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Triglyceride (TAG) deposition in the liver is associated with metabolic disorders. In lower vertebrate, the propensity to accumulate hepatic TAG varies widely among fish species. Diacylglycerol acyltransferases (DGAT1 and DGAT2) are major enzymes for TAG synthesis. Here we show that large yellow croaker (Larimichthys crocea) has significantly higher hepatic TAG level than that in rainbow trout (Oncorhynchus mykiss) fed with same diet. Hepatic expression of DGATs genes in croaker is markedly higher compared with trout under physiological condition. Meanwhile, DGAT1 and DGAT2 in both croaker and trout are required for TAG synthesis and lipid droplet formation in vitro. Furthermore, oleic acid treatment increases DGAT1 expression in croaker hepatocytes rather than in trout and has no significant difference in DGAT2 expression in two fish species. Finally, effects of various transcription factors on croaker and trout DGAT1 promoter are studied. We find that DGAT1 is a target gene of the transcription factor CREBH in croaker rather than in trout. Overall, hepatic expression and transcriptional regulation of DGATs display significant species differences between croaker and trout with distinct hepatic triglyceride deposition, which bring new perspectives on the use of fish models for studying hepatic TAG deposition. Two diacylglycerol acyltransferases were shown to be differently regulated in large yellow croaker and rainbow trout. While DGAT1 is increased upon oleic acid treatment more in croaker than in trout, DGAT2 showed no significant expression difference. [ABSTRACT FROM AUTHOR]

The mall heterodimer partner (SHP) plays an important regulatory role in mammal inflammation. The main objective of this study was to investigate the response of SHP to inflammatory stimulation and its underlying mechanism. The shp gene from large yellow croakers, was cloned, and this gene is mainly expressed in the liver and intestine. Lipopolysaccharide (LPS) stimulation induced the mRNA expression and protein level of SHP in macrophages of large yellow croakers. Overexpression of SHP significantly decreased mRNA expression of tnfα , il-1β , il-6 and cox2 induced by LPS treatment in macrophages. LPS stimulation increased the phosphorylation level of Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) in macrophages. AMPK inhibitor treatment significantly decreased the expression of SHP induced by LPS while AMPK activator significantly increased the expression of SHP. The nuclear factor-erythroid 2-related factor 2 (NRF2) increased the promoter activity of SHP in large yellow croakers and the level of nuclear NRF2 was increased by LPS stimulation and AMPK activation. NRF2 inhibitor treatment significantly decreased mRNA expression of shp induced by LPS and AMPK activator. In conclusion, LPS can induce SHP expression by activating the AMPK-NRF2 pathway while SHP could negatively regulate LPS-induced inflammation in large yellow croakers. This study may be benefit to the development of immunology of marine fish and provide new ideas for inflammation-related diseases. [ABSTRACT FROM AUTHOR]

Background: High linoleic acid (LA) intake leads to inflammation that adversely influences health in fish. However, whether the farnesoid X receptor (FXR) could be an effective target for regulating LA-induced inflammation remains unknown.Objective: The purpose of this study was to investigate the role of FXR in the regulation of LA-induced inflammation in large yellow croakers.Methods: Large yellow croakers (initial weight of 10.03 ± 0.02 g) were allocated to 4 groups and fed a fish oil diet (6% FO), a soybean oil diet (6% SO), or the SO diet supplemented with 300 or 900 mg chenodeoxycholic acid (CDCA)/kg for 10 wk. The cultured kidney cell line PCK and primary hepatocytes from large yellow croakers were stimulated by LA (50 μM) after pretreatment with an FXR ligand (GW4064 or CDCA) or transfection with fxr-small interfering RNA (siFXR). mRNA expression of proinflammatory genes in the head kidney and liver tissues, PCK cells, and primary hepatocytes was determined by qPCR. The luciferase reporter assay, electrophoretic mobility shift assay, and immunoprecipitation assay were conducted in HEK 293T cells to determine the transcriptional activity of P65 and protein interactions between P65 and FXR or the small heterodimer partner (SHP).Results: Proinflammatory genes were 93-1180% higher in the SO group compared with the FO group. CDCA supplementation decreased mRNA expression of proinflammatory genes by 17-87% while increasing fxr and shp expression by 120-460%. In PCK cells and primary hepatocytes, ligand-mediated activation of FXR decreased the LA-induced expression of proinflammatory genes by 18-67%, whereas siRNA-mediated knockdown of FXR increased the LA-induced expression of proinflammatory genes by 64-96%. FXR bound to the promoter of shp and regulated its mRNA expression. Both FXR and SHP could bind to P65 to suppress the transcriptional activity of P65.Conclusions: These results indicate that FXR has anti-inflammatory properties in large yellow croakers by directly and indirectly suppressing NFκB activity. [ABSTRACT FROM AUTHOR]

In the present study, farnesoid X receptor (FXR) was cloned and characterized from liver of large yellow croaker ( L crocea ) and the effects of dietary chenodeoxycholic acid (CDCA), a nature ligand of FXR, on the inflammatory genes expression in the intestine and spleen of large yellow croaker were investigated. Multiple alignments showed that FXR of large yellow croaker contained highly conserved DNA-binding domain and ligand binding domain compared with other species. The subcellular localization analysis showed that FXR-GFP fusion protein could target to the nucleus in HEK 293 t. The tissue specific results demonstrated that FXR was highly expressed in liver, intestine and kidney of large yellow croaker. In addition, dietary soybean oil decreased the expression of FXR and IL-10 and significantly increased the expression of the pro-inflammatory genes in the intestine or spleen, such as TNFα, COX-2, IL-1β, IL-6, while the supplementation of CDCA could partly reverse these effects. These results suggested that the supplementation of CDCA may relieve the inflammation of intestine and spleen in large yellow croaker via the activation of FXR. [ABSTRACT FROM AUTHOR]

An experiment was conducted to determine the effects of dietary chenodeoxycholic acid (CDCA) on the growth performance, body composition and lipid deposition of juvenile large yellow croaker ( Larimichthys crocea ) (initial weight, 10.03 ± 0.02 g) fed a soybean oil diet. The practical diet with 6% soybean oil (SO) was used as the control, and a fish oil (FO) diet was designed with 6% fish oil. On the basis of the soybean oil diet, 300 mg and 900 mg/kg (CDCA) were added, respectively. After 10-week growth trial, results showed that survival rate (SR) and condition factor (CF) were not significantly different among dietary treatments. Compared with the FO group, final weight (FW) and weight gain rates (WGR) in the SO group significantly decreased while the groups with the supplementation of CDCA show significantly better growth performance than the SO group and FO group. The lipid content of liver was significantly increased by the replacement of FO with SO but decreased with the increase of the supplementation of CDCA. The activity of lipoprotein lipase was significantly higher in fish fed the diet with 900 mg/kg CDCA supplementation. The expression of PPARα decreased while the expression of SREBP-1 increased significantly in fish fed the SO diet compared with fish fed the FO diet. Meanwhile, dietary 900 mg/kg CDCA significantly upregulated the expression of PPARα and FXR while the expression of SREBP-1 was decreased by the supplementation of CDCA. The results suggested that the supplementation of CDCA could improve the growth performance and lipid deposition of liver in large yellow croaker which were negatively affected by the replacement of dietary fish oil with soybean oil. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the effects of dietary bile acid (BA) on the growth performance, body composition, antioxidant responses and expression of lipid metabolism-related genes of juvenile large yellow croaker (Larimichthys crocea) (average weight, 12.00 ± 0.20 g). An optimal lipid diet formulated with 4.0% fish oil and 4.0% soybean oil was set as the positive control diet (MO), while a high-lipid diet formulated with 6.5% fish oil and 6.5% soybean oil was used as the negative control diet (HO). The other three diets were supplemented with 150 (HOB150), 300 (HOB300) and 450 mg/kg (HOB450) BA on the basis of the negative control diet. The results showed that the survival rate (SR) was not significantly different among dietary treatments (P > 0. 05). Compared with the positive control, there were no significant differences in final body weight (FBW) and weight gain rate (WGR) among fish fed diets with high lipid contents. With increasing supplementation of BA in diets, the FBW and WGR gradually increased. Compared with the negative control, fish fed the diet with 300 mg/kg BA had significantly higher FBW and WGR (P <.05). The liver lipid content and liver malondialdehyde (MDA) content significantly decreased with increasing dietary BA (P <.05). In fish fed diets with 300 mg/kg-450 mg/kg BA, the activities of lipoprotein lipase (LPL) and hepatic lipase (HL) were significantly increased (P <.05). The sterol regulatory element binding protein-1 (SREBP-1) mRNA expression levels in the liver significantly decreased with increasing dietary BA (P <.05). Furthermore, increasing dietary BA from 150 mg/kg to 450 mg/kg significantly improved the mRNA expression levels of peroxisome proliferator activated receptor α (PPARα), carnitine palmitoyltransferase 1 (CPT1) and acyl-CoA oxidase (ACO) in the liver (P <.05). These results suggested that dietary BA supplementation could improve the digestion and absorption capacity of lipids, which might be the reason for the improvement in the growth performance of large yellow croaker. • Bile acid in high-lipid diets can significantly improve the growth of juvenile large yellow croaker. • The content ratio of n-3PUFA and n-6PUFA in muscle was increased with increasing dietary bile acid. • Dietary bile acid can improve the antioxidant capacity of juvenile large yellow croaker. • Bile acid significantly reduce liver lipid deposition by regulating lipid synthesis and oxidation pathways. [ABSTRACT FROM AUTHOR]