Fig. 5: Exploring the role of cecal microbial metabolites in modulating brain energy metabolism via the gut-brain axis during dietary restriction.

A Partial Least Squares—Discriminant Analysis (PLS-DA) analysis of the differences in cecal metabolite samples between groups. The closer the interpretation rate R2Y (cum) and the prediction rate Q2 (cum) are to 1, the better the PLS-DA model can explain and predict the differences between the two groups of samples, representing a better predictive ability of the model. B Cluster heatmap for Pearson correlation analysis of the top 30 microbials and the top 30 metabolites profiles between two groups. In the figure, each column represents a different species, and each row represents the corresponding metabolite. Metabolites on the horizontal axis are color-coded according to functional categories: those in green denote neurotransmitter-related metabolites, red represents tryptophan derivatives, purple indicates neuropeptide analogs, and black corresponds to neuroexcitatory substances. Orange-red indicates a positive correlation, while blue indicates a negative correlation. The deeper the color, the stronger the correlation, and colors closer to white represent correlations closer to zero. The significance of the correlation (*p < 0.05, **p < 0.01 and ***p < 0.001) is indicated. C Bubble plot displaying enriched metabolic pathways for intergroup differential metabolites. The y-axis shows pathway names, and the x-axis represents the enrichment factor (Rich factor-differential metabolites/total metabolites in pathway), with higher values indicating greater enrichment. Point color corresponds to the enrichment p-value (green: higher p-value; red: lower p-value), and point size reflects the number of enriched metabolites. Pathway enrichment significance in figure was determined by Fisher’s exact test with FDR correction (Benjamini-Hochberg method, q < 0.05). D Differential analysis of neuroactive-related metabolites secreted by the cecal microbiota between groups. The plot displays the top 20 differential metabolites, consisting of the 10 most significantly upregulated (red) and the 10 most significantly downregulated (blue) metabolites based on p-value. The x-axis represents log₂(FoldChange), while the y-axis indicates metabolite names. Statistical significance is denoted by asterisks (“*” represents p < 0.05 and “**” represents p < 0.01). Dot size corresponds to VIP value. E Diagram showing the analysis of the interaction between the rabbit’s cecum and cerebral cortex under dietary restriction.