Pancreatic polypeptide

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Pancreatic polypeptide
Pancreatic hormone 1TZ5.png
Identifiers
SymbolPPY
NCBI gene 5539
HGNC 9327
OMIM 167780
RefSeq NM_002722
UniProt P01298
Other data
Locus Chr. 17 p11.1-qter
Search for
Structures Swiss-model
Domains InterPro
Immunohistochemistry for pancreatic polypeptide in a mouse pancreas, 200x PancreaticPolypeptide.jpg
Immunohistochemistry for pancreatic polypeptide in a mouse pancreas, 200×

Pancreatic polypeptide (PP) is a polypeptide secreted by PP cells in the endocrine pancreas. It regulates pancreatic secretion activities, and also impacts liver glycogen storage and gastrointestinal secretion. Its secretion may be impacted by certain endocrine tumours.

Contents

Gene

The PPY gene encodes an unusually short protein precursor. [1] This precursor is cleaved to produce pancreatic polypeptide, pancreatic icosapeptide, and a 5- to 7- amino-acid oligopeptide. [1]

Structure

Pancreatic polypeptide consists of 36 amino acids. [2] [3] It has a molecular weight about 4200 Da. [2] It has a similar structure to neuropeptide Y. [3]

Synthesis

Pancreatic polypeptide is synthesised and secreted by PP cells (also known as gamma cells or F cells) of the pancreatic islets of the pancreas. [3] [4] These are found predominantly in the head of the pancreas.[ citation needed ]

Function

Pancreatic polypeptide regulates pancreatic secretion activities by both endocrine and exocrine tissues. It also affects hepatic glycogen levels and gastrointestinal secretions.

Its secretion in humans is increased after a protein meal, fasting, exercise, and acute hypoglycaemia, and is decreased by somatostatin and intravenous glucose.

Plasma pancreatic polypeptide has been shown to be reduced in conditions associated with increased food intake and elevated in anorexia nervosa. In addition, peripheral administration of polypeptide has been shown to decrease food intake in rodents. [5] Pancreatic polypeptide inhibits pancreatic secretion of fluid, bicarbonate, and digestive enzymes. [3] It also stimulates gastric acid secretion. [3] It is the antagonist of cholecystokinin and opposes pancreatic secretion stimulated by cholecystokinin. [3] It may stimulate the migrating motor complex, synergistic with motilin. [3]

On fasting, pancreatic polypeptide concentration is 80 pg/ml; after the meal, it rises up from 8 to 10 times more; glucose and fats also induce PP's level increase, but on parenteral introduction of those substances, the level of hormones doesn't change. The administration of atropine, the vagotomy, blocks pancreatic polypeptide secretion after meals. The excitation of the vagus nerve, the administration of gastrin, secretin or cholecystokinin induce PP secretion.

Clinical significance

The secretion of pancreatic polypeptide may be increased by pancreatic tumours (insulin, glucagon), by Verner-Morrison syndrome, and by gastrinoma.

See also

Related Research Articles

<span class="mw-page-title-main">Endocrine system</span> Hormone-producing glands of a body

The endocrine system is a messenger system in an organism comprising feedback loops of hormones that are released by internal glands directly into the circulatory system and that target and regulate distant organs. In vertebrates, the hypothalamus is the neural control center for all endocrine systems.

<span class="mw-page-title-main">Pancreas</span> Organ of the digestive system and endocrine system of vertebrates

The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e., it has both an endocrine and a digestive exocrine function. 99% of the pancreas is exocrine and 1% is endocrine. As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones insulin, glucagon, somatostatin and pancreatic polypeptide. As a part of the digestive system, it functions as an exocrine gland secreting pancreatic juice into the duodenum through the pancreatic duct. This juice contains bicarbonate, which neutralizes acid entering the duodenum from the stomach; and digestive enzymes, which break down carbohydrates, proteins and fats in food entering the duodenum from the stomach.

<span class="mw-page-title-main">Beta cell</span> Type of cell found in pancreatic islets

Beta cells (β-cells), are specialized endocrine cells located within the pancreatic islets of Langerhans responsible for the production and release of insulin and amylin. Constituting ~50–70% of cells in human islets, beta cells play a vital role in maintaining blood glucose levels. Problems with beta cells can lead to disorders such as diabetes.

<span class="mw-page-title-main">Secretin</span> Hormone involved in stomach, pancreas and liver secretions

Secretin is a hormone that regulates water homeostasis throughout the body and influences the environment of the duodenum by regulating secretions in the stomach, pancreas, and liver. It is a peptide hormone produced in the S cells of the duodenum, which are located in the intestinal glands. In humans, the secretin peptide is encoded by the SCT gene.

<span class="mw-page-title-main">Glucagon</span> Peptide hormone

Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It raises the concentration of glucose and fatty acids in the bloodstream and is considered to be the main catabolic hormone of the body. It is also used as a medication to treat a number of health conditions. Its effect is opposite to that of insulin, which lowers extracellular glucose. It is produced from proglucagon, encoded by the GCG gene.

<span class="mw-page-title-main">Cholecystokinin</span> Hormone of the gastrointestinal system

Cholecystokinin is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein. Cholecystokinin, formerly called pancreozymin, is synthesized and secreted by enteroendocrine cells in the duodenum, the first segment of the small intestine. Its presence causes the release of digestive enzymes and bile from the pancreas and gallbladder, respectively, and also acts as a hunger suppressant.

<span class="mw-page-title-main">Alpha cell</span> Glucagon secreting cell

Alpha cells(α cells) are endocrine cells that are found in the Islets of Langerhans in the pancreas. Alpha cells secrete the peptide hormone glucagon in order to increase glucose levels in the blood stream.

<span class="mw-page-title-main">Pancreatic polypeptide cells</span>

Pancreatic polypeptide cells, or formerly as gamma cells (γ-cells), or F cells, are cells in the pancreatic islets of the pancreas. Their main role is to help synthesize and regulate the release of pancreatic polypeptide (PP), after which they have been named. The pancreatic islets, where PP cells reside, was discovered in 1869 by a German pathological anatomist and scientist, Paul Langerhans. PP cells help to make up the pancreas but are smallest in proportion to the other cells previously stated. The proportions can vary based on which animals are being studied, but in humans, PP cells make up less than 2% of the pancreatic islet cell population.

<span class="mw-page-title-main">Insulinoma</span> Medical condition

An insulinoma is a tumour of the pancreas that is derived from beta cells and secretes insulin. It is a rare form of a neuroendocrine tumour. Most insulinomas are benign in that they grow exclusively at their origin within the pancreas, but a minority metastasize. Insulinomas are one of the functional pancreatic neuroendocrine tumour (PNET) group. In the Medical Subject Headings classification, insulinoma is the only subtype of "islet cell adenoma".

<span class="mw-page-title-main">Digestive enzyme</span> Class of enzymes

Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of animals and in the tracts of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular survival. Digestive enzymes of diverse specificities are found in the saliva secreted by the salivary glands, in the secretions of cells lining the stomach, in the pancreatic juice secreted by pancreatic exocrine cells, and in the secretions of cells lining the small and large intestines.

<span class="mw-page-title-main">Incretin</span> Group of gastrointestinal hormones

Incretins are a group of metabolic hormones that stimulate a decrease in blood glucose levels. Incretins are released after eating and augment the secretion of insulin released from pancreatic beta cells of the islets of Langerhans by a blood-glucose–dependent mechanism.

<span class="mw-page-title-main">Glucose-dependent insulinotropic polypeptide</span> Mammalian protein found in Homo sapiens

Glucose-dependent insulinotropic polypeptide, abbreviated as GIP, is an inhibiting hormone of the secretin family of hormones. While it is a weak inhibitor of gastric acid secretion, its main role, being an incretin, is to stimulate insulin secretion.

<span class="mw-page-title-main">Motilin</span>

Motilin is a 22-amino acid polypeptide hormone in the motilin family that, in humans, is encoded by the MLN gene.

<span class="mw-page-title-main">Gastrinoma</span> Medical condition

Gastrinomas are neuroendocrine tumors (NETs), usually located in the duodenum or pancreas, that secrete gastrin and cause a clinical syndrome known as Zollinger–Ellison syndrome (ZES). A large number of gastrinomas develop in the pancreas or duodenum, with near-equal frequency, and approximately 10% arise as primary neoplasms in lymph nodes of the pancreaticoduodenal region.

<span class="mw-page-title-main">Peptide YY</span> Peptide released from cells in the ileum and colon in response to feeding

Peptide YY (PYY) also known as peptide tyrosine tyrosine is a peptide that in humans is encoded by the PYY gene. Peptide YY is a short peptide released from cells in the ileum and colon in response to feeding. In the blood, gut, and other elements of periphery, PYY acts to reduce appetite; similarly, when injected directly into the central nervous system, PYY is also anorexigenic, i.e., it reduces appetite.

Somatostatinomas are a tumor of the delta cells of the endocrine pancreas that produces somatostatin. Increased levels of somatostatin inhibit pancreatic hormones and gastrointestinal hormones. Thus, somatostatinomas are associated with mild diabetes mellitus, steatorrhoea and gallstones, and achlorhydria. Somatostatinomas are commonly found in the head of pancreas. Only ten percent of somatostatinomas are functional tumours [9], and 60–70% of tumours are malignant. Nearly two-thirds of patients with malignant somatostatinomas will present with metastatic disease.

The gastrointestinal hormones constitute a group of hormones secreted by enteroendocrine cells in the stomach, pancreas, and small intestine that control various functions of the digestive organs. Later studies showed that most of the gut peptides, such as secretin, cholecystokinin or substance P, were found to play a role of neurotransmitters and neuromodulators in the central and peripheral nervous systems.

<span class="mw-page-title-main">Enteroendocrine cell</span>

Enteroendocrine cells are specialized cells of the gastrointestinal tract and pancreas with endocrine function. They produce gastrointestinal hormones or peptides in response to various stimuli and release them into the bloodstream for systemic effect, diffuse them as local messengers, or transmit them to the enteric nervous system to activate nervous responses. Enteroendocrine cells of the intestine are the most numerous endocrine cells of the body. They constitute an enteric endocrine system as a subset of the endocrine system just as the enteric nervous system is a subset of the nervous system. In a sense they are known to act as chemoreceptors, initiating digestive actions and detecting harmful substances and initiating protective responses. Enteroendocrine cells are located in the stomach, in the intestine and in the pancreas. Microbiota play key roles in the intestinal immune and metabolic responses in these enteroendocrine cells via their fermentation product, acetate.

The insulin transduction pathway is a biochemical pathway by which insulin increases the uptake of glucose into fat and muscle cells and reduces the synthesis of glucose in the liver and hence is involved in maintaining glucose homeostasis. This pathway is also influenced by fed versus fasting states, stress levels, and a variety of other hormones.

<span class="mw-page-title-main">Human digestive system</span> Digestive system in humans

The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion. Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The process of digestion has three stages: the cephalic phase, the gastric phase, and the intestinal phase.

References

  1. 1 2 Boel E, Schwartz TW, Norris KE, Fiil NP (April 1984). "A cDNA encoding a small common precursor for human pancreatic polypeptide and pancreatic icosapeptide". The EMBO Journal. 3 (4): 909–12. doi:10.1002/j.1460-2075.1984.tb01904.x. PMC   557446 . PMID   6373251.
  2. 1 2 Lonovics J, Devitt P, Watson LC, Rayford PL, Thompson JC (October 1981). "Pancreatic polypeptide. A review". Archives of Surgery. 116 (10): 1256–64. doi:10.1001/archsurg.1981.01380220010002. PMID   7025798.
  3. 1 2 3 4 5 6 7 Washabau RJ (2013). "Chapter 1 - Integration of Gastrointestinal Function". Canine and Feline Gastroenterology. Saunders. pp. 1–31. doi:10.1016/B978-1-4160-3661-6.00001-8. ISBN   978-1-4160-3661-6.
  4. Cozzi B, Huggenberger S, Oelschläger H (2017-01-01). "Chapter 7 - Body Control: The Endocrine System and the Peripheral Nervous System". Anatomy of Dolphins. Academic Press. pp. 305–338. doi:10.1016/B978-0-12-407229-9.00007-5. ISBN   978-0-12-407229-9.
  5. Batterham RL, Le Roux CW, Cohen MA, Park AJ, Ellis SM, Patterson M, et al. (August 2003). "Pancreatic polypeptide reduces appetite and food intake in humans". The Journal of Clinical Endocrinology and Metabolism. 88 (8): 3989–92. doi: 10.1210/jc.2003-030630 . PMID   12915697.

Further reading