insulin

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WordNet

1. hormone secreted by the isles of Langerhans in the pancreas; regulates storage of glycogen in the liver and accelerates oxidation of sugar in cells
2. a form of insulin (trade name Humulin) made from recombinant DNA that is identical to human insulin; used to treat diabetics who are allergic to preparations made from beef or pork insulin (同)Humulin

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1. インシュリン(膵臓(すいぞう)ホルモンで糖尿病治療剤)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/06/28 10:47:38」(JST)

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Not to be confused with Inulin.

Insulin
Computer-generated image of six insulin molecules assembled in a hexamer, highlighting the threefold symmetry, the zinc ions holding it together, and the histidine residues involved in zinc binding. Insulin is stored in the body as a hexamer, while the active form is the monomer.
Available structures PDB Ortholog search: PDBe, RCSB List of PDB id codes 1A7F, 1AI0, 1AIY, 1B9E, 1BEN, 1EFE, 1EV3, 1EV6, 1EVR, 1FU2, 1FUB, 1G7A, 1G7B, 1GUJ, 1HIQ, 1HIS, 1HIT, 1HLS, 1HTV, 1HUI, 1IOG, 1IOH, 1J73, 1JCA, 1JCO, 1K3M, 1KMF, 1LKQ, 1LPH, 1MHI, 1MHJ, 1MSO, 1OS3, 1OS4, 1Q4V, 1QIY, 1QIZ, 1QJ0, 1RWE, 1SF1, 1SJT, 1SJU, 1T0C, 1T1K, 1T1P, 1T1Q, 1TRZ, 1TYL, 1TYM, 1UZ9, 1VKT, 1W8P, 1XDA, 1XGL, 1XW7, 1ZEG, 1ZEH, 1ZNJ, 2AIY, 2C8Q, 2C8R, 2CEU, 2G54, 2G56, 2H67, 2HH4, 2HHO, 2HIU, 2JMN, 2JUM, 2JUU, 2JUV, 2JV1, 2JZQ, 2K91, 2K9R, 2KJJ, 2KJU, 2KQP, 2KQQ, 2KXK, 2L1Y, 2L1Z, 2LGB, 2M1D, 2M1E, 2M2M, 2M2N, 2M2O, 2M2P, 2OLY, 2OLZ, 2OM0, 2OM1, 2OMG, 2OMH, 2OMI, 2QIU, 2R34, 2R35, 2R36, 2RN5, 2VJZ, 2VK0, 2W44, 2WBY, 2WC0, 2WRU, 2WRV, 2WRW, 2WRX, 2WS0, 2WS1, 2WS4, 2WS6, 2WS7, 3AIY, 3BRR, 3BXQ, 3E7Y, 3E7Z, 3EXX, 3FQ9, 3HYD, 3I3Z, 3I40, 3ILG, 3INC, 3IR0, 3JSD, 3KQ6, 3P2X, 3P33, 3Q6E, 3ROV, 3TT8, 3U4N, 3UTQ, 3UTS, 3UTT, 3V19, 3V1G, 3W11, 3W12, 3W13, 3ZI3, 3ZQR, 3ZS2, 3ZU1, 4AIY, 4AJX, 4AJZ, 4AK0, 4AKJ, 4EFX, 4EWW, 4EWX, 4EWZ, 4EX0, 4EX1, 4EXX, 4EY1, 4EY9, 4EYD, 4EYN, 4EYP, 4F0N, 4F0O, 4F1A, 4F1B, 4F1C, 4F1D, 4F1F, 4F1G, 4F4T, 4F4V, 4F51, 4F8F, 4FG3, 4FKA, 4GBC, 4GBI, 4GBK, 4GBL, 4GBN, 4IUZ, 5AIY
Identifiers
Symbols	INS; IDDM2; ILPR; IRDN; MODY10
External IDs	OMIM: 176730 MGI: 96573 HomoloGene: 173 ChEMBL: 5881 GeneCards: INS Gene
Gene Ontology Molecular function • protease binding • insulin receptor binding • insulin-like growth factor receptor binding • hormone activity • protein binding Cellular component • extracellular region • extracellular space • endoplasmic reticulum lumen • Golgi lumen • endosome lumen • secretory granule lumen Biological process • MAPK cascade • negative regulation of acute inflammatory response • glucose metabolic process • energy reserve metabolic process • regulation of transcription, DNA-dependent • regulation of cellular amino acid metabolic process • acute-phase response • G-protein coupled receptor signaling pathway • cell-cell signaling • positive regulation of cell proliferation • insulin receptor signaling pathway • positive regulation of phosphatidylinositol 3-kinase cascade • glucose transport • regulation of transmembrane transporter activity • positive regulation of cell growth • positive regulation of cell migration • endocrine pancreas development • positive regulation of protein autophosphorylation • activation of protein kinase B activity • positive regulation of cellular protein metabolic process • negative regulation of protein oligomerization • regulation of protein localization • negative regulation of NAD(P)H oxidase activity • wound healing • negative regulation of protein catabolic process • glucose homeostasis • negative regulation of apoptotic process • positive regulation of MAPK cascade • cellular protein metabolic process • small molecule metabolic process • positive regulation of nitric oxide biosynthetic process • positive regulation of cell differentiation • negative regulation of gluconeogenesis • positive regulation of glycogen biosynthetic process • positive regulation of DNA replication • negative regulation of glycogen catabolic process • positive regulation of glycolysis • positive regulation of mitosis • negative regulation of proteolysis • negative regulation of vasodilation • positive regulation of vasodilation • negative regulation of fatty acid metabolic process • positive regulation of glucose import • positive regulation of insulin receptor signaling pathway • alpha-beta T cell activation • positive regulation of lipid biosynthetic process • regulation of protein secretion • negative regulation of protein secretion • positive regulation of cytokine secretion • positive regulation of peptidyl-tyrosine phosphorylation • regulation of insulin secretion • negative regulation of lipid catabolic process • positive regulation of nitric-oxide synthase activity • positive regulation of NF-kappaB transcription factor activity • positive regulation of protein kinase B signaling cascade • fatty acid homeostasis • negative regulation of respiratory burst involved in inflammatory response • positive regulation of respiratory burst • positive regulation of peptide hormone secretion • positive regulation of brown fat cell differentiation • negative regulation of feeding behavior Sources: Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	3630	16334
Ensembl	ENSG00000254647	ENSMUSG00000000215
UniProt	P01308	P01326
RefSeq (mRNA)	NM_000207	NM_001185083
RefSeq (protein)	NP_000198	NP_001172012
Location (UCSC)	Chr 11: 2.18 – 2.18 Mb	Chr 7: 142.68 – 142.7 Mb
PubMed search	[1]	[2]

Insulin is a peptide hormone, produced by beta cells of the pancreas, and is central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, skeletal muscles, and fat tissue to absorb glucose from the blood. In the liver and skeletal muscles, glucose is stored as glycogen, and in fat cells (adipocytes) it is stored as triglycerides.

Insulin stops the use of fat as an energy source by inhibiting the release of glucagon. With the exception of the metabolic disorder diabetes mellitus and metabolic syndrome, insulin is provided within the body in a constant proportion to remove excess glucose from the blood, which otherwise would be toxic. When blood glucose levels fall below a certain level, the body begins to use stored sugar as an energy source through glycogenolysis, which breaks down the glycogen stored in the liver and muscles into glucose, which can then be utilized as an energy source. As a central metabolic control mechanism, its status is also used as a control signal to other body systems (such as amino acid uptake by body cells). In addition, it has several other anabolic effects throughout the body.

When control of insulin levels fails, diabetes mellitus can result. As a consequence, insulin is used medically to treat some forms of diabetes mellitus. Patients with type 1 diabetes depend on external insulin (most commonly injected subcutaneously) for their survival because the hormone is no longer produced internally. Patients with type 2 diabetes are often insulin resistant and, because of such resistance, may suffer from a "relative" insulin deficiency. Some patients with type 2 diabetes may eventually require insulin if other medications fail to control blood glucose levels adequately. Over 40% of those with Type 2 diabetes require insulin as part of their diabetes management plan.

The human insulin protein is composed of 51 amino acids, and has a molecular weight of 5808 Da. It is a dimer of an A-chain and a B-chain, which are linked together by disulfide bonds.

Insulin's name is derived from the Latin insula for "island". Insulin's structure varies slightly between species of animals. Insulin from animal sources differs somewhat in "strength" (in carbohydrate metabolism control effects) in humans because of those variations. Porcine insulin is especially close to the human version.

Gene

The preproinsulin precursor of insulin is encoded by the INS gene.

Alleles

A variety of mutant alleles with changes in the coding region have been identified. A read-through gene, INS-IGF2, overlaps with this gene at the 5' region and with the IGF2 gene at the 3' region.

Regulation

Several regulatory sequences in the promoter region of the human insulin gene bind to transcription factors. In general, the A-boxes bind to Pdx1 factors, E-boxes bind to NeuroD, C-boxes bind to MafA, and cAMP response elements to CREB. There are also silencers that inhibit transcription.

Regulatory sequences and their transcription factors for the insulin gene.

Regulatory sequence	binding transcription factors
ILPR	Par1
A5	Pdx1
negative regulatory element (NRE)	glucocorticoid receptor, Oct1
Z (overlapping NRE and C2)	ISF
C2	Pax4, MafA(?)
E2	USF1/USF2
A3	Pdx1
CREB RE	-
CREB RE	CREB, CREM
A2	-
CAAT enhancer binding (CEB) (partly overlapping A2 and C1)	-
C1	-
E1	E2A, NeuroD1, HEB
A1	Pdx1
G1	-

Protein structure

See also: Insulin/IGF/Relaxin family

Within vertebrates, the amino acid sequence of insulin is strongly conserved. Bovine insulin differs from human in only three amino acid residues, and porcine insulin in one. Even insulin from some species of fish is similar enough to human to be clinically effective in humans. Insulin in some invertebrates is quite similar in sequence to human insulin, and has similar physiological effects. The strong homology seen in the insulin sequence of diverse species suggests that it has been conserved across much of animal evolutionary history. The C-peptide of proinsulin (discussed later), however, differs much more among species; it is also a hormone, but a secondary one.

The primary structure of bovine insulin was first determined by Frederick Sanger in 1951. After that, this polypeptide was synthesized independently by several groups.

Insulin is produced and stored in the body as a hexamer (a unit of six insulin molecules), while the active form is the monomer. The hexamer is an inactive form with long-term stability, which serves as a way to keep the highly reactive insulin protected, yet readily available. The hexamer-monomer conversion is one of the central aspects of insulin formulations for injection. The hexamer is far more stable than the monomer, which is desirable for practical reasons; however, the monomer is a much faster-reacting drug because diffusion rate is inversely related to particle size. A fast-reacting drug means insulin injections do not have to precede mealtimes by hours, which in turn gives diabetics more flexibility in their daily schedules. Insulin can aggregate and form fibrillar interdigitated beta-sheets. This can cause injection amyloidosis, and prevents the storage of insulin for long periods.

Synthesis, physiological effects, and degradation

Synthesis

Insulin is produced in the pancreas and released when any of several stimuli are detected. These stimuli include ingested protein and glucose in the blood produced from digested food.^{[citation needed]} Carbohydrates can be polymers of simple sugars or the simple sugars themselves. If the carbohydrates include glucose, then that glucose will be absorbed into the bloodstream and blood glucose level will begin to rise. In target cells, insulin initiates a signal transduction, which has the effect of increasing glucose uptake and storage. Finally, insulin is degraded, terminating the response.

Insulin undergoes extensive posttranslational modification along the production pathway. Production and secretion are largely independent; prepared insulin is stored awaiting secretion. Both C-peptide and mature insulin are biologically active. Cell components and proteins in this image are not to scale.

In mammals, insulin is synthesized in the pancreas within the β-cells of the islets of Langerhans. One million to three million islets of Langerhans (pancreatic islets) form the endocrine part of the pancreas, which is primarily an exocrine gland. The endocrine portion accounts for only 2% of the total mass of the pancreas. Within the islets of Langerhans, beta cells constitute 65–80% of all the cells.

Insulin consists of two polypeptide chains, the A- and B- chains, linked together by disulfide bonds. It is however first synthesized as a single polypeptide called preproinsulin in pancreatic β-cells. Preproinsulin contains a 24-residue signal peptide which directs the nascent polypeptide chain to the rough endoplasmic reticulum (RER). The signal peptide is cleaved as the polypeptide is translocated into lumen of the RER, forming proinsulin. In the RER the proinsulin folds into the correct conformation and 3 disulfide bonds are formed. About 5–10 min after its assembly in the endoplasmic reticulum, proinsulin is transported to the trans-Golgi network (TGN) where immature granules are formed. Transport to the TGN may take about 30 min.

Proinsulin undergoes maturation into active insulin through the action of cellular endopeptidases known as prohormone convertases (PC1 and PC2), as well as the exoprotease carboxypeptidase E. The endopeptidases cleave at 2 positions, releasing a fragment called the C-peptide, and leaving 2 peptide chains, the B- and A- chains, linked by 2 disulfide bonds. The cleavage sites are each located after a pair of basic residues (lysine-64 and arginine-65, and arginine-31 and -32), and after cleavage these 2 pairs of basic residues are removed by the carboxypeptidase. The C-peptide is the central portion of proinsulin, and the primary sequence of proinsulin goes in the order "B-C-A" (the B and A chains were identified on the basis of mass and the C-peptide was discovered later).

The resulting mature insulin is packaged inside mature granules waiting for metabolic signals (such as leucine, arginine, glucose and mannose) and vagal nerve stimulation to be exocytosed from the cell into the circulation.

The endogenous production of insulin is regulated in several steps along the synthesis pathway:

• At transcription from the insulin gene
• In mRNA stability
• At the mRNA translation
• In the posttranslational modifications

Insulin and its related proteins have been shown to be produced inside the brain, and reduced levels of these proteins are linked to Alzheimer's disease.

Release

See also: Blood glucose regulation

Beta cells in the islets of Langerhans release insulin in two phases. The first phase release is rapidly triggered in response to increased blood glucose levels. The second phase is a sustained, slow release of newly formed vesicles triggered independently of sugar. The description of first phase release is as follows:

• Glucose enters the β-cells through the glucose transporter, GLUT2.
• Glucose goes into glycolysis and the respiratory cycle, where multiple, high-energy ATP molecules are produced by oxidation, leading to a rise in the ATP:ADP ratio within the cell.
• An increased intracellular ATP:ADP ratio closes the ATP-sensitive SUR1/Kir6.2 potassium channel (see sulfonylurea receptor). This prevents potassium ions (K⁺) from leaving the cell by facilitated diffusion, leading to a build up of potassium ions. As a result, the inside of the cell becomes more positive with respect to the outside, leading to the depolarisation of the cell surface membrane.
• On depolarisation, voltage-gated calcium ion (Ca²⁺) channels open which allows calcium ions to move into the cells by facilitated diffusion.
• An increased intracellular calcium ion concentration causes the activation of phospholipase C, which cleaves the membrane phospholipid phosphatidyl inositol 4,5-bisphosphate into inositol 1,4,5-trisphosphate and diacylglycerol.
• Inositol 1,4,5-trisphosphate (IP3) binds to receptor proteins in the plasma membrane of the endoplasmic reticulum (ER). This allows the release of Ca²⁺ ions from the ER via IP3-gated channels, and further raises the intracellular concentration of calcium ions.
• Significantly increased amounts of calcium ions in the cells causes the release of previously synthesized insulin, which has been stored in secretory vesicles.

This is the primary mechanism for release of insulin. Other substances known to stimulate insulin release include the amino acids arginine and leucine, parasympathetic release of acetylcholine (via phospholipase C), sulfonylurea, cholecystokinin (CCK, via phospholipase C), and the gastrointestinally derived incretins glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP).

Release of insulin is strongly inhibited by the stress hormone norepinephrine (noradrenaline), which leads to increased blood glucose levels during stress. It appears that release of catecholamines by the sympathetic nervous system has conflicting influences on insulin release by beta cells, because insulin release is inhibited by α₂-adrenergic receptors and stimulated by β₂-adrenergic receptors. The net effect of norepinephrine from sympathetic nerves and epinephrine from adrenal glands on insulin release is inhibition due to dominance of the α-adrenergic receptors.

When the glucose level comes down to the usual physiologic value, insulin release from the β-cells slows or stops. If blood glucose levels drop lower than this, especially to dangerously low levels, release of hyperglycemic hormones (most prominently glucagon from islet of Langerhans alpha cells) forces release of glucose into the blood from cellular stores, primarily liver cell stores of glycogen. By increasing blood glucose, the hyperglycemic hormones prevent or correct life-threatening hypoglycemia.

Evidence of impaired first-phase insulin release can be seen in the glucose tolerance test, demonstrated by a substantially elevated blood glucose level at 30 minutes, a marked drop by 60 minutes, and a steady climb back to baseline levels over the following hourly time points.

Oscillations

Main article: Insulin oscillations

Insulin release from pancreas oscillates with a period of 3–6 minutes.

Even during digestion, in general, one or two hours following a meal, insulin release from the pancreas is not continuous, but oscillates with a period of 3–6 minutes, changing from generating a blood insulin concentration more than about 800 pmol/l to less than 100 pmol/l. This is thought to avoid downregulation of insulin receptors in target cells, and to assist the liver in extracting insulin from the blood. This oscillation is important to consider when administering insulin-stimulating medication, since it is the oscillating blood concentration of insulin release, which should, ideally, be achieved, not a constant high concentration. This may be achieved by delivering insulin rhythmically to the portal vein or by islet cell transplantation to the liver. Future insulin pumps hope to address this characteristic. (See also Pulsatile Insulin.)

Blood content

The idealized diagram shows the fluctuation of blood sugar (red) and the sugar-lowering hormone insulin (blue) in humans during the course of a day containing three meals. In addition, the effect of a sugar-rich versus a starch-rich meal is highlighted.

The blood content of insulin can be measured in international units, such as µIU/mL or in molar concentration, such as pmol/L, where 1 µIU/mL equals 6.945 pmol/L. A typical blood level between meals is 8–11 μIU/mL (57–79 pmol/L).

Signal transduction

Special transporter proteins in cell membranes allow glucose from the blood to enter a cell. These transporters are, indirectly, under blood insulin's control in certain body cell types (e.g., muscle cells). Low levels of circulating insulin, or its absence, will prevent glucose from entering those cells (e.g., in type 1 diabetes). More commonly, however, there is a decrease in the sensitivity of cells to insulin (e.g., the reduced insulin sensitivity characteristic of type 2 diabetes), resulting in decreased glucose absorption. In either case, there is 'cell starvation' and weight loss, sometimes extreme. In a few cases, there is a defect in the release of insulin from the pancreas. Either way, the effect is the same: elevated blood glucose levels.

Activation of insulin receptors leads to internal cellular mechanisms that directly affect glucose uptake by regulating the number and operation of protein molecules in the cell membrane that transport glucose into the cell. The genes that specify the proteins that make up the insulin receptor in cell membranes have been identified, and the structures of the interior, transmembrane section, and the extra-membrane section of receptor have been solved.

Two types of tissues are most strongly influenced by insulin, as far as the stimulation of glucose uptake is concerned: muscle cells (myocytes) and fat cells (adipocytes). The former are important because of their central role in movement, breathing, circulation, etc., and the latter because they accumulate excess food energy against future needs. Together, they account for about two-thirds of all cells in a typical human body.

Insulin binds to the extracellular portion of the alpha subunits of the insulin receptor. This, in turn, causes a conformational change in the insulin receptor that activates the kinase domain residing on the intracellular portion of the beta subunits. The activated kinase domain autophosphorylates tyrosine residues on the C-terminus of the receptor as well as tyrosine residues in the IRS-1 protein.

1. phosphorylated IRS-1, in turn, binds to and activates phosphoinositol 3 kinase (PI3K)
2. PI3K catalyzes the reaction PIP2 + ATP → PIP3 + ADP
3. PIP3 activates protein kinase B (PKB)
4. PKB phosphorylates glycogen synthase kinase (GSK) and thereby inactivates GSK
5. GSK can no longer phosphorylate glycogen synthase (GS)
6. unphosphorylated GS makes more glycogen
7. PKB also facilitates vesicle fusion, resulting in an increase in GLUT4 transporters in the plasma membrane

After the signal has been produced, termination of signaling is then needed. As mentioned below in the section on degradation, endocytosis and degradation of the receptor bound to insulin is a main mechanism to end signaling. In addition, signaling can be terminated by dephosphorylation of the tyrosine residues by tyrosine phosphatases. Serine/Threonine kinases are also known to reduce the activity of insulin. Finally, with insulin action being associated with the number of receptors on the plasma membrane, a decrease in the amount of receptors also leads to termination of insulin signaling.

The structure of the insulin–insulin receptor complex has been determined using the techniques of X-ray crystallography.

Physiological effects

Effect of insulin on glucose uptake and metabolism. Insulin binds to its receptor (1), which starts many protein activation cascades (2). These include translocation of Glut-4 transporter to the plasma membrane and influx of glucose (3), glycogen synthesis (4), glycolysis (5) and triglyceride (6).

The actions of insulin on the global human metabolism level include:

• Control of cellular intake of certain substances, most prominently glucose in muscle and adipose tissue (about two-thirds of body cells)
• Increase of DNA replication and protein synthesis via control of amino acid uptake
• Modification of the activity of numerous enzymes.

The actions of insulin (indirect and direct) on cells include:

• Increased glycogen synthesis – insulin forces storage of glucose in liver (and muscle) cells in the form of glycogen; lowered levels of insulin cause liver cells to convert glycogen to glucose and excrete it into the blood. This is the clinical action of insulin, which is directly useful in reducing high blood glucose levels as in diabetes.
• Increased lipid synthesis – insulin forces fat cells to take in blood lipids, which are converted to triglycerides; lack of insulin causes the reverse.
• Increased esterification of fatty acids – forces adipose tissue to make fats (i.e., triglycerides) from fatty acid esters; lack of insulin causes the reverse.
• Decreased proteolysis – decreasing the breakdown of protein
• Decreased lipolysis – forces reduction in conversion of fat cell lipid stores into blood fatty acids; lack of insulin causes the reverse.
• Decreased gluconeogenesis – decreases production of glucose from nonsugar substrates, primarily in the liver (the vast majority of endogenous insulin arriving at the liver never leaves the liver); lack of insulin causes glucose production from assorted substrates in the liver and elsewhere.
• Decreased autophagy - decreased level of degradation of damaged organelles. Postprandial levels inhibit autophagy completely.
• Increased amino acid uptake – forces cells to absorb circulating amino acids; lack of insulin inhibits absorption.
• Increased potassium uptake – forces cells to absorb serum potassium; lack of insulin inhibits absorption. Insulin's increase in cellular potassium uptake lowers potassium levels in blood. This possibly occurs via insulin-induced translocation of the Na+/K+-ATPase to the surface of skeletal muscle cells.
• Arterial muscle tone – forces arterial wall muscle to relax, increasing blood flow, especially in microarteries; lack of insulin reduces flow by allowing these muscles to contract.
• Increase in the secretion of hydrochloric acid by parietal cells in the stomach
• Decreased renal sodium excretion.

Insulin also influences other body functions, such as vascular compliance and cognition. Once insulin enters the human brain, it enhances learning and memory and benefits verbal memory in particular. Enhancing brain insulin signaling by means of intranasal insulin administration also enhances the acute thermoregulatory and glucoregulatory response to food intake, suggesting that central nervous insulin contributes to the control of whole-body energy homeostasis in humans.

Degradation

Once an insulin molecule has docked onto the receptor and effected its action, it may be released back into the extracellular environment, or it may be degraded by the cell. The two primary sites for insulin clearance are the liver and the kidney. The liver clears most insulin during first-pass transit, whereas the kidney clears most of the insulin in systemic circulation. Degradation normally involves endocytosis of the insulin-receptor complex, followed by the action of insulin-degrading enzyme. An insulin molecule produced endogenously by the pancreatic beta cells is estimated to be degraded within about one hour after its initial release into circulation (insulin half-life ~ 4–6 minutes).

Hypoglycemia

Main article: Hypoglycemia

Although other cells can use other fuels (most prominently fatty acids), neurons depend on glucose as a source of energy in the nonstarving human. They do not require insulin to absorb glucose, unlike muscle and adipose tissue, and they have very small internal stores of glycogen. Glycogen stored in liver cells (unlike glycogen stored in muscle cells) can be converted to glucose, and released into the blood, when glucose from digestion is low or absent, and the glycerol backbone in triglycerides can also be used to produce blood glucose.

Sufficient lack of glucose and scarcity of these sources of glucose can dramatically make itself manifest in the impaired functioning of the central nervous system: dizziness, speech problems, and even loss of consciousness. Low blood glucose level is known as hypoglycemia or, in cases producing unconsciousness, "hypoglycemic coma" (sometimes termed "insulin shock" from the most common causative agent). Endogenous causes of insulin excess (such as an insulinoma) are very rare, and the overwhelming majority of insulin excess-induced hypoglycemia cases are iatrogenic and usually accidental. A few cases of murder, attempted murder, or suicide using insulin overdoses have been reported, but most insulin shocks appear to be due to errors in dosage of insulin (e.g., 20 units instead of 2) or other unanticipated factors (did not eat as much as anticipated, or exercised more than expected, or unpredicted kinetics of the subcutaneously injected insulin itself).

Possible causes of hypoglycemia include:

• External insulin (usually injected subcutaneously)
• Oral hypoglycemic agents (e.g., any of the sulfonylureas, or similar drugs, which increase insulin release from β-cells in response to a particular blood glucose level)
• Ingestion of low-carbohydrate sugar substitutes in people without diabetes or with type 2 diabetes. Animal studies show these can trigger insulin release, albeit in much smaller quantities than sugar, according to a report in Discover magazine, August 2004, p 18. (This can never be a cause of hypoglycemia in patients with type 1 diabetes, since there is no endogenous insulin production to stimulate.)

Diseases and syndromes

There are several conditions in which insulin disturbance is pathologic:

• Diabetes mellitus – general term referring to all states characterized by hyperglycemia
  • Type 1 – autoimmune-mediated destruction of insulin-producing β-cells in the pancreas, resulting in absolute insulin deficiency
  • Type 2 – multifactoral syndrome with combined influence of genetic susceptibility and influence of environmental factors, the best known being obesity, age, and physical inactivity, resulting in insulin resistance in cells requiring insulin for glucose absorption. This form of diabetes is strongly inherited.
  • Other types of impaired glucose tolerance (see the Diabetes)
• Insulinoma - a tumor of pancreatic β-cells producing excess insulin or reactive hypoglycemia.
• Metabolic syndrome – a poorly understood condition first called Syndrome X by Gerald Reaven, Reaven's Syndrome after Reaven, CHAOS in Australia (from the signs that seem to travel together). It is currently not clear whether these signs have a single, treatable cause, or are the result of body changes leading to type 2 diabetes. It is characterized by elevated blood pressure, dyslipidemia (disturbances in blood cholesterol forms and other blood lipids), and increased waist circumference (at least in populations in much of the developed world). The basic underlying cause may be the insulin resistance that precedes type 2 diabetes, which is a diminished capacity for insulin response in some tissues (e.g., muscle, fat). It is common that morbidities, such as essential hypertension, obesity, type 2 diabetes, and cardiovascular disease (CVD) develop.
• Polycystic ovary syndrome – a complex syndrome in women in the reproductive years where anovulation and androgen excess are commonly displayed as hirsutism. In many cases of PCOS, insulin resistance is present.

As a medication

Main article: Insulin therapy

Insulin vial

Biosynthetic "human" insulin is now manufactured for widespread clinical use using recombinant DNA technology. More recently, researchers have succeeded in introducing the gene for human insulin into plants and in producing insulin in them, to be specific safflower. This technique is anticipated to reduce production costs.

Several of these slightly modified versions of human insulin, while having a clinical effect on blood glucose levels as though they were exact copies, have been designed to have somewhat different absorption or duration of action characteristics. They are usually referred to as "insulin analogues". For instance, the first one available, Humalog (insulin lispro), does not exhibit a delayed absorption effect found in regular insulin, and begins to have an effect in as little as 15 minutes. Other rapid-acting analogues are NovoRapid and Apidra, with similar profiles. All are rapidly absorbed due to a mutation in the sequence that prevents the insulin analogue from forming dimers and hexamers. Instead, the insulin molecule is a monomer, which is more rapidly absorbed. Using it, therefore, does not require the planning required for other insulins that begin to take effect much later (up to many hours) after administration. Another type is extended-release insulin; the first of these was Lantus (insulin glargine). These have a steady effect for the entire time they are active, without the peak and drop off effect in other insulins; typically, they continue to have an insulin effect for an extended period from 18 to 24 hours. Likewise, another protracted insulin analogue (Levemir) is based on a fatty acid acylation approach. A myristyric acid molecule is attached to this analogue, which in turn associates the insulin molecule to the abundant serum albumin, which in turn extends the effect and reduces the risk of hypoglycemia. Both protracted analogues need to be taken only once-daily, and are very much used in the type 1 diabetes market as the basal insulin. A combination of a rapid acting and a protracted insulin is also available for the patients, making it more likely for them to achieve an insulin profile that mimics that of the body´s own insulin release.

Insulin is usually taken as subcutaneous injections by single-use syringes with needles, via an insulin pump, or by repeated-use insulin pens with needles.

Unlike many medicines, insulin currently cannot be taken orally because, like nearly all other proteins introduced into the gastrointestinal tract, it is reduced to fragments (even single amino acid components), whereupon all activity is lost. There has been some research into ways to protect insulin from the digestive tract, so that it can be administered orally or sublingually. While experimental, several companies now have various formulations in human clinical trials, and one, the India-based Biocon, has formed an agreement with BMS to produce an oral-insulin alternative.

History

Discovery

In 1869 Paul Langerhans, a medical student in Berlin, was studying the structure of the pancreas under a microscope when he identified some previously unnoticed tissue clumps scattered throughout the bulk of the pancreas. The function of the "little heaps of cells", later known as the islets of Langerhans, was unknown, but Edouard Laguesse later suggested they might produce secretions that play a regulatory role in digestion. Paul Langerhans' son, Archibald, also helped to understand this regulatory role. The term "insulin" originates from insula, the Latin word for islet/island.

In 1889, the Polish-German physician Oscar Minkowski, in collaboration with Joseph von Mering, removed the pancreas from a healthy dog to test its assumed role in digestion. Several days after the dog's pancreas was removed, Minkowski's animal keeper noticed a swarm of flies feeding on the dog's urine. On testing the urine, they found there was sugar in the dog's urine, establishing for the first time a relationship between the pancreas and diabetes. In 1901, another major step was taken by Eugene Lindsay Opie, when he clearly established the link between the islets of Langerhans and diabetes: "Diabetes mellitus . . . is caused by destruction of the islets of Langerhans and occurs only when these bodies are in part or wholly destroyed." Before his work, the link between the pancreas and diabetes was clear, but not the specific role of the islets.

The structure of insulin. The left side is a space-filling model of the insulin monomer, believed to be biologically active. Carbon is green, hydrogen white, oxygen red, and nitrogen blue. On the right side is a ribbon diagram of the insulin hexamer, believed to be the stored form. A monomer unit is highlighted with the A chain in blue and the B chain in cyan. Yellow denotes disulfide bonds, and magenta spheres are zinc ions.

Over the next two decades, several attempts were made to isolate whatever it was the islets produced as a potential treatment. In 1906, George Ludwig Zuelzer was partially successful treating dogs with pancreatic extract, but was unable to continue his work. Between 1911 and 1912, E.L. Scott at the University of Chicago used aqueous pancreatic extracts, and noted "a slight diminution of glycosuria", but was unable to convince his director of his work's value; it was shut down. Israel Kleiner demonstrated similar effects at Rockefeller University in 1915, but his work was interrupted by World War I, and he did not return to it.

In 1916 Nicolae Paulescu, a Romanian professor of physiology at the University of Medicine and Pharmacy in Bucharest, developed an aqueous pancreatic extract which, when injected into a diabetic dog, had a normalizing effect on blood sugar levels. He had to interrupt his experiments because of World War I, and in 1921 he wrote four papers about his work carried out in Bucharest and his tests on a diabetic dog. Later that year, he published "Research on the Role of the Pancreas in Food Assimilation".

Extraction and purification

In October 1920, Canadian Frederick Banting concluded that it was the very digestive secretions that Minkowski had originally studied that were breaking down the islet secretion(s), thereby making it impossible to extract successfully. He jotted a note to himself: "Ligate pancreatic ducts of the dog. Keep dogs alive till acini degenerate leaving islets. Try to isolate internal secretion of these and relieve glycosurea."

The idea was the pancreas's internal secretion, which, it was supposed, regulates sugar in the bloodstream, might hold the key to the treatment of diabetes. A surgeon by training, Banting knew certain arteries could be tied off that would lead to atrophy of most of the pancreas, while leaving the islets of Langerhans intact. He theorized a relatively pure extract could be made from the islets once most of the rest of the pancreas was gone.

In the spring of 1921, Banting traveled to Toronto to explain his idea to J.J.R. Macleod, who was Professor of Physiology at the University of Toronto, and asked Macleod if he could use his lab space to test the idea. Macleod was initially skeptical, but eventually agreed to let Banting use his lab space while he was on holiday for the summer. He also supplied Banting with ten dogs on which to experiment, and two medical students, Charles Best and Clark Noble, to use as lab assistants, before leaving for Scotland. Since Banting required only one lab assistant, Best and Noble flipped a coin to see which would assist Banting for the first half of the summer. Best won the coin toss, and took the first shift as Banting's assistant. Loss of the coin toss may have proved unfortunate for Noble, given that Banting decided to keep Best for the entire summer, and eventually shared half his Nobel Prize money and a large part of the credit for the discovery of insulin with the winner of the toss. Had Noble won the toss, his career might have taken a different path. Banting's method was to tie a ligature around the pancreatic duct; when examined several weeks later, the pancreatic digestive cells had died and been absorbed by the immune system, leaving thousands of islets. They then isolated an extract from these islets, producing what they called "isletin" (what we now know as insulin), and tested this extract on the dogs starting July 27. Banting and Best were then able to keep a pancreatectomized dog named Marjorie alive for the rest of the summer by injecting her with the crude extract they had prepared. Removal of the pancreas in test animals in essence mimics diabetes, leading to elevated blood glucose levels. Marjorie was able to remain alive because the extracts, containing isletin, were able to lower her blood glucose levels.

Banting and Best presented their results to Macleod on his return to Toronto in the fall of 1921, but Macleod pointed out flaws with the experimental design, and suggested the experiments be repeated with more dogs and better equipment. He then supplied Banting and Best with a better laboratory, and began paying Banting a salary from his research grants. Several weeks later, the second round of experiments was also a success; and Macleod helped publish their results privately in Toronto that November. However, they needed six weeks to extract the isletin, which forced considerable delays. Banting suggested they try to use fetal calf pancreas, which had not yet developed digestive glands; he was relieved to find this method worked well. With the supply problem solved, the next major effort was to purify the extract. In December 1921, Macleod invited the biochemist James Collip to help with this task, and, within a month, the team felt ready for a clinical test.

On January 11, 1922, Leonard Thompson, a 14-year-old diabetic who lay dying at the Toronto General Hospital, was given the first injection of insulin. However, the extract was so impure, Thompson suffered a severe allergic reaction, and further injections were canceled. Over the next 12 days, Collip worked day and night to improve the ox-pancreas extract, and a second dose was injected on January 23. This was completely successful, not only in having no obvious side-effects but also in completely eliminating the glycosuria sign of diabetes. The first American patient was Elizabeth Hughes Gossett, the daughter of the governor of New York. The first patient treated in the U.S. was future woodcut artist James D. Havens; Dr. John Ralston Williams imported insulin from Toronto to Rochester, New York, to treat Havens.

Children dying from diabetic ketoacidosis were kept in large wards, often with 50 or more patients in a ward, mostly comatose. Grieving family members were often in attendance, awaiting the (until then, inevitable) death.

In one of medicine's more dramatic moments, Banting, Best, and Collip went from bed to bed, injecting an entire ward with the new purified extract. Before they had reached the last dying child, the first few were awakening from their coma, to the joyous exclamations of their families.

Banting and Best never worked well with Collip, regarding him as something of an interloper, and Collip left the project soon after.

Over the spring of 1922, Best managed to improve his techniques to the point where large quantities of insulin could be extracted on demand, but the preparation remained impure. The drug firm Eli Lilly and Company had offered assistance not long after the first publications in 1921, and they took Lilly up on the offer in April. In November, Lilly made a major breakthrough and was able to produce large quantities of highly refined insulin. Insulin was offered for sale shortly thereafter.

Synthesis

Purified animal-sourced insulin was the only type of insulin available to diabetics until genetic advances occurred later with medical research. The amino acid structure of insulin was characterized in the early 1950s by Frederick Sanger, and the first synthetic insulin was produced simultaneously in the labs of Panayotis Katsoyannis at the University of Pittsburgh and Helmut Zahn at RWTH Aachen University in the early 1960s.

The first genetically engineered, synthetic "human" insulin was produced in a laboratory in 1977 by Arthur Riggs, PhD and Keiichi Itakura, PhD at City of Hope and Herbert Boyer at Genentech using E. coli. Partnering with Genentech founded by Swanson, Boyer and Eli Lilly and Company went on in 1982 to sell the first commercially available biosynthetic human insulin under the brand name Humulin. The vast majority of insulin currently used worldwide is now biosynthetic recombinant "human" insulin or its analogues.

Recombinant insulin is produced either in yeast (usually saccharomyces cerevisiae) or E. coli. In yeast, insulin may be engineered as a single-chain protein with a KexII endoprotease (a yeast homolog of PCI/PCII) site that separates the insulin A chain from a c-terminally truncated insulin B chain. A chemically synthesized c-terminal tail is then grafted onto insulin by reverse proteolysis using the inexpensive protease trypsin; typically the lysine on the c-terminal tail is protected with a chemical protecting group to prevent proteolysis. The ease of modular synthesis and the relative safety of modifications in that region accounts for common insulin analogs with c-terminal modifications (e.g. lispro, aspart, glulisine). The Genentech synthesis and completely chemical synthesis such as that by Bruce Merrifield are not preferred because the efficiency of recombining the two insulin chains is low, primarily due to competition with the precipitation of insulin B chain.

Nobel Prizes

Frederick Banting joined by Charles Best in office, 1924

The Nobel Prize committee in 1923 credited the practical extraction of insulin to a team at the University of Toronto and awarded the Nobel Prize to two men: Frederick Banting and J.J.R. Macleod. They were awarded the Nobel Prize in Physiology or Medicine in 1923 for the discovery of insulin. Banting, insulted that Best was not mentioned, shared his prize with him, and Macleod immediately shared his with James Collip. The patent for insulin was sold to the University of Toronto for one half-dollar.

The primary structure of insulin was determined by British molecular biologist Frederick Sanger. It was the first protein to have its sequence be determined. He was awarded the 1958 Nobel Prize in Chemistry for this work.

In 1969, after decades of work, Dorothy Hodgkin determined the spatial conformation of the molecule, the so-called tertiary structure, by means of X-ray diffraction studies. She had been awarded a Nobel Prize in Chemistry in 1964 for the development of crystallography.

Rosalyn Sussman Yalow received the 1977 Nobel Prize in Medicine for the development of the radioimmunoassay for insulin.

George Minot, co-recipient of the 1934 Nobel Prize for the development of the first effective treatment for pernicious anemia, had diabetes mellitus. Dr. William Castle observed that the 1921 discovery of insulin, arriving in time to keep Minot alive, was therefore also responsible for the discovery of a cure for pernicious anemia.

Nobel Prize controversy

Nicolae Paulescu

The work published by Banting, Best, Collip and Macleod represented the preparation of purified insulin extract suitable for use on human patients. Although Paulescu discovered the principles of the treatment his saline extract could not be used on humans, and he was not mentioned in the 1923 Nobel Prize. Professor Ian Murray was particularly active in working to correct "the historical wrong" against Nicolae Paulescu. Murray was a professor of physiology at the Anderson College of Medicine in Glasgow, Scotland, the head of the department of Metabolic Diseases at a leading Glasgow hospital, vice-president of the British Association of Diabetes, and a founding member of the International Diabetes Federation. Murray wrote:

Insufficient recognition has been given to Paulesco, the distinguished Roumanian scientist, who at the time when the Toronto team were commencing their research had already succeeded in extracting the antidiabetic hormone of the pancreas and proving its efficacy in reducing the hyperglycaemia in diabetic dogs.

In a recent private communication Professor Tiselius, head of the Nobel Institute, has expressed his personal opinion that Paulescu was equally worthy of the award in 1923.

See also

• Insulin analog
• Anatomy and physiolology
  • Pancreas
  • Islets of Langerhans
  • Endocrinology
  • Leptin (The only other known adiposity signal besides insulin).
• Forms of diabetes mellitus
  • Diabetes mellitus
  • Diabetes mellitus type 1
  • Diabetes mellitus type 2
• Treatment
  • Diabetic coma
  • Insulin therapy
  • Intensive insulinotherapy
  • Insulin pump
  • Conventional insulinotherapy
• Other medical / diagnostic uses
  • Insulin tolerance test
  • Triple bolus test

References

Further reading

• Reaven, Gerald M.; Ami Laws (ed.) (1999--04-15). Insulin Resistance: The Metabolic Syndrome X (1st ed.). Totowa, New Jersey: Humana Press. doi:10.1226/0896035883. ISBN 0-89603-588-3. 
• Leahy, Jack L.; William T. Cefalu (ed.) (2002-03-22). Insulin Therapy (1st ed.). New York: Marcel Dekker. ISBN 0-8247-0711-7. 
• Kumar, Sudhesh; Stephen O'Rahilly (ed.) (2005-01-14). Insulin Resistance: Insulin Action and Its Disturbances in Disease. Chichester, England: Wiley. ISBN 0-470-85008-6. 
• Ehrlich, Ann; Carol L. Schroeder (2000-06-16). Medical Terminology for Health Professions (4th ed.). Thomson Delmar Learning. ISBN 0-7668-1297-9. 
• Draznin, Boris; Derek LeRoith (September 1994). Molecular Biology of Diabetes: Autoimmunity and Genetics; Insulin Synthesis and Secretion. Totowa, New Jersey: Humana Press. doi:10.1226/0896032868. ISBN 0-89603-286-8. 
• Famous Canadian Physicians: Sir Frederick Banting at Library and Archives Canada
• McKeage K, Goa KL (2001). "Insulin glargine: a review of its therapeutic use as a long-acting agent for the management of type 1 and 2 diabetes mellitus". Drugs 61 (11): 1599–624. doi:10.2165/00003495-200161110-00007. PMID 11577797. 

External links

• Insulin: entry from protein databank
• The History of Insulin
• CBC Digital Archives - Banting, Best, Macleod, Collip: Chasing a Cure for Diabetes
• Discovery and Early Development of Insulin, 1920–1925
• Secretion of Insulin and Glucagon
• Insulin signaling pathway
• Animations of insulin's action in the body at AboutKidsHealth.ca

UpToDate Contents

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• 1. 2型糖尿病におけるインスリン療法 insulin therapy in type 2 diabetes mellitus
• 2. 糖尿病におけるインスリン療法の一般原則 general principles of insulin therapy in diabetes mellitus
• 3. 成人の1型糖尿病におけるインスリン療法 insulin therapy in adults with type 1 diabetes mellitus
• 4. インスリン作用 insulin action
• 5. インスリン分泌および膵β細胞の機能 insulin secretion and pancreatic beta cell function

English Journal

• Insulin resistance is increased in alopecia areata patients.

• Karadag AS, Ertugrul DT, Gunes Bilgili S, Takci Z, Tutal E, Yilmaz H.SourceFaculty of Medicine, Dermatology, Yuzuncu Yil University , Van , Turkey.
• Cutaneous and ocular toxicology.Cutan Ocul Toxicol.2013 Jun;32(2):102-6. doi: 10.3109/15569527.2012.713418. Epub 2012 Aug 24.
• Increased insulin resistance (IR) has been found in androgenetic alopecia in several studies. However, IR has not been investigated in alopecia areata (AA). We aimed to investigate IR in AA patients and the controls. Anthropometric and demographic data were obtained from 51 AA patients and 36 contro
• PMID 22916967

• Biochemical alterations and liver toxicity analysis with pioglitazone in healthy subjects.

• Saha SK, Das SC, Abdullah-Al-Emran, Sarker M, Uddin MA, Chowdhury AK, Bachar SC.SourceClinical Pharmacy and Pharmacology, University of Dhaka , Dhaka , Bangladesh.
• Drug and chemical toxicology.Drug Chem Toxicol.2013 Apr;39(2):149-54. doi: 10.3109/01480545.2012.658920. Epub 2012 Apr 10.
• Pioglitazone, a member of the thiazolidinediones, is a potent, highly selective agonist for peroxisome proliferator-activated receptor gamma and is an excellent insulin sensitizer used in treating type 2 diabetes mellitus. The present study investigated the effect of pioglitazone on glucose, total c
• PMID 22486205

• Insulin signalling to the kidney in health and disease.

• Hale LJ, Coward RJ.SourceAcademic and Children's Renal Unit, University of Bristol, Learning and Research, Southmead Hospital, Bristol BS10 5NB, U.K.
• Clinical science (London, England : 1979).Clin Sci (Lond).2013 Mar 1;124(6):351-70. doi: 10.1042/CS20120378.
• Ninety-one years ago insulin was discovered, which was one of the most important medical discoveries in the past century, transforming the lives of millions of diabetic patients. Initially insulin was considered only important for rapid control of blood glucose by its action on a restricted number o
• PMID 23190266

Japanese Journal

• 小児・思春期1型糖尿病患者における基礎および追加インスリン量を規定する因子の検討

• 鶴原 昭史
• 大阪市医学会雑誌 61(1/2), 27-35, 2012-06
• NAID 110009396057

• Inverse correlation between serum levels of selenoprotein p and adiponectin in patients with type 2 diabetes

• Misu Hirofumi,Ishikura Kazuhide,Kurita Seiichiro,Takeshita Yumie,Ota Tsuguhito,Saito Yoshiro,Takahashi Kazuhiko,Kaneko Shuichi,Takamura Toshinari
• PLoS ONE 7(4), e34952, 2012-04-04
• … Background: We recently identified selenoprotein P (SeP) as a liver-derived secretory protein that causes insulin resistance in the liver and skeletal muscle; … SeP was a predictor of both total and high-molecular adiponectin, independently of age, body weight, and quantitative insulin sensitivity index (β = -0.343, P = 0.022; …
• NAID 120004140847

• Severe Superimposed Preeclampsia with Obesity, Diabetes and a Mild Imbalance of Angiogenic Factors

• Masuyama Hisashi,Nobumoto Etsuko,Segawa Tomonori,Hiramatsu Yuji
• Acta Medica Okayama 66(2), 171-175, 2012-04
• … After administration of insulin and hydralazine with diet therapy, her hypertension and proteinuria were ameliorated with a 15-kg weight loss. …
• NAID 120004040532

Related Links

• What is Insulin? - Important hormone allows your body to use ...

Insulin is a hormone made by the pancreas that allows your body to use sugar (glucose) from carbohydrates in the food that you eat for energy or to store glucose for future use. Insulin helps keeps your blood sugar level ...

• Insulin: 20 Types, Names, Side Effects, Preparatoins & Dosage

Insulin is a drug prescribed to treat type 1 and type 2 diabetes. Common side effects include headache, nausea, tiredness, blurred vision, and excessive yawning. Types, preparations, drug interactions, dosage, and pregnancy and ...

• 基礎・追加インスリン療法（Basal-bolus）のメリット | インスリン ...

基礎・追加インスリン療法（Basal-Bolus療法） （持効型インスリン製剤1～2回、超速効型インスリン製剤3回など） 本来人間には2つのインスリン分泌のパターンがあります。ひとつは24時間続けて分泌する基礎インスリン(Basalインスリン ...

Related Pictures

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★リンクテーブル★

リンク元	「意識障害」「インスリン」「type I insulin」
拡張検索	「insulin-propranolol test」「compensatory hyperinsulinemia」「propranolol-insulin test」「insulin aspart」

「意識障害」

　　[★]

英

consciousness disturbance, disturbance of consciousness

関

意識

分類

時間による分類

急性/慢性, 持続性/一過性

• 急性＋一過性：失神、てんかん
• 慢性＋持続性：植物状態、認知症

PSY.38

• 単純な意識障害

明識困難状態 < 昏蒙 < 傾眠 < 昏眠 < 昏睡

• 複雑な意識障害

• せん妄　　　　　意識混濁　＋　(高度)精神運動興奮

• 振戦せん妄

• 作業せん妄

• 夜間せん妄

• もうろう状態　　意識狭窄　＋　(軽度)精神運動興奮
• アメンチア

• 意識障害に関連した特殊な病態

• 失外套症候群
• 無動無言症
• 閉じ込め症候群

意識レベルの分類 覚醒度

Mayo Clinicの分類

• 清明：alert
• 傾眠：somnolence
• 昏迷：stupor
• 半昏睡：semicoma
• 昏睡：coma

救急 意識障害をみたら

• AIUEOTIPS (also see DIF.96)

	症候学プリント		DIF.95
A	alcohol	アルコール関連	accidents, arterial occlusions, arteriosclerosis, aneurysms, autoimmune disorders
I	insulin	インスリン関連(低血糖、糖尿病性ケトアシドーシス、非ケトン性高浸透圧性昏睡)	inflammatory, intoxication (encephalitis, cerebral abcess, meningitis, alcoholism, opiates, barbiturates)
U	uremia	尿毒症、電解質異常、内分泌異常、肝性脳症	undefined disorders (narcolepsy, conversion hysteria)
E	encephalopathy, endocrinopathy, electrolyte	脳症(脳炎、脳血管障害)、てんかん後	endocrine disorders(myxedema coma, hyperparathyroidism, diabetic coma, insulin shock), epileptic coma
O	opiate, other overdose of O2 & CO2	薬物中毒	organ failure(hepatic coma, respiratory failure, uremia)
T	trauma, tumor, temparature	頭部外傷、脳挫傷、硬膜外血腫、硬膜下血腫
I	infection	感染症、髄膜炎
P	psychogenic	精神疾患
S	syncope, seizure, stroke, shock, senile	失神、クモ膜下出血

意識障害を来した患者が来た場合：どのような疾患を鑑別に挙げるべきか(IMD.237)

• 1. 脳原発の疾患(一次性)

• a. テント上病変(脳幹の圧迫性病変ないし脳ヘルニアをきたす疾患)

• 1) 脳血管障害:脳出血、脳梗塞
• 2) 硬膜下血腫
• 3) 脳腫瘍:原発性、転移性
• 4) 脳膿瘍

• b. テント下病変(脳幹網様体の障害)

• 1) 脳幹出血、脳幹梗塞、小脳出血、小脳梗塞、脳腫痛、多発性硬化症など

• c. びまん性病変

• 1) くも膜下出血、中枢神経感染症:髄膜炎、脳炎、 播種性血管内凝固症候群など

• 2. 全身疾患に伴う病態(二次性)

• a. 代謝性またはびまん性病変

• 1) ショック:心筋梗塞、大出血など
• 2) 薬物、毒物
• 3) 無酸素ないし低酸素血症
• 4) DIC、全身性感染症:敗血症など
• 5) 肝不全、腎不全、糖尿病性高血糖、重症肝炎、内分泌疾患など
• 6) 低血糖、ビタミンB1欠乏: Wernicke脳症
• 7) 脳振盪、てんかん大発作後
• 8) 酸塩基平衡および電解質異常
• 9) 栄養障害

• b. 心因性無反応

• 1) ヒステリー、統合失調症

意識障害をきたす電解質異常

QB.D-345

カリウムは静止膜電位にかかわるが、ニューロンの活動にはそれほど関わらないから、意識障害はきたしにくいのかもしれない。

pHの異常も局所的に干渉されるため意識障害をきたしにくいのかもしれない。

• 高カルシウム血症　：ニューロンの活動に関わる？
• 高ナトリウム血症、低ナトリウム血症　：APの発生に関わる
• 低リン血症　　　：ATP産生↓
• 低酸素血症　　　：ATP産生↓
• 高炭酸ガス血症　：CO2麻酔

意識障害の評価法

英

evaluation of consciousness disturbance

• Glasgow coma scale GCS
• Japan coma scale JCS

「インスリン」

　　[★]

英

insulin (Z)

同

immunoreactive insulin IRI　←　ELISAを利用して定量されるインスリン(臨床検査医学)

関

インスリン製剤、インスリン受容体

レギュラーインスリン、1型インスリン

分類

• ペプチド

産生組織

• 膵臓β細胞

プレプロインスリンの生合成＠粗面小胞体　→　プレプロインスリン　－(切断＠小胞体)→　プロインスリンはゴルジ体に輸送　－(切断＠ゴルジ体小胞体)→　インスリン

作用

• 全般的な傾向として、同化作用↑、異化作用↓(糖新生↓)

• グルコースの細胞内取り込み→血糖値↓

• インスリン受容体→ GLUTの細胞膜上への移動

• K⁺の細胞内取り込み↑

• 肝臓・筋肉でNa-Kポンプを活性化(PT. 482)。Na/H交換体、Na-K-2Cl共輸送体、Na/K-ATPaseを活性化。
• 高カリウム血症の治療にはインスリン＆グルコースの投与

• 肝細胞でグリコーゲン合成↑
• アミノ酸取り込み↑→タンパク質合成↑
• 脂肪合成↑
• 脂肪分解↓

分泌の調節

• インスリン分泌↑

• 血中グルコース濃度↑
• アミノ酸、消化管ホルモン
• アセチルコリン受容体(迷走神経)
• スルホニル尿素
• 血中K濃度↑

• 細胞外K濃度↑→膵臓β細胞脱分極→インスリン分泌↑

• インスリン分泌↓

• アドレナリン受容体(α₂受容体)(交感神経)
• 血中K濃度↓

• 細胞外K濃度↓→膵臓β細胞再分極→インスリン分泌↓

分泌機構

• 1. グルコース→解糖系→ATP↑→KATP閉鎖→脱分極→VDCC解放→[Ca2+]i↑→インスリン開口分泌*2a. ペプチドホルモン→Gsα活性化→AC↑→cAMP↑→PKA↑→インスリン開口分泌
• 2b. ノルアドレナリン→Giα活性化→AC↓→cAMP↓→PKA↓→インスリン分泌抑制
• 3. アセチルコリン→PLC活性化→
  

　　　→IP3↑→[Ca2+]i↑→インスリン開口分泌
　　　→DAG↑→PKC活性化→インスリン開口分泌

作用機序

• 受容体型チロシンキナーゼ

臨床関連

• 糖尿病

インスリン作用不足による代謝障害

血漿中：ブドウ糖↑、アミノ酸↑、遊離脂肪酸↑、ケトン体↑

• 高血圧とインスリン抵抗性の関連

→インスリン抵抗性

• 高インスリン血症

「type I insulin」

　　[★]

• 1型インスリン

関

insulin、regular insulin

「insulin-propranolol test」

　　[★] プロプラノロール・インスリン試験。インスリン・プロプラノロール試験

「compensatory hyperinsulinemia」

　　[★]

代償性高インスリン血症

関

hyperinsulinemia、hyperinsulinism

「propranolol-insulin test」

　　[★] プロプラノロール・インスリン試験

「insulin aspart」

　　[★] インスリンアスパルト