Author: Unnikrishnan A1, Freeman WM2, Jackson J3, Wren JD4, Porter H5, Richardson A6
Affiliation: <sup>1</sup>Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA. Electronic address: archana-unnikrishnan@ouhsc.edu.
<sup>2</sup>Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Oklahoma City VA Medical Center, Oklahoma City, OK, USA.
<sup>3</sup>Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
<sup>4</sup>Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Arthritis & Clinical Immunology Program, Division of Genomics and Data Sciences, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA.
<sup>5</sup>Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
<sup>6</sup>Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Oklahoma City VA Medical Center, Oklahoma City, OK, USA.
Conference/Journal: Pharmacol Ther.
Date published: 2018 Nov 9
Other:
Pages: S0163-7258(18)30198-0 , Special Notes: doi: 10.1016/j.pharmthera.2018.11.001. [Epub ahead of print] , Word Count: 329
Recent research suggests that epigenetics, especially DNA methylation, plays a mechanistic role in aging. Epigenetic clocks, which measure changes in a few hundred specific CpG sites, can accurately predict chronological age in a variety of species, including humans. These clocks are currently the best biomarkers for predicting mortality in humans. Additionally, several studies have characterized the effects of aging across the methylome in a wide variety of tissues from humans and mice. A small fraction (~2%) of the CpG sites show age-related changes, either hypermethylation or hypomethylation with aging. Evaluation of non-CpG site methylation has only been examined in a few studies, with about ~0.5% of these sites showing a change with age. Therefore, while only a small fraction of cytosines in the genome show changes in DNA methylation with age, this represents 2 to 3 million cytosines in the genome. Importantly, the only study to compare the effect of aging on DNA methylation in male and female mice and humans found that >95% of the age-related changes in DNA methylation in the hippocampus were sexually divergent, i.e., the methylation did not differ between males and females at young age but age-related changes occurred in one sex but not the other. The age-related changes in DNA methylation tend to be enriched and under-represented in specific genomic contexts, with some commonalities between tissues and species that require further investigation. The strongest evidence that the age-related changes in DNA methylation play a role in aging comes from studies of anti-aging interventions (e.g., caloric restriction, dwarfism, and rapamycin treatment) in mice. These anti-aging interventions deaccelerate the epigenetic clocks and reverse/prevent 20 to 40% of the age-related changes in DNA methylation. It will be important in the future to demonstrate that at least some of the age-related changes in DNA methylation directly lead to alterations in the transcriptome of cells/tissues that could potentially contribute to aging.
KEYWORDS: 5-hydroxymethyl cytosine; 5-methyl cytosine; Aging; Caloric restriction; DNA methylation; Epigenetic clocks; Epigenetics; Gene Expression
PMID: 30419258 DOI: 10.1016/j.pharmthera.2018.11.001