Disease ⇒ Major depressive disorder ⇒ Depression {40000197}

References Notes

Shared Reference Notes

• [1.5] 
  -The levels of fecal GABA and its relevant metabolites (N-acetylornithine, proline, oxoproline, and glutathione) were consistently decreased in MDD relative to HCs, suggesting a decrease in GABA content in the intestine.
  - A microbial enzyme–related gene (BetB) that participated in arginine metabolism to GABA was down-regulated in MDD.
  - Three microbial genes involved in the metabolism of glutamine to GABA was up-regulated in MDD.
  - Fecal GABA level in the patients with MDD may be modulated by a panel of gut microbes, which may be implicated in the development of MDD.
  - Majority of genes involved in the phenylalanine catabolic pathways were decreased in MDD, suggesting an inhibition of fecal phenylalanine degradation.
  - A downstream catabolic product of homovanillate was also decreased in MDD. These findings were consistent with disturbances of phenylalanine metabolism in MDD.
  - A gene (kynu) involved in kynurenic acid to quinolinic acid was enriched in MDD subjects relative to HCs, yielding an increased synthesis of the neurotoxic metabolite quinolinic acid.
  - A lower fecal quinolinic acid level in MDD.
  - These preliminary findings may account for the higher blood level of quinolinic acid observed in MDD.
  - Microbial GABA, phenylalanine, and quinolinic acid metabolisms were linked with MDD onset
• [1.10] 
  - Major depression and anxiety states, are common in patients presenting with irritable bowel syndrome (IBS)
• [1.11] 
  - Patients with major depressive disorder showed a statistically significant overrepresentation of Bacteroides enterotype 2 compared to controls.
• [1.12] 
  - γ-aminobutyric acid (GABA) production by human-derived Bacteroides is widespread, and there is a correlation between brain signatures of depression and fecal Bacteroides levels in patients with major depressive disorder.
• [1.13] 
  - 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)
• [1.7] 
  - Mendelian randomization analysis indicated a potential causal effect of Morganella on major depressive disorder, consistent with observational incident
• - Actinobacteria were found to be increased, whereas Bacteroidetes were decreased in relation to other phyla, and some studies suggested decreased microbial diversity in MDD patients