Figure 2.

Experimentally demonstrating how metabolically deficient cells impact islet function via gap-junction coupling. (A) Representative images of NAD(P)H at 20 mM glucose in islets from GK^lox/lox;Pdx-Cre^ER mice injected with differing levels of tamoxifen, as indicated, are shown. (B) Change in NAD(P)H from 2 to 20 mM (ΔNAD(P)H) compared to total tamoxifen dose is shown. For control, n = 24 mice; for 10 mg/kg, n = 3; for 25 mg/kg, n = 4; for 50 mg/kg, n = 9; for 100 mg/kg, n = 3; and for 250 mg/kg, n = 3 (two to seven islets per mouse). (C) Representative images of fluorescence from the [Ca²⁺]-sensitive dye Fluo-4 at 11 mM glucose when injected with varying amounts of tamoxifen are shown. (D) The fraction of cells showing elevated [Ca²⁺] activity (“active cells”) at 11 mM glucose compared to total tamoxifen dose is shown. For control, n = 19 mice; for 10 mg/kg, n = 3; for 25 mg/kg, n = 4; for 50 mg/kg, n = 9; for 100 mg/kg, n = 5; and for 250 mg/kg, n = 3 (two to seven islets per mouse). (E) Representative time courses of individual cells, shown by yellow boxes in (C), at 11 mM glucose within islets from mice treated with varying amounts of tamoxifen are given (from left to right: control, 10, 50, 250 mg/kg with KCl). Red arrow in (E) indicates time point at which images in (C) are displayed. (F) The fraction of cells showing elevated [Ca²⁺] after KCl compared to total tamoxifen dose is shown. For control, n = 5 mice; for 50 mg/kg, n = 6; and for 250 mg/kg, n = 3 (two to four islets per mouse). (G) Scatter plot (dots) plus linear regression ±95% confidence interval (solid and dashed lines) of mean active cells for islets from GK^lox/lox;Pdx-Cre^ER mice versus mean ΔNAD(P)H for islets from the same mice (n = 41 mice) are given. p represents significance of linear trend slope. (H) A comparison of ΔNAD(P)H for islets from GK^lox/lox;Pdx-Cre^ER;Cx36^+/+ and GK^lox/lox;Pdx-Cre^ER;Cx36^−/− mice for the tamoxifen doses indicated is shown. For 25 mg/kg, n = 4; for 50 mg/kg, n = 5; and for 250 mg/kg, n = 2 (two to seven islets per mouse). (I) A comparison of fraction of active cells at 11 mM glucose for islets from GK^lox/lox;Pdx-Cre^ER;Cx36^+/+ and GK^lox/lox;Pdx-Cre^ER;Cx36^−/− mice is shown for the tamoxifen doses indicated. For 25 mg/kg, n = 3; for 50 mg/kg, n = 6; and for 250 mg/kg, n = 2 (two to seven islets per mouse). Scale bars in (A) and (C) represent 10 μm; scale bars in (E) represent dF/F of 50%. Error bars in (B), (D), (F), (H), (I) represent SEM. To see this figure in color, go online.