Farnesoid X receptor regulates PI3K/AKT/mTOR signaling pathway, lipid metabolism, and immune response in hybrid grouper

Dietary high lipid and high plant-protein affected growth performance, liver health, bile acid metabolism and gut microbiota in groupers

High lipid diets (HLD) and high plant-protein diets (HPD) exhibit potential fishmeal-saving effects but negatively impact liver health and growth performance in fish. We hypothesized that HLD and HPD impair liver health in pearl gentian groupers (Epinephelus fuscoguttatus♂ × Epinephelus lanceolatus♀) through the modulation of intestinal microbiota and bile acid (BA) metabolism. Four diet groups were tested: control diet (CD, 46.21% crude protein, 9.48% crude lipid), HLD (46.37% crude protein, 16.70% crude lipid), HPD (46.50% crude protein, 9.38% crude lipid), and high lipid-high plant-protein diet (HLPD, 46.54% crude protein, 16.67% crude lipid). A total of 300 fish (average body weight = 15.22 ± 0.03 g) were randomly divided into 4 diet treatments (ensuring 3 tanks replicates of each diet treatment, each tank containing 25 fish). After an eight-week feeding period, the HLD and HPD significantly decreased the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and feed intake (FI) in comparison to CD group, with HLPD exacerbating these indicators (P < 0.05). Compared to CD group, the content of total cholesterol (T-CHO) and triglyceride (TG) in liver and serum were significantly increased in HLD group (P < 0.05). Compared to HPD group, the content of T-CHO in liver was significantly decreased, the content of TG in liver and serum were significantly increased in HLPD group (P < 0.05). HLD, HPD, and HLPD impaired liver health by inducing histological damage, inflammation, and oxidative stress. Compared to CD group, the mRNA relative expression of bile salt export pump (bsep) and multidrug resistance protein 3 (mdr3) were significantly increased in HLD group, whereas the mRNA relative expression of sterol-27-hydroxylase (cyp27a1), microsomal epoxide hydrolase (meh), apical sodium-dependent bile acid transporter (asbt), multidrug resistance-associated protein 3 (mrp3), farnesoid X receptor (fxr) and G protein-coupled bile acid receptor 5 (tgr5) were significantly decreased (P < 0.05). Compared to CD group, the mRNA relative expression of mdr3, asbt, mrp3, organic anion transporters 1 (oatp1), meh, fxr and tgr5 were significantly decreased in HPD group (P < 0.05). In summary, HLD affects intestinal microbiota, BA metabolism, and lipid metabolism, leading to lipid deposition and liver damage. HPD regulates gut microbiota, BA metabolism, inflammatory responses, and BA receptor expression, impairing grouper liver health. HLPD synergistically combines the adverse effects of HLD and HPD on grouper liver health.

MiR-210, not let-7, regulates Akt gene expression against Vibrio splendidus infection in the sea cucumber Apostichopus japonicus

The immune regulatory roles of microRNAs (miRNAs) have recently attracted considerable attention. Bioinformatics prediction revealed that both let-7 and miR-210 provide potential binding sites for the Akt (rac-alpha serine/threonine-protein kinase) gene sequence in the sea cucumber Apostichopus japonicus (termed AjAkt). In this study, we first used a dual-luciferase reporter assay and functional validation techniques to verify the interactions between these two miRNAs (let-7 and miR-210) and AjAkt, and then investigated the functions of the validated miRNA/mRNA pair as part of the innate immune response against Vibrio splendidus infection. We found that AjAkt interacts with miR-210 rather than let-7, and miR-210 negatively regulates the expression of AjAkt. From 8 to 48 h after infection with V. splendidus, opposite trends were observed in the expression levels of miR-210 and AjAkt (mRNA and protein) in coelomocytes, suggesting that the miR-210/AjAkt pair is involved in immune regulation during this period after infection. Both AjAkt silencing and miR-210 overexpression enhanced the phagocytic capacity and reduced the infectivity of A. japonicus after pathogen infection, suggesting that the miR-210/AjAkt pair may regulate the innate immune response of A. japonicus by altering phagocytic capacity. The findings of this study enrich our knowledge of the role of miRNA/mRNA pairs in immune regulation in sea cucumbers and provide insights into the molecular mechanisms of the innate immune response in marine echinoderms.

Elucidating the Effects of the Lipids Regulators Fibrates and Statins on the Health Status of Finfish Species: A Review

The most documented fibrates are gemfibrozil, clofibrate and bezafibrate, while for statins, the majority of the published literature focuses on atorvastatin and simvastatin. The present work reviews previously published research concerning the effects of these hypocholesterolaemic pharmaceuticals on fish, with a particular focus on commercially important species, commonly produced by the European aquaculture industry, specifically in recirculated aquaculture systems (RAS). Overall, results suggest that both acute and chronic exposures to lipid-lowering compounds may have adverse effects on fish, disrupting their capacity to excrete exogenous substances, as well as both lipid metabolism and homeostasis, causing severe ontogenetic and endocrinological abnormalities, leading to hampered reproductive success (e.g., gametogenesis, fecundity), and skeletal or muscular malformations, having serious repercussions on fish health and welfare. Nonetheless, the available literature focusing on the effects of statins or fibrates on commonly farmed fish is still limited, and further research is required to understand the implications of this matter on aquaculture production, global food security and, ultimately, human health.