So far, however, it appears that the potential existence of neuropeptides encrypted in the proteins produced by human intestinal microbes has not been explored.
In the study published in the Food Research International journal, Blanco-Míguez and colleagues, in a collaboration between Spanish and Portuguese research institutes, performed a large-scale screening of the human gut microbiome in search for specific bacterial genus that produces bioactive neuropetides.
The authors used the amino acid sequences of the 5949 neuropeptides from the Neuropepdatabase. In addition, all the 91.325.790 sequences of potential bioactive peptides from the bioactive section of Mechanism of Action of the Human Microbiome (MAHMI) database were screened. From the screening, 581 peptides matched human neuropeptides, non-human peptides, or digestive hormones. From the 581 peptides, 258 could be found in human neuropeptide databases, 313 in non-human neuropeptide databases, and 10 as digestive hormones.
Considering the potential bacterial genus that produces potential neuropeptides, 14% were members of the genera Ruminococcus, 10% members of genera Clostridium, 7% members of genera Firmicutes, and 3% from the genera Lactobacillus, Streptococcus, and Escherichia. Some of these genera are known to expand regulatory T Cells (Treg) population of lymphocytes and are important in intestinal homeostasis (Atarashi et al., Nature, 500, 232–236, 2013).
Thus, this study appears to provide the first in silico evidence indicating the production of peptides with a double bioactivity: neuropeptide or digestive-related, and immunomodulatory or anti-inflammatory by specific genus of gut bacteria.
Interestingly, and as stated by the authors, “Classical (Lactobacillus sp.) and next-generation (Faecalibacterium sp.) probiotics are shown to produce these peptides, which are proposed as a potential mechanism of action of psychobiotics”.
This may also indicate that different gut microbiotas, via the release of these neuropetides can influence host immunity, and the gut-brain cross-talk, which in turn, may have important implications for conditions such as depression,pain, etc.
Source: Food Res Int, 2018. 119:221-226. doi: 10.1016/j.foodres.2019.01.069