Short and long telomeres increase risk of amnestic mild cognitive impairment

Association between telomere length and cognitive function among cognitively unimpaired individuals at risk of Alzheimer's disease

INTRODUCTION

Leukocyte telomere length (LTL) is an objective biomarker of biological aging, and it is proposed to play a crucial role in Alzheimer's disease (AD) risk. We aimed at evaluating the cross-sectional association between LTL and cognitive performance in middle-aged cognitively unimpaired individuals at increased risk of AD.

METHODS

A total of 1520 participants from the ALFA cohort were included. Relative telomere length was measured in leukocytes through qPCR. LTL was residualized against age and sex, and associations with cognitive performance were assessed in short and long groups based on residualized LTL (rLTL). Interactions with sex and genetic risk of AD were tested.

RESULTS

Non-linear associations were found between LTL and episodic memory (EM). Better EM was associated with longer rLTL among women in the short rLTL group.

DISCUSSION

Results suggest a potential role of telomeres in the cognitive aging process with sex-specific patterns.

Alzheimer's therapeutic development: shifting neurodegeneration to neuroregeneration

Alzheimer's disease (AD), similar to AD-related dementias, is characterized by impaired/lost neuronal structures and functions due to a long progression of neurodegeneration. Derailed endogenous signal pathways and disease processes have critical roles in neurodegeneration and are pharmacological targets in inducing neuroregeneration. Pharmacologically switching/shifting the brain status from neurodegeneration to neuroregeneration is emerging as a new therapeutic concept, one that is not only achievable, but also essential for effective therapy for AD. The results of the pharmacological-induced shift from neurodegeneration to neuroregeneration are twofold: arresting cognitive deterioration (and directing the brain toward cognitive recovery) in established AD, and preventing neurodegeneration through building up cognitive resilience in patients with preclinical or probable AD. In this review, we discuss these new developments in AD pharmacology and relevant clinical trials.

The Shortening of Leukocyte Telomere Length Contributes to Alzheimer's Disease: Further Evidence from Late-Onset Familial and Sporadic Cases

Telomeres are structures at the ends of eukaryotic chromosomes that help maintain genomic stability. During aging, telomere length gradually shortens, producing short telomeres, which are markers of premature cellular senescence. This may contribute to age-related diseases, including Alzheimer's disease (AD), and based on this, several studies have hypothesized that telomere shortening may characterize AD. Current research, however, has been inconclusive regarding the direction of the association between leukocyte telomere length (LTL) and disease risk. We assessed the association between LTL and AD in a retrospective case-control study of a sample of 255 unrelated patients with late-onset AD (LOAD), including 120 sporadic cases and 135 with positive family history for LOAD, and a group of 279 cognitively healthy unrelated controls, who were all from Calabria, a southern Italian region. Following regression analysis, telomeres were found significantly shorter in LOAD cases than in controls (48% and 41% decrease for sporadic and familial cases, respectively; p < 0.001 for both). Interestingly, LTL was associated with disease risk independently of the presence of conventional risk factors (e.g., age, sex, MMSE scores, and the presence of the APOE-ε4 allele). Altogether, our findings lend support to the notion that LTL shortening may be an indicator of the pathogenesis of LOAD.

Leucocyte telomere length, brain volume and risk of dementia: a prospective cohort study

Background

The evidence regarding the association between leucocyte telomere length (LTL) and brain health is sparse and inconclusive.

Aims

To investigate the associations of LTL with brain structure and the risk of dementia based on a large-scale prospective study.

Methods

LTL in the peripheral blood was measured by the quantitative polymerase chain reaction (qPCR) assay from 439 961 individuals in the UK Biobank recruited between 2006 and 2010 and followed up until 2020. Electronic health records were used to record the incidence of dementia, including Alzheimer's disease (AD) and vascular dementia (VD). The brain structure, including total and regional brain volume, of 38 740 participants was then assessed by magnetic resonance imaging (MRI).

Results

During a median follow-up of 11.6 years, a total of 5 820 (1.3%) dementia cases were documented. The restricted cubic spline model showed significant overall associations between LTL and the risk of dementia and AD (p for overall <0.05). The multivariable adjusted hazard ratios (HRs) for the lowest LTL tertile compared with the highest LTL tertile were 1.14 (95% confidence interval (CI): 1.06 to 1.21) for dementia, 1.28 (95% CI: 1.12 to 1.46) for AD and 1.18 (95% CI: 0.98 to 1.42) for VD. Furthermore, we found that shorter LTL was associated with smaller total brain volume (β=-0.012 8, p=0.003), white matter volume (β=-0.022 4, p<0.001), hippocampus volume (β=-0.017 2, p<0.001), thalamus volume (β=-0.023 9, p<0.001) and accumbens (β=-0.015 5, p=0.001).

Conclusions

Shorter LTL is associated with total and regional brain structure and a higher risk of incident dementia and AD, implying the potential of telomere length as a predictive biomarker of brain health.

Evaluating genomic signatures of aging in brain tissue as it relates to Alzheimer's disease

Telomere length (TL) attrition, epigenetic age acceleration, and mitochondrial DNA copy number (mtDNAcn) decline are established hallmarks of aging. Each has been individually associated with Alzheimer's dementia, cognitive function, and pathologic Alzheimer's disease (AD). Epigenetic age and mtDNAcn have been studied in brain tissue directly but prior work on TL in brain is limited to small sample sizes and most studies have examined leukocyte TL. Importantly, TL, epigenetic age clocks, and mtDNAcn have not been studied jointly in brain tissue from an AD cohort. We examined dorsolateral prefrontal cortex (DLPFC) tissue from N = 367 participants of the Religious Orders Study (ROS) or the Rush Memory and Aging Project (MAP). TL and mtDNAcn were estimated from whole genome sequencing (WGS) data and cortical clock age was computed on 347 CpG sites. We examined dementia, MCI, and level of and change in cognition, pathologic AD, and three quantitative AD traits, as well as measures of other neurodegenerative diseases and cerebrovascular diseases (CVD). We previously showed that mtDNAcn from DLPFC brain tissue was associated with clinical and pathologic features of AD. Here, we show that those associations are independent of TL. We found TL to be associated with β-amyloid levels (beta = - 0.15, p = 0.023), hippocampal sclerosis (OR = 0.56, p = 0.0015) and cerebral atherosclerosis (OR = 1.44, p = 0.0007). We found strong associations between mtDNAcn and clinical measures of AD. The strongest associations with pathologic measures of AD were with cortical clock and there were associations of mtDNAcn with global AD pathology and tau tangles. Of the other pathologic traits, mtDNAcn was associated with hippocampal sclerosis, macroscopic infarctions and CAA and cortical clock was associated with Lewy bodies. Multi-modal age acceleration, accelerated aging on both mtDNAcn and cortical clock, had greater effect size than a single measure alone. These findings highlight for the first time that age acceleration determined on multiple genomic measures, mtDNAcn and cortical clock may have a larger effect on AD/AD related disorders (ADRD) pathogenesis than single measures.

The relationship between longer leukocyte telomeres and dNCR in non-cardiac surgery patients: a retrospective analysis

BACKGROUND

Cognitive decline following surgery is a common concern among elderly individuals. Leukocyte telomere length (LTL) can be assessed as a biological clock connected to an individual lifespan. However, the mechanisms causing this inference are still not fully understood. As a result of this, LTL has the potential to be useful as an aging-related biomarker for assessing delayed neurocognitive recovery (dNCR) and related diseases.

METHODS

For this study, 196 individuals over 60 who were scheduled due to major non-cardiac surgical operations attended neuropsychological testing before surgery, followed by additional testing one week later. The finding of dNCR was based on a measured Z-score ≤ -1.96 on two or more separate tests. The frequency of dNCR was presented as the primary outcome of the study. Secondly, we evaluated the association between dNCR and preoperative LTL.

RESULTS

Overall, 20.4% [40/196; 95% confidence interval (CI), 14.7-26.1%] of patients exhibited dNCR 1-week post-surgery. Longer LTL was identified as a predictor for the onset of early cognitive impairment resulting in postoperative cognitive decline [odds ratio (OR), 14.82; 95% CI, 4.01-54.84; P < 0.001], following adjustment of age (OR, 12.33; 95% CI, 3.29-46.24; P < 0.001). The dNCR incidence based on LTL values of these patients, the area under the receiver operating characteristic (ROC) curve was 0.79 (95% CI, 0.722-0.859; P < 0.001). At an optimal cut-off value of 0.959, LTL values offered respective specificity and sensitivity values of 64.7% and 87.5%.

CONCLUSIONS

In summary, the current study revealed that the incidence of dNCR was strongly associated with prolonged LTL. Furthermore, this biomarker could help identify high-risk patients and offer insight into the pathophysiology of dNCR.

The relationship between cognitive clusters and telomere length in bipolar-schizophrenia spectrum disorders

BACKGROUND

Schizophrenia and bipolar disorder are complex mental illnesses that are associated with cognitive deficits. There is considerable cognitive heterogeneity that exists within both disorders. Studies that cluster schizophrenia and bipolar patients into subgroups based on their cognitive profile increasingly demonstrate that, relative to healthy controls, there is a severely compromised subgroup and a relatively intact subgroup. There is emerging evidence that telomere shortening, a marker of cellular senescence, may be associated with cognitive impairments. The aim of this study was to explore the relationship between cognitive subgroups in bipolar-schizophrenia spectrum disorders and telomere length against a healthy control sample.

METHODS

Participants included a transdiagnostic group diagnosed with bipolar, schizophrenia or schizoaffective disorder (n = 73) and healthy controls (n = 113). Cognitive clusters within the transdiagnostic patient group, were determined using K-means cluster analysis based on current cognitive functioning (MATRICS Consensus Cognitive Battery scores). Telomere length was determined using quantitative PCRs genomic DNA extracted from whole blood. Emergent clusters were then compared to the healthy control group on telomere length.

RESULTS

Two clusters emerged within the patient group that were deemed to reflect a relatively intact cognitive group and a cognitively impaired subgroup. Telomere length was significantly shorter in the severely impaired cognitive subgroup compared to the healthy control group.

CONCLUSIONS

This study replicates previous findings of transdiagnostic cognitive subgroups and associates shorter telomere length with the severely impaired cognitive subgroup. These findings support emerging literature associating cognitive impairments in psychiatric disorders to accelerated cellular aging as indexed by telomere length.

The Relationship Between Telomeres, Cognition, Mood, and Physical Function: A Systematic Review

Background and Purpose: Cognitive, affective, and physical symptoms and alterations in their function are seen across chronic illnesses. Data suggest that environmental, psychological, and physiological factors contribute to symptom experience, potentially through loss of telomeres (telomere attrition), structures at the ends of chromosomes. Telomere length is affected by many factors including environmental (e.g., exercise, diet, smoking) and physiological (e.g., response to stress), as well as from oxidative damage and inflammation that occurs in many disease processes. Moreover, telomere attrition is associated with chronic disease (cancer, cardiovascular disease, Alzheimer's disease) and predicts higher morbidity and mortality rates. However, findings are inconsistent among telomere roles and relationships with health outcomes. This article aims to synthesize the current state-of-the-science of telomeres and their relationship with cognitive, affective, and physical function and symptoms. Method: A comprehensive literature search was performed in two databases: CINAHL and PUBMED. A total of 33 articles published between 2000 and 2022 were included in the final analysis. Results: Telomere attrition is associated with various changes in cognitive, affective, and physical function and symptoms. However, findings are inconsistent. Interventional studies (e.g., meditation and exercise) may affect telomere attrition, potentially impacting health outcomes. Conclusion: Nursing research and practice are at the forefront of furthering the understanding of telomeres and their relationships with cognitive, affective, and physical function and symptoms. Future interventions targeting modifiable risk factors may be developed to improve health outcomes across populations.

Leukocyte telomere length and bipolar disorder risk: evidence from Mendelian randomization analysis

Objective

We aim to test whether leukocyte telomere length (LTL) is causally associated with the risk of bipolar disorder (BD) using the Mendelian randomization (MR) method.

Methods

Results of a genome-wide association study (GWAS) conducted with 472,174 individuals of European descent were used to screen for single-nucleotide polymorphisms (SNPs) related with LTL traits. Summary-level data for BD (7,647 cases and 27,303 controls) were obtained from UK Biobank. An inverse-variance-weighted (IVW) method was employed as the primary MR analysis. Sensitivity analyses were conducted via MR-Egger, maximum likelihood, MR-pleiotropy residual sum outlier (MR-PRESSO), and MR-robust adjusted profile score (MR-RAPS) methods. Finally, the MR Steiger test was utilized to validate the hypothesized relationship between exposure and outcome.

Results

Two-sample MR analysis revealed inverse relationships between genetically predicted LTL and BD risk (IVW OR [odds ratio] = 0.800, 95% CI [0.647–0.989] P = 0.039). Genetically predicted LTL exhibits a consistent connection with BD across five MR methods. Sensitivity analyses showed that the genetically determined effect of LTL on BD was stable and reliable. Furthermore, the MR Steiger test demonstrated that LTL was causal for BD rather than the opposite (P < 0.001).

Conclusion

Our findings show that genetically determined LTL reduces the risk of BD. More research is required to clarify the mechanisms underlying this apparent causal connection. In addition, these findings may be useful for developing strategies for the prevention and treatment of BD.

Fine or Gross Motor Index as a Simple Tool for Predicting Cognitive Impairment in Elderly People: Findings from The Irish Longitudinal Study on Ageing (TILDA)

BACKGROUND

Several kinds of motor dysfunction can predict future cognitive impairment in elderly individuals. However, the ability of the fine motor index (FINEA) and gross motor index (GROSSA) to predict the risk of cognitive impairment has not been assessed.

OBJECTIVE

We investigated the associations between FINEA/GROSSA and cognitive impairment.

METHODS

The data of 4,745 participants from The Irish Longitudinal Study on Ageing (TILDA) were analyzed. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). We first assessed the correlation between the FINEA/GROSSA and MMSE in a cross-sectional study. Then, we further investigated the predictive role of the incidence of cognitive impairment in a prospective cohort study.

RESULTS

We found that both FINEA and GROSSA were negatively correlated with MMSE in both the unadjusted (FINEA: B = -1.00, 95%confidence intervals (CI): -1.17, -0.83, t = -11.53, p < 0.001; GROSSA: B = -0.85, 95%CI: -0.94, -0.76, t = -18.29, p < 0.001) and adjusted (FINEA: B = -0.63, 95%CI: -0.79, -0.47, t = -7.77, p < 0.001; GROSSA: B = -0.57, 95%CI: -0.66, -0.48, t = -12.61, p < 0.001) analyses in a cross-sectional study. In a prospective cohort study, both high FINEA and high GROSSA were associated with an increased incidence of cognitive function impairment (FINEA: adjusted odds ratios (OR) = 2.35, 95%CI: 1.05, 5.23, p = 0.036; GROSSA adjusted OR = 3.00, 95%CI: 1.49, 6.03, p = 0.002) after 2 years of follow-up.

CONCLUSION

Higher FINEA and GROSSA scores were both associated with an increased incidence of cognitive impairment. FINEA or GROSSA might be a simple tool for identifying patients with cognitive impairment.

Short leukocyte telomeres predict 25-year Alzheimer's disease incidence in non-APOE ε4-carriers

BACKGROUND

Leukocyte telomere length (LTL) has been shown to predict Alzheimer's disease (AD), albeit inconsistently. Failing to account for the competing risks between AD, other dementia types, and mortality, can be an explanation for the inconsistent findings in previous time-to-event analyses. Furthermore, previous studies indicate that the association between LTL and AD is non-linear and may differ depending on apolipoprotein E (APOE) ε4 allele carriage, the strongest genetic AD predictor.

METHODS

We analyzed whether baseline LTL in interaction with APOE ε4 predicts AD, by following 1306 initially non-demented subjects for 25 years. Gender- and age-residualized LTL (rLTL) was categorized into tertiles of short, medium, and long rLTLs. Two complementary time-to-event models that account for competing risks were used; the Fine-Gray model to estimate the association between the rLTL tertiles and the cumulative incidence of AD, and the cause-specific hazard model to assess whether the cause-specific risk of AD differed between the rLTL groups. Vascular dementia and death were considered competing risk events. Models were adjusted for baseline lifestyle-related risk factors, gender, age, and non-proportional hazards.

RESULTS

After follow-up, 149 were diagnosed with AD, 96 were diagnosed with vascular dementia, 465 died without dementia, and 596 remained healthy. Baseline rLTL and other covariates were assessed on average 8 years before AD onset (range 1-24). APOE ε4-carriers had significantly increased incidence of AD, as well as increased cause-specific AD risk. A significant rLTL-APOE interaction indicated that short rLTL at baseline was significantly associated with an increased incidence of AD among non-APOE ε4-carriers (subdistribution hazard ratio = 3.24, CI 1.404-7.462, P = 0.005), as well as borderline associated with increased cause-specific risk of AD (cause-specific hazard ratio = 1.67, CI 0.947-2.964, P = 0.07). Among APOE ε4-carriers, short or long rLTLs were not significantly associated with AD incidence, nor with the cause-specific risk of AD.

CONCLUSIONS

Our findings from two complementary competing risk time-to-event models indicate that short rLTL may be a valuable predictor of the AD incidence in non-APOE ε4-carriers, on average 8 years before AD onset. More generally, the findings highlight the importance of accounting for competing risks, as well as the APOE status of participants in AD biomarker research.

Telomeric alterations in the default mode network during the progression of Alzheimer's disease: Selective vulnerability of the precuneus

AIMS

Although telomere length (TL) and telomere maintenance proteins (shelterins) are markers of cellular senescence and peripheral blood biomarkers of Alzheimer's disease (AD), little information is available on telomeric alterations during the prodromal stage (MCI) of AD. We investigated TL in the default mode network (DMN), which underlies episodic memory deficits in AD, as well as shelterin protein and mRNA levels in the precuneus (PreC).

METHODS

Telomere length was evaluated in DMN hubs and visual cortex using quantitative PCR (qPCR). In the PreC, western blotting and NanoString nCounter expression analyses evaluated shelterin protein and mRNA levels, respectively, in cases with an antemortem clinical diagnosis of no cognitive impairment (NCI), MCI and AD.

RESULTS

TL was significantly reduced in the PreC in MCI and AD compared to NCI, but stable in frontal, inferior temporal, posterior cingulate and visual cortex. PreC TL correlated significantly with performance on cognitive tests. NCI cases with high vs low Braak scores displayed significantly shorter TL in posterior cingulate and frontal cortex, which correlated significantly with neuritic and diffuse amyloid-β plaque counts. Shelterin protein levels (TIN2, TRF1, TRF2 and POT1) declined in MCI and AD compared to NCI. The PreC displayed stable expression of shelterins TERF1, TERF2, POT1, RAP1 and TPP1, while TINF2 mRNA significantly increased in AD compared to NCI.

CONCLUSIONS

These findings indicate a selective vulnerability to telomere attrition within different nodes of the DMN in prodromal AD and in aged NCI individuals with high Braak scores highlighting a putative role in the pathogenesis of AD.

Telomere Length and the Risk of Alzheimer's Disease: The Rotterdam Study

There is a wide interest in biomarkers that capture the burden of detrimental factors as these accumulate with the passage of time, i.e., increasing age. Telomere length has received considerable attention as such a marker, because it is easily quantified and it may aid in disentangling the etiology of dementia or serve as predictive marker. We determined the association of telomere length with risk of Alzheimer’s disease and all-cause dementia in a population-based setting. Within the Rotterdam Study, we performed quantitative PCR to measure mean leukocyte telomere length in blood. We determined the association of telomere length with risk of Alzheimer’s disease until 2016, using Cox regression models. Of 1,961 participants (mean age 71.4±9.3 years, 57.1% women) with a median follow-up of 8.3 years, 237 individuals were diagnosed with Alzheimer’s disease. We found a U-shaped association between telomere length and risk of Alzheimer’s disease: compared to the middle tertile the adjusted hazard ratio was 1.59 (95% confidence interval (CI), 1.13–2.23) for the lowest tertile and 1.47 (1.03–2.10) for the highest tertile. Results were similarly U-shaped but slightly attenuated for all-cause dementia. In conclusion, shorter and longer telomere length are both associated with an increased risk of Alzheimer’s disease in the general population.

Leukocyte Telomere Length Is Unrelated to Cognitive Performance Among Non-Demented and Demented Persons: An Examination of Long Life Family Study Participants

OBJECTIVE

Leukocyte telomere length (LTL) is a widely hypothesized biomarker of biological aging. Persons with shorter LTL may have a greater likelihood of developing dementia. We investigate whether LTL is associated with cognitive function, differently for individuals without cognitive impairment versus individuals with dementia or incipient dementia.

METHOD

Enrolled subjects belong to the Long Life Family Study (LLFS), a multi-generational cohort study, where enrollment was predicated upon exceptional family longevity. Included subjects had valid cognitive and telomere data at baseline. Exclusion criteria were age ≤ 60 years, outlying LTL, and missing sociodemographic/clinical information. Analyses were performed using linear regression with generalized estimating equations, adjusting for sex, age, education, country, generation, and lymphocyte percentage.

RESULTS

Older age and male gender were associated with shorter LTL, and LTL was significantly longer in family members than spouse controls (p < 0.005). LTL was not associated with working or episodic memory, semantic processing, and information processing speed for 1613 cognitively unimpaired individuals as well as 597 individuals with dementia or incipient dementia (p < 0.005), who scored significantly lower on all cognitive domains (p < 0.005).

CONCLUSIONS

Within this unique LLFS cohort, a group of families assembled on the basis of exceptional survival, LTL is unrelated to cognitive ability for individuals with and without cognitive impairment. LTL does not change in the context of degenerative disease for these individuals who are biologically younger than the general population.

Telomere Shortening in the Alzheimer's Disease Neuroimaging Initiative Cohort

BACKGROUND

Although shorter telomeres have been associated with Alzheimer's disease (AD), it is unclear whether longitudinal change in telomere length is associated with AD progression.

OBJECTIVE

To investigate the association of telomere length change with AD diagnosis and progression.

METHODS

In 653 individuals from the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort, T/S ratio (telomere versus single copy gene), a proxy of telomere length, was measured for up to five visits per participant (N = 1918 samples post-QC) using quantitative PCR (qPCR). T/S ratio was adjusted for batch effects and DNA storage time. A mixed effects model was used to evaluate association of telomere length with AD diagnostic group and interaction of age and diagnosis. Another mixed effects model was used to compare T/S ratio changes pre- to post-conversion to MCI or AD to telomere change in participants with stable diagnoses.

RESULTS

Shorter telomeres were associated with older age (Effect Size (ES) = -0.23) and male sex (ES = -0.26). Neither baseline T/S ratio (ES = -0.036) nor T/S ratio change (ES = 0.046) differed significantly between AD diagnostic groups. MCI/AD converters showed greater, but non-significant, telomere shortening compared to non-converters (ES = -0.186).

CONCLUSIONS

Although AD compared to controls showed small, non-significant effects for baseline T/S ratio and T/S ratio shortening, we did observe a larger, though still non-significant effect for greater telomere shortening in converters compared to non-converters. Although our results do not support telomere shortening as a robust biomarker of AD progression, further investigation in larger samples and for subgroups of participants may be informative.

Relationship between proinflammatory cytokines (Il-1beta, Il-18) and leukocyte telomere length in mild cognitive impairment and Alzheimer's disease

Inflammation plays a crucial role in Alzheimer's disease (AD). AD neurodegeneration and concurrent involvement of the peripheral immune system may promote leukocyte division and telomere shortening. We examined genotypes and plasma levels of two proinflammatory cytokines, IL-1beta and IL-18, and leukocyte telomere length (LTL) in patients with mild cognitive impairment (MCI) and AD. We wanted to determine whether changes in plasma IL-1beta and IL-18 levels, together with LTL shortening, could be diagnostic for disease progression from MCI to AD. Median plasma IL-1beta levels were in the order MCI patients (2.2 pg/ml) < AD patients (4.0 pg/ml), both of which differed significantly from the controls (0.0 pg/ml). In the AD patients, the lowest IL-1beta levels were associated with the presence of the C allele of IL-1beta rs16944 SNP. Median plasma IL-18 levels were in the order MCI patients (116.3 pg/ml) > AD patients (85.8 pg/ml), both of which were significantly higher than in the controls (17.6 pg/ml). Analysis of LTL showed a progressive reduction in the order controls > MCI > AD patients (p < 0.0001). Overall LTL reduction was correlated with increased plasma IL-1beta levels, substantiating the hypothesis that inflammatory processes secondary to neuroinflammation may trigger telomere attrition. Changes in plasma IL-1beta and Il-18 levels, and LTL seem to reflect shifts in AD stage; they may have potential use as blood biomarkers to monitor disease onset and progression from MCI to AD.

Telomere length associations with cognition depend on Alzheimer's disease biomarkers

Introduction

While telomere shortening, a marker of cellular aging, may impact the progression of age-related neurodegenerative diseases, its association with cognition is unclear, particularly in the context of Alzheimer's disease (AD) pathology.

Methods

Telomere, cognitive, and CSF data from 482 participants in the AD Neuroimaging Initiative (148 cognitively normal, 283 mild cognitive impairment, 51 AD) was leveraged to assess telomere length associations with cognition (measured by memory and executive function) and interactions with CSF amyloid-β, tau, and APOE -ε4. Secondary analyses assessed brain volume and thickness outcomes.

Results

Longer telomeres at baseline were associated with faster executive function decline. Amyloid-β and tau interacted with telomere length on cognition, with longer telomeres related to faster decline among biomarker-positive individuals.

Discussion

Telomere associations with cognition shift with AD progression, with longer telomeres related to worse outcomes as pathology increases, highlighting the need for further investigation of telomere length along the AD neuropathological cascade.

Biological Hallmarks of Cancer in Alzheimer's Disease

Although Alzheimer's disease (AD) is an international health research priority for our aging population, little therapeutic progress has been made. This lack of progress may be partially attributable to disease heterogeneity. Previous studies have identified an inverse association of cancer and AD, suggesting that cancer history may be one source of AD heterogeneity. These findings are particularly interesting in light of the number of common risk factors and two-hit models hypothesized to commonly drive both diseases. We reviewed the ten hallmark biological alterations of cancer cells to investigate overlap with the AD literature and identified overlap of all ten hallmarks in AD, including (1) potentially common underlying risk factors, such as increased inflammation, deregulated cellular energetics, and genome instability; (2) inversely regulated mechanisms, including cell death and evading growth suppressors; and (3) functions with more complex, pleiotropic mechanisms, some of which may be stage-dependent in AD, such as cell adhesion/contact inhibition and angiogenesis. Additionally, we discuss the recent observation of a biological link between cancer and AD neuropathology. Finally, we address the therapeutic implications of this topic. The significant overlap of functional pathways and molecules between these diseases, some similarly and some oppositely regulated or functioning in each disease, supports the need for more research to elucidate cancer-related AD genetic and functional heterogeneity, with the aims of better understanding AD risk mediators, as well as further exploring the potential for some types of drug repurposing towards AD therapeutic development.

Cognitive frailty among Malaysian older adults: baseline findings from the LRGS TUA cohort study

PURPOSE

This study was aimed at determining the presence of cognitive frailty and its associated factors among community-dwelling older adults from the "LRGS-Towards Useful Aging (TUA)" longitudinal study.

PATIENTS AND METHODS

The available data related to cognitive frailty among a sub-sample of older adults aged 60 years and above (n=815) from two states in Malaysia were analysed. In the LRGS-TUA study, a comprehensive interview-based questionnaire was administered to obtain the socio-demographic information of the participants, followed by assessments to examine the cognitive function, functional status, dietary intake, lifestyle, psychosocial status and biomarkers associated with cognitive frailty. The factors associated with cognitive frailty were assessed using a bivariate logistic regression (BLR).

RESULTS

The majority of the older adults were categorized as robust (68.4%), followed by cognitively pre-frail (37.4%) and cognitively frail (2.2%). The data on the cognitively frail and pre-frail groups were combined for comparison with the robust group. A hierarchical BLR indicated that advancing age (OR=1.04, 95% CI:1.01-1.08, p<0.05) and depression (OR=1.49, 95% CI:1.34-1.65, p<0.001) scored lower on the Activity of Daily Living (ADL) scale (OR=0.98, 95% CI:0.96-0.99, p<0.05), while low social support (OR=0.98, 95% CI:0.97-0.99, p<0.05) and low niacin intake (OR=0.94, 95% CI:0.89-0.99, p<0.05) were found to be significant factors for cognitive frailty. Higher oxidative stress (MDA) and lower telomerase activity were also associated with cognitive frailty (p<0.05).

CONCLUSION

Older age, a lower niacin intake, lack of social support, depression and lower functional status were identified as significant factors associated with cognitive frailty among older Malaysian adults. MDA and telomerase activity can be used as potential biomarkers for the identification of cognitive frailty.

Evaluation of oxidative stress mechanisms and the effects of phytotherapic extracts on Parkinson's disease Drosophila PINK1B9 model

Oxidative stress is commonly observed in both idiopathic and genetic cases of Parkinson's disease (PD). It plays an important role in the degeneration of dopaminergic neurons, and it has been associated with altered telomere length (TL). There is currently no cure for PD, and extracts of antioxidative plant, such as Mucuna pruriens and Withania somnifera, are commonly used in Ayurveda to treat patients with PD. In this study, we evaluated 2 enzymatic markers of oxidative stress, glutathione (GSH) system and superoxide dismutase (SOD), and TL in a Drosophila melanogaster model for PD [phosphatase and tensin homolog-induced putative kinase 1 (PINK1)^B9]. This evaluation was also performed after treatment with the phytoextracts. PINK1^B9 mutants showed a decrease in GSH amount and SOD activity and unexpected longer telomeres compared with wild-type flies. M. pruriens treatment seemed to have a beneficial effect on the oxidative stress conditions. On the other hand, W. somnifera treatment did not show any improvements in the studied oxidative stress mechanisms and even seemed to favor the selection of flies with longer telomeres. In summary, our study suggests the importance of testing antioxidant phytoextracts in a PINK1^B9 model to identify beneficial effects for PD.-Baroli, B., Loi, E., Solari, P., Kasture, A., Moi, L., Muroni, P., Kasture, S., Setzu, M. D., Liscia, A., Zavattari, P. Evaluation of oxidative stress mechanisms and the effects of phytotherapic extracts on Parkinson's disease Drosophila PINK1^B9 model.

Baseline Telomere Length and Effects of a Multidomain Lifestyle Intervention on Cognition: The FINGER Randomized Controlled Trial

Leukocyte telomere length (LTL) is a biomarker of aging, and it is associated with lifestyle. It is currently unknown whether LTL is associated with the response to lifestyle interventions. The goal is to assess whether baseline LTL modified the cognitive benefits of a 2-year multidomain lifestyle intervention (exploratory analyses). The Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) was a 2-year randomized controlled trial including 1,260 people at risk of cognitive decline, aged 60–77 years identified from the general population. Participants were randomly assigned to the lifestyle intervention (diet, exercise, cognitive training, and vascular risk management) and control (general health advice) groups. Primary outcome was change in cognition (comprehensive neuropsychological test battery). Secondary outcomes were changes in cognitive domains: memory, executive functioning, and processing speed. 775 participants (392 control, 383 intervention) had baseline LTL (peripheral blood DNA). Mixed effects regression models with maximum likelihood estimation were used to analyze change in cognition as a function of randomization group, time, baseline LTL, and their interaction. Intervention and control groups did not significantly differ at baseline. Shorter LTL was related to less healthy baseline lifestyle. Intervention benefits on executive functioning were more pronounced among those with shorter baseline LTL (p-value for interaction was 0.010 adjusted for age and sex, and 0.007 additionally adjusted for baseline lifestyle factors). The FINGER intervention cognitive benefits were more pronounced with shorter baseline LTL, particularly for executive functioning, indicating that the multidomain lifestyle intervention was especially beneficial among higher-risk individuals.

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.

Effects of Meditation and Music-Listening on Blood Biomarkers of Cellular Aging and Alzheimer's Disease in Adults with Subjective Cognitive Decline: An Exploratory Randomized Clinical Trial

BACKGROUND

Telomere length (TL), telomerase activity (TA), and plasma amyloid-β (Aβ) levels have emerged as possible predictors of cognitive decline and dementia.

OBJECTIVE

To assess the: 1) effects of two 12-week relaxation programs on TL, TA, and Aβ levels in adults with subjective cognitive decline; and 2) relationship of biomarker changes to those in cognitive function, psychosocial status, and quality of life (QOL).

METHODS

Participants were randomized to a 12-week Kirtan Kriya meditation (KK) or music listening (ML) program and asked to practice 12 minutes/day. Plasma Aβ(38/40/42) and peripheral blood mononuclear cell TL and TA were measured at baseline and 3 months. Cognition, stress, sleep, mood, and QOL were assessed at baseline, 3 months, and 6 months.

RESULTS

Baseline blood samples were available for 53 participants (25 KK, 28 ML). The KK group showed significantly greater increases in Aβ40 than the ML group. TA rose in both groups, although increases were significant only among those with higher practice adherence and lower baseline TA. Changes in both TL and TA varied by their baseline values, with greater increases among participants with values ≤50th percentile (ps-interaction <0.006). Both groups improved in cognitive and psychosocial status (ps ≤0.05), with improvements in stress, mood, and QOL greater in the KK group. Rising Aβ levels were correlated with gains in cognitive function, mood, sleep, and QOL at both 3 and 6 months, associations that were particularly pronounced in the KK group. Increases in TL and TA were also correlated with improvements in certain cognitive and psychosocial measures.

CONCLUSION

Practice of simple mind-body therapies may alter plasma Aβ levels, TL, and TA. Biomarker increases were associated with improvements in cognitive function, sleep, mood, and QOL, suggesting potential functional relationships.

Identification of Neuroprotective Factors Associated with Successful Ageing and Risk of Cognitive Impairment among Malaysia Older Adults

The increase of ageing population has raised public attention on the concept of successful ageing. Studies have shown that vitamin D, telomere length, and brain-derived neurotrophic factor (BDNF) have been associated with cognitive function. Therefore, this study aimed to identify neuroprotective factors for cognitive decline in different ageing groups. A total of 300 older adults aged 60 years and above were recruited in this population based cross-sectional study. Participants were categorized into three groups: mild cognitive impairment (MCI) (n = 100), usual ageing (UA) (n = 100), and successful ageing (SA) (n = 100). Dietary vitamin D intake was assessed through Diet History Questionnaire (DHQ). Out of the 300 participants, only 150 were subjected to fasting blood sample collection. These samples were used for serum vitamin D and plasma BDNF measurements. Whole blood telomere length was measured using RT-PCR method. The results show that the reduction of the risk of MCI was achieved by higher serum vitamin D level (OR: 0.96, 95% CI: 0.92–0.99, p < 0.05), higher plasma BDNF level (OR: 0.51, 95% CI: 0.30–0.88,  p < 0.05), and longer telomere (OR: 0.97, 95% CI: 0.95–0.99,  p < 0.001). In conclusion, participants with higher vitamin D level, higher BDNF level, and longer telomere length were more likely to age successfully.

Leukocyte telomere length in mild cognitive impairment and Alzheimer's disease patients

Numerous studies have reported an association between shortened leukocyte telomere length (LTL) and increased risk of Alzheimer's disease (AD). In this study we investigated the relationship between LTL and AD development, including in the analysis patients with amnestic mild cognitive impairment (aMCI), a clinical entity considered prodromal of AD. LTL (T/S ratio) was measured in patients with AD (n=61) or aMCI (n=46), and compared with LTL of age-matched controls (n=56). Significant LTL differences were observed between controls, aMCI and AD patients (p<0.0001), with mean LTL values (±s.d) in the order: AD patients (0.70±0.15)<aMCI patients (0.80±0.14)<controls (0.88±0.15). A positive relationship (linear regression p=0.004) was observed between LTL and cognitive performance (measured by Mini Mental State Examination score). LTL did not differ by APOE genotype. The shortened LTL observed in AD patients appears to stem from progressive telomere erosion possibly correlated with the cognitive decline characterizing conversion from aMCI to AD. LTL reduction, indicating active cell proliferation, may reflect immune system involvement in AD pathogenesis.

Dietary acrylamide exposure was associated with mild cognition decline among non-smoking Chinese elderly men

The aim of the study is to explore the longitudinal association of dietary acrylamide exposure with cognitive performance in Chinese elderly. The analysis was conducted among 2534 non-smoking elderly men and women based on a prospective study, Mr. and Ms. OS Hong Kong. Dietary acrylamide intake was assessed by food frequency questionnaires with data on local food contamination, derived from the first Hong Kong Total Diet Study. Global cognitive function was assessed by Cantonese version of Mini-Mental State Exam (MMSE) at the baseline and the 4^th year of follow-up. Multivariable-adjusted linear and logistic regression models were used to assess the associations of dietary acrylamide with MMSE score changes or risk of poor cognition. The results indicated that among men with MMSE ≥ 18, each one SD increase of acrylamide decreased MMSE score by 7.698% (95%CI: -14.943%, -0.452%; p = 0.037). Logistic regression revealed an increased risk of poor cognition (MMSE ≤ 26) in men with HR of 3.356 (1.064~10.591, p = 0.039). The association became non-significance after further adjustment for telomere length. No significant association was observed in women. Dietary acrylamide exposure was associated with a mild cognitive decline or increased risk of poor cognition over a 4-year period in non-smoking Chinese elderly men.

Telomere Length, Long-Term Black Carbon Exposure, and Cognitive Function in a Cohort of Older Men: The VA Normative Aging Study

BACKGROUND

Long-term air pollution exposure has been associated with age-related cognitive impairment, possibly because of enhanced inflammation. Leukocytes with longer telomere length (TL) are more responsive to inflammatory stimuli, yet TL has not been evaluated in relation to air pollution and cognition.

OBJECTIVES

We assessed whether TL modifies the association of 1-year exposure to black carbon (BC), a marker of traffic-related air pollution, with cognitive function in older men, and we examined whether this modification is independent of age and of C-reactive protein (CRP), a marker of inflammation.

METHODS

Between 1999 and 2007, we conducted 1-3 cognitive examinations of 428 older men in the Veterans Affairs (VA) Normative Aging Study. We used covariate-adjusted repeated-measure logistic regression to estimate associations of 1-year BC exposure with relative odds of being a low scorer (≤ 25) on the Mini-Mental State Examination (MMSE), which is a proxy of poor cognition. Confounders included age, CRP, and lifestyle and sociodemographic factors.

RESULTS

Each doubling in BC level was associated with 1.57 (95% CI: 1.20, 2.05) times higher odds of low MMSE scores. The BC-MMSE association was greater only among individuals with longer blood TL (5th quintile) (OR = 3.23; 95% CI: 1.37, 7.59; p = 0.04 for BC-by-TL-interaction). TL and CRP were associated neither with each other nor with MMSE. However, CRP modified the BC-MMSE relationship, with stronger associations only at higher CRP (5th quintile) and reference TL level (1st quintile) (OR = 2.68; 95% CI: 1.06, 6.79; p = 0.04 for BC-by-CRP-interaction).

CONCLUSIONS

TL and CRP levels may help predict the impact of BC exposure on cognitive function in older men. Citation: Colicino E, Wilson A, Frisardi MC, Prada D, Power MC, Hoxha M, Dioni L, Spiro A III, Vokonas PS, Weisskopf MG, Schwartz JD, Baccarelli AA. 2017. Telomere length, long-term black carbon exposure, and cognitive function in a cohort of older men: the VA Normative Aging Study. Environ Health Perspect 125:76-81; http://dx.doi.org/10.1289/EHP241.

Micronucleus frequency in peripheral blood lymphocytes and frailty status in elderly. A lack of association with clinical features

Frailty is a condition of vulnerability that carries an increased risk of poor outcome in elder adults. Frail individuals show fatigue, weight loss, muscle weakness, and a reduced physical function, and are known to frequently experience disability, social isolation, and institutionalization. Identifying frail people is a critical step for geriatricians to provide timely geriatric care and, eventually, to improve the quality of life in elderly. The aim of the present study is to investigate the association between frailty status and micronucleus (MN) frequency, a known marker of genomic instability, in a sample of elder adults. Several clinical features were evaluated and their possible association with MN frequency was tested. Criteria proposed by Fried were used to identify frail subjects. Overall, 180 elder adults entered the study, 93 of them (51.7%) frail. No association between MN frequency and frailty status was found under the specific conditions tested in this study (mean ratio=1.06; 95% CI 0.96-1.18). The inclusion of MN frequency in the Fried's frailty scale minimally improved the classification of study subjects according to the multidimensional prognostic index (MPI). The presence of genomic instability in the ageing process and in most chronic diseases, demands further investigation on this issue.