Telomeres are ribonucleoprotein structures at the end of all eukaryotic chromosomes that protect DNA from damage and preserve chromosome stability. Telomere length (TL) has been associated with various exposures, biological processes, and health outcomes. This article describes the monochrome multiplex quantitative polymerase chain reaction (MMqPCR) assay protocol routinely conducted in our laboratory for measuring relative mean TL from human DNA. There are several different PCR-based TL measurement methods, but the specific protocol for the MMqPCR method presented in this publication is repeatable, efficient, cost-effective, and suitable for population-based studies. This detailed protocol outlines all information necessary for investigators to establish this assay in their laboratory. In addition, this protocol provides specific steps to increase the reproducibility of TL measurement by this assay, defined by the intraclass correlation coefficient (ICC) across repeated measurements of the same sample. The ICC is a critical factor in evaluating expected power for a specific study population; as such, reporting cohort-specific ICCs for any TL assay is a necessary step to enhance the overall rigor of population-based studies of TL. Example results utilizing DNA samples extracted from peripheral blood mononuclear cells demonstrate the feasibility of generating highly repeatable TL data using this MMqPCR protocol.
Abstract Background Age is the most significant predictor of Alzheimer’s disease and related dementias (ADRD). Biological age, in contrast to chronological age, is modifiable – shaped by environmental and social factors which contribute to the functional declines observed in aging. Accelerated biological aging has been observed in historically underrepresented populations in ADRD research who are at highest risk for developing ADRD. Telomere length (TL) is a marker of biological age and empirically associated with cognitive aging. However, this association has not been investigated in historically underrepresented populations such as American Indians / Alaska Natives (AI/AN). This study reports on the utility of TL to predict cognitive performance in a sample of middle‐aged and older adults from Wisconsin communities historically underrepresented in ADRD research. Method The Wisconsin Alzheimer’s Disease Research Center’s (WADRC) Inclusion of Underrepresented Groups Core engages AI/AN, Blacks / African Americans (B/AA), and participants of multi‐race and ethnicity identities through community based participatory research practices. A sample (n = 188) identifying their race as AI/AN or B/AA were included if they provided whole blood and completed the Rey Auditory Verbal Learning Test (RAVLT, Trials 1‐5) and the Trails Making Test (TMT, A and B times) for verbal learning and executive functioning, respectively. DNA was extracted from whole blood and analyzed with monochrome multiplex quantitative polymerase chain reaction for TL. Multivariable linear regression analyses tested relationships between TL and cognitive test performance. Result The participants (mean age = 60.88 ±9.06) were majority female, with 79.26% B/AA and 12.77% AI/AN (Table 1). In bivariate analyses, TL significantly correlated with all outcomes: longer telomeres correlated with better verbal learning and executive functioning performance (Figure 1A‐C). In multivariable regression models, TL significantly predicted cognitive performance for all outcomes independent of participant sex, race, age, and cognitive status (Table 2). Conclusion These findings suggest that TL is a strong predictor of cognitive performance for historically underrepresented populations, offering potential opportunities for screening of accelerated biological aging and interventions. The community‐led research at the WADRC makes this analysis the first of its kind to include AI/AN participants. Future ADRD research should consider behavioral and socioeconomic interventions shown to modify biological aging.
Abstract Objective Accelerated biological aging is a plausible and modifiable determinant of dementia burden facing minoritized communities, but is not well-studied in these historically underrepresented populations. Our objective was to preliminarily characterize relationships between telomere length and cognitive health among American Indian/Alaska Native (AI/AN) and Black/African American (B/AA) middle-aged and older adults. Methods This study included data on telomere length and cognitive test performance from 187 participants, enrolled in one of two community-based cognitive aging cohorts and who identified their primary race as AI/AN or B/AA. Results Nested multivariable regression models revealed preliminary evidence for associations between telomere length and cognitive performance, and these associations were partially independent of chronological age. Discussion Small sample size limited estimate precision, however, findings suggest future work on telomere length and cognitive health in underrepresented populations at high risk for dementia is feasible and valuable as a foundation for social and behavioral intervention research.
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