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.

α-lipoic acid ameliorates n-3 highly-unsaturated fatty acids induced lipid peroxidation via regulating antioxidant defenses in grass carp (Ctenopharyngodon idellus).

This study evaluated the protective effect of α-lipoic acid (LA) on n-3 highly unsaturated fatty acids (HUFAs)-induced lipid peroxidation in grass carp. The result indicated that diets with n-3 HUFAs increased the production of malondialdehyde (MDA) (P < 0.05), thereby inducing lipid peroxidation in liver and muscle of grass carp. Meanwhile, compared with control group, the hepatosomatic index (HSI) and kidney index (KI) of grass carp were markedly increased in n-3 HUFAs-only group. However, diets with LA remarkably inhibited the n-3 HUFAs-induced increase of HSI, KI, and MDA level in serum, liver and muscle (P < 0.05). Interestingly, LA also significantly elevated the ratio of total n-3 HUFAs in fatty acid composition of muscle and liver (P < 0.05). Furthermore, LA significantly promoted the activity of antioxidant enzymes in serum, muscle and liver of grass carp (P < 0.05), including superoxide dismutase (SOD), catalase (CAT), and glutathione s-transferase (GST). The further results showed that LA significantly elevated mRNA expression of antioxidant enzymes with promoting the mRNA expression of NF-E2-related nuclear factor 2 (Nrf2) and decreasing Kelch-like-ECH-associated protein 1 (Keap1) mRNA level. From the above, these results suggested that LA could attenuate n-3 HUFAs-induced lipid peroxidation, remit the toxicity of the lipid peroxidant, and protect n-3 HUFAs against lipid peroxidation to promote its deposition in fish, likely strengthening the activity of antioxidant enzymes through regulating mRNA expressions of antioxidant enzyme genes via mediating Nrf2-Keap1 signaling pathways.