As it turns out, a healthy gut microbiome could affect the development of conditions relate to anxiety or anxiety-like behavior. The new study by researchers from the APC Microbiome Institute showed the connection in tests involving mice.

Study co-author Dr. Gerard Clarke, of the APC Microbiome Institute at University College Cork in the Republic of Ireland, and colleagues recently reported their findings in the journal Microbiome.

“Gut microbes seem to influence miRNAs in the amygdala and the prefrontal cortex,” lead research Gerard Clarke said in a press release provided by BioMed Central. “This is important because these miRNAs may affect physiological processes that are fundamental to the functioning of the central nervous system and in brain regions, such as the amygdala and prefrontal cortex, which are heavily implicated in anxiety and depression.”

miRNAs are a short sequence of nucleotides – which are the building blocks of DNA and RNA – that control how genes are expressed.

When they don’t function properly, it’s thought miRNAs contribute significantly to stress-related psychiatric disorders, neurodegenerative diseases and neurodevelopmental abnormalities.


Dr Clarke said: “It may be possible to modulate miRNAs in the brain for the treatment of psychiatric disorders but research in this area has faced several challenges, for example, finding safe and biologically stable compounds that are able to cross the blood-brain barrier and then act at the desired location in the brain. Our study suggests that some of the hurdles that stand in the way of exploiting the therapeutic potential of miRNAs could be cleared by instead targeting the gut microbiome.”


Compared with the conventional mice, the researchers found that the germ-free mice showed differences in 103 miRNAs in the amygdala – which is the brain region involved in emotional processing – and 31 changes in miRNAs in the prefrontal cortex – which is the brain region involved in behavior, planning, and impulse control, among other functions.

Importantly, when the researchers introduced bacteria to the guts of the germ-free mice in later life, some of the differences in miRNAs within the amygdala and the prefrontal cortex disappeared.

As such, the team speculates that a healthy gut microbiome is required for normal miRNA regulation.

The authors note that the exact mechanism by which the gut microbiota is able to influence the miRNAs in the brain remains unclear. Even though the study shows that effects of the microbiota on miRNAs are present in more than one species (mice and rats), further research into the possible connection between gut bacteria, miRNAs and anxiety-like behaviors is needed before the findings can be translated to a clinical setting.

Dr Clarke said: This is early stage research but the possibility of achieving the desired impact on miRNAs in specific brain regions by targeting the gut microbiota — for example by using psychobiotics — is an appealing prospect.”