Ghrelin's Effects on Proinflammatory Cytokine Mediated Apoptosis and Their Impact on β-Cell Functionality.

Antonia Diaz-Ganete,Jose Francisco Lopez-Acosta,Isabel M Lomas-Romero,Alfonso M Lechuga-Sancho,Francisco Medina,Irene Cozar-Castellano,Carmen Segundo,Gloria Baena-Nieto

doi:10.1155/2015/235727

Abstract

Ghrelin is a peptidic hormone, which stimulates cell proliferation and inhibits apoptosis in several tissues, including pancreas. In preclinical stage of type 1 diabetes, proinflammatory cytokines generate a destructive environment for β-cells known as insulitis, which results in loss of β-cell mass and impaired insulin secretion, leading to diabetes. Our aim was to demonstrate that ghrelin could preserve β-cell viability, turnover rate, and insulin secretion acting as a counter balance of cytokines. In the present work we reproduced proinflammatory milieu found in insulitis stage by treating murine cell line INS-1E and rat islets with a cytokine cocktail including IL-1β, IFNγ, and TNFα and/or ghrelin. Several proteins involved in survival pathways (ERK 1/2 and Akt/PKB) and apoptosis (caspases and Bcl-2 protein family and endoplasmic reticulum stress markers) as well as insulin secretion were analyzed. Our results show that ghrelin alone has no remarkable effects on β-cells in basal conditions, but interestingly it activates cell survival pathways, downregulates apoptotic mediators and endoplasmic reticulum stress, and restores insulin secretion in response to glucose when beta-cells are cytokine-exposed. These data suggest a potential role of ghrelin in preventing or slowing down the transition from a preclinical to clinically established diabetes by ameliorating the effects of insulitis on β-cells.

Highlights

Ghrelin, a 28-amino acid peptidic hormone, is the endogenous ligand of the orphan receptor of growth hormone secretagogues (GHS-R)
Before the clinical onset of the disease, an inflammatory lesion known as insulitis develops due to the recruitment of macrophages and CD8+ T lymphocytes to the islets and the release of several soluble mediators and cytokines, mainly IFN-γ, TNFα, and IL-1β, causing β-cells apoptosis [6]
INS-1E cells were routinely cultured in RPMI 1640 supplemented with 10% FBS, 1% PenicillinStreptomycin, 1 mM sodium pyruvate, mM Hepes buffer in 0.85% NaCl (Lonza, Barcelona, Spain), 0.05 mM β-mercaptoethanol (Sigma-Aldrich), and mM D-glucose (Merck, Darmstadt, Germany)

Summary

Introduction

A 28-amino acid peptidic hormone, is the endogenous ligand of the orphan receptor of growth hormone secretagogues (GHS-R). Before the clinical onset of the disease, an inflammatory lesion known as insulitis develops due to the recruitment of macrophages and CD8+ T lymphocytes to the islets and the release of several soluble mediators and cytokines, mainly IFN-γ, TNFα, and IL-1β, causing β-cells apoptosis [6]. This inflammatory microenvironment observed in pancreatic islets during type 1 diabetes can be mimicked by adding these cytokines to β-cell cultures

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