The Akt/FoxO1/p27 pathway mediates the proliferative action of liraglutide in β cells

Abstract

Numerous studies have shown that liraglutide, a modified form of human glucagon-like peptide-1 (GLP-1), increases β-cell mass. However, the underlying molecular mechanisms remain unclear. In the present study, we investigated the role of Akt/FoxO1/p27 signaling in liraglutide-induced β-cell proliferation. INS-1 rat insulinoma cells were exposed to two different concentrations of liraglutide. MTT assay was performed to evaluate β-cell proliferation. The expression of Akt/FoxO1/p27 was detected by quantitative real-time PCR and Western blotting. The results revealed that in comparison to the non-treatment group, stimulating INS-1 cells with 10 and 100 nM liraglutide caused β-cell proliferation to be significantly enhanced. The mRNA levels of p27 in INS-1 cells declined upon treatment with liraglutide compared to the non-treatment group. Western blot analysis revealed that the phosphorylation of Akt and FoxO1 was markedly elevated following exposure to liraglutide. Moreover, LY294002, a phosphatidylinositol 3-kinase (PI-3K) inhibitor, significantly abrogated liraglutide-induced effects. Therefore, we conclude that liraglutide increased the β-cell mass by upregulating β-cell proliferation and that the proliferative action of liraglutide in β cells was mediated by activation of PI-3K/Akt, which resulted in inactivation of FoxO1 and decreased p27.