It has always been thought that our DNA is set in stone from the moment we are conceived and that our risk of suffering from hereditary diseases such as Alzheimer’s, certain cancers, diabetes, and Huntington’s disease depends mostly on the genes that our parents passed to us through their DNA. However, it has been shown through research over the last 30 years that these genes can be altered and affected by your childhood environment.
Researchers are now able to accurately predict whether certain genes that are responsible for regulating inflammation are altered by childhood events. For many, childhood is a memorable and defining part of life, but for many others, those early life experiences can change the body on the genetic level.
DNA determines who we are as humans including our personalities and physical traits. DNA is basically an instruction manual made up of a 4-letter alphabet for making proteins. The order of the letters is the DNA sequence defines the genes that an individual has and will remain the same throughout the body. However, only some of this information is necessary for each cell type to function properly.
Epigenetic marks can be thought of as highlighters that indicate what genes a cell should express, or have “turned on”. The most important of these epigenetic marks is methylation.
Methylation of DNA
During methylation, a methyl group is attached to the DNA molecule for the purpose of promoting or inhibiting the expression of certain proteins. These protein expressions depend on which gene is at the methylation site and where on the gene it is located, but this process is not completely understood. It is important to note, that DNA methylation does not change the sequence of the DNA, it simply turns the gene expressions on or off.
In an interview with the Smithsonian, Professor Thomas McDade of Northwestern University explains, “We could have genes in our bodies that might lead to some bad outcomes or adverse health outcomes, but if those genes are silent, if they’re turned off due to epigenetic processes, that can be a good thing.”
McDade went on to further explain that once a gene is methylated, it will remain that way permanently. This is a good thing when it comes to those “bad” genes.
It has been shown that DNA methylation is vital to a number of cellular processes including embryonic development, chromosomal stability, X-chromosome inactivation, genomic imprinting, and gene suppression. Abnormal DNA methylation has been linked to several diseases including a range of birth defects, muscular dystrophy, lupus, and certain cancers.
Much of the current research on the effects of methylation on DNA has focused on cancer and tumor-suppressing genes. Tumor-suppressing genes have been shown to often be silenced in cancer cells due to hypermethylation. In contrast to this, cancer cell genomes appear to be hypo-methylated when compared to normal cells. Hypermethylation can be detected early in cancer cells of the colon and could serve as a biomarker for the disease.
Recent research published in the journal Proceedings of the National Academy of Sciences has suggested that our DNA might not be as set in stone as previously thought, and that DNA can be altered by your childhood environment. In fact, the team of researchers from Northwestern University has concluded that the DNA modifications caused by the environmental factors during childhood can have an influence on how or when you may develop certain diseases in adulthood.
Lead researcher Professor Thomas McDade and his team began their study by testing their hypothesis that early life nutritional, microbial, and psychosocial exposures that were previously associated with levels of inflammation could predict the patterns of DNA methylation in inflammatory genes of young people. The data used comes from a population-based cohort study done in the metropolitan area of Cebu in the Philippines that contains a lifetime of information on the participants.
The participants consisted of more than 3000 pregnant women that came from all walks of life. The researchers looked at 500 of those women to understand the correlation between the child’s environment and epigenetic changes to their DNA that would later result in inflammatory proteins within their blood as adults. The scientist took whole blood samples from 494 participants at ages 20-22 years old for the analysis of DNA methylation.
The analysis focused on 114 target genes that are involved in the regulation of inflammation. The analysis identified 10 sites across nine different genes in which the level of DNA methylation could be significantly predicted by five variables including:
- Household socioeconomic status in childhood
- Extended absences of a parent during childhood
- Exposure to animal feces in infancy
- Birth in a dry season
- Duration of exclusive breastfeeding
To evaluate the significance of these methylation sites, the McDade and his team tested the associations with a panel of inflammatory biomarkers measured in the plasma that was obtained at the same age as the DNA methylation assessment. They were also able to show that DNA methylation in certain genes directly relates to levels of inflammatory biomarkers which have been implicated in cardiovascular disease and other diseases.
The results of this research suggest that epigenetic mechanisms may help explain how environments during childhood shape inflammatory phenotypes across a lifetime and affect how the body responds to inflammation and inflammatory-related diseases.
Inflammation is known to be an underlying cause of most illnesses and diseases. While inflammation is a sign that the body’s immune system is doing its job, prolonged chronic inflammation can put a toll on the immune system. Chronic inflammation has serious effects on cellular health and has been linked to several degenerative diseases including heart disease, Alzheimer’s, diabetes, and cancer to name a few.
As more laboratory techniques become available and new genomes are mapped, scientists will be able to gain a better understanding of how, when, where, and why DNA is methylated. But for now, we have enough evidence to conclude that our childhood experiences and living environment have a lasting impact on our entire lives and health. To what extent that impact is, is yet to be determined.