Nrf2 bindng in C2C12 myotubes. Mus musculus

Nrf2 (NF-E2-related-factor-2) contributes to the maintenance of glucose homeostasis in vivo. Nrf2 suppresses blood glucose levels by protecting pancreatic β-cells from oxidative stress and improving peripheral tissue glucose utilization. To elucidate the molecular mechanisms by which Nrf2 contributes to the maintenance of glucose homeostasis, we generated skeletal muscle (SkM)-specific Keap1-knockout (Keap1MuKO) mice that express abundant Nrf2 in SkM and then examined Nrf2-target gene expression in this tissue. In Keap1MuKO mice, blood glucose levels were significantly downregulated, and the levels of glycogen branching enzyme (Gbe1) mRNA, along with those of glycogen branching enzyme (GBE) protein, were significantly upregulated in mouse SkM. Consistent with this result, chemical Nrf2-inducers promoted Gbe1 mRNA expression in both mouse SkM and C2C12 myotubes. Chromatin-immunoprecipitation analysis demonstrated that Nrf2 binds the Gbe1 upstream promoter regions. In Keap1MuKO mice, muscle glycogen content was strongly reduced, and forced GBE expression in C2C12 myotubes promoted glucose uptake. Therefore, our results demonstrate that Nrf2-induction in SkM increases GBE expression and reduces muscle glycogen content, resulting in improved glucose tolerance. Overall design: Chromatin occupancy of Nrf2 under CDDO-Im-treated condition were generated by deep sequencing, in dupliplicate