title: Leptin inhibits glycogen catabolism but does not modify acutely the suppressive effect of insulin on glucose production and glycogenolysis stimulated by 8-Br-cAMP in rat liver perfused in situ.
abstract: Leptin, a hormone secreted by the adipocytes, plays a central role in glucose metabolism and the action of insulin. Here we assessed, by means of rat-liver perfusion, the direct influence of physiological (10 ng/ml) and supraphysiological (50 or 100 ng/ml) concentrations of leptin on the suppressive effect of insulin on the glucose production and glycogenolysis stimulated by 8-bromoadenosine-3':5'-monophosphate (8-Br-cAMP). Portal infusion of insulin (20 microU/ml) or leptin (10 ng/ml) reduced (p<0.05) the glucose production and glycogenolysis induced by 8-Br-cAMP (0.3 microM). However, portal infusion of physiological (10 ng/ml) and supraphysiological (50 or 100 ng/ml) concentrations of leptin together with the insulin did not modify the suppressive effect of the latter on the glucose production and glycogenolysis stimulated by 8-Br-cAMP. Moreover, prolonging the period of leptin infusion from 20 to 40 min also failed to influence the liver response to insulin. Thus, we conclude that: (a) leptin, at physiological levels, has a direct and acute effect, inhibiting the glucose production and glycogenolysis stimulated by 8-Br-cAMP; (b) leptin, at either physiological or supraphysiological concentrations, has no short-term influence on the suppressive effect of insulin on glycogen catabolism stimulated by 8-Br-cAMP.
authors.affiliation: Department of Physiological Sciences, State University of Londrina, 86051-990 Londrina, PR, Brazil.
authors.forename: Eledir Silveira
authors.initials: ES
authors.lastname: Leonardo
authors.forename: Bruna Kempfer
authors.initials: BK
authors.lastname: Bassoli
authors.forename: Priscila
authors.initials: P
authors.lastname: Cassolla
authors.forename: Glaucia Regina
authors.initials: GR
authors.lastname: Borba-Murad
authors.forename: Roberto Barbosa
authors.initials: RB
authors.lastname: Bazotte
authors.forename: Helenir Medri
authors.initials: HM
authors.lastname: De Souza
mesh_terms: D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D005947:Glucose / Q000096:biosynthesis*; D050261:Glycogenolysis / Q000187:drug effects*; D007328:Insulin / Q000494:pharmacology*; D020738:Leptin / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008112:Liver Glycogen / Q000378:metabolism*; D008297:Male; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar
chemical_list: D007328:Insulin; D020738:Leptin; D008112:Liver Glycogen; C016276:8-bromocyclic GMP; D006152:Cyclic GMP; D005947:Glucose