Theres more to your DNA than your DNA. We are now becoming aware of the epigenome. While DNA controls you, your epigenome may help control your DNA, or rather, it can have an extensive impact on how your DNA is expressed. The epigenome consists of changes in the structure of your DNA, how it is packaged, what parts of it are available for expression into RNA and proteins. For example, adding methyls to DNA tends to decrease the gene expression of that DNA segment, while taking away methyl groups increases it. The cool thing about epigenetics is that the methylation can vary from tissue to tissue, controlling how different genes are expressed in say, liver vs spleen.

(I cant wait til Jonathan Coulton writes a song about the epigenome)

One of the most interesting things about the epigenome is that you can pass it along in the germline. To your kids. So in theory, if you had methylation in certain parts of your genome, your kids could as well. But were starting to realize that epigenetics is more malleable than that.

Take muscle tissue for instance. Gene expression in muscle tissue can change the efficiency of glucose metabolism by muscle. And glucose metabolism has a very large effect on many bodily processes, include weight gain and problems like cardiovascular disease and type II diabetes. Muscle itself is very plastic, and responds quickly to changes in the environment (which for a muscle, means increases and decreases in exercise or how many calories are getting in). We know that exercise can change gene expression in muscle, but can it also change the epigenome? While immediate changes in gene expression can be very short, changes to the epigenome indicate much longer-term changes. Could bouts of exercise influence the methylation of muscle, and thus have long-term effects?

Barres et al. Acute Exercise Remodels Promoter Methylation in Human Skeletal Muscle Cell Metabolism, 2012.

The cool thing is that the authors of this study were able to do large sections of this study in humans. Humans, at least, who did not object to getting muscle biopsies.

They took 14 sedentary humans and had them exercise to fatigue (a pretty difficult exercise bout). They biopsied the muscles before and after the exercise, and looked to see what the methylation in the muscle looked like.

What you can see here is that the acute bout of exercise decreased the methylation in the muscle tissue. When they looked a little closer, the authors found that the methylation was particularly decreased in the promotor regions of metabolically related genes. Many of these promotor regions, which directly control the expression of a gene, show changes in methylation during type II diabetes. After exercise the methylation in these promotor regions was decreased, which could result in more gene expression of those genes, and thus result in changes in metabolism.

Further studies showed that this change in methylation depended on exercise intensity. In a group of mice exposed to low or high intensity exercise, only the high intensity produced the gene methylation changes seen in humans.

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Methylating Your Muscle DNA