High-intensity ultrasound treatment of Atlantic cod: Impact on nutrients, structure, sensory quality, bioactivity, and in-vitro digestibility.

This study evaluates the impact of high-intensity ultrasound (HIU) on the physicochemical properties and in-vitro digestibility of Atlantic cod (Gadus morhua). Various ultrasound durations (0-60 min) were applied to assess changes in color attributes, total antioxidant capacity (TAC), total flavonoid content (TFC), total phenolic content (TPC), total protein content, and in-vitro protein digestibility (IVPD). Results indicated HIU maximumly increased TAC, TFC, TPC, and peptide content before digestion by 7.28 % (US60), 3.00 % (US30), 32.43 % (US10), and 18.93 % (US60), respectively. While HIU reduced total protein content, it enhanced IVPD by up to 12.24 % (US30). Color attributes electron microscopy reflected structural changes in the cod samples, suggesting the effectiveness of HIU in altering protein structures. These findings highlight HIU's potential as a non-thermal technique for improving the sensory and nutritional quality of Atlantic cod, offering valuable insights for the seafood processing industry and consumers.

Varying temporal trends in the levels of six groups of legacy persistent organic pollutants (POPs) in liver of three gadoid species from the North Sea.

From 2005 to 2019, three gadoid species, Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and saithe (Pollachius virens), were sampled approximately every third year in the northeastern part of the North Sea. Liver samples were analyzed to investigate levels and temporal trends of six groups of persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and its degradation products, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), trans-nonachlor (TNC), and polybrominated diphenyl ethers (PBDEs). Some of the highest average concentrations were found in cod, the levels otherwise being similar between the three species and mostly below established threshold values. The levels of all the contaminants except HCB and TNC were higher than previously reported for cod and haddock in the Barents Sea. Significantly decreasing levels were found for Σ7PCBs, ΣDDTs, ΣHCHs and Σ15PBDEs in all three species, and for TNC in haddock and saithe, while there was no significant trend for TNC in cod. HCB levels increased significantly in cod and haddock and showed only a minor decrease in saithe. The observed time trends of legacy POPs demonstrate the persistence of some of the studied pollutants despite efforts to eliminate them from the marine environment.

Diverse Transcriptome Responses to Salinity Change in Atlantic Cod Subpopulations.

Adaptation to environmental variation caused by global climate change is a significant aspect of fisheries management and ecology. A reduction in ocean salinity is visible in near-shore areas, especially in the Baltic Sea, where it is affecting the Atlantic cod population. Cod is one of the most significant teleost species, with high ecological and economical value worldwide. The population of cod in the Baltic Sea has been traditionally divided into two subpopulations (western and eastern) existing in higher- and lower-salinity waters, respectively. In recent decades, both Baltic cod subpopulations have declined massively. One of the reasons for the poor condition of cod in the Baltic Sea is environmental factors, including salinity. Thus, in this study, an oligonucleotide microarray was applied to explore differences between Baltic cod subpopulations in response to salinity fluctuations. For this purpose, an exposure experiment was conducted consisting of salinity elevation and reduction, and gene expression was measured in gill tissue. We found 400 differentially expressed genes (DEGs) involved in the immune response, metabolism, programmed cell death, cytoskeleton, and extracellular matrix that showed a subpopulation-dependent pattern. These findings indicate that osmoregulation in Baltic cod is a complex process, and that western and eastern Baltic cod subpopulations respond differently to salinity changes.

Environmentally realistic concentrations of chlorinated, brominated, and fluorinated persistent organic pollutants induce the unfolded protein response as a shared stress pathway in the liver of Atlantic cod (Gadus morhua).

In the North Sea and North Atlantic coastal areas, fish experience relatively high background levels of persistent organic pollutants. This study aimed to compare the mode of action of environmentally relevant concentrations of mixtures of halogenated compounds in Atlantic cod. Juvenile male cod with mean weight of 840 g were exposed by gavage to dietary mixtures of chlorinated (PCBs, DDT analogs, chlordane, lindane, and toxaphene), brominated (PBDEs), and fluorinated (PFOS) compounds for 4 weeks. One group received a combined mixture of all three compound groups. The results showed that the accumulated levels of chemicals in cod liver after 4 weeks of exposure reflected concentrations found in wild fish in this region. Pathway analysis revealed that the treatment effects by each of the three groups of chemicals (chlorinated, brominated, and fluorinated) converged on activation of the unfolded protein response (UPR). Upstream regulator analysis predicted that almost all the key transcription factors (XBP1, ERN1, ATF4, EIF2AK3, and NFE2L2) regulating the UPR were significantly activated. No additive effect was observed in cod co-treated with all three compound groups. In conclusion, the genome-wide transcriptomic study suggests that the UPR pathway is a sensitive common target of halogenated organic environmental pollutants in fish.

Connecting gut microbiome changes with fish health conditions in juvenile Atlantic cod (Gadus morhua) exposed to dispersed crude oil.

Polycyclic aromatic hydrocarbons found in crude oil can impair fish health following sublethal exposure. However, the dysbiosis of microbial communities within the fish host and influence it has on the toxic response of fish following exposure has been less characterized, particularly in marine species. To better understand the effect of dispersed crude oil (DCO) on juvenile Atlantic cod (Gadus morhua) microbiota composition and potential targets of exposure within the gut, fish were exposed to 0.05 ppm DCO for 1, 3, 7, or 28 days and 16 S metagenomic and metatranscriptomic sequencing on the gut and RNA sequencing on intestinal content were conducted. In addition to assessing species composition, richness, and diversity from microbial gut community analysis and transcriptomic profiling, the functional capacity of the microbiome was determined. Mycoplasma and Aliivibrio were the two most abundant genera after DCO exposure and Photobacterium the most abundant genus in controls, after 28 days. Metagenomic profiles were only significantly different between treatments after a 28-day exposure. The top identified pathways were involved in energy and the biosynthesis of carbohydrates, fatty acids, amino acids, and cellular structure. Biological processes following fish transcriptomic profiling shared common pathways with microbial functional annotations such as energy, translation, amide biosynthetic process, and proteolysis. There were 58 differently expressed genes determined from metatranscriptomic profiling after 7 days of exposure. Predicted pathways that were altered included those involved in translation, signal transduction, and Wnt signaling. EIF2 signaling was consistently dysregulated following exposure to DCO, regardless of exposure duration, with impairments in IL-22 signaling and spermine and spermidine biosynthesis in fish after 28 days. Data were consistent with predictions of a potentially reduced immune response related to gastrointestinal disease. Herein, transcriptomic-level responses helped explain the relevance of differences in gut microbial communities in fish following DCO exposure.

Intergenerational effects of early life-stage temperature modulation on gene expression and DNA methylation in Atlantic cod (Gadus morhua).

After suffering several collapses, the cod farming industry is now in the process of trying to re-establish itself. We have used material from Norway's National Cod Breeding Program to study how different early life-stage temperature regimes affect DNA methylation and gene expression. Long-term effects were detected by sampling fish several weeks after the end of differential treatments, and offspring from the different exposure groups was also sampled. Many overlapping genes were found between the different exposure groups and generations, coupled with genes associated with differential CpG methylation levels. Genes involved in muscle fibre development, general metabolic processes and formation of deformities were significantly affected, and genes relevant for intergenerational transfer of epigenetic marks were also detected. We believe the use of environmental cues can be a useful strategy for improving the production of Atlantic cod.

Long-Term Influence of PCB- and PBDE-Spiked Microplastic Spheres Fed through Rotifers to Atlantic Cod (Gadus morhua) Larvae.

Omnipresent microplastics (MPs) in marine ecosystems are ingested at all trophic levels and may be a vector for the transfer of persistent organic pollutants (POPs) through the food web. We fed rotifers polyethylene MPs (1-4 µm) spiked with seven congeners of polychlorinated biphenyls (PCBs) and two congeners of polybrominated diphenyl ethers (PBDEs). In turn, these rotifers were fed to cod larvae from 2-30 days post-hatching (dph), while the control groups were fed rotifers without MPs. After 30 dph, all the groups were fed the same feed without MPs. Whole-body larvae were sampled at 30 and 60 dph, and four months later the skin of 10 g juveniles was sampled. The PCBs and PBDEs concentrations were significantly higher in MP larvae compared to the control larvae at 30 dph, but the significance dissipated at 60 dph. Expression of stress-related genes in cod larvae at 30 and 60 dph showed inconclusive minor random effects. The skin of MP juveniles showed disrupted epithelial integrity, fewer club cells and downregulation of a suite of genes involved in immunity, metabolism and the development of skin. Our study showed that POPs were transferred through the food web and accumulated in the larvae, but that the level of pollutants decreased once the exposure was ceased, possibly related to growth dilution. Considering the transcriptomic and histological findings, POPs spiked to MPs and/or MPs themselves may have long-term effects in the skin barrier defense system, immune response and epithelium integrity, which may potentially reduce the robustness and overall fitness of the fish.

Influence of Fermentation by Lactobacillus helveticus on the Immunoreactivity of Atlantic Cod Allergens.

Fermentation techniques may induce alterations in fish allergen immunoreactivity. In this study, the influence of fermentation with three different strains of Lactobacillus helveticus (Lh187926, Lh191404, and Lh187926) on the immunoreactivity of Atlantic cod allergens was investigated via several methods. Gradually reduced protein composition and band intensity due to the fermentation by strain Lh191404 were found in SDS-PAGE analysis, and decreased immunoreactivity of fish allergens was confirmed by Western blotting and ELISA analysis due to the fermentation of strain Lh191404. Additionally, results from nLC-MS/MS and immunoinformatics tools analysis demonstrated that the protein polypeptide and allergen composition of Atlantic cod showed evident alterations after fermentation, with the epitopes of the main fish allergens being heavily exposed and destroyed. These results indicated that the fermentation of L. helveticus Lh191404 could destroy the structure and linear epitopes of the allergens from Atlantic cod and may have considerable potential in mitigating the allergenicity of fish.

Potential of Atlantic Codfish (Gadus morhua) Skin Collagen for Skincare Biomaterials.

Collagen is the major structural protein in extracellular matrix present in connective tissues, including skin, being considered a promising material for skin regeneration. Marine organisms have been attracting interest amongst the industry as an alternative collagen source. In the present work, Atlantic codfish skin collagen was analyzed, to evaluate its potential for skincare. The collagen was extracted from two different skin batches (food industry by-product) using acetic acid (ASColl), confirming the method reproducibility since no significant yield differences were observed. The extracts characterization confirmed a profile compatible with type I collagen, without significant differences between batches or with bovine skin collagen (a reference material in biomedicine). Thermal analyses suggested ASColl's native structure loss at 25 °C, and an inferior thermal stability to bovine skin collagen. No cytotoxicity was found for ASColl up to 10 mg/mL in keratinocytes (HaCaT cells). ASColl was used to develop membranes, which revealed smooth surfaces without significative morphological or biodegradability differences between batches. Their water absorption capacity and water contact angle indicated a hydrophilic feature. The metabolic activity and proliferation of HaCaT were improved by the membranes. Hence, ASColl membranes exhibited attractive characteristics to be applied in the biomedical and cosmeceutical field envisaging skincare.

Identification of umami peptides based on virtual screening and molecular docking from Atlantic cod (Gadus morhua).

Umami peptides have currently become the research focus in the food umami science field and the key direction for umami agent development. This is because umami peptides have good processing characteristics, umami and nutritional values. We here used virtual screening (including online enzymolysis through ExPASy PeptideCutter, bioactivity screening using the PeptideRanker, toxicity and physicochemical property prediction using Innovagen and ToxinPred software), molecular docking, and electronic tongue analysis to identify umami peptides generated from Atlantic cod myosin. Twenty-three putative umami peptides were screened from the myosin. Molecular docking results suggested that these 23 peptides could enter the binding pocket in the T1R3 cavity, wherein Glu128 and Asp196 were the main amino acid residues, and that hydrogen bonding and electrostatic interactions were the main binding forces. Twelve synthetic peptides tested on the electronic tongue exhibited umami taste and a synergistic effect with monosodium glutamate (MSG). Among them, GGR, AGCD, and SGDAW had higher umami intensities than the other peptides, while SGDAW and NDDGW exhibited stronger umami-enhancing capabilities in 0.1% MSG solution. This study offers a method for the rapid screening of umami peptides from marine protein resources and places the foundation for their application in the food industry.

Composition, structural configuration, and antigenicity of Atlantic cod (Gadus morhua) tropomyosin.

Tropomyosin, a myofibrillar muscle protein, has been recognized as a finfish allergen. In this study, tropomyosin from Atlantic cod fillets (Gadus morhua, CTM) was purified using a two-step purification strategy (isoelectric precipitation and anion-exchange chromatography). CTM structural configuration in two sample matrices (impure and pure) were elaborated using different polyacrylamide gel electrophoresis (native, non-reducing, and reducing PAGE). Their corresponding immunoblots were conducted to investigate CTM antigenicity under three conditions. Overall, CTM retained solubility, integrity, and antigenicity after heat treatment. Three CTM monomeric α-type isoforms (33 kDa) were identified using two-dimensional PAGE. Under native condition, the vast majority of CTM existed in the disulfide-reduced dimeric form (66 kDa). Under non-reducing condition, sodium dodecyl sulfate (anionic surfactant) broke CTM dimers, leaving monomers and disulfide-induced tetramers. Under reducing condition, ß-mercaptoethanol (thiol reducing agent) dissociated disulfide-linked CTM tetramers (132 kDa) into monomers (33 kDa). CTM retained antigenicity regardless of structural configuration under different conditions.

Protein phosphorylation profile of Atlantic cod (Gadus morhua) in response to pre-slaughter pumping stress and postmortem time.

This study aimed to evaluate the effect of pumping stress (pumping and pumping-resting) and postmortem time (before and after rigor mortis) on phosphorylation profiles of myofibrillar protein (MP) and sarcoplasmic protein (SP) of Atlantic cod (Gadus morhua) fillets. The result showed that MP had higher global phosphorylation levels than SP regardless of stress condition and postmortem time. The pumping process resulted in significant changes in phosphorylation of structural proteins including myosin heavy and light chains. Pumping also affected the phosphorylation status of heat shock proteins and metabolic enzymes involved in the glycolytic pathways, indicating the possible role of phosphorylation in regulating energy hemostasis of fish under stressful conditions. The pumping-induced phosphorylation changes mainly occurred before rigor mortis, and postmortem time affected the phosphorylation status to a less extent. This work contributes to a deeper understanding on protein phosphorylation affected by pre-slaughter stress and postmortem time of fish.

Mechanism of enhancing the water-solubility and stability of curcumin by using self-assembled cod protein nanoparticles at an alkaline pH.

Curcumin (Cur) is a bioactive phytochemical which is claimed to have several health-promoting benefits, whose applications are challenging due to its poor water-solubility, chemical instability, and low bioavailability. In this research, Cur was encapsulated in the cod protein (CP) using a pH-driven method to enhance its solubility and stability. The physicochemical and structural properties of cod protein-curcumin nanoparticles (CP-Cur) formed were characterized. Fluorescence spectroscopy (FL), ultraviolet spectroscopy (UV), circular dichroism (CD), and dynamic light scattering (DLS) results collectively suggest that the protein originally with a molten-globule state refolded into a more ordered structure after neutralization, during which Cur was incorporated. Fluorescence quenching and isothermal titration calorimetry (ITC) further showed that the CP/Cur binding was mainly driven by hydrophobic interactions, resulting in static fluorescence quenching and energy release. Up to 99.50% of Cur was loaded in the CP delivery system. Furthermore, the thermal stability and photostability of Cur were greatly improved due to the protection of the protein. The present study proved that cod protein could be a great potential edible carrier for encapsulating curcumin.

Structural Identification of the Pacemaker Cells and Expression of Hyperpolarization-Activated Cyclic Nucleotide-Gated (HCN) Channels in the Heart of the Wild Atlantic Cod, Gadus morhua (Linnaeus, 1758).

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are proteins that contain highly conserved functional domains and sequence motifs that are correlated with their unique biophysical activities, to regulate cardiac pacemaker activity and synaptic transmission. These pacemaker proteins have been studied in mammalian species, but little is known now about their heart distribution in lower vertebrates and c-AMP modulation. Here, we characterized the pacemaker system in the heart of the wild Atlantic cod (Gadus morhua), with respect to primary pacemaker molecular markers. Special focus is given to the structural, ultrastructural and molecular characterization of the pacemaker domain, through the expression of HCN channel genes and the immunohistochemistry of HCN isoforms, including the location of intracardiac neurons that are adjacent to the sinoatrial region of the heart. Similarly to zebrafish and mammals, these neurons are immunoreactive to ChAT, VAChT and nNOS. It has been shown that cardiac pacemaking can be modulated by sympathetic and parasympathetic pathways, and the existence of intracardiac neurons projecting back to the central nervous system provide a plausible link between them.

Differences in metabolic rate between two Atlantic cod (Gadus morhua) populations estimated with carbon isotopic composition in otoliths.

The isotopic composition of inorganic carbon in otoliths (δ13Coto) can be a useful tracer of metabolic rates and a method to study ecophysiology in wild fish. We evaluated environmental and physiological sources of δ13Coto variation in Icelandic and Northeast Arctic (NEA) cod (Gadus morhua) over the years 1914-2013. Individual annual growth increments of otoliths formed at age 3 and 8 were micromilled and measured by isotope-ratio mass spectrometry. Simultaneously, all annual increment widths of the otoliths were measured providing a proxy of fish somatic growth. We hypothesized that changes in the physiological state of the organism, reflected by the isotopic composition of otoliths, can affect the growth rate. Using univariate and multivariate mixed-effects models we estimated conditional correlations between carbon isotopic composition and growth of fish at different levels (within individuals, between individuals, and between years), controlling for intrinsic and extrinsic effects on both otolith measurements. δ13Coto was correlated with growth within individuals and between years, which was attributed to the intrinsic effects (fish age or total length). There was no significant correlation between δ13Coto and growth between individuals, which suggests that caution is needed when interpreting δ13Coto signals. We found a significant decrease in δ13Coto through the century which was explained by the oceanic Suess effect-admixture of isotopically light carbon from fossil fuel. We calculated the proportion of the respired carbon in otolith carbonate (Cresp) using carbon isotopic composition in diet and dissolved inorganic carbon of the seawater. This approach allowed us to correct the values for each stock in relation to these two environmental baselines. Cresp was on average 0.275 and 0.295 in Icelandic and NEA stock, respectively. Our results provide an insight into the physiological basis for differences in growth characteristics between these two cod stocks, and how that may vary over time.

Amyloid formation of fish ß-parvalbumin involves primary nucleation triggered by disulfide-bridged protein dimers.

Amyloid formation involves the conversion of soluble protein species to an aggregated state. Amyloid fibrils of ß-parvalbumin, a protein abundant in fish, act as an allergen but also inhibit the in vitro assembly of the Parkinson protein α-synuclein. However, the intrinsic aggregation mechanism of ß-parvalbumin has not yet been elucidated. We performed biophysical experiments in combination with mathematical modeling of aggregation kinetics and discovered that the aggregation of ß-parvalbumin is initiated by the formation of dimers stabilized by disulfide bonds and then proceeds via primary nucleation and fibril elongation processes. Dimer formation is accelerated by H2O2 and hindered by reducing agents, resulting in faster and slower aggregation rates, respectively. Purified ß-parvalbumin dimers readily assemble into amyloid fibrils with similar morphology as those formed when starting from monomer solutions. Furthermore, addition of preformed dimers accelerates the aggregation reaction of monomers. Aggregation of purified ß-parvalbumin dimers follows the same kinetic mechanism as that of monomers, implying that the rate-limiting primary nucleus is larger than a dimer and/or involves structural conversion. Our findings demonstrate a folded protein system in which spontaneously formed intermolecular disulfide bonds initiate amyloid fibril formation by recruitment of monomers. This dimer-induced aggregation mechanism may be of relevance for human amyloid diseases in which oxidative stress is often an associated hallmark.

Proteomics and lipidomics analyses reveal modulation of lipid metabolism by perfluoroalkyl substances in liver of Atlantic cod (Gadus morhua).

The aim of the present study was to investigate effects of defined mixtures of polycyclic aromatic hydrocarbons (PAHs) and perfluoroalkyl substances (PFASs), at low, environmentally relevant (1× = L), or high (20× = H) doses, on biological responses in Atlantic cod (Gadus morhua). To this end, farmed juvenile cod were exposed at day 0 and day 7 via intraperitoneal (i.p.) injections, in a two-week in vivo experiment. In total, there were 10 groups of fish (n = 21-22): two control groups, four separate exposure groups of PAH and PFAS mixtures (L, H), and four groups combining PAH and PFAS mixtures (L/L, H/L, L/H, H/H). Body burden analyses confirmed a dose-dependent accumulation of PFASs in cod liver and PAH metabolites in bile. The hepatosomatic index (HSI) was significantly reduced for three of the combined PAH/PFAS exposure groups (L-PAH/H-PFAS, H-PAH/L-PFAS, H-PAH/H-PFAS). Analysis of the hepatic proteome identified that pathways related to lipid degradation were significantly affected by PFAS exposure, including upregulation of enzymes in fatty acid degradation pathways, such as fatty acid ß-oxidation. The increased abundances of enzymes in lipid catabolic pathways paralleled with decreasing levels of triacylglycerols (TGs) in the H-PFAS exposure group, suggest that PFAS increase lipid catabolism in Atlantic cod. Markers of oxidative stress, including catalase and glutathione S-transferase activities were also induced by PFAS exposure. Only minor and non-significant differences between exposure groups and control were found for cyp1a and acox1 gene expressions, vitellogenin concentrations in plasma, Cyp1a protein synthesis and DNA fragmentation. In summary, our combined proteomics and lipidomics analyses indicate that PFAS may disrupt lipid homeostasis in Atlantic cod.

Expression and localization of the aryl hydrocarbon receptors and cytochrome P450 1A during early development of Atlantic cod (Gadus morhua).

The aryl hydrocarbon receptor (Ahr) is a ligand-activated transcription factor that mediates the toxicity of dioxins and dioxin-like compounds (DLCs) in vertebrates. Two clades of the Ahr family exist in teleosts (Ahr1 and Ahr2), and it has been demonstrated that Ahr2 is the main protein involved in mediating the toxicity of dioxins and DLCs in most teleost species. Recently, we characterized the Atlantic cod (Gadus morhua) Ahr1a and Ahr2a receptors. To further explore a possible subfunction partitioning of Ahr1a and Ahr2a in Atlantic cod we have mapped the expression and localization of ahr1a and ahr2a in early developmental stages. Atlantic cod embryos were continuously exposed in a passive-dosing exposure system to the Ahr agonist, benzo[a]pyrene (B[a]P), from five days post fertilization (dpf) until three days post hatching (dph). Expression of ahr1a, ahr2a, and the Ahr-target genes, cyp1a and ahrrb, was assessed in embryos (8 dpf and 10 dpf) and larvae (3 dph) with quantitative real-time PCR analyses (qPCR), while in situ hybridization was used to assess the localization of expression of ahr1a, ahr2a and cyp1a. Quantitative measurements showed an increased cyp1a expression in B[a]P-exposed samples at all sampling points, and for ahr2a at 10 dpf, confirming the activation of the Ahr-signalling pathway. Furthermore, B[a]P strongly induced ahr2a and cyp1a expression in the cardiovascular system and skin, respectively, of embryos and larvae. Induced expression of both ahr2a and cyp1a was also revealed in the liver of B[a]P-exposed larvae. Our results suggest that Ahr2a is the major subtype involved in mediating responses to B[a]P in early developmental stages of Atlantic cod, which involves transcriptional regulation of biotransformation genes, such as cyp1a. The focused expression of ahr1a in the eye of embryos and larvae, and the presence of ahr2a transcripts in the jaws and fin nodes, further indicate evolved specialized roles of the two Ahrs in ontogenesis.

Synthesis of trans-dihydronaphthalene-diols and evaluation of their use as standards for PAH metabolite analysis in fish bile by GC-MS.

Phenols and trans-1,2-dihydro-1,2-diols are metabolites commonly formed in vivo in fish upon exposure to polycyclic aromatic hydrocarbons (PAHs). These metabolites are excreted via the bile and gas chromatography-mass spectrometry (GC-MS) analysis of bile is becoming more frequently used for evaluating PAH exposure levels in fish. Current protocols focus on the detection and quantification of phenols formed during in vivo oxidation of PAHs, leaving out analyses and quantification of other oxidation products such as trans-1,2-dihydro-1,2-diols, potentially underestimating exposure levels. Herein, four trans-1,2-dihydro-1,2-diols, namely trans-1,2-dihydronaphthalene-1,2-diol, trans-6-methyl-1,2-dihydronaphthalene-1,2-diol, trans-5,7-dimethyl-1,2-dihydronaphthalene-1,2-diol, and trans-4,6,7-trimethyl-1,2-dihydronaphthalene-1,2-diol, were successfully prepared and used as standards in the GC-MS analysis, aiming to further develop this qualitative and quantitative analytical method for the determination of PAH exposures. This study shows that the currently used GC-MS analysis, including sample workup, is not suitable for determining the quantity of the corresponding diols derived from naphthalene and methylated naphthalenes. Alternative approaches are needed to provide a correct estimate of PAH exposure levels.

Differential gene expression patterns related to lipid metabolism in response to ocean acidification in larvae and juveniles of Atlantic cod.

Elevated environmental carbon dioxide (pCO2) levels have been found to cause organ damage in the early life stages of different commercial fish species, including Atlantic cod (Gadus morhua). To illuminate the underlying mechanisms causing pathologies in the intestines, the kidney, the pancreas and the liver in response to elevated pCO2, we examined related gene expression patterns in Atlantic cod reared for two months under three different pCO2 regimes: 380 µatm (control), 1800 µatm (medium) and 4200 µatm (high). We extracted RNA from whole fish sampled during the larval (32 dph) and early juvenile stage (46 dph) for relative expression analysis of 18 different genes related to essential metabolic pathways. At 32 dph, larvae subjected to the medium treatment displayed an up-regulation of genes mainly associated with fatty acid and glycogen synthesis (GYS2, 6PGL, ACoA, CPTA1, FAS and PPAR1b). Larvae exposed to the high pCO2 treatment upregulated fewer but similar genes (6PGL, ACoA and PPAR1b,). These data suggest stress-induced alterations in the lipid and fatty acid metabolism and a disrupted lipid homeostasis in larvae, providing a mechanistic link to the findings of lipid droplet overload in the liver and organ pathologies. At 46 dph, no significant differences in gene expression were detected, confirming a higher resilience of juveniles in comparison to larvae when exposed to elevated pCO2 up to 4200 µatm.