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Background: The intestine is the main organ for absorbing dietary fat. High dietary lipid intake leads to fat deposition in the intestine and adversely influences fat absorption and health, but the underlying mechanism is unknown.Objectives: We used yellow catfish and their isolated intestinal epithelial cells to test the hypothesis that endoplasmic reticulum (ER) stress, autophagy, and apoptosis mediate fat-induced changes in lipid metabolism.Methods: Male and female yellow catfish (weight: 3.79 ± 0.16 g; age: 3 mo) were fed diets containing lipid at 6.98% (low-fat diet; LFD), 11.3% (middle-fat diet; MFD), or 15.4% (high-fat diet; HFD) (by weight) for 8 wk. Each dietary group had 3 replicates, 30 fish per replicate. Their intestinal epithelial cells were isolated and incubated for 24 h in control solution or various concentrations of fatty acids (FAs) with or without 2-h pretreatment with an inhibitor [3-methyladenine (3-MA), 4-phenyl butyric acid (4-PBA), or Ac-DVED-CHO (AC)]. Triglyceride (TG) contents, genes, and enzymes involved in lipid metabolism, ER stress, autophagy, and apoptosis were determined in intestinal tissue and cells; immunoblotting, BODIPY 493/503 staining, ultrastructural observation, and the detection of autophagic and apoptotic vesicles were performed on intestinal cells.Results: Compared with the LFD and MFD, the HFD increased intestinal TG content by 120-226%, activities of lipogenic enzymes by 19.0-245%, expression of genes related to lipogenesis (0.77-8.4-fold), lipolysis (0.36-6.0-fold), FA transport proteins (0.79-1.7-fold), ER stress (0.55-7.5-fold), autophagy (0.56-4.2-fold), and apoptosis (0.80-5.2-fold). Using isolated intestinal epithelial cells and inhibitors (4-PBA, 3-MA, and AC), we found that ER stress mediated FA-induced activation of autophagy (11.0-50.1%) and apoptosis (10.4-32.0%), and lipophagy and apoptosis mediated FA-induced lipolysis (3.40-41.6%).Conclusions: An HFD upregulated lipogenesis, lipolysis, and FA transport, induced ER stress, and activated autophagy and apoptosis. ER stress, autophagy, and apoptosis play important regulatory roles in fat-induced changes in lipid metabolism in the intestine and intestinal epithelial cells of yellow catfish. [ABSTRACT FROM AUTHOR]

Selenium (Se) functions through selenoproteins and is essential to growth and metabolism of vertebrates. The present study was conducted to identify twelve selenoproteins genes (selenoe , selenof , selenoh , selneoi , selenom , selenok , selneon , selenoo , selenot , selenos , selenou and msrb1) from yellow catfish. Their mRNA expression patterns, as well as their response to dietary oxidized fish oils and Se addition were explored. We use 3′and 5′ RACE PCR to clone full-length cDNA sequence of twelve selenoprotein genes from yellow catfish. Their mRNA expression patterns were assessed via quantitative real-time PCR. Yellow catfish were fed diet adequate Se+ fresh fish oil, adequate Se+ oxidized fish oil, high Se+ fresh fish oil and high Se+ oxidized fish oil, respectively, for 10 weeks. Their kidney, heart, brain and testis were used to assess the mRNA expression of twelve selenoprotein. Twelve selenoprotein genes had similar domains with mammals and the other fish. Their mRNAs were expressed widely in eleven tissues but varied with the tissues. Dietary oxidized fish oils and Se addition influenced their mRNA abundances of twelve selenoproteins in a tissue-dependent manner. Our study demonstrated the characterization and expression of twelve selenoproteins, and elucidated their responses in yellow catfish fed diets varying in oxidized fish oils and Se addition, which increased our knowledge into the biological function and regulatory mechanism of Se and selenoproteins in fish. [ABSTRACT FROM AUTHOR]

• We obtained the 1993-bp, 2000-bp and 1959-bp promoters of three selenoproteins. • Se increase the activities of the selenok , selenot and selenop promoters. • Functional FoxO4, Nrf2, KLF4 and ATF4 sites were identified on their promoters. • Se promoted FoxO4, Nrf2, KLF4 and ATF4 binding ability to their promoters. The selenok , selenot and selenop are three key selenoproteins involved in stress response. Our study, using the yellow catfish Pelteobagrus fulvidraco as the experimental animal, obtained the 1993-bp, 2000-bp and 1959-bp sequences of selenok , selenot and selenop promoters, respectively, and predicted the binding sites of several transcriptional factors on their promoters, such as Forkhead box O 4 (FoxO4), activating transcription factor 4 (ATF4), Kruppel-like factor 4 (KLF4) and nuclear factor erythroid 2-related factor 2 (NRF2). Selenium (Se) increased the activities of the selenok , selenot and selenop promoters. FoxO4 and Nrf2 can directly bind with selenok promoter and controlled selenok promoter activities positively; KLF4 and Nrf2 can directly bind with selenot promoter and controlled selenot promoter activities positively; FoxO4 and ATF4 can directly bind to selenop promoter and regulated selenop promoter activities positively. Se promoted FoxO4 and Nrf2 binding to selenok promoter, KLF4 and Nrf2 binding to selenot promoter, and FoxO4 and ATF4 binding to selenop promoter. Thus, we provide the first evidence for FoxO4 and Nrf2 bindnig elements in selenok promoter, KLF4 and Nrf2 binding elements in selenot promoter, and FoxO4 and ATF4 binding elements in selenop promoter, and offer novel insight into regulatory mechanism of these selenoproteins induced by Se. [ABSTRACT FROM AUTHOR]

Lipid overload-induced hepatic cholesterol accumulation is a major public health problem worldwide, and choline has been reported to ameliorate cholesterol accumulation, but its mechanism remains unclear. Our study found that choline prevented high-fat diet (HFD)-induced cholesterol metabolism disorder and enhanced choline uptake and phosphatidylcholine synthesis in the liver tissues; choline incubation prevented fatty acid (FA)-induced cholesterol accumulation and FA-induced inhibition of bile acid synthesis. Moreover, compared to single FA incubation, choline incubation or FA + choline co-incubation increased the mRNA abundances and protein levels of HNF4α and up-regulated the degradation of cholesterol into bile acids. Mechanistically, choline prevented the FA-induced accumulation of SREBP2 protein and the interaction between SREBP2 and HNF4α, thereby enhancing the DNA binding capacity of the HNF4α to the CYP7A1 promoter, and promoting the degradation of cholesterol into bile acids. Our study elucidated the novel regulatory mechanisms of choline preventing HFD-induced cholesterol accumulation and increasing bile acid synthesis by SREBP-2/HNF-4α/CYP7A1 pathway. • Choline prevented high-fat diet-induced cholesterol metabolism disorder. • Choline prevented FA-induced cholesterol accumulation and inhibition of bile acid synthesis. • Choline increased HNF4α expression and up-regulated cholesterol degradation. • Choline prevented the FA-induced interaction between SREBP2 and HNF4α. • Choline enhanced HNF4α binding capacity to CYP7A1 promoter, and promoted cholesterol degradation. [ABSTRACT FROM AUTHOR]

Mounting evidence showed that excess selenium (10.0–15.0-fold of adequate Se) intake caused severe hepatic lipid deposition in the vertebrate. However, the underlying mechanism remains unclear. The study was performed to elucidate the mechanism of Se supranutrition mediated-changes of lipid deposition and metabolism. We found that dietary excessive Se addition increased hepatic TGs and glucose contents, up-regulated lipogenic enzyme activities and reduced hepatic glycogen contents. Transcriptomic and immunoblotting analysis showed that Se supranutrition significantly influenced serine/threonine kinase 1 (AKT1)-forkhead box O3a (FOXO3a)-PYGL signaling and protein levels of SELENOF. Knockdown of SELENOF and PYGL by RNA interference revealed that the AKT1-FOXO3a-PYGL axis was critical for Se supranutrition-induced lipid accumulation. Moreover, Se supranutrition-induced lipid accumulation was via the increased DNA binding capacity of FOXO3a to PYGL promoter, which increased glycogenolysis, and accordingly promoted lipogenesis and lipid accumulation. Our finding provides new insight into the mechanism of Se supranutrition-induced lipid accumulation and suggests that SELENOF may be a therapeutic target for Se supranutrition induced-lipid disorders in the vertebrates. [Display omitted] • Excessive Se intake increased induced lipid deposition and decreased glycogen content; • Se decreased phosphorylation of AKT1 and affected FOXO3a nuclear translocation; • SELENOF mediated Se-induced changes of TGs and glycogen contents; • AKT1-FOXO3a-PYGL pathway mediated these physiological processes.. [ABSTRACT FROM AUTHOR]

At present, studies involved in the effects of dietary Se sources on lipid metabolism were very scarce and the underlying mechanism remains unknown. Previous studies reported that dietary Se sources differentially affected selenoprotein S (SELENOS) expression and SELENOS affected lipid metabolism via the inositol-requiring enzyme 1α (IRE1α)- spliced X-box binding protein 1 (XBP1s) pathway. Thus, we used yellow catfish as an experimental model to explore whether dietary selenium sources affected the hepatic lipid metabolism, and further determined the role of SELENOS-IRE1α-XBP1s pathway in dietary selenium sources affecting hepatic lipid metabolism. Compared with the selenomethionine (S-M) group, sodium selenite (S S) group possessed higher liver triglycerides (TGs) (34.7%), lipogenic enzyme activities (57.9–70.6%), and lower antioxidant enzyme activities (23.3–35.5%), increased protein levels of heat shock transcription factor 1 (HSF1) and SELENOS (1.17-fold and 47.4%, respectively), and XBP1s- peroxisome proliferators-activated receptor γ (PPARγ) pathway. Blocking SELENOS and PPARγ by RNA interference demonstrated that the SELENOS/XBP1s/PPARγ axis was critical for S-S-induced lipid accumulation. Moreover, S-S-induced upregulation of SELENOS was via the increased DNA binding capacity of HSF1 to SELENOS promoter, which activated the XBP1s/PPARγ pathway and promoted lipogenesis and lipid accumulation. XBP1s is required for S-S-induced upregulation of PPARγ expression. Our finding elucidated the mechanism of dietary Se sources affecting the lipid metabolism in the liver of yellow catfish and demonstrated novel function of SELENOS in metabolic regulation. Our study also suggested that seleno-methionine was a better Se source than selenite against abnormal lipid deposition in the liver of yellow catfish. [Display omitted] • Dietary inorganic Se increased TGs content and up-regulated lipogenesis. • Dietary inorganic Se increased protein levels of HSF1 and SELENOS. • SELENOS/XBP1s/PPARγ axis was critical for inorganic Se-induced TG deposition. • Inorganic Se induced SELENOS expression via the increased HSF1 binding to its promoter. • XBP1s is required for inorganic Se-induced upregulation of PPARγ expression and lipogenesis. [ABSTRACT FROM AUTHOR]

• Oxidized fish oil increased lipid content by ROS-induced mitochondria dysfunction. • OxEPA-activated lipophagy was via inhibiting the CREB-1-Bcl-2-Beclin1 pathway. • Our study demonstrated the mechanisms of oxidized fish oils increasing lipid deposition. • Fish oils supplements after oxidization is harmful for obese and NAFLD patients. At present, the harmful effects and relevant mechanism of oxidized fish oils on fish and fish cells remain unknown. Our study found that oxidized fish oils increased lipogenesis, and reduced lipolysis, activated oxidative stress by decreasing glutathione peroxidase (GPX) activity, increasing malondialdhyde (MDA) content and damaging mitochondrial structure, and activated autophagy in the liver of yellow catfish; oxidized eicosapentaenoic acid (oxEPA) induced oxidative stress in yellow catfish hepatocytes. Oxidative stress, mitochondrial dysfunction and lipophagy mediated oxEPA induced-variations in lipid metabolism. Our further investigation indicated that oxEPA-activated lipophagy was via inhibiting the DNA binding capacity of the cAMP-response element binding protein (CREB)-1 to the region of Bcl-2 promoter, which in turn suppressed the binding activity of Bcl-2 to Beclin1 and promoted autophagosome formation. For the first time, our study elucidated the mechanisms of oxidized fish oils-induced lipid deposition by the oxidative stress, mitochondrial dysfunction and CREB1-Bcl-2-Beclin1 pathway in fish. [ABSTRACT FROM AUTHOR]

• The present study cloned and characterized the sequences of seven selenoproteins. • Their mRNAs were widely expressed in various tissues, but at variable levels. • Dietary Se influenced mRNA levels of selenoproteins in different tissues. • The study increased our understanding of biological functions of Se and selenoproteins. Selenium (Se) appears in the selenoproteins in the form of selenocysteine (Sec) and is important for the growth and development of vertebrates. The present study characterized seven selenoproteins, consisting of the GPX1, GPX3, GPX4, SELENOW, SELENOP, TXNRD2 and TXNRD3 cDNAs in various tissues of yellow catfish, explored their regulation to dietary Se addition. 3′ and 5′ RACE PCR were used to clone full-length cDNA sequences of seven selenoprotein genes (GPX1, GPX3, GPX4, SELENOW, SELENOP, TXNRD2 and TXNRD3). Their molecular characterizations were analyzed, including conservative motifs and the SECIS elements. The phylogenetic trees were generated through neighbor-joining (NJ) method with MEGA 6.0 with 1000 bootstrap replications. Quantitative real-time PCR was used to explore their mRNA tissue distribution in the heart, anterior intestine, dorsal muscle, head kidney, gill, liver, brain, spleen and mesenteric fat. Yellow catfish (mixed sex) were fed diets with dietary Se contents at 0.03 (low Se), 0.25 (adequate Se) and 6.39 (high Se) mg Se/kg, respectively, for 12 weeks, and their spleen, kidney, testis and brain were used for the determination of the mRNA levels of the seven selenoproteins. The seven selenoproteins had similar domains to their corresponding members of other vertebrates. They were widely expressed in nine tissues, including heart, liver, brain, spleen, head kidney, dorsal muscle, mesenteric fat, anterior intestine and gill, but showed tissue-dependent expression patterns. Dietary Se addition affected the expression of the seven genes in spleen, kidney, testis and brain tissues of yellow catfish. Taken together, our study demonstrated the characterization, expression and regulation of seven selenoproteins, which increased our understanding of the biological functions of Se and selenoproteins in fish. [ABSTRACT FROM AUTHOR]

Enrofloxacin (ENR) is a kind of widespread hazardous pollutant on aquatic ecosystems and causes toxic effects, such as disorders of metabolism, on aquatic animals. However, its potential mechanisms at an environmental concentration on metabolic disorders of aquatic organisms remain unclear. Herin, we found that hepatic lipotoxicity was induced by ENR exposure, which led to ENR accumulation, oxidative stress, mitochondrial fragmentation, and fatty acid transfer blockage from lipid droplets into fragmented mitochondria. ENR-induced lipotoxicity and mitochondrial β-oxidation down-regulation were mediated by reactive oxygen species (ROS). Moreover, dynamin-like protein 1 (DRP1) mediated ENR-induced mitochondrial fragmentation and changes of lipid metabolism. Mechanistically, ENR induced increment of DRP1 mitochondrial localization via dephosphorylating DRP1 at S627 and promoted its interaction with mitochondrial fission factor (MFF), leading to mitochondria fragmentation. For the first time, our study provides an innovative mechanistic link between hepatic lipotoxicity and mitochondrial fragmentation under ENR exposure, and thus identifies previously unknown mechanisms for the direct relationship between environmental ENR concentration and lipotoxicity in aquatic animals. Our study provides innovative insights for toxicological mechanisms and environmental risk assessments of antibiotics in aquatic environment. [Display omitted] • Enrofloxacin (ENR) induced lipotoxicity and promoted mitochondrial fragmentation. • ENR blocked fatty acids transfer from lipid droplets into mitochondria. • Reactive oxygen species mediated ENR-induced lipotoxicity. • Dynamin-like protein 1 (DRP1) mediated ENR-induced mitochondrial fragmentation. • ENR induced mitochondria fragmentation via dephosphorylating DRP1 at S627. [ABSTRACT FROM AUTHOR]

The goal of this study was to clone and characterize complete cDNA sequences of three important development-relevant genes of yellow catfish Pelteobagrus fulvidraco , including lrp6 , sox9a1 and fgfr2c , and explore their transcriptional responses in several tissues of P . fulvidraco to high fat diet. The predicted amino acid sequences of P . fulvidraco Lrp6, Sox9a1 and Fgfr2c contained all of the conserved structural features that were characteristic of these genes in other species, including YWTD domains, EGF-like repeats, LDLR ligand binding repeats, PPSP repeats motifs, HMG box, TA-binding functional domain, Ig I-III and PTK I-II. The mRNAs of the three genes were expressed in various tissues, but their mRNA levels varied among tissues. Compared to the control, high fat diet tended to down-regulate the mRNA expression of sox9a1 and fgfr2c in mesenteric fat, liver and ovary, and up-regulate their mRNA levels in muscle and kidney; in contrast, high fat diet down-regulated lrp6 mRNA levels in the ovary and muscle, but had no significant effects on lrp6 mRNA expression in mesenteric fat, liver and kidney. Our findings provide the first data about their expression responses to dietary lipid in teleosts and reinforce the multiple functions at the molecular level. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the influences of five dietary manganese (Mn) sources on growth, feed utilization, lipid metabolism, antioxidant capacity, inflammatory response and endoplasmic reticulum stress in intestinal tissues of yellow catfish Pelteobagrus fulvidraco. Five Mn sources include Mn sulfate monohydrate (MnSO 4 ·H 2 O), Mn dioxide (MnO 2), Mn dioxide nanoparticles (MnO 2 NPs), Mn glycine chelate (Mn-Gly) and hydroxymethionine-chelated Mn (Mn-MHA). Yellow catfish (initial body weight: 2.69 ± 0.01 g/fish) were fed five experimental diets for 10 weeks. Dietary Mn sources significantly affected intestinal Mn content and metabolism. Compared to other Mn sources, yellow catfish fed organic Mn sources (Mn-Gly and Mn-MHA) tended to improve growth, feed utilization, intestinal histology, up-regulated mRNA abundance of tight junction-relevant genes, increased intestinal fatty acid uptake and transport and triglyceride deposition, and reduced inflammatory responses. These dietary organic Mn supplements also increased intestinal antioxidant capacity by up-regulating antioxidant gene expression and enzymatic activities. Yellow catfish fed two organic Mn diets had the lower mRNA expressions of endoplasmic reticulum stress-relevant gene and protein expression. Based on these observations above, dietary organic supplements (Mn-Gly and Mn-MHA) improved the growth and feed utilization, and promoted intestinal health of yellow catfish, and accordingly seems to be optimal Mn sources for yellow catfish. Our results provided the innovative insights into dietary Mn sources influencing tight junction, antioxidant capacity and inflammatory responses, endoplasmic reticulum stress and fatty acid uptake and uptake in the fish intestine, and found that organic Mn sources were more suitable as the Mn supplements in yellow catfish feeds, and also possibly in other aquatic feed. • Two organic Mn sources in yellow catfish diet positively affect growth performance. • Two organic Mn sources in yellow catfish diet improved intestinal tight junction. • Two organic Mn in yellow catfish diet increased fatty acid uptake and TG deposition. • Two organic Mn reduced intestinal inflammation and increased antioxidant capacity. • Two organic Mn sources in yellow catfish diet improved the ER function. [ABSTRACT FROM AUTHOR]