The impact of Akkermansia muciniphila and its extracellular vesicles in the regulation of serotonergic gene expression in a small intestine of mice.

ABSTRACT

OBJECTIVES: A better understanding of host-microbe interactions as a cross-talk between the gastrointestinal (GI) tract and the gut microbiota can help treat and prevent GI disorders by improving the maintenance of GI homeostasis. The gut microbiota can affect signaling molecules, such as serotonin, which regulates endocrine systems through the GI tract. Moreover, studying the effects of gut microbiota in the small intestine on the human GI tract health is pivotal. METHODS: Male C57BL/6J mice (n = 30, 10 mice per group) were orally gavaged with 200 µL of PBS (control group); mice in group II were orally gavaged with 109 colony-forming units (CFU)/200 µL of viable A. muciniphila, suspended in PBS (A. muciniphila group); and mice in group III were orally gavaged with 10 µg of protein/200 µL of EVs (A. muciniphila-EV group) once daily for four weeks. The gene expression of serotonin system-related genes (Slc6a4, Tph1, Mao, Htr3, Htr4, and Htr7) was examined by quantitative real-time PCR (qPCR) method. RESULTS: Based on the results, A. muciniphila significantly affected the mRNA expression of genes related to the serotonin system (Tph1, Mao, Htr3B, and Htr7) in the duodenum and (Htr3B, Htr4 and Htr7) in the ileum of mice (P < 0.05). Moreover, A. muciniphila-derived EVs affected the expression of major genes related to the serotonin system (Tph1, slc6a4a, Mao, Htr3B, Htr4, and Htr7) in the duodenum and ileum of mice (P < 0.05). CONCLUSIONS: The present findings may pave the way for further investigation of the effects of strain-specific probiotics on the serotonergic system, which is currently in its infancy.