The underlying genetic code stays the same. However, the DNA molecules within the muscle cells gets chemically and structurally altered in very particular ways, by gaining or loosing marks of methyl groups on certain familiar DNA sequences. Those so called epigenetic modifications to the DNA, at precise locations, appear to be an important part of the physiological benefits of exercise.
“Our muscles are really plastic,” says Juleen Zierath, Professor of Clinical Integrative Physiology at the Department of Molecular Medicine and Surgery. “We often say ‘You are what you eat.’ Well, muscle adapts to what you do. If you don’t use it, you lose it and this is one of the mechanisms that allow that to happen.”
The current study in Cell Metabolism shows that the DNA within skeletal muscle taken from people after a burst of exercise bears fewer methyl groups than it did before exercise. Those changes occur in stretches of DNA that serve as landing sites for different kinds of enzymes, called transcription factors, which in turn are involved in turning ‘on’ genes already known to be important in muscles’ adaptation to exercise.
Juleen Zierath likens transcription factors to keys that unlock our genes. With those methyl groups firmly in place, transcription factor ‘keys’ are prevented from entering those DNA ‘locks’. But when the methyl groups are removed, it allows the keys to turn the locks and boosts the capacity of muscle for work.
“Exercise is already known to induce changes in muscle, including increased metabolism of sugar and fat”, Zierath says, “Our discovery is that the methylation change comes first.”
When the researchers made muscles contract in lab dishes, they saw a similar loss of methyl groups. Exposure of those muscles to caffeine had the same effect as well, as caffeine induces a release of calcium in a way that mimics the muscle contraction that comes with exercise. However, the researchers don’t recommend anyone to drink a cup of coffee in place of exercise, as it isn’t clear that caffeine has all the other beneficial effects of exercise.
“Exercise is medicine, and it seems the means to alter our epigenomes for better health may be only a jog away”, says Juleen Zierath.
Acute Exercise Remodels Promoter Methylation in Human Skeletal Muscle
Cell Metabolism, online ahead of print 7 March 2012
For further information, please contact:
Professor i klinisk integrativ fysiologi Juleen Zierath
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