Translating Measures of Biological Aging to Test Effectiveness of Geroprotective Interventions: What Can We Learn from Research on Telomeres?

DNA methylation-based telomere length is associated with HIV infection, physical frailty, cancer, and all-cause mortality

Telomere length (TL) is an important indicator of cellular aging. Shorter TL is associated with several age-related diseases including coronary heart disease, heart failure, diabetes, osteoporosis, and cancer. Recently, a DNA methylation-based TL (DNAmTL) estimator has been developed as an alternative method for directly measuring TL. In this study, we examined the association of DNAmTL with cancer prevalence and mortality risk among people with and without HIV in the Veterans Aging Cohort Study Biomarker Cohort (VACS, N = 1917) and Women's Interagency HIV Study Cohort (WIHS, N = 481). We profiled DNAm in whole blood (VACS) or in peripheral blood mononuclear cells (WIHS) using an array-based method. Cancer prevalence was estimated from electronic medical records and cancer registry data. The VACS Index was used as a measure of physiologic frailty. Models were adjusted for self-reported race and ethnicity, batch, smoking status, alcohol consumption, and five cell types (CD4, CD8, NK, B cell, and monocyte). We found that people with HIV had shorter average DNAmTL than those without HIV infection [beta = -0.25, 95% confidence interval (-0.32, -0.18), p = 1.48E-12]. Greater value of VACS Index [beta = -0.002 (-0.003, -0.001), p = 2.82E-05] and higher cancer prevalence [beta = -0.07 (-0.10, -0.03), p = 1.37E-04 without adjusting age] were associated with shortened DNAmTL. In addition, one kilobase decrease in DNAmTL was associated with a 40% increase in mortality risk [hazard ratio: 0.60 (0.44, 0.82), p = 1.42E-03]. In summary, HIV infection, physiologic frailty, and cancer are associated with shortening DNAmTL, contributing to an increased risk of all-cause mortality.

Cross-tissue comparison of telomere length and quality metrics of DNA among individuals aged 8 to 70 years

Telomere length (TL) is an important biomarker of cellular aging, yet its links with health outcomes may be complicated by use of different tissues. We evaluated within- and between-individual variability in TL and quality metrics of DNA across five tissues using a cross-sectional dataset ranging from 8 to 70 years (N = 197). DNA was extracted from all tissue cells using the Gentra Puregene DNA Extraction Kit. Absolute TL (aTL) in kilobase pairs was measured in buccal epithelial cells, saliva, dried blood spots (DBS), buffy coat, and peripheral blood mononuclear cells (PBMCs) using qPCR. aTL significantly shortened with age for all tissues except saliva and buffy coat, although buffy coat was available for a restricted age range (8 to 15 years). aTL did not significantly differ across blood-based tissues (DBS, buffy coat, PBMC), which had significantly longer aTL than buccal cells and saliva. Additionally, aTL was significantly correlated for the majority of tissue pairs, with partial Spearman's correlations controlling for age and sex ranging from ⍴ = 0.18 to 0.51. We also measured quality metrics of DNA including integrity, purity, and quantity of extracted DNA from all tissues and explored whether controlling for DNA metrics improved predictions of aTL. We found significant tissue variation: DNA from blood-based tissues had high DNA integrity, more acceptable A260/280 and A260/230 values, and greater extracted DNA concentrations compared to buccal cells and saliva. Longer aTL was associated with lower DNA integrity, higher extracted DNA concentrations, and higher A260/230, particularly for saliva. Model comparisons suggested that incorporation of quality DNA metrics improves models of TL, although relevant metrics vary by tissue. These findings highlight the merits of using blood-based tissues and suggest that incorporation of quality DNA metrics as control variables in population-based studies can improve TL predictions, especially for more variable tissues like buccal and saliva.

Telomere length and chronological age across the human lifespan: A systematic review and meta-analysis of 414 study samples including 743,019 individuals

Telomere attrition is a proposed hallmark of aging. To evaluate the association of telomere length (TL) with chronological age across the human lifespan, we conducted a systematic review and meta-analysis of 414 study samples comprising 743,019 individuals aged 0-112 years. We examined both cross-sectional and longitudinal data, and evaluated the impact of various biological and methodological factors including sex, health status, tissue types, DNA extraction procedures, and TL measurement methods. The pooled corrected correlation between TL and age from cross-sectional samples was -0.19 (95%CI: -0.22 to -0.15), which weakened with increased chronological age (β = 0.003, p < 0.001). Z-score change rates of TL across the lifespan showed a gradual decrease in shortening rate until around age 50 and remained at a relatively stable rate towards the elderly period. A greater attrition rate was observed in longitudinal than cross-sectional evaluations. For TL measured in base pairs, the median change rate of TL was -23 bp/year in cross-sectional samples and -38 bp/year in longitudinal samples. Methodological factors including TL measurement methods and tissue types impacted the TL-age correlation, while sex or disease status did not. This meta-analysis revealed the non-linear shortening trend of TL across the human lifespan and provides a reference value for future studies. Results also highlight the importance of methodological considerations when using TL as an aging biomarker.

Association of Telomere Length with Cognitive Impairment

Telomere attrition is attributed to Alzheimer's disease (AD), major depressive disorder, stress levels, physical inactivity, short sleep duration, and reduced educational abilities. In this article, we tried to assess the association between the telomere length in peripheral blood leukocytes and level of cognitive impairment and its dependence on age and sex. Healthy subjects and patients with amnestic mild cognitive impairment (aMCI) and different AD stages were recruited in the study. All patients were assessed by the same standard diagnostic procedure, including neurological examination-Mini-Mental State Examination (MMSE). Blood samples from 66 subjects (18 men and 48 women, mean age 71.2 ± 0.56 years) were collected for DNA extraction from peripheral mononuclear cells (PBMC). Relative telomere length (RTL) was measured by monochrome multiplex polymerase chain reaction. The data obtained in the study indicate that RTL in PBMCs has a statistically significant association with MMSE score (p < 0.02). Moreover, the sex-specific difference was observed for the association between telomere length and various parameters of MMSE. Also, it has been found that a decrease in RTL by one unit is associated with an increase in the odds to get AD at a ratio of 2.54 (95% CI, 1.25 to 5.17). The results obtained in this research are in coherence with other studies that telomere length may be a valuable biomarker of cognitive decline. However, the potential need for longitudinal studies of telomere length, in order to estimate the influence of hereditary and environmental factors, remains.

Associations between exposure to ambient air pollution and changes in blood telomeres in young people: A repeated-measure study

Telomere length (TL) is one of the early biomarkers of aging. Air pollutants play an important role in promoting the aging process. However, few studies have explored how they adversely affect human health by altering telomeres. This study aims to investigate the associations between telomere alterations and exposure to ambient air pollutants, thereby shedding light on the intrinsic and profound link between these pollutants and aging. We recruited 26 healthy young people and conducted 7 repeated measure studies from 2019 to 2021, and TL and telomerase (TA) in the blood samples. We analyzed the associations between air pollutants, including ozone (O₃), particulate matter in diameter smaller than 2.5 μm (PM_2.5) and 10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and carbon monoxide (CO) and telomere variability, and explored the lagged effects by linear mixed-effects model. The result showed that short-term exposure to O₃ was negatively associated with TL, and this effect in the lag days went up to around 0. In contrast, the associations between O₃ and TA presented positive tendency and gradually decreased to around 0 in the lag days. The association between PM_2.5 and TL showed positive tendency and gradually decreased to negative. There was no statistically significant association between PM_2.5 and TA. Other pollutants (PM₁₀, NO₂, SO₂, CO) showed similar patterns of variation to that of PM_2.5. Our findings suggest that short-term exposure to O₃ shortens TL, which can be gradually recovered through activating TA activity, while exposure to PM_2.5, PM₁₀, NO₂, SO₂ and CO lengthens TL and then becomes shorter over time. This implies that the human body has some ability to self-repair telomere changes after exposure to air pollutants, and predictably, when this exposure exceeds a certain threshold, it cannot be repaired, leading to aging of the body.

Association of the dietary inflammatory index with phenotypic age in the United States adults

OBJECTIVES

One of the underlying mechanisms of aging is chronic inflammation, which has been closely associated with daily diet. Phenotypic age (PhenoAge) has been used as an index to track the aging process before diseases show clinical symptoms. The present study aimed to explore the association between the dietary inflammatory index (DII) and PhenoAge.

METHODS

In total, 9,275 adults aged 20 years old and over in the National Health and Nutrition Examination Survey were involved in this study. Dietary patterns were classified as pro-inflammatory or anti-inflammatory according to the DII. PhenoAge was regarded as a continuous variable, and linear regression was used to explore its association with dietary inflammation. Stratified analyses by sex, age, race, physical exercise, smoking status, drinking status, and body mass index were used to test the sensitivity of these associations.

RESULTS

The median value of PhenoAge was 38.60 years and 39.76 years for the participants with anti-inflammatory and pro-inflammatory diets, respectively. A pro-inflammatory diet was positively associated with PhenoAge (β=0.73; 95% confidence interval, 0.31 to 1.14), compared with participants who had an anti-inflammatory diet. There was an interaction between dietary inflammation and age for PhenoAge (pinteraction<0.001). The strength of the association between a pro-inflammatory diet and PhenoAge was stronger as age increased.

CONCLUSIONS

A pro-inflammatory diet was associated with a higher PhenoAge, and the association was strongest in the elderly. We recommended reducing dietary inflammation to delay phenotypic aging, especially for the elderly.

The Relevance of Telomerase and Telomere-Associated Proteins in B-Acute Lymphoblastic Leukemia

Telomeres and telomerase are closely linked to uncontrolled cellular proliferation, immortalization and carcinogenesis. Telomerase has been largely studied in the context of cancer, including leukemias. Deregulation of human telomerase gene hTERT is a well-established step in leukemia development. B-acute lymphoblastic leukemia (B-ALL) recovery rates exceed 90% in children; however, the relapse rate is around 20% among treated patients, and 10% of these are still incurable. This review highlights the biological and clinical relevance of telomerase for B-ALL and the implications of its canonical and non-canonical action on signaling pathways in the context of disease and treatment. The physiological role of telomerase in lymphocytes makes the study of its biomarker potential a great challenge. Nevertheless, many works have demonstrated that high telomerase activity or hTERT expression, as well as short telomeres, correlate with poor prognosis in B-ALL. Telomerase and related proteins have been proven to be promising pharmacological targets. Likewise, combined therapy with telomerase inhibitors may turn out to be an alternative strategy for B-ALL.

Comparing qPCR and DNA methylation-based measurements of telomere length in a high-risk pediatric cohort

Various approaches exist to assess population differences in biological aging. Telomere length (TL) is one such measure, and is associated with disease, disability and early mortality. Yet, issues surrounding precision and reproducibility are a concern for TL measurement. An alternative method to estimate TL using DNA methylation (DNAmTL) was recently developed. Although DNAmTL has been characterized in adult and elderly cohorts, its utility in pediatric populations remains unknown. We examined the comparability of leukocyte TL measurements generated using qPCR (absolute TL; aTL) to those estimated using DNAmTL in a high-risk pediatric cohort (N = 269; age: 8–13 years, 83% investigated for maltreatment). aTL and DNAmTL measurements were correlated with one another (r = 0.20, p = 0.001), but exhibited poor measurement agreement and were significantly different in paired-sample t-tests (Cohen’s d = 0.77, p < 0.001). Shorter DNAmTL was associated with older age (r = −0.25, p < 0.001), male sex (β = −0.27, p = 0.029), and White race (β = −0.74, p = 0.008). By contrast, aTL was less strongly associated with age (r = −0.13, p = 0.040), was longer in males (β = 0.31, p = 0.012), and was not associated with race (p = 0.820). These findings highlight strengths and limitations of high-throughput measures of TL; although DNAmTL replicated hypothesized associations, aTL measurements were positively skewed and did not replicate associations with external validity measures. These results also extend previous research in adults and suggest that DNAmTL is a sensitive TL measure for use in pediatric populations.

Telomere length as a biomarker of aging and diseases

As research related to healthspan and lifespan has become a hot topic, the necessity for a reliable and practical biomarker of aging (BoA), which can provide information about mortality and morbidity risk, along with remaining life expectancy, has increased. The chromosome terminus non-coding protective structure that prevents genomic instability is called a telomere. The continual shortening of telomeres, which affects their structure as well as function, is a hallmark of agedness. The aforementioned process is a potential cause of age-related diseases (ARDs), leading to a bad prognosis and a low survival rate, which compromise health and longevity. Hence, studies scrutinizing the BoAs often include telomere length (TL) as a prospective candidate. The results of these studies suggest that TL measurement can only provide an approximate appraisal of the aging rate, and its implementation into clinical practice and routine use as a BoA has many limitations and challenges. Nevertheless, measuring TL while determining other biomarkers can be used to assess biological age. This review focuses on the importance of telomeres in health, senescence, and diseases, as well as on summarizing the results and conclusions of previous studies evaluating TL as a potential BoA.

Telomere shortening in patients on long-term hemodialysis

Background

Leukocyte telomere length shortening is a characteristic of premature senescence, a process that can be accelerated by oxidative stress. In general, patients with end-stage renal disease undergoing regular hemodialysis (HD) are repeatedly exposed to oxidative stress. Patients undergoing HD tend to have cardiovascular diseases associated with oxidative stress and inflammation. Therefore, we assumed that telomere length is associated with HD vintage and the degree of vascular calcification.

Methods

A total of 144 patients undergoing regular HD before kidney transplantation and 62 patients on hemodialysis, but not undergoing kidney transplantation, were enrolled. We measured common laboratory values, such as calcium, phosphate, and hemoglobin levels, and assessed the degree of vascular calcification in the patients. The leukocyte telomere length was measured using reverse transcription polymerase chain reaction, and Spearman correlation was used for correlation analysis.

Results

The leukocyte telomere length was negatively associated with age (rho = −0.306, P＜0.01); it was shorter in middle-aged patients than in young patients (13.48 ± 4.80 vs. 15.86 ± 4.51, P < 0.01). The telomere length was significantly different among patients aged 52–74 years in groups with different HD vintages. Additionally, the telomere length was positively associated with serum hemoglobin (Hb) levels in all patients (rho = 0.290, P < 0.01). There was a significant difference among patients divided into three groups according to the degree of anemia (17.09 ± 5.64 vs. 14.40 ± 4.07 vs. 13.99 ± 3.95, P < 0.01). Further, a significant difference was observed in the telomere length among patients with different degrees of vascular calcification (16.79 ± 4.91 vs. 13.61 ± 2.82 vs. 14.62 ± 3.63 vs. 10.71 ± 3.74, P < 0.01). The telomere length was shorter in the patients on hemodialysis who did not receive a kidney transplant than in the surgical patients (8.12 ± 1.83 vs. 14.33 ± 4.63, P < 0.01).

Conclusion

This study demonstrated that the telomere length was significantly correlated with HD vintage in patients of a certain age group. The telomere length was shorter in patients on hemodialysis who matched for age and dialysis vintage with kidney transplant patients. It was also associated with vascular calcification and serum Hb levels in all patients undergoing HD.

Impact of Amplification Efficiency Approaches on Telomere Length Measurement via Quantitative-Polymerase Chain Reaction

Background: Precise determination of amplification efficiency is critical for reliable conversion of within-sample changes in fluorescence occurring on a logarithmic scale to between-sample differences in DNA content occurring on a linear scale. This endeavor is especially challenging for the telomere length (TL) quantitative-PCR (qPCR) assay, where amplification efficiency can vary between reactions targeting telomeric repeats (T) and those targeting a single-copy gene (S) to calculate TL as the T/S ratio. Methods: We compared seven different approaches toward estimating amplification efficiency, including the standard-curve method utilized by the qPCR instrument software, and alternative approaches which estimate efficiency on a reaction-by-reaction basis using the stand-alone program LinRegPCR. After calculating T/S ratios using efficiency estimates from each approach (N = 363), we tested their relative performance on metrics of assay precision and correlates of external validity including chronological age (age range = 1-72 years), across tissues within-person (leukocyte-buccal), and between parents and offspring. Results: Estimated amplification efficiency for telomere reactions was significantly lower than estimates for single-copy gene reactions. Efficiency estimates for both reaction sets were significantly higher when estimated with the standard-curve method utilized by the qPCR instrument relative to estimates reconstructed during the log-linear phase with LinRegPCR. While estimates of single-copy gene efficiency reconstructed using LinRegPCR measured within 90% of perfect exponential doubling (E = 1.92), estimates generated using the standard-curve method were inflated beyond 100% (E = 2.10-2.12), indicating poor fidelity. Despite differences in raw value, TL measurements calculated with LinRegPCR efficiency estimates exhibited similar relationships with external validity correlates to measurements generated using the qPCR instrument software. Conclusion: Since methods to estimate amplification efficiency can vary across qPCR instruments, we suggest that future analyses empirically consider external methods of efficiency calculations such as LinRegPCR, and that already generated data be re-analyzed to glean possible improvements.

Ranking Biomarkers of Aging by Citation Profiling and Effort Scoring

Aging affects most living organisms and includes the processes that reduce health and survival. The chronological and the biological age of individuals can differ remarkably, and there is a lack of reliable biomarkers to monitor the consequences of aging. In this review we give an overview of commonly mentioned and frequently used potential aging-related biomarkers. We were interested in biomarkers of aging in general and in biomarkers related to cellular senescence in particular. To answer the question whether a biological feature is relevant as a potential biomarker of aging or senescence in the scientific community we used the PICO strategy known from evidence-based medicine. We introduced two scoring systems, aimed at reflecting biomarker relevance and measurement effort, which can be used to support study designs in both clinical and research settings.

Biological Aging and Periodontal Disease: Analysis of NHANES (2001-2002)

INTRODUCTION

Periodontitis is a chronic inflammatory disease caused by multiple potential contributing factors such as bacterial biofilm infection of the tissues surrounding the teeth and environmental determinants and a dysregulated host response for modifying and resolving the inflammation. Because periodontal disease is a major public health concern with substantial increases in the prevalence and severity in aging populations, previous studies of periodontitis tended to approach the disease as an age-associated outcome across the life span. However, few investigations have considered that, as a chronic noncommunicable disease, periodontitis may not simply be a disease that increases with age but may contribute to more rapid biologic aging.

OBJECTIVES

Increasing population data supports the potential disconnect between chronological aging and biologic aging, which would contribute to the heterogeneity of aging phenotypes within chronologic ages across populations. Thus, our aim was to test whether periodontal disease affects biological aging across the life span.

METHODS

The prevalence of periodontitis in the adult US population is a portion of the assessment of the National Health and Nutrition Examination Survey (NHANES), which has been ongoing since 1971 through 2-y cycles sampling populations across the country. We used NHANES 2001-2002 to test the hypothesis that the presence/severity of periodontal disease as an exposure variable would negatively affect telomere length, a measure of biological aging, and that this relationship is modified by factors that also affect the progression of periodontitis, such as sex, race/ethnicity, and smoking.

RESULTS

The data demonstrated a significant impact of periodontitis on decreasing telomere lengths across the life span. These differences were modulated by age, sex, race/ethnicity, and smoking within the population.

CONCLUSION

The findings lay the groundwork for future studies documenting broader effects on biological aging parameters as well as potential intervention strategies for periodontitis in driving unhealthy aging processes.

KNOWLEDGE TRANSFER STATEMENT

Periodontitis is a chronic inflammatory disease and dysregulated host response. Shortening of telomeres is a reflection of biologic aging. Decreased telomere lengths with periodontitis are seemingly related to chronic infection and persistent local and systemic inflammation. These findings suggest that periodontitis is not simply a disease of aging but may also transmit chronic systemic signals that could affect more rapid biological aging. Clinicians can use this outcome to recognize the role of periodontitis in driving unhealthy aging processes in patients.

Telomere Length as a Marker of Biological Age: State-of-the-Art, Open Issues, and Future Perspectives

Telomere shortening is a well-known hallmark of both cellular senescence and organismal aging. An accelerated rate of telomere attrition is also a common feature of age-related diseases. Therefore, telomere length (TL) has been recognized for a long time as one of the best biomarkers of aging. Recent research findings, however, indicate that TL per se can only allow a rough estimate of aging rate and can hardly be regarded as a clinically important risk marker for age-related pathologies and mortality. Evidence is obtained that other indicators such as certain immune parameters, indices of epigenetic age, etc., could be stronger predictors of the health status and the risk of chronic disease. However, despite these issues and limitations, TL remains to be very informative marker in accessing the biological age when used along with other markers such as indices of homeostatic dysregulation, frailty index, epigenetic clock, etc. This review article is aimed at describing the current state of the art in the field and at discussing recent research findings and divergent viewpoints regarding the usefulness of leukocyte TL for estimating the human biological age.

Uninterruptible Power Supply Improves Precision and External Validity of Telomere Length Measurement via qPCR

Technical challenges associated with telomere length (TL) measurements have prompted concerns regarding their utility as a biomarker of aging. Several factors influence TL assessment via qPCR, the most common measurement method in epidemiological studies, including storage conditions and DNA extraction method. Here, we tested the impact of power supply during the qPCR assay. Momentary fluctuations in power can affect the functioning of high-performance electronics, including real-time thermocyclers. We investigated if mitigating these fluctuations by using an uninterruptible power supply (UPS) influenced TL assessment via qPCR. Samples run with a UPS had significantly lower standard deviation (p < 0.001) and coefficient of variation (p < 0.001) across technical replicates than those run without a UPS. UPS usage also improved exponential amplification efficiency at the replicate, sample, and plate levels. Together these improvements translated to increased performance across metrics of external validity including correlation with age, within-person correlation across tissues, and correlation between parents and offspring.

Development and Validation of 2 Composite Aging Measures Using Routine Clinical Biomarkers in the Chinese Population: Analyses From 2 Prospective Cohort Studies

BACKGROUND

This study aimed to: (i) develop 2 composite aging measures in the Chinese population using 2 recent advanced algorithms (the Klemera and Doubal method and Mahalanobis distance); and (ii) validate the 2 measures by examining their associations with mortality and disease counts.

METHODS

Based on data from the China Nutrition and Health Survey (CHNS) 2009 wave (N = 8119, aged 20-79 years, 53.5% women), a nationwide prospective cohort study of the Chinese population, we developed Klemera and Doubal method-biological age (KDM-BA) and physiological dysregulation (PD, derived from Mahalanobis distance) using 12 biomarkers. For the validation analysis, we used Cox proportional hazard regression models (for mortality) and linear, Poisson, and logistic regression models (for disease counts) to examine the associations. We replicated the validation analysis in the China Health and Retirement Longitudinal Study (CHARLS, N = 9304, aged 45-99 years, 53.4% women).

RESULTS

Both aging measures were predictive of mortality after accounting for age and gender (KDM-BA, per 1-year, hazard ratio [HR] = 1.14, 95% confidence interval [CI] = 1.08, 1.19; PD, per 1-SD, HR = 1.50, 95% CI = 1.33, 1.69). With few exceptions, these mortality predictions were robust across stratifications by age, gender, education, and health behaviors. The 2 aging measures were associated with disease counts both cross-sectionally and longitudinally. These results were generally replicable in CHARLS although 4 biomarkers were not available.

CONCLUSIONS

We successfully developed and validated 2 composite aging measures-KDM-BA and PD, which have great potentials for applications in early identifications and preventions of aging and aging-related diseases in China.

Does Salivary Telomere Length Explain Race/Ethnic Differences in Aging?

Telomere length (TL) is a biomarker that can be used to characterize variability in aging and may explain race/ethnic differences in aging. Yet, it remains unclear if TL is related to aging-associated health risks in multi-ethnic populations or if it explains race/ethnic differences in health. We examine whether salivary TL (STL) explains any of the race/ethnic variability in 15 indicators of high-risk biological, physical and cognitive health among 4,074 white, black, and Latinx older adults ages 54+ in the 2008 Health and Retirement Study. TL was assayed from saliva using quantitative PCR (T/S ratio). Decomposition analyses from logistic regression models show variation in STL does not account for any of the observed race/ethnic differences health. In age-adjusted, race-stratified models, STL was associated with HDL, total cholesterol, and lung function among whites, but was not associated with any markers of health among black or Latinx groups. In this diverse national sample of older adults, STL does not account for race/ethnic differences in late life health, is associated with relatively few indicators of health among whites, and is not associated with indicators of health among black or Latinx groups. STL may not be a useful biomarker for understanding racial/ethnic differences in population aging among older adults.

Comparability of biological aging measures in the National Health and Nutrition Examination Study, 1999-2002

BACKGROUND

Biological processes of aging are thought to be modifiable causes of many different chronic diseases. Measures of biological aging could provide sensitive endpoints for studies of risk factors hypothesized to shorten healthy lifespan and/or interventions that extend it. But uncertainty remains about how to measure biological aging and if proposed measures assess the same thing.

METHOD

We tested four proposed measures of biological aging that could be quantified with available data from the National Health and Nutrition Examination Survey (NHANES), Klemera-Doubal method (KDM) Biological Age, homeostatic dysregulation, Levine Method (LM) Biological Age, and leukocyte telomere length.

RESULTS

We analyzed data collected during 1999-2002, when all four biological aging meausres could be taken. Participants' KDM biological ages, homeostatic dysregulation levels, LM biological ages, and telomere length were all correlated with their chronological ages. KDM Biological Age, homeostatic dysregulation, and LM Biological Age were all correlated with one another, but these measures were uncorrelated with telomere length. Participants' with more advanced biological aging performed worse on tests of physical, cognitive, and perceptual functioning and reported more limitations to their daily activities and more pain, and rated themselves as being in worse health. In parallel, participants with risk factors for shorter healthy lifespan exhibited more advanced biological aging. In both sets of analyses, effect-sizes tended to be larger for KDM Biological Age, homeostatic dysregulation, and LM Biological Age as compared to telomere length.

DISCUSSION

The cellular-level aging biomarker telomere length may measure different aspects of the aging process as compared to the patient-level physiological composite measures KDM Biological Age, homeostatic dysregulation, and LM Biological Age. Studies aiming to test if risk factors accelerate aging or if interventions may slow aging should not treat proposed measures of aging as interchangeable.

Exploring the Relationship of Relative Telomere Length and the Epigenetic Clock in the LipidCardio Cohort

Telomere length has been accepted widely as a biomarker of aging. Recently, a novel candidate biomarker has been suggested to predict an individual's chronological age with high accuracy: The epigenetic clock is based on the weighted DNA methylation (DNAm) fraction of a number of cytosine-phosphate-guanine sites (CpGs) selected by penalized regression analysis. Here, an established methylation-sensitive single nucleotide primer extension method was adapted, to estimate the epigenetic age of the 1005 participants of the LipidCardio Study, a patient cohort characterised by high prevalence of cardiovascular disease, based on a seven CpGs epigenetic clock. Furthermore, we measured relative leukocyte telomere length (rLTL) to assess the relationship between the established and the promising new measure of biological age. Both rLTL (0.79 ± 0.14) and DNAm age (69.67 ± 7.27 years) were available for 773 subjects (31.6% female; mean chronological age= 69.68 ± 11.01 years; mean DNAm age acceleration = -0.01 ± 7.83 years). While we detected a significant correlation between chronological age and DNAm age (n = 779, R = 0.69), we found neither evidence of an association between rLTL and the DNAm age (β = 3.00, p = 0.18) nor rLTL and the DNAm age acceleration (β = 2.76, p = 0.22) in the studied cohort, suggesting that DNAm age and rLTL measure different aspects of biological age.

Developments in molecular epidemiology of aging

The field of molecular epidemiology of aging involves the application of molecular methods to measure aging processes and their genetic determinants in human cohorts. Over the last decade, the field has undergone rapid progress with a dramatic increase in the number of papers published. The aim of this review is to give an overview of the research field, with a specific focus on new developments, opportunities, and challenges.

Aging occurs at multiple hierarchical levels. There is increasing consensus that aging-related changes at the molecular level cause declines in physiological integrity, functional capacity, and ultimately lifespan. Molecular epidemiology studies seek to quantify this process. Telomere length, composite scores integrating clinical biomarkers, and omics clocks are among the most well-studied metrics in molecular epidemiology studies.

New developments in the field include bigger data and hypothesis-free analysis together with new modes of collaborations in interdisciplinary teams and open access norms around data sharing. Key challenges facing the field are the lack of a gold standard by which to evaluate molecular measures of aging, inconsistency in which metrics of aging are measured and analyzed across studies, and a need for more longitudinal data necessary to observe change over time.

The telomere world and aging: Analytical challenges and future perspectives

Telomeres, the terminal nucleoprotein structures of eukaryotic chromosomes, play pleiotropic functions in cellular and organismal aging. Telomere length (TL) varies throughout life due to the influence of genetic factors and to a complex balancing between "shortening" and "elongation" signals. Telomerase, the only enzyme that can elongate a telomeric DNA chain, and telomeric repeat-containing RNA (TERRA), a long non-coding RNA involved in looping maintenance, play key roles in TL during life. Despite recent advances in the knowledge of TL, TERRA and telomerase activity (TA) biology and their measurement techniques, the experimental and theoretical issues involved raise a number of problems that should carefully be considered by researchers approaching the "telomere world". The increasing use of such parameters - hailed as promising clinically relevant biomarkers - has failed to be paralleled by the development of automated and standardized measurement technology. Consequently, associating given TL values to specific pathological conditions involves on the one hand technological issues and on the other clinical-biological issues related to the planning of clinically relevant association studies. Addressing these issues would help avoid major biases in association studies involving TL and a number of outcomes, especially those focusing on psychological and bio-behavioral variables. The main challenge in telomere research is the development of accurate and reliable measurement methods to achieve simple and sensitive TL, TERRA, and TA detection. The discovery of the localization of telomeres and TERRA in cellular and extracellular compartments had added an additional layer of complexity to the measurement of these age-related biomarkers. Since combined analysis of TL, TERRA and TA may well provide more exhaustive clinical information than a single parameter, we feel it is important for researchers in the various fields to become familiar with their most common measurement techniques and to be aware of the respective merits and drawbacks of these approaches.

Age and Periodontal Health - Immunological View

PURPOSE OF THE REVIEW

Aging clearly impacts a wide array of systems, in particular the breadth of the immune system leading to immunosenescence, altered immunoactivation, and coincident inflammaging processes. The net result of these changes leads to increased susceptibility to infections, increased neoplastic occurrences, and elevated frequency of autoimmune diseases with aging. However, as the bacteria in the oral microbiome that contribute to the chronic infection of periodontitis is acquired earlier in life, the characteristics of the innate and adaptive immune systems to regulate these members of the autochthonous microbiota across the lifespan remains ill defined.

RECENT FINDINGS

Clear data demonstrate that both cells and molecules of the innate and adaptive immune response are adversely impacted by aging, including in the oral cavity, yielding a reasonable tenet that the increased periodontitis noted in aging populations is reflective of the age-associated immune dysregulation. Additionally, this facet of host-microbe interactions and disease needs to accommodate the population variation in disease onset and progression, which may also reflect an accumulation of environmental stressors and/or decreased protective nutrients that could function at the gene level (ie. epigenetic) or translational level for production and secretion of immune system molecules.

SUMMARY

Finally, the majority of studies of aging and periodontitis have emphasized the increased prevalence/severity of disease with aging, all based upon chronological age. However, evolving areas of study focusing on "biological aging" to help account for population variation in disease expression, may suggest that chronic periodontitis represents a co-morbidity that contributes to "gerovulnerability" within the population.

A new aging measure captures morbidity and mortality risk across diverse subpopulations from NHANES IV: A cohort study

BACKGROUND

A person's rate of aging has important implications for his/her risk of death and disease; thus, quantifying aging using observable characteristics has important applications for clinical, basic, and observational research. Based on routine clinical chemistry biomarkers, we previously developed a novel aging measure, Phenotypic Age, representing the expected age within the population that corresponds to a person's estimated mortality risk. The aim of this study was to assess its applicability for differentiating risk for a variety of health outcomes within diverse subpopulations that include healthy and unhealthy groups, distinct age groups, and persons with various race/ethnic, socioeconomic, and health behavior characteristics.

METHODS AND FINDINGS

Phenotypic Age was calculated based on a linear combination of chronological age and 9 multi-system clinical chemistry biomarkers in accordance with our previously established method. We also estimated Phenotypic Age Acceleration (PhenoAgeAccel), which represents Phenotypic Age after accounting for chronological age (i.e., whether a person appears older [positive value] or younger [negative value] than expected, physiologically). All analyses were conducted using NHANES IV (1999-2010, an independent sample from that originally used to develop the measure). Our analytic sample consisted of 11,432 adults aged 20-84 years and 185 oldest-old adults top-coded at age 85 years. We observed a total of 1,012 deaths, ascertained over 12.6 years of follow-up (based on National Death Index data through December 31, 2011). Proportional hazard models and receiver operating characteristic curves were used to evaluate all-cause and cause-specific mortality predictions. Overall, participants with more diseases had older Phenotypic Age. For instance, among young adults, those with 1 disease were 0.2 years older phenotypically than disease-free persons, and those with 2 or 3 diseases were about 0.6 years older phenotypically. After adjusting for chronological age and sex, Phenotypic Age was significantly associated with all-cause mortality and cause-specific mortality (with the exception of cerebrovascular disease mortality). Results for all-cause mortality were robust to stratifications by age, race/ethnicity, education, disease count, and health behaviors. Further, Phenotypic Age was associated with mortality among seemingly healthy participants-defined as those who reported being disease-free and who had normal BMI-as well as among oldest-old adults, even after adjustment for disease prevalence. The main limitation of this study was the lack of longitudinal data on Phenotypic Age and disease incidence.

CONCLUSIONS

In a nationally representative US adult population, Phenotypic Age was associated with mortality even after adjusting for chronological age. Overall, this association was robust across different stratifications, particularly by age, disease count, health behaviors, and cause of death. We also observed a strong association between Phenotypic Age and the disease count an individual had. These findings suggest that this new aging measure may serve as a useful tool to facilitate identification of at-risk individuals and evaluation of the efficacy of interventions, and may also facilitate investigation into potential biological mechanisms of aging. Nevertheless, further evaluation in other cohorts is needed.

Anti-senescence compounds: A potential nutraceutical approach to healthy aging

The desire of eternal youth seems to be as old as mankind. However, the increasing life expectancy experienced by populations in developed countries also involves a significantly increased incidence of the most common age-related diseases (ARDs). Senescent cells (SCs) have been identified as culprits of organismal aging. Their number rises with age and their senescence-associated secretory phenotype fuels the chronic, pro-inflammatory systemic state (inflammaging) that characterizes aging, impairing the regenerative ability of stem cells and increasing the risk of developing ARDs. A variegated class of molecules, including synthetic senolytic compounds and natural compounds contained in food, have been suggested to possess anti-senescence activity. Senolytics are attracting growing interest, and their safety and reliability as anti-senescence drugs are being assessed in human clinical trials. Notably, since SCs spread inflammation at the systemic level through pro-oxidant and pro-inflammatory signals, foods rich in polyphenols, which exert antioxidant and anti-inflammatory actions, have the potential to be harnessed as "anti-senescence foods" in a nutraceutical approach to healthier aging. We discuss the beneficial effects of polyphenol-rich foods in relation to the Mediterranean diet and the dietary habits of long-lived individuals, and examine their ability to modulate bacterial genera in the gut.

Hyperglycemia attenuates the association between telomere length and age in Ukrainian population

Diabetes-related conditions such as chronic hyperglycemia and related oxidative stress and inflammation were repeatedly associated with accelerated telomere shortening in epidemiological studies, although some findings are inconsistent. In present study, we aimed to assess the impact of disturbances in glucose metabolism on association between age and leukocyte telomere length (LTL) in the Ukrainian population. The study was conducted on the 119 adult subjects aged between 43 and 87 years residing in the Kyiv region, Ukraine. LTL was determined by a quantitative PCR-based method. LTL was negatively correlated with the measure of abdominal obesity such as waist-hip ratio, as well as with both fasting plasma glucose (FPG) and two-hour post-load glucose (2hPG) levels. Consistently with previous studies, a significant negative association between LTL and age was observed in individuals with normal (<5.6 mmol/L) FPG levels. Unexpectedly, however, no association was found in subjects with impaired glucose metabolism assessed by abnormal FPG or/and 2hPG levels. No association between LTL and age was observed in a logistic regression model; the association between LTL and age became significant after adjusting for FPG level. In the FPG-adjusted model, 1.6-time lower odds to have long telomere length were indicated for each 10 years increase in age. We hypothesize that the attenuation of association between LTL and age in hyperglycemic persons can likely be attributed to the interaction of multidirectional processes determining this relationship.