Mineral Dietary Supplement To Decrease Cadmium Relative Bioavailability in Rice Based on a Mouse Bioassay

Co-foliar application of zinc and nano-silicon to rice helps in reducing cadmium exposure risk: Investigations through in-vitro digestion with human cell line bioavailability assay

Foliar application of zinc (Zn) or silicon nanoparticles (Si-NPs) may exert regulatory effects on cadmium (Cd) accumulation in rice grains, however, their impact on Cd bioavailability during human rice consumption remains elusive. This study comprehensively investigated the application of Zn with or without Si-NPs in reducing Cd accumulation in rice grains as well to exactly evaluate the potential risk of Cd exposure resulting from the rice consumption by employing field experiment as well laboratory bioaccessibility and bioavailability assay. Sole Zn (ZnSO4) or in combination with Si (ZnSO4 +Si and ZnO+Si) efficiently lowered the Cd concentration in rice grains. However, the impact of bioaccessible (0.1215-0.1623 mg kg-1) and bioavailable Cd (0.0245-0.0393 mg kg-1) during simulated human rice consumption depicted inconsistent trend. The straw HCl-extractable fraction of Cd (FHCl-Cd) exhibited a significant correlation with total, bioaccessible, and bioavailable Cd in grains, indicating the critical role of FHCl-Cd in Cd accumulation and translocation from grains to human. Additionally, foliar spraying of Zn+Si raised the nutritional value of rice grains, leading to increased protein content and reduced phytic acid concentration. Overall, this study demonstrates the potential of foliar application of ZnSO4 +Si in mitigating the Cd levels in rice grains and associated health risks upon consumption.

Effects of wollastonite and phosphate treatments on cadmium bioaccessibility in pak choi (Brassica rapa L. ssp. chinensis) grown in contaminated soils

Cadmium (Cd) contamination of soil can strongly impact human health through the food chain due to uptake by crop plants. Inorganic immobilizing agents such as silicates and phosphates have been shown to effectively reduce Cd transfer from the soil to cereal crops. However, the effects of such agents on total Cd and its bioaccessibility in leafy vegetables are not yet known. Pak choi (Brassica rapa L. ssp. chinensis) was here selected as a representative leafy vegetable to be tested in pots to reveal the effects of silicate-phosphate amendments on soil Cd chemical fractions, total plant Cd levels, and plant bioaccessibility. The collected Cd contaminated soil was mixed with control soil at 1:0, 1:1, 1:4, 0:1 with a view to Cd high/moderate/mild/control soil samples. Three heavy metal-immobilizing agents: wollastonite (W), potassium tripolyphosphate (KTPP), and sodium hexametaphosphate (SHMP) were added to the soil in order to get four different treatment groups, i.e., control (CK), application of wollastonite alone (W), wollastonite co-applied with KTPP (WKTPP), application of wollastonite co-applied with SHMP (WSHMP) for remediation of soils with different levels of Cd contamination. All three treatments increased the effective bio-Cd concentration in the soils with varying levels of contamination, except for W under moderate and heavy Cd contamination. The total Cd concentration in pak choi plants grown in mildly Cd-contaminated soil was elevated by 86.2% after WKTPP treatment compared to the control treatment could function as a phytoremediation aid for mildly Cd-contaminated soil. Using an in vitro digestion method (physiologically based extraction test) combined with transmission electron microscopy, silicate and phosphorus agents were found to reduce the bioaccessibility of Cd in pak choi by up to 66.13% with WSHMP treatment. Application of silicate alone reduced soil bio-Cd concentration through the formation of insoluble complexes and silanol groups with Cd, but the addition of phosphate may have facilitated Cd translocation into pak choi by first co-precipitating with Ca in wollastonite while simultaneously altering soil pH. Meanwhile, wollastonite and phosphate treatments may cause Cd to be firmly enclosed in the cell wall in an insoluble form, reducing its translocation to edible parts and decreasing the bioaccessibility of Cd in pak choi. This study contributes to the mitigation of Cd bioaccessibility in pak choi by reducing soil Cd concentration through in situ remediation and will help us to extend the effects of wollastonite and phosphate on Cd bioaccessibility to other common vegetables. Therefore, this study thus reveals effective strategies for the remediation of soil Cd and the reduction of Cd bioaccessibility in crops based on two indicators: total Cd and Cd bioaccessibility. Our findings contribute to the development of methods for safer cultivation of commonly consumed leafy vegetables and for soil remediation.

Cd immobilization efficacy of biogenic Mn oxide formed by Cladosporium sp. XM01 and its biological response in sediment

Biogenic Mn oxides (BMOs), the main component of natural Mn oxides, closely relate to Cd in sediment. However, the immobilization behavior of Cd in sediments by BMOs is currently unclear. This study explores the role of BMO produced by the Mn-oxidizing fungus Cladosporium sp. XM01 in mediating the Cd immobilization and its biological response in sediment. A comparison is made with those of a chemical Mn oxide (CMO, triclinic birnessite). After 45 d of remediation, the results showed that the application of BMO reduced the extractable Cd by 32.20-64.40% based on the TCLP (toxicity characteristic leaching procedure) and by 26.16-51.43% based on the PBET (physiologically based extraction test). Additionally, BMO was more effective at immobilizing Cd than CMO in sediments. The BCR (Community Bureau of Reference) extraction results suggested that BMO converted some acid-soluble components (20.63-33.23%) of Cd into residual components (9.40-20.68%). Moreover, the urease and catalase activity gradually increased within the first 25 days and then stabilized after applying BMO. Microbial community analysis revealed that the addition of a high-dose BMO was more conducive to increasing microbial abundance and biodiversity. This study verifies that BMO is a low-cost, high-efficiency, and eco-friendly material for immobilizing Cd in sediment.

Lowered oral bioaccessibility of cadmium and selenium and associated health risk by co-digestion of rice and vegetables

Since foods are not ingested individually, co-digestion, in accordance with human daily diet conditions, should be stressed when assessing elements bioaccessibility and associated health risks. The oral bioaccessibility of cadmium (Cd) and selenium (Se) in 11 types of crops (rice, maize, pakchoi, eggplant, red pepper, towel gourd, kidney bean, soybean, cowpea, sweet potato, and taro) were determined, and the effects of co-digestion of 7 types of rice and vegetables on the bioaccessibility of Cd and Se were evaluated and validated with in vitro PBET method. The underlying mechanism was revealed by observing the surface morphological characteristics of digested substrates, and the exposure risk of Cd and Se were assessed. The results showed that the average bioaccessibility of Cd and Se in 11 types of crops varied from 58.7 % to 39.1 % and 48.4 % to 62.6 % from the gastric phase (GP) to the intestinal phase (IP). Interestingly, co-digestion of rice and vegetables reduced the bioaccessibility of Cd and Se to varying degrees compared to theoretical values. Great reduction in the bioaccessibility of Cd and Se in the GP (16.9-36.4 % and 9.9-23.2 %) than that in the IP (0.2-6.62 % and 0.23-12.3 %) were detected, which was attributed to the rice-vegetable aggregates formed during co-digestion. Rice-vegetable aggregates inhibited the release of Cd and Se, which was more pronounced in the GP than in the IP. Consequently, co-digestion of rice and vegetables reduced the oral exposure to Cd by 35.8 % and to Se by 19.6 %. The areas with higher non-carcinogenic risk of Cd and Se in the study region were reduced by 17 % and 10 %, respectively. Therefore, the role of co-digestion in assessing Cd and Se bioaccessibility and associated health risk cannot be neglected. This study has significant implications for investigating elements bioaccessibility and optimizing associated health risk assessment from a novel perspective.

Dietary intake of household cadmium-contaminated rice caused genome-wide DNA methylation changes on gene/hubs related to metabolic disorders and cancers

Cadmium (Cd) contamination in food has raised broad concerns in food safety and human health. The toxicity of Cd to animals/humans have been widely reported, yet little is known about the health risk of dietary Cd intake at the epigenetic level. Here, we investigated the effect of a household Cd-contaminated rice (Cd-rice) on genome-wide DNA methylation (DNAm) changes in the model mouse. Feeding Cd-rice increased kidney Cd and urinary Cd concentrations compared with the Control rice (low-Cd rice), whereas supplementation of ethylenediamine tetraacetic acid iron sodium salt (NaFeEDTA) in the diet significantly increased urinary Cd and consequently decreased kidney Cd concentrations. Genome-wide DNAm sequencing revealed that dietary Cd-rice exposure caused the differentially methylated sites (DMSs), which were mainly located in the promoter (32.5%), downstream (32.5%), and intron (26.1%) regions of genes. Notably, Cd-rice exposure induced hypermethylation at the promoter sites of genes Caspase-8 and interleukin-1β (Il-1β), and consequently, their expressions were down-regulated. The two genes are critical in apoptosis and inflammation, respectively. In contrast, Cd-rice induced hypomethylation of the gene midline 1 (Mid1), which is vital to neurodevelopment. Furthermore, 'pathways in cancer' was significantly enriched as the leading canonical pathway. Supplementation of NaFeEDTA partly alleviated the toxic symptoms and DNAm alternations induced by Cd-rice exposure. These results highlight the broad effects of elevated dietary Cd intake on the level of DNAm, providing epigenetic evidence on the specific endpoints of health risks induced by Cd-rice exposure.

Cadmium mobility and health risk assessment in the soil-rice-human system using in vitro biaccessibility and in vivo bioavailability assay: Two year field experiment

Humans are mainly exposed to cadmium (Cd) due to the rice consumption, however there exist considerable differences across rice cultivars in terms of Cd absorption and accumulation in the grains, and subsequent release after digestion (bioaccessibility), as well as uptake by Caco-2 cells of humans (bioavailability). This study comprised of field and lab simulation trials where in the field, firstly 39 mid-rice cultivars were screened for their phytoremediation potential coupled with safe production in relation to uptake and translocation of Cd. Lower Cd concentrations (˂0.2 mg kg^-1) in polished rice of 74 % cultivars were ascribed to the increased root to straw translocation indicating that straw may acquire higher accumulation of Cd. Furthermore, the ionomic profile demonstrated that the spatial distribution of metals in different rice organs corresponds to the plant growth morphology. In the second year, in vitro-in vivo assay model was employed to assess the bioaccessibility and bioavailability of Cd in polished rice and to further estimate the daily Cd intake by humans through rice grains. The results of bioaccessibility and bioavailability assays and daily estimated Cd intake presented the corresponding values of 39.02-59.76 %, 8.69-24.26 %, and 0.0185-0.9713 μg kg^-1 body weight day^-1, respectively. There exists a strong connection between total Cd and bioaccessible Cd to humans (R² = 0.94, P < 0.01). Polynomial fitting (R² = 0.91, P < 0.01) showed a better statistically significant correlation between total Cd contents and bioavailable levels, suggesting that in vitro-in vivo assays should be considered in future studies. The results of field experiments and in vitro-in vivo assays recommended the Tianyouhuazhan (MR-29), Heliangyou1hao (MR-17), and Yongyou15 (MR-1) as suitable mid-rice cultivars for the phytoremediation of slightly Cd contaminated soils coupled with rice agro-production due to their high nutritional value and low total and bioavailable Cd for human.

Amelioration of cadmium cytotoxicity to human cells by nutrient cation contents and the building of a biotic ligand model

A variety of important major and trace elements may competitively inhibit cadmium (Cd) absorption in human cells and reduce Cd toxicity. However, the impact of essential elements on the cytotoxicity of metals can be difficult to quantify and anticipate. Cd acute toxicity to Caco-2 cell viability was studied in culture solutions and modeled by a biotic ligand model (BLM). The individual effects of the cations potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), ferrous ion(Fe²⁺), zinc (Zn²⁺) and manganese (Mn²⁺) on Cd toxicity were also investigated. The results indicated that the toxicity of Cd in culture solutions to cell viability declined with increasing concentrations of Zn²⁺ and Mn²⁺ in the solutions, while K⁺, Ca^{2 +}, Mg^{2 +} and Fe²⁺ had no significant effect. Using the BLM, the stability constants for the binding of Cd^{2 +}, Zn²⁺, and Mn²⁺ to biotic ligands were determined to be logK_CdBL = 5.76, logK_ZnBL = 4.39 and logK_MnBL = 5.31, respectively. Moreover, it was calculated that 51% occupancy of the biotic ligand sites for Cd by Cd was required to cause a 50% reduction in Caco-2 cell viability. A BLM was successfully established using the estimated constants to predict the Cd cytotoxicity to Caco-2 cell viability as a function of solution characteristics, so that the effective concentrations that reduced cell viability by 50% (EC50) could be predicted by the BLM within 1.6 fold changes of the observed EC50. The application's viability and precision for foretelling Cd toxicity in Caco-2 cells are discussed.

Relative Bioavailability of Cadmium in Rice: Assessment, Modeling, and Application for Risk Assessment

Rice consumption is the primary route of cadmium (Cd) exposure to the populations with rice as the staple food. To accurately assess the potential health risks of Cd exposure via rice consumption, determination of Cd relative bioavailability (RBA) in rice is necessary. However, large variations exist in Cd-RBA, hindering the application of source-specific Cd-RBA values to different rice samples. In this study, we collected 14 rice samples from Cd contaminated areas and determined both rice compositions and Cd-RBA using in vivo mouse bioassay. Total Cd concentration varied from 0.19 to 2.54 mg/kg in the 14 rice samples, while Cd-RBA in rice ranged from 42.10% to 76.29%. Cadmium-RBA in rice correlated positively with calcium (Ca) (R = 0.76) and amylose content (R = 0.75) but negatively with the concentrations of sulfur (R = -0.85), phosphorus (R = -0.73), phytic acid (R = -0.68), and crude protein (R = -0.53). Cd-RBA in rice can be predicted by Ca and phytic acid concentrations in a regression model (R² = 0.80). Based on the total and bioavailable Cd concentrations in rice, weekly dietary Cd intake for adults was estimated to be 4.84-64.88 and 2.04-42.29 μg/kg bw/week, respectively. This work demonstrates the possibility of Cd-RBA prediction based on rice compositions and provides valuable suggestions for health risk assessment with consideration of Cd-RBA.

Removal of cadmium in aqueous solutions using a ball milling-assisted one-pot pyrolyzed iron-biochar composite derived from cotton husk

A novel iron-biochar composite adsorbent was produced via ball milling-assisted one-pot pyrolyzed BM-nZVI-BC 800. Characterization proved that nano zero valent iron was successfully embedded in the newly produced biochar, and the nZVI payload was higher than that of traditional one-pot pyrolyzed methods. BM-nZVI-BC 800 provided a high adsorption performance of cadmium reaching 96.40 mg·g^-1 during batch testing. Alkaline conditions were beneficial for cadmium removal of BM-nZVI-BC 800. The pseudo-second-order kinetic model and Langmuir isotherm fitted better, demonstrating that the Cd adsorption on the BM-nZVI-BC 800 was a chemical and surface process. The intraparticle diffusion controlled the adsorption of BM-nZVI-BC 800. The physisorption dominated by high specific surface area and mesoporous structure was the primary mechanism in the removal of cadmium, though electrostatic attraction and complexation also played a secondary role in cadmium adsorption. Compared to adsorbents prepared by more traditional methods, the efficiencies of the ball milling-assisted one-pot pyrolyzed method appears superior.

Ca Minerals and Oral Bioavailability of Pb, Cd, and As from Indoor Dust in Mice: Mechanisms and Health Implications

BACKGROUND

Elevating dietary calcium (Ca) intake can reduce metal(loid)oral bioavailability. However, the ability of a range of Ca minerals to reduce oral bioavailability of lead (Pb), cadmium (Cd), and arsenic (As) from indoor dust remains unclear.

OBJECTIVES

This study evaluated the ability of Ca minerals to reduce Pb, Cd, and As oral bioavailability from indoor dust and associated mechanisms.

METHODS

A mouse bioassay was conducted to assess Pb, Cd, and As relative bioavailability (RBA) in three indoor dust samples, which were amended into mouse chow without and with addition of CaHPO4,  CaCO3, Ca gluconate, Ca lactate, Ca aspartate, and Ca citrate at 200-5,000μg/g Ca. The mRNA expression of Ca and phosphate (P) transporters involved in transcellular Pb, Cd and As transport in the duodenum of mice was quantified using real-time polymerase chain reaction. Serum 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], parathyroid hormone (PTH), and renal CYP27B1 activity controlling 1,25(OH)2D3 synthesis were measured using ELISA kits. Metal(loid) speciation in the feces of mice was characterized using X-ray absorption near-edge structure (XANES) spectroscopy.

RESULTS

In general, mice exposed to each of the Ca minerals exhibited lower Pb-, Cd-, and As-RBA for three dusts. However, RBAs with the different Ca minerals varied. Among minerals, mice fed dietary CaHPO4 did not exhibit lower duodenal mRNA expression of Ca transporters but did have the lowest Pb and Cd oral bioavailability at the highest Ca concentration (5,000μg/g Ca; 51%-95% and 52%-74% lower in comparison with the control). Lead phosphate precipitates (e.g., chloropyromorphite) were observed in feces of mice fed dietary CaHPO4. In comparison, mice fed organic Ca minerals (Ca gluconate, Ca lactate, Ca aspartate, and Ca citrate) had lower duodenal mRNA expression of Ca transporters, but Pb and Cd oral bioavailability was higher than in mice fed CaHPO4. In terms of As, mice fed Ca aspartate exhibited the lowest As oral bioavailability at the highest Ca concentration (5,000μg/g Ca; 41%-72% lower) and the lowest duodenal expression of P transporter (88% lower). The presence of aspartate was not associated with higher As solubility in the intestine.

DISCUSSION

Our study used a mouse model of exposure to household dust with various concentrations and species of Ca to determine whether different Ca minerals can reduce bioavailability of Pb, Cd, and As in mice and elucidate the mechanism(s) involved. This study can contribute to the practical application of optimal Ca minerals to protect humans from Pb, Cd, and As coexposure in the environment. https://doi.org/10.1289/EHP11730.

Screening of low-Cd accumulating early rice cultivars coupled with phytoremediation and agro-production: Bioavailability and bioaccessibility tests

Previous studies have focused on total cadmium (Cd) accumulation in rice or its transformation in soil, but only a few have examined the entire soil-rice-human system. This study investigated the Cd bioaccessibility and bioavailability for humans from grains of early rice cultivars grown in a Cd-polluted field and further combined with multi-traits to discover and evaluate the optimum safe production and phytoremediation potential cultivars. The results revealed that Cd concentration in polished rice was <0.20 mg kg^-1 in 79 % of early rice cultivars, implying that Cd levels in rice might be reduced by cultivar selection. Furthermore, the higher values of root to straw translocation factor indicates the maximal accumulation of Cd in straw and with highest soil to straw accumulation factor (>1.0) in 66.67 % of cultivars. However, bioaccessibility and bioavailability varied greatly among cultivars with corresponding values ranging from 5.68 to 7.67 % and 1.87 to 5.71 ng g^-1, respectively. Despite the fact that polynomial fitting revealed a statistically significant relationship between Cd content in polished rice and bioavailable Cd in humans (R² = 0.718, P = 0.025), poor goodness of fit for bioaccessibility, bioavailability, and toxicity varied even within low-Cd accumulating cultivars. As a result of multi trait analysis and bioavailability, Zhuliangyou4024 (ER-9), Lingliangyou211 (ER-3), and Yonxian15 (ER-28) were found to be the three best early rice cultivars with higher essential nutrients, less total and bioavailable Cd, and relative high phytoremediation potential and are suitable for healthy rice production and soil remediation.

Effect of Nanoscale Zero-Valent Iron on Arsenic Bioaccessibility and Bioavailability in Soil

Hand-to-mouth activity is considered to be the main way for children to come into contact with contaminated soil, and bioavailability is an important factor affecting their health risk. To reduce soil As risk to humans by oral exposure, nanoscale zero-valent iron (nZVI) has been extensively studied for immobilizing As-contaminated soil, but its efficiency has not been investigated using in vitro assay and its influence on As-RBA. In this study, two contaminated soil samples (A and B) were amended with 1% and 2% (w/w) nZVI for 56 days to study its effect on As fraction by sequence extraction, As bioaccessibility by SBRC assay, and As relative bioavailability (RBA) by the mouse liver and kidney model. Based on the sequence extraction, the As associated with the E1 (exchangeable fraction) and C2 (carbonate fraction) fractions were decreased from 3.00% to 1.68% for soil A and from 21.6% to 7.86% for soil B after being treated with 2% nZVI for 56 days. When assessing As bioaccessibility in all soils treated with nZVI by SBRC assay, it was found that As bioaccessibility was significantly higher in the gastric phase (GP) and lower in the intestinal phase (IP) (p < 0.05), and the bioaccessible Fe concentration decreased significantly from the gastric to intestinal phase at the same time. Based on the mouse liver–kidney model, the As-RBA in soil A increased from 21.6% to 22.3% and 39.9%, but in soil B decreased from 73.0% to 55.3% and 68.9%, respectively. In addition, there was a significant difference between As bioaccessibility based on GP or IP of SBRC assay and As-RBA in two soils after being treated with nZVI for 56 days. To more accurately assess the effects of nZVI human arsenic exposure, As-RBA should be considered in concert with secondary evidence provided through fraction and bioaccessibility assessments. In addition, it is necessary to develop a suitable in vitro assay to predict As-RBA in nZVI-amended soils.

Joint approaches to reduce cadmium exposure risk from rice consumption

In-situ soil cadmium (Cd) immobilization helps to reduce Cd accumulation in rice grain, while its effects on bioaccessibility of Cd in rice during digestion and the associated health risk from rice consumption remain unclear. Here, we combined in-situ soil Cd immobilization and bioaccessibility-corrected health risk assessment (HRA) to minimize both the risk and uncertainty of Cd exposure from rice consumption. Wollastonite with or without four different phosphates (P) were applied to immobilize soil Cd at paddy fields, and their influences on Cd, essential elements, and amino acids in rice grain were analyzed. Moreover, a bioaccessibility-corrected HRA was conducted to accurately reflect the Cd exposure risk from ingesting these rices. The results showed the co-application of wollastonite and four different P reduced Cd concentrations in rice grain equally, while their impacts on bioaccessibility of Cd in rice during simulated human digestion were inconsistent (53-71%). The HRA based on bioaccessibility of Cd in rice revealed that Cd exposure risk from rice consumption was lowest with the application of wollastonite, followed by the co-application of wollastonite and sodium hexametaphosphate. This work highlights the value of bioaccessibility-corrected HRA for screening the optimal Cd immobilization strategy to achieve safer rice consumption.

Cadmium oral bioavailability is affected by calcium and phytate contents in food: Evidence from leafy vegetables in mice

To test high cadmium (Cd) concentration may not be high in health risk when considering Cd bioavailability, we assessed variation of Cd relative bioavailability (RBA, relative to CdCl₂) using a mouse assay for 14 vegetables of water spinach, amaranth, and pakchoi. Cadmium concentration varied from 0.13 ± 0.01-0.37 ± 0.00 μg g^-1 fw. Cadmium-RBA also varied significantly from 22.9 ± 2.12-77.2 ± 4.46%, however, the variation was overall opposite to that of Cd concentration, as indicated by a strong negative correlation between Cd-RBA and Cd concentration (R² = 0.43). Based on both Cd concentration and bioavailability, the identified high-Cd pakchoi variety resulted in significantly lower Cd intake than the high-Cd varieties of water spinach and amaranth (4.74 ± 0.05 vs. 10.1 ± 0.54 and 8.03 ± 0.04 μg kg^-1 bw week^-1) due to significantly lower Cd-RBA (22.9 ± 2.12 vs. 77.2 ± 4.46 and 51.3 ± 2.93%). The lower Cd-RBA in pakchoi was due to its significantly higher Ca and lower phytate concentrations, which facilitated the role of Ca in inhibiting intestinal Cd absorption. This was ascertained by observation of decreased Cd-RBA (90.5 ± 12.0% to 63.5 ± 5.53%) for a water spinach when elevating its Ca concentration by 30% with foliar Ca application. Our results suggest that to assess food Cd risk, both total Cd and Cd bioavailability should be considered.

Metabolomics reveals the mechanism of Antarctic yeast Rhodotorula mucliaginosa AN5 to cope with cadmium stress

Heavy metal pollution in Antarctica has far exceeded expectations. Antarctic yeast is widely present in polar marine environment. The mechanisms of metabolomics effect of heavy metal on polar yeast have not been reported previously. In this study, gas chromatography-mass spectrometry (GC-MS) wascarried out to performed the metabolite profiling analysis of Antarctic sea-ice yeast Rhodotorula mucilaginosa AN5 exposed to different cadmium (Cd) stresses of 5 mM (HM5), 10 mM (HM10) and 20 mM (HM20), respectively. Metabolic profile analysis showed that the composition and contents of cellular metabolites have been altered by cadmium. 93 different metabolites were identified altogether, among which 23, 58 and 81 different metabolites were found in HM5, HM10 and HM20 group respectively. MetaboAnalyst analysis showed that in HM5, HM10 and HM20 groups, 12, 24 and 31 metabolic pathways were involved in the stress of cadmium to R. mucilaginosa, respectively. By contrasting with Kyoto Encyclopedia of Genes and Genomes database, we discovered that exposure of yeast AN5 to Cd stress resulted in profound biochemical changes including amino acids, organic acids and saccharides. These results will supply a nonnegligible basis of studying the adaptive resistance mechanism of Antarctic yeast Rhodotorula mucilaginosa to heavy metal.

In Vivo-In Vitro Correlations for the Assessment of Cadmium Bioavailability in Vegetables

The correlation of in vitro and in vivo assays for determining bioavailable Cd amounts in vegetables is limited. Herein, the correlations between Cd relative bioavailability (Cd-RBA) in rat models and Cd bioaccessibility in four in vitro assays were examined in vegetables. Results showed that the combined liver plus kidney data provided the appropriate endpoint and was used as a biomarker to estimate Cd-RBA. The Cd-RBA was negatively correlated with the mole ratio of Ca/Cd and Fe/Cd in vegetables. Strong in vivo-in vitro correlations were found from physiologically based extraction test (PBET) and in vitro gastrointestinal (IVG) (R² = 0.66-0.69). We concluded that PBET and IVG were optimal models for Cd-RBA determination in vegetables. The nutritional elements in the vegetables could affect Cd absorption. Furthermore, the Cd bioavailability in vegetables should be considered because risk estimates solely based on the total Cd concentration in vegetables would overestimate Cd intake.

Evaluation of Cadmium Transfer from Soil to the Human Body Through Maize Consumption in a Cadmium Anomaly Area of Southwestern China

Evaluating the bioavailability, bioaccessibility, and transferability of cadmium (Cd) in soil-grain-human systems is essential in areas with a Cd anomaly in the karst region of southwestern China. In the present study, the main controlling factors and prediction models for Cd transfer in a soil-grain-human system were investigated in a typical area where natural processes and anthropogenic activities interact in the karst region of southwestern China. The environmental availability of Cd (diethylenetriaminepentaacetic acid- and CaCl₂ -extractable Cd [ CdCaCl2 ]) in the soil varies significantly because of the diversity of soil properties. However, Cd concentrations in the maize grain were significantly related only to the CdCaCl2 concentrations in the soil (r = 0.595, p < 0.01), indicating that soil CdCaCl2 is a good indicator for evaluating Cd uptake by maize grain. Of all the measured soil properties, the soil cation exchange capacity (CEC) and the soil calcium (Ca_soil ) were the most important factors influencing Cd accumulation in the soil-maize grain system. A transfer model combining CdCaCl2 , soil CEC, and Ca_soil was sufficiently reliable for predicting Cd accumulation in the maize grain (R²  = 0.505). Although there is room for improvement regarding the prediction performance of the chain model combining soil CdCaCl2 with Ca_soil to predict the bioaccessible Cd concentration in maize grain (R²  = 0.344 for the gastric phase and R²  = 0.356 for the gastrointestinal phase), our findings provide a useful reference to further explore a model that can be used for a relatively rapid and reliable estimation of dietary Cd exposure for specific regions prior to crop harvest. Environ Toxicol Chem 2021;40:2923-2934. © 2021 SETAC.

Arsenic bioaccessibility in rice grains via modified physiologically-based extraction test (MPBET): Correlation with mineral elements and comparison with As relative bioavailability

Rice consumption is a major dietary source of human exposure to arsenic (As), with As bioavailability being an important factor influencing its health risk. In this study, the As bioaccessibility was measured in 11 rice grains (140-335 μg As kg^-1), which were compared to As relative bioavailability previously measured based on a mouse bioassay (Li et al., 2017). Using modified physiologically-based extraction test for rice (MPBET), As bioaccessibility in raw rice samples (44-88% in the gastric phase and 47-102% in the intestinal phase) was similar to those in cooked rice (42-73% and 43-99%). Arsenic bioaccessibility in rice was generally higher in the intestinal phase than in the gastric phase, with Fe and Ca concentrations in rice being negatively correlated with As bioaccessibility in the gastric phase (R² = 0.47-0.49). In addition, for cooked rice, strong positive correlation was observed between bioaccessible As and inorganic As (R² = 0.63-0.72), suggesting inorganic As in rice was easier to dissolve than organic As in gastrointestinal digestive fluids. Due to limited variation in As bioaccessibility and As bioavailability among the 11 samples, a weak correlation was observed between them (R² = 0.01-0.03); however, As bioaccessibility values measured by the gastric phase (GP) of the MPBET agreed with As bioavailability values based on a mouse bioassay, suggesting the potential of the MPBET_GP to predict As bioavailability in rice. Future work is needed to ascertain the robustness of the MPBET_GP in predicting As bioavailability in rice using additional samples.

Exploration of the optimal strategy for dietary calcium intervention against the toxicity of liver and kidney induced by cadmium in mice: An in vivo diet intervention study

Cadmium (Cd) is a toxic non-essential element, while calcium (Ca) is an essential element with high chemical similarity to Cd. Dietary intake is the major Cd exposure pathway for non-smokers. A multi-concentration dietary intervention experiment was designed to explore the optimum concentration of Ca in diet with obvious protective effects against the toxicity of livers and kidneys induced by Cd in mice. The mice were divided into six groups with different concentrations of Cd and Ca in their food: control-group (no Cd or Ca), Ca-group (100 g/kg Ca, without Cd), Cd-group (2 mg/kg Cd, without Ca), Ca_L+Cd-group (2 mg/kg Cd, 2 g/kg Ca), Ca_M+Cd-group (2 mg/kg Cd, 20 g/kg Ca) and Ca_H+Cd-group (2 mg/kg Cd, 100 g/kg Ca). The organ indexes, oxidative stress biomarkers, lesions and Cd concentrations were detected after a 30-day exposure period. Results showed that serum Aspartate Aminotransferase (AST) level in Ca_H+Cd-group was significantly lower than that in Cd-group, while close to that in control-group. The contents of Serum Blood Urea Nitrogen (BUN) in different groups showed the same trend. Concentrations of all oxidative stress biomarkers (GSH-Px, SOD, CAT, GSH and MDA) in Ca_H+Cd-group were close to the normal levels of control-group while significantly different from those in Cd-group. The only exception was the Malondialdehyde (MDA) levels in kidneys. This study suggests that Ca plays a protective role in relieving the Cd-induced toxicity of livers and kidneys and a concentration of 100 g/kg for Ca in diet showed the best protective effects. These findings could provide a clue for further studies concerning human diet intervention for Cd control.

Foliar application of zinc and selenium alleviates cadmium and lead toxicity of water spinach - Bioavailability/cytotoxicity study with human cell lines

The present study investigated the effects of foliar application of zinc (Zn) and selenium (Se) on bioavailability of Zn and Se and toxicity of cadmium (Cd) and lead (Pb) to different water spinach ecotypes (LA and HA) grown in slightly (XZ) or moderately (LJY) contaminated fields via in vitro digestion combined with Caco-2/HL-7702 cell model. The obtained results revealed that foliar application of Zn and Se promoted yield, increased total, bioaccessible and bioavailable fractions of Zn and Se in plants, indicating that foliar application is a feasible way of biofortification. Although there was no significant effect on liver cell proliferation (MTT), membrane stability (LDH) and hepatocyte enzyme (ALT and AST) activities, the obvious ecotype and soil dependent fluctuations of lipid peroxidation (MDA) and antioxidant enzyme (SOD, POD and CAT) activities in serum highly suggest that the low accumulator and clean field should be used in agricultural production rather than the high accumulator and contaminated farmland. Moreover, foliar application of Zn and Se improved nutritional quality of all water spinach genotypes in both fields, including increased Fe, vitamin C, cellulose and chlorophyll, maintained concentrations of potassium (K), manganese (Mn), copper (Cu), protein, and nitrate. These results demonstrate that this agricultural management practice may prove to be an effective approach for minimizing health risk and alleviating "hidden hunger" in the developing countries.

Use of Dietary Components to Reduce the Bioaccessibility and Bioavailability of Cadmium in Rice

Reducing Cd bioavailability in the systemic circulation is an alternative strategy to reduce Cd exposure. The influence of 39 dietary components on Cd bioaccessibility in water or rice was determined using an in vitro gastrointestinal model, following which an in vivo bioassay was used to determine the most effective components on Cd bioavailability in rice. The results showed that several components significantly reduced the solubility of Cd (10-98%) in the intestinal phase. Tannic acid, TiO₂, zinc gluconate, CaCl₂, and proanthocyanidins were the most effective in decreasing Cd bioaccessibility in rice, with reductions of 93-97, 54-61, 32-49, 24-32, and 11-14%, respectively. Upon adding the dietary components, the reduction rates of the Cd-relative bioavailability (Cd-RBA) were 20-58 and 10-31% in the kidneys and the liver, respectively. The results may have important implications for reducing health risks associated with Cd exposure via consumption of rice.

Maize cultivars relieve health risks of Cd-Polluted Soils: In vitro Cd bioaccessibility and bioavailability

Dietary grain ingestion is the primary route of human exposure to the adverse effects of Cd; therefore, an understanding of the transfer characteristics of Cd in a system involving soil, grain, and humans is crucial for health risk alleviation and pollution control. In this study, Cd bioaccessibility and bioavailability for humans from grains of sweet maize (Zea mays convar. saccharata var. rugosa) cultivars grown on a contaminated field (1.05 mg Cd kg^-1 soil) were assessed by combining a simulated in vitro digestion method with a Caco-2 cell model. Results showed that cultivars differed significantly in grain Cd concentration, bioaccessibility, and bioavailability with the corresponding values of 0.07 to 0.20 mg kg^-1 DW (dry weight), 4.10 to 6.20%, and 0.01 to 0.04 µg g^-1grain, respectively. The estimated daily intake of Cd through sweet maize grain was within the range of 0.04 and 0.25 μg kg^-1 body weight, which is lower than the tolerable limit recommended by the Joint FAO/WHO Expert Committee on Food Additives (JEFCA). Conclusively, results from the present study indicate that most grain Cd remains non-bioaccessible and thus might not present adverse health effects in humans. Therefore, sweet maize cultivars could be used to produce healthy food crops in low-to-moderately Cd-contaminated soil.

Antagonistic Interactions between Arsenic, Lead, and Cadmium in the Mouse Gastrointestinal Tract and Their Influences on Metal Relative Bioavailability in Contaminated Soils

Soils are often co-contaminated with As, Pb, and Cd. To what extent ingested metal(loid)s interact with each other in the gastrointestinal tract and influence their RBA (relative bioavailability) is largely unknown. Three soils predominantly contaminated with As (MS, mining/smelting impacted), Pb (WR, wire rope production impacted), and Cd (EP, enamel pottery production impacted) were administered to mice individually or in binary and tertiary combinations with sodium arsenate, Cd chloride, and/or Pb acetate. In binary combinations, ∼10-fold higher Pb addition decreased As-RBA in MS (26.0 ± 6.28% to 17.1 ± 1.08%), while ∼10-fold higher As addition decreased Pb-RBA in WR (61.3 ± 2.41% to 28.8 ± 5.45%). This was possibly due to the formation of insoluble Pb arsenate in mouse intestinal tract, as indicated by the formation of precipitates when As and Pb co-occurred in water or simulated human gastrointestinal fluids. Due to competition for shared absorption transporters, ∼10- and 100-fold higher Pb addition decreased Cd-RBA in EP (95.8 ± 12.9% to 67.8 ± 12.8% and 62.8 ± 8.24%). Tertiary combinations showed that interactions between two metal(loid)s were affected by the presence of the third metal(loid). Our study suggests that As oxyanion could interact with Pb or Cd ions in the mouse gastrointestinal tract, and the interactions vary depending on concentration and solution characteristics.

Oral Bioavailability of As, Pb, and Cd in Contaminated Soils, Dust, and Foods based on Animal Bioassays: A Review

Metal contamination in soil, dust, and food matrices impacts the health of millions of people worldwide. During the past decades, various animal bioassays have been developed to determine the relative bioavailability (RBA) of As, Pb, and Cd in contaminated soils, dust, and foods, which vary in operational approaches. This review discusses the strengths and weaknesses of different animal models (swine and mice), dosing schemes (single gavage dose, repeated gavage dose, daily repeated feeding, and free access to diet), and end points (blood, urine, and tissue) in metal-RBA measurement; compares metal-RBA obtained using mouse and swine bioassays, different dosing schemes, and different end points; and summarizes key findings on As-, Pb-, and Cd-RBA values in contaminated soils, dust, and foods. Future directions related to metal-RBA research are highlighted, including (1) comparison of metal-RBA determinations between different bioassays and different laboratories to ensure robust bioavailability data, (2) enhancing the metal-RBA database for contaminated dust and foods, (3) identification of physiological and physicochemical mechanisms responsible for variability in metal-RBA values, (4) formulation of strategies to decrease metal-RBA values in contaminated soils, dust, and foods, and (5) assessing the impacts of cocontaminants on metal-RBA measurement.

Protective Effects of Moderate Ca Supplementation against Cd-Induced Bone Damage under Different Population-Relevant Doses in Young Female Rats

Estimation of the skeleton-protective effects of Ca in Cd-induced bone damage is helpful in the assessment of Cd health risk. The aim of this study was to identify whether Ca supplementation during exposure to different population-relevant doses of Cd can prevent Cd-induced bone damage under the tolerable upper intake level of Ca supplementation. Young female Sprague-Dawley rats were given different population-relevant doses of Cd (1, 5, and 50 mg Cd/kg diet) and Ca supplementation (0.4% Ca supplementation) intervention. Ca supplementation significantly decreased Cd-induced bone microstructure damage, increased bone biomechanics (p < 0.05), serum bone formation marker level (p < 0.05) and expression of osteogenic gene markers exposure to the 5 and 50 mg Cd/kg diets. However, it had no impact on these indicators under the 1 mg Cd/kg diets, with the exception of expression of osteogenic marker genes. Ca supplementation significantly decreased serum Klotho level (p < 0.05), and fibroblast growth factor 23/Klotho-associated gene expression in the kidney and bone showed significant changes. In conclusion, Ca supplementation has a positive effect on bone formation and bone quality against the damaging impact of Cd, especially with exposure to the 5 mg and 50 mg Cd/kg diet, which may be related to its impact on the fibroblast growth factor 23/Klotho axis.

In Vitro and In Vivo Testing to Determine Cd Bioaccessibility and Bioavailability in Contaminated Rice in Relation to Mouse Chow

A combination of an in vitro physiologically based extraction test (PBET) and an in vivo mouse model was used to determine Cd oral bioaccessibility and estimate bioavailability in Cd-contaminated rice. The PBET found lower Cd bioaccessibility in the intestinal stage (40–50%) than in the gastric stage (93–98%) for both rice and mouse chow. No significant difference was found in Cd bioaccessibility between contaminated rice and Cd-amended mouse chow in the gastric or gastrointestinal phase (except for rice 1). The result of the in vivo bioassay revealed that Cd absorption in the kidney or liver of mice fed with contaminated rice were significantly higher than in the mouse chow group containing an equal Cd concentration. Correlation analysis between concentrations of different elements in mouse chow or rice and Cd concentrations in mice kidney or liver showed that Fe, Ca, Cu, and Zn had significant negative correlation (r² > 0.7, p < 0.01). These results suggest that nutritional elements in the diet could affect Cd absorption and distribution in organs and that different food matrices may result in unequal Cd health risks at an equal Cd concentration due to the specific mineral content of food.

An interventional study of rice for reducing cadmium exposure in a Chinese industrial town

BACKGROUND

Reducing cadmium (Cd) exposure in Cd-polluted areas in Asia is urgently needed given the toxic effects of Cd. The short-term and long-term benefits of lowering Cd exposure are unknown because of its long half-life in the body.

OBJECTIVES

We aimed to investigate whether an intervention with low-Cd rice in a contaminated area of China reduced urinary Cd (UCd) levels and improved blood pressure and kidney function outcomes compared to no-intervention in consumers of high-Cd rice in the same region.

METHODS

106 non-smoking subjects were divided into three treatment groups: the intervention group (replacing homegrown high-Cd rice with market low-Cd rice, n = 34), the non-intervention group (continue eating high-Cd rice, n = 36) and the control group (continued eating low-Cd rice they have been eating for years, n = 36). The intervention period lasted for almost 8 months, during which participants were visited on up to 4 occasions and UCd, systolic and diastolic blood pressure (SBP, DBP), kidney function biomarkers (β2-microglobulin and N-acetyl-β-D-glucosaminidase) were measured.

RESULTS

After 3 months, the geometric mean UCd in the intervention (Int) group decreased significantly by 0.32 μg/g (p = 0.007), while changes were not significant in the non-intervention (non-Int) group (0.13 μg/g, p = 0.95) or the control group (-0.01 μg/g, p = 0.52). UCd in the Int group remained lower than in the non-Int group but higher than in the Control group through the end of follow up. DBP in the Int group decreased significantly from 80 mm Hg at month three (p = 0.03) and stayed around 74 mm Hg for the remainder of the study. SBP also decreased in the Int group but with variations similar to those observed in the other two groups. The two kidney biomarkers showed variations without a clear pattern.

CONCLUSION

This study suggested that UCd reflected both short-term (<3 months) and long-term Cd exposure. In addition, the low-Cd rice intervention showed initial benefits in lowering blood pressure levels, especially DBP, but not kidney biomarkers.

Coupling bioavailability and stable isotope ratio to discern dietary and non-dietary contribution of metal exposure to residents in mining-impacted areas

Both dietary and non-dietary pathways contribute to metal exposure in residents living near mining-impacted areas. In this study, bioavailability-based metal intake estimation coupled with stable Pb isotope ratio fingerprinting technique were used to discern dietary (i.e., rice consumption) and non-dietary (i.e., housedust ingestion) contribution to As, Cd, and Pb exposure in residents living near mining-impacted areas. Results showed that not only rice (n = 44; 0.10-0.56, 0.01-1.77, and 0.03-0.88 mg kg^-1) but also housedust (n = 44; 2.15-2380, 2.55-329, and 87.0-56,184 mg kg^-1) were contaminated with As, Cd, and Pb. Based on in vivo mouse bioassays, bioavailability of As, Cd, and Pb in rice (n = 11; 34 ± 15, 59 ± 13, and 31 ± 15%) were greater than housedust (n = 14; 17 ± 6.7, 46 ± 10, and 25 ± 6.8%). Estimated daily intake of As, Cd, and Pb after incorporating metal bioavailability showed that As intake via rice was 5-fold higher than housedust for adults, whereas As intake via housedust was 3-fold higher than rice for children. For both adults and children, rice was the main source for Cd exposure, while housedust was the predominant Pb contributor. To ascertain the dominant Pb source from housedust ingestion, stable Pb isotope ratios (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb) of hair samples of local residents (n = 27, 0.8481 ± 0.0049 and 2.0904 ± 0.0102) were compared to housedust (n = 27, 0.8485 ± 0.0047 and 2.0885 ± 0.0107) and rice (n = 27, 0.8369 ± 0.0057 and 2.0521 ± 0.0119), showing an overlap between hair and housedust, but not rice, confirming that incidental housedust ingestion was the main source of Pb exposure. This study coupled bioavailability and stable isotope techniques to accurately identify the source of metal exposure as well as their potential health risk.

Cadmium detoxification induced by salt stress improves cadmium tolerance of multi-stress-tolerant Pichia kudriavzevii

Heavy metal tolerance of microorganisms is the basis of heavy metal removal by growing cells. In this study, a cross-protection effect generated by salt stress significantly enhanced the cadmium tolerance of multi-stress-tolerant Pichia kudriavzevii. Comparative transcriptome analysis using RNA-Seq linked with physiological and biochemical observation was used to elucidate the underlying mechanisms of the improved cadmium tolerance. The expression of cadmium transport related genes (GSTY2, GLR1, GLO2, YCF1 and YOR1), GSH content and GST activity were elevated by salt stress, suggesting enhanced cadmium conjugation and detoxification in yeast cells. The inhibited cadmium uptake by ZRT1 and enhanced cadmium efflux by YOR1 contributed to the decrease in the intracellular cadmium concentration. The improved expression of antioxidant enzyme genes (SOD1, SOD2, SOD6, CAT1 and PRXIID), along with the enhanced activities of antioxidant enzymes (SOD, CAT and POD) resulted in a decrease in cadmium-induced ROS production, protein carbonylation, lipid peroxidation and cell death. The abundant expression of heat shock protein genes (HSP12, HSP10 and SSC1) and genes related to trehalose synthesis (TPS1 and TSL1) induced by salt stress protected yeast cells against complex stress conditions, contributing to the improved cadmium tolerance. These findings will be useful to develop cadmium-tolerant yeasts for cadmium removal by growing cells.