Keeping track of time
All of us have a constant reminder of the passage of time by means of clocks and watches. The hour hand, the minute hand and the swift transient nature of time. Our age is a function of us keeping a steady track of time. Interestingly, our bodies and especially brains are also tracking time, referred to as our physiological age. Our legal age is also known as our chronological age. But does it always agree with our physiological age? Can external factors play a role in ageing?
Genetics v Epigenetics
While most of us are familiar with the term genetics, the addition of the prefix ‘epi’ is significant. Genetics deals with DNA, RNA, proteins and genes. Epigenetics involves modifying genetic material due to the epi or additional factors, the outer environment that might ultimately influence how genes behave.
A simple analogy would be saplings of the same tree planted in different environments. While the plant is the same in all cases, the degree to which it flourishes depends on external factors like rainfall, sunlight, soil quality, etc. In epigenetics, these factors include one’s lifestyle, disease conditions and environment.
DNA methylation and biomarkers
DNA, as we know, it is one of the chief ingredients in a cell’s nucleus. DNA methylation is basically the addition of a methyl group to DNA. These are referred to as DNAm. DNAm forms an important part of epigenetics.
What was true in the case of the saplings is also true for DNA. DNAm acts like a series of switches regulating gene expression. Although the basic code is the same, its expression depends on factors like DNAm.
DNAm acts as a biomarker. In other words, the presence of DNAm in blood and other tissues can help us to track the body’s ageing process. Not chronological, but physiological age. While chronological age is the number of years a person has been alive, physiological or biological age is estimated using biomarkers. It is the age and years that our bodies keep track of.
DNAm and the epigenetic clock
Steve Horvath and his team at UCLA developed an epigenetic clock based on biomarkers. Since it was found that DNAm was associated with ageing, the task was simple- track the presence of DNAm in blood and various tissues like the brain and determine its accuracy.
The finding and its significance
On investigation, Horvath and his team found that this technique could accurately predict the chronological age of most of the specimens by finding out the biological age using DNAm. In other words, for most specimens, biological and chronological age were in agreement.
What is significant, however, is that the ages did diverge in a few cases. In some cases, women’s breast tissues were biologically older than the other tissues. This meant that biologically older tissues and their ageing process acted as a potential contributor to cancer. In some cases, it was found that cancerous breast tissues were as much as 36 years biologically older than other body tissues.
Other than this, lifestyle choices like smoking were also associated with the interruption of a healthy methylation cycle.
It is worthy to note that an imbalance of methylation (disproportionate increase or a lack) was also associated with cancer.
This is vitally important, as it enables tracking epigenetic ageing, correlating it with disease incidence.
Brain health and ageing
Using the same technique, the incidence of many neurodegenerative disorders like Alzheimer’s and Parkinson’s can be predicted through epigenetic clocks. Epigenetic ageing shows as much as a 30% correlation with the presence of a disease like Alzheimer’s. Whether it has a role to play in the pathology of Parkinson’s, dementia, or cognitive decline remains a matter of further research and investigation.
Tick Tock Clock
Epigenetics shows us that the biological clock is not as steady as the mechanical clock. While some organs may age due to epigenetic factors, others may follow the chronological age. Moreover, the content of our environment in terms of lifestyle, sleep, diet is as central as the content of our genetic code. It is fascinating that instead of being associated with abdication, this finding allows us to seek more responsible choices.
References
1)The association of epigenetic clocks in brain tissue with brain pathologies and common aging phenotypes
https://doi.org/10.1016/j.nbd.2021.105428
2)https://www.whatisepigenetics.com/dna-methylation/
3)DNA methylation and the epigenetic clock in relation to physical frailty in older people: the Lothian Birth Cohort 1936
https://doi.org/10.1186/s13148-018-0538-4
4)http://brainbased.info/epigenetic-clock-for-predicting-brain-age
5)https://newsroom.ucla.edu/releases/ucla-scientist-uncovers-biological-248950
6)https://hms.harvard.edu/news/epigenetic-clock
7) https://info.trudiagnostic.com/dna-methylation/
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Writer
Maitreyee Upadhye
Maitreyee is a student of Pharmacy at AISSMS and aims to pursue research in Molecular Biology. She
hopes to combine her love for languages and Science to reach out to those who are less
privileged. Being an ardent Oprah devotee, her goal is to evolve to be the best version of herself.
She’s usually found around bookshelves and dogs.
Illustrator
Jayakrishnan Nair
He has completed his Masters in Medical Biotechnology from The Maharaja Sayajirao University of Baroda and is currently an active researcher in Molecular Epidemiology at The Centre for Cancer Epidemiology, Navi Mumbai. His journey in Science and Creativity began together during his childhood days. He believes that Art and Science indeed have a beautiful world altogether in them and sailing across its spectrum inspires him to sow his thoughts deep into Science and carve out the pillars of Art through them! Being a Science enthusiast and an Artist, he wishes to devote a good share of his life to wildlife and marine conservation as he feels that the creativity of nature needs to be taken care of in the current era.