title: Contribution of dietary starch to hepatic and systemic carbohydrate fluxes in European seabass (Dicentrarchus labrax L.).
abstract: In the present study, the effects of partial substitution of dietary protein by digestible starch on endogenous glucose production were evaluated in European seabass (Dicentrarchus labrax). The fractional contribution of dietary carbohydrates v. gluconeogenesis to blood glucose appearance and hepatic glycogen synthesis was quantified in two groups of seabass fed with a diet containing 30% digestible starch (DS) or without a carbohydrate supplement as the control (CTRL). Measurements were performed by transferring the fish to a tank containing water enriched with 5% (2)H2O over the last six feeding days, and quantifying the incorporation of (2)H into blood glucose and hepatic glycogen by (2)H NMR. For CTRL fish, gluconeogenesis accounted for the majority of circulating glucose while for the DS fish, this contribution was significantly lower (CTRL 85 (SEM 4) % v. DS 54 (SEM 2) %; P < 0.001). Hepatic glycogen synthesis via gluconeogenesis (indirect pathway) was also significantly reduced in the DS fish, in both relative (CTRL 100 (SEM 1) % v. DS 72 (SEM 1) %; P < 0.001) and absolute terms (CTRL 28 (SEM 1) v. DS 17 (sem 1) μmol/kg per h; P < 0.001). A major fraction of the dietary carbohydrates that contributed to blood glucose appearance (33 (sem 1) % of the total 47 (SEM 2) %) had undergone exchange with hepatic glucose 6-phosphate. This indicated the simultaneous activity of hepatic glucokinase and glucose 6-phosphatase. In conclusion, supplementation of digestible starch resulted in a significant reduction of gluconeogenic contributions to systemic glucose appearance and hepatic glycogen synthesis.
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal,3004-517Coimbra,Portugal.
authors.forename: Ivan
authors.identifier: http://orcid.org/0000-0003-2589-2212
authors.initials: I
authors.lastname: Viegas
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal,3004-517Coimbra,Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Rito
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal,3004-517Coimbra,Portugal.
authors.forename: Ivana
authors.initials: I
authors.lastname: Jarak
authors.affiliation: CFE - Center for Functional Ecology, Department Life Sciences, University of Coimbra, Calçada Martins de Freitas,3000-456Coimbra,Portugal.
authors.forename: Sara
authors.initials: S
authors.lastname: Leston
authors.affiliation: Departament d'Ecologia,Facultat de Biologia, Universitat de Barcelona,Avenida Diagonal 645,08028Barcelona,Spain.
authors.forename: Albert
authors.initials: A
authors.lastname: Caballero-Solares
authors.affiliation: Departament de Bioquímica i Biologia Molecular,Facultat de Farmàcia, Universitat de Barcelona, Joan XXIII s/n,08028Barcelona,Spain.
authors.forename: Isidoro
authors.initials: I
authors.lastname: Metón
authors.affiliation: CFE - Center for Functional Ecology, Department Life Sciences, University of Coimbra, Calçada Martins de Freitas,3000-456Coimbra,Portugal.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Pardal
authors.affiliation: Departament de Bioquímica i Biologia Molecular,Facultat de Farmàcia, Universitat de Barcelona, Joan XXIII s/n,08028Barcelona,Spain.
authors.forename: Isabel V
authors.initials: IV
authors.lastname: Baanante
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal,3004-517Coimbra,Portugal.
authors.forename: John G
authors.initials: JG
authors.lastname: Jones
mesh_terms: D000818:Animals; D001492:Bass / Q000254:growth & development / Q000378:metabolism*; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism; D003903:Deuterium; D017666:Deuterium Oxide; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism*; D015870:Gene Expression; D005941:Glucokinase / Q000235:genetics / Q000378:metabolism; D005943:Gluconeogenesis; D005952:Glucose-6-Phosphatase / Q000235:genetics / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008112:Liver Glycogen / Q000096:biosynthesis; D012333:RNA, Messenger / Q000032:analysis; D013213:Starch / Q000008:administration & dosage*
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D008112:Liver Glycogen; D012333:RNA, Messenger; D019298:Glucose-6-Phosphate; D013213:Starch; D003903:Deuterium; D005941:Glucokinase; D005952:Glucose-6-Phosphatase; D017666:Deuterium Oxide
keywords:       2H2O; Endogenous glucose production; Glucokinase; Gluconeogenesis; Starch utilisation