Indeed, enteroendocrine cells secrete a number of different hormones such as glucagon-like peptide 1 (GLP-1), peptide-YY (PYY), cholecystokinin (CCK) and serotonin (5-hydroxytriptamine, 5-HT), with a key impact on nutrient absorption, metabolism and appetite [9,10], and also modulation of anxiety-like behaviors [11]. This evidence concerns the gene PYY and Anxiety.