Fish Physiology and Biochemistry最新文献

Preventive health management is central to modern aquaculture practices, within which functional feed additives are a key tool to optimising fish robustness and disease resilience. Despite being well documented, only few studies have assessed the dose-effect of graded levels of S. cerevisiae yeast cell wall (YCW) on fish performance and mucosal barrier immunity. A 9-week trial was conducted to assess the impact of graded levels of YCW on the performance and mucosal barriers of the European seabass under period: (1) non-challenge (43 days) then (2) with an applied husbandry stressors (20 days) in the form of high stocking density, low water oxygen level, and repetitive handling. The four experimental diets were produced by incorporating graded levels of YCW (0.0, control; 1.5; 3.0 or 4.5 kg/MT) which were top dressed on the basal diet prior extrusion. At the end of the period 1, fish supplemented with YCW at 4.5 kg/MT revealed a 5% increase in body-weight compared to the control. Likewise, throughout the experimental period SGR and FCR were also improved by YCW supplementation (+ 5.8% and + 8.3% with YCW4.5, respectively). Supplemented diets increased intraepithelial lymphocytes density and the highest level of intake was associated with increased skin mucus secretion (+ 31% with YCW 4.5 kg/MT). Finally, we observed a linear relationship between fecal calprotectin-like levels and the YCW gradient: a positive correlation during period 1 and a negative correlation during period 2. In contrast, YCW supplementation levels were characterized by a positive linear relationship with fecal mucins across both periods. These results provide novel insights on the benefits and associated mechanisms of YCW extracts and reveal an optimal dose response with inclusion levels between 3.0 and 4.5 kg/MT. This study demonstrates that YCW dietary inclusion enhances growth performance, feed utilization, and mucosal immune barrier function in European seabass, with improved stress resilience evidenced by biomarkers fecal calprotectin-like and fecal mucins.

This study investigated the effects of substituting Tenebrio molitor larvae meal (TM) for fishmeal at varying inclusion levels (0%-TM0, 50%-TM50, 75%-TM75 and 100%-TM100) on growth performance, digestive enzyme activities, and antioxidant responses in Nile tilapia (Oreochromis niloticus). Four different isonitrogenous and isolipidic experimental diets were formulated and fed to the fish for 12 weeks. The highest growth performance was observed in the TM75 group, while polynomial regression analysis indicated an optimal replacement level around 66%. TM inclusion significantly modulated the activities of digestive enzymes amylase, lipase, pepsin, and trypsin. Antioxidant enzymes including catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) showed increased activity in TM-fed groups, particularly at moderate inclusion levels. However, elevated levels of lipid peroxidation (LPO) in the TM75 and TM100 groups indicated a threshold beyond which oxidative stress may arise despite enhanced antioxidant defense. These results suggest that TM meal can be a promising alternative protein source in tilapia diets when used at optimized inclusion levels, supporting both physiological performance and oxidative balance. The findings contribute to sustainable aquafeed strategies by identifying the biological and functional limits of insect meal use in freshwater fish.

The binding of fatty acid (FA) to fatty acid translocase (FAT/CD36) and subsequent regulation of lipid metabolism transcription factors, such as peroxisome proliferator-activated receptors α (PPARα) and sterol regulatory element-binding protein-1c (SREBP-1c), is an important hypothalamic fatty acid-sensing mechanism in vertebrates. The hypothalamus exhibits responsiveness to specific fatty acids and is involved in reproductive regulation. However, the link between FA sensing and reproductive regulation in the hypothalamus remains poorly understood teleosts. Therefore, the expression of genes involved in the FA-sensing mechanism-such as fat/cd36, pparα, and srebp1c, as well as gonadotropin-releasing hormone (GnRH: cgnrh, sgnrh, sbgnrh) in the hypothalamus-was investigated after intracranial administration and hypothalamic incubation of polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA), eicosapentanoic acid (EPA), and linoleic acid (LA) for 4 h in the spotted scat (Scatophagus argus). Compared to the control, intracranial administration and hypothalamic incubation of DHA and LA, as well as hypothalamic incubation of EPA, increased the levels of fat/cd36, pparα, and srebp1c. However, the expression of fat/cd36 and pparα was significantly decreased, and the level of srebp1c showed a downward trend only in the EPA group when co-incubated with the FAT/CD36 inhibitor Sulfo-N-succinimidyl oleate sodium (SSO), compared to incubation with EPA alone. After the application of PPARα antagonist GW6471, the expression of pparα in the hypothalamus decreased significantly in the DHA, EPA, and LA treatment groups, compared to incubation with DHA, EPA, and LA alone. Levels of fsh and lh in the pituitary gland were changed significantly after the intracranial administration of DHA, EPA, and LA. Compared to the control, the levels of cgnrh, sgnrh, and sbgnrh increased in the hypothalamus after both hypothalamic incubation and intracranial administration of EPA and LA. Levels of cgnrh increased in the hypothalamus after incubation, but not after intracranial administration of DHA. However, compared to the control, levels of sgnrh and sbgnrh increased after hypothalamic incubation with DHA and EPA. Only sgnrh levels decreased after incubation with LA in the presence of SSO compared to the FA treatment group alone. In the presence of GW6471, only sgnrh levels decreased after incubation with LA in the presence of SSO compared to the FA treatment group alone; the levels of cgnrh, sgnrh, and sbgnrh after LA incubation, the levels of sbgnrh after EPA incubation, and the levels of sbgnrh after DHA incubation were all significantly decreased compared to the control. These results showed that DHA, EPA, and LA could activate fat/cd36 and pparα, which are involved in reproductive regulation in the hypothalamus of the spotted scat. These results provide evidence that hypothalamic FA sensing is involved in regulating reproduction in teleosts.

Environmental contamination with heavy metals increases the risk of copper (Cu²⁺) exposure in fish, animals, and humans, potentially leading to poisoning and even fatality. This study aimed to assess the alleviating effects of α-lipoic acid (α-LA), a potent antioxidant, on oxidative stress and lipid metabolism disorders elicited by Cu²⁺. Swamp eel (Monopterus albus) were randomly divided into four groups: control group (untreated), α-LA group (+ α-LA 1000 mg/kg), Cu²⁺ group (+ Cu²⁺ 500 mg/kg), and Cu²⁺ + α-LA (+ Cu²⁺ 500 mg/kg + α-LA 1000 mg/kg) group, and were fed for 56 days. Subsequently, the effects of α-LA on Cu²⁺-induced toxicity were investigated by analyzing histopathological alterations, biochemical indicators and gene expression profile alterations. Our findings demonstrated that α-LA administration significantly diminishes hepatic Cu²⁺ accumulation and mitigates hepatic histopathological lesions caused by Cu²⁺. Moreover, α-LA invigorated the potency of antioxidant enzymes, including POD, GPx, and GST, and diminished GSSG levels. Besides, α-LA alleviated Cu²⁺-induced oxidative stress via the Nrf2 signaling pathway by its fine-tuning towards various genes (up-regulation of nrf2, cat, and gclc, and down-regulation of ho-1, sod1, and nqo1). Meanwhile, α-LA also alleviated dyslipidemia by reducing Cu²⁺-induced steatosis and lowering serum levels of T-CHO, LDL-CHO, and TG, while increasing HDL-CHO and LPL + HL. Furthermore, α-LA relieved Cu²⁺-induced lipid metabolic disorders induced by upregulating the expression levels of genes related to the PPARα signaling pathway, encompassing pparα-like, rxrα, lpl-like, acsl4a, acox1, and me1, and promoted lipolysis and decreased lipid accumulation. In summary, α-LA possesses protective effects against Cu²⁺-induced oxidative stress and lipid metabolism disorders by activating the Nrf2/PPARα signaling pathway in swamp eel. This study provides insights into alleviating the toxicity of heavy metals in aquatic organisms.

Anaesthesia is a necessary step during fish manipulation. Tricaine methane-sulfonate (MS-222) is the most commonly used anaesthetic in experimental trials; however, its use in food fish production is strictly regulated. This study aimed to evaluate clove oil, less persistent and authorized in European countries, as an alternative to MS-222 for skin mucus analyses in aquaculture settings. For this purpose, rainbow trout individuals from a commercial factory were sedated with clove oil or MS-222. The concentration of protein, glucose, lactate, and cortisol and the antibacterial activity were measured in both skin mucus and plasma. Additionally, FRAP, total protease activity, and lysozyme activity were also analysed for mucus samples. Recovery times differed significantly between treatments, being approximately four times longer for clove oil (at the farm's standard dose) than for MS-222 (at the standard laboratory dose). However, none of the stress-related biomarkers in mucus were affected by the anaesthetic treatment, whereas plasma from clove oil-treated fish showed increased lactate and reduced cortisol levels. The in vitro bacterial growth inhibition assay using mucus and plasma provides a reliable and rapid method for assessing fish innate immunity. No significant differences were observed between treatments against any of the bacterial strains tested. Overall, the findings strongly endorse the use of skin mucus as an effective method for studying and monitoring trout in aquaculture settings.

The present research examined the use of a commercial acidifier blend (CAB) as a feed supplement on growth, digestive enzymes, antioxidant, immunological biomarkers, and defense of Nile tilapia (Oreochromis niloticus) against Aeromonas sobria disease. Fish (22.7 ± 0.76 g) were fed on 0.0 (the control), 1.0, 2.0, 4.0, or 8.0 g CAB/kg feed for 60 days. After that, fish were intraperitoneally injected with A. sobria, and their survival was monitored for a further 10 days. The fish group that received 4.0 g CAB/kg feed showed the highest growth rate. The improved growth in this group is correlated with the upregulation of mRNA expressions of growth-related genes (IGF-1 and GH). In addition, the highest activities of intestinal proteases, lipase, and α-amylase were observed in fish fed with 4.0 g CAB/kg feed. Compared to the control group, fish fed on CAB-containing diets showed significantly higher activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx). In a parallel way, the mRNA expression of SOD, CAT, and GPx genes were upregulated in CAB-fed groups, particularly at levels of 4.0-8.0 g CAB/kg feed. Conversely, malondialdehyde levels were maximized in the control group but were reduced in CAB-fed fish. Additionally, dietary CAB, especially at levels of 4-8 g/kg diet progressively enhanced the immune function and upregulated the expression of IL-1ß, IL-8, and IL-10 genes. The bactericidal and challenge tests against A. sobria evoked that CAB exhibited antibacterial properties; the maximum mortality rate following the bacterial infection was noted in the control group (90%); meanwhile, CAB-fed fish, especially at a rate of 4.0-8.0 g/kg feed exhibited lower mortality rates (40% and 45%, respectively). Overall, this study recommends incorporating 4.0 g CAB/kg feed to mitigate the negative impacts of dietary soybean and improve the growth, antioxidant, and immunological indices in Nile tilapia fingerlings.

Eugenol is a widely used plant-based anesthetic in aquaculture. However, its anticholinesterase activity may affect reproductive physiology, particularly in gravid females. This study examined the effects of eugenol on the anesthetic response, acetylcholinesterase (AChE) activity, and parasite abundance in wild-caught adult females of the Neotropical fish Cnesterodon decemmaculatus. Ninety females were exposed to five eugenol concentrations (10, 20, 30, 40, and 50 mgL⁻¹), and a control group without anesthetic. Anesthesia induction and recovery times were recorded, and AChE activity was estimated in gravid females. Induction time decreased with increasing eugenol concentration up to 40 mgL⁻¹, with no further reduction at 50 mgL⁻¹. Recovery times did not differ significantly among treatments. AChE activity was significantly inhibited, and both abortion and mortality were observed in gravid females exposed to 10 mgL^-1. Additionally, a reduction in the mean abundance of the Eschistostomatidae family was detected only after the 40 mgL⁻¹ treatment, in all treated specimens. These findings highlight the physiological vulnerability of gravid females to eugenol exposure and suggest a potential antiparasitic effect at specific concentrations. The results emphasise the importance of considering reproductive status when assessing anesthetic safety in ovoviviparous fish.

Improving farmed fish carbohydrate utilization reduces the feed fish meal level and lessens water pollution. Herein, the effects of glycerol kinase (gyk) and forkhead box (fox)-q1 on Micropterus salmoides glucose homeostasis were investigated, and a growth-linked marker in gyk on a carbohydrate-rich diet was developed. The data showed that gyk and foxq1 expression is negatively correlated with plasma glucose level. Although gyk and foxq1 showed no effect on plasma triglyceride, cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, hepatic triglyceride, and muscular triglyceride content, positive regulation of insulin secretion, hepatic glycogen, and muscular glycogen level was observed. Overexpression and shRNA-mediated knockdown assays indicated that gyk and foxq1 positively regulate hepatic and muscular gene expression involved in triglyceride synthesis (fatty acid synthetase, acetyl-CoA carboxylase), glycolysis (phosphofructokinase, glucokinase), glycogen synthesis (glycogen synthase), and pentose phosphate pathway (glucose-6-phosphate dehydrogenase), but negatively regulate gluconeogenesis gene (phosphoenolpyruvate carboxykinase, glucose-6-phosphatase). In vitro, - 1652 ~  - 2056 bp was determined to be the core promoter sequence of gyk using progressive deletion. Luciferase activity showed that gyk promoter activity decreased following foxq1 binding site mutation in this sequence, and it was enhanced by foxq1 overexpression. Moreover, foxq1 inhibition attenuated hypoglycemia induced by gyk overexpression, and its suppression relieved the increase in gyk-mediated plasma glucose. Besides, an insertion-deletion marker located at rs16857996 in gyk was developed. Individuals without deletion (aaaac) of this site had higher body weight, full length, and body length. This regulatory axis provides a theoretical target and breeding indicator for increasing carbohydrate utilization and reducing the dietary fish meal in M. salmoides.

Cell culture plays a crucial role in various fields of life science research such as cancer, immunology, and virology. Numerous cell lines have been established in mammals, while fish cell lines remain comparatively limited in number. This study established a spontaneously immortalized cell line from the muscle of red sea bream, Pagrus major, which is a commercially important fish in Japan. Primary cells were isolated from muscle tissue using 0.2% collagenase and cultured in Leibovitz's L-15 medium without CO₂. The cells required fetal bovine serum in a dose-dependent manner at 28 °C for optimal growth. The cells were also able to grow in F12 medium, but not in Dulbecco's modified Eagle's medium. RNA-sequencing analysis raised the possibility that myosatellite cells/myoblasts in primary culture would gradually be replaced with fibroblasts or epithelial-like cells with an increasing number of passages because collagen-related genes were expressed more than in muscle tissue. Upon serum starvation, the cells differentiated into adipocyte-like cells because of slight lipid accumulation. Therefore, the established cells were considered to lack myogenic potential. In conclusion, we established the Nagasaki University Fisheries-P. major 1 (NUF-PM1) cell line, which consisted of fibroblast/epithelial-like cells, but not myosatellite cells/myoblasts, from the muscle of P. major, and we observed the cells over 80 passages. This study adds to the limited number of fish cell lines available for research, which can be used to develop fish cultured meat and as a model for fish adipocyte differentiation.

Myocyte Enhancer Factor 2 (Mef2) is a transcription factor that exert crucial functions in muscle cells, neurons and other cell types. These Mef2 family members modulate the expression of target genes to participate in a broad spectrum of biological processes, such as, but not restricted to, muscle differentiation and heart development. Myostatin (mstn), a protein from the Transforming Growth Factor-β (TGF-β) superfamily, is of great significance in muscle growth and development. Its principal function lies in suppressing the proliferation and differentiation of skeletal muscle cells, thus controlling muscle mass. In this study, we obtained the genomic sequence of mstn1 from Acanthopagrus latus, which is 2,198 bp in length and encodes 384 amino acids. It consists of three distinct domains: a TGF-β domain, a TGF-β propeptide domain and a signal peptide. Through phylogenetic analysis, it was found that mstn1 and mstn2 from A. latus are closely grouped with those from Sparus aurata, which implies a high level of similarity between the two species. Additionally, mstn1 was mainly expressed in the brain, white muscle, and skin. To further investigate the regulatory mechanisms underlying mstn1 in muscle growth, we analyzed the transcriptional levels of mstn1 in white muscle under conditions of starvation and refeeding. The results indicated that during the 56-day experimental period, the expression of the mstn1 gene decreased notably as the starvation period extended. Truncation experiments revealed that the region from - 645 to + 112 bp constitutes the core promoter region responsive to Mef2a and Mef2b. The point mutation analysis verified that the transcriptional activity of mstn1 is contingent upon the mutation of binding site 3 (M3) regulated by Mef2a and Mef2b. Moreover, siRNA-mediated knockdown experiments demonstrated that downregulation of mef2a or mef2b significantly decreased the transcription of mstn1. These findings provide novel insights into how Mef2 transcription factors regulate mstn1 expression, enhancing our understanding of the molecular mechanisms underlying muscle development in teleost fish.