| 1. |
- Lund, Mari L., et al.
(author)
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Enterochromaffin 5-HT cells : A major target for GLP-1 and gut microbial metabolites
- 2018
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In: MOLECULAR METABOLISM. - : Elsevier. - 2212-8778. ; 11, s. 70-83
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Journal article (peer-reviewed)abstract
- Objectives5-HT storing enterochromaffin (EC) cells are believed to respond to nutrient and gut microbial components, and 5-HT receptor-expressing afferent vagal neurons have been described to be the major sensors of nutrients in the GI-tract. However, the molecular mechanism through which EC cells sense nutrients and gut microbiota is still unclear.Methods and resultsTPH1, the 5-HT generating enzyme, and chromogranin A, an acidic protein responsible for secretory granule storage of 5-HT, were highly enriched in FACS-purified EC cells from both small intestine and colon using a 5-HT antibody-based method. Surprisingly, EC cells from the small intestine did not express GPCRsensors for lipid and protein metabolites, such as FFAR1, GPR119, GPBAR1(TGR5), CaSR, and GPR142, in contrast to the neighboring GLP-1 storing enteroendocrine cell. However, the GLP-1 receptor was particularly highly expressed and enriched in EC cells as judged both by qPCR and by immunohistochemistryusing a receptor antibody. GLP-1 receptor agonists robustly stimulated 5-HT secretion from intestinal preparations using both HPLC and a specific amperometricmethod. Colonic EC cells expressed many different types of known and potential GPCR sensors of microbial metabolites including three receptors for SCFAs, i.e. FFAR2, OLF78, and OLF558 and receptors for aromatic acids, GPR35; secondary bile acids GPBAR1; and acyl-amides and lactate, GPR132.ConclusionNutrient metabolites apparently do not stimulate EC cells of the small intestine directly but through a paracrine mechanism involving GLP-1 secreted from neighboring enteroendocrine cells. In contrast, colonic EC cells are able to sense a multitude of different metabolites generated by the gut microbiota as well as gut hormones, including GLP-1.
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| 2. |
- Egerod, Kristoffer L, et al.
(author)
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A Major Lineage of Enteroendocrine Cells Coexpress CCK, Secretin, GIP, GLP-1, PYY, and Neurotensin but Not Somatostatin.
- 2012
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In: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170.
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Journal article (peer-reviewed)abstract
- Enteroendocrine cells such as duodenal cholecystokinin (CCK cells) are generally thought to be confined to certain segments of the gastrointestinal (GI) tract and to store and release peptides derived from only a single peptide precursor. In the current study, however, transgenic mice expressing enhanced green fluorescent protein (eGFP) under the control of the CCK promoter demonstrated a distribution pattern of CCK-eGFP positive cells that extended throughout the intestine. Quantitative PCR and liquid chromatography-mass spectrometry proteomic analyses of isolated, FACS-purified CCK-eGFP-positive cells demonstrated expression of not only CCK but also glucagon-like peptide 1 (GLP-1), gastric inhibitory peptide (GIP), peptide YY (PYY), neurotensin, and secretin, but not somatostatin. Immunohistochemistry confirmed this expression pattern. The broad coexpression phenomenon was observed both in crypts and villi as demonstrated by immunohistochemistry and FACS analysis of separated cell populations. Single-cell quantitative PCR indicated that approximately half of the duodenal CCK-eGFP cells express one peptide precursor in addition to CCK, whereas an additional smaller fraction expresses two peptide precursors in addition to CCK. The coexpression pattern was further confirmed through a cell ablation study based on expression of the human diphtheria toxin receptor under the control of the proglucagon promoter, in which activation of the receptor resulted in a marked reduction not only in GLP-1 cells, but also PYY, neurotensin, GIP, CCK, and secretin cells, whereas somatostatin cells were spared. Key elements of the coexpression pattern were confirmed by immunohistochemical double staining in human small intestine. It is concluded that a lineage of mature enteroendocrine cells have the ability to coexpress members of a group of functionally related peptides: CCK, secretin, GIP, GLP-1, PYY, and neurotensin, suggesting a potential therapeutic target for the treatment and prevention of diabetes and obesity.
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| 3. |
- Egerod, Kristoffer L., et al.
(author)
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beta-Cell Specific Overexpression of GPR39 Protects against Streptozotocin-Induced Hyperglycemia
- 2011
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In: International Journal of Endocrinology. - : Hindawi Limited. - 1687-8337 .- 1687-8345.
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Journal article (peer-reviewed)abstract
- Mice deficient in the zinc-sensor GPR39, which has been demonstrated to protect cells against endoplasmatic stress and cell death in vitro, display moderate glucose intolerance and impaired glucose-induced insulin secretion. Here, we use the Tet-On system under the control of the proinsulin promoter to selectively overexpress GPR39 in the beta cells in a double transgenic mouse strain and challenge them with multiple low doses of streptozotocin, which in the wild-type littermates leads to a gradual increase in nonfasting glucose levels and glucose intolerance observed during both food intake and OGTT. Although the overexpression of the constitutively active GPR39 receptor in animals not treated with streptozotocin appeared by itself to impair the glucose tolerance slightly and to decrease the beta-cell mass, it nevertheless totally protected against the gradual hyperglycemia in the steptozotocin-treated animals. It is concluded that GPR39 functions in a beta-cell protective manner and it is suggested that it is involved in some of the beneficial, beta-cell protective effects observed for Zn(++) and that GPR39 may be a target for antidiabetic drug intervention.
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| 4. |
- Holst, Birgitte, et al.
(author)
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G Protein-Coupled Receptor 39 Deficiency Is Associated with Pancreatic Islet Dysfunction
- 2009
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In: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 150, s. 2577-2585
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Journal article (peer-reviewed)abstract
- G protein-coupled receptor (GPR)-39 is a seven-transmembrane receptor expressed mainly in endocrine and metabolic tissues that acts as a Zn++ sensor signaling mainly through the G(q) and G(12/13) pathways. The expression of GPR39 is regulated by hepatocyte nuclear factor (HNF)-1 alpha and HNF-4 alpha, and in the present study, we addressed the importance of GPR39 for glucose homeostasis and pancreatic islets function. The expression and localization of GPR39 were characterized in the endocrine pancreas and pancreatic cell lines. Gpr39(-/-) mice were studied in vivo, especially in respect of glucose tolerance and insulin sensitivity, and in vitro in respect of islet architecture, gene expression, and insulin secretion. Gpr39 was down-regulated on differentiation of the pluripotent pancreatic cell line AR42J cells toward the exocrine phenotype but was along with Pdx-1 strongly up-regulated on differentiation toward the endocrine phenotype. Immunohistochemistry demonstrated that GRP39 is localized selectively in the insulin-storing cells of the pancreatic islets as well as in the duct cells of the exocrine pancreas. Gpr39(-/-) mice displayed normal insulin sensitivity but moderately impaired glucose tolerance both during oral and iv glucose tolerance tests, and Gpr39(-/-) mice had decreased plasma insulin response to oral glucose. Islet architecture was normal in the Gpr39 null mice, but expression of Pdx-1 and Hnf-1 alpha was reduced. Isolated, perifused islets from Gpr39 null mice secreted less insulin in response to glucose stimulation than islets from wild-type littermates. It is concluded that GPR39 is involved in the control of endocrine pancreatic function, and it is suggested that this receptor could be a novel potential target for the treatment of diabetes. (Endocrinology 150: 2577-2585, 2009)
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