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A 70-day feeding trial was conducted to determine the effects of the replacement of fishmeal (FM) by soybean meal (SM) in diets on growth performance, digestion, hepatic metabolism, antioxidant capacity, and innate immunity of juvenile large yellow croaker (Larimichthys crocea). Four iso-lipidic and iso-nitrogenous diets replacing 0, 15, 30, and 45 FM protein by SM protein were formulated, named FM, SM15, SM30, and SM45, respectively. Results indicated that the specific growth rate (FM = 1.55, SM15 = 1.50, SM30 = 1.48, and SM45 = 1.34%) of fish showed a significant linear trend (P < 0.05). With increasing dietary SM, the activity of trypsin (262.02, 179.34, 144.41, and 123.92 U/mg·prot) significantly decreased (linear trend, P < 0.05). The content of high-density lipoprotein cholesterol showed a significant linear trend and quadratic trend, and the maximum was observed in fish fed the diet with 45% protein from SM (P < 0.05). The mRNA expression of the mechanistic target of rapamycin (m-tor) and ribosomal protein S6 (rps6) showed a significant linear trend (P < 0.05). The content of malondialdehyde (81.82, 92.91, 79.64, and 126.45 nmol/mg·prot) showed a significant linear trend and quadratic trend; the minimum was observed in fish fed the diet with 30% protein from SM (P < 0.05). The activity of acid phosphatase (328.45, 300.08, 254.03, and 223.51 U/mg·prot) significantly decreased with increasing dietary SM substitution levels (linear trend, P < 0.05). A significant quadratic trend was observed in the mRNA expression of interferon-γ and interleukin-1β, while the maximum was observed in fish fed the diet with 45% protein from SM (P < 0.05). In conclusion, this study demonstrated that the replacement of FM by SM in diets can decrease the growth performance, digestion, antioxidant capacity, and innate immunity and affect the hepatic metabolism of juvenile large yellow croaker. The minimum negative effect was obtained when 30% of FM was replaced by SM. [ABSTRACT FROM AUTHOR]

A 70-day feeding experiment was carried out to assess the replacement of dietary fishmeal (FM) protein with degossypolized cottonseed protein (DCP) on large yellow croaker (Larimichthys crocea) with initial body weight (13.09 ± 0.50 g). Five isonitrogenous and isolipidic diets replaced fishmeal protein with 0%, 20%, 40%, 60%, and 80% DCP were formulated and named as FM (the control group), DCP20, DCP40, DCP60, and DCP80, respectively. Results displayed that weight gain rate (WGR) and specific growth rate (SGR) in the DCP20 group (263.91% and 1.85% d-1) were significantly increased compared with the control group (194.79% and 1.54% d-1) (P < 0.05). Furthermore, fish fed the diet with 20% DCP significantly increased the activity of hepatic superoxide dismutase (SOD) compared with the control group (P < 0.05). Meanwhile, the content of hepatic malondialdehyde (MDA) in the DCP20, DCP40, and DCP80 groups was significantly lower than that in the control group (P < 0.05). The activity of intestinal trypsin in the DCP20 group was significantly degraded compared with that in the control group (P < 0.05). The transcription of hepatic proinflammatory cytokine genes (interleukin-6 (il-6); tumor necrosis factor-α (tnf-α); and interferon-γ (ifn-γ)) in the DCP20 and DCP40 groups was significantly upregulated compared with that in the control group (P < 0.05). As to the target of rapamycin (TOR) pathway, the transcription of hepatic target of rapamycin (tor) and ribosomal protein (s6) was significantly up-regulated, while the transcription of hepatic eukaryotic translation initiation factor 4E binding protein 1 (4e-bp1) gene was significantly downregulated in the DCP group compared with the control group (P < 0.05). In summary, based on the broken line regression model analysis of WGR and SGR against dietary DCP replacement levels, the optimal replacement level was recommended to be 8.12% and 9.37% for large yellow croaker, respectively. These results revealed that FM protein replaced with 20% DCP could promote digestive enzyme activities and antioxidant capacity and further activate immune response and the TOR pathway so that growth performance of juvenile large yellow croaker was improved. [ABSTRACT FROM AUTHOR]

Octanoate is a type of classical medium-chain fatty acids, which is widely used to treat neurological and metabolic syndrome. However, the specific role of octanoate in repairing intestinal health impairment is currently unknown. Therefore, we investigated whether dietary octanoate repaired the intestinal damage induced by surplus soybean oil in Larimichthys crocea. In this study, dietary octanoate alleviated abnormal morphology of the intestine and enhanced expression of ZO-1 and ZO-2 to improve intestinal physical barrier. Further, dietary octanoate increased antioxidant enzymic activities and decreased the level of ROS to alleviate the intestinal oxidative stress. Dietary octanoate also attenuated the expression of proinflammatory cytokines and the polarity of macrophage to reduce the intestinal inflammatory response. Moreover, the result of intestinal microbial 16S rRNA sequence showed that dietary octanoate repaired the intestinal mucosal microbial dysbiosis, and increased the relative abundance of Lactobacillus. Dietary octanoate supplementation also increased the level of acetic acid in intestinal content and serum through increasing the abundance of acetate-producing strains. Overall, in Larimichthys crocea , dietary octanoate might alleviated oxidative stress, inflammatory response and microbial dysbiosis to repair the intestinal damage induced by surplus soybean oil. This work provides vital insights into the underlying mechanisms and treatment strategies for intestinal damage in vertebrates. [ABSTRACT FROM AUTHOR]

Glycerol monolaurate (GML) is a potential candidate for regulating metabolic syndrome and inflammatory response. However, the role of GML in modulating intestinal health in fish has not been well determined. In this study, a 70-d feeding trial was conducted to evaluate the effect of GML on intestinal barrier, antioxidant capacity, inflammatory response and microbiota community of large yellow croaker (13.05 ± 0.09 g) fed with high level soybean oil (SO) diets. Two basic diets with fish oil (FO) or SO were formulated. Based on the SO group diet, three different levels of GML 0.02% (SO0.02), 0.04% (SO0.04) and 0.08% (SO0.08) were supplemented respectively. Results showed that intestinal villus height and perimeter ratio were increased in SO0.04 treatment compared with the SO group. The mRNA expressions of intestinal physical barrier-related gene odc and claudin-11 were significantly up-regulated in different addition of GML treatments compared with the SO group. Fish fed SO diet with 0.04% GML addition showed higher activities of acid phosphatase and lysozyme compared with the SO group. The content of malonaldehyde was significantly decreased and activities of catalase and superoxide dismutase were significantly increased in 0.02% and 0.04% GML groups compared with those in the SO group. The mRNA transcriptional levels of inflammatory response-related genes (il-1β , il-6 , tnf-α and cox-2) in 0.04% GML treatment were notably lower than those in the SO group. Meanwhile, sequencing analysis of bacterial 16S rRNA V4–V5 region showed that GML addition changed gut microbiota structure and increased alpha diversity of large yellow croaker fed diets with a high level of SO. The correlation analysis results indicated that the change of intestinal microbiota relative abundance strongly correlated with intestinal health indexes. In conclusion, these results demonstrated that 0.02%–0.04% GML addition could improve intestinal morphology, physical barrier, antioxidant capacity, inflammatory response and microbiota dysbiosis of large yellow croaker fed diets with a high percentage of SO. • Dietary glycerol monolaurate improved intestinal antioxidant capacity and inflammation of large yellow croaker. • Dietary glycerol monolaurate could effectively modulate intestinal microbiota structure and composition. • Glycerol monolaurate at an appropriate level (0.02%–0.04%) improved intestinal health. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the effect of supplemental glycerol monolaurate (GML) on growth performance, hepatic lipid metabolism, antioxidant capacity and mitochondrial function in large yellow croaker (Larimichthys crocea) fed diets with high soybean oil (SBO) level. The trial diet with 7% fish oil (FO) was designed as the negative control while the diet with 7% SBO was designed as the positive control. The other three diets were formulated with the administration of 400, 800 and 1600 mg/kg GML (0.04%, 0.08% and 0.16%) on basis of the positive control diet. Results showed that the specific growth rate (SGR) was increased and the feed conversion ratio (FCR) was decreased significantly in fish fed diets with GML supplementation compared with the positive control diet, while no difference was observed in the survival rate (SR) among dietary treatments. Fish fed the diet with 0.04% GML supplementation had significantly lower triglycerides and total cholesterol contents compared with those in the positive control group. The mRNA expression of lipogenesis-related genes (srebp1c and acc) were down-regulated while the mRNA expression of lipolysis and fatty acid β-oxidation-related genes (atgl , pparα and cpt1) were up-regulated in fish fed diets with 0.04% and 0.08% GML. Compared with the positive control diet, fish fed diets with 0.04% and 0.08% GML supplementation exhibited remarkably higher activities of superoxide dismutase, catalase and the content of glutathione, as well as lower malondialdehyde level. Furthermore, in fish fed diets with 0.04% and 0.08% GML, the morphology of mitochondria was improved and their number was increased. The mRNA expression of genes related to mitochondrial biogenesis (pgc1-α, tfam and nrf1) were significantly increased in fish fed with 0.04% and 0.08% GML supplementation. Meanwhile, the content of triphosadenine (ATP), the activity of citrate synthase (CS) and succinate dehydrogenase (SDH) in liver were increased significantly in 0.04% and 0.08% treatments compared with the positive control group. Conclusively, these results indicated that dietary GML supplementation (0.04%–0.08%) could promote growth performance, improve liver lipid metabolism, antioxidant capacity and enhance mitochondrial function in large yellow croaker fed with the SBO based diet. • Supplemental glycerol monolaurate improved lipid metabolism and enhanced antioxidant capacity of large yellow croaker. • The improvement of lipid metabolism and antioxidant capacity may be mediated by enhancing mitochondrial function. • The appropriate supplemental glycerol monolaurate level for decreasing hepatic lipid content was 0.04%–0.08%. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate effects of supplemental phytosterol (PS) on growth performance, body composition, serum biochemical indexes, and lipid metabolism of juvenile large yellow croaker (Larimichthys crocea) fed with high lipid diet. The diet with high lipid content (lipid level at 18%) was used as the control diet, and other three diets were formulated with supplementation of 0.5%, 1.0%, and 1.5% PS, respectively, on basis of the control diet. Each diet was randomly fed to triplicate cages for 10 weeks. Results showed that the survival rate, final body weight, specific growth rate, and feed conversion ratio were not significantly different among dietary treatments (P > 0.05). Oil red O staining analysis showed that the diet with PS significantly reduced the number and volume of lipid droplets in liver compared with the control diet (P < 0.05). The liver and serum lipid levels were also significantly lower in diets with 0.5% and 1.0% PS than those in the control diet (P < 0.05). Fish fed diets with 0.5% and 1.0% PS showed significantly higher activities of catalase and superoxide dismutase, and lower malondialdehyde content in the liver than those in the control diet (P < 0.05). In the intestine, genes expression of lipid absorption (srbi and npc1l1) and esterification (acat , mtp , and apob100) in fish fed with 0.5% PS were significantly lower than those in the control diet whereas genes expression of cholesterol reverses transport (abca1 , abcg5 , and abcg8) in diets with PS were significantly higher than those in the control diet (P < 0.05). In the liver, compared with the control diet, supplemented with 0.5% PS significantly downregulated genes expression of lipid synthesis (srebp1 , acc , fas , scd1 , dgat2 , srebp2 , hmgcr , and dhcr7) whereas genes expression of lipid catabolism (pparα , aco , cpt1 , atgl , and cyp7a1) and cholesterol reverse transport (abcg5 and abcg8) were significantly upregulated (P < 0.05). Thus, dietary PS could reduce adverse effects of high lipid diet on juvenile large yellow croaker by the beneficial regulation of lipid metabolism-related genes in the intestine and liver, and the optimal supplement level of PS in high lipid diet was approximately 0.5% in this study. • Dietary phytosterol markedly reduce lipid metabolism disturbance in liver caused by high lipid diet on large yellow croaker. • It might be related to the increase of antioxidant capacity and the beneficial regulation of lipid metabolism-related genes. • The optimal supplement level of phytosterol in high lipid diet was approximately 0.5% in this study. [ABSTRACT FROM AUTHOR]

A 70-day feeding trial was conducted to investigate effects of dietary lysolecithin on growth performance, serum biochemical indexes, antioxidant capacity, lipid metabolism and inflammation-related genes expression of juvenile large yellow croaker (Larimichthys crocea) with initial weight of 6.04 ± 0.08 g. A formulated diet containing approximately 42% crude protein and 12.5% crude lipid was used as the control diet (CON). The other three experimental diets were formulated with supplementation of 0.2%, 0.4% and 0.6% lysolecithin based on the control diet, respectively. Results showed that weight gain rate (WGR) and specific growth rate (SGR) significantly increased in fish fed diets with lysolecithin compared with those in the control diet (P < 0.05). Fish fed diets with 0.4% and 0.6% lysolecithin had notably higher lipid content in muscle than that in the control diet (P < 0.05). When fish were fed diets with lysolecithin, serum high-density lipoprotein cholesterol (HDL-c) content was notably higher than that in the control diet (P < 0.05), while fish fed the diet with 0.6% lysolecithin had a significant lower serum low-density lipoprotein cholesterol (LDL-c) content than that in the control diet (P < 0.05). Meanwhile, serum aspartate transaminase (AST) and alanine transaminase (ALT) activities in fish fed diets with lysolecithin were remarkably lower than those in the control diet (P < 0.05). With the increase of dietary lysolecithin from 0.2% to 0.6%, mRNA expression of stearoyl-coenzyme A desaturase 1 (scd1), diacylglycerol acyltransferase 2 (dgat2) and sterol-regulatory element binding protein 1 (srebp1) showed decreasing trends. Furthermore, mRNA expression of carnitine palmitoyl transferase 1 (cpt1) and lipoprotein lipase (lpl) among each dietary lysolecithin treatment were significantly higher than those in the control diet (P < 0.05). In terms of inflammation, mRNA expression of tumor necrosis factor α (tnf-α) and interleukin-1 β (il-1β) were significantly down-regulated in fish fed diets with lysolecithin compared with those in the control diet (P < 0.05), while the mRNA expression of interleukin-10 (il-10) was significantly higher than that in the control diet (P < 0.05). In conclusion, dietary lysolecithin could promote the growth performance, improve hepatic lipid metabolism and regulate inflammation response in juvenile large yellow croaker, and the optimal supplement level of lysolecithin was approximately 0.4% in this study. • Dietary lysolecithin could significantly improve growth performance of juvenile large yellow croaker. • Diets supplemented with lysolecithin could enhance lipid metabolism and alleviate fat accumulation in liver. • Lysolecithin could exert beneficial effects on antioxidant capacity and inflammation response to improve health status. [ABSTRACT FROM AUTHOR]

A ten-week culture trial in juvenile large yellow croaker (Larimichthys crocea) (10.80 ± 0.10 g) was conducted to assess the impact of supplementing heat-killed Lactobacillus acidophilus (HLA) on growth performance, intestinal digestive enzyme activity, antioxidant capacity and inflammatory response. Five iso-nitrogenous (42 % crude protein) and iso-lipidic (12 % crude lipid) experimental feeds with different levels of HLA (0.0 %, 0.1 %, 0.2 %, 0.4 %, or 0.8 %) were prepared. They were named FO (control group), HLA0.1, HLA0.2, HLA0.4 and HLA0.8, respectively. The results indicated that HLA addition had no impact on survival (P > 0.05). In this experiment, the final body weight, weight gain rate and specific growth rate showed a quadratic regression trend, initially increasing and subsequently decreasing with the increasing in HLA levels, and attained the peak value at 0.2 % HLA supplemental level (P < 0.05). In contrast to the control group, in terms of digestive ability, amylase, lipase and trypsin exhibited a notable linear and quadratic pattern, demonstrating a substantial increase when 0.1% 0.2 % HLA was added in the diets (P < 0.05). Notably, elevated levels of catalase (CAT) activity, superoxide dismutase (SOD) activity, and total antioxidant capacity (T-AOC) were observed in the liver when adding 0.1%–0.2 % HLA, and the level of malondialdehyde (MDA) was significantly decreased and the liver exhibited a notable upregulation in the mRNA expression levels of nrf2 , cat , sod2 , and sod3 (P < 0.05). Additionally, the mRNA levels of genes associated with tight junctions in the intestines (zo-1 , zo-2 and occludin) exhibited a significant upregulation when 0.2 % HLA was added in the feed (P < 0.05). Furthermore, the levels of mRNA expression for proinflammatory genes in the intestines including tnf-α , il-1β , il-6 and il-8 exhibited a quadratic regression trend, characterized by an initial decline followed by subsequent growth (P < 0.05). Meanwhile, the levels of mRNA expression for genes linked to anti-inflammatory responses in the intestines (including il-10 , tgf-β , and arg 1) exhibited a quadratic regression pattern, initially increasing and subsequently decreasing (P < 0.05). Compare with the control group, the levels of tnf-α , il-1β and il-8 expression were notably downregulated in all HLA addition groups (P < 0.05). When 0.2 % HLA was added, the expression levels of il-10 , tgf-β and arg 1 in the intestinal tract were markedly increased (P < 0.05). Overall, the supplementation of 0.2 % HLA in the feed has been shown to enhance the growth performance. The enhancement was attributed to HLA's capacity to improve antioxidant function, intestinal barrier integrity, and mitigate inflammatory responses. This research offers a scientific foundation for the utilization of HLA in aquaculture. • Growth performance of large yellow croaker was enhanced when heat-killed Lactobacillus acidophilus was added to the diet. • Dietary supplementation with 0.2 % HLA can enhance the antioxidant capacity and liver digestive enzyme activities in large yellow croaker. • Dietary supplementation with 0.2 % HLA can enhance the intestinal barrier and inflammatory response in large yellow croaker. [ABSTRACT FROM AUTHOR]

The high inclusion of soybean oil in fish diets can lead to abnormal lipid deposition in the liver and induce oxidative stress of fish. Therefore, effective nutritional strategies are imperative to alleviate the negative consequences resulting from a high-proportion of soybean oil in fish diets. In the current research, we formulated five diets with equivalent nitrogen levels (46% crude protein) and lipid levels (12% crude lipid), 8% SO as the main lipid source was taken as the control group (SO group). On the basis of the control group, 25, 50, 100 and 200 mg/kg piperine were added as treatment groups (SO, PIP25, PIP50, PIP100 and PIP200). After 10-weeks feeding, the inclusion of PIP with 25, 50, and 200 mg/kg in the diets exhibited significant enhancements in the growth performance in comparison to the control group (P < 0.05). Meanwhile, dietary addition of piperine significantly enhanced the activities of intestinal digestive enzymes (amylase, lipase and trypsin) (P < 0.05). Addition with 50, 100, and 200 mg/kg piperine resulted in a substantial reduction in serum contents of triglycerides, cholesterol, and free fatty acids (P < 0.05), while the addition of 25 mg/kg and 50 mg/kg piperine resulted in a substantial reduction in hepatic triglyceride and cholesterol levels. Meanwhile, there was a noticeably increasing trend in the activities of superoxide dismutase (SOD) and catalase (CAT) (P < 0.05). Furthermore, the inclusion of piperine significantly suppressed the mRNA expression of genes associated with lipogenesis, containing scd1 , fas , srebp1 , acc1 , and pparγ , as well as fatty acid transport (mtp , apob100 , cd36 , fabp3 , and fabp10) compared with the control group (P < 0.05). The mRNA expression of genes associated with lipid catabolism (pgc1α, pparα, lpl, hl and cpt1) in the liver of large yellow croaker exhibited a statistically significant linear and quadratic down-regulation as a reaction to the escalating levels of piperine supplementation (P < 0.05). In the meantime, a statistically significant linear and quadratic pattern (P < 0.05) was observed within the mRNA expression of genes associated with antioxidant activities, comprising gpx, cat, sod1 and sod2. In brief, the results of this research suggest the addition of dietary supplements with 50 mg/kg piperine enhances growth performance and digestive enzyme activity, while reducing abnormal fat deposition and oxidative stress in large yellow croaker fed high soybean oil diets. • The growth performance of large yellow croaker could potentially be enhanced by dietary addition of 25–50 mg/kg piperine. • Dietary addition with an appropriate level of piperine could optimize hepatic lipid metabolism of large yellow croaker. • Dietar piperine to the diets can promote the liver antioxidant capacity and digestive enzyme activity of large yellow croaker. [ABSTRACT FROM AUTHOR]

Low-density lipoprotein (LDL) is the main carrier of cholesterol transport in plasma, which participates in regulating lipid homeostasis. Studies in mammals have shown that high levels of LDL in plasma absorbed by macrophages trigger the formation of lipid-rich foam cells, leading to the development of atherosclerotic plaques. Although lipid-rich atherosclerosis-like lesions have been discovered in the aorta of several fish species, the physiological function of LDL in fish macrophages remains poorly understood. In the present study, LDL was isolated from the plasma of large yellow croaker (Larimichthys crocea), and mass spectrometry analysis identified two truncated forms of apolipoprotein B100 in the LDL protein profile. Transcriptomic analysis of LDL-stimulated macrophages revealed that differentially expressed genes (DEGs) were enriched in various pathways related to lipid metabolism, as confirmed by the fact that LDL increased total cholesterol and cholesteryl esters content. Meanwhile, the gene and protein expression levels of perilipin2 (PLIN2), a DEG enriched in the PPAR signaling pathway, were upregulated in response to LDL stimulation. Importantly, knocking down plin2 significantly attenuates LDL-induced cholesterol accumulation and promotes cholesterol efflux. Furthermore, the transcription factor PPARγ, which is upregulated in response to LDL stimulation, can enhance the promoter activity of plin2. In conclusion, this study suggests that LDL may upregulate plin2 expression through PPARγ, resulting in cholesterol accumulation in fish macrophages. This study will facilitate the investigation of the function of LDL in regulating lipid homeostasis in macrophages and shed light on the evolutionary origin of LDL metabolism in vertebrates. [Display omitted] • Characterization of apolipoprotein composition of LDL during evolution. • LDL significantly affects lipid metabolism homeostasis in fish macrophages. • LDL activates PLIN2 through PPARγ to promote cholesterol accumulation. [ABSTRACT FROM AUTHOR]