Fig. 9

Metabolic activity of the gut microbiota in male mice exposed to Ref-Au or E175. A–C Orthogonal projection on latent structure-discriminant analysis (O-PLS-DA) score plots derived from ¹H-NMR spectra of faecal extract from males exposed to E175 at 0.1 (A), 1 (B) and 10 (C) µg/kg BW/day and males exposed to untreated food pellets (Ctrl). D–F Coefficient plots related to the O-PLS-DA models discriminating between males exposed to E175 at 0.1 (D), 1 (E) and 10 (F) µg/kg BW/day and males exposed to untreated food pellets (Ctrl). The figure shows the discriminant metabolites that are higher or lower in males exposed to E175 at 0.1 (D), 1 (E) and 10 (F) µg/kg BW/day compared to males exposed to untreated food pellets. Metabolites are colour-coded according to their correlation coefficient, with red indicating a very strong positive correlation. The direction of the metabolite indicates the group with which it is positively associated, as labelled on the diagram. G–J The area under the curve (AUC) of the ¹H-NMR spectra was integrated for aspartate (G), acetate (H), propionate (I) and medium-chain fatty acid (MCFA) (J) signals for male mice exposed to Ref-Au (10 µg/kg BW/d) or E175 (0.1, 1 and 10 µg/kg BW/d) for 13 weeks. Each dot represents an individual mouse. Data from one independent experiment are presented as the mean ± SEM. Statistical significance was determined by one-way ANOVA with Sidak’s post hoc test; *p < 0.05, **p < 0.01, ***p < 0.001