The effect of HP7 on enhancing 5-HT receptor expression may be related to our previous finding indicating that HP7 increases the expression of brain-derived neurotrophic factor (BDNF) [26], a vital neutrophil factor in the GI tract that controls visceral sensation, motility, and intestinal barrier function and is observed at low levels in patients with FD [27]. Here, BDNF is linked to Fabry disease.