Waterborne Zn influenced Zn uptake and lipid metabolism in two intestinal regions of juvenile goby Synechogobius hasta

Association of Blood Trace Elements Levels with Cardiovascular Disease in US Adults: a Cross-Sectional Study from the National Health and Nutrition Examination Survey 2011-2016

We aimed to explore the overall association between trace elements and cardiovascular disease (CVD) and its types in humans. A total of 5101 participants' blood samples from the 2011-2016 National Health and Nutrition Examination Survey were included. Biochemical data were collected from laboratory tests conducted at mobile screening centers. After assessing linearity, weighted logistic regression estimated the association between trace elements and various CVD types. Weighted quantile sum (WQS) regression and quantile-based g-computation (Qgcomp) evaluated the overall relationship between biological trace elements and CVD types. After fully adjusting for confounding factors, the odds ratios of overall CVD morbidity corresponding to the second, third, and fourth quartiles of higher selenium (Se) concentration were 0.711 (95% CI, 0.529-0.956, p = 0.024), 0.734 (95% CI, 0.546-0.987, p = 0.041), and 0.738 (95% CI, 0.554-0.983, p = 0.038), respectively. Moreover, an increase in the concentration of copper (Cu) was associated with an increased risk of stroke (95% CI, 1.012-1.094, p = 0.01), heart failure (95% CI, 1.001-1.095, p = 0.046), and heart attack (95% CI, 1.001-1.083, p = 0.046). As the concentration of trace elements in the body increased, there was a significant positive association between Cu and CVD prevalence. On the other hand, Se and zinc were negatively associated with CVD prevalence. A nonlinear relationship between Se and CVD was found, and an appropriate Se intake may reduce the risk of CVD. Cu levels positively correlated with CVD risk. However, prospective cohort studies are warranted to confirm the causal effects of the micronutrients on CVD and its types.

Transcriptional regulation of Znt family members znt4, znt5 and znt10 and their function in zinc transport in yellow catfish (Pelteobagrus fulvidraco)

The study characterized the transcriptionally regulatory mechanism and functions of three zinc (Zn) transporters (znt4, znt5 and znt10) in Zn2+ metabolism in yellow catfish (Pelteobagrus fulvidraco), commonly freshwater fish in China and other countries. We cloned the sequences of znt4 promoter, spanning from -1217 bp to +80 bp relative to TSS (1297 bp); znt5, spanning from -1783 bp to +49 bp relative to TSS (1832 bp) and znt10, spanning from -1923 bp to +190 bp relative to TSS (2113 bp). In addition, after conducting the experiments of sequential deletion of promoter region and mutation of potential binding site, we found that the Nrf2 binding site (-607/-621 bp) and Klf4 binding site (-5/-14 bp) were required on znt4 promoter, the Mtf-1 binding site (-1674/-1687 bp) and Atf4 binding site (-444/-456 bp) were required on znt5 promoter and the Atf4 binding site (-905/-918 bp) was required on znt10 promoter. Then, according to EMSA and ChIP, we found that Zn2+ incubation increased DNA affinity of Atf4 to znt5 or znt10 promoter, but decreased DNA affinity of Nrf2 to znt4 promoter, Klf4 to znt4 promoter and Mtf-1 to znt5 promoter. Using fluorescent microscopy, it was revealed that Znt4 and Znt10 were located in the lysosome and Golgi, and Znt5 was located in the Golgi. Finally, we found that znt4 knockdown reduced the zinc content of lysosome and Golgi in the control and zinc-treated group; znt5 knockdown reduced the zinc content of Golgi in the control and zinc-treated group and znt10 knockdown reduced the zinc content of Golgi in the zinc-treated group. High dietary zinc supplement up-regulated Znt4 and Znt5 protein expression. Above all, for the first time, we revealed that Klf4 and Nrf2 transcriptionally regulated the activities of znt4 promoter; Mtf-1 and Atf4 transcriptionally regulated the activities of znt5 promoter and Atf4 transcriptionally regulated the activities of znt10 promoter, which provided innovative regulatory mechanism of zinc transporting in yellow catfish. Our study also elucidated their subcellular location, and regulatory role of zinc homeostasis in yellow catfish.

Starvation Affects the Muscular Morphology, Antioxidant Enzyme Activity, Expression of Lipid Metabolism-Related Genes, and Transcriptomic Profile of Javelin Goby (Synechogobius hasta)

Fish in natural and cultivated environments can be challenged by starvation. However, inducing starvation in a controlled manner cannot only reduce feed consumption but also reduces aquatic eutrophication and even improves farmed fish quality. This study investigated the effects of starvation on the muscular function, morphology, and regulatory signaling in javelin goby (Synechogobius hasta) by evaluating the biochemical, histological, antioxidant, and transcriptional changes in the musculature of S. hasta subjected to 3, 7, and 14 days fasting. The muscle glycogen and triglyceride levels in S. hasta were gradually reduced under starvation, reaching their lowest at the end of the trial (P < 0.05). The levels of glutathione and superoxide dismutase were significantly elevated after 3-7 days of starvation (P < 0.05), but later returned to the level of the control group. The muscle of starved S. hasta developed structural abnormalities in some areas after 7 days of food deprivation, and more vacuolation and more atrophic myofibers were observed in 14-day fasted fish. The transcript levels of stearoyl-CoA desaturase 1 (scd1), the key gene involved in the biosynthesis of monounsaturated fatty acids, were markedly lower in the groups starved for 7 or more days (P < 0.05). However, the relative expressions of genes associated with lipolysis were decreased in the fasting experiment (P < 0.05). Similar declines in the transcriptional response to starvation were found in muscle fatp1 and ppar γ abundance (P < 0.05). Furthermore, the de novo transcriptome of muscle tissue from the control, 3-day and 14-day starved S. hasta generated 79,255 unigenes. The numbers of differentially expressed genes (DEGs) identified by pairwise comparisons among three groups were 3276, 7354, and 542, respectively. The enrichment analysis revealed that the DEGs were primarily involved in metabolism-related pathways, including ribosome, TCA pathway, and pyruvate metabolism. Moreover, the qRT-PCR results of 12 DEGs validated the expression trends observed in the RNA-seq data. Taken together, these findings demonstrated the specific phenotypical and molecular responses of muscular function and morphology in starved S. hasta, which may offer preliminary reference data for optimizing operational strategies incorporating fasting/refeeding cycles in aquaculture.

Effects of Zinc Adaptation on Histological Morphology, Antioxidant Responses, and Expression of Immune-Related Genes of Grass Carp (Ctenopharyngodon idella)

The study was conducted to evaluate the effect of zinc adaptation on histological morphology and antioxidant and immune responses of grass carp(Ctenopharyngodon idella). A total of 180 young grass carp (20.0 ± 2.0 g) was equally distributed into 9 groups, and triplicate groups were subjected to 0 μg/L Zn²⁺ (control group), 200 μg/L Zn²⁺, and 300 μg/L Zn²⁺ solution for 42 days, respectively. The results indicated that the liver and gill have obvious pathological changes after long-term adaptation to zinc except the intestine; the zinc adaptation can positively influence intestinal morphology. The activities of GPX (glutathione peroxidase activity), SOD (superoxide dismutase), and CAT (Catalase) were significantly increased in zinc treatment groups (P < 0.05). The genes expression levels of CuZnSOD (copper zinc superoxide dismutase), CAT, Hsp70 (heat shock protein-70), IL-1b (interleukin-1-b), and TGF-β1 (transforming growth factor-β1) were upregulated in the gill and intestine of grass carp following waterborne adaptation to zinc solution for 42 days (P < 0.05). In conclusion, zinc adaptation has different effects on organs of grass carp and may reduce the inflammatory response of the body's gills and intestines by improving the body's antioxidant and anti-stress defense capabilities.

Distinct responses from triglyceride and cholesterol metabolism in common carp (Cyprinus carpio) upon environmental cadmium exposure

Due to high persistence and bioavailability, Cadmium (Cd) is one of the most prevalent environmental contaminants, posing an elevating threat to the ecosystems. It has been evidenced that high-dose Cd elicits deleterious effects on aquatic organisms, but the potential toxicities of Cd at environmentally relevant concentrations remains underappreciated. In this study, we used common carp to investigate how environmental Cd exposure affects triglyceride (TG) and cholesterol metabolism and underlying mechanisms. The data indicated that Cd resulted in the shift of TG from the liver to blood and the movement of cholesterol in the opposite direction, ultimately giving rise to the storage of crude lipid in liver and muscle, especially hepatic cholesterol retention. Cholesterol, instead of TG, became the principal cause during the progression of hepatic lipid accumulation. Mechanistic investigations at transcriptional and translational levels further substantiated that Cd blocked hepatic biosynthesis of TG and enhanced TG efflux out of the liver and fatty acid β-oxidation, which collectively led to the compromised TG metabolism in the liver and accelerated TG export to the serum. Additionally, strengthened synthesis, retarded export and oxidation of cholesterol detailed the hepatic prominent cholesterol retention. Taken together, our results demonstrated that environmental exposure to Cd perturbed lipid metabolism through triggering distinct responses from hepatic TG and cholesterol homeostasis. These indicated that environmental factors (such as waterborne Cd) could be a potential contributor to the prevalence of non-alcoholic fatty-liver disease in aquaculture and more efforts should be devoted to the ecological risk assessment of pollutants under environmental scenarios.

KLF7 Alleviates Atherosclerotic Lesions and Inhibits Glucose Metabolic Reprogramming in Macrophages by Regulating HDAC4/miR-148b-3p/NCOR1

OBJECTIVES

Atherosclerosis (AS) remains a major contributor to death worldwide. This study sought to explore the role of Krüppel-like factor 7 (KLF7) in AS lesions via regulating glucose metabolic reprogramming (GMR) in macrophages.

METHODS

AS mouse and cell models were established via high-fat-diet feeding and oxidized low-density lipoprotein (ox-LDL) induction. KLF7, histone deacetylase 4 (HDAC4), miR-148b-3p, and nuclear receptor corepressor 1 (NCOR1) expressions in aortic tissue and cells were detected via reverse transcription quantitative polymerase chain reaction or Western blotting. Parameters of AS lesions and mouse metabolism were detected via hematoxylin-eosin, oil red O, and Masson staining, assay kits, glucose tolerance test, and enzymatic analysis. Peritoneal macrophages of mice were isolated and cellular metabolism was detected via Seahorse metabolic flux analysis, assay kits, ELISA, and Western blotting. Bindings among KLF7, HDAC4, microRNA (miR)-148b-3p, and NCOR1 were testified via the dual-luciferase assay and chromatin immunoprecipitation assay.

RESULTS

KLF7 was poorly expressed in AS mice and ox-LDL-induced RAW264.7 cells. KLF7 overexpression attenuated AS lesions and rescued metabolic abnormities in AS mice, and reduced glucose intake and GMR in ox-LDL-induced RAW264.7 cells. Mechanically, KLF7 bound to the HDAC4 promoter to activate HDAC4. HDAC4 reduced H3 and H4 acetylation levels in the miR-148b promoter to inhibit miR-148b-3p and promote NCOR1 transcription. HDAC4 downregulation abolished the protective role of KLF7 overexpression in AS mice and ox-LDL-induced RAW264.7 cells via the miR-148b-3p/NCOR1 axis.

CONCLUSION

KLF7 bound to the HDAC4 promoter to activate HDAC4, inhibit miR-148b-3p via reducing acetylation level, and promote NCOR1 transcription, thereby limiting GMR in macrophages and alleviating AS lesions.

Phylogeny of the HO family in cyprinus carpio and the response of the HO-1 gene to adding Bacillus coagulans in feed under Cd2+ stress

The heavy metal cadmium (Cd²⁺) is an environmental pollutant that poses serious health hazards. Due to the increasing contamination of aquatic systems with Cd²⁺, the increased accumulation of Cd²⁺ in fish has become a food safety and public health concern. Heme oxygenase (HO) is an important antioxidant enzyme that plays a key role in defending the body against oxidative damage, but little research has been done in common carp. In this study, 6 HO genes were identified in the common carp genome database. Comparative genomics analysis showed considerable expansion of the HO genes and verified the four-round whole genome duplication (WGD) event in common carp. Phylogenetic analysis revealed that all HO genes of common carp were clustered into orthologous groups, indicating high conservation during evolution. In addition, the tissue distribution results showed that most HO genes had extensive tissue distribution and showed tissue-specific expression patterns. Exposure to 0.5 mg/L Cd²⁺ significantly reduced the expression of TGF-β and IL-10 in common carp, which may indicate that Cd²⁺ exposure can destroy the physical barrier function of the intestine, inhibit intestinal immune defense and induce intestinal inflammation. To find a suitable concentration of Bacillus coagulans that could activate HO-1 genes and the immunity of the organism, we investigated the changes in HO-1 gene expression levels in the intestinal tract of common carp under Cd²⁺ stress at 30 days and 60 days by adding different concentrations of B. coagulans to the feed. Compared with the Cd²⁺ stress group without supplementation, the expression levels of the HO-1 gene in the gut of three different concentrations of B. coagulans were almost increased. And B. coagulans with L2 concentrations had better activation effect on the HO-1 gene. Similarly, compared to the Cd²⁺ stressed group, adding B. coagulans to the diet can almost cause the early upregulation of IL-10 and TGF-β genes. Therefore, the addition of appropriate concentrations of B. coagulans may be a good way to activate HO-1, IL-10, and TGF-β genes, reduce oxidative damage, and encourage the immune.

Intestinal response characteristic and potential microbial dysbiosis in digestive tract of Bufo gargarizans after exposure to cadmium and lead, alone or combined

The gastrointestinal tract is the largest immune organ in the body and meanwhile, accommodates a large number of microorganisms. Heavy metals could disturb the intestinal homeostasis and change the gut microbial composition. However, the information regarding the links between dysbiosis of gut microbiota and imbalance of host intestinal homeostasis induced by the mixture of heavy metals is insufficient. The present study investigates the effects of Cd/Pb, both single and combination exposure, on the growth performance, intestinal histology, digestive enzymes activity, oxidative stress and immune parameters, and intestinal microbiota in Bufo gargarizans tadpoles. Our results revealed that co-exposure of Cd-Pb induced more severe impacts not only on the host, but the intestinal microbiota. On the one hand, co-exposure of Cd-Pb significantly induced growth retardation, intestinal histological injury, decreased activities of digestive enzymes. On the other hand, Cd and Pb exposure, especially in mixed form, changed the diversity and richness, structure of microbiota. Also, the intestinal microbial composition was altered by Cd/Pb exposure (alone and combination) both at the different levels. Proteobacteria, act as front-line responder, was significantly increased in tadpoles under the exposure of metals. Finally, the functional prediction revealed that the disorders of metabolism and immune responses of intestinal microbiota was increased in tadpoles exposed to Cd/Pb (especially the mixture of Cd and Pb). Our research complements the understanding of links between changes in host fitness loss and intestinal microbiota and will add a new dimension of knowledge to the ecological risks of mixed heavy metals in amphibian.

Zn Induces Lipophagy via the Deacetylation of Beclin1 and Alleviates Cu-Induced Lipotoxicity at Their Environmentally Relevant Concentrations

In this study, the mechanisms of environmentally relevant doses of Cu and Zn mixtures influencing lipid deposition and metabolism were investigated in freshwater teleost yellow catfish Pelteobagrus fulvidraco (2 months old, 4.95 (t0.01 g, mean ± SEM). Our study indicated that waterborne Cu exposure increased lipid content, while Zn activated lipophagic flux and alleviated Cu-induced lipid accumulation. Yellow catfish hepatocytes treated with Zn or Zn + Cu activated autophagy-specific lipophagy, decreased lipid storage, and increased nonesterified fatty acid (NEFA) release, suggesting a causal relationship between lipophagy and lipid droplet (LD) breakdown under Zn and Zn + Cu conditions. Our further investigation found that Beclin1 deacetylation by sirtuin 1 (SIRT1) was required for Zn- and Zn + Cu-induced lipophagy and lipolysis, and lysine residues 427 and 434 were key sites for Beclin1 deacetylation. Taken together, these findings show that the Zn-induced deacetylation of Beclin1 promotes lipophagy as an important pathway to alleviate Cu-induced lipid accumulation in fish, which reveals a previously unidentified mechanism for understanding the antagonistic effects of Cu and Zn on metabolism at their environmentally relevant concentrations. Our results highlight the importance of combined exposure when the biological effects of heavy metals are evaluated during environmental risk assessments.

Dietary Marginal and Excess Selenium Increased Triglycerides Deposition, Induced Endoplasmic Reticulum Stress and Differentially Influenced Selenoproteins Expression in the Anterior and Middle Intestines of Yellow Catfish Pelteobagrus fulvidraco

Selenium (Se) is an essential micro-mineral and plays important roles in antioxidant responses, and also influences lipid metabolism and selenoprotein expression in vertebrates, but the effects and mechanism remain unknown. The study was undertaken to decipher the insights into dietary Se influencing lipid metabolism and selenoprotein expression in the anterior and middle intestine (AI and MI) of yellow catfish Pelteobagrus fulvidraco. Yellow catfish (weight: 8.27 ± 0.03 g) were fed a 0.03- (M-Se), 0.25- (A-Se), or 6.39- (E-Se) mg Se/kg diet for 12 wk. AI and MI were analyzed for triglycerides (TGs) and Se concentrations, histochemistry and immunofluorescence, enzyme activities, and gene and protein levelsassociated with antioxidant responses, lipid metabolism, endoplasmic reticulum (ER) stress, and selenoproteome. Compared to the A-Se group, M-Se and E-Se diets significantly decreased weight gain (WG) and increased TGs concentration in the AI and MI. In the AI, compared with A-Se group, M-Se and E-Se diets significantly increased activities of fatty acid synthase, expression of lipogenic genes, and suppressed lipolysis. In the MI, compared to the A-Se group, M-Se and E-Se diets significantly increased activities of lipogenesis and expression of lipogenic genes. Compared with A-Se group, E-Se diet significantly increased glutathione peroxidase (GPX) activities in the AI and MI, and M-Se diet did not significantly reduce GPX activities in the AI and MI. Compared with the A- Se group, E-Se diet significantly increased glutathione peroxidase (GPX) activities in the plasma and liver, and M-Se diet significantly reduced GPX activities in the plasma and liver. Compared with the A-Se group, M-Se and E-Se groups also increased glucose-regulated protein 78 (GRP78, ER stress marker) protein expression of the intestine. Dietary Se supplementation also differentially influenced the expression of the 28 selenoproteins in the AI and MI, many of which possessed antioxidant characteristics. Compared with the A-Se group, the M-Se group significantly decreased mRNA levels of txnrd2 and txnrd3, but made no difference on mRNA levels of these seven GPX proteins in the MI. Moreover, we characterized sterol regulatory element binding protein 1c (SREBP1c) binding sites of three ER-resident proteins (selenom, selenon, and selenos) promoters, and found that Se positively controlled selenom, selenon, and selenos expression via SREBP1c binding to the selenom, selenon, and selenos promoter. Thus, dietary marginal and excess Se increased TGs deposition of yellow catfish P. fulvidraco, which might be mediated by ER-resident selenoproteins expression and ER stress.

Effects of dechlorane plus on intestinal barrier function and intestinal microbiota of Cyprinus carpio L

Dechlorane Plus (DP) is a typical polychlorinated flame retardant that has been emerged in chemical products. Due to its accumulation and amplification effect, the toxicity of DP has become a widespread environmental safety issue. However, whether DP can affect the intestinal tract of teleost fish remains largely unclear. To understand its effects on the intestinal barrier, morphological characteristics and intestinal microbiome of common carp, different concentrations (30, 60 and 120 μg/L) of DP were exposed to common carps for 4 weeks. The results indicated that DP evidently shortened the intestinal folds and damaged the intestinal epithelium layer. In addition, the mRNA expression levels of occludin, claudin-2 and zonula occludens-1 (ZO-1) were significantly decreased with increasing DP concentrations. Furthermore, the relative abundance of some microbiota species were also changed significantly. Our study first demonstrated that DP could cause damage to the intestinal epithelium and destroy the intestinal barrier and increase the relative abundance of pathogenic bacteria, thereby increasing the probability of contact between intestinal epithelium and pathogenic bacteria, which in turn lead to an increased susceptibility to various diseases and poor health. In summary, our findings reveal that chronic DP exposure can have a harmful effect on the intestinal flora balance and is potentially linked to human disease.

Functional Analysis of Two Zinc (Zn) Transporters (ZIP3 and ZIP8) Promoters and Their Distinct Response to MTF1 and RREB1 in the Regulation of Zn Metabolism

ZIP (zinc-regulated transporters, iron-regulated transporter-like protein) family plays an important role in organism Zn balance. This research identified the promoter regions of ZIP3 and ZIP8, two members of ZIP family, from a freshwater teleost yellow catfish Pelteobagrus fulvidraco, characterized the binding sequences of the metal-responsive transcription factor-1 (MTF-1) and Ras responsive element binding protein 1 (RREB1) on their promoter regions. The present study cloned and obtained the 2027 bp of ZIP3 promoter and 1664 bp of ZIP8 promoter, and predicted several key elements on their promoters, such as the binding sites of CREB (cAMP-response element binding protein), KLF4 (Kruppel like factor 4), MTF-1 and RREB1. The sequence deletion from −361 bp to −895 bp down-regulated the luciferase activity of ZIP3 promoter, and the deletion from −897 bp to −1664 bp down-regulated the luciferase activity of ZIP8 promoter. Within different deletion plasmids, the relative luciferase activities of ZIP3 and ZIP8 promoters changes to Zn incubation in a Zn concentration-dependent manner. The site mutagenesis and EMSA (electrophoretic mobility shift assay) found that the −1327 bp/−1343 bp MTF-1 binding site and the −248 bp/−267 bp RREB1 binding site on the ZIP3 promoter, and the −1543 bp/−1557 bp MTF-1 binding site on the ZIP8 promoter are functional sites. Low Zn increased the binding capability between MTF-1 and its responsive site on the ZIP3 promoter, and high Zn increased the transcriptional activation ZIP3 by RREB1; Zn also promoted the binding ability between MTF-1 and its responsive element on the ZIP8 promoter. This study provides the first direct evidence for the response elements of MTF-1 and RREB1 on ZIP3 and MTF-1 on ZIP8 to Zn, which are very important for the evaluation of Zn nutrition and toxicity in vertebrates.

Molecular cloning, tissue expression, and transcriptional regulation of fabp1 and fabp2 in javelin goby (Synechogobius hasta) in response to starvation stress

Fatty acid binding proteins (FABPs) are intracellular lipid chaperones with low molecular weight, which are widely distributed in a variety of tissues, participating in fatty acid transport, cell proliferation, and angiogenesis. In this study, full-length sequences of two fabp genes (fabp1 and fabp2) from javelin goby (Synechogobius hasta) were cloned via RACE PCR, followed by bioinformatic analyses and gene expression evaluation. The fabp1 and fabp2 cDNA sequences were 493 and 626 bp in length, encoding 126 and 132 amino acids, respectively. Phylogenetic analysis revealed that both genes from S. hasta were clustered with those of other fish species in accordance with their known taxonomic relationships. fabp1 and fabp2 mRNA showed distinct expression patterns in different tissues, with fabp1 being most expressed in the liver and fabp2 in the intestine. Furthermore, the expression of fabp1 in the liver was significantly up-regulated during starvation, whereas fabp2 mRNA level in the intestine initially increased and then decreased, indicating that the transcriptional responses of the two genes could be influenced by malnourishment/starvation. Changes in the transcriptional levels of fabp1 and fabp2 also suggested that glycogen was catabolized in the liver of S. hasta at the beginning of starvation prior to lipid depletion, whereas lipids served as fuel reserves in the intestine during short-term starvation. In conclusion, this study provides fundamental insights into the role of Fabps in S. hasta lipid metabolism.

Effects of dietary zinc level on growth performance, lipolysis and expression of genes involved in the calcium/calmodulin-dependent protein kinase kinase-β/AMP-activated protein kinase pathway in juvenile Pacific white shrimp

The present study evaluated the effects of dietary Zn level on growth performance, serum and hepatopancreas metabolites, expression of genes involved in lipid and energy metabolism, and the signalling pathway of dietary Zn-induced lipolysis. Five isonitrogenous and isolipidic diets were formulated to contain different Zn levels: 46·4 (basal diet), 77·2, 87·0, 117·1 and 136·8 mg/kg, respectively. The results indicated that shrimp fed the diet containing Zn at 117·1 mg/kg had higher weight gain and specific growth rate, and the lowest feed intake and feed conversion rate, than shrimp fed the other diets. The deposition rate of Zn in whole body significantly decreased with increasing dietary Zn level. Dietary Zn prevented the accumulation of free radicals and improved antioxidant activities by increasing Cu/Zn superoxide dismutase and reducing malondialdehyde in hepatopancreas. Dietary Zn supplementation enhanced lipase activity and adiponectin, which could promote TAG breakdown and fatty acid oxidation and lead to reduced lipid in hepatopancreas. The mRNA expressions ofob-rb,adipor,camkkβ,ampk,cd36,mcdandcpt1involved in Zn-induced lipid catabolism were up-regulated, and the expressions ofsrebp,acc,fasandscd1were down-regulated. The mRNA levels of SLC39 family genes (zip3,zip9,zip11andzip14) in hepatopancreas were up-regulated with increasing dietary Zn level. The results demonstrated that dietary Zn level could significantly affect growth performance, tissue deposition of Zn, lipid metabolites and expression of genes involved in lipogenesis and lipolysis inLitopenaeus vannamei.

Molecular characterization of ten zinc (Zn) transporter genes and their regulation to Zn metabolism in freshwater teleost yellow catfish Pelteobagrus fulvidraco

BACKGROUND

Zn is an essential trace element for vertebrates, and Zn uptake and transport is related with the ZIP family of Zn transporters. Meantime, Zn also influenced the expression of ZIP family members.

METHODS

We cloned and characterized the full-length cDNA sequences of ten Zn transport-relevant genes (ZIP1, ZIP3, ZIP6, ZIP7, ZIP8, ZIP9, ZIP10, ZIP11, ZIP13 and ZIP14) from yellow catfish Pelteobagrus fulvidraco, investigated their mRNA tissue expression. These ZIP mRNA expression was also assessed in the primary hepatocytes and intestinal epithelial cells of yellow catfish in response to three Zn levels (0, 30 μM and 60 μM, respectively).

RESULTS

All these genes shared the similar domains with the corresponding members in mammals. The mRNA expression of the ten ZIP genes was detected in nine-tested tissues, but variable among these tissues. Flow cytometry analysis and confocal microscopy observation indicated that intracellular free Zn²⁺ concentration in hepatocytes and intestinal epithelial cells increased with increasing Zn incubation concentration at both 24 h and 48 h. Zn incubation differentially influenced mRNA levels of ZIP transporters in the hepatocytes and intestinal epithelial cells, in a time- and cells-dependent manners. In the hepatocytes, at 24 h, compared to the control, Zn addition down-regulated mRNA levels of ZIP1, ZIP3, ZIP6, ZIP7, ZIP8, ZIP9, ZIP11 and ZIP14; however, ZIP10 mRNA levels were lower in 60 μM Zn group than those in the control and 30 μM Zn group. At 48 h, mRNA levels of ZIP1, ZIP6, ZIP7, ZIP9, ZIP10 and ZIP14 declined with increasing Zn incubation concentrations; ZIP3 mRNA levels were the lowest in 60 μM Zn group and showed no significant differences between the control and 30 μM Zn group. In the intestinal epithelial cells, at 24 h, Zn addition down-regulated mRNA levels of ZIP1, ZIP6, ZIP7, ZIP8, ZIP9, ZIP10, ZIP11, ZIP13 and ZIP14; ZIP3 mRNA levels were lower in 60 μM Zn group than those in the control and 30 μM Zn group. At 48 h, Zn addition up-regulated mRNA levels of ZIP6 and ZIP9, but down-regulated mRNA levels of ZIP8, ZIP10 and ZIP13. ZIP7, ZIP11 and ZIP14 mRNA abundances were the lowest in 60 μM Zn group and showed no significant differences between the control and 30 μM Zn group.

CONCLUSION

For the first time, our study characterized ten ZIP family members in yellow catfish, explored their mRNA tissue expression. Their regulation to Zn addition were also investigated in the hepatocytes and intestinal epithelial cells of yellow catfish. Our study revealed the mechanism of cells exposed to Zn addition and provided novel insights for the regulatory mechanism of Zn homeostasis.

Zinc alleviates arsenism in common carp: Varied change profiles of cytokines and tight junction proteins among two intestinal segments

This study was designed to evaluate the effects of zinc on inflammation and tight junction (TJ) in different intestinal regions of common carp under sub-chronic arsenic insult. Fish were exposed to zinc (0, 1 mg/L) and arsenic trioxide (0, 2.83 mg/L) in individual or combination for a month. Inflammatory infiltration and TJ structure changes were displayed by H&E staining and transmission electron microscope. To further explore these changes, biochemical indicator (SOD), gene or protein expressions of inflammatory responses (NF-κB, IL-1β, IL-6 and IL-8) and TJ proteins (Occludin, Claudins and ZOs) were determined. In the anterior intestine, arsenic decreased activity of SOD, mRNA levels of Occludin, Claudins and ZOs, increased mRNA levels of ILs. However, unlike the anterior intestine, arsenic has an upregulation effects of Occludin and Claudin-4 in the mid intestine. These anomalies induced by arsenic, except IL-8, were completely or partially recovered by zinc co-administration. Furthermore, transcription factor (NF-κB) nuclear translocation paralleled with its downstream genes in both intestinal regions. In conclusion, our results unambiguously suggested that under arsenic stress, zinc can partly relieve intestinal inflammation and disruption of tight junction segment-dependently.

Endoplasmic Reticulum Stress-Mediated Autophagy and Apoptosis Alleviate Dietary Fat-Induced Triglyceride Accumulation in the Intestine and in Isolated Intestinal Epithelial Cells of Yellow Catfish

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.

Inhibitory effect of cadmium exposure on digestive activity, antioxidant capacity and immune defense in the intestine of yellow catfish (Pelteobagrus fulvidraco)

Cadmium (Cd) is a toxic heavy metal that can pose a serious threat to aquatic organisms. To evaluate the physiological response and defense mechanism of fish intestine to Cd toxicity, yellow catfish (Pelteobagrus fulvidraco) were exposed to 0 (control), 50 μg/L and 200 μg/L Cd²⁺ for a period of 8 weeks, and then histological changes, digestive activity, antioxidant status and immune responses in the anterior intestine were assessed. After exposure, significant growth retardation and Cd accumulation were observed, and obvious histopathological lesions in the intestine such as increased goblet cells, excessive mucus, vacuolization and thickened lamina propria were detected. Intestinal digestive enzymes activities and related gene expression were inhibited markedly in Cd²⁺ treatments. Furthermore, Cd exposure induced oxidative stress inhibiting antioxidant activity, characterized by an increase in malondialdehyde level as well as the decrease in the activity and transcription level of antioxidant enzymes. In addition, exposure to Cd²⁺ down-regulated the expression of key genes involved in the immune response (lys, c3, tor, tgf-β, il-10, tnf-α and il-8), suggesting immune defense was inhibited. Taken together, the decreased digestive enzyme activity and Cd-induced toxicity stress for antioxidant and immune systems in the intestine might be account for individual growth retardation.

Toxicological effects of waterborne Zn on the proximal and distal intestines of large yellow croaker Larimichthys crocea

The aim of the present study was to compare the differences of Zn-induced antioxidant defense, immunotoxicity and Zn homeostasis between the proximal and distal intestines of the large yellow croaker Larimichthys crocea. Fish were exposed to Zn (2 and 10 mg L^-1) for 96 h. In the proximal intestine, high-concentration Zn increased mortality and oxidative damage, but reactive oxygen species (ROS), lipid peroxidation (LPO), protein carbonylation (PC) levels were not affected by low-concentration Zn, indicating Zn-induced oxidative damage was concentration-dependent. Antioxidant defense and immunotoxicity in response to Zn exposure may be involved in ROS/ NFE2-related nuclear factor 2 (Nrf2) and ROS/nuclear transcription factor κB (NF-κB) signaling pathways. In the distal intestine, Zn exposures did not induce oxidative damage, which may result from the improvement of Zn transport, antioxidant and immune defenses. Nrf2 was positively correlated with antioxidant-related gene in the distal intestine, but no relationship was observed between Nrf2 and CAT gene expressions in the proximal intestine. In conclusion, Zn induced toxicological effects were intestinal-region-dependent, which provided some novel insights into Zn toxicology.

Differential effects of β-glucan on oxidative stress, inflammation and copper transport in two intestinal regions of large yellow croaker Larimichthys crocea under acute copper stress

The aim of the present study was to evaluate investigate the effects of β-glucan on oxidative stress, inflammation and copper transport in two intestinal regions of large yellow croaker under acute copper stress. Fish were injected with β-glucan at a dose of 0 or 5 mg kg^-1 body weight on 6, 4 and 2 days before exposed to 0 and 368 μg Cu L^-1 for 48 h. Biochemical indicators (MDA, Cu content, MTs protein levels, Cu/Zn-SOD, CAT and iNOS activities), gene expressions of oxidative stresses (Cu/Zn-SOD, CAT, Nrf2, MTs and MTF-1), inflammatory responses (NF-κB, iNOS, IL-1β, IL-6 and TNF-α) and Cu transporters (ATP7A, ATP7B and CTR1) were determined. In the anterior intestine, β-glucan increased MTs levels, activities of Cu/Zn-SOD, CAT and iNOS, mRNA levels of MTs, CAT, iNOS, ATP7A and ATP7B, and reduced Cu content and CTR1 gene expression to inhibite Cu-induced MDA. But β-glucan had no effect on inflammatory gene expressions. In the mid intestine, β-glucan increased activities of Cu/Zn-SOD and iNOS, mRNA levels of Cu/Zn-SOD, CAT and iNOS to maintain MDA content. However, unlike the anterior intestine, β-glucan had no effect on Cu transporter gene expressions. Furthermore, transcription factors (Nrf2, NF-κB and MTF-1) paralleled with their target genes in the mid intestine, but no correlation was observed between NF-κB and IL-1β and TNF-α gene expressions in the anterior intestine. In conclusion, our results unambiguously showed that β-glucan induced oxidative stress, inflammation and copper transport were varied between the anterior and mid intestines of fish under Cu stress.