Effect of interleukin-1β and interferon-γ on the insulin secretion in mice βTC-6 cells in vitro

Objective To investigate the effect of interleukin(IL)-1β and interferon(IFN)-γ on the insulin secretion in mice βTC-6 cells in vitro. Methods βTC-6 cells were cultured in DMEM for 48 hours then pre-incubated for 30 minutes in Krebs-Ringer bicarbonate-Hepes (KRBH) buffer without glucose. The KRBH was then discarded and replaced with fresh buffer containing 1.38 mmol/L or 5.50 mmol/L or 11.10 mmol/L glucose for 1 hour. Supernatants were collected for insulin assays by an insulin radioimmunoassay (RIA) kit (GSIS). IL-1β (0.15, 1.50 μg/L) and/or IFN-γ (10, 100 U/ml) were added in βTC-6 cells for 24 hours then GSIS was measured as indicated with 1.38 mmol/L glucose stimulation. Data were analyzed by ONE-way ANOVA with correction for multiple comparisons or by Student's t-test for comparison between two groups. Results The insulin level reaches a peak in 1.38 mmol/L stimulation group compared with 0 mmol/L glucose stimulation group ((151±14) vs (120±4) mU/L, t=-4.215, P=0.006). The insulin level 5.50 mmol/L and 11.10 mmol/L glucose stimulation groups were significantly lower than that in 1.38 mmol/L glucose stimulation group(all P<0.05). Compared with 1.38 mmol/L glucose stimulation alone group, the insulin level was significantly lower in IL-1β(0.15 μg/L) group ((85.53±5.06) vs (103.11±0.27) mU/L, t=4.897, P=0.039); IL-1β(1.50 μg/L) group ((62.62±0.64) vs (103.11±0.27) mU/L, t=212.66, P<0.001) and IFN-γ(100 U/ml) group ((73.2±1.6) vs (105.2±1.8) mU/L, t=19.52, P=0.003). Compared with IL-1β (0.15 μg/L) and IFN-γ(100 U/ml)groups, the insulin level in 1.38 mmol/L glucose stimulation with IL-1β plus IFN-γ group was significantly lower (F=77.38, P<0.001). Conclusion IL-1β or IFN-γ alone can inhibit the glucose-induced insulin secretion in βTC-6 cells or in a synergistic manner. Key words: Insulin; Interleukin-1 beta; Interferon-gamma; Mice; β cell line