Gut microbiota significantly different in patients with bipolar disorder.

Causing contrasting episodes of mania and depression bipolar disorder (BD) can be an exhausting illness.  BD is a chronic and recurrent mental disorder with a worldwide prevalence of around 0.8%, associated with severe impairment in cognitive and social functions, and increased risk of disability and suicide, especially in young individuals.  However, the pathogenesis of BD is still unclear. 

Now, a study from researchers at Zhejiang University demonstrates how the gut microbiota’s taxonomic composition and diversity are significantly different in BD patients.  The team states their findings provide further evidence the microbiota-gut-brain axis is involved in BD pathogenesis.  The opensource study is published in the journal Advanced Science.

The gut-brain axis

Previous studies indicate the role of the brain-gut–microbiota axis in maintaining physical and mental well‐being is attracting a lot of attention. It has been described as a bidirectional modulation system consisting of a bridge between the brain and the gut via neuroanatomical, neuroimmune, and neuroendocrine pathways. 

Gut microbial alterations have been observed in many diseases, including inflammatory bowel disease, autoimmune diseases, obesity, metabolic syndrome, and neuropsychiatric disorders.  However, the available evidence of gut microbiota in maintaining health is mostly obtained from animal studies, and relevant human studies are still in the infancy stage.  The current study characterizes the gut microbiota in depressed BD patients, before and after quetiapine administration.

The current study analyses 16S-ribosomal RNA gene sequences of a total of 52 BD patients and 45 healthy controls.  Results show Bacteroidetes phylum, Parabacteroides, Bacteroides, and Halomonas genera were greatly enriched in BD patients, while Firmicutes phylum, Roseburia, Faecalibacterium, and Coprococcus genera were consistently higher in healthy controls.

Data findings show less butyrate-producing bacteria present in the guts of untreated BD patients; notably, butyrate can affect the function of the hippocampus and promote the expression of brain-derived neurotrophic factor, which is known to play a critical role in mood disorders.

The team states microbial composition changed following quetiapine treatment in BD patients, with the study also revealing the amounts of specific genera were correlated with clinical parameters and depressive severity. 

Microbe species in bipolar disorder

Results show at the genus level, Klebsiella, Lactobacillus, Anaeroglobus, Collinsella, Paraprevotella, Solobacterium, and Veillonella were enriched in treated BD patients, while Alistipes abundance was higher in untreated BD patients.  They go on to add their results indicate BD patients and healthy controls could potentially be distinguished by the gut microbiota, and treatment outcome might also be predicted by microbial markers.

The team surmises their study characterizes the gut microbiota in BD and is the first to evaluate microbial changes following quetiapine monotherapy.  For the future, the researchers state investigations should dig deeper to clarify the connections between gut microbiota and brain function in BD patients.

Source: Zhejiang University

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