Metabolomic investigations of American oysters using H-NMR spectroscopy

Microplastics and low tide warming: Metabolic disorders in intertidal Pacific oysters (Crassostrea gigas)

Sessile intertidal organisms live in a harsh environment with challenging environmental conditions and increasing anthropogenic pressure such as microplastic (MP) pollution. This study focused on effects of environmentally relevant MP concentrations on the metabolism of intertidal Pacific oyster Crassostrea gigas, and its potential MP-induced vulnerability to warming during midday low tide. Oysters experienced a simulated semidiurnal tidal cycle based on their natural habitat, and were exposed to a mixture of polystyrene microbeads (4, 7.5 and 10 µm) at two environmentally relevant concentrations (0.025 µg L-1 and 25 µg L-1) for 16 days, with tissue samplings after 3 and 12 days to address dose-dependent effects over time. On the last day of exposure, the remaining oysters were additionally exposed to low tide warming (3 °C h-1) to investigate possible MP-induced susceptibility to aerial warming. Metabolites of digestive gland and gill tissues were analysed by using untargeted 1H nuclear magnetic resonance (NMR) based metabolomics. For the digestive gland metabolite profiles were comparable to each other independent of MP concentration, exposure time, or warming. In contrast, gill metabolites were significantly affected by high MP exposure and warming irrespective of MP, initiating the same cellular stress response to counteract induced oxidative stress. The activated cascade of antioxidant defence mechanisms required energy on top of the general energy turnover to keep up homeostasis, which in turn may lead to subtle, and likely sub-lethal, effects within intertidal oyster populations. Present results underline the importance of examining the effects of environmentally relevant MP concentrations not only alone but in combination with other environmental stressors.

Metabolomics and lipidomics reveal the effects of the toxic dinoflagellate Alexandrium catenella on immune cells of the blue mussel, Mytilus edulis

The increasing occurrence of harmful algal blooms, mostly of the dinoflagellate Alexandrium catenella in Canada, profoundly disrupts mussel aquaculture. These filter-feeding shellfish feed on A. catenella and accumulate paralytic shellfish toxins, such as saxitoxin, in tissues, making them unsafe for human consumption. Algal toxins also have detrimental effects upon several physiological functions in mussels, but particularly on the activity of hemocytes - the mussel immune cells. The objective of this work was to determine the effects of experimental exposure to A. catenella upon hemocyte metabolism and activity in the blue mussel, Mytilus edulis. To do so, mussels were exposed to cultures of the toxic dinoflagellate A. catenella for 120 h. The resulting mussel saxitoxin load had measurable effects upon survival of hemocytes and induced a stress response measured as increased ROS production. The neutral lipid fraction of mussel hemocytes decreased two-fold, suggesting a differential use of lipids. Metabolomic 1H nuclear magnetic resonance (NMR) analysis showed that A. catenella modified the energy metabolism of hemocytes as well as hemocyte osmolyte composition. The modified energy metabolism was reenforced by contrasting plasma metabolomes between control and exposed mussels, suggesting that the blue mussel may reduce feed assimilation when exposed to A. catenella.

Common fear molecules induce defensive responses in marine prey across trophic levels

Predator-prey interactions are a key feature of ecosystems and often chemically mediated, whereby individuals detect molecules in their environment that inform whether they should attack or defend. These molecules are largely unidentified, and their discovery is important for determining their ecological role in complex trophic systems. Homarine and trigonelline are two previously identified blue crab (Callinectes sapidus) urinary metabolites that cause mud crabs (Panopeus herbstii) to seek refuge, but it was unknown whether these molecules influence other species within this oyster reef system. In the current study, homarine, trigonelline, and blue crab urine were tested on juvenile oysters (Crassostrea virginica) to ascertain if the same molecules known to alter mud crab behavior also affect juvenile oyster morphology, thus mediating interactions between a generalist predator, a mesopredator, and a basal prey species. Oyster juveniles strengthened their shells in response to blue crab urine and when exposed to homarine and trigonelline in combination, especially at higher concentrations. This study builds upon previous work to pinpoint specific molecules from a generalist predator's urine that induce defensive responses in two marine prey from different taxa and trophic levels, supporting the hypothesis that common fear molecules exist in ecological systems.

Metabolomics-Based Investigation on the Metabolic Changes in Crassostrea gigas Experimentally Exposed to Galvanic Anodes

Cathodic protection is widely used to protect metal structures from corrosion in marine environments using sacrificial galvanic anodes. These anodes, either in Zinc, or preferentially nowadays in Al-Zn-In alloys, are expected to corrode instead of the metal structures. This leads to the release of dissolved species, Zn²⁺, Al³⁺, and In³⁺, and solid phases such as Al(OH)₃. Few studies have been conducted on their effects on marine organisms, and they concluded that further investigations are needed. We therefore evaluated the effects of Zn and Al-Zn-In anodes on oysters stabulated in tanks, under controlled conditions defined through a comparison with those prevailing in a given commercial seaport used as reference. We analyzed the entire metabolome of gills with a non-targeted metabolomic approach HRMS. A modelling study of the chemical species, corresponding to the degradation products of the anodes, likely to be present near the exposed oysters, was also included. We identified 16 and two metabolites modulated by Zn- and Al-Zn-In-anodes, respectively, that were involved in energy metabolism, osmoregulation, oxidative stress, lipid, nucleotide nucleoside and amino acid metabolisms, defense and signaling pathways. The combination of chemical modelling and metabolomic approach, used here for the first time, enlightened the influence of Zn present in the Al-Zn-In anodes.

Wastewater effluent affects behaviour and metabolomic endpoints in damselfly larvae

Wastewater treatment plant effluents have been identified as a major contributor to increasing anthropogenic pollution in aquatic environments worldwide. Yet, little is known about the potentially adverse effects of wastewater treatment plant effluent on aquatic invertebrates. In this study, we assessed effects of wastewater effluent on the behaviour and metabolic profiles of damselfly larvae (Coenagrion hastulatum), a common aquatic invertebrate species. Four key behavioural traits: activity, boldness, escape response, and foraging (traits all linked tightly to individual fitness) were studied in larvae before and after one week of exposure to a range of effluent dilutions (0, 50, 75, 100%). Effluent exposure reduced activity and foraging, but generated faster escape response. Metabolomic analyses via targeted and non-targeted mass spectrometry methods revealed that exposure caused significant changes to 14 individual compounds (4 amino acids, 3 carnitines, 3 lysolipids, 1 peptide, 2 sugar acids, 1 sugar). Taken together, these compound changes indicate an increase in protein metabolism and oxidative stress. Our findings illustrate that wastewater effluent can affect both behavioural and physiological traits of aquatic invertebrates, and as such might pose an even greater threat to aquatic ecosystems than previously assumed. More long-term studies are now needed evaluate if these changes are linked to adverse effects on fitness. The combination of behavioural and metabolomic assessments provide a promising tool for detecting effects of wastewater effluent, on multiple biological levels of organisation, in aquatic ecosystems.

Preparation and Characterization of Calcium-Incorporated Rosa roxburghii Tratt and Its Efficacy on Bone Mineral Density in Rats

The deficiency of traditional calcium preparation will gradually be replaced by the new type of calcium preparation. Rosa roxburghii fruit (R. roxburghii) is popular for its rich nutrients and functional ingredients. The fermentation broth of R. roxburghii, involving amino acids, flavonoids, triterpenes, polysaccharides, and other compounds, is favorable for calcium chelation. Thus, this study fabricated calcium-incorporated R. roxburghii (FECa) and further illustrated its efficacy on bone mineral density (BMD) in rats. The calcium holding capacity of FECa was identified and confirmed using AAS. Ion complexation of FECa was characterized using ¹H-NMR, UV, SEM and EDS, and FTIR. The calcium contents of femurs were increased by 36%, and the bone trabeculae of femurs were significantly increased. Net calcium balance was enhanced to further improve BMD by oral administration of FECa. The above results indicate that FECa can be a potential and efficient calcium supplementation agent.

1H-NMR-Based Metabolomic Study of Potato Cultivars, Markies and Fianna, Exposed to Different Water Regimes

This study investigated the effects of varying soil moisture conditions (through either flooding, drought, or provision of a moderate water supply) on the metabolomic profile of two potato cultivars, namely, Markies and Fianna. Representative tubers of the treated plants were collected 91 days after planting. The samples were freeze-dried, and ground to a fine powder in liquid nitrogen. The fine powder of the tuber samples was analyzed by nuclear magnetic resonance spectroscopy (NMR) to identify their metabolomic profiles. The NMR data was analyzed using principal component analysis and orthogonal partial least square-discriminant analysis to identify any variations between the treatments. In both models, plants exposed to drought clearly separated from the plants that received either excess or moderate water (control). The potato tubers that experienced drought and flood treatments had the highest quantities of aspartic acid, asparagine, and isoleucine. Furthermore, the potatoes exposed to either drought or flood had higher levels of valine and leucine (which are essential for plant defense and resistance against plant pathogens). Potato plants can respond metabolically to varying soil moisture stress.

NMR Metabolite Profiles of the Bivalve Mollusc Mytilus galloprovincialis Before and After Immune Stimulation With Vibrio splendidus

The hemolymph metabolome of Mytilus galloprovincialis injected with live Vibrio splendidus bacteria was analyzed by ¹H-NMR spectrometry. Changes in spectral hemolymph profiles were already detected after mussel acclimation (3 days at 18 or 25 °C). A significant decrease of succinic acid was accompanied by an increase of most free amino acids, mytilitol, and, to a smaller degree, osmolytes. These metabolic changes are consistent with effective osmoregulation, and the restart of aerobic respiration after the functional anaerobiosis occurred during transport. The injection of Vibrio splendidus in mussels acclimated at 18°C caused a significant decrease of several amino acids, sugars, and unassigned chemical species, more pronounced at 24 than at 12 h postinjection. Correlation heatmaps indicated dynamic metabolic adjustments and the relevance of protein turnover in maintaining the homeostasis during the response to stressful stimuli. This study confirms NMR-based metabolomics as a feasible analytical approach complementary to other omics techniques in the investigation of the functional mussel responses to environmental challenges.

Microbiome Analysis Reveals Diversity and Function of Mollicutes Associated with the Eastern Oyster, Crassostrea virginica

Despite their biological and ecological significance, a mechanistic characterization of microbiome function is frequently missing from many nonmodel marine invertebrates. As an initial step toward filling this gap for the eastern oyster, Crassostrea virginica, this study provides an integrated taxonomic and functional analysis of the oyster microbiome using samples from a coastal salt pond in August 2017.

Marine invertebrate microbiomes play important roles in diverse host and ecological processes. However, a mechanistic understanding of host-microbe interactions is currently available for a small number of model organisms. Here, an integrated taxonomic and functional analysis of the microbiome of the eastern oyster, Crassostrea virginica, was performed using 16S rRNA gene-based amplicon profiling, shotgun metagenomics, and genome-scale metabolic reconstruction. Relatively high variability of the microbiome was observed across individual oysters and among different tissue types. Specifically, a significantly higher alpha diversity was observed in the inner shell than in the gut, gill, mantle, and pallial fluid samples, and a distinct microbiome composition was revealed in the gut compared to other tissues examined in this study. Targeted metagenomic sequencing of the gut microbiota led to further characterization of a dominant bacterial taxon, the class Mollicutes, which was captured by the reconstruction of a metagenome-assembled genome (MAG). Genome-scale metabolic reconstruction of the oyster Mollicutes MAG revealed a reduced set of metabolic functions and a high reliance on the uptake of host-derived nutrients. A chitin degradation and an arginine deiminase pathway were unique to the MAG compared to closely related genomes of Mollicutes isolates, indicating distinct mechanisms of carbon and energy acquisition by the oyster-associated Mollicutes. A systematic reanalysis of public eastern oyster-derived microbiome data revealed a high prevalence of the Mollicutes among adult oyster guts and a significantly lower relative abundance of the Mollicutes in oyster larvae and adult oyster biodeposits.

IMPORTANCE Despite their biological and ecological significance, a mechanistic characterization of microbiome function is frequently missing from many nonmodel marine invertebrates. As an initial step toward filling this gap for the eastern oyster, Crassostrea virginica, this study provides an integrated taxonomic and functional analysis of the oyster microbiome using samples from a coastal salt pond in August 2017. The study identified high variability of the microbiome across tissue types and among individual oysters, with some dominant taxa showing higher relative abundance in specific tissues. A high prevalence of Mollicutes in the adult oyster gut was revealed by comparative analysis of the gut, biodeposit, and larva microbiomes. Phylogenomic analysis and metabolic reconstruction suggested the oyster-associated Mollicutes is closely related but functionally distinct from Mollicutes isolated from other marine invertebrates. To the best of our knowledge, this study represents the first metagenomics-derived functional inference of Mollicutes in the eastern oyster microbiome.

Combined metabolomics and histological analysis of the tissues from cuttlefish Sepia pharaonis exposed to inking stress

Inking is part of a defensive stress response in cephalopods (cuttlefish, squid, and octopus). Some individual cuttlefish (Sepia pharaonis) die after continued stress and inking; however, the physiological effects of cephalopods in response to stress and inking remain unknown. The present study investigated the metabolic profile and discussed the physiological roles of S. pharaonis tissues in response to continuous inking using the ¹H NMR spectroscopy coupled with multivariate data analysis. A total of 50 metabolites, including amino acids, organic osmolytes, nucleotides, energy storage compounds, and obvious tissue-specific metabolites induced by inking stress, were identified in S. pharaonis tissues. Exposure to inking stress had different effects on the levels of the studied metabolites, for example, the levels of isoleucine, trimethylamine-N-oxide, and betaine increased, but those of arginine and ATP decreased in the liver; inosine and lactate were accumulated whereas glutamate and choline were depleted in the gill; the levels of lactate and isoleucine were elevated but those of arginine and glycogen were depleted in the muscle tissue. Furthermore, the corresponding metabolic pathways of the characteristic metabolites indicated major changes in the functions of these metabolites. Histological changes in the studied tissues revealed liver lobule damage immediately after inking, with the presence of disordered epithelial cells and partial cell necrosis in the gill. Our results demonstrated that a combination of metabolomics and histological analyses could provide molecular-level insights for elucidating the defense response of cuttlefish against predators.

1H-NMR metabolomics profiling of zebra mussel (Dreissena polymorpha): A field-scale monitoring tool in ecotoxicological studies

Biomonitoring of aquatic environments requires new tools to characterize the effects of pollutants on living organisms. Zebra mussels (Dreissena polymorpha) from the same site in north-eastern France were caged for two months, upstream and downstream of three wastewater treatment plants (WWTPs) in the international watershed of the Meuse (Charleville-Mézières "CM" in France, Namur "Nam" and Charleroi "Cr" in Belgium). The aim was to test ¹H-NMR metabolomics for the assessment of water bodies' quality. The metabolomic approach was combined with a more "classical" one, i.e., the measurement of a range of energy biomarkers: lactate dehydrogenase (LDH), lipase, acid phosphatase (ACP) and amylase activities, condition index (CI), total reserves, electron transport system (ETS) activity and cellular energy allocation (CEA). Five of the eight energy biomarkers were significantly impacted (LDH, ACP, lipase, total reserves and ETS), without a clear pattern between sites (Up and Down) and stations (CM, Nam and Cr). The metabolomic approach revealed variations among the three stations, and also between the upstream and downstream of Nam and CM WWTPs. A total of 28 known metabolites was detected, among which four (lactate, glycine, maltose and glutamate) explained the observed metabolome variations between sites and stations, in accordance with chemical exposure levels. Metabolome changes suggest that zebra mussel exposure to field contamination could alter their osmoregulation and anaerobic metabolism capacities. This study reveals that lactate is a potential biomarker of interest, and ¹H-NMR metabolomics can be an efficient approach to assess the health status of zebra mussels in the biomonitoring of aquatic environments.

Metabolomics comparison of rumen fluid and milk in dairy cattle using proton nuclear magnetic resonance spectroscopy

Objective

The metabolites that constitute the rumen fluid and milk in dairy cattle were analyzed using proton nuclear magnetic resonance (¹H-NMR) spectroscopy and compared with the results obtain for other dairy cattle herds worldwide. The aim was to provide basic dataset for facilitating research on metabolites in rumen fluid and milk.

Methods

Six dairy cattle were used in this study. Rumen fluid was collected using a stomach tube, and milk was collected using a pipeline milking system. The metabolites were determined by ¹H-NMR spectroscopy, and the obtained data were statistically analyzed by principal component analysis, partial least squares discriminant analysis, variable importance in projection scores, and metabolic pathway data using Metaboanalyst 4.0.

Results

The total numbers of metabolites in rumen fluid and milk were measured to be 186 and 184, and quantified as 72 and 109, respectively. Organic acid and carbohydrate metabolites exhibited the highest concentrations in rumen fluid and milk, respectively. Some metabolites that have been associated with metabolic diseases (acidosis and ketosis) in cows were identified in rumen fluid, and metabolites associated with ketosis, somatic cell production, and coagulation properties were identified in milk.

Conclusion

The metabolites measured in rumen fluid and milk could potentially be used to detect metabolic diseases and evaluate milk quality. The results could also be useful for metabolomic research on the biofluids of ruminants in Korea, while facilitating their metabolic research.

The Zebra Mussel (Dreissena polymorpha) as a Model Organism for Ecotoxicological Studies: A Prior 1H NMR Spectrum Interpretation of a Whole Body Extract for Metabolism Monitoring

The zebra mussel (Dreissena polymorpha) represents a useful reference organism for the ecotoxicological study of inland waters, especially for the characterization of the disturbances induced by human activities. A nuclear magnetic resonance (NMR)-based metabolomic approach was developed on this species. The investigation of its informative potential required the prior interpretation of a reference ¹H NMR spectrum of a lipid-free zebra mussel extract. After the extraction of polar metabolites from a pool of whole-body D. polymorpha powder, the resulting highly complex 1D ¹H NMR spectrum was interpreted and annotated through the analysis of the corresponding 2D homonuclear and heteronuclear NMR spectra. The spectrum interpretation was completed and validated by means of sample spiking with 24 commercial compounds. Among the 238 detected ¹H signals, 53% were assigned, resulting in the identification of 37 metabolites with certainty or high confidence, while 5 metabolites were only putatively identified. The description of such a reference spectrum and its annotation are expected to speed up future analyses and interpretations of NMR-based metabolomic studies on D. polymorpha and to facilitate further explorations of the impact of environmental changes on its physiological state, more particularly in the context of large-scale ecological and ecotoxicological studies.

Single and combined effects of the "Deadly trio" hypoxia, hypercapnia and warming on the cellular metabolism of the great scallop Pecten maximus

In the ocean the main climate drivers affecting marine organisms are warming, hypercapnia, and hypoxia. We investigated the acute effects of warming (W), warming plus hypercapnia (WHc, ~1800 μatm CO₂), warming plus hypoxia (WHo, ~12.1 kPa O₂), and a combined exposure of all three drivers (Deadly Trio, DT) on king scallops (Pecten maximus). All exposures started at 14 °C and temperature was increased by 2 °C once every 48 h until the lethal temperature was reached (28 °C). Gill samples were taken at 14 °C, 18 °C, 22 °C, and 26 °C and analyzed for their metabolic response by ¹H-nuclear magnetic resonance (NMR) spectroscopy. Scallops were most tolerant to WHc and most susceptible to oxygen reduction (WHo and DT). In particular under DT, scallops' mitochondrial energy metabolism was affected. Changes became apparent at 22 °C and 26 °C involving significant accumulation of glycogenic amino acids (e.g. glycine and valine) and anaerobic end-products (e.g. acetic acid and succinate). In line with these observations the LT₅₀ was lower under the exposure to DT (22.5 °C) than to W alone (~ 25 °C) indicating a narrowing of the thermal niche due to an imbalance between oxygen demand and supply.

1H NMR Metabolic Profile of Scyphomedusa Rhizostoma pulmo (Scyphozoa, Cnidaria) in Female Gonads and Somatic Tissues: Preliminary Results

The Mediterranean basin is one of the regions heavily affected by jellyfish bloom phenomena, mainly due to the presence of scyphozoans, such as Rhizostoma pulmo. The jellyfish have few natural predators, and their bodies represent an organic-rich substrate that can support rapid bacterial growth with great impact on the structure of marine food webs. In Asiatic countries, jellyfish are widely studied for their health benefits, but their nutritional and nutraceutical values still remain poorly characterized. In this study, the differences in the ¹H NMR spectroscopy metabolic profiles of R. pulmo female gonads and body fractions (including umbrella and oral arms), in different sampling periods, were studied. For each body compartment both lipid and aqueous extracts were characterized and their ¹H NMR metabolic profiles subjected to multivariate analysis. From a statistical analysis of the extracts, a higher contents of ω-3 polyunsaturated fatty acids (PUFAs), amino acid and osmolytes (homarine, betaine, taurine) with important roles in marine invertebrates were observed in female gonads, whereas umbrella and oral arms showed similar metabolic profiles. These results support a sustainable exploitation of the jellyfish for the extraction of bioactive compounds useful in nutraceutical, nutricosmetics, and functional food fields.

Metabolomic Investigations of the Temporal Effects of Exposure to Pharmaceuticals and Personal Care Products and Their Mixture in the Eastern Oyster (Crassostrea virginica)

The eastern oyster (Crassostrea virginica) supports a large aquaculture industry and is a keystone species along the Atlantic seaboard. Native oysters are routinely exposed to a complex mixture of contaminants that increasingly includes pharmaceuticals and personal care products (PPCPs). Unfortunately, the biological effects of chemical mixtures on oysters are poorly understood. Untargeted gas chromatography-mass spectrometry metabolomics was utilized to quantify the response of oysters exposed to fluoxetine, N,N-diethyl-meta-toluamide, 17α-ethynylestradiol, diphenhydramine, and their mixture. Oysters were exposed to 1 µg/L of each chemical or mixture for 10 d, followed by an 8-d depuration period. Adductor muscle (n = 14/treatment) was sampled at days 0, 1, 5, 10, and 18. Trajectory analysis illustrated that metabolic effects and class separation of the treatments varied at each time point and that, overall, the oysters were only able to partially recover from these exposures post-depuration. Altered metabolites were associated with cellular energetics (i.e., Krebs cycle intermediates), as well as amino acid metabolism and fatty acids. Exposure to these PPCPs also affected metabolic pathways associated with anaerobic metabolism, osmotic stress, and oxidative stress, in addition to the physiological effects of each chemical's postulated mechanism of action. Following depuration, fewer metabolites were altered, but none of the treatments returned them to their initial control values, indicating that metabolic disruptions were long-lasting. Interestingly, the mixture did not directly cluster with individual treatments in the scores plot from partial least squares discriminant analysis, and many of its affected metabolic pathways were not well predicted from the individual treatments. The present study highlights the utility of untargeted metabolomics in developing exposure biomarkers for compounds with different modes of action in bivalves. Environ Toxicol Chem 2020;39:419-436. © 2019 SETAC.

Quantitative magnetic resonance imaging and histological hoof wall assessment of 3-year-old Quarter Horses

BACKGROUND

Few noninvasive methods are available for equine hoof wall evaluation. The highly organised wall structures and composition of proteoglycans and collagens may make this region amenable to quantitative MRI (qMRI) techniques of T1ρ and T2 mapping to identify pathology related to proteoglycan content and collagen organisation respectively.

OBJECTIVE

To establish normative T1ρ and T2 values of the equine hoof wall of 3-year-old Quarter Horses with histological comparison.

STUDY DESIGN

Cadaveric anatomical study.

METHODS

Six cadaveric left thoracic feet from 3-year-old racing Quarter Horses with no reported lameness were evaluated using T1ρ and T2 mapping. Mapping was performed at six regions of interest at the toe of each hoof including proximal and distal regions of the inner epidermis, stratum lamellatum and corium. Histology was evaluated for standard hoof morphology and proteoglycan staining.

RESULTS

T2 values of the stratum lamellatum and corium were similar (42.9 [95% CI: 41.6-44.2] ms and 44 [95% CI: 42.7-45.3] ms respectively), but both were significantly different to the inner epidermis (35.8 [95% CI: 34.5-37.1] ms, P<0.001). T1ρ values for the inner epidermis, stratum lamellatum and corium were significantly different (25.1 [95% CI: 23.1-27.1] ms, 44.4 [95% CI: 42.4-46.4] ms and 50.1 [95% CI: 48.1-52.1] ms, respectively, P<0.001). Histology demonstrated normal organised morphology. Proteoglycan staining was only visible in the stratum lamellatum and corium.

MAIN LIMITATIONS

Cadaveric study with frozen samples used.

CONCLUSIONS

Variation of qMRI metrics through the depth of the equine hoof wall was found. Although the highly ordered environment of collagen may contribute to T2 values, there was lack of evidence to support proteoglycan content as a major contributor of T1ρ values. It is possible T1ρ values had a greater dependence on total water content as the lowest values were seen in the epidermis. Additional research using qMRI is needed to determine mapping values in different disease states.

Evaluating sub-lethal stress from Roundup® exposure in Artemia franciscana using 1H NMR and GC-MS

Global salinization trends present an urgent need for methods to monitor aquatic ecosystem health and characterize known and emerging stressors for water bodies that are becoming increasingly saline. Environmental metabolomics methods that combine quantitative measurements of metabolite levels and multivariate statistical analysis are powerful tools for ascertaining biological impacts and identifying potential biomarkers of exposure. We propose the use of the saltwater aquatic crustacean, Artemia franciscana, as a model organism for environmental metabolomics in saltwater ecosystems. Artemia are a good choice for ecotoxicity assays and metabolomics analysis because they have a short life cycle, their hemolymph is rich in metabolites and they tolerate a wide salinity range. In this work we explore the potential of Artemia franciscana for environmental metabolomics through exposure to the broad-spectrum herbicide, glyphosate. The LC50 for a 48 h exposure of Roundup® was determined to be 237 ± 23 ppm glyphosate in the Roundup® formulation. Artemia cysts were hatched and exposed to sub-lethal glyphosate concentrations of 1.00, 10.0, 50.0, or 100 ppm glyphosate in Roundup®. We profiled 48 h old Artemia extracts using 1H NMR and GC-MS. Dose-dependent metabolic perturbation was evident for several metabolites using univariate and multivariate analyses. Metabolites significantly affected by Roundup® exposure included aspartate, formate, betaine, glucose, tyrosine, phenylalanine, gadusol, and isopropylamine. Biochemical pathway analysis with the KEGG database suggests impairment of carbohydrate and energy metabolism, folate-mediated one-carbon metabolism, Artemia molting and development, and microbial metabolism.

NMR Metabolomics as an Effective Tool To Unravel the Effect of Light Intensity and Temperature on the Composition of the Marine Microalgae Isochrysis galbana

NMR spectroscopy coupled with multivariate data analysis techniques was applied to obtain meaningful information about nontargeted metabolic changes on  Isochrysis galbana upon acclimation to different environmental conditions at indoor lab-scale. The effects of temperature (from 15 to 30 °C) and incident irradiance (from 250 to 1600 μmol m^-2 s^-1) at a constant dilution rate of 0.3 h^-1 were evaluated. High irradiances stimulated a decrease of chlorophyll a, fucoxanthin and amino acids content, and the conversion of polar fatty acids (PLs, GLs, DGDGs, SGDGs) to neutral fatty acids (saturated and unsaturated). High temperatures together with high irradiances decreased PUFAs concentration, including omega-3 fatty acids. Under low irradiance and temperature organic osmolytes (homarine, DMSP, GBT, and glycerol), and sugars (glucose, trehalose, and galactose) were also reduced.

The Jellyfish Rhizostoma pulmo (Cnidaria): Biochemical Composition of Ovaries and Antibacterial Lysozyme-like Activity of the Oocyte Lysate

Jellyfish outbreaks in marine coastal areas represent an emergent problem worldwide, with negative consequences on human activities and ecosystem functioning. However, potential positive effects of jellyfish biomass proliferation may be envisaged as a natural source of bioactive compounds of pharmaceutical interest. We investigated the biochemical composition of mature female gonads and lysozyme antibacterial activity of oocytes in the Mediterranean barrel jellyfish Rhizostoma pulmo. Chemical characterization was performed by means of multinuclear and multidimensional NMR spectroscopy. The ovaries of R. pulmo were mainly composed of water (93.7 ± 1.9% of wet weight), with organic matter (OM) and dry weight made respectively of proteins (761.76 ± 25.11 µg mg-1 and 45.7 ± 1.5%), lipids (192.17 ± 10.56 µg mg-1 and 9.6 ± 0.6%), and carbohydrates (59.66 ± 2.72 µg mg-1 and 3.7 ± 0.3%). The aqueous extract of R. pulmo gonads contained free amino acids, organic acids, and derivatives; the lipid extract was composed of triglycerides (TG), polyunsaturated fatty acids (PUFAs), diunsaturated fatty acids (DUFAs), monounsaturated fatty acids (MUFAs), saturated fatty acids (SFAs), and minor components such as sterols and phospholipids. The R. pulmo oocyte lysate exhibited an antibacterial lysozyme-like activity (mean diameter of lysis of 9.33 ± 0.32 mm corresponding to 1.21 mg/mL of hen egg-white lysozyme). The occurrence of defense molecules is a crucial mechanism to grant healthy development of mature eggs and fertilized embryos (and the reproductive success of the species) by preventing marine bacterial overgrowth. As a corollary, these results call for future investigations for an exploitation of R. pulmo biomasses as a resource of bioactive metabolites of biotechnological importance including pharmaceuticals and nutrition.

Biomarker of Aflatoxin Ingestion: ¹H NMR-Based Plasma Metabolomics of Dairy Cows Fed Aflatoxin B₁ with or without Sequestering Agents

The study applied ¹H NMR-based plasma metabolomics to identify candidate biomarkers of aflatoxin B1 (AFB₁) ingestion in dairy cows fed no sequestering agents and evaluate the effect of supplementing clay and/or a Saccharomyces cerevisiae fermentation product (SCFP) on such biomarkers. Eight lactating cows were randomly assigned to 1 of 4 treatments in a balanced 4 × 4 Latin square design with 2 squares. Treatments were: control, toxin (T; 1725 µg AFB₁/head/day), T with clay (CL; 200 g/head/day), and CL with SCFP (CL + SCFP; 35 g of SCFP/head/day). Cows in T, CL, and CL + SCFP were dosed with AFB₁ from d 26 to 30. The sequestering agents were top-dressed from d 1 to 33. On d 30 of each period, 15 mL of blood was taken from the coccygeal vessels and plasma samples were prepared by centrifugation. Compared to the control, T decreased plasma concentrations of alanine, acetic acid, leucine, arginine and valine. In contrast, T increased plasma ethanol concentration 3.56-fold compared to control. Treatment with CL tended to reduce sarcosine concentration, whereas treatment with CL + SCFP increased concentrations of mannose and 12 amino acids. Based on size of the area under the curve (AUC) of receiver operating characteristic and fold change (FC) analyses, ethanol was the most significantly altered metabolite in T (AUC = 0.88; FC = 3.56); hence, it was chosen as the candidate biomarker of aflatoxin ingestion in dairy cows fed no sequestering agent.

An integrated metabolomic and proteomic study of toxic effects of Benzo[a]pyrene on gills of the pearl oyster Pinctada martensii

Benzo[a]pyrene (BaP) is one of the most important polycyclic aromatic hydrocarbons (PAHs), which are widely present in the marine environment. Because of its teratogenic, mutagenic, and carcinogenic effects on various organisms, the toxicity of BaP is of great concern. In this study, we focused on the toxic effects of BaP (1 µg/L and 10 µg/L) on gills of the pearl oyster Pinctada martensii using combined metabolomic and proteomic approaches. At the metabolome level, the high concentration of BaP mainly caused abnormal energy metabolism, osmotic regulation and immune response marked by significantly altered metabolites in gills. At the proteome level, both concentrations of BaP mainly induced signal transduction, transcription regulation, cell growth, stress response, and energy metabolism. Overall, the research demonstrated that the combination of proteomic and metabolomic approaches could provide a significant way to elucidate toxic effects of BaP on P. martensii.

Tissue-specific metabolic responses of the pearl oyster Pinctada martensii exposed to benzo[a]pyrene

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) that is well known for its teratogenic, mutagenic and carcinogenic effects. In this study, we applied metabolomics to investigate the tissue-specific metabolic responses of the Pinctada martensii digestive glands and gills after a short-duration exposure to BaP (1 μg/L and 10 μg/L). After 72 h of exposure to BaP, the majority of metabolite changes were related to osmolytes, energy metabolites, and amino acids. BaP (1 μg/L) accelerated energy deterioration and decreased osmotic regulation, while BaP (10 μg/L) disturbed energy metabolism and increased osmotic stress in the digestive glands. Both BaP doses disturbed osmotic regulation and energy metabolism in the gills. BaP also induced neurotoxicity in both tissues. These findings demonstrated that BaP exhibited tissue-specific metabolic responses in P. martensii. The difference in these metabolite responses between the digestive glands and gills might prove to be suitable biomarkers for indicating exposure to specific marine pollutants.

Stimulation of Vibrio vulnificus Pyruvate Kinase in the Presence of Glucose to Cope With H2O2 Stress Generated by Its Competitors

The bacterial phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS) regulates a variety of cellular processes in addition to catalyzing the coupled transport and phosphorylation of carbohydrates. We recently reported that, in the presence of glucose, HPr of the PTS is dephosphorylated and interacts with pyruvate kinase A (PykA) catalyzing the conversion of PEP to pyruvate in Vibrio vulnificus. Here, we show that this interaction enables V. vulnificus to survive H₂O₂ stress by increasing pyruvate production. A pykA deletion mutant was more susceptible to H₂O₂ stress than wild-type V. vulnificus without any decrease in the expression level of catalase, and this sensitivity was rescued by the addition of pyruvate. The H₂O₂ sensitivity difference between wild-type and pykA mutant strains becomes more apparent in the presence of glucose. Fungi isolated from the natural habitat of V. vulnificus retarded the growth of the pykA mutant more severely than the wild-type strain in the presence of glucose by glucose oxidase-dependent generation of H₂O₂. These data suggest that V. vulnificus has evolved to resist the killing action of its fungal competitors by increasing pyruvate production in the presence of glucose.

Baseline levels of metabolites in different tissues of mussel Mytilus galloprovincialis (Bivalvia: Mytilidae)

The Mediterranean mussel Mytilus galloprovincialis (Lamarck 1819) is a popular shellfish commonly included in human diet and is routinely used as bioindicator in environmental monitoring programmes worldwide. Recently, metabolomics has emerged as a powerful tool both in food research and ecotoxicology for monitoring mussels' freshness and assessing the effects of environmental changes. However, there is still a paucity of data on complete metabolic baseline of mussel tissues. To mitigate this knowledge gap, similarities and differences in metabolite profile of digestive gland (DG), gills (G), and posterior adductor muscle (PAM) of aquaculture-farmed M. galloprovincialis were herein investigated by a proton nuclear magnetic resonance (¹H NMR)-based metabolomic approach and discussed considering their physiological role. A total of 44 metabolites were identified in mussel tissues and grouped in amino acids, energy metabolites, osmolytes, neurotransmitters, nucleotides, alkaloids, and miscellaneous metabolites. A PCA showed that mussel tissues clustered separately from each other, suggesting a clear differentiation in their metabolic profiles. A Venn diagram revealed that mussel DG, G and PAM shared 27 (61.36%) common metabolites, though with different concentrations. Osmolytes were found to dominate the metabolome of all tissues. The DG exhibited higher level of glutathione and carbohydrates. The G showed greater level of osmolytes and the exclusive presence of neurotransmitters, namely acetylcholine and serotonin. In PAM higher levels of energetics-related metabolites were found. Overall, findings from this study are helpful for a better understanding of mussel tissue-specific physiological functions as well as for future NMR-based metabolomic investigations of marine mussel health and safety.

Compatible osmolytes modulate mitochondrial function in a marine osmoconformer Crassostrea gigas (Thunberg, 1793)

Salinity is an important environmental factor affecting physiology of marine organisms. Osmoconformers such as marine mollusks maintain metabolic function despite changes of the osmolarity and composition of the cytosol during salinity shifts. Currently, metabolic responses to the salinity-induced changes of the intracellular milieu are not well understood. We studied the effects of osmolarity (450 vs. 900 mOsm) and compatible osmolytes (70-590 mM of taurine or betaine) on isolated gill mitochondria of a marine osmoconformer, the Pacific oyster Crassostrea gigas. Physiological concentrations of taurine enhanced mitochondrial ATP synthesis and electron transport system (ETS) capacity, increased mitochondrial coupling and stimulated the forward flux through the Complex I. Notably, the stimulatory effects of taurine were more pronounced at 900 mOsm compared to 450 mOsm. In contrast, betaine proportionally increased the rates of the mitochondrial proton leak, oxidative phosphorylation and ETS flux (with no net effect on the mitochondrial coupling) and suppressed the activity of cytochrome c oxidase in oyster mitochondria. However, the effective concentration of betaine (590 mM) was higher than typically found in bivalves, and thus betaine is not likely to affect oyster mitochondria under the physiological conditions in vivo. Our findings indicate that taurine may support the mitochondrial bioenergetics during hyperosmotic stress in oysters. Compatibility of taurine with the metabolic functions and its beneficial effects on mitochondria may have contributed to its broad distribution as an osmolyte in marine osmoconformers and might explain the earlier reports of the positive effects of taurine supplementation on energy metabolism of other organisms, including mammals.

Untargeted metabolic profiling reveals distinct patterns of thermal sensitivity in two related notothenioids

Antarctic marine ectothermal animals may be affected more than temperate species by rising temperatures due to ongoing climate change. Their specialisation on stable cold temperatures makes them vulnerable to even small degrees of warming. Thus, addressing the impacts of warming on Antarctic organisms and identifying their potentially limited capacities to respond is of interest. The objective of the study was to determine changes in metabolite profiles related to temperature acclimation. In a long-term experiment adult fish of two Antarctic sister species Notothenia rossii and Notothenia coriiceps were acclimated to 0°C and 5°C for three months. Impacts and indicators of acclimation at the cellular level were determined from metabolite profiles quantified in gill tissue extracts using nuclear magnetic resonance (NMR) spectroscopy. Furthermore, the metabolite profiles of the two con-generic species were compared. NMR spectroscopy identified 37 metabolites that were present in each sample, but varied in their absolute concentration between species and between treatments. A decrease in amino acid levels indicated an increased amino acid catabolism after incubation to 5°C. In addition, long term warming initiated shifts in organic osmolyte concentrations and modified membrane structure observed by altered levels of phospholipid compounds. Differences in the metabolite profile between the two notothenioid species can be related to their divergent lifestyles, especially their different rates of motor activity. Increased levels of the Krebs cycle intermediate succinate and a higher reduction of amino acid concentrations in warm-acclimated N. rossii showed that N. rossii is more affected by warming than N. coriiceps.

NMR Profiling of Metabolites in Larval and Juvenile Blue Mussels (Mytilus edulis) under Ambient and Low Salinity Conditions

Blue mussels (Mytilus edulis) are ecologically and economically important marine invertebrates whose populations are at risk from climate change-associated variation in their environment, such as decreased coastal salinity. Blue mussels are osmoconfomers and use components of the metabolome (free amino acids) to help maintain osmotic balance and cellular function during low salinity exposure. However, little is known about the capacity of blue mussels during the planktonic larval stages to regulate metabolites during osmotic stress. Metabolite studies in species such as blue mussels can help improve our understanding of the species’ physiology, as well as their capacity to respond to environmental stress. We used 1D ¹H nuclear magnetic resonance (NMR) and 2D total correlation spectroscopy (TOCSY) experiments to describe baseline metabolite pools in larval (veliger and pediveliger stages) and juvenile blue mussels (gill, mantle, and adductor tissues) under ambient conditions and to quantify changes in the abundance of common osmolytes in these stages during low salinity exposure. We found evidence for stage- and tissue-specific differences in the baseline metabolic profiles of blue mussels, which reflect variation in the function and morphology of each larval stage or tissue type of juveniles. These differences impacted the utilization of osmolytes during low salinity exposure, likely stemming from innate physiological variation. This study highlights the importance of foundational metabolomic studies that include multiple tissue types and developmental stages to adequately evaluate organismal responses to stress and better place these findings in a broader physiological context.

Pyruvate Kinase Inhibits Proliferation during Postnatal Cerebellar Neurogenesis and Suppresses Medulloblastoma Formation

Aerobic glycolysis supports proliferation through unresolved mechanisms. We have previously shown that aerobic glycolysis is required for the regulated proliferation of cerebellar granule neuron progenitors (CGNP) and for the growth of CGNP-derived medulloblastoma. Blocking the initiation of glycolysis via deletion of hexokinase-2 (Hk2) disrupts CGNP proliferation and restricts medulloblastoma growth. Here, we assessed whether disrupting pyruvate kinase-M (Pkm), an enzyme that acts in the terminal steps of glycolysis, would alter CGNP metabolism, proliferation, and tumorigenesis. We observed a dichotomous pattern of PKM expression, in which postmitotic neurons throughout the brain expressed the constitutively active PKM1 isoform, while neural progenitors and medulloblastomas exclusively expressed the less active PKM2. Isoform-specific Pkm2 deletion in CGNPs blocked all Pkm expression. Pkm2-deleted CGNPs showed reduced lactate production and increased SHH-driven proliferation. ¹³C-flux analysis showed that Pkm2 deletion reduced the flow of glucose carbons into lactate and glutamate without markedly increasing glucose-to-ribose flux. Pkm2 deletion accelerated tumor formation in medulloblastoma-prone ND2:SmoA1 mice, indicating the disrupting PKM releases CGNPs from a tumor-suppressive effect. These findings show that distal and proximal disruptions of glycolysis have opposite effects on proliferation, and that efforts to block the oncogenic effect of aerobic glycolysis must target reactions upstream of PKM. Cancer Res; 77(12); 3217-30. ©2017 AACR.

Natural Products Diversity of Marine Ascidians (Tunicates; Ascidiacea) and Successful Drugs in Clinical Development

This present study reviewed the chemical diversity of marine ascidians and their pharmacological applications, challenges and recent developments in marine drug discovery reported during 1994-2014, highlighting the structural activity of compounds produced by these specimens. Till date only 5% of living ascidian species were studied from <3000 species, this study represented from family didemnidae (32%), polyclinidae (22%), styelidae and polycitoridae (11-12%) exhibiting the highest number of promising MNPs. Close to 580 compound structures are here discussed in terms of their occurrence, structural type and reported biological activity. Anti-cancer drugs are the main area of interest in the screening of MNPs from ascidians (64%), followed by anti-malarial (6%) and remaining others. FDA approved ascidian compounds mechanism of action along with other compounds status of clinical trials (phase 1 to phase 3) are discussed here in. This review highlights recent developments in the area of natural products chemistry and biotechnological approaches are emphasized.

Relating metals with major cations in oyster Crassostrea hongkongensis: A novel approach to calibrate metals against salinity

Despite salinity has been well documented for its significant effects on the bioaccumulation of many trace elements in biomonitors, no calibration method has been proposed to reduce such influences. For the first time, the present study established a novel method to calibrate biomonitoring data against salinity. Relationships between trace element concentration in oyster Crassostrea hongkongensis and the biological proxy for salinity were quantified based on laboratory exposure experiments. The method was then verified by the biomonitoring data of Pearl River Estuary (PRE). Tissue concentrations of trace elements (Cu, Zn, Ag, Cd, Pb, Cr, As, Se, and Ni) and major cations (Na, Mg, K, and Ca) in oysters exposed at 4 salinities (5, 12, 20, and 28psu) and low concentrations for 6weeks were measured to establish such quantitative relationships. Tissue Na, Mg, and K could be the proxy for salinity, while Na was the best one. Negative correlations between tissue concentrations of trace elements and Na after exposure were observed for metal cations such as Cu, Zn, Ag, Cd, and Pb, while tissue As, Se, and Ni were positively correlated with Na. In PRE, salinity significantly influenced the bioaccumulation of trace elements even under the multifactor-affected field conditions. The calibration method applied to the biomonitoring of PRE was verified to be feasible, and effectively reduced the influences of salinity. Therefore, calibration against salinity could facilitate the interpretation, comparability, and analysis of biomonitoring data.

The effect of lipid extraction on carbon and nitrogen stable isotope ratios in oyster tissues: Implications for glycogen-rich species

RATIONALE

Extraction of lipids from tissues prior to carbon stable isotope analysis (SIA) has become a common practice, despite a lack of species-specific data to indicate when lipid extraction is needed. Marine invertebrates, including bivalves, are known to store carbon as glycogen and less in the form of lipids than other species, potentially reducing the need for lipid extraction even when C:N values are above 3.5, a value that previous studies suggest indicates a need for lipid extraction of animal tissues.

METHODS

We investigated the need for lipid extraction on individual tissues (adductor muscle, gut gland, gill) and whole tissue of a glycogen-storing species, the oyster Crassostrea virginica. Bulk and lipid-extracted samples were analyzed for their C and N stable isotope ratios by continuous flow isotope ratio mass spectrometry (IRMS). Samples were analyzed on a 20-20 isotope ratio mass spectrometer (PDZ Europa) after combustion in an elemental analyzer (PDZ Europa Automatic Analyzer-Gas Solid Liquid).

RESULTS

Although the C:N values for most bulk (unextracted) tissue samples were greater than 3.5, the lipid-extracted δ¹³ C values did not differ from the bulk values. Lipid extraction, however, affected δ¹⁵ N values in all tissue types except adductor muscle, indicating that separate SIA may be required when tissues are lipid extracted.

CONCLUSIONS

These data demonstrate that it is not necessary to lipid extract oyster tissues in all cases, and that C:N thresholds for lipid extraction in other species may not be reliable for organisms such as oysters that store glycogen. Our data indicate that minimizing unnecessary lipid extraction through preliminary testing will save researchers time and expense by avoiding superfluous sample handling, reducing concern over secondary effects on data quality, and reducing the costs of reagents and additional separate stable isotope analysis to ensure analytical accuracy. Copyright © 2016 John Wiley & Sons, Ltd.

Oxidative effects of the pharmaceutical drug paracetamol on the edible clam Ruditapes philippinarum under different salinities

Paracetamol, a drug with analgesic and antipyretic properties, is one of the most used substances in human therapeutics, being also frequently detected in aquatic environments. Recent studies report its toxicity towards aquatic species, but the overall amount of data concerning its effects is still scarce. Global changes, likely alterations in abiotic conditions, including salinity, can modulate the interactions of contaminants with biota, conditioning the toxicological responses elicited also by pharmaceuticals. The present article describes the oxidative toxic effects posed by paracetamol on the clam species Ruditapes philippinarum under different salinity conditions. The results demonstrated the establishment of an oxidative-based effect, with significant alteration of several parameters, such as superoxide dismutase (SOD) and the ratio of reduced/oxidized glutathione (GSH/GSSG). Water salinity influenced the response of clams exposed to different paracetamol concentrations, showing the importance of studying physiological traits under realistic test conditions, which are likely to vary in great extent as a result of climate change.

(1)H NMR metabolomic profiling of the blue crab (Callinectes sapidus) from the Adriatic Sea (SE Italy): A comparison with warty crab (Eriphia verrucosa), and edible crab (Cancer pagurus)

The metabolomic profile of blue crab (Callinectes sapidus) captured in the Acquatina lagoon (SE Italy) was compared to an autochthonous (Eriphia verrucosa) and to a commercial crab species (Cancer pagurus). Both lipid and aqueous extracts of raw claw muscle were analyzed by (1)H NMR spectroscopy and MVA (multivariate data analysis). Aqueous extracts were characterized by a higher inter-specific discriminating power compared to lipid fractions. Specifically, higher levels of glutamate, alanine and glycine characterized the aqueous extract of C. sapidus, while homarine, lactate, betaine and taurine characterized E. verrucosa and C. pagurus. On the other hand, only the signals of monounsaturated fatty acids distinguished the lipid profiles of the three crab species. These results support the commercial exploitation and the integration of the blue crab in human diet of European countries as an healthy and valuable seafood.

Key metabolites in tissue extracts of Elliptio complanata identified using (1)H nuclear magnetic resonance spectroscopy

We used (1)H nuclear magnetic resonance spectroscopy to describe key metabolites of the polar metabolome of the freshwater mussel, Elliptio complanata. Principal components analysis documented variability across tissue types and river of origin in mussels collected from two rivers in North Carolina (USA). Muscle, digestive gland, mantle and gill tissues yielded identifiable but overlapping metabolic profiles. Variation in digestive gland metabolic profiles between the two mussel collection sites was characterized by differences in mono- and disaccharides. Variation in mantle tissue metabolomes appeared to be associated with sex. Nuclear magnetic resonance spectroscopy is a sensitive means to detect metabolites in the tissues of E. complanata and holds promise as a tool for the investigation of freshwater mussel health and physiology.

Crassaostrea gigas Oyster Shell Extract Inhibits Lipogenesis via Suppression of Serine Palmitoyltransferase

Oysters are widely consumed seafood, but their shells impose a serious environmental problem. To extend the utilization of oyster shell waste, we investigated the biological role of oyster shell extract. In this study, we verified that the ethanol extract of oyster shell (EOS) contains taurine and betaine, the major components of oyster body. EOS downregulated transcription of Sptlc1 and Sptlc2 mRNA, the subunits of serine palmitoyltransferase (SPT). Suppression of SPT subunits reduced sphinganine and sphingomyelin by inhibiting de novo sphingolipid biosynthesis. Inhibition of sphingomyelin biosynthesis resulted in downregulation of lipogenic gene expression such as ACC, FAS, SCD1, and DGAT2. Consistent with inhibition of lipogenesis, cellular triglyceride levels were diminished by EOS, but cholesterol levels were not altered. Taken together, these results suggest that EOS has a lipid-lowering effect and could be applied as either a therapeutic or preventive measure for metabolic dysfunction.

Application of NMR-based metabolomics for environmental assessment in the Great Lakes using zebra mussel (Dreissena polymorpha)

Zebra mussel, Dreissena polymorpha, in the Great Lakes is being monitored as a bio-indicator organism for environmental health effects by the National Oceanic and Atmospheric Administration's Mussel Watch program. In order to monitor the environmental effects of industrial pollution on the ecosystem, invasive zebra mussels were collected from four stations-three inner harbor sites (LMMB4, LMMB1, and LMMB) in Milwaukee Estuary, and one reference site (LMMB5) in Lake Michigan, Wisconsin. Nuclear magnetic resonance (NMR)-based metabolomics was used to evaluate the metabolic profiles of the mussels from these four sites. The objective was to observe whether there were differences in metabolite profiles between impacted sites and the reference site; and if there were metabolic profile differences among the impacted sites. Principal component analyses indicated there was no significant difference between two impacted sites: north Milwaukee harbor (LMMB and LMMB4) and the LMMB5 reference site. However, significant metabolic differences were observed between the impacted site on the south Milwaukee harbor (LMMB1) and the LMMB5 reference site, a finding that correlates with preliminary sediment toxicity results. A total of 26 altered metabolites (including two unidentified peaks) were successfully identified in a comparison of zebra mussels from the LMMB1 site and LMMB5 reference site. The application of both uni- and multivariate analysis not only confirmed the variability of altered metabolites but also ensured that these metabolites were identified via unbiased analysis. This study has demonstrated the feasibility of the NMR-based metabolomics approach to assess whole-body metabolomics of zebra mussels to study the physiological impact of toxicant exposure at field sites.

Metabolomic, behavioral, and reproductive effects of the aromatase inhibitor fadrozole hydrochloride on the unionid mussel Lampsilis fasciola

Androgen-induced masculinization of female aquatic biota poses concerns for natural population stability. This research evaluated the effects of a twelve day exposure of fadrozole hydrochloride on the metabolism and reproductive status of the unionid mussel Lampsilis fasciola. Although this compound is not considered to be widespread in the aquatic environment, it was selected as a model aromatase (enzyme that converts testosterone to estradiol) inhibitor. Adult mussels were exposed to a control and 3 concentrations of fadrozole (2μg/L, 20μg/L, and 50μg/L), and samples of gill tissue were taken on days 4 and 12 for metabolomics analysis. Gills were used because of the variety of critical processes they mediate, such as feeding, ion exchange, and siphoning. Daily observed mussel behavior included female mantle display, foot protrusion, siphoning, and larval (glochidia) releases. Glochidia mortality was significantly higher in the 20μg/L treatment. Fewer conglutinate (packets of glochidia) releases were observed in the 50μg/L treatment, and mortality was highly correlated to release numbers. Foot protrusion was significantly higher in females in nearly all treatments, including the control, during the first 4days of observations. However, this sex difference was observed only in the 50μg/L treatment during the last 8days. Generally, metabolites were significantly altered in female gill tissue in the 2μg/L treatment whereas males were mostly affected only at the highest (50μg/L) treatment. Both sexes also revealed significant reductions in fadrozole-induced metabolic effects in gill tissue sampled after 12days compared to tissue sampled after 4days, indicating time-dependent mechanisms of disruptions in metabolic pathways and homeostatic processes to compensate for such disruptions.

(1)H NMR metabolomics reveals contrasting response by male and female mussels exposed to reduced seawater pH, increased temperature, and a pathogen

Human activities are fundamentally altering the chemistry of the world's oceans. Ocean acidification (OA) is occurring against a background of warming and an increasing occurrence of disease outbreaks, posing a significant threat to marine organisms, communities, and ecosystems. In the current study, (1)H NMR spectroscopy was used to investigate the response of the blue mussel, Mytilus edulis, to a 90-day exposure to reduced seawater pH and increased temperature, followed by a subsequent pathogenic challenge. Analysis of the metabolome revealed significant differences between male and female organisms. Furthermore, males and females are shown to respond differently to environmental stress. While males were significantly affected by reduced seawater pH, increased temperature, and a bacterial challenge, it was only a reduction in seawater pH that impacted females. Despite impacting males and females differently, stressors seem to act via a generalized stress response impacting both energy metabolism and osmotic balance in both sexes. This study therefore has important implications for the interpretation of metabolomic data in mussels, as well as the impact of environmental stress in marine invertebrates in general.

Metabolomic, behavioral, and reproductive effects of the synthetic estrogen 17 α-ethinylestradiol on the unionid mussel Lampsilis fasciola

The endocrine disrupting effects of estrogenic compounds in surface waters on fish, such as feminization of males and altered sex ratios, may also occur in aquatic invertebrates. However, the underlying mechanisms of action and toxicity, especially in native freshwater mussels (Order Unionoida), remain undefined. This study evaluated the effects of a 12-day exposure of 17 α-ethinylestradiol (EE2), a synthetic estrogen in oral contraceptives commonly found in surface waters, on the behavior, condition, metabolism, and reproductive status of Lampsilis fasciola. Adult mussels of both sexes were exposed to a control and two concentrations of EE2 (0 ng/L, 5 ng/L considered to be environmentally relevant, and 1,000 ng/L designed to provide a positive metabolic response), and samples of gill tissue were taken on days 4 and 12; gills were used because of the variety of critical processes they mediate, such as feeding, ion exchange, and siphoning. Observations of mussel behavior (mantle display, siphoning, and foot movement) were made daily, and condition of conglutinates (packets of eggs and/or glochidia) released by females was examined. No significant effects of EE2 on glochidia mortality, conglutinate condition, female marsupial gill condition, or mussel foot extension were observed. However, exposure to both concentrations of EE2 significantly reduced male siphoning and mantle display behavior of females. Metabolomics analyses identified 207 known biochemicals in mussel gill tissue and showed that environmentally relevant EE2 concentrations led to decreases in glycogen metabolism end products, glucose, and several essential fatty acids in females after 12 days, indicating reductions in energy reserves that could otherwise be used for growth or reproduction. Moreover, males and females showed significant alterations in metabolites involved in signal transduction, immune response, and neuromodulation. Most of these changes were apparent at 1,000 ng/L EE2, but similar metabolites and pathways were also affected at 5 ng/L EE2. Components of the extracellular matrix of gill tissue were also altered. These results demonstrate the utility of metabolomics when used in conjunction with traditional physiological and behavioral toxicity test endpoints and establish the usefulness of this approach in determining possible underlying toxicological mechanisms of EE2 in exposed freshwater mussels.

Fluxomics of the eastern oyster for environmental stress studies

The metabolism of 2-13C/15N-glycine and U-13C-glucose was determined in four tissue blocks (adductor muscle, stomach and digestive gland, mantle, and gills) of the Eastern oyster (Crassostrea virginica) using proton (1H) and carbon-13 (13C) nuclear magnetic resonance (NMR) spectroscopy. The oysters were treated in aerated seawater with three treatments (5.5 mM U-13C-glucose, 2.7 mM 2-13C/15N-glycine, and 5.5 mM U-13C-glucose plus 2.7 mM 2-13C/15N-glycine) and the relative mass balance and 13C fractional enrichments were determined in the four tissue blocks. In all tissues, glycine was metabolized by the glycine cycle forming serine exclusively in the mitochondria by the glycine cleavage system forming 2,3-13C-serine. In muscle, a minor amount of serine-derived pyruvate entered the Krebs cycle as substantiated by detection of a trace of 2,3-13C-aspartate. In all tissues, U-13C-glucose formed glycogen by glycogen synthesis, alanine by glycolysis, and glutamate and aspartate through the Krebs cycle. Alanine was formed exclusively from glucose via alanine transaminase and not glycine via alanine-glyoxylate transaminase. Based on isotopomer analysis, pyruvate carboxylase and pyruvate dehydrogenase appeared to be equal points for pyruvate entry into the Krebs cycle. In the 5.5 mM U-13C-glucose plus 2.7 mM 2-13C/15N-glycine emergence treatment used to simulate 12 h of "low tide", oysters accumulated more 13C-labeled metabolites, including both anaerobic glycolytic and aerobic Krebs cycle intermediates. The aerobic metabolites could be the biochemical result of the gaping behavior of mollusks during emergence. The change in tissue distribution and mass balance of 13C-labeled nutrients (U-13C-glucose and 2-13C/15N-glycine) provides the basis for a new quantitative fluxomic method for elucidating sub-lethal environmental effects in marine organisms called whole body mass balance phenotyping (WoMBaP).

Impact of environmental pollution on caged mussels Mytilus galloprovincialis using NMR-based metabolomics

Metabolic responses to environmental pollution, mainly related to Hg and PAHs, were investigated in mussels. Specimens of Mytilus galloprovincialis, sedentary filter-feeders, were caged in anthropogenic-impacted and reference sites along the Augusta coastline (Sicily, Italy). The gills, mainly involved in nutrient uptake, digestion and gas exchange, were selected as target organ being the first organ to be affected by pollutants. Severe alterations in gill tissue were observed in mussels from the industrial area compared with control, while gill metabolic profiles, obtained by (1)H NMR spectroscopy and analyzed by multivariate statistics, exhibited significant changes in amino acids, energy metabolites, osmolytes and neurotransmitters. Overall, the morphological changes and metabolic disturbance detected in gill tissues may suggest that the mussels transplanted to the contaminated field site were suffering from adverse environmental condition. The concurrent morphological and metabolomic investigations as applied here result effective in assessing the environmental influences on health status of aquatic organisms.

A metabolomic investigation on arsenic-induced toxicological effects in the clam Ruditapes philippinarum under different salinities

Arsenic is an important contaminant in the Bohai marine ecosystem due to the anthropogenic activities. In this work, we investigated the toxicological effects of arsenic in Ruditapes philippinarum under different seawater salinities using NMR-based metabolomics. Under normal salinity (31.1 ppt), arsenic decreased the levels of amino acids (glutamate, β-alanine, etc.), and increased the levels of betaine and fumarate. The metabolic biomarkers including decreased threonine, histidine, ATP and fumarate were found in the muscles of arsenic-treated clams under medium salinity (23.3 ppt). However, only elevated ATP and depleted succinate were detected in the arsenic-exposed clam samples under low salinity (15.6 ppt). These differential metabolic biomarkers indicated that arsenic could induce osmotic stress and disturbance in energy metabolism in clam under normal and medium salinities. However, arsenic caused only disturbance in energy metabolism in clam under low salinity. Overall, our results demonstrated that seawater salinity could influence the toxicological effects of arsenic.

Hexokinase-2-mediated aerobic glycolysis is integral to cerebellar neurogenesis and pathogenesis of medulloblastoma

Background

While aerobic glycolysis is linked to unconstrained proliferation in cancer, less is known about its physiological role. Why this metabolic program that promotes tumor growth is preserved in the genome has thus been unresolved. We tested the hypothesis that aerobic glycolysis derives from developmental processes that regulate rapid proliferation.

Methods

We performed an integrated analysis of metabolism and gene expression in cerebellar granule neuron progenitors (CGNPs) with and without Sonic Hedgehog (Shh), their endogenous mitogen. Because our analysis highlighted Hexokinase-2 (Hk2) as a key metabolic regulator induced by Shh, we studied the effect of conditional genetic Hk2 deletion in CGNP development. We then crossed Hk2 conditional knockout mice with transgenic SmoM2 mice that develop spontaneous medulloblastoma and determined changes in SmoM2-driven tumorigenesis.

Results

We show that Shh and phosphoinositide 3-kinase (PI3K) signaling combine to induce an Hk2-dependent glycolytic phenotype in CGNPs. This phenotype is recapitulated in medulloblastoma, a malignant tumor of CGNP origin. Importantly, cre-mediated ablation of Hk2 abrogated aerobic glycolysis, disrupting CGNP development and Smoothened-induced tumorigenesis. Comparing tumorigenesis in medulloblastoma-prone SmoM2 mice with and without functional Hk2, we demonstrate that loss of aerobic glycolysis reduces the aggressiveness of medulloblastoma, causing tumors to grow as indolent lesions and allowing long-term survival of tumor bearing mice.

Conclusions

Our investigations demonstrate that aerobic glycolysis in cancer derives from developmental mechanisms that persist in tumorigenesis. Moreover, we demonstrate in a primary tumor model the anti-cancer potential of blocking aerobic glycolysis by targeting Hk2.

See commentary article:http://www.biomedcentral.com/1741-7007/11/3

Metabolomic investigation of Mytilus galloprovincialis (Lamarck 1819) caged in aquatic environments

Environmental metabolomics was applied to assess the metabolic responses in transplanted mussels to environmental pollution. Specimens of Mytilus galloprovincialis, sedentary filter-feeders, were caged in anthropogenic-impacted and reference sites along the Augusta coastline (Sicily, Italy). Chemical analysis revealed increased levels of PAHs in the digestive gland of mussels from the industrial area compared with control, and marked morphological changes were also observed. Digestive gland metabolic profiles, obtained by 1H NMR spectroscopy and analyzed by multivariate statistics, showed changes in metabolites involved in energy metabolism. Specifically, changes in lactate and acetoacetate could indicate increased anaerobic fermentation and alteration in lipid metabolism, respectively, suggesting that the mussels transplanted to the contaminated field site were suffering from adverse environmental condition. The NMR-based environmental metabolomics applied in this study results thus in it being a useful and effective tool for assessing environmental influences on the health status of aquatic organisms.

Proteomic research in bivalves: towards the identification of molecular markers of aquatic pollution

Biomonitoring of aquatic environment and assessment of ecosystem health play essential roles in the development of effective strategies for the protection of the environment, human health and sustainable development. Biomarkers of pollution exposure have been extensively utilized in the last few decades to monitor the health of organisms and hence assess environmental status. However, the use of single biomarkers against biotic or abiotic stressors may be limited by the lack of sensitivity and specificity. Therefore, more recently, the search for novel biomarkers has been focused on the application of OMICS methodologies. Environmental proteomics focuses on the analysis of an organism's proteome and the detection of changes in the level of individual proteins/peptides in response to environmental stressors. Proteomics can provide a more robust approach for the assessment of environmental stress and therefore exposure to pollutants. This review aims to summarize the proteomic research in bivalves, a group of sessile and filter feeding organisms that play an important function as "sentinels" of the aquatic environment. A description of the main proteomic methodologies is provided. The current knowledge in bivalves' toxicology, achieved with proteomics, is reported describing the main biochemical markers identified. A brief discussion regarding future challenges in this area of research emphasizing the development of more descriptive gene/protein databases that could support the OMICs approaches is presented.

Expression of candidate genes related to metabolism, immunity and cellular stress during massive mortality in the American oyster Crassostrea virginica larvae in relation to biochemical and physiological parameters

Quantification of mRNA of genes related to metabolism, immunity and cellular stress was examined in relation to a massive mortality event during the culture of American oyster larvae, Crassostrea virginica which was probably, in regard to previous microbiological analysis, induced by Vibrio infection. To document molecular changes associated with the mortality event, mRNA levels were compared to biochemical and physiological data, previously described in a companion paper. Among the 18 genes studied, comparatively to the antibiotic control, 10 showed a lower relative gene expression when the massive mortality occurred. Six of them are presumed to be related to metabolism, corroborating the metabolic depression associated with the mortality event suggested by biochemical and physiological analyses. Relationships between the regulation of antioxidant enzyme activities, lipid peroxidation, and the mRNA abundance of genes linked to oxidative stress, cytoprotection, and immune response are also discussed. Finally, we observed an increase in the transcript abundance of two genes involved in apoptosis and cell regulation simultaneously with mortality, suggesting that these processes might be linked.