Depressive Disorders, major depressive disorder, MDD
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- One previously uncultured bacterium, provisionally named Evtepia gabavorous KLE1738, which required the presence of Bacteroides fragilis KLE1758 for growth. Using bio-assay driven purification of B. fragilis supernatant, Gama-aminobutyric acid (GABA), the major inhibitory neurotransmitter of the mammalian central nervous system, was identified as the growth factor of E. gabavorous. In vitro feeding experiments and genomic analysis of E. gabavorous suggests an unusual metabolism focused on consuming GABA.
- Using growth of E. gabavorous as an indicator. Reduced levels of GABA are associated with depression, and we found fewer GABA producers in a human cohort of depressed, bipolar, and/or schizophrenic individuals. By modulating the level of GABA, microbial producers and consumers of this neurotransmitter may be influencing host . (1)
- Further biological testing and purification led to the isolation of GABA as the growth factor produced by Bacteroides fragilis. (3)
- The researchers found an inverse relationship between the relative abundance of fecal Bacteroidesand functional connectivity in a part of the brain associated with elevated activity during depression. This means that low abundance of Bacteroides was associated with high activity in that part of the brain, and vice versa.(3)
- Researchers identified two bacterial genera " Coprococcus and Dialister " were depleted in patients with depression whether or not they were taking antidepressants.
-The ability of microorganisms to produce DOPAC, a metabolite of the human neurotransmitter dopamine, was associated with better mental quality of life. (4)
- Lactobacillus rhamnosus reduce stress-induced corticosterone and anxiety- and depression-related behavior. (5)
- MDD is associated with higher relative abundance of Clostridiales , OTU16802 Bacteroides and Prevotellaceae.
- Similar association directions of for Blautia with MDD and SCZ.
- Increased Bacilli is potentially associated with a higher risk of MDD, possibly involving dopamine metabolism which might play a role in the major symptoms of MDD.
- Animal models found increased levels of Gammaproteobacteria were also associated with higher MDD risk and fluoxetine treatment was effective, implying strong correlations between gut microbiota and anxiety- and depression-like behaviors. (6)