Glucagon Acting at the GLP-1 Receptor Contributes to β-Cell Regeneration Induced by Glucagon Receptor Antagonism in Diabetic Mice
Tianjiao Wei, Xiaona Cui, Yafei Jiang, Kangli Wang, Dandan Wang, Fei Li, Xiafang Lin, Liangbiao Gu, Kun Yang, Jin Yang, Tianpei Hong, Rui Wei
Abstract
Dysfunction of glucagon-secreting α-cells participates in the progression of diabetes, and glucagon receptor (GCGR) antagonism is regarded as a novel strategy for diabetes therapy. GCGR antagonism upregulates glucagon and glucagon-like peptide 1 (GLP-1) secretion and, notably, promotes β-cell regeneration in diabetic mice. Here, we aimed to clarify the role of GLP-1 receptor (GLP-1R) activated by glucagon and/or GLP-1 in the GCGR antagonism-induced β-cell regeneration. We showed that in db/db mice and type 1 diabetic wild-type or Flox/cre mice, GCGR monoclonal antibody (mAb) improved glucose control, upregulated plasma insulin level, and increased β-cell area. Notably, blockage of systemic or pancreatic GLP-1R signaling by exendin 9-39 (Ex9) or Glp1r knockout diminished the above effects of GCGR mAb. Furthermore, glucagon-neutralizing antibody (nAb), which prevents activation of GLP-1R by glucagon, also attenuated the GCGR mAb-induced insulinotropic effect and β-cell regeneration. In cultured primary mouse islets isolated from normal mice and db/db mice, GCGR mAb action to increase insulin release and to upregulate β-cell-specific marker expression was reduced by a glucagon nAb, by the GLP-1R antagonist Ex9, or by a pancreas-specific Glp1r knockout. These findings suggest that activation of GLP-1R by glucagon participates in β-cell regeneration induced by GCGR antagonism in diabetic mice. ARTICLE HIGHLIGHTS: Glucagon receptor (GCGR) antagonism promotes β-cell regeneration in type 1 and type 2 diabetic mice and in euglycemic nonhuman primates. Glucagon and glucagon-like peptide 1 (GLP-1) can activate the GLP-1 receptor (GLP-1R), and their levels are upregulated following GCGR antagonism. We investigated whether GLP-1R activated by glucagon and/or GLP-1 contributed to β-cell regeneration induced by GCGR antagonism. We found that blockage of glucagon-GLP-1R signaling attenuated the GCGR monoclonal antibody-induced insulinotropic effect and β-cell regeneration in diabetic mice. Our study reveals a novel mechanism of β-cell regeneration and uncovers the communication between α-cells and β-cells in regulating β-cell mass.