In addition to regulating the motor function, the SNS and parasympathetic nervous system (PNS) regulate the postprandial GI peptides secretion by enteroendocrine cells (EEC). EECs are the first line components of the Brain-Gut axis. Multiple peptides, such as incretins (GLP-1, GLP-2, GIP), and PYY (peptide YY) are important for the maintenance of glucose homeostasis. They are secreted by a different type of EEC in the GI tract. Prior to their absorption, nutrients in the GI lumen are important stimuli for peptide secretion in the ileum in rats, pigs , and humans. These peptides are secreted before the bulk of ingested meal reaches to the ileum, suggesting the presence of a neuronal/endocrine pathway in GI tract.