Page 15 - 《水产学报》2025年第10期

孟迎冬，等 水产学报, 2025, 49(10): 109601

Effects of mTOR signalling pathway activation on growth performance,
amino acid metabolism and intestinal health of sea bass
(Lateolabrax maculatus) fed low-protein diets

*
MENG Yingdong , WANG Xuan , LIU Chengdong , ZHOU Huihui , MAI Kangsen , HE Gen
Key Laboratory of Mariculture, Ministry of Education, Key Laboratory of Aquaculture Nutrition and Feed, Ministry of
Agriculture and Rural Affairs, Fisheries College, Ocean University of China, Qingdao 266003, China

Abstract: This study examined how activation of the mTOR pathway influences growth, amino-acid metabolism, and intest-
inal health in juvenile spotted seabass (Lateolabrax maculatus) fed a low-protein diet. Triplicate groups received, for eight
weeks, either a 50% crude-protein control diet (CON), a 48% crude-protein diet (P48), or the P48 diet supplemented with 0.1%
of a specific mTOR activator (P48S). Fish [(21.20 ± 0.20) g] were reared in a recirculating aquaculture system under controlled
conditions. Relative to CON, P48 depressed weight gain rate (WGR) and specific growth rate (SGR) and increased feed-con-
version ratio (FCR). Supplementation in P48S reversed these deficits: WGR rose 25.12%, SGR 12.03%, and FCR fell 8.33%
compared with P48. Whole-body crude protein increased 4.45%, while plasma total cholesterol and triglycerides declined
12.57% and 20.44%, respectively. Blood analysis revealed that the P48S group had significantly higher plasma levels of total
free amino acids (TAA), total essential amino acids (EAA), and total non-essential amino acids (NEAA) compared to both the
CON and P48 groups, coupled with elevated muscle free EAA content. Morphologically, villus height was 22.82% greater in
P48S than in P48. Complementing these findings, further biochemical analysis uncovered enhanced activity of key intestinal
digestive enzymes, specifically trypsin and lipase, in the P48S group. Additionally, gene expression analysis indicated upregu-
lated levels of crucial amino acid and small peptide transporters (pept1, lat1, and asct2) within the intestines of the P48S group.
In conclusion, while reducing dietary protein levels clearly suppresses growth performance in L. maculatus, the activation of
the mTOR signaling pathway presents a viable strategy to counteract these effects. This activation improves protein synthesis
by enhancing feed protein digestion, promoting amino acid absorption and metabolism, and thereby significantly restoring and
enhancing growth performance, even under suboptimal protein dietary conditions.
Key words: Lateolabrax maculatus; mTOR signalling pathway; growth; feed utilisation rate; amino acid metabolism

Corresponding author: WANG Xuan. E-mail: xuanwang@ouc.edu.cn
Funding projects: National Key Research and Development Program of China (2023YFD2400600); National Modern Agricul-
tural Industrial Technology System Project (CARS-47-G10)

https://www.china-fishery.cn 中国水产学会主办 sponsored by China Society of Fisheries
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