Serum GDF15 levels in male mice measured 2, 4, or 8 hours after a
single gavage dose of metformin (300mg/kg). a, mice ad
libitum overnight fed prior to gavage. b, mice
fasted for 12 hour prior to gavage. Data are mean ± SEM
(a; n=6/group, b; n= 4/group); P by 2-way
ANOVA with Tukeys correction for multiple comparisons.