Purpose: To investigate the effect of geniposide on the biosynthesis of insulin and the expression protein disulfide isomerase (PDI) and endoplasmic reticulum oxidoreductin 1 (ERO1) in the presence of low (5 mM) and high (25 mM) glucose in pancreatic β cells.
Methods: The content of insulin was measured by ELISA, the number of SH groups was determined with the classical chromogenic reagent, 5,5ʹ-dithiobis-(2-nitrobenzoic) acid (DTNB; also known as Ellman’s reagent), the expressions of PDI and ERO1 were analyzed by Western blot.
Results: Geniposide played contrary roles on the accumulation of H ₂O ₂, the ratio of GSH/GSSG and the thiol–disulfide balance in the presence of low (5 mM) and high (25 mM) glucose in rat pancreatic INS-1 cells. Geniposide also regulated the protein levels of protein disulfide isomerase (PDI) and endoplasmic reticulum oxidoreductin1 (ERO1), the two key enzymes for the production of H ₂O ₂ during the biosynthesis of insulin in INS-1 cells.
Conclusion: Geniposide affects glucose-stimulated insulin secretion by modulating the thiol–disulfide balance that is controlled by the redox signaling in pancreatic β cells.
Keywords: endoplasmic reticulum oxidoreductin1, ERO1, geniposide, protein disulfide isomerase, PDI, glucose-stimulated insulin secretion, GSIS, type 2 diabetes mellitus, T2DM