An animal study revealed that FGF21 specifically upregulates the glucose transporter 1 (GLUT1) with greater expression of GLUT1 mRNA at the adipocyte cellular membrane and then induces noninsulin-dependent glucose uptake in the insulin resistance model and obesity (ob/ob mice) [6]. Here, SLC2A1 is linked to obesity due to melanocortin 4 receptor deficiency.