For determination of d-glucose and insulin blood was collected from the tail. Concentrations of d-glucose were determined with an Ascensia CONTOUR Meter using Ascensia MICROFIL Test Strips (Bayer Vial GmbH, Leverkusen). Insulin levels were measured with the Insulin (Mouse) Ultrasensitive EIA from ALPCO Diagnostics (Salem, NH). For determination of enterohormones, mice were anesthetized with isoflurane and blood was collected after heart tap. For GLP-1 determination blood was immediately mixed with a dipeptidyl peptidase (DPP)-IV inhibitor yielding a final concentration of 100 μmol/L (Millipore Corporation, Billerica, MA). Active GLP-1 was determined by an ELISA kit supplied by Millipore Corporation (GLP-1(7–36) active, kit EGLP-35 K) (Fig. 5C). Total GLP-1 was determined by an ELISA kit provided by MesoScale Discovery (Gaithersburg, MD; kit K150JVC-4; Fig. 5D and Supplementary Fig. 5B). GIP was determined by an ELISA kit obtained from Millipore Corporation that is specific for both active GIP (1–42) and inactivated GIP (3–42) of rat and mouse (kit EZRMGIP-55 K).