FFAR2 and obesity due to melanocortin 4 receptor deficiency: Indeed, SCFAs ameliorate obesity [26,32,49,121], diabetes [27,29,153], and colitis [2,34,44] which involves activation of FFAR2/3, indicating that gut microbiota-derived SCFAs’ mediated activation of FFAR2/3 signaling plays a crucial role not only in maintaining normal physiological and cellular functions but also protecting from diseases.