Dietary methionine affects growth and the expression of key genes involved in hepatic lipogenesis and glucose metabolism in cobia (Rachycentron canadum)

Abstract

Juvenile cobia (Rachycentron canadum), a carnivorous fish, was chosen to examine the effects of methionine (Met) supplementation of low fishmeal diets on growth and the expression of key genes related to hepatic lipogenesis and glucose metabolism. Seven isonitrogenous and isolipidic diets were formulated to contain 7.2, 9.0, 10.0, 12.4, 14.1, 16.3 and 18.6 g/kg dietary Met levels. Healthy cobia (initial average weight ± SE = 9.79 ± 0.04 g) were randomly assigned into seven groups in triplicate with 40 individuals per sea cage for 8 weeks. The results showed that the weight gain rate (WGR) of fish increased as the dietary Met was increased up to 12.4 g/kg and then decreased. The expression of insulin‐like growth factor‐I (IGF‐I) and target of rapamycin (TOR) genes was inhibited by the Met‐deficient diets. The mRNA levels of fatty acid synthase (FAS) and sterol regulatory element‐binding protein‐1 (SREBP1) genes increased with increasing dietary Met until 12.4 g/kg after which the former remained constant, whereas the latter decreased from 12.4 to 18.6 g/kg Met. The mRNA levels of pyruvate kinase (PK) increased as the dietary Met levels increased, reaching a peak at 12.4 g/kg, and then decreased with further increases in Met. However, the mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) decreased as the dietary Met was increased up to 12.4 g/kg and then remained constant from 12.4 to 18.6 g/kg Met. In conclusion, based on the straight broken‐line analysis of WGR against dietary Met levels, the optimal dietary Met requirement for juvenile cobia was estimated to be 12.4 g/kg (26.9 g/kg dietary protein). A diet with the optimal level of Met induces fish growth and is associated with increased IGF‐I and TOR.

Tissue-specific Nutrient Metabolism in the Liver and Muscle of Juvenile Blunt Snout Bream (Megalobrama Amblycephala) in Response to Dietary Methionine Levels

“…The present data about glycolysis revealed that 0.84% dietary Met potentially promoted hepatic glucose utilization while muscular glucose utilization was enhanced by 1.28% dietary Met. Similar results were observed in cobia, in which 1.24% dietary Met enhanced hepatic glycolysis via increased PK mRNA levels compared with an 0.70% diet [14]. Primary muscle cells of turbot treated with Met deprivation exhibited decreased GK and PK expression levels compared with the control [13].…”

“…The assay used β-actin as the reference gene, and the target gene expression levels were analyzed using the 2 −∆∆ct model. TTCAGTGTCACGCTGTTCCT TCTGGACTGACGCACCATTT FBP 9 CGGCAGCCCATTATCATTGC GCGTACACTGGACTCTCCAC GS 10 TTACACGGTCATTGCGTCCA GACACAGCTCAGTCGGTGAA G6PD 11 TGGAGAAACCTTTTGGCCGT CTGGGTACCAAACGGCTCTT GLUT2 12 CGGTGAAACCGAACAGGAGT TTCTTTGAGATCGGGCCTGG GLUT4 13 CCATTGCTGAGCTCTTTCGC GCGTACACTGGACTCTCCAC ACC 14 TAGCAGTGAGCATTGGCACA CATCGCTGGCGTATGAGGAT FAS 15 GTTTGCCAACCGCTTGTCTT GGCCATGGCGAATAGCATTG SREBP1 16 ACAACAGTAGCGACACCCTG AGGAGCGGTAGCGTTTTTCA CPT1 Trace). The blot was blocked with 5% nonfat dry milk in TBST for 2 h at room temperature.…”

“…The primary muscle cells of turbot (Scophthalmus maximus L.) under Met deprivation showed inhibited expression of key target of rapamycin (TOR) pathway elements, and genes related to glycolysis and fatty acid synthesis, while induced fatty acid β-oxidation [13]. Similarly, in cobia (Rachycentron canadum), Met de ciency suppressed hepatic lipogenesis related gene (sterol regulatory element-binding protein (SREBP) and fatty acid synthetase (FAS)) expression and upregulated fatty acid oxidation-related gene (carnitine palmitoyl transferase 1 (CPT1), peroxisome proliferator activated receptor alpha (PPARα), and lipoprotein lipase (LPL)) expression, while increased phosphoenolpyruvate carboxykinase (PEPCK) mRNA levels [14,15]. Moreover, the nutrient metabolism response to dietary Met showed species-speci c and tissue-speci c responses.…”

A review on cobia, Rachycentron canadum, aquaculture

“…The authors established that to obtain the maximum growth and the lowest feed conversion ratio, the methionine requirement is 1.19% (dry diet) in the presence of 0.67% cysteine; this corresponds to 2.64% dry weight of the dietary protein. Based on the straight broken-line analysis of weight gain ratio against dietary methionine levels, Chi et al (2020) estimated the optimal dietary methionine requirement for juvenile cobia to be 12.4 g/kg (26.9 g/kg dietary protein). A diet with the optimal level of methionine induces fish growth and is associated with increased IGF-I (the expression of insulin-like growth factor) and TOR (rapamycin [TOR] genes).…”

Nutrient metabolism in the liver and muscle of juvenile blunt snout bream (Megalobrama amblycephala) in response to dietary methionine levels

“…The primary muscle cells of turbot ( Scophthalmus maximus L.) under Met deprivation showed inhibited expression of the key target of rapamycin (TOR) pathway elements, and genes related to glycolysis and fatty acid synthesis, while inducing fatty acid β-oxidation 4 . In cobia ( Rachycentron canadum ), Met deficiency suppressed hepatic lipogenesis related gene ( sterol regulatory element-binding protein ( srebp1 ) and fatty acid synthetase ( fas )) mRNA expressions and upregulated fatty acid oxidation-related gene ( carnitine palmitoyl transferase 1 ( cpt1 ), peroxisome proliferator activated receptor alpha ( pparα ), and lipoprotein lipase ( lpl )), phosphoenolpyruvate carboxykinase ( pepck ) relative mRNA expression levels 5 , 6 . Moreover, the nutrient metabolism response to dietary Met showed species-specific responses.…”