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Gene expression changes in rat islets with glucolipotoxic conditions with or without protective compound

ABSTRACT: To determine which GLT-regulated genes might be affected by compound D, we performed an RNA-sequencing analysis of rat islets treated ex-vivo with or without GLT and compound D for 3 hours and 24 hours. Compound E (related inactive compound) was used to account for non-specific scaffold effects.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE134272 | GEO | 2019/07/16

REPOSITORIES: GEO

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Project description:Immune-mediated beta cell destruction and lack of alpha cell responsiveness to hypoglycaemia are hallmarks of type 1 diabetes pathology. The incretin hormone glucose-dependent insulinotropic polypeptide (GIP) may hold therapeutic potential for type 1 diabetes due to its insulinotropic and glucagonotropic effects as well as its beta cell protective effects shown in rodent islets. Here, we examined the functional and transcriptomic effects of GIP treatment upon diabetogenic cytokine exposure to interleukin (IL)-1β ± interferon (IFN)-γ in human EndoC-βH5 beta cells and isolated human islets, respectively. GIP dose-dependently augmented glucose-stimulated insulin secretion from EndoC-βH5 cells and increased insulin and glucagon secretion from human islets during high and low glucose concentrations, respectively. The insulinotropic effect of GIP in EndoC-βH5 cells was abrogated by KN-93, an inhibitor of calcium/calmodulin-dependent protein kinase 2 (CaMK2). GIP did not prevent cytokine-induced apoptosis or cytokine-induced functional impairment of human EndoC-βH5 cells. GIP also did not prevent cytokine-induced apoptosis in human islets. GIP treatment of human islets with or without cytokines for 24 hours did not significantly impact the transcriptome. GIP potentiated cytokine-induced secretion of IL-10 and c-c motif chemokine ligand (CCL)-2 from human islets while decreasing the secretion of c-x-c motif chemokine ligand (CXCL)-8. In EndoC-βH5 cells, GIP reduced IFN-γ-induced secretion of tumor necrosis factor (TNF)-α, IL-2, IL-6, and IL-10, but increased the secretion of CXCL8, CCL2, CCL4, and CCL11. In conclusion, our results suggest that the insulinotropic effect of GIP is CaMK2-dependent. Furthermore, our results indicate that GIP does not provide substantial cytoprotective effects against diabetogenic cytokine challenge or significantly modulate the transcriptome of human islets when applied at a supraphysiological level. GIP may, however, still exert selective inflammation-modulatory effects upon diabetogenic cytokine exposure.

Project description:Purpose: In the early phases of T1D development exposure of β-cells to IFNγ, IL-1β, and TNFα is thought to induce β-cell dysfunction and the expression of chemokines and cytokines. These changes are mediated in part by post-translational histone modifications within cis-regulatory regions. The purpose of this study was to determine if prevention of these epigenetic changes can alter cytokine induced gene expression changes. Methods: Pancreatic islets were isolated from both male and female CD1 mice by collagenase digestion and were picked by hand. Hand-picked islets were cultured for four days with 1.6ng/ml IFNγ, 0.25ng/ml IL-1β and 0.16ng/ml TNFα (cytokine) or were left untreated (nocytokine). For RNA-seq islets were collected and processed for NGS using the Illumina TruSeq library prep kit. Chromatin immunoprecipitation (ChIP) was performed using 3μg of anti-H3K4me1 (Abcam) with islets from at least 10 adult ICR mice (8-10 weeks old) exposed to 1.6ng/ml IFNγ, 0.25ng/ml Il-1β and 0.16ng/ml TNFα for four days. DNA from 4 separate ChIP experiments was pooled for library construction and sequencing using the Illumina platform. Results: Comparison of gene expression levels between untreated and cytokine-treated islets resulted in the identification of 205 genes that showed an IFNγ, Il-1β, and TNFα-induced chromatin state change (from repressed or inactive to H3K4me1 enriched, i.e. the de novo regions), or increased H3K4me1 enrichment, that were associated with genes with up-regulated expression in response to IFNγ, Il-1β, and TNFα, and 111 genes with reduced H3K4me1 and down-regulated expression in response to IFNγ, Il-1β, and TNFα. Conclusions: Our study confirms that exposure of islets to pro-inflammatory cytokines induces the expression of chemokines and that these changes are the result of a switch from an inactive to an active chromatin state. Further we show that disruption of the trithorax group complex inhibits the upregulation of pro-inflammatory gene expression.

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Gene expression changes in rat islets with glucolipotoxic conditions with or without protective compound

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