Additional characterization of β cell compensation-to-decompensation model and dietary intervention model. (a) Body weight of mice fed with HFD for 1, 3, 5, and 6 mo. Littermates fed with chow diet were used as controls. Data represent mean ± SEM (n = 4–6 mice per group); ***, P < 0.001; two-tailed unpaired Student’s t test. (b) Overnight fasting blood glucose levels in mice as treated in a. Data represent mean ± SEM (n = 4–6 mice per group); **, P < 0.01; ***, P < 0.001; two-tailed unpaired Student’s t test. (c) Representative images of mice in Chow, HFD, and HFD-Chow groups. (d) Body composition of mice in indicated groups. Data represent mean ± SEM (n = 4–5 mice per group); **, P < 0.01; ***, P < 0.001; one-way ANOVA. (e) AUC quantification of GTT and ITT results shown in Fig. 2 d. Data represent mean ± SEM (n = 4–5 mice per group); ***, P < 0.001; one-way ANOVA. (f) Representative images of mouse islets isolated from indicated groups. Scale bar, 5 mm. (g) Representative immunofluorescent images (left panel) and quantification (right panel) of Ngn3⁺ cells in islets from indicated groups. Scale bar, 100 μm. Data represent mean ± SEM (n = 25–33 islets from 4 to 5 mice per group); ***, P < 0.001; one-way ANOVA. (h) Glucose-stimulated Ca²⁺ influx in mouse islets isolated from Chow (n = 53 islets), HFD (n = 52 islets), and HFD-Chow (n = 63 islets) groups. Each islet sample was pooled from at least three animals. Representative fluorescence images of calcium signal in islets treated with high glucose (16.8 mM) for 400 s (left), and dynamic Ca²⁺ fluorescence intensity in response to high-glucose treatment (right). Scale bar, 100 μm. Data represent mean ± SEM two-way ANOVA with multiple comparisons. Data are representative of at least two independent experiments for all panels.