducing effect on the mtDNA copy number also in stem cell-derived human neurons in vitro at therapeutic plasma levels. For patients not on these drugs, psychosis severity had an effect (β = −0.129, p = 0.017), similar to age (β = −0.159, p = 0.003) and LDL (β = −0.119, p = 0.029) on whole blood mtDNAcn_res. Further research is required to determine if mtDNAcn_res reflects any psychosis-intrinsic mitochondrial changes.

Determinants of dopaminergic neuron loss in Parkinson's disease

The cardinal motor symptoms of Parkinson's disease (PD) are caused by the death of dopaminergic neurons in the substantia nigra pars compacta (SNc). Alpha-synuclein (aSYN) pathology and mitochondrial dysfunction have been implicated in PD pathogenesis, but until recently it was unclear why SNc dopaminergic neurons should be particularly vulnerable to these two types of insult. In this brief review, the evidence that SNc dopaminergic neurons have an anatomical, physiological, and biochemical phenotype that predisposes them to mitochondrial dysfunction and synuclein pathology is summarized. The recognition that certain traits may predispose neurons to PD-linked pathology creates translational opportunities for slowing or stopping disease progression.

Early life adiposity and telomere length across the life course: a systematic review and meta-analysis

Background: The relationship between adiposity at birth and in childhood, and telomere length is yet to be determined. We aimed to systematically review and meta-analyse the results of studies assessing associations between neonatal and later childhood adiposity, and telomere length. Methods: We searched Medline, EMBASE and PubMed for studies reporting associations between adiposity measured in the neonatal period or later childhood/adolescence, and leucocyte telomere length, measured at any age via quantitative polymerase chain reaction, or terminal restriction fragment analysis, either cross-sectionally, or longitudinally. Papers published before April 2017 were included. Results: Out of 230 abstracts assessed, 23 papers (32 estimates) were retained, from which 19 estimates were meta-analysed (15 cross-sectional, four longitudinal). Of the 15 cross-sectional estimates, seven reported on neonates: four used binary exposures of small-for-gestational-age vs. appropriate-for-gestational age (or appropriate- and large-for-gestational age), and three studied birth weight continuously. Eight estimates reported on later childhood or adolescent measures; five estimates were from studies of binary exposures (overweight/obese vs. non-obese children), and three studies used continuous measures of body mass index. All four longitudinal estimates were of neonatal adiposity, with two estimates for small-for-gestational-age vs. appropriate-for-gestational age neonates, and two estimates of birth weight studied continuously, in relation to adult telomere (49-61 years). There was no strong evidence of an association between neonatal or later childhood/adolescent adiposity, and telomere length. However, between study heterogeneity was high, and there were few combinable studies. Conclusions: Our systematic review and meta-analysis found no strong evidence of an association between neonatal or later childhood or adolescent adiposity and telomere length.

Tight co-twin similarity of monozygotic twins for hTERT protein level of T cell subsets, for telomere length and mitochondrial DNA copy number, but not for telomerase activity

Our study analyzed lymphocyte subpopulations of 32 monozygotic twins and compared the level of the catalytic reverse transcriptase protein subunit (hTERT) in T lymphocytes (Tly), helper- (Th), cytotoxic- (Tc) and regulatory T cell (Treg) subgroups. Four variables related to telomere and mitochondrial biology were simultaneously assessed, applying multi-parametric flow cytometry, TRAP-ELISA assay and qPCR standard curve method on peripheral blood mononuclear cell (PBMC) samples of genetically matched individuals. Twin data of telomerase activity (TA), hTERT protein level, telomere length (TL) and mitochondrial DNA copy number (mtDNAcn) were analyzed for co-twin similarity. The present study has provided novel information by demonstrating very high intraclass correlation (ICC) of hTERT protein level in T lymphocytes (0.891) and in both Th (0.896), Treg (0.885) and Tc (0.798) cell subgroups. When comparing results measured from PBMCs, intraclass correlation was also high for telomere length (0.815) and considerable for mtDNA copy number (0.524), and again exceptionally high for the rate-limiting telomerase subunit, hTERT protein level (0.946). In contrast, telomerase activity showed no co-twin similarity (ICC 0). By comparing relative amounts of hTERT protein levels in different lymphocyte subgroups of twin subjects, in Treg cells significantly higher level could be detected compared to Tly, Th or Tc cell subgroups. This is the first study that simultaneously analyzed co-twin similarity in MZ twins for the above four variables and alongside assessed their relationship, whereby positive association was found between TL and mtDNAcn.

Ageing at the level of telomeres in association to residential landscape and air pollution at home and work: a review of the current evidence

Studies suggest that leukocyte telomere length is an index of systemic ageing. Here, we discuss telomere length as a marker of biological ageing in relation to residential landscape (greenness), residential air pollution and work-related exposures. Telomere lengths are memories of cumulative oxidative and inflammatory stress, and show to have inverse associations with the risk of non-communicable diseases. For this reason, telomeres are considered as markers of biological ageing. Studies at birth, in children, young adulthood, and elderly show that residential green space, lower traffic exposure and long-term lower exposure to particulate air pollution are associated with longer telomeres. Work-related exposures including exposure to toxic metals, polycyclic aromatic hydrocarbons and particulate matter are associated with shorter telomeres for a given age. In contrast to chronic exposures, evidence is present of the observation that recent exposure is associated with longer telomeres. Our overview shows that the magnitude of residential and work-related environmental factors on telomere length are often as important as many classical lifestyle factors.

Targeting the association between telomere length and immuno-cellular bioenergetics in female patients with Major Depressive Disorder

Major Depressive Disorder (MDD) has been associated with telomere dysfunction and alterations in mitochondrial activity, which seem to be co-regulated in human cells. To investigate this co-regulation in MDD, we assessed telomere length (TL) in peripheral blood mononuclear cells (PBMC) and selected immune cell subsets by quantitative fluorescence in situ hybridization and mitochondrial respiratory activity in PBMC by high-resolution respirometry in a study cohort of 18 MDD patients and 21 non-depressed controls. We provide initial evidence for a differential vulnerability to telomere attrition in selected adaptive immune cell populations. Here we found the highest difference in TL between depressed and control subjects for memory cytotoxic T cells. Depression was associated with reduced mitochondrial activity (mitochondrial bioenergetics), but increased mitochondrial density (mitochondrial biogenesis) in PBMC. Exploratory post-hoc analyses indicated that the changes in TL and immune cell bioenergetics were most pronounced in MDD patients who reported experiences of childhood sexual abuse. Among MDD patients, PBMC TL was as a trend positively associated with mitochondrial density and negatively associated with mitochondrial leak respiration, but not with mitochondrial activity related to biological energy production. These initial findings support the hypothesis of a co-regulation between telomeres and mitochondrial biogenesis but not mitochondrial bioenergetics among MDD patients.

Promoter methylation of PGC1A and PGC1B predicts cancer incidence in a veteran cohort

AIM

Previous studies suggest telomere shortening represses PGC1A and PGC1B expression leading to mitochondrial dysfunction. Methylation of CpG sites within these genes may interact with these factors to affect cancer risk.

MATERIALS & METHODS

Among 385 men, we identified 84 incidents of cancers (predominantly prostate and nonmelanoma skin). We examined associations between leukocyte DNA methylation of 41 CpGs from PGC1A and PGC1B with telomere length, mitochondrial 8-OHdG lesions, mitochondrial abundance and cancer incidence.

RESULTS

Methylation of five and eight CpG sites were significantly associated with telomere length and mitochondrial abundance at p < 0.05. Two CpG sites were independently associated with cancer risk: cg27514608 (PGC1A, TSS1500; HR: 1.55, 95% CI: 1.19-2.03, FDR = 0.02), and cg15219393 (PGC1B, first exon/5'UTR; HR: 3.71, 95% CI: 1.82-7.58, FDR < 0.01). Associations with cg15219393 were observed primarily among men with shorter leukocyte telomeres.

CONCLUSION

PGC1A and PGC1B methylation may serve as early biomarkers of cancer risk.

Advances in PCOS Pathogenesis and Progression-Mitochondrial Mutations and Dysfunction

Polycystic ovary syndrome (PCOS) is a common female endocrine disorder, which still remains largely unsolved in terms of etiology and pathogenesis despite important advances in our understanding of its genetic, epigenetic, or environmental factor implications. It is a heterogeneous disease, frequently associated with insulin resistance, chronic inflammation, and oxidative stress and probably accompanied with subclinical cardiovascular disease (CVD) and some malignant lesions as well, such as endometrial cancer. Discrepancies in the clinical phenotype and progression of PCOS exist between different population groups, which nuclear genetic studies have so far failed to explain. Over the last years, mitochondrial dysfunction has been increasingly recognized as an important contributor to an array of diseases. Because mitochondria are under the dual genetic control of both the mitochondrial and nuclear genomes, mutations within either DNA molecule may result in deficiency in respiratory chain function that leads to a reduced ability to produce cellular adenosine-5'-triphosphate and to an excessive production of reactive oxygen species. However, the association between variants in mitochondrial genome, mitochondrial dysfunction, and PCOS has been investigated to a lesser extent. May mutations in mitochondrial DNA (mtDNA) become an additional target of investigations on the missing PCOS heritability? Are mutations in mtDNA implicated in the initiation and progression of PCOS complications, e.g., CVDs, diabetes mellitus, cancers?

NADPH Oxidases and Mitochondria in Vascular Senescence

Aging is the major risk factor in the development of cardiovascular diseases (CVDs), including hypertension, atherosclerosis, and myocardial infarction. Oxidative stress caused by overproduction of reactive oxygen species (ROS) and/or by reduced expression of antioxidant enzymes is a major contributor to the progression of vascular senescence, pathologic remodeling of the vascular wall, and disease. Both oxidative stress and inflammation promote the development of senescence, a process by which cells stop proliferating and become dysfunctional. This review focuses on the role of the mitochondria and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases Nox1 and Nox4 in vascular senescence, and their contribution to the development of atherosclerosis. Recent findings are reviewed, supporting a critical role of the mitochondrial regulator peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1α (PGC-1α), the inflammatory gene nuclear factor κB (NF-κB), zinc, the zinc transporters (ZnTs) ZnT3 and ZnT10, and angiotensin II (Ang II) in mitochondrial function, and their role in telomere stability, which provides new mechanistic insights into a previously proposed unified theory of aging.

Mitochondrial Fission Is Required for Angiotensin II-Induced Cardiomyocyte Apoptosis Mediated by a Sirt1-p53 Signaling Pathway

Hypertension-induced cardiac apoptosis is a major contributor to early-stage heart-failure. Our previous studies have found that p53-mediated mitochondrial fission is involved in aldosterone-induced podocyte apoptosis. However, it is not clear that whether p53-induced mitochondrial fission is critical for hypertensive Angiotensin II (AngII)-induced cardiomyocyte apoptosis. In this study, we found that inhibition of the mitochondrial fission protein Drp1 (dynamin-related protein 1) by Mdivi-1 prevented cardiomyocyte apoptosis and cardiac remodeling in SHRs. In vitro we found that treatment of cultured neonatal rat cardiomyocytes with AngII induced Drp1 expression, mitochondrial fission, and apoptosis. Knockdown of Drp1 inhibited AngII-induced mitochondrial fission and cardiomyocyte apoptosis. Furthermore, AngII induced p53 acetylation. Knockdown of p53 inhibited AngII-induced Drp1 expression, mitochondrial fission, and cardiomyocyte apoptosis. Besides, we found that Sirt1 was able to reverse AngII-induced p53 acetylation and its binding to the Drp1 promoter, which subsequently inhibited mitochondrial fission and eventually attenuated cardiomyocyte apoptosis. Collectively, these results suggest that AngII degrades Sirt1 to increase p53 acetylation, which induces Drp1 expression and eventually results in cardiomyocyte apoptosis. Sirt1/p53/Drp1dependent mitochondrial fission may be a valuable therapeutic target for hypertension induced heart failure.

Vascular Senescence in Cardiovascular and Metabolic Diseases

In mammals, aging is associated with accumulation of senescent cells. Stresses such as telomere shortening and reactive oxygen species induce “cellular senescence”, which is characterized by growth arrest and alteration of the gene expression profile. Chronological aging is associated with development of age-related diseases, including heart failure, diabetes, and atherosclerotic disease, and studies have shown that accumulation of senescent cells has a causative role in the pathology of these age-related disorders. Endothelial cell senescence has been reported to develop in heart failure and promotes pathologic changes in the failing heart. Senescent endothelial cells and vascular smooth muscle cells are found in atherosclerotic plaque, and studies indicate that these cells are involved in progression of plaque. Diabetes is also linked to accumulation of senescent vascular endothelial cells, while endothelial cell senescence per se induces systemic glucose intolerance by inhibiting skeletal muscle metabolism. A close connection between derangement of systemic metabolism and cellular senescence is also well recognized. Aging is a complex phenomenon, and there is no simple approach to understanding the whole process. However, there is accumulating evidence that cellular senescence has a central role in the development and progression of various undesirable aspects of aging. Suppression of cellular senescence or elimination of senescent cells reverses phenotypic changes of aging in several models, and proof-of-concept has been established that inhibiting accumulation of senescent cells could become a next generation therapy for age-related disorders. It is clear that cellular senescence drives various pathological changes associated with aging. Accordingly, further investigation into the role of this biological process in age-related disorders and discovery of senolytic compounds are important fields for future exploration.

Cardiometabolic phenotypes and mitochondrial DNA copy number in two cohorts of UK women

The mitochondrial genome is present at variable copy number between individuals. Mitochondria are vulnerable to oxidative stress, and their dysfunction may be associated with cardiovascular disease. The association of mitochondrial DNA copy number with cardiometabolic risk factors (lipids, glycaemic traits, inflammatory markers, anthropometry and blood pressure) was assessed in two independent cohorts of European origin women, one in whom outcomes were measured at mean (SD) age 30 (4.3) years (N=2278) and the second at 69.4 (5.5) years (N=2872). Mitochondrial DNA copy number was assayed by quantitative polymerase chain reaction. Associations were adjusted for smoking, sociodemographic status, laboratory factors and white cell traits. Out of a total of 12 outcomes assessed in both cohorts, mitochondrial DNA copy number showed little or no association with the majority (point estimates were close to zero and nearly all p-values were >0.01). The strongest evidence was for an inverse association in the older cohort with insulin (standardised beta [95%CI]: -0.06, [-0.098, -0.022], p=0.002), but this association did not replicate in the younger cohort. Our findings do not provide support for variation in mitochondrial DNA copy number having an important impact on cardio-metabolic risk factors in European origin women.

Targeting cancer stem cell propagation with palbociclib, a CDK4/6 inhibitor: Telomerase drives tumor cell heterogeneity

In this report, we systematically examined the role of telomerase activity in lung and ovarian cancer stem cell (CSC) propagation. For this purpose, we indirectly gauged telomerase activity, by linking the hTERT-promoter to eGFP. Using lung (A549) and ovarian (SKOV3) cancer cells, transduced with the hTERT-GFP reporter, we then employed GFP-expression levels to fractionate these cell lines into GFP-high and GFP-low populations. We functionally compared the phenotype of these GFP-high and GFP-low populations. More specifically, we now show that the cancer cells with higher telomerase activity (GFP-high) are more energetically activated, with increased mitochondrial mass and function, as well as increased glycolytic activity. This was further validated and confirmed by unbiased proteomics analysis. Cells with high telomerase activity also showed an increased capacity for stem cell activity (as measured using the 3D-spheroid assay) and cell migration (as measured using a Boyden chamber approach). These enhanced biological phenotypes were effectively inhibited by classical modulators of energy metabolism, which target either i) mitochondrial metabolism (i.e., oligomycin) or ii) glycolysis (i.e., 2-deoxy-glucose), or iii) by using the FDA-approved antibiotic doxycycline, which inhibits mitochondrial biogenesis. Finally, the level of telomerase activity also determined the ability of hTERT-high cells to proliferate, as assessed by measuring DNA synthesis via EdU incorporation. Consistent with these observations, treatment with an FDA-approved CDK4/6 inhibitor (PD-0332991/palbociclib) specifically blocked the propagation of both lung and ovarian CSCs. Virtually identical results were obtained with breast CSCs, which were also highly sensitive to palbociclib at concentrations in the nanomolar range. In summary, CSCs with high telomerase activity are among the most energetically activated, migratory and proliferative cell sub-populations. These observations may provide a mechanistic explanation for tumor metabolic heterogeneity, based on telomerase activity. FDA-approved drugs, such as doxycycline and palbociclib, were both effective at curtailing CSC propagation. Thus, these FDA-approved drugs could be used to target telomerase-high proliferative CSCs, in multiple cancer types. Finally, our experiments also allowed us to distinguish two different cellular populations of hTERT-high cells, one that was proliferative (i.e., replicative immortality) and the other that was non-proliferative (i.e., quiescent). We speculate that the non-proliferative population of hTERT-high cells that we identified could be mechanistically involved in tumor dormancy.

Air Pollution Stress and the Aging Phenotype: The Telomere Connection

Aging is a complex physiological phenomenon. The question why some subjects grow old while remaining free from disease whereas others prematurely die remains largely unanswered. We focus here on the role of air pollution in biological aging. Hallmarks of aging can be grouped into three main categories: genomic instability, telomere attrition, and epigenetic alterations leading to altered mitochondrial function and cellular senescence. At birth, the initial telomere length of a person is largely determined by environmental factors. Telomere length shortens with each cell division and exposure to air pollution as well as low residential greens space exposure is associated with shorter telomere length. Recent studies show that the estimated effects of particulate air pollution exposure on the telomere mitochondrial axis of aging may play an important role in chronic health effects of air pollution. The exposome encompasses all exposures over an entire life. As telomeres can be considered as the cellular memories of exposure to oxidative stress and inflammation, telomere maintenance may be a proxy for assessing the "exposome". If telomeres are causally related to the aging phenotype and environmental air pollution is an important determinant of telomere length, this might provide new avenues for future preventive strategies.

Leukocyte mitochondrial DNA copy number, anthropometric indices, and weight change in US women

OBJECTIVES

To examine the association between leukocyte mitochondrial DNA copy number (mtCN) and different anthropometric indices as well as weight changes; and to compare mtCN and telomere length with respect to their associations with BMI and age.

DESIGN

Population based cohort study.

SETTING

Nurses' Health Study, an ongoing prospective cohort study of 121,700 nurses enrolled in 1976; in 1989-1990 a subset of 32,826 women provided blood samples.

PARTICIPANTS

1,700 disease-free US women from case-control studies nested within the Nurses' Health Study with mtCN and telomere length measured who also have anthropometric measurements.

MAIN OUTCOME MEASURE

Relative mtCN and telomere lengths in peripheral blood leukocytes measured by quantitative real time polymerase chain reaction and various anthropometric measurements data from initial questionnaire.

RESULTS

Leukocyte mtCN was inversely associated with current weight (LS means Q1-Q4: 0.07, 0.04, 0.03, -0.17; P trend =0.002), waist size (LS means Q1-Q4: 0.06, 0.05, -0.04, -0.06; P trend = 0.04), BMI (LS means normal light, normal heavy, overweight, pre-obese, obese: 0.11, -0.01, -0.04, 0.04, -0.25; P trend<0.0001), and waist-hip ratio (WHR) (LS means Q1-Q4: 0.06, 0.08, -0.04, -0.06; P trend = 0.03). A one-unit decrease in mtCN z score was equivalent to approximately 3.5 pounds of weight gain for an adult of 5'10''. In addition, weight gain was bi-directionally and inversely associated with mtCN. Moreover, mtCN was strongly positively correlated with telomere length (LS means Q1-Q4: -0.02, 0.09, 0.11, 0.33; P trend <0.0001). MtCN was inversely associated with BMI even after adjusting for telomere length (P trend =0.003), while telomere length was not associated with BMI. On the other hand, telomere length was inversely associated with age after adjusting for mtCN (P trend =0.04), while mtCN was not associated with age.

CONCLUSIONS

Our results provide compelling evidence for a potential bi-directional temporal relationship between mitochondrial-mediated oxidative stress-defense mechanisms and weight change.

Precancer in ulcerative colitis: the role of the field effect and its clinical implications

Cumulative evidence indicates that a significant proportion of cancer evolution may occur before the development of histological abnormalities. While recent improvements in DNA sequencing technology have begun to reveal the presence of these early preneoplastic clones, the concept of 'premalignant field' was already introduced by Slaughter more than half a century ago. Also referred to as 'field effect', 'field defect' or 'field cancerization', these terms describe the phenomenon by which molecular alterations develop in normal-appearing tissue and expand to form premalignant patches with the potential to progress to dysplasia and cancer. Field effects have been well-characterized in ulcerative colitis, an inflammatory bowel disease that increases the risk of colorectal cancer. The study of the molecular alterations that define these fields is informative of mechanisms of tumor initiation and progression and has provided potential targets for early cancer detection. Herein, we summarize the current knowledge about the molecular alterations that comprise the field effect in ulcerative colitis and the clinical utility of these fields for cancer screening and prevention.

Metabolic Pathways of the Warburg Effect in Health and Disease: Perspectives of Choice, Chain or Chance

Focus on the Warburg effect, initially descriptive of increased glycolysis in cancer cells, has served to illuminate mitochondrial function in many other pathologies. This review explores our current understanding of the Warburg effect’s role in cancer, diabetes and ageing. We highlight how it can be regulated through a chain of oncogenic events, as a chosen response to impaired glucose metabolism or by chance acquisition of genetic changes associated with ageing. Such chain, choice or chance perspectives can be extended to help understand neurodegeneration, such as Alzheimer’s disease, providing clues with scope for therapeutic intervention. It is anticipated that exploration of Warburg effect pathways in extreme conditions, such as deep space, will provide further insights crucial for comprehending complex metabolic diseases, a frontier for medicine that remains equally significant for humanity in space and on earth.

Early life adiposity and telomere length across the life course: a systematic review and meta-analysis

Background: The relationship between adiposity at birth and in childhood, and telomere length is yet to be determined. We aimed to systematically review and meta-analyse the results of studies assessing associations between neonatal and childhood adiposity, and telomere length. Methods: We searched Medline, EMBASE and PubMed for studies reporting associations between adiposity measured in the neonatal period or childhood, and leucocyte telomere length, measured at any age via quantitative polymerase chain reaction, or terminal restriction fragment analysis, either cross-sectionally, or longitudinally. Papers published before April 2017 were included. Results: Out of 230 abstracts assessed, 23 papers (32 estimates) were retained, from which 19 estimates were meta-analysed (15 cross-sectional, four longitudinal). Of the 15 cross-sectional estimates, seven reported on neonates: four used binary exposures of small-for-gestational-age vs. appropriate-for-gestational age (or appropriate- and large-for-gestational age), and three studied birth weight continuously. Eight estimates reported on childhood measures; five estimates were from studies of binary exposures (overweight/obese vs. non-obese children), and three studies used continuous measures of body mass index. All four longitudinal estimates were of neonatal adiposity, with two estimates for small-for-gestational-age vs. appropriate-for-gestational age neonates, and two estimates of birth weight studied continuously, in relation to adult telomere (49-61 years). There was no strong evidence of an association between neonatal or childhood adiposity, and telomere length. However, between study heterogeneity was high, and there were few combinable studies. Conclusions: Our systematic review and meta-analysis found no strong evidence of an association between neonatal or childhood adiposity and telomere length.

Regulation of chromosome segregation in oocytes and the cellular basis for female meiotic errors

BACKGROUND

Meiotic chromosome segregation in human oocytes is notoriously error-prone, especially with ageing. Such errors markedly reduce the reproductive chances of increasing numbers of women embarking on pregnancy later in life. However, understanding the basis for these errors is hampered by limited access to human oocytes.

OBJECTIVE AND RATIONALE

Important new discoveries have arisen from molecular analyses of human female recombination and aneuploidy along with high-resolution analyses of human oocyte maturation and mouse models. Here, we review these findings to provide a contemporary picture of the key players choreographing chromosome segregation in mammalian oocytes and the cellular basis for errors.

SEARCH METHODS

A search of PubMed was conducted using keywords including meiosis, oocytes, recombination, cohesion, cohesin complex, chromosome segregation, kinetochores, spindle, aneuploidy, meiotic cell cycle, spindle assembly checkpoint, anaphase-promoting complex, DNA damage, telomeres, mitochondria, female ageing and female fertility. We extracted papers focusing on mouse and human oocytes that best aligned with the themes of this review and that reported transformative and novel discoveries.

OUTCOMES

Meiosis incorporates two sequential rounds of chromosome segregation executed by a spindle whose component microtubules bind chromosomes via kinetochores. Cohesion mediated by the cohesin complex holds chromosomes together and should be resolved at the appropriate time, in a specific step-wise manner and in conjunction with meiotically programmed kinetochore behaviour. In women, the stage is set for meiotic error even before birth when female-specific crossover maturation inefficiency leads to the formation of at-risk recombination patterns. In adult life, multiple co-conspiring factors interact with at-risk crossovers to increase the likelihood of mis-segregation. Available evidence support that these factors include, but are not limited to, cohesion deterioration, uncoordinated sister kinetochore behaviour, erroneous microtubule attachments, spindle instability and structural chromosomal defects that impact centromeres and telomeres. Data from mice indicate that cohesin and centromere-specific histones are long-lived proteins in oocytes. Since these proteins are pivotal for chromosome segregation, but lack any obvious renewal pathway, their deterioration with age provides an appealing explanation for at least some of the problems in older oocytes.

WIDER IMPLICATIONS

Research in the mouse model has identified a number of candidate genes and pathways that are important for chromosome segregation in this species. However, many of these have not yet been investigated in human oocytes so it is uncertain at this stage to what extent they apply to women. The challenge for the future involves applying emerging knowledge of female meiotic molecular regulation towards improving clinical fertility management.

Relevance of the p53-MDM2 axis to aging

In response to varying stress signals, the p53 tumor suppressor is able to promote repair, survival, or elimination of damaged cells - processes that have great relevance to organismal aging. Although the link between p53 and cancer is well established, the contribution of p53 to the aging process is less clear. Delineating how p53 regulates distinct aging hallmarks such as cellular senescence, genomic instability, mitochondrial dysfunction, and altered metabolic pathways will be critical. Mouse models have further revealed the centrality and complexity of the p53 network in aging processes. While naturally aged mice have linked longevity with declining p53 function, some accelerated aging mice present with chronic p53 activation, whose phenotypes can be rescued upon p53 deficiency. Further, direct modulation of the p53-MDM2 axis has correlated elevated p53 activity with either early aging or with delayed-onset aging. We speculate that p53-mediated aging phenotypes in these mice must have (1) stably active p53 due to MDM2 dysregulation or chronic stress or (2) shifted p53 outcomes. Pinpointing which p53 stressors, modifications, and outcomes drive aging processes will provide further insights into our understanding of the human aging process and could have implications for both cancer and aging therapeutics.

Molecular response of mitochondria to a short-duration femtosecond-laser stimulation

The research of mitochondrial dysfunction is of great importance and implicated in a range of neurodegenerative diseases. Traditionally, to investigate mitochondrial dynamics and functions, mitochondria are usually stimulated indirectly by treating cells with exogenous chemicals like oxidative agents. Such treatment lacks precision and controllability, and will simultaneously activate unknown complex cell processes. In this study, we report that two-photon 100-μs line scan by a femtosecond laser can induce restorable fragmentation or swelling of any targeted mitochondria instead of ablation or disruption. It can be defined by a customized two-photon line scan and inserted into any microscopy sequence as a single frame. The mitochondrial response is dependent on the peak power of laser pulses, cellular oxidative environment, and membrane permeability transition pores of mitochondria. The translocation of cytochrome C and Bax can be regulated by the photostimulation. Moreover, significant upregulation of Bcl-2 can be observed if the whole cell is stimulated. Those results suggest the mitochondrial and molecular response to photostimulation is quite complex. This femtosecond-laser stimulation method can thus provide a very noninvasive, precise, and controllable method to stimulate single target mitochondria for related biological research.

Serum polychlorinated biphenyls and leukocyte telomere length in a highly-exposed population: The Anniston Community Health Survey

BACKGROUND

Serum polychlorinated biphenyls (PCBs) have previously been associated with longer leukocyte telomere length (LTL) in most, but not all, of the few previous studies. PCBs were produced in Anniston, Alabama from 1929 to 1971 and participants of the Anniston Community Health Survey (ACHS) were highly exposed.

OBJECTIVES

We evaluated serum levels of 35 PCBs and relative telomere length in 559 ACHS participants.

METHODS

Relative LTL was measured in DNA extracted from blood clots. We assessed PCBs individually, grouped by chlorination, and summed PCBs. We used linear regression to assess the association between each PCB metric while adjusting for pertinent covariates.

RESULTS

Serum PCBs were associated with longer LTL among white participants and the oldest age group of black participants. Among white participants, compared with those in the first quartile of sum PCBs those in the third quartile of sum PCBs had 8.09% longer relative LTL (95% CI: 1.99; 14.55) and those in the fourth had 7.58% longer relative LTL (95%CI: -0.01; 15.76) (p-quadratic=0.05). Among African American participants, serum PCBs were associated with longer relative LTL among those over age 64 only. Tests for interaction were not statistically significant.

CONCLUSIONS

We observed a non-linear positive association between serum PCBs and LTL among white participants. Serum PCBs were associated with longer LTL in the oldest age group of African Americans. This association may provide insight into the cancers previously associated with exposure to PCBs, melanoma and non-Hodgkin lymphoma, which have been associated with long LTL in previous studies.

Neonatal exposure to environmental pollutants and placental mitochondrial DNA content: A multi-pollutant approach

BACKGROUND

Placental mitochondrial DNA (mtDNA) content can be indicative of oxidative damage to the placenta during fetal development and is responsive to external stressors. In utero exposure to environmental pollutants that may influence placental mtDNA needs further exploration.

OBJECTIVES

We evaluated if placental mtDNA content is altered by environmental pollution in newborns and identified pollutants independently associated to alterations in placental mtDNA content.

METHODS

mtDNA content was measured in placental tissue of 233 newborns. Four perfluoroalkyl compounds and nine organochlorine compounds were quantified in cord blood plasma samples and six toxic metals in whole cord blood. We first applied a LASSO (least absolute shrinkage and selection operator) penalized regression model to identify independent associations between environmental pollutants and placental mtDNA content, without penalization of several covariates. Then adjusted estimates were obtained using an ordinary least squares (OLS) regression model evaluating the pollutants' association with placental mtDNA content, adjusted for several covariates.

RESULTS

Based on LASSO penalized regression, oxychlordane, p,p'-dichlorodiphenyldichloroethylene, β-hexachlorocyclohexane, perfluorononanoic acid, arsenic, cadmium and thallium were identified to be independently associated with placental mtDNA content. The OLS model showed a higher placental mtDNA content of 2.71% (95% CI: 0.3 to 5.2%; p=0.03) and 1.41% (0.1 to 2.8%, p=0.04) for a 25% concentration increase of respectively cord blood β-hexachlorocyclohexane and arsenic. For a 25% concentration increase of cord blood thallium, a 4.88% lower placental mtDNA content (95% CI: -9.1 to -0.5%, p=0.03) was observed.

CONCLUSION

In a multi-pollutant approach, low fetal exposure levels of environmental organic and inorganic pollutants might compromise placental mitochondrial function as exemplified in this study by alterations in mtDNA content.

FTO associations with obesity and telomere length

This review examines the biology of the Fat mass- and obesity-associated gene (FTO), and the implications of genetic association of FTO SNPs with obesity and genetic aging. Notably, we focus on the role of FTO in the regulation of methylation status as possible regulators of weight gain and genetic aging. We present a theoretical review of the FTO gene with a particular emphasis on associations with UCP2, AMPK, RBL2, IRX3, CUX1, mTORC1 and hormones involved in hunger regulation. These associations are important for dietary behavior regulation and cellular nutrient sensing via amino acids. We suggest that these pathways may also influence telomere regulation. Telomere length (TL) attrition may be influenced by obesity-related inflammation and oxidative stress, and FTO gene-involved pathways. There is additional emerging evidence to suggest that telomere length and obesity are bi-directionally associated. However, the role of obesity risk-related genotypes and associations with TL are not well understood. The FTO gene may influence pathways implicated in regulation of TL, which could help to explain some of the non-consistent relationship between weight phenotype and telomere length that is observed in population studies investigating obesity.

The aetiology of cardiovascular disease: a role for mitochondrial DNA?

Cardiovascular disease (CVD) is a world-wide cause of mortality in humans and its incidence is on the rise in Africa. In this review, we discuss the putative role of mitochondrial dysfunction in the aetiology of CVD and consequently identify mitochondrial DNA (mtDNA) variation as a viable genetic risk factor to be considered. We then describe the contribution and pitfalls of several current approaches used when investigating mtDNA in relation to complex disease. We also propose an alternative approach, the adjusted mutational load hypothesis, which would have greater statistical power with cohorts of moderate size, and is less likely to be affected by population stratification. We therefore address some of the shortcomings of the current haplogroup association approach. Finally, we discuss the unique challenges faced by studies done on African populations, and recommend the most viable methods to use when investigating mtDNA variation in CVD and other common complex disease.

Amalaki rasayana, a traditional Indian drug enhances cardiac mitochondrial and contractile functions and improves cardiac function in rats with hypertrophy

We evaluated the cardioprotective effect of Amalaki Rasayana (AR), a rejuvenating Ayurvedic drug prepared from Phyllanthusemblica fruits in the reversal of remodeling changes in pressure overload left ventricular cardiac hypertrophy (LVH) and age-associated cardiac dysfunction in male Wistar rats. Six groups (aging groups) of 3 months old animals were given either AR or ghee and honey (GH) orally; seventh group was untreated. Ascending aorta was constricted using titanium clips in 3 months old rats (N = 24; AC groups) and after 6 months, AR or GH was given for further 12 months to two groups; one group was untreated. Histology, gene and protein expression analysis were done in heart tissues. Chemical composition of AR was analyzed by HPLC, HPTLC and LC-MS. AR intake improved (P < 0.05) cardiac function in aging rats and decreased LVH (P < 0.05) in AC rats as well as increased (P < 0.05) fatigue time in treadmill exercise in both groups. In heart tissues of AR administered rats of both the groups, SERCA2, CaM, Myh11, antioxidant, autophagy, oxidative phosphorylation and TCA cycle proteins were up regulated. ADRB1/2 and pCREB expression were increased; pAMPK, NF-kB were decreased. AR has thus a beneficial effect on myocardial energetics, muscle contractile function and exercise tolerance capacity.

Standardized Kaempferia parviflora Extract Inhibits Intrinsic Aging Process in Human Dermal Fibroblasts and Hairless Mice by Inhibiting Cellular Senescence and Mitochondrial Dysfunction

Intrinsic skin aging is a complex biological phenomenon mainly caused by cellular senescence and mitochondrial dysfunction. This study evaluated the inhibitory effect of Kaempferia parviflora Wall ex. Baker ethanol extract (KPE) on H₂O₂-stimulated cellular senescence and mitochondrial dysfunction both in vitro and in vivo. KPE significantly increased cell growth and suppressed senescence-associated β-galactosidase activation. KPE inhibited the expression of cell-cycle inhibitors (p53, p21, p16, and pRb) and stimulated the expression of cell-cycle activators (E2F1 and E2F2). H₂O₂-induced hyperactivation of the phosphatidylinositol 3-kinase/protein kinase B (AKT) signaling pathway was suppressed by KPE through regulated expression of forkhead box O3a (FoxO3a) and mammalian target of rapamycin (mTOR). KPE attenuated inflammatory mediators (interleukin-6 (IL-6), IL-8, nuclear factor kappa B (NF-κB), and cyclooxygenase-2 (COX-2)) and increased the mRNA expression of PGC-1α, ERRα, NRF1, and Tfam, which modulate mitochondrial biogenesis and function. Consequently, reduced ATP levels and increased ROS level were also reversed by KPE treatment. In hairless mice, KPE inhibited wrinkle formation, skin atrophy, and loss of elasticity by increasing the collagen and elastic fibers. The results indicate that KPE prevents intrinsic aging process in hairless mice by inhibiting cellular senescence and mitochondrial dysfunction, suggesting its potential as a natural antiaging agent.

mTOR Inhibition Rejuvenates the Aging Gingival Fibroblasts through Alleviating Oxidative Stress

The aging periodontium may be vulnerable to periodontal pathogens and poor response to inflammation and susceptible to tumorigenesis. Human gingival fibroblasts (hGFs) through continuously replicative culture served as an in vitro surrogate for aging. To investigate the effects of the mechanistic target of rapamycin (mTOR) inhibition on the aging gingiva, we stimulated the high-passage hGFs with rapamycin (20 nmol/L) for 3 days and 30 days. The cellular and biological changes were examined by immunofluorescence, real-time PCR, ELISA, Western blotting, and flow cytometry. The data demonstrated that the inhibition of mTOR signaling led to fewer senescence-associated beta-galactosidase- (SA-β-Gal-) positive cells, delayed the onset of senescence, preserved the capability of proliferation, and lowered the expression levels of relevant senescence-associated markers, such as p16^INK4a, p21^CIP1a, interleukin-6 (IL-6), and IL-8. In addition, when infected by prominent periodontal pathogens, Porphyromonas gingivalis (ATCC 33277), rapamycin-pretreated groups decreased the expression of inflammatory cytokines (IL-6 and IL-8) compared with the control group. mTOR inhibition upregulated the gene expression of antioxidant components (Cat, Sod2, and Prdx3; P < 0.05) and consequently neutralized the excessive reactive oxygen species (ROS). In conclusion, our results indicated that mTOR inhibition might rejuvenate the aging gingiva to some extent and relieve inflammation through eliminating oxidative stress.

Catalytic assembly of DNA nanostructures on a nanoporous gold array as 3D architectures for label-free telomerase activity sensing

Telomerase, an enzyme known to catalyze telomere elongation by adding TTAGGG [thymine (T), adenine (A), and guanine (G)] repeats to the end of telomeres, is vital for cell proliferation. Overexpression of telomerase has been found in most tumor cells, resulting in telomere dysfunction and uncontrolled cellular proliferation. Thus, telomerase has been considered as a potential cancer biomarker, as well as a potential target in cancer therapy. In this study, telomerase-catalyzed growth of tandem G-quadruplex (G4) assembled on a nanoporous gold array (NPGA) resulted in the formation of three-dimensional hybrid nanoarchitectures. The generated nanostructure then captured malachite green (MG) (reporter molecule) without the need of a complicated labeling process. Upon laser irradiation, the captured MG molecules produced a surface-enhanced Raman scattering (SERS) signal that was generated by an abundant amount of plasmonic hot spots in the NPGA substrates. A limit of detection (LOD) of 10^-10 IU along with a linear range, which was 3 orders of magnitude, was achieved, which was equivalent to the telomerase amount extracted from 20 HeLa cells. The LOD is 2 orders of magnitude better than that of the commercial enzyme-linked immunosorbent assay (ELISA), and it approaches that of the most sensitive technique, telomeric repeat amplification protocols (TRAP), which require a laborious and equipment-intensive polymerase chain reaction (PCR). In addition, X-ray photoelectron spectroscopy (XPS) was used to chemically identify and quantify the telomerase activity on the sensitized NPGA surface. Furthermore, the sensor was applied to screen the effectiveness of anti-telomerase drugs such as zidovudine, thus demonstrating the potential use of the sensor in telomerase-based diagnosis and drug development. Moreover, the framework represents a novel paradigm of collaborative plasmonic intensification and catalytic multiplication (c-PI/CM) for label-free biosensing.

p53/Drp1-dependent mitochondrial fission mediates aldosterone-induced podocyte injury and mitochondrial dysfunction

Mitochondrial dysfunction is increasingly recognized as an important factor in glomerular diseases. Previous study has shown that mitochondrial fission contributed to mitochondrial dysfunction. However, the mechanism of mitochondrial fission on mitochondrial dysfunction in aldosterone-induced podocyte injury remains ambiguous. This study aimed to investigate the pathogenic effect of mitochondrial fission both in vivo and in vitro. In an animal model of aldosterone-induced nephropathy, inhibition of the mitochondrial fission protein dynamin-related protein 1 (Drp1) suppressed aldosterone-induced podocyte injury. In cultured podocytes, aldosterone dose dependently induced Drp1 expression. Knockdown of Drp1 inhibited aldosterone-induced mitochondrial fission, mitochondrial dysfunction, and podocyte apoptosis. Furthermore, aldosterone dose dependently induced p53 expression. Knockdown of p53 inhibited aldosterone-induced Drp1 expression, mitochondrial dysfunction, and podocyte apoptosis. These findings implicated that aldosterone induced mitochondrial dysfunction and podocyte injury mediated by p53/Drp1-dependent mitochondrial fission, which may provide opportunities for therapeutic intervention for podocyte injury.

Aberrant telomere length and mitochondrial DNA copy number in suicide completers

Short telomere length (TL) occurs in individuals under psychological stress, and with various psychiatric diseases. Recent studies have also reported mitochondrial DNA copy number (mtDNAcn) alterations under several neuropsychiatric conditions. However, no study has examined whether aberrant TL or mtDNAcn occur in completed suicide, one of the most serious outcomes of mental illnesses. TL and mtDNAcn in post-mortem samples from 528 suicide completers without severe physical illness (508 peripheral bloods; 20 brains) and 560 samples from control subjects (peripheral bloods from 535 healthy individuals; 25 post-mortem brains) were analysed by quantitative polymerase chain reaction. Suicide completers had significantly shorter TL and higher mtDNAcn of peripheral bloods with sex/age-dependent differences (shorter TL was more remarkably in female/young suicides; higher mtDNAcn more so in male/elderly suicides). The normal age-related decline of TL and mtDNAcn were significantly altered in suicide completers. Furthermore, shorter TL and lower mtDNAcn of post-mortem prefrontal cortex were seen in suicide completers compared to controls. This study shows the first association of aberrant telomeres and mtDNA content with suicide completion. Our results indicate that further research on telomere shortening and mitochondrial dysfunction may help elucidate the molecular underpinnings of suicide-related pathophysiology.

Comparison of Sirtuin 3 Levels in ALS and Huntington's Disease-Differential Effects in Human Tissue Samples vs. Transgenic Mouse Models

Neurodegenerative diseases are characterized by distinct patterns of neuronal loss. In amyotrophic lateral sclerosis (ALS) upper and lower motoneurons degenerate whereas in Huntington’s disease (HD) medium spiny neurons in the striatum are preferentially affected. Despite these differences the pathophysiological mechanisms and risk factors are remarkably similar. In addition, non-neuronal features, such as weight loss implicate a dysregulation in energy metabolism. Mammalian sirtuins, especially the mitochondrial NAD+ dependent sirtuin 3 (SIRT3), regulate mitochondrial function and aging processes. SIRT3 expression depends on the activity of the metabolic master regulator peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a modifier of ALS and HD in patients and model organisms. This prompted us to systematically probe Sirt3 mRNA and protein levels in mouse models of ALS and HD and to correlate these with patient tissue levels. We found a selective reduction of Sirt3 mRNA levels and function in the cervical spinal cord of end-stage ALS mice (superoxide dismutase 1, SOD1^G93A). In sharp contrast, a tendency to increased Sirt3 mRNA levels was found in the striatum in HD mice (R6/2). Cultured primary neurons express the highest levels of Sirt3 mRNA. In primary cells from PGC-1α knock-out (KO) mice the Sirt3 mRNA levels were highest in astrocytes. In human post mortem tissue increased mRNA and protein levels of Sirt3 were found in the spinal cord in ALS, while Sirt3 levels were unchanged in the human HD striatum. Based on these findings we conclude that SIRT3 mediates the different effects of PGC-1α during the course of transgenic (tg) ALS and HD and in the human conditions only partial aspects Sirt3 dysregulation manifest.

Selective neuronal vulnerability in Parkinson disease

Intracellular α-synuclein (α-syn)-rich protein aggregates called Lewy pathology (LP) and neuronal death are commonly found in the brains of patients with clinical Parkinson disease (cPD). It is widely believed that LP appears early in the disease and spreads in synaptically coupled brain networks, driving neuronal dysfunction and death. However, post-mortem analysis of human brains and connectome-mapping studies show that the pattern of LP in cPD is not consistent with this simple model, arguing that, if LP propagates in cPD, it must be gated by cell- or region-autonomous mechanisms. Moreover, the correlation between LP and neuronal death is weak. In this Review, we briefly discuss the evidence for and against the spreading LP model, as well as evidence that cell-autonomous factors govern both α-syn pathology and neuronal death.

Signaling Networks Determining Life Span

The health of an organism is orchestrated by a multitude of molecular and biochemical networks responsible for ensuring homeostasis within cells and tissues. However, upon aging, a progressive failure in the maintenance of this homeostatic balance occurs in response to a variety of endogenous and environmental stresses, allowing the accumulation of damage, the physiological decline of individual tissues, and susceptibility to diseases. What are the molecular and cellular signaling events that control the aging process and how can this knowledge help design therapeutic strategies to combat age-associated diseases? Here we provide a comprehensive overview of the evolutionarily conserved biological processes that alter the rate of aging and discuss their link to disease prevention and the extension of healthy life span.

The Crosstalk between the Gut Microbiota and Mitochondria during Exercise

Many physiological changes occur in response to endurance exercise in order to adapt to the increasing energy needs, mitochondria biogenesis, increased reactive oxygen species (ROS) production and acute inflammatory responses. Mitochondria are organelles within each cell that are crucial for ATP production and are also a major producer of ROS and reactive nitrogen species during intense exercise. Recent evidence shows there is a bidirectional interaction between mitochondria and microbiota. The gut microbiota have been shown to regulate key transcriptional co-activators, transcription factors and enzymes involved in mitochondrial biogenesis such as PGC-1α, SIRT1, and AMPK genes. Furthermore, the gut microbiota and its metabolites, such as short chain fatty acids and secondary bile acids, also contribute to host energy production, ROS modulation and inflammation in the gut by attenuating TNFα- mediated immune responses and inflammasomes such as NLRP3. On the other hand, mitochondria, particularly mitochondrial ROS production, have a crucial role in regulating the gut microbiota via modulating intestinal barrier function and mucosal immune responses. Recently, it has also been shown that genetic variants within the mitochondrial genome, could affect mitochondrial function and therefore the intestinal microbiota composition and activity. Diet is also known to dramatically modulate the composition of the gut microbiota. Therefore, studies targeting the gut microbiota can be useful for managing mitochondrial related ROS production, pro-inflammatory signals and metabolic limits in endurance athletes.

Associations of Leukocyte Telomere Length With Aerobic and Muscular Fitness in Young Adults

Decline in both telomere length and physical fitness over the life course may contribute to increased risk of several chronic diseases. The relationship between telomere length and aerobic and muscular fitness is not well characterized. We examined whether there are cross-sectional associations of mean relative leukocyte telomere length (LTL) with objective measures of aerobic fitness, muscle strength, and muscle endurance, using data on 31-year-old participants of the Northern Finland Birth Cohort 1966 (n = 4,952–5,205, varying by exposure-outcome analysis). Aerobic fitness was assessed by means of heart rate measurement following a standardized submaximal step test; muscular fitness was assessed by means of a maximal isometric handgrip strength test and a test of lower-back trunk muscle endurance. Longer LTL was associated with higher aerobic fitness and better trunk muscle endurance in models including adjustment for age, sex, body mass index, socioeconomic position, diet, smoking, alcohol consumption, physical activity level, and C-reactive protein. In a sex-stratified analysis, LTL was not associated with handgrip strength in either men or women. LTL may relate to aspects of physical fitness in young adulthood, but replication of these findings is required, along with further studies to help assess directions and causality in these associations.

Photostimulation by femtosecond laser triggers restorable fragmentation in single mitochondrion

Mitochondrial research is important to the study of ageing, apoptosis, and metabolic diseases. Over the years, mitochondria have been studied with stimulation by chemical agents in a global manner for basic and applied research. This approach lacks of precision and accuracy in terms of spatial and temporal resolution. Here we demonstrate a direct and well-defined photostimulation targeting on single mitochondrial tubular structure using a tightly-focused femtosecond (fs) laser that could precisely activate mitochondria at single tubule level to show restorable fragmentation and subsequent recovery after tens of seconds. In these two processes, a series of mitochondrial reactive oxygen species (mROS) flashes was observed and found critical to the mitochondrial fragmentation. Meanwhile, transient openings of mitochondrial permeability transition pores (mPTP) were seen with oscillations of mitochondrial membrane potential. These activities were crucial for the recovery through scavenging the mROS. Without the feedback mechanisms, the fragmented mitochondria could not return back to their original tubular structure. These interesting observations show that photostimulation by fs laser is an active, precise, clean and well-defined approach to dissect the role of mitochondria in normal physiology and different kinds of diseases.

Systematic analysis of telomere length and somatic alterations in 31 cancer types

Cancer cells survive cellular crisis through telomere maintenance mechanisms. We report telomere lengths in 18,430 samples, including tumors and non-neoplastic samples, across 31 cancer types. Telomeres were shorter in tumors than in normal tissues and longer in sarcomas and gliomas than in other cancers. Among 6,835 cancers, 73% expressed telomerase reverse transcriptase (TERT), which was associated with TERT point mutations, rearrangements, DNA amplifications and transcript fusions and predictive of telomerase activity. TERT promoter methylation provided an additional deregulatory TERT expression mechanism. Five percent of cases, characterized by undetectable TERT expression and alterations in ATRX or DAXX, demonstrated elongated telomeres and increased telomeric repeat-containing RNA (TERRA). The remaining 22% of tumors neither expressed TERT nor harbored alterations in ATRX or DAXX. In this group, telomere length positively correlated with TP53 and RB1 mutations. Our analysis integrates TERT abnormalities, telomerase activity and genomic alterations with telomere length in cancer.

Convergence of The Nobel Fields of Telomere Biology and DNA Repair

The fields of telomere biology and DNA repair have enjoyed a great deal of cross-fertilization and convergence in recent years. Telomeres function at chromosome ends to prevent them from being falsely recognized as chromosome breaks by the DNA damage response and repair machineries. Conversely, both canonical and nonconical functions of numerous DNA repair proteins have been found to be critical for preserving telomere structure and function. In 2009, Elizabeth Blackburn, Carol Greider and Jack Szostak were awarded the Nobel prize in Physiology or Medicine for the discovery of telomeres and telomerase. Four years later, pioneers in the field of DNA repair, Aziz Sancar, Tomas Lindahl and Paul Modrich were recognized for their seminal contributions by being awarded the Nobel Prize in Chemistry. This review is part of a special issue meant to celebrate this amazing achievement, and will focus in particular on the convergence of nucleotide excision repair and telomere biology, and will discuss the profound implications for human health.

Blockade of telomerase reverse transcriptase enhances chemosensitivity in head and neck cancers through inhibition of AKT/ERK signaling pathways

Head and Neck squamous cell carcinomas (HNSCC), characterized by the high frequency of local recurrence and distant metastases, is mostly related to highly malignant and resistant to apoptosis, resulting in significant insensitivity to chemotherapy. Telomerase reverse transcriptase (TERT), as the catalytic subunit of telomerase, was implicated in the telomerase-mediated cellular transformation, proliferation, stemness and cell survival. Moreover, overexpression of human TERT (hTERT) is reported to be correlated with advanced invasive stage of the tumor progression and poor prognosis. Here, we show that hTERT potentially mediated the apoptotic resistance and blockade of telomerase reverse transcriptase could enhance chemosensitivity in head and neck cancers. Mechanistically, hTERT interacts with the phosphorylation of AKT and ERK to suppress the expression of p53, ultimately, leading to modulation of the cellular sensitivity to chemotherapy. Thus, these findings suggest that hTERT targeting could be an attractive approach in combination with conventional chemotherapies for patients suffering from chemoinsensitivity or refractory HNSCC.

Lifespan adversity and later adulthood telomere length in the nationally representative US Health and Retirement Study

Stress over the lifespan is thought to promote accelerated aging and early disease. Telomere length is a marker of cell aging that appears to be one mediator of this relationship. Telomere length is associated with early adversity and with chronic stressors in adulthood in many studies. Although cumulative lifespan adversity should have bigger impacts than single events, it is also possible that adversity in childhood has larger effects on later life health than adult stressors, as suggested by models of biological embedding in early life. No studies have examined the individual vs. cumulative effects of childhood and adulthood adversities on adult telomere length. Here, we examined the relationship between cumulative childhood and adulthood adversity, adding up a range of severe financial, traumatic, and social exposures, as well as comparing them to each other, in relation to salivary telomere length. We examined 4,598 men and women from the US Health and Retirement Study. Single adversities tended to have nonsignificant relations with telomere length. In adjusted models, lifetime cumulative adversity predicted 6% greater odds of shorter telomere length. This result was mainly due to childhood adversity. In adjusted models for cumulative childhood adversity, the occurrence of each additional childhood event predicted 11% increased odds of having short telomeres. This result appeared mainly because of social/traumatic exposures rather than financial exposures. This study suggests that the shadow of childhood adversity may reach far into later adulthood in part through cellular aging.