**3. Intestinal immunity**

The SCFAs activate different G-protein-coupled receptors (GPCR) e.g. propionate (C2), which is an activator of GPR43. The expression of GPR43 has been reported in the entire gastrointestinal tract including the cells of both the nervous and immune systems. In the GI tract, GPR43 is significantly expressed in endocrine L-cells of the ileum and colon of intestinal, PYY, and GLP-1 producing cells, as well as on colonocytes and enterocytes [9], that maintains the immunity and function of the intestine [10].
