Coenzyme Q10, as a natural fat-soluble compound, can play a role in protecting mitochondria, but the mechanism is still unclear. Here, we explored the mechanism of coenzyme Q10 enhancing mitochondrial function using hepatocytes of spotted seabass. Three groups were set: normal medium as control group, fatty acid group containing 100 μmol/L FA (FA group), and 100 μmol/L FA and 5 μmol/L coenzyme Q10 group (FA+COQ10). After the culture, the results showed that FA treatment significantly increased the triglyceride content in the cells. Bodipy staining showed that many lipid droplets appeared in the FA group, while coenzyme Q10 reduced triglycerides content and lipid droplets. Moreover, coenzyme Q10 significantly reduced the content of ROS in cells. After scavenging ROS, the liver cell damage caused by FA was alleviated, the mitochondrial membrane potential and its mitochondrial metabolic enzyme activity were restored, and the ATP content was increased. Further analysis showed that FA significantly down-regulated the expression of mitophagy key genes pink, parkin and lc3b, while up-regulated the expression of p62. Through mitochondrial fluorescence staining and mtDNA content detection, it was found that the number of mitochondria in FA-treated cells decreased significantly, while the number of mitochondria increased significantly after FA+COQ10 treatment. This indicates that coenzyme Q10 can significantly promote the mitophagy process. In order to further study whether the enhancement of mitochondrial function by coenzyme Q10 is related to the activation of autophagy, we set up FA group, FA+COQ10 group and FA+COQ10+Mdivi-1 group (pretreatment with mitophagy inhibitor Mdivi-1). After Mtphagy Dye staining, it was found that the number of autophagosomes in the FA+COQ10+Mdivi-1 group was lower than that in the FA+COQ10 group, indicating that the activation of mitophagy by coenzyme Q10 was inhibited. The results of this study indicate that coenzyme Q10 enhances mitochondrial function and alleviates excessive fat deposition dependent on PINK1-mediated mitophagy. ### Competing Interest Statement The authors have declared no competing interest.

Nitrite is a common pollutant in aquaculture systems and can pose serious threats to fish health, especially under high-temperature conditions. This study aimed to investigate the impact of nitrite stress on the growth, glycolipid metabolism, and hepatic metabolomic profiles in the spotted seabass fry (Lateolabrax maculatus) under elevated temperature conditions at 33 °C. A total of 450 fish (28.52 ± 0.84 g) were randomly distributed into nine tanks and exposed to three nitrite concentrations (0, 8, and 16 mg/L), with samples collected on days 1, 3, 7, 14, 21, and 28. Results showed that higher nitrite levels significantly reduced final body weight, weight gain, survival rate, hepatosomatic index, and viscerosomatic index. Blood glucose and triglyceride levels, whole-body crude lipid, liver total cholesterol, and hepatic glycogen content also declined significantly under higher nitrite stress. In contrast, hepatic lactate and lactate dehydrogenase increased in the high-nitrite group. Gene expression analysis revealed suppressed lipid synthesis and enhanced lipolysis under nitrite exposure. Metabolomic analysis further demonstrated disruptions in key energy-related pathways, including the TCA cycle, pentose phosphate pathway, and insulin signaling. These findings indicate that nitrite stress impairs growth and energy metabolism in spotted seabass, which respond by mobilizing energy reserves to cope with combined stress of high temperature and nitrite.

An 8-week feeding experiment was carries out to explore the impacts of dietary tauroursodeoxycholic acid (TUDCA) on growth and gut integrity in spotted seabass (Lateolabrax maculatus) under heat stress (33 °C). Three hundred fish (2 ± 0.02 g) were allocated to triplicate groups and fed five diets containing graded levels of TUDCA at 0, 10, 20, 30, or 40 mg/kg (designated as Con, T10, T20, T30 and T40 diets). Growth performance was significantly (P < 0.05) enhanced in fish receiving ≥30 mg/kg TUDCA compared to the control group. Progressive increases in intestinal total antioxidant capacity and superoxide dismutase activity, accompanied by decreased malondialdehyde concentration, were observed as TUDCA dose increased. TUDCA application modulated the expression of intestinal antioxidant-related genes, downregulating keap1 and upregulating nrf2. Notably, supplementation with 40 mg/kg TUDCA improved intestinal morphology, as evidenced by increased villus height and number. Furthermore, in the T40 group, a marked downregulation of pro-apoptotic genes (caspase3, caspase8, caspase9, and bax) and reduced immunofluorescence intensity were observed, while the expression of the anti-apoptotic gene bcl was significantly up-regulated. Additionally, the expression of pro-inflammatory genes (il-1β, il-8, and tnf-α) and immunofluorescence intensity were significantly reduced in the T40 group compared to control. In contrast, the expression of anti-inflammatory genes (il-4, il-10, and tgf-β) was markedly upregulated. Furthermore, dietary inclusion of 40 mg/kg TUDCA suppressed the expression of endoplasmic reticulum stress-related genes (grp78, chop, perk, atf6, and ire1) and activated the bile acid receptor gene tgr5 in the intestine. Concurrently, TUDCA treatment enhanced the PI3K-Akt signaling pathway, contributing to the inhibition of apoptosis. The data generated in this study demonstrated that dietary supplementation with 40 mg/kg TUDCA promotes growth, activates the Nrf2-Keap1 and PI3K-AKT signaling pathways, enhances intestinal antioxidant defenses, suppresses inflammation and apoptosis, alleviates endoplasmic reticulum stress, and mitigates the physiological impacts of heat stress in L. maculatus reared at elevated temperatures.

This study explored the metabolic effects of branched-chain amino acids (BCAAs) on the hepatocytes of spotted seabass (Lateolabrax maculatus) under high-glucose (HG) or high-fat (HF) conditions. Hepatocytes were cultured under five different conditions: control, high glucose (HG), HG + BCAAs (Leu 0.8 mM, Ile 0.4 mM, Val 0.8 mM), high fat (HF), and HF + BCAAs (Leu 0.8 mM, Ile 0.8 mM, Val 0.8 mM). After 72 h of culture, cells and cell supernatants were collected to measure relevant indicators. The results revealed that BCAAs supplementation significantly reduced glycogen and lipid accumulation in hepatocytes exposed to HG or HF conditions (p < 0.05). Additionally, alanine aminotransferase and aspartate aminotransferase activities in the supernatant were significantly decreased, indicating that BCAAs supplementation alleviated hepatocyte damage induced by these conditions. Furthermore, BCAAs addition markedly enhanced antioxidant defense by increasing superoxide dismutase and catalase activities, improving total antioxidant capacity, and reducing malondialdehyde levels. Metabolic enzyme activity analysis revealed that BCAAs significantly increased the activities of citrate synthase (CS), alpha-ketoglutarate dehydrogenase complex (α-KGDHC), succinate dehydrogenase (SDH), phosphoenolpyruvate carboxykinase (PEPCK), and liver pyruvate kinase (LPS), while significantly decreasing fatty acid synthase (FAS) activity. Gene expression analysis further demonstrated that BCAAs supplementation downregulated the expression of lipogenic genes (fas and srebp-1c) and upregulated the expression of lipolytic genes (ppaα and atgl) and glucose metabolism-related genes (g6pd, hk, pfk, pk, fbp, and g6pase). Under HG or HF conditions, hepatocytes exhibited decreased adenosine triphosphate (ATP) content, increased reactive oxygen species (ROS) levels, and reduced mitochondrial membrane potential. These adverse effects were mitigated by BCAAs supplementation. In conclusion, BCAAs supplementation alleviated hepatocyte damage caused by HG or HF conditions, enhanced antioxidant defenses, and protected mitochondrial activity and function by promoting glucose and lipid metabolism.

This study investigated the metabolic effects of branched-chain amino acids (BCAAs) on the hepatocytes of Lateolabrax maculatus under high glucose or high fat conditions. Hepatocytes were cultured under five different conditions: control, high glucose, high fat, high glucose + BCAAs, and high fat + BCAAs. After 72 hours of culture, cells and cell supernatants were collected to measure relevant indicators. The results showed that BCAAs supplementation significantly reduced glycogen and lipid accumulation in hepatocytes exposed to high glucose or high fat conditions (P

A 56-day feeding trial was carried out to compare the effects of big clitocybe (Clitocybe maxima) stalk waste and soybean meal (SBM) mixture fermented by microorganisms alone (BFBS) or in combination with enzymes (EBFBS) on growth performance, serum biochemistry, and gut health in large yellow croaker (Larimichthys crocea). Fermented ingredients (BFBS and EBFBS) were included at 10 % in the diet, replacing SBM. Large yellow croaker was randomly assigned to three groups (control, BFPS, and EBFPS) with four replicates per group. Results showed that BFBS and EBFBS improved growth performance, feed utilization, and organ-somatic indices. Dietary BFBS and EBFBS significantly elevated serum alkaline phosphatase and acid phosphatase activities, and reduced serum aspartate transaminase and alanine transferase activities, IL-1 beta and TGF-beta 1 contents, indicating systemic immune stimulation and inflammation inhibition in croakers. Dietary BFBS and EBFBS decreased serum D-lactate content and diamine oxidase activities, in parallel with the enhancements of muscle thickness, villus height, and expressions of zo-1 and claudin-11 mRNA. Moreover, BFBS and EBFBS moderately activated intestinal inflammation and inhibited TLRs signaling, showing up-regulation of pro-inflammatory il-1 beta and il-6 and downregulation of tlr1, tlr2b, and anti-inflammatory il-4/13a, il-10, and tgf-beta 1. BFBS and EBFBS increased diversities of gut microbiota; meanwhile, the enhancement of Firmicutes (only in BFBS group) and the reduction of Proteobacteria (only in BFBS group) and Brevinema were observed in BFBS and EBFBS groups, suggesting that fermented feedstuffs could positively shape the gut microbiota. In conclusion, BFBS and EBFBS have excellent potential in improving growth, immunity, and intestinal health of large yellow croaker (L. crocea). It is worth noting that EBFBS, in particular, showed superior performance in these aspects compared to BFBS, indicating that enzyme-assisted bacterial fermentation may be a more effective approach for ingredient fermentation. The work will provide a novel insight into the development of effective protein sources for aquafeeds and high-value utilization of residual wastes in the mushrooms processing chain.

The present study aimed to assess the influence of pomelo (Citrus grandis) peel and soybean meal co-fermented protein (CFP) on growth performance, feed utilization, immune response, as well as hepatic and intestinal health in largemouth bass (Micropterus salmoides). Fish weighing 5.80 +/- 0.01 g were allocated into five groups and given diets containing 0 %, 5 %, 10 %, 15 % and 20 % CFP for a duration of eight weeks. The growth performance and dietary utilization were not influenced by the supplementation of 5 %, 10 % and 15 % CFP. Otherwise, the total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity were slightly improved by 5 %, 10 %, and 15 % CFP, while the malondialdehyde (MDA) content was reduced. Simultaneously, elevated alkaline phosphatase (AKP) activity and immunoglobulin M (IgM) content in groups with 5 % and 10 % CFP (P < 0.05). The intestinal barrier function was enhanced in groups containing 5 % and 10 % CFP, which is evidenced by the reduction in serum diamine oxidase (DAO) activity and the increased expression of intestinal Claudin-1 and ZO-1. Nevertheless, the inclusion of 20 % CFP damaged the development of villi and muscle, and inhibited the expression of Occludin. The intestinal pro-inflammatory cytokines (TNF-alpha, IL-1) and IL-8) were downregulated while the anti-inflammatory cytokines (IL-10 and TGF-)) expression were upregulated in groups supplemented with 5 %, 10 % and 15 % CFP. The expression of intestinal immune effector LYZ was significantly up-regulated in the group with 10 % CFP. Furthermore, the incorporation of 10 % CFP was found to effectively remodel the intestinal microbiota, as evidenced by an augmentation in the relative abundance of beneficial Firmicutes and a concurrent decrease in the abundance of potentially pathogenic Proteobacteria. In conclusion, the 5 %, 10 % and 15 % inclusion level of CFP in diets is conducive to enhancing the immunity, hepatic and intestinal health of largemouth bass, without compromising it's feeding and growth performance.

This experiment was conducted to investigate the effects of adding phytase to a high plant protein diet on growth performance, digestion, absorption and intestinal health in bullfrogs (Lithobates catesbeianus). Six experimental diets were prepared with normal phosphorus (NP), low phosphorus-high plant protein (LP0), and then 750, 1500, 2250 and 3000 phytase units (FTU)/kg phytase were added to the LP0 diet, named LP750, LP1500, LP2250 and LP3000, respectively. Bullfrogs (33.21 +/- 0.12 g) were fed each of the six diets for 56 days. Bullfrogs fed the LP2250 and LP3000 diets showed higher weight gain rate than bullfrogs fed the LP0 diet. Bullfrogs fed the LP1500, LP2250 and LP3000 diets showed higher lysozyme activity and lower diamine oxidase activity in the serum than bullfrogs fed the LP0 diet. Apparent digestibility of P in bullfrogs fed the LP2250 and LP3000 diets was higher than that of bullfrogs fed the LP0, LP750, and LP1500 diets, with no significant difference from bullfrogs fed the NP diet. Protein efficiency ratio of bullfrogs fed the LP1500, LP2250, and LP3000 diets was higher, and trypsin activity of bullfrogs fed the LP2250 and LP3000 diets was higher than that of bullfrogs fed the LP0 diet. Compared to the LP0 group, the expression of interleukin-1 beta and tumour necrosis factor alpha genes was significantly decreased, and the expression of interleukin-10, occludin and zonula occludens-1 genes was significantly increased in bullfrogs fed the LP750, LP1500, LP2250 and LP3000 diets. Compared to bullfrogs fed the LP and NP diets, bullfrogs fed the LP3000 diet had an increased abundance of beneficial bacteria Firmicutes and Bacillus in the intestine. In summary, the addition of 2250-3000 FTU/kg phytase to a high plant protein diet improved growth and nutrient absorption, and alleviated intestinal inflammation and damage in bullfrogs.

Global warming raises coastal water temperatures, affecting fish tissue structure, function, and survival. It is essential to understand these changes to develop effective mitigation strategies. This study investigates the changes in gill, liver, intestine, and head kidney structure and function of spotted seabass (Lateolabrax maculatus) after 56 days of cultivation at 27 degrees C (N, normal), 31 degrees C (M, moderate), and 35 degrees C (H, high). The results indicate that increased water temperature induced gill remodeling, liver vacuolization, reduced and broken intestinal villi, and increased melanin macrophages in head kidney of spotted seabass. The mRNA levels of hif alpha in gill of the H group were markedly elevated than those observed in N and M groups (P < 0.05). The mRNA levels of autophagy-related genes (beclin1, ulk1) in liver were significantly reduced in the H group in comparison to both the N and M groups (P < 0.05). The activities of trypsin (TRY), lipase (LPS), and amylase (AMS) in intestinal were lowest in H group and these levels were markedly lower than those observed in N group (P < 0.05). The mRNA levels of pro-inflammatory genes (il1 beta, il8) in intestinal were significantly elevated in H group than in N and M groups (P < 0.05). Furthermore, the activities of acid phosphatase (ACP), alkaline phosphatase (AKP), total nitric oxide synthase (T-NOS), and nitric oxide (NO) concentration in head kidney were markedly reduced in H group than N group (P < 0.05). Additionally, the mRNA levels of endoplasmic reticulum (ER) stress-related and mitochondrial homeostasis-related genes in liver indicate that high temperature induce ER stress and mitochondrial homeostasis imbalance. Conclusion: Elevated temperatures altered the morphological structure of the gill, liver, intestine, and kidney tissues in seabass, reducing oxygen absorption, self-repair, digestion, and nonspecific immune capabilities. Additionally, high temperature induced ER stress and mitochondrial homeostasis imbalance in liver, thereby inhibiting the thermal tolerance of seabass.

After 56 days of culture experiment, spotted seabass ( Lateolabrax japonicus ) (10 fish per tank) fed diets with similar dietary iron levels (63, 188, and 554 mg/kg) were subjected to a 24-hour nitrite stress challenge at 27 °C and 33 °C, respectively. Nitrite stress significantly reduced the levels of hematocrit (HCT), red blood cell (RBC) and hemoglobin (Hb). The reduction in the 33 ℃ group was greater than that in the 27 ℃ group, and the decrease in the 63 mg/kg iron level group was the largest. The main impact analysis revealed that when the dietary iron level rose from 63 mg/kg to 554 mg/kg, the contents of red blood cell (RBC), white blood cell (WBC), and hemoglobin (Hb) in the blood and the activities of total antioxidant capacity (T-AOC) and catalase (CAT) in the serum significantly increased (P< 0.05). The group with an iron level of 188 mg/kg showed a considerably lower serum malondialdehyde (MDA) content than the group with an iron level of 63 mg/kg (P< 0.05). The 63 mg/kg iron level group observed substantial decreases (P< 0.05) in hemoglobin (Hb) and total antioxidant capacity (T-AOC) under 27 °C, but dietary 188 and 554 mg/kg iron mitigated this phenomenon. Iron deficiency and high temperatures facilitated the formation of methemoglobin (MetHb). This study demonstrated that spotted seabass is more susceptible to the physiological harm caused by nitrite at 33 ℃ than at 27 ℃. Iron deficiency exacerbated the risk of hemocytopenia, oxidative stress and hypoxia. Dietary iron fortification could enhance tolerance by enhancing antioxidant capacity and blood homeostasis.

This study elucidated the impacts of coenzyme Q10 (COQ10) supplementation in a high-fat diet (HFD) on growth, lipid metabolism and mitochondrial function in spotted seabass (Lateolabrax maculatus). Totally five diets were formulated: a diet with normal fat content (11 % lipid, NFD), a HFD (17 % lipid) and three additional diets by supplementing 5, 20 or 80 mg/kg of COQ10 to the HFD. After an 8-week culture period, samples were collected and analysed. The results demonstrated that COQ10 inclusion prevented the HFD-induced deterioration of growth performance and feed utilisation. COQ10 alleviated the deposition of saturated fatty acids following HFD intake and promoted the assimilation of n-3 and n-6 PUFA. Moreover, COQ10 administration inhibited the surge in serum transaminase activity and reduced hepatic lipid content following HFD ingestion, which was consistent with the results of oil red O staining. In addition, HFD feeding led to reduced hepatic citrate synthase and succinate dehydrogenase activities and decreased ATP content. Notably, COQ10 administration improved these indices and up-regulated the expression of mitochondrial biogenesis-related genes (pgc-1α, pgc-1β, nrf-1, tfam) and autophagy-related genes (pink1, mul1, atg5). In summary, supplementing 20-80 mg/kg of COQ10 in the HFD promoted growth performance, alleviated hepatic fat accumulation and enhanced liver mitochondrial function in spotted seabass.

BACKGROUND:Low phosphorus (LP) diets perturb hepatic energy metabolism homeostasis in fish. However, the specific mechanisms in LP-induced hepatic energy metabolism disorders remain to be fully elucidated. OBJECTIVES:This study sought to elucidate the underlying mechanisms of mitochondria involved in LP-induced energy metabolism disorders. METHODS:Spotted seabass were fed diets with 0.72% (S-AP, control) or 0.36% (S-LP) available phosphorus for 10 wk. Drp1 was knocked down or protein kinase (PK) A was activated using 8Br-cAMP (5 μM, a PKA activator) in spotted seabass hepatocytes under LP medium. Zebrafish were fed Z-LP diets (0.30% available phosphorus) containing Mdivi-1 (5 mg/kg, a Drp1 inhibitor) or 8Br-cAMP (0.5 mg/kg) for 6 wk. Biochemical and molecular parameters, along with transmission electron microscopy and immunofluorescence, were used to assess hepatic glycolipid metabolism, mitochondrial function, and morphology. RESULTS:Spotted seabass fed S-LP diets showed reduced ATP (52%) and cAMP (52%) concentrations, along with reduced Drp1 (s582) (38%) and PKA (61%) phosphorylation concentrations in the liver compared with those fed S-AP diets (P < 0.05). Drp1 knockdown elevated ATP concentrations (1.99-fold), decreased mitochondrial DRP1 protein amounts (45%), and increased mitochondrial aspect ratio (1.82-fold) in LP-treated hepatocytes (P < 0.05). Furthermore, 8Br-cAMP-treated hepatocytes exhibited higher PKA phosphorylation (2.85-fold), ATP concentrations (1.60-fold), and mitochondrial aspect ratio (2.00-fold), along with decreased mitochondrial DRP1 protein concentrations (29%) under LP medium (P < 0.05). However, mutating s582 to alanine mimic Drp1 dephosphorylation decreased ATP concentrations (63%) and mitochondrial aspect ratio (53%) in 8Br-cAMP-treated hepatocytes (P < 0.05). In addition, zebrafish fed Z-LP diets containing Mdivi-1 or 8Br-cAMP had higher ATP concentrations (3.44-fold or 1.98-fold) than those fed Z-LP diets (P < 0.05). CONCLUSIONS:These findings provide a potential mechanistic elucidation for LP-induced energy metabolism disorders through the cAMP/PKA/Drp1-mediated mitochondrial fission signaling pathway.

Aquaculture water eutrophication is primarily driven by nitrogen (N) and phosphorus (P), partly derived from animal excretions. Understanding the N and P metabolism is crucial for mitigating environmental pollution caused by aquaculture. This study investigated N and P budgets in bullfrogs (Aquarana catesbeiana) ) of varying body weights: 52.63 +/- 0.33 (50 g), 98.64 +/- 0.55 (100 g), 159.97 +/- 0.58 (150 g) and 250.01 +/- 2.61 (250 g). Our findings highlighted the significant influence of body size on N and P budgets in bullfrogs. As body weight increased, feed intake rate, N and P intake rates, growth rate, N and P growth rates, N and P metabolism rates, feces rate, while the N and P feces rates all decreased. The relationship between each index and body weight was expressed as a power function (Y = aWb). b ). The N and P budget equations for bullfrogs were established as follows: 100 Intake N (IN) N ) = 30.75 Growth N (GN) N ) + 62.48 Metabolism N (MN) N ) + 2.10 Feces N (FN) N ) + 4.67 Others (ON), N ), and 100 P Intake P (IP) P ) = 74.16 Growth P (GP) P ) + 4.18 Metabolism P (MP) P ) + 7.92 Feces P (FP) P ) + 13.75 Others (OP). P ). In conclusion, daily feeding per body weight of bullfrog should be reduced as their body weight increased. Consequently, the dietary protein should be progressively lowered to minimize nitrogen waste, while bullfrogs demonstrated effective utilization of P in the soybean meal diet.

This study evaluated the effects of low phosphorus on spotted seabass (Lateolabrax maculatus) from the perspective of phospholipid content and function, endoplasmic reticulum (ER) stress, inflammatory response and gut microbiota. Two diets were prepared to contain available phosphorus levels of 0.37% (low-phosphorus, LP) and 0.75% (normal-phosphorus, NP) and feed fish (3.53 ± 0.34 g) to satiety twice daily for 10 weeks. Compared with fish fed the NP diet, fish fed the LP diet showed lower body weight gain and higher abdominal fat percentage. Further studies showed that the LP diet decreased the content of phospholipid in the serum, liver, and abdominal fat tissue and induced ER stress and disruption of lipid metabolism in both of the liver and abdominal fat tissue and inflammatory responses in abdominal fat tissue. Furthermore, compared with fish fed the NP diet, the LP diet reduced microbial diversity in the gut. In contrast to fish fed the NP diet, fish fed the LP diet exhibited a decrease in the abundance of potential metabolically promoted probiotics (e.g., Lactococcus lactis) and an increase in the abundance of potential pathogenic bacteria (e.g., Plesiomonas) in the gut. The results of PICRUSt2 functional prediction also validated the metabolic disorders occurring in fish fed the LP diet as well as the reduced metabolic capacity. These results suggested that the LP diet decreased phospholipid content, induced ER stress and inflammatory responses then disturbed lipid metabolism and gut microbiota in spotted seabass. These negative effects contributed to poorer growth and higher percentage of abdominal fat in spotted seabass fed the LP diet than those of spotted seabass fed the NP diet.

Coenzyme Q10 (COQ10), a natural fat-soluble compound, is known to protect mitochondria, though the exact mechanism remains unclear. Here, we explored the mechanism through which COQ10 enhances mitochondrial function using hepatocytes from spotted seabass (Lateolabrax maculatus). Three experimental groups were established: a normal medium control group, a fatty acid (FA) group containing 100 μM FA, and a group containing100 μM FA plus 5 μM COQ10 (FA + COQ10). After incubation, the results showed that FA treatment significantly increased triglyceride content in the cells, while COQ10 treatment reduced triglycerides content (P < 0.05). Additionally, COQ10 alleviated FA-induced hepatocyte damage, restored mitochondrial membrane potential and increased ATP content (P < 0.05). Further analysis showed that FA downregulated key mitophagy genes (PINK1, PARKIN, and LC3B) while upregulating P62 (P < 0.05). To investigate whether the enhancement of mitochondrial function by COQ10 is dependent on mitophagy activation, we used the mitophagy inhibitor Mdivi-1 and set it to FA + COQ10 + Mdivi-1 group. After mtphagy Dye staining, the number of autophagosomes in the FA + COQ10 + Mdivi-1 group was lower than in the FA + COQ10 group, indicating that the mitophagy activation by COQ10 was inhibited. Overall, these results demonstrated that COQ10 enhances mitochondrial function and alleviates excessive fat deposition in hepatocytes via PINK1-mediated mitophagy. This also indicates that COQ10 can be potentially applied to improve the metabolic disorders of fish in aquaculture.

Pomelo peel is a main by-product of pomelo consumption, while most of the by-products are discarded as wastes with environmental threats. Indeed, it contains many nutrients and bioactive ingredients, which makes it a promising source of aquatic feedstuff. In this study, a 56-day feeding trial was set out to assess the dietary application of pomelo peel and soybean meal (SBM) (1:4 ratio) fermented compound (PSFC) in large yellow croaker (Larimichthys crocea). Results indicated that dietary PSFC improved weight gain rate (WGR) and specific growth rate (SGR), but did not affect feed utilization, body shape parameters and survival rate (SR) of croakers. Moreover, PSFC significantly decreased serum diamine oxidase (DAO) activity and D-lactate concentration, increased muscle thickness and villus height, as well as upregulated occludin, claudin-11, ZO-1 and JAM mRNA levels. The inhibition of proinflammatory IL-1β and promotion of anti-inflammatory IL-4/13b and IL-10 expressions were documented in croakers fed with PSFC. Dietary PSFC upregulated intestinal TLR1, TLR2A, and TLR2B expression, which had significantly positive correlations with improved inflammatory status. Furthermore, PSFC application caused clear alterations in the intestinal microbiota of croakers, which characterized with decreased relative abundances of Verrucomicrobiota and Acidobacteriota and increased relative abundances of unclassified_Muribaculaceae and Akkermansia. Overall, PSFC can significantly improve growth and intestinal health of L. crocea, and showed potential as protein source on L. crocea culture. This work offers a novel insight into the development of fermented protein sources for aquafeeds using pomelo peel and SBM as fermentation ingredients.

Spotted seabass (Lateolabrax maculatus) is an economically important fish species in China. In this study, the muscle of L. maculatus was used as a material, and the muscle cell line was successfully established using the tissue block method. The established muscle cell line exhibited vigorous growth and had been successfully passaged for more than 100 generations, maintaining stable polygonal cell morphology. The cell viability of L. maculatus muscle cell line exhibited a notable increase following a 24-h treatment with 30 M taurine, and the relative expression of myogenic regulatory factors myf5 and myf6 was significantly increased. Therefore, the muscle cell line of L. maculatus was successfully established and served as a valuable resource for conducting fundamental research in L. maculatus, providing essential materials for gene function analysis, cytogenetics, and nutritional metabolism mechanism in L. maculatus.

Our study assessed the impacts of black soldier fly larvae meal (BSFLM) substituting fishmeal at various levels in isolipidic and isonitrogenous diets on the growth performance, antioxidant capacity, intestinal health status, muscle texture and lipid metabolism of the bullfrog (Aquarana catesbeiana) with an initial body weight of (32 +/- 0.5 g) over an 8-week period. The results revealed that BSFLM substitution had no significant impact on the growth performance of bullfrog, as demonstrated by no significant differences in weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR), and survival rate (SR) (P > 0.05). However, substitution levels exceeding 80 % led to a decrease in whole-body and muscle crude protein content, compromised antioxidant capacity, reduced intestinal amylase activity, and impaired intestinal tissue structure. Additionally, high levels of substitution promoted the expression of genes linked to lipid synthesis (acc1, ppar gamma), while suppressing the expression of genes linked to lipid catabolism (atgl, hsl). This resulted in significantly elevated content of serum triglyceride (TG), total cholesterol (TC), whole-body crude lipid and abdominal fat rate (AFR) in D6 (P < 0.05). This also led to liver structural damage, evidenced by elevated activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Overall, complete substitution of fishmeal with BSFLM didn't influence the growth performance of bullfrog, but substitution levels exceeding 80 % reduce whole-body crude protein content and antioxidant capacity, leading to liver and intestinal damage as well as lipid metabolism disorders. Based on serum ALT activity as evaluation indicators, the optimal level of BSFLM substitution for fishmeal in bullfrog diets is 66.6 %.

Tianchongyou (TC), is a feed ingredient that contains defatted yellow mealworm and the medium during their growth with a crude protein content of more than 65 %. Our previous research found that TC utilization of spotted seabass (Lateolabrax maculatus) was limited. This research was conducted to examine whether indigenous intestinal probiotics can improve the utilization of TC in spotted seabass. The experiment includes a control group (TC, fed basal diet) and five treated groups, fed the diets prepared by supplementing the basal diet (TC) with Bacillus licheniformis (BL), Virgibacillus salarius (VS), Alkalihalobacillus clausii (AC), Virgibacillus pantothenticus (VP), and Bacillus safensis subsp. safensis (BS). The results indicated that the final body weight, weight gain, and specific growth rate of spotted seabass in both the VS and VP groups exhibited a significant increase compared to those in the TC group (P < 0.05). There were no statistically significant alterations observed in the levels of serum AKP, LZM, and complement 3 among the treated groups when compared to the TC group (P > 0.05). Intestinal health of spotted seabass in VS and VP groups were well than that of TC group. The VP and VS groups showed significant enhancements in intestinal morphology (P < 0.05) when compared to the TC group. Furthermore, there was a significant elevation in the relative mRNA expression level of claudin in the VS group (P < 0.05). The VS and VP groups exhibited a higher prevalence of potential probiotics, such as Bacillus, and Acinetobacter, in comparison to the TC group. In summary, V. salaries, V. pantothenticus could be further researched as potential probiotics to improve the intestinal health of aquatic animal fed TC diet.

Soybean meal (SM) serves as a primary alternative to fish meal in aquafeeds. However, a high-SM diet may result in intestinal injury. Our previous study demonstrated the probiotic effects of heat-inactivated Bacillus subtilis (LCBS1) on bullfrogs (Aquarana catesbeianus) fed a high-SM diet, probably attributed to the bioactive constituent of cell wall. Therefore, in this study, the main constituents of cell wall from LCBS1, including peptidoglycan (PGN), lipoteichoic acid (LTA), cell wall protein (CWP), and whole cell wall (WCW), were extracted and added to a high-SM (~55 %) diet to investigate their probiotic effects on bullfrogs and reveal the possible mechanisms. The results indicated that bullfrogs fed the LTA of LCBS1 showed the highest weight gain, feed efficiency, and protein efficiency ratio. Additionally, the LTA of LCBS1 could activate the humoral immunity and modulate intestinal microbiota. It might activate JAK2-STAT3 and MAPK-ERK pathways, as well as up-regulate tlr5 gene to promote intestinal cell proliferation, thereby alleviating jejunal injury. The WCW of LCBS1 effectively increased the growth performance of bullfrogs by improving the humoral immunity, enhancing intestinal barrier function, and alleviating intestinal inflammatory response. The PGN and CWP of LCBS1 could stimulate the humoral immunity and enhance intestinal barrier function, but had no significant effect on the growth performance of bullfrogs. In conclusion, the LTA might be the primary bioactive constituent of heat-inactivated LCBS1, with the beneficial effects of promoting intestinal cell proliferation and enhancing intestinal barrier function, therefore alleviating the intestinal injury induced by SM on bullfrogs. This study establishes a theoretical basis for the efficient utilization of plant proteins by the application of postbiotics additive in aquafeed, which further saves the feed costs and promotes development of economically sustainable aquaculture.