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. 2023 Apr 26;26(5):106748. doi: 10.1016/j.isci.2023.106748

Figure 2.

Figure 2

Islets from HFD-fed Dpp4β-cell−/− mice have significantly reduced islet DPP4 activity and expression

(A) mRNA abundance of Dpp4 in islets isolated from 52-week-old wild-type C57BL/6J mice fed chow or a high-fat diet.

(B) DPP4 activity normalized to total protein in isolated islets from young female mice fed chow or high-fat diet (5 weeks).

(C and D) Active GLP-1 and insulin in perfusate from islets of WT male and female mice fed chow or HFHC (12 weeks) diets exposed to 16.7 mM and 10 mM glucose in dynamic perifusion.

(E) Insulin content measured in the pancreas of 12-week-old Dpp4+/+ or Dpp4−/− littermate controls fed chow or HFD (4 weeks).

(F) DPP4 activity normalized to total protein measured in whole extracts of tissues (liver, spleen, gut, heart, pancreas, islets) control (WT, MIP-Cre, Dpp4fl/fl) and Dpp4β-cell−/− male mice.

(G and H) Plasma DPP4 activity (G) and concentration (H) in plasma of HFD-fed control and Dpp4β-cell−/− male mice.

(I) Immunofluorescence staining of glucagon (purple) and DPP4 (green) and insulin (purple) and DPP4 (green) in HFD-fed male and female mouse pancreatic sections (20X) (WT – top, Dpp4−/− – middle, Dpp4β-cell−/− – bottom). DAPI staining (blue) was used to identify nuclei. DPP4 staining in liver sections of WT – top, Dpp4−/− – middle, Dpp4β-cell−/− – bottom mice.

(J) Magnified Dpp4β-cell−/− islet cells showing presence of lack of double glucagon and DPP4 or insulin and DPP4 stain.

(K–M) Glucose-stimulated insulin secretion (GSIS) and area under the curve (AUC) measured in islets isolated from control (WT, Dpp4fl/fl, and MIP-Cre) and Dpp4β-cell−/− (n = 3–5) 40-week-old HFD-fed male mice in response to perifusion with buffer containing 2.8 mM glucose, 16.7 mM glucose, or 2.8 mM glucose + KCl (30 mM). (L,M) GSIS measured in islets isolated from 40-week-old HFD-fed control (n = 9) (L) or Dpp4β-cell−/− (n = 6) (M) male mice in response to perifusion with and without DPP4 inhibitor sitagliptin. Graphs were analyzed using mixed-effects analysis and Sidak’s multiple comparisons (C-E, K-M) or unpaired t test (A, B, F, G, H and AUCs). Data are represented as the mean ± SEM. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001. Scale bars represent 50 μm (I) and 10 μm (J).