Antibiotics affect tryptophan-kynurenine metabolism. (a) Relative concentration of tryptophan metabolites in serum. (b) The ratio of kynurenine to tryptophan (IDO1 indicator) and kynurenic acid to kynurenine (KAT indicator) from serum profiles. n = 11, 10, 13, 14 for NDL, NDL+Abx, KDL, KDL+Abx groups, respectively (a, b). (c) Heatmap of discriminant metabolites in hippocampus. (d) The ratio of kynurenine to tryptophan and kynurenic acid to kynurenine in the hippocampal profiles. n = 13, 14, 14, 14 for NDL, NDL+Abx, KDL, KDL+Abx groups, respectively (C, D). (e) Summary of antibiotic effects on metabolism. Data are presentd as mean±SEM (a, b, d). One-way ANOVA followed by Turkey's post-hoc test (a, b, d): *p < 0.05. NDL, normal diet and intracerebral lesion; NDL+Abx, normal diet and intracerebral lesion with oral antibiotics; KDL, ketogenic diet and intracerebral lesion; KDL+Abx, ketogenic diet and intracerebral lesion with oral antibiotics; IDO1, indoleamine 2, 3-dioxygenase 1; KAT, kynurenine aminotransferase; KYN, kynurenine; KA, kynurenic acid; PLP, pyridoxal phosphate; TRP, tryptophan.