摘要：A 75-day rearing trial was designed to study the response of juvenile
Megalobrama amblycephala to dietary methionine (Met) levels. Three practical diets with graded Met levels (0.40%, 0.84% and 1.28% dry matter) were prepared to feed the juvenile fish. The results showed that the 0.84% Met diet significantly improved the growth compared with 0.40% diets. Compared with 0.84% and 1.28% Met, 0.40% Met significantly increased the hepatic lipid content, while decreasing the muscular lipid and glycogen contents. 0.40% Met decreased the protein levels of phospho-Eukaryotic initiation factor 4E binding protein-1 (p-4e-bp1), 4e-bp1 and Ribosomal protein S6 kinase 1 in the liver, compared with 0.84% diet, while an increasing trend was observed in the muscle. Met supplementation tended to decrease and increase lipid synthesis in the liver and muscle, respectively, via changing mRNA levels of
sterol regulatory element-binding protein 1,
fatty acid synthetase and
acetyl-CoA carboxylase. 1.28% dietary Met promoted fatty acid β-oxidation and lipolysis in both the liver and muscle by increasing
carnitine palmitoyl transferase 1,
peroxisome proliferator activated receptor alpha,
lipoprotein lipase and
lipase mRNA levels. Compared with 0.40% and 0.84% dietary Met, 1.28% Met enhanced the mRNA levels of hepatic gluconeogenesis related genes
phosphoenolpyruvate carboxykinase (
pepck), and
glucose-6-phosphatase, and muscular glycolysis related genes
phosphofructokinase (
pfk), and
pyruvate kinase (
pk). The mRNA levels of hepatic
pfk,
pk and
glucokinase were markedly downregulated by 1.28% Met compared with 0.84% level. Muscular
pepck,
glycogen synthase, and hepatic
glucose transporters 2 mRNA levels were induced by 1.28% Met. Generally, deficient Met level decreased the growth of juvenile
Megalobrama amblycephala, and the different nutrient metabolism responses to dietary Met were revealed in the liver and muscle.
