title: Mechanism of rapid-phase insulin response to elevation of portal glucose concentration.
abstract: The hepatoportal region is important for glucose sensing; however, the relationship between the hepatoportal glucose-sensing system and the postprandial rapid phase of the insulin response has been unclear. We examined whether a rapid-phase insulin response to low amounts of intraportal glucose infusion would occur, compared that with the response to intrajugular glucose infusion in conscious rats, and assessed whether this sensing system was associated with autonomic nerve activity. The increases in plasma glucose concentration did not differ between the two infusions at 3 min, but the rapid-phase insulin response was detected only in the intraportal infusion. A sharp and rapid insulin response was observed at 3 min after intraportal infusion of a small amount of glucose but not after intrajugular infusion. Furthermore, this insulin response was also induced by intraportal fructose infusion but not by nonmetabolizable sugars. The rapid-phase insulin response at 3 min during intraportal infusion did not differ between rats that had undergone hepatic vagotomy or chemical sympathectomy with 6-hydroxydopamine compared with control rats, but this response disappeared in rats that had undergone chemical vagotomy with atropine. We conclude that the elevation of glucose concentration in the hepatoportal region induced afferent signals from undetectable sensors and that these signals stimulate pancreas to induce the rapid-phase insulin response via cholinergic nerve action.
authors.affiliation: Department of Clinical Nutrition, University of Tokushima School of Medicine, Tokushima, Japan. fukayan@nutr.med.tokushima-u.ac.jp
authors.forename: Makiko
authors.initials: M
authors.lastname: Fukaya
authors.forename: Akira
authors.initials: A
authors.lastname: Mizuno
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Arai
authors.forename: Kazusa
authors.initials: K
authors.lastname: Muto
authors.forename: Takashi
authors.initials: T
authors.lastname: Uebanso
authors.forename: Kaoru
authors.initials: K
authors.lastname: Matsuo
authors.forename: Hironori
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Taketani
authors.forename: Toshio
authors.initials: T
authors.lastname: Doi
authors.forename: Eiji
authors.initials: E
authors.lastname: Takeda
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis* / Q000187:drug effects; D005632:Fructose / Q000008:administration & dosage; D005947:Glucose / Q000008:administration & dosage; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D007601:Jugular Veins / Q000502:physiology; D008297:Male; D008358:Mannose / Q000008:administration & dosage; D011169:Portal Vein / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013563:Sympathectomy, Chemical; D013997:Time Factors; D014628:Vagotomy
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005632:Fructose; D005947:Glucose; D008358:Mannose