Table 4.
Association of mental/neurological disorders with microbiota, metabolites, or neurotransmitter changes.
| Disorder | Associated microbiota | Metabolite/neurotransmitter change/mechanism | Reference |
|---|---|---|---|
| Attention-deficit-hyperactive disorder (ADHD) | Lactobacillus spp., and Bifidobacterium spp. | Tryptophan ↑ SCFAs ↑ Polyunsaturated fatty acids ↓ Dopamine |
Barrett et al. (2013), Dinan et al. (2013), Erny et al. (2015), O’Mahony et al. (2015), Pärtty et al. (2015), and Bassett et al. (2019) |
| ↑ Bifidobacterium genus | It was assumed that the increase of Bifidobacterium was linked to significantly enhanced 16S-based predicted bacterial gene functionality encoding cyclohexadienyl dehydratase, the enzyme that is involved in the synthesis of phenylalanine (precursor of DA). | Aarts et al. (2017) | |
| Enterococcus spp., Escherichia spp., and Streptococcus spp. | ↓ 5-HT | Bull-Larsen and Mohajeri (2019) | |
|
Bifidobacterium spp., Enterococcus spp., Escherichia spp., Lactobacillus spp., Clostridia spp., Streptococcus spp. |
↓ 5-HT | Dam et al. (2019), Boonchooduang et al. (2020), and Eicher and Mohajeri (2022) | |
|
↑ Actinobacteria (genus Bifidobacterium)
↓ Firmicutes |
Compensatory ↑ DA | Aarts et al. (2017) | |
| Autism spectrum disorder (ASD) |
↓ fermenting bacteria: Coprococcus, Prevotella, and Veillonellaceae |
Kang et al. (2013) | |
|
↑ Bacteroidetes, Proteobacterium, Desulfovibrio species and Bacteroides vulgatus; ↓ Bifidobacterium genus, Firmicutes and Actinobacterium |
LPS-induced inflammation LPS decreases levels of glutathione, an important antioxidant involved in heavy metal detoxification in the brain |
Zhu et al. (2007) and Finegold et al. (2010) | |
|
Hespellia, Anaerostipes, Desulfovibrio spp. |
Finegold et al. (2010) | ||
| Alzheimer’s disease (AD) | Escherichia coli, Bacillus subtilis, Mycobacterium tuberculosis, Salmonella enterica, Salmonella typhimurium, Staphylococcus aureus | ↑ Bacterial amyloids production | Jiang et al. (2017), Megur et al. (2021), Tran and Mohajeri (2021), and Eicher and Mohajeri (2022) |
| Anxiety-like behavior | Lactobacillus spp. | Glutamate is a key excitatory neurotransmitter in the CNS and excitatory amino acids | Henter et al. (2021) |
|
Bifidobacterium dentium, ↓ Lactobacillus brevis |
↓ GABA | Barrett et al. (2012) | |
| Bipolar disorder (BD) | Toxoplasma gondii | Chronic inflammation | Sutterland et al. (2015) |
| ↑ Bifidobacterium, Oscillibacter, Enterococcus, Flavonifractor, Streptococcus and Megasphaera; ↓ Roseburia, Faecalibacterium, and Ruminococcus | McGuinness et al. (2022) | ||
| Fibromyalgia | ↓ Diversity of bacteria; ↓ Bifidobacterium and Eubacterium genera | Altered levels of glutamate and serine | Clos-Garcia et al. (2019) |
| ↓ Bacteroides thetaiotaomicron, Bacteroides uniformis, Prevotella copri; ↑ Clostridium scindens, Enterocloster bolteae | ↓ α-Muricholic acid and other secondary bile acids | Minerbi et al. (2023) | |
| Major depressive disorder (MDD) | ↓ Coprococcus spp. and Dialister | ↓ SCFAs | Valles-Colomer et al. (2019), Socała et al. (2021), and Modesto Lowe et al. (2023) |
| ↑ Flavonifractor, Escherichia/Shigella and Veillonella; ↓ Prevotella and Ruminococcus |
↑ Bacteria associated with glutamate and GABA metabolism and ↓ bacteria producing SCFA(e.g., butyrate) | McGuinness et al. (2022) | |
| ↑ Lactobacillus, Streptococcus, and Enterococcus | ↑ Increased lactic acid | Valles-Colomer et al. (2019) and McGuinness et al. (2022) | |
| ↓ Faecalibacterium and Coprococcus | ↓ SCFAs (mainly butyrate) | ||
| Migraine | ↓ Firmicutes family: Clostridial Clusters IV and XIVa, Coprococus spp., Eubacterium hallii Faecalibacterium prausnitzii, Lachnosiraceae spp., and Roseburia spp. | ↓ 5-HT ↓ SCFAs (mainly butyrate) |
Kappéter et al. (2023) |
| Akkermansia mucinophila, Alistipes putredinis, ↓ Bacteroides vulgatus and uniformis, Prevotella copri, Roseburia inulinivorans, Veilonella spp. | ↓ Propionate synthesis and BBB protection from oxidative stress | ||
| ↑ Alcaligenes spp., Candida spp., Clostridium coccoides and propionicum, Eggerthella lenta, Micromycetes spp., Pseudonocardia spp., and Rhodococcus spp. | Kopchak and Hrytsenko (2022) | ||
| ↑ Bacteroides and Coprococcus ↓ Prevotella and Escherichia-shigella |
↓ L-tryptophan, linoleic acid, and nicotinamide; ↑ L-arginine, glutamic acid, L-tyrosine, L-DOPA, 3-indoxyl sulfate |
Wen et al. (2019) | |
| Neuropathic pain | ↑ Lactobacillus | 41 Upregulated metabolites and 31 downregulated metabolites, among these, differentially expressed metabolites including allantoin, D-quinovose and D(−)-beta-hydroxy butyric acid, N6,N6,N6-trimethyl-l-lysine, 3-methylhistidine, exhibited consistent expression trends. The lower level of 2-hydroxybutyric acid was in both serum and spinal cord samples from CCI rats in comparison to sham rats | Chen et al., 2021 |
| ↑ Lactobacillus | ↑ SCFAs (propionate, and butyrate) | Zhou et al. (2022) | |
| Parkinson’s disease (PD) |
↑ Bacteroidetes, Proteobacteria, and Verrucomicrobia; ↓ Firmicutes |
↓ SCFAs chronic systemic inflammation | (Shannon, 2022) |
|
↓ Genera Blautia, Coprococcus, and Roseburia (butyrate-producing bacteria with anti-inflammatory properties) ↑ Proteobacteria (genus Ralstonia) with proinflammatory properties |
↓ SCFAs | (Keshavarzian et al., 2015) | |
| Schizophrenia (SZ) | Succinvibrio and Corynebacterium | Association with the severity of symptoms | Li et al. (2020) |
| ↑ Prevotella, Megasphaera; ↑ Escherichia/Shigella and Veillonella; ↓ Bacteroides, Haemophilus, Roseburia, and Streptococcus |
McGuinness et al. (2022) | ||
|
Bacteroides, Prevotella, and Clostridium are among the top 3 altered genera, Bacteroides-Prevotella ratio ↑ |
↑ SCFAs | Nguyen et al. (2019) and Li et al. (2023) | |
| Ruminococcus | Li et al. (2020) | ||
| Blautia | Shen et al. (2018) | ||
| Toxoplasma gondii can cause a risk of mania developing | Chronic inflammation | Dickerson et al. (2014) | |
| Stroke | ↑ Enterobacteriaceae and Prevotella; ↓ SCFA-producing bacteria; ↓ Lachnospiraceae and Ruminococcaceae; ↓ Firmicutes and Faecalibacterium; ↓↑ Bacteroidetes |
↑ LPS, ↓ Butyric acid, ↓ SCFAs |
Benakis and Liesz (2022) |
| ↑ Enterobacteriaceae ↓ Clostridium tyrobutyricum |
↑ LPS, ↓ Metabolites of the tryptophan-kynurenine pathway and ↑ indole metabolites, impairing the integrity of BBB; ↓ SCFAs and bile acids |
Zeng et al. (2023) | |
| Traumatic brain injury | ↑ Metabolites concerned with late glycolysis, cysteine, and one carbon metabolites, as well as metabolites affected by arginine metabolism, endothelial dysfunction, and responses to hypoxia | Coleman et al. (2023) | |
| 7-Day post-TBI: ↑ Streptococcus (Streptococcaceae) ↓ Akkermansia (Verrucomicrobia) |
↓ Bacterial secretion system, sulfur metabolism, biosynthesis of steroids, no-homologous end-joining, and protein processing in the endoplasmic reticulum; ↑ Epithelial cell signaling in Helicobacter pylori infection and pentose as well as glucuronate interconversions; ↑ Indole-3-acetaldehyde (IAAld) and indole-3-ethanol (IEt); ↑ 5-HT; ↓ Indole-3-lactic acid (ILA) and skatole; ↓ Melatonin and 5-hydroxy indole acetic acid (5-HIAA); Tryptophan metabolism through the ↑ kynurenine (KYN) and ↓ neuroprotective kynurenic acid (KYNA); ↓ Xanthurenic acid (XA); ↑ KYN/Tryptophan and ↓ KYNA/KYN correlation indicates increased metabolism through the neurotoxic pathway |
Zheng et al. (2022) | |
| 28-Day post-TBI: ↑ Streptococcus (Streptococcaceae), Proteobacteria, TM7 and Actinobacteria; ↓Verrucomicrobia, Bacteroidetes, Cyanobacteria, and Deferribacteres |
↓ Gut microbiota functions of biosynthesis, including lipopolysaccharide, n-Glycan, primary and secondary bile acid, and steroids; ↑ Metabolism of chlorophyll, glycerophospholipid, thiamine, porphyrin, and riboflavin; ↑ 5-HT; ↑ Tryptophan metabolism through the kynurenine KYNA is often considered to be neuroprotective; ↑ The ratio KYNA/KYN; ↓ Melatonin, 5-HIAA and XA |
Zheng et al. (2022) | |
| Visceral pain | ↑ Phylum Bacteroidetes, Proteobacteria, and Tenericutes; ↓ Phylum Firmicutes and Actinobacteria |
In rats aged 4 and 8 weeks during 4 and 6 weeks after vancomycin administration in dose 100 mg/kg | (O’Mahony et al., 2014) |
| Activation of the immune, humoral, and neuroendocrine (hypothalamic–pituitary–adrenal axis) systems, both autonomic (nervus vagus) and enteric nervous systems, spinal afferents nerves, 5-HT, SCFAs, tryptophan-related metabolites, and neurometabolites (dopamine, GABA, noradrenaline) potentially modulating function of CNS Histamine produced by microbiota and visceral pain |
Moloney et al. (2015, 2016), Agirman et al. (2021), and De Palma et al. (2022) |