饲料脂肪对翘嘴红鲌生长、葡萄糖激酶和葡萄糖-6-磷酸酶活性与基因表达的影响

Effects of dietary lipids on growth, GK and G6Pase activities and mRNA levels in top-mouth cutler (Erythrocutler ilishaeformis Bleeker)

选用360尾翘嘴红鲌(Erythrocutler ilishaeformis Bleeker),体质量约40g。随机分成为2组,分别为高脂组(脂肪质量分数19.93%,碳水化合物质量分数14.45%)、低脂组(脂肪质量分数9.92%,碳水化合物质量分数12.38%),每组设3个重复,饲养8周。分别于摄食后0h、3h、6h、12h、24h测定血液指标、糖代谢酶葡萄糖激酶(Glucokinase,GK,E.C.2.7.1.1)以及葡萄糖-6-磷酸酶(glucose-6-phosphatase,G6Pase,E.C.3.1.3.9)活性及基因表达,并分析高脂肪与低脂肪水平日粮对翘嘴红鲌生长的影响。与低脂水平日粮相比,高脂水平日粮组血液甘油三酯水平和游离脂肪酸水平分别在摄食后3h、12h有增加现象,肝胰脏粗蛋白与脂肪含量有显著增加(P<0.05)。与低脂水平日粮相比,在摄食后3～12h高脂肪水平日粮组糖代谢酶GK的mRNA水平显著增加(P<0.05),但是日粮脂肪水平并不能显著影响GK活性(P>0.05)。在摄食后3～24h高脂肪水平日粮组糖代谢酶G6Pase的mRNA水平得到显著促进,并在摄食后24hG6Pase活性显著增加(P<0.05)。因此,摄食高脂肪水平日粮能增加肝胰脏粗蛋白与脂肪含量,造成翘嘴红鲌高血糖效应,诱导G6Pase酶活性及基因的表达,这可能是影响翘嘴红鲌碳水化合物利用的原因之一。

Top-mouth culter （Erythroculter ilishaeformis Bleeker） is also called white fish from Taihu Lake in China. It is a carnivorous fish belonging to cypriniformes, Cyprinidae, Culterinae. It is one of four famous freshwater fish species and now becomes one of the main cultured species in China. There were some investigations on the biology of top-mouth culter. However, few studies have been reported on its nutritional requirements. The objectives of this study were to evaluate the effects of dietary high lipids on postprandial plasma metabolites including glucose, triglycerides, fatty acids and cholesterol, as well as expression and activities of hepatic GK, Gopase and PEPCK enzymes, and to explore the carbohydrate utilization in fish.In the present study, 360 top-mouth cutler with average weight 40.53 ± 0.66 g were randomly divided into two groups. Each group with triplication was fed with diets containing high lipid （HL） level （19.93% lipid, 14.45% carbohydrate） or with low lipid （LL） level （9.92% lipid, 12.38% carbohydrate）. After 8 weeks, plasma biochemical indices and glucokinase （GK）, glucose-6-phosphatase （G6Pase） activities and mRNA levels were determined at 0, 3,6, 12 and 24 h after feeding. The results showed that compared with the low level of dietary lipids, the high dietary lipids level promoted fish hepatic crude protein and fat content; increased triglyceride content at 3 h after the meal and free fatty acids concentrations of plasma at 12 h after taking food. The level of dietary lipids did not significantly affect GK activity even though GK mRNA level were increased at 3-24 h after taking high level of lipids. The high level of dietary lipids significantly increased mRNA level of G6Pase at 3,6, 12 and 24 h and G6Pase activity at 24 h as well after food ingestion.Therefore, these data suggest ingestion of high dietary lipids would increase the hepatic crude protein and fat content causing high glycaemia, inducing G6Pase activity and gene expression, which may affect carbohydrate utilization rate of top-mouth cutler at least as part of reasons. [Jousnal of Fishery Sciences of China,2008, 15 （6）： 1 024-1 033]