Figure 4. Chronic ingestion of subtoxic doses of Cd alters the gut microbiome, and luminal metabolite and proteomic profiles.

Mice (n=5 per group) were provided CdCl₂ [10 μM (Cd10) or 25 μM (Cd25)] in drinking water for 28 days. (A) Intestinal permeability was analyzed by measuring serum FITC-dextran (4 kDa). (B) Fecal IgA levels. Total IgA levels in freshly emitted feces were analyzed by ELISA. The amounts of IgA were normalized by total protein content. (C) Relative proteins expression in mice treated with Cd10 vs. NoCd mice. (D) Bacterial load in fecal extracts. Dilution of fecal pellets were normalized by mass (g) of feces and plated on blood agar, and bacteria (CFU) were counted after 48 h of culture. (E) Relative abundance of Firmicutes to Bacteroidetes (upper) and other less dominant phyla (lower). (F and G) Metabolites in fecal extracts. (F) Principal component analysis of metabolite profiles. (G) Heat map of relative expression of metabolites with significantly different concentrations in samples from Cd-treated mice vs. NoCd mice (*p < 0.05). Data are expressed as the mean ± SD. *p < 0.05; **p < 0.01 (4–5 mice per group).