GLP-1-related Proteins Attenuate the Effects of Mitochondrial Membrane Damage in Pancreatic β Cells

Glucagon-like peptide (GLP)-1 analog based therapies are used not only for their insulinotropic effects, but also for their pleiotropic effects that improve pancreatic β cell function. Liraglutide is a long acting derivative of human GLP-1(7-37), which is a cleavage product encompassing amino acids 7-37 of GLP-1. In this study, we examined whether Liraglutide treatment restore the glucose-stimulated mitochondrial response of β cells with chemically induced mitochondrial damage. We tested three GLP-1-related proteins: human GLP-1(1-37), GLP-1(7-37) and Liraglutide. To measure changes of the mitochondrial pH quantitatively in real-time, we have developed a bioengineered β cell line. We generated a mitochondrial damaged model by treating β cells with ethidium bromide (EtBr; 0.5 or 1 μg/mL for 48 h). EtBr treatment reduced the response to 25 mM glucose in mitochondrial pH in a dose- and time-dependent manner. GLP-1(7-37) (100 nM) enhanced the response of mitochondria to glucose stimulation in undamaged β cells. Preincubation with Liraglutide (1 nM) or GLP-1 (100 nM) for 3h recovered the mitochondrial response to glucose in damaged β cells, however, GLP-1(7-37) (100 nM) did not. When GLP-1(7-37) was administered in stepwise increments (i.e., starting with 20 nM to reach 100 nM in 3h), similar recovery of the mitochondrial function was observed. The results suggest that Liraglutide is effective to recover glucose-stimulated mitochondrial response in damaged β cells.