Comparative Study Of Carbohydrate And Lipid Metabolism Of Juvenile Golden Pompano (Trachinotus Ovatus) And Juvenile Largemouth Bass (Micropterus Salmoides)

Two kind of carnivorous fishes,juvenile golden pompano(Trachinotus ovatus)and juvenile largemouth bass(Micropterus salmoides)were selected as objiects of study.Golden pompano can be fed formula feed in the whole process of farming without any questions,even include the broodstocks.However,if largemouth bass were fed by formula feed will induce liver lesions and the liver become white.Juvenile golden pompano and juvenile largemouth bass were fed for 8 weeks,to investigate the nutritional physiology response for different levels of dietary carbohydrate and different sources of dietary lipid.The experiments for golden pompano were conducted in sea cages(1m×1m×1.5m),and largemouth bass were raised in indoor culture system(500 L/tank).Results of these studies are presented as follows:1.An 8-week feeding trial was conducted to evaluate the effect of different levels of dietary carbohydrate on carbohydrate metabolism of juvenile golden pompano(Trachinotus ovatu).Three isonitrogenous and isoenergetic diets(L,M,H)were formulated to contain three carbohydrate levels which were 101.1 g kg-1,211.0 g kg-1 and 313.0 g kg-1,respectively.Quadruplicate groups of 40 fish(initial weight 54.75±0.25g)were stocked in 16 sea cages(1.0m×1.0m×1.5 m),and were fed twice daily to apparent satiation for 8 weeks.The results indicated that growth performance and nutrition physiology related to carbohydrate metabolism were significantly influenced by the dietary carbohydrate levels.Fish fed diet M obtained significantly higher specific growth rate(SGR).Hepatic glycogen content,muscle glycogen content,and hepato-smatic index(HSI)increased significantly with dietary carbohydrate level increase(P?0.05).However,lipid content in liver and muscle showed the adverse variation trend.Serum cholesterol contents decreased with dietary carbohydrate increase,serum triglyceride and glucose contents increased significantly with dietary carbohydrate levels increase(P?0.05).High level of dietary carbohydrate notably reduced the serum glucagon concentration(P?0.05),however,the different levels of dietary carbohydrate had no influence on serum insulin-like growth factor-I(IGF-I)and insulin contents.Gene expressions of pentose phosphate pathway relative enzymes(Glucose 6-phosphate dehydrogenase(G6PDH)and 6-phosphaogluconate dehydrogenase(6PGDH))were not influenced by level of dietary carbohydrate.Gene expressions of glycolysis relative enzymes(hexokinase(HK)and glucokinase(GK))increased with dietary carbohydrate level increase(P?0.05),and genes expressions of gluconeogenesis relative enzymes showed negative relation with dietary carbohydrate levels(P?0.05).Gene expression of muscle glucose transporter 4(GLUT4)increased with dietary carbohydrate level increase(P?0.05).These results showed that golden pompano had the ability to utilize middle level of dietary carbohydrate.Meanwhile,nutritional physiology of golden pompano showed a positive changed to adapt the increasing of dietary carbohydrate level.2.An 8-week feeding trial was conducted to evaluate the effect of dietary carbohydrate levels on carbohydrate metabolism of juvenile largemouth bass(Micropterus salmoides).Three isonitrogenous and isoenergetic diets(L,M,H)were formulated to contain three carbohydrate levels which were 101.1 g kg-1,211.0 g kg-1 and 313.0 g kg-1,respectively.Quadruplicate groups of 40 fish(initial weight 33.9±1.18g)were stocked in 16 tanks(500L),and were fed twice daily to apparent satiation for 8 weeks.The results indicated that growth performance and nutrition physiology related to carbohydrate metabolism were significantly influenced by the dietary carbohydrate levels(P?0.05).Fish fed diet L obtained significantly higher specific growth rate(SGR).Hepatic glycogen content and hepato-smatic index(HSI)increased with dietary carbohydrate level increase(P?0.05).However,lipid content in liver and muscle showed the adverse variation trend.Serum cholesterol contents were not influenced by levels of dietary carbohydrate,serum triglyceride and glucose contents increased significantly with dietary carbohydrate levels increase(P?0.05).Serum glucagon and insulin-like growth factor-I(IGF-I)concentrations decreased with dietary carbohydrate level increase(P?0.05),however,the different levels of dietary carbohydrate had no influence on serum insulin contents.Gene expressions of pentose phosphate pathway relative enzymes(Glucose 6-phosphate dehydrogenase(G6PDH)and 6-phosphaogluconate dehydrogenase(6PGDH))increased with level of dietary carbohydrate increase(P?0.05).Hepatic G6 PDH activity also showed positive relationship with level of dietary carbohydrate.Gene expressions of glycolysis relative enzymes(hexokinase(HK),glucokinase(GK)and phosphofructokinase-1(PFK-1))increased with dietary carbohydrate level increase(P?0.05),however,the activities of hepatic HK,hepatic GK and muscle HK were not influenced by level of dietary carbohydrate.Gene expression and activity of phosphoenolpyruvate carboxykinase(PEPCK)showed no influence by levels dietary carbohydrate.Gene expression of glucose-6-phosphatase(G6Pase)decreased firstly with dietary carbohydrate level increase and then increased when level of dietary carbohydrate still increase(P?0.05).Gene expressions of hormone receptors were also influenced by level of dietary carbohydrate(P?0.05).However,the above gene expression showed an abnormal variation trend in fish fed diet H.These results mean that largemouth bass showed a positive changed to adapt the increasing of dietary carbohydrate level from L to M,however,largemouth bass showed disturbance of carbohydrate metabolism when fed diet H.3.Juvenile golden pompano(Trachinotus ovatus)(54.75±0.25g)were fed diets containing three different lipid sources: fish oil(FO),soybean oil(SO),and lard oil(LO).Fish were reared in sea cages(1m×1m×1.5m)for 8 weeks and the fish fed FO diet had significantly higher specific growth rate(SGR)but lower condition factor(CF)than the other treatments(P?0.05).Fatty acid(FA)composition of whole body lipid was closely correlated with those in the diets.Despite no differences in hepatic fatty acid synthase(FAS)activity,the carnitine palmitoyl transterase-I(CPT-I)activity in fish fed FO diet was significantly higher than that in other treatments(P?0.05).The relative genes expressions of lipid metabolism related enzymes(CPT-I,FAS,apolipoprotein B100(aproB100),delt-6 fatty acyl desaturase(?6 Fad)and fatty acid-binding protein-1(FABP-1))were also influenced by different sources of dietary lipid(P?0.05).Gene expression of CPT-I in liver of fish fed diet FO was significantly higher than that of in the other treatments(P?0.05).However,gene expressions of FAS,aproB100 and ?6 Fad in liver of fish fed diet FO were significantly lower than that of in the other treatments(P?0.05).Gene expression of FABP-1 in liver of golden pompano fed diet SO was highest,and that in LO treatment was lowest(P?0.05).Serum glucose content in fish fed FO diets was higher than that in LO group.It can be concluded that FO could not be completely replaced by SO or LO in golden pompano diets.The different sources of lipid could significantly affect body condition factor and hepatic lipid metabolism of golden pompano.4.Juvenile largemouth bass(Micropterus salmoides)(33.83±0.15g)were fed diets containing three different lipid sources: fish oil(FO),soybean oil(SO),and lard oil(LO).Fish were reared in tanks(500L)for 8 weeks and the specific growth rate(SGR)showed no significant difference.Fish fed diet FO obtained the lowest condition factor(P ?0.05).Fatty acids composition of whole body was reflected by dietary fatty acids composition.Despite no differences in hepatic fatty acid synthase(FAS)activity,the carnitine palmitoyl transterase-I(CPT-I)activity in fish fed FO diet was significantly higher than that in other treatments(P?0.05).The relative genes expressions of lipid metabolism related enzymes(CPT-I,FAS,apolipoprotein B100(apro B100),delt-6 fatty acyl desaturase(?6 Fad)and fatty acid-binding protein-1(FABP1))were also influenced by different sources of dietary lipid(P?0.05).Gene expressions of CPT-I and FAS in live of fish fed FO diet were significantly higher than that of in other treatments;however,gene expressions of aproB100 and?6 Fad were significantly lower than that of in other treatments(P?0.05).Gene expressions of aproB100 and ?6 Fad in liver of fish fed SO diet were significantly higher than that of in other treatments;however,gene expression of CPT-I was significantly lower than that of in other treatments(P?0.05).Gene expressions of FAS and FABP-1 in fish fed LO diet were significantly lower than that of in other treatments(P?0.05).Serum glucose content in fish fed diet FO was significantly higher than that in other groups(P?0.05).It can be concluded that FO could be completely replaced by SO or LO in largemouth bass diet in 8 weeks of breeding period.Different sources of dietary lipid could significantly affect body condition factor and hepatic lipid metabolism of largemouth bass.5.In the present study,high-throughput illumina HiSeq2000 RNA-Seq was used to examine the difference of gene expression in golden pompano and largemouth bass which were fed different diets.In total,62377 and 50743 unigenes were generated from golden pompano and largemouth bass,respectively.The average length of assembled transcripts was 822 bp and 1168 bp,respectively.Annotation of differentially expressed sequences including alignment by sequence similarity blasting against COG,GO and KEGG.Differential gene expression analysis indicated that gene expression in golden pompano showed significant difference except PFO and PSO treatment,gene expression in largemouth bass also showed significantly different in all treatments.Based on hotmap of clustering analysis,the PA and PSO treatments have the similar gene expression profiles,PH,PLO and PL treatments have the similar gene expression profiles,POO treatment has a significantly different gene expression profiles with those of other treatments.BA and BLO,BH and BSO,BL and BM have similar gene expression profiles,respectively.Gene expression profiles of BOO treatment was more similar to those of BA and BLO than those of other treatments.