diabetes

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diabetes

or

diabetes mellitus

(məlī`təs), chronic disorder 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.
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 (sugar) metabolism caused by inadequate production or use of insulininsulin,
hormone secreted by the β cells of the islets of Langerhans, specific groups of cells in the pancreas. Insufficiency of insulin in the body results in diabetes. Insulin was one of the first products to be manufactured using genetic engineering.
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, a 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.
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 produced in specialized cells (beta cells in the islets of Langerhans) 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).
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 that allows the body to use and store glucose. It is a leading cause of death in the United States and is especially prevalent among African Americans. The treatment of diabetes was revolutionized when F. 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.
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 and C. H. BestBest, Charles Herbert,
1899–1978, Canadian physiologist, b. West Pembroke, Maine. With F. G. Banting he discovered (1921) the use of insulin in the treatment of diabetes. He was appointed professor of physiology at the Univ.
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 isolated insulin in 1921.

The Disorder

The lack of insulin results in an inability to metabolize glucose, and the capacity to store 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.
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 (a form of glucose) in the liver and the active transport of glucose across cell membranes are impaired. The symptoms are elevated sugar levels in the urine and blood, increased urination, thirst, hunger, weakness, weight loss, and itching. Prolonged hyperglycemia (excess blood glucose) leads to increased protein and fat catabolism, a condition that can cause premature vascular degeneration and atherosclerosis (see arteriosclerosisarteriosclerosis
, general term for a condition characterized by thickening, hardening, and loss of elasticity of the walls of the blood vessels. These changes are frequently accompanied by accumulations inside the vessel walls of lipids, e.g.
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). Uncontrolled diabetes leads to diabetic acidosis, in which ketones build up in the blood. Patients have sweet-smelling breath, and may suffer confusion, unconsciousness, and death. There are two distinct types of diabetes mellitus: insulin-dependent and noninsulin-dependent.

Insulin-dependent Diabetes

Insulin-dependent diabetes (Type I), also called juvenile-onset diabetes, is the more serious form of the disease; about 10% of diabetics have this form. It is caused by destruction of pancreatic cells that make insulin and usually develops before age 30. Type I diabetics have a genetic predisposition to the disease. There is some evidence that it is triggered by a virus that changes the pancreatic cells in a way that prompts the immune system to attack them. The symptoms are the same as in the non-insulin-dependent variant, but they develop more rapidly and with more severity. Treatment includes a diet limited in carbohydrates and saturated fat, exercise to burn glucose, and regular insulin injections, sometimes administered via a portable insulin pump. Transplantation of islet cells has also proved somewhat successful since 1999, after new transplant procedures were developed, but the number of pancreases available for extraction of the islet cells is far smaller than the number of Type I diabetics. Patients receiving a transplant must take immunosuppressive drugs to prevent rejection of the cells, and many ultimately need to resume insulin injections, but despite that transplants provide real benefits for some whose diabetes has become difficult to control.

Noninsulin-dependent diabetes

Noninsulin-dependent diabetes (Type 2), also called adult-onset diabetes, results from the inability of the cells in the body to respond to insulin. About 90% of diabetics have this form, which is more prevalent in minorities and usually occurs after age 40. Although the cause is not completely understood, there is a genetic factor and 90% of those affected are obese. As in Type I diabetes, treatment includes exercise and weight loss and a diet low in total carbohydrates and saturated fat. Some individuals require insulin injections; many rely on oral drugs, such as sulphonylureas, metformin, acarbose or another alpha-glucosidase inhibitor, thiazolidinediones, or dipeptidyl peptidase–4 (DPP-4) inhibitors.

Complications

Diabetes affects the way the body handles fats, leading to fat accumulation in the arteries and potential damage to the kidneys, eyes, heart, and brain, and statins (cholesterol-lowering drugs) may be prescribed to prevent heart disease. It is the leading cause of kidney disease. Many patients require dialysisdialysis
, in chemistry, transfer of solute (dissolved solids) across a semipermeable membrane. Strictly speaking, dialysis refers only to the transfer of the solute; transfer of the solvent is called osmosis.
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 or kidney transplants (see transplantation, medicaltransplantation, medical,
surgical procedure by which a tissue or organ is removed and replaced by a corresponding part, usually from another part of the body or from another individual.
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). Most cases of acquired blindnessblindness,
partial or complete loss of sight. Blindness may be caused by injury, by lesions of the brain or optic nerve, by disease of the cornea or retina, by pathological changes originating in systemic disorders (e.g.
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 in the United States are caused by diabetes. Diabetes can also affect the nerves, causing numbness or pain in the face and extremities. A complication of insulin therapy is insulin shock, a hypoglycemic condition that results from an oversupply of insulin in relation to the glucose level in the blood (see hyperinsulinismhyperinsulinism,
presence in the system of an above-normal amount of insulin, the substance secreted by the pancreas and needed by the body to utilize sugar. An increased amount of insulin in the body results in below-normal amounts of sugar in the system, giving rise to such
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).

Bibliography

See A. Bloom, Diabetes Explained (1973); Portland Area Diabetes Program, Diabetes and Insulin (1988); M. Davidson, Diabetes Mellitus: Diagnosis and Treatment (1991).

diabetes

[‚dī·ə′bēd·ēz]
(medicine)
Any of various abnormal conditions characterized by excessive urinary output, thirst, and hunger; usually refers to diabetes mellitus.

diabetes

any of various disorders, esp diabetes mellitus, characterized by excretion of an abnormally large amount of urine
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