Fig. 3

Glu level and GABA metabolism were significantly altered in CADASIL patients. A Volcano plot of the significantly different neurotransmitters between serum samples from the case and control groups. “Up” indicates the neurotransmitter was upregulated in the case group compared to the control group. B–D The content of serum glutamic acid (B), alpha-ketoglutaric acid (C), and GABA (D) in the samples from the case and control groups were identified by targeted neurotransmitter profiling. E The comparison of Glu/GABA ratio in serum samples between the case and the control group. A–E Case, n = 12; control, n = 10. F The schematic diagram of the main pathway about 4-aminobutanoate (GABA) degradation V and GABA shunt in bacteria and involved enzymes. G The abundance of the five enzymes in fecal metagenomic samples from patients and healthy controls. H Stacked bar plot of the average relative abundance of the top 10 contributing species to EC2.6.1.19 in the case and control groups, respectively. I The relative abundance of EC2.6.1.19 contributed by the top four species in the case and control groups. J The relative abundance of these four species in fecal metagenomics samples. G–J Case, n = 24; control, n = 28. Significance levels between the case and control groups were tested by Student’s t-test (B–E) and Wilcoxon rank-sum test (G, I, J). *p-value < 0.05; **p-value < 0.01; ns, not significant