Stearidonic acid promotes insulin secretion via stimulation of G protein-coupled receptor 40 in MIN6 pancreatic β-cells

The aim of this study is to research whether stearidonic acid (SDA) has insulinotropic effect and the mechanisms. MIN6 pancreatic β-cells were treated with SDA and effects were analyzed. Protein and mRNA expressions of G protein-coupled receptor 40 (GPR40) increased after 24-h SDA treatment, whereas there was no statistical difference of cellular SDA composition between SDA and control groups. The cytosolic Ca2+ increased in 15 s after treatment, but increment was inhibited when MIN6 cells were preincubated with U-73122 (phospholipase C inhibitor) or BAPTA-AM (Ca2+ chelator). The glucose-stimulated insulin secretion (GSIS) increased after treatment, and GSIS was also inhibited by SDA plus U-73122 or BAPTA-AM. The presence of SDA antagonized palmitic acid-mediated MIN6 cells death. These findings indicate for the first time that SDA can promote GSIS in pancreatic β-cells via stimulation of GPR40-related signaling pathway (direct effect), and via antagonistic effect on long chain saturated fatty acid-mediated impairment (indirect effect).