Cadmium absorption and retention by rats fed durum wheat (Triticum turgidum L. var. durum) grain

Rice hull insoluble dietary fiber alleviated experimental colitis induced by low dose of dextran sulfate sodium in cadmium-exposed mice

Cadmium (Cd), an important toxic environmental pollutant, can invade the gastrointestinal tract and induce the occurrence of gastrointestinal diseases. This study aimed to investigate the protective effect of rice hull insoluble dietary fiber (RHF) on Cd-promoted colitis induced by low dose of dextran sulfate sodium. Administration of RHF attenuated inflammation by limiting Cd accumulation and regulating intestinal immune homeostasis in colitis mice with Cd exposure. RHF could maintain the structure of the gut barrier by increasing mucin secretion and intestinal tight connectivity in mice. Subsequently, RHF repressed the colonic inflammation mediated by the TLR4/MyD88/NF-κB pathway, and inhibited the transcription regulation of inflammatory cytokines. Furthermore, RHF showed an enhancement of a variety of probiotics, such as Eubacterium and Faecalibaculum. RHF also inhibited the growth of pathogenic bacteria, including Erysipelatoclostridium, Helicobacter and Bacteroides. The growth of beneficial bacteria was also accompanied by reversing the decline in short-chain fatty acids, supporting the initial potentiality of RHF as a prebiotic in cases of damage by Cd exposure in colitis mice. Importantly, RHF also remained resistant to Cd toxicity in colitis mice when the gut microbiota was depleted by antibiotics. We suggest that RHF could be used as a novel dietary supplement strategy against Cd-exacerbated colitis.

Probiotics and gut microbiome - Prospects and challenges in remediating heavy metal toxicity

The gut microbiome, often referred to as "super organ", comprises up to a hundred trillion microorganisms, and the species diversity may vary from person to person. They perform a decisive role in diverse biological functions related to metabolism, immunity and neurological responses. However, the microbiome is sensitive to environmental pollutants, especially heavy metals. There is continuous interaction between heavy metals and the microbiome. Heavy metal exposure retards the growth and changes the structure of the phyla involved in the gut microbiome. Meanwhile, the gut microbiome tries to detoxify the heavy metals by altering the physiological conditions, intestinal permeability, enhancing enzymes for metabolizing heavy metals. This review summarizes the effect of heavy metals in altering the gut microbiome, the mechanism by which gut microbiota detoxifies heavy metals, diseases developed due to heavy metal-induced dysbiosis of the gut microbiome, and the usage of probiotics along with advancements in developing improved recombinant probiotic strains for the remediation of heavy metal toxicity.

Gut microbiota: A target for heavy metal toxicity and a probiotic protective strategy

There is growing epidemiological evidence that heavy metals (HMs) may contribute to the progression of various metabolic diseases and that the etiology and progression of these diseases is partly due to HM-induced perturbations of the gut microbiota. Importantly, the gut microbiota are the first line of defense against the toxic effects of HMs, and there is a bidirectional relationship between the two. Thus, HM exposure alters the composition and metabolic profile of the gut microbiota at the functional level, and in turn, the gut microbiota alter the uptake and metabolism of HMs by acting as a physical barrier to HM absorption and by altering the pH, oxidative balance, and concentrations of detoxification enzymes or proteins involved in HM metabolism. Moreover, the gut microbiota can affect the integrity of the intestinal barrier, which may also in turn affect the absorption of HMs. Specifically, probiotic have been shown to reduce the absorption of HMs in the intestinal tract via the enhancement of intestinal HM sequestration, detoxification of HMs in the gut, changing the expression of metal transporter proteins, and maintaining the gut barrier function. This review is a summary of the bidirectional relationship between HMs and gut microbiota and of the probiotic-based protective strategies against HM-induced gut dysbiosis, with reference to strategies used in the food industry or for medically alleviating HM toxicity.

Selenium and zinc protections against metal-(loids)-induced toxicity and disease manifestations: A review

Metals are ubiquitous in the environment due to huge industrial applications in the form of different chemicals and from extensive mining activities. The frequent exposures to metals and metalloids are crucial for the human health. Trace metals are beneficial for health whereas non-essential metals are dangerous for the health and some are proven etiological factors for diseases including cancers and neurological disorders. The interactions of essential trace metals such as selenium (Se) and zinc (Zn) with non-essential metals viz. lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) in biological system are very critical and complex. A huge number of studies report the protective role of Se and Zn against metal toxicity, both in animal and cellular levels, and also explain the numerous mechanisms involved. However, it has been considered that a tiny dyshomeostasis in the metals/trace metals status in biological system could induce severe deleterious effects that can manifest to numerous diseases. Thus, in this particular review, we have demonstrated the critical protection mechanism/s of Se and Zn against Cd, Pb, As and Hg toxicity in a one by one manner to clarify the up-to-date findings and perspectives. Furthermore, biomolecular consequences are comprehensively presented in light of particular cellular/biomolecular events which are somehow linked to a subsequent disease. The analyzed reports support significant protection potential of Se and Zn, either alone or in combination with other agents, against each of the abovementioned non-essential metals. However, Se and Zn are still not being used as detoxifying agents due to some unexplained reasons. We hypothesized that Se could be a potential candidate for detoxifying As and Hg regardless of their chemical speciations, but requires intensive clinical trials. However, particularly Zn-Hg interaction warrants more investigations both in animal and cellular level.

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.

Toxic trace elements at gastrointestinal level

Many trace elements are considered essential [iron (Fe), zinc (Zn), copper (Cu)], whereas others may be harmful [lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As)], depending on their concentration and chemical form. In most cases, the diet is the main pathway by which they enter our organism. The presence of toxic trace elements in food has been known for a long time, and many of the food matrices that carry them have been identified. This has led to the appearance of legislation and recommendations concerning consumption. Given that the main route of exposure is oral, passage through the gastrointestinal tract plays a fundamental role in their entry into the organism, where they exert their toxic effect. Although the digestive system can be considered to be of crucial importance in their toxicity, in most cases we do not know the events that occur during the passage of these elements through the gastrointestinal tract and of ascertaining whether they may have some kind of toxic effect on it. The aim of this review is to summarize available information on this subject, concentrating on the toxic trace elements that are of greatest interest for organizations concerned with food safety and health: Pb, Cd, Hg and As.

Effect of wheat bran and flaxseed on cadmium effects and retention in rats

Dietary fiber can affect cadmium (Cd) absorption and toxicity, but the effect appears to depend on the type of dietary fiber. The aim of the present study was to compare the effect of dietary sources containing distinct amounts of soluble and insoluble fiber on Cd absorption, accumulation and toxicity in growing rats. The absorption of essential macrominerals (Ca, P and Mg) was also evaluated. Animals received a nutritionally balanced diet with cellulose (cel - control), wheat bran or flaxseed as the fiber source with 0 or 50 mg Cd kg(-1) diet, during 30 days. Cd exposure reduced body weight gain, feed efficiency ratio, epididymal fat relative weight and liver relative weight, and increased plasma alanine aminotransferase activity in all fiber groups. The apparent Cd absorption was similar among Cd-groups, but the flax-Cd group had a higher hepatic and renal Cd concentration. Cd decreased the absorption of Ca and P, and increased Mg absorption in the wheat bran and flaxseed groups, but not in the cel group. Although the different fiber sources investigated had no effect on Cd toxicity, the major soluble fiber source, flaxseed, increased Cd retention. Thus, caution should be taken in the intake of flaxseed by Cd-exposed populations.

Influence of cereal bran supplement on cadmium effects in growing rats

Strategies to diminish cadmium (Cd) absorption are highly desirable especially where Cd exposure due to environmental contamination is still inevitable. Cd toxicity may be influenced by dietary components, such as fiber and minerals. Multimixtures are low-cost cereal bran supplements used in Brazil and in other countries to counteract malnutrition in low-income populations. This study was aimed at evaluating whether multimixture would reduce Cd effects in young rats. Animals received a diet with or without the multimixture plus 0, 5, or 25 mg Cd/kg (control, Cd-5, and Cd-25 groups) during 30 days. The Cd-5 groups were similar to control groups in all parameters analyzed, except in the higher renal Cd concentration. However, the Cd-25 groups had lower biological growth parameters and renal delta-aminolevulinate dehydratase activity, besides higher renal Cd concentration and plasma alanine aminotransferase activity compared to the controls. The multimixture did not prevent Cd effects in the Cd-25 group, but caused a small reduction in renal Cd concentration in the Cd-5 group. Although this multimixture was ineffective to prevent Cd effects at the higher concentration, it seemed to reduce Cd accumulation at the lower Cd dietary concentration, which is similar to levels of human exposure in some polluted areas.

Geochemistry in the modern soil survey program

Elemental analysis has played an important role in the characterization of soils since inception of the soil survey in the US. Recent efforts in analysis of trace and major elements (geochemistry) have provided necessary data to soil survey users in a variety of areas. The first part of this paper provides a brief overview of elemental sources, forms, mobility, and bioavailability; critical aspects important to users of soil survey geochemical data for appropriate use and interpretations. Examples are provided based on data gathered as part of the US soil survey program. The second part addresses the organization of sample collection in soil survey and how soil surveys are ideally suited as a sampling strategy for soil geochemical studies. Geochemistry is functional in characterization of soil types, determining soil processes, ecological evaluation, or issues related to soil quality and health, such as evaluating suitability of soils for urban or agricultural land use. Applications of geochemistry are on-going across the US and are documented herein. This analytical direction of soil survey complements historic efforts of the National Cooperative Soil Survey Program and addresses the increasing need of soil survey users for data that assists in understanding the influence of human activities on soil properties.

Maternal flaxseed diet during pregnancy or lactation increases female rat offspring's susceptibility to carcinogen-induced mammary tumorigenesis

Flaxseed contains several dietary components that have been linked to low breast cancer risk; i.e., n-3 polyunsaturated fatty acids (PUFAs), lignans and fiber, but it also contains detectable levels of cadmium, a heavy metal that activates the estrogen receptor (ER). Since estrogenic exposures early in life modify susceptibility to develop breast cancer, we wondered whether maternal dietary intake of 5% or 10% flaxseed during pregnancy or lactation (between postpartum days 5 and 25) might affect 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumorigenesis in the rat offspring. Our data indicated that both in utero and postnatal 5% and 10% flaxseed exposures shortened mammary tumor latency, and 10% flaxseed exposure increased tumor multiplicity, compared to the controls. Further, when assessed in 8-week-old rats, in utero 10% flaxseed exposure increased lobular ER-alpha protein levels, and both in utero and postnatal flaxseed exposures dose-dependently reduced ER-beta protein levels in the terminal end buds (TEBs) lobules and ducts. Exposures to flaxseed did not alter the number of TEBs or affect cell proliferation within the epithelial structures. In a separate group of immature rats that were fed 5% defatted flaxseed diet (flaxseed source different than in the diets fed to pregnant or lactating rats) for 7 days, cadmium exposure through the diet was six-fold higher than allowed for humans by World Health Organization, and cadmium significantly accumulated in the liver and kidneys of the rats. It remains to be determined whether the increased mammary cancer in rats exposed to flaxseed through a maternal diet in utero or lactation was caused by cadmium present in flaxseed, and whether the reduced mammary ER-beta content was causally linked to increased mammary cancer risk among the offspring.