Hevrøy E M, El-Mowafi A, Taylor R G, Olsvik P A, Norberg B, Espe M
National Institute of Nutrition and Seafood Research (NIFES), PO Box 2029, Nordnes, N-5817 Bergen, Norway.
Gen Comp Endocrinol. 2007 May 15;152(1):39-46. doi: 10.1016/j.ygcen.2007.02.015. Epub 2007 Feb 23.
Nutritional factors influence regulation of the growth hormone (GH) and the insulin-like growth factor (IGF) system in fish, but so far there are no published studies describing how single indispensable amino acids influence these systems. Therefore, the present study aimed to test whether lysine (Lys) intake at low (LL=2.85 g/16 gN), medium (ML=4.91 g/16 gN) and high levels (HL=9.19 g/16 gN) affected the expression of genes related to the GH-IGF system (i.e. GH receptor, GH-R, IGF-I, IGF-II, IGF binding protein 1, IGFBP-1, IGF-I receptor IGF-IR) in Atlantic salmon during seawater growth phase. Salmon fed the HL diet significantly up-regulated hepatic IGF-I mRNA level by a factor of 2.2 as compared to those with medium Lys intake. In addition a significant up-regulation of 2.7-fold in muscle IGF-II mRNA was present. Low Lys intake decreased the nitrogen deposition and muscle protein accretion in fish and significantly down-regulated hepatic IGFBP-1 as well as muscle GH-R and IGF-II, as compared to those fed the ML diet. mRNA of IGF-IR on the other hand was not affected by Lys intake. High Lys intake resulted in a 7-fold up-regulation of muscle IGF-II mRNA level as compared to low Lys intake, and thus might be an important local anabolic regulator in fast muscle tissue. The single indispensable amino acid Lys indeed affected signalling through the genes of IGF-I, IGFBP-1 in hepatic tissue and GH-R, IGF-II in fast muscle in Atlantic salmon. Concomitantly the higher Lys intake increased nitrogen deposition to a certain level.
营养因素会影响鱼类生长激素（GH）和胰岛素样生长因子（IGF）系统的调节，但迄今为止，尚无已发表的研究描述单一必需氨基酸如何影响这些系统。因此，本研究旨在测试低水平（LL = 2.85 g/16 gN）、中等水平（ML = 4.91 g/16 gN）和高水平（HL = 9.19 g/16 gN）的赖氨酸（Lys）摄入量是否会影响海水生长阶段大西洋鲑鱼中与GH-IGF系统相关基因（即GH受体、GH-R、IGF-I、IGF-II、IGF结合蛋白1、IGFBP-1、IGF-I受体IGF-IR）的表达。与中等Lys摄入量的鲑鱼相比，喂食HL日粮的鲑鱼肝脏中IGF-I mRNA水平显著上调了2.2倍。此外，肌肉中IGF-II mRNA显著上调了2.7倍。与喂食ML日粮的鱼相比，低Lys摄入量降低了鱼的氮沉积和肌肉蛋白质积累，并显著下调了肝脏IGFBP-1以及肌肉GH-R和IGF-II。另一方面，IGF-IR的mRNA不受Lys摄入量的影响。与低Lys摄入量相比，高Lys摄入量导致肌肉IGF-II mRNA水平上调了7倍，因此可能是快速肌肉组织中重要的局部合成代谢调节因子。单一必需氨基酸Lys确实影响了大西洋鲑鱼肝脏组织中IGF-I、IGFBP-1以及快速肌肉中GH-R、IGF-II基因的信号传导。同时，较高的Lys摄入量将氮沉积提高到了一定水平。
