Impact of an Exercise Intervention on DNA Methylation in Skeletal Muscle From First-Degree Relatives of Patients With Type 2 Diabetes

Impact of a 6-month exercise intervention on DNA methylation in human skeletal muscle. A: Exercise-induced changes in DNA methylation of THADA, MEF2A, RUNX1, and NDUFC2. Data are presented as mean ± SEM, and P values were corrected for multiple testing using Bonferroni corrections. Gene expression of THADA (B), MEF2A (C), RUNX1 (D), and NDUFC2 (E) correlates negatively with DNA methylation of respective gene. F: A diagram of the four luciferase reporter plasmids used to test the effect of DNA methylation on THADA, MEF2A, RUNX1, and NDUFC2 promoter activity and the empty vector are visualized. The four plasmids contain either 2,580 bp of the human THADA promoter, 2,460 bp of the human MEF2A promoter, 2,700 bp of the human RUNX1 promoter, or 2,500 bp of the human NDUFC2 promoter region inserted into a pCpGL-basic vector. Methylated (gray and black bars) or mock-methylated (white bars) promoter constructs were transfected into HEK293 cells for 48 h prior to luciferase assay. The data were normalized with cotransfected renilla luciferase control vector and are the average from three separate experiments of five replicates each. In each experiment, cells were transfected with an empty pCpGL-vector as a background control. A Student t test was used for statistical comparisons, and data are presented as relative expression compared with the nonmethylated construct including the promoter regions. G: Mitochondrial density, lipid content, and IL-7 mRNA expression in skeletal muscle as well as serum levels of IL-7 before and after exercise. Results are expressed as mean ± SEM. The analyses of mitochondrial density and lipid content were performed in 10 images covering at least 50 muscle fiber profiles. *P < 0.05.

The top KEGG pathways of genes, which are differentially methylated in skeletal muscle after exercise. KEGG pathways of genes, which exhibit decreased (A) and increased (B) methylation in skeletal muscle of all men (n = 28) after a 6-month exercise intervention with the expected number of genes (white), the observed number of genes (black), and the total number of genes in the pathway in parentheses. The P values were adjusted for multiple testing. C: Diagram showing the genes in the starch and sucrose metabolism pathway with decreased DNA methylation in skeletal muscle of all men (n = 28) after a 6-month exercise intervention. P, phosphate.