Vasoactive intestinal peptide

Vasoactive intestinal peptide (VIP, also polypeptide ) is a peptide hormone containing 28 amino acid residues and is produced in many areas of the human body including the gut, pancreas and suprachiasmatic nuclei of the hypothalamus in the brain.

It has a half-life in the blood of about two minutes.

Function
VIP is a peptide that is present throughout the body, however it is at its highest concentration in the nervous and gastrointestinal systems.

There are increasing rates of gyconenolysis, water & electrolyte secretion from the pancreas and gut. Thus, stimulating bile flow, inhibiting gastrin and gastric acid secretion. VIP has an effect on several different parts of the body:


 * 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 dilating intestinal 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 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.

Pathology
VIP is overproduced in VIPoma.

Differential Diagnosis of Elevated VIP
Causes include;
 * VIP-secreting tumors
 * Can lead to Verner Morrison Syndrome
 * includes watery diarrhea, hypokalemia & achlorhydria