Anti-miR33 therapy improved hepatopancreatic lipid and immune metabolism disorders in grass carp, Ctenopharyngodon idella.

Lipid metabolism disorders are found ubiquitously in farmed fish and occur as a result of excessive fat accumulation. Previous studies have found that miR-33 is involved in lipid metabolism; however, its role in fish lipid metabolism is unclear. We sought to clarify this relationship in grass carp in vivo and in vitro. Our findings revealed the length of miR-33 to be 65 bp. Phylogenetic tree analysis showed that grass carp miR-33 was most closely related to fish miR-33 (Siganus canaliculatus). Hepatocytes transfected with miR-33 mimic displayed markedly raised TG content (P < 0.05) as well as increased levels of lipid synthesis-related transcription factors (P < 0.05). Compared with blank and saline groups, total serum cholesterol, AST, and LDL levels were suppressed in groups treated with the miR-33 antagomir (P < 0.05). Moreover, the expression levels of PPARγ and SREBP-1c mRNA were significantly decreased in contrast to those found in the control group (P < 0.05). Similar findings were noted in the expression of immune-related proinflammatory molecules (TNFα, IL-1ß, IL-6, and NF-κB), which also demonstrated decreased levels (P < 0.05). Conversely, high expressions of anti-inflammatory factors (TGF-ß1 and IL-10) were noted (P < 0.05). This investigation strongly supports the role of miR-33 in hepatopancreas-based lipid metabolism and immunity. miR-33 may have been highly conserved in early vertebrates in order to facilitate liver-specific metabolic and immunomodulatory functions. Our findings provide a basis for further investigations exploring the mechanisms surrounding fish lipid metabolism and may aid in preventing and treating immunocompromised fish as well as fish with fatty hepatopancreas, and other metabolic diseases.

Grape seed proanthocyanidin extract ameliorates hepatic lipid accumulation and inflammation in grass carp (Ctenopharyngodon idella).

Hepatic lipid metabolism disorder due to excessive fat accumulation in fish is a significant problem in aquaculture. Studies have shown that grape seed procyanidin extract (GSPE) can regulate fish lipid metabolism and improve fish immunity. However, the mechanism is unclear. In this study, we used grass carp that stores excess fat in the liver as a model. In vitro, GSPE treatment of hepatocytes for 3 h significantly decreased TG content, accompanied with decreased expression of SREBP-1c, FAS, and ACC and increased expression of PPARα, ATGL, and LPL. GSPE treatment for 1 h significantly decreased expression of pro-inflammatory cytokines (TNFα, IL-6, IL-1ß, and NF-κB) and increased the expression of anti-inflammatory cytokines (IL-10 and TGF-ß1). In vivo, the administration of GSPE significantly reduced high-fat diet-induced increase of serum CHOL, TG, and HDL, but increased LDL content. GSPE treatment for 3 h increased expression of ATGL and LPL, and significantly decreased the expression of HFD-fed-induced SREBP-1c, ACC, FAS, PPARγ, PPARα, and H-FABP. GSPE treatment for 3 h also significantly decreased the expression of pro-inflammatory cytokines (TNFα, IL-6, and IL-1ß) and increased the expression of the anti-inflammatory cytokine IL-10. The expression levels of the lipogenic miRNAs, miR-33, and miR-122, were suppressed both in vivo and in vitro by GSPE. In summary, GSPE had hypolipidemic and potential anti-inflammatory effects in the liver, potentially mediated by miR-33 and miR-122.

Regulation of growth performance and lipid metabolism in juvenile grass carp (Ctenopharyngodon idella) with honeysuckle (Lonicera japonica) extract.

This study investigated the effects of honeysuckle extract (Lonicera japonica, HE) on the growth performance and lipid metabolism of juvenile grass carp (Ctenopharyngodon idella). HE at doses of 10 g kg-1 (LHE), 20 g kg-1 (MHE), and 40 g kg-1 (HHE) were individually mixed with the basal diet and fed to grass carp for 10 weeks, and ginseng extract (20 g kg-1, GSE) was used as a positive control. The results showed that HE administration exerted no effect on growth performance, but the hepatosomatic index (HSI) and muscle and liver lipid contents were significantly decreased in the LHE and MHE groups. The serum levels of LDL-c, total triglyceride (TG) and total cholesterol (TC) also declined in the HE-treated groups. Moreover, the disordered vacuolization and nucleus migration in the liver were alleviated in the MHE and HHE groups, and mRNA expressions of lipogenesis-related genes, such as acc1, fas, srebp1, and pparγ decreased. Similarly, the expression of genes related to lipolysis, such as cpt1, atgl, lpl, and pparα, was found to be significantly increased in the MHE and HHE groups compared with the control. Taken together, HE can effectively improve the lipid metabolism and ameliorate the lipid deposition of grass carp and thus may be a promising feed additive in aquaculture.

Comparative analysis of the hepatopancreas transcriptome of grass carp (Ctenopharyngodon idellus) fed with lard oil and fish oil diets.

n-3 highly unsaturated fatty acids (n-3 HUFAs) have been shown to suppress lipid accumulation and improve protein utilization in grass carp; however, little is known about the underlying molecular mechanism. Hence, we analyzed the hepatopancreas transcriptome of grass carp (Ctenopharyngodon idellus) fed either lard oil (LO) or fish oil (FO) diets. RNA-seq data showed that 125 genes were significantly up-regulated and 107 were significantly down-regulated in the FO group. Among them, 17 lipid metabolism related genes, 12 carbohydrate metabolism related genes, and 34 protein metabolism related genes were selected. Lipid metabolism related genes, such as very long-chain acyl-CoA synthetase (ACSVL),carnitine O-palmitoyltransferase 1 (CPT1) and carnitine-acylcarnitine translocase (CACT), were up-regulated in the FO group. But the genes of diacylglycerol O-acyltransferase 2 (DGAT2) and stearoyl-CoA desaturase (SCD) were down-regulated. Down-regulation of glycolysis related genes, such as 6-phosphofructokinase (PFK), phosphoglycerate kinase (PGK) and pyruvate dehydrogenase kinase (PDK), added with up-regulation of gluconeogenesis related genes, such as phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase), suggests lower utilization of carbohydrate of the FO group. Besides, dietary FO also influenced the protein metabolism related genes, such as up-regulation of genes involved in digestion of dietary protein, mRNA transcription, protein translation and amino acid utilization, down-regulation of genes involved in mRNA degradation and ubiquitination of protein. Interestingly, the up-regulation of mitochondrial uncoupling protein 2 (UCP2) and down-regulation of oxidative phosphorylation related genes (cytochrome c oxidase subunit 4 isoform 2 [COX4I2], HIG1 domain family member 1A [HIGD1A] and cytochrome-b5 reductase [CYB5R]) suggest that energy metabolism may be also influenced by dietary fatty acid composition. These findings presented here provide a comprehensive understanding of the molecular mechanisms governing the effects of fish oil in grass carp.