Article

Diabetologia

, Volume 53, Issue 12, pp 2600-2610

First online:

Conditional ablation of Gsk-3β in islet beta cells results in expanded mass and resistance to fat feeding-induced diabetes in mice

  • Y. LiuAffiliated withDivision of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine
  • , K. TanabeAffiliated withDivision of Endocrinology, Metabolism, and Lipid Research, Washington University School of MedicineDivision of Endocrinology, Metabolism, Hematological Sciences and Therapeutics, Department of Bio-Signal Analysis, Yamaguchi University Graduate School of Medicine
  • , D. BaronnierAffiliated withDivision of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine
  • , S. PatelAffiliated withSamuel Lunenfeld Research Institute Mount Sinai Hospital
  • , J. WoodgettAffiliated withSamuel Lunenfeld Research Institute Mount Sinai Hospital
  • , C. Cras-MéneurAffiliated withDivision of Metabolism, Endocrinology and Diabetes, University of Michigan
  • , M. A. PermuttAffiliated withDivision of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine Email author 

Abstract

Aims/hypothesis

Glycogen synthase kinase 3β (GSK-3β) is an enzyme that is suppressed by insulin and when elevated results in insulin resistance in skeletal muscle and diabetes. Its role in beta cell development and function is little known. Because of the enzyme’s anti-proliferative and pro-apoptotic properties, the hypothesis to be tested here was that beta cell specific deficiency of GSK-3β in mice would result in enhanced beta cell mass and function.

Methods

Mice with beta cell deficiency of GSK-3β (β-Gsk-3β [also known as Gsk3b]−/−) were generated by breeding Gsk-3β flox/flox mice with mice overexpressing the Cre recombinase gene under the control of the rat insulin 2 gene promoter (RIP-Cre mice), and glucose tolerance, insulin secretion, islet mass, proliferation and apoptosis were measured. Changes in islet proteins were investigated by western blotting.

Results

On a normal diet β-Gsk-3β –/– mice were found to have mild improvement of glucose tolerance and glucose-induced insulin secretion, and increased beta cell mass accompanied by increased proliferation and decreased apoptosis. On a high-fat diet β-Gsk-3β –/– mice exhibited improved glucose tolerance and expanded beta cell mass with increased proliferation relative to that in control mice, resisting fat-fed diabetes. Molecular mechanisms accounting for these phenotypic changes included increased levels of islet IRS1 and IRS2 proteins and phospho-Akt, suggesting enhanced signalling through the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, and increased islet levels of pancreas/duodenum homeobox protein 1 (PDX1). Inhibition of GSK3 in MIN6 cells in vitro led to increased IRS1 and IRS2 protein levels through inhibition of proteosomal degradation.

Conclusions/interpretation

These results are consistent with a mechanism whereby endogenous GSK-3β activity controls islet beta cell growth by feedback inhibition of the insulin receptor/PI3K/Akt signalling pathway.

Keywords

Glycogen synthase kinase 3β Islet beta cells Islet mass IRS1 IRS2 PDX1 Proliferation