Fig. 1.

Pharmacological suppression of ATP-sensitive potassium (K_ATP) channels or L-type Ca²⁺ channels inhibits overnutrition-induced β-cell differentiation. A and B: β-cell number following overnutrition in the presence or absence of the K_ATP channel activator diazoxide (Diaz, 300 μM). Tg(−1.2ins:H2BmCherry) larvae cultured in 5% egg yolk (Yolk) (A) or 20 mM glucose (Glu) (B) for 8 h at 6 days postfertilization (dpf) induced β-cell differentiation, whereas inclusion of diazoxide in 5% egg yolk (A) or 20 mM glucose (B) suppressed the increase. CTL, control. C and D: β-cell number in 6 dpf Tg(−1.2ins:H2BmCherry) larvae following overnutrition in the presence or absence of the L-type Ca²⁺ channel blocker verapamil (Vera, 10 μM). Verapamil suppressed β-cell differentiation following 8-h culture in 5% egg yolk (C) or 20 mM glucose (D). E and F: total free glucose levels in 6 dpf Tg(−1.2ins:H2BmCherry) larvae. Diazoxide incubation for 8 h significantly increased free glucose levels, which was exacerbated by 5% egg yolk but not 20 mM glucose (E). Verapamil incubation alone did not increase free glucose levels but significantly increased free glucose levels when coadministered with 5% egg yolk or 20 mM glucose (F). All values are means ± SE; n are shown inside of the bars. Groups labeled with different letters are significantly different from each other (P < 0.05).