Endurance exercise has been shown to improve lipid oxidation and increase mitochondrial content in skeletal muscle, two features that have shown dependence on increased expression of the peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α). It is also hypothesized that exercise-related alterations in PGC1α expression occur through epigenetic regulation of nucleosome positioning in association with differential DNA methylation status within the PGC1α promoter. In this study, we show that when primary human myotubes from obese patients with type 2 diabetes are exposed to lipolytic stimulus (palmitate, forskolin, inomycin) in vitro, nucleosome occupancy surrounding the -260 nucleotide (nt) region, a known regulatory DNA methylation site, is reduced. This finding is reproduced in vivo in the vastus lateralis from 11 healthy males after a single, long endurance exercise bout in which participants expended 650 kcal. Additionally, we show a significant positive correlation between fold change of PGC1α messenger RNA expression and -1 nucleosome repositioning away from the -260 nt methylation site in skeletal muscle tissue following exercise. Finally, we found that when exercise participants are divided into high and low responders based on the -260 nt methylation status, the -1 nucleosome is repositioned away from the regulatory -260 nt methylation site in high responders, those exhibiting a significant decrease in -260 nt methylation, but not in low responders. Additionally, high but not low responders showed a significant decrease in intramyocellular lipid content after exercise. These findings suggest a potential target for epigenetic modification of the PGC1α promoter to stimulate the therapeutic effects of endurance exercise in skeletal muscle.
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