Glucose-stimulated insulin secretion (GSIS) assay

Min6 cells (5×10⁴ cells per well) were incubated with various concentrations of ICA for 2 h, followed by incubation with 5 mg/dl UA for an additional 4 h. The cells were subsequently incubated with 0.1% BSA (Sigma Aldrich; St. Louis, MO, USA) in KRB buffer (Sigma Aldrich) for 1 h, followed by incubation with KRB buffer containing low or high concentrations of glucose for another 1 h. Insulin secretion was measured by radioimmunoassays, as described previously. Each experiment was repeated three times, all on cells of the same passage number.