Dietary arachidonic acid decreases the expression of transcripts related to adipocyte development and chronic inflammation in the adipose tissue of juvenile grass carp, Ctenopharyngodon idella.

Overdevelopment of adipose tissue in cultured fish is one of the biggest issues plaguing current aquaculture industry, leading to unhealthy status of fishes and production losses. Diet supplemented with 0.30% arachidonic acid (ARA) has been found to reduce adipogenesis and inflammation in grass carp, but the potential mechanism is not comprehensively understood. To fully reveal the effects of dietary ARA on the mRNA profiles of adipose tissue, transcriptome techniques were applied in this study. A 10-weeks feeding experiment was performed using two isonitrogenous and isoenergetic purified diets, namely ARA-free (control) and 0.30% ARA (ARA group). Results showed increased ARA content and decreased intraperitoneal fat index and adipocyte size in the adipose tissue of fish fed ARA (P < 0.05). A total of 611 and 973 genes of the adipose tissue were significantly up-regulated and down-regulated, respectively, in fish fed ARA (P < 0.05). Dietary ARA upregulated LOX pathway but downregulated CYP450 pathway annotated genes expression. A total of 65 cell development annotated genes including 30 adipocyte proliferation, 21 adipocyte differentiation, and 14 cell apoptosis annotated genes were down-regulated in the ARA group. In addition, 19 lipid catabolism annotated genes were increased. The mRNA expression levels of 5 chemokines, 10 cytokines, 26 cytokine and chemokine receptors, 15 cell adhesion, 6 oxidative stress, and 6 angiogenesis annotated genes were all down-regulated in fish fed ARA. Finally, dietary ARA also decreased the expression of transcripts annotated with glucose transportation, glycolysis and gluconeogenesis. Overall, our results demonstrate that dietary ARA has a fat reducing role, and tends to retard adipocyte development and attenuate chronic inflammation based on these adipose transcript expression results in grass carp.

Proteomic signature of muscle fibre hyperplasia in response to faba bean intake in grass carp.

Fish muscle growth is important for the rapidly developing global aquaculture industry, particularly with respect to production and quality. Changes in muscle fibre size are accomplished by altering the balance between protein synthesis and proteolysis. However, our understanding regarding the effects of different protein sources on fish muscle proteins is still limited. Here we report on the proteomic profile of muscle fibre hyperplasia in grass carp fed only with whole faba bean. From the results, a total of 99 significantly changed proteins after muscle hyperplasia increase were identified (p < 0.05, ratio <0.5 or >2). Protein-protein interaction analysis demonstrated the presence of a network containing 56 differentially expressed proteins, and muscle fibre hyperplasia was closely related to a protein-protein network of 12 muscle component proteins. Muscle fibre hyperplasia was also accompanied by decreased abundance in the fatty acid degradation and calcium signalling pathways. In addition, metabolism via the pentose phosphate pathway decreased in grass carp after ingestion of faba bean, leading to haemolysis. These findings could provide a reference for the prevention and treatment of human glucose-6-phosphate dehydrogenase deficiency ("favism").