Gut Microbiota Influencing Mind

Abstract

The gut microbiota has received increasing attention for its potential impact on bodily functions, particularly through the gut-brain axis. This complex interplay allows the gut to impact mood, cognition, and mental health, while also enabling the brain to modulate intestinal activities [1]. The composition of gut microbiota varies widely among individuals. Lower microbiota diversity has been associated with various brain disorders [1]. Therefore, probiotics are considered as a potential supplementary treatment for these conditions [2]. The metabolites produced by gut microbiota, used as precursors to neurotransmitters, or affecting CNS via the vagus nerve, play a crucial role in this effect [3].

This research project is conducted as a literature review with the aim to further describe and summarize the effects of Lactobacillus on cognition and to identify gaps. PubMed and Google Scholar were utilized, excluding journals with an impact factor below 3. Keywords such as Lactobacillus, cognition, gut-brain axis, human, and rodent were used.

Lactobacillus is one of the most common bacterial species in humans that positively affect the body. Lactobacillus probiotics were found to have an antidepressant effect on rodents [2]. After being exposed to chronic-restraint stress, rodents treated with Lactobacillus had lower levels of corticosterone hormone. They exhibited less depressive and anxious behavior and better performance on the maze task. Similar reductions in cortisol levels have been observed in human studies, with probiotic-treated patients displaying reduced reactivity to sad mood. However, it is worth noting that the benefits of probiotics may have a ceiling effect, with no further improvement seen in individuals who are already happy [2].

Overall, there is increasing evidence supporting the positive effects of Lactobacillus species on rodents, and some showing similar effects on humans. The research field primarily focuses on impairments and diseases, and there is a lack of studies involving healthy individuals. Direct causal effect and mechanism of influence on human cognition is still not clear. Further studies are necessary to address these gaps.

References

[1] Y. Chen, J. Xu, and Y. Chen, “Regulation of neurotransmitters by the gut microbiota and effects on cognition in neurological disorders,” Nutrients, vol. 13, no. 6. MDPI, Jun. 01, 2021. doi:10.3390/nu13062099

[2] A. Sarkar, S. M. Lehto, S. Harty, T. G. Dinan, J. F. Cryan, and P. W. J. Burnet, “Psychobiotics and the Manipulation of Bacteria–Gut–Brain Signals,” Trends Neurosci, vol. 39, no. 11, pp. 763–781, Nov. 2016. doi:10.1016/j.tins.2016.09.002

[3] J. A. Bravo et al., “Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve,” Proc Natl Acad Sci U S A, vol. 108, no. 38, pp. 16050–16055, Oct. 2011. doi:10.1073/pnas.1102999108