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Studies on Cadmium in Wheat and Its Effects on the Human Gut Microbiome
Due to its genetic ability to accumulate cadmium in its grains, wheat is a major route of exposure to cadmium. Cadmium is associated to cancer in adults and disturbed neurodevelopment in children. Therefore, this work aimed at elucidating the accumulation of cadmium in a panel of historical and modern bread wheat cultivars, study strategies to reduce the bioavailability of cadmium from whole wheat flour, and to investigate the effect of cadmium on the human gut microbiome. Plant breeding has successfully improved the yield capacity of wheat cultivars released over the past 80 years in the Great Plains. Nevertheless, inadvertently, yield has had a dilution effect in the grain concentration of the micronutrients iron and zinc. On the contrary, cadmium is unaffected by this dilution, thus posing a threat to public health. Here, the in vitro cellular bioavailability of cadmium from raw whole wheat flour was determined to be low (0.2%) and unaffected by boiling or germination. Nevertheless, fermentation improved it by 2.3-fold. Additionally, cadmium dializability was found as a good indicator of cadmium bioavailability. Thus, dializability could be used for the screening of strategies to decrease cadmium bioavailability from wheat. As cadmium presents low bioavailability in the small intestine, it passes to the colon to directly interact with the gut microbiota. To evaluate its bioavailability during colonic fermentation, we developed Dialysis BioReactor Arrays (DBRAs) to study the dializability of cadmium. Cadmium presented low dializability after 24h fermentations (0.4%). Finally, we evaluated the effect of cadmium on the gut microbiome utilizing bioreactor communities from two human microbiomes. Cadmium presented a profound toxicity by abolishing butyrate production and simplifying one microbiome to mainly 6 cadmium-tolerant operational taxonomic units. Bacteria isolated from this community included E. faecium, E. cloacae, and L. lactis species able to grow under 100 ppm cadmium. This work demonstrated the high sensitivity of beneficial gut bacteria to cadmium stress and the potential of bacteria autochthonous to the human gut to be used as bioremediants.
Romero, Hollman Andres Motta, "Studies on Cadmium in Wheat and Its Effects on the Human Gut Microbiome" (2022). ETD collection for University of Nebraska - Lincoln. AAI29998414.