title: Expressional regulation of key hepatic enzymes of intermediary metabolism in European seabass (Dicentrarchus labrax) during food deprivation and refeeding.
abstract: We hypothesized that the analysis of mRNA level and activity of key enzymes in amino acid and carbohydrate metabolism in a feeding/fasting/refeeding setting could improve our understanding of how a carnivorous fish, like the European seabass (Dicentrarchus labrax), responds to changes in dietary intake at the hepatic level. To this end cDNA fragments encoding genes for cytosolic and mitochondrial alanine aminotransferase (cALT; mALT), pyruvate kinase (PK), glucose 6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) were cloned and sequenced. Measurement of mRNA levels through quantitative real-time PCR performed in livers of fasted seabass revealed a significant increase in cALT (8.5-fold induction) while promoting a drastic 45-fold down-regulation of PK in relation to the levels found in fed seabass. These observations were corroborated by enzyme activity meaning that during food deprivation an increase in the capacity of pyruvate generation happened via alanine to offset the reduction in pyruvate derived via glycolysis. After a 3-day refeeding period cALT returned to control levels while PK was not able to rebound. No alterations were detected in the expression levels of G6PDH while 6PGDH was revealed to be more sensitive specially to fasting, as confirmed by a significant 5.7-fold decrease in mRNA levels with no recovery after refeeding. Our results indicate that in early stages of refeeding, the liver prioritized the restoration of systemic normoglycemia and replenishment of hepatic glycogen. In a later stage, once regular feeding is re-established, dietary fuel may then be channeled to glycolysis and de novo lipogenesis.
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal; CFE - Center for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martins de Freitas 3000-456 Coimbra, Portugal. Electronic address: iviegas@ci.uc.pt.
authors.forename: Ivan
authors.initials: I
authors.lastname: Viegas
authors.affiliation: Departament d'Ecologia, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain.
authors.forename: Albert
authors.initials: A
authors.lastname: Caballero-Solares
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal; CFE - Center for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martins de Freitas 3000-456 Coimbra, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Rito
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Spain.
authors.forename: Marina
authors.initials: M
authors.lastname: Giralt
authors.affiliation: CFE - Center for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martins de Freitas 3000-456 Coimbra, 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, Av. Joan XXIII s/n, 08028 Barcelona, Spain.
authors.forename: Isidoro
authors.initials: I
authors.lastname: Metón
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal.
authors.forename: John G
authors.initials: JG
authors.lastname: Jones
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Spain.
authors.forename: Isabel V
authors.initials: IV
authors.lastname: Baanante
mesh_terms: D000818:Animals; D017756:Aquaculture; D001492:Bass / Q000502:physiology*; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D004435:Eating / Q000502:physiology*; D005215:Fasting / Q000502:physiology*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D050155:Lipogenesis; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D008930:Mitochondria, Liver / Q000201:enzymology / Q000378:metabolism; D010427:Pentose Phosphate Pathway; D011174:Portugal; D012333:RNA, Messenger / Q000378:metabolism; D064210:Secondary Metabolism
chemical_list: D029941:Fish Proteins; D012333:RNA, Messenger
keywords: Alanine aminotransferase; Dicentrarchus labrax; Food deprivation; Lipogenesis; Pentose phosphate pathway; Pyruvate kinase; Refeeding