Fig. 4: The key metabolites, including arginine and propionate, are upregulated in LBF individuals.

A OPLS-DA result of metabolites derived from LBF individuals (green points) and HBF individuals (plum points) (n = 5). R2X and R2Y represent the fraction of variance of the X and Y matrices, respectively, and Q2Y: the predictive accuracy of the model. B Volcano plot displays the significantly different metabolites (SDMs) identified by comparing the metabolites dataset between LBF and HBF individuals. The data were compared by using a two-tailed Student’s t-test (unpaired). C The KEGG pathway analysis of SDMs. Metabolites with VIP score > 1, fold change (FC) ≥ 1.5 and ≤ 0.5, and p value < 0.05 were significant. Points and arc-shaped bars with different colors in the internal cycle represent SDMs and the enriched pathways, respectively. The second, third, and fourth inter-cycle represent the upregulation and downregulation status of metabolites, the Spearman’s correlation coefficient between SDMs and P. succinatutens, and VIP values, respectively. The external bar plot displays the relative concentration (log10 normalized) of each metabolite. D The levels of inflammatory factors (IL-1β, TNF-α, and IL-6) in serum between LBF and HBF individuals (n = 6). E The concentrations of SCFAs in fecal samples between LBF and HBF individuals (n = 6). F Multiple correlation analysis among SDMs enriched in different pathways, LBF individual-related bacterial species, SCFAs, and inflammatory factors. Spearman’s correlation test. Significance between every two groups was analyzed using a two-tailed (unpaired) Student’s t-test. The bar charts are presented as mean ± SD. *p < 0.05, **p < 0.01, ***p < 0.001, ns not significant difference.