Glucose and Insulin Tolerance Tests

At 16 weeks of age, the mice fed with HF/HS were subjected to intraperitoneal glucose tolerance test (GTT) and insulin tolerance test (ITT) using standard protocols, as described in detail previously^{16 (link)}. Briefly, for GTT, the mouse was fasted overnight and then challenged with 2 g/kg d-glucose (Sigma-Aldrich), followed by serial measurements of blood glucose up to 120 min using a blood glucose level monitor (Glutest Ace, Sanwa Kagaku Kenkyusho Co, Nagoya, Japan). For ITT, the mouse was fasted for 16 h before testing. Insulin (0.75 U/kg, Actrapid Penfill, NovoNordisk) was injected intraperitoneally, and blood glucose level was measured serially.