Bioavailability of arsenic, cadmium, lead and mercury as measured by intestinal permeability

Bioaccessibility of lead and cadmium in soils around typical lead-acid power plants and their effect on gut microorganisms

Potentially toxic elements (Pb and Cd) contamination of soil can adversely affect human health. Moreover, these metal ions interact with the gut microbiota after entering the human digestive system. Based on the physiologically based extraction test and the simulator of human intestinal microbial ecosystem, the bioaccessibility of Pb and Cd in soils contaminated with lead-acid power plants was assessed. The gastric stage exhibited the greatest average bioaccessibility of lead and cadmium (63.39% and 57.22%), followed by the small intestinal stage (6.86% and 36.29%); due to gut microorganisms, the bioaccessibility of lead and cadmium was further reduced in the colon stage (1.86% and 4.22%). Furthermore, to investigate soil contamination's effects on gut microbes, 16S rRNA high-throughput sequencing was used to identify the gut microbial species after the colon period. Due to Pb and Cd exposure, the relative abundance of Firmicutes and unidentified_Bacteria decreased, while the relative abundance of Proteobacteria, Synergistota, and Bacteroidota increased. The relationship between environmental factors and the number of microbial species in the gut was also examined using Spearman correlation analysis. Pb and Cd exposure has been found to affect the composition and structure of the gut microbiota.

Cadmium promotes colorectal cancer metastasis through EGFR/Akt/mTOR signaling cascade and dynamics

Cadmium (Cd) is a hazardous environmental heavy metal with a prolonged biological half-life. Due to the main route of foodborne exposure, the intestinal tract is particularly vulnerable to Cd-induced toxicity. However, the chronic toxicity and underlying mechanisms of Cd in intestinal diseases, including colorectal cancer (CRC), still remain vague. Herein, we aim to investigate the long-term effects of Cd exposure on CRC development and the key signaling event. Our findings indicate that chronic and low-dose exposure to Cd promoted the invasion and metastasis capability of CRC cells in vitro and in mice, with a marginal increase in cell growth. The expression of cell junction-related genes was down-regulated while those molecules that facilitate cell mobility were significantly increased by Cd exposure. Epidermal growth factor receptor (EGFR) signaling was identified to play the dominant role in Cd-promoted CRC metastasis. Interestingly, Cd activated EGFR in a non-canonical manner that exhibited distinct signaling dynamics from the canonical ligand. In contrast to EGF, which induced transient EGFR signaling and ERK activation, Cd promoted sustained EGFR signaling to trigger Akt/mTOR cascade. The unique signaling dynamics of EGFR induced by Cd provoked responses that preferably enhanced the metastatic capacity rather than the growth. Furthermore, blockade of EGFR abrogated the promoting effects of Cd on the liver metastasis of CRC cells. In conclusion, this study provides a better understanding of the long-term influences of environmental Cd on CRC metastasis and reveals the unique EGFR signaling dynamics induced by Cd exposure.

Bioavailability-based risk assessment of various heavy metals via multi-exposure routes for children and teenagers in Beijing, China

Assessing the health risks of sensitive population, such as children and teenagers, through multiple exposure routes (MERs) such as ingestion, inhalation, and dermal contact is critical for policy creation that protects or reduces exposure to pollutants for all populations. Heavy metal (HM) contents in food and environmental media in Beijing, capital of China, were collected. Furthermore, on the basis of considering the bioavailability of HMs, we evaluated the multiple environmental routes and health risks to HMs in children and teenagers of eight age groups (2-<3, 3-<4, 4-<5, 5-<6, 6-<9, 9-<12, 12-<15, and 15-<18) in Beijing, China by Monte Carlo simulation approach. The main findings are as follows: lead exposure in children aged 2-<3 years exceeds the exposure dose (0.3 μg·kg-1·d-1) of 0.5 point reduction in intelligence quotient. Moreover, children aged 2-<3 and 6-<9 years have relatively high non-carcinogenic risk (NCR) of 1.32 and 1.30, respectively. The carcinogenic risk (CR) for children aged 6-<9 and 9-<12 years is 2.73×10-6 and 2.39×10-6, respectively. Specifically, the contributions of oral ingestion, dermal contact, and inhalation to the NCR were 69.5%, 18.9%, and 11.6%, respectively. Moreover, the combined NCR contributions of copper, cadmium, mercury, and arsenic (As) were about 69.4%. The contributions of the above three routes to the CR were 93.4%, 4.1%, and 2.5%, in that order, with the largest CR contribution of As being about 92.0%. This study can provide new ideas for accurately assessing the exposure and health risks of HMs in the population, and we believe that it is necessary to update the national standards for food and soil based on the bioavailability of HMs.

Uranium-bearing dust induces differentiation and expansion of enteroendocrine cells in human colonoids

Chronic exposure to environmental toxins and heavy metals has been associated with intestinal inflammation, increased susceptibility to pathogen-induced diseases, and higher incidences of colorectal cancer, all of which have been steadily increasing in prevalence for the past 40 years. The negative effects of heavy metals on barrier permeability and inhibition of intestinal epithelial healing have been described; however, transcriptomic changes within the intestinal epithelial cells and impacts on lineage differentiation are largely unknown. Uranium exposure remains an important environmental legacy and physiological health concern, with hundreds of abandoned uranium mines located in the Southwestern United States largely impacting underserved indigenous communities. Herein, using human colonoids, we defined the molecular and cellular changes that occur in response to uranium bearing dust (UBD) exposure. We used single cell RNA sequencing to define the molecular changes that occur to specific identities of colonic epithelial cells. We demonstrate that this environmental toxicant disrupts proliferation and induces hyperplastic differentiation of secretory lineage cells, particularly enteroendocrine cells (EEC). EECs respond to UBD exposure with increased differentiation into de novo EEC sub-types not found in control colonoids. This UBD-induced EEC differentiation does not occur via canonical transcription factors NEUROG3 or NEUROD1. These findings highlight the significance of crypts-based proliferative cells and secretory cell differentiation as major colonic responses to heavy metal-induced injury.

Challenges and strategies for preventing intestinal damage associated to mercury dietary exposure

Food represents the major risk factor for exposure to mercury in most human populations. Therefore, passage through the gastrointestinal tract plays a fundamental role in its entry into the organism. Despite the intense research carried out on the toxicity of Hg, the effects at the intestinal level have received increased attention only recently. In this review we first provide a critical appraisal of the recent advances on the toxic effects of Hg at the intestinal epithelium. Next, dietary strategies aimed to diminish Hg bioavailability or modulate the epithelial and microbiota responses will be revised. Food components and additives, including probiotics, will be considered. Finally, limitations of current approaches to tackle this problem and future lines of research will be discussed.

Nutraceuticals as Alternative Approach against Cadmium-Induced Kidney Damage: A Narrative Review

Cadmium (Cd) represents a public health risk due to its non-biodegradability and long biological half-life. The main target of Cd is the kidney, where it accumulates. In the present narrative review, we assessed experimental and clinical data dealing with the mechanisms of kidney morphological and functional damage caused by Cd and the state of the art about possible therapeutic managements. Intriguingly, skeleton fragility related to Cd exposure has been demonstrated to be induced both by a direct Cd toxic effect on bone mineralization and by renal failure. Our team and other research groups studied the possible pathophysiological molecular pathways induced by Cd, such as lipid peroxidation, inflammation, programmed cell death, and hormonal kidney discrepancy, that, through further molecular crosstalk, trigger serious glomerular and tubular injury, leading to chronic kidney disease (CKD). Moreover, CKD is associated with the presence of dysbiosis, and the results of recent studies have confirmed the altered composition and functions of the gut microbial communities in CKD. Therefore, as recent knowledge demonstrates a strong connection between diet, food components, and CKD management, and also taking into account that gut microbiota are very sensitive to these biological factors and environmental pollutants, nutraceuticals, mainly present in foods typical of the Mediterranean diet, can be considered a safe therapeutic strategy in Cd-induced kidney damage and, accordingly, could help in the prevention and treatment of CKD.

New insights into the role of metal(loid)s in the development of ulcerative colitis: a systematic review

The relationship between heavy metals and ulcerative colitis (UC) was investigated in several studies, but their results were not consistent. Therefore, in this systematic review study, the positive and negative effects of metal(loid)s (Zn, Cu, Fe, Se, Pb, Ni, and As) on UC disease were investigated. In this systematic search, 13 original articles from 1993 to 2021 were identified in Google Scholar, Science Direct, Scopus, PubMed, and the Web of Science databases. In included studies, the concentrations of heavy metals and essential elements were measured in the blood, serum, intestinal biopsies, and hair samples of the patients. Some studies have also examined the heavy metal concentration in UC patients' diet and their drinking water. In the serum samples, Pb (220 ± 108 mg/L) and Cu (401.5 ± 104 µg/L) had the maximum concentrations among the other elements, as well as Zn and Fe had the highest levels in hair and intestinal tissue samples, respectively. In light of the selected articles, there is a possibility of a preventive role for Se and Zn in UC development. Moreover, exposure to Fe can exacerbate the symptoms of the disease. In conclusion, this review reveals that toxic metals, as ubiquitous environmental pollutants, can contribute to the exacerbation of inflammatory intestinal symptoms, and consumption of essential elements can play a vital role in the control of UC, and it is important to pay attention to them in health decisions.

Characterization of childhood exposure to environmental contaminants using stool in a semi-urban middle-class cohort from eastern Canada

Children are exposed to various environmental organic and inorganic contaminants with effects on health outcomes still largely unknown. Many matrices (e.g., blood, urine, nail, hair) have been used to characterize exposure to organic and inorganic contaminants. The sampling of feces presents several advantages; it is non-invasive and provides a direct evaluation of the gut microbiome exposure to contaminants. The gut microbiome is a key factor in neurological development through the brain-gut axis. Its composition and disturbances can affect the neurodevelopment of children. Characterization of children exposure to contaminants is often performed on vulnerable populations (e.g., from developing countries, low-income neighborhoods, and large urban centers). Data on the exposure of children from middle-class, semi-urban, and mid-size populations to contaminants is scarce despite representing a significant fraction of the population in North America. In this study, 73 organics compounds from different chemical classes and 22 elements were analyzed in 6 years old (n = 84) and 10 years old (n = 119) children's feces from a middle-class, semi-urban, mid-size population cohort from Eastern Canada. Results show that 67 out of 73 targeted organics compounds and all elements were at least detected in one child's feces. Only caffeine (97% & 80%) and acetaminophen (28% & 48%) were detected in more than 25% of the children's feces, whereas all elements besides titanium were detected in more than 50% of the children.

Dietary Exposure to Toxic Elements and the Health of Young Children: Methodological Considerations and Data Needs

Concerns have been raised regarding toxic-element (arsenic, cadmium, lead, and mercury) contamination of commercially available infant foods around the world. Young children are vulnerable to the effects of toxic elements, based on higher absorption levels and potentially poorer detoxification capacities. Toxic-element exposures in early life exact high societal costs, but it is unclear how much dietary exposure to these elements contributes to adverse health outcomes. Well-designed epidemiological studies conducted in different geographical and socioeconomic contexts need to estimate dietary toxicant exposure in young children and to determine whether causal links exist between toxicants in children's diets and health outcomes. This commentary outlines the methodological considerations and data needs to advance such research.

Toxic metal exposures from infant diets: Risk prevention strategies for caregivers and health care professionals

Concerns are growing regarding the presence of toxic elements such as arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) in the ingredients and prepared foods for infants and young children. There are few clear, evidence-based, guidelines on the maximum tolerable limits of toxicants in foods and little understanding of toxicant exposure or adverse health effects attributable to dietary exposure. Caregivers are faced with the burden of making decisions about which foods to select, how often to feed them to their children, and what foods to limit. This article reviews the current literature and existing recommendations on dietary exposure to toxic elements in children under 2 years of age, and their health effects in early childhood-focusing on growth, neurodevelopment, and immune function. The article also outlines best practices for healthcare providers to address the concerns of toxic element exposure through the diet in young children. Several foods consistently appear in the literature as potential sources of toxic element exposure. Contaminated drinking and cooking water, including water used to prepare infant formula, could also be a major exposure source. In the absence of stronger evidence on effects of dietary modification, exclusive breastfeeding until six months of age, followed by a diverse diet are some strategies to reduce dietary toxic element exposure while ensuring an adequate and balanced nutrient intake. Healthcare providers can support families by sharing information and encouraging blood Pb testing, the only element for which such testing is currently recommended.

Bioactive compounds, antibiotics and heavy metals: effects on the intestinal structure and microbiome of monogastric animals – a non-systematic review

The intestinal structure and gut microbiota are essential for the animals‘ health. Chemical components taken with food provide the right environment for a specific microbiome which, together with its metabolites and the products of digestion, create an environment, which in turn is affects the population size of specific bacteria. Disturbances in the composition of the gut microbiota can be a reason for the malformation of guts, which has a decisive impact on the animal‘ health. This review aimed to analyse scientific literature, published over the past 20 years, concerning the effect of nutritional factors on gut health, determined by the intestinal structure and microbiota of monogastric animals. Several topics have been investigated: bioactive compounds (probiotics, prebiotics, organic acids, and herbal active substances), antibiotics and heavy metals (essentaial minerals and toxic heavy metals).

The Role of Nutritional Factors in the Modulation of the Composition of the Gut Microbiota in People with Autoimmune Diabetes

Type 1 diabetes mellitus (T1DM) is a disease marked by oxidative stress, chronic inflammation, and the presence of autoantibodies. The gut microbiota has been shown to be involved in the alleviation of oxidative stress and inflammation as well as strengthening immunity, thus its’ possible involvement in the pathogenesis of T1DM has been highlighted. The goal of the present study is to analyze information on the relationship between the structure of the intestinal microbiome and the occurrence of T1DM. The modification of the intestinal microbiota can increase the proportion of SCFA-producing bacteria, which could in turn be effective in the prevention and/or treatment of T1DM. The increased daily intake of soluble and non-soluble fibers, as well as the inclusion of pro-biotics, prebiotics, herbs, spices, and teas that are sources of phytobiotics, in the diet, could be important in improving the composition and activity of the microbiota and thus in the prevention of metabolic disorders. Understanding how the microbiota interacts with immune cells to create immune tolerance could enable the development of new therapeutic strategies for T1DM and improve the quality of life of people with T1DM.