ABSTRACT
GLP-1 and its analog have been used in diabetes treatment; however, the direct alteration of gene expression profile in human islets induced by GLP-1 has not been reported. In present study, transcriptional gene expression in the liraglutide-treated human islets was analyzed with 12 human U133A chips including 23000 probe sets. The data compared between liraglutide and control groups showed a significant difference on glucose-induced insulin secretion, rather than viability. Microarray analysis identified 7000 genes expressed in human islets. Eighty genes were found to be modulated by liraglutide treatment. Furthermore, the products of these genes are proteins involved in binding capability, enzyme activity, transporter function, signal transduction, cell proliferation, apoptosis, and cell differentiation. Our data provides a set of information in the complex events, following the activation of the GLP-1 receptor in the islets of Langerhans.
ABSTRACT
OBJECTIVES: That glucagonlike peptide-1 (GLP-1) induces differentiation of primate embryonic stem (ES) cells into insulin-producing cells has been reported by several groups and also confirmed with our observations. METHODS: To further elucidate the process in detail and the signaling pathways involved in this differentiation, we induced human ES cells HUES1 differentiated into insulin secretion cells by GLP-1 treatment. RESULTS: A time-dependent pattern of down expression of the stem cell markers (human telomerase reverse transcriptase and octamer-4), and the appearance of multiple beta-cell-specific proteins (insulin, glucokinase, glucose transporter, type 2, and islet duodenal homeobox 1) and hedgehog signal molecules (Indian hedgehog, sonic hedgehog, and hedgehog receptor, patched) have been identified. Cotreatment with hedgehog signal inhibitor cytopamine was able to block this differentiation, providing evidence of the involvement of the hedgehog signaling pathway in GLP-1-induced differentiation. We also observed increased transcripts of the transcription factors of activator protein 1, serum response element-1, DNA-binding transcription factors, and cAMP response element in GLP-1-induced ES cell differentiation. Inhibition profile by its specific inhibitors indicated that the cyclic adenosine monophosphate and phosphatidylinositol-3-kinase pathways, but not the mitogen-activated protein kinase pathway, were required for the induced differentiation of ES cells. CONCLUSIONS: These data support that GLP-1 directs human ES cell differentiation into insulin-producing cells via hedgehog, cyclic adenosine monophosphate, and phosphatidylinositol-3-kinase pathways.
