Study On The Bioaccessbility In Vitro And Bioavalibility In Vitro And In Vitro Of Cadmium From Various Food

Backgrounds:As anthropogenic activities increase,especially the application of modern’s technology,cadmium pollution of soil has been dramatically increased.And thus,contamination of human food chain by Cd has become inevitable.Chronic intake of Cd will lead Cd accumulated,and only the fraction of the ingested Cd in food that reaches the systemic circulation and can exert its toxic effects.At present,the health risk assessments to human of consuming the Cd contaminated food is usually assumed that all of the Cd in the food can be absorbed by human body.However,the total amount of an ingested contaminant Cd does not always reflect the amount that is available to the body.Only a certain amount of the Cd is bioavailable.Meanwhile,different kind of food that is the main factor could affect the Cd bioavailability.Consequently,the human health risk assessments of Cd must be taken account of Cd bioavailability of different types of food.Therefore,this study explored the Bioaccessibility in vitro and Bioavailability in vitro and in vivo of Cadmium from various food for revising the limits standards of Cd in food for our country.Methods:Pig kidney（FK） and lettuce（FL） were randomly acquired in local（Wuhan）supermarkets.And cadmium contaminated Indica（FI） was purchased from Jiujiang.Using FK,FL and FC as the row material to study the bioaccessibility and bioavailability of cadmium from various food.1.The digestion conditions of RIVM were optimized by single factor experiment analysis.and to find the worst-case situation for digesting cadmium contaminated foods,As the information regarding to effect of food matrices on the Cd bioaccessibility from food is very limited,it is if interest,to assess and compare the bioaccessibility of Cd from rice（FI）,vegetable（FL） and animal-based foods（FK） by means of optimized in vitro digestion（RIVM）.2.Caco-2 cells in a monolayer state were established and assessed as the absorption model.And using Caco-2 cell model to evaluate the in vitro bioavailability of Cadmium from FK,FL and FI.3.Thirty 25 g ICR mice were randomly divided into 5 groups:negative control group,CdCl₂ group and experimental group（cadmium contaminated FK,FL and FI）.Each mouse was provided 10 g of feed per day（cadmium concentration of 80μg/kg）,the experiment needed to last for 21 days for the entire experimental period.During the experimental period,record the feed consumption,collect urine every day for each mouse.In order to make each mouse received the same level of Cd during the experiment.The Cd level of feed in CdCl₂ group and experimental group（FK,FL and FI） are same（0.4 mg/kg）.After 21 days,all the experiment mice were sacrificed after collect blood.Organs were collected and cadmium levels in blood and organs were measured by ICP-MS.Results:1.In vitro bioaccessibility of cadmium from different types of foods The digestion conditions of RIVM were optimized by single factor experiment analysis.The average recoveries of optimized RIVM were 94.74%-97.874%.and the relative deviation of accuracy was range from 2.06%-4.73%.The in vitro digestion model（RIVM） was applied to access the Cd bioaccessibility from various of food available.The result showed that in all three kinds of food,CdCl₂ and CdCl₂ mixed milk powder group,a considerable amount of cadmium was released during the in vitro digestion process.The CdCl₂ and CdCl₂ mixed milk powder group’s cadmium bioaccessibility were higher than FK,FL and FI groups.Cadmium bioaccessibility in in FK,FL and FI were 90.77±3.00%,86.48±4.24% and 90.92±6.63%,by using optimize in vitro digestion model.And the CdCl₂ group’s cadmium bioaccessibility is significant higher than FK（p<0.05）,FL（p<0.01） and FI groups（p<0.05）.The result demonstrated that compared with CdCl₂ group.The cadmium in food matrix is more difficultly to release from food matrix to digestive juice.2.In vitro bioavailability of cadmium from different types of foods Caco-2 cells in a monolayer state were successfully established and assessed as the absorption model.The TEER values of the cells monolayer reached values from 130 to 575 Ω·cm² after 21 days in vitro,as a culture.The mannitol efflux of fluorescein sodium was lower than Papp<10^-7 cm/s.Tight junction between the Caco-2 cells was formed with good permeability as well,which suggested that the established monolayer can be used as a model for absorption studies in vitro.Cadmium safe concentrations for Caco-2 cell were lower than 12μg/L.The soluble fraction obtain from small intestinal digestion phase was used to conduct the Cd bioavailability experiments in Caco-2 cells.The Cd bioavailability in the Caco-2 cell incubated with supernatants of different types of food was ranked from FI（23.72±0.78%）>FL（13.90±1.67%）>FK（13.22±1.66%）.Compared with CdCl₂ group,the bioavailability of Cd in FK and FL group were significantly decreased（p<0.01）,and FI group was significantly decreased（p<0.05）.The result demonstrated that compared with CdCl₂ group,the cadmium in food matrix is more difficulty to be absorbed by human small intestine.Meanwhile,the bioavailability of mixed CdCl2 with milk powder group was extremely significantly decreased than the other groups（p<0.01）.The results suggested that the trace elements（Fe,Ca,Zn） and protein in infant formula milk powder may interfere the absorption of cadmium in small intestine.At the same time,preliminary health risk assessment of three different cadmium-contaminated foods were carried out.The results showed that the THQ values which bioavailability of cadmium was not taken account of three different cadmium-contaminated foods were 4-7 times higher than those the THQ values which bioavailability was taken account.3.In vivo bioavailability of cadmium from different types of foods The microwave-digested inductively coupled plasma mass spectrometry was used to detect and analyze the cadmium content in tissues,blood and urine of mice in experimental groups.The in vivo absorption,distribution and bioavailability of cadmium in contaminated food and inorganic cadmium were analyzed and compared.After 21 days of cadmium contaminated Food（FK,FL and FI）and CdCl₂ exposure,the absorption distribution in the target organ of mice was mainly concentrated in the liver and kidney.While the cadmium nearly not accumulated in the blood,lung,spleen,and heart.After cadmium exposure for 21 days,the accumulation rate of cadmium in three kinds of foods group was lower than that in cadmium chloride group The results showed that cadmium in foods is not easy to accumulate compared with inorganic cadmium in vivo The result demonstrated that after 21 days of cadmium exposure,cadmium contaminated Food groups（FK,FL and FI）cadmium bioavailability in vivo were7.80±0.53%,8.45±0.76%,10.95±1.69%lower than CdCl₂ group（13.70±1.58%）.Compared with CdCl₂ group,the FK and FL groups cadmium bioavailability were significantly decreased（p<0.01）.The result showed that the cadmium binding with food matrix is not easy to absorb and available for body compared with inorganic cadmium in vivo.The results showed that the THQ values which bioavailability of cadmium was not taken account of three different cadmium-contaminated foods were 9-12 times higher than those the THQ values which bioavailability was taken account.Conclusion the bioaccessibility of cadmium and bioavailability of cadmium both in vitro and in vivo were studied by using RIVM/Caco-2 cell model and ICR experiment mice.In conclusion,from the present study,in all three kinds of contaminated food,CdCl₂ and CdCl₂ mixed milk powder group,a considerable amount of cadmium was released during the in vitro digestion process.Cadmium bioaccessibility in in FK,FL and FI were 90.77±3.00%,86.48±4.24%and 90.92±6.63%.And the CdCl₂ group’s cadmium bioaccessibility is significant higher than FK,FL and FI groups（p<0.05）.The result demonstrated that compared with CdCl₂ group.The cadmium in food matrix is more difficultly to release from food matrix to digestive juice;The Cd bioavailability in the Caco-2 cell incubated with supernatants of different types of food was ranked from FI（23.72±0.78%）>FL（13.90±1.67%）>FK（13.22±1.66%）.Compared with CdCl₂ group,the bioavailability of Cd in FK and FL group were significantly decreased（p<0.01）,and FI group was significantly decreased（p<0.05）.The result demonstrated that compared with CdCl₂ group,the cadmium in food matrix is more difficulty to be absorbed by human small intestine;After 21 days of cadmium contaminated Food（FK,FL and FI） and CdCl₂exposure,the absorption distribution in the target organ of mice was mainly concentrated in the liver and kidney.cadmium contaminated Food groups（FK,FL and FI）cadmium bioavailability in vivo were 7.80±0.53%,8.45±0.76%,10.95±1.69%lower than CdCl₂ group（13.70±1.58%）.Compared with CdCl₂ group,the FK and FL groups cadmium bioavailability were significantly decreased（p<0.01）.The result showed that the cadmium binding with food matrix is not easy to absorb and available for body compared with inorganic cadmium in vivo.