Article Addendum

GLP-1 protects β-cells against apoptosis by enhancing the activity of an IGF-2/IGF1-receptor autocrine loop

Marion Cornu and Bernard Thorens

Volume 1, Issue 3
November/December 2009
Pages 280 – 282

This is an open-access article

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GLP-1 protects β-cells against apoptosis by still incompletely understood mechanisms. In a recent study, we searched for novel anti-apoptotic pathways by performing comparative transcriptomic analysis of islets from Gipr-/-;Glp-1r-/- mice, which show increased susceptibility to cytokine-induced apoptosis. We observed a strong reduction in IGF-1R expression in the knockout islets suggesting a link between the gluco-incretin and IGF-1R signaling pathways. Using MIN6 and primary islet cells, we demonstrated that GLP-1 strongly stimulates IGF-1R expression and that activation of the IGF-1R/Akt signaling pathway required active secretion of IGF-2 by the β-cells. We showed that inactivation of the IGF-1 receptor gene in β-cells or preventing its up-regulation by GLP-1, as well as suppressing IGF-2 expression or action, blocked the protective effect of GLP-1 against cytokine-induced apoptosis. Thus, an IGF-2/IGF-1 receptor autocrine loop operates in β-cells and GLP-1 increases its activity by enhancing IGF-1R expression and by stimulating IGF-2 secretion. This mechanism is required for GLP-1 to protect β-cells against apoptosis.

Cornu M, Yang JY, Jaccard E, Poussin C, Widmann C, Thorens B. Glucagon-like peptide-1 protects beta-cells against apoptosis by increasing the activity of an IGF-2/IGF-1 receptor autocrine loop. Diabetes 2009; 58: 1816-25.