Taurine modulates hepatic oxidative status and gut inflammatory markers of European seabass (Dicentrarchus labrax) fed plant feedstuffs-based diets

Unlocking the potential of N-acetylcysteine: Improving hepatopancreas inflammation, antioxidant capacity and health in common carp (Cyprinus carpio) via the MAPK/NF-κB/Nrf2 signalling pathway

N-acetylcysteine (NAC) positively contributes to enhancing animal health, regulating inflammation and reducing stress by participating in the synthesis of cysteine, glutathione, and taurine in the body. The present study aims to investigate the effects of dietary different levels of NAC on the morphology, function and physiological state of hepatopancreas in juvenile common carp (Cyprinus carpio). 450 common carps were randomly divided into 5 groups: N1 (basal diet), N2 (1.5 g/kg NAC diet), N3 (3.0 g/kg NAC diet), N4 (4.5 g/kg NAC diet) and N5 (6.0 g/kg NAC diet), and fed for 8 weeks. The results indicated that dietary 3.0-6.0 g/kg NAC reduced hepatopancreas lipid vacuoles and nuclear translocation, and inhibited apoptosis in common carp. Simultaneously, the activities of hepatopancreas alanine aminotransferase and aspartate aminotransferase progressively increased with rising dietary NAC levels. Dietary NAC enhanced the non-specific immune function of common carp, and exerted anti-inflammatory effects by inhibiting the MAPK/NF-κB signaling pathway. Additionally, dietary 3.0-6.0 g/kg NAC significantly improved the antioxidant capacity of common carp, which was associated with enhanced glutathione metabolism, clearance of ROS and the activation of Nrf2 signaling pathway. In summary, NAC has the potential to alleviate inflammation, mitigate oxidative stress and inhibit apoptosis via the MAPK/NF-κB/Nrf2 signaling pathway, thereby improving hepatopancreas function and health of common carp. The current findings provide a theoretical basis for promoting the application of NAC in aquaculture and ecological cultivation of aquatic animals.

Taurine Supplementation to Plant-Based Diets Improves Lipid Metabolism in Senegalese Sole

Taurine is a sulphur-containing amino acid with important physiological roles and a key compound for the synthesis of bile salts, which are essential for the emulsion and absorption of dietary lipids. This study aimed to evaluate the effects of taurine supplementation to low-fishmeal diets on the metabolism of taurine, bile acids, and lipids of Senegalese sole. A fishmeal (FM) and a plant-protein-based (PP0) diet were formulated, and the latter was supplemented with taurine at 0.5 and 1.5% (diets PP0.5 and PP1.5). Diets were assigned to triplicate tanks containing 35 fish (initial weight ~14 g) for 6 weeks. Fish from the PP0 treatment presented lower taurine and bile-acid concentrations compared with the FM treatment, and a downregulation of cyp7a1 and abcb11 was observed. Triolein catabolism decreased in PP0-fed fish, resulting in increased hepatic fat content and plasma triglycerides, while no effects on plasma cholesterol were observed. Taurine supplementation to plant-based diets resulted in a higher taurine accumulation in fish tissues, increased bile-acid concentration, and upregulation of cyp7a1 and abcb11. Hepatic fat content and plasma triglycerides decreased with increasing dietary taurine supplementation. Taurine supplementation mitigated part of the negative effects of plant-based diets, leading to better lipid utilisation.

Taurine metabolism is modulated in Vibrio-infected Penaeus vannamei to shape shrimp antibacterial response and survival

BACKGROUND

Numerous microorganisms are found in aquaculture ponds, including several pathogenic bacteria. Infection of cultured animals by these pathogens results in diseases and metabolic dysregulation. However, changes in the metabolic profiles that occur at different infection stages in the same ponds and how these metabolic changes can be modulated by exogenous metabolites in Penaeus vannamei remain unknown.

RESULTS

Here, we collected gastrointestinal tract (GIT) samples from healthy, diseased, and moribund P. vannamei in the same aquaculture pond for histological, metabolic, and transcriptome profiling. We found that diseased and moribund shrimp with empty GITs and atrophied hepatopancreas were mainly infected with Vibrio parahaemolyticus and Vibrio harveyi. Although significant dysregulation of crucial metabolites and their enzymes were observed in diseased and moribund shrimps, diseased shrimp expressed high levels of taurine and taurine metabolism-related enzymes, while moribund shrimp expressed high levels of hypoxanthine and related metabolism enzymes. Moreover, a strong negative correlation was observed between taurine levels and the relative abundance of V. parahaemolyticus and V. harveyi. Besides, exogenous taurine enhanced shrimp survival against V. parahaemolyticus challenge by increasing the expression of key taurine metabolism enzymes, mainly, cysteine dioxygenase (CDO) and cysteine sulfinic acid decarboxylase (CSD).

CONCLUSIONS

Our study revealed that taurine metabolism could be modulated by exogenous supplementation to improve crustacean immune response against pathogenic microbes. Video Abstract.

Effects of exogenous taurine supplementation on the growth, antioxidant capacity, intestine immunity, and resistance against Streptococcus agalactiae in juvenile golden pompano (Trachinotus ovatus) fed with a low-fishmeal diet

Taurine has various biological functions in fish, playing an essential role in growth, resistance to oxidative stress, and intestine immunity. Here, we evaluated the effects of exogenous taurine added to low-fishmeal diets on the growth, anti-oxidative stress, intestine immunity, and Streptococcus agalactiae resistance in juvenile golden pompano (Trachinotus ovatus). Our study showed that exogenous taurine supplementation of 1.2% (T3 group) greatly enhanced the weight gain rate and specific growth rate (SGR) of juvenile golden pompano, significantly upregulating growth-related factor expression in the brain and liver, as well as the levels of growth-related parameters in the serum. Polynomial regression analysis using SGR estimated the optimal dietary taurine level for golden pompano at 1.18%. Moderate exogenous taurine also increased the muscular thickness and villus length within the intestine, maintained intestinal physical barrier stability, activated the Nrf2/Keap-1/HO-1 signaling pathway, increased intestinal antioxidant enzyme gene expression and antioxidant enzyme activity in the serum, and upregulated immunoglobulin and complement levels in parallel with declining reactive oxygen species (ROS) levels in the serum. Antioxidant factor expression was also upregulated in the intestine. Furthermore, supplementation suppressed NF-κB signaling and intestinal pro-inflammatory cytokine gene expression, increased anti-inflammatory cytokine gene expression, and improved intestine immunity. Finally, taurine supplementation improved the survival rate of golden pompano challenged with S. agalactiae. Overall, our findings provide additional information and support for the rational use of taurine in healthy aquatic animal farming.

Taurine can improve intestinal function and integrity in juvenile Rhynchocypris lagowskii Dybowski fed high-dose glycinin

The present study evaluated the protective effect and the regulatory mechanism of taurine on growth inhibition and intestinal damage induced by glycinin in juvenile Rhynchocypris lagowskii Dybowski. The control diets had no glycinin and taurine, the glycinin diets contained only 80 g/kg glycinin, and the glycinin + taurine diets contained 80 g/kg glycinin+10 g/kg taurine. Juvenile Rhynchocypris lagowskii Dybowski (4.65 ± 0.03 g/tail) were respectively fed with these 3 diets for 8 weeks. The results showed that glycinin significantly decreased the final body weight, weight gain rate, specific growth rate, protein efficiency rate, feed efficiency rate and feeding rate of fish compared with the control group (P < 0.05). While taurine supplementation improved the growth performance and feed efficiency, but final body weight, weight gain rate, specific growth rate of the glycinin + taurine group were still significantly lower than the control group (P < 0.05). Compared with the glycinin group, taurine supplementation significantly increased whole-body and muscle crude protein content, and hepatopancreas and intestinal protease activities (P < 0.05). Distal intestinal villous dysplasia and mucosal damage, and increased intestinal mucosal permeability were observed in the glycinin group, while taurine supplementation alleviated these adverse effects. Usefully, taurine supplementation could also partially restore the impaired immune function and antioxidant capacity of fish fed glycinin diets. Compared with the glycinin group, taurine supplementation down-regulated pro-inflammatory cytokines TNF-α and IL-1β mRNA levels, and up-regulated anti-inflammatory cytokines IL-10 and TGF-β mRNA levels. Furthermore, taurine partially reversed the reduction of antioxidant genes Nrf2、HO-1, CAT and GPx mRNA levels in distal intestine induced by glycinin. Concluded, 80 g/kg glycinin led to intestinal damage, digestive dysfunction and increased intestinal mucosal permeability in juvenile Rhynchocypris lagowskii Dybowski, and these adverse effects were ultimately manifested in growth inhibition. But taurine supplementation could partially mitigate the negative effects induced by glycinin.

Adequate levels of dietary sulphur amino acids impart improved liver and gut health in juvenile yellowtail kingfish (Seriola lalandi)

The sulphur amino acids methionine (Met) and cysteine (Cys) and their derivative taurine (Tau) are metabolically active molecules with interlinked roles in nutritional requirements. Deficiencies in these nutrients are linked to poor growth and health; however, the impacts of these deficiencies on organ structure and function are largely unknown. This study examined the effects of dietary Met, Cys and Tau fed at different levels on yellowtail kingfish (YTK) liver histology and surface colour, plasma biochemistry and posterior intestine histology. Samples were collected from two dose-response feeding trials that quantified (1) the Tau requirement and sparing effect of Met by feeding YTK diets containing one of seven levels of Tau at one of two levels of Met and (2) the Met requirement and sparing effect of Cys by feeding YTK diets containing one of five levels of Met at one of two levels of Cys. YTK fed inadequate levels of dietary Met, Cys and Tau exhibited thicker bile ducts, less red livers, more intestinal acidic goblet cell mucus and supranuclear vacuoles and less posterior intestinal absorptive surface area. Further, thicker bile ducts correlated with less red livers (a*, R), whereas increased hepatic fat correlated with a liver yellowing (b*). Our results indicate a shift towards histological properties and functions indicative of improved intrahepatic biliary condition, posterior intestinal nutrient absorption and homoeostasis of YTK fed adequate amounts of Met, Cys and Tau. These findings may assist in formulating aquafeed for optimised gastrointestinal and liver functions and maintaining good health in YTK.

Metabolic and nutritional responses of Nile tilapia juveniles to dietary methionine sources

Commercial diets for tilapia juveniles contain high levels of plant protein sources. Soybean meal has been utilised due to its high protein content; however, soy-based diets are limited in methionine (Met) and require its supplementation to fulfil fish requirements. dl-Methinone (dl-Met) and Ca bis-methionine hydroxyl analogue (MHA-Ca) are synthetic Met sources supplemented in aquafeeds, which may differ in biological efficiency due to structural differences. The present study evaluated the effect of both methionine sources on metabolism and growth of Nile tilapia. A growth trial was performed using three isonitrogenous and isoenergetic diets, containing plant ingredients as protein sources: DLM and MHA diets were supplemented on equimolar levels of Met, while REF diet was not supplemented. Hepatic free Met and one-carbon metabolites were determined in fish fed for 57 d. Metabolism of dl-Met and MHA was analysed by an in vivo time-course trial using ¹⁴C-labelled tracers. Only dl-Met supplementation significantly increased final body weight and improved feed conversion and protein efficiency ratios compared with the REF diet. Our findings indicate that Met in DLM fed fish follows the transsulphuration pathway, while in fish fed MHA and REF diets it is remethylated. The in vivo trial revealed that ¹⁴C-dl-Met is absorbed faster and more retained than ¹⁴C-MHA, resulting in a greater availability of free Met in the tissues when fish is fed with DLM diet. Our study indicates that dietary dl-Met supplementation improves growth performance and N retention, and that Met absorption and utilisation are influenced by the dietary source in tilapia juveniles.

Dietary taurine modulates hepatic oxidative status, ER stress and inflammation in juvenile turbot (Scophthalmus maximus L.) fed high carbohydrate diets

This study was conducted to explore the beneficial role of taurine against chronic high carbohydrate diet-induced oxidative stress, endoplasmic reticulum (ER) stress and inflammation, and to understand the underlying molecular mechanisms in turbot. Two 10-week feeding trials were simultaneously conducted. For the one, six experimental diets with graded levels of taurine supplementation (0, 0.4%, 0.8%, 1.2%, 1.6% and, 2.0%, respectively) and 15% of carbohydrate were used. For the other one, three graded levels of dietary taurine supplementation (0.4%, 1.2% and 2.0%, respectively) with 21% of carbohydrate were used. The results showed that higher expression level of inflammation cytokines and ER stress related genes were detected in higher dietary carbohydrate group. In both feeding trials, 1.2% of dietary taurine supplementation improved anti-oxidative status by decreasing the content of malondialdehyde, increasing the catalase activity and total anti-oxidative capacities. In feeding trial 1, appropriate taurine supplementation lowered contents of tumour necrosis factor-a, interleukin-6, aspartate aminotransferase and alkaline phosphatase in plasma, and decreased the expressions of pro-inflammatory cytokines, such as interleukin-8 (il-8) and interferon-γ (ifn-γ). Furthermore, dietary taurine reduced ER stress by decreasing the mRNA levels of activating transcription factor 6, protein kinase R-like endoplasmic reticulum kinase and G protein-coupled receptor 78. The optimal dietary taurine content was estimated as 1.40% based on the analysis of specific growth rate. In feeding trial 2, dietary taurine supplementation attenuated liver inflammation partly referring to significantly down-regulated mRNA levels of nuclear transcription factor-κB p65, ifn-γ, interleukin1β and up-regulate the transcript of ribosomal protein S6 kinase 1. Dietary taurine supplementation in feeding trial 2 significantly increased the Nrf2-related factor 2 protein level and decreased the NFκB p65 protein level only at 21% of dietary carbohydrate level. Taurine can alleviate the oxidative damage and inflammation caused by 21% of dietary carbohydrate to a certain degree. Overall, the present study confirmed that dietary taurine supplementation improved growth performance and anti-oxidative response, and reduced liver inflammatory and ER stress processes induced by high dietary carbohydrate in turbot.

Dietary taurine incorporation to high plant protein-based diets improved growth, biochemical, immunity, and antioxidants biomarkers of African catfish, Clarias gariepinus (B.)

Plant protein (PP) sources are generally used in high levels in fish diets. Mostly, PP sources are deficient in taurine; hence, there is a need for its supplementation to fish fed high PP diets. Therefore, effects of dietary taurine were examined on growth performance, feed utilization, immunity, and antioxidant parameters of African catfish, Clarias gariepinus (B.). Fish (10.3 ± 0.4 g) were fed on diets (40% crude protein) containing different taurine levels of 0 (control), 10, 20, 30, or 40 g/kg diet for 12 weeks. Fish fed a taurine-free diet (the control) with high PP sources showed poor growth as compared with these fed taurine-enriched diets where taurine stimulatory effects were observed on fish growth and feed intake. Feed conversion ratio and fish survival rate were not significantly differed among different treatments. Fish fed taurine-enriched diets showed also higher levels of serum glucose, cholesterol, total protein, albumin, globulin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, urea, and creatinine over that fed the control diet. Furthermore, lysozyme and respiratory burst activities as well as superoxide dismutase and catalase activities were significantly elevated in fish fed taurine-enriched diets (P < 0.05) and their highest levels were observed in fish fed 30 g/kg diet. Additionally, taurine deposition in fish muscles was positively correlated with dietary taurine levels (P < 0.05). The present study concludes that taurine is a limiting factor for growth, immunity, and antioxidants responses of African catfish fed high PP-based diets and it should be incorporated in its diets with an optimum level of 20 g/kg diet.

High taurine supplementation in plant protein-based diets improves growth and organoleptic characteristics of European seabass (Dicentrarchus labrax)

Plant-based proteins are increasingly being used in aquafeeds, but one of the limitations is taurine deficiency that can be especially detrimental for carnivorous fish. In this study, taurine supplementation in high plant protein diets (low fish meal, 15%) was investigated on the growth performance and fillet organoleptic characteristics of European seabass (Dicentrarchus labrax), juveniles (78 ± 0.4 g). Five diets were formulated to contain 0 (C−), 5 (T5), 10 (T10) or 20 (T20) added taurine (g/kg), while a control diet (C+) included two-fold higher amount of fishmeal (30%) with no taurine supplementation. Seabass fed the T20 or C+ diet showed similar growth, which was significantly higher compared to those in the C-treatment. Histological examination of the muscle, liver and intestine were similar among treatments. No effect on spoilage bacterial growth or production of total volatile basic nitrogen was observed. Taurine supplementation significantly reduced fillet drip loss, while the fillets of European seabass fed the T10 and T20 diets showed significant higher and lower hardness and adhesiveness values, respectively. Moreover, fillet chewiness was also found to be significantly higher in fish fed the T20 diet compared to C+ and C− diets. Overall, it seems that high dietary taurine supplementation acted as a growth promoter and concurrently improved significantly the postharvest quality characteristics of seabass, which may be attributed to its role in maintaining cell membrane integrity and permeability.