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Short food deprivation inhibits orexin receptor 1 expression and orexin-A induced intracellular calcium signaling in acutely isolated duodenal enterocytes
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
Oulu University, Finland.
Oulu University, Finland.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
2009 (English)In: American Journal of Physiology - Gastrointestinal and Liver Physiology, ISSN 0193-1857, E-ISSN 1522-1547, Vol. 296, no 3, G651-G658 p.Article in journal (Refereed) Published
Abstract [en]

Bengtsson MW, Makela K, Herzig KH, Flemstrom G. Short food deprivation   inhibits orexin receptor 1 expression and orexin-A induced   intracellular calcium signaling in acutely isolated duodenal   enterocytes. Am J Physiol Gastrointest Liver Physiol 296: G651-G658,   2009. First published December 31, 2008;   doi:10.1152/ajpgi.90387.2008.-Close intra-arterial infusion of the   appetite regulating peptide orexin-A stimulates bicarbonate secretion   from the duodenal mucosa. The aim of the present study was to elucidate   the ability of orexin-A to induce intracellular calcium signaling in   acutely isolated duodenal enterocytes. Freshly isolated clusters of   enterocytes, obtained from rat duodenal mucosa or human duodenal   biopsies, were loaded with fura 2-AM and mounted in a perfusion   chamber. Cryptlike enterocytes were selected (caged), and changes in   intracellular calcium concentration ([Ca2+](i)) were evaluated by   fluorescence imaging. Total RNA was extracted from pellets of   enterocytes and reverse transcribed to cDNA, and expression of orexin   receptors 1 and 2 (OX1R and OX2R) was measured by quantitative   real-time PCR. Orexin-A at all concentrations tested (1-100 nM)   increased [Ca2+](i) in enterocytes isolated from continuously fed rats,   and the OX1R-antagonist SB-334867 (10 nM) attenuated the response. The   primary [Ca2+](i) response was a slow increase to a sustained plateau   persisting after orexin-A removal, and a similar response was observed   in enterocytes from human biopsies. In contrast to orexin-A, the OX2R   agonist (Ala(11), D-Leu(15))orexin-B (1-10 nM) did not induce calcium   signaling. There were no significant [Ca2+](i) responses in enterocytes   from animals food deprived overnight, and overnight fasting decreased   (P < 0.01) enterocyte OX1R as well as OX2R mRNA. Induction of   intracellular calcium signaling in isolated duodenal enterocytes is   thus mediated primarily by OX1R receptors. Short (overnight) food   deprivation markedly depresses receptor expression and inhibits   orexin-A induced increases in [Ca2+](i). Studies of enterocyte   signaling and intestinal secretion requires particular evaluation   regarding feeding status.

Place, publisher, year, edition, pages
2009. Vol. 296, no 3, G651-G658 p.
Keyword [en]
(Ala(11), D-Leu(15))-orexin-B, bicarbonate secretion, fasting, feeding, SB-334867
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-97104DOI: 10.1152/ajpgi.90387.2008ISI: 000263900800022PubMedID: 19118115OAI: oai:DiVA.org:uu-97104DiVA: diva2:171899
Available from: 2009-04-02 Created: 2008-05-15 Last updated: 2010-08-25Bibliographically approved
In thesis
1. Effects of Orexins, Guanylins and Feeding on Duodenal Bicarbonate Secretion and Enterocyte Intracellular Signaling
Open this publication in new window or tab >>Effects of Orexins, Guanylins and Feeding on Duodenal Bicarbonate Secretion and Enterocyte Intracellular Signaling
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The duodenal epithelium secretes bicarbonate ions and this is regarded as the primary defence mechanism against the acid discharged from the stomach. For an efficient protection, the duodenum must also function as a sensory organ identifying luminal factors. Enteroendocrine cells are well-established intestinal “taste” cells that express signaling peptides such as orexins and guanylins. Luminal factors affect the release of these peptides, which may modulate the activity of nearby epithelial and neural cells.

The present thesis considers the effects of orexins and guanylins on duodenal bicarbonate secretion. The duodenal secretory response to the peptides was examined in anaesthetised rats in situ and the effects of orexin-A on intracellular calcium signaling by human as well as rat duodenal enterocytes were studied in vitro.

Orexin-A, guanylin and uroguanylin were all stimulants of bicarbonate secretion. The stimulatory effect of orexin-A was inhibited by the OX1-receptor selective antagonist SB-334867. The muscarinic antagonist atropine on the other hand, did not affect the orexin-A-induced secretion, excluding involvement of muscarinic receptors. Orexin-A induced calcium signaling in isolated duodenocytes suggesting a direct effect at these cells. Interestingly, orexin-induced secretion and calcium signaling as well as mucosal orexin-receptor mRNA and OX1-receptor protein levels were all substantially downregulated in overnight fasted rats compared with animals with continuous access to food. Further, secretion induced by Orexin-A was shown to be dependent on an extended period of glucose priming.

The uroguanylin-induced bicarbonate secretion was reduced by atropine suggesting involvement of muscarinic receptors. The melatonin receptor antagonist luzindole attenuated the secretory response to intra-arterially administered guanylins but had no effect on secretion when the guanylins were given luminally.

In conclusion, the results suggest that orexin-A as well as guanylins may participate in the regulation of duodenal bicarbonate secretion. Further, the duodenal orexin system is dependent on the feeding status of the animals.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 70 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 337
Physiology, alkaline secretion, carbohydrates, central nervous system, cholinergic stimulation, duodenum, enteric nervous system, enterochromaffin cell, fasting, feeding, glucose, guanylyl cyclase C, humans, hypocretin, intra-arterial, in situ, intracerebroventricular, luminal acid, luzindole, orexin-B, SB-334867, Fysiologi
urn:nbn:se:uu:diva-8664 (URN)978-91-554-7173-6 (ISBN)
Public defence
2008-05-15, B21, Uppsala Biomedicinska Centrum (BMC), Norra vägen, Uppsala, 13:15
Available from: 2008-04-23 Created: 2008-04-23Bibliographically approved

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