Role of endogenous glucagon-like peptide-1 in islet regeneration after partial pancreatectomy

A reduction in beta-cell mass is an important causative factor in type I and type 2 diabetes. Glucagon-like peptide-1 (GLP-1) and the long-acting agonist exendin 4 (Ex-4) expand beta-cell mass by stimulating neogenesis and proliferation. In the partial pancreatectomy (Ppx) model, exogenous Ex-4 promotes islet regeneration, leading to sustained improvement in glucose tolerance. In this study, we investigate the potential role of endogenous GLP-1 in islet growth. We examined beta-cell mass regeneration after 70% Ppx in mice receiving the GLP-1 antagonist Ex9-39 and in GLP-1R(-/-) mice. In Ex9-39-treated sham-operated mice, persistent fasting hyperglycemia was observed, but beta-cell mass was not diminished. In pancreatectomized mice, persistent glucose intolerance was noted, but this was not further exacerbated by Ex9-39. Accordingly, beta-cell mass recovery of Ppx mice was not impaired by Ex9-39. In contrast, GLP-1R(-/-) CD1 mice showed worse glucose intolerance after Ppx compared with wild-type CD1 Ppx mice, and this correlated with a significant defect in beta-cell mass regeneration. The recovery of beta-cell mass differed markedly in the BALB/c and CD1 control mice, indicating a significant role of genetic background in the regulation of beta-cell mass. These studies point to a role for endogenous GLP-1 in beta-cell regeneration after Ppx in mice.