Dietary phenylalanine level could improve growth performance, glucose metabolism and insulin and mTOR signaling pathways of juvenile swimming crabs, Portunus trituberculatus
Chen Guo, Xiangsheng Zhang, Shichao Xie, Jiaxiang Luo, Tingting Zhu, Yuhang Yang, Xiangkai Li, Chaokai Huang, Yunfei Dang, Qicun Zhou, Min Jin
Abstract
An 8-week feeding trial was conducted to determine the optimal dietary phenylalanine requirement of juvenile swimming crab (Portunus trituberculatus). Six experimental diets (45.0% crude protein and 8.0% crude lipid) were formulated to contain 0.89%, 1.15%, 1.41%, 1.64%, 1.90% and 2.18% phenylalanine, respectively. Each diet was randomly divided into triplicate groups with 30 juvenile swimming crabs (initial weight 22.87 ± 0.03 g). The highest percent weight gain (PWG) and feed efficiency (FE) were presented in crabs fed with 1.64% phenylalanine diet, and the lowest PWG and FE were observed in crabs fed diet with 0.89% phenylalanine (P < 0.05), while no significant difference was presented in survival among all treatments (P > 0.05). Crabs fed the diet containing 0.89% phenylalanine had the lowest content of crude lipid in hepatopancreas among all treatments (P < 0.05). Hematological parameters related to glucose and lipids metabolism and enzyme activities involved in glycolysis and gluconeogenesis were significantly affected by dietary phenylalanine levels (P < 0.05). The contents of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), n-6 polyunsaturated fatty acids (n-6 PUFAs) and n-3 polyunsaturated fatty acids (n-3 PUFAs) in the hepatopancreas were notably affected by the dietary phenylalanine levels (P < 0.05). The enzyme activities related to glycolysis, gluconeogenesis and glycogen content in hepatopancreas were significantly influenced by dietary phenylalanine levels (P < 0.05). The mRNA levels of genes related to glycolysis and gluconeogenesis in the hepatopancreas were significantly affected by dietary phenylalanine levels (P < 0.05). Moreover, the insulin and mammalian target of rapamycin (mTOR) signaling pathway were notably activated by dietary phenylalanine levels (P < 0.05). Based on two slope broken-line regression analysis of PWG against the dietary phenylalanine levels, the optimal dietary phenylalanine requirement was estimated to be 1.60% dry matter (3.55% dietary protein) for juvenile swimming crab.