Association of critically short telomeres with brain and blood markers of ageing and Alzheimer's disease in older adults

BACKGROUND

Accumulation of critically short telomeres (CST) is implicated in decreased tissular regenerative capacity and increased susceptibility to degenerative diseases such as Alzheimer's disease (AD). Telomere shortening has also been associated with age-related brain changes. However, it remains unclear whether CST accumulation is directly associated with AD markers or instead amplifies age-related effects, potentially increasing susceptibility of developing AD in cognitively healthy older adults.

METHODS

This cross-sectional study used baseline data of 129 community-dwelling cognitively healthy older adults from the Age-Well trial (NCT02977819), aged 65 years and older enrolled between 2016 and 2018, in France. Using linear regressions, we analyzed the relationship between an innovative marker of telomere shortening, the percentage of CST (%CST), structural, functional and molecular neuroimaging outcomes, and multiple blood-based biomarkers related to AD pathophysiology. The effect of apolipoprotein E ε4 genotype (APOE4) was assessed on these relationships using interaction analysis.

RESULTS

A higher %CST was associated with lower global kurtosis fractional anisotropy (β = -.230; P = .010), particularly in frontal and temporal regions. A higher %CST was also related to higher plasma levels of Neurofilament light chain (β = .195; P = .020) and a lower subiculum volume (β = -.206; P = .020), although these associations did not meet the threshold for multiple comparisons. %CST was not associated with AD-related neuroimaging markers, including the AD-sensitive gray matter pattern (β = -.060; P = .441), glucose metabolism pattern (β = -.099; P = .372), brain perfusion pattern (β = -.106; P = .694) or hippocampus volume (β = -.106; P = .194). In APOE4 carriers, higher %CST was associated with lower subiculum (β = -.423; P = 0.003), DG (β = -.410; P = 0.018) and CA1 volumes (β = -.373; P = 0.024), even though associations with DG and CA1 volumes did not survive multiple comparison.

CONCLUSIONS

Although an increase in %CST does not appear to be directly linked to the pathophysiology of AD in cognitively healthy older adults, it could heighten the susceptibility of APOE4 carriers to develop AD plausibly due to greater vulnerability to age-related effects. However, longitudinal studies would be necessary to determine whether %CST influences the development and progression of AD later in life.

Leukocyte Telomere Length as a Molecular Biomarker of Coronary Heart Disease

Background. This work is a review of preclinical and clinical studies of the role of telomeres and telomerase in the development and progression of coronary heart disease (CHD). Materials and methods. A search for full-text publications (articles, reviews, meta-analyses, Cochrane reviews, and clinical cases) in English and Russian was carried out in the databases PubMed, Oxford University Press, Scopus, Web of Science, Springer, and E-library electronic library using keywords and their combinations. The search depth is 11 years (2010–2021). Results. The review suggests that the relative leukocyte telomere length (LTL) is associated with the development of socially significant and widespread cardiovascular diseases such as CHD and essential hypertension. At the same time, the interests of researchers are mainly focused on the study of the relative LTL in CHD. Conclusions. Despite the scientific and clinical significance of the analyzed studies of the relative length of human LTL as a biological marker of cardiovascular diseases, their implementation in real clinical practice is difficult due to differences in the design and methodology of the analyzed studies, as well as differences in the samples by gender, age, race, and ethnicity. The authors believe that clinical studies of the role of the relative length of leukocyte telomeres in adult patients with coronary heart disease are the most promising and require large multicenter studies with a unified design and methodology.

The functional and structural connectomes of telomere length and their association with cognition in mild cognitive impairment

Previous findings on the relationship between telomere length and cognition have inconclusive, despite the relatively consistent telomere-shortening associated atrophy in the subcortical regions. Perhaps, there could be other more important telomere-associated factors in the brain, such as functional connectivity (FC) and structural connectivity (SC) that modulate cognition. The current study examined the relationship between telomere length, connectivity, and cognition. Telomere length measurements, neurocognitive scores, diffusion tensor and resting-state functional magnetic resonance imaging scans were collected from 82 older adults with mild cognitive impairment. SC and FC matrices were derived from these scans and, in various combinations, entered into connectome-based predictive models to predict telomere length. The telomere-associated features were then used to predict memory and executive functions. Leave-one-out cross-validation was performed. Predictive accuracy was assessed via the correlation between predicted and observed scores (r_{predicted-observed}). Correlation analyses were carried out between cognition and telomere length. Telomere length was significantly and negatively correlated with executive functions (EF), after controlling for demographical confounds. Telomere length was best predicted by negative SC and positive FC features (r_{predicted-observed} = .57; p < .001). The telomere-associated negative SC features significantly predicted EF scores (r_{predicted-observed} = -.26; p = .015). Telomere-shortening was associated with better EF and alterations in both FC and SC. This enhanced EF can be partly attributed to the telomere-associated changes in SC. Given that telomere is known to be a nonspecific marker of health, our findings illustrated a potential clinical use of telomere length to predict individualized health-related information from FC and SC features.

Religiosity and Telomere Length: Moderating Effect of Religiosity on the Relationship Between High-Risk Polymorphisms of the Apolipoprotein E and TOMM40 Gene and Telomere Length

Objective: The current study seeks to examine the relationship between religiosity and telomere length (TL) in an older Chinese Muslim sample and to explore the moderating effect of religiosity on the relationship between high-risk polymorphisms and TL. Methods: A cross-sectional study of 1,692 community-dwelling adults aged 55 or older was conducted. Apolipoprotein E and TOMM40 (rs2075650) gene polymorphisms and TL were determined using standard procedures. Ordinal logistic regression was used to examine the associations. Results: Religiosity was significantly and positively related to TL. A significant interaction emerged between religiosity and the rs2075650 G polymorphism in predicting TL. Stratified multivariate analyses demonstrated that the relationship between the rs2075650 G state and TL was particularly strong among those who were more religious, as hypothesized. Conclusion: The findings revealed that religiosity may influence cellular aging in part by modifying the effect that high-risk genes have on increasing vulnerability to dementia and cognitive impairment.