Effects of Mct1 overexpression in β-cells on blood glucose homeostasis in vivo. A: Blood glucose after overnight fast was not significantly different between ST and DT mice without doxycycline treatment.
After treatment with 1 g/L doxycycline in the drinking water for 5 days, fasting blood glucose in DT mice was significantly
lower than in ST controls (n = 13 for both groups). B: Fasting plasma insulin levels were not significantly different between ST and DT mice (n = 14 for both groups). C and D: Pyruvate tolerance test. ST and DT mice were tested both before (−Dox) and after (+Dox) induction with doxycycline. Pyruvate
(0.5 g/kg) was injected intraperitoneally into mice after an overnight fast, and blood glucose was measured at the time points
indicated. Two-way ANOVA with Bonferroni post test was performed to detect differences between genotypes for each time point
(ST n = 6, DT n = 12). E: Pyruvate-stimulated insulin secretion. ST and DT mice were tested after induction with doxycycline. Pyruvate (2 g/kg) was
injected intraperitoneally into mice after an overnight fast, and blood was collected at time points indicated. Plasma insulin
was measured by enzyme-linked immunosorbent assay (n = 5 for both groups). F and G: Plasma pyruvate (F) and lactate (G) levels both before and 15 min after injection with 2 g/kg pyruvate (n = 3 for both groups). H and I: Glucose tolerance test. ST and DT mice were induced with doxycycline as previously described, fasted overnight, then injected
intraperitoneally with 1 g/kg glucose. Blood glucose was measured at the time points indicated. Because of sex-specific differences
in glucose tolerance, data for females (H) and males (I) are displayed separately (ST females n = 6, DT females n = 8; ST males n = 8, DT males n = 12). No significant differences between genotypes were detected by two-way ANOVA with Bonferroni post hoc test. All data
are presented as mean ± SEM. *P < 0.05; **P < 0.001.