Vasoactive Intestinal Peptide (VIP)
A 28 amino acid neuropeptide found in the gut, pancreas, and nervous system that stimulates intestinal water and electrolyte secretion, relaxes smooth muscle, and has anti-inflammatory properties. VIP biology is relevant to understanding gastrointestinal peptide signalling and neuroendocrine tumour biology.
Technical Context
VIP (28 aa) belongs to the secretin/glucagon peptide superfamily. It acts through VPAC1 and VPAC2 receptors (class B GPCRs, Gαs-coupled) expressed widely in the GI tract, respiratory system, immune cells, and nervous system. VIP stimulates intestinal water and electrolyte secretion, relaxes smooth muscle (vasodilation, bronchodilation), inhibits gastric acid secretion, and has immunomodulatory effects (promoting Th2 over Th1 responses). VIPomas (VIP-secreting neuroendocrine tumours) cause watery diarrhoea syndrome (Verner-Morrison syndrome), which is effectively treated with somatostatin analogues (octreotide, lanreotide) that suppress VIP secretion and its intestinal effects.