Supplementary Material for: DNA Methylation Changes Induced by a High-Fat Diet and Fish Oil Supplementation in the Skeletal Muscle of Mice

<b><i>Background/Aims:</i></b> To investigate the global changes in DNA methylation and methylation of the promoter region of the peroxisome proliferator-activated receptor gamma transcript variant 2 <i>(Pparg2)</i> gene resulting from a high-fat diet (HFD) and/or fish oil supplementation. <b><i>Methods:</i></b> Fish oil, rich in omega-3 polyunsaturated fatty acids, or water was orally administered to male mice for 12 weeks. After the first 4 weeks, the animals were fed a control diet or an HFD until the end of the experimental protocol, when the epididymal fat, gastrocnemius muscle and liver were excised. <b><i>Results:</i></b><i>Pparg2</i> mRNA expression was upregulated by obesity and downregulated by fish oil supplementation in the liver. In the gastrocnemius muscle, diet-induced obesity increased global DNA methylation. Fish oil prevented the decrease in <i>Pparg2</i> promoter methylation induced by obesity in the gastrocnemius muscle. Regardless of the diet given, fish oil supplementation increased <i>Pparg2</i> promoter methylation at CpG-263 in muscle and adipose tissue. <b><i>Conclusion:</i></b> HFD and fish oil modified global and <i>Pparg2</i> promoter DNA methylation in a tissue-specific manner. Fish oil supplementation attenuated body weight gain, abolished the increase in <i>Pparg2</i> expression in the liver and prevented the decrease in <i>Pparg2</i> promoter methylation in the muscle induced by the HFD.