Glucagon-like peptide 1 receptor plays an essential role in geniposide attenuating lipotoxicity-induced β-cell apoptosis

beta-Cell apoptosis is considered to be a major cause of loss of beta cells in diabetes. Geniposide could prevent oxidative stress-induced neuron apoptosis, and improved glucose stimulated insulin secretion by activating glucagon-like peptide 1 receptor (GLP-1R) in INS-1 cells. Here we have investigated whether geniposide can exert a direct effect against pancreatic beta-cell lipoapoptosis. The results indicated that pretreatment pancreatic INS-1 cells with geniposide for 7 h attenuated palmitate-induced beta-cell apoptosis and active caspase-3 expression, but this effect was disappeared at 18 h. Long-term incubation with palmitate decreased GLP-1R expression in INS-1 cells, and exendin (9-39), an antagonist for GLP-1R, inhibited the effect of geniposide on palmitate-induced apoptosis in INS-1 cells. Moreover, geniposide also improved the impairment of GLP-1R signaling through enhancing the phosphorylation of Akt and Foxo1, and increased the expression of PDX-1 in palmitate-treated INS-1 cells. These results suggest that geniposide inhibits early stage of lipotoxicity-induced beta-cell apoptosis, and GLP-1R plays a critical role in geniposide counteracting the action of lipotoxicity in INS-1 pancreatic beta cells. (C) 2012 Elsevier Ltd. All rights reserved.