Cholecystokinin: what it is, and effects of this hormone and neurotransmitter.

This substance is related to the feeling of satiety in eating.

Cholecystokinin (CCK) is a hormone that is secreted in the intestine and is activated in response to the ingestion of certain foods. and is activated in response to the ingestion of certain foods. It is involved in processes such as digestion and appetite, generating a feeling of satiety that helps us to regulate our appetite.

In this article we explain in more detail what this hormone is and what functions it performs, how the satiety effect is produced and what the most recent research says about its possible role in the prevention of cognitive deterioration.

What is cholecystokinin?

Cholecystokinin is produced in the small intestine, specifically in the duodenum and jejunum, and causes gallbladder contraction and pancreatic secretion. This hormone is also considered a neurotransmitter that is released in the nervous system, especially in the hypothalamus.especially in the hypothalamus.

This hormone belongs to the quinine group, which is formed from globulins (a group of water-soluble proteins present in animals and plants) by proteolytic enzymatic action. Proteolysis consists of the degradation of proteins, either by specific enzymes or through intracellular degradation.

The secretion or production of cholecystokinin depends on factors such as the presence of some nutrients from the food stored in the intestine, mainly fats and proteins (fatty acids).mainly fats and proteins (fatty acids and amino acids).

Functions

Cholecystokinin has several functions, both in its role as a gastrointestinal hormone and as a neurotransmitter in the nervous system.

As a gastrointestinal hormone

Cholecystokinin, together with gastrin and secretin, constitutes one of the main hormones secreted at the gastrointestinal level. It is known that CCK secretion and its effects on gastric motility depend on the fats ingested, specifically on the length of the fatty acid chain.specifically on the length of the fatty acid chain.

• CCK acts as a satiety signal and once released has multiple effects on the gastrointestinal system, performing the following functions:
• It causes contraction of the gallbladder, facilitating the excretion of bile into the duodenum, which is involved in digestion processes.
• Stimulates the secretion of hydrochloric acid in the stomach, to promote digestion by breaking down food.
• It regulates pancreatic secretion of enzymes and hormones, such as insulin and glucagon, regulating hepatic and Blood glucose production.
• It stimulates relaxation and opening of the sphincter of Oddi, a muscle that opens in response to food so that bile and pancreatic digestive juices enter the duodenum and mix with food for digestion.

As a neurotransmitter

cholecystokinin has also been found in the brain (mainly in the cortex, but also in other areas such as the retina, hippocampus, hypothalamus and spinal cord) and exerts a role as a neurotransmitter or neuromodulator, acting on neurons in the periaqueductal gray matter, which are related to pain perception, and on neurons in the medial hypothalamus, which are responsible for controlling food intake.

CCK levels are usually elevated towards the end of the meal, triggering the mechanisms of pain perception.triggering satiety mechanisms. The presence of CCK in the amygdala and in some areas of the cerebral cortex has led researchers to suggest that this hormone could have a role related to emotions.

It has also been found that cholecystokinin has an anxiogenic (anxiety-causing) function in the brain, since several studies have shown that injecting agonists into one of the CCK receptors produces autonomic and behavioral changes associated with sensations such as fear and anxiety, while antagonistic substances cause the opposite.

CCK, in addition, appears to interact at synapses with another neurotransmitter, dopamine, especially in the nigral fibers.especially in the nigrostriatal fibers that innervate the striatum and the nucleus accumbens, a brain structure involved in reward systems and responsible for integrating motivational information with emotions and motor actions.

CCK and the satiety effect

Cholecystokinin (CCK) is the best-studied satiety-inducing peptide.. Let us now see how this effect is produced.

CCK is secreted by the mucosal I cells of the duodenum and jejunum in response to the presence of partially digested fats and carbohydrates from the stomach.

This hormone, as mentioned above, causes contraction of the gallbladder, causes contraction of the gallbladder, release of pancreatic enzymes, inhibition of gastric motility and gastric emptying, thereby decreasing the size of the stomach.thus decreasing the size of the food ingested.

Cholecystokinin secretion is activated by the presence of breakdown products of dietary fats, peptides, amino acids and, to a lesser extent, carbohydrates; and is inhibited by the intestinal concentration of pancreatic proteases (trypsin and chymotrypsin) and bile, following ingestion of a food.

CCK causes contraction of the pylorus (the lower opening of the stomach). (the lower opening of the stomach that communicates with the small intestine), generating a gastric distension that activates the vagal afferents that relay to the nucleus of the solitary tract to finally stimulate the satiety center; a satiating effect that lasts approximately 90 minutes.

Recent research

Recent research conducted by scientists at the University of Iowa in the United States suggests that a high level of cholecystokinin may decrease a person's likelihood of developing Alzheimer's disease..

The researchers conducted a study with 287 subjects and chose this hormone, which acts as a neurotransmitter in the brain, for its high expression in the formation of a cognitive process such as memory.

Their objective was to detect whether there is a relationship between cholecystokinin levels and memory, and the state of gray matter in the hippocampus and other related brain areas.

At the same time, the neuroscientists studied tau proteins (whose accumulation is related to the development of Alzheimer's disease), with the aim of observing how they might interact with cholecystokinin and memory.

The results of the study concluded that, as tau protein levels increased, an equally high level of cholecystokinin was associated with the development of Alzheimer's disease, an equally high level of cholecystokinin was no longer associated with less memory impairment..

This research highlights the importance of studying the nutritional aspect of diets, as well as their relationship with mental health and their involvement in the prevention of cognitive impairment and neurodegenerative disorders such as Alzheimer's disease.