Effects Of Different Starch Levels On Glucose And Lipid Metabolism Of Lateolabrax Maculatus And Acipenser Schrenckii

Carbohydrates are wide and the least cost feed source.Under the background that the global fishmeal resources are very limited and the price of fishmeal continues to rise,the utilization of carbohydrates to replace part of the dietary protein has always been one of the directions explored by aquaculture.Spotted seabass(Lateolabrax maculatus)and Amur sturgeon(Acipenser schrenckii)are both important economic fishes in China.Both of them belong to carnivorous fishes fed with high trophic levels,but their taxonomic status is quite different.At present,there are few studies on the utilization ability of higher carbohydrate in spotted seabass and Amur sturgeon.This article comparatively reported that the effects of high-starch diets on growth performance and glucose and lipid metabolism of spotted seabass and Amur sturgeon during long-term feeding and short-term starvation.Two diets with isonitrogenous and isoenergetic were prepared.A basal diet contained 13.0% starch(LS)and the other experimental diet contained 20.2% starch(HS).Two diets with equal protein-to-energy ratios were prepared.A basal diet contained 43.0% protein and 11.5% starch(HPLC)and the other experimental diet contained 38.9% protein and 23.6% starch(LPHC).Spotted seabass(initial body weight = 10.43 ± 0.01 g)and Amur sturgeon(initial body weight = 69.99 ± 0.01 g)were randomly selected and transferred to 5 tanks per treatment respectively for 8 w long-term feeding(8 w)and 1 w short-term starvation(S1 w)growth trial.Experiment 1: Effects of different starch levels on growth performance and glucose and lipid metabolism of spotted seabass(Lateolabrax maculatus)The 20.2% starch levels diet did not negatively affect growth of spotted seabass.A well-regulated glucose metabolism response was observed with significant downregulation of gluconeogenesis(g6p)and upregulation of glycolysis(pk)in the HS group at 3 h postprandial(8 w P3 h)and downregulation of glycolysis(gk and pfk-1)at the transcription level at 24 h postprandial(8 w P24 h).However,hyperglycemic was still observed in the HS group with upregulation of gluconeogenesis(G6P)pathway and upregulation of glycolytic(PK)at 24 h postprandial(8 w P24 h),indicating that the fish could not effectively regulate glycolytic under starvation conditions(8 w P24 h).Excessive starch intake signif icantly increased hepatic c AMP content,which enhanced the rate of basal metabolism to relieve hyperglycemia and avoid glycogen accumulation.The lipogenesis(acc1 and fasn)was effectively inhibited to avoid fatty liver after fed HS diet.The β-oxidation(cpt1α and pparα)was downregulated in the HS group at 8 w P24 h.In the initial starvation,hepatic glycogen was decomposed to satisfy energetic requirements.After 1 week starvation,lipolys is(atgl)was upregulated and hepatic lipid was decomposed to satisfy energetic requirements to protect whole-body protein from excessive consumption.Experiment 2: Effects of different protein and starch levels on growth performance and glucose and lipid metabolism of Amur sturgeon(Acipenser schrenckii)The 38.9% protein and 23.6% starch levels diet did not negatively affect growth of Amur sturgeon.A well-regulated glucose metabolism response was observed that signif icant upregulation of glycolysis(gk and pk)after fed LPHC diet at 8 w P24 h and upregulation of gluconeogenesis(pepck and g6p)during S1 w phase to maintain normal plasma glucose levels.In addition,chrebp activated by high-starch intake induced excess glucose conversion to TG in the liver,which led to downregulation of lipogenes is(acc1 and fasn)and upregulation of lipolysis/β-oxidation(HSL,cpt1α,and pparα)to prevent excessive fat accumulation after fed LPHC diet during long-term feeding phase.Hepatic glycogen and lipid(HS L and pparα)were effectively catabolism to satisfy energetic requirements in the LPHC group during S1 w phase,thereby promoting whole-body protein deposition.Experiment 3: Comparative study on the effects of different starch levels on spotted seabass(Lateolabrax maculatus)and Amur sturgeon(Acipenser schrenckii)A comparative study showed that two diets with different starch levels(13.0-20.2%)(11.5%-23.6%)had no signif icant effect on the growth performance of spotted seabass and Amur sturgeon during longterm feeding.During starvation phases,hepatic glycogen contents of spotted seabass and Amur sturgeon decreased significantly,and whole-body lipid and protein contents did not change signif icantly.Both fish decomposed hepatic glycogen for energy supply to prevent excessive decomposition of whole-body lipid and protein to fight with long-term starvation.38.9% protein and 23.6% starch levels diet intake accelerated glycolysis(GK and PK)and upregulated gluconeogenesis(PEPCK and G6P)of Amur sturgeon under starvation condition to maintain blood glucose homeostasis.However,hyperglycemic was observed with upregulation of gluconeogenesis(G6P)and upregulation of glycolytic(PK)in spotted seabass after fed 20.2% starch levels diet,indicating that it could not effectively regulate glycolytic in 8 w P24 h.Excess starch intake inhibited lipogenesis(acc1 and fasn)of spotted seabass and Amur sturgeon to prevent fat accumulation.During initial starvation phase,glycogenolysis(pygl)was upregulated and lipid β-oxidation was downregulated to preferentially catabolize hepatic glycogen to provide energy.During later starvation phase,hepatic lipolys is(atgl)was accelerated to provide energy in spotted seabass.Hepatic lipid and glycogen were decomposed mainly for energy supply in Amur sturgeon under initial starvation conditions,and hepatic lipolys is(hsl)was accelerated to satisfy energetic requirements under later starvation conditions.