Systematic Review of Gut Microbiota and Major Depression

Abstract

Background: Recently discovered relationships between the gastrointestinal microbiome and the brain have implications for psychiatric disorders, including major depressive disorder (MDD). Bacterial transplantation from MDD patients to rodents produces depression-like behaviors. In humans, case-control studies have examined the gut microbiome in healthy and affected individuals. We systematically reviewed existing studies comparing gut microbial composition in MDD and healthy volunteers.Methods: A PubMed literature search combined the terms “depression,” “depressive disorder,” “stool,” “fecal,” “gut,” and “microbiome” to identify human case-control studies that investigated relationships between MDD and microbiota quantified from stool. We evaluated the resulting studies, focusing on bacterial taxa that were different between MDD and healthy controls.Results: Six eligible studies were found in which 50 taxa exhibited differences (p < 0.05) between patients with MDD and controls. Patient characteristics and methodologies varied widely between studies. Five phyla—Bacteroidetes, Firmicutes, Actinobacteria, Fusobacteria, and Protobacteria—were represented; however, divergent results occurred across studies for all phyla. The largest number of differentiating taxa were within phylum Firmicutes, in which nine families and 12 genera differentiated the diagnostic groups. The majority of these families and genera were found to be statistically different between the two groups in two identified studies. Family Lachnospiraceae differentiated the diagnostic groups in four studies (with an even split in directionality). Across all five phyla, nine genera were higher in MDD (Anaerostipes, Blautia, Clostridium, Klebsiella, Lachnospiraceae incertae sedis, Parabacteroides, Parasutterella, Phascolarctobacterium, and Streptococcus), six were lower (Bifidobacterium, Dialister, Escherichia/Shigella, Faecalibacterium, and Ruminococcus), and six were divergent (Alistipes, Bacteroides, Megamonas, Oscillibacter, Prevotella, and Roseburia). We highlight mechanisms and products of bacterial metabolism as they may relate to the etiology of depression.Conclusions: No consensus has emerged from existing human studies of depression and gut microbiome concerning which bacterial taxa are most relevant to depression. This may in part be due to differences in study design. Given that bacterial functions are conserved across taxonomic groups, we propose that studying microbial functioning may be more productive than a purely taxonomic approach to understanding the gut microbiome in depression.

Effects of regulating gut microbiota on the serotonin metabolism in the chronic unpredictable mild stress rat model

“…Recent study has established noteworthy changes in profusion levels among phyla and genera in the gut microbial community; in the meantime, the metabolism of tryptophan and bile acids was also disturbed after chronic variable stress intervention . Recently, Stephanie Cheung et al reported that the largest number of differentiating taxa was within phylum Firmicutes; nine genera were higher in major depressive disorder . Jessica M et al have reported that indigenous spore‐forming bacteria control metabolites that stimulate colon 5‐HT biosynthesis from colonic enterochromaffin cells .…”

Variation in the pH of experimental diets affects the performance ofLymantria dispar asiaticalarvae and its gut microbiota

“…Clinical investigations suggested that intestinal microflora is closely related to the health of an individual (Sekirov, 2010). Many diseases or conditions associated with suboptimal health are proved to be related with intestinal microbiota, such as depression (Cheung et al, 2019), chronic constipation (Ohkusa, Koido, Nishikawa, & Sato, 2019), and nonalcoholic liver disease (Ding et al, 2019). Similarly, numerous investigations have been devoted to elucidating the role of intestinal microflora in mammals (Pasinetti et al, 2018;Roselli et al, 2017) and fishes (Gómez & José Luis, 2010;Zhou, Ringø, Olsen, & Song, 2018).…”

Ambient temperature‐mediated enzymic activities and intestinal microflora in Lymantria dispar larvae

“…Traditional cultivation‐dependent technique for microorganism research was limited by numerous microorganisms that cannot be cultured now, and cannot reflect the alteration of microbiota community. However, the advent of amplicon sequencing offered us an insight of the entire community structure and those uncultured microorganisms (B. Chen et al, ; Cheung et al, ; Shao et al, ). More and more nonegligible roles of intestinal microflora were revealed by sequencing technology.…”

“…However, the advent of amplicon sequencing offered us an insight of the entire community structure and those uncultured microorganisms (B. Chen et al, 2016;Cheung et al, 2019;Shao et al, 2017). More and more nonegligible roles of intestinal microflora were revealed by sequencing technology.…”