REGULATION OF HEPATIC LIPOGENESIS BY DIETARY PROTEIN ENERGY IN JUVENILE EUROPEAN SEA-BASS (DICENTRARCHUS-LABRAX)/

A growth trial was conducted with groups of European seabass having an initial weight of 6 g to study the lipogenic action of dietary protei n and non-protein energy supplies. Six experimental diets were formula ted to contain one of two crude protein levels (43 and 52%) with diges tible protein (DP) to digestible energy (DE) ratios ranging from 19 to 26 mg/kJ. At the end of the growth trial(12 weeks), the activities of liver glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49), malic en zyme (ME, EC 1.1.1.40), ATP citrate lyase (ACL, EC 4.1.3.8), acetyl-Co A carboxylase (ACoAC, EC 6.4.1.2) and fatty acid synthetase (FAS, EC 2 .3.1.38) were measured. Digestibility of main dietary components was a lso determined over a three-week period. At each protein level, an inc rease in dietary DE led to improved growth performance, protein effici ency, daily N deposition and to a reduction of N loss. Best results we re achieved at 40% DP and a DP/DE ratio of 19-20 mg/kJ. G6PD, ME and A CoAC were found to be the key regulatory enzymes in the lipogenic path way, with G6PD being the main NADPH-generating enzyme. Activities of G 6PD, ME, ACL and FAS were reduced with increasing fat intake. Activiti es of G6PD, ME and ACL were increased with increasing starch intake. A CoAC activity was negatively correlated with starch intake and positiv ely with fat intake. (C) 1998 Elsevier Science B.V.