Microalgae as a safe food source for animals: nutritional characteristics of the acidophilic microalga Coccomyxa onubensis.

BACKGROUND: Edible microalgae are marine or fresh water mesophilic species. Although the harvesting of microalgae offers an abundance of opportunities to the food and pharmaceutical industries, the possibility to use extremophilic microalgae as a food source for animals is not well-documented. OBJECTIVE: We studied the effects of dietary supplementation of a powdered form of the acidophilic microalga Coccomyxa onubensis on growth and health parameters of laboratory rats. METHOD: Four randomly organized groups of rats (n=6) were fed a standard diet (Diet 1, control) or with a diet in which 0.4% (Diet 2), 1.25% (Diet 3), or 6.25% (Diet 4) (w/w) of the standard diet weight was substituted with dried microalgae powder, respectively. The four groups of animals were provided ad libitum access to feed for 45 days. RESULTS: C. onubensis biomass is rich in protein (44.60% of dry weight) and dietary fiber (15.73%), and has a moderate carbohydrate content (24.8%) and a low lipid content (5.4%) in which polyunsaturated fatty acids represent 65% of the total fatty acid. Nucleic acids are present at 4.8%. No significant difference was found in growth rates or feed efficiency ratios of the four groups of rats. Histological studies of liver and kidney tissue revealed healthy organs in control and C. onubensis-fed animals, while plasma hematological and biochemical parameters were within healthy ranges for all animals. Furthermore, animals fed a microalgae-enriched diet exhibited a statistically significant decrease in both blood cholesterol and triglyceride levels. The blood triglyceride content and very low density lipoprotein-cholesterol levels decreased by about 50% in rats fed Diet 4. CONCLUSIONS: These data suggest that C. onubensis may be useful as a food supplement for laboratory animals and may also serve as a nutraceutical in functional foods. In addition, microalgae powder-supplemented diets exerted a significant hypocholesterolemic and hypotriglyceridemic effect in animals.

Environmental metabolomics: Biological markers for metal toxicity.

Environmental metabolomics is an emerging field referred to the application of metabolomics to characterize the interactions of living organisms with their environment. In this sense, the importance of monitoring the effects of toxic metals on living organisms has increased as a consequence of natural changes and anthropogenic activities that have led to an increase of toxic metal levels in terrestrial and aquatic ecosystems. For this purpose, the use of metabolomics based on MS to study metal toxicity is gaining importance in recent years. Environmental metabolomics can be used to: discover the mode of action (MOA) of toxic metals through controlled laboratory experiments; evaluate toxicity (biological adverse response to a substance), that may be useful in risk assessment; and develop new biomarkers (based in metabolome shifts discovered through controlled laboratory experiments) that may be applied in environmental biomonitoring (environmental realistic scenario). In this review, it is discussed how metabolomics based on MS can be applied to study metal toxicity, considering the most important hallmarks related to metabolomic experiments.

Use of elemental and molecular-mass spectrometry to assess the toxicological effects of inorganic mercury in the mouse Mus musculus.

The biochemical response of mice (Mus musculus) to acute subcutaneous inorganic-mercury exposure was assessed over a 14-day period by analyzing cytosolic extracts of the liver, the kidneys, and blood plasma. Integrated metallomic and metabolomic approaches using elemental and molecular-mass spectrometry were used to obtain comprehensive insight into the toxicological effects of mercury regarding its distribution and possible perturbation of metabolic pathways. The metallomic approach involved the use of size-exclusion chromatography (SEC) coupled with multiaffinity chromatography inductively coupled plasma-mass spectrometry (ICP-MS) and isotopic-dilution analysis. The metabolomic approach involved the direct infusion of polar and lipophilic tissue extracts into a mass spectrometer (DIMS) in the positive and negative acquisition mode (ESI+and ESI-). The use of SEC-ICP-MS enabled us to detect changes in the metalloproteome in the liver and the kidneys during the exposure period, and revealed that interactions between Hg and endogenous Cu and Zn adversely affected the homeostasis of these essential metals. The detection of an Hg-Se detoxification product in mouse plasma substantiated the known interaction between Hg and Se in mammals. Use of DIMS in conjunction with partial-least-squares discriminant analysis (PLS-DA) uncovered time-dependent changes of endogenous metabolites over time, corroborated by histopathology investigation of specific mouse tissues. The perturbations of endogenous metabolic profiles were explained in terms of the adverse effect of mercury on energy metabolism (e.g. glycolysis, Krebs cycle), the degradation of membrane phospholipids (apoptosis), and increased levels of specific lipids in plasma. In summary, use of an SEC-ICP-MS-based metallomics approach in conjunction with molecular-mass-spectrometry-based metabolomics is revealed as a promising strategy to more comprehensively investigate the toxicological effects of harmful environmental pollutants and xenobiotics.

Omics technologies and their applications to evaluate metal toxicity in mice M. spretus as a bioindicator.

Metals are important components of living organisms since many biological functions critically depend on their interaction with some metal in the cell. However, human activities have increased toxic metal levels in the terrestrial and aquatic ecosystems affecting living organisms. The impact of metals on cellular metabolism and global homeostasis has been traditionally assessed in free-living organisms by using conventional biomarkers; however, to obtain a global vision of metal toxicity mechanisms and the responses that metals elicit in the organisms, new analytical methodologies are needed. We review the use of omics approaches to assess the response of living organisms under metal stress illustrating the possibilities of different methodologies on the basis of our previous results. Most of this research has been based on free-living mice Mus spretus, a conventional bioindicator used to monitor metal pollution in Doñana National Park (DNP) (SW Spain), which is an important European biological reserve for migrating birds affected by agricultural, mining and industrial activities. The benefits of using omic techniques such as heterologous microarrays, proteomics methodologies (2-DE, iTRAQ®), metallomics, ionomics or metabolomics has been remarked; however, the complexity of these areas requires the integration of omics to achieve a comprehensive assessment of their environmental status. This article is part of a Special Issue entitled: Environmental and structural proteomics. BIOLOGICAL SIGNIFICANCE: This work presents new contributions in the study of environmental metal pollution in terrestrial ecosystems using Mus spretus mice as bioindicator in Doñana National Park (SW Spain) and surroundings. In addition, it has been demonstrated that the integration of omics multi-analytical approaches provides a very suitable approach for the study of the biological response and metal interactions in exposed and free-living mice (Mus musculus and Mus spretus, respectively) under metal pollution.

A combination of metallomics and metabolomics studies to evaluate the effects of metal interactions in mammals. Application to Mus musculus mice under arsenic/cadmium exposure.

Arsenic and cadmium are toxic metals of environmental significance with harmful effects on man. To study the toxicological and biochemical effects of arsenic/cadmium in mammals a combined metallomic and metabolomic approach has been developed, complemented with the measurement of biochemical parameters in blood and histopathological evaluation of liver injury in mice Mus musculus under exposure to both xenobiotics. Size-exclusion chromatography (SEC) was combined with affinity chromatography (AF) and ICP-MS detection using species unspecific isotopic dilution analysis (SUID) to characterize the biological effects of As/Cd on selenium containing proteins in the bloodstream of exposed mice. On the other hand, both direct infusion mass spectrometry (DIMS) and gas chromatography-mass spectrometry (GC-MS) provided information about changes in metabolites caused by metals. The results show that As/Cd exposure produces interactions in the distribution of both toxics between organs and plasma of mice and antagonistic interactions with selenium containing proteins in the bloodstream. Interplay with essential metabolic pathways, such as energy metabolism and breakdown of membrane phospholipids were observed, which are more pronounced under As/Cd exposure. In addition, heavy metal and metalloid causes differential liver injury, manifested by steatosis (non-alcoholic fatty liver disease, NAFLD) and infiltration of blood cells into the space of Disse. BIOLOGICAL SIGNIFICANCE: This work presents new contributions in the study of arsenic/cadmium interactions in mice Mus musculus under controlled exposure. With the combination of metallomic and metabolomic approaches the traffic of As and Cd from liver to kidney by means of blood was observed and excretion of As (as arsenic metabolites) or Cd (as MTCd) is inhibited with the simultaneous administration of As/Cd, and these toxic elements have important influence in the levels of seleno-proteins in the plasma. In addition, the metabolomic approach reveals inhibition of different metabolic cycles such as tricarboxylic acid and phospholipid degradation that causes membrane damage and apoptosis that is histopathologically confirmed. This article is part of a Special Issue entitled: Environmental and structural proteomics.

Heterologous microarray analysis of transcriptome alterations in Mus spretus mice living in an industrial settlement.

This work demonstrates the successful application of a commercial oligonucleotide microarray containing Mus musculus whole-genome probes to assess the biological effects of an industrial settlement on inhabitant Mus spretus mice. The transcriptomes of animals in the industrial settlement contrasted with those of specimens collected from a nearby protected ecosystem. Proteins encoded by the differentially expressed genes were broadly categorized into six main functional classes. Immune-associated genes were mostly induced and related to innate and acquired immunity and inflammation. Genes sorted into the stress-response category were mainly related to oxidative-stress tolerance and biotransformation. Metabolism-associated genes were mostly repressed and related to lipid metabolic pathways; these included genes that encoded 11 of the 20 cholesterol biosynthetic pathway enzymes. Crosstalk between members of different functional categories was also revealed, including the repression of serine-protease genes and the induction of protease-inhibitor genes to control the inflammatory response. Absolute quantification of selected transcripts was performed via RT-PCR to verify the microarray results and assess interindividual variability. Microarray data were further validated by immunoblotting and by cholesterol and protein-thiol oxidation level determinations. Reported data provide a broad impression of the biological consequences of residing in an industrial area.