Figure 1

(A) Fasting glucose levels were increased in Cre⁺Ex⁻mice. This increase was not reversed by exendin-4 treatment (Cre⁺Ex⁺). (B) Glucose tolerance tests showed an enhanced ability to respond to a glucose load in control Cre⁻ mice with exendin-4 treatment (Cre⁻Ex⁺). A defect in glucose tolerance was seen in Cre⁺Ex⁻ mice that could not be salvaged with exendin-4 (Cre⁺Ex⁻). (C) β-cell mass was significantly increased in control mice as compared with Cre⁺ mice. (D) Insulin content mirrors β-cell mass. (E) Islet size was significantly increased in control mice after exendin-4 treatment (Cre⁻Ex⁺), as compared with Cre⁺Ex⁺ and Cre⁺Ex⁻ mice. n = 5. All results were mean ± S.E. * #, p < 0.05, NS, no significance). (F) In vitro GSIS shows significantly increased insulin release in control mice with exendin-4 treatment (Cre⁻Ex⁺) at low and high glucose concentrations. At high glucose concentrations, there is significantly less insulin secretion in Cre⁺ mice, regardless of treatment with exendin-4, as compared to control Cre⁻ mice.