Supplementary Figure 5: Uptake and inhibition studies in Xenopus laevis oocytes expressing human GLUT2 (SLC2A2).

(a–c) Uptake of model substrate (¹⁴C-2-deoxyglucose (2-DG)) (a) and metformin (Metf.) (b,c) in Xenopus laevis oocytes expressing GLUT2. (a) At 30 min, uptake of the model substrate is significantly higher than in oocytes injected with saline. In the presence of GLUT2 inhibitor, phloretin (200 μM), GLUT2-mediated uptake of ¹⁴C-2-deoxyglucose is inhibited. (b,c) However, uptake of ¹⁴C-metformin (at 30 and 60 min) is not significantly different between oocytes injected with saline or GLUT2 and also in the presence of GLUT2 inhibitor, phloretin. (d) Inhibition of GLUT2-mediated uptake of ¹⁴C-2-deoxyglucose by phloretin (200 μM) and metformin (30 and 50 mM). Phloretin significantly inhibit GLUT2-mediated uptake of ¹⁴C-2-deoxyglucose but not metformin. Xenopus laevis oocytes were purchased from Ecocytes. Capped cRNA was synthesized in vitro from human GLUT2 expression vector (pSP64T) (from G.I. Bell, University of Chicago) linearized using the mMessage mMachine SP6 kit (Ambion). 50 ng of the synthesized cRNA was injected into each oocyte. Modified Barth solution was used as the uptake buffer. DPM, disintegrations per minute, measure of the activity of the source of ¹⁴C-2-deoxyglucose radioactivity.