Telomere length is highly inherited and associated with hyperactivity-impulsivity in children with attention deficit/hyperactivity disorder

Association between telomere length and neuropsychological function at 4-5 years in children from the INMA project: a cross-sectional study

Shortened telomere length (TL) has been associated with lower cognitive performance, different neurological diseases in adults, and certain neurodevelopmental disorders in children. However, the evidence about the association between TL and neuropsychological developmental outcomes in children from the general population is scarce. Therefore, this study aimed to explore the association between TL and neuropsychological function in children 4-5 years of age. We included 686 children from the INMA Project, a population-based birth cohort in Spain. Leucocyte TL was determined by quantitative PCR method, and neuropsychological outcomes were measured using the McCarthy Scales of Children's Abilities (MCSA). Multiple linear regression models were used to estimate associations adjusted for potential confounding variables. Main findings showed that a longer TL was associated with a higher mean working memory score (β = 4.55; 95% CI = 0.39, 8.71). In addition, longer TL was associated with a higher mean global quantitative score (β = 3.85; 95% CI = -0.19, 7.89), although the association was marginally significant. To our knowledge, this is the first study that shows a positive association between TL and better neuropsychological outcomes in children. Although further research is required to confirm these results, this study supports the hypothesis that TL is essential in protecting and maintaining a child's health, including cognitive functions such as working memory.

Choice of gDNA isolation method has a significant impact on average murine Telomere Length estimates

Telomere Length (TL) and integrity is significantly associated with age-related disease, multiple genetic and environmental factors. We observe mouse genomic DNA (gDNA) isolation methods to have a significant impact on average TL estimates. The canonical qPCR method does not measure TL directly but via the ratio of telomere repeats to a single copy gene (SCG) generating a T/S ratio. We use a monochromatic-multiplex-qPCR (mmqPCR) method which multiplexes the PCR and enables quantification of the target and the single copy gene within the same qPCR reaction. We demonstrate that TL measurements, from murine gDNA, isolated via Spin Columns (SC) and Magnetic Beads (MB), generate significantly smaller T/S ratios compared to gDNA isolated via traditional phenol/chloroform methods. The former methods may impede correct TL estimation by producing non representative fragment sets and reducing qPCR efficacy. This work highlights discrepancies in TL measurements due to different extraction techniques. We recommend the use of gDNA isolation methods that are shown to preserve DNA length and integrity, such as phenol/chloroform isolation. We propose that widely used high throughput DNA isolation methodologies can create spurious associations within a sample set, thus creating misleading data. We suggest that published TL associations should be revisited in the light of these data.

Telomere length in early childhood and its association with attention: a study in 4-6 year old children

Telomere length (TL), a marker of cellular aging, has been studied in adults with regard to its connection to cognitive function. However, little is known about the association between TL and cognitive development in children. This study investigated the interplay between TL and cognitive functioning in 283 Belgian children aged four to six years of the Environmental Influence on Aging in Early Life (ENVIRONAGE) birth cohort. Child leukocyte TL was measured using qPCR, while cognitive functioning, including attention and memory, was assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB). Linear regression models were employed to examine the association between TL and cognitive outcomes, adjusting for potential confounders. We found an inverse association between TL and the spatial errors made during the Motor Screening task (p = 0.017), indicating a higher motor accuracy in children with longer telomeres. No significant associations were found between TL and other cognitive outcomes. Our results suggest a specific link between TL and motor accuracy but not with the other cognitive domains.

Association of Relative Telomere Length and LINE-1 Methylation with Autism but not with Severity

Autism is associated with genomic instability, which is regulated by telomere length (TL) and index of global methylation (LINE-1). This study will determine relative TL (RTL) and LINE-1 methylation percentage for 69 patients and 33 control subjects to evaluate their potential role as biomarkers for autism. The results displayed a significant decrease of both RTL and LINE-1 methylation in autistic cases relative to controls (P < 0.001). Analysis of receiver operating characteristics curve revealed that both of RTL and LINE-1 methylation percentage have the ability to serve as autism biomarkers (area under the curve = 0.817 and 0.889, respectively). The statistical analysis revealed positive correlation between the two biomarkers (correlation coefficient = 0.439 and P < 0.001).

Involvement of Inheritance in Determining Telomere Length beyond Environmental and Lifestyle Factors

All linear chromosomal ends have specific DNA-protein complexes called telomeres. Telomeres serve as a "molecular clock" to estimate the potential length of cell replication. Shortening of telomere length (TL) is associated with cellular senescence, aging, and various age-related diseases in humans. Here we reviewed the structure, function, and regulation of telomeres and the age-related diseases associated with telomere attrition. Among the various determinants of TL, we highlight the connection between TL and heredity to provide a new overview of genetic determinants for TL. Studies across multiple species have shown that maternal and paternal TL influence the TL of their offspring, and this may affect life span and their susceptibility to age-related diseases. Hence, we reviewed the linkage between TL and parental influences and the proposed mechanisms involved. More in-depth studies on the genetic mechanism for TL attrition are needed due to the potential application of this knowledge in human medicine to prevent premature frailty at its earliest stage, as well as promote health and longevity.

Associations Between Children's Telomere Length, Parental Intrusiveness, and the Development of Early Externalizing Behaviors

Shorter telomeres mark cellular aging and are linked to chronic stress exposure as well as negative physical and psychological outcomes. However, it is unclear whether telomere length mediates associations between early stress exposure and later externalizing problems, or whether boys and girls differ in pathways to these concerns. We therefore examined associations between telomere length, early stress via negative caregiving, and children's externalizing symptom development over time in 409 three-year-old children and their parents. Telomere length mediated the association between early parental intrusiveness and later rule-breaking behavior; however, this association was moderated by children's biological sex such that parent intrusiveness was related only to boys' rule-breaking. Findings support the notion that children's telomere length may mark individual differences in responses to negative early caregiving, and highlight a potential mechanism contributing to the development of rule-breaking problems in boys.

de Paula V, Pires T, Michelon L, Camilo C, Esteban N, Pereira A, Schalling M, Vallada H. Shorter telomere length and suicidal ideation in familial bipolar disorder

Bipolar Disorder (BD) has recently been related to a process of accelerated aging, with shortened leukocyte telomere length (LTL) in this population. It has also been observed that the suicide rate in BD patients is higher than in the general population, and more recently the telomere length variation has been described as shorter in suicide completers compared with control subjects. Objectives The aim of the present study was to investigate if there is an association between LTL and BD in families where two or more members have BD including clinical symptomatology variables, along with suicide behavior. Methods Telomere length and single copy gene ratio (T/S ratio) was measured using quantitative polymerase chain reaction in a sample of 143 relatives from 22 families, of which 60 had BD. The statistical analysis was performed with a polygenic mixed model. Results LTL was associated with suicidal ideation (p = 0.02) as that there is an interaction between suicidal ideation and course of the disorder (p = 0.02). The estimated heritability for LTL in these families was 0.68. In addition, covariates that relate to severity of disease, i.e. suicidal ideation and course of the disorder, showed an association with shorter LTL in BD patients. No difference in LTL between BD patients and healthy relatives was observed. Conclusion LTL are shorter in subjects with familial BD suggesting that stress related sub-phenotypes possibly accelerate the process of cellular aging and correlate with disease severity and suicidal ideation.

Non-Linear and Sex-Specific Effect of Maternal Pre-Pregnancy BMI on Emotional and Behavioral Development of Preschool Children: A Population-Based Cohort Study

(1) Background: The aim was to examine the non-linear and sex-specific outcomes of maternal pre-pregnancy BMI on emotional and behavioral development of preschool children; (2) Methods: This study was based on the China-Anhui Birth Cohort (C-ABCS), including 3648 mother-child pairs. Maternal pre-pregnancy BMI was calculated from the maternal pre-pregnancy height and weight measured at the first antenatal checkup. Main caregivers completed the Strengths and Difficulties Questionnaire (SDQ) to assess children's preschool emotional and behavioral development. A restricted cubic spline model was drawn using Stata version 15.1 to analyze the association between maternal pre-pregnancy BMI and preschoolers' SDQ scores by sex; (3) Results: Among boys, maternal pre-pregnancy underweight was associated with the increased risk of conduct problems and pro-social behaviors, and pre-pregnancy overweight/obesity related with the increased risk of peer problems. Interestingly, when maternal pre-pregnancy BMI was between 18.50 kg/m² and 18.67 kg/m², boys had the increased risk of conduct problems. When pre-pregnancy BMI was between 18.50 kg/m² and 19.57 kg/m², boys had the increased risk of pro-social problems. No significant associations were observed; (4) Conclusions: A non-linear effect of maternal pre-pregnancy BMI on emotional and behavioral development has been found in preschool boys. In particular, pre-pregnancy normal weight may still affect boys' emotional and behavioral development.

Leukocyte telomere length and obesity in children and adolescents: A systematic review and meta-analysis

Background: Several studies have revealed the negative effects of adiposity on telomere length shortening. However, the results of the studies assessing the negative relationship between obesity and leukocyte telomere length (LTL) are not consistent. This systematic review and meta-analysis are aimed to pool the results of articles assessing the relationship between obesity and LTL among children and adolescents. Methods: To retrieve the related studies, four online databases including PubMed, Embase, ProQuest, and Scopus were searched until May 2022. Observational studies evaluating the relationship between obesity and LTL among apparently healthy children and adolescents (aged ≤18 years) were included in the study. We considered the studies that had reported a mean ± standard deviation of LTL. The random-effects model was used to assess the pooled weighted mean difference (WMD) and a 95% confidence interval (CI). Results: The search yielded seven studies from an initial 3,403 records identified. According to the results of seven articles with 4,546 participants, obesity was associated with LTL shortening among children and adolescents (WMD = -0.081; 95% CI: -0.137 to -0.026; p = 0.004; I2 = 99.9%). Also, no publication bias was observed. According to the results of subgrouping, significant results were only attributed to the studies conducted in Europe, with high quality scores, among overweight and obese adolescents, with a baseline LTL lower than 1, and performed in community-based school settings. Also, according to the subgrouping and meta-regression results, the obesity definition criteria and baseline LTL were the possible sources of between-study heterogeneity. Conclusion: We observed shorter LTL among overweight and obese children and adolescents. To obtain more reliable results, further longitudinal prospective studies with large sample sizes and more consistent and accurate definitions of obesity are required.

Impact of prenatal tobacco smoking on infant telomere length trajectory and ADHD symptoms at 18 months: a longitudinal cohort study

BACKGROUND

Prenatal maternal tobacco smoking is a predictor of child attention-deficit/hyperactivity disorder (ADHD) and is associated with offspring telomere length (TL). In this study, we examine the relationship between maternal prenatal smoking, infant TL, and maternal report of early childhood symptoms of ADHD.

METHODS

One-hundred and eighty-one mother-infant dyads were followed prospectively for the infant's first 18 months of life. Prenatal smoking was assessed from maternal report and medical records. TL was measured from infant buccal swab DNA obtained across the first 18 months of life. ADHD symptoms were obtained from maternal report on the Child Behavior Check List. Multiple regression models tested the relation between prenatal smoking and both ADHD symptoms and infant TL. Additional analyses tested whether the change in infant TL influenced the relation between prenatal smoking and ADHD symptoms.

RESULTS

Sixteen percent of mothers reported prenatal smoking. Infant TL at 4, 12, and 18 months of age were correlated. Consistent with previous cross-sectional studies linking shorter offspring TL to maternal prenatal smoking, maternal prenatal smoking predicted greater telomere shortening from four to 18 months of infant age (β = - 5.797, 95% CI [-10.207, -1.386]; p = 0.010). Maternal depression was positively associated with both prenatal smoking (odds ratio (OR): 4.614, 95% CI [1.733, 12.282]; p = 0.002) and child ADHD symptoms (β = 4.713, 95% CI [2.073, 7.354]; p = 0.0006). To prevent confounding, analyses examined the relation between TL, ADHD symptoms, and prenatal smoking only in non-depressed mothers. In non-depressed mothers, infant TL attrition across the first 18 months moderated the relation between smoking and child ADHD.

CONCLUSIONS

The findings extend previous studies linking prenatal smoking to shorter infant TL by providing data demonstrating the effect on TL trajectory. The relation between prenatal smoking and early infant ADHD symptoms was moderated by the change in TL. The findings provide novel initial evidence suggesting that TL dynamics are one mechanistic pathway influencing the relation between maternal prenatal smoking and ADHD.

Shortened Infant Telomere Length Is Associated with Attention Deficit/Hyperactivity Disorder Symptoms in Children at Age Two Years: A Birth Cohort Study

Environmental factors can accelerate telomere length (TL) attrition. Shortened TL is linked to attention deficit/hyperactivity disorder (ADHD) symptoms in school-aged children. The onset of ADHD occurs as early as preschool-age, but the TL-ADHD association in younger children is unknown. We investigated associations between infant TL and ADHD symptoms in children and assessed environmental factors as potential confounders and/or mediators of this association. Relative TL was measured by quantitative polymerase chain reaction in cord and 12-month blood in the birth cohort study, the Barwon Infant Study. Early life environmental factors collected antenatally to two years were used to measure confounding. ADHD symptoms at age two years were evaluated by the Child Behavior Checklist Attention Problems (AP) and the Attention Deficit/Hyperactivity Problems (ADHP). Associations between early life environmental factors on TL or ADHD symptoms were assessed using multivariable regression models adjusted for relevant factors. Telomere length at 12 months (TL12), but not at birth, was inversely associated with AP (β = −0.56; 95% CI (−1.13, 0.006); p = 0.05) and ADHP (β = −0.66; 95% CI (−1.11, −0.21); p = 0.004). Infant secondhand smoke exposure at one month was independently associated with shorter TL12 and also higher ADHD symptoms. Further work is needed to elucidate the mechanisms that influence TL attrition and early neurodevelopment.

Subclinical atherosclerosis and immune activation in young HIV-infected patients with telomere shortening

Background: To date, available data on premature aging in young HIV-infected adults are scarce and no reports offer comprehensive assessment of telomere shortening (TS) in relation to subclinical atherosclerosis (SCA). In this study, we investigate if telomere shortening and immune activation markers are associated with SCA, which is one of the main degenerative diseases in young HIV-infected adults.

Methods: A descriptive cross-sectional study was carried out in 149 HIV-infected patients on stable antiretroviral regimen (ART). Carotid intima-media thickness (cIMT) was estimated by carotid ultrasound. Quantitative singleplex PCR was performed to evaluate TS. The expression of activation/senescence markers was evaluated by multiparametric flow cytometry.

Results: TS was observed in 73 patients (49%). Higher cIMT was observed in patients with TS than those without it (0.86 vs. 0.80 mm; p=0.041). Patients under the age of 50 (defined as young adults) with TS showed higher absolute numbers of activated lymphocyte T cells CD8+CD38+ (3.94 vs. 2.34 cell/μl; p=0.07) and lymphocyte B cells CD19+CD38+ (3.07 vs. 2.10 cell/μl; p=0.004) compared to those without TS. In the multivariate analysis, the only factor independently associated with TS was the absolute number of lymphocyte T cells CD8+CD38+ T cells (OR = 1.18; 95%-CI = 1.00-1.39; p = 0.05).

Conclusion: Young HIV-infected adults show premature biological aging with accentuated immune activation. Chronic inflammation with excessive T-cells activation could be associated to TS, premature aging, and SCA in young HIV-infected adults.

Telomere Length and ADHD Symptoms in Young Adults

Objective: Previous research examining telomeres in individuals with neuropsychiatric disorders shows that greater illness, symptoms, or cognitive impairment are linked with shorter telomeres. However, the relationships of telomere length and neuropsychological processes or psychiatric symptoms are not understood in individuals with Attention Deficit/Hyperactivity Disorder (ADHD). Method: 390 young adults with and without ADHD completed a multi-informant diagnostic assessment and neuropsychological testing battery. Participant DNA was isolated from saliva samples, and telomere length was determined using qPCR. Results: Linear regression models demonstrated the only significant association to survive correction for multiple testing was for childhood hyperactivity-impulsivity symptoms and longer telomere length. Conclusion: Contrary to expectations, longer telomere length in young adults was associated only with childhood ADHD symptoms, particularly hyperactivity-impulsivity, in this sample. These findings are an important demonstration that the neuropsychological deficits and symptoms experienced by individuals diagnosed with ADHD during adulthood may not be negatively associated with telomere length.

The Association Between Adverse Childhood Experiences and Child Telomere Length: Examining Self-Regulation as a Behavioral Mediator

Childhood adversity is linked to shortened telomere length (TL), but behavioral indicators of telomere attrition remain unclear. This study examined the association between adverse childhood experiences (ACEs) and child TL, and if ACEs were indirectly associated with TL through children's self-regulatory abilities (i.e., effortful control and self-control). Hypotheses were tested using national data from teachers, parents, and their children (N = 2,527; M_age  = 9.35, SD = .36 years). More ACEs were uniquely associated with short TL, and low self-control mediated the association between more ACEs and short TL. While longitudinal studies are needed to strengthen claims of causation, this study identifies a pathway from ACEs to TL that should be explored further.

Association of greenspace exposure with telomere length in preschool children

Exposure to greenspace has been associated with a wide range of health benefits; however, the available evidence on the association of this exposure with telomere length (TL), an early marker of ageing, is still scarce. We investigated the association of greenspace exposure with TL in a sample of 200 preschool children (aged 5-7 years) residing in Sabzevar, Iran (2017). We comprehensively characterized different aspects of greenspace exposure encompassing residential, kindergarten, and total (including both residential and kindergarten) surrounding greenspace (using satellite-derived Normalized Difference Vegetation Index), residential and kindergarten distance to green spaces, time spent in private gardens and public green spaces, and the number of plant pots at home. Relative leukocyte TL (LTL) in blood samples of the study participants was measured using quantitative polymerase chain reaction (qPCR). We applied mixed effects linear regression models with kindergarten and qPCR plate as random effects, to estimate the association of indicators of greenspace exposure (one at a time) with LTL, controlled for relevant covariates. We observed an inverse association between distance from home and kindergarten to green spaces larger than 5000 m² and LTL. Moreover, higher total surrounding greenspace at 300m and 500m buffers and higher surrounding greenspace at 300m buffer around kindergarten and home were associated with longer LTL. Furthermore, longer time spent (h/week) in the public green spaces was associated with longer LTL. Our findings for residential and kindergarten distance to any green space (regardless of the size), residential surrounding greenspace at 100m and 500m buffers, kindergarten surrounding greenspace at 100m buffer, time spent in private gardens (h/week) and the number of plant pots at home were not conclusive. Our findings were generally suggestive for a positive association between greenspace exposure and LTL in preschool children. More studies are needed to confirm these findings in other settings with different climates and populations.

Evidence supporting the role of telomerase, MMP-9, and SIRT1 in attention-deficit/hyperactivity disorder (ADHD)

Growing evidence suggests that telomeres, telomerase, matrix metalloproteinase-9 (MMP-9), and SIRT1 (sirtuin1) are involved in the pathophysiology of neuropsychiatric and neurodevelopmental disorders. However, whether these molecules are contributors to attention-deficit/hyperactivity disorder (ADHD) has been little explored and poorly understood. This study aimed to determine the potential role of telomerase, MMP-9, and SIRT1 in children with ADHD. The study was performed on 46 children with ADHD aged between 8 and 14 and 43 healthy children matching in age and gender. Children were evaluated by Kiddie-Sads-Present and Lifetime Version, Conners' Parent Rating Scale-Revised Short Form (CPRS-RS) and Stroop test. Serum telomerase, MMP-9, and SIRT1 levels were measured by a quantitative sandwich enzyme-linked immunosorbent assay. MMP-9 and telomerase levels were significantly higher and SIRT1 levels were significantly lower in patients with ADHD than those of controls. All three molecules were significantly associated with both the severity of ADHD symptoms and cognitive functions. This is the first attempt to indicate that the important role of telomerase, MMP-9, and SIRT1 in ADHD, and the association of all these molecules with the severity of ADHD and cognitive functions, but future studies are required to verify these results.

Telomere Length and Psychopathology: Specificity and Direction of Effects Within the Bucharest Early Intervention Project

OBJECTIVE

Telomere length (TL) has been linked to several psychiatric conditions in children and adults. Telomere shortening is accelerated by early adversity, including maltreatment and psychosocial deprivation. These experiences also increase the risk of psychopathology in many domains. Two fundamental issues remain unresolved. The first concerns the specificity of the relations between TL and different dimensions of psychopathology; and the second relates to the direction of association between TL and psychopathology.

METHOD

This study addressed these shortcomings in a 2-fold manner. First, the association between TL and statistically independent general, internalizing, and externalizing psychopathology factors was examined to determine the specificity of this relation. Second, a 2-wave longitudinal cross-lagged model was used to explicitly examine the direction of the relation between TL and each psychopathology factor. Data were drawn from the Bucharest Early Intervention Project, a longitudinal study exploring the impact of severe psychosocial deprivation on child health and development (N = 195). At 8 to 10 and 12 to 14 years of age, buccal DNA was collected and teachers and/or caregivers reported on different domains of psychopathology.

RESULTS

Longitudinal path analyses showed that shorter TL was specifically associated with higher internalizing psychopathology at 8 to 10 years of age. In contrast, at 12 to 14 years, shorter TL was associated with higher general psychopathology. Most telling, internalizing psychopathology at 8 to 10 years predicted shorter TL at 12 to 14 years, with no reciprocal effects.

CONCLUSION

Results suggest that telomere erosion could be a consequence of distress-related psychopathology rather than a selection mechanism for later psychiatric problems.

CLINICAL TRIAL REGISTRATION INFORMATION

The Bucharest Early Intervention Project; https://clinicaltrials.gov/; NCT00747396.

Heritability of telomere variation: it is all about the environment!

Individual differences in telomere length have been linked to survival and senescence. Understanding the heritability of telomere length can provide important insight into individual differences and facilitate our understanding of the evolution of telomeres. However, to gain accurate and meaningful estimates of telomere heritability it is vital that the impact of the environment, and how this may vary, is understood and accounted for. The aim of this review is to raise awareness of this important, but much under-appreciated point. We outline the factors known to impact telomere length and discuss the fact that telomere length is a trait that changes with age. We highlight statistical methods that can separate genetic from environmental effects and control for confounding variables. We then review how well previous studies in vertebrate populations including humans have taken these factors into account. We argue that studies to date either use methodological techniques that confound environmental and genetic effects, or use appropriate methods but lack sufficient power to fully separate these components. We discuss potential solutions. We conclude that we need larger studies, which also span longer time periods, to account for changing environmental effects, if we are to determine meaningful estimates of the genetic component of telomere length.

This article is part of the theme issue ‘Understanding diversity in telomere dynamics'.

A scoping systematic review of social stressors and various measures of telomere length across the life course

Numerous studies examine the relationship between social stressors and telomere length (TL). Beyond considering methods and major findings, this scoping systematic review takes a novel approach as it groups studies according to the types of social stressor considered and by age groups. Following PRISMA guidelines, we searched PubMed, Web of Science, Embase, and Scopus. We included all English-language human subject research articles that modeled any measure of TL as a dependent variable and exposure to a social stressor as an independent variable. For the sample of 105 articles, we summarized methods and findings by type of social stressor (socioeconomic stressors, stressful life events, work-related stressors, and neighborhood stressors) and by age of the study population (infants/children, middle-aged adults, older adults, and mixed samples of middle-aged and older adults). We found more variation in TL measurement methodology in studies of infants/children and older adults than in studies focusing on middle-aged adults. The most consistent finding was a relationship between early-life stressors and shorter TL. Work and neighborhood stressors, and older populations, are currently understudied. Across all stressors, limited evidence suggests that the stress-TL relationship may be moderated by characteristics such as age, sex, and race/ethnicity. We conclude with specific suggestions for future research.

Why are there associations between telomere length and behaviour?

Individual differences in telomere length are associated with individual differences in behaviour in humans and birds. Within the human epidemiological literature this association is assumed to result from specific behaviour patterns causing changes in telomere dynamics. We argue that selective adoption-the hypothesis that individuals with short telomeres are more likely to adopt specific behaviours-is an alternative worthy of consideration. Selective adoption could occur either because telomere length directly affects behaviour or because behaviour and telomere length are both affected by a third variable, such as exposure to early-life adversity. We present differential predictions of the causation and selective adoption hypotheses and describe how these could be tested with longitudinal data on telomere length. Crucially, if behaviour is causal then it should be associated with differential rates of telomere attrition. Using smoking behaviour as an example, we show that the evidence that smoking accelerates the rate of telomere attrition within individuals is currently weak. We conclude that the selective adoption hypothesis for the association between behaviour and telomere length is both mechanistically plausible and, if anything, more compatible with existing empirical evidence than the hypothesis that behaviour is causal.This article is part of the theme issue 'Understanding diversity in telomere dynamics'.

Stress, Telomeres, and Psychopathology: Toward a Deeper Understanding of a Triad of Early Aging

Telomeres play an important part in aging and show relationships to lifetime adversity, particularly childhood adversity. Meta-analyses demonstrate reliable associations between psychopathology (primarily depression) and shorter telomere length, but the nature of this relationship has not been fully understood. Here, we review and evaluate the evidence for impaired telomere biology as a consequence of psychopathology or as a contributing factor, and the important mediating roles of chronic psychological stress and impaired allostasis. There is evidence for a triadic relationship among stress, telomere shortening, and psychiatric disorders that is positively reinforcing and unfolds across the life course and, possibly, across generations. We review the role of genetics and biobehavioral responses that may contribute to shorter telomere length, as well as the neurobiological impact of impaired levels of telomerase. These complex interrelationships are important to elucidate because they have implications for mental and physical comorbidity and, potentially, for the prevention and treatment of depression.

The association between early-life relative telomere length and childhood neurodevelopment

PURPOSE

To examine the association between telomere length and neurodevelopment in children.

METHODS

We examined the relationship between relative telomere length (rTL) and neurodevelopmental outcomes at 9 and 30 months, and 5 years of age in children enrolled in the Seychelles Child Development Study Nutrition Cohort 1 (NC1). Relative telomere length was measured in cord blood and in child blood at age five. Multivariable linear regression examined associations between neurodevelopmental outcomes and rTL adjusting for relevant covariates.

RESULTS

Mean rTL was 1.18 at birth and 0.71 at age five. Increased cord blood rTL was associated with better scores on two neurodevelopmental tests, the psychomotor developmental index (β = 4.01; 95% confidence interval (CI) = 0.17, 7.85) at age 30 months, and the Woodcock Johnson test of achievement letter-word score (β = 2.88; CI = 1.21-4.56) at age five. The Woodcock Johnson test of achievement letter-word score remained statistically significant after two outliers were excluded (β = 2.83; CI = 0.69, 4.97); the psychomotor developmental index did not (β = 3.62; CI = -1.28, 8.52). None of the neurodevelopmental outcomes at age five were associated with five-year rTL.

CONCLUSION

Although increased cord blood rTL was associated with better test scores for a few neurodevelopmental outcomes, this study found little consistent evidence of an association between rTL and neurodevelopment. Future studies with a larger sample size, longer follow-up, and other relevant biological markers (e.g. oxidative stress) are needed to clarify the role of rTL in neurodevelopment and its relevance as a potential surrogate measure for oxidative stress in the field of developmental neurotoxicity.

PUFA Status and Methylmercury Exposure Are Not Associated with Leukocyte Telomere Length in Mothers or Their Children in the Seychelles Child Development Study

Background: Leukocyte telomere length (TL) is associated with age-related diseases and early mortality, but there is a lack of data on the determinants of TL in early life. Evidence suggests that dietary intake of marine n-3 (ω-3) polyunsaturated fatty acids (PUFAs) is protective of telomere attrition, yet the effect of methylmercury exposure, also found in fish, on TL is unknown.Objective: The aim of this study was to investigate the associations between prenatal PUFA status, methylmercury exposure, and TL in mothers and children in the SCDS (Seychelles Child Development Study), for whom fish consumption is high.Methods: Blood samples collected from 229 mothers (at 28 wk gestation and delivery) and children (at 5 y of age) in the SCDS first nutrition cohort were analyzed for PUFA concentrations. Prenatal mercury was measured in maternal hair collected at delivery. Postnatal mercury was also measured in children's hair samples with the use of a cumulative metric derived from values obtained at 3-5 y of age. Relative TL was measured in blood obtained from mothers at delivery, in cord blood, and in children at 5 y of age by quantitative polymerase chain reaction. Linear regression models were used to investigate the associations between PUFA status, methylmercury exposure, and TL.Results: Neither prenatal PUFA status or methylmercury exposure was associated with TL of the mother or child or with TL attrition rate. However, a higher prenatal n-6:n-3 PUFA ratio was significantly associated with longer TLs in the mothers (β = 0.001, P = 0.048). Child PUFA status and methylmercury exposure were not associated with child TL. However, higher family Hollingshead socioeconomic status (SES) scores at 9 mo of age were significantly associated with longer TLs in cord blood (β = 0.005, P = 0.03).Conclusions: We found no evidence that PUFA status or methylmercury exposure are determinants of TL in either the mother or child. However, our results support the hypothesis that family SES may be associated with child TL.

FEATURES OF STOMATOLOGIC STATUS, TELOMERE LENGTHS AND PHENOTYPE OF IMMUNOCOMPETENT CELLS OF PERIPHERAL BLOOD IN CHILDREN – RESIDENTS OF UKRAINIAN TERRITORIES, CONTAMINATED WITH RADIONUCLIDES

Objective of research. To analyze features of stomatological status indexes, relative length of telomeres and phenotype of immunocompetent cells of peripheral blood in children with chronological enamel hypoplasia – residents of Ukrainian territories, contaminated with radionuclides after the Chornobyl NPP accident. Materials and methods. The object of research is chronological enamel hypoplasia (CEH) of permanent teeth, and lymphocytes of peripheral blood (PB). The subject of research is the state of oral cavity hygiene, caries intensity, gingivitis severity degree, relative telomere length (RTL), and phenotype of immunocompetent cells (ICC) of peripheral blood (PB). Methods of the research: stomatological, immunological (flow cytofluorometry), molecular genetic (fluorescence in situ hybridization-flow cytometry – flow-FISH), statistical. Results. Two types of the analysis of the stomatologic status, RTL and phenotype of PB ICC were carried out: the first is the comparison of indexes of the combined group of children with anamnesis complicated by radiation (group No. 1 with CEH + group No. 2 without CEH) comparing with the control group No. 3; the second is the analysis of indeces of the group No. 1 comparing with the same markers in children of the groups No. 2 and No. 3. The first stage of the analysis shows thesignificant worsening of oral hygien indices , high DMFTand DMFS in children with permanent dentition, higher degree of gums inflamation and moresignificant RTL shortening in children of the combined group (No. 1 + No. 2) comparing with the control. Changes of the same character, but more expressed observed during the another analysis concerning the children with anamnesis complicated by radiation and CEH comparing with the control. Reliable changes in the content of PB ICC subpopulations in the examined children of all groups were not identified. Conclusions. 1. Inchildren with CEH, complicated by ionizing radiation (IR) influence in low doses diapason the highest degree of stomatological status disorders comparing with the examined reference and control groups was determined: unsatisfactory and poor oral cavity hygiene according to OHI-S (1.76±0.41, р˂0.0001 and р˂0.0001, respectively) and Silness-Loe index (1.73±0.45, р˂0.0001 and р˂0.0001, respectively); very high intensity of dental caries ((DMFT=7.0±2.29, р=0.003and р˂0.0001; DMFS=8.74±2.58, р=0.0004 and р˂0.0001, respectively); mean degree of gingivitis severity (РМА 47.55±14.27 %, р˂0.0001 and р˂0.0001, respectively). 2. At CEH, which occurs due to the complex of negative factors during first years of life, including IR in residents of territories with effective doses more than 1.0 mSv/year, reliable shortening of relative telomeres length of PB lymphocytes comparing with the control group (15.17±3.20, р=0.0002) was found. Reliable differences in the content of peripheral blood immunocompetent cells when compared the examined groups were not identified. 3. Results of indices of the groups No. 1, No. 2 and No. 3 comparison are agreed with the data, obtained in result of dispersive analysis that allowed to separate the most informative indices concerning stomatological examination of children: OHI-S index (F=34.92; р˂0.001); Silness-Loe index (F=27.01; р˂0.001); dft+DMFT (F=82.23; р˂0.001); dfs+DMFS (F=49.41; р˂0.001); DMFT (F=13.94; р˂0.001); DMFS(F=19.41; р˂0.001); РМА (F=41.25; р˂0.001); RTL (F=7.53; р=0.001).

Predicting attention-deficit/hyperactivity disorder severity from psychosocial stress and stress-response genes: a random forest regression approach

Identifying genetic variants contributing to attention-deficit/hyperactivity disorder (ADHD) is complicated by the involvement of numerous common genetic variants with small effects, interacting with each other as well as with environmental factors, such as stress exposure. Random forest regression is well suited to explore this complexity, as it allows for the analysis of many predictors simultaneously, taking into account any higher-order interactions among them. Using random forest regression, we predicted ADHD severity, measured by Conners' Parent Rating Scales, from 686 adolescents and young adults (of which 281 were diagnosed with ADHD). The analysis included 17 374 single-nucleotide polymorphisms (SNPs) across 29 genes previously linked to hypothalamic-pituitary-adrenal (HPA) axis activity, together with information on exposure to 24 individual long-term difficulties or stressful life events. The model explained 12.5% of variance in ADHD severity. The most important SNP, which also showed the strongest interaction with stress exposure, was located in a region regulating the expression of telomerase reverse transcriptase (TERT). Other high-ranking SNPs were found in or near NPSR1, ESR1, GABRA6, PER3, NR3C2 and DRD4. Chronic stressors were more influential than single, severe, life events. Top hits were partly shared with conduct problems. We conclude that random forest regression may be used to investigate how multiple genetic and environmental factors jointly contribute to ADHD. It is able to implicate novel SNPs of interest, interacting with stress exposure, and may explain inconsistent findings in ADHD genetics. This exploratory approach may be best combined with more hypothesis-driven research; top predictors and their interactions with one another should be replicated in independent samples.

Attention-Deficit/Hyperactivity Disorder: Focus upon Aberrant N-Methyl-D-Aspartate Receptors Systems

Attention-deficit/hyperactivity disorder (ADHD) pathophysiology persists in an obscure manner with complex interactions between symptoms, staging, interventions, genes, and environments. Only on the basis of increasing incidence of the disorder, the need for understanding is greater than ever. The notion of an imbalance between central inhibitory/excitatory neurotransmitters is considered to exert an essential role. In this chapter, we first review how the default mode network functions and dysfunction in individuals diagnosed with ADHD. We also present and briefly review some of the animal models used to examine the neurobiological aspects of ADHD. There is much evidence indicating that compounds/interventions that antagonize/block glutamic acid receptors and/or block the glutamate signal during the "brain growth spurt" or in the adult animal may induce functional and biomarker deficits. Additionally, we present evidence suggesting that animals treated with glutamate blockers at the period of the "brain growth spurt" fail to perform the exploratory activity, observed invariably with control mice, that is associated with introduction to a novel environment (the test cages). Later, when the control animals show less locomotor and rearing activity, i.e., interest in the test cages, the MK-801, ketamine and ethanol treated mice showed successively greater levels of locomotion and rearing (interest), i.e., they fail to "habituate" effectively, implying a cognitive dysfunction. These disturbances of glutamate signaling during a critical period of brain development may contribute to the ADHD pathophysiology. As a final addition, we have briefly identified new research venues in the interaction between ADHD, molecular studies, and personality research.