A REVIEW OF THE EPIGENETIC CLOCK: EMERGING BIOMARKERS FOR ASTHMA AND
ALLERGIC DISEASE
Abstract
DNA methylation (DNAm) is a dynamic, age-dependent, epigenetic
modification that can be used to study interactions between genetic and
environmental factors. Environmental exposures during critical periods
of growth and development may alter DNAm patterns, leading to increased
susceptibility to diseases such as asthma and allergy. One method to
study the role of DNAm is the epigenetic clock – an algorithm that uses
DNAm levels at select age informative Cytosine-phosphate-Guanine (CpG)
dinucleotides to predict epigenetic age (EA). The difference between EA
and calendar age (CA) is termed epigenetic age acceleration (EAA) and
reveals information about the biological capacity of an individual.
Associations between EAA and disease susceptibility have been
demonstrated for a variety of age-related conditions and, more recently,
phenotypes such asthma and allergic diseases which often begin in
childhood and progress throughout the lifespan. In this review, we
explore different epigenetic clocks and how they have been applied,
particularly as related to childhood asthma and in utero and
early life exposures (e.g., smoking, diet, and drugs) that result in
methylation changes.