Among the underlying mechanisms proposed, the production of SCFAs is the most deeply investigated; the production of SCFAs has been demonstrated to protect against colitis by increasing the number of forkhead box P3 (Foxp3+) regulatory T cells in the colon and through the activation of the G-protein coupled receptor 43 (GPR43) expressed by immune cells and colonic epithelium [33,61,62]. The gene discussed is FFAR2; the disease is colitis.