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Epigenetic Clocks
Also known as Epigenetic clock, Aging clock
Definition
Epigenetic clocks are biomarkers of ageing based on DNA methylation data that enable accurate age estimates across tissues and the entire life course. [1] DNA methylation patterns have been employed as a measure of biological age, currently referred to as the epigenetic clock, and various kinds continue to emerge including Horvath's clock, Hannum's clock, DNA PhenoAge, and DNA GrimAge. [2] Among candidate biological age predictors such as telomere length and proteomic or metabolomic measures, the epigenetic clock is currently the most promising, although its value as a biomarker of aging requires longitudinal confirmation. [3]
How it works
Methylation levels of certain CpG sites display a strong correlation with age that is common between individuals of the same species, and collectively these sites can be used as an epigenetic clock to predict biological age. [4] Clocks are computational models, such as elastic net regressions, that take DNA methylation sites as inputs to make an age prediction. [5] It remains unclear whether the methylation changes used to train the clocks reflect other underlying cellular or molecular processes or whether methylation itself is involved in the ageing process, and the precise aspects of ageing captured seem to vary between predictors. [6]
Connected concepts
How it's measured
Epigenetic clocks are computed from genome-wide DNA methylation data, most commonly measured in blood, and most existing blood-based clocks were compiled and catalogued in a systematic review of the field. [7] The difference between epigenetic age and chronological age is expressed as epigenetic age acceleration or deceleration, a relative measure rather than an absolute concentration. [7] [5]
What levels mean
When an individual's epigenetic age is higher than their chronological age they are said to experience epigenetic age acceleration, a phenomenon linked to a higher risk of premature mortality. [5] Acceleration of one or more epigenetic clocks has been significantly associated with mortality, cardiovascular disease, cancer, and diabetes, and factors such as body mass index and male sex are associated with faster epigenetic aging. [7]
Community knowledge
## Clock Generations And Limits
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- 1.Horvath S, Raj K. DNA methylation-based biomarkers and the epigenetic clock theory of ageing. Nat Rev Genet · 2018
- 2.Duan R, Fu Q, Sun Y, Li Q. Epigenetic clock: A promising biomarker and practical tool in aging. Ageing Res Rev · 2022
- 3.Jylhävä J, Pedersen NL, Hägg S. Biological Age Predictors. EBioMedicine · 2017
- 4.Ashapkin VV, Kutueva LI, Vanyushin BF. Epigenetic Clock: Just a Convenient Marker or an Active Driver of Aging? Adv Exp Med Biol · 2019
- 5.Johnson AA, English BW, Shokhirev MN, Sinclair DA, Cuellar TL. Human age reversal: Fact or fiction? Aging Cell · 2022
- 6.Simpson DJ, Chandra T. Epigenetic age prediction.
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