Feeling anxious? Your gut bacteria might be to blame


Researchers have shed further light on the link between gut bacteria and anxiety. All of us experience anxiety at one point or another; whether down to a job interview or a first date, that nervous feeling in the gut often takes hold. Interestingly, a new study suggests that when it comes to anxiety, the gut could play a key role.
Researchers found that the absence of gut bacteria in mice altered the expression of microRNAs (miRNAs) in regions of the brain that play a role in anxiety and depression.
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.
This is not the first study to suggest a link between gut bacteria and anxiety. A study reported by Medical News Today in 2015, for example, found that stress in early life may alter gut bacteria in a way that may increase the risk of anxiety in later life.
But what are the mechanisms that underly the possible link between gut bacteria and anxiety? The new study from Dr. Clarke and team helps to shed light.
The team notes that mice bred in germ-free conditions are more likely to develop symptoms of anxiety, depression, problems with sociability, and cognitive dysfunctions. As part of the study, the team looked at how the absence of gut bacteria affected miRNAs in the rodents’ brains. miRNAs are tiny RNA molecules that regulate gene expression.
Researchers suggest that a compound produced by gut bacteria could help humans to live a longer, healthier life.
Specifically, the researchers sought to pinpoint which miRNAs were present in the amygdala and prefrontal cortex of the mice in each gut bacteria condition.
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.
“Gut microbes seem to influence miRNAs in the amygdala and the prefrontal cortex,” says Dr. Clarke.

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