Phosphate Uptake and Its Relation to Arsenic Toxicity in Lactobacilli.

The use of probiotic lactobacilli has been proposed as a strategy to mitigate damage associated with exposure to toxic metals. Their protective effect against cationic metal ions, such as those of mercury or lead, is believed to stem from their chelating and accumulating potential. However, their retention of anionic toxic metalloids, such as inorganic arsenic, is generally low. Through the construction of mutants in phosphate transporter genes (pst) in Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains, coupled with arsenate [As(V)] uptake and toxicity assays, we determined that the incorporation of As(V), which structurally resembles phosphate, is likely facilitated by phosphate transporters. Surprisingly, inactivation in Lc. paracasei of PhoP, the transcriptional regulator of the two-component system PhoPR, a signal transducer involved in phosphate sensing, led to an increased resistance to arsenite [As(III)]. In comparison to the wild type, the phoP strain exhibited no differences in the ability to retain As(III), and there were no observed changes in the oxidation of As(III) to the less toxic As(V). These results reinforce the idea that specific transport, and not unspecific cell retention, plays a role in As(V) biosorption by lactobacilli, while they reveal an unexpected phenotype for the lack of the pleiotropic regulator PhoP.

Arsenic speciation in cooked food and its bioaccessible fraction using X-ray absorption spectroscopy.

Thermal processing or the digestion process can alter the forms of arsenic (As) present in food. Identification of As species is necessary to accurately determine the risk associated with food consumption. X-ray absorption near-edge structure (XANES) was used to investigate As species in rice, asparagus, and garlic boiled in water containing As(V), and in their bioaccessible fractions (solubilized As after gastrointestinal digestion). The XANES analysis revealed the presence of As(III) (11871.5 eV) or As(III)-S [As(III)-Cys, 11869.6 eV] solution in the cooked foods and in their bioaccessible fractions. The percentage of trivalent species (12-55%) followed the order asparagus ≫ rice ≈ garlic. In the asparagus and garlic samples, part of the As(V) (tetrahedral form) [11875 eV] that had been added appeared in the form of an octahedral As(V) compound [As(V)-glycerol, 11876 eV]. All these changes could considerably modify the risk associated with ingestion of As-contaminated food.

Toxic trace elements in dried mushrooms: Effects of cooking and gastrointestinal digestion on food safety.

Mushrooms can accumulate toxic trace elements. The objectives of the present study are to evaluate levels of mercury, cadmium, lead, and arsenic in dried mushrooms, to determine the effect of cooking on the contents of these elements, and to evaluate their bioaccessibility in the mushrooms ready for consumption. The results showed that Hg levels in Amanita ponderosa, Boletus edulis, Marasmius oreades, and Tricholoma georgii, as well as Cd levels in some samples of Amanita caesarea and T. georgii, exceeded the legislated limits. Cooking significantly reduced the levels of As (26-72%), whereas the reduction in levels of Hg, Cd, and Pb was much lower. However, the bioaccessibility of As (63-81%) was higher than the values obtained for the metals (<40%). Taking the effects of cooking and gastrointestinal digestion into account gives a more realistic estimate of the risk associated with the consumption of mushrooms.

Dietary Compounds To Reduce In Vivo Inorganic Arsenic Bioavailability.

It is estimated that approximately 200 million people are exposed to arsenic levels above the World Health Organization provisional guideline value, and various agencies have indicated the need to reduce this exposure. In view of the difficulty of removing arsenic from water and food, one alternative is to reduce its bioavailability (the amount that reaches the systemic circulation after ingestion). In this study, dietary components [glutathione, tannic acid, and Fe(III)] were used to achieve this goal. As(III) or As(V) (1 mg/kg body weight) was administered daily to BALB/c mice, along with the dietary components, for 15 days. The results confirm the efficacy of Fe(III) and glutathione as reducers of arsenic bioavailability and tissue accumulation. Also, these treatments did not result in reductions of Ca, K, P, and Fe contents in the liver. These data suggest that use of these two compounds could be part of valid strategies for reducing inorganic arsenic exposure in chronically exposed populations.

Dietary compounds as modulators of metals and metalloids toxicity.

A large part of the population is exposed to metals and metalloids through the diet. Most of the in vivo studies on its toxicokinetics and toxicity are conducted by means of exposure through drinking water or by intragastric or intraperitoneal administration of aqueous standards, and therefore they do not consider the effect of the food matrix on the exposure. Numerous studies show that some components of the diet can modulate the toxicity of these food contaminants, reducing their effect on a systemic level. Part of this protective role may be due to a reduction of intestinal absorption and subsequent tissue accumulation of the toxic element, although it may also be a consequence of their ability to counteract the toxicity directly by their antioxidant and/or anti-inflammatory activity, among other factors. The present review provides a compilation of existing information about the effect that certain components of the diet have on the toxicokinetics and toxicity of the metals and metalloids of greatest toxicological importance that are present in food (arsenic, cadmium, lead, and mercury), and of their most toxic chemical species.

Influence of Physiological Gastrointestinal Parameters on the Bioaccessibility of Mercury and Selenium from Swordfish.

Swordfish tend to accumulate mercury (Hg), but they are rich in selenium (Se), an element that can counteract the toxic effects of Hg. The aim of the present study was to evaluate the concentrations and bioaccessibility of Hg and Se in cooked swordfish and to identify the digestion parameters (pH, residence time, and enzyme concentrations) that may influence their bioaccessibility. The Hg concentrations ranged between 0.17 and 2.82 mg/kg wet weight (ww) and the bioaccessibility between 14 and 92%. The range for Se concentrations was narrower (0.29-1.17 mg/kg ww), with a bioaccessibility that was generally greater than that of Hg (59-103%). Most of the solubilization took place in the gastric step, where acidic pH and the increase in the pepsin concentration led to greater bioaccessibility, especially for Hg. In the intestinal stage, the most notable effect was the decrease in the bioaccessibility of Hg in the presence of bile salts.

Dietary Strategies To Reduce the Bioaccessibility of Arsenic from Food Matrices.

The main route of exposure to arsenic (As) is the consumption of water and foods, in which the forms with greatest toxicity are inorganic As and dimethylarsinic acid, DMA(V). The objective of this study was to search for dietary components that reduce the bioaccessibility of As from food and water, in order to reduce the amount of As available for absorption. For this purpose, 35 compounds were assayed by use of a static in vitro model of gastrointestinal digestion. Sulfates of Fe(II) and Fe(III) reduced the solubility of inorganic As (86-99%) and DMA(V) in aqueous solution (40-66%). This reduction was also observed in rice (100%) and seaweed (60%). Aluminum, titanium, and tannic acid also reduced the bioaccessibility of As from food (42-70%). These data show that the use of dietary components may be a good strategy to reduce the entry of As into systemic circulation.

Quantification of fluoride in food by microwave acid digestion and fluoride ion-selective electrode.

To quantify fluoride in food it is necessary to extract the fluoride from the matrix. Dry ashing (alkali fusion) and facilitated diffusion are the methods most commonly used, but their application requires lengthy treatments. The present study proposes the use of a microwave oven and 7 mol/L nitric acid for simple, rapid digestion of foods for fluoride analysis. The analyte is subsequently quantified by fluoride ion-selective electrode. The various steps of the method were optimized and an in-house validation was performed. The limit of quantification (0.130 mg/kg), trueness (92%), recovery (84-101%), and precision (1-8%) were determined. These analytical characteristics are satisfactory and show the suitability of the method for analysis of fluoride in foods of various kinds. The method's ease of application and the use of equipment normally found in food analysis laboratories may help to further increase research on fluoride concentrations in foods consumed by the population.

Total arsenic, inorganic arsenic, lead and cadmium contents in edible seaweed sold in Spain.

Total arsenic, inorganic arsenic, lead and cadmium contents were determined in 112 samples of seaweed preparations sold in Spain (seaweed packed in plastic or cardboard box, seaweed in the form of tablets and concentrates, foods containing seaweed, and canned seaweed). The concentration ranges found, expressed in mg/kg, dry weight, were: total As (0.031-149), inorganic As (<0.014-117), Pb (<0.050-12.1) and Cd (<0.003-3.55). For all the contaminants there were failures to comply with legislated values. In particular, all the samples of Hizikia fusiforme exceeded the inorganic As limit established in some countries, and a considerable number of species exceeded the Cd limit set by international regulations. With respect to food safety, consumption of 3 g/day of the samples analysed could represent up to 15% of the respective Tolerable Daily Intakes (TDI) established by the WHO. The situation is especially alarming for intake of inorganic As from H. fusiforme, which can be three times the TDI established.

Organoarsenical species contents in fresh and processed seafood products.

A study was carried out to determine organic species of arsenic in the main varieties of seafood consumed in the Basque country (Spain). The concentrations of arsenobetaine (AB), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenocholine (AC), and tetramethylarsonium ion (TMA(+)) in 64 samples corresponding to different food items are presented. The study provides information about a possible distribution pattern of organoarsenical species in seafood products. AB was detected in all of the samples [0.3-104.1 microg g(-1) dry weight (dw)]. DMA was detected in all of the samples except squid and salted cod (0.027-1.757 microg g(-1) dw). MMA was detected only in certain fatty fish (0.004-0.028 microg g(-1) dw) and bivalves (0.031-0.047 microg g(-1) dw). AC was only present in some samples of lean fish (0.014-0.089 microg g(-1) dw), and TMA(+) was detected only in anchovy (0.039-0.169 microg g(-1) dw) and crustaceans (0.044-0.966 microg g(-1) dw).