不同糖源及糖水平对大菱鲆糖代谢酶活性的影响

采用34双因素实验设计, 以初始质量为(8.060.08) g的大菱鲆幼鱼(Scophthalmus maximus L.)为对象, 研究在饲料中添加3种糖源(葡萄糖、蔗糖和糊精)及4个水平(0、5%、15%、28%)对大菱鲆肝脏糖酵解关键酶己糖激酶(HK)、葡萄糖激酶(GK)、磷酸果糖激酶(PFK)、丙酮酸激酶(PK)和糖异生关键酶磷酸烯醇式丙酮酸羧激酶(PEPCK)、1, 6-二磷酸果糖酶(FBPase)活性的影响。结果表明: 饲料糖添加量从0升高到15%时, 大菱鲆的糖酵解酶GK和PK活性随饲料葡萄糖或糊精含量的增加而增加; 当饲料中葡萄糖或糊精含量为28%时, GK和PK活性有下降的趋势。3种糖源的4个添加水平对HK和PFK活性均无显著影响(P 0.05)。添加不同水平的葡萄糖对大菱鲆糖异生途径的PEPCK活性无显著影响(P 0.05), 但在饲料中葡萄糖添加量为5%时显著促进了FBPase活性(P 0.05), 当葡萄糖添加量升高为15%或28%时, FBPase活性与对照组无显著差异(P 0.05)。糊精作为饲料糖源时抑制了大菱鲆肝脏FBPase和PEPCK的活性, 而添加不同水平的蔗糖对FBPase和PEPCK活性的影响均不显著(P 0.05)。总的来说, 从大菱鲆幼鱼肝脏糖代谢角度而言, 在饲料中添加15%的葡萄糖或糊精时, 可以有效促进大菱鲆肝脏糖酵解能力; 较添加葡萄糖, 糊精在促进大菱鲆肝脏糖酵解的同时对糖异生存在一定程度的抑制。蔗糖作为饲料糖源时, 仅在添加量为28%时显著促进糖酵解酶GK活性, 糖酵解其他酶活性以及糖异生酶活性均不受蔗糖水平的显著影响。  

EFFECTS OF DIETARY CARBOHYDRATE SOURCES AND LEVELS ON THE ACTIVITIES OF CARBOHYDRATE METABOLIC ENZYMES IN TURBOT

A 34 two-factorial experiment was conducted to investigate the effects of dietary carbohydrate sources (glucose, sucrose and dextrin) and levels (0, 5%, 15% and 28%) on the activities of glycolytic and gluconeogenic enzymes in turbot (Scophthalmus maximus L.). The initial weight of the turbot was (8.060.08) g. Each diet was fed to triplicate groups of turbot in a flow-through water system for 9 weeks. Activities of hexokinase (HK), glucokinase (GK), 6-phosphofructokinase-1 (PFK), pyruvate kinase (PK), phosphoenolpyruvate carboxykinase (PEPCK) and fructose-1, 6-bisphosphatase (FBPase) were examined. The results showed that hepatic GK and PK activity significantly increased with the increase of dietary carbohydrate level from 0 to 15%. However, there was a lack of further increase of them with 28% of dietary glucose or dextrin. HK and PFK activities were not significantly affected by dietary carbohydrate levels (P 0.05). Activities of FBPase, not PEPCK, were significantly increased by 5% of dietary glucose. Diets supplemented with dextrin depressed hepatic FBPase and PEPCK activity in comparison to that without carbohydrate supplements. Activities of these two enzymes were not significantly affected by dietary sucrose levels (P 0.05). The data suggested that diets supplemented with 15% of glucose or dextrin was effective in enhancing liver glycolytic enzyme activity. Dietary dextrin was more effective than glucose in depressing liver gluconeogenic enzyme activities. Only GK activity was significantly promoted by 28% of dietary sucrose, and no significant effect of dietary sucrose levels on the other enzymes was found.