Peptide YY
Encyclopedia
Peptide YY is a short protein
released by cells in the ileum
and colon
in response to feeding. In humans it appears to reduce appetite.
It is also known as PYY, Peptide Tyrosine Tyrosine, or Pancreatic Peptide YY3-36.
s with structural homology
to NPY and pancreatic polypeptide
.
, especially in ileum
and colon
. There is also a small amount of PYY, about 1-10 percent, in esophagus
, stomach
, duodenum
and jejunum
. PYY concentration in the circulation increases postprandially (after food ingestion) and decreases by fasting
. In addition, PYY is produced by a discrete population of neurons in the brainstem, specifically localized to the gigantocellular reticular nucleus of the medulla oblongata
. C. R. Gustavsen et al. had found PYY producing cells located in the islets af Langerhans in rats. They were observed either alone or co-localized with glucagon or PP.
s, inhibits gastric motility
and increases water and electrolyte
absorption in the colon. PYY may also suppress pancreatic
secretion
. It is secreted by the neuroendocrine cell
s in the ileum
and colon
in response to a meal, and has been shown to reduce appetite
. PYY works by slowing the gastric emptying; hence, it increases efficiency of digestion and nutrient absorption after meal. Research has also indicated that PYY may be useful in removing aluminium
(aluminum) accumulated in the brain
.
have been done, and the result has revealed that there is no anorectic
effect on Y2R-knock out mice. This findings indicate that PYY3-36 has anorectic ( losing appetite) effect, which is suggested to be mediated by Y2R. Some studies have been done to investigate the effect of PYY on mice. Pyy-knock out female mice increase in body weight and fat mass. Pyy-knockout mice, on the other hand, are resistant to obesity
but have higher fat mass and lower glucose tolerance when fed with high-fat diet, compare to control mice. Thus PYY also plays very important role in energy homeostasis by balancing the food intake.
also reduces appetite in response to feeding, but obese
people develop a resistance to leptin. It has also been known that obese people secrete less PYY than non-obese people. On the other hand, attempts to use PYY directly as a weight-loss drug have met with some success. Researchers noted that caloric intake during a buffet lunch offered two hours after the infusion of PYY was decreased by 30 percent in obese subjects (P<0.001) and 31 percent in lean subjects (P<0.001).
While some studies have shown that obese persons have lower circulating level of PYY postprandially, other studies have reported that obese people have normal sensitivity to anoretic effect of PYY3-36. Thus, reduction in PYY secretion may not be one of the causes of obesity. However, the anoretic effect of PYY could possibly be a future obesity drug.
Research done in 2006 showed that consumption of protein boosts PYY levels, therefore some benefit was observed in experimental subjects in terms of reducing hunger and promoting weight loss. This would help explain the weight-loss experienced with high-protein diets.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
released by cells in the ileum
Ileum
The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum.The ileum follows the duodenum...
and colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
in response to feeding. In humans it appears to reduce appetite.
It is also known as PYY, Peptide Tyrosine Tyrosine, or Pancreatic Peptide YY3-36.
Structure
Peptide YY is related to the pancreatic peptide family by having 18 of its 36 amino acids located in the same positions as pancreatic peptide. There are two major forms of Peptide YY: PYY1-36 and PYY3-36 which have PP fold structural motif. However, the most common form of circulating PYY immunoreactivity is PYY3-36, which binds to Y2 receptor (Y2R) of Y family receptors. Peptide YY3-36 (PYY) is a linear polypeptide consisting of 36 amino acidAmino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s with structural homology
Homology (chemistry)
In chemistry, homology refers to the appearance of homologues. A homologue is a compound belonging to a series of compounds differing from each other by a repeating unit, such as a methylene group, a peptide residue, etcetera....
to NPY and pancreatic polypeptide
Pancreatic polypeptide
Pancreatic polypeptide is a polypeptide secreted by PP cells in the endocrine pancreas predominantly in the head of the pancreas. It consists of 36 amino acids and has molecular weight about 4200 Da....
.
Release
PYY is found in L cells in the mucosa of gastrointestinal tractGastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
, especially in ileum
Ileum
The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum.The ileum follows the duodenum...
and colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
. There is also a small amount of PYY, about 1-10 percent, in esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
, stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
, duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
and jejunum
Jejunum
The jejunum is the middle section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms middle intestine or mid-gut may be used instead of jejunum.The jejunum lies between the duodenum...
. PYY concentration in the circulation increases postprandially (after food ingestion) and decreases by fasting
Fasting
Fasting is primarily the act of willingly abstaining from some or all food, drink, or both, for a period of time. An absolute fast is normally defined as abstinence from all food and liquid for a defined period, usually a single day , or several days. Other fasts may be only partially restrictive,...
. In addition, PYY is produced by a discrete population of neurons in the brainstem, specifically localized to the gigantocellular reticular nucleus of the medulla oblongata
Medulla oblongata
The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
. C. R. Gustavsen et al. had found PYY producing cells located in the islets af Langerhans in rats. They were observed either alone or co-localized with glucagon or PP.
Function
PYY exerts its action through NPY receptorNeuropeptide Y receptor
Neuropeptide Y receptors are a class of G-protein coupled receptors which are activated by the closely related peptide hormones neuropeptide Y, peptide YY and pancreatic polypeptide...
s, inhibits gastric motility
Gastrointestinal physiology
Gastrointestinal physiology is a branch of human physiology addressing the physical function of the gastrointestinal system. The major processes occurring in the GI system are that of motility, secretion, regulation, digestion and circulation...
and increases water and electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
absorption in the colon. PYY may also suppress pancreatic
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...
secretion
Secretion
Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland. In contrast to excretion, the substance may have a certain function, rather than being a waste product...
. It is secreted by the neuroendocrine cell
Neuroendocrine cell
Neuroendocrine cells are cells that receive neuronal input and, as a consequence of this input, release message molecules to the blood. In this way they bring about an integration between the nervous system and the endocrine system, a process known as neuroendocrine integration...
s in the ileum
Ileum
The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum.The ileum follows the duodenum...
and colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
in response to a meal, and has been shown to reduce appetite
Appetite
The appetite is the desire to eat food, felt as hunger. Appetite exists in all higher life-forms, and serves to regulate adequate energy intake to maintain metabolic needs. It is regulated by a close interplay between the digestive tract, adipose tissue and the brain. Decreased desire to eat is...
. PYY works by slowing the gastric emptying; hence, it increases efficiency of digestion and nutrient absorption after meal. Research has also indicated that PYY may be useful in removing aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
(aluminum) accumulated in the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
.
Animal studies
Several studies have shown that acute peripheral administration of PYY3-36 inhibits feeding of rodents and primates. Some more studies on Y2R-knockout miceKnockout mouse
A knockout mouse is a genetically engineered mouse in which researchers have inactivated, or "knocked out," an existing gene by replacing it or disrupting it with an artificial piece of DNA...
have been done, and the result has revealed that there is no anorectic
Anorectic
An anorectic or anorexic , also known as anorexigenic or appetite suppressant, is a dietary supplement and/or drug which reduces appetite, food consumption, and as a result, causes weight loss to occur.-List of anorectics:Numerous pharmaceutical compounds are marketed as appetite suppressants.The...
effect on Y2R-knock out mice. This findings indicate that PYY3-36 has anorectic ( losing appetite) effect, which is suggested to be mediated by Y2R. Some studies have been done to investigate the effect of PYY on mice. Pyy-knock out female mice increase in body weight and fat mass. Pyy-knockout mice, on the other hand, are resistant to obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
but have higher fat mass and lower glucose tolerance when fed with high-fat diet, compare to control mice. Thus PYY also plays very important role in energy homeostasis by balancing the food intake.
Relevance to obesity
LeptinLeptin
Leptin is a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism. It is one of the most important adipose derived hormones...
also reduces appetite in response to feeding, but obese
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
people develop a resistance to leptin. It has also been known that obese people secrete less PYY than non-obese people. On the other hand, attempts to use PYY directly as a weight-loss drug have met with some success. Researchers noted that caloric intake during a buffet lunch offered two hours after the infusion of PYY was decreased by 30 percent in obese subjects (P<0.001) and 31 percent in lean subjects (P<0.001).
While some studies have shown that obese persons have lower circulating level of PYY postprandially, other studies have reported that obese people have normal sensitivity to anoretic effect of PYY3-36. Thus, reduction in PYY secretion may not be one of the causes of obesity. However, the anoretic effect of PYY could possibly be a future obesity drug.
Research done in 2006 showed that consumption of protein boosts PYY levels, therefore some benefit was observed in experimental subjects in terms of reducing hunger and promoting weight loss. This would help explain the weight-loss experienced with high-protein diets.