This study was performed to compare the effects of high carbohydrate and high lipid diets reception on the growth, feed utilization and glucose homeostasis of genetically improved farmed tilapia Oreochromis niloticus. Three isonitrogenous (ca 30.2% protein) diets were formulated with different levels of starch and lipid: the control (CON, 24.2% starch and 6.57% lipid), high carbohydrate diet (HCD, 33.8% starch and 6.91% lipid), and high lipid diet (HLD, 24.0% starch and 16.5% lipid). Tilapia juveniles (initial mean body weight: 32.2 ± 0.2 g/fish) were randomly divided into 12 rectangular tanks (250 L) with 20 fish per tank, and fed the diets to apparent satiation for 8 weeks. The results showed that mean body weight was lower in the HLD fish (183 g/fish) than in the CON (212 g/fish) and HCD fish (206 g/fish). Feeding ratio and feed efficiency ratio were not affected by different treatments. Both dietary starch and lipid provision in excess exhibited poor protein-sparing effect, as protein efficiency ratio and protein productive value were not affected while whole-body protein percentages were lower in the HCD and HLD fish than in the CON fish. High lipid diets reception exerted a greater impact on proximate composition of the whole fish and intraperitoneal fat deposition, while high carbohydrate diets reception exerted a greater impact on liver size through promoting glycogen deposition. Plasma glucose level sharply increased in the HLD fish (7.17 mmol/L) as compared with the CON fish (4.66 mmol/L). Evidences from the molecular level revealed that hyperglycemia of the HLD fish was probably resulted from hepatic glucose output (represented by mRNA levels of glucose transporter 2 and glucose-6-phosphatase catalytic subunit a2) through stimulating gluconeogenesis (the expression of phosphoenolpyruvate carboxykinase 2) rather than glycogenolysis. In addition, high lipid diets reception suppressed hepatic de novo lipogenesis (mRNA level of fatty acid synthase (fas)) along with muscular glucose transport (mRNA level of glucose transporter 4) and glycogenesis (the expression of glycogen synthase 1), which aggravated the hyperglycemia of the HLD fish. In contrast, high carbohydrate diets reception did not affect the expression of representative genes involved with glycolysis and gluconeogenesis, but sharply upregulated the mRNA abundances of lipogenic acetyl-CoA carboxylase α and fas in the liver of tilapia. Except lipid, glycogen concentration also increased in the liver of the HCD fish as compared with the CON fish. Thus, plasma glucose slightly increased in the HCD fish (5.58 mmol/L) as compared with the CON fish. The overall results of this study suggested that tilapia possessed a better capability to tolerate high carbohydrate diets (33.8%) than high lipid diets (16.5%) based on growth performance and the maintenance of glucose homeostasis. This conclusion might have limitations, because the energy density of diets HCD and HLD was different. Further studies are still warranted to compare the glucose homeostasis of tilapia in response to high carbohydrate and high lipid diets reception on an isoenergetic basis.

本研究旨在比较接受高碳水化合物和高脂日粮对遗传改良的养殖罗非鱼尼罗罗非鱼生长、饲料利用率和葡萄糖稳态的影响。用不同水平的淀粉和脂质配制了三种等氮（约 30.2% 蛋白质）日粮：对照（CON，24.2% 淀粉和 6.57% 脂质）、高碳水化合物日粮（HCD、33.8% 淀粉和 6.91% 脂质）和高碳水化合物日粮（HCD、33.8% 淀粉和 6.91%脂质饮食（HLD，24.0% 淀粉和 16.5% 脂质）。罗非鱼幼鱼（初始平均体重：32.2 ± 0.2 g/鱼）被随机分成 12 个矩形水箱（250 L），每个水箱 20 条鱼，喂食至明显饱食 8 周。结果表明，HLD 鱼（183 g/鱼）的平均体重低于 CON（212 g/鱼）和 HCD 鱼（206 g/鱼）。饲喂比和饲料效率比不受不同处理的影响。过量的膳食淀粉和脂质供应都表现出较差的蛋白质节约效果，因为蛋白质效率比和蛋白质生产值不受影响，而 HCD 和 HLD 鱼的全身蛋白质百分比低于 CON 鱼。接受高脂饮食对整鱼的近端成分和腹腔内脂肪沉积产生更大的影响，而接受高碳水化合物饮食通过促进糖原沉积对肝脏大小产生更大的影响。与 CON 鱼 (4.66 mmol/L) 相比，HLD 鱼 (7.17 mmol/L) 的血浆葡萄糖水平急剧增加。分子水平的证据表明，HLD 鱼的高血糖可能是由于肝脏葡萄糖输出（以葡萄糖转运蛋白 2 和葡萄糖-6-磷酸酶催化亚基 a2 的 mRNA 水平为代表）通过刺激糖异生（磷酸烯醇丙酮酸羧激酶 2 的表达）而不是比糖原分解。此外，接受高脂饮食会抑制肝脏从头脂肪生成（脂肪酸合酶的 mRNA 水平（fas )) 以及肌肉葡萄糖转运（葡萄糖转运蛋白 4 的 mRNA 水平）和糖生成（糖原合酶 1 的表达），这加剧了 HLD 鱼的高血糖。相比之下，高碳水化合物饮食的接受并不影响参与糖酵解和糖异生的代表性基因的表达，但会急剧上调脂肪生成乙酰辅酶A羧化酶α和fas的mRNA丰度在罗非鱼的肝脏中。除脂质外，HCD 鱼肝脏中的糖原浓度也比 CON 鱼增加。因此，与 CON 鱼相比，HCD 鱼的血浆葡萄糖略有增加（5.58 mmol/L）。这项研究的总体结果表明，基于生长性能和维持葡萄糖稳态，罗非鱼比高脂饮食（16.5%）具有更好的高碳水化合物饮食（33.8%）耐受能力。这个结论可能有局限性，因为 HCD 和 HLD 的能量密度不同。仍然需要进一步的研究来比较罗非鱼的葡萄糖稳态，以在等能量的基础上响应高碳水化合物和高脂饮食的接受。