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It is the primary hormone responsible for the contraction of the gallbladder and the secretion of pancreatic enzymes. It is also known as Cholecystokinin.
The original discovery of Cholecystokinin was in 1928 and was based on the observation that a substance within intestinal extracts stimulated the gallbladder contraction.
In 1943, a similar extract (called pancreozimine) was observed to stimulate the secretion of pancreatic enzymes.
However, the purification of the hormone and the determination of its amino acid sequence showed that the actions in the gallbladder and the pancreas were due to the same hormone.
Like other gastrointestinal hormones, Cholecystokinin is produced in discrete endocrine cells that line the mucosa of the small intestine.
It is also found in the central nervous system and the peripheral nerves that innervate the intestine.
In these locations, Cholecystokinin probably functions as a neurotransmitter.
Cholecystokinin plays a crucial role in facilitating digestion within the small intestine.
It is secreted from mucosal epithelial cells in the first segment of the small intestine (duodenum). It stimulates the supply to the small intestine of digestive enzymes from the pancreas and bile from the gallbladder.
Cholecystokinin is also produced by neurons in the enteric nervous system and is widely and abundantly distributed in the brain.
Cholecystokinin, also known as CCK or CCK-PZ, is a hormone once called pancreozimine due to its actions on the pancreas.
Cholecystokinin is a hormone produced in I cells that line the duodenum. It is a hormone that is also released by some neurons in the brain.
Cholecystokinin appears to be involved in addition to controlling appetite, anxiety, and panic disorders.
Control and physiological effects of Cholecystokinin
Food that flows into the small intestine consists mainly of large macromolecules (proteins, polysaccharides, and triglycerides) that must be digested into small molecules (amino acids, monosaccharides, fatty acids) be absorbed.
The digestive enzymes of the pancreas and the bile salts of the liver (which are stored in the gallbladder) are essential for this digestion.
Cholecystokinin is the primary stimulus for the supply of pancreatic enzymes and bile in the small intestine.
The most potent stimuli for cholecystokinin secretion are the presence of partially digested fats and proteins in the lumen of the duodenum.
An elevation in the blood concentration of Cholecystokinin has two main effects that facilitate digestion:
- Release of digestive enzymes from the pancreas into the duodenum. Previous literature refers to Cholecystokinin as pancreozyme, a term coined to describe this effect.
- Contraction of the gallbladder to deliver bile into the duodenum. The name cholecystokinin (“move the gallbladder”) described this effect. Cholecystokinin is also known to stimulate the secretion of bile salts in the biliary system.
The physiological properties of Cholecystokinin also include delaying gastric emptying, enhancing insulin secretion, and regulating food intake.
Additionally, Cholecystokinin regulates intestinal motility and has growth-promoting effects on the pancreas.
Pancreatic enzymes and bile flow through ducts into the duodenum, leading to the digestion and absorption of the same molecules that stimulate cholecystokinin secretion.
Therefore, when absorption is complete, cholecystokinin secretion ceases.
In addition to its synthesis in the epithelial cells of the small intestine, Cholecystokinin has been found in neurons, within the wall of the intestine, and in many areas of the brain.
It appears to be the most abundant neuropeptide in the central nervous system.
The secretion of Cholecystokinin from neurons appears to modulate the activity of other hormones and neuropeptides. Still, it seems safe to say that understanding its role in brain function is rudimentary at best.
Disease states
Diseases that result from excessive or deficient secretion of Cholecystokinin are rare.
Cholecystokinin deficiency has been described in humans as part of the autoimmune polyglandular syndrome and manifested as a malabsorption syndrome clinically similar to pancreatic exocrine insufficiency.
Furthermore, there is growing evidence that aberrations in the expression of Cholecystokinin or its receptor in the human brain may play a role in the pathogenesis of certain types of anxiety and schizophrenia.
Possible problems with the hormone cholecystokinin or Cholecystokinin
People who have cholecystokinin levels that are too high have no known harmful effects.
Cholecystokinin’s lack of side effects prompted research on its use as a weight-loss option, as the hormone has an appetite-reducing effect.
Too little Cholecystokinin can hurt the body.
Obese people have been found to have lower-than-average levels of Cholecystokinin, which can contribute to problems with increased appetite and more incredible difficulty losing weight.
