In mammals, cholesterol accumulation always results in health damage such as oxidative stress. In fact, cholesterol accumulation is frequently observed in fish fed high-energy diets. However, the adverse effects of cholesterol accumulation on the physiological health of fish remain largely unexplored. The present study investigated the impacts of cholesterol accumulation on oxidative stress and its potential mechanism in Nile tilapia (Oreochromis niloticus). Thus, Nile tilapia were fed a control or a high cholesterol (1.6%) diets for eight weeks. The results showed that high cholesterol intake significantly increased visceral somatic index and hepatic-somatic index of tilapia. Accordingly, high cholesterol intake caused obvious accumulation of cholesterol in the liver, intestine, head kidney and spleen of fish. However, elevated levels of malondialdehyde (MDA) were only observed in the liver and head kidney of fish fed high-cholesterol diet. Additionally, the activities of superoxide dismutase (SOD) and catalase (CAT) enzymes either remained unchanged or significantly decreased in the liver and head kidney of fish fed high-cholesterol diet, suggested the impaired antioxidant capability in the liver and head kidney. Moreover, cholesterol accumulation induced endoplasmic reticulum stress, inflammation, and apoptosis in the liver, while these effects were less pronounced in the head kidney. Additionally, metabolome analysis indicated that differences in metabolite levels were primarily enriched in glutamine and glutamate and glutathione metabolism, as well as tricarboxylic acid cycle (TCA), with significant reductions of contents observed in glutamine, glutamate, glycine, citrate, isocitrate, aconitate, malate and oxalate. Accordingly, transmission electron microscopy analysis showed conspicuous accumulation of lipid droplets within hepatocytes and distinct alterations in the morphology of mitochondria in fish fed high-cholesterol diet. These results indicated that cholesterol accumulation impaired antioxidant capability and mitochondrial function in the liver of fish. Therefore, significantly elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzyme activities were found in fish fed high-cholesterol diet. In general, these results indicated that high cholesterol intake induced oxidative stress and health damage in the liver of tilapia. The oxidative stress induced by cholesterol accumulation might be associated with impaired antioxidant capability and mitochondrial function, as mitochondria are the primary site of cellular production of reactive oxygen species. This is the first study to reveal the impacts of cholesterol accumulation on oxidative stress and health damage in aquatic animals, and suggested targeted cholesterol-lowering interventions as a promising therapeutic strategy for addressing health issues in aquatic animal.
Butyrate-producing bacteria (BPB) benefit the health of aquatic animals. This current study aimed to isolate BPB from the intestines of Nibea coibor and assess their probiotic potential. The results showed that nine isolates were obtained in vitro from the gut of N. coibor, including six Clostridium butyricum, two Proteocatella sphenisci, and one Fusobacterium varium. The representative bacteria, C. butyricum CG-3 and P. sphenisci DG-1, which produce high butyrate levels, were further studied for short-chain fatty acid (SCFA) production and antibiotic susceptibility. The effects of BPB singly (CB: basal diet + CG-3 and PS: basal diet + DG-1, at 107 CFU/g) or in combination with galactooligosaccharides (GOS) (0.5%) and inulin (0.5%) (CBIG) or D-sorbitol (0.5%) (PSGS) on the growth and health status of N. coibor were investigated. Results showed an increase in growth parameters in the CB, CBIG, and PSGS groups, except for the PS group. Alterations in intestinal microbiota (including diversity, abundance, and function) were observed in four experimental groups (CB, CBIG, PS, and PSGS groups). SCFA contents increased in treated groups; butyrate production was positively related to bacterial abundance. Compared to control, levels of complement C3, complement C4, immunoglobulin M (IgM), transforming growth factor-β (TGF-β), interleukin (IL)-10, IL-1β, and lysozyme (LZM) increased, while malondialdehyde (MDA) decreased in treated groups. Contents of IL-6 (PS and PSGS groups), tumor necrosis factor-alpha (TNF-α) (CB, PS, and PSGS groups), total antioxidant capacity (T-AOC) (CB and PS groups), total superoxide dismutase (T-SOD) (PS group), catalase (CAT) (CB and PSGS groups), and activities of amylase (PS and PSGS groups), trypsin (CB group), and lipase (CBIG group) were increased. Our results suggested the potential use of C. butyricum CG-1 or P. sphenisci DG-1 singly or in combination with prebiotics improved growth and health conditions in N. coibor.
The ~24-amino-acid leucine-rich tandem repeat motif (PXXXXXLXXLXXLXLSXNXLXGXI) of carrot antifreeze protein comprises most of the processed protein and should contribute at least partly to the ice-binding site. Structural predictions using publicly available online sources indicated that the theoretical three-dimensional model of this plant protein includes a 10-loop β-helix containing the ~24-amino-acid tandem repeat. This theoretical model indicated that conservative asparagine residues create putative ice-binding sites with surface complementarity to the 1010 prism plane of ice. We used site-specific mutagenesis to test the importance of these residues, and observed a distinct loss of thermal hysteresis activity when conservative asparagines were replaced with valine or glutamine, whereas a large increase in thermal hysteresis was observed when phenylalanine or threonine residues were replaced with asparagine, putatively resulting in the formation of an ice-binding site. These results confirmed that the ice-binding site of carrot antifreeze protein consists of conservative asparagine residues in each β-loop. We also found that its thermal hysteresis activity is directly correlated with the length of its asparagine-rich binding site, and hence with the size of its ice-binding face.
Abstract Vibrio spp. is one of the main pathogens to cause high levels of mortality in the culture industry of mud crabs, Scylla paramamosain . Although considerable efforts have been devoted to understanding the immune response of S. paramamosain against pathogens, both immune‐response proteins and systematic responses to foreign agent invasions have yet to be investigated in detail. Hence, in this study, we challenged S. paramamosain with bacterial lipopolysaccharides ( LPS ) by injection. We examined a number of immune‐related indices in the crabs at 0, 2, 6, 12, 24, 36, 48, and 72 h postinjection, that is, the total hemocyte counts in hemolymph; the serum activities of phenoloxidase, superoxide dismutase, lysozyme, acid phosphatase, and alkaline phosphatase; and the mRNA levels of immune‐related genes encoding prophenoloxidase, serine protease inhibitors, antimicrobial peptide scygonadin, crustin, anti‐lipopolysaccharide factor, and catalase in hemocytes. In addition, the immune‐response proteins were identified in hemocytes at 24 h postinjection using two‐dimensional polyacrylamide gel electrophoresis. The results showed that the immune‐related enzymes and genes examined were induced in a time‐dependent manner post‐ LPS challenge. Moreover, 18 altered proteins were present in the hemocytes and the main proteins to be altered were highly homologous to hemocyanin and protein kinase. Ultimately, this study provides useful information for understanding the immune response of S. paramamosain to bacterial infection.
Texture is an important factor determining the quality, acceptability of aquatic products to consumers. Swim bladder from croakers is a traditionally important and high-valued aquatic product in Asia. It was generally considered that swim bladder from male croaker has higher texture quality than those from female. Therefore, mono-sex breeding or nutritional regulation represent promising strategies for improving the texture quality and value of swim bladder in the aquaculture industry of croaker. However, no direct evidence has been reported and the molecular basis associated with the sexual difference in the texture properties remains unknown. Here, we investigated the sexual dimorphism in the texture traits of swim bladder of an important marine economic fish, Chu's croaker (Nibea coibor) and its possible molecular mechanism by comparative transcriptome analysis. Results showed that the tested texture parameters (springiness, hardness, chewiness, shear force, etc.) of the swim bladder in male fish (MSB) were significantly higher than those in female (FSB). A total of 143 differentially expressed genes (DEGs) were acquired between sexes. GO and KEGG pathway enrichment analysis indicated that regulation of extracellular matrix component (ECM), ECM-receptor interaction and primary bile acid synthesis pathway may contribute to the sexual difference. Furthermore, 6 validated DEGs (tnc, gjc1, colgalt1, col12a1, cyp27a1, qpct) were demonstrated to be closely correlated with at least four texture traits. In conclusion, for the first time we demonstrated the sexual dimorphism in the texture traits of swim bladder and the result could provide potential molecular targets for regulating the texture quality of swim bladder of the Chu's croaker during aquaculture practice.
Terrestrial compound protein (Cpro) can be potentially used to replace fishmeal (FM) in the marine carnivorous teleost, golden pompano (Trachinotus ovatus). Four isonitrogenous (45%) and isolipidic (12%) diets named FM30, AP80, PP80, and CP80 were formulated. FM30 (control) contained 30% FM and 25% basic protein, while AP80, PP80, and CP80 only contained 6% FM, where 80% FM and 25% basic protein of control diet were completely replaced by animal protein, plant protein, and Cpro, respectively. After golden pompano juveniles (initial weight: 10.32 ± 0.09 g) were, respectively, fed the four diets in floating sea cages for 10 weeks, the growth performance, intestinal digestive enzyme activity, and immune responses, protein metabolism indices of the CP80 group were similar to or better than those of the FM30 group (P > 0.05), and significantly better than those of the AP80 and PP80 groups. Specifically, the weight gain (WG), feed conversion ratio (FCR), activity of alanine transaminase (ALT), growth hormone (GH), and insulin-like growth factor-1 (IGF-1) contents of serum, mRNA level of interleukin-10 (il-10), zonula occludens-2 (zo-2), claudin-3, claudin-12, and eukaryotic translation initiation factor 4G (eif4g) were significantly higher, and the activity of α-amylase (AMS), lipase (LPS) in the foregut and midgut, interleukin-8 (il-8) expression in the intestine was significantly lower than that in the CP80 group, compared with those in AP80 and PP80 groups (P < 0.05). Moreover, the intestinal microflora composition of golden pompano fed with the CP80 diet was improved. Specifically, at the phylum level, the relative abundance of harmful bacterial strains cyanobacteria and TM7 of CP80 group was similar to those of FM30 group (P > 0.05), but was significantly lower than those of AP80 and PP80 groups (P < 0.05). At the genus level, the beneficial bacterial strains Agrobacterium and Blantia of CP80 group were also similar to those of FM30 group (P < 0.05), which were significantly higher than those of AP80 and PP80 groups, but the beneficial bacterial strains Bifidobacterium and Devosia of CP80 group were significantly higher than that in the other groups (P < 0.05). Besides, in diet CP80, the contents of amino acids and anti-nutritional factor, as well as the in vitro digestion rate were comparable to those of FM30, and the anti-nutritional factor content was between AP80 and PP80; total essential amino acids (EAAs) and methionine contents were higher than those in AP80, the glycine content was higher than that in PP80. Taken together, these results indicated that the CP80 diet had better amino acid composition and relatively low content of anti-nutritional factors, as well as high-digestion rate, and thus leads to the fish fed CP80 displaying improved effects in digestive enzyme activity, immune response, protein metabolism, and intestinal microbiota composition, which may be the important reasons to explain why that 80% of FM can be replaced by Cpro in the diet of golden pompano.
Perfluoroalkyl substance (PFAS) existed ubiquitously in the environment and could be ingested unconsciously with food which posed a disease risk to human health. Swordtip squid (Uroteuthis edulis) is one of the most popular and highly consumed seafood worldwide, with wide distribution and abundant biomass. Therefore, it is of great importance to the health of the public by reducing the health risks of squid consumption while preserving the benefits of squid to humans. In this study, the PFAS and fatty acids in squids were tested from the southeast coastal regions of China, a major habitat for squids. Relative higher concentrations of PFAS in squid were found in the subtropical zone of southern China (mean: 15.90 ng/g·dw) compared to those of the temperate zone of northern China (mean: 11.77 ng/g·dw). The digestive system had high tissue/muscle ratio (TMR) values, and the pattern of TMR among the same carbon-chain PFAS was similar. Cooking methods have a significant contribution to eliminating PFAS (in squids). PFAS were transferred from squids to other mediums after cooking, so juice and oil should be poured out to minimize PFAS exposure into body. The result showed that squids can be regarded as a healthy food by health benefits associated with fatty acids. Estimated daily intake (EDI) had the highest level in Korea via consuming squids through cooking processes compared with other countries. Based on the assessment of the hazard ratios (HRs), there was a high exposure risk of perfluoropentanoic acid (PFPeA) via taking squids for human health. This research provided the theoretical guidance of aquatic product processing in improving nutrition and reducing harmful substances.
Abstract To investigate the influences of dietary protein and lipid levels on the growth, feed utilization, body composition, and lipid metabolism of golden pompano (Trachinotus ovatus), nine test diets containing three protein levels (35%, 40% and 45%) and three lipid levels (8%, 13% and 18%) were designed in the present study. Each diet (named D1-D9) was randomly assigned to feed triplicate groups of golden pompano juvenile (initial weight ~ 70 g) for 50 days. The results showed that the dietary lipid levels positively correlated with weight gain, specific growth rate, and protein efficiency ratio (PER), suggesting that the high lipid diets (18%) can be efficiently utilized in this fish species. The dietary protein levels have no significant influences on the growth and feed utilization except for the PER. Increasing dietary protein levels resulted in a decrease in HSI, VSI, and ISI, while the dietary lipid level did not have a significant impact on morphological indices except for ISI. The dietary protein and lipid levels had no significant influences on the contents of crude lipid, crude ash, and moisture of whole body, while the crude protein contents was significantly affected by the dietary protein levels. Serum biochemical indexes, including cholesterol (CHO), TG, HDL, and LDL, as well as HDL/CHO ratio were significantly affected by the dietary lipid levels, but not by the dietary protein levels. The expression levels of genes and their associated proteins involved in hepatic lipogenesis (Srebp-1c and Fas) as well as lipolysis (Pparα and Cpt-1) were up-regulated with increasing dietary lipid levels. With dietary protein levels increasing, the expression levels of genes and their associated proteins involved in hepatic lipolysis (Pparα and Cpt-1) and lipogenesis (Srebp-1c and Fas) were up-regulated and down-regulated. Considering the present results in terms of growth performance, feed utilization, morphometric parameters, and lipid metabolism, the recommended dietary protein and lipid levels for golden pompano are 40% and 18%, respectively. The findings suggested that this species exhibits a significant protein-sparing effect on lipid utilization.
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