Study schematic. 2DG, 2-deoxy-glucose (6 mg/kg); Ctrl, control group; D2O, deuterium (7.2 mL/kg); Fndc5, fibronectin type III domain-containing 5; IPGTT, intraperitoneal glucose tolerance test (2 g/kg); IVE, in vitro electroporation; OE, overexpressed group.