Tryptophan (TRP) is an essential amino acid for protein synthesis. However, besides this role, it is an important precursor for numerous metabolites that can impact nerve system functioning and behavior. Latest research points out to TRP as one of the key players in bidirectional communication of microbiota-gut-brain axis, showing that its metabolism is under direct or indirect control of gut microbiota. Two major host TRP metabolic pathways are serotonin pathway, leading to production of serotonin and melatonin, and kynurenin pathway, leading to production of kynurenin and its downstream metabolites. Additionally, certain gut bacteria are able to convert TRP to several molecules, including indole and its derivatives, which can as well modulate host physiology and brain functioning. Therefore, research related to learning about complex interplay between TRP metabolism of the host and its commensal bacteria can be a gateway for understanding brain functioning and behavior, as well as etiology of psychiatric disorders.
So far, it is shown that brain levels of serotonin, which is involved in regulation of mood, cognition and stress response, are regulated by TRP availability to the brain that can be modulated by gut microbiota. On the other hand, host enzymes involved in TRP metabolism can affect composition of gut bacteria as well, which could in return also impact host behavior.
Further, levels of kynurenin and its downstream metabolites, which are implicated in depressive behavior, cognition and neurodevelopmental disorders, are influenced by gut microbes at multiple levels. For example, gut bacteria can regulate expression of kynurenin pathway enzymes by affecting host inflammatory response or certain microRNA levels.
Finally, some studies have shown that microbiota producing indole and its certain derivatives could be associated with neurodevelopmental disorders, as well as anxiety and depression. On the other hand, some indole metabolites were shown be neuroprotective.
Thus, the goal of this Research Topic would be to further advance our understanding about the role of gut bacteria in bidirectional communication along the microbiota-gut-brain axis, through effects on TRP metabolism, influencing host behavior and development of neuropsychiatric diseases. We also aim to explore manipulations of gut bacterial composition in order to modulate TRP metabolism as a possible future way for treatment of pathological conditions.
We encourage submission of Original Research Articles, Brief Research Reports, Reviews and Mini-Reviews. Research done using animal models as well as clinical studies are welcome. The contributors are invited to deal with, but are not limited to, the following themes:
1. Serotonin pathway of TRP metabolism: its modulation by gut microbiota and effects on brain and behavior;
2. Kynurenin pathway of TRP metabolism: its modulation by gut microbiota and effects on brain and behavior;
3. Microbial TRP metabolism: its effects on the host brain and behavior;
4. Targeting gut microbiota as a way to modulate TRP metabolism in order to improve brain functioning and behavior.
Tryptophan (TRP) is an essential amino acid for protein synthesis. However, besides this role, it is an important precursor for numerous metabolites that can impact nerve system functioning and behavior. Latest research points out to TRP as one of the key players in bidirectional communication of microbiota-gut-brain axis, showing that its metabolism is under direct or indirect control of gut microbiota. Two major host TRP metabolic pathways are serotonin pathway, leading to production of serotonin and melatonin, and kynurenin pathway, leading to production of kynurenin and its downstream metabolites. Additionally, certain gut bacteria are able to convert TRP to several molecules, including indole and its derivatives, which can as well modulate host physiology and brain functioning. Therefore, research related to learning about complex interplay between TRP metabolism of the host and its commensal bacteria can be a gateway for understanding brain functioning and behavior, as well as etiology of psychiatric disorders.
So far, it is shown that brain levels of serotonin, which is involved in regulation of mood, cognition and stress response, are regulated by TRP availability to the brain that can be modulated by gut microbiota. On the other hand, host enzymes involved in TRP metabolism can affect composition of gut bacteria as well, which could in return also impact host behavior.
Further, levels of kynurenin and its downstream metabolites, which are implicated in depressive behavior, cognition and neurodevelopmental disorders, are influenced by gut microbes at multiple levels. For example, gut bacteria can regulate expression of kynurenin pathway enzymes by affecting host inflammatory response or certain microRNA levels.
Finally, some studies have shown that microbiota producing indole and its certain derivatives could be associated with neurodevelopmental disorders, as well as anxiety and depression. On the other hand, some indole metabolites were shown be neuroprotective.
Thus, the goal of this Research Topic would be to further advance our understanding about the role of gut bacteria in bidirectional communication along the microbiota-gut-brain axis, through effects on TRP metabolism, influencing host behavior and development of neuropsychiatric diseases. We also aim to explore manipulations of gut bacterial composition in order to modulate TRP metabolism as a possible future way for treatment of pathological conditions.
We encourage submission of Original Research Articles, Brief Research Reports, Reviews and Mini-Reviews. Research done using animal models as well as clinical studies are welcome. The contributors are invited to deal with, but are not limited to, the following themes:
1. Serotonin pathway of TRP metabolism: its modulation by gut microbiota and effects on brain and behavior;
2. Kynurenin pathway of TRP metabolism: its modulation by gut microbiota and effects on brain and behavior;
3. Microbial TRP metabolism: its effects on the host brain and behavior;
4. Targeting gut microbiota as a way to modulate TRP metabolism in order to improve brain functioning and behavior.
