Vasoactive intestinal peptide, also known as the vasoactive intestinal polypeptide or VIP, is a peptide hormone that is vasoactive in the intestine. VIP is a neuropeptide of 28 amino acid residues that belongs to a glucagon/secretin superfamily, the ligand of class II G protein–coupled receptors. VIP is produced in many tissues of vertebrates including the gut, pancreas, and suprachiasmatic nuclei of the hypothalamus in the brain. VIP stimulates contractility in the heart, causes vasodilation, increases glycogenolysis, lowers arterial blood pressure and relaxes the smooth muscle of trachea, stomach and gall bladder. In humans, the vasoactive intestinal peptide is encoded by the VIP gene.
VIP has a half-life (t½) in the blood of about two minutes.
VIP has an effect on several tissues:
With respect to the digestive system, VIP seems to induce smooth muscle relaxation (lower esophageal sphincter, stomach, gallbladder), stimulate secretion of water into pancreatic juice and bile, and cause inhibition of gastric acid secretion and absorption from the intestinal lumen. Its role in the intestine is to greatly stimulate secretion of water and electrolytes, as well as relaxation of enteric smooth muscle, dilating peripheral blood vessels, stimulating pancreatic bicarbonate secretion, and inhibiting gastrin-stimulated gastric acid secretion. These effects work together to increase motility.It also has the function of stimulating pepsinogen secretion by chief cells.It is also found in the brain and some autonomic nerves. One region of the brain includes a specific area of the suprachiasmatic nuclei (SCN), the location of the 'master circadian pacemaker'. The SCN coordinates daily timekeeping in the body and VIP plays a key role in communication between individual brain cells within this region. Further, VIP is also involved in synchronising the timing of SCN function with the environmental light-dark cycle. Combined, these roles in the SCN make VIP a crucial component of the mammalian circadian timekeeping machinery.VIP helps to regulate prolactin secretion; it stimulates prolactin release in the domestic turkey.It is also found in the heart and has significant effects on the cardiovascular system. It causes coronary vasodilation as well as having a positive inotropic and chronotropic effect. Research is being performed to see if it may have a beneficial role in the treatment of heart failure.VIP provokes vaginal lubrication in normal women, doubling the total volume of lubrication produced.The growth-hormone-releasing hormone (GH-RH) is a member of the VIP family and stimulates growth hormone secretion in the anterior pituitary gland.VIP is overproduced in VIPoma. Can be associated with Multiple Endocrine Neoplasia Type 1 (Pituitary, parathyroid and pancreatic tumors). Symptoms are typically:
Profuse non-bloody/non-mucoid diarrhea (3L+) causing dehydration and the associated electrolyte disturbances such as hypokalemia and metabolic acidosis.Lethargy and exhaustion may ensue
