Butyrate prevents cytokine induced impairment of glucose-stimulated insulin secretion in human EndoC-βH1 cells and rat INS-1E cells. (A) Human EndoC-βH1 cells were cultured for 7 days in the absence or presence of the cytokine mixture (500 pg/mL IL-1β + 2 ng/mL INF-γ + 2 ng/mL TNF-α) and/or butyrate (0.1 mM or 0.4 mM). Insulin secretion was measured by static batch incubations for 45 min in response to 0.5 mmol/L glucose, 11.2 mmol/L glucose followed by 11.2 mmol/L glucose plus 50 µM forskolin and normalized to cell number. Each condition was tested in quadruplicate. Data are shown as means ± SD for n = 5 and analyzed by a 2-sided paired t-test. * p < 0.05, ** p < 0.01 vs. control, # p < 0.05 vs. cytokine mixture. (B) INS-1E cells were cultured for 3 days in the absence or presence of 12.5 pg/mL IL-1β and/or 0.4 mM butyrate. Insulin secretion was measured by static batch incubations for 30 min in response to 2 mmol/L glucose followed by 20 mmol/L and normalized to DNA content. (C) Total insulin content was measured post-glucose stimulation. Data are shown as means ± SD for n = 6 and analyzed by a 2-sided paired t-test. ** p < 0.01, *** p < 0.001 vs. control, ## p < 0.01 vs. IL-1β.