Researchers recruited slightly overweight men in their 30s and 40s who led an inactive lifestyle. After six months of weekly spin classes and group aerobics, they all showed improved fitness and weight loss due to the exercise regime, despite not making changes to their normal daily tasks or diets. This may be an expected result, but interestingly, biopsies of fat tissue showed differences in the regulation of 7,663 genes, suggesting that exercise was driving epigenetic changes.
'Our study shows the positive effects of exercise, because the epigenetic pattern of genes that affect fat storage in the body changes', says Dr Charlotte Ling, from Lund University in Sweden, who led the research.
Epigenetics is the study of how changes in our environment influence the regulation of our genes. This can affect how cells function and there is evidence to suggest these changes can be linked to lifestyle-related diseases. One epigenetic mechanism is DNA methylation, where methyl groups on DNA prevent gene transcription, silencing gene expression. Levels of DNA methylation in the fat tissue of the 23 volunteers were analysed and changes in mRNA expression monitored. The team found that 7,663 genes were differently methylated in fat tissue as a direct effect of exercise.
Dr Ling's group focused on three genes which showed increased levels of DNA methylation after exercise and have been previously linked to type 2 diabetes, metabolic syndrome and obesity. In vitro assays were used to confirm the gene-silencing effect of DNA methylation.
'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', says Tina Rönn, who conducted the study.
It is important to note that this study was performed in a relatively small trial cohort. The absolute changes in DNA methylation in response to exercise were modest, but Dr Ling argues that the large number of sites of methylation found on different genes could contribute to an overall physiological response.More than one billion people worldwide are now categorised as obese and there is a clear link between obesity and type 2 diabetes. Understanding the underlying genetic profiles of these disorders, and how epigenetic factors such as exercise can alter gene expression may one day suggest new strategies for targeted therapies.