Telomere length shortening in patients with dementia with Lewy bodies

Telomere length and cognitive function among middle-aged and older participants from communities underrepresented in aging research: A preliminary study

Objective

Accelerated biological aging is a plausible and modifiable determinant of dementia burden facing minoritized communities, but is not well-studied in these historically underrepresented populations. Our objective was to preliminarily characterize relationships between telomere length and cognitive health among American Indian/Alaska Native (AI/AN) and Black/African American (B/AA) middle-aged and older adults.

Methods

This study included data on telomere length and cognitive test performance from 187 participants, enrolled in one of two community-based cognitive aging cohorts and who identified their primary race as AI/AN or B/AA.

Results

Nested multivariable regression models revealed preliminary evidence for associations between telomere length and cognitive performance, and these associations were partially independent of chronological age.

Discussion

Small sample size limited estimate precision, however, findings suggest future work on telomere length and cognitive health in underrepresented populations at high risk for dementia is feasible and valuable as a foundation for social and behavioral intervention research.

Role of Telomeres and Telomerase in Parkinson's Disease-A New Theranostics?

Parkinson's disease (PD) is a complex condition that is significantly influenced by oxidative stress and inflammation. It is also suggested that telomere shortening (TS) is regulated by oxidative stress which leads to various diseases including age-related neurodegenerative diseases like PD. Thus, it is anticipated that PD would result in TS of peripheral blood mononuclear cells (PBMCs). Telomeres protect the ends of eukaryotic chromosomes preserving them against fusion and destruction. The TS is a normal process because DNA polymerase is unable to replicate the linear ends of the DNA due to end replication complications and telomerase activity in various cell types counteracts this process. PD is usually observed in the aged population and progresses over time therefore, disparities among telomere length in PBMCs of PD patients are recorded and it is still a question whether it has any useful role. Here, the likelihood of telomere attrition in PD and its implications concerning microglia activation, ageing, oxidative stress, and the significance of telomerase activators are addressed. Also, the possibility of telomeres and telomerase as a diagnostic and therapeutic biomarker in PD is discussed.

Induced pluripotent stem cell-derived and directly reprogrammed neurons to study neurodegenerative diseases: The impact of aging signatures

Many diseases of the central nervous system are age-associated and do not directly result from genetic mutations. These include late-onset neurodegenerative diseases (NDDs), which represent a challenge for biomedical research and drug development due to the impossibility to access to viable human brain specimens. Advancements in reprogramming technologies have allowed to obtain neurons from induced pluripotent stem cells (iPSCs) or directly from somatic cells (iNs), leading to the generation of better models to understand the molecular mechanisms and design of new drugs. Nevertheless, iPSC technology faces some limitations due to reprogramming-associated cellular rejuvenation which resets the aging hallmarks of donor cells. Given the prominent role of aging for the development and manifestation of late-onset NDDs, this suggests that this approach is not the most suitable to accurately model age-related diseases. Direct neuronal reprogramming, by which a neuron is formed via direct conversion from a somatic cell without going through a pluripotent intermediate stage, allows the possibility to generate patient-derived neurons that maintain aging and epigenetic signatures of the donor. This aspect may be advantageous for investigating the role of aging in neurodegeneration and for finely dissecting underlying pathological mechanisms. Here, we will compare iPSC and iN models as regards the aging status and explore how this difference is reported to affect the phenotype of NDD in vitro models.

Mitochondrial biogenesis, telomere length and cellular senescence in Parkinson's disease and Lewy body dementia

Progressive age is the single major risk factor for neurodegenerative diseases. Cellular aging markers during Parkinson's disease (PD) have been implicated in previous studies, however the majority of studies have investigated the association of individual cellular aging hallmarks with PD but not jointly. Here, we have studied the association of PD with three aging hallmarks (telomere attrition, mitochondrial dysfunction, and cellular senescence) in blood and the brain tissue. Our results show that PD patients had 20% lower mitochondrial DNA copies but 26% longer telomeres in blood compared to controls. Moreover, telomere length in blood was positively correlated with medication (Levodopa Equivalent Daily Dose, LEDD) and disease duration. Similar results were found in brain tissue, where patients with Parkinson's disease (PD), Parkinson's disease dementia (PDD) and Dementia with Lewy Bodies (DLB) showed (46-95%) depleted mtDNA copies, but (7-9%) longer telomeres compared to controls. In addition, patients had lower mitochondrial biogenesis (PGC-1α and PGC-1β) and higher load of a cellular senescence marker in postmortem prefrontal cortex tissue, with DLB showing the highest effect among the patient groups. Our results suggest that mitochondrial dysfunction (copy number and biogenesis) in blood might be a valuable marker to assess the risk of PD. However, further studies with larger sample size are needed to evaluate these findings.

Association of Oxidative Stress-Induced Nucleic Acid Damage With Psychiatric Disorders in Adults: A Systematic Review and Meta-analysis

IMPORTANCE

Nucleic acid damage from oxidative stress (NA-OXS) may be a molecular mechanism driving the severely increased morbidity and mortality from somatic causes in adults with psychiatric disorders.

OBJECTIVE

To systematically retrieve and analyze data on NA-OXS across the psychiatric disorder diagnostic spectrum.

DATA SOURCES

The PubMed, Embase, and PsycINFO databases were searched from inception to November 16, 2021. A hand search of reference lists of relevant articles was also performed.

STUDY SELECTION

Key study inclusion criteria in this meta-analysis were as follows: adult human study population, measurement of any marker of DNA or RNA damage from oxidative stress, and either a (1) cross-sectional design comparing patients with psychiatric disorders (any diagnosis) with a control group or (2) prospective intervention. Two authors screened the studies, and 2 senior authors read the relevant articles in full and assessed them for eligibility.

DATA EXTRACTION AND SYNTHESIS

The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed. Two authors performed data extraction independently, and a senior coauthor was consulted in cases of disagreement. Data were synthesized with random-effects and multilevel meta-analyses.

MAIN OUTCOMES AND MEASURES

The predefined hypothesis was that individuals with psychiatric disorders have increased NA-OXS levels. The main outcome was the standardized mean differences (SMDs) among patients and controls in nucleic acid oxidation markers compared across diagnostic groups. Analyses were divided into combinations of biological matrices and nucleic acids.

RESULTS

Eighty-two studies fulfilled the inclusion criteria, comprising 205 patient vs control group comparisons and a total of 10 151 patient and 10 532 control observations. Overall, the data showed that patients with psychiatric disorders had higher NA-OXS levels vs controls across matrices and molecules. Pooled effect sizes ranged from moderate for urinary DNA markers (SMD = 0.44 [95% CI, 0.20-0.68]; P < .001) to very large for blood cell DNA markers (SMD = 1.12 [95% CI, 0.69-1.55; P < .001). Higher NA-OXS levels were observed among patients with dementias followed by psychotic and bipolar disorders. Sensitivity analyses excluding low-quality studies did not materially alter the results. Intervention studies were few and too heterogenous for meaningful meta-analysis.

CONCLUSIONS AND RELEVANCE

The results of this meta-analysis suggest that there is an association with increased NA-OXS levels in individuals across the psychiatric disorder diagnostic spectrum. NA-OXS may play a role in the somatic morbidity and mortality observed among individuals with psychiatric disorders.

α-synucleinopathy exerts sex-dimorphic effects on the multipurpose DNA repair/redox protein APE1 in mice and humans

Lewy body disorders are characterized by oxidative damage to DNA and inclusions rich in aggregated forms of α-synuclein. Among other roles, apurinic/apyrimidinic endonuclease 1 (APE1) repairs oxidative DNA damage, and APE1 polymorphisms have been linked to cases of Lewy body disorders. However, the link between APE1 and α-synuclein is unexplored. We report that knockdown or inhibition of APE1 amplified inclusion formation in primary hippocampal cultures challenged with preformed α-synuclein fibrils. Fibril infusions into the mouse olfactory bulb/anterior olfactory nucleus (OB/AON) elicited a modest decrease in APE1 expression in the brains of male mice but an increase in females. Similarly, men with Lewy body disorders displayed lower APE1 expression in the OB and amygdala compared to women. Preformed fibril infusions of the mouse OB/AON induced more robust base excision repair of DNA lesions in females than males. No fibril-mediated loss of APE1 expression was observed in male mice when the antioxidant N-acetylcysteine was added to their diet. These findings reveal a potential sex-biased link between α-synucleinopathy and APE1 in mice and humans. Further studies are warranted to determine how this multifunctional protein modifies α-synuclein inclusions and, conversely, how α-synucleinopathy and biological sex interact to modify APE1.

Telomere length and urinary 8-hydroxy-2'-deoxyguanosine and essential trace element concentrations in female Japanese university students

Telomere length is thought to be a biomarker of biological aging. This study examined whether telomere length was associated with urinary concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative stress, and antioxidative trace elements in 73 female Japanese university students (age: 19.2 ± 0.7 years). We quantified 8-OHdG and selenium in urine by liquid chromatography-mass spectrometry and inductively coupled plasma-mass spectrometry, respectively. Telomere length and urinary concentrations of other essential trace elements (molybdenum, cobalt, and chromium) that were previously measured in the same study participants, were used in this study. We used multiple linear regression analysis to examine the associations of telomere length with urinary 8-OHdG and essential trace element concentrations (covariates: urinary cotinine concentration, age, BMI, and drinking status). The geometric means (geometric standard deviation) of 8-OHdG and selenium were 3.4 (1.5) and 31 (1.3) µg/g creatinine, respectively. Telomere length was not associated with urinary 8-OHdG concentration, but was negatively associated with urinary selenium concentration. In conclusion, telomere length was not associated with urinary 8-OHdG concentration in the young women in this study. Longitudinal studies should be conducted to clarify the association between telomere shortening rate and oxidative stress level.

Increased telomere length in patients with frontotemporal dementia syndrome

BACKGROUND

Telomeres are repetitive DNA sequences of TTAGGG at the ends of chromosomes. Many studies have shown that telomere shortening is associated with aging-related diseases, such as cardiovascular diseases, hypertension, diabetes, cancer, and various neurodegenerative diseases, including Alzheimer's disease, vascular dementia, Parkinson's disease, and dementia with Lewy bodies. However, changes in telomere length (TL) in patients with frontotemporal dementia (FTD) syndrome are unclear. Accordingly, in this study, we assessed TL in blood samples from patients with FTD syndrome.

METHODS

Absolute TL was measured in peripheral blood leukocytes from 53 patients with FTD syndromes (25 with behavioral variant FTD, 19 with semantic variant primary progressive aphasia [PPA], six with nonfluent/agrammatic variant PPA, and three with amyotrophic lateral sclerosis [ALS] plus) and 28 cognitively unimpaired (CU) controls using terminal restriction fragment analysis.

RESULTS

TL was significantly longer in the FTD group than in the CU group. All FTD subtypes had significantly longer TL than controls. There were no significant differences in TL among FTD syndromes. No significant correlations were found between TL and demographic factors in the FTD group.

CONCLUSIONS

Longer telomeres were associated with FTD syndrome, consistent with a recent report demonstrating that longer telomeres are related to ALS. Therefore, our results may support a shared biology between FTD and ALS. More studies with larger sample sizes are needed.

Cadmium Exposure and Blood Telomere Length in Female University Students in Japan

Cadmium is a toxic metal found ubiquitously throughout the world. Our study evaluated whether cadmium exposure was associated with telomere length in 73 female university students. Determination of telomere length was performed by quantitative polymerase chain reaction using DNA in blood. Urinary cadmium concentration was measured by inductively coupled plasma mass spectrometry. The students' physiological attributes and lifestyle were surveyed by means of a self-administered questionnaire. The geometric mean of urinary cadmium concentration was 0.312 μg/g creatinine, which was lower than the levels previously reported for Japan. Urinary cadmium concentration was not significantly associated with telomere length, though the exposure level of the present subjects was similar to that of previous study subjects which found significantly negative associations. It is possible that other factors affected telomere length in this study population.

Telomere length and cognitive function: Differential patterns across sociodemographic groups

OBJECTIVE

The present study investigates whether associations between telomere length (TL) and cognitive performance across multiple domains are moderated by poverty status and race.

METHOD

Participants were 325 African American and White urban-dwelling adults (M age = 47.9 years; 49.5% African American; 50.2% female; 48.9% living in poverty) from the Healthy Aging in Neighborhoods of Diversity across the Life Span study. TL was assayed from peripheral blood mononuclear cells using quantitative polymerase chain reactions. Multivariable regression analyses examined interactions of TL, poverty status, and race with performance on the following cognitive tests: Trail-Making Test Parts A and B, Digit Span Forward and Backward, semantic verbal fluency, Brief Test of Attention, Benton Visual Retention Test (BVRT), and California Verbal Learning Test-II total learning, short-delay free recall, and long-delay free recall scores. Analyses adjusted for age, sex, and high school-or-greater educational attainment.

RESULTS

Significant three-way interactions of TL × Poverty Status × Race revealed that, among White participants living in poverty, shorter TL was associated with worse performance on Digit Span Forward and Backward (ps<.05). Additionally, significant two-way interactions of TL × Poverty Status revealed that, among all participants living in poverty, shorter TL was associated with worse performance on the Trail-Making Test Part B and the BVRT (ps<.05).

CONCLUSIONS

TL may be differentially associated with aspects of attention, executive functioning, and memory among individuals living in poverty, who may be uniquely vulnerable to adverse effects of shorter telomeres. Replication of these findings is needed to determine their generalizability. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Generating Late-Onset Human iPSC-Based Disease Models by Inducing Neuronal Age-Related Phenotypes through Telomerase Manipulation

Modeling late-onset disorders such as Parkinson's disease (PD) using iPSC technology remains a challenge, as current differentiation protocols yield cells with the properties of fetal-stage cells. Here, we tested whether it is possible to accelerate aging in vitro to trigger late-onset disease phenotypes in an iPSC model of PD. In order to manipulate a factor that is involved in natural aging as well as in premature aging syndromes, we used telomere shortening as an age-inducing tool. We show that shortened telomeres result in age-associated as well as potentially disease-associated phenotypes in human pluripotent stem cell (hPSC)-derived midbrain dopamine (mDA) neurons. Our approach provides proof of concept for the further validation of telomere shortening as an induced-aging tool for late-onset-disease modeling.

Is telomere length a biomarker of neurological disorders?

Telomeres are DNA-protein complexes that form protective caps at the termini of chromosomes, maintaining genomic stability. In this review, we provide a comprehensive overview on the usefulness of telomere length (TL) as biomarkers of neurological disorders. The implications of TL in relation to cognitive ability, cognitive aging and cognitive decline in neurodegenerative disorders are also briefly discussed. Our review suggests that at present it is difficult to draw a reliable conclusion regarding the contribution of TL to neurological disorders. Further, it needs to be examined whether leukocyte TL, which is generally considered as a surrogate marker of TL in other tissues, serves as an indicator of central nervous system TL.

Calcium: Alpha-Synuclein Interactions in Alpha-Synucleinopathies

Aggregation of the pre-synaptic protein, α-synuclein (α-syn), is the key etiological factor in Parkinson's disease (PD) and other alpha-synucleinopathies, such as multiple system atrophy (MSA) and Dementia with Lewy bodies (DLB). Various triggers for pathological α-syn aggregation have been elucidated, including post-translational modifications, oxidative stress, and binding of metal ions, such as calcium. Raised neuronal calcium levels in PD may occur due to mitochondrial dysfunction and/or may relate to calcium channel dysregulation or the reduced expression of the neuronal calcium buffering protein, calbindin-D28k. Recent results on human tissue and a mouse oxidative stress model show that neuronal calbindin-D28k expression excludes α-syn inclusion bodies. Previously, cell culture model studies have shown that transient increases of intracellular free Ca(II), such as by opening of the voltage-gated plasma calcium channels, could induce cytoplasmic aggregates of α-syn. Raised intracellular free calcium and oxidative stress also act cooperatively to promote α-syn aggregation. The association between raised neuronal calcium, α-syn aggregation, oxidative stress, and neurotoxicity is reviewed in the context of neurodegenerative α-syn disease and potential mechanism-based therapies.

Alpha-synuclein aggregates are excluded from calbindin-D28k-positive neurons in dementia with Lewy bodies and a unilateral rotenone mouse model

α-Synuclein (α-syn) aggregates (Lewy bodies) in Dementia with Lewy Bodies (DLB) may be associated with disturbed calcium homeostasis and oxidative stress. We investigated the interplay between α-syn aggregation, expression of the calbindin-D28k (CB) neuronal calcium-buffering protein and oxidative stress, combining immunofluorescence double labelling and Western analysis, and examining DLB and normal human cases and a unilateral oxidative stress lesion model of α-syn disease (rotenone mouse). DLB cases showed a greater proportion of CB+ cells in affected brain regions compared to normal cases with Lewy bodies largely present in CB- neurons and virtually undetected in CB+ neurons. The unilateral rotenone-lesioned mouse model showed a greater proportion of CB+ cells and α-syn aggregates within the lesioned hemisphere than the control hemisphere, especially proximal to the lesion site, and α-syn inclusions occurred primarily in CB- cells and were almost completely absent in CB+ cells. Consistent with the immunofluorescence data, Western analysis showed the total CB level was 25% higher in lesioned compared to control hemisphere in aged animals that are more sensitive to lesion and 20% higher in aged compared to young mice in lesioned hemisphere, but not significantly different between young and aged in the control hemisphere. Taken together, the findings show α-syn aggregation is excluded from CB+ neurons, although the increased sensitivity of aged animals to lesion was not related to differential CB expression.

Telomere shortening leads to an acceleration of synucleinopathy and impaired microglia response in a genetic mouse model

Parkinson’s disease is one of the most common neurodegenerative disorders of the elderly and ageing hence described to be a major risk factor. Telomere shortening as a result of the inability to fully replicate the ends of linear chromosomes is one of the hallmarks of ageing. The role of telomere dysfunction in neurological diseases and the ageing brain is not clarified and there is an ongoing discussion whether telomere shortening is linked to Parkinson’s disease. Here we studied a mouse model of Parkinson’s disease (Thy-1 [A30P] α-synuclein transgenic mouse model) in the background of telomere shortening (Terc knockout mouse model). α-synuclein transgenic mice with short telomeres (αSYN^tg/tg G3Terc^-/-) developed an accelerated disease with significantly decreased survival. This accelerated phenotype of mice with short telomeres was characterized by a declined motor performance and an increased formation of α-synuclein aggregates. Immunohistochemical analysis and mRNA expression studies revealed that the disease end-stage brain stem microglia showed an impaired response in αSYN^tg/tg G3Terc^-/- microglia animals. These results provide the first experimental data that telomere shortening accelerates α-synuclein pathology that is linked to limited microglia function in the brainstem.

Telomere shortening leads to earlier age of onset in ALS mice

Telomere shortening has been linked to a variety of neurodegenerative diseases. Recent evidence suggests that reduced telomerase expression results in shorter telomeres in leukocytes from sporadic patients with amyotrophic lateral sclerosis (ALS) compared with healthy controls. Here, we have characterized telomere length in microglia, astroglia and neurons in human post mortem brain tissue from ALS patients and healthy controls. Moreover, we studied the consequences of telomerase deletion in a genetic mouse model for ALS. We found a trend towards longer telomeres in microglia in the brains of ALS patients compared to non-neurologic controls. Knockout of telomerase leading to telomere shortening accelerated the ALS phenotype inSOD1G93A-transgenic mice. Our results suggest that telomerase dysfunction might contribute to the age-related risk for ALS.

Early Life Epidemiology of Alzheimer's Disease--A Critical Review

BACKGROUND

As adult brain structure is primarily established in early life, genetic and environmental exposures in infancy and childhood influence the risk for Alzheimer disease (AD). In this systematic review, we identified several early life risk factors and discussed the evidence and underlying mechanism for each.

SUMMARY

Early risk factors for AD may alter brain anatomy, causing vulnerability to AD-related dementia later in life. In the perinatal period, both genes and learning disabilities have been associated with the development of distinct AD phenotypes. During early childhood, education and intellect, as well as body growth, may predispose to AD through alterations in cognitive and brain reserve, though the specific mediators of neural injury are disputed. Childhood socioeconomic status (SES) may predispose to AD by influencing adult SES and cognition. Association of these risk factors with underlying AD pathology (rather than just clinical diagnosis) has not been sufficiently examined.

KEY MESSAGES

Factors that impede or alter brain growth during early life could render certain brain regions or networks selectively vulnerable to the onset, accumulation or spread of AD-related pathology during later life. Careful life-course epidemiology could provide clues as to why the brain systematically degenerates during AD.

Soluble CD163 is associated with shortened telomere length in HIV-infected patients

Telomere length (TL) and immune activation markers were measured in a cohort of HIV-infected (n = 102) and age-matched non-HIV-infected (n = 41) men. TL was significantly shorter in HIV-infected compared with non-HIV-infected subjects (P = 0.04). Univariate analysis revealed a strong inverse relationship of TL to sCD163, and thus, monocyte/macrophage activation, among the HIV group (ρ = -0.30, P = 0.003). In multivariate modeling among the whole group, HIV-positive serostatus (P = 0.06) and sCD163 (P = 0.05) remained predictors of TL controlling for age and smoking status. Our data demonstrate that increased immune activation relates to shorter TL in HIV.

Reduced telomere length in subjects with dementia and diabetes mellitus type 2 is independent of apolipoprotein E4 genotype

Apolipoprotein E4 gene is associated with increased risk of dementia with comorbid diabetes mellitus. Both dementia and diabetes mellitus type 2 are independently associated with telomere shortening. We assessed relative telomere length and apolipoprotein E genotype in subjects with dementia (n=70) and cognitively normal control groups (n=55) with and without comorbid diabetes mellitus type 2. Relative telomere length was highest in the control group (Q2=0.91) followed by dementia (Q2=0.48) and dementia with comorbid diabetes mellitus type 2 (Q2=0.39). Apolipoprotein E4 allele frequency was highest in dementia with comorbid diabetes mellitus type 2 (0.26). Apolipoprotein E4 allele was not significantly associated with telomere attrition in both dementia and cognitively normal group irrespective of comorbid diabetes mellitus type 2 (P>0.05). The findings suggest that relative telomere length is unrelated to apolipoprotein E4 genotype in dementia and cognitive normal subjects with or without comorbid diabetes mellitus type 2.

Telomere shortening in neurological disorders: an abundance of unanswered questions

Telomeres, ribonucleoprotein complexes that cap eukaryotic chromosomes, typically shorten in leukocytes with aging. Aging is a primary risk factor for neurodegenerative disease (ND), and a common assumption has arisen that leukocyte telomere length (LTL) can serve as a predictor of neurological disease. However, the evidence for shorter LTL in Alzheimer's and Parkinson's patients is inconsistent. The diverse causes of telomere shortening may explain variability in LTL between studies and individuals. Additional research is needed to determine whether neuronal and glial telomeres shorten during aging and in neurodegenerative disorders, if and how LTL is related to brain cell telomere shortening, and whether telomere shortening plays a causal role in or exacerbates neurological disorders.

Neurodegeneration-associated instability of ribosomal DNA

Homologous recombination (HR)-mediated instability of the repetitively organized ribosomal DNA (rDNA) has been proposed as a mediator of cell senescence in yeast triggering the DNA damage response. High individual variability in the content of human rDNA suggests that this genomic region remained relatively unstable throughout evolution. Therefore, quantitative real-time polymerase chain reaction was used to determine the genomic content of rDNA in post mortem samples of parietal cortex from 14 young and 9 elderly individuals with no diagnosis of a chronic neurodegenerative/neurological disease. In addition, rDNA content in that brain region was compared between 10 age-matched control individuals and 10 patients with dementia with Lewy bodies (DLB) which involves neurodegeneration of the cerebral cortex. Probing rRNA-coding regions of rDNA revealed no effects of aging on the rDNA content. Elevated rDNA content was observed in DLB. Conversely, in the DLB pathology-free cerebellum, lower genomic content of rDNA was present in the DLB group. In the parietal cortex, such a DLB-associated instability of rDNA was not accompanied by any major changes of cytosine-phosphate-guanine methylation of the rDNA promoter. As increased cerebro-cortical rDNA content was previously reported in Alzheimer's disease, neurodegeneration appears to be associated with instability of rDNA. The hypothetical origins and consequences of this phenomenon are discussed including possibilities that the DNA damage-induced recombination destabilizes rDNA and that differential content of rDNA affects heterochromatin formation, gene expression and/or DNA damage response. This article is part of a Special Issue entitled: Role of the Nucleolus in Human Disease.

Telomere length and Parkinson's disease in men: a nested case-control study

BACKGROUND AND PURPOSE

Telomere shortening has been implicated in neurodegenerative disorders. However, available data on the association between telomere length and Parkinson's disease (PD) are inconclusive.

METHODS

A nested case-control design was used amongst men participating in the prospective Physicians' Health Study. A large proportion of participants provided blood samples in 1997 and they were followed through 2010. Men with self-reported PD were age-matched to controls in a 1:2 ratio. Quantitative PCR was used to determine the telomere repeat copy number to single gene copy number ratio (TSR) in genomic DNA extracted from peripheral blood leukocytes. TSR was used as a measure for relative telomere length (RTL) in our analyses. Conditional logistic regression was used to determine the risk of PD associated with RTL.

RESULTS

Data on RTL were available from 408 cases and 809 controls. Median TSR was shorter in controls than in cases (47.7 vs. 50.2; P = 0.02). The age-adjusted odds ratio (OR) for PD was 0.66 [95% confidence interval (CI) 0.46-0.95; Ptrend over quartiles 0.02] comparing the lowest to the highest quartile. The pattern of association was unchanged when comparing RTL below versus above the median (age-adjusted OR 0.75; 95% CI 0.59-0.96). Associations were similar after additional adjustment for many covariates.

CONCLUSION

Contrary to what was expected, in this large nested case-control study amongst men shorter telomeres were associated with reduced PD risk. Future research on the nature of this counterintuitive association is warranted.

Potential epigenetic mechanism(s) associated with the persistence of psychoneurological symptoms in women receiving chemotherapy for breast cancer: a hypothesis

Due to recent treatment advances, there have been improvements in the proportion of women surviving a diagnosis of breast cancer (BC). However, many of these survivors report persistent adverse side effects following treatment, such as cognitive dysfunction, depressive symptoms, anxiety, fatigue, sleep disturbances, and pain. Investigators have examined circulating levels of inflammatory markers, particularly serum cytokines, for a potential causal relationship to the development/persistence of these psychoneurological symptoms (PNS). While inflammatory activation, resulting from perceived stress or other factors, may directly contribute to the development of PNS, we offer an alternative hypothesis, suggesting that these symptoms are an early step in a cascade of biological changes leading to epigenetic alterations at the level of deoxyribonucleic acid (DNA) methylation, histone modifications, and/or chromatin structure/chromosomal instability. Given that epigenetic patterns have plasticity, if this conjectured relationship between epigenomic/acquired genomic alterations and the development/persistence of PNS is confirmed, it could provide foundational knowledge for future research leading to the recognition of predictive markers and/or treatments to alleviate PNS in women with BC. In this article, we discuss an evolving theory of the biological basis of PNS, integrating knowledge related to inflammation and DNA repair in the context of genetic and epigenetic science to expand the paradigm for understanding symptom acquisition/persistence following chemotherapy.

Blood and dried blood spot telomere length measurement by qPCR: assay considerations

Measurement of telomere length is crucial for the study of telomere maintenance and its role in molecular pathophysiology of diseases and in aging. Several methods are used to measure telomere length, the choice of which usually depends on the type and size of sample to be assayed, as well as cost and throughput considerations. The goal of this study was to investigate the factors that may influence the reliability of qPCR-based relative telomere length measurements in whole blood. Day to day intra-individual variability, types of blood anticoagulant, sample storage conditions, processing and site of blood draw were investigated. Two qPCR-based methods to measure telomere length (monoplex vs. multiplex) were also investigated and showed a strong correlation between them. Freezing and thawing of the blood and storage of the blood at 4°C for up to 4 days did not affect telomere length values. Telomere lengths in dried blood spots were significantly higher than both whole blood and peripheral mononuclear blood cells, and were highly correlated with both. We found that telomere length measurements were significantly higher in dried blood spots collected directly from fingertip prick compared to dried blood spots prepared with anticoagulated whole blood collected from the finger, and non-blotted whole blood taken from both finger and arm venipuncture. This suggests that DNA from cells blotted on paper is not equivalent to that collected from venipuncture whole blood, and caution should be taken when comparing between blood sample types.

Oxidative Stress and Its Clinical Applications in Dementia

Dementia is a complex disorder that mostly affects the elderly and represents a significant and growing public health burden in the world. Alzheimer's disease (AD)- associated dementia and dementia with Lewy bodies (DLB) are the most common forms of dementia, in which oxidative stress is significantly involved. Oxidative stress mechanisms may have clinical applications, that is, providing information for potential biomarkers. Thus brain-rich peptides with an antioxidant property, such as CART (cocaine- and amphetamine-regulated transcript), may be promising new markers. This paper summarizes the progress in research regarding oxidative stress in dementia with a focus on potential biomarkers in the cerebrospinal fluid (CSF) in the main forms of dementia. Other central and peripheral biomarkers, especially those considered oxidative stress related, are also discussed. This paper aims to provide information to improve current understanding of the pathogenesis and progression of dementia. It also offers insight into the differential diagnosis of AD and DLB.