Table 3.
The studies associated with changes in brain regions and gut microbiota.
| Study Design (subjects, intervention) | Bacteries | Changes in brain region (intestinal dysbacteriosis) | Reference |
|---|---|---|---|
| GF and SPF NMRI mice | / | noradrenaline, dopamine, and 5-HT turnover↑ in the striatum; NGFI-A mRNA↓ in the orbital frontal cortex, striatum, hippocampus (CA1,CA3 region, dentate gyrus), amygdala; BDNF mRNA↓ in the hippocampus, amygdala, cingulate cortex in GF mice compared with SPF mice. Synaptophysin and PSD-95 in the striatum↓ in SPF and CON mice compared with GF mice. | (Diaz Heijtz et al., 2011) |
| 5 weeks male C57BL/6 mice (bacitracin, neomycin, natamycin, meropenem, vancomycin) | Firmicutes, Bacteroidetes↓, Proteobacteria↑ | tight-junction proteins↓ of the brain blood vessels and BBB permeability↑ in antibiotic treated mice | (Sun et al., 2021) |
| male Wistar rats (T2DM; Lactobacillus plantarum, inulin, or synbiotic) | dominant populations were lactobacillus | Lactobacillus plantarum led to a significant decrease in TLR-2 as well as GDNF and GFAP only in the amygdala | (Hosseinifard et al., 2019) |
| Healthy women (FMPP: 12, controls: 11, no intervention: 13) | / | FMPP reduces the reactivity of a widely distributed network of brain regions (primary interoceptive and somatosensory regions, and a cluster in the midbrain region centered on the periaqueductal gray, the prefrontal cortex, precuneus, basal ganglia, and the parahippocampal gyrus) to an emotional attention task. | (Tillisch et al., 2013) |
| Swiss Webster (GF and CON mice); Adult male Sprague Dawley rats (ampicillin, vancomycin, ciprofloxacin HCL, imipenem, metronidazole) | / | 103 miRNAs (61 downregulated, 42 upregulated) changed in the amygdala, and 31 miRNAs (21 downregulated, 10 upregulated) altered in the PFC in GF animals | (Hoban et al., 2017) |
| BALB/c mice (SPF and GF mice) | / | l-aspartic acid in striatum, cerebral cortex and hippocampus, and l-arginine, l-alanine and l-valine in striatum↑ in SPF mice than in GF mice | (Kawase et al., 2017) |
| 12 weeks C57BL/6J mice (SPF and GF mice) | / | microbiota dependent-hypomyelination of several gray matter structures (neocortex, HIP, brainstem) and major white matter tracts (the corpus callosum, anterior commissure, internal capsule) specifically in GF mice using MPF imaging. | (Lu et al., 2018) |
| Swiss Webster (GF and CC mice) | / | the volumes of ACC↓and periaqueductal grey↑, dendritic changes in the ACC were evident in GFmice. | (Luczynski et al., 2017) |
| 6 weeks male C57BL/6J mice (ampicillin, streptomycin, clindamycin) | Bifidobacterium, Escherichia Coli, Lactobacillus↓ | Fos immunoreactive (ir) neurons in mPFC and HIP↓, in ACC and IC↑ in antibiotic treated mice | (Wang et al., 2021b) |
| GF mice (E. coli JM83, complex microbiota, or no microbiota) | / | displayed disorganization of gene co-expression networks in HIP, amygdala, mPFC in E. coli JM83 treated mice | (Philip et al., 2021) |
↑, indicates increase; ↓, indicates decrease.
ACC, anterior cingulate cortex; BBB, blood-brain barrier; CC, conventionally colonized; FMPP, fermented milk product with probiotic, containing Bifidobacterium animalis subsp Lactis, Streptococcus thermophiles, Lactobacillus bulgaricus, and Lactococcus lactis subsp Lactis; GDNF, glial cell-derived neurotrophic factor; GFAP, glial fibrillary acidic protein; GF, germ-free; HIP, hippocampus; IC, insular cortex; PFC, prefrontal cortex; SPF, specific pathogen -free; T2DM, type 2 diabetes mellitus.