Orexins control intestinal glucose transport by distinct neuronal, endocrine and direct epithelial pathways.: Orexins regulate intestinal glucose absorption

International audienceObjective : Orexins are neuropeptides involved in energy homeostasis. We investigated the effect of orexin A (OxA) and OxB on intestinal glucose transport in the rat. Research Design and Methods : Injection of orexins led to a decrease in the blood glucose level in OGTT. Effects of orexins on glucose entry were analysed in Ussing chamber using the Na+-dependent increase in short-circuit current to quantify jejunal glucose transport. Results & Conclusions : The rapid and marked increase in Isc induced by luminal glucose was inhibited by 10 nmol/l OxA or OxB (53 and 59% respectively). Response' curves to OxA and OxB were not significantly different with IC50 at 0.9 and 0.4 nmol/l, respectively. On the one hand, OxA-induced inhibition of Isc was reduced by the neuronal blocker TTX, and by a CCK2R antagonist, indicating involvement of neuronal and endocrine CCK-releasing cells. The OX1R antagonist SB334867 had no effect on OxA-induced inhibition, which is likely to occur via a neuronal and/or endocrine OX2R. On the other hand, SB334867 induced a significant right shift of the concentration-effect curve for OxB. This OxB-preferring OX1R pathway was not sensitive to TTX or to CCKR antagonists, suggesting that OxB may act directly on enterocytic OX1R. These distinct effects of OxA and OxB are consistent with the expression of OX1R and OX2R mRNA in the epithelial and non-epithelial tissues, respectively. Our data delineate a new function for orexins as inhibitors of intestinal glucose absorption and provide a new basis for orexin-induced short-term control of energy homeostasis