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Diabetologia. 2004 Mar;47(3):478-487. doi: 10.1007/s00125-004-1327-5. Epub 2004 Feb 5.

Glucagon-like peptide-1 regulates proliferation and apoptosis via activation of protein kinase B in pancreatic INS-1 beta cells.

Wang Q1,2,3, Li L1, Xu E1,3, Wong V1, Rhodes C4, Brubaker PL5,6,7.

Author information

1
Department of Physiology, University of Toronto, Toronto, Ontario, Canada.
2
Department of Medicine, Division of Endocrinology and Metabolism, University of Toronto, Toronto, Ontario, Canada.
3
St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada.
4
Pacific Northwest Research Institute, Seattle, Washington, USA.
5
Department of Physiology, University of Toronto, Toronto, Ontario, Canada. p.brubaker@utoronto.ca.
6
Department of Medicine, Division of Endocrinology and Metabolism, University of Toronto, Toronto, Ontario, Canada. p.brubaker@utoronto.ca.
7
Room 3366, Medical Sciences Building, University of Toronto, Toronto, Ontario, M5S 1A8, Canada. p.brubaker@utoronto.ca.

Abstract

AIMS/HYPOTHESIS:

The incretin hormone glucagon-like peptide-1 augments islet cell mass in vivo by increasing proliferation and decreasing apoptosis of the beta cells. However, the signalling pathways that mediate these effects are mostly unknown. Using a clonal rat pancreatic beta cell line (INS-1), we examined the role of protein kinase B in mediating beta-cell growth and survival stimulated by glucagon-like peptide-1.

METHODS:

Immunoblot analysis was used to detect active (phospho-) and total protein kinase B. Proliferation was assessed using (3)H-thymidine incorporation, while apoptosis was quantitated using 4'-6-diamidino-2-phenylindole staining and APO percentage apoptosis assay. Kinase-dead and wild-type protein kinase B was introduced into cells using adenoviral vectors.

RESULTS:

Glucagon-like peptide-1 rapidly activated protein kinase B in INS-1 cells (by 2.7+/-0.7-fold, p<0.05). This effect was completely abrogated by inhibition, with wortmannin, of the upstream activator of protein kinase B, phosphatidylinositol-3-kinase. Glucagon-like peptide-1 also stimulated INS-1 cell proliferation in a dose-dependent manner (by 1.8+/-0.5-fold at 10(-7) mol/l, p<0.01), and inhibited staurosporine-induced apoptosis (by 69+/-12%, p<0.05). Both of these effects were also prevented by wortmannin treatment. Ablation of protein kinase B by adenovirus-mediated overexpression of the kinase-dead form of protein kinase Balpha prevented protein kinase B phosphorylation and completely abrogated both cellular proliferation ( p<0.05) and protection from drug-induced cellular death ( p<0.01) induced by glucagon-like peptide-1.

CONCLUSIONS/INTERPRETATION:

These results identify protein kinase B as an essential mediator linking the glucagon-like peptide-1 signal to the intracellular machinery that modulates beta-cell growth and survival.

PMID:
14762654
DOI:
10.1007/s00125-004-1327-5
[Indexed for MEDLINE]

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