Fig. 4. Age-related gut functional characteristics.

a Box plot and bar chart showing the gut microbial KEGG pathway annotation (xenobiotics biodegradation and metabolism, amino acid metabolism, carbohydrate metabolism, lipid metabolism, biosynthesis of other secondary metabolites, metabolism of other amino acids, metabolism of cofactors and vitamins, glycan biosynthesis and metabolism, metabolism of terpenoids and polyketides). P values were obtained from two-sided Wilcoxon rank-sum tests. For all box and whisker plots, the center line represents median. The bounds of box represent the first and third quartiles. The upper whisker extends from the hinge to the largest value no further than 1.5 * interquartile range (IQR) from the hinge. The lower whisker extends from the hinge to the smallest value at most 1.5 * IQR of the hinge. b Heatmap showing the gut microbial functions of RNA polymerase, dehydrogenase, methyltransferase, oxidoreductase, acetyltransferase betwween six age groups. Box plot showing the changes of superoxide dismutase, glutathione stransferase, and catalase with age groups. c, d Correlations between the selected age-related bacterial genus and metabolic pathway and oxidoreductase. * indicates p < 0.05; ** indicates p < 0.01; *** indicates p < 0.001 by Wilcoxon rank-sum test.