insulin

insulin,

hormonehormone,
secretory substance carried from one gland or organ of the body via the bloodstream to more or less specific tissues, where it exerts some influence upon the metabolism of the target tissue.
..... Click the link for more information. secreted by the β cells of the islets of Langerhans, specific groups of cells in the pancreaspancreas
, glandular organ that secretes digestive enzymes and hormones. In humans, the pancreas is a yellowish organ about 7 in. (17.8 cm) long and 1.5 in. (3.8 cm) wide. It lies beneath the stomach and is connected to the small intestine at the duodenum (see digestive system).
..... Click the link for more information. . Insufficiency of insulin in the body results in diabetesdiabetes
or diabetes mellitus
, chronic disorder of glucose (sugar) metabolism caused by inadequate production or use of insulin, a hormone produced in specialized cells (beta cells in the islets of Langerhans) in the pancreas that allows the body to use and store
..... Click the link for more information. . Insulin was one of the first products to be manufactured using genetic engineeringgenetic engineering,
the use of various methods to manipulate the DNA (genetic material) of cells to change hereditary traits or produce biological products. The techniques include the use of hybridomas (hybrids of rapidly multiplying cancer cells and of cells that make a
..... Click the link for more information. .

Action

In general, insulin acts to reduce extracellular (including blood plasma) levels of glucoseglucose,
dextrose,
or grape sugar,
monosaccharide sugar with the empirical formula C₆H₁₂O₆ . This carbohydrate occurs in the sap of most plants and in the juice of grapes and other fruits.
..... Click the link for more information. by interacting in some way yet unknown with various cell membranes. In adipose (fatty) tissue it facilitates the cellular uptake of glucose and its subsequent conversion to fatty acidsfatty acid,
any of the organic carboxylic acids present in fats and oils as esters of glycerol. Molecular weights of fatty acids vary over a wide range. The carbon skeleton of any fatty acid is unbranched. Some fatty acids are saturated, i.e.
..... Click the link for more information. , and it inhibits the breakdown of fatty acids to simpler compounds. In muscle it again facilitates the transport of glucose into cells and in addition stimulates its conversion to glycogenglycogen
, starchlike polysaccharide (see carbohydrate) that is found in the liver and muscles of humans and the higher animals and in the cells of the lower animals. Chemically it is a highly branched condensation polymer of glucose; it is readily hydrolyzed to glucose.
..... Click the link for more information. . It also increases protein synthesis in muscle. In the liver, insulin facilitates glucose catabolismcatabolism
, subdivision of metabolism involving all degradative chemical reactions in the living cell. Large polymeric molecules such as polysaccharides, nucleic acids, and proteins are first split into their constituent monomeric units, such as amino acids, after which the
..... Click the link for more information. and its conversion to glycogen and inhibits its synthesis from simpler compounds.

Isolation and Structure

Frederick G. BantingBanting, Sir Frederick Grant,
1891–1941, Canadian physician, M.D. Univ. of Toronto, 1922. From 1923 he was professor of medical research at Toronto. Working with C. H. Best under the direction of J. J. R.
..... Click the link for more information. , Charles H. BestBest, Charles Herbert,
1899–1978, Canadian physiologist, b. West Pembroke, Maine. With F. G. Banting and J. R. R. Macleod he discovered (1921) the use of insulin in the treatment of diabetes. He was appointed professor of physiology at the Univ.
..... Click the link for more information. , and J. J. R. MacleodMacleod, John James Rickard
, 1876–1935, Scottish physiologist, educated at Aberdeen and Leipzig. He was a professor at Western Reserve Univ. (1903–18) and at the Univ. of Toronto (1918–28) and later taught at the Univ. of Aberdeen.
..... Click the link for more information. were the first to obtain, from extracts of pancreas (1921–22), a preparation of insulin that could serve to replace a deficiency of the hormone in the human body. The complete amino acid sequence of the insulin molecule was described in the early 1950s; insulin was the first protein to be sequenced entirely. This pioneering work was confirmed from 1963 to 1966, when several groups reported laboratory synthesis of biologically active insulin. The three-dimensional structure of the crystalline hormone was published in 1969.

Insulin has been shown to be a protein consisting of two polypeptide chains (see peptidepeptide,
organic compound composed of amino acids linked together chemically by peptide bonds. The peptide bond always involves a single covalent link between the α-carboxyl (oxygen-bearing carbon) of one amino acid and the amino nitrogen of a second amino acid.
..... Click the link for more information. ), one of 21 amino acid residues and the other of 30, joined by two disulfide bridges (see cysteinecysteine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of mammalian protein.
..... Click the link for more information. ). The two chains are synthesized in the β cells as part of one continuous polypeptide chain called proinsulin; a 32-amino acid sequence (the connecting peptide) is subsequently split out of the proinsulin molecule by an enzyme resembling trypsintrypsin,
enzyme that acts to degrade protein; it is often referred to as a proteolytic enzyme, or proteinase. Trypsin is one of the three principal digestive proteinases, the other two being pepsin and chymotrypsin.
..... Click the link for more information. to yield active insulin.

Insulin in Diabetes Treatment

Many, but not all, of the symptoms of diabetes can be controlled by the administration of insulin. The forms of insulin available early in the 20th cent. had to be injected frequently because they were quick-acting. Later modifications gave the insulin solution a more prolonged action so that hypodermic injections could be made less frequently. Some now control their insulin levels via a small, portable insulin pump. In certain cases of mild diabetes, oral medications that stimulate production of insulin can be taken in lieu of insulin. See glucagonglucagon
, hormone secreted by the α cells of the islets of Langerhans, specific groups of cells in the pancreas. It tends to counteract the action of insulin, i.e., it raises the concentration of glucose in the blood.
..... Click the link for more information. .

Bibliography

See M. Bliss, The Discovery of Insulin (1982).

Insulin

Produced and secreted by the beta cells of the islets (insulae) of Langerhans of the pancreas, the hormone which regulates the use and storage of foodstuffs, especially the carbohydrates. Chemically insulin is a small, simple protein. Insulins from various species differ in the composition; these differences account for the fact that diabetics treated with animal insulins develop antibodies which may sometimes interfere with the action of the hormone. The structure has been verified by synthesis of insulin from pure amino acids in the laboratory. See Carbohydrate metabolism, Immunology, Pancreas

Insulin, being a polypeptide, can also be broken down by many proteolytic enzymes to its constituent amino acids. Because of these breakdown systems, the turnover of insulin in the body is rapid; its “half-life” has been estimated to be 10–30 min. The liver alone is capable of destroying about 50% of the insulin passing through it on its way from the pancreas to the bodily tissues.

The role played by insulin in the body is most clearly approached by considering the abnormalities resulting from removing insulin from an organism by surgical excision of the pancreas or by the chemical destruction of the insulin-producing cells: A state of severe diabetes is produced. Normally the blood glucose level is about 100 mg/100 ml. A carbohydrate meal raises the blood sugar to about 150 mg and the premeal value is reached again within 1.5 h. The normal organism manages to dispose of food by storage and oxidation within this period because insulin is present. When food (carbohydrate and protein) reaches the upper intestine, a substance is liberated which in turn stimulates the beta cells to secrete extra insulin. Insulin acts on most tissues to speed the uptake of glucose. In the cells the glucose is burned for energy, stored as glycogen, or transformed to and stored as fat. The human pancreas probably produces 1–2 mg of the hormone per day. This is sufficient to regulate the metabolism of more than 250 g of carbohydrate, 70 g of protein, and 75 g of fat, the usual composition of an ordinary 2000-calorie diet.

In diabetes the rate of glucose uptake is slowed, the level of circulating blood sugar rises, and sugar spills over into the excreted urine. Calories are wasted, more water is excreted, and there is muscular weakness and weight loss; hence urinary frequency, hunger, thirst, and fatigue. Whenever glucose metabolism is defective, stored fat is broken down to fatty acids because of the actions of adrenaline and the pituitary growth hormone. Insulin is able to reverse all these phenomena by favoring storage and swift intake of glucose into the tissues, by decreasing the breakdown of stored fat, and by promoting protein synthesis.

When insulin is secreted or given in excess, it may lower the blood sugar level much below its normal value, causing hypoglycemia. Hypoglycemia is dangerous because the metabolism in the brain cells depends primarily upon an adequate supply of glucose.

The precise molecular mechanisms of insulin action are still not known. The initial step is the binding of the hormone to a specific receptor on the cell membrane. This event somehow activates a set of transport molecules, so that glucose, potassium, and amino acids enter cells more freely. At the same time, fat breakdown is slowed and glycogen storage increased. All these actions depend upon the integrity of the outer cell membrane. See Cell permeability

Not all the cells of the body require or respond to insulin. The insulin-responsive tissues are the liver, skeletal muscle, the heart, and the adipose tissue. Sensitivity to insulin is affected by many conditions. Obesity, antibodies to the hormone or its receptor, oversecretion of growth hormone or adrenal steroids, ketosis, and unknown genetic factors all cause insulin resistance. Muscular exercise, correction of obesity, and a deficiency of pituitary or adrenal hormones are associated with an increased sensitivity to the hormone.

Insulin

a protein hormone formed by the beta cells of the islets of Langerhans in the pancreas. It was first isolated by the Canadian scientists F. Banting and C. Best (1921–22). The structural unit of insulin is a monomer with a molecular weight of about 6,000. Under varying conditions, the molecular weight may be 12,000 or 36,000 because the insulin molecule combines different numbers of monomers, depending on the experimental conditions. Every monomer contains 51 amino acids arranged in two peptide chains, A and B, linked by two disulfide bridges (—S—S—). The presence of these bridges is needed for the hormonal activity of insulin to be manifested. If they are destroyed, insulin becomes inactive. Insulin differs from one animal species to another solely in the position of certain amino acids in the chain. The structure of the insulin monomer, that is, the sequence in which the amino acid residues are arranged, was elucidated by the British biochemist F. Sanger (1945–56). This led to the chemical synthesis of insulin.

Insulin lowers blood sugar levels, delaying the breakdown of glycogen and the synthesis of glucose in the liver. At the same time it increases the permeability of the cell membranes to glucose, assisting its passage into the tissues. It also increases the utilization of glucose in reactions of the pentose phosphate cycle and accelerates the glycogen synthesis in the muscles. The presence of insulin is responsible for the dominance of the synthesis of proteins and fatty acids over their decomposition and promotes the conversion of carbohydrates to fatty acids and the formation of fats.

An insulin insufficiency causes a metabolic disorder—diabetes mellitus. Insulin preparations obtained from the pancreas of slaughtered cattle and other animals are used in the treatment of diabetes. Insulin activity is determined biologically (from the ability to lower blood sugar levels in rabbits). A quantity of 0.04082 mg of pure crystalline insulin is taken as a unit of activity (international unit, IU). Insulin is injected subcutaneously or intramuscularly (it is destroyed by gastric juice when taken orally). Free insulin is quickly inactivated by the enzyme insulinase. Various insulin preparations have more prolonged action than insulin, for example, a suspension of amorphous zinc insulin, a solution of protamine zinc insulin, and a suspension of protamine insulin. Low doses of insulin (also in the form of injections) are used for general exhaustion, weight loss, and some other disorders. In psychiatric practice, insulin is injected to induce hypoglycemia.

G. A. SOLOV’EVA

insulin

[′in·sə·lən] (biochemistry) A protein hormone produced by the beta cells of the islets of Langerhans which participates in carbohydrate and fat metabolism.

insulin

a protein hormone, secreted in the pancreas by the islets of Langerhans, that controls the concentration of glucose in the blood. Insulin deficiency results in diabetes mellitus

insulin

[in´su-lin] 1. the major fuel-regulating hormone of the body, a double-chain protein formed from proinsulin in the beta cells of the islets of Langerhans in the pancreas. Insulin promotes the storage of glucose and the uptake of amino acids, increases protein and lipid synthesis, and inhibits lipolysis and gluconeogenesis. Secretion of insulin is a response of the beta cells to a stimulus; the primary stimulus is glucose, and others are amino acids and hormones such as secretin, pancreozymin, and gastrin. These chemicals play an important role in maintaining normal blood glucose levels by triggering insulin release after a meal. After insulin is released from the beta cells, it enters the blood stream and is transported to cells throughout the body. The cell membranes have insulin receptors to which the hormone becomes bonded or “fixed.” An interaction between the insulin and its receptors leads to biochemical processes that include (1) the transport of glucose, amino acids, and certain ions across the membrane and into the cell body; (2) the storage of glycogen in liver and muscle cells; (3) the synthesis of triglycerides and storage of fat; (4) the synthesis of protein, RNA, and DNA, and (5) inhibition of gluconeogenesis, degradation of glycogen and protein, and lipolysis. Although insulin increases the transport of glucose across the cell membrane of most cells, in the brain glucose enters the cells by simple diffusion through the blood--brain barrier.2. a preparation of the hormone, first discovered in 1921, used in treatment of diabetes mellitus; it may be bovine or porcine in origin (prepared from the pancreas of the animals) or a recombinant human type, although insulin of bovine origin is no longer available in the United States. Recombinant human types may duplicate exactly the human insulin protein sequence, or may be analogues with small differences in sequence. Commercially prepared insulin is available in various types that differ in the speed with which they act and in the duration of their effectiveness. There are several different types of insulin, usually classified by their onset and duration of action. (See table.)
Patients with diabetes react differently in the rate at which they absorb and utilize exogenous insulin; therefore, the duration of action varies from person to person. Moreover, the site of injection, volume of injection, and the condition of the tissues into which the insulin is injected can alter its rate of absorption and peak action times, and exercising the limb which has been injected immediately after injection can increase the speed of absorption. Insulin is measured in units.Problems of Insulin Therapy. The problem of either too much or too little insulin is always a potential hazard for the person on insulin therapy. The causes, symptoms, and treatment of hypoglycemic or insulin reaction and hyperglycemia are discussed under diabetes mellitus. Other problems of insulin therapy include insulin allergy, insulin resistance, insulin rebound due to the somogyi effect, and lipodystrophies or other localized tissue changes at injection sites.
Lipodystrophies are localized manifestations of disordered fat metabolism at the sites of insulin injection. Tissue hypertrophy can be seen as a mass of fibrous scar tissue and is sometimes called “insulin tumor.” atrophy of the tissues at the injection site appears as dimpling and pitting of the skin and underlying tissues. These problems are more common in adult females and in children. Atrophy of the tissues is relatively harmless, but hypertrophy can cause malabsorption of the insulin and a possible misdiagnosis of insulin resistance. Measures that can help prevent lipodystrophies include (1) systematic rotation of injection sites, (2) warming insulin to room temperature before injection, (3) pinching the skin when injecting the insulin so that it is deposited between fat and muscle tissue, and (4) use of human insulin.insulin allergy a hypersensitivity reaction to insulin, usually a reaction to its protein components. More purified insulins have now been developed that are less likely to cause an allergic reaction and other complications. Human insulin, prepared by recombinant genetic engineering, eliminates many problems associated with repeated insulin injections, because of reduced antibody concentrations.insulin pump a device consisting of a syringe filled with a predetermined amount of short-acting insulin, a plastic cannula and a needle, and a pump that periodically delivers the desired amount of insulin. The basal rate of insulin delivery usually is one pulse every 8 minutes, but the pump can deliver as many as 60 pulses at a time. Before each meal or snack the patient manually administers a bolus of insulin by adjusting the pump setting to the desired one-time dose. Some insulin pumps will automatically reset themselves to the basal rate of infusion after each bolus. Research is ongoing regarding implantable pumps that release insulin in response to the pump's glucose sensor. This method could potentially administer insulin in a manner resembling the normal absorption from the pancreas.

Insulin pumps are worn externally and connected to an indwelling subcutaneous needle, usually inserted in the abdomen. From Black and Matassarin-Jacobs, 2001.insulin rebound extreme fluctuations in blood sugar levels owing to overreaction of the body's homeostatic feedback mechanisms for control of glucose metabolism. When exogenous insulin is given, the hypoglycemia triggers an outpouring of glucagon and epinephrine, both of which raise the blood sugar concentration markedly. Although the patient may actually have periods of hypoglycemia, urine and blood glucose tests will show hyperglycemia. Treatment is aimed at modifying the extremes by gradually lowering the insulin dosage so as to reduce stimulation of the feedback system of glucose regulation. The patient may need to take smaller doses of insulin or take it at more frequent intervals and at different times during the dayinsulin resistance impairment of the normal biologic response to insulin, which may result from abnormalities in the B-cell products, binding of insulin to antagonists such as anti-insulin antibodies, defects in or reduced numbers of receptors, and defects in the insulin action cascade in the target cell. Diabetic persons with this problem require more than 100 units daily, and some may need as much as 500 or 1000 units daily. Besides diabetes, the condition has also been associated with diseases such as obesity, acromegaly, uremia, and certain rare, possibly genetic, autoimmune diseases.insulin sensitivity test a test used to differentiate diabetes mellitus from pituitary and adrenal diabetes. A test dose of exogenous insulin will produce a rapid and marked decrease in blood glucose if the pancreas is not secreting sufficient quantities of insulin. A much less dramatic response is produced if hyperglycemia is due to excessive secretion of either pituitary or adrenocortical hormones rather than insufficient insulin production.

insulin, regular (insulin injection)

Humulin R, Humulin-R Regular U-500 (concentrate), Insulin-Toronto (CA)

insulin (lispro)

Humalog, Humalog Pen

insulin glulisine, recombinant

Apidra, Apidra SoloSTAR

insulin lispro protamine, human

Humalog Mix 50/50, Humalog Mix 75/25

isophane insulin suspension (NPH insulin)

Humulin N, Novolin N

isophane insulin suspension (NPH) and insulin injection (regular)

Humulin 70/30 (70% isophane insulin and 30% insulin injection), Humulin 70/30 PenFill, Novolin 70/30, Novolin 70/30 PenFill

Pharmacologic class: Pancreatic hormone

Therapeutic class: Hypoglycemic

Pregnancy risk category B

Action

Promotes glucose transport, which stimulates carbohydrate metabolism in skeletal and cardiac muscle and adipose tissue. Also promotes phosphorylation of glucose in liver, where it is converted to glycogen. Directly affects fat and protein metabolism, stimulates protein synthesis, inhibits release of free fatty acids, and indirectly decreases phosphate and potassium.

Availability

Glulisine, recombinant: 100 units/ml in 10-ml vials, 100 units/ml in 3-ml cartridge system, 100 units/ml in 3-ml prefilled pen

Isophane suspension, injection (regular): 70 units NPH and 30 units regular insulin/ml (100 units/ml total), 50 units NPH and 50 units regular insulin/ml (100 units/ml total)

Isophane suspension (NPH insulin): 100 units/ml

Lispro: 100 units/ml in 10-ml vials and 1.5-ml cartridges

Regular insulin injection: 100 units/ml

Regular U-500 (concentrated), insulin human injection: 500 units/ml

Zinc suspension, extended (ultralente): 100 units/ml

Zinc suspension (lente insulin): 100 units/ml

Indications and dosages

➣ Type 1 (insulin-dependent) diabetes mellitus; type 2 (non-insulin-dependent) diabetes mellitus unresponsive to diet and oral hypoglycemics

Adults and children: In newly diagnosed diabetes, total of 0.5 to 1 unit/kg/day subcutaneously as part of multidose regimen of short- and long-acting insulin. Dosage individualized based on patient's glucose level, adjusted to premeal and bedtime glucose levels. Reserve concentrated insulin (500 units/ml) for patients requiring more than 200 units/day.

➣ Diabetic ketoacidosis

Adults and children: Loading dose of 0.15 units/kg (nonconcentrated regular insulin) I.V. bolus, followed by continuous infusion of 0.1 unit/kg/hour until glucose level drops. Then administer subcutaneously, adjusting dosage according to glucose level.

Contraindications

• Hypersensitivity to drug or its components

• Hypoglycemia

Precautions

Use cautiously in:

• hepatic or renal impairment, hypothyroidism, hyperthyroidism

• elderly patients

• pregnant or breastfeeding patients

• children.

Administration

See Be aware that insulin is a high-alert drug whether given subcutaneously or I.V.

See Don't give insulin I.V. (except nonconcentrated regular insulin), because anaphylactic reaction may occur.

• When mixing two types of insulin, draw up regular insulin into syringe first.

• For I.V. infusion, mix regular insulin only with normal or half-normal saline solution, as prescribed, to yield a concentration of 1 unit/ml. Give every 50 units I.V. over at least 1 minute.

• Rotate subcutaneous injection sites to prevent lipodystrophy.

• Administer mixtures of regular and NPH or regular and lente insulins within 5 to 15 minutes of mixing.

Adverse reactions

Metabolic: hypokalemia, sodium retention, hypoglycemia, rebound hyperglycemia (Somogyi effect)

Skin: urticaria, rash, pruritus

Other: edema; lipodystrophy; lipohypertrophy; erythema, stinging, or warmth at injection site; allergic reactions including anaphylaxis

Interactions

Drug-drug. Acetazolamide, albuterol, antiretrovirals, asparaginase, calcitonin, corticosteroids, cyclophosphamide, danazol, dextrothyroxine, diazoxide, diltiazem, diuretics, dobutamine, epinephrine, estrogens, hormonal contraceptives, isoniazid, morphine, niacin, phenothiazines, phenytoin, somatropin, terbutaline, thyroid hormones: decreased hypoglycemic effect

Anabolic steroids, angiotensin-converting enzyme inhibitors, calcium, chloroquine, clofibrate, clonidine, disopyramide, fluoxetine, guanethidine, mebendazole, MAO inhibitors, octreotide, oral hypoglycemics, phenylbutazone, propoxyphene, pyridoxine, salicylates, sulfinpyrazone, sulfonamides, tetracyclines: increased hypoglycemic effect

Beta-adrenergic blockers (nonselective): masking of some hypoglycemia symptoms, delayed recovery from hypoglycemia

Lithium carbonate: decreased or increased hypoglycemic effect

Pentamidine: increased hypoglycemic effect, possibly followed by hyperglycemia

Drug-diagnostic tests. Glucose, inorganic phosphate, magnesium, potassium: decreased levels

Liver and thyroid function tests: interference with test results

Urine vanillylmandelic acid: increased level

Drug-herbs. Basil, burdock, glucosamine, sage: altered glycemic control Chromium, coenzyme Q10, dandelion, eucalyptus, fenugreek, marshmallow: increased hypoglycemic effect

Garlic, ginseng: decreased blood glucose level

Drug-behaviors. Alcohol use: increased hypoglycemic effect

Marijuana use: increased blood glucose level

Smoking: increased blood glucose level, decreased response to insulin

Patient monitoring

• Monitor glucose level frequently to assess drug efficacy and appropriateness of dosage.

• Watch blood glucose level closely if patient is converting from one insulin type to another or is under unusual stress (as from surgery or trauma).

See Monitor for signs and symptoms of hypoglycemia. Keep glucose source at hand in case hypoglycemia occurs.

See Assess for signs and symptoms of hyperglycemia, such as polydipsia, polyphagia, polyuria, and diabetic ketoacidosis (as shown by blood and urinary ketones, metabolic acidosis, extremely elevated blood glucose level).

• Monitor for glycosuria.

• Closely evaluate kidney and liver function test results in patients with renal or hepatic impairment.

Patient teaching

• Teach patient how to administer insulin subcutaneously as appropriate.

• Advise patient to draw up regular insulin into syringe first when mixing two types of insulin. Caution him not to change order of mixing insulins.

• Instruct patient to rotate subcutaneous injection sites and keep a record of sites used, to prevent fatty tissue breakdown.

See Teach patient how to recognize and report signs and symptoms of hypoglycemia and hyperglycemia. Advise him to carry a glucose source at all times.

• Instruct patient to store insulin in refrigerator (not freezer).

• Teach patient how to monitor and record blood glucose level and, if indicated, urine glucose and ketone levels.

• Tell patient that dietary changes, activity, and stress can alter blood glucose level and insulin requirements.

• Instruct patient to wear medical identification stating that he is diabetic and takes insulin.

• Advise patient to have regular medical, vision, and dental exams.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.

in·su·lin

(in'sŭ-lin), [MIM*176730] A polypeptide hormone, secreted by β cells in the islets of Langerhans, which promotes glucose use, protein synthesis, and the formation and storage of neutral lipids; available in various preparations including genetically engineered human insulin, which is currently favored. Insulin is used parenterally in the treatment of diabetes mellitus. [L. insula, island, + -in]

insulin

(ĭn′sə-lĭn)n.1. A polypeptide hormone that is secreted by the beta cells of the islets of Langerhans in the pancreas and functions in the regulation of carbohydrate and fat metabolism, especially the conversion of glucose to glycogen, which lowers the blood glucose level. It consists of two linked polypeptide chains called A and B.2. Any of various pharmaceutical preparations containing this hormone or a close chemical analog, derived from the pancreas of certain animals or produced through genetic engineering and used in the medical treatment and management of type 1 and type 2 diabetes.

insulin

Physiology A disulfide-linked polypeptide hormone produced by the beta cells of the pancreatic islets, which controls serum glucose and anabolism of carbohydrates, fat, protein. See Biphasic insulin, PEPCK, Proinsulin, rDNA insulin.

in·su·lin

(in'sŭ-lin) A polypeptide hormone, secreted by beta cells in the islets of Langerhans, which promotes glucose use, protein synthesis, and the formation and storage of neutral lipids; available in a variety of preparations including genetically engineered human insulin, which is currently favored, insulin is used parenterally in the treatment of diabetes mellitus.
Compare: bioregulator[L. insula, island, + -in]

insulin

(in'su-lin) [L. insula, island + -in]

INSULIN AND GLUCAGON FUNCTIONSA hormone secreted by the beta cells of the pancreas. As a drug, insulin is used principally to control diabetes mellitus. Insulin therapy is required in the management of type 1 diabetes mellitus because patients with this illness do not make enough insulin on their own to survive. The drug also is used in the care of patients with gestational diabetes to prevent fetal complications caused by maternal hyperglycemia (insulin itself does not cross the placenta or enter breast milk). In type 2 diabetes mellitus, its use typically is reserved for those patients who have failed to control their blood sugars with diet, exercise, and oral drugs. See: illustration; diabetes mellitus

Insulin preparations differ with respect to the speed with which they act and their duration and potency following subcutaneous injection. See: table

In the past, insulin for injection was obtained from beef or swine pancreas. These peptides differed from human insulin by a few amino acids, causing some immune reactions and drug resistance. Most insulin now in use is made by recombinant DNA technology and from an immunological perspective is equivalent to human insulin.

Physiology

In health, the pancreas secretes insulin in response to elevations of blood glucose, such as occur after meals. It stimulates cells, esp. in muscular tissue, to take up sugar from the bloodstream. It also facilitates the storage of excess glucose as glycogen in the liver and prevents the breakdown of stored fats. In type 1 diabetes mellitus, failure of the beta cells to produce insulin results in hyperglycemia and ketoacidosis.

Dosage

The insulin dosage should always be expressed in units. There is no average dose of insulin for diabetics; each patient must be assessed and treated individually Doses are titrated gradually to achieve near normal glucose levels, about 90–125 mg/dl.

Storage

The FDA requires that all preparations of insulin contain instructions to keep in a cold place and to avoid freezing.

CAUTION!

Those who use insulin should wear an easily seen bracelet or necklace stating that they have diabetes and use the drug. This helps to ensure that patients with hypoglycemic reactions will be diagnosed and treated promptly.

insulin analog

See: analog

insulin aspart

A rapidly acting insulin administered subcutaneously, with action similar to that of insulin lispro. Aspartic acid replaces proline at a crucial position in the insulin molecule.

biphasic insulin

An insulin preparation that includes two components, typically a rapidly acting insulin, e.g., regular insulin, and an insulin that has a longer duration of action, e.g., NPH insulin.

insulin glargine

A form of insulin that provides basal insulin coverage throughout the day, with little variation in drug levels. It is typically administered as a single injection (often at bedtime) and is usually part of a regimen that includes multiple injections of short-acting insulins or multiple doses of metformin at meal time. It is made by changing the glycine and arginine content of the insulin polypeptide.

human insulin

Insulin prepared by recombinant DNA technology utilizing strains of Escherichia coli. In its effect it is similar to insulins secreted by the human pancreas. Trade names are Humulin and Novolin. Synonym: Novolin 70/30 See: Humulin 50/50; Humulin 70/30; insulin for table

inhaled insulin

Insulin given by inspiration, with the use of an inhaler. It may be composed of liquid droplets or a dry powder. One inhaled insulin product was removed from use in 2008 because of its adverse effects on the lungs.

insulin injection site

See: site

insulin isophane suspension

Intermediate-acting insulin with onset in 1 2 to 1 hr and a duration of 18 to 28 hr. See: insulin for table

insulin lipodystrophy

See: lipodystrophy

insulin lispro

A synthetic insulin with a very rapid onset and short duration of action. Diabetic patients typically use it immediately before meals to prevent postprandial hyperglycemia. Its absorption is more rapid than regular insulin. It is made by reversing the amino acids lysine and proline in the beta chain of the insulin polypeptide (hence its name lispro).

monocomponent insulin

Single-component insulin.

insulin protamine zinc suspension

Long-acting insulin with onset in 6 to 8 hr and a duration of 30 to 36 hr. See: insulin for table

insulin pump

See: pump

insulin shock

Hypoglycemic shock.

single-component insulin

Highly purified insulin that contains less than 10 parts per million of proinsulin, which is capable of inducing formation of anti-insulin antibodies. Synonym: monocomponent insulin

synthetic insulin

Insulin made by the use of recombinant DNA technology.

insulin zinc extended suspension

Long-acting insulin with onset in 5 to 8 hr and duration of more than 36 hr.

insulin zinc prompt suspension

Fast-acting insulin with onset less than 1 hr and a duration of 12 to 16 hr. * These times are estimates and may vary in individual patients. ** Contain NPH plus a rapid-acting insulin (Aspart, Lispro, or Regular); Novolog 70/30 contains 70% NPH, 30% Novolog

Type of Insulin	Generic (Trade Names)	Onset (hr)	Maximum (hr)	Duration (hr)
Very rapid	Aspart (NovoLog)	0.2–0.5	1–3	3–5
Very rapid	Lispro (Humalog)	0.2–0.5	0.5–2.5	3–5
Very rapid	Glulisine (Apidra)	0.2–0.5	1.6–2.8	3–4
Rapid	Regular	0.5–1.0	2.5–5	4–6
Intermediate-acting	NPH (Humulin N, Novolin N)	2–4	4–12	10–18
Fixed-dose combination insulins **	70/30, 50/50, etc.	Variable, depending on mixture used
Very long- acting	Lantus (Glargine)	2–4	none	11–32
Very long- acting	determir (Levemir)	3–4	3–9	6–23 Dose dependent
U 500 regular very concentrated (5 X U100)		0.5–1.0	2.5–5	up to 24 hr

insulin

A peptide hormone produced in the beta cells of the Islets of Langerhans in the PANCREAS. Insulin facilitates and accelerates the movement of glucose and amino acids across cell membranes. It also controls the activity of certain enzymes within the cells concerned with carbohydrate, fat and protein metabolism. Insulin production is regulated by constant monitoring of the blood glucose levels by the beta cells. Deficiency of insulin causes DIABETES. Insulin preparations may be in the ‘soluble’ form for immediate action or in a ‘retard’ form for prolonged action or as mixtures of these. Most insulins for medical use are now produced by recombinant DNA methods (genetic engineering) and are identical to human insulin. Bovine and porcine insulins are still used. Brand names include: Neutral Insulin injections: Humalog, Actrapid, Velosulin, Humulin S, Hypurin Bovine Neutral, Hypurin Porcine Neutral, Insuman Rapid, NovoRapid and Pork Actrapid. Biphasic Insulin injections: Humalog Mix25 and Mix50, Mixtard, Humulin, Hypurin Porcine, Insuman Comb, NovoMix 30 and Pork Mixtard 30. Isophane Insulin injections: Insulatard, Humulin, Hypurin Bovine Isophane, Isuman Basal and Pork Insulatard. Insulin Zinc Suspension (Mixed): Monotard, Humulin Lente and Hypurin Bovine Lente. Insulin Zinc Suspension (Crystalline): Ultratard and Humulin Zn. Protamine Zinc Insulin injection: Hypurin Bovine PZI. Long-acting Insulin Analogue: Lantus. The prefix ‘Human’ was deleted from insulin products in mid-2003.

insulin

the hormone controlling the amount of blood sugar, which is secreted by the beta cells of the ISLETS OF LANGERHANS in the pancreas. Insulin has three targets: the liver, the muscles, and adipose tissue, where its action helps to reduce the blood sugar level in the following ways:

it stimulates the absorption of more glucose from the blood into respiring cells, by altering cell-membrane permeability;
it stimulates the conversion of glucose into GLYCOGEN in the liver and muscles, reducing the supply of free glucose;
it promotes the conversion of glucose into fats in the liver and adipose cells (LIPOGENESIS);
it inhibits GLUCONEOGENESIS;
it promotes GLYCOLYSIS of glucose in all cells.

Underproduction of insulin causes diabetes mellitus , resulting in an increase in blood sugar (hyperglycaemia) and sugar appearing in the urine (see GLYCOSURIA). The condition can be fatal if untreated, treatment being by injection of insulin into the blood stream. The hormone cannot be taken orally as, being a protein, it would be digested. Insulin was discovered by BANTING and BEST in 1921. The control of blood sugar, where a change in its level automatically brings about the opposite effect, is a good example of a negative FEEDBACK MECHANISM.

Insulin

A hormone secreted by the pancreas in response to high blood sugar levels that induces hypoglycemia. Insulin regulates the body's use of glucose and the levels of glucose in the blood by acting to open the cells so that they can intake glucose.Mentioned in: Diabetes Mellitus, Diabetic Ketoacidosis, Gestational Diabetes, Hypothermia, Insulin Resistance

in·su·lin

(in'sŭ-lin) [MIM*176730] Polypeptide hormone, secreted by β cells in islets of Langerhans, which promotes glucose use, protein synthesis, and formation and storage of neutral lipids; available in various preparations including genetically engineered human insulin, which is currently favored; used parenterally to treat diabetes mellitus. [L. insula, island, + -in]

Patient discussion about insulin

Q. what does an insulin shot do? and what is it good for? A. Insulin is a hormone (substance that controls the activity of the body) that enables muscles and fat to use the glucose (sugar) we get from the diet as a source of energy for activity or for storage as fat. Thus, it lowers the concentration of glucose in the blood. It's produced and secreted from the pancreas, a gland located in the back of the abdomen. When people don't have insulin, or if the body doesn't respond to insulin (essentially diabetes mellitus type 1 and 2, respectively), therapy with insulin helps the body maintain a normal level of glucose. Excessive concentration of glucose in the blood is termed "hyperglycemia" and is deleterious in the long term.
You may read more here: http://en.wikipedia.org/wiki/Insulin

Q. Why is insulin injected and not taken as a pill? A. so if that's the case, why can't you use a patch (like a nicotine patch)? wouldn't that do the same trick?

Q. is there an alternative for the Insulin shots? something less painful but yet effective as the old way? A. Here is a good site on alternative insulin delivery: http://www.diabetes.org/for-parents-and-kids/diabetes-care/alternative-insulin.jsp Hope this helps.

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Words related to insulin

noun hormone secreted by the isles of Langerhans in the pancreas

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