DNA methylation

Methylation levels vary throughout life, but with age they tend to decrease overall. Methylation is a phenomenon in which a methyl chemical group (-CH3) is added to a cytosine base (C) of DNA. It causes DNA condensation, the form in which genes are not transcribed.

Gene modulation is an essential process for maintaining cellular balance. Indeed, all the cells of the body carry the same genome, but they do not all have the same purpose. As a result, a liver cell does not synthesize the same proteins as a skin cell. The expression of certain genes must therefore be activated or repressed, depending on the fate of the cell. Age-related methylation changes occur either randomly on certain cytosines (“Epigenetic drift”) or on specific regions of DNA where methylation changes are associated with age. The latter are used to measure aging.

DNA methylation at the root of the epigenetic clock principle

DNA methylation has been used in recent years as a reliable measurement tool for estimating biological age. This phenomenon, called the epigenetic clock, is based on CpG sites (DNA portion of two bases, the first of which is a cytosine and the second a guanine and linked together by a phosphate bond) associated with age and whose methylation profile can be used as an accurate indicator of biological age[6].