不同蛋白质水平下葡萄糖添加水平对大黄鱼生长性能、糖酵解和糖异生关键酶活性的影响

Effects of Glucose Supplemental Level at Different Protein Levels on Growth Performance,Hepatic Glycolysis and Gluconeogenic Key Enzyme Activities of Large YellowCroaker(Larmichthys crocea Richardson)

本试验旨在研究不同蛋白质水平下葡萄糖添加水平对大黄鱼生长性能、血清指标、肝脏糖酵解和糖异生关键酶活性、糖原含量以及消化酶活性的影响。采用2×3双因素试验设计,其中蛋白质水平设42%、48%2个水平,葡萄糖添加水平设10%、20%、30%3个水平,共配制6种试验饲料。每种饲料设3个重复,每个重复放养平均体重为(14.89±0.11)g的大黄鱼幼鱼50尾。试验期为8周。结果表明:饲料蛋白质水平和葡萄糖添加水平的交互作用对大黄鱼的增重率(WGR)和特定生长率(SGR)有显著影响(P<0.05),在42%蛋白质水平下,WGR和SGR均随饲料葡萄糖添加水平的增加呈上升趋势;而在48%蛋白质水平下,葡萄糖添加水平为10%组的WGR和SGR要高于葡萄糖添加水平为30%组(P>0.05)。饲料蛋白质水平和葡萄糖添加水平的交互作用对大黄鱼肝脏葡萄糖激酶(GK)、6-磷酸果糖激酶(PFK)、丙酮酸激酶(PK)、葡萄糖-6-磷酸酶(G6Pase)、果糖-1,6-二磷酸酶(FBPase)及磷酸烯醇式丙酮酸羧激酶(PEPCK)活性有显著影响(P<0.05)。在42%蛋白质水平下,饲料葡萄糖添加水平对肝脏GK、PFK、PK、G6 Pase、FBPase及PEPCK活性有显著影响(P<0.05),且GK活性随饲料葡萄糖添加水平的升高呈显著上升(P<0.05),PEPCK活性随饲料葡萄糖添加水平的升高呈降低的趋势;在48%蛋白质水平下,饲料葡萄糖添加水平对肝脏GK、G6Pase及FBPase活性有显著影响(P<0.05),且GK活性随着饲料葡萄糖添加水平的升高呈上升的趋势。饲料蛋白质水平和葡萄糖添加水平的交互作用对肝糖原含量有显著影响(P<0.05),在42%或48%蛋白质水平下,肝糖原含量随饲料葡萄糖添加水平的升高呈上升的趋势。饲料蛋白质水平和葡萄糖添加水平的交互作用仅对大黄鱼少量血清指标[如血清总蛋白(TP)、葡萄糖含量及丙氨酸转氨酶(ALT)、天冬氨酸转氨酶(AST)活性]有显著影响(P<0.05),且对胃蛋白酶及肠道淀粉酶和脂肪酶活性无显著影响(P>0.05)。由此得出,当蛋白质水平为42%时,随着饲料葡萄糖添加水平的升高,大黄鱼能够通过调节糖酵解和糖异生关键酶活性及肝糖原含量来维持血糖含量的平衡,改善对葡萄糖的利用能力;而当蛋白质水平为48%时,随着饲料葡萄糖添加水平的升高,大黄鱼对葡萄糖的利用能力降低。

An 8-week feeding trial was conducted to evaluate the effects of glucose supplemental level at different protein levels on growth performance,serum indices,hepatic glycolysis and gluconeogenic key enzyme activities,glycogen content and digestive enzyme activities of large yellowcroaker（Larmichthys crocea Richardson）.Six experimental diets were formulated to contain two protein levels（42% and 48%,respectively） and three glucose supplemental levels（10%,20% and 30%,respectively）.Each diet was randomly assigned to 3 replicates,and each replicate had 50 juvenile large yellowcroaker with the average body weight of（14.89 ±0.11） g.The results showed that weight gain rate（WGR） and specific growth rate（SGR） were significantly affected by the interaction of dietary protein level and glucose supplemental level（P〈0.05）.When the dietary protein level was 42%,the WGR and SGR showed a increasing trend with the glucose supplemental level increasing; however,when the dietary protein was 48%,fish fed the diet supplemented with 10% glucose had higher WGR and SGR than fish fed the diet supplemented with 30% glucose（P〈0.05）.The interaction of dietary protein level and glucose supplemental level had a significant effects on the ativities of glucokinase（GK）,phosphofructokinase（PFK）,pyruvate kinase（PK）,glucose-6-phosphatase（G6Pase）,fructose-1,6-bisphosphatase（FBPase）,phosphoenolpyruvate（PEPCK） in liver（P〈0.05）.When the dietary protein level was42%,the activities of GK,PFK,PK,G6 Pase,FBPase and PEPCK in liver were significantly affected by dietary glucose supplemental level（P〈0.05）,and the GK activity was significantly increased with the glucose supplemental level increasing（P〈0.05）,while the PEPCK activity had a decreasing trend with the glucose supplemental level increasing.When the dietary protein level was 48%,the activities of GK,G6 Pase and FBPase in liver were significantly affected by dietary glucose supplemental level（P〈0.05）,and the GK activity had a increasing trend with the glucose supplemental level increasing.The interaction of dietary protein level and glucose supplemental level had a significant effect on hepatic glycogen content（P〈0.05）,and the hepatic glycogen content had a increasing trend with the glucose supplemental level increasing when dietary protein level was 42%or 48%.The interaction of dietary protein level and glucose supplemental level only significantly affected a fewserum indices（such as total protein and glucose contents,and alanine aminotransferase and aspartate aminotransferase activities in serum）（P〈0.05）,and did not significantly affected pepsin,intestinal amylase and lipase activities（P〈0.05）.The results indicated that,when the dietary glucose level is 42%,large yellowcroaker has the ability to maintain blood glucose content by adjusting the hepatic glycogen,glycolysis and gluconeogenic key enzymes activities with the glucose supplemental level increasing; while,when the dietary glucose level is48%,the ability of glucose utilization is decreased with the glucose supplemental level increasing.