Pancreatic polypeptide cells

The typical pancreatic lesion of type 1 diabetes is the selective loss of almost all 3-cells, whereas other islet cell types (a, 8, and pancreatic polypeptide cells) remain intact. The most common mechanism for 3-cell destruction is thought to be autoimmune-mediated inflammatory damage. Prospective family studies strongly support a genetic basis for susceptibility to this autoimmune process and suggest that the underlying immune abnormalities precede clinical insulin deficiency by many years. However, not all spontaneous type 1 diabetes is the result of autoimmune mechanisms. 

The word hormone is derived from the Greek hormaein, meaning to set in motion or to excite. It was used initially to define the activity of secretin [1393-25-5] (1), a gastrointestinal polypeptide released into the blood by the duodenal mucosa to stimulate pancreatic acinar cells to release bicarbonate and water. 

The hormone pancreatic polypeptide (PP) is a 36 amino acid peptide, which is closely related to neuropeptide Y and peptide YY PP is mainly found in pancreatic cells distinct from those storing insulin, glucagon or somatostatin. It acts on receptors that belong to the family of neuropeptide Y receptors, particularly on the Y4 subtype. 

With in pancreatic polypeptide-rich lobules of adult islets, located only in the posterior portion of the head of the human pancreas, glucagon cells are scarce (< 0.5%) and F cells make up as much as 80% of the cells. 

Neuropeptides Y (NFY) and YY are 36-residue amidated peptides that are members of the pancreatic polypeptide (PP) family (Fig. 30-5). NPY is produced both in the peripheral nervous system and in the brain,110 134 where it is one of the most abundant neuropeptides. Another member of the PP family is semi-nalplasmin, a regulator of calcium ion transport in bovine sperm.135 NPY is best known for its stimulation of appetite. It also inhibits anxiety and increases memory retention. It has a vasoconstrictive effect on blood vessels, participating in cardiovascular regulation.136 137 Peptide YY is formed in endocrine cells of the intestine, while NPY is formed in neurons of the parasympathetic system.138 Both participate in regulation of fluid and electrolyte secretion. Both are found in other vertebrate species.139... 

The pancreatic islets consist of four primary cell types alpha (A) cells, which produce glucagon beta (B) cells, which produce insulin delta (D) cells, which produce somatostatin and (F) cells, which produce pancreatic polypeptide. As previously mentioned, this chapter focuses on the functions of insulin and glucagon. The exact physiologic roles of the other pancreatic hormones are not entirely clear. For example, the function of the pancreatic polypeptide released from pancreatic F cells remains to be determined. 

The endocrine islet cells comprise only 1-2% of the pancreatic tissue. They synthesize the hormones insulin, glucagon, somatostatin, and pancreatic polypeptide. Insulin and glucagon maintain glucose homeostasis via their actions on lipid, carbohydrate, and protein metabolism. The pancreas originates from two patches of epithelium in the duodenum during the fifth week of gestation in humans. The endocrine pancreatic cells begin to differentiate very... 

Pancreatic polypeptide is a peptide hormone secreted by pancreatic polypeptide-producing cells in the islets of Langerhans... 

Secretin is a 27-amino-aeid polypeptide that is slruciurally. similar to glucagon. The presence of acid in the. small intestine is the most important physiological stimulus for the secretion of secretin. The primary action of secretin Ls on pancreatic acinar cells that regulate the secretion of water and bicarbonate. Secretin also promotes the secretion of pancreatic enzymes, to a lesser extent. Secretin inhibits the release of gastrin and. therefore. ga.slric acid. It also increases stomach-emptying time by reducing the conlraction of the pyloric sphincter. ... 

FIGURE 10.40 Nonfunctional pancreatic endocrine tumor. Im-munoperoxidase stain for pancreatic polypeptide shows positivity in scattered individual tumor cells. 

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