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Gut microbiota shaping brain by PGN-PRRs

A new pathway for the gut microbiota to modulate the brain: activation of pattern-recognition receptors by microbial products

Molecular Psychiatry volume 22, pages 162–163 (2017)Cite this article

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Gut microbiome has been increasingly recognized as a new environmental factor that can influence the brain through the microbiota–gut–brain axis.1 In physiological conditions, most of the research effort to date has been focused on the identification of differently expressed brain molecules, construction and psychobehavioral characteristics in germ-free (GF) mice and conventionally raised specific pathogen-free counterparts.2, 3 These studies have shown a close interaction between gut microbiota and the brain. In pathological conditions, the research has been mainly focused on the identification of disease-related bacterial species, and further uncovering the underlying molecular basis by metagenomic and metabolomic methods. Using this strategy, dysbiosis of gut microbiota had been implicated in the onset of several mental disorders, such as depression and autism.4, 5, 6 Although great advances have been achieved in this field within short time, the signal pathways of how microbial products derived from gut microbiota influence the brain remain largely unknown.

A recent Molecular Psychiatry paper by Arentsen et al7 shows that peptidoglycan (PNG), one kind of microbial product, can cross the blood–brain barrier (BBB) and influence PGN-sensing molecules (for example, pattern-recognition receptors, PRRs), and PGN transporters. PNG levels were quantified in the developing brain of healthy animals, showing that increased PGN levels paralleled the postnatal bacterial colonization process. This study provides a simple, economical, but effective, strategy to directly determine whether gut microbial products can be detected in developing brain and influence brain function. However, one should be vigilant as this method may not be widely used for majority of the brain molecules, such as neurotransmitters, which are regulated by both gut microbiota and the brain.8 For those purposes, GF mice, which are devoid of any bacterial contamination, should be used. For example, treatment of GF mice with special gut microbiota can result in increased host neurotransmitters, which may be another way to modulate the direct mechanisms of products derived from gut microbiota.

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Acknowledgements

This work was supported by the National Basic Research Program of China (973 Program, grant no. 2009CB918300) and the National Natural Science Foundation of China (grant no. 81401140 and 30900456).

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Authors and Affiliations

  1. Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China

    P Zheng, K Cheng, L Zeng, C-J Zhou & P Xie

  2. Chongqing Key Laboratory of Neurobiology, Chongqing Medical University, Chongqing, China

    P Zheng, K Cheng, L Zeng, C-J Zhou & P Xie

  3. Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China

    P Zheng, K Cheng, L Zeng, C-J Zhou & P Xie

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Correspondence to P Xie.

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Zheng, P., Cheng, K., Zeng, L. et al. A new pathway for the gut microbiota to modulate the brain: activation of pattern-recognition receptors by microbial products. Mol Psychiatry 22, 162–163 (2017). https://doi.org/10.1038/mp.2016.210

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