Telomere length - a cellular aging marker for depression and Post-traumatic Stress Disorder

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

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

A Systematic Review of the Association Between Muscular Fitness and Telomere Length Across the Adult Lifespan

This study aimed to systematically review the association between telomere length (TL) and muscular fitness. In October 2020, an articles search was applied to PubMed, Scopus, and Web of Science. Eligibility criteria included: cross-sectional, prospective, and experimental study design; outcomes included TL; results expressed the relationship between muscular fitness and TL; studies published in English, Portuguese, or Spanish. Nine studies were included in the review. Results from the four prospective studies are mixed. In one study, the changes in TL were associated with grip strength. Another study concluded that longer mid-life TL was associated with increased grip strength later in life. However, in the other two studies, the association between TL and sarcopenia was not strong. Nevertheless, longer TL was associated with a slower decline in grip strength in older people. From the four cross-sectional studies, three indicated that TL was associated with muscular fitness. On the other hand, in a study with powerlifters, TL remained within the range of values found in subjects with no history of regular strength training, supporting the notion that muscular fitness was not associated with TL. The cross-sectional and prospective studies showed that the relationship between TL and muscular fitness is not conclusive. It seems that there is a positive association between TL and muscular fitness in middle-aged and older adults. However, among younger adults, this relationship was not observed.

Association of Childhood Socioeconomic Status with Leukocyte Telomere Length Among African Americans and the Mediating Role of Behavioral and Psychosocial Factors: Results from the GENE-FORECAST Study

Purpose

We examined if childhood socioeconomic status (SES) was related to adult leucocyte telomere length (TL) using the data of 361 African American (AA) participants from the GENE-FORECAST Study. We also assessed the mediating role of behavioral and psychosocial factors in the association between childhood SES and adult TL.

Methods

Childhood SES was assessed individually by using participant’s mother’s education and occupation, father’s education and occupation, parental home ownership, and family structure. TL was assessed using the quantitative polymerase chain reaction method. Information on potential confounders and mediators were collected. The associations of childhood SES with TL were assessed using multivariable linear regression models. We used path analysis to quantify and test the share of these associations that was statistically explained by each of the mediators (participant’s educational attainment, smoking status, physical activity, dietary habit, perceived stress, and depressive symptoms).

Results

Mother’s education was associated with longer average TL (β: 0.021; 95% CI: 0.001, 0.04, p=0.038) in confounder adjusted models. Once mediators were introduced in the model, the estimates were reduced and remained marginally significant (β: 0.017; 95% CI: −0.003, 0.038, p=0.061). According to path model, approximately 19% of the effect of mother’s education on TL (β: 0.004; 95% CI: −0.001, 0.01, p < 0.10) was mediated through participant’s own education level. No significant mediation effect was observed for any other mediators.

Conclusions

These data provide evidence that participant’s mother’s education was positively linked to adult TL in AA population. Participant’s own educational level partially explained this association.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40615-021-01040-5.

Stabilization of telomere by the antioxidant property of polyphenols: Anti-aging potential

Aging is a form of a gradual loss of physiological integrity that results in impaired cellular function and ultimately increased vulnerability to disease and death. This process is a significant risk factor for critical age-related disorders such as cancer, diabetes, cardiovascular disease, and neurological conditions. Several mechanisms contribute to aging, most notably progressive telomeres shortening, which can be counteracted by telomerase enzyme activity and increasing in this enzyme activity associated with partly delaying the onset of aging. Individual behaviors and environmental factors such as nutrition affect the life-span by impact the telomerase activity rate. Healthy eating habits, including antioxidant intakes, such as polyphenols, can have a positive effect on telomere length by this mechanism. In this review, after studying the underlying mechanisms of aging and understanding the relationships between telomeres, telomerase, and aging, it has been attempted to explain the effect of polyphenols on reversing the oxidative stress and aging process.

Altered circulatory levels of miR-128, BDNF, cortisol and shortened telomeres in patients with type 2 diabetes and depression

AIMS

Several studies have reported the role of biomarkers either in diabetes or depression. The present study is aimed at profiling the circulating levels of miR-128, brain-derived neurotrophic factor (BDNF), cortisol and telomere length in patients with type 2 diabetes with and without depression compared to individuals with normal glucose tolerance.

METHODS

Study subjects (n = 160) were recruited from an ongoing epidemiological study in southern India. Non-diabetic and diabetic individuals were diagnosed as per the World Health Organization criteria. Depression score was derived using PHQ-12 questionnaire. Real-time quantitative PCR and ELISA methodologies were used to quantify the biomarkers.

RESULTS

Circulatory levels of miR-128 and cortisol were significantly (p < 0.05) increased with decreased BDNF levels and shortened telomeres in T2DM patients with or without depression compared to NGT individuals. T2DM patients with depression had the highest levels of miR-128 and cortisol and lowest levels of BDNF and telomere length compared to other groups. Pearson correlation analysis showed miR-128 levels were negatively associated with BDNF, telomere length and HDL cholesterol and positively correlated with cortisol, depression score, poor glycemic control and insulin resistance. Regression analysis confirmed that miR-128 was significantly associated with depression score even after adjusted for several confounding factors. However, this association was lost when adjusted for cortisol or telomere length.

CONCLUSIONS

Patients with type 2 diabetes and depression exhibited increased circulatory levels of miR-128 and serum cortisol and decreased levels of BDNF and shortened telomeres. These neuroendocrine signatures were more markedly altered in those with combined diabetes and depression.

Cardiorespiratory fitness and telomere length: a systematic review

This study aimed to systematically review the association between cardiorespiratory fitness and telomere length (TL). Studies were identified from searches in Cochrane Central, PubMed, Scopus, Sportdiscus, and Web of Science databases through July 2019. Eligibility criteria included: cross-sectional, prospective, and experimental study design; outcomes included TL; results expressed the relationship between cardiorespiratory fitness and TL; studies published in English, Portuguese, or Spanish. A total of 20 articles met the inclusion criteria. Sixteen studies (80%) reported a significant relationship between cardiorespiratory fitness, or training load, and TL. Better cardiorespiratory fitness or a large cardiorespiratory training load are associated with an increase in TL. Although, TL was related to regular moderate-to-vigorous aerobic exercise and cardiorespiratory fitness in older healthy humans, it was not related to cardiorespiratory fitness among young subjects. There seems to be a positive and significant relationship between cardiorespiratory fitness and TL, mainly among middle age and older people, which emphasizes the importance of cardiorespiratory fitness for healthy ageing. Therefore, endurance exercise and better cardiorespiratory fitness may regulate the TL in middle age and older adults, slowing the cellular ageing process.

Psychological Stress and Cellular Aging in Cancer: A Meta-Analysis

BACKGROUND

Epidemiological evidence continues to accumulate on the effect of psychosocial and behavioral factors in relation to cancer risk, progression, and mortality.

MATERIAL AND METHODS

This article presents the current evidence on the relationship between psychological stress and the risk of cancer and cellular aging process. Ten databases were searched to identify publications up to September 2019. References from retrieved articles were also reviewed. We included nine review papers and 26 cohort or case-control studies based on inclusion/exclusion criteria.

RESULTS

Results of previously published review articles did not show consistent evidence for the association between cancer risk and psychological stress, while previous evidence is stronger regarding the role of chronic psychological stress on cancer growth and metastasis and aging. In seven observational studies, severe life events, anxiety, depression, insufficient social support perception, or avoiding coping strategy were significantly associated with breast cancer risk. For other specific types of cancer, 11 studies reported increased risk factors for stressful life events, and two others found increased mortality or a decline in treatment adherence.

CONCLUSIONS

Recent epidemiological evidence generally suggests psychosocial factors may be considered risk factors for specific types of cancer and play a key role in the cellular aging process. Understanding molecular mechanisms of the stress interaction is important in cancer management and prevention. The psychological stressors should be considered when developing or evaluating change in psychosocial practice.

Association between leukocyte telomere length and hostility in US army service members

Hostility is a common form of emotionally charged anger which can lead to maladaptive and unhealthy behaviors. Significant association between shortened telomeres and greater levels of hostility has been observed in civilian populations, but has not yet been comprehensively studied in military populations. Our study investigates the relationship between hostility, post-traumatic stress disorder (PTSD), and leukocyte telomere length (LTL) in a sample of United States Army Special Operations personnel (n = 474) who deployed to Iraq and/or Afghanistan as part of combat operations. Hostility was measured with five items from the Brief Symptom Inventory (BSI). PTSD was determined using the PTSD Checklist (PCL) total score. The LTL was assessed using quantitative polymerase chain reaction methods and regression analyses were conducted to determine the association of hostility and telomere length. PTSD subjects reported higher hostility scores compared with those without PTSD. Among the participants with PTSD, those with medium or high level of hostility had shorter LTL than those with low level hostility (P < 0.01). Stepwise regression indicated that hostility level and age, but not gender and PTSD, were negatively correlated with LTL. Univariate regression showed that total hostility score was negatively associated with LTL (CI= -0.06 to -0.002, Beta= -0.095, p < 0.039) as well as a significant correlation between LTL and hostility impulses (HI) (CI= -0.108 to -0.009, Beta= -0.106, p < 0.021) and hostility controlling (HC) (CI= -0.071 to -0.002, Beta= -0.095, p < 0.004). Multiple regression analyses revealed that, while HC has no significant association with LTL, HI was still negatively correlated with LTL (p = 0.021). Our data indicates that LTL is associated with HI levels. Prevention and treatment efforts designed to reduce hostility may help mitigate risk for LTL shortening, a process of cellular aging, and thus slow accelerated aged-related health outcomes.

Metabolomic analysis of male combat veterans with post traumatic stress disorder

Posttraumatic stress disorder (PTSD) is associated with impaired major domains of psychology and behavior. Individuals with PTSD also have increased co-morbidity with several serious medical conditions, including autoimmune diseases, cardiovascular disease, and diabetes, raising the possibility that systemic pathology associated with PTSD might be identified by metabolomic analysis of blood. We sought to identify metabolites that are altered in male combat veterans with PTSD. In this case-control study, we compared metabolomic profiles from age-matched male combat trauma-exposed veterans from the Iraq and Afghanistan conflicts with PTSD (n = 52) and without PTSD (n = 51) (‘Discovery group’). An additional group of 31 PTSD-positive and 31 PTSD-negative male combat-exposed veterans was used for validation of these findings (‘Test group’). Plasma metabolite profiles were measured in all subjects using ultrahigh performance liquid chromatography/tandem mass spectrometry and gas chromatography/mass spectrometry. We identified key differences between PTSD subjects and controls in pathways related to glycolysis and fatty acid uptake and metabolism in the initial ‘Discovery group’, consistent with mitochondrial alterations or dysfunction, which were also confirmed in the ‘Test group’. Other pathways related to urea cycle and amino acid metabolism were different between PTSD subjects and controls in the ‘Discovery’ but not in the smaller ‘Test’ group. These metabolic differences were not explained by comorbid major depression, body mass index, blood glucose, hemoglobin A1c, smoking, or use of analgesics, antidepressants, statins, or anti-inflammatories. These data show replicable, wide-ranging changes in the metabolic profile of combat-exposed males with PTSD, with a suggestion of mitochondrial alterations or dysfunction, that may contribute to the behavioral and somatic phenotypes associated with this disease.

Prospective longitudinal study of the pregnancy DNA methylome: the US Pregnancy, Race, Environment, Genes (PREG) study

PURPOSE

The goal of the Pregnancy, Race, Environment, Genes study was to understand how social and environmental determinants of health (SEDH), pregnancy-specific environments (PSE) and biological processes influence the timing of birth and account for the racial disparity in preterm birth. The study followed a racially diverse longitudinal cohort throughout pregnancy and included repeated measures of PSE and DNA methylation (DNAm) over the course of gestation and up to 1 year into the postpartum period.

PARTICIPANTS

All women were between 18 and 40 years of age with singleton pregnancies and no diagnosis of diabetes or indication of assisted reproductive technology. Both mother and father had to self-identify as either African-American (AA) or European-American (EA). Maternal peripheral blood samples along with self-report questionnaires measuring SEDH and PSE factors were collected at four pregnancy visits, and umbilical cord blood was obtained at birth. A subset of participants returned for two additional postpartum visits, during which additional questionnaires and maternal blood samples were collected. The pregnancy and postpartum extension included n=240 (AA=126; EA=114) and n=104 (AA=50; EA=54), respectively.

FINDINGS TO DATE

One hundred seventy-seven women (AA=89, EA=88) met full inclusion criteria out of a total of 240 who were initially enrolled. Of the 63 participants who met exclusion criteria after enrolment, 44 (69.8%) were associated with a medical reason. Mean gestational age at birth was significantly shorter for the AA participants by 5.1 days (M=272.5 (SD=10.5) days vs M=277.6 (SD=8.3)).

FUTURE PLANS

Future studies will focus on identifying key environmental factors that influence DNAm change across pregnancy and account for racial differences in preterm birth.

Religiosity and Telomere Length in Colorectal Cancer Patients in Saudi Arabia

Numerous studies have reported a significant relationship between psychological stress, depression, and telomere length (TL), an indicator of cellular lifespan. Religious involvement, which is associated with lower levels of stress and depression, has also recently been related to TL. To our knowledge, this relationship has not yet been examined in Muslims, colorectal cancer patients, cancer patients more generally, or any population outside the USA. A convenience sample of 50 colorectal patients was recruited from hospital-based oncology clinics in Jeddah, Saudi Arabia. Religious involvement was assessed with the 13-item Muslim Religiosity Scale. Social and psychological mediators were measured using established scales. TL was determined from whole-blood leukocytes using quantitative PCR technology. Bivariate analyses indicated a positive but nonsignificant relationship between religiosity and TL (r = 0.13, p = 0.35). Controlling for age, did not affect the relationship (B = 15.6, SE = 17.3, p = 0.37), nor did controlling for other demographic, social or psychological factors. Religious involvement was unrelated to TL in this small sample of colorectal patients. Future cross-sectional and prospective studies in different populations with larger samples are needed.

A Clinician's Guide to PTSD Biomarkers and Their Potential Future Use

No clinically validated biomarkers have yet been found to assist in the diagnosis and treatment of posttraumatic stress disorder (PTSD). Innovation in clinical trial design, however, has led to the study of biomarkers as part of testing new medications and psychotherapies. There may soon be viable biomarkers to assist in diagnosis of PTSD and prediction of illness trajectory, severity, and functional outcomes; subtyping; and treatment selection. Processes for the identification and validation of biomarker findings are complex, involving several stages of clinical testing before use. The authors provide an overview of issues regarding the clinical use of PTSD biomarkers and examine a set of genetic, epigenetic, and other blood-based markers along with physiological markers currently proposed as candidate tests for PTSD. Studies that have identified candidate biomarkers with relevance to treatment selection in PTSD are discussed as a promising area of research that may lead to changes in clinical practice.

Prospective association between major depressive disorder and leukocyte telomere length over two years

BACKGROUND

Reduced leukocyte telomere length (LTL) has been found to be associated with multiple common age-related diseases, including heart disease, diabetes, and cancer. A link has also been suggested between shortened LTL and major depressive disorder (MDD), suggesting that MDD may be a disease of accelerated aging. This prospective, longitudinal study examined the association between depression diagnosis at baseline and change in LTL over two years in a well-characterized sample of N = 117 adults with or without MDD at baseline, using rigorous entry criteria.

METHODS

Participants aged 18-70 were assessed with validated instruments by trained, doctoral-level clinician raters at baseline and at two-year follow-up, and blood samples were obtained at both visits. LTL was assayed under identical methods using quantitative polymerase chain reaction (qPCR). The effect of an MDD diagnosis at baseline on change in LTL over two years was examined via hierarchical mixed models, which included potential confounders.

RESULTS

Individuals with MDD at baseline had greater LTL shortening over two years than individuals without MDD (p = 0.03), even after controlling for differences in age, sex, and body mass index (BMI). In the sub-sample of individuals with MDD diagnoses at baseline, no significant associations between LTL change and symptom severity or duration were found.

CONCLUSION

A baseline diagnosis of MDD prospectively predicted LTL shortening over two years. Our results provide further support for MDD as a disease associated with accelerated aging in a well-characterized sample using validated, clinician-rated measures.

A review of telomere length in sarcopenia and frailty

Sarcopenia and frailty are associated with several important health-related adverse events, including disability, loss of independence, institutionalization and mortality. Sarcopenia can be considered a biological substrate of frailty, and the prevalence of both these conditions progressively increases with age. Telomeres are nucleoprotein structures located at the end of linear chromosomes and implicated in cellular ageing, shorten with age, and are associated with various age-related diseases. In addition, telomere length (TL) is widely considered a molecular/cellular hallmark of the ageing process. This narrative review summarizes the knowledge about telomeres and analyzes for the first time a possible association of TL with sarcopenia and frailty. The overview provided by the present review suggests that leukocyte TL as single measurement, calculated by quantitative real-time polymerase chain reaction (qRT-PCR), cannot be considered a meaningful biological marker for complex, multidimensional age-related conditions, such as sarcopenia and frailty. Panels of biomarkers, including TL, may provide more accurate assessment and prediction of outcomes in these geriatric syndromes in elderly people.

Neurobiological Mechanisms of Stress Resilience and Implications for the Aged Population

BACKGROUND

Stress is a common reaction to an environmental adversity, but a dysregulation of the stress response can lead to psychiatric illnesses such as major depressive disorder (MDD), post-traumatic stress disorder (PTSD), and anxiety disorders. Yet, not all individuals exposed to stress will develop psychiatric disorders; those with enhanced stress resilience mechanisms have the ability to adapt successfully to stress without developing persistent psychopathology. Notably, the potential to enhance stress resilience in at-risk populations may prevent the onset of stress-induced psychiatric disorders. This novel idea has prompted a number of studies probing the mechanisms of stress resilience and how it can be manipulated.

METHODS

Here, we review the neurobiological factors underlying stress resilience, with particular focus on the serotoninergic (5-HT), glutamatergic, and γ-Aminobutyric acid (GABA) systems, as well as the hypothalamic-pituitary axis (HPA) in rodents and in humans. Finally, we discuss stress resiliency in the context of aging, as the likelihood of mood disorders increases in older adults.

RESULTS

Interestingly, increased resiliency has been shown to slow aging and improved overall health and quality of life. Research in the neurobiology of stress resilience, particularly throughout the aging process, is a nascent, yet, burgeoning field.

CONCLUSION

Overall, we consider the possible methods that may be used to induce resilient phenotypes, prophylactically in at-risk populations, such as in military personnel or in older MDD patients. Research in the mechanisms of stress resilience may not only elucidate novel targets for antidepressant treatments, but also provide novel insight about how to prevent these debilitating disorders from developing.

Race-specific associations between health-related quality of life and cellular aging among adults in the United States: evidence from the National Health and Nutrition Examination Survey

PURPOSE

Poor health-related quality of life (HRQOL) could lead to higher morbidity and mortality through telomere attrition or accelerated cellular aging. We conducted a cross-sectional analysis to examine the relationship between four dimensions of HRQOL and leukocyte telomere length (LTL) among a nationally representative sample of 3547 US adults (≥20 years) using the data from the 2001-2002 National Health and Nutrition Examination Survey.

METHOD

We used HRQOL survey information collected on individuals' self-rated general health, recent physical health, recent mental health, and recent activity limitation. Telomere length was assessed using quantitative polymerase chain reaction. Multiple linear regressions were used to estimate the relationship between each dimension of HRQOL and log-transformed values of LTL with adjustment for sample weights and design effects.

RESULTS

HRQOL-race interactions were significant, and the results were stratified by race. After controlling for demographic factors, disease conditions, and lifestyle variables, worse general health was significantly associated with shorter LTL for Blacks (coefficient, β: -0.022, 95% Confidence Interval, 95% CI: -0.03 to -0.01), but not for Whites or Mexican Americans. Unwell physical health was associated with shorter telomere length for Whites (β: -0.005, 95% CI: -0.01 to -0.001) only. Unwell mental health showed no significant association with LTL in any race.

CONCLUSIONS

Although longitudinal studies are needed to prove causality, our findings suggest that HRQOL could be associated with LTL shortening. We also found a possible racial difference in this association and recommend additional multiethnic studies to confirm this and to understand the reasons and consequences of this difference.

Whole-genome DNA methylation status associated with clinical PTSD measures of OIF/OEF veterans

Emerging knowledge suggests that post-traumatic stress disorder (PTSD) pathophysiology is linked to the patients' epigenetic changes, but comprehensive studies examining genome-wide methylation have not been performed. In this study, we examined genome-wide DNA methylation in peripheral whole blood in combat veterans with and without PTSD to ascertain differentially methylated probes. Discovery was initially made in a training sample comprising 48 male Operation Enduring Freedom (OEF)/Operation Iraqi Freedom (OIF) veterans with PTSD and 51 age/ethnicity/gender-matched combat-exposed PTSD-negative controls. Agilent whole-genome array detected ~5600 differentially methylated CpG islands (CpGI) annotated to ~2800 differently methylated genes (DMGs). The majority (84.5%) of these CpGIs were hypermethylated in the PTSD cases. Functional analysis was performed using the DMGs encoding the promoter-bound CpGIs to identify networks related to PTSD. The identified networks were further validated by an independent test set comprising 31 PTSD+/29 PTSD- veterans. Targeted bisulfite sequencing was also used to confirm the methylation status of 20 DMGs shown to be highly perturbed in the training set. To improve the statistical power and mitigate the assay bias and batch effects, a union set combining both training and test set was assayed using a different platform from Illumina. The pathways curated from this analysis confirmed 65% of the pool of pathways mined from training and test sets. The results highlight the importance of assay methodology and use of independent samples for discovery and validation of differentially methylated genes mined from whole blood. Nonetheless, the current study demonstrates that several important epigenetically altered networks may distinguish combat-exposed veterans with and without PTSD.

Genetic predisposition to advanced biological ageing increases risk for childhood-onset recurrent major depressive disorder in a large UK sample

BACKGROUND

Previous studies have revealed increased biological ageing amongst major depressive disorder (MDD) patients, as assayed by shorter leukocyte telomere lengths (TL). Stressors such as childhood maltreatment are more common amongst MDD patients, and it has been suggested that this might contribute to shorter TL present amongst patients. However, to our knowledge, no study has yet tested for reverse causality, i.e. whether a genetic predisposition to shorter TL might predispose to MDD or an earlier onset of MDD.

METHODS

This study used a Mendelian randomisation design to investigate if shortened TL might increase risk for recurrent MDD in a relatively large UK sample (1628 MDD cases, 1140 controls). To achieve this, we used a subset of our sample, for which TL data was available, to identify a suitable instrumental variable. We performed single nucleotide polymorphism (SNP) genotyping on rs10936599, a SNP upstream of telomerase RNA component (TERC), and rs2736100, a SNP within telomerase reverse transcriptase (hTERT), and attempted to replicate findings which identified these SNPs as predictors of TL. After which, we performed regressions to test if genetic risk for shortened TL increased risk for MDD, childhood-onset MDD or childhood/adolescent-onset MDD.

RESULTS

T-carriers of rs10936599 demonstrated shorter TL compared to CC-carriers (p≤0.05; 3% of variance explained) and was subsequently used as our instrumental variable. We found that the T-allele of rs10936599 predicted increased risk for childhood-onset MDD relative to controls (p≤0.05), and increased risk for childhood-onset MDD relative to adult-onset MDD cases (p≤0.001), but rs10936599 did not predict adult-onset MDD risk.

LIMITATIONS

Limitations include a relatively small sample of early-onset cases, and the fact that age-of-onset was ascertained by retrospective recall.

CONCLUSION

Genetic predisposition to advanced biological ageing, as assayed using rs10936599, predicted a small, but significant, increased risk for childhood-onset recurrent MDD. Genetic predisposition to advanced biological ageing may be one factor driving previously reported associations (or lack of associations) between shorter TL and MDD. Our results also suggest that the telomerase enzyme may act as a potentially important drug target for the prevention of childhood-onset MDD, at least in a subset of cases. Future studies should attempt to replicate our findings in a larger cohort.

How age, sex and genotype shape the stress response

Exposure to chronic stress is a leading pre-disposing factor for several neuropsychiatric disorders as it often leads to maladaptive responses. The response to stressful events is heterogeneous, underpinning a wide spectrum of distinct changes amongst stress-exposed individuals'. Several factors can underlie a different perception to stressors and the setting of distinct coping strategies that will lead to individual differences on the susceptibility/resistance to stress. Beyond the factors related to the stressor itself, such as intensity, duration or predictability, there are factors intrinsic to the individuals that are relevant to shape the stress response, such as age, sex and genetics. In this review, we examine the contribution of such intrinsic factors to the modulation of the stress response based on experimental rodent models of response to stress and discuss to what extent that knowledge can be potentially translated to humans.

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Effect of age in the stress response.

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Effect of sex in the stress response.

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Effect of genotype in the stress response.

The relationship between positive psychological characteristics and longer telomeres

OBJECTIVE

Longer telomeres are associated with better health and longevity. This research investigated the relationship between positive psychological dispositional traits and telomere length. Positive traits examined were typical high positive affect, typical low negative affect, life satisfaction, trait mindfulness, trait emotional intelligence, general self-efficacy and optimism.

DESIGN AND MEASURES

One hundred and twenty women and men, with a mean age of 40.92, completed measures of positive characteristics and provided samples for telomere length analysis.

RESULTS

Together the positive dispositional characteristics explained significant variance in telomere length, R = .40. Among the individual characteristics, greater optimism and higher emotional intelligence were associated with longer telomeres after adjustment for age and gender and the association between optimism and telomere length remained significant after adjusting for age and gender as well as the other positive characteristics, with a partial correlation r of .30.

CONCLUSION

These results in conjunction with previous research findings provide a platform for further exploration of biological pathways connecting positive characteristics such as optimism to telomere length and investigation of the impact of increasing a characteristic such as optimism on telomere functioning.

Direct Regulation of TLR5 Expression by Caveolin-1

Toll-like receptor 5 (TLR5) is a specific receptor for microbial flagellin and is one of the most well-known receptors in the TLR family. We reported previously that TLR5 signaling is well maintained during aging and that caveolin-1 may be involved in TLR5 signaling in aged macrophages through direct interactions. Therefore, it is important to clarify whether caveolin-1/TLR5 interactions affect TLR5 expression during aging. To assess the effect of caveolin-1 on TLR5, we analyzed TLR5 expression in senescent fibroblasts and aged tissues expressing high levels of caveolin-1. As expected, TLR5 mRNA and protein expression was well maintained in senescent fibroblasts and aged tissues, whereas TLR4 mRNA and protein were diminished in those cells and tissues. To determine the mechanism of caveolin-1-dependent TLR5 expression, we examined TLR5 expression in caveolin-1 deficient mice. Interestingly, TLR5 mRNA and protein levels were decreased dramatically in tissues from caveolin-1 knockout mice. Moreover, overexpressed caveolin-1 in vitro enhanced TLR5 mRNA through the MAPK pathway and prolonged TLR5 protein half-life through direct interaction. These results suggest that caveolin-1 may play a crucial role in maintaining of TLR5 by regulating transcription systems and increasing protein half-life.

Stress in biology and medicine, role in aging

In this review, we present a short description of the history of stress in the medical literature followed by a recapitulation of its mechanisms, from the cellular to the organismal level and its role in aging. The medical importance of stress was first taken up as a subject of experimental medicine by physiologists, starting from Claude Bernard's concept of the stability of the "milieu intérieur", altered by stress, followed by others, culminating recently by the elucidation of its mechanisms at the cellular and molecular level. These studies showed that oxidative stress is one of the most important and most frequent form of biological aggression. Its accumulation over time is important for the burnout syndrome and for neuronal aging. There is however a positive side to it also, redox signaling plays an important role in the functional coordination of cellular activities. These mechanisms, still to be more completely evaluated, have to be taken in account for planning efficient protective therapeutic interventions.

Effects of physical activity in telomere length: Systematic review and meta-analysis

The aim of this systematic review is to assess the effects of exercise on telomeres length. We searched the following databases: MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), Scopus, LILACS, SPORTDiscus and Web of Science from inception to August 2014. All articles that assessed the effects of exercise in telomere length were included in this review. The search strategy used the following combinations of terms: telomere AND "motor activity" OR exercise OR "physical activity". Two reviewers, working independently, screened all titles and abstracts to identify studies that could meet inclusion criteria. Whenever possible, and if appropriate, we performed a random-effect meta-analysis of study outcomes. Thirty-seven original studies were included in this systematic review, including 41,230 participants. Twenty articles did not find statistically significant association, whereas 15 described a positive association. Two papers found an inverted "U" correlation. There is a tendency toward demonstrating an effect of exercise on telomere length. Few prospective studies were found, many studies did not reach statistical significance and there was an important methodological diversity. For this reason, a possible significant association between physical activity and telomere length remains an open question.

Molecular consequences of psychological stress in human aging

Psychological stress has often been described as a feeling of being overwhelmed by the necessity of constant adjustment to an individual's changing environment. Stress affects people of all ages, but the lives of the elderly may particularly be affected. Major changes can cause anxiety leading to feelings of insecurity and/or loss of self-esteem and depression. The cellular mechanisms underlying psychological stress are poorly understood. This review focuses on the physical and molecular consequences of psychological stress linked to aging processes and, in particular, how molecular changes induced by psychological stress can compromise healthy aging.

Stress responsive biochemical anabolic/catabolic ratio and telomere length in older adults

It has been hypothesized that chronic psychological stress is associated with shorter telomere length; however, the mechanisms that link stress and telomere length are not well understood. To examine the interplay between biochemical factors related to stress arousal and cellular aging, we investigate the association between anabolic/catabolic (A/C) imbalance and leukocyte telomere length (LTL) in the Social Environment and Biomarkers of Aging Study (SEBAS), conducted in Taiwan (N = 925). SEBAS participants aged 54 and older (mean age 68.3) with values for two anabolic hormones (serum dehydroepiandrosterone sulfate [DHEAS] and insulin growth factor [IGF]-1), four catabolic hormones (cortisol, epinephrine, norepinephrine, and interleukin-6 [IL-6]), and LTL were examined. We found that high IL-6 was associated with short LTL (≤ 0.88 T/S ratio; odds ratio [OR] 1.41, 95% confidence interval [CI] = 1.04-1.92). Neither DHEAS/cortisol nor IGF-1/cortisol ratio was associated with telomere length; however, a high A/C imbalance summary score was associated with greater odds of having a short LTL relative to long LTL (OR 1.19, 95% CI = 1.05-1.35). These results indicate that our A/C imbalance score, defined by several anabolic and catabolic biochemical factors, may be one mechanism through which psychological stress is associated with short LTL and possibly cellular senescence.