Fig. 1

Changes in serum DPP-4 activity and active GLP-1 concentrations in db/+ mice and db/db mice during an oral meal tolerance test. The experiments were performed in db/+ or db/db mice fed an SL diet, an SO diet, or a diet containing the DPP-4 inhibitor 0.4 % des-fluoro-sitagliptin or 0.0045 % MK-0626. a Serum DPP-4 activity was measured in mice fed the indicated diets ad libitum (n = 5). *P < 0.05 vs. db/db SL. ^†P < 0.05 vs. db/db SO. b Serum active GLP-1 concentration at 0 min (fasted > 20 h), 30, and 120 min after the oral administration of each diet test meal (12 mg/g body weight) in db/+ mice and db/db mice that had been fed either the SO or SL diet (n = 3–4). To obtain a sufficient amount of whole blood to measure the biologically active form of GLP-1, blood was collected from the inferior vena cava with a DPP-4 inhibitor (Millipore) at the time points indicated. *P < 0.05 vs. db/db SL. ^†P < 0.05 vs. db/db SO