title: Hepatic glycogen synthesis in farmed European seabass (Dicentrarchus labrax L.) is dominated by indirect pathway fluxes.
abstract: Hepatic glycogen synthesis fluxes from direct and indirect pathways were quantified in seabass by postmortem (2)H NMR analysis of plasma water (PW) and glycogen glucosyl (2)H enrichments from (2)H-enriched seawater. Eighteen fish (28.0 ± 1.7 cm and 218.0 ± 43.0 g) were divided into three groups of 6 and studied over 24 days with transfer to 5% (2)H-seawater after day 21. Over this period, one group was fed daily with fishmeal, a second group was fasted, and a third group was fasted for 21 days followed by 3 days refeeding. Glycogen turnover and sources were determined from the ratio of glucosyl position 5 enrichment to that of plasma water (H5/PW). Glycogen levels of fed fish were significantly higher than fasted (665.4 ± 345.2 μmol.g(-1) liver versus 77.2 ± 59.5 μmol.g(-1) liver, P<0.05) while refed fish had comparable levels to fed (584.6 ± 140.4 μmol.g(-1) liver). Glycogen enrichment of fed fish was undetectable indicating negligible turnover over 3 days. For fasted fish, H5/PW was ~50% indicating that half of the glycogen had turned over via indirect pathway flux. For refed fish, H5/PW was ~100% indicating that the indirect pathway accounted for all net glycogen synthesis. Direct pathway conversion of dietary carbohydrate to glycogen was not detected in any of the groups.
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal.
authors.forename: Ivan
authors.initials: I
authors.lastname: Viegas
authors.forename: João
authors.initials: J
authors.lastname: Rito
authors.forename: Ivana
authors.initials: I
authors.lastname: Jarak
authors.forename: Sara
authors.initials: S
authors.lastname: Leston
authors.forename: Rui A
authors.initials: RA
authors.lastname: Carvalho
authors.forename: Isidoro
authors.initials: I
authors.lastname: Metón
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Pardal
authors.forename: Isabel V
authors.initials: IV
authors.lastname: Baanante
authors.forename: John G
authors.initials: JG
authors.lastname: Jones
mesh_terms: D000818:Animals; D001492:Bass / Q000378:metabolism*; D005060:Europe; D006003:Glycogen / Q000096:biosynthesis* / Q000097:blood; D008099:Liver / Q000378:metabolism*; D053858:Metabolic Networks and Pathways
chemical_list: D006003:Glycogen