insulin
The definitions used in this glossary of terminology either have been provided by the authors of the articles, or have been extracted wholly or in part, or paraphrased from the following sources: The American Medical Association Encyclopedia of Medicine, Charles B. Clayman, MD, Medical Editor, Random House, New York, 1989; Biotechnology from A to Z, 2d Edition, William Bains, Oxford University Press, New York, New York, 2002; A Dictionary of Genetics, 6th Edition, Robert C. King and William D. Stansfield, Oxford University Press, New York, New York, 2002; Dorland's Illustrated Medical Dictionary, 29th and 30th Editions, W. B. Saunders Company, Philadelphia, 2000, 2003; Genes VII, Benjamin Lewin, Oxford University Press, New York, New York, 2000; The Gale Encyclopedia of Genetic Disorders, Volumes I and II, Stacey L. Blachford, Ed., Thomson Learning, New York, New York, 2002; The Merriam-Webster Dictionary, Merriam-Webster, Inc., Springfield, Massachusetts, 1997; Molecular Biology of the Cell, 3rd Edition, Bruce Alberts, et al., Garland Publishing, 1994; The Random House Dictionary of the English Language, Unabridged Edition, 1966; Webster's Ninth New Collegiate Dictionary, 1991.
DEFINITION:
- insulin
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A protein hormone secreted by the beta cells of the pancreatic islets that serves as a hormonal signal of the fed state; it is secreted in response to elevated blood levels of glucose and amino acids and promotes the efficient storage and utilization of these fuel molecules by controlling the transport of metabolites and ions across cell membranes and regulating various intracellular biosynthetic pathways. Insulin promotes the entry of glucose, fatty acids, and amino acids into cells; promotes glycogen, protein, and lipid synthesis; and inhibits gluconeogenesis, glycogen degradation, protein degradation, and lipolysis. Insulin secretion is also influenced by several gastrointestinal hormones and by autonomic nervous activity. Insulin is formed from a single polypeptide chain (proinsulin) that is cleaved by specific proteases at two points; the two end pieces (the A and B chains) held together by two disulfide bridges, make up insulin; the middle piece (the connecting peptide or C-peptide) is also secreted but has no physiologic activity. Relative insulin deficiency is the cause of most cases of diabetes mellitus. Exogenous insulin is used for control of diabetes; various preparations differ in regard to source (bovine, porcine, a mixture of the two, or recombinant human types), rapidity of onset and duration of action and degree of purification (most preparations contain some proinsulin and other antigenic components).
Used in 4 Article abstracts
Used in 4 Article abstracts