Variability of arsenic bioaccessibility and metabolism in soils by human gut microbiota using different in vitro methods combined with SHIME

Abstract

• Five in vitro gastrointestinal methods combined with SHIME (colon phase) were used.• As bioaccessibility varied in the colon phase among these methods.• Plenty of As(III) and methylated arsenicals by microbial transformation were observed.• As bioaccessibility in PBET/SBRC-SHIME colon phase were closer to in vivo results for NIST 2710a. Arsenic (As) speciation analysis is essential when evaluating the risks upon oral exposure to As-contaminated soils. In this study, we first investigated the variability in the As bioaccessibility and speciation using a combination of five common in vitro methods (SBRC, PBET, DIN, UBM and IVG) (gastric and small intestinal phases) and the SHIME model (colon phase). Our results indicate that the As bioaccessibility varies in the colon phase. An increase in the As bioaccessibility for SBRC and PBET, and a decrease for UBM and IVG were observed in the colon phase. In addition, we found different extents of methylation and large amounts of arsenite [As(III)] due to microbial reduction in the colon digests. The UBM-SHIME method displayed a higher methylation percentage of 13.5-82.1%, but a lower methylation percentage of 0.2-21.8% was observed in the SBRC-SHIME method. Besides, The MMA V levels in the colon digests were positively correlated with those of As(III) and DMA V , so DMA V can be considered an indicator to evaluate the As metabolic speed of in vitro cultured human gut microbiota. Based on the standard reference soil of NIST 2710a, the As bioaccessibility in the colon phase of PBET-SHIME and SBRC-SHIME were the closest to the in vivo results. Combining in vitro methods and SHIME will remarkably affect the accurate assessment of potential risks to human health associated with oral exposure to soil As.

Investigation of bioaccessibility of Cu, Fe, Mn, and Zn in market vegetables in the colon using PBET combined with SHIME

“…Feed solution specified by Yin et al . 20 was refreshed three times per day to provide digested nutrition for the colon microorganisms. The temperature (37 °C) and pH (5.6–5.9, 6.15–6.4, and 6.7–6.9 in the ascending colon, transverse colon and descending colon, respectively) were automatically maintained.…”

In vitro study of soil arsenic release by human gut microbiota and its intestinal absorption by Caco-2 cells

“…Briefly, the different colon compartments were inoculated with fresh fecal microorganisms. Feed solution detailed in Yin et al (2016) was added three times per day to provide digested nutrition for the colon microorganisms. After 3e4 weeks of adaptation, stable microbial communities were obtained in the colon compartments.…”

Arsenic and the gastrointestinal tract microbiome

“…This clinical case is consistent with the view that mineralization of ingested As results in reduced bioavailability during GIT transit and thus reduced toxicity. Depending on the form ingested, As bioavailability will vary along the different phases of the GIT (Yin et al, 2016), and levels and rates of SO 4 2− and As(V) reductions may have varying biochemical endpoints that vary in toxicity. Arsenic adsorption to solid phases will also limit As bioaccessibility, again with the expectation being reduced overall exposure and toxicity in the GIT.…”