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Liver is considered the critical tissue for metabolic processing of dietary nutrients including lipids. High-fat diets (HFD) can induce hepatic lipotoxic injury, but the mechanism is unclear. This study aimed to elucidate the underlying role of endoplasmic reticulum stress (ERS) in mediating HFD-induced hepatic lipotoxic injury in black seabream (Acanthopagrus schlegelii) via in vitro and in vivo experiments. For the in vitro experiment, isolated hepatocytes from black seabream were incubated for 24 h in medium (Control), or medium supplemented with 200 μM oleic acid (OA) alone or in combination with 20 μM 4-phenyl butyric acid (OA + 4-PBA). In the in vivo experiment, black seabream juveniles (3.30 ± 0.10 g) were fed diets containing lipid at 12.4% (Control) or 18.6% (HFD) for 8 weeks, after which the HFD-fed fish were divided into three groups and, on alternate days over a period of 8 days, subjected to intraperitoneal injections of 50 mg/kg 4-PBA in hydroxypropyl-β-cyclodextrin (HBC) (treatment 4-PBA) or carrier alone (treatment HFD + HBC) versus no injection (HFD). The contents of triglyceride and non-esterified fatty acid, as well as expression levels of genes and proteins involved in lipid metabolism, ERS, apoptosis and inflammation were determined in liver and isolated hepatocytes, and oil-red O staining, ultrastructural observation, flow cytometry assay of apoptosis rate, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) staining were performed on hepatocytes. The in vitro experiment showed that 4-PBA treatment significantly decreased lipid accumulation, and the OA-induced expression levels of genes/proteins linked to ERS, lipogenesis, inflammation and apoptosis in hepatocytes. Transmission Electron Microscope (TEM) imaging showed that 4-PBA treatment mitigated the ER swelling induced by OA. These results were confirmed in the in vivo experiment, where 4-PBA injection reduced lipid deposition and expression levels of genes/proteins related to ERS, lipogenesis, inflammation and apoptosis in liver compared to the HFD treatment. In conclusion, these results confirmed that ERS plays a contributing regulatory role in HFD- and OA-induced lipotoxic damage including lipid accumulation, apoptosis and inflammation in liver and isolated hepatocytes of black seabream, which supply a new perspective in the cross-talk of ERS and hepatic lipotoxic damage in hepatocytes/liver of marine fish and provide theoretical guidance for the prevention and treatment of hepatic lipotoxic damage. [Display omitted] • High lipid caused lipid deposition and endoplasmic reticulum stress (ERS). • ERS further increased lipid accumulation by regulating lipid metabolism. • ERS mediated apoptosis via promoting the Perk/Atf4/Chop and Ire1α/Jnk pathways. • ERS triggered inflammation by activating Nf-κb p65 phosphorylation. • ERS plays a key role in mediating high lipid -induced lipotoxic damage. [ABSTRACT FROM AUTHOR]

Salmon farming in Chile faces the dual challenge of maintaining growth while improving sustainability. One approach to advance sustainability involves the feeds without marine-fishery inputs. This study aimed to evaluate the effect of completely replacing fish oil (FO) on the performance of Salmo salar throghout marine grow-out. The investigation involved fish ranging from 400 g to 4000 g and explored three diets without fish meal, each which included 2.2% EPA + DHA from different sources: FO (control), transgenic canola oil (Can n-3) and Schizochytrium sp. oil (AOV) as unique type of oils. Each diet was randomly distributed in triplicate among nine tanks with a recirculation system maintained at 12 °C, with automatic feeding and a 24-h light photoperiod. Fish density was 29 fish m−3 at day 133 of the experiment and seven fish m−3 at day 319. The diets were isoproteic, isolipidic and isoenergetic. Fish were evaluated at 133 and 319 days of experiment in terms of productive performance, liver health, EPA + DHA and lipid retention efficiency, fatty acid metabolism, response to acute stress, and final product quality. The results showed similar productive performance and liver health among the three diets during both sampling periods. No differences were observed in lipid or EPA + DHA retention efficiency in the whole body or fillet. Eicosanoids and receptors for anti-inflammatory mediators derived from EPA and DHA showed similar or higher capacities in fish fed with Can n-3 and AOV than those fed FO. Responses to induced stress, measured through lactate, cortisol, sodium, potassium, chloride, glucose, and the liver profile were similar between the three diets. Similarly in fillet quality between the three diets. However, sensory analysis revealed a lower intensity of "global aroma" in Can n-3-fed fish fillets and lower evaluations in "typical salmon aroma", "oily aroma" and "fresh flavor" in AOV-fed fish fillets when they are compared with FO. The nutritional indicators of the final product were similar between the three diets, except for PUFA/SFA, the thrombogenicity index, hypercholesterolemia/hypocholesterolemia, and the health promotion index. In these specific indicators, fish fed with Can n-3 and AOV demonstrated more favorable results for consumer health than the FO-fed fish. • Lower "global aroma" for Can n-3 and lower "typical salmon and oily aroma" and lower "fresh flavor" for AOV compared to FO. • anti- inflammatory capacity from EPA and DHA is similar or higher in fish fed Can n-3 and AOV than those fed FO. • TI, and HPI revealed advantages for consumer in fish fed canola n-3 and algae oil compared to FO. [ABSTRACT FROM AUTHOR]

Corbicula fluminea meal was added to a high-fat diet for eight weeks to determine its effects on growth, lipid metabolism, and intestinal microbiota in juvenile rice field eel (Monopterus albus). C. fluminea meal was made of dried and crushed soft parts of freshwater clam. The study included four diets: a normal fat diet (6.63% lipid, CON), a high fat diet (12.61% lipid, HFD), and a high fat diet supplemented with 1% or 2% C. fluminea meal (CFM1 and CFM2, respectively). The results showed that: (1) the growth performance was higher in the HFD, CFM1 and CFM2 group compared with the CON group, the hepatosomatic index (HSI) was significantly higher in fish fed the high-fat diet than in those fed other diets. (2) Compared with the CON group, The levels of serum triacylglycerol (TG), low-density lipoprotein cholesterol (LDL-C) contents, glutamate pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT) activities and the number of hepatic lipid droplets were significantly increased in the HFD group. The addition of C. fluminea meal both reduced liver damage and fat deposition. (3) The mRNA expressions of pparγ , fas , acc , me1 , srebp1 , g6pdh , hsl , lpl , cpt1, and cpt2 in the HFD group were significantly upregulated, while HFD supplemented with C. fluminea meal significantly downregulated the mRNA expressions of pparγ , fas , acc , me1 , srebp1 and g6pdh and significantly upregulated the mRNA expressions of hsl and lpl. (4) The alpha diversity of intestinal microbial community in the HFD group was higher than those in the CON and CFM1 groups. The beta diversity revealed the microbial composition differed in the HFD group from the CON and CFM1 groups. The abundance of Firmicutes in the HFD group increased significantly compared with the CON and CFM1 groups, while the abundances of Cetobacterium decreased. In conclusion, the high-fat diet resulted in abnormal liver fat deposits and intestinal microbiota dysfunction in M. albus , but HFD supplemented with 1% or 2% C. fluminea meal reduced these negative effects. • The effects of high-fat feed on lipid metabolism and intestinal flora of eels were revealed. • 1% or 2% C. fluminea meal can mitigated the negative effects of high-fat feeds on the liver. • 1% C. fluminea meal improving the intestinal flora structure of eel. • C. fluminea meal may play a vital role in liver protection and energy metabolism of eels. [ABSTRACT FROM AUTHOR]

In recent decades, frequent extreme cold spells have led to fluctuations in water temperature. As poikilotherm, fish adapt to the environmental temperature through a series of physiological and metabolic regulation. Silver pomfret (Pampus argenteus) is an economical marine fish, a potential candidate for aquaculture. To investigate the impact of cold stress and subsequent rewarming on the energy metabolism of silver pomfret, we simulated an extreme cold spell by gradually lowering water temperature from 18 °C to 6 °C, followed by a gradual rise to 12 °C. The findings revealed notable trends: as the water temperature dropped to 12 °C, there was a significant increase in fatty acid content. However, upon reaching 6 °C, the condition factor (CF) decreased, accompanied by a reduction in liver mass. During the rewarming phase, severe tissue damage was observed in both muscle and liver tissues, alongside elevated AST and ALT activity. Besides, silver pomfret consumed stored fatty acids, CF, hepatosomatic index and n-3/n-6 fatty acid ratio were higher than other groups once the water temperature returned to 12 °C. Further transcriptome sequencing of the liver revealed significant enrichment in numerous metabolism-related pathways through KEGG and GO analyses. Ten differentially expressed genes (DEGs), encoding pivotal enzymes in lipid metabolism, were identified from pathways such as the PPAR signaling pathway and fatty acid degradation. Based on these results, it was hypothesized that silver pomfret shields against injury by modulating fatty acid composition. This hypothesis found validation in P. argenteus liver cells, where acsl 1, cpt 1 and cpt 2 were identified to facilitate lipid activation and transportation. Knocking down acsl 1 impacted the utilization of lipid droplets, further affirming this mechanism. This study sheds light on the adaptive strategies of economically significant fish species in confronting extreme cold spells, providing valuable insights for future reference. [Display omitted] • Extreme climate events including La Niña, abnormal cold winter and cold spells occurred frequently in the past few years, affected marine ecosystems and fisheries. • We adjusted water temperature by cooling and rewarming to simulate cold spells, and investigated the effects of cold spells on the economic fish by detecting various indicators of silver pomfret. • Growth index, biochemical detection, histological observation, transcriptome sequencing, and cell-level validation were employed to clarify the lipid metabolism of silver pomfret response to cold stress and rewarming. • Silver pomfret stored fatty acids in the initial cooling process, fatty acids utilization lagged behind temperature changes. Drastic changes in temperature can damage the liver, rewarming process was even more serious. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate seminal and sperm production, growth, health, and lipid metabolism of male silver catfish (Rhamdia quelen) fed diets containing l -carnitine and varying lipid sources. Herein, males and females (167.33 ± 9.24 g) were both fed across 223 d with eight (08) isoproteic (282 g of digestible protein kg of ration −1) and isoenergetic (13.34 MJ of digestible energy kg of ration −1) diets, containing 0.00, 0.15, 0.45, and 0.75 g l -carnitine kg −1 of feed, soybean, and marine fish oils. Feeding males with diets containing l -carnitine and different oils resulted in an interactive effect (p < 0.05) that improved sperm production. Furthermore, males fed soybean oil and 0.45 g l -carnitine kg −1 had the highest seminal pH and sperm velocities. Fish fed fish oil and 0.75 g l -carnitine kg−1 had the highest gonadosomatic indexes, sperm production, and superoxide dismutase activities recorded in the testes. The testes of these fish also showed increases in docosahexaenoic acid (DHA), polyunsaturated fatty acids (PUFAs), n-3 fatty acids, and higher n-3: n-6 ratios. The individual effect of oils produced viscera with more (p < 0.05) fat, in addition to having higher (p < 0.05) blood levels of albumin, total cholesterol, triglycerides, alongside the lowest level of aspartate aminotransferase in fish fed marine fish oil. The individual effect of l -carnitine also produced muscles with less (p < 0.05) fat, in addition to the highest (p < 0.05) amount of total cholesterol with the lowest amount of high-density lipoprotein (HDL) cholesterol in the blood of fish fed with 0.75 g l -carnitine kg−1. l -carnitine and oils in the diets promoted hepatic and testicular protection whilst regulating lipid metabolism and fatty acid profile in the liver and testes of silver catfish (Rhamdia quelen) males. These benefits led to greater sperm production when fish oil and 0.75 g kg −1 were used, and faster spermatozoa with soybean oil and 0.45 g kg −1. • Diets with 0.75 g kg−1 l -carnitine and fish oil improved the Rhamdia sperm production. • Rations with l -carnitine and fish oil increased PUFAs deposition in Rhamdia testes. • Dietary l -carnitine and fish oil improved the antioxidant status of Rhamdia testes. • Lipid metabolism of Rhamdia male were regulated by dietary l -carnitine and oil source. [ABSTRACT FROM AUTHOR]

The current study aims to investigate the role of high-fat diet (HFD) and ammonia nitrogen (AN) in the fatty liver disease progression in farmed fish. In the present study, grass carp were fed the normal fat diet or HFD for 4 weeks to set up the Control group, HFD group, AN group and HFD + AN group. In the AN group and HFD + AN group, grass carp were exposed to 0.52 mg/L NH 3 -N for the last week. The results show that HFD feeding had no effect on the growth of grass carp but AN stress significantly inhibited it. Further, the HFD feeding and AN challenge both significantly increased the level of alanine aminotransferase (ALT) and reduced the total antioxidant capacity (T-AOC) significantly. Moreover, a further aggravated liver injury appeared in HFD-fed grass carp after AN challenge, as evidenced by the significant increasing of the level of ALT, AST and malondialdehyde (MDA) and marked reducing of glutathione (GSH) and T-AOC. Moreover, the results of Oil Red O and TG contents in liver all indicate that HFD and AN challenge both promoted the lipid accumulation in grass carp liver. Corresponding to this, the results of genes and protein related to lipid metabolism reveal that AN challenge dramatically inhibited lipid hydrolysis, lipophagy and fatty acid oxidation in HFD-fed grass carp liver but the single HFD feeding or AN challenge did not have this effect. Moreover, the single HFD feeding and AN challenge both promoted fatty acid transport to the liver and lipid synthesis in grass carp liver. In summary, the HFD feeding and AN challenge both can disturb the lipid metabolism in grass carp liver. In parallel, the results of expression levels of genes and protein related to inflammation indicate that the single HFD feeding might not significantly contribute to the inflammation in grass carp liver, but the single AN challenge apparently promoted the inflammatory process. Most importantly, inflammatory progression in liver was further aggravated in the HFD-fed grass carp after AN challenge compared to grass carp with only AN stress, mostly evidenced by the increased levels of inflammatory factors (il1β , il2 , TNF-α, etc.). In summary, AN challenge significantly promoted the lipid accumulation and inflammatory process in the liver of HFD-fed grass carp, which might have further aggravated liver injury. • AN challenge inhibited growth of grass carp. • AN challenge and HFD both promoted the lipid accumulation in the liver of grass carp. • AN challenge markedly suppressed the lipid synthesis and β-oxidation in the liver of HFD-fed grass carp. • AN challenge is the primary factor for the inflammatory process in the grass carp liver. [ABSTRACT FROM AUTHOR]

Long-term high-fat diets (HF) lead to lipid accumulation and an oxidative stress response, which deteriorates the chemical and physical characteristics of fish muscle. Green tea extracts, such as (−)-epigallocatechin-3-O-gallate (EGCG) and (−)-epicatechin (EC), have been found to regulate antioxidant ability and lipid metabolism. However, the effects of EGCG and EC on alleviating oxidative stress and lipid metabolism disorders caused by HF are unclear. Furthermore, the underlying mechanisms remain unknown. In this study, a total of 360 carp (average weight: 9.75 ± 0.09 g) were provided with four experimental diets: a control diet (CN, 6.15% dietary lipids), a high-fat diet (HF, 14.05% dietary lipids), HF supplemented with EGCG (HF + EGCG, 14.05% dietary lipids +50 mg/kg EGCG), and a HF diet supplemented with EC (HF + EC, 14.05% dietary lipids +1000 mg/kg EC) for a duration of 84 days. The results indicated that EGCG or EC ameliorated the negative effects of the HF diet on muscle tissue. Apart from muscle physical characteristics, EGCG decreased yellowness (b *), redness (a *), and dripping loss (P < 0.05). Apart from muscle nutritional composition and antioxidant status, EC mitigated the reduction in protein levels in the muscle induced by the HF diet. Similarly, EGCG and EC mitigated the excessive accumulation of lipids and reactive oxygen species (ROS) in the muscle induced by the HF diet (P < 0.05). Further study showed that EGCG or EC facilitated the phosphorylation of AMP-activated protein kinase (AMPK) and increased silent information regulator 1 (Sirt1) and PPARγ coactivator-1 alpha (PGC-1α) expression in muscle. Taken together, the results of this study revealed that EGCG or EC enhance lipid metabolism and antioxidant capacity in the muscle of common carp (Cyprinus carpio L.) via the AMPK/Sirt1/PGC-1α pathway. [Display omitted] • EGCG or EC improved the flesh color and physicochemical properties of common carp. • EGCG or EC alleviated oxidative stress of common carp induced by high-fat diet. • EGCG or EC mitigated lipid deposition and protein reduction caused by high-fat diet. • EGCG or EC regulated lipid metabolism via AMPK/Sirt1/PGC-1α pathway. [ABSTRACT FROM AUTHOR]

Tadpole cultivation is a crucial step in the artificial production of bullfrogs (Lithobates catesbeiana), but its feed nutrition is poorly understood. This study examined how dietary lipid and protein levels affect metamorphosis, growth and intestinal health of tadpole. Six groups of tadpoles were fed six diets with two lipid levels (7% and 10%) and three protein levels (36%, 40% and 44%) for 70 days. The results showed that at 7% lipid level, increasing protein enhanced metamorphosis rate and mean weight of tadpoles, reaching the optimal value at 40% protein (P < 0.05). At 10% lipid level, increasing protein also improved mean weight, peaking at 40% protein. Dietary nutrition also influenced liver amino acid and lipid metabolism directly. At 7% lipid level, increasing protein significantly increased the activities of hepatic enzymes GLS, PDH, ALT, AST, etc. (P < 0.05), and up-regulated the expression of hepatic genes fas , accb , fadd6 and cpt1a involved in lipid metabolism (P < 0.05). At 10% lipid level, increasing protein also up-regulated fadd6 and cpt1a genes (P < 0.05), but down-regulated acadl gene. Meanwhile, increasing dietary lipid level elevated TG and T-CHO levels in liver. Increasing dietary protein enhanced gut microbiota richness, while increasing lipid reduced it. Moreover, different gut microbiota groups had distinct biomarkers, such as Rikenellaceae , Desulfovibrionaceae , Burkholderiales and Bacteroidales, which were related to amino acid or lipid metabolism. In summary, under the test conditions, 7% lipid and 40% protein in diet are suitable levels, which can promote metamorphosis, growth and metabolism of tadpoles, and are more economical than high-lipid and high-protein diets. • Diet (7% lipids, 40% protein) accelerates tadpole development/metabolism. • The strategic increase in dietary protein enhances lipid and protein metabolism. • Gut microbiota adjusts to diet changes, impacts host metabolism. [ABSTRACT FROM AUTHOR]

This study was conducted to explore the impacts of nuciferine (NF) on growth performance, body composition, lipid metabolism and antioxidant capacity of juvenile large yellow croaker (Larmichthys crocea) fed diets with high palm oil level. Five diets were formulated with fish oil (FO), palm oil (PO) and PO supplemented with 0.01%NF, 0.05%NF and 0.25%NF. After feeding for 10 weeks, the results showed that the growth performance (final body weight and specific growth rate) exhibited a significantly quadratic trend with the increase of NF addition, and the maximums were observed in PO supplemented with 0.05%NF group. Moreover, dietary PO diet with NF addition relieved the abnormal lipid accumulation (hepatosomatic index, crude lipid and triglyceride contents, total cholesterol contents, low-density lipoprotein-cholesterol contents in liver and serum) induced by PO diet. Simultaneously, NF addition inhibited PO diet-induced increase in the mRNA expressions of lipid synthesis-related genes and PO diet-induced activation of SREBP1. In addition, dietary PO diet with NF addition impeded PO diet-induced increase of hepatic MDA contents and recovered PO diet-induced inhibition of SOD and CAT activities. Similarly, NF addition alleviated PO diet-induced decrease in the mRNA expressions of antioxidant-related genes and PO diet-induced inhibition of SOD protein expression. Thus, addition of NF in PO diet might effectively ameliorate PO diet-induced growth retardation, lipid metabolism disorder and oxidative stress in croaker, and the optimal addition dose of NF in PO diet was approximately 0.05%. • Added appropriate dose of nuciferine (NF) in palm oil (PO) diet promotes the growth and antioxidant capacity of large yellow croaker. • Addition of NF in PO diet effectively ameliorates PO diet-induced hepatic lipid accumulation via inhibiting lipid synthesis in croaker. • The optimal supplementation of NF in diets with high PO level is recommended to be 0.05% for large yellow croaker. [ABSTRACT FROM AUTHOR]

The nutrient removal, biomass production and nutritional value of the halophyte Salicornia ramosissima were evaluated in the context of an Integrated Multi-Trophic Aquaculture (IMTA) system. The experiment consisted of an indoor fish RAS whose effluent was used to feed two different halophyte hydroponic systems: a Nutrient Film Technique (NFT) system or a Deep Water Culture (DWC) system. The highest yield of S. ramosissima was observed in the DWC (320 g m−2 day−1), this system showed significantly higher yields compared to the NFT. Both hydroponic systems were effective in removing nutrients from the fish RAS wastewater, contributing to the wastes valorization process. Maximal nutrient uptake efficiencies were: 82.8% and 68.6% NO 3 − in the DWC and the NFT, respectively; 72.6% PO 4 3− in the DWC and 82.9% in the NFT; 63.6% NO 2 − in the DWC vs 56.4% in the NFT; and 89.2% NH 4 + in the DWC vs 94.1% in the NFT. The lipid profile of the halophytes in the DWC was analysed. The total lipid content ranged from 2.99% to 3.83%. The fatty acids (FA) profile in the leaves was dominated by polyunsaturated fatty acids (about 66%), which were represented by α-linolenic acid (41%) and linoleic acid (24%), followed by saturated fatty acids (28%) with palmitic acid (22%) as the major component. A small component of monounsaturated fatty acids accounts for about 12% of total FA. Regarding lipid classes, pigments were the most abundant compounds followed by glycolipids, phospholipids, flavonoids and sterols. The study supports the potential of S. ramosissima to valorise aquaculture wastes and its high nutritional interest. The experimental systems minimized waste and maximized resources utilization. Such integrated approaches can contribute to the sustainability and resilience of aquaculture systems while providing additional economic opportunities through the production of high value halophyte products. • Salicornia ramosissima was hydroponically cultivated in a NFT system and in a DWC system with fish RAS effluents. • The DWC system provided the best yield (320 g m−2 day−1). • Both systems removed >75% of DIN and 80% of DIP present in the effluent. • The lipid profile of S. ramosissima is affected by nutritional stress and cultivation conditions. [ABSTRACT FROM AUTHOR]

Thraustochytrids are a group of unicellular marine protists that are noted for their ability to produce high amounts of lipids, especially docosahexaenoic acid (DHA), making them a valuable source for replacing fish oil in aquafeeds. Varying levels of Aurantiochrytrium acetophilum meal (TM) were evaluated as replacement of fish oil in extruded diets for juvenile Atlantic salmon on growth, nutrient apparent digestibility, fatty acid composition in muscle and liver and expression of genes associated with lipid metabolism. Four experimental diets were tested: a control diet without the inclusion of A. acetophilum meal and three experimental diets derived from the control diet, in which fish oil was progressively replaced by the addition of A. acetophilum meal at 2.5% (TM 2.5), 6.5% (TM 6.5) and 12% (TM 12) respectively. After 12 weeks of feeding, the growth, feed conversion, condition factor and survival of the fish were not affected by the inclusion of A. acetophilum in the diet. However, the 12% inclusion significantly decreased the viscerosomatic index of the fish and the digestibility of protein, lipids, ash and energy compared to the other experimental diets. The lipid content and fatty acid profile of the liver and muscle were significantly affected by diet composition. In both tissues, fish fed the TM 12 diet retained the highest levels of DHA. However, it was also observed that EPA concentrations lessened with increasing dietary content of A. acetophilum meal. Finally, the decrease in the expression of Δ5fad in the fish fed with the TM 6.5 and TM 12 diets showed that fish do not require a higher expression of this desaturase for DHA production, due to the high content of this fatty acid in A. acetophilum meal. • A. acetophilum meal can be used as lipids source in Atlantic salmon diets. • Higher dietary inclusions of A. acetophilum meal modify visceral fat reserves in Atlantic salmon. • Substitution of fish oil with 12% A. acetophilum meal affects nutrient digestibility in Atlantic salmon juvenile. • DHA retention in liver and muscle of Atlantic salmon increased with the dietary concentration of A. acetophilum meal. • Diets with high levels of DHA from A. acetophilum meal depressed expression of the Δ5fad. [ABSTRACT FROM AUTHOR]

The intricate and paradoxical relationship between branched-chain amino acids (BCAAs) and lipid metabolism has been focused on the field of nutrition. However, the molecular mechanism mediated by BCAAs in the lipid metabolism of fish is poorly understood. To address this knowledge gap, we characterized the transcriptome and metabolome in the liver of largemouth bass (Micropterus salmoides), an extensively cultivated fish with high commercial value. Dietary BCAA supplementation significantly enhanced growth performance, combined with the elevation of essential amino acid levels and the improvement of liver health. Moreover, enzymatic detection and RT–qPCR results showed that BCAAs decreased lipid deposition in the liver. Integrated transcriptomics and metabolomics analysis revealed that the inhibition of lipid synthesis and enhancement of fatty acid degradation may explain the mechanism by which BCAAs relieved lipid accumulation in the liver. The metabolic enzymes acaca , acaa2 , cpt2 , acat , and aldh9a1 , which were regulated by all three BCAAs, are key targets linking BCAA metabolism and lipid metabolism. Considering that farmed fish suffer from abnormal lipid accumulation in the liver, appropriate BCAA supplementation is an effective nutritional strategy to improve lipid metabolism disorders in aquaculture. [Display omitted] • BCAAs supplementation enhanced growth performance and antioxidant capacity. • BCAAs treatment relieved hepatic lipid accumulation and improved liver structure. • BCAAs supplementation inhibited lipid synthesis and promoted lipid oxidation. [ABSTRACT FROM AUTHOR]

Decrease in the inclusion of fish oil (FO) in current aquafeed formulations reduces the availability of omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA) to marine fish like the European seabass Dicentrarchus labrax. Here we investigated the compositional and physiological responses of European seabass to a dietary gradient of n-3 LC-PUFA. Six isoenergetic and isonitrogenous diets (D1-D6) were fed to triplicate groups of juvenile seabass (23 g), containing blends of FO and vegetable oil (VO) that resulted in a gradient of n-3 LC-PUFA varying from 0.23 to 3.40% of diet as fed. Sampling was carried out after four months feeding and biochemical composition, as well as lipid metabolic gene expression in liver and mid-intestine analysed. The only effect of diet on proximate composition was a decrease in hepatic lipid content as dietary n-3 LC-PUFA increase whereas, in contrast, fatty acid (FA) compositions of both tissues were substantially modified by diet. Concentrations of LC-PUFA biosynthesis intermediates decreased in both tissues as dietary n-3 LC-PUFA increased with some preference detected towards n-6 FA. Two genes, namely fads2 and igf1 , were moderately influenced by dietary VO in liver while genes involved in lipogenesis (srebp1, srebp2 and fas) and LC-PUFA biosynthesis (fads2 and elovl5) were markedly down-regulated, in mid-intestine of seabass in response to increasing dietary n-3 LC-PUFA. The expression of genes of β-oxidation (ppara, cpt1a and fabp1) did not vary among treatment. Collectively, our data suggest that the nutritional regulation of key lipid metabolic genes in European seabass was more pronounced in mid-intestine than in liver. Overall, when compared to a previous study of similar design in gilthead seabream (Sparus aurata), the European seabass seems less sensitive to a dietary gradient of vegetable oil. • Dietary VO increases hepatic lipid in Dicentrarchus labrax juveniles. • Fatty acid profiles in liver and intestine reflects that of diet. • Regulation of lipid metabolic genes was more obvious in intestine than liver. • Increasing dietary EPA + DHA down-regulated lipogenesis and LC-PUFA biosynthesis. [ABSTRACT FROM AUTHOR]

Arachidonic acid (ARA) is becoming increasingly important due to significant reductions in fishmeal (FM) and fish oil (FO), the primary sources of ARA, in aquafeeds. ARA is an essential omega-6 fatty acid in some fish species and plays a wide range of physiological roles. However, studies reported to date have demonstrated contrasting findings concerning the effects of ARA in fish growth and health, regardless of the fish's trophic level. Additionally, limited research has addressed energy allocation during reproduction and growth in sub-adult rainbow trout as they approach reproductive maturity. Therefore, a study was conducted to evaluate the effects of different levels of ARA on growth performance, the fatty acid composition of whole-body and ovary, intestinal inflammatory gene expression, gut histology, antioxidant activity, and non-specific immunity in sub-adult rainbow trout (Oncorhynchus mykiss). Four isonitrogenous (51% crude protein), isolipidic (15% crude lipid), and isocaloric (23 MJ/kg) diets were formulated and supplemented with ARA-enriched oil (40%), resulting in analyzed ARA levels of 0.10 (ARA 0.10), 3.95 (ARA 3.95), 7.67 ARA(7.67), and 14.8% (ARA 14.8) of total fatty acid, respectively. Rainbow trout (307 ± 3.64 g) were fed to apparent satiation three times a day for 12 weeks to assess growth performance, feed utilization, and intestinal inflammatory response. The fish were then exposed to acute stress to evaluate circulating cortisol, prostaglandin E 2 , antioxidant activity, and non-specific immune response. The 12-week growth trial demonstrated that dietary ARA did not affect rainbow trout growth performance and feed utilization during the final grow-out. Whole-body fatty acid profiles reflected those of the diets except for eicosapentaenoic acid (EPA) content being significantly lower in the ARA 14.8 group than in the ARA 0.10 and ARA 3.95 groups. EPA and docosahexaenoic acid (DHA) contents in the ovary were less affected by dietary ARA supplementation, likely reflecting the selective deposition of those fatty acids in embryonic development. The expression of tnf-α was significantly downregulated in ARA 7.67 and ARA 14.8 groups relative to other treatment groups, and only distal intestinal villus height was significantly increased in the ARA 3.95 group, suggesting that dietary ARA supported intestinal health. Plasma superoxide dismutase, catalase, and lysozyme activity significantly increased in both pre- and post-stress groups due to incremental increases in dietary ARA. These results suggest that a moderate level of dietary ARA in low FM and FO-free enhances innate immune function and antioxidant responses while supporting intestinal health in sub-adult rainbow trout. • Dietary ARA did not affect sub-adult trout growth, feed utilization and survival. • Dietary ARA increased antioxidant activities and non-specific immune parameters. • A moderate level of ARA in a low FM/FO-free diet improved intestinal health. [ABSTRACT FROM AUTHOR]

Parental nutrition plays important roles in reproductive performance and offspring health of broodstock yellow catfish. However, there is a lack of relevant knowledge concerning the broodstocks of many fish species. This study investigated the influence of dietary lipid levels on growth, spawning performance, tissue fatty acid profiles, sex hormone secretion, and offspring health status of yellow catfish (Pelteobagrus fulvidraco). Five experimental diets were designed containing a 7:3 ratio of fish oil and corn oil blends with graded lipid levels (6.3%, 8.2%, 10.8%, 12.2%, and 14.4% by dry weight) and were fed to female broodstock yellow catfish for 8 weeks. The results showed that weight gain, egg diameter, fertilization ratio, and hatching ratio increased initially and then decreased with increasing dietary lipid levels, reaching optimal peaks in the L10.8 group. Broodstock fed a diet with 10.8% lipid obtained the highest 17-β estradiol concentration. The deposition of highly unsaturated fatty acids in tissues increased initially and then decreased with the increase in dietary lipids, reaching a peak in the 10.8% group. Plasma superoxide dismutase activity and total glutathione content were lowest in fish fed a diet with a 6.3% lipid level, while the contents of malondialdehyde and cortisol in larvae 3 days post-hatching showed an opposite trend, indicating that a low-fat diet reduced the antioxidant capacity of broodstock and induced a stress response that had negative effects on offspring health. Broodstock fed a diet with an appropriate lipid level could increase the expression of antioxidant enzymes by activating the nrf2 signaling pathway. Based on the regression of dietary lipid level and weight gain, reproductive performance, and egg quality of fish, the optimal dietary lipid level was 10.1–11.7% for broodstock yellow catfish. • The optimal dietary lipid requirement of broodstock P. fulvidraco is 10% -11.1%. • Optimal lipid diet could improve reproductive performance and egg quality of P. fulvidraco. • Appropriate dietary lipid intake promotes HUFA deposition in the ovary. • Insufficient lipid diet reduced the antioxidant capacity of broodstock. • Insufficient lipid diet induced stress responses in offspring larvae. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the effects of dietary inclusion of black soldier fly (Hermetia illucens) larvae oil (HIO) on fillet fatty acid (FA) profiles and other nutritional traits of gilthead seabream (Sparus aurata). Four experimental diets were formulated with 45% crude protein and 18% lipids (circa 50:50 of fish oil and vegetable oil (VO) blend: 20% rapeseed, 30% palm, and 50% linseed oil) and HIO was used to replace VO blend at 42%, 84%, and 100%, corresponding to a dietary inclusion level of 4%, 7.9%, and 9.5%, respectively. After a feeding trial of 10 weeks, several fillet quality traits were analyzed, including morphometric and somatometric indexes, physical and chemical characteristics, FA profile, and lipid peroxidation products. No differences were found in the morphometric and somatometric parameters, or skin and fillet color. The fillets FA profile was significantly modulated by the experimental diets, showing an increase in saturated fatty acids (SFA), particularly lauric acid, and a decrease in monosaturated FA and n-3 and n-6 polyunsaturated fatty acids (PUFA) with the increase of HIO inclusion, while eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents were not affected. Fillets FA quality indexes (PUFA/SFA, n-3/n-6 PUFA ratio, hypocholesterolemic/hypercholesterolemic ratio, thrombogenicity, and atherogenicity indexes) were also modulated by dietary HIO inclusion. Fillets pH was reduced and water holding capacity increased with dietary HIO inclusion. Fillet lipid peroxidation level (measured as TBARS) was significantly decreased with dietary HIO inclusion despite an increase in conjugated dienes. Overall, results showed that HIO can efficiently replace VO in gilthead seabream diets, without major negative effects on fillet characteristics and quality traits while decreasing fillet lipid oxidation. • Dietary replacement of vegetable oils with Hermetia illucens larvae oil (HIO) impacted the fillet's fatty acid (FA) profile. • Although saturated FA content increased with HIO inclusion, EPA and DHA levels were maintained in the fillet. • Lipid quality indexes were within the recommended levels for a healthy human diet. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the reproduction, growth, biochemical parameters of blood, hepatic and gonadal redox parameters, hepatic and gonadal histology, and lipid metabolism of silver catfish females (Rhamdia quelen) fed diets containing l -carnitine and different lipid sources. Females were fed for 223 days with eight (08) isoproteic (282 g of digestible protein kg of ration−1) and isoenergetic (13.34 MJ of digestible energy kg of ration−1) diets, containing 0.00, 0.15, 0.45, and 0.75 g l -carnitine kg−1 of feed, and soybean or marine fish oils. Feeding the females diets containing l -carnitine and the different oils resulted in an interactive effect (p < 0.05) that improved the growth and reproduction of the fish. Females fed soybean oil and 0.45 g l -carnitine kg−1 had the highest growth rates, the largest ovaries, and produced the most fertile oocytes, which resulted in the highest hatching rates. These females also showed higher levels of total cholesterol and high-density lipoprotein (HDL) cholesterol, and alterations in the levels of alanine aminotransferase in the blood, in addition to greater activity of hepatic superoxide dismutase and a greater amount of saturated fatty acids in the liver. The ovaries of these females also had the highest amount of docosahexaenoic fatty acid (DHA), highest amount of polyunsaturated fatty acids and fatty acids from the n-3 and n-6 series, and the lowest crude protein content. The interaction between l -carnitine and the lipid source of the diets promoted hepatic protection and regulated lipid metabolism and the fatty acid profile in the liver and ovaries of silver catfish females. The benefits of these interactions improved the growth and reproduction of females fed diets containing soybean oil and 0.45 g l -carnitine kg−1. • Replacing fish oil with soybean oil associated with l -carnitine improves reproduction • Soybean oil and 0.45 g l -carnitine kg−1 diets promote fertility rate and egg hatching • Growth and lipid metabolism is improved with soybean oil and 0.45 g l -carnitine kg−1 • l -carnitine with soybean oil improves the antioxidant status of silver catfish female [ABSTRACT FROM AUTHOR]

The nutritional requirements and metabolism of bivalves remain largely unknown. In this study, we investigated the effects of dietary carbohydrate/lipid ratios on growth performance, body composition, digestive enzyme activities, oxidative status, and transcriptome profile in juvenile razor clam Sinonovacula constricta. Five microcapsule diets with varying levels of carbohydrate (30–45%) and lipid (2–15%) were prepared and designated as C45L2 (45% carbohydrate and 2% lipid), C41L5, C36L8, C33L11, and C30L15 groups. Juvenile S. constricta with an initial shell length of 4.9 mm were fed with these microcapsule diets for 2 weeks. The results showed that the clam in the C33L11 group exhibited the fastest growth rate. The body protein content decreased with the decreasing dietary carbohydrate/lipid ratio. The clam in the C33L11 group showed significantly higher glycogen content compared to the C45L2, C41L5, or C30L5 group. The amylase activity of the clam in the C45L2 and C41L5 group was significantly higher than that in the C36L8, C33L11, and C30L15 group. The clam in the C33L11 group showed significantly higher catalase and superoxide dismutase activities compared to other microcapsule groups. The malondialdehyde level of the clam in the C30L15 group was significantly higher than that in the C45L2, C41L5, and C33L11 group. Transcriptome analysis showed that the autophagy pathway in the clam fed C41L5 was upregulated compared with those fed C33L11. Meanwhile, the protein levels of microtubule-associated protein 1 A/1B-light chain 3 membrane type (LC3-II) in the C41L5 group were also significantly higher than those in the C33L11 group. Moreover, the clam in the C41L5 group exhibited increased phosphorylation levels of the eukaryotic translation initiation factor 4E-binding protein (4E-BP) and decreased phosphorylation levels of the ribosomal protein S6 kinase beta-1 (S6K). Our results revealed that the optimal dietary carbohydrate/lipid ratio for juvenile S. constricta was approximately 3.01. The high-carbohydrate/low-lipid diet may repress the growth of clam by inhibiting mammalian target of rapamycin complex 1 (mTORC1) and subsequently activating autophagy, while the poor growth performance in the low-carbohydrate/high-lipid diet group may be associated with high lipid peroxidation levels in juvenile S. constricta. • The optimal carbohydrate/lipid ratio for juvenile S. constricta was about 3.01. • The body protein content was decreased with the decline of carbohydrate/lipid ratio. • Amylase activity increased with the increase of dietary carbohydrate. • Fit carbohydrate/lipid ratio enhanced SOD, CAT activities, and lower carbohydrate to lipid ratio increased MDA level. • Compared to C33L11 diet, C41L5 diet might lead to autophagy through mTORC1 pathway. [ABSTRACT FROM AUTHOR]

Various combinations of alternative marine lipid sources were evaluated for their potential to replace commercially available fish oil, specifically sardine oil (SO), in turbot (Scophthalmus maximus). A commercially based diet was used as a control (CTRL) containing sardine oil (7.0%) and rapeseed oil (RO; 3.8%) as the main lipid sources, providing 1.9% EPA + DHA. A positive control (SARDINE) was also included, which used SO as the sole lipid source to provide 2.6% EPA + DHA. Two other diets were formulated to target approximately the same levels of EPA + DHA as the positive control: ALGA (2.7% algae oil, 5.4% SO, and 2.7% RO), and ALGAMIX (a blend of 2.0% micro and macro algae biomass, 9.5% SO, and 0.7% salmon oil, a by-product of the salmon industry). SO was completely replaced in two alternative diets, ALT1 and ALT2, by different ratios of salmon and algae oils: 8.0/2.9 and 6.0/4.9%, providing 2.0% and 2.8% EPA + DHA, respectively. In these alternative diets, 30% of the fish meal was also replaced, by Tenebrio molitor meal and a single-cell protein concentrate from Corynebacterium glutamicum. After 75 days of feeding, all diets were equally well-accepted by the fish, and no significant differences were found in feed efficiency, growth performance, and somatic indexes. All fish had similar muscle EPA + DHA values, but only the ALGAMIX group exceeded the European Food Safety Authority (EFSA) recommended EPA + DHA levels for human daily consumption. Hepatic lipogenesis was decreased in fish fed with higher levels of EPA + DHA, suggesting that increased n-3 LC-PUFA negatively affects lipid metabolism. Additionally, the mixture of algae oil, sardine oil, and rapeseed oil (ALGA diet) showed potential for improving muscle antioxidant capacity. Overall, this study showed that combining expensive sources of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) with less expensive oils, such as salmon by-product oil or vegetable oils, may be a viable cost-efficient strategy for replacing SO in diets for turbot. This can be achieved without compromising growth and while ensuring high flesh n-3 LC-PUFA content and improving its antioxidant potential. • Alternative marine lipid sources did not hamper turbot growth performance or flesh quality. • Muscle of ALGAMIX fed fish had EPA + DHA levels above recommended for human consumption. • Hepatic lipogenic activity was hampered by higher levels of n-3 LC-PUFA. • A blend of algae, sardine and rapeseed oils enhanced muscle antioxidant potential. • Blending alternative marine lipid sources is a cost-efficient sardine oil replacement. [ABSTRACT FROM AUTHOR]

Alternative feeds are critical for the sustainable expansion of the marine finfish aquaculture industry. The industry uses wild-caught forage fish as a primary ingredient in farmed fish feeds. Alternative ingredients are needed to safeguard fisheries' sustainability and future aquaculture development. While there have been successes in alternative feeds, it is necessary to improve the existing options and identify alternative ingredients with higher concentrations of omega-3 polyunsaturated fatty acids (PUFAs). This study was designed to test a microalga, Schizochytrium sp., as a feed ingredient for sablefish (Anoplopoma fimbria) using six test diets. There were two fish-ingredient control diets: +FM+FO, which contained both fishmeal and fish oil, and −FM+FO, which contained fish oil, but no fishmeal. The remaining four diets contained alternative lipids and were completely fish-free. FF Flax contained flax oil as the only lipid source replacing fish oil. FF LowSc, FF ModSc, and FF HighSc contained a low, moderate, and high level of Schizochytrium sp. to replace fish oil, with flax oil content decreasing as the microalga increased. After a 20-week trial, sablefish growth differed across the feed treatments, with fish fed the high microalga-inclusion diet (FF HighSc) performing similarly to fish fed the fish-ingredient controls. Fulton's K condition factor, dry feed intake (DFI), and lipid productive value (LPV) were also influenced by treatment. For the four fish-free diets, specific growth rate increased with increasing inclusion of Schizochytrium sp. in the feed. Fillet fatty acid profiles were similarly influenced by diet treatment, generally reflecting the fatty acid profiles of the feed. Total fillet PUFAs were higher in sablefish from the fish-free treatments than the control treatments, with DHA increasing with increasing inclusion of dietary Schizochytrium. In contrast, EPA was higher in fillets from both fish-ingredient control treatments compared to fillets from the fish-free treatments, yet EPA remained higher than expected in sablefish fed the fish-free diets. Histologic evaluation of sablefish distal intestine and liver demonstrated that the microalga-inclusion diets were well tolerated and did not cause histomorphological changes in the tissues. These results suggest Schizochytrium sp. can increase PUFA concentrations in fish fillets without compromising fish health and growth, making it a viable ingredient for alternative sablefish feeds. • Sablefish were grown on fish-free feeds without negative impacts to growth, condition, and nutrient utilization. • Dietary microalga inclusion did not negatively impact sablefish intestine or liver tissue. • Omega-3 DHA in sablefish fillets increased as dietary microalga inclusion increased. • Fillet omega-3 PUFA concentrations were highest in sablefish fed the fish-free diets. [ABSTRACT FROM AUTHOR]