饲料中三种不同碳水化合物对大黄鱼生长性能和肝脏糖代谢关键酶活性的影响

为研究饲料中添加3种不同的碳水化合物对大黄鱼生长性能、饲料利用以及糖代谢关键酶活性的影响,进行为期8周的生长实验和持续24 h的饥饿实验。以葡萄糖、小麦淀粉和糊精这3种碳水化合物作为糖源,设计3组等氮等脂(48%粗蛋白和12%粗脂肪)的饲料。选用初始体质量为(8.51±0.02)g的大黄鱼450尾,随机分为3组(每组3个重复,每个重复50尾)。养殖实验结束后进行饥饿实验,分别在饥饿实验开始后的0、1、3、5、7、9、11和24 h取样。结果显示,小麦淀粉组和糊精组大黄鱼的增重率和特定生长率显著高于葡萄糖组,且这2个饲料组的饲料系数显著低于葡萄糖组。糊精组大黄鱼的肝体比显著高于其余2组大黄鱼的肝体比。饲料中添加3种不同碳水化合物对大黄鱼成活率、脏体比和肥满度无显著性影响。葡萄糖组和小麦淀粉组大黄鱼血糖含量在饥饿1 h后都开始显著上升,葡萄糖组高血糖水平持续至少10 h;小麦淀粉组3 h显著下降至初始水平左右,未达到高血糖水平;糊精组大黄鱼血糖含量随着时间的推移持续升高,在11 h达到最大值,高血糖水平持续4 h。饲料中添加3种不同碳水化合物对大黄鱼血清胰岛素和肝糖原含量有显著性影响。小麦淀粉对大黄鱼肝脏葡萄糖激酶(GK)活性的升高有诱导作用。大黄鱼摄食3种不同碳水化合物饲料后鱼体血糖水平升高,但糖异生关键酶如葡萄糖-6-磷酸酶(G6Pase)、果糖-1,6-二磷酸酶(FBPase)和磷酸烯醇式丙酮酸羧激酶(PEPCK)的活性并不降低。饲料中添加葡萄糖和小麦淀粉对大黄鱼肝脏丙酮酸激酶(PK)活性有显著性影响。研究表明,大黄鱼利用结构复杂的多糖(如小麦淀粉和糊精)的能力要高于单糖(如葡萄糖),3种不同碳水化合物对大黄鱼血糖调节及糖酵解和糖异生途径关键酶活性的影响存在差异。

Effects of three different carbohydrate sources on growth performance and hepatic glucose metabolism key enzyme activities in large yellow croaker (Larimichthys crocea)

An 8-week feeding trial and a 24-hour starvation trial were conducted to evaluate the effects of three different carbohydrate sources on growth performance, feed utilization and glucose metabolism key enzyme activities of large yellow croaker. Three isonitrogenous and isoenergetic diets (about 48% crude protein and 12% crude lipid) were formulated to supplement with three different carbohydrate sources, namely glucose, wheat starch and dextrin, respectively. Each diet was randomly assigned to feed three replicate groups of 50 juvenile large yellow croakers with the initial weight of (8.51±0.02) g twice daily to apparent satiation. After the end of the feeding trial, the fish was continuously starved for 24 h and samples were taken at 0, 1, 3, 5, 7, 9, 11, 24 h, respectively. The results indicated that fish fed the diets containing wheat starch and dextrin had significantly higher weight gain rate (WGR) and specific growth rate (SGR) than those fed the diet containing glucose, moreover, feed conversion ratio (FCR) of these two diets was significantly lower than that of diet containing glucose. Fish fed the diet containing dextrin had significantly higher hepatosomatic index (HSI) than those fed the other diets. However, survival rate (SR), viscerosomatic index (VSI) and condition factor (CF) were not significantly affected by three different carbohydrate sources. Serum glucose (GLU) concentration of the diet containing glucose and wheat starch significantly increased after starving 1 h and glucose diet group presented high serum glucose levels which lasted for at least 10 h. However, serum glucose concentration of the diet containing wheat starch significantly decreased to initial level and didn''t display high serum glucose level. Serum glucose concentration of the dextrin diet group continuously increased as time went on, peaked at 11 h, and high serum glucose level lasted for at least 4 h. The concentration of serum insulin and hepatic glycogen were significantly affected by diets supplemented with three different carbohydrates. The results indicated that the increasing of glucokinase (GK) can be induced by wheat starch. While serum glucose concentration increased after feeding trial, the activities of gluconeogenic key enzymes such as glucose-6-phosphatase (G6Pase), fructose-1,6-bisphosphatase (FBPase) and phosphoenolpyruvate carboxykinase (PEPCK) didn''t decrease. The activities of pyruvate kinase (PK) were significantly influenced by the dietary glucose and wheat starch. The results demonstrated that the ability of utilizing structure-complicated polysaccharide (such as wheat starch and dextrin) was higher than that of utilizing monosaccharide (such as glucose). Not only the serum glucose regulation but also the activities of glycolysis and gluconeogenic key enzymes were affected by different dietary carbohydrate sources.