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Glucagon-like peptide-1 protects beta cells from cytokine-induced apoptosis and necrosis: role of protein kinase B.

Abstract：

AIMS/HYPOTHESIS:The gut hormone glucagon-like peptide-1 (GLP-1) decreases beta cell apoptosis in a protein kinase B (PKB)-dependent fashion, and increases islet cell mass and function in vivo. In contrast, cytokines induce beta cell apoptosis, leading to decreased islet mass and type 1 diabetes. In the present study we used rat INS-1E beta cells and primary rat islet cells to examine the potential role of PKB as a mediator of the effect of GLP-1 on cytokine-induced apoptosis. METHODS:Cell viability was determined by MTT assay, and apoptosis and necrosis by Hoechst 33342-propidium iodide staining. Immunoblot analysis was used to detect changes in protein expression, including active (phosphorylated) and total PKB, phosphorylated and total glycogen synthase kinase-3beta, activated caspase-3 and inducible nitric oxide synthase. Reactive oxygen species were determined by 1,7-dichlorofluorescein (DCF) analysis, and mutant forms of PKB were introduced into cells using adenoviral vectors. RESULTS:Incubation of INS-1E cells with cytokines (IL-1beta, TNF-alpha and interferon-gamma; 10-50 ng/ml) for 18 h significantly decreased cell viability (by 44%, p<0.001), cell proliferation (by 80%, p<0.001), and activation of PKB (by 67%, p<0.001). Pre-treatment with exendin-4 (10(-7) mol/l), a long-acting GLP-1 receptor agonist, partially protected the cells against cytokine-induced toxicity (p<0.01) in association with a reduction in cytokine-induced inhibition of PKB phosphorylation (p<0.05). Exendin-4 pre-treatment did not change cell proliferation. Cytokine treatment increased apoptosis (by 156%, p<0.05) and necrosis (from undetectable to 2.6% of cells). These increases were both reduced by pre-treatment with exendin-4 (p<0.05-0.01). Furthermore, cytokine-induced apoptosis and necrosis were significantly increased in cells infected with kinase-dead PKB (p<0.05), and the protective effect of exendin-4 on both parameters was fully abolished in these cells. Similar changes were observed in primary islet cells. In parallel with these changes, exendin-4 decreased the cytokine-induced activation of caspase-3 (by 46%, p<0.05), and decreased levels of inducible nitric oxide synthase (by 71%, p<0.05) and reactive oxygen species (by 27%, p<0.05). CONCLUSIONS/INTERPRETATION:The results of our study indicate that GLP-1 plays a protective role against cytokine-induced apoptosis and necrosis in beta cells through a PKB-dependent signalling pathway.

journal_name

Diabetologia

journal_title

Diabetologia

authors

Li L,El-Kholy W,Rhodes CJ,Brubaker PL

doi

10.1007/s00125-005-1787-2

subject

Has Abstract

pub_date

2005-07-01 00:00:00

pages

1339-49

issue

eissn

0012-186X

issn

1432-0428

journal_volume

pub_type

杂志文章

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Glucagon-like peptide-1 protects beta cells from cytokine-induced apoptosis and necrosis: role of protein kinase B.