Effects of dietary supplementation with apple peel powder on the growth, blood and liver parameters, and transcriptome of genetically improved farmed tilapia (GIFT, Oreochromis niloticus)

Effect of Blood Orange (Citrus sinensis L. Osbeck) Peel Waste as a Feed Additive on the Growth Performance, Digestive Enzyme Activity, Antioxidant Capacity, and Immune Response in Juvenile Black Rockfish (Sebastes schlegelii)

This study evaluated bioactive compounds in blood orange (Citrus sinensis (L.) Osbeck) peel (BOP) as dietary additives. An 8-week feeding trial was conducted to investigate the effects of dietary supplementation on the growth performance, body composition, digestive enzyme activity, antioxidant capacity, and immune response of juvenile black rockfish. A total of 1260 juvenile rockfish (1.4 ± 0.01 g) were randomly distributed into seven treatment groups, each with 50 fish per circular tank. The groups were fed seven different diets containing graded levels of 0 (control, BOP0), 1 (BOP1), 2 (BOP2), 3 (BOP3), 5 (BOP5), 7 (BOP7), and 10 (BOP10) g kg-1, respectively. The BOP10 diet significantly enhanced the final weight, weight gain, specific growth rate, protein efficiency ratio, and protein retention in fish. The BOP treatments notably affected the fishes' whole-body crude protein and lipid contents. Plasma total cholesterol levels of fish fed the BOP0 and BOP1 diets were significantly higher than those fed the BOP7 and BOP10 diets. The activities of trypsin and lipase were significantly affected by dietary BOP levels. The antioxidant enzyme activity in the plasma of fish fed the BOP10 diet was significantly higher than those fed the BOP0 diet. The lysozyme activity and levels of immunoglobulin M and G in fish fed the BOP0 diet were significantly lower than those in fish fed the BOP10 diet. In conclusion, dietary supplementation of BOP at 10 g kg-1 improved the growth performance and overall health of juvenile black rockfish.

Regulatory mechanism of Sarmentosin and Quercetin on lipid accumulation in primary hepatocyte of GIFT tilapia (Oreochromis niloticus) with fatty liver

Sarmentosin (SA) and Quercetin (QC) are two active components of Sedum Sarmentosum Bunge, which is a traditional Chinese herbal medicine. This study aimed to investigate the role and regulatory mechanism of SA and QC in fatty liver of Genetic Improvement of Farmed Tilapia (GIFT) tilapia. GIFT tilapia were randomly divided into two groups with three replicates per treatment (30 fish in each replicate): normal diet group (average weight 3.51±0.31 g) and high-fat diet group (average weight 3.44±0.09 g). After 8 weeks feeding trial, growth index, lipid deposition, and biochemical indexes were measured. Lipid deposition, and lipid and inflammation-related gene expression were detected in a primary hepatocyte model of fatty liver of GIFT tilapia treated with SA or QC. Our results showed that high-fat diet caused lipid deposition and peroxidative damage in the liver of GIFT tilapia. The cell counting kit-8 assay results indicated that 10 μM SA and 10 μM of QC both had the least effect on hepatocyte proliferation. Moreover, both 10 μM of SA and 10 μM of QC showed lipolytic effects and inhibited the expression of lipid-related genes (FAS, Leptin, SREBP-1c, and SREBP2) in fatty liver cells. Interestingly, QC induced autophagosome-like subcellular structure and increased the expression of IL-8 in fatty liver cells. In conclusion, this study confirmed that SA and QC improved fatty liver caused by high-fat diet, providing a novel therapeutic approach for fatty liver of GIFT tilapia.

Differences in diacylglycerol acyltransferases expression patterns and regulation cause distinct hepatic triglyceride deposition in fish

Triglyceride (TAG) deposition in the liver is associated with metabolic disorders. In lower vertebrate, the propensity to accumulate hepatic TAG varies widely among fish species. Diacylglycerol acyltransferases (DGAT1 and DGAT2) are major enzymes for TAG synthesis. Here we show that large yellow croaker (Larimichthys crocea) has significantly higher hepatic TAG level than that in rainbow trout (Oncorhynchus mykiss) fed with same diet. Hepatic expression of DGATs genes in croaker is markedly higher compared with trout under physiological condition. Meanwhile, DGAT1 and DGAT2 in both croaker and trout are required for TAG synthesis and lipid droplet formation in vitro. Furthermore, oleic acid treatment increases DGAT1 expression in croaker hepatocytes rather than in trout and has no significant difference in DGAT2 expression in two fish species. Finally, effects of various transcription factors on croaker and trout DGAT1 promoter are studied. We find that DGAT1 is a target gene of the transcription factor CREBH in croaker rather than in trout. Overall, hepatic expression and transcriptional regulation of DGATs display significant species differences between croaker and trout with distinct hepatic triglyceride deposition, which bring new perspectives on the use of fish models for studying hepatic TAG deposition.

High-fat diet disrupts the gut microbiome, leading to inflammation, damage to tight junctions, and apoptosis and necrosis in Nyctereutes procyonoides intestines

Given the burgeoning Nyctereutes procyonoides breeding industry and its growing scale, it is imperative to investigate the impact of high-fat diets on the health of these animals. This study involved 30 male Nyctereutes procyonoides of comparable weights (3 kg ±0.5), randomly assigned to either a control group or a high-fat diet group (n = 15 each). The latter group was fed a mixture of lard and basal diet in a 2:5 ratio, establishing a high-fat diet model in Nyctereutes procyonoides. This diet induced diarrhea and histopathological changes in the Nyctereutes procyonoides. Analysis of the small intestine contents using 16S rRNA sequencing revealed a high-fat diet-induced disruption in the gut microbiota. Specifically, Escherichia-Shigella emerged as the biomarker in the high-fat diet group (P = 0.049), while Vagococcus was prevalent in the control group (P = 0.049), indicating a significant increase in harmful bacteria in the high-fat diet group. Furthermore, this disrupted gut flora correlated with inflammation and oxidative stress, as evidenced by marked increases in TNF-α (P < 0.01), IL-1β (P < 0.05), and IL-6 (P < 0.05) levels, measured via q-PCR, Western blot, and oxidative stress assays. In addition, q-PCR analysis revealed significant upregulation of apoptosis and necrosis markers, including Bax, Caspase3, Caspase9, Caspase12, RIPK3, and RIPK1 (P < 0.01 to P < 0.001), and a concurrent downregulation of the anti-apoptotic gene Bcl-2 (P < 0.01) in the high-fat diet group, consistent with protein expression trends. These findings suggest that a high-fat diet alters the gut microbiome toward a more harmful bacterial composition, escalating inflammatory responses and intestinal tissue permeability, culminating in intestinal cell apoptosis and necrosis.IMPORTANCEThis study examines the impact of high-fat diets on Nyctereutes procyonoides. Our research established a Nyctereutes procyonoides model on a high-fat diet, revealing significant health impacts, such as diarrhea, histological anomalies, and alterations in the gut microbiota. These findings emphasize the importance of preventing health issues and promoting sustainable industry growth. They highlight the significant impact of diet on gut microbiota and overall animal health.

Effects of different combinations of koumine and gelsemine on growth performance, intestinal health, and transcriptome of Cyprinus carpio

Koumine (KM) and gelsemine (GS) have shown significant benefits in livestock production, but their potential in aquaculture remains largely unexplored. This study examined the impact of different KM and GS combinations as feed additives on C. carpio (90 fish per group, initial weight 1.95 ± 0.08 g). KM and GS were introduced in ratios of 2:2 (mg/kg), 2:1 (mg/kg), and 2:0.67 (mg/kg) over a 10-week aquaculture experiment. The results demonstrate that the 2:1 (mg/kg) group increases the villus length, muscular layer thickness, crude protein, and crude fat content. Regarding fatty acid content, KM and GS enhance the levels of various fatty acids, including the total saturated fatty acid and total monounsaturated fatty acid. Additionally, KM and GS improve the composition and function of the intestinal microbiota. The 2:1 (mg/kg) group significantly elevates the enzymatic activities of SOD, MDA, CAT and upregulates the expression of immune-related genes such as toll-like receptor 2, transforming growth factor β, and glutathione S-transferase. Transcriptomic analysis suggests that KM and GS may have potential benefits for nutrient utilization and immune regulation in C. carpio. In summary, this study provides valuable insights into the use of KM and GS as feed additives in aquaculture.

Dietary antarctic krill improves antioxidant capacity, immunity and reduces lipid accumulation, insights from physiological and transcriptomic analysis of Plectropomus leopardus

BACKGROUND

Due to its enormous biomass, Antarctic krill (Euphausia superba) plays a crucial role in the Antarctic Ocean ecosystem. In recent years, Antarctic krill has found extensive application in aquaculture, emerging as a sustainable source of aquafeed with ideal nutritional profiles. However, a comprehensive study focused on the detailed effects of dietary Antarctic krill on aquaculture animals, especially farmed marine fishes, is yet to be demonstrated.

RESULTS

In this study, a comparative experiment was performed using juvenile P. leopardus, fed with diets supplemented with Antarctic krill (the krill group) or without Antarctic krill (the control group). Histological observation revealed that dietary Antarctic krill could reduce lipid accumulation in the liver while the intestine exhibited no obvious changes. Enzyme activity measurements demonstrated that dietary Antarctic krill had an inhibitory effect on oxidative stress in both the intestine and the liver. By comparative transcriptome analysis, a total of 1,597 and 1,161 differentially expressed genes (DEGs) were identified in the intestine and liver, respectively. Functional analysis of the DEGs showed multiple enriched terms significantly related to cholesterol metabolism, antioxidants, and immunity. Furthermore, the expression profiles of representative DEGs, such as dhcr7, apoa4, sc5d, and scarf1, were validated by qRT-PCR and fluorescence in situ hybridization. Finally, a comparative transcriptome analysis was performed to demonstrate the biased effects of dietary Antarctic krill and astaxanthin on the liver of P. leopardus.

CONCLUSIONS

Our study demonstrated that dietary Antarctic krill could reduce lipid accumulation in the liver of P. leopardus, enhance antioxidant capacities in both the intestine and liver, and exhibit molecular-level improvements in lipid metabolism, immunity, and antioxidants. It will contribute to understanding the protective effects of Antarctic krill in P. leopardus and provide insights into aquaculture nutritional strategies.

Apple Peel Supplementation Potential in Metabolic Syndrome Prevention

(1) Introduction: Apples are a source of bioactive substances, e.g., anthocyanidins and flavonols, and dietary fiber. Their highest concentrations are observed in the skin. Metabolic syndrome (MetS) is a set of conditions originally associated with obesity. Excessive adipose tissue accompanying obesity leads to chronic inflammation and metabolic disorders, which result in the development of dyslipidemia, elevated blood pressure, and glucose levels. Thus, supplementation of apple peels, a source of antioxidant substances and fiber, could potentially be a method supporting the prevention of MetS. This paper summarizes the results of available research on the potential impact of apple peel supplementation on the components of MetS. (2) Results: The results from in vitro and animal model studies indicate a positive effect of apple peel supplementation on lipid profile, glucose levels, and blood pressure regulation mediators. Only one human study was performed, and it showed that the consumption of apple peels had an effect on endothelial function but not on other clinical parameters. At the moment, there are no results from observations on large groups of people available. (3) Conclusions: The results of in vitro and animal-model studies indicate the potential of apple peel supplementation in MetS prevention, but it has not been clinically confirmed in human studies. Conducting large human studies could allow a definite clarification of the role of apple peel supplementation in MetS prevention.

Transcriptome and 16S rRNA Analyses Reveal That Hypoxic Stress Affects the Antioxidant Capacity of Largemouth Bass (Micropterus salmoides), Resulting in Intestinal Tissue Damage and Structural Changes in Microflora

Dissolved oxygen (DO) is a key factor affecting the health of aquatic organisms in an intensive aquaculture environment. In this study, largemouth bass (Micropterus salmoides) were subjected to acute hypoxic stress for 96 h (DO: 1.00 mg/L) followed by recovery under sufficient DO conditions (DO: 7.50 mg/L) for 96 h. Serum biochemical indices, intestinal histomorphology, the transcriptome, and intestinal microbiota were compared between hypoxia-treated fish and those in a control group. The results showed that hypoxia caused oxidative stress, exfoliation of the intestinal villus epithelium and villus rupture, and increased cell apoptosis. Transcriptome analyses revealed that antioxidant-, inflammation-, and apoptosis-related pathways were activated, and that the MAPK signaling pathway played an important role under hypoxic stress. In addition, 16S rRNA sequencing analyses revealed that hypoxic stress significantly decreased bacterial richness and identified the dominant phyla (Proteobacteria, Firmicutes) and genera (Mycoplasma, unclassified Enterobacterales, Cetobacterium) involved in the intestinal inflammatory response of largemouth bass. Pearson's correlation analyses showed that differentially expressed genes in the MAPK signaling pathway were significantly correlated with some microflora. The results of this study will help to develop strategies to reduce damage caused by hypoxic stress in aquacultured fish.

Thermal Stress Induces Metabolic Responses in Juvenile Qingtian Paddy Field Carp Cyprinus carpio var qingtianensis

Extreme fluctuations in water temperature lead to significant economic losses for the aquaculture industry. Cyprinus carpio var qingtianensis (locally called Qingtian paddy field carp), is a local variety commonly found in Zhejiang province, China. Unlike traditional aquaculture environments, the water temperature range between day and night in the rice field environment is much larger, and the high temperature in summer may exceed the growth threshold of fish because there is no manual intervention; therefore, the study of how the Qingtian paddy field carp (PF carp) adapts to high-temperature conditions can shed light how the species adapt to the rice field environment. To investigate the molecular mechanisms of this fish under thermal stress, the liver metabolomics of Qiangtian paddy field carp (PF carp) were analyzed. In this study, metabolomics was used to examine the metabolic reaction of PF carp (102 days old, 104.69 ± 3.08 g in weight, 14.65 ± 0.46 cm in length) at water temperatures of 28 °C (control group, CG), 34 °C (experimental group (EG) 34), and 38 °C (EG38). The results show that 175 expression profile metabolites (DEMs), including 115 upregulated and 60 downregulated metabolites, were found in the CG vs. EG34. A total of 354 DEMs were inspected in CG vs. EG38, with 85 metabolites downregulated and 269 metabolites upregulated. According to the pathway enrichment study, various pathways were altered by thermal stress, including those of lipid, amino-acid, and carbohydrate metabolism. Our study presents a potential metabolic profile for PF carp under thermal stress. It also demonstrates how the host responds to thermal stress on a metabolic and molecular level.

Antioxidative and immunostimulant potential of fruit derived biomolecules in aquaculture

Huge amounts of non-edible by-products could be generated from fruit industrial processes. They consist mainly of peels together with low amounts of pulp and seeds. These by-products pose an environmental hazard due to soil, air, and water pollution. Moreover, treating these by-products is very expensive and under strict governmental regulations. Nevertheless, they are an excellent source of bioactive constituents, such as phenols, flavonoids, terpenes, and glucans. Based on their constituents, these by-products can significantly enhance the antioxidant defense, immune response, and modulation of gut microbiota and host resistance against various diseases. Therefore, sustainable valorization of fruits by-products can efficiently obtain value-added products that improve the well-being of organisms and reduce environmental stress, in addition to earning an additional industrial income. Since aquaculture is a vital economic sector, there is urgent to look for inexpensive natural food additives that improve health and maintain high nutritional quality for farming organisms without harming the environment and human health. Therefore, using fruit wastes as feed additives represents a striking alternative for fruitful aquaculture. In order to make use of these value-added products, it is a dire need to determine their biological effects on aquaculture organisms by understanding their mechanism of action. In this context, this review will holistically address a comprehensive focus on utilizing fruits by-products and their immunostimulant and antioxidative action.

Tolerance Assessment of Atractylodes macrocephala Polysaccharide in the Diet of Largemouth Bass (Micropterus salmoides)

Atractylodes macrocephala polysaccharide (AMP) can enhance antioxidant defense and anti-inflammation, as the tolerance levels of AMP in aquaculture is important for additive utilization. However, the tolerance dose of AMP is unknown. We assess the tolerance levels of AMP in juvenile largemouth bass (3.38 ± 0.11 g) by feeding them a 0, 400, 4000, or 8000 mg/kg AMP supplemented diet for 10 weeks. The 400 mg/kg AMP dose increased growth performance. The Nrf2/Keap1 signaling pathway was activated, as indicated by Keap1 and Nrf2 protein levels in the liver. Enhanced activity of antioxidant enzymes (SOD, GPx), together with increased mRNA levels of antioxidant genes (sod, gpx) and decreased accumulation of reactive oxygen species (ROS) and MDA, was found in the liver, implying the antioxidant effect of AMP. Nutrient absorption was enhanced by AMP, as reflected by the increased length of intestinal villi and microvilli. However, 4000 and 8000 mg/kg AMP induced oxidant stress, as indicated by increased plasma ALT and AST content and decreased mRNA levels of antioxidant genes (sod, gpx) in the liver and intestinal tissues. Inflammatory reactions were also induced by high doses of AMP, as reflected by enhanced levels of pro-inflammatory cytokines (tnfα, nfκb) in the liver, intestinal, and kidney tissues and inhibited levels of anti-inflammatory cytokines (tgfβ, iκb). Histological analysis reveals inflammatory cell infiltration and tissue damage. Thus, the safe tolerance margin of AMP supplement for largemouth bass was 400–4000 mg/kg.

Effects of Elephantopus scaber extract on growth, proximate composition, immunity, intestinal microbiota and resistance of the GIFT strain of Nile tilapia Oreochromis niloticus to Streptococcus agalactiae

This study aimed to investigate the effects of Elephantopus scaber extract on the GIFT (genetic improvement of farmed tilapia) strain of Nile tilapia Oreochromis niloticus. A total of 800 tilapia with an initial body weight of 1.34 ± 0.09 g each were randomly divided into five groups. The tilapia in the control group (E0 group) were fed on a basal diet only. Meanwhile, tilapia in the four experimental groups were fed on a basal diet supplemented with 1 g/kg (E1 group), 3 g/kg (E2 group), 5 g/kg (E3 group), and 7 g/kg (E4 group) of E. scaber extract for 10 weeks. Results showed that the survival rate was higher in the experimental groups than in the control group. Compared with the control group, some growth parameters (FW, WGR, SGR, VSI, and HSI) were significantly improved in the E1 group and E2 group. The crude lipid content in the dorsal muscle and liver was lower in the E1 group than in the control group. After E. scaber extract supplementation, activities of immunity-related enzymes (ACP, AKP, T-AOC, SOD, CAT, GSH-Px and LZM) in plasma, liver, spleen and head kidney, and expressions of immunity-related genes (IL-1β, IFN-γ, TNF-α, and CCL-3) in liver, spleen and head kidney showed various degrees of improvement, while MDA content and Hsp70 expression level were decreased. The survival rate of tilapia increased in all the supplementation groups after Streptococcus agalactiae treatment. E. scaber extract addition changed the species composition, abundance, and diversity of intestinal microbiota in tilapia. These results demonstrate that E. scaber extract supplementation in diet can improve the growth, immunity, and disease resistance of GIFT against S. agalactiae. E. scaber extract supplementation can also change intestinal microbiota and reduce crude lipid content in dorsal muscle and liver. The above indicators show that the optimal dose of E. scaber extract for GIFT is 1 g/kg.

Effect of Siberian Ginseng Water Extract as a Dietary Additive on Growth Performance, Blood Biochemical Indexes, Lipid Metabolism, and Expression of PPARs Pathway-Related Genes in Genetically Improved Farmed Tilapia (Oreochromis niloticus)

Overnutrition in high-density aquaculture can negatively affect the health of farmed fish. The Chinese herbal medicine Siberian ginseng (Acanthopanax senticosus, AS) can promote animal growth and immunity, and regulate lipid metabolism. Therefore, we conducted an 8-week experiment, in which Oreochromis niloticus was fed with a diet supplemented with different concentrations of AS water extract (ASW) (0‰, 0.1‰, 0.2‰, 0.4‰, 0.8‰, and 1.6‰). The ASW improved the growth performance and increased the specific growth rate (SGR). Linear regression analysis based on the SGR estimated that the optimal ASW amount was 0.74‰. Dietary supplementation with 0.4–0.8‰ ASW reduced the triglyceride and total cholesterol levels in the serum and liver, and regulated lipid transport by increasing the high-density lipoprotein cholesterol concentration and lowering the low-density lipoprotein cholesterol concentration. Dietary supplementation with ASW increased the activities of superoxide dismutase and catalase in the liver, thereby improving the antioxidant capacity. Moreover, ASW modulated the transcription of genes in the peroxisome proliferator-activated receptor signaling pathway in the liver (upregulation of PPARα, APOA1b, and FABP10a and downregulation of PPARγ), thereby regulating fatty acid synthesis and metabolism and slowing fat deposition. These results showed that 0.4–0.8‰ ASW can slow fat deposition and protected the liver from cell damage and abnormal lipid metabolism.

Dietary inclusion of rambutan (Nephelium lappaceum L.) seed to Nile tilapia (Oreochromis niloticus) reared in biofloc system: Impacts on growth, immunity, and immune-antioxidant gene expression

An eight-week feeding trial was carried out to determine the effects of rambutan seed (RS) as a feed additive on the growth, skin mucus, serum immune parameters, and gene expression of Nile tilapia (Oreochromis niloticus) raised under a biofloc system. Nile tilapia fingerlings (14.77 ± 0.80 g fish^-1) were fed five experimental diets containing 0, 5, 10, 20, and 40 g kg^-1 of RS, corresponding to five treatments (RS0, RS5, RS10, RS20, and RS40) with three replications per treatment. The results showed that fish consuming the RS10 and RS20 diets presented a substantial (P < 0.05) improvement in specific growth rate (SGR), weight gain (WG), and feed conversion ratio (FCR) after eight weeks. The highest values were recorded in the RS10 diet; however, there were no significant (P > 0.05) differences exhibited in the fish survival rates between treatments. The RS supplementation diets demonstrated greater immunological parameters, particularly skin mucus and serum immune responses (P < 0.05), than that of the control after eight the eight-week feeding trial. The highest level was seen in fish fed the RS10; followed by the RS20, RS40 (P > 0.05), and RS5 diets. Regarding gene expressions, IL1, IL8, LBP, GSTa, and GSR genes were significantly up-regulated in fish provided the RS10 diet in comparison to the control and other supplemented diets (P < 0.05). However, no significant up-regulation was found in these genes among the RS0, RS5, RS20, and RS40 diets, with the exception of the GPX gene. Similarly, up-regulation of IL-8, LBP, GSTa, GPX, and GSR were noted in fish fed the RS10 diet (P < 0.05). Notably, no significant differences were evident in these genes among the RS5, RS20, and RS40 diets. In conclusion, fish fed RS10 (10 g kg^-1) significantly enhanced growth, skin mucus, serum immunities, and immune-antioxidants related gene expressions of Nile tilapia raised under biofloc system.

Growth performance, physiological parameters, and transcript levels of lipid metabolism-related genes in hybrid yellow catfish (Tachysurus fulvidraco ♀ × Pseudobagrus vachellii ♂) fed diets containing Siberian ginseng

In high-density aquaculture, fish health can suffer because of excessive feeding, which causes fatty liver disease. Siberian ginseng (Acanthopanax senticosus) has been used as a feed additive to promote animal growth, immunity, and lipid metabolism. In this study, we explored the effects of A. senticosus on the physiology of hybrid yellow catfish (Tachysurus fulvidraco ♀ × Pseudobagrus vachellii ♂). A control group and five groups fed diets containing A. senticosus (0.5, 1, 2, 4, and 8 g A. senticosus/kg feed) were established and maintained for 8 weeks. Dietary supplementation with A. senticosus at 4 g/kg promoted growth of the hybrid yellow catfish. Serum total cholesterol (TC) and triacylglycerol (TG) levels at 2 g/kg A. senticosus (TC: 1.31 mmol/L; TG: 1.08 mmol/L) were significantly lower than in the control group (TC: 1.51 mmol/L; TG: 1.41 mmol/L), and 4 g/kg A. senticosus (17.20 μmol/g tissue) reduced the liver TG level compared with the control group (21.36 μmol/g tissue) (P <0.05). Comparative transcriptomic analysis of liver tissue between the control group and the group showing optimum growth (4 g/kg A. senticosus) revealed 820 differentially expressed genes and 44 significantly enriched pathways, especially lipid metabolism pathways such as unsaturated fatty acid and fatty acid metabolism. The transcript levels of five lipid metabolism-related genes were determined by quantitative real-time PCR. The results showed that 2–4 g/kg A. senticosus supplementation reduced the FADS2, ELOVL2, CYP24a, and PLPP3 transcript levels and 4 g/kg A. senticosus increased the DIO2 transcript level (P <0.05), leading to altered synthesis of TG and thyroxine and reduced fat deposition in the liver. Our results show that dietary A. senticosus affects the regulation of fat metabolism and promotes the growth of hybrid yellow catfish. A. senticosus is a healthy feed additive, and the appropriate dietary supplementation rate is 2–4 g/kg.

Multi-omics analysis reveals the glycolipid metabolism response mechanism in the liver of genetically improved farmed Tilapia (GIFT, Oreochromis niloticus) under hypoxia stress

BACKGROUND

Dissolved oxygen (DO) in the water is a vital abiotic factor in aquatic animal farming. A hypoxic environment affects the growth, metabolism, and immune system of fish. Glycolipid metabolism is a vital energy pathway under acute hypoxic stress, and it plays a significant role in the adaptation of fish to stressful environments. In this study, we used multi-omics integrative analyses to explore the mechanisms of hypoxia adaptation in Genetically Improved Farmed Tilapia (GIFT, Oreochromis niloticus).

RESULTS

The 96 h median lethal hypoxia (96 h-LH50) for GIFT was determined by linear interpolation. We established control (DO: 5.00 mg/L) groups (CG) and hypoxic stress (96 h-LH50: 0.55 mg/L) groups (HG) and extracted liver tissues for high-throughput transcriptome and metabolome sequencing. A total of 581 differentially expressed (DE) genes and 93 DE metabolites were detected between the CG and the HG. Combined analyses of the transcriptome and metabolome revealed that glycolysis/gluconeogenesis and the insulin signaling pathway were down-regulated, the pentose phosphate pathway was activated, and the biosynthesis of unsaturated fatty acids and fatty acid metabolism were up-regulated in GIFT under hypoxia stress.

CONCLUSIONS

The results show that lipid metabolism became the primary pathway in GIFT under acute hypoxia stress. Our findings reveal the changes in metabolites and gene expression that occur under hypoxia stress, and shed light on the regulatory pathways that function under such conditions. Ultimately, this information will be useful to devise strategies to decrease the damage caused by hypoxia stress in farmed fish.

Transcriptome profiling reveal Acanthopanax senticosus improves growth performance, immunity and antioxidant capacity by regulating lipid metabolism in GIFT (Oreochromis niloticus)

Acanthopanax senticosus (APS) is a natural and officinal herb with an impressive range of health benefits for animal. An 8-week feeding trail with different APS levels (0, 0.5, 1, 2, 4, and 8‰) was conducted to evaluate the promotive effects of APS in GIFT. Results indicate that APS improved the growth performance, improved specific growth ratio (SGR) and feed efficiency ratio (FER), the optimum APS supplementation was estimated to 1.97‰ based on the regression analysis of SGR. Meanwhile, 2‰ and 4‰ APS improved the immune and antioxidant capacity in some extent evidenced by the plasma and hepatic biomarkers. With the analysis of transcriptome sequencing, 293 differentially expressed genes (DEGs) were identified, including 106 up-regulated and 187 down-regulated. According to the GO and KEGG enrichments, DEGs were mainly involved in lipid metabolism regulation, followed by amino acid metabolism, carbohydrate metabolism, immunity, and antioxidant response. Transcriptional expression of PPARs signaling and key genes retrieved from transcriptome database confirmed that lipid metabolism was the main active biological process in response to dietary APS administration. These results indicate optimum APS (2‰) could be used as a feed additive that improve the growth performance by regulating lipid metabolism. This may provide insights for Chinese herb additive application in aquaculture production.