Commonwealth Scientific Industrial Research Organisation (CSIRO) Agriculture and Food, Queensland Biosciences Precinct, St Lucia, QLD4067, Australia.
School of Agricultural and Food Sciences, The University of Queensland, St Lucia, QLD4067, Australia.
Br J Nutr. 2020 Aug 28;124(4):363-373. doi: 10.1017/S0007114520001051. Epub 2020 Mar 19.
Barramundi (Lates calcarifer) are a highly valued aquaculture species, and, as obligate carnivores, they have a demonstrated preference for dietary protein over lipid or starch to fuel energetic growth demands. In order to investigate how carnivorous fish regulate nutritional cues, we examined the metabolic effects of feeding two isoenergetic diets that contained different proportions of digestible protein or starch energy. Fish fed a high proportion of dietary starch energy had a higher proportion of liver SFA, but showed no change in plasma glucose levels, and few changes in the expression of genes regulating key hepatic metabolic pathways. Decreased activation of the mammalian target of rapamycin growth signalling cascade was consistent with decreased growth performance values. The fractional synthetic rate (lipogenesis), measured by TAG 2H-enrichment using 2H NMR, was significantly higher in barramundi fed with the starch diet compared with the protein diet (0·6 (se 0·1) v. 0·4 (se 0·1) % per d, respectively). Hepatic TAG-bound glycerol synthetic rates were much higher than other closely related fish such as sea bass, but were not significantly different (starch, 2·8 (se 0·3) v. protein, 3·4 (se 0·3) % per d), highlighting the role of glycerol as a metabolic intermediary and high TAG-FA cycling in barramundi. Overall, dietary starch significantly increased hepatic TAG through increased lipogenesis. Compared with other fish, barramundi possess a unique mechanism to metabolise dietary carbohydrates and this knowledge may define ways to improve performance of advanced formulated feeds.
巴沙鱼（Lates calcarifer）是一种极具价值的水产养殖品种，作为肉食性鱼类，它们在能量生长需求方面表现出对膳食蛋白质的偏好，而不是脂质或淀粉。为了研究肉食性鱼类如何调节营养线索，我们研究了两种等能量饲料对代谢的影响，这两种饲料中可消化蛋白质或淀粉能量的比例不同。摄食高比例淀粉能量饲料的鱼类肝脏中 SFA 的比例更高，但血浆葡萄糖水平没有变化，调节关键肝脏代谢途径的基因表达也没有多少变化。哺乳动物雷帕霉素靶蛋白（mTOR）生长信号通路的激活减少与生长性能值下降一致。使用 2H NMR 通过 TAG 2H 富集测量的脂肪酸合成率（脂肪生成）在摄食淀粉饲料的巴沙鱼中明显高于摄食蛋白质饲料的巴沙鱼（分别为 0.6（se 0.1）%/d 和 0.4（se 0.1）%/d）。与其他密切相关的鱼类（如海鲈）相比，肝脏 TAG 结合甘油的合成率要高得多，但没有显著差异（淀粉，2.8（se 0.3）%/d；蛋白质，3.4（se 0.3）%/d），这突出了甘油作为代谢中间产物和巴沙鱼高 TAG-FA 循环的作用。总的来说，饲料淀粉通过增加脂肪生成显著增加了肝脏中的 TAG。与其他鱼类相比，巴沙鱼具有独特的代谢膳食碳水化合物的机制，这一知识可能为改进高级配方饲料的性能提供途径。
