INS and pancreatic insulinoma: For further verification of the inhibitory action of D-Pinitol on insulin secretion, we performed a set of in vitro experiments in rat insulinoma INS 1 cells under basal conditions (3 mM glucose), or stimulated by high glucose (11 mM) glucose to insulin secretion in the absence or presence of different concentrations of D-Pinitol (1, 10, 100 and 1000 μM).