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Islets of Langerhans
 
 
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The islets of Langerhans are the regions of the pancreas
Pancreas

The pancreas is a gland Organ in the digestive system and endocrine system of vertebrates. It is both an endocrine gland , as well as an exocrine gland, secreting pancreatic juice containing Digestion enzymes that pass to the small intestine....
 that contain its endocrine (i.e., hormone-producing) cells.






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Islet
Langerhanssche Insel
Gray1105
The islets of Langerhans are the regions of the pancreas
Pancreas

The pancreas is a gland Organ in the digestive system and endocrine system of vertebrates. It is both an endocrine gland , as well as an exocrine gland, secreting pancreatic juice containing Digestion enzymes that pass to the small intestine....
 that contain its endocrine (i.e., hormone-producing) cells. Discovered in 1869 by German pathological anatomist Paul Langerhans
Paul Langerhans

Paul Langerhans was a Germany pathology, physiologist biology....
, the islets of Langerhans constitute approximately 1 to 2% of the mass of the pancreas. There are about one million islets in a healthy adult human pancreas, which are distributed throughout the organ; their combined mass is 1 to 1.5 grams.

Cell types

Hormones produced in the Islets of Langerhans are secreted directly into the blood flow by (at least) five different types of cells. In rat islets, endocrine cell subsets are distributed as follows:
  • Alpha cell
    Alpha cell

    Alpha cells are endocrine system cell s in the islets of Langerhans of the pancreas. They make up 15-20% of the cells in the islets. They are responsible for synthesizing and secreting the peptide hormone glucagon, which elevates the glucose levels in the blood....
    s producing glucagon
    Glucagon

    Glucagon is an important hormone involved in carbohydrate metabolism. Produced by the pancreas, it is released when the glucose level in the blood is low , causing the liver to convert stored glycogen into glucose and release it into the bloodstream....
     (15-20% of total islet cells)
  • Beta cell
    Beta cell

    Beta cells are a type of cell in the pancreas in areas called the islets of Langerhans. They make up 65-80% of the cells in the islets....
    s producing insulin
    Insulin

    Insulin is a hormone with extensive effects on both metabolism and several other body systems . Insulin causes most of the body's cells to take up glucose from the blood , storing it as glycogen in the liver and muscle, and stops use of fat as an energy source....
     and amylin
    Amylin

    Amylin, or Islet Amyloid Polypeptide , is a 37-residue peptide hormone secreted by pancreas beta cell at the same time as insulin . Islet, or insulinoma, amyloid polypeptide is commonly found in Islets of Langerhans of patients suffering diabetes mellitus type 2, or harboring an insulinoma....
     (65-80%)
  • Delta cell
    Delta cell

    Delta cells are somatostatin producing cell s.They can be found in the stomach, intestine and the Islets of Langerhans in the pancreas.In rodents delta-cells are located in the periphery of the islets; in humans the islet architecture is generally less organized and delta-cells are frequently observed inside the islets as well....
    s producing somatostatin
    Somatostatin

    Somatostatin is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G-protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones....
     (3-10%)
  • PP cell
    PP cell

    PP cells are pancreatic polypeptide producing cell in the islets of Langerhans in the pancreas. They are very few in number and are polygonal in shape....
    s producing 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 Dalton_%28unit%29....
     (3-5%)
  • Epsilon cell
    Epsilon cell

    Epsilon cells are endocrine Cell found in the Islets of Langerhans and produce the hormone ghrelin. They were recently discovered in mice....
    s producing ghrelin
    Ghrelin

    Ghrelin is a hormone produced mainly by P/D1 cells lining the fundus of the human stomach and epsilon cells of the pancreas that stimulates appetite....
    . (<1%)


It has been recognized that the cytoarchitecture of pancreatic differs between species. In particular, while rodent islets are characterized by a predominant proportion of insulin-producing beta cells in the core of the cluster and by scarse alpha, delta and PP cells in the periphery, human islets display alpha and beta cells in close relationship with each other throughout the cluster.

Islets can influence each other through paracrine and autocrine communication, and beta-cells are coupled electrically to beta cells (but not to other cell types).

Paracrine feedback

The paracrine feedback system of the islets of Langerhans has the following structure:
  • Insulin: secreted by beta cells and inhibits alpha cells, moves glucose into the cells and activates glycogen formation
  • Glucagon: secreted alpha which inhibits beta cells and delta cells. Causes glycogen to be broken down into glucose in the liver
  • Somatostatin: Inhibits alpha cells and beta cells


Electrical activity

Electrical activity of pancreatic islets has been studied using patch clamp
Patch clamp

The patch clamp technique is a laboratory technique in electrophysiology that allows the study of single or multiple ion channels in cell . The technique can be applied to a wide variety of cells, but is especially useful in the study of excitable cells such as neurons, cardiac cells, muscle fibers and the beta cells of the pancreas....
 techniques, and it has turned out that the behavior of cells in intact islets differs significantly from the behavior of dispersed cells.

As a treatment for Type 1 Diabetes


Because the beta cells in the islets of Langerhans are selectively destroyed by an autoimmune process in Type 1 Diabetes, clinicians and researchers are actively pursuing islet transplantation as a means of restoring physiological beta cell function in patients with Type 1 Diabetes . Recent clinical trials have shown that insulin independence and improved metabolic control can be reproducibly obtained after transplantation of cadaveric donor islets into patients with unstable Type 1 Diabetes..

Islet transplantation for Type 1 Diabetes currently requires potent immunosuppression
Immunosuppression

Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other conditions....
 to prevent host rejection
Rejection

The word "rejection" was first used in 1415. The original meaning was "to throw" or "to throw back".Rejection may mean:* Social rejection, in psychology, an interpersonal situation that occurs when a person or group of people exclude an individual from a social relationship...
 of donor islets..

Rachel Harris, islet cell recipient, was transplanted at the Diabetes Research Institute in Miami, Florida. In June of 2004, Rachel became the world's longest surviving insulin-free diabetic according to the Miami Herald (published Feb. 13, 2004).

An alternative source of beta cell
Beta cell

Beta cells are a type of cell in the pancreas in areas called the islets of Langerhans. They make up 65-80% of the cells in the islets....
s, such an islets derived from adult stem cells or progenitor cell
Progenitor cell

Like stem cells, progenitor cells have a capacity to differentiate into a specific type of cell. In contrast to stem cells, however, they are already far more specific: they are pushed to differentiate into their "target" cell....
s of a diabetic would contribute overcoming the current shortage of donor organs for transplantation. The field of regenerative medicine is rapidly evolving, and offers great hope for the nearest future. However, Type 1 Diabetes is the result of the autoimmune destruction of beta cells in the pancreas. Therefore, an effective cure for Type 1 Diabetes will require a sequential, integrated approach that combines adequate and safe immune interventions with beta cell regenerative approaches...

Transplantation

Islet cell transplantation has the possibility of restoring beta cells and curing diabetes, offering an alternative to a complete pancreas transplantation
Pancreas transplantation

A pancreas transplant is an organ transplant that involves implanting a healthy pancreas into a person who usually has diabetes. Because the pancreas is a vital organ, performing functions necessary in the digestion process, the recipient's native pancreas is left in place, and the donated pancreas is attached in a different location....
 or an artificial pancreas
Artificial pancreas

The artificial pancreas is a technology in development to help people with diabetes automatically control their blood glucose level by providing the substitute endocrine functionality of a healthy pancreas....
.

The Chicago Project headed at University of Illinois at Chicago Medical Center is investigating ways to regenerate beta cells in vivo. With that being said, beta cells experience apoptosis
Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed Cell death involves a series of biochemical events leading to a characteristic cell Morphology and death, in more specific terms, a series of biochemical events that lead to a variety of morphological changes, including Bleb , changes...
 early and thus are destroyed within a normal-functioning pancreas. The source of this seems to come from the transfer of Pander
Pander

Pander may refer to:* Derek Pander, a fictional comedy character* Pander , the facilitation or provision of a prostitute in the arrangement of a sex act with a customer...
, a gene that works by attaching to RNA
RNA

Ribonucleic acid is a type of molecule that consists of a long chain of nucleotide units. Each nucleotide consists of a nucleobase, a ribose sugar, and a phosphate....
. Pander, when active, causes the beta cells to be blocked at S phase
S phase

The S phase, short for synthesis phase, is a period in the cell cycle during interphase, between G1 phase and the G2 phase. Following G1, the cell enters the S stage, when DNA DNA synthesis or DNA replication occurs....
, which induces apoptosis. This loss of beta cell mass eventually leads to a loss of most of the transplanted beta cells.

Gallery

Hormones/Islet Architecture

See also

  • Human anatomy
    Human anatomy

    Human anatomy, which, with physiology and biochemistry, is a complementary basic medical science is primarily the scientific study of the morphology of the adult human body....


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