Alpha Cell Hyperplasia
   HOME

TheInfoList



Click Here for Items Related To - Alpha Cell Hyperplasia
OR:
Alpha Cell Hyperplasia on:   [Wikipedia]   [Google]   [Amazon]

Alpha cell hyperplasia is defined as a specific (without similar change in other islet cells), diffuse (not limited to a particular part of pancreas), and overwhelming (many-fold) increase of the number of pancreatic
alpha cells 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. Discovery Islets of Langerhans were ...
. The
pancreatic islets The pancreatic islets or islets of Langerhans are the regions of the pancreas that contain its endocrine (hormone-producing) cells, discovered in 1869 by German pathological anatomist Paul Langerhans. The pancreatic islets constitute 1–2% of ...
normally contain 4 types of cells; the alpha cells produce and release
glucagon Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It raises 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 Glucagon (medicati ...
, a hormone that regulates the metabolism of
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
and
amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
. Although first described in early 1990s, alpha cell hyperplasia had remained an esoteric topic until the mid-2010s. Based on the pathogenesis and clinical presentation, alpha cell hyperplasia can be divided into 3 types: reactive, nonfunctional, and functional.


Reactive alpha cell hyperplasia

Any means to inhibit normal
glucagon Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It raises 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 Glucagon (medicati ...
signaling in any vertebrate animals tested so far (zebra fish, mice, monkeys, and humans) causes reactive alpha cell hyperplasia. There is a
negative feedback Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused by ...
loop linking the pancreatic
alpha cells 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. Discovery Islets of Langerhans were ...
and the liver. When glucagon signaling is inhibited, the liver (the main target organ of glucagon) releases excess amounts of
amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
into the circulation (
hyperaminoacidemia Hyperaminoacidemia refers to the condition of having an excess of amino acids in the bloodstream The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire b ...
) which stimulate the
alpha cells 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. Discovery Islets of Langerhans were ...
to proliferate and to produce and release more
glucagon Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It raises 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 Glucagon (medicati ...
. Humans and animals with reactive alpha cell hyperplasia do not exhibit signs of glucagon excess as their glucagon signaling is inhibited at the first place. Reactive alpha cell hyperplasia is a preneoplastic lesion. Humans with inactivating glucagon mutations (i.e.
Mahvash disease Mahvash disease is an autosomal recessive, hereditary pancreatic neuroendocrine tumor syndrome. The genetic defect that causes Mahvash disease is biallelic inactivating mutations of the glucagon receptor gene (''GCGR''). Mahvash disease was discov ...
) and several murine models of reactive alpha cell hyperplasia all eventually develop
pancreatic neuroendocrine tumor Pancreatic neuroendocrine tumours (PanNETs, PETs, or PNETs), often referred to as "islet cell tumours", or "pancreatic endocrine tumours" are neuroendocrine neoplasms that arise from cells of the endocrine (hormonal) and nervous system within t ...
s.


Nonfunctional alpha cell hyperplasia

Nonfunctional and reactive alpha cell hyperplasia are indistinguishable histologically. Nonfunctional alpha cell hyperplasia, however, is not associated with hyperglucagonemia. The cause of nonfunctional alpha cell hyperplasia in humans requires further investigation. Nonfunctional alpha cell hyperplasia is also a preneoplastic lesion.


Functional alpha cell hyperplasia

Functional alpha cell hyperplasia differs from reactive and nonfunctional alpha cell hyperplasia in that the functional alpha cell hyperplasia is associated with hyperglucagonemia and the hyperglucagonemia results in glucagonoma syndrome. Functional alpha cell hyperplasia is poorly characterized so far.


See also

*
Glucagon receptor The glucagon receptor is a 62 kDa protein that is activated by glucagon and is a member of the class B G-protein coupled family of receptors, coupled to G alpha i, Gs and to a lesser extent G alpha q. Stimulation of the receptor results in the ...
*
Pancreatic neuroendocrine tumor Pancreatic neuroendocrine tumours (PanNETs, PETs, or PNETs), often referred to as "islet cell tumours", or "pancreatic endocrine tumours" are neuroendocrine neoplasms that arise from cells of the endocrine (hormonal) and nervous system within t ...
*
Mahvash disease Mahvash disease is an autosomal recessive, hereditary pancreatic neuroendocrine tumor syndrome. The genetic defect that causes Mahvash disease is biallelic inactivating mutations of the glucagon receptor gene (''GCGR''). Mahvash disease was discov ...


References

{{reflist Anatomical pathology