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A smartphone-integrated Pt@Cu-HCF nanozyme-based paper sensor for on-site determination of total antioxidant capacity in marine oils.

Total antioxidant capacity (TAC) serves as a key indicator for evaluating the nutritional quality of foods. In this study, we designed a platinum-embedded copper hexacyanoferrate (denoted as Pt@Cu-HCF) nanozyme that exhibits high oxidase-like activity, efficiently catalyzing the oxidation of chromogenic substrates to generate robust colorimetric signals. Antioxidants quench hydroxyl radicals (∙OH) produced during the catalytic process, leading to a concentration-dependent suppression of the color signal. Leveraging this mechanism, a smartphone-integrated, colorimetric paper sensor for on-site TAC quantification was developed, using vitamin E as the calibration standard. The sensor was applied to determine TAC in fish oil, algal oil, and krill oil, demonstrating a linear response range of 9.78-312.5 μM and a limit of detection (LOD) of 6.41 μM. Validation using real-world marine oil samples showed excellent agreement with a commercial assay kit, confirming the reliability and practical applicability of this portable sensor for TAC measurement in complex biological matrices.

Antioxidants

Proteomic responses of the oil palm pest Metisa plana (Psychidae) to farnesyl acetate exposure.

Metisa plana Walker (Lepidoptera: Psychidae) is a major defoliator of oil palm in Malaysia, causing substantial economic losses. Farnesyl acetate (FA), a sesquiterpenoid compound, has been proposed as a potential insecticidal agent against M. plana, yet its molecular impact on larval physiology remains poorly understood. Here, we employed label-free quantitative proteomics, functional enrichment analysis, and targeted transcript assessment to characterize the temporal proteomic response of M. plana larvae at 7 and 14 days after treatment (DAT) with FA. Principal component analysis revealed robust separation between treated and control samples at both time points, indicating sustained treatment-driven proteomic restructuring. Early exposure (7 DAT) elicited a heterogeneous response involving stress-associated proteins, redox enzymes, and cytoskeletal regulators, whereas later exposure (14 DAT) produced a consolidated profile characterized by metabolic reprogramming, downregulation of ribosomal proteins, induction of heat shock proteins, and enrichment of RNA surveillance and mitochondrial pathways. Targeted transcript analysis qualitatively supported proteomic trends for HSP83 and aldehyde dehydrogenase X, although limited amplification precluded quantitative inference. Collectively, these findings demonstrate that FA exposure drives a shift from acute proteomic perturbation toward a maintenance-oriented physiological state, prioritizing proteostasis, energy management, and stress adaptation over growth and development. This integrated molecular perspective provides mechanistic insight into the chronic effects of FA, highlighting its potential to suppress larval performance and informing the development of biorational, physiology-based pest management strategies in non-model insects.

Animals

Long-term petroleum pollution alters soil microbial communities via electron transfer capacity: Evidence from a 35-year chronosequence.

Petroleum pollution poses a serious threat to soil ecosystems, especially in areas surrounding oil wells, where contamination should not be overlooked. Through a 35-year longitudinal study of soils surrounding oil wells, we demonstrate that petroleum hydrocarbons accumulate predominantly in the top 10 cm of soil, reducing the electron acceptor capacity (EAC) by 61.59 % (from 12.68 to 4.87 μmole-/gC) and decreasing the electron transfer capacity (ETC) by 43 %. Structural equation modeling identified ETC as the critical mediator of microbial community shifts, with EAC playing a pivotal role in sustaining redox processes. Notably, hydrocarbon accumulation triggered a microbial succession: The abundance of Actinomycetota (including genera Rhodococcus, Arthrobacter, and Rubrobacter) showed the most significant fluctuations within 2 years, while Pseudomonadota (genera Methylobacter, Thiobacillus, and Pseudomonas), which were dominant in uncontaminated soils, decreased markedly during this period. This transition coincided with peak microbial dysbiosis (microbial dysbiosis index in 2022 reached 31.41 times that of controls). Within two to four years following mild petroleum stress, the bacterial community established a new structural configuration, revealing a crucial window for ecological recovery. The coupling between ETC reduction and microbial succession highlights the pivotal role of electron flux in soil recovery. Our findings establish a mechanistic framework for ETC-targeted restoration strategies to enhance bioremediation in petroleum-contaminated soils.

Soil Microbiology

Integrated miRNA-mRNA profiling reveals candidate regulatory relationships associated with high-fat diet-induced muscle lipid deposition in black seabream (Acanthopagrus schlegelii).

High-fat diets are increasingly used in aquaculture due to their protein-sparing effects; however, the post-transcriptional regulatory mechanisms of fish muscle in response to high-fat diets (HFD) remain unclear. In this study, juvenile black seabream were fed either a normal-fat diet (NFD) or a HFD to investigate the miRNA-mRNA regulatory network associated with diet-induced muscle lipid deposition. Oil Red O staining and biochemical analysis showed that high-fat diet feeding markedly increased lipid droplet accumulation and crude lipid content in muscle, indicating significant induction of muscle lipid deposition. Integrated mRNA and miRNA expression profiling revealed substantial transcriptomic and post-transcriptional responses to high-fat diet challenge. A total of 271 differentially expressed genes were identified, including 120 upregulated and 151 downregulated genes. Through combined target prediction and expression correlation analysis, thirteen candidate inverse miRNA-mRNA relationships were subsequently identified, and RT-qPCR supported the expression patterns of selected miRNAs and mRNAs. These pairs included miR-499-x-dmgdh, miR-499-y-gatm, miR-727-y-ass1, miR-4649-x-foxo4, miR-9129-z-myl7, and several novel miRNA-mediated interactions involving adk, chst11, lypla2, frem2, kcnc4, wars1, bag2, and capn2. Functional analysis suggested that these regulatory pairs were mainly associated with metabolic adaptation, structural remodeling, and cellular stress responses. In particular, gatm, dmgdh, ass1, and adk were associated with energy metabolism-related processes, including pathways previously linked to Ampk regulation, whereas myl7, frem2, and kcnc4 may contribute to muscle structural maintenance and excitability regulation. Overall, this study provides candidate miRNA-mRNA regulatory relationships potentially involved in high-fat diet-induced muscle lipid deposition and adaptive remodeling in black seabream, offering a basis for future functional studies on muscle metabolism and quality regulation in marine fish.

Animals

Tracking microplastic contamination across seasons in a freshwater reservoir: Evidence from surface water, sediments, and fishes.

Microplastics (MPs) are prevalent contaminants in aquatic environments, posing substantial ecological and health risks. These particles migrate within the different layers of aquatic bodies with time and affect the respective biota. Thus, to get an in-depth understanding of the particles, this current study investigated the seasonal distribution, morphological and chemical characteristics, along with potential ecological and human health impacts in the samples including surface water, sediment, and fish from a drinking water supplying reservoir in eastern India. Across three different seasons, pre-monsoon, monsoon, and post-monsoon samples were collected using optimized methods. Results revealed distinct seasonal trends: MP abundance in surface water peaked during the monsoon (mean: 1.15 MPs/L), while sediment showed the highest concentrations in the pre-monsoon (mean: 596 MPs/kg), indicating temporal accumulation dynamics influenced by runoff, hydrodynamics, and sedimentation. Fish gut analysis confirmed ingestion of MPs across five species, with concentrations ranging from 26 to 100 MPs/kg, depending on feeding habits. The most dominant MP type were fragments, followed by fibers, films, and beads. Polymer analysis via µFTIR identified polyethylene, polypropylene, and polyvinyl chloride as prevalent, with hazard assessments (i.e., Polymer Hazard Index (PHI)) indicating medium to very high ecological risks. Heavy metal association was more dominant in the MPs isolated from sediments than the waterborne MPs. Pollution Load Index (PLI) values were > 1 in most seasons, confirming contamination. Health risk analysis suggested potential exposure through both drinking water and fish consumption. This study emphasizes the need for seasonal monitoring, improved waste management, and mitigation strategies to address MP pollution in freshwater ecosystems.

Microplastics

Optimization of a niosomal formulation for Quercetin delivery: Comparative effects on growth performance, antioxidant and immune responses, and disease resistance against Streptococcus iniae in rainbow trout (Oncorhynchus mykiss).

Quercetin (QUR) is a flavonoid with antibacterial and antioxidant properties that has been studied for its effects on fish health and the immune system. Due to the low bioavailability of QUR, the present study was primarily aimed at developing a niosomal formulation of QUR to enhance its bioavailability and therapeutic properties. The performance of niosomal QUR was then compared with that of its free form by evaluating their effects on the growth and immune system of rainbow trout, Oncorhynchus mykiss. For this purpose, an optimal QUR-containing niosome was formulated by testing different proportions of cholesterol, surfactant, and stabilizer, and the niosomes were then added to the fish diet. A QUR-free diet and a diet containing QUR-free niosomes (QFN) were considered control groups. Niosomes prepared at low hydrophilic-lipophilic balance (HLB) values showed higher QUR entrapment efficiency (QUR-EE%) (P&#x202f;<&#x202f;0.01). An increase in the molar ratio of cholesterol to surfactant significantly reduced QUR-EE% (P&#x202f;<&#x202f;0.05). A surfactant/cholesterol/stabilizer ratio of 1:1:0.1 increased QUR-EE% (P&#x202f;<&#x202f;0.05). The particle size of the niosomes was also affected by HLB and the surfactant/cholesterol/stabilizer ratio. Low HLB values resulted in smaller particle sizes (P&#x202f;<&#x202f;0.01). Furthermore, a surfactant/cholesterol/stabilizer ratio of 1:1:0.1 resulted in the smallest niosomal particle size (P&#x202f;<&#x202f;0.05). The presence of diacetyl phosphate as the stabilizer in the formulation improved the niosomal zeta potential to -40.55&#x202f;mV. The optimal niosomal formulation (HLB&#x202f;=&#x202f;6.6; surfactant/cholesterol/stabilizer ratio of 1:1:0.1) remained stable at 2&#x202f;&#xb0;C over 10 days of storage, as the niosomal QUR content and size did not show significant changes during this period (P&#x202f;>&#x202f;0.01). After preparation of the diets containing the optimal niosomal QUR, fish were fed the experimental diets for two months. QUR, in both niosomal and free forms, resulted in better growth performance than the QUR-free diets (P&#x202f;<&#x202f;0.01). There were no significant differences in growth performance between the free and niosomal forms of QUR; however, 500&#x202f;mg/kg QUR showed significantly better growth performance than 250&#x202f;mg/kg QUR (P&#x202f;<&#x202f;0.01). Although both the niosomal and free forms of QUR enhanced immune and antioxidant components in the fish, the effects of the niosomal form were more significant (P&#x202f;<&#x202f;0.01). In addition, QUR in both free and niosomal forms reduced fish mortality after challenge with Streptococcus iniae. In conclusion, the results of this study suggest that the niosomal form of QUR has strong potential for improving the immune system of fish and increasing resistance to S. iniae infection.

Animals

Comparative assessment of post-transport disease susceptibility in Asian seabass (Lates calcarifer): Associations with oxidative stress, immune responses, gut microbiota, and tissue pathology.

Stress is a crucial factor that affects aquaculture systems, particularly during transportation, which often leads to deteriorated fish health and reduced survival rates. This study aimed to investigate the comparative differences in physiological changes, oxidative stress parameters, and immune responses between clinically healthy and diseased Asian seabass (Lates calcarifer) following commercial transportation. The study compared the health status of fish after transportation, categorized into healthy (Healthy) and diseased (Disease) groups. Assessments were conducted on oxidative stress parameters, immune responses, gut microbiota composition, and tissue pathology. The results showed that diseased fish exhibited significantly higher oxidative stress levels (P&#xa0;<&#xa0;0.05), as indicated by an increase in malondialdehyde (MDA) levels and altered antioxidant and redox-related markers, including superoxide dismutase (SOD), nitric oxide (NO), catalase (CAT), glutathione (GSH), glutathione reductase (GR), and glutathione peroxidase (GPx), measured across multiple target tissues (head kidney, gills, liver, intestine, and brain), compared with healthy fish. Furthermore, the expression of immune-related genes was significantly downregulated in diseased fish after transportation, indicating immune suppression. In contrast, healthy fish maintained a more balanced immune response, which may partially mitigate the adverse effects of transport-induced stress. Gut microbiota analysis revealed that diseased fish had a significant reduction in beneficial bacteria such as Cetobacterium somerae and Bacillus spp., accompanied by a significant (P&#xa0;<&#xa0;0.05) increase in opportunistic pathogens including Aeromonas spp., Photobacterium spp., and Vibrio spp. Histopathological examination showed severe damage in the gills, liver, and intestines of diseased fish (P&#xa0;<&#xa0;0.05), while only minor tissue alterations were observed in healthy fish. Overall, the findings indicate that post-transport diseased Asian seabass exhibit marked oxidative stress, impaired antioxidant defense, altered immune responses, gut microbial dysbiosis, and multi-organ tissue damage compared with clinically healthy post-transport fish. These results suggest that deterioration of transport conditions may contribute to post-transport morbidity and disease susceptibility.

Animals

Liver transcriptome analysis revealed multiple immune processes and lipid metabolism pathways involved in the defense response of the turbot (Scophthalmus maximus) against Aeromonas salmonicida.

Aeromonas salmonicida is a significant pathogen causing notable economic losses in Scophthalmus maximus aquaculture. This study utilized Illumina sequencing technology to examine the transcriptional response characteristics of S. maximus liver at 24&#xa0;h following A. salmonicida infection. A total of 2363 differentially expressed genes (DEGs) were identified when compared to the negative control group. The immunity-related Toll-like receptor signaling pathway, NOD-like receptor signaling pathway, as well as metabolism-related PPAR signaling pathway and insulin signaling pathway, were notably enriched. Significant differences exist in the expression of key genes within the PPAR pathway, particularly cd36, acsl4a, ppar&#x3b1;a, and plin2, all of which mediate the interaction between lipid metabolism and the immune response. These results offer valuable insights into the immunometabolic regulatory mechanism of S. maximus response to A. salmonicida infection.

Animals

Pre-transport dietary chitosan improves the physiological robustness of juvenile largemouth bass (Micropterus salmoides) by modulating antioxidant and inflammatory responses.

The acute stress caused by long-distance transport can lead to oxidative damage, immune dysfunction, and health deterioration in fish. This study evaluated dietary chitosan as a pre-transport nutritional strategy for juvenile largemouth bass (Micropterus salmoides). Five experimental diets contained chitosan at 0, 2.5, 5.0, 7.5, or 10.0&#x202f;g/kg, designated as p0, p25, p50, p75, and p100, respectively, for 56&#x202f;d. The effects of dietary chitosan were evaluated using growth performance, feed utilization, digestive function, antioxidant capacity, nonspecific immunity, and resistance to Aeromonas hydrophila infection. Then, fish from the p0 and p50 groups underwent a 12-h transport stress test, with samples collected before, during, and 7&#x202f;d after transport. Dietary chitosan improved most of these parameters. Among the treatment groups, p50 and p75 showed the best overall performance. The dose-response analysis further indicated that the appropriate dietary inclusion range was 5.0-7.5&#x202f;g/kg. Under transport stress, fish in the p50 group exhibited more stable antioxidant enzyme responses and lower lipid peroxidation, as indicated by reduced MDA levels. Consistent with these enzyme responses, antioxidant-related genes remained relatively stable. At the same time, expression patterns related to the Nrf2-Keap1 and NF-&#x3ba;B signaling pathways suggested that 5.0&#x202f;g/kg chitosan alleviated transport-induced oxidative damage and inflammation. Dietary chitosan also attenuated pro-inflammatory gene induction and altered the temporal expression patterns of anti-inflammatory genes. Overall, 5.0-7.5&#x202f;g/kg dietary chitosan is suitable for juvenile largemouth bass, and 5.0&#x202f;g/kg may serve as an effective pre-transport dietary inclusion level.

Animals

Comparative analyses of olfactory receptor repertoires in Schizothorax fish based on the chromosome-level genomes: Implications for regulatory roles of dietary differentiation and ploidy variation.

The olfactory receptor (OR) genes constitute the molecular basis of fish olfaction, mediating survival behaviors and environmental adaptation while coevolving with habitat-driven evolution. Schizothorax, a cyprinid genus endemic to the Qinghai-Tibetan Plateau, exhibits remarkable dietary divergence and ploidy variation in response to plateau environmental changes, which presumably facilitates the adaptive evolution of OR genes. However, the evolutionary patterns of OR genes associated with trophic divergence and ploidy variation in this genus remain unclear. In this study, three species were selected: the herbivorous diploid S. macropogon, the carnivorous diploid S. lantsangensis, and the herbivorous tetraploid S. curvilabiatus. S. macropogon possessed 142 OR genes (92.25% functional), primarily located on chromosomes 14 and 24, with the fewest sequence clusters. Such compact gene repertoire and highly overlapping chromosomal clusters indicated specialization for a herbivorous olfactory niche. S. lantsangensis contained 127 OR genes (93.70% functional), concentrated on chromosomes 4 and 5, with fewer sequence clusters and a scattered distribution, reflecting evolution of OR genes under carnivorous feeding habits. The herbivorous tetraploid S. curvilabiatus exhibited striking features: 316 OR genes (94.30% functional), the most subfamilies, unique &#x3b5; and &#x3ba; OR subfamilies, and species-specific motifs. These characteristics revealed that ploidy, rather than herbivory, dominated OR gene evolution. In conclusion, dietary differentiation and ploidy variation together drove olfactory adaptive evolution in Schizothorax, providing new insights into vertebrate OR gene ecological adaptation.

Animals

Multi-omics analysis reveals stage-associated differences in gut immunity and microbiota between juvenile and adult common carp (Cyprinus carpio).

In vertebrates, the development of intestinal immunity is closely associated with dynamic changes in the gut microbiota. However, stage-associated differences in intestinal immunity and gut microbial communities remain poorly characterized in teleost fish. In this study, transcriptomic analysis combined with 16S rRNA gene sequencing was employed to characterize intestinal immunity and gut microbial communities in juvenile and adult common carp (Cyprinus carpio). Transcriptomic profiling revealed marked developmental differences in intestinal immune function. Juvenile carp exhibited a predominantly innate immune phenotype, characterized by elevated expression of pro-inflammatory cytokines, antimicrobial peptides, and lysozyme-related genes. This immune profile was accompanied by enhanced mucosal barrier function and a relatively pro-inflammatory intestinal environment. In contrast, adult carp displayed increased expression of genes associated with adaptive immunity, suggesting that adult common carp exhibit relatively stronger adaptive immune characteristics than juvenile fish. Gut microbiota analysis demonstrated significant stage-dependent differences in microbial diversity and community composition. Juvenile fish were enriched with bacterial taxa potentially associated with innate immune activation, whereas adult fish harbored distinct microbial communities linked to intestinal homeostasis and barrier maintenance. Furthermore, correlation analyses identified significant associations between specific microbial taxa and innate immune-related gene expression, suggesting a close association between gut microbiota composition and intestinal immune characteristics in juvenile and adult common carp. Collectively, these findings reveal stage-associated differences in intestinal immunity and gut microbial communities between juvenile and adult common carp, thereby providing insights into intestinal immune characteristics at different developmental stages in teleost fish.

Animals

Construction of circRNA-miRNA-mRNA regulatory networks in the intestine of turbot (Scophthalmus maximus) following Vibrio anguillarum infection.

Circular RNAs (circRNAs) play pivotal roles in post-transcriptional regulation by acting as molecular sponges for microRNAs (miRNAs) within the competitive endogenous RNA (ceRNA) network. However, the regulatory mechanisms in teleost immune responses remain poorly understood. In this study, circRNA-miRNA-mRNA networks were investigated in turbot (Scophthalmus maximus) following Vibrio anguillarum infection to elucidate host-pathogen interactions. Through high-throughput sequencing of intestinal tissues, a total of 50 differentially expressed circRNAs (DE-circRNAs) (18 at 2 hpi, 16 at 12 hpi, 16 at 48 hpi), 212 DE-miRNAs (11 at 2 hpi, 70 at 12 hpi, 15 at 48 hpi), and 1774 DE-mRNAs were identified. Functional enrichment analyses (GO/KEGG) revealed significant associations with immune pathways, including the MAPK signaling pathway and gap junction. An integrated circRNA-miRNA-mRNA regulatory network was constructed, highlighting key interactions including novel_circ_0002573/DE-miR-27a-3p/FGB and novel_circ_0002423/novel_347/GNE, which may regulate inflammatory and antibacterial responses. The expression patterns of selected circRNAs, miRNAs and mRNAs were validated using qRT-PCR, confirming the reliability of the sequencing results. Importantly, fibrinogen beta chain (FGB) and CXCR4/CXCL12 signaling were identified as critical immune modulators. These findings provide insights of the ceRNA regulatory networks involved in teleost intestinal immunity and provide potential molecular targets for selective breeding of disease resistance in this species.

Animals

Long-term heat exposure reshapes muscle molecular regulation and enhances thermal tolerance in Clarias fuscus.

Rapid fluctuations in water temperature driven by global warming have become a major abiotic stressor affecting muscle function in teleost fish. This study examined the effects of long-term thermal conditions on heat tolerance in Clarias fuscus. Fish were maintained for 90&#xa0;days at either a normal temperature group (NT, 26&#xa0;&#xb0;C) or a high-temperature group (HT, 34&#xa0;&#xb0;C). Subsequently, muscle histology, and transcriptomic profiles were observed following acute high-temperature exposure (34&#xa0;&#xb0;C) and after temperature recovery (26&#xa0;&#xb0;C). Histological analysis showed that fish from the NT under acute high-temperature stress exhibited severe muscle damage (atrophy, myofilament disruption, and myolysis), whereas fish from the HT displayed markedly reduced lesions. RNA-seq profiling revealed 5769 differentially expressed genes (DEGs) in the NT and 3292 DEGs in the HT following acute temperature challenges. Functional enrichment indicated that, in the HT, modulation of key cell cycle regulators (e.g., ccna, ccnb, cdk1, cdk2) contributed to alleviating muscle damage caused by temperature fluctuations. In the NT, genes associated with ribosome biogenesis (e.g., nop56, riok2, riok1) were up-regulated and then down-regulated during temperature fluctuation, whereas p53 in the cell cycle pathway showed the opposite expression pattern. These findings demonstrate long-term heat exposure reshapes molecular expression and regulatory mechanisms in the muscle of C. fuscus, thereby enhancing thermal tolerance and adaptability, and providing a theoretical basis for breeding heat-resistant, high-quality aquaculture strains.

Animals

Integrative machine learning and transcriptomic analysis reveals molecular mechanisms underlying low survival rate in larval Chinese Bahaba (Bahaba taipingensis).

Chinese Bahaba (Bahaba taipingensis) is a Class I protected marine fish endemic to China. Low larvae survival during artificial breeding severely hinder population recovery. To investigate the molecular mechanism of high mortality in larval fish, this study performed RNA-seq on liver from naturally deceased (ND) and mass-dead (MD) individuals, combined with least absolute shrinkage and selection operator (LASSO) regression and random forest (RF) algorithms to screen for core signature genes. A total of 873 differentially expressed genes (DEGs) were identified, including 112 upregulated and 761 downregulated genes. GO and KEGG enrichment analyses revealed significant enrichment in amino acid metabolism disorders, one&#x2011;carbon folate pool impairment, PPAR signaling abnormalities, ECM-receptor interaction, focal adhesion pathway, indicating widespread metabolic suppression accompanied by extracellular matrix remodeling and signaling disturbances in the livers of MD fish. MAD pre-filtering combined with dual machine learning algorithms yielded 18 robust core signature genes, among which SLC38A4, MMP1, FADD, FKBP5, and APOB were consistently identified as high-frequency core genes by both algorithms. SLC38A4 exhibited the highest importance score in the RF model and was significantly downregulated, making it the primary molecule distinguishing ND from MD phenotypes. ROC curve analysis showed that both models achieved an AUC of 1.000 (95% CI lower bound: 0.610), confirming the precise discriminatory ability of the core genes. GSEA further demonstrated significant enrichment of this core gene set in ND samples. This study provides the first systematic elucidation of the molecular mechanisms underlying liver dysfunction in low survival rate B. taipingensis, characterized by amino acid transport impairment, metabolic reprogramming, and structural remodeling, offering theoretical foundations for health assessment, early mortality risk warning, and artificial breeding conservation of this species.

Animals

Glycerophospholipid remodeling under osmotic stress in grass carp gills.

Salinity fluctuations represent a pervasive environmental challenge for freshwater fishes, yet the cellular and metabolic programs governing early osmoregulatory responses remain understudied. Here, we investigated the time-dependent gill responses of juvenile grass carp (Ctenopharyngodon idella) subjected to an acute, sublethal salinity increase 9 parts per thousand (ppt). Histological and biochemical analyses revealed progressive gill lesions accompanied by elevated lactate dehydrogenase (LDH) activity and lipid peroxidation, indicating rapid tissue injury under osmotic stress. Integrative metabolomic and transcriptomic profiling uncovered pronounced temporal reprogramming, consistently highlighting glycerophospholipid metabolism as a central axis of response. In particular, phosphatidylcholine (PC) species exhibited dynamic remodeling, coupled with transcriptional enrichment of lipid turnover, membrane transport, and innate immune pathways. Network-based integration identified a PC-centered remodeling module characterized by accelerated PC headgroup turnover, disruption of the PLA2-LPCAT2 lyso-PC reacylation cycle, and enhanced ABC transporter-associated lipid and sterol export, reflected by cholesteryl sulfate accumulation and a shifted n-6 polyunsaturated fatty acid-derived oxylipin signature. Functional assays further demonstrated that PC and linoleic acid (LA) supplementation improved cell viability and alleviated oxidative stress and pro-inflammatory signaling in grass carp cells under salinity challenge. Collectively, these findings reveal phospholipid-centered membrane remodeling as an early, integrative mechanism linking osmotic stress to gill injury and immune activation in freshwater fish, providing insights into potential strategies of environmental stress adaptation.

Animals

Fasting-refeeding regimes induce compensatory growth and muscle transcriptomic remodeling in juvenile Qihe gibel carp (Carassius gibelio var. Qihe).

Compensatory growth, an important adaptive response in fish, holds considerable potential for improving feeding efficiency in aquaculture. To identify an optimal fasting-refeeding strategy for juvenile Qihe gibel carp (Carassius gibelio var. Qihe) and to clarify the mechanisms underlying the compensatory growth, we divided two-month-old fish into four groups, namely S0 group (continuous feeding for 28&#xa0;days), S2 group (4&#xa0;cycles of 2-day fasting followed by 5-day refeeding), S4 group (fasting for 4&#xa0;days followed by refeeding for 24&#xa0;days), and S8 group (fasting for 8&#xa0;days followed by refeeding for 20&#xa0;days), then growth performance, muscle tissue morphology, biochemical responses, and muscle transcriptomic profiles under different feeding regimes were investigated. After a 28-day aquaculture experiment, fish in the S4 group exhibited significantly greater body length and weight than those in the S0, S2, and S8 groups, indicating over-compensatory growth. Histological analysis further showed that muscle growth in the S4 group was mainly associated with myofiber hyperplasia. Different feeding regimes also induced distinct changes in hepatic antioxidant and metabolic enzyme activities, as well as intestinal digestive enzyme activities. Transcriptome analysis revealed that the forkhead box O (FoxO) signaling pathway was significantly enriched during compensatory growth. Key genes, including serum/glucocorticoid regulated kinase 1 (sgk1) and insulin receptor substrate 1 (irs1), were predicted to play important roles in this process. Overall, these results indicate that fasting for 4&#xa0;days followed by refeeding for 24&#xa0;days (the S4 regime) is the optimal strategy for inducing compensatory growth in juvenile Qihe gibel carp. This study provides new insights into the morphological, physiological, and molecular basis of compensatory growth and offers a scientific foundation for developing efficient and sustainable feeding strategies for this species.

Animals

Plasticity of hepatic metabolism in Arctic char (Salvelinus alpinus) in response to cyclic hypoxia.

The emergence of cyclic hypoxia puts aquatic organisms' homeostasis under significant strain. Energetic metabolism as well as protein synthesis and folding are particularly altered during hypoxia, while reoxygenation imposes an oxidative challenge. Currently, little is known about how hypoxia-sensitive organisms respond to large oxygen fluctuations. Our previous work on Arctic char revealed that this salmonid, despite being strongly affected by acute hypoxia and reoxygenation (H/R), can successfully reestablish homeostasis, notably through adjustments to hepatic mitochondrial metabolism. However, the mechanisms underlying this acclimation remain poorly understood. We hypothesized that Arctic char remodel their hepatic proteome to optimize energy metabolism, reorganize oxygen-demanding pathways, and maintain cellular homeostasis during repeated H/R cycles. By exposing Arctic char to two or fifteen days of diel cyclic hypoxia, we confirmed this species' limited capacity to respond to acute H/R. Nevertheless, after fifteen cycles, fish adjusted their energetic metabolism through coordinated regulation of carbohydrate and lipid pathways and upregulation of amino acid metabolism. Mitochondrial metabolism was strongly reorganized, particularly at the ubiquinone-Complex III interaction level, alongside adjustments in proline utilization and protein processing. Moreover, protein processing and folding pathways were stimulated in both mitochondria and the endoplasmic reticulum. However, chronic cyclic hypoxia may still promote non-mitochondrial ROS production, DNA replication stress, and impaired immune function. This study highlights how a hypoxia-sensitive fish progressively reorganizes its metabolism and oxygen-demanding pathways to establish a phenotype adapted to chronic cyclic hypoxia, while also revealing the physiological costs associated with this acclimation.

Animals

Uncovering molecular regulatory networks of low-temperature stress response in Trachinotus ovatus via integrated transcriptome and metabolome analyses.

Golden pompano (Trachinotus ovatus) is one of the most economically important marine fish species in China. It is susceptible to low-temperature stress, which significantly challenges its production and supply. Nevertheless, study on the regulatory mechanisms underlying low-temperature stress responses in golden pompano remains limited. Here, we firstly performed a time-series transcriptome analysis to reconstruct dynamic response patterns under low-temperature stress in golden pompano. Transcriptome profiling identified common differentially expressed genes (DEGs), including fos, hlf, and hmgb1, as well as condition-specific DEGs across distinct low-temperature stress groups. Based on cluster analysis, all DEGs were classified into five distinct expression patterns, reflecting diversified regulation of expression in golden pompano during low-temperature stress. Furthermore, condition-specific regulatory modules were explored via weighted gene co-expression network analysis (WGCNA), highlighting that the two module hub genes, serbf2 and lipc, might respond to low-temperature stress by regulating the lipid catabolic process. Subsequently, untargeted metabolomic analysis revealed that glycerophospholipid metabolism was a significantly enriched common pathway, highlighting its crucial role in mediating the response to low-temperature stress. Finally, by integrating transcriptomic and metabolomic analyses, a gene-metabolite interaction network associated with glycerophospholipid metabolism under low-temperature stress was established. These findings underscore the significance of multiple candidate genes and glycerophospholipid metabolism in golden pompano's response to low-temperature stress, thereby laying a solid molecular foundation for the development of low-temperature-tolerant fish strains.

Animals