Nature versus Nurture: this age-old topic has been at the root of more scientific and social psychology debates than just about any other subject over the past several decades. The notion that genetics loads the pistol and society pulls the trigger is gaining in popularity, carrying with it the implication that forces around us may actually have a powerful influence on that with which Mother Nature endowed us at birth. The emerging field of study known as epigenetics is studying this specific phenomenon.
Epigenetics delves into the manner in which we can potentially affect our health by changing how our genes are expressed, and more specifically, how that expression can be altered through mechanisms that are independent of our innate DNA sequences.
As a brief overview, consider the following: the genes in our body are coded in such a way as to be responsible for deciding just about everything from eye color to height to preponderance toward color-blindness. There is a caveat though: not all of our genes are always being expressed, and only the ones that are expressed are actually affecting us on a daily basis. As a matter of fact, the genome (complete set of genes) of every cell in the human body is exactly the same. The structure and function of each cell is determined by their epigenome, or the set of genes that are actually expressed. A clear example of how this manifests itself is in the development of some cancers. According to a widely-accepted theory, one of the key steps in cancer formation is the activation, or “turning on”, of certain genes (known as oncogenes) and the deactivation, or “turning off”, of other genes (tumor suppressor genes). These genes control many of the proteins involved in cell growth and proliferation. When oncogenes are activated or tumor suppressor genes are deactivated, the normal cell processes that prevent malignancy are unable to occur. As it turns out, most of our genes work in a similar manner, affecting every aspect of our physiology.
To date, the most thoroughly studied aspects of controlling gene expression are through modification of DNA methylation and histone acetylation. Methylation can be viewed as an “on/off switch” for gene expression, while histone acetylation is more of an intensity dial, exerting control over how much or how little a gene is expressed. While this is very exciting knowledge within the confines of the research lab walls, it is even more astounding when we see how it can be put into actual use through simple modifications in our daily lifestyles. In July 2013, scientists from Lund University in Sweden announced that for the first time, data has demonstrated how even short bouts of exercise can change the epigenetic pattern of fat storage in the human body. While the genes we inherit cannot be changed, of course, exercise and diet can have a positive effect on the DNA methylation. Using technology that analyses 480,000 positions throughout the genome, researchers were able to see that epigenetic changes had taken place in 7,000 genes (individuals typically possess anywhere from 20,000 to 25,000 genes). They then went on to look specifically at the methylation in those genes linked to Type 2 diabetes and obesity.
“We found changes in those genes too, which suggests that altered DNA methylation as a result of physical activity could be one of the mechanisms of how these genes affect the risk of disease,” said Tina Rönn, Associate Researcher at Lund University. The exciting news does not end there.
Another research group concluded from their studies that genome methylation was decreased in skeletal muscle biopsies obtained from healthy sedentary men and women after acute exercise. These results provide evidence that acute gene activation is associated with a change (a lowering) in DNA methylation in skeletal muscle.
Together, these two studies have far-reaching implications for viewing just how important lifestyle changes can be in determining our health and well-being. By providing us with the first detailed map of the genome-wide DNA methylation pattern in human fat tissue, we are now able to definitively link exercise to altered adipose tissue DNA methylation, which may facilitate our understanding of how the human body stores and metabolizes fat cells.
If exercise can delay the onset of diabetes by boosting the expression of genes involved in muscle oxidation and glucose regulation, those individuals suffering from Type 2 diabetes may be well advised to start hitting the gym. Diabetics tend to be less responsive to insulin than healthy individuals, and thus have trouble maintaining normal blood sugar levels. Certain genes, such as those involved in glucose transport and mitochondrial regulation, have been shown to be expressed at lower levels in diabetics, possibly explaining their decreased insulin responsiveness. In addition, such individuals have different DNA methylation patterns within their muscle tissue. Knowing now that exercise can have a dynamic effect on methylation, scientists are suggesting that we may be looking at a potential positive epigenetic mechanism whereby exercise can be a strong preventative measure for those dealing with diabetes.
The only downside to this otherwise very exciting find is that the positive changes didn’t last long: within a few hours of the initial post-exercise increases in gene expression, the muscle methylation and expression levels of the research subjects returned to baseline. The question remains as to whether the effects will eventually stabilize with regular bouts of exercise. Might we, over the long haul, be able to change our genome, conferring more protection from diabetes due to epigenetic change? Clearly more studies will be necessary to answer questions of this nature. However, results tentatively suggest that it may just be possible to “in some way manage the metabolism of your body through a lifestyle practice,” according to molecular exercise physiologist Perla Kaliman from the August Pi i Sunyer Biomedical Research Institute in Barcelona, Spain.
As trainers, we have always held to the belief that including a prudent diet and moderate exercise into our activities of daily life will be beneficial in almost every aspect of health and wellness. Now it seems we can harness the power to change certain aspects of our DNA by being even more vigilant with our lifestyle. Exercise might soon be viewed as the next best medicine not found on the shelves at your local pharmacy!
4. R. Barres et al., “Acute Exercise Remodels Promoter Methylation in Human Skeletal Muscle,” Cell Metabolism 15:405-11, 2012.
5. Tina Rönn, Petr Volkov, Cajsa Davegårdh, Tasnim Dayeh, Elin Hall, Anders H. Olsson, Emma Nilsson, Åsa Tornberg, Marloes Dekker Nitert, Karl-Fredrik Eriksson, Helena A. Jones, Leif Groop, Charlotte Ling. A Six Months Exercise Intervention Influences the Genome-wide DNA Methylation Pattern in Human Adipose Tissue. PLoS Genetics, 2013; 9 (6): e1003572 DOI
About the Author
Cathleen Kronemer is an AFAA-Certified Group Exercise Instructor, NSCA-Certified Personal Trainer, competitive bodybuilder and freelance writer. She is employed at the Jewish Community Center in St. Louis, MO. Cathleen has been involved in the fitness industry for 22 years. Look for her on www.WorldPhysique.com.
She welcomes your feedback and your comments!